Method for producing lithium fluorosulfonate, lithium fluorosulfonate, nonaqueous electrolyte, and nonaqueous electrolyte secondary battery

Abstract

The present invention relates to a process for producing lithium fluorosulfonate, which comprises a step of reacting a lithium salt and fluorosulfonic acid in a non-aqueous solvent, wherein the lithium salt is a lithium salt which does not produce water as a result of the reaction step.

Description

[0001] This application is a divisional application of the application filed on April 10, 2012, with application number 202010371692.6 and entitled "Method for manufacturing lithium fluorosulfonate, lithium fluorosulfonate, non-aqueous electrolyte, and non-aqueous electrolyte secondary battery". Technical Field

[0002] This invention relates to a method for manufacturing lithium fluorosulfonate and to lithium fluorosulfonate itself. Specifically, it relates to a method for manufacturing lithium fluorosulfonate by reacting lithium halide with fluorosulfonic acid in a non-aqueous solvent, and to lithium fluorosulfonate. Additionally, it relates to a non-aqueous electrolyte containing lithium fluorosulfonate and a non-aqueous electrolyte secondary battery. Background Technology

[0003] Non-aqueous electrolyte secondary batteries, such as lithium-ion batteries, are finding practical applications in a wide range of uses, from consumer power supplies like mobile phones and laptops to automotive power supplies and large-scale stationary power supplies. However, in recent years, the demand for high-performance non-aqueous electrolyte secondary batteries has been increasing, requiring high levels of battery characteristics such as high capacity, high output, high-temperature storage characteristics, and cycle performance.

[0004] In particular, when using lithium-ion batteries as a power source for electric vehicles, the high energy required for starting and acceleration, and the efficient regeneration of energy generated during deceleration, necessitate lithium-ion batteries with high output and input characteristics. Furthermore, since electric vehicles are intended for outdoor use, high input-output characteristics (low internal resistance) are essential for rapid starting and acceleration, especially at temperatures as low as -30°C, to ensure optimal performance in cold conditions. Additionally, minimal capacity degradation and a small increase in internal impedance are also required after repeated charge-discharge cycles at high temperatures.

[0005] Furthermore, beyond electric vehicles, when lithium-ion batteries are used as large-scale stationary power sources for various backup applications, load balancing of power supply, and output stabilization of natural energy generation, not only must individual cells be made larger, but multiple cells must also be connected in series and parallel. This can easily lead to reliability and safety issues due to various inconsistencies such as uneven discharge characteristics, uneven temperature between cells, and uneven capacity or state of charge among individual cells. If the battery design and management are improper, the following problems may occur: only a portion of the cells constituting the battery pack may maintain a high state of charge, or the internal temperature of the battery may rise and enter a high-temperature state.

[0006] In other words, for current non-aqueous electrolyte secondary batteries, the following requirements must be met at an extremely high level: high initial capacity and input / output characteristics, low internal impedance, high capacity retention after durability tests such as high-temperature storage tests or cycle tests, and excellent input / output performance and impedance characteristics even after durability tests.

[0007] To date, various technologies have been studied as methods to improve the characteristics of non-aqueous electrolyte secondary batteries. For example, Patent Document 1 describes a battery with high discharge capacity during charge-discharge cycle evaluation at 60°C when using lithium fluorosulfonate as the electrolyte. According to Patent Document 1, when LiClO4 is used as the electrolyte, it decomposes at a high potential of the positive electrode active material to generate active oxygen, which attacks the solvent and promotes its decomposition. Furthermore, when CF3SO3Li, LiBF4, and LiPF6 are used as electrolytes, the electrolyte decomposes at a high potential of the positive electrode active material to generate fluorine, which attacks the solvent and promotes its decomposition.

[0008] Only two methods for manufacturing this lithium fluorosulfonate have been reported (Non-Patent Document 1, Patent Document 2).

[0009] Non-patent literature 1 reports a method for obtaining lithium fluorosulfonate trihydrate by mixing ammonium fluorosulfonate and an aqueous solution of lithium hydroxide.

[0010] However, this method requires a separate cation exchange of lithium salt after the ammonium salt is synthesized, which is not only cumbersome but also poses a risk of contamination by the released ammonia.

[0011] Furthermore, the literature reports that potassium fluorosulfonate is hydrolyzable, and lithium salts are also highly likely to undergo hydrolysis. Therefore, questions remain about whether the hydrates can be stored stably for a long period of time.

[0012] Furthermore, when dissolved in the electrolyte, this water may cause adverse effects such as the decomposition of lithium hexafluorophosphate and the production of hydrogen fluoride as a byproduct. Therefore, it is necessary to remove the water of crystallization in advance, which makes the operation more complicated.

[0013] Patent Document 2 describes the manufacture of various lithium salts, including lithium fluorosulfonate, by subjecting lithium chloride or lithium sulfate to salt exchange reactions with various sodium / potassium salts in various solutions. However, the examples in this patent document only relate to the manufacture of water-stable lithium nitrate and lithium bromide in aqueous solutions, and do not report examples of manufacturing lithium fluorosulfonate, which may have hydrolytic issues. Furthermore, this patent document utilizes the difference in solubility between the various lithium salts as the target and the sodium or potassium hydrochloride or sulfate salts as byproducts. The low-solubility byproducts are first precipitated by concentrating the solution, and then the solution containing the various lithium salts as the target is extracted by filtration of the concentrated solution. In this method, a high recovery rate cannot be expected without using a solvent that maximizes the difference in solubility between the target lithium salt and the byproduct salt, and the recovery rate under conditions suitable for the manufacture of lithium fluorosulfonate remains unknown.

[0014] On the other hand, for sodium / potassium salts, which are also alkali metals like lithium but are more widely used than lithium, the following manufacturing methods are known.

[0015] (1) A method for reacting sodium fluoride / potassium fluoride with sulfur trioxide or fuming sulfuric acid (Patent Documents 3 and 4 and Non-Patent Document 2).

[0016] (2) A method for reacting inorganic fluoride salts with sulfur trioxide (Non-Patent Literature 3 (Hexafluorosilicate), Non-Patent Literature 4 (Hexafluorophosphate))

[0017] (3) A method for causing a salt exchange reaction between fluorosulfonic acid and potassium acetate in acetic acid solvent (Non-Patent Literature 5)

[0018] Existing technical documents

[0019] Patent documents

[0020] Patent Document 1: Japanese Patent Application Publication No. 7-296849

[0021] Patent Document 2: International Publication No. 1998 / 013297

[0022] Patent Document 3: German Patent No. 1010503

[0023] Patent Document 4: USSR Patent No. 223070

[0024] Non-patent literature

[0025] Non-patent literature 1: Berichte der Deutschen Chemischen Gesellschaft (1919), 52B 1272

[0026] Non-patent literature 2: Inorganic Chemistry (1967), 6(2), 416

[0027] Non-patent literature 3: Journal of Fluorine Chemistry (1984), 24(4), 399

[0028] Non-patent literature 4: Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry (1992), 22(10), 1533

[0029] Non-patent literature 5: Journal of the Chemical Society [Section] A, (1967), (3), 355 Summary of the Invention

[0030] The problem the invention aims to solve

[0031] However, for (1) above, highly reactive sulfur trioxide (or fuming sulfuric acid containing sulfur trioxide) must be used; for (2) above, gaseous inorganic fluorides are produced as a byproduct of the reaction, and these gaseous inorganic fluorides can be hydrolyzed to generate hydrogen fluoride. Therefore, both methods are difficult to implement using conventional reaction equipment, leading to increased manufacturing costs. For (3) above, it can be considered that the product is highly likely to adsorb acetic acid, and its removal is problematic. Therefore, in view of the above problems, the object of the present invention is to provide a method for stably manufacturing high-purity lithium fluorosulfonate under mild conditions.

[0032] Furthermore, the present invention also aims to provide an additive for a non-aqueous electrolyte and a non-aqueous electrolyte, as well as a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte. The additive for the non-aqueous electrolyte and the non-aqueous electrolyte improve the initial charging capacity, input-output characteristics, and impedance characteristics, thereby enabling the non-aqueous electrolyte secondary battery to not only have initial battery characteristics and durability, but also maintain high input-output characteristics and impedance characteristics after durability.

[0033] Problem Solving Methods

[0034] To solve the above-mentioned problems, the inventors conducted in-depth research and found that by reacting fluorosulfonic acid and a specific lithium salt in a non-aqueous solvent, high-purity lithium fluorosulfonate can be produced in high yield under mild conditions, thus completing the present invention.

[0035] Furthermore, it was discovered that by adding lithium fluorosulfonate containing a specific amount of sulfate ions to the non-aqueous electrolyte, a non-aqueous electrolyte secondary battery with improved initial charging capacity and input / output characteristics can be obtained, thus completing the present invention.

[0036] That is, the present invention relates to the following key points.

[0037] <1> A method for manufacturing lithium fluorosulfonate includes a step of reacting a lithium salt and fluorosulfonic acid in a non-aqueous solvent, wherein the lithium salt is a lithium salt that does not produce water due to the reaction step.

[0038] <2> The above <1> The method for manufacturing lithium fluorosulfonate, wherein the lithium salt is lithium halide or lithium carboxylate.

[0039] <3> The above <1> or <2> In the method for manufacturing lithium fluorosulfonate, the non-aqueous solvent used in the above reaction steps is a non-aqueous solvent other than a carboxylic acid.

[0040] <4> The above <1> ~ <3> The method for manufacturing lithium fluorosulfonate according to any one of the above-mentioned reaction steps, wherein the non-aqueous solvent used in the above-mentioned reaction steps is a polar aprotic organic solvent.

[0041] <5> The above <1> ~ <4> The method for manufacturing lithium fluorosulfonate according to any one of the above-mentioned reaction steps, wherein the non-aqueous solvent used in the above-mentioned reaction steps is a chain carbonate.

[0042] <6> The above <1> ~ <5> The method for manufacturing lithium fluorosulfonate according to any one of the above reaction steps includes a step of removing the by-product carboxylic acid after the above reaction steps.

[0043] <7> The above <6> In the method for manufacturing lithium fluorosulfonate, the process of removing carboxylic acid is carried out by distillation.

[0044] <8> The above <6> or <7> The method for manufacturing lithium fluorosulfonate, wherein the process of removing carboxylic acid is carried out in a solution of a non-aqueous solvent, wherein the non-aqueous solvent has a boiling point higher than that of the carboxylic acid byproduct produced after the reaction process.

[0045] <9> The above <6> ~ <8> The method for manufacturing lithium fluorosulfonate according to any one of the above-mentioned steps for removing carboxylic acid is wherein the non-aqueous solvent used is a polar aprotic organic solvent.

[0046] <10> The above <1> ~ <9> The method for manufacturing lithium fluorosulfonate according to any one of the above-mentioned reaction steps or the above-mentioned steps for removing carboxylic acids includes a purification step.

[0047] <11> The above <10> The method for manufacturing lithium fluorosulfonate, wherein the purification step comprises the following operation: further mixing a non-aqueous solvent into a solution containing crude fluorosulfonic acid obtained in the reaction step.

[0048] <12> The above <1> ~ <11> The method for manufacturing lithium fluorosulfonate according to any one of the above-mentioned reaction steps includes a solid-liquid separation step, which recovers the crude lithium fluorosulfonate obtained in the above-mentioned reaction step in solid form from a non-aqueous solvent.

[0049] <13> The above <1> ~ <12> The method for manufacturing lithium fluorosulfonate according to any one of the above-mentioned reaction steps, wherein the following operation is performed at least once: contacting the crude lithium fluorosulfonate obtained in the above-mentioned reaction step with a non-aqueous solvent solution containing water.

[0050] <14> The above <13> The method for manufacturing lithium fluorosulfonate includes at least one solid-liquid separation step, which recovers lithium fluorosulfonate in solid form from a non-aqueous solvent solution, wherein the lithium fluorosulfonate is obtained by contacting the crude lithium fluorosulfonate with a non-aqueous solvent solution containing water.

[0051] <15> The above <13> or <14> In the method for manufacturing lithium fluorosulfonate, the non-aqueous solvent in the aqueous solution used in the operation of contacting the crude lithium fluorosulfonate with a non-aqueous solvent solution containing water is a polar aprotic organic solvent.

[0052] <16> A lithium fluorosulfonate, which is obtained through the above... <1> ~ <15> The lithium fluorosulfonate obtained by any one of the manufacturing methods, wherein the carboxylic acid content in the lithium fluorosulfonate is 2.5 × 10⁻⁶ relative to the total amount of lithium fluorosulfonate. -2 Below mol / kg.

[0053] <17> A lithium fluorosulfonate wherein the carboxylic acid content relative to the total lithium fluorosulfonate is 2.5 × 10⁻⁶. -2 Below mol / kg.

[0054] <18> A non-aqueous electrolyte containing lithium fluorosulfonate with a carboxylic acid ion content of 1.0 × 10⁻⁶. -7 mol / L or higher and 4.0 × 10 -3 Below mol / L.

[0055] <19> A lithium fluorosulfonate, which is obtained through the above... <1> ~ <15> The lithium fluorosulfonate obtained by any one of the methods for manufacturing lithium fluorosulfonate, wherein the halogen content is 1.5 × 10⁻⁶. -3 Below mol / kg.

[0056] <20> A lithium fluorosulfonate, wherein the halogen content is 1.5 × 10⁻⁶.-3 Below mol / kg.

[0057] <21> A non-aqueous electrolyte containing lithium fluorosulfonate, wherein the content of halide ions other than fluoride ions in the non-aqueous electrolyte is 1.0 × 10⁻⁶. -7 mol / L or higher and 1.0 × 10 -3 Below mol / L.

[0058] <22> A lithium fluorosulfonate wherein the molar content of sulfate ions relative to the weight of lithium fluorosulfonate is 2.5 × 10⁻⁶. -1 Below mol / kg.

[0059] <23> A non-aqueous electrolyte containing lithium fluorosulfonate, wherein the sulfate ion content in the non-aqueous electrolyte is 1.0 × 10⁻⁶. -7 mol / L or higher and 1.0 × 10 -2 Below mol / L.

[0060] <24> A non-aqueous electrolyte for use in a non-aqueous electrolyte battery having a negative electrode and a positive electrode capable of absorbing and releasing lithium ions, comprising the above-mentioned... <16> , <17> , <19> , <20> or <22> The lithium fluorosulfonate mentioned above.

[0061] <25> A non-aqueous electrolyte is disclosed for use in a non-aqueous electrolyte battery having a negative electrode and a positive electrode capable of absorbing and releasing lithium ions.

[0062] This non-aqueous electrolyte contains lithium fluorosulfonate, lithium salts other than lithium fluorosulfonate, and a non-aqueous solvent.

[0063] The non-aqueous electrolyte contains lithium fluorosulfonate at a molar concentration of 0.0005 mol / L or higher and 0.5 mol / L or lower, and the non-aqueous electrolyte contains sulfate ions at a molar concentration of 1.0 × 10⁻⁶. -7 mol / L or higher and 1.0 × 10 -2 Below mol / L.

[0064] <26> The above <24> or <25> The non-aqueous electrolyte wherein the lithium salt other than lithium fluorosulfonate is at least one of LiPF6 and LiBF4.

[0065] <27> The above <24> ~ <26> The non-aqueous electrolyte according to any one of the following methods, wherein the non-aqueous electrolyte contains a cyclic carbonate having fluorine atoms.

[0066] <28> The above <27> In the aforementioned non-aqueous electrolyte, the content of the cyclic carbonate containing fluorine atoms in the non-aqueous electrolyte is more than 0.001% by mass and less than 85% by mass.

[0067] <29> The above <24> ~ <28> The non-aqueous electrolyte in any one of the following methods contains a cyclic carbonate having carbon-carbon unsaturated bonds.

[0068] <30> The above <29> The non-aqueous electrolyte contains 0.001% by mass and 10% by mass of the aforementioned cyclic carbonate having carbon-carbon unsaturated bonds.

[0069] <31> The above <24> ~ <30> The non-aqueous electrolyte in any one of the following methods contains a cyclic sulfonate ester.

[0070] <32> The above <31> In the non-aqueous electrolyte, the content of the above-mentioned cyclic sulfonate in the non-aqueous electrolyte is more than 0.001% by mass and less than 10% by mass.

[0071] <33> The above <24> ~ <32> The non-aqueous electrolyte in any one of the following methods contains a compound having a cyano group.

[0072] <34> The above <33> The non-aqueous electrolyte, wherein the content of the aforementioned cyano group compound in the non-aqueous electrolyte is 0.001% by mass or more and 10% by mass or less.

[0073] <35> The above <24> ~ <34> The non-aqueous electrolyte in any one of the following methods contains a diisocyanate compound.

[0074] <36> The above <35> The non-aqueous electrolyte, wherein the content of the above-mentioned diisocyanate compound in the non-aqueous electrolyte is more than 0.001% by mass and less than 5% by mass.

[0075] <37> The above <24> ~ <36> The non-aqueous electrolyte in any one of the following methods contains lithium oxalate salts.

[0076] <38> A non-aqueous electrolyte secondary battery includes a negative electrode and a positive electrode capable of absorbing and releasing lithium ions, as well as the aforementioned... <24> ~ <37> The non-aqueous electrolyte as described in any one of the following.

[0077] <39> The above <38> In the aforementioned non-aqueous electrolyte secondary battery, the negative electrode has a negative electrode active material layer on the current collector, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material containing at least one of elemental metals, alloys and compounds of silicon, and elemental metals, alloys and compounds of tin.

[0078] <40> The above <38> In the aforementioned non-aqueous electrolyte secondary battery, the negative electrode has a negative electrode active material layer on the current collector, the negative electrode active material layer contains a negative electrode active material, and the negative electrode active material contains a carbonaceous material.

[0079] <41> The above <38> In the aforementioned non-aqueous electrolyte secondary battery, the negative electrode has a negative electrode active material layer on the current collector, the negative electrode active material layer contains a negative electrode active material, and the negative electrode active material contains a lithium titanium composite oxide.

[0080] <42> The above <38> ~ <41> The non-aqueous electrolyte secondary battery according to any one of the following, wherein the positive electrode has a positive electrode active material layer on the current collector, the positive electrode active material layer containing at least one selected from the group consisting of lithium-cobalt composite oxide, lithium-cobalt-nickel composite oxide, lithium-manganese composite oxide, lithium-cobalt-manganese composite oxide, lithium-nickel composite oxide, lithium-cobalt-nickel composite oxide, lithium-nickel-manganese composite oxide, and lithium-nickel-cobalt-manganese composite oxide.

[0081] <43> The above <38> ~ <41> The non-aqueous electrolyte secondary battery as described in any one of the following embodiments, wherein the positive electrode has a positive electrode active material layer on the current collector, the positive electrode active material layer containing LixMPO4 (where M is at least one element selected from transition metals of Group 4 to Group 11 of Period 4 in the periodic table, and x is 0). <x<1.2)。

[0082] The effects of the invention

[0083] By employing the manufacturing method of the present invention, high-purity lithium fluorosulfonate can be produced in high yield under mild conditions.

[0084] Furthermore, the inventors discovered that by including lithium fluorosulfonate containing a specific amount of sulfate ions in the non-aqueous electrolyte, excellent characteristics such as decreased battery internal impedance and improved low-temperature output performance can be observed. They also found that the initial battery internal impedance characteristics and high output performance can be maintained even after extended use. Based on these insights, the inventors completed this invention. The detailed mechanism is not yet clear, but it is believed that a synergistic effect can be achieved by including lithium fluorosulfonate in a specific proportion of sulfate ions.

[0085] That is, the non-aqueous electrolyte according to the present invention can provide a non-aqueous electrolyte secondary battery capable of improving the initial charge capacity, input-output characteristics, and internal impedance characteristics of the battery. Also, the non-aqueous electrolyte according to the present invention can provide a non-aqueous electrolyte battery having a high capacity retention rate, excellent input-output performance, and excellent impedance characteristics even after durability tests such as high-temperature storage tests and cycle tests. Thus, from an industrial perspective, it is possible to provide excellent batteries applicable to various aspects such as the above-mentioned portable device applications, electric vehicle applications, and fixed large power source applications. Detailed Embodiments

[0086] Hereinafter, the embodiments of the present invention will be described in detail. However, the present invention is not limited to these embodiments and can be implemented with any changes. Among them, "weight %" and "mass %", "parts by weight" and "parts by mass", "weight ppm" and "mass ppm" are synonymous, respectively. In addition, when only "ppm" is noted, it means "weight ppm".

[0087] <Method for Manufacturing Lithium Fluorosulfonate>

[0088] The present invention relates to a method for manufacturing lithium fluorosulfonate, which includes a reaction step of a lithium salt and fluorosulfonic acid in a non-aqueous solvent. It is characterized in that water is not generated from the lithium salt in the above reaction step. Examples of lithium salts that generate water include lithium hydroxide, lithium carbonate, lithium hydrogencarbonate, etc. The lithium salt used in the present invention can be any lithium salt other than the above, but preferably includes: lithium carboxylate, lithium halide, lithium phosphate, lithium phosphite, lithium sulfate, lithium sulfite, lithium borate, lithium nitrate, and lithium hydride, etc. From the aspect of easy removal of by-products, lithium carboxylate and lithium halide are particularly preferred.

[0089] Hereinafter, the manufacturing method in the case of using lithium carboxylate or lithium halide as the lithium salt will be described in detail.

[0090] <Method for Manufacturing Lithium Fluorosulfonate A Starting Material: Lithium Carboxylate>

[0091] <A1. Reaction Step of Lithium Carboxylate and Fluorosulfonic Acid>

[0092] The present invention relates to a method for manufacturing lithium fluorosulfonate, which is characterized in that lithium fluorosulfonate is obtained through a reaction step of lithium carboxylate and fluorosulfonic acid in a non-aqueous solvent.

[0093] The lithium carboxylate used in the present invention is not particularly limited, and specific examples are as follows.

[0094] 1) Aliphatic Monocarboxylic Acid

[0095] Lithium formate, lithium acetate, lithium propionate, lithium butyrate, lithium isobutyrate, lithium phenylacetate, etc.

[0096] 2) Aliphatic dicarboxylic acid monolithium

[0097] Lithium hydrogen oxoate, lithium hydrogen malonate, lithium hydrogen succinate, lithium hydrogen fumarate, lithium hydrogen maleate, etc.

[0098] 3) Lithium aliphatic dicarboxylate

[0099] Lithium oxalate, lithium malonate, lithium succinate, lithium fumarate, lithium maleate, etc.

[0100] 4) Aromatic monocarboxylic acids

[0101] Lithium benzoate, etc.

[0102] 5) Aromatic dicarboxylic acid monolithium

[0103] Lithium hydrogen phthalate, lithium hydrogen terephthalate, etc.

[0104] 6) Dilithium dicarboxylic acid of aromatic compounds

[0105] Lithium phthalate, lithium terephthalate, etc.

[0106] Among these lithium carboxylate products, from the viewpoint that they are inexpensive and readily available in high purity, aliphatic monocarboxylate lithium and aliphatic dicarboxylate dilithium are preferred.

[0107] Furthermore, considering the ease of removal of by-products from lithium monocarboxylic acids, low-boiling-point aliphatic monocarboxylic acids are preferred, specifically lithium formate and lithium acetate.

[0108] Furthermore, regarding dilithium dicarboxylate, from the viewpoint of reducing waste, it is preferable to have a high proportion of lithium in the intramolecular elements. Specifically, lithium oxalate, lithium malonate, and lithium succinate are preferred.

[0109] Among these, lithium formate and lithium acetate are preferred, and lithium acetate is the most preferred in terms of ease of acquisition.

[0110] These lithium carboxylate products can be used alone or in combination, but to avoid complicating the operation, it is preferred to use them alone.

[0111] The lithium carboxylate used in the reaction of this invention can be a commercially available product, or it can be used after purification, or it can be manufactured from other compounds. There is no particular limitation on its purity, but when lithium fluorosulfonate contains impurities from lithium halides, there is a risk of deterioration in the performance of batteries, etc. Therefore, higher purity is preferred, preferably 99% by mass or higher.

[0112] The fluorosulfonic acid used in the reaction of this invention can be a commercially available product, or it can be used after purification, or it can be manufactured from other compounds. There is no particular limitation on its purity, but when impurities from fluorosulfonic acid remain in lithium fluorosulfonate, there is a risk of deterioration in the performance of batteries, etc. Therefore, higher purity is preferred, preferably 99% by mass or higher.

[0113] The feed ratio of fluorosulfonic acid to lithium in lithium carboxylate used in the reaction process of the present invention is not particularly limited, but from the viewpoint of raw material consumption efficiency, it is preferable that the ratio does not deviate significantly from 1:1.

[0114] As a lower limit for the feed ratio of fluorosulfonic acid to lithium in lithium carboxylate (the ratio of lithium halide to fluorosulfonic acid) used in the reaction process of the present invention, when the feed amount of fluorosulfonic acid is greater than that of lithium in lithium carboxylate, it may cause problems such as fluorosulfonic acid residue in lithium fluorosulfonate leading to a decrease in purity. Therefore, the feed ratio of fluorosulfonic acid to lithium in lithium carboxylate (the ratio of lithium halide to fluorosulfonic acid) is preferably 1 molar ratio or more, more preferably 1.01 molar ratio or more, and even more preferably 1.05 molar ratio or more. As an upper limit, it is preferably 2 molar ratio or less, more preferably 1.5 molar ratio or less, and even more preferably 1.2 molar ratio or less. When the ratio of lithium halide to fluorosulfonic acid is adjusted to the above range, high-purity lithium fluorosulfonate can be produced in high yield without a cumbersome purification process, which is therefore preferred.

[0115] The non-aqueous solvent used in the reaction process of this invention can be any solvent other than water, and there are no particular limitations. However, from the viewpoint of easily removing the byproduct carboxylic acid, a non-aqueous solvent other than carboxylic acid is preferred. Furthermore, since fluorosulfonic acid is a strong protic acid, a polar aprotic organic solvent with low reactivity with protic acids is preferred. Additionally, from the viewpoint of ensuring stable reaction, a solvent with not extremely low solubility for the generated lithium fluorosulfonate is preferred. The solubility of lithium fluorosulfonate in the non-aqueous solvent used in the reaction process is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 5% by mass or more at room temperature.

[0116] Furthermore, regarding the boiling point of the non-aqueous solvent used in the reaction process, to avoid performance degradation of the battery or similar components due to solvent residue, it is preferable that its boiling point is not too high. Specifically, it is preferable that its boiling point at atmospheric pressure is below 300°C, more preferably below 200°C, and even more preferably below 150°C. If the boiling point is outside the above range, although it varies depending on the non-aqueous solvent used, it may remain in the resulting lithium fluorosulfonate and adversely affect battery performance.

[0117] The non-aqueous solvent used in the reaction process of this invention is preferably anhydrous hydrofluoric acid or an organic solvent, more preferably an organic solvent, and particularly preferably a polar aprotic organic solvent. Examples of polar aprotic organic solvents include: chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate; chain sulfonates such as methyl methanesulfonate, ethyl methanesulfonate, and methyl ethanesulfonate; chain nitriles such as acetonitrile and propionitrile; chain ethers such as diisopropyl ether, diisopropyl ether, and tert-butyl methyl ether; tetrahydrofuran, tetrahydropyran, 1,3-dioxane, and 1,3-dioxane. Alkane, 1,4-di Cyclic ethers such as alkanes; etc.

[0118] Among the solvents mentioned above, preferred are chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate; and chain nitriles such as acetonitrile and propionitrile. Furthermore, considering ease of acquisition, preferred are dimethyl carbonate, diethyl carbonate, ethyl acetate, and acetonitrile.

[0119] On the other hand, considering the impact of residues on battery characteristics, chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferred. From these perspectives, dimethyl carbonate and diethyl carbonate are preferred; furthermore, since carboxylic acids with boiling points lower than diethyl carbonate exist, diethyl carbonate is the most preferred.

[0120] These non-aqueous solvents can be used alone or in combination, but to avoid complicating the operation, it is preferred to use them alone.

[0121] The ratio of the non-aqueous solvent to fluorosulfonic acid used in the reaction process of this invention is not particularly limited, but is preferably 100 times or less by volume, more preferably 50 times or less, and even more preferably 25 times or less. Furthermore, the ratio of the solvent to fluorosulfonic acid used in the reaction is preferably 2 times or more by volume, more preferably 3 times or more, and even more preferably 5 times or more. Within the above ranges, the manufacturing efficiency is excellent, the resulting lithium fluorosulfonate does not excessively precipitate during the reaction, and problems such as hindering stirring are less likely to occur.

[0122] Furthermore, the initial temperature of the reaction process in this invention is not particularly limited, but is preferably below 100°C, more preferably below 80°C, and even more preferably below 60°C. Additionally, the temperature during the reaction is preferably above -20°C, more preferably above -10°C, and even more preferably above 0°C. When the initial temperature of the reaction process in this invention is within the above range, problems such as solvent evaporation and unpredictable side reactions are less likely to occur, and problems such as a decrease in reaction rate can also be prevented.

[0123] The order of addition to the reaction system in the reaction process of this invention is not particularly limited. Solid lithium carboxylate can be added while stirring the fluorosulfonic acid solution, or fluorosulfonic acid can be added dropwise while suspending the solid lithium carboxylate in the solvent. Furthermore, the added fluorosulfonic acid may or may not be diluted with a solvent. When fluorosulfonic acid is diluted with a solvent before being added dropwise, the volume ratio is preferably 5 times or less, more preferably 3 times or less, and even more preferably 2 times or less. When the amount of diluent is within the above range, the total amount of solvent in the reaction system is appropriate.

[0124] The reaction time in this invention is not particularly limited, but is preferably 10 hours or less, more preferably 5 hours or less, and even more preferably 1 hour or less. Furthermore, the reaction time in this invention is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. By keeping the reaction time in this invention within the above range, excellent manufacturing efficiency can be obtained.

[0125] The initial temperature during the reaction process of this invention is not particularly limited, but is preferably below +20°C, more preferably below +10°C, and even more preferably below +5°C. The initial temperature during the reaction process of this invention is preferably above -20°C, more preferably above -10°C, and even more preferably above -5°C, and particularly preferably maintained around the initial temperature. When the initial temperature during the reaction process of this invention is within the above range, problems such as solvent evaporation, unpredictable side reactions, and reduced reaction rate are less likely to occur.

[0126] In the reaction process of this invention, a curing process is preferably performed after the input of the solvent. The curing temperature in the curing process is not particularly limited, but is preferably below the reaction temperature +100°C, more preferably below the reaction temperature +80°C, and even more preferably below the reaction temperature +50°C. Furthermore, the curing temperature is preferably above the reaction temperature +5°C, more preferably above the reaction temperature +10°C, and even more preferably above the reaction temperature +20°C. When the curing temperature in the curing process is within the above range, problems such as solvent evaporation, unpredictable side reactions, and reduced reaction rate are less likely to occur.

