Electrolyte, battery secondary liquid injection method and battery

Abstract

The invention relates to the technical field of batteries, in particular to an electrolyte, a battery secondary liquid injection method and a battery. The electrolyte comprises a first electrolyte and a second electrolyte, the first electrolyte comprises a first electrolyte salt, a first organic solvent and a second additive; the second electrolyte comprises a second electrolyte salt, a second organic solvent and a first additive; wherein the first additive comprises an isocyanate group and a silane group; and the second additive comprises fluorine-containing phosphate. The electrolyte can be applied to a secondary electrolyte injection method of the battery, primary electrolyte injection is carried out through the first electrolyte, and secondary electrolyte injection is carried out through the second electrolyte. According to the invention, the fast charging and interface stability of the electrolyte can be considered, the fast charging performance, the cycling stability and the high-temperature performance of the electrolyte can be improved at the same time, and the electrolyte can show excellent comprehensive performance.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an electrolyte, a battery secondary liquid injection method and a battery. Background Art

[0002] Lithium-ion batteries have been widely used in various energy storage devices including portable electronic devices due to their advantages such as high energy density, long cycle life and no memory effect. At present, with the rapid promotion and popularization of new energy vehicles, people have also put forward higher requirements on the performance of lithium-ion batteries. At present, energy replenishment anxiety has become one of the key limiting factors restricting the further expansion of the market for new energy vehicles. How to further improve the fast charging capability (fast charging performance) of lithium-ion batteries is an important indicator to solve the above problems. Among them, the electrolyte is called the "blood" of lithium-ion batteries. It plays the role of transporting ions in the lithium-ion battery system. Its ability to transport ions has a key influence on the kinetic performance of lithium-ion batteries. It is also one of the important factors limiting the fast charging performance of batteries.

[0003] At present, the relevant technology mainly uses low viscosity, low freezing point, and low boiling point solvents to improve the fast charging performance of the electrolyte. However, such solvents have poor chemical and electrochemical stability and poor interface compatibility with the graphite negative electrode, which will have a negative impact on the high temperature performance and cycle life of the battery, resulting in poor overall performance of the battery. Therefore, how to improve the fast charging performance of the electrolyte without damaging its cycle stability or high temperature performance is the key to solving the above problems. Summary of the invention

[0004] In view of this, the present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, the present invention provides an electrolyte, a secondary battery injection method and a battery, which can take into account the fast charging and interface stability of the electrolyte, that is, it is conducive to taking into account the fast charging performance, cycle stability and high temperature performance of the electrolyte, and can make the electrolyte show excellent comprehensive performance.

[0005] In order to solve the above technical problems, this application is implemented as follows:

[0006] According to one aspect of the present application, an embodiment of the present application provides an electrolyte, wherein the electrolyte includes a first electrolyte and a second electrolyte;

[0007] The first electrolyte includes a first electrolyte salt, a first organic solvent, and a second additive;

[0008] The second electrolyte comprises a second electrolyte salt, a second organic solvent and a first additive;

[0009] wherein the first additive comprises an isocyanate group and a silane group;

[0010] The second additive includes a fluorine-containing phosphate.

[0011] In addition, the electrolyte according to the present application may also have the following additional technical features:

[0012] In some embodiments, the first additive includes an isocyanate-containing silyl compound, and the isocyanate-containing silyl compound has a structural formula as shown in Formula I below:

[0013]

[0014] Among them, R1 is selected from substituted or unsubstituted C0~C4 alkyl, and R2, R3, and R4 are each independently selected from substituted or unsubstituted C1~C4 alkyl, substituted or unsubstituted C1~C4 alkoxy, substituted or unsubstituted C1~C4 isocyanate, substituted or unsubstituted C2~C4 alkenyl, substituted or unsubstituted C1~C4 haloalkyl, substituted or unsubstituted C1~C4 haloalkoxy, and substituted or unsubstituted C2~C4 haloalkenyl.

[0015] In some embodiments, the isocyanate-containing silyl compound is selected from at least one of the compounds represented by the following structural formulas S1-S9:

[0016]

[0017] In some embodiments, the second additive includes at least one of lithium difluorophosphate, lithium tetrafluorooxalate phosphate, or lithium difluorooxalate phosphate.

[0018] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the first additive is W1, the mass proportion of the second additive is W2, and W1 and W2 satisfy: 0.01%≤W2≤W1≤5%.

[0019] In some embodiments, based on the total mass of the electrolyte, the mass of the second electrolyte accounts for 10% to 30%.

[0020] In some embodiments, based on the total mass of the electrolyte, the mass of the first electrolyte accounts for 70% to 90%.

[0021] In some embodiments, the mass percentage of the second additive in the first electrolyte is 0.01% to 10%.

[0022] In some embodiments, the mass percentage of the first additive in the second electrolyte is 0.01% to 15%.

[0023] In some embodiments, the first electrolyte salt and the second electrolyte salt respectively include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluoroarsenate or lithium perchlorate.

[0024] In some embodiments, the first organic solvent and the second organic solvent include carbonate and / or carboxylate, respectively.

[0025] In some embodiments, the carboxylic acid ester includes at least one of methyl acetate, ethyl formate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, or ethyl butyrate.

[0026] In some embodiments, the carbonate includes at least one of ethylene carbonate, propylene carbonate, vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate.

[0027] In some embodiments, based on the total mass of the electrolyte, the sum of the mass of the first organic solvent and the second organic solvent accounts for 70% to 85%.

[0028] In some embodiments, based on the total mass of the electrolyte, the sum of the mass of the first electrolyte salt and the second electrolyte salt accounts for 6% to 23%.

[0029] According to another aspect of the present application, an embodiment of the present application provides a battery secondary liquid injection method, using the aforementioned electrolyte, the battery secondary liquid injection method comprising:

[0030] Filling the battery with a first electrolyte for the first time;

[0031] Forming the battery after the first injection;

[0032] filling the battery a second time with a second electrolyte;

[0033] Wherein, the first electrolyte comprises a first electrolyte salt, a first organic solvent and a second additive; the second electrolyte comprises a second electrolyte salt, a second organic solvent and a first additive;

[0034] The first additive comprises an isocyanate group and a silane group; and the second additive comprises a fluorine-containing phosphate.

[0035] According to another aspect of the present application, an embodiment of the present application provides a battery, which includes a positive electrode, a negative electrode and the electrolyte as described above, or is prepared by the above-mentioned method.

