WO2023000214A1 - 电解液、二次电池、电池模块、电池包和用电装置 - Google Patents

电解液、二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023000214A1
WO2023000214A1 PCT/CN2021/107669 CN2021107669W WO2023000214A1 WO 2023000214 A1 WO2023000214 A1 WO 2023000214A1 CN 2021107669 W CN2021107669 W CN 2021107669W WO 2023000214 A1 WO2023000214 A1 WO 2023000214A1
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secondary battery
electrolyte
positive electrode
battery
sodium dithionite
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PCT/CN2021/107669
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English (en)
French (fr)
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吴则利
韩昌隆
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宁德时代新能源科技股份有限公司
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Priority to KR1020227031024A priority Critical patent/KR20230015309A/ko
Priority to PCT/CN2021/107669 priority patent/WO2023000214A1/zh
Priority to JP2022552905A priority patent/JP7469496B2/ja
Priority to EP21926054.4A priority patent/EP4148854A4/en
Priority to CN202180076040.2A priority patent/CN116420259A/zh
Priority to US17/822,079 priority patent/US20230043895A1/en
Publication of WO2023000214A1 publication Critical patent/WO2023000214A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • 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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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
    • 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
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0034—Fluorinated solvents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of lithium batteries, in particular to electrolytes, secondary batteries, battery modules, battery packs and electrical devices.
  • secondary batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind and solar power plants, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields. Due to the great development of secondary batteries, higher requirements have been put forward for their initial DCR, storage gas production and rate performance.
  • the existing secondary battery positive electrode materials (especially ternary materials) will have side reactions such as oxygen release due to material instability under high temperature or high voltage, which seriously affects the life of lithium batteries. Therefore, the positive electrode needs to be further protected, and the initial DCR, high-temperature storage gas production and rate performance of the battery still need to be improved.
  • This application is made in view of the above problems, and its purpose is to provide an electrolyte to further improve the overall performance of the secondary battery (such as reducing the initial DCR, storing gas, improving the rate performance, etc.).
  • the present application provides an electrolyte, a secondary battery, a battery module, a battery pack and an electrical device.
  • the first aspect of the present application provides an electrolytic solution, including an electrolyte, a solvent and an additive, and the additive includes sodium dithionite.
  • the present application uses sodium dithionite as an additive, and sodium dithionite can form an interface film on the surface of the positive electrode and the negative electrode during the charging and discharging process of the lithium secondary battery, and the formed interface film has a technical effect of lower impedance, It can reduce the initial DCR of the battery, store gas, and improve the rate performance.
  • the mass percentage of the sodium dithionite in the electrolyte is greater than 0 and less than or equal to 0.5%; optionally, the mass percentage of the sodium dithionite in the electrolyte is 0.2% ⁇ 0.4%; further optionally, the mass percentage of the sodium dithionite in the electrolyte is 0.25% ⁇ 0.35%. Therefore, by limiting the dosage of the sodium dithionite additive to the above range, the secondary battery can have low initial DCR, low high-temperature storage gas production and excellent discharge rate performance.
  • the additive further includes a combination of one or more of 1,3-propane sultone, fluoroethylene carbonate, and ethylene sulfate. Therefore, through the synergistic effect of sodium dithionite and one or more of 1,3-propane sultone and fluoroethylene carbonate, various performances of the secondary battery are further improved.
  • the mass percentage of the total mass of the additives in the electrolyte is greater than 0 and less than or equal to 5%.
  • the molar concentration of the electrolyte is 0.8-1.2 mol/L. Therefore, by limiting the molar concentration of the electrolyte to the above range, the electrolyte can have good conductivity and viscosity properties, and at the same time, the secondary battery using the electrolyte can have a relatively excellent initial DCR value.
  • the solvent includes one or a combination of chain esters and cyclic esters.
  • the electrolyte solution can have low viscosity and high conductivity.
  • the chain esters include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propionic acid Propyl ester, ethyl butyrate, ethyl propionate, the combination of one or more in propyl butyrate;
  • described cyclic ester comprises ethylene carbonate, propylene carbonate, butylene carbonate, One or more combinations of ⁇ -butyrolactone and tetrahydrofuran. Therefore, by selecting the above-mentioned chain ester and/or cyclic ester as the aprotic solvent, the overall performance of the secondary battery can be exhibited more effectively.
  • the second aspect of the present application also provides a secondary battery, including a positive pole piece, a negative pole piece, a separator and the electrolyte described in the first aspect of the present invention, and the separator is located between the positive pole piece and the negative pole piece between.
  • the performance of the secondary battery can be effectively improved.
  • sodium dithionite can be preferentially used over solvents such as chain esters and cyclic esters, respectively. Oxidation on the surface of the positive electrode and reduction on the surface of the negative electrode form a low-impedance interfacial film first, thereby improving the performance of the secondary battery.
  • the positive electrode sheet includes a positive electrode material, and the positive electrode material includes a nickel-rich ternary positive electrode active material. Therefore, the high Ni content in the high-nickel ternary positive electrode active material can increase the energy density of the battery and reduce the use of cobalt. However, as the Ni content increases, its ability to oxidize and decompose the electrolyte solvent becomes stronger.
  • the mass percentage of Ni element is ⁇ 80%.
  • the activity of the material can be improved, and the energy density can be increased, but its ability to oxidize and decompose the electrolyte solvent is very strong.
  • Solvents such as chain esters and cyclic esters are oxidized on the surface of the positive electrode to form a low-impedance interfacial film first, thereby improving battery performance.
  • the chemical structural formula (1) of the high-nickel ternary positive electrode active material is as follows: Li 1+y Ni a Co b Me 1-ab O 2-z A z formula (1); wherein, -0.1 ⁇ y ⁇ 0.2, 0.5 ⁇ a ⁇ 0.9, 0 ⁇ b ⁇ 0.5, 0.5 ⁇ a+b ⁇ 1, 0 ⁇ z ⁇ 0.2; the Me is selected from Mn, Fe, Cr, Ti, Zn, V, One or more of Al, Zr, Ce; said A is selected from one or more of S, N, F, Cl, Br, I.
  • the activity of the material can be improved, and the energy density can be improved, but its ability to oxidize and decompose the electrolyte solvent is very strong, so by using the sodium dithionite additive, its It can be preferentially oxidized on the surface of the positive electrode over solvents such as chain esters and cyclic esters, and forms a low-impedance interfacial film at the earliest, thereby improving battery performance.
  • the positive electrode material has a specific surface area BET ranging from 0.15 to 0.75 m 2 /g. Therefore, by limiting the specific surface area BET of the positive electrode material to this range, the secondary battery can have good kinetic performance and lifespan.
  • the negative electrode sheet includes a negative electrode material
  • the negative electrode material includes natural graphite, artificial graphite, mesophase micro carbon spheres, hard carbon, soft carbon, silicon oxide, silicon-carbon composite, Li- A combination of one or more of Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO 2 , lithiated spinel structures, and Li-Al alloys. Therefore, the above-mentioned negative electrode material has high activity, but has strong reductive decomposition ability to the electrolyte solution solvent.
  • the negative electrode material has a specific surface area BET ranging from 0.8 m 2 /g to 1.5 m 2 /g. Therefore, the specific surface area BET of the negative electrode material has strong activity within the above numerical range, but it has a strong ability to reduce and decompose the electrolyte solvent.