[0127] In addition, the temperature during maturation can be higher or lower than the temperature at which the ingredients were added, but to improve the maturation effect, it is preferable to use a temperature higher than that at which the ingredients were added.

[0128] When the temperature of the curing process is within the above range, the evaporation of solvent and the occurrence of side reactions can be suppressed, and the curing effect can be fully obtained because the manufacturing efficiency can be improved.

[0129] The time of the aging process in the reaction process of the present invention is not particularly limited, preferably 20 hours or less, more preferably 10 hours or less, and further preferably 5 hours or less. In addition, the reaction time in the reaction of the present invention is preferably 1 minute or more, more preferably 10 minutes or more, and further preferably 30 minutes or more. When the time of the aging process is within the above range, the manufacturing efficiency becomes good, and the aging effect can be fully obtained.

[0130] The gas atmosphere in the reaction process of the present invention is not particularly limited. However, since there is a risk that the starting material fluorosulfonic acid or the product lithium fluorosulfonate decomposes in the presence of water, it is preferably mixed in a gas atmosphere that blocks outside air, and more preferably mixed in an inert gas atmosphere such as a dry air or nitrogen atmosphere, or an argon atmosphere. These gases can be introduced into the equipment at the start of the reaction process and then sealed, or can be continuously supplied to and discharged from the device.

[0131] The reaction equipment in the reaction process of the present invention may be made of any material that can be used for the manufacture of ordinary chemicals, and there is no special limitation. However, when fluorosulfonic acid hydrolyzes due to the mixing of water in the atmosphere, there is a possibility of generating hydrofluoric acid. Therefore, it is preferably made of a material that is not easily corroded by hydrofluoric acid. In particular, for parts such as reaction tanks that are in contact with the reaction solution for a long time, it is preferably made of a material that is not corroded by hydrofluoric acid. Specifically, the reaction tank is preferably made of a material other than glass.

[0132] <A2. Removal of Excessive Lithium Carboxylate>

[0133] There is no special limitation on the method for recovering (crude) lithium fluorosulfonate from the non-aqueous solution after the above reaction process.

[0134] In addition, when an excessive amount of lithium carboxylate is used in the reaction process, there may be a case where the excessive lithium carboxylate remains as an insoluble component due to the combination of the type of lithium carboxylate and the type of non-aqueous solvent selected. In this case, it is best to separate the insoluble component of the excessive lithium carboxylate in advance before the purification process. The method for separating the insoluble component of lithium carboxylate is not particularly limited, and methods such as vacuum filtration, pressure filtration, centrifugal filtration, etc., or taking the supernatant after sedimentation by standing or centrifugation can be used. In addition, these methods can be combined or the same method can be repeated. It should be noted that this process can be implemented at any of the following stages: after the reaction process, after or during the process of removing the non-aqueous solvent used in the reaction process, or during the process of removing carboxylic acid.

[0135] Hereinafter, the process of removing the non-aqueous solvent used in the reaction process and the process of removing the by-produced carboxylic acid will be described. However, depending on the type of the by-produced carboxylic acid and the type of the selected non-aqueous solvent, the order of the processes can be switched, or the two processes can be combined into one process.

[0136] <A3. Process of removing the non-aqueous solvent used in the reaction process>

[0137] There is no particular limitation on the method of removing the non-aqueous solvent used in the reaction process, and methods such as removal by concentration distillation can be adopted. The temperature during concentration distillation removal is not particularly limited, and it is preferably controlled to a temperature that does not exceed the temperature during the reaction process by a large margin. When the temperature during concentration distillation removal is too high, there are problems such as unpredictable side reactions, so it is not preferred. It is preferably 50 °C or lower than the temperature during aging, more preferably 40 °C or lower than the temperature during aging, and further preferably 30 °C or lower than the temperature during aging. The pressure during concentration distillation removal can be any pressure of normal pressure or reduced pressure, and it needs to be set according to the preferred temperature during concentration.

[0138] There is no particular limitation on the removal amount of the non-aqueous solvent used in the reaction process. It can be dried and solidified ( ), or a part of it can remain. However, when it is not completely dried and solidified, there is a possibility that the purification effect achieved by crystallization is also worthy of expectation, so it is preferred.

[0139] Regarding the residual amount of the solvent used during the reaction, since too much residual amount may lead to a decrease in the amount recovered in solid form, it is preferably 20 times or less, more preferably 15 times or less, and further preferably 10 times or less in terms of the volume ratio of the fluorosulfonic acid introduced. On the other hand, since it will become a viscous slurry state when the residual amount is too small, making the operation difficult, the residual amount of the solvent used during the reaction is preferably 0.3 times or more, more preferably 0.5 times or more, and further preferably 1 times or more in terms of the volume ratio of the fluorosulfonic acid introduced.

[0140] It should be noted that in the case of drying and solidifying until it can be processed in solid form, it is not subject to this limitation.

[0141] When the non-aqueous solvent used during the reaction process remains, it is necessary to separate the solvent from the solid. There is no particular limitation on the separation method, and methods such as filtration such as vacuum filtration, pressure filtration, and centrifugal filtration, and taking out the supernatant after sedimentation by standing or centrifugation can be adopted.

[0142] It should be noted that depending on the type of the by-produced carboxylic acid and the type of the selected non-aqueous solvent, these two processes, this process and the process described in the following item, can be combined into one process.

[0143] <Step of removing carboxylic acid>

[0144] For the step of removing by - product carboxylic acid, two methods can be appropriately selected according to the physical properties of the by - product carboxylic acid.

[0145] 1) When the by - product carboxylic acid is a liquid at the temperature of the operation

[0146] It is removed by distillation operation.

[0147] 2) When the by - product carboxylic acid is a solid at the temperature of the operation

[0148] Lithium fluorosulfonate is dissolved in a solvent in which lithium fluorosulfonate is soluble while the by - product carboxylic acid is poorly soluble / insoluble and easy to remove, and the by - product carboxylic acid is separated from the obtained slurry by various methods for separating solids and liquids.

[0149] For case 1), there are no special restrictions on the pressure and temperature during the removal by distillation operation, but it is preferably controlled at a temperature that does not greatly exceed the temperature during the reaction step. When the temperature during removal is too high, there is a risk of unpredictable side reactions, etc., so it is not preferred. It is preferably at or below the temperature during aging + 50°C, more preferably at or below the temperature during aging + 40°C, and further preferably at or below the temperature during aging + 30°C. The pressure during removal can be any pressure of normal pressure or reduced pressure, but it needs to be set according to the preferred temperature during removal.

[0150] In addition, in order to more completely remove the by - product carboxylic acid, it is preferable to perform the following operation: use a solvent in which lithium fluorosulfonate is soluble, the boiling point of which is higher than the boiling point of the by - product carboxylic acid and is easy to remove, and remove part or all of this solvent.

[0151] This operation can be carried out by further adding a non - aqueous solvent in which lithium fluorosulfonate is soluble and the boiling point of which is higher than the boiling point of the by - product carboxylic acid and is easy to remove after the reaction step, or a non - aqueous solvent in which lithium fluorosulfonate is soluble and the boiling point of which is higher than the boiling point of the by - product carboxylic acid and is easy to remove can be pre - selected as the reaction solvent, and the removal of the reaction solvent and the removal of the by - product carboxylic acid are combined into one step. To simplify the process, it is more preferably combined into one step.

[0152] In addition, the following operation can also be added before performing this operation: add a non - aqueous solvent that has an azeotropic property with the carboxylic acid and is easy to remove, and remove the carboxylic acid by azeotropy. In the case of implementing this operation, if a non - aqueous solvent with a boiling point lower than the non - aqueous solvent in which lithium fluorosulfonate is soluble and the boiling point of which is higher than the boiling point of the by - product carboxylic acid and is easy to remove is used, it can make the removal of the solvent that has an azeotropic property with the carboxylic acid used and is easy to remove easier, so it is preferred.

[0153] The non-aqueous solvent used in this step, in which lithium fluoro sulfonate is soluble, has a boiling point higher than that of the by-produced carboxylic acid, and is easily removed, varies depending on the type of the by-produced carboxylic acid. For example, for lithium formate, methyl ethyl carbonate, diethyl carbonate, etc. are preferred; for lithium acetate, diethyl carbonate, etc. are preferred.

[0154] When removing these solvents by distillation operation, it is more preferred to use a rectifying column with multiple theoretical plates.

[0155] Regarding the structure of the rectifying column, there is no particular limitation, and a rectifying column adopted industrially can be appropriately used. In addition, regarding the number of theoretical plates of the rectifying column, since it will not achieve the rectification effect when it is too low, it is preferably 2 or more, more preferably 3 or more, and further preferably 5 or more; while it will lead to a decline in industrial productivity when it is too high, so it is preferably 50 or less, more preferably 30 or less, and further preferably 10 or less.

[0156] For case 2), there is no particular limitation on the removal method, and methods such as vacuum filtration, pressure filtration, centrifugal filtration, etc. can be adopted, or supernatant can be taken out after sedimentation by standing or centrifugation. In addition, these methods can be combined, or the same method can be repeated.

[0157] After removing the excessive lithium carboxylate, the non-aqueous solvent used in the reaction can be removed first, and then a non-aqueous solvent in which lithium fluoro sulfonate is soluble and the by-produced carboxylic acid is hardly soluble / insoluble and is easily removed can be added again for implementation; or a non-aqueous solvent in which lithium fluoro sulfonate is soluble and the by-produced carboxylic acid is hardly soluble / insoluble and is easily removed can be used in advance as the non-aqueous solvent used in the reaction step to remove the excessive lithium carboxylate and the by-produced carboxylic acid at one time. Regarding the removal of the solvent after removing the by-produced carboxylic acid, it can be carried out according to the process of removing the non-aqueous solvent used in the reaction step.

[0158] The non-aqueous solvent used in this step, in which lithium fluoro sulfonate is soluble and the by-produced carboxylic acid is hardly soluble / insoluble and is easily removed, varies depending on the type of the by-produced carboxylic acid. For example, in the case of using lithium oxalate, lithium malonate, lithium succinate, there is no particular limitation, but methyl carbonate, methyl ethyl carbonate, diethyl carbonate, etc. are preferred.

[0159] <A5. Purification step>

[0160] In this invention, to further improve the purity of lithium fluorosulfonate, a purification process is preferred. Specifically, by contacting the (crude) lithium fluorosulfonate obtained from the reaction process with a non-aqueous solvent, followed by washing, recrystallization, and reprecipitation, high purity can be achieved. Among the above operations, recrystallization is more preferred. Furthermore, washing is preferably performed after recrystallization. The number of recrystallizations is not particularly limited and can be repeated. The number of washings is also not particularly limited and can be repeated. When recrystallization is repeated, it is preferable to perform washing at least once per recrystallization, but there is no particular limitation.

[0161] As a solvent used in the purification process, there are no special limitations as long as it is not water, but organic solvents are preferred, and polar aprotic organic solvents are more preferred.

[0162] As polar aprotic organic solvents, specific examples include: chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate; chain sulfonates such as methyl methanesulfonate, ethyl methanesulfonate, and methyl ethanesulfonate; chain nitriles such as acetonitrile and propionitrile; chain ethers such as diethyl ether, diisopropyl ether, and tert-butyl methyl ether; tetrahydrofuran, tetrahydropyran, 1,3-dioxane, and 1,3-dioxane. Alkane, 1,4-di Cyclic ethers such as alkanes; etc.

[0163] Among these, preferred solvents include chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate; and chain nitriles such as acetonitrile and propionitrile. Furthermore, considering their ease of acquisition, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, and acetonitrile are preferred. On the other hand, considering the impact of residues on battery characteristics, chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferred. From these perspectives, dimethyl carbonate and diethyl carbonate are most preferred. These solvents can be used alone or in combination.

[0164] It should be noted that the unsuitable solvent used in the reprecipitation method is not limited to this; any solvent with a lower polarity than the solvent that can dissolve it is acceptable, without any special restrictions.

[0165] There is no special limitation on the amount of solvent used for recrystallization in the pure chemical process, but at least once, it should be the amount that can dissolve (crude) lithium fluorosulfonate. On the other hand, if the amount of solvent is too large, the recovery efficiency during recrystallization will decrease, so it is not preferred. Regarding the preferred amount, since the solubility of lithium fluorosulfonate varies depending on the solvent used, there is no special limitation. For example, when using dimethyl carbonate, it is preferably more than 2 times the mass of the crude lithium fluorosulfonate solid, more preferably more than 3 times, and further preferably more than 5 times. Additionally, for example, when using dimethyl carbonate, it is preferably not more than 20 times the mass of the crude lithium fluorosulfonate solid, more preferably not more than 15 times, and further preferably not more than 10 times.

[0166] When recrystallization is carried out for purification, there is no special limitation on the temperature during dissolution. However, if the temperature is too high, there is a risk of decomposition due to heating, so it is not preferred. If the temperature is too low, a large amount of solvent is required to achieve substantially complete dissolution, so it is not preferred. When recrystallization is carried out for purification, the temperature during dissolution is preferably 100 °C or lower, more preferably 80 °C or lower, and further preferably 70 °C or lower.

[0167] During recrystallization, insoluble impurities may remain after dissolution and before crystallization. Therefore, it is preferred to perform an operation to remove the insoluble matter using methods such as filtration.

[0168] Regarding the temperature of crystallization during recrystallization, there is no special limitation as long as the temperature is lower than the dissolution temperature. However, to improve the recovery efficiency, a lower crystallization temperature is preferred. On the other hand, if the recovery efficiency is excessively increased, there is a risk that soluble impurities to be removed will also precipitate. The preferred temperature during crystallization varies depending on the recrystallization solvent used and there is no special limitation. For example, when using dimethyl carbonate, the temperature during crystallization is preferably 50 °C or lower, more preferably 40 °C or lower, and further preferably 30 °C or lower. Additionally, it is preferably -50 °C or higher, more preferably -20 °C or higher, and further preferably 0 °C or higher.

[0169] <A6. Post-treatment after the purification process>

[0170] The solid lithium fluorosulfonate obtained through the above purification process contains the non-aqueous solvent used in the above purification process, so it is preferably removed by drying. The method for removing the solvent is not particularly limited, but since thermal decomposition may occur when the temperature reaches a high level during the removal operation, it is not preferred. On the other hand, if the temperature is too low, there is a possibility that sufficient removal cannot be achieved, so it is not preferred. The removal temperature is preferably 100 °C or lower, more preferably 80 °C or lower, and still more preferably 50 °C or lower. In addition, it is preferably 0 °C or higher, more preferably 10 °C or higher, and still more preferably 20 °C or higher. The longer the removal time, the higher the removal efficiency, so it is preferred. On the other hand, it will lead to a decrease in production efficiency. Based on this, it is preferably carried out within an appropriate range of time. The removal time is preferably 30 minutes or longer, more preferably 1 hour or longer, and still more preferably 2 hours or longer. In addition, the removal time is preferably 24 hours or shorter, more preferably 10 hours or shorter, and still more preferably 5 hours or shorter.

[0171] <Method B for manufacturing lithium fluorosulfonate Starting material: lithium halide>

[0172] <B1. Reaction step of lithium halide and fluorosulfonic acid>

[0173] The present invention relates to a method for manufacturing lithium fluorosulfonate, which obtains lithium fluorosulfonate through a reaction step of lithium halide and fluorosulfonic acid in a non-aqueous solvent.

[0174] The lithium halide used in the present invention is not particularly limited. Considering the ease of acquisition, lithium fluoride, lithium chloride, lithium bromide, and lithium iodide are preferred. In addition, considering high reactivity, lithium chloride, lithium bromide, and lithium iodide are preferred. Furthermore, considering low cost, lithium chloride and lithium bromide are preferred. In addition, considering less generation of by-products during manufacturing, lithium chloride is most preferred.

[0175] These lithium halides can be used alone or in combination, but in order not to complicate the operation, it is preferred to use them alone.

[0176] The lithium halide used in the reaction step of the present invention can be directly used as a commercially available product, or can be used after purification, or can be used after being manufactured from other compounds. There is no particular limitation on its purity, but when impurities from the lithium halide remain in the lithium fluorosulfonate, there is a risk of deteriorating the performance of batteries, etc., so a higher purity is preferred, and the purity is preferably 99% by mass or more.

[0177] The fluorosulfonic acid used in the reaction process of this invention can be a commercially available product, or it can be used after purification, or it can be manufactured from other compounds. There is no particular limitation on its purity, but when impurities from fluorosulfonic acid remain in lithium fluorosulfonate, there is a risk of deterioration in the performance of batteries, etc. Therefore, higher purity is preferred, preferably 99% by mass or higher.

[0178] The feed ratio of fluorosulfonic acid to lithium halide used in the reaction process of the present invention is not particularly limited, but from the viewpoint of raw material consumption efficiency, it is preferable that the ratio does not deviate significantly from 1:1.

[0179] Regarding the ratio of fluorosulfonic acid to lithium halide used in the reaction process of the present invention, it is preferable that the ratio of lithium halide to fluorosulfonic acid is generally 1 molar ratio or more, more preferably 1.01 molar ratio or more, and even more preferably 1.05 molar ratio or more. On the other hand, the upper limit is generally 2 molar ratio or less, preferably 1.5 molar ratio or less, and even more preferably 1.2 molar ratio or less.

[0180] When the ratio of lithium halide to fluorosulfonic acid is adjusted to the above range, high-purity lithium fluorosulfonate can be produced in high yield without a cumbersome purification process, which is therefore preferred.

[0181] The non-aqueous solvent used in the reaction process of this invention can be any solvent other than water, without particular limitation. However, since fluorosulfonic acid is a strong protic acid, a non-aqueous solvent with low reactivity with protic acids is preferred. Furthermore, from the perspective of ensuring stable reaction, a solvent with not extremely low solubility for the generated lithium fluorosulfonate is preferred. The solubility of lithium fluorosulfonate in the non-aqueous solvent used in the reaction process is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 5% by mass or more at room temperature.

[0182] Furthermore, regarding the boiling point of the non-aqueous solvent used in the reaction process, it is preferable that its boiling point at atmospheric pressure is below 300°C, more preferably below 200°C, and even more preferably below 150°C. If the boiling point is not within the above range, although it varies depending on the solvent used, it may remain in the resulting lithium fluorosulfonate and adversely affect the battery performance.

[0183] The non-aqueous solvent used in the reaction process of this invention is preferably anhydrous hydrofluoric acid or an organic solvent, more preferably an organic solvent, and particularly preferably a polar aprotic organic solvent. Examples of polar aprotic organic solvents include: chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate; chain sulfonates such as methyl methanesulfonate, ethyl methanesulfonate, and methyl ethanesulfonate; chain nitriles such as acetonitrile and propionitrile; chain ethers such as diisopropyl ether, diisopropyl ether, and tert-butyl methyl ether; tetrahydrofuran, tetrahydropyran, 1,3-dioxane, and 1,3-dioxane. Alkane, 1,4-di Cyclic ethers such as alkanes; etc.

[0184] Among the solvents mentioned above, preferred are chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate; and chain nitriles such as acetonitrile and propionitrile. Furthermore, considering ease of acquisition, preferred are dimethyl carbonate, diethyl carbonate, ethyl acetate, and acetonitrile.

[0185] On the other hand, considering the impact of residues on battery characteristics, chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferred. From these perspectives, dimethyl carbonate and diethyl carbonate are the most preferred.

[0186] These non-aqueous solvents can be used alone or in combination, but to avoid complicating the operation, it is preferred to use them alone.

[0187] The ratio of the non-aqueous solvent to fluorosulfonic acid used in the reaction process of this invention is not particularly limited, but is preferably 100 times or less by volume, more preferably 50 times or less, and even more preferably 25 times or less. Furthermore, the ratio of the solvent to fluorosulfonic acid used in the reaction is preferably 2 times or more by volume, more preferably 3 times or more, and even more preferably 5 times or more. Within the above ranges, the manufacturing efficiency is excellent, the resulting lithium fluorosulfonate does not excessively precipitate during the reaction, and problems such as hindering stirring are less likely to occur.

[0188] Furthermore, the initial temperature of the reaction process in this invention is not particularly limited, but is preferably below 100°C, more preferably below 80°C, and even more preferably below 60°C. Additionally, the temperature during the reaction is preferably above -20°C, more preferably above -10°C, and even more preferably above 0°C. When the initial temperature of the reaction process in this invention is within the above range, problems such as solvent evaporation and unpredictable side reactions are less likely to occur, and problems such as a decrease in reaction rate can also be prevented.

[0189] The order of addition to the reaction system in the reaction process of this invention is not particularly limited. Solid lithium halide can be added while stirring the solution of fluorosulfonic acid, or fluorosulfonic acid can be added dropwise while suspending the solid lithium halide in the solvent. Furthermore, the added fluorosulfonic acid may or may not be diluted with a solvent. When fluorosulfonic acid is diluted with a solvent before being added dropwise, the volume ratio is preferably 5 times or less, more preferably 3 times or less, and even more preferably 2 times or less. When the amount of diluent is within the above range, the total amount of solvent in the reaction system is appropriate.

[0190] The reaction time in this invention is not particularly limited, but is preferably 10 hours or less, more preferably 5 hours or less, and even more preferably 1 hour or less. Furthermore, the reaction time in this invention is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. By keeping the reaction time in this invention within the above range, excellent manufacturing efficiency can be obtained.

[0191] The initial temperature during the reaction process of this invention is not particularly limited, but is preferably below +20°C, more preferably below +10°C, and even more preferably below +5°C. The initial temperature during the reaction process of this invention is preferably above -20°C, more preferably above -10°C, and even more preferably above -5°C, and particularly preferably maintained around the initial temperature. When the initial temperature during the reaction process of this invention is within the above range, problems such as solvent evaporation, unpredictable side reactions, and reduced reaction rate are less likely to occur.

[0192] In the reaction process of this invention, a curing process is preferably performed after the input of the solvent. The curing temperature is not particularly limited, but is preferably below the reaction temperature +100°C, more preferably below the reaction temperature +80°C, and even more preferably below the reaction temperature +50°C. Furthermore, the curing temperature is preferably above the reaction temperature +5°C, more preferably above the reaction temperature +10°C, and even more preferably above the reaction temperature +20°C. When the curing temperature is within the above range, problems such as solvent evaporation, unpredictable side reactions, and reduced reaction rate are less likely to occur.

[0193] In addition, the temperature during maturation can be higher or lower than the temperature at which the ingredients were added, but to improve the maturation effect, it is preferable to use a temperature higher than that at which the ingredients were added.

[0194] When the temperature of the curing process is within the above range, the evaporation of solvent and the occurrence of side reactions can be suppressed, and the curing effect can be fully obtained because the manufacturing efficiency can be improved.

[0195] The time for the curing process in the reaction step of the present invention is not particularly limited, but is preferably 20 hours or less, more preferably 10 hours or less, and even more preferably 5 hours or less. Furthermore, the reaction time in the reaction of the present invention is preferably 1 minute or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more. When the curing time is within the above range, the manufacturing efficiency becomes good, and the curing effect can be fully obtained.

[0196] The gas atmosphere in the reaction process of the present invention is not particularly limited. However, since there is a risk that the starting material fluorosulfonic acid or the product lithium fluorosulfonate may decompose in the presence of water, it is preferably mixed in a gas atmosphere that blocks external air, and more preferably mixed in an inert gas atmosphere such as a dry air or nitrogen atmosphere, or an argon atmosphere. These gases can be introduced into the equipment at the start of the reaction process and then sealed, or can be continuously supplied to and discharged from the device.

[0197] The reaction equipment in the reaction process of the present invention may be made of any material that can be used for ordinary chemical production without special limitation. However, when fluorosulfonic acid is hydrolyzed due to the intrusion of water in the atmosphere, there is a possibility of generating hydrofluoric acid. Therefore, it is preferably made of a material that is not easily corroded by hydrofluoric acid. In particular, for parts such as reaction tanks that are in contact with the reaction solution for a long time, it is preferably made of a material that is not corroded by hydrofluoric acid. Specifically, the reaction tank is preferably made of a material other than glass.

[0198] Although the details are not clear, in the reaction process of the present invention, lithium fluorosulfonate is produced while generating hydrogen halide. In the equipment used in the present invention, it is preferable to have a device for removing the by-produced and vaporized hydrogen halide. As methods for removing hydrogen halide, examples include reacting with solid bases, or neutralizing and rendering harmless after being adsorbed by solid adsorbents, absorbed by solvents such as water, etc. Among them, the method of being absorbed by solvents such as water is the simplest and thus preferred.

[0199] When implementing absorption by solvents such as water, absorption and harmless treatment can be carried out in one step by using a solution in which an alkali is dissolved in the solvent, or a two-step method such as subsequent ion exchange treatment by adding an alkali can be adopted. As the solvent, there is no special limitation, but considering the ease of the above treatment, water is most preferably used. As the absorption method, the gas containing hydrogen halide in the system can be bubbled into the solvent or passed through the system in which the solvent is dispersed.

[0200] For the gas containing hydrogen halide in the system, the gas sealed in the reaction vessel can be discharged by pressurization / vacuum ([ ). In addition, when the gas is continuously supplied to the device, it is preferable to continuously remove the discharged gas.

[0201] <B2. Solid-liquid separation process for recovering (crude) lithium fluorosulfonate in solid form from a non-aqueous solvent (solution)>

[0202] Preferably, it includes a solid-liquid separation process for recovering crude lithium fluorosulfonate obtained in the above reaction process in solid form from a non-aqueous solvent. Thereby, the halogen components mixed as impurities can be removed. There is no special limitation on the method for recovering crude lithium fluorosulfonate or lithium fluorosulfonate in solid form from the solution after the reaction process.

[0203] If an excess of lithium halide is used in the reaction process, it is preferable to separate the excess insoluble lithium halide components first. There are no particular limitations on the method for separating the insoluble lithium halide components. Methods such as vacuum filtration, pressure filtration, centrifugal filtration, sedimentation by settling and centrifugation followed by collection of the supernatant can be used. In addition, these methods can be combined or the same method can be repeated.

[0204] There are no particular limitations on the method for removing the solvent used in the reaction process; methods such as concentration distillation can be used. There are no particular limitations on the temperature during concentration distillation, but it is preferable to control it to a temperature that does not significantly exceed the reaction temperature. Preferably, it is below the aging temperature +50°C, more preferably below the aging temperature +40°C, and even more preferably below the aging temperature +30°C. The pressure during concentration distillation can be any pressure, including atmospheric pressure and reduced pressure, and needs to be set according to the preferred concentration temperature. Excessively high temperatures during concentration distillation can easily lead to unpredictable side reactions and other problems.

[0205] There is no particular limitation on the amount of solvent removed during the reaction. It can be dried and solidified, or it can be partially left behind. However, if it is not completely dried and solidified, there is a possibility that purification can be achieved through crystallization, which is therefore preferred.

[0206] The upper limit of the residual amount of solvent used in the reaction is preferably 20 times or less, more preferably 15 times or less, and even more preferably 10 times or less, based on the volume ratio of the added fluorosulfonic acid. Within this range, the recovery rate is improved when recovering in solid form, which is therefore preferred. On the other hand, the lower limit is preferably 1 times or more, more preferably 3 times or more, and even more preferably 5 times or more, based on the volume ratio of the added fluorosulfonic acid. Within this range, it is less likely to become a viscous slurry, making operation easier. It should be noted that this limitation does not apply to cases where drying and solidification are carried out until the material can be processed in solid form.

[0207] If solvent residues remain from the reaction process, it is necessary to separate the solvent from the solid. There are no specific limitations on the separation method; methods such as vacuum filtration, pressure filtration, centrifugal filtration, or settling by centrifugation followed by collection of the supernatant can be used.

[0208] It should be noted that there is a possibility that residual hydrogen halide in the solution may vaporize and be released during this process. For this released gas, it is preferable to perform the same treatment as the removal of hydrogen halide in the reaction process. The treatment method can be selected from the treatment method used in the reaction process; the method can be the same or different.

[0209] <B3. Operation of contacting crude lithium fluorosulfonate with a non-aqueous solvent solution containing water>

[0210] In the present invention, it is preferable to perform the operation of contacting the crude lithium fluorosulfonate obtained in the reaction step of 1. with a non-aqueous solvent solution containing water. The operation of contacting the crude lithium fluorosulfonate with the non-aqueous solvent solution containing water can be carried out before recovering the crude lithium fluorosulfonate obtained in the reaction step of 1. in solid form, or can be carried out on the obtained crude lithium fluorosulfonate after passing through a solid-liquid separation step of recovering the above-mentioned crude lithium fluorosulfonate in solid form from the non-aqueous solvent.

[0211] That is, it is preferable to perform the step of contacting the crude lithium fluorosulfonate with a non-aqueous solvent solution containing water at any stage after the reaction step.

[0212] Compared with lithium fluorosulfonate obtained without this operation, the amount of halogen element contained in lithium fluorosulfonate obtained by the present invention is less.

[0213] The specific effect of this operation is not yet clear and is not particularly limited, but it is considered that in the step of manufacturing lithium fluorosulfonate by reacting fluorosulfonic acid with lithium halide, at least one of chlorosulfonic acid and lithium chlorosulfonate is by-produced.

[0214] Compared with lithium fluorosulfonate, chlorosulfonic acid and lithium chlorosulfonate have higher reactivity with water and are considered to preferentially undergo hydrolysis in the presence of a small amount of water to generate any of hydrogen halide and lithium halide that are relatively easy to remove. On the other hand, in the case of not passing through this step, it can be presumed that chlorosulfonic acid and lithium chlorosulfonate with high structural similarity are difficult to remove by other purification methods.

[0215] There is no special limitation on the method of contacting with a non-aqueous solvent solution containing water. The following method is preferred: in one or more of the purification steps such as washing, recrystallization, and reprecipitation, it is contacted with a non-aqueous solvent mixed with a small amount of water. In addition, a non-aqueous solvent mixed with a small amount of water can be introduced into the reaction solution after the reaction. Among these, especially the treatment during the recrystallization and reprecipitation steps has a purification effect, so it is preferred, and the treatment during recrystallization has a high purification effect, so it is more preferred.

[0216] In the case of performing washing, it is preferable to use a solvent pre-mixed with water. On the other hand, in the case of performing recrystallization / reprecipitation, it can be dissolved using a solvent pre-mixed with water, or water can be added after dissolution, but in order to ensure the uniformity of the reaction, it is preferred to add water after dissolution. In addition, when water is added to the solid before dissolution and then a non-aqueous solvent is added to dissolve it, the effect of water becomes non-uniform, so it is not preferred. It is considered that due to passing through this step, a small amount of insoluble matter is generated due to hydrolysis. Therefore, it is preferred to separate the insoluble matter in advance before recovering lithium fluorosulfonate in solid form from the non-aqueous solvent.