[0036] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0037] In an embodiment of the present application, the provided electrolyte includes a first electrolyte and a second electrolyte, the first electrolyte includes a second additive, and the second electrolyte includes a first additive, wherein the first additive includes an isocyanate group and a silane group, and the second additive includes a fluorine-containing phosphate. Thus, the isocyanate group and the silane group in the first additive can be used to remove trace water or other acidic substances in the electrolyte to eliminate its side effects such as corrosion to the interface, and the isocyanate group can react at the negative electrode interface to generate an organic polymer protective layer containing nitrogen and oxygen elements, which can further inhibit the occurrence of interface side reactions and improve interface stability; the presence of the fluorophosphate group in the second additive can generate fluorine-containing and phosphorus-containing inorganic substances at the interface, which has high ion conductivity and high surface energy, can reduce the transmission impedance and charge transfer impedance of lithium ions at the interface, and can inhibit the film-forming consumption of the first additive in the whole life cycle of the battery, alleviate the side effects of the impedance increase brought by the first additive, and inhibit the excessive growth of impedance. Furthermore, the combination of the first additive and the second additive in the electrolyte of the present application can effectively take into account the fast charging and interface stability of the electrolyte, which is beneficial to simultaneously improve the fast charging performance, cycle stability and high temperature performance of the electrolyte, and can make the electrolyte exhibit excellent comprehensive performance, thereby improving the fast charging performance, cycle stability and high temperature performance of the battery using the electrolyte.

[0038] Additional aspects and advantages of the present application will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0039] The present application is further described below in conjunction with specific embodiments. It should be understood that these embodiments of the present application are only used to illustrate the present application and are not used to limit the scope of the present application.

[0040] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0041] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0042] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0043] The technical solution of this application is completed by the inventor based on the following discovery: Improving battery performance, such as fast charging performance, cycle performance or high temperature performance, is conducive to extending the service life of the battery. Taking lithium-ion batteries as an example,

[0044] At present, in the design of electrolytes, solvents with low viscosity, low freezing point and low boiling point, including carboxylic acid esters, are usually selected to improve the ability of electrolytes to transport lithium ions and improve the fast charging performance of electrolytes. However, such solvents often have poor chemical and electrochemical stability, poor compatibility with the negative electrode interface, and cannot generate stable SEI, resulting in the continuous occurrence of side reactions of the electrolyte at the negative electrode interface, which damages the battery cycle stability and high temperature performance. Functional additives, as one of the main components of battery electrolytes, play a key role in the good electrochemical performance of batteries. Lithium-ion batteries have problems such as poor compatibility between electrolytes and graphite negative electrode interfaces, which cause problems such as poor fast charging performance and cycle performance or high temperature performance of batteries. These problems can be improved by selecting a suitable combination of electrolyte functional additives or coordinating different injection methods. Therefore, how to improve the fast charging performance of the electrolyte while ensuring its excellent compatibility and stability with the electrode interface to better meet people's requirements for the comprehensive performance of lithium-ion batteries is a major challenge facing the current development of electrolytes.

[0045] In view of this, in order to alleviate the problem of insufficient fast charging capability (or poor dynamic performance) of the battery electrolyte system, while taking into account excellent cycle stability and high temperature performance, the present invention optimizes the battery electrolyte formula, under the joint action of a unique combination of multiple components, and cooperates with the operation mode of multiple injections, so that the electrolyte system has both fast charging and interface stability, which is conducive to meeting the electrolyte's requirements for fast charging, circulation, and high-temperature storage performance, and giving the electrolyte excellent comprehensive performance. Next, this application is described in detail.

[0046] In some embodiments, an electrolyte is provided, the electrolyte comprising: a first electrolyte and a second electrolyte;

[0047] The first electrolyte includes a first electrolyte salt, a first organic solvent and a second additive; the second electrolyte includes a second electrolyte salt, a second organic solvent and the first additive.

[0048] The first additive comprises an isocyanate group and a silane group; and the second additive comprises a fluorine-containing phosphate.

[0049] In the present application, the electrolyte may include a first electrolyte and a second electrolyte, wherein the first electrolyte is mainly composed of a first electrolyte salt, a first organic solvent, and a second additive, and the second electrolyte is mainly composed of a second electrolyte salt, a second organic solvent, and the first additive; that is, the first electrolyte may contain the second additive, and the second electrolyte may contain the first additive. The first electrolyte may be used for primary injection, and the second electrolyte may be used for secondary injection.

[0050] In the first electrolyte and the second electrolyte, the first electrolyte salt and the second electrolyte salt may be lithium salts, which may be used to participate in the electrochemical reaction, and the first organic solvent and the second organic solvent may be used to dissolve the first electrolyte salt and the second electrolyte salt. In particular, the composite functional additive scheme and the secondary injection method of the present invention can greatly improve the kinetic performance of the electrolyte under fast charging conditions, while ensuring that it has excellent cycle life and high temperature stability.

[0051] In the electrolyte of the present application, the first additive and the second additive can play a synergistic role with each other, which can alleviate the problem that the existing electrolyte cannot take into account the fast charging, long cycle and high temperature performance. Among them, the compound containing isocyanate group and silane group is used as the first additive, which can not only remove the acidic substances in the electrolyte, avoid the instability of the carboxylate solvent itself caused by the increase in electrolyte acidity, and the corrosion of the interface, but also participate in the formation of the interface film and improve the interface stability; at the same time, the fluorine-containing phosphate is introduced as the second additive. The presence of the fluorophosphate group in the second additive can generate fluorine-containing and phosphorus-containing inorganic substances at the interface, which have high ion conductivity and high surface energy, can reduce the transmission impedance and charge transfer impedance of lithium ions at the interface, and can overcome the side effect of the impedance increase brought by the first additive. Thus, this composite scheme can play a certain role in taking into account the fast charging and interface stability of the electrolyte.

[0052] In the present application, although compounding the first additive and the second additive can play a certain improvement role, since the first additive is often accompanied by an increase in interface impedance while improving interface stability, the inventors of the present application have discovered through research and further proposed a secondary injection method, that is, by using the first electrolyte and the second electrolyte in combination, and at the same time cooperating with the secondary injection operation method, such as using the first electrolyte containing the second additive for injection during the first injection, and using the second electrolyte containing the first additive for injection during the second injection, the above-mentioned problem can be effectively alleviated.

