A phosphite-based acid scavenger, a lithium ion battery electrolyte and a lithium ion battery

Abstract

The application provides a phosphite-based acid scavenger with a structure as shown in formula (I). When added into an electrolyte of a lithium ion battery as an acid and water scavenger, the phosphite-based acid scavenger can effectively remove water and hydrofluoric acid in the electrolyte, inhibit continuous decomposition of lithium salt and solvent in the electrolyte, inhibit high-temperature decomposition of FEC-based electrolyte, improve cycle performance and safety of the battery, participate in formation of a positive CEI film to improve stability of the interface film and promote charge transmission, thereby inhibiting dissolution of transition metals in the positive electrode and slowing down capacity attenuation of the battery. The phosphite-based acid scavenger provided by the application can not only remove water and acid in the electrolyte, but also strengthen protection of the positive electrode structure, and can effectively improve high-temperature cycle performance, long cycle performance and high-temperature storage performance of the battery.

Description

Technical Field

[0001] This invention belongs to the technical field of dehydration and deacidification agents for lithium-ion battery electrolytes, and relates to a phosphite-based deacidifying agent, a lithium-ion battery electrolyte, and a lithium-ion battery, particularly a phosphite-based dehydration and deacidification agent, a lithium-ion battery electrolyte, and a lithium-ion battery. Background Technology

[0002] Rechargeable lithium-ion batteries, with their advantages of high operating voltage, high energy density, and environmental friendliness, have become the mainstream energy storage device in the portable electronics market. While the future of lithium-ion batteries is promising, commercial lithium-ion batteries still face the problem of capacity decay during use. Currently, commercial lithium-ion battery electrolytes mainly consist of lithium hexafluorophosphate (LiPF6) and organic carbonate solvents. Lithium hexafluorophosphate has poor thermal stability and is easily hydrolyzed. Trace amounts of water in the electrolyte react with lithium hexafluorophosphate to generate HF, which damages the solid electrolyte interface film. HF dissolves the positive electrode material and destroys the active material. The addition of transition metals, especially Mn, leads to dissolution, causing rapid capacity decay in the battery.

[0003] In recent years, methods to mitigate trace water and HF in batteries have mainly focused on strictly controlling moisture content during battery production and adding functional film-forming additives. However, neither process control nor additives can completely eliminate trace water and acidity from the electrolyte. Therefore, introducing electrolyte dehydrating and deacidifying agents to react with trace water and acid in the battery and inhibit their destructive effects on the battery is of great significance. Existing technologies include adding oxides of metals such as aluminum, magnesium, and zinc to the electrolyte to remove HF. However, this method is slow and easily introduces metal ion impurities, which negatively impact the battery. Other solutions exist, such as patent CN102437372, which reports a nitrogen-silane derivative electrolyte deacidifying agent. This agent reacts with hydrogen ions in the electrolyte to generate stable compounds, effectively controlling electrolyte acidity and improving the cycle life and high-temperature storage performance of lithium-ion batteries. Although this nitrogen-silane derivative can reduce the acidity of the electrolyte to some extent, it remains to be investigated whether the product after its combination with H protons will affect the battery performance. Moreover, this additive cannot form a film on the electrode surface, and film-forming additives are needed to enhance the stability of the film and suppress the damage of HF to the battery material structure.

[0004] Therefore, how to develop a more suitable dehydration and deacidification additive to solve the above-mentioned problems of existing dehydration and deacidification agents, and remove trace amounts of water and acid from the electrolyte without causing adverse effects on the battery, so as to enable the battery to perform better, has become one of the problems that many leading researchers and scientific research companies in the industry urgently need to solve. Summary of the Invention

[0005] In view of this, the present invention provides a phosphite-based deacidifying agent, a lithium-ion battery electrolyte, and a lithium-ion battery, particularly a phosphite-based dehydrating and deacidifying agent. The phosphite-based deacidifying agent provided by the present invention, as an electrolyte dehydrating and deacidifying additive, can effectively remove water and hydrofluoric acid from the electrolyte, inhibit the continuous decomposition of lithium salts and solvents in the electrolyte, and form a highly uniform and thin SEI film on the positive electrode surface by reacting with HF to generate ester compounds, effectively promoting charge transport.

[0006] This invention provides a phosphite-based acid remover having a structure as shown in formula (I):

[0007]

[0008] R1 and R2 are each independently selected from cyano, isocyanate, trimethylsilyl, trifluoromethylsilyl, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C6-C26 aryl, and substituted or unsubstituted C6-C22 aromatic heteroyl.

