WO2022205172A1 - 电解液、电化学装置以及电子装置 - Google Patents

电解液、电化学装置以及电子装置 Download PDF

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WO2022205172A1
WO2022205172A1 PCT/CN2021/084677 CN2021084677W WO2022205172A1 WO 2022205172 A1 WO2022205172 A1 WO 2022205172A1 CN 2021084677 W CN2021084677 W CN 2021084677W WO 2022205172 A1 WO2022205172 A1 WO 2022205172A1
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electrolyte
anhydride
formula
substituted
unsubstituted
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PCT/CN2021/084677
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English (en)
French (fr)
Inventor
王翔
刘奥
唐超
崔辉
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宁德新能源科技有限公司
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Priority to CN202180004733.0A priority Critical patent/CN114207903A/zh
Priority to PCT/CN2021/084677 priority patent/WO2022205172A1/zh
Publication of WO2022205172A1 publication Critical patent/WO2022205172A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemistry, and in particular, to an electrolyte, an electrochemical device, and an electronic device.
  • the application provides an electrolyte solution comprising a compound represented by formula (I),
  • X is selected from substituted or unsubstituted acid anhydrides; when substituted, the substituent includes at least one of alkyl, aryl, acyloxy, aldehyde, cyano or halogen.
  • the anhydride is selected from the group consisting of succinic anhydride, maleic anhydride, benzomaleic anhydride, glutaric anhydride, benzoic anhydride, crotonic anhydride, itroic anhydride, itaconic anhydride, phthalic anhydride , at least one of benzoic anhydride, methylacetic anhydride, propionic anhydride, butyric anhydride or hydrogenated norbornene dianhydride.
  • the compound represented by formula (I) includes at least one of compounds represented by formula (I-1) to formula (I-8);
  • the content of the compound represented by the formula (I) is n %, 0.05 ⁇ n ⁇ 5.
  • the content of the compound represented by formula (I) is 0.1% to 3% based on the weight of the electrolyte.
  • the electrolyte further includes at least one of fluoroethylene carbonate and vinylene carbonate; based on the weight of the electrolyte, the content of fluoroethylene carbonate is k %, and the content of vinylene carbonate is k%.
  • the content is m%, where k ⁇ 0, m ⁇ 0, k+m>0, and k, m, and n satisfy 1 ⁇ k+m+n ⁇ 15; in some embodiments, 3 ⁇ k+m+ n ⁇ 15.
  • the electrolyte further includes carboxylate; based on the weight of the electrolyte, the content of the carboxylate is a%, 5 ⁇ a ⁇ 60, and a and n satisfy the relationship: 0.0005 ⁇ n/a ⁇ 0.7.
  • the content of the carboxylate is less than or equal to 50%, and the ratio of the content of the compound of formula (I) to the carboxylate is 0.02 to 0.2.
  • the carboxylate includes at least one of ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, or butyl propionate.
  • the electrolyte further includes at least one of a sulfonate compound or a nitrile compound.
  • the sulfonate compound includes at least one of 1,3-propane sultone, 2,4-butanesultone, and methyl ethyl sulfone.
  • the total content of the sulfonate compound and the nitrile compound is 0.1% to 15% based on the weight of the electrolyte.
  • the total content of the sulfonate compound and the nitrile compound is 3% to 10% based on the weight of the electrolyte.
  • the content of the sulfonate compound is 0.1% to 5% based on the weight of the electrolyte.
  • the nitrile compound includes at least one of the compounds represented by formula (II) to formula (V);
  • R 21 is selected from substituted or unsubstituted C 1 -C 12 alkylene, substituted or unsubstituted C 1 -C 12 alkyleneoxy;
  • R 31 and R 32 are each independently selected from mono bond, substituted or unsubstituted C 1 -C 12 alkylene;
  • R 41 , R 42 , R 43 are each independently selected from single bond, substituted or unsubstituted C 1 -C 12 alkylene, Substituted or unsubstituted C 1 -C 12 alkyleneoxy;
  • R 51 is selected from substituted or unsubstituted C 1 -C 12 alkylene, substituted or unsubstituted C 2 -C 12 Alkenylene, substituted or unsubstituted C 6 -C 12 arylene, substituted or unsubstituted C 3 -C 12 cyclylene; wherein when substituted, the substituent is halogen.
  • the nitrile compound includes at least one of the following compounds:
  • the weight content of the nitrile compound in the electrolyte is b%, 0.1 ⁇ b ⁇ 10.
  • the weight content of the nitrile compound in the electrolyte is 0.5% to 7% based on the weight of the electrolyte.
  • the present application also provides an electrochemical device, including a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte described in the present application.
  • the end-of-charge voltage of the electrochemical device is 4.4V to 4.8V
  • present application also provides an electronic device, including the electrochemical device described in the present application.
  • the electrolyte provided by the present application can significantly improve the high-temperature cycle performance of electrochemical devices using the same at a high voltage of 4.4 to 4.8V.
  • an alkyleneoxy group is a divalent group formed by the loss of two hydrogen atoms of an ether, which may contain one or more ether linkages.
  • the electrolyte contains additive A, which is a compound represented by formula (I), and in formula (I), X is selected from substituted or unsubstituted acid anhydrides; when substituted, the substituent Include at least one of alkyl, aryl, acyloxy, aldehyde, cyano or halogen.
  • additive A is a bridge compound of phthalimide and acid anhydride, wherein the acid anhydride can be reduced to form an SEI film, which has obvious protective effect on graphite or silicon anode, while phthalimide can form a SEI film after being reduced.
  • the imide has a positive-electrode complexed transition metal oxide, which can suppress the contact between the solvent and the positive-electrode active material.
  • the anhydride is selected from the group consisting of succinic anhydride, maleic anhydride, benzomaleic anhydride, glutaric anhydride, benzoic anhydride, crotonic anhydride, itatoic anhydride, itaconic anhydride, phthalic anhydride, benzene At least one of formic anhydride, methylacetic anhydride, propionic anhydride, butyric anhydride or hydrogenated norbornene dianhydride.
  • the compound represented by formula (I) includes at least one of the compounds represented by formula (I-1) to formula (I-8):
  • the content of the compound represented by the formula (I) is n%, 0.05 ⁇ n ⁇ 5, when the content of the compound represented by the formula (I) is too low, the protection If the membrane is insufficient, the improvement of the performance of the electrochemical device is not obvious; when the content of the compound represented by the formula (I) is too high, the resistance of the formed membrane will be large, which will affect the cycle performance of the electrochemical device.
  • the content of the compound represented by formula (I) is 0.1% to 3% based on the weight of the electrolyte.
  • the electrolyte may further include an additive B, and the additive B is at least one of fluoroethylene carbonate (FEC) and vinylene carbonate (VC).
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • Both additive B and additive A can form a good solid-state interfacial dielectric layer (SEI) on the negative electrode, and the combined use of the two is beneficial to the composite formation of the organic layer and the inorganic layer, and enhances the stability of the SEI.
  • SEI solid-state interfacial dielectric layer
  • the content of fluoroethylene carbonate is k%
  • the content of vinylene carbonate is m%, wherein k ⁇ 0, m ⁇ 0, k+m>0 , and k, m and n satisfy 1 ⁇ k+m+n ⁇ 15, in some embodiments, 3 ⁇ k+m+n ⁇ 15, when the total content of additive B and additive A is too low, the two cannot be
  • the composite forms an effective electrolyte interface protective film, which does not significantly improve the performance of lithium-ion batteries; when the total content of additive B and additive A is too high, on the one hand, the formed film has a large impedance, which will affect the cycle performance of the electrochemical device, and on the other hand , fluoroethylene carbonate and/or vinylene carbonate will also decompose and produce gas at the positive electrode, thereby affecting the cycle thickness expansion ratio.