  • sodium dithionite as an additive, it can be prioritized over solvents such as chain esters and cyclic esters. It is reduced on the surface of the negative electrode to form a low-resistance interfacial film first, thereby improving battery performance.
  • the upper limit voltage of the secondary battery is ⁇ 4.15V. Therefore, a secondary battery having a voltage upper limit above this range has characteristics of high capacity and strong oxidative properties.
  • sodium dithionite in combination with the positive electrode material of the present application, the advantages of this type of ternary positive electrode material can be better utilized, namely improving high-temperature storage performance, high-rate discharge capability and reducing initial DCR.
  • a third aspect of the present application provides a battery module including the secondary battery of the second aspect of the present application.
  • a fourth aspect of the present application provides a battery pack, including the battery module of the third aspect of the present application.
  • the fifth aspect of the present application provides an electric device, including at least one selected from the secondary battery of the second aspect of the present application, the battery module of the third aspect of the present application, or the battery pack of the fourth aspect of the present application. kind.
  • the present invention has the following beneficial effects:
  • the electrolyte solution provided by the present invention can reduce the initial DCR of the battery, store gas production, and improve the rate performance by using sodium dithionite as the electrolyte additive of the secondary battery.
  • sodium dithionite As the electrolyte additive of the secondary battery.
  • the mechanism is not very clear, it is speculated that the valence state of the S element in sodium dithionite is +3 state, which is the intermediate valence state of the S element, and the S element in this valence state usually has a relatively strong activity. Therefore, sodium dithionite can be first reduced on the surface of the negative electrode, and the interface film formed by its reduction has the effect of low impedance. Overall performance of the battery.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • the present application proposes an electrolyte, and the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the electrolytic solution includes an electrolyte, a solvent, and additives including sodium dithionite.
  • the chemical properties of sodium dithionite are mainly used to absorb oxygen, and sodium dithionite is used as a positive electrode slurry additive.
  • sodium dithionite has a good electrochemical effect.
  • the present application adopts the scheme that the additive includes sodium dithionite and mixes it with electrolyte and solvent to obtain an electrolyte solution, which can reduce the initial DCR of the battery, store gas production, and improve the rate performance.
  • the mechanism is not clear, it is speculated that the valence state of the S element in sodium dithionite is +3, which is the intermediate valence state of the S element, and the S element in this valence state usually has a relatively strong activity. Therefore, sodium dithionite can be first reduced on the surface of the negative electrode, and the interface film formed by its reduction has a low impedance effect. Overall performance of the battery.
  • the mass percentage of the sodium dithionite in the electrolyte can be, for example, greater than 0 and less than or equal to 0.5%, 0.001%-0.1%, 0.1%-0.2%, 0.2%-0.4%, 0.4% % ⁇ 0.5%; 0.001% ⁇ 0.15%, 0.015% ⁇ 0.25%, 0.25% ⁇ 0.35%, or 0.35% ⁇ 0.5%, etc.
  • the mass percentage of the sodium dithionite in the electrolyte is 0.2% to 0.4%; further optionally, the mass percentage of the sodium dithionite in the electrolyte is 0.25% to 0.35% .
  • the secondary battery can have low initial DCR, low high-temperature storage gas production and excellent discharge rate performance.
  • additives in addition to sodium dithionite, other additives may also be contained.
  • the additive may also include, for example, one or more combinations of 1,3-propane sultone, fluoroethylene carbonate, ethylene sulfate and the like. Therefore, sodium dithionite can have a synergistic effect with one or more of 1,3-propane sultone, fluoroethylene carbonate, ethylene sulfate, etc., so that the storage of the secondary battery produces gas and rate performance have been further improved.
  • the mass percentage of the total mass of the additives in the electrolyte can be, for example, greater than 0 and less than or equal to 5%, 0.001%-1%, 1%-2%, 2%-3%, 3% to 4%, 4% to 5%, 0.001% to 2%, or 2% to 5%, etc. Therefore, by limiting the total mass of each additive within the above range, the sodium dithionite and other additives can work together better to improve the performance of the secondary battery, especially to avoid excessive participation of additives on the surface of the positive and negative electrodes. Deterioration of initial DCR due to filming.
  • the molar concentration of the electrolyte can be 0.8mol/L ⁇ 1.2mol/L, 0.8mol/L ⁇ 1.0mol/L, 1.0mol/L ⁇ 1.2mol/L; 0.8mol/L ⁇ 0.9 mol/L, 0.9mol/L ⁇ 1.0mol/L, 1.0mol/L ⁇ 1.1mol/L, or 1.1mol/L ⁇ 1.2mol/L, etc. Therefore, by limiting the molar concentration of the electrolyte to the above range, the electrolyte of the secondary battery can have good conductivity and viscosity properties, and at the same time, the secondary battery using the electrolyte can have a relatively excellent initial DCR value.
  • the electrolyte includes a lithium salt.
  • the electrolyte includes LiPF 6 , LiBF 4 , LiBOB, LiDFOB, LiSO 3 CF 3 , LiClO 4 , LiAsF 6 , Li(FSO 2 ) 2 N, Li(CF 3 SO 2 ) 2 N and LiC(CF 3 One or more combinations of SO 2 ) 3 and the like.
  • the lithium salt may be LiPF 6 and Li(FSO 2 ) 2 N.
  • the concentration of the lithium salt can be 0.8mol/L ⁇ 1.2mol/L, 0.8mol/L ⁇ 1.0mol/L, 1.0mol/L ⁇ 1.2mol/L; 0.8mol/L ⁇ 0.9 mol/L, 0.9mol/L ⁇ 1.0mol/L, 1.0mol/L ⁇ 1.1mol/L, or 1.1mol/L ⁇ 1.2mol/L, etc.
  • lithium salt concentration By limiting the lithium salt concentration to this range, the following situations can be avoided: too low lithium salt concentration leads to a small amount of lithium ions provided in the solution, which is not conducive to the diffusion of lithium ions, causing the electrolyte conductivity to become low, and lithium salt The viscosity of the solution caused by too high concentration is not conducive to the transmission of lithium ions, resulting in a decrease in conductivity. That is, thereby, the electrical conductivity and viscosity of the electrolytic solution can be improved.
  • the type of the solvent is not specifically limited, and can be selected according to actual needs.
  • the solvent may include, for example, an organic solvent, and further, the solvent may include one or a combination of chain esters and cyclic esters.
  • the dielectric constant of cyclic ester is large, which can dissociate lithium salt of electrolyte well, but the viscosity of cyclic ester solvent is relatively high, while the viscosity of chain ester is low, therefore, through the cyclic ester and cyclic ester Used in combination, the electrolyte solution can have low viscosity and high conductivity.
  • the chain esters include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl formate , ethyl formate, methyl acetate, ethyl acetate, propyl propionate, ethyl butyrate, ethyl propionate, propyl butyrate; and/or, the cyclic Esters include ethylene carbonate (1,3-dioxolane-2-one, 1,3-dioxolanone, Ethylene carbonate) CAS No.
  • the electrolyte solution provided by the first aspect of the present invention can be prepared by methods known in the art, for example, a specific proportion of electrolyte, solvent and additive can be mixed uniformly.
  • the present application proposes the use of the electrolyte solution according to the first aspect of the present invention in the field of secondary battery preparation.
  • a secondary battery is provided.
