Lithium primary battery and non-aqueous electrolyte for lithium primary battery

Abstract

A lithium primary battery comprises: a positive electrode, a negative electrode and a non-aqueous electrolyte. The positive electrode comprises LixMnO2 (0≤x≤0.05). The negative electrode comprises at least one of metallic lithium and a lithium alloy. The non-aqueous electrolyte comprises an oxalate borate complex component and a cyclic imide component. In the non-aqueous electrolyte, the concentration of the oxalate borate complex component is 5.5% by mass or less, and the concentration of the cyclic imide component is 1% by mass or less. The mass ratio of the cyclic imide component contained in the non-aqueous electrolyte to the oxalate borate complex component is 0.02 or more and 10 or less.

Description

Technical Field

[0001] The present disclosure relates to a non-aqueous electrolyte for a lithium primary battery and a lithium primary battery using the same. Background Art

[0002] Lithium primary batteries have high energy density and low self-discharge, so they are used in many electronic devices. Lithium primary batteries contain: a negative electrode containing metallic lithium, a positive electrode, and a non-aqueous electrolyte. The positive electrode uses graphite fluoride, manganese dioxide, or thionyl chloride as an active material.

[0003] In lithium primary batteries, as discharge progresses, internal resistance increases and discharge capacity may decrease. From the viewpoint of suppressing such an increase in internal resistance, the use of additives for electrolyte solutions has been proposed.

[0004] For example, Patent Document 1 proposes a non-aqueous organic electrolyte for lithium primary batteries using manganese dioxide as a positive electrode active material and lithium metal or lithium alloy as a negative electrode active material, which contains LiCF3SO3 as a supporting salt and is added with LiB(C2O4)2. From the viewpoint of suppressing the increase in the internal resistance of a primary battery or a secondary battery and improving the charge and discharge cycle characteristics of a secondary battery, Patent Document 2 proposes the use of a non-aqueous electrolyte containing additives such as phthalimide.

[0005] As an electrolyte for an electrochemical device having high heat resistance and hydrolysis resistance, Patent Document 3 proposes a substance containing LiB(C2O4)F2 or the like.

[0006] It should be noted that Patent Document 4 proposes an additive composition for an electrolyte for a non-aqueous power storage device, which comprises an additive formed by a compound (A) in which at least one of the acidic protons of a specific acid is substituted by a silyl group having three hydrocarbon groups. Patent Document 4 suggests that the additive suppresses gas generation during use of a lithium-ion secondary battery and does not cause battery expansion.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2015-22985

[0010] Patent document 2: International Publication No. 01 / 41247

[0011] Patent Document 3: Japanese Patent Application Publication No. 2002-110235

[0012] Patent Document 4: Japanese Patent Application Publication No. 2016-189327 Summary of the invention

[0013] In lithium primary batteries, components of the electrolyte such as non-aqueous solvents decompose during storage and gas generation may become significant. If gas generation becomes significant, the pressure inside the battery increases, which may cause battery expansion or electrolyte leakage.

[0014] Patent Document 1 proposes a non-aqueous electrolyte solution containing lithium bis(oxalatoborate) (LiB(C2O4)2(LiBOB)). However, when such a non-aqueous electrolyte solution containing an oxalatoborate complex component is used in a lithium primary battery having a positive electrode using manganese dioxide and a negative electrode using lithium metal or a lithium alloy, the oxalatoborate complex component decomposes during storage of the battery and sometimes generates gas.

[0015] A first aspect of the present disclosure relates to a lithium primary battery comprising: a positive electrode, a negative electrode, and a non-aqueous electrolyte.

[0016] The positive electrode contains a positive electrode mixture including LixMnO2 (0≤x≤0.05),

[0017] The negative electrode comprises at least one of metallic lithium and a lithium alloy.

[0018] The non-aqueous electrolyte solution comprises an oxalate borate complex component and a cyclic imide component.

[0019] The concentration of the oxalate borate complex component in the non-aqueous electrolyte is 5.5% by mass or less,

[0020] The concentration of the cyclic imide component in the non-aqueous electrolyte is 1% by mass or less,

[0021] The mass ratio of the cyclic imide component to the oxalatoborate complex component contained in the non-aqueous electrolyte is 0.02 or more and 10 or less.

[0022] A second aspect of the present disclosure relates to a lithium primary battery comprising: a positive electrode, a negative electrode, and a non-aqueous electrolyte.

[0023] The positive electrode contains a positive electrode mixture including LixMnO2 (0≤x≤0.05),

[0024] The negative electrode comprises at least one of metallic lithium and a lithium alloy.

[0025] The non-aqueous electrolyte solution comprises an oxalate borate complex component and a cyclic imide component.

[0026] The concentration of the oxalatoborate complex component in the non-aqueous electrolyte is 0.1 mass % or more and 5.5 mass % or less,

[0027] The concentration of the cyclic imide component in the nonaqueous electrolyte is 0.1 mass % or more and 1 mass % or less.

[0028] A third aspect of the present disclosure relates to a non-aqueous electrolyte for a lithium primary battery, which is used in a lithium primary battery, wherein the lithium primary battery comprises: a positive electrode containing a positive electrode mixture containing LixMnO2 (0≤x≤0.05), a negative electrode containing at least one of metallic lithium and a lithium alloy, and the non-aqueous electrolyte,

[0029] The non-aqueous electrolyte solution comprises an oxalate borate complex component and a cyclic imide component.

[0030] The concentration of the oxalatoborate complex component in the non-aqueous electrolyte is 0.1 mass % or more and 5.5 mass % or less,

[0031] The concentration of the cyclic imide component in the nonaqueous electrolyte is 0.1 mass % or more and 1 mass % or less.

