Positive electrode active material for lithium primary battery, and lithium primary battery

Abstract

Disclosed is a positive electrode active material for a lithium primary battery, said positive electrode active material comprising: active material particles that are represented by the compositional formula LixMnO2 (where 0≤x≤0.05); and a zinc-containing oxide that covers a part of the surfaces of the active material particles. The coverage of the active material particles by the zinc-containing oxide falls within the range of 0.10-65%.

Description

Positive electrode active material for lithium primary battery and lithium primary battery

[0001] The present disclosure relates to a positive electrode active material for a lithium primary battery and a lithium primary battery using the same.

[0002] Lithium primary batteries are used in many electronic devices due to their high energy density and low self-discharge. Various types of lithium primary batteries have been proposed.

[0003] Patent Document 1 (JP 2003-249213 A) discloses "a positive electrode for a lithium primary battery, characterized in that at least one metal oxide selected from the group consisting of titanium oxide, alumina, zinc oxide, chromium oxide, lithium oxide, nickel oxide, copper oxide, and iron oxide is dispersed between manganese dioxide particles."

[0004] As a method for producing the above-mentioned positive electrode, Patent Document 1 discloses "a method for producing a positive electrode for a lithium primary battery, comprising the steps of: (I) adding and mixing manganese dioxide and an alkoxide of at least one metal selected from the group consisting of titanium, aluminum, zinc, chromium, lithium, nickel, copper, and iron into an organic solvent to produce a mixed solution; (II) adding water to the mixed solution to produce a metal hydroxide; (III) heating and drying the solution containing the produced metal hydroxide to convert the metal hydroxide into a metal oxide, and producing a positive electrode powder in which the metal oxide is dispersed between manganese dioxide particles; and (IV) molding the positive electrode powder to produce a positive electrode."

[0005] Patent Document 2 (WO 2001 / 041247) discloses a nonaqueous electrolyte battery using a nonaqueous electrolyte containing an additive such as phthalimide. The invention described in Patent Document 2 aims to "prevent the formation of an organic coating on the negative electrode surface due to a chemical reaction during high-temperature storage of a nonaqueous electrolyte battery, suppress an increase in the internal resistance of primary and secondary batteries, and further improve the charge-discharge cycle characteristics of the secondary battery."

[0006] Patent Document 1: JP 2003-249213 A, International Publication No. 2001 / 041247

[0007] In lithium primary batteries, when stored at high temperatures, resistance increases significantly and pulse discharge performance decreases significantly. In this situation, one object of the present disclosure is to provide a lithium primary battery and a positive electrode active material used therein that can suppress performance degradation (e.g., increase in resistance and decrease in pulse discharge performance) due to storage at high temperatures.

[0008] One aspect of the present disclosure relates to a positive electrode active material for a lithium primary battery. The positive electrode active material has the composition formula Li ｘ MnO ２ (where 0≦x≦0.05) and a zinc-containing oxide that coats a portion of the surface of the active material particle, and the coating rate of the active material particle with the zinc-containing oxide is in the range of 0.10% to 65%.

[0009] One aspect of the present disclosure relates to a lithium primary battery including a positive electrode containing a positive electrode active material, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode active material is the positive electrode active material for lithium primary batteries according to the present disclosure, and the negative electrode contains at least one selected from the group consisting of metallic lithium and a lithium alloy.

[0010] According to the present disclosure, a lithium primary battery capable of suppressing performance degradation due to storage at high temperatures can be obtained. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0011] 2B is a diagram illustrating a step of a method for evaluating a coverage rate; FIG. 2C is a diagram illustrating a step following the step of FIG. 2A; FIG. 2D is a diagram illustrating a step following the step of FIG. 2C; and FIG. 2E is a diagram illustrating an example of a spectrum measured by EDS analysis.

[0012] The following describes examples of embodiments of lithium primary batteries according to the present disclosure, 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 expression "numerical value A to numerical value B" includes numerical value A and numerical value B and can be interpreted as "numerical value A or greater and numerical value B or less." In the following description, when lower and upper limits for specific physical properties or conditions are exemplified, 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 greater than the upper limit. In the following description, with respect to a certain element Z, the expression "including Z" can include "a form including Z and other elements," "a form substantially consisting of Z," and "a form consisting of Z."

[0013] (Positive Electrode Active Material) The positive electrode active material for the lithium primary battery according to this embodiment is a material having the composition formula Li ｘ MnO ２ (where 0≦x≦0.05) and a zinc-containing oxide that covers a part of the surface of the active material particles. The coverage of the active material particles with the zinc-containing oxide is in the range of 0.10% to 65%. Hereinafter, the composition formula Li ｘ MnO ２ (where 0≦x≦0.05) may be referred to as "particles (P1)." In the following, particles (P1) coated with a zinc-containing oxide at a coverage of 0.10% to 65% may be referred to as "particles (P2)." Particles (P2) include particles (P1) and a zinc-containing oxide disposed on the surface of particles (P1).

[0014] As a result of investigation, the present inventors have newly discovered that by setting the coverage rate in the range of 0.10 to 65%, it is possible to significantly suppress the deterioration of performance of a lithium primary battery due to storage at high temperatures. The present disclosure is based on this new finding.

[0015] Although the reason for the above-mentioned effect is not clear at present, it is believed that coating the particles (P1) with a zinc-containing oxide can reduce side reactions during high-temperature storage without interfering with the forward reaction of the active material, which in turn can suppress an increase in internal resistance due to high-temperature storage and a decrease in low-temperature pulse discharge performance due to high-temperature storage.

[0016] The method described in Patent Document 1 also makes it possible to cover the surface of manganese dioxide particles with a metal oxide. However, it is difficult to achieve a coverage rate within the above range using the method described in Patent Document 1. As a result of further investigation, the present inventors have found that the above coverage rate can be achieved using a method not described in Patent Document 1. This new method will be described below.

[0017] The coverage may be 0.10% or more, 0.20% or more, 0.7% or more, 7.0% or more, or 48% or more. The coverage may be 65% or less, 61% or less, 48% or less, 25% or less, or 7.0% or less. The coverage may be in the range of 0.10 to 65%, 0.20 to 65%, 0.70 to 65%, 7.0 to 65%, or 48 to 65%. Within these ranges, the upper limit may be 61%, 48%, or 7.0%, as long as the lower limit is not greater than or equal to the upper limit.

