Electrolyte, battery secondary injection method and battery

Abstract

The present invention relates to the field of battery technology, and in particular to an electrolyte, a secondary battery injection method, and a battery. The provided 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 a fluorine-containing phosphate. The electrolyte of the present invention can be applied to a secondary battery injection method, with the first electrolyte being used for primary injection and the second electrolyte being used for secondary injection. The present invention can take into account both the fast charging and interface stability of the electrolyte, and is conducive to simultaneously improving the fast charging performance, cycle stability, and high-temperature performance of the electrolyte, enabling the electrolyte to exhibit 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 for 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 the lithium-ion battery. 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 the lithium-ion battery. It is also one of the important factors limiting the fast charging performance of the battery.

[0003] Currently, related technologies primarily use low-viscosity, low-freezing-point, and low-boiling-point solvents to improve the fast-charging performance of electrolytes. However, these solvents have poor chemical and electrochemical stability and poor interfacial compatibility with graphite anodes, negatively impacting the battery's high-temperature performance and cycle life, resulting in poor overall battery performance. Therefore, the key to solving these problems is improving the fast-charging performance of electrolytes while not compromising their cycle stability or high-temperature performance. Summary of the Invention

[0004] In view of this, the present invention aims to solve, at least to some extent, one of the technical problems in the related art. To this end, the present invention provides an electrolyte, a secondary battery injection method, and a battery that can balance fast charging and interface stability of the electrolyte. In other words, it is conducive to balancing fast charging performance, cycle stability, and high-temperature performance of the electrolyte, enabling the electrolyte to exhibit excellent overall 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 structural formula of the isocyanate-containing silyl compound is shown in Formula I below:

[0013]

[0014] Wherein, 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 tetrafluorooxalophosphate, or lithium difluorooxalophosphate.

[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 proportion 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 each 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 respectively comprise carbonate and / or carboxylate.

[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 filling method, using the aforementioned electrolyte, the battery secondary liquid filling method comprising:

[0030] Filling the battery with the 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 using the above method.

[0036] The implementation of 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, 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 side effects such as corrosion of the interface, while 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 fluorophosphate groups 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 suppress the film-forming consumption of the first additive over the entire life cycle of the battery, alleviate the side effect of the increased impedance brought by the first additive, and suppress the rapid 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 invention. DETAILED DESCRIPTION

[0039] The present application will be further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application.

[0040] The endpoints of the ranges and any values ​​disclosed herein 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 endpoints of each range, the endpoints 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 to be specifically disclosed herein.

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0042] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are 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] Currently, 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 electrolyte's ability to transport lithium ions and enhance the electrolyte's fast-charging performance. However, such solvents often have poor chemical and electrochemical stability and poor compatibility with the negative electrode interface, and are unable to form a stable SEI. This leads to the continuous occurrence of side reactions of the electrolyte at the negative electrode interface, which impairs the battery's cycling stability and high-temperature performance. Functional additives, as one of the main components of battery electrolytes, play a key role in ensuring the good electrochemical performance of the battery. Lithium-ion batteries suffer from problems such as poor compatibility between the electrolyte and the graphite negative electrode interface, which leads to problems such as the inability to balance fast-charging performance, cycling performance, or high-temperature performance. These problems can be improved by selecting a suitable combination of electrolyte functional additives or using different injection methods. Therefore, how to improve the electrolyte's fast-charging performance 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. The following is a detailed description of this application.

[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 primarily composed of a first electrolyte salt, a first organic solvent, and a second additive, and the second electrolyte is primarily composed of a second electrolyte salt, a second organic solvent, and the first additive. That is, the first electrolyte may contain the second additive, while the second electrolyte contains 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 and second electrolytes, the first and second electrolyte salts may be lithium salts that participate in the electrochemical reaction, and the first and second organic solvents may be used to dissolve the first and second electrolyte salts. Particularly notable is the use of the composite functional additive solution and secondary injection method of the present invention, which significantly improves the electrolyte's kinetic performance under fast-charging conditions while ensuring 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 fast charging, long cycle and high temperature performance cannot be taken into account. Among them, a compound containing an isocyanate group and a silane group is used as the first additive. It 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 corrosion of the interface, but also participate in the formation of the interface film and improve the interface stability. At the same time, a 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. It has high ion conductivity and high surface energy, which 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 the interface stability, the inventors of the present application have discovered through research that they have 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] Therefore, the provided electrolyte can be used for secondary filling of the battery. Secondary filling means performing two electrolyte filling operations on the battery, and performing a formation operation during the two filling processes. The first filling can be performed using the first electrolyte, and the second filling can be performed using the second electrolyte. In other words, the electrolyte includes the first electrolyte for the first filling and the second electrolyte for the second filling.