  • 0 ⁇ k+m ⁇ 14 0 ⁇ k+m ⁇ 14.
  • the electrolyte may further include an additive C, where the additive C is at least one of a sulfonate compound or a nitrile compound.
  • the sulfonate compound includes at least one of 1,3-propane sultone, 2,4-butanesultone, and methyl ethyl sulfone.
  • the total content of the sulfonate compound and the nitrile compound is 0.1% to 15% based on the weight of the electrolyte.
  • the compound of formula I is added in an appropriate amount, when the sum of the content of the sulfonate compound and the nitrile compound is 3% to 10%, the film formation stability of the positive and negative electrodes of the lithium ion battery can be effectively improved, thereby improving the high temperature performance of the battery. . If the c value is too small, it cannot form an effective synergistic effect with the compound of formula I, and if the c value is too large, the cycle performance of the battery will be affected to a certain extent.
  • the content of the sulfonate compound is 0.1% to 5% based on the weight of the electrolyte.
  • the nitrile compound includes at least one of the compounds represented by formula (II) to formula (V);
  • R 21 is selected from substituted or unsubstituted C 1 -C 12 alkylene, substituted or unsubstituted C 1 -C 12 alkyleneoxy;
  • R 31 and R 32 are each independently selected from mono bond, substituted or unsubstituted C 1 -C 12 alkylene;
  • R 41 , R 42 , R 43 are each independently selected from single bond, substituted or unsubstituted C 1 -C 12 alkylene, Substituted or unsubstituted C 1 -C 12 alkyleneoxy;
  • R 51 is selected from substituted or unsubstituted C 1 -C 12 alkylene, substituted or unsubstituted C 2 -C 12 Alkenylene, substituted or unsubstituted C 6 -C 12 arylene, substituted or unsubstituted C 3 -C 12 cyclylene; wherein when substituted, the substituent is halogen.
  • the nitrile compound comprises at least one of the following compounds:
  • the weight content of the nitrile compound in the electrolyte is b%, 0.1 ⁇ b ⁇ 10.
  • the weight content of the nitrile compound in the electrolyte is 0.5% to 7% based on the weight of the electrolyte.
  • the electrolyte further includes an organic solvent.
  • the organic solvent is an organic solvent known to those skilled in the art and suitable for electrochemical devices, for example, a non-aqueous organic solvent is generally used.
  • the non-aqueous organic solvent includes at least one of a carbonate-based solvent and a carboxylate-based solvent.
  • the organic solvent content is 20% to 90% by weight of the electrolyte.
  • the carbonate-based solvent includes cyclic esters and chain esters.
  • the cyclic ester solvent comprises at least one of ethylene carbonate (EC), propylene carbonate (PC), ⁇ -butyrolactone (BL), butylene carbonate.
  • the chain ester solvent comprises dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propyl ethyl carbonate, fluoroethyl methyl carbonate, fluoro At least one of dimethyl carbonate, fluorodiethyl carbonate, and the like.
  • the atoms on the carbonate can be substituted, and the substituents include halogen atoms.
  • the carboxylate-based solvent comprises ethyl acetate (EA), propyl acetate (PA), butyl acetate (BA), ethyl propionate (EP), propyl propionate (PP), or propyl acetate At least one of butyl acid (BP).
  • EA ethyl acetate
  • PA propyl acetate
  • BA butyl acetate
  • EP ethyl propionate
  • PP propyl propionate
  • BP propyl acetate
  • BP butyl acid
  • the content of the carboxylate is a%, 5 ⁇ a ⁇ 60, when the electrolyte contains n% by mass of the compound represented by formula (I), a and n satisfy the relationship: 0.0005 ⁇ n/a ⁇ 0.7, if the ratio of n/a is low, the positive electrode protection of the electrolyte is insufficient, and the solvent is easily decomposed to produce gas; if the ratio of n/a is too high, the film-forming resistance of the positive and negative electrodes is large , can not provide a smooth lithium ion transport channel, affecting the charge and discharge performance.
  • the content of the carboxylate is less than or equal to 50%, and the ratio of the content of the compound of formula (I) to the carboxylate is 0.02 to 0.2.
  • one non-aqueous organic solvent can be used as the organic solvent in the electrolyte, or multiple non-aqueous organic solvents can be mixed.
  • mixed solvents electrochemical devices with different performances can be obtained by controlling the mixing ratio.
  • the electrolyte further includes an electrolyte salt.
  • Electrolyte salts are those known to those skilled in the art that are suitable for use in electrochemical devices. Appropriate electrolyte salts can be selected for different electrochemical devices. For example, for lithium ion batteries, lithium salts are generally used as electrolyte salts.
  • the lithium salt comprises at least one of an organic lithium salt or an inorganic lithium salt.
  • the lithium salt includes LiPF 6 , LiBF 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3. At least one of LiSiF 6 , LiBOB or LiDFOB, preferably LiPF 6 .
  • the content of the electrolyte is not specifically limited, and can be reasonably added according to actual needs.
  • the preparation method of the electrolyte solution is not limited, and can be prepared according to the conventional preparation method of the electrolyte solution known to those skilled in the art.
  • the electrochemical device of the present application may be any one selected from the following devices: lithium secondary battery and sodium ion battery.
  • the electrochemical device is a lithium secondary battery.
  • the electrochemical device includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte as previously described herein.
  • the positive electrode sheet is known in the art as a positive electrode sheet that can be used in electrochemical devices.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.
  • the positive electrode active material layer may contain a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.
  • the positive active material contains at least one lithiated intercalation compound capable of reversibly intercalating and deintercalating lithium ions.
  • the positive electrode active material includes a composite oxide.
  • the composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel.
  • the positive active material is selected from lithium cobalt oxide (LiCoO 2 ), lithium nickel cobalt manganese (NCM) ternary material, lithium iron phosphate (LiFePO 4 ), lithium manganate (LiMn 2 O 4 ), or their any combination of .
  • the positive electrode conductive agent is used to provide conductivity for the positive electrode, which can improve the conductivity of the positive electrode.
  • the positive electrode conductive agent is a conductive material known in the art that can be used as the positive electrode active material layer.
  • the positive electrode conductive agent may be selected from any conductive material as long as it does not cause chemical changes.
  • the positive conductive agent comprises carbon-based materials (eg, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber), metal-based materials (eg, metals including copper, nickel, aluminum, silver, etc.) powder or metal fibers), conductive polymers (such as polyphenylene derivatives) at least one.
  • the positive electrode binder is known in the art and can be used as a binder for the positive electrode active material layer.
  • the positive electrode binder can improve the bonding performance between the positive electrode active material particles and between the positive electrode active material particles and the positive electrode current collector.
  • the positive binder comprises polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyvinyl Ethoxylated polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (esterified) styrene-butadiene rubber, epoxy resin, nylon at least one of.
  • the positive current collector is a metal, in some embodiments, a metal such as, but not limited to, aluminum foil.
  • the structure of the positive electrode sheet is known in the art as the structure of the positive electrode sheet that can be used in an electrochemical device.
  • the preparation method of the positive electrode sheet is known in the art and can be used for the preparation of the positive electrode sheet of the electrochemical device.