[0018] The coverage indicates the ratio of the surface area of ​​the particles (P1) that is covered with the zinc-containing oxide, and is measured by the method described in the Examples.

[0019] As described above, the positive electrode active material has the composition formula Li ｘ MnO ２ (where 0≦x≦0.05). That is, the particles (P1) have a composition represented by the composition formula. ｘ MnO ２As the active material represented by the formula (where 0≦x≦0.05), manganese dioxide or lithium-doped manganese dioxide can be used. The Li ratio x may be 0.05 or less in the initial state of discharge of the lithium primary battery. The Li ratio x generally increases as the discharge of the lithium primary battery progresses. Theoretically, the oxidation number of manganese contained in manganese dioxide is tetravalent. However, if other manganese oxides are contained in the positive electrode or if manganese dioxide is doped with lithium, the oxidation number of manganese may increase or decrease slightly from tetravalent. Therefore, Li ｘ MnO ２ In the present invention, the average oxidation state of manganese is allowed to vary slightly from tetravalent.

[0020] The particles (P2) may have a median particle size of 10 μm or more and 40 μm or less. When the median particle size is in this range, gas generation can be more effectively suppressed in a lithium primary battery, and high current collection performance in the positive electrode can be easily ensured.

[0021] The median particle diameter of the particles (P2) is, for example, the median of the particle size distribution determined by quantitative laser diffraction / scattering (qLD) method. ｘ MnO ２ The measurement may be performed using, for example, an SALD-7500 nano manufactured by Shimadzu Corporation.

[0022] When the surface of the positive electrode active material (particles (P2)) is measured by energy dispersive X-ray analysis, the ratio Iz / Im of the net intensity Iz of the peak at about 8.6 keV of the Zn Kα ray to the net intensity Im of the peak at about 5.9 keV of the Mn Kα ray may be in the range of 0.0001 to 0.08 (for example, in the range of 0.01 to 0.05). The ratio Iz / Im can be determined by a method described in the Examples.

[0023] The zinc-containing oxide may be zinc oxide. Examples of zinc oxide include oxides represented by ZnO and oxides in which some of the oxygen atoms of the oxide are missing. The zinc oxide may be ZnO doped with another element (e.g., aluminum).

[0024] The content of the zinc-containing oxide (e.g., zinc oxide) may be greater than 0% by mass, and may be 0.05% by mass or more, 0.1% by mass or more, 0.5% by mass or more, or 1.0% by mass or more. The content may be 1.5% by mass or less, or 1.0% by mass or less. The content may be in the range of 0.05 to 1.5% by mass (e.g., 0.1 to 1.0% by mass). By setting the content to 1.5% by mass or less, it becomes easier to achieve the coverage within the above range.

[0025] A portion of the zinc-containing oxide may penetrate into the active material particles (particles (P1)) to a depth of 15 nm or more from the surface. For example, the zinc-containing oxide may penetrate into the grain boundaries of the particles (P1). The particles (P1) may have voids inside. For example, when the particles (P1) include secondary particles formed by agglomeration of a plurality of primary particles represented by the above composition formula, the particles (P1) have voids between the plurality of primary particles. In this case, the zinc-containing oxide may penetrate into the voids between the plurality of primary particles. The zinc-containing oxide may penetrate into the grain boundaries of the primary particles. In other words, the penetrated zinc-containing oxide may be present in the voids between the plurality of primary particles and / or in the grain boundaries of the primary particles. When the active material particles (particles (P1)) are secondary particles that are agglomerates of primary particles, the surface of the active material particles refers to the surface of the secondary particles.

[0026] The depth D (depth from the surface of the particle (P1)) reached by the zinc-containing oxide may be 15 nm or more, or 32 nm or more. The depth D may be 300 nm or less, 200 nm or less, 142 nm or less, or 107 nm or less. The depth D may be in the range of 15 to 300 nm, or 15 to 200 nm. By allowing the zinc-containing oxide to penetrate to these depths D, it is possible to obtain a high effect of improving battery characteristics by coating manganese dioxide with the zinc-containing oxide without impairing battery performance. If the penetration depth is less than 15 nm, protection of the internal particles by the zinc-containing oxide may be insufficient, and the effect of improving battery characteristics may be reduced. If the penetration depth is too deep, the zinc-containing oxide may interfere with the forward reaction, thereby reducing the effect of improving battery characteristics.

[0027] (Manufacturing Method of Positive Electrode Active Material) An example of a manufacturing method of the positive electrode active material according to this embodiment will be described. Hereinafter, this manufacturing method may be referred to as "manufacturing method (M)." However, the positive electrode active material according to this embodiment may be manufactured by a method other than the method described below.

[0028] The production method (M) includes a mixing step of mixing manganese dioxide particles with a material that will become a zinc-containing oxide to obtain a mixture, and a step of firing the mixture to obtain particles (P2).

[0029] Examples of a material (hereinafter sometimes referred to as "material (X)") that becomes a zinc-containing oxide upon firing include zinc acetate, zinc hydroxide, zinc carbonate, etc. The amount of material (X) added to the mixture is selected so that the content of zinc-containing oxide in particles (P2) becomes a desired value. For example, material (X) may be added to the mixture so that the content of zinc-containing oxide becomes the above-mentioned value when it is assumed that all of material (X) becomes a zinc-containing oxide.

[0030] In the mixture, the coverage of the particles (P1) with the zinc-containing oxide can be increased by increasing the ratio of the material (X) to the particles (P2). Therefore, the amount of the material (X) added is selected so that the coverage is the above-mentioned value.

[0031] If necessary, the mixture may contain substances other than the above materials, for example, the mixture may contain a dispersion medium (such as water).

[0032] In the calcination step, the mixture obtained in the mixing step is calcined. By the calcination, part of the surface of the particles (P1) is coated with a zinc-containing oxide, thereby obtaining particles (P2). The calcination is carried out under conditions that convert the material (X) into a zinc-containing oxide. The calcination temperature may be in the range of 380 to 450°C (e.g., in the range of 380 to 420°C). The calcination time may be in the range of 1 to 20 hours (e.g., in the range of 5 to 10 hours).