[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, the second electrolyte containing the first additive is used for injection during the secondary injection, which 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. These substances have high ion conductivity and high surface energy, which 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 throughout the battery life cycle. Therefore, the secondary injection of the present application, combined with the first and second additives, 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 this application has a simple formula and is easy to prepare. When used in secondary batteries (such as lithium-ion batteries), the electrolyte 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 Formula I below:

[0058]

[0059] Wherein, 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 this application, the term "substituted" refers to the replacement of at least one hydrogen atom of a compound or chemical moiety with another chemical moiety. Among them, R1, R2, R3, and R4, the substituents used to replace alkyl, alkoxy, isocyanate, alkenyl, haloalkyl, haloalkoxy, haloalkenyl, etc., can be independently selected from hydroxyl, thiol, amino, cyano, nitro, aldehyde, alkynyl, aryl, heteroaryl, etc., and this 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] Illustratively, the isocyanate-containing silyl compound is selected from at least one of the compounds represented by the following structural formulas S1-S9:

[0063]

[0064] Preferably, the isocyanate-containing 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 exemplify several isocyanate-containing silyl compounds, but the present application is not limited thereto. When the above formula I is satisfied, there are more options for isocyanate-containing silyl compounds, 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 tetrafluorooxalophosphate (LiOTFP), lithium difluorooxalophosphate (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 overall performance of the lithium battery. In practical applications, the first additive and the second additive can 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 shortcomings, thereby achieving a better overall effect. Using them in the electrolyte of secondary batteries can further enable the battery to take into account better cycle performance, fast charging performance and high temperature performance, thereby enabling the battery to obtain better overall performance.

[0072] In some embodiments, the second additive accounts for 0.01% to 10% by weight of the first electrolyte. As an example, the second additive accounts for 0.01%, 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 5%, 6%, 8%, 10% by weight of the first electrolyte, or a range consisting of any two of the foregoing values.

[0073] By regulating the concentration of the second additive within the above range, fluorine- and phosphorus-containing inorganic substances can be generated at the interface. Utilizing their 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 can be suppressed throughout the battery's life cycle. Furthermore, by controlling the mass ratio 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, cycling performance, and high-temperature performance, achieving better overall performance.

[0074] In some embodiments, the first additive accounts for 0.01% to 15% by weight of the second electrolyte. For example, the first additive accounts for 0.01%, 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 5%, 6%, 8%, 10%, 12%, 13%, 14%, 15% by weight of the second electrolyte, or a range consisting of any two of the foregoing 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 achieve better improvement effects 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.

[0076] In some embodiments, the second electrolyte accounts for 10% to 30% of the total mass of the electrolyte. 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. For example, the second electrolyte can account for 10%, 15%, 20%, 25%, 30%, or a range consisting of any two of the foregoing values.

[0077] In some embodiments, the mass proportion of the first electrolyte is 70% to 90% of the total mass of the electrolyte. That is, the amount of electrolyte injected in a single 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 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 1 g / Ah, 1.5 g / Ah, 2 g / Ah, 2.5 g / Ah, 3 g / Ah, 3.5 g / Ah, 4 g / Ah, 5 g / 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 different types of additives. The first electrolyte and the second electrolyte must adjust and change the types and components of their additives, and the electrolyte salts such as lithium salts and organic solvents in the first electrolyte and the second electrolyte can be the same, or 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 or a combination of at least two 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). For the sake of brevity, the combinations within the above range are no longer 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 or a combination of at least two 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). For the sake of brevity, the combinations within the above range are no longer listed one by one.

[0083] In the present application, the first electrolyte lithium salt and the second electrolyte salt can be of the same type. Furthermore, the present application is not limited to these lithium salts and may also utilize other conventional or novel materials that can be used as lithium salts in battery electrolytes. These lithium salts may be used singly or in combination of two or more.

[0084] In some embodiments, the sum of the mass of the first electrolyte salt and the second electrolyte salt accounts for 6% to 23% of the total mass of the electrolyte, 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 a range consisting of 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 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 each include a carbonate and / or a carboxylate. That is, the first organic solvent may include a carbonate, a carboxylate, or both; and the second organic solvent may include a carbonate, a carboxylate, or both.

