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 containing lithium, magnesium, and at least one metal element M selected from the group consisting of strontium and barium. The content of lithium in the alloy is 89 mass% or more. The content of magnesium in the alloy is 0.01 mass%-10 mass% inclusive. The content of the metal element M in the alloy is 0.00001 mass%-0.05 mass% inclusive.

Description

Lithium primary battery CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2024-044815, filed on March 21, 2024 in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to lithium primary batteries.

[0003] 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.

[0004] 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.

[0005] JP 2011-192627 A

[0006] In a lithium primary battery, the internal resistance may increase toward the end of discharge, causing a decrease in discharge voltage.

[0007] 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 at least one metal element M selected from the group consisting of strontium and barium, the content of lithium in the alloy is 89% by mass or more, the content of magnesium in the alloy is 0.01% by mass or more and 10% by mass or less, and the content of metal element M in the alloy is 0.00001% by mass or more and 0.05% by mass or less.

[0008] According to the present disclosure, it is possible to suppress a decrease in discharge voltage due to an increase in internal resistance at the end of discharge of a lithium primary battery.

[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 (hereinafter also referred to as "lithium alloy") containing lithium (Li), magnesium (Mg), and at least one metal element M selected from the group consisting of strontium (Sr) and barium (Ba). The Li content in the lithium alloy is 89% by mass or more. The Mg content in the lithium alloy is 0.01% by mass or more and 10% by mass or less. The content of the metal element M in the lithium alloy (the total content of Sr and Ba in the lithium alloy) is 0.00001% by mass or more and 0.05% by mass or less. In the lithium primary battery according to the embodiment of the present disclosure, the discharge voltage at the end of discharge (for example, the voltage during pulse discharge in a low-temperature environment) can be increased.

[0013] By adding Mg to a negative electrode containing Li, the strength of the negative electrode is improved and the decrease in discharge voltage due to the occurrence of cracks or partial defects in the negative electrode at the end of discharge is suppressed. On the other hand, because Mg easily alloys with Li, the movement of Li is easily inhibited at the end of discharge, which increases the internal resistance and tends to decrease the discharge voltage.

[0014] Therefore, the present inventors conducted extensive research to suppress the voltage drop at the end of discharge as described above, and discovered that by adding a metal element M to a negative electrode containing Li and Mg, the inhibition of Li migration at the end of discharge is suppressed, and the drop in discharge voltage due to an increase in internal resistance at the end of discharge is significantly suppressed.

[0015] The voltage drop at the end of discharge is significantly suppressed by the combination of the effect of improving the negative electrode strength by adding Mg and the effect of suppressing the inhibition of Li migration when Mg is included by adding the metal element M. In addition, the metal element M improves the chemical stability of the coating formed on the surface of the lithium alloy (negative electrode), and also plays a role in suppressing side reactions due to contact between the negative electrode and the nonaqueous electrolyte.

[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 cause a voltage drop at the end of discharge.If the Mg content in the lithium alloy is less than 0.01% by mass, the effect of adding Mg is reduced, which may cause a voltage drop at the end of discharge.

[0017] If the content of metal element M in the lithium alloy is greater than 0.05% by mass, the proportion of metal element M in the negative electrode increases, which may increase the negative electrode resistance and cause a voltage drop at the end of discharge. If the content of Mn in the lithium alloy is less than 0.00001% by mass, the effect of adding metal element M becomes smaller and may cause a voltage drop at the end of discharge.

[0018] If the Li content in the lithium alloy is less than 89 mass %, the proportion of Li in the negative electrode will be small, which may result in a decrease in discharge voltage.

[0019] (Lithium Alloy) The lithium alloy contains Li, Mg, and a metal element M. From the viewpoint of reducing internal resistance and ensuring capacity, the Li content in the lithium alloy is 89% by mass or more, may be 90% by mass or more, or may be 95% by mass or more. The Li content in the lithium alloy may be 99.98999% by mass or less. In the lithium alloy, elements other than Mg and the metal element M may be Li.

