WO2023220857A1 - 电解液及包含其的二次电池、电池模块、电池包和用电装置 - Google Patents

电解液及包含其的二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023220857A1
WO2023220857A1 PCT/CN2022/093000 CN2022093000W WO2023220857A1 WO 2023220857 A1 WO2023220857 A1 WO 2023220857A1 CN 2022093000 W CN2022093000 W CN 2022093000W WO 2023220857 A1 WO2023220857 A1 WO 2023220857A1
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electrolyte
solvent
optionally
secondary battery
fluorine
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PCT/CN2022/093000
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English (en)
French (fr)
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彭畅
陈培培
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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 PCT/CN2022/093000 priority Critical patent/WO2023220857A1/zh
Priority to CN202280041239.6A priority patent/CN117501497A/zh
Publication of WO2023220857A1 publication Critical patent/WO2023220857A1/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
    • 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, and in particular to an electrolyte and secondary batteries, battery modules, battery packs and electrical devices containing the same.
  • This application was made in view of the above-mentioned problems, and its purpose is to provide an electrolyte that has good stability under high-voltage conditions and helps improve the storage performance and cycle performance of secondary batteries.
  • the present application provides an electrolyte and a secondary battery, a battery module, a battery pack and an electrical device containing the electrolyte.
  • the S F is the fluorine other than lithium salt corresponding to fluorine and 4-fluoropyridine corresponding to fluorine in the range of -280ppm to 80ppm when NMR fluorine spectrum is tested on a mixture of electrolyte and 4-fluoropyridine with a weight ratio of 1:1
  • the peak area of , where the peak area of 4-fluoropyridine corresponding to fluorine in the range of -102ppm to -104ppm is normalized to 1;
  • the S H is the value of hydrogen except for deuterated acetonitrile and 4-fluoropyridine corresponding hydrogen in the range of 0.5ppm to 10ppm when a mixture of electrolyte and 4-fluoropyridine with a weight ratio of 1:1 is tested by hydrogen nuclear magnetic spectrum. Peak area, where the peak area of the corresponding hydrogen of 4-fluoropyridine in the range of 7.0ppm to 7.2ppm and 8.45ppm to 8.65ppm is normalized to 1;
  • the electrolyte does not contain deuterated acetonitrile and 4-fluoropyridine.
  • the electrolyte When the chemical stability coefficient of the electrolyte satisfies the above relationship, the electrolyte has good stability and is compatible with both high-voltage positive and negative electrodes, thereby improving the storage performance and cycle performance of the secondary battery.
  • the electrolyte includes a first solvent and a second solvent
  • the first solvent is selected from one or more of fluoroether, fluorocarbonate, fluorocarboxylate, fluorobenzene or fluorosulfone;
  • R 1 , R 3 , R 5 and R 13 are independently selected from C 1 to C 6 fluoroalkane
  • R 2 , R 4 , R 6 , R 14 , R 15 and R 16 are independently selected from C 1 to C 6 alkanes or C 1 to C 6 fluoroalkane
  • R 7 to R 12 are independently selected from C 1 to C 6 fluoroalkane, fluorine or hydrogen, wherein R 7 to R At least one of 12 is selected from fluorine or fluoroalkane, and at least one of R 15 and R 16 is selected from C 1 to C 6 fluoroalkane;
  • the second solvent is selected from one or more of non-fluorinated carbonates, non-fluorinated carboxylates, non-fluorinated ethers or non-fluorinated sulfones;
  • R 1 ', R 2 ', R 3 ', R 13 ', R 14 ' and R 16 ' are independently selected from C 1 to C 6 alkanes, R 4 ' and R 15 'Selected independently from each other from C 1 to C 6 alkanes or hydrogen;
  • More optional options include ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, One or more of ethyl propionate and propyl propionate.
  • the solvent can form a special solvation structure with the lithium salt in the electrolyte, which is beneficial to reducing side reactions of the solvent on the positive and negative electrode surfaces and improving the performance of the secondary battery. life.
  • the content y1 of the first solvent is 10-100%, optionally 45-100%, more optionally 80-100%, based on the first solvent and the based on the total weight of the second solvent.
  • the content y2 of the second solvent is 0-90%, optionally 0-55%, more optionally 0-20%, based on the first solvent and the based on the total weight of the second solvent.
  • the content y1 of the first solvent and the content y2 of the second solvent satisfy: y1/y2 ⁇ 0.82, optionally y1/y2 ⁇ 2.33, more optionally y1/ y2 ⁇ 4, further optional y1/y2 ⁇ 5.67.
  • the electrolyte further includes a film-forming additive selected from the group consisting of chain or cyclic sulfate esters, chain or cyclic sulfonate esters, chain or cyclic carbonates, polycyclic One or more of sulfate esters or polycyclic sulfonate esters;
  • the film-forming additive can form a film preferentially on the negative electrode, reducing the loss of active lithium, thereby improving battery performance.
  • the content of the film-forming additive is 0.1-10%, optionally 0.5-7%, more optionally 1-5%, based on the first solvent and the third solvent. Based on the total weight of the two solvents.
  • the film-forming additive includes 0.5-1.0% 0.5-2.5% 0.5-2% or 0.5-2% Based on the total weight of the first solvent and the second solvent.
  • the electrolyte solution includes the above-mentioned amount of the film-forming additive, it is beneficial to further improve the stability of the electrolyte solution, thereby further improving the storage performance and cycle performance of the corresponding secondary battery.
  • the lithium salt includes one or more of lithium hexafluorophosphate and lithium bisfluorosulfonimide.
  • the electrolyte solution includes the above-mentioned lithium salt, it is beneficial to improve the conductivity of the electrolyte solution, thereby improving the performance of the secondary battery.
  • the concentration of the lithium salt is 0.7-2.5 mol/L, optionally 1-1.5 mol/L.
  • the acidity of the electrolyte is ⁇ 50 ppm, and the purity of each solvent used is ⁇ 99.8%.
  • the electrolyte When the acidity and purity of the electrolyte are within the above range, the electrolyte has good stability and is less prone to side reactions, which is beneficial to improving the cycle performance of the secondary battery.
  • a second aspect of the application provides a secondary battery, including the electrolyte of the first aspect of the application.
  • the secondary battery can be prepared by a method commonly used in the art for preparing secondary batteries.
  • the Mn element percentage of the positive active material of the secondary battery is ⁇ 25%, based on the total weight of the positive active material
  • LiNi 0.5 Mn 1.5 O 4 LiNi 0.5 Co 0.2 Mn 0.3 O 2 , Li 2 MnO 3 , and LiMnPO 4 can be selected.
  • the positive active material of the secondary battery is selected from the above types, it is beneficial to increase the energy density of the secondary battery, reduce manufacturing costs, and cause less environmental pollution.
  • the particles of the cathode active material are single crystals or quasi-single crystals.
  • the positive active material is a single crystal, the active material itself is not easily broken, which can reduce the probability of exposing new surfaces, thereby reducing side reactions of the electrolyte and improving the stability of the electrolyte.
  • the particle size of the positive active material is 1-20 ⁇ m, optionally 3-15 ⁇ m.
  • the specific surface area of the cathode active material is no more than 1.5m 2 /g, and can optionally be 0.1m 2 /g-1m 2 /g.
