Binder composition for positive electrode of energy storage device and application of binder composition

Abstract

The invention aims to provide a binder composition for a positive electrode of an energy storage device and application of the binder composition. The binder composition comprises a polymer A, a polymer B and a metal salt, the polymer A contains an unsaturated nitrile monomer unit, the polymer B contains at least one of an unsaturated carboxylic acid monomer unit, an unsaturated carboxylic acid amide monomer unit or an unsaturated carboxylic ester monomer unit, and both the polymer A and the polymer B do not contain a fluorine element; metal elements in the metal salt comprise at least one of calcium, nickel, zinc and cobalt; when the solid content of the binder composition is 100 wt%, the content of the metal salt is 3 wt% or less. When the binder composition for the positive electrode is used for the energy storage device, the prepared positive electrode is excellent in flexibility and not prone to powder falling, and the energy storage device can exert the excellent high-potential durability characteristic.

Description

Technical Field

[0001] This application belongs to the technical field of energy storage, and particularly relates to 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 an important solution. Therefore, more stringent requirements are put forward for the main binder type polyvinylidene fluoride (PVDF) system for electrode materials, requiring further improvement of its bonding force and increasing the softness of the electrode sheet.

[0003] In order to meet this requirement, further copolymer modification of PVDF is needed. However, the copolymer modification of vinylidene fluoride (VDF) is difficult, and due to the reactivity ratio problem of the VDF material itself, its modification is difficult, functionalization cannot be achieved, and the VDF raw material for synthesizing PVDF is a highly hazardous environmental pollutant, with limited raw material supply, unable to meet the growing demand of lithium-ion batteries, and there are also problems such as gelation, film peeling and powder falling after being infiltrated by the electrolyte in the actual application process.

[0004] In view of the above problems, the market hopes to develop a new technology that can solve the above technical problems, and polyacrylonitrile-based binders are one of the most promising directions. However, in the process of direct use of existing polyacrylonitrile-based binders, the dissolution performance of the binder is poor, the processing process is too complex, which is not conducive to industrial production. Moreover, the toughness of acrylonitrile-based polymers is poor, and cracking and other phenomena are likely to occur during the processes of rolling, winding and assembly. And when charging and discharging repeatedly at high potentials, gas will be generated by decomposition, resulting in battery swelling and posing a safety hazard. Summary of the Invention

[0005] Problems to be Solved by the Invention

[0006] The binding materials of the existing fluorine-containing positive electrode binder compositions, such as polyvinylidene fluoride, have problems such as gelation, film peeling and powder falling after being infiltrated by the electrolyte, and their durability (high-potential durability) when repeatedly exposed at high potentials is not good. Therefore, for a secondary battery having a positive electrode formed using the existing positive electrode binder composition, when charging and discharging repeatedly at high potentials, the gas generation amount increases and the battery performance may decrease, so there is room for improvement in this regard.

[0007] Therefore, the purpose of this application is to provide a binder composition for the positive electrode of an energy storage device and a slurry composition with excellent high-potential durability.

[0008] In addition, an object of the present application is to provide a positive electrode for an energy storage device with excellent high-potential durability.

[0009] Furthermore, an object of the present application is to provide an energy storage device in which the amount of gas generated is small even when charged and discharged repeatedly at a high potential.

[0010] Means for Solving the Problem

[0011] 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 binder composition has excellent high-potential durability, thus completing the present application. The binder composition contains polymer A, polymer B, and a metal salt. Polymer A contains an unsaturated nitrile monomer unit, and polymer B contains at least one of an unsaturated carboxylic acid monomer unit, an unsaturated carboxylic acid amide monomer unit, or an unsaturated carboxylic acid ester monomer unit, and neither polymer A nor polymer B contains a fluorine element; the metal element in the metal salt includes at least one of calcium, nickel, zinc, and cobalt; when the solid content of the binder composition for the positive electrode is 100 wt%, the content of the metal salt is 3 wt% or less. This binder composition for the positive electrode has excellent electrolyte resistance and is not easily decomposed at a high potential. When used in an energy storage device, the positive electrode produced has excellent flexibility and is not easily powdered, and can enable the energy storage device to exhibit excellent high-potential durability characteristics.

[0012] That is, an object of the present application is to advantageously solve all or part of the above problems. According to the present application, there can be provided the following binder composition for a positive electrode for an energy storage device electrode, an energy storage device electrode, and an energy storage device.

[0013] A first aspect of the present application is to provide a binder composition for a positive electrode of an energy storage device, the binder composition containing polymer A, polymer B, and a metal salt; polymer A contains an unsaturated nitrile monomer unit, polymer B contains at least one of an unsaturated carboxylic acid monomer unit, an unsaturated carboxylic acid amide monomer unit, or an unsaturated carboxylic acid ester monomer unit, and neither polymer A nor polymer B contains a fluorine element; the metal element in the metal salt includes at least one of calcium, nickel, zinc, and cobalt; based on the solid content of the binder composition being 100 wt%, the content of the metal salt is 3 wt% or less.

[0014] By making the binder composition for the positive electrode contain specific polymer A, polymer B, and a metal salt, and the content of the metal salt is within a specified range, a binder composition for the positive electrode with excellent flexibility and adhesiveness can be produced.

[0015] In some embodiments, the content of the metal salt is 1 wt% or less, preferably 0.5 wt% or less, and more preferably 0.1 wt% or more. The content of the metal salt is, for example, 0.01 - 3 wt%, preferably 0.1 - 1 wt%.

[0016] If the metal salt content meets the above range, the flexibility and adhesiveness of the binder composition for the positive electrode can be further improved.

[0017] In some embodiments, the content of the polymer A is 67-90 wt%, preferably 80-90 wt%.

[0018] If the above conditions are met, the flexibility and adhesiveness of the binder composition for the positive electrode can be further improved.

[0019] In some embodiments, the content of the polymer B is 10-30 wt%, preferably 10-20 wt%.

