WO2023184143A1 - 电解液、电化学装置及电子装置 - Google Patents

电解液、电化学装置及电子装置 Download PDF

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WO2023184143A1
WO2023184143A1 PCT/CN2022/083644 CN2022083644W WO2023184143A1 WO 2023184143 A1 WO2023184143 A1 WO 2023184143A1 CN 2022083644 W CN2022083644 W CN 2022083644W WO 2023184143 A1 WO2023184143 A1 WO 2023184143A1
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Prior art keywords
electrolyte
lithium
formula
compound represented
mass
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PCT/CN2022/083644
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English (en)
French (fr)
Inventor
袁晓
林孟衍
唐超
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宁德新能源科技有限公司
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Priority to PCT/CN2022/083644 priority Critical patent/WO2023184143A1/zh
Priority to CN202280003035.3A priority patent/CN115298875A/zh
Publication of WO2023184143A1 publication Critical patent/WO2023184143A1/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
    • 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 solution, an electrochemical device and an electronic device.
  • Electrochemical devices e.g., lithium-ion batteries
  • electrochemical devices With the development of lightweight electrochemical devices, there is a need to further develop electrochemical devices with high capacity density.
  • lithium-ion batteries when the charging cut-off voltage of lithium-ion batteries is increased from 4.45V to 4.55V, its effective capacity is significantly increased, but subsequently, the performance of lithium-ion batteries is significantly reduced, especially It is the cycle performance and high-temperature storage performance; under high voltage, the oxidation activity of the positive electrode active material is high, the electrolyte is accelerated oxidation and decomposition on the surface of the positive electrode material, producing a large amount of gas, and the oxidation products are continuously deposited on the surface of the positive electrode, causing the internal resistance of the battery And the thickness continues to grow, causing the capacity of lithium-ion batteries to rapidly decay and the expansion to increase significantly.
  • electrolyte As an important component of an electrochemical device, electrolyte has a great impact on the cycle performance and storage performance of the electrochemical device. Therefore, it is urgent to provide an electrolyte to improve the cycle performance and high-temperature storage performance of the electrochemical device.
  • the purpose of this application is to provide an electrolyte, an electrochemical device and an electronic device.
  • an electrolyte solution which includes a compound represented by formula I,
  • X is selected from Li + , Na + , K + or Rb + .
  • the mass percentage of the compound represented by Formula I is 0.005%-1.5%.
  • the mass percentage of the compound represented by Formula I is 0.01%-1%.
  • the electrolyte further includes fluorinated ethylene carbonate; in some embodiments, the mass percentage of the fluorinated ethylene carbonate is 1%-10% based on the mass of the electrolyte. .
  • the compound represented by Formula I includes at least one of the following compounds:
  • the electrolyte further includes a nitrile compound, and the nitrile compound includes a compound represented by Formula II:
  • R 1 is selected from substituted or unsubstituted C 1-10 alkyl group, substituted or unsubstituted C 1-10 alkenyl group, substituted or unsubstituted C 1-10 alkynyl group , one of a substituted or unsubstituted C 1-10 alkoxy group and a substituted or unsubstituted C 1-10 heterocyclyl group, wherein when substituted, the substituent is halogen;
  • R 2 , R 3 , and R 4 are independently selected from hydrogen atoms or cyano groups
  • the mass percentage of the compound represented by Formula II is 0.1% to 5%.
  • the nitrile-based compound includes at least one of the following compounds:
  • the electrolyte further includes lithium difluorophosphate; in some embodiments, based on the mass of the electrolyte, the mass percentage of the lithium difluorophosphate is 0.005% to 1%.
  • the present application provides an electrochemical device, including a positive electrode sheet, a negative electrode sheet, a separator, and the above-mentioned electrolyte.
  • the present application also provides an electronic device including the above electrochemical device.
  • the electrolyte in this application can effectively improve the cycle performance and high-temperature storage performance of the electrochemical device.
  • the electrolyte solution includes a compound of formula I,
  • X is selected from Li + , Na + , K + or Rb + .
  • the compound represented by Formula I can be oxidized on the positive electrode to form a dense solid electrolyte (CEI) film, which can improve the stability of the positive electrode, reduce side reactions of the electrolyte at the positive electrode interface, reduce gas production, and improve the normal temperature cycle performance and high-temperature storage of the electrochemical device. performance.
  • CEI dense solid electrolyte
  • the mass percentage of the compound represented by Formula I is 0.005%-1.5%. In some embodiments, based on the mass of the electrolyte, the mass percentage of the compound represented by Formula I is 0.005%-1%. In some embodiments, based on the quality of the electrolyte, the content of the compound represented by Formula I in the electrolyte can be 0.005%, 0.015%, 0.05%, 0.2%, 0.3%, 0.4%, 0.5%, 1.0%, 1.5%, or any range in between.
  • the electrolyte further includes fluorinated ethylene carbonate; based on the mass of the electrolyte, the mass percentage of the fluorinated ethylene carbonate is 1%-10%. In some embodiments, based on the quality of the electrolyte, the content of the fluoroethylene carbonate in the electrolyte may be 1.0%, 2.5%, 5.0%, 7.5%, 10% or any range therebetween.
  • FEC fluoroethylene carbonate
  • SEI solid electrolyte
  • the CEI film formed by the compound represented by Formula I on the positive electrode interface can inhibit the etching of the positive electrode by FEC. Stabilize the positive electrode interface, and the two work together to improve the room temperature cycle performance of the electrochemical device through synergy.
  • the amount of FEC added is too high, it will increase the impedance of the negative electrode interface, and may also cause side reactions at the electrode interface, resulting in increased gas production. Affects the high-temperature storage performance of electrochemical devices.
