WO2021243701A1 - 电化学装置和电子装置 - Google Patents

电化学装置和电子装置 Download PDF

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WO2021243701A1
WO2021243701A1 PCT/CN2020/094652 CN2020094652W WO2021243701A1 WO 2021243701 A1 WO2021243701 A1 WO 2021243701A1 CN 2020094652 W CN2020094652 W CN 2020094652W WO 2021243701 A1 WO2021243701 A1 WO 2021243701A1
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active material
material layer
positive electrode
lithium
electrochemical device
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PCT/CN2020/094652
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English (en)
French (fr)
Inventor
王可飞
师亮
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宁德新能源科技有限公司
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Application filed by 宁德新能源科技有限公司 filed Critical 宁德新能源科技有限公司
Priority to CN202080049701.8A priority Critical patent/CN114072950A/zh
Priority to JP2022516733A priority patent/JP7368607B2/ja
Priority to KR1020227009413A priority patent/KR20220044604A/ko
Priority to PCT/CN2020/094652 priority patent/WO2021243701A1/zh
Priority to EP20939107.7A priority patent/EP4148851A4/en
Publication of WO2021243701A1 publication Critical patent/WO2021243701A1/zh
Priority to US18/074,973 priority patent/US20230106176A1/en

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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/46—Metal oxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/50—Electrodes characterised by their material specially adapted for lithium-ion capacitors, e.g. for lithium-doping or for intercalation
    • 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
    • H01M10/0567—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
    • H01M10/056—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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/38—Carbon pastes or blends; Binders or additives therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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

  • This application relates to the field of energy storage, in particular to an electrochemical device and an electronic device, especially a lithium ion battery.
  • Lithium-ion batteries will have a decrease in charge/discharge capacity during cycling, thereby reducing the performance of lithium-ion batteries.
  • the performance of lithium-ion batteries mainly depends on the characteristics of the electrode, electrolyte and separator.
  • the performance of the electrode not only depends on the characteristics of the current collector and the active material layer, but also closely related to the additives in the active material layer.
  • the auxiliary agent contributes to the dispersion of particles in the active material layer or the bonding of the interface.
  • problems such as difficulty in compounding caused by poor matching of raw materials are usually encountered, which will adversely affect the performance of lithium-ion batteries.
  • the embodiments of the present application provide an electrochemical device and an electronic device to at least to some extent solve at least one problem existing in the related field.
  • the present application provides an electrochemical device, which includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a positive electrode active material layer, wherein the positive electrode active material layer is determined by a contact angle measurement method.
  • the contact angle of the relative non-aqueous solvent is not more than 45°.
  • the contact angle measurement method refers to the test that 3 microliters of diethyl carbonate droplets are dropped on the surface of the positive electrode active material layer, and the droplets are tested on the positive electrode within 100 seconds. The contact angle of the surface of the active material layer.
  • the positive active material layer includes an auxiliary agent having a hydrophilic group and a lipophilic group.
  • the adjuvant has at least one of the following characteristics:
  • the oxidation potential is not less than 4.5V, and the reduction potential is not more than 0.5V;
  • the content of the auxiliary agent is not more than 3000 ppm.
  • the auxiliary agent includes 2-dodecyl acrylate, polyethylene glycol monomethyl ether acrylate, polyethylene glycol dimethacrylate, (2-ethylhexyl) acrylate , Acrylate non-ionic fluorocarbon surfactant, dodecyl methacrylate, dodecyl methacrylate, acrylic acid (ester) copolymer, maleic acid acrylic acid copolymer or ethylene acrylic acid copolymer At least one.
  • the electrolyte contains a compound of formula 1:
  • R is a substituted or unsubstituted C 1 -C 10 hydrocarbon group, and when substituted, the substituent is halogen
  • the content of the compound of Formula 1 is 0.001 wt% to 2 wt%.
  • the compound of Formula 1 includes at least one of the following structural formulas:
  • the content X mg of the compound of formula 1 in the electrolyte and the reaction area Y m 2 of the positive electrode active material layer satisfy the following relationship: 10 ⁇ X/Y ⁇ 100.
  • the positive active material layer includes a positive active material, and the positive active material includes lithium-containing transition metal oxides having different median particle diameters.
  • the lithium-containing transition metal oxide includes a compound represented by general formula (1),
  • M1 is selected from at least one of Co, Ni or Mn;
  • M2 is selected from at least one of Mg, Ti, Zr, Ge, Nb, Al and Sn;
  • M3 is an element other than Li, M1 and M2;
  • the lithium-containing transition metal oxide includes Mg and at least one metal element selected from Ti, Zr, Ge, Nb, Al, and Sn.
  • the present application provides an electronic device including the electrochemical device according to the present application.
  • a list of items connected by the term "at least one of” can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (exclude B); B and C (exclude A); or all of A, B, and C.
  • Project A can contain a single element or multiple elements. Project B can contain a single element or multiple elements. Project C can contain a single element or multiple elements.
  • the term "at least one of" has the same meaning as the term "at least one of”.
  • the electrode (positive or negative electrode) of an electrochemical device (for example, a lithium ion battery) is usually prepared by the following method: mixing the active material, conductive agent, thickener, binder, and solvent, and then coating the mixed slurry On the current collector.
  • the matching between the solvent and the binder or the solvent and the active material is usually poor, making compounding difficult.
  • the theoretical capacity of the electrochemical device may vary with the type of active material.
  • electrochemical devices As the cycle progresses, electrochemical devices usually experience a decrease in charge/discharge capacity. This is because the electrode interface changes during the charging and/or discharging of the electrochemical device.
  • the interface includes the interface between the electrode and the electrolyte, the interface between the current collector and the electrode, the interface between the electrode active material and the additive, and the like. Decreased interface stability will cause the electrode active material to fail to perform its function.
  • This application uses a specific positive electrode material to ensure the interface stability of the electrochemical device during the cycle, thereby improving the cycle performance, rate performance, and DC impedance of the electrochemical device.
  • the specific positive electrode material of this application is realized by controlling the contact angle of the surface of the positive electrode active material layer. As a method of controlling the contact angle, it can be achieved by adding an auxiliary agent to the positive electrode slurry or setting an auxiliary agent coating on the surface of the positive electrode active material layer. control.
  • the present application provides an electrochemical device, which includes a positive electrode, a negative electrode, and an electrolyte as described below.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on one or both surfaces of the positive electrode current collector.
  • the positive electrode active material layer contains a positive electrode active material.
  • the positive electrode active material layer may be one layer or multiple layers, and each layer of the multilayer positive electrode active material may contain the same or different positive electrode active materials.
  • the contact angle of the positive electrode active material layer with respect to the non-aqueous solvent is not greater than 45° as measured by the contact angle measurement method. In some embodiments, the contact angle of the positive active material layer with respect to the non-aqueous solvent is not greater than 40° as determined by the contact angle measurement method. In some embodiments, the contact angle of the positive active material layer with respect to the non-aqueous solvent is not greater than 35° as determined by the contact angle measurement method.
  • the positive electrode active material layer interface has a suitable surface tension, is well infiltrated into the electrolyte, and has good stability during the charge and discharge cycles of the electrochemical device, which can be significant Improve the cycle performance, rate performance and DC impedance of electrochemical devices.
  • the contact angle of the positive electrode active material layer relative to the non-aqueous solvent can reflect the surface properties of the positive electrode active material layer, which is one of the physical and chemical parameters that characterize the positive electrode active material layer.
  • the smaller the contact angle the smaller the surface tension of the positive electrode active material layer, which can significantly improve the cycle performance, rate performance and DC internal resistance of the electrochemical device.
  • the contact angle of the positive active material layer relative to the non-aqueous solvent can be affected by many factors, including additives.
  • the contact angle measurement method means that after 3 microliters of diethyl carbonate droplets are dropped on the surface of the positive electrode active material layer, the activity of the droplets on the positive electrode is tested within 100 seconds. The contact angle of the surface of the material layer.
  • the contact angle of the positive active material layer relative to the non-aqueous solvent and the diameter of the non-aqueous solvent droplet can be measured by the following method: drop 3 microliters of diethyl carbonate on the surface of the positive active material layer, and use the JC2000D3E contact angle within 100 seconds
  • the measuring instrument measures the diameter of the droplet, and uses the 5-point fitting method (that is, first take 2 points on the left and right planes of the droplet, determine the liquid-solid interface, and then take 3 points on the droplet arc) for fitting to obtain the positive active material
  • the contact angle of the layer with respect to the non-aqueous solvent Each sample is measured at least 3 times, at least 3 data with a difference of less than 5° are selected, and the average value is taken to obtain the contact angle of the positive electrode active material layer with respect to the non-aqueous solvent.
  • the non-aqueous solvent used in the contact angle test can be commonly used electrolyte solvents such as diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl propyl carbonate, or methyl isopropyl carbonate.
  • the positive active material layer includes an auxiliary agent.
  • the auxiliary agent has a hydrophilic group and a lipophilic group.
  • the oxidation potential of the additive is not less than 4.5V, and the reduction potential is not greater than 0.5V. In some embodiments, the oxidation potential of the additive is not less than 5V, and the reduction potential is not greater than 0.3V.
  • the electrochemical performance of the auxiliary agent with the above oxidation/reduction potential is stable, which helps to improve the cycle performance, rate performance and DC impedance of the electrochemical device.
  • the surface tension of the additives can be determined by the following method: use the JC2000D3E contact angle measuring instrument to test the NMP solution of the additives with a solid content of 1%, test each sample at least 3 times, select at least 3 data, and take the average value. Get the surface tension of the additive.
  • the adjuvant includes an unsaturated carboxylic acid group.
  • the unsaturated carboxylic acid group includes vinyl ester, vinyl chloride, acrylate, vinyl ether acrylate, crotonate, propiolate, butynoate or contains propylene At least one of amide, acrylonitrile, and vinyl ether group-modified carboxylic acid ester.
  • the adjuvant includes at least one of the following: 2-dodecyl acrylate, polyethylene glycol monomethyl ether acrylate, polyethylene glycol dimethacrylate, acrylic acid (2 -Ethylhexyl) ester, acrylate non-ionic fluorocarbon surfactant, dodecyl methacrylate, dodecyl methacrylate, acrylic acid (ester) copolymer, maleic acid acrylic copolymer or Ethylene acrylic acid copolymer.
  • the content of the auxiliary agent is not more than 3000 ppm. In some embodiments, based on the total weight of the positive active material layer, the content of the auxiliary agent is not more than 2500 ppm. In some embodiments, based on the total weight of the positive active material layer, the content of the auxiliary agent is not more than 2000 ppm. In some embodiments, based on the total weight of the positive active material layer, the content of the auxiliary agent is not more than 1500 ppm. In some embodiments, based on the total weight of the positive active material layer, the content of the auxiliary agent is not more than 1000 ppm.
  • the content of the auxiliary agent is not more than 500 ppm. In some embodiments, based on the total weight of the positive active material layer, the content of the auxiliary agent is not more than 200 ppm. When the content of the auxiliary agent is within the above range, it helps to improve the cycle performance, rate performance and DC resistance of the electrochemical device.
  • the type of the positive electrode active material is not particularly limited, as long as it can electrochemically store and release metal ions (for example, lithium ions).
  • the positive active material is a material containing lithium and at least one transition metal.
  • the positive electrode active material may include, but are not limited to, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.
  • the lithium-containing transition metal oxide includes a compound represented by general formula (1),
  • M1 is selected from at least one of Co, Ni or Mn;
  • M2 is selected from at least one of Mg, Ti, Zr, Ge, Nb, Al and Sn;
  • M3 is an element other than Li, M1 and M2;
  • M1 includes at least one of Co or Ni.
  • the content of at least one of Co or Ni in the lithium-containing transition metal oxide is not less than 50 mol%; in some embodiments, it is not less than 60 mol% ; In some embodiments, not less than 70 mol%; in some embodiments, not less than 80 mol%; or in some embodiments, not less than 90 mol%.
  • M1 includes Co. In some embodiments, M1 is Co.
  • M1 includes Co
  • the content of Co in the lithium-containing transition metal oxide is not less than 30 mol%; in some embodiments, not less than 50 mol%; in some embodiments, not less than 65 mol%; In some embodiments, it is not less than 80 mol%; in some embodiments, it is not less than 90 mol%; or in some embodiments, it is not less than 95 mol%.
  • the lithium-containing transition metal oxide contains Co, it helps to increase the density of the positive electrode active material layer.
  • the content of Co in the lithium-containing transition metal oxide is within the above range, the density of the positive electrode active material layer can be further improved.
  • M2 includes Mg.
  • the content of Mg is not less than 0.01 mol%. In some embodiments, relative to the content of M1, the content of Mg is not less than 0.05 mol%. In some embodiments, relative to the content of M1, the content of Mg is not less than 0.07 mol%. In some embodiments, relative to the content of M1, the content of Mg is not more than 0.5 mol%. In some embodiments, relative to the content of M1, the content of Mg is not more than 0.2 mol%. In some embodiments, relative to the content of M1, the content of Mg is not more than 0.1 mol%.
  • M2 further includes at least one of Ti, Zr, Ge, Nb, Al, and Sn.
  • M2 further includes at least one of Ti, Zr, Ge, or Nb.
  • the content of at least one of Ti, Zr, Ge, or Nb is not less than 0.005 mol%. In some embodiments, relative to the content of M1, the content of at least one of Ti, Zr, Ge, or Nb is not less than 0.008 mol%. In some embodiments, relative to the content of M1, the content of at least one of Ti, Zr, Ge, or Nb is not less than 0.01 mol%. In some embodiments, relative to the content of M1, the content of at least one of Ti, Zr, Ge, or Nb is not more than 0.3 mol%.
  • the content of at least one of Ti, Zr, Ge, or Nb is not more than 0.1 mol%. In some embodiments, relative to the content of M1, the content of at least one of Ti, Zr, Ge, or Nb is not more than 0.05 mol%. In some embodiments, relative to the content of M1, the content of at least one of Ti, Zr, Ge, or Nb is within a range composed of any two endpoints described above. When the content of at least one of Ti, Zr, Ge, or Nb in the lithium-containing transition metal oxide is within the above range, it helps to further improve the cycle performance, rate performance, and DC resistance of the electrochemical device.
  • M2 further includes at least one of Al or Sn.
  • the content of at least one of Al or Sn is not less than 0.01 mol% relative to the content of M1.
  • the content of at least one of Al or Sn is not less than 0.05 mol%.
  • the content of at least one of Al or Sn is not less than 0.07 mol%.
  • the content of at least one of Al or Sn is not more than 0.5 mol%.
  • relative to the content of M1, the content of at least one of Al or Sn is not more than 0.2 mol%.
  • the content of at least one of Al or Sn is not more than 0.1 mol%. In some embodiments, relative to the content of M1, the content of at least one of Al or Sn is within a range composed of any two endpoints described above. When the content of at least one of Al or Sn in the lithium-containing transition metal oxide is within the above range, it helps to further improve the cycle performance, rate performance, and DC resistance of the electrochemical device.
  • c is within the above range, the cycle performance, rate performance, and DC resistance of the lithium ion battery can be further improved.
  • the lithium-containing transition metal oxide may contain M2 in various ways, and it is not particularly limited.
  • M2 is present on lithium-containing transition metal oxide particles.
  • M2 is uniformly solid dispersed in the lithium-containing transition metal oxide.
  • the M2 lithium-containing transition metal oxide has a concentration distribution within the segregation.
  • M2 forms a compound layer on the surface of the lithium-containing transition metal oxide.
  • M3 includes at least one of the following elements: Na, K, Rb, Be, Ca, Sr, Ba, Sc, Y, La, Hf, V, Ta, Cr, Mo, W, Tc, Re, Fe, Ru, Rh, Cu, Ag, Au, Zn, B, Ca, In, Si, P, or Bi.
