Lithium primary battery

Abstract

This lithium primary battery comprises: a positive electrode; a negative electrode; and a non-aqueous electrolyte solution. The positive electrode contains a positive electrode mixture, and the positive electrode mixture contains manganese dioxide and an oxide of a metal Me. The metal Me has a valence number of 2 or more, an ion radius of 0.8 Å or less, and an electronegativity of 1.65 or less. The amount of the oxide of the metal Me contained in the positive electrode mixture is 0.1 parts by mass to 5 parts by mass with respect to 100 parts by mass of the manganese dioxide contained in the positive electrode mixture. The negative electrode contains an alloy containing lithium and magnesium. 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%.

Description

Lithium primary battery

[0001] The present disclosure relates to 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 proposes "a lithium negative electrode in which a lithium salt is dissolved in an electrolyte, and a separator is placed opposite the negative electrode, in which an aluminum-magnesium alloy coating layer is initially laminated on the surface of the lithium body adjacent to the separator, and an aluminum-magnesium-lithium ternary alloy is formed by diffusion, increasing the surface area of ​​the negative electrode and improving the pulse performance of the battery."

[0004] Patent Document 2 proposes "a battery comprising a negative electrode using a light metal as an active material, an organic electrolyte, and a positive electrode using manganese dioxide as an active material, the positive electrode being characterized in that the positive electrode is made by mixing an oxide of an alkaline earth metal."

[0005] Patent Document 3 proposes "a positive electrode for a lithium primary battery, characterized in that at least one metal oxide selected from the group consisting of titanium oxide, alumina, zinc oxide, chromium oxide, lithium oxide, nickel oxide, copper oxide, and iron oxide is dispersed between manganese dioxide particles."

[0006] Japanese Patent Application Laid-Open No. 58-209862 Japanese Patent Application Laid-Open No. 56-103864 Japanese Patent Application Laid-Open No. 2003-249213

[0007] In lithium primary batteries, the internal resistance may increase after long-term storage, resulting in a deterioration in discharge characteristics.

[0008] One aspect of the present disclosure relates to a lithium primary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte solution, wherein the positive electrode includes a positive electrode mixture that includes manganese dioxide and an oxide of a metal other than manganese (Me), the metal Me having a valence of 2 or greater, an ionic radius of 0.8 Å or less, and an electronegativity of 1.65 or less, the amount of the oxide of the metal Me included in the positive electrode mixture being 0.1 parts by mass or greater and 5 parts by mass or less per 100 parts by mass of the manganese dioxide included in the positive electrode mixture, and the negative electrode includes an alloy containing lithium and magnesium, the content of the lithium in the alloy being greater than 88% by mass, and the content of the magnesium in the alloy being 0.01% by mass or greater and 10% by mass or less.

[0009] According to the present disclosure, it is possible to suppress the deterioration of discharge characteristics of a lithium primary battery after long-term storage.

[0010] 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.

[0011] FIG. 1 is a partially cross-sectional front view of a lithium primary battery according to an embodiment of the present disclosure.

[0012] 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.

[0013] A lithium primary battery according to an embodiment of the present disclosure includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode includes a positive electrode mixture, which includes manganese dioxide (positive electrode active material) and an oxide of a metal other than manganese (Me) (additive). The metal Me has a valence of 2 or greater, an ionic radius of 0.8 Å (angstroms) or less, and an electronegativity of 1.65 or less. The amount of the oxide of the metal Me included in the positive electrode mixture is 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of manganese dioxide included in the positive electrode mixture. The negative electrode includes an alloy containing lithium (Li) and magnesium (Mg). Hereinafter, this alloy is also referred to as a "lithium alloy containing Mg." The lithium alloy contains more than 88% by mass of Li. The lithium alloy contains 0.01% by mass or more and 10% by mass or less of Mg.

[0014] By including an oxide of metal Me in the positive electrode mixture, deterioration of the non-aqueous electrolyte during storage (decomposition of the solvent) is suppressed, and gas generation and an increase in internal resistance associated with the decomposition of the solvent are suppressed, thereby suppressing deterioration of storage characteristics to a certain extent. The decomposition of the solvent involves hydroxyl groups present on the surface of manganese dioxide and trace amounts of water inevitably contained in the non-aqueous electrolyte during production. However, the storage characteristics remain insufficient, and the inventors have conducted extensive research to improve the storage characteristics. As a result, they have newly discovered that deterioration of storage characteristics is significantly suppressed by including an oxide of metal Me in the positive electrode mixture and including Mg in the lithium alloy of the negative electrode.