[0009] Preferably, the substituents include halogens;

[0010] The phosphite-based deacidifying agent is a phosphite-based deacidifying agent containing a cyano group;

[0011] The phosphite-based deacidifying agent is used in combination with fluoroethylene carbonate;

[0012] The phosphite-based deacidifying agent is specifically a phosphite-based dehydrating and deacidifying agent.

[0013] Preferably, the additive has a structure as shown in any one of formulas (1) to (6):

[0014]

[0015]

[0016] Preferably, the phosphite-based deacidifying agent is a deacidifying agent for lithium-ion batteries;

[0017] The lithium-ion battery specifically includes a lithium-ion battery electrolyte;

[0018] The acid remover has a mass percentage of 0.5% to 2% in the electrolyte;

[0019] The phosphite-based deacidifying agent inhibits the high-temperature ring-opening reaction of fluoroethylene carbonate and / or participates in the formation of the SEI film in lithium-ion batteries.

[0020] This invention provides a lithium-ion battery electrolyte, wherein the electrolyte comprises a phosphite-based deacidifying agent as described in any one of the above technical solutions.

[0021] Preferably, the electrolyte further includes lithium salt, non-aqueous organic solvent and film-forming additive;

[0022] The lithium salt includes one or more of LiPF6, LiBF4, LiClO4, and LiBOB;

[0023] The non-aqueous organic solvents include cyclic carbonate solvents and linear carbonate solvents.

[0024] Preferably, the cyclic carbonate solvent includes ethylene carbonate and / or propylene carbonate;

[0025] The linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and ethyl propyl carbonate.

[0026] The film-forming additive includes fluoroethylene carbonate.

[0027] Preferably, the cyclic carbonate solvent has a mass percentage of 15% to 30% in the electrolyte;

[0028] The linear carbonate solvent has a mass percentage of 40% to 70% in the electrolyte.

[0029] Preferably, the film-forming additive includes one or more of vinylene carbonate, fluorovinyl carbonate, 1,3-propanesulfonate lactone, tris(trimethylsilyl)phosphate, and tris(trimethylsilyl)borate.

[0030] The film-forming additive has a mass percentage content of 0.5% to 5% in the electrolyte;

[0031] The phosphite-based deacidifying agent has a mass percentage of 0.5% to 2% in the electrolyte.

[0032] The present invention also provides a lithium-ion battery, comprising a positive electrode, a negative electrode and an electrolyte;

[0033] The electrolyte includes any of the phosphite-based deacidifying agents described in any of the above technical solutions, or any of the lithium-ion battery electrolytes described in any of the above technical solutions.

[0034] This invention provides a phosphite-based deacidifying agent with the structure shown in formula (I). Compared with the prior art, this invention specifically designs a phosphite-based deacidifying agent with a specific structure and composition. When added to the electrolyte of a lithium-ion battery as a deacidifying and dehydrating agent, it can effectively remove water and hydrofluoric acid from the electrolyte, inhibit the continuous decomposition of lithium salts and solvents in the electrolyte, and form a highly uniform and thin SEI film on the positive electrode surface by reacting with HF to generate ester compounds, effectively promoting charge transport. Moreover, this additive contains -CN bonds, which can coordinate with metal ions, weakening the oxidation effect of positive electrode metal ions on the electrolyte, inhibiting the dissolution of positive electrode transition metals, and slowing down battery capacity decay. In addition, -CN can react with water under the action of acid to form amides, which have a certain deacidifying and dehydrating effect. The generated amides are themselves non-electrochemically active substances, which can avoid the adverse effects of adding strong alkalis to the electrolyte.

[0035] Furthermore, the phosphite-based acid remover provided by this invention exhibits a specific synergistic effect. Fluoroethylene carbonate (FEC) is a major solvent in explosion-proof electrolytes for high-rate power lithium-ion batteries and a key material specifically developed for power lithium batteries. FEC can increase the flash point of the electrolyte, improving the battery's high-temperature safety. Simultaneously, FEC forms a more effective SEI film on the battery electrode surface, reducing battery impedance and significantly improving the battery's charge-discharge performance at high rates. Lithium batteries with added FEC are more suitable for hybrid vehicles and hold promise for energy storage in solar and wind power fields, showing a broad market prospect. However, FEC can lead to a decrease in the battery's high-temperature performance. This invention suggests that this is mainly because FEC decomposes under the action of Lewis acids (PF5) at high temperatures, producing HF, which causes the dissolution of the transition metal elements in the positive electrode. Meanwhile, FEC makes the electrolyte more sensitive to moisture. This is mainly because trace amounts of moisture can cause LiPF6 to decompose, producing HF, PF5, etc., which in turn triggers the ring-opening reaction of FEC. This process is more pronounced at high temperatures. Therefore, adding components that can remove moisture to FEC-containing electrolytes can further improve the performance of lithium-ion batteries using FEC, and is expected to further expand the application market of FEC. The phosphite-based deacidifying agent provided in this invention can inhibit the high-temperature decomposition of FEC-based electrolytes, suppress battery gas production, and improve battery cycle performance and safety.