  • the lithium-containing transition metal oxide includes LiNi 0.81 Co 0.16 Al 0.03 O 2 , LiNi 0.81 Co 0.16 Mg 0.03 O 2 , LiNi 0.81 Co 0.16 Si 0.03 O 2 , LiNi 0.81 Co 0.16 Ti 0.03 O 2 , LiCo 0.96 Ti 0.04 O 2 , LiCo 0.998 Mg 0.0008 Ti 0.0004 Al 0.0008 O 2 , LiCo 0.994 Mg 0.0024 Ti 0.0012 Al 0.0024 O 2 , LiCo 0.9988 Mg 0.0008 Ti 0.0004 O 2 , LiCo 0.9964 Mg 0.0024 Ti 0.0012 O 2 or LiCo 0.334 At least one of Ni 0.33 Mn 0.33 Mg 0.0024 Ti 0.0012 Al 0.0024 O 2.
  • the content of each element in the lithium-containing transition metal oxide can be obtained by inductively coupled plasma (ICP) analysis.
  • the lithium content in the lithium-containing transition metal oxide can also be measured by other methods (for example, atomic absorption method) and the like. Specifically, approximately 5g of lithium-containing transition metal oxides are accurately weighed, added to a 200ml beaker, and then 100ml of aqua regia is added, heated and concentrated to a liquid volume of 20-25ml, cooled, and quantitative filter paper "No.5B made by Advantec" is used.
  • the content of the lithium-containing transition metal oxide is not more than 99 wt%. In some embodiments, based on the total weight of the positive active material layer, the content of the lithium-containing transition metal oxide is not more than 97.5% by weight. In some embodiments, based on the total weight of the positive active material layer, the content of the lithium-containing transition metal oxide is not more than 97 wt%. In some embodiments, based on the total weight of the positive active material layer, the content of the lithium-containing transition metal oxide is not more than 98 wt%.
  • the content of the lithium-containing transition metal oxide is not more than 95 wt%. In some embodiments, based on the total weight of the positive active material layer, the content of the lithium-containing transition metal oxide is not less than 85% by weight. In some embodiments, based on the total weight of the positive active material layer, the content of the lithium-containing transition metal oxide is not more than 90 wt%. In some embodiments, based on the total weight of the positive active material layer, the content of the lithium-containing transition metal oxide is not more than 92 wt%.
  • the lithium-containing transition metal oxide includes first particles and second particles, the first particles have a first median diameter, and the second particles have a second median diameter.
  • the first median particle size is smaller than the second median particle size.
  • the first median particle size is 0.5 ⁇ m to 10 ⁇ m. In some embodiments, the first median particle size is 1 ⁇ m to 8 ⁇ m. In some embodiments, the first median particle size is 2 ⁇ m to 6 ⁇ m. In some embodiments, the second median particle size is 11 ⁇ m to 30 ⁇ m. In some embodiments, the second median particle size is 12 ⁇ m to 25 ⁇ m. In some embodiments, the second median particle size is 13 ⁇ m to 20 ⁇ m.
  • the discharge capacity of the positive active material is less than the chargeable capacity of the negative active material to prevent lithium metal from unintentionally precipitating on the negative electrode during charging.
  • the median diameter of the lithium-containing transition metal oxide can be adjusted by the following method: NaOH is added dropwise to the acidic aqueous solution of the transition metal element M1, and the hydroxide of M1 is obtained by precipitation. The hydroxide of M1 is fired to obtain the oxide of M1.
  • the median diameter of the lithium-containing transition metal oxide can be controlled by controlling the precipitation time, the precipitation particle size, and the particle size of the fired M1 oxide.
  • the discharge capacity of the positive active material is less than the chargeable capacity of the negative active material to prevent lithium metal from unintentionally precipitating on the negative electrode during charging.
  • the density of the positive active material layer is not less than 3.5 g/cm 3 . In some embodiments, the density of the positive active material layer is not less than 3.6 g/cm 3 . In some embodiments, the density of the positive active material layer is not less than 3.8 g/cm 3 . In some embodiments, the density of the positive active material layer is not greater than 4.6 g/cm 3 . In some embodiments, the density of the positive active material layer is not greater than 4.4 g/cm 3 . In some embodiments, the density of the positive active material layer is not more than 4.2 g/cm 3 . In some embodiments, the density of the positive active material layer is within a range composed of any two endpoints described above. When the density of the positive electrode active material layer is within the above range, the positive electrode active material layer has good wettability, which helps to improve the performance of the electrochemical device.
  • the density of the positive electrode active material layer can be measured by the following method: cut the positive electrode in a certain area, measure its weight W1 with an electronic balance with a minimum scale of 1 mg, and measure the thickness T1 of the positive electrode with a micrometer with a minimum scale of 1 ⁇ m.
  • the positive electrode current collector is peeled off, its weight W2 is measured using an electronic balance, and the thickness T2 of the positive electrode current collector is measured with a micrometer.
  • W1-W2 is recorded as the weight of the positive electrode active material layer
  • T1-T2 is recorded as the thickness of the positive electrode active material layer.
  • the volume of the positive active material layer is calculated based on the thickness and area of the positive active material layer, and then the density of the positive active material layer is calculated based on the weight and volume of the positive active material layer.
  • the thickness of the positive electrode active material layer is the thickness of the positive electrode active material layer
  • the thickness of the positive active material layer is 30 ⁇ m to 200 ⁇ m. In some embodiments, the thickness of the positive active material layer is 50 ⁇ m to 180 ⁇ m. In some embodiments, the thickness of the positive active material layer is 80 ⁇ m to 150 ⁇ m. In some embodiments, the thickness of the positive active material layer is 100 ⁇ m to 120 ⁇ m. In some embodiments, the thickness of the positive active material layer is 30 ⁇ m, 50 ⁇ m, 80 ⁇ m, 100 ⁇ m, 120 ⁇ m, 150 ⁇ m, 180 ⁇ m, 200 ⁇ m, or within a range composed of any two of the foregoing values.
  • the thickness of the positive electrode active material layer can be measured by the following method: cut out the positive electrode, and measure the thickness T1 of the positive electrode using a micrometer with a minimum graduation of 1 ⁇ m.
  • the positive electrode current collector is peeled off, and the thickness T2 of the positive electrode current collector is measured with a micrometer. T1-T2 is recorded as the thickness of the positive electrode active material layer.
  • the positive active material layer may further include a conductive layer including a conductive agent.
  • the conductive layer does not contain a positive active material. Examples of conductive agents include, but are not limited to, graphite, carbon black, or acetylene black.
  • the content of the conductive agent is not less than 1 wt% based on the total weight of the positive active material layer. In some embodiments, the content of the conductive agent is not less than 1.1 wt% based on the total weight of the positive active material layer. In some embodiments, the content of the conductive agent is not less than 1.2 wt% based on the total weight of the positive active material layer. In some embodiments, based on the total weight of the positive active material layer, the content of the conductive agent is not more than 3 wt%. In some embodiments, based on the total weight of the positive active material layer, the content of the conductive agent is not more than 2 wt%.
  • the content of the conductive agent is not more than 1.5 wt%. In some embodiments, based on the total weight of the positive active material layer, the content of the conductive agent is within a range composed of any two of the foregoing values. When the content of the conductive agent in the positive electrode active material layer is within the above range, it helps to improve the density and capacity of the positive electrode active material layer, thereby improving the cycle performance of the electrochemical device and reducing its load characteristics.
  • the positive active material layer includes a binder.
  • the binder include, but are not limited to, polyvinylidene fluoride or polytetrafluoroethylene.
  • the content of the binder is not less than 1 wt%. In some embodiments, the content of the binder is not less than 1.3 wt% based on the total weight of the positive active material layer. In some embodiments, the content of the binder is not less than 1.5 wt% based on the total weight of the positive active material layer. In some embodiments, based on the total weight of the positive active material layer, the content of the binder is not more than 4 wt%. In some embodiments, based on the total weight of the positive active material layer, the content of the binder is not more than 3 wt%.
  • the content of the binder is not more than 2 wt%. In some embodiments, based on the total weight of the positive active material layer, the content of the binder is within a range composed of any two of the foregoing values. When the content of the binder in the positive electrode active material layer is within the above range, the positive electrode active material layer and the positive electrode current collector have good adhesion, avoiding the possibility of pulverization and falling off of the positive electrode, thereby helping to improve the performance of the positive electrode. stability.
  • the type of the positive electrode current collector is not particularly limited, and it can be any material known to be suitable for use as a positive electrode current collector.
  • Examples of the positive electrode current collector may include, but are not limited to, at least one of aluminum, aluminum alloy, nickel-plated aluminum, stainless steel, titanium, or tantalum; carbon materials such as carbon cloth and carbon paper.
  • the positive electrode current collector is a metal material.
  • the positive current collector is aluminum.
  • the form of the positive electrode current collector is not particularly limited.
  • the form of the positive electrode current collector may include, but is not limited to, metal foil, metal cylinder, metal coil, metal plate, metal film, metal plate mesh, stamped metal, foamed metal, and the like.
  • the positive electrode current collector is a carbon material
  • the form of the positive electrode current collector may include, but is not limited to, a carbon plate, a carbon film, a carbon cylinder, and the like.
  • the positive electrode current collector is a metal thin film.
  • the metal film is mesh-shaped.
  • the thickness of the positive electrode current collector is 8 ⁇ m to 20 ⁇ m. In some embodiments, the thickness of the positive electrode current collector is 10 ⁇ m to 18 ⁇ m. In some embodiments, the thickness of the positive electrode current collector is 12 ⁇ m to 15 ⁇ m. In some embodiments, the thickness of the positive electrode current collector is within a range composed of any two values mentioned above.
  • the surface of the positive electrode current collector may include a conductive agent.
  • the conductive agent may include, but are not limited to, carbon and noble metals such as gold, platinum, and silver.
  • the preparation method of the positive electrode of the present application is not limited.
  • the positive electrode can be manufactured by the following method: mixing two or more lithium-containing transition metal oxides with different median particle diameters in a certain weight ratio, adding a conductive agent and a binder, and adding a solvent as needed to obtain a positive electrode mixture slurry .
  • the obtained positive electrode mixture slurry is coated on a positive electrode current collector (for example, aluminum foil) and dried to form a positive electrode active material layer.
  • the positive electrode active material layer is applied to one or both surfaces of the positive electrode current collector, and a rolling step is performed as needed to prepare a positive electrode.
  • the electrolytic solution used in the electrochemical device of the present application includes an electrolyte and a solvent that dissolves the electrolyte.
  • the electrolyte used in the electrochemical device of the present application further includes additives.
  • the electrolyte contains a compound of formula 1:
  • R is a substituted or unsubstituted C 1 -C 10 hydrocarbon group, and when substituted, the substituent is halogen.
  • the compound of Formula 1 includes at least one of the following structural formulas:
  • the content of the compound of Formula 1 is 0.001 wt% to 2 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of Formula 1 is 0.01 wt% to 1 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of Formula 1 is 0.05 wt% to 0.5 wt%. In some embodiments, based on the total weight of the electrolyte, the content of the compound of Formula 1 is 0.1 wt% to 0.3 wt%.
  • the content of the compound of formula 1 is 0.001 wt%, 0.005 wt%, 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.3 wt%, 0.5 wt% , 0.8% by weight, 1% by weight, 1.2% by weight, 1.5% by weight, 1.8% by weight, 2% by weight, or within a range composed of any two of the above values.
  • the content of the compound of Formula 1 in the electrolyte is within the above range, it helps to further improve the cycle performance, rate performance and DC resistance of the lithium ion battery.
  • the content X mg of the compound of formula 1 in the electrolyte and the reaction area Y m 2 of the positive electrode active material layer satisfy the following relationship: 10 ⁇ X/Y ⁇ 100. In some embodiments, X and Y satisfy the following relationship: 20 ⁇ X/Y ⁇ 100. In some embodiments, X and Y satisfy the following relationship: 20 ⁇ X/Y ⁇ 70. When X and Y conform to the above relationship, it helps to further improve the cycle performance, rate performance, and DC impedance of the lithium-ion battery.
  • the reaction area of the positive electrode active material layer can be measured by the following method: using a surface area meter (a fully automatic surface area measuring device manufactured by Okura Riken), pre-drying the sample at 350°C under nitrogen flow for 15 minutes, and then using nitrogen The nitrogen-helium mixed gas whose relative pressure value of the atmospheric pressure is accurately adjusted to 0.3 is measured by the nitrogen adsorption BET single-point method using the gas flow method. According to this method, the specific surface area of the positive electrode active material layer is measured.
  • the specific surface area of the positive electrode active material layer refers to the ratio of the entire positive electrode active material layer containing the positive electrode active material and additives (binder, conductive agent, thickener, filler, etc.) Surface area.
  • the weight of the positive electrode active material layer is measured, that is, the total weight of the entire positive electrode active material layer containing the positive electrode active material and additives (binder, conductive agent, thickener, filler, etc.).
  • the reaction area of the positive electrode active material layer is calculated by the following formula:
  • reaction area the specific surface area of the positive electrode active material layer x the weight of the positive electrode active material layer.
  • the electrolyte further includes any non-aqueous solvent known in the prior art that can be used as a solvent for the electrolyte.
  • the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, cyclic Ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents and aromatic fluorine-containing solvents.
  • examples of the cyclic carbonate may include, but are not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate.
  • the cyclic carbonate has 3-6 carbon atoms.
  • examples of the chain carbonate may include, but are not limited to, one or more of the following: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl carbonate Chain carbonates such as n-propyl carbonate, ethyl n-propyl carbonate, and di-n-propyl carbonate.
  • dimethyl carbonate ethyl methyl carbonate
  • DEC diethyl carbonate
  • Chain carbonates such as n-propyl carbonate, ethyl n-propyl carbonate, and di-n-propyl carbonate.
  • chain carbonates substituted by fluorine may include, but are not limited to, one or more of the following: bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl) Base) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethyl Methyl carbonate, 2,2-difluoroethyl methyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, etc.
  • examples of the cyclic carboxylic acid ester may include, but are not limited to, one or more of the following: one or more of ⁇ -butyrolactone and ⁇ -valerolactone.
  • part of the hydrogen atoms of the cyclic carboxylic acid ester may be substituted by fluorine.
  • examples of the chain carboxylic acid ester may include, but are not limited to, one or more of the following: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate Ester, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, butyrate Propyl ester, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate, etc.
  • part of the hydrogen atoms of the chain carboxylic acid ester may be replaced by fluorine.
  • examples of fluorine-substituted chain carboxylic acid esters may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and trifluoroacetic acid 2,2,2-Trifluoroethyl and so on.
  • examples of the cyclic ether may include, but are not limited to, one or more of the following: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1,3-dioxolane, 4-methyl 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane.
  • examples of the chain ether may include, but are not limited to, one or more of the following: dimethoxymethane, 1,1-dimethoxyethane, 1,2- Dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxy Methoxyethane and 1,2-ethoxymethoxyethane, etc.
  • examples of the phosphorus-containing organic solvent may include, but are not limited to, one or more of the following: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl phosphate Diethyl, Ethylene Methyl Phosphate, Ethylene Ethyl Phosphate, Triphenyl Phosphate, Trimethyl Phosphite, Triethyl Phosphite, Triphenyl Phosphite, Tris(2,2,2- Trifluoroethyl) ester and tris(2,2,3,3,3-pentafluoropropyl) phosphate, etc.
  • examples of the sulfur-containing organic solvent may include, but are not limited to, one or more of the following: sulfolane, 2-methyl sulfolane, 3-methyl sulfolane, dimethyl sulfone, two Ethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate , Diethyl sulfate and Dibutyl sulfate.
