Electrolytes, secondary batteries, battery modules, battery packs, and power consumption devices

Abstract

The present application provides an electrolyte, a secondary battery, a battery module, a battery pack and a power consumption device. The electrolyte of the present application includes a first additive, the first additive being a sulfur-containing compound with a boiling point not exceeding 70°C under standard atmospheric pressure, and the mass content of the first additive in the electrolyte is 0.05%-6%. The electrolyte of the present application can form a stable interface film on the surface of the negative electrode plate, inhibit the occurrence of side reactions between the electrolyte and the negative electrode plate, reduce the interface impedance of the negative electrode, reduce sodium precipitation, and improve the cycle performance and safety performance of the secondary battery.

Description

[Technical Field]

[0001] This application relates to the field of secondary battery technology, and in particular electrolyte This relates to secondary batteries, battery modules, battery packs, and power consumption devices. [Background technology]

[0002] In recent years, as the range of applications for secondary batteries has expanded, they are widely used in energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in many fields including power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Due to the remarkable development of secondary batteries, higher demands are being placed on their energy density, cycle performance, and safety performance.

[0003] Currently, the negative electrode interface film in sodium-ion secondary batteries is not stable. electrolyte Side reactions are likely to occur. electrolyte The additives in this system tend to form by-products that increase interfacial impedance at the negative electrode, leading to sodium deposition problems and significantly reducing the battery's cycle performance and safety performance. Therefore, this situation needs to be rectified urgently. [Overview of the Initiative]

[0004] This application was made in view of the above-mentioned problems, and its purpose is to electrolyte The purpose of this application is to provide secondary batteries, battery modules, battery packs, and power consumption devices, and this application is to provide the above electrolyte By employing this method, a stable negative electrode interface film is obtained, and the negative electrode plate and electrolyte This reduces the likelihood of side reactions, lowers the interface impedance of the negative electrode, reduces sodium deposition, and improves the cycle performance and safety performance of the secondary battery.

[0005] To achieve the above objective, according to the first aspect of this application, electrolyte Provided, this electrolyteThis includes a first additive, the first additive being a sulfur-containing compound whose boiling point does not exceed 70°C under standard atmospheric pressure, and the first additive electrolyte The mass content is 0.05%-6%, and optionally, the first additive electrolyte The mass content is 0.05%-5%, and optionally 0.1%-2%.

[0006] As a result, electrolyte This forms a stable negative electrode interface film on the surface of the negative electrode plate. electrolyte This invention can suppress the occurrence of side reactions with the negative electrode, thereby reducing the interface impedance of the negative electrode, decreasing sodium deposition, and improving the cycle performance and safety performance of the secondary battery. electrolyte The viscosity is low, and the first additive electrolyte The rapid diffusion rate allows for rapid film formation on the negative electrode surface, and the good migration rate of sodium ions on the negative electrode surface after film formation further reduces the interfacial impedance of the negative electrode.

[0007] In any embodiment, the first additive is one or more selected from sulfur fluorides, sulfur oxides, sulfur-carbon compounds, thioethers, sulfuryl compounds (optionally being fluorine-containing sulfuryl compounds), and sulfinyl compounds (optionally being fluorine-containing sulfinyl compounds). Optionally, the first additive is one or more selected from SF6, SF4, SO2F2, SO2, SO3, CS2, dimethyl sulfide, methyl ethyl sulfide, S2F2, SF2, SOF2, and SOF4.

[0008] The first selected additive has low viscosity after dissolving in the solvent, a fast diffusion rate, and can react faster than the solvent on the negative electrode surface to form a sulfur-containing inorganic salt, which exhibits good sodium ion migration rate. electrolyte This reduces the likelihood of side reactions, improves the stability of the negative electrode interface film, reduces the interface impedance of the negative electrode, decreases sodium deposition, and improves the cycle performance and safety performance of secondary batteries.

[0009] In any embodiment, electrolyte The second additive further comprises a second additive, the second additive being one or more selected from fluorinated carbonate esters and fluorinated carboxylic acid esters. electrolyte The mass content is 0.005%-12%, and optionally 0.01%-10%. Optionally, the second additive is fluorinated ethylene carbonate and / or 2,2-difluoroethyl acetate. Optionally, the second additive electrolyte The mass content is 0.1%-5%.