[0032] According to the lithium primary battery and the nonaqueous electrolyte for lithium primary battery of the present disclosure, gas generation during storage of the lithium primary battery can be suppressed, and capacity reduction can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a front view showing a portion of a lithium primary battery according to an embodiment of the present disclosure in cross section. DETAILED DESCRIPTION

[0034] In a lithium primary battery having a positive electrode containing LixMnO2 (0≤x≤0.05) and a negative electrode containing at least one of metallic lithium and a lithium alloy, it is shown that when a non-aqueous electrolyte containing an oxalate borate complex component is used, the reduction in capacity during storage of the battery is suppressed to a certain extent compared to the case of using a non-aqueous electrolyte not containing an oxalate borate complex component, but the amount of gas generated increases. Since the amount of gas generated increases, it is believed that in a lithium primary battery having the above-mentioned positive and negative electrodes, the oxalate borate complex component decomposes and generates gas when the battery is stored. It should be noted that this gas generation is particularly significant when the battery is stored at high temperatures.

[0035] On the other hand, in lithium primary batteries, a coating derived from components contained in the electrolyte is sometimes formed on the surface of the positive electrode. If a coating is formed, it is believed that the decomposition of the electrolyte at the positive electrode surface is suppressed, and therefore, gas generation can be reduced. However, if the positive electrode surface is covered with a dense coating, the side reaction associated with the decomposition of the electrolyte is suppressed, and on the other hand, the lithium ion conductivity of the coating is low, thereby reducing the capacity. When the battery is stored, the coating is easy to grow. Therefore, the suppression of the reduction in capacity after the battery is stored is in a compromise relationship with the suppression of gas generation, and it is not easy to take both into account. It should be noted that the growth of the coating is particularly significant when the battery is stored at high temperature.

[0036] The lithium primary battery disclosed in the present invention comprises: a positive electrode containing a positive electrode mixture including LixMnO2 (0≤x≤0.05), a negative electrode containing at least one of metallic lithium and a lithium alloy, and a non-aqueous electrolyte. The non-aqueous electrolyte contains an oxalate borate complex component and a cyclic imide component. In this lithium primary battery, the non-aqueous electrolyte satisfies at least one of the following conditions (a) and (b).

[0037] (a) The concentration of the oxalate borate complex component in the non-aqueous electrolyte is 5.5% by mass or less, the concentration of the cyclic imide component in the non-aqueous electrolyte is 1% by mass or less, and the mass ratio of the cyclic imide component contained in the non-aqueous electrolyte to the oxalate borate complex component is 0.02 or more and 10 or less.

[0038] (b) The concentration of the oxalatoborate complex component in the nonaqueous electrolyte is 0.1 mass % to 5.5 mass %, and the concentration of the cyclic imide component in the nonaqueous electrolyte is 0.1 mass % to 1 mass %.

[0039] According to the present disclosure, the lithium primary battery is provided with the above-mentioned non-aqueous electrolyte, so that although the non-aqueous electrolyte contains an oxalate borate complex component, it is possible to suppress the generation of gas when the battery is stored. In addition, the reduction in capacity after the lithium primary battery is stored can be suppressed. In particular, when the lithium primary battery is stored at high temperature, gas generation can also be suppressed, and the reduction in capacity can be suppressed. In the present disclosure, it is believed that this effect is obtained based on the following reasons.

[0040] In a lithium primary battery having the positive electrode, the negative electrode and the non-aqueous electrolyte, when the non-aqueous electrolyte contains a cyclic imide component but does not contain an oxalate borate complex component, the amount of gas generated is reduced compared to the case where the non-aqueous electrolyte does not contain both the oxalate borate complex component and the cyclic imide component, and on the other hand, the capacity after storage is significantly reduced. It is believed that this is because a dense film containing a component derived from the cyclic imide component is formed on the surface of the positive electrode, thereby suppressing the contact between the electrolyte solvent and the positive electrode and suppressing the generation of gas derived from the decomposition of the solvent, but on the other hand, the lithium ion conductivity of the above-mentioned film is low, thereby hindering the discharge reaction and reducing the discharge capacity.

[0041] When the non-aqueous electrolyte contains an oxalate borate complex component but does not contain a cyclic imide component, the capacity reduction after storage is suppressed to some extent compared to the case where both the oxalate borate complex component and the cyclic imide component are not contained, but the amount of gas generated increases. It is believed that the increase in the amount of gas generated is due to the decomposition of the oxalate borate complex component on the positive electrode surface, generating gas.

[0042] In contrast, in the lithium primary battery disclosed in the present invention, although the non-aqueous electrolyte contains an oxalate borate complex component, gas generation is greatly suppressed compared to the case where the oxalate borate complex component and the cyclic imide component are not contained. In addition, compared with the case where the non-aqueous electrolyte contains an oxalate borate complex component but does not contain a cyclic imide component, the reduction in capacity after storage can be significantly suppressed. In the lithium primary battery disclosed in the present invention, the reduction in capacity after storage is greatly suppressed compared to the case where the non-aqueous electrolyte contains either an oxalate borate complex component and a cyclic imide component. Therefore, when the non-aqueous electrolyte satisfies at least one of the conditions of (a) and (b) above, it can be said that the synergistic effect based on the oxalate borate complex component and the cyclic imide component is obtained in the suppression of the reduction in capacity after storage. In this way, in the lithium primary battery disclosed in the present invention, although gas generation is greatly suppressed, the factor that the reduction in capacity after storage is significantly suppressed is not clear, but it can be considered as follows. It is believed that when the cyclic imide component is decomposed on the positive electrode surface to form a coating, the oxalate borate complex component is also mixed in the decomposition reaction to form a coating containing components derived from both the oxalate borate complex component and the cyclic imide component. It is believed that this coating, unlike a coating formed only by the cyclic imide component, has high lithium ion conductivity and inhibits contact between the solvent and the positive electrode, thereby inhibiting a decrease in capacity while inhibiting an increase in side reactions accompanied by gas generation.