  • a positive electrode active material, a binder, and a conductive material and a thickener are added as required, and then the positive electrode slurry is dissolved or dispersed in a solvent.
  • the solvent is evaporated and removed during the drying process.
  • the solvent is known in the art and can be used as the positive electrode active material layer, such as but not limited to N-methylpyrrolidone (NMP).
  • NMP N-methylpyrrolidone
  • the negative electrode sheet is a negative electrode sheet known in the art that can be used in an electrochemical device.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.
  • the negative electrode active material layer may include a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.
  • the negative active material includes at least one of lithium metal, lithium metal alloy, transition metal oxide, carbon material, and silicon-based material.
  • the anode binder may include various polymeric binders.
  • the negative electrode binder comprises vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxylate Methyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, poly At least one of propylene, styrene-butadiene rubber, acrylic (esterified) styrene-butadiene rubber, epoxy resin and nylon.
  • PVDF-co-HFP vinylidene fluoride-hexafluoropropylene copolymer
  • PVDF-co-HFP vinylidene fluoride
  • the negative electrode active material layer further includes a negative electrode conductive agent.
  • the negative electrode conductive agent is used to provide conductivity for the negative electrode and can improve the conductivity of the negative electrode.
  • the negative electrode conductive agent is a conductive material known in the art that can be used as the negative electrode active material layer.
  • the negative electrode conductive agent may be selected from any conductive material as long as it does not cause chemical changes.
  • the structure of the negative electrode sheet is known in the art as the structure of the negative electrode sheet that can be used in an electrochemical device.
  • the preparation method of the negative electrode sheet is known in the art for the preparation method of the negative electrode sheet that can be used in an electrochemical device.
  • negative electrode active material and binder are usually added, and conductive material and thickener are added as required, and then dissolved or dispersed in a solvent to prepare negative electrode slurry.
  • the solvent is evaporated and removed during the drying process.
  • the solvent is known in the art and can be used as the negative electrode active material layer, and the solvent is, for example, but not limited to, water.
  • Thickeners are known in the art and can be used as a thickener for the negative active material layer, such as, but not limited to, sodium carboxymethylcellulose.
  • the electrochemical devices of the present application include a separator.
  • the separator is a separator known in the art that can be used in electrochemical devices, such as, but not limited to, a polyolefin-based porous membrane.
  • the base material of the polyolefin-based porous film comprises polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methyl Monolayer or multi-layer composed of one or more of methyl acrylate copolymers.
  • the present application has no particular restrictions on the shape and thickness of the separator.
  • the preparation method of the separator is well known in the art and can be used for the preparation of the separator for electrochemical devices, for example: mixing boehmite with polyacrylate and dissolving it in deionized water to form a coating slurry Then, the coating slurry is uniformly coated on both surfaces of the porous substrate by a gravure coating method, and the desired separator is obtained after drying treatment.
  • an electrochemical device includes an electrolyte as described herein.
  • the electrochemical device comprises the electrolyte described herein and the electrochemical device has a charge termination voltage of 4.4V to 4.8V.
  • the positive electrode active material includes at least one of LCO and NCM, and when the negative electrode adopts a Gr and Si system, further electrochemical performance can be obtained.
  • the electronic device of the present application can be any electronic device, such as but not limited to notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headphone, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, assisted bicycles, bicycles, Lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large storage batteries for household use, and lithium-ion capacitors.
  • the electrochemical device of the present application is not only applicable to the electronic devices listed above, but also applicable to energy storage power stations, marine vehicles, and air vehicles.
  • Airborne vehicles include airborne vehicles within the atmosphere and airborne vehicles outside the atmosphere.
  • the electronic device comprises an electrochemical device as described herein.
  • the lithium ion batteries of the examples and comparative examples were prepared according to the following methods.
  • the positive active material lithium cobaltate (LiCoO 2 ), the conductive agent Super P, and the binder polyvinylidene fluoride are mixed according to the weight ratio of 98:0.4:1.6, and N-methylpyrrolidone (NMP) is added.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry is uniformly coated on the aluminum foil of the positive electrode current collector, and the aluminum foil is dried, and then subjected to cold pressing, cutting, slitting, and drying under vacuum conditions to obtain the positive electrode sheet.
  • the negative active material artificial graphite, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) were mixed according to the weight ratio of 97:1:2, deionized water was added, and under the action of a vacuum mixer A negative electrode slurry is obtained; the negative electrode slurry is uniformly coated on the negative electrode current collector copper foil; the copper foil is dried, and then subjected to cold pressing, cutting, slitting, and drying under vacuum conditions to obtain a negative electrode sheet.
  • the boehmite and polyacrylate were mixed and dissolved in deionized water to form a coating slurry. Then, the coating slurry is uniformly coated on both surfaces of the polyethylene porous substrate by a gravure coating method, and the desired separator is obtained by drying treatment.
  • Example 3 are based on the settings of Example 2-11, and the differences from Example 2-11 are listed in Table 3; the examples in Table 4 are based on the settings of Example 3-17, which are different from those of Example 3-17. The differences are listed in Table 4.
  • the positive electrode sheet, the separator film and the negative electrode sheet in order, so that the separator film is placed between the positive and negative electrode sheets for isolation, and then coil to obtain a bare cell; after welding the tabs, place the bare cell in the outer package
  • the electrolyte prepared above is injected into the dried bare cell, and the soft-pack lithium-ion battery is obtained through the processes of vacuum packaging, standing, forming, shaping, and capacity testing.
  • the lithium-ion battery that has reached a constant temperature is charged with a constant current of 0.7C to a voltage of 4.5V, and then charged with a constant voltage of 4.5V to a current of 0.025C, and the thickness of the battery is tested and recorded with a micrometer as D 0 , followed by a constant current of 1C. Discharge to a voltage of 3.0V, which is one charge-discharge cycle.
  • the charge-discharge cycle was repeated for 300 cycles, the test was stopped, and the thickness D n and the cycle capacity retention rate of the battery when fully charged were recorded as indicators for evaluating the cycle performance of lithium-ion batteries.
  • cycle capacity retention rate capacity at a certain cycle/capacity at the first discharge ⁇ 100%;
  • thickness expansion ratio (D n -D 0 )/D 0 ⁇ 100% .
  • Table 1 shows the influence of the compound represented by formula (I) in the electrolyte on the high-pressure and high-temperature cycle performance of the lithium ion battery.
  • Table 2 shows the influence of the content relationship between the compound represented by the formula (I) and the carbonate-based additive in the electrolyte on the high-pressure and high-temperature cycle performance of the lithium ion battery.
  • Table 3 shows the influence of the content relationship between the compound represented by formula (I) and the carboxylate solvent in the electrolyte on the high-pressure and high-temperature cycle performance of the lithium ion battery.
  • Table 4 shows the influence of the content relationship between the compound represented by formula (I) and the nitrile compound on the high-pressure and high-temperature cycle performance of the lithium ion battery.
  • Comparative Example 1-1 when the compound shown in Formula I is not added to the electrolyte, the high-temperature cycle capacity retention rate of the lithium-ion battery is poor, the thickness growth rate is high, and the lithium-ion battery is under high voltage. The high temperature cycle performance is poor. It can be seen from Comparative Examples 1-1 to 1-3 and Example 1-4 that, compared with the low-voltage system additives of lithium ion batteries, phthalimide and glutaric anhydride, the compound of formula I provided by the present application has better performance high temperature cycling capacity retention and thickness growth inhibition. This is because the two monomer groups are bridged at the molecular level. When used as an additive in the electrolyte, the protective layer formed on the positive and negative electrodes is more stable, effectively suppressing the formation of by-products, and protecting the structural stability of the positive electrode active material. high temperature and long cycle at high voltage over 4.4V.
