Lithium primary battery and negative electrode for lithium primary battery

Abstract

This lithium primary battery is provided with: a positive electrode; a negative electrode; and a nonaqueous electrolyte solution. The positive electrode contains LixMnO2 (0 ≤ x ≤ 0.05). The negative electrode contains an alloy that contains lithium, magnesium, and manganese. The content of lithium in the alloy is more than 88 mass%, and the content of magnesium in the alloy is 0.01 mass% to 10 mass% inclusive. The content of manganese in the alloy is 0.001 mass% to 5 mass% inclusive.

Description

Lithium primary batteries and negative electrodes for lithium primary batteries

[0001] The present disclosure relates to lithium primary batteries and negative electrodes for lithium primary batteries.

[0002] Lithium primary batteries are used as power sources for many electronic devices due to their high energy density and low self-discharge. Manganese dioxide or the like is used for the positive electrode of a lithium primary battery. For example, sheet-shaped (foil-shaped) lithium metal or a lithium alloy is used for the negative electrode of a lithium primary battery.

[0003] Patent Document 1 discloses that in a high-temperature lithium battery that uses graphite fluoride for the positive electrode, a lithium alloy for the negative electrode, and an ionic liquid as the electrolyte, the lithium alloy is a Li-Al alloy, a Li-Mg alloy, a Li-B alloy, a Li-B-Mg alloy, or a Li-Si alloy.

[0004] JP 2011-192627 A

[0005] In lithium primary batteries, the internal resistance may increase after long-term storage, resulting in a deterioration in discharge characteristics.

[0006] One aspect of the present disclosure is a battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte solution, wherein the positive electrode contains Li ｘ MnO ２ (0≦x≦0.05), the negative electrode comprises an alloy containing lithium, magnesium, and manganese, the lithium content in the alloy being greater than 88% by mass, the magnesium content in the alloy being 0.01% by mass or more and 10% by mass or less, and the manganese content in the alloy being 0.001% by mass or more and 5% by mass or less.

[0007] Another aspect of the present disclosure is a negative electrode for use in a lithium primary battery, the positive electrode of the lithium primary battery comprising: Li ｘ MnO ２(0≦x≦0.05), wherein the negative electrode comprises 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 0.01% by mass or more and 10% by mass or less, and the manganese content in the alloy is 0.001% by mass or more and 5% by mass or less.

[0008] According to the present disclosure, it is possible to suppress the deterioration of discharge characteristics of a lithium primary battery after long-term storage.

[0009] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0010] FIG. 1 is a partially cross-sectional front view of a lithium primary battery according to an embodiment of the present disclosure.

[0011] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits are exemplified for numerical values ​​of specific physical properties or conditions, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one of the materials may be selected and used alone, or two or more materials may be used in combination.

[0012] A lithium primary battery according to an embodiment of the present disclosure includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. ｘ MnO ２(0≦x≦0.05). The negative electrode includes an alloy containing lithium (Li), magnesium (Mg), and manganese (Mn) (hereinafter also referred to as "lithium alloy") as a 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 0.01% by mass or more and 10% by mass or less. The Mn content in the lithium alloy is 0.001% by mass or more and 5% by mass or less.

[0013] By incorporating Mg into a negative electrode containing Li, the strength of the negative electrode is improved, suppressing the increase in internal resistance associated with the occurrence of cracks or partial defects in the negative electrode at the end of discharge and the resulting deterioration in discharge characteristics. Meanwhile, during battery storage, Mn contained in the positive electrode active material dissolves from the positive electrode into the nonaqueous electrolyte, and Mg, which easily alloys with Mn, forms a nucleus to precipitate Mn-containing organic compounds, which may then block the pores of the separator. Furthermore, a coating containing relatively high-resistance precipitates may form on the surface of the negative electrode. Therefore, the internal resistance of the battery increases after storage, which may result in a deterioration in discharge characteristics. In other words, the storage characteristics may be degraded.

[0014] Therefore, the present inventors conducted extensive research to improve the storage characteristics, and discovered that by incorporating Mn into a negative electrode containing Li and Mg in advance, the deterioration of discharge characteristics (deterioration of storage characteristics) due to an increase in internal resistance after storage can be significantly suppressed.

[0015] Adding Mn to a Mg-containing Li alloy (negative electrode) significantly improves discharge characteristics after storage (e.g., low-temperature pulse discharge characteristics after storage). While the detailed reasons for this are unclear, they are speculated to be as follows: When Mn is pre-added to a negative electrode containing Li and Mg from a Mn-containing organic compound, the pre-added Mn alloys with the Mg, resulting in a decrease in Mg activity. Therefore, even if Mn leaches from the positive electrode, precipitation of the Mn-containing organic compound and the resulting decrease in storage characteristics are suppressed. The combined effect of improving negative electrode strength by adding Mg and the suppression of precipitation of the Mn-containing organic compound by adding Mn significantly improves discharge characteristics after storage. When the negative electrode contains Mg, Mn can reduce negative electrode resistance and also reduce Mg activity.