  • part of the hydrogen atoms of the sulfur-containing organic solvent may be replaced by fluorine.
  • the aromatic fluorine-containing solvent includes, but is not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene And trifluoromethylbenzene.
  • the solvent used in the electrolyte of the present application includes cyclic carbonate, chain carbonate, cyclic carboxylic acid ester, chain carboxylic acid ester, and combinations thereof.
  • the solvent used in the electrolyte of the present application includes ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, or ethyl acetate. At least one of them.
  • the solvent used in the electrolyte of the present application includes: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, and combinations thereof .
  • the chain carboxylic acid ester and/or cyclic carboxylic acid ester can form a passivation film on the electrode surface, thereby improving the intermittent charging of the electrochemical device Capacity retention rate after cycling.
  • the electrolyte contains 1% to 60% of chain carboxylic acid esters, cyclic carboxylic acid esters, and combinations thereof.
  • the electrolyte contains ethyl propionate, propyl propionate, ⁇ -butyrolactone, and combinations thereof. Based on the total weight of the electrolyte, the content of the combination is 1% to 60%, 10%.
  • the electrolyte contains 1% to 60%, 10% to 60%, 20% to 50%, 20% to 40%, or 30% of propyl propionate. .
  • examples of the additives may include, but are not limited to, one or more of the following: fluorocarbonate, carbon-carbon double bond-containing ethylene carbonate, sulfur-oxygen double bond-containing compound, and acid anhydride .
  • the content of the additive is 0.01% to 15%, 0.1% to 10%, or 1% to 5%.
  • the content of the propionate is 1.5 to 30 times, 1.5 to 20 times, 2 to 20 times, or 5 to 20 times of the additive.
  • the additives include one or more fluorocarbonates.
  • the fluorocarbonate can work together with the propionate to form a stable protective film on the surface of the negative electrode, thereby inhibiting the decomposition reaction of the electrolyte.
  • examples of the fluorocarbonate may include, but are not limited to, one or more of the following: fluoroethylene carbonate, cis-4,4-difluoroethylene carbonate, trans-4 ,4-Difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, trifluoromethyl methyl carbonate , Trifluoroethyl methyl carbonate and ethyl trifluoroethyl carbonate, etc.
  • the additives include one or more ethylene carbonates containing carbon-carbon double bonds.
  • the carbon-carbon double bond-containing ethylene carbonate may include, but are not limited to, one or more of the following: vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, carbonic acid-1 ,2-Dimethylvinylene carbonate, -1,2-diethylvinylene carbonate, fluorovinylene carbonate, trifluoromethyl vinylene carbonate; vinyl ethylene carbonate, 1-methyl carbonate 2-vinyl ethylene, 1-ethyl-2-vinyl ethylene carbonate, 1-n-propyl-2-vinyl ethylene carbonate, 1-methyl-2-ethylene carbonate Ethylene carbonate, 1,1-divinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, 1,1-dimethyl-2-methylene ethylene carbonate, and Carbonic acid-1,1-diethyl-2-methylene ethylene and the like.
  • vinylene carbonate
  • the additives include one or more compounds containing sulfur-oxygen double bonds.
  • the sulfur-oxygen double bond-containing compound may include, but are not limited to, one or more of the following: cyclic sulfate, chain sulfate, chain sulfonate, cyclic sulfonate, chain Sulfite and cyclic sulfite, etc.
  • cyclic sulfate may include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfate, 1,2-propanediol sulfate, 1,3-propanediol sulfate, 1 , 2-butanediol sulfate, 1,3-butanediol sulfate, 1,4-butanediol sulfate, 1,2-pentanediol sulfate, 1,3-pentanediol sulfate, 1 ,4-Pentanediol sulfate and 1,5-Pentanediol sulfate, etc.
  • chain sulfate may include, but are not limited to, one or more of the following: dimethyl sulfate, ethyl methyl sulfate, diethyl sulfate, and the like.
  • chain sulfonate may include, but are not limited to, one or more of the following: fluorosulfonates such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, methanesulfonic acid Ethyl ester, butyl dimethanesulfonate, 2-(methanesulfonyloxy) methyl propionate and 2-(methanesulfonyloxy) ethyl propionate, etc.
  • fluorosulfonates such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, methanesulfonic acid Ethyl ester, butyl dimethanesulfonate, 2-(methanesulfonyloxy) methyl propionate and 2-(methanesulfonyloxy) ethyl propionate, etc.
  • Examples of the cyclic sulfonate may include, but are not limited to, one or more of the following: 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2- Fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone, 2-methyl-1,3- Propylene sultone, 3-methyl-1,3-propane sultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro -1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1- Fluoro-2-propene-1,3-sultone, 2-fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sul
  • chain sulfite may include, but are not limited to, one or more of the following: dimethyl sulfite, ethyl methyl sulfite, diethyl sulfite, and the like.
  • cyclic sulfite may include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfite, 1,2-propylene glycol sulfite, 1,3-propylene glycol sulfite Sulfate, 1,2-butanediol sulfite, 1,3-butanediol sulfite, 1,4-butanediol sulfite, 1,2-pentanediol sulfite, 1,3 -Pentylene glycol sulfite, 1,4-pentanediol sulfite and 1,5-pentanediol sulfite, etc.
  • the additives include one or more acid anhydrides.
  • the acid anhydride may include, but are not limited to, one or more of cyclic phosphoric anhydride, carboxylic anhydride, disulfonic anhydride, and carboxylic sulfonic anhydride.
  • the cyclic phosphoric anhydride may include, but are not limited to, one or more of trimethylphosphoric acid cyclic anhydride, triethylphosphoric acid cyclic anhydride, and tripropylphosphoric acid cyclic anhydride.
  • the carboxylic acid anhydride may include, but are not limited to, one or more of succinic anhydride, glutaric anhydride, and maleic anhydride.
  • Examples of the disulfonic acid anhydride may include, but are not limited to, one or more of ethane disulfonic acid anhydride and propane disulfonic acid anhydride.
  • Examples of the carboxylic acid sulfonic anhydride may include, but are not limited to, one or more of sulfobenzoic anhydride, sulfopropionic anhydride, and sulfobutyric anhydride.
  • the additive is a combination of fluorocarbonate and ethylene carbonate containing carbon-carbon double bonds. In some embodiments, the additive is a combination of a fluorocarbonate and a compound containing a sulfur-oxygen double bond. In some embodiments, the additive is a combination of a fluorocarbonate and a compound having 2-4 cyano groups. In some embodiments, the additive is a combination of fluorocarbonate and cyclic carboxylic acid ester. In some embodiments, the additive is a combination of fluorocarbonate and cyclic phosphoric anhydride. In some embodiments, the additive is a combination of fluorocarbonate and carboxylic anhydride. In some embodiments, the additive is a combination of fluorocarbonate and Huangan anhydride. In some embodiments, the additive is a combination of fluorocarbonate and carboxylic acid anhydride.
  • the electrolyte is not particularly limited, and any known substance as an electrolyte can be used arbitrarily.
  • a lithium salt is generally used.
  • electrolytes may include, but are not limited to, LiPF 6 , LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , LiTaF 6 , LiWF 7 and other inorganic lithium salts; LiWOF 5 and other lithium tungstates; HCO 2 Li, CH 3 CO 2 Li, CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li and other carboxylic acid lithium salts; FSO 3 Li, CH 3 SO 3 Li, CH 2 FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li ,
  • the electrolyte is selected from LiPF 6 , LiSbF 6 , LiTaF 6 , FSO 3 Li, CF 3 SO 3 Li, LiN(FSO 2 ) 2 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic 1,2-perfluoroethane bissulfonimide lithium, cyclic 1,3-perfluoropropane bissulfonimide lithium, LiC(FSO 2 ) 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 ( C 2 F 5 ) 3 , lithium difluorooxalate borate, lithium bis(oxalate) borate or lithium difluorobis(oxalate) phosphate
  • the content of the electrolyte is not particularly limited, as long as the effect of the application is not impaired.
  • the total molar concentration of lithium in the electrolyte is greater than 0.3 mol/L, greater than 0.4 mol/L, or greater than 0.5 mol/L.
  • the total molar concentration of lithium in the electrolyte is less than 3 mol/L, less than 2.5 mol/L, or less than 2.0 mol/L.
  • the total molar concentration of lithium in the electrolyte is within a range composed of any two of the foregoing values. When the electrolyte concentration is within the above range, lithium as the charged particles will not be too small, and the viscosity can be in an appropriate range, so it is easy to ensure good electrical conductivity.
  • the electrolyte includes at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate.
  • the electrolyte includes a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate.
  • the electrolyte includes a lithium salt.
  • the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is greater than 0.01 wt% or greater than 0.1 wt% based on the total weight of the electrolyte.
  • the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is less than 20% by weight or less than 10% by weight based on the total weight of the electrolyte. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is within the range consisting of any two of the foregoing values.
  • the electrolyte includes one or more substances selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate, and one or more other salts.
  • the lithium salts exemplified above can be cited, and in some embodiments are LiPF 6 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN( C 2 F 5 SO 2 ) 2 , cyclic 1,2-perfluoroethane bissulfonimide lithium, cyclic 1,3-perfluoropropane bissulfonimide lithium, LiC(FSO 2 ) 3 , LiC (CF 3 SO 2 ) 3 , LiC (C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3 .
  • the other salts the lithium salts exempl
  • the content of other salts is greater than 0.01 wt% or greater than 0.1 wt%. In some embodiments, based on the total weight of the electrolyte, the content of other salts is less than 20 wt%, less than 15 wt%, or less than 10 wt%. In some embodiments, the content of other salts is within the range composed of any two values mentioned above. Salts other than those having the above content help balance the conductivity and viscosity of the electrolyte.
  • the electrolyte solution may contain additional additives such as a negative electrode film forming agent, a positive electrode protective agent, and an overcharge prevention agent as needed.
  • additives generally used in non-aqueous electrolyte secondary batteries can be used, and examples thereof can include, but are not limited to, vinylene carbonate, succinic anhydride, biphenyl, cyclohexylbenzene, 2,4-difluorobenzyl Ether, propane sultone, propene sultone, etc. These additives can be used alone or in any combination.
  • the content of these additives in the electrolytic solution is not particularly limited, and may be appropriately set according to the type of the additives and the like. In some embodiments, based on the total weight of the electrolyte, the content of the additive is less than 5 wt%, in the range of 0.01 wt% to 5 wt%, or in the range of 0.2 wt% to 5 wt%.
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector.
  • the negative electrode active material layer includes a negative electrode active material layer, and the negative electrode active material layer contains a negative electrode active material.
  • the negative electrode active material layer may be one layer or multiple layers, and each layer in the multilayer negative electrode active material may contain the same or different negative electrode active materials.
  • the negative electrode active material is any material that can reversibly insert and extract metal ions such as lithium ions.
  • the chargeable capacity of the negative active material is greater than the discharge capacity of the positive active material to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
  • any known current collector can be used arbitrarily.
  • the negative electrode current collector include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative electrode current collector is copper.
  • the negative electrode current collector may include, but is not limited to, metal foil, metal cylinder, metal coil, metal plate, metal film, metal plate mesh, stamped metal, foamed metal, etc.
  • the negative electrode current collector is a metal thin film.
  • the negative electrode current collector is copper foil.
  • the negative electrode current collector is a rolled copper foil based on a rolling method or an electrolytic copper foil based on an electrolytic method.
  • the thickness of the negative electrode current collector is greater than 1 ⁇ m or greater than 5 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is less than 100 m or less than 50 m. In some embodiments, the thickness of the negative electrode current collector is within a range composed of any two values mentioned above.
  • the negative electrode active material is not particularly limited, as long as it can reversibly occlude and release lithium ions.
  • Examples of the negative electrode active material may include, but are not limited to, carbon materials such as natural graphite and artificial graphite; metals such as silicon (Si) and tin (Sn); or oxides of metal elements such as Si and Sn.
  • the negative electrode active material can be used alone or in combination.
  • the anode active material layer may further include an anode binder.
  • the negative electrode binder can improve the bonding between the negative active material particles and the bonding between the negative active material and the current collector.
  • the type of the negative electrode binder is not particularly limited, as long as it is a material that is stable to the electrolyte or the solvent used in the manufacture of the electrode.
  • the negative electrode binder includes a resin binder.
  • resin binders include, but are not limited to, fluororesins, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, and the like.
  • the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salt, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or Its salt, polyvinyl alcohol, etc.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • Its salt polyvinyl alcohol, etc.
  • the negative electrode can be prepared by the following method: coating a negative electrode mixture slurry containing a negative electrode active material, a resin binder, etc. on the negative electrode current collector, and after drying, rolling is performed to form a negative electrode active material layer on both sides of the negative electrode current collector, thereby A negative electrode can be obtained.
  • a separator is usually provided between the positive electrode and the negative electrode.
  • the electrolyte solution of the present application is usually used by infiltrating the separator.
  • the isolation film may be resin, glass fiber, inorganic substance, etc. formed of a material that is stable to the electrolyte of the present application.
  • the isolation membrane includes a porous sheet or a non-woven fabric-like material with excellent liquid retention properties.
  • the material of the resin or glass fiber isolation membrane may include, but are not limited to, polyolefin, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, glass filter, and the like.
  • the material of the isolation membrane is a glass filter.
  • the polyolefin is polyethylene or polypropylene.
  • the polyolefin is polypropylene.
  • the isolation film may also be a material formed by laminating the above-mentioned materials, and examples thereof include, but are not limited to, a three-layer isolation film laminated in the order of polypropylene, polyethylene, and polypropylene.
  • inorganic materials may include, but are not limited to, oxides such as alumina, silicon dioxide, nitrides such as aluminum nitride, silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.).
  • the form of the inorganic substance may include, but is not limited to, granular or fibrous.
  • the form of the isolation membrane may be a thin film form, and examples thereof include, but are not limited to, non-woven fabrics, woven fabrics, microporous membranes, and the like.
  • the pore size of the isolation membrane is 0.01 ⁇ m to 1 ⁇ m, and the thickness is 5 ⁇ m to 50 ⁇ m.
  • the following separator can also be used: a separator formed by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and/or negative electrode using a resin-based binder,
  • the thickness of the isolation film is arbitrary. In some embodiments, the thickness of the isolation film is greater than 1 ⁇ m, greater than 5 ⁇ m, or greater than 8 ⁇ m. In some embodiments, the thickness of the isolation film is less than 50 ⁇ m, less than 40 ⁇ m, or less than 30 ⁇ m. In some embodiments, the thickness of the isolation film is within a range composed of any two values mentioned above. When the thickness of the isolation film is within the above range, insulation and mechanical strength can be ensured, and the rate characteristics and energy density of the electrochemical device can be ensured.
  • the porosity of the separator is arbitrary. In some embodiments, the porosity of the isolation membrane is greater than 20%, greater than 35%, or greater than 45%. In some embodiments, the porosity of the isolation membrane is less than 90%, less than 85%, or less than 75%. In some embodiments, the porosity of the isolation membrane is within a range composed of any two values mentioned above. When the porosity of the isolation membrane is within the above range, insulation and mechanical strength can be ensured, and membrane resistance can be suppressed, so that the electrochemical device has good rate characteristics.
  • the average pore diameter of the separation membrane is also arbitrary. In some embodiments, the average pore diameter of the isolation membrane is less than 0.5 ⁇ m or less than 0.2 ⁇ m. In some embodiments, the average pore diameter of the isolation membrane is greater than 0.05 ⁇ m. In some embodiments, the average pore size of the isolation membrane is within a range composed of any two of the foregoing values. If the average pore diameter of the isolation membrane exceeds the above-mentioned range, a short circuit is likely to occur. When the average pore diameter of the isolation membrane is within the above range, the membrane resistance can be suppressed while preventing short circuits, so that the electrochemical device has good rate characteristics.
