Nitrile rubber, binder composition for positive electrode of energy storage device and application of binder composition

Abstract

The invention provides nitrile rubber, a binder composition for a positive electrode of an energy storage device and application of the binder composition. The nitrile rubber contains 20 to 80 wt% of an alpha, beta-ethylenically unsaturated nitrile monomer unit, 20 to 80 wt% of a conjugated diene monomer unit, and 0 to 30 wt% of a cationic monomer unit, and the iodine value of the nitrile rubber is 55 mg / 100 mg or more and 150 mg / 100 mg or less. The binder composition contains the nitrile rubber, and the content of the nitrile rubber is 70 wt% or above based on 100 wt% of the solid content of the binder composition. When the binder composition is used for the energy storage device, the prepared positive electrode has excellent flexibility and penetration resistance, and the energy storage device can exert excellent high-temperature storage characteristics.

Description

Technical Field

[0001] This application belongs to the technical field of energy storage, and particularly relates to a nitrile rubber, a binder composition for the positive electrode of an energy storage device, and its application. Background Art

[0002] With the development of energy storage technology, the requirements for the energy density of batteries are also getting higher and higher. In addition to developing high-energy-density electrode material systems, reducing the proportion of inactive materials by coating ultra-thick electrode sheets or reducing the amount of binder used is also one of the solutions. Therefore, more stringent requirements are put forward for the binder polyvinylidene fluoride (PVDF) system mainly used in current electrode materials, requiring further improvement of its binding force and increasing the softness of the electrode sheet.

[0003] To meet this requirement, it is necessary to further copolymerize and modify PVDF. However, the copolymerization modification of vinylidene fluoride (VDF) is difficult. At the same time, due to the problem of the reactivity ratio of VDF material itself, its modification is difficult, and functionalization cannot be achieved. Moreover, the VDF raw material for synthesizing PVDF is a highly hazardous environmental pollutant, and the raw material supply is limited, unable to meet the growing demand of lithium-ion batteries. There are also problems such as gelation in the actual application process. Summary of the Invention

[0004] Problems to be Solved by the Invention

[0005] The binder material of the existing binder composition for the positive electrode of an energy storage device is not excellent in durability (high-temperature storage property) when repeatedly exposed to high temperatures. Therefore, for a secondary battery having a positive electrode formed by using the existing binder composition for the positive electrode, when it is repeatedly charged and discharged under high-temperature conditions, the gas generation amount increases and the battery performance may decrease. Therefore, there is room for improvement in this regard.

[0006] Therefore, the main object of this application is to provide a nitrile rubber, a binder composition for the positive electrode of an energy storage device, and a slurry composition with excellent high-temperature storage property.

[0007] In addition, the object of this application is to provide a positive electrode for an energy storage device with excellent high-temperature storage property.

[0008] Furthermore, the object of this application is to provide an energy storage device with less gas generation even when repeatedly charged and discharged under high-temperature conditions.

[0009] Means for Solving the Problems

[0010] In order to solve all or part of the above problems, the present applicant has conducted in-depth research. Then, the present applicant found that the following nitrile rubber and binder composition have excellent high-temperature storage stability, thus completing the present application. The nitrile rubber of the present application contains 20-80 wt% of α,β-ethylenically unsaturated nitrile monomer units, 20-80 wt% of conjugated diene monomer units, and 0-30 wt% of cationic monomer units, and the iodine value of the nitrile rubber is 55 mg / 100 mg or more and 150 mg / 100 mg or less. The binder composition of the present application contains the above-mentioned nitrile rubber, and based on the solid content of the binder composition for the positive electrode being 100 wt%, the content of the nitrile rubber is 70 wt% or more. When the nitrile rubber and the binder composition for the positive electrode are used in an energy storage device, the positive electrode produced has excellent flexibility and puncture resistance, and can enable the energy storage device to exhibit excellent high-temperature storage characteristics.

[0011] That is, the object of the present application is to advantageously solve all or part of the above technical problems. According to the present application, a binder composition for a positive electrode of an energy storage device, a positive electrode of an energy storage device, and an energy storage device can be provided.

[0012] The first aspect of the present application is to provide a nitrile rubber containing 20-80 wt% of α,β-ethylenically unsaturated nitrile monomer units, 20-80 wt% of conjugated diene monomer units, and 0-30 wt% of cationic monomer units, and the iodine value of the nitrile rubber is 55 mg / 100 mg or more and 150 mg / 100 mg or less.

[0013] When the nitrile rubber is used for the positive electrode of an energy storage device, the positive electrode produced has excellent flexibility and puncture resistance, and can enable the energy storage device to exhibit excellent high-temperature storage characteristics.

[0014] Furthermore, the nitrile rubber contains 30-70 wt% of α,β-ethylenically unsaturated nitrile monomer units, preferably 50-60 wt% of α,β-ethylenically unsaturated nitrile monomer units.

[0015] Furthermore, the nitrile rubber contains 30-60 wt% of conjugated diene monomer units, preferably 40-50 wt% of conjugated diene monomer units.

[0016] Furthermore, the nitrile rubber contains 0.1-5 wt% of the cationic monomer units, preferably 0.3-2 wt% of the cationic monomer units.

[0017] In some embodiments, the monomer forming the cationic monomer unit includes a group containing a nitrogen-containing aromatic heterocycle.

[0018] Furthermore, the monomer forming the cationic monomer unit contains at least one of imidazole ring, pyrrole ring, thiazole ring, oxazole ring, pyrazole ring, isoxazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, quinoline ring, isoquinoline ring, quinoxaline ring, quinazoline ring, cinnoline ring, purine ring, indole ring, isoindole ring, benzimidazole ring, benzoxazole ring, and benzisoxazole ring fused heterocycles.

[0019] Still further, the monomer forming the cationic monomer unit contains an imidazole ring.

[0020] Still further, the monomer forming the cationic monomer unit includes one or a combination of more than one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, or 1-ethyl-3-methylimidazolium methyl sulfate.

[0021] In some embodiments, the iodine value of the nitrile rubber is 60 mg / 100 mg or more and 120 mg / 100 mg or less.

[0022] The second aspect of the present application is to provide a binder composition for a positive electrode of an energy storage device, which includes the above-mentioned nitrile rubber. Based on 100 wt% of the solid content of the binder composition, the content of the nitrile rubber is 70 wt% or more.

[0023] By making the binder composition for a positive electrode contain a nitrile rubber with a specific composition and the content of the nitrile rubber is within a specified range, a positive electrode with excellent flexibility and puncture resistance can be fabricated.

[0024] In some embodiments, the content of the nitrile rubber is 80 wt% or more, preferably 90 wt% or more.

[0025] If the above range is satisfied, the flexibility and puncture resistance of the positive electrode can be further improved.

[0026] In some embodiments, the binder composition further includes a thermoplastic resin.

[0027] In some embodiments, the thermoplastic resin includes at least one of vinyl chloride resin or acrylic resin.

[0028] If the above conditions are satisfied, the flexibility and puncture resistance of the positive electrode can be further improved.

[0029] Furthermore, based on 100 wt% of the solid content of the binder composition, the thermoplastic resin is 10 - 30 wt%.

[0030] Furthermore, the thermoplastic resin is a granular resin, and its volume average particle size is 0.01 μm - 1 mm.

[0031] The binder composition further includes a plasticizer, and the plasticizer includes at least one of triethylene glycol bis(2-ethylpropionate), triethylene glycol bis(2-ethylbutyrate), triethylene glycol bis(2-ethylhexanoate), triethylene glycol dioctanoate, triethylene glycol bis(n-octanoate), and triethylene glycol bis(n-heptanoate).

[0032] If the above conditions are satisfied, the flexibility and puncture resistance of the positive electrode can be further improved.

[0033] Furthermore, based on the solid content of the binder composition being 100 wt%, the content of the plasticizer is 0.1 - 3 wt%.

[0034] A third aspect of the present invention is to provide a slurry composition for a positive electrode of an energy storage device, which includes a positive electrode active material, a binder material, and a conductive material, and the binder material includes the above-mentioned nitrile rubber or the binder composition for a positive electrode of an energy storage device.

[0035] A fourth aspect of the present invention is to provide a positive electrode of an energy storage device, and the positive electrode of the energy storage device includes a current collector and a positive electrode mixture layer formed on the current collector, and the positive electrode mixture layer includes a cured product of the above-mentioned slurry composition.

[0036] If the above-mentioned nitrile rubber and the binder composition for a positive electrode are used, the positive electrode produced has excellent flexibility and puncture resistance.

[0037] A fifth aspect of the present invention is to provide an energy storage device, which includes a positive electrode, a negative electrode, and an electrolyte, and the positive electrode is the positive electrode of the energy storage device mentioned above.

[0038] If the above-mentioned energy storage device electrode is used, the energy storage device can exhibit excellent high-temperature storage characteristics.

[0039] In some embodiments, the electrolyte of the energy storage device includes additive A, and additive A includes at least one of lithium difluorophosphate, vinylene sulfate, vinylene carbonate, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, and crown ether.

[0040] If the above-mentioned additive A is used, swelling of the n-butyl nitrile rubber or the binder composition in the electrolyte of the present application can be inhibited, and the energy storage device can exhibit excellent high-temperature storage characteristics.

[0041] Furthermore, the crown ether includes one or a combination of more than one of 15-crown-5, 18-crown-6, 21-crown-7, 24-crown-8, dibenzo-15-crown-5, dibenzo-18-crown-6, dibenzo-21-crown-7, dibenzo-24-crown-8, 1-aza-15-crown-5, 1-aza-18-crown-6, 1-aza-21-crown-7, and 1-aza-24-crown-8.

