WO2023116271A1 - 二次电池 - Google Patents

二次电池 Download PDF

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Publication number
WO2023116271A1
WO2023116271A1 PCT/CN2022/132196 CN2022132196W WO2023116271A1 WO 2023116271 A1 WO2023116271 A1 WO 2023116271A1 CN 2022132196 W CN2022132196 W CN 2022132196W WO 2023116271 A1 WO2023116271 A1 WO 2023116271A1
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Prior art keywords
negative electrode
silicon
material layer
secondary battery
structural formula
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PCT/CN2022/132196
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English (en)
French (fr)
Inventor
邓永红
钱韫娴
胡时光
孙桂岩
向晓霞
林雄贵
曹朝伟
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深圳新宙邦科技股份有限公司
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Priority to EP22821832.7A priority Critical patent/EP4224589A1/en
Publication of WO2023116271A1 publication Critical patent/WO2023116271A1/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
    • H01M10/052—Li-accumulators
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • 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
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M2004/027—Negative 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

  • the invention belongs to the technical field of energy storage battery devices, and in particular relates to a secondary battery.
  • lithium-ion batteries with the advantages of high energy density, long cycle life, and environmental protection have been widely used in 3C digital devices and new energy vehicles, but end users in the power field still have urgent requirements for the improvement of mileage. Therefore, further improving the energy density of power batteries is an urgent problem in the field of lithium-ion batteries.
  • silicon anode materials have become an important direction for improving the energy density of lithium-ion batteries because of their theoretical specific capacity (silicon: 4200mAh/g, graphite: 372mAh/g) which is much higher than that of graphite anode materials.
  • the alloying of silicon and lithium in the charged state will lead to serious volume expansion of the negative electrode, up to 300%, which will lead to the destruction of the solid electrolyte interface film on the surface of the negative electrode.
  • Solvents and additives combined with active lithium ions generate a new interfacial film again, so the high-temperature storage performance of negative silicon-containing batteries has always been one of the problems of this system.
  • the invention provides a secondary battery.
  • the invention provides a secondary battery, comprising a positive electrode, a negative electrode having a negative electrode material layer, and a non-aqueous electrolyte, the negative electrode material layer comprising a negative electrode active material, the negative electrode active material comprising a silicon-based material;
  • the non-aqueous electrolytic solution includes a solvent, an electrolyte salt and an additive, and the additive includes a compound shown in Structural Formula 1;
  • n 0 or 1
  • A is selected from C or O
  • X is selected from R 1 and R 2 are each independently selected from H
  • R1 and R2 are not selected from H at the same time
  • X, R1 and R2 contain at least one sulfur atom
  • the secondary battery satisfies the following conditions:
  • m is the percentage of non-aqueous electrolyte mass and negative electrode material layer mass, and the unit is %;
  • n is the mass percentage of the compound shown in structural formula 1 in the non-aqueous electrolyte, and the unit is %;
  • r is the compacted density of the negative electrode material layer, in g/cm 3 ;
  • S is the mass percentage content of silicon element in the negative electrode material layer, and the unit is %.
  • the secondary battery meets the following conditions:
  • the percentage m of the mass of the non-aqueous electrolyte to the mass of the negative electrode material layer is 45%-80%.
  • the mass percentage n of the compound represented by the structural formula 1 in the non-aqueous electrolyte solution is 0.05%-1%.
  • the compacted density r of the negative electrode material layer is 1.4 ⁇ 1.7 g/cm 3 .
  • the mass percentage S of the silicon element in the negative electrode material layer is 5%-20%.
  • the compound represented by the structural formula 1 is selected from one or more of the following compounds 1-18:
  • the silicon-based material is selected from at least one of silicon materials, silicon oxides, silicon-carbon composite materials and silicon alloy materials.
  • the non-aqueous electrolyte also includes auxiliary additives, the auxiliary additives include cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, phosphate compounds, borates At least one of compound and nitrile compound;
  • the amount of the auxiliary additive added is 0.01%-30%.
  • the cyclic sulfate ester compound is selected from at least one of vinyl sulfate, propylene sulfate or vinyl methyl sulfate;
  • the sultone compound is selected from methylene disulfonate, 1,3-propane sultone, 1,4-butane sultone or 1,3-propene sultone at least one of
  • the cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate or the compound shown in structural formula 2,
  • R 21 , R 22 , R 23 , R 24 , R 25 , and R 26 are each independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group;
  • the phosphoric acid ester compound is selected from at least one of tris(trimethylsilyl) phosphate and the compound shown in structural formula 3:
  • R 31 , R 32 , and R 33 are each independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 ) 3 , m is 1 to A natural number of 3, and at least one of R 31 , R 32 , and R 33 is an unsaturated hydrocarbon group;
  • the borate compound is selected from three (trimethylsilane) borates;
  • the nitrile compound is selected from succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile one or more of .
  • an additive with a specific structure (the compound shown in structural formula 1) is added in the battery containing the silicon negative electrode, because the compound shown in structural formula 1 has a higher reduction potential, the additive will be in During the formation process, the solvent is reductively decomposed at the negative electrode to form a layer of solid electrolyte interfacial film (SEI), and the formed interfacial film contains S element at the same time. Since the lithium sulfate salt (ROSO 3 Li) formed by the compound shown in structural formula 1 on the negative electrode interface is the main component of the SEI film instead of the lithium carbonate salt (ROCO 2 Li), it has a good coordination relationship with silicon-based materials.
  • the lithium sulfate salt (ROSO 3 Li) formed by the compound shown in structural formula 1 on the negative electrode interface is the main component of the SEI film instead of the lithium carbonate salt (ROCO 2 Li), it has a good coordination relationship with silicon-based materials.
  • the high-temperature storage performance of the battery can be improved on the premise of ensuring that the battery has excellent energy density.
  • An embodiment of the present invention provides a secondary battery, including a positive electrode, a negative electrode having a negative electrode material layer, and a non-aqueous electrolyte, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material;
  • the non-aqueous electrolytic solution includes a solvent, an electrolyte salt and an additive, and the additive includes a compound shown in Structural Formula 1;
  • n 0 or 1
  • A is selected from C or O
  • X is selected from R 1 and R 2 are each independently selected from H
  • R1 and R2 are not selected from H at the same time
  • X, R1 and R2 contain at least one sulfur atom
  • the secondary battery satisfies the following conditions:
  • m is the percentage of non-aqueous electrolyte mass and negative electrode material layer mass, and the unit is %;
  • n is the mass percentage of the compound shown in structural formula 1 in the non-aqueous electrolyte, and the unit is %;
  • r is the compacted density of the negative electrode material layer, in g/cm 3 ;
  • S is the mass percentage content of silicon element in the negative electrode material layer, and the unit is %.
  • the additive will be reduced and decomposed at the negative electrode prior to the solvent during the formation process to form a solid electrolyte interfacial film (SEI), and the formed interfacial film also contains S elements.
  • SEI solid electrolyte interfacial film
  • the lithium sulfate salt (ROSO 3 Li) formed by the compound shown in structural formula 1 on the negative electrode interface is the main component of the SEI film instead of the lithium carbonate salt (ROCO 2 Li), it has a good coordination relationship with silicon-based materials. , so in the process of high-temperature storage, the resistance growth caused by side reactions and the generation of CO 2 and other gases are avoided, and the high-temperature storage performance is effectively improved.
  • the invention Based on the coordination relationship between the compound shown in structural formula 1 and the silicon-based material, the invention After a lot of research, people have found that when the percentage m of the mass of the non-aqueous electrolyte to the mass of the negative electrode material layer, the mass percentage n of the compound shown in structural formula 1 in the non-aqueous electrolyte, the compaction density r of the negative electrode material layer and the negative electrode The mass percentage S of the silicon element in the material layer satisfies the relational formula: At this time, the high-temperature storage performance of the battery can be improved on the premise of ensuring that the battery has excellent energy density.
  • the secondary battery satisfies the following conditions:
  • the percentage m of the non-aqueous electrolyte quality and the mass of the negative electrode material layer, the mass percent content n of the compound shown in structural formula 1 in the non-aqueous electrolyte, the compaction density r of the negative electrode material layer and the silicon element in the negative electrode material layer The mass percentage S is correlated, and the influence of the negative electrode of the silicon-based material and the non-aqueous electrolyte additive on the performance of the battery can be integrated to a certain extent, so as to obtain a secondary battery with excellent high-temperature storage performance.
  • the percentage m of the mass of the nonaqueous electrolyte to the mass of the negative electrode material layer is 40% to 90%
  • the percentage m of the mass of the non-aqueous electrolyte to the mass of the negative electrode material layer is 45%-80%.
  • the percentage m of the mass of the non-aqueous electrolyte to the mass of the negative electrode material layer is 40%, 41%, 43%, 47%, 50%, 51%, 54%, 56%, 59%, 61%, 63%, 64% or 65%.
  • the content of the non-aqueous electrolyte will directly affect the injection and retention coefficient of the battery, which is different from the quality of the compound shown in structural formula 1 in the non-aqueous electrolyte.
  • the percentage content n jointly determines the total content of the compound shown in structural formula 1 in the battery; at the same time, the mass percentage content S of the silicon element in the negative electrode active material quality and the negative electrode material layer determines the total silicon content, therefore, the nonaqueous electrolyte quality
  • the percentage m of the mass of the negative electrode material layer is a limiting condition directly related to the battery system. If the percentage m of the mass of the non-aqueous electrolyte to the mass of the negative electrode material layer is too large or too small, it is not conducive to the interaction between the compound represented by the structural formula 1 and the silicon-based material.
  • the total mass percentage n of the compound represented by structural formula 1 is 0.05%, 0.09%, 0.1%, 0.2%, 0.4%, 0.8%, 1.1%, 1.5%, 1.7% %, 1.9% or 2%.
  • the mass percentage n of the compound represented by structural formula 1 in the non-aqueous electrolyte solution is 0.05%-1%.