  • a secondary battery includes a positive pole piece, a negative pole piece, a separator and the electrolyte as described in the first aspect of the present invention.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the positive electrode sheet includes a positive electrode collector and a positive electrode film layer arranged on at least one surface of the positive electrode collector, and the positive electrode film layer includes a positive electrode material.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode material can be a positive electrode material known in the art for batteries.
  • the cathode material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as battery cathode materials can also be used.
  • These positive electrode materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also abbreviated as NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon At least one of composite materials, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composite materials.
  • the positive electrode material includes a high-nickel ternary positive electrode active material. Because Ni in the high-nickel ternary positive electrode active material A high content can improve the activity of the material and increase the energy density, but it has a strong ability to oxidize and decompose the electrolyte solvent.
  • the mass percentage of Ni element may be ⁇ 80%, 80%-85%, 85%-90%, or 90%-95%. Therefore, when the Ni content of the positive electrode is limited to ⁇ 80%, the ability to oxidize and decompose the electrolyte solvent is very strong. At this time, by using the additive sodium dithionite, it can preferentially oxidize the solvent on the surface of the positive electrode to form a low-impedance interface film. So as to improve the overall performance of the battery.
  • the chemical structural formula (1) of the high-nickel ternary positive electrode active material is as follows: Li 1+y Ni a Co b Me 1-ab O 2-z A z formula (1); wherein, y can usually satisfy -0.1 ⁇ y ⁇ 0.2, -0.1 ⁇ y ⁇ 0, 0 ⁇ y ⁇ 0.1, 0.1 ⁇ y ⁇ 0.2; -0.1 ⁇ y ⁇ -0.05, -0.05 ⁇ y ⁇ 0, 0 ⁇ y ⁇ 0.05 , 0.05 ⁇ y ⁇ 0.1, 0.1 ⁇ y ⁇ 0.15, or 0.15 ⁇ y ⁇ 0.2, etc.
  • a usually satisfies 0.5 ⁇ a ⁇ 0.9, 0.5 ⁇ a ⁇ 0.7, 0.7 ⁇ a ⁇ 0.9;0.5 ⁇ a ⁇ 0.6,0.6 ⁇ a ⁇ 0.7,0.7 ⁇ a ⁇ 0.8, or 0.8 ⁇ a ⁇ 0.9, etc.
  • b can usually satisfy 0 ⁇ b ⁇ 0.5, 0 ⁇ b ⁇ 0.1, 0.1 ⁇ b ⁇ 0.2, 0.2 ⁇ b ⁇ 0.3, 0.3 ⁇ b ⁇ 0.4, 0.4 ⁇ b ⁇ 0.5;0 ⁇ b ⁇ 0.3, or 0.3 ⁇ b ⁇ 0.5 etc.
  • a+b can usually satisfy 0.5 ⁇ a+b ⁇ 1, 0.5 ⁇ a+b ⁇ 0.8, 0.8 ⁇ a+b ⁇ 1, 0.5 ⁇ a+b ⁇ 0.6, 0.6 ⁇ a+b ⁇ 0.7, 0.7 ⁇ a+ b ⁇ 0.8, 0.8 ⁇ a+b ⁇ 0.9, or 0.9 ⁇ a+b ⁇ 1, etc.
  • z can usually satisfy 0 ⁇ z ⁇ 0.2, 0 ⁇ z ⁇ 0.1, 0.1 ⁇ z ⁇ 0.2, 0 ⁇ z ⁇ 0.05, 0.05 ⁇ z ⁇ 0.1, 0.1 ⁇ z ⁇ 0.15, or 0.15 ⁇ z ⁇ 0.2, etc.
  • the Me is selected from one or more of Mn, Fe, Cr, Ti, Zn, V, Al, Zr, Ce. Me may be selected from Mn or Al.
  • the A is selected from one or more of S, N, F, Cl, Br, I.
  • the A may be selected from S, N, F. Therefore, due to the selection of the high-nickel ternary positive electrode active material with the above chemical structural formula (1), it has a strong ability to oxidize and decompose the electrolyte solvent. By using sodium dithionite as an additive, it can be preferred over chain esters and cyclic esters. When the solvent is oxidized on the surface of the positive electrode, a low-impedance interfacial film is formed first, thereby improving the overall performance of the battery.
  • the specific surface area BET of the positive electrode material needs to meet a certain range, and the specific surface area BET range of the positive electrode material can be, for example, 0.15m 2 /g ⁇ 0.75m 2 /g, 0.15m 2 /g ⁇ 0.45m 2 /g, 0.45m 2 /g ⁇ 0.75m 2 /g ; 0.15m 2 /g ⁇ 0.25m 2 /g, 0.25m 2 /g ⁇ 0.35m 2 /g, 0.35m 2 /g ⁇ 0.45m 2 /g g, 0.45m 2 /g ⁇ 0.55m 2 /g, 0.55m 2 /g ⁇ 0.65m 2 /g, or 0.65m 2 /g ⁇ 0.75m 2 /g, etc. Therefore, by limiting the specific surface area BET of the positive electrode material to this range, the secondary battery can have good kinetic performance and cycle life.
  • the positive electrode film layer may further optionally include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer may also optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive electrode material, conductive agent, binder and any other components, are dispersed in a solvent (such as N- Methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N- Methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode material.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector can use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode material can be a negative electrode material known in the art for batteries.
  • negative electrode materials include natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, soft carbon, silicon oxide, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, A combination of one or more of SnO 2 , lithiated spinel structures, and Li-Al alloys.
  • the molecular formula of the silicon oxide may be SiOx, and x is 0.5-2.
  • the lithiated compound with a spinel structure can be, for example, TiO 2 —Li 4 Ti 5 O 12 .
  • the above-mentioned negative electrode material has high activity and strong ability to reduce and decompose the electrolyte solvent, which can make the technical effect of the secondary battery better.
  • These negative electrode materials may be used alone or in combination of two or more.
  • the negative electrode material includes one or a combination of artificial graphite or natural graphite.
  • the specific surface area BET of the negative electrode material may range from 0.8m 2 /g to 1.5m 2 /g, from 0.8m 2 /g to 1.0m 2 /g, from 1.0m 2 /g to 1.2m 2 /g, 1.2m 2 /g ⁇ 1.5m 2 /g ; 0.8m 2 /g ⁇ 0.9m 2 /g, 0.9m 2 /g ⁇ 1.0m 2 /g, 1.0m 2 /g ⁇ 1.1m 2 /g , 1.1m 2 /g ⁇ 1.2m 2 /g, 1.2m 2 /g ⁇ 1.3m 2 /g, 1.3m 2 /g ⁇ 1.4m 2 /g, or 1.4m 2 /g ⁇ 1.5m 2 /g, etc.
  • the activity of the material can be improved by the specific surface area BET of the negative electrode material within the above numerical range, but as the activity of the negative electrode material increases, its ability to reduce and decompose the electrolyte solvent becomes stronger.
  • Sodium sulfite additive which can be preferentially reduced on the surface of the negative electrode prior to solvents such as chain esters and cyclic esters, forms a low-impedance interfacial film at the earliest, thereby improving the overall performance of the battery.
  • the negative electrode film layer may further optionally include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA), carboxymethyl chitosan (CMCS), and sodium carboxymethylcellulose (CMC-Na).
