WO2022174547A1 - 电化学装置和包含该电化学装置的电子装置 - Google Patents

电化学装置和包含该电化学装置的电子装置 Download PDF

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WO2022174547A1
WO2022174547A1 PCT/CN2021/104736 CN2021104736W WO2022174547A1 WO 2022174547 A1 WO2022174547 A1 WO 2022174547A1 CN 2021104736 W CN2021104736 W CN 2021104736W WO 2022174547 A1 WO2022174547 A1 WO 2022174547A1
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negative electrode
electrochemical device
electrolyte
oxide
silicon
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PCT/CN2021/104736
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English (en)
French (fr)
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袁晓
张水蓉
张丽兰
唐超
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宁德新能源科技有限公司
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Publication of WO2022174547A1 publication Critical patent/WO2022174547A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—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
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to an electrochemical device and an electronic device including the electrochemical device.
  • Electrochemical devices eg, lithium-ion batteries
  • Silicon material has a large lithium storage capacity and is abundant in the earth, making it an ideal anode material for lithium-ion batteries.
  • the present application provides an electrochemical device comprising a positive electrode, a negative electrode, a separator and an electrolyte, the negative electrode comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector,
  • the negative electrode active material layer includes a silicon material
  • the electrolyte includes fluoroethylene carbonate
  • the electrochemical device satisfies the following relationship: 0.014 ⁇ X/(Y ⁇ 2 ⁇ Z) ⁇ 1.28, wherein X represents fluorine The weight percentage of ethylene carbonate in the electrolyte, and 5% ⁇ X ⁇ 30%, Y represents, in mg/ cm2 , the weight of the negative active material layer per unit area on one side, and 1.95 ⁇ Y ⁇ 11.69, Z represents the weight percentage of silicon material in the negative electrode active material layer.
  • 5% ⁇ Z ⁇ 60% 5% ⁇ Z ⁇ 60%.
  • the electrolyte further comprises a non-fluorinated cyclic carbonate and a chain carbonate, wherein the weight of the non-fluorinated cyclic carbonate accounts for the weight of the non-fluorinated cyclic carbonate And the percentage of the total amount of chain carbonate is 5% to 50%. Within this range, the lithium ion dissociation performance of the electrolyte is maintained at a high level.
  • the electrolytic solution further comprises a polynitrile compound that satisfies at least one of the conditions (a) to (c): (a) the polynitrile compound is in the electrolytic solution The weight percentage is 0.1% to 6%; (b) the polynitrile compound includes the compound of formula II:
  • R 21 , R 22 , R 23 and R 24 are each independently selected from hydrogen, cyano, C 1 -C 10 alkyl, cyano-containing C 1 -C 10 alkyl or cyano-containing C 1 - C 10 ether group, the total number of cyano groups contained in R 21 , R 22 , R 23 and R 24 is two or more; (c) the polynitrile compound contains 1,2,3-tri-(2-cyanoethyl) oxy) propane, 1,3,6-hexanetrinitrile, adiponitrile, succinonitrile,
  • the electrolyte further comprises a boron-containing lithium salt, and the weight percentage of the boron-containing lithium salt in the electrolyte is A, and the boron-containing lithium salt satisfies the condition (d ) to at least one of (f):
  • the boron-containing lithium salt compound includes or is selected from the following substances At least one of:
  • a and Z satisfy 0.002 ⁇ A/Z ⁇ 1.5.
  • the electrolyte further comprises a cyclic ether, and the weight percentage B of the cyclic ether in the electrolyte is 0.4% ⁇ B ⁇ 1%.
  • 0.004 ⁇ B/Z ⁇ 1 is satisfied between B and Z.
  • the silicon material includes silicon oxide, simple silicon, or a mixture of the two.
  • the Dv50 of the silicon material ranges from 2.5 ⁇ m to 20 ⁇ m.
  • At least a part of the surface of the silicon material has an oxide coating layer, wherein the oxide coating layer comprises aluminum oxide, titanium oxide, manganese oxide, vanadium oxide, At least one of silicon oxide, chromium oxide, zirconium oxide, or cobalt oxide.
  • the oxide cladding layer has a thickness of 2 nm to 1000 nm.
  • the present application further provides an electronic device, the electronic device comprising the electrochemical device described in the first aspect of the present application.
  • the electrochemical device provided by the present application includes a positive electrode, a negative electrode and an electrolyte
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer coated on at least one surface of the negative electrode current collector
  • the negative electrode active material layer includes a silicon material
  • the electrolyte contains fluoroethylene carbonate
  • the electrochemical device satisfies the following relationship: 0.014 ⁇ X/(Y ⁇ 2 ⁇ Z) ⁇ 1.28, where X represents the amount of fluoroethylene carbonate in the electrolyte % by weight, and 5% ⁇ X ⁇ 30%, Y represents, in mg/ cm2 , the weight of the negative electrode active material layer coated on one side of the negative electrode current collector per unit area, and 1.95 ⁇ Y ⁇ 11.69, Z Indicates the weight percentage of silicon material in the negative electrode active material layer.
  • Fluorinated ethylene carbonate can form an SEI film on the surface of the negative electrode, and repair the SEI film during the cycle, and then equipped with the weight of the negative electrode active material and the ratio of silicon material in the active material, the prepared electrochemical device can take into account high Cycling performance and storage performance, as well as higher energy density, have broad application prospects.
  • X/(Y ⁇ 2 ⁇ Z) is 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.12, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.5, 0.6, 0.8, 0.9, 1.1, or a range of any two values.
  • X is 5%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 28%, 30%, or a range of any two values.
  • Z is 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 28%, 30%, 35%, 38%, 40%, 45%, 48% %, 50%, 55%, 60%, or a range of any two values.
  • Y is 1.95, 2.0, 2.1, 2.5, 2.8, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or a range of any two values. In some embodiments, Y is 5.19 to 9.59.
  • the electrolyte further comprises a non-fluorinated cyclic carbonate and a chain carbonate, wherein the weight of the non-fluorinated cyclic carbonate accounts for the weight of the non-fluorinated cyclic carbonate And the percentage of the total amount of chain carbonate is 5% to 50%. Within this range, the lithium ion dissociation performance of the electrolyte is maintained at a high level.
  • the non-fluorinated cyclic carbonate can be selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, and ⁇ -butyrolactone.
  • the chain carbonate can be selected from one or more selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and propyl methyl carbonate.
  • the electrolyte further comprises a carboxylate
  • the carboxylate can be selected from ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, ethyl butyrate, butyl One or more of propyl esters.
  • the electrolytic solution further comprises a polynitrile compound, and the weight percentage of the polynitrile compound in the electrolytic solution is 0.1% to 6%.
  • the weight percentage of the polynitrile compound in the electrolyte is 1.0%, 1.1%, 1.2%, 1.3%, 1.5%, 1.6%, 1.8%, 2.0%, 2.5%, 3.0%, 4.0%, 5.0%, 6.0% or a range of any two values.
  • the polynitrile compound includes a compound of formula II:
  • R 21 , R 22 , R 23 and R 24 are each independently selected from hydrogen, cyano, C 1 -C 10 alkyl, cyano-containing C 1 -C 10 alkyl or cyano-containing C 1 - C 10 ether group, the total number of cyano groups contained in R 21 , R 22 , R 23 and R 24 is two or more.
  • the cyano-containing alkyl group is -(CH 2 )a-CN or Among them, a is an integer of 1-10, b is an integer of 0-10, and c is an integer of 0-10.
