Lithium primary battery

Abstract

This lithium primary battery comprises a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. The positive electrode includes a positive electrode active material and a conductive material. The positive electrode active material contains at least one of manganese dioxide and graphite fluoride. The conductive material contains carbon black. The carbon black contains a metal element at an amount of 0.02-0.4 at%. The negative electrode includes a lithium alloy. The lithium alloy contains magnesium. The content of the magnesium in the lithium alloy is 0.01-11 mass%.

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 describes a lithium battery in which the negative electrode active material is metallic lithium or a lithium-aluminum alloy, the positive electrode active material is an inorganic material other than carbon fluoride, and the electrolyte is a non-aqueous electrolyte, in which the positive electrode active material has a primary particle size of 25 nm or less and a specific surface area of ​​500 m ２ / g or more and metal impurities of 500 ppm or less are further contained in acetylene black.

[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]

[0034] 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 %."

[0006] JP 62-188167 A JP 2011-60655 A

[0007] Lithium primary batteries are used as power sources for devices such as AEDs (Automated External Defibrillators). In such devices, the lithium primary batteries are suddenly discharged with a large current after long-term storage. However, it may not be possible to extract a sufficient large current from the lithium primary batteries after long-term storage.

[0008] In response to this issue, it is believed that the discharge performance can be improved by incorporating carbon black as a conductive material into the positive electrode. However, metal elements used during manufacturing may remain in the carbon black. It is believed that the metal elements in the carbon black precipitate on the surface of metallic lithium or lithium alloys used as the negative electrode, causing internal short circuits and a decrease in discharge capacity.

[0009] Furthermore, Patent Document 1 also describes that if the metal impurities in acetylene black exceed 500 ppm, the inorganic substance in the positive electrode and the metal impurities form a local battery, and the rate at which the elementary reaction between lithium and the inorganic substance is inhibited increases, resulting in a shortened battery life.

[0010] One aspect of the present disclosure relates to a lithium primary battery including: a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte; the positive electrode includes a positive electrode active material and a conductive material, the positive electrode active material including at least one of manganese dioxide and graphite fluoride, the conductive material including carbon black, the carbon black including 0.02 atomic % or more and 0.4 atomic % or less of a metal element; the negative electrode includes a lithium alloy, the lithium alloy including magnesium, and a content of the magnesium in the lithium alloy of 0.01 mass % or more and 11 mass % or less.

[0011] According to the present disclosure, sufficient discharge characteristics can be obtained when discharging a lithium primary battery at a large current after storage.

[0012] 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.

[0013] 1 is a cross-sectional view of a lithium primary battery according to one embodiment of the present invention.

[0014] 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.

[0015] 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.

[0016] A lithium primary battery according to an embodiment of the present disclosure includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The separator is disposed between the positive electrode and the negative electrode. The structure and shape of the lithium primary battery are not particularly limited. The lithium primary battery may be coin-shaped, cylindrical, prismatic, or flat.

[0017] The positive electrode, negative electrode, and separator may form a wound electrode group. The wound electrode group is formed by spirally winding a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator disposed between the positive and negative electrodes. Either the negative electrode or the positive electrode may be disposed on the outermost periphery of the electrode group. Either the positive electrode or the negative electrode may be disposed on the innermost periphery of the electrode group.

[0018] The positive electrode includes a positive electrode active material and a conductive material. The positive electrode active material includes at least one of manganese dioxide and graphite fluoride. The conductive material includes carbon black. The carbon black includes 0.02 atomic % or more and 0.4 atomic % or less of a metal element. The content of the metal element in the carbon black may be 0.02 atomic % or more and 0.3 atomic % or less, or 0.05 atomic % or more and 0.2 atomic % or less.

[0019] Here, the content of metal elements in carbon black refers to the ratio (%) of the number of atoms of metal elements to the total number of atoms of carbon elements and metal elements contained in carbon black, which is 100%.

[0020] The content of metal elements in carbon black can be determined by inductively coupled plasma (ICP) emission spectrometry or atomic absorption spectrometry (AAS).

