Lithium primary battery
阅读说明：本技术 锂一次电池 (Lithium primary battery ) 是由 中井美有纪 中堤贵之 福井厚史 于 2019-11-27 设计创作，主要内容包括：锂一次电池,其具备电池外壳、收纳在电池外壳内的电极组和非水电解质,非水电解质包含非水溶剂、溶质和添加剂,电极组具备正极、负极和夹设在这些之间的分隔件,负极具有金属锂或锂合金的箔,且具备具有长度方向和短边方向的形状,在负极的至少一个主面上沿长度方向贴附有长条的带,带具备树脂基材和粘合层,带的宽度为0.5mm以上且3mm以下,添加剂包含：具备具有磷原子和与磷原子键合的n个氧原子的PO-n结构、n＝3或4的磷化合物。(A lithium primary battery comprising a battery case, an electrode group housed in the battery case, and a nonaqueous electrolyte, wherein the nonaqueous electrolyte contains a nonaqueous solvent, a solute, and an additive, the electrode group comprises a positive electrode, a negative electrode, and a separator interposed therebetween, the negative electrode comprises a foil of metallic lithium or a lithium alloy, and has a shape having a longitudinal direction and a short-side direction, a long tape is attached to at least one main surface of the negative electrode in the longitudinal direction, the tape comprises a resin base material and an adhesive layer, and the tape has a width of 0.5mm or more and 3mm or less, and the additive comprises: PO having phosphorus atom and n oxygen atoms bonded to phosphorus atom n Structure, n-3 or 4.)
1. A lithium primary battery is provided with: a battery case, an electrode group and a non-aqueous electrolyte housed in the battery case,
the non-aqueous electrolyte comprises a non-aqueous solvent, a solute and an additive,
the electrode group includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
the negative electrode has a foil of metallic lithium or lithium alloy, has a shape having a longitudinal direction and a width direction, and has a long tape adhered to at least one main surface of the negative electrode along the longitudinal direction,
the tape comprises a resin base material and an adhesive layer,
the width of the belt is more than 0.5mm and less than 3mm,
the additive comprises: PO having phosphorus atom and n oxygen atoms bonded to the phosphorus atomnStructure, n-3 or 4.
2. The lithium primary cell of claim 1, wherein the phosphorus compound further comprises a silicon atom bonded to at least one of the oxygens.
3. The lithium primary battery according to claim 1, wherein the phosphorus compound is at least one selected from the group consisting of phosphoric acid, phosphorous acid, a phosphate ester, a phosphite ester, a silyl phosphate ester, and a silyl phosphite ester.
4. The lithium primary battery according to claim 3,
the phosphorus compound is at least one selected from the group consisting of a1 st compound represented by formula (1), a 2 nd compound represented by formula (2), a 3 rd compound represented by formula (3), and a 4 th compound represented by formula (4),
formula (1):
formula (2):
formula (3):
formula (4):
in the formulas (1) to (4), R1 to R24 are each independently a hydrogen atom, a saturated aliphatic group, an unsaturated aliphatic group, or an aromatic group, and at least 1 hydrogen atom in each of the saturated aliphatic group, the unsaturated aliphatic group, and the aromatic group is optionally substituted with a fluorine atom.
5. The lithium primary battery according to claim 4, wherein all of R1 to R24 in the formulae (1) to (4) are the saturated aliphatic group.
6. The lithium primary battery according to claim 4 or 5,
in the formula (1), R1-R3 are the same,
in the formula (2), R4-R6 are all the same groups,
in the formula (3), R7 to R15 are all the same groups, and/or
In the formula (4), all of R16 to R24 are the same groups.
7. The lithium primary battery according to any one of claims 4 to 6, wherein all of R1 to R24 in the formulae (1) to (4) are methyl groups.
8. According to claimThe lithium primary battery according to 1 or 2, wherein the phosphorus compound is tris (trimethylsilyl) phosphate (O ═ P (O-Si (CH))3)3)3) And/or tris (trimethylsilyl) phosphite (P (O-Si (CH))3)3)3)。
9. The lithium primary battery according to any one of claims 1 to 8, wherein a content of the phosphorus compound in the nonaqueous electrolyte is 0.002mol/L or more and 1.0mol/L or less.
10. The lithium primary battery according to any one of claims 1 to 9, wherein the resin base material of the tape comprises a polyolefin.
