Lithium primary battery and negative electrode for lithium primary battery

Abstract

A lithium primary battery having a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode contains Li x MnO2 (0≤x≤0.05). The negative electrode contains an alloy containing lithium, magnesium, and manganese. The content of lithium in the alloy is greater than 88 mass%, the content of magnesium in the alloy is 0.01 mass% or greater and 10 mass% or less. The content of manganese in the alloy is 0.001 mass% or greater and 5 mass% or less.

Description

Technical Field

[0001] This disclosure relates to lithium primary batteries and negative electrodes for lithium primary batteries. Background Technology

[0002] Lithium-ion primary batteries have high energy density and low self-discharge, making them a popular power source for many electronic devices. The positive electrode of a lithium-ion primary battery uses materials such as manganese dioxide. The negative electrode uses, for example, sheet-like (foil-like) metallic lithium or lithium alloys.

[0003] Patent document 1 discloses a high-temperature lithium battery in which fluorinated graphite is used as the positive electrode, a lithium alloy is used as the negative electrode, and an ionic liquid is used as the electrolyte. The lithium alloy used is Li-Al alloy, Li-Mg alloy, Li-B alloy, Li-B-Mg alloy, or Li-Si alloy.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-192627 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] When lithium primary batteries are stored for a long time, their internal resistance will increase and their discharge characteristics will decrease.

[0009] Problem-solving methods

[0010] One aspect of the present invention relates to a lithium primary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode contains Li x MnO2 (0≤x≤0.05), wherein the negative electrode contains an alloy containing lithium, magnesium and manganese, wherein the lithium content in the alloy is greater than 88% by mass, the magnesium content in the alloy is greater than 0.01% by mass and less than 10% by mass, and the manganese content in the alloy is greater than 0.001% by mass and less than 5% by mass.

[0011] Another aspect of this disclosure relates to a negative electrode for a lithium primary battery, which is used in a lithium primary battery where the positive electrode contains Li. x MnO2 (0≤x≤0.05), wherein the negative electrode contains an alloy containing lithium, magnesium and manganese, wherein the lithium content in the alloy is greater than 88% by mass, the magnesium content in the alloy is greater than 0.01% by mass and less than 10% by mass, and the manganese content in the alloy is greater than 0.001% by mass and less than 5% by mass.

[0012] Invention Effects

[0013] According to this disclosure, it is possible to suppress the decrease in discharge characteristics of lithium primary batteries after long-term storage.

[0014] Although novel features of the invention are set forth in the appended claims, the invention will be more clearly understood, in both its composition and content, by taking into account other objects and features of the invention and by referring to the accompanying drawings, through the following detailed description. Attached Figure Description

[0015] Figure 1 This is a front view showing a portion of a lithium primary battery according to one embodiment of the present disclosure in cross-section. Detailed Implementation

[0016] The following examples illustrate embodiments of this disclosure, but this disclosure is not limited to the examples described below. In the following description, specific values ​​and materials are sometimes illustrated, but other values ​​or materials can be applied as long as the effects of this disclosure are achieved. In this specification, the description of "value A to value B" includes both value A and value B, and can be replaced with "value A or higher and value B or lower." In the following description, when lower and upper limits are illustrated for values ​​related to specific physical properties or conditions, any combination of the illustrated lower limit and any illustrated upper limit can be used as long as the lower limit is not higher than the upper limit. When multiple materials are illustrated, one can be selected for use alone, or two or more can be combined.

[0017] The lithium primary battery of this disclosure includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode contains Li. x MnO2 (0≤x≤0.05) is used as the positive electrode active material. The negative electrode contains an alloy containing lithium (Li), magnesium (Mg), and manganese (Mn) (hereinafter also referred to as "lithium alloy") as the negative electrode active material. The Li content in the lithium alloy is greater than 88% by mass. The Mg content in the lithium alloy is greater than 0.01% by mass and less than 10% by mass. The Mn content in the lithium alloy is greater than 0.001% by mass and less than 5% by mass.

[0018] By including Mg in the Li-containing negative electrode, the strength of the negative electrode is improved, which suppresses the increase in internal resistance and the resulting decrease in discharge characteristics caused by "cracking on the negative electrode at the end of discharge" and "partial defects".

[0019] On the other hand, during battery storage, manganese (Mn) contained in the positive electrode active material dissolves from the positive electrode into the non-aqueous electrolyte. Mn-containing organic compounds precipitate, using Mg, which readily alloys with Mn, as nuclei. Sometimes, the growth of these precipitates can clog the pores of the separator. Additionally, a film containing precipitates with relatively high resistivity can sometimes form on the surface of the negative electrode. Therefore, the internal resistance of the battery increases after storage, and its discharge characteristics may sometimes decrease. In other words, its storage performance can sometimes be compromised.

[0020] Therefore, the inventors conducted in-depth research to improve the above-mentioned preservation characteristics and found that by pre-containing Mn in the negative electrode containing Li and Mg, the decrease in discharge characteristics caused by the increase in internal resistance after preservation (decrease in preservation characteristics) can be significantly suppressed.

[0021] Adding Mn to a Mg-containing Li alloy (anode) significantly improves the discharge characteristics after storage (e.g., low-temperature pulsed discharge characteristics after storage). The exact reasons are unclear, but are speculated as follows: If Mn is pre-contained in the Li and Mg-containing anode, the pre-contained Mn alloys with Mg, thereby reducing the activity of Mg. Therefore, even if Mn dissolves from the cathode, the precipitation of Mn-containing organic compounds and the resulting decrease in storage characteristics can be suppressed. The increased anode strength from the addition of Mg and the suppression of Mn-containing organic compound precipitation from the addition of Mn mutually reinforce each other, resulting in a significant improvement in the discharge characteristics after storage. When the anode contains Mg, Mn can reduce the anode resistance and simultaneously reduce the activity of Mg.