[0217] If the amount of water added is too small, the halogen elements cannot be removed sufficiently, so it is not preferred. The reason can be speculated as follows: at least one of chlorosulfonic acid and lithium chlorosulfonate, which are presumed impurities, cannot be hydrolyzed sufficiently. On the other hand, if the amount of water added is too large, the yield will decrease, so it is not preferred. The reason can be speculated as follows: after decomposing at least one of chlorosulfonic acid and lithium chlorosulfonate, the remaining water will cause the hydrolysis of lithium fluorosulfonate. The amount of water added is preferably such that the molar ratio to the halogen component analyzed immediately before this step is 1:1 or more, more preferably 1:1.02 or more, and further preferably 1:1.05 or more.

[0218] In addition, the amount of water added is preferably such that the molar ratio to the halogen component analyzed immediately before this step is 1:3 or less, more preferably 1:2 or less, and further preferably 1:1.5 or less.

[0219] When this step is carried out by a recrystallization or reprecipitation process, the product after crystallization / precipitation can be directly used as the final product, but it is preferred to carry out purification by reusing a water-free solvent system for recrystallization or reprecipitation.

[0220] <B4. Purification Process>

[0221] In the present invention, in order to further improve the purity of lithium fluorosulfonate, a purification process is preferably carried out. Specifically, high purity can be achieved by operations such as washing, recrystallization, and reprecipitation after bringing (crude) lithium fluorosulfonate into contact with a non-aqueous solvent. Among the above operations, the recrystallization method is more preferably used. Further, it is preferred to carry out washing after the recrystallization method. The number of recrystallizations is not particularly limited and can be repeated. The number of washings is not particularly limited and can be repeated. When recrystallization is repeated, it is preferred to carry out at least one or more washings each time recrystallization is carried out, but there is no particular limitation.

[0222] The solvent used in the purification process is not particularly limited as long as it is a solvent other than water, and an organic solvent is preferred, and a polar aprotic organic solvent is more preferred.

[0223] Specific examples of the polar aprotic organic solvent include: chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate; chain sulfonic acid esters such as methyl methanesulfonate, ethyl methanesulfonate, and methyl ethanesulfonate; chain nitriles such as acetonitrile and propionitrile; chain ethers such as diethyl ether, diisopropyl ether, and tert-butyl methyl ether; cyclic ethers such as tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,3-di ane, 1,4-di ane, etc.

[0224] Among them, preferred are chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate; and chain nitriles such as acetonitrile and propionitrile. Furthermore, from the perspective of their ease of acquisition, preferred are dimethyl carbonate, diethyl carbonate, ethyl acetate, and acetonitrile.

[0225] On the other hand, considering the impact on battery characteristics when there is residue, chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferred.

[0226] Considering these factors, dimethyl carbonate and diethyl carbonate are the preferred choices.

[0227] These solvents can be used alone or in combination.

[0228] It should be noted that the unsuitable solvent used in the reprecipitation method is not limited to this; any solvent with a lower polarity than the solvent that can dissolve it is acceptable, without any special restrictions.

[0229] There is no particular limitation on the amount of solvent used for recrystallization during the purification process, but it must be at least enough to dissolve the (crude) lithium fluorosulfonate. On the other hand, if the amount of solvent is too large, the recovery efficiency during recrystallization will decrease, which is not preferred. Regarding preferred amounts, since the solubility of lithium fluorosulfonate varies depending on the solvent used, it cannot be generalized. For example, when using dimethyl carbonate, it is preferable to use an amount that is at least 2 times the mass of the crude lithium fluorosulfonate solid, more preferably at least 3 times, and even more preferably at least 5 times. Furthermore, when using dimethyl carbonate, it is preferable to use an amount that is at least 20 times the mass of the crude lithium fluorosulfonate solid, more preferably at least 15 times, and even more preferably at least 10 times.

[0230] When performing purification by recrystallization, there is no particular limitation on the dissolution temperature. However, if the temperature is too high, there is a risk of decomposition due to heating, which is not preferred. If the temperature is too low, a large amount of solvent is required to achieve near-complete dissolution, which is also not preferred. When performing purification by recrystallization, the dissolution temperature is preferably below 100°C, more preferably below 80°C, and even more preferably below 70°C.

[0231] During recrystallization, insoluble impurities may remain before crystallization after dissolution. Therefore, it is preferable to remove the insoluble substances by means of filtration or other methods.

[0232] Regarding the crystallization temperature during recrystallization, there is no particular limitation as long as it is lower than the dissolution temperature. However, in order to improve the recovery efficiency, a lower crystallization temperature is preferred. On the other hand, if the recovery efficiency is excessively increased, there is a risk that even the soluble impurities to be removed will precipitate. The preferred temperature during crystallization varies depending on the recrystallization solvent used and is not particularly limited. For example, when using dimethyl carbonate, the temperature during crystallization is preferably 50°C or lower, more preferably 40°C or lower, and further preferably 30°C or lower. Additionally, it is preferably -50°C or higher, more preferably -20°C or higher, and further preferably 0°C or higher.

[0233] <B5. After the operation of bringing the above-mentioned crude lithium fluorosulfonate into contact with a non-aqueous solvent solution containing water, the treatment after the solid-liquid separation step>

[0234] After the operation of bringing the above-mentioned crude lithium fluorosulfonate into contact with a non-aqueous solvent solution containing water, the non-aqueous solvent used in the above-mentioned purification step etc. will remain in the solid of lithium fluorosulfonate obtained after the solid-liquid separation step. Therefore, it is preferably removed by drying. The method of removal is not particularly limited, but since thermal decomposition may be caused when reaching a high temperature during the removal operation, it is not preferred. On the other hand, if the temperature is too low, there is a possibility that sufficient removal cannot be performed, so it is not preferred. The removal temperature is preferably 100°C or lower, more preferably 80°C or lower, and further preferably 50°C or lower. Additionally, it is preferably 0°C or higher, more preferably 10°C or higher, and further preferably 20°C or higher. The longer the removal time, the higher the removal efficiency, so it is preferred. On the other hand, it will result in a decrease in production efficiency. Based on this, it is preferably carried out within an appropriate range of time. The removal time is preferably 30 minutes or longer, more preferably 1 hour or longer, and further preferably 2 hours or longer. Additionally, the removal time is preferably 24 hours or shorter, more preferably 10 hours or shorter, and further preferably 5 hours or shorter.

[0235] <Lithium fluorosulfonate>

[0236] When lithium fluorosulfonate is used for batteries etc., in order to exhibit higher performance, high purity is preferred.

[0237] Among them, for example, when manufacturing using lithium carboxylate, from the aspect of controlling battery characteristics, it is preferred to remove carboxylate ions that are likely to oxidize in the battery so that they do not dissolve in the electrolyte. This can be confirmed by measuring the amount of carboxylate ions when dissolved in water.

[0238] The upper limit value of the content of carboxylate ions in lithium fluorosulfonate is 2.5×10 -2 mol / kg or lower, preferably 2.0×10 -2 mol / kg or lower, more preferably 1.5×10 -2Below mol / kg. On the other hand, its lower limit is 1.0 × 10⁻⁶. -5 mol / kg or higher, preferably 5.0 × 10⁻⁶ -5 mol / kg or higher, more preferably 1.0 × 10 -4 Above mol / kg.

[0239] In addition, when the electrolyte contains lithium fluorosulfonate, the upper limit for the content of carboxylic acid ions in the non-aqueous electrolyte is 4.0 × 10⁻⁶. -3 Below mol / L, preferably 2.0 × 10⁻⁶ -3 Below mol / L, more preferably 1.5 × 10⁻⁶ -3 Below mol / L, more preferably 1.0 × 10⁻⁶ -3 Below mol / L, the optimal value is 5.0 × 10⁻⁶. -4 Below mol / L. On the other hand, the lower limit is 1.0 × 10⁻⁶. -7 mol / L or higher, preferably 5.0 × 10⁻⁶ -7 mol / L or higher, more preferably 1.0 × 10 -6 The molar concentration of carboxylic acid ions is above mol / L. When the molar concentration of carboxylic acid ions is within the above range, the internal impedance of the battery decreases, and the input-output characteristics and durability are more easily displayed. In addition, the above values ​​are at least one of the values ​​calculated from the amount added and the values ​​calculated appropriately from the content contained in the electrolyte after analysis of the electrolyte.

[0240] Furthermore, from the perspective of controlling battery characteristics, it is preferable to remove halide ions that are prone to oxidation within the battery, chemical species that easily generate halide ions in the presence of trace amounts of water mixed into the battery, or halogen-containing compounds that may generate halide ions through reactions within the battery, so that they are insoluble in the electrolyte. This can be confirmed by measuring the amount of halide ions dissolved in water. On the other hand, it is also known that the introduction of trace amounts of halide salts can improve battery performance.

[0241] The upper limit for the halogen content of lithium fluorosulfonate is 1.5 × 10⁻⁶. -3 Below mol / kg, preferably 1.0 × 10⁻⁶ -3 Below mol / kg, more preferably 5.0 × 10⁻⁶ -4 Below mol / kg, more preferably 3.0 × 10⁻⁶ -4 Below mol / kg. On the other hand, its lower limit is 1.0 × 10⁻⁶. -5 mol / kg or higher, preferably 5.0 × 10⁻⁶ -5 mol / kg or higher, more preferably 1.0 × 10 -4 mol / / kg or more.

[0242] In addition, when the electrolyte contains lithium fluorosulfonate, the upper limit for the content of halide ions other than fluoride ions in the non-aqueous electrolyte is 1.0 × 10⁻⁶. -3 Below mol / L, preferably 5.0 × 10⁻⁶ -4 Below mol / L, more preferably 1.0 × 10⁻⁶ -4 Below mol / L, more preferably 5.0 × 10⁻⁶ -5 Below mol / L, the optimal value is 3.0 × 10⁻⁶. -5 Below mol / L. On the other hand, its lower limit is 1.0 × 10⁻⁶. -7 mol / L or higher, preferably 5.0 × 10⁻⁶ -7 mol / L or higher, more preferably 1.0 × 10 -6 The molar concentration of halide ions (excluding fluoride ions) is above mol / L. When the molar concentration of halide ions is within the above range, the internal impedance of the battery decreases, and the input / output characteristics and durability are more easily displayed. Furthermore, the above values ​​are at least one of the following: values ​​calculated from the amount added, and values ​​calculated appropriately from the content contained in the electrolyte after analysis.

[0243] Furthermore, this invention relates to lithium fluorosulfonate containing a specific amount of sulfate ions. Sulfate ions are sometimes a byproduct, for example, during the manufacture of lithium fluorosulfonate using lithium halides described above. Sulfate ions can be contained in any form of lithium sulfate, lithium bisulfate, or sulfuric acid. In the lithium fluorosulfonate of this invention, the lower limit of the molar content of sulfate ions relative to the weight of lithium fluorosulfonate is 1.0 × 10⁻⁶. -5 mol / kg or higher, preferably 5.0 × 10⁻⁶ -5 mol / kg or higher, more preferably 1.0 × 10 -4 Above mol / kg. Additionally, the upper limit for the molar content of sulfate ions in lithium fluorosulfonate is 2.5 × 10⁻⁶. -1 Below mol / kg, preferably 2.0 × 10⁻⁶ -1 Below mol / kg, more preferably 1.5 × 10⁻⁶ -1 Below mol / kg. By keeping the molar content of sulfate ions within the above range, the effect of sulfate ions in the battery can be fully demonstrated when added to the electrolyte, and the increase in resistance caused by side reactions can be suppressed.

[0244] In addition, when the electrolyte contains lithium fluorosulfonate, the upper limit for sulfate ion content in the non-aqueous electrolyte is 1.0 × 10⁻⁶. -2 Below mol / L, preferably 8.0 × 10⁻⁶ -3 Below mol / L, more preferably 5.0 × 10⁻⁶ -3Below mol / L, more preferably 1.0 × 10⁻⁶ -3 Below mol / L, the optimal value is 5.0 × 10⁻⁶. -4 Below mol / L. On the other hand, its lower limit is 1.0 × 10⁻⁶. -7 mol / L or higher, preferably 5.0 × 10⁻⁶ -7 mol / L or higher, more preferably 8.0 × 10 mol / L -7 The molar concentration of sulfate ions is above mol / L. When the molar concentration of sulfate ions is within the above range, the internal impedance of the battery decreases, and the input-output characteristics and durability are more easily displayed. In addition, the above values ​​are at least one of the values ​​calculated from the amount added, and the values ​​calculated appropriately from the content contained in the electrolyte after analysis of the electrolyte.

[0245] The method for synthesizing and obtaining lithium fluorosulfonate in this invention is not particularly limited, and lithium fluorosulfonate synthesized or obtained by any method can be used.

[0246] Here, the following methods can be listed as methods for synthesizing lithium fluorosulfonate: for example, reacting lithium fluoride or lithium fluorosilide compounds with sulfur trioxide or fluorosulfonic acid to obtain lithium fluorosulfonate; reacting fluorosulfonic acid with lithium to obtain lithium fluorosulfonate; reacting an ammonium salt of fluorosulfonic acid with lithium to obtain lithium fluorosulfonate; reacting fluorosulfonic acid with lithium carboxylate and obtaining lithium fluorosulfonate by salt exchange; reacting fluorosulfonic acid with lithium halide and obtaining lithium fluorosulfonate by salt exchange; fluorinating lithium substituted sulfonates such as chlorosulfonic acid and other halosulfonic acids with functional groups that are easily substituted by fluorine using fluoride salts such as fluoride salts such as acidic potassium fluoride, non-metallic inorganic fluorides, or organic fluorinating agents to obtain lithium fluorosulfonate; and so on.

[0247] In these reactions, there are no particular restrictions on whether or not a solvent is used. However, when a solvent is used, it can be selected from various organic solvents and inorganic solvents other than water, depending on the reagents being reacted. In this case, it is preferable to use a solvent that does not leave residues or whose impact is minimal even if residues are present. Examples of organic solvents include aprotic solvents such as carbonates, and examples of inorganic solvents include anhydrous hydrofluoric acid.

[0248] <1. Non-aqueous electrolyte>

[0249] The non-aqueous electrolyte of the present invention contains at least lithium fluorosulfonate, lithium salts other than lithium fluorosulfonate, and a non-aqueous solvent for dissolving them.

[0250] <1-1. Lithium fluorosulfonate>

[0251] The lithium fluorosulfonate used in the non-aqueous electrolyte of this invention may be the lithium fluorosulfonate described in the preceding paragraph.

[0252] In the non-aqueous electrolyte of the present invention, the lower limit of the molar content of lithium fluorosulfonate in the non-aqueous electrolyte is 0.0005 mol / L or more, preferably 0.01 mol / L or more, and more preferably 0.02 mol / L or more. The upper limit is 0.5 mol / L or less, preferably 0.45 mol / L or less, and more preferably 0.4 mol / L or less. The concentration range of lithium fluorosulfonate is 0.0005 mol / L or more and 0.5 mol / L or less, preferably 0.01 mol / L or more and 0.5 mol / L or less, more preferably 0.01 mol / L or more and 0.45 mol / L or less, and particularly preferably 0.01 mol / L or more and 0.40 mol / L or less. When the molar concentration of lithium fluorosulfonate is within the above range, the internal impedance of the battery is reduced, and the input / output characteristics and durability are excellent.

[0253] In addition, the above value is at least one of the values ​​calculated from the amount added, and the value calculated appropriately from the content contained in the electrolyte after analysis of the electrolyte.

[0254] Furthermore, in the non-aqueous electrolyte of the present invention, FSO3 serves as a counterion species for lithium fluorosulfonate in the non-aqueous electrolyte. - The molar content of the [specific substance] is preferably 0.0005 mol / L or more, more preferably 0.01 mol / L or more, and particularly preferably 0.02 mol / L or more. Furthermore, the upper limit is preferably 0.5 mol / L or less, more preferably 0.45 mol / L or less, and particularly preferably 0.4 mol / L or less. [This is related to] the counterion species FSO3. - When the concentration is within the above range, the battery's internal impedance decreases, making it easier to exhibit input / output characteristics and durability. As a counterion species, FSO3... - The concentration range is preferably 0.0005 mol / L or more and 0.5 mol / L or less, more preferably 0.01 mol / L or more and 0.5 mol / L or less, more preferably 0.01 mol / L or more and 0.45 mol / L or less, and particularly preferably 0.01 mol / L or more and 0.40 mol / L or less. Furthermore, the above values ​​are at least one of those calculated from the amount added and those appropriately calculated from the content contained in the electrolyte after analysis.

[0255] It should be noted that the counter ion species FSO3 in non-aqueous electrolytes - The molar content can be determined based on, for example, the amount of lithium fluorosulfonate used when preparing a non-aqueous electrolyte.

[0256] <1-2. Lithium salts other than lithium fluorosulfonate>

[0257] The non-aqueous electrolyte of the present invention contains lithium fluorosulfate containing a specific amount of sulfate ions, but preferably further contains one or more other lithium salts.

[0258] As for other lithium salts, there are no special restrictions as long as they are known to be suitable for this purpose. Examples are listed below.

[0259] For example,

[0260] Inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, LiTaF6, and LiWF7;

[0261] Lithium fluorophosphates other than LiPF6, such as LiPO3F and LiPO2F2;

[0262] Lithium tungstate salts such as LiWOF5;

[0263] Lithium carboxylate salts such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, CF3CF2CF2CF2CO2Li, etc.

[0264] Lithium sulfonate salts such as CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, and CF3CF2CF2CF2SO3Li;

[0265] LiN(FCO2)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethanedisulfonylimide lithium, cyclic 1,3-perfluoropropanedisulfonylimide lithium, LiN(CF3SO2)(C4F9SO2) and other imine lithium salts;

[0266] Methylated lithium salts such as LiC(FSO2)3, LiC(CF3SO2)3, and LiC(C2F5SO2)3;

[0267] Lithium oxalate salts such as lithium difluorooxalate borate, lithium di(oxalate)borate, lithium tetrafluorooxalate phosphate, lithium difluorodi(oxalate) phosphate, and lithium tri(oxalate) phosphate.

[0268] And, fluorine-containing organic lithium salts such as LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2; etc.

[0269] Among the above, preferred materials include LiPF6, LiBF4, LiSbF6, LiTaF6, LiPO2F2, CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethanedisulfonylimide lithium, cyclic 1,3-perfluoropropanedisulfonylimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, lithium di(oxalate)borate, lithium difluorooxalate borate, lithium tetrafluorooxalate phosphate, lithium difluorodi(oxalate)phosphate, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, and LiPF3(C2F5)3. Furthermore, among these lithium salts, LiPF6 and LiBF4 are preferred, with LiPF6 being the most preferred.

[0270] In the non-aqueous electrolyte of the present invention, PF6 is used as a counter ion species for lithium salts other than lithium fluorosulfonate in the non-aqueous electrolyte (for example, in the case where the lithium salt other than lithium fluorosulfonate is LiPF6). ‐ The molar content of the lithium salt other than lithium fluorosulfonate is preferably 0.5 mol / L or more, more preferably 0.6 mol / L or more, and particularly preferably 0.7 mol / L or more. Furthermore, the upper limit is preferably 3.0 mol / L or less, more preferably 2.0 mol / L or less, and particularly preferably 1.5 mol / L or less. The concentration range of the counterion species of lithium salt other than lithium fluorosulfonate is preferably 0.5 mol / L or more and 3.0 mol / L or less, more preferably 0.5 mol / L or more and 2.0 mol / L or less, and even more preferably 0.5 mol / L or more and 1.5 mol / L or less. When the concentration of the counterion species of lithium salt other than lithium fluorosulfonate is within the above range, the total ion content in the non-aqueous electrolyte achieves a suitable balance between the amount present and the viscosity of the electrolyte, which can reduce the internal impedance of the battery without reducing the ionic conductivity, and easily exhibit the effect of input-output characteristics.

[0271] In this invention, the ratio of the molar content of lithium fluorosulfonate in the non-aqueous electrolyte to the molar content of lithium in lithium salts other than lithium fluorosulfonate ([lithium fluorosulfonate] / [lithium salts other than lithium fluorosulfonate]) is preferably 0.001 or more and 1.2 or less.

[0272] When the ratio of [lithium fluorosulfonate] to [lithium salt other than lithium fluorosulfonate] is within the above-mentioned range, the input-output characteristics and durability characteristic of fluorosulfonates are easily exhibited. To more significantly enhance the effects of the present invention, the ratio of [lithium fluorosulfonate] to [lithium salt other than lithium fluorosulfonate] is preferably 0.01 or more, more preferably 0.02 or more, and preferably 1.1 or less, more preferably 1.0 or less, and even more preferably 0.7 or less. Furthermore, the range of [lithium fluorosulfonate] to [lithium salt other than lithium fluorosulfonate] is preferably 0.001 or more and 1.2 or less, more preferably 0.01 or more and 1.1 or less, even more preferably 0.01 or more and 1.0 or less, and particularly preferably 0.01 or more and 0.7 or less.

[0273] In addition to the above, considering the effects of improved output characteristics, high-speed charge-discharge characteristics, high-temperature storage characteristics, and cycle characteristics, it is sometimes preferable to contain lithium salts selected from lithium fluorophosphates, lithium imines, and lithium oxalate salts other than LiPF6. Specifically, these lithium salts are preferably selected from LiPO2F2, LiBF4, LiN(CF3SO2)2, LiN(FSO2)2, lithium difluorooxalate borate, lithium di(oxalate)borate, lithium difluorodi(oxalate)phosphate, and lithium tetrafluorodi(oxalate)phosphate.

[0274] Within a range that does not significantly impair the effects of the present invention, the content of lithium salts selected from LiPO2F2, LiBF4, LiN(CF3SO2)2, LiN(FSO2)2, lithium difluorooxalate borate, lithium di(oxalate)borate, lithium difluorodi(oxalate)phosphate, and lithium tetrafluorodi(oxalate)phosphate in the present invention can be arbitrary, but as a lower limit, it is preferably 0.0005 mol / L or more, more preferably 0.001 mol / L or more, and particularly preferably 0.01 mol / L or more. Furthermore, its upper limit is preferably 0.5 mol / L or less, more preferably 0.45 mol / L or less, and particularly preferably 0.4 mol / L or less.

[0275] In the case where the electrolyte contains LiPO2F2, the preparation of the electrolyte can be carried out by the following methods: adding LiPO2F2 synthesized by other known methods to an electrolyte containing LiPF6; pre-containing water in the active material, electrode plates and other battery components, and using an electrolyte containing LiPF6 to generate LiPO2F2 in the system during battery assembly. In this invention, any method can be used.

[0276] There are no special restrictions on the methods for determining the LiPO2F2 content in the aforementioned non-aqueous electrolytes and non-aqueous electrolyte batteries. Any well-known method can be used, such as ion chromatography and nuclear magnetic resonance spectroscopy (hereinafter referred to as NMR).

[0277] <1-3. Non-aqueous solvents>

[0278] Representative examples of non-aqueous solvents used in this invention to dissolve lithium salts other than lithium fluorosulfonate are listed below. In this invention, these non-aqueous solvents can be used alone or in the form of a mixture of multiple solvents in any proportion, and are not limited to these examples without significantly impairing the effects of this invention.

[0279] <Saturated cyclic carbonates>

[0280] Saturated cyclic carbonates that can be used as non-aqueous solvents in this invention include carbonates having alkylene groups having 2 to 4 carbon atoms.

[0281] Specifically, examples of saturated cyclic carbonates with 2 to 4 carbon atoms include ethylene carbonate, propylene carbonate, and butyl carbonate. Among these, ethylene carbonate and propylene carbonate are particularly preferred considering the improved battery performance resulting from increased lithium-ion dissociation.

[0282] Saturated cyclic carbonates can be used alone or in combination of two or more in any proportion.

[0283] The amount of saturated cyclic carbonate is not particularly limited and can be any amount without significantly impairing the effects of the present invention. When using a single saturated cyclic carbonate, the lower limit of its amount in 100% by volume of a non-aqueous solvent is 3% by volume or more, more preferably 5% by volume or more. By keeping the amount of saturated cyclic carbonate within this range, the decrease in conductivity caused by the reduction in the dielectric constant of the non-aqueous electrolyte can be avoided, making it easier to control the high-current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte secondary battery within a good range. Furthermore, the upper limit is 90% by volume or less, more preferably 85% by volume or less, and even more preferably 80% by volume or less. By keeping the amount of saturated cyclic carbonate within this range, the viscosity of the non-aqueous electrolyte can be kept within an appropriate range, suppressing the decrease in ionic conductivity, and thus making it easier to control the load characteristics of the non-aqueous electrolyte secondary battery within a good range.

[0284] Furthermore, saturated cyclic carbonates can be used in any combination of two or more. One preferred combination is that of ethylene carbonate and propylene carbonate. In this case, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99:1 to 40:60, particularly preferably 95:5 to 50:50. In addition, the amount of propylene carbonate in the total non-aqueous solvent is 1% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more, and its upper limit is generally 20% by volume or less, preferably 8% by volume or less, more preferably 5% by volume or less. When propylene carbonate is contained in this range, excellent low-temperature properties can be further obtained while maintaining the combined characteristics of ethylene carbonate and dialkyl carbonates, and therefore it is preferred.

[0285] <Chain carbonates>

[0286] Chain carbonates that can be used as non-aqueous solvents in this invention include carbonates with 3 to 7 carbon atoms.

[0287] Specifically, examples of chain carbonates with 3 to 7 carbon atoms include: dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, methyl ethyl carbonate, methyl n-propyl carbonate, methyl n-butyl carbonate, methyl isobutyl carbonate, methyl tert-butyl carbonate, ethyl n-propyl carbonate, ethyl n-butyl carbonate, ethyl isobutyl carbonate, ethyl tert-butyl carbonate, etc.

[0288] Among them, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, methyl ethyl carbonate, and methyl n-propyl carbonate are preferred, with dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate being particularly preferred.

[0289] Furthermore, fluorine-containing chain carbonates (hereinafter also referred to as "fluorinated chain carbonates") are preferred. There are no particular restrictions on the number of fluorine atoms in a fluorinated chain carbonate, as long as it is 1 or more, but it is usually 6 or less, preferably 4 or less. When a fluorinated chain carbonate has multiple fluorine atoms, these fluorine atoms can be bonded to the same carbon atom or to different carbon atoms. Examples of fluorinated chain carbonates include dimethyl fluorocarbonate derivatives, methyl ethyl fluorocarbonate derivatives, and diethyl fluorocarbonate derivatives.

[0290] Examples of fluorodimethyl carbonate derivatives include: methyl fluoromethyl carbonate, methyl difluoromethyl carbonate, methyl trifluoromethyl carbonate, di(fluoromethyl) carbonate, di(difluoromethyl) carbonate, and di(trifluoromethyl) carbonate.

[0291] Examples of fluoromethyl ethyl carbonate derivatives include: methyl 2-fluoroethyl carbonate, fluoromethyl ethyl carbonate, methyl 2,2-difluoroethyl carbonate, fluoromethyl 2-fluoroethyl carbonate, difluoromethyl ethyl carbonate, methyl 2,2,2-trifluoroethyl carbonate, fluoromethyl 2,2-difluoroethyl carbonate, difluoromethyl 2-fluoroethyl carbonate, and trifluoromethyl ethyl carbonate.

[0292] Examples of fluorodiethyl carbonate derivatives include: ethyl(2-fluoroethyl) carbonate, ethyl(2,2-difluoroethyl) carbonate, di(2-fluoroethyl) carbonate, ethyl(2,2,2-trifluoroethyl) carbonate, 2,2-difluoroethyl-2'-fluoroethyl carbonate, di(2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2'-fluoroethyl carbonate, 2,2,2-trifluoroethyl-2',2'-difluoroethyl carbonate, and di(2,2,2-trifluoroethyl) carbonate.

[0293] Chain carbonates can be used alone or in combination of two or more in any combination and proportion.

[0294] Of the 100 vol% of non-aqueous solvent, the chain carbonate is preferably 15 vol% or more. By making the chain carbonate 15 vol% or more, the viscosity of the non-aqueous electrolyte can be kept within an appropriate range, suppressing the decrease in ionic conductivity, and thus making it easier to control the high-current discharge characteristics of the non-aqueous electrolyte secondary battery within a good range. Furthermore, of the 100 vol% of non-aqueous solvent, the chain carbonate is preferably 90 vol% or less. By making the chain carbonate 90 vol% or less, the decrease in conductivity caused by the decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, and it is easier to control the high-current discharge characteristics of the non-aqueous electrolyte secondary battery within a good range. The amount of chain carbonate is more preferably 20 vol% or more, more preferably 25 vol% or more, more preferably 85 vol% or less, and more preferably 80 vol% or less.

[0295] Furthermore, battery performance can be significantly improved by combining ethylene carbonate in specific amounts, relative to specific chain carbonates.

[0296] For example, when dimethyl carbonate and methyl ethyl carbonate are selected as specific chain carbonates, it is preferable that the amount of ethylene carbonate is 15% to 40% by volume or more, the amount of dimethyl carbonate is 20% to 50% by volume or more, and the amount of methyl ethyl carbonate is 20% to 50% by volume or more. By selecting such amounts, the low-temperature precipitation temperature of the electrolyte can be lowered, and the viscosity of the non-aqueous electrolyte can also be reduced, thereby increasing its ionic conductivity and achieving high output even at low temperatures. It is particularly preferable that the amount of ethylene carbonate is 25% to 35% by volume or more, the amount of dimethyl carbonate is 30% to 40% by volume or more, and the amount of methyl ethyl carbonate is 30% to 40% by volume or more.

[0297] <Cyclic carbonates containing fluorine atoms>

[0298] As a non-aqueous solvent, the cyclic carbonate with fluorine atoms (hereinafter also referred to as "fluorinated cyclic carbonate") is not particularly limited as long as it is a cyclic carbonate with fluorine atoms.

[0299] As fluorinated cyclic carbonates, examples include derivatives of cyclic carbonates having alkylene groups having 2 to 6 carbon atoms, such as ethylene carbonate derivatives. Examples of ethylene carbonate derivatives include, for instance, fluorinated ethylene carbonates or ethylene carbonates substituted with alkyl groups (e.g., alkyl groups having 1 to 4 carbon atoms), wherein carbonates having 1 to 8 fluorine atoms are preferred.

[0300] Specific examples include: ethylene monofluorocarbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4-(fluoromethyl)ethylene carbonate, 4-(difluoromethyl)ethylene carbonate, 4-(trifluoromethyl)ethylene carbonate, 4-(fluoromethyl)-4-fluoroethylene carbonate, 4-(fluoromethyl)-5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethylethylene carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate, etc.

[0301] Among these, from the perspective of imparting high ionic conductivity and forming an ideal interfacial protective film, at least one of ethylene monofluorocarbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate and 4,5-difluoro-4,5-dimethylethylene carbonate is more preferred.

[0302] Fluorinated cyclic carbonates can be used alone or in combination of two or more in any proportion. There are no particular limitations on the amount of fluorinated cyclic carbonates used; any amount can be used without significantly impairing the effects of the invention. However, in 100% by mass of the non-aqueous electrolyte, it is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, and preferably 85% by mass or less, more preferably 80% by mass or less, and further preferably 75% by mass or less. Furthermore, the concentration range of the fluorinated cyclic carbonates is preferably 0.001% by mass or more and 85% by mass or less, more preferably 0.01% by mass or more and 80% by mass or less, and further preferably 0.1% by mass or more and 75% by mass or less.