  • the compound represented by Formula I includes at least one of the following compounds:
  • the electrolyte further includes a nitrile compound, and the nitrile compound includes a compound represented by Formula II:
  • R 1 is selected from substituted or unsubstituted C 1-10 alkyl group, substituted or unsubstituted C 1-10 alkenyl group, substituted or unsubstituted C 1-10 alkynyl group , one of a substituted or unsubstituted C 1-10 alkoxy group, a substituted or unsubstituted C 1-10 heterocyclyl group, wherein when substituted, the substituent is halogen;
  • R 2 , R 3 and R 4 are each independently selected from a hydrogen atom or a cyano group. Based on the mass of the electrolyte, the mass percentage of the compound represented by Formula II is 0.1% to 5%.
  • the content of the compound represented by Formula II in the electrolyte can be 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3%, 3.5%, 4.0%, 4.5%, 5.0% or any range therebetween.
  • the compound of formula II is further added. Since the compound of formula II contains a cyano substituent, it can be adsorbed on the cathode surface to form Protective film.
  • the formed protective film can effectively block the contact between the solvent molecules in the electrolyte and the surface of the positive electrode, significantly reduce the oxidation of the electrolyte on the surface of the positive electrode of the electrochemical device during the cycle, and further reduce the side reactions between the positive electrode and the electrolyte. This effectively improves the normal temperature cycle performance of the electrochemical device and improves its high-temperature storage performance.
  • the nitrile-based compound includes at least one of the following compounds:
  • the electrolyte further includes lithium difluorophosphate; based on the mass of the electrolyte, the mass percentage of the lithium difluorophosphate is 0.01% to 1%. In some embodiments, based on the mass of the electrolyte, the mass percentage of the lithium difluorophosphate in the electrolyte can be 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5 %, 1.0%, or any range in between.
  • lithium difluorophosphate When lithium difluorophosphate is further added to the electrolyte containing the compound represented by formula I or the electrolyte containing fluoroethylene carbonate (FEC) or the electrolyte containing the compound represented by formula II, because lithium difluorophosphate can also be Participating in the formation of the SEI film at the negative electrode interface and further modifying the formed SEI film can increase the ionic conductivity and stability of the SEI film formed at the negative electrode interface, inhibit side reactions between the negative electrode and the electrolyte, and reduce gas production. At the same time, the transmission impedance of active metal ions at the negative electrode interface is reduced, further improving the cycle performance of the electrochemical device and enhancing its high-temperature storage performance.
  • FEC fluoroethylene carbonate
  • the electrolyte further includes a lithium salt and a non-aqueous organic solvent.
  • the lithium salt includes or is selected from at least one of organic lithium salts and inorganic lithium salts.
  • the lithium salt includes or is selected from lithium hexafluorophosphate (LiPF 6 ), lithium bisoxaloborate (LiB(C 2 O 4 ) 2 , LiBOB), lithium difluorooxaloborate (LiBF 2 (C 2 O 4 ), LiDFOB), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroantimonate (LiSbF 6 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium perfluorobutanesulfonate (LiC 4 F 9 SO 3 ), Lithium perchlorate (LiClO 4 ), lithium aluminate (LiAlO 2 ), lithium tetrachloroaluminate (LiAlCl 4 ), lithium disulfonimide (LiN(C x F 2x+1 SO 2 ) (C y F 2y +1 SO 2 ), where x and
  • the mass percentage of the lithium salt is 10% to 15%, preferably 12% to 15%.
  • the non-aqueous organic solvent may include carbonate solvents, carboxylate solvents, ether solvents, sulfone solvents, other organic solvents, or combinations thereof.
  • the carbonate solvent may include, but is not limited to, at least one of a chain carbonate compound or a cyclic carbonate compound.
  • the above-mentioned chain carbonate compound may include, but is not limited to, at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate or methylethyl carbonate.
  • the above-mentioned cyclic carbonate may include, but is not limited to, at least one of ethylene carbonate (also known as ethylene carbonate), vinylene carbonate, propylene carbonate, butylene carbonate (or vinylethylene carbonate).
  • carboxylate solvents may include, but are not limited to, methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propionic acid At least one of propyl ester, ⁇ -butyrolactone, decanolide, valerolactone or caprolactone.
  • ether compounds may include but are not limited to dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1- At least one of ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran.
  • the ether solvent includes at least one of tetrahydrofuran, ethylene glycol dimethyl ether, diglyme, 1.4-dioxane, and 1,3-dioxane.
  • the sulfone solvent includes at least one of sulfolane, dimethyl sulfoxide, and methyl sulfolane.
  • organic solvents include 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, phosphoric acid At least one of triethyl ester, trioctyl phosphate, and phosphate ester.
  • the organic solvent in the electrolyte can be a non-aqueous organic solvent, or a mixture of multiple non-aqueous organic solvents can be used.
  • the mixing ratio can be controlled according to the required performance of the electrochemical device. .
  • the electrochemical device of the present application is not particularly limited and may include any device that undergoes electrochemical reactions.
  • the electrochemical device may include, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the electrochemical device includes a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte solution mentioned above in this application.
  • the preparation process of the electrochemical device is well known to those skilled in the art, and the application is not particularly limited. For example, it may include but is not limited to the following steps: stack the positive electrode sheet, the isolation film and the negative electrode sheet in order, and stack them as needed. Winding, folding and other operations are performed to obtain the electrode assembly of the rolled structure.
  • the electrode assembly is put into the packaging bag, the electrolyte is injected into the packaging bag and sealed to obtain an electrochemical device; or, the positive electrode sheet, isolation film and negative electrode sheet are placed in order Stack, and then use tape to fix the four corners of the entire laminated structure to obtain an electrode assembly of the laminated structure. Place the electrode assembly into a packaging bag, inject electrolyte into the packaging bag and seal it to obtain an electrochemical device.
