WO2023240404A1 - 电解质、二次电池、电池模块、电池包及用电装置 - Google Patents

电解质、二次电池、电池模块、电池包及用电装置 Download PDF

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WO2023240404A1
WO2023240404A1 PCT/CN2022/098423 CN2022098423W WO2023240404A1 WO 2023240404 A1 WO2023240404 A1 WO 2023240404A1 CN 2022098423 W CN2022098423 W CN 2022098423W WO 2023240404 A1 WO2023240404 A1 WO 2023240404A1
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electrolyte
additive
negative electrode
secondary battery
battery
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PCT/CN2022/098423
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English (en)
French (fr)
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邹海林
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/CN2022/098423 priority Critical patent/WO2023240404A1/zh
Publication of WO2023240404A1 publication Critical patent/WO2023240404A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives

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  • the present application relates to the technical field of secondary batteries, and in particular, to an electrolyte, a secondary battery, a battery module, a battery pack and an electrical device.
  • secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power 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 energy density, cycle performance and safety performance.
  • the negative electrode interface film of sodium-ion secondary batteries is unstable and prone to side reactions with the electrolyte.
  • Additives in the electrolyte easily form by-products in the negative electrode that increase the interface resistance, causing the problem of sodium precipitation and seriously reducing the cycle performance of the battery. and safety performance. Therefore, there is an urgent need to improve this situation.
  • This application was made in view of the above-mentioned problems, and its purpose is to provide electrolytes, secondary batteries, battery modules, battery packs and electrical devices.
  • This application uses the above-mentioned electrolytes to obtain a stable negative electrode interface film, making it difficult for the negative electrode sheet to interact with Side reactions occur in the electrolyte, reducing the interface resistance of the negative electrode, reducing the precipitation of sodium, and improving the cycle performance and safety performance of the secondary battery.
  • the first aspect of the present application provides an electrolyte, including a first additive, the first additive is a sulfur-containing compound with a boiling point not exceeding 70°C under a standard atmospheric pressure, and the mass of the first additive in the electrolyte The content is 0.05%-6%; optionally, the mass content of the first additive in the electrolyte is 0.05%-5%, more optionally 0.1%-2%.
  • the electrolyte further contains a second additive, the second additive is one or more selected from fluorocarbonate and fluorocarboxylate, and the mass content of the second additive in the electrolyte is 0.005%- 12%, optional 0.01%-10%;
  • the mass content of the second additive in the electrolyte is 0.1%-5%.
  • the mass content of the second additive in the electrolyte is 0.01%-10%, which can form a negative electrode interface film with moderate thickness and good toughness and strength, further inhibiting side reactions between the negative electrode and the electrolyte, further improving the stability of the interface film, and further reducing the negative electrode
  • the interface impedance reduces the precipitation of sodium to improve the cycle performance and safety performance of secondary batteries.
  • the mass content of the first additive in the electrolyte is W1%
  • the mass content of the second additive in the electrolyte is W2%
  • the product of W1 and W2 is any value in the range of 0.01-24, which can be Select any value from the range 0.05-16, and further select any value from the range 0.05-10.
  • the first additive and the second additive respectively form a strong inorganic-rich film and a tough organic-rich film
  • they can Ensure the toughness and strength of the negative electrode interface film, improve the stability of the negative electrode interface film, thereby improving the life of the battery core.
  • it can reduce the thickness of the interface film, reduce the interface impedance of the negative electrode, and improve the power performance of the battery core.
  • the electrolyte further includes a solvent and/or an electrolyte salt; optionally, the solvent is a carbonate solvent.
  • a second aspect of the application also provides a secondary battery, including a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte of the first aspect of the application.
  • 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; the mass content of sulfur element in the negative electrode film layer is 0.01%-1.14%, optionally 0.01%- 1%, more optional is 0.05%-0.5%.
  • the stability of the negative electrode interface film is further improved, the negative electrode interface resistance is further reduced, the transmission rate of sodium ions in the electrode piece is increased, and the precipitation of sodium is further reduced, thereby further improving the cycle performance and safety of the secondary battery. performance.
  • 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 application provides a battery pack, including the battery module of the third aspect of the application.
  • 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, and the battery pack of the fourth aspect of the present application. kind.
  • 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 .
  • 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
  • a 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) can be added to the method in any order.
  • the method may include steps (a), (b) and (c), and may also include step (a). , (c) and (b), and may also include steps (c), (a) and (b), etc.
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • the secondary battery is a sodium-ion secondary battery.