  • the electrochemical device assembly includes an electrode group, a current collecting structure, an outer casing and a protection element.
  • the electrode group may have a layered structure in which the positive electrode and the negative electrode are laminated with the separator film interposed therebetween, and a structure in which the positive electrode and the negative electrode are wound in a spiral shape with the separator film interposed therebetween.
  • the ratio of the mass of the electrode group to the internal volume of the battery is greater than 40% or greater than 50%.
  • the electrode group occupancy rate is less than 90% or less than 80%.
  • the occupancy rate of the electrode group is within a range composed of any two of the foregoing values.
  • the capacity of the electrochemical device can be ensured, and at the same time, the reduction in characteristics such as repeated charge and discharge performance and high-temperature storage associated with the increase in internal pressure can be suppressed, and the operation of the gas release valve can be prevented.
  • the current collection structure is not particularly limited. In some embodiments, the current collection structure is a structure that reduces the resistance of the wiring part and the junction part.
  • the electrode group has the above-mentioned layered structure, it is suitable to use a structure in which the metal core portions of each electrode layer are bundled and welded to the terminal.
  • the electrode area increases, the internal resistance increases, so it is also suitable to provide two or more terminals in the electrode to reduce the resistance.
  • the electrode group has the above-mentioned wound structure, by arranging two or more lead structures on the positive electrode and the negative electrode, and bunching them on the terminals, the internal resistance can be reduced.
  • the material of the outer casing is not particularly limited, as long as it is stable to the electrolyte used.
  • the outer casing can be used, but is not limited to nickel-plated steel, stainless steel, aluminum or aluminum alloy, magnesium alloy and other metals, or a laminated film of resin and aluminum foil.
  • the outer casing is a metal or laminated film of aluminum or aluminum alloy.
  • Metallic outer casings include, but are not limited to, a packaged hermetic structure formed by welding metals together by laser welding, resistance welding, or ultrasonic welding; or a riveted structure formed by using the above-mentioned metals via a resin gasket.
  • the exterior case using the above-mentioned laminated film includes, but is not limited to, a sealing structure formed by thermally bonding resin layers to each other, and the like. In order to improve the sealability, a resin different from the resin used in the laminated film may be sandwiched between the above-mentioned resin layers.
  • the shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminated type, a button type, and a large size, for example.
  • the protection element can be used as a positive temperature coefficient (PTC), temperature fuse, thermistor, which increases resistance when abnormal heat is released or excessive current flows, and it is cut off by a sharp rise in the internal pressure or internal temperature of the battery when abnormal heat is released. Valves (current cutoff valves) for the current flowing in the circuit, etc.
  • the above-mentioned protection element can be selected as an element that does not work in the normal use of high current, or it can be designed to prevent abnormal heat generation or thermal runaway even if there is no protection element.
  • the electrochemical device of the present application includes any device that undergoes an electrochemical reaction, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the application also provides an electronic device, which includes the electrochemical device according to the application.
  • the use of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, and headsets.
  • Stereo headsets video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, power assistance Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries, lithium-ion capacitors, etc.
  • lithium ion battery is taken as an example and the preparation of a lithium ion battery is described in conjunction with specific examples. Those skilled in the art will understand that the preparation methods described in this application are only examples, and any other suitable preparation methods are described in this application. Within range.
  • the artificial graphite, styrene butadiene rubber and sodium carboxymethyl cellulose are mixed with deionized water in a mass ratio of 96%: 2%: 2%, and stirred uniformly to obtain a negative electrode slurry.
  • This negative electrode slurry was coated on a 12 ⁇ m copper foil. After drying, cold pressing, cutting pieces and welding tabs, a negative electrode is obtained.
  • the positive electrode active material conductive material (Super-P) and polyvinylidene fluoride (PVDF) with N-methylpyrrolidone (NMP) in a mass ratio of 95%:2%:3%, then add additives, and stir well , Get the positive electrode slurry.
  • the positive electrode slurry was coated on a 12 ⁇ m aluminum foil, dried, cold pressed, and then cut into pieces and welded tabs to obtain a positive electrode.
  • auxiliary agents used in the examples or comparative examples are shown in the following table:
  • Polyethylene (PE) porous polymer film is used as the isolation membrane.
  • the obtained positive electrode, separator film and negative electrode are wound in order and placed in an outer packaging foil, leaving a liquid injection port.
  • the electrolyte is poured from the injection port, encapsulated, and then undergoes processes such as formation and capacity to prepare a lithium-ion battery.
  • Use the 5-point fitting method that is, first take 2 points on the left and right planes of the droplet to determine the liquid-solid transfer Then, take 3 points on the arc of the droplet to perform fitting to obtain the contact angle of the positive electrode active material layer with respect to the non-aqueous solvent. Each sample is measured at least 3 times, at least 3 data with a difference of less than 5° are selected, and the average value is taken to obtain the contact angle of the positive electrode active material layer with respect to the non-aqueous solvent.
  • the specific surface area (m 2 /mg) of the positive electrode active material layer was measured by the nitrogen adsorption BET single-point method using the gas flow method.
  • the reaction area (Y) of the positive electrode active material layer is calculated by the following formula:
  • Y specific surface area of the positive electrode active material layer ⁇ weight of the positive electrode active material layer.
  • the lithium-ion battery is charged to 4.45V at a constant current of 1C, then charged at a constant voltage of 4.45V to a current of 0.05C, and then discharged at a constant current of 1C to 3.0V, which is the first cycle.
  • the lithium ion battery was cycled 200 times under the above conditions.
  • “1C” refers to the current value at which the capacity of the lithium ion battery is completely discharged within 1 hour.
  • Capacity retention rate after cycling (discharge capacity after 200 cycles/discharge capacity at first cycle) ⁇ 100%.
  • the lithium-ion battery was charged to 4.45V at a constant current of 1.5C, then charged to 0.05C at a constant voltage of 4.45V, and left to stand for 30 minutes. Then discharge at 0.1C for 10 seconds, and record the voltage value as U1. Then discharge at 1C for 360 seconds, and record the voltage value as U2).
  • “1C” is the current value that fully discharges the battery capacity within 1 hour.