[0036] The phosphite-based deacidifying agent provided by this invention can effectively control electrolyte acidity, inhibit the ring-opening reaction of FEC at high temperatures, suppress the decomposition of FEC-based electrolytes at high temperatures, suppress battery gas production, and improve the high-temperature cycle performance and safety performance of the battery. Simultaneously, this additive can preferentially participate in SEI film formation through oxidation, and its -CN functional group, combined with the complexation effect of high-valence metal ions in the positive electrode active material, also plays a role in inhibiting the dissolution of transition metals and protecting the positive electrode structure. The phosphite-based deacidifying agent provided by this invention not only removes moisture and acid from the electrolyte but also strengthens the protection of the positive electrode structure, effectively improving the battery's high-temperature cycle performance, long-cycle performance, and high-temperature storage performance.

[0037] Experimental results show that adding the acid-removing additive provided by this invention to the electrolyte can, to a certain extent, improve the acidity growth of the electrolyte during high-temperature storage and improve the battery's high-temperature cycle capacity retention rate. Attached Figure Description

[0038] Figure 1 LSV curves of the electrolytes in Example 1 and Comparative Example 1 provided for this invention;

[0039] Figure 2 The 45°C high-temperature cycling performance of Example 2 and Comparative Example 2 provided by the present invention. Detailed Implementation

[0040] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0042] There are no particular restrictions on the purity of any of the raw materials used in this invention. However, it is preferred to use analytical grade or conventional purity in the field of lithium-ion battery electrolyte additives.

[0043] This invention provides a phosphite-based acid remover having a structure as shown in formula (I):

[0044]

[0045] R1 and R2 are each independently selected from cyano, isocyanate, trimethylsilyl, trifluoromethylsilyl, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C6-C26 aryl, and substituted or unsubstituted C6-C22 aromatic heteroyl.

[0046] In this invention, the C1-C12 alkyl group can also be a C3-C10 alkyl group, or a C5-C8 alkyl group. The C6-C26 aryl group can also be a C10-C22 aryl group, or a C14-C18 aryl group. The C6-C22 aromatic heterol group can also be a C9-C19 aromatic heterol group, or a C12-C16 aryl group.

[0047] In this invention, the substituents preferably include halogens.

[0048] In this invention, the additive preferably has a structure as shown in any one of formulas (1) to (6):

[0049]

[0050] In this invention, the phosphite-based deacidifying agent is preferably a phosphite-based deacidifying agent containing a cyano group.

[0051] In this invention, the phosphite-based deacidifying agent is specifically a phosphite-based dehydrating and deacidifying agent.

[0052] In this invention, the phosphite-based deacidifying agent is preferably a deacidifying agent for lithium-ion batteries. Specifically, the lithium-ion battery preferably includes a lithium-ion battery electrolyte. That is, the phosphite-based deacidifying agent is preferably a deacidifying agent for lithium-ion battery electrolytes.

[0053] In this invention, the mass percentage of the deacidifying agent in the electrolyte is preferably 0.5% to 2%, more preferably 0.8% to 1.7%, and even more preferably 1.1% to 1.4%.

[0054] In this invention, the lithium-ion battery electrolyte preferably comprises a lithium-ion battery electrolyte containing fluoroethylene carbonate (FEC). The phosphite-based deacidifying agent is used in conjunction with the fluoroethylene carbonate.

[0055] In this invention, the phosphite-based deacidifying agent in lithium-ion batteries preferably inhibits the high-temperature ring-opening reaction of FEC and / or participates in the formation of SEI film, more preferably inhibits the high-temperature ring-opening reaction of FEC and participates in the formation of SEI film.