[0042] Further, based on 100 parts by mass of the electrolyte, the content of lithium difluorophosphate is 0.01 to 0.8 parts by mass; and / or, the content of vinylene sulfate is 0.01 to 0.8 parts by mass; and / or, the content of vinylene carbonate is 0.01 to 0.5 parts by mass; and / or, the content of lithium tetrafluoroborate is 0.01 to 1.5 parts by mass; and / or, the content of lithium difluoro(oxalato)borate is 0.01 to 0.8 parts by mass; and / or, the content of bis(oxalato)borate lithium is 0.01 to 0.5 parts by mass; and / or, the content of crown ether is 0.1 to 2.5 parts by mass.

[0043] If the electrolyte components with the above contents are used, swelling of the nitrile rubber or binder composition for the positive electrode in the electrolyte can be suppressed, and excellent high-temperature storage characteristics can be exhibited by the energy storage device.

[0044] Technical effects

[0045] When the nitrile rubber or binder composition for the positive electrode of the energy storage device of the present application is used in the energy storage device, the produced positive electrode has excellent flexibility and penetration resistance, and excellent high-temperature storage characteristics can be exhibited by the energy storage device. Detailed description of the specific embodiments

[0046] Hereinafter, embodiments of the present application are described in detail. However, these embodiments are exemplary, and the present application is not limited thereto.

[0047] The nitrile rubber of the present application contains 20 to 80 wt% of αα,β-ethylenically unsaturated nitrile monomer units, 20 to 80 wt% of conjugated diene monomer units, and 0 to 30 wt% of cationic monomer units, and the iodine value of the nitrile rubber is 55 mg / 100 mg or more and 150 mg / 100 mg or less. When this nitrile rubber is used for the positive electrode of the energy storage device, the produced positive electrode has excellent flexibility and penetration resistance, and excellent high-temperature storage characteristics can be exhibited by the energy storage device.

[0048] Examples of the energy storage device in the present application include various energy storage devices such as electric double layer capacitors, lithium ion batteries, sodium ion batteries, aluminum ion batteries, and aluminum solid capacitors. The nitrile rubber and the binder composition for the positive electrode of the present application are particularly suitable for electric double layer capacitors and lithium ion batteries.

[0049] Binder composition for positive electrode

[0050] In the present application, the binder composition for the positive electrode of the energy storage device includes nitrile rubber, and the nitrile rubber contains 20 to 80 wt% of α,β-ethylenically unsaturated nitrile monomer units, 20 to 80 wt% of conjugated diene monomer units, and 0 to 30 wt% of cationic monomer units. The iodine value of the nitrile rubber is 55 mg / 100 mg or more and 150 mg / 100 mg or less; based on 100 wt% of the solid content of the binder composition, the content of the nitrile rubber is 70 wt% or more. When the binder composition for the positive electrode is used in an energy storage device, the fabricated positive electrode has excellent flexibility and penetration resistance, and can enable the energy storage device to exhibit excellent high-temperature storage characteristics.

[0051] The nitrile rubber used in the present application is a nitrile rubber containing 20 to 80 wt% of α,β-ethylenically unsaturated nitrile monomer units, 20 to 80 wt% of conjugated diene monomer units, and 0 to 30 wt% of cationic monomer units.

[0052] In the present application, the iodine value of the nitrile rubber is 55 mg / 100 mg or more and 150 mg / 100 mg or less, preferably 130 mg / 100 mg or less, more preferably 120 mg / 100 mg or less, and further preferably 60 mg / 100 mg or more and 120 mg / 100 mg or less. If the iodine value of the nitrile rubber is above the above lower limit value, the dispersibility of the solid component in the slurry composition can be moderately improved, and the penetration resistance of the positive electrode can be improved. In addition, if the iodine value of the nitrile rubber is below the above upper limit value, the structural stability of the nitrile rubber is high, and the high-temperature storage characteristics of the secondary battery can be improved. Furthermore, it is speculated that since the structural stability of the nitrile rubber is high when the iodine value of the nitrile rubber is below the above upper limit value, swelling of the nitrile rubber in the positive electrode during charge and discharge can be suppressed, and thus the high-temperature storage characteristics of the secondary battery can also be improved. Furthermore, in addition, if the iodine value of the nitrile rubber is below the above upper limit value, the nitrile rubber has appropriate flexibility, can improve the ease of pressing in the pressing process, and can suppress springback. In addition, the iodine value of the nitrile rubber can be controlled by adjusting, for example, the composition of the nitrile rubber and the hydrogenation rate in the case where the nitrile rubber is a hydrogenated polymer.

[0053] Determination of iodine value: After solidifying the NMP dispersion (binder composition) of the prepared nitrile rubber with 1 L of methanol, vacuum drying is carried out at a temperature of 60 °C for 12 hours. Then, the iodine value of the obtained dried nitrile rubber is measured according to JIS K6235 (2006).

[0054] As the α,β-ethylenically unsaturated nitrile monomer that forms an α,β-ethylenically unsaturated nitrile monomer unit, any α,β-ethylenically unsaturated compound having a nitrile group may be used, and there is no particular limitation. Examples include acrylonitrile; α-halopropionitriles such as αα-chloropropionitrile and α-bromopropionitrile; α-alkylacrylonitriles such as methacrylonitrile, etc. Among them, acrylonitrile and methacrylonitrile are preferred, and acrylonitrile is particularly preferred. They can be used alone or in combination of two or more.

[0055] The content of the α,β-ethylenically unsaturated nitrile monomer unit in the nitrile rubber is 20 to 80 wt% relative to all monomer units, preferably 30 to 70 wt%, more preferably 50 to 60 wt%. If the content of the α,β-ethylenically unsaturated nitrile monomer unit is too low, the heat resistance of the obtained rubber crosslinking product deteriorates. On the other hand, if the content of the α,β-ethylenically unsaturated nitrile monomer unit is too high, the embrittlement temperature of the obtained rubber crosslinking product increases and the cold resistance is poor.

[0056] In order to make the obtained rubber crosslinking product have rubber elasticity, the nitrile rubber used in this application contains a conjugated diene monomer unit.

[0057] As the conjugated diene monomer that forms the conjugated diene monomer unit, a conjugated diene monomer having 4 to 6 carbon atoms is preferred. Examples include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, etc. Among them, 1,3-butadiene is preferred. They can be used alone or in combination of two or more.

[0058] The content ratio of the conjugated diene monomer unit in the nitrile rubber is 20 to 80 wt% relative to all monomer units, preferably 30 to 60 wt%, more preferably 40 to 50 wt%.

[0059] If the content of the conjugated diene monomer unit is too low, the rubber elasticity of the obtained rubber crosslinking product may decrease. On the other hand, if the content of the conjugated diene monomer unit is too high, the heat resistance of the obtained rubber crosslinking product may deteriorate.

[0060] In addition, the nitrile rubber used in this application preferably contains a cationic monomer unit. The cationic monomer unit refers to at least one of a monomer unit containing a cation and a monomer unit capable of forming a cation.

[0061] The cationic monomer unit preferably contains a group of a nitrogen-containing aromatic heterocycle.

[0062] Regarding the nitrogen-containing aromatic heterocycles, if they have a nitrogen atom in the ring and are aromatic, there is no particular limitation. Examples include: five-membered heterocycles such as imidazole ring, pyrrole ring, thiazole ring, oxazole ring, pyrazole ring, isoxazole ring, etc.; six-membered heterocycles such as pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, etc.; fused heterocycles such as quinoline ring, isoquinoline ring, quinoxaline ring, quinazoline ring, cinnoline ring, purine ring, indole ring, isoindole ring, benzimidazole ring, benzoxazole ring, benzisoxazole ring, etc. Among these, five-membered heterocycles and six-membered heterocycles are preferred, and imidazole ring is more preferred.

[0063] As the substituents of the above nitrogen-containing aromatic heterocycles, there is no particular limitation. Examples include: alkyl group; cycloalkyl group; alkenyl group; aryl group; arylalkyl group; alkylaryl group; alkoxy group; alkoxyalkyl group; aryloxy group; alkanol group; hydroxyl group; carbonyl group; alkoxycarbonyl group; amino group; imino group; nitrile group; alkylsilyl group; halogen atom, etc.

[0064] In addition, the nitrile rubber containing cationic monomer units used in the present application may also contain anions. The types of anions are not particularly limited. Examples include: halide ions such as fluoride ion, chloride ion, bromide ion, iodide ion, etc.; sulfate ion; sulfite ion; hydroxide ion; carbonate ion; bicarbonate ion; nitrate ion; acetate ion; perchlorate ion; phosphate ion; alkoxy ion; trifluoromethanesulfonate ion; bis(trifluoromethanesulfonyl)imide ion; hexafluorophosphate ion; tetrafluoroborate ion, etc.

[0065] In addition, the monomers containing cationic monomer units and anions used in the present application preferably include one or a combination of more than one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, or 1-ethyl-3-methylimidazolium methyl sulfate.

[0066] The content of the cationic monomer units is 0 to 5 wt% based on all the monomer units. In the embodiments containing cationic monomer units, the content of the cationic monomer units is 0.1 to 5 wt%, preferably 0.1 to 3 wt%, and more preferably 0.3 to 2 wt%. By containing cationic monomer units, the heat resistance of the resulting rubber crosslink is better.

[0067] In addition, the nitrile rubber used in the present application, in addition to the above α,β-ethylenically unsaturated nitrile monomer units, conjugated diene monomer units, and cationic monomer units, may also contain other monomer units that can copolymerize with the monomers forming these monomer units. The content of the other monomer units is preferably 30 wt% or less, more preferably 20 wt% or less, and further preferably 10 wt% or less based on all the monomer units.