[0022] However, if the Mg content in the lithium alloy is greater than 10% by mass, the negative electrode resistance increases due to the higher proportion of Mg in the negative electrode, and the discharge characteristics may sometimes decrease. If the Mg content in the lithium alloy is less than 0.01% by mass, the effect of the increased negative electrode strength brought about by the presence of Mg in the negative electrode is smaller, and the discharge characteristics may sometimes decrease.

[0023] If the Mn content in the lithium alloy is greater than 5% by mass, the proportion of Mn in the negative electrode increases, thereby increasing the negative electrode resistance and sometimes reducing discharge characteristics. If the Mn content in the lithium alloy is less than 0.001% by mass, the effect of pre-containing Mn in the negative electrode becomes smaller, and discharge characteristics may sometimes decrease.

[0024] If the Li content in the lithium alloy is below 88% by mass, the proportion of Li in the negative electrode becomes smaller, which increases the negative electrode resistance and sometimes reduces the discharge characteristics.

[0025] (Lithium alloy)

[0026] From the perspective of reducing internal resistance and ensuring capacity, the Li content in the lithium alloy is greater than 88% by mass, which can be 89% or more by mass, 90% or more by mass, or 95% or more by mass. From the perspective of suppressing the decline in storage properties, the Mg content in the lithium alloy is 0.01% by mass or more and less than 10% by mass, and the Mn content in the lithium alloy is 0.001% by mass or more and less than 5% by mass.

[0027] From the viewpoint of improving the negative electrode strength, the Mg content in the lithium alloy is 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more or 0.2% by mass or more, and may also be 1% by mass or more. From the viewpoint of reducing the negative electrode resistance, the Mg content in the lithium alloy is 10% by mass or less, preferably 8% by mass or less, more preferably 7% by mass or less or 4% by mass or less. The range of Mg content in the lithium alloy may be, for example, 0.2% by mass or more and 7% by mass or less, or 1% by mass or more and 4% by mass or less.

[0028] From the viewpoint of suppressing the precipitation of Mn-containing organic compounds, the Mn content in the lithium alloy is 0.001% by mass or more, preferably 0.005% by mass or more, more preferably 0.01% by mass or more, or 0.02% by mass or more. From the viewpoint of reducing the negative electrode resistance, the Mn content in the lithium alloy is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less, or 1% by mass or less. Even if the Mn content in the lithium alloy is small, such as 1% by mass or less (or 0.5% by mass or less), the precipitation of Mn-containing organic compounds in lithium alloys containing Mg can be sufficiently suppressed. The range of Mn content in the lithium alloy can be, for example, 0.005% by mass or more and 2% by mass or less, or 0.01% by mass or more and 1% by mass or less (or 0.5% by mass or less). The molar ratio of Mn to Mg, i.e., Mn / Mg, can be, for example, in the range of 0.0008 to 5.

[0029] Lithium alloys can contain metallic elements other than Li, Mg, and Mn. Examples of such metallic elements include Al, Sn, Ni, Pb, In, Na, K, and Ca. The composition of lithium alloys can be determined using inductively coupled plasma (ICP) emission spectroscopy or atomic absorption spectroscopy (AAS).

[0030] The lithium alloy preferably contains Al. A portion of the Mg contained in the lithium alloy can be replaced by Al. In this case, the storage properties are further improved. The exact reason is unclear, but it is speculated that the Mg alloyed with Mn is protected by Al, further reducing the activity of Mg, thereby further suppressing the precipitation of Mn-containing compounds dissolved from the positive electrode, and further suppressing the increase in internal resistance.

[0031] The addition of Al suppresses the increase in internal resistance during storage. Furthermore, Al tends to segregate in Li, while Mg exhibits excellent dispersion in Li. When the lithium alloy contains both Mg and Al, the good dispersion of Mg suppresses Al segregation, thus preventing the uneven Li consumption caused by Al segregation. In this case, the effects of Mg and Al can be stably obtained throughout the negative electrode, while Li is uniformly consumed on the negative electrode surface, resulting in a higher proportion of Li available for the discharge reaction at the end of the discharge phase. When Al is present along with Mg, a low-resistivity film is easily and stably formed, further increasing the voltage at the end of the discharge phase and further suppressing the decline in storage characteristics.

[0032] From the viewpoint of suppressing the reduction of storage properties, the Al content in the lithium alloy is preferably 0.01% by mass or more (or 0.1% by mass or more) and 5% by mass or less, more preferably 1% by mass or more and 2% by mass or less. From the same viewpoint, the combined Mg and Al content in the lithium alloy is preferably 0.02% by mass or more and 10% by mass or less. The molar ratio of Al to Mg, i.e., Al / Mg, can be in the range of, for example, 0.01 to 45.

[0033] (Additives for non-aqueous electrolytes)

[0034] The non-aqueous electrolyte preferably contains at least one additive selected from cyclic imide compounds, phthalate compounds, and isocyanate compounds. When the non-aqueous electrolyte contains the above-mentioned additive, a composite coating containing "components from the lithium alloy (Mg, Mn)" and "components from the additive" can be formed on the surface of the Mg-containing lithium alloy (anode). This coating has excellent chemical stability, and since it contains Mg and Mn from the lithium alloy, the resistance of the anode is reduced. Furthermore, even within the coating, Mg alloys with Mn, thereby reducing activity. The lithium alloy is protected by a high-quality composite coating. Therefore, through the formation of the above-mentioned composite coating, even if Mn dissolves from the cathode, the precipitation of Mn-containing organic compounds with Mg as the core is easily suppressed. As a result, it is easier to suppress the degradation of storage properties.