11. The lithium primary battery according to any one of claims 1 to 10, wherein the adhesive layer of the tape contains at least one selected from the group consisting of a rubber component, a silicone component, and an acrylic resin component.
12. The lithium primary battery according to any one of claims 1 to 11, wherein the area S of the striptArea S relative to the negative electrodenThe proportion of (A): st/SnX 100 is 0.5% or more and 4% or less.
13. The lithium primary battery according to any one of claims 1 to 12, wherein the nonaqueous electrolyte contains at least one solvent having a viscosity of 1 mPa-s or less at 25 ℃.
14. The lithium primary cell of claim 13, wherein the solvent comprises dimethoxyethane.
15. The lithium primary battery according to any one of claims 1 to 14, wherein the non-aqueous electrolyte comprises phthalimide.
Technical Field
The present invention relates to a lithium primary battery.
Background
In recent years, the range of applications of electronic devices using a lithium primary battery as a power source has been expanded, and the lithium primary battery tends to be used for driving the devices for a long period of time. In a lithium primary battery, a foil of metallic lithium or lithium alloy (hereinafter referred to as a negative electrode foil) is used for a negative electrode. The negative electrode foil has both functions of a negative electrode active material and a negative electrode current collector. When lithium in the negative electrode foil is consumed by discharge, the function as a current collector gradually decreases. Therefore, the actual battery capacity tends to be smaller than the design capacity.
Patent document 1 proposes a lithium primary battery in which manganese dioxide is used for the positive electrode and a lithium negative electrode is used for the negative electrode, wherein a long and thin tape is attached to the lithium negative electrode in the longitudinal direction. This suppresses the dissolution reaction of the lithium negative electrode that is carried over during discharge, and the function as a current collector is maintained.
Patent document 2 proposes that an electrolyte solution contains a silyl compound having a specific structure in order to maintain the cycle characteristics of a lithium ion secondary battery and reduce the amount of gas generated.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 61-281466
Patent document 2: japanese patent laid-open publication No. 2016-189327
Disclosure of Invention
In the case of the lithium primary battery disclosed in patent document 1, the electrolyte solution easily enters the gap of the binder of the tape. The electrolyte solution penetrating into the gap of the adhesive reduces the adhesive force of the adhesive, and causes the tape to float due to peeling. The floating band cannot sufficiently suppress the dissolution reaction of the lithium negative electrode, and the function as a current collector of the lithium negative electrode is impaired at the end of discharge, making it difficult to obtain a designed capacity.
According to the inventionOne aspect of the present invention relates to a lithium primary battery including a battery case, an electrode group housed in the battery case, and a nonaqueous electrolyte, the nonaqueous electrolyte including a nonaqueous solvent, a solute, and an additive, the electrode group including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, the negative electrode including a foil of metal lithium or a lithium alloy and having a shape having a longitudinal direction and a short-side direction, at least one main surface of the negative electrode having a long tape attached thereto in the longitudinal direction, the tape including a resin base material and an adhesive layer, the tape having a width of 0.5mm or more and 3mm or less, the additive including: PO having phosphorus atom and n oxygen atoms bonded to phosphorus atomnStructure, n-3 or 4.
The present invention can provide a lithium primary battery that can maintain the function of a current collector as a negative electrode even at the end of discharge.
Drawings
Fig. 1 is a diagram showing the structure of a negative electrode of a lithium primary battery according to an embodiment of the present invention.
Fig. 2 is a front view showing a part of a lithium primary battery according to an embodiment of the present invention in section.
Detailed Description
A lithium primary battery of the present invention includes a battery case, an electrode group housed in the battery case, and a nonaqueous electrolyte. The nonaqueous electrolyte includes a nonaqueous solvent, a solute, and an additive. The electrode group is provided with: the battery includes a positive electrode containing manganese dioxide, a negative electrode containing metallic lithium or a metallic lithium alloy, and a separator interposed between the positive electrode and the negative electrode. The positive electrode and the negative electrode may be wound with a separator interposed therebetween.