[0010] The first and second additives can form a tough and high-strength interfacial film on the negative electrode, thereby reducing the likelihood of the interfacial film rupturing due to the expansion and contraction of the negative electrode active material volume, further improving the stability of the interfacial film, reducing the interfacial impedance of the negative electrode, decreasing sodium deposition, and improving the cycle performance and safety performance of the secondary battery. At the same time, the reduction potential of the first additive is higher than that of the second additive, which can suppress the side reactions of the second additive at the negative electrode, thereby improving the cycle performance of the secondary battery.

[0011] The second additive electrolyte The mass content is 0.01%-10%, and it forms a negative electrode interface film with appropriate thickness, good toughness and strength, and the negative electrode and electrolyte This further suppresses the occurrence of side reactions, improves the stability of the interfacial film, further reduces the interfacial impedance of the negative electrode, and reduces sodium deposition, thereby improving the cycle performance and safety performance of the secondary battery.

[0012] In any embodiment, the first additive electrolyte The mass content in is W1%, and the second additive is electrolyteThe mass content in is W2%, and the product of W1 and W2 is any value within the range of 0.01 to 24, optionally any value selected from the range of 0.05 to 16, and further optionally any value selected from the range of 0.05 to 10.

[0013] The first additive and the second additive respectively form a film containing a large amount of high-strength inorganic substance and a film containing a large amount of high-toughness organic substance. Therefore, when the mass content of the first additive and the mass content of the second additive satisfy the above relationship, the toughness and strength of the negative electrode interface film can be ensured, and the stability of the negative electrode interface film can be improved, thereby improving the service life of the battery core, while reducing the thickness of the interface film, reducing the interface impedance of the negative electrode, and improving the power performance of the battery core.

[0014] In any embodiment, electrolyte further comprises a solvent and / or an electrolyte salt, and optionally, the solvent is a carbonate-based solvent.

[0015] According to a second aspect of the present application, a secondary battery is further provided, the secondary battery comprising a positive electrode plate, a negative electrode plate, a separator, and the secondary battery according to the first aspect of the present application electrolyte comprising.

[0016] Accordingly, the secondary battery of the present application can form a stable negative electrode interface film by the above electrolyte , and side reactions with the negative electrode are less likely to occur electrolyte , thereby reducing the interface impedance of the negative electrode, reducing sodium precipitation, and improving the cycle performance and safety performance of the secondary battery.

[0017] In any embodiment, the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the mass content of elemental sulfur in the negative electrode film layer is 0.01%-1.14%, optionally 0.01%-1%, and further optionally 0.05%-0.5%.

[0018] This further improves the stability of the negative electrode interface film, reduces negative electrode interface impedance, increases the transport rate of sodium ions on the electrode plate, and further reduces sodium deposition, thereby further improving the cycle performance and safety performance of the secondary battery.

[0019] According to a third aspect of this application, a battery module including a secondary battery according to a second aspect of this application is provided.

[0020] According to a fourth aspect of this application, a battery pack is provided that includes the battery module of a third aspect of this application.

[0021] According to a fifth aspect of this application, a power consumption device is provided, which includes at least one selected from a secondary battery according to a second aspect of this application, a battery module according to a third aspect of this application, and a battery pack according to a fourth aspect of this application. [Brief explanation of the drawing]

[0022] [Figure 1] This is a schematic diagram of a secondary battery according to one embodiment of the present application. [Figure 2] Figure 1 is an exploded view of a secondary battery according to one embodiment of this application. [Figure 3] This is a schematic diagram of a battery module according to one embodiment of the present application. [Figure 4] This is a schematic diagram of a battery pack according to one embodiment of the present application. [Figure 5] Figure 4 is an exploded view of a battery pack according to one embodiment of this application. [Figure 6] This is a schematic diagram of a power consumption device in which a secondary battery is used as a power source according to one embodiment of this application. [Modes for carrying out the invention]

[0023] The following describes the sodium-ion secondary battery used in this application, with appropriate reference to the drawings. electrolyteEmbodiments specifically disclosing sodium-ion secondary batteries, battery modules, battery packs, and power consumption devices will be described in detail. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters and redundant explanations of structures that are actually the same may be omitted. This is to avoid making the following explanation unnecessarily long and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and do not limit the subject matter described in the claims.