[0056] This invention aims to complete and refine the overall technical solution, better ensure the structure of phosphite-based deacidifying agents, improve the application performance of phosphite-based deacidifying agents, better inhibit FEC decomposition, and improve the high-temperature cycle performance, long-cycle performance, and high-temperature storage performance of subsequent lithium-ion batteries. The aforementioned phosphite-based dehydration and deacidification agent specifically includes the following structure:

[0057] An electrolyte deacidifying agent, wherein the deacidifying agent is a phosphite containing a cyano group.

[0058] The cyanophosphite is selected from compounds having the formula (I):

[0059]

[0060] R1 and R2 are selected from cyano, isocyanate, trimethylsilyl, trifluoromethylsilyl, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C6-C26 aryl, substituted or unsubstituted C6-C22 aromatic heteroyl, and the substituent is halogen.

[0061] Specifically, the structural formula of the additive is shown in the figure below. The acid-removing additive in this invention is selected from at least one of the following compounds:

[0062]

[0063] This invention provides a lithium-ion battery electrolyte, wherein the electrolyte comprises a phosphite-based deacidifying agent as described in any one of the above technical solutions.

[0064] In this invention, the electrolyte preferably includes lithium salt, non-aqueous organic solvent and film-forming additive.

[0065] In this invention, the lithium salt preferably includes one or more of LiPF6, LiBF4, LiClO4 and LiBOB, and more preferably LiPF6, LiBF4, LiClO4 or LiBOB.

[0066] In this invention, the non-aqueous organic solvent preferably includes cyclic carbonate solvents and linear carbonate solvents.

[0067] In this invention, the film-forming additive preferably includes fluoroethylene carbonate.

[0068] In this invention, the cyclic carbonate solvent preferably includes ethylene carbonate and / or propylene carbonate, more preferably ethylene carbonate or propylene carbonate.

[0069] In this invention, the linear carbonate solvent preferably includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and ethyl propyl carbonate, more preferably dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, or ethyl propyl carbonate.

[0070] In this invention, the mass percentage of the cyclic carbonate solvent in the electrolyte is preferably 15% to 30%, more preferably 18% to 27%, and even more preferably 21% to 24%.

[0071] In this invention, the linear carbonate solvent has a preferred mass percentage of 40% to 70% in the electrolyte, more preferably 45% to 65%, and even more preferably 50% to 60%.

[0072] In this invention, the film-forming additive preferably includes one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, tris(trimethylsilyl)phosphate, and tris(trimethylsilyl)borate, more preferably vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, tris(trimethylsilyl)phosphate, or tris(trimethylsilyl)borate, and even more preferably contains at least fluoroethylene carbonate.

[0073] In this invention, the mass percentage of the film-forming additive in the electrolyte is preferably 0.5% to 5%, more preferably 1% to 4%, and even more preferably 2% to 3%.

[0074] In this invention, the mass percentage of the phosphite-based deacidifying agent in the electrolyte is preferably 0.5% to 2%, more preferably 0.8% to 1.7%, and even more preferably 1.1% to 1.4%.

[0075] This invention provides a complete and refined overall technical solution to better improve the application performance of phosphite-based deacidifying agents, better inhibit FEC decomposition, and improve the high-temperature cycle performance, long-cycle performance, and high-temperature storage performance of subsequent lithium-ion batteries. The aforementioned lithium-ion battery electrolyte specifically includes the following:

[0076] A lithium-ion battery electrolyte, the lithium-ion battery electrolyte comprising lithium salt, non-aqueous organic solvent, acid remover, and film-forming additive.

[0077] Specifically, the lithium salt is selected from one or more of LiPF6, LiBF4, LiClO4, and LiBOB.

[0078] Specifically, the electrolyte solvent includes cyclic carbonate solvents and linear carbonate solvents.

[0079] Specifically, the cyclic carbonate solvent includes any one or a combination of two of ethylene carbonate or propylene carbonate.

[0080] Specifically, the mass percentage of cyclic carbonate solvent in the non-aqueous electrolyte of the lithium-ion battery is 15% to 30%.

[0081] Specifically, the linear carbonate solvent includes any one or a combination of at least two of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, or ethyl propyl carbonate.

[0082] Specifically, the linear carbonate solvent in the non-aqueous electrolyte of the lithium-ion battery has a mass percentage content of 40% to 70%.

[0083] Specifically, the film-forming additive is one or more of the following: vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, tris(trimethylsilyl)phosphate, and tris(trimethylsilyl)borate.

[0084] Specifically, the amount of the film-forming additive added is 0.5% to 5% by mass in the electrolyte.