[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] The lithium alloy contains Sr and / or Ba as the metal element M. From the viewpoint of suppressing a voltage drop at the end of discharge, the lithium alloy preferably contains both Sr and Ba. In this case, the mass ratio of Sr to Ba in the lithium alloy (Sr / Ba) may be 40 / 60 or more and 60 / 40 or less.

[0022] From the viewpoint of suppressing voltage drop at the end of discharge, the content of the metal element M in the lithium alloy is 0.00001% by mass or more, preferably 0.00002% by mass or more, more preferably 0.0001% by mass or more or 0.0004% by mass or more. From the viewpoint of reducing the negative electrode resistance, the content of the metal element M in the lithium alloy is 0.05% by mass or less, preferably 0.01% by mass or less, more preferably 0.005% by mass or less. The range of the content of the metal element M in the lithium alloy may be, for example, 0.00002% by mass or more and 0.05% by mass or less, 0.0001% by mass or more and 0.01% by mass or less, or 0.0004% by mass or more and 0.01% by mass or less. The molar ratio of the metal element M to Mg: M / Mg may be, for example, within the range of 0.000001 to 0.5.

[0023] The lithium alloy may contain metal elements other than Li, Mg, and the metal element M. Examples of the other metal elements include 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).

[0024] It is preferable that the lithium alloy further contains Al. A portion of the Mg contained in the lithium alloy may be replaced with Al. In this case, the voltage drop at the end of discharge is further suppressed. Although the detailed reason is unknown, it is presumed that the addition of Al makes it easy to form a portion where Al and the metal element M aggregate, and Li is less likely to alloy with Mg in the vicinity of this portion, thereby further suppressing the inhibition of Li migration at the end of discharge when Mg is contained. Furthermore, it is presumed that when Al is contained together with Mg and the metal element M, a low-resistance coating is easily formed stably.

[0025] From the viewpoint of suppressing voltage drop at the end of discharge, the Al content in the lithium alloy may be 0.01% by mass or more and 10% by mass or less, preferably 0.01% by mass or more (or 0.1% by mass or more) and 5% by mass or less, and more preferably 0.1% 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, and more preferably 0.2% by mass or more and 4% by mass or less. Approximately half of the mass of Mg may be substituted with Al. The molar ratio of Al to Mg: Al / Mg may be, for example, within 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 derived from the lithium alloy (negative electrode) (Mg, metal element M) and components derived from the additive can be formed on the surface of the lithium alloy (negative electrode). The formation of such a composite coating further suppresses the increase in internal resistance and the accompanying voltage drop at the end of discharge. Since the composite coating contains Mg and metal element M, the negative electrode resistance (reaction resistance) is reduced. Furthermore, the composite coating has excellent chemical stability, and the high-quality composite coating protects the lithium alloy.

[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 can 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 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 at least one metal element M selected from the group consisting of strontium and barium, wherein the lithium content in the alloy is 89% by mass or more, the magnesium content in the alloy is 0.01% by mass or more and 10% by mass or less, and the metal element M content in the alloy is 0.00001% by mass or more and 0.05% by mass or less. (Technology 3) A 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) A lithium primary battery according to Technology 1, wherein the negative electrode comprises an alloy containing lithium, magnesium, and at least one metal element M selected from the group consisting of strontium and barium, wherein the lithium content in the alloy is 89% by mass or more, the magnesium content in the alloy is 0.01% by mass or more and 10% by mass or less, and the metal element M content in the alloy is 0.00001% by mass or more and 0.05% by mass or less. 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.

[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 A18, Batteries B1 to B11>> (Preparation of Positive Electrode) For the positive electrode, 100 parts by mass of baked 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, and the mixture was kneaded 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 lithium alloy foils had the foil compositions shown in Tables 1 to 3. In addition to lithium, the lithium alloy foils contained the metal elements (Mg, Sr, Ba, and / or Al) shown in Tables 1 to 3. The content of each metal element in the lithium alloy foil was the value shown in Tables 1 to 3. "0" in the content column in Tables 1 to 3 means that the content was 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 A18 are examples, and batteries B1 to B11 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] The aging-treated batteries were discharged to a depth of discharge (DOD) of 90%. The internal resistance (frequency: 1 kHz) of the batteries at the end of discharge was measured using an AC resistance meter at 20°C. The batteries at the end of discharge were then left to stand for 2 hours at -30°C, and then pulse-discharged at 300 mA for 1 second at -30°C. The minimum voltage at this time was determined as the pulse discharge voltage.