  • the negative electrode film layer may also optionally include a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • CMC-Na sodium carboxymethylcellulose
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water ) to form the negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • a separator is further included in the secondary battery.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the upper limit voltage of the secondary battery may be ⁇ 4.15V.
  • the upper limit voltage of the secondary battery can be, for example, 4.15V-5V, 4.15V-4.5V, or 4.5V-5V, etc. . Therefore, the secondary battery with the upper limit of the passing voltage in the above-mentioned range often has the characteristics of high capacity and strong oxidizing property.
  • the advantages of this type of ternary positive electrode material can be better utilized, namely improving high-temperature storage performance, high-rate discharge capability and reducing initial DCR.
  • the additive can function well.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 1 shows a square-shaped secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating chamber. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a case having an accommodation space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric devices may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 6 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • the non-aqueous organic solvent is a mixed solution containing ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC), wherein the volume ratio of EC, PC and DEC is 1:1:1.
  • EC ethylene carbonate
  • PC propylene carbonate
  • DEC diethyl carbonate
  • the content of additives is the weight percent calculated based on the total weight of the electrolyte.
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 1, except that 0.2% of sodium dithionite is added as an additive in the preparation step of the electrolyte.
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 1, except that 0.3% of sodium dithionite is added as an additive in the preparation step of the electrolyte.
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 1, except that 0.4% of sodium dithionite is added as an additive in the preparation step of the electrolyte.
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 1, except that 0.5% of sodium dithionite is added as an additive in the preparation step of the electrolyte.
  • the preparation process of the lithium-ion secondary battery refers to Example 3 as a whole, the difference is that other additives are also included in the preparation step of the electrolyte, and the other additives include 0.3% DTD (ethylene sulfate), 0.3% 1,3- PS (1,3-propane sultone) and 1% FEC (fluoroethylene carbonate).
  • DTD ethylene sulfate
  • 1,3- PS 1,3-propane sultone
  • FEC fluoroethylene carbonate
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 1, except that in the preparation step of the positive electrode sheet, the ternary material of the positive electrode active material is LiNi 0.5 Co 0.2 Mn 0.3 O 2 .
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 3, except that in the preparation step of the positive electrode sheet, the ternary material of the positive electrode active material is LiNi 0.5 Co 0.2 Mn 0.3 O 2 .
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 5, except that in the preparation step of the positive electrode sheet, the ternary material of the positive electrode active material is LiNi 0.5 Co 0.2 Mn 0.3 O 2 .
  • the preparation process of the lithium-ion secondary battery refers to Example 7 as a whole, the difference is that other additives are also included in the preparation step of the electrolyte, and the other additives include 0.3% DTD (ethylene sulfate), 0.3% 1,3- PS (1,3-propane sultone) and 1% FEC (fluoroethylene carbonate).
  • DTD ethylene sulfate
  • 1,3- PS 1,3-propane sultone
  • FEC fluoroethylene carbonate
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 1, except that 0.6% of sodium dithionite is added as an additive in the preparation step of the electrolyte.
