Lithium primary battery

Abstract

Disclosed is a lithium primary battery which comprises a wound electrode group and a nonaqueous electrolyte solution. The electrode group is configured by spirally winding a band-like positive electrode, a band-like negative electrode, and a separator that is disposed between the positive electrode and the negative electrode. The positive electrode contains both manganese dioxide and graphite fluoride. The negative electrode contains a lithium alloy. The lithium alloy contains magnesium, and the content ratio of the magnesium in the lithium alloy is 0.01% by mass to 11% by mass inclusive.

Description

Lithium primary battery

[0001] The present disclosure relates to lithium primary batteries.

[0002] Lithium primary batteries have a high energy density and low self-discharge, and are therefore used as power sources for many electronic devices. A wound electrode group of a lithium primary battery is composed of a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator disposed between the positive and negative electrodes, wound together in a spiral shape. For example, a sheet-shaped (foil-shaped) lithium metal or lithium alloy is used for the negative electrode.

[0003] Patent Document 1 proposes "a nonaqueous electrolyte battery comprising a positive electrode using a mixture of manganese dioxide and graphite fluoride as an active material, a negative electrode using metallic lithium or a substance capable of absorbing and releasing lithium ions as a negative electrode material, and a nonaqueous electrolyte, wherein the graphite fluoride is represented by the formula (CFx)n (where 1.2≦x≦1.4) and accounts for 0.1 to 4% by weight of the mixture."

[0004] Patent Document 2 proposes "a lithium battery comprising a positive electrode containing manganese dioxide as a positive electrode active material, a negative electrode containing at least one of lithium metal and a lithium alloy as a negative electrode active material, a porous insulator disposed between the positive electrode and the negative electrode, and an organic electrolyte, wherein the organic electrolyte contains 0.001 to 1% by weight of a hydroxycarboxylic acid ester."

[0005] Patent Document 2 states that "at least one of lithium metal and a lithium alloy is used as the negative electrode active material. Examples of the lithium alloy include an alloy of lithium and at least one metal selected from the group consisting of aluminum, tin, magnesium, indium, and calcium. The content of metals other than lithium in the lithium alloy is preferably 0.1 to 3 wt %" (

[0034] ).

[0006] Japanese Patent Laid-Open No. 7-50165 Japanese Patent Laid-Open No. 2011-60655

[0007] Patent Document 1 describes that by mixing manganese dioxide with graphite fluoride, the reaction products generated by the reaction between manganese dioxide and a non-aqueous electrolyte are captured by the graphite fluoride, making it difficult for the reaction products to react with lithium on the negative electrode side (self-discharge) (

[0012] ).

[0008] However, because graphite fluoride has a larger theoretical capacity than manganese dioxide, mixing it with manganese dioxide increases the positive electrode capacity. As a result, in lithium primary batteries using sheet-shaped (foil-shaped) metallic lithium or lithium alloys as the negative electrode, parts of the negative electrode can be damaged or broken at the end of discharge, resulting in a decrease in discharge performance. While changing the capacity balance between the positive and negative electrodes is an option, it is more desirable to increase the overall battery capacity without reducing discharge performance.

[0009] One aspect of the present disclosure relates to a lithium primary battery including: a wound electrode group; and a nonaqueous electrolyte; the electrode group is configured by spirally winding a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator disposed between the positive electrode and the negative electrode; the positive electrode contains both manganese dioxide and graphite fluoride; the negative electrode contains a lithium alloy, which contains magnesium, and the magnesium content in the lithium alloy is 0.01 mass % or more and 11 mass % or less.

[0010] According to the present disclosure, the discharge performance of a lithium primary battery can be improved.

[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] 1 is a partially cross-sectional front view of a lithium primary battery according to one embodiment of the present invention.

[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 may be selected from them and used alone, or two or more may be used in combination.

[0014] The present disclosure also encompasses combinations of two or more features arbitrarily selected from the appended claims, i.e., two or more features arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0015] A lithium primary battery according to an embodiment of the present disclosure includes a wound electrode group and a nonaqueous electrolyte. The electrode group is configured by spirally winding a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator disposed between the positive electrode and the negative electrode. The negative electrode may be disposed on the outermost periphery of the electrode group. The positive electrode may be disposed on the innermost periphery of the electrode group.