The negative electrode has a foil of metallic lithium or lithium alloy, and has a shape having a longitudinal direction and a short-side direction. A long tape is attached to at least one main surface of the negative electrode in the longitudinal direction. The tape comprises a resin base material and an adhesive layer. In the region of the negative electrode covered with the tape, the dissolution reaction of the negative electrode at the time of discharge is suppressed, and therefore, even at the end of discharge, breakage or the like of the negative electrode hardly occurs, and the function as a current collector is maintained.
However, if the width of the band is too large, the dissolution reaction of lithium during discharge is suppressed, and a sufficient capacity may not be exhibited. In order to obtain a high-capacity lithium primary battery, it is required to limit the width of the ribbon to 3mm or less. On the other hand, if the width of the band is less than 0.5mm, it is difficult to maintain the function as a current collector of the negative electrode. Therefore, the width of the belt is limited to 0.5mm or more and 3mm or less.
The nonaqueous electrolyte contains additives including: PO having phosphorus atom and n oxygen atoms bonded to phosphorus atomnStructure, n-3 or 4. That is, the phosphorus compound may be an oxa compound having a P — O bond or an oxo compound having a P ═ O bond. The phosphorus compound may further comprise: silicon atoms bonded to at least 1 of the oxygen bonded to the phosphorus atoms (i.e., P-O-Si bonds).
The above-mentioned phosphorus compound was confirmed to have an effect of suppressing the penetration of the nonaqueous electrolyte into the gap of the adhesive layer of the tape. The detailed mechanism is not clear, and it is presumed that the phosphorus compound reacts or interacts with a component contained in the adhesive layer of the tape to improve the adhesion. Such reactions or interactions are thought to be associated with the cleavage of P-O bonds, P-O-Si bonds, and the like. This is considered to suppress the formation of a gap due to a decrease in the adhesion between the negative electrode and the adhesive layer, and to suppress the floating of the resin base material of the tape. Therefore, the effect of suppressing the discharge depletion of the area of the negative electrode covered with the band can be sustained for a long time.
As the phosphorus compound, for example, at least 1 selected from the group consisting of phosphoric acid, phosphorous acid, phosphoric acid ester, phosphorous acid ester, silyl phosphate ester and silyl phosphite ester can be used. Among them, at least 1 selected from the group consisting of silyl phosphate and silyl phosphite has a significant effect of suppressing a decrease in adhesion between the negative electrode and the adhesive layer. In the nonaqueous electrolyte, phosphoric acid, phosphorous acid, or the like, P — OH groups can be dissociated to form P — O "anions.
At least 1 kind selected from the group consisting of the following 1 st to 4 th compounds can be used as the phosphorus compound.
The compound of formula 1 is represented by formula (1),
formula (1)
The compound of formula 2 is represented by formula (2),
formula (2)
The compound of formula 3 is represented by formula (3),
formula (3)
The compound of formula 4 is represented by formula (4),
formula (4)
In the formulae (1) to (4), R1 to R24 may be each independently a hydrogen atom, a saturated aliphatic group, an unsaturated aliphatic group, or an aromatic group. In addition, from the viewpoint of oxidation resistance, at least 1 hydrogen atom is optionally substituted by a fluorine atom for each of the saturated aliphatic group, the unsaturated aliphatic group and the aromatic group. In addition, 2 groups may be bonded to form a ring. R1-R6 are all bonded with oxygen atoms, and R7-R24 are all bonded with silicon atoms.
The saturated aliphatic group is preferably an alkyl group, and among them, an alkyl group having preferably from C1 to C6 may be an alkyl group having from C1 to C3. At least 1 hydrogen atom in the alkyl group is optionally substituted with a fluorine atom, and may also be a perfluoroalkyl group. Specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, fluoromethyl and fluoroethyl. The saturated aliphatic group is preferably an alkenyl group, and examples thereof include a vinyl group, an allyl group, and a 1-methylvinyl group. Examples of the aromatic group include benzyl, phenyl, and fluorophenyl.
Among them, saturated aliphatic groups are preferable, and methyl group, ethyl group, and the like are particularly preferable. That is, all of R1 to R3 in formula (1) may be saturated aliphatic groups, all of R4 to R6 in formula (2) may be saturated aliphatic groups, all of R7 to R15 in formula (3) may be saturated aliphatic groups, and all of R16 to R24 in formula (4) may be saturated aliphatic groups.