  • the cyano-containing ether group is -(CH 2 ) d -O-(CH 2 ) e -CN or Wherein, d is an integer of 0-10, e is an integer of 1-10, f and h are each independently an integer of 0-10, and g and i are each independently an integer of 1-10.
  • the integer of 0-10 refers to 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10; the integer of 1-10 refers to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
  • the alkyl group is a C 1 -C 6 alkyl group. According to some embodiments, the alkyl group is ethyl, propyl, butyl, or pentyl, and the like.
  • the polynitriles include 1,2,3-tris-(2-cyanoethoxy)propane, 1,3,6-hexanetrinitrile, adiponitrile, succinic acid Nitrile,
  • the polynitrile compound includes a dinitrile compound and a polynitrile compound having two or more cyano groups, the dinitrile compound includes at least one of adiponitrile or succinonitrile, the two
  • the polynitrile compounds having more than one cyano group include 1,2,3-tri-(2-cyanoethoxy)propane, 1,3,6-hexanetrinitrile,
  • the electrolyte further comprises a boron-containing lithium salt
  • the weight percentage of the boron-containing lithium salt in the electrolyte is A, 0.1% ⁇ A ⁇ 1.5%.
  • A is 0.1%, 0.2%, 0.5%, 0.6%, 0.8%, 0.9%, 1.0%, 1.1%, 1.3%, 1.4%, 1.5%, or a range of any two values.
  • the introduction of boron-containing lithium salts will preferentially form films to protect the positive and negative electrodes, thereby improving the cycle stability of the electrochemical device.
  • a and Z satisfy 0.002 ⁇ A/Z ⁇ 1.5, such as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.1, 0.2, 0.5, 0.7, 0.9, 1.1, 1.3 or A range composed of any two values, within this range, the capacity retention rate is high.
  • the boron-containing lithium salt compound includes or is selected from at least one of the following substances:
  • the boron-containing lithium salt includes or is lithium difluorooxalate borate. According to some embodiments, the boron-containing lithium salt includes or is lithium bisoxalatoborate. The boron-containing lithium salts include lithium difluorooxalate borate and lithium bisoxalate borate.
  • the electrolyte further comprises a cyclic ether
  • the weight percentage B of the cyclic ether in the electrolyte is 0.4% ⁇ B ⁇ 1%, for example, B is 0.5%, 0.6% %, 0.7%, 0.8%, 0.9% or a range of any two values.
  • B and Z satisfy 0.004 ⁇ B/Z ⁇ 1, for example, B/Z is 0.005, 0.008, 0.01, 0.015, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.1 , 0.2, 0.5, 0.6, 0.7, 0.8, 0.9, or a range of any two values.
  • the introduction of cyclic ethers can improve storage and keep capacity retention at a high level.
  • the cyclic ether is selected from 1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, 1,3-dioxolane at least one of ring, 2-methyl-1,3-dioxolane, tetrahydropyran and tetrahydrofuran.
  • the silicon material includes silicon oxide, simple silicon, or a mixture of the two.
  • the silicon material includes nano-silicon, silicon oxide, silicon alloy or silicon nanowire.
  • the silicon-based negative electrode materials can be of three types, one is a composite material composed of elemental silicon or the same carbon; the other is a composite material of silicon oxide or a carbon material. The third is the alloy material composed of silicon and other metal elements.
  • the Dv50 of the silicon material ranges from 2.5 ⁇ m to 20 ⁇ m.
  • the average particle diameter D50 of the negative electrode active material is 5 ⁇ m to 15 ⁇ m.
  • the oxide coating layer comprises aluminum (Al) oxide, titanium (Ti) oxide, manganese ( At least one of Mn) oxide, vanadium (V) oxide, silicon (Si) oxide, chromium (Cr) oxide, zirconium (Zr) oxide, or cobalt (Co) oxide.
  • the oxide cladding layer has a thickness of 2 nm to 1000 nm.
  • the oxide cladding layer has a thickness of 100 nm to 800 nm.
  • the oxide cladding layer has a thickness of 200 nm to 600 nm.
  • the negative electrode further includes a conductive layer
  • the conductive layer includes a conductive material.
  • conductive materials include carbon-based materials (eg, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotubes, graphene, etc.), metal-based materials (eg, metal powders, metal fibers, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (eg, polyphenylene derivatives), and mixtures thereof.
  • the negative current collectors used in the present application may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, conductive metal clad polymer substrates, and combinations thereof.
  • the electrolyte includes a lithium salt selected from lithium hexafluorophosphate (LiPF 6 ), lithium bistrifluoromethanesulfonimide LiN(CF 3 SO 2 ) 2 (LiTFSI), or bismuth At least one of lithium (fluorosulfonyl)imide (Li(N(SO 2 F) 2 )).
  • the lithium salt concentration is 0.3 mol/L to 2 mol/L.
  • the lithium salt concentration is between 0.8 mol/L and 1.3 mol/L.
  • the electrolyte further comprises at least one of unsaturated acid anhydrides, cyclic sulfates, cyclic sultones or sulfones.
  • the unsaturated acid anhydride can be selected from at least one of succinic anhydride, maleic anhydride and 2-methylmaleic anhydride;
  • the cyclic sulfate can be selected from one of vinyl sulfate and propylene sulfate or Two kinds;
  • the cyclic sultone can be selected from 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone and methylene disulfonate at least one of sulfolane;
  • the sulfone can be sulfolane.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material disposed on the positive electrode current collector.
  • the specific types of the positive electrode active materials are not specifically limited, and can be selected according to requirements.
  • the positive electrode active material can be selected from lithium cobalt oxide (LiCoO 2 ), lithium nickel manganese cobalt ternary material, lithium manganate (LiMn 2 O 4 ), lithium nickel manganate (LiNi 0.5 Mn 1.5 O 4 ), phosphoric acid
  • LiCoO 2 lithium cobalt oxide
  • LiMn 2 O 4 lithium nickel manganese cobalt ternary material
  • LiMn 2 O 4 lithium manganate
  • LiNi 0.5 Mn 1.5 O 4 lithium nickel manganate
  • phosphoric acid One or more of lithium iron (LiFePO 4 ) and its doping and/or coating modification compounds, but this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials can also be used s material.
  • These positive electrode active materials may be used alone or in combination of two or more.
  • a coating layer is provided on at least a part of the surface of the positive electrode active material particle.
  • the coating layer can play the role of isolating the electrolyte, which can greatly reduce the side reaction between the electrolyte and the positive electrode active material, reduce the dissolution of transition metals, and improve the electrochemical stability of the positive electrode active material.
  • the coating layer can be a carbon layer, a graphene layer, an oxide layer, an inorganic salt layer or a conductive polymer layer.
  • Oxides can be oxides formed by one or several elements of Al, Ti, Mn, Zr, Mg, Zn, Ba, Mo, B; inorganic salts can be Li 2 ZrO 3 , LiNbO 3 , Li 4 Ti 5 One or more of O 12 , Li 2 TiO 3 , Li 3 VO 4 , LiSnO 3 , Li 2 SiO 3 , LiAlO 2 ; the conductive polymer can be polypyrrole (PPy), polyethylene 3,4-ethylene oxythiophene (PEDOT) or polyamide (PI).
  • PPPy polypyrrole
  • PEDOT polyethylene 3,4-ethylene oxythiophene
  • PI polyamide
  • the positive electrode current collector for the electrochemical device according to the present application may be aluminum (Al), but is not limited thereto.
  • the material and shape of the separator used in the electrochemical device of the present application are not particularly limited, and it may be any technique disclosed in the prior art.