[0024] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the endpoints, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 can also be assumed. Furthermore, if 1 and 2 are listed as the minimum range values ​​and 3, 4, and 5 are listed as the maximum range values, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 can all be assumed. In this application, unless otherwise specified, the numerical range “a-b” represents an abbreviated expression for any combination of real numbers a-b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" have already been listed in this specification, and "0 to 5" is simply an abbreviated representation of combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that this parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0025] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical inventions.

[0026] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts.

[0027] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if it is stated that the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if it is stated that the method may further include step (c), it means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), and so on.

[0028] Unless otherwise specified, the terms “include” and “inclusion” as used in this application may be open or closed. For example, “include” and “inclusion” may further include or include other components not listed, or they may include or include only the listed components.

[0029] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the conditions A is true (or exists) and B is false (or does not exist), the condition A is false (or does not exist) but B is true (or exists), and the condition both A and B are true (or exist) all satisfy "A or B."

[0030] [Secondary battery] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be used continuously after being discharged by activating the active material through a charging method.

[0031] A rechargeable battery generally consists of a positive electrode plate, a negative electrode plate, and a separator. electrolyte This includes the following. During charging and discharging of the battery, active ions (e.g., sodium ions) move back and forth between the positive and negative electrodes, being absorbed and released. The separator is provided between the positive and negative electrodes and mainly serves to prevent short circuits between the positive and negative electrodes, while also allowing active ions to pass through. electrolyte Its primary role is to conduct active ions between the positive and negative electrodes.

[0032] In some embodiments, the secondary battery is a sodium-ion secondary battery.

[0033] [ electrolyte ] electrolyte This plays a role in conducting ions between the positive and negative electrode plates. electrolyte It may be in liquid or gel form.

[0034] One embodiment of this application is, electrolyte Provided, this electrolyte This includes a first additive, the first additive being a sulfur-containing compound whose boiling point does not exceed 70°C under standard atmospheric pressure, and the first additive electrolyte The mass content is 0.05%-6%, and optionally, the first additive electrolyte The mass content is 0.05%-5%, and optionally 0.1%-2%, for example, 1% or 2%.

[0035] Therefore, although the mechanism is not yet well understood, the first additive is more soluble than the solvent. electrolyte In the reaction at the negative electrode surface, a sulfur-containing inorganic salt product is formed, and such a product electrolyte The applicant unexpectedly discovered that the occurrence of side reactions with the negative electrode can be suppressed, thereby improving the stability of the negative electrode interface film, reducing sodium deposition, decreasing the interface impedance of the negative electrode, and improving the cycle performance and safety performance of the secondary battery. Furthermore, the first additive is electrolyteThe first additive has low viscosity after dissolution, a fast diffusion rate, and readily forms a film on the negative electrode surface. The inorganic salt product formed on the negative electrode surface by the first additive has a good sodium ion transfer rate, further reducing the interfacial impedance of the negative electrode.

[0036] In some embodiments, the first additive is one or more selected from sulfur fluorides, sulfur oxides, sulfur-carbon compounds, thioethers, sulfuryl compounds (optionally being fluorine-containing sulfuryl compounds), and sulfinyl compounds (optionally being fluorine-containing sulfinyl compounds). Optionally, the first additive is one or more selected from SF6, SF4, SO2F2, SO2, SO3, CS2, dimethyl sulfide, methyl ethyl sulfide, S2F2, SF2, SOF2, and SOF4.

[0037] The first selected additive has low viscosity after dissolving in the solvent, a fast diffusion rate, and can react faster than the solvent on the negative electrode surface to form a sulfur-containing inorganic salt, which exhibits good sodium ion migration rate. electrolyte This reduces the likelihood of side reactions, improves the stability of the negative electrode interface film, reduces the interface impedance of the negative electrode, decreases sodium deposition, and improves the cycle performance and safety performance of secondary batteries.