  • the DC impedance mentioned in this application refers to the value of a lithium-ion battery in a 50% state of charge (SOC) state.
  • Table 1 shows the contact angle of the positive electrode active material layer relative to the non-aqueous solvent in each example and comparative example and the influence of the additives in the positive electrode active material layer on the performance of the lithium ion battery.
  • the positive electrode active material is material 1
  • the electrolyte contains 0.2 wt% of the compound of formula 1a.
  • the specific additives can increase the interaction between the components in the positive active material slurry, make the slurry distribution more uniform, and thereby reduce the contact angle of the positive active material layer with respect to the non-aqueous solvent.
  • the contact angle of the positive active material layer to the non-aqueous solvent is not greater than 45°, the capacity retention and rate percentage of the lithium ion battery after cycling can be significantly improved, and the DC resistance of the lithium ion battery can be significantly reduced.
  • the content of the control auxiliary agent is not more than 3000ppm, which can further improve the capacity retention and rate percentage of the lithium ion battery after cycling, and further reduce the lithium ion battery The DC resistance.
  • Table 2 shows the influence of the positive electrode active material on the performance of the lithium ion battery. The difference between Examples 11-15 and Example 3 is only the positive active material listed in Table 2.
  • the positive electrode active material includes lithium-containing transition metal oxides with different median particle diameters
  • the capacity retention rate and rate percentage of the lithium ion battery after cycling can be further improved, and the DC resistance thereof can be further reduced.
  • the lithium-containing transition metal oxide contains Mg and at least one metal element selected from Ti, Zr, Ge, Nb, Al, and Sn
  • the cycle performance, rate performance, and DC resistance of the lithium ion battery are particularly improved.
  • Table 3 shows the influence of the content of the compound of formula 1a in the electrolyte on the performance of the lithium ion battery. The difference between Examples 16-22 and Example 3 is only the parameters listed in Table 3.
  • Example 20 0.005 72% 80% 36
  • Example 21 0.0008 66% 71% 49
  • Example 22 3 70% 68% 51
  • Table 4 shows the influence of the relationship between the weight of the compound of Formula 1 and the reaction area of the positive electrode active material layer on the performance of the lithium ion battery.
  • the difference between Examples 23-26 and Example 3 is only the parameters listed in Table 4.
  • Table 5 shows the effect of additives in the electrolyte on the performance of lithium-ion batteries. The difference between Examples 27-34 and Example 3 is only the parameters listed in Table 5.
  • references to “embodiments”, “parts of embodiments”, “one embodiment”, “another example”, “examples”, “specific examples” or “partial examples” throughout the specification mean that At least one embodiment or example in this application includes the specific feature, structure, material, or characteristic described in the embodiment or example. Therefore, the descriptions appearing in various places throughout the specification, such as: “in some embodiments”, “in embodiments”, “in one embodiment”, “in another example”, “in an example “In”, “in a specific example” or “exemplified”, which are not necessarily quoting the same embodiment or example in this application.
  • the specific features, structures, materials, or characteristics herein can be combined in one or more embodiments or examples in any suitable manner.

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Abstract

一种电化学装置和电子装置。具体而言，一种电化学装置，其包括：正极、负极和电解液，其中所述正极包括正极活性物质层，其中所述正极活性物质层相对非水溶剂具有较小的接触角。电化学装置具有改进的循环性能、倍率性能和直流阻抗。

Description

电化学装置和电子装置 技术领域
本申请涉及储能领域，具体涉及一种电化学装置和电子装置，特别是锂离子电池。
背景技术
随着技术的发展和对移动装置需求的增加，人们对电化学装置(例如，锂离子电池)的需求显著增加，由此对锂离子电池的性能提出了更高的要求，尤其是锂离子电池的循环性能等。
锂离子电池在循环过程中会产生充电/放电容量降低的现象，从而降低锂离子电池的性能。锂离子电池的性能主要取决于电极、电解液和隔离膜的特性。电极的性能不仅取决于集流体和活性物质层的特征，还与活性物质层中的助剂紧密相关。助剂有助于活性物质层中颗粒的分散或界面的粘结。然而，在锂离子电池的制备过程中通常会遇到原料匹配性不佳导致的配料困难等问题，其会对锂离子电池的性能带来不利影响。
有鉴于此，确有必要提供一种具有改进的性能的电化学装置和电子装置。
发明内容
本申请实施例通过提供一种电化学装置和电子装置以在至少某种程度上解决至少一种存在于相关领域中的问题。
在本申请的一方面，本申请提供了一种电化学装置，其包括正极、负极和电解液，其中所述正极包括正极活性物质层，其中经接触角测定法测定，所述正极活性物质层相对非水溶剂的接触角不大于45°。
根据本申请的实施例，所述接触角测定法是指在所述正极活性物质层表面滴加3微升碳酸二乙酯的液滴后，在100秒内测试所述液滴在所述正极活性物质层的表面的接触角。
根据本申请的实施例，所述正极活性物质层包括具有亲水基团和亲油基团的助剂。
根据本申请的实施例，所述助剂具有以下特征中的至少一者：
(a)氧化电位不小于4.5V，且还原电位不大于0.5V；
(b)表面张力不大于40mN/m；
(c)包括不饱和羧基；
(d)基于所述正极活性物质层的总重量，所述助剂的含量为不大于3000ppm。
根据本申请的实施例，所述助剂包括2-丙烯酸十二烷基酯、聚乙二醇单甲醚丙烯酸酯、聚乙二醇二甲基丙烯酸酯、丙烯酸(2-乙基己基)酯、丙烯酸酯非离子氟碳表面活性剂、甲基丙烯酸十二烷基酯、甲基丙烯酸十二烷基酯、丙烯酸(酯)类共聚物、马来酸丙烯酸共聚物或乙烯丙烯酸共聚物中的至少一种。
根据本申请的实施例，所述电解液包含式1化合物：
Figure PCTCN2020094652-appb-000001
其中R为取代或未取代的C 1-C 10烃基，且当取代时，取代基为卤素，
基于所述电解液的总重量，所述式1化合物的含量为0.001wt％至2wt％。
根据本申请的实施例，所述式1化合物包含以下结构式中的至少一种：
Figure PCTCN2020094652-appb-000002
根据本申请的实施例，所述式1化合物在所述电解液中的含量X mg与所述正极活性物质层的反应面积Y m 2满足如下关系：10≤X/Y≤100。
根据本申请的实施例，所述正极活性物质层包括正极活性物质，所述正极活性物质包括具有不同中值粒径的含锂过渡金属氧化物。
根据本申请的实施例，所述含锂过渡金属氧化物包括通式(1)表示的化合物，
Li aM1 bM2 cM3 dO 2               (1)
其中：
M1选自Co、Ni或Mn中的至少一种；
M2选自Mg、Ti、Zr、Ge、Nb、Al和Sn中的至少一种；
M3是除Li、M1和M2以外的元素；
0.5≤a＜1.1；
0.8≤b＜1.2；
0.002≤c≤0.05；以及
0≤d≤0.05。
根据本申请的实施例，所述含锂过渡金属氧化物包括Mg和选自Ti、Zr、Ge、Nb、Al和Sn中的至少一种金属元素。
在本申请的另一方面，本申请提供一种电子装置，其包括根据本申请的电化学装置。
本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
具体实施方式
本申请的实施例将会被详细的描示在下文中。本申请的实施例不应该被解释为对本申请的限制。
除非另外明确指明，本文使用的下述术语具有下文指出的含义。
在具体实施方式及权利要求书中，由术语“中的至少一者”连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。术语“中的至少一种”具有与术语“中的至少一者”相同的含义。
电化学装置(例如，锂离子电池)的电极(正极或负极)通常通过以下方法制备：将活性物质、导电剂、增稠剂、粘结剂和溶剂混合，然后将混合后的浆料涂布于集流体上。然而，溶剂与粘结剂或者溶剂与活性物质之间的匹配性通常不 佳，使得配料困难。此外，电化学装置的理论容量可随着活性物质的种类而变化。随着循环的进行，电化学装置通常会产生充电/放电容量降低的现象。这是因为电化学装置在充电和/或放电过程中电极界面会发生变化。所述界面包括电极与电解液之间的界面、集流体与电极之间的界面和电极活性物质与添加剂之间的界面等。界面稳定性降低会导致电极活性物质不能发挥其功能。
本申请通过使用特定的正极材料保证了电化学装置在循环过程中的界面稳定性，从而提高了电化学装置的循环性能、倍率性能和直流阻抗。本申请特定的正极材料是通过控制正极活性物质层表面的接触角来实现，作为接触角的控制方法，可以通过在正极浆料中添加助剂或在正极活性物质层表面设置助剂涂层来控制。
本申请提供了一种电化学装置，其包括如下所述的正极、负极和电解液。
I、正极
正极包括正极集流体和设置在所述正极集流体的一个或两个表面上的正极活性物质层。
正极活性物质层
正极活性物质层包含正极活性物质。正极活性物质层可以是一层或多层，多层正极活性物质中的每层可以包含相同或不同的正极活性物质。
接触角
本申请的电化学装置的一个特征在于经接触角测定法测定，所述正极活性物质层相对非水溶剂的接触角不大于45°。在一些实施例中，经接触角测定法测定，所述正极活性物质层相对非水溶剂的接触角不大于40°。在一些实施例中，经接触角测定法测定，所述正极活性物质层相对非水溶剂的接触角不大于35°。当正极活性物质层相对非水溶剂具有如上所述的接触角时，正极活性物质层界面具有适宜的表面张力，对电解液浸润良好，在电化学装置的充放电循环中稳定性良好，可显著改善电化学装置的循环性能、倍率性能和直流阻抗。
正极活性物质层相对非水溶剂的接触角可反映出正极活性物质层的表面性质，其是表征正极活性物质层的物理化学参数之一。接触角越小，正极活性物质层表面张力越小，可显著改善电化学装置的循环性能、倍率性能和直流内阻。正极活性物质层相对非水溶剂的接触角可受多种因素影响，主要包括助剂等。
在一些实施例中，所述接触角测定法是指在所述正极活性物质层表面滴加3 微升碳酸二乙酯的液滴后，在100秒内测试所述液滴在所述正极活性物质层的表面的接触角。
正极活性物质层相对非水溶剂的接触角和非水溶剂液滴的直径可通过以下方法测定：在正极活性物质层表面滴加3微升碳酸二乙酯，在100秒内使用JC2000D3E型接触角测量仪进行测试液滴直径，并选用5点拟合法(即，先取液滴左右平面2点，确定液固交接面，然后在液滴圆弧上取3点)进行拟合，得到正极活性物质层相对非水溶剂的接触角。每个样品至少测量3次，选取至少3个差值小于5°的数据，取平均值，得到正极活性物质层相对非水溶剂的接触角。
接触角测试使用的非水溶剂可以选用碳酸二乙酯、碳酸甲乙酯、碳酸二甲酯、碳酸甲丙酯或碳酸甲异丙酯等常用电解液溶剂。
助剂
根据本申请的一些实施例，所述正极活性物质层包括助剂。在一些实施例中，所述助剂具有亲水基团和亲油基团。
在一些实施例中，所述助剂的氧化电位不小于4.5V，且还原电位不大于0.5V。在一些实施例中，所述助剂的氧化电位不小于5V，且还原电位不大于0.3V。具有上述氧化/还原电位的助剂电化学性能稳定，有助于改善电化学装置的循环性能、倍率性能和直流阻抗。
在一些实施例中，所述助剂的表面张力为不大于40mN/m。在一些实施例中，所述助剂的表面张力为不大于30mN/m。在一些实施例中，所述助剂的表面张力为不大于25mN/m。在一些实施例中，所述助剂的表面张力为不大于20mN/m。在一些实施例中，所述助剂的表面张力为不大于15mN/m。在一些实施例中，所述助剂的表面张力为不大于10mN/m。所述助剂的表面张力是在固含量为1％的助剂NMP溶液条件下测定的。具有如上所述的表面张力的助剂使得正极活性物质层具有良好的界面，有助于改善电化学装置的循环性能、倍率性能和直流阻抗。
助剂的表面张力可通过如下方法测定：使用JC2000D3E型接触角测量仪对固含量为1％的助剂NMP溶液进行测试，每个样品至少测试3次，选取至少3个数据，取平均值，得到助剂的表面张力。
在一些实施例中，所述助剂包括不饱和羧酸基团。在一些实施例中，所述不饱和羧酸基团包括乙烯酸酯、氯乙烯酸酯、丙烯酸酯、乙烯基醚丙烯酸酯、丁烯酸酯、丙炔酸酯、丁炔酸酯或含有丙烯酰胺、丙烯腈、乙烯基醚基团修饰的羧酸 酯中的至少一种。
在一些实施例中，所述助剂包括以下中的至少一种：2-丙烯酸十二烷基酯、聚乙二醇单甲醚丙烯酸酯、聚乙二醇二甲基丙烯酸酯、丙烯酸(2-乙基己基)酯、丙烯酸酯非离子氟碳表面活性剂、甲基丙烯酸十二烷基酯、甲基丙烯酸十二烷基酯、丙烯酸(酯)类共聚物、马来酸丙烯酸共聚物或乙烯丙烯酸共聚物。