  • the separator includes a polymer or inorganic or the like formed from a material that is stable to the electrolyte of the present application.
  • the separator may include a substrate layer and a surface treatment layer.
  • the base material layer is a non-woven fabric, film or composite film with a porous structure, and the material of the base material layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected.
  • At least one surface of the base material layer is provided with a surface treatment layer, and the surface treatment layer may be a polymer layer or an inorganic material layer, or a layer formed by mixing a polymer and an inorganic material.
  • the inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, At least one of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.
  • the binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinylalkoxy , at least one of polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer is selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinylalkoxy, polyvinylidene fluoride, At least one of poly(vinylidene fluoride-hexafluoropropylene).
  • the present application further provides an electronic device comprising the electrochemical device described herein.
  • the electrolyte solution according to the present application can suppress an increase in the direct current internal resistance of the electrochemical device, so that the electrochemical device thus manufactured is suitable for electronic equipment or devices in various fields.
  • electronic devices of the present application include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets , VCR, LCD TV, Portable Cleaner, Portable CD Player, Mini CD, Transceiver, Electronic Notepad, Calculator, Memory Card, Portable Recorder, Radio, Backup Power, Motor, Automobile, Motorcycle, Power-assisted Bicycle, Bicycle , lighting equipment, toys, game consoles, clocks, power tools, flashes, cameras, large household batteries and lithium-ion capacitors, etc.
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with any other lower limit to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range.
  • each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range that is not expressly recited.
  • a list of items to which the terms "at least one of,” “at least one of,” “at least one of,” or other similar terms are linked to can mean any combination of the listed items. For example, if items A and B are listed, the phrase “at least one of A and B” means A only; B only; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C” means A only; or B only; C only; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • the lithium ion batteries in the examples and comparative examples were prepared according to the following methods:
  • Electrolytes were set up according to the following examples and comparative examples.
  • the positive electrode active material lithium cobalt oxide (LiCoO 2 ), the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) were mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 96:2:2. Stir and mix to form a uniform positive electrode slurry; coat the slurry on the aluminum foil of the positive electrode current collector, dry, cold-press and weld the tabs to obtain the positive electrode.
  • NMP N-methylpyrrolidone
  • the specific preparation process is as follows: weigh the negative electrode active material (mixture of artificial graphite and silicon-oxygen negative electrode active material), carbon nanotube conductive agent, and thickener sodium carboxymethyl cellulose (CMC) in the material tank in proportion to carry out pre-treatment Mix for 30min, then add adhesive (50% styrene-butadiene rubber (SBR) aqueous emulsion, half of 10% polyacrylic acid aqueous solution), add an appropriate amount of deionized water as solvent, and mechanically mix to make a viscous negative electrode The slurry is uniformly coated on the copper foil, dried, cold-pressed, and welded to the tabs to obtain a negative electrode.
  • adhesive 50% styrene-butadiene rubber (SBR) aqueous emulsion, half of 10% polyacrylic acid aqueous solution
  • the diaphragm is made of polyethylene (PE) diaphragm.
  • the positive electrode, the separator and the negative electrode are stacked in order so that the separator is placed between the positive electrode and the negative electrode to isolate the positive electrode and the negative electrode. Then, the separator is wound and placed in the outer packaging foil. , After vacuum packaging, standing, forming, shaping and other processes, the preparation of lithium-ion batteries is completed.
  • the double-sided negative electrode active material takes a 5cm ⁇ 5cm area, scrape off the material except the current collector, weigh it, add a certain amount of concentrated nitric acid for microwave digestion, and obtain a solution, and the obtained solution and filter residue are multiplied.
  • the plasma intensity of silicon in it is tested by ICP-OES, and the silicon content in the solution is calculated according to the standard curve of the measured elements, so as to calculate the amount of silicon contained in the material; silicon element Divide the amount by the weight of the negative electrode material to obtain the weight percentage of silicon in the negative electrode material.
  • Capacity retention rate residual discharge capacity/initial discharge capacity ⁇ 100%.
  • Table 1 shows the weight percentage X of FEC in the electrolyte, the coating weight value Y per unit area of the single side of the negative active material layer and the weight percentage Z of the silicon material in the negative active material for the lithium ion battery at 80°C The effect of storage expansion rate and capacity retention rate for 6h.
  • the weight ratio of ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) was 1:2:7.
  • the total amount of cyclic carbonate (EC and PC) was 30% based on the total weight of carbonate.
  • Comparative Example 1 does not satisfy 0.014 ⁇ X/(Y ⁇ 2 ⁇ Z) ⁇ 1.28, and its capacity retention rate is poor.
  • Comparative Examples 2 and 3 satisfy 0.014 ⁇ X/(Y ⁇ 2 ⁇ Z) ⁇ 1.28, X or Y exceeds the desired range of the present application (ie, 5% ⁇ X ⁇ 30% and 1.95 ⁇ Y ⁇ 11.69) , the capacity retention rate of lithium-ion batteries has not been effectively improved.
  • Examples 1-15 not only satisfy 0.014 ⁇ X/(Y ⁇ 2 ⁇ Z) ⁇ 1.28, but also 5% ⁇ X ⁇ 30% and 1.95 ⁇ Y ⁇ 11.65, so the capacity retention rate of the lithium-ion battery is significantly improved.
  • the volume expansion of the Si anode is large during the cycling process, and the SEI film is easily damaged, which deteriorates the cycling performance. Destruction of the SEI film during cycling while reducing electrolyte consumption in Li-ion batteries. As a result, the capacity retention rate of the lithium-ion battery is significantly improved.
  • Example 12 to Example 15 when X was gradually increased in the range of 5% to 30%, the capacity retention rate of the lithium-ion battery gradually increased, and the swelling rate also increased gradually after storage at 80 °C for 6 h. This is because FEC is unstable at high temperature and is prone to side reactions, resulting in an increase in the expansion rate during storage, while an increase in FEC content enhances the SEI repair ability during cycling, thereby increasing the capacity retention rate of lithium-ion batteries.
  • Table 2 shows the effect of the total amount and proportion of cyclic carbonates (EC and PC) on the capacity retention of Li-ion batteries.
  • the examples shown in Table 2 are further improvements based on Example 1, that is, the difference is only in the parameters in Table 2.
  • the contents of EC, PC, and DEC in Table 2 are calculated based on the total weight of the solvent system.
  • Example 16 to Example 22 As shown in Example 16 to Example 22, as EC:PC was varied in the range of 0.2-2, the capacity retention of lithium-ion batteries was affected, and the storage expansion rate was affected by the change of EC content. This is because EC has a high reduction potential and is easy to participate in film formation on the negative electrode. With the increase of its content, the film formation reaction increases, and it is easy to decompose and produce gas during storage and cycling, resulting in a decrease in the capacity retention rate and an increase in the battery expansion rate. When the EC:PC is between 0.3 and 1, the lithium-ion battery not only has a high dissociation ability, but also maintains a high capacity retention rate and a low storage expansion rate.
  • Example 23 to Example 24 although EC:PC is in the range of 0.3-1, since the sum of EC and PC is greater than 50%, the overall viscosity of the electrolyte is higher at this time, which affects ion dissociation and migration, So that the capacity retention rate is at a lower level.
  • Table 3 shows the effect of polynitrile additives on the expansion rate and capacity retention rate of lithium-ion batteries stored at 80°C for 6 hours.
  • the examples shown are improvements based on Example 1, that is, the difference is only in Table 3.
  • the contents of dinitrile and polynitrile compounds with more than two cyano groups in Table 3 are calculated based on the total weight of the electrolyte.