  • the applicant unexpectedly discovered that the first additive in the electrolyte is better than the solvent in reacting on the surface of the negative electrode to form a sulfur-containing inorganic salt product.
  • This product can inhibit side reactions between the electrolyte and the negative electrode. This improves the stability of the negative electrode interface film, reduces the precipitation of sodium, reduces the interface resistance of the negative electrode, and improves the cycle performance and safety performance of the secondary battery.
  • the first additive has low viscosity and fast diffusion speed after being dissolved in the electrolyte, and is easy to quickly form a film on the surface of the negative electrode.
  • the inorganic salt product formed by the first additive on the surface of the negative electrode has a good migration rate of sodium ions, further reducing the resistance of the negative electrode. Interface impedance.
  • the electrolyte further contains a second additive
  • the second additive is one or more selected from fluorocarbonate and fluorocarboxylate, and the mass content of the second additive in the electrolyte is 0.005%- 12%, optionally 0.01%-10%; optionally, the second additive is fluoroethylene carbonate (also known as fluoroethylene carbonate) and/or ethyl 2,2-difluoroacetate; wherein, The structural formula of fluoroethylene carbonate (also called fluoroethylene carbonate) is
  • the mass content of the second additive in the electrolyte is 0.1%-5%.
  • the first additive and the second additive can form an interface film with good toughness and high strength on the negative electrode interface, so that the interface film is not easily ruptured due to the expansion and contraction of the volume of the negative electrode active material, further improving the stability of the negative electrode interface film and reducing the The interface resistance of the negative electrode is reduced, the precipitation of sodium is reduced, and the cycle performance and safety performance of the secondary battery are improved.
  • the reduction potential of the first additive is higher than that of the second additive, which can inhibit the side reaction of the second additive on the negative electrode, thereby improving the cycle performance of the secondary battery.
  • the mass content of the second additive in the electrolyte is 0.01%-10%, which can form a negative electrode interface film with moderate thickness and good toughness and strength, further inhibiting side reactions between the negative electrode and the electrolyte, further improving the stability of the negative electrode interface film, and further reducing the The interface resistance of the negative electrode reduces the precipitation of sodium to improve the cycle performance and safety performance of the secondary battery.
  • the mass content of the first additive in the electrolyte is W1%
  • the mass content of the second additive in the electrolyte is W2%
  • the product of W1 and W2 is any value selected from the range of 0.01-24 , can be selected as any value in the range of 0.05-16, and can be selected as any value in the range of 0.05-10.
  • the first additive and the second additive respectively form a strong inorganic-rich film and a tough organic-rich film
  • they can Ensure the toughness and strength of the negative electrode interface film, improve the stability of the negative electrode interface film, thereby improving the life of the battery core.
  • it can reduce the thickness of the interface film, reduce the interface impedance of the negative electrode, and improve the power performance of the battery core.
  • the electrolyte further includes a solvent and/or an electrolyte salt; optionally, the solvent is a carbonate solvent.
  • the electrolyte salt can be selected from the group consisting of NaPF 6 , NaBF 4 , NaN(SO 2 F) 2 (abbreviated as NaFSI), NaClO 4 , NaAsF 6 , NaB(C 2 O 4 ) 2 (abbreviated as NaBOB), One or more of NaBF 2 (C 2 O 4 ) (abbreviated as NaDFOB), NaN (SO 2 RF ) 2 and NaN (SO 2 F) (SO 2 R F ); where RF represents C b F 2b+1 , b is an integer in the range of 1-10, optionally an integer in the range of 1-3, optionally, R F is -CF 3 , -C 2 F 5 or -CF 2 CF 2 CF 3 ;
  • the electrolyte salt is selected from one of NaPF 6 , NaN(SO 2 F) 2 , NaN(CF 3 SO 2 ) 2 , NaB(C 2 O 4 ) 2 and NaBF 2 (C 2 O 4 ) or variety;
  • the electrolyte salt is selected from one or more of NaPF 6 , NaN(SO 2 F) 2 and NaBF 2 (C 2 O 4 ).
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, 1,3-dioxolane, tetrahydrofuran, ethylene glycol dimethyl ether and acetonitrile.
  • the electrolyte optionally includes other additives besides the first additive and the second additive; for example, vinyl sulfate, maleic anhydride, propylene sultone, succinonitrile, adiponitrile, carbonate Vinyl ester, succinic anhydride, 1,3-propane sultone, triethanolamine borate, triphenylborate, triallyl phosphate, tris(trimethylsilane)phosphate, etc.