[0016] However, if the Mg content in the lithium alloy is greater than 10% by mass, the proportion of Mg in the negative electrode increases, which may increase the negative electrode resistance and deteriorate the discharge characteristics.If the Mg content in the lithium alloy is less than 0.01% by mass, the effect of adding Mg to the negative electrode to improve its strength is reduced, which may deteriorate the discharge characteristics.

[0017] If the Mn content in the lithium alloy is greater than 5% by mass, the proportion of Mn in the negative electrode increases, which may increase the negative electrode resistance and deteriorate the discharge characteristics. If the Mn content in the lithium alloy is less than 0.001% by mass, the effect of previously incorporating Mn into the negative electrode is reduced, which may deteriorate the discharge characteristics.

[0018] If the Li content in the lithium alloy is 88 mass % or less, the proportion of Li in the negative electrode will be small, which may increase the negative electrode resistance and deteriorate the discharge characteristics.

[0019] (Lithium alloy) From the viewpoint of reducing internal resistance and ensuring capacity, the Li content in the lithium alloy is more than 88% by mass, and may be 89% by mass or more, 90% by mass or more, or even 95% by mass or more. From the viewpoint of suppressing deterioration of storage characteristics, the Mg content in the lithium alloy is 0.01% by mass or more and 10% by mass or less, and the Mn content in the lithium alloy is 0.001% by mass or more and 5% by mass or less.

[0020] From the viewpoint of improving the strength of the negative electrode, 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 0.2% by mass or more, and may 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 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.

[0021] 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 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 as small as 1% by mass or less (or 0.5% by mass or less), the precipitation of Mn-containing organic compounds when the lithium alloy contains Mg is sufficiently suppressed. The Mn content in the lithium alloy may 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, Mn / Mg, may be, for example, within the range of 0.0008 to 5.

[0022] The lithium alloy may contain metal elements other than Li, Mg, and Mn, such as Al, Sn, Ni, Pb, In, Na, K, and Ca. The composition of the lithium alloy can be determined by inductively coupled plasma (ICP) emission spectroscopy or atomic absorption spectroscopy (AAS).

[0023] The lithium alloy preferably further contains Al. A portion of the Mg contained in the lithium alloy may be substituted with Al. In this case, the storage characteristics are further improved. Although the detailed reason for this is unclear, it is presumed that the activity of Mg is further reduced by protecting the Mg alloyed with Mn with Al, which further suppresses the precipitation of compounds containing Mn dissolved from the positive electrode, and further suppresses the increase in internal resistance.

[0024] While the addition of Al suppresses the increase in internal resistance during storage, Al is prone to segregation in Li. On the other hand, Mg has very good dispersibility in Li. When a lithium alloy contains both Mg and Al, the good dispersibility of Mg suppresses Al segregation, and uneven Li consumption due to Al segregation is suppressed. In this case, the effects of Mg and Al are stably obtained throughout the negative electrode, and Li is uniformly consumed on the negative electrode surface, resulting in a larger proportion of Li that can contribute to the discharge reaction at the end of discharge. When Al is contained together with Mg, a low-resistance coating is easily formed stably, the voltage at the end of discharge is further increased, and the deterioration of storage characteristics is further suppressed.

[0025] From the viewpoint of suppressing deterioration of storage characteristics, 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, and more preferably 1% by mass or more and 2% by mass or less. From the same viewpoint, the total content of Mg and Al 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, Al / Mg, may be, for example, in the range of 0.01 to 45.

[0026] (Additives for Nonaqueous Electrolyte) The nonaqueous electrolyte preferably contains at least one additive selected from the group consisting of cyclic imide compounds, phthalate ester compounds, and isocyanate compounds. When the nonaqueous electrolyte contains the additive, a composite coating containing components (Mg, Mn) derived from the lithium alloy and components derived from the additive can be formed on the surface of the Mg-containing lithium alloy (negative electrode). This coating has excellent chemical stability, and since the coating contains Mg and Mn derived from the lithium alloy, the resistance of the negative electrode is reduced. Furthermore, even in the coating, Mg alloys with Mn, reducing activity. A high-quality composite coating protects the lithium alloy. Therefore, the formation of the composite coating easily suppresses the precipitation of Mn-containing organic compounds with Mg as a nucleus, even if Mn elutes from the positive electrode. As a result, deterioration of storage characteristics is further easily suppressed.

[0027] The content of the additive in the non-aqueous electrolyte is, for example, 0.01% by mass or more and 5% by mass or less. The content of the additive in the non-aqueous electrolyte is the mass ratio (percentage) of the additive to the entire non-aqueous electrolyte. For example, immediately after the battery is manufactured (or when the non-aqueous electrolyte is prepared), it is desirable that the content of the additive in the non-aqueous electrolyte is within the above range. In contrast, in a battery that has been manufactured for a certain period of time, part of the additive is consumed in the formation of a coating, and the content of the additive in the non-aqueous electrolyte may be smaller than the above range. In this case, even if the content of the additive in the non-aqueous electrolyte is small (for example, a value close to the detection limit), the above effect of the additive is observed. The same can be said for the content of various compounds such as cyclic imide compounds described below.