[0015] When the above configuration is satisfied, an increase in internal resistance after long-term storage and a resulting decrease in discharge characteristics (e.g., a decrease in voltage during low-temperature pulse discharge after storage) are suppressed. That is, the deterioration of storage characteristics is suppressed. Although the detailed mechanism is unknown, it is speculated as follows. During long-term storage, metal Me contained in the positive electrode mixture elutes from the positive electrode and precipitates on the negative electrode. The metal Me is then incorporated into a coating formed on the surface of the negative electrode upon contact between the negative electrode and the nonaqueous electrolyte. If the dispersibility of metal Me in the coating is low, Li ions may not be able to move within the coating, resulting in an increase in negative electrode resistance. In contrast, when the negative electrode (lithium alloy) contains Mg, some kind of interaction occurs between Mg and metal Me, improving the dispersibility of metal Me in the coating and suppressing the increase in negative electrode resistance. The good dispersibility of Mg is thought to be involved in this interaction.

[0016] If the amount of the oxide of the metal Me contained in the positive electrode mixture is less than 0.1 parts by mass per 100 parts by mass of manganese dioxide contained in the positive electrode mixture, the effect of adding the oxide of the metal Me will be small, and the suppression of deterioration in storage characteristics will be insufficient. If the amount of the oxide of the metal Me contained in the positive electrode mixture is more than 5 parts by mass per 100 parts by mass of manganese dioxide contained in the positive electrode mixture, the proportion of the oxide of the metal Me in the positive electrode mixture will be large, which may increase the positive electrode resistance and deteriorate the discharge characteristics.

[0017] 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 result in an increase in negative electrode resistance and a decrease in discharge characteristics. If the Li content in the lithium alloy is 88% by mass or less, the proportion of Li in the negative electrode decreases, which may result in an increase in negative electrode resistance and a decrease in discharge characteristics.

[0018] (Oxide of Metal Me) The metal Me has a valence of 2 or more, an ionic radius of 0.8 Å or less, and an electronegativity of 1.65 or less. When the valence of the metal Me is within the above range, the presence of metal Me in the coating, which has a valence greater than that of Li, improves the Li ion conductivity in the coating. When the ionic radius and electronegativity of the metal Me are within the above range, the migration of lithium ions in the coating is less likely to be hindered due to factors such as a small difference from the ionic radius and electronegativity of Li.

[0019] The valence of the metal Me is the valence when the metal Me exists as an oxide of the metal Me. The ionic radius and electronegativity of the metal Me are Pauling ionic radius and electronegativity. One type of metal Me may be used alone, or two or more types may be used in combination.

[0020] The metal Me preferably contains at least one selected from the group consisting of magnesium (Mg), aluminum (Al), titanium (Ti), zinc (Zn), zirconium (Zr), and niobium (Nb). Of these, zinc (Zn) is particularly preferred as the metal Me from the viewpoint of high surface coverage of manganese dioxide.

[0021] The oxides of the metal Me include MgO, Al ２ O ３ , TiO ２ , ZnO, ZrO ２ , and Nb ２ O ５ It is preferable that the positive electrode mixture contains at least one selected from the group consisting of: The positive electrode mixture contains, for example, positive electrode active material particles, an oxide of the metal Me, a binder, etc. The positive electrode mixture may contain a composite in which the surfaces of positive electrode active material particles are coated with an oxide of the metal Me. To obtain the composite, a composite treatment may be performed using the positive electrode active material particles and the oxide particles of the metal Me. The positive electrode mixture may also contain a mixture of the positive electrode active material particles and the oxide particles of the metal Me. One type of oxide of the metal Me may be used alone, or two or more types may be used in combination.

[0022] The amount of the oxide of the metal Me contained in the positive electrode mixture is 0.1 parts by mass or more and 5 parts by mass or less, and preferably 0.5 parts by mass or more and 2 parts by mass or less, per 100 parts by mass of manganese dioxide contained in the positive electrode mixture.