[0035] The content of additives in the non-aqueous electrolyte is, for example, 0.01% by mass or more and 5% by mass or less. Furthermore, the content of additives in the non-aqueous electrolyte is the mass fraction (percentage) of the additives relative to the total mass of the non-aqueous electrolyte. For example, when the battery is first manufactured (or when preparing the non-aqueous electrolyte), it is preferable that the content of additives in the non-aqueous electrolyte is within the above-mentioned range. In contrast, in batteries that have been manufactured for a certain period of time, some of the additives are consumed in the formation of the film, and the content of additives in the non-aqueous electrolyte can be a value smaller than the above-mentioned range. In this case, even if the content of additives in the non-aqueous electrolyte is small (e.g., close to the detection limit), the aforementioned effects brought about by the additives can be confirmed. The same applies to the content of various compounds such as cyclic imide compounds, which will be described later.

[0036] (Cyclic imide compounds)

[0037] Examples of cyclic imide compounds include, for instance, cyclic diacylimide compounds. A cyclic imide compound only needs to possess a diacylimide ring (hereinafter also referred to as an imide ring). The imide ring can also condense with other rings (hereinafter also referred to as a second ring). In non-aqueous electrolytes, cyclic imide compounds can exist as imides, or as anions or salts. When existing as imides in non-aqueous electrolytes, cyclic imide compounds can exist in the form of free NH groups or as tertiary amines.

[0038] Examples of second rings include aromatic rings, saturated or unsaturated aliphatic rings, etc. The second ring may contain at least one heteroatom. Examples of heteroatoms include oxygen atoms, sulfur atoms, and nitrogen atoms.

[0039] Examples of cyclic imide compounds include, for example, aliphatic dicarboxylic acid imide compounds and cyclic imide compounds having a second ring. Examples of aliphatic dicarboxylic acid imide compounds include, for example, succinimide. Examples of cyclic imide compounds having a second ring include imide compounds of aromatic or alicyclic dicarboxylic acids. Examples of aromatic or alicyclic dicarboxylic acids include compounds having carboxyl groups on two adjacent atoms forming the ring. Examples of cyclic imide compounds having a second ring include, for example, phthalimide and hydrides of phthalimide. Examples of hydrides of phthalimide include, for example, cyclohexane-3-ene-1,2-dicarboximide and cyclohexane-1,2-dicarboximide.

[0040] The imide ring can be an N-substituted imide ring with a substituent on the nitrogen atom of the imide. Examples of such substituents include hydroxyl, alkyl, alkoxy, and halogen atoms. Examples of alkyl groups include C1 to C4 alkyl groups, as well as methyl and ethyl groups. Examples of alkoxy groups include C1 to C4 alkoxy groups, as well as methoxy and ethoxy groups. Examples of halogen atoms include chlorine and fluorine atoms.

[0041] The cyclic imide compound is preferably selected from at least one of phthalimide and N-substituted phthalimide. The substituent on the nitrogen atom of the N-substituted phthalimide can be selected from substituents exemplified with respect to the N-substituted imide ring. The N-substituted phthalimide preferably contains at least one selected from, for example, N-hydroxyphthalimide, N-(2-hydroxyethyl)phthalimide, N-(cyclohexylthio)phthalimide, and N-(phenylthio)phthalimide. The phthalimide and / or N-substituted phthalimide may constitute 50% or more by mass of the cyclic imide compound, and further may constitute 70% or more by mass or 90% or more by mass.

[0042] The non-aqueous electrolyte may contain one or more cyclic imide compounds. The content of cyclic imide compounds in the non-aqueous electrolyte may be less than 1% by mass, more than 0.001% by mass and less than 1% by mass, or more than 0.001% by mass and less than 0.8% by mass.

[0043] (Phthyl ester compounds)

[0044] Phthalate ester compounds include phthalates and their derivatives. Derivatives may have substituents linked to an aromatic ring derived from phthalic acid. Examples of such substituents include hydroxyl, alkyl, alkoxy, and halogen atoms. Examples of alkyl groups include, for example, C1-C4 alkyl groups, such as methyl and ethyl. Examples of alkoxy groups include, for example, C1-C4 alkoxy groups, such as methoxy and ethoxy. Examples of halogen atoms include chlorine and fluorine atoms.

[0045] Phthalate esters can be monophthalic acid esters, but phthalic acid diesters are preferred from the viewpoint that the resulting coating easily protects the surface of the Li alloy. As the alcohol that forms an ester with phthalic acid (or its derivatives), saturated or unsaturated aliphatic alcohols of C1 to C20 (preferably C1 to C6) are preferred.

[0046] Specific examples of phthalate diester compounds include dimethyl phthalate, diethyl phthalate, diallyl phthalate, dibutyl phthalate, diisobutyl phthalate, and di(2-ethylhexyl) phthalate. They can be used alone or in combination of two or more. The phthalate diester compound can constitute 50% or more, and further 70% or more, or 90% or more of the phthalate ester compound by mass.

[0047] Non-aqueous electrolytes may contain one or more phthalate compounds. The content of phthalate compounds in non-aqueous electrolytes may be less than 1% by mass, or more than 0.1% by mass and less than 1% by mass.