  • the particle size and surface area of the cathode active material are within the above range, it will help reduce side reactions and improve the stability of the electrolyte; it will also help avoid increased process energy consumption and deterioration of the cathode due to excessive particle size. chip processing performance.
  • a third aspect of the present application provides a battery module including the secondary battery of the second aspect of the present application.
  • the battery module can be manufactured using methods commonly used in the art to prepare battery modules.
  • a fourth aspect of the application provides a battery pack, including the battery module of the third aspect of the application.
  • the battery pack can be prepared using methods commonly used in the art for preparing battery packs.
  • a fifth aspect of the present application provides an electrical 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.
  • the electrochemical stability coefficient within the above range also helps to reduce the damage of the generated hydrofluoric acid to the negative electrode SEI film (Solid Electrolyte Interface), and avoids the reduction of a large amount of solvent in the negative electrode, resulting in A large amount of active lithium is lost, thereby deteriorating the storage performance and cycle performance of the secondary battery.
  • the battery modules, battery packs and electrical devices of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary 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 the 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.
  • Figure 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 an embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. 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 of the endpoints, and may be arbitrarily combined, that is, 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, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then 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" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • 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 sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • 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), etc.
  • condition "A or B” is satisfied by any of the following conditions: 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 electrolyte has good electrochemical stability even under high voltage conditions and is well compatible with the positive and negative electrodes, reducing the damage to the positive and negative electrode materials after the electrolyte generates hydrofluoric acid. This further improves the storage performance and cycle performance of secondary batteries.
  • the types and amounts of various solvents and additives in the electrolyte the storage performance and cycle performance of the secondary battery can be further improved.
  • the S F is the fluorine other than lithium salt corresponding to fluorine and 4-fluoropyridine corresponding to fluorine in the range of -280ppm to 80ppm when NMR fluorine spectrum is tested on a mixture of electrolyte and 4-fluoropyridine with a weight ratio of 1:1
  • the peak area of , where the peak area of 4-fluoropyridine corresponding to fluorine in the range of -102ppm to -104ppm is normalized to 1;
  • the S H is the value of hydrogen except for deuterated acetonitrile and 4-fluoropyridine corresponding hydrogen in the range of 0.5ppm to 10ppm when a mixture of electrolyte and 4-fluoropyridine with a weight ratio of 1:1 is tested by hydrogen nuclear magnetic spectrum. Peak area, where the peak area of the corresponding hydrogen of 4-fluoropyridine in the range of 7.0ppm to 7.2ppm and 8.45ppm to 8.65ppm is normalized to 1;
  • the electrolyte does not contain deuterated acetonitrile and 4-fluoropyridine.
  • the electrochemical stability coefficient within the above range also helps to reduce the damage of the generated hydrofluoric acid to the SEI film of the negative electrode, and avoids the reduction of a large amount of solvent in the negative electrode, resulting in the loss of a large amount of active lithium. This further deteriorates the storage performance and cycle performance of the secondary battery.
  • x is 0.25-0.55, it is beneficial to further improve the compatibility between the electrolyte and the positive and negative electrodes, thereby improving the storage performance and cycle performance of the secondary battery.
  • the electrolyte solution specified in this application does not contain deuterated acetonitrile and 4-fluoropyridine, this is because when measuring SF and S H by nuclear magnetic resonance, deuterated acetonitrile needs to be used as the nuclear magnetic test solvent, and 4-fluoropyridine is required. Fluoropyridine is used as a reference substance. If the electrolyte solution also contains the reference substance, it will result in the inability to distinguish the characteristic peaks of the same component in the reference substance and the electrolyte solution, thereby causing inaccurate determination of SF and S H. Those skilled in the art should understand that when performing NMR spectrum testing, different deuterated solvents and reference substances can be selected according to testing needs. In addition, the mass addition ratio of electrolyte solution and 4-fluoropyridine can be determined according to test needs. For example, the mass addition ratio of electrolyte solution and 4-fluoropyridine can be 1:1.
  • the electrolyte solution includes a first solvent and a second solvent
  • the first solvent is selected from one or more of fluoroether, fluorocarbonate, fluorocarboxylate, fluorobenzene or fluorosulfone;
  • R 1 , R 3 , R 5 and R 13 are independently selected from C 1 to C 6 fluoroalkane
  • R 2 , R 4 , R 6 , R 14 , R 15 and R 16 are independently selected from C 1 to C 6 alkanes or C 1 to C 6 fluoroalkane
  • R 7 to R 12 are independently selected from C 1 to C 6 fluoroalkane, fluorine or hydrogen, wherein R 7 to R At least one of 12 is selected from fluorine or fluoroalkane, and at least one of R 15 and R 16 is selected from C 1 to C 6 fluoroalkane;
  • the second solvent is selected from one or more of non-fluorinated carbonates, non-fluorinated carboxylates, non-fluorinated ethers or non-fluorinated sulfones;
  • R 1 ', R 2 ', R 3 ', R 13 ', R 14 ' and R 16 ' are independently selected from C 1 to C 6 alkanes, R 4 ' and R 15 'Selected independently from each other from C 1 to C 6 alkanes or hydrogen;
  • More optional options include ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, One or more of ethyl propionate and propyl propionate.
  • the solvent can form a special solvation structure with the lithium salt in the electrolyte, promote the formation of a dense protective film during the initialization stage, promote desolvation, and thereby reduce the amount of solvent in the normal process. Side reactions on the surface of the negative electrode improve the cycle performance of the secondary battery.
  • the content y1 of the first solvent is 10-100%, optionally 45-100%, more optionally 80-100%, based on the first solvent and the based on the total weight of the second solvent.
  • the content y1 of the first solvent may be 10%, 30%, 45%, 70%, 80%, 90% or 100%.
  • the content y2 of the second solvent is 0-90%, optionally 0-55%, more optionally 0-20%, based on the first solvent and the based on the total weight of the second solvent.
  • the content y2 of the second solvent may be 70%, 55%, 40%, 30%, 20%, 10% or 0%.
  • the sum of the weights of the first solvent and the second solvent accounts for 60-90% of the total weight of the electrolyte of the present application, optionally 60-87.5%.
  • the content y1 of the first solvent and the content y2 of the second solvent satisfy: y1/y2 ⁇ 0.82, optionally y1/y2 ⁇ 2.33, more optionally y1/ y2 ⁇ 4, further optional y1/y2 ⁇ 5.67.
  • the electrolyte has better electrochemical stability, which helps to further improve the compatibility between the electrolyte and the positive and negative electrodes, reduce side reactions, and improve Storage performance and cycle performance of secondary batteries.
  • the content y1 of the first solvent and the content y2 of the second solvent satisfy: 0 ⁇ y1 ⁇ y2/(y1+y2) ⁇ 0.25, optionally 0 ⁇ y1 ⁇ y2/(y1+y2) ⁇ 0.16, more optionally 0 ⁇ y1 ⁇ y2/(y1+y2) ⁇ 0.09.