[0043] The present disclosure also includes: a non-aqueous electrolyte for a lithium primary battery having a positive electrode containing a positive electrode mixture containing LixMnO2 (0≤x≤0.05), a negative electrode containing at least one of metallic lithium and a lithium alloy, and a non-aqueous electrolyte. Here, the non-aqueous electrolyte contains an oxalate borate complex component and a cyclic imide component. The non-aqueous electrolyte satisfies the condition (b) above. In addition, the present disclosure also includes: the use of such a non-aqueous electrolyte in a lithium primary battery having a positive electrode containing a positive electrode mixture containing LixMnO2 (0≤x≤0.05), a negative electrode containing at least one of metallic lithium and a lithium alloy, and a non-aqueous electrolyte.

[0044] Hereinafter, the lithium primary battery, the nonaqueous electrolyte solution, and the method for producing the lithium primary battery of the present disclosure will be described in more detail.

[0045] [Lithium primary battery]

[0046] (positive electrode)

[0047] The positive electrode contains a positive electrode mixture. The positive electrode mixture contains a positive electrode active material. As the positive electrode active material contained in the positive electrode, manganese dioxide can be cited. The positive electrode containing manganese dioxide exhibits a higher voltage and excellent pulse discharge characteristics. Manganese dioxide can be a mixed crystal state containing multiple crystal states. The positive electrode may contain manganese oxides other than manganese dioxide. As manganese oxides other than manganese dioxide, MnO, Mn3O4, Mn2O3, Mn2O7, etc. can be cited. The main component of the manganese oxide contained in the positive electrode is preferably manganese dioxide.

[0048] A portion of the manganese dioxide contained in the positive electrode may be doped with lithium. As long as the amount of lithium doping is small, high capacity can be ensured. Manganese dioxide and manganese dioxide doped with a small amount of lithium can be represented by LixMnO2 (0≤x≤0.05). It should be noted that the average composition of the manganese oxide contained in the positive electrode as a whole only needs to be LixMnO2 (0≤x≤0.05). It should be noted that the ratio x of Li only needs to be less than 0.05 in the initial state of discharge of the lithium primary battery. The ratio x of Li usually increases as the discharge of the lithium primary battery proceeds. The oxidation number of manganese contained in manganese dioxide is theoretically 4-valent. However, by including other manganese oxides in the positive electrode or doping manganese dioxide with lithium, the oxidation number of manganese sometimes deviates slightly from 4-valent. Therefore, in LixMnO2, the average oxidation number of manganese is allowed to deviate slightly from 4-valent.

[0049] The positive electrode may include other positive electrode active materials for lithium primary batteries in addition to LixMnO2. As other positive electrode active materials, graphite fluoride and the like can be cited. From the viewpoint of the effect of using a non-aqueous electrolyte that satisfies the above conditions (a) or (b) to be easily exerted, the proportion of LixMnO2 in the overall positive electrode active material is preferably 90% by mass or more.

[0050] Electrolytic manganese dioxide is preferably used as the manganese dioxide. Electrolytic manganese dioxide that has been subjected to at least one of a neutralization treatment, a washing treatment, and a calcination treatment as necessary can be used.

[0051] Electrolytic manganese dioxide is usually obtained by electrolysis of an aqueous solution of manganese sulfate. Therefore, electrolytic manganese dioxide inevitably contains sulfate ions. The positive electrode mixture made using this electrolytic manganese dioxide inevitably contains sulfur atoms. The amount of sulfur atoms contained in the positive electrode mixture can be more than 0.05 parts by mass and less than 3 parts by mass relative to 100 parts by mass of manganese atoms contained in the positive electrode mixture. It is believed that when the sulfur atoms are in this range, in lithium primary batteries, sulfate ions and unstable Mn generated by the insertion of lithium into LixMnO2 3+ Interaction occurs, Mn 3+ The unevenness of Mn 2+The generation of Mn is suppressed. 2+ The dissolution into the non-aqueous electrolyte and the precipitation of Mn in the negative electrode are suppressed. As a result, it is possible to ensure high capacity while ensuring high reliability of the lithium primary battery. On the other hand, in the lithium secondary battery, a part of the sulfate ions are decomposed during the charging process. Therefore, even if the positive electrode mixture contains sulfate in an amount of sulfur atoms in the above range, it is difficult to fully ensure the above effect. The proportion of sulfur atoms contained in the positive electrode mixture can be adjusted by adjusting the conditions of the cleaning treatment and the neutralization treatment. As the cleaning treatment, for example, at least one of a water washing treatment and a cleaning treatment using an acid can be cited. As the neutralizer used in the neutralization treatment, for example, an inorganic base such as ammonia and a hydroxide is used.

[0052] If the conditions during electrolytic synthesis are adjusted, the crystallinity of manganese dioxide can be increased and the specific surface area of ​​electrolytic manganese dioxide can be reduced. The BET specific surface area of ​​LixMnO2 can be 20m 2 / g or more and 50m 2 When the BET specific surface area of ​​LixMnO2 is within this range, the positive electrode mixture layer can be easily formed in the lithium primary battery while suppressing gas generation more effectively.

[0053] The BET specific surface area of ​​LixMnO2 can be measured by a known method, for example, using a specific surface area measuring device (for example, manufactured by Mountech Co., Ltd.) based on the BET method. For example, LixMnO2 separated from the positive electrode taken out of the battery can be used as a measurement sample.

[0054] The median value of the particle size of LixMnO2 may be 10 μm or more and 40 μm or less. When the median value of the particle size is within this range, gas generation can be more effectively suppressed in a lithium primary battery, and high current collection in the positive electrode can be easily ensured.

[0055] The median value of the particle size of LixMnO2 is, for example, the median value of the particle size distribution obtained by the quantitative laser diffraction / scattering method (qLD method). For example, LixMnO2 separated from the positive electrode taken out of the battery can be used as a measurement sample. For example, SALD-7500nano manufactured by Shimadzu Corporation is used in the measurement.

[0056] The positive electrode mixture may contain a binder in addition to the positive electrode active material. The positive electrode mixture may contain a conductive agent.

[0057] Examples of the binder include fluororesins, rubber particles, and acrylic resins.

[0058] Examples of the conductive agent include conductive carbon materials, such as natural graphite, artificial graphite, carbon black, and carbon fibers.