[0048] (Isocyanate compounds)

[0049] Isocyanate compounds have, for example, "at least one isocyanate group" and "a C1-C20 aliphatic hydrocarbon group or a C6-C20 aromatic hydrocarbon group". The aliphatic and aromatic hydrocarbon groups constituting the isocyanate compound may also have substituents. Substituents can be any stable group, such as a halogen atom or a nitrile group. The aliphatic group can be an alicyclic aliphatic group, or a straight-chain or branched aliphatic group. The aromatic hydrocarbon group is a hydrocarbon group having one or more aromatic rings, or a group formed by the linkage of an aromatic ring and an aliphatic group.

[0050] The isocyanate compound can be a monoisocyanate compound having one isocyanate group, but a diisocyanate compound having two isocyanate groups is preferred. It is believed that diisocyanate compounds can form composite films with higher chemical stability than monoisocyanate compounds and lower resistivity than triisocyanates. Furthermore, even in small amounts, diisocyanate compounds exhibit a high ability to form composite films and demonstrate excellent stability within the battery.

[0051] Specific examples of diisocyanate compounds include compounds represented by OCN-C nH2n-NCO (n being an integer from 1 to 10) (e.g., hexamethylene diisocyanate), compounds containing alicyclic dimethyl groups (e.g., 1,3-bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane-4,4'-diisocyanate, bicyclo[2.2.1]heptane-2,5-dimethylbis(methyl)isocyanate, bicyclo[2.2.1]heptane-2,6-dimethylbis(methyl)isocyanate, isophorone diisocyanate), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, hexyl isocyanate, etc. Preferably, at least one of hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and isophorone diisocyanate is selected. The proportion of the above-mentioned substances in the isocyanate compound can be 50% by mass or more, and can further reach 70% by mass or more or 90% by mass or more.

[0052] When diisocyanate compounds are added to a non-aqueous electrolyte, these compounds can react with each other within the battery (in the non-aqueous electrolyte) to form isocyanurate esters, urea esters, and biuret esters. Therefore, when analyzing the non-aqueous electrolyte after battery disassembly, isocyanurate esters, urea esters, and biuret esters derived from diisocyanate compounds are sometimes detected.

[0053] Non-aqueous electrolytes may contain one or more isocyanate compounds. The content of isocyanate compounds in non-aqueous electrolytes may be less than 3% by mass, more than 0.01% by mass and less than 2% by mass, or more than 0.01% by mass and less than 1.5% by mass.

[0054] For the analysis of non-aqueous electrolytes (additives), methods such as liquid chromatography-mass spectrometry (LC / MS) or gas chromatography-mass spectrometry (GC / MS) can be used. Ultraviolet (UV) spectroscopy can be performed in conjunction with nuclear magnetic resonance (NMR), infrared absorption spectroscopy (IR), and mass spectrometry (MS).

[0055] The lithium primary battery disclosed herein will now be described in more detail.

[0056] [Lithium primary battery]

[0057] (positive electrode)

[0058] The positive electrode contains a positive electrode additive. This additive contains manganese dioxide as the active material. Positive electrodes containing manganese dioxide exhibit relatively high voltage and excellent pulse discharge characteristics. Preferably, the manganese dioxide used is produced by sintering electrolytic manganese dioxide. The manganese dioxide can also be in a mixed crystal state containing various crystalline phases. The positive electrode may contain manganese oxides other than manganese dioxide. Examples of manganese oxides other than manganese dioxide include MnO, Mn3O4, Mn2O3, and Mn2O7. The main component of the manganese oxides in the positive electrode is preferably manganese dioxide.

[0059] The manganese dioxide in the positive electrode can be doped with a small amount of lithium. If the lithium doping level is low, high capacity can be ensured. Manganese dioxide and manganese dioxide doped with a small amount of lithium can be processed using Li... x MnO2 (0≤x≤0.05) is used. Furthermore, the overall average composition of the manganese oxide in the positive electrode is primarily Li. x MnO2 (0 ≤ x ≤ 0.05) is sufficient. Additionally, the Li ratio x should be below 0.05 during the initial discharge phase of a lithium-ion battery. The Li ratio x generally increases as the lithium-ion battery discharges. Theoretically, the oxidation state of manganese in manganese dioxide is tetravalent. However, due to the presence of other manganese oxides in the positive electrode, or the doping of lithium into manganese dioxide, the oxidation state of manganese can sometimes fluctuate from tetravalent. Therefore, in Li... x In MnO2, the average oxidation number of manganese can vary from 4 to some extent.

[0060] In the positive electrode, besides Li x In addition to MnO2, other positive electrode active materials suitable for use in lithium primary batteries may also be included. Examples of other positive electrode active materials include fluorinated graphite. The proportion of manganese dioxide in the total positive electrode active material is preferably 90% by mass or more.

[0061] Electrolytic manganese dioxide is preferred as the manganese dioxide. Adjusting the calcination conditions can increase the crystallinity of manganese dioxide and decrease its specific surface area. Li x The BET specific surface area of ​​MnO2 can be 5m². 2 / g or more and 40m 2 / g or less. When Li x When the BET specific surface area of ​​MnO2 is within the above range, it can suppress self-discharge and further suppress the decrease in pulse discharge characteristics after storage.

[0062] Li xThe BET specific surface area of ​​MnO2 can be determined using known methods, such as a specific surface area measuring device (e.g., manufactured by Mountec Corporation) based on the BET method. For example, the Li2O2 separated from the "positive electrode taken from the battery" can be measured using this method. x MnO2 was used as the test sample.

[0063] Li x The median particle size of MnO2 can be greater than 5 μm and less than 40 μm. When the median particle size is within this range, self-discharge can be suppressed, further suppressing the decrease in pulse discharge characteristics after storage.

[0064] Li x The median particle size of MnO2 is the center value of the particle size distribution obtained, for example, by quantitative laser diffraction-scattering (qLD) method. For instance, it can be used to separate Li from the "positive electrode taken from the battery". x MnO2 was used as the test sample. In the test, for example, the SALD-7500nano manufactured by Shimadzu Corporation was used.