  • the electrolyte further includes a film-forming additive selected from chain or cyclic sulfate esters, chain or cyclic sulfonate esters, chain or cyclic carbonates, polycyclic One or more of sulfate esters or polycyclic sulfonate esters;
  • the film-forming additive can form a film on the negative electrode preferentially, reducing the loss of active lithium, thereby improving the storage performance and cycle performance of the secondary battery.
  • the content of the film-forming additive is 0.1-10%, optionally 0.5-7%, more optionally 1-5%, based on the first solvent and the third solvent. Based on the total weight of the two solvents.
  • the film-forming additive includes 0.5-1.0% 0.5-2.5% 0.5-2% or 0.5-2% Based on the total weight of the first solvent and the second solvent.
  • the electrolyte solution includes the above-mentioned amount of the film-forming additive, it is beneficial to further improve the stability of the electrolyte solution, thereby further improving the storage performance and cycle performance of the corresponding secondary battery.
  • the lithium salt includes one or more of lithium hexafluorophosphate and lithium bisfluorosulfonimide.
  • the concentration of the lithium salt is 0.7-2.5 mol/L, optionally 1-1.5 mol/L.
  • the viscosity of the electrolyte solution is moderate, which is beneficial to improving the conductivity of the electrolyte solution and thereby improving the performance of the secondary battery.
  • the concentration of the electrolyte lithium salt is too high, the overall concentration of the electrolyte increases, but the dissociation degree of the salt in the electrolyte decreases, and the viscosity of the electrolyte also increases, which in turn causes the conductivity of the electrolyte to decrease.
  • the electrolyte of the present application also contains other functional additives, which may be any additives known in the art that are suitable in the context of the present application.
  • the electrolyte further includes at least one of a flame retardant additive, an anti-overcharge additive, and a conductive additive. Including the above additives in the electrolyte can further improve the performance of the electrolyte.
  • the acidity of the electrolyte is ⁇ 50 ppm, and the purity of each solvent used is ⁇ 99.8%.
  • the electrolyte When the acidity and purity of the electrolyte are within the above range, the electrolyte has good stability and is less prone to side reactions, which is beneficial to improving the cycle performance of the secondary battery.
  • the acidity of the electrolyte in this application can be tested using methods commonly used in this field.
  • the electrolyte solution described in the present application can be prepared by methods commonly used by those skilled in the art.
  • the electrolyte described in the present application can be prepared by mixing and stirring the first solvent, the second solvent, the lithium salt, the film-forming additive, and other additives in a certain proportion under the protection of an inert gas.
  • a second aspect of the application provides a secondary battery, including the electrolyte of the first aspect of the application.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the injection coefficient of the electrolyte in the secondary battery described in this application is 1.8-4g/Ah, optionally 2.4-3.2g/Ah.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the Mn element percentage of the positive active material of the secondary battery is ⁇ 25%, based on the total weight of the positive active material
  • LiNi 0.5 Mn 1.5 O 4 LiNi 0.5 Co 0.2 Mn 0.3 O 2 , Li 2 MnO 3 , and LiMnPO 4 can be selected.
  • the positive active material of the secondary battery is selected from the above types, it is beneficial to increase the energy density of the secondary battery, reduce manufacturing costs, and cause less environmental pollution.
  • the particles of the cathode active material are single crystals or quasi-single crystals.
  • the positive active material is a single crystal, the active material itself is not easily broken, which can reduce the probability of exposing new surfaces, thereby reducing side reactions of the electrolyte and improving the stability of the electrolyte.
  • the particle size of the positive active material is 1-20 ⁇ m, optionally 3-15 ⁇ m.
  • the particle size of the positive active material can be determined by methods commonly used in this field. For example, the standard GB/T 19077-2016/ISO 13320:2009 can be used for testing.
  • the specific surface area of the cathode active material is no more than 1.5m 2 /g, and optionally 0.1m 2 /g-1m 2 /g.
  • the specific surface area of the positive active material can be measured by methods commonly used in this field. For example, the test can be carried out with reference to the standard GB/T19587-2004 "Determination of the Specific Surface Area of Solid Materials by Gas Adsorption BET Method".
  • the particle size and surface area of the cathode active material are within the above range, it will help reduce side reactions and improve the stability of the electrolyte; it will also help avoid increased process energy consumption and deterioration of the cathode due to excessive particle size. chip processing performance.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of fluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the binder accounts for 0.1-3.5%, optionally 0.5-2.5%, of the total weight of the positive electrode film layer.
  • the positive electrode film layer optionally further includes 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 conductive agent accounts for 0.05-5%, optionally 0.5-3%, of the total weight of the positive electrode film layer.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components 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 piece 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 disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may 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 optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a 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 piece can be obtained.
  • a solvent such as deionized water
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • a third aspect of the present application provides a battery module, including the secondary battery described in the second aspect of the present application.
  • a fourth aspect of the application provides a battery pack, including the battery module described in the third aspect of the application.
  • a fifth aspect of the present application provides an electrical device, including at least one of the secondary battery of the second aspect of the present application, the battery module of the third aspect, or the battery pack of the fourth aspect of the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, battery module or battery pack can be selected according to its usage requirements.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • 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 bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 1 shows a square-structured 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 side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into 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.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number 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 can be fixed by fasteners.
  • the battery module 4 may also include a housing 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.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number 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 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 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.
  • FIG. 6 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • the positive active material LNMO i.e. LiNi 0.5 Mn 1.5 O 4
  • Super P conductive agent carbon black
  • PVDF binder polyvinylidene fluoride
  • the loading amount of the negative active material on one side of the negative current collector is 0.008g/cm 2 .
  • the secondary battery of Example 1 was prepared by processes such as standing.
  • the liquid injection coefficient in the obtained secondary battery was 2.8 g/Ah.
  • Example 11 and Comparative Example 3 are NCM523 (ie, LiNi 0.5 Co 0.2 Mn 0.3 O 2 ), Examples 2-11 and Comparative Examples 1-3 Other conditions are the same as Example 1.
  • the secondary battery At 25°C, charge the secondary battery with a constant current of 0.1C to the upper limit cut-off voltage, and then charge it with a constant voltage of this cut-off voltage until the current is 0.05C. At this time, the secondary battery is in a fully charged state. Store the fully charged secondary battery in an environment of 60°C, take it out every 10 days, and discharge it to the lower limit cut-off voltage at a constant current of 0.1C to obtain the discharge capacity after storage for a period of time; then the secondary battery is stored according to After the battery is fully charged in the above method, it is stored in a 60°C environment again until the discharge capacity of the secondary battery attenuates to 70% of the initial discharge capacity. The test ends and the total number of storage days of the secondary battery is recorded. The longer the storage days of the secondary battery, the longer the expected life of the secondary battery in high-temperature storage.
  • Example 1-11 and Comparative Example 1-2 is 4.9V, and the lower limit cut-off voltage is 3.5V; the upper limit cut-off voltage of Example 11 and Comparative Example 3 is 4.5V, the lower limit cut-off voltage is 2.8V.
  • Table 1 shows the performance test results of Examples 1-12 and Comparative Examples 1-3.