[0020] If the above conditions are met, the flexibility and adhesiveness of the binder composition for the positive electrode can be further improved.

[0021] Furthermore, the metal element in the metal salt includes calcium. The metal salt includes calcium chloride and / or calcium carbonate.

[0022] If the above conditions are met, the flexibility and adhesiveness of the binder composition for the positive electrode can be further improved.

[0023] Furthermore, the metal salt includes a chloride salt and / or a carbonate salt of the corresponding metal element.

[0024] In some embodiments, the polymer A contains an unsaturated nitrile monomer unit, and optionally includes a (meth)acrylate monomer unit and / or an alkylene structure unit having 4 or more carbon atoms.

[0025] If the above conditions are met, the flexibility and adhesiveness of the binder composition for the positive electrode can be further improved.

[0026] Furthermore, the monomer for forming the unsaturated nitrile monomer unit includes at least one of (meth)acrylonitrile, α-chloropropionitrile, α-ethylacrylonitrile, or vinylidene cyanide.

[0027] If the above conditions are met, the flexibility and adhesiveness of the binder composition for the positive electrode can be further improved.

[0028] In some embodiments, the monomer for forming the unsaturated carboxylic acid monomer unit of the polymer B includes at least one of acrylic acid and methacrylic acid.

[0029] In some embodiments, the monomer for forming the unsaturated carboxylic acid amide monomer unit of the polymer B includes at least one of methacrylamide and acrylamide.

[0030] In some embodiments, the monomers for forming the unsaturated carboxylic acid ester monomer units of the polymer B include at least one of n-butyl methacrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, 4-methylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, cyclooctyl (meth)acrylate, cyclodecyl (meth)acrylate, or menthyl (meth)acrylate.

[0031] If the polymer B is formed using the above monomers, the flexibility and adhesiveness of the binder composition for the positive electrode can be further improved.

[0032] In some embodiments, the binder composition for the positive electrode further includes a plasticizer, and the plasticizer includes at least one of dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-n-butyl adipate, bis(2-ethylhexyl) adipate, diisodecyl adipate, di-n-butyl maleate, dimethyl maleate, diethyl maleate, di-n-butyl fumarate, tri-n-octyl trimellitate, triethyl citrate, tri-n-butyl citrate, acetyltriethyl citrate, diglycol monolaurate, diglycol dibenzoate, or dipropylene glycol dibenzoate.

[0033] In some embodiments, based on the solid content of the binder composition being 100 wt%, the content of the plasticizer is 0.1 to 5 wt%, more preferably 0.1 to 3 wt%.

[0034] If the above conditions are met, the flexibility and adhesiveness of the binder composition for the positive electrode can be further improved.

[0035] A second aspect of the present invention is to provide a slurry composition for a positive electrode of an energy storage device, the slurry composition including a positive electrode active material, a binder material, and a conductive material, and the binder material including the binder composition for a positive electrode of an energy storage device according to any one of the above.

[0036] A third aspect of the present invention is to provide a positive electrode of an energy storage device, the positive electrode of the energy storage device including a current collector and a positive electrode mixture layer, and the positive electrode mixture layer including a cured product of the slurry composition for a positive electrode of the energy storage device.

[0037] If the above binder composition for the positive electrode or a slurry composition containing the binder composition is used to prepare the positive electrode, the prepared positive electrode has excellent flexibility and is not prone to powder shedding.

[0038] A fourth aspect of the present invention is to provide an energy storage device including a positive electrode, a negative electrode, and an electrolyte, and the positive electrode being the positive electrode of the energy storage device.

[0039] If the above positive electrode of the energy storage device is used, the energy storage device can exhibit excellent high-potential durability characteristics.

[0040] In some embodiments, the energy storage device is a lithium-ion battery or an electric double layer capacitor.

[0041] In some embodiments, the electrolyte of the energy storage device includes an electrolyte salt, an organic solvent, and an additive, and the additive includes at least one of lithium difluorophosphate, vinylene sulfate, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, and crown ether.

[0042] If the above additives are used, it is possible to suppress the swelling of the binder composition for the positive electrode in the electrolyte of the present application, and it is possible to enable the energy storage device to exhibit excellent high-potential durability characteristics.

[0043] 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.

[0044] If an electrolyte containing the above additives is used, it is possible to suppress the swelling of the binder composition for the positive electrode in the electrolyte, and it is possible to enable the energy storage device to exhibit excellent high-potential durability characteristics.

[0045] In some embodiments, 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 succinonitrile is 0.5 to 7 parts by mass; and / or, the content of adiponitrile is 1.9 to 4.3 parts by mass; and / or, the content of 1,3,6-hexanetricarbonitrile is 0.9 to 3.5 parts by mass; and / or, the content of glycerol trinitrile is 0.1 to 2.8 parts by mass; and / or, the content of crown ether is 0.1 to 2.5 parts by mass.

[0046] If an electrolyte component containing the above content of additives is used, it is possible to suppress the swelling of the binder composition for the positive electrode in the electrolyte, and it is possible to enable the energy storage device to exhibit excellent high-potential durability characteristics.

[0047] Technical Effects

[0048] When the binder composition for the positive electrode of the present application is used in an energy storage device, the positive electrode produced has excellent softness and is not prone to powder falling, and it is possible to enable the energy storage device to exhibit excellent high-potential durability characteristics. Detailed Embodiments

[0049] In the following, embodiments of the present application are described in detail. However, these embodiments are exemplary, and the present application is not limited thereto.

[0050] The binder composition for the positive electrode of the present application contains polymer A, polymer B, and a metal salt. Polymer A contains unsaturated nitrile monomer units, polymer B contains at least one of unsaturated carboxylic acid monomer units, unsaturated carboxylic acid amide monomer units, or unsaturated carboxylic acid ester monomer units, and neither polymer A nor polymer B contains fluorine elements; the metal elements in the metal salt include at least one of calcium, nickel, zinc, and cobalt; based on the solid content of the binder composition for the positive electrode being 100 wt%, the content of the metal salt is 3 wt% or less. When the binder composition for the positive electrode is used in an energy storage device, the fabricated positive electrode has excellent flexibility and is not prone to powder shedding, and can enable the energy storage device to exhibit excellent high-potential durability characteristics.