  • Example 1-1 By comparing Example 1-1 to Example 1-25 with Comparative Example 1-1, it can be seen that when the compound represented by formula I is added to the electrolyte, the capacity retention rate of the lithium ion battery after 300 cycles of cycling under high temperature and high voltage is all The increase is increased, and the thickness growth rate is significantly decreased, that is, the high temperature cycle performance of the lithium ion battery under high voltage can be improved by adding the compound represented by formula I to the electrolyte.
  • Example 1-7 It can be seen from the performance test results of Example 1-1 to Example 1-7 that the mass percentage content of the compound represented by Formula I in the electrolyte of Example 1-1 is only 0.05%, and the mass of the compound represented by Formula I is only 0.05%. The content is too small, the stability of the positive and negative protective films is insufficient, and the cycle capacity retention rate of lithium ion batteries at high temperature and high cut-off voltage is not significantly improved compared with Comparative Example 1-1, and compared with Example 1-2 to implementation Examples 1-6 also performed poorly.
  • the mass percentage content of the compound shown in formula I in the electrolyte of Example 1-7 is 6%, and the mass content of the compound shown in formula I is too much, causing the membrane impedance to be larger, causing irreversible lithium precipitation, and possibly hindering the electrolyte solution. ion transport channels, accelerating capacity decay.
  • the percentage content of the compound represented by formula I in the electrolyte is 0.05% to 5%, and further preferably, the mass percentage content of the compound represented by formula I in the electrolyte is 0.5% % to 3%.
  • Example 1-1 to Example 1-25 From the performance test results of Example 1-1 to Example 1-25, it can be seen that when the compound represented by formula I is specifically the compound represented by formula I-1 or I-3, I-6, it has no effect on lithium ions The performance improvement effect of the battery is better.
  • Example 2-1 to Example 2-13 By analyzing the data of Comparative Example 1-1, Example 2-1 to Example 2-13, it can be seen that when the total amount of carbonate additive and compound represented by formula I is 1% to 15%, compared with not using these two types material, the cycle performance of lithium-ion batteries at high voltages has been improved to varying degrees. When the mass percentage content of carbonate additives and compounds represented by formula I in the electrolyte is controlled at 3% to 15%, the performance of lithium-ion batteries is improved. The improvement is the best.
  • the compound of formula I can be combined in a certain proportion.
  • the additive can further improve the lithium ion The capacity retention rate and gas production of the battery after high voltage and high temperature cycling.
  • the nitrile compounds effectively inhibit the oxidation reaction of the positive electrode surface of the lithium ion battery in the charged state to the electrolyte, and the sulfonate compounds are preferentially oxidized on the surface of the positive electrode active material over the compound of formula I, and synergistically form a stable compound with the compound of formula I.
  • the SEI film reduces side reactions between the electrolyte and the surface of the positive active material, thereby synergistically improving the high-temperature cycle performance and gas production of lithium-ion batteries.