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Abstract

一种电解液，电池模块（4）、电池包（1）和用电装置。电解液包括溶剂和含氟的锂盐，其中电解液的电化学稳定系数x＝S F/(S F+4S H)为0.18-0.6，可选为0.25-0.55，其中S F和S H可通过记载的测量方法确定。应用电解液的二次电池（5）具备良好的电化学稳定性，有助于改善二次电池（5）的存储性能和循环性能。

Description

电解液及包含其的二次电池、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，尤其涉及一种电解液及包含其的二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着二次电池在众多行业如电动汽车、电动摩托车、航空航天、水力、风力、太阳能电站等领域的应用越来越广泛，人们对二次电池的性能提出了越来越多的要求，其中之一就是希望二次电池具备良好的存储性能和循环性能。然而，现有的可工业化电解液在高电压工况下容易被氧化分解，从而恶化二次电池性能。因此，如何提供一种在高电压工况下性能稳定的电解液，从而改善二次电池的存储性能和循环性能，仍然是技术人员亟需解决的一项技术问题。
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，所述电解液在高电压工况下具备良好的稳定性，有助于改善二次电池的存储性能和循环性能。
为达到上述目的，本申请提供了一种电解液及包含其的二次电池、电池模块、电池包和用电装置。
本申请的第一方面提供一种电解液，包括溶剂和含氟的锂盐，其中所述电解液的电化学稳定系数x＝S F/(S F+4S H)为0.18-0.6，可选为0.25-0.55，
所述S F为对重量比为1∶1的电解液和4-氟吡啶的混合物进行核磁氟谱测试时，-280ppm至80ppm范围内除锂盐对应氟、4-氟吡啶对应氟以外的氟的峰面积，其中将-102ppm至-104ppm范围内4-氟吡啶对应氟的峰面积归一化为1；
所述S H为对重量比为1∶1的电解液和4-氟吡啶的混合物进行核磁氢谱测试时，0.5ppm至10ppm范围内除氘代乙腈、4-氟吡啶对应氢以外的氢的峰面积，其中将7.0ppm至7.2ppm和8.45ppm至8.65ppm范围内4-氟吡啶对应氢的峰面积归一化为1；
所述电解液不含氘代乙腈、4-氟吡啶。
当电解液化学稳定系数满足上述关系时，电解液具备良好的稳定性，可同时与高电压正负极兼容，进而改善二次电池的存储性能和循环性能。
在任意实施方式中，可选地，所述电解液包含第一溶剂和第二溶剂，
所述第一溶剂选自氟代醚、氟代碳酸酯、氟代羧酸酯、氟代苯或氟代砜中的一种或多种；
可选为
Figure PCTCN2022093000-appb-000001
Figure PCTCN2022093000-appb-000002
中的一种或多种，其中R 1、R 3、R 5和R 13彼此独立地选自C 1至C 6氟代烷烃，R 2、R 4、R 6、R 14、R 15和R 16彼此独立地选自C 1至C 6烷烃或C 1至C 6氟代烷烃，R 7至R 12彼此独立地选自C 1至C 6氟代烷烃、氟或氢，其中R 7至R 12中至少一个选自氟或氟代烷烃，R 15和R 16中至少有一个选自C 1至C 6氟代烷烃；
更可选为
Figure PCTCN2022093000-appb-000003
Figure PCTCN2022093000-appb-000004
Figure PCTCN2022093000-appb-000005
中的一种或多种；
所述第二溶剂选自非氟代碳酸酯、非氟代羧酸酯、非氟代醚或非氟代砜中的一种或多种；
可选为
Figure PCTCN2022093000-appb-000006
中的一种或多种，其中R 1’、R 2’、R 3’、R 13’、R 14’和R 16’彼此独立地选自C 1至C 6烷烃，R 4’和R 15’彼此独立地选自C 1至C 6烷烃或氢；
更可选为碳酸甲乙酯、碳酸二甲酯、碳酸二乙酯、碳酸亚乙酯、碳酸亚丙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯中的一种或多种。
当第一溶剂和第二溶剂选自上述溶剂时，所述溶剂可与电解液中的锂盐形成特殊的溶剂化结构，有利于减少溶剂在正负极表面的副反应，提升二次电池的寿命。
在任意实施方式中，可选地，所述第一溶剂的含量y1为10-100％，可选为45-100％，更可选为80-100％，基于所述第一溶剂和所述第二溶剂的总重量计。
在任意实施方式中，可选地，所述第二溶剂的含量y2为0-90％，可选为0-55％，更可选为0-20％，基于所述第一溶剂和所述第二溶剂的总重量计。
在任意实施方式中，可选地，所述第一溶剂的含量y1与所述第二溶剂的含量y2满足：y1/y2≥0.82，可选为y1/y2≥2.33，更可选为y1/y2≥4，进一步可选为y1/y2≥5.67。
当第一溶剂和第二溶剂的含量在上述范围内时，有利于进一步改善电解液的稳定性。
在任意实施方式中，可选地，所述电解液还包括成膜添加剂，选自链状或环状硫酸酯、链状或环状磺酸酯、链状或环状碳酸酯、多环状硫酸酯或多环状磺酸酯中的一种或多种；
可选为
Figure PCTCN2022093000-appb-000007
Figure PCTCN2022093000-appb-000008
中的一种或多种；
更可选为
Figure PCTCN2022093000-appb-000009
中的一种或多种。
所述成膜添加剂能够优先在负极成膜，减少活性锂损失，进而改善电池性能。
在任意实施方式中，可选地，所述成膜添加剂的含量为0.1-10％，可选为0.5-7％，更可选为1-5％，基于所述第一溶剂和所述第二溶剂的总重量计。
在任意实施方式中，可选地，所述成膜添加剂包括0.5-1.0％的
Figure PCTCN2022093000-appb-000010
0.5-2.5％的
Figure PCTCN2022093000-appb-000011
0.5-2％的
Figure PCTCN2022093000-appb-000012
或0.5-2％的
Figure PCTCN2022093000-appb-000013
基于所述第一溶剂和所述第二溶剂的总重量计。
当电解液包括所述量的上述成膜添加剂时，有利于进一步改善电解液的稳定性，从而进一步改善相应二次电池的存储性能和循环性能。
在任意实施方式中，可选地，所述锂盐包括六氟磷酸锂和双氟磺酰亚胺锂中的一种或多种。
当电解液包括上述锂盐时，有利于改善电解液的电导率，进而提升二次电池性能。
在任意实施方式中，可选地，所述锂盐的浓度为0.7-2.5mol/L，可选为1-1.5mol/L。
在任意实施方式中，可选地，所述电解液的酸度≤50ppm，使用的各溶剂纯度≥99.8％。
当电解液的酸度和纯度在上述范围内时，电解液具备良好的稳定性，不易发生副反应，从而有利于改善二次电池的循环性能。
本申请的第二方面提供一种二次电池，包括本申请第一方面的电解液。二次电池可采用本领域通常使用的制备二次电池的方法制备。
在任意实施方式中，可选地，所述二次电池的正极活性物质的Mn元素百分含量≥25％，基于所述正极活性物质的总重量计；
可选为LiM pMn 2-pO 4、LiN qMn 1-qPO 4或Li 1+tMn 1-wL wO 2+t中的一种或多种，其中0≤p≤1，0≤q≤0.5，0≤t≤1，0≤w≤0.5，M、N、L各自独立地表示Ni、Co、Fe、Cr、V、Ti、Zr、La、Ce、Rb、P、W、Nb、Mo、Sb、B、Al、Si中的一种或多种；
更可选为LiM pMn 2-pO 4或Li 1+tMn 1-wL wO 2+t中的一种或多种；