[0038] In some embodiments, electrolyte The second additive further comprises a second additive, the second additive being one or more selected from fluorinated carbonate esters and fluorinated carboxylic acid esters. electrolyte The mass content in is 0.005%-12%, optionally 0.01%-10%, and optionally the second additive is fluorinated ethylene carbonate (also called fluoroethylene carbonate) and / or 2,2-difluoroethyl acetate, where the structural formula of fluorinated ethylene carbonate (also called fluoroethylene carbonate) is: The filename is JPEG0007927080000001.jpg19170. Optionally, the second additive electrolyte The mass content is 0.1%-5%.

[0039] The first and second additives can form a tough and high-strength interfacial film on the negative electrode interface, thereby reducing the likelihood of the interfacial film rupturing due to the expansion and contraction of the negative electrode active material volume, further improving the stability of the negative electrode interfacial film, reducing the interfacial impedance of the negative electrode, decreasing sodium deposition, and improving the cycle performance and safety performance of the secondary battery. At the same time, the reduction potential of the first additive is higher than that of the second additive, which can suppress the side reactions of the second additive at the negative electrode, thereby improving the cycle performance of the secondary battery.

[0040] The second additive electrolyte The mass content is 0.01%-10%, and it forms a negative electrode interface film with appropriate thickness, good toughness and strength, and the negative electrode and electrolyte This further suppresses the occurrence of side reactions, improves the stability of the negative electrode interface film, further reduces the interface impedance of the negative electrode, and decreases sodium deposition, thereby improving the cycle performance and safety performance of the secondary battery.

[0041] In some embodiments, the first additive electrolyte The mass content in is W1%, and the second additive is electrolyte The mass content in is W2%, and the product of W1 and W2 is any number selected from the range of 0.01-24, and optionally any number selected from the range of 0.05-16, and optionally any number selected from the range of 0.05-10.

[0042] The first and second additives form a film containing a large amount of high-strength inorganic material and a film containing a large amount of tough organic material, respectively. Therefore, when the mass content of the first and second additives satisfies the above relationship, the toughness and strength of the negative electrode interface film can be ensured, and the stability of the negative electrode interface film can be improved. This improves the service life of the battery core, while also reducing the thickness of the interface film, lowering the interface impedance of the negative electrode, and improving the power performance of the battery core.

[0043] In some embodiments, electrolyte The solution further comprises a solvent and / or an electrolyte salt, and optionally the solvent is a carbonate-based solvent.

[0044] In some embodiments, the electrolyte salt is NaPF6, NaBF4, NaN(SO2F)2 (abbreviated as NaFSI), NaClO4, NaAsF6, NaB(C2O4)2 (abbreviated as NaBOB), NaBF2(C2O4) (abbreviated as NaDFOB), NaN(SO2R F )2 and NaN(SO2F)(SO2R F ) may be one or more selected from the following, where R F C b F 2b+1 This represents a function where b is an integer in the range of 1-10, and arbitrarily selected as an integer in the range of 1-3, and arbitrarily selected as R F These are -CF3, -C2F5, or -CF2CF2CF3. The electrolyte salt is optionally selected from one or more of the following: NaPF6, NaN(SO2F)2, NaN(CF3SO2)2, NaB(C2O4)2, and NaBF2(C2O4). Furthermore, the electrolyte salt is optionally selected from one or more of the following: NaPF6, NaN(SO2F)2, and NaBF2(C2O4).

[0045] In some embodiments, the solvent may be at least one selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluorinated ethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, 1,3-dioxolane, tetrahydrofuran, ethylene glycol dimethyl ether, and acetonitrile.

[0046] In some embodiments, electrolyte The compound further comprises, optionally, other additives other than the first and second additives, such as vinyl sulfate, maleic anhydride, propylene sultone, succinonitrile, adiponitrile, vinylene carbonate, succinic anhydride, 1,3-propane sultone, triethanolamine borate, triphenylborate, triallyl phosphate, tris(trimethylsilane) phosphate, and the like.

[0047] In some embodiments, electrolyte This is used in sodium-ion secondary batteries. electrolyte That is the case.

[0048] [negative electrode plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer placed on at least one surface of the negative electrode current collector, the negative electrode film layer containing a negative electrode active material.