  • the additive shown in structural formula 1 is applied to silicon-containing batteries. During the battery formation process, the additive undergoes reduction and decomposition on the surface of the silicon-based negative electrode to participate in the formation of the SEI film.
  • the sulfuric acid contained in the formed interface film Ester lithium salt (ROSO 3 Li) replaces most of carbonate lithium salt (ROCO 2 Li) as the main organic component, and at the same time, the S-containing group with electron-withdrawing effect in the interface film is complexed with Si element in the negative electrode, The interface structure is further stabilized.
  • the above interfacial film components effectively suppress the impedance growth and the generation of CO2 and other gases caused by side reactions during high-temperature storage. Therefore, in the silicon-containing negative electrode battery system, the application of this additive can achieve the effect of effectively improving high-temperature storage.
  • the compacted density r of the negative electrode material layer is 1.2g/cm 3 , 1.25g/cm 3 , 1.3g/cm 3 , 1.35g/cm 3 , 1.4g/cm 3 , 1.45g/cm 3 , 1.5g /cm 3 , 1.55g/cm 3 , 1.6g/cm 3 , 1.65g/cm 3 , 1.7g/cm 3 , 1.75g/cm 3 or 1.8g/cm 3 .
  • the compacted density r of the negative electrode material layer is 1.4 ⁇ 1.7 g/cm 3 .
  • the negative electrode material layer has a porous structure, and the charging and discharging process of the battery actually includes the liquid phase conduction of ions in the negative electrode material layer, so the richness of the pores in the negative electrode material layer will directly affect the fast charging and life performance of the battery. Under other conditions being the same, the smaller the compaction density of the negative electrode material layer, the more developed its pore structure, which is more conducive to the liquid phase conduction of active ions, especially under the harsh conditions of repeated expansion of the battery after repeated charging and discharging. Down.
  • the compaction density of the negative electrode will affect the wetting effect of the non-aqueous electrolyte on the silicon-containing negative electrode and the volume expansion rate of the silicon-containing negative electrode, the compaction size is also directly related to the performance of the battery system. When the compacted density of the negative electrode material layer is in the above range, the battery has the best performance.
  • the mass percentage S of silicon in the negative electrode material layer is 5%, 7%, 10%, 13%, 15%, 16%, 18%, 21%, 23%, 24%, 26%, 27% %, 29% or 30%.
  • the mass percentage S of silicon element in the negative electrode material layer is 5%-20%.
  • silicon-based materials act as a carrier for lithium ion deintercalation and intercalation. Compared with other negative electrode active materials, such as graphite, silicon-based materials have a higher theoretical capacity.
  • the silicon element in the negative electrode material layer When the mass percentage content S is within the above range, the battery capacity can be effectively improved, and at the same time, the problem of excessive volume change during battery cycle caused by excessive silicon content can be avoided.
  • the medium content is 0.05-2%
  • the negative electrode compaction of the battery does not exceed 1.2-1.8g/cm 3 , and the relationship between the above parameters satisfy Then the storage performance of the system is significantly improved.
  • the compound represented by structural formula 1 is selected from one or more of the following compounds 1-18:
  • compound 7 can be prepared by the following method:
  • the silicon-based material is at least one selected from silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials.
  • the silicon material is one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon films, 3D porous silicon, and hollow porous silicon.
  • the negative electrode further includes a negative electrode current collector, and the negative electrode material layer covers the surface of the negative electrode current collector.
  • the part of the negative electrode in this application other than the negative electrode current collector is referred to as the negative electrode material layer.
  • the negative electrode current collector is selected from metal materials that can conduct electrons.
  • the negative electrode current collector includes one or more of Al, Ni, tin, copper, and stainless steel.
  • the negative electrode The current collector is selected from aluminum foil.
  • the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer.
  • the negative electrode binder includes polyvinylidene fluoride, copolymer of vinylidene fluoride, polytetrafluoroethylene, copolymer of vinylidene fluoride-hexafluoropropylene, copolymer of tetrafluoroethylene-hexafluoropropylene, tetrafluoroethylene- Copolymer of perfluoroalkyl vinyl ether, copolymer of ethylene-tetrafluoroethylene, copolymer of vinylidene fluoride-tetrafluoroethylene, copolymer of vinylidene fluoride-trifluoroethylene, copolymer of vinylidene fluoride-trichloroethylene Copolymers, vinylidene fluoride-fluor
  • the negative electrode conductive agent includes one or more of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene or reduced graphene oxide.
  • the positive electrode includes a positive electrode material layer containing a positive electrode active material
  • the type of the positive electrode active material is not particularly limited, and can be selected according to actual needs, as long as it can reversibly intercalate/deintercalate metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions, etc.) positive electrode active material or conversion type positive electrode material.
  • the battery is a lithium ion battery
  • its positive electrode active material can be selected from LiFe 1-x' M' x' PO 4 , LiMn 2-y' M y' O 4 and LiNi x Co y Mn z
  • M 1-xyz O 2 wherein M' is selected from one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti
  • M is selected from one or more of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0 ⁇ x' ⁇ 1,0 ⁇ y' ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ x ⁇ 1, 0 ⁇ z ⁇ 1, x+y+z ⁇ 1
  • the positive active material can also be selected from sulfide, selenide , one or more of the halides.
  • the positive electrode active material can be selected from LiCoO 2 , LiFePO 4 , LiFe 0.8 Mn 0.2 PO 4 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 One or more of O 2 , LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O 2 , LiMn 2 O 4 , LiNi 0.5 Co 0.2 Al 0.3 O 2 .
  • the battery is a sodium ion battery
  • its positive electrode active material can be selected from metal sodium, carbon materials, alloy materials, overplated metal oxides, overplated metal sulfides, phosphorus-based materials, titanate materials , one or more of the Prussian blue materials.
  • the carbon material can be selected from one or more of graphite, soft carbon, and hard carbon
  • the alloy material can be an alloy material composed of at least two of Si, Ge, Sn, Pb, and Sb.
  • the alloy material can also be an alloy material composed of at least one of Si, Ge, Sn, Pb, Sb and C, the chemical formula of the overplated metal oxide and the overplated metal sulfide is M1 x N y , M1 can be selected from one or more of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V, N is selected from O or S, and the phosphorus-based material can be selected from red phosphorus, white phosphorus, black One or more of phosphorus, the titanate material can be selected from Na 2 Ti 3 O 7 , Na 2 Ti 6 O 13 , Na 4 Ti 5 O 12 , Li 4 Ti 5 O 12 , NaTi 2 (PO 4 ) One or more of 3 , the molecular formula of the Prussian blue material is Na x M [M'(CN) 6 ] y zH 2 O, wherein, M is a transition metal, M' is a transition metal, 0 ⁇ x ⁇ 2, 0.8 ⁇ y ⁇ 1, 0 ⁇ z ⁇
  • the positive electrode further includes a positive electrode current collector, and the positive electrode material layer covers the surface of the positive electrode current collector.
  • the parts of the positive electrode other than the positive electrode current collector are referred to as the positive electrode material layer.
  • the positive electrode current collector is selected from metal materials that can conduct electrons.
  • the positive electrode current collector includes one or more of Al, Ni, tin, copper, and stainless steel.
  • the positive electrode The current collector is selected from aluminum foil.
  • the positive electrode material layer further includes a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder and the positive electrode conductive agent are blended to obtain the positive electrode material layer.
  • the positive electrode binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene Copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, copolymer of ethylene-tetrafluoroethylene, copolymer of vinylidene fluoride-tetrafluoroethylene, copolymer of vinylidene fluoride-trifluoroethylene, copolymer of vinylidene fluoride Ethylene-trichloroethylene copolymer, vinylidene fluoride-fluorinated vinyl copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, thermoplastic polyimi
  • the positive electrode conductive agent includes one or more of metal conductive agents, carbon-based materials, metal oxide-based conductive agents, and composite conductive agents.
  • the metal conductive agent can be copper powder, nickel powder, silver powder and other metals
  • the carbon-based material can be carbon-based materials such as conductive graphite, conductive carbon black, conductive carbon fiber or graphene
  • the metal oxide-based conductive agent can be tin oxide , iron oxide, zinc oxide, etc.
  • the composite conductive agent can be composite powder, composite fiber, etc.
  • the conductive carbon black can be one or more of acetylene black, 350G, Ketjen black, carbon fiber (VGCF), and carbon nanotubes (CNTs).
  • the electrolyte salt includes one or more of lithium salts, sodium salts, potassium salts, magnesium salts, zinc salts and aluminum salts. In a preferred embodiment, the electrolyte salt is selected from lithium salts or sodium salts.
  • the electrolyte salt is selected from LiPF 6 , LiPO 2 F 2 , LiBF 4 , LiBOB, LiSbF 6 , LiAsF 6 , LiCF 3 SO 3 , LiDFOB, LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 C 2 F 5 ) 2 , LiN(SO 2 F) 2 , LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiAlCl 4 , lithium chloroborane, At least one of lower aliphatic lithium carboxylate, lithium tetraphenylborate, and lithium imide having 4 or less carbon atoms.
  • the electrolyte salt can be inorganic electrolyte salts such as LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , LiTaF 6 , LiWF 7 ; fluorophosphate electrolyte salts such as LiPF 6 ; tungstate electrolyte salts such as LiWOF 5 ; 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 , CF 3 CF 2 CF 2 CO 2 Li and other carboxylic acid electrolyte salts; CH 3 SO 3 Li and other sulfonic acid electrolyte salts; LiN(FCO 2 ) 2 , LiN(FCO)(FSO 2 ), LiN(
  • the electrolyte salt is selected from other salts such as sodium salt, potassium salt, magnesium salt, zinc salt or aluminum salt
  • the lithium in the above lithium salt can be replaced with sodium, potassium, magnesium, zinc or aluminum.