[0068] As other monomer units copolymerizable with the monomers forming these monomer units, non-conjugated diene compounds such as 1,4-pentadiene, 1,4-hexadiene, vinyl norbornene, dicyclopentadiene, etc.; ethylene; α-olefin compounds such as propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, etc.; α,β-ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, etc.; α,β-ethylenically unsaturated polycarboxylic acids such as maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, etc. and their anhydrides; α,β-ethylenically unsaturated carboxylic acid alkyl esters such as (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid butyl ester, (meth)acrylic acid 2-ethylhexyl ester, etc.; mono-esters and di-esters of α,β-ethylenically unsaturated polycarboxylic acids such as monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, dibutyl itaconate, etc.; alkoxyalkyl esters of α,β-ethylenically unsaturated carboxylic acids such as (meth)acrylic acid methoxyethyl ester, (meth)acrylic acid methoxypropyl ester, (meth)acrylic acid butoxyethyl ester, etc.; hydroxyalkyl esters of α,β-ethylenically unsaturated carboxylic acids such as (meth)acrylic acid 2-hydroxyethyl ester, (meth)acrylic acid 3-hydroxypropyl ester, etc.; divinyl compounds such as divinylbenzene; di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, etc.; polyfunctional ethylenically unsaturated monomers such as trimethylolpropane tri(meth)acrylate, etc. In addition, self-crosslinking compounds such as N-methylol(meth)acrylamide, N,N'-dimethylol(meth)acrylamide, etc. can also be exemplified.

[0069] The nitrile rubber used in the present application can be produced by copolymerizing the respective monomers constituting the nitrile rubber. There is no particular limitation on the method of copolymerizing the respective monomers. For example, an emulsion polymerization method using an emulsifier such as sodium dodecylbenzenesulfonate to obtain a latex of a copolymer having an average particle size of about 50 to 1000 nm; a suspension polymerization method (including a fine suspension polymerization method) using a dispersant such as polyvinyl alcohol to obtain an aqueous dispersion of a copolymer having an average particle size of about 0.2 to 200 μm can be preferably adopted. Among them, since the polymerization reaction is easy to control, the emulsion polymerization method is more preferably used.

[0070] There is no particular limitation on the method of adding the remaining monomers. They can be added together, separately, or continuously. In the present application, from the viewpoint of more easily controlling the composition distribution of the obtained copolymer, it is preferred to add the remaining monomers separately, and particularly preferably to add them in 1 to 6 portions. When adding the remaining monomers separately, the amount of the monomers added separately and the timing of addition only need to be adjusted to match the progress of the polymerization reaction so as to obtain the desired nitrile rubber.

[0071] After the polymerization reaction is completed, unreacted monomers are removed by known methods such as heating distillation, vacuum distillation, steam distillation, etc. as needed, thereby obtaining a latex of nitrile rubber. In the present application, the solid content concentration of the latex of nitrile rubber obtained by the emulsion polymerization method is preferably 5 to 70 wt%, more preferably 10 to 60 wt%, and particularly preferably 15 to 50 wt%.

[0072] The binder composition based on nitrile rubber of the present application may further contain other polymers such as other rubbers and resins in addition to nitrile rubber, and preferably further contains a thermoplastic resin, which includes at least one of a vinyl chloride resin and an acrylic resin. By containing a vinyl chloride resin and / or an acrylic resin, the high-temperature resistance can be further improved when a rubber crosslinked product is formed.

[0073] In the vinyl chloride resin used in the present application, the main constituent monomer constituting the resin is vinyl chloride, and the content of vinyl chloride monomer units is preferably 50 to 100 wt%, more preferably 60 to 100 wt%, and particularly preferably 70 to 100 wt%.

[0074] In addition, in the acrylic resin used in the present application, the main constituent monomer constituting the resin is an alkyl (meth)acrylate, and the content of alkyl (meth)acrylate monomer units is preferably 50 to 100 wt%, more preferably 60 to 100 wt%, and particularly preferably 70 to 100 wt%. In addition, the number of carbon atoms of the alkyl group of the alkyl (meth)acrylate is preferably 1 to 20, more preferably 1 to 18, and particularly preferably 1 to 10.

[0075] The acrylic resin of the present application is preferably synthesized from raw materials such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, n-decyl acrylate, lauryl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, n-decyl methacrylate, lauryl methacrylate.

[0076] These thermoplastic resins are preferably in granular form, and their volume average particle size is preferably from 0.01 μm to 1 mm, more preferably from 0.05 to 100 μm, and particularly preferably from 0.1 to 10 μm. The volume average particle size is measured using a laser diffraction scattering particle size measuring device. If the volume average particle size of the thermoplastic resin is too small, the high-temperature resistance of the rubber cross-linked product may decrease. On the contrary, if it is too large, poor dispersion may occur during mixing.

[0077] Based on the solid content of the binder composition being 100 wt%, the thermoplastic resin is 10 to 30 wt%, more preferably 15 to 25 wt%. If the content of the thermoplastic resin is too small, it is difficult to obtain its additive effect. On the other hand, if it is too large, the high-temperature storage performance may decrease.

[0078] In the present application, from the viewpoint of improving the penetration resistance of the binder composition for the positive electrode of the energy storage device, when the solid content of the binder composition is set to 100 wt%, the content of the nitrile rubber is 70 wt% or more, preferably 80 wt% or more; more preferably 90 wt% or more.

[0079] In the present application, from the viewpoint of improving the flexibility of the positive electrode, the binder composition further includes a plasticizer, and the plasticizer includes at least one of triethylene glycol di-2-ethylpropionate, triethylene glycol di-2-ethylbutyrate, triethylene glycol di-2-ethylhexanoate, triethylene glycol dioctanoate, triethylene glycol di-n-octanoate, and triethylene glycol di-n-heptanoate.

[0080] Based on the solid content of the binder composition being 100 wt%, the content of the plasticizer is 0.1 to 3 wt%, preferably 0.1 to 2 wt%.

[0081] Energy storage device electrode

[0082] The positive electrode of the energy storage device of the present application includes a current collector and a positive electrode mixture layer formed on the current collector. The positive electrode mixture layer includes a cured product of a positive electrode slurry composition, and the positive electrode slurry composition includes a positive electrode active material, a binder material, and a conductive material, wherein the binder material includes the nitrile rubber of the present application or the binder composition for the positive electrode of the present application.

[0083] As the positive electrode active material, various active materials conventionally used in the positive electrode of the energy storage device can be used.

[0084] The positive electrode active material may include a lithiated intercalation compound that can reversibly intercalate and deintercalate lithium ions.

[0085] For example, at least one composite oxide of lithium with at least one metal of cobalt, manganese, nickel, or a combination thereof can be used.

[0086] A composite oxide having a coating on its surface may be used, or a mixture of a composite oxide and a composite oxide having a coating may be used. The coating may include a coating element compound selected from the following: an oxide of the coating element, a hydroxide of the coating element, a hydroxyoxide of the coating element, an oxycarbonate of the coating element, or a basic carbonate of the coating element. The compound used for the coating may be amorphous or crystalline. The coating element included in the coating may be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, W, La, Y, Ce, or a mixture thereof. The coating process may include any suitable process commonly used in the art, as long as it does not (or substantially does not) cause any side effects (e.g., any undesirable side effects) on the properties of the positive electrode active material (e.g., spraying, dipping), which will be obvious to those of ordinary skill in the art after reading this application, and thus need not be described in detail herein.

[0087] For example, the positive electrode active material may include lithium cobalt oxide.

[0088] In some embodiments, the positive electrode active material may include a lithium cobalt oxide represented by Chemical Formula 1 below:

[0089] Chemical Formula 1: Li a11 Co x11 M 11 y11 O2.

[0090] In Chemical Formula 1, 0.9 ≤ a11 ≤ 1.8, 0.9 ≤ x11 ≤ 1, 0 ≤ y11 ≤ 0.1, x11 + y11 = 1, and M 11 is at least one of Al, B, Ce, Cr, F, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, and Zr.

[0091] For example, the positive electrode active material may be LiCoO2.

[0092] In some embodiments, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 2:

[0093] Chemical Formula 2: Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 .

[0094] In Chemical Formula 2, 0.9 ≤ a1 ≤ 1.2, 0.7 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, 0 ≤ z1 ≤ 0.2, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1; M 1 and M 2 are each independently one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr; and X is one or more elements selected from F, P, and S.

[0095] In Chemical Formula 2, 0.75 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.18, and 0 ≤ z1 ≤ 0.18; 0.85 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.15, and 0 ≤ z1 ≤ 0.15; or 0.9 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.1, and 0 ≤ z1 ≤ 0.1.

[0096] For example, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 3. The compound represented by Chemical Formula 3 may be referred to as a lithium nickel cobalt-based composite oxide:

[0097] Chemical Formula 3: Li a2 Ni x2 Co y2 M 3 22 O 2-b2 X b2 .

[0098] In Chemical Formula 3, 0.9 ≤ a2 ≤ 1.8, 0.7 ≤ x2 < 1, 0 < y2 ≤ 0.2, 0 ≤ z2 ≤ 0.2, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 3 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from F, P, and S.

[0099] In Chemical Formula 3, 0.75 ≤ x2 ≤ 0.99, 0 ≤ y2 ≤ 0.15, and 0 ≤ z2 ≤ 0.15; 0.85 ≤ x2 ≤ 0.99, 0.01 ≤ y2 ≤ 0.15, and 0.01 ≤ z2 ≤ 0.15; or 0.9 ≤ x2 ≤ 0.99, 0.01 ≤ y2 ≤ 0.1, and 0.01 ≤ z2 ≤ 0.1.

[0100] As an example, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 4. The compound represented by Chemical Formula 4 may be referred to as a lithium nickel cobalt aluminum oxide or a lithium nickel cobalt manganese oxide.

[0101] Chemical Formula 4: Lia3 Ni x3 Co y3 M 4 z3 M 5 w3 O 2-b3 X b3

[0102] In Chemical Formula 4, 0.9 ≤ a3 ≤ 1.8, 0.7 ≤ x3 ≤ 0.98, 0.01 ≤ y3 ≤ 0.19, 0.01 ≤ z3 ≤ 0.19, 0 ≤ w3 ≤ 0.19, 0.9 ≤ x3 + y3 + z3 + w3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, M 4 is one or more elements selected from Al and Mn, M 5 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from F, P, and S.