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 1, except that 0.7% of sodium dithionite is added as an additive in the preparation step of the electrolyte.
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 7, except that 0.6% of sodium dithionite is added as an additive in the preparation step of the electrolyte.
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 1, the difference is that sodium dithionite is not added in the preparation step of the electrolyte.
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 3, with the difference that 0.3% of sodium dithionite is added to the total mass of the positive pole piece during the preparation of the positive pole piece. Sodium dithionite is not added in the preparation step of the electrolyte.
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 3, except that 0.3% of sodium dithionite is added to the negative electrode sheet during the preparation of the negative electrode sheet. Sodium dithionite is not added in the preparation step of the electrolyte.
  • the preparation process of the lithium-ion secondary battery is generally referred to in Example 7, the difference is that sodium dithionite is not added in the preparation step of the electrolyte.
  • the lithium-ion secondary battery At 60°C, charge the lithium-ion secondary battery at a constant current of 0.5C to 4.35V, and then charge it at a constant voltage until the current is 0.05C. At this time, the thickness of the lithium-ion secondary battery is measured and recorded as h 0 ; Put the ion secondary battery into a constant temperature box at 60°C, store it for 30 days and take it out, measure the thickness of the lithium ion secondary battery at this time and record it as h 1 .
  • the thickness expansion rate of the lithium-ion secondary battery after storage for 30 days [(h 1 -h 0 )/h 0 ] ⁇ 100%.
  • Example 1 and Comparative Example 1 the difference is only whether sodium dithionite is added, but the battery performance of the example is obviously better than that of the comparison example.
  • Example 8 From the test results of Example 8 and Example 3, when the ternary material of the positive electrode active material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 , the storage volume expansion rate at 60°C, the initial DCR, and the 4C discharge capacity retention rate are relatively good. In LiNi 0.5 Co 0.2 Mn 0.3 O 2 .
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请提供了电解液、二次电池、电池模块、电池包和用电装置。所述电解液包括电解质、溶剂和添加剂，所述添加剂包括连二亚硫酸钠。本申请用以进一步提升二次电池的如初始DCR、存储产气和倍率性能等综合性能。

Description

电解液、二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及锂电池技术领域，尤其涉及电解液、二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次电池取得了极大的发展，因此对其初始DCR、存储产气和倍率性能等也提出了更高的要求。
但是现有的二次电池正极材料(特别是三元材料)在高温或高电压下由于材料的不稳定，会发生释氧等副反应，严重影响锂电池的寿命。因此，需要进一步保护正极，且电池初始DCR，高温存储产气和倍率性能仍有待改进。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种电解液，以进一步提升二次电池的综合性能(如降低初始DCR、存储产气，提升倍率性能等)。
为了达到上述目的，本申请提供了电解液、二次电池、电池模块、电池包和用电装置。
本申请的第一方面提供了一种电解液，包括电解质、溶剂和添加剂，所述添加剂包括连二亚硫酸钠。
由此，本申请通过连二亚硫酸钠作为添加剂，连二亚硫酸钠能够在所述锂二次电池充放电过程中于正极和负极的表面形成界面膜，其形成的界面膜具有较低阻抗的技术效果，能够降低电池的初始DCR、 存储产气，提升倍率性能。
在任意实施方式中，所述连二亚硫酸钠在电解液中所占的质量百分比为大于0且小于等于0.5％；可选的，所述连二亚硫酸钠在电解液中所占的质量百分比为0.2％～0.4％；进一步可选的，所述连二亚硫酸钠在电解液中所占的质量百分比为0.25％～0.35％。由此，通过限定连二亚硫酸钠添加剂用量在上述范围，能够使二次电池具有低的初始DCR，低的高温存储产气和优异的放电倍率性能。
在任意实施方式中，所述添加剂还包括1,3-丙磺酸内酯、氟代碳酸亚乙酯、硫酸亚乙酯中的一种或多种的组合。由此，通过连二亚硫酸钠可以与1,3-丙磺酸内酯、氟代碳酸亚乙酯中的一种或多种进行协同效应，使得二次电池的各项性能得到进一步的改善。
在任意实施方式中，所述添加剂的总质量在电解液中所占的质量百分比为大于0且小于等于5％。由此，通过限定各添加剂的总质量在上述范围内，能够更好地发挥连二亚硫酸钠与其他添加剂的协同效应。
在任意实施方式中，所述电解液中，所述电解质的摩尔浓度为0.8～1.2mol/L。由此，通过限定电解液摩尔浓度在上述范围，能够使电解液拥有良好的电导率和粘度性能，同时能够使应用该电解液的二次电池具有较为优异的初始DCR值。
在任意实施方式中，所述溶剂包括链状酯、环状酯中的一种或多种的组合。由此，通过链状酯与环状酯的搭配，能够使电解液具有低粘度高电导率。
在任意实施方式中，所述链状酯包括碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸甲丙酯、甲酸甲酯、甲酸乙酯、乙酸甲酯、乙酸乙酯、丙酸丙酯、丁酸乙酯、丙酸乙酯、丁酸丙酯中的一种或多种的组合；和/或，所述环状酯包括碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、γ-丁内酯、四氢呋喃中的一种或多种的组合。由此，通过选择上述链状酯、和/或环状酯作为非质子溶剂，能够更有效地发挥二次电池的综合性能。
本申请的第二方面还提供一种二次电池，包括正极极片、负极极片、隔离膜和本发明第一方面所述的电解液，所述隔离膜位于正极极片和负极极片之间。