  • overcurrent prevention components, guide plates, etc. can also be placed in the packaging bag as needed to prevent pressure rise inside the electrochemical device and overcharge and discharge.
  • the positive electrode sheet includes a current collector and a positive active material layer disposed on the current collector.
  • the positive electrode current collector is not particularly limited as long as it can achieve the purpose of this application.
  • it may include but is not limited to aluminum foil, aluminum alloy foil or composite current collector.
  • the thickness of the positive electrode current collector there is no particular restriction on the thickness of the positive electrode current collector, as long as the purpose of this application can be achieved, for example, the thickness is 8 ⁇ m to 12 ⁇ m.
  • the cathode material layer may be disposed on one surface or both surfaces along the thickness direction of the cathode current collector.
  • the "surface" here can be the entire area of the positive electrode current collector, or it can be a partial area of the positive electrode current collector. There is no particular limitation in this application, as long as the purpose of this application can be achieved.
  • the positive active material includes a compound that reversibly intercalates and deintercalates lithium ions.
  • the positive active material may include at least one of lithium cobalt oxide, lithium manganate, lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, or lithium nickel manganate,
  • the above-mentioned positive active material may be doped and/or coated.
  • cladding elements for the cladding layer may include K, Na, Ca, Mg, B, Al, Co, Si, V, Ga, Sn, Zr, or mixtures thereof.
  • the positive active material layer further includes a binder and a conductive agent.
  • the conductive agent in the cathode active material layer may include at least one of conductive carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes or carbon fibers.
  • the binder in the positive active material layer may include polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, styrene -Acrylate copolymer, styrene-butadiene copolymer, polyamide, sodium carboxymethylcellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, polyhexafluoropropylene Or at least one of polymethylmethacrylate.
  • the positive electrode may further include a conductive layer located between the positive electrode current collector and the positive electrode material layer. This application has no particular limitation on the composition of the conductive layer, and it can be a conductive layer commonly used in this field.
  • the negative electrode sheet includes a negative electrode active material layer on a current collector.
  • This application has no special restrictions on the negative electrode current collector, as long as it can achieve the purpose of this application.
  • it may include but is not limited to copper foil, copper Alloy foil, aluminum foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collector, etc.
  • the thickness of the negative electrode current collector there is no particular limit on the thickness of the negative electrode current collector, as long as the purpose of this application can be achieved, for example, the thickness is 4 ⁇ m to 12 ⁇ m.
  • the negative electrode material layer may be disposed on one surface or both surfaces along the thickness direction of the negative electrode current collector.
  • the "surface" here can be the entire area of the negative electrode current collector, or it can be a partial area of the negative electrode current collector. There is no particular limitation in this application, as long as the purpose of this application can be achieved.
  • the negative active material layer includes a negative active material, and the negative active material includes a material that can reversibly intercalate/deintercalate lithium ions.
  • materials that can reversibly intercalate/deintercalate lithium ions include, but are not limited to, natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys , Li-Sn-O alloy, Sn, SnO, SnO 2 , spinel structure lithiated TiO 2 -Li 4 Ti 5 O 12 or at least one of Li-Al alloy.
  • a conductive agent and/or a binder may also be included in the negative active material layer.
  • the conductive agent in the negative active material layer may include at least one of carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes, carbon fibers or carbon nanowires.
  • the binder in the negative active material layer may include carboxymethylcellulose (CMC), polyacrylic acid, polyacrylate, polyacrylate, polyvinylpyrrolidone, polyaniline, polyimide, At least one of polyamide-imide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.
  • the negative electrode plate may further include a conductive layer located between the negative electrode current collector and the negative electrode material layer.
  • a conductive layer located between the negative electrode current collector and the negative electrode material layer.
  • This application has no particular limitation on the composition of the conductive layer. It can be a conductive layer commonly used in this field.
  • the conductive layer can include but is not limited to the above-mentioned conductive agent and the above-mentioned adhesive.
  • the negative electrode can be prepared by preparation methods known in the art.
  • the negative electrode can be obtained by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and coating the active material composition on a current collector.
  • the electrochemical device of the present application is provided with an isolation film between the positive electrode and the negative electrode to prevent short circuit.
  • the isolation film includes a substrate layer and a surface treatment layer.
  • the material of the base material layer is selected from at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide or aramid.
  • the polyethylene includes at least one selected from high density polyethylene, low density polyethylene or ultra-high molecular weight polyethylene.
  • the isolation membrane of the present application may have a porous structure, and the size of the pore diameter is not particularly limited as long as the purpose of the present application can be achieved. For example, the size of the pore diameter may be 0.01 ⁇ m to 1 ⁇ m.
  • the thickness of the isolation film is not particularly limited as long as the purpose of this application can be achieved. For example, the thickness may be 5 ⁇ m to 500 ⁇ m.
  • the surface of the isolation film may also be provided with a surface treatment layer.
  • the surface treatment layer is disposed on at least one surface of the base material of the isolation film, and the surface treatment layer includes at least one of an inorganic layer or a polymer layer.
  • the inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from aluminum oxide (Al 2 O 3 ), silicon oxide (SiO 2 ), magnesium oxide (MgO), titanium oxide (TiO 2 ), Hafnium dioxide (HfO 2 ), tin oxide (SnO 2 ), ceria (CeO 2 ), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO 2 ), yttrium oxide At least one of (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate.
  • the binder is selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, carboxymethyl At least one of sodium cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the porous layer on the surface of the isolation membrane can improve the heat resistance, oxidation resistance and electrolyte wetting performance of the isolation membrane, and enhance the adhesion between the isolation membrane and the pole piece.
