Lithium primary battery

Abstract

A lithium primary battery 10 disclosed herein comprises a positive electrode 1, a negative electrode 2, and a non-aqueous electrolyte. The positive electrode 1 contains manganese dioxide. The negative electrode 2 contains at least one among metallic lithium and a lithium alloy. The non-aqueous electrolyte contains: at least one compound selected from the group consisting of oxalate salts, sulfonylimide salts, and isocyanate compounds; and a cyclic imide compound.

Description

Lithium primary battery Cross-reference of related applications

[0001] This disclosure claims priority rights to Japanese Patent Application No. 2024-208681, filed with the Japan Patent Office on 29 November 2024, and the entirety of the said patent application is incorporated herein by reference.

[0002] This disclosure relates to lithium primary batteries.

[0003] Lithium primary batteries are suitable for long-term use due to their high energy density and low self-discharge. Their adoption as power sources for long-term use in equipment is increasing. For example, smart meters transmit data on gas and electricity usage and are required to operate maintenance-free for extended periods. During this time, lithium primary batteries must maintain high internal electromotive force and low internal resistance.

[0004] Patent Document 1 proposes a lithium primary battery in which a positive electrode and a negative electrode are wound around each other with a separator in between, forming a columnar electrode group in which the outermost circumference of the negative electrode is positioned outside the outermost circumference of the positive electrode, the negative electrode contains metallic lithium or a lithium alloy, a copper-based metal foil is attached to the negative electrode, the copper-based metal foil extends from a first position on the outer or inner surface of the negative electrode, either opposite to the end of the winding of the positive electrode or on the outer circumference of that opposing end, the copper-based metal foil winds around the electrode group one or more times from the first position, a tab lead is electrically connected to at least one of the negative electrode and the copper-based metal foil, and the tab lead is electrically connected to a metal case.

[0005] Patent Document 2 proposes a spiral-type battery in which a positive electrode and a negative electrode are superimposed on each other via a separator and wound in a spiral shape as the power generation element, and the group retaining plate and bottom plate are cup-shaped molded products attached to the top and bottom of the power generation element. The group retaining plate covers the upper corner of the positive electrode close to the negative electrode casing, and the bottom plate covers the lower corner of the positive electrode close to the negative electrode casing.

[0006] Japanese Patent Publication No. 2018-56075, Japanese Utility Model Publication No. Hei 6-28995

[0007] Primary batteries with low self-discharge are used as the power source for devices such as gas and water meters that operate maintenance-free for a long time. These devices have a very long installation period. If a battery that has hardly been discharged in the device is forcibly discharged while connected in series, the battery at the end of discharge will have an amount of electricity flowing through it that exceeds the theoretical capacity of the positive electrode (the limit value of lithium that the positive electrode active material can theoretically accept). This state becomes a so-called over-discharge state. Lithium dissolved from the negative electrode due to the over-discharge current cannot be accepted into the positive electrode and will be electrodeposited on the positive electrode. If this over-discharge state continues, the excess lithium electrodeposited on the positive electrode becomes dendrite-shaped, significantly increasing the possibility of piercing the separator and causing an internal short circuit. When an internal short circuit occurs, a large current flows concentratedly in the short-circuited part, resulting in a rapid temperature rise.

[0008] One aspect of the present disclosure relates to a lithium primary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode includes manganese dioxide, the negative electrode includes at least one of metallic lithium and a lithium alloy, and the non-aqueous electrolyte includes at least one compound selected from the group consisting of oxalate salts, sulfonylimide salts, and isocyanate compounds and a cyclic imide compound.

[0009] According to the present disclosure, it is possible to provide a lithium primary battery capable of suppressing the operation of a safety valve by suppressing dendrite formation of lithium. The novel features of the present invention are described in the appended claims. However, the present invention will be better understood by reference to the following detailed description taken in conjunction with the drawings, with respect to both the structure and the content, and in combination with other objects and features of the present invention.

[0010] It is a front view of a cross-section of a part of a lithium primary battery according to an embodiment of the present disclosure.

[0011] In the following, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less". In the following description, when the lower limit and the upper limit are exemplified for numerical values such as specific physical properties and conditions, any combination of any of the exemplified lower limits and any of the exemplified upper limits can be made as long as the lower limit is not more than the upper limit. When a plurality of materials are exemplified, one of them may be selected and used alone, or two or more of them may be used in combination.

[0012] In the following, the primary lithium battery according to this embodiment may be referred to as "primary lithium battery (L)" or "primary battery (L)". The primary lithium battery (L) includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode contains manganese dioxide. The negative electrode contains at least one of metallic lithium and a lithium alloy. The non-aqueous electrolyte contains at least one compound selected from the group consisting of an oxalate salt, a sulfonylimide salt, and an isocyanate compound, and a cyclic imide compound. At least one compound selected from the group consisting of an oxalate salt, a sulfonylimide salt, and an isocyanate compound may be referred to as "compound (C)" below.

[0013] Compound (C) may be dissolved in the non-aqueous electrolyte. Compound (C) may be dissolved in the non-aqueous electrolyte to generate anions and cations. The primary battery (L) may contain only an oxalate salt as compound (C), may contain only a sulfonylimide salt as compound (C), or may contain only an isocyanate compound as compound (C). Alternatively, the primary battery (L) may contain two compounds selected from the above three compounds as compound (C). Alternatively, the primary battery (L) may contain all of the above three compounds as compound (C).

[0014] When the non-aqueous electrolyte contains only cyclic imide compounds, a film derived from the cyclic imide compounds forms on the positive electrode surface. Because this film has low lithium ion conductivity, it can, for example, cause dendritation of lithium electrodeposited on the positive electrode surface, activating the safety valve. Furthermore, this film significantly increases the internal resistance both initially and after high-temperature storage. In addition, this film tends to reduce the initial electromotive force of lithium primary batteries and promote self-discharge.

[0015] When the non-aqueous electrolyte contains a cyclic imide compound and an oxalate salt, a coating containing components derived from both the cyclic imide compound and the oxalate salt is formed on the positive electrode surface. This composite coating has higher lithium ion conductivity than a coating derived solely from the cyclic imide compound, resulting in lower resistance and improved chemical and thermal stability. Therefore, this composite coating suppresses the dendrite formation of lithium electrodeposited on the positive electrode due to over-discharge. Furthermore, this composite coating suppresses side reactions that occur when the positive electrode and the non-aqueous electrolyte come into contact during high-temperature storage.

[0016] As a result, in the lithium primary battery (L) of this disclosure, the non-aqueous electrolyte contains a cyclic imide compound and an oxalate salt, thereby suppressing the operation of the safety valve. Furthermore, it becomes easier to effectively reduce the amount of gas generated during high-temperature storage (e.g., 85°C). In addition, the deterioration of pulse characteristics after high-temperature storage is suppressed.

[0017] When the non-aqueous electrolyte contains a cyclic imide compound and a sulfonylimide salt, a coating containing components derived from both the cyclic imide compound and the sulfonylimide salt is formed on the positive electrode surface. This composite coating has low resistance and excellent durability. This composite coating suppresses the dendritation of lithium electrodeposited on the positive electrode due to over-discharge.