  • Example 25 to Example 30 As shown in Example 25 to Example 30, as the total amount of nitrile was changed in the range of 0.5% to 6%, the stability of the polynitrile compound to the positive electrode was gradually enhanced, so the storage expansion rate of the lithium ion battery gradually decreased. As shown in Example 31, when the total amount of polynitriles reached 8%, although the storage expansion ratio was low, the capacity retention ratio deteriorated remarkably. This is because when the total content of polynitriles is low, the interface of the positive electrode cannot be effectively protected, and the transition metal ions are dissolved during the storage process, and the structure of the positive electrode material collapses, which affects the storage expansion rate. The viscosity of the polynitrile compound is high.
  • Table 4 lists the effects of boron-containing lithium salts on the storage expansion rate and capacity retention rate of lithium-ion batteries. Each embodiment shown in Table 4 is an improvement on the basis of Embodiment 1, that is, the difference lies in the parameters in Table 4.
  • Example 35 to Example 38 the addition of boron-containing lithium salt can effectively improve the capacity retention.
  • Example 39 and 40 when more boron-containing lithium salt was added, the capacity retention rate decreased, and the storage expansion rate at 80°C increased, because the high content of boron-containing lithium salt would increase the battery impedance, Lithium precipitation is prone to occur during the cycle, which reduces the capacity retention rate, and the boron-containing lithium salt is easily decomposed during storage to produce gas, which affects the storage at 80 °C. Therefore, it is necessary to control the content of boron-containing lithium salt within a certain range.
  • Example 41 shows that the ratio of the content of boron-containing lithium salt to the content of Si needs to be between 0.002 and 1.5, and a higher capacity retention rate can be obtained.
  • Table 5 lists the effects of cyclic ether content and its ratio to Si content on the storage expansion rate and capacity retention rate of lithium-ion batteries. Each embodiment shown in Table 5 is an improvement on the basis of Embodiment 1, that is, the difference only lies in the parameters in Table 5.
  • Example 42 to Example 48 when B/Z is between 0.04 and 1, the storage expansion rate decreases. It can be seen from Examples 49 to 51 that the content of 1,3 dioxane needs to be within Within a certain range, the storage can be improved while keeping the capacity retention rate at a high level.
  • Table 6 lists the effect of the Dv50 of the anode silicon material on the storage expansion rate and capacity retention rate of the lithium-ion battery. Each embodiment shown in Table 6 is an improvement on the basis of Embodiment 1, that is, the difference only lies in the parameters in Table 6.
  • Example 52 and Example 54 By comparing Example 52 and Example 54 to Example 57 in Table 6, it can be seen that when the Dv50 of the silicon material is less than 2.5 ⁇ m, the capacity retention rate of the lithium ion battery is low. As shown in Example 58, the silicon material has a lower capacity retention rate. When the Dv50 is greater than 20 ⁇ m, the capacity retention rate of lithium-ion batteries is low. Compared with Example 52 and Example 53, when Dv50 is less than 2.5 ⁇ m, increasing X can improve the capacity retention rate. This is because the negative electrode silicon particles are small and easy to pulverize after coating, which increases the contact surface between the negative electrode material and the electrolyte, and increases the side reactions. The SEI is easily broken during the cycle, thereby deteriorating the capacity retention rate. By increasing the content of FEC, the SEI on the surface of the negative electrode can be repaired and the capacity retention rate can be improved.