[0021] The metal element is not particularly limited, but may be, for example, at least one selected from the group consisting of Fe, Sr, V, Ni, and Nb. Among them, it is preferable to use Fe, which has high electronic conductivity and is inexpensive. Fe may account for 50 atomic % or more, further 70 atomic % or more, or even 90 atomic % or more of the metal elements.

[0022] Metal elements in carbon black have the effect of bringing the carbon black structures into contact with each other. The higher the content of metal elements in carbon black, the better the electronic conductivity of the carbon black, and as a result, it is expected that the discharge characteristics of the battery will improve.

[0023] However, when carbon black with a high metal element content is used as a positive electrode active material such as manganese dioxide or graphite fluoride, the metal element may dissolve into the electrolyte due to the potential difference with the positive electrode active material. On the other hand, lithium (Li) has the lowest potential among metal elements, so metal elements present in the battery are likely to precipitate on the surface of the lithium alloy. Therefore, it is thought that the metal elements in the carbon black may precipitate on the surface of the lithium alloy, causing an internal short circuit or a decrease in discharge capacity.

[0024] Although alloying Li with other metal elements can make the potential of the alloy surface more noble, the solid solution state of the alloyed metals is not completely uniform. Therefore, potential spots (states in which the potential level varies) occur on the surface of the lithium alloy. For example, lithium alloys containing aluminum (Al) tend to have a mixed form of Li and Li-Al alloy, which makes potential spots likely to occur. When such potential spots occur, it is difficult to suppress the deposition of metal elements.

[0025] On the other hand, the negative electrode according to the present disclosure includes a lithium alloy, and the lithium alloy includes magnesium (Mg), with the Mg content in the lithium alloy being 0.01% by mass or more and 11% by mass or less. Because lithium alloys containing Mg tend to form uniform Li-Mg alloys, the potential of the alloy surface can be made more noble while maintaining a state in which potential spots are less likely to occur. Therefore, precipitation of metal elements is less likely to occur on the surface of the negative electrode or lithium alloy according to the present disclosure, and the disadvantages of precipitation of metal elements can be suppressed while improving the discharge characteristics by improving the electronic conductivity of the carbon black. As a result, the discharge characteristics of the battery after storage are significantly improved.

[0026] If the metal element content in the carbon black is less than 0.02 atomic %, the effect of improving the electronic conductivity of the carbon black is not sufficiently obtained, and if the metal element content in the carbon black is more than 0.4 atomic %, the amount of non-aqueous electrolyte retained by the carbon black decreases, making it difficult to improve the discharge characteristics.

[0027] If the Mg content in the lithium alloy is less than 0.01% by mass, the effect of suppressing the precipitation of metal elements by Mg is not sufficiently obtained, and if the Mg content in the lithium alloy exceeds 11% by mass, the activity of the lithium alloy decreases and the resistance of the negative electrode increases, making it difficult to improve the discharge characteristics.

[0028] From the viewpoint of further enhancing the effect of suppressing precipitation of metal elements, the Mg content in the lithium alloy may be 0.02% by mass or more, 0.05% by mass or more, and preferably 0.1% by mass or more or 0.3% by mass or more. Also, from the viewpoint of maintaining the activity of the lithium alloy as high as possible and reducing the resistance of the negative electrode, the Mg content in the lithium alloy may be 7% by mass or less, 5% by mass or less, or 2% by mass or less, and preferably 1% by mass or less.

[0029] The lithium alloy containing Mg may further contain Al. When the lithium alloy containing Mg contains Al, the potential of the alloy surface becomes more noble. Even in the case of a lithium alloy containing Al, if the lithium alloy contains Mg, a state in which potential spots are less likely to occur is maintained. In other words, the potential of the alloy surface can be made more noble while maintaining a state in which potential spots are less likely to occur. Therefore, the effect of suppressing the deposition of metal elements is enhanced.

[0030] Al also promotes the formation of a low-resistance coating on the alloy surface, so using a lithium alloy containing Mg and Al can increase the output voltage compared to using a lithium alloy containing only Mg.

[0031] 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.).