更可选为LiNi 0.5Mn 1.5O 4、LiNi 0.5Co 0.2Mn 0.3O 2、Li 2MnO 3、LiMnPO 4中的一种或多种。
当二次电池的正极活性物质选自上述类型时，有利于提升二次电池的能量密度，降低制造成本，并且环境污染小。
在任意实施方式中，可选地，所述正极活性物质的颗粒为单晶或类单晶。
当正极活性物质为单晶时，活性物质本身不易破碎，可减少暴露新表面的概率，进而减少电解液的副反应，提升电解液的稳定性。
在任意实施方式中，可选地，所述正极活性物质的粒径为1-20μm，可选为3-15μm。
在任意实施方式中，可选地，所述正极活性物质的比表面积不大于1.5m 2/g，可选为0.1m 2/g-1m 2/g。
当正极活性物质的粒径和表面积在上述范围内时，有利于减少副反应，提升电解液的稳定性；同时有助于避免因过大的粒径而导致工艺能耗增加，并且恶化正极极片的加工性能。
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。电池模块可采用本领域通常使用的制备电池模块的方法制各。
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。电池包可采用本领域通常使用的制备电池包的方法制备。
本申请的第五方面提供一种用电装置，包括选自本申请第二方面的二次电池、本申请第三方面的电池模块或本申请第四方面的电池包中的至少一种。
[有益效果]
本申请所述的电解液中，电化学稳定系数x＝S F/(S F+4S H)为0.18-0.6，可选为0.25-0.55，这有利于改善电解液的稳定性，使得电解液与正负极具备良好的兼容性，减少电解液在产生氢氟酸后对正极活性材料表面的破坏，减少裸露出新的活性位点，从而减少电解液的副反应，改善二次电池的存储性能和循环性能；同时，电化学稳定系数在上述范围内也有助于减少产生的氢氟酸对负极SEI膜(固态电解质界面膜，Solid Electrolyte Interface)的破坏，避免大量溶剂在负极还原，从而导致大量活性锂损失，进而恶化二次电池的存储性能和循环性能。
本申请的电池模块、电池包和用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
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、电池包和用电装置的实施方式。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)。
发明人在实际作业中发现，现有技术中的电解液大多不适用于在高电压如4.2V以上电压下工作，这是由于这些电解液的稳定性较差，在高电压工况下容易分解，产生大量HF，腐蚀正极活性材料，恶化二次电池性能。
发明人在经过大量实验后意外发现，当电解液在核磁氢谱和核磁氟谱中对应的积分面积S H和S F满足x＝S F/(S F+4S H)为0.18-0.6，可选为0.25-0.55时，电解液即使在高电压工况下也具备良好的电化学稳定性，可与正负极良好兼容，减少电解液在产生氢氟酸后对正负极材料的破坏，进而改善二次电池的存储性能和循环性能。此外，通过进一步调节电解液中各种溶剂、添加剂的类型和用量，可进一步改善二次电池的存储性能和循环性能。
[电解液]
本申请的第一方面提供一种电解液，包括溶剂和含氟的锂盐，其中所述电解液的电化学稳定系数x＝S F/(S F+4S H)为0.18-0.6，可选为0.25-0.55，
所述S F为对重量比为1∶1的电解液和4-氟吡啶的混合物进行核磁氟谱测试时，-280ppm至80ppm范围内除锂盐对应氟、4-氟吡啶对应氟以外的氟的峰面积，其中将-102ppm至-104ppm范围内4-氟吡啶对应氟的峰面积归一化为1；
所述S H为对重量比为1∶1的电解液和4-氟吡啶的混合物进行核磁氢谱测试时，0.5ppm至10ppm范围内除氘代乙腈、4-氟吡啶对应氢以外的氢的峰面积，其中将7.0ppm至7.2ppm和8.45ppm至8.65ppm范围内4-氟吡啶对应氢的峰面积归一化为1；
所述电解液不含氘代乙腈、4-氟吡啶。
虽然机理尚不明确，但发明人发现，当本申请所述的电解液中，电化学稳定系数x＝S F/(S F+4S H)为0.18-0.6时，有利于改善电解液的稳定性，使得电解液与正负极具备良好的兼容性，减少电解液在产生氢氟酸后对正极活性材料表面的破坏，减少裸露出新的活性位点，从而减少电解液的副反应，改善二次电池的存储性能和循环性能；同时，电化学稳定系数在上述范围内也有助于减少产生的氢氟酸对负极SEI膜的破坏，避免大量溶剂在负极还原，从而导致大量活性锂损失，进而恶化二次电池的存储性能和循环性能。可选地，当x为0.25-0.55时，有利于进一步提高电解液与正负极的兼容性，进而改善二次电池的存储性能和循环性能。
需要说明的是，尽管本申请限定电解液不含氘代乙腈、4-氟吡啶，但这是因为在通过核磁测定S F和S H时，需要使用氘代乙腈作为核磁测试溶剂，需要4-氟吡啶作为参照物，如果电解液中也包含所述参照物，会导致无法区分参照物和电解液中相同组分的特征峰，进而造成S F和S H的测定不准确。本领域技术人员应当理解，在进行核磁谱图测试时，根据测试需要，可以选用不同的氘代溶剂和参照物。此外，电解液和4-氟吡啶的质量加入比例可根据测试需要确定，例如电解液和4-氟吡啶的质量加入比例可为1∶1。
在一些实施方式中，可选地，所述电解液包含第一溶剂和第二溶剂，
所述第一溶剂选自氟代醚、氟代碳酸酯、氟代羧酸酯、氟代苯或氟代砜中的一种或多种；
可选为
Figure PCTCN2022093000-appb-000014
Figure PCTCN2022093000-appb-000015
中的一种或多种，其中R 1、R 3、R 5和R 13彼此独立地选自C 1至C 6氟代烷烃，R 2、R 4、R 6、R 14、R 15和R 16彼此独立地选自C 1至C 6烷烃或C 1至C 6氟代烷烃，R 7至R 12彼此独立地选自C 1至C 6氟代烷烃、氟或氢，其中R 7至R 12中至少一个选自氟或氟代烷烃，R 15和R 16中至少有一个选自C 1至C 6氟代烷烃；
更可选为
Figure PCTCN2022093000-appb-000016
Figure PCTCN2022093000-appb-000017
Figure PCTCN2022093000-appb-000018
中的一种或多种；
所述第二溶剂选自非氟代碳酸酯、非氟代羧酸酯、非氟代醚或非氟代砜中的一种或多种；
可选为
Figure PCTCN2022093000-appb-000019
中的一种或多种，其中R 1’、R 2’、R 3’、R 13’、R 14’和R 16’彼此独立地选自C 1至C 6烷烃，R 4’和R 15’彼此独立地选自C 1至C 6烷烃或氢；
更可选为碳酸甲乙酯、碳酸二甲酯、碳酸二乙酯、碳酸亚乙酯、碳酸亚丙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯中的一种或多种。
当第一溶剂和第二溶剂选自上述溶剂时，所述溶剂可与电解液中 的锂盐形成特殊的溶剂化结构，促进初始化阶段形成致密保护膜，促进脱溶剂化，进而减少溶剂在正负极表面的副反应，提升二次电池的循环性能。
在一些实施方式中，可选地，所述第一溶剂的含量y1为10-100％，可选为45-100％，更可选为80-100％，基于所述第一溶剂和所述第二溶剂的总重量计。作为示例，例如所述第一溶剂的含量y1可为10％、30％、45％、70％、80％、90％或100％。
在一些实施方式中，可选地，所述第二溶剂的含量y2为0-90％，可选为0-55％，更可选为0-20％，基于所述第一溶剂和所述第二溶剂的总重量计。作为示例，例如所述第二溶剂的含量y2可为70％、55％、40％、30％、20％、10％或0％。