[0033] The particles (P1) may have voids inside. For example, when the particles (P1) are secondary particles formed by aggregation of primary particles, the particles (P1) have voids inside. When the particles (P1) have voids inside, compounds other than manganese dioxide may enter the particles during the manufacturing process, etc. For example, ammonium salts may be present in the voids inside the particles (P1) (e.g., electrolytic manganese dioxide). Furthermore, the particles (P1) (e.g., electrolytic manganese dioxide) may contain structural water. In the above-mentioned calcination step, calcination at a high temperature of 380°C or higher facilitates decomposition and removal of compounds other than manganese dioxide and structural water present inside the particles (P1). As a result, the zinc-containing oxide can easily penetrate into the voids from which they have been removed. Therefore, the calcination temperature is preferably 380°C or higher. On the other hand, if the temperature to which manganese dioxide is heated is 350°C or lower, the decomposition and removal effect is reduced, and if the temperature is 300°C or lower, the decomposition and removal effect is particularly reduced. Therefore, when the temperature is low, the penetration depth D of the zinc-containing oxide becomes small.

[0034] According to the above-mentioned production method, it is easy to set the coverage within the above-mentioned range. On the other hand, when the sol-gel method described in JP 2003-249213 A is used, the metal oxide formed covers most of the surface of the particles (P1), making it difficult to set the coverage within the above-mentioned range.

[0035] In the above-described manufacturing method, the zinc-containing oxide can be permeated into the particles (P1) during the process of converting the material (X) into a zinc-containing oxide. By performing calcination at a temperature higher than the melting point of the material (X), such as zinc acetate (melting point: 237°C), the material (X) melts during the calcination process and permeates into the particles (P1). As a result, the zinc-containing oxide can easily permeate to a certain depth into the particles (P1).

[0036] (Lithium Primary Battery) The lithium primary battery according to this embodiment includes a positive electrode containing a positive electrode active material, a negative electrode, and a non-aqueous electrolyte. The positive electrode active material is the positive electrode active material for lithium primary batteries described above. The negative electrode includes at least one selected from the group consisting of metallic lithium and a lithium alloy.

[0037] The non-aqueous electrolyte may contain a non-aqueous solvent and a cyclic imide compound. This configuration can suppress gas generation during high-temperature storage, as described in the examples. Furthermore, this configuration can particularly enhance the effect of suppressing a decrease in low-temperature pulse discharge voltage due to high-temperature storage. The effect of using a zinc-containing oxide and a cyclic imide compound is greater than the combined effect of coating the active material particles with a zinc-containing oxide and the effect of using a cyclic imide compound alone. This is thought to be due to some kind of synergistic effect.

[0038] The reason why the use of a cyclic imide compound can suppress the deterioration of battery characteristics due to high-temperature storage is currently unclear. However, it is thought that the cyclic imide compound covers part of the surface of the zinc-containing oxide, suppressing the elution of the zinc-containing oxide. By suppressing the elution of the zinc-containing oxide, the effect of the zinc-containing oxide can be maintained at a high level.

[0039] When a battery is stored at high temperatures, gas is likely to be generated due to the decomposition of components in the non-aqueous electrolyte. On the other hand, in lithium primary batteries, a coating derived from components contained in the electrolyte may form on the surface of the positive electrode active material. The formation of this coating is thought to suppress the decomposition of the non-aqueous electrolyte on the surface of the active material, thereby reducing gas generation. However, if the surface of the active material is covered with a dense coating, the internal resistance increases and the capacity decreases. Therefore, it is important to strike a balance between suppressing gas generation and maintaining battery characteristics. In particular, because a coating is likely to grow during battery storage, it is important not to cover the entire surface of the active material with a coating.

[0040] The concentration of the cyclic imide compound in the non-aqueous electrolyte may be 0.05% by mass or more, 0.10% by mass or more, 0.20% by mass or more, or 0.50% by mass or more, and may be 1.5% by mass or less, 1.0% by mass or less, or 0.5% by mass or less. The concentration may be in the range of 0.05 to 1.5% by mass (e.g., 0.10 to 1.0% by mass). By setting the concentration to 0.10% by mass or more, high effects can be obtained. By setting the concentration to 1.5% by mass or less, it is possible to prevent the cyclic imide compound from excessively covering the active material particles (P2), thereby preventing a decrease in characteristics.

[0041] The ratio Wz / Wi of the mass Wz of the zinc-containing oxide contained in the positive electrode to the mass Wi of the cyclic imide compound contained in the non-aqueous electrolyte may be 0.5 or more, 0.6 or more, 2.1 or more, 3.0 or more, 5.0 or more, or 6.0 or more, and may be 64 or less, 15 or less, 10 or less, 6.0 or less, or 5.0 or less. The ratio Wz / Wi may be in the range of 0.5 to 15 (e.g., in the range of 0.6 to 10). This configuration particularly suppresses gas generation and deterioration of battery performance due to storage at high temperatures. Note that a portion of the cyclic imide compound contained in the non-aqueous electrolyte is contained in the non-aqueous electrolyte that has permeated the positive electrode, negative electrode, and separator. In a preferred example, the ratio Wz / Wi is in the range of 0.5 to 15 (e.g., in the range of 0.6 to 10), the content of the zinc-containing oxide in the positive electrode active material is 1.5 mass% or less, and the concentration of the cyclic imide compound in the non-aqueous electrolyte is 1.5 mass% or less.

[0042] The cyclic imide compound may be phthalimide. Other examples of the cyclic imide compound will be described later.

[0043] Examples of the configuration of the positive electrode active material and the lithium primary battery according to this embodiment will be described below, but the configurations of the positive electrode active material and the lithium primary battery are not limited to the following examples. The parts other than the components essential to the positive electrode active material and the lithium primary battery according to this embodiment are not limited as long as the effects of the present disclosure can be obtained, and known configurations may be used.

[0044] The lithium primary battery may include a positive electrode, a negative electrode, a non-aqueous electrolyte, a separator, and an exterior body. The separator is disposed between the positive electrode and the negative electrode. The lithium primary battery may include an electrode group composed of a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The electrode group may be a wound type or a stacked type. A wound type electrode group is formed by winding a positive electrode, a negative electrode, and a separator so that the separator is disposed between the positive electrode and the negative electrode. A stacked type electrode group is formed by stacking a positive electrode, a negative electrode, and a separator so that the separator is disposed between the positive electrode and the negative electrode.

[0045] The shape of the lithium primary battery is not particularly limited, and may be rectangular, cylindrical, or coin-shaped. Except for the method of forming the positive electrode active material, the method of manufacturing the lithium primary battery is not particularly limited, and known manufacturing methods may be used. The lithium primary battery can be manufactured by housing the battery components (such as a positive electrode, a negative electrode, and a non-aqueous electrolyte) in an exterior body (e.g., a battery case).