R1 to R3 in formula (1) may be all the same groups, R4 to R6 in formula (2) may be all the same groups, R7 to R15 in formula (3) may be all the same groups, and R16 to R24 in formula (4) may be all the same groups. For example, all of R1 to R3 in formula (1) may be methyl groups, all of R4 to R6 in formula (2) may be methyl groups, all of R7 to R15 in formula (3) may be methyl groups, and all of R16 to R24 in formula (4) may be methyl groups.
Specific examples of the compound 1 include phosphoric acid, trimethyl phosphate, triethyl phosphate, tris (2,2, 2-trifluoroethyl) phosphate, and the like. Specific examples of the compound 2 include phosphorous acid, trimethyl phosphite, triethyl phosphite, tris (2,2, 2-trifluoroethyl) phosphite, and the like. Specific examples of the compound 3 include tris (trimethylsilyl) phosphate and tris (triethylsilyl) phosphate. Specific examples of the compound 4 include tris (trimethylsilyl) phosphite and tris (triethylsilyl) phosphite. Among them, tris (trimethylsilyl) phosphate (O ═ P (O-Si (CH)) is preferable from the viewpoint of having a reactive S-O-Si bond rich3)3)3) (hereinafter also referred to as TTSPa. ) And tris (trimethylsilyl) phosphite (P (O-Si (CH))3)3)3) (hereinafter also referred to as TTSPi. ).
The content of the phosphorus compound in the nonaqueous electrolyte may be, for example, 0.002mol/L or more, and may be 0.01mol/L or more, and may be 0.1mol/L or more. In addition, the content of the phosphorus compound in the nonaqueous electrolyte is preferably 1.0mol/L or less, may be 0.5mol/L or less, and may be 0.3mol/L or less, from the viewpoint of satisfactory solubility of the phosphorus compound in the nonaqueous electrolyte.
Next, a tape including a resin base material and an adhesive layer will be described.
Examples of the resin base material include fluororesins, polyimides, polyolefins such as polyphenylene sulfide, polyether sulfone, polyethylene, and polypropylene, and polyethylene terephthalate. Among them, polyolefin is preferable, and polypropylene is more preferable.
The adhesive layer contains, for example, at least 1 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, or the like can be used. Examples of the synthetic rubber include butyl rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber, polyisobutylene rubber, acrylonitrile-butadiene rubber, styrene-isoprene block copolymer, styrene-butadiene block copolymer, and styrene-ethylene-butadiene block copolymer. As the silicone component, an organic compound having a polysiloxane structure, a silicone polymer, or the like can be used. Examples of the silicone-based polymer include peroxide-curable silicones and addition-reaction silicones. As the acrylic resin component, a polymer containing an acrylic monomer such as acrylic acid, methacrylic acid, acrylic ester, methacrylic ester and the like 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, 2-ethylhexyl methacrylate and the like. The adhesive layer may contain a crosslinking agent, a plasticizer, and an adhesion imparting agent.
The width of the tape may be 0.5mm or more, and from the viewpoint of appropriately suppressing discharge consumption of the negative electrode covered with the tape, it is preferably 1mm or more, and more preferably 1.5mm or more. The width of the band may be 3mm or less, and is preferably 2.5mm or less, and more preferably 2mm or less, from the viewpoint of sufficiently suppressing a decrease in the discharge capacity (output capacity) of the battery. The tape may be attached to one side or both sides of the negative electrode.
As one embodiment of the present invention, the area S of the belttArea S relative to negative electrodenThe proportion of (A): st/SnThe value of X100 is preferably 0.5% or more and 4% or less. Here, the area S of the negative electrodenRefers to the width W of the negative electrodenAnd length LnProduct of (b), by Sn＝Wn×LnAnd (4) showing. In addition, the area S of the belttIs the width W of the belttAnd length LtProduct of (b), by St＝Wt×LtAnd (4) showing. St/SnWhen x 100 is 0.5% or more, the effect of suppressing discharge depletion of the portion of the negative electrode covered with the tape becomes remarkable. In addition, St/SnWhen x 100 is 4% or less, the effect of suppressing a decrease in the discharge capacity (output capacity) of the battery becomes remarkable.
As one embodiment of the present invention, the nonaqueous electrolyte may contain at least 1 kind of solvent having a viscosity of 1mPa · s or less. This improves the discharge characteristics of the lithium primary battery. As the solvent, dimethoxyethane is preferable, for example. The volume ratio of dimethoxyethane in the solvent is preferably 5 to 80%.