在一些实施例中，基于所述正极活性物质层的总重量，所述助剂的含量为不大于3000ppm。在一些实施例中，基于所述正极活性物质层的总重量，所述助剂的含量为不大于2500ppm。在一些实施例中，基于所述正极活性物质层的总重量，所述助剂的含量为不大于2000ppm。在一些实施例中，基于所述正极活性物质层的总重量，所述助剂的含量为不大于1500ppm。在一些实施例中，基于所述正极活性物质层的总重量，所述助剂的含量为不大于1000ppm。在一些实施例中，基于所述正极活性物质层的总重量，所述助剂的含量为不大于500ppm。在一些实施例中，基于所述正极活性物质层的总重量，所述助剂的含量为不大于200ppm。当助剂的含量在上述范围内时，有助于改善电化学装置的循环性能、倍率性能和直流阻抗。
正极活性物质
正极活性物质的种类没有特别限制，只要是能够以电化学方式吸藏和释放金属离子(例如，锂离子)即可。在一些实施例中，正极活性物质为含有锂和至少一种过渡金属的物质。正极活性物质的实例可包括，但不限于，锂过渡金属复合氧化物和含锂过渡金属磷酸化合物。
在一些实施例中，所述正极活性物质包括具有不同中值粒径的含锂过渡金属氧化物。在一些实施例中，具有不同中值粒径的含锂过渡金属氧化物具有相同或不同的化学组成。
在一些实施例中，所述含锂过渡金属氧化物包括通式(1)表示的化合物，
Li aM1 bM2 cM3 dO 2               (1)
其中：
M1选自Co、Ni或Mn中的至少一种；
M2选自Mg、Ti、Zr、Ge、Nb、Al和Sn中的至少一种；
M3是除Li、M1和M2以外的元素；
0.5≤a＜1.1；
0.8≤b＜1.2；
0.002≤c≤0.05；以及
0≤d≤0.05。
在一些实施例中，M1包括Co或Ni中的至少一种。当M1包括Co或Ni中的至少一种时，所述含锂过渡金属氧化物中Co或Ni中的至少一种的含量为不小于50摩尔％；在一些实施例中为不小于60摩尔％；在一些实施例中为不小于70摩尔％；在一些实施例中为不小于80摩尔％；或者在一些实施例中为不小于90摩尔％。
在一些实施例中，M1包括Co。在一些实施例中，M1为Co。当M1包括Co时，所述含锂过渡金属氧化物中Co的含量为不小于30摩尔％；在一些实施例中为不小于50摩尔％；在一些实施例中为不小于65摩尔％；在一些实施例中为不小于80摩尔％；在一些实施例中为不小于90摩尔％；或者在一些实施例中为不小于95摩尔％。当含锂过渡金属氧化物包含Co时，有助于提高正极活性物质层的密度。当含锂过渡金属氧化物中Co的含量在上述范围内时，可进一步改善正极活性物质层的密度。
在一些实施例中，M2包括Mg。在一些实施例中，相对于M1的含量，Mg的含量为不小于0.01摩尔％。在一些实施例中，相对于M1的含量，Mg的含量为不小于0.05摩尔％。在一些实施例中，相对于M1的含量，Mg的含量为不小于0.07摩尔％。在一些实施例中，相对于M1的含量，Mg的含量为不大于0.5摩尔％。在一些实施例中，相对于M1的含量，Mg的含量为不大于0.2摩尔％。在一些实施例中，相对于M1的含量，Mg的含量为不大于0.1摩尔％。在一些实施例中，相对于M1的含量，Mg的含量在由上述任意两个端点所组成的范围内。当含锂过渡金属氧化物中Mg的含量在上述范围内时，Mg元素可有效地发挥作用，改善电化学装置的循环性能、倍率性能和直流阻抗。
在一些实施例中，M2进一步包括Ti、Zr、Ge、Nb、Al和Sn中的至少一种。
在一些实施例中，M2进一步包括Ti、Zr、Ge或Nb中的至少一种。在一些实施例中，相对于M1的含量，Ti、Zr、Ge或Nb中的至少一种的含量为不小于0.005摩尔％。在一些实施例中，相对于M1的含量，Ti、Zr、Ge或Nb中的至少一种的含量为不小于0.008摩尔％。在一些实施例中，相对于M1的含量，Ti、Zr、Ge或Nb中的至少一种的含量为不小于0.01摩尔％。在一些实施例中，相 对于M1的含量，Ti、Zr、Ge或Nb中的至少一种的含量为不大于0.3摩尔％。在一些实施例中，相对于M1的含量，Ti、Zr、Ge或Nb中的至少一种的含量为不大于0.1摩尔％。在一些实施例中，相对于M1的含量，Ti、Zr、Ge或Nb中的至少一种的含量为不大于0.05摩尔％。在一些实施例中，相对于M1的含量，Ti、Zr、Ge或Nb中的至少一种的含量在由上述任意两个端点所组成的范围内。当含锂过渡金属氧化物中Ti、Zr、Ge或Nb中的至少一种的含量在上述范围内时，有助于进一步改善电化学装置的循环性能、倍率性能和直流阻抗。
在一些实施例中，M2进一步包括Al或Sn中的至少一种。在一些实施例中，相对于M1的含量，Al或Sn中的至少一种的含量为不小于0.01摩尔％。在一些实施例中，相对于M1的含量，Al或Sn中的至少一种的含量为不小于0.05摩尔％。在一些实施例中，相对于M1的含量，Al或Sn中的至少一种的含量为不小于0.07摩尔％。在一些实施例中，相对于M1的含量，Al或Sn中的至少一种的含量为不大于0.5摩尔％。在一些实施例中，相对于M1的含量，Al或Sn中的至少一种的含量为不大于0.2摩尔％。在一些实施例中，相对于M1的含量，Al或Sn中的至少一种的含量为不大于0.1摩尔％。在一些实施例中，相对于M1的含量，Al或Sn中的至少一种的含量在由上述任意两个端点所组成的范围内。当含锂过渡金属氧化物中Al或Sn中的至少一种的含量在上述范围内时，有助于进一步改善电化学装置的循环性能、倍率性能和直流阻抗。
在一些实施例中，0.004≤c≤0.02。在一些实施例中，0.006≤c≤0.01。当c在上述范围内时，可进一步改善锂离子电池的循环性能、倍率性能和直流阻抗。
含锂过渡金属氧化物可以多种方式包含M2，其没有特别限制。在一些实施例中，M2存在于含锂过渡金属氧化物粒子上。在一些实施例中，M2均匀地固体分散在含锂过渡金属氧化物内。在一些实施例中，M2含锂过渡金属氧化物内具有浓度分布地偏聚。在一些实施例中，M2在含锂过渡金属氧化物表面上形成化合物层。
在一些实施例中，M3包括以下元素中的至少一种：除Li以外的碱金属元素、除Mg以外的碱土金属元素、IIIa族金属元素、除Ti和Zr以外的IVb族金属元素、除Nb以外的Vb族金属元素、VIb族金属元素、除Mn以外的VIIb族金属元素、除Co和Ni以外的VIII族金属元素、Ib族金属元素、Zn、除Al以外的IIIa族金属元素、除Sn和Pb以外的IVa族金属元素、P或Bi。
在一些实施例中，M3包括以下元素中的至少一种：Na、K、Rb、Be、Ca、Sr、Ba、Sc、Y、La、Hf、V、Ta、Cr、Mo、W、Tc、Re、Fe、Ru、Rh、Cu、Ag、Au、Zn、B、Ca、In、Si、P或Bi。
在一些实施例中，所述含锂过渡金属氧化物不含M3(即，d＝0)。
在一些实施例中，所述含锂过渡金属氧化物包括LiNi 0.81Co 0.16Al 0.03O 2、LiNi 0.81Co 0.16Mg 0.03O 2、LiNi 0.81Co 0.16Si 0.03O 2、LiNi 0.81Co 0.16Ti 0.03O 2、LiCo 0.96Ti 0.04O 2、LiCo 0.998Mg 0.0008Ti 0.0004Al 0.0008O 2、LiCo 0.994Mg 0.0024Ti 0.0012Al 0.0024O 2、LiCo 0.9988Mg 0.0008Ti 0.0004O 2、LiCo 0.9964Mg 0.0024Ti 0.0012O 2或LiCo 0.334Ni 0.33Mn 0.33Mg 0.0024Ti 0.0012Al 0.0024O 2中的至少一种。
含锂过渡金属氧化物中的各元素含量可通过感应耦合等离子体(ICP)分析得到。含锂过渡金属氧化物中的锂含量也可使用其它方法(例如，原子吸收法)等来测定。具体地，精确秤量约5g含锂过渡金属氧化物，加入至200ml的烧杯中，然后加入100ml王水，加热浓缩到液量为20-25ml，冷却，用Advantec公司制造的定量滤纸“No.5B”分离固形物，将滤液和洗液加入100ml量瓶中定容稀释后，使用日本Nippon Jarrell-Ash有限公司制造的顺序型ICP型分析装置“IPIS1000”来测定元素含量。
在一些实施例中，基于正极活性物质层的总重量，所述含锂过渡金属氧化物的含量为不大于99wt％。在一些实施例中，基于正极活性物质层的总重量，所述含锂过渡金属氧化物的含量为不大于97.5wt％。在一些实施例中，基于正极活性物质层的总重量，所述含锂过渡金属氧化物的含量为不大于97wt％。在一些实施例中，基于正极活性物质层的总重量，所述含锂过渡金属氧化物的含量为不大于98wt％。在一些实施例中，基于正极活性物质层的总重量，所述含锂过渡金属氧化物的含量为不大于95wt％。在一些实施例中，基于正极活性物质层的总重量，所述含锂过渡金属氧化物的含量为不小于85wt％。在一些实施例中，基于正极活性物质层的总重量，所述含锂过渡金属氧化物的含量为不大于90wt％。在一些实施例中，基于正极活性物质层的总重量，所述含锂过渡金属氧化物的含量为不大于92wt％。在一些实施例中，基于正极活性物质层的总重量，所述含锂过渡金属氧化物的含量在上述任意两个端点所组成的范围内。当正极活性物质层中含锂过渡金属氧化物的含量在上述范围内时，正极活性物质层具有高容量和低电阻，并有助于正极的形成。
在一些实施例中，所述含锂过渡金属氧化物包含第一颗粒和第二颗粒，所述第一颗粒具有第一中值粒径，所述第二颗粒具有第二中值粒径，所述第一中值粒径小于所述第二中值粒径。
在一些实施例中，所述第一中值粒径为0.5μm至10μm。在一些实施例中，所述第一中值粒径为1μm至8μm。在一些实施例中，所述第一中值粒径为2μm至6μm。在一些实施例中，所述第二中值粒径为11μm至30μm。在一些实施例中，所述第二中值粒径为12μm至25μm。在一些实施例中，所述第二中值粒径为13μm至20μm。
在一些实施例中，正极活性物质的放电容量小于负极活性物质的可充电容量，以防止在充电期间锂金属无意地析出在负极上。
含锂过渡金属氧化物的中值粒径可通过以下方法调节：向过渡金属元素M1的酸性水溶液中滴加NaOH，沉淀得到M1的氢氧化物。将M1的氢氧化物烧制得到M1的氧化物。通过控制沉淀时间、沉淀粒径和烧制的M1的氧化物的粒径可控制含锂过渡金属氧化物的中值粒径。
在一些实施例中，正极活性物质的放电容量小于负极活性物质的可充电容量，以防止在充电期间锂金属无意地析出在负极上。
正极活性物质层的密度
在一些实施例中，所述正极活性物质层的密度为不小于3.5g/cm 3。在一些实施例中，所述正极活性物质层的密度为不小于3.6g/cm 3。在一些实施例中，所述正极活性物质层的密度为不小于3.8g/cm 3。在一些实施例中，所述正极活性物质层的密度为不大于4.6g/cm 3。在一些实施例中，所述正极活性物质层的密度为不大于4.4g/cm 3。在一些实施例中，所述正极活性物质层的密度为不大于4.2g/cm 3。在一些实施例中，所述正极活性物质层的密度在由上述任意两个端点所组成的范围内。当正极活性物质层的密度在上述范围内时，正极活性物质层具有良好的可润湿性，有助于改善电化学装置的性能。
正极活性物质层的密度可通过以下方法测定：以一定面积切取正极，使用最小刻度为1mg的电子天平测定其重量W1，用最小刻度为1μm的千分尺测定正极的厚度T1。剥离正极集流体，使用电子天平测定其重量W2，并用千分尺测定正极集流体的厚度T2。W1-W2记为正极活性物质层的重量，T1-T2记为正极活性物质层的厚度。根据正极活性物质层的厚度和面积计算正极活性物质层的体 积，然后根据正极活性物质层的重量和体积计算正极活性物质层的密度。
正极活性物质层的厚度
在一些实施例中，所述正极活性物质层的厚度为30μm至200μm。在一些实施例中，所述正极活性物质层的厚度为50μm至180μm。在一些实施例中，所述正极活性物质层的厚度为80μm至150μm。在一些实施例中，所述正极活性物质层的厚度为100μm至120μm。在一些实施例中，所述正极活性物质层的厚度为30μm、50μm、80μm、100μm、120μm、150μm、180μm、200μm或在由上述任意两个数值所组成的范围内。
正极活性物质层的厚度可通过以下方法测定：切取正极，使用最小刻度为1μm的千分尺测定正极的厚度T1。剥离正极集流体，用千分尺测定正极集流体的厚度T2。T1-T2记为正极活性物质层的厚度。
导电层
在一些实施例中，正极活性物质层可进一步包括导电层，所述导电层包括导电剂。在一些实施例中，所述导电层不含正极活性物质。导电剂的实例包括，但不限于，石墨、碳黑或乙炔黑。
在一些实施例中，基于正极活性物质层的总重量，所述导电剂的含量为不小于1wt％。在一些实施例中，基于正极活性物质层的总重量，所述导电剂的含量为不小于1.1wt％。在一些实施例中，基于正极活性物质层的总重量，所述导电剂的含量为不小于1.2wt％。在一些实施例中，基于正极活性物质层的总重量，所述导电剂的含量为不大于3wt％。在一些实施例中，基于正极活性物质层的总重量，所述导电剂的含量为不大于2wt％。在一些实施例中，基于正极活性物质层的总重量，所述导电剂的含量为不大于1.5wt％。在一些实施例中，基于正极活性物质层的总重量，所述导电剂的含量在由上述任意两个数值所组成的范围内。当正极活性物质层中导电剂的含量在上述范围内时，有助于改善正极活性物质层的密度和容量，从而提升电化学装置的循环性能并降低其负荷特性。
粘合剂
在一些实施例中，所述正极活性物质层包括粘合剂。粘合剂的实例包括，但不限于，聚偏氟乙烯或聚四氟乙烯。
在一些实施例中，基于正极活性物质层的总重量，所述粘合剂的含量为不小于1wt％。在一些实施例中，基于正极活性物质层的总重量，所述粘合剂的含量 为不小于1.3wt％。在一些实施例中，基于正极活性物质层的总重量，所述粘合剂的含量为不小于1.5wt％。在一些实施例中，基于正极活性物质层的总重量，所述粘合剂的含量为不大于4wt％。在一些实施例中，基于正极活性物质层的总重量，所述粘合剂的含量为不大于3wt％。在一些实施例中，基于正极活性物质层的总重量，所述粘合剂的含量为不大于2wt％。在一些实施例中，基于正极活性物质层的总重量，所述粘合剂的含量在由上述任意两个数值所组成的范围内。当正极活性物质层中粘合剂的含量在上述范围内时，正极活性物质层与正极集流体具有良好的粘合性，避免了正极粉化脱落的可能性，由此有助于改善正极的稳定性。
正极集流体
正极集流体的种类没有特别限制，其可为任何已知适于用作正极集流体的材质。正极集流体的实例可包括，但不限于，铝、铝合金、镀镍铝、不锈钢、钛或钽中的至少一种；碳布、碳纸等碳材料。在一些实施例中，正极集流体为金属材料。在一些实施例中，正极集流体为铝。
正极集流体的形式没有特别限制。当正极集流体为金属材料时，正极集流体的形式可包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属薄膜、金属板网、冲压金属、发泡金属等。当正极集流体为碳材料时，正极集流体的形式可包括，但不限于，碳板、碳薄膜、碳圆柱等。在一些实施例中，正极集流体为金属薄膜。在一些实施例中，所述金属薄膜为网状。
在一些实施例中，所述正极集流体的厚度为8μm至20μm。在一些实施例中，所述正极集流体的厚度为10μm至18μm。在一些实施例中，所述正极集流体的厚度为12μm至15μm。在一些实施例中，所述正极集流体的厚度在由上述任意两个数值所组成的范围内。
为了降低正极集流体和正极活性物质层的电子接触电阻，正极集流体的表面可包括导电剂。导电剂的实例可包括，但不限于，碳和金、铂、银等贵金属类。
本申请的正极的制备方法不受限制。例如，正极可通过以下方法制造：将两种以上具有不同中值粒径的含锂过渡金属氧化物以一定重量比混合，根据需要添加导电剂和粘合剂，加入溶剂，得到正极合剂浆料。在正极集流体(例如，铝箔)上涂布得到的正极合剂浆料，干燥，形成正极活性物质层。将正极活性物质层施加至正极集流体的一个或两个表面，根据需要进行压延步骤，制得正极。
II、电解液
本申请的电化学装置中的使用的电解液包括电解质和溶解该电解质的溶剂。在一些实施例中，本申请的电化学装置中的使用的电解液进一步包括添加剂。
在一些实施例中，所述电解液包含式1化合物：
Figure PCTCN2020094652-appb-000003
其中R为取代或未取代的C 1-C 10烃基，且当取代时，取代基为卤素。
在一些实施例中，所述式1化合物包含以下结构式中的至少一种：
Figure PCTCN2020094652-appb-000004
在一些实施例中，基于所述电解液的总重量，所述式1化合物的含量为0.001wt％至2wt％。在一些实施例中，基于所述电解液的总重量，所述式1化合物的含量为0.01wt％至1wt％。在一些实施例中，基于所述电解液的总重量，所述式1化合物的含量为0.05wt％至0.5wt％。在一些实施例中，基于所述电解液的总重量，所述式1化合物的含量为0.1wt％至0.3wt％。在一些实施例中，基于所述电解液的总重量，所述式1化合物的含量为0.001wt％、0.005wt％、0.01wt％、0.05wt％、0.1wt％、0.3wt％、0.5wt％、0.8wt％、1wt％、1.2wt％、1.5wt％、1.8wt％、2wt％或在由上述任意两个数值所组成的范围内。当电解液中式1化合物的含量在上述范围内时，有助于进一步改善锂离子电池的循环性能、倍率性能和直流阻抗。
在一些实施例中，所述式1化合物在所述电解液中的含量X mg与所述正极活性物质层的反应面积Y m 2满足如下关系：10≤X/Y≤100。在一些实施例中，X和Y满足如下关系：20≤X/Y<100。在一些实施例中，X和Y满足如下关系： 20≤X/Y<70。当X和Y符合上述关系时，有助于进一步改善锂离子电池的循环性能、倍率性能和直流阻抗。
正极活性物质层的反应面积可通过以下方法测定：使用表面积计(大仓理研制造的全自动表面积测定装置)，在氮气流通下于350℃对试样进行15分钟预干燥，然后使用氮气相对于大气压的相对压力值准确调节为0.3的氮氦混合气体，通过采用气体流动法的氮吸附BET单点法进行测定。依此方法测试正极活性物质层的比表面积，正极活性物质层的比表面积是指含有正极活性物质和添加剂(粘结剂、导电剂、增稠剂和填料等)的正极活性物质层全体的比表面积。测量正极活性物质层的重量，即含有正极活性物质和添加剂(粘结剂、导电剂、增稠剂和填料等)的正极活性物质层全体的总重量。通过下式计算正极活性物质层的反应面积：