[0059] The positive electrode may further include a positive electrode current collector that holds the positive electrode mixture. Examples of the material of the positive electrode current collector include stainless steel, aluminum, and titanium.

[0060] In the case of a coin-shaped battery, a positive electrode current collector having an L-shaped cross section may be mounted on positive electrode mixture pellets to form a positive electrode, or the positive electrode may be formed only by positive electrode mixture pellets. The positive electrode mixture pellets may be obtained, for example, by compression molding a wet positive electrode mixture prepared by adding an appropriate amount of water to a positive electrode active material and an additive, and drying the mixture.

[0061] In the case of a cylindrical battery, a positive electrode having a sheet-shaped positive electrode collector and a positive electrode mixture layer held on the positive electrode collector can be used. The sheet-shaped positive electrode collector can be, for example, a porous metal mesh, a net, a punched metal, etc. The positive electrode mixture layer can be obtained, for example, by applying the above-mentioned wet positive electrode mixture to the surface of the sheet-shaped positive electrode collector, pressing and drying in the thickness direction, thereby obtaining it.

[0062] (negative electrode)

[0063] The negative electrode may contain metallic lithium or a lithium alloy, or may contain both metallic lithium and a lithium alloy. For example, a composite containing metallic lithium and a lithium alloy may be used for the negative electrode.

[0064] Examples of lithium alloys include Li-Al alloys, Li-Sn alloys, Li-Ni-Si alloys, and Li-Pb alloys. From the perspective of ensuring discharge capacity and stabilizing internal resistance, the content of metal elements other than lithium contained in the lithium alloy is preferably 0.05 to 15% by mass.

[0065] Metal lithium, lithium alloy, or a composite thereof is molded into an arbitrary shape and thickness according to the shape, size, specification and performance of the lithium primary battery.

[0066] In the case of a coin-shaped battery, a ring-shaped metal lithium, a lithium alloy, or a composite thereof can be punched into a disc-shaped one for use as the negative electrode. In the case of a cylindrical battery, a sheet of metal lithium, a lithium alloy, or a composite thereof can be used as the negative electrode. The sheet can be obtained, for example, by extrusion molding. More specifically, in a cylindrical battery, a foil of metal lithium or a lithium alloy having a shape in a length direction and a width direction is used.

[0067] In the case of a cylindrical battery, a long tape having a resin substrate and an adhesive layer may be adhered to the main surface of at least one of the negative electrodes along the length direction. The main surface refers to the surface opposite to the positive electrode. The width of the tape can be set to, for example, not less than 0.5 mm and not more than 3 mm. When the lithium component of the negative electrode is consumed by reaction at the end of discharge, the tape has the function of preventing the negative electrode foil from breaking and causing poor current collection. If poor current collection occurs, the battery capacity is reduced. However, the adhesive force of the tape decreases during long-term storage depending on the electrolyte. When an electrolyte containing an oxalate borate complex component and a cyclic imide component is used, the reduction in its adhesive force can be suppressed, and the negative electrode foil from breaking and the occurrence of poor current collection can be more effectively prevented.

[0068] As the material of the resin substrate, for example, fluororesin, polyimide, polyphenylene sulfide, polyethersulfone, polyolefins such as polyethylene and polypropylene, polyethylene terephthalate, etc. can be used. Among them, polyolefins are preferred, and polypropylene is more preferred.

[0069] The adhesive layer, for example, comprises at least one component selected from the group consisting of a rubber component, a silicone component and an acrylic resin component. Specifically, as the rubber component, synthetic rubber, natural rubber, etc. can be used. As the synthetic rubber, butyl rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber, polyisobutylene, acrylonitrile-butadiene rubber, styrene-isoprene block copolymer, styrene-butadiene block copolymer, styrene-ethylene-butadiene block copolymer, etc. can be cited. As the silicone component, organic compounds with a polysiloxane structure, silicone-based polymers, etc. can be used. As silicone-based polymers, peroxide-cured silicones, addition reaction silicones, etc. can be cited. As the acrylic resin component, a polymer containing acrylic monomer units such as acrylic acid, methacrylic acid, acrylic ester, and methacrylic ester can be used, 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. It should be noted that the adhesive layer may contain a crosslinking agent, a plasticizer, and a tackifier.

[0070] (Non-aqueous electrolyte)

[0071] The non-aqueous electrolyte solution includes, for example, an oxalate borate complex component and a cyclic imide component, and a non-aqueous solvent for dissolving these components. The non-aqueous electrolyte solution includes a lithium salt or lithium ions. At least one of the oxalate borate complex component and the cyclic imide component may be a lithium salt or may generate lithium ions. In addition, the non-aqueous electrolyte solution may include a lithium salt other than the oxalate borate complex component and the cyclic imide component.

[0072] (oxalate borate complex ingredient)

[0073] The oxalate borate complex component may have at least the structure represented by the following formula (1). The non-aqueous electrolyte may contain one type of oxalate borate complex component, or may contain two or more types of oxalate borate complex components.

[0074]

[0075] (In formula (1), * represents an atomic bond.)

[0076] The oxalate borate complex component may be included in the non-aqueous electrolyte in any form of an acid (or anion) and a salt. The oxalate borate complex component may be any form as long as it can generate at least an oxalate borate complex anion in the non-aqueous electrolyte. The oxalate borate complex component may be a salt of an oxalate borate complex anion and a cation contained in the non-aqueous electrolyte.

[0077] In the oxalate borate complex component, as long as at least one oxalate ligand is coordinated to one boron atom, two oxalate ligands may be coordinated. The oxalate borate complex component may have a structure in which one oxalate ligand and two halogen atoms are coordinated to one boron atom. The oxalate borate complex component having such a structure can generate an anion represented by the following formula (2).

[0078]

[0079] X 1 and X 2 Examples of the halogen atom coordinated to the boron atom include a fluorine atom and a chlorine atom.