  • the sodium salt is selected from sodium perchlorate (NaClO 4 ), sodium hexafluorophosphate (NaPF 6 ), sodium tetrafluoroborate (NaBF 4 ), sodium trifluoromethanesulfonate (NaFSI), At least one of sodium trifluoromethanesulfonate (NaTFSI).
  • the electrolyte salt in the electrolyte is the transfer unit of lithium ions.
  • concentration of the electrolyte salt directly affects the transfer speed of lithium ions, and the transfer speed of lithium ions will affect the potential change of the negative electrode.
  • the total concentration of the electrolyte salt in the electrolyte can be 0.5mol/L-2.0mol/L, 0.5mol/L-0.6mol/L, 0.6mol/L-0.7mol/L, 0.7mol/L ⁇ 0.8mol/L, 0.8mol/L ⁇ 0.9mol/L, 0.9mol/L ⁇ 1.0mol/L, 1.0mol/L ⁇ 1.1mol/L, 1.1mol/L ⁇ 1.2mol/L, 1.2mol/L ⁇ 1.3mol/L, 1.3mol/L ⁇ 1.4mol/L, 1.4mol/L ⁇ 1.5mol/L, 1.5mol/L ⁇ 1.6mol/L, 1.6mol/L ⁇ 1.7mol/L, 1.7mol/L ⁇ 1.8mol/L, 1.8mol/L ⁇ 1.9mol/L, or 1.9mol/L ⁇ 2.0mol/L, more preferably 0.6mol/L ⁇ 1.8mol/L, 0.7mol/L ⁇ 1.7mol/L L, or 0.8mol/L ⁇ 1.5mol/L.
  • the non-aqueous electrolyte also includes auxiliary additives, and the auxiliary additives include cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, phosphoric acid ester compounds, boric acid At least one of ester compounds and nitrile compounds;
  • the cyclic sulfate ester compound is selected from at least one of vinyl sulfate, propylene sulfate or vinyl methyl sulfate;
  • the sultone compound is selected from methylene disulfonate, 1,3-propane sultone, 1,4-butane sultone or 1,3-propene sultone at least one of
  • the cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate or the compound shown in structural formula 2,
  • R 21 , R 22 , R 23 , R 24 , R 25 , and R 26 are each independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group;
  • the phosphoric acid ester compound is selected from at least one of tris(trimethylsilyl) phosphate and the compound shown in structural formula 3:
  • R 31 , R 32 , and R 33 are each independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 ) 3 , m is 1 to 3, and at least one of R 31 , R 32 , and R 33 is an unsaturated hydrocarbon group.
  • the unsaturated phosphate compound can be tris(trimethylsilane) phosphate, tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate , Dipropargyl propyl phosphate, Dipropargyl trifluoromethyl phosphate, Dipropargyl-2,2,2-trifluoroethyl phosphate, Dipropargyl-3,3,3- Trifluoropropyl Phosphate, Dipropargyl Hexafluoroisopropyl Phosphate, Triallyl Phosphate, Diallyl Methyl Phosphate, Diallyl Ethyl Phosphate, Diallyl Propyl Phosphate ester, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, di
  • the borate compound is selected from three (trimethylsilane) borates;
  • the nitrile compound is selected from succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile one or more of .
  • the auxiliary additives may also include other additives that can improve battery performance: for example, additives that improve battery safety performance, specifically flame retardant additives such as fluorophosphate esters and cyclophosphazene, or tert-amyl Benzene, tert-butylbenzene and other anti-overcharge additives.
  • additives that improve battery safety performance specifically flame retardant additives such as fluorophosphate esters and cyclophosphazene, or tert-amyl Benzene, tert-butylbenzene and other anti-overcharge additives.
  • the amount of the auxiliary additive is 0.01%-30%.
  • the addition amount of any optional substance in the auxiliary additive in the non-aqueous electrolyte is less than 10%, preferably, the addition amount is 0.1-5%, more Preferably, the added amount is 0.1%-2%.
  • the addition amount of any optional substance in the auxiliary additive can be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2% %, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.
  • the auxiliary additive is selected from fluoroethylene carbonate, based on 100% of the total mass of the non-aqueous electrolyte, the added amount of the fluoroethylene carbonate is 0.05%-30%.
  • the solvent includes one or more of ether solvents, nitrile solvents, carbonate solvents and carboxylate solvents.
  • ether solvents include cyclic ethers or chain ethers, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms.
  • the cyclic ethers can specifically be but not limited to It is 1,3-dioxolane (DOL), 1,4-dioxane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH 3 -THF), 2-tri One or more of fluoromethyltetrahydrofuran (2-CF 3 -THF);
  • the chain ether can be, but not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane , Ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether.
  • Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane which are low in viscosity and impart high ion conductivity, are particularly preferred because the solvation ability of chain ethers with lithium ions is high and ion dissociation can be improved.
  • methyl methane One kind of ether compound may be used alone, or two or more kinds may be used in any combination and ratio.
  • the addition amount of the ether compound is not particularly limited, and it is arbitrary within the scope of not significantly destroying the effect of the high-compression lithium-ion battery of the present invention.
  • the volume ratio of the non-aqueous solvent is 100%, the volume ratio is usually more than 1%, preferably 1% by volume.
  • the ratio is 2% or more, more preferably 3% or more by volume, and usually 30% or less by volume, preferably 25% or less by volume, more preferably 20% or less by volume.
  • the total amount of the ether compounds may satisfy the above range.
  • the addition amount of the ether compound is within the above-mentioned preferred range, it is easy to ensure the effect of improving the ion conductivity by increasing the lithium ion dissociation degree of the chain ether and reducing the viscosity.
  • the negative electrode active material is a carbon material, co-intercalation of the chain ether and lithium ions can be suppressed, so that input-output characteristics and charge-discharge rate characteristics can be brought into appropriate ranges.
  • the nitrile solvent may specifically be, but not limited to, one or more of acetonitrile, glutaronitrile, and malononitrile.
  • the carbonate solvents include cyclic carbonates or chain carbonates
  • the cyclic carbonates can specifically be, but not limited to, ethylene carbonate (EC), propylene carbonate (PC), gamma-butyrolactone One or more of (GBL), butylene carbonate (BC);
  • the chain carbonate can specifically be, but not limited to, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC ), one or more of dipropyl carbonate (DPC).
  • the content of cyclic carbonate is not particularly limited, and it is arbitrary within the scope of not significantly destroying the effect of the secondary battery of the present invention, but in the case of using one kind alone, the lower limit of its content is relative to the total amount of solvent in the non-aqueous electrolyte Generally, the volume ratio is 3% or more, preferably 5% or more. By setting this range, it is possible to avoid a decrease in conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte, and it is easy to make the large-current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery reach a good range.
  • the upper limit is usually 90% or less by volume, preferably 85% or less by volume, and more preferably 80% or less by volume.
  • the content of the chain carbonate is not particularly limited, but is usually 15% or more by volume, preferably 20% or more by volume, and more preferably 25% or more by volume relative to the total amount of solvent in the nonaqueous electrolyte.
  • the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less.
  • the content of the chain carbonate in the above-mentioned range it is easy to make the viscosity of the non-aqueous electrolyte solution reach an appropriate range, suppress the reduction of ion conductivity, and contribute to making the output characteristics of the non-aqueous electrolyte battery reach a good range.
  • the total amount of the chain carbonates may satisfy the above-mentioned range.
  • chain carbonates having fluorine atoms may also be preferably used.
  • the number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less.
  • these fluorine atoms may be bonded to the same carbon or to different carbons.
  • the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.
  • Carboxylate solvents include cyclic carboxylates and/or chain carbonates.
  • cyclic carboxylic acid esters include one or more of ⁇ -butyrolactone, ⁇ -valerolactone, and ⁇ -valerolactone.
  • chain carbonates include: methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate one or more of .
  • the sulfone solvent includes cyclic sulfone and chain sulfone.
  • cyclic sulfone it usually has 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms.
  • a sulfone it is usually a compound having 2 to 6 carbon atoms, preferably a compound having 2 to 5 carbon atoms.
  • the amount of sulfone solvent added is not particularly limited, and it is arbitrary within the scope of not significantly destroying the effect of the secondary battery of the present invention.
  • the volume ratio is usually more than 0.3%, preferably 0.3% by volume.
  • the total amount of the sulfone-based solvent may satisfy the above range.
  • the added amount of the sulfone solvent is within the above range, an electrolytic solution having excellent high-temperature storage stability tends to be obtained.
  • the solvent is a mixture of cyclic carbonates and chain carbonates.
  • the battery further includes a separator, and the separator is located between the positive electrode and the negative electrode.
  • the diaphragm can be an existing conventional diaphragm, which can be a polymer diaphragm, non-woven fabric, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP/PE, double-layer PP /PP and three-layer PP/PE/PP separators.
  • This embodiment is used to illustrate the secondary battery disclosed in the present invention and its preparation method, including the following steps:
  • LiPF 6 lithium hexafluorophosphate
  • positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF) at a mass ratio of 97:1.5:1.5, and then disperse them in N-methyl -2-pyrrolidone (NMP) to obtain positive electrode slurry.
  • NMP N-methyl -2-pyrrolidone
  • the slurry is uniformly coated on both sides of the aluminum foil, dried, calendered and vacuum-dried, and an aluminum lead-out wire is welded on by an ultrasonic welder to obtain a positive plate with a thickness of 120-150 ⁇ m.
  • a three-layer separator with a thickness of 20 ⁇ m was placed between the positive plate and the negative plate, and then the sandwich structure composed of the positive plate, the negative plate and the separator was wound, and then the wound body was flattened and put into an aluminum foil packaging bag. Vacuum bake at 75°C for 48 hours to obtain the cell to be filled with liquid.
  • Examples 2-40 are used to illustrate the battery disclosed in the present invention and its preparation method, including most of the operation steps in Example 1, the differences are:
  • the electrolyte solution shown in Table 1 was used to add the components and the negative electrode material layer.