[0051] 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 binder composition for the positive electrode of the present application can be particularly suitable for electric double layer capacitors and lithium ion batteries.

[0052] Binder composition for positive electrode

[0053] In the present application, the binder composition for the positive electrode of the energy storage device contains polymer A, polymer B, and a metal salt. Polymer A contains unsaturated nitrile monomer units, polymer B contains at least one of unsaturated carboxylic acid monomer units, unsaturated carboxylic acid amide monomer units, or unsaturated carboxylic acid ester monomer units, and neither polymer A nor polymer B contains fluorine elements; the metal elements in the metal salt include at least one of calcium, nickel, zinc, and cobalt; based on the solid content of the binder composition for the positive electrode being 100 wt%, the content of the metal salt is 3 wt% or less.

[0054] As polymer A used in the present application, it contains monomer units containing a nitrile group.

[0055] Polymer A contains unsaturated nitrile monomer units, and optionally contains (meth)acrylate monomer units or alkylene structural units having 4 or more carbon atoms.

[0056] It should be noted that in the present application, "containing alkylene structural units having 4 or more carbon atoms" means "the polymer contains repeating units composed of alkylene structures represented by the general formula -CnH2n- [where n is an integer of 4 or more]".

[0057] In addition, "comprising monomer units" in the present application means "the polymer obtained using the monomer contains repeating units derived from the monomer". The content ratio of "monomer units" (including "structural units") in the polymer in the present application can be measured by nuclear magnetic resonance (NMR) methods such as 1H-NMR.

[0058] In addition, "(meth)acrylic acid" in the present application represents acrylic acid and / or methacrylic acid.

[0059] There is no particular limitation on the method for preparing Polymer A. It can be obtained, for example, by polymerizing a monomer composition containing the above-mentioned monomers, and optionally, by hydrogenating the obtained polymer.

[0060] Among them, the content ratio of each monomer in the monomer composition in the present application can be determined based on the content ratio of each monomer unit and structural unit (repeating unit) in Polymer A.

[0061] There is no particular limitation on the polymerization method, and any one of solution polymerization method, suspension polymerization method, bulk polymerization method, emulsion polymerization method, etc. can be used. In each polymerization method, known emulsifiers and polymerization initiators can be used as needed.

[0062] The monomers for forming the unsaturated nitrile monomer units of Polymer A preferably include at least one of (meth)acrylonitrile, α-chloropropionitrile, α-ethylacrylonitrile, or vinylidene cyanide.

[0063] As Polymer B used in the present application, it includes at least one of unsaturated carboxylic acid monomer units, unsaturated carboxylic acid amide monomer units, and unsaturated carboxylic acid ester monomer units.

[0064] In the present application, "unsaturated carboxylic acid monomer" corresponds to an unsaturated carboxylic acid containing an ethylenic unsaturated bond, and includes its acid anhydride.

[0065] In the present application, "unsaturated carboxylic acid amide monomer" corresponds to an amide of an unsaturated carboxylic acid containing an ethylenic unsaturated bond, and corresponds to a compound having a chemical structure formed by dehydration condensation of an unsaturated carboxylic acid with ammonia, a primary amine, or a secondary amine.

[0066] In the present application, "unsaturated carboxylic acid ester monomer" corresponds to an ester of an unsaturated carboxylic acid containing an ethylenic unsaturated bond, and corresponds to a compound having a chemical structure formed by condensation of an unsaturated carboxylic acid with a hydroxy-containing compound.

[0067] Unsaturated carboxylic acid monomer units

[0068] The unsaturated carboxylic acid monomer used to form the unsaturated carboxylic acid monomer unit is not particularly limited. The unsaturated carboxylic acid monomer unit can be a single type or a combination of two or more types in any proportion. The carboxyl group (-COOH) in the unsaturated carboxylic acid monomer can be in the form of a salt. In this case, it is preferably an alkali metal salt (such as Na salt, K salt, Li salt, etc.) or an ammonium salt.

[0069] As the unsaturated carboxylic acid monomer, a monofunctional unsaturated carboxylic acid monomer having one ethylenic unsaturated bond is preferred.

[0070] Examples of the unsaturated monocarboxylic acid include unsaturated aliphatic monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, 2-ethylacrylic acid, and isocrotonic acid. It is also possible to use α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, β-diaminoacrylic acid, etc.

[0071] Examples of the unsaturated dicarboxylic acid include unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, maleic anhydride, diacrylic anhydride, methylmaleic anhydride, dimethylmaleic anhydride, and methylmaleic acid. It is also possible to use phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, etc.

[0072] From the viewpoint of enabling the polymerization of polymers into high molecular weights, the unsaturated carboxylic acid monomer is preferably acrylic acid or methacrylic acid, and more preferably acrylic acid.

[0073] The unsaturated carboxylic acid monomer unit can be a single type or a combination of two or more types in any proportion. Based on 100 parts by mass of the polymer B, the unsaturated carboxylic acid monomer unit is 5 parts by mass or more in the polymer B. From the viewpoint of improving the cycle characteristics in secondary batteries, it is preferably 20 parts by mass or more, and more preferably 30 parts by mass or more. The unsaturated carboxylic acid monomer unit can be 100 parts by mass, but according to the desired properties, units other than the unsaturated carboxylic acid monomer unit may also be contained.

[0074] Unsaturated carboxylic acid amide monomer unit

[0075] By containing the unsaturated carboxylic acid amide monomer unit, the gelation of the positive electrode paste composition and the sedimentation of the solid components can be inhibited, and the storage stability of the paste can be improved.