  • Table 7 lists the effect of M oxide coating on the capacity retention of Li-ion batteries.
  • Each of the embodiments shown in Embodiment 59 to Embodiment 65 is an improvement on the basis of Embodiment 1, that is, the difference lies in the parameters in Table 7.
  • the mass ratio of Ti and Mn in Examples 64 to 65 was 1:1.
  • the surface of the silicon material contains an oxide coating layer, wherein M includes Ti and Mn, and the coating layer thickness is within a certain range, and its The capacity retention rate is better.
  • Example 66 to Example 68 are improvements based on Example 28, that is, the difference is characterized by the parameters in Table 8.
  • the mass ratio of Ti and Mn in Examples 69 to 71 was 2:1.
  • the surface of the silicon material contains an oxide coating layer, wherein M includes Ti and Mn, and the coating layer thickness is within a certain range, and its Better capacity retention and improved high temperature storage performance.

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Abstract

本申请公开了一种电化学装置及包含该电化学装置的电子装置。本申请的电化学装置包括正极、负极、隔膜和电解液，所述负极包括负极集流体和设置在所述负极集流体至少一个表面上的负极活性物质层，所述负极活性物质层包含硅材料，所述电解液包含氟代碳酸乙烯酯，所述电化学装置满足以下关系式：0.014≤X/(Y×2×Z)≤1.28，其中，X表示氟代碳酸乙烯酯在电解液中所占的重量百分比，并且5％≤X≤30％，Y表示，以mg/cm 2计，单面单位面积的负极活性物质层的重量，并且1.95≤Y≤11.69，Z表示硅材料在负极活性物质层中所占的重量百分比。本申请提供的电化学装置具有较长的循环寿命和良好的存储性能。

Description

电化学装置和包含该电化学装置的电子装置
相关申请的交叉引用
本申请基于申请号为202110199799.1、申请日为2021年2月22日，名称为“电化学装置和包含该电化学装置的电子装置”的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为本申请公开的一部分。
技术领域
本申请涉及一种电化学装置和包含该电化学装置的电子装置。
背景技术
电化学装置(例如，锂离子电池)具有优良的高温保存性能，高能量密度以及长循环寿命，已然成为当今世界最具发展潜力的新型绿色化学电源。随着锂离子电池更轻更小的趋势，需要进一步开发具有高容量密度的锂电池。硅材料具有较大的储锂容量，在地球中的丰富含量，为锂离子电池的理想负极材料。
采用硅材料作为锂离子电池的负极，在电池充放电循环过程中，Li-Si合金的可逆生成与分解伴随着巨大的体积变化，SEI不断的被破坏，引起合金的粉化或裂缝，导致硅材料结构的崩塌和电极材料的剥落，而使电极材料失去电接触，造成硅负极锂离子电池的循环性能急剧下降，同时由于SEI需要不断修复，导致电解液消耗，副反应增多，在充放电过程中会产生大量的气体，容易使电池内部胀气。
发明内容
在第一方面，本申请提供一种电化学装置，其包括正极、负极、隔膜和电解液，所述负极包括负极集流体和设置在所述负极集流体至少一个表面上的负极活性物质层，所述负极活性物质层包含硅材料，所述电解液包含氟代碳酸乙烯酯，所述电化学装置满足以下关系式：0.014≤X/(Y×2×Z)≤1.28，其中，X表示氟代碳酸乙烯酯在电解液中所占的重量百分比，并且5％≤X≤30％，Y表示，以mg/cm 2计，单面单位面积的负极活性物质层的重量，并且1.95≤Y≤11.69，Z表示硅材料在负极活性物质层中所占的重量百分比。
根据本申请的一些实施方式，1％≤Z≤90％。
根据本申请的一些实施方式，5％≤Z≤60％。
根据本申请的一些实施方式，所述电解液还包含非氟代环状碳酸酯和链状碳酸酯，其中，所述非氟代环状碳酸酯的重量占所述非氟代环状碳酸酯和链状碳酸酯总量量的百分比为5％至50％。在此范围内，电解液的锂离子解离性能保持在较高的水平。
根据本申请的一些实施方式，所述电解液进一步包含多腈化合物，所述多腈化合物满足条件(a)至(c)中的至少一种：(a)所述多腈化合物在电解液中所占的重量百分比为0.1％至6％；(b)所述多腈化合物包括式II化合物：
Figure PCTCN2021104736-appb-000001
其中，R 21、R 22、R 23和R 24各自独立地选自氢、氰基、C 1-C 10烷基、含氰基的C 1-C 10烷基或含氰基的C 1-C 10醚基，R 21、R 22、R 23和R 24所含有的氰基的总数为两个以上；(c)所述多腈化合物包含1,2,3-三-(2-氰乙氧基)丙烷、1,3,6-己烷三腈、己二腈、丁二腈、
Figure PCTCN2021104736-appb-000002
Figure PCTCN2021104736-appb-000003
中的至少一种。
根据本申请的一些实施方式，所述电解液进一步包含含硼锂盐，并且所述含硼锂盐在所述电解液中所占的重量百分比为A，所述含硼锂盐满足条件(d)至(f)中的至少一者：
(d)0.1％＜A＜1.5％；(e)所述A与所述Z之间满足0.002＜A/Z＜1.5；(f)所述含硼锂盐化合物包括或者选自以下物质中的至少一种：
Figure PCTCN2021104736-appb-000004
含硼锂盐的引入，会优先成膜，对正负极加以保护，进而提升电化学装置的循环稳定性。根据本发明的一些优选实施方式，A与Z之间满足0.002＜A/Z＜1.5。
根据本申请的一些实施方式，所述电解液进一步包含环醚，并且所述环醚在所述电解液中所占的重量百分比B，0.4％＜B＜1％。
根据本发明的一些实施方式，B与Z之间满足0.004＜B/Z＜1。
根据本申请的一些实施方式，所述硅材料包括硅氧化物、硅单质或二者的混合物。根 据本申请的一些实施方式，所述硅材料的Dv50范围为2.5μm至20μm。
根据本申请的一些实施方式，所述硅材料表面至少一部分区域上具有氧化物包覆层，其中，所述氧化物包覆层包含铝氧化物、钛氧化物、锰氧化物、钒氧化物、硅氧化物、铬氧化物、锆氧化物或钴氧化物中的至少一种。
根据本申请的一些实施方式，所述氧化物包覆层的厚度为2nm至1000nm。
在第二方面，本申请还提供了一种电子装置，所述电子装置包括本申请第一方面所述的电化学装置。
具体实施方式
本申请的实施方式将会被详细的描示在下文中。
本申请提供的电化学装置包括正极、负极和电解液，所述负极包括负极集流体和涂布在所述负极集流体至少一个表面上的负极活性物质层，所述负极活性物质层包含硅材料，所述电解液包含氟代碳酸乙烯酯，所述电化学装置满足以下关系式：0.014≤X/(Y×2×Z)≤1.28，其中，X表示氟代碳酸乙烯酯在电解液中所占的重量百分比，并且5％≤X≤30％，Y表示，以mg/cm 2计，在负极集流体单面单位面积涂布的负极活性物质层的重量，并且1.95≤Y≤11.69，Z表示硅材料在负极活性物质层中所占的重量百分比。
氟代碳酸乙烯酯可以在负极表面形成SEI膜，并在循环过程中对SEI膜进行修复，再配备负极活性物质的重量以及硅材料在活性物质中的比例，所制备的电化学装置可兼顾高循环性能和存储性能，以及较高能量密度，具有广阔的应用前景。