[0016] The positive electrode contains both manganese dioxide and graphite fluoride as positive electrode active materials. The theoretical capacity per mass of manganese dioxide is approximately 308 mAh / g, and the theoretical capacity per mass of graphite fluoride is approximately 864 mAh / g. Therefore, the greater the proportion of graphite fluoride in the total of manganese dioxide and graphite fluoride, the greater the capacity per mass of the positive electrode active material.

[0017] On the other hand, graphite fluoride has a lower operating voltage than manganese dioxide, and manganese dioxide is also superior in pulse discharge characteristics. Therefore, in order to obtain a battery with a high operating voltage and excellent pulse discharge characteristics, it is preferable to use manganese dioxide and replace a portion of the manganese dioxide with graphite fluoride.

[0018] The proportion of graphite fluoride in the total of manganese dioxide and graphite fluoride is, for example, preferably 0.1 mass % or more and 10 mass % or less, and more preferably 0.1 mass % or more and 5 mass % or less.

[0019] The negative electrode contains a lithium alloy as the negative electrode active material. The negative electrode may be composed of a sheet (foil) of lithium alloy or may not include a negative electrode current collector. If the positive electrode capacity increases, part of the sheet (foil) of lithium alloy may be chipped or broken at the end of discharge, resulting in a decrease in discharge performance. In contrast, changing the capacity balance between the positive and negative electrodes can diminish the benefits of increased positive electrode capacity or increase the amount of expensive lithium used.

[0020] On the other hand, when a lithium alloy containing magnesium (Mg) is used for the negative electrode and the Mg content in the lithium alloy is 0.01% by mass or more and 11% by mass or less, the phenomenon of partial loss or breakage of the sheet-like lithium alloy at the end of discharge is significantly reduced. When a lithium alloy containing Mg is used at the above content, the lithium (Li) consumption reaction at the negative electrode proceeds uniformly throughout the negative electrode during the battery discharge process. Therefore, at the end of discharge, the lithium alloy containing Mg tends to remain in a thin foil (sheet), which suppresses partial loss or breakage of the negative electrode and maintains discharge performance. Therefore, the overall capacity of the battery can be improved without reducing discharge performance.

[0021] If the Mg content is less than 0.01% by mass, this effect is not fully realized, and discharge performance may be reduced due to the negative electrode. If the Mg content exceeds 11% by mass, further improvement in discharge performance cannot be expected. Furthermore, if the Mg content is too high, the proportion of Li decreases, making it difficult to improve the overall battery capacity.

[0022] From the viewpoint of more reliably increasing the amount of Li that can contribute to the discharge reaction at the end of discharge, the Mg content in the lithium alloy may be 0.02% by mass or more, or 0.05% by mass or more, and preferably 0.1% by mass or more. Also, from the viewpoint of ensuring a higher proportion of Li contained in the negative electrode, the Mg content in the lithium alloy may be 7% by mass or less, or 5% by mass or less, or 2% by mass or less, and preferably 1% by mass or less.

[0023] The lithium alloy containing Mg may further contain aluminum. When the lithium alloy contains Al, a low-resistance coating is formed on the surface of the negative electrode. Therefore, it is preferable that the lithium alloy contains Al. In the lithium alloy containing both Mg and Al, a low-resistance coating is formed on the surface, and the output voltage can be increased compared to lithium metal or a lithium alloy containing only one of Mg and Al.

[0024] When a lithium alloy contains only Al, uneven consumption of Li may occur due to segregation of Al. However, when a lithium alloy containing Mg contains Al, such a phenomenon is suppressed. Therefore, the effects of Mg and Al are stably expressed throughout the negative electrode. As a result, the proportion of Li that can contribute to the discharge reaction at the end of discharge is increased.

[0025] Hereinafter, a lithium alloy containing Mg and 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 amount of Al is below the detection limit in a composition analysis of the lithium alloy (for example, ICP atomic emission spectroscopy, atomic absorption spectroscopy, etc.).