[0076] The unsaturated carboxylic acid amide monomer used to form the unsaturated carboxylic acid amide monomer unit is not particularly limited. Examples include compounds having a chemical structure formed by dehydration condensation of the compounds exemplified above as the unsaturated carboxylic acid monomer with ammonia, a primary amine, or a secondary amine. Examples of the primary amine include methylamine, ethylamine, isopropylamine, isobutylamine, etc., and examples of the secondary amine include dimethylamine, diethylamine, etc.

[0077] As the unsaturated carboxylic acid amide monomer unit, a (meth)acrylamide monomer unit is preferred. Herein, the (meth)acrylamide monomer unit means a methacrylamide monomer unit and / or an acrylamide monomer unit.

[0078] Examples of the (meth)acrylamide monomer for forming the (meth)acrylamide monomer unit include compounds having a chemical structure formed by dehydration condensation of (meth)acrylic acid with ammonia, a primary amine, or a secondary amine.

[0079] Examples of the (meth)acrylamide monomer include acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-isopropylacrylamide, N-isobutylacrylamide, etc. From the viewpoint of being able to enhance the intermolecular interaction by using hydrogen bonds when forming a polymer, acrylamide and methacrylamide are preferred, and acrylamide is more preferred.

[0080] Unsaturated carboxylic acid ester monomer unit

[0081] By containing the unsaturated carboxylic acid ester monomer unit, the swelling degree of the polymer in the electrolyte can be moderately and easily adjusted.

[0082] The unsaturated carboxylic acid ester monomer for forming the unsaturated carboxylic acid ester monomer unit is not particularly limited, and examples include compounds having a chemical structure formed by dehydration condensation of the compounds exemplified above as the unsaturated carboxylic acid monomer with a hydroxyl group-containing compound such as an alcohol. As the alcohol, an alcohol having 1 to 10 carbon atoms can be mentioned.

[0083] In the present application, the monomer for forming the monomer unit of polymer B preferably includes at least one of (meth)acrylic acid, (meth)acrylamide, n-butyl methacrylate, (meth)acrylic acid cyclohexyl ester, (meth)acrylic acid cycloheptyl ester, 4-methylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, (meth)acrylic acid cyclooctyl ester, (meth)acrylic acid cyclodecyl ester, or (meth)acrylic acid menthyl ester.

[0084] In the present application, from the viewpoint of improving the adhesiveness of the positive electrode binder composition, when the solid content of the positive electrode binder composition is set to 100 wt%, the content of the polymer A is 67 to 90 wt%, and the preferred content is 80 to 90 wt%.

[0085] In the present application, from the viewpoint of improving the adhesiveness of the positive electrode binder composition, when the solid content of the positive electrode binder composition is set to 100 wt%, the content of the polymer B is 10 to 30 wt%, and the preferred content is 10 to 20 wt%.

[0086] In the present application, from the perspective of improving the flexibility of the positive electrode, the metal element in the metal salt includes at least one of calcium, nickel, zinc, and cobalt. The metal salt can be a chloride salt, carbonate salt, etc. of calcium, nickel, zinc, or cobalt. The metal element in the metal salt preferably includes calcium, and thus calcium chloride, carbonic acid, preferably calcium carbonate can be used.

[0087] In the present application, from the perspective of improving the flexibility of the positive electrode, when the solid content of the binder composition for the positive electrode is set to 100 wt%, the content of the metal salt is 3 wt% or less, preferably 1 wt% or less, more preferably 0.5 wt% or less, and further preferably 0.1 wt% or more. The content of the metal salt is, for example, 0.01 - 3 wt%, preferably 0.1 - 1 wt%, and more preferably 0.1 - 0.5 wt%.

[0088] In the present application, from the perspective of improving the flexibility of the positive electrode, the composition further includes a plasticizer, and the plasticizer includes at least one of dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-n-butyl adipate, bis(2-ethylhexyl) adipate, diisodecyl adipate, di-n-butyl maleate, dimethyl maleate, diethyl maleate, di-n-butyl fumarate, tri-n-octyl trimellitate, triethyl citrate, tri-n-butyl citrate, acetyltriethyl citrate, diglycol monolaurate, diglycol dibenzoate, or dipropylene glycol dibenzoate.

[0089] Based on the solid content of the binder composition being 100 wt%, the content of the plasticizer is 0.1 - 5 wt%, and more preferably 0.1 - 3 wt%.

[0090] Energy storage device electrode

[0091] 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 positive electrode active material and a binder material, and the binder material includes the binder composition of the present application.

[0092] The positive electrode mixture layer on the positive electrode of the energy storage device of the present application can be formed by using a positive electrode paste composition, which includes a positive electrode active material, a binder material, and a conductive material, and the binder material includes the binder composition for the positive electrode of the energy storage device as described in any one of the above.

[0093] As the positive electrode active material, various active materials conventionally used in positive electrodes of energy storage devices can be used.

[0094] The positive electrode active material may include a lithiated insertion compound that can reversibly insert and extract lithium ions.

[0095] 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.

[0096] 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 apparent to those of ordinary skill in the art after reading this application, and thus need not be described in detail herein.

[0097] For example, the positive electrode active material may include lithium cobalt oxide.

[0098] In some embodiments, the positive electrode active material may include a lithium cobalt oxide represented by the following Chemical Formula 1:

[0099] Chemical Formula 1: Li a11 Co x11 M 11 y11 O2.

[0100] 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.

[0101] For example, the positive electrode active material may be LiCoO2.

[0102] In some embodiments, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 2:

[0103] Chemical Formula 2: Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 .

[0104] 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.

[0105] 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.

[0106] 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:

[0107] Chemical Formula 3: Li a2 Ni x2 Co y2 M 3 z2 O 2-b2 X b2 .

[0108] 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.

[0109] 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.

[0110] 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.

[0111] Chemical Formula 4: Lia3 Ni x3 Co y3 M 4 z3 M 5 w3 O 2-b3 X b3 。

[0112] 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.