  • 1,3,6-hexanetrinitrile in combination with two dinitriles has advantages over single use. improve the cycle performance of lithium-ion batteries. This may be because, when other nitrile compounds are used at the same time, the chain molecules with less steric hindrance than trinitrile can play a synergistic effect with the trinitrile compound, forming between the easily oxidizable components in the electrolyte and the surface of the positive electrode effective isolation.

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Abstract

本申请提供了一种电解液、电化学装置以及电子装置。所述电解液包括式(I)表示的化合物；在式(I)中，X选自经取代或未经取代基的酸酐；经取代时，取代基包括烷基、芳基、酰氧基、醛基、氰基或卤素中的至少一种。所述电解液可以显著改善所述电化学装置在4.4至4.8V高电压下的高温循环性能。

Description

电解液、电化学装置以及电子装置 技术领域
本申请涉及电化学领域，具体涉及一种电解液、电化学装置以及电子装置。
背景技术
伴随近年来电气制品的轻量化、小型化，提高电化学装置(例如，锂离子电池)的能量密度已经成为了锂离子电池的重要研发方向，其中提高设计使用上限电压是提高其能量密度的重要方式。目前钴酸锂体系的锂离子电池额定电压可达4.45V至4.5V，这意味着电池需要实现高电压下的存储及充放电，因此对正、负极结构的破坏愈加严重，这也对电解液本身的耐氧化能力及成膜稳定性都提出了更高的需求。
因此，如何开发出能够改善高电压下电池循环性能的电解液添加剂，成为提高电池性能的重要课题。
发明内容
在一些实施例中，本申请提供了一种电解液，其包括式(I)表示的化合物，
Figure PCTCN2021084677-appb-000001
在式(I)中，X选自经取代或未经取代基的酸酐；经取代时，取代基包括烷基、芳基、酰氧基、醛基、氰基或卤素中的至少一种。
在一些实施例中，所述酸酐选自琥珀酸酐、马来酸酐、苯并马来酸酐、戊二酸酐、苯并戊二酸酐、巴豆酸酐、衣托酸酐、衣康酸酐、邻苯二甲酸酐、苯甲酸酐、甲乙酐、丙酸酐、丁酸酐或氢化降冰片烯二酸酐中的至少一种。
在一些实施例中，所述式(I)表示的化合物包括式(I-1)至式(I-8)表示的化合物中的至少一种；
Figure PCTCN2021084677-appb-000002
在一些实施例中，基于所述电解液的重量，所述式(I)表示的化合物的含量为n％，0.05≤n≤5。
在一些实施例中，基于所述电解液的重量，所述式(I)表示的化合物的含量为0.1％至3％。
在一些实施例中，电解液还包括氟代碳酸乙烯酯、碳酸亚乙烯酯中的至少一种；基于所述电解液的重量，氟代碳酸乙烯酯的含量为k％，碳酸亚乙烯酯的含量为m％，其中，k≥0，m≥0，k+m＞0，且k、m和n满足1≤k+m+n≤15；在一些实施例中，3≤k+m+n≤15。
在一些实施例中，0＜k+m≤14。
在一些实施例中，所述电解液还包括羧酸酯；基于所述电解液的重量，所述羧酸酯的含量为a％，5≤a≤60，且a和n满足关系：0.0005≤n/a≤0.7。
在一些实施例中，基于所述电解液的重量，羧酸酯的含量小于等于50％，式(I)化合物与羧酸酯的含量之比为0.02至0.2。
在一些实施例中，所述羧酸酯包括乙酸乙酯、乙酸丙酯、乙酸丁酯、丙酸乙酯、丙酸丙酯或丙酸丁酯中的至少一种。
在一些实施例中，所述电解液还包括磺酸酯类化合物或腈类化合物中的至少一种。
在一些实施例中，所述磺酸酯类化合物包括1,3-丙烷磺内酯、2,4-丁磺内酯、甲基乙基砜中的至少一种。
在一些实施例中，基于所述电解液的重量，所述磺酸酯类化合物和腈 类化合物的含量之和为0.1％至15％。
在一些实施例中，基于所述电解液的重量，所述磺酸酯类化合物和腈类化合物的含量之和为3％至10％。
在一些实施例中，基于所述电解液的重量，所述磺酸酯类化合物含量为0.1％至5％。
在一些实施例中，所述腈类化合物包括式(Ⅱ)至式(Ⅴ)表示的化合物中的至少一种；
N≡C-R 21-C≡N   式(Ⅱ)
Figure PCTCN2021084677-appb-000003
Figure PCTCN2021084677-appb-000004
Figure PCTCN2021084677-appb-000005
其中，R 21选自经取代或未经取代的C 1-C 12亚烷基、经取代或未经取代的C 1-C 12亚烷氧基；R 31、R 32各自独立地选自单键、经取代或未经取代的C 1-C 12亚烷基；R 41、R 42、R 43各自独立地选自单键、经取代或经未取代的C 1-C 12亚烷基、经取代或未经取代的C 1-C 12亚烷氧基；R 51选自经取代或经未经取代的C 1-C 12亚烷基、经取代或未经取代的C 2-C 12亚烯基、经取代或未经取代的C 6-C 12亚芳基、经取代或未经取代的C 3-C 12亚环基；其中经取代时，取代基为卤素。
在一些实施例中，所述腈类化合物包括以下化合物中的至少一种：
Figure PCTCN2021084677-appb-000006
Figure PCTCN2021084677-appb-000007
在一些实施例中，基于所述电解液的重量，所述腈类化合物在电解液中重量含量为b％，0.1≤b≤10。
在一些实施例中，基于所述电解液的重量，所述腈类化合物在电解液中重量含量为0.5％至7％。
在一些实施例中，本申请还提供了一种电化学装置，包括正极片、负极片、隔离膜以及本申请所述的电解液。
在一些实施例中，所述电化学装置的充电终止电压为4.4V至4.8V
进一步，本申请还提供了一种电子装置，包括本申请所述的电化学装置。
本申请提供的电解液可以显著改善使用其的电化学装置在4.4至4.8V高电压下的高温循环性能。
具体实施方式
应理解的是，所公开的实施例仅是本申请的示例，本申请可以以各种形式实施，因此，本文公开的具体细节不应被解释为限制，而是仅作为权利要求的基础且作为表示性的基础用于教导本领域普通技术人员以各种方式实施本申请。
在本申请的说明中，除非另有说明，所有化合物中的基团可以是经取代的或未经取代的。
在本申请的说明中，亚烷氧基为醚失去两个氢原子形成的二价基团，所述醚可以包含一个或多个醚键。
在本申请的说明中，未明确说明的术语、结构式中的取代等，均应按照本领域普通技术人员的公知的、常规的、惯用的手段或方式去理解。
下面详细说明本申请的电解液、电化学装置及电子装置。
[电解液]
<添加剂A>
在一些实施例中，电解液中含有添加剂A，添加剂A为式(I)表示的化合物，在式(I)中，X选自经取代或未经取代基的酸酐；经取代时，取代基包括烷基、芳基、酰氧基、醛基、氰基或卤素中的至少一种。
Figure PCTCN2021084677-appb-000008
在本申请的电解液中，添加剂A为邻苯二甲酰亚胺与酸酐的桥联物，其中的酸酐被还原后可以形成SEI膜，对石墨或硅负极保护作用明显，而邻苯二甲酰亚胺有正极络合过渡金属氧化物，可以抑制溶剂与正极活性物质的接触。当两种单体基团在分子水平桥联时，相比单体使用阻抗更小，高温稳定性更强，在超过4.4V高电压下可以实现电化学装置的稳定高温长循环性能。
在一些实施例中，酸酐选自琥珀酸酐、马来酸酐、苯并马来酸酐、戊二酸酐、苯并戊二酸酐、巴豆酸酐、衣托酸酐、衣康酸酐、邻苯二甲酸酐、苯甲酸酐、甲乙酐、丙酸酐、丁酸酐或氢化降冰片烯二酸酐中的至少一种。
在一些实施例中，式(I)表示的化合物包括式(I-1)至式(I-8)表示的化合物中的至少一种：
Figure PCTCN2021084677-appb-000009