[0065] In addition to the positive electrode active material, the positive electrode mixture may also contain a binder. The positive electrode mixture may also contain a conductive agent.

[0066] Examples of adhesives include fluoropolymers, rubber particles, and acrylic resins.

[0067] Examples of conductive agents include conductive carbon materials. Examples of conductive carbon materials include natural graphite, synthetic graphite, carbon black, and carbon fiber.

[0068] The positive electrode may also contain a positive current collector to retain the positive electrode flux. Materials used for the positive current collector include, for example, stainless steel, aluminum, and titanium.

[0069] In the case of a coin-shaped battery, the positive electrode can be formed by mounting an L-shaped annular positive current collector on a positive electrode compound sheet, or the positive electrode can be formed solely by the positive electrode compound sheet. The positive electrode compound sheet is obtained, for example, by pressing and drying a "wet positive electrode compound prepared by adding an appropriate amount of water to the positive electrode active material".

[0070] In the case of a cylindrical battery, a positive electrode with a sheet-like positive current collector and a positive electrode flux layer held on the positive current collector can be used. As the sheet-like positive current collector, a porous current collector is preferred. Examples of porous current collectors include expanded metal mesh, wire mesh, and perforated metal plates. The positive electrode flux layer is obtained, for example, by coating the surface of the sheet-like positive current collector or filling it into the positive current collector with the aforementioned wetted flux, followed by pressing and drying in the thickness direction.

[0071] The positive electrode preferably comprises a porous current collector as described above and a positive electrode filler filled in the current collector. Preferably, a current collector containing at least one material selected from SUS444, SUS430, and SUS316 is used. By using such a current collector, in a lithium primary battery, side reactions with the aforementioned non-aqueous electrolyte and corrosion of the current collector can be suppressed, as can the increase in internal resistance and the generation of gas. In particular, when such a current collector is combined with a non-aqueous electrolyte containing at least one of LiCF3SO3 and LiClO4, which are typically used as lithium salts in lithium primary batteries, side reactions between the current collector and the non-aqueous electrolyte can be suppressed more effectively. The thickness of the positive electrode is, for example, 300 μm or more and 900 μm or less.

[0072] (negative electrode)

[0073] The negative electrode may contain, for example, a foil (sheet) lithium alloy. The lithium alloy is formed into any shape and thickness according to the shape, size, specifications, and performance of the primary lithium battery.

[0074] In the case of cylindrical batteries, the negative electrode can have a negative electrode current collector (e.g., copper foil) carrying a lithium alloy, or it can be a foil (sheet) lithium alloy without a negative electrode current collector. When the lithium alloy contains Mg, since a relatively high strength of Mg remains at the end of discharge, the negative electrode can be constructed using only the foil (sheet) lithium alloy without a negative electrode current collector. By using a lithium alloy containing Mg, the cracking or partial loss of the negative electrode at the end of discharge, which occurs when the negative electrode does not have a negative electrode current collector, can be suppressed. The shape of the negative electrode (lithium alloy) can be maintained even at the end of discharge, ensuring the overall conductivity of the negative electrode even without a negative electrode current collector.

[0075] In the case of coin-shaped batteries, rolled lithium alloy can be punched into a disc shape for use as the negative electrode. In the case of cylindrical batteries, sheet-shaped lithium alloy can be used as the negative electrode. The sheet material is obtained, for example, by extrusion molding. More specifically, in cylindrical batteries, lithium alloy foil or the like with a shape having "a long side direction and a short side direction" is used.

[0076] (Non-aqueous electrolyte)

[0077] As a non-aqueous electrolyte, it is a liquid in which lithium salts are dissolved as solutes in a non-aqueous solvent.

[0078] As non-aqueous solvents, examples of organic solvents commonly used in non-aqueous electrolytes for primary lithium batteries include ethers, esters, and carbonates. Other non-aqueous solvents that can be used include dimethyl ether, γ-butyrolactone, propylene carbonate, ethylene carbonate, and 1,2-dimethoxyethane. Non-aqueous electrolytes may contain one or more non-aqueous solvents.

[0079] From the viewpoint of improving the discharge characteristics of lithium primary batteries, the non-aqueous solvent preferably contains a cyclic carbonate with a high boiling point and a chain ether with low viscosity even at low temperatures. The cyclic carbonate preferably contains at least one selected from propylene carbonate (PC) and ethylene carbonate (EC), with PC being particularly preferred.

[0080] The chain ether preferably has a viscosity of less than 1 mPa·s at 25°C, and is particularly preferably containing dimethoxyethane (DME). It should be noted that the viscosity of the non-aqueous solvent was determined using a micro-sample viscometer m-VROC manufactured by Rheosense, by measuring at 25°C and a shear rate of 10000 (1 / s).

[0081] Examples of lithium salts include LiCF3SO3, LiClO4, LiBF4, LiPF6, LiRaSO3 (Ra is a fluoroalkyl group with 1 to 4 carbon atoms), LiFSO3, LiN(SO2Rb)(SO2Rc) (Rb and Rc are each a fluoroalkyl group with 1 to 4 carbon atoms), and LiN(FSO2)2. A single lithium salt can be used, or two or more can be used in combination.

[0082] The concentration of lithium ions (total concentration of lithium salts) in the non-aqueous electrolyte is, for example, 0.2 mol / L or more and 2.0 mol / L or less, or 0.3 mol / L or more and 1.5 mol / L or less.

