Electrolyte, secondary battery, battery module, battery pack, and power-consuming device

Abstract

An electrolyte for a lithium ion secondary battery and a battery, the electrolyte comprising a solvent, an additive composition, and a lithium salt, the additive composition comprising at least one of compounds of formula (II) and (III) and a compound of formula (I). The resulting battery has a high voltage and good cycle performance and storage performance at high temperature.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to an electrolyte, a secondary battery, a battery module, a battery pack, and an electrical device. Background Technology

[0002] Lithium-ion batteries have become the most popular energy storage system due to their high operating potential, long lifespan, and environmental friendliness, and are now widely used in pure electric vehicles, hybrid electric vehicles, smart grids, and other fields. With increasing demands for longer driving range and the need to alleviate range anxiety associated with electric vehicles, there is an urgent need to develop lithium-ion battery systems with higher energy density.

[0003] To improve battery energy density, increasing the operating potential of the cathode material has become a primary strategy for researchers. For example, the operating voltage of conventional ternary cathode materials has been increased to above 4.4V. However, this higher voltage makes the electrolyte susceptible to oxidation, resulting in extremely poor cell lifespan. Current technologies typically add film-forming additives (such as tetravinylsilane) to the electrolyte. While this enhances anode film formation and reduces the damage to the anode from byproducts of cathode oxidation, it also results in excessive film resistance, severely deteriorating the battery's initial impedance. Therefore, existing electrolyte additives still require improvement. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte and a battery for lithium-ion secondary batteries, wherein the resulting battery has a high voltage and good cycle performance and storage performance at high temperature.

[0005] To achieve the above objectives, a first aspect of this application provides an electrolyte for lithium-ion secondary batteries, comprising a solvent, an additive composition, and a lithium salt, characterized in that the additive composition comprises at least one compound of formula II and formula III, and a compound of formula I.

[0006]

[0007] R1, R2, and R3 are each independently H or F, and at least one of R1, R2, and R3 is F;

[0008]

[0009] R4 and R5 are each independently hydrogen, vinyl, allyl, oxyvinyl or oxyallyl, and at least one of R4 and R5 is not H;

[0010]

[0011] R6, R7, R8 and R9 are each independently selected from one or more of allyl, vinyl and allyl groups.

[0012] Therefore, the electrolyte of this application, by containing compound I and compound II or III, ensures that the resulting battery has a high voltage and good cycle performance and storage performance at high temperatures.

[0013] In any embodiment, the compound of formula I is

[0014]

[0015] The compound of formula II is

[0016]

[0017] The compound of formula III is

[0018]

[0019] Therefore, the electrolyte of this application, by including compound I and compound II or III with the above-described structure, further enables the corresponding battery to have high voltage and good cycle performance and storage performance at high temperature.

[0020] In any embodiment, if the content of compound I in the electrolyte is a% by weight, and the content of compound II or compound III, or a mixture of both, in the electrolyte is b% by weight, then...

[0021] 0.05≤a / b≤4.

[0022] Thus, by including compound I and compound II or III in the aforementioned proportions, the corresponding battery further exhibits high voltage and good cycle and storage performance at high temperatures.

[0023] In any embodiment, if the content of compound I in the electrolyte is a% by weight, and the content of compound II or compound III, or a mixture of both, in the electrolyte is b% by weight, then...

[0024] 0.1≤a+b≤10.

[0025] Thus, by including compound I and compound II or III in the aforementioned proportions, the corresponding battery further exhibits high voltage and good cycle and storage performance at high temperatures.

[0026] In any embodiment, the content of the compound of Formula II or the compound of Formula III, or a mixture of both, in the electrolyte is 0.06-8% by weight.

[0027] Thus, by including compounds II or III in the aforementioned proportions, the corresponding batteries further achieve high voltage and good cycle and storage performance at high temperatures.

[0028] In any embodiment, the solvent is an aprotic organic solvent selected from one or more of fluorinated and non-fluorinated cyclic and chain organic carbonates, fluorinated and non-fluorinated ethers, fluorinated and non-fluorinated cyclic ethers, fluorinated and non-fluorinated carboxylic esters, fluorinated and non-fluorinated chain sulfones, or cyclic sulfones.

[0029] Therefore, by including solvents of the aforementioned types, the corresponding batteries further achieve high voltage and good cycle and storage performance at high temperatures.

[0030] In any embodiment, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP), and may be selected as one or two of lithium hexafluorophosphate or lithium bis(fluorosulfonyl)imide.

[0031] Therefore, by including the aforementioned types of lithium salts, the corresponding batteries further possess high voltage and good cycle performance and storage performance at high temperatures.

[0032] In any embodiment, in the electrolyte,

[0033] The solvent is 60-85% by weight.

[0034] The additive composition is 0.01-20% by weight.