Figure PCTCN2021084677-appb-000010
在一些实施例中，基于所述电解液的重量，式(I)表示的化合物的含量为n％，0.05≤n≤5，当式(I)表示的化合物的含量过低时，形成的保护膜不充分，对电化学装置性能的提升不明显；当式(I)表示的化合物的含量过高，其形成的膜阻抗较大，会影响电化学装置的循环性能。在一些实施例中，基于所述电解液的重量，式(I)表示的化合物的含量为0.1％至3％。
<添加剂B>
在一些实施例中，电解液中可还包含添加剂B，添加剂B为氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)中的至少一种。
添加剂B、添加剂A均能在负极形成良好的固态界面电介质层(SEI)，两者复合使用有利于有机层与无机层的复合生成，加强SEI稳定性。
在一些实施例中，基于所述电解液的重量，氟代碳酸乙烯酯的含量为k％，碳酸亚乙烯酯的含量为m％，其中，k≥0，m≥0，k+m＞0，且k、m和n满足1≤k+m+n≤15，在一些实施例中，3≤k+m+n≤15，当添加剂B和添加剂A的总含量过低时，两者无法复合形成有效的电解质界面保护膜，对锂离子电池性能改善不明显；当添加剂B和添加剂A总含量过高时，一方面形成的膜阻抗大，会影响电化学装置的循环性能，另一方面，氟代碳酸乙烯酯和/或碳酸亚乙烯酯还会在正极分解产气，从而影响循环厚度膨胀率。在一些实施例中，0＜k+m≤14。
<添加剂C>
在一些实施例中，电解液中可还包含添加剂C，添加剂C为磺酸酯类化合物或腈类化合物中的至少一种。
在一些实施例中，所述磺酸酯类化合物包括1,3-丙烷磺内酯、2,4-丁磺内酯、甲基乙基砜中的至少一种。
在一些实施例中，基于所述电解液的重量，所述磺酸酯类化合物和腈类化合物的含量之和为0.1％至15％。在适量添加式I化合物的基础上，磺酸酯类化合物与腈类化合物含量之和在3％至10％时，可有效改善锂离子电池正负极成膜稳定性，从而改善电池的高温性能。若c值偏小，则无法与式I化合物构成有效协同作用，若c值偏大，则在一定程度影响电池的循环性能。
在一些实施例中，基于所述电解液的重量，所述磺酸酯类化合物含量为0.1％至5％。
在一些实施例中，腈类化合物包括式(Ⅱ)至式(Ⅴ)表示的化合物中的至少一种；
N≡C-R 21-C≡N    式(Ⅱ)
Figure PCTCN2021084677-appb-000011
Figure PCTCN2021084677-appb-000012
Figure PCTCN2021084677-appb-000013
其中，R 21选自经取代或未经取代的C 1-C 12亚烷基、经取代或未经取代的C 1-C 12亚烷氧基；R 31、R 32各自独立地选自单键、经取代或未经取代的C 1-C 12亚烷基；R 41、R 42、R 43各自独立地选自单键、经取代或经未取代的C 1-C 12亚烷基、经取代或未经取代的C 1-C 12亚烷氧基；R 51选自经取代或经未经取代的C 1-C 12亚烷基、经取代或未经取代的C 2-C 12亚烯基、经取代或未经取代的C 6-C 12亚芳基、经取代或未经取代的C 3-C 12亚环基；其中经取代时，取代基为卤素。
在一些实施例中，腈类化合物包含以下化合物中的至少一种：
Figure PCTCN2021084677-appb-000014
在一些实施例中，基于电解液的重量，腈类化合物在电解液中重量含量为b％，0.1≤b≤10。
在一些实施例中，基于电解液的重量，腈类化合物在电解液中重量含量为0.5％至7％。
<有机溶剂>
在一些实施例中，电解液还包含有机溶剂。有机溶剂是本领域技术公知的适用于电化学装置的有机溶剂，例如通常使用非水有机溶剂。在一些实施例中，非水有机溶剂包含碳酸酯类溶剂、羧酸酯类溶剂中的至少一种。在一些实施例中，有机溶剂含量占所述电解液重量的20％至90％。
在一些实施例中，碳酸酯类溶剂包含环状酯和链状酯。在一些实施例中，环状酯类溶剂包含碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、γ-丁内酯(BL)、碳酸丁烯酯中的至少一种。在一些实施例中，链状酯类溶剂包含碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸丙乙酯、氟代碳酸甲乙酯、氟代碳酸二甲酯、氟代碳酸二乙酯等中的至少一种。在一些实施例中，碳酸酯上的原子可被取代，取代基包含卤素原子。
在一些实施例中，羧酸酯类溶剂包含乙酸乙酯(EA)、乙酸丙酯(PA)、乙酸丁酯(BA)、丙酸乙酯(EP)、丙酸丙酯(PP)或丙酸丁酯(BP)的至少一种。
在一些实施例中，基于所述电解液的重量，羧酸酯的含量为a％，5≤a≤60，当电解液中含有质量含量为n％的式(I)表示的化合物时，a和n满足关系：0.0005≤n/a≤0.7，如果n/a比例较低，则电解液正极保护不足，溶剂容易分解产气；如果n/a比例过高，则正负极成膜阻抗大，不能提供通畅的锂离子传输通道，影响充放电性能。在一些实施例中，基于所述电解液的重量，羧酸酯的含量小于等于50％，式(I)化合物与羧酸酯的含量之比为0.02至0.2。
在本申请中，电解液中的有机溶剂可以使用一种非水有机溶剂，也可以使用多种非水有机溶剂混合，当使用混合溶剂时，可以通过控制混合比获得不同性能的电化学装置。
<电解质盐>
在一些实施例中，电解液还包含电解质盐。电解质盐是本领域技术公知的适用于电化学装置的电解质盐。针对不同的电化学装置，可以选用合适的电解质盐。例如对于锂离子电池，电解质盐通常使用锂盐。
在一些实施例中，锂盐包含有机锂盐或无机锂盐中的至少一种。
在一些实施例中，锂盐包含LiPF 6、LiBF 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或LiDFOB中的至少一种，优选LiPF 6。
在本申请中，电解液的含量不受具体限制，可根据实际需要进行合理添加。在本申请中，电解液的制备方法不受限制，可按照本领域技术人员公知的常规电解液的制备方法制备得到。
[电化学装置]
其次说明本申请的电化学装置。
本申请电化学装置可以是选自如下装置中的任意一种：锂二次电池、钠离子电池。特别地，所述电化学装置为锂二次电池。
在一些实施例中，电化学装置包含正极片、负极片、隔离膜以及本申请前述的电解液。
<正极片>
正极片是本领域技术公知的可被用于电化学装置的正极片。在一些实施例中，正极片包含正极集流体以及设置在正极集流体上的正极活性物质层。正极活性物质层可包含正极活性物质、正极导电剂以及正极粘结剂。
正极活性材料包含能够可逆地嵌入和脱嵌锂离子的至少一种锂化插层化合物。在一些实施例中，正极活性材料包含复合氧化物。在一些实施例中，该复合氧化物含有锂以及从钴、锰和镍中选择的至少一种元素。
在一些实施例中，正极活性材料选自钴酸锂(LiCoO 2)、锂镍钴锰(NCM)三元材料、磷酸亚铁锂(LiFePO 4)、锰酸锂(LiMn 2O 4)或它们的任意组合。
正极导电剂用于为正极提供导电性，可改善正极导电率。正极导电剂是本领域公知的可被用作正极活性物质层的导电材料。正极导电剂可以选自任何导电的材料，只要它不引起化学变化即可。在一些实施例中，正极导电剂包含碳基材料(例如天然石墨、人造石墨、炭黑、乙炔黑、科琴黑、碳纤维)、金属基材料(例如包括铜、镍、铝、银等的金属粉或金属纤维)、导电聚合物(例如聚亚苯基衍生物)中的至少一种。
正极粘结剂是本领域公知的可被用作正极活性物质层的粘结剂。正极粘结剂可以改善正极活性物质颗粒彼此之间以及正极活性物质颗粒与正极集流体之间的粘结性能。在一些实施例中，正极粘结剂包含聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙中的至少一种。
正极集流体为金属，在一些实施例中，金属例如但不限于铝箔。
在一些实施例中，正极片的结构为本领域技术公知的可被用于电化学装置的正极片的结构。
在一些实施例中，正极片的制备方法是本领域技术公知的可被用于电化学装置的正极片的制备方法。在一些实施例中，在正极浆料的制备中，通常加入正极活性物质、粘结剂，并根据需要加入导电材料和增稠剂后溶解或分散于溶剂中制成正极浆料。溶剂在干燥过程中挥发去除。溶剂是本领域公知的可被用作正极活性物质层的溶剂，溶剂例如但不限于N-甲基吡咯烷酮 (NMP)。