  • the polymer material in the polymer layer is selected from at least one of polyacrylonitrile, polyacrylate, polyamide, polyvinylidene fluoride, and polyvinylpyrrolidone.
  • the casing is used to encapsulate the electrode assembly.
  • the shell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.; or it can be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag can be plastic, such as polypropylene (PP). ), at least one of polybutylene terephthalate (PBT) and polybutylene succinate (PBS).
  • the positive electrode sheet, the negative electrode sheet and the isolation film can be made into an electrode assembly through a winding process or a lamination process.
  • the electrode assembly is placed in the case, the electrolyte is injected, and then vacuum sealed, left to stand, and formed.
  • the electrochemical device can be obtained after processes such as , shaping, and volume fractionation.
  • the present application also provides an electronic device, which includes the electrochemical device in any of the foregoing embodiments.
  • the electrochemical device provided by this application has good cycle performance and high temperature storage performance, so that the electronic device provided by this application has a long service life.
  • the electronic device of this application is 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, stereo headsets, video recorders , LCD TV, portable cleaner, portable CD player, mini CD, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle, lighting Appliances, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, lithium-ion capacitors.
  • the electrochemical device of the present application is also applicable to energy storage power stations, maritime vehicles, and air vehicles.
  • Air transport devices include air transport devices within the atmosphere and air transport devices outside the atmosphere.
  • the lithium ion batteries in Examples 1-49 and Comparative Example 1 were prepared according to the following methods:
  • LiCoO 2 lithium cobalt oxide
  • conductive agent acetylene black conductive agent acetylene black
  • binder polyvinylidene fluoride PVDF
  • NMP N-methylpyrrolidone
  • SBR styrene-butadiene rubber
  • CMC thickener sodium carboxymethyl cellulose
  • the electrolytes and lithium ion batteries of the Examples and Comparative Examples were prepared according to the above methods and tested.
  • difluorophosphoric acid is further added to the electrolyte containing the compound represented by formula I or the electrolyte containing fluoroethylene carbonate (FEC) or the electrolyte containing the compound represented by formula II.
  • Lithium because lithium difluorophosphate further modifies the formed solid electrolyte membrane, increases the ionic conductivity and stability of the negative electrode graphite SEI membrane, inhibits side reactions between the electrode and the electrolyte, and further improves the cycle performance of the battery. , improve high-temperature storage performance.