[0049] For example, the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0050] In some embodiments, the mass content of sulfur in the negative electrode film layer is 0.01%-1.14%, optionally 0.01%-1%, and optionally 0.05%-0.5%. The negative electrode film layer described above is the negative electrode film layer on the negative electrode plate after chemical formation of a secondary battery.

[0051] This further improves the stability of the negative electrode interface film, reduces negative electrode interface impedance, increases the transport rate of sodium ions on the electrode plate, and further reduces sodium deposition, thereby further improving the cycle performance and safety performance of the secondary battery.

[0052] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, copper foil may be used as the metal foil sheet. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0053] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries that is well known in the art. For example, the negative electrode active material may include at least one of materials such as artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material may be selected from at least one of elemental tin, tin oxide, and tin alloy. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used individually or in combination of two or more.

[0054] In some embodiments, the negative electrode film layer optionally further comprises a binder. For example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0055] In some embodiments, the negative electrode film layer optionally further comprises a conductive agent. For example, 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.

[0056] In some embodiments, the negative electrode film layer optionally further comprises other auxiliary agents, such as thickeners (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0057] In some embodiments, the negative electrode plate may be manufactured by the following method: The above components for manufacturing the negative electrode plate, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry; the negative electrode slurry is applied to a negative electrode current collector; and the negative electrode plate is obtained through processes such as drying and cold pressing.

[0058] [Positive plate] A positive electrode plate generally includes a positive electrode current collector and a positive electrode film layer placed on at least one surface of the positive electrode current collector, the positive electrode film layer containing a positive electrode active material.

[0059] For example, a positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is placed on one or both of the two opposing surfaces of the positive electrode current collector.

[0060] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0061] In some embodiments, the positive electrode active material may be a positive electrode active material for batteries well known in the art. By way of example, the positive electrode active material may comprise at least one material selected from the group consisting of Prussian blue analogs, sodium-containing phosphates, sodium-containing transition metal oxides, and respective modified compounds thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. Only one of these positive electrode active materials may be used alone, or two or more of them may be used in combination. Herein, the Prussian blue analog is Na x P[R(CN)6] δ ·zH2O, wherein P and R are each independently at least one selected from transition metal elements, 0<x≦2, 0<δ≦1 and 0≦z≦10, and the sodium-containing phosphate is Na b Me c (PO4) d O2X, wherein Me is one or more selected from Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X is one or more selected from F, Cl and Br, 0<b≦4, 0<c≦2, 1≦d≦3, and the sodium-containing transition metal oxide is Na a M b Fe c O2, wherein M is a transition metal ion, 0.67<a<1.1, 0.5<b<1, and 0<c<0.5.

[0062] In some embodiments, the positive electrode membrane layer optionally further comprises a binder. By way of example, the binder may comprise at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0063] In some embodiments, the cathode film layer optionally further comprises a conductive agent. For example, 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.

[0064] In some embodiments, the positive electrode plate may be manufactured by the following method: The above components for manufacturing the positive electrode plate, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is applied to a positive electrode current collector; and the positive electrode plate is obtained through processes such as drying and cold pressing.

[0065] [Separator] In some embodiments, the secondary battery further includes a separator. This application does not particularly limit the type of separator, and any well-known porous separator having good chemical and mechanical stability may be selected.

[0066] In some embodiments, the material of the separator may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer thin film or a multilayer composite thin film, and is not particularly limited. If the separator is a multilayer composite thin film, the materials of each layer may be the same or different, and is not particularly limited.

[0067] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator may be manufactured as an electrode assembly by a winding process or a lamination process.

[0068] In some embodiments, the secondary battery may include an outer casing. This outer casing includes the electrode assembly and electrolyte It may be used in packaging.

[0069] In some embodiments, the casing of the secondary battery may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0070] This application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a rectangular secondary battery 5 as an example.

[0071] In some embodiments, referring to Figure 2, the casing may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates surround and form a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 can close the housing cavity by covering the opening. The positive electrode plate, the negative electrode plate and the separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged within the housing cavity. electrolyte The solution permeates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and a person skilled in the art can select them according to the actual specific needs.

