Lithium primary battery

Abstract

This lithium primary battery comprises: a positive electrode; a negative electrode; and an electrolyte solution. The positive electrode contains at least one substance that is selected from the group consisting of manganese dioxide and graphite fluoride. The negative electrode contains a lithium alloy. The lithium alloy contains magnesium, and the content of magnesium in the lithium alloy is 10 mass% or less. The electrolyte solution contains a nonaqueous solvent and a solute. the solute contains a sulfonyl imide compound.

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 cylindrical electrolyte primary battery having an electrode group with a wound structure in which a manganese dioxide-containing positive electrode and a negative electrode are spirally wound with a separator interposed therebetween, the negative electrode having a metallic lithium-containing layer constituted by only one continuous layer on one side of a current collector, the metallic lithium-containing layer covering 85% or more of the area of ​​the surface of the current collector on which the metallic lithium-containing layer is formed, and a lithium-aluminum alloy being formed on at least a portion of the surface of the metallic lithium-containing layer opposite the current collector."

[0005] Patent Document 3 proposes "a lithium primary battery comprising a positive electrode using iron disulfide as a positive electrode active material, a negative electrode using a lithium alloy as a negative electrode active material, an electrode group in which the positive electrode and the negative electrode are wound with a separator interposed therebetween, and an electrolyte solution, wherein the lithium alloy contains 0.02 to 0.2 mol % of at least one of magnesium and tin."

[0006] Patent Document 4 describes an alkali metal battery in which a battery element including a positive electrode, a negative electrode, and a non-aqueous electrolyte solution in which an electrolyte is dissolved in a non-aqueous solvent is housed in a metal exterior material, and the electrolyte is MN(R 1 SO2)(R 2 SO2) (wherein M represents an alkali metal ion, R 1 , R 2 are independently a fluorine atom or a fluoroalkyl group having 1 to 6 carbon atoms), a cyclic carbonate having an unsaturated bond, and another alkali metal salt containing fluorine, wherein the metal exterior material contains stainless steel on at least a portion of the surface that comes into contact with the non-aqueous electrolyte.

[0007] Japanese Patent Application Laid-Open No. 58-209862 Japanese Patent Application Laid-Open No. 2012-138225 International Publication No. 2012 / 066709 Pamphlet Japanese Patent Application Laid-Open No. 2013-125696

[0008] When a lithium primary battery is used for a long period of time, its internal resistance increases and its output characteristics may decrease.

[0009] One aspect of the present disclosure relates to a lithium primary battery including a positive electrode, a negative electrode, and an electrolyte solution, wherein the positive electrode includes at least one selected from the group consisting of manganese dioxide and graphite fluoride, the negative electrode includes a lithium alloy, the lithium alloy includes magnesium, and the content of the magnesium in the lithium alloy is 10 mass % or less, and the electrolyte solution includes a non-aqueous solvent and a solute, and the solute includes a sulfonylimide compound.

[0010] According to the present disclosure, it is possible to suppress the deterioration of the output characteristics of a lithium primary battery during long-term use.

[0011] 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.

[0012] FIG. 1 is a partially cross-sectional front view of a lithium primary battery according to an embodiment of the present disclosure.

[0013] 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.

[0014] A lithium primary battery according to one embodiment of the present disclosure includes a positive electrode, a negative electrode, and an electrolyte (non-aqueous electrolyte). The positive electrode includes at least one material selected from the group consisting of manganese dioxide and graphite fluoride. The negative electrode includes a lithium alloy, and the lithium alloy includes magnesium (Mg), and the Mg content in the lithium alloy is 10 mass% or less. The electrolyte includes a non-aqueous solvent and a solute, and the solute includes a sulfonylimide compound.

[0015] When the above configuration is satisfied, an increase in internal resistance during long-term use is suppressed, and a decrease in output characteristics (e.g., low-temperature pulse characteristics) due to an increase in internal resistance is suppressed. For example, the output decrease rate described below is reduced. While the detailed mechanism is unknown, it is speculated as follows. A solvent (e.g., carbonate ester) and a sulfonylimide compound contained in the electrolyte react on the surface of the negative electrode containing Mg, forming an organic-inorganic hybrid coating containing an organic component derived from the solvent and an inorganic component derived from the sulfonylimide compound on the surface of the negative electrode (lithium alloy containing Mg). This coating has low resistance and excellent durability. Furthermore, since this coating has good wettability with the negative electrode (lithium alloy containing Mg), the effects of the coating on the negative electrode, which reduces resistance and improves durability, are significantly achieved. This uniformity in the reaction on the negative electrode surface leads to uniform lithium consumption at the negative electrode, suppressing negative electrode damage (foil tearing) at the end of discharge, and efficiently utilizing the lithium at the negative electrode. These factors suppress a decrease in output characteristics during long-term use.