由此，通过使用添加有连二亚硫酸钠的电解液，能够有效地改善二次电池性能，虽然机理尚不十分清楚，但推测是由于连二亚硫酸钠能够优先于链状酯、环状酯等溶剂分别在正极表面氧化、负极表面还原，最早形成低阻抗的界面膜，从而改善二次电池性能。
在任意实施方式中，所述正极极片包括正极材料，所述正极材料包括高镍三元正极活性物质。由此，通过高镍三元正极活性物质中Ni含量高，能够实现电池能量密度的提升，并减少了钴的使用，但随着Ni含量增高，其对电解液溶剂的氧化分解能力变强。
在任意实施方式中，所述高镍三元正极活性物质中，Ni元素所占的质量百分比≥80％。由此，当限定正极为Ni含量≥80％时，能够提高材料活性，使能量密度提高，但其对电解液溶剂的氧化分解能力很强，此时通过使用连二亚硫酸钠添加剂，其能够优先于链状酯、环状酯等溶剂在正极表面氧化，最早形成低阻抗的界面膜，从而改善电池性能。
在任意实施方式中，所述高镍三元正极活性物质的化学结构式(1)如下所示：Li 1+yNi aCo bMe 1-a-bO 2-zA z式(1)；其中，-0.1≤y≤0.2，0.5<a<0.9，0<b<0.5，0.5<a+b<1，0≤z<0.2；所述Me选自Mn、Fe、Cr、Ti、Zn、V、Al、Zr、Ce中的一种或多种；所述A选自S、N、F、Cl、Br、I中的一种或多种。由于选用具有上述化学结构式(1)的高镍三元正极活性物质，能够提高材料活性，使能量密度提高，但其对电解液溶剂的氧化分解能力很强，因而通过使用连二亚硫酸钠添加剂，其可以优先于链状酯、环状酯等溶剂在正极表面氧化，最早形成低阻抗的界面膜，从而改善电池性能。
在任意实施方式中，所述正极材料的比表面积BET范围为0.15～0.75m 2/g。由此，通过限制正极材料的比表面积BET在此范围，能够使二次电池具有良好的动力学性能和寿命。
在任意实施方式中，所述负极极片包括负极材料，所述负极材料包括天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅氧化物、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化物、Li-Al合金中的一种或多种的组合。由此，上述的负极材料活性高，但对电解液溶剂的还原分解能力强。
在任意实施方式中，所述负极材料的比表面积BET范围为0.8m 2/g～1.5m 2/g。由此，负极材料的比表面积BET在上述数值范围内活性强，但对电解液溶剂的还原分解能力强，此时通过使用连二亚硫酸钠添加剂，其可以优先于链状酯、环状酯等溶剂在负极表面还原，最早形成低阻抗的界面膜，从而改善电池性能。
在任意实施方式中，所述二次电池的使用上限电压≥4.15V。由此，电压上限在此范围以上的二次电池，具有高容量、强氧化性的特性。通过组合使用连二亚硫酸钠与本申请的正极材料，能够更好的发挥此类三元正极材料的优点，即提高高温存储性能、大倍率放电能力以及降低初始DCR。
本申请的第三方面提供一种电池模块，包括本申请的第二方面的二次电池。
本申请的第四方面提供一种电池包，包括本申请的第三方面的电池模块。
本申请的第五方面提供一种用电装置，包括选自本申请的第二方面的二次电池、本申请的第三方面的电池模块或本申请的第四方面的电池包中的至少一种。
相比于现有技术，本发明具有以下有益效果：
本发明所提供的电解液，通过使用连二亚硫酸钠作为二次电池电解液添加剂，能够降低电池的初始DCR、存储产气，提升倍率性能。虽然机理尚不十分清楚，但推测是由于连二亚硫酸钠中的S元素价态为+3态、即为S元素的中间价态，处于这个价态的S元素通常具有比较强的活泼性。因此连二亚硫酸钠能够最早在负极表面还原，其还原形成的界面膜具有低阻抗的效果，其同时亦可以最早在正极表面被 氧化，其形成的界面膜同样具有低阻抗的效果，从而能够改善二次电池的综合性能。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的电解液、二次电池、电池模块、电池包和电学装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的 范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
电解液
本申请的一个实施方式中，本申请提出了一种电解液，电解液在正极极片和负极极片之间起到传导离子的作用。电解液包括电解质、溶剂和添加剂，所述添加剂包括连二亚硫酸钠。
现有技术中主要利用连二亚硫酸钠的化学特性具有吸附氧的功能，将连二亚硫酸钠用作正极浆料添加剂使用，在本申请之前并没有发现连二亚硫酸钠具备良好的电化学作用。而本申请通过采用添加剂中包括连二亚硫酸钠，并与电解质、溶剂混合获得电解液的方案，能够降低电池的初始DCR、存储产气，提升倍率性能。虽然机理尚不明确，但推测这是由于连二亚硫酸钠中的S元素价态为+3态，即为S元素的中间价态，处于这个价态的S元素通常具有比较强的活泼性。因此连二亚硫酸钠能够最早在负极表面还原，其还原形成的界面膜具有低阻抗的效果，其同时亦能够最早在正极表面被氧化，其形成的界面膜同样具有低阻抗的效果，从而能够提升二次电池的综合性能。
[添加剂]
在一些实施方式中，所述连二亚硫酸钠在电解液中所占的质量百分比例如可以为大于0且小于等于0.5％、0.001％～0.1％、0.1％～0.2％、0.2％～0.4％、0.4％～0.5％；0.001％～0.15％、0.015％～0.25％、0.25％～0.35％、或0.35％～0.5％等。可选的，所述连二亚硫酸钠在电解液中所占的质量百分比为0.2％～0.4％；进一步可选的，所述连二亚硫酸钠在电解液中所占的质量百分比为0.25％～0.35％。由此，通过限定连二亚硫酸钠添加剂用量在上述范围，能够避免过量的连二亚硫酸钠可能导致的二次电池电解液的粘度恶化，同时还能够避免连二亚硫酸钠过度在正负极表面参与成膜，从而导致的初始DCR恶化。因而通过限定连二亚硫酸钠添加剂用量在上述范围，能够使二次电池具有低的初始DCR，低的高温存储产气和优异的放电倍率性能。
在一些实施方式中，通常情况下，除连二亚硫酸钠外，也可以含有其他的添加剂。所述添加剂例如还可以包括1,3-丙磺酸内酯、氟代 碳酸亚乙酯、硫酸亚乙酯等中的一种或多种的组合。由此，通过连二亚硫酸钠可以与1,3-丙磺酸内酯、氟代碳酸亚乙酯、硫酸亚乙酯等中的一种或多种进行协同效应，使得二次电池的存储产气和倍率性能等性能得到进一步的改善。
在一些实施方式中，所述添加剂的总质量在电解液中所占的质量百分比例如可以为大于0且小于等于5％、0.001％～1％、1％～2％、2％～3％、3％～4％、4％～5％、0.001％～2％、或2％～5％等。由此，通过限定各添加剂的总质量在上述范围内，所述连二亚硫酸钠与其他添加剂能够更好的协同作用，提升二次电池的各项性能，尤其是避免添加剂过度在正负极表面参与成膜而导致的初始DCR恶化。
[电解质]
在一些实施方式中，所述电解质的摩尔浓度可以为0.8mol/L～1.2mol/L、0.8mol/L～1.0mol/L、1.0mol/L～1.2mol/L；0.8mol/L～0.9mol/L、0.9mol/L～1.0mol/L、1.0mol/L～1.1mol/L、或1.1mol/L～1.2mol/L等。由此，通过限定电解液摩尔浓度在上述范围，能够使二次电池的电解液拥有良好的电导率和粘度性能，同时能够使应用该电解液的二次电池具有较为优异的初始DCR值。
在一些实施方式中，所述电解质包括锂盐。具体的，所述电解质包括LiPF 6、LiBF 4、LiBOB、LiDFOB、LiSO 3CF 3、LiClO 4、LiAsF 6、Li(FSO 2) 2N、Li(CF 3SO 2) 2N和LiC(CF 3SO 2) 3等中的一种或多种的组合。所述锂盐可选为LiPF 6和Li(FSO 2) 2N。
在一些实施方式中，所述锂盐的浓度可以为0.8mol/L～1.2mol/L、0.8mol/L～1.0mol/L、1.0mol/L～1.2mol/L；0.8mol/L～0.9mol/L、0.9mol/L～1.0mol/L、1.0mol/L～1.1mol/L、或1.1mol/L～1.2mol/L等。通过限定锂盐浓度在此范围，能够避免以下情况：锂盐浓度过低导致溶液中提供的锂离子数量较少，不利于锂离子的扩散，引起电解液电导率变低的情况，以及锂盐浓度过高导致的溶液粘度较大，不利于锂 离子的传输，导致电导率下降的情况。也就是说，由此，能够提高电解液的电导率和粘度。
[溶剂]
在一些实施方式中，所述溶剂的种类并没有具体的限制，可根据实际需求进行选择。所述溶剂例如可以包括有机溶剂，进一步的，溶剂可以包括链状酯、环状酯中的一种或多种的组合。通常，环状酯的介电常数大，能够良好的解离电解质锂盐，但环状酯溶剂的粘度比较大，而链状酯的粘度较低，因此，通过环状酯与环状酯的组合使用，能够使得电解液具有低粘度高电导率。
在一些实施方式中，从良好地适用于二次电池的溶剂体系的角度出发，所述链状酯包括碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸甲丙酯、甲酸甲酯、甲酸乙酯、乙酸甲酯、乙酸乙酯、丙酸丙酯、丁酸乙酯、丙酸乙酯、丁酸丙酯中的一种或多种的组合；和/或，所述环状酯包括碳酸乙烯酯(1,3-二氧戊环-2-酮、1,3-二氧杂环戊酮、Ethylene carbonate)CAS号96-49-1、碳酸丙烯酯(丙二醇碳酸酯、1,2-丙二醇碳酸、4-甲基-1,3-二氧戊-2-酮、Propylene carbonate)CAS号108-32-7、碳酸丁烯酯(碳酸-2,3-丁二醇酯、2,3-Butylene carbonate)CAS号4437-85-8、γ-丁内酯、四氢呋喃中的一种或多种的组合。