[0018] As a result, in the lithium primary battery (L) of this disclosure, the non-aqueous electrolyte contains a cyclic imide compound and a sulfonylimid salt, thereby suppressing the activation of the safety valve. In addition, the deterioration of the initial pulse characteristics is suppressed.

[0019] When the non-aqueous electrolyte contains a cyclic imide compound and an isocyanate compound, a coating containing components derived from both the cyclic imide compound and the isocyanate compound is formed on the positive electrode surface. This composite coating suppresses the dendritation of lithium electrodeposited on the positive electrode due to over-discharge. Furthermore, this composite coating suppresses the side reactions of the cyclic imide compound at the positive electrode.

[0020] As a result, in the lithium primary battery (L) of this disclosure, the non-aqueous electrolyte contains a cyclic imide compound and an isocyanate compound, thereby suppressing the operation of the safety valve. Furthermore, it becomes easier to effectively reduce the amount of gas generated during high-temperature storage (e.g., 85°C). In addition, the deterioration of pulse characteristics after high-temperature storage is suppressed.

[0021] When the non-aqueous electrolyte contains two compounds selected from oxalate salts, sulfonylimide salts, and isocyanate compounds, and a cyclic imide compound, a coating containing components derived from these compounds is formed. This composite coating is more chemically and thermally stable than a composite coating formed when it contains one compound selected from sulfonylimide salts, oxalate salts, and isocyanate compounds, and a cyclic imide compound. Therefore, this composite coating suppresses side reactions that occur when the positive electrode and the non-aqueous electrolyte come into contact during high-temperature storage. It also suppresses the dendrite formation of lithium electrodeposited on the positive electrode due to over-discharge.

[0022] As a result, in the lithium primary battery (L) of this disclosure, the operation of the safety valve is suppressed by the non-aqueous electrolyte containing two compounds selected from compound (C) and a cyclic imide compound. Furthermore, the amount of gas generated during high-temperature storage (e.g., 85°C) is more effectively reduced. In addition, the deterioration of pulse characteristics after high-temperature storage is suppressed. Moreover, self-discharge during storage of the lithium primary battery (L) is reduced, and the increase in insulation resistance is also suppressed.

[0023] When the non-aqueous electrolyte contains a cyclic imide compound, an oxalate salt, a sulfonylimide salt, and an isocyanate compound, a coating containing components derived from these is formed. This composite coating is more chemically and thermally stable than a composite coating formed when it contains two compounds selected from sulfonylimide salts, oxalate salts, and isocyanate compounds, along with a cyclic imide compound. Furthermore, this composite coating has low resistance and excellent durability. In addition, this composite coating suppresses side reactions of the cyclic imide compound at the positive electrode. Therefore, this composite coating suppresses side reactions that occur when the positive electrode and the non-aqueous electrolyte come into contact during high-temperature storage. It also suppresses the dendrite formation of lithium electrodeposited on the positive electrode due to over-discharge.

[0024] As a result, in the lithium primary battery (L) of this disclosure, the operation of the safety valve is suppressed by the non-aqueous electrolyte containing all three compounds selected from the group consisting of compound (C) and a cyclic imide compound. Furthermore, the amount of gas generated during high-temperature storage (e.g., 85°C) can be reduced more effectively. In addition, the deterioration of pulse characteristics during initial and high-temperature storage is suppressed. Moreover, self-discharge during storage of the lithium primary battery (L) is reduced, and the increase in insulation resistance can also be suppressed.

[0025] (Cyclic Imide Compounds) The cyclic imide compound may contain at least one of phthalimide and N-substituted phthalimide. In other words, at least one of phthalimide and N-substituted phthalimide may be dissolved in the non-aqueous electrolyte. The substituent on the nitrogen atom of the N-substituted phthalimide can be selected from the substituents exemplified for the N-substituted imide ring described later. These compounds are preferred not only because they form a film on the positive electrode surface, but also because they readily form a good composite film with all three compounds selected from the group consisting of compound (C).

[0026] The N-substituted phthalimide may include at least one selected from the group consisting of N-hydroxyphthalimide, N-(cyclohexylthio)phthalimide, and N-(phenylthio)phthalimide.

[0027] The cyclic imide compound only needs to have a diacylamine ring (imide ring). Another ring (second ring) may be fused to the imide ring. The second ring may be an aromatic ring, or a saturated or unsaturated aliphatic ring. The second ring may contain at least one heteroatom. Examples of heteroatoms include oxygen, sulfur, and nitrogen atoms. The non-aqueous electrolyte may contain one cyclic imide compound, or two or more.

[0028] The cyclic imide compound may be included in the form of a tertiary amine, or in the form of an anion or salt.

[0029] The cyclic imide compound may also be an N-substituted imide compound having a substituent on the nitrogen atom of the imide. Examples of substituents include hydroxyl groups, alkyl groups, alkoxy groups, and halogen atoms. Examples of alkyl groups include C1 to C4 alkyl groups, and may also include methyl groups and ethyl groups. Examples of alkoxy groups include C1 to C4 alkoxy groups, and may also include methoxy groups and ethoxy groups. Examples of halogen atoms include chlorine atoms and fluorine atoms.

[0030] The cyclic imide compound may be a hydrogenated compound, for example, a hydrogenated phthalimide.

[0031] Specific examples of cyclic imide compounds include phthalimide, hexahydrophthalimide, N-methylphthalimide, N-hydroxyphthalimide, N-hydroxymethylphthalimide, N-(2-hydroxyethyl)phthalimide, N-fluorophthalimide, N-(phenylthio)phthalimide, N-(cyclohexylthio)phthalimide, N-(propanthio)butafluorophthalimide, succinimide, N-hydroxysuccinimide, N-fluorosuccinimide, cyclohexa-3-ene-1,2-dicarboxymide, cyclohexane-1,2-dicarboxymide, and N-(phenylthio)imide. These may be used individually or in combination of two or more. At least one compound selected from the group consisting of phthalimide, N-hydroxyphthalimide, N-(cyclohexylthio)phthalimide, and N-(phenylthio)phthalimide is preferred because it readily forms a high-quality composite film with all three compounds selected from the group consisting of compound (C).

[0032] The content of the cyclic imide compound in the non-aqueous electrolyte may be 0.002% by mass or more, 0.1% by mass or more, 0.2% by mass or more, 0.3% by mass or more, 0.4% by mass or more, 0.5% by mass or more, or 0.6% by mass or more. The content of the cyclic imide compound in the non-aqueous electrolyte may be 1.0% by mass or less, 0.8% by mass or less, 0.6% by mass or less, 0.5% by mass or less, 0.4% by mass or less, or 0.3% by mass or less. It is desirable that the content of the cyclic imide compound in the non-aqueous electrolyte be within the above range immediately after the battery is manufactured (or when the non-aqueous electrolyte is prepared).

[0033] As described above, the cyclic imide compound may be present in the non-aqueous electrolyte in the form of a salt.

[0034] (Oxalate salt) The oxalate salt may contain at least one of an oxalate borate complex component and an oxalate phosphate complex component. The oxalate borate complex component and the oxalate phosphate complex component may each contain at least one cation of a lithium ion and a manganese ion.