[0084] The evaluation results are shown in Tables 1 to 3. In Tables 1 to 3, the internal resistance is expressed as a relative value when the internal resistance of Battery B2 is set to 100. The pulse discharge voltage is expressed as a relative value when the pulse discharge voltage of Battery B2 is set to 100.

[0085]

[0086]

[0087]

[0088] In the batteries A1 to A18, the internal resistance was low and the pulse discharge voltage was high at the end of the discharge.

[0089] In batteries B1 to B4 and B8 to B9, Li metal foil or Li alloy foil not containing Mg and / or metal element M was used as the negative electrode, resulting in a decrease in voltage at the end of discharge. Battery B5 used Li-Mg-Sr-Ba alloy foil, but the Mg content was greater than 10% by mass, resulting in a decrease in voltage at the end of discharge. Battery B6 to B7 used Li-Mg-Sr-Ba alloy foil, but the combined Sr and Ba content was less than 0.00001% by mass or greater than 0.05% by mass, resulting in a decrease in voltage at the end of discharge. Battery B10 to B11 used Li-Mg-Sr-Ba-Al alloy foil, but the Li content was less than 89% by mass, resulting in a decrease in voltage at the end of discharge.

[0090] When the negative electrode did not contain Mg, the improvement in pulse discharge voltage at the end of discharge due to the addition of metal element M was small (B1: 89 → B3: 91, B4: 92). In contrast, when the negative electrode contained Mg, the addition of metal element M significantly improved the pulse discharge voltage at the end of discharge (B2: 100 → A2: 113, A4: 111). This shows that the effect of adding metal element M to suppress the voltage drop at the end of discharge is significantly achieved when the negative electrode (lithium alloy) contains Mg.

[0091] As shown in Table 1, batteries A1 to A7, which had an Mg content of 0.5 mass% and a combined Sr and Ba content of 0.00001 to 0.05 mass%, achieved a high voltage at the end of discharge. Batteries A8 to A13, which had an Sr and Ba content of 0.005 mass% and a Mg content of 0.01 to 10 mass%, achieved a high voltage at the end of discharge.

[0092] As shown in Table 3, the voltage at the end of discharge was further increased in batteries A14 to A18, which used Li-Mg-Sr-Ba-Al foil for the negative electrode. For example, the pulse discharge voltage was 111 in battery A11 (Li-Mg-Sr-Ba foil, Mg content: 1% by mass, Sr + Ba content: 0.005% by mass), and the pulse discharge voltage was 114 in battery A16 (Li-Mg-Sr-Ba-Al foil, Mg content: 1% by mass, Sr + Ba content: 0.005% by mass, Al content: 1% by mass), further improving the voltage at the end of discharge.

[0093] <Batteries A19 to A26> In preparing the non-aqueous electrolyte solution, an additive was further added to the non-aqueous electrolyte solution. The additives used were the compounds shown in Table 4. The additive contents (mass %) in the non-aqueous electrolyte solution were the values ​​shown in Table 4. Except for the above, Batteries A19 to A26 were fabricated and evaluated in the same manner as Battery A3.

[0094] The evaluation results are shown in Table 4. In Table 4, the internal resistance is expressed as a relative value when the internal resistance of Battery B2 is set to 100. The pulse discharge voltage is expressed as a relative value when the pulse discharge voltage of Battery B2 is set to 100.

[0095]

[0096] As shown in Table 4, in the batteries A19 to A26 in which the additive was contained in the non-aqueous electrolyte, the internal resistance at the end of discharge was further reduced and the pulse discharge voltage was further increased.

[0097] 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.).

[0098] 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.

[0099] 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 at least one metal element M selected from the group consisting of strontium and barium, wherein the lithium content in the alloy is 89% by mass or more, the magnesium content in the alloy is 0.01% by mass or more and 10% by mass or less, and the metal element M content in the alloy is 0.00001% by mass or more and 0.05% 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.

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