[0053] Thus, the provided electrolyte can be used for secondary injection of the battery, which means that the battery is injected with electrolyte twice, and the formation operation is performed during the two injections; the first electrolyte can be used for the first injection, and the second electrolyte can be used for the second injection. That is, the electrolyte includes the first electrolyte used for the first injection and the second electrolyte used for the second injection.

[0054] In detail: a compound containing isocyanate groups and silane groups is used as the first additive. The isocyanate groups and silane groups in the first additive can remove trace water or other acidic substances in the electrolyte to eliminate their side effects such as corrosion on the interface. At the same time, the isocyanate groups can react at the negative electrode interface to generate an organic polymer protective layer containing nitrogen and oxygen elements, which can further inhibit the occurrence of interfacial side reactions and improve interfacial stability, but is often accompanied by an increase in interfacial impedance; therefore, in order to overcome its shortcomings, the present invention introduces a secondary injection method, and adds it during the secondary injection after formation to overcome its influence on the initial internal resistance; that is, using the second electrolyte containing the first additive for injection during the secondary injection can not only help improve the interface stability, but also alleviate the influence of the first additive on the initial internal resistance. In addition, a fluorine-containing phosphate is introduced as a second additive, and the first electrolyte containing the second additive is used for injection during the first injection. The presence of the fluorine-containing phosphate group in the second additive can generate fluorine-containing and phosphorus-containing inorganic substances at the interface, which have high ion conductivity and high surface energy, can reduce the transmission impedance and charge transfer impedance of lithium ions at the interface, and can inhibit the film-forming consumption of the first additive during the entire life cycle of the battery. Therefore, the secondary injection of the present application, the composite solution of the first additive and the second additive, can effectively take into account the fast charging and interface stability of the electrolyte, and is conducive to improving the fast charging performance, cycle stability and high temperature performance of the electrolyte at the same time, giving the electrolyte excellent comprehensive performance.

[0055] Therefore, the electrolyte provided in the present application has a simple formula and is easy to prepare. When the electrolyte is used in a secondary battery (such as a lithium-ion battery), it can effectively improve the battery's fast charging performance (or dynamic performance), cycle performance and high temperature performance, thereby obtaining better overall performance and improving the battery's performance and life.

[0056] In a specific embodiment of the present invention, at least one or more of the following conditions are met:

[0057] In the present application, the first additive includes an isocyanate-containing silyl compound, and the structural formula of the isocyanate-containing silyl compound is shown in the following formula I:

[0058]

[0059] Among them, R1 is selected from substituted or unsubstituted C0~C4 alkyl, and R2, R3, and R4 are each independently selected from substituted or unsubstituted C1~C4 alkyl, substituted or unsubstituted C1~C4 alkoxy, substituted or unsubstituted C1~C4 isocyanate, substituted or unsubstituted C2~C4 alkenyl, substituted or unsubstituted C1~C4 haloalkyl, substituted or unsubstituted C1~C4 haloalkoxy, and substituted or unsubstituted C2~C4 haloalkenyl.

[0060] In the present application, the term "substituted" means that at least one hydrogen atom of the compound or chemical moiety is replaced by another chemical moiety. Among them, in R1, R2, R3, and R4, the substituents used to replace alkyl, alkoxy, isocyanate, alkenyl, haloalkyl, haloalkoxy, haloalkenyl, etc. can be independently selected from hydroxyl, sulfhydryl, amino, cyano, nitro, aldehyde, alkynyl, aryl, heteroaryl, etc., and the present application does not limit the substituents.

[0061] Preferably, the halogen element in the haloalkyl, haloalkoxy or haloalkenyl group may be selected from one or more of F, Cl and Br. Preferably, the halogen element in the haloalkyl, haloalkoxy or haloalkenyl group may be selected from F. That is, the haloalkyl, haloalkoxy or haloalkenyl group is preferably a fluoroalkyl, fluoroalkoxy or fluoroalkenyl group.

[0062] Exemplarily, the isocyanate silyl compound is selected from at least one of the compounds represented by the following structural formulas S1-S9:

[0063]

[0064] Preferably, the isocyanate silyl compound is selected from at least one of the compounds represented by the structural formulas S1, S2, S3, S7 and S9.

[0065] It should be understood that the above S1-S9 exemplarily list several isocyanate-containing silyl compounds, but the present application is not limited thereto. When the above formula I is satisfied, the isocyanate-containing silyl compounds may have more options, which are not listed one by one here.

[0066] In some embodiments, the second additive includes, but is not limited to, any one or a combination of at least two of lithium difluorophosphate (LiPO2F2), lithium tetrafluorooxalate phosphate (LiOTFP), lithium difluorooxalate phosphate (LiODFP), etc. For the sake of brevity, the combinations within the above range are no longer listed one by one.

[0067] By including the above-mentioned fluorine-containing phosphates in the electrolyte, the fast charging performance, cycle performance and high temperature performance of the battery can be effectively improved, thereby obtaining better overall performance and improving the battery's performance and life.

[0068] It should be understood that different first additives and second additives may have certain effects on the comprehensive performance of the lithium battery. In practical applications, the first additive and the second additive may be flexibly selected according to actual needs.

[0069] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the first additive is W1, the mass proportion of the second additive is W2, and W1 and W2 satisfy: 0.01%≤W2≤W1≤5%.

[0070] In the present application, the mass fraction of the first additive to the total mass of the electrolyte is W1, the mass fraction of the second additive to the total mass of the electrolyte is W2, and the relationship between the two satisfies 0.01%≤W2≤W1≤5%.

[0071] By controlling the mass ratio of the first additive and the second additive within the above range, it is beneficial to exert the synergistic effect of the two, so that the two can play their respective advantages and interact with each other to make up for their respective deficiencies, thereby achieving a better overall effect. Using them in the electrolyte of secondary batteries can further enable the battery to have better cycle performance, fast charging performance and high temperature performance, thereby enabling the battery to obtain better overall performance.

[0072] In some embodiments, the mass proportion of the second additive in the first electrolyte is 0.01% to 10%. As an example, the mass proportion of the second additive in the first electrolyte can be 0.01%, 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 5%, 6%, 8%, 10%, or a range consisting of any two of the above values.