  • the above example data shows that adding the compound of formula I or the combination of the compound of formula I and one or more other additives to the electrolyte can significantly improve the cycle performance and high-temperature storage performance of lithium-ion batteries.

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Abstract

本申请提供一种电解液，其中，包括式I所示化合物，其中，X选自Li+、Na+、K+或Rb+。本申请的电解液可有效降低电化学装置的阻抗以及改善电化学装置的循环性能和高温循环性能。

Description

电解液、电化学装置及电子装置 技术领域
本申请涉及电化学领域，尤其涉及一种电解液、电化学装置及电子装置。
背景技术
电化学装置(例如，锂离子电池)具有高能量密度、宽工作温度范围以及长循环寿命，已然成为目前移动电子设备的主要能源。随着电化学装置的轻量化发展，需要进一步开发具有高容量密度的电化学装置。目前，以锂离子电池为例，将锂离子电池的充电截止电压从4.45V提高到4.55V时，其有效发挥容量显著提高，但随之而来的是，锂离子电池的性能明显降低，尤其是循环性能和高温存储性能；在高电压下，正极活性材料的氧化活性较高，电解液在正极材料表面被加速氧化分解，产生大量气体，而氧化产物不断在正极表面沉积，导致电池内阻和厚度不断增长，引起锂离子电池的容量快速衰减以及膨胀明显增加。
电解液作为电化学装置的重要组成部分，对电化学装置的循环性能和存储性能的影响较大，因此亟需提供一种电解液，以改善电化学装置的循环性能和高温存储性能。
发明内容
鉴于背景技术中存在的问题，本申请的目的在于提供一种电解液、电化学装置及电子装置。
为了达到上述目的，本申请提供一种电解液，其中，包括式I所示化合物，
Figure PCTCN2022083644-appb-000001
其中，X选自Li +、Na +、K +或Rb +。
在一些实施例中，基于所述电解液的质量，所述式I所示化合物的质量百分含量为0.005％-1.5％。
在一些实施例中，基于所述电解液的质量，所述式I所示化合物的质量百分含量为0.01％-1％。
在一些实施例中，所述电解液还包括氟代碳酸乙烯酯；在一些实施例中，基于所述电解液的质量，所述氟代碳酸乙烯酯的质量百分含量为1％-10％。
在一些实施例中，所述式I所示化合物包括如下化合物中的至少一种：
Figure PCTCN2022083644-appb-000002
在一些实施例中，所述电解液还包括腈基化合物，所述腈基化合物包括式II所示化合物：
Figure PCTCN2022083644-appb-000003
其中，R 1选自经取代或未经取代的C 1-10的烷基、经取代或未经取代的C 1-10的烯基、经取代或未经取代的C 1-10的炔基、经取代或未经取代的C 1-10的烷氧基、经取代或未经取代的C 1-10的杂环基中的一种，其中，经取代时，取代基为卤素；
R 2、R 3、R 4分别独立地选自氢原子或氰基；
基于所述电解液的质量，所述式II所示的化合物的质量百分含量为0.1％～5％。
在一些实施例中，所述腈基化合物包括如下化合物中的至少一种：
Figure PCTCN2022083644-appb-000004
Figure PCTCN2022083644-appb-000005
在一些实施例中，所述电解液还包括二氟磷酸锂；在一些实施例中，基于所述电解液的质量，所述二氟磷酸锂的质量百分含量为0.005％～1％。
在一些实施例中，本申请提供了一种电化学装置，包括正极片、负极片、隔离膜以及上述电解液。
在一些实施例中，本申请还提供了一种电子装置，所述电子装置包括上述电化学装置。
本申请至少包括如下有益效果：
本申请中的电解液可有效改善电化学装置的循环性能和高温存储性能。
具体实施方式
将理解的是，所公开的实施例仅仅是本申请的示例，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，除非另有明确的规定和限定，术语“式I”、“式II”等仅用于说明的目的，而不能理解为指示或暗示相对重要性以及相互存在关系。
(电解液)
在一些实施例中，所述电解液包括式I所示化合物，
Figure PCTCN2022083644-appb-000006
其中，X选自Li +、Na +、K +或Rb +。
式I所示化合物可在正极氧化形成致密的固体电解质(CEI)膜，能够提高正极的稳定性，减少电解液在正极界面副反应，降低产气，改善电化学装置的常温循环性能和高温存储性能。
在一些实施例中，基于所述电解液的质量，所述式I所示化合物的质量百分含量为0.005％-1.5％。在一些实施例中，基于所述电解液的质量，所述式I所示化合物的质量百分含量为0.005％-1％。在一些实施例中，基于所述电解液的质量，所述式I所示化合物在电解液中的含量可为0.005％、0.015％、0.05％、0.2％、0.3％、0.4％、0.5％、1.0％、1.5％或其间的任意范围。
在一些实施例中，所述电解液还包括氟代碳酸乙烯酯；基于所述电解液的质量，所述氟代碳酸乙烯酯的质量百分含量为1％-10％。在一些实施例中，基于所述电解液的质量，所述氟代碳酸乙烯酯在电解液中的含量可以为1.0％、2.5％、5.0％、7.5％、10％或其间的任意范围。
在含有式I所示化合物的电解液中进一步加入氟代碳酸乙烯酯(FEC)，可进一步提升电化学装置的循环性能，原因是FEC能够在负极还原形成固体电解质(SEI)膜，并且在电化学装置循环过程中不断修复负极表面，抑制循环过程中电解液中的溶剂和其他成膜添加剂的消耗；同时，式I所示化合物在正极界面形成的CEI膜可抑制FEC对正极的刻蚀，稳定正极界面，二者通过协同作用共同改善电化学装置的常温循环性能，但当FEC添加量过高时，会增加负极界面的阻抗，也可能会引起电极界面的副反应，造成产气增加，影响电化学装置的高温存储性能。
在一些实施例中，所述式I所示化合物包括如下化合物中的至少一种：
Figure PCTCN2022083644-appb-000007
在一些实施例中，所述电解液还包括腈基化合物，所述腈基化合物包括式II所示化合物：