在一些实施例中，0.05≤X/(Y×2×Z)≤0.38。在一些实施例中，X/(Y×2×Z)为0.015、0.020、0.025、0.030、0.035、0.040、0.045、0.05、0.06、0.07、0.08、0.09、0.10、0.12、0.15、0.20、0.25、0.30、0.35、0.40、0.5、0.6、0.8、0.9、1.1或者任意两个数值组成的范围。在一些实施例中，X为5％、5％、8％、10％、12％、15％、18％、20％、25％、28％、30％或者任意两个数值组成的范围。在一些实施例，Z为5％、8％、10％、12％、15％、18％、20％、25％、28％、30％、35％、38％、40％、45％、48％、50％、55％、60％或者任意两个数值组成的范围。在一些实施例，Y为1.95、2.0、2.1、2.5、2.8、3.0、4.0、5.0、6.0、7.0、8.0、9.0或者任意两个数值组成的范围。在一些实施例，Y为5.19至9.59。
根据本申请的一些实施方式，所述电解液还包含非氟代环状碳酸酯和链状碳酸酯，其中，所述非氟代环状碳酸酯的重量占所述非氟代环状碳酸酯和链状碳酸酯总量量的百分比 为5％至50％。在此范围内，电解液的锂离子解离性能保持在较高的水平。根据一些实施例，非氟代环状碳酸酯可选自碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、γ-丁内酯中的一种或几种。根据一些实施例，链状碳酸酯可选自可选自碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸甲丙酯中的一种或几种。
根据本申请的一些实施方式，所述电解液还包含羧酸酯，所述羧酸酯可选自乙酸乙酯、乙酸丙酯、丙酸乙酯、丙酸丙酯、丁酸乙酯、丁酸丙酯中的一种或几种。
根据本申请的一些实施方式，所述电解液进一步包含多腈化合物，所述多腈化合物在所述电解液中所占的重量百分比为0.1％至6％。在一些实施例中，所述多腈化合物在所述电解液中所占的重量百分比为1.0％、1.1％、1.2％、1.3％、1.5％、1.6％、1.8％、2.0％、2.5％、3.0％、4.0％、5.0％、6.0％或任意两个数值组成的范围。
根据本申请的一些实施方式，所述多腈化合物包括式II化合物：
Figure PCTCN2021104736-appb-000005
其中，R 21、R 22、R 23和R 24各自独立地选自氢、氰基、C 1-C 10烷基、含氰基的C 1-C 10烷基或含氰基的C 1-C 10醚基，R 21、R 22、R 23和R 24所含有的氰基的总数为两个以上。
根据本申请的一些实施方式，所述含氰基的烷基为-(CH 2)a-CN或
Figure PCTCN2021104736-appb-000006
其中，a为1-10的整数，b为0-10的整数，c为0-10的整数。
根据本申请的一些实施方式，所述含氰基的醚基为-(CH 2) d-O-(CH 2) e-CN或
Figure PCTCN2021104736-appb-000007
其中，d为0-10的整数，e为1-10的整数，f和h各自独立为0-10的整数，g和i各自独立为1-10的整数。
本申请中，0-10的整数指0、1、2、3、4、5、6、7、8、9、10；1-10的整数指1、2、3、4、5、6、7、8、9、10。
根据本申请的一些实施方式，式II中，所述的烷基为C 1-C 6烷基。根据一些实施例，所述烷基为乙基、丙基、丁基或戊基等。
根据本申请的一些实施方式，所述多腈类化合物包含1,2,3-三-(2-氰乙氧基)丙烷、1,3,6-己烷三腈、己二腈、丁二腈、
Figure PCTCN2021104736-appb-000008
Figure PCTCN2021104736-appb-000009
中的至少一种。
根据本申请的一些实施方式，所述多腈化合物包含二腈化合物和两个氰基以上的多腈化合物，所述二腈化合物包含己二腈或丁二腈中的至少一种，所述两个氰基以上的多腈化合物包含1,2,3-三-(2-氰乙氧基)丙烷、1,3,6-己烷三腈、
Figure PCTCN2021104736-appb-000010
Figure PCTCN2021104736-appb-000011
中的至少一种。
根据本申请的一些实施方式，所述电解液进一步包含含硼锂盐，并且所述含硼锂盐在所述电解液中所占的重量百分比为A，0.1％＜A＜1.5％。根据一些实施例，A为0.1％、0.2％、0.5％、0.6％、0.8％、0.9％、1.0％、1.1％、1.3％、1.4％、1.5％或者任意两个数值组成的范围。含硼锂盐的引入，会优先成膜，对正负极加以保护，进而提升电化学装置的循环稳定性。根据本发明的一些优选实施方式，A与Z之间满足0.002＜A/Z＜1.5，例如0.01、0.02、0.03、0.04、0.05、0.06、0.1、0.2、0.5、0.7、0.9、1.1、1.3或者任意两个数值组成的范围，在此范围内，容量保持率较高。
根据本申请的一些实施方式，所述含硼锂盐化合物包括或者选自以下物质中的至少一种：
Figure PCTCN2021104736-appb-000012
根据一些实施例，所述含硼锂盐包括或者为二氟草酸硼酸锂。根据一些实施例，所述含硼锂盐包括或者为双草酸硼酸锂。所述含硼锂盐包括二氟草酸硼酸锂和双草酸硼酸锂。
根据本申请的一些实施方式，所述电解液进一步包含环醚，并且所述环醚在所述电解液中所占的重量百分比B，0.4％＜B＜1％，例如B为0.5％、0.6％、0.7％、0.8％、0.9％或者任意两个数值组成的范围。根据本发明的一些实施方式，B与Z之间满足0.004＜B/Z＜1，例如B/Z为0.005、0.008、0.01、0.015、0.02、0.03、0.04、0.05、0.06、0.07、0.08、0.1、0.2、0.5、0.6、0.7、0.8、0.9或者任意两个数值组成的范围。环醚的引入能够改善存储，并使容量保持率处于较高水平。
根据一些实施例，所述环醚选自1,3-二氧六环、4-甲基-1,3-二氧六环、1,4-二氧六环、1,3-二氧戊环、2-甲基-1,3-二氧戊环、四氢吡喃和四氢呋喃中的至少一种。
根据本申请的一些实施方式，所述硅材料包括硅氧化物、硅单质或二者的混合物。根据本申请的一些实施方式，所述的硅材料包括纳米硅、氧化亚硅、硅合金或硅纳米线。为 了进一步提高电化学装置的能量密度及动力学性能，所述硅基负极材料可以为三种，一是单质硅或其同碳组成的复合材料；二是硅氧化合物或其同碳材料的复合材料；三是硅同其他金属元素组成的合金材料。
根据本申请的一些实施方式，所述硅材料的Dv50范围为2.5μm至20μm。根据本申请的一些实施方式，，所述负极活性材料的平均粒径D50为5μm至15μm。负极活性材料的粒径落入上述范围内时，负极活性物质层的均一性更高，可以避免粒径太小与电解液产生较多的副反应而影响电池的性能，还可以避免粒径太大阻碍锂离子的传输而影响电池的性能。
根据本申请的一些实施方式，所述硅材料表面至少一部分区域上具有氧化物包覆层，其中，所述氧化物包覆层包含铝(Al)氧化物、钛(Ti)氧化物、锰(Mn)氧化物、钒(V)氧化物、硅(Si)氧化物、铬(Cr)氧化物、锆(Zr)氧化物或钴(Co)氧化物中的至少一种。根据本申请的一些实施方式，所述氧化物包覆层的厚度为2nm至1000nm。根据一些实施例，所述氧化物包覆层的厚度为100nm至800nm。根据一些实施例，所述氧化物包覆层的厚度为200nm至600nm。
根据本申请的实施方式，所述负极进一步包括导电层，所述导电层包含导电材料。导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维、碳纳米管、石墨烯等)、基于金属的材料(例如，金属粉、金属纤维等，例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。
用于本申请所述的负极集流体可以选自铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、覆有导电金属的聚合物基底和它们的组合。
根据本申请的一些实施方式，所述电解液包括锂盐，所述锂盐选自六氟磷酸锂(LiPF 6)、双三氟甲烷磺酰亚胺锂LiN(CF 3SO 2) 2(LiTFSI)或双(氟磺酰)亚胺锂(Li(N(SO 2F) 2))中的至少一种。根据本申请的一些实施方式，锂盐浓度在0.3mol/L至2mol/L。根据本申请的一些实施方式，锂盐浓度介于0.8mol/L至1.3mol/L之间。
根据本申请的一些实施方式，所述电解液进一步包含不饱和酸酐、环状硫酸酯、环状磺酸内酯或砜类化合物中至少一种。所述不饱和酸酐可以选自丁二酸酐、马来酸酐和2-甲基马来酸酐中的至少一种；所述环状硫酸酯可以选自硫酸乙烯酯和硫酸丙烯酯中的一种或两种；所述环状磺酸内酯可以选自1,3-丙烷磺内酯、1,4-丁烷磺内酯、1,3-丙烯磺内酯和甲烷二磺酸亚甲酯中的至少一种；所述砜类物质可以为环丁砜。
在根据本申请所述的电化学装置中，正极包括正极集流体和设置在所述正极集流体上的正极活性材料。正极活性材料的具体种类均不受到具体的限制，可根据需求进行选择。
