Lithium silicon oxide, a negative electrode containing the same, and a lithium secondary battery containing the negative electrode

Abstract

The present invention relates to a lithium silicon oxide in which gas generation is suppressed when an aqueous slurry is applied, a negative electrode containing the same, and a lithium secondary battery containing the negative electrode, and provides a lithium silicon oxide that satisfies mathematical formula 1, a negative electrode containing the same, and a lithium secondary battery containing the negative electrode.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2023-0075098 dated June 12, 2023, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to a lithium silicon oxide in which gas generation is suppressed when an aqueous slurry is applied, a negative electrode containing the same, and a lithium secondary battery containing the negative electrode. [Background technology]

[0003] Recently, as the application areas of lithium-ion batteries have rapidly expanded from power supply for electronic devices such as electrical, electronic, telecommunications, and computers to power storage and supply for large-area equipment such as automobiles and power storage devices, the need for high-capacity, high-output, and highly stable lithium-ion batteries is increasing.

[0004] Lithium-ion secondary batteries are generally manufactured by applying a slurry of a positive electrode material capable of inserting and removing lithium ions, or a negative electrode material capable of intercalating and releasing lithium ions, along with a binder and a conductive material, to the positive electrode current collector and negative electrode current collector, respectively, and removing the solvent by heat or other means. These electrodes are then stacked on both sides of a separator to form electrode current collectors of a predetermined shape, and finally, these electrode current collectors and a non-aqueous electrolyte are inserted into a battery case.

[0005] Graphite-based anode materials, a typical anode material, exhibit excellent structural stability during lithium insertion and removal, and stable capacity retention characteristics even over long cycles. However, their low theoretical capacity (350 mAh / g for LiC6) makes them unsuitable as high-capacity, high-power materials currently required. Therefore, silicon-based anode materials such as silicon and silicon oxide offer a low reduction potential with lithium, abundant reserves, and a theoretical capacity (2700-4200 mAh / g for LiC6) that is more than 10 times higher than graphite. 4.4Because of its properties, silicon (Si) is attracting attention as a negative electrode material for next-generation lithium-ion batteries. However, despite these advantages, silicon-based negative electrode materials consume about three times more lithium than graphite-based negative electrode materials. When lithium-ion batteries using silicon-based negative electrode materials are charged and discharged, volume expansion and surface side reactions prevent a large amount of lithium inserted into the negative electrode from returning to the positive electrode during initial charging, resulting in a problem of large initial irreversible capacity.

[0006] Also, in particular, silicon oxide (SiO x In the case of particles, various methods have been attempted to improve initial efficiency by doping with Mg or prelithiating silicon oxide particles with Li, in order to solve the problem of initial efficiency due to irreversible reactions of Li ions. However, when using this to manufacture a negative electrode material slurry by an aqueous process, the lithium compound formed inside the prelithiated silicon oxide particles reacts with H2O to produce LiOH byproducts, which reduces the viscosity of the slurry, generates hydrogen, and deteriorates the coating properties of the slurry. As a result, problems of reduced adhesion between the negative electrode material layer and the current collector and volume expansion still exist.

[0007] Therefore, there is a need to develop an anode material that exhibits excellent initial capacity and capacity retention, minimal viscosity changes during the manufacturing of the anode material slurry using an aqueous process, suppresses hydrogen generation, and exhibits suppressed volume expansion during charging and discharging of the anode using this material. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] KR10-2014-0091388A [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention has been derived to solve the above problems of the prior art, and provides a lithium silicon oxide useful as a negative electrode material, which is excellent in initial capacity and capacity retention rate, has almost no change in viscosity, and suppresses hydrogen generation during the production of slurry by an aqueous process.

[0010] Further, an object of the present invention is to provide a negative electrode containing the above lithium silicon oxide.

[0011] In addition, an object of the present invention is to provide a lithium secondary battery including the above negative electrode.

Means for Solving the Problems

[0012] To solve the above problems, the present invention provides a lithium silicon oxide, a negative electrode containing the same, and a lithium secondary battery.

[0013] (1) The present invention provides a lithium silicon oxide that satisfies the following Mathematical Formula 1. [Mathematical Formula 1] 0.45 ≦ PX 512 / PX T In the above Mathematical Formula 1, PX T is 900, which is the total number of pixels obtained by equally dividing a 150 μm × 150 μm region on the surface of lithium silicon oxide into 5 μm × 5 μm pixels by a Raman mapping technique, PX 512 is the number of pixels having a maximum peak among the Raman spectra from 200 cm -1 to 520 cm -1 obtained by a Raman mapping technique for each of the 900 total pixels, and is within the range of 512 cm -1 or more and 520 cm -1 or less.

[0014] (2) In the above (1), the present invention provides a lithium silicon oxide that satisfies the following Mathematical Formula 2. [Mathematical Formula 2] 5 ≦ PX512 / PX 500 In the aforementioned mathematical formula 2, PX 512 This involves using the Raman mapping technique to divide a 150 μm × 150 μm area of ​​lithium silicon oxide surface into 900 pixels of equal size (5 μm × 5 μm), and then applying a Raman shift of 200 cm to each of these pixels. -1 From 520cm -1 Of the Raman spectra up to 512 cm⁻¹, -1 More than 520cm -1 The following is the number of pixels with the maximum peak: PX 500 This is a Raman shift of 200 cm for each of the 900 pixels mentioned above. -1 From 520cm -1 Of the Raman spectra up to 490 cm² -1 More than 500cm -1 The following is the number of pixels with the maximum peak.