[0103] In Chemical Formula 4, 0.75 ≤ x3 ≤ 0.98, 0 ≤ y3 ≤ 0.16, 0 ≤ z3 ≤ 0.16, and 0 ≤ w3 ≤ 0.16; 0.85 < x3 < 0.98, 0.01 ≤ y3 ≤ 0.14, 0.01 < z3 < 0.14, and 0 ≤ w3 ≤ 0.14; or 0.9 ≤ x3 ≤ 0.98, 0.01 ≤ y3 ≤ 0.09, 0.01 ≤ z3 ≤ 0.09, and 0 ≤ w3 ≤ 0.09.

[0104] As an example, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 5. The compound represented by Chemical Formula 5 may be referred to as a cobalt-free lithium nickel manganese oxide.

[0105] Chemical Formula 5: Li a4 Ni x4 Mn y4 M 6 z4 O 2-b4 X b4

[0106] In Chemical Formula 5, 0.9 ≤ a4 ≤ 1.8, 0.7 ≤ x4 < 1, 0 < y4 ≤ 0.2, 0 ≤ z4 ≤ 0.2, 0.9 ≤ x4 + y4 + z4 ≤ 1.1, and 0 ≤ b4 ≤ 0.1, M 6 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from F, P, and S.

[0107] In some exemplary embodiments of the positive electrode, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material may be 90 wt% to 98 wt%, 50 wt% to 99 wt%, 60 wt% to 99 wt%, 70 wt% to 99 wt%, 80 wt% to 99 wt%, or 90 wt% to 99 wt%.

[0108] In some embodiments of the present application, the positive electrode active material layer may optionally include a conductive material (e.g., a conductivity material). In some embodiments, based on the total weight of the positive electrode active material layer, the content of the conductive material may be 1.0 wt% to 5.0 wt%.

[0109] The conductive material is used to impart conductivity (e.g., conductivity) to the electrode, and any suitable conductivity material can be used as the conductive material (e.g., a conductivity material), unless it causes chemical changes in the battery (e.g., undesired changes in a rechargeable lithium battery). Examples of the conductive material may include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.); metal-based materials (such as metal powders or metal fibers of copper, nickel, aluminum, silver, etc.); conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0110] The binder improves the binding properties of the positive electrode active material particles to each other and the binding properties of the positive electrode active material particles to the positive electrode current collector. In addition to using the nitrile rubber or binder composition of the present application, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. may also be included, but are not limited thereto.

[0111] The negative electrode of the energy storage device can be appropriately selected and used from known materials.

[0112] The negative electrode active material may be a material that can reversibly intercalate / deintercalate lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and dedoping lithium, and / or a transition metal oxide.

[0113] The material that can reversibly intercalate / deintercalate lithium ions includes carbon materials. The carbon materials may be any suitable carbon-based negative electrode active materials commonly used in rechargeable lithium batteries. Examples of the carbon materials include crystalline carbon, amorphous carbon, and combinations thereof. The crystalline carbon may be amorphous natural graphite and / or artificial graphite, and / or flaky, sheet-like, spherical, and / or fibrous natural graphite and / or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0114] The lithium metal alloy may include lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0115] The material capable of doping and de-doping lithium may include Si, SiO x (0 < x < 2), Si-Q alloy (where Q is selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements other than Si, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof), Sn, SnO2, Sn-R alloy (where R is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element other than Sn, Group 15 element, Group 16 element, transition metal, rare earth element, or a combination thereof), etc. At least one of them may be mixed with SiO2.

[0116] The element Q and the element R may be selected from Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn (the element R does not include Sn), In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0117] The transition metal oxide may be vanadium oxide, lithium vanadium oxide, etc.

[0118] In some exemplary embodiments, the negative electrode active material may include at least one selected from graphite and Si composite.

[0119] The Si composite may include: a core including Si particles and amorphous carbon, and for example, the Si particles may include at least one selected from Si-C composite, SiO k (0 < k ≤ 2) and Si alloy.

[0120] For example, the Si-C composite may include: a core including Si particles and amorphous carbon.

[0121] The central part of the core may include pores, and the radius of the central part may correspond to about 30% to about 50% of the radius of the Si composite.

[0122] The Si particles may have a median particle size of 10 nm to 200 nm.

[0123] As used herein, the median particle size (D50) may be the particle size at which the volume ratio is 50% in the cumulative size distribution curve.

[0124] When the median particle size of the Si particles is within the above range, volume expansion occurring during charging and discharging can be suppressed or reduced, and disconnection of the conduction path due to particle pulverization during charging and discharging can be prevented or reduced.

[0125] Based on the total weight of the Si composite, the amount of Si particles included can be 1 wt% to 60 wt%, for example, 3 wt% to 60 wt%.

[0126] The central portion may not include amorphous carbon, but amorphous carbon may be present only on the surface portion of the negative electrode active material.

[0127] In the present text, the surface portion indicates the region from the central portion of the negative electrode active material (for example, the region just outside the central portion) to the outermost surface of the negative electrode active material.

[0128] In some embodiments, Si particles are included substantially uniformly throughout the negative electrode active material. For example, Si particles are present in the central portion and the surface portion of the negative electrode active material at a substantially uniform concentration.

[0129] The amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, or a combination thereof.

[0130] The negative electrode active material may further include crystalline carbon.

[0131] When the negative electrode active material includes both the Si composite and crystalline carbon, the Si composite and crystalline carbon can be included in the form of a mixture, and in some embodiments, the Si composite and crystalline carbon can be included at a weight ratio of 1:99 to 50:50. In some embodiments, the Si composite and crystalline carbon can be included at a weight ratio of 3:97 to 20:80 or 5:95 to 20:80.

[0132] The crystalline carbon can be, for example, graphite, and can be, for example, natural graphite, artificial graphite, or a mixture thereof.

[0133] The crystalline carbon can have a median particle size of 5 μm to 30 μm.

[0134] The amorphous carbon precursor can include coal tar pitch, mesophase pitch, petroleum pitch, coal tar, petroleum heavy oil, and / or polymer resins (such as phenolic resin, furan resin, and / or polyimide resin).

[0135] In the negative electrode active material layer, based on the total weight of the negative electrode active material layer, the amount of the negative electrode active material included can be 95 wt% to 99 wt%.

[0136] In some exemplary embodiments, the negative electrode active material layer may further include a binder for the negative electrode and optionally may include a conductive material (e.g., a conductivity material). In the negative electrode active material layer, based on the total weight of the negative electrode active material layer, the amount of the binder for the negative electrode may be 1 wt% to 5 wt%. When the negative electrode active material layer further includes a conductive material, the negative electrode active material layer may include 90 wt% to 98 wt% of the negative electrode active material, 1 wt% to 5 wt% of the binder for the negative electrode, and 1 wt% to 5 wt% of the conductive material.

[0137] The binder for the negative electrode improves the binding characteristics between the negative electrode active material particles and the binding characteristics between the negative electrode active material and the current collector. The binder for the negative electrode may be polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof. The binder for the negative electrode may also be a rubber-based binder and / or a polymer resin binder. The rubber-based binder may be selected from styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and a combination thereof. The polymer resin binder may be selected from polytetrafluoroethylene, ethylene-propylene copolymer, poly(ethylene oxide), polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and a combination thereof.

[0138] A conductive material is included to provide electrode conductivity (e.g., conductivity), and any suitable conductivity material may be used as the conductive material (e.g., conductivity material), unless it causes a chemical change (e.g., unless it causes an undesirable change in a rechargeable lithium battery). Examples thereof may be carbonaceous materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.); metallic materials (such as metal powders or metal fibers of copper, nickel, aluminum, silver, etc.); conductive polymers (such as polyphenylene derivatives, etc.); or mixtures thereof.

[0139] In addition, in the case of an electric double layer capacitor, a carbonaceous material can be used as the active material.

[0140] As the carbonaceous material, activated carbon etc. can be cited, for example, activated carbon obtained by carbonizing a phenolic resin and then subjecting it to an activation treatment can be cited.

[0141] Energy storage device

[0142] The energy storage device related to the present application has the above-mentioned energy storage device positive electrode. The energy storage device is characterized by using the above-mentioned energy storage device positive electrode, and thus, as the negative electrode, separator, electrolyte, etc. constituting other devices, they can be appropriately selected and used from known materials.

[0143] The separator may be a porous substrate; or may be a composite porous substrate.

[0144] The porous substrate may be a substrate including pores, and lithium ions can move through the pores. The porous substrate may include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer separator formed of these (such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, and a polypropylene / polyethylene / polypropylene trilayer separator).

[0145] The composite porous substrate may, for example, include a porous substrate and a functional layer formed on the porous substrate. From the perspective of ensuring additional functions, the functional layer may be selected from at least one of a heat-resistant layer and a bonding layer. The heat-resistant layer may, for example, include a heat-resistant resin and optionally may include a filler.

[0146] In some embodiments, the bonding layer may include a binder resin and optionally may include a filler.

[0147] The filler may be an organic filler and / or an inorganic filler.

[0148] As the electrolyte, both liquid and solid are acceptable, and in addition, both aqueous and non-aqueous are acceptable. The positive electrode of the energy storage device of the present application can also exhibit practically sufficient performance when applied to a device using a non-aqueous electrolyte.

[0149] As the non-aqueous electrolyte, a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous organic solvent can be cited.

[0150] In some embodiments, the electrolyte solution includes additive A, and additive A includes at least one of lithium difluorophosphate, vinylene sulfate, vinylene carbonate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(oxalato)borate, and crown ether. These additive A can further reduce the swelling of the binder composition for the positive electrode, inhibit the high-temperature decomposition of the binder, and the improvement effect is beyond expectation.

[0151] The description of the electrolyte solution including the above additive A is as follows.