[0035] The lithium salt content is 10-40% by weight;

[0036] The total weight of the above components is 100% by weight, and each weight percentage is based on the total weight of the electrolyte.

[0037] Therefore, by including the components in the aforementioned amounts, the corresponding battery further exhibits high voltage and good cycle performance and storage performance at high temperatures.

[0038] A second aspect of this application also provides a secondary battery, characterized in that...

[0039] Including the electrolyte described in the first aspect of this application.

[0040] Therefore, the battery has a high voltage and good cycle performance and storage performance at high temperatures.

[0041] A third aspect of this application provides a battery module, including the secondary battery of the second aspect of this application.

[0042] A fourth aspect of this application provides a battery pack that includes the battery module of the third aspect of this application.

[0043] The fifth aspect of this application provides an electrical device including at least one selected from the second aspect of this application, the third aspect of this application, or the fourth aspect of this application.

[0044] This application ensures that the resulting battery has high voltage and good cycle and storage performance at high temperatures by including compound I and compound II or III in the electrolyte. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0046] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0047] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0048] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0049] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0050] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0051] Explanation of reference numerals in the attached figures:

[0052] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Top cover assembly Detailed Implementation

[0053] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the electrolyte, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0054] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 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. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0055] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0056] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0057] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0058] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0059] 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 condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0060] To improve battery energy density, increasing the operating potential of the cathode material has become a primary strategy for researchers. For example, the operating voltage of conventional ternary cathode materials has been increased to above 4.4V. However, this increased voltage leads to poor electrolyte oxidation resistance, resulting in extremely poor cell lifespan. Current technologies typically add film-forming additives (such as tetravinylsilane) to the electrolyte. While this enhances anode film formation and reduces the damage to the anode caused by byproducts of cathode oxidation, it results in excessive film resistance, severely deteriorating the battery's initial impedance. Therefore, existing electrolyte additives still require improvement. This application addresses the above-mentioned issues, aiming to provide an electrolyte and battery for lithium-ion secondary batteries, resulting in a battery with high voltage and good cycle and storage performance at high temperatures.

[0061] Electrolyte for lithium-ion secondary batteries

[0062] In one embodiment of this application, an electrolyte for a lithium-ion secondary battery is provided, comprising a solvent, an additive composition, and a lithium salt, characterized in that the additive composition comprises at least one compound of formula II and formula III, and a compound of formula I.

[0063]

[0064] R1, R2, and R3 are each independently H or F, and at least one of R1, R2, and R3 is F;

[0065]

[0066] R4 and R5 are each independently hydrogen, vinyl, allyl, oxyvinyl or oxyallyl, and at least one of R4 and R5 is not H;

[0067]

[0068] R6, R7, R8 and R9 are each independently selected from one or more of allyl, vinyl and allyl groups.

[0069] Therefore, the electrolyte of this application contains compound I and compound II or III, so that in the corresponding battery, during the negative electrode reduction film formation process, compound II or compound III is preferentially reduced to form free radicals containing sulfonic acid groups, and then further reacts with compound I to form polypropylene sulfonate-polypropylene copolymer or polybutene sulfonate-polypropylene copolymer with appropriate molecular weight. In addition, it also contains inorganic components such as silicates, sulfonates or lithium salts. The SEI film component composed of these components not only has high ion conduction, but also has appropriate rigidity and flexibility, which can effectively protect the negative electrode interface and resist the damage of the negative electrode SEI film by the byproducts generated by the subsequent positive electrode oxidation. This ensures that the resulting battery has high voltage and good cycle performance and storage performance at high temperature.

[0070] In some embodiments, the compound of formula I is

[0071]

[0072] The compound of formula II is

[0073]

[0074] The compound of formula III is

[0075]

[0076] Therefore, the electrolyte of this application, by including compound I and compound II or III with the above-described structure, further enables the corresponding battery to have high voltage and good cycle performance and storage performance at high temperature.

[0077] In some embodiments, the content of compound I in the electrolyte is a% by weight, and the content of compound II or compound III, or a mixture of both, in the electrolyte is b% by weight.

[0078] 0.05≤a / b≤4, preferably 0.05≤a / b≤2, and even more preferably 0.5≤a / b≤1.

[0079] Thus, by including compound I and compound II or III in the aforementioned proportions, the corresponding battery further exhibits high voltage and good cycle and storage performance at high temperatures.

[0080] In some embodiments, the content of compound I in the electrolyte is a% by weight, and the content of compound II or compound III, or a mixture of both, in the electrolyte is b% by weight.

[0081] 0.1≤a+b≤10, preferably 0.1≤a+b≤6.

[0082] Thus, by including compound I and compound II or III in the aforementioned proportions, the corresponding battery further exhibits high voltage and good cycle and storage performance at high temperatures.