[0080] As the oxalate borate complex component, a dioxalate borate complex component and a difluorooxalate borate complex component are suitable. Among them, as the oxalate borate complex component, lithium dioxalate borate and lithium difluorooxalate borate are preferred. The dioxalate borate complex component has a structure in which two oxalate ligands are coordinated on one boron atom. The oxalate borate complex component having such a structure can generate an anion shown in the following formula (3). In addition, the difluorooxalate borate complex component has a structure in which one oxalate ligand and two fluorine atoms are coordinated on one boron atom.

[0081]

[0082] When the non-aqueous electrolyte satisfies the condition (a) above, the concentration of the oxalate borate complex component in the non-aqueous electrolyte is 5.5% by mass or less, and may be 5% by mass or less. If the concentration of the oxalate borate complex component exceeds 5.5% by mass, gas generation during storage becomes significant. The concentration of the oxalate borate complex component in the non-aqueous electrolyte may be 0.1% by mass or more or 0.5% by mass or more as long as it is above the detection limit. These upper and lower limits may be combined arbitrarily.

[0083] During the storage or discharge of the lithium primary battery, the oxalate borate complex component is consumed by the formation of the coating in the lithium primary battery, and the concentration of the oxalate borate complex component in the non-aqueous electrolyte changes. The concentration of the oxalate borate complex component in the non-aqueous electrolyte used in assembling or manufacturing lithium primary batteries is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. In this case, the capacity reduction after the lithium primary battery is stored can be significantly suppressed. It is preferred that the concentration of the oxalate borate complex component in the non-aqueous electrolyte used in assembling or manufacturing lithium primary batteries is 5.5% by mass or less or 5% by mass or less. In this case, the generation of gas during the storage of lithium primary batteries can be effectively suppressed. These lower limits and upper limits can be combined arbitrarily.

[0084] When the non-aqueous electrolyte satisfies the condition of (b) above, the concentration of the oxalate borate complex component in the non-aqueous electrolyte can be 0.1% by mass or more and 5.5% by mass or less, 0.1% by mass or more and 5% by mass or less, 0.5% by mass or more and 5.5% by mass or less, or 0.5% by mass or more and 5% by mass or less. When the concentration of the oxalate borate complex component is within this range, the gas generation during storage of the lithium primary battery can be suppressed, while the capacity reduction after storage can be significantly suppressed.

[0085] As described above, the oxalate borate complex component can be included in the non-aqueous electrolyte in the form of an acid (or an anion). In this specification, the concentration or mass-based amount of the oxalate borate complex component in the non-aqueous electrolyte is set to: the value converted from the concentration or mass-based amount of the lithium salt of the oxalate borate complex.

[0086] (Cyclic imide component)

[0087] As the cyclic imide component, for example, a cyclic diamide can be cited. The cyclic imide component only needs to have a diamide ring (or also referred to as an imide ring). Other rings (also referred to as the second ring) can be condensed on the imide ring. The non-aqueous electrolyte may contain one cyclic imide component, or may contain two or more cyclic imide components. The cyclic imide component 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 component is contained in the non-aqueous electrolyte in the form of an imide, it may be contained in the form of a free NH group, or in the form of a tertiary amine.

[0088] Examples of the second ring include an aromatic ring, a saturated or unsaturated aliphatic ring, etc. The second ring may contain at least one hetero atom. Examples of the hetero atom include an oxygen atom, a sulfur atom, and a nitrogen atom.

[0089] Examples of cyclic imides constituting the cyclic imide component include aliphatic dicarboxylic acid imides and cyclic imides having a second ring. Examples of aliphatic dicarboxylic acid imides include succinic acid imide and the like. Examples of cyclic imides having a second ring include imides of aromatic or alicyclic dicarboxylic acids and the like. Examples of aromatic dicarboxylic acids or alicyclic dicarboxylic acids include those having carboxyl groups on two adjacent atoms constituting the ring. Examples of cyclic imides having a second ring include phthalimide and hydrogenated products of phthalimide. Examples of hydrogenated products of phthalimide include cyclohex-3-ene-1,2-dicarboximide and cyclohexane-1,2-dicarboximide.

[0090] The imide ring may be an N-substituted imide ring having a substituent on the nitrogen atom of the imide. Examples of such substituents include hydroxyl groups, alkyl groups, alkoxy groups, and halogen atoms. Examples of alkyl groups include C 1-4 The alkyl group may be a methyl group, an ethyl group, or the like. Examples of the alkoxy group include C 1-4 The alkoxy group may be a methoxy group, an ethoxy group, etc. Examples of the halogen atom include a chlorine atom, a fluorine atom, and the like.

[0091] Among the cyclic imide components, 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 further preferred to use a cyclic imide component containing at least phthalimide.

[0092] When the non-aqueous electrolyte satisfies the condition (a) above, the mass ratio of the cyclic imide component contained in the non-aqueous electrolyte to the oxalate borate complex component is 0.02 or more and 10 or less, more preferably 0.02 or more and 7 or 0.02 or more and 5 or less. By making the mass ratio in this range, it becomes easy to further form a coating with excellent lithium ion conductivity on the positive electrode surface. Thus, it is possible to suppress the gas generation when storing the lithium primary battery while significantly suppressing the capacity reduction after storage.

[0093] The concentration of the cyclic imide component in the non-aqueous electrolyte is 1% by mass or less, and can be 0.7% by mass or less. When the concentration of the cyclic imide component is in this range, the decrease in capacity after the lithium primary battery is stored can be further suppressed. The concentration of the cyclic imide component in the non-aqueous electrolyte can be 0.1% by mass or more as long as it is above the detection limit.

[0094] During the storage or discharge of the lithium primary battery, the cyclic imide component is consumed in the lithium primary battery due to film formation, etc., and the concentration of the cyclic imide component in the non-aqueous electrolyte changes. The concentration of the cyclic imide component in the non-aqueous electrolyte used in assembling or manufacturing the lithium primary battery is preferably 0.1% by mass or more. In this case, the generation of gas during the storage of the lithium primary battery can be effectively suppressed. It is preferred that the concentration of the cyclic imide component in the non-aqueous electrolyte used in assembling or manufacturing the lithium primary battery is 1% by mass or less or 0.7% by mass or less. In this case, the reduction in capacity after the lithium primary battery is stored can be significantly suppressed.