  • the electrolyte is an electrolyte for sodium ion secondary batteries.
  • 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.
  • 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 mass content of sulfur in the negative electrode film layer is 0.01%-1.14%, optionally 0.01%-1%; more optionally, the mass content of sulfur in the negative electrode film layer is 0.05% -0.5%.
  • the above negative electrode film layer is the negative electrode film layer on the negative electrode sheet after the secondary battery is formed.
  • the stability of the negative electrode interface film is further improved, the negative electrode interface resistance is further reduced, the transmission rate of sodium ions in the electrode piece is increased, and the precipitation of sodium is further reduced, thereby further improving the cycle performance and safety of the secondary battery. performance.
  • 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 electrode film layer optionally further includes a binder.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), At least one of polymethacrylic 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 positive electrode sheet usually 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 a positive electrode active material.
  • 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 cathode active material may be a cathode active material known in the art for batteries.
  • the cathode active material may include at least one of the following materials: Prussian blue analogues, sodium-containing phosphates, sodium-containing transition metal oxides and their respective modified compounds.
  • Prussian blue analogues sodium-containing phosphates
  • sodium-containing transition metal oxides sodium-containing transition metal oxides
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • 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 tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.
  • 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 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.
  • 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 impregnates 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.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • 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.
  • secondary batteries, battery modules or battery packs can be selected according to its usage requirements.
  • Preparation of the positive electrode sheet Mix the positive active material sodium vanadium phosphate Na 3 V 2 (PO 4 ) 3 , the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) in a weight ratio of 90:5:5.
  • the N-methylpyrrolidone solvent system is thoroughly stirred and evenly mixed to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and then dried, cold-pressed, and cut to obtain positive electrode pieces.
  • Preparation of the negative electrode sheet Combine the negative active material hard carbon, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener carbon methylcellulose sodium (CMC) in a weight ratio of 90:4:4 : 2 In the deionized water solvent system, stir thoroughly and mix evenly to prepare a negative electrode slurry; coat the negative electrode slurry on the negative electrode current collector aluminum foil, and then dry, cold press, and cut to obtain the negative electrode sheet.
  • SBR binder styrene-butadiene rubber
  • CMC thickener carbon methylcellulose sodium
  • Preparation of secondary batteries stack and wind the above-mentioned positive electrode sheets, isolation films, and negative electrode sheets in order to obtain an electrode assembly; put the electrode assembly into the outer packaging, add the electrolyte prepared above, and package and statically After processes such as placement, formation, and aging, a secondary battery is obtained.
  • Examples 2-27 and Comparative Examples 1-11 are similar to the secondary battery preparation methods of Example 1, but the parameters are adjusted. The different parameters are detailed in Table 1.
  • Capacity retention rate (%) of the secondary battery 100% ⁇ discharge capacity at the 800th cycle/discharge capacity at the 1st cycle.
  • Example 1 Comparing the results of Example 1 with Examples 20-23 and 25, and comparing the results of Example 5 with Examples 18 and 26, it can be concluded that the mass content of the second additive of the present application in the electrolyte is 0.01%-10 %, due to better negative electrode film formation quality, the cycle capacity retention rate of the secondary battery is further improved.
  • the electrolyte of the present application can obtain a stable negative electrode interface film, making the negative electrode piece less likely to have side reactions with the electrolyte, reducing the precipitation of sodium, reducing the DC internal resistance of the secondary battery, and improving the cycle performance and safety performance of the secondary battery.