[0015] (3) The present invention provides a lithium silicon oxide that satisfies the following mathematical formula 1-1 in (1) or (2) above. [Mathematical formula 1-1] 0.45 ≤ PX 512 / PX T ≤1.00 In the above mathematical formula 1-1, PX T and PX 512 This is as defined in mathematical formula 1.

[0016] (4) The present invention provides a lithium silicon oxide that satisfies the following mathematical formula 2-1 in any one of (1) to (3) above. [Mathematical formula 2-1] 5≦PX 512 / PX 500 ≤100 In the above mathematical formula 2-1, PX 512 and PX 500 This is as defined in the above mathematical formula 2.

[0017] (5) The present invention provides a lithium silicon oxide containing Si, SiO x (0 < x ≤ 2) and a lithium-containing compound in any one of the above (1) to (4).

[0018] (6) The present invention provides a lithium silicon oxide in which the Si and SiO x (0 < x ≤ 2) include a carbon coating layer on the surface in the above (5).

[0019] (7) The present invention provides a lithium silicon oxide in which the lithium-containing compound includes one or more of lithium disilicate and lithium silicide in the above (5) or (6).

[0020] (8) The present invention provides a negative electrode including a conductive metal current collector and a negative electrode material layer provided on at least one surface of the current collector, and the negative electrode material layer includes a lithium silicon oxide according to any one of the above (1) to (7).

[0021] (9) The present invention provides a lithium secondary battery including the negative electrode according to the above (8), a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. [Effect of the Invention]

[0022] The lithium silicon oxide negative electrode material according to the present invention, even when manufactured with an aqueous negative electrode material slurry, suppresses a decrease in the viscosity of the slurry and the generation of hydrogen due to LiOH by-products, is excellent in initial capacity and capacity retention rate, has less change in viscosity compared to an aqueous negative electrode material slurry containing ordinary silicon particles or silicon oxide particles, and reduces the generation of hydrogen. Therefore, coating defects of the slurry and a decrease in adhesive force due to a decrease in the viscosity of the slurry can be suppressed, and there is an effect of excellent storage stability.

[0023] In addition, the negative electrode according to the present invention includes a negative electrode material layer containing lithium silicon oxide as a negative electrode material, so that it is excellent in initial efficiency and suppresses volume expansion of the negative electrode, and thus can be excellent in capacity retention rate. [Modes for carrying out the invention]

[0024] The present invention will be described in more detail below to facilitate understanding of it.

[0025] The terms and words used in the description and claims of this invention should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​this invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0026] Measurement method In this specification, Raman analysis is performed using a Ramanforce (Nanophoton) Raman spectrometer. Specifically, lithium silicon oxide powder is coated onto a glass slide, and then XY Raman mapping is performed using a Raman spectrometer (532 nm laser) to map 900 pixels (5 μm × 5 μm / pixel) in a 150 μm × 150 μm area per sample at 5 μm intervals, with a Raman shift of 200 cm². -1 ~520cm -1 The Raman spectrum was measured, and the Raman shift was 490 cm⁻¹. -1 More than 500cm -1 The following and 512cm -1 More than 520cm -1 The number of pixels with the highest peak was measured for each of the following parameters.

[0027] Lithium silicon oxide The present invention provides a lithium silicon oxide useful as a negative electrode material, which exhibits excellent initial capacity and capacity retention, and shows almost no change in viscosity and suppresses hydrogen generation during slurry production using an aqueous process.

[0028] A lithium silicon oxide according to one embodiment of the present invention is characterized by satisfying the following mathematical formula 1.

[0029] [Mathematical formula 1] 0.45 ≤ PX512 / PX T

[0030] In the above mathematical formula 1, PX T This refers to the total number of pixels obtained by evenly dividing a 150 μm × 150 μm area of ​​lithium silicon oxide surface into 5 μm × 5 μm pixels using the Raman mapping technique, resulting in 900 pixels. 512 This is a Raman shift of 200 cm obtained by the Raman mapping technique for each of the 900 pixels mentioned above. -1 From 520cm -1 Of the Raman spectra up to 512 cm⁻¹, -1 More than 520cm -1 The following is the number of pixels with the maximum peak.

[0031] As a negative electrode material, graphite-based negative electrode materials are known. Graphite-based negative electrode materials exhibit excellent structural stability during lithium insertion and removal, and show stable capacity retention characteristics even over long cycles. However, due to their low theoretical capacity (350mAh / g for LiC6), they are not suitable as the high-capacity, high-power materials currently required. Therefore, materials with a theoretical capacity approximately 10 times higher than graphite (~4200mAh / g for LiC6) are being sought. 4.4Silicon and silicon oxides containing Si are attracting attention. However, silicon-based anode materials consume about three times more lithium than graphite-based anode materials, and have the problem of large irreversible capacity. To solve the problem of initial efficiency due to the irreversible reaction of lithium ions, methods are being attempted to improve initial efficiency by prelithiation of Li. Prelithiated silicon-based anode materials have the advantages of excellent charge-discharge efficiency and favorable cycle characteristics, but they have the problems of reduced capacity and gas generation during the process. In particular, pre-lithified silicon-based anode materials include crystalline lithium silicate, crystalline silicon (Si), and amorphous silicon (Si). However, crystalline lithium silicate is easily soluble in water, and when manufacturing an aqueous anode slurry using the aforementioned pre-lithified silicon-based anode material, it dissolves in water, causing the silicon to oxidize upon contact with the water, while the water is reduced to generate hydrogen gas. This alters the slurry viscosity, degrades the slurry's coating properties, and leads to serious defects in the slurry coating. As a result, critical problems such as a sudden decrease in capacity due to an electrical short circuit with the current collector can occur.