[0083] As needed, the non-aqueous electrolyte may contain additives. Examples of such additives include phthalimides, N-substituted phthalimide compounds, dimethyl phthalate, phthalate ester compounds, propanesulfonate lactone, and vinylene carbonate. The total concentration of such additives in the non-aqueous electrolyte is, for example, 0.003–5 mol / L.

[0084] (Diaphragm)

[0085] Lithium-ion primary batteries typically have a separator between the positive and negative electrodes. As a separator, a porous sheet formed of an insulating material resistant to the internal environment of the lithium-ion primary battery can be used. Specifically, examples include nonwoven fabrics made of synthetic resin, microporous membranes made of synthetic resin, or laminates thereof.

[0086] Examples of synthetic resins used in nonwoven fabrics include polypropylene, polyphenylene sulfide, and polybutylene terephthalate. Examples of synthetic resins used in microporous membranes include polyethylene, polypropylene, and polyolefin resins such as ethylene-propylene copolymer. Microporous membranes may also contain inorganic particles as needed.

[0087] The thickness of the diaphragm is, for example, greater than 5 μm and less than 100 μm.

[0088] There are no particular limitations on the structure of a primary lithium battery. A primary lithium battery can also be a coin-shaped battery with a "layered electrode assembly consisting of a circular plate-shaped positive electrode and a circular plate-shaped negative electrode stacked together via a separator". Alternatively, it can be a cylindrical battery with a "wound electrode assembly consisting of a strip-shaped positive electrode and a strip-shaped negative electrode wound together in a spiral shape via a separator".

[0089] Figure 1 A front view showing a cross-section of a portion of a cylindrical lithium primary battery according to one embodiment of the present disclosure is shown. The positive electrode 1 and negative electrode 2 of the lithium primary battery 10, wound together via a separator 3, are housed together with a non-aqueous electrolyte (not shown) within a battery casing 9. A sealing plate 8 is installed at the opening of the battery casing 9. A positive electrode lead 4, connected to the current collector 1a of the positive electrode 1, is connected to the sealing plate 8. A negative electrode lead 5, connected to the negative electrode 2, is connected to the casing 9. Furthermore, to prevent internal short circuits, an upper insulating plate 6 and a lower insulating plate 7 are respectively disposed above and below the electrode assembly.

[0090] Postscript

[0091] Based on the description of the above embodiments, the following technology is disclosed.

[0092] (Technology 1)

[0093] A primary lithium battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte.

[0094] The positive electrode contains Li x MnO2 (0≤x≤0.05),

[0095] The negative electrode contains an alloy containing lithium, magnesium, and manganese.

[0096] The lithium content in the alloy is greater than 88% by mass.

[0097] The magnesium content in the alloy is 0.01% by mass or more and 10% by mass or less.

[0098] The manganese content in the alloy is more than 0.001% by mass and less than 5% by mass.

[0099] (Technology 2)

[0100] The lithium primary battery as described in Technique 1, wherein the alloy contains aluminum.

[0101] The total content of magnesium and aluminum in the alloy is more than 0.02% by mass and less than 10% by mass.

[0102] (Technology 3)

[0103] Lithium primary batteries as described in technology 1 or 2, wherein Li x The median particle size of MnO2 is greater than 5 μm and less than 40 μm.

[0104] (Technology 4)

[0105] The lithium primary battery as described in any one of techniques 1 to 3, wherein Li x The BET specific surface area of ​​MnO2 is 5m². 2 / g or more and 40m 2 / g or less.

[0106] (Technology 5)

[0107] The lithium primary battery according to any one of techniques 1 to 4, wherein the non-aqueous electrolyte contains at least one additive selected from cyclic imide compounds, phthalate compounds and isocyanate compounds.

[0108] (Technology 6)

[0109] The lithium primary battery of the present invention, as described in Technique 5, wherein the cyclic imide compound contains at least one selected from phthalimide and N-substituted phthalimide.

[0110] (Technology 7)

[0111] The lithium primary battery as described in Technique 6, wherein the N-substituted phthalimide contains at least one selected from N-hydroxyphthalimide, N-(2-hydroxyethyl)phthalimide, N-(cyclohexylthio)phthalimide and N-(phenylthio)phthalimide.

[0112] (Technology 8)

[0113] In the lithium primary battery according to any one of techniques 5 to 7, the content of the cyclic imide compound in the non-aqueous electrolyte is less than 1% by mass.

[0114] (Technology 9)

[0115] The lithium primary battery as described in any one of techniques 5 to 8, wherein the phthalate compound contains a phthalate diester compound.

[0116] (Technology 10)

[0117] The lithium primary battery as described in Technique 9, wherein the phthalate compound contains dimethyl phthalate.

[0118] (Technology 11)

[0119] In the lithium primary battery according to any one of techniques 5 to 10, the phthalate compound content in the non-aqueous electrolyte is less than 1% by mass.

[0120] (Technology 12)

[0121] The lithium primary battery as described in any one of techniques 5 to 11, wherein the isocyanate compound contains a diisocyanate compound.

[0122] (Technology 13)

[0123] The lithium primary battery of Technique 12, wherein the diisocyanate compound contains at least one selected from hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and isophorone diisocyanate.

[0124] (Technology 14)

[0125] In the lithium primary battery according to any one of techniques 5 to 13, the content of the isocyanate compound in the non-aqueous electrolyte is less than 3% by mass.

[0126] (Technology 15)

[0127] A negative electrode for a lithium primary battery, which is used in a lithium primary battery.

[0128] The positive electrode of the lithium primary battery contains Li x MnO2, where 0 ≤ x ≤ 0.05,

[0129] The negative electrode contains an alloy containing lithium, magnesium, and manganese.

[0130] The lithium content in the alloy is greater than 88% by mass.