[0032] In the case of a Li-Mg-Al alloy, the Al content in the lithium alloy is preferably 0.01% by mass or more and 3.0% by mass or less. If the Al content is 0.01% by mass or more, the effect of making the potential of the alloy surface more noble can be obtained. Furthermore, if the Al content is 3.0% by mass or less, the effect of making the potential of the alloy surface more noble can be maintained while maintaining good workability of the lithium alloy. The Al content in the lithium alloy may be 0.05% by mass or more, or may be 0.1% by mass or more. The Al content in the lithium alloy may be 2.0% by mass or less, or may be 1.0% by mass or less.

[0033] In the case of a Li-Mg-Al alloy, the total content of Mg and Al in the lithium alloy is, for example, preferably 0.01% by mass or more and 11.5% by mass or less, or may be 0.02% by mass or more and 11.5% by mass or less, 0.03% by mass or more and 5.5% by mass or less, 0.11% by mass or more and 1.5% by mass or less, or 0.2% by mass or more and 1.3% by mass or less.

[0034] The mass ratio of Mg to Al: Mg / Al may be, for example, 0.2 or more and 50 or less.

[0035] 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.

[0036] The composition of the lithium alloy can be determined by inductively coupled plasma (ICP) emission spectroscopy or atomic absorption spectroscopy (AAS).

[0037] The lithium primary battery of the present disclosure will be described in more detail below.

[0038] [Lithium Primary Battery] (Positive Electrode) The positive electrode contains at least one of manganese dioxide and graphite fluoride as a positive electrode active material. Manganese dioxide has a high operating voltage and excellent output characteristics and discharge characteristics (pulse discharge characteristics). On the other hand, graphite fluoride has excellent high-temperature characteristics and long-term reliability, and has a higher capacity than manganese dioxide.

[0039] 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, 20 μm to 60 μm.

[0040] 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.

[0041] The positive electrode contains a positive electrode active material and a conductive material as essential components, and may contain a positive electrode mixture containing a binder and the like as optional components.

[0042] The conductive material is carbon black containing the metal element described above. The conductive material may also contain a material having electronic conductivity other than carbon black. Examples of such materials include natural graphite, artificial graphite, and carbon fiber.

[0043] The type of carbon black is not particularly limited, but examples thereof include acetylene black, channel black, furnace black, lamp black, thermal black, graphitized black, etc. These may be used alone or in combination of two or more.

[0044] The content of carbon black in the positive electrode is, for example, 1.0 part by mass or more and 10 parts by mass or less, and preferably 3.0 parts by mass or more and 6.0 parts by mass or less, relative to 100 parts by mass of the total positive electrode active material (i.e., manganese dioxide and / or graphite fluoride).

[0045] Examples of the binder include fluororesins such as polytetrafluoroethylene, rubber particles, and acrylic resins. The content of the binder in the positive electrode is, for example, 0.1 parts by mass or more and 10 parts by mass or less, and preferably 3.0 parts by mass or more and 6.0 parts by mass or less, relative to 100 parts by mass of the total positive electrode active material (i.e., manganese dioxide and / or graphite fluoride).

[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 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. A perforated current collector is preferable as the sheet-shaped positive electrode 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 a sheet-shaped positive electrode current collector or filling the positive electrode current collector, pressing in the thickness direction, and drying. In the case of a coin-shaped battery, the positive electrode can be constructed by attaching a ring-shaped positive electrode current collector with an L-shaped cross section to a positive electrode mixture pellet, or the positive electrode can be constructed solely from a positive electrode mixture pellet. The positive electrode mixture pellet can be obtained, for example, by compression-molding a wet positive electrode mixture and drying it.

[0048] (Negative Electrode) The negative electrode contains the above-mentioned lithium alloy, which is formed into any shape and thickness depending on the shape, dimensions, performance specifications, etc. of the lithium primary battery.

[0049] In the case of a cylindrical battery, a foil (sheet) of lithium alloy may be used as the negative electrode. The sheet may be obtained, for example, by extrusion molding. More specifically, a lithium alloy foil having a shape with a longitudinal direction and a transverse direction may be used in a cylindrical battery. In the case of a coin-shaped battery, the lithium alloy foil may be punched into a coin shape and used as the negative electrode.