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Abstract

本申请提供了一种电解质、二次电池、电池模块、电池包和用电装置。本申请的电解质包含第一添加剂，第一添加剂为在一个标准大气压下的沸点不超过70℃的含硫化合物，第一添加剂在电解质中的质量含量为0.05％-6％。本申请电解质能在负极极片表面形成稳定的界面膜，抑制电解质与负极极片发生副反应，降低负极的界面阻抗，减少钠的析出，提高二次电池的循环性能和安全性能。

Description

电解质、二次电池、电池模块、电池包及用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种电解质、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，因此对其能量密度、循环性能和安全性能等也提出了更高的要求。
目前，钠离子二次电池的负极界面膜不稳定，容易与电解质发生副反应，电解质中的添加剂在负极容易形成导致界面阻抗增加的副产物，造成析钠的问题，严重降低了电池的循环性能和安全性能。因此亟需改善这一状况。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供电解质、二次电池、电池模块、电池包和用电装置，本申请采用上述电解质能获得稳定的负极界面膜，使负极极片不易与电解质发生副反应，降低负极的界面阻抗，减少钠的析出，提高二次电池的循环性能和安全性能。
为了达到上述目的，本申请的第一方面提供了一种电解质，包含第一添加剂，第一添加剂为在一个标准大气压下的沸点不超过70℃的含硫化合物，第一添加剂在电解质中的质量含量为0.05％-6％；可选地，第一添加剂在电解质中的质量含量为0.05％-5％，更可选为0.1％-2％。
由此，本申请电解质能在负极极片表面形成稳定的负极界面膜，抑制电解质与负极发生副反应，从而降低负极的界面阻抗，减少钠的 析出，提高二次电池的循环性能和安全性能。本申请电解质的粘度低，第一添加剂在电解质中的扩散速度快，能在负极表面迅速成膜，成膜后的负极表面的钠离子迁移速率良好，从而进一步降低了负极的界面阻抗。
在任意实施方式中，所第一添加剂为选自硫的氟化物、硫的氧化物、硫碳化合物、硫醚、硫酰基化合物(可选为含氟的硫酰基化合物)和亚硫酰基化合物(可选为含氟的亚硫酰基化合物)中的一种或多种；
可选地，第一添加剂为选自SF 6、SF 4、SO 2F 2、SO 2、SO 3、CS 2、二甲硫醚、甲基乙基硫醚、S 2F 2、SF 2、SOF 2和SOF 4中的一种或多种。
所选的第一添加剂溶于溶剂后的粘度低、扩散速度快，能优于溶剂在负极表面迅速反应形成含硫的无机盐，该无机盐具有良好的钠离子迁移速率、不易与电解质发生副反应，提高了负极界面膜的稳定性，降低了负极的界面阻抗，减少了钠的析出，提升了二次电池的循环性能和安全性能。
在任意实施方式中，电解质还包含第二添加剂，第二添加剂为选自氟代碳酸酯和氟代羧酸酯中的一种或多种，第二添加剂在电解质中的质量含量为0.005％-12％，可选为0.01％-10％；
可选地，第二添加剂为氟代碳酸亚乙酯和/或2,2-二氟乙酸乙酯；
可选地，第二添加剂在电解质中的质量含量为0.1％-5％。
第一添加剂和第二添加剂能在负极上形成韧性好、强度高的界面膜，从而使界面膜不易因负极活性材料体积的膨胀收缩而发生破裂，进一步提高了界面膜的稳定性，降低了负极的界面阻抗，减少了钠的析出，提升了二次电池的循环性能和安全性能。同时，第一添加剂的还原电位高于第二添加剂，能抑制第二添加剂在负极上的副反应，从而改善二次电池的循环性能。
第二添加剂在电解质中的质量含量为0.01％-10％，能够形成厚度适中且韧性和强度良好的负极界面膜，进一步抑制负极与电解质发生副反应，进一步提高界面膜的稳定性，进一步降低负极的界面阻抗，减少钠的析出，以改善二次电池的循环性能和安全性能。
在任意实施方式中，第一添加剂在电解质中的质量含量为W1％，第二添加剂在电解质中的质量含量为W2％，并且，W1与W2的乘积 为0.01-24范围内的任意数值，可选为选自0.05-16范围内的任意数值，更可选为选自0.05-10范围内的任意数值。
由于第一添加剂和第二添加剂分别形成强度高的富含无机物的膜和韧性强的富含有机物的膜，第一添加剂的质量含量和第二添加剂的质量含量满足上述关系时，一方面能保证负极界面膜的韧性和强度，提高负极界面膜的稳定性，从而改善电芯寿命，另一方面能降低界面膜的厚度，降低负极的界面阻抗，改善电芯的功率性能。
在任意实施方式中，电解质还包含溶剂和/或电解质盐；可选地，溶剂为碳酸酯类溶剂。
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、隔膜以及本申请第一方面的电解质。
由此，本申请二次电池通过上述电解质能形成稳定的负极界面膜，使负极不易与电解质发生副反应，从而降低负极的界面阻抗，减少钠的析出，提高二次电池的循环性能和安全性能。
在任意实施方式中，负极极片包括负极集流体和设置在负极集流体至少一个表面的负极膜层；负极膜层中的硫元素的质量含量为0.01％-1.14％，可选为0.01％-1％，更可选为0.05％-0.5％。
由此，进一步提高了负极界面膜的稳定性，进一步降低了负极界面阻抗、提高了极片中钠离子的传输速率，进一步减少了钠的析出，从而进一步提高了二次电池的循环性能和安全性能。