[0035] The oxalate salt (oxalate complex) may be at least one selected from the group consisting of an oxalate borate complex component and an oxalate phosphate complex component.

[0036] The anion of the oxalate complex may contain boron and / or phosphorus. Examples of the anion of the oxalate complex include bisoxalate borate anion, difluorooxalate borate anion (BF ２ (C ２ O ４ ) － ), PF ４ (C ２ O ４ ) － , PF ２ (C ２ O ４ ) ２ － and the like. The non-aqueous electrolyte may contain these anions alone or in combination of two or more.

[0037] When the non-aqueous electrolyte contains the anion of the oxalate complex, the precipitation of lithium metal in a dendrite form can be particularly suppressed. The anion of the oxalate complex preferably has fluorine. Due to the interaction between the anion of the oxalate complex having fluorine and lithium, a high-quality film such as lithium fluoride is likely to be formed. Therefore, it becomes easy to suppress the local precipitation of lithium metal. The anion of the oxalate complex having fluorine may be combined with other anions. The other anion may be PF ６ － and / or an anion of imides.

[0038] (Oxalate Borate Complex Component) The oxalate borate complex component may be dissolved in the non-aqueous electrolyte solution in either the form of an acid (or anion) or a salt. The oxalate borate complex component only needs to be capable of generating at least the anion of the oxalate borate complex in the non-aqueous electrolyte solution. The oxalate borate complex component may be a salt of the anion of the oxalate borate complex and the cation contained in the non-aqueous electrolyte solution.

[0039] In the oxalate borate complex component, it is sufficient for at least one oxalate ligand to be coordinated to one boron atom, and two oxalate ligands may be coordinated. The oxalate borate complex component may also have a structure in which one oxalate ligand and two halogen atoms are coordinated to one boron atom.

[0040] The oxalate borate complex component may contain at least one of a bis(oxalate)borate complex component and a difluoro(oxalate)borate complex component. These compounds are preferred not only because they form a film on the positive electrode surface, but also because they readily combine with cyclic imide compounds.

[0041] The bis(oxalate)boric acid complex component has a structure in which two oxalate ligands are coordinated to one boron atom. The difluoro(oxalate)boric acid complex component has a structure in which one oxalate ligand and two fluorine atoms are coordinated to one boron atom.

[0042] (Oxalate Phosphate Complex Component) The oxalate phosphate complex component may be present in the non-aqueous electrolyte in either the form of an acid (or anion) or a salt. The oxalate phosphate complex component only needs to be capable of generating at least an oxalate phosphate complex anion in the non-aqueous electrolyte. The oxalate phosphate complex component may also be a salt of the oxalate phosphate complex anion and a cation contained in the electrolyte.

[0043] The oxalate phosphate complex component may include at least one selected from the group consisting of tetrafluoro(oxalate) phosphate complex components, difluorobis(oxalate) phosphate complex components, and tris(oxalate) phosphate complex components, or it may be at least one of these. These compounds are preferred in that they form a film on the positive electrode surface and are readily compounded with cyclic imide compounds.

[0044] The oxalate phosphate complex component may be, for example, a difluorobis(oxalate) phosphate complex component. The difluorobis(oxalate) phosphate complex component has a structure capable of generating an anion represented by the following formula (1). The non-aqueous electrolyte may contain one oxalate phosphate complex component or two or more.

[0045]

[0046] The oxalate phosphate complex component may dissolve in a non-aqueous electrolyte to produce at least an oxalate phosphate complex anion. The oxalate phosphate complex component may also be a salt of the oxalate phosphate complex anion and a cation contained in the non-aqueous electrolyte.

[0047] In the oxalate phosphate complex component, one phosphorus atom may be coordinated with at least one oxalate ligand, two oxalate ligands, or three oxalate ligands.

[0048] The oxalate phosphate complex component may have a structure in which one phosphorus atom is coordinated with one oxalate ligand and four halogen atoms.

[0049] Furthermore, the oxalate phosphate complex component may have a structure in which one phosphorus atom is coordinated with two oxalate ligands and two halogen atoms.

[0050] Tetrafluoro(oxalate) phosphate complex components have a structure in which one phosphorus atom is coordinated to one oxalate ligand and four fluorine atoms. Difluorobis(oxalate) phosphate complex components have a structure in which one phosphorus atom is coordinated to two oxalate ligands and two fluorine atoms. Tris(oxalate) phosphate complex components can generate anions having a structure in which one phosphorus atom is coordinated to three oxalate ligands.

[0051] The content of oxalate complex components in the non-aqueous electrolyte (total content of oxalate borate complex components and oxalate phosphate complex components) may be 2.5% by mass or less, or 2.0% by mass or less. The content of oxalate complex components in the non-aqueous electrolyte may be 0.1% by mass or more, or 0.2% by mass or more. It is desirable that the content of oxalate complex components in the non-aqueous electrolyte be within the above range immediately after the manufacture of the battery (or during the preparation of the non-aqueous electrolyte).

[0052] (Sulfonylimid salts) Sulfonylimid salts may contain at least one cation of a lithium ion or a manganese ion, and at least one anion of bis(fluorosulfonyl)imide anion and bis(trifluoromethanesulfonyl)imide anion.

[0053] Examples of sulfonylimide salts include fluorine-containing sulfonylimide compounds. Such compounds include LiN(SO4). ２ Ra) (SO ２ Examples include compounds represented by the formula Rb). In the formula, Ra and Rb are each independently a fluorine atom or a fluorinated alkyl group having 1 to 4 carbon atoms. The fluorinated alkyl group may be linear or branched. Examples of fluorinated alkyl groups include CF ３ , C ２ F ５ , C ３ F ７ , C ４ F ９ This includes things like:

[0054] A specific example of a sulfonylimid salt is lithium bis(fluorosulfonyl)imide: LiN(SO ２ F) ２ (Hereafter also referred to as LiFSI), Lithium bis(trifluoromethanesulfonyl)imide: LiN(CF ３ SO ２ ) ２ (Hereinafter also referred to as LiTFSI), Lithium (fluorosulfonyl) (trifluoromethanesulfonyl)imide: LiN(SO ２ F) (CF３ SO ２ ), lithium bis(pentafluoroethanesulfonyl)imide:LiN(CF ３ CF ２ SO ２ ) ２ These are some examples. In the non-aqueous electrolyte, at least one cation of lithium ions or manganese ions is dissolved, along with at least one anion of bis(fluorosulfonyl)imide anion (FSI) and bis(trifluoromethanesulfonyl)imide anion (TFSI). In addition to forming a film on the positive electrode surface, it is preferable that the sulfonylimid salt contains at least one of Li and Mn, along with at least one of FSI and TFSI, in order to obtain the effect of being easily compounded with cyclic imide compounds.

[0055] The sulfonylimide salt content in the electrolyte may be 0.1% by mass or more, or 0.5% by mass or more. The sulfonylimide salt content in the electrolyte may be 20% by mass or less, or 15.8% by mass or less. It is desirable that the sulfonylimide salt content in the non-aqueous electrolyte be within the above range immediately after the battery is manufactured (or when the non-aqueous electrolyte is prepared).

[0056] The anion produced from the sulfonylimid salt is, for example, FSI, and has the structure represented by the following formula (2).