[0073] By regulating the concentration of the second additive within the above range, fluorine-containing and phosphorus-containing inorganic substances can be generated at the interface. By utilizing its high ion conductivity and high surface energy, the transmission impedance and charge transfer impedance of lithium ions at the interface can be reduced, and the film-forming consumption of the first additive during the entire life cycle of the battery can be suppressed. By controlling the mass proportion of the second additive to meet the above range, the electrolyte additive can achieve a better improvement effect at a lower dosage, thereby enabling the battery to have better fast charging performance, cycle performance and high temperature performance, and obtain better overall performance.

[0074] In some embodiments, the mass proportion of the first additive in the second electrolyte is 0.01% to 15%. As an example, the mass proportion of the first additive in the second electrolyte can be 0.01%, 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 5%, 6%, 8%, 10%, 12%, 13%, 14%, 15%, or a range consisting of any two of the above values.

[0075] By regulating the concentration of the first additive within the above range, the occurrence of interfacial side reactions can be suppressed and the interface stability can be improved; and by controlling the mass proportion of the first additive to meet the above range, the electrolyte additive can play a better improvement effect on the basis of a lower dosage, thereby enabling the battery to have better fast charging performance, cycle performance and high temperature performance, and obtain better overall performance.

[0076] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the second electrolyte is 10% to 30%. That is, the amount of electrolyte injected in the secondary injection step accounts for 10% to 30% of the total mass of the electrolyte injected. As an example, the mass proportion of the second electrolyte can be 10%, 15%, 20%, 25%, 30% or a range composed of any two of the above values.

[0077] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the first electrolyte is 70% to 90%. That is, the amount of electrolyte injected in one injection step accounts for 70% to 90% of the total mass of the electrolyte injected. As an example, the mass proportion of the first electrolyte can be 70%, 75%, 80%, 85%, 90% or a range consisting of any two of the above values.

[0078] By controlling the mass ratio of the first electrolyte and the second electrolyte within the above range, it is helpful to fully form the film and enable the additives to play a better improvement effect, thereby ensuring battery performance.

[0079] Optionally, after the second liquid injection is completed, the total amount of the first electrolyte and the second electrolyte in the battery is 1 to 5 g / Ah, preferably 1.5 to 4 g / Ah; for example, it can be 1g / Ah, 1.5g / Ah, 2g / Ah, 2.5g / Ah, 3g / Ah, 3.5g / Ah, 4g / Ah, 5g / Ah, etc., of course, it can also be other values ​​within the above range, which is not limited here.

[0080] In the present application, the compositions of the first electrolyte and the second electrolyte are different, in particular, the types of additives in the first electrolyte and the second electrolyte are different, that is, the difference between the first electrolyte and the second electrolyte mainly lies in the types of additives, and the first electrolyte and the second electrolyte must adjust and change the types and components of their additives, while the electrolyte salts such as lithium salts and organic solvents in the first electrolyte and the second electrolyte may be the same, or may be different, and are preferably the same.

[0081] In some embodiments, the first electrolyte salt can be a lithium salt, such as a lithium salt including, but not limited to, any one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorooxalatoborate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluoroarsenate (LiAsF6) or lithium perchlorate (LiClO4) or a combination of at least two thereof. For the sake of brevity, the combinations within the above range are not listed one by one.

[0082] In some embodiments, the second electrolyte salt can be a lithium salt, such as a lithium salt including, but not limited to, any one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorooxalatoborate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluoroarsenate (LiAsF6) or lithium perchlorate (LiClO4) or a combination of at least two thereof. For the sake of brevity, the combinations within the above range are not listed one by one.

[0083] In the present application, the first electrolyte lithium salt and the second electrolyte salt may be of the same type; in addition, the present application is not limited to these lithium salts, and the present application may also use other traditional or new materials that can be used as lithium salts in battery electrolytes. These lithium salts may be used alone or in combination of two or more.

[0084] In some embodiments, based on the total mass of the electrolyte, the sum of the mass of the first electrolyte salt and the second electrolyte salt accounts for 6% to 23%, preferably 6.5% to 22.5%. As an example, the sum of the mass of the first electrolyte salt and the second electrolyte salt can account for 6%, 6.5%, 7%, 8%, 10%, 12%, 15%, 5%, 18%, 20%, 22%, 22.5%, 23%, or any two of the above values.

[0085] In one embodiment, the mass of the lithium salt (the first electrolyte salt and the second electrolyte salt) accounts for 6.5% to 22.5% of the total mass of the electrolyte, that is, each gram of the electrolyte includes 0.065 g to 0.225 g of the lithium salt.

[0086] By controlling the concentration of lithium salt within the above range, the viscosity and conductivity of the electrolyte can reach a relative balance value, avoiding excessively high viscosity affecting the transmission of lithium ions during the cycle, or avoiding excessively low concentration of active ions causing a decrease in conductivity or affecting the capacity of the battery.

[0087] In some embodiments, the first organic solvent and the second organic solvent include carbonate and / or carboxylate, respectively. That is, the first organic solvent may include carbonate, may include carboxylate, may include carbonate and carboxylate; the second organic solvent may include carbonate, may include carboxylate, may include carbonate and carboxylate.

[0088] Preferably, the first organic solvent comprises carbonate ester and carboxylic acid ester; and the second organic solvent comprises carbonate ester and carboxylic acid ester.

[0089] In some embodiments, the carboxylic acid ester includes, but is not limited to, any one or a combination of at least two of methyl acetate (MA), ethyl formate (EF), ethyl acetate (EA), methyl propionate (MP), ethyl propionate (EP), methyl butyrate (MB), and ethyl butyrate (EB). For the sake of brevity, the combinations within the above range are no longer listed one by one.

[0090] In some embodiments, the carbonate includes, but is not limited to, any one or a combination of at least two of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). For the sake of brevity, the combinations within the above range are no longer listed one by one.

[0091] In the present application, the first organic solvent and the second organic solvent may be of the same type, or may be of different types, preferably of the same type. In addition, the present application is not limited to these solvents, and other traditional or new materials that can be used as solvents in battery electrolytes may also be used in the present application. These solvents may be used alone or in combination of two or more.

[0092] In some embodiments, based on the total mass of the electrolyte, the sum of the mass of the first organic solvent and the second organic solvent accounts for 70% to 85%. As an example, the sum of the mass of the first organic solvent and the second organic solvent may account for 70%, 72%, 75%, 78%, 80%, 82%, 85%, or any two of the above values.

[0093] In the present application, the mass of the non-aqueous solvent (organic solvent, namely the first organic solvent and the second organic solvent) accounts for 70% to 85% of the total mass of the electrolyte, that is, each gram of the electrolyte includes 0.70 g to 0.85 g of solvent.