[0046] (Positive Electrode) The positive electrode includes a positive electrode mixture. The positive electrode mixture includes a positive electrode active material. The positive electrode may include a positive electrode current collector and a positive electrode mixture (positive electrode mixture layer) disposed on the positive electrode current collector. Examples of materials for the positive electrode current collector include stainless steel, aluminum, and titanium.

[0047] In the case of a coin-type battery, a pellet obtained by compression-molding a positive electrode mixture paste and then drying it may be used as the positive electrode. Alternatively, the positive electrode may be formed by applying the positive electrode mixture paste to a positive electrode current collector to form a coating film, and then drying and rolling the coating film.

[0048] The positive electrode active material includes the above-mentioned positive electrode active material (particles (P2)). The positive electrode may include a positive electrode active material other than the particles (P2). However, the main component (50% by mass or more) of the positive electrode active material is the particles (P2). Examples of other positive electrode active materials include graphite fluoride. The proportion of the particles (P2) in the positive electrode active material is preferably in the range of 90% by mass to 100% by mass. In a typical example, the positive electrode active material contained in the positive electrode is only the particles (P2).

[0049] As the manganese dioxide constituting the particles (P1), electrolytic manganese dioxide is preferably used. If necessary, electrolytic manganese dioxide that has been subjected to at least one of a neutralization treatment, a washing treatment, and a calcination treatment may be used.

[0050] The particles (P1) may be secondary particles formed by aggregation of a plurality of primary particles represented by the above composition formula. Such particles (P1) may be commercially available particles or may be synthesized by a known method (e.g., electrolysis).

[0051] Electrolytic manganese dioxide is generally obtained by electrolysis of a manganese sulfate aqueous solution. Therefore, sulfate ions are inevitably contained in electrolytic manganese dioxide. A positive electrode mixture prepared using such electrolytic manganese dioxide inevitably contains sulfur atoms. The amount of sulfur atoms contained in the positive electrode mixture may be 0.05 parts by mass or more and 3 parts by mass or less per 100 parts by mass of manganese atoms contained in the positive electrode mixture. When the amount of sulfur atoms is within this range, in a lithium primary battery, sulfate ions and MnO ２ The unstable M produced by lithium insertion into ３＋ and interact to form Mn ３＋ Mn by disproportionation ２＋ This is thought to suppress the generation of Mn ２＋It is believed that this suppresses the dissolution of Mn into the non-aqueous electrolyte and the precipitation of Mn at the negative electrode. As a result, high capacity and high reliability of the lithium primary battery can be ensured. On the other hand, in lithium secondary batteries, some sulfate ions are decomposed during the charging process, so even if the positive electrode mixture contains sulfate in an amount that satisfies the above-mentioned range, it is difficult to fully ensure the above-mentioned effects. The proportion of sulfur atoms contained in the positive electrode mixture can be adjusted by adjusting the conditions of the washing treatment and neutralization treatment. Examples of the washing treatment include at least one of a water washing treatment and an acid washing treatment. Examples of the neutralizing agent used in the neutralization treatment include inorganic bases such as ammonia and hydroxides.

[0052] By adjusting the conditions during electrolytic synthesis, the crystallinity of manganese dioxide can be increased and the specific surface area of ​​electrolytic manganese dioxide can be reduced. ｘ MnO ２ The BET specific surface area of ２ / g or more 50m ２ / g or less. ｘ MnO ２ When the BET specific surface area is within this range, a positive electrode mixture layer can be easily formed in a lithium primary battery while more effectively suppressing gas generation.

[0053] Li ｘ MnO ２ The BET specific surface area is measured based on the BET method using a specific surface area measuring device (for example, manufactured by Mountec Co., Ltd.).

[0054] The positive electrode mixture may contain additives other than the active material (such as a binder or a conductive agent). Examples of the binder include fluororesin, rubber particles, and acrylic resin. Examples of the conductive agent include a conductive carbon material. Examples of the conductive carbon material include natural graphite, artificial graphite, carbon black, and carbon fiber.

[0055] (Negative Electrode) The negative electrode may contain metallic lithium or a lithium alloy, or may contain both metallic lithium and lithium metal. For example, a composite containing metallic lithium and a lithium alloy may be used for the negative electrode.

[0056] Examples of lithium alloys include Li—Al alloys, Li—Sn alloys, Li—Ni—Si alloys, Li—Pb alloys, etc. The content of metal elements other than lithium contained in the lithium alloy is preferably 0.05 to 15 mass % from the viewpoints of ensuring discharge capacity and stabilizing internal resistance.

[0057] The metallic lithium, lithium alloy, or composite thereof is formed into any shape and thickness depending on the shape, dimensions, performance specifications, etc. of the lithium primary battery.

[0058] In the case of coin-type batteries, a sheet of metallic lithium, a lithium alloy, or a composite thereof punched into a disk shape may be used as the negative electrode. In the case of cylindrical batteries, a sheet of metallic lithium, a lithium alloy, or a composite thereof may be used as the negative electrode. The sheet may be obtained, for example, by extrusion molding. In cylindrical batteries, a foil of metallic lithium or a lithium alloy having a shape with a longitudinal direction and a transverse direction is used.

[0059] In the case of a cylindrical battery, a long tape including a resin substrate and an adhesive layer may be attached to at least one main surface of the negative electrode along the longitudinal direction of the negative electrode. The width of this tape is, for example, 0.5 mm or more and 3 mm or less. This tape prevents the negative electrode from tearing and current collection failure when the lithium component of the negative electrode is consumed by a reaction at the end of discharge. However, the adhesive strength of the tape decreases due to the electrolyte during long-term storage. When an electrolyte containing a cyclic imide compound is used, this decrease in adhesive strength can be suppressed, and the negative electrode from tearing and current collection failure can be more effectively prevented.

[0060] Examples of materials that can be used for the resin substrate include fluororesin, polyimide, polyphenylene sulfide, polyethersulfone, polyolefins such as polyethylene and polypropylene, polyethylene terephthalate, etc. Among these, polyolefins are preferred, and polypropylene is more preferred.