当第一溶剂和第二溶剂的含量在上述范围内时，有利于进一步改善电解液的稳定性，提升二次电池的存储性能和循环性能。
在一些实施方式中，可选地，所述第一溶剂和所述第二溶剂的重量之和占本申请电解液总重量的60-90％，可选为60-87.5％。
当第一溶剂和第二溶剂重量之和占本申请电解液的重量百分比处于上述范围内时，有利于进一步提升电解液的稳定性。
在一些实施方式中，可选地，所述第一溶剂的含量y1与所述第二溶剂的含量y2满足：y1/y2≥0.82，可选为y1/y2≥2.33，更可选为y1/y2≥4，进一步可选为y1/y2≥5.67。
当第一溶剂的含量y1与第二溶剂的含量y2满足上述关系时，电解液具备更好的电化学稳定性，有助于进一步改善电解液与正负极的兼容性，减少副反应，提升二次电池的存储性能和循环性能。
在一些实施方式中，可选地，所述第一溶剂的含量y1与所述第二溶剂的含量y2满足：0≤y1×y2/(y1+y2)≤0.25，可选为0≤y1×y2/(y1+y2)≤0.16，更可选为0≤y1×y2/(y1+y2)≤0.09。
当第一溶剂的含量y1与第二溶剂的含量y2满足上述关系时，有助于进一步提升电解液的稳定性，从而提升二次电池的存储性能和循环性能。
在一些实施方式中，可选地，所述电解液还包括成膜添加剂，选自链状或环状硫酸酯、链状或环状磺酸酯、链状或环状碳酸酯、多环状硫酸酯或多环状磺酸酯中的一种或多种；
可选为
Figure PCTCN2022093000-appb-000020
Figure PCTCN2022093000-appb-000021
中的一种或多种；
更可选为
Figure PCTCN2022093000-appb-000022
中的一种或多种。
所述成膜添加剂能够优先在负极成膜，减少活性锂损失，进而改善二次电池的存储性能和循环性能。
在一些实施方式中，可选地，所述成膜添加剂的含量为0.1-10％，可选为0.5-7％，更可选为1-5％，基于所述第一溶剂和所述第二溶剂的总重量计。
在一些实施方式中，可选地，所述成膜添加剂包括0.5-1.0％的
Figure PCTCN2022093000-appb-000023
0.5-2.5％的
Figure PCTCN2022093000-appb-000024
0.5-2％的
Figure PCTCN2022093000-appb-000025
或0.5-2％的
Figure PCTCN2022093000-appb-000026
基于所述第一溶剂和所述第二溶剂的总重量计。
当电解液包括所述量的上述成膜添加剂时，有利于进一步改善电解液的稳定性，从而进一步改善相应二次电池的存储性能和循环性能。
在一些实施方式中，可选地，所述锂盐包括六氟磷酸锂和双氟磺酰亚胺锂中的一种或多种。
在一些实施方式中，可选地，所述锂盐的浓度为0.7-2.5mol/L，可选为1-1.5mol/L。
当电解液包括所述浓度的上述锂盐时，电解液的粘度适中，有利于改善电解液的电导性，进而提升二次电池性能。但是，电解质锂盐浓度过高时，电解液总体浓度增加，电解液中盐的解离度却降低，并且电解液粘度也会增加，从而反而会导致电解液的电导率下降。
在本文中，浓度单位“M”和“mol/L”可互换使用。
在一些实施方式中，可选地，本申请的电解液还包含其他功能性添加剂，其可以是在本申请背景下适用的、本领域已知的任何添加剂。作为示例，所述电解液还包括阻燃添加剂、防过充添加剂和导电添加剂中的至少一种。电解液中包含上述添加剂能够进一步改进电解液的性能。
在一些实施方式中，可选地，所述电解液的酸度≤50ppm，使用的各溶剂纯度≥99.8％。
当电解液的酸度和纯度在上述范围内时，电解液具备良好的稳定性，不易发生副反应，从而有利于改善二次电池的循环性能。
需要说明的是，本申请中电解液的酸度可采用本领域通常使用的方法进行测试，具体可参考HG/T4067-2015，采用三乙胺标准溶液滴定电解液中的游离酸。
需要说明的是，本领域技术人员理解，可通过本领域技术人员通常使用的方法来制备本申请所述的电解液。例如，可在惰性气体保护下将第一溶剂、第二溶剂、锂盐、成膜添加剂、其他添加剂等按照一定的比例混合搅拌均匀，即可制备本申请所述电解液。
[二次电池]
本申请的第二方面提供一种二次电池，包括本申请第一方面的电解液。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。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。电解质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。
在一些实施方式中，可选地，本申请所述二次电池中电解液的注液系数为1.8-4g/Ah，可选为2.4-3.2g/Ah。作为示例，当二次电池的注液系数为2.8g/Ah，电芯容量设计为3Ah时，注液量为2.8*3g＝8.4g。
以下详细对本申请所述二次电池的正极极片、负极极片和隔离膜进行说明。
[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，所述正极膜层包括本申请第一方面的正极活性材料。
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，可选地，所述二次电池的正极活性物质的Mn元素百分含量≥25％，基于所述正极活性物质的总重量计；
可选为LiM pMn 2-pO 4、LiN qMn 1-qPO 4或Li 1+tMn 1-wL wO 2+t中的一种或多种，其中0≤p≤1，0≤q≤0.5，0≤t≤1，0≤w≤0.5，M、N、L各自独立地表示Ni、Co、Fe、Cr、V、Ti、Zr、La、Ce、Rb、P、W、Nb、Mo、Sb、B、Al、Si中的一种或多种；
更可选为LiM pMn 2-pO 4或Li 1+tMn 1-wL wO 2+t中的一种或多种；
更可选为LiNi 0.5Mn 1.5O 4、LiNi 0.5Co 0.2Mn 0.3O 2、Li 2MnO 3、LiMnPO 4中的一种或多种。
当二次电池的正极活性物质选自上述类型时，有利于提升二次电池的能量密度，降低制造成本，并且环境污染小。
在一些实施方式中，可选地，所述正极活性物质的颗粒为单晶或类单晶。
当正极活性物质为单晶时，活性物质本身不易破碎，可减少暴露新表面的概率，进而减少电解液的副反应，提升电解液的稳定性。
在一些实施方式中，可选地，所述正极活性物质的粒径为1-20μm，可选为3-15μm。可通过本领域通常使用的方法来测定正极活性物质的粒径，例如可参考标准GB/T 19077-2016/ISO 13320：2009进行测试。
在一些实施方式中，可选地，所述正极活性物质的比表面积不大于1.5m 2/g，可选为0.1m 2/g-1m 2/g。可通过本领域通常使用的方法来测定正极活性物质的比表面积，例如可参考标准GB/T19587-2004《气体吸附BET法测定固态物质比表面积》进行测试。
当正极活性物质的粒径和表面积在上述范围内时，有利于减少副反应，提升电解液的稳定性；同时有助于避免因过大的粒径而导致工艺能耗增加，并且恶化正极极片的加工性能。
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二氟乙烯(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，可选地，所述粘结剂占正极膜层总重量的0.1-3.5％，可选为0.5-2.5％。
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，可选地，所述导电剂占正极膜层总重量的0.05-5％，可选为0.5-3％。