[0026] In the case of a Li-Mg-Al alloy, the Al content in the lithium alloy is, for example, 0.01% by mass or more, or may be 0.02% by mass or more, 0.05% by mass or more, or 0.1% by mass or more. From the viewpoint of ensuring a higher proportion of Li contained in the negative electrode and ensuring ease of winding of the negative electrode, the Al content in the lithium alloy is, for example, preferably 0.5% by mass or less, and more preferably 0.3% by mass or less.

[0027] In the case of a Li-Mg-Al alloy, the total content of Mg and Al in the lithium alloy is, for example, 0.02% by mass or more and 11.5% by mass or less, or may be 0.03% by mass or more and 5.5% by mass or less, or 0.11% by mass or more and 1.5% by mass or less, or may be 0.2% by mass or more and 1.3% by mass or less.

[0028] The mass ratio of Mg to Al: Mg / Al may be, for example, 0.2 or more and 50 or less.

[0029] In addition to Mg and Al, the lithium alloy may contain one or more metal elements capable of alloying with lithium. Examples of metals capable of alloying with lithium include, but are not limited to, Na, Ca, Sn, Ni, Pb, In, K, Fe, and Si. However, 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 15% by mass or less or 11% by mass or less. That is, the content of Li in the lithium alloy used in the negative electrode is preferably 85% by mass or more or 89% by mass or more, and more preferably 95% by mass or more.

[0030] The composition of the lithium alloy can be determined by inductively coupled plasma (ICP) emission spectroscopy or atomic absorption spectroscopy (AAS).

[0031] The lithium primary battery of the present disclosure will be described in more detail below.

[0032] [Lithium Primary Battery] (Positive Electrode) The positive electrode contains both manganese dioxide and graphite fluoride as positive electrode active materials. Manganese dioxide has a high operating voltage and excellent output and discharge characteristics (pulse discharge characteristics). On the other hand, graphite fluoride has a higher capacity than manganese dioxide. By using both, a lithium primary battery with high capacity and excellent output characteristics can be obtained.

[0033] The manganese dioxide may be electrolytic manganese dioxide. The manganese dioxide may be in a mixed crystal state including a plurality of crystal states. The positive electrode may contain a manganese oxide other than manganese dioxide. The manganese oxide contained in the positive electrode may be mainly composed of manganese dioxide, and the proportion of manganese dioxide in the manganese oxide may be 50% by mass or more, 70% by mass or more, or 90% by mass or more. Examples of manganese oxide other than manganese dioxide include MnO, Mn ３ O ４ , Mn ２ O ３ , Mn ２ O ７ The particle diameter D at a volume fraction of 50% in the volume cumulative particle size distribution of manganese dioxide is 50 is, for example, 30 μm to 60 μm.

[0034] Graphite fluoride can be obtained, for example, by fluorinating a carbon material containing a graphite structure. Fluorination proceeds by heating the carbon material together with fluorine gas. The particle diameter D at a volume fraction of 50% in the volume cumulative particle size distribution of graphite fluoride is 50 is, for example, 10 μm to 30 μm. Graphite fluoride (CF x ) n In the formula, x is, for example, 0.4≦x≦1.15, and may be 0.5 to 1.1.

[0035] The positive electrode may include a positive electrode mixture containing a positive electrode active material, a binder, a conductive agent, etc. Examples of the binder include fluororesin such as polytetrafluoroethylene, rubber particles, and acrylic resin. 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.

[0036] 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.

[0037] 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 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 it in the thickness direction, and drying it.

[0038] (Negative Electrode) The negative electrode contains the lithium alloy described above. The lithium alloy is formed into any shape and thickness depending on the shape, dimensions, performance specifications, etc. of the lithium primary battery.

[0039] In the case of a cylindrical battery, a foil (sheet) of lithium alloy may be used for the negative electrode. The sheet may be obtained, for example, by extrusion molding. More specifically, a cylindrical battery may use a lithium alloy foil having a shape with a longitudinal direction and a transverse direction.