[0028] (Cyclic imide compound) Examples of the cyclic imide compound include cyclic diacylamine compounds. The cyclic imide compound may have a diacylamine ring (hereinafter also referred to as an imide ring). The imide ring may be condensed with another ring (hereinafter also referred to as a second ring). The cyclic imide compound may be contained in the non-aqueous electrolyte in the form of an imide, or in the form of an anion or a salt. When the cyclic imide compound is contained in the non-aqueous electrolyte in the form of an imide, it may be contained in the form having a free NH group, or in the form of a tertiary amine.

[0029] The second ring may be an aromatic ring, a saturated or unsaturated aliphatic ring, or the like. The second ring may contain at least one heteroatom. Examples of the heteroatom include an oxygen atom, a sulfur atom, and a nitrogen atom.

[0030] Examples of cyclic imide compounds include aliphatic dicarboxylic acid imide compounds and cyclic imide compounds having a second ring. Examples of aliphatic dicarboxylic acid imide compounds include succinimide. Examples of cyclic imide compounds having a second ring include imide compounds of aromatic or alicyclic dicarboxylic acids. Examples of aromatic dicarboxylic acids or alicyclic dicarboxylic acids include those having a carboxy group on each of two adjacent atoms constituting the ring. Examples of cyclic imide compounds having a second ring include phthalimide and hydrogenated phthalimide. Examples of hydrogenated phthalimide include cyclohex-3-ene-1,2-dicarboximide and cyclohexane-1,2-dicarboximide.

[0031] The imide ring may be an N-substituted imide ring having a substituent on the nitrogen atom of the imide. Examples of such a substituent include a hydroxy group, an alkyl group, an alkoxy group, and a halogen atom. Examples of the alkyl group include a C1 to C4 alkyl group, which may be a methyl group, an ethyl group, or the like. Examples of the alkoxy group include a C1 to C4 alkoxy group, which may be a methoxy group, an ethoxy group, or the like. Examples of the halogen atom include a chlorine atom, a fluorine atom, or the like.

[0032] The cyclic imide compound is preferably at least one selected from the group consisting of phthalimide and N-substituted phthalimide. The substituent on the nitrogen atom of the N-substituted phthalimide can be selected from the substituents exemplified for the N-substituted imide ring. The N-substituted phthalimide preferably includes at least one selected from the group consisting of N-hydroxyphthalimide, N-(2-hydroxyethyl)phthalimide, N-(cyclohexylthio)phthalimide, and N-(phenylthio)phthalimide. The phthalimide and / or N-substituted phthalimide may account for 50% by mass or more, further 70% by mass or more, or 90% by mass or more of the cyclic imide compound.

[0033] The non-aqueous electrolyte solution may contain one or more cyclic imide compounds, and the content of the cyclic imide compounds in the non-aqueous electrolyte solution may be 1% by mass or less, 0.001% by mass or more and 1% by mass or less, or 0.001% by mass or more and 0.8% by mass or less.

[0034] (Phthalate Ester Compounds) Phthalate ester compounds include phthalate esters and their derivatives. The derivatives may have a substituent bonded to an aromatic ring derived from phthalic acid. Examples of such substituents include a hydroxy group, an alkyl group, an alkoxy group, and a halogen atom. Examples of the alkyl group include a C1 to C4 alkyl group, which may be a methyl group, an ethyl group, or the like. Examples of the alkoxy group include a C1 to C4 alkoxy group, which may be a methoxy group, an ethoxy group, or the like. Examples of the halogen atom include a chlorine atom, a fluorine atom, or the like.

[0035] The phthalate ester compound may be a phthalate monoester compound, but a phthalate diester compound is preferable from the viewpoint that the resulting coating film easily protects the Li alloy surface. The alcohol that constitutes the ester with phthalic acid (or its derivative) is preferably a C1 to C20 (preferably C1 to C6) saturated or unsaturated aliphatic alcohol.

[0036] Specific examples of the phthalate diester compound include dimethyl phthalate, diethyl phthalate, diallyl phthalate, dibutyl phthalate, diisobutyl phthalate, and bis(2-ethylhexyl) phthalate. These compounds may be used alone or in combination of two or more. The phthalate diester compound may account for 50% by mass or more, or even 70% by mass or more, or 90% by mass or more of the phthalate ester compounds.

[0037] The non-aqueous electrolyte may contain one or more phthalate ester compounds, and the content of the phthalate ester compounds in the non-aqueous electrolyte may be 1% by mass or less, or may be 0.1% by mass or more and 1% by mass or less.

[0038] (Isocyanate Compound) The isocyanate compound has, for example, at least one isocyanate group and a C1 to C20 aliphatic hydrocarbon group or a C6 to C20 aromatic hydrocarbon group. The aliphatic hydrocarbon group and aromatic hydrocarbon group constituting the isocyanate compound may have a substituent. The substituent may be any group that can exist stably, and may be, for example, a halogen atom or a nitrile group. The aliphatic group may be an alicyclic aliphatic group, or may be a linear or branched aliphatic group. The aromatic hydrocarbon group is a hydrocarbon group having one or more aromatic rings, and may be a group in which an aromatic ring and an aliphatic group are linked.