[0095] When the nonaqueous electrolyte satisfies the condition of (b) above, the concentration of the cyclic imide component in the nonaqueous electrolyte can be 0.1% by mass or more and 1% by mass or less, and can be 0.1% by mass or more and 0.7% by mass or less. When the concentration of the cyclic imide component is in this range, the gas generation during storage of the lithium primary battery can be suppressed, while the capacity reduction after storage can be significantly suppressed.

[0096] In addition, the mass ratio of the cyclic imide component to the oxalate borate complex component contained in the non-aqueous electrolyte can be 0.02 to 10, or 0.02 to 7 or 0.02 to 5. By making the mass ratio within such a range, the amount of gas generated during storage of the lithium primary battery can be more effectively suppressed, and the capacity reduction after storage can be further suppressed.

[0097] As described above, the cyclic imide component may be contained in the non-aqueous electrolyte in the form of a salt. However, in this specification, the concentration or mass-based amount of the cyclic imide component in the non-aqueous electrolyte is set to be a value converted from the concentration or mass-based amount of the cyclic imide having a free NH group.

[0098] (Non-aqueous solvent)

[0099] As the non-aqueous solvent, an organic solvent that can be generally used for a non-aqueous electrolyte of a lithium primary battery can be cited. As the non-aqueous solvent, ethers, esters, carbonates, etc. can be cited. As the non-aqueous solvent, dimethyl ether, γ-butyrolactone, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, etc. can be used. The non-aqueous electrolyte can contain one non-aqueous solvent, or it can contain two or more non-aqueous solvents.

[0100] From the viewpoint of improving the discharge characteristics of lithium primary batteries, the non-aqueous solvent preferably includes: a cyclic carbonate with a high boiling point and a chain ether with a low viscosity even at low temperatures. The cyclic carbonate preferably includes at least one selected from the group consisting of propylene carbonate (PC) and ethylene carbonate (EC), and PC is particularly preferred. The chain ether preferably has a viscosity of 1 mPa·s or less at 25°C, and dimethoxyethane (DME) is particularly preferred. It should be noted that the viscosity of the non-aqueous solvent is determined by using a micro-sample viscometer m-VROC manufactured by RheoSense at a temperature of 25°C and based on a shear rate of 10000 (1 / s).

[0101] (Lithium Salt)

[0102] The non-aqueous electrolyte may contain a lithium salt other than the oxalate borate complex component and the cyclic imide component. As the lithium salt, for example, a lithium salt used as a solute in a lithium primary battery can be cited. As such a lithium salt, for example, LiCF3SO3, LiClO4, LiBF4, LiPF6, LiRaSO3 (Ra is a fluoroalkyl group having 1 to 4 carbon atoms), LiFSO3, LiN(SO2Rb)(SO2Rc)(Rb and Rc are each independently a fluoroalkyl group having 1 to 4 carbon atoms), LiN(FSO2)2, LiPO2F2 can be cited. The non-aqueous electrolyte may contain one of these lithium salts, or may contain two or more of these lithium salts.

[0103] (other)

[0104] The concentration of lithium ions (total concentration of lithium salts) contained in the non-aqueous electrolyte is, for example, 0.2 to 2.0 mol / L, or 0.3 to 1.5 mol / L.

[0105] The non-aqueous electrolyte solution may contain additives as necessary. Examples of such additives include propane sultone and vinylene carbonate. The total concentration of such additives contained in the non-aqueous electrolyte solution is, for example, 0.003 to 5 mol / L.

[0106] The non-aqueous electrolyte preferably does not contain: a silyl ester in which at least one of the acidic protons of an acid containing phosphorus or boron is substituted by a silyl group having three hydrocarbon groups. In a lithium primary battery, there is no process in which the positive electrode is oxidized and becomes high potential by charging as in a secondary battery. Therefore, when the non-aqueous electrolyte contains such a silyl ester, it is difficult to form a coating containing a component derived from the silyl ester on the positive electrode. On the other hand, it is reduced and decomposed on the negative electrode to cause gas generation, etc., which sometimes leads to a reduction in the reliability of the lithium primary battery.

[0107] (Separator)

[0108] A lithium primary battery generally has a separator sandwiched between the positive electrode and the negative electrode. As the separator, a porous sheet formed of an insulating material that is resistant to the internal environment of the lithium primary battery can be used. Specifically, a nonwoven fabric made of a synthetic resin, a microporous film made of a synthetic resin, or a laminate thereof can be cited.

[0109] As the synthetic resin used in the nonwoven fabric, for example, polypropylene, polyphenylene sulfide, polybutylene terephthalate, etc., can be cited. As the synthetic resin used in the microporous film, for example, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer can be cited. The microporous film can contain inorganic particles as needed.

[0110] The thickness of the separator is, for example, 5 μm or more and 100 μm or less.

[0111] The structure of the lithium primary battery is not particularly limited. The lithium primary battery may be a coin-shaped battery having a stacked electrode group composed of a disk-shaped positive electrode and a disk-shaped negative electrode stacked with a separator. It may also be a cylindrical battery having a wound electrode group composed of a strip-shaped positive electrode and a strip-shaped negative electrode wound in a spiral shape with a separator.

[0112] Figure 1 , a front view showing a portion of a cylindrical lithium primary battery of one embodiment of the present disclosure as a cross section is shown. In the lithium primary battery 10, an electrode group formed by winding a positive electrode 1 and a negative electrode 2 with a separator 3 interposed therebetween is housed in a battery case 9 together with a non-aqueous electrolyte. A sealing plate 8 is installed at the opening of the battery case 9. A positive electrode lead 4 connected to the collector 1a of the positive electrode 1 is connected to the sealing plate 8. A negative electrode lead 5 connected to the negative electrode 2 is connected to the case 9. In addition, an upper insulating plate 6 and a lower insulating plate 7 are respectively arranged at the upper and lower parts of the electrode group to prevent internal short circuits.