[0072] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, the specific number which can be selected by those skilled in the art based on the application and capacity of the battery module.

[0073] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, the multiple secondary batteries 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged according to any other method. Furthermore, the multiple secondary batteries 5 may be fixed with fasteners.

[0074] Optionally, the battery module 4 may further include a housing having a housing space, and a plurality of secondary batteries 5 are housed in the housing space.

[0075] In some embodiments, the battery modules may be further assembled into a battery pack, the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0076] Figures 4 and 5 show an example of a battery pack 1. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, the upper housing 2 covering the lower housing 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged inside the battery box in any manner.

[0077] Furthermore, this application provides a power consumption device comprising at least one of a secondary battery, a battery module, or a battery pack as described herein. The secondary battery, battery module, or battery pack may be used as a power source for the power consumption device or as an energy storage unit for the power consumption device. The power consumption device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, energy storage systems, etc.

[0078] As a power consumption device, a secondary battery, battery module, or battery pack can be selected according to the user's needs.

[0079] Figure 6 shows an example of a power consumption device. This power consumption device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the power consumption device's demand for high power and high energy density of secondary batteries, a battery pack or battery module may be employed.

[0080] [Examples] The following describes embodiments of this application. The embodiments described below are illustrative and are for interpretive purposes only, and should not be considered as limitations thereon. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in the art or in the product instructions shall be followed. Unless the manufacturer is specified for the reagents or instruments used, they are all common products that can be purchased commercially.

[0081] Example 1 1. Manufacturing of the positive electrode plate: A positive electrode slurry was prepared by thoroughly stirring and uniformly mixing the positive electrode active material, sodium vanadium phosphate (Na3V2(PO4)3), the conductive agent, acetylene black, and the binder, polyvinylidene fluoride (PVDF), in a weight ratio of 90:5:5 in an N-methylpyrrolidone solvent system. The positive electrode slurry was then uniformly applied to the positive electrode current collector aluminum foil, followed by drying, cold pressing, and cutting to obtain the positive electrode plate.

[0082] 2. Manufacturing of the negative electrode plate: Hard carbon (negative electrode active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binding agent), and sodium carboxymethylcellulose (CMC-Na) (thickener) were mixed uniformly in a deionized water solvent system in a weight ratio of 90:4:4:2 by thorough stirring to produce a negative electrode slurry. The negative electrode slurry was then applied to an aluminum foil negative electrode current collector, followed by drying, cold pressing, and cutting to obtain the negative electrode plate.

[0083] 3. Separator: A porous polymer thin film of PE was used.

[0084] 4. electrolyte Manufacturing: Mix ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 30:70, and dissolve NaPF6 sodium salt in the above solution. electrolyte The molar concentration of NaPF6 sodium salt was set to 1M, and SO2 gas was introduced into the electrolyte and stirred to dissolve it, resulting in a mass content of the first additive SO2 in the electrolyte of 1%.

[0085] 5. Manufacturing of secondary batteries: The positive electrode plate, separator, and negative electrode plate are stacked and wound in order to obtain an electrode assembly, and the electrode assembly is placed in an outer casing, and the batteries manufactured as described above electrolyte By adding the following, and going through processes such as sealing, settling, chemical formation, and aging, a secondary battery was obtained.

[0086] Examples 2-27 and Comparative Examples 1-11 Examples 2-27 and Comparative Example 1-11 are similar to the secondary battery manufacturing method of Example 1, but with adjusted parameters. Details of the differing parameters are shown in Table 1.

[0087] JPEG0007927080000002.jpg250146JPEG0007927080000003.jpg250160JPEG0007927080000004.jpg250160JPEG0007927080000005.jpg250160

[0088] Battery testing (1) Measurement of the mass content of sulfur element in the negative electrode film layer of a secondary battery: At 25°C, the new sodium-ion secondary batteries manufactured in the examples and comparative examples were left for 5 minutes, then charged with a constant current at a 1C multiplier up to 4.2V, and further charged with a constant voltage until the current was less than 0.05C. After being left for another 5 minutes, they were discharged with a constant current at a 1C multiplier up to 2.0V to obtain fully discharged battery cores. The fully discharged battery cores were disassembled, the negative electrode plate was removed, and the negative electrode film layer on the negative electrode plate was scraped off with a blade. The mass content of sulfur element in the scraped material, i.e., the mass content of sulfur element in the negative electrode film layer, was measured using an inductively coupled plasma atomic emission spectrometer in accordance with the EPA 6010D-2014 test standard.