[0113] 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.

[0114] 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.

[0115] Chemical Formula 5: Li a4 Ni x4 Mn y4 M 6 z4 O 2-b4 X b4 。

[0116] 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 A1, 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.

[0117] 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%.

[0118] In some embodiments of the present application, the positive electrode binder layer includes a conductive material (e.g., a conductivity material). In some embodiments, based on the total weight of the positive electrode binder layer, the content of the conductive material may be 1.0 wt% to 5.0 wt%.

[0119] The conductive material is used to impart conductivity (e.g., electrical 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., undesirable 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.

[0120] The binder material improves the binding characteristics between the positive electrode active material particles and the binding characteristics between the positive electrode active material particles and the positive electrode current collector. In addition to using the binder composition for the positive electrode of the present application, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, a polymer 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. Based on the total weight of the positive electrode binder layer, the content of the binder material may be 1.0 wt% to 5.0 wt%.

[0121] The negative electrode of the present application includes a current collector and a binder layer formed on the current collector, and the binder layer includes a negative electrode active material. 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] The transition metal oxide may be vanadium oxide, lithium vanadium oxide, etc.

[0127] In some exemplary embodiments, the negative electrode active material may include at least one selected from graphite and Si composite.

[0128] 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.

[0129] For example, the Si-C composite may include: a core including Si particles and amorphous carbon.

[0130] 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.

[0131] The Si particles may have a median particle size of 10 nm to 200 nm.

[0132] 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.

[0133] 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.

[0134] 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%.

[0135] 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.

[0136] In the present disclosure, the surface portion indicates a region from the central portion of the negative electrode active material (e.g., a region just outside the central portion) to the outermost surface of the negative electrode active material.

[0137] In some embodiments, the negative electrode active material substantially uniformly includes Si particles. For example, the Si particles are present in the central portion and the surface portion of the negative electrode active material at a substantially uniform concentration.

[0138] The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, or a combination thereof.

[0139] The negative electrode active material may further include crystalline carbon.

[0140] When the negative electrode active material includes both the Si composite and crystalline carbon, the Si composite and crystalline carbon may be included in the form of a mixture, and in some embodiments, the Si composite and crystalline carbon may be included at a weight ratio of 1:99 to 50:50. In some embodiments, the Si composite and crystalline carbon may be included at a weight ratio of 3:97 to 20:80 or 5:95 to 20:80.

[0141] The crystalline carbon may be, for example, graphite, and may be, for example, natural graphite, artificial graphite, or a mixture thereof.

[0142] The crystalline carbon may have a median particle size of 5 μm to 30 μm.

[0143] The amorphous carbon precursor may 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).

[0144] In the negative electrode binder layer, based on the total weight of the negative electrode binder layer, the amount of the negative electrode active material included can be 95 wt% to 99 wt%.

[0145] In some example embodiments, the negative electrode mixture layer may further include a binder and may optionally include a conductive material (e.g., a conductivity material). In the negative electrode mixture layer, based on the total weight of the negative electrode mixture layer, the amount of the binder may be 1 wt% to 5 wt%. When the negative electrode mixture layer further includes a conductive material, the negative electrode mixture layer may include 90 wt% to 98 wt% of a negative electrode active material, 1 wt% to 5 wt% of a binder, and 1 wt% to 5 wt% of a conductive material.

[0146] The binder improves the binding characteristics of the negative electrode active material particles to each other and the binding characteristics of the negative electrode active material to the negative electrode current collector. The binder may be polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof. The binder may also be a rubbery binder and / or a polymer resin binder. The rubbery 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.

[0147] The conductive material provides 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 undesired 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.

[0148] In addition, in the case of an electric double layer capacitor, a carbonaceous material can be used as the active material.

[0149] Examples of the carbonaceous material include activated carbon, and for example, activated carbon obtained by carbonizing and then activating a phenolic resin can be cited.

[0150] Energy storage device

[0151] The energy storage device related to the present application includes at least a pair of positive and negative electrodes, a separator present between these positive and negative electrodes, and an electrolyte, and at least one positive electrode is the positive electrode of the above-mentioned energy storage device.

[0152] The energy storage device is characterized by using the above-mentioned positive electrode of the energy storage device. Therefore, for components such as separators, electrolytes, and negative electrodes that are components of other devices, they can be appropriately selected and used from well-known materials.

[0153] The separator can be a porous substrate or a composite porous substrate.

[0154] The porous substrate can be a substrate including pores, and lithium ions can move through the pores. The porous substrate includes, for example, a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer separator formed from these (such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, and a polypropylene / polyethylene / polypropylene trilayer separator).

[0155] The composite porous substrate can include a porous substrate and a functional layer formed on the porous substrate. From the perspective of ensuring additional functions, the functional layer can be at least one of a heat-resistant layer and a bonding layer. For example, the heat-resistant layer can include a heat-resistant resin and optionally can include fillers.

[0156] In some embodiments, the bonding layer can include a binder resin and optionally can include fillers.

[0157] The filler can be an organic filler and / or an inorganic filler.

[0158] As the electrolyte, both liquid and solid are acceptable, and both aqueous and non-aqueous are acceptable. When the positive electrode of the energy storage device of the present application is applied to a device using a non-aqueous electrolyte, it can also exhibit practically sufficient performance.

[0159] As the non-aqueous electrolyte, a non-aqueous electrolyte solution obtained by dissolving an electrolyte salt in a non-aqueous organic solvent can be cited.

[0160] In some embodiments, when the electrolyte includes additives, and the additives include at least one of lithium difluorophosphate, ethylene sulfate, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, and crown ether, it is possible to further reduce the swelling of the binder composition for the positive electrode, inhibit the decomposition of the binder at high potentials, and the improvement effect is beyond expectation.

[0161] The description of the electrolyte including the above additives is as follows.

[0162] The electrolyte includes a non-aqueous organic solvent, an electrolyte salt, additives, and optionally other additives.