[0023] When the positive electrode mixture contains MgO and manganese dioxide, the amount of Mg atoms contained in the positive electrode mixture is preferably 0.1 parts by mass or more and 4.8 parts by mass or less, and more preferably 0.48 parts by mass or more and 1.9 parts by mass or less, per 100 parts by mass of Mn atoms contained in the positive electrode mixture. ２ O ３ and manganese dioxide, the amount of Al atoms contained in the positive electrode mixture is preferably 0.08 parts by mass or more and 4.2 parts by mass or less, and more preferably 0.42 parts by mass or more and 1.7 parts by mass or less, per 100 parts by mass of Mn atoms contained in the positive electrode mixture.

[0024] The positive electrode mixture is TiO ２ and manganese dioxide, the amount of Ti atoms contained in the positive electrode mixture is preferably 0.095 parts by mass or more and 4.7 parts by mass or less, and more preferably 0.47 parts by mass or more and 1.9 parts by mass or less, per 100 parts by mass of Mn atoms contained in the positive electrode mixture. When the positive electrode mixture contains ZnO and manganese dioxide, the amount of Zn atoms contained in the positive electrode mixture is preferably 0.13 parts by mass or more and 6.4 parts by mass or less, and more preferably 0.64 parts by mass or more and 2.5 parts by mass or less, per 100 parts by mass of Mn atoms contained in the positive electrode mixture.

[0025] The positive electrode mixture is ZrO ２ and manganese dioxide, the amount of Zr atoms contained in the positive electrode mixture is preferably 0.12 parts by mass or more and 5.9 parts by mass or less, and more preferably 0.59 parts by mass or more and 2.3 parts by mass or less, per 100 parts by mass of Mn atoms contained in the positive electrode mixture. ２ O ５ and manganese dioxide, the amount of Nb atoms contained in the positive electrode mixture is preferably 0.11 parts by mass or more and 5.5 parts by mass or less, and more preferably 0.55 parts by mass or more and 2.2 parts by mass or less, per 100 parts by mass of Mn atoms contained in the positive electrode mixture.

[0026] In the above case, Mg, Al, Ti, Zn, Zr, and Nb are respectively MgO, Al ２ O ３ , TiO ２ , ZnO, ZrO ２ , and Nb ２ O ５ Mn comes from manganese dioxide.

[0027] The amount (parts by mass) of metal Me atoms contained in the positive electrode mixture can be determined as follows. An initial battery (for example, an unused battery immediately after manufacture or within one week of purchase) is disassembled to remove the positive electrode mixture, which is then dissolved in an acid solution (such as hydrochloric acid). The insoluble matter is separated by filtration or centrifugation to obtain a sample solution. The amount of metal Me (WMe) (mass%) and the amount of Mn (WMn) (mass%) in the sample solution are measured using inductively coupled plasma (ICP) atomic emission spectroscopy, and the amount (parts by mass) of the metal Me atoms is calculated as (WMe / WMn) x 100. For example, a Thermo Fisher Scientific "iCAP7400 Duo" can be used as the measurement device.

[0028] (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 95% by mass or more. The Li content in the lithium alloy may be 99.99% by mass or less. 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.

[0029] From the viewpoint of improving storage characteristics, it is preferable that the lithium alloy further contains Al. Hereinafter, a lithium alloy containing Mg but substantially no Al will also be referred to as a "Li-Mg alloy." A lithium alloy containing Mg and Al will also be referred to as a "Li-Mg-Al alloy." Note that "substantially no Al" means that the content is below the detection limit in composition analysis of the lithium alloy (for example, ICP atomic emission spectroscopy, atomic absorption spectroscopy, etc.).

[0030] While the addition of Al suppresses the increase in internal resistance during storage (long-term use), 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.

[0031] From the viewpoint of suppressing deterioration of storage characteristics, the Mg content in the lithium alloy is 0.01% by mass or more, preferably 0.2% by mass or more, and more preferably 0.5% by mass or more. From the viewpoint of reducing negative electrode resistance, the Mg content in the lithium alloy is 10% by mass or less, preferably 5% by mass or less, and more preferably 2% by mass or less. The Mg content in the lithium alloy may be, for example, 0.2% by mass or more and 5% by mass or less, or 0.5% by mass or more and 2% by mass or less. The Mg content in the lithium alloy is the Mg content in a Li-Mg alloy or a Li-Mg-Al alloy.