[0303] It should be noted that fluorinated cyclic carbonates can be used as the main solvent or as a secondary solvent in this non-aqueous electrolyte. When used as the main solvent, the amount of fluorinated cyclic carbonate in 100% by mass of the non-aqueous electrolyte is preferably 8% by mass or more, more preferably 10% by mass or more, and even more preferably 12% by mass or more, and preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less. Within this range, the non-aqueous electrolyte secondary battery readily exhibits a sufficient improvement in cycle characteristics and easily avoids a decrease in discharge capacity retention. Furthermore, when used as a secondary solvent, the amount of fluorinated cyclic carbonate in 100% by mass of the non-aqueous electrolyte is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.1% by mass or more, and preferably 8% by mass or less, more preferably 6% by mass or less, and even more preferably 5% by mass or less. Within this range, the non-aqueous electrolyte secondary battery readily exhibits sufficient output characteristics.

[0304] <Chain carboxylic esters>

[0305] As a chain carboxylic acid ester that can be used as a non-aqueous solvent in this invention, examples include carboxylic acid esters with a total number of carbon atoms of 3 to 7 in their structural formula.

[0306] Specific examples include: methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, tert-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, n-propyl isobutyrate, isopropyl isobutyrate, etc.

[0307] Among them, considering the increase in ionic conductivity caused by the decrease in viscosity, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, methyl butyrate, and ethyl butyrate are preferred.

[0308] Preferably, the chain carboxylic acid ester comprises 5% by volume or more in 100% by volume of the non-aqueous solvent. By comprising 5% by volume or more of the chain carboxylic acid ester, the conductivity of the non-aqueous electrolyte can be improved, making it easier to improve the high-current discharge characteristics of the non-aqueous electrolyte secondary battery. Furthermore, it is preferable that the chain carboxylic acid ester comprises 80% by volume or less in 100% by volume of the non-aqueous solvent. By comprising 80% by volume or less of the chain carboxylic acid ester, the increase in negative electrode impedance can be suppressed, making it easier to achieve good high-current discharge characteristics and cycle characteristics of the non-aqueous electrolyte secondary battery. More preferably, the amount of chain carboxylic acid ester is 8% by volume or more, and even more preferably, 70% by volume or less.

[0309] <Cyclic carboxylic esters>

[0310] As cyclic carboxylic acid esters that can be used as non-aqueous solvents in this invention, examples include carboxylic acid esters with a total number of carbon atoms of 3 to 12 in their structural formulas.

[0311] Specific examples include γ-butyrolactone, γ-valerolactone, γ-caprolactone, and δ-caprolactone. Among them, γ-butyrolactone is particularly preferred because it can improve the degree of lithium-ion dissociation and thus improve battery characteristics.

[0312] The cyclic carboxylic acid ester is preferably 3% by volume or more in 100% of the non-aqueous solvent. By including 3% by volume or more of the cyclic carboxylic acid ester, the conductivity of the non-aqueous electrolyte can be improved, making it easier to improve the high-current discharge characteristics of the non-aqueous electrolyte secondary battery. Furthermore, the cyclic carboxylic acid ester is preferably 60% by volume or less. By including 60% by volume or less of the cyclic carboxylic acid ester, the viscosity of the non-aqueous electrolyte can be made within an appropriate range, avoiding a decrease in conductivity, suppressing an increase in negative electrode impedance, and making it easier to achieve a good range of high-current discharge characteristics for the non-aqueous electrolyte secondary battery. The amount of cyclic carboxylic acid ester is more preferably 5% by volume or more, and even more preferably 50% by volume or less.

[0313] <Ether compounds>

[0314] Examples of ether compounds that can be used as non-aqueous solvents in this invention include chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms.

[0315] Examples of chain ethers with 3 to 10 carbon atoms include: diethyl ether, di(2-fluoroethyl) ether, di(2,2-difluoroethyl) ether, di(2,2,2-trifluoroethyl) ether, ethyl(2-fluoroethyl) ether, ethyl(2,2,2-trifluoroethyl) ether, ethyl(1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl)(2,2,2-trifluoroethyl) ether, (2-fluoroethyl)(1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl)(1,1,2,2-tetrafluoroethyl) ether, ethyl n-propyl ether, ethyl(3-fluoron-propyl) ether, ethyl(3,3,3-trifluoron-propyl) ether, ethyl(2,2,3,3-tetrafluoron-propyl) ether, ethyl(2,2,3,3,3-pentafluoron-propyl) ether. (2-fluoroethyl)(3-fluoropropyl) ether, (2-fluoroethyl)(3,3,3-trifluoropropyl) ether, (2-fluoroethyl)(2,2,3,3-tetrafluoropropyl) ether, (2-fluoroethyl)(2,2,3,3,3-pentafluoropropyl) ether, 2,2,2-trifluoroethyl propyl ether, (2,2,2-trifluoroethyl)(3-fluoropropyl) ether, (2,2,2-trifluoroethyl)(3,3,3-trifluoropropyl) ether, (2,2,2-trifluoroethyl)(2,2,3,3-tetrafluoropropyl) ether, (2,2,2-trifluoroethyl)(2,2,3,3,3-pentafluoropropyl) ether, 1,1,2,2-tetrafluoroethyl propyl ether, (1,1, 2,2-Tetrafluoroethyl)(3-fluoropropyl) ether, (1,1,2,2-tetrafluoroethyl)(3,3,3-trifluoropropyl) ether, (1,1,2,2-tetrafluoroethyl)(2,2,3,3-tetrafluoropropyl) ether, (1,1,2,2-tetrafluoroethyl)(2,2,3,3,3-pentafluoropropyl) ether, di-n-propyl ether, (n-propyl)(3-fluoropropyl) ether, (n-propyl)(3,3,3-trifluoropropyl) ether, (n-propyl)(2,2,3,3-tetrafluoropropyl) ether, (n-propyl)(2,2,3,3,3-pentafluoropropyl) ether, di(3-fluoropropyl) ether, (3-fluoropropyl)(3,3,3-trifluoropropyl) ether, (3-fluoropropyl)(2,2,3,3) (3-Fluoropropyl)(2,2,3,3,3-pentafluoropropyl) ether, di(3,3,3-trifluoropropyl) ether, (3,3,3-trifluoropropyl)(2,2,3,3-tetrafluoropropyl) ether, (3,3,3-trifluoropropyl)(2,2,3,3,3-pentafluoropropyl) ether, di(2,2,3,3-tetrafluoropropyl) ether, (2,2,3,3-tetrafluoropropyl)(2,2,3,3,3-pentafluoropropyl) ether, di(2,2,3,3,3-pentafluoropropyl) ether, di(2,2,3,3,3-pentafluoropropyl) ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, methoxy(2-fluoroethoxy)methane, methoxy(2,2,2-trifluoroethoxy)methane, methoxy(1,1,2,2-Tetrafluoroethoxy)methane, diethoxymethane, ethoxy(2-fluoroethoxy)methane, ethoxy(2,2,2-trifluoroethoxy)methane, ethoxy(1,1,2,2-tetrafluoroethoxy)methane, di(2-fluoroethoxy)methane, (2-fluoroethoxy)(2,2,2-trifluoroethoxy)methane, (2-fluoroethoxy)(1,1,2,2-tetrafluoroethoxy)methane, 、 Di(2,2,2-trifluoroethoxy)methane, (2,2,2-trifluoroethoxy)(1,1,2,2-tetrafluoroethoxy)methane, di(1,1,2,2-tetrafluoroethoxy)methane, dimethoxyethane, methoxyethoxyethane, methoxy(2-fluoroethoxy)ethane, methoxy(2,2,2-trifluoroethoxy)ethane, methoxy(1,1,2,2-tetrafluoroethoxy)ethane, diethoxyethane, ethoxy(2-fluoroethoxy)ethane, ethoxy(2,2,2-trifluoroethoxy)ethane, Ethoxy(1,1,2,2-tetrafluoroethoxy)ethane, di(2-fluoroethoxy)ethane, (2-fluoroethoxy)(2,2,2-trifluoroethoxy)ethane, (2-fluoroethoxy)(1,1,2,2-tetrafluoroethoxy)ethane, di(2,2,2-trifluoroethoxy)ethane, (2,2,2-trifluoroethoxy)(1,1,2,2-tetrafluoroethoxy)ethane, di(1,1,2,2-tetrafluoroethoxy)ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, etc.

[0316] Examples of cyclic ethers with 3 to 6 carbon atoms include: tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, and 1,3-dihydrofuran. Alkane, 2-methyl-1,3-di Alkane, 4-methyl-1,3-di Alkane, 1,4-di Alkanes, and their fluorinated compounds.

[0317] Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether are preferred because they have high solubility with lithium ions and can improve ion dissociation. Considering low viscosity and the ability to impart high ionic conductivity, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferred.

[0318] Typically, in 100% by volume of a non-aqueous solvent, the amount of ether compound is preferably 3% by volume or more, more preferably 4% by volume or more, further preferably 5% by volume or more, and preferably 70% by volume or less, more preferably 65% ​​by volume or less, and further preferably 60% by volume or less. Within this range, it is easy to ensure the improvement in ionic conductivity caused by the increased lithium-ion dissociation degree and decreased viscosity of the chain ether, and it is easy to avoid the problem of capacity reduction due to co-intercalation of the chain ether and lithium ions when the negative electrode active material is a carbonaceous material.

[0319] <sulfone compounds>

[0320] Examples of sulfone compounds that can be used as non-aqueous solvents in this invention include cyclic sulfones with 3 to 6 carbon atoms and chain sulfones with 2 to 6 carbon atoms. Preferably, the number of sulfonyl groups in one molecule is 1 or 2.

[0321] Examples of cyclic sulfones include: trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones as monosulfone compounds; and trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones as disulfone compounds. From the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, and hexamethylene disulfones are more preferred, and tetramethylene sulfones (sulfolane) are particularly preferred.

[0322] As a sulfolane class, at least one of sulfolane and sulfolane derivatives is preferred (hereinafter, sulfolane will also be referred to as "sulfolane class"). As a sulfolane derivative, compounds obtained by replacing one or more hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring with fluorine atoms or alkyl groups are preferred.

[0323] Among these, considering high ionic conductivity and high input-output ratio, the preferred ions are 2-methylcyclobutanesulfone, 3-methylcyclobutanesulfone, 2-fluorocyclobutanesulfone, 3-fluorocyclobutanesulfone, 2,2-difluorocyclobutanesulfone, 2,3-difluorocyclobutanesulfone, 2,4-difluorocyclobutanesulfone, 2,5-difluorocyclobutanesulfone, 3,4-difluorocyclobutanesulfone, 2-fluoro-3-methylcyclobutanesulfone, 2-fluoro-2-methylcyclobutanesulfone, 3-fluoro-3-methylcyclobutanesulfone, 3-fluoro-2-methylcyclobutanesulfone, and 4-fluoro-3-methylcyclobutanesulfone. Sulfones, 4-fluoro-2-methylcyclobutane sulfone, 5-fluoro-3-methylcyclobutane sulfone, 5-fluoro-2-methylcyclobutane sulfone, 2-fluoromethylcyclobutane sulfone, 3-fluoromethylcyclobutane sulfone, 2-difluoromethylcyclobutane sulfone, 3-difluoromethylcyclobutane sulfone, 2-trifluoromethylcyclobutane sulfone, 3-trifluoromethylcyclobutane sulfone, 2-fluoro-3-(trifluoromethyl)cyclobutane sulfone, 3-fluoro-3-(trifluoromethyl)cyclobutane sulfone, 4-fluoro-3-(trifluoromethyl)cyclobutane sulfone, 5-fluoro-3-(trifluoromethyl)cyclobutane sulfone, etc.

[0324] In addition, examples of chain sulfones include: dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n-butyl methyl sulfone, n-butyl ethyl sulfone, tert-butyl methyl sulfone, tert-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl... Trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di(trifluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl n-propyl sulfone, difluoromethyl n-propyl sulfone, trifluoromethyl n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl n-propyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl n-propyl sulfone, pentafluoroethyl isopropyl sulfone, trifluoroethyl n-butyl sulfone, trifluoroethyl tert-butyl sulfone, pentafluoroethyl n-butyl sulfone, pentafluoroethyl tert-butyl sulfone, etc.

[0325] Among these, considering high ionic conductivity and high input-output ratio, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, tert-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, trifluoromethyl n-propyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl n-butyl sulfone, trifluoroethyl tert-butyl sulfone, trifluoromethyl n-butyl sulfone, trifluoromethyl tert-butyl sulfone, etc. are preferred.

[0326] Preferably, the sulfone compound is present in an amount of 0.3% by volume or more in 100% of the non-aqueous solvent, and more preferably 80% by volume or less. Within this range, it is easy to obtain improved durability, such as cycling characteristics and storage properties, and it is also easy to achieve an appropriate viscosity range for the non-aqueous electrolyte, thus avoiding a decrease in conductivity. This prevents a decrease in charge / discharge capacity retention when charging and discharging the non-aqueous electrolyte secondary battery at high current densities. The amount of the sulfone compound is more preferably 0.5% by volume or more, further preferably 1% by volume or more, more preferably 75% by volume or less, and more preferably 70% by volume or less.

[0327] <1-4. Additives>

[0328] In this invention, the non-aqueous solvent may contain the following additives, but there are no particular limitations on the examples thereto, provided that they do not significantly impair the effects of this invention.

[0329] Cyclic carbonates with carbon-carbon unsaturated bonds

[0330] In order to form a film on the negative electrode surface of a non-aqueous electrolyte battery and achieve a longer battery life, cyclic carbonates with carbon-carbon unsaturated bonds (hereinafter also referred to as "unsaturated cyclic carbonates") can be used in the non-aqueous electrolyte of the present invention.

[0331] As for cyclic carbonates with carbon-carbon unsaturated bonds, any cyclic carbonate with carbon-carbon double bonds is acceptable, without special restrictions; any carbonate with carbon-carbon unsaturated bonds can be used. It should be noted that cyclic carbonates with substituents containing aromatic rings are also included in cyclic carbonates with carbon-carbon unsaturated bonds.

[0332] Examples of unsaturated cyclic carbonates include: vinylene carbonates, ethylene carbonates obtained by substitution with substituents containing aromatic rings or carbon-carbon unsaturated bonds, phenyl carbonates, ethylene carbonates, allyl carbonates, etc.

[0333] Examples of vinylene carbonates include: vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, allyl vinylene carbonate, etc.

[0334] Specific examples of ethylene carbonates obtained by substitution with substituents containing aromatic rings or carbon-carbon unsaturated bonds include: vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, etc.

[0335] Among them, vinylene carbonates are preferred, as are ethylene carbonates obtained by substituting with substituents containing aromatic rings or carbon-carbon unsaturated bonds. In particular, vinylene carbonates, 4,5-diphenylvinylene carbonates, 4,5-dimethylvinylene carbonates, vinyl ethylene carbonates, and ethynyl ethylene carbonates are more preferred because they can form a stable interfacial protective film.

[0336] There are no particular limitations on the molecular weight of the unsaturated cyclic carbonate, and it can be any molecular weight without significantly impairing the effects of the present invention. The molecular weight is preferably 50 or more and 250 or less. Within this range, it is easy to ensure the solubility of the unsaturated cyclic carbonate in non-aqueous electrolytes, and the effects of the present invention are easily and fully manifested. More preferably, the molecular weight of the unsaturated cyclic carbonate is 80 or more, and even more preferably 150 or less. There are no particular limitations on the method of manufacturing the unsaturated cyclic carbonate, and any known method can be selected.

[0337] Unsaturated cyclic carbonates can be used alone or in combination of two or more in any proportion. Furthermore, there are no particular limitations on the amount of unsaturated cyclic carbonates used; any amount can be used without significantly impairing the effects of the invention. Preferably, the amount of unsaturated cyclic carbonates in 100% by mass of the non-aqueous electrolyte is 0.001% by mass or more, more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 5% by mass or less. Additionally, the concentration range of the unsaturated cyclic carbonates is preferably 0.001% by mass or more and 10% by mass or less, more preferably 0.001% by mass or more and 8% by mass or less, and further preferably 0.001% by mass or more and 5% by mass or less.

[0338] Within the aforementioned range, non-aqueous electrolyte secondary batteries are more likely to exhibit a significant improvement in cycle performance and are more likely to avoid problems such as reduced high-temperature storage performance, increased gas generation, and decreased discharge capacity retention.

[0339] Fluorinated unsaturated cyclic carbonates

[0340] As fluorinated cyclic carbonates, cyclic carbonates having unsaturated bonds and fluorine atoms (hereinafter also referred to as "fluorinated unsaturated cyclic carbonates") are preferred. There are no particular limitations on fluorinated unsaturated cyclic carbonates. Among them, cyclic carbonates with one or two fluorine atoms are preferred.

[0341] Examples of fluorinated unsaturated cyclic carbonates include: vinylene carbonate derivatives and vinylene carbonate derivatives obtained by substitution with substituents containing aromatic rings or carbon-carbon unsaturated bonds.

[0342] Examples of vinylene carbonate derivatives include: 4-fluoroethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, and 4,5-difluoroethylene carbonate.

[0343] Examples of ethylene carbonate derivatives obtained by substitution with substituents containing aromatic rings or carbon-carbon unsaturated bonds include: 4-fluoro-4-vinyl ethylene carbonate, 4-fluoro-5-vinyl ethylene carbonate, 4,4-difluoro-4-vinyl ethylene carbonate, 4,5-difluoro-4-vinyl ethylene carbonate, 4-fluoro-4,5-divinyl ethylene carbonate, 4,5-difluoro-4,5-divinyl ethylene carbonate, 4-fluoro-4-phenyl ethylene carbonate, 4-fluoro-5-phenyl ethylene carbonate, 4,4-difluoro-5-phenyl ethylene carbonate, 4,5-difluoro-4-phenyl ethylene carbonate, etc.

[0344] The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited, and can be any molecular weight without significantly impairing the effects of the present invention. The molecular weight is preferably 50 or more, and more preferably 250 or less. Within this range, it is easy to ensure the solubility of the fluorinated cyclic carbonate in non-aqueous electrolytes, and the effects of the present invention are easily demonstrated. The method for manufacturing the fluorinated unsaturated cyclic carbonate is not particularly limited, and any known method can be selected. The molecular weight is more preferably 80 or more, and more preferably 150 or less.

[0345] Fluorinated unsaturated cyclic carbonates can be used alone or in combination of two or more in any proportion. Furthermore, there are no particular limitations on the amount of fluorinated unsaturated cyclic carbonates used; any amount can be used without significantly impairing the effects of the invention. Preferably, the amount of fluorinated unsaturated cyclic carbonates in 100% by mass of the non-aqueous electrolyte is 0.01% by mass or more, and more preferably 5% by mass or less. Within this range, the non-aqueous electrolyte secondary battery readily exhibits a significant improvement in cycle characteristics, and problems such as reduced high-temperature storage characteristics, increased gas generation, and decreased discharge capacity retention are easily avoided. More preferably, the amount of fluorinated unsaturated cyclic carbonates used is 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 4% by mass or less, and more preferably 3% by mass or less.

[0346] <Cyclic sulfonate compounds>

[0347] There are no particular limitations on the types of cyclic sulfonate compounds that can be used in the non-aqueous electrolyte of the present invention, and compounds represented by general formula (1) can be listed.

[0348] [Chemical Formula 1]

[0349]

[0350] In the formula, R 1 and R 2 Each independently represents an organic group composed of at least one atom selected from carbon, hydrogen, nitrogen, oxygen, sulfur, phosphorus, and halogen atoms. 1 and R 2 They can also contain unsaturated bonds together with -O-SO2-.

[0351] R 1 and R 2 Preferably, it is an organic group composed of atoms including carbon atoms, hydrogen atoms, oxygen atoms and sulfur atoms, and more preferably a hydrocarbon group with 1 to 3 carbon atoms or an organic group having -O-SO2-.

[0352] The molecular weight of the cyclic sulfonate compound is not particularly limited and can be any molecular weight without significantly impairing the effects of the present invention. The molecular weight is preferably 100 or higher, and more preferably 250 or lower. Within this range, it is easy to ensure the solubility of the cyclic sulfonate compound in non-aqueous electrolytes, and the effects of the present invention are readily apparent. The method for manufacturing the cyclic sulfonate compound is not particularly limited, and any known method can be selected.

[0353] Specific examples of compounds represented by general formula (1) can be listed as follows:

[0354] 1,3-Propanesulfonate lactone,

[0355] 1-Fluoro-1,3-propanesulfonic acid lactone,

[0356] 2-Fluoro-1,3-propanesulfonic acid lactone,

[0357] 3-Fluoro-1,3-propanesulfonic acid lactone,

[0358] 1-Methyl-1,3-propanesulfonic acid lactone,

[0359] 2-Methyl-1,3-propanesulfonic acid lactone,

[0360] 3-Methyl-1,3-propanesulfonic acid lactone,

[0361] 1-Propylene-1,3-sulfonyl lactone,

[0362] 2-Propylene-1,3-sulfonyl lactone,

[0363] 1-Fluoro-1-propene-1,3-sulfonyl lactone,

[0364] 2-Fluoro-1-propene-1,3-sulfonyl lactone,

[0365] 3-Fluoro-1-propene-1,3-sulfonyl lactone,

[0366] 1-Fluoro-2-propene-1,3-sulfonyl lactone,

[0367] 2-Fluoro-2-propene-1,3-sulfonyl lactone,

[0368] 3-Fluoro-2-propene-1,3-sulfonyl lactone,

[0369] 1-Methyl-1-propene-1,3-sulfonyl lactone,

[0370] 2-Methyl-1-propene-1,3-sulfonyl lactone,

[0371] 3-Methyl-1-propene-1,3-sulfonyl lactone,

[0372] 1-Methyl-2-propene-1,3-sulfonyl lactone,

[0373] 2-Methyl-2-propene-1,3-sulfonyl lactone,

[0374] 3-Methyl-2-propen-1,3-sulfonyl lactone,

[0375] 1,4-Butyryl lactone,

[0376] 1-Fluoro-1,4-Butyrylolactone,

[0377] 2-Fluoro-1,4-Butyrolactone,

[0378] 3-Fluoro-1,4-Butyrolactone,

[0379] 4-Fluoro-1,4-Butyrolactone,

[0380] 1-Methyl-1,4-butyric acid lactone,

[0381] 2-Methyl-1,4-butyric acid lactone,

[0382] 3-Methyl-1,4-butyric acid lactone,

[0383] 4-Methyl-1,4-butyric acid lactone,

[0384] 1-Butene-1,4-sulfonyl lactone,

[0385] 2-Butene-1,4-sulfonyl lactone,

[0386] 3-Butene-1,4-sulfonyl lactone,

[0387] 1-Fluoro-1-butene-1,4-sulfonyl lactone,

[0388] 2-Fluoro-1-butene-1,4-sulfonyl lactone,

[0389] 3-Fluoro-1-butene-1,4-sulfonyl lactone,

[0390] 4-Fluoro-1-butene-1,4-sulfonyl lactone,

[0391] 1-Fluoro-2-butene-1,4-sulfonyl lactone,

[0392] 2-Fluoro-2-butene-1,4-sulfonyl lactone,

[0393] 3-Fluoro-2-butene-1,4-sulfonyl lactone,

[0394] 4-Fluoro-2-butene-1,4-sulfonyl lactone,

[0395] 1-Fluoro-3-butene-1,4-sulfonyl lactone,

[0396] 2-Fluoro-3-butene-1,4-sulfonyl lactone,

[0397] 3-Fluoro-3-butene-1,4-sulfonyl lactone,

[0398] 4-Fluoro-3-butene-1,4-sulfonyl lactone,

[0399] 1-Methyl-1-butene-1,4-sulfonyl lactone,

[0400] 2-Methyl-1-butene-1,4-sulfonyl lactone,

[0401] 3-Methyl-1-butene-1,4-sulfonyl lactone,

[0402] 4-Methyl-1-butene-1,4-sulfonyl lactone,

[0403] 1-Methyl-2-butene-1,4-sulfonyl lactone,

[0404] 2-Methyl-2-butene-1,4-sulfonyl lactone,

[0405] 3-Methyl-2-butene-1,4-sulfonyl lactone,

[0406] 4-Methyl-2-butene-1,4-sulfonyl lactone,

[0407] 1-Methyl-3-butene-1,4-sulfonyl lactone,

[0408] 2-Methyl-3-butene-1,4-sulfonyl lactone,

[0409] 3-Methyl-3-butene-1,4-sulfonyl lactone,

[0410] 4-Methyl-3-butene-1,4-sulfonyl lactone,

[0411] 1,5-pentanesulfonyl lactone,

[0412] 1-Fluoro-1,5-pentanesulfonic acid lactone,

[0413] 2-Fluoro-1,5-pentanesulfonic acid lactone,

[0414] 3-Fluoro-1,5-pentanesulfonic acid lactone,

[0415] 4-Fluoro-1,5-pentanesulfonic acid lactone,

[0416] 5-Fluoro-1,5-pentanesulfonic acid lactone,

[0417] 1-Methyl-1,5-pentanesulfonic acid lactone,

[0418] 2-Methyl-1,5-pentanesulfonic acid lactone,

[0419] 3-Methyl-1,5-pentanesulfonic acid lactone,

[0420] 4-Methyl-1,5-pentanesulfonic acid lactone,

[0421] 5-Methyl-1,5-pentanesulfonic acid lactone,

[0422] 1-Pentene-1,5-sulfonyl lactone,

[0423] 2-Pentene-1,5-sulfonyl lactone,

[0424] 3-Pentene-1,5-sulfonyl lactone,

[0425] 4-Pentene-1,5-sulfonyl lactone,

[0426] 1-Fluoro-1-pentene-1,5-sulfonyl lactone,

[0427] 2-Fluoro-1-pentene-1,5-sulfonyl lactone,

[0428] 3-Fluoro-1-pentene-1,5-sulfonyl lactone,

[0429] 4-Fluoro-1-pentene-1,5-sulfonyl lactone,

[0430] 5-Fluoro-1-pentene-1,5-sulfonyl lactone,

[0431] 1-Fluoro-2-pentene-1,5-sulfonyl lactone,

[0432] 2-Fluoro-2-pentene-1,5-sulfonyl lactone,

[0433] 3-Fluoro-2-pentene-1,5-sulfonyl lactone,

[0434] 4-Fluoro-2-pentene-1,5-sulfonyl lactone,

[0435] 5-Fluoro-2-pentene-1,5-sulfonyl lactone,

[0436] 1-Fluoro-3-pentene-1,5-sulfonyl lactone,

[0437] 2-Fluoro-3-pentene-1,5-sulfonyl lactone,

[0438] 3-Fluoro-3-pentene-1,5-sulfonyl lactone,

[0439] 4-Fluoro-3-pentene-1,5-sulfonyl lactone,

[0440] 5-Fluoro-3-pentene-1,5-sulfonyl lactone,

[0441] 1-Fluoro-4-pentene-1,5-sulfonyl lactone,

[0442] 2-Fluoro-4-pentene-1,5-sulfonyl lactone,

[0443] 3-Fluoro-4-pentene-1,5-sulfonyl lactone,

[0444] 4-Fluoro-4-pentene-1,5-sulfonyl lactone,

[0445] 5-Fluoro-4-pentene-1,5-sulfonyl lactone,

[0446] 1-Methyl-1-pentene-1,5-sulfonyl lactone,

[0447] 2-Methyl-1-pentene-1,5-sulfonyl lactone,

[0448] 3-Methyl-1-pentene-1,5-sulfonyl lactone,

[0449] 4-Methyl-1-pentene-1,5-sulfonyl lactone,

[0450] 5-Methyl-1-pentene-1,5-sulfonyl lactone,

[0451] 1-Methyl-2-pentene-1,5-sulfonyl lactone,

[0452] 2-Methyl-2-pentene-1,5-sulfonyl lactone,

[0453] 3-Methyl-2-pentene-1,5-sulfonyl lactone,

[0454] 4-Methyl-2-pentene-1,5-sulfonyl lactone,

[0455] 5-Methyl-2-pentene-1,5-sulfonyl lactone,

[0456] 1-Methyl-3-pentene-1,5-sulfonyl lactone,

[0457] 2-Methyl-3-pentene-1,5-sulfonyl lactone,

[0458] 3-Methyl-3-pentene-1,5-sulfonyl lactone,

[0459] 4-Methyl-3-pentene-1,5-sulfonyl lactone,

[0460] 5-Methyl-3-pentene-1,5-sulfonyl lactone,

[0461] 1-Methyl-4-pentene-1,5-sulfonyl lactone,

[0462] 2-Methyl-4-pentene-1,5-sulfonyl lactone,

[0463] 3-Methyl-4-pentene-1,5-sulfonyl lactone,

[0464] 4-Methyl-4-pentene-1,5-sulfonyl lactone,

[0465] Sulfolactone compounds such as 5-methyl-4-pentene-1,5-sulfonate lactone;

[0466] Methyl sulfate,

[0467] Ethylene sulfate,

[0468] Sulfate compounds such as propylene sulfate;

[0469] Methylene methane disulfonate,

[0470] Disulfonate compounds such as ethylene methane disulfonate;

[0471] 1,2,3-oxathiazolidine-2,2-dioxide

[0472] 3-Methyl-1,2,3-oxathiazolidin-2,2-dioxide,

[0473] 3H-1,2,3-oxathiazole-2,2-dioxide

[0474] 5H-1,2,3-oxathiazole-2,2-dioxide

[0475] 1,2,4-oxathiazolidin-2,2-dioxide,

[0476] 4-Methyl-1,2,4-oxathiazolidin-2,2-dioxide,

[0477] 3H-1,2,4-oxathiazole-2,2-dioxide

[0478] 5H-1,2,4-oxathiazole-2,2-dioxide

[0479] 1,2,5-oxathiazoline-2,2-dioxide,

[0480] 5-Methyl-1,2,5-oxathiazolidin-2,2-dioxide

[0481] 3H-1,2,5-oxathiazole-2,2-dioxide

[0482] 5H-1,2,5-oxathiazole-2,2-dioxide

[0483] 1,2,3-oxathiazinane-2,2-dioxide

[0484] 3-Methyl-1,2,3-oxathiazine-2,2-dioxide,

[0485] 5,6-Dihydro-1,2,3-oxathiazin-2,2-dioxide

[0486] 1,2,4-oxathiazine-2,2-dioxide

[0487] 4-Methyl-1,2,4-oxathiazine-2,2-dioxide,

[0488] 5,6-Dihydro-1,2,4-oxathiazine-2,2-dioxide

[0489] 3,6-Dihydro-1,2,4-oxathiazine-2,2-dioxide

[0490] 3,4-Dihydro-1,2,4-oxathiazine-2,2-dioxide

[0491] 1,2,5-oxathiazine-2,2-dioxide

[0492] 5-Methyl-1,2,5-oxathiazine-2,2-dioxide

[0493] 5,6-Dihydro-1,2,5-oxathiazine-2,2-dioxide

[0494] 3,6-Dihydro-1,2,5-oxathiazine-2,2-dioxide

[0495] 3,4-Dihydro-1,2,5-oxathiazine-2,2-dioxide

[0496] 1,2,6-oxathiazine-2,2-dioxide

[0497] 6-Methyl-1,2,6-oxathiazine-2,2-dioxide

[0498] 5,6-Dihydro-1,2,6-oxathiazine-2,2-dioxide

[0499] 3,4-Dihydro-1,2,6-oxathiazine-2,2-dioxide

[0500] Nitrogen-containing compounds such as 5,6-dihydro-1,2,6-oxathiazine-2,2-dioxide;