[0016] However, if the Mg content in the lithium alloy is greater than 10 mass %, the proportion of Mg in the negative electrode increases, which may increase the negative electrode resistance and reduce the output characteristics.

[0017] (Sulfonylimide Compound) The sulfonylimide compound (sulfonylimide salt) as a solute can generate a sulfonylimide anion and a cation (for example, an alkali metal ion such as a Li ion) in the electrolyte solution. Examples of the sulfonylimide compound include fluorine-containing sulfonylimide compounds. Examples of such compounds include LiN(SO ２ Ra) (SO ２ In the formula, Ra and Rb are each independently a fluorine atom or a fluorinated alkyl group having 1 to 4 carbon atoms. The fluorinated alkyl group may be linear or branched. Examples of the fluorinated alkyl group include CF ３ , C ２ F ５ , C ３ F ７ , C ４ F ９Specific examples of sulfonylimide compounds include lithium bis(fluorosulfonyl)imide: LiN(SO ２ F) ２ (hereinafter also referred to as LiFSI), lithium bis(trifluoromethanesulfonyl)imide: LiN(CF ３ SO ２ ) ２ , lithium (fluorosulfonyl) (trifluoromethanesulfonyl) imide: LiN(SO ２ F) (CF ３ SO ２ ), lithium bis(pentafluoroethanesulfonyl)imide: LiN(CF ３ CF ２ SO ２ ) ２ Among them, LiFSI is particularly preferred as the sulfonylimide compound. The proportion of LiFSI in the sulfonylimide compound may be 60% by mass or more, 70% by mass or more, 90% by mass or more, or even 100% by mass. The sulfonylimide compound may be used alone or in combination of two or more.

[0018] The content of the sulfonylimide compound in the electrolyte solution may be 0.1% by mass or more and 20% by mass or less, 0.5% by mass or more and 20% by mass or less, or 4% by mass or more and 20% by mass or less. The content of the sulfonylimide compound in the electrolyte solution is the mass ratio (percentage) of the sulfonylimide compound to the entire electrolyte solution. For example, immediately after the battery is manufactured (or when the electrolyte solution is prepared), it is desirable that the content of the sulfonylimide compound in the electrolyte solution be within the above range. In batteries that have been manufactured for a certain period of time, a portion of the sulfonylimide compound is consumed in the formation of a coating, and the content of the sulfonylimide compound in the electrolyte solution may be smaller than the above range. Even in this case, the above-mentioned effects of the Mg-containing lithium alloy and the sulfonylimide compound are observed.

[0019] The electrolyte solution can be analyzed by, for example, liquid chromatography-mass spectrometry (LC / MS) or gas chromatography-mass spectrometry (GC / MS). Nuclear magnetic resonance spectrometry (NMR), infrared spectrometry (IR), mass spectrometry (MS), and ultraviolet spectrometry (UV) may also be performed.

[0020] (Lithium Alloy) The negative electrode contains a lithium alloy, and the lithium alloy contains 10% by mass or less of Mg. From the viewpoint of reducing internal resistance and ensuring capacity, the Li content in the lithium alloy may be 89% by mass or more, 90% by mass or more, or even 95% by mass or more.

[0021] From the viewpoint of improving output characteristics during long-term use, 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 (e.g., ICP atomic emission spectroscopy, atomic absorption spectroscopy, etc.).

[0022] While the addition of Al suppresses the increase in internal resistance during 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 the segregation of Al, thereby suppressing the non-uniformity of the Li reaction during battery use. In this case, the effects of Mg and Al are stably obtained throughout the negative electrode, and Li is uniformly consumed in the negative electrode, increasing the 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 output voltage at the end of discharge is further increased, and the increase in internal resistance during long-term use and the resulting decrease in output characteristics are further suppressed.