[0088] Preferably, the first organic solvent includes carbonate ester and carboxylic acid ester; and the second organic solvent includes 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 not 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 different types, preferably the same type. Furthermore, the present application is not limited to these solvents; other conventional or novel materials that can be used as solvents in battery electrolytes may also be used. These solvents may be used singly or in combination of two or more.

[0092] In some embodiments, the sum of the mass of the first organic solvent and the second organic solvent accounts for 70% to 85% of the total mass of the electrolyte. For example, the sum of the mass of the first organic solvent and the second organic solvent can account for 70%, 72%, 75%, 78%, 80%, 82%, 85%, or a range consisting of any two of the foregoing values.

[0093] In the present application, the mass of the non-aqueous solvent (organic solvent, ie, 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 0.70g to 0.85g of solvent.

[0094] In this way, lithium-ion batteries can have good fast charging performance, cycle performance and high-temperature performance, and achieve 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 temperature, 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 at 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 formation impedance to a certain extent. In addition, 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 can inhibit the film formation consumption of the first additive throughout the life cycle of the battery, while overcoming the side effect of increased impedance brought about by the first additive, and further improving 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 filling method, using the electrolyte described in any of the above embodiments, the battery secondary filling method comprising:

[0098] Filling the battery with the 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 the 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 "battery secondary liquid filling method" and the aforementioned "electrolyte" are based on the same inventive concept. All the features and advantages described above for the "electrolyte" are also applicable to the "battery secondary liquid filling method" and will not be repeated 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, sealed, and allowed to stand for a period of time (such as 24 hours) before 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 second formation is performed again after sealing.

[0104] It should be noted 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 the above-mentioned electrolyte, or is prepared using the above-mentioned 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 a positive electrode active material such as a lithium compound, and the negative electrode may include an active material such as a graphite-based carbon material. The battery structure is not particularly limited and can employ button-type batteries, cylindrical batteries, prismatic batteries, pouch cells, and the like with single- or multi-layer separators. The battery exhibits strong stability, good cycling performance, and a 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 or polypropylene, fiber, or glass fiber.

[0109] Since the battery provided by 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. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents, materials, or instruments used that do not specify the manufacturer are all conventional products that can be purchased 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, 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 a blank electrolyte and stirred uniformly to produce a first electrolyte. The first additive, an isocyanate-containing silyl compound (compound shown as S2), is mixed with the blank electrolyte and stirred uniformly to produce a 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 prepare the positive electrode slurry. Then, the slurry was evenly coated on the aluminum foil current collector (thickness of 12 μm), and then transferred to a 120 ° C oven for 4 hours. After that, it was cold pressed (compacted density of 2.5 g / cm 3 ), 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 a copper current collector (thickness of 8 μm), and then transferred to a 120 ° C oven for 4 hours. After that, it was cold pressed (compacted density of 1.6 g / cm 3 ), 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 tabs, and place the bare cell in the outer packaging in preparation for a liquid injection. Add the first electrolyte to the battery, seal it, and perform the first formation. Use a current of 0.1C to charge and discharge once. After the first formation is completed, use the second electrolyte to perform a second injection on the battery after the first formation. After sealing, perform high-temperature aging at 45°C for 24 hours, and then use a current of 0.33C to charge and discharge once to obtain a lithium-ion battery. 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 during the preparation of the electrolyte, lithium difluorooxalophosphate (LiODFP) is used as the second additive.

[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 instead of 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] Example 11

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

[0163] That is, the electrolyte of Comparative Example 1 includes a non-aqueous organic solvent and a lithium salt. 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:

[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:

[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:

[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, 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, the isocyanate silyl compound (the compound shown as S2), and the blank electrolyte are mixed and stirred evenly to prepare an electrolyte.

[0176] Among them, based on 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 simply illustrate 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 testing methods are as follows:

[0185] (1) Rate discharge performance test: At 25°C, the battery 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, and then charged to a current of 0.05C at a constant voltage, with the discharge capacity recorded as C1. Then, they were discharged to 2.0V at a constant current of 5C, with the discharge capacity recorded as C2. The ratio of the 5C discharge capacity to the 1 / 3C discharge capacity is the rate discharge capacity retention rate, i.e., the rate discharge capacity retention rate = C2 / C1. This test result 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 to 2.0V at a constant current of 1C 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 (%) after 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 cycle performance of the battery 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 a constant current of 1C to 2.0V, then charged at a constant current of 1C to 3.75V, then charged at a constant voltage to a current of 0.05C, and then discharged at a constant current of 1C to 2.0V. The discharge capacity was recorded as C3, and the battery thickness was recorded as D1. The cells were then charged at a constant current of 1C to 3.75V, and then charged at a constant voltage to a current of 0.05C. The battery cell was placed in a 60°C oven for 30 days. The thickness of the battery tested in the oven was recorded as D2. Then it was placed at room temperature and first discharged to 2.0V at a constant current of 1C, then charged to 3.75V at a constant current of 1C, then charged at a constant voltage to a current of 0.05C, and then discharged to 2.0V at a constant current of 1C. 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, by comparing Example 1 with Comparative Examples 1-4, it can be seen that in the secondary battery injection method, 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 their corrosion to the interface, inhibit the dissolution of positive electrode metal ions, and prevent their crosstalk on 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 effect 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] Comparing Example 2 with Example 1 shows that increasing the content of the first additive S2 slightly reduces the electrolyte kinetics, but improves the cycling and high-temperature storage performance, and the overall performance is better than that of Comparative Examples 1-4. Comparing Example 3 with Example 1 shows that decreasing the content of the first additive S2 improves the electrolyte kinetics, slightly deteriorates the high-temperature storage performance, but the overall performance is better than that of Comparative Examples 1-4.

[0195] Comparing Example 4 with Example 1 shows 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. Comparing Example 5 with Example 1 shows that the content of the second additive LiPO2F2 is increased, and the cycle 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 when the second additive is replaced by LiODFP instead of LiPO2F2, the battery kinetics and cycle performance are not much different, and the gas production during high-temperature storage is slightly deteriorated, but the overall performance is better than that of Comparative Examples 1-4.

[0197] Comparing Example 7 with Example 1 shows that when S1 replaces S2 as the first additive, the battery's kinetics and cycle performance are similar, and the overall performance is superior to Comparative Examples 1-4. Comparing Example 8 with Example 1 shows that when S9 replaces S2 as the first additive, the battery's high-temperature storage performance is improved, the power performance is slightly deteriorated, and the overall performance is superior to Comparative Examples 1-4.

[0198] Comparing Example 9 with Example 1 shows that using MA instead of EA improves the battery kinetics and deteriorates the high-temperature storage performance, but the overall performance is better than Comparative Examples 1-4. Comparing Example 10 with Example 1 shows that using EP instead of EA improves the battery cycling and high-temperature storage performance, and the overall performance is better than Comparative Examples 1-4.

[0199] Comparing Example 11 with Example 1 shows that the use of LiPF6 instead of LiFSI slightly deteriorates the battery kinetics, while improving the cycling and high-temperature storage performance, but the overall performance is better than that of Comparative Examples 1-4. Comparing Example 12 with Example 1 shows that the use of LiFSI instead of LiPF6 improves the battery kinetics, while deteriorating the high-temperature storage performance, but the overall performance is better than that of Comparative Examples 1-4.

[0200] Comparing Example 13 with Example 1 shows that when the secondary injection electrolyte content is increased to 20%, the electrolyte performance is not much different, and the overall performance is better than that of Comparative Examples 1-4. Comparing Example 14 with Example 1 shows that when the secondary injection electrolyte content is increased to 30%, the electrolyte rate and storage performance are slightly reduced, but the overall 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 principles of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in the present invention are merely illustrative and non-limiting, and should not be construed as necessarily possessed by each embodiment of the present invention. Furthermore, the specific details disclosed above are provided for illustrative purposes and to facilitate understanding, and are not intended to be limiting. These details do not necessarily limit the present invention to being implemented using these specific details.

[0203] It should be noted that the terms "and / or" or " / " used herein are merely a description of an association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone. The singular forms "a," "the," and "the" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[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 and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and 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 contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain 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 various 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 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; 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: Formula I; wherein 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; The second additive includes a fluorine-containing phosphate; 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 W2 satisfy: 0.01%≤W2≤W1≤5%.

2. The electrolyte according to claim 1, 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: 。 3. The electrolyte according to claim 1, characterized in that The second additive includes at least one of lithium difluorophosphate, lithium tetrafluorooxalophosphate, or lithium difluorooxalophosphate.

4. 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%.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The first electrolyte salt and the second electrolyte salt each 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 respectively include carbonate and / or carboxylate.

6. The electrolyte according to claim 5, 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%.

7. A secondary battery injection method, characterized in that: Using the electrolyte according to any one of claims 1 to 6, the battery secondary injection method comprises: Filling the battery with the 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.

8. 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 6, or is prepared by the method according to claim 7.

Images