[0163] As electrolyte salts, LiPF6, LiBF4, LiDFOP, LiDFOB, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide: LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiN(CxF 2x+1 SO2)(C y F 2y+1 SO2)(wherein, x and y are natural numbers, for example, integers from 1 to 20), LiCl, LiI, and LiB(C2O4)2 (lithium bis(oxalato)borate: LiBOB). The concentration of the lithium salt can be about 0.1 M to about 2.0 M. When the lithium salt is included in the above concentration range, the electrolyte can have excellent performance and lithium ion mobility due to appropriate or optimal electrolyte conductivity and viscosity.

[0164] The non-aqueous organic solvent is used as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0165] The non-aqueous organic solvent may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, and / or aprotic solvents.

[0166] 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.

[0167] 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.

[0168] The additive provided by the present application can effectively inhibit the swelling of the binder composition for the positive electrode, thereby inhibiting the decomposition of the binder composition for the positive electrode generated during charge and discharge cycles, and further improving the high-potential durability characteristics of the energy storage device.

[0169] The additive includes at least one of lithium difluorophosphate, vinylene sulfate, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, and crown ether.

[0170] 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.

[0171] 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 succinonitrile is 0.5 to 7 parts by mass; and / or the content of adiponitrile is 1.9 to 4.3 parts by mass; and / or the content of 1,3,6-hexanetricarbonitrile is 0.9 to 3.5 parts by mass; and / or the content of glycerol trinitrile is 0.1 to 2.8 parts by mass; and / or the content of crown ether is 0.1 to 2.5 parts by mass.

[0172] When using the electrolyte containing the additive with the above content, the decomposition of the binder composition for the positive electrode generated during charge and discharge cycles can be further inhibited, and the high-potential durability characteristics of the energy storage device can be further improved.

[0173] 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 type, flat wound laminated type, and laminated composite type can be adopted.

[0174] Examples

[0175] The following examples and comparative examples are listed to illustrate the present application more specifically, but the present application is not limited to the following examples.

[0176] Binder composition for positive electrode

[0177] Example 1-1

[0178] The binder composition includes: when the solid content of the binder composition for the positive electrode is set to 100 wt%, the content of polyacrylonitrile is 90 wt%, the content of n-butyl polymethacrylate is 7 wt%, and calcium chloride is 3 wt%.

[0179] Example 1-2

[0180] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of polyacrylonitrile is 67 wt%, the content of n-butyl polymethacrylate is 30 wt%, and calcium chloride is 3 wt%.

[0181] Example 1-3

[0182] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of polyacrylonitrile is 80 wt%, the content of n-butyl polymethacrylate is 18 wt%, and calcium chloride is 2 wt%.

[0183] Example 1-4

[0184] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of polymethacrylonitrile is 80 wt%, the content of polyacrylamide is 18 wt%, and calcium chloride is 2 wt%.

[0185] Example 1-5

[0186] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 80 wt%, the content of cyclohexyl polymethacrylate is 18 wt%, and calcium chloride is 2 wt%.

[0187] Example 1-6

[0188] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 80 wt%, the content of cyclohexyl polymethacrylate is 18 wt%, and nickel chloride is 2 wt%.

[0189] Example 1-7

[0190] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 80 wt%, the content of polyacrylamide is 18 wt%, and zinc chloride is 2 wt%.

[0191] Example 1-8A

[0192] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 80 wt%, the content of polyacrylamide is 18 wt%, and cobalt chloride is 2 wt%.

[0193] Example 1-8B

[0194] The binder composition comprises: when the solid content of the cathode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 80 wt%, the content of polymethacrylamide is 18 wt%, and nickel chloride is 2 wt%.

[0195] Example 1-8C

[0196] The binder composition comprises: when the solid content of the cathode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 80 wt%, the content of polymethacrylamide is 18 wt%, and calcium chloride is 2 wt%.

[0197] Example 1-8ID

[0198] The binder composition comprises: when the solid content of the cathode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 80 wt%, the content of polymethacrylamide is 18 wt%, and calcium carbonate is 2 wt%.

[0199] Example 1-9

[0200] The binder composition comprises: when the solid content of the cathode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 80 wt%, the content of poly(cyclohexyl methacrylate) is 18 wt%, and calcium carbonate is 2 wt%.

[0201] Example 1-10

[0202] The binder composition comprises: when the solid content of the cathode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 80 wt%, the content of polymethacrylamide is 19 wt%, and calcium carbonate is 1 wt%.

[0203] Example 1-11

[0204] The binder composition comprises: when the solid content of the cathode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 85 wt%, the content of polymethacrylamide is 14.2 wt%, and calcium carbonate is 0.8 wt%.

[0205] Example 1-12

[0206] The binder composition comprises: when the solid content of the cathode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 85 wt%, the content of polymethacrylamide is 14 wt%, calcium carbonate is 0.5 wt%, and dimethyl phthalate is 0.5 wt%.

[0207] Example 1-13

[0208] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 85 wt%, the content of polymethacrylamide is 14 wt%, calcium carbonate is 0.5 wt%, and triethyl citrate is 0.5 wt%.

[0209] Examples 1-14

[0210] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of poly(α-ethylacrylonitrile) is 85 wt%, the content of polymethacrylamide is 9.9 wt%, calcium carbonate is 0.1 wt%, and tributyl citrate is 5 wt%.

[0211] Comparative Example 1-1

[0212] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of polyacrylonitrile is 100 wt%.

[0213] Comparative Example 1-2

[0214] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of n-butyl polymethacrylate is 100 wt%.

[0215] Comparative Example 1-3

[0216] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of polyacrylonitrile is 90 wt%, the content of n-butyl polymethacrylate is 5 wt%, and calcium chloride is 5 wt%.

[0217] Comparative Example 1-4

[0218] The binder composition comprises: when the solid content of the positive electrode binder composition is set to 100 wt%, the content of polyvinylidene fluoride is 98 wt%, and calcium carbonate is 2 wt%.