Figure PCTCN2022083644-appb-000008
其中，R 1选自经取代或未经取代的C 1-10的烷基、经取代或未经取代的C 1-10的烯基、经取代或未经取代的C 1-10的炔基、经取代或未经取代的C 1-10的烷氧基、经取代或未经取代的C 1-10的杂环基中的一种，其中，经取代时，取代基为卤素；R 2、R 3、R 4分别独立地选自氢原子或氰基。基于所述电解液的质量，所述式II所示化合物的质量百分含量为0.1％～5％。在一些实施例中，基于所述电解液的质量，所述式II所示化合物在电解液中的含量可以为0.1％、0.5％、1.0％、1.5％、2.0％、2.5％、3％、3.5％、4.0％、4.5％、5.0％或其间的任意范围。
在含有式I所示化合物的电解液或加氟代碳酸乙烯酯(FEC)的电解液中进一步加入式II所示化合物，由于式II所示化合物含有氰基取代基，可吸附在阴极表面形成保护膜，所形成的保护膜可以有效阻隔电解液中溶剂分子与正极表面接触，显著降低循环过程中的电化学装置的正极表面对电解液的氧化，进一步减少正极与电解液间的副反应，从而有效改善电化学装置的常温循环性能，同时提升其高温存储性能。
在一些实施例中，所述腈基化合物包括如下化合物中的至少一种：
Figure PCTCN2022083644-appb-000009
Figure PCTCN2022083644-appb-000010
在一些实施例中，所述电解液还包括二氟磷酸锂；基于所述电解液的质量，所述二氟磷酸锂的质量百分含量为0.01％～1％。在一些实施例中，基于所述电解液的质量，所述二氟磷酸锂在电解液中的质量百分含量可以为0.01％、0.05％、0.1％、0.2％、0.3％、0.4％、0.5％、1.0％或其间的任意范围。
在含有式I所示化合物的电解液或加氟代碳酸乙烯酯(FEC)的电解液或加含有式II所示化合物的电解液中进一步加入二氟磷酸锂时，由于二氟磷酸锂也可在负极界面参与形成SEI膜，同时对形成的SEI膜做进一步的修饰，能够增加负极界面形成的SEI膜的离子导电性和稳定性，抑制负极与电解液之间的副反应，减少产气，同时降低负极界面活性金属离子的传输阻抗，进一步改善电化学装置的循环性能和提升其高温存储性能。
在一些实施例中，所述电解液进一步包括锂盐和非水有机溶剂。
在一些实施例中，所述锂盐包括或选自有机锂盐和无机锂盐中的至少一种。
在一些实施例中，所述锂盐包括或选自六氟磷酸锂(LiPF 6)、双草酸硼酸锂(LiB(C 2O 4) 2，LiBOB)、二氟草酸硼酸锂(LiBF 2(C 2O 4)，LiDFOB)、四氟硼酸锂(LiBF 4)、六氟锑酸锂(LiSbF 6)、六氟砷酸锂(LiAsF 6)、全氟丁基磺酸锂(LiC 4F 9SO 3)、高氯酸锂(LiClO 4)、铝酸锂(LiAlO 2)、四氯铝酸锂(LiAlCl 4)、双磺酰亚胺锂(LiN(C xF 2x+1SO 2)(C yF 2y+1SO 2)，其中x和y是自然数)、氯化锂(LiCl)或氟化锂(LiF)中的至少一种。
在一些实施例中，基于电解液的质量，锂盐的质量百分含量为10％ 至15％，优选为12％至15％。
在一些实施例中，所述非水有机溶剂可以包括碳酸酯类溶剂、羧酸酯类溶剂、醚类溶剂、砜类溶剂、其他有机溶剂或它们的组合。
在一些实施例中，碳酸酯类溶剂可以包括但不限于链状碳酸酯化合物或环状碳酸酯化合物中的至少一种。上述链状碳酸酯化合物可以包括但不限于碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯或碳酸甲乙酯中的至少一种。上述环状碳酸酯可以包括但不限于碳酸乙烯酯(也称为碳酸亚乙酯)、碳酸亚乙烯酯、碳酸亚丙酯、碳酸亚丁酯(或碳酸乙烯基亚乙酯中的至少一种。
在一些实施例中，羧酸酯类溶剂可以包括但不限于甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯或己内酯中的至少一种。上述醚化合物可以包括但不限于二丁醚、四甘醇二甲醚、二甘醇二甲醚、1，2-二甲氧基乙烷、1，2-二乙氧基乙烷、1-乙氧基-1-甲氧基乙烷、2-甲基四氢呋喃或四氢呋喃中的至少一种。
在一些实施例中，醚类溶剂包括四氢呋喃、乙二醇二甲醚、二乙二醇二甲醚、1.4-二氧六环、1，3-二氧六环中的至少一种。
在一些实施例中，砜类溶剂包括环丁砜、二甲亚砜、甲基环丁砜中的至少一种。
在一些实施例中，其他有机溶剂包括1，3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、磷酸酯中的至少一种。
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，可以根据需要的电化学装置性能进行混合比例的控制。
(电化学装置)
其次说明本申请的电化学装置。
本申请的电化学装置没有特别限制，其可以包括发生电化学反应的任何 装置。在一些实施例中，电化学装置可以包括但不限于：锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
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。
电化学装置的制备过程为本领域技术人员所熟知的，本申请没有特别的限制，例如，可以包括但不限于以下步骤：将正极片、隔离膜和负极片按顺序堆叠，并根据需要将其卷绕、折叠等操作得到卷绕结构的电极组件，将电极组件放入包装袋内，将电解液注入包装袋并封口，得到电化学装置；或者，将正极片、隔离膜和负极片按顺序堆叠，然后用胶带将整个叠片结构的四个角固定好得到叠片结构的电极组件，将电极组件置入包装袋内，将电解液注入包装袋并封口，得到电化学装置。此外，也可以根据需要将防过电流元件、导板等置于包装袋中，从而防止电化学装置内部的压力上升、过充放电。
[正极片]
在一些实施例中，所述正极片包括集流体和设置在集流体上的正极活性物质层。在本申请中，正极集流体没有特别限制，只要能够实现本申请目的即可，例如可以包括但不限于铝箔、铝合金箔或复合集流体等。在本申请中，对正极集流体的厚度没有特别限制，只要能够实现本申请目的即可，例如厚度为8μm至12μm。在本申请中，正极材料层可以设置于沿正极集流体厚度方向的一个表面或两个表面上。需要说明，这里的“表面”可以是正极集流体的全部区域，也可以是正极集流体的部分区域，本申请没有特别限制，只要能实现本申请目的即可。
在一些实施例中，正极活性物质包括可逆地嵌入和脱嵌锂离子的化合物。在一些实施例中，正极活性材料可以包括钴酸锂、锰酸锂、磷酸铁锂、磷酸锰铁锂、镍钴锰酸锂、镍钴铝酸锂或镍锰酸锂中的至少一种，上述正极活性材料可以经过掺杂和/或包覆处理。在一些实施例中，用于包覆层的包覆元素可以包括K、Na、Ca、Mg、B、Al、Co、Si、V、Ga、Sn、Zr或它们的混合物。