[0113] [Method for manufacturing lithium primary battery]

[0114] A lithium primary battery can be manufactured by housing a positive electrode, a negative electrode, and a non-aqueous electrolyte in a battery case. The manufacturing method of the lithium primary battery disclosed in the present invention at least comprises: a step of preparing a non-aqueous electrolyte containing an oxalate borate complex component and a cyclic imide component and satisfying the above-mentioned condition (b). In the lithium primary battery obtained by the manufacturing method having such a step, the amount of gas generated during storage can be suppressed while the capacity reduction after storage can be significantly suppressed. In the manufacturing method of the lithium primary battery, a known manufacturing method can be adopted according to the type of battery, etc., except for the preparation step of the non-aqueous electrolyte.

[0115] [Example]

[0116] 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.

[0117] 《Examples 1 to 7 and Comparative Examples 1 to 7》

[0118] (1) Preparation of positive electrode

[0119] As a positive electrode, 5 parts by mass of Ketjen black as a conductive agent, 5 parts by mass of polytetrafluoroethylene as a binder, and an appropriate amount of pure water were added to 100 parts by mass of electrolytic manganese dioxide and kneaded to prepare a wet positive electrode mixture.

[0120] Next, the positive electrode mixture is filled into a positive electrode current collector formed by a porous metal mesh with a thickness of 0.1 mm made of stainless steel (SUS444) to make a positive electrode precursor. Afterwards, the positive electrode precursor is dried, rolled by roller pressure until the thickness becomes 0.4 mm, and cut into sheets of 2.2 cm in length and 1.5 cm in width to obtain a positive electrode. Next, a portion of the filled positive electrode mixture is stripped, and a TAB lead (Japanese original: タブリード) made of SUS444 is resistance welded to the portion where the positive electrode current collector is exposed.

[0121] (2) Preparation of negative electrode

[0122] A metal lithium foil having a thickness of 300 μm was cut into a size of 4 cm in length and 2.5 cm in width to obtain a negative electrode. A nickel TAB lead was connected to a predetermined position of the negative electrode by crimping.

[0123] (3) Preparation of electrode group

[0124] The separator was wound around the positive electrode and overlapped so as to face the negative electrode to prepare an electrode group. A microporous film made of polypropylene with a thickness of 25 μm was used as the separator.

[0125] (4) Preparation of non-aqueous electrolyte

[0126] PC, EC and DME are mixed in a volume ratio of 4:2:4. LiCF3SO3 is dissolved in the obtained mixture in a concentration of 0.5 mol / L, and the oxalate borate complex component shown in Table 1 and phthalimide as a cyclic imide component are dissolved in a concentration shown in Table 1. In this way, a non-aqueous electrolyte is prepared. As the oxalate borate complex component, LiBOB or lithium difluorooxalatoborate (LiB(C2O4)F2(LiFOB)) is used.

[0127] (5) Assembly of lithium primary batteries

[0128] The electrode group was placed in a cylindrical aluminum-laminated bag with a length of 9 cm and a width of 6 cm in such a way that a portion of the TAB lead connected to the positive and negative electrodes was exposed from the bag, and the opening on the TAB lead side was sealed. 0.5 mL of electrolyte was injected from the opening opposite to the TAB lead, and the opening was sealed by vacuum heat sealing. In this way, a lithium primary battery for testing was prepared. The design capacity of the lithium primary battery is 301 mAh / g.

[0129] It should be noted that in the lithium primary battery of the embodiment, the amount of sulfur atoms derived from sulfate contained in the positive electrode mixture is 0.05 mass parts or more and 1.25 mass parts or less relative to 100 mass parts of manganese atoms contained in the positive electrode mixture. In the lithium primary battery of the embodiment, the median value of the particle size of LixMnO2 contained in the positive electrode is 25μm to 27μm, and the BET specific surface area is 38 to 42m 2 / g.

[0130] (6) Evaluation

[0131] (6-1) Capacity reduction after storage

[0132] For the lithium primary battery just assembled, discharge to a capacity equivalent to 2.5% of the designed capacity (C0), and store at 60°C for 3 days. The stored lithium primary battery is discharged at a current of 4.5 mA per unit mass (g) of manganese dioxide until the battery voltage reaches 2V. Calculate the discharge capacity C1 (mAh / g) at this time. By reducing C0 from C1, the reduction in capacity is calculated. Calculate the ratio (%) of the reduction in capacity in each lithium primary battery when the reduction in capacity in the lithium primary battery of Comparative Example 7 is set to 100%, as the capacity reduction rate after storage. The lower the capacity reduction rate, the more suppressed the capacity reduction is.

[0133] (6-2) Gas Generation

[0134] For the newly assembled lithium primary battery, discharge to a capacity equivalent to 2.5% of the designed capacity and store it at 85°C for 2 weeks. Disassemble the stored lithium primary battery and capture the gas contained in the battery. Analyze the captured gas by gas chromatography to find the gas amounts of H2, CO, CO2, and CH4. Find the ratio (%) of the volume-based gas amount in each lithium primary battery when the volume-based gas amount in the lithium primary battery of Comparative Example 7 is set to 100%. The smaller the ratio, the less gas is generated.

[0135] The results of Examples and Comparative Examples are shown in Table 1. In Table 1, E1 to E7 are Examples 1 to 7, and R1 to R7 are Comparative Examples 1 to 7. In Table 1, the oxalatoborate complex component is referred to as the first component, and the cyclic imide component is referred to as the second component.

[0136] [Table 1]

[0137]

[0138] As shown in Table 1, when the non-aqueous electrolyte contains the first component but does not contain the second component, the gas generation increases by 6% compared to the case where the non-aqueous electrolyte does not contain both the first component and the second component (comparison between Comparative Example 1 and Comparative Example 7). Therefore, it is believed that the gas generation is due to the decomposition of the first component. In contrast, when the non-aqueous electrolyte contains the second component in addition to the first component, the gas generation during the storage of the lithium primary battery can be suppressed (comparison between Comparative Example 7 and Examples 1 to 7).