  • Comparative Examples 1-10 are used to illustrate the battery disclosed in the present invention and its preparation method, including most of the operation steps in Example 1, the difference being:
  • the electrolyte solution shown in Table 1 was used to add the components and the negative electrode material layer.
  • the prepared lithium-ion battery was charged to 4.2V at constant current and constant voltage, and then stored in an oven at a constant temperature of 60°C. After 30 days of storage, the discharge capacity, volume, and internal resistance were tested. Record the discharge capacity, volume and impedance before storage, and the discharge capacity, volume and impedance after 30 days of storage.
  • Capacity retention rate discharge capacity after storage / capacity before storage ⁇ 100%
  • Impedance growth rate (impedance after storage-impedance before storage)/impedance before storage ⁇ 100%
  • Inflation rate (battery volume after storage-initial battery volume)/initial battery volume ⁇ 100%.
  • the compound shown in Structural Formula 1 can be decomposed on the surface of the silicon-based negative electrode to form S-rich elements due to its low reduction potential.
  • passivation film by adjusting the percentage of the mass of the non-aqueous electrolyte to the mass of the negative electrode material layer and the compaction density of the negative electrode material layer, the non-aqueous electrolyte is fully infiltrated in the negative electrode material layer, ensuring that the compound shown in structural formula 1 and silicon Full contact with the elements, the passivation film obtained by decomposing the compound shown in Structural Formula 1 has the characteristics of compactness and high strength, and there is chemical bonding between the silicon element of the silicon-based negative electrode and the S-containing passivation film obtained by decomposing the compound shown in Structural Formula 1 Effect, the passivation film can limit the expansion volume of the silicon-based material during the charge and discharge expansion of the silicon-based material, thereby avoiding the splitting of the passivation film during charge and discharge under high temperature conditions,
  • the mass percentage n of the compound shown in the non-aqueous electrolyte quality and the negative electrode material layer mass, the compound shown in structural formula 1, the compaction density r of the negative electrode material layer and the silicon element in the negative electrode material layer has a strong correlation in improving the high-temperature storage performance of the battery.
  • the decomposition product should be short, can fill up the gap that the compound shown in structural formula 1 forms passivation film, and three (trimethylsilane) borates, tripropargyl phosphate, succinonitrile have lower reduction potential equally, and its
  • the contained silane, boron, phosphorus, and nitrogen elements can reinforce the passivation film to form a more stable passivation film structure in the negative electrode material layer, so as to improve the high-temperature storage stability of the battery.

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Abstract

为克服现有含硅基材料的电池存在高温存储性能不足问题，本发明提供了一种二次电池，包括正极、具有负极材料层的负极和非水电解液，所述负极材料层包括负极活性材料，所述负极活性材料包括硅基材料；所述非水电解液包括溶剂、电解质盐和添加剂，所述添加剂包括结构式(I)所示的化合物；其中，n为0或(1)，A选自C或O，X选自（II）或(III)， R 1、R 2各自独立选自H、(IV)或(V)， R 1和R 2不同时选自H，且X、R 1和R 2中至少含有一个硫原子；所述二次电池满足以下条件：（VI）；且40％≤m≤90％，0.05％≤n≤2％，1.2g/cm 3≤r≤1.8g/cm 3，5％≤S≤30％。本发明提供的二次电池能够在保证电池具有优异能量密度的前提下，提高电池的高温存储性能。

Description

二次电池 技术领域
本发明属于储能电池器件技术领域，具体涉及一种二次电池。
背景技术
当前具有能量密度高、循环寿命长、绿色环保等优点的锂离子电池已经被广泛应用于3C数码设备和新能源动力汽车领域，但动力领域的终端用户仍对于续航里程的提升存在着迫切要求，因此进一步提高动力电池的能量密度是锂离子电池领域亟需解决的问题。
在锂离子电池市场常见负极材料中，硅负极材料因具有远高于石墨负极材料的理论比容量(硅：4200mAh/g，石墨：372mAh/g)，成为锂离子电池能量密度提升的一个重要方向。根据硅基负极的充放电原理，在充电状态下硅与锂的合金化，会导致负极严重的体积膨胀，最大可达300％，进而导致负极表面的固态电解质界面膜被破坏，随后电解液中的溶剂和添加剂结合活性锂离子再次生成新的界面膜，因此负极含硅电池的高温存储性能一直是该体系的难题之一。
发明内容
针对现有含硅基材料的电池存在高温存储性能不足问题，本发明提供了一种二次电池。
本发明解决上述技术问题所采用的技术方案如下：
本发明提供了一种二次电池，包括正极、具有负极材料层的负极和非水电解液，所述负极材料层包括负极活性材料，所述负极活性材料包括硅基材料；
所述非水电解液包括溶剂、电解质盐和添加剂，所述添加剂包括结构式1所示的化合物；
Figure PCTCN2022132196-appb-000001
其中，n为0或1，A选自C或O，X选自
Figure PCTCN2022132196-appb-000002
R 1、R 2各自独立选自H、
Figure PCTCN2022132196-appb-000003
R 1和R 2不同时选自H，且X、R 1和R 2中至少含有一个硫原子；
所述二次电池满足以下条件：
Figure PCTCN2022132196-appb-000004
且40％≤m≤90％，0.05％≤n≤2％，1.2g/cm 3≤r≤1.8g/cm 3，5％≤S≤30％；
其中，m为非水电解液质量与负极材料层质量的百分比，单位为％；
n为结构式1所示的化合物在非水电解液中的质量百分含量，单位为％；
r为负极材料层的压实密度，单位为g/cm 3；
S为负极材料层中硅元素的质量百分含量，单位为％。
可选的，所述二次电池满足以下条件：
Figure PCTCN2022132196-appb-000005
可选的，所述非水电解液质量与负极材料层质量的百分比m为45％～80％。