[0089] (2) Test of the room temperature cycle performance of secondary batteries: At 25°C, the sodium-ion secondary battery was left for 5 minutes, then charged with a constant current at a 1C multiplier up to 4.2V, and further charged with a constant voltage until the current was less than 0.05C. After leaving it for another 5 minutes, it was discharged with a constant current at a 1C multiplier up to 2.0V. This constituted one charge-discharge cycle, and the discharge capacity at this time was recorded as the discharge capacity of the first cycle of the sodium-ion secondary battery. The sodium-ion secondary battery was subjected to 800 cycle charge-discharge tests using the above method, and the discharge capacity of each cycle was recorded. The capacity retention rate of the secondary battery was calculated using the following formula.

[0090] The capacity retention rate (%) of a secondary battery = 100% × discharge capacity after 800 cycles / discharge capacity after 1 cycle.

[0091] (3) DC impedance test of secondary batteries: At 25°C, a sodium-ion secondary battery was left for 5 minutes, then charged with a constant current at a 1C multiplier to 4.2V, and further charged with a constant voltage until the current was less than 0.05C. At this point, the state of charge (SOC) of the battery was 100%. After leaving it for another 5 minutes, it was discharged with a constant current at a 1C multiplier to adjust the state of charge (SOC) of the sodium-ion secondary battery to 50%. The sodium-ion secondary battery with 50% SOC was then left for another 10 minutes, and the voltage U1 during the last second of the discharge period was recorded. Then, it was discharged with a constant current at a 4C multiplier for 30 seconds, and the discharge current I and the voltage U2 during the last second of the discharge were recorded. The DC impedance of the secondary battery was calculated using the following formula.

[0092] The DC impedance of a secondary battery is (U2 - U1) / I.

[0093] The results of the above tests are shown in Table 1.

[0094] As can be seen from Table 1, Comparing the results of Examples 1-6 and Comparative Examples 1-3, and comparing the results of Example 9 and Comparative Examples 10-11, the first additive of this application electrolyte When the mass content is 0.05%-5%, the DC internal resistance of the secondary battery is lower, and the first additive of this application electrolyte It was found that when the mass content of the first additive is 1%-6%, the cycle capacity retention rate of the secondary battery is higher. electrolyte When the mass content is less than 0.05% (Comparative Examples 2 and 11), the amount of sulfur-containing inorganic salt product formed is relatively small. electrolyte This was insufficient to suppress the occurrence of the side reaction, resulting in poor cycle performance of the secondary battery and a slightly high DC internal resistance. electrolyte When the mass content was greater than 6% (Comparative Examples 3 and 10), the excess of the first additive caused a clear increase in the internal resistance of the secondary battery, resulting in slightly poorer cycle performance.

[0095] Comparing the results of Examples 1, 7-17 and Comparative Examples 4-5, and comparing the results of Example 20 and Comparative Example 9, it was found that in this application, a sulfur-containing compound with a boiling point not exceeding 70°C is used as the first additive. electrolyte By adding this, it became clear that the DC internal resistance of the manufactured secondary batteries was lower and the cycle capacity retention rate was higher.

[0096] When comparing Examples 20, 21, and 23 with the results of Comparative Examples 6-8, only the second additive was found to be effective. electrolyte In contrast to adding the above, this application uses a sulfur-containing compound with a boiling point not exceeding 70°C as the first additive. electrolyte It has become clear that by adding this, the DC internal resistance of the secondary battery is significantly reduced, and the cycle capacity retention rate of the secondary battery can be significantly improved.

[0097] Comparing the results of Example 1 with Examples 20-23 and 25, and comparing the results of Example 5 with Examples 18 and 26, the second additive of this application electrolyte It was found that when the mass content was between 0.01% and 10%, the negative electrode film deposition quality was better, resulting in a further improvement in the cycle capacity retention rate of the secondary battery.