The following description will be given of specific embodiments of the present invention, and the following embodiments are only a part of specific examples of the present invention and do not limit the technical scope of the present invention.
(Positive electrode)
The positive electrode active material contains at least 1 selected from the group consisting of manganese oxide and graphite fluoride. The positive electrode active material may be manganese dioxide alone, or may be used in combination with manganese oxide or graphite fluoride. The battery including manganese dioxide generates a relatively high voltage and is excellent in pulse discharge characteristics. As manganese dioxide, electrolytic manganese dioxide neutralized with ammonium, sodium, lithium, or the like is preferably used. More preferably, the fired electrolytic manganese dioxide is used. Specifically, it is preferable to electrolyze manganese dioxide in air or oxygen at 300 to 450 ℃ for 6 to 12 hoursLeft and right baking. The oxidation number of manganese contained in manganese dioxide is typically 4, but is not limited to 4, and appropriate increase and decrease are permissible. Manganese dioxide which can be used includes MnO and Mn3O4、Mn2O3、MnO2、MnO3Etc., typically, manganese dioxide is used as the main component. Manganese dioxide can be in a mixed crystal state comprising a plurality of crystalline states. When unfired electrolytic manganese dioxide is used, manganese dioxide having a high crystallinity and a low specific surface area is preferable depending on the conditions during electrolytic synthesis. In addition, if the amount is small, chemical manganese dioxide, or the like may be added.
The positive electrode is provided with: a positive electrode mixture layer containing a positive electrode active material, and a positive electrode collector to which the positive electrode mixture layer is attached. The positive electrode mixture layer is formed, for example, on one surface or both surfaces of a sheet-shaped positive electrode collector (for example, a metal mesh made of stainless steel, a net, a punched metal, or the like) so as to embed the positive electrode collector. As the positive electrode current collector, for example, stainless steel, aluminum, titanium, or the like can be used. The positive electrode mixture layer may contain a resin material such as a fluororesin as a binder in addition to the positive electrode active material. The positive electrode mixture layer may contain a conductive material such as a carbon material as a conductive agent.
As the binder, for example, fluororesin, rubber particles, acrylic resin, or the like can be used. As the fluororesin, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride can be used. As the rubber particles, Styrene Butadiene Rubber (SBR) and modified acrylonitrile rubber can be used. Examples of the acrylic resin include ethylene-acrylic acid copolymers. The amount of the binder contained in the positive electrode mixture is more preferably 10 to 25% by mass, still more preferably 12 to 23% by mass, and still more preferably 15 to 20% by mass. One kind of the binder may be used alone, or two or more kinds may be used in combination.
As the conductive agent, for example, natural graphite, artificial graphite, carbon black, carbon fiber, and the like can be used. Examples of the carbon black include acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. These may be used alone or in combination of two or more. The amount of the conductive agent contained in the positive electrode mixture is, for example, 1 to 30 parts by mass per 100 parts by mass of the positive electrode active material.
The positive electrode is produced, for example, in the following manner.
First, manganese dioxide, a conductive agent, and a binder are mixed to prepare a positive electrode mixture. The method of mixing the manganese dioxide, the conductive agent and the binder is not particularly limited, and for example, a mixture obtained by mixing the manganese dioxide and the conductive agent in a dry or wet manner is filled in a stainless steel expanded metal of the current collector, pressed by a roll, and then cut into a predetermined size to obtain the positive electrode.
(cathode)
Lithium metal, Li-Al, Li-Sn, Li-NiSi, Li-Pb, and other lithium alloys can be used for the negative electrode. These can be used as a negative electrode plate directly in a state of being formed into a sheet shape. Among the lithium alloys, the Li-Al alloy is preferable. From the viewpoint of ensuring the stabilization of the discharge capacity and the internal resistance, the content of the metal element other than lithium contained in the lithium alloy is preferably 0.05 to 15 mass%. The lithium metal or lithium alloy is formed into any shape and thickness according to the shape, size, standard performance, and the like of the lithium primary battery.