在一些实施方式中，本发明第一方面提供的电解液可以采用本领域的公知方法进行制备，例如可将特定比例的电解质、溶剂和添加剂混合均匀即可。
在一些实施方式中，本申请提出了如本发明第一方面所述的电解液在二次电池制备领域的用途。
另外，以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
二次电池
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜和如本发明第一方面所述的电解液。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解液在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极材料可采用本领域公知的用于电池的正极材料。作为示例，正极材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极材料的传统材料。这些正极材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2 (也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。可选的，所述正极材料包括高镍三元正极活性物质。由于高镍三元正极活性物质中Ni含量高，能够提高材料活性，使能量密度提高，但其对电解液溶剂的氧化分解能力强。
在一些实施方式中，所述高镍三元正极活性物质中，Ni元素所占的质量百分比可以为≥80％、80％～85％、85％～90％、或90％～95％等。由此，当限定正极为Ni含量≥80％时，对电解液溶剂的氧化分解能力很强，此时通过使用连二亚硫酸钠添加剂，其能够优先溶剂在正极表面氧化，形成低阻抗的界面膜，从而达到改善电池的综合性能。
在一些实施方式中，所述高镍三元正极活性物质的化学结构式(1)如下所示：Li 1+yNi aCo bMe 1-a-bO 2-zA z式(1)；其中，y通常可以满足-0.1≤y≤0.2、-0.1≤y≤0、0≤y≤0.1、0.1≤y≤0.2；-0.1≤y≤-0.05、-0.05≤y≤0、0≤y≤0.05、0.05≤y≤0.1、0.1≤y≤0.15、或0.15≤y≤0.2等。a通常可以满足0.5<a<0.9、0.5<a<0.7、0.7<a<0.9；0.5<a<0.6、0.6<a<0.7、0.7<a<0.8、或0.8<a<0.9等。b通常可以满足0<b<0.5、0<b<0.1、0.1<b<0.2、0.2<b<0.3、0.3<b<0.4、0.4<b<0.5；0<b<0.3、或0.3<b<0.5等。a+b通常可以满足0.5<a+b<1、0.5<a+b<0.8、0.8<a+b<1、0.5<a+b<0.6、0.6<a+b<0.7、0.7<a+b<0.8、0.8<a+b<0.9、或0.9<a+b<1等。z通常可以满足0≤z<0.2、0≤z<0.1、0.1≤z<0.2、0≤z<0.05、0.05≤z<0.1、0.1≤z<0.15、或0.15≤z<0.2等。所述Me选自Mn、Fe、Cr、Ti、Zn、V、Al、Zr、Ce中的一种或多种。Me可选选自Mn或者Al。所述A选自S、N、F、Cl、Br、I中的一种或多种。所述A可选选自S、N、F。由此，由于选用具有上述化学结构式(1)的高镍三元正极活性物质，对电解液溶剂的氧化 分解能力很强，通过使用连二亚硫酸钠添加剂，其能够优先于链状酯、环状酯等溶剂在正极表面氧化，最早形成低阻抗的界面膜，从而改善电池的综合性能。
在一些实施方式中，正极材料的比表面积BET需要满足一定的范围，所述正极材料的比表面积BET范围例如可以为0.15m 2/g～0.75m 2/g、0.15m 2/g～0.45m 2/g、0.45m 2/g～0.75m 2/g；0.15m 2/g～0.25m 2/g、0.25m 2/g～0.35m 2/g、0.35m 2/g～0.45m 2/g、0.45m 2/g～0.55m 2/g、0.55m 2/g～0.65m 2/g、或0.65m 2/g～0.75m 2/g等。由此，通过限制正极材料的比表面积BET在此范围，能够使二次电池具有良好的动力学性能和循环寿命。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极材料可采用本领域公知的用于电池的负极材料。作为示例，负极材料包括天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅氧化物、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化物、Li-Al合金中的一种或多种的组合。其中，需要进一步说明的是，硅氧化物的分子式可以为SiOx，x为0.5～2。尖晶石结构的锂化物例如可以为TiO 2-Li 4Ti 5O 12。由此，上述的负极材料活性高，对电解液溶剂的还原分解能力强，可以使得二次电池的技术效果更佳优异。这些负极材料可以仅单独使用一种，也可以将两种以上组合使用。可选的，负极材料包括人造石墨或天然石墨中的一种及两种的组合。
在一些实施方式中，所述负极材料的比表面积BET范围可以为0.8m 2/g～1.5m 2/g、0.8m 2/g～1.0m 2/g、1.0m 2/g～1.2m 2/g、1.2m 2/g～1.5m 2/g；0.8m 2/g～0.9m 2/g、0.9m 2/g～1.0m 2/g、1.0m 2/g～1.1m 2/g、1.1m 2/g～1.2m 2/g、1.2m 2/g～1.3m 2/g、1.3m 2/g～1.4m 2/g、或1.4m 2/g～1.5m 2/g等。由此，通过负极材料的比表面积BET在上述数值范围内，能够提高材料的活性，但由于随着负极材料的活性增强，其对电解液溶剂的还原分解能力变强，此时通过使用连二亚硫酸钠添加剂，其能够优先于链状酯、环状酯等溶剂在负极表面还原，最早形成低阻抗的界面膜，从而改善电池的综合性能。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙 烯酸(PMAA)及羧甲基壳聚糖(CMCS)、羧甲基纤维素钠(CMC-Na)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，对二次电池的使用上限有一定要求，例如所述二次电池的使用上限电压可以为≥4.15V。通常情况下，对于上限电压的最大值没有特定要求，在一些具体实施方式中，所述二次电池的使用上限电压例如可以是4.15V～5V、4.15V～4.5V、或4.5V～5V等。由此，通过电压上限在上述范围的二次电池，往往具有高容量，强氧化性的特点。通过使用连二亚硫酸钠搭配本申请的正极材料，可以更好的发挥此类三元正极材料的优点，即提高高温存储性能、大倍率放电能力以及降低初始DCR。而当所述二次电池的使用上限电压为 4.15V以上时，能够良好地发挥添加剂的作用。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
电池模块
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次 电池5容纳于该容纳空间。
电池包
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
用电装置
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
(1)正极极片的制备：
将正极活性材料三元材料(LiNi 0.8Co 0.1Mn 0.1O 2)、粘结剂聚偏氟乙烯、导电剂乙炔黑与N-甲基吡咯烷酮(NMP)按照重量比98:1:1:100混合，在真空搅拌机作用下搅拌至体系成均一透明状，获得正极浆料；将正极浆料按单面涂覆量为0.3g/1540.25mm 2均匀涂覆于厚度为12μm的铝箔上；将涂覆后的铝箔在室温晾干后转移至120℃烘箱干燥1h，然后经过冷压、分切得到正极极片。
(2)负极极片的制备：
将人造石墨、导电剂碳黑、粘结剂羧甲基纤维素钠与去离子水按照质量比92:2:6:100混合，在真空搅拌机作用下获得负极浆料；将负极浆料按单面涂覆量为0.17g/1540.25mm 2均匀涂覆在厚度为8μm的负极集流体铜箔上；将铜箔在室温晾干后转移至120℃烘箱干燥1h，然后经过冷压、分切得到负极极片。
(3)隔离膜
Cellgard企业，型号为cellgard2400
(4)电解液的制备
非水有机溶剂为含有碳酸乙烯酯(EC)、碳酸丙烯酯(PC)和碳酸二乙酯(DEC)的混合液，其中，EC、PC和DEC的体积比为1:1:1。在含水量<10ppm的氩气气氛手套箱中，向上述混合后的溶剂中加入溶质LiPF 6获得含1mol/L的LiPF 6的母液，向上述母液中加入含量为0.1％的作为添加剂的连二亚硫酸钠。在表1中，添加剂的含量为基于电解液的总重量计算得到的重量百分数。
(5)锂离子二次电池的制备
将正极极片、隔离膜、负极极片按顺序重叠，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到裸电芯；将容量为4.3Ah的裸电芯置于外包装箔中，得到电池，将8.6g上述制备好的电解液注入到干燥后的上述制备的电池中，经过真空封装、静置、化成、整形等工序，获得锂离子二次电池。
实施例2
锂离子二次电池的制备过程整体上参照实施例1，区别在于，电解液的制备步骤中加入含量为0.2％的作为添加剂的连二亚硫酸钠。
实施例3