[0085] Specifically, the deacidifying agent has a mass percentage of 0.5% to 2% in the electrolyte. This invention has found that controlling the concentration within this preferred range helps to achieve the optimal effect of the deacidifying agent.

[0086] The present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode and an electrolyte.

[0087] The electrolyte includes any of the phosphite-based deacidifying agents described in any of the above technical solutions, or any of the lithium-ion battery electrolytes described in any of the above technical solutions.

[0088] In this invention, the lithium-ion battery preferably includes a power lithium-ion battery, and more preferably a high-rate power lithium-ion battery.

[0089] In this invention, the electrolyte preferably includes an explosion-proof electrolyte.

[0090] This invention also provides the application of the phosphite-based deacidifying agents described in any one of the above technical solutions in lithium-ion batteries. More preferably, their application in lithium-ion battery electrolytes is preferred.

[0091] The present invention provides a phosphite-based dehydrating and deacidifying agent, a lithium-ion battery electrolyte, a lithium-ion battery, and its application. This invention specifically designs a phosphite-based dehydrating agent with a specific structure and composition. When added to the electrolyte of a lithium-ion battery as a dehydrating and deacidifying agent, it effectively removes water and hydrofluoric acid from the electrolyte, inhibits the continuous decomposition of lithium salts and solvents in the electrolyte, and forms a highly uniform and thin SEI film on the positive electrode surface by reacting with HF to generate ester compounds, effectively promoting charge transport. Furthermore, this additive contains -CN bonds, which can coordinate with metal ions, weakening the oxidation effect of positive electrode metal ions on the electrolyte, inhibiting the dissolution of positive electrode transition metals, and slowing down battery capacity decay. In addition, -CN can react with water under acidic conditions to form amides, which have a certain dehydrating and deacidifying effect. The generated amides are themselves non-electrochemically active substances, avoiding the adverse effects of adding strong alkalis to the electrolyte. Furthermore, the phosphite-based deacidifying agent provided by this invention can, through specific synergistic effects, inhibit the high-temperature decomposition of FEC-based electrolytes, suppress battery gas production, and improve battery cycle performance and safety.

[0092] The phosphite-based deacidifying agent provided by this invention can effectively control electrolyte acidity, inhibit the ring-opening reaction of FEC at high temperatures, suppress the decomposition of FEC-based electrolytes at high temperatures, suppress battery gas production, and improve the high-temperature cycle performance and safety performance of the battery. Simultaneously, this additive can preferentially participate in SEI film formation through oxidation, and its -CN functional group, combined with the complexation effect with high-valence metal ions in the positive electrode active material, also plays a role in inhibiting the dissolution of transition metals and protecting the positive electrode structure. The phosphite-based deacidifying agent provided by this invention not only removes moisture and acid from the electrolyte but also strengthens the protection of the positive electrode structure, effectively improving the long-cycle performance and high-temperature storage performance of lithium-ion batteries.

[0093] Experimental results show that adding the acid-removing additive provided by this invention to the electrolyte can, to a certain extent, improve the acidity growth of the electrolyte during high-temperature storage and improve the battery's high-temperature cycle capacity retention rate.

[0094] To further illustrate the present invention, the following detailed description of a phosphite-based deacidifying agent, a lithium-ion battery electrolyte, and a lithium-ion battery provided by the present invention is provided in conjunction with embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are given only to further illustrate the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0095] All reagents used in the following embodiments of the present invention are commercially available products.

[0096] Examples and Comparative Examples

[0097] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 02. The conductive agent acetylene black (SP) and the binder polyvinylidene fluoride (PVDF) are dissolved in NMP in a ratio of 96:2:2. After homogenization, the mixture is coated on aluminum foil, dried, rolled, and cut into sheets to prepare the positive electrode sheet.

[0098] Preparation of negative electrode sheet: The negative electrode active material artificial graphite, the conductive agent acetylene black (SP), the binder styrene-butadiene latex (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water in a ratio of 95:2:1.5:1.5. After homogenization, the mixture is coated onto copper foil, dried, rolled, and cut into sheets to prepare the negative electrode sheet.

[0099] In an argon-filled glove box (moisture content <10ppm, oxygen content <1ppm), the electrolyte solvents of the examples and comparative examples were mixed in a certain proportion, and then a certain amount of lithium salt and additives were added in sequence and stirred evenly (electrolyte formula is shown in Table 1). After passing the tests for moisture and free acid, the electrolyte was obtained.