<负极片>
负极片是本领域技术公知的可被用于电化学装置的负极片。在一些实施例中，负极片包含负极集流体以及设置在负极集流体上的负极活性物质层。在一些实施例中，负极活性物质层可包含负极活性物质、负极导电剂以及负极粘结剂。
在一些实施例中，负极活性物质包含锂金属、锂金属合金、过渡金属氧化物、碳材料、硅基材料中的至少一种。
在一些实施例中，负极粘结剂可以包含各种聚合物粘合剂。在一些实施例中，负极粘合剂包含二氟乙烯-六氟丙烯共聚物(PVDF-co-HFP)、聚偏二氟乙烯、聚丙烯腈、聚甲基丙烯酸甲酯、聚乙烯醇、羧甲基纤维素、羟丙基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙中的至少一种。
在一些实施例中，负极活性物质层还包含负极导电剂。负极导电剂用于为负极提供导电性，可改善负极导电率。负极导电剂是本领域公知的可被用作负极活性物质层的导电材料。负极导电剂可以选自任何导电的材料，只要它不引起化学变化即可。
在一些实施例中，负极片的结构为本领域技术公知的可被用于电化学装置的负极片的结构。
在一些实施例中，负极片的制备方法是本领域技术公知的可被用于电化学装置的负极片的制备方法。在一些实施例中，在负极浆料的制备中，通常加入负极活性物质、粘合剂，并根据需要加入导电材料和增稠剂后溶解或分散于溶剂中制成负极浆料。溶剂在干燥过程中挥发去除。溶剂是本领域公知的可被用作负极活性物质层的溶剂，溶剂例如但不限于水。增稠剂是本领域公知的可被用作负极活性物质层的增稠剂，增稠剂例如但不限于羧甲基纤维素钠。
<隔离膜>
在一些实施例中，本申请的电化学装置包含隔离膜。隔离膜是本领域技术公知的可被用于电化学装置的隔离膜，例如但不限于聚烯烃类多孔膜。在 一些实施例中，聚烯烃类多孔膜的基材包含聚乙烯(PE)、乙烯-丙烯共聚物、聚丙烯(PP)、乙烯-丁烯共聚物、乙烯-己烯共聚物、乙烯-甲基丙烯酸甲酯共聚物中的一种或几种组成的单层或多层。
本申请对隔离膜的形态和厚度没有特别的限制。
隔离膜的制备方法是本领域技术公知的可被用于电化学装置的隔离膜的制备方法，例如：将勃姆石与聚丙烯酸酯混合并将其溶入到去离子水中以形成涂层浆料，随后采用微凹涂布法将所述涂层浆料均匀涂布到多孔基材的两个表面上，经过干燥处理以获得所需的隔离膜。
在一些实施例中，电化学装置包含本申请所述的电解液。
在一些实施例中，电化学装置包含本申请所述的电解液且电化学装置的充电终止电压为4.4V至4.8V。
在一些实施例中，当电化学装置包含本申请所述的电解液时，正极活性物质包括LCO、NCM中的至少一种，负极采用Gr、Si体系时，能获得进一步的电化学性能。
[电子装置]
本申请的电子装置可以是任何电子装置，例如但不限于笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池、锂离子电容器。注意的是，本申请的电化学装置除了适用于上述列举的电子装置外，还适用于储能电站、海运运载工具、空运运载工具。空运运载装置包含在大气层内的空运运载装置和大气层外的空运运载装置。
在一些实施例中，电子装置包含本申请所述的电化学装置。
下面结合实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。在本申请的下述具体实施例中，仅示出电池为锂离子电池的实施例，但本申请不限于此。在下述实施例、对比例中，所使用到的试剂、材料等如没有特殊的说明，均可商购获得或合成获得。
实施例和对比例的锂离子电池均按照下述方法制备。
1)正极片的制备
将正极活性材料钴酸锂(LiCoO 2)、导电剂Super P、粘结剂聚偏二氟乙烯按照重量比98:0.4:1.6进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌均匀，获得正极浆料；将正极浆料均匀涂覆于正极集流体铝箔上；将铝箔烘干，然后经过冷压、裁片、分切后，在真空条件下干燥，得到正极片。
2)负极片的制备
将负极活性材料人造石墨、增稠剂羧甲基纤维素钠(CMC)、粘结剂丁苯橡胶(SBR)按照重量比97:1:2进行混合，加入去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在负极集流体铜箔上；将铜箔烘干，然后经过冷压、裁片、分切后，在真空条件下干燥，得到负极片。
3)隔离膜的制备
将勃姆石与聚丙烯酸酯混合并将其溶入到去离子水中以形成涂层浆料。随后采用微凹涂布法将所述涂层浆料均匀涂布到聚乙烯多孔基材的两个表面上，经过干燥处理以获得所需的隔离膜。
4)电解液的制备
在干燥的氩气气氛手套箱中，采用EC(碳酸乙烯酯):PC(碳酸丙烯酯):DEC(碳酸二乙酯)＝2:2:6作为基础溶剂，并参照表1至表4含量加入各组分，溶解并充分搅拌后加入锂盐LiPF 6，混合均匀后获得LiPF 6的含量为1mol/L的电解液。电解液中所用到的溶剂及添加剂的具体种类以及含量如表1至表4所示，其中，表中各组分含量均为基于电解液的质量计算得到的质量百分数。
需要说明的是：其中表3中示例基于实施例2-11设置，与实施例2-11的区别列举于表3；表4中示例基于实施例3-17设置，与实施例3-17的区别列举于表4。
5)锂离子电池的制备
将正极片、隔离膜、负极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，然后卷绕得到裸电芯；焊接极耳后将裸电芯置于外包装箔铝塑膜中，将上述制备好的电解液注入到干燥后的裸电芯中，经过真 空封装、静置、化成、整形、容量测试等工序，获得软包锂离子电池。
接下来说明锂离子电池的高压、高温循环性能测试过程。
将锂离子电池置于45℃恒温箱中，静置30min，使锂离子电池达到恒温。将达到恒温的锂离子电池以0.7C恒流充电至电压为4.5V，然后以4.5V恒压充电至电流为0.025C，用千分尺测试并记录电池的厚度记为D 0，接着以1C恒流放电至电压为3.0V，此为1个充放电循环。以首次放电的容量为100％，反复进行充放电循环300圈，停止测试，记录满充时电池的厚度D n、循环容量保持率，作为评价锂离子电池循环性能的指标。
其中，(1)循环容量保持率＝循环至某一圈时的容量/第一次放电时的容量×100％；(2)厚度膨胀率＝(D n-D 0)/D 0×100％。
实施例和对比例的锂离子电池的相关参数以及锂离子电池的性能测试结果如表1-表4所示。
其中，表1展示了电解液中式(I)表示的化合物对锂离子电池的高压、高温循环性能的影响。
表2展示了电解液中式(I)表示的化合物与碳酸酯类添加剂的含量关系对锂离子电池的高压、高温循环性能的影响。
表3展示了电解液中式(I)表示的化合物与羧酸酯溶剂的含量关系对锂离子电池的高压、高温循环性能的影响。
表4展示了式(I)表示的化合物与腈类化合物的含量关系对锂离子电池的高压、高温循环性能的影响。
表1
Figure PCTCN2021084677-appb-000015
Figure PCTCN2021084677-appb-000016
注：“\”表示未添加该组分的物质。
参见表1，从对比例1-1可知，当电解液中没有加入式I所示化合物时，锂离子电池的高温循环容量保持率较差，厚度增长率较高，锂离子电池在高电压下的高温循环性能较差。从对比例1-1至1-3、实施例1-4可知，相比于锂离子电池低电压体系添加剂邻苯二甲酰亚胺和戊二酸酐，本申请提供的式I化合物具有更优异的高温循环容量保持率和厚度增长抑制作用。这是由于两种单体基团在分子水平桥联，在电解液中作为添加剂使用时，在正负极形成的保护层更为稳定，有效抑制副产物生成，并保护正极活性物质的结构稳定性，在超过4.4V高电压下实现高温长循环。
通过对比实施例1-1至实施例1-25与对比例1-1可知，当电解液中加入了式I所示化合物后，锂离子电池高温高电压下循环300圈后的容量保持率均有所增加、厚度增长率下降明显，即通过在电解液中加入式I所示化合物可以提高锂离子电池在高电压下的高温循环性能。这可能是由于式I化合物中多基团参与锂离子电池电极界面的成膜，在高温存储中能够有效延后正负极固体电解质界面膜失效，抑制电解液分解产气生成，从而提高了锂离子电池的高温循环性能。