[0032] From the viewpoint of suppressing deterioration of storage characteristics, the Al content in the lithium alloy (Li—Mg—Al 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 0.1% by mass or more and 4% by mass or less (or 3% by mass or less). From the same viewpoint, the total content of Mg and Al in the Li—Mg—Al alloy is preferably 0.02% by mass or more and 10% by mass or less. The molar ratio of Mg to Al (Mg / Al) may be, for example, in the range of 0.02 to 3.

[0033] The lithium alloy may contain metal elements other than Li, Mg, and Al, such as Sn, Ni, Pb, In, Na, K, and Ca.

[0034] The composition of the lithium alloy can be determined by inductively coupled plasma (ICP) emission spectroscopy or atomic absorption spectroscopy (AAS).

[0035] The lithium primary battery of the present disclosure will be described in more detail below.

[0036] [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.

[0037] 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 ２In the present invention, the average oxidation state of manganese is allowed to vary slightly from tetravalent.

[0038] The positive electrode may contain, in addition to manganese dioxide, other positive electrode active materials used in lithium primary batteries. Examples of such positive electrode active materials include graphite fluoride. The proportion of manganese dioxide in the total positive electrode active material is preferably 90 mass% or more.

[0039] As the manganese dioxide, electrolytic manganese dioxide is preferably used. By adjusting the conditions during firing, the crystallinity of the manganese dioxide can be increased and the specific surface area of ​​the electrolytic manganese dioxide can be reduced. The BET specific surface area of ​​manganese dioxide is 5 m ２ / g or more, 40m ２ When the BET specific surface area of ​​manganese dioxide is within the above range, self-discharge is suppressed, and the deterioration of pulse discharge characteristics after storage can be further suppressed.

[0040] The BET specific surface area of ​​manganese dioxide may be measured by a known method, for example, by the BET method using a specific surface area measuring device (for example, manufactured by Mountec Co., Ltd.) For example, manganese dioxide separated from the positive electrode removed from a battery may be used as a measurement sample.

[0041] The manganese dioxide may have a median particle size of 5 μm or more and 40 μm or less. When the median particle size is within the above range, self-discharge is suppressed, and deterioration of pulse discharge characteristics after storage can be further suppressed.

[0042] The median particle size of manganese dioxide is the median of the particle size distribution determined, for example, by quantitative laser diffraction / scattering (qLD) method. For example, manganese dioxide separated from the positive electrode removed from a battery can be used as a measurement sample. For example, a SALD-7500 nano manufactured by Shimadzu Corporation is used for the measurement.

[0043] The positive electrode mixture may contain a binder in addition to the positive electrode active material and the oxide of the metal Me. The positive electrode mixture may also contain a conductive agent.

[0044] Examples of the binder include fluororesin, rubber particles, and acrylic resin.

[0045] Examples of the conductive agent include conductive carbon materials, such as natural graphite, artificial graphite, carbon black, and carbon fiber.

[0046] 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.

[0047] 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 compression-molding a wet positive electrode mixture prepared by adding an appropriate amount of water to a positive electrode active material and an additive, and then drying the resulting mixture.

[0048] 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.

[0049] 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 ３ and 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.

[0050] (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.

[0051] 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.

[0052] 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.

[0053] (Non-aqueous Electrolyte) The non-aqueous electrolyte is prepared by dissolving a lithium salt as a solute in a non-aqueous solvent.

[0054] 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.

[0055] 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).

[0056] 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.

[0057] 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.

[0058] 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.

[0059] (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.

[0060] 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.

[0061] The thickness of the separator is, for example, 5 μm or more and 100 μm or less.

[0062] 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.

[0063] 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.