[0152] The electrolyte solution includes a non-aqueous organic solvent, an electrolyte salt, additive A, and optionally other additives.

[0153] As the electrolyte salt, LiPF6, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide: LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(Cy F 2y+1 SO2) (where x and y are natural numbers, such as integers from 1 to 20). The concentration of the lithium salt can be in the range of about 0.1 M to about 2.0 M. When the lithium salt is contained in the above concentration range, the electrolyte conductivity and viscosity are appropriate or optimal, and the electrolyte can have excellent performance and lithium ion mobility.

[0154] The non-aqueous organic solvent is used as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0155] The non-aqueous organic solvent may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, and / or aprotic solvents.

[0156] The carbonate solvents may include ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. The ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanolide, mevalonolactone, caprolactone, etc. The ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. The ketone solvents may include cyclohexanone, etc. The alcohol solvents may include ethanol, isopropanol, etc., and examples of aprotic solvents include nitriles (such as R-CN, where R is a C2-C20 straight-chain hydrocarbon group, branched-chain hydrocarbon group, or cycloalkyl group, and may include double bonds, aromatic rings, or ether bonds), amides (such as dimethylformamide), dioxolanes (such as 1,3-dioxolane), sulfolane, etc.

[0157] A single non-aqueous organic solvent can be used or one or more of them can be used in combination, and when one or more are used in combination, the mixing ratio can be appropriately or suitably adjusted according to the appropriate or desired battery performance, which should be fully understood by those skilled in the art after reading this application.

[0158] Additive A of the present application can effectively inhibit the swelling of the nitrile rubber and the binder composition for the positive electrode of the present application, thereby inhibiting the decomposition of the binder for the positive electrode generated during charge and discharge cycles at high temperatures, and further improving the high-temperature storage performance of the energy storage device.

[0159] Additive A includes at least one of lithium difluorophosphate, vinylene sulfate, vinylene carbonate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(oxalate) borate, and crown ether.

[0160] The crown ethers include one or more of 15-crown-5, 18-crown-6, 21-crown-7, 24-crown-8, dibenzo-15-crown-5, dibenzo-18-crown-6, dibenzo-21-crown-7, dibenzo-24-crown-8, 1-aza-15-crown-5, 1-aza-18-crown-6, 1-aza-21-crown-7, and 1-aza-24-crown-8.

[0161] Among them, based on 100 parts by mass of the electrolyte, the content of lithium difluorophosphate is 0.01 to 0.8 parts by mass; and / or, the content of vinylene sulfate is 0.01 to 0.8 parts by mass; and / or, the content of vinylene carbonate is 0.01 to 0.5 parts by mass; and / or, the content of lithium tetrafluoroborate is 0.01 to 1.5 parts by mass; and / or, the content of lithium difluoro(oxalato)borate is 0.01 to 0.8 parts by mass; and / or, the content of lithium bis(oxalato)borate is 0.01 to 0.5 parts by mass; and / or, the content of the crown ether is 0.1 to 2.5 parts by mass. If the electrolyte components with the above contents are used, swelling of the nitrile rubber or binder composition for the positive electrode in the electrolyte can be suppressed, and excellent high-temperature storage characteristics of the energy storage device can be exhibited.

[0162] There is no particular limitation on the form of the energy storage device, and various conventionally known forms of batteries such as cylindrical, flat wound square, laminated square, coin-shaped, flat wound laminated, and laminated composite can be adopted.

[0163] Examples

[0164] Examples and comparative examples are listed below for a more specific description of the present application, but the present application is not limited to the following examples. Unless otherwise specified, "parts" in the following examples are all parts by mass.

[0165] Manufacture of the Binder Composition for the Positive Electrode

[0166] Example 1-1

[0167] Preparation of nitrile rubber:

[0168] Charge 300 parts of water, 20 parts of acrylonitrile, and 5 parts of sodium dodecylbenzenesulfonate (emulsifier) into a reaction vessel, and adjust the temperature to 2 °C. Then, reduce the pressure of the gas phase to fully degas, and then add 40 parts of 1,3-butadiene, 0.1 part of ammonium persulfate as a polymerization initiator, 0.05 part of sodium ethylenediaminetetraacetate, 0.02 part of copper acetate, and 1 part of tert-dodecyl mercaptan as a chain transfer agent to initiate the first-stage reaction of emulsion polymerization. After the reaction is initiated, when the polymerization conversion rate of the filler monomer reaches 42% (by weight), add 20 parts of 1,3-butadiene to the reaction vessel to carry out the second-stage polymerization reaction. Then, when the polymerization conversion rate of the filler monomer reaches 60% (by weight), add 20 parts of 1,3-butadiene to the reaction vessel to carry out the third-stage polymerization reaction. After that, when the polymerization conversion rate of the total filler monomer reaches 75% (by weight), add 0.2 part of potassium hydroxide to stop the polymerization reaction. After the reaction is stopped, heat the content of the reaction vessel to 70 °C, and recover the unreacted monomers by steam distillation under reduced pressure to obtain a nitrile rubber latex.

[0169] Collect a part of the above latex, coagulate it with a large amount of methanol, filter, and dry it to obtain nitrile rubber. Using an FT-NMR apparatus (JNM-Ex400WB) manufactured by JEOL Ltd., according to 1 When the content ratio of each monomer unit constituting the obtained nitrile rubber is determined by 1H-NMR, the acrylonitrile unit is 20 wt%, the 1,3-butadiene unit is 80 wt%, and the iodine value is 55 mg / 100 mg.

[0170] Use this nitrile rubber as a binder.

[0171] Example 1-2

[0172] Preparation of Nitrile Rubber

[0173] Charge 300 parts of water, 80 parts of acrylonitrile, and 5 parts of sodium dodecylbenzenesulfonate (emulsifier) into a reaction vessel, and adjust the temperature to 2 °C. Then, reduce the pressure of the gas phase to fully degas, and then add 10 parts of 1,3-butadiene, 0.1 part of ammonium persulfate as a polymerization initiator, 0.02 part of sodium ethylenediaminetetraacetate, 0.02 part of copper acetate, and 1 part of tert-dodecyl mercaptan as a chain transfer agent to initiate the first-stage reaction of emulsion polymerization.

[0174] After the reaction is initiated, at the moment when the polymerization conversion rate relative to the filler monomer reaches 42% (by weight), 5 parts of 1,3-butadiene are added to the reaction vessel to carry out the second-stage polymerization reaction. Then, at the moment when the polymerization conversion rate relative to the filler monomer reaches 60% (by weight), 5 parts of 1,3-butadiene are added to the reaction vessel to carry out the third-stage polymerization reaction. After that, at the moment when the polymerization conversion rate relative to the total filler monomer reaches 75% (by weight), 0.2 parts of potassium hydroxide are added to stop the polymerization reaction. After the reaction stops, the content of the reaction vessel is heated to 70 °C, and the unreacted monomers are recovered by steam distillation under reduced pressure to obtain a nitrile rubber latex.

[0175] A part of the above latex is collected, coagulated with a large amount of methanol, filtered and dried to obtain nitrile rubber. Using an FT-NMR apparatus (JNM-Ex400WB) manufactured by JEOL Ltd., according to 1 When the content ratio of each monomer unit constituting the obtained nitrile rubber is measured by 1H-NMR, the acrylonitrile unit is 80% (by weight), the 1,3-butadiene unit is 20% (by weight), and the iodine value is 150 mg / 100 mg.

[0176] This nitrile rubber is used as a binder.

[0177] Examples 1-3

[0178] Preparation of nitrile rubber

[0179] 300 parts of water, 50 parts of acrylonitrile, and 8 parts of sodium dodecylbenzenesulfonate (emulsifier) are charged into a reaction vessel, and the temperature is adjusted to 2 °C. Then, the gas phase is depressurized for sufficient degassing, and then 30 parts of 1,3-butadiene, 0.1 part of ammonium persulfate as a polymerization initiator, 0.02 part of sodium ethylenediaminetetraacetate, 0.02 part of copper acetate, and 1 part of tert-dodecyl mercaptan as a chain transfer agent are added to initiate the first-stage reaction of emulsion polymerization. After the reaction is initiated, at the moment when the polymerization conversion rate relative to the filler monomer reaches 42% (by weight), 10 parts of 1,3-butadiene are added to the reaction vessel to carry out the second-stage polymerization reaction. Then, at the moment when the polymerization conversion rate relative to the filler monomer reaches 60% (by weight), 10 parts of 1,3-butadiene are added to the reaction vessel to carry out the third-stage polymerization reaction. After that, at the moment when the polymerization conversion rate relative to the total filler monomer reaches 75% (by weight), 0.2 parts of potassium hydroxide are added to stop the polymerization reaction. After the reaction stops, the content of the reaction vessel is heated to 70 °C, and the unreacted monomers are recovered by steam distillation under reduced pressure to obtain a nitrile rubber latex.

[0180] A part of the above latex is collected, coagulated with a large amount of methanol, filtered and dried to obtain nitrile rubber. Using an FT-NMR apparatus (JNM-Ex400WB) manufactured by JEOL Ltd., according to 1When determining the content ratio of each monomer unit constituting the obtained nitrile rubber by \(^1H-NMR\), the acrylonitrile unit is 50% (by weight), the 1,3-butadiene unit is 50% (by weight), and the iodine value is 60 mg / 100 mg.

[0181] This nitrile rubber is used as a binder.