可选的，所述结构式1所示的化合物在非水电解液中的质量百分含量n为0.05％～1％。可选的，所述负极材料层的压实密度r为1.4～1.7g/cm 3。
可选的，所述负极材料层中硅元素的质量百分含量S为5％～20％。
可选的，所述结构式1所示的化合物选自以下化合物1～18中的一种或多种：
Figure PCTCN2022132196-appb-000006
Figure PCTCN2022132196-appb-000007
Figure PCTCN2022132196-appb-000008
可选的，所述硅基材料选自硅材料、硅的氧化物、硅碳复合材料以及硅合金材料中的至少一种。
可选的，所述非水电解液中还包括辅助添加剂，所述辅助添加剂包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳酸酯类化合物、磷酸酯类化合物、硼酸酯类化合物和腈类化合物中的至少一种；
优选的，以所述非水电解液的总质量为100％计，所述辅助添加剂的添加量为0.01％～30％。
可选的，所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯或甲基硫酸乙烯酯中的至少一种；
所述磺酸内酯类化合物选自甲基二磺酸亚甲酯、1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯或1,3-丙烯磺酸内酯中的至少一种；
所述环状碳酸酯类化合物选自碳酸亚乙烯酯、碳酸乙烯亚乙酯、氟代碳酸乙烯酯或结构式2所示化合物中的至少一种，
Figure PCTCN2022132196-appb-000009
所述结构式2中，R 21、R 22、R 23、R 24、R 25、R 26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种；
所述磷酸酯类化合物选自三(三甲基硅烷)磷酸酯、结构式3所示化合物中的至少一种：
Figure PCTCN2022132196-appb-000010
所述结构式3中，R 31、R 32、R 33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(C mH 2m+1) 3，m为1～3的自然数，且R 31、R 32、R 33中至少有一个为不饱和烃基；
所述硼酸酯类化合物选自三(三甲基硅烷)硼酸酯；
所述腈类化合物选自丁二腈、戊二腈、乙二醇双(丙腈)醚、己烷三腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的一种或多种。
根据本发明提供的二次电池，将具有特定结构的添加剂(结构式1所示的化合物)加入到含有硅负极的电池中，由于结构式1所示的化合物具有较高的还原电位，该添加剂会在化成过程中先于溶剂在负极还原分解形成一层固态电解质界面膜(SEI)，形成的界面膜中同时 含有S元素。由于该结构式1所示的化合物在负极界面形成的硫酸酯锂盐(ROSO 3Li)而非碳酸酯锂盐(ROCO 2Li)占SEI的膜主要成分，与硅基材料具有较好的配合关系，因此在高温保存的过程中，避免了因副反应导致的阻抗增长和CO 2等气体产生，有效改善了高温存储性能，基于结构式1所示的化合物与硅基材料之间的配合关系，发明人经过大量研究发现，当非水电解液质量与负极材料层质量的百分比m、结构式1所示的化合物在非水电解液中的质量百分含量n、负极材料层的压实密度r和负极材料层中硅元素的质量百分含量S满足关系式：
Figure PCTCN2022132196-appb-000011
时，能够在保证电池具有优异能量密度的前提下，提高电池的高温存储性能。
具体实施方式
为了使本发明所解决的技术问题、技术方案及有益效果更加清楚明白，以下结合实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本发明实施例提供了一种二次电池，包括正极、具有负极材料层的负极和非水电解液，所述负极材料层包括负极活性材料，所述负极活性材料包括硅基材料；
所述非水电解液包括溶剂、电解质盐和添加剂，所述添加剂包括结构式1所示的化合物；
Figure PCTCN2022132196-appb-000012
其中，n为0或1，A选自C或O，X选自
Figure PCTCN2022132196-appb-000013
R 1、R 2各自独立选自H、
Figure PCTCN2022132196-appb-000014
R 1和R 2不同时选自H，且X、R 1和R 2中至少含有一个硫原子；
所述二次电池满足以下条件：
Figure PCTCN2022132196-appb-000015
且40％≤m≤90％，0.05％≤n≤2％，1.2g/cm 3≤r≤1.8g/cm 3，5％≤S≤30％；
其中，m为非水电解液质量与负极材料层质量的百分比，单位为％；
n为结构式1所示的化合物在非水电解液中的质量百分含量，单位为％；
r为负极材料层的压实密度，单位为g/cm 3；
S为负极材料层中硅元素的质量百分含量，单位为％。
由于结构式1所示的化合物具有较高的还原电位，该添加剂会在化成过程中先于溶剂在负极还原分解形成一层固态电解质界面膜(SEI)，形成的界面膜中同时含有S元素。由于该 结构式1所示的化合物在负极界面形成的硫酸酯锂盐(ROSO 3Li)而非碳酸酯锂盐(ROCO 2Li)占SEI的膜主要成分，与硅基材料具有较好的配合关系，因此在高温保存的过程中，避免了因副反应导致的阻抗增长和CO 2等气体产生，有效改善了高温存储性能，基于结构式1所示的化合物与硅基材料之间的配合关系，发明人经过大量研究发现，当非水电解液质量与负极材料层质量的百分比m、结构式1所示的化合物在非水电解液中的质量百分含量n、负极材料层的压实密度r和负极材料层中硅元素的质量百分含量S满足关系式：
Figure PCTCN2022132196-appb-000016
时，能够在保证电池具有优异能量密度的前提下，提高电池的高温存储性能。
在优选的实施例中，所述二次电池满足以下条件：
Figure PCTCN2022132196-appb-000017
将非水电解液质量与负极材料层质量的百分比m、结构式1所示的化合物在非水电解液中的质量百分含量n、负极材料层的压实密度r和负极材料层中硅元素的质量百分含量S相关联，能够一定程度上综合硅基材料负极与非水电解液添加剂对于电池性能的影响，以得到一种高温存储性能优异的二次电池。
在一些实施例中，非水电解液质量与负极材料层质量的百分比m为40％～90％；
在优选的实施例中，非水电解液质量与负极材料层质量的百分比m为45％～80％。
具体的，非水电解液质量与负极材料层质量的百分比m为40％、41％、43％、47％、50％、51％、54％、56％、59％、61％、63％、64％或65％。
由于结构式1所示的化合物在硅表面还原分解形成界面膜，而非水电解液的含量会直接影响电池的注液和保液系数，与结构式1所示的化合物在非水电解液中的质量百分含量n共同决定电池中结构式1所示的化合物的总含量；同时，负极活性材料质量和负极材料层中硅元素的质量百分含量S决定总含硅量，因此，非水电解液质量与负极材料层质量的百分比m是与该电池体系直接相关的限制条件。非水电解液质量与负极材料层质量的百分比m过大或过小均不利于结构式1所示的化合物与硅基材料的相互作用。
具体的，所述非水电解液中，结构式1所示的化合物的总质量百分含量n为0.05％、0.09％、0.1％、0.2％、0.4％、0.8％、1.1％、1.5％、1.7％、1.9％或2％。
在优选的实施例中，结构式1所示的化合物在非水电解液中的质量百分含量n为0.05％～1％。
硅基负极材料在存储过程中因负极体积效应带来的性能快速衰减是抑制其商业化应用的原因之一，而结构式1所示化合物应用在电池中时，会有轻微增大阻抗的现象。根据本发明人的研究验证，将结构式1所示添加剂应用于含硅电池中，在电池化成过程中，该添加剂在硅基负极表面发生还原分解参与形成SEI膜，形成的界面膜中含有的硫酸酯锂盐(ROSO 3Li)取代大部分碳酸酯锂盐(ROCO 2Li)成为主要有机成分，同时界面膜中具有吸电子效应的含S基团，与负极中的Si元素等进行络合，进一步稳定了界面结构。以上界面膜成分有效抑制了高温存储过程中因副反应导致的阻抗增长和CO 2等气体产生。因此在含硅负极电池体系当中，应用该添加剂均可以达到有效改善高温存储的效果。
当结构式1所示的化合物的总质量百分含量n过低时，则难以形成具有足够硫酸酯锂盐(ROSO 3Li)的界面膜；当结构式1所示的化合物的总质量百分含量n过高时，则容易在电池循环的过程中产生过多的副产物，从而影响非水电解液的稳定性。
具体的，负极材料层的压实密度r为1.2g/cm 3、1.25g/cm 3、1.3g/cm 3、1.35g/cm 3、1.4g/cm 3、1.45g/cm 3、1.5g/cm 3、1.55g/cm 3、1.6g/cm 3、1.65g/cm 3、1.7g/cm 3、1.75g/cm 3或1.8g/cm 3。
在优选的实施例中，负极材料层的压实密度r为1.4～1.7g/cm 3。
所述负极材料层为多孔结构，电池的充放电过程实际包含离子在负极材料层中的液相传导，故负极材料层中的孔道丰富程度将直接影响电池的快充和寿命性能。在其它条件相同的情况下，负极材料层的压实密度越小，则其孔道结构越发达，越有利于活性离子的液相传导， 尤其是在电池经历多次充放电反复膨胀的严苛条件下。但压实密度过小，会导致负极极片脱膜掉粉，充电时电子电导率较差而产生析锂，影响电池的快充和寿命性能，同时也会降低电池的能量密度。由于负极压实密度会影响非水电解液对含硅负极的浸润效果和含硅负极的体积膨胀率，因此压实大小同样与该电池体系性能直接相关。当负极材料层的压实密度处于上述范围中时，电池具有最佳的性能。
具体的，负极材料层中硅元素的质量百分含量S为5％、7％、10％、13％、15％、16％、18％、21％、23％、24％、26％、27％、29％或30％。
在优选的实施例中，所述负极材料层中硅元素的质量百分含量S为5％～20％。
硅基材料作为负极活性材料，起到锂离子脱嵌和嵌入的载体作用，相比于其他负极活性材料，如石墨等，硅基材料具有更高的理论容量，当负极材料层中硅元素的质量百分含量S处于上述范围中时，能够有效提高电池容量，同时也避免硅含量过大而导致电池循环时体积变化过大的问题。
以上分析仅基于每个参数或多个参数单独存在时对电池的影响，但实际电池应用过程中，电池中电解液的质量、电解液中结构式1所代表的化合物的含量、负极活性物质质量和硅元素在其中所占的比例，以及负极压实等参数存在一定的内在关联，当电解液的质量与负极活性材料总质量的比值在40～90％范围内，结构式1所示添加剂在电解液中含量为0.05～2％条件下，应用于负极含硅量在5～30％的电池体系中时，如果该电池负极压实不超过1.2～1.8g/cm 3，且以上参数之间的关系满足
Figure PCTCN2022132196-appb-000018