[0032] However, the lithium silicon oxide according to the present invention contains a mixture of crystalline silicon (Si) and amorphous silicon (Si), and satisfies mathematical formula 1, or more specifically, mathematical formulas 1 and 2. As a result, the proportion of crystalline Si, which has lower solubility in water compared to amorphous Si, increases, and even when manufactured in a water-based anode material slurry, it does not dissolve in water. This prevents slurry coating defects and a decrease in adhesive strength due to hydrogen generation, resulting in excellent anode stability (integrity) and capacity retention, and excellent initial capacity characteristics.

[0033] The lithium silicon oxide according to the present invention will be described in detail below.

[0034] The lithium silicon oxide according to one embodiment of the present invention is useful as a negative electrode material, particularly as a negative electrode material for aqueous slurries, and satisfies the following mathematical formula 1.

[0035] [Mathematical formula 1] 0.45 ≤ PX 512 / PX T

[0036] In the above mathematical formula 1, PX T This refers to the total number of pixels obtained by evenly dividing a 150 μm × 150 μm area of ​​lithium silicon oxide surface into 5 μm × 5 μm pixels using the Raman mapping technique, resulting in 900 pixels. 512 This is a Raman shift of 200 cm obtained by the Raman mapping technique for each of the 900 pixels mentioned above. -1 From 520cm -1 Of the Raman spectra up to 512 cm⁻¹, -1 More than 520cm -1 The following is the number of pixels with the maximum peak.

[0037] Furthermore, the lithium silicon oxide can satisfy the following mathematical formula 1-1.

[0038] [Mathematical formula 1-1] 0.45 ≤ PX 512 / PX T ≤1.00

[0039] In the above mathematical formula 1-1, PX T and PX 512 This is as defined in mathematical formula 1.

[0040] Furthermore, in the above mathematical formula 1, PX 512 / PX T This value may be between 0.45 and 0.80. When the above mathematical formula 1-1 is satisfied, hydrogen generation is further suppressed, preventing slurry coating defects and a decrease in adhesive strength, resulting in superior anode integrity and capacity retention, and further improving initial capacity characteristics.

[0041] Furthermore, the lithium silicon oxide according to one embodiment of the present invention is characterized in that it satisfies the following mathematical formula 2.

[0042] [Mathematical formula 2] 5≦PX 512 / PX 500

[0043] In the above mathematical formula 2, PX 512 This involves using the Raman mapping technique to divide a 150 μm × 150 μm area of ​​lithium silicon oxide surface into 900 pixels of equal size (5 μm × 5 μm), and then applying a Raman shift of 200 cm to each of these pixels. -1 From 520cm -1 Of the Raman spectra up to 512 cm⁻¹, -1 More than 520cm -1 The following is the number of pixels with the highest peak, PX 500 This is a Raman shift of 200 cm for each of the 900 pixels mentioned above. -1 From 520cm -1 Of the Raman spectra up to 490 cm² -1 More than 500cm -1 The following is the number of pixels with the maximum peak.

[0044] As yet another example, the lithium silicon oxide can satisfy the following mathematical formula 2-1.

[0045] [Mathematical formula 2-1] 5≦PX 512 / PX 500 ≤100

[0046] In the above mathematical formula 2-1, PX 512 and PX 500 This is as explained in mathematical formula 2.

[0047] As yet another example, in the above mathematical formula 2-1, PX 512 / PX 500 It may be 5 to 60 or 5 to 55.

[0048] When the above mathematical formula 2-1 is satisfied, hydrogen generation is further suppressed, preventing slurry coating defects and a decrease in adhesive strength, resulting in superior anode integrity and capacity retention, and further improving initial capacity characteristics.

[0049] As yet another example, the lithium silicon oxide satisfies both mathematical formula 1 and mathematical formula 2.

[0050] On the other hand, in the Raman spectrum, crystalline Si has a Raman shift of 500 cm. -1 Super 520cm -1 The following peaks were observed, and amorphous Si is found at a Raman shift of 490 cm⁻¹. -1 More than 500cm -1 A peak is observed below. Therefore, in the Raman spectrum measured by the Raman mapping technique according to one embodiment of the present invention, at 512 cm⁻¹ -1 Pixels with the largest peak are those with a higher proportion of crystalline Si, at 500 cm². -1 Pixels with the largest peak indicate pixels with a higher proportion of amorphous Si.

[0051] In the present invention, the lithium silicon oxide is produced by pre-lithifying a silicon-based compound, such as silicon and / or silicon oxide, with Li.