[0501] 1,2,3-oxathiaphosrane-2,2-dioxide

[0502] 3-Methyl-1,2,3-oxothiophosphazenecyclopentane-2,2-dioxide

[0503] 3-Methyl-1,2,3-oxothiophosphazenecyclopentane-2,2,3-trioxide

[0504] 3-Methoxy-1,2,3-oxothiophosphazenecyclopentane-2,2,3-trioxide

[0505] 1,2,4-Oxythiophosphoric pentan-2,2-dioxide

[0506] 4-Methyl-1,2,4-oxothiophosphazenecyclopentane-2,2-dioxide

[0507] 4-Methyl-1,2,4-oxothiophosphazenecyclopentane-2,2,4-trioxide

[0508] 4-Methoxy-1,2,4-oxothiophosphazenecyclopentane-2,2,4-trioxide

[0509] 1,2,5-Oxythiophosphoric pentane-2,2-dioxide,

[0510] 5-Methyl-1,2,5-oxothiophosphazenecyclopentane-2,2-dioxide

[0511] 5-Methyl-1,2,5-oxothiophosphazenecyclopentane-2,2,5-trioxide

[0512] 5-Methoxy-1,2,5-oxothiophosphazenecyclopentane-2,2,5-trioxide

[0513] 1,2,3-oxathiaphosphinane-2,2-dioxide

[0514] 3-Methyl-1,2,3-oxothiophosphazenecyclohexane-2,2-dioxide

[0515] 3-Methyl-1,2,3-oxothiophosphazenecyclohexane-2,2,3-trioxide

[0516] 3-Methoxy-1,2,3-oxothiophosphoric acid-2,2,3-trioxide

[0517] 1,2,4-Oxythiophosphoric hexane-2,2-dioxide

[0518] 4-Methyl-1,2,4-oxothiophosphazenecyclohexane-2,2-dioxide

[0519] 4-Methyl-1,2,4-oxothiophosphazenecyclohexane-2,2,3-trioxide

[0520] 4-Methyl-1,5,2,4-dioxothiophosphazenecyclohexane-2,4-dioxide

[0521] 4-Methoxy-1,5,2,4-dioxothiophosphazenecyclohexane-2,4-dioxide

[0522] 3-Methoxy-1,2,4-oxothiophosphoric acid-2,2,3-trioxide

[0523] 1,2,5-Oxythiophosphoric hexane-2,2-dioxide

[0524] 5-Methyl-1,2,5-oxothiophosphazenecyclohexane-2,2-dioxide

[0525] 5-Methyl-1,2,5-oxothiophosphazenecyclohexane-2,2,3-trioxide

[0526] 5-Methoxy-1,2,5-oxothiophosphoric acid-2,2,3-trioxide

[0527] 1,2,6-Oxythiophosphoric hexane-2,2-dioxide

[0528] 6-Methyl-1,2,6-oxothiophosphazenecyclohexane-2,2-dioxide

[0529] 6-Methyl-1,2,6-oxothiophosphazenecyclohexane-2,2,3-trioxide

[0530] Phosphorus-containing compounds such as 6-methoxy-1,2,6-oxothiophosphoric acid-2,2,3-trioxide;

[0531] From the perspective of improving preservation properties, 1,3-propanesulfonic acid lactone, 1-fluoro-1,3-propanesulfonic acid lactone, 2-fluoro-1,3-propanesulfonic acid lactone, 3-fluoro-1,3-propanesulfonic acid lactone, 1-propene-1,3-sulfonic acid lactone, 1-fluoro-1-propene-1,3-sulfonic acid lactone, 2-fluoro-1-propene-1,3-sulfonic acid lactone, 3-fluoro-1-propene-1,3-sulfonic acid lactone, 1,4-butanesulfonic acid lactone, methanedisulfonate methylene ester, and methanedisulfonate ethylene ester are preferred, and 1,3-propanesulfonic acid lactone, 1-fluoro-1,3-propanesulfonic acid lactone, 2-fluoro-1,3-propanesulfonic acid lactone, 3-fluoro-1,3-propanesulfonic acid lactone, and 1-propene-1,3-sulfonic acid lactone are even more preferred.

[0532] The cyclic sulfonate compound can be used alone or in combination of two or more in any proportion. There is no limitation on the amount of the cyclic sulfonate compound relative to the total amount of the non-aqueous electrolyte of the present invention; any amount can be used without significantly impairing the effects of the present invention. However, relative to the non-aqueous electrolyte of the present invention, its content is typically 0.001% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and typically 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less. Meeting the above ranges can further improve output characteristics, load characteristics, low-temperature characteristics, cycle characteristics, high-temperature storage characteristics, and other effects.

[0533] <Compounds containing cyanide>

[0534] As for compounds with cyano groups that can be used in the non-aqueous electrolyte of the present invention, there are no special restrictions on the types of compounds that have cyano groups in their molecules, and compounds represented by general formula (2) can be listed.

[0535] [Chemical Formula 2]

[0536]

[0537] (In the formula, T represents an organic group composed of atoms selected from carbon, hydrogen, nitrogen, oxygen, sulfur, phosphorus, and halogen atoms, and U is an organic group with 1 to 10 carbon atoms that may have a substituent. V is an integer greater than or equal to 1. When V is greater than or equal to 2, T can be the same or different from each other.)

[0538] The molecular weight of the cyano-containing compound is not particularly limited and can be any molecular weight without significantly impairing the effects of the present invention. The molecular weight is preferably 50 or more, more preferably 80 or more, further preferably 100 or more, and less than 200. Within this range, it is easy to ensure the solubility of the cyano-containing compound in non-aqueous electrolytes, and the effects of the present invention are readily apparent. The method for manufacturing the cyano-containing compound is not particularly limited, and any known method can be used.

[0539] Specific examples of compounds represented by general formula (2) can be listed as follows:

[0540] Compounds containing one cyano group, including acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauryl nitrile, 2-methylbutyronitrile, 2,2-dimethylbutyronitrile, hexanonitrile, cyclovaleronitrile, cyclohexanonitrile, acrylonitrile, methacrylonitrile, butenonitrile, 3-methylbutenonitrile, 2-methyl-2-butenonitrile, 2-pentenonitrile, 2-methyl-2-pentenonitrile, 3-methyl-2-pentenonitrile, 2-hexenonitrile, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3'-oxodipropionitrile, 3,3'-thiodipropionitrile, 1,2,3-propanetrionitrile, 1,3,5-pentanetrionitrile, pentafluoropropionitrile, etc.

[0541] Compounds containing two cyano groups, such as malononitrile, succinic anionitrile, glutaronitrile, adiponitrile, heptacyanide, octanoic anionitrile, nonadionitrile, decanadionitrile, undecanedionitrile, dodecanedionitrile, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinic anionitrile, 2,2-dimethylsuccinic anionitrile, 2,3-dimethylsuccinic anionitrile, trimethylsuccinic anionitrile, tetramethylsuccinic anionitrile, 1,2-bis(cyanoethoxy)ethane (3,3'-(ethylenedioxy)dipropiononitrile), and 1,2-bis(cyanoethio)ethane (3,3'-(ethylenedithio)dipropiononitrile);

[0542] Compounds containing three cyano groups, such as 1,2,3-tris(2-cyanoethoxy)propane and tris(2-cyanoethyl)amine;

[0543] Cyanate esters such as methyl cyanate, ethyl cyanate, propyl cyanate, butyl cyanate, pentyl cyanate, hexyl cyanate, and heptyl cyanate;

[0544] Methyl thiocyanate, ethyl thiocyanate, propyl thiocyanate, butyl thiocyanate, pentyl thiocyanate, hexyl thiocyanate, heptyl thiocyanate, methanesulfonyl cyanide, ethanesulfonyl cyanide, propanesulfonyl cyanide, butanesulfonyl cyanide, pentasulfonyl cyanide, hexyl sulfonyl cyanide, heptyl sulfonyl cyanide, methyl cyanosulfonate, ethyl cyanosulfonate, propyl cyanosulfonate, butyl cyanosulfonate, pentyl cyanosulfonate, hexyl cyanosulfonate, heptyl cyanosulfonate, and other sulfur-containing compounds;

[0545] Phosphorus-containing compounds such as cyanodimethylphosphine, cyanodimethylphosphine oxide, methyl cyanomethylphosphine, methyl cyanomethyltrivalent phosphine, dimethyl phosphine cyanide, dimethyl dimethyl cyanophosphite, dimethyl cyanophosphite, methyl cyano methyl methyl phosphite, dimethyl cyano phosphate, and dimethyl cyanite phosphite; etc.

[0546] From the perspective of improving preservation properties, compounds with two cyano groups, such as acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeritrile, isovaleritrile, lauryl nitrile, butenocyanate, 3-methylbutenocyanate, malonitrile, butyronitrile, glutaritrile, adiponitrile, heptacyanate, octanocyanate, nonadionitrile, decanadionitrile, undecanedionitrile, and dodecanedionitrile, are preferred. More preferred compounds include malonitrile, butyronitrile, glutaritrile, adiponitrile, heptacyanate, octanocyanate, nonadionitrile, decanadionitrile, undecanedionitrile, and dodecanedionitrile.

[0547] The cyano compound can be used alone or in combination with two or more compounds in any proportion. There is no limitation on the amount of the cyano compound relative to the total amount of the non-aqueous electrolyte of this invention; any amount can be used without significantly impairing the effects of this invention. However, relative to the non-aqueous electrolyte of this invention, the concentration of the cyano compound is typically 0.001% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and typically 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less. Meeting the above ranges can further improve output characteristics, load characteristics, low-temperature characteristics, cycle characteristics, and high-temperature storage characteristics.

[0548] <Diisocyanate compounds>

[0549] As for the diisocyanate compound that can be used in the non-aqueous electrolyte of the present invention, there is no particular limitation on the type of compound as long as it has two isocyanate groups in the molecule, and the compound represented by the following general formula (3) is preferred.

[0550] [Chemical Formula 3]

[0551]

[0552] (In the formula, X is a hydrocarbon group with 1 to 16 carbon atoms that can be substituted by fluorine.)

[0553] In the above general formula (3), X is a hydrocarbon group with 1 to 16 carbon atoms that is optionally substituted with fluorine. The number of carbon atoms in X is preferably 2 or more, more preferably 3 or more, particularly preferably 4 or more, and preferably 14 or less, more preferably 12 or less, particularly preferably 10 or less, and most preferably 8 or less. Furthermore, there are no particular restrictions on the type of X as long as it is a hydrocarbon group. It can be any group among aliphatic chain alkylene, aliphatic cyclic alkylene, and hydrocarbon groups containing aromatic rings, preferably aliphatic chain alkylene or aliphatic cyclic alkylene.

[0554] Specific examples of diisocyanates in this invention include:

[0555] Linear polymethylene diisocyanates, including ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, and tetradecamethylene diisocyanate;

[0556] Branched alkylene diisocyanates such as 1-methylhexamethylene diisocyanate, 2-methylhexamethylene diisocyanate, 3-methylhexamethylene diisocyanate, 1,1-dimethylhexamethylene diisocyanate, 1,2-dimethylhexamethylene diisocyanate, 1,3-dimethylhexamethylene diisocyanate, 1,4-dimethylhexamethylene diisocyanate, 1,5-dimethylhexamethylene diisocyanate, 1,6-dimethylhexamethylene diisocyanate, and 1,2,3-trimethylhexamethylene diisocyanate;

[0557] Diisocyanate alkenes include 1,4-diisocyanate-2-butene, 1,5-diisocyanate-2-pentene, 1,5-diisocyanate-3-pentene, 1,6-diisocyanate-2-hexene, 1,6-diisocyanate-3-hexene, 1,8-diisocyanate-2-octene, 1,8-diisocyanate-3-octene, and 1,8-diisocyanate-4-octene.

[0558] 1,3-Diisocyanate-2-fluoropropane, 1,3-Diisocyanate-2,2-difluoropropane, 1,4-Diisocyanate-2-fluorobutane, 1,4-Diisocyanate-2,2-difluorobutane, 1,4-Diisocyanate-2,3-difluorobutane, 1,6-Diisocyanate-2-fluorohexane, 1,6-Diisocyanate-3-fluorohexane, 1,6-Diisocyanate-2,2-difluorohexane, 1,6-Diisocyanate-2,3-difluorohexane, 1,6-Diisocyanate-2,4-difluorohexane, 1,6-Diisocyanate-2,5-difluorohexane, 1,6-Diisocyanate-2,5-difluorohexane, 1,6-Diisocyanate-2-fluorohexane Fluorinated diisocyanate alkanes include esters such as 3,3-difluorohexane, 1,6-diisocyanate-3,4-difluorohexane, 1,8-diisocyanate-2-fluorooctane, 1,8-diisocyanate-3-fluorooctane, 1,8-diisocyanate-4-fluorooctane, 1,8-diisocyanate-2,2-difluorooctane, 1,8-diisocyanate-2,3-difluorooctane, 1,8-diisocyanate-2,4-difluorooctane, 1,8-diisocyanate-2,5-difluorooctane, 1,8-diisocyanate-2,6-difluorooctane, and 1,8-diisocyanate-2,7-difluorooctane.

[0559] Diisocyanates containing cycloalkane rings, such as 1,2-diisocyanate cyclopentane, 1,3-diisocyanate cyclopentane, 1,2-diisocyanate cyclohexane, 1,3-diisocyanate cyclohexane, 1,4-diisocyanate cyclohexane, 1,2-bis(isocyanate methyl)cyclohexane, 1,3-bis(isocyanate methyl)cyclohexane, 1,4-bis(isocyanate methyl)cyclohexane, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, and dicyclohexylmethane-4,4'-diisocyanate.

[0560] 1,2-Phenylidene diisocyanate, 1,3-Phenylidene diisocyanate, 1,4-Phenylidene diisocyanate, Toluene-2,3-Diisocyanate, Toluene-2,4-Diisocyanate, Toluene-2,5-Diisocyanate, Toluene-2,6-Diisocyanate, Toluene-3,4-Diisocyanate, Toluene-3,5-Diisocyanate, 1,2-Bis(isocyanate methyl)benzene, 1,3-Bis(isocyanate methyl)benzene, 1,4-Bis(isocyanate methyl)benzene, 2,4-Diisocyanate biphenyl, 2,6-Diisocyanate biphenyl, 2,2'-Diisocyanate biphenyl, 3,3'-Diisocyanate biphenyl, 4,4'-Diisocyanate -2-methylbiphenyl, 4,4'-diisocyanate-3-methylbiphenyl, 4,4'-diisocyanate-3,3'-dimethylbiphenyl, 4,4'-diisocyanate-diphenylmethane, 4,4'-diisocyanate-2-methyldiphenylmethane, 4,4'-diisocyanate-3-methyldiphenylmethane, 4,4'-diisocyanate-3,3'-dimethyldiphenylmethane, 1,5-diisocyanate naphthalene, 1,8-diisocyanate naphthalene, 2,3-diisocyanate naphthalene, 1,5-bis(isocyanate methyl)naphthalene, 1,8-bis(isocyanate methyl)naphthalene, 2,3-bis(isocyanate methyl)naphthalene, and other diisocyanates containing aromatic rings; etc.

[0561] Among them, the preferred option is:

[0562] Linear polymethylene diisocyanates, including ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, and tetradecamethylene diisocyanate;

[0563] Branched alkylene diisocyanates such as 1-methylhexamethylene diisocyanate, 2-methylhexamethylene diisocyanate, 3-methylhexamethylene diisocyanate, 1,1-dimethylhexamethylene diisocyanate, 1,2-dimethylhexamethylene diisocyanate, 1,3-dimethylhexamethylene diisocyanate, 1,4-dimethylhexamethylene diisocyanate, 1,5-dimethylhexamethylene diisocyanate, 1,6-dimethylhexamethylene diisocyanate, and 1,2,3-trimethylhexamethylene diisocyanate;

[0564] Diisocyanates containing cycloalkane rings include 1,2-diisocyanate cyclopentane, 1,3-diisocyanate cyclopentane, 1,2-diisocyanate cyclohexane, 1,3-diisocyanate cyclohexane, 1,4-diisocyanate cyclohexane, 1,2-bis(isocyanate methyl)cyclohexane, 1,3-bis(isocyanate methyl)cyclohexane, 1,4-bis(isocyanate methyl)cyclohexane, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, and dicyclohexylmethane-4,4'-diisocyanate.

[0565] Furthermore, a preferred option is:

[0566] Selected from linear polymethylene diisocyanates, including tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, and octamethylene diisocyanate;

[0567] Selected from cyclopentane, cyclopentane, cyclohex ...

[0568] In addition, the diisocyanate of the present invention can be used alone or in combination of two or more in any combination and proportion.

[0569] The content of diisocyanate that can be used in the non-aqueous electrolyte of the present invention is, relative to the total mass of the non-aqueous electrolyte, typically 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.3% by mass or more, and typically 5% by mass or less, preferably 4.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2% by mass or less. When the content is within the above range, the durability such as cycling and storage can be improved, and the effects of the present invention can be fully realized.

[0570] Overcharge prevention agent

[0571] In order to effectively prevent the non-aqueous electrolyte secondary battery from cracking or catching fire when it reaches an overcharged state, an overcharge prevention agent can be used in the non-aqueous electrolyte of the present invention.

[0572] Examples of overcharge inhibitors include: aromatic compounds such as biphenyl, alkyl biphenyl, terphenyl, partially hydrides of terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, diphenyl ether, and dibenzofuran; partially fluorinated compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, and p-cyclohexylfluorobenzene; and fluorinated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole. Among these, aromatic compounds such as biphenyl, alkyl biphenyl, terphenyl, partially hydrides of terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, diphenyl ether, and dibenzofuran are preferred. These compounds can be used individually or in combination of two or more. When using two or more compounds in combination, considering the balance between overcharge prevention characteristics and high-temperature storage characteristics, it is particularly preferred to use cyclohexylbenzene in combination with tert-butylbenzene or tert-amylbenzene; or to use at least one of the non-oxygen aromatic compounds selected from biphenyl, alkylbiphenyl, terphenyl, partial hydrides of terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, etc., in combination with at least one of the oxygen-containing aromatic compounds selected from diphenyl ether, dibenzofuran, etc.

[0573] There are no particular limitations on the amount of the overcharge inhibitor, and any amount can be used within a range that does not significantly impair the effect of the present invention. The overcharge inhibitor is preferably 0.1% by mass or more, and more preferably 5% by mass or less, in 100% by mass of the non-aqueous electrolyte. Within this range, the effect of the overcharge inhibitor is easily and sufficiently manifested, and problems such as degradation of battery characteristics due to high-temperature storage are also easily avoided. More preferably, the overcharge inhibitor is 0.2% by mass or more, further preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and more preferably 3% by mass or less, and more preferably 2% by mass or less.

[0574] <Other Additives>

[0575] Other known additives can be used in the non-aqueous electrolyte of this invention. Examples of such additives include: erythritan carbonate, spirobis(dimethylene) carbonate, etc. Diethylene-carbonate), methoxyethyl methyl carbonate and other carbonate compounds; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, pentene anhydride, itaconic anhydride, diethylene glycol anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic anhydride and phenylsuccinic anhydride and other carboxylic anhydrides; 2,4,8,10-tetraoxaspiro[5.5]undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane and other spirocyclic compounds; ethylene glycol sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, butylene glycol methanesulfonate (Busulfan), cyclobutene sulfone, ethylene glycol sulfate, vinylene sulfate, diphenyl sulfone, N,N-dimethylmethanesulfonamide, N,N-diethylmethanesulfonamide and other sulfur-containing compounds; 1-methyl-2-pyrrolidone, 1-methyl-2-piperidinone, 3-methyl-2- Nitrogen-containing compounds such as zolinones, 1,3-dimethyl-2-imidazolinone, and N-methylsuccinimide; hydrocarbon compounds such as heptane, octane, nonane, decane, and cycloheptane; fluorinated aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene, and trifluorotoluene; and silane compounds such as tri(trimethylsilyl)borate, tri(trimethoxysilyl)borate, tri(trimethylsilyl)phosphate, tri(trimethoxysilyl)phosphate, dimethoxyaluminoxyltrimethoxysilane, diethoxyaluminoxyltriethoxysilane, dipropoxyaluminoxyltriethoxysilane, dibutoxyaluminoxyltrimethoxysilane, dibutoxyaluminoxyltriethoxysilane, tetra(trimethylsiloxy)titanium, and tetra(triethylsiloxy)titanium. These additives can be used alone or in combination. Adding these additives can improve capacity retention and cycling characteristics after high-temperature storage.

[0576] There are no particular restrictions on the amount of other additives, and any amount can be used as long as it does not significantly impair the effect of the present invention. The amount of other additives in 100% by mass of the non-aqueous electrolyte is preferably 0.01% by mass or more, and more preferably 5% by mass or less. Within this range, the effects of the other additives are easily and fully manifested, and problems such as reduced battery characteristics under high load discharge are easily avoided. The amount of other additives is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 3% by mass or less, and more preferably 1% by mass or less.

[0577] The aforementioned non-aqueous electrolyte also includes the electrolyte present inside the non-aqueous electrolyte battery of the present invention. Specifically, it also includes the following cases: separately synthesizing the constituent elements of the non-aqueous electrolyte such as lithium salts, solvents, and additives, preparing the non-aqueous electrolyte from the substantially separated portion, and injecting it into a separately assembled battery using the method described below to obtain the non-aqueous electrolyte in the non-aqueous electrolyte battery; adding each constituent element of the non-aqueous electrolyte of the present invention to the battery in advance, and mixing them in the battery to obtain a non-aqueous electrolyte with the same composition as the non-aqueous electrolyte of the present invention; and generating the compound constituting the non-aqueous electrolyte of the present invention in the non-aqueous electrolyte battery to obtain a non-aqueous electrolyte with the same composition as the non-aqueous electrolyte of the present invention.

[0578] <2. Non-aqueous electrolyte secondary batteries>

[0579] The non-aqueous electrolyte secondary battery of the present invention comprises a negative electrode and a positive electrode capable of adsorbing and releasing ions, and the non-aqueous electrolyte of the present invention described above.

[0580] <2-1. Battery Composition>

[0581] The components of the non-aqueous electrolyte secondary battery of the present invention, except for the negative electrode and the non-aqueous electrolyte, are the same as those of conventionally known non-aqueous electrolyte secondary batteries, and generally have the following form: the positive electrode and the negative electrode are separated by a porous membrane (separator) stack impregnated with the non-aqueous electrolyte of the present invention, and they are housed in a casing (outer body). Therefore, there are no special limitations on the shape of the non-aqueous electrolyte secondary battery of the present invention, and it can be any shape such as cylindrical, square, laminated, coin-shaped, or large.

[0582] <2-2. Non-aqueous electrolyte>

[0583] The non-aqueous electrolyte of the present invention described above is used as a non-aqueous electrolyte.

[0584] <2-3. Negative electrode>

[0585] The negative electrode is an electrode with a layer of negative electrode active material on the current collector. The following is an explanation of the negative electrode active material.

[0586] As a negative electrode active material, any material capable of electrochemically adsorbing and releasing lithium ions is acceptable, with no particular restrictions. Specific examples include carbonaceous materials, alloy materials, and lithium-containing metal composite oxide materials. One of these materials can be used alone, or any combination of two or more can be used.

[0587] <2-3-1. Carbonaceous Materials>

[0588] As a carbonaceous material that can be used as a negative electrode active material, the carbonaceous materials selected from (1) to (4) below are preferred because they can achieve a good balance between initial irreversible capacity and high current density charge-discharge characteristics. In addition, one type of carbonaceous material (1) to (4) can be used alone, or two or more types can be used in any combination and proportion.

[0589] (1) Natural graphite;

[0590] (2) Carbonaceous materials obtained by subjecting artificial carbonaceous materials and artificial graphitic materials to heat treatment once or more in the range of 400~3200℃.

[0591] (3) The negative electrode active material layer is composed of at least two kinds of carbonaceous materials with different crystallinity, and / or carbonaceous materials with different crystallinity having a joint interface;

[0592] (4) The negative electrode active material layer is composed of at least two kinds of carbonaceous materials with different orientations, and / or carbonaceous materials with different orientations having interfaces.

[0593] Specific examples of the artificial carbonaceous materials and artificial graphitic materials mentioned in (2) above include: natural graphite, coal coke, petroleum coke, coal pitch, petroleum pitch, or substances obtained by oxidizing these pitches, needle coke, pitch coke and carbon materials obtained by partially graphitizing them, furnace black, acetylene black, pitch-based carbon fibers and other organic materials, carbonizable organic materials and their carbides, or solutions obtained by dissolving carbonizable organic materials in low molecular weight organic solvents such as benzene, toluene, xylene, quinoline, n-hexane and their carbides.

[0594] <2-3-2. Composition, physical properties, and preparation methods of carbon-based anodes>

[0595] Regarding the properties of carbonaceous materials, negative electrode containing carbonaceous materials and polarization method, current collector, and non-aqueous electrolyte secondary battery, it is preferred to simultaneously satisfy any one or more of the following (1) to (13).

[0596] (1) X-ray parameters

[0597] The d-value (interlayer distance) of the lattice plane (002 plane) of carbonaceous materials, determined by X-ray diffraction using the vibratory diffraction method, is typically 0.335~0.340 nm, particularly preferably 0.335~0.338 nm, and especially preferably 0.335~0.337 nm. Furthermore, the crystallite size (Lc) determined by X-ray diffraction using the vibratory diffraction method is typically 1.0 nm or more, preferably 1.5 nm or more, and especially preferably 2 nm or more.

[0598] (2) Volume-based average particle size

[0599] The volume-based average particle size of carbonaceous materials, i.e., the average particle size (median particle size) determined by laser diffraction / scattering, is typically 1 μm or more, preferably 3 μm or more, further preferably 5 μm or more, particularly preferably 7 μm or more, and typically 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, further preferably 30 μm or less, and particularly preferably 25 μm or less. When the volume-based average particle size is below the above range, it may lead to irreversible capacity increase and cause initial battery capacity loss. Furthermore, when it exceeds the above range, uneven coating surfaces are easily formed during electrode fabrication by coating, which may be undesirable in the battery manufacturing process.

[0600] The volume-based average particle size was determined as follows: carbon powder was dispersed in a 0.2% by mass aqueous solution (approximately 10 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and the particle size was measured using a laser diffraction / scattering particle size analyzer (LA-700 manufactured by Horiba Seisakusho). The median particle size obtained by this determination was defined as the volume-based average particle size of the carbonaceous material in this invention.

[0601] [Rhombohedral Crystallinity]

[0602] The rhombohedral crystallinity defined in this invention can be obtained by the following formula, based on the ratio of rhombohedral graphite layers (ABC stacked layers) to hexagonal graphite layers (AB stacked layers) measured by wide-angle X-ray diffraction (XRD).

[0603] Rhombohedral crystallinity (%) = Integrated intensity of ABC(101) peak in XRD ÷ Integrated intensity of AB(101) peak in XRD × 100

[0604] Here, the rhombohedral crystallinity of the graphite particles of the present invention is generally 0% or more, preferably greater than 0%, more preferably 3% or more, further preferably 5% or more, particularly preferably 12% or more, and generally within the range of 35% or less, preferably 27% or less, further preferably 24% or less, and particularly preferably 20% or less. Wherein, a rhombohedral crystallinity of 0% means that no XRD peaks originating from the ABC stacked layer are detected at all. Furthermore, greater than 0% means that only a very small number of XRD peaks originating from the ABC stacked layer are detected.

[0605] If the rhombohedral crystallinity is too high, the graphite particles contain numerous defects in their crystal structure, leading to a reduction in Li intercalation and a tendency to fail to achieve high capacity. Furthermore, the presence of these defects can cause electrolyte decomposition during cycling, resulting in decreased cycling performance. Conversely, when the rhombohedral crystallinity is within the range of this invention, for example, the graphite particles have fewer defects in their crystal structure, exhibit lower reactivity with the electrolyte, and experience less electrolyte consumption during cycling, resulting in excellent cycling performance; therefore, this is preferred.

[0606] The XRD method for determining the crystallinity of rhombohedrons is described below.

[0607] Graphite powder was filled into a 0.2 mm sample plate without orientation, and X-ray diffraction was performed using an X-ray diffraction apparatus (e.g., an X'Pert Pro MPD from PANalytical, employing CuKα rays, with an output power of 45 kV and 40 mA). Using the obtained diffraction pattern, the integral intensity of the peaks was calculated using the analytical software JADE 5.0 by fitting the peak shape with an asymmetric Pearson VII function, and the rhombohedral crystallinity was determined from the above formula.

[0608] The X-ray diffraction measurement conditions are shown below. It should be noted that "2θ" represents the diffraction angle.

[0609] • Target: Cu (Kα ray) graphite monochromator

[0610] • Narrow slit:

[0611] Solar slit: 0.04 degrees

[0612] Diverging slit degree 0.5

[0613] Lateral divergence mask 15mm

[0614] Scattering prevents slits of 1 degree

[0615] • Measurement range and step angle / measurement time:

[0616] (101) Plane: 41 degrees ≤ 2θ ≤ 47.5 degrees 0.3 degrees / 60 seconds

[0617] • Background correction: Connect the area between 42.7 and 45.5 degrees with a straight line to form the background and then subtract it.

[0618] • Peak in the rhombohedral graphite particle layer: refers to the peak around 43.4 degrees.

[0619] • Peak in hexagonal graphite particle layer: refers to the peak around 44.5 degrees.

[0620] As a method for obtaining graphite particles with a rhombohedral crystallinity within the aforementioned range, existing manufacturing methods can be used without particular limitation, but heat treatment of the graphite particles at a temperature of 500°C or higher is preferred. Furthermore, applying mechanical actions such as compression, friction, and shearing forces, primarily impact forces but also including particle interactions, to the graphite particles is also preferred. In addition, the rhombohedral crystallinity can be adjusted by varying the intensity of the mechanical action, processing time, and the presence or absence of repetition. As a specific device for adjusting the rhombohedral crystallinity, a preferred device is one that has a rotor with multiple blades inside a casing, and applies mechanical actions such as impact compression, friction, and shearing forces to the carbon material introduced inside by the high-speed rotation of this rotor, thereby performing surface treatment. Furthermore, a device having a mechanism for repeatedly applying mechanical actions by circulating the carbon material is preferred, or a device without a circulation mechanism but having a mechanism for connecting multiple devices for processing is preferred. As an example of a preferred device, the Hybridization System manufactured by Nara Machinery Co., Ltd. is an example.