Fig. 1 shows a configuration of a negative electrode of a lithium primary battery according to an embodiment of the present invention. The negative electrode 21 has a strip shape having a longitudinal direction and a short-side direction. A long tape 22 is attached to one main surface of the negative electrode 21 in the longitudinal direction. The tape 22 includes a resin base material and an adhesive layer, and the width of the tape 22 is 0.5mm to 3 mm. A negative electrode lead 23 for discharging current is attached to one end of the negative electrode 21 in the longitudinal direction. A lead protective tape 24 is attached to one end portion in the longitudinal direction of the negative electrode 21 to which the negative electrode lead 23 is attached. In fig. 1, the tape 22 is shown in a state of being attached to the back surface of the negative electrode 21.
(spacer)
As the separator, a porous sheet made of an insulating material having resistance to the internal environment of the lithium primary battery may be used. Specifically, a nonwoven fabric made of a synthetic resin, a microporous membrane made of a synthetic resin, and the like can be given. Examples of the synthetic resin used for the nonwoven fabric include polypropylene, polyphenylene sulfide, and polybutylene terephthalate. Among these, polyphenylene sulfide and polybutylene terephthalate are excellent in high temperature resistance, solvent resistance and liquid retention. Examples of the synthetic resin used for the microporous membrane include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers. The microporous membrane may contain inorganic particles as necessary. The thickness of the separator is preferably 5 μm or more and 100 μm or less, for example.
(non-aqueous electrolyte)
As the nonaqueous electrolyte, a solution obtained by dissolving a lithium salt as a solute in a nonaqueous solvent can be used. Additives may be contained as required. As the nonaqueous solvent, an organic solvent generally used in a nonaqueous electrolyte of a lithium primary battery, for example, dimethyl ether, γ -butyrolactone, propylene carbonate, ethylene carbonate, 1, 2-dimethoxyethane, or the like can be used. These may be used alone or in combination of two or more. From the viewpoint of improving the discharge characteristics of the lithium primary battery, the nonaqueous solvent preferably contains a cyclic carbonate having a high boiling point and a chain ether having a low viscosity even at low temperatures. The cyclic carbonate preferably contains at least 1 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 1mPa · s or less at 25 ℃, and particularly preferably contains Dimethoxyethane (DME). The viscosity of the nonaqueous solvent was determined by measuring the shear rate 10000(1/s) at 25 ℃ using a micro sample viscometer m-VROC manufactured by LEOSENSE.
The solute may comprise LiCF3SO3、LiClO4、LiBF4、LiPF6、LiRaSO3(Ra is C1-4 fluorinated alkyl group), LiFSO3、LiN(SO2Rb)(SO2Rc) (Rb and Rc are each independently a fluorinated alkyl group having 1 to 4 carbon atoms), LiN (FSO)2)2、LiPO2F2And the like lithium salts. These may be used alone or in combination of two or more. The total concentration of lithium salts contained in the nonaqueous electrolyte is preferably 0.2 to 2.0mol/L, and may be 0.3 to 1.5mol/L, and may be 0.4 to 1.2 mol/L.
The nonaqueous electrolyte may contain, in addition to the above-described materials, a 2 nd additive such as phthalimide, propane sultone, and vinylene carbonate. Part of the hydrogen groups of the 2 nd additive may be substituted with hydroxyl groups, halogen groups, alkyl groups, etc. The 2 nd additive may be used alone or in combination of two or more. From the viewpoint of improving the stability of the battery, at least phthalimide is preferably used. The nonaqueous electrolyte preferably contains the 2 nd additive in a total concentration of 0.003 to 5mol/L, more preferably 0.003 to 3 mol/L.
(cylindrical Battery)
Fig. 2 is a front view of a lithium primary battery according to an embodiment of the present invention, partially cut away. In a lithium primary battery, an electrode group 10 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 nonaqueous electrolyte (not shown). A sealing plate 8 is attached to an opening of the battery case 9. The sealing plate 8 is connected to a positive electrode lead 4 connected to the current collector 1a of the positive electrode 1. The negative electrode lead 5 to which the negative electrode 2 is connected to the case 9. In addition, an upper insulating plate 6 and a lower insulating plate 7 are disposed on the upper and lower portions of the electrode group 10, respectively, in order to prevent internal short circuits.
The present invention will be described in more detail below with reference to examples. However, the following examples do not limit the present invention. In this example, a cylindrical lithium primary battery having a structure as shown in fig. 2 was produced.