[0052] On the other hand, when silicon-based compounds are pre-lithified, crystalline lithium silicate (Li2SiO3) and lithium disilicate (Li2Si2O5) are generally produced. However, lithium silicate is easily soluble in water, and when used to produce an aqueous slurry, there are problems with process and efficiency reduction due to the generation of hydrogen gas.

[0053] However, the lithium silicon oxide according to the present invention is produced by a prelithiation process described below using a specific concentration of LiBP (lithium biphenyl), and can contain only crystalline lithium disilicate that does not contain crystalline lithium silicate and is insoluble in water. At the same time, it can satisfy Mathematical Formula 1 and / or Mathematical Formula 2.

[0054] By satisfying the above properties, the lithium silicon oxide according to the present invention can prevent the generation of hydrogen during the production of slurry by an aqueous process, has no coating defects and reduction in adhesive strength, and can be excellent in initial capacity characteristics and capacity retention rate.

[0055] Further, the lithium silicon oxide can contain Si (silicon particles), SiO x (0 < x ≤ 2) (silicon oxide particles) and a lithium-containing compound.

[0056] The Si and SiO x can each have an amorphous structure, and the Si has an average particle size (D 50 ) of 1 μm to 20 μm, and the SiO x can have an average particle size (D 50 ) of 5 nm to 1 μm.

[0057] Further, the Si or SiO x can contain a carbon coating layer on its surface, where the thickness of the carbon coating layer may be 1 nm to 1 μm, or 100 nm to 1 μm.

[0058] The carbon coating layer contains a carbon-based substance, and the carbon-based substance can contain at least one of amorphous carbon and crystalline carbon.

[0059] The crystalline carbon can further improve the conductivity of the negative electrode material, and exemplarily, it may be any one or more selected from the group consisting of fluorene, carbon nanotube, and graphene.

[0060] In addition, the amorphous carbon appropriately maintains the strength of the carbon coating layer. Exemplarily, it can be at least one carbide selected from the group consisting of tar, pitch, and other organic substances, or a carbon-based substance formed using a hydrocarbon as a source in a chemical vapor deposition method. The carbide of the other organic substances may be a carbide of sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose, or ketohexose, and combinations thereof.

[0061] In addition, the hydrocarbon can be a substituted or unsubstituted aliphatic or alicyclic hydrocarbon, or a substituted or unsubstituted aromatic hydrocarbon. Exemplarily, it may be methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, or hexane, benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, or phenanthrene, etc.

[0062] The lithium-containing compound is a compound formed by pre-lithiation of Si and / or SiO x and doping of lithium metal into Si and / or SiO x Specifically, it can contain one or more of lithium disilicate and lithium silicide.

[0063] The lithium silicide can contain Li y Si(2 < y < 5). Exemplarily, it may be one or more selected from the group consisting of Li 4.4 Si, Li 3.75 Si, Li 3.25 Si, and Li 2.33 Si.

[0064] Method for manufacturing lithium silicon oxide The present invention provides a method for manufacturing the lithium silicon oxide.

[0065] According to one embodiment of the present invention, the method for producing the lithium silicon oxide includes a step (S1) of adding Si or SiO x (0 < x ≤ 2) particles and stirring in an inert atmosphere, and a step (S2) of separating the generated particles and then drying and firing. The concentration of the lithium compound-containing solution may be more than 0.5 M and less than 1.0 M.

[0066] According to one embodiment of the present invention, the method for producing lithium silicon oxide is to add a silicon-based negative electrode material to a lithium compound-containing solution of more than 0.5 M and less than 1.0 M in which a lithium compound is dissolved at a specific concentration in an organic solvent, and stir and heat-treat to produce it. Thereby, Li is inserted and diffused inside the silicon-based negative electrode, and an appropriate redox process is performed, whereby lithium silicon oxide having the above-described physical properties can be produced.

[0067] Hereinafter, the method for producing a lithium silicon oxide composite according to one embodiment of the present invention will be described more specifically step by step.

[0068] (S1) Step The step (S1) is a step of pre-lithiation of Si or SiO x (0 < x ≤ 2) to generate lithium silicon oxide particles. In an inert gas atmosphere, Si or SiO x (0 ≤ x ≤ 2) particles are added and stirred. The lithium compound-containing solution may be more than 0.5 M and less than 1.0 M. Specifically, the lithium compound-containing solution may be 0.6 M or more and 0.8 M or less.

[0069] Here, when the lithium compound-containing solution is more than 0.5 M and less than 1.0 M, it means that more than 0.5 mol and less than 1.0 mol of the lithium compound are dissolved per 1 L of the solution.

[0070] In one embodiment of the present invention, the Si and SiOx (0 < x ≤ 2) can each have an amorphous structure, and the silicon (Si) has an average particle size (D 50 ) of 1 μm to 20 μm, and the silicon oxide (SiO x (0 < x ≤ 2)) can have an average particle size (D 50 ) of 5 nm to 1 μm.

[0071] In addition, the silicon and silicon oxide can include a carbon coating layer on the surface, where the thickness of the carbon coating layer can be 1 nm to 1 μm, or 100 nm to 1 μm.

[0072] The carbon coating layer contains a carbon-based substance, and the carbon-based substance can include at least one of amorphous carbon and crystalline carbon.