[0621] Furthermore, it is preferable to perform heat treatment after applying the aforementioned mechanical action.

[0622] Furthermore, it is particularly preferred that the mixture be compounded with a carbon precursor after the aforementioned mechanical action is applied, and then subjected to heat treatment at a temperature of 700°C or higher.

[0623] (3) Raman R value, Raman full width at half maximum (FWHM)

[0624] The Raman R value of carbonaceous materials is a value determined by argon-ion laser Raman spectroscopy, which is typically 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and typically 1.5 or less, preferably 1.2 or less, further preferably 1 or less, and particularly preferably 0.5 or less.

[0625] When the Raman R value is below the aforementioned range, the excessive crystallinity of the particle surface may lead to a reduction in the sites for Li to enter the interlayer during charging and discharging. That is, it may result in decreased charge acceptability. Furthermore, when high-density anodes are achieved by pressing carbonaceous material onto the current collector, crystals tend to align parallel to the electrode plate, which may reduce loading characteristics. On the other hand, exceeding the aforementioned range reduces the crystallinity of the particle surface, increasing reactivity with non-aqueous electrolytes, potentially leading to decreased efficiency or increased gas generation.

[0626] In addition, carbonaceous materials at 1580cm -1 There are no special restrictions on the width of the Raman peak in the vicinity, but it is usually 10cm. -1 The above, preferably 15cm -1Above, and usually 100cm -1 The following, preferably 80cm -1 The following, or more preferably, is 60cm -1 The following, especially preferred, is 40cm. -1 the following.

[0627] When the Raman full width at half maximum (FWHM) is below the aforementioned range, the excessive crystallinity of the particle surface may lead to a reduction in the sites for Li to enter the interlayer during charging and discharging. This could result in decreased charge acceptability. Furthermore, when high-density anodes are achieved by pressing carbonaceous materials onto the current collector, crystals tend to align parallel to the electrode plate, potentially reducing loading characteristics. On the other hand, exceeding the aforementioned range decreases the crystallinity of the particle surface, increasing reactivity with non-aqueous electrolytes, which may lead to reduced efficiency or increased gas generation.

[0628] Raman spectroscopy was performed as follows: Using a Raman spectrometer (manufactured by Nippon Spectrophotometer Co., Ltd.), the sample was allowed to fall naturally and fill the measurement cell. An argon-ion laser was used to irradiate the surface of the sample within the cell, while the measurement cell was rotated in a plane perpendicular to the laser. The resulting Raman spectra were measured at 1580 cm⁻¹. -1 The intensity of the nearby peak PA is IA, and at 1360 cm⁻¹ -1 The intensity IB of the nearby peak PB is calculated, and its intensity ratio R (R=IB / IA) is calculated. The Raman R value obtained using this measurement is defined as the Raman R value of the carbonaceous material in this invention. Furthermore, the obtained Raman spectrum is at 1580 cm⁻¹. -1 The half-maximum width of the nearby peak PA is defined as the Raman half-maximum width of the carbonaceous material in this invention.

[0629] In addition, the Raman measurement conditions described above are as follows.

[0630] Argon ion laser wavelength: 514.5nm

[0631] Laser power on the sample: 15~25mW

[0632] • Resolution: 10~20cm -1

[0633] • Measurement range: 1100cm -1 ~1730cm -1

[0634] Raman R-value and Raman full width at half maximum (FWHM) analysis: Background processing

[0635] • Smoothing processes: simple averaging, 5-point convolution.

[0636] (4) BET specific surface area

[0637] The BET specific surface area of ​​carbonaceous materials, determined by the BET method, is typically 0.1 m². 2 ·g -1 The above, preferably 0.7m 2 ·g -1 The above, and more preferably 1.0m 2 ·g -1 The above, and especially preferred, is 1.5m 2 ·g -1 The above, and usually 100m 2 ·g -1 The following, preferably 25m 2 ·g -1 The following, and more preferably 15m 2 ·g -1 The following, especially preferred, is 10m 2 ·g -1 the following.

[0638] When the BET specific surface area is below this range, using it as a negative electrode material can easily lead to poor lithium acceptance during charging, causing lithium to easily deposit on the electrode surface, which may result in decreased stability. On the other hand, when it exceeds this range, using it as a negative electrode material can easily lead to increased reactivity with non-aqueous electrolytes, resulting in more gas generation and potentially preventing the acquisition of an ideal battery.

[0639] The specific surface area was determined using the BET method as follows: Using a surface area meter (a fully automated surface area measuring device manufactured by Riken Okura), the sample was pre-dried for 15 minutes in a nitrogen stream at 350°C. Then, a nitrogen-helium mixed gas with the relative pressure of nitrogen to atmospheric pressure accurately adjusted to 0.3 was used for measurement via the nitrogen adsorption BET one-point method employing gas flow. The specific surface area obtained using this method is defined as the BET specific surface area of ​​the carbonaceous material in this invention.

[0640] (5) Circularity

[0641] When measuring the roundness of a carbonaceous material as a measure of its sphericity, it is preferable that the roundness falls within the following range. It should be noted that roundness is defined as: "Roundness = (Circumference of an equivalent circle with the same area as the particle's projected shape) / (Actual circumference of the particle's projected shape)". When the roundness is 1, it is theoretically a perfect sphere.

[0642] The more the sphericity of the carbonaceous material particles with a particle size in the range of 3 to 40 μm is close to 1, the better. It is preferably 0.1 or more, more preferably 0.5 or more, more preferably 0.8 or more, further preferably 0.85 or more, and particularly preferably 0.9 or more.

[0643] The greater the sphericity, the better the high-current-density charge-discharge characteristics. Therefore, when the sphericity is below the above range, the filling capacity of the negative electrode active material decreases and the resistance between particles increases, which may lead to a decrease in short-term high-current-density charge-discharge characteristics.

[0644] Circularity was determined using a flow cytometry particle image analysis system (FPIA, manufactured by Sysmex). Approximately 0.2 g of sample was dispersed in a 0.2% by mass aqueous solution (approximately 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant. The sample was irradiated with ultrasound at 28 kHz and an output power of 60 W for 1 minute. The detection range was specified as 0.6–400 μm, and particles with a diameter in the range of 3–40 μm were measured. The circularity determined using this method is defined as the circularity of the carbonaceous material in this invention.

[0645] There are no particular limitations on the methods for improving roundness, but when particles are made spherical through spheroidization, the shape of the gaps between particles can be uniform when applied to the electrode body, which is therefore preferred. Examples of spheroidization include methods that mechanically approach a spherical shape by applying shear or compressive forces, and mechanical / physical processing methods that granulate multiple microparticles using adhesives or the adhesion of the particles themselves.

[0646] (6) Tap density

[0647] The tap density of carbonaceous materials is typically 0.1 g·cm³. -3 The above, preferably 0.5 g·cm -3 The above, and more preferably 0.7 g·cm -3 The above, and especially preferred, is 1 g·cm³. -3 The above, and preferably 2 g·cm³ -3 The following, and more preferably, is 1.8 g·cm³. -3 The following, particularly preferred, dosage is 1.6 g·cm³. -3 the following.

[0648] When the tap density is below the above range, it is difficult to increase the fill density when used as a negative electrode, which may prevent the acquisition of a high-capacity battery. Furthermore, when the tap density exceeds the above range, the gaps between particles in the electrode become too small, making it difficult to ensure interparticle conductivity and potentially preventing the achievement of ideal battery characteristics.

[0649] The tap density was determined as follows: the sample was passed through a sieve with a mesh size of 300 μm and then dropped into a 20 cm sieve. 3 In a tapped container, after the sample has filled to the top surface of the container, it is vibrated 1000 times with a stroke length of 10 mm using a powder density meter (e.g., a Tap densor manufactured by Seishin Corporation). The tap density is then determined from the volume and mass of the sample at that point. The tap density calculated using this measurement is defined as the tap density of the carbonaceous material in this invention.

[0650] (7) Orientation ratio

[0651] The orientation ratio of carbonaceous materials is typically 0.005 or higher, preferably 0.01 or higher, more preferably 0.015 or higher, and typically 0.67 or lower. An orientation ratio below these ranges may lead to a decrease in high-density charge-discharge characteristics. It should be noted that the upper limit of the above range is a theoretical upper limit for the orientation ratio of carbonaceous materials.

[0652] The orientation ratio was determined by X-ray diffraction after the sample was pressurized and molded. 0.47 g of the sample was filled into a molding machine with a diameter of 17 mm, and the sample was subjected to X-ray diffraction at 58.8 MN·m. -2 The sample is compressed to obtain a molded body, and then the sample for measurement is fixed with clay so that the surface of the sample is the same as that of the sample holder for measurement, thereby performing X-ray diffraction measurement. The ratio of (110) diffraction peak intensity to (004) diffraction peak intensity is calculated from the peak intensities of the (110) diffraction and (004) diffraction of the obtained carbon. The orientation ratio calculated using this measurement is defined as the orientation ratio of the carbonaceous material in this invention.

[0653] The X-ray diffraction measurement conditions are shown below. It should be noted that "2θ" represents the diffraction angle.

[0654] Target: Cu (Kα ray) graphite monochromator

[0655] • Slit:

[0656] Diverging slit = 0.5 degrees

[0657] Light-receiving slit = 0.15mm

[0658] Scattering slit = 0.5 degrees

[0659] • Measurement range and step angle / measurement time:

[0660] (110) Plane: 75 degrees ≤ 2θ ≤ 80 degrees 1 degree / 60 seconds

[0661] (004) Plane: 52 degrees ≤ 2θ ≤ 57 degrees 1 degree / 60 seconds

[0662] (8) Aspect Ratio (Powder)

[0663] The aspect ratio of carbonaceous materials is typically 1 or higher, and usually 10 or lower, preferably 8 or lower, and more preferably 5 or lower. When the aspect ratio exceeds the above range, streaks may occur or a uniform coating surface may not be obtained during electrodeation, resulting in a decrease in high current density charge-discharge characteristics. It should be noted that the lower limit of the above range is the theoretical lower limit of the aspect ratio of carbonaceous materials.

[0664] The aspect ratio was determined by magnifying the carbonaceous material particles using a scanning electron microscope. Fifty arbitrary graphite particles were selected and fixed to a metal end face less than 50 micrometers thick. For each of these graphite particles, the stage on which the sample was fixed was rotated and tilted. The longest diameter A and the shortest diameter B perpendicular to these particles were measured during three-dimensional observation, and the average value of A / B was calculated. The aspect ratio (A / B) determined using this method is defined as the aspect ratio of the carbonaceous material in this invention.

[0665] (9) Electrode fabrication

[0666] Within the scope of not significantly limiting the effects of the present invention, any known method can be used to manufacture the electrode. For example, an electrode can be formed by adding a binder, solvent, thickener, conductive material, filler, etc., to the negative electrode active material to make a slurry, coating the slurry onto a current collector, drying it, and then pressing it.

[0667] In the stage preceding the non-aqueous electrolyte injection process, the thickness of the negative electrode active material layer on each side of the battery is typically 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and typically 150 μm or less, preferably 120 μm or less, more preferably 100 μm or less. When the thickness of the negative electrode active material exceeds this range, the non-aqueous electrolyte has difficulty penetrating to the vicinity of the current collector interface, which may lead to a decrease in high current density charge-discharge characteristics. Furthermore, when the thickness is below this range, the volume ratio of the current collector to the negative electrode active material increases, which may lead to a decrease in battery capacity. Additionally, the negative electrode active material can be rolled to form a sheet electrode, or compressed to form a granular electrode.

[0668] (10) Current collector

[0669] As the current collector that can maintain the active material of the negative electrode, any known current collector can be used. Examples of metal materials that can be used as the current collector for the negative electrode include copper, nickel, stainless steel, and nickel-plated steel, but copper is particularly preferred from the perspective of ease of processing and cost.

[0670] Furthermore, as for the shape of the current collector, when the current collector is made of a metallic material, examples include metal foil, metal cylinder, metal coil, metal plate, metal film, expanded alloy, perforated metal, foamed metal, etc. Among these, metal film is preferred, copper foil is more preferred, and rolled copper foil obtained by rolling method and electrolytic copper foil obtained by electrolysis method are even more preferred. Any of the above can be used as a current collector.

[0671] In addition, when the thickness of the copper foil is less than 25 μm, copper alloys with higher strength than pure copper (phosphor bronze, titanium copper, Cosun alloy, Cu-Cr-Zr alloy, etc.) can be used.

[0672] (10-1) Thickness of the collector

[0673] The current collector can have any thickness, but is typically 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and typically 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. When the thickness of the metal film is less than 1 μm, it may cause difficulties in coating due to reduced strength. Furthermore, when the thickness of the metal film is greater than 100 μm, it may cause deformation of the electrode shape, such as winding. It should be noted that the current collector can also be in the form of a mesh.

[0674] (11) The thickness ratio of the current collector to the negative electrode active material layer

[0675] There is no particular limitation on the ratio of the thickness of the current collector to the thickness of the negative electrode active material layer, but the value of "(thickness of the negative electrode active material layer on one side before the non-aqueous electrolyte is injected) / (thickness of the current collector)" is preferably 150 or less, more preferably 20 or less, particularly preferably 10 or less, and preferably 0.1 or more, more preferably 0.4 or more, particularly preferably 1 or more.

[0676] When the thickness ratio of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heating during high current density charging and discharging. Conversely, when the ratio is below the above range, the volume ratio of the current collector to the negative electrode active material increases, which may lead to a reduction in battery capacity.

[0677] (12) Electrode density

[0678] There are no particular restrictions on the electrode structure when polarizing the negative electrode active material, but the density of the negative electrode active material present on the current collector is preferably 1 g·cm³. -3 The above, and more preferably 1.2 g·cm -3 The above, and especially preferred, is 1.3 g·cm³. -3 The above, and preferably 2.2 g·cm³ -3 The following, and more preferably, is 2.1 g·cm⁻¹ -3The following, and more preferably 2.0 g·cm -3 The following, particularly preferred, value is 1.9 g·cm³. -3 The following applies: When the density of the negative electrode active material on the current collector exceeds the above range, it may cause damage to the negative electrode active material particles, leading to an initial irreversible increase in capacity, or a deterioration in high-current-density charge-discharge characteristics due to decreased permeability of the non-aqueous electrolyte near the current collector / negative electrode active material interface. Conversely, when the density is below the above range, it may lead to decreased conductivity between negative electrode active materials, increased battery resistance, and decreased capacity per unit volume.

[0679] (13) Adhesive

[0680] As a binder for bonding negative electrode active materials, any material that is stable relative to non-aqueous electrolytes and solvents used in electrode manufacturing is acceptable, without any special restrictions.

[0681] Specific examples include: resin-like polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (nitrile rubber), and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers or their hydrogenated products; thermoplastic elastomers such as EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymers or their hydrogenated products; soft resin-like polymers such as syndiotactic 1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, and propylene-α-olefin copolymer; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymer; and polymer compositions with ionic conductivity of alkali metal ions (especially lithium ions). These adhesives can be used alone or in any combination and proportion of two or more.

[0682] As a solvent used to form the slurry, any solvent that can dissolve or disperse the negative electrode active material, binder, and thickener and conductive material as needed can be used. There are no special restrictions on its type; any solvent among aqueous solvents and organic solvents can be used.

[0683] Examples of aqueous solvents include water and alcohols; examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphoramide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, and hexane.

[0684] In particular, when using aqueous solvents, it is preferable to include dispersants in the solvent along with thickeners, and to use latex such as SBR for slurry preparation. It should be noted that these solvents can be used individually, or in any combination and proportion.

[0685] The proportion of the binder relative to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, further preferably 10% by mass or less, and particularly preferably 8% by mass or less. When the proportion of the binder relative to the negative electrode active material exceeds the above range, it may lead to an increase in the proportion of binder that does not contribute to the battery capacity, resulting in a decrease in battery capacity. In addition, when it is below the above range, it may lead to a decrease in the strength of the negative electrode.

[0686] In particular, when the main components contain rubber-like polymers represented by SBR, the proportion of the binder relative to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less.

[0687] Furthermore, when the main component contains fluorinated polymers such as polyvinylidene fluoride, its proportion relative to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, and usually 15% by mass or less, preferably 10% by mass or less, more preferably 8% by mass or less.

[0688] Thickeners are commonly used to adjust the viscosity of slurries. There are no particular limitations on thickeners; examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts. These thickeners can be used individually or in any combination and proportion.

[0689] Furthermore, when using a thickener, the ratio of the thickener to the negative electrode active material is typically 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and typically 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. When the ratio of the thickener to the negative electrode active material is lower than the above range, it may lead to a significant decrease in coatability. Additionally, when it exceeds the above range, the proportion of the negative electrode active material in the negative electrode active material layer decreases, which may cause problems such as reduced battery capacity or increased resistance between negative electrode active materials.

[0690] <2-3-3. Composition, properties, and preparation methods of metal compound materials and negative electrodes using metal compound materials>

[0691] As a metal compound material that can be used as a negative electrode active material, it can be any material that can adsorb and release lithium, and can be a single metal or alloy that forms a lithium alloy, or a compound such as its oxide, carbide, nitride, silicide, sulfide, or phosphide, without any particular limitation. Examples of such metal compounds include compounds containing metals such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, and Zn. Among these, single metals or alloys that form lithium alloys are preferred, materials containing Group 13 or Group 14 metals / metalloids (i.e., other than carbon) are more preferred, single metals of silicon (Si), tin (Sn), or lead (Pb) (hereinafter, these three elements are also referred to as "specific metal elements") or alloys containing these atoms, or compounds of these metals (specific metal elements) are even more preferred, and single metals, alloys, and compounds of silicon, as well as single metals, alloys, and compounds of tin, are particularly preferred. These materials can be used alone, or two or more can be used in any combination and proportion.

[0692] Examples of negative electrode active materials having at least one atom selected from a specific metallic element include elemental metals of any specific metallic element, alloys formed from two or more specific metallic elements, alloys formed from one or more specific metallic elements and one or more other metallic elements, and compounds containing one or more specific metallic elements, or composite compounds such as oxides, carbides, nitrides, silicides, sulfides, and phosphides of such compounds. High battery capacity can be achieved by using these elemental metals, alloys, or metallic compounds as negative electrode active materials.

[0693] Furthermore, examples of compounds obtained by complexly combining the aforementioned composite compounds with various elements such as metallic elements, alloys, or non-metallic elements can also be cited. More specifically, for elements such as silicon and tin, alloys formed from these elements and metals that do not act as negative electrodes can be used. Additionally, for elements such as tin, complex compounds containing 5 to 6 elements can be used, obtained by combining metals other than tin and silicon that act as negative electrodes, metals that cannot act as negative electrodes, and non-metallic elements.

[0694] Among the aforementioned negative electrode active materials, considering the maximum capacity per unit mass when manufacturing a battery, elemental metals of any one specific metal element, alloys of two or more specific metal elements, oxides, carbides, nitrides, etc. of a specific metal element are preferred. In particular, considering the capacity per unit mass and the environmental burden, elemental silicon and tin, as well as their alloys, oxides, carbides, nitrides, etc., are preferred.

[0695] In addition, although the capacity per unit mass of the following compounds containing at least one of silicon and tin is lower than that of the use of elemental metals or alloys, they are preferred due to their excellent cycle characteristics.

[0696] • “an oxide of at least one of silicon and tin”, wherein the elemental ratio of at least one of silicon and tin to oxygen is generally 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and generally 1.5 or less, preferably 1.3 or less, more preferably 1.1 or less.

[0697] • "a nitride of at least one of silicon and tin", wherein the elemental ratio of at least one of silicon and tin to nitrogen is generally 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and generally 1.5 or less, preferably 1.3 or less, more preferably 1.1 or less.

[0698] • "Carbides of at least one of silicon and tin", wherein the elemental ratio of at least one of silicon and tin to carbon is generally 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and generally 1.5 or less, preferably 1.3 or less, more preferably 1.1 or less.

[0699] It should be noted that any one of the above-mentioned negative electrode active materials can be used alone, or two or more can be used in any combination and proportion.

[0700] The negative electrode in the non-aqueous electrolyte secondary battery of the present invention can be manufactured using any known method. Specifically, methods for manufacturing the negative electrode include, for example, adding a binder, conductive material, etc., to the aforementioned negative electrode active material, and then directly rolling the resulting material to form a sheet electrode; or manufacturing a particulate electrode by compression molding. However, a common method is to form a thin film layer (negative electrode active material layer) containing the aforementioned negative electrode active material on a negative electrode current collector (hereinafter also referred to as "negative electrode current collector") using methods such as coating, vapor deposition, sputtering, or plating. In this case, a binder, thickener, conductive material, solvent, etc., are added to the aforementioned negative electrode active material to form a slurry, which is then coated onto the negative electrode current collector and dried. The slurry is then pressed to achieve high density, thereby forming a negative electrode active material layer on the negative electrode current collector.

[0701] Materials that can be used as negative electrode current collectors include steel, copper alloys, nickel, nickel alloys, and stainless steel. Among these, copper foil is preferred due to its ease of processing into thin films and its cost considerations.

[0702] The thickness of the negative electrode current collector is typically 1 μm or more, preferably 5 μm or more, and typically 100 μm or less, preferably 50 μm or less. This is because if the thickness of the negative electrode current collector is too thick, the overall capacity of the battery may become too low; conversely, if it is too thin, it may cause operational difficulties.

[0703] It should be noted that, in order to improve the adhesion effect with the negative electrode active material layer formed on the surface, it is preferable to roughen the surface of these negative electrode current collectors beforehand. Examples of surface roughening methods include: sandblasting, calendering using rough-surfaced rollers, mechanical polishing using abrasive paper with adhering abrasive particles, grinding stones, diamond wheels, wire brushes with steel wires, etc., electrolytic polishing, and chemical polishing.

[0704] In addition, to reduce the mass of the negative electrode current collector and increase the energy density per unit mass of the battery, open-type negative electrode current collectors such as expanded alloys and perforated metals can be used. For this type of negative electrode current collector, its mass can be arbitrarily changed by altering its aperture ratio. Furthermore, when negative electrode active material layers are formed on both sides of this type of negative electrode current collector, the anchoring effect of the through-hole makes peeling of the negative electrode active material layer less likely. However, if the aperture ratio is too high, the contact area between the negative electrode active material layer and the negative electrode current collector will be smaller, which may actually reduce the adhesion strength.

[0705] The slurry used to form the negative electrode active material layer is usually made by adding binders, thickeners, etc., to the negative electrode material. It should be noted that the term "negative electrode material" in this specification refers to materials including both the negative electrode active material and conductive materials.

[0706] The content of negative electrode active material in the negative electrode material is typically 70% by mass or more, particularly preferably 75% by mass or more, and typically 97% by mass or less, particularly preferably 95% by mass or less. If the content of negative electrode active material is too low, the secondary battery using the obtained negative electrode tends to have insufficient capacity; if the content of negative electrode active material is too high, the strength of the obtained negative electrode tends to be insufficient due to the relatively insufficient content of binders, etc. It should be noted that when using two or more negative electrode active materials in combination, it is sufficient to ensure that the total amount of negative electrode active material meets the above-mentioned range.

[0707] Examples of conductive materials used for the negative electrode include metallic materials such as copper and nickel, and carbon materials such as graphite and carbon black. These conductive materials can be used individually or in any combination and proportion. In particular, carbon materials are preferred as they also function as active materials. The content of conductive material in the negative electrode material is typically 3% by mass or more, particularly preferably 5% by mass or more, and typically 30% by mass or less, particularly preferably 25% by mass or less. If the content of conductive material is too low, there is a tendency for insufficient conductivity; if the content of conductive material is too high, it will lead to a relative deficiency in the content of the negative electrode active material, thus tending to reduce battery capacity and strength. It should be noted that when using two or more conductive materials in combination, it is sufficient to ensure that the total amount of conductive material meets the above-mentioned range.

[0708] As a binder for the negative electrode, any material safe for the solvents and electrolytes used in electrode manufacturing can be used. Examples include: polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, etc. These binders can be used individually or in any combination and proportion. The binder content is typically 0.5 parts by mass or more, particularly preferably 1 part by mass or more, and typically 10 parts by mass or less, particularly preferably 8 parts by mass or less, relative to 100 parts by mass of the negative electrode material. If the binder content is too low, the resulting negative electrode tends to have insufficient strength; if too high, the content of the negative electrode active material will be relatively insufficient, thus tending to result in insufficient battery capacity and conductivity. It should be noted that when using two or more binders in combination, the total amount of binder only needs to meet the above-mentioned range.

[0709] Examples of thickeners used for the negative electrode include: carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These thickeners can be used individually or in combination or proportions of two or more. Thickeners should be used only as needed, but when using thickeners, the content of the thickener in the negative electrode active material layer is generally preferably in the range of 0.5% by mass or more and 5% by mass or less.

[0710] The slurry used to form the negative electrode active material layer can be prepared as follows: A conductive material, binder, and thickener, as needed, are mixed into the aforementioned negative electrode active material, and an aqueous solvent or an organic solvent is used as the dispersion medium to prepare the slurry. Water is typically used as the aqueous solvent, but solvents other than water, such as alcohols like ethanol and cyclic amides like N-methylpyrrolidone, can also be used in combination at a ratio of approximately 30% by mass or less relative to water. As for organic solvents, examples typically include cyclic amides like N-methylpyrrolidone, linear amides like N,N-dimethylformamide and N,N-dimethylacetamide, aromatic hydrocarbons like anisole, toluene, and xylene, and alcohols like butanol and cyclohexanol. Cyclic amides like N-methylpyrrolidone, linear amides like N,N-dimethylformamide and N,N-dimethylacetamide are preferred. It should be noted that any one of the above solvents can be used alone, or two or more can be used in any combination and proportion.

[0711] The viscosity of the slurry is not particularly limited as long as it is suitable for coating onto the current collector. It can be appropriately prepared by changing the amount of solvent used in the slurry preparation to achieve the desired coating viscosity.

[0712] The obtained slurry is coated onto the aforementioned negative electrode current collector and dried. Then, a negative electrode active material layer is formed by pressing. There are no particular limitations on the coating method; any known method can be used. There are also no particular limitations on the drying method; known methods such as natural drying, heat drying, and reduced pressure drying can be used.

[0713] There are no particular restrictions on the electrode structure when polarizing the negative electrode active material using the above method, but the density of the active material present on the current collector is preferably 1 g·cm³. -3 The above, and more preferably 1.2 g·cm -3 The above, and especially preferred, is 1.3 g·cm³. -3 The above, and preferably 2.2 g·cm³ -3 The following, and more preferably, is 2.1 g·cm⁻¹ -3 The following, and more preferably 2.0 g·cm -3 The following, particularly preferred, value is 1.9 g·cm³. -3 the following.

[0714] When the density of active material on the current collector exceeds the above range, it may cause damage to the active material particles, leading to an initial irreversible increase in capacity, or a deterioration in high-current-density charge-discharge characteristics due to decreased permeability of the non-aqueous electrolyte near the current collector / active material interface. Conversely, when the density is below the above range, it may lead to decreased conductivity between active materials, increased battery resistance, and decreased capacity per unit volume.

[0715] <2-3-4. Composition, properties, and preparation methods of lithium-containing metal composite oxide materials and negative electrodes using lithium-containing metal composite oxide materials>

[0716] As a lithium-containing metal composite oxide material that can be used as a negative electrode active material, there are no special restrictions as long as it can absorb and release lithium. However, lithium-containing composite metal oxide materials containing titanium are preferred, and composite oxides of lithium and titanium (hereinafter referred to as "lithium-titanium composite oxides") are particularly preferred. That is, when lithium-titanium composite oxides with a spinel structure are included and used in the negative electrode active material for non-aqueous electrolyte secondary batteries, the output resistance will be greatly reduced, and therefore it is particularly preferred.

[0717] In addition, it is preferred that the lithium and titanium in the lithium-titanium composite oxide are obtained by replacing the lithium and titanium with other metal elements, such as at least one element selected from Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb.

[0718] The above-mentioned metal oxide is a lithium-titanium composite oxide represented by general formula (3). In general formula (3), when 0.7≤x≤1.5, 1.5≤y≤2.3, and 0≤z≤1.6, the lithium ion structure is stable during doping / dedoping, and therefore is preferred.

[0719] Li x Ti y M z O4 (3)

[0720] [In general formula (3), M represents at least one element selected from Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb.]

[0721] In the composition shown in the above general formula (3), the structures (a), (b), and (c) below have a good balance of battery performance and are therefore particularly preferred.

[0722] (a) 1.2≤x≤1.4, 1.5≤y≤1.7, z=0

[0723] (b) 0.9≤x≤1.1, 1.9≤y≤2.1, z=0

[0724] (c) 0.7≤x≤0.9, 2.1≤y≤2.3, z=0

[0725] The particularly preferred representative composition of the above compounds is as follows: for (a), it is Li 4 / 3 Ti 5 / 3 O4; for (b), it is Li1Ti2O4; for (c), it is Li 4 / 5 Ti 11 / 5 O4. Additionally, for structures where Z≠0, examples include Li. 4 / 3Ti 4 / 3 Al 1 / 3 O4 is the preferred structure.

[0726] In addition to meeting the above requirements, the lithium-titanium composite oxide used as the negative electrode active material in this invention preferably also meets at least one of the physical properties and shape characteristics shown in (1) to (13) below, and particularly preferably meets two or more of (1) to (13) below simultaneously.

[0727] (1) BET specific surface area

[0728] The preferred BET specific surface area of ​​the lithium-titanium composite oxide used as the negative electrode active material, as determined by the BET method, is 0.5 m². 2 ·g -1 The above, and more preferably 0.7m 2 ·g -1 The above, and more preferably 1.0m 2 ·g -1 The above, and especially preferred, is 1.5m 2 ·g -1 The above, and preferably 200m 2 ·g -1 The following, or more preferably 100m 2 ·g -1 The following, and more preferably 50m 2 ·g -1 The following, particularly preferred, is 25m 2 ·g -1 the following.

[0729] If the BET specific surface area is below the above range, the reaction area in contact with the non-aqueous electrolyte phase will decrease when used as a negative electrode material, potentially leading to an increase in output resistance. On the other hand, exceeding the above range will result in an increase in the crystalline surface and end-face portions of the titanium-containing metal oxide, and may also induce crystal defects. With irreversible capacity becoming a significant factor, it may be difficult to obtain an ideal battery.