所述正极活性材料可选自选自钴酸锂(LiCoO 2)、锂镍锰钴三元材料、锰酸锂(LiMn 2O 4)、镍锰酸锂(LiNi 0.5Mn 1.5O 4)、磷酸铁锂(LiFePO 4)及其掺杂和/或包覆改性化合物中的一种或几种，但本申请并不限定于这些材料，还可以使用其他可被用作正极活性材料的传统公知的材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方案中，正极活性材料颗粒表面至少一部分区域上具有包覆层。包覆层可以起到隔绝电解液的作用，可以在很大程度上减少电解液与正极活性材料之间的副反应，减少过渡金属溶出，提高正极活性材料的电化学稳定性。其中，包覆层可为碳层、石墨烯层、氧化物层、无机盐层或导电高分子层。氧化物可为Al、Ti、Mn、Zr、Mg、Zn、Ba、Mo、B中的一种或几种元素形成的氧化物；无机盐可为Li 2ZrO 3、LiNbO 3、Li 4Ti 5O 12、Li 2TiO 3、Li 3VO 4、LiSnO 3、Li 2SiO 3、LiAlO 2中的一种或几种；导电高分子可为聚吡咯(PPy)、聚3,4-亚乙二氧基噻吩(PEDOT)或聚酰胺(PI)。
用于根据本申请的电化学装置的正极集流体可以是铝(Al)，但不限于此。
本申请的电化学装置中使用的隔膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施例中，隔膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。
例如隔膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜，基材层的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。具体的，可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。
基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。
无机物层包括无机颗粒和粘结剂，无机颗粒选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡中的至少一种。粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯烷氧、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的至少一 种。
聚合物层中包含聚合物，聚合物的材料选自聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯烷氧、聚偏氟乙烯、聚(偏氟乙烯-六氟丙烯)中的至少一种。
本申请进一步提供了一种电子装置，其包括本申请所述的电化学装置。
根据本申请的电解液能够抑制电化学装置的直流内阻的增加，使得由此制造的电化学装置适用于各种领域的电子设备或装置。
本申请的电子设备或装置没有特别限定。在一些实施例中，本申请的电子设备包括但不限于，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。
为了简明，本文仅具体地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，除非另有说明，“以上”、“以下”包含本数。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。
术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所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可包含单个组分或多个组分。项目B可包含单个组分或多个组分。项目C可包含单个组分或多个组分。
下面结合实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
1、电池制备
实施例以及对比例中的锂离子电池均按照下述方法进行制备：
(1)电解液制备
在含水量<10ppm的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)按一定重量比均匀混合，加入LiPF 6搅拌均匀，形成基础电解液，其中LiPF 6的浓度为1.15mol/L。根据以下各实施例和对比例设置电解液。
(2)正极制备
将正极活性物质钴酸锂(LiCoO 2)、导电剂乙炔黑和粘结剂聚偏二氟乙烯(PVDF)按重量比96:2:2在适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料；将此浆料涂覆于正极集流体铝箔上，烘干、冷压、焊接极耳，得到正极。
(3)负极制备
具体制备过程如下：按比例称取负极活性材料(人造石墨与硅氧负极活性材料的混合物)，碳纳米管导电剂，增稠剂羧甲基纤维素钠(CMC)于料罐中，进行预混合30min，然后加入粘接剂(浓度为50％的丁苯橡胶(SBR)水乳液，10％的聚丙烯酸水溶液各一半)，并加入适量去离子水为溶剂，机械混合制成粘稠状负极浆料，并均匀的涂布铜箔上，烘干、冷压、焊接极耳，得到负极。
(4)隔膜制备
隔膜选用聚乙烯(PE)隔膜。
(5)锂离子电池的制备
将正极、隔膜、负极按顺序叠好，使隔膜处于正极和负极之间起到隔离的作用，然后卷绕，置于外包装箔中，将上述制备好的电解液注入到干燥后的电池中，经过真空封装、静置、化成、整形等工序，即完成锂离子电池的制备。
2、测试方法
1)负极材料中硅元素所占的重量百分比测试方法
在双面负极活性材料的区域，取5cm×5cm区域，刮下除集流体外的材料，称重，加入一定量的浓硝酸进行微波消解后得溶液，并将所得到的溶液和滤渣进行多次洗涤并定容到一定的体积，通过ICP-OES测试其中硅的等离子体强度，根据所测元素的标准曲线计算 出溶液中硅含量，从而计算出材料中所含的硅的量；硅元素的量除以负极材料的重量得到负极材料中硅元素所占的重量百分比。
2)锂离子电池的常温循环性能的测试方法
将锂离子电池放至25℃恒温箱中，以恒定电流0.5C充电至4.45V，在4.45V下恒压充电至0.025C，再0.5C恒流放电至3.0V，此记为一个充放电循环过程，记录初始放电容量。按上述方式进行500次循环充放电测试，记录剩余放电容量。通过下式计算锂离子电池的容量保持率：
容量保持率＝剩余放电容量/初始放电容量×100％。
3)锂离子电池的高温存储性能的测试方法
将锂离子电池在25℃下以0.5C放电至3.0V，在以0.7C充电至4.45V，4.45V下恒压充电至0.05C，用千分尺测试并记录锂离子电池的厚度H 1，将锂离子电池放置到80℃烘箱当中，6小时结束后用千分尺测试并记录锂离子电池的厚度H 2。厚度膨胀率＝(H 2-H 1)/H 1×100％。
3、测试结果
表1展示了FEC在电解液中的重量百分含量X，负极活性物质层单面单位面积的涂覆重量值Y和硅材料占负极活性物质的重量百分含量Z对锂离子电池的80℃存储6h膨胀率和容量保持率的影响。在表1所示的各实施例和对比例中，碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)的重量比为1:2:7。基于碳酸酯的总重量，环状碳酸酯(EC和PC)的总量为30％。负极活性物质硅材料(Dv50＝5μm，基于负极活性物质层的总重量，导电剂的质量占比为1.5％、增稠剂的质量占比为0.5％、粘结剂的质量占比为2％。
表1
Figure PCTCN2021104736-appb-000013
Figure PCTCN2021104736-appb-000014
如表1所示，对比例1不满足0.014≤X/(Y×2×Z)≤1.28，其容量保持率较差。对比例2和3虽然满足0.014≤X/(Y×2×Z)≤1.28，但X或Y超出了本申请所希望的范围(即，5％≤X≤30％以及1.95≤Y≤11.69)，锂离子电池的容量保持率没有得到有效改善。实施例1-15不仅满足0.014≤X/(Y×2×Z)≤1.28，而且5％≤X≤30％以及1.95≤Y≤11.65，因此锂离子电池的容量保持率得到显著提升。
如实施例1至实施例4所示，当Y在11.69至1.95的范围内逐渐减少时，锂离子电池的容量保持率随之略有降低，这是因为当X、Y和Z之间的关系一定时，在相同的容量范围内，随着负极单面单位面积的涂覆重量值CW(即Y)的减小，Z将随之变化。当电解液中FEC的含量过高时(例如，对比例2中X＝40％)，电解液对应的溶剂含量下降，电解液中锂盐解离困难；同时FEC易分解，加速电解液中HF的形成，导致电解液酸度升高，并且HF将攻击正极界面，使得过渡金属溶出加剧，破坏电池性能，从而导致锂离子电池的容量保持率下降。如实施例5-8和9-11所示，当Z在1％至90％范围内逐渐减少或Y逐渐降低时，锂离子电池的容量保持率逐渐升高，80℃存储6h膨胀率逐渐降低，这是由于Si含量或者单位面积涂覆重量降低时，对应于单位面积Si负极材料的FEC含量升高。Si负极在循环过程中体积膨胀大，SEI膜容易被破坏，恶化循环性能，FEC能够先于溶剂在负极表面还原形成稳定的钝化膜，并且在循环过程中可以对损坏的SEI进行修复，缓解循环过程中SEI膜的破坏，同时降低电解液在锂离子电池中的消耗。由此，锂离子电池的容量保持率得到显著改善。
