Battery electrolyte additive, battery electrolyte and application thereof

Abstract

The application provides a battery electrolyte additive, a battery electrolyte and application thereof, the battery electrolyte additive is an alkyl ether alkoxysilane compound, the compound has a structure shown in formula (A), wherein R1, R2, R3 and R4 are each independently selected from one of C1-C20 alkyl, 1<=n<=20, and n is an integer. The structure contains not only Si-O ether group and C-O ether group, but also a long chain composed of Si-O ether group and C-O ether group and an alkyl chain. Under the synergistic effect of the above functional groups, the viscosity of the battery electrolyte additive can be reduced, the surface tension of the battery electrolyte can be reduced, and the wettability of the battery electrolyte can be improved. In addition, the above structure can also increase the dissociation degree of lithium salt, reduce the battery impedance, improve the kinetic performance of the battery, so that the battery electrolyte will not cause lithium precipitation due to too low temperature, and the low-temperature discharge and low-temperature cycle performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a battery electrolyte additive, a battery electrolyte and applications thereof. Background Art

[0002] Lithium-ion batteries, due to their high operating voltage, high specific energy density, long cycle life, and environmentally friendly properties, have become an indispensable and important chemical energy source in fields such as digital electronics, electric vehicles, energy storage applications, and aerospace. The electrolyte is a crucial component of lithium-ion batteries. As the electrochemical reaction medium in lithium-ion batteries, its primary function is to provide a conductive environment for the transmission and reaction of lithium ions. Its performance plays a decisive role in the battery's energy density, safety, and cycle life. The electrolyte is generally composed of a solvent, a lithium salt, and additives. The solvent serves as the main component of the electrolyte, the lithium salt serves as the conductive salt, and the additives can modify the electrolyte's conductivity, thermal stability, thermal decomposition products, and lithium ion conductivity.

[0003] The fixed size of battery cells dictates that increasing the energy density of individual cells requires designing the material system. The use of high-capacity, high-density positive and negative electrodes is currently the most effective way to increase cell energy density. However, high-density electrodes slow the absorption of electrolyte during cell filling. This is particularly true for the electrodes within the cell, where the electrolyte gradually seeps from the outside of the wound core to the inside, leading to uneven electrolyte distribution. This results in a series of issues after the cell is manufactured, including low capacity, high resistance, and a short lifespan.

[0004] Currently, the problem of poor wettability of lithium-ion batteries is mostly solved by adding additives to the electrolyte to change the electrolyte absorption speed and the uniformity of the infiltration. Commonly used additives are fluorobenzene additives. Although fluorobenzene additives can improve wettability by reducing the surface tension of the electrolyte, there are relatively strict requirements on the amount of fluorobenzene additives added. In addition, fluorobenzene additives have a relatively high acquisition cost and may decompose into fluorine-containing hazardous substances in the environment, causing adverse effects on the environment. In addition, fluorobenzene additives cannot effectively prevent the precipitation of lithium salts under low temperature conditions, which seriously limits the discharge performance and cycle stability of the battery in low temperature environments.

[0005] Therefore, developing a battery electrolyte additive that can not only effectively improve wettability and conductivity, but also be cost-effective, environmentally friendly, and maintain stable performance over a wide temperature range is one of the important research directions for lithium-ion battery electrolytes. Summary of the Invention

[0006] The main purpose of the present invention is to solve the problem that existing battery electrolyte additives cannot achieve both effective improvement of wettability and improvement of conductivity while also taking into account reasonable cost, environmental friendliness and maintaining stable performance over a wide temperature range.

[0007] In order to solve the above problems, the present invention provides a battery electrolyte additive, a battery electrolyte and its application. The battery electrolyte additive is an alkyl ether alkoxysilane compound, and the alkyl ether alkoxysilane compound has a structure shown in formula (A): wherein R1, R2, R3, and R4 are each independently selected from a C1-C20 alkyl group, 1≤n≤20, and n is an integer. The battery electrolyte additive having the above structure can effectively improve the surface tension of the battery electrolyte, enhance the wettability and conductivity of the battery electrolyte, reduce battery impedance, and effectively improve the low-temperature discharge and low-temperature cycling performance of the battery.

[0008] Furthermore, R1, R2, R3, and R4 in the alkyl ether alkoxysilane compound are each independently selected from a C1-C5 alkyl group, 1≤n≤5, and n is an integer. These structural features enable the battery electrolyte additive to possess improved physical and chemical properties such as viscosity and system compatibility, and are more conducive to improving the surface tension and wettability of the battery electrolyte.

[0009] Furthermore, in the alkyl ether alkoxysilane compound, R1, R2, R3, and R4 are each independently selected from methyl, ethyl, propyl, and butyl, 3≤n≤4, and n is an integer. The specific branched substituent groups and alkyl chain length are selected to make the battery electrolyte additive more effective in improving the wettability and conductivity of the battery electrolyte.

[0010] Furthermore, the battery electrolyte additive is selected from one or more of the following structures:

[0011]

[0012] Preferably, the battery electrolyte additive is a compound of one or more of Formula I, Formula II, Formula III, Formula IV, Formula V, and Formula VI; further preferably, the battery electrolyte additive is a compound of Formula I and Formula V in a weight percentage ratio of 2:(1-2); or, the battery electrolyte additive is a compound of Formula II and Formula III in a weight percentage ratio of (3-4):1; or, the battery electrolyte additive is a compound of Formula IV and Formula VI in a weight percentage ratio of 3:(1-3). Compounding the battery electrolyte additive in the above manner can achieve an optimal balance in terms of battery electrolyte viscosity, surface tension, and dissociation degree of lithium salt, which is beneficial to further improve the overall performance of the battery.

[0013] According to another aspect of the present invention, a battery electrolyte is provided, comprising a lithium salt, an organic solvent, and the aforementioned battery electrolyte additive. Application of the battery electrolyte additive to the battery electrolyte can significantly reduce the viscosity and surface tension of the battery electrolyte, and improve the wettability and conductivity of the battery electrolyte.

[0014] Furthermore, by weight, the battery electrolyte comprises 8-15% lithium salt, 0.5-10% battery electrolyte additive, and the balance is an organic solvent. Preferably, by weight, the battery electrolyte comprises 9-14% lithium salt, 0.5-3% battery electrolyte additive, and the balance is an organic solvent. Controlling the addition amounts of the components in the battery electrolyte within the aforementioned ratios is beneficial for further improving the wettability and conductivity of the battery electrolyte.

[0015] Further, the lithium salt is one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium trifluoromethanesulfonate, lithium bis(pentafluoroethylsulfonylimide), lithium bis(trifluoromethylsulfonylimide), lithium bis(fluorosulfonylimide), lithium difluoro(bis(oxalato)phosphate and lithium tetrafluoro(oxalato)phosphate; preferably, the lithium salt is lithium hexafluorophosphate and / or lithium hexafluoroarsenate; preferably, the organic solvent is an organic carbonate, an ionic liquid, a polyether , aromatic ether, C1-C30 alkyl ether, cyclic ether, carboxylate, sulfone, nitrile and