则该体系存储性能有明显的改善。
在一些实施例中，结构式1所示的化合物选自以下化合物1～18中的一种或多种：
Figure PCTCN2022132196-appb-000019
Figure PCTCN2022132196-appb-000020
Figure PCTCN2022132196-appb-000021
需要说明的是，以上仅是本发明优选的化合物，并不代表对于本发明的限制。
本领域技术人员在知晓结构式1的化合物的结构式的情况下，根据化学合成领域的公知常识可以知晓上述化合物的制备方法。例如：化合物7可通过以下方法制成：
将山梨醇、碳酸二甲酯、甲醇碱性物质催化剂氢氧化钾以及DMF等有机溶剂置于反应容器中，在加热条件下进行反应数小时后，加入一定量的草酸调节pH至中性，过滤、重结晶后即可得到中间产物1，接着将中间产物1、碳酸酯、二氯亚砜等在高温条件下发生酯化反应得到中间产物2，再使用高碘酸钠等氧化剂将中间产物2氧化即可得到化合物7。
在一些实施例中，所述硅基材料选自硅材料、硅的氧化物、硅碳复合材料以及硅合金材料中的至少一种。
所述硅材料为硅纳米颗粒、硅纳米线、硅纳米管、硅薄膜、3D多孔硅、中空多孔硅中的一种或几种。
在一些实施例中，所述负极还包括负极集流体，所述负极材料层覆盖于所述负极集流体的表面。本申请负极中除负极集流体之外的部分均称之为负极材料层。
所述负极集流体选自可传导电子的金属材料，优选的，所述负极集流体包括Al、Ni、锡、铜、不锈钢的一种或多种，在更优选的实施例中，所述负极集流体选自铝箔。
在一些实施例中，所述负极材料层还包括有负极粘结剂和负极导电剂，所述负极活性材料、所述负极粘结剂和所述负极导电剂共混得到所述负极材料层。所述负极粘结剂包括聚偏氟乙烯、偏氟乙烯的共聚物、聚四氟乙烯、偏氟乙烯-六氟丙烯的共聚物、四氟乙烯-六氟丙烯的共聚物、四氟乙烯-全氟烷基乙烯基醚的共聚物、乙烯-四氟乙烯的共聚物、偏氟乙烯-四氟乙烯的共聚物、偏氟乙烯-三氟乙烯的共聚物、偏氟乙烯-三氯乙烯的共聚物、偏氟乙烯-氟代乙烯的共聚物、偏氟乙烯-六氟丙烯-四氟乙烯的共聚物、热塑性聚酰亚胺、聚乙烯及聚丙烯等热塑性树脂；丙烯酸类树脂；羟甲基纤维素钠；以及苯乙烯丁二烯橡胶中的一种或多种。
所述负极导电剂包括导电炭黑、导电碳球、导电石墨、导电碳纤维、碳纳米管、石墨烯或还原氧化石墨烯中的一种或多种。
在一些实施例中，所述正极包括含有正极活性材料的正极材料层，所述正极活性材料的种类没有特别限制，可以根据实际需求进行选择，只要是能够可逆地嵌入/脱嵌金属离子(锂离子、钠离子、钾离子、镁离子、锌离子、铝离子等)的正极活性材料或转换型正极材料即可。
在优选实施例中，所述电池为锂离子电池，其正极活性材料可选自LiFe 1-x’M’ x’PO 4、LiMn 2-y’M y’O 4和LiNi xCo yMn zM 1-x-y-zO 2中的一种或多种，其中，M’选自Mn、Mg、Co、Ni、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的一种或多种，M选自Fe、Co、Ni、Mn、Mg、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的一种或多种，且0≤x’＜1，0≤y’≤1，0≤y≤1，0≤x≤1，0≤z≤1，x+y+z≤1，所述正极活性材料还可以选自硫化物、硒化物、卤化物中的一种或几种。更为优选的，所述正极活性材料可选自LiCoO 2、LiFePO 4、LiFe 0.8Mn 0.2PO 4、LiNi 0.5Co 0.2Mn 0.3O 2、LiNi 0.6Co 0.2Mn 0.2O 2、LiNi 0.8Co 0.1Mn 0.1O 2、LiNi 0.5Co 0.2Mn 0.2Al 0.1O 2、LiMn 2O 4、LiNi 0.5Co 0.2Al 0.3O 2中的一种或多种。
在优选实施例中，所述电池为钠离子电池，其正极活性材料可选自金属钠、碳材料、合金材料、过镀金属氧化物、过镀金属硫化物、磷基材料、钛酸盐材料、普鲁士蓝类材料中的一种或几种。所述碳材料可选自石墨、软碳、硬碳中的一种或几种，所述合金材料可选自由Si、Ge、Sn、Pb、Sb中的至少两种组成的合金材料，所述合金材料还可选自由Si、Ge、Sn、Pb、Sb中的至少一种与C组成的合金材料，所述过镀金属氧化物和所述过镀金属硫化物的化学式为M1 xN y，M1可选自Fe、Co、Ni、Cu、Mn、Sn、Mo、Sb、V中的一种或几种，N选自O或S，所述磷基材料可选自红磷、白磷、黑磷中的一种或几种，所述钛酸盐材料可选自 Na 2Ti 3O 7、Na 2Ti 6O 13、Na 4Ti 5O 12、Li 4Ti 5O 12、NaTi 2(PO 4) 3中的一种或几种，所述普鲁士蓝类材料的分子式为Na xM[M′(CN) 6] y·zH 2O，其中，M为过渡金属，M′为过渡金属，0<x≤2，0.8≤y<1，0<z≤20。
在一些实施例中，所述正极还包括正极集流体，所述正极材料层覆盖于所述正极集流体的表面。本申请正极中除正极集流体之外的部分均称之为正极材料层。
所述正极集流体选自可传导电子的金属材料，优选的，所述正极集流体包括Al、Ni、锡、铜、不锈钢的一种或多种，在更优选的实施例中，所述正极集流体选自铝箔。
在一些实施例中，所述正极材料层还包括有正极粘结剂和正极导电剂，所述正极活性材料、所述正极粘结剂和所述正极导电剂共混得到所述正极材料层。
在一些实施例中，所述正极粘结剂包括聚偏氟乙烯、偏氟乙烯的共聚物、聚四氟乙烯、偏氟乙烯-六氟丙烯的共聚物、四氟乙烯-六氟丙烯的共聚物、四氟乙烯-全氟烷基乙烯基醚的共聚物、乙烯-四氟乙烯的共聚物、偏氟乙烯-四氟乙烯的共聚物、偏氟乙烯-三氟乙烯的共聚物、偏氟乙烯-三氯乙烯的共聚物、偏氟乙烯-氟代乙烯的共聚物、偏氟乙烯-六氟丙烯-四氟乙烯的共聚物、热塑性聚酰亚胺、聚乙烯及聚丙烯等热塑性树脂；丙烯酸类树脂；以及苯乙烯丁二烯橡胶中的一种或多种。
在一些实施例中，所述正极导电剂包括金属导电剂、碳系材料、金属氧化物系导电剂、复合导电剂中的一种或多种。具体的，金属导电剂可以为铜粉、镍粉、银粉等金属；碳系材料可为导电石墨、导电炭黑、导电碳纤维或石墨烯等碳系材料；金属氧化物系导电剂可为氧化锡、氧化铁、氧化锌等；复合导电剂可以为复合粉、复合纤维等。更具体的，导电炭黑可以为乙炔黑、350G、科琴黑、碳纤维(VGCF)、碳纳米管(CNTs)中的一种或几种。
在一些实施例中，所述电解质盐包括锂盐、钠盐、钾盐、镁盐、锌盐和铝盐中的一种或多种。在优选的实施例中，所述电解质盐选自锂盐或钠盐。
在优选实施例中，所述电解质盐选自LiPF 6、LiPO 2F 2、LiBF 4、LiBOB、LiSbF 6、LiAsF 6、LiCF 3SO 3、LiDFOB、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiN(SO 2C 2F 5) 2、LiN(SO 2F) 2、LiCl、LiBr、LiI、LiClO 4、LiBF 4、LiB 10Cl 10、LiAlCl 4、氯硼烷锂、具有4个以下的碳原子的低级脂族羧酸锂、四苯基硼酸锂以及亚氨基锂中的至少一种。具体的，电解质盐可以为LiBF 4、LiClO 4、LiAlF 4、LiSbF 6、LiTaF 6、LiWF 7等无机电解质盐；LiPF 6等氟磷酸电解质盐类；LiWOF 5等钨酸电解质盐类；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等羧酸电解质盐类；CH 3SO 3Li等磺酸电解质盐类；LiN(FCO 2) 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-全氟乙二磺酰亚胺锂、环状1,3-全氟丙二磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)等酰亚胺电解质盐类；LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3等甲基电解质盐类；二氟草酸根合硼酸锂、二(草酸根合)硼酸锂、四氟草酸根合磷酸锂、二氟二(草酸根合)磷酸锂、三(草酸根合)磷酸锂等草酸电解质盐类；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等含氟有机电解质盐类等。
若所述电解质盐选自钠盐、钾盐、镁盐、锌盐或铝盐等其它盐时，可将上述锂盐中的锂对应换成钠、钾、镁、锌或铝等。
在优选实施例中，所述钠盐选自高氯酸钠(NaClO 4)、六氟磷酸钠(NaPF 6)、四氟硼酸钠(NaBF 4)、三氟甲基磺酸钠(NaFSI)、双三氟甲基磺酸钠(NaTFSI)中的至少一种。
通常，电解液中的电解质盐是锂离子的传递单元，电解质盐的浓度大小直接影响锂离子的传递速度，而锂离子的传递速度会影响负极的电位变化。在电池快速充电过程中，需要尽量提高锂离子的移动速度，防止负极电位下降过快导致锂枝晶的形成，给电池带来安全隐患，同时还能防止电池的循环容量过快衰减。优选的，所述电解质盐在电解液中的总浓度可以为0.5mol/L～2.0mol/L、0.5mol/L～0.6mol/L、0.6mol/L～0.7mol/L、0.7mol/L～0.8mol/L、 0.8mol/L～0.9mol/L、0.9mol/L～1.0mol/L、1.0mol/L～1.1mol/L、1.1mol/L～1.2mol/L、1.2mol/L～1.3mol/L、1.3mol/L～1.4mol/L、1.4mol/L～1.5mol/L、1.5mol/L～1.6mol/L、1.6mol/L～1.7mol/L、1.7mol/L～1.8mol/L、1.8mol/L～1.9mol/L、或1.9mol/L～2.0mol/L，进一步优选的可以为0.6mol/L～1.8mol/L、0.7mol/L～1.7mol/L、或0.8mol/L～1.5mol/L。
在一些实施例中，所述非水电解液中还包括辅助添加剂，所述辅助添加剂包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳酸酯类化合物、磷酸酯类化合物、硼酸酯类化合物和腈类化合物中的至少一种；
在优选的实施例中，所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯或甲基硫酸乙烯酯中的至少一种；
所述磺酸内酯类化合物选自甲基二磺酸亚甲酯、1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯或1,3-丙烯磺酸内酯中的至少一种；
所述环状碳酸酯类化合物选自碳酸亚乙烯酯、碳酸乙烯亚乙酯、氟代碳酸乙烯酯或结构式2所示化合物中的至少一种，
Figure PCTCN2022132196-appb-000022