[0040] The negative electrode may include a negative electrode current collector (e.g., copper foil) that supports the lithium alloy. However, since the lithium alloy contains Mg, and the relatively strong Mg can remain in a thin foil (sheet) at the end of discharge, the negative electrode can be constructed using only a foil (sheet) of lithium alloy without using a negative electrode current collector.

[0041] (Non-aqueous electrolyte) The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt. The concentration of lithium ions (concentration of lithium salt) contained in the non-aqueous electrolyte is, for example, 0.2 mol / L or more and 2.0 mol / L or less, and may be 0.3 mol / L or more and 1.5 mol / L or less.

[0042] Examples of non-aqueous solvents include organic solvents that are commonly used in non-aqueous electrolytes for lithium primary batteries. Specific examples include ethers, esters, and carbonate esters. More specific examples include dimethyl ether, γ-butyl lactone, propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane (DME), 1,2-diethoxyethane, methyl acetate, ethyl acetate, and propyl acetate. These non-aqueous solvents may be used singly or in combination.

[0043] 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.

[0044] Examples of the lithium salt include lithium salts used as solutes in lithium primary batteries. Specifically, 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 , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ F) (POF ２ ), LiPO ２ F ２ , LiB(C ２ O ４ ) ２ , LiBF ２ (C ２ O ４Among them, from the viewpoint of stability with lithium alloys containing Al and Mg, LiCF ３ SO ３ , LiBF ４ and LiN(FSO ２ ) ２ The non-aqueous electrolyte may contain one or more of these lithium salts.

[0045] The non-aqueous electrolyte may further contain an additive such as propane sultone, propene sultone, ethylene sulfite, 3,2-dioxathiolane-2,2-dioxide, vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, adiponitrile, succinonitrile, or succinic anhydride.

[0046] (Separator) A lithium primary battery typically includes a separator interposed between the positive electrode and the negative electrode. The separator may be a porous sheet made of an insulating material that is resistant to the internal environment of a lithium primary battery. Specific examples include a synthetic resin nonwoven fabric, a synthetic resin microporous membrane, or a laminate thereof. The thickness of the separator is, for example, 5 μm or more and 100 μm or less.

[0047] 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.

[0048] (Lithium Primary Battery) FIG. 1 shows a partially cross-sectional front view of a lithium primary battery according to one embodiment of the present invention. A battery case 9 of the lithium primary battery 10 contains a wound electrode group and a nonaqueous electrolyte. The electrode group is formed by spirally winding a strip-shaped positive electrode 1 and a strip-shaped negative electrode 2 with a separator 3 interposed therebetween. A sealing plate 8 is attached to the opening of the battery case 9. The positive electrode 1 includes a positive electrode current collector 1a and a positive electrode mixture layer carried on one or both sides of the positive electrode current collector 1a. The positive electrode current collector 1a and the sealing plate 8 are connected via a positive electrode lead 4. The negative electrode 2 includes at least a foil-shaped (or sheet-shaped) negative electrode alloy. The negative electrode 2 and the battery case 9 are connected via a negative electrode lead 5. An upper insulating plate 6 and a lower insulating plate 7 are disposed on the upper and lower parts of the electrode group, respectively, to prevent internal short circuits.

[0049] The structure and shape of the lithium primary battery are not particularly limited. The wound electrode group may be cylindrical or flat. The shape of the lithium primary battery may be cylindrical or prismatic.

[0050] <<Appendix>> The above embodiments disclose the following technologies. (Technology 1) A lithium primary battery comprising a wound electrode group and a nonaqueous electrolyte, wherein the electrode group is configured by spirally winding a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode contains both manganese dioxide and graphite fluoride, the negative electrode contains a lithium alloy, and the lithium alloy contains magnesium, and the magnesium content in the lithium alloy is 0.01% by mass or more and 11% by mass or less. (Technology 2) The lithium primary battery according to Technology 1, wherein a proportion of the graphite fluoride in the total of the manganese dioxide and the graphite fluoride is 0.1% by mass or more and 10% by mass or less. (Technology 3) The lithium primary battery according to Technology 1 or 2, wherein the proportion of the graphite fluoride in the total of the manganese dioxide and the graphite fluoride is 0.1 mass% or more and 5 mass% or less. (Technology 4) The lithium primary battery according to any one of Technology 1 to 3, wherein the content of magnesium in the lithium alloy is 0.1 mass% or more and 1 mass% or less. (Technology 5) The lithium primary battery according to any one of Technology 1 to 4, wherein the lithium alloy further contains aluminum, and the content of aluminum in the lithium alloy is 0.01 mass% or more and 0.5 mass% or less. (Technology 6) The lithium primary battery according to any one of Technology 1 to 5, wherein the negative electrode is a foil of the lithium alloy and does not include a negative electrode current collector.