[0039] The isocyanate compound may be a monoisocyanate compound having one isocyanate group, but a diisocyanate compound having two isocyanate groups is preferable. Diisocyanate compounds are thought to form composite coatings with higher chemical stability than monoisocyanate compounds and lower resistance than triisocyanates. Furthermore, diisocyanate compounds have a high ability to form composite coatings even in small amounts and have excellent stability within the battery.

[0040] Specific examples of diisocyanate compounds include OCN-C ｎ H ２ｎExamples of such compounds include compounds represented by the formula -NCO (where n is an integer of 1 to 10) (e.g., hexamethylene diisocyanate), compounds having an alicyclic diyl group (e.g., 1,3-bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane-4,4'-diisocyanate, bicyclo[2.2.1]heptane-2,5-diylbis(methyl isocyanate), bicyclo[2.2.1]heptane-2,6-diylbis(methyl isocyanate), isophorone diisocyanate), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and hexyl isocyanate. Among these, at least one selected from the group consisting of hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and isophorone diisocyanate is preferred. These may account for 50% by mass or more, further 70% by mass or more, or even 90% by mass or more of the isocyanate compounds.

[0041] When a diisocyanate compound is added to a non-aqueous electrolyte, the diisocyanate compounds may react with each other in the battery (in the non-aqueous electrolyte) to form isocyanurates, ureas, and biurets. Therefore, when the battery is disassembled and the non-aqueous electrolyte is analyzed, isocyanurates, ureas, and biurets derived from the diisocyanate compound may be detected.

[0042] The non-aqueous electrolyte may contain one or more isocyanate compounds, and the content of the isocyanate compounds in the non-aqueous electrolyte may be 3% by mass or less, 0.01% by mass or more and 2% by mass or less, or 0.01% by mass or more and 1.5% by mass or less.

[0043] The nonaqueous electrolyte (additive) can be analyzed by, for example, liquid chromatography-mass spectrometry (LC / MS) or gas chromatography-mass spectrometry (GC / MS). Ultraviolet spectrometry (UV) may also be performed in addition to nuclear magnetic resonance spectrometry (NMR), infrared spectrometry (IR), and mass spectrometry (MS).

[0044] The lithium primary battery of the present disclosure will be described in more detail below.

[0045] [Lithium Primary Battery] (Positive Electrode) The positive electrode contains a positive electrode mixture. The positive electrode mixture contains manganese dioxide as a positive electrode active material. A positive electrode containing manganese dioxide exhibits a relatively high voltage and has excellent pulse discharge characteristics. As the manganese dioxide, one obtained by calcining electrolytic manganese dioxide is preferably used. The manganese dioxide may be in a mixed crystal state containing a plurality of crystal states. The positive electrode may contain manganese oxides other than manganese dioxide. Examples of manganese oxides other than manganese dioxide include MnO, Mn ３ O ４ , Mn ２ O ３ , Mn ２ O ７ The main component of the manganese oxide contained in the positive electrode is preferably manganese dioxide.

[0046] The manganese dioxide contained in the positive electrode may be doped with a small amount of lithium. If the amount of lithium doped is small, a high capacity can be ensured. Manganese dioxide and manganese dioxide doped with a small amount of lithium are ｘ MnO ２ (0≦x≦0.05). The average composition of the manganese oxide as a whole contained in the positive electrode is Li ｘ MnO ２ (0≦x≦0.05). The Li ratio x may be 0.05 or less in the initial discharge state of the lithium primary battery. The Li ratio x generally increases as the discharge of the lithium primary battery progresses. Theoretically, the oxidation number of manganese contained in manganese dioxide is tetravalent. However, if other manganese oxides are contained in the positive electrode or if lithium is doped into manganese dioxide, the oxidation number of manganese may increase or decrease slightly from tetravalent. Therefore, Li ｘ MnO ２ In the present invention, the average oxidation state of manganese is allowed to vary slightly from tetravalent.

[0047] The positive electrode is Li ｘ MnO ２In addition, other positive electrode active materials used in lithium primary batteries may be included. Examples of other positive electrode active materials include graphite fluoride. The proportion of manganese dioxide in the entire positive electrode active material is preferably 90 mass% or more.

[0048] As the manganese dioxide, electrolytic manganese dioxide is preferably used. By adjusting the firing conditions, the crystallinity of the manganese dioxide can be increased and the specific surface area of ​​the electrolytic manganese dioxide can be reduced. ｘ MnO ２ The BET specific surface area of ２ / g or more, 40m ２ / g or less. ｘ MnO ２ When the BET specific surface area is within the above range, self-discharge is suppressed, and the deterioration of pulse discharge characteristics after storage can be further suppressed.

[0049] Li ｘ MnO ２ The BET specific surface area may be measured by a known method, for example, by a specific surface area measuring device (for example, manufactured by Mountec Co., Ltd.) based on the BET method. ｘ MnO ２ can be used as the measurement sample.

[0050] Li ｘ MnO ２ The median particle diameter of the battery may be 5 μm or more and 40 μm or less. When the median particle diameter is within the above range, self-discharge is suppressed, and deterioration of pulse discharge characteristics after storage can be further suppressed.