[0094] In this way, lithium-ion batteries can have good fast charging performance, cycle performance and high temperature performance, and obtain better overall performance.

[0095] It should be noted that, in any of the above embodiments, based on the total mass of the electrolyte being 100%, the sum of the mass fractions of the organic solvent, the electrolyte salt such as lithium salt, and the additive does not exceed 100%.

[0096] Therefore, based on the above settings, the isocyanate group and the silane group in the first additive have the ability to remove trace water or other acidic substances in the electrolyte. Especially under high temperature conditions, the high-temperature decomposition of lithium salts and additives in the electrolyte can produce acidic substances, resulting in an increase in the acidity of the electrolyte, thereby aggravating the corrosion interface and further leading to the dissolution of positive electrode metal ions. The dissolved metal ions can be deposited at the negative electrode interface, aggravating the side reaction consumption of the electrolyte, causing the interface film to thicken and the structure to become looser. The presence of the first additive can eliminate the side effects of acidic substances on the interface at high temperatures, such as corrosion, and inhibit the dissolution of positive electrode metal ions. The isocyanate group can be deposited at the negative electrode interface. The first additive and the second additive react at the interface to form an organic polymer protective layer containing nitrogen and oxygen elements, which can further reduce the occurrence of side reactions on the interface and improve the interface stability. At the same time, the introduction of the secondary injection method can eliminate the influence of the first additive on the initial film-forming impedance to a certain extent; in addition, the presence of the fluorophosphate group in the second additive can generate fluorine-containing and phosphorus-containing inorganic substances at the interface, which have high ion conductivity and high surface energy, can reduce the transmission impedance and charge transfer impedance of lithium ions at the interface, and can inhibit the film-forming consumption of the first additive during the entire life cycle of the battery, while overcoming the side effect of increased impedance brought by the first additive, and can further improve the interface. The composite scheme of the first additive and the second additive of the present application can effectively take into account the fast charging and interface stability of the electrolyte.

[0097] In some embodiments, the present application further provides a battery secondary liquid injection method, using the electrolyte described in any of the above embodiments, the battery secondary liquid injection method comprises:

[0098] Filling the battery with a first electrolyte for the first time;

[0099] Forming the battery after the first injection;

[0100] filling the battery a second time with a second electrolyte;

[0101] The first electrolyte includes a first electrolyte salt, a first organic solvent and a second additive; the second electrolyte includes a second electrolyte salt, a second organic solvent and a first additive; the first additive contains an isocyanate group and a silane group; and the second additive includes a fluorine-containing phosphate.

[0102] It should be understood that the “secondary liquid filling method for a battery” and the aforementioned “electrolyte” are based on the same inventive concept, and all the features and advantages described above for the “electrolyte” are also applicable to the “secondary liquid filling method for a battery” and will not be described one by one here.

[0103] In the present application, in the secondary liquid injection method of the battery, the first electrolyte can be first configured according to a preset ratio, the first electrolyte can be injected into the battery, the battery is sealed, and after standing for a period of time (such as standing for 24 hours), the first formation is performed; after the first formation is completed, the second electrolyte is used to perform a second liquid injection on the battery after the first formation, and the battery is sealed and then the second formation is performed.

[0104] It should be pointed out that the present application does not limit the specific chemical formation process, and conventional chemical formation methods in the art can be adopted, which will not be described in detail here.

[0105] In some embodiments, the present application further provides a battery, which includes a positive electrode, a negative electrode, a separator and an electrolyte as described above, or is prepared by the aforementioned method.

[0106] In the present application, the battery is preferably a lithium ion battery, but is not limited thereto, and may also be a sodium ion battery, a magnesium ion battery, and the like.

[0107] In the battery of the present application, the positive electrode may include positive electrode active materials such as lithium compounds, and the negative electrode may include active materials such as graphite carbon materials. The structure of the battery is not particularly limited, and button batteries, cylindrical batteries, square batteries, soft-pack batteries, etc. with single-layer or multi-layer separators can be used. The battery has strong stability, good cycle effect, and long service life.

[0108] Optionally, the positive electrode includes a composite material such as lithium iron phosphate (LiFePO4), and the negative electrode sheet includes a carbon material such as graphite. The separator may include a polyolefin such as polyethylene, polypropylene, fiber, or glass fiber.

[0109] Since the battery provided in the embodiment of the present invention adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0110] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in this area or the product instructions are used. If the manufacturer of the reagents, materials or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0111] It should be noted that in the specific examples and comparative examples, the electrolyte was prepared in a glove box or a dry room, and the content of each substance shown in Table 1 is the mass percentage based on the total mass of the electrolyte.

[0112] Example 1

[0113] 1. Preparation of electrolyte, including:

[0114] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), vinylene carbonate (VC) and ethyl acetate (EA) are mixed to prepare an organic solvent, and lithium salt lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6) are dissolved in the organic solvent and stirred evenly to prepare a blank electrolyte.

[0115] The second additive lithium difluorophosphate (LiPO2F2) is mixed with the blank electrolyte and stirred evenly to obtain the first electrolyte. The first additive containing isocyanate silyl compound (compound shown in S2) is mixed with the blank electrolyte and stirred evenly to obtain the second electrolyte. The electrolyte consists of the first electrolyte and the second electrolyte.

[0116] Among them, taking the mass of the electrolyte as 100%, the second electrolyte (secondary injection electrolyte) accounts for 10% of the total mass of the electrolyte, the mass fraction of the lithium salt LiFSI in the electrolyte is 3%, and the mass fraction of the lithium salt LiPF6 in the electrolyte is 12.0%; the first additive S2 accounts for 8% of the mass of the second electrolyte, and the corresponding mass fraction of the total mass of the electrolyte is 0.8%; the second additive LiPO2F2 accounts for 0.6% of the mass of the first electrolyte, and the corresponding mass fraction of the total mass of the electrolyte is 0.54%; in the organic solvent, the mass fraction of the carboxylate EA in the electrolyte is 30%, and the mass fractions of the carbonates EC, EMC and VC in the electrolyte are 25%, 26.66% and 2% respectively.