[0051] [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.

[0052] Examples 1 to 8 and Comparative Examples 1 to 8 (Preparation of Positive Electrodes) 100 parts by mass of a positive electrode active material was mixed with 5 parts by mass of Ketjen Black (a conductive agent), 5 parts by mass of polytetrafluoroethylene (a binder), and an appropriate amount of pure water to prepare a wet positive electrode mixture. A mixture of electrolytic manganese dioxide and graphite fluoride was used as the positive electrode active material. The proportion of graphite fluoride in the total of electrolytic manganese dioxide and graphite fluoride was 0.1%, 1%, 5%, or 10% by mass.

[0053] Next, the positive electrode mixture was filled into a 0.1 mm thick stainless steel expanded metal positive electrode current collector to prepare a positive electrode precursor. The positive electrode precursor was then dried, rolled using a roll press, and cut to obtain a strip-shaped 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.

[0054] The mass of the positive electrode mixture contained in the positive electrode, as well as the width and length of the positive electrode, were standardized for all batteries as follows: Mass of positive electrode mixture: 9.7 g Width of positive electrode: 38 mm Length of positive electrode: 190 mm

[0055] When the positive electrode active material is entirely electrolytic manganese dioxide, the thickness of the positive electrode is 0.51 mm and the theoretical capacity of the positive electrode is 2420 mAh. When 1 mass % of the positive electrode active material is replaced from electrolytic manganese dioxide with graphite fluoride, the increase in capacity is 49.0 mAh.

[0056] (Preparation of Negative Electrode) The following lithium metal foils and lithium alloy foils were prepared as negative electrodes. The thickness of the negative electrode was 0.21 mm for pure lithium alloy foils, and the thickness of the negative electrode containing Mg and / or Al was increased by the amount of added Mg and / or Al.

[0057] Batteries B1 to B4: Pure lithium foil Batteries B5 to B8: Lithium alloy containing no Mg and 0.3% by mass of Al (Li-Al0.3) Batteries A1 to A4: Lithium alloy containing no Al and 0.3% by mass of Mg (Li-Mg0.3) Batteries A5 to A8: Lithium alloy containing 0.1% by mass of Al and 0.3% by mass of Mg (Li-Al0.1-Mg0.3)

[0058] The mass of Li contained in the negative electrode, and the width and length of the negative electrode were standardized for all batteries as follows: The thickness of the negative electrode was 0.21 mm to 0.24 mm. The mass of Li was 0.80 g, the width of the negative electrode was 34 mm, and the length of the negative electrode was 210 mm.

[0059] A nickel negative electrode lead was pressure-welded to the end of the lithium alloy foil, and a synthetic resin adhesive tape was attached to cover the negative electrode lead except for the tip.

[0060] (Preparation of Electrode Assembly) A strip-shaped separator of a predetermined size was prepared. A 25 μm thick polyethylene microporous membrane was used as the separator. The separator was placed between the positive electrode and the negative electrode and spirally wound with the positive electrode on the inside. In this way, an electrode assembly was prepared with a negative electrode at the outermost periphery. The tip of the negative electrode lead was exposed from one end surface of the electrode assembly, and the tip of the positive electrode lead was exposed from the other end surface of the electrode assembly.

[0061] (Preparation of non-aqueous electrolyte) LiCF was dissolved in a mixed solvent of PC, EC, and DME (volume ratio 3:2:5). ３ SO ３ was dissolved in the solution at a concentration of 0.5 mol / L to prepare a non-aqueous electrolyte solution.

[0062] (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 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 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 manner, a lithium primary battery was fabricated.