从实施例1-1到实施例1-7的性能测试结果可以看出，实施例1-1的电解液中的式I所示化合物的质量百分比含量仅为0.05％，式I所示化合物质量含量过少，正负极保护膜稳定性不足，锂离子电池在高温高截止电压下的循环 容量保持率相比于对比例1-1无明显提高，且相比于实施例1-2到实施例1-6也表现较差。实施例1-7的电解液中的式I所示化合物的质量百分比含量为6％，式I所示化合物质量含量过多，造成膜阻抗较大，导致不可逆锂析出，反而有可能阻碍电解液的离子传输通道，加速容量衰减。
根据实施例1-1到实施例1-7的性能测试结果可以看出，当电解液中式I所示化合物的质量含量在0.05％至5％时，对锂离子电池在高温高截至电压下的综合性能有显著的改善作用。这是因为合适含量的式I所示化合物参与正负极成膜，提高了SEI膜的稳定性，有利于抑制高电压高温下的反应副产物累计。因此，在本申请的一些实施例中，式I所示化合物在电解液中的量百分比含量为0.05％至5％，进一步优选地，式I所示化合物在电解液中的质量百分比含量为0.5％至3％。
从实施例1-1到实施例1-25的性能测试结果可以看出，当式I所示化合物具体为式I-1或I-3、I-6所示的化合物时，其对锂离子电池的性能改善效果较优。
表2
Figure PCTCN2021084677-appb-000017
注：“\”表示未添加该组分的物质。
参见表2，通过对比分析实施例1-4、实施例2-1至实施例2-13的数据可知，当电解液中加入0.5％至14％的氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯 (VC)，锂离子电池在高温高充电截止电压下的循环容量保持率上升。对照对比例2-1可知，FEC、VC和式I所示化合物协同作用，可以进一步抑制厚度增长，提示循环容量保持率。
通过分析对比例1-1、实施例2-1至实施例2-13的数据可知，当碳酸酯添加剂和式I所示化合物总量在1％至15％，相比于不使用这两类物质，锂离子电池在高电压下的循环性能有不同程度的改善，当电解液中碳酸酯添加剂和式I所示化合物的质量百分比含量控制在3％至15％时，对锂离子电池的性能改善效果最佳。
表3
Figure PCTCN2021084677-appb-000018
注：“/”表示未添加该组分的物质。
参见表3，通过分析对比例3-1、实施例2-9、实施例3-1至3-19的数据可知：协同式Ⅰ化合物添加剂，一定含量的羧酸酯对锂离子电池的高温循环容量和厚度增长有改善作用，其中丙酸乙酯、丙酸丙酯改善效果较乙酸乙酯较优。
通过分析对比例3-11至对比例3-16可知：通过调节羧酸酯的种类和含量，当羧酸酯总量小于50％时，以一定比例组合式Ⅰ化合物添加剂，可以进一步改善锂离子电池的高电压高温循环后的容量保持率及产气。
表4
Figure PCTCN2021084677-appb-000019
注：“/”表示未添加该组分的物质。
参见表4，通过分析对比例3-1、对比例4-1、对比例4-2、实施例3-17、实施例4-1至实施例4-20的数据可知，当电解液中加入腈类化合物和磺酸酯类化合物时，在和式I所示化合物协同作用下，锂离子电池的高温循环容量保持率上升，厚度增长率下降，显著改善锂离子电池在高电压下的循 环性能。这是因为腈类化合物有效抑制了充电态的锂离子电池的正极表面对电解液的氧化反应，磺酸酯类化合物优先于式I化合物在正极活性材料的表面氧化，和式I化合物协同形成稳定的SEI膜，减少电解液与正极活性材料表面的副反应，从而协同改善锂离子电池的高温循环性能和产气。
其中，当电解液中加入的腈类化合物质量百分比含量过高时，锂离子电池的高温循环容量保持率反而有所下降，厚度增长也增加。这可能是因为过量的腈类化合物导致正极表面副产物覆层增加严重，阻碍了锂离子脱出和嵌回的通道，反而恶化了锂离子电池的高温循环性能。
在产气抑制和循环容量保持率上，1,3,6-己烷三腈组合两种二腈使用，较单一使用均有优势，其中含量之和在3％至7％，能较大程度地改善锂离子电池循环性能。这可能是由于，在同时使用其它腈类化合物时，相对于三腈位阻较小的链状分子能与三腈化合物起到协同作用，在电解液中的易氧化组分与正极表面间形成有效隔离。
以上所述，仅是本申请的示例，并非对本申请做任何形式的限制，虽然本申请以较佳实施例揭示如上，然而并非用以限制本公开，任何熟悉本专业的技术人员，在不脱离本申请技术方案的范围内，利用上述揭示的技术内容做出些许的变动或修饰均等同于等效实施案例，均在本申请技术方案的范围内。

Claims (14)

  1. 一种电解液，其中，包括式(I)表示的化合物，
    Figure PCTCN2021084677-appb-100001
    在式(I)中，X选自经取代或未经取代基的酸酐；经取代时，取代基包括烷基、芳基、酰氧基、醛基、氰基或卤素中的至少一种。
  2. 根据权利要求1所述的电解液，其中，所述酸酐包括琥珀酸酐、马来酸酐、苯并马来酸酐、戊二酸酐、苯并戊二酸酐、巴豆酸酐、衣托酸酐、衣康酸酐、邻苯二甲酸酐、苯甲酸酐、甲乙酐、丙酸酐、丁酸酐或氢化降冰片烯二酸酐中的至少一种。
  3. 根据权利要求1所述的电解液，其中，所述式(I)表示的化合物包括式(I-1)至式(I-8)表示的化合物中的至少一种；
    Figure PCTCN2021084677-appb-100002
  4. 根据权利要求1所述的电解液，其中，基于所述电解液的重量，所述式(I)表示的化合物的含量为n％，0.05≤n≤5。
  5. 根据权利要求4所述的电解液，其中，电解液还包括氟代碳酸乙烯酯、碳酸亚乙烯酯中的至少一种；
    基于所述电解液的重量，氟代碳酸乙烯酯的含量为k％，碳酸亚乙烯酯的含量为m％，其中，k≥0，m≥0，k+m＞0，且k、m和n满足1≤k+m+n≤15。
  6. 根据权利要求4所述电解液，其中，所述电解液还包括羧酸酯；基于所述电解液的重量，所述羧酸酯的含量为a％，5≤a≤60，且a和n满足关系：0.0005≤n/a≤0.7。
  7. 根据权利要求6所述电解液，其中，所述羧酸酯包括乙酸乙酯、乙酸丙酯、乙酸丁酯、丙酸乙酯、丙酸丙酯或丙酸丁酯中的至少一种。
  8. 根据权利要求1-7中任一项所述电解液，其中，所述电解液还包括1,3-丙烷磺内酯、2,4-丁磺内酯、甲基乙基砜或腈类化合物中的至少一种。
  9. 根据权利要求8所述电解液，其中，所述腈类化合物包括式(Ⅱ)至式(Ⅴ)表示的化合物中的至少一种；
    N≡C-R 21-C≡N  式(Ⅱ)
    Figure PCTCN2021084677-appb-100003
    Figure PCTCN2021084677-appb-100004
    Figure PCTCN2021084677-appb-100005
    其中，R 21选自经取代或未经取代的C 1-C 12亚烷基、经取代或未经取代的C 1-C 12亚烷氧基；
    R 31、R 32各自独立地选自单键、经取代或未经取代的C 1-C 12亚烷基；
    R 41、R 42、R 43各自独立地选自单键、经取代或经未取代的C 1-C 12亚烷基、经取代或未经取代的C 1-C 12亚烷氧基；
    R 51选自经取代或经未经取代的C 1-C 12亚烷基、经取代或未经取代的C 2-C 12亚烯基、经取代或未经取代的C 6-C 12亚芳基、经取代或未经取代的C 3-C 12亚环基；
    其中经取代时，取代基为卤素。
  10. 根据权利要求9所述电解液，其中，所述腈类化合物包括以下化合物中的至少一种：
    Figure PCTCN2021084677-appb-100006
    Figure PCTCN2021084677-appb-100007
  11. 根据权利要求9所述电解液，其中，基于所述电解液的重量，所述腈类化合物在电解液中重量含量为b％，0.1≤b≤10。
  12. 一种电化学装置，包括正极片、负极片、隔离膜以及根据权利要求1-11中任一项所述的电解液。
  13. 根据权利要求12所述的电化学装置，其中，所述电化学装置的充电终止电压为4.4V至4.8V。
  14. 一种电子装置，包括根据权利要求12-13所述的电化学装置。
PCT/CN2021/084677 2021-03-31 2021-03-31 电解液、电化学装置以及电子装置 WO2022205172A1 (zh)

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