[0057]

[0058] (Isocyanate compound) The isocyanate compound may be a monoisocyanate compound having one isocyanate group, a diisocyanate compound having two isocyanate groups, or a polyisocyanate compound having three or more isocyanate groups. The isocyanate compound may have five or fewer isocyanate groups, or four or fewer.

[0059] An isocyanate compound may have at least one isocyanate group and a C1-C20 aliphatic hydrocarbon group or a C6-C20 aromatic hydrocarbon group. C1, C6, and C20 indicate that the number of carbon atoms is 1, 6, and 20, respectively (the same applies hereinafter). The aliphatic hydrocarbon group and aromatic hydrocarbon group constituting the isocyanate compound may have substituents. Examples of substituents include halogen atoms and nitrile groups. The aliphatic group may be an alicyclic aliphatic group, or a linear or branched aliphatic group. The aromatic hydrocarbon group is a hydrocarbon group having one or more aromatic rings, and may be a group in which an aromatic ring and an aliphatic group are linked.

[0060] Specific examples of isocyanate compounds include methyl isocyanate, ethyl isocyanate, propyl isocyanate, butyl isocyanate, pentyl isocyanate, hexyl isocyanate, heptyl isocyanate, octyl isocyanate, cyclohexane isocyanate, phenyl isocyanate, fluorophenyl isocyanate, methoxycarbonyl isocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (HMDI), and peptamethylene diisocyanate. Socyanates, octamethylene diisocyanates, 1,2-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanate methyl)cyclohexane (1,3-H6XDI), 1,4-bis(isocyanate methyl)cyclohexane, 1,2-bis(isocyanate ethyl)cyclohexane, 1,3-bis(isocyanate ethyl)cyclohexane, 1,4-bis(isocyanate ethyl)cyclohexane, isophorone diisocyanate (IPDI), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate Socyanates, xylylene diisocyanate, phenyl diisocyanate, toluene diisocyanate, diisocyanatonaphthalene, o-tolidine diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, bis(4-isocyanatephenyl)methane, 1,6,11-triisocyanatondecane, 1,3,5-tris(6-isocyanatehexa-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(6-isocyanate) Examples include tri-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(6-isocyanate penta-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(6-isocyanate tetra-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 1,3,5-tris(6-isocyanate hepta-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. These may be used individually or in combination of two or more.

[0061] OCN-C ｎ H ２ｎ Compounds represented as -NCO (where n is an integer from 1 to 10) (e.g., hexamethylene diisocyanate (HMDI)), compounds having an alicyclic diyl group (e.g., 1,3-bis(isocyanate methyl)cyclohexane (1,3-H6XDI), dicyclohexylmethane-4,4'-diisocyanate, bicyclo[2.2.1]heptane-2,5-diylbis(methylisocyanate), bicyclo[2.2.1]heptane-2,6-diylbis(methylisocyanate), isophorone diisocyanate (IPDI)), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, hexyl isocyanates, etc. are readily available.

[0062] Here, diisocyanate compounds are thought to form composite films with lower resistance than monoisocyanate compounds and with higher homogeneity than triisocyanate compounds. Furthermore, diisocyanate compounds have a high ability to form composite films even in small amounts and exhibit excellent stability within the battery. For these reasons, among isocyanate compounds, the use of diisocyanate compounds is preferable.

[0063] The diisocyanate compound may be at least one selected from the group consisting of hexamethylene diisocyanate (HMDI), 1,3-bis(isocyanatemethyl)cyclohexane (1,3-H6XDI), and isophorone diisocyanate (IPDI). By using these compounds, in addition to forming a film on the positive electrode surface, the effect of easily compounding with cyclic imide compounds can be obtained.

[0064] The isocyanate compound may be hexamethylene diisocyanate. Hexamethylene diisocyanate is represented by the following formula (3).

[0065]

[0066] The content of isocyanate compounds in the non-aqueous electrolyte may be 2.5% by mass or less, or 2.0% by mass or less. The content of isocyanate compounds in the non-aqueous electrolyte may be 0.1% by mass or more, or 0.3% by mass or more. It is desirable that the content of isocyanate compounds in the non-aqueous electrolyte be within the above range immediately after the manufacture of the battery (or when the non-aqueous electrolyte is prepared).

[0067] For the analysis of non-aqueous electrolytes, liquid chromatography-mass spectrometry (LC / MS) or gas chromatography-mass spectrometry (GC / MS) can be used, for example. Ultraviolet spectroscopy (UV) may also be performed in conjunction with nuclear magnetic resonance analysis (NMR), infrared absorption spectroscopy (IR), and mass spectrometry (MS).

[0068] (Manganese Dioxide) Manganese dioxide may contain sulfates. The ratio Ws / Wm of the mass of sulfur atoms in manganese dioxide to the mass Wm of manganese atoms in manganese dioxide may be 2.0 / 100 or less.

[0069] Ws / Wm may be 0.02 / 100 or greater, or 0.05 / 100 or greater. Ws / Wm may be 2.0 / 100 or less, or 1.6 / 100 or less. Ws / Wm may be in the range of 0.02 / 100 to 2.0 / 100, or in the range of 0.05 / 100 to 2.0 / 100. Within these ranges, the upper limit may be 0.02 / 100 or 0.05 / 100, as long as the lower limit does not exceed the upper limit.

[0070] When the above conditions are met, gas generation after high-temperature storage is particularly suppressed. The detailed mechanism is unknown, but it is presumed to be as follows: Sulfates contained in the positive electrode mixture dissolve from the positive electrode during high-temperature storage, and upon contact between the negative electrode and the non-aqueous electrolyte, components derived from the sulfates (sulfate ions) are incorporated into the film formed on the surface of the positive electrode. At this time, the formed positive electrode film is mainly composed of organic materials formed from the solvent, cyclic imide compounds, and isocyanate compounds in the non-aqueous electrolyte, and inorganic components such as sulfonylime salts, oxalate salts, and sulfates dissolved from the positive electrode are incorporated, forming an organic-inorganic hybrid film. This is thought to provide a higher-than-usual positive electrode protection effect at high temperatures and suppress gas generation. If the ratio of the mass of sulfur atoms in manganese dioxide to the mass of manganese atoms in manganese dioxide, Ws / Wm, exceeds 2.0 / 100, then the coating contains an excess of sulfate-derived components, which can accelerate corrosion of the positive electrode core material and dissolution of the positive electrode manganese dioxide during high-temperature storage.

[0071] It is preferable to use manganese dioxide produced by electrolysis for the positive electrode of a lithium primary battery. Manganese dioxide produced by electrolysis usually contains sulfates.

[0072] Examples of components of the lithium primary battery (L) according to this disclosure will be described in detail below. Note that the components described below are examples, and the components of the lithium primary battery (L) in this embodiment are not limited to the examples described below. Known components may be used for components other than those characteristic of the lithium primary battery (L). As described above, the lithium primary battery (L) includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The lithium primary battery (L) may also include a separator and an outer casing.