[0061] The adhesive layer contains, for example, at least one component selected from the group consisting of a rubber component, a silicone component, and an acrylic resin component. Specifically, the rubber component may be a synthetic rubber or a natural rubber. Examples of synthetic rubber include butyl rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, neoprene, polyisobutylene, acrylonitrile-butadiene rubber, styrene-isoprene block copolymer, styrene-butadiene block copolymer, and styrene-ethylene-butadiene block copolymer. Examples of silicone components may include organic compounds having a polysiloxane structure, silicone-based polymers, and the like. Examples of silicone-based polymers include peroxide-curable silicones and addition reaction silicones. The acrylic resin component can be a polymer containing an acrylic monomer such as acrylic acid, methacrylic acid, an acrylic acid ester, or a methacrylic acid ester, and examples thereof include homopolymers or copolymers of acrylic monomers such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, octyl acrylate, octyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate. The adhesive layer may contain a crosslinking agent, a plasticizer, and a tackifier.

[0062] (Non-aqueous electrolyte) The non-aqueous electrolyte (non-aqueous electrolyte solution) contains a non-aqueous solvent and a cyclic imide compound that dissolves in the non-aqueous solvent. The non-aqueous electrolyte contains a lithium salt or lithium ions. The cyclic imide compound may be a lithium salt or may be capable of generating lithium ions. The non-aqueous electrolyte may contain a lithium salt (solute) other than the cyclic imide compound.

[0063] (Cyclic Imide Compound) Examples of cyclic imide compounds include cyclic diacylamines. The cyclic imide compound may have a diacylamine ring (also referred to as an imide ring). The imide ring may be condensed with another ring (also referred to as a second ring). The non-aqueous electrolyte may contain one type of cyclic imide compound, or may contain two or more types. The cyclic imide compound may be contained in the non-aqueous electrolyte in the form of an imide, or in the form of an anion or a salt. When the cyclic imide compound is contained in the non-aqueous electrolyte in the form of an imide, it may be contained in the form having a free NH group, or in the form of a tertiary amine.

[0064] The second ring may be an aromatic ring, a saturated or unsaturated aliphatic ring, or the like. The second ring may contain at least one heteroatom. Examples of the heteroatom include an oxygen atom, a sulfur atom, and a nitrogen atom.

[0065] Examples of cyclic imides constituting the cyclic imide compound include aliphatic dicarboxylic acid imides and cyclic imides having a second ring. Examples of aliphatic dicarboxylic acid imides include succinimide. Examples of cyclic imides having a second ring include imides of aromatic or alicyclic dicarboxylic acids. Examples of aromatic dicarboxylic acids or alicyclic dicarboxylic acids include those having a carboxy group on each of two adjacent atoms constituting the ring. Examples of cyclic imides having a second ring include phthalimide and hydrogenated phthalimide. Examples of hydrogenated phthalimides include cyclohex-3-ene-1,2-dicarboximide and cyclohexane-1,2-dicarboximide.

[0066] The imide ring may be an N-substituted imide ring having a substituent on the nitrogen atom of the imide. Examples of such a substituent include a hydroxy group, an alkyl group, an alkoxy group, and a halogen atom. Examples of the alkyl group include, for example, C １－４ Examples of the alkoxy group include alkyl groups, such as methyl groups and ethyl groups. １－４Examples of the halogen atom include chlorine atoms, fluorine atoms, and the like.

[0067] Of the cyclic imide compounds, phthalimide and N-substituted phthalimide are more preferred. The substituent on the nitrogen atom of the N-substituted phthalimide can be selected from the substituents exemplified for the N-substituted imide ring. It is more preferred to use a cyclic imide compound containing at least phthalimide.

[0068] (Non-aqueous solvent) Examples of the non-aqueous solvent include organic solvents that can be commonly used in non-aqueous 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, ethylene carbonate, and 1,2-dimethoxyethane. The non-aqueous electrolyte may contain one type of non-aqueous solvent, or may contain two or more types of non-aqueous solvents.

[0069] From the viewpoint of improving the discharge characteristics of the 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, and the cyclic carbonate preferably contains at least one selected from the group consisting of propylene carbonate (PC) and ethylene carbonate (EC).

[0070] (Lithium Salt) The non-aqueous electrolyte may contain a lithium salt other than the cyclic imide compound. Examples of the lithium salt include lithium salts used as solutes in lithium primary batteries. Examples of such lithium salts include LiCF ３ SO ３ , LiClO ４ , LiBF ４ , LiPF ６ , LiRaSO ３ (Ra is a fluorinated alkyl group having 1 to 4 carbon atoms), LiFSO3, LiN(SO ２ Rb)(SO ２ Rc) (Rb and Rc each independently represent a fluorinated alkyl group having 1 to 4 carbon atoms), LiN(FSO2)2, LiPO ２F ２ , LiB(C ２ O ４ ) ２ , LiBF ２ (C ２ O ４ ), LiPF4(C ２ O ４ ), LiPF2(C ２ O ４ ) ２ , LiP(C ２ O ４ ) ３ The non-aqueous electrolyte may contain one or more of these lithium salts.

[0071] The concentration of lithium ions contained in the non-aqueous electrolyte (total concentration of lithium salts) is, for example, 0.2 to 2.0 mol / L, and may be 0.3 to 1.5 mol / L.

[0072] The non-aqueous electrolyte may contain additives as needed. Examples of additives include propane sultone and vinylene carbonate. The total concentration of such additives contained in the non-aqueous electrolyte is, for example, 0.003 to 5 mol / L.

[0073] (Separator) A lithium primary battery usually includes a separator disposed between the positive electrode and the negative electrode. The separator may be a porous sheet formed of an insulating material that is resistant to the internal environment of a lithium primary battery. Specific examples of the separator include a synthetic resin nonwoven fabric, a synthetic resin microporous membrane, or a laminate thereof.

[0074] 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 may be 5 μm or more and 100 μm or less.

[0075] FIG. 1 shows a partially cross-sectional front view of a cylindrical lithium primary battery according to one embodiment of the present disclosure. The lithium primary battery 10 includes an electrode group, in which a positive electrode 1 and a negative electrode 2 are wound with a separator 3 interposed therebetween, housed in a battery case 9 together with a non-aqueous 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. 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. The positive electrode 1 includes a positive electrode mixture layer disposed on the current collector 1a. The positive electrode mixture layer includes the above-described positive electrode active material (particles (P2)). The non-aqueous electrolyte preferably includes the above-described cyclic imide compound.

[0076] The present disclosure will be specifically described below based on examples, but the present disclosure is not limited to the following examples.

[0077] Experimental Example 1 In Experimental Example 1, a plurality of positive electrode active materials and a plurality of lithium primary batteries using the same were manufactured and evaluated.