[0182] Examples 1 - 4

[0183] Preparation of nitrile rubber

[0184] Charge 300 parts of water, 60 parts of acrylonitrile, and 5 parts of sodium dodecylbenzenesulfonate (emulsifier) into a reaction vessel, and adjust the temperature to 2 °C. Then, reduce the pressure of the gas phase for sufficient degassing, and then add 20 parts of 1,3-butadiene, 0.1 part of ammonium persulfate as a polymerization initiator, 0.02 part of sodium ethylenediaminetetraacetate, 0.02 part of copper acetate, and 1 part of tert-dodecyl mercaptan as a chain transfer agent to initiate the first-stage reaction of emulsion polymerization. After the reaction is initiated,

[0185] At the moment when the polymerization conversion rate of the monomer relative to the filler reaches 42% (by weight), add 10 parts of 1,3-butadiene to the reaction vessel respectively for the second-stage polymerization reaction. Then, at the moment when the polymerization conversion rate of the monomer relative to the filler reaches 60% (by weight), add 10 parts of 1,3-butadiene to the reaction vessel respectively for the third-stage polymerization reaction. After that, at the moment when the polymerization conversion rate of the total monomer relative to the filler reaches 75% (by weight), add 0.2 part of potassium hydroxide to stop the polymerization reaction. After the reaction stops, heat the content of the reaction vessel to 70 °C, and recover the unreacted monomer by steam distillation under reduced pressure to obtain a nitrile rubber latex.

[0186] Collect a part of the above latex, coagulate it with a large amount of methanol, filter, and dry to obtain nitrile rubber. Using an FT-NMR apparatus (JNM-Ex400WB) manufactured by JEOL Ltd., according to 1 When determining the content ratio of each monomer unit constituting the obtained nitrile rubber by \(^1H-NMR\), the acrylonitrile unit is 60% (by weight), the 1,3-butadiene unit is 40% (by weight), and the iodine value is 80 mg / 100 mg.

[0187] This nitrile rubber is used as a binder.

[0188] Examples 1 - 5

[0189] Preparation of nitrile rubber

[0190] Charge 300 parts of water, 75 parts of acrylonitrile, and 10 parts of sodium dodecylbenzenesulfonate (emulsifier) into a reaction vessel, and adjust the temperature to 2°C. Then, reduce the pressure of the gas phase to degas sufficiently, and thereafter add 10 parts of 1,3-butadiene, 0.1 part of ammonium persulfate as a polymerization initiator, 0.02 part of sodium ethylenediaminetetraacetate, 0.02 part of copper acetate, and 1 part of tert-dodecyl mercaptan as a chain transfer agent to initiate the first-stage reaction of emulsion polymerization. After the reaction is initiated, at the moment when the polymerization conversion rate relative to the monomer of the filler reaches 42% (by weight), add 5 parts of 1,3-butadiene to the reaction vessel respectively to carry out the second-stage polymerization reaction. Next, at the moment when the polymerization conversion rate relative to the monomer of the filler reaches 60% (by weight), add 5 parts of 1,3-butadiene to the reaction vessel respectively to carry out the third-stage polymerization reaction. Thereafter, at the moment when the polymerization conversion rate relative to the total monomer of the filler reaches 75% (by weight), add 5 parts of 1-ethyl-3-methylimidazolium tetrafluoroborate and 0.2 part of potassium hydroxide to stop the polymerization reaction. After the reaction stops, heat the content of the reaction vessel to 70°C, and recover the unreacted monomer by steam distillation under reduced pressure to obtain a nitrile rubber latex.

[0191] Collect a part of the above latex, coagulate it with a large amount of methanol, filter, and dry it to obtain nitrile rubber. Using an FT-NMR apparatus (JNM-Ex400WB) manufactured by JEOL Ltd., according to 1 When measuring the content ratio of each monomer unit constituting the obtained nitrile rubber by 1H-NMR, the acrylonitrile unit is 75% (by weight), the 1,3-butadiene unit is 20% (by weight), the 1-ethyl-3-methylimidazolium tetrafluoroborate unit is 5% (by weight), and the iodine value is 100 mg / 100 mg.

[0192] Use this nitrile rubber as a binder.

[0193] Examples 1-6

[0194] Charge 300 parts of water, 80 parts of acrylonitrile, and 10 parts of sodium dodecylbenzenesulfonate (emulsifier) into a reaction vessel, and adjust the temperature to 2 °C. Then, reduce the pressure of the gas phase to degas sufficiently, and then add 10 parts of 1,3-butadiene, 0.1 part of ammonium persulfate as a polymerization initiator, 0.02 part of sodium ethylenediaminetetraacetate, 0.02 part of copper acetate, and 1 part of tert-dodecyl mercaptan as a chain transfer agent to initiate the first-stage reaction of emulsion polymerization. After the reaction is initiated, when the polymerization conversion rate relative to the monomer in the filler reaches 42% (by weight), add 10 parts of 1,3-butadiene to the reaction vessel to carry out the second-stage polymerization reaction. When the polymerization conversion rate relative to the monomer in the filler reaches 60% (by weight), add 15 parts of 1,3-butadiene to the reaction vessel to carry out the third-stage polymerization reaction. Then, when the polymerization conversion rate relative to the total monomer in the filler reaches 75% (by weight), add 5 parts of 1-ethyl-3-methylimidazolium hexafluorophosphate and 0.2 part of potassium hydroxide to stop the polymerization reaction. After the reaction is stopped, heat the content of the reaction vessel to 70 °C, and recover the unreacted monomer by steam distillation under reduced pressure to obtain a nitrile rubber latex.

[0195] Collect a part of the above latex, coagulate it with a large amount of methanol, filter, and dry to obtain nitrile rubber. Using an FT-NMR apparatus (JNM-Ex400WB) manufactured by JEOL Ltd., according to 1 When measuring the content ratio of each monomer unit constituting the obtained nitrile rubber by 1H-NMR, the acrylonitrile unit is 80% (by weight), the 1,3-butadiene unit is 15% (by weight), the 1-ethyl-3-methylimidazolium hexafluorophosphate unit is 5% (by weight), and the iodine value is 120 mg / 100 mg.

[0196] Use this nitrile rubber as a binder.

[0197] Examples 1-7

[0198] Charge 300 parts of water, 50 parts of acrylonitrile, and 30 parts of sodium dodecylbenzenesulfonate (emulsifier) into a reaction vessel, and adjust the temperature to 2°C. Then, reduce the pressure of the gas phase to fully degas, and then add 10 parts of 1,3-butadiene, 0.1 part of ammonium persulfate as a polymerization initiator, 0.02 part of sodium ethylenediaminetetraacetate, 0.02 part of copper acetate, and 1 part of tert-dodecyl mercaptan as a chain transfer agent to initiate the first-stage reaction of emulsion polymerization. After the reaction is initiated, when the polymerization conversion rate of the filler monomer reaches 42% (by weight), add 10 parts of 1,3-butadiene to the reaction vessel to carry out the second-stage polymerization reaction. Then, when the polymerization conversion rate of the filler monomer reaches 60% (by weight), add 9.9 parts of 1,3-butadiene to the reaction vessel to carry out the third-stage polymerization reaction. After that, when the polymerization conversion rate of the total filler monomer reaches 75% (by weight), add 0.1 part of 1-ethyl-3-methylimidazolium methyl sulfate and 0.2 part of potassium hydroxide to stop the polymerization reaction. After the reaction stops, heat the content of the reaction vessel to 70°C, and recover the unreacted monomer by steam distillation under reduced pressure to obtain a nitrile rubber latex.

[0199] Collect a part of the above latex, coagulate it with a large amount of methanol, filter, and dry it to obtain nitrile rubber. When using an FT-NMR apparatus (JNM-Ex400WB) manufactured by JEOL Ltd. to determine the content ratio of each monomer unit constituting the obtained nitrile rubber according to 1 1H-NMR, the acrylonitrile unit is 50% (by weight), the 1,3-butadiene unit is 49.9% (by weight), the 1-ethyl-3-methylimidazolium methyl sulfate unit is 0.1% (by weight), and the iodine value is 60 mg / 100 mg.

[0200] Use this nitrile rubber as a binder.

[0201] Examples 1-8

[0202] The binder composition includes: the nitrile rubber of Examples 1-4 and n-butyl methacrylate resin. Based on the solid content of the binder composition being 100 wt%, the content of the nitrile rubber is 90 wt%, and the content of the n-butyl methacrylate resin is 10 wt%.

[0203] Examples 1-9

[0204] The binder composition includes: the nitrile rubber of Examples 1-4 and n-butyl methacrylate resin. Based on the solid content of the binder composition being 100 wt%, the content of the nitrile rubber is 80 wt%, and the content of the n-butyl methacrylate resin is 20 wt%.

[0205] Examples 1-10

[0206] The binder composition comprises: the nitrile rubber and n-butyl methacrylate resin of Examples 1-4. Based on the solid content of the binder composition being 100 wt%, the content of the nitrile rubber is 70 wt% and the content of the n-butyl methacrylate resin is 30 wt%.

[0207] Examples 1-11

[0208] The binder composition comprises: the nitrile rubber, n-butyl methacrylate resin and plasticizer triethylene glycol di-2-ethylhexanoate of Examples 1-4. Based on the solid content of the binder composition being 100 wt%, the content of the nitrile rubber is 75 wt%, the content of the n-butyl methacrylate resin is 22 wt%, and the content of the triethylene glycol di-2-ethylhexanoate is 3 wt%.

[0209] Examples 1-12

[0210] The binder composition comprises: the nitrile rubber, vinyl chloride resin and plasticizer triethylene glycol di-2-ethylhexanoate of Examples 1-4. Based on the solid content of the binder composition being 100 wt%, the content of the nitrile rubber is 75 wt%, the content of the vinyl chloride resin is 24 wt%, and the content of the triethylene glycol di-2-ethylhexanoate is 1 wt%.

[0211] Examples 1-13

[0212] The binder composition comprises: the nitrile rubber, n-butyl methacrylate resin and plasticizer triethylene glycol di-2-ethylhexanoate of Examples 1-4. Based on the solid content of the binder composition being 100 wt%, the content of the nitrile rubber is 75 wt%, the content of the n-butyl methacrylate resin is 24.9 wt%, and the content of the triethylene glycol di-2-ethylhexanoate is 0.1 wt%.