[0073] The crystalline carbon can further improve the conductivity of the negative electrode material. Exemplarily, it can be any one or more selected from the group consisting of fluorene, carbon nanotubes, and graphene.

[0074] In addition, the amorphous carbon can appropriately maintain the strength of the carbon coating layer. Exemplarily, it can be at least one carbide selected from the group consisting of tar, pitch, and other organic substances, or a carbon-based substance formed using a hydrocarbon as a source in chemical vapor deposition method. The carbide of the other organic substances can be a carbide of sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose, or ketohexose, and combinations thereof.

[0075] Furthermore, the hydrocarbon may be a substituted or unsubstituted aliphatic or alicyclic hydrocarbon, or a substituted or unsubstituted aromatic hydrocarbon, and examples include methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane or hexane, benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene or phenanthrene.

[0076] In one embodiment of the present invention, the silicon or silicon oxide can be added in an amount greater than 0.131 parts by weight and less than 0.142 parts by weight per 100 parts by weight of the lithium compound-containing solution.

[0077] Here, the lithium compound-containing solution can be produced by adding a polycyclic aromatic compound or a linear polyphenylene compound to an organic solvent, stirring, producing a polycyclic aromatic compound solution or a linear polyphenylene compound solution, and then adding lithium particles to the polycyclic aromatic compound solution or linear polyphenylene compound solution and reacting them.

[0078] Furthermore, the lithium particles react with the polycyclic aromatic compound or linear polyphenylene compound in a polycyclic aromatic compound solution or linear polyphenylene compound solution in a 1:1 mole ratio.

[0079] Furthermore, the polycyclic aromatic compound may be one or more selected from the group consisting of naphthalene, anthracene, phenanthrene, naphthacene, pentacene, pyrene, picene, triphenylene, coronene, chrysene, fluorene, and 9,9-dimethylfluorene, and the linear polyphenylene compound may be one or more selected from the group consisting of biphenyl, terphenyl, and 4,4-dimethylbiphenyl. Specifically, the polycyclic aromatic compound may be any one selected from naphthalene, fluorene, and 9,9-dimethylfluorene, and the linear polyphenylene compound may be biphenyl or 4,4-dimethylbiphenyl.

[0080] Furthermore, the organic solvent can be an ether-based solvent, a ketone-based solvent, an ester-based solvent, an alcohol-based solvent, an amine-based solvent, or a mixture thereof. For example, the ether-based solvent can be diethyl ether, tert-butyl methyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or a mixture thereof. Among these, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, and 1,2-dimethoxyethane are preferred.

[0081] Furthermore, as the ketone solvent, acetone, acetophenone, etc., can be used, and as the ester solvent, methyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, or a mixture thereof can be used.

[0082] Furthermore, as alcohol-based solvents, methanol, ethanol, propanol, isopropyl alcohol, or mixtures thereof can be used, and as amine-based solvents, methylamine, ethylamine, ethylenediamine, or mixtures thereof can be used.

[0083] Furthermore, the reaction to obtain the lithium compound-containing solution can be carried out at a temperature range of 20°C to 90°C while stirring for 0.5 to 6.0 hours, and stirring at the above temperature for the above time allows for more effective formation of the lithium compound.

[0084] In step (S1) above, the stirring may be performed by primary stirring at a temperature range of 30°C to 90°C for 1 hour or more, and secondary stirring while cooling to room temperature, taking into consideration the adjustment of the lithium ion diffusion rate and appropriate pre-lithiation. The primary and secondary stirring may be performed for the same amount of time.

[0085] (S2) Step Step (S2) is a step for producing lithium silicon oxide by separating the lithium silicon oxide particles generated in step (S1), drying and calcining them, and can be carried out by separating the particles generated in step (S1), followed by drying and calcining them.

[0086] The generated particles can be separated from the solution by means of conventional methods in the industry, for example, by centrifuging the solution to separate the supernatant from the precipitate, which is the generated particles.

[0087] The aforementioned drying can be carried out by conventional means in this industry, for example, by letting it stand at a temperature range of 70°C to 90°C, or at 75°C to 85°C for two hours or more.

[0088] Furthermore, the firing process can be carried out by heat treatment in an inert gas atmosphere at a temperature range of 850°C to 900°C for 1 to 2 hours.

[0089] On the other hand, in the method for producing lithium silicon oxide according to one embodiment of the present invention, the inert gas may be argon, nitrogen, or a combination thereof.

[0090] negative electrode The present invention provides a negative electrode containing the lithium silicon oxide.

[0091] The negative electrode according to one embodiment of the present invention comprises a conductive metal current collector and a negative electrode material layer provided on at least one surface of the current collector, wherein the negative electrode material layer comprises the lithium silicon oxide.

[0092] The anode according to the present invention includes an anode material layer containing lithium silicon oxide, which provides excellent initial efficiency, suppresses volume expansion of the anode, and enables excellent capacity retention and long-term stability.

[0093] The conductive metal current collector contains a highly conductive metal, and there are no particular limitations on the conductive metal current collector as long as it is unreactive within the battery voltage range. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. can be used. The current collector can also have a thickness of 3 μm to 500 μm.

[0094] On the other hand, the negative electrode can be manufactured by mixing an aqueous solvent, the lithium silicon oxide, a binder, and a conductive material to produce a negative electrode material slurry, applying the negative electrode material slurry to at least one surface of a conductive metal current collector, and drying it. Here, the aqueous solvent can be water.