[0083] In some embodiments, the content of the compound of Formula II or the compound of Formula III, or a mixture thereof, in the electrolyte is 0.06-8% by weight, preferably 1-8% by weight.

[0084] Thus, by including compounds II or III in the aforementioned proportions, the corresponding batteries further achieve high voltage and good cycle and storage performance at high temperatures.

[0085] In some embodiments, the solvent is an aprotic organic solvent selected from one or more of fluorinated and non-fluorinated cyclic and chain organic carbonates, fluorinated and non-fluorinated ethers, fluorinated and non-fluorinated cyclic ethers, fluorinated and non-fluorinated carboxylic esters, fluorinated and non-fluorinated chain sulfones, or cyclic sulfones; preferably one or more of fluorinated carbonates and fluorinated carboxylic esters.

[0086] Therefore, by including solvents of the aforementioned types, the corresponding batteries further achieve high voltage and good cycle and storage performance at high temperatures.

[0087] In some embodiments, the solvent is also selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0088] In some embodiments, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP), and may be selected from one or two of LiPF6 or LiFSI.

[0089] Therefore, by including the aforementioned types of lithium salts, the corresponding batteries further possess high voltage and good cycle performance and storage performance at high temperatures.

[0090] In some embodiments, in the electrolyte,

[0091] The solvent is 60-85% by weight, preferably 80-88% by weight.

[0092] The additive composition is 0.01-20% by weight, preferably 0.3-15% by weight;

[0093] The lithium salt is 10-40% by weight, preferably 10-15% by weight;

[0094] The total weight of the above components is 100% by weight, and each weight percentage is based on the total weight of the electrolyte.

[0095] Therefore, by including the components in the aforementioned amounts, the corresponding battery further exhibits high voltage and good cycle performance and storage performance at high temperatures.

[0096] In some embodiments, the additive composition may further include negative electrode film-forming additives and positive electrode film-forming additives, and may also include additives capable of improving certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, such as lithium difluorophosphate (LiPO2F2) and lithium fluorinated sulfate (LiSO3F). The negative electrode film-forming additive is one or more of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate.

[0097] A second aspect of this application also provides a secondary battery, characterized in that...

[0098] Including the electrolyte described in the first aspect of this application.

[0099] Therefore, the battery has a high voltage and good cycle performance and storage performance at high temperatures.

[0100] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0101] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0102] [Positive electrode plate]

[0103] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0104] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0105] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM)333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0107] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0108] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0109] In some embodiments, 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 (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0110] [Negative electrode plate]

[0111] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0112] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0113] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0114] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. 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 alone or in combination of two or more.

[0115] In some embodiments, the negative electrode film layer may optionally include a binder. 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).

[0116] In some embodiments, the negative electrode film may optionally include 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.

[0117] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0118] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0119] [Electrolytes]

[0120] The electrolyte plays a role in conducting ions between the positive and negative electrode plates.

[0121] In some embodiments, the electrolyte is the electrolyte of the first aspect of this application.

[0122] [Isolation membrane]

[0123] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0124] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0125] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0126] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0127] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0128] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0129] In some implementations, refer to Figure 2The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0130] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0131] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0132] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0133] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0134] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0135] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical 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.), electric trains, ships and satellites, energy storage systems, etc.

[0136] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0137] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0138] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0139] Example

[0140] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0141] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0142] Example 1

[0143] 1) Preparation of positive electrode sheet

[0144] The positive electrode active material is a single-crystal LiNi with a Dv50 of 3.8 μm. 0.5 Mn 0.3 Co 0.2O2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 96:2:2. After thorough stirring and mixing, a positive electrode slurry is obtained. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, followed by drying, cold pressing, and slitting to obtain the positive electrode sheet.

[0145] 2) Preparation of negative electrode sheet

[0146] The negative electrode active material is graphite (BET is 1.2m). 3 / g,D v50 A negative electrode slurry is prepared by dissolving a conductive agent (18μm), a conductive agent (acetylene black), a binder (styrene-butadiene rubber (SBR), and a thickener (sodium carboxymethyl cellulose (CMC)) in deionized water at a weight ratio of 95:2:2:1. The slurry is then uniformly mixed with the deionized water to form a negative electrode slurry. This negative electrode slurry is then uniformly coated onto a copper foil current collector, dried, and the resulting negative electrode film is cold-pressed and slit to obtain the negative electrode sheet.

[0147] 3) Separating membrane

[0148] Conventional polypropylene film is used as the separator.

[0149] 4) Preparation of electrolyte

[0150] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), organic solvent EC / EMC was mixed evenly at a volume ratio of 3 / 7. 1 M LiPF6 lithium salt was added and dissolved in the organic solvent. 0.5 wt% tetravinylsilane and 1 wt% 2-fluoro-1,3-propanesulfonate lactone were added based on the weight of the electrolyte. The mixture was stirred evenly to obtain the corresponding electrolyte.