[0098] Comparing Examples 18-23 and 25 with Examples 24, 26, and 27, it became clear that in this application, when the product of W1 and W2 is any value between 0.05 and 10, the negative electrode interface film of the manufactured secondary battery is stable, the DC internal resistance is at an appropriate level, and the cycle capacity retention rate is further improved.

[0099] Comparing Examples 1-5 with Example 6 and Comparative Examples 2-3, and comparing Example 9 with Comparative Examples 10-11, it became clear that when the mass content of sulfur element in the negative electrode film layer of this application is 0.01%-1%, the manufactured secondary battery has a stable negative electrode interface film, the DC internal resistance is at an appropriate level, and the cycle capacity retention rate is further improved.

[0100] In summary, the present application electrolyteThis allows for obtaining a stable negative electrode interface film, and the negative electrode plate electrolyte This reduces the likelihood of side reactions, decreases sodium deposition, lowers the DC internal resistance of the secondary battery, and improves the cycle performance and safety performance of the secondary battery.

[0101] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are illustrative, and any embodiment that has substantially the same configuration as the technical idea and produces the same effects within the scope of the technical proposal of this application is included within the scope of the technical proposal. Furthermore, other forms constructed by combining some of the components of the embodiments, with various modifications that a person skilled in the art could conceive of, are also included within the scope of this application, as long as they do not depart from the spirit of this application. [Explanation of Symbols]

[0102] 1 Battery pack, 2 Upper casing, 3 Lower casing, 4 Battery module, 5 Rechargeable battery, 51 Case, 52 Electrode assembly, 53 Top cover assembly.

Claims

Claims 1. An electrolyte solution for a sodium ion secondary battery, comprising a solvent, an electrolyte salt and a first additive, wherein the first additive is SF ６ , SF ４ , SO ２ F ２ , SO ２ , SO ３ , CS ２ , dimethyl sulfide, methyl ethyl sulfide, S ２ F ２ , SF ２ , SOF ２ and SOF ４ one or more selected from the group consisting of, wherein the mass content of the first additive in the electrolyte solution is 0.05% to 6%, The aforementioned solvent is a carbonate-based solvent. The electrolyte salt is one or more selected from NaPF₂₆, NaBF₄, NaN(SO₂F)₂, NaClO₄, NaAsF₆, NaB(C₂O₄)₂, NaBF₂(C₂O₄), NaN(SO₂R₄F)₂, and NaN(SO₂F)(SO₂R₄F), where R₄F represents CbF₂b+1 and b is an integer in the range of 1 to 10.

2. The electrolyte according to claim 1, wherein the mass content of the first additive in the electrolyte is 0.05% to 5%, and optionally 0.1% to 2%.

3. The solution further comprises a second additive, the second additive being one or more selected from fluorinated carbonate esters and fluorinated carboxylic acid esters, and the mass content of the second additive in the electrolyte is 0.005%–12%, optionally 0.01%–10%. The electrolyte according to claim 1 or 2, wherein the second additive is optionally fluorinated ethylene carbonate and / or 2,2-difluoroethyl acetate.

4. The electrolyte according to claim 3, wherein the mass content of the second additive in the electrolyte is 0.1% to 5%.

5. The electrolyte according to claim 3, wherein the mass content of the first additive in the electrolyte is 1%, the mass content of the second additive in the electrolyte is 2%, and the product of W1 and W2 is any number selected from the range of 0.01 to 24, optionally any number selected from the range of 0.05 to 16, and optionally any number selected from the range of 0.05 to 10.

6. A secondary battery comprising a positive electrode plate, a negative electrode plate, a separator, and the electrolyte according to claim 1 or 2.

7. The secondary battery according to claim 6, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer installed on at least one surface of the negative electrode current collector, and the mass content of sulfur element in the negative electrode film layer is 0.01% to 1.14%, and optionally 0.01% to 1%.

8. The secondary battery according to claim 7, wherein the mass content of sulfur element in the negative electrode film layer is 0.05% to 0.5%.

9. A battery module comprising the secondary battery described in claim 6.

10. A battery pack comprising the battery module described in claim 9.

11. A power consumption device including the battery pack described in claim 10.

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