[0139] In the case where the non-aqueous electrolyte contains the second component but does not contain the first component, the capacity reduction rate after storage is significantly reduced to 200% compared with the case where the non-aqueous electrolyte does not contain both the first component and the second component (comparison of Comparative Example 6 and Comparative Example 7). In the case where the non-aqueous electrolyte contains the first component but does not contain the second component, the capacity reduction rate after storage is 71%, which is improved by 29% (comparison of Comparative Example 1 and Comparative Example 7). By analogy with these results: in the case where the non-aqueous electrolyte contains both the first component and the second component, the capacity reduction rate after storage is 200%-29%=171%. Therefore, in fact, in the case where the non-aqueous electrolyte contains both the first component and the second component, the capacity reduction rate after storage is 11%, and the capacity reduction is significantly suppressed compared with the analogous value of 171% (Example 1). It can be said that this effect is obviously due to the synergistic effect of the first component and the second component.

[0140] The above effects of the examples are obtained when the nonaqueous electrolyte satisfies at least one of the above conditions (a) and (b) (comparison between Examples 1 to 7 and Comparative Examples 2 to 5).

[0141] Industrial Applicability

[0142] The lithium primary battery disclosed herein can suppress the decrease in capacity and gas generation associated with storage. Therefore, the lithium primary battery is suitable for use as a main power source or memory backup power source for various instruments, for example. However, the uses of the lithium primary battery are not limited to these.

[0143] Description of Reference Numerals

[0144] 1 Positive electrode

[0145] 1a Positive electrode collector

[0146] 2 Negative electrode

[0147] 3 Dividers

[0148] 4 Positive lead

[0149] 5 Negative lead

[0150] 6 Upper insulation board

[0151] 7 Lower insulation board

[0152] 8 Sealing plate

[0153] 9Battery housing

[0154] 10 Lithium primary battery

Claims

1. A lithium primary battery, comprising: Positive electrode, negative electrode and non-aqueous electrolyte, The positive electrode contains a positive electrode mixture including LixMnO2, wherein 0≤x≤0.05, The negative electrode comprises at least one of metallic lithium and a lithium alloy, The non-aqueous electrolyte solution comprises an oxalate borate complex component and a cyclic imide component, The concentration of the oxalatoborate complex component in the non-aqueous electrolyte is 5.5% by mass or less, The concentration of the cyclic imide component in the non-aqueous electrolyte is 1% by mass or less, The mass ratio of the cyclic imide component to the oxalate borate complex component contained in the non-aqueous electrolyte is 0.02 or more and 10 or less, The cyclic imide component includes at least one selected from the group consisting of phthalimide and N-substituted phthalimide.

2. A lithium primary battery, comprising: Positive electrode, negative electrode and non-aqueous electrolyte, The positive electrode contains a positive electrode mixture including LixMnO2, wherein 0≤x≤0.05, The negative electrode comprises at least one of metallic lithium and a lithium alloy, The non-aqueous electrolyte solution comprises an oxalate borate complex component and a cyclic imide component, The concentration of the oxalatoborate complex component in the non-aqueous electrolyte is 0.1 mass % or more and 5.5 mass % or less, The concentration of the cyclic imide component in the non-aqueous electrolyte is 0.1 mass % or more and 1 mass % or less, The cyclic imide component includes at least one selected from the group consisting of phthalimide and N-substituted phthalimide.

3. The lithium primary battery according to claim 2, wherein: A mass ratio of the cyclic imide component to the oxalatoborate complex component contained in the non-aqueous electrolyte is 0.02 or more and 10 or less.

4. The lithium primary battery according to any one of claims 1 to 3, wherein The oxalatoborate complex component includes at least one selected from the group consisting of a dioxalatoborate complex component and a difluorooxalatoborate complex component.

5. The lithium primary battery according to any one of claims 1 to 3, wherein The oxalatoborate complex component includes at least one selected from the group consisting of lithium bis(oxalatoborate) and lithium difluoro(oxalatoborate).

6. The lithium primary battery according to any one of claims 1 to 3, wherein The cyclic imide component contains at least phthalimide.

7. The lithium primary battery according to any one of claims 1 to 3, wherein The positive electrode mixture further comprises sulfate, The amount of sulfur atoms contained in the positive electrode mixture is 0.05 parts by mass or more and 3 parts by mass or less relative to 100 parts by mass of manganese atoms contained in the positive electrode mixture.

8. The lithium primary battery according to any one of claims 1 to 3, wherein The median value of the particle size of LixMnO2 is greater than or equal to 10 μm and less than or equal to 40 μm.

9. The lithium primary battery according to any one of claims 1 to 3, wherein The BET specific surface area of ​​LixMnO2 is 20 m 2 / g or more and 50m 2 / g or less.

10. The lithium primary battery according to any one of claims 1 to 3, wherein The negative electrode includes a foil of the metallic lithium or the lithium alloy and has a shape having a length direction and a width direction, and a long tape including a resin substrate and an adhesive layer is adhered to a main surface of at least one of the negative electrodes along the length direction.

11. A non-aqueous electrolyte for a lithium primary battery, which is used for a lithium primary battery, wherein the lithium primary battery comprises: a positive electrode containing a positive electrode mixture containing LixMnO2, a negative electrode containing at least one of metallic lithium and a lithium alloy, and a non-aqueous electrolyte, wherein 0≤x≤0.05, The non-aqueous electrolyte solution comprises an oxalate borate complex component and a cyclic imide component, The concentration of the oxalatoborate complex component in the non-aqueous electrolyte is 0.1 mass % or more and 5.5 mass % or less, The concentration of the cyclic imide component in the non-aqueous electrolyte is 0.1 mass % or more and 1 mass % or less, The cyclic imide component includes at least one selected from the group consisting of phthalimide and N-substituted phthalimide.

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