(examples 1 to 8 and comparative examples 1 to 15)
(1) Positive electrode
A positive electrode mixture was prepared by mixing 5 parts by mass of ketjen black as a conductive agent and 5 parts by mass of polytetrafluoroethylene as a binder with respect to 100 parts by mass of manganese dioxide as a positive electrode active material.
Next, the positive electrode mixture was passed through a pair of rotating rolls rotating at a constant speed together with a positive electrode current collector made of a metal lath made of ferrite stainless steel (SUS430) and having a thickness of 0.1mm, the positive electrode mixture was filled in the pores of the metal lath, dried, rolled by a roll press until the thickness became 0.4mm, and cut into predetermined dimensions (width 45mm, length 165mm) to obtain a positive electrode plate. The positive electrode mixture is peeled off from a part of the positive electrode plate to expose the positive electrode current collector, and the positive electrode lead is welded to the exposed portion. The upper part of the positive electrode lead is provided with a lead protection tape for the purpose of preventing short circuit.
(2) Negative electrode
A metal lithium plate having a thickness of 0.15mm was cut into predetermined dimensions (width 42mm, length 190mm) and used as a negative electrode plate. The negative plate is connected with a negative lead. The upper part of the negative electrode lead is also provided with a lead protective tape for the purpose of preventing short circuit. A long tape is attached to one or both surfaces of the negative electrode in the longitudinal direction. The resin base material of the long tape was made of polypropylene having a thickness of 40 μm, the main component of the adhesive layer was rubber, and the width of the tape was set to the length shown in table 1.
(3) Electrode group
The positive and negative electrode plates were wound in a spiral shape with a microporous film of polypropylene 25 μm thick as a separator interposed between the positive and negative electrode plates to form a columnar electrode group.
(4) Non-aqueous electrolyte
And (2) mixing the components in a volume ratio of 4: 2: and 4, mixing Propylene Carbonate (PC), Ethylene Carbonate (EC) and 1, 2-Dimethoxyethane (DME) to obtain the non-aqueous solvent. Using the nonaqueous solvent, LiCF was prepared to be contained at a ratio of 0.5mol/L3SO3A non-aqueous electrolyte as a solute.
Further, as an additive in the prepared nonaqueous electrolyte, a phosphorus compound shown in table 1, namely tris (trimethylsilyl) phosphate (P ═ O (O — Si (CH)) was added with the exception of a part of the comparison3)3)3) (TTSPa) or tris (trimethylsilyl) phosphite (P (O-Si (CH))3)3)3) (TTSPi). The content of the phosphorus compound in the nonaqueous electrolyte was set to 0.2 mol/L.
(5) Assembly of cylindrical battery
The electrode assembly thus obtained was inserted into a bottomed cylindrical battery case with an annular lower insulating plate disposed at the bottom thereof. Then, a positive electrode lead connected to the positive electrode current collector of the positive electrode plate is connected to the inner surface of the sealing plate, and a negative electrode lead connected to the negative electrode plate is connected to the inner bottom surface of the battery case.
Next, the nonaqueous electrolyte was injected into the battery case, the upper insulating plate was disposed on the electrode group, and the opening of the battery case was sealed with a sealing plate, thereby completing a cylindrical lithium primary battery having a diameter of 14mm and a height of 50mm as shown in fig. 2. Batteries A1 to A8 correspond to examples 1 to 8, respectively, and batteries B1 to B15 correspond to comparative examples 1 to 15, respectively.
[ evaluation ]
For each of the batteries a1 to A8 and the batteries B1 to B15, 10 of the batteries were subjected to constant resistance discharge (1k Ω) at room temperature, and the discharge capacity up to 2V was measured to obtain the increase/decrease ratio of the actual discharge capacity to the design capacity, and the average value of the 10 batteries was calculated. The results are shown in Table 1. When some of the 10 batteries had run out of lithium as described below, the average value of the remaining batteries was calculated. The occurrence of lithium depletion described below in all 10 batteries is denoted as ND.
The battery after the discharge was decomposed to confirm the presence or absence of breakage of the negative electrode. The notation "lithium depletion" in table 1 is as follows.