[0078] (Production of Positive Electrode Active Material A1) First, manganese dioxide powder (particles) was prepared. Next, zinc acetate was added to the manganese dioxide powder and mixed for 10 minutes to obtain a mixture. At this time, zinc acetate was added so that the amount of ZnO would be a predetermined amount when the zinc acetate converted to ZnO. The molecular weight of ZnO is approximately 81.4, and the molecular weight of zinc acetate is approximately 183.5. Therefore, zinc acetate was added in a mass that was 2.25 times the target mass of ZnO (183.5 / 81.4). In producing active material A1, zinc acetate was added so that the content of ZnO formed would be 1.0 mass% of the particles (P2) formed.

[0079] Next, the mixture was baked at 420°C for 8.5 hours. In this way, active material A1 (particles (P2)) was obtained. Active material A1 is manganese dioxide particles whose surfaces are partially coated with ZnO. The above-described method for producing an active material is referred to as Method 1.

[0080] (Evaluation of Coverage Rate) The coverage rate of the active material A1 with ZnO was measured by EDS (energy dispersive X-ray analysis). Specifically, first, to determine the EDS measurement points, the surface of the active material A1 was observed using a scanning electron microscope (SU-70, manufactured by Hitachi High-Tech Corporation). At this time, an acceleration voltage of 2 kV was set, and 10 points were selected at a 5000x field of view where the surface of the active material A1 filled the entire screen. Then, at each selected point, area analysis was performed by EDS. The EDS analysis was performed using an energy dispersive X-ray analyzer (EDAX Genesis, manufactured by AMETEK) at an acceleration voltage of 15 kV. Next, the coverage rate was calculated based on the Zn Kα ray mapping image obtained by area analysis.

[0081] Image analysis software (ImageJ) was used to calculate the coverage. Figure 2A shows an example of an image in which an SEM image and an EDS Zn mapping image are superimposed. Only the EDS measurement results were extracted from the image of Figure 2A to obtain the image of Figure 2B. Next, the image of Figure 2C was obtained by cutting out the steeply inclined slopes relative to the surface of the image of Figure 2B from the image of Figure 2B. This is because the steeply inclined slopes have low detection levels and do not reflect the actual coverage. Next, the image of Figure 2C was binarized to obtain the image of Figure 2D. The number of pixels in the area where Zn was present was calculated from the image of Figure 2D. The number of pixels in the area where manganese dioxide particles were present was calculated from the total number of pixels in Figure 2C. The presence of Mn throughout Figure 2C was confirmed by EDS analysis. The coverage was calculated by dividing the number of pixels in the area where Zn was present by the number of pixels in the area where manganese dioxide particles were present. The coverage calculated for the image of Figure 2D was 57%. This calculation was performed for each of the selected 10 points. The arithmetic mean of the obtained 10 coverage rates was then calculated to determine the coverage rate of ZnO in the active material A1.

[0082] (Evaluation of the ratio Iz / Im) For the positive electrode active material A1, the ratio Iz / Im of the net intensity Iz of the Zn Kα ray peak and the net intensity Im of the Mn Kα ray peak was determined by EDS (energy dispersive X-ray analysis). Specifically, first, to determine the EDS measurement points, the surface of the active material A1 was observed using a scanning electron microscope (manufactured by Hitachi High-Tech Corporation, SU-70). At this time, the acceleration voltage was set to 2 kV, and 10 points were selected at a 5000x magnification where the surface of the active material A1 fit within the screen. Then, EDS analysis was performed on each of the selected points.

[0083] EDS analysis was performed using an energy dispersive X-ray analyzer (EDAX Genesis, manufactured by AMETEK) at an acceleration voltage of 15 kV. An example of the measured spectrum is shown in Figure 3. From the obtained peaks, a peak near 8.6 keV of the Zn Kα line and a peak near 5.9 keV of the Mn Kα line were selected, and the net intensity Iz of the Zn Kα line peak and the net intensity Im of the Mn Kα line peak were calculated. The net intensity was obtained by subtracting the background integral value of a specified region of the peak from the integral value of that region and dividing by the measurement time. The region was set to 1.1 times the full width at half maximum (FWHM). Iz / Im was calculated for each of the selected 10 points, and the arithmetic average of the 10 Iz / Im values ​​was used as the ratio Iz / Im of active material A1. The Zn Kα ray peak near 8.6 keV is located in the vicinity of 8.6 to 8.7 keV, with the peak top located in the vicinity of 8.61 keV. The Mn Kα ray peak near 5.9 keV is located in the vicinity of 5.8 to 5.9 keV, with the peak top located in the vicinity of 5.89 keV.

[0084] (Evaluation of penetration depth of zinc-containing oxide) For active material A1, a cross section of the particle was exposed, and STEM-EELS (scanning transmission microscope-electron energy loss spectroscopy) analysis of the active material cross section was performed. This analysis evaluated the penetration depth of the zinc-containing oxide from the surface of the active material particle toward the interior of the active material particle. Specifically, first, the active material particle (active material A1) was embedded in resin, and the cross section of the active material particle was exposed by gallium ion focused ion beam processing using a focused ion / electron beam processing and observation device (manufactured by Hitachi High-Tech Corporation, nanoDUE TNB5000). Then, the surface vicinity of the active material particle was observed using a STEM device (manufactured by JEOL, scanning transmission electron microscope JEM-ARM200F with spherical aberration correction). At this time, STEM observation was performed at an acceleration voltage of 200 kV, a beam diameter of 0.1 nm, and a field of view of 70,000 times. Ten points were selected where the surface of the active material particle was visible and the interior of the active material particle was fully captured on the screen. At each point, the location of the zinc element was analyzed using an EELS analyzer (GIF Quantum-ER, manufactured by Gatan) at an acceleration voltage of 200 kV and a beam diameter of 0.1 nm, similar to the STEM observation. The location of ZnO was confirmed by this analysis. The shortest distance from the surface of the active material particle to the ZnO that had penetrated most deeply was calculated, and this was taken as the penetration depth of the zinc-containing oxide within the active material particle. To calculate the distance, image analysis software (ImageJ) was used to calculate the distance on the image, and the actual distance was calculated from the number of pixels in the STEM image and the measurement magnification.

[0085] (Production of Positive Electrode Active Materials A2 to A5, C1 to C2) Positive electrode active materials A2 to A5 and C1 to C2 were produced in the same manner as the production method for active material A1 (Method 1), except that the amount of zinc acetate added was changed so that the ZnO content would be the value shown in Table 1. The obtained active materials were evaluated in the same manner as active material A1.