[0023] From the viewpoint of suppressing a decrease in output characteristics during long-term use, the Mg content in the lithium alloy is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 8% by mass or less, and even more preferably 0.1% by mass or more and 7% by mass or less. Note that the Mg content in the lithium alloy is the Mg content in a Li—Mg alloy or a Li—Mg—Al alloy.

[0024] From the viewpoint of suppressing a decrease in output characteristics during long-term use, the Al content in the lithium alloy (Li—Mg—Al alloy) may be 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. From the same viewpoint, the total content of Mg and Al in the Li—Mg—Al alloy is preferably 0.01% 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 0.05 to 13.

[0025] The lithium alloy may contain metal elements other than Li, Mg, and Al. Examples of the other metal elements include Sn, Ni, Pb, In, Na, K, Ca, Fe, Ba, and Sr. From the viewpoint of ensuring discharge capacity and stabilizing internal resistance, the total content of metal elements other than lithium contained in the lithium alloy is preferably 11 mass% or less.

[0026] The composition of the lithium alloy can be determined by inductively coupled plasma (ICP) emission spectroscopy or atomic absorption spectroscopy (AAS).

[0027] The lithium primary battery of the present disclosure will be described in more detail below.

[0028] [Lithium Primary Battery] (Positive Electrode) The positive electrode contains at least one material selected from the group consisting of manganese dioxide and graphite fluoride as a positive electrode active material. As the manganese dioxide, calcined electrolytic manganese dioxide is preferably used. A positive electrode containing manganese dioxide exhibits a relatively high voltage and has excellent pulse discharge characteristics. The manganese dioxide may be in a mixed crystal state containing multiple types of crystalline states. The positive electrode may contain manganese oxides other than manganese dioxide. Examples of manganese oxides other than manganese dioxide include MnO, Mn３ 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. Here, "main component" means that the proportion of manganese dioxide in the manganese oxide is 50% by mass or more. The proportion of manganese dioxide in the manganese oxide may be 70% by mass or more, or may be 90% by mass or more.

[0029] The positive electrode includes, for example, a positive electrode current collector and a positive electrode mixture layer held on the positive electrode current collector. The positive electrode mixture layer is formed, for example, by applying a 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 the positive electrode current collector in the thickness direction, and drying the positive electrode mixture layer.

[0030] The positive electrode mixture may contain a positive electrode active material, a binder, a conductive agent, etc. Examples of the binder include fluororesins such as polytetrafluoroethylene, rubber particles, and acrylic resins. Examples of the conductive agent include conductive carbon materials. Examples of the conductive carbon materials include natural graphite, artificial graphite, carbon black, and carbon fiber.

[0031] Examples of materials for the positive electrode current collector include stainless steel, aluminum, and titanium. The positive electrode current collector is preferably a perforated current collector. Examples of perforated current collectors include expanded metal, net, and punched metal.

[0032] 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.

[0033] 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.

[0034] (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.

[0035] 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.

[0036] 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.

[0037] (Electrolyte) The electrolyte contains a non-aqueous solvent and a solute that dissolves in the non-aqueous solvent. Examples of the non-aqueous solvent include organic solvents that are commonly used in electrolytes for lithium primary batteries. Examples of the non-aqueous solvent include ethers, esters, and carbonate esters. Examples of the non-aqueous solvent that can be used include dimethyl ether, γ-butyl lactone, propylene carbonate (PC), ethylene carbonate (EC), and 1,2-dimethoxyethane (DME). One type of non-aqueous solvent may be used alone, or two or more types may be used in combination.

[0038] From the viewpoint of improving the discharge characteristics of a lithium primary battery, the nonaqueous solvent preferably contains a cyclic carbonate having a high boiling point and a chain ether having low viscosity even at low temperatures. The cyclic carbonate preferably contains at least one selected from the group consisting of PC and EC, with PC being particularly preferred. The chain ether preferably contains DME.

[0039] The solute contains at least a sulfonylimide compound (sulfonylimide salt), and may contain a compound other than the sulfonylimide compound. Examples of the solute other than the sulfonylimide compound include LiCF ３ SO ３ , LiClO ４ , LiBF ４ , LiPF ６ , LiRcSO ３ (Rc is a fluorine atom or a fluorinated alkyl group having 1 to 4 carbon atoms). The solute (lithium salt) may be used alone or in combination of two or more. The proportion of the sulfonylimide compound in the solute may be 60% by mass or more, 70% by mass or more, 90% by mass or more, or even 100% by mass.