在一些实施例中，正极活性材料层还包括粘结剂和导电剂。在一些实 施例中，正极活性材料层中的导电剂可以包括导电炭黑、乙炔黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种。在一些实施例中，正极活性材料层中的粘结剂可以包括聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、苯乙烯-丙烯酸酯共聚物、苯乙烯-丁二烯共聚物、聚酰胺、羧甲基纤维素钠、聚醋酸乙烯酯、聚乙烯呲咯烷酮、聚乙烯醚、聚四氟乙烯、聚六氟丙烯或聚甲基丙烯酸甲酯中的至少一种。任选地，正极还可以包括导电层，导电层位于正极集流体和正极材料层之间。本申请对导电层的组成没有特别限制，可以是本领域常用的导电层。
[负极片]
在一些实施例中，所述负极片包括集流体上的负极活性物质层，本申请对负极集流体没有特别限制，只要能够实现本申请目的即可，例如，可以包括但不限于铜箔、铜合金箔、铝箔、不锈钢箔、钛箔、泡沫镍、泡沫铜或复合集流体等。在本申请中，对负极集流体的厚度没有特别限制，只要能够实现本申请目的即可，例如厚度为4μm至12μm。在本申请中，负极材料层可以设置在沿负极集流体厚度方向的一个表面或两个表面上。需要说明，这里的“表面”可以是负极集流体的全部区域，也可以是负极集流体的部分区域，本申请没有特别限制，只要能实现本申请目的即可。
所述负极活性物质层包括负极活性物质，负极活性物质包括可逆地嵌入/脱嵌锂离子的材料。在一些实施例中，可逆地嵌入/脱嵌锂离子的材料包括但不限于天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12或Li-Al合金中的至少一种。
在一些实施例中，负极活性材料层中还可以包括导电剂和/或粘结剂。负极活性材料层中的导电剂可以包括炭黑、乙炔黑、科琴黑、片层石墨、石墨烯、碳纳米管、碳纤维或碳纳米线中的至少一种。在一些实施例中，负极活性材料层中的粘结剂可以包括羧甲基纤维素(CMC)、聚丙烯酸、聚丙烯酸盐、聚丙烯酸酯、聚乙烯基吡咯烷酮、聚苯胺、聚酰亚胺、聚酰 胺酰亚胺、聚硅氧烷、丁苯橡胶、环氧树脂、聚酯树脂、聚氨酯树脂或聚芴中的至少一种。任选地，负极极片还可以包括导电层，导电层位于负极集流体和负极材料层之间。本申请对导电层的组成没有特别限制，可以是本领域常用的导电层，导电层可以包括但不限于上述导电剂和上述粘结剂。
负极可以通过本领域公知的制备方法制备。例如，负极可以通过如下方法获得：在溶剂中将活性材料、导电材料和粘合剂混合，以制备活性材料组合物，并将该活性材料组合物涂覆在集流体上。
[隔离膜]
在一些实施例中，本申请的电化学装置在正极与负极之间设有隔离膜以防短路。
在一些实施例中，所述隔离膜包括基材层和表面处理层。所述基材层的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。在一些实施例中，所述聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。本申请的隔离膜可以具有多孔结构，孔径的尺寸没有特别限制，只要能实现本申请的目的即可，例如，孔径的尺寸可以为0.01μm至1μm。在本申请中，隔离膜的厚度没有特别限制，只要能实现本申请的目的即可，例如厚度可以为5μm至500μm。
在一些实施例中，隔离膜表面还可以设置有表面处理层。所述表面处理层设置在隔离膜的基材的至少一个表面上，表面处理层包括无机物层或聚合物层中的至少一种。在一些实施例中，无机物层包括无机颗粒和粘结剂，无机颗粒选自氧化铝(Al 2O 3)、氧化硅(SiO 2)、氧化镁(MgO)、氧化钛(TiO 2)、二氧化铪(HfO 2)、氧化锡(SnO 2)、二氧化铈(CeO 2)、氧化镍(NiO)、氧化锌(ZnO)、氧化钙(CaO)、氧化锆(ZrO 2)、氧化钇(Y 2O 3)、碳化硅(SiC)、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。
在一些实施例中，所述粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧 甲基纤维素钠、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。
所述隔离膜表面的多孔层可以提升隔离膜的耐热性能、抗氧化性能和电解质浸润性能，增强隔离膜与极片之间的粘接性。在一些实施例中，聚合物层中的聚合物材料选自聚丙烯腈、聚丙烯酸盐、聚酰胺、聚偏氟乙烯、聚乙烯吡咯烷酮中的至少一种。
[壳体]
壳体用于封装电极组件。在一些实施例中，壳体可以是硬壳，例如硬塑料壳、铝壳、钢壳等；也可以是软包，例如袋式软包，软包的材质可以是塑料，例如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)中的至少一种。
在一些实施例中，正极片、负极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件，将电极组件置于壳体内，注入所述电解液，经过真空封装、静置、化成、整形、分容等工序后可以得到电化学装置。
[电子装置]
本申请还提供一种电子装置，其包括前述任一实施例中的电化学装置。本申请提供的电化学装置具有良好的循环性能和高温存储性能，从而本申请提供的电子装置具有较长的使用寿命。
本申请的电子装置是任何电子装置，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例举的电子装置外，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。
[测试]
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。
在下述实施例、对比例中，所使用到的试剂、材料以及仪器如没有特殊的说明，均可商购获得或合成获得。
实施例1-49和对比例1中的锂离子电池均按照下述方法制备：
(1)电解液的制备
在含水量＜10ppm的氩气气氛手套箱中，将碳酸乙烯酯、碳酸二乙酯、碳酸丙烯酯、按照2∶7∶1的质量比混合均匀，再将充分干燥的锂盐LiPF 6溶解于上述溶剂获得电解液，其中，LiPF 6质量百分含量12.5wt％。向上述制备的电解液中加入一定质量的式I所示化合物、FEC、式II化合物或二氟磷酸锂。
(2)正极片的制备：
将正极活性物质钴酸锂(LiCoO 2)、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量96∶2∶2的比例溶于适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌，使其形成均匀的正极浆料。将正极浆料均匀涂覆于正极集流体铝箔上，将铝箔在85℃下烘干，然后通过辊压机压实、裁片、分切后，在85℃真空条件下干燥4小时得到正极。