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。
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和本申请的第四方面的电池包中的至少一种。
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用于钠离子二次电池的电解质、钠离子二次电池、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，方法包括步骤(a)和(b)，表示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，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，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，“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)。
[二次电池]
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解质。在电池充放电过程中，活性离子(例如钠离子)在正极极片和负极极片之间往返嵌入和脱出。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，同时可以使活性离子通过。电解质在正极极片和负极极片之间，主要起到传导活性离子的作用。
在一些实施方式中，二次电池为钠离子二次电池。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请电解质可以是液态的或凝胶态。
本申请的一个实施方式提供一种电解质，包含第一添加剂，第一添加剂为在一个标准大气压下的沸点不超过70℃的含硫化合物，第一添加剂在电解质中的质量含量为0.05％-6％；可选地，第一添加剂在电解质中的质量含量为0.05％-5％，更可选为0.1％-2％，例如1％、2％。
由此，虽然机理尚不明确，但本申请人意外地发现：第一添加剂在电解质中优于溶剂在负极表面反应形成含硫的无机盐产物，这种产物能够抑制电解质与负极发生副反应，从而提高了负极界面膜的稳定性，减少了钠的析出，降低了负极的界面阻抗，提升了二次电池的循环性能和安全性能。并且，第一添加剂在电解质中溶解后的粘度低、扩散速度快，容易在负极表面迅速成膜，第一添加剂在负极表面形成的无机盐产物具有良好的钠离子迁移速率，进一步降低了负极的界面阻抗。
在一些实施方式中，所第一添加剂为选自硫的氟化物、硫的氧化物、硫碳化合物、硫醚、硫酰基化合物(可选为含氟的硫酰基化合物)和亚硫酰基化合物(可选为含氟的亚硫酰基化合物)中的一种或多种；
可选地，第一添加剂为选自SF 6、SF 4、SO 2F 2、SO 2、SO 3、CS 2、二甲硫醚、甲基乙基硫醚、S 2F 2、SF 2、SOF 2和SOF 4中的一种或多种。
所选的第一添加剂溶于溶剂后的粘度低、扩散速度快，能优于溶剂在负极表面迅速反应形成含硫的无机盐，该无机盐具有良好的钠离子迁移速率、不易与电解质发生副反应，提高了负极界面膜的稳定性，降低了负极的界面阻抗，减少了钠的析出，提升了二次电池的循环性能和安全性能。
在一些实施方式中，电解质还包含第二添加剂，第二添加剂为选自氟代碳酸酯和氟代羧酸酯中的一种或多种，第二添加剂在电解质中的质量含量为0.005％-12％，可选为0.01％-10％；可选地，第二添加剂为氟代碳酸亚乙酯(也称氟代碳酸乙烯酯)和/或2,2-二氟乙酸乙酯；其中，氟代碳酸亚乙酯(也称氟代碳酸乙烯酯)的结构式为
Figure PCTCN2022098423-appb-000001
可选地，第二添加剂在电解质中的质量含量为0.1％-5％。
第一添加剂和第二添加剂能在负极界面上形成韧性好、强度高的界面膜，从而使界面膜不易因负极活性材料体积的膨胀收缩而发生破裂，进一步提高了负极界面膜的稳定性，降低了负极的界面阻抗，减少了钠的析出，提升了二次电池的循环性能和安全性能。同时，第一添加剂的还原电位高于第二添加剂，能抑制第二添加剂在负极上的副反应，从而改善二次电池的循环性能。
第二添加剂在电解质中的质量含量为0.01％-10％，能够形成厚度适中且韧性和强度良好的负极界面膜，进一步抑制负极与电解质发生副反应，进一步提高负极界面膜的稳定性，进一步降低负极的界面阻抗，减少钠的析出，以改善二次电池的循环性能和安全性能。
在一些实施方式中，第一添加剂在电解质中的质量含量为W1％，第二添加剂在电解质中的质量含量为W2％，并且，W1与W2的乘积为选自0.01-24范围内的任意数值，可选为选自0.05-16范围内的任意数值，更可选为选自0.05-10范围内的任意数值。
由于第一添加剂和第二添加剂分别形成强度高的富含无机物的膜和韧性强的富含有机物的膜，第一添加剂的质量含量和第二添加剂的质量含量满足上述关系时，一方面能保证负极界面膜的韧性和强度，提高负极界面膜的稳定性，从而改善电芯寿命，另一方面能降低界面膜的厚度，降低负极的界面阻抗，改善电芯的功率性能。
在一些实施方式中，电解质还包含溶剂和/或电解质盐；可选地，溶剂为碳酸酯类溶剂。
在一些实施方式中，电解质盐可选自NaPF 6、NaBF 4、NaN(SO 2F) 2(简写为NaFSI)、NaClO 4、NaAsF 6、NaB(C 2O 4) 2(简写为NaBOB)、NaBF 2(C 2O 4)(简写为NaDFOB)、NaN(SO 2R F) 2和NaN(SO 2F)(SO 2R F)中的一种或多种；其中，R F代表C bF 2b+1，b为1-10范围内的整数，可选为1-3范围内的整数，可选地，R F为-CF 3、-C 2F 5或-CF 2CF 2CF 3；