[0073] (Positive Electrode) The positive electrode contains a positive electrode mixture. The positive electrode mixture contains a positive electrode active material. The positive electrode active material contains manganese dioxide. A positive electrode containing manganese dioxide as the positive electrode active material exhibits relatively high voltage and excellent pulse discharge characteristics. Manganese dioxide may be in a mixed crystal state containing multiple crystalline states. The positive electrode may also contain manganese oxides other than manganese dioxide. Examples of manganese oxides other than manganese dioxide include MnO and Mn ３ O ４ Mn ２ O ３ Examples include Mn2O7. The main component of the manganese oxide contained in the positive electrode (for example, 50% by mass or more) should be manganese dioxide.

[0074] A portion of the manganese dioxide contained in the positive electrode may be doped with lithium. A small amount of lithium doping can ensure high capacity. Manganese dioxide and manganese dioxide doped with a small amount of lithium are Li ｘ MnO ２ It can be expressed as (0 ≤ x ≤ 0.05). The average composition of the entire manganese oxide contained in the positive electrode is Li ｘ MnO ２ The condition (0 ≤ x ≤ 0.05) is sufficient. The ratio of Li x should be 0.05 or less in the initial discharge state of the lithium primary battery (L). The ratio of Li x increases as the discharge of the lithium primary battery (L) progresses. Theoretically, the oxidation state of manganese in manganese dioxide is tetravalent, but the average oxidation state of manganese is allowed to fluctuate slightly from tetravalent.

[0075] The degree of crystallinity of manganese dioxide is determined by the peaks attributed to the (110) plane of manganese dioxide in the X-ray diffraction pattern. Crystallinity is defined as the value obtained by dividing the peak height (intensity) by its full width at half maximum (FWHM). The FWHM of a peak attributed to the (110) plane, obtained using X-ray diffraction, may be between 0.4 and 4.0.

[0076] Within the above range, gas generation after high-temperature storage is suppressed. The detailed mechanism is unknown, but it is presumed to be as follows: Sulfates contained in the positive electrode mixture dissolve from the positive electrode during high-temperature storage, and components derived from sulfates (sulfate ions) are incorporated into the film formed on the surface of the positive electrode through contact between the negative electrode and the non-aqueous electrolyte. At this time, the formed positive electrode film is mainly composed of organic materials, formed from the solvent, cyclic imide compounds, and isocyanate compounds in the non-aqueous electrolyte, and inorganic components such as sulfonylime salts, oxalate salts, and sulfates dissolved from the positive electrode are incorporated, forming an organic-inorganic hybrid film. This is thought to provide a higher-than-usual positive electrode protection effect at high temperatures and suppress gas generation. If the full width at half maximum (FWHM) of the (110) plane peak in the X-ray diffraction pattern of positive electrode manganese dioxide is less than 0.4, the crystallinity of the manganese dioxide is too high, reducing the surface area. This leads to the formation of an excessive positive electrode coating, increased resistance, and a larger amount of sulfuric acid leached from the positive electrode per unit area, resulting in increased leaching and gas generation of positive electrode manganese dioxide. On the other hand, if the FWHM of the (110) plane peak exceeds 4.0, the crystallinity of the manganese dioxide is low, increasing the surface area. This results in an insufficient positive electrode coating effect, leading to increased leaching and gas generation of positive electrode manganese dioxide.

[0077] The BET specific surface area of ​​manganese dioxide is, for example, 5 m². ２ 40m at 1g or more ２ It may be less than / g. When the BET specific surface area of ​​manganese dioxide is within this range, a higher self-discharge suppression effect can be obtained in lithium primary batteries (L). In addition, the positive electrode mixture layer can be easily formed.

[0078] The BET specific surface area of ​​manganese dioxide can be measured by known methods, for example, using a specific surface area measuring device (e.g., manufactured by Mountec Co., Ltd.) based on the BET method. For example, manganese dioxide separated from the positive electrode of a battery can be used as the measurement sample.

[0079] The median particle size of manganese dioxide may be between 5 μm and 40 μm. When the median particle size is within this range, the effect of suppressing self-discharge in lithium primary batteries (L) is further enhanced, and it is easier to ensure high current collection performance at the positive electrode. The median particle size of manganese dioxide is, for example, the median of the volume-based particle size distribution determined by quantitative laser diffraction-scattering (qLD) method. For example, Li separated from the positive electrode taken from a battery ｘ MnO ２ The sample to be measured should be [the sample shown]. For measurement, for example, the SALD-7500nano manufactured by Shimadzu Corporation can be used.

[0080] The positive electrode may contain manganese dioxide as well as other positive electrode active materials used in lithium primary batteries (L). Examples of other positive electrode active materials include graphite fluoride. The proportion of manganese dioxide in the total positive electrode active material may be 90% by mass or more.

[0081] The positive electrode mixture may contain, in addition to the positive electrode active material, a binder, a conductive agent, and the like. Examples of binders include fluororesins, rubber particles, and acrylic resins.

[0082] Examples of conductive materials include conductive carbon materials. Examples of conductive carbon materials include natural graphite, artificial graphite, carbon black, and carbon fibers.

[0083] The positive electrode may further include a positive electrode current collector that holds the positive electrode mixture. Examples of materials for the positive electrode current collector include stainless steel, aluminum, and titanium.

[0084] In the case of a cylindrical battery, a positive electrode can be used that comprises a sheet-shaped positive electrode current collector and a positive electrode mixture layer held by the positive electrode current collector. The sheet-shaped positive electrode current collector may be a perforated current collector. Examples of perforated current collectors include expanded metal, net, and punched metal. The positive electrode mixture layer can be obtained, for example, by coating the above-mentioned wet positive electrode mixture onto the surface of the sheet-shaped positive electrode current collector or filling the positive electrode current collector with it, applying pressure in the thickness direction, and drying it.

[0085] (Negative electrode) A negative electrode containing metallic lithium and / or a lithium alloy can be used. The negative electrode may contain both metallic lithium and lithium metal. A composite of metallic lithium and a lithium alloy may be used for the negative electrode.

[0086] Examples of lithium alloys include Li-Al alloy, Li-Sn alloy, Li-Ni-Si alloy, Li-Pb alloy, Li-Mg alloy, Li-Zn alloy, Li-In alloy, and Li-Al-Mg alloy.

[0087] The negative electrode may contain a lithium alloy, and the lithium alloy may contain aluminum and magnesium. In this case, the combined content of aluminum and magnesium in the lithium alloy may be 0.01% by mass or more and 20% by mass or less. In this case, the discharge capacity and internal resistance of the lithium primary battery (L) can be ensured. This is because a film is formed on the negative electrode when the metallic lithium of the negative electrode comes into contact with the additives and solvents contained in the non-aqueous electrolyte, thereby suppressing side reactions. When the lithium alloy contains Al, the reaction activity of the negative electrode surface is somewhat suppressed compared to when the negative electrode is composed of metallic lithium, so the density of the film formed on the negative electrode surface increases. Consequently, the rate of film formation is also suppressed, so the amount of additives and solvents in the non-aqueous electrolyte incorporated into the film increases, resulting in the formation of a higher quality and more functional film. This suppresses side reactions such as gas generation during high-temperature storage.