反应面积＝正极活性物质层的比表面积×正极活性物质层的重量。
在一些实施例中，所述电解液进一步包含现有技术中已知的任何可作为电解液的溶剂的非水溶剂。
在一些实施例中，所述非水溶剂包括，但不限于，以下中的一种或多种：环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯、环状醚、链状醚、含磷有机溶剂、含硫有机溶剂和芳香族含氟溶剂。
在一些实施例中，所述环状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸亚乙酯(EC)、碳酸亚丙酯(PC)和碳酸亚丁酯。在一些实施例中，所述环状碳酸酯具有3-6个碳原子。
在一些实施例中，所述链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯(DEC)、碳酸甲基正丙基酯、碳酸乙基正丙基酯、碳酸二正丙酯等链状碳酸酯等。被氟取代的链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：双(氟甲基)碳酸酯、双(二氟甲基)碳酸酯、双(三氟甲基)碳酸酯、双(2-氟乙基)碳酸酯、双(2,2-二氟乙基)碳酸酯、双(2,2,2-三氟乙基)碳酸酯、2-氟乙基甲基碳酸酯、2,2-二氟乙基甲基碳酸酯和2,2,2-三氟乙基甲基碳酸酯等。
在一些实施例中，所述环状羧酸酯的实例可包括，但不限于，以下中的一种或多种：γ-丁内酯和γ-戊内酯中的一种或多种。在一些实施例中，环状羧酸酯的部分氢原子可被氟取代。
在一些实施例中，所述链状羧酸酯的实例可包括，但不限于，以下中的一种或多种：乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸异丙酯、乙酸丁酯、乙酸仲丁酯、乙酸异丁酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸异丙酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、异丁酸甲酯、异丁酸乙酯、戊酸甲酯、戊酸乙酯、特戊酸甲酯和特戊酸乙酯等。在一些实施例中，链状羧酸酯的部分氢原子可被氟取代。在一些实施例中，氟取代的链状羧酸酯的实例可包括，但不限于，三氟乙酸甲酯、三氟乙酸乙酯、三氟乙酸丙酯、三氟乙酸丁酯和三氟乙酸2,2,2-三氟乙酯等。
在一些实施例中，所述环状醚的实例可包括，但不限于，以下中的一种或多种：四氢呋喃、2-甲基四氢呋喃、1,3-二氧戊环、2-甲基1,3-二氧戊环、4-甲基1,3-二氧戊环、1,3-二氧六环、1,4-二氧六环和二甲氧基丙烷。
在一些实施例中，所述链状醚的实例可包括，但不限于，以下中的一种或多种：二甲氧基甲烷、1,1-二甲氧基乙烷、1,2-二甲氧基乙烷、二乙氧基甲烷、1,1-二乙氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基甲烷、1,1-乙氧基甲氧基乙烷和1,2-乙氧基甲氧基乙烷等。
在一些实施例中，所述含磷有机溶剂的实例可包括，但不限于，以下中的一种或多种：磷酸三甲酯、磷酸三乙酯、磷酸二甲基乙酯、磷酸甲基二乙酯、磷酸亚乙基甲酯、磷酸亚乙基乙酯、磷酸三苯酯、亚磷酸三甲酯、亚磷酸三乙酯、亚磷酸三苯酯、磷酸三(2,2,2-三氟乙基)酯和磷酸三(2,2,3,3,3-五氟丙基)酯等。
在一些实施例中，所述含硫有机溶剂的实例可包括，但不限于，以下中的一种或多种：环丁砜、2-甲基环丁砜、3-甲基环丁砜、二甲基砜、二乙基砜、乙基甲基砜、甲基丙基砜、二甲基亚砜、甲磺酸甲酯、甲磺酸乙酯、乙磺酸甲酯、乙磺酸乙酯、硫酸二甲酯、硫酸二乙酯和硫酸二丁酯。在一些实施例中，含硫有机溶剂的部分氢原子可被氟取代。
在一些实施例中，所述芳香族含氟溶剂包括，但不限于，以下中的一种或多种：氟苯、二氟苯、三氟苯、四氟苯、五氟苯、六氟苯和三氟甲基苯。
在一些实施例中，本申请的电解液中使用的溶剂包括环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯及其组合。在一些实施例中，本申请的电解液中使用的溶剂包括碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、乙酸正丙酯、或乙酸乙酯中的至少一种。在一些实施例中，本申请的电解液中使用 的溶剂包含：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、γ-丁内酯及其组合。
在电解液中加入链状羧酸酯及/或环状羧酸酯后，链状羧酸酯及/或环状羧酸酯可在电极表面形成钝化膜，从而提高电化学装置的间歇充电循环后的容量保持率。在一些实施例中，所述电解液中含有1％至60％的链状羧酸酯、环状羧酸酯及其组合。在一些实施例中，所述电解液中含有丙酸乙酯、丙酸丙酯、γ-丁内酯及其组合，基于电解液的总重量，该组合的含量为1％至60％、10％至60％、10％至50％、20％至50％。在一些实施例中，基于电解液的总重量，所述电解液中含有1％至60％、10％至60％、20％至50％、20％至40％或30％的丙酸丙酯。
在一些实施例中，所述添加剂的实例可包括，但不限于，以下的一种或多种：氟代碳酸酯、含碳碳双键的碳酸乙烯酯、含硫氧双键的化合物和酸酐。
在一些实施例中，基于所述电解液的总重量，所述添加剂的含量为0.01％至15％、0.1％至10％或1％至5％。
根据本申请的实施例，基于所述电解液的总重量，所述丙酸酯的含量为所述添加剂的1.5至30倍、1.5至20倍、2至20倍或5至20倍。
在一些实施例中，所述添加剂包含一种或多种氟代碳酸酯。在锂离子电池充电/放电时，氟代碳酸酯可与丙酸酯共同作用以在负极的表面上形成稳定的保护膜，从而抑制电解液的分解反应。
在一些实施例中，所述氟代碳酸酯具有式C＝O(OR 1)(OR 2)，其中R 1和R 2各自选自具有1-6个碳原子的烷基或卤代烷基，其中R 1和R 2中的至少一者选自具有1-6个碳原子的氟代烷基，且R 1和R 2任选地连同其所连接的原子形成5元至7元环。
在一些实施例中，所述氟代碳酸酯的实例可包括，但不限于，以下的一种或多种：氟代碳酸乙烯酯、顺式4,4-二氟碳酸乙烯酯、反式4,4-二氟碳酸乙烯酯、4,5-二氟碳酸乙烯酯、4-氟-4-甲基碳酸乙烯酯、4-氟-5-甲基碳酸乙烯酯、碳酸三氟甲基甲酯、碳酸三氟乙基甲酯和碳酸乙基三氟乙酯等。
在一些实施例中，所述添加剂包含一种或多种含碳碳双键的碳酸乙烯酯。所述含碳碳双键的碳酸乙烯酯的实例可包括，但不限于，以下的一种或多种：碳酸亚乙烯酯、碳酸甲基亚乙烯酯、碳酸乙基亚乙烯酯、碳酸-1,2-二甲基亚乙烯酯、碳酸-1,2-二乙基亚乙烯酯、碳酸氟亚乙烯酯、碳酸三氟甲基亚乙烯酯；碳酸乙烯 基亚乙酯、碳酸-1-甲基-2-乙烯基亚乙酯、碳酸-1-乙基-2-乙烯基亚乙酯、碳酸-1-正丙基-2-乙烯基亚乙酯、碳酸1-甲基-2-乙烯基亚乙酯、碳酸-1,1-二乙烯基亚乙酯、碳酸-1,2-二乙烯基亚乙酯、碳酸-1,1-二甲基-2-亚甲基亚乙酯和碳酸-1,1-二乙基-2-亚甲基亚乙酯等。在一些实施例中，所述含碳碳双键的碳酸乙烯酯包括碳酸亚乙烯酯，其易于获得并可实现更为优异的效果。
在一些实施例中，所述添加剂包含一种或多种含硫氧双键的化合物。所述含硫氧双键的化合物的实例可包括，但不限于，以下的一种或多种：环状硫酸酯、链状硫酸酯、链状磺酸酯、环状磺酸酯、链状亚硫酸酯和环状亚硫酸酯等。
所述环状硫酸酯的实例可包括，但不限于，以下的一种或多种：1,2-乙二醇硫酸酯、1,2-丙二醇硫酸酯、1,3-丙二醇硫酸酯、1,2-丁二醇硫酸酯、1,3-丁二醇硫酸酯、1,4-丁二醇硫酸酯、1,2-戊二醇硫酸酯、1,3-戊二醇硫酸酯、1,4-戊二醇硫酸酯和1,5-戊二醇硫酸酯等。
所述链状硫酸酯的实例可包括，但不限于，以下的一种或多种：硫酸二甲酯、硫酸甲乙酯和硫酸二乙酯等。
所述链状磺酸酯的实例可包括，但不限于，以下的一种或多种：氟磺酸甲酯和氟磺酸乙酯等氟磺酸酯、甲磺酸甲酯、甲磺酸乙酯、二甲磺酸丁酯、2-(甲磺酰氧基)丙酸甲酯和2-(甲磺酰氧基)丙酸乙酯等。
所述环状磺酸酯的实例可包括，但不限于，以下的一种或多种：1,3-丙磺酸内酯、1-氟-1,3-丙磺酸内酯、2-氟-1,3-丙磺酸内酯、3-氟-1,3-丙磺酸内酯、1-甲基-1,3-丙磺酸内酯、2-甲基-1,3-丙磺酸内酯、3-甲基-1,3-丙磺酸内酯、1-丙烯-1,3-磺酸内酯、2-丙烯-1,3-磺酸内酯、1-氟-1-丙烯-1,3-磺酸内酯、2-氟-1-丙烯-1,3-磺酸内酯、3-氟-1-丙烯-1,3-磺酸内酯、1-氟-2-丙烯-1,3-磺酸内酯、2-氟-2-丙烯-1,3-磺酸内酯、3-氟-2-丙烯-1,3-磺酸内酯、1-甲基-1-丙烯-1,3-磺酸内酯、2-甲基-1-丙烯-1,3-磺酸内酯、3-甲基-1-丙烯-1,3-磺酸内酯、1-甲基-2-丙烯-1,3-磺酸内酯、2-甲基-2-丙烯-1,3-磺酸内酯、3-甲基-2-丙烯-1,3-磺酸内酯、1,4-丁磺酸内酯、1,5-戊磺酸内酯、甲烷二磺酸亚甲酯和甲烷二磺酸亚乙酯等。
所述链状亚硫酸酯的实例可包括，但不限于，以下的一种或多种：亚硫酸二甲酯、亚硫酸甲乙酯和亚硫酸二乙酯等。
所述环状亚硫酸酯的实例可包括，但不限于，以下的一种或多种：1,2-乙二醇亚硫酸酯、1,2-丙二醇亚硫酸酯、1,3-丙二醇亚硫酸酯、1,2-丁二醇亚硫酸酯、 1,3-丁二醇亚硫酸酯、1,4-丁二醇亚硫酸酯、1,2-戊二醇亚硫酸酯、1,3-戊二醇亚硫酸酯、1,4-戊二醇亚硫酸酯和1,5-戊二醇亚硫酸酯等。
在一些实施例中，所述添加剂包含一种或多种酸酐。所述酸酐的实例可包括，但不限于，环状磷酸酐、羧酸酐、二磺酸酐和羧酸磺酸酐中的一种或多种。所述环状磷酸酐的实例可包括，但不限于，三甲基磷酸环酐、三乙基磷酸环酐和三丙基磷酸环酐中的一种或多种。所述羧酸酐的实例可包括，但不限于，琥珀酸酐、戊二酸酐和马来酸酐中的一种或多种。所述二磺酸酐的实例可包括，但不限于，乙烷二磺酸酐和丙烷二磺酸酐中的一种或多种。所述羧酸磺酸酐的实例可包括，但不限于，磺基苯甲酸酐、磺基丙酸酐和磺基丁酸酐中的一种或多种。
在一些实施例中，所述添加剂为氟代碳酸酯与含碳碳双键的碳酸乙烯酯的组合。在一些实施例中，所述添加剂为氟代碳酸酯与含硫氧双键的化合物的组合。在一些实施例中，所述添加剂为氟代碳酸酯与具有2-4个氰基的化合物的组合。在一些实施例中，所述添加剂为氟代碳酸酯与环状羧酸酯的组合。在一些实施例中，所述添加剂为氟代碳酸酯与环状磷酸酐的组合。在一些实施例中，所述添加剂为氟代碳酸酯与羧酸酐的组合。在一些实施例中，所述添加剂为氟代碳酸酯与璜酸酐的组合。在一些实施例中，所述添加剂为氟代碳酸酯与羧酸璜酸酐的组合。
电解质没有特别限制，可以任意地使用作为电解质公知的物质。在锂二次电池的情况下，通常使用锂盐。电解质的实例可包括，但不限于，LiPF 6、LiBF 4、LiClO 4、LiAlF 4、LiSbF 6、LiTaF 6、LiWF 7等无机锂盐；LiWOF 5等钨酸锂类；HCO 2Li、CH 3CO 2Li、CH 2FCO 2Li、CHF 2CO 2Li、CF 3CO 2Li、CF 3CH 2CO 2Li、CF 3CF 2CO 2Li、CF 3CF 2CF 2CO 2Li、CF 3CF 2CF 2CF 2CO 2Li等羧酸锂盐类；FSO 3Li、CH 3SO 3Li、CH 2FSO 3Li、CHF 2SO 3Li、CF 3SO 3Li、CF 3CF 2SO 3Li、CF 3CF 2CF 2SO 3Li、CF 3CF 2CF 2CF 2SO 3Li等磺酸锂盐类；LiN(FCO) 2、LiN(FCO)(FSO 2)、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)等酰亚胺锂盐类；LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3等甲基化锂盐类；双(丙二酸根合)硼酸锂盐、二氟(丙二酸根合)硼酸锂盐等(丙二酸根合)硼酸锂盐类；三(丙二酸根合)磷酸锂、二氟双(丙二酸根合)磷酸锂、四氟(丙二酸根合)磷酸锂等(丙二酸根合)磷酸锂盐类；以及LiPF 4(CF 3) 2、LiPF 4(C 2F 5) 2、LiPF 4(CF 3SO 2) 2、LiPF 4(C 2F 5SO 2) 2、LiBF 3CF 3、LiBF 3C 2F 5、LiBF 3C 3F 7、LiBF 2(CF 3)2、LiBF 2(C 2F 5) 2、LiBF 2(CF 3SO 2) 2、 LiBF 2(C 2F 5SO 2) 2等含氟有机锂盐类；二氟草酸硼酸锂、双(草酸)硼酸锂等草酸硼酸锂盐类；四氟草酸根合磷酸锂、二氟双(草酸根合)磷酸锂、三(草酸根合)磷酸锂等草酸根合磷酸锂盐类等。
在一些实施例中，电解质选自LiPF 6、LiSbF 6、LiTaF 6、FSO 3Li、CF 3SO 3Li、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3、二氟草酸硼酸锂、双(草酸)硼酸锂或二氟双(草酸根合)磷酸锂，其有助于改善电化学装置的输出功率特性、高倍率充放电特性、高温保存特性和循环特性等。
电解质的含量没有特别限制，只要不损害本申请的效果即可。在一些实施例中，电解液中的锂的总摩尔浓度为大于0.3mol/L以上、大于0.4mol/L或大于0.5mol/L。在一些实施例中，电解液中的锂的总摩尔浓度为小于3mol/L、小于2.5mol/L或小于2.0mol/L以下。在一些实施例中，电解液中的锂的总摩尔浓度在由上述任意两个数值所组成的范围内。当电解质浓度在上述范围内时，作为带电粒子的锂不会过少，并且可以使粘度处于适当的范围，因而容易确保良好的电导率。
当使用两种以上的电解质的情况下，电解质包括至少一种为选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括选自由单氟磷酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括锂盐。在一些实施例中，基于电解质的总重量，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为大于0.01wt％或大于0.1wt％。在一些实施例中，基于电解质的总重量，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为小于20wt％或小于10wt％。在一些实施例中，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量在由上述任意两个数值所组成的范围内。
在一些实施例中，电解质包含选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的一种以上物质和除此以外的一种以上的盐。作为除此以外的盐，可以举出在上文中例示的锂盐，在一些实施例中为LiPF 6、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、 LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3。在一些实施例中，除此以外的盐为LiPF 6。
在一些实施例中，基于电解质的总重量，除此以外的盐的含量为大于0.01wt％或大于0.1wt％。在一些实施例中，基于电解质的总重量，除此以外的盐的含量为小于20wt％、小于15wt％或小于10wt％。在一些实施例中，除此以外的盐的含量在由上述任意两个数值所组成的范围内。具有上述含量的除此以外的盐有助于平衡电解液的电导率和粘度。
在电解液中，除了含有上述溶剂、添加剂和电解质盐以外，可以根据需要含有负极被膜形成剂、正极保护剂、防过充电剂等额外添加剂。作为添加剂，可使用一般在非水电解质二次电池中使用的添加剂，其实例可包括，但不限于，碳酸亚乙烯酯、琥珀酸酐、联苯、环己基苯、2,4-二氟苯甲醚、丙烷磺内酯、丙烯磺内酯等。这些添加剂可以单独使用或任意组合使用。另外，电解液中的这些添加剂的含量没有特别限制，可以根据该添加剂的种类等适当地设定即可。在一些实施例中，基于电解液的总重量，添加剂的含量为小于5wt％、在0.01wt％至5wt％的范围内或在0.2wt％至5wt％的范围内。
III、负极
负极包括负极集流体和设置在所述负极集流体的一个或两个表面上的负极活性物质层。负极活性物质层包括负极活性物质层，负极活性物质层包含负极活性物质。负极活性物质层可以是一层或多层，多层负极活性物质中的每层可以包含相同或不同的负极活性物质。负极活性物质为任何能够可逆地嵌入和脱嵌锂离子等金属离子的物质。在一些实施例中，负极活性物质的可充电容量大于正极活性物质的放电容量，以防止在充电期间锂金属无意地析出在负极上。
作为保持负极活性物质的集流体，可以任意使用已知的集流体。负极集流体的实例包括，但不限于，铝、铜、镍、不锈钢、镀镍钢等金属材料。在一些实施例中，负极集流体为铜。
在负极集流体为金属材料的情况下，负极集流体形式可包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属薄膜、金属板网、冲压金属、发泡金属等。在一些实施例中，负极集流体为金属薄膜。在一些实施例中，负极集流体为铜箔。在一些实施例中，负极集流体为基于压延法的压延铜箔或基于电解法的电解铜箔。
在一些实施例中，负极集流体的厚度为大于1μm或大于5μm。在一些实施 例中，负极集流体的厚度为小于100μm或小于50μm。在一些实施例中，负极集流体的厚度在由上述任意两个数值所组成的范围内。
负极活性物质没有特别限制，只要能够可逆地吸藏、放出锂离子即可。负极活性物质的实例可包括，但不限于，天然石墨、人造石墨等碳材料；硅(Si)、锡(Sn)等金属；或Si、Sn等金属元素的氧化物等。负极活性物质可以单独使用或组合使用。
负极活性物质层还可包括负极粘合剂。负极粘合剂可提高负极活性物质颗粒彼此间的结合和负极活性物质与集流体的结合。负极粘合剂的种类没有特别限制，只要是对于电解液或电极制造时使用的溶剂稳定的材料即可。在一些实施例中，负极粘合剂包括树脂粘合剂。树脂粘合剂的实例包括，但不限于，氟树脂、聚丙烯腈(PAN)、聚酰亚胺树脂、丙烯酸系树脂、聚烯烃树脂等。当使用水系溶剂制备负极合剂浆料时，负极粘合剂包括，但不限于，羧甲基纤维素(CMC)或其盐、苯乙烯-丁二烯橡胶(SBR)、聚丙烯酸(PAA)或其盐、聚乙烯醇等。