[0100] See Table 1, which shows the electrolyte formulations in the embodiments and comparative examples of the present invention.

[0101] Table 1

[0102]

[0103]

[0104] The positive and negative electrode sheets prepared above were used to fabricate pouch cells for testing. Using the Xinwei Battery Testing System, the cells were charged at a constant current of 1C to 4.5V in a 45℃ constant temperature chamber, followed by constant voltage charging until the charging current reached 0.05C. Charging was then stopped, and the cells were discharged at a constant current of 1C until the cutoff voltage of 3V. This cycle charge-discharge test was repeated.

[0105] See Table 2, which shows the acidity and color of the electrolytes in the embodiments and comparative examples provided by the present invention at a high temperature of 45°C.

[0106] Table 2

[0107] Comparative Example 1 30 352 Comparative Example 2 42 395 Example 2 19 202 Example 3 26 310 Example 4 33 246 Example 5 30 277

[0108] See Figure 1 , Figure 1 The LSV curves of the electrolyte in Example 1 and Comparative Example 1 provided for this invention.

[0109] See Figure 2 , Figure 2 The 45°C high-temperature cycling performance of Example 2 and Comparative Example 2 provided by the present invention.

[0110] It can be seen that the cyanophosphite provided by this invention can improve the high-temperature cycling performance of the electrolyte because it can effectively remove hydrofluoric acid and water, and the cyano structure can complex transition metals. Figure 1 The LSV curves of the electrolyte show that phosphite participates in the formation of the positive electrode CEI film, improving interfacial film stability. This triple effect inhibits the damage of hydrofluoric acid to the positive electrode material and improves battery cycle performance. Furthermore, this acid-removing additive can inhibit the high-temperature decomposition of FEC-based electrolytes, suppress battery gas generation, and improve battery cycle performance and safety.

[0111] The foregoing has provided a detailed description of a phosphite-based dehydrating and deacidifying agent, a lithium-ion battery electrolyte, and a lithium-ion battery provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the wording of the claims, or if they include equivalent structural elements that are not substantially different from the wording of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. Application of phosphite-based acid removers in lithium-ion batteries; The acid-removing agent has a structure as shown in formula (I): （I）； in, R1 and R2 are each independently selected from cyano, isocyanate, trimethylsilyl, trifluoromethylsilyl, substituted or unsubstituted C1~C12 alkyl, substituted or unsubstituted C6~C26 aryl, substituted or unsubstituted C6~C22 aromatic heterol.

2. The application according to claim 1, characterized in that, The substituents include halogens; The phosphite-based deacidifying agent is a phosphite-based deacidifying agent containing a cyano group; The phosphite-based deacidifying agent is used in combination with fluoroethylene carbonate; The phosphite-based deacidifying agent is specifically a phosphite-based dehydrating and deacidifying agent.

3. The application according to claim 1, characterized in that, The phosphite-based deacidifying agent has a structure as shown in any one of formulas (1) to (6): （1） （2）； （3） （4）； （5） （6）。 4. The application according to claim 3, characterized in that, The lithium-ion battery specifically includes a lithium-ion battery electrolyte; The acid remover has a mass percentage of 0.5% to 2% in the electrolyte; The phosphite-based deacidifying agent inhibits the high-temperature ring-opening reaction of fluoroethylene carbonate and / or participates in the formation of the SEI film in lithium-ion batteries.

5. The application according to claim 4, characterized in that, The electrolyte also includes lithium salt, non-aqueous organic solvent, and film-forming additives.

6. The application according to claim 5, characterized in that, The lithium salt includes one or more of LiPF6, LiBF4, LiClO4, and LiBOB; The non-aqueous organic solvents include cyclic carbonate solvents and linear carbonate solvents.

7. The application according to claim 6, characterized in that, The cyclic carbonate solvent includes ethylene carbonate and / or propylene carbonate; The linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and ethyl propyl carbonate. The film-forming additive includes fluoroethylene carbonate.

8. The application according to claim 7, characterized in that, The cyclic carbonate solvent has a mass percentage content of 15% to 30% in the electrolyte; The linear carbonate solvent has a mass percentage of 40% to 70% in the electrolyte.

9. The application according to claim 5, characterized in that, The film-forming additives also include one or more of vinylene carbonate, 1,3-propanesulfonate lactone, tris(trimethylsilyl)phosphate, and tris(trimethylsilyl)borate.

10. The application according to claim 5, characterized in that, The film-forming additive has a mass percentage content of 0.5% to 5% in the electrolyte.

Images