[0051] Li ｘ MnO ２ The median particle size of the Li particles is the median of the particle size distribution determined by, for example, quantitative laser diffraction / scattering (qLD) method. ｘ MnO ２ The measurement may be performed using, for example, an SALD-7500 nano manufactured by Shimadzu Corporation.

[0052] The positive electrode mixture may contain a binder in addition to the positive electrode active material. The positive electrode mixture may also contain a conductive agent.

[0053] Examples of the binder include fluororesin, rubber particles, and acrylic resin.

[0054] Examples of the conductive agent include conductive carbon materials, such as natural graphite, artificial graphite, carbon black, and carbon fiber.

[0055] The positive electrode may further include a positive electrode current collector that holds the positive electrode mixture. Examples of materials for the positive electrode current collector include stainless steel, aluminum, and titanium.

[0056] In the case of a coin-type battery, the positive electrode may be constructed by attaching a ring-shaped positive electrode current collector having an L-shaped cross section to a positive electrode mixture pellet, or by using only the positive electrode mixture pellet. The positive electrode mixture pellet can be obtained, for example, by adding an appropriate amount of water to a positive electrode active material to prepare a wet positive electrode mixture, compressing the wet positive electrode mixture, and drying the compressed positive electrode mixture.

[0057] In the case of a cylindrical battery, a positive electrode including a sheet-shaped positive electrode current collector and a positive electrode mixture layer supported on the positive electrode current collector can be used. The sheet-shaped positive electrode current collector is preferably a perforated current collector. Examples of perforated current collectors include expanded metal, netting, and punched metal. The positive electrode mixture layer can be obtained, for example, by applying the above-mentioned wet positive electrode mixture to the surface of the sheet-shaped positive electrode current collector or by filling the positive electrode current collector with the wet positive electrode mixture, pressing it in the thickness direction, and drying it.

[0058] The positive electrode preferably comprises a porous current collector as described above and a positive electrode mixture filled in the current collector. In particular, it is preferable to use a current collector containing at least one material selected from the group consisting of SUS444, SUS430, and SUS316. By using such a current collector, it is possible to suppress side reactions with the nonaqueous electrolyte and corrosion of the current collector in a lithium primary battery, thereby suppressing an increase in internal resistance and gas generation. In particular, it is preferable to use such a current collector and LiCF4, which is typically used as a lithium salt in lithium primary batteries. ３ SO ３and LiClO ４ When the positive electrode is combined with a non-aqueous electrolyte solution containing at least one of the above, side reactions between the current collector and the non-aqueous electrolyte solution can be more effectively suppressed. The thickness of the positive electrode is, for example, 300 μm or more and 900 μm or less.

[0059] (Negative Electrode) The negative electrode may include, for example, a foil (sheet) of a lithium alloy. The lithium alloy is formed into any shape and thickness depending on the shape, dimensions, performance specifications, etc. of the lithium primary battery.

[0060] In the case of a cylindrical battery, the negative electrode may include a negative electrode current collector (e.g., copper foil) supporting the lithium alloy, or may be a foil (sheet) lithium alloy without a negative electrode current collector. When the lithium alloy contains Mg, the relatively high strength of Mg remains at the end of discharge, allowing the negative electrode to be constructed using only a foil (sheet) lithium alloy without a negative electrode current collector. By using a lithium alloy containing Mg, breakage or partial loss of the negative electrode at the end of discharge, which occurs when the negative electrode does not include a negative electrode current collector, is suppressed. The shape of the negative electrode (lithium alloy) is maintained even at the end of discharge, and the conductivity of the entire negative electrode is ensured even without a negative electrode current collector.

[0061] In the case of coin-type batteries, a hoop-shaped lithium alloy may be punched into a disk shape and used as the negative electrode. In the case of cylindrical batteries, a sheet-shaped lithium alloy may be used as the negative electrode. The sheet may be obtained, for example, by extrusion molding. More specifically, in cylindrical batteries, a lithium alloy foil or the like having a shape with a longitudinal direction and a lateral direction is used.

[0062] (Non-aqueous Electrolyte) The non-aqueous electrolyte is prepared by dissolving a lithium salt as a solute in a non-aqueous solvent.

[0063] Examples of non-aqueous solvents include organic solvents that are commonly used in non-aqueous electrolytes for lithium primary batteries. Examples of non-aqueous solvents include ethers, esters, and carbonate esters. Examples of non-aqueous solvents that can be used include dimethyl ether, γ-butyl lactone, propylene carbonate, ethylene carbonate, and 1,2-dimethoxyethane. The non-aqueous electrolyte may contain one type of non-aqueous solvent, or may contain two or more types of non-aqueous solvents.

[0064] From the viewpoint of improving the discharge characteristics of lithium primary batteries, the nonaqueous solvent preferably contains a cyclic carbonate ester having a high boiling point and a chain ether having low viscosity even at low temperatures. The cyclic carbonate ester preferably contains at least one selected from the group consisting of propylene carbonate (PC) and ethylene carbonate (EC), with PC being particularly preferred. The chain ether preferably has a viscosity of 1 mPa·s or less at 25°C, and particularly preferably contains dimethoxyethane (DME). The viscosity of the nonaqueous solvent is measured using a Rheosens m-VROC micro-sample viscometer at 25°C and a shear rate of 10,000 (1 / s).