[0088] Furthermore, by mixing Al and Mg in the lithium alloy, segregation of Al in the lithium alloy is suppressed, and the suppression effect of Al on the above-mentioned side reactions is stably obtained throughout the entire negative electrode. As a result, a uniform film is formed on the surface of the negative electrode, so the surface activity is suppressed compared to Li-Al alloys, a higher quality and more functional film is formed, and side reactions such as gas generation during high-temperature storage are further suppressed.

[0089] However, if the total content of Al and Mg in the lithium alloy is less than 0.01% by mass, the effects of Al and Mg may be insufficient. Also, if the total content of Al and Mg in the lithium alloy exceeds 20% by mass, the amount of Li in the negative electrode decreases, which may reduce the discharge capacity.

[0090] Lithium metal, lithium alloys, and composites thereof are molded into any shape and thickness according to the shape, dimensions, and performance specifications of the lithium primary battery (L).

[0091] In the case of coin-type batteries, a hoop-shaped piece of metallic lithium or lithium alloy may be punched out into a disc shape and used as the negative electrode. In the case of cylindrical batteries, a sheet of metallic lithium or lithium alloy may be used as the negative electrode. The sheet can be obtained, for example, by extrusion molding. The negative electrode may also be metallic lithium foil or lithium alloy foil.

[0092] (Non-aqueous electrolyte) The non-aqueous electrolyte contains a non-aqueous solvent, a cyclic imide compound dissolved in the non-aqueous solvent, and compound (C).

[0093] (Non-aqueous solvents) Examples of non-aqueous solvents include ethers, esters, and carbonate esters. More specifically, dimethyl ether, γ-butyl lactone, propylene carbonate, ethylene carbonate, and 1,2-dimethoxyethane can be used. Non-aqueous solvents may be used individually or in combination of two or more.

[0094] From the viewpoint of improving the discharge characteristics of the lithium primary battery (L), the non-aqueous solvent may contain a cyclic carbonate ester with a high boiling point and a chain ether with low viscosity at low temperatures. The cyclic carbonate ester preferably contains at least one selected from the group consisting of propylene carbonate (PC) and ethylene carbonate (EC), with PC being particularly preferred. The chain ether preferably contains, for example, dimethoxyethane (DME).

[0095] (Lithium salts) Examples of lithium salts include LiCF ３ SO ３ LiClO ４LiBF ４ LiPF ６ LiRaSO ３ (Ra is a C1-C4 alkyl fluoride), LiFSO ３ , LiN (SO ２ Rb) (SO ２ Rc) (Rb and Rc are each independently C1-C4 alkyl fluoride groups), LiN (FSO ２ ) ２ LiPO ２ F ２ LiB(C) ２ O ４ ) ２ LiBF ２ (C ２ O ４ ) are examples. The non-aqueous electrolyte may contain one of these lithium salts, or it may contain two or more.

[0096] (Other) The concentration of lithium salt (or lithium ions) contained in the non-aqueous electrolyte is, for example, 0.2 to 2.0 mol / L, and may also be 0.3 to 1.5 mol / L.

[0097] The non-aqueous electrolyte may contain additives as needed. Examples of additives include propanesultone and vinylene carbonate. The total concentration of such additives in the non-aqueous electrolyte may be, for example, 0.003 to 5 mol / L.

[0098] (Separator) Lithium primary batteries (L) typically include a separator interposed between the positive and negative electrodes. Examples of separators include nonwoven fabrics, microporous membranes, or laminates thereof. The thickness of the separator is, for example, 5 μm or more and 100 μm or less.

[0099] Nonwoven fabrics are composed of fibers including, for example, polypropylene, polyphenylene sulfide, and polybutylene terephthalate. Microporous membranes include, for example, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer.

[0100] The structure of the lithium primary battery (L) is not particularly limited. The lithium primary battery (L) may be a coin-type battery constructed by stacking a disc-shaped positive electrode and a disc-shaped negative electrode with a separator in between. The lithium primary battery (L) may also be a cylindrical battery having an electrode group constructed by spirally winding a strip-shaped positive electrode and a strip-shaped negative electrode with a separator in between.

[0101] Figure 1 shows a cross-sectional front view of a part of a cylindrical lithium primary battery according to one embodiment. The lithium primary battery 10 has an electrode group in which a positive electrode 1 and a negative electrode 2 are wound around a separator 3, and this electrode group is 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. The positive electrode lead 4, which is connected to the current collector 1a of the positive electrode 1, is connected to the sealing plate 8. The negative electrode lead 5, which is connected to the negative electrode 2, is connected to the case 9. An upper insulating plate 6 and a lower insulating plate 7 are arranged above and below the electrode group, respectively.

[0102] (Note) The above description of embodiments discloses the following technologies. (Technology 1) A lithium primary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode comprises manganese dioxide, the negative electrode comprises at least one of metallic lithium and a lithium alloy, and the non-aqueous electrolyte comprises at least one compound selected from the group consisting of oxalate salts, sulfonylimide salts, and isocyanate compounds, and a cyclic imide compound. (Technology 2) The lithium primary battery according to Technology 1, wherein the cyclic imide compound comprises at least one of phthalimide and N-substituted phthalimide. (Technology 3) The lithium primary battery according to Technology 2, wherein the N-substituted phthalimide comprises at least one selected from the group consisting of N-hydroxyphthalimide, N-(cyclohexylthio)phthalimide, and N-(phenylthio)phthalimide. (Technical 4) The lithium primary battery according to Technical 1, wherein the oxalate salt comprises at least one of an oxalate boric acid complex component and an oxalate phosphate complex component, and the oxalate boric acid complex component and the oxalate phosphate complex component each comprise at least one cation of a lithium ion and a manganese ion. (Technical 5) The lithium primary battery according to Technical 4, wherein the oxalate boric acid complex component comprises at least one of a bis(oxalate)boric acid complex component and a difluoro(oxalate)boric acid complex component, and the oxalate phosphate complex component comprises at least one selected from the group consisting of a tetrafluoro(oxalate)phosphate complex component, a difluorobis(oxalate)phosphate complex component, and a tris(oxalate)phosphate complex component. (Technical 6) The lithium primary battery according to Technical 1, wherein the sulfonylimide salt comprises at least one cation of a lithium ion or a manganese ion and at least one anion of a bis(fluorosulfonyl)imide anion and a bis(trifluoromethanesulfonyl)imide anion. (Technical 7) The lithium primary battery according to Technical 1, wherein the isocyanate compound comprises a diisocyanate compound having two or more isocyanate groups.(Technical 8) The lithium primary battery according to Technical 7, wherein the diisocyanate compound comprises at least one selected from the group consisting of hexamethylene diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, and isophorone diisocyanate. (Technical 9) The lithium primary battery according to any one of Technical 1 to 8, wherein the manganese dioxide comprises a sulfate, and the ratio Ws / Wm of the mass of sulfur atoms in the manganese dioxide to the mass Wm of manganese atoms in the manganese dioxide is 2.0 / 100 or less.

[0103] The present disclosure will be described in detail below based on examples, but the present disclosure is not limited to the following examples. In these examples, multiple lithium primary batteries (L) were fabricated and evaluated.