[0040] The concentration of lithium ions contained in the electrolyte solution (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.

[0041] The electrolytic solution may contain additives, examples of which include cyclic sulfonate esters (such as propane sultone), ethylene sulfites (such as ethylene sulfite), cyclic carbonates (such as vinylene carbonate and fluoroethylene carbonate), nitrile compounds (such as adiponitrile and succinonitrile), isocyanates (such as hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane and isophorone diisocyanate), cyclic imides (such as phthalimide and hydroxyphthalimide), and phthalate esters (such as dimethyl phthalate and diethyl phthalate).

[0042] (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.

[0043] 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. The thickness of the separator is, for example, 5 μm or more and 100 μm or less.

[0044] 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.

[0045] 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 an 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 battery case 9. In addition, an upper insulating plate 6 and a lower insulating plate 7 are disposed on the top and bottom of the electrode group, respectively, to prevent internal short circuits.

[0046] <<Appendix>> The above embodiments disclose the following technologies. (Technology 1) A lithium primary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode contains at least one selected from the group consisting of manganese dioxide and graphite fluoride, the negative electrode contains a lithium alloy, the lithium alloy contains magnesium, the content of the magnesium in the lithium alloy is 10 mass% or less, the electrolyte contains a non-aqueous solvent and a solute, and the solute contains a sulfonylimide compound. (Technology 2) The lithium primary battery according to Technology 1, wherein the lithium alloy contains aluminum, and the total content of the magnesium and the aluminum in the lithium alloy is 0.01 mass% or more and 10 mass% or less. (Technology 3) The lithium primary battery according to Technology 2, wherein the molar ratio of the magnesium to the aluminum in the lithium alloy is 0.05 or more and 13 or less. (Technology 4) The lithium primary battery according to any one of Technology 1 to Technology 3, wherein the sulfonylimide compound contains lithium bis(fluorosulfonyl)imide. (Technology 5) The lithium primary battery according to any one of Technologies 1 to 4, wherein the content of the sulfonylimide compound in the electrolyte solution is 0.1% by mass or more and 20% by mass or less.

[0047] [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.

[0048] <Batteries A1 to A11 and B1 to B5> (Preparation of Positive Electrodes) 100 parts by mass of the positive electrode active material were mixed with 5 parts by mass of Ketjen Black as a conductive agent, 5 parts by mass of polytetrafluoroethylene as a binder, and an appropriate amount of pure water to prepare a wet positive electrode mixture. Electrolytic manganese dioxide (MnO) that had been baked at 400°C for 5 hours was used as the positive electrode active material. ２ ), or graphite fluoride (CF ｎ ) was used.

[0049] Next, the positive electrode mixture was filled into a 0.1 mm thick stainless steel expanded metal positive electrode collector to prepare a positive electrode precursor. The positive electrode precursor was then dried, rolled using a roll press, and cut into a size of 3.5 cm long and 20 cm wide 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 collector.

[0050] (Preparation of Negative Electrode) A lithium alloy foil (thickness: 250 μm) was cut into a size of 3.7 cm length and 22 cm width to obtain a negative electrode. One end of a nickel negative electrode lead was connected to a predetermined location on the negative electrode by pressure 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 Table 1. In Table 1, 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).

[0051] (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.

[0052] (Preparation of Electrolyte Solution) An electrolyte solution was prepared by dissolving a lithium salt in a mixed solvent of PC, EC, and DME (volume ratio 3:2:5). In batteries A2 to A11 and batteries B3 and B5, lithium bis(fluorosulfonyl)imide (LiFSI) was used as the lithium salt, and the content of LiFSI in the electrolyte solution was set to the value shown in Table 1. In battery A1, LiCF ３ SO ３(10 mass%) and LiFSI (0.1 mass%) were used. In batteries B1, B2, and B4, LiCF was used as the lithium salt. ３ SO ３ (10% by mass) was used. The value in parentheses (% by mass) is the content in the electrolyte solution.