[0063] In the table, batteries A1 to A8 are the batteries of Examples 1 to 8. Batteries B1 to B8 are the batteries of Comparative Examples 1 to 8.

[0064]

[0065] After assembly, the resulting batteries of the Examples and Comparative Examples were aged for 7 days in an atmosphere at 45° C., and then evaluated as follows.

[0066] [Evaluation] The aged batteries were connected to a resistor of 1 kΩ in an environment of 20° C. and discharged until the voltage reached 2 V, and the discharge capacity was measured. For each positive electrode composition, the relative value when the discharge capacity of batteries B1 to B4 using pure lithium foil was set at 100 is shown in Table 1.

[0067] In Comparative Examples 5 to 8, which used Li-Al0.3 lithium alloy foil, no increase in discharge capacity was observed. On the other hand, in Examples 1 to 8, which used Li-Mg0.3 and Li-Al0.1-Mg0.3 lithium alloy foils, the discharge capacity increased by 10% or more, and the increase became larger as the proportion of graphite fluoride increased. This tendency is specific to lithium alloys containing Mg. In Examples 5 to 8, which used Li-Al0.1-Mg0.3 lithium alloy foil, the discharge capacity further increased due to the improved effect (lower resistance) of the negative electrode coating by Al.

[0068] Examples 9 to 24 Batteries A9 to A24 were fabricated and evaluated in the same manner as Batteries A1 to A4, except that the composition of the Li—Mg alloy was changed as follows: For each positive electrode composition and negative electrode composition, the discharge capacity relative to the discharge capacity of Batteries B1 to B4 using pure lithium foil is set at 100 is shown in Table 2.

[0069]

[0070] The discharge capacity increased as the Mg content in the lithium alloy foil increased, and the discharge capacity also increased as the proportion of graphite fluoride in the positive electrode active material increased.

[0071] When only manganese dioxide was used as the positive electrode active material, the discharge capacity was smaller than that of Batteries B1 to B4. When the Mg content of the lithium alloy foil was changed to 12 mass%, no increase in discharge capacity was observed compared to Batteries 21 to 24. On the other hand, when the Mg content of the lithium alloy foil was changed to 12 mass%, the diameter of the electrode group became too large, and the number of defective battery fabrications increased.

[0072] In the above examples, the Al content of the Li-Mg-Al alloy was fixed at 0.1 mass % and the Mg content was fixed at 0.3 mass %, but it was confirmed that a similar tendency was obtained when the Mg content was in the range of 0.01 mass % to 11 mass %, and that a similar tendency was obtained when the Al content was in the range of 0.01 mass % to 0.5 mass %.

[0073] The lithium primary battery of the present disclosure is suitable for use as, for example, a power source for an AED (automated external defibrillator), a main power source for various meters (for example, smart meters for electricity, water, gas, etc.), and a memory backup power source.

[0074] 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.

[0075] 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 wound electrode group; and a non-aqueous electrolyte; the electrode group is configured by spirally winding a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator disposed between the positive electrode and the negative electrode; the positive electrode contains both manganese dioxide and graphite fluoride; the negative electrode contains a lithium alloy; the lithium alloy contains magnesium; and the magnesium content in the lithium alloy is 0.01% by mass or more and 11% by mass or less.

2. The lithium primary battery according to claim 1, wherein the proportion of said graphite fluoride in the total of said manganese dioxide and said graphite fluoride is 0.1 mass % or more and 10 mass % or less.

3. The lithium primary battery according to claim 1, wherein the proportion of said graphite fluoride in the total of said manganese dioxide and said graphite fluoride is 0.1 mass % or more and 5 mass % or less.

4. The lithium primary battery according to any one of claims 1 to 3, wherein the magnesium content in the lithium alloy is 0.1 mass % or more and 1 mass % or less.

5. The lithium primary battery according to any one of claims 1 to 3, wherein the lithium alloy further contains aluminum, and the content of the aluminum in the lithium alloy is 0.01 mass % or more and 0.5 mass % or less.

6. The lithium primary battery according to any one of claims 1 to 3, wherein the negative electrode is a foil of the lithium alloy and does not include a negative electrode current collector.