可选地，电解质盐选自NaPF 6、NaN(SO 2F) 2、NaN(CF 3SO 2) 2、NaB(C 2O 4) 2和NaBF 2(C 2O 4)中的一种或多种；
更可选地，电解质盐选自NaPF 6、NaN(SO 2F) 2和NaBF 2(C 2O 4)中的一种或多种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、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、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜、二乙砜、1,3-二氧环戊烷、四氢呋喃，乙二醇二甲醚和乙腈中的至少一种。
在一些实施方式中，电解质还可选地包括除第一添加剂和第二添加剂以外的其他添加剂；例如硫酸乙烯酯、马来酸酐、丙烯磺酸内酯、丁二腈、己二腈、碳酸亚乙烯酯、丁二酸酐、1,3-丙烷磺内酯、硼酸三乙醇胺酯、三苯基硼酸酯、磷酸三烯丙酯、三(三甲基硅烷)磷酸酯等。
在一些实施方式中，电解质为用于钠离子二次电池的电解质。
[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，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，负极膜层中的硫元素的质量含量为0.01％-1.14％，可选为0.01％-1％；更可选地，负极膜层中的硫元素的质量含量为0.05％-0.5％。以上的负极膜层为二次电池化成后的负极极片上的负极膜层。
由此，进一步提高了负极界面膜的稳定性，进一步降低了负极界面阻抗，提高了极片中钠离子的传输速率，进一步减少了钠的析出，从而进一步提高了二次电池的循环性能和安全性能。
在一些实施方式中，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。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。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。作为示例，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。作为示例，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。
[正极极片]
正极极片通常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，正极膜层包括正极活性材料。
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，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，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：普鲁士蓝类似物、含钠磷酸盐、含钠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活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，普鲁士蓝类似物为Na xP[R(CN) 6] δ·zH 2O，其中，P和R各自独立地选自过渡金属元素中的至少一种，0<x≤2，0<δ≤1且0≤z≤10；含钠磷酸盐为Na bMe c(PO 4) dO 2X，Me为选自Ti、Cr、Mn、Fe、Co、Ni、V、Cu及Zn中的一种或多种，X为选自F、Cl及Br中的一种或多种，0＜b≤4，0＜c≤2，1≤d≤3；含钠过渡金属氧化物为Na aM bFe cO 2，M为过渡金属离子，0.67<a<1.1,0.5<b<1,0<c<0.5。
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，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，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。
[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，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能够盖设于开口，以封闭容纳腔。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封装于容纳腔内。电解质浸润于电极组件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。
另外，本申请还提供一种用电装置，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。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。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。