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，例如正极活性材料、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活性材料。
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，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，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)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，例如负极活性材料、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。
本申请的第三方面提供一种电池模块，包括本申请第二方面所述的二次电池。
本申请的第四方面提供一种电池包，包括本申请第三方面所述的电池模块。
本申请的第五方面提供一种用电装置，包括本申请第二方面的二次电池、第三方面的电池模块或第四方面的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。
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。
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。
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。
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。
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。
本申请实施例中使用的原材料来源如下表所示：
Figure PCTCN2022093000-appb-000027
Figure PCTCN2022093000-appb-000028
实施例1
电解液的制备
在氩气气氛手套箱中(H 2O＜0.1ppm，O 2＜0.1ppm)，参照表1，将各种有机溶剂按照所示质量比混合均匀，并加入表1中所示的盐和添加剂，搅拌均匀，得到实施例1的电解液。
正极极片的制备
将正极活性材料LNMO(即LiNi 0.5Mn 1.5O 4)、导电剂炭黑(Super P)、粘结剂聚偏二氟乙烯(PVDF)按照质量比96∶2.5∶1.5在适量的溶剂NMP中充分搅拌混合，形成均匀的正极浆料；将正极浆料均匀涂覆于正极集流体铝箔的表面上，涂覆两面。经干燥、冷压后，得到正极极片。正极集流体单侧上正极活性材料的负载量为0.02g/cm 2。
负极极片的制备
将负极活性材料人造石墨、导电剂炭黑(Super P)、粘结剂丁苯橡胶、增稠剂羧甲基纤维素钠按照质量比96∶1∶1∶2在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，涂覆一面。经干燥、冷压后，得到负极极片。负极集流体单侧上负极活性材料的负载量为0.008g/cm 2。
隔离膜
以聚丙烯膜作为隔离膜。
二次电池的制备
将正极片、隔离膜、负极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，将电极组件置于电池壳体中，干燥后注入电解液，再经过化成、静置等工艺制得实施例1的二次电池。所得二次电池中的注液系数为2.8g/Ah。
实施例2-11和对比例1-3
除如表1中所示的条件不同，以及实施例11和对比例3使用的正极活性物质为NCM523(即LiNi 0.5Co 0.2Mn 0.3O 2)以外，实施例2-11和对比例1-3的其他条件与实施例1相同。
相关参数测试方法
1.核磁测试
1.1氢谱测试
将25mg电解液和25mg 4-氟吡啶混合，然后将混合物加入0.5g氘代乙腈中，进行核磁氢谱测试。在所得谱图中，4-氟吡啶的氢的化学位移为7.09ppm和8.57ppm，对7.0ppm至7.2ppm和8.45ppm至8.65ppm范围内的峰面积进行积分，将积分获得的面积归一化为1。采用类似的方法，对0.5ppm至10ppm范围内的峰进行积分，减去上述4-氟吡啶的氢对应的峰面积以及2.0ppm至1.9ppm范围内的氘代乙 腈的氢对应的峰面积，将剩余氢谱峰面积归一化后记为S H。
1.2氟谱测试
将25mg电解液和25mg 4-氟吡啶混合，然后将混合物加入0.5g氘代乙腈中，进行核磁氟谱测试。在所得谱图中，对-102ppm至-104ppm范围内4-氟吡啶对应氟的峰面积进行积分，将积分获得的面积归一化为1。采用类似的方法，对-280ppm至80ppm范围内的峰面积进行积分，减去-72ppm至-75ppm(LiPF 6)和51ppm至60ppm(LiFSI)范围内锂盐氟的氟对应的峰面积、-102ppm至-104ppm范围内4-氟吡啶的氟对应的峰面积，将剩余氟谱峰面积归一化后记为S F。
2.电芯容量(C)测试
在25℃下，将锂离子电池以0.1C恒流充电至上限截止电压，然后以该电压恒压充电至电流小于0.05C，然后再以0.1C放电到下限截止电压，得到放电容量C(Ah)。
3.二次电池的循环性能测试
在25℃下，将二次电池以0.1C恒流充电至上限截止电压，然后以该截止电压恒压充电至电流为0.05C；静置5min之后，将二次电池以0.1C恒流放电至下限截止电压，此为一个充放电循环过程，此次的放电容量为二次电池的初始放电容量。将二次电池按上述方法循环充放电，直至循环后的放电容量衰减为初始放电容量的70％，结束测试，记录此时二次电池的循环圈数。二次电池的循环圈数越高，表明二次电池的循环预期寿命越长。
4.二次电池存储性能测试
在25℃下，将二次电池以0.1C恒流充电至上限截止电压，然后以该截止电压恒压充电至电流为0.05C，此时二次电池处于满充状态。将满充状态的二次电池置于60℃环境中存储，每隔10天取出一次， 并以0.1C恒流放电至下限截止电压，得到存储一段时间后的放电容量；之后将二次电池按照上述方式满充后再次置于60℃环境中存储，直至二次电池存储后的放电容量衰减为初始放电容量的70％，结束测试，记录二次电池总的存储天数。二次电池的存储天数越多，表明二次电池的高温存储预期寿命越长。
需要说明的是，在上述各性能测试中，实施例1-11和对比例1-2的上限截止电压为4.9V，下限截止电压为3.5V；实施例11和对比例3的上限截止电压为4.5V，下限截止电压为2.8V。表1示出实施例1-12和对比例1-3的性能测试结果。
表1实施例1-12和对比例1-3的实验条件及测试结果
Figure PCTCN2022093000-appb-000029
表1(续)
Figure PCTCN2022093000-appb-000030
从表1中可以看出，相对于对比例1-3，当电解液的电化学稳定系数x为0.18-0.60时，应用所述电解液的二次电池具备更好的存储性能和循环性能。此外，当x为0.25-0.55时，相应二次电池的存储性能和循环性能更好。另外，通过调节第一溶剂和第二溶剂的用量以及成膜添加剂的类型和用量，可以进一步改善二次电池的存储性能和循环性能。
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 (19)

  1. 一种电解液，包括溶剂和含氟的锂盐，其中所述电解液的电化学稳定系数x＝S F/(S F+4S H)为0.18-0.6，可选为0.25-0.55，
    所述S F为对重量比为1∶1的电解液和4-氟吡啶的混合物进行核磁氟谱测试时，-280ppm至80ppm范围内除锂盐对应氟、4-氟吡啶对应氟以外的氟的峰面积，其中将-102ppm至-104ppm范围内4-氟吡啶对应氟的峰面积归一化为1；