[0151] 5) Battery manufacturing

[0152] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound to obtain the electrode assembly. The electrode assembly is placed in the battery casing, dried, and then injected with electrolyte. After formation and settling processes, a lithium-ion battery is obtained.

[0153] The secondary batteries of Examples 2-19 and Comparative Examples 1-4 were prepared using methods similar to those of Example 1, but the composition and parameters of the additives, solvents, and positive electrode active materials in the electrolyte were adjusted, as detailed in Table 1.

[0154]

[0155]

[0156] II. Battery Performance Testing

[0157] 1. Cyclic performance test of lithium-ion batteries at 25℃

[0158] At 25°C, the lithium-ion battery was charged at a constant current of 0.5C to 4.45V, then charged at a constant voltage of 4.45V until the current was less than 0.05C. Next, the lithium-ion battery was discharged at a constant current of 0.5C to 2.8V, yielding the initial discharge capacity C0, which is recorded as the first cycle. This charging and discharging process was repeated, and the number of cycles required to reach 80% of the discharge capacity C0 was calculated.

[0159] 2. Cyclic performance test of lithium-ion batteries at 45℃

[0160] At 45°C, the lithium-ion battery is charged at a constant current of 1C to 4.45V, then charged at a constant voltage of 4.45V until the current is less than 0.05C. The lithium-ion battery is then discharged at a constant current of 1C to 2.8V, yielding the initial discharge capacity C0, which is recorded as the first cycle. This charging and discharging process is repeated, and the number of cycles required to reach 80% of the discharge capacity C0 is calculated.

[0161] 3. Storage performance test of lithium-ion batteries at 60℃

[0162] At 25°C, the lithium-ion battery was charged at a constant current of 0.5C to 4.45V, and then charged at a constant voltage of 4.45V until the current was less than 0.05C. The battery cell was then stored at 60°C. Every 10 days, the battery cell was taken out, fully charged, and then stored again. The battery cell was stored for a total of 100 days, and the corresponding remaining reversible capacity was recorded.

[0163] III. Test Results of Each Embodiment and Comparative Example

[0164] Batteries for each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 2 below.

[0165] Table 2 Battery performance of each embodiment and comparative example

[0166]

[0167] As can be seen from Tables 1 and 2, the battery of the present invention improves the high-temperature cycle life and high-temperature storage performance by including compound I and compound II or III in the electrolyte.

[0168] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An electrolyte for lithium-ion secondary batteries, comprising a solvent, an additive composition, and a lithium salt, characterized in that, The additive composition comprises compounds of formula II, formula III and formula I. Formula II R1, R2, and R3 are each independently H or F, and at least one of R1, R2, and R3 is F; Formula III, R4 and R5 are each independently hydrogen, vinyl, allyl, oxyvinyl or oxyallyl, and at least one of R4 and R5 is not H; Formula I R6, R7, R8 and R9 are each independently selected from one or more of allyl, vinyl and allyl groups; The content of compound I in the electrolyte is a% by weight, and the content of the mixture of compounds II and III in the electrolyte is b% by weight. 0.05≤a / b≤4, 0.1≤a+b≤10.

2. The electrolyte according to claim 1, characterized in that, The compound of formula I is ； The compound of formula II is , or ; The compound of formula III is or .

3. The electrolyte according to claim 1, characterized in that, The content of the compound of Formula II or the compound of Formula III or a mixture thereof in the electrolyte is 0.06-8 by weight.

4. The electrolyte according to claim 1, characterized in that, The solvent is an aprotic organic solvent, which is selected from one or more of the following: fluorinated and non-fluorinated cyclic and chain organic carbonates, fluorinated and non-fluorinated ethers, fluorinated and non-fluorinated cyclic ethers, fluorinated and non-fluorinated carboxylic esters, fluorinated and non-fluorinated chain sulfones, or cyclic sulfones.

5. The electrolyte according to claim 1, characterized in that, The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorophosphate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

6. The electrolyte according to claim 5, characterized in that, The lithium salt is selected from one or both of lithium hexafluorophosphate or lithium difluorosulfonylimide.

7. The electrolyte according to claim 1, characterized in that, In the electrolyte, The solvent is 60-85% by weight. The additive composition is 0.01-20% by weight. The lithium salt content is 10-40% by weight. The total weight of the above components is 100% by weight, and each weight percentage is based on the total weight of the electrolyte.

8. A secondary battery, characterized in that, The electrolyte includes any one of claims 1-7.

9. A battery module, characterized in that, Includes the secondary battery as described in claim 8.

10. A battery pack, characterized in that, Includes the battery module as described in claim 9.

11. An electrical appliance, characterized in that, It includes at least one selected from the secondary battery of claim 8, the battery module of claim 9, or the battery pack of claim 10.

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