[0104] (Battery A1) Battery A1 was manufactured using the following procedure. (1) Preparation of the positive electrode First, 100 parts by mass of manganese dioxide was mixed with 5 parts by mass of Ketjenblack (conductive agent), 5 parts by mass of polytetrafluoroethylene (binding agent), and an appropriate amount of pure water to prepare a wet positive electrode mixture. For the manganese dioxide, manganese dioxide produced by electrolysis was used, which was then calcined at 400°C for 5 hours. For the manganese dioxide, manganese dioxide with a Ws / Wm ratio (the ratio of the mass Ws of sulfur atoms in manganese dioxide to the mass Wm of manganese atoms in manganese dioxide) of the values ​​shown in Table 1 was used.

[0105] Next, a positive electrode precursor was prepared by filling a positive electrode current collector made of expanded metal (thickness: 0.4 mm) made of stainless steel (SUS444) with the positive electrode mixture. The positive electrode precursor was then dried, rolled to a thickness of 0.5 mm using a roll press, and cut to a predetermined size. In this way, a positive electrode was obtained. Subsequently, a portion of the filled positive electrode mixture was peeled off, and one end of a stainless steel positive electrode lead was resistance-welded to the portion of the positive electrode current collector that was exposed.

[0106] (2) Preparation of the negative electrode A negative electrode was obtained by cutting a lithium metal foil or lithium alloy foil (thickness: 200 μm) to a predetermined size. One end of a nickel negative electrode lead was connected to a predetermined location on the negative electrode by ultrasonic welding.

[0107] (3) Fabrication of electrode groups Electrode groups were fabricated by winding a positive electrode and a negative electrode with a separator in between. A microporous film made of polypropylene (thickness: 25 μm) was used as the separator.

[0108] (4) Preparation of non-aqueous electrolyte Propylene carbonate, ethylene carbonate, and 1,2-dimethoxyethane were mixed in a volume ratio of 4:2:4 to obtain a non-aqueous solvent. LiCF4 ３ SO ３ The compound was dissolved at a concentration of 0.5 mol / L. In addition, a non-aqueous electrolyte was prepared by dissolving the cyclic imide compound and the sulfonylimide salt in a non-aqueous solvent so that each component was at the concentrations shown in Table 1. In Table 1, FSI represents bis(fluorosulfonyl)imide and TFSI represents bis(trifluoromethanesulfonyl)imide.

[0109] (5) Assembly of the lithium primary battery The electrode group was housed in a cylindrical battery case that also served as the negative electrode terminal. An iron case (outer diameter: 17 mm, height: 45.5 mm) was used for the battery case. Next, a non-aqueous electrolyte was injected into the battery case, and the opening of the battery case was closed using a metal sealing body that also served as the positive electrode terminal. A sealing body equipped with a safety valve was used. The other end of the positive electrode lead was connected to the sealing body, and the other end of the negative electrode lead was connected to the inner bottom surface of the battery case. In this way, battery A1 (lithium primary battery (L)) was manufactured. The battery immediately after assembly was discharged at 1 A for 1 minute, and then aged for 3 days in an atmosphere of 45°C. The manufactured battery A1 was evaluated as follows.

[0110] (1) Over-discharge test 100 batteries A1 were discharged until their remaining capacity was 200 mAh to obtain batteries for the over-discharge test. Then, three of the undischarged batteries were connected in series to one battery A1 and short-circuited with a 10 mΩ fixed resistor. This forced the battery A1 to discharge. At this time, it was checked whether the safety valve on the sealing plate was activated by the forced discharge. More specifically, the above over-discharge test was performed on each of the 100 (N=100) batteries A1, and the number n of batteries in which the safety valve was activated was investigated. The percentage n / N of batteries in which the safety valve was activated was calculated.

[0111] (2) Gas generation amount: Immediately after assembly, battery A1 was discharged to a capacity equivalent to 2.5% of its design capacity, and then stored at 85°C for 1000 hours. The stored lithium primary battery (L) was placed in a Tedlar pack and sealed. A hole was made in the battery can inside the Tedlar pack to collect the gas contained in the battery into the Tedlar pack. The volume V of the collected gas was calculated using the Archimedes method.

[0112] (Batteries A2 to A12) Batteries A2 to A12 were manufactured using the same method and conditions as battery A1, except that at least one of the following was changed: the type of manganese dioxide, the type of compound (C), and the content of compound (C) in the electrolyte. For the manganese dioxide, different manganese dioxide with different ratios Ws / Wm were used as shown in Table 1. For compound (C), the compounds shown in Table 1 were used. The content in Table 1 is the content in the electrolyte.

[0113] (Battery CA1) Battery CA1 was prepared using the same method and conditions as battery A1, except that manganese dioxide with a positive electrode active material ratio Ws / Wm of the values ​​shown in Table 1 was used, and no cyclic imide compound was added to the aqueous solvent.

[0114] (Battery R1) Battery R1 was prepared using the same method and conditions as battery A1, except that manganese dioxide with a positive electrode active material ratio Ws / Wm of the values ​​shown in Table 1 was used, and neither the cyclic imide compound nor compound (C) was added to the non-aqueous solvent.

[0115] Batteries A2-A12, CA1, and R1 were evaluated in the same manner as battery A1. The evaluation results for batteries A1-A12, CA1, and R1 are shown in Table 1. Batteries A1-A12 are lithium primary batteries (L) according to this disclosure, while batteries CA1 and R1 are comparative examples.

[0116] The "Gas Generation Rate" in Table 1 is the ratio of the gas volume V of each battery to the gas volume V of battery R1 in the test described in "(2) Gas Generation Amount" above, with R1's gas volume V being set to 100%. A smaller gas generation rate indicates less gas generation.

[0117]

[0118] Batteries A1 to A12, whose non-aqueous electrolyte contained a cyclic imide compound and a sulfonylimide salt, showed suppressed safety valve activation compared to battery CA1, whose non-aqueous electrolyte did not contain a cyclic imide compound, and battery R1, whose non-aqueous electrolyte did not contain a cyclic imide compound or compound (C). Furthermore, the gas generation rate of batteries A1 to A12 was significantly lower than that of batteries CA1 and R1.

[0119] (Batteries B1 to B12) Batteries B1 to B12 were manufactured using the same method and conditions as battery A1, except that manganese dioxide with a positive electrode active material ratio Ws / Wm of the values ​​shown in Table 2 was used, and the types and content of the cyclic imide compound and compound (C) were changed as shown in Table 2. In Table 2, BOB represents bis(oxalate)boric acid, DFOB represents difluoro(oxalate)boric acid, TFOP represents tetrafluoro(oxalate)phosphate, DFBOP represents difluorobis(oxalate)phosphate, and TOP represents tris(oxalate)phosphate.

[0120] (Battery CB1) Battery CB1 was prepared using the same method and conditions as battery A1, except that manganese dioxide with a positive electrode active material ratio Ws / Wm of the values ​​shown in Table 2 was used, and no cyclic imide compound was added to the non-aqueous solvent.

[0121] Batteries B1 to B12, CB1, and R1 were evaluated in the same manner as battery A1. The evaluation results are shown in Table 2. Batteries B1 to B12 are lithium primary batteries (L) according to this disclosure, and batteries CB1 and R1 are comparative examples. The "gas generation rate" in Table 2 is the ratio of the gas volume V of each battery to the gas volume V of battery R1 in the test described in "(2) Gas generation amount" above, with the gas volume V of battery R1 being set to 100%.