[0131] The magnesium content in the alloy is 0.01% by mass or more and 10% by mass or less.

[0132] The manganese content in the alloy is more than 0.001% by mass and less than 5% by mass.

[0133] (Technology 16)

[0134] The negative electrode for a primary lithium battery as described in Technique 15, wherein the alloy contains aluminum, and the total content of the magnesium and the aluminum in the alloy is 0.02% by mass or more and 10% by mass or less.

[0135] [Example]

[0136] The present disclosure will be specifically described below based on embodiments and comparative examples, but the present disclosure is not limited to the following embodiments.

[0137] Batteries A1-A20, Batteries B1-B10

[0138] (The production of the positive electrode)

[0139] As the positive electrode, 3 parts by mass of Ketjen black as a conductive agent, 5 parts by mass of polytetrafluoroethylene as a binder, and an appropriate amount of pure water are added to 100 parts by mass of calcined electrolytic manganese dioxide and mixed to prepare a moist positive electrode mixture.

[0140] Next, the positive electrode filler is filled into a positive electrode current collector made of 0.4 mm thick expanded metal mesh made of stainless steel (SUS444) to create the positive electrode precursor. Then, the positive electrode precursor is dried, rolled to a thickness of 0.5 mm using a roll press, and cut to the specified size to obtain the positive electrode. Next, a portion of the filled positive electrode filler is peeled off, and one end of a stainless steel positive electrode lead is resistance welded to the exposed portion of the positive electrode current collector.

[0141] (Making the negative electrode)

[0142] The negative electrode is obtained by cutting lithium metal foil or lithium alloy foil (200 μm thick) to a specified size. One end of a nickel negative electrode lead is connected to a specified location on the negative electrode by ultrasonic welding.

[0143] The lithium alloy foil contains Mg, Mn, and / or Al, with the exception of Li. The content of each metal element in the lithium alloy foil is shown in Tables 1-4. A "0" in the content column of Tables 1-3 means that the content is less than the detection limit in compositional analysis (ICP emission spectroscopy, etc.).

[0144] (Fabrication of the electrode assembly)

[0145] An electrode assembly is fabricated by winding the positive and negative electrodes through a separator. A microporous membrane made of polypropylene with a thickness of 25 μm is used as the separator.

[0146] (Preparation of non-aqueous electrolytes)

[0147] A non-aqueous solvent was obtained by mixing propylene carbonate (PC), ethylene carbonate (EC), and 1,2-dimethoxyethane (DME) in a volume ratio of 4:2:4. A non-aqueous electrolyte was prepared by dissolving LiCF3SO3 in the non-aqueous solvent at a concentration of 0.5 mol / L.

[0148] (Assembly of primary lithium batteries)

[0149] The electrode assembly is housed within a cylindrical battery casing that also serves as the negative terminal. An iron casing (17 mm outer diameter, 45.5 mm height) is used as the battery casing. Next, a non-aqueous electrolyte is injected into the battery casing, and then the opening of the battery casing is closed using a metal sealing plate that also serves as the positive terminal. The other end of the positive electrode lead is connected to the sealing plate, and the other end of the negative electrode lead is connected to the inner bottom surface of the battery casing. This completes the fabrication of a cylindrical lithium primary battery. The assembled battery is then aged for 7 days at 45°C after being discharged at 2.4A for 2 minutes. Furthermore, the aged positive electrode active material is treated with Li... x The formula for MnO2 represents the lithium doping amount x, which is in the range of 0 < x ≤ 0.05. In the table, batteries A1 to A20 are examples, and batteries B1 to B10 are comparative examples.

[0150] In addition, the positive electrode mixture contains Li x The median particle size of MnO2 is 21–23 μm, and the BET specific surface area is 14–15 m². 2 / g.

[0151] [evaluate]

[0152] (Internal resistance of the stored battery)

[0153] The aged batteries were stored at 70°C for 4 months. The internal resistance of the stored batteries was measured using an AC ohmmeter (frequency 1kHz) at 20°C.

[0154] (Low-temperature pulse discharge test of the stored battery)

[0155] The aged batteries were stored at 70°C for 4 months. After storage, the batteries were left to stand at -30°C for 2 hours, and then subjected to a 1-second pulse discharge at 300mA at -30°C. The lowest voltage at this point was determined as the pulse discharge voltage.

[0156] The evaluation results are shown in Tables 1-4. In Tables 1-4, the internal resistance is expressed as a relative value with the internal resistance of battery B3 taken as 100. The pulse discharge voltage is expressed as a relative value with the pulse discharge voltage of battery B3 taken as 100.

[0157]

[0158]

[0159]

[0160]

[0161] Batteries A1 to A20 exhibit excellent preservation characteristics due to their low internal resistance and high pulse discharge voltage after storage.

[0162] Batteries B1-B5 have reduced storage characteristics because the negative electrode uses Li metal foil or Li alloy foil without Mg and / or Mn. Battery B6 uses Li-Mg-Mn alloy foil, but its storage characteristics are reduced because the Mg content is greater than 10% by mass. Batteries B7-B8 use Li-Mg-Mn alloy foil, but their storage characteristics are reduced because the Mn content is less than 0.001% by mass or greater than 5% by mass. Batteries B9-B10 use Li-Mg-Mn alloy foil with a Li content of less than 88% by mass, resulting in reduced storage characteristics.

[0163] When the negative electrode does not contain Mg, the addition of Mn has a relatively small effect on improving the pulse discharge voltage and internal resistance (B1→B2). In contrast, when the negative electrode contains Mg, the addition of Mn significantly improves the pulse discharge voltage and internal resistance (B3→A3). Therefore, it can be seen that when the negative electrode (lithium alloy) contains Mg, the improved storage characteristics brought about by the addition of Mn can be significantly obtained.