如实施例12至实施例15所示，当X在5％至30％范围内逐渐增加时，锂离子电池的容量保持率逐渐升高，80℃存储6h膨胀率也逐渐增加。这是由于FEC在高温下不稳定， 容易发生副反应，导致存储过程中的膨胀率增加，而FEC含量增加对循环过程中的SEI修复能力增强，从而使锂离子电池的容量保持率升高。
表2展示了环状碳酸酯(EC和PC)总量及比例对锂离子电池容量保持率的影响。表2所示的各实施例是基于实施例1的进一步改进，也即区别仅在于表2中的参数，表2中EC、PC、DEC的含量是基于溶剂体系的总重量计算。
表2
Figure PCTCN2021104736-appb-000015
如实施例16至实施例22所示，随着EC:PC在0.2-2的范围内变化，锂离子电池的容量保持率受到影响，存储膨胀率随着EC含量的变化而受到影响。这是因为EC还原电位较高，易参与在负极成膜，随其含量增加，成膜反应增加，在存储和循环过程中易分解产气，使得容量保持率下降，电池膨胀率增大。当EC：PC在0.3-1之间时，锂离子电池不仅具有较高的解离能力，还能保持较高的容量保持率以及较低的存储膨胀率。
如实施例23至实施例24所示，虽然EC：PC在0.3-1的范围内，但由于EC和PC的总和大于50％，此时电解液整体粘度较高，影响离子解离和迁移，从而使容量保持率处于较低的水平。
表3展示了多腈类添加剂对锂离子电池80℃存储6h膨胀率和容量保持率的影响，所示的各实施例是在实施例1的基础上的改进，也即区别仅在于表3中的参数，表3中二腈和两个氰基以上的多腈化合物的含量是基于电解液的总重量计算。
表3
Figure PCTCN2021104736-appb-000016
如实施例25至实施例30所示，随着腈类总量在0.5％至6％范围内变化，多腈化合物对正极的稳定能力逐渐增强，因此锂离子电池的存储膨胀率逐渐降低。如实施例31所示，当多腈类化合物总量达到8％时，虽然存储膨胀率较低，但容量保持率显著恶化。这是因为当多腈总含量较低时，正极的界面得不到有效的保护，在存储过程中过渡金属离子溶出，正极材料结构坍塌，影响存储膨胀率。多腈化合物粘度大，当多腈化合物的含量增多时，电解液的电导率降低，阻抗增大，且过量的多腈化合物易在负极活性位点还原，形成不稳定的SEI膜，导致容量保持率下降。因此需要控制多腈含量在一定范围内，且二腈和二个氰基以上的多腈化合物联合使用，一方面有效地稳定正极界面，另一方面调节电解液粘度，才能取得较低的存储膨胀率和较好的容量保持率。
表4中列出了含硼锂盐对锂离子电池存储膨胀率和容量保持率的影响。表4所示的各实施例是在实施例1的基础上的改进，也即区别在于表4中的参数。
表4
Figure PCTCN2021104736-appb-000017
如实施例35至实施例38所示，加入含硼锂盐可以有效改善容量保持率。在实施例39和40中，当添加了较多的含硼锂盐时，容量保持率降低，且80℃存储膨胀率升高，这是因为高含量的含硼锂盐会使电池阻抗增加，在循环过程中易发生析锂，从而使得容量保持率下降，而且含硼锂盐在存储过程中易分解产气，影响80℃存储，因此需要控制含硼锂盐的含量在一定范围内通过实施例41可知，含硼锂盐的含量与Si含量的比值需在0.002至1.5之间，能取得较高的容量保持率。
表5中列出了环醚含量及与Si含量的比例对锂离子电池存储膨胀率和容量保持率的影响。表5所示的各实施例是在实施例1的基础上的改进，也即区别仅在于表5中的参数。
表5
Figure PCTCN2021104736-appb-000018
如实施例42至实施例48所示，随着B/Z在0.04至1之间时，存储膨胀率下降，通过实施例49至51可以看出，1,3二氧六环的含量需在一定的范围内，能够改善存储，同时使容量保持率处于较高的水平。
表6中列出了负极硅材料的Dv50对锂离子电池存储膨胀率和容量保持率的影响。表6所示的各实施例是在实施例1的基础上的改进，也即区别仅在于表6中的参数。
表6
Figure PCTCN2021104736-appb-000019
通过表6中实施例52和实施例54至实施例57对比，可以看出，硅材料的Dv50小于 2.5μm时，锂离子电池的容量保持率较低，如实施例58所示，硅材料的Dv50大于20μm时，锂离子电池的容量保持率较低。通过实施例52和实施例53相比，当Dv50小于2.5μm时，增加X，可以改善容量保持率。这是由于负极硅颗粒较小，在涂覆后易粉化，使负极材料与电解液接触面增大，副反应增多，在循环过程中SEI容易破裂，从而恶化容量保持率。通过增加FEC的含量，可以修复负极表面的SEI，改善容量保持率。
表7中列出了M氧化物包覆层对锂离子电池容量保持率的影响。实施例59至实施例65所示的各实施例是在实施例1的基础上的改进，即区别在于表7中的参数。在实施例64至实施例65中Ti和Mn的质量比为1:1。
表7
Figure PCTCN2021104736-appb-000020
通过表7的实施例59至实施例65与实施例1对比，可以看出，硅材料的表面含有氧化物包覆层，其中M包括Ti、Mn，且包覆层厚度在一定范围内，其容量保持率较优。
表8中列出了M氧化物包覆层对锂离子电池容量保持率的影响。实施例66至实施例68是在实施例28的基础上的改进，即区别特征在于表8中的参数。在实施例69至实施例71中Ti和Mn的质量比为2:1。
表8
Figure PCTCN2021104736-appb-000021
通过表8的实施例66至实施例71与实施例28对比，可以看出，硅材料的表面含有氧化物包覆层，其中M包括Ti、Mn，且包覆层厚度在一定范围内，其容量保持率较优且高温存储性能得到改善。
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 (11)

  1. 一种电化学装置，包括正极、负极、隔膜和电解液，所述负极包括负极集流体和设置在所述负极集流体至少一个表面上的负极活性物质层，所述负极活性物质层包含硅材料，所述电解液包含氟代碳酸乙烯酯，
    所述电化学装置满足以下关系式：0.014≤X/(Y×2×Z)≤1.28，
    其中，X表示氟代碳酸乙烯酯在电解液中所占的重量百分比，并且5％≤X≤30％，Y表示，以mg/cm 2计，单面单位面积的负极活性物质层的重量，并且1.95≤Y≤11.69，Z表示硅材料在负极活性物质层中所占的重量百分比。
  2. 根据权利要求1所述的电化学装置，其中，1％≤Z≤90％。
  3. 根据权利要求1所述的电化学装置，其中，5％≤Z≤60％。
  4. 根据权利要求1所述的电化学装置，其中，所述电解液还包含非氟代环状碳酸酯和链状碳酸酯，其中，所述非氟代环状碳酸酯的重量占所述非氟代环状碳酸酯和链状碳酸酯总量量的百分比为5％至50％。
  5. 根据权利要求1所述的电化学装置，其中，所述电解液进一步包含多腈化合物，所述多腈化合物满足条件(a)至(c)中的至少一种：
    (a)所述多腈化合物在电解液中所占的重量百分比为0.5％至6％；
    (b)所述多腈化合物包括式II化合物：
    Figure PCTCN2021104736-appb-100001
    其中，R 21、R 22、R 23和R 24各自独立地选自氢、氰基、C 1-C 10烷基、含氰基的C 1-C 10烷基或含氰基的C 1-C 10醚基，R 21、R 22、R 23和R 24所含有的氰基的总数为两个以上；
    (c)所述多腈化合物包含1,2,3-三-(2-氰乙氧基)丙烷、1,3,6-己烷三腈、己二腈、丁二腈、
    Figure PCTCN2021104736-appb-100002
    Figure PCTCN2021104736-appb-100003
    中的至少一种。
  6. 根据权利要求1所述的电化学装置，其中，所述电解液进一步包含含硼锂盐，所述含硼锂盐在电解液中所占的重量百分比为A，所述含硼锂盐满足条件(d)至(f)中的至少一者：
    (d)0.1％＜A＜1.5％；
    (e)所述A与所述Z之间满足0.002＜A/Z＜1.5；
    (f)所述含硼锂盐化合物包括或者选自以下物质中的至少一种：
    Figure PCTCN2021104736-appb-100004
    Figure PCTCN2021104736-appb-100005
  7. 根据权利要求1所述的电化学装置，其中，所述电解液进一步包含环醚，所述环醚在电解液中所占的重量百分比为B，0.4％＜B＜1％。
  8. 根据权利要求7所述的电化学装置，其中，B与Z之间满足0.004＜B/Z＜1。
  9. 根据权利要求1所述的电化学装置，其中，所述硅材料包括硅氧化物、硅单质或者二者的混合物，并且所述硅材料的Dv50为2.5μm至20μm。
  10. 根据权利要求1所述的电化学装置，其中，所述硅材料表面至少一部分区域上具有氧化物包覆层，其中，所述氧化物包覆层包含铝氧化物、钛氧化物、锰氧化物、钒氧化物、硅氧化物、铬氧化物、锆氧化物或钴氧化物中的至少一种；所述氧化物包覆层的厚度为2nm至1000nm。
  11. 一种电子装置，包括权利要求1-10中任一项所述的电化学装置。
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