锂离子二次电池的制备过程整体上参照实施例1，区别在于，电解液的制备步骤中加入含量为0.3％的作为添加剂的连二亚硫酸钠。
实施例4
锂离子二次电池的制备过程整体上参照实施例1，区别在于，电解液的制备步骤中加入含量为0.4％的作为添加剂的连二亚硫酸钠。
实施例5
锂离子二次电池的制备过程整体上参照实施例1，区别在于，电解液的制备步骤中加入含量为0.5％的作为添加剂的连二亚硫酸钠。
实施例6
锂离子二次电池的制备过程整体上参照实施例3，区别在于，电解液的制备步骤中还包括其他添加剂，所述其他添加剂包括0.3％DTD(硫酸亚乙酯)、0.3％1,3-PS(1,3-丙磺酸内酯)和1％FEC(氟代碳酸亚乙酯)。
实施例7
锂离子二次电池的制备过程整体上参照实施例1，区别在于，正极极片的制备步骤中，正极活性材料三元材料为LiNi 0.5Co 0.2Mn 0.3O 2。
实施例8
锂离子二次电池的制备过程整体上参照实施例3，区别在于，正极极片的制备步骤中，正极活性材料三元材料为LiNi 0.5Co 0.2Mn 0.3O 2。
实施例9
锂离子二次电池的制备过程整体上参照实施例5，区别在于，正极极片的制备步骤中，正极活性材料三元材料为LiNi 0.5Co 0.2Mn 0.3O 2。
实施例10
锂离子二次电池的制备过程整体上参照实施例7，区别在于，电解液的制备步骤中还包括其他添加剂，所述其他添加剂包括0.3％DTD(硫酸亚乙酯)、0.3％1，3-PS(1,3-丙烷磺酸内酯)和1％FEC(氟代碳酸亚乙酯)。
实施例11
锂离子二次电池的制备过程整体上参照实施例1，区别在于，电解液的制备步骤中加入含量为0.6％的作为添加剂的连二亚硫酸钠。
实施例12
锂离子二次电池的制备过程整体上参照实施例1，区别在于，电解液的制备步骤中加入含量为0.7％的作为添加剂的连二亚硫酸钠。
实施例13
锂离子二次电池的制备过程整体上参照实施例7，区别在于，电解液的制备步骤中加入含量为0.6％的作为添加剂的连二亚硫酸钠。
对比例1
锂离子二次电池的制备过程整体上参照实施例1，区别在于，电解液的制备步骤中不添加连二亚硫酸钠。
对比例2
锂离子二次电池的制备过程整体上参照实施例3，区别在于，正极极片的制备过程中加入占正极极片总质量为0.3％的连二亚硫酸钠。电解液的制备步骤中不添加连二亚硫酸钠。
对比例3
锂离子二次电池的制备过程整体上参照实施例3，区别在于，负极极片的制备过程中加入占负极极片总质量为0.3％的连二亚硫酸钠。电解液的制备步骤中不添加连二亚硫酸钠。
对比例4
锂离子二次电池的制备过程整体上参照实施例7，区别在于，电解液的制备步骤中不添加连二亚硫酸钠。
上述实施例1～13、对比例1～4的相关参数如下述表1所示。
表1：实施例1～13与对比例1～4的参数结果
Figure PCTCN2021107669-appb-000001
Figure PCTCN2021107669-appb-000002
二、电池性能测试
(1)锂离子二次电池60℃存储测试
在60℃下，将锂离子二次电池以0.5C恒流充电至4.35V，再恒压充电至电流为0.05C，此时测试锂离子二次电池的厚度并记为h 0；之后将锂离子二次电池放入60℃的恒温箱，储存30days后取出，测试此时锂离子二次电池的厚度并记为h 1。锂离子二次电池存储30days后的厚度膨胀率＝[(h 1-h 0)/h 0]×100％。
(2)锂离子二次电池初始的DCR性能测试
将刚刚制备完成的电芯1C充电到4.35V，随后恒压充电到0.05C，然后1C放电30min，此时电压是V1；随后4C(I)放电30s，在30s放电过程中，采用0.1s采点记录电压值，并最终记录放电末期电压是V2，得到电芯50％SOC的放电DCR即(V1-V2)/I。
(3)锂离子二次电池的4C放电容量保持率
在25℃下，将锂离子二次电池以1C恒流充电至4.35V，然后恒压充电至电流为0.05C，再用1C恒流放电至2.8V，将此时的放电容量设定为1C标称容量，并标定为100％。
然后继续1C恒流充电至4.35V，恒压充电至电流为0.05C，再用4C恒流放电至2.8V，得到此时的放电容量作为4C放电容量。
4C放电容量保持率＝放电容量/标称容量×100％
三、各实施例、对比例测试结果
上述实施例1～13、对比例1～4的测试结果如下述表2所示。
表2：实施例1～13与对比例1～4的测试结果
Figure PCTCN2021107669-appb-000003
Figure PCTCN2021107669-appb-000004
根据表2结果可知，实施例1～13中，通过在电解液中添加连二亚硫酸钠，相对于对比例1～4，锂离子二次电池的60℃存储体积膨胀率、初始的DCR、4C放电容量保持率有明显改善，均取得了良好的效果。
另外，从实施例1与对比例1、实施例7与对比例4的测试结果来看，区别仅在于是否添加连二亚硫酸钠，但是实施例电池性能明显优于对比例。
从实施例6与实施例3对比来看，其他添加剂的增加，与连二亚硫酸钠的协同作用，使60℃存储体积膨胀率和初始的DCR降低，且能够适当的提高4C放电容量保持率。
从实施例8与实施例3的测试结果来看，正极活性材料三元材料为LiNi 0.8Co 0.1Mn 0.1O 2时，60℃存储体积膨胀率、初始的DCR、4C放电容量保持率效果相对优于LiNi 0.5Co 0.2Mn 0.3O 2。
从实施例3与对比例2、对比例3的测试结果来看，在电解液中添加连二亚硫酸钠、电池性能的效果要明显优于在正极或负极中添加连二亚硫酸钠。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (18)

  1. 一种电解液，其特征在于，包括电解质、溶剂和添加剂，所述添加剂包括连二亚硫酸钠。
  2. 根据权利要求1所述的电解液，其特征在于，所述连二亚硫酸钠在电解液中所占的质量百分比为大于0且小于等于0.5％；
    可选的，所述连二亚硫酸钠在电解液中所占的质量百分比为0.2％～0.4％；
    进一步可选的，所述连二亚硫酸钠在电解液中所占的质量百分比为0.25％～0.35％。
  3. 根据权利要求1或2所述的电解液，其特征在于，所述添加剂还包括1,3-丙磺酸内酯、氟代碳酸亚乙酯、硫酸亚乙酯中的一种或多种的组合。
  4. 根据权利要求1～3中任一项所述的电解液，其特征在于，所述添加剂的总质量在电解液中所占的质量百分比为大于0且小于等于5％。
  5. 根据权利要求1～4中任一项所述的电解液，其特征在于，所述电解液中，所述电解质的摩尔浓度为0.8～1.2mol/L。
  6. 根据权利要求1～5中任一项所述的电解液，其特征在于，所述溶剂包括链状酯、环状酯中的一种或多种的组合。
  7. 根据权利要求6所述的电解液，其特征在于，所述链状酯包括碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸甲丙酯、甲酸甲酯、甲酸乙酯、乙酸甲酯、乙酸乙酯、丙酸丙酯、丁酸乙酯、丙酸乙酯、丁酸丙酯中的一种或多种的组合；
    和/或，所述环状酯包括碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、γ-丁内酯、四氢呋喃中的一种或多种的组合。
  8. 一种二次电池，其特征在于，包括正极极片、负极极片、隔离膜和权利要求1～7中任一项所述的电解液，所述隔离膜位于正极极片和负极极片之间。
  9. 根据权利要求8所述的二次电池，其特征在于，所述正极极片包括正极材料，所述正极材料包括高镍三元正极活性物质。
  10. 根据权利要求9所述的二次电池，其特征在于，所述高镍三元正极活性物质中，Ni元素所占的质量百分比≥80％。
  11. 根据权利要求9～10中任一项所述的二次电池，其特征在于，所述高镍三元正极活性物质的化学结构式(1)如下所示：
    Li 1+yNi aCo bMe 1-a-bO 2-zA z     式(1)；
    其中，-0.1≤y≤0.2，0.5<a<0.9，0<b<0.5，0.5<a+b<1，0≤z<0.2；
    所述Me选自Mn、Fe、Cr、Ti、Zn、V、Al、Zr、Ce中的一种或多种；
    所述A选自S、N、F、Cl、Br、I中的一种或多种。
  12. 根据权利要求9～11中任一项所述的二次电池，其特征在于， 所述正极材料的比表面积BET范围为0.15～0.75m 2/g。
  13. 根据权利要求8～12中任一项所述的二次电池，其特征在于，所述负极极片包括负极材料，所述负极材料包括天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅氧化物、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化物、Li-Al合金中的一种或多种的组合。
  14. 根据权利要求13所述的二次电池，其特征在于，所述负极材料的比表面积BET范围为0.8～1.5m 2/g。
  15. 根据权利要求8～14中任一项所述的二次电池，其特征在于，所述二次电池的使用上限电压≥4.15V。
  16. 一种电池模块，其特征在于，包括权利要求8～15中任一项所述的二次电池。
  17. 一种电池包，其特征在于，包括权利要求16所述的电池模块。
  18. 一种用电装置，其特征在于，包括权利要求1～7中任一项所述的电解液、权利要求8～15中任一项所述的二次电池、权利要求16所述的电池模块、或权利要求17所述的电池包。
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