[0065] Examples of lithium salts include LiCF ３ SO ３ , LiClO ４ , LiBF ４ , LiPF ６ , LiRaSO ３ (Ra is a fluorinated alkyl group having 1 to 4 carbon atoms), LiFSO ３ , LiN(SO ２ Rb)(SO ２ Rc) (Rb and Rc each independently represent a fluorinated alkyl group having 1 to 4 carbon atoms), LiN(FSO ２ ) ２ The lithium salts may be used alone or in combination of two or more.

[0066] The concentration of lithium ions contained in the nonaqueous electrolyte (total concentration of lithium salts) may be, 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.

[0067] The non-aqueous electrolyte may contain additives as needed. Examples of such additives include phthalimide, N-substituted phthalimide compounds, dimethyl phthalate, phthalate ester compounds, propane sultone, and vinylene carbonate. The total concentration of such additives contained in the non-aqueous electrolyte is, for example, 0.003 to 5 mol / L.

[0068] (Separator) A lithium primary battery usually includes a separator interposed between the positive electrode and the negative electrode. As the separator, a porous sheet formed of an insulating material that is resistant to the internal environment of a lithium primary battery may be used. Specific examples include a synthetic resin nonwoven fabric, a synthetic resin microporous membrane, or a laminate thereof.

[0069] Examples of synthetic resins used for nonwoven fabrics include polypropylene, polyphenylene sulfide, and polybutylene terephthalate. Examples of synthetic resins used for microporous membranes include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers. The microporous membrane may contain inorganic particles as needed.

[0070] The thickness of the separator is, for example, 5 μm or more and 100 μm or less.

[0071] The structure of the lithium primary battery is not particularly limited. The lithium primary battery may be a coin battery having a stacked electrode group formed by stacking a disc-shaped positive electrode and a disc-shaped negative electrode with a separator interposed therebetween. Alternatively, the lithium primary battery may be a cylindrical battery having a wound electrode group formed by spirally winding a strip-shaped positive electrode and a strip-shaped negative electrode with a separator interposed therebetween.

[0072] 1 shows a partially cross-sectional front view of a cylindrical lithium primary battery according to one embodiment of the present disclosure. In the lithium primary battery 10, an electrode group, in which a positive electrode 1 and a negative electrode 2 are wound with a separator 3 interposed therebetween, is housed in a battery case 9 together with a nonaqueous electrolyte (not shown). A sealing plate 8 is attached to the opening of the battery case 9. A positive electrode lead 4 connected to a 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 case 9. In addition, an upper insulating plate 6 and a lower insulating plate 7 are arranged at the top and bottom of the electrode group, respectively, to prevent internal short circuits.

[0073] <<Supplementary Note>> The above-described embodiments disclose the following technology: (Technology 1) A battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte solution, wherein the positive electrode contains Li ｘ MnO ２(Technology 2) A lithium primary battery according to Technology 1, wherein the negative electrode comprises an alloy containing lithium, magnesium, and manganese, the lithium content in the alloy being greater than 88% by mass, the magnesium content in the alloy being 0.01% by mass or more and 10% by mass or less, and the manganese content in the alloy being 0.001% by mass or more and 5% by mass or less. (Technology 3) The lithium primary battery according to Technology 1, wherein the alloy contains aluminum, and the total content of the magnesium and aluminum in the alloy is 0.02% by mass or more and 10% by mass or less. (Technology 4) Li ｘ MnO ２ The lithium primary battery according to Technology 1 or 2, wherein the median particle size of Li is 5 μm or more and 40 μm or less. ｘ MnO ２ The BET specific surface area of ２ / g or more, 40m ２ / g or less. (Technology 5) The lithium primary battery according to any one of Technologies 1 to 3, wherein the non-aqueous electrolyte solution contains at least one additive selected from the group consisting of a cyclic imide compound, a phthalate ester compound, and an isocyanate compound. (Technology 6) The lithium primary battery according to Technology 5, wherein the cyclic imide compound includes at least one selected from the group consisting of phthalimide and N-substituted phthalimide. (Technology 7) The lithium primary battery according to Technology 6, wherein the N-substituted phthalimide includes at least one selected from the group consisting of N-hydroxyphthalimide, N-(2-hydroxyethyl)phthalimide, N-(cyclohexylthio)phthalimide, and N-(phenylthio)phthalimide. (Technology 8) The lithium primary battery according to any one of Technologies 5 to 7, wherein the content of the cyclic imide compound in the non-aqueous electrolyte solution is 1 mass% or less. (Technology 9) The lithium primary battery according to any one of Technologies 5 to 8, wherein the phthalate ester compound includes a phthalate diester compound. (Technology 10) The lithium primary battery according to Technology 9, wherein the phthalate diester compound includes dimethyl phthalate. (Technology 11) The lithium primary battery according to any one of Technology 5 to 10, wherein the content of the phthalate ester compound in the non-aqueous electrolyte is 1 mass % or less. (Technology 12) The lithium primary battery according to any one of Technology 5 to 11, wherein the isocyanate compound includes a diisocyanate compound. (Technology 13) The lithium primary battery according to Technology 12, wherein the diisocyanate compound includes at least one selected from the group consisting of hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and isophorone diisocyanate. (Technology 14) The lithium primary battery according to any one of Technology 5 to 13, wherein the content of the isocyanate compound in the non-aqueous electrolyte is 3 mass % or less. (Technology 15) A negative electrode for use in a lithium primary battery, wherein the positive electrode of the lithium primary battery is Li ｘ MnO ２(Technology 16) The negative electrode for a lithium primary battery according to Technology 15, wherein the alloy contains aluminum, and the total content of the magnesium and aluminum in the alloy is 0.02 mass% or more and 10 mass% or less, and the negative electrode comprises an alloy containing lithium, magnesium, and manganese, wherein the lithium content in the alloy is greater than 88 mass%, the magnesium content in the alloy is 0.01 mass% or more and 10 mass% or less, and the manganese content in the alloy is 0.001 mass% or more and 5 mass% or less.