[0053] (Assembly of Lithium Primary Battery) The electrode group was housed in a cylindrical battery case that also served as the negative electrode terminal. An iron case (outer diameter 17 mm, height 45.5 mm) was used as the battery case. Next, an electrolyte solution was poured into the battery case, and the opening of the battery case was closed with a metal sealing plate that also served as the 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 manner, a lithium primary battery was produced. The battery immediately after assembly was discharged at 1 A for 1 minute and then aged for 3 days in a 45°C atmosphere. In Table 1, Batteries A1 to A11 are examples, and Batteries B1 to B5 are comparative examples.

[0054] The following pulse discharge characteristics (output characteristics) were evaluated for each of the obtained batteries of the Examples and Comparative Examples.

[0055] [Evaluation] (Initial and Post-Storage Output Voltage) The aged battery was subjected to a 1-second pulse discharge at 200 mA in a −30° C. environment, and the minimum voltage at this time was determined as the initial output voltage X1. Subsequently, in a 25° C. environment, a constant current discharge was performed at 2.5 mA until the depth of discharge (DOD) reached 75% (until the discharged quantity of electricity reached 75% of the battery capacity). The discharged battery was stored for 120 days in a 70° C. environment. The stored battery was subjected to a pulse discharge in the same manner as above, and the minimum voltage at this time was determined as the post-storage output voltage X2.

[0056] (Output Reduction Rate) Using the X1 and X2 obtained above, the output reduction rate was calculated from the formula (X1-X2) / X1x100.

[0057] The evaluation results are shown in Table 1. The output voltages in Table 1 are expressed as relative values ​​(indexes) when the initial output voltage of Battery B1 of Comparative Example 1 is set to 100.

[0058]

[0059] In batteries A1 to A11, which used a lithium alloy containing Mg and an electrolyte containing a sulfonylimide compound, the deterioration of output characteristics during storage was suppressed. In particular, in batteries A7 to A11, which used a Li-Mg-Al alloy, the deterioration of output characteristics during storage was further suppressed. In batteries B1 to B4, which used a lithium alloy (negative electrode) that did not contain Mg and / or an electrolyte that did not contain a sulfonylimide compound, the output characteristics deteriorated during storage. In battery B5, which used an electrolyte containing a sulfonylimide compound, the Mg content in the lithium alloy was greater than 10% by mass, so the initial and post-storage output voltages decreased, and the rate of output deterioration increased.

[0060] Battery B1, which used a Li—Al alloy containing no Mg in the negative electrode and no sulfonylimide compound as the lithium salt in the electrolyte, showed almost no improvement in output characteristics during storage (output decline rate: 31.0% → 29.3%), while Battery B2, which used a Li—Mg alloy foil in the negative electrode and no sulfonylimide compound as the lithium salt in the electrolyte, showed very little improvement in output characteristics during storage (output decline rate: 31.0% → 27.0%) compared to Battery B1, which used a Li—Al alloy containing no Mg and an electrolyte containing 10% by mass of a sulfonylimide compound (LiFSI).

[0061] Battery A4, which used a Li-Mg alloy and an electrolyte containing 10% by mass of a sulfonylimide compound (LiFSI), showed a significant improvement in output characteristics during storage compared to Battery B1 (output reduction rate: 31.0% → 22.1%). This indicates that when the lithium alloy in the negative electrode contains Mg and the electrolyte contains a sulfonylimide compound, a significant effect of suppressing the reduction in output characteristics during storage can be obtained.

[0062] 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.).

[0063] 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.

[0064] 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 an electrolyte; the positive electrode comprises at least one selected from the group consisting of manganese dioxide and graphite fluoride; the negative electrode comprises a lithium alloy; the lithium alloy comprises magnesium; a content of the magnesium in the lithium alloy is 10 mass % or less; the electrolyte comprises a non-aqueous solvent and a solute; and the solute comprises a sulfonylimide compound.

2. The lithium primary battery according to claim 1, wherein the lithium alloy contains aluminum, and the combined content of the magnesium and aluminum in the lithium alloy is 0.01 mass % or more and 10 mass % or less.

3. The lithium primary battery according to claim 2, wherein in the lithium alloy, a molar ratio of said magnesium to said aluminum is 0.05 or more and 13 or less.

4. The lithium primary battery according to claim 1, wherein the sulfonylimide compound comprises lithium bis(fluorosulfonyl)imide.

5. The lithium primary battery according to claim 1, wherein the content of the sulfonylimide compound in the electrolyte is 0.1% by mass or more and 20% by mass or less.

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