[0095] Furthermore, the conductive material can be any material that does not cause chemical changes and has electronic conductivity, without any particular limitations. Specifically, the conductive material may include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these materials alone or a mixture of two or more materials can be used.

[0096] Furthermore, the binder is usually added in an amount of 0.1% to 10% by weight relative to the total weight of the negative electrode material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0097] Lithium-ion battery The present invention provides a lithium secondary battery including the negative electrode.

[0098] According to one embodiment of the present invention, the lithium secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. The lithium secondary battery may also optionally further include a battery container for housing the electrode assembly of the negative electrode, positive electrode, and separator, and a sealing member for sealing the battery container.

[0099] According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode material layer located on the positive electrode current collector.

[0100] According to one embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy can be used. The positive electrode current collector can also typically have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on its surface to strengthen the bonding force of the positive electrode material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0101] According to one embodiment of the present invention, the cathode material layer may selectively include a binder and a conductive material together with the cathode material.

[0102] According to one embodiment of the present invention, the cathode material may be LiCoO2, LiCoPO4, LiNiO2, Li x Ni a Co b M 1 c M 2 d O2(M 1 and M 2 Each is independently selected from the group consisting of Al, Mn, Cu, Fe, V, Cr, Mo, Ga, B, W, Mo, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and Y, and 0.9 ≤ x ≤ 1.1, 0 <a<1.0、0<b<1.0、0≦c<0.5、0≦d<0.5、a+b+c+d=1である。)、LiMnO2、LiMnO3、LiMn2O3、LiMn2O4、LiMn 2-e M 3 e O2(M 3 ( is one or more elements selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and 0.01 ≤ e ≤ 0.1. ), Li2Mn3M 4 O8(M 4 (This is one or more selected from the group consisting of Ci, Ni, Fe, Cu, and Zn.) It can also be one selected from the group consisting of LiFePO4, Li2CuO2, LiV3O8, V2O5, Cu2V2O7, and lithium metal.

[0103] According to one embodiment of the present invention, the binder is a component that helps to bond the conductive material, the positive electrode material, and the current collector, and is usually added in an amount of 0.1% to 10% by weight relative to the total weight of the positive electrode material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0104] According to one embodiment of the present invention, the conductive material in the positive electrode layer is a component for further improving the conductivity of the positive electrode material, and can be added in an amount of 10% by weight or less, preferably 5% by weight or less, relative to the total weight of the positive electrode layer. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0105] According to one embodiment of the present invention, the positive electrode can be manufactured by applying a slurry for forming a positive electrode material layer, which is prepared by dissolving or dispersing a positive electrode material and a binder and a conductive material selectively in a solvent, onto the positive electrode current collector and drying it, or by casting the slurry for forming a positive electrode material layer onto another support, peeling it off the support, and laminating the resulting film onto the positive electrode current collector.

[0106] According to one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. It can be used without particular limitations as long as it is a separator that is normally used in lithium secondary batteries, and it is especially preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte impregnation ability. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof can be used. In addition, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, coated separators containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength, and can be selectively used as a single-layer or multi-layer structure.

[0107] According to one embodiment of the present invention, the electrolyte can be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte, which can be used in the manufacture of lithium secondary batteries, and is not limited to these. Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0108] According to one embodiment of the present invention, the organic solvent can be used without particular limitations as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0109] According to one embodiment of the present invention, the lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the lithium salt is F - Cl - , Br - , I - NO3 - , N(CN)2 - BF4 - CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - , (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - Or (CF3CF2SO2)2N - The lithium salt may be at least one selected from the group consisting of the following, and the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably used in the range of 0.1M to 2.0M. When the concentration of the lithium salt falls within this range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0110] According to one embodiment of the present invention, the electrolyte may also contain, in addition to the electrolyte components, other components for improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity, such as vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), propane sultone (PS), 1,3-propane sultone (PRS), ethylene sulfate (Esa), succinonitrile (SN), adiponitrile (AN), hexane tricarbonitrile (HTCN), γ-butyrolactone, biphenyl (BP), cyclohexylbenzene (CHB), and t-amylbenzene (tert-amyl The mixture may further contain one or more additives selected from the group consisting of benzene, TAB, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. Here, the additives may be present in an amount of 0.1% to 5% by weight relative to the total weight of the electrolyte.

[0111] The lithium secondary battery containing the negative electrode according to the present invention exhibits excellent capacity characteristics, output characteristics, and life characteristics in a stable manner, making it useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the electric vehicle field, including hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0112] The external shape of the lithium secondary battery of the present invention is not particularly limited, but it can be cylindrical, rectangular, pouch-shaped, or coin-shaped, using a can.

[0113] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for small devices, but also preferably as a unit battery in medium- and large-sized battery modules containing a large number of battery cells.

[0114] Accordingly, according to one embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0115] According to one embodiment of the present invention, the battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0116] Examples Hereinafter, embodiments of the present invention will be described in detail so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0117] Example 1 3.7 g of biphenyl was added to 30 ml of 2-methyltetrahydrofuran and stirred for 10 minutes. When the solution turned clear, 0.166 g of Li powder was added thereto and stirred for 6 hours to produce a dark green 0.8 M LiBP solution.