[0086] (Preparation of Positive Electrode Active Material C4) 2.3 g (13 mmol) of zinc isopropoxide (Zn[O(CH ２ ) ２ CH ３ ] ２) was added to the ethanol solution, and the mixture was stirred for 30 minutes in the air to dissolve the ethanol solution. Next, 100 g of manganese dioxide powder (particles) was added to the ethanol solution while stirring to prepare a dispersion. The manganese dioxide powder used was the same as the manganese dioxide powder used in producing active material A1 (the same applies to the production of the following active materials).

[0087] Next, 25 mL (1.35 mol) of water was added to the dispersion while cooling it with ice. This converted zinc isopropoxide to zinc hydroxide (Zn(OH) ２ ) to obtain a mixed solution containing zinc hydroxide. Next, the mixed solution was heated and dried at 80°C, and further baked at 300°C for 1 hour to convert the zinc hydroxide into zinc oxide. In this way, a powder in which 1 wt% of ZnO was dispersed was obtained. The above manufacturing method is referred to as Method 2.

[0088] (Production of Positive Electrode Active Materials C3 and C5) Active materials C3 and C5 were produced by the same production method as active material C4 (Method 2), except that the amounts of zinc isopropoxide and water added to 10 mL of ethanol were changed. Zinc isopropoxide was added so that the ZnO content would be the value shown in Table 1, assuming that all of the added zinc isopropoxide was converted to ZnO. The obtained active materials C3 to C5 were evaluated in the same manner as active material A1.

[0089] (Production of Positive Electrode Active Material C6) Positive electrode active material C6 was obtained by firing manganese dioxide powder (particles) for 8.5 hours at 420° C. The particles of active material C6 were not coated with ZnO.

[0090] (Production of Battery A1) The above active material A1 was used to produce a battery A1 (lithium primary battery) according to the following procedure.

[0091] (1) Preparation of Positive Electrode A positive electrode mixture was obtained by mixing 100 parts by mass of active material A1 with 3 parts by mass of Ketjen black (conductive agent) and 5 parts by mass of polytetrafluoroethylene (binder). The positive electrode mixture was filled into a stainless steel (SUS444) expanded metal (thickness 0.1 mm), dried, and then rolled to a thickness of 0.5 mm. A positive electrode plate was thus obtained. The positive electrode plate was cut into a size of 2 cm x 2.5 cm, and a SUS444 tab lead was connected to obtain a positive electrode.

[0092] (2) Preparation of Negative Electrode A metallic lithium foil (thickness: 300 μm) was cut into a size of 3 cm×4 cm, and a nickel tab lead was connected to obtain a negative electrode.

[0093] (3) Preparation of non-aqueous electrolyte First, propylene carbonate (PC), ethylene carbonate (EC), and 1,2-dimethoxyethane (DME) were mixed in a volume ratio of 4:2:4 to obtain a non-aqueous solvent. ３ SO ３ was dissolved in water to a concentration of 0.5 mol / L to prepare a non-aqueous electrolyte.

[0094] (4) Battery Assembly A separator was wrapped around the positive electrode. A polypropylene microporous membrane (25 μm thick) was used as the separator. Next, the separator-wrapped positive electrode and the negative electrode were placed opposite each other to obtain an electrode group. The electrode group was placed in a cylindrical bag (9 cm x 6 cm) made of aluminum laminate film, and the tab lead side of the cylindrical bag was sealed. Next, 0.5 mL of nonaqueous electrolyte was injected through the opening on the side opposite the sealed side, and then the opening was sealed. In this manner, Battery A1 was obtained.

[0095] (Measurement of Discharge Capacity) The discharge capacity of Battery A1 was measured. Specifically, Battery A1 immediately after assembly was discharged to 1.5 V at a constant current of 0.02 C (3.9 mA) in an environment of 25° C., and the discharge capacity was measured. From this discharge capacity, the discharge capacity per 1 g of active material (mAh / g) was calculated.

[0096] (Measurement of Resistance Value After High-Temperature Storage) The resistance value of Battery A1 after high-temperature storage was measured by the following method. First, Battery A1 immediately after assembly was discharged to 75% of its design capacity, and then Battery A1 was stored in a high-temperature atmosphere at 70° C. for two months. Then, the 1 kHz AC resistance value of Battery A1 after high-temperature storage was measured.

[0097] (Measurement of voltage drop during pulse discharge after high-temperature storage) For Battery A1, the voltage drop during pulse discharge at low temperatures after high-temperature storage was measured using the following method. First, Battery A1 was discharged to 75% of its design capacity immediately after assembly, and then stored in a high-temperature atmosphere at 70°C for two months. After high-temperature storage, Battery A1 was then left in a −30°C atmosphere for one hour. Next, the open-circuit voltage V0 of Battery A1 was measured, and then the minimum discharge voltage V1 was determined when a current of 10.4 mA was applied for one second. The difference between the open-circuit voltage V0 and the minimum value V1 (V0−V1) was taken as the voltage drop during pulse discharge.

[0098] (Manufacture of Batteries A2 to A5 and C1 to C6) Batteries A2 to A5 and C1 to C6 were manufactured in the same manner as the manufacturing method of Battery A1, except that active materials A2 to A5 and C1 to C6 were used instead of active material A1. The resulting batteries were evaluated in the same manner as Battery A1.

[0099] Active materials A1 to A5 and batteries A1 to A5 are active materials and batteries according to the present disclosure, and active materials C1 to C6 and batteries C1 to C6 are active materials and batteries of comparative examples.

[0100] Some of the manufacturing conditions for the active materials and the evaluation results of the batteries are shown in Table 1. The discharge capacity is a relative value when the discharge capacity of Battery C6 is set to 100. The resistance value after high-temperature storage is a relative value when the resistance value of Battery C6 is set to 100. The voltage drop during pulse discharge is the voltage drop during pulse discharge after the above-mentioned high-temperature storage. This voltage drop is a relative value when the voltage drop of Battery C6 is set to 100. A higher discharge capacity is preferable, a lower resistance value after high-temperature storage is preferable, and a lower voltage drop during pulse discharge is preferable.

[0101]

[0102] As shown in Table 1, when the coverage is in the range of 0.10 to 65%, the discharge capacity is comparable to that of the comparative batteries C1 to C6, but the deterioration of the characteristics (resistance value and voltage during pulse discharge) due to high-temperature storage can be significantly suppressed.