[0219] Fabrication of Lithium-Ion Batteries

[0220] Preparation of the positive electrode sheet: Lithium cobaltate, the conductive agent Super-P carbon black, and the positive electrode 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 the positive electrode active film layer slurry, and the solid content of the slurry was 73%; then the positive electrode active film layer slurry was uniformly coated on the aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0221] Preparation of the negative electrode sheet: Artificial graphite and silicon-carbon material with a mass ratio of 90:10 are used as the negative electrode active materials. The negative electrode active materials, conductive agent conductive carbon black, and binder styrene-butadiene rubber (SBR) are dissolved in deionized water according to a weight ratio of 98:0.5:1.5, and sodium carboxymethyl cellulose (CMC-Na) as a thickening agent is added. After mixing evenly, a negative electrode active film layer slurry is prepared; the negative electrode slurry is evenly coated on a copper foil, and after drying, cold pressing, and slitting, the negative electrode sheet is obtained.

[0222] Separator: A polypropylene film is used as the separator.

[0223] Preparation of the 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) / ethyl propionate (EP) / propyl propionate (PP) are mixed evenly according to a mass ratio of 1:1.2:0.5:2.7. 10.5 mass% of LiPF6 lithium salt is added and dissolved in the organic solvent, and then 4 mass% of fluoroethylene carbonate and 1 mass% of 1,3-propane sultone are added to obtain a basic electrolyte (denoted as EL-0). Functional additives are added to the basic electrolyte to obtain the electrolyte shown in Table 1 below. The functional additives are selected from at least one of lithium difluorophosphate, ethylene sulfate, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, 18-crown-6, dibenzo-18-crown-6, 1-aza-18-crown-6. The mass parts of the functional additives shown in Table 1 are based on 100 mass parts of the total mass of the electrolyte.

[0224] Table 1 Electrolyte additives used in the following batteries and their contents

[0225] Electrolyte code Component A (parts by mass) EL-1 Adiponitrile (2.5) EL-2 1,3,6-Hexanetricarbonitrile (1.3) EL-3 Succinonitrile (0.7), Vinylene sulfate (0.3) EL-4 Vinylene sulfate (0.1), Adiponitrile (2.6) EL-5 Lithium difluorophosphate (0.1), Glycerol trinitrile (1.6) EL-6 Lithium difluorophosphate (0.01), 18-Crown-6 (0.3) EL-7 Lithium difluorophosphate (0.3), Dibenzo-18-crown-6 (0.2) EL-8 Lithium difluorophosphate (0.5), 1-Aza-18-crown-6 (0.1) EL-0 None

[0226] Preparation of the 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).

[0227] Preparation of the 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. The obtained battery cell is formed to obtain a lithium-ion battery.

[0228] Examples 2-1 ~~~ 2-35

[0229] Examples 2-1 to 2-35 prepare lithium-ion batteries according to the same method as above, except that the binder composition and electrolyte used for the positive electrode are changed as shown in Table 2.

[0230] Comparative Examples 2-1 ~~~ 2-5

[0231] Comparative Examples 2-1 to 2-5 were prepared into lithium-ion batteries according to the same method as above, except that the binder used for the positive electrode was changed as shown in Table 2.

[0232] Table 2 Binder Compositions, Electrolytes for Preparing Batteries, and Battery-Related Properties

[0233]

[0234]

[0235] The battery performances shown in Table 2 above were tested according to the following method:

[0236] (1) Flexibility

[0237] The positive electrode with a single-sided adhesive layer was wound around a stainless-steel cylinder with a diameter of 3.0 mm (the current collector was used as the inner side). Then, visually observe whether cracks are generated on the surface of the wound positive electrode adhesive layer. If no cracks are confirmed, the diameter of the stainless-steel cylinder was successively reduced to 2.5 mm, 2.0 mm, and 1.5 mm, and the same operation was performed. Then, record the diameter of the cylinder when cracks were 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 means that the flexibility of the positive electrode is very excellent. The A+, A, B, C, D, and E in the "Flexibility" column shown in Table 2 represent:

[0238] A+: No cracks were confirmed even when the cylinder diameter was 0.5 mm;

[0239] A: The cylinder diameter when cracks are generated is 1.0 mm;

[0240] B: The cylinder diameter when cracks are generated is 1.5 mm;

[0241] C: The cylinder diameter when cracks are generated is 2.0 mm;

[0242] D: The cylinder diameter when cracks are generated is 2.5 mm;

[0243] E: The cylinder diameter when cracks are generated is 3.0 mm.

[0244] (2) Peel Strength of the Positive Electrode

[0245] The fabricated sheet-shaped positive electrode was cut into a rectangle with a width of 2.5 cm and a length of 10 cm as a test piece, and fixed with the surface of the positive electrode mixture layer facing upward. Then, after pasting an adhesive tape (transparent tape specified in JIS Z1522) on the surface of the test piece on the positive electrode mixture layer side, the adhesive tape was peeled off from one end of the test piece at a speed of 50 mm / min in the 180° direction (the other end side of the test piece), and the stress at this time was measured. Ten measurements were carried out, and the average value of the stress was obtained and used as the peel strength, which was evaluated according to the following criteria. The greater the peel strength, the more excellent the adhesion of the positive electrode mixture layer to the current collector. In the column of "Peel Strength" shown in Table 2, A+, A, B, C, D, and E represent:

[0246] A+: The peel strength is 30 N / m or more;

[0247] A: The peel strength is 25 N / m or more and less than 30 N / m;

[0248] B: The peel strength is 20 N / m or more and less than 25 N / m;

[0249] C: The peel strength is 15 N / m or more and less than 20 N / m;

[0250] D: The peel strength is 10 N / m or more and less than 15 N / m;

[0251] E: The peel strength is less than 10 N / m.