[0118] To the LiBP solution, 4 g of SiO 50 / C (0 < x ≤ 2) powder having a carbon coating layer on the surface with an average particle diameter (D x ) of 5 μm was added and stirred at 80°C for 1 hour. The volatilized solvent was collected by a reflux condenser to maintain a constant concentration. Next, it was further stirred for 1 hour while cooling to room temperature (25°C). Here, all processes were carried out under an argon atmosphere.

[0119] Next, the solution was centrifuged to separate only the powder particles, and the separated particles were dried at 80°C for 6 hours, heated to 900°C, and heat-treated under an argon atmosphere for 2 hours to produce lithium silicon oxide.

[0120] Example 2 In Example 1 above, 0.6 M LiBP solution was produced using 2.77 g of biphenyl and 0.126 g of Li powder, and lithium silicon oxide was produced in the same manner as in Example 1 except for using this.

[0121] Comparative Example 1 In Example 1 above, 0.5 M LiBP solution was produced using 2.31 g of biphenyl and 0.104 g of Li powder, and lithium silicon oxide was produced in the same manner as in Example 1 except for using this.

[0122] Comparative Example 2 In Example 1 above, 1.0 M LiBP solution was produced using 4.62 g of biphenyl and 0.21 g of Li powder, and lithium silicon oxide was produced in the same manner as in Example 1 except for using this.

[0123] Experimental Example 1 The characteristics of each lithium silicon oxide produced in the examples and comparative examples were analyzed and shown in Table 1 below.

[0124] (1) Raman analysis Raman analysis was performed using a Ramanforce (Nanophoton) Raman spectrometer. Specifically, after coating each lithium silicon oxide powder from the examples and comparative examples onto a glass slide, the Raman spectrometer (532 nm laser) was used to map 900 pixels (5 μm × 5 μm / pixel) in a 150 μm × 150 μm area per sample using the XY Raman mapping technique, with a Raman shift of 200 cm². -1 ~520cm -1 The Raman spectrum was measured, and the Raman shift was 490 cm⁻¹. -1 More than 500cm -1 The following and 512cm -1 More than 520cm -1 The number of pixels with the highest peak was measured for each of the following parameters.

[0125] Furthermore, we checked whether the following mathematical formulas 1 and 2 were satisfied.

[0126] [Mathematical formula 1] 0.45 ≤ PX 512 / PX T

[0127] In the above mathematical formula 1, PX T This refers to the total number of pixels obtained by evenly dividing a 150 μm × 150 μm area of ​​lithium silicon oxide surface into 5 μm × 5 μm pixels using the Raman mapping technique, resulting in 900 pixels. 512 This is a Raman shift of 200 cm obtained by the Raman mapping technique for each of the 900 pixels mentioned above. -1 From 520cm -1 Of the Raman spectra up to 512 cm⁻¹, -1 More than 520cm -1 The following is the number of pixels with the maximum peak.

[0128] [Mathematical formula 2] 5≦PX 512 / PX 500

[0129] In the aforementioned mathematical formula 2, PX 512 This involves using the Raman mapping technique to divide a 150 μm × 150 μm area of ​​lithium silicon oxide surface into 900 pixels of equal size (5 μm × 5 μm), and then applying a Raman shift of 200 cm to each of these pixels. -1 Of the Raman spectra from 512 cm⁻¹ to 520 cm⁻¹, -1 More than 520cm -1 The following is the number of pixels with the highest peak, PX 500 This is a Raman shift of 200 cm for each of the 900 pixels mentioned above. -1 From 520cm -1 Of the Raman spectra up to 490 cm² -1 More than 500cm -1 The following is the number of pixels with the maximum peak.

[0130] (2)XRD analysis XRD analysis was performed to confirm the presence or absence of lithium silicate (Li2SiO3) and lithium disilicate (Li2Si2O5).

[0131] XRD analysis was performed using a Brucker D8 ADNAVCE powder x-ray diffractiometer (Bruker) with a current of 49kV, a voltage of 40mA CuKα, a Bragg angle (2θ) of 15° to 95°, and a scan speed of 0.02° / 0.20sec. The presence or absence of peaks at 24.0±0.5° and 24.5±0.5° confirmed the presence of lithium disilicate (Li2Si2O5), and the presence or absence of a peak at 2θ=27.0±0.5° confirmed the presence of lithium silicate (Li2SiO3).

[0132] [Table 1]

[0133] As can be seen by referring to Table 1 above, the lithium silicon oxides of Examples 1 and 2 did not show lithium silicate in the XRD patterns and simultaneously satisfied mathematical formulas 1 and 2. On the other hand, the lithium silicon oxides of Comparative Examples 1 and 2 could not satisfy either mathematical formula 1 or 2, and in the case of Comparative Example 2, a lithium silicate peak was also observed in the XRD pattern.

[0134] Experimental Example 2 Aqueous anode material slurries were prepared using lithium silicon oxide produced in the examples and comparative examples, and the amount of gas generated was measured. The results are shown in Table 2 below.