[0074] [Examples] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0075] <<Batteries A1 to A20, Batteries B1 to B10>> (Preparation of Positive Electrode) For the positive electrode, 100 parts by mass of fired electrolytic manganese dioxide was mixed with 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 to prepare a wet positive electrode mixture.

[0076] Next, the positive electrode mixture was filled into a positive electrode current collector made of expanded metal of stainless steel (SUS444) with a thickness of 0.4 mm to prepare a positive electrode precursor. The positive electrode precursor was then dried, rolled to a thickness of 0.5 mm using a roll press, and cut to a predetermined size to obtain a positive electrode. Subsequently, a portion of the filled positive electrode mixture was peeled off, and one end of a stainless steel positive electrode lead was resistance-welded to the exposed portion of the positive electrode current collector.

[0077] (Preparation of Negative Electrode) A lithium metal foil or a lithium alloy foil (thickness: 200 μm) was cut to a predetermined size to obtain a negative electrode. One end of a nickel negative electrode lead was connected to a predetermined position of the negative electrode by ultrasonic welding.

[0078] The elements contained in the lithium alloy foil other than Li were Mg, Mn, and / or Al. The content of each metal element in the lithium alloy foil was the value shown in Tables 1 to 4. "0" in the content column in Tables 1 to 3 means that the content is below the detection limit in composition analysis (such as ICP atomic emission spectroscopy).

[0079] (Preparation of Electrode Assembly) An electrode assembly was prepared by winding a positive electrode and a negative electrode with a separator interposed therebetween, the separator being a microporous polypropylene film having a thickness of 25 μm.

[0080] (Preparation of non-aqueous electrolyte) Propylene carbonate (PC), ethylene carbonate (EC), and 1,2-dimethoxyethane (DME) were mixed in a volume ratio of 4:2:4 to obtain a non-aqueous solvent. ３ SO ３ was dissolved in a concentration of 0.5 mol / L to prepare a non-aqueous electrolyte solution.

[0081] (Assembly of Lithium Primary Battery) The electrode group was housed in a cylindrical battery case that also served as a negative electrode terminal. An iron case (outer diameter 17 mm, height 45.5 mm) was used as the battery case. Next, a nonaqueous electrolyte was poured into the battery case, and the opening of the battery case was closed with a metal sealing plate that also served as a positive electrode terminal. The other end of the positive electrode lead was connected to the sealing plate, and the other end of the negative electrode lead was connected to the inner bottom surface of the battery case. In this way, a cylindrical lithium primary battery was produced. The battery immediately after assembly was discharged at 2.4 A for 2 minutes and then aged for 7 days in an atmosphere at 45°C. Note that the positive electrode active material after aging was Li ｘ MnO ２ The x value, which indicates the amount of lithium doped, was 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.

[0082] In addition, the Li contained in the positive electrode mixture ｘ MnO ２ has a median particle size of 21 to 23 μm and a BET specific surface area of ​​14 to 15 m ２ / g.

[0083] [Evaluation] (Internal Resistance of Battery After Storage) The battery after aging treatment was stored for 4 months at 70° C. The internal resistance (frequency 1 kHz) of the battery after storage was measured in an environment of 20° C. using an AC resistance meter.

[0084] (Low-Temperature Pulse Discharge Test of Stored Batteries) The aging-treated batteries were stored for 4 months at 70° C. The stored batteries were left to stand in an environment of −30° C. for 2 hours, and then pulse-discharged at 300 mA for 1 second in an environment of −30° C. The minimum voltage at this time was determined as the pulse discharge voltage.

[0085] The evaluation results are shown in Tables 1 to 4. In Tables 1 to 4, the internal resistance is expressed as a relative value when the internal resistance of Battery B3 is set to 100. The pulse discharge voltage is expressed as a relative value when the pulse discharge voltage of Battery B3 is set to 100.

[0086]

[0087]

[0088]

[0089]

[0090] The batteries A1 to A20 exhibited low internal resistance and high pulse discharge voltage after storage, and exhibited excellent storage characteristics.