    所述S H为对重量比为1∶1的电解液和4-氟吡啶的混合物进行核磁氢谱测试时，0.5ppm至10ppm范围内除氘代乙腈、4-氟吡啶对应氢以外的氢的峰面积，其中将7.0ppm至7.2ppm和8.45ppm至8.65ppm范围内4-氟吡啶对应氢的峰面积归一化为1；
    所述电解液不含氘代乙腈、4-氟吡啶。
  2. 根据权利要求1所述的电解液，其中所述电解液包含第一溶剂和第二溶剂，
    所述第一溶剂选自氟代醚、氟代碳酸酯、氟代羧酸酯、氟代苯或氟代砜中的一种或多种；
    可选为
    Figure PCTCN2022093000-appb-100001
    Figure PCTCN2022093000-appb-100002
    中的一种或多种，其中R 1、R 3、R 5和R 13彼此独立地选自C 1至C 6氟代烷烃，R 2、R 4、R 6、R 14、R 15和R 16彼此独立地选自C 1至C 6烷烃或C 1至C 6氟代烷烃，R 7至R 12彼此独立地选自C 1至C 6氟代烷烃、氟或氢，其中R 7至R 12中至少一个选自氟或氟代烷烃，R 15和R 16中至少有一个选自C 1至C 6氟代烷烃；
    更可选为
    Figure PCTCN2022093000-appb-100003
    Figure PCTCN2022093000-appb-100004
    Figure PCTCN2022093000-appb-100005
    Figure PCTCN2022093000-appb-100006
    中的一种或多种；
    所述第二溶剂选自非氟代碳酸酯、非氟代羧酸酯、非氟代醚或非氟代砜中的一种或多种；
    可选为
    Figure PCTCN2022093000-appb-100007
    中的一种或多种，其中R 1’、R 2’、R 3’、R 13’、R 14’和R 16’彼此独立地选自C 1至C 6烷烃，R 4’和R 15’彼此独立地选自C 1至C 6烷烃或氢；
    更可选为碳酸甲乙酯、碳酸二甲酯、碳酸二乙酯、碳酸亚乙酯、碳酸亚丙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯中的一种或多种。
  3. 根据权利要求2所述的电解液，其中所述第一溶剂的含量y1为10-100％，可选为45-100％，更可选为80-100％，基于所述第一溶剂和所述第二溶剂的总重量计。
  4. 根据权利要求2或3所述的电解液，其中所述第二溶剂的含量y2为0-90％，可选为0-55％，更可选为0-20％，基于所述第一溶剂和所述第二溶剂的总重量计。
  5. 根据权利要求3至4中任一项所述的电解液，其中所述第一溶剂的含量y1与所述第二溶剂的含量y2满足：y1/y2≥0.82，可选为y1/y2≥2.33，更可选为y1/y2≥4，进一步可选为y1/y2≥5.67。
  6. 根据权利要求1至5中任一项所述的电解液，其中所述电解液还包括成膜添加剂，选自链状或环状硫酸酯、链状或环状磺酸酯、链状或环状碳酸酯、多环状硫酸酯或多环状磺酸酯中的一种或多种；
    可选为
    Figure PCTCN2022093000-appb-100008
    Figure PCTCN2022093000-appb-100009
    中的一种或多种；
    更可选为
    Figure PCTCN2022093000-appb-100010
    中的一种或多种。
  7. 根据权利要求6所述的电解液，其中所述成膜添加剂的含量为0.1-10％，可选为0.5-7％，更可选为1-5％，基于所述第一溶剂和所述第二溶剂的总重量计。
  8. 根据权利要求6或7所述的电解液，其中所述成膜添加剂包括0.5-1.0％的
    Figure PCTCN2022093000-appb-100011
    0.5-2.5％的
    Figure PCTCN2022093000-appb-100012
    0.5-2％的
    Figure PCTCN2022093000-appb-100013
    或0.5-2％的
    Figure PCTCN2022093000-appb-100014
    基于所述第一溶剂和所述第二溶剂的总重量计。
  9. 根据权利要求1至8中任一项所述的电解液，其中所述锂盐包括六氟磷酸锂和双氟磺酰亚胺锂中的一种或多种。
  10. 根据权利要求1至9中任一项所述的电解液，其中所述锂盐的浓度为0.7-2.5mol/L，可选为1-1.5mol/L。
  11. 根据权利要求1至10中任一项所述的电解液，其中所述电解液的酸度≤50ppm，使用的各溶剂纯度≥99.8％。
  12. 一种二次电池，其包括根据权利要求1至11中任一项所述的电解液。
  13. 根据权利要求12所述的二次电池，其中
    所述二次电池的正极活性物质的Mn元素百分含量≥25％，基于所述正极活性物质的总重量计；
    可选为LiM pMn 2-pO 4、LiN qMn 1-qPO 4或Li 1+tMn 1-wL wO 2+t中的一种或多种，其中0≤p≤1，0≤q≤0.5，0≤t≤1，0≤w≤0.5，M、N、L各自独立地表示Ni、Co、Fe、Cr、V、Ti、Zr、La、Ce、Rb、P、W、Nb、Mo、Sb、B、Al、Si中的一种或多种；
    更可选为LiM pMn 2-pO 4或Li 1+tMn 1-wL wO 2+t中的一种或多种；
    更可选为LiNi 0.5Mn 1.5O 4、LiNi 0.5Co 0.2Mn 0.3O 2、Li 2MnO 3、LiMnPO 4 中的一种或多种。
  14. 根据权利要求12或13所述的二次电池，其中所述正极活性物质的颗粒为单晶或类单晶。
  15. 根据权利要求12至14中任一项所述的二次电池，其中所述正极活性物质的粒径为1-20μm，可选为3-15μm。
  16. 根据权利要求12至15中任一项所述的二次电池，其中所述正极活性物质的比表面积不大于1.5m 2/g，可选为0.1m 2/g-1m 2/g。
  17. 一种电池模块，包括权利要求12至16中任一项所述的二次电池。
  18. 一种电池包，包括权利要求17所述的电池模块。
  19. 一种用电装置，包括权利要求12至16中任一项所述的二次电池、权利要求17所述的电池模块或权利要求18所述的电池包中的至少一种。
PCT/CN2022/093000 2022-05-16 2022-05-16 电解液及包含其的二次电池、电池模块、电池包和用电装置 WO2023220857A1 (zh)

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CN117895084A (zh) * 2024-03-18 2024-04-16 宁德时代新能源科技股份有限公司 锂离子电池及用电装置

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WO2015025915A1 (ja) * 2013-08-23 2015-02-26 日本電気株式会社 二次電池
JP2016098189A (ja) * 2014-11-19 2016-05-30 セントラル硝子株式会社 含フッ素エーテル化合物、非水電解液、及び非水電解液電池
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JP2016098189A (ja) * 2014-11-19 2016-05-30 セントラル硝子株式会社 含フッ素エーテル化合物、非水電解液、及び非水電解液電池

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