[0064] <<Supplementary Note>> The above embodiments disclose the following technology: (Technology 1) A lithium primary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode mixture, and the positive electrode mixture includes manganese dioxide and an oxide of a metal other than manganese (Me), the metal Me having a valence of 2 or greater, an ionic radius of 0.8 Å or less, and an electronegativity of 1.65 or less, the amount of the oxide of the metal Me included in the positive electrode mixture is 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of manganese dioxide included in the positive electrode mixture, the negative electrode includes an alloy containing lithium and magnesium, the content of the lithium in the alloy is greater than 88% by mass, and the content of the magnesium in the alloy is 0.01% by mass or more and 10% by mass or less. (Technology 2) The lithium primary battery according to Technology 1, 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. (Technology 3) The lithium primary battery according to Technology 1 or 2, wherein the metal Me contains at least one selected from the group consisting of magnesium, aluminum, titanium, zinc, zirconium, and niobium. (Technology 4) The lithium primary battery according to any one of Technology 1 to 3, wherein the median particle size of the manganese dioxide is 5 μm or more and 40 μm or less. (Technology 5) The manganese dioxide has a BET specific surface area of ​​5 m ２ / g or more, 40m ２ / g or less.

[0065] [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.

[0066] (Preparation of Positive Electrode) The calcined electrolytic manganese dioxide and the oxide of the metal Me were mixed and subjected to a composite treatment. For the composite treatment, a dry particle composite device "Nobilta NOB-130" manufactured by Hosokawa Micron Corporation was used. In this way, a composite material was obtained in which the surface of manganese dioxide particles was covered with the oxide of the metal Me. The metal elements used for the metal Me were those shown in the table. The oxide of the metal Me included MgO, Al２ O ３ , TiO ２ , ZnO, ZrO ２ , Nb ２ O ５ , Y ２ O ３ , MoO ３ , CdO, or In ２ O ３ was used.

[0067] To 100 parts by mass of the positive electrode active material, 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 were added and kneaded to prepare a wet positive electrode mixture. The positive electrode active material used was the composite material obtained above or calcined electrolytic manganese dioxide.

[0068] The content of the metal Me oxide in the positive electrode mixture was the value shown in the table. Note that the "content of the metal Me oxide" in the column for the positive electrode mixture in the table is the amount (parts by mass) per 100 parts by mass of manganese dioxide contained in the positive electrode mixture. As a result, the content of the metal Me atoms in the positive electrode mixture was the value shown in the table. Note that the "content of the metal Me atoms" in the column for the positive electrode mixture in the table is the amount (parts by mass) per 100 parts by mass of manganese atoms contained in the positive electrode mixture. The metal Me atoms are derived from the oxide of the metal Me, and the manganese atoms are derived from manganese dioxide.

[0069] 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.

[0070] (Preparation of Negative Electrode) A lithium metal foil or 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 location on the negative electrode by ultrasonic welding. The elements contained in the lithium alloy foil other than Li were Mg and / or Al. The Mg content and Al content in the lithium alloy foil were the values ​​shown in the table. In the table, a "-" in the Mg content (or Al content) column means that the Mg content (or Al content) was below the detection limit in composition analysis (such as ICP atomic emission spectroscopy).

[0071] (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.

[0072] (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.

[0073] (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.

[0074] In addition, the Li contained in the positive electrode mixture ｘ MnO ２has a median particle size of 21 to 23 μm and a BET specific surface area of ​​14 to 15 m ２ / g.

[0075] In the table, A1-1 to A1-16, A2-1 to A2-16, A3-1 to A3-16, A3-1 to A3-16, A4-1 to A4-16, A5-1 to A5-16, A6-1 to A6-16, and A7-1 to A7-3 are batteries of the example. Also, in the table, B1-1 to B1-7, B2-1 to B2-7, B3-1 to B3-7, B4-1 to B4-7, B5-1 to B5-7, and B6-1 to B6-7 are batteries of the comparative example. In the table, R1-1 to R1-3, R2-1 to R2-3, R3-1 to R3-3, R4-1 to R4-3, and R5-1 to R5-3 are batteries of the comparative example.

[0076] [Evaluation] (Internal Resistance of Battery After Storage) The battery after the aging treatment was stored for 4 months at 70° C. The internal resistance of the battery after storage was measured in an environment of 20° C.

[0077] (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.

[0078] The evaluation results are shown in Tables 1 to 13. In Tables 1 to 13, the internal resistance is expressed as a relative value when the internal resistance of Battery B1-2 is set to 100. The pulse discharge voltage is expressed as a relative value when the pulse discharge voltage of Battery B1-2 is set to 100. Note that A7-1 to A7-3 in Table 13 are examples in which oxides of two types of metal Me (composite materials in which the surfaces of manganese dioxide particles are covered with oxides of two types of metal Me) were used.