所述结构式2中，R 21、R 22、R 23、R 24、R 25、R 26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种；
所述磷酸酯类化合物选自三(三甲基硅烷)磷酸酯、结构式3所示化合物中的至少一种：
Figure PCTCN2022132196-appb-000023
所述结构式3中，R 31、R 32、R 33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(C mH 2m+1) 3，m为1～3的自然数，且R 31、R 32、R 33中至少有一个为不饱和烃基。
在优选的实施例中，所述不饱和磷酸酯类化合物可为三(三甲基硅烷)磷酸酯、磷酸三炔丙酯、二炔丙基甲基磷酸酯、二炔丙基乙基磷酸酯、二炔丙基丙基磷酸酯、二炔丙基三氟甲基磷酸酯、二炔丙基-2,2,2-三氟乙基磷酸酯、二炔丙基-3,3,3-三氟丙基磷酸酯、二炔丙基六氟异丙基磷酸酯、磷酸三烯丙酯、二烯丙基甲基磷酸酯、二烯丙基乙基磷酸酯、二烯丙基丙基磷酸酯、二烯丙基三氟甲基磷酸酯、二烯丙基-2,2,2-三氟乙基磷酸酯、二烯丙基-3,3,3-三氟丙基磷酸酯、二烯丙基六氟异丙基磷酸酯中的至少一种。
所述硼酸酯类化合物选自三(三甲基硅烷)硼酸酯；
所述腈类化合物选自丁二腈、戊二腈、乙二醇双(丙腈)醚、己烷三腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的一种或多种。
在另一些实施例中，所述辅助添加剂还可包括其它能改善电池性能的添加剂：例如，提升电池安全性能的添加剂，具体如氟代磷酸酯、环磷腈等阻燃添加剂，或叔戊基苯、叔丁基苯等防过充添加剂。
在一些实施例中，以所述非水电解液的总质量为100％计，所述辅助添加剂的添加量为0.01％～30％。
需要说明的是，除非特殊说明，一般情况下，所述辅助添加剂中任意一种可选物质在非水电解液中的添加量为10％以下，优选的，添加量为0.1-5％，更优选的，添加量为0.1％～2％。具体的，所述辅助添加剂中任意一种可选物质的添加量可以为0.05％、0.08％、0.1％、0.5％、0.8％、1％、1.2％、1.5％、1.8％、2％、2.2％、2.5％、2.8％、3％、3.2％、3.5％、3.8％、4％、4.5％、5％、5.5％、6％、6.5％、7％、7.5％、7.8％、8％、8.5％、9％、9.5％、10％。
在一些实施例中，当辅助添加剂选自氟代碳酸乙烯酯时，以所述非水电解液的总质量为100％计，所述氟代碳酸乙烯酯的添加量为0.05％～30％。
在一些实施例中，所述溶剂包括醚类溶剂、腈类溶剂、碳酸酯类溶剂和羧酸酯类溶剂中的一种或多种。
在一些实施例中，醚类溶剂包括环状醚或链状醚，优选为碳原子数3～10的链状醚及碳原子数3～6的环状醚，环状醚具体可以但不限于是1,3-二氧戊烷(DOL)、1,4-二氧惡烷(DX)、冠醚、四氢呋喃(THF)、2-甲基四氢呋喃(2-CH 3-THF)，2-三氟甲基四氢呋喃(2-CF 3-THF)中的一种或多种；所述链状醚具体可以但不限于是二甲氧基甲烷、二乙氧基甲烷、乙氧基甲氧基甲烷、乙二醇二正丙基醚、乙二醇二正丁基醚、二乙二醇二甲基醚。由于链状醚与锂离子的溶剂化能力高、可提高离子解离性，因此特别优选粘性低、可赋予高离子电导率的二甲氧基甲烷、二乙氧基甲烷、乙氧基甲氧基甲烷。醚类化合物可以单独使用一种，也可以以任意的组合及比率组合使用两种以上。醚类化合物的添加量没有特殊限制，在不显著破坏本发明高压实锂离子电池效果的范围内是任意的，在非水溶剂体积比为100％中通常体积比为1％以上、优选体积比为2％以上、更优选体积比为3％以上，另外，通常体积比为30％以下、优选体积比为25％以下、更优选体积比为20％以下。在将两种以上醚类化合物组合使用的情况下，使醚类化合物的总量满足上述范围即可。醚类化合物的添加量在上述的优选范围内时，易于确保由链状醚的锂离子离解度的提高和粘度降低所带来的离子电导率的改善效果。另外，负极活性材料为碳素材料的情况下，可抑制因链状醚与锂离子共同发生共嵌入的现象，因此能够使输入输出特性、充放电速率特性达到适当的范围。
在一些实施例中，腈类溶剂具体可以但不限于是乙腈、戊二腈、丙二腈中的一种或多种。
在一些实施例中，碳酸酯类溶剂包括环状碳酸酯或链状碳酸酯，环状碳酸酯具体可以但不限于是碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、γ-丁内酯(GBL)、碳酸亚丁酯(BC)中的一种或多种；链状碳酸酯具体可以但不限于是碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)中的一种或多种。环状碳酸酯的含量没有特殊限制，在不显著破坏本发明二次电池效果的范围内是任意的，但在单独使用一种的情况下其含量的下限相对于非水电解液的溶剂总量来说，通常体积比为3％以上、优选体积比为5％以上。通过设定该范围，可避免由于非水电解液的介电常数降低而导致电导率降低，易于使非水电解质电池的大电流放电特性、相对于负极的稳定性、循环特性达到良好的范围。另外，上限通常体积比为90％以下、优选体积比为85％以下、更优选体积比为80％以下。通过设定该范围，可提高非水电解液的氧化/还原耐性，从而有助于提高高温保存时的稳定性。链状碳酸酯的含量没有特殊限定，相对于非水电解液的溶剂总量，通常为体积比为15％以上、优选体积比为20％以上、更优选体积比为25％以上。另外，通常体积比为90％以下、优选体积比为85％以下、更优选体积比为80％以下。通过使链状碳酸酯的含量在上述范围，容易使非水电解液 的粘度达到适当范围，抑制离子电导率的降低，进而有助于使非水电解质电池的输出特性达到良好的范围。在组合使用两种以上链状碳酸酯的情况下，使链状碳酸酯的总量满足上述范围即可。
在一些实施例中，还可优选使用具有氟原子的链状碳酸酯类(以下简称为“氟化链状碳酸酯”)。氟化链状碳酸酯所具有的氟原子的个数只要为1以上则没有特殊限制，但通常为6以下、优选4以下。氟化链状碳酸酯具有多个氟原子的情况下，这些氟原子相互可以键合于同一个碳上，也可以键合于不同的碳上。作为氟化链状碳酸酯，可列举，氟化碳酸二甲酯衍生物、氟化碳酸甲乙酯衍生物、氟化碳酸二乙酯衍生物等。
羧酸酯类溶剂包括环状羧酸酯和/或链状碳酸酯。作为环状羧酸酯的例子，可以列举如：γ-丁内酯、γ-戊内酯、δ-戊内酯中的一种或多种。作为链状碳酸酯的例子，可以列举如：乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(EP)、乙酸丁酯、丙酸丙酯(PP)、丙酸丁酯中的一种或多种。
在一些实施例中，砜类溶剂包括环状砜和链状砜，优选地，在为环状砜的情况下，通常为碳原子数3～6、优选碳原子数3～5，在为链状砜的情况下，通常为碳原子数2～6、优选碳原子数2～5的化合物。砜类溶剂的添加量没有特殊限制，在不显著破坏本发明二次电池效果的范围内是任意的，相对于非水电解液的溶剂总量，通常体积比为0.3％以上、优选体积比为0.5％以上、更优选体积比为1％以上，另外，通常体积比为40％以下、优选体积比为35％以下、更优选体积比为30％以下。在组合使用两种以上砜类溶剂的情况下，使砜类溶剂的总量满足上述范围即可。砜类溶剂的添加量在上述范围内时，倾向于获得高温保存稳定性优异的电解液。
在优选的实施例中，所述溶剂为环状碳酸酯和链状碳酸酯的混合物。
在一些实施例中，所述电池中还包括有隔膜，所述隔膜位于所述正极和所述负极之间。
所述隔膜可为现有常规隔膜，可以是聚合物隔膜、无纺布等，包括但不限于单层PP(聚丙烯)、单层PE(聚乙烯)、双层PP/PE、双层PP/PP和三层PP/PE/PP等隔膜。
以下通过实施例对本发明进行进一步的说明。
以下实施例和对比例涉及的化合物如下表所示：
Figure PCTCN2022132196-appb-000024
Figure PCTCN2022132196-appb-000025
表1实施例和对比例各参数设计
Figure PCTCN2022132196-appb-000026
Figure PCTCN2022132196-appb-000027
实施例1
本实施例用于说明本发明公开的二次电池及其制备方法，包括以下操作步骤：
1)电解液的制备
将碳酸乙烯酯(EC)、氟代碳酸乙烯酯(FEC)、碳酸二乙酯(DEC)和碳酸甲乙酯(EMC)按质量比为EC:FEC:DEC:EMC＝20:10:30:40进行混合，然后加入六氟磷酸锂(LiPF 6)至摩尔浓度为1mol/L，然后按照表1加入添加剂。添加剂的用量，按照占电解液的总质量的百分比计。
2)正极板的制备
按97:1.5:1.5的质量比混合正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2、导电碳黑Super-P和粘结剂聚偏二氟乙烯(PVDF)，然后将它们分散在N-甲基-2-吡咯烷酮(NMP)中，得到正极浆料。将浆料均匀涂布在铝箔的两面上，经过烘干、压延和真空干燥，并用超声波焊机焊上铝制引出线后得到正极板，极板的厚度在120-150μm。
3)负极板的制备
按94:1.5:3:1.5的质量比混合负极活性材料SiO-C、导电碳黑Super-P，粘结剂丁苯橡胶(SBR)和羧甲基纤维素(CMC)，然后将它们分散在去离子水中，得到负极浆料。将浆料 涂布在铜箔的两面上，经过烘干、压延和真空干燥，并用超声波焊机焊上镍制引出线后得到负极板，极板的厚度在120-150μm，负极含硅量和压实密度如表1所示。
4)电芯的制备
在正极板和负极板之间放置厚度为20μm的三层隔离膜，然后将正极板、负极板和隔膜组成的三明治结构进行卷绕，再将卷绕体压扁后放入铝箔包装袋，在75℃下真空烘烤48h，得到待注液的电芯。
5)电芯的注液和化成
在水氧含量分别20ppm、50ppm以下的手套箱中，将上述制备的电解液注入电芯中，注液量以表1限制为准，经真空封装，45℃搁置24h。
然后按以下步骤进行首次充电的常规化成：0.05C恒流充电180min,0.1C恒流充电180min，0.2C恒流充电120min，在45℃老化48h后，二次真空封口，然后进一步以0.2C的电流恒流充电至4.2V，以0.2C的电流恒流放电至2.75V。
实施例2～40
实施例2～40用于说明本发明公开的电池及其制备方法，包括实施例1中大部分操作步骤，其不同之处在于：
采用表1所示的电解液添加组分和负极材料层。
对比例1～10
对比例1～10用于说明本发明公开的电池及其制备方法，包括实施例1中大部分操作步骤，其不同之处在于：
采用表1所示的电解液添加组分和负极材料层。
性能测试
对上述制备得到的锂离子电池进行如下性能测试：
将制备的锂离子电池恒流恒压充电至4.2V后置于恒温60℃的烘箱中保存，并在存储30天后进行放电容量、体积、内阻的测试。记录存储之前的放电容量和体积及阻抗，和存储30天之后的放电容量和体积及阻抗。