负极可以通过以下方法制备：在负极集流体上涂布包含负极活性物质、树脂粘结剂等的负极合剂浆料，干燥后，进行压延而在负极集流体的两面形成负极活性物质层，由此可以得到负极。
IV、隔离膜
为了防止短路，在正极与负极之间通常设置有隔离膜。这种情况下，本申请的电解液通常渗入该隔离膜而使用。
对隔离膜的材料及形状没有特别限制，只要不显著损害本申请的效果即可。所述隔离膜可为由对本申请的电解液稳定的材料所形成的树脂、玻璃纤维、无机物等。在一些实施例中，所述隔离膜包括保液性优异的多孔性片或无纺布状形态的物质等。树脂或玻璃纤维隔离膜的材料的实例可包括，但不限于，聚烯烃、芳香族聚酰胺、聚四氟乙烯、聚醚砜、玻璃过滤器等。在一些实施例中，所述隔离膜的材料为玻璃过滤器。在一些实施例中，所述聚烯烃为聚乙烯或聚丙烯。在一些实施例中，所述聚烯烃为聚丙烯。上述隔离膜的材料可以单独使用或任意组合使用。
所述隔离膜还可为上述材料层积而成的材料，其实例包括，但不限于，按照聚丙烯、聚乙烯、聚丙烯的顺序层积而成的三层隔离膜等。
无机物的材料的实例可包括，但不限于，氧化铝、二氧化硅等氧化物、氮化 铝、氮化硅等氮化物、硫酸盐(例如，硫酸钡、硫酸钙等)。无机物的形式可包括，但不限于，颗粒状或纤维状。
所述隔离膜的形态可为薄膜形态，其实例包括，但不限于，无纺布、织布、微多孔性膜等。在薄膜形态中，所述隔离膜的孔径为0.01μm至1μm，厚度为5μm至50μm。除了上述独立的薄膜状隔离膜以外，还可以使用下述隔离膜：通过使用树脂类的粘合剂在正极和/或负极的表面形成含有上述无机物颗粒的复合多孔层而形成的隔离膜，例如，将氟树脂作为粘合剂使90％粒径小于1μm的氧化铝颗粒在正极的两面形成多孔层而形成的隔离膜。
所述隔离膜的厚度是任意的。在一些实施例中，所述隔离膜的厚度为大于1μm、大于5μm或大于8μm。在一些实施例中，所述隔离膜的厚度为小于50μm、小于40μm或小于30μm。在一些实施例中，所述隔离膜的厚度在由上述任意两个数值所组成的范围内。当所述隔离膜的厚度在上述范围内时，则可以确保绝缘性和机械强度，并可以确保电化学装置的倍率特性和能量密度。
在使用多孔性片或无纺布等多孔质材料作为隔离膜时，隔离膜的孔隙率是任意的。在一些实施例中，所述隔离膜的孔隙率为大于20％、大于35％或大于45％。在一些实施例中，所述隔离膜的孔隙率为小于90％、小于85％或小于75％。在一些实施例中，所述隔离膜的孔隙率在由上述任意两个数值所组成的范围内。当所述隔离膜的孔隙率在上述范围内时，可以确保绝缘性和机械强度，并可以抑制膜电阻，使电化学装置具有良好的倍率特性。
所述隔离膜的平均孔径也是任意的。在一些实施例中，所述隔离膜的平均孔径为小于0.5μm或小于0.2μm。在一些实施例中，所述隔离膜的平均孔径为大于0.05μm。在一些实施例中，所述隔离膜的平均孔径在由上述任意两个数值所组成的范围内。若所述隔离膜的平均孔径超过上述范围，则容易发生短路。当隔离膜的平均孔径在上述范围内时，在防止短路的同时可抑制了膜电阻，使电化学装置具有良好的倍率特性。
V、电化学装置组件
电化学装置组件包括电极组、集电结构、外装壳体和保护元件。
电极组
电极组可以是由上述正极和负极隔着上述隔离膜层积而成的层积结构、以及上述正极和负极隔着上述隔离膜以漩涡状卷绕而成的结构中的任一种。在一些实 施例中，电极组的质量在电池内容积中所占的比例(电极组占有率)为大于40％或大于50％。在一些实施例中，电极组占有率为小于90％或小于80％。在一些实施例中，电极组占有率在由上述任意两个数值所组成的范围内。当电极组占有率在上述范围内时，可以确保电化学装置的容量，同时可以抑制与内部压力上升相伴的反复充放电性能及高温保存等特性的降低，进而可以防止气体释放阀的工作。
集电结构
集电结构没有特别限制。在一些实施例中，集电结构为降低配线部分及接合部分的电阻的结构。当电极组为上述层积结构时，适合使用将各电极层的金属芯部分捆成束而焊接至端子上所形成的结构。电极面积增大时，内部电阻增大，因而在电极内设置2个以上的端子而降低电阻也是适合使用的。当电极组为上述卷绕结构时，通过在正极和负极分别设置2个以上的引线结构，并在端子上捆成束，从而可以降低内部电阻。
外装壳体
外装壳体的材质没有特别限制，只要是对于所使用的电解液稳定的物质即可。外装壳体可使用，但不限于，镀镍钢板、不锈钢、铝或铝合金、镁合金等金属类、或者树脂与铝箔的层积膜。在一些实施例中，外装壳体为铝或铝合金的金属或层积膜。
金属类的外装壳体包括，但不限于，通过激光焊接、电阻焊接、超声波焊接将金属彼此熔敷而形成的封装密闭结构；或者隔着树脂制垫片使用上述金属类形成的铆接结构。使用上述层积膜的外装壳体包括，但不限于，通过将树脂层彼此热粘而形成的封装密闭结构等。为了提高密封性，还可以在上述树脂层之间夹入与层积膜中所用的树脂不同的树脂。在通过集电端子将树脂层热粘而形成密闭结构时，由于金属与树脂的接合，可使用具有极性基团的树脂或导入了极性基团的改性树脂作为夹入的树脂。另外，外装体的形状也是任意的，例如可以为圆筒形、方形、层积型、纽扣型、大型等中的任一种。
保护元件
保护元件可以使用在异常放热或过大电流流过时电阻增大的正温度系数(PTC)、温度熔断器、热敏电阻、在异常放热时通过使电池内部压力或内部温度急剧上升而切断在电路中流过的电流的阀(电流切断阀)等。上述保护元件可 选择在高电流的常规使用中不工作的条件的元件，亦可设计成即使不存在保护元件也不至于发生异常放热或热失控的形式。
VI、应用
本申请的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容器。特别地，该电化学装置是锂二次电池，包括锂金属二次电池、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。
本申请另提供了一种电子装置，其包括根据本申请的电化学装置。
本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何电子装置。在一些实施例中，本申请的电化学装置可用于，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、家庭用大型蓄电池和锂离子电容器等。
下面以锂离子电池为例并且结合具体的实施例说明锂离子电池的制备，本领域的技术人员将理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
实施例
以下说明根据本申请的锂离子电池的实施例和对比例进行性能评估。
一、锂离子电池的制备
1、负极的制备
将人造石墨、丁苯橡胶和羧甲基纤维素钠按照96％:2％:2％的质量比例与去离子水混合，搅拌均匀，得到负极浆料。将该负极浆料涂布在12μm的铜箔上。干燥，冷压，再经过裁片、焊接极耳，得到负极。
2、正极的制备
将正极活性物质、导电材料(Super-P)和聚偏氟乙烯(PVDF)按照95％:2％:3％的质量比例与N-甲基吡咯烷酮(NMP)混合，再加入助剂，搅拌均匀，得到正极浆料。将该正极浆料涂布在12μm的铝箔上，干燥，冷压，再经过裁片、焊接 极耳，得到正极。
实施例或对比例中使用的正极活性物质通过商购获得，具体如下表所示：
Figure PCTCN2020094652-appb-000005
实施例或对比例中使用的助剂如下表所示：
助剂 名称(商品名) 氧化电位 还原电位 表面张力
1 丙烯酸(2-乙基己基)酯 4.75V 0.1V 38mN/m
2 丙烯酸酯非离子氟碳表面活性剂 4.8V 0.2V 35mN/m
3 甲基丙烯酸十二烷基酯 4.7V 0.2V 38mN/m
4 丙烯酸(酯)类共聚物 4.8V 0.2V 36mN/m
5 马来酸丙烯酸 4.7V 0.3V 37mN/m
6 聚乙烯吡咯烷酮(缩写PVP) 4.5V 0.1V 45mN/m
7 聚醚硅氧烷 4.7V 0.5V 45mN/m
8 平平加 4.6V 0.8V 47mN/m
9 十六烷基磺酸钠 4.7V 0.7V 46mN/m
3、电解液的制备
在干燥氩气环境下，将EC、PC、PP和DEC(重量比1:1:1:1)混合，加入LiPF 6混合均匀，形成基础电解液，其中LiPF 6的浓度为1.15mol/L。在基础电解液中加入不同含量的添加剂得到不同实施例和对比例的电解液。
实施例中使用的电解液组分如下表所示：
材料名称 缩写 材料名称 缩写
碳酸乙烯酯 EC 碳酸丙烯酯 PC
碳酸二乙酯 DEC 丙酸乙酯 EP
丙酸丙酯 PP γ-丁内酯 GBL
丁二腈 SN 己二腈 ADN
乙二醇二(2-氰基乙基)醚 EDN 1,3,6-己烷三腈 HTCN
1,2,3-三(2-氰基乙氧基)丙烷 TCEP 式1化合物 1a
1,3-丙磺酸内酯 PS 氟代碳酸乙烯酯 FEC
4、隔离膜的制备
以聚乙烯(PE)多孔聚合物薄膜作为隔离膜。
5、锂离子电池的制备
将得到的正极、隔离膜和负极按次序卷绕，置于外包装箔中，留下注液口。从注液口灌注电解液，封装，再经过化成、容量等工序制得锂离子电池。
二、测试方法
1、正极活性物质层相对非水溶剂的接触角的测试方法
在正极活性物质层表面滴加3微升碳酸二乙酯，在100秒内使用JC2000D3E型接触角测量仪进行测试，选用5点拟合法(即，先取液滴左右平面2点，确定液固交接面，然后在液滴圆弧上取3点)进行拟合，得到正极活性物质层相对非水溶剂的接触角。每个样品至少测量3次，选取至少3个差值小于5°的数据，取平均值，得到正极活性物质层相对非水溶剂的接触角。
2、正极活性物质层的反应面积(Y)的测试方法
使用表面积计(大仓理研制造的全自动表面积测定装置)，在氮气流通下于350℃对样品进行15分钟预干燥，然后使用氮气相对于大气压的相对压力值准确调节为0.3的氮氦混合气体，通过采用气体流动法的氮吸附BET单点法测定正极活性物质层的比表面积(m 2/mg)。通过下式计算正极活性物质层的反应面积(Y)：
Y＝正极活性物质层的比表面积×正极活性物质层的重量。
3、锂离子电池的循环后容量保持率的测试方法
在45℃下，将锂离子电池以1C恒流充电至4.45V，然后以4.45V恒压充电至电流为0.05C，再以1C恒流放电至3.0V，此为首次循环。按照上述条件对锂离子电池进行200次循环。“1C”是指在1小时内将锂离子电池容量完全放完的电流值。通过下式计算锂离子电池的循环后容量保持率：
循环后容量保持率＝(循环200次后的放电容量/首次循环的放电容量)×100％。
4、锂离子电池的倍率性能的测试方法
在25℃下，将锂离子电池以0.2C放电至3.0V，静置5分钟。然后将锂离子电池以0.5C充电到4.45V，以4.45V恒压充电到0.05C，静置5分钟。调整放电倍率，分别以0.2C和1.5C进行放电测试，得到放电容量，以1.5C倍率下得到的容量与0.2C得到的容量的比值记为倍率百分比。
5、锂离子电池的直流阻抗(DCR)的测试方法
在25℃下，将锂离子电池以1.5C恒流充电至4.45V，再以4.45V恒压充电至0.05C，静置30分钟。然后以0.1C放电10秒，记录电压值为U1。然后以1C放电360秒，记录电压值为U2)。“1C”是在1小时内将电池容量完全放完的电流值。按如下公式计算得出锂离子电池的直流阻抗：
直流阻抗＝(U2-U1)/(1C-0.1C)。
除非有特殊说明，本申请所述的直流阻抗指的是锂离子电池在50％荷电状态(SOC)状态下的值。
三、测试结果
表1展示了各实施例和对比例中正极活性物质层相对非水溶剂的接触角以及正极活性物质层中的助剂对锂离子电池的性能的影响。在表1所示各实施例和对比例中，正极活性物质为材料1，电解液包含0.2wt％的式1a化合物。
表1
Figure PCTCN2020094652-appb-000006
结果表明，助剂及其含量可影响正极活性物质层相对非水溶剂的接触角。特定添加剂可增加正极活性物质浆料中各组分之间的相互作用，使浆料分布更均匀，从而降低正极活性物质层相对非水溶剂的接触角。当正极活性物质层相对非水溶剂的接触角不大于45°时，可显著提升锂离子电池的循环后容量保持率和倍率百分比，并显著降低锂离子电池的直流电阻。在正极活性物质层相对非水溶剂的接触角不大于45°的基础上，控制助剂的含量不大于3000ppm可进一步提升锂离子电池的循环后容量保持率和倍率百分比，并进一步降低锂离子电池的直流电阻。
表2展示了正极活性物质对锂离子电池的性能的影响。实施例11-15与实施例3的区别仅在于表2中所列的正极活性物质。
表2
  正极活性物质 循环后容量保持率 倍率百分比 DCR(mΩ)
实施例3 材料1 79％ 77％ 45
实施例11 材料2 82％ 81％ 34
实施例12 材料3 85％ 84％ 32
实施例13 材料4 86％ 85％ 30
实施例14 材料5 81％ 82％ 37
实施例15 材料6 82％ 85％ 32
结果表明，当正极活性物质包括具有不同中值粒径的含锂过渡金属氧化物时，可进一步提升锂离子电池的循环后容量保持率和倍率百分比并进一步降低其直流电阻。当含锂过渡金属氧化物含有Mg和选自Ti、Zr、Ge、Nb、Al和Sn中的至少一种金属元素时，锂离子电池的循环性能、倍率性能和直流电阻的改善尤为明显。
表3展示了电解液中式1a化合物的含量对锂离子电池的性能的影响。实施例16-22与实施例3的区别仅在于表3中所列的参数。
表3
  1a含量(wt％) 循环后容量保持率 倍率百分比 DCR(mΩ)
实施例3 0.2 79％ 77％ 45
实施例16 0.5 85％ 83％ 26
实施例17 1 86％ 87％ 23
实施例18 2 80％ 81％ 29
实施例19 0.001 71％ 75％ 38
实施例20 0.005 72％ 80％ 36
实施例21 0.0008 66％ 71％ 49
实施例22 3 70％ 68％ 51
结果表明，当式1a化合物在电解液中的含量在0.001wt％至2wt％范围内时，可进一步显著改善锂离子电池的循环性能、倍率性能和直流电阻。式1b和式1c与式1a的区别仅在于碳链长度，其可实现与式1a基本相当的效果。
表4展示了式1化合物的重量与正极活性物质层的反应面积的关系对锂离子电池的性能的影响。实施例23-26与实施例3的区别仅在于表4中所列的参数。
表4
Figure PCTCN2020094652-appb-000007
结果表明，当式1化合物在电解液中的含量X mg与正极活性物质层的反应面积Y m 2满足10≤X/Y≤100时，有助于进一步提升锂离子电池的循环性能、倍率性能和直流电阻。
表5展示了电解液中添加剂对锂离子电池的性能的影响。实施例27-34与实施例3的区别仅在于表5中所列的参数。
表5
Figure PCTCN2020094652-appb-000008
结果表明，当电解液进一步包含添加剂时，有助于进一步改善锂离子电池的循环性能、倍率性能和直流电阻。
整个说明书中对“实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例”，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (12)

  1. 一种电化学装置，其包括正极、负极和电解液，其中所述正极包括正极活性物质层，其中经接触角测定法测定，所述正极活性物质层相对非水溶剂的接触角不大于45°。
  2. 根据权利要求1所述的电化学装置，其中所述接触角测定法是指在所述正极活性物质层表面滴加3微升碳酸二乙酯的液滴后，在100秒内测试所述液滴在所述正极活性物质层的表面的接触角。
  3. 根据权利要求1所述的电化学装置，其中所述正极活性物质层包括具有亲水基团和亲油基团的助剂。
  4. 根据权利要求3所述的电化学装置，其中所述助剂具有以下特征中的至少一者：
    (a)氧化电位不小于4.5V，且还原电位不大于0.5V；
    (b)表面张力不大于40mN/m；
    (c)包括不饱和羧酸基团；
    (d)基于所述正极活性物质层的总重量，所述助剂的含量为不大于3000ppm。
  5. 根据权利要求3所述的电化学装置，其中所述助剂包括2-丙烯酸十二烷基酯、聚乙二醇单甲醚丙烯酸酯、聚乙二醇二甲基丙烯酸酯、丙烯酸(2-乙基己基)酯、丙烯酸酯非离子氟碳表面活性剂、甲基丙烯酸十二烷基酯、甲基丙烯酸十二烷基酯、丙烯酸(酯)类共聚物、马来酸丙烯酸共聚物或乙烯丙烯酸共聚物中的至少一种。
  6. 根据权利要求1所述的电化学装置，其中所述电解液包含式1化合物：
    Figure PCTCN2020094652-appb-100001
    其中R为取代或未取代的C 1-C 10烃基，且当取代时，取代基为卤素，
    基于所述电解液的总重量，所述式1化合物的含量为0.001wt％至2wt％。
  7. 根据权利要求6所述的电化学装置，其中所述式1化合物包含以下结构式中的至少一种：
    Figure PCTCN2020094652-appb-100002
  8. 根据权利要求6所述的电化学装置，其中所述式1化合物在所述电解液中的含量X mg与所述正极活性物质层的反应面积Y m 2满足如下关系：10≤X/Y≤100。
  9. 根据权利要求1所述的电化学装置，其中所述正极活性物质层包括正极活性物质，所述正极活性物质包括具有不同中值粒径的含锂过渡金属氧化物。
  10. 根据权利要求9所述的电化学装置，其中所述含锂过渡金属氧化物包括通式(1)表示的化合物，
    Li aM1 bM2 cM3 dO 2   (1)
    其中：
    M1选自Co、Ni或Mn中的至少一种；
    M2选自Mg、Ti、Zr、Ge、Nb、Al或Sn中的至少一种；
    M3是除Li、M1和M2以外的元素；
    0.5≤a＜1.1；
    0.8≤b＜1.2；
    0.002≤c≤0.05；以及
    0≤d≤0.05。
  11. 根据权利要求10所述的电化学装置，其中所述含锂过渡金属氧化物包括Mg和选自Ti、Zr、Ge、Nb、Al和Sn中的至少一种金属元素。
  12. 一种电子装置，其包括根据权利要求1-11中任一项所述的电化学装置。
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