[0135] A negative electrode aqueous slurry was prepared by mixing various lithium silicon oxides, graphite, Super-C65 as a conductive material, and carboxymethyl cellulose and styrene-butadiene rubber binders in a weight ratio of 77:19.2:1:1.1:1.6 under the solvent of water. Next, 5 g of the negative electrode aqueous slurry was placed in an aluminum pouch, sealed, and stored in a 60°C oven, and the amount of gas generated was measured using a specific gravity balance.

[0136] [Table 2]

[0137] As can be seen by referring to Table 2 above, the negative electrode material slurries containing lithium silicon oxide of Example 1 and Example 2 showed a reduced amount of gas generation compared to Comparative Examples 1 and 2. In particular, compared to Comparative Example 2, in which lithium silicate was observed in the XRD pattern in Table 1 and did not satisfy mathematical formulas 1 and 2, the amount of gas generated was significantly reduced to 1 / 8 of the original level after long-term storage.

[0138] Experimental Example 3 Half-cells were manufactured using the lithium silicon oxides of the examples and comparative examples, and the characteristics of the batteries were measured. The results are shown in Table 3 below.

[0139] Each lithium silicon oxide was mixed with the conductive material Super-C65 and the binder li-PAA in a weight ratio of 70:15:15 to produce a negative electrode slurry. This slurry was then applied to copper foil, and the negative electrode was manufactured through drying, rolling, and punching processes.

[0140] A lithium metal was used as the relative electrode, and a porous polyethylene separator was interposed between the negative electrode and the lithium metal. An electrolyte solution containing 1 M LiPF6, 1.5 wt% VC, and 0.5 wt% PS was injected, which was a solvent mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70. A coin half-cell was then manufactured.

[0141] After leaving the coin half-cell for 24 hours, it was charged to 0.005V with a constant current (CC) of 0.1C in the 0.005-1.5V vs. Li / Li+ range, then charged with a constant voltage (CV) until the charging current reached 0.02C, and finally discharged with a constant current (CC) of 0.1C. The charge / discharge capacity and initial efficiency of the first cycle were measured.

[0142] [Table 3]

[0143] As can be seen by referring to Table 3, it can be confirmed that Examples 1 and 2 have superior initial efficiency compared to Comparative Examples 1 and 2. From the results in Tables 1 to 3, it can be seen that the lithium silicon oxide according to the present invention satisfies mathematical formula 1, more preferably mathematical formulas 1 and 2 simultaneously, and does not contain lithium silicate. Therefore, even when manufactured in an aqueous anode material slurry, it does not dissolve in water, and gas generation can be significantly reduced. This results in superior anode integrity, superior storage stability, and superior initial capacity and capacity retention.

Claims

1. A lithium silicon oxide that satisfies the following mathematical formula 1. [Mathematical formula 1] 0.45≦PX ５１２ / PX Ｔ In the above mathematical formula 1, PX Ｔ This refers to the total number of pixels obtained by equally dividing a 150 μm × 150 μm area of ​​the lithium silicon oxide surface into 5 μm × 5 μm pixels using the Raman mapping technique, resulting in 900 pixels. PX ５１２ This is a Raman shift of 200 cm obtained by the Raman mapping technique for each of the 900 pixels in total. －１ 520cm －１ Of the Raman spectra up to 512 cm⁻¹, －１ 520cm or more －１ The following is the number of pixels with the maximum peak.

2. The lithium silicon oxide according to claim 1, satisfying the following mathematical formula 2. [Mathematical formula 2] 5≦PX ５１２ / PX ５００ In the aforementioned mathematical formula 2, PX ５１２ This involves using the Raman mapping technique to divide a 150 μm x 150 μm area of ​​lithium silicon oxide surface into 900 pixels of equal size (5 μm x 5 μm), and then applying a Raman shift of 200 cm to each of these pixels. －１ 520cm －１ Of the Raman spectra up to 512 cm⁻¹, －１ 520cm or more －１ The following is the number of pixels with the maximum peak: PX ５００ This is a Raman shift of 200 cm for each of the 900 pixels mentioned above. －１ 520cm －１ Of the Raman spectra up to 490 cm² －１ More than 500cm －１ The following is the number of pixels with the maximum peak.

3. The lithium silicon oxide according to claim 1, satisfying the following mathematical formula 1-1. [Mathematical formula 1-1] 0.45≦PX ５１２ / PX Ｔ ≦1.00 In the above mathematical formula 1-1, PX Ｔ and PX ５１２ This is as defined in mathematical formula 1.

4. The lithium silicon oxide according to claim 2, satisfying the following mathematical formula 2-1. [Mathematical formula 2-1] 5≦PX ５１２ / PX ５００ ≦100 In the above mathematical formula 2-1, PX ５１２ and PX ５００ This is as defined in the above mathematical formula 2.

5. Si, SiO ｘ The lithium silicon oxide according to claim 1, comprising (0 < x ≤ 2) and a lithium-containing compound.

6. The Si and SiO mentioned above ｘ (0 < x ≤ 2) is the lithium silicon oxide according to claim 5, wherein the surface includes a carbon coating layer.

7. The lithium silicon oxide according to claim 5, wherein the lithium-containing compound comprises one or more lithium disilicate and lithium silicide.

8. Conductive metal current collector, The current collector includes a negative electrode material layer provided on at least one surface of the current collector, The negative electrode material layer comprises the lithium silicon oxide described in claim 1.

9. A lithium secondary battery comprising a negative electrode according to claim 8, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

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