[0730] The specific surface area was determined using the BET method as follows: Using a surface area meter (fully automated surface area measuring device developed by Okura Risa), the sample was pre-dried for 15 minutes in a nitrogen stream at 350°C. Then, a nitrogen-helium mixed gas with the relative pressure of nitrogen to atmospheric pressure accurately adjusted to 0.3 was used. The specific surface area was measured using the nitrogen adsorption BET one-point method employed in the gas flow method. The specific surface area obtained using this method is defined as the BET specific surface area of ​​the lithium-titanium composite oxide in this invention.

[0731] (2) Volume-based average particle size

[0732] The volume-based average particle size of lithium-titanium composite oxides is defined by the average particle size (median particle size) obtained by laser diffraction / scattering method (for the case where primary particles agglomerate to form secondary particles, it is the secondary particle size).

[0733] The volume-based average particle size of the lithium titanium composite oxide is typically 0.1 μm or more, preferably 0.5 μm or more, more preferably 0.7 μm or more, and typically 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and particularly preferably 25 μm or less.

[0734] The volume-based average particle size was determined as follows: carbon powder was dispersed in a 0.2% by mass aqueous solution (10 mL) of the surfactant polyoxyethylene (20) sorbitan monolaurate, and the particle size was measured using a laser diffraction / scattering particle size analyzer (LA-700 manufactured by Horiba Corporation). The median particle size obtained by this determination was defined as the volume-based average particle size of the carbonaceous material in this invention.

[0735] When the volume average particle size of lithium titanium composite oxide is below the above range, a large amount of binder is required during electrode fabrication, which may result in a reduction in battery capacity. Furthermore, when the particle size exceeds the above range, uneven coating surfaces are easily formed during electrode plate fabrication, which may be undesirable in the battery manufacturing process.

[0736] (3) Average primary particle size

[0737] When secondary particles are formed by the aggregation of primary particles, the average primary particle size of the lithium titanium composite oxide is typically 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, particularly preferably 0.2 μm or more, and typically 2 μm or less, preferably 1.6 μm or less, more preferably 1.3 μm or less, particularly preferably 1 μm or less. When the volume-based average primary particle size exceeds the above range, it is difficult to form spherical secondary particles, which may adversely affect the powder filling properties or lead to a significant decrease in specific surface area, thus increasing the possibility of reduced battery performance such as output characteristics. In addition, when it is below the above range, since crystallization is usually incomplete, it may lead to reduced secondary battery performance such as poor charge-discharge reversibility.

[0738] It should be noted that the primary particle size is determined by observation using a scanning electron microscope (SEM). Specifically, in an image at a magnification where particles can be identified, for example, 10,000 to 100,000 times magnification, for any 50 primary particles, the longest intercept of the left and right boundary lines of the primary particles relative to the horizontal straight line is calculated, and then the average value is taken to obtain the primary particle size.

[0739] (4) Shape

[0740] The particle shape of lithium titanium composite oxide can be blocky, polyhedral, spherical, ellipsoidal, plate-like, needle-like, columnar, etc., which are commonly used in the past. Among them, it is preferred that the secondary particles are formed by the aggregation of primary particles and that the shape of the secondary particles is spherical or ellipsoidal.

[0741] Typically, in electrochemical devices, the active material in the electrodes expands and contracts during charging and discharging. This stress can easily lead to damage to the active material and deterioration such as loss of conductivity. Therefore, it is preferable for primary particles to agglomerate and form secondary particles compared to single-particle active material. This is because the expansion and contraction stress is mitigated when secondary particles are formed, preventing deterioration.

[0742] Furthermore, spherical or ellipsoidal particles are preferred over plate-shaped equiaxed particles because spherical or ellipsoidal particles have weaker orientation during electrode forming, resulting in less expansion and contraction of the electrode during charging and discharging. In addition, uniform mixing can be easily achieved when mixing with conductive materials during electrode fabrication.

[0743] (5) Tap density

[0744] The tap density of the lithium-titanium composite oxide is preferably 0.05 g·cm³. -3 The above, and more preferably 0.1 g·cm -3 The above, and more preferably 0.2 g·cm -3The above, and especially preferred, is 0.4 g·cm³. -3 The above, and preferably 2.8 g·cm³ -3 The following, and more preferably, is 2.4 g·cm³. -3 The following, especially preferred, is 2g·cm -3 The following applies. When the tap density is below the above range, it is difficult to increase the packing density when used as a negative electrode, and the contact area between particles decreases, which may lead to increased interparticle resistance and increased output resistance. Furthermore, when the tap density exceeds the above range, the interparticle gaps in the electrode become too small, reducing the flow path of the non-aqueous electrolyte, which may also lead to increased output resistance.

[0745] The tap density was determined as follows: the sample was passed through a sieve with a mesh size of 300 μm and then dropped into a 20 cm sieve. 3 In a tapped container, after the sample has filled to the top surface of the container, it is vibrated 1000 times with a stroke length of 10 mm using a powder density meter (e.g., a Tap densor manufactured by Seishin Corporation). The density is calculated from the volume and mass of the sample at this point. The tapped density calculated using this measurement is defined as the tapped density of the lithium titanium composite oxide in this invention.

[0746] (6) Circularity

[0747] When measuring the roundness of lithium titanium composite oxides, it is preferable that the roundness is within the following range. Roundness is defined as: "Roundness = (circumference of an equivalent circle with the same area as the particle projection shape) / (actual circumference of the particle projection shape)", and when the roundness is 1, it is theoretically a perfect sphere.

[0748] The closer the sphericity of the lithium titanium composite oxide is to 1, the better. It is typically 0.10 or higher, preferably 0.80 or higher, more preferably 0.85 or higher, and particularly preferably 0.90 or higher. Higher sphericity results in superior high-current-density charge-discharge characteristics. Therefore, when the sphericity is below the above range, the filling capacity of the negative electrode active material decreases, and the interparticle impedance increases, which may lead to a decrease in short-term high-current-density charge-discharge characteristics.

[0749] Circularity was determined using a flow cytometry particle image analysis system (FPIA, manufactured by Sysmex). Approximately 0.2 g of sample was dispersed in a 0.2% by mass aqueous solution (approximately 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant. The sample was irradiated with ultrasound at 28 kHz and an output power of 60 W for 1 minute. The detection range was specified as 0.6–400 μm, and particles with a diameter in the range of 3–40 μm were measured. The circularity determined using this method is defined as the circularity of the lithium-titanium composite oxide in this invention.

[0750] (7) Aspect Ratio

[0751] The aspect ratio of lithium-titanium composite oxides is typically 1 or higher, and typically 5 or lower, preferably 4 or lower, more preferably 3 or lower, and particularly preferably 2 or lower. When the aspect ratio exceeds the above range, streaks may occur during electrodeposition, making it impossible to obtain a uniform coating surface, resulting in a decrease in short-time high-current-density charge-discharge characteristics. It should be noted that the lower limit of the above range is the theoretical lower limit of the aspect ratio of lithium-titanium composite oxides.

[0752] The aspect ratio was determined by magnifying the particles of the lithium-titanium composite oxide using a scanning electron microscope. Fifty arbitrary particles were selected and fixed on a metal end face less than 50 μm thick. For each particle, the stage on which the sample was fixed was rotated and tilted, and the longest diameter A and the shortest diameter B perpendicular to it were measured during three-dimensional observation. The average value of A / B was then calculated. The aspect ratio (A / B) determined using this method is defined as the aspect ratio of the lithium-titanium composite oxide in this invention.

[0753] (8) Method for manufacturing negative electrode active material

[0754] There are no special limitations on the manufacturing method of lithium-titanium composite oxide without exceeding the scope of the present invention. Several methods can be listed. As for the manufacturing method of inorganic compound, conventional methods can be used.

[0755] For example, one method can be described as uniformly mixing titanium raw materials such as titanium oxide, raw materials of other elements used as needed, and Li sources such as LiOH, Li2CO3, and LiNO3, and then firing them at high temperature to obtain active materials.

[0756] In particular, various methods can be considered to produce spherical or ellipsoidal active substances. As one example, the following method can be listed: titanium raw materials such as titanium oxide, and other raw materials of elements used as needed, are dissolved or pulverized and dispersed in a solvent such as water, while stirring and adjusting the pH to produce and recover spherical precursors. After drying them as needed, Li sources such as LiOH, Li2CO3, and LiNO3 are added, and the mixture is calcined at a high temperature to obtain the active substance.

[0757] In addition, as another example, the following method can be listed: titanium raw materials such as titanium oxide, and other raw materials of other elements used as needed, are dissolved or pulverized and dispersed in solvents such as water, and dried and shaped into spherical or ellipsoidal precursors using a spray dryer, and then Li sources such as LiOH, Li2CO3, and LiNO3 are added to them and calcined at high temperature to obtain active substances.

[0758] As another method, the following methods can also be listed: dissolve or pulverize titanium raw materials such as titanium oxide, Li sources such as LiOH, Li2CO3, LiNO3, and other raw materials of other elements used as needed in a solvent such as water, dry them using a spray dryer or the like to form a spherical or ellipsoidal precursor, and then calcine the precursor at a high temperature to obtain the active material.

[0759] In addition, during the above process, elements other than Ti, such as Al, Mn, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, C, Si, Sn, and Ag, can be present in the structure of a titanium-containing metal oxide and / or in a form similar to a titanium-containing oxide. The presence of these elements allows for control over the battery's operating voltage and capacity.

[0760] (9) Electrode fabrication

[0761] Electrodes can be manufactured using any known method. For example, an electrode can be formed by adding binders, solvents, thickeners, conductive materials, fillers, etc., to the negative electrode active material to make a slurry, coating the slurry onto a current collector, drying it, and then pressing it.

[0762] In the stage before the non-aqueous electrolyte injection process, the thickness of the negative electrode active material layer on each side of the battery is typically 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and its upper limit is 150 μm or less, preferably 120 μm or less, more preferably 100 μm or less.

[0763] Beyond this range, the non-aqueous electrolyte has difficulty penetrating to the vicinity of the current collector interface, which may lead to a decrease in high-current-density charge-discharge characteristics. Conversely, below this range, the volume ratio of the current collector to the negative electrode active material increases, potentially reducing battery capacity. Furthermore, the negative electrode active material can be rolled to form sheet electrodes or compressed to form granular electrodes.

[0764] (10) Current collector

[0765] As the current collector that can maintain the active material of the negative electrode, any known current collector can be used. Examples of current collectors for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Among these, copper is particularly preferred from the perspective of ease of processing and cost.

[0766] Furthermore, when the current collector is made of a metallic material, examples of suitable shapes include metal foil, metal cylinder, metal coil, metal plate, metal film, expanded alloy, perforated metal, and foamed metal. Among these, a metal foil containing at least one of copper (Cu) and aluminum (Al) is preferred, copper foil or aluminum foil is more preferred, and rolled copper foil obtained by a rolling process and electrolytic copper foil obtained by an electrolytic process are even more preferred; any of these can be used as a current collector.

[0767] Furthermore, when the thickness of the copper foil is less than 25 μm, copper alloys with higher strength than pure copper (phosphor bronze, titanium copper, Cosun alloy, Cu-Cr-Zr alloy, etc.) can be used. In addition, since aluminum foil is lightweight, its use as a current collector can reduce the battery weight, making it a preferred choice.

[0768] In the current collector formed by the copper foil produced by the rolling process, the copper crystals are arranged along the rolling direction. Therefore, even if the negative electrode is tightly rolled and rolled into an acute angle, it is not easy to break, which is suitable for small cylindrical batteries.

[0769] Electrolytic copper foil can be obtained by, for example, immersing a metal cylinder in a non-aqueous electrolyte containing dissolved copper ions, rotating the cylinder and passing an electric current through it to cause copper to deposit on the surface of the cylinder, which is then peeled off to obtain electrolytic copper foil. Alternatively, copper can be deposited on the surface of the aforementioned rolled copper foil using electrolysis. Roughening or surface treatments (e.g., chromate treatment with a thickness of approximately several nm to 1 μm, substrate treatment with Ti, etc.) can also be applied to one or both sides of the copper foil.

[0770] Furthermore, the current collector substrate preferably has the following physical properties.

[0771] (10-1) Average surface roughness (Ra)

[0772] There are no particular limitations on the average surface roughness (Ra) of the active material thin film formation surface of the current collector substrate as specified in the method described in JISB0601-1994, but it is generally 0.01 μm or more, preferably 0.03 μm or more, and generally 1.5 μm or less, preferably 1.3 μm or less, and more preferably 1.0 μm or less.

[0773] When the average surface roughness (Ra) of the current collector substrate is within the above-mentioned range, good charge-discharge cycle characteristics can be expected. Furthermore, the increased interface area with the active material film improves the adhesion between the substrate and the negative electrode active material film. It should be noted that there is no particular upper limit to the average surface roughness (Ra), but when the average surface roughness (Ra) exceeds 1.5 μm, it is generally difficult to obtain a foil of practical thickness for battery fabrication. Therefore, current collector substrates with an average surface roughness (Ra) of 1.5 μm or less are typically used.

[0774] (10-2) Tensile strength

[0775] The tensile strength is the value obtained by dividing the maximum tensile force required for the test piece to break by the cross-sectional area of ​​the test piece. The tensile strength in this invention is determined using the same apparatus and method as described in JIS Z2241 (Metallic Materials, Tensile Testing).

[0776] There are no special limitations on the tensile strength of the current collector substrate, but it is typically 50 N·mm. -2 The above, preferably, is 100 N·mm. -2 The above, and more preferably, is 150 N·mm. -2 The above. A higher tensile strength value is preferred, but considering industrial availability, 1000 N·mm is generally preferred. -2 the following.

[0777] If the current collector substrate has high tensile strength, it can suppress cracking of the current collector substrate caused by the expansion / contraction of the active material film during charging / discharging, thus obtaining good cycle characteristics.

[0778] (10-3) 0.2% yield strength

[0779] The 0.2% yield strength refers to the load required to produce 0.2% plastic (permanent) strain, after which, even after the load is removed, 0.2% deformation will still be maintained. The 0.2% yield strength is determined using the same apparatus and method as the tensile strength.

[0780] There are no particular limitations on the 0.2% yield strength of the current collector substrate, but it is typically 30 N·mm. -2 The above, preferably, is 100 N·mm. -2 The above, and especially preferred, is 150 N·mm. -2 The above. A higher yield strength value of 0.2% is preferred, but considering industrial availability, 900 N·mm is generally preferred. -2 the following.

[0781] If the current collector substrate has a high yield strength of 0.2%, the plastic deformation of the current collector substrate caused by the expansion / contraction of the active material film during charging / discharging can be suppressed, and good cycle characteristics can be obtained.

[0782] (10-4) Thickness of the collector

[0783] The current collector can have any thickness, but it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually less than 1 mm, preferably less than 100 μm, more preferably less than 50 μm.

[0784] When the thickness of the metal coating is less than 1 μm, the strength decreases, which may make coating difficult. In addition, when the thickness exceeds 100 μm, it may cause deformation of the electrode shape, such as when it is wound.

[0785] It should be noted that metal films can also be in the form of a mesh.

[0786] (11) The thickness ratio of the current collector to the active material layer

[0787] There is no particular limitation on the ratio of the thickness of the current collector to the thickness of the active material layer, but the value of "(thickness of the active material layer on one side before the non-aqueous electrolyte is injected) / (thickness of the current collector)" is usually 150 or less, preferably 20 or less, more preferably 10 or less, and usually 0.1 or more, preferably 0.4 or more, more preferably 1 or more.

[0788] When the thickness ratio of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heating during high current density charging and discharging. Conversely, when the thickness ratio is below the above range, the volume ratio of the current collector to the negative electrode active material increases, which may lead to a reduction in battery capacity.

[0789] (12) Electrode density

[0790] There are no particular restrictions on the electrode structure when polarizing the negative electrode active material, but the density of the active material present on the current collector is preferably 1 g·cm³. -3 The above, and more preferably 1.2 g·cm -3 The above, and more preferably 1.3 g·cm -3 The above, and especially preferred, is 1.5 g·cm³. -3 The above, and preferably 3g·cm -3 The following, and more preferably, is 2.5 g·cm³. -3 The following, and more preferably, is 2.2 g·cm³. -3 The following, especially preferred, is 2g·cm -3 the following.

[0791] When the density of active material on the current collector exceeds the above range, the adhesion between the current collector and the negative electrode active material weakens, potentially causing the electrode to detach from the active material. Conversely, when the density is below the above range, it may lead to decreased conductivity between the negative electrode active materials, resulting in increased battery resistance.

[0792] (13) Adhesive

[0793] As a binder for bonding negative electrode active materials, any material that is stable relative to non-aqueous electrolytes and solvents used in electrode manufacturing is acceptable, without any special restrictions.

[0794] Specific examples include: resin-like polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (nitrile rubber), and ethylene-propylene rubber; thermoplastic elastomers such as styrene-butadiene-styrene block copolymers and their hydrogenated products; thermoplastic elastomers such as EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymers and their hydrogenated products; soft resin-like polymers such as syndiotactic 1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, and propylene-α-olefin copolymer; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymer; and polymer compositions with ionic conductivity of alkali metal ions (especially lithium ions). These adhesives can be used alone or in any combination and proportion of two or more.

[0795] As a solvent used to form the slurry, any solvent that can dissolve or disperse the negative electrode active material, binder, and thickener and conductive material as needed can be used. There are no special restrictions on its type; any solvent among aqueous solvents and organic solvents can be used.

[0796] Examples of aqueous solvents include water and alcohols; examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphoramide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, and hexane. In particular, when using aqueous solvents, dispersants can be added simultaneously with the aforementioned thickeners, and latex such as SBR can be used for slurry preparation. It should be noted that these solvents can be used individually or in any combination and proportion.

[0797] The proportion of the binder to the negative electrode active material is typically 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and typically 20% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 8% by mass or less.

[0798] When the ratio of binder to negative electrode active material exceeds the above range, it may lead to an increase in the proportion of binder components that do not contribute to battery capacity, resulting in a decrease in battery capacity. Conversely, when the ratio is below the above range, it may lead to a decrease in the strength of the negative electrode, which is not preferable in the battery manufacturing process.

[0799] In particular, when the main component contains a rubber-like polymer represented by SBR, the proportion of the adhesive relative to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less.

[0800] Furthermore, when the main component contains fluorinated polymers such as polyvinylidene fluoride, its proportion relative to the active substance is 1% or more by mass, preferably 2% or more by mass, more preferably 3% or more by mass, and usually 15% or less by mass, preferably 10% or less by mass, more preferably 8% or less by mass.

[0801] Thickeners are commonly used to adjust the viscosity of slurries. There are no particular limitations on thickeners; examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts. These thickeners can be used individually or in any combination and proportion.

[0802] Furthermore, when using a thickener, the proportion of the thickener relative to the negative electrode active material is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and typically 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. When the proportion of the thickener relative to the negative electrode active material is lower than the above range, it may lead to a significant decrease in coatability. Additionally, when it exceeds the above range, the proportion of active material in the negative electrode active material layer decreases, which may cause problems such as reduced battery capacity or increased resistance between negative electrode active materials.

[0803] <2-4 Positive Electrode>

[0804] The positive electrode is an electrode with a layer of positive active material on the current collector. The following is an explanation of the positive active material.

[0805] <2-4-1 Positive Electrode Active Material>

[0806] The following section explains the positive electrode active material used in the positive electrode.

[0807] (1) Composition

[0808] As a positive electrode active material, there are no particular restrictions on any material that can electrochemically adsorb and release lithium ions; preferred materials include, for example, those containing lithium and at least one transition metal. Specific examples include lithium transition metal composite oxides and lithium transition metal phosphate compounds.

[0809] The preferred transition metals for lithium transition metal composite oxides are V, Ti, Cr, Mn, Fe, Co, Ni, and Cu. Specific examples include lithium-cobalt composite oxides such as LiCoO2, lithium-manganese composite oxides such as LiMnO2, LiMn2O4, and Li2MnO4, and lithium-nickel composite oxides such as LiNiO2. Furthermore, composite oxides obtained by replacing a portion of the main transition metal atoms in the aforementioned lithium transition metal composite oxides with other metals such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Si can be cited as examples. Specific examples include lithium-cobalt-nickel composite oxides, lithium-cobalt-manganese composite oxides, lithium-nickel-manganese composite oxides, and lithium-nickel-cobalt-manganese composite oxides.

[0810] Specific examples of composite oxides obtained through substitution include: Li 1+a Ni 0.5 Mn 0.5 O2, Li 1+ a Ni 0.8 Co 0.2 O2, Li 1+a Ni 0.85 Co 0.10 Al 0.05 O2, Li 1+a Ni 0.33 Co 0.33 Mn 0.33 O2, Li 1+a Ni 0.45 Co 0.45 Mn 0.1 O2, Li 1+ a Mn 1.8 Al 0.2 O4, Li 1+a Mn 1.5 Ni 0.5 O4、xLi2MnO3･(1-x)Li 1+a MO2 (M = transition metal) etc. (a = 0 < a ≤ 3.0).

[0811] Lithium-containing transition metal phosphate compounds can be represented as LixMPO4 (M = an element selected from transition metals of group 4 to group 11 of period 4 in the periodic table, where x is 0 < x < 1.2). The transition metal (M) is preferably selected from at least one element chosen from V, Ti, Cr, Mg, Zn, Ca, Cd, Sr, Ba, Co, Ni, Fe, Mn, and Cu, and more preferably from at least one element chosen from Co, Ni, Fe, and Mn. Examples include iron phosphates such as LiFePO4, Li3Fe2(PO4)3, and LiFeP2O7; cobalt phosphates such as LiCoPO4; manganese phosphates such as LiMnPO4; and nickel phosphates such as LiNiPO4. These lithium transition metal phosphate compounds are obtained by replacing a portion of the main transition metal atom with other metals such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, and Si. Among them, lithium-manganese composite oxides such as LiMnO2, LiMn2O4, and Li2MnO4, as well as iron phosphates such as LiFePO4, Li3Fe2(PO4)3, and LiFeP2O7, are preferred because they are less prone to metal leaching at high temperatures and under charging conditions, and are also inexpensive.

[0812] It should be noted that the phrase "based on LixMPO4" includes not only the composition expressed by its formula, but also the composition obtained by replacing a portion of Fe and other sites in the crystal structure with other elements. Furthermore, it includes not only the stoichiometric composition but also non-stoichiometric compositions such as those with elemental deficiencies. The other elements used for substitution are preferably Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Si. When the above-mentioned substitutions are performed, the amounts are preferably 0.1 mol% or more and 5 mol% or less, more preferably 0.2 mol% or more and 2.5 mol% or less.

[0813] The above-mentioned positive electrode active materials can be used alone or in combination of two or more.

[0814] (2) Surface coating

[0815] Alternatively, a substance with a different composition from the main body of the positive electrode active material (hereinafter appropriately referred to as "surface-attached substance") can be used, which is attached to the surface of the aforementioned positive electrode active material. Examples of surface-attached substances include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; and carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate.

[0816] These surface-adhering substances can be attached to the surface of the positive electrode active material by the following methods: for example, dissolving or suspending the surface-adhering substance in a solvent to impregnate it in the positive electrode active material, and then drying it; dissolving or suspending the surface-adhering substance precursor in a solvent to impregnate it in the positive electrode active material, and then reacting it by heating or the like; adding the surface-adhering substance to the positive electrode active material precursor while simultaneously calcining it; and so on.

[0817] The mass of the surface-attached material adhering to the surface of the positive electrode active material is typically 0.1 ppm or more, preferably 1 ppm or more, more preferably 10 ppm or more, and typically 20% or less, preferably 10% or less, more preferably 5% or less, relative to the mass of the positive electrode active material.

[0818] Utilizing surface-attached substances can suppress the oxidation reaction of non-aqueous electrolytes on the surface of the positive electrode active material, thereby improving battery life. However, if the amount of attached material is below the aforementioned range, its effect cannot be fully realized. Furthermore, exceeding the aforementioned range can hinder the entry and exit of lithium ions, potentially leading to increased resistance. Therefore, the aforementioned range is preferred.

[0819] (3) Shape

[0820] The shape of the positive electrode active material particles can be blocky, polyhedral, spherical, ellipsoidal, plate-like, needle-like, columnar, etc., which are commonly used in the past. Among them, it is preferred that the secondary particles are formed by the aggregation of primary particles and that the shape of the secondary particles is spherical or ellipsoidal.

[0821] Typically, in electrochemical devices, the active material in the electrodes expands and contracts during charging and discharging. This stress can easily lead to damage to the active material and deterioration such as loss of conductivity. Therefore, it is preferable for primary particles to agglomerate and form secondary particles compared to single-particle active material. This is because the expansion and contraction stress is mitigated when secondary particles are formed, preventing deterioration.

[0822] Furthermore, spherical or ellipsoidal particles are preferred over plate-shaped equiaxed particles because spherical or ellipsoidal particles have weaker orientation during electrode forming, resulting in less expansion and contraction of the electrode during charging and discharging. In addition, uniform mixing can be easily achieved when mixing with conductive materials during electrode fabrication.

[0823] (4) Tap density

[0824] The tap density of the positive electrode active material is typically 0.4 g·cm³. -3 The above, preferably 0.6 g·cm -3 The above, and more preferably 0.8 g·cm -3The above, and especially preferred, is 1.0 g·cm³. -3 The above, and usually 4.0 g·cm³ -3 The following, preferably 3.8 g·cm -3 the following.

[0825] By using metal composite oxide powders with high tap density, a high-density positive electrode active material layer can be formed. Therefore, when the tap density of the positive electrode active material is below the aforementioned range, the amount of dispersion medium required to form the positive electrode active material layer increases, as does the necessary amount of conductive material and binder. This limits the filling rate of the positive electrode active material in the positive electrode active material layer, potentially limiting battery capacity. Furthermore, a higher tap density is generally preferred, with no particular upper limit. However, below the aforementioned range, the diffusion rate of lithium ions within the positive electrode active material layer, using a non-aqueous electrolyte as the medium, becomes the primary determining factor, potentially leading to a decrease in load characteristics.

[0826] The tap density was determined as follows: the sample was passed through a sieve with a mesh size of 300 μm and then dropped into a 20 cm sieve. 3 In a tapped container, after the sample has filled the container's volume, it is vibrated 1000 times with a stroke length of 10 mm using a powder density meter (e.g., a Tap densor manufactured by Seishin Corporation). The density is calculated from the volume at that point and the mass of the sample. The tap density calculated using this measurement is defined as the tap density of the positive electrode active material in this invention.

[0827] (5) Median particle size d50

[0828] The median particle size d50 of the positive electrode active material (which is the secondary particle size when primary particles agglomerate to form secondary particles) can also be measured using a laser diffraction / scattering particle size distribution measuring device.

[0829] The median particle size d50 is typically 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, particularly preferably 3 μm or more, and typically 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less, particularly preferably 15 μm or less. When the median particle size d50 is below the above range, it may be impossible to obtain a product with high bulk density. When it exceeds the above range, since the diffusion of lithium within the particles takes time, it may lead to a decrease in battery characteristics, or the formation of streaks or other issues when manufacturing the battery cathode, i.e., when the active material, conductive material, binder, etc., are made into a slurry using a solvent and coated into a thin film.

[0830] It should be noted that the filling properties of the cathode can be further improved by mixing two or more cathode active materials with different median particle sizes d50 in any proportion.

[0831] The median particle size d50 can be determined as follows: using a 0.1% (w / w) sodium hexametaphosphate aqueous solution as the dispersion medium, and using a Horiba Seisakusho LA-920 particle size analyzer, after ultrasonic dispersion for 5 minutes, the refractive index is set to 1.24 for measurement.

[0832] (6) Average primary particle size

[0833] When primary particles agglomerate to form secondary particles, the average primary particle size of the positive electrode active material is typically 0.03 μm or more, preferably 0.05 μm or more, more preferably 0.08 μm or more, particularly preferably 0.1 μm or more, and typically 5 μm or less, preferably 4 μm or less, more preferably 3 μm or less, particularly preferably 2 μm or less. When the particle size exceeds these ranges, it becomes difficult to form spherical secondary particles, which may adversely affect powder filling properties or lead to a significant decrease in specific surface area, thus increasing the likelihood of reduced battery performance, such as output characteristics. Furthermore, when the particle size is below these ranges, incomplete crystallization may occur, potentially leading to poor charge-discharge reversibility and reduced secondary battery performance.

[0834] It should be noted that the average primary particle size was determined by observation using a scanning electron microscope (SEM). Specifically, in a photograph at 10,000x magnification, for any 50 primary particles, the longest intercept of the left and right boundary lines of the primary particles relative to the horizontal straight line was calculated, and then the average value was taken to obtain the primary particle size.

[0835] (7) BET specific surface area

[0836] The BET specific surface area of ​​the positive electrode active material, as determined by the BET method, is typically 0.1 m². 2 ·g -1 The above, preferably 0.2m 2 ·g -1 The above, and more preferably 0.3m 2 ·g -1 Above, and usually 50m 2 ·g -1 The following, preferably 40m 2 ·g -1 The following, or more preferably 30m 2 ·g -1 Below are some points. When the BET specific surface area is below the range mentioned above, it can easily lead to a decrease in battery performance. Additionally, when it exceeds the range, the tap density is difficult to increase, which may result in reduced coating properties during the formation of the positive electrode active material.

[0837] The BET specific surface area was measured using a surface area meter (a fully automated surface area measuring device manufactured by Riken Okura). The sample was pre-dried for 30 minutes in a nitrogen stream at 150°C. Then, a nitrogen-helium mixture was used, with the relative pressure of nitrogen to atmospheric pressure precisely adjusted to 0.3. The BET specific surface area was measured using the nitrogen adsorption BET one-point method employed in the gas flow method. The specific surface area obtained using this measurement is defined as the BET specific surface area of ​​the anolyte active material in this invention.

[0838] (8) Method for manufacturing positive electrode active material

[0839] There are no particular limitations on the method of manufacturing the positive electrode active material without departing from the essential points of this invention. Several methods can be listed. As for the method of manufacturing inorganic compounds, conventional methods can be used.

[0840] In particular, various methods can be considered to produce spherical or ellipsoidal active substances. One example is the following method: Transition metal precursors such as nitrates and sulfates, and other elemental precursors used as needed, are dissolved or pulverized and dispersed in a solvent such as water. The pH is adjusted while stirring to produce and recover spherical precursors. After drying as needed, Li sources such as LiOH, Li₂CO₃, and LiNO₃ are added, and the mixture is calcined at high temperature to obtain the active substance.

[0841] Another example of a method is as follows: Transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, and oxides, and other raw materials of other elements used as needed, are dissolved or pulverized and dispersed in a solvent such as water, and dried and shaped using a spray dryer to form a spherical or ellipsoidal precursor. Then, Li sources such as LiOH, Li2CO3, and LiNO3 are added to it, and it is calcined at a high temperature to obtain an active substance.

[0842] In addition, as another example, the following method can be listed: Transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, oxides, etc., Li sources such as LiOH, Li2CO3, LiNO3, and other raw materials of other elements used as needed are dissolved or pulverized and dispersed in solvents such as water, dried and shaped using a spray dryer, etc., to form a spherical or ellipsoidal precursor, and then the precursor is calcined at high temperature to obtain the active material.