[0050] The foil-shaped (sheet-shaped) lithium alloy may be provided with a negative electrode current collector (e.g., copper foil) to support it. On the other hand, if the lithium alloy contains Mg, the relatively strong Mg may remain in a thin foil-shaped (sheet-shaped) form at the end of discharge. Therefore, the negative electrode may be constructed using only the foil-shaped (sheet-shaped) lithium alloy without using a negative electrode current collector.

[0051] (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.

[0052] 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.

[0053] 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.

[0054] 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 ４ Among 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.

[0055] 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, succinic anhydride, or phthalic anhydride.

[0056] (Separator) The separator interposed between the positive electrode and the negative electrode 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.

[0057] 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.

[0058] (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.

[0059] <<Appendix>> The above embodiments disclose the following technologies. (Technology 1) A lithium primary battery comprising: a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode active material and a conductive material, wherein the positive electrode active material includes at least one of manganese dioxide and graphite fluoride, wherein the conductive material includes carbon black, and wherein the carbon black includes a metal element in an amount of 0.02 atomic % or more and 0.4 atomic % or less, and the negative electrode includes a lithium alloy, wherein the lithium alloy includes magnesium, and wherein the magnesium content in the lithium alloy is 0.01 mass % or more and 11 mass % or less. (Technology 2) The lithium primary battery according to Technology 1, wherein the magnesium content in the lithium alloy is 0.1 mass % or more and 1 mass % or less. (Technology 3) The lithium alloy further contains aluminum, the content of the aluminum in the lithium alloy is 0.01 mass% or more and 3.0 mass% or less, and the total content of the magnesium and the aluminum in the lithium alloy is 0.01 mass% or more and 11.5 mass% or less. (Technology 4) The lithium primary battery according to any one of Technologies 1 to 3, wherein the metal element includes at least one selected from the group consisting of Fe, Sr, V, Ni, and Nb.

[0060] [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.

[0061] Examples 1 to 12 and Comparative Examples 1 to 23 (Synthesis of Carbon Black) Carbon black was obtained by incomplete combustion of raw material oil. Carbon black (CB1 to CB5) containing the metal element iron (Fe) was then synthesized by adding an aqueous solution containing a predetermined amount of iron ions to the carbon black and treating it in an environment of 1200 K. Specifically, Fe was incorporated into the carbon black at the content shown in Table 1. The Fe content in the carbon black was quantified by dissolving the synthesized carbon black in aqua regia and filtering the filtrate, followed by ICP emission spectroscopy.

[0062]

[0063] (Preparation of Positive Electrode) 100 parts by mass of the positive electrode active material was mixed with 5 parts by mass of the above-mentioned carbon black as a conductive material, 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 was used as the positive electrode active material.

[0064] 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 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 collector. The theoretical capacity of the positive electrode was 1600 mAh.

[0065] (Preparation of Negative Electrode) The following lithium metal foil and lithium alloy foil were prepared as negative electrodes. The theoretical capacity of the negative electrodes was 1750 mAh.

[0066] Negative electrode 1: pure lithium foil Negative electrode 2: lithium alloy containing no Mg and 0.2% by mass of Al (Li-Al0.2) Negative electrode 3: lithium alloy containing no Al and 0.01% by mass of Mg (Li-Mg0.01) Negative electrode 4: lithium alloy containing no Al and 0.3% by mass of Mg (Li-Mg0.3) Negative electrode 5: lithium alloy containing no Al and 5% by mass of Mg (Li-Mg5) Negative electrode 6: lithium alloy containing no Al and 11% by mass of Mg (Li-Mg11) Negative electrode 7: lithium alloy containing no Al and 13% by mass of Mg (Li-Mg13)

[0067] 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.

[0068] (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 a positive electrode using a predetermined carbon black and a predetermined negative electrode, and then 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.

[0069] (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.

[0070] (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 33.5 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.

[0071] In Table 2, batteries A1 to A12 are the batteries of Examples 1 to 12. Batteries B1 to B23 are the batteries of Comparative Examples 1 to 23.

[0072]

[0073] After assembly, the resulting batteries of the Examples and Comparative Examples were aged for two days in an atmosphere at 60° C., and then evaluated as follows.