[0164] As shown in Table 3, excellent storage characteristics were obtained in batteries A1 to A8 with Mg content of 0.5% by mass and Mn content of 0.001 to 5% by mass. Excellent storage characteristics were also obtained in batteries A9 to A15 with Mg content of 0.02% by mass and Mg content of 0.01 to 10% by mass.

[0165] As shown in Table 4, the storage characteristics of batteries A16 to A20, which use Li-Mg-Mn-Al foil as the negative electrode, are further improved. For example, in battery A13, which uses Li-Mg-Mn foil (Mg content: 2% by mass, Mn content: 0.02% by mass) as the negative electrode, the pulse discharge voltage after storage is 111. In battery A18, which uses Li-Mg-Mn-Al foil (Mg content: 1% by mass, Mn content: 0.02% by mass, Al content: 1% by mass) as the negative electrode, the pulse discharge voltage after storage is 114, indicating further improvement in storage characteristics.

[0166] Batteries A21-A28

[0167] In the preparation of the non-aqueous electrolyte, additives are further included. The compounds shown in Table 5 are used as additives. The content (mass %) of the additives in the non-aqueous electrolyte is shown in Table 5.

[0168] In addition to the above, batteries A21 to A28 were manufactured and evaluated in the same manner as battery A4.

[0169] The evaluation results are shown in Table 5. In Table 5, the internal resistance is expressed as a relative value with the internal resistance of battery B3 taken as 100. The pulse discharge voltage is expressed as a relative value with the pulse discharge voltage of battery B3 taken as 100.

[0170]

[0171] As shown in Table 5, batteries A21 to A28, which contain additives in non-aqueous electrolytes, exhibit a further increase in pulse discharge voltage and improved storage characteristics after storage.

[0172] Industry availability

[0173] The lithium primary battery disclosed herein is suitable for use as a main power source or a backup power source for various instruments (e.g., smart meters for electricity, tap water, gas, etc.).

[0174] Although the invention has been described in conjunction with presently preferred embodiments, this disclosure should not be interpreted as restrictive. Various variations and modifications will become apparent to those skilled in the art upon reading the foregoing disclosure. Therefore, the appended claims should be construed as encompassing all modifications and changes without departing from the true spirit and scope of the invention.

[0175] Explanation of symbols in attached drawings

[0176] 1: Positive electrode; 1a: Positive current collector; 2: Negative electrode; 3: Separator; 4: Positive electrode lead; 5: Negative electrode lead; 6: Upper insulating plate; 7: Lower insulating plate; 8: Sealing plate; 9: Battery casing; 10: Primary lithium battery

Claims

1. A primary lithium battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode contains Li x MnO2, where, 0≤x≤0.05， The negative electrode contains an alloy containing lithium, magnesium, and manganese. The lithium content in the alloy is greater than 88% by mass. The magnesium content in the alloy is 0.01% by mass or more and 10% by mass or less. The manganese content in the alloy is more than 0.001% by mass and less than 5% by mass.

2. The lithium primary battery as described in claim 1, wherein the alloy contains aluminum. The total content of magnesium and aluminum in the alloy is more than 0.02% by mass and less than 10% by mass.

3. The lithium primary battery as described in claim 1, wherein, Li x The median particle size of MnO2 is greater than 5 μm and less than 40 μm.

4. The lithium primary battery as described in claim 1, wherein, Li x The BET specific surface area of ​​MnO2 is 5m². 2 / g or more and 40m 2 / g or less.

5. The lithium primary battery of claim 1, wherein the non-aqueous electrolyte contains at least one additive selected from cyclic imide compounds, phthalate compounds, and isocyanate compounds.

6. The lithium primary battery of claim 5, wherein the cyclic imide compound contains at least one selected from phthalimide and N-substituted phthalimide.

7. The lithium primary battery of claim 6, wherein the N-substituted phthalimide contains at least one selected from N-hydroxyphthalimide, N-(2-hydroxyethyl)phthalimide, N-(cyclohexylthio)phthalimide and N-(phenylthio)phthalimide.

8. The lithium primary battery according to claim 5, wherein the content of the cyclic imide compound in the non-aqueous electrolyte is less than 1% by mass.

9. The lithium primary battery of claim 5, wherein the phthalate compound contains a phthalate diester compound.

10. The lithium primary battery of claim 9, wherein the phthalate compound contains dimethyl phthalate.

11. The lithium primary battery of claim 5, wherein the phthalate compound in the non-aqueous electrolyte is present in an amount of less than 1% by mass.

12. The lithium primary battery of claim 5, wherein the isocyanate compound contains a diisocyanate compound.

13. The lithium primary battery of claim 12, wherein the diisocyanate compound contains at least one selected from hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane and isophorone diisocyanate.

14. The lithium primary battery of claim 5, wherein the isocyanate compound in the non-aqueous electrolyte is present in an amount of 3% by mass or less.

15. A negative electrode for a lithium primary battery, which is used in a lithium primary battery. The positive electrode of the lithium primary battery contains Li x MnO2, where, 0≤x≤0.05， The negative electrode contains an alloy containing lithium, magnesium, and manganese. The lithium content in the alloy is greater than 88% by mass. The magnesium content in the alloy is 0.01% by mass or more and 10% by mass or less. The manganese content in the alloy is more than 0.001% by mass and less than 5% by mass.

16. The negative electrode for a primary lithium battery as claimed in claim 15, wherein the alloy contains aluminum, and the total content of the magnesium and the aluminum in the alloy is 0.02% by mass or more and 10% by mass or less.

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