[0843] <2-4-2 Electrode Structure and Fabrication Method>

[0844] The following describes the structure and manufacturing method of the positive electrode used in this invention.

[0845] (1) Method for manufacturing the positive electrode

[0846] The positive electrode can be fabricated by forming a layer of positive electrode active material containing positive electrode active material particles and a binder on a current collector. The positive electrode using the positive electrode active material can be manufactured using any known method. Specifically, the positive electrode active material, binder, conductive material, and thickener (if desired) can be dry-mixed and formed into a sheet, which is then pressed onto the positive electrode current collector. Alternatively, these materials can be dissolved or dispersed in a liquid medium to form a slurry, which is then coated onto the positive electrode current collector and dried, thereby forming a layer of positive electrode active material on the current collector, thus obtaining the positive electrode.

[0847] The content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. Furthermore, its upper limit is preferably 99% by mass or less, more preferably 98% by mass or less. A low content of the positive electrode active material in the positive electrode active material layer may lead to insufficient capacitance. Conversely, if the content is too high, it may lead to insufficient strength of the positive electrode. It should be noted that the positive electrode active material powder in this invention can be used alone, or two or more powders with different compositions or different powder properties can be used in any combination and proportion.

[0848] (2) Conductive materials

[0849] As a conductive material, any known conductive material can be used. Specific examples include metallic materials such as copper and nickel; graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. It should be noted that the above-mentioned conductive materials can be used alone, or two or more can be combined in any combination and proportion.

[0850] The conductive material used typically comprises 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and typically 50% by mass or less, preferably 30% by mass or less, more preferably 15% by mass or less. Content below these ranges may result in insufficient conductivity. Furthermore, content exceeding these ranges may lead to a reduction in battery capacity.

[0851] (3) Adhesive

[0852] There are no special restrictions on the binder used when manufacturing the positive electrode active material layer, as long as it is a material that is stable relative to the non-aqueous electrolyte or the solvent used when manufacturing the electrode.

[0853] When using a coating method, any material that can be dissolved or dispersed in the liquid medium used in electrode manufacturing is acceptable. Specific examples include: resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamides, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), NBR (nitrile rubber), fluororubber, isoprene rubber, butadiene rubber, and ethylene propylene rubber; styrene-butadiene-styrene block copolymers or their hydrogenated products; and EPDM (ethylene-propylene-dimethyl ether...). Thermoplastic elastomers such as terpolymers of olefins, styrene-ethylene-butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers, or their hydrogenated products; soft resinous polymers such as syndiotactic 1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions with ionic conductivity of alkali metal ions (especially lithium ions). It should be noted that one of the above substances may be used alone, or two or more may be used in any combination and proportion.

[0854] The proportion of binder in the positive electrode active material layer is typically 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and typically 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, and particularly preferably 8% by mass or less. When the proportion of binder is below the above range, the positive electrode active material cannot be adequately maintained, which may lead to insufficient mechanical strength of the positive electrode and degradation of battery performance such as cycle characteristics. In addition, when it exceeds the above range, it may cause a decrease in battery capacity or conductivity.

[0855] (4) Liquid medium

[0856] As a liquid medium for forming the slurry, any solvent that can dissolve or disperse the positive electrode active material, conductive material, binder, and thickener used as needed is acceptable, and there are no special restrictions on its type. Any solvent among aqueous solvents and organic solvents can be used.

[0857] Examples of aqueous media include water and mixtures of alcohol and water. Examples of organic media include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and polar aprotic solvents such as hexamethylphosphoramide and dimethyl sulfoxide. It should be noted that one of the above solvents can be used alone, or two or more can be used in any combination and proportion.

[0858] (5) Thickener

[0859] When using an aqueous medium as the liquid medium for forming the slurry, it is preferable to use a thickener and a latex such as styrene-butadiene rubber (SBR) for slurry preparation. Thickeners are typically used to adjust the viscosity of the slurry.

[0860] As a thickener, there are no limitations without significantly restricting the effects of the present invention. Specific examples include: carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts. One of the above thickeners can be used alone, or two or more can be used in any combination and proportion.

[0861] Furthermore, when using a thickener, the ratio of the thickener to the active material is typically 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and typically 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Below these ranges, the coatability may be significantly reduced. Furthermore, exceeding these ranges reduces the proportion of the active material in the positive electrode active material layer, potentially leading to reduced battery capacity or increased resistance between the positive electrode active materials.

[0862] (6) Compaction

[0863] To increase the filling density of the positive electrode active material, it is preferable to use a manual press or roller press to compact the positive electrode active material layer obtained after coating and drying. The preferred density of the positive electrode active material layer is 1 g·cm³. -3 The above, and more preferably 1.5 g·cm -3 The above, especially preferred, is 2g·cm -3 The above, and preferably 4g·cm -3 The following, and more preferably, is 3.5 g·cm³. -3 The following, especially preferred, is 3g·cm -3 the following.

[0864] When the density of the positive electrode active material layer exceeds the above range, it may lead to a decrease in the permeability of the non-aqueous electrolyte near the current collector / active material interface, especially a reduction in charge-discharge characteristics at high current densities. Furthermore, exceeding the above range may result in a decrease in the conductivity between active materials, leading to an increase in battery resistance.

[0865] (7) Current collector

[0866] There are no special restrictions on the material used for the positive current collector; any known material can be used. Specific examples include metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbonaceous materials such as carbon cloth and carbon paper. Among these, metallic materials are preferred, with aluminum being particularly preferred.

[0867] Regarding the shape of the current collector, for metallic materials, examples include metal foil, metal cylinder, metal coil, metal plate, metal film, expanded alloy, perforated metal, and foamed metal; for carbonaceous materials, examples include carbon plate, carbon film, and carbon cylinder. Metal film is preferred. It should be noted that the film can also be appropriately formed into a mesh.

[0868] The current collector can have any thickness, but is typically 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and typically 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. A film thickness less than the above range may result in insufficient strength as a current collector. Furthermore, a film thickness exceeding the above range may impair operability.

[0869] There is no particular limitation on the thickness ratio of the current collector to the positive electrode active material layer, but the value of (thickness of the positive electrode active material layer on one side before electrolyte injection) / (thickness of the current collector) is preferably 20 or less, more preferably 15 or less, and most preferably 10 or less, with a lower limit preferably in the range of 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. Exceeding this range, the current collector may generate heat due to Joule heating during high current density charge and discharge. Furthermore, below this range, the volume ratio of the current collector to the positive electrode active material increases, which may lead to a decrease in battery capacity.

[0870] <2-5. Partition>

[0871] To prevent short circuits, a separator is typically sandwiched between the positive and negative electrodes. In this case, the separator is usually impregnated with the non-aqueous electrolyte of this invention before use.

[0872] There are no special restrictions on the material and shape of the separator. Any known separator can be used without significantly impairing the effect of the present invention. Among them, resins, glass fibers, inorganic materials, etc., formed from materials that are stable to the non-aqueous electrolyte of the present invention can be used. Porous sheet materials or non-woven fabric-like materials with excellent liquid retention properties are preferred.

[0873] Materials used for resin and fiberglass separators include, for example, polyethylene, polypropylene and other polyolefins, polytetrafluoroethylene, polyethersulfone, and glass filters. Among these, glass filters and polyolefins are preferred, and polyolefins are more preferred. One of the above materials can be used alone, or two or more can be used in any combination and proportion.

[0874] The thickness of the separator described above is arbitrary, but is typically 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and typically 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. Separator thicknesses less than these ranges may lead to reduced insulation or mechanical strength. Furthermore, thicknesses exceeding these ranges may not only cause a decrease in battery performance such as rate characteristics, but may also lead to a decrease in the overall energy density of the non-aqueous electrolyte secondary battery.

[0875] Furthermore, when using porous materials such as porous sheets or non-woven fabrics as separators, the porosity of the separator is arbitrary, but it is typically 20% or more, preferably 35% or more, more preferably 45% or more, and typically 90% or less, preferably 85% or less, more preferably 75% or less. When the porosity is below the above range, it may lead to an increase in film resistance and a deterioration in rate characteristics. Furthermore, when it exceeds the above range, it may cause a decrease in the mechanical strength and insulation of the separator.

[0876] Furthermore, the average pore size of the separator is arbitrary, but it is typically 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. When the average pore size exceeds this range, short circuits are more likely to occur. Conversely, when it is below this range, it may lead to increased film resistance and decreased rate characteristics.

[0877] On the other hand, as inorganic materials, materials such as oxides like alumina and silicon dioxide, nitrides like aluminum nitride and silicon nitride, and sulfates like barium sulfate and calcium sulfate can be used. Inorganic materials in particle or fibrous shape can also be used.

[0878] As its form, it can be a thin film such as non-woven fabric, woven fabric, or microporous membrane. Among the thin film shapes, a thin film with a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferred. In addition to the above-mentioned independent thin film shapes, the following separator can also be used: a separator obtained by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of at least one of the positive and negative electrodes using a resin-based binder. For example, a porous layer can be formed on both sides of the positive electrode using a fluororesin as a binder, with 90% of the alumina particles having a particle size of less than 1 μm.

[0879] <2-6. Battery Design>

[0880] [Electrode Set]

[0881] The electrode assembly can be any structure formed by stacking the positive and negative electrode plates separated by the separator, or by winding the positive and negative electrode plates into a spiral shape separated by the separator. The proportion of the electrode assembly volume in the battery's internal volume (hereinafter referred to as the electrode assembly occupancy rate) is typically 40% or more, preferably 50% or more, and typically 90% or less, preferably 80% or less. An electrode assembly occupancy rate below the above range will result in a decrease in battery capacity. Furthermore, exceeding the above range leads to less open space, which may cause component expansion or an increase in the vapor pressure of the electrolyte liquid components due to high battery temperatures, resulting in increased internal pressure. This leads to a decrease in battery performance during repeated charge-discharge cycles and high-temperature storage characteristics, potentially requiring the operation of a gas release valve to release internal pressure to the outside.

[0882] [Cell current collector structure]

[0883] There are no particular limitations on the current collector structure, but in order to more effectively realize the improved discharge characteristics caused by the non-aqueous electrolyte of the present invention, it is preferable to make a structure that reduces the resistance of the wiring and bonding portions. In this way, the effects of using the non-aqueous electrolyte of the present invention can be particularly well utilized while reducing the internal resistance.

[0884] When the electrode assembly has the aforementioned stacked structure, it is preferable to use a structure formed by bundling the metal core portions of each electrode layer together and welding them to terminals. Since the internal resistance increases as the area of ​​a single electrode increases, it is also preferable to use a method that provides multiple terminals within the electrode to reduce resistance. When the electrode assembly has the aforementioned wound structure, the internal resistance can be reduced by providing multiple lead structures on the positive and negative electrodes respectively and bundling them to terminals.

[0885] [Outer casing]

[0886] As for the material of the outer casing, there are no special restrictions as long as it is a substance stable to the non-aqueous electrolyte used. Specifically, it can be made of: nickel-plated steel plate, stainless steel, aluminum or aluminum alloy, magnesium alloy, or laminated film of resin and aluminum foil. From the perspective of lightweighting, aluminum or aluminum alloy laminated film is preferred.

[0887] Among the metal-based outer casings used above, examples include casings with the following structures: a sealed encapsulation structure formed by fusing metals together using laser welding, resistance welding, or ultrasonic welding; or a riveted structure formed by using the aforementioned metals with a resin gasket in between. Among the laminated film-based outer casings used above, examples include sealed encapsulation structures formed by thermally fusing resin layers together. To improve sealing, a resin different from the resin used in the laminated film can be sandwiched between the resin layers. In particular, when forming a sealed structure by thermally fusing resin layers using current collectors, due to the bonding between the metal and resin, it is preferable to use a resin with polar groups or a modified resin with introduced polar groups as the resin sandwiched between the resin layers.

[0888] [Protective Components]

[0889] Examples of such protective components include PTC (Positive Temperature Coefficient) devices that increase resistance when abnormally heated or when excessive current flows, temperature fuses, thermistors, and valves (current cut-off valves) that cut off the current flowing through the circuit by causing a rapid increase in the internal pressure or temperature of the battery when abnormal heating occurs. Preferably, these protective components are chosen to be those that do not operate under conditions of normal high-current use. From a high-output perspective, it is even more preferable to design them in a way that prevents abnormal heating or thermal runaway even without protective components.

[0890] [Exterior body]

[0891] The non-aqueous electrolyte secondary battery of the present invention is typically constructed by housing the aforementioned non-aqueous electrolyte, negative electrode, positive electrode, separator, etc., within an external casing. There are no limitations on this external casing; any known external casing may be used without significantly impairing the effects of the present invention.

[0892] Specifically, the material of the outer casing is arbitrary, but commonly used materials include, for example, nickel-plated iron, stainless steel, aluminum or its alloys, nickel, titanium, etc.

[0893] In addition, the shape of the outer casing is arbitrary, and can be any shape such as cylindrical, square, laminated, coin-shaped, large, etc.

[0894] Example

[0895] The present invention will now be described in more detail with reference to embodiments and comparative examples. However, the present invention is not limited to these embodiments and can be implemented in any way without departing from the spirit of the present invention.

[0896] <Examples 1-1 to 1-5, Comparative Example 1-1>

[0897] Analysis was performed using ion chromatography and nuclear magnetic resonance (NMR) spectroscopy. Additionally, when removing carboxylic acids, the amount of carboxylic acids in the distilled components was analyzed using gas chromatography.

[0898] Ion chromatography was performed using a Dionex ICS-3000 column, following the manufacturer's recommended analytical conditions for inorganic anions. Pure water was used as the dilution solvent for the samples.

[0899] NMR was performed using dimethyl sulfoxide-d6 as the solvent and trifluorotoluene as the internal standard. The ratio of fluorosulfonic acid ions to solvent was determined from the signal peaks and integral values.

[0900] Gas chromatography was performed using a GC-17A manufactured by Shimadzu Corporation with an FID detector. The chromatographic column used was a TC-1 manufactured by GLSCIENCES Corporation (0.53 μm in diameter, 0.2 μm in film thickness, and 50 m in total length). The detection area ratio of each component was compared with the detection area ratio of the reagents.

[0901] (Example 1-1)

[0902] <Reaction Process>

[0903] In a dry nitrogen stream, 6.8 g (103.1 mmol) of lithium acetate was weighed into a 200 mL PFA four-necked flask and 125 mL of dimethyl carbonate was added. While stirring the solution in an ice bath, 5 mL (8.6 g, 86.2 mmol) of fluorosulfonic acid was added dropwise over approximately 10 minutes. The solution temperature was 10 °C before addition, rose to 20 °C due to the exothermic reaction of the acid addition, but quickly returned to its original temperature after addition. As the addition proceeded, lithium acetate, which is sparingly soluble in dimethyl carbonate, dissolved. The mixture was cooled and stirred in an ice-water bath for 2 hours, then the ice-water bath was removed, and the mixture was stirred at room temperature for 1 hour. Excess lithium acetate was filtered from the final solution using a membrane filter (PTFE, nominal pore size 0.5 μm).

[0904] <The process of removing non-aqueous solvents used in the reaction process>

[0905] Dimethyl carbonate was removed from the above reaction solution by distillation at approximately 10 kPa and 40 °C until the distillation was complete, yielding a transparent and viscous liquid.

[0906] According to NMR analysis, the obtained powder is a mixture of lithium fluorosulfonate, acetic acid, and dimethyl carbonate. According to ion chromatography, the sulfate ion content is 0.3 mol / kg.

[0907] <Process for removing carboxylic acid>

[0908] Add 150 ml of diethyl carbonate to the above viscous liquid, and begin vacuum distillation using a Helipack No.1 distillation column filled with TO-TOKU Engineering material at 60°C and 6.0 kPa, allowing the vacuum level to change slowly until it reaches 2.4 kPa. The outflow is 135 ml.

[0909] The residual diethyl carbonate was removed by distillation using a rotary evaporator, yielding a white solid. Ion chromatography analysis showed that the acetate ion content was below 0.001 mol / kg.

[0910] (Examples 1-2)

[0911] <Reaction Process>

[0912] In a dry nitrogen stream, 7.9 g (120.1 mmol) of lithium acetate was weighed into a 500 mL PFA four-necked flask and 250 mL of dimethyl carbonate was added. While stirring the solution in an ice bath, 5.43 mL (10.0 g, 100 mmol) of fluorosulfonic acid was added dropwise over approximately 10 minutes. The solution temperature was 25 °C before addition, rose to 30 °C due to the exothermic reaction of the acid addition, but quickly returned to its original temperature after the addition was complete. As the addition proceeded, lithium acetate, which is sparingly soluble in dimethyl carbonate, dissolved. The solution was stirred in a water bath for 1 hour.

[0913] <The process of removing non-aqueous solvents used in the reaction process>

[0914] For the above reaction solution, approximately 220 ml of dimethyl carbonate was removed by distillation under controlled vacuum at a bath temperature of 45°C. After restoring to atmospheric pressure in a dehydrated, inert gas atmosphere, 300 ml of diethyl carbonate was added. Excess lithium acetate was then filtered out from the solution using a membrane filter (PTFE, nominal pore size 0.5 μm).

[0915] <Process for removing carboxylic acid>

[0916] For the above solution, a 10cm distillation column filled with Helipack No.2 manufactured by TO-TOKU Engineering was used to remove the residual dimethyl carbonate and diethyl carbonate at a bath temperature of 45°C while controlling the vacuum level, until the residual diethyl carbonate reached about 10ml.

[0917] <Purification Process>

[0918] After restoring to atmospheric pressure in a dehydrated, inert gas atmosphere, 40 ml of dimethyl carbonate was added while maintaining the bath temperature at 45°C. The resulting solution was then hot-filtered using a membrane filter (PTFE, nominal pore size 0.5 μm) in a dehydrated, inert gas atmosphere. The solution was then slowly cooled to 4°C in the inert gas atmosphere, yielding white crystals. The yield was 66%, with sulfate ion content below 0.01 mol / kg and acetate ion content below 0.001 mol / kg. The resulting solid was then dissolved in 50 ml of DMC at 45°C, and the same procedure was performed, yielding white crystals with a 90% recovery rate and a total sulfate and acetate ion content below 0.001 mol / kg.

[0919] (Examples 1-3)

[0920] <Reaction Process>

[0921] In a dry nitrogen stream, 7.9 g (120.1 mmol) of lithium acetate was weighed into a 500 mL PFA four-necked flask and 300 mL of diethyl carbonate was added. While stirring the solution in an ice bath, 5.43 mL (10.0 g, 100 mmol) of fluoxetine was added dropwise over approximately 10 minutes. The solution temperature was 25 °C before addition, rose to 30 °C due to the exothermic reaction of the acid addition, but quickly returned to its original temperature after the addition was complete. During the addition, lithium acetate, which is sparingly soluble in diethyl carbonate, dissolved. The solution was stirred in a water bath for 1 hour.

[0922] This process combines the steps for removing non-aqueous solvents used in the reaction process and the step for removing carboxylic acids.

[0923] For the above solution, 220 ml of diethyl carbonate was distilled off using a 10 cm distillation column filled with a TO-TOKU Engineering Helipack No. 2 distillation column at a bath temperature of 45°C under controlled vacuum. After restoring to atmospheric pressure in a dehydrated, inert gas environment, excess lithium acetate was filtered out from the solution using a membrane filter (PTFE, nominal pore size 0.5 μm).

[0924] Diethyl carbonate was further removed from the filtered solution by distillation under the same conditions until approximately 10 ml of diethyl carbonate remained.

[0925] <Purification Process>

[0926] The same procedures as in Examples 1-2 were performed, yielding white crystals in 65% yield. The sulfate ion content was less than 0.01 mol / kg, and the acetate ion content was less than 0.001 mol / kg, consistent with Examples 1-2. The resulting solid was then dissolved in 50 ml of DMC at 45°C, and the same process was repeated, yielding white crystals with a total sulfate and acetate ion content of less than 0.001 mol / kg and a recovery rate of 90%. This result was also consistent with Examples 1-2.

[0927] (Comparative Example 1-1)

[0928] Except that water was used as the solvent, the same reaction procedure as in Example 1-1 was performed.

[0929] The resulting solution was concentrated using the same method as the concentration procedure in Example 1-1, and no solid precipitated.

[0930] The results of ion chromatography analysis confirmed that fluorosulfonic acid was completely hydrolyzed into sulfuric acid.

[0931] (Examples 1-4)

[0932] The reaction process was carried out in the same manner as in Examples 1-2. Dimethyl carbonate was removed by distillation under the same conditions as in the process of removing the non-aqueous solvent used in the reaction process until about 40 ml of dimethyl carbonate was reached. The distillation was then stopped. Cooling was performed in the same manner as in the purification process. No crystal formation was observed.

[0933] However, when the residual dimethyl carbonate is removed by distillation under reduced pressure to below approximately 0.2 kPa, a white, waxy solid is obtained. The amount of acetate ions in this solid relative to lithium fluorosulfonate is 0.063 mol / kg.

[0934] (Examples 1-5)

[0935] After performing the reaction steps in the same manner as in Examples 1-3, 200 ml of diethyl para-carbonate was continuously distilled off while maintaining a rotary evaporator temperature below 5 Torr. Excess lithium acetate was filtered off in the same manner as in Examples 1-3, and the mixture was further concentrated to approximately 10 ml while maintaining a rotary evaporator temperature below 5 Torr. The purification steps were performed in the same manner as in Examples 1-3, resulting in a white powder with a 50% yield. The acetate ion content was as high as 0.11 mol / kg, while the sulfate ion content was suppressed to below 0.01 mol / kg. The resulting solid was then dissolved in 50 ml of DMC at 45°C, and the same procedure was performed, yielding white crystals with a 90% recovery rate. Although the acetate ion content did not decrease significantly, the sulfate ion content was further reduced to below 0.001 mol / kg.

[0936] <Examples 2-1~2-3, Comparative Examples 2-1~2-4>

[0937] The analysis employed ion chromatography and nuclear magnetic resonance (NMR) spectroscopy.

[0938] Ion chromatography was performed using a Dionex ICS-3000 column and employing well-known inorganic anion analysis methods. Pure water was used as the dilution solvent for the samples.

[0939] NMR was performed using dimethyl sulfoxide-d6 as the solvent and trifluorotoluene as the internal standard. The ratio of fluorosulfonic acid ions to the solvent was determined from the signal peaks and integral values.

[0940] (Example 2-1)

[0941] <Reaction>

[0942] In a dry nitrogen stream, 4.4 g (103.5 mmol) of lithium chloride was weighed into a 200 mL PFA four-necked flask and 125 mL of dimethyl carbonate was added. While stirring the solution in an ice bath, 5 mL (8.63 g, 86.24 mmol) of fluorosulfonic acid was added dropwise over approximately 10 minutes. The solution temperature was 10 °C before addition, rose to 20 °C due to the exothermic reaction of the acid addition, but quickly returned to its original temperature after addition. As the addition proceeded, lithium chloride, which is sparingly soluble in dimethyl carbonate, dissolved. The mixture was stirred for 2 hours while cooling in an ice-water bath, then the ice-water bath was removed, and the mixture was stirred at room temperature for 1 hour. Excess lithium chloride was filtered from the final solution using a membrane filter (PTFE, nominal pore size 0.5 μm).

[0943] <Concentrated>

[0944] 100 ml of dimethyl carbonate was distilled off from the above reaction solution at approximately 10 kPa and 40 °C. The solution was then left to stand, resulting in a white powder.

[0945] According to NMR analysis, the obtained powder is a complex of lithium fluorosulfonate and dimethyl carbonate in a molar ratio of 1:1. According to ion chromatography, the sulfate ion content is 0.30 mol / kg and the chloride ion content is 0.56 mol / kg.

[0946] <Recrystallization 1>

[0947] The crude product was dispersed in 50 ml of dimethyl carbonate under a dry, inert gas atmosphere and dissolved by heating and stirring at 60 °C for 30 minutes. Undissolved trace amounts of powder were removed by filtration using a membrane filter (PTFE, nominal pore size 0.5 μm). The filtrate was allowed to cool naturally to room temperature and then allowed to stand at 5 °C for 10 hours to obtain colorless crystals.

[0948] According to NMR analysis, the obtained powder is a complex of lithium fluorosulfonate and dimethyl carbonate in a molar ratio of 1:1. According to ion chromatography, the sulfate ion content is 0.12 mol / kg and the chloride ion content is 0.11 mol / kg.

[0949] The yield of lithium fluorosulfonate was 4.9 g. The recrystallization yield was 72%, and the overall yield after the entire process was 54%.

[0950] <Recrystallization 2>

[0951] The lithium fluorosulfonate was recrystallized again using the same method, resulting in a yield of 3.5 g of lithium fluorosulfonate containing 0.062 mol / kg sulfate ions and 0.056 mol / kg chloride ions. The yield after this operation was 71%, and the yield after the entire operation was 39%.

[0952] (Example 2-2)

[0953] The same method as described in Example 2-1 is applied to the <concentration> process.

[0954] <Recrystallization 1>

[0955] The crude product was dispersed in 50 ml of dimethyl carbonate under a dry, inert gas atmosphere. 140 μL of pure water (1.2 mol times the amount of chloride ions) was added, and the solution was dissolved by heating and stirring at 60 °C for 30 minutes. Undissolved trace amounts of powder were removed by filtration through a PTFE membrane filter (0.5 μm nominal pore size). The filtrate was allowed to cool naturally to room temperature and then allowed to stand at 5 °C for 10 hours to obtain colorless crystals.

[0956] According to the NMR analysis results, the obtained powder is a complex of lithium fluorosulfonate and dimethyl carbonate in a molar ratio of 1:1, similar to that in Example 2-1. According to the results of ion chromatography, the sulfate ion content is 0.083 mol / kg and the chloride ion content is 0.0011 mol / kg.

[0957] <Recrystallization 2>

[0958] The lithium fluorosulfonate was recrystallized again using the same method as in Example 2-1 without the addition of pure water, resulting in lithium fluorosulfonate containing 0.062 mol / kg sulfate ions and 0.00056 mol / kg chloride ions, with a yield of 2.58 g. The yield after the entire operation was 29.8%.

[0959] <Dimethyl decarbonate>

[0960] The obtained lithium fluorosulfonate was added into a vacuum container, and after being reduced to 100 Pa, it was heated to 40 °C and left to stand for 4 hours. The proportion of dimethyl carbonate was 1.3 mol.

[0961] <Example 2-3>

[0962] The reaction was carried out using 50 ml of acetonitrile instead of 125 ml of dimethyl carbonate as the solvent. Otherwise, the reaction was performed in the same manner as in Example 2-1, and the yield was confirmed to be the same. Furthermore, during the concentration process, the same procedures as in Example 2-1 were performed, except that all the solvent was removed by distillation.

[0963] After recrystallization, 1.52 g of lithium fluorosulfonate in solid form containing 0.62 mol / kg sulfate ions and 0.056 mol / kg chloride ions was obtained.

[0964] (Comparative Example 2-1)

[0965] Except that water was used as the solvent, the same reaction procedure as in Example 2-1 was performed.

[0966] The resulting solution was concentrated using the same method as the concentration procedure in Example 2-1, and no solid precipitated.

[0967] The results of ion chromatography analysis confirmed that fluorosulfonic acid was completely hydrolyzed into sulfuric acid.

[0968] (Comparative Example 2-2)

[0969] Water was used as the solvent, and 4.4 g (104.8 mmol) of lithium chloride monohydrate was used instead of lithium chloride. Acid-base neutralization was performed using lithium hydroxide. Otherwise, the same reaction procedures as in Example 2-1 were performed.

[0970] The resulting solution was concentrated using the same method as the concentration procedure in Example 2-1, and no solid precipitated. Ion chromatography analysis confirmed that the fluorosulfonic acid was completely hydrolyzed to sulfuric acid.

[0971] (Comparative Examples 2-3)

[0972] Except that 3.3 g (51.4 mmol, or 102.8 mmol in lithium content) of lithium carbonate was used instead of lithium chloride, the same reaction procedure as in Example 2-1 was performed.

[0973] Ion chromatography analysis confirmed that all fluorosulfonic acid was hydrolyzed into sulfuric acid. It can be inferred that lithium carbonate underwent hydrolysis due to water produced as a byproduct during neutralization....

Claims

1. A non-aqueous electrolyte secondary battery, comprising a negative electrode and a positive electrode capable of absorbing and releasing lithium ions, and a non-aqueous electrolyte, encapsulated in an outer casing, wherein, The non-aqueous electrolyte contains lithium fluorosulfonate and sulfate ions, and the sulfate ion content in the non-aqueous electrolyte is 1.0 × 10⁻⁶. -7 mol / L or higher and 1.0 × 10 -2 The molar concentration of lithium fluorosulfonate in the non-aqueous electrolyte is above 0.0005 mol / L and below 0.40 mol / L. The non-aqueous electrolyte also contains lithium salts other than lithium fluorosulfonate. The ratio of the molar content of lithium fluorosulfonate in the non-aqueous electrolyte to the molar content of lithium in the lithium salts other than lithium fluorosulfonate, expressed as [lithium fluorosulfonate] / [lithium salts other than lithium fluorosulfonate], is 0.001 or more and 1.2 or less. Furthermore, the outer casing is a laminated film.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The molar content of lithium fluorosulfonate in the non-aqueous electrolyte is above 0.001 mol / L and below 0.40 mol / L.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The lithium salt other than lithium fluorosulfonate is at least one of LiPF6 and LiBF4.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The non-aqueous electrolyte contains cyclic carbonates with fluorine atoms.

5. The non-aqueous electrolyte secondary battery according to claim 4, wherein, The non-aqueous electrolyte contains 0.001% by mass and less than 85% by mass of the cyclic carbonate having fluorine atoms.

6. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The non-aqueous electrolyte contains cyclic carbonates with carbon-carbon unsaturated bonds.

7. The non-aqueous electrolyte secondary battery according to claim 6, wherein, The non-aqueous electrolyte contains more than 0.001% by mass and less than 10% by mass of the cyclic carbonate having carbon-carbon unsaturated bonds.

8. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The non-aqueous electrolyte contains cyclic sulfonate esters.

9. The non-aqueous electrolyte secondary battery according to claim 8, wherein, The content of the cyclic sulfonate in the non-aqueous electrolyte is more than 0.001% by mass and less than 10% by mass.

10. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The non-aqueous electrolyte contains a compound with a cyano group.

11. The non-aqueous electrolyte secondary battery according to claim 10, wherein, The content of the cyano compound in the non-aqueous electrolyte is more than 0.001% by mass and less than 10% by mass.

12. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The non-aqueous electrolyte contains a diisocyanate compound.

13. The non-aqueous electrolyte secondary battery according to claim 12, wherein, The content of the diisocyanate compound in the non-aqueous electrolyte is more than 0.001% by mass and less than 5% by mass.

14. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 13, wherein, The non-aqueous electrolyte contains lithium oxalate salts.

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