[0213] Examples 1-14

[0214] The binder composition comprises: the nitrile rubber and n-butyl methacrylate resin of Examples 1-6. Based on the solid content of the binder composition being 100 wt%, the content of the nitrile rubber is 90 wt% and the content of the n-butyl methacrylate resin is 10 wt%.

[0215] Examples 1-15

[0216] The binder composition comprises: the nitrile rubber and n-butyl methacrylate resin of Examples 1-6. Based on the solid content of the binder composition being 100 wt%, the content of the nitrile rubber is 80 wt% and the content of the n-butyl methacrylate resin is 20 wt%.

[0217] Examples 1-16

[0218] The binder composition comprises: the nitrile rubber and n-butyl methacrylate resin of Examples 1-6. Based on 100 wt% of the solid content of the binder composition, the content of the nitrile rubber is 70 wt%, and the content of the n-butyl methacrylate resin is 30 wt%.

[0219] Examples 1-17

[0220] The binder composition comprises: the nitrile rubber, n-butyl methacrylate resin and plasticizer triethylene glycol di-2-ethylhexanoate of Examples 1-6. Based on 100 wt% of the solid content of the binder composition, the content of the nitrile rubber is 75 wt%, the content of the n-butyl methacrylate resin is 22 wt%, and the content of the triethylene glycol di-2-ethylhexanoate is 3 wt%.

[0221] Examples 1-18

[0222] The binder composition comprises: the nitrile rubber, vinyl chloride resin and plasticizer triethylene glycol di-2-ethylhexanoate of Examples 1-6. Based on 100 wt% of the solid content of the binder composition, the content of the nitrile rubber is 75 wt%, the content of the vinyl chloride resin is 24 wt%, and the content of the triethylene glycol di-2-ethylhexanoate is 1 wt%.

[0223] Examples 1-19

[0224] The binder composition comprises: the nitrile rubber, n-butyl methacrylate resin and plasticizer triethylene glycol di-2-ethylhexanoate of Examples 1-6. Based on 100 wt% of the solid content of the binder composition, the content of the nitrile rubber is 75 wt%, the content of the n-butyl methacrylate resin is 24.5 wt%, and the content of the triethylene glycol di-2-ethylhexanoate is 0.1 wt%.

[0225] Comparative Example 1-1

[0226] Preparation of nitrile rubber

[0227] Charge 300 parts of water, 10 parts of acrylonitrile, and 50 parts of sodium dodecylbenzenesulfonate (emulsifier) into a reaction vessel, and adjust the temperature to 2 °C. Then, reduce the pressure of the gas phase to fully degas, and thereafter add 40 parts of 1,3-butadiene, 0.1 part of ammonium sulfate as a polymerization initiator, 0.05 part of sodium ethylenediaminetetraacetate, 0.02 part of copper acetate, and 1 part of tert-dodecyl mercaptan as a chain transfer agent to initiate the first-stage reaction of emulsion polymerization. After the reaction is initiated, when the polymerization conversion rate relative to the monomer of the filler reaches 42% (by weight), 20 parts of 1,3-butadiene are added to the reaction vessel to carry out the second-stage polymerization reaction. Next, when the polymerization conversion rate relative to the monomer of the filler reaches 60% (by weight), 20 parts of 1,3-butadiene are added to the reaction vessel to carry out the third-stage polymerization reaction. Thereafter, when the polymerization conversion rate relative to the total monomer of the filler reaches 75% (by weight), 0.2 part of potassium hydroxide is added to stop the polymerization reaction. After the reaction stops, heat the content of the reaction vessel to 70 °C, and recover the unreacted monomer by steam distillation under reduced pressure to obtain a nitrile rubber latex.

[0228] Collect a part of the above latex, coagulate it with a large amount of methanol, filter, and dry to obtain nitrile rubber. Using an FT-NMR apparatus (JNM-Ex400WB) manufactured by JEOL Ltd., according to 1 When measuring the content ratio of each monomer unit constituting the obtained nitrile rubber by 1H-NMR, the acrylonitrile unit is 10% (by weight), the 1,3-butadiene unit is 90% (by weight), and the iodine value is 50 mg / 100 mg.

[0229] Use this nitrile rubber as a binder.

[0230] Comparative Examples 1-2

[0231] Preparation of Nitrile Rubber

[0232] Charge 300 parts of water, 90 parts of acrylonitrile, and 5 parts of sodium dodecylbenzenesulfonate (emulsifier) into a reaction vessel, and adjust the temperature to 2 °C. Then, reduce the pressure of the gas phase to fully degas, and thereafter add 40 parts of 1,3-butadiene, 0.1 part of ammonium persulfate as a polymerization initiator, 0.05 part of sodium ethylenediaminetetraacetate, 0.02 part of copper acetate, and 1 part of tert-dodecyl mercaptan as a chain transfer agent to initiate the first-stage reaction of emulsion polymerization.

[0233] After the reaction was initiated, at the moment when the polymerization conversion rate of the filler monomer reached 42% (by weight), 2 parts of 1,3-butadiene were added to the reaction vessel respectively to carry out the second-stage polymerization reaction. Then, at the moment when the polymerization conversion rate of the filler monomer reached 60% (by weight), 3 parts of 1,3-butadiene were added to the reaction vessel respectively to carry out the third-stage polymerization reaction. After that, at the moment when the polymerization conversion rate of the total filler monomer reached 75% (by weight), 0.2 part of potassium hydroxide was added to stop the polymerization reaction. After the reaction stopped, the content of the reaction vessel was heated to 70 °C, and the unreacted monomers were recovered by steam distillation under reduced pressure to obtain nitrile rubber latex.

[0234] A part of the above latex was collected, coagulated with a large amount of methanol, filtered and dried to obtain nitrile rubber. Using an FT-NMR apparatus (JNM-Ex400WB) manufactured by JEOL Ltd., according to 1 When the content ratio of each monomer unit constituting the obtained nitrile rubber was determined by 1H-NMR, the acrylonitrile unit was 90% (by weight), the 1,3-butadiene unit was 10% (by weight), and the iodine value was 165 mg / 100 mg.

[0235] This nitrile rubber was used as a binder.

[0236] Comparative Examples 1-3

[0237] The binder compositions of Comparative Examples 1-3 included: the nitrile rubber of Examples 1-4 and n-butyl methacrylate resin. Based on the solid content of the binder composition being 100 wt%, the content of the nitrile rubber was 60 wt%, and the content of the n-butyl methacrylate resin was 40 wt%.

[0238] Fabrication of Lithium-Ion Batteries

[0239] Preparation of the positive electrode sheet: Lithium iron phosphate, conductive agent Super-P carbon black, and the nitrile rubber or binder composition prepared in the above examples and comparative examples were stirred and mixed evenly at a weight ratio of 97:2:1, and the solvent N-methylpyrrolidone was added to obtain a positive electrode active film layer slurry with a solid content of 73%; then the positive electrode active film layer slurry was evenly coated on the aluminum foil, and after drying, cold pressing, and slitting, the positive electrode sheet was obtained.

[0240] Preparation of the negative electrode sheet: Artificial graphite and silicon-carbon material with a mass ratio of 90:10 were used as the negative electrode active material. The negative electrode active material, conductive agent Super-P carbon black, and binder styrene-butadiene rubber (SBR) were dissolved in deionized water at a weight ratio of 98:0.5:1.5, and sodium carboxymethyl cellulose (CMC-Na) was added as a thickening agent. After mixing evenly, a negative electrode active film layer slurry was prepared; the negative electrode slurry was evenly coated on the copper foil, and after drying, cold pressing, and slitting, the negative electrode sheet was obtained.

[0241] Separator: A polypropylene film is used as the separator.

[0242] Preparation of electrolyte: In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), organic solvents ethylene carbonate (EC) / propylene carbonate (PC) / propyl propionate (EP) / propyl propionate (PP) are mixed evenly according to a mass ratio of 1:1.2:0.5:2.7. 10.5% lithium hexafluorophosphate (LiPF6) lithium salt is added and dissolved in the organic solvent, and then 4% fluoroethylene carbonate and 1% 1,3 - propane sultone are added to obtain a basic electrolyte (denoted as EL - 0). Additive A is added to the basic electrolyte, and additive A is selected from at least one of lithium difluorophosphate, ethylene sulfate, vinylene carbonate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(oxalato)borate, 18 - crown - 6, dibenzo - 18 - crown - 6, 1 - aza - 18 - crown - 6. The electrolyte prepared based on this is shown in Table 1, and the mass parts of additive A shown in Table 1 are calculated based on the total mass of the electrolyte being 100 mass parts.

[0243] Table 1 Electrolyte and Additive A Contained therein

[0244]

[0245]

[0246] Preparation of wound - structure battery cell: The negative electrode sheet, positive electrode sheet, and separator prepared above are wound together to form a wound - structure battery cell (abbreviated as the core).

[0247] Preparation of lithium - ion battery: After the prepared wound - structure battery cell is hot - pressed and shaped, it is packaged with an aluminum - plastic film, baked to remove moisture, and then the electrolyte is injected, and the obtained battery cell is formed to obtain a lithium - ion battery.

[0248] Examples 2 - 1 ~ 2 - 34

[0249] Examples 2 - 1 to 2 - 34 prepare lithium - ion batteries based on the same method as above, with the only difference being that the binder of the positive electrode material and the electrolyte are changed as shown in Table 2.

[0250] Comparative Examples 2 - 1 ~ 2 - 4

[0251] Comparative Examples 2 - 1 to 2 - 4 prepare lithium - ion batteries based on the same method as above, with the only difference being that the binder of the positive electrode material and the electrolyte are changed as shown in Table 2.