[0091] Batteries B1 to B5 used Li metal foil or Li alloy foil containing no Mg and / or Mn as the negative electrode, resulting in poor storage characteristics. Battery B6 used Li-Mg-Mn alloy foil, but the Mg content was greater than 10% by mass, resulting in poor storage characteristics. Batteries B7 and B8 used Li-Mg-Mn alloy foil, but the Mn content was less than 0.001% by mass or greater than 5% by mass, resulting in poor storage characteristics. Batteries B9 and B10 used Li-Mg-Mn alloy foil, but the Li content was 88% by mass or less, resulting in poor storage characteristics.

[0092] When the negative electrode did not contain Mg, the improvement in pulse discharge voltage and internal resistance due to the addition of Mn was small (B1 → B2). In contrast, when the negative electrode contained Mg, the addition of Mn significantly improved the pulse discharge voltage and internal resistance (B3 → A3). This shows that the effect of improving storage characteristics due to the addition of Mn is significantly obtained when the negative electrode (lithium alloy) contains Mg.

[0093] As shown in Table 3, batteries A1 to A8, which had an Mg content of 0.5% by mass and an Mn content of 0.001 to 5% by mass, exhibited excellent storage characteristics. Batteries A9 to A15, which had an Mg content of 0.02% by mass and an Mg content of 0.01 to 10% by mass, exhibited excellent storage characteristics.

[0094] As shown in Table 4, batteries A16 to A20 using Li-Mg-Mn-Al foil for the negative electrode had further improved storage characteristics. For example, battery A13 using Li-Mg-Mn foil (Mg content: 2% by mass, Mn content: 0.02% by mass) for the negative electrode had a pulse discharge voltage of 111 after storage, and battery A18 using Li-Mg-Mn-Al foil (Mg content: 1% by mass, Mn content: 0.02% by mass, Al content: 1% by mass) for the negative electrode had a pulse discharge voltage of 114 after storage, further improving storage characteristics.

[0095] <Batteries A21 to A28> In preparing the nonaqueous electrolyte solution, an additive was further added to the nonaqueous electrolyte solution. The additives used were the compounds shown in Table 5. The additive contents (mass %) in the nonaqueous electrolyte solution were the values ​​shown in Table 5. Except for the above, Batteries A21 to A28 were fabricated and evaluated in the same manner as Battery A4.

[0096] The evaluation results are shown in Table 5. In Table 5, the internal resistance is expressed as a relative value when the internal resistance of Battery B3 is set to 100. The pulse discharge voltage is expressed as a relative value when the pulse discharge voltage of Battery B3 is set to 100.

[0097]

[0098] As shown in Table 5, in the batteries A21 to A28 in which the additive was added to the non-aqueous electrolyte, the pulse discharge voltage after storage further increased, and the storage characteristics were further improved.

[0099] The lithium primary battery of the present disclosure is suitable for use, for example, as a main power source or memory backup power source for various meters (for example, smart meters for electricity, water, gas, etc.).

[0100] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0101] 1: positive electrode, 1a: positive electrode 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 case, 10: lithium primary battery

Claims

1. A battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode is Li ｘ MnO ２ (0≦x≦0.05), wherein the negative electrode comprises an alloy containing lithium, magnesium, and manganese, wherein a content of the lithium in the alloy is greater than 88% by mass, a content of the magnesium in the alloy is 0.01% by mass or more and 10% by mass or less, and a content of the manganese in the alloy is 0.001% by mass or more and 5% by mass or less.

2. The lithium primary battery according to claim 1, wherein the alloy contains aluminum, and the total content of the magnesium and aluminum in the alloy is 0.02 mass % or more and 10 mass % or less.

3. Li ｘ MnO ２ 2. The lithium primary battery according to claim 1, wherein the median particle size is 5 μm or more and 40 μm or less.

4. Li ｘ MnO ２ The BET specific surface area of ２ / g or more, 40m ２ 2. The lithium primary battery according to claim 1, wherein the Cr content is 0.15 / g or less.

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

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

7. The lithium primary battery according to claim 6, wherein the N-substituted phthalimide includes at least one selected from the group consisting of 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 1 mass % or less.

9. The lithium primary battery according to claim 5, wherein the phthalate ester compound includes a phthalate diester compound.

10. The lithium primary battery of claim 9, wherein the phthalic acid diester compound comprises dimethyl phthalate.

11. The lithium primary battery according to claim 5, wherein the content of the phthalate ester compound in the non-aqueous electrolyte is 1 mass % or less.

12. The lithium primary battery according to claim 5, wherein the isocyanate compound includes a diisocyanate compound.

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

14. The lithium primary battery according to claim 5, wherein the content of the isocyanate compound in the non-aqueous electrolyte is 3 mass % or less.

15. A negative electrode used in a lithium primary battery, wherein the positive electrode of the lithium primary battery is Li ｘ MnO ２ (0≦x≦0.05), wherein the negative electrode comprises an alloy containing lithium, magnesium, and manganese, wherein a content of the lithium in the alloy is greater than 88% by mass, a content of the magnesium in the alloy is 0.01% by mass or more and 10% by mass or less, and a content of the manganese in the alloy is 0.001% by mass or more and 5% by mass or less.

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

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