[0117] 2. Preparation of positive electrode: The positive electrode active material lithium iron phosphate, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black were mixed in a mass ratio of 94:3:3, and then N-methylpyrrolidone (NMP) solvent was added and stirred with a vacuum mixer to obtain a positive electrode slurry, which was then evenly coated on an aluminum foil current collector (thickness of 12 μm), and then transferred to a 120 ° C oven for drying for 4 hours, and then cold pressed (compacted density of 2.5 g / cm 3 ) and cut to obtain the positive electrode sheet.

[0118] 3. Preparation of negative electrode: The negative electrode active material graphite, conductive agent conductive carbon black Super-P (SP), thickener sodium carboxymethyl cellulose (CMC) solution, and binder styrene butadiene rubber latex were mixed in a mass ratio of 96:0.8:1.2:2, and then deionized water solvent was added. After stirring with a vacuum mixer, the negative electrode slurry was obtained, and then evenly coated on the copper current collector (thickness of 8 μm), and then transferred to a 120 ° C oven for drying for 4 hours, and then cold pressed (compacted density of 1.6 g / cm 3 ) and cut to obtain the negative electrode sheet.

[0119] 4. Preparation of diaphragm: Use polyethylene film as the isolation membrane.

[0120] 5. Battery assembly: stack the positive electrode sheet, separator, and negative electrode sheet in order, so that the separator is in the middle of the positive and negative electrode sheets to isolate the positive and negative electrodes, stack the sheets to obtain a bare cell, weld the pole ears, and place the bare cell in the outer package to prepare for a liquid injection. Add the first electrolyte to the battery, seal it for the first formation, and use a current of 0.1C to charge and discharge it once. After the first formation, use the second electrolyte to inject the second liquid into the battery after the first formation, seal it, and perform high-temperature aging at 45°C for 24 hours, and then use a current of 0.33C to charge and discharge it once to obtain a lithium-ion battery. Among them, the mass ratio of the first electrolyte to the second electrolyte is 9:1.

[0121] Example 2

[0122] Example 2 is basically the same as Example 1, except that: in the preparation of the electrolyte, the mass fraction of the first additive S2 in the total mass of the electrolyte is 1.0%.

[0123] The rest are the same as in Example 1.

[0124] Example 3

[0125] Example 3 is basically the same as Example 1, except that: in the preparation of the electrolyte, the mass fraction of the first additive S2 in the total mass of the electrolyte is 0.5%.

[0126] The rest are the same as in Example 1.

[0127] Example 4

[0128] Example 4 is basically the same as Example 1, except that in the preparation of the electrolyte, the mass fraction of the second additive LiPO2F2 in the total mass of the electrolyte is 0.36%.

[0129] The rest are the same as in Example 1.

[0130] Example 5

[0131] Example 5 is basically the same as Example 1, except that in the preparation of the electrolyte, the mass fraction of the second additive LiPO2F2 in the total mass of the electrolyte is 0.72%.

[0132] The rest are the same as in Example 1.

[0133] Example 6

[0134] Example 6 is basically the same as Example 1, except that in the preparation of the electrolyte, the second additive is lithium difluorooxalophosphate (LiODFP).

[0135] The rest are the same as in Example 1.

[0136] Example 7

[0137] Example 7 is basically the same as Example 1, except that in the preparation of the electrolyte, the first additive is the compound shown in S1.

[0138] The rest are the same as in Example 1.

[0139] Example 8

[0140] Example 8 is basically the same as Example 1, except that in the preparation of the electrolyte, the first additive is the compound shown in S9.

[0141] The rest are the same as in Example 1.

[0142] Example 9

[0143] Example 9 is basically the same as Example 1, except that in the preparation of the electrolyte, methyl acetate (MA) is used to replace EA in the organic solvent.

[0144] The rest are the same as in Example 1.

[0145] Example 10

[0146] Example 10 is basically the same as Example 1, except that in the preparation of the electrolyte, ethyl propionate (EP) is used to replace EA in the organic solvent.

[0147] The rest are the same as in Example 1.

[0148] Embodiment 11

[0149] Example 11 is basically the same as Example 1, except that: in the preparation of the electrolyte, LiPF6 is used in the lithium salt to replace LiFSI; that is, the lithium salt of Example 11 is all LiPF6.

[0150] The rest are the same as in Example 1.

[0151] Example 12

[0152] Example 11 is basically the same as Example 1, except that: in the preparation of the electrolyte, LiFSI is used to replace LiPF6 in the lithium salt; that is, the lithium salt of Example 12 is all LiFSI.

[0153] The rest are the same as in Example 1.

[0154] Embodiment 13

[0155] Example 13 is basically the same as Example 1, except that: in the preparation of the electrolyte, the second electrolyte (secondary injection electrolyte) accounts for 20% of the total mass of the electrolyte, that is, the mass ratio of the first electrolyte to the second electrolyte is 8:2.

[0156] The rest are the same as in Example 1.

[0157] Embodiment 14

[0158] Example 13 is basically the same as Example 1, except that: in the preparation of the electrolyte, the second electrolyte (secondary injection electrolyte) accounts for 30% of the total mass of the electrolyte, that is, the mass ratio of the first electrolyte to the second electrolyte is 7:3.

[0159] The rest are the same as in Example 1.

[0160] Comparative Example 1

[0161] The difference between Comparative Example 1 and Example 1 is:

[0162] In the preparation of the electrolyte of the battery of Comparative Example 1, the additive was omitted.

[0163] That is, the electrolyte of Comparative Example 1 includes a non-aqueous organic solvent and a lithium salt. Among them, the lithium salt includes LiFSI and LiPF6; the solvent includes carbonates and carboxylates, wherein the carbonates include EC, EMC and VC, and the carboxylates include EA. Specifically, based on the mass of the electrolyte as 100%, the mass of the secondary injection electrolyte accounts for 10% of the total mass of the electrolyte, the mass fraction of LiFSI in the electrolyte is 3%, and the mass fraction of LiPF6 in the electrolyte is 12.0%; the mass fraction of EA in the electrolyte is 30%, and the mass fractions of EC, EMC and VC in the electrolyte are 25%, 28% and 2%, respectively.

[0164] Comparative Example 2

[0165] The difference between Comparative Example 2 and Comparative Example 1 is that:

[0166] The electrolyte includes a second additive LiPO2F2, and the mass fraction of the second additive LiPO2F2 in the total mass of the electrolyte is 0.54%.

[0167] Comparative Example 3

[0168] The difference between Comparative Example 3 and Comparative Example 1 is that:

[0169] The electrolyte includes a first additive containing an isocyanate silyl compound (compound shown as S2), and the mass fraction of the first additive S2 to the total mass of the electrolyte is 0.8%.