[0252] Table 2 Binder for Battery Positive Electrode, Electrolyte, and Battery - Related Performance

[0253]

[0254]

[0255] The battery performance shown in Table 2 above was tested by the following method:

[0256] (1) Flexibility

[0257] Wind the positive electrode of the single-sided adhesive layer around a stainless steel cylinder with a diameter of 3.0 mm (with the current collector on the inside). Then, visually check whether cracks are generated on the surface of the wound positive electrode adhesive layer. If no cracks are confirmed, successively reduce the diameter of the stainless steel cylinder to 2.5 mm, 2.0 mm, and 1.5 mm, and perform the same operation. Then, record the diameter of the cylinder when cracks are first confirmed on the surface of the positive electrode adhesive layer of this positive electrode (the cylinder diameter when cracks are generated), and evaluate it according to the following criteria. The smaller the cylinder diameter when cracks are generated, the better the flexibility of the positive electrode. Moreover, if no cracks are generated even when using a cylinder with a diameter of 1.5 mm, it indicates that the flexibility of the positive electrode is very excellent. In Table 2, A+, A, B, C, D, and E in the "Flexibility" column represent:

[0258] A+: No cracks were confirmed even when the cylinder diameter was 0.5 mm;

[0259] A: The cylinder diameter when cracks are generated is 1.0 mm;

[0260] B: The cylinder diameter when cracks are generated is 1.5 mm;

[0261] C: The cylinder diameter when cracks are generated is 2.0 mm;

[0262] D: The cylinder diameter when cracks are generated is 2.5 mm;

[0263] E: The cylinder diameter when cracks are generated is 3.0 mm.

[0264] (2) Penetration resistance of the positive electrode

[0265] Immerse the fabricated positive electrode in an electrolytic solution at 60 °C. After 12 hours, take out the immersed positive electrode, wash it appropriately with diethyl carbonate (DEC), and gently wipe it with a paper towel. In addition, as the electrolytic solution, use a solution in which LiPF6 is dissolved at a concentration of 1 mol / L in a mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of EC:EMC = 3:7 (at 20 °C).

[0266] Thereafter, the positive electrode was clamped with a gold-plated jig and pressed at a pressure of 10 MPa. Then, using the terminal of the gold-plated jig and a multi-channel potentiostat, the voltage when a current of 10 mA flowed was measured. The voltage after 10 minutes was read, and based on the calculated resistance value, the thickness and area of the positive electrode, the volume resistivity ρ (Ω·cm) was calculated and evaluated according to the following criteria. The smaller the volume resistivity ρ, the lower the puncture resistance.

[0267] In Table 2, A+, A, B, C, D, and E in the "Puncture Resistance" column represent:

[0268] A+: The volume resistivity ρ is less than 50 Ω·cm;

[0269] A: The volume resistivity ρ is 50 Ω·cm or more and less than 60 Ω·cm;

[0270] B: The volume resistivity ρ is 60 Ω·cm or more and less than 90 Ω·cm;

[0271] C: The volume resistivity p is 90 Ω·cm or more and less than 180 Ω·cm;

[0272] D: The volume resistivity p is 180 Ω·cm or more and less than 270 Ω·cm;

[0273] E: The volume resistivity p is 270 ΩΩ·cm or more.

[0274] (3) High-temperature storage characteristics of the secondary battery

[0275] For the fabricated lithium-ion secondary battery, in an environment of 25°C, it was charged to 4.5 V by a constant current method of 0.1C and then stored at 80°C for 100 hours. The open circuit voltage (hereinafter marked as "OCV") before the start of storage at 80°C and the OCV of the cell after storage at 80°C for 100 hours were measured, and the ratio of the OCV after storage at 80°C for 100 hours to the OCV before the start of storage at 80°C was calculated as the OCV retention rate and evaluated according to the following criteria. The larger the OCV retention rate, the better the high-temperature storage characteristics, that is, the better the life characteristics.

[0276] A+: The OCV retention rate is 99.2% or more;

[0277] A: The OCV retention rate is 99.0% or more and less than 99.2%;

[0278] B: The OCV retention rate is 98.5% or more and less than 99.0%;

[0279] C: The OCV retention rate is 98.0% or more and less than 98.5%;

[0280] D: OCV maintenance rate is 97.5% or more and less than 98.0%;

[0281] E: OCV maintenance rate is less than 97.5%.

[0282] The present invention provides a positive electrode binder composition containing a nitrile rubber of a specific structure, and the content of the nitrile rubber is within a specified range, so that a positive electrode binder composition with excellent flexibility and penetration resistance can be prepared. The prepared positive electrode has excellent flexibility and penetration resistance, and can enable the energy storage device to exhibit excellent high-temperature storage characteristics.

[0283] The applicant has also found that when the binder composition further contains at least one thermoplastic resin selected from the group consisting of vinyl chloride resin and acrylic resin, a further improved effect is obtained. When the binder composition also contains a plasticizer, a further improved effect is obtained. When the electrolyte system contains at least one additive A selected from lithium difluorophosphate, vinyl sulfate, vinylene carbonate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium bisoxalatoborate, and crown ether, the high temperature storage characteristics are further significantly improved.

[0284] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A nitrile rubber, characterized in that: The nitrile rubber contains 20 to 80 wt% of α,β-ethylenically unsaturated nitrile monomer units, 20 to 80 wt% of conjugated diene monomer units, and 0 to 30 wt% of cationic monomer units, and the iodine value of the nitrile rubber is 55 mg / 100 mg or more and 150 mg / 100 mg or less.

2. The nitrile rubber according to claim 1, wherein: The nitrile rubber contains 30 to 70 wt% of α,β-ethylenically unsaturated nitrile monomer units, preferably 50 to 60 wt% of α,β-ethylenically unsaturated nitrile monomer units; And / or, the nitrile rubber contains 30 to 60 wt% of conjugated diene monomer units, preferably 40 to 50 wt% of conjugated diene monomer units; And / or, the nitrile rubber contains 0.1 to 5 wt% of the cationic monomer units, preferably 0.3 to 2 wt% of the cationic monomer units; And / or, the monomer forming the cationic monomer units includes a group containing a nitrogen-containing aromatic heterocycle. Preferably, the monomer forming the cationic monomer units contains at least one of an imidazole ring, a pyrrole ring, a thiazole ring, an oxazole ring, a pyrazole ring, an isoxazole ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, a quinazoline ring, a cinnoline ring, a purine ring, an indole ring, an isoindole ring, a benzimidazole ring, a benzoxazole ring, a benzoisoxazole ring fused heterocycle; More preferably, the monomer forming the cationic monomer units contains an imidazole ring; Further preferably, the monomer forming the cationic monomer units includes one or more combinations of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, or 1-ethyl-3-methylimidazolium methyl sulfate; And / or, the iodine value of the nitrile rubber is 60 mg / 100 mg or more and 120 mg / 100 mg or less.

3. A binder composition for the positive electrode of an energy storage device, characterized in that: The binder composition includes the nitrile rubber according to claim 1 or 2. Based on 100 wt% of the solid content of the binder composition, the content of the nitrile rubber is 70 wt% or more.

4. The binder composition according to claim 3, wherein: The content of the nitrile rubber is 80 wt% or more, preferably 90 wt% or more.

5. The binder composition according to claim 3, characterized in that: The binder composition further includes a thermoplastic resin; Preferably, the thermoplastic resin includes at least one of a vinyl chloride resin or an acrylic resin; Preferably, based on 100 wt% of the solid content of the binder composition, the thermoplastic resin is 10 to 30 wwt%; Preferably, the thermoplastic resin is a granular resin, and its volume average particle size is 0.01 μm to 1 mm.

6. The binder composition according to claim 3, wherein: The binder composition further includes a plasticizer, and the plasticizer includes at least one of triethylene glycol bis-2-ethylpropionate, triethylene glycol bis-2-ethylbutyrate, triethylene glycol bis-2-ethylhexanoate, triethylene glycol dioctanoate, triethylene glycol bis-n-octanoate, triethylene glycol bis-n-heptanoate; Preferably, based on 100 wt% of the solid content of the binder composition, the content of the plasticizer is 0.1 to 3 wt%.

7. A paste composition for a positive electrode of an energy storage device, characterized in that, It includes a positive electrode active material, a binder material, and a conductive material, and the binder material includes the nitrile rubber described in Claim 1 or 2 or the binder composition for the positive electrode of the energy storage device described in any one of Claims 4-6.

8. A positive electrode of an energy storage device, characterized in that: The positive electrode of the energy storage device includes a current collector and a positive electrode mixture layer formed on the current collector, and the positive electrode mixture layer includes a cured product of the slurry composition described in Claim 7.

9. An energy storage device, comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The positive electrode is the positive electrode of the energy storage device described in Claim 8.

10. The energy storage device according to claim 9, characterized in that: The electrolyte of the energy storage device includes additive A, and additive A includes at least one of lithium difluorophosphate, vinylene sulfate, vinylene carbonate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(oxalate) borate, and crown ether; Preferably, the crown ether includes one or a combination of more than one of 15-crown-5, 18-crown-6, 21-crown-7, 24-crown-8, dibenzo-15-crown-5, dibenzo-18-crown-6, dibenzo-21-crown-7, dibenzo-24-crown-8, 1-aza-15-crown-5, 1-aza-18-crown-6, 1-aza-21-crown-7, and 1-aza-24-crown-8; Preferably, based on 100 parts by mass of the electrolyte, the content of lithium difluorophosphate is 0.01 to 0.8 parts by mass; and / or, the content of vinylene sulfate is 0.01 to 0.8 parts by mass; and / or, the content of vinylene carbonate is 0.01 to 0.5 parts by mass; and / or, the content of lithium tetrafluoroborate is 0.01 to 1.5 parts by mass; and / or, the content of lithium difluorooxalate borate is 0.01 to 0.8 parts by mass; and / or, the content of lithium bis(oxalate) borate is 0.01 to 0.5 parts by mass; and / or, the content of crown ether is 0.1 to 2.5 parts by mass.

Images