[0103] Experimental Example 2 In Experimental Example 2, a plurality of positive electrode active materials and a plurality of lithium primary batteries using the same were manufactured and evaluated.

[0104] (Manufacture of Battery B1) Except for changing the nonaqueous electrolyte, Battery B1 was manufactured by the same method as that for Battery A1 in Experimental Example 1. The nonaqueous electrolyte for Battery B1 was prepared by adding phthalimide (PhI) to the nonaqueous electrolyte used in the manufacture of Battery A1 to a concentration of 0.5 mass %.

[0105] (Manufacture of Batteries B2 to B9 and C7 to C8) Batteries B2 to B9 and C7 to C8 were manufactured by the same method as battery B1, except that the active material and / or non-aqueous electrolyte was changed. The active materials coated with zinc-containing oxides shown in Table 2 were used for batteries B2 to B9. These active materials were manufactured by the same method as active material A1. The active material for batteries C7 and C8 was the same active material as active material C6 in Experimental Example 1 (active material not coated with zinc-containing oxide). The non-aqueous electrolyte was prepared by adding phthalimide (PhI) to the non-aqueous electrolyte used in the manufacture of battery A1 to a concentration shown in Table 2.

[0106] The voltage drop during pulse discharge after high-temperature storage was measured for the batteries B1 to B9 and C7 to C8 by the method described above.

[0107] (Measurement of Amount of Gas Generated After High-Temperature Storage) The amount of gas generated after high-temperature storage was measured for Battery B1 using the following method. First, the mass of Battery B1 in air and in water was measured, and the volume V0 of Battery B1 was calculated using the Archimedes method. Next, Battery B1 was stored in a high-temperature atmosphere at 85°C for two months, and then the volume V1 of Battery B1 after high-temperature storage was measured using the same method as above. The difference in volume before and after high-temperature storage (V1 - V0) was defined as the amount of gas generated after high-temperature storage. Similar evaluations were performed on the other batteries B2 to B9 and C7 to C8.

[0108] Batteries B1 to B9 are batteries according to the present disclosure, and batteries C7 and C8 are comparative examples.

[0109] Table 2 shows some of the manufacturing conditions for the active material, the amount of additive in the non-aqueous electrolyte, the ratio Wz / Wi, and the evaluation results of the batteries. As described above, the ratio Wz / Wi is the ratio between the mass Wz of the zinc-containing oxide contained in the positive electrode and the mass Wi of the cyclic imide compound contained in the non-aqueous electrolyte. The amount of gas generated after high-temperature storage is a relative value when the amount of gas generated in Battery B7 is set to 100. The amount of voltage drop during pulse discharge shown in Table 2 is the amount of voltage drop during pulse discharge after the above-mentioned high-temperature storage. This amount of voltage drop is a relative value when the amount of voltage drop in Battery B7 is set to 100. A lower amount of gas generation is preferable, and a lower amount of voltage drop during pulse discharge is also preferable.

[0110]

[0111] As is clear from a comparison of batteries B1, B2, and B7 to B9, adding phthalimide to the nonaqueous electrolyte significantly reduces the amount of gas generated after high-temperature storage and the voltage drop during pulse discharge. As is clear from a comparison of batteries B1, B7, C7, and C8, the effect of using a zinc-containing oxide and a cyclic imide compound is greater than the combined effect of simply coating the active material particles with a zinc-containing oxide and the effect of using a cyclic imide compound. This is thought to be because, in addition to the effect of adding phthalimide, the phthalimide coating prevents the zinc-containing oxide from eluting during high-temperature storage, making it less likely that the effects of the zinc-containing oxide will be impaired.

[0112] The present disclosure can be used for positive electrode active materials for lithium primary batteries and lithium primary batteries. Although the present invention has been described with reference to presently preferred embodiments, such disclosure should not be interpreted as limiting. Various modifications and alterations will undoubtedly become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. Therefore, the appended claims should be construed to cover all modifications and alterations without departing from the true spirit and scope of the present invention.

[0113] REFERENCE SIGNS LIST 1 positive electrode 1a positive electrode current collector 2 negative electrode 3 separator 4 positive electrode lead 5 negative electrode lead 8 sealing plate 9 battery case 10 lithium primary battery

Claims

1. A positive electrode active material for a lithium primary battery, comprising: Composition formula Li ｘ MnO ２ (where 0≦x≦0.05), and a zinc-containing oxide that coats a portion of the surface of the active material particles; A positive electrode active material for a lithium primary battery, wherein the coverage of the active material particles with the zinc-containing oxide is in the range of 0.10% to 65%.

2. 2. The positive electrode active material for a lithium primary battery according to claim 1, wherein, when the surface is measured by energy dispersive X-ray analysis, the ratio Iz / Im of the net intensity Iz of the peak at about 8.6 keV of the Zn Kα ray to the net intensity Im of the peak at about 5.9 keV of the Mn Kα ray is in the range of 0.0001 to 0.

08.

3. 2. The positive electrode active material for a lithium primary battery according to claim 1, wherein the zinc-containing oxide is zinc oxide.

4. 2. The positive electrode active material for a lithium primary battery according to claim 1, wherein the content of the zinc-containing oxide is 1.5 mass % or less.

5. 2 . The positive electrode active material for a lithium primary battery according to claim 1 , wherein a part of the zinc-containing oxide penetrates into the inside of the active material particle to a position at a depth of 15 nm or more from the surface of the active material particle.

6. A lithium primary battery including a positive electrode including a positive electrode active material, a negative electrode, and a non-aqueous electrolyte, The positive electrode active material is a positive electrode active material for a lithium primary battery according to any one of claims 1 to 5, The negative electrode of the lithium primary battery comprises at least one selected from the group consisting of metallic lithium and a lithium alloy.

7. The lithium primary battery according to claim 6 , wherein the non-aqueous electrolyte contains a non-aqueous solvent and a cyclic imide compound.

8. The ratio Wz / Wi of the mass Wz of the zinc-containing oxide contained in the positive electrode to the mass Wi of the cyclic imide compound contained in the non-aqueous electrolyte is in the range of 0.5 to 15. The lithium primary battery according to claim 7.

9. 9. The lithium primary battery according to claim 7, wherein the concentration of the cyclic imide compound in the non-aqueous electrolyte is 1.5 mass % or less.

10. 9. The lithium primary battery according to claim 7, wherein the cyclic imide compound is phthalimide.