[0252] (3) High-potential gas generation amount of the secondary battery

[0253] The fabricated battery was charged at 600 mA until the voltage reached 4.7 V in an environment at a temperature of 25°C, and then the initial volume of the battery was measured. Next, in an environment at 60°C, an operation of charging (float charging) for one week in such a way that the voltage became 4.7 V was carried out, and the volume of the battery was measured again (volume after float charging). Then, the volume increase amount of the battery (volume after float charging - initial volume) was calculated and used as the high-potential gas generation amount, which was evaluated according to the following criteria. The less the high-potential gas generation amount, the more excellent the high-potential durability of the binder composition. In the column of "High-potential gas generation amount" shown in Table 3, A+, A, B, C, D, and E represent:

[0254] A+: The volume increase amount is 2 mL or less;

[0255] A: The volume increase amount exceeds 2 mL and is 5 mL or less;

[0256] B: The volume increase amount exceeds 5 mL and is 8 mL or less;

[0257] C: The volume increase amount exceeds 8 mL and is 11 mL or less;

[0258] D: The volume increase is more than 11 mL and less than or equal to 15 mL;

[0259] E: The volume increase is more than 15 mL.

[0260] In this application, by making the positive electrode binder composition contain a specific polymer A, polymer B, and a metal salt, and the content of the metal salt is within a specified range, a positive electrode binder composition with excellent flexibility and adhesiveness can be produced. The produced positive electrode has excellent flexibility and is not prone to powder falling, and can enable the energy storage device to exhibit excellent high-potential durability characteristics.

[0261] The applicant also found that when the metal salt includes calcium carbonate, a further improved effect is obtained; when the content of the metal salt is 1 wt% or less, a further improved effect is obtained; when the electrolyte system includes at least one of lithium difluorophosphate, vinylene sulfate, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, and crown ether, the high-potential durability characteristics are further significantly improved.

[0262] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same constituent elements in essence as the technical idea and the same function and effect within the scope of the technical solution of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other embodiments constructed by combining some constituent elements of the embodiments are also included in the scope of this application.

Claims

1. A binder composition for a positive electrode of an energy storage device, characterized in that: The binder composition contains polymer A, polymer B, and a metal salt; polymer A contains unsaturated nitrile monomer units, polymer B contains at least one of unsaturated carboxylic acid monomer units, unsaturated carboxylic acid amide monomer units, or unsaturated carboxylic acid ester monomer units, and neither polymer A nor polymer B contains fluorine; the metal elements in the metal salt include at least one of calcium, nickel, zinc, and cobalt; based on the solid content of the binder composition being 100 wt%, the content of the metal salt is 3 wt% or less.

2. The binder composition according to claim 1, characterized in that: the content of the metal salt is 1 wt% or less, preferably 0.5 wt% or less, and more preferably 0.1 wt% or more; and / or, based on the solid content of the binder composition being 100 wt%, the content of polymer A is 67 - 90 wt%; and / or, based on the solid content of the binder composition being 100 wt%, the content of polymer B is 10 - 30 wt%.

3. The binder composition according to claim 1, wherein: The metal elements in the metal salt include calcium; and / or, the metal salt includes calcium chloride and / or calcium carbonate; and / or, the metal salt includes the chloride and / or carbonate of the corresponding metal element.

4. The binder composition for a positive electrode according to claim 1, wherein: Polymer A contains unsaturated nitrile monomer units, optionally containing (meth)acrylate monomer units and / or alkylene structural units having 4 or more carbon atoms; Preferably, the monomers for forming the unsaturated nitrile monomer units of polymer A include at least one of (meth)acrylonitrile, α-chloropropionitrile, α-ethylacrylonitrile, or vinylidene cyanide.

5. The binder composition according to claim 1, characterized in that: The monomers for forming the unsaturated carboxylic acid monomer units of polymer B include at least one of acrylic acid and methacrylic acid; The monomers for forming the unsaturated carboxylic acid amide monomer units of polymer B include at least one of methacrylamide and acrylamide; The monomers for forming the unsaturated carboxylic acid ester monomer units of polymer B include at least one of n-butyl methacrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, 4-methylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, cyclooctyl (meth)acrylate, cyclodecyl (meth)acrylate, or menthyl (meth)acrylate.

6. The binder composition according to claim 1, characterized in that: The binder composition further includes a plasticizer, and the plasticizer includes at least one of dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-n-butyl adipate, bis(2-ethylhexyl) adipate, diisodecyl adipate, di-n-butyl maleate, dimethyl maleate, diethyl maleate, di-n-butyl fumarate, tri-n-octyl trimellitate, triethyl citrate, tri-n-butyl citrate, acetyltriethyl citrate, diglycol monolaurate, diglycol dibenzoate, or dipropylene glycol dibenzoate; Preferably, based on the solid content of the binder composition being 100 wt%, the content of the plasticizer is 0.1 - 5 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 binder composition for the positive electrode of the energy storage device according to any one of claims 1-6.

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 for the positive electrode of the energy storage device according to claim 7.

9. A 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 according to claim 8; Preferably, the energy storage device is a lithium-ion battery or an electric double layer capacitor; Preferably, the electrolyte of the energy storage device includes an electrolyte salt, an organic solvent, and an additive, and the additive includes at least one of lithium difluorophosphate, vinylene sulfate, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, glycerol trinitrile, and crown ether.

10. The energy storage device according to claim 9, characterized in that: 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; And / or, based on 100 parts by mass of the electrolyte, the content of lithium difluorophosphate is 0.01-0.8 parts by mass; and / or, the content of vinylene sulfate is 0.01-0.8 parts by mass; and / or, the content of succinonitrile is 0.5-7 parts by mass; and / or, the content of adiponitrile is 1.9-4.3 parts by mass; and / or, the content of 1,3,6-hexanetricarbonitrile is 0.9-3.5 parts by mass; and / or, the content of glycerol trinitrile is 0.1-2.8 parts by mass; and / or, the content of crown ether is 0.1-2.5 parts by mass.

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