[0122]

[0123] Batteries B1 to B12, whose non-aqueous electrolyte contained a cyclic imide compound and an oxalate salt, showed suppressed safety valve activation compared to battery CB1, whose non-aqueous electrolyte did not contain a cyclic imide compound, and battery R1, whose non-aqueous electrolyte did not contain a cyclic imide compound or compound (C). Furthermore, the gas generation rate of batteries B1 to B12 was significantly lower than that of batteries CB1 and R1.

[0124] (Batteries C1 to C11) Batteries C1 to C11 were prepared using the same method and conditions as for battery A1, except that manganese dioxide with a positive electrode active material ratio Ws / Wm shown in Table 3 was used, and the type and content of the cyclic imide compound and compound (C) were changed as shown in Table 3. In Table 3, HMDI represents hexamethylene diisocyanate, IPDI represents isophorone diisocyanate, and 1,3-H6XDI represents 1,3-bis(isocyanatemethyl)cyclohexane.

[0125] (Battery CC1) Battery CC1 was prepared using the same method and conditions as battery A1, except that manganese dioxide with a positive electrode active material ratio Ws / Wm of the values ​​shown in Table 3 was used, and no cyclic imide compound was added to the non-aqueous solvent.

[0126] Table 3 shows the evaluation results for batteries C1 to C11, CC1, and R1. In Table 3, batteries C1 to C11 are examples, and batteries CC1 and R1 are comparative examples. The "gas generation rate" in Table 3 is the ratio of the gas volume V of each battery to the gas volume V of battery R1 in the "(2) Gas generation amount" test described above, with the gas volume V of battery R1 being set to 100%.

[0127]

[0128] Batteries C1 to C11, whose non-aqueous electrolyte contained cyclic imide compounds and isocyanate compounds, showed suppressed safety valve activation compared to battery CC1, whose non-aqueous electrolyte did not contain cyclic imide compounds, and battery R1, whose non-aqueous electrolyte did not contain cyclic imide compounds or compound (C). Furthermore, the gas generation rates of batteries C1 to C9 and C11 were lower than those of batteries CC1 and R1.

[0129] (Batteries D1 to D5) Batteries D1 to D5 were prepared using the same method and conditions as battery A1, except that manganese dioxide with a positive electrode active material ratio Ws / Wm shown in Table 4 was used, and the types and content of the cyclic imide compound and compound (C) were changed as shown in Table 4. The abbreviation for compound (C) in Table 4 is as described above.

[0130] (Battery CD1) Battery CD1 was prepared using the same method and conditions as battery A1, except that manganese dioxide with a ratio Ws / Wm of manganese dioxide as the positive electrode active material was used, and neither the cyclic imide compound nor compound (C) was added to the non-aqueous solvent.

[0131] (Battery CD2) Battery CD2 was prepared using the same method and conditions as battery A1, except that manganese dioxide with a positive electrode active material ratio Ws / Wm shown in Table 4 was used, and compound (C) was not added to the non-aqueous solvent.

[0132] (Battery CD3) Battery CD3 was prepared using the same method and conditions as battery A1, except that manganese dioxide with a positive electrode active material ratio Ws / Wm of the values ​​shown in Table 4 was used, and no cyclic imide compound was added to the non-aqueous solvent.

[0133] The fabricated batteries D1-D5, CD1-3, and battery R1 were evaluated in the same manner as battery A1. The evaluation results for batteries D1-D5, CD1-3, and battery R1 are shown in Table 4. Batteries D1-D5 are lithium primary batteries (L) according to this disclosure, and batteries CD1-3 and R1 are comparative examples.

[0134] The "Gas Generation Rate" in Table 4 is the ratio of the gas volume V of each battery to the gas volume V of battery R1 in the test described in "(2) Gas Generation Amount" above, with R1's gas volume V being set to 100%. A smaller gas generation rate indicates less gas generation.

[0135]

[0136] Batteries D1 to D5, in which the non-aqueous electrolyte contains at least two compounds selected from the group consisting of cyclic imide compounds and compound (C), showed suppressed safety valve operation compared to batteries CD1 and R1, which do not contain cyclic imide compounds and compound (C) in the non-aqueous electrolyte, battery CD2, which does not contain compound (C) in the non-aqueous electrolyte, and battery CD3, which does not contain cyclic imide compounds in the non-aqueous electrolyte. Furthermore, the gas generation rate of batteries D1 to D4 was lower than that of batteries CD1 to CD3 and R1.

[0137] From these findings, it can be seen that a synergistic effect is exhibited when at least one compound selected from the group consisting of compound (C) is used in combination with a cyclic imide compound.

[0138] This disclosure can be used in lithium primary batteries (L).

[0139] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0140] 1. Positive electrode 1a. Positive electrode current collector 2. Negative electrode 3. Separator 4. Positive electrode lead 5. Negative electrode lead 6. Upper insulating plate 7. Lower insulating plate 8. Sealing plate 9. Battery case 10. Lithium primary battery

Claims

1. A lithium primary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode comprises manganese dioxide, the negative electrode comprises at least one of metallic lithium and a lithium alloy, and the non-aqueous electrolyte comprises at least one compound selected from the group consisting of oxalate salts, sulfonylimide salts, and isocyanate compounds, and a cyclic imide compound.

2. The lithium primary battery according to claim 1, wherein the cyclic imide compound comprises at least one of phthalimide and N-substituted phthalimide.

3. The lithium primary battery according to claim 2, wherein the N-substituted phthalimide comprises at least one selected from the group consisting of N-hydroxyphthalimide, N-(cyclohexylthio)phthalimide, and N-(phenylthio)phthalimide.

4. The lithium primary battery according to claim 1, wherein the oxalate salt comprises at least one of an oxalate boric acid complex component and an oxalate phosphate complex component, and each of the oxalate boric acid complex component and the oxalate phosphate complex component comprises at least one cation of a lithium ion and a manganese ion.

5. The lithium primary battery according to claim 4, wherein the oxalate borate complex component comprises at least one of a bis(oxalate)borate complex component and a difluoro(oxalate)borate complex component, and the oxalate phosphate complex component comprises at least one selected from the group consisting of a tetrafluoro(oxalate) phosphate complex component, a difluorobis(oxalate) phosphate complex component, and a tris(oxalate) phosphate complex component.

6. The lithium primary battery according to claim 1, wherein the sulfonylimid salt comprises at least one cation of a lithium ion or a manganese ion and at least one anion of a bis(fluorosulfonyl)imide anion and a bis(trifluoromethanesulfonyl)imide anion.

7. The lithium primary battery according to claim 1, wherein the isocyanate compound comprises a diisocyanate compound having two or more isocyanate groups.

8. The lithium primary battery according to claim 7, wherein the diisocyanate compound comprises at least one selected from the group consisting of hexamethylene diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, and isophorone diisocyanate.

9. The lithium primary battery according to any one of claims 1 to 8, wherein the manganese dioxide contains a sulfate, and the ratio Ws / Wm of the mass of sulfur atoms in the manganese dioxide to the mass Wm of manganese atoms in the manganese dioxide is 2.0 / 100 or less.

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