[0170] Comparative Example 4

[0171] The difference between Comparative Example 4 and Example 1 is that:

[0172] The battery of Comparative Example 4 adopts a one-time liquid injection method.

[0173] The preparation of the electrolyte of Comparative Example 4 includes:

[0174] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), vinylene carbonate (VC) and ethyl acetate (EA) are mixed to prepare an organic solvent, and lithium salt lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6) are dissolved in the organic solvent and stirred evenly to prepare a blank electrolyte.

[0175] The second additive lithium difluorophosphate (LiPO2F2), the first additive containing an isocyanate silyl compound (the compound shown in S2) and the blank electrolyte are mixed and stirred evenly to prepare an electrolyte.

[0176] Among them, taking the mass of the electrolyte as 100%, the mass fraction of the lithium salt LiFSI in the electrolyte is 3%, the mass fraction of the lithium salt LiPF6 in the electrolyte is 12.0%; the mass fraction of the carboxylate EA in the electrolyte is 30%, the mass fraction of the carbonates EC, EMC and VC in the electrolyte are 25%, 26.66% and 2% respectively; the mass fraction of the first additive S2 in the electrolyte is 0.8%; the mass fraction of the second additive LiPO2F2 in the electrolyte is 0.54%.

[0177] It is easy to understand that in order to more easily and conveniently explain Examples 1 to 14 and Comparative Examples 1 to 4, the specific components in the electrolyte are expressed in abbreviated chemical formulas, and their names can be obtained from the above and reference books.

[0178] Please refer to Table 1. The batteries of Examples 1 to 14 and Comparative Examples 1 to 4 were prepared according to the following method.

[0179] Table 1

[0180]

[0181]

[0182]

[0183] Performance Testing

[0184] The batteries prepared in Examples 1-14 and Comparative Examples 1-4 were subjected to performance tests such as cycle performance, rate performance (fast charging capability), and high temperature performance. The specific test methods are as follows:

[0185] (1) Rate discharge performance test: At 25°C, the cells of Examples 1 to 14 and Comparative Examples 1 to 4 were first discharged to 2.0V at a constant current of 1 / 3C, then charged to 3.75V at a constant current of 1C, then charged to a current of 0.05C at a constant voltage, and the discharge capacity was recorded as C1, and then discharged to 2.0V at a constant current of 5C, and the discharge capacity was recorded as C2. The ratio of the 5C discharge capacity to the 1 / 3C discharge capacity is the rate discharge capacity retention rate, that is, the rate discharge capacity retention rate = C2 / C1. The test results can reflect the rate discharge performance of the battery. The higher the value of the capacity retention rate, the better the battery rate performance.

[0186] (2) 25°C cycle performance test: At 25°C, the battery cells of Examples 1 to 14 and Comparative Examples 1 to 4 were first discharged at a constant current of 1C to 2.0V and then subjected to a cycle test. The test process is to first charge to 3.75V at a constant current of 1C, then charge at a constant voltage to a current of 0.05C, and then discharge to 2.0V at a constant current of 1C, cycle charge / discharge, and calculate the capacity retention rate of the battery after 1000 cycles, that is, compared with the initial capacity, after the battery has undergone the above cycles, the ratio of the retained capacity of the battery to the initial capacity, that is, the capacity retention rate (%) of 1000 cycles at 1C at 25°C = retained capacity / initial capacity. This parameter can provide feedback on the cycle performance of the battery. The higher the value of the capacity retention rate, the better the battery cycle performance of this embodiment.

[0187] (3) 60°C storage test: At 25°C, the cells of Examples 1 to 14 and Comparative Examples 1 to 4 were first discharged at 1C constant current to 2.0V, then charged at 1C constant current to 3.75V, then charged at constant voltage to a current of 0.05C, and then discharged at 1C constant current to 2.0V, the discharge capacity was recorded as C3, and the battery thickness was recorded as D1. The cells were then charged at 1C constant current to 3.75V, and then charged at constant voltage to a current of 0.05C. The battery cell was placed in a 60°C oven for storage for 30 days. The thickness of the battery tested in the oven was recorded as D2. Then it was placed at room temperature, first discharged to 2.0V at 1C constant current, then charged to 3.75V at 1C constant current, then charged at constant voltage to a current of 0.05C, and then discharged to 2.0V at 1C constant current, and the discharge capacity was recorded as C4. The capacity retention rate after 60 days of storage at 60°C = C4 / C3, and the battery thickness expansion rate = (D2-D1) / D1. This test can provide feedback on the high-temperature storage performance of the battery. The higher the capacity retention rate and the smaller the battery thickness expansion rate, the better the high-temperature storage performance of the battery under this embodiment.

[0188] The test results are shown in Table 2.

[0189] Table 2

[0190]

[0191]

[0192] It can be seen from the data in Table 2 that, compared with Comparative Examples 1-4, the lithium batteries provided by Examples 1-14 of the present invention have better cycle performance, better rate performance (fast charging capability), and better high temperature storage performance.

[0193] Specifically, through the comparison between Example 1 and Comparative Examples 1-4, it can be seen that in the secondary injection method of the battery, the combination of the first additive and the second additive can effectively improve the kinetic performance of the electrolyte, as well as the cycle and high-temperature storage performance. The first additive S2 and other isocyanate-containing silane compounds can remove acidic substances in the electrolyte, prevent its corrosion to the interface, inhibit the dissolution of positive electrode metal ions, and prevent its crosstalk to the negative electrode interface. At the same time, a polymer interface containing nitrogen oxides can be generated at the interface to further improve the interface stability. Adding it to the secondary injection can overcome the impact on the initial impedance and further improve the fast charging performance of the battery. The presence of fluorophosphate groups in the second additive can generate fluorine-containing and phosphorus-containing inorganic substances at the interface, which have high ion conductivity and high surface energy, can reduce the transmission impedance and charge transfer impedance of lithium ions at the interface, and at the same time play a role in inhibiting the rapid consumption of the first additive, thereby overcoming the side effect of increased impedance brought about by the first additive.

[0194] By comparing Example 2 with Example 1, it can be seen that the content of the first additive S2 is increased, the kinetic performance of the electrolyte is slightly reduced, but the cycle and high-temperature storage performance are improved, and the overall performance is better than that of Comparative Examples 1-4. By comparing Example 3 with Example 1, it can be seen that the content of the first additive S2 is reduced, the kinetic performance of the electrolyte is improved, and the high-temperature storage is slightly deteriorated, but the overall performance is better than that of Comparative Examples 1-4.