按下式计算高温存储的容量保持率、阻抗增长率和气胀率：
容量保持率＝存储后的放电容量/存储前的容量×100％；
阻抗增长率＝(存储后的阻抗-存储前的阻抗)/存储前的阻抗×100％；
气胀率＝(存储后电池体积-初始电池体积)/初始电池体积×100％。
(1)实施例1～29和对比例1～9得到的测试结果填入表2。
表2
Figure PCTCN2022132196-appb-000028
Figure PCTCN2022132196-appb-000029
从表2的测试结果可以看出，实施例1～实施例29中，当非水电解液质量与负极材料层质量的百分比m、结构式1所示的化合物在非水电解液中的质量百分含量n、负极材料层的压实密度r和负极材料层中硅元素的质量百分含量S满足关系式：
Figure PCTCN2022132196-appb-000030
且40％≤m≤90％，0.05％≤n≤2％，1.2g/cm 3≤r≤1.8g/cm 3，5％≤S≤30％时，能够有效提高锂离子电池在高温环境下的容量保持率，降低其阻抗增长率和气胀率，实施例1～实施例29中，结构式1所示的化合物由于其较低的还原电位，能够在硅基负极表面分解形成富含S元素的钝化膜，同时通过调节非水电解液质量与负极材料层质量的百分比和负极材料层的压实密度，使得非水电解液在负极材料层中充分浸润，保证结构式1所示的化合物与硅元素的充分接触，结构式1所示的化合物分解得到的钝化膜具有致密和强度高的特点，硅基负极的硅元素与结构式1所示的化合物分解得到含S钝化膜之间具有化学键合效果，钝化膜在硅基材料充放电膨胀的过程中，能限制硅基材料的膨胀体积，进而避免高温条件下钝化膜充放电的分裂，提高钝化膜的性质稳定性，以降低电池高温下阻抗的增长，以及减少由于非水电解液持续分解导致的气胀问题。
从对比例2～7的测试结果可以看出，即使
Figure PCTCN2022132196-appb-000031
值处于0.21和40之间，但非水电解液质量与负极材料层质量的百分比m、结构式1所示的化合物在非水电解液中的质量百分含量n、负极材料层的压实密度r和负极材料层中硅元素的质量百分含量S不满足其范围限制时，同样无法得到高温存储性能优异的锂离子电池，而从对比例8和对比例9可以看出，即使非水电解液质量与负极材料层质量的百分比m、结构式1所示的化合物在非水电解液中的质量百分含量n、负极材料层的压实密度r和负极材料层中硅元素的质量百分含量S满足范围限制，但
Figure PCTCN2022132196-appb-000032
值过小时，同样无法提高锂离子电池的高温存储性能。可知，非水电解液质量与负极材料层质量的百分比m、结构式1所示的化合物在非水电解液中的质量百分含量n、负极材料层的压实密度r和负极材料层中硅元素的质量百分含量S在提高电池高温存储性能方面具有强关联性，当非水电解液质量与负极材料层质量的百分比m和负极材料层的压实密度r无法适配结构式1所示的化合物在非水电解液中的质量百分含量n和负极材料层中硅元素的质量百分含量S时，会影响结构式1所示化合物与硅基负极表面的接触，进而影响结构式1所示化合物形成钝化膜的质量，当该钝化膜强度不足时，容易在硅基负极体积变化的过程中发生破裂，进而在破裂的表面重新导致非水电解液的分解，影响非水电解液的高温稳定性，导致电池产气严重，也增加了钝化膜厚度，提高电池阻抗；因此通过对
Figure PCTCN2022132196-appb-000033
值进行限定，能够共同促进锂离子电池在高温条件下的性能稳定性，避免负极材料或非水电解液的失效影响电池容量。
从实施例1～5、7～10的测试结果可以看出，随着负极活性材料中硅含量的提升，负极活性材料在高温存储过程中与非水电解液的反应加剧，锂离子电池的高温存储容量保持率降低，而阻抗增长率和气胀率提升，导致高温存储性能劣化；而随着结构式1所示的化合物的含量的增加，在负极活性材料表面形成了钝化膜，对硅基负极形成了较好的隔离作用，避免非水电解液与硅基负极的直接接触，能够有效逆转由于硅基负极带来的高温性能劣化，保证锂离子电池的性能平衡。
从实施例13～15的测试结果可以看出，随着非水电解液质量与负极材料层质量的百分比m的提高，电池中非水电解液的含量增加，可促进锂离子在负极材料层中的嵌入和脱出，降低了电池的阻抗，同时，由于游离的非水电解液的增加，使得其易在高温条件下与硅基负极发生反应分解而产气，因此也提高了电池的气胀率。
(2)实施例2、30～35得到的测试结果填入表3
表3
Figure PCTCN2022132196-appb-000034
从表3的测试结果可知，实施例2、30～35中，当采用不同的结构式1所示的化合物所示 的化合物时，同样满足
Figure PCTCN2022132196-appb-000035
以及对于m值、n值、r值和S值的范围限定，说明不同的结构式1所示的化合物中共有的环状硫酸酯基团在参与硅基负极表面钝化膜的形成过程中产生了决定性的作用，其分解产生的富含S元素的钝化膜与硅基负极均具有较好的结合强度，抑制硅基负极与非水电解液的持续反应，从而对于电池的高温存储性能具有普适性的提升。
(3)实施例2、36～40得到的测试结果填入表4
表4
Figure PCTCN2022132196-appb-000036
从表4的测试结果可知，实施例2、36～40中，在本发明提供的锂离子电池体系的基础上，添加PS、DTD、三(三甲基硅烷)硼酸酯、磷酸三炔丙酯、丁二腈等作为辅助添加剂，能够进一步的提高电池的循环性能，推测可能是由于PS、DTD中含有的小分子环状含S化合物分解得到的产物组分链长相对结构式1所示化合物的分解产物要短，能够填补结构式1所示化合物形成钝化膜的间隙，而三(三甲基硅烷)硼酸酯、磷酸三炔丙酯、丁二腈同样具有较低的还原电位，其含有的硅烷、硼、磷、氮元素对钝化膜起到补强作用，以在负极材料层中形成更加稳定的钝化膜结构，以提高电池的高温存储稳定性。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (11)

  1. 一种二次电池，其特征在于，包括正极、具有负极材料层的负极和非水电解液，所述负极材料层包括负极活性材料，所述负极活性材料包括硅基材料；
    所述非水电解液包括溶剂、电解质盐和添加剂，所述添加剂包括结构式1所示的化合物；
    Figure PCTCN2022132196-appb-100001
    其中，n为0或1，A选自C或O，X选自
    Figure PCTCN2022132196-appb-100002
    R 1、R 2各自独立选自H、
    Figure PCTCN2022132196-appb-100003
    Figure PCTCN2022132196-appb-100004
    R 1和R 2不同时选自H，且X、R 1和R 2中至少含有一个硫原子；
    所述二次电池满足以下条件：
    Figure PCTCN2022132196-appb-100005
    且40％≤m≤90％，0.05％≤n≤2％，1.2g/cm 3≤r≤1.8g/cm 3，5％≤S≤30％；
    其中，m为非水电解液质量与负极材料层质量的百分比，单位为％；
    n为结构式1所示的化合物在非水电解液中的质量百分含量，单位为％；
    r为负极材料层的压实密度，单位为g/cm 3；
    S为负极材料层中硅元素的质量百分含量，单位为％。
  2. 根据权利要求1所述的二次电池，其特征在于，所述二次电池满足以下条件：
    Figure PCTCN2022132196-appb-100006
  3. 根据权利要求1所述的二次电池，其特征在于，所述非水电解液质量与负极材料层质量的百分比m为45％～80％。
  4. 根据权利要求1所述的二次电池，其特征在于，所述结构式1所示的化合物在非水电解液中的质量百分含量n为0.05％～1％。
  5. 根据权利要求1所述的二次电池，其特征在于，所述负极材料层的压实密度r为1.4～1.7g/cm 3。
  6. 根据权利要求1所述的二次电池，其特征在于，所述负极材料层中硅元素的质量百分含量S为5％～20％。
  7. 根据权利要求1所述的二次电池，其特征在于，所述结构式1所示的化合物选自以下化合物1～18中的一种或多种：
    Figure PCTCN2022132196-appb-100007
    Figure PCTCN2022132196-appb-100008
  8. 根据权利要求1所述的二次电池，其特征在于，所述硅基材料选自硅材料、硅的氧化物、硅碳复合材料以及硅合金材料中的至少一种。
  9. 根据权利要求1所述的二次电池，其特征在于，所述非水电解液中还包括辅助添加剂，所述辅助添加剂包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳酸酯类化合物、磷酸酯类化合物、硼酸酯类化合物和腈类化合物中的至 少一种。
  10. 根据权利要求9所述的二次电池，其特征在于，以所述非水电解液的总质量为100％计，所述辅助添加剂的添加量为0.01％～30％。
  11. 根据权利要求9所述的锂离子电池，其特征在于，所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯或甲基硫酸乙烯酯中的至少一种；
    所述磺酸内酯类化合物选自甲基二磺酸亚甲酯、1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯或1,3-丙烯磺酸内酯中的至少一种；
    所述环状碳酸酯类化合物选自碳酸亚乙烯酯、碳酸乙烯亚乙酯、氟代碳酸乙烯酯或结构式2所示化合物中的至少一种，
    Figure PCTCN2022132196-appb-100009
    所述结构式2中，R 21、R 22、R 23、R 24、R 25、R 26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种；
    所述磷酸酯类化合物选自三(三甲基硅烷)磷酸酯、结构式3所示化合物中的至少一种：
    Figure PCTCN2022132196-appb-100010
    所述结构式3中，R 31、R 32、R 33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(C mH 2m+1) 3，m为1～3的自然数，且R 31、R 32、R 33中至少有一个为不饱和烃基；
    所述硼酸酯类化合物选自三(三甲基硅烷)硼酸酯；
    所述腈类化合物选自丁二腈、戊二腈、乙二醇双(丙腈)醚、己烷三腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的一种或多种。
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