[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：将正极活性材料磷酸钒钠Na 3V 2(PO 4) 3、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比90：5：5在N-甲基吡咯烷酮溶剂体系中充分搅拌混合均匀后制备成正极浆料；将正极浆料均匀涂覆在正极集流体铝箔上，之后经过烘干、冷压、分切，得到正极极片。
2、负极极片的制备：将负极活性材料硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂碳甲基纤维素钠(CMC)按照重量比90：4：4：2在去离子水溶剂体系中，充分搅拌混合均匀后制备成负极浆料；将负极浆料涂覆在负极集流体铝箔上，之后经过烘干、冷压、分切，得到负极极片。
3、隔离膜：采用PE多孔聚合薄膜。
4、电解质的制备：将碳酸乙烯酯(EC)和碳酸甲乙酯(EMC)按照30:70的质量比混合，将NaPF 6钠盐溶解在上述溶液中，使电解质中NaPF 6钠盐的摩尔浓度为1M，然后将SO 2气体通入电解液中搅拌溶解，使第一添加剂SO 2在电解液中的质量含量为1％。
5、二次电池的制备：将上述正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件放入外包装中，加入上述制备的电解质，经封装、静置、化成、老化等工序后，得到二次电池。
实施例2-27和对比例1-11
实施例2-27和对比例1-11与实施例1的二次电池制备方法相似，但是调整了参数，不同的参数详见表1。
Figure PCTCN2022098423-appb-000002
Figure PCTCN2022098423-appb-000003
Figure PCTCN2022098423-appb-000004
Figure PCTCN2022098423-appb-000005
Figure PCTCN2022098423-appb-000006
电池测试
(1)二次电池的负极膜层中的硫元素质量含量的测定：
在25℃下，将实施例和对比例制得的新鲜钠离子二次电池搁置5分钟后，以1C倍率恒流充电至4.2V，再恒压充电至电流小于或等于0.05C，之后搁置5分钟，再以1C倍率恒流放电至2.0V获得满放的电芯。将满放的电芯拆解，取出负极极片，用刀片刮下负极极片上的负极膜层，按照EPA 6010D-2014测试标准利用电感耦合等离子体原子发射光谱仪测试刮下材料中的硫元素质量含量，即为负极膜层中的硫元素质量含量。
(2)二次电池的常温循环性能测试：
在25℃下，将钠离子二次电池搁置5分钟后，以1C倍率恒流充电至4.2V，再恒压充电至电流小于或等于0.05C，之后搁置5分钟，再以1C倍率恒流放电至2.0V，此为一个充放电循环，此时的放电容量记为钠离子二次电池第1次循环的放电容量。将钠离子二次电池按照上述方法进行800次循环充放电测试，记录每次循环的放电容量，按照下述公式计算二次电池的容量保持率；
二次电池的容量保持率(％)＝100％×第800次循环的放电容量/第1次循环的放电容量。
(3)二次电池的直流阻抗测试：
在25℃下，将钠离子二次电池搁置5分钟，以1C倍率恒流充电至4.2V，再恒压充电至电流小于或等于0.05C，此时电池的荷电状态(SOC)为100％，之后搁置5分钟，再以1C倍率恒流放电，将钠离子二次电池的荷电状态(SOC)调整至50％。将50％SOC的钠离子二次电池继续搁置10分钟，记录搁置最后1秒的电压U1，然后以4C倍率恒流放电30秒钟，记录恒流放电的电流I及恒流放电最后1秒的电压U2，按照下述公式计算二次电池的直流阻抗；
二次电池的直流阻抗＝(U2-U1)/I。
上述测试结果见上面的表1。
由表1可知：
将实施例1-6与对比例1-3的结果比较，将实施例9与对比例10-11的结果比较，可以得出，本申请第一添加剂在电解质中的质量含量在0.05％-5％时，二次电池的直流内阻更低，本申请第一添加剂在电解质中的质量含量在1％-6％时，二次电池的循环容量保持率更高。第一添加剂在电解质中的质量含量小于0.05％时(对比例2、11)，形成含硫无机盐产物的量较少，不足以抑制电解质发生副反应，导致二次电池的循环性能差、直流内阻稍高。而第一添加剂在电解质中的质量含量大于6％时(对比例3、10)，过量的第一添加剂造成二次电池的内阻明显增加，循环性能稍差。
将实施例1、7-17与对比例4-5的结果比较，及将实施例20与对比例9的结果比较，可以得出，本申请采用沸点不超过70℃的含硫化合物作为第一添加剂加入电解质中，所制二次电池的直流内阻更低、循环容量保持率更高。
将实施例20、21、23对应地与对比例6-8的结果比较，可以得出，与仅将第二添加剂加入电解质相比，本申请同时将沸点不超过70℃的含硫化合物作为第一添加剂加入电解质中可以明显降低二次电池的直流内阻，明显提高二次电池的循环容量保持率。
将实施例1与实施例20-23、25的结果比较、实施例5与实施例18、实施例26的结果比较可以得出，本申请第二添加剂在电解质中的质量含量为0.01％-10％时，由于负极成膜质量更好，二次电池的循环容量保持率进一步提高。
将实施例18-23、25与实施例24、26、27比较可以得出，本申请中，当W1与W2的乘积为0.05-10的任意数值时，所制二次电池的负极界面膜稳定，直流内阻也在合适的水平，循环容量保持率进一步提高。