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085]

[0086]

[0087]

[0088]

[0089]

[0090]

[0091]

[0092] The batteries A1-1 to A1-16, A2-1 to A2-16, A3-1 to A3-16, A3-1 to A3-16, A4-1 to A4-16, A5-1 to A5-16, and A6-1 to A6-16 exhibited excellent storage characteristics (Tables 2 to 12).

[0093] The storage characteristics of batteries R1-1 to R1-3, B1-1 to B1-7, B2-1 to B2-7, B3-1 to B3-7, B4-1 to B4-7, B5-1 to B5-7, and B6-1 to B6-7 were degraded. These batteries used negative electrodes with a Li content of 88% by mass or less or a Mg content outside the range of 0.01 to 10% by mass, and / or positive electrodes with a metal Me oxide content outside the range of 0.1 to 5 parts by mass. The storage characteristics of batteries R2-1 to R2-3, R3-1 to R3-3, R4-1 to R4-3, and R5-1 to R5-3 were degraded because the metal Me had an ionic radius greater than 0.8 Å and / or an electronegativity greater than 1.65.

[0094] In comparison with batteries R1-1 to R1-3 in Table 1, which did not contain any metal Me oxide, battery R1-3, which used Li-Mg foil, showed a smaller increase in pulse discharge voltage after storage than batteries R1-1 and R1-2, which used Li foil or Li-Al foil (88, 90 → 93). On the other hand, in comparison with batteries B1-1, B1-2, and A1-1 in Table 2, which used Mg metal Me and contained an oxide of metal Me, battery A1-1, which used Li-Mg foil, showed a larger increase in pulse discharge voltage after storage than batteries B1-1 and B1-2, which used Li foil or Li-Al foil (98, 100 → 122). Similar trends were observed when the metal Me was Al, Ti, Zn, Zr, or Nb (Tables 2 and 3). This shows that the effect of improving the storage characteristics is significantly achieved when an oxide of metal Me is added to the positive electrode and an alloy containing Li and Mg is used for the negative electrode.

[0095] Comparing batteries B1-1, B1-2, A1-1, and A1-2 in Table 2, in which the metal Me was Mg, battery B1-2 using Li-Al foil (Al content: 1% by mass) showed a smaller increase in pulse discharge voltage after storage (98 → 100) than battery B1-1 using Li foil. On the other hand, battery A1-1 using Li-Mg foil (Mg content: 1% by mass) showed a significant increase in pulse discharge voltage as described above, and battery A1-2 using Li-Mg-Al foil (Mg content: 1% by mass, Al content: 1% by mass) showed an even greater increase in pulse discharge voltage after storage (122 → 125). Similar trends were observed when the metal Me was Al, Ti, Zn, Zr, or Nb (Tables 2 and 3).

[0096] The batteries A7-1 to A7-3, in which the oxides of two types of metal Me were added, also exhibited excellent storage characteristics (Table 13).

[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] REFERENCE SIGNS LIST 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 lithium primary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode mixture, the positive electrode mixture includes manganese dioxide and an oxide of a metal Me other than manganese, the metal Me having a valence of 2 or more, an ionic radius of 0.8 Å or less, and an electronegativity of 1.65 or less, the amount of the oxide of the metal Me included in the positive electrode mixture is 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the manganese dioxide included in the positive electrode mixture, the negative electrode includes an alloy containing lithium and magnesium, the content of the lithium in the alloy is more than 88% by mass, and the content of the magnesium in the alloy is 0.01% by mass or more and 10% 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 the aluminum in the alloy is 0.02 mass % or more and 10 mass % or less.

3. The lithium primary battery according to claim 1, wherein the metal Me comprises at least one selected from the group consisting of magnesium, aluminum, titanium, zinc, zirconium, and niobium.

4. The lithium primary battery according to claim 1, wherein the manganese dioxide has a median particle size of 5 μm or more and 40 μm or less.

5. The BET specific surface area of ​​the manganese dioxide is 5 m ２ / g or more, 40m ２ 2. The lithium primary battery according to claim 1, wherein the capacitance is 0.1 μm or less.

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