[0074] [Evaluation] The aged batteries were stored at 60°C for one month, and then discharged at a current of 1 A in an environment of 20°C until the voltage reached 1.5 V, and the discharge capacity was measured. This evaluation assumes a situation in which the batteries are discharged at a large current after long-term storage. For each battery, the relative value, with the discharge capacity of battery B6 set at 100, is shown in Table 2.

[0075] In the batteries B1 to B5 of Comparative Examples 1 to 5 using lithium foil and the batteries B6 to B10 of Comparative Examples 6 to 10 using Li-Al0.2, it is believed that the deposition of Fe on the negative electrode surface could not be suppressed, resulting in a decrease in discharge capacity.

[0076] In the batteries B19 to B23 of Comparative Examples 19 to 23 using Li—Mg13, the activity of the negative electrode decreased, and the internal resistance increased, which is thought to be the reason for the decrease in discharge capacity.

[0077] In the batteries B11, B13, B15, and B17 of Comparative Examples 11, 13, 15, and 17, the Fe content in the carbon black was too small to achieve the effect of improving the electronic conductivity of the positive electrode, and it is thought that the discharge capacity did not increase.

[0078] In the batteries B12, B14, B16, and B18 of Comparative Examples 12, 14, 16, and 18, the Fe content in the carbon black was too high, which reduced the amount of nonaqueous electrolyte retained by the carbon black, presumably resulting in a decrease in discharge capacity.

[0079] Examples 13 to 24, Comparative Examples 24 to 31 The following lithium alloy foils were prepared as negative electrodes. The theoretical capacity of the negative electrodes was set to 1750 mAh.

[0080] Negative electrode 8: Lithium alloy containing 0.01% by mass of Al and 0.3% by mass of Mg (Li-Mg0.3-Al0.01) Negative electrode 9: Lithium alloy containing 0.05% by mass of Al and 0.3% by mass of Mg (Li-Mg0.3-Al0.05) Negative electrode 10: Lithium alloy containing 0.2% by mass of Al and 0.3% by mass of Mg (Li-Mg0.3-Al0.2) Negative electrode 11: Lithium alloy containing 3% by mass of Al and 0.3% by mass of Mg (Li-Mg0.3-Al3)

[0081] Batteries A13 to A24 of Examples 13 to 24 and Batteries B24 to B31 of Comparative Examples 24 to 31 were fabricated and evaluated in the same manner as Batteries A1 to A5, except that the negative electrode was changed to one of negative electrodes 8 to 12. Table 3 shows the relative discharge capacity of each battery, with the discharge capacity of Battery B6 in Table 2 taken as 100.

[0082]

[0083] The discharge capacity further increased when Al was added to the lithium alloy foil containing Mg. This is thought to be because the potential of the alloy surface became more noble, and the deposition of Fe was more significantly suppressed.

[0084] In Table 3, the Mg content in the lithium alloy was fixed at 0.3% by mass, but the same effect of improving discharge characteristics due to Al was observed when the Mg content in the lithium alloy was varied within the range of 0.01% by mass to 11% by mass.

[0085] Furthermore, carbon black containing Sr, V, Ni, and Nb in the above content ratios instead of Fe was synthesized and similar evaluation was carried out, confirming that similar trends were obtained.

[0086] 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.

[0087] 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.

[0088] 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, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte; the positive electrode includes a positive electrode active material and a conductive material; the positive electrode active material includes at least one of manganese dioxide and graphite fluoride; the conductive material includes carbon black; the carbon black includes a metal element of 0.02 atomic % or more and 0.4 atomic % or less; the negative electrode includes a lithium alloy; the lithium alloy includes magnesium; and a content of the magnesium in the lithium alloy is 0.01 mass % or more and 11 mass % or less.

2. The lithium primary battery according to claim 1, wherein the magnesium content in the lithium alloy is 0.1% by mass or more and 1% by mass or less.

3. The lithium primary battery according to claim 1 or 2, wherein the lithium alloy further contains aluminum, the content of the aluminum in the lithium alloy is 0.01 mass% or more and 3.0 mass% or less, and the total content of the magnesium and the aluminum in the lithium alloy is 0.01 mass% or more and 11.5 mass% or less.

4. The lithium primary battery according to claim 1 or 2, wherein the metal element comprises at least one selected from the group consisting of Fe, Sr, V, Ni and Nb.

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