将实施例1-5与实施例6、对比例2-3相比较，将实施例9与对比例10-11相比较，可以得出，本申请负极膜层中的硫元素的质量含量为0.01％-1％时，所制二次电池具有稳定的负极界面膜，并且直流内阻也在合适的水平，循环容量保持率进一步提高。
综上，本申请电解质能获得稳定的负极界面膜，使负极极片不易与电解质发生副反应，减少钠的析出，降低二次电池的直流内阻，提高二次电池的循环性能和安全性能。
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 (13)

  1. 一种电解质，包含第一添加剂，所述第一添加剂为在一个标准大气压下的沸点不超过70℃的含硫化合物，所述第一添加剂在所述电解质中的质量含量为0.05％-6％。
  2. 根据权利要求1所述的电解质，其中，所述第一添加剂在所述电解质中的质量含量为0.05％-5％，可选为0.1％-2％。
  3. 根据权利要求1所述的电解质，其中，所述第一添加剂为选自硫的氟化物、硫的氧化物、硫碳化合物、硫醚、硫酰基化合物和亚硫酰基化合物中的一种或多种；
    可选地，所述第一添加剂为选自SF 6、SF 4、SO 2F 2、SO 2、SO 3、CS 2、二甲硫醚、甲基乙基硫醚、S 2F 2、SF 2、SOF 2和SOF 4中的一种或多种。
  4. 根据权利要求1-3中任一项所述的电解质，其还包含第二添加剂，所述第二添加剂为选自氟代碳酸酯和氟代羧酸酯中的一种或多种，所述第二添加剂在所述电解质中的质量含量为0.005％-12％，可选为0.01％-10％；
    可选地，所述第二添加剂为氟代碳酸亚乙酯和/或2,2-二氟乙酸乙酯。
  5. 根据权利要求4所述的电解质，其中，所述第二添加剂在所述电解质中的质量含量为0.1％-5％。
  6. 根据权利要求4或5所述的电解质，其中，所述第一添加剂在所述电解质中的质量含量为W1％，所述第二添加剂在所述电解质中的质量含量为W2％，并且，W1与W2的乘积为选自0.01-24范围内的任意数值，可选为选自0.05-16范围内的任意数值，更可选为选 自0.05-10范围内的任意数值。
  7. 根据权利要求1-6中任一项所述的电解质，其还包含溶剂和/或电解质盐；
    可选地，所述溶剂为碳酸酯类溶剂。
  8. 一种二次电池，包括正极极片、负极极片、隔膜以及权利要求1-7中任一项所述的电解质。
  9. 根据权利要求8所述的二次电池，其中，所述负极极片包括负极集流体和设置在所述负极集流体至少一个表面的负极膜层；所述负极膜层中的硫元素的质量含量为0.01％-1.14％，可选为0.01％-1％。
  10. 根据权利要求9所述的二次电池，其中，所述负极膜层中的硫元素的质量含量为0.05％-0.5％。
  11. 一种电池模块，包括权利要求8-10中任一项所述的二次电池。
  12. 一种电池包，包括权利要求11所述的电池模块。
  13. 一种用电装置，包括选自权利要求8-10中任一项所述的二次电池、权利要求11所述的电池模块和权利要求12所述的电池包中的至少一种。
PCT/CN2022/098423 2022-06-13 2022-06-13 电解质、二次电池、电池模块、电池包及用电装置 WO2023240404A1 (zh)

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Publication number Priority date Publication date Assignee Title
JP2008311211A (ja) * 2007-05-16 2008-12-25 Sanyo Electric Co Ltd 非水電解質二次電池
CN103078141A (zh) * 2013-01-25 2013-05-01 宁德新能源科技有限公司 锂离子二次电池及其电解液
CN111864261A (zh) * 2019-04-26 2020-10-30 宁德时代新能源科技股份有限公司 电解液及锂离子电池
CN112310473A (zh) * 2019-07-30 2021-02-02 东莞市杉杉电池材料有限公司 一种兼顾高低温型锂离子电池电解液及锂离子电池
CN112331914A (zh) * 2019-08-05 2021-02-05 杉杉新材料（衢州）有限公司 一种不含碳酸乙烯酯溶剂的锂离子电池非水电解液及电池

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Publication number Priority date Publication date Assignee Title
JP2008311211A (ja) * 2007-05-16 2008-12-25 Sanyo Electric Co Ltd 非水電解質二次電池
CN103078141A (zh) * 2013-01-25 2013-05-01 宁德新能源科技有限公司 锂离子二次电池及其电解液
CN111864261A (zh) * 2019-04-26 2020-10-30 宁德时代新能源科技股份有限公司 电解液及锂离子电池
CN112310473A (zh) * 2019-07-30 2021-02-02 东莞市杉杉电池材料有限公司 一种兼顾高低温型锂离子电池电解液及锂离子电池
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