[0195] By comparing Example 4 with Example 1, it can be seen that the content of the second additive LiPO2F2 is reduced, and the high temperature storage performance of the electrolyte is slightly reduced, but the overall performance is better than that of Comparative Examples 1-4. By comparing Example 5 with Example 1, it can be seen that the content of the second additive LiPO2F2 is increased, the circulation and rate performance of the electrolyte are slightly improved, and the overall performance is better than that of Comparative Examples 1-4.

[0196] By comparing Example 6 with Example 1, it can be seen that the second additive uses LiODFP instead of LiPO2F2, the battery dynamics and cycle performance are not much different, the high-temperature storage gas production is slightly deteriorated, but the overall performance is better than that of Comparative Examples 1-4.

[0197] By comparing Example 7 with Example 1, it can be seen that the first additive is replaced by S1 instead of S2, and the performance of the battery such as dynamics and cycle performance is not much different, and the overall performance is better than that of Comparative Examples 1-4. By comparing Example 8 with Example 1, it can be seen that the first additive is replaced by S9 instead of S2, the high temperature storage performance of the battery is improved, the power performance is slightly deteriorated, and the overall performance is better than that of Comparative Examples 1-4.

[0198] By comparing Example 9 with Example 1, it can be seen that the battery kinetic performance is improved by replacing EA with MA, and the high-temperature storage performance is deteriorated, but the overall performance is better than that of Comparative Examples 1-4. By comparing Example 10 with Example 1, it can be seen that the battery cycle and high-temperature storage performance are improved by replacing EA with EP, and the overall performance is better than that of Comparative Examples 1-4.

[0199] By comparing Example 11 with Example 1, it can be seen that the battery kinetic performance is slightly deteriorated by replacing LiFSI with LiPF6, and the cycle and high-temperature storage are improved, but the overall performance is better than that of Comparative Examples 1-4. By comparing Example 12 with Example 1, it can be seen that the battery kinetic performance is improved by replacing LiPF6 with LiFSI, and the high-temperature storage is deteriorated, but the overall performance is better than that of Comparative Examples 1-4.

[0200] By comparing Example 13 with Example 1, it can be seen that when the content of the secondary injection electrolyte increases to 20%, the electrolyte performance is not much different, and the comprehensive performance is better than that of Comparative Examples 1-4. By comparing Example 14 with Example 1, it can be seen that when the content of the secondary injection electrolyte increases to 30%, the electrolyte rate and storage performance are slightly reduced, but the comprehensive performance is better than that of Comparative Examples 1-4.

[0201] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0202] The basic principle of the present invention is described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, strengths, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. must be possessed by each embodiment of the present invention. In addition, the specific details disclosed above are only for the purpose of illustration and facilitation of understanding, rather than limitation, and the above details do not limit the present invention to being implemented by adopting the above specific details.

[0203] It should be noted that the term "and / or" or " / " used in this document is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The singular forms of "a", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0204] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A, B are listed, the phrase "at least one of A, B" means only A; only B; or A and B. In another example, if items A, B, C are listed, the phrase "at least one of A, B, C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that: The electrolyte includes a first electrolyte and a second electrolyte; The first electrolyte includes a first electrolyte salt, a first organic solvent, and a second additive; The second electrolyte includes a second electrolyte salt, a second organic solvent and a first additive; wherein the first additive comprises an isocyanate group and a silane group; The second additive includes a fluorine-containing phosphate.

2. The electrolyte according to claim 1, characterized in that The first additive includes an isocyanate-containing silyl compound, and the structural formula of the isocyanate-containing silyl compound is shown in Formula I below: Among them, R1 is selected from substituted or unsubstituted C0~C4 alkyl, and R2, R3, and R4 are each independently selected from substituted or unsubstituted C1~C4 alkyl, substituted or unsubstituted C1~C4 alkoxy, substituted or unsubstituted C1~C4 isocyanate, substituted or unsubstituted C2~C4 alkenyl, substituted or unsubstituted C1~C4 haloalkyl, substituted or unsubstituted C1~C4 haloalkoxy, and substituted or unsubstituted C2~C4 haloalkenyl.

3. The electrolyte according to claim 2, characterized in that The isocyanate-containing silyl compound is selected from at least one of the compounds represented by the following structural formulas S1-S9:

4. The electrolyte according to claim 1, characterized in that The second additive includes at least one of lithium difluorophosphate, lithium tetrafluorooxalate phosphate, or lithium difluorooxalate phosphate.

5. The electrolyte according to claim 1, characterized in that Based on the total mass of the electrolyte, the mass proportion of the first additive is W1, the mass proportion of the second additive is W2, and the W1 and the W2 satisfy: 0.01%≤W2≤W1≤5%.

6. The electrolyte according to claim 1, characterized in that Based on the total mass of the electrolyte, the mass proportion of the second electrolyte is 10% to 30%; and / or, Based on the total mass of the electrolyte, the mass proportion of the first electrolyte is 70% to 90%.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The first electrolyte salt and the second electrolyte salt respectively include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluoroarsenate or lithium perchlorate; and / or, The first organic solvent and the second organic solvent include carbonate and / or carboxylate, respectively.

8. The electrolyte according to claim 7, characterized in that Based on the total mass of the electrolyte, the sum of the mass of the first organic solvent and the second organic solvent accounts for 70% to 85%; and / or, Based on the total mass of the electrolyte, the sum of the mass of the first electrolyte salt and the second electrolyte salt accounts for 6% to 23%.

9. A secondary battery injection method, characterized in that: Using the electrolyte according to any one of claims 1 to 8, the battery secondary injection method comprises: Filling the battery with a first electrolyte for the first time; Forming the battery after the first injection; filling the battery a second time with a second electrolyte; Wherein, the first electrolyte comprises a first electrolyte salt, a first organic solvent and a second additive; the second electrolyte comprises a second electrolyte salt, a second organic solvent and a first additive; The first additive comprises an isocyanate group and a silane group; and the second additive comprises a fluorine-containing phosphate.

10. A battery, characterized in that: The battery comprises a positive electrode, a negative electrode and the electrolyte according to any one of claims 1 to 8, or is prepared by the method according to claim 9.

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