(3)负极片的制备：
将负极活性材料石墨、粘结剂丁苯橡胶(SBR)、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC)按重量比95∶2∶2∶1的比例溶于去离子水中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料均匀涂覆在负极集流体铜箔上，铜箔在85℃下烘干，然后进行冷压、裁片、分切后；在120℃真空条件下干燥12小时，得到负极。
(4)隔离膜的制备：
7μm厚的PE多孔聚合物薄膜。
(5)锂离子电池的制备：
将正极、隔离膜、负极按顺序依次叠好，使隔离膜处于正极和负极中间起到隔离的作用，并卷绕得到裸电芯，焊接极耳后，将裸电芯用铝塑膜包装，在80℃下使水含量在一定值以下，注入上述制备的电解液，真空封装后，静置、化成、整形后得到软包锂离子电池(厚度3.3mm、宽度39mm、长96mm)，完成锂离子电池的制备。
接下来说明锂离子电池的性能测试过程以及测试结果。
(1)25℃循环测试
将锂离子电池之于25℃恒温箱中，静置至锂离子电池达到恒温；0.5C恒流充电至4.55V，恒压充电至电流为0.025C；1C放电至3.0V，以此步容量为初始容量C 0；重复上述步骤至循环100圈，记录100圈循环的容量为C 1。根据下式计算锂离子电池25℃循环100圈容量保持率：
容量保持率＝C 1/C 0×100％
(2)60℃高温存储测试
将锂离子电池在25℃下以0.5C放电至3.0V，再以0.2C恒流充电至4.55V，4.55V下恒压充电至电流为0.025C，用千分尺测试并记录锂离子电池的厚度记为H 1；在60℃满充存储4天，之后，用千分尺测试并记录锂离子电池的厚度，记为H 2。
根据下式计算锂离子电池60℃存储厚度膨胀率＝(H 2-H 1)/H 1×100％。
按照上述方法制备实施例和对比例的电解液以及锂离子电池，并进行测试。
表1对比例1及实施例1-20的参数
Figure PCTCN2022083644-appb-000011
Figure PCTCN2022083644-appb-000012
通过实施例1-9和对比例1可以看出，在锂离子电池的电解液中添加特定含量的式I所示化合物，可以在显著改善常温循环的同时改善电池的高温存储性能。其原因为式I所示化合物在正极优先氧化形成致密的CEI膜，防止正极表面结构的损坏，提高正极的稳定性，减少电解液在正极界面副反应，降低产气，从而改善电池的循环和高温存储性能。
通过实施例1-9和实施例10-20可以看出，在含有式I所示化合物的电解液中进一步加入氟代碳酸乙烯酯(FEC)，电池的循环性能得到进一步改善，这是因为FEC在负极还原形成SEI膜，并且在循环过程中不断修复负极表面，抑制循环过程中溶剂和其他成膜添加剂的消耗，式I所示化合物形成的CEI膜可抑制FEC对正极的刻蚀，通过协同作用改善锂离子电池的常温循环性能。
表2实施例2，实施例12及实施例21-33的参数
Figure PCTCN2022083644-appb-000013
Figure PCTCN2022083644-appb-000014
通过表2的实施例可以看出，在含有式I所示化合物的电解液或加氟代碳酸乙烯酯(FEC)的电解液中进一步加入式II所示化合物，由于所含有氰基的分子吸附在阴极表面时可以有效阻隔溶剂分子与正极表面接触，大大降低了充电态的锂离子电池正极表面对电解液的氧化，从而改善常温循环性能，同时提升高温存储性能。
表3实施例2，实施例12及实施例34-49的参数
Figure PCTCN2022083644-appb-000015
Figure PCTCN2022083644-appb-000016
通过表3的实施例可以看出，在含有式I所示化合物的电解液或加氟代碳酸乙烯酯(FEC)的电解液或加含有式II所示化合物的电解液中进一步加入二氟磷酸锂，由于二氟磷酸锂对所形成的固体电解质膜做进一步的修饰，增加了负极石墨SEI膜的离子导电性和稳定性，抑制电极与电解液之间的副反应，进一步改善电池的循环性能，提升高温存储性能。
以上实施例数据表明，在电解液中加入式I所示化合物或是式I所示化合物与其他一种或多种添加剂的组合可显著改善锂离子电池的循环性能和高温存储性能。
上述公开特征并非用来限制本公开的实施范围，因此，以本公开权利要求所述内容所做的等效变化，均应包括在本公开的权利要求范围之内。

Claims (10)

  1. 一种电解液，其中，包括式I所示化合物，
    Figure PCTCN2022083644-appb-100001
    其中，X选自Li +、Na +、K +或Rb +。
  2. 根据权利要求1所述的电解液，其中，
    基于所述电解液的质量，所述式I所示化合物的质量百分含量为0.005％-1.5％。
  3. 根据权利要求1所述的电解液，其中，
    基于所述电解液的质量，所述式I所示化合物的质量百分含量为0.01％-1％。
  4. 根据权利要求1所述的电解液，其中，
    所述电解液还包括氟代碳酸乙烯酯；
    基于所述电解液的质量，所述氟代碳酸乙烯酯的质量百分含量为1％-10％。
  5. 根据权利要求1所述的电解液，其中，所述式I所示化合物包括如下化合物中的至少一种：
    Figure PCTCN2022083644-appb-100002
  6. 根据权利要求1所述的电解液，其中，
    所述电解液还包括腈基化合物，所述腈基化合物包括式II所示化合物：
    Figure PCTCN2022083644-appb-100003
    其中，R 1选自经取代或未经取代的C 1-10的烷基、经取代或未经取代的C 1-10的烯基、经取代或未经取代的C 1-10的炔基、经取代或未经取代的C 1-10的烷氧基、经取代或未经取代的C 1-10的杂环基中的一种，其中，经取代时，取代基为卤素；
    R 2、R 3、R 4分别独立地选自氢原子或氰基；
    基于所述电解液的质量，所述式II所示的化合物的质量百分含量为0.1％～5％。
  7. 根据权利要求6所述的电解液，其中，
    所述腈基化合物包括如下化合物中的至少一种：
    Figure PCTCN2022083644-appb-100004
  8. 根据权利要求1所述的电解液，其中，
    所述电解液还包括二氟磷酸锂；
    基于所述电解液的质量，所述二氟磷酸锂的质量百分含量为0.005％～1％。
  9. 一种电化学装置，包括正极片、负极片、隔离膜以及权利要求1-8中任一项所述的电解液。
  10. 一种电子装置，包括权利要求9所述的电化学装置。
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