O: lithium depletion did not occur in all 10
And (delta): lithium depletion occurred in a part of 10
X: lithium depletion occurred in all 10 of the cells
[ Table 1]
From table 1, it can be seen that: when the tape is disposed on one surface of the negative electrode and the tape width is set to 0.5mm to 3mm, lithium depletion does not occur when the additive is used in a nonaqueous electrolyte, and the capacity does not decrease from the designed value. On the other hand, in the battery of the comparative example, the capacity with respect to the design value was almost decreased.
When the tape is disposed on both sides of the negative electrode, the function of the negative electrode as a current collector is easily maintained. However, when the tape attachment position is deviated, it is considered that the area for suppressing the negative electrode reaction increases, and the output capacity with respect to the design value decreases. Further, when the electrode plate is wound, elongation of the electrode plate occurs, but when the tape is arranged on both surfaces, it is difficult to relax the elongation stress as compared with the case where the tape is arranged on one surface. Therefore, it is considered that the negative electrode and the tape are likely to be peeled off during winding. From the above, it is considered that the tape is more preferably disposed only on one side of the negative electrode.
Next, the peel strength between the negative electrode and the belt after immersion in the nonaqueous electrolyte was evaluated.
Reference examples 1 to 15
A metal lithium plate having a thickness of 0.15mm was cut into predetermined dimensions (width 42mm, length 195mm), and a long tape was attached in the longitudinal direction to prepare a test piece. The resin base material of the long tape was made of polypropylene having a thickness of 40 μm, the main components of the adhesive layer were the components shown in Table 2, and the width of the tape was 10 mm.
And (2) mixing the components in a volume ratio of 4: 2: and 4, mixing Propylene Carbonate (PC), Ethylene Carbonate (EC) and Dimethoxyethane (DME) to obtain the non-aqueous solvent. Using the non-aqueous solvent, LiCF was contained at a ratio of 0.5mol/L3SO3Further, as a solute, nonaqueous electrolytes C1 to C15 containing 0.2mol/L of additives shown in table 2, i.e., TTSPa, TTSPi, PS (propane sultone), or VC (vinylene carbonate), were prepared, except for a part thereof. Nonaqueous electrolytes C1 to C15 correspond to reference examples 1 to 15, respectively.
The peel strength between the lithium metal plate and the tape of the test piece was measured. The peel strength was measured by a 90-degree peel test according to JIS K6854, using 10 test pieces immersed in 25 ℃ nonaqueous electrolytes C1 to C15 for 1 hour, and 10 test pieces not immersed in nonaqueous electrolytes. The average peel strength of the test piece not immersed in the nonaqueous electrolyte was F1, and the average peel strength of the test piece immersed in the nonaqueous electrolyte was F2, and the change rate of the peel strength from F1 to F2 was determined. The results are shown in Table 2.
[ Table 2]
Non-aqueous electrolyte
Adhesive agent
Additive agent
Peeling Strength Change Rate (%)
C1
Rubber composition
TTSPa
0
C2
Silicone
TTSPa
1
C3
Acrylic resin
TTSPa
0
C4
Rubber composition
TTSPi
0
C5
Silicone
TTSPi
1
C6
Acrylic resin
TTSPi
1
C7
Rubber composition
Is free of
-40
C8
Silicone
Is free of
-38
C9
Acrylic resin
Is free of
-24
C10
Rubber composition
PS
-33
C11
Silicone
PS
-30
C12
Acrylic resin
PS
-28
C13
Rubber composition
VC
-37
C14
Silicone
VC
-38
C15
Acrylic resin
VC
-30
As can be seen from table 2, when a phosphorus compound is used as an additive in the nonaqueous electrolyte, the peel strength between the negative electrode and the tape does not change regardless of the material of the tape binder. On the other hand, when no additive is included, the peel strength is significantly reduced when a cyclic sultone derivative (for example, PS) or a cyclic carbonate (for example, VC) which has been known as an additive for improving high-temperature storage characteristics in a nonaqueous electrolyte battery is used as an additive.
Industrial applicability
The lithium primary battery of the present invention is suitable for use in driving a device for a long period of time. The lithium primary battery of the present invention is applicable to, for example, a meter for gas or tap water.
Description of the reference numerals
1 positive electrode
1a Positive electrode Current collector
2. 21 negative electrode
3 separating element
4 positive electrode lead
5. 23 cathode lead
6 upper insulating plate
7 lower insulating plate
8 sealing plate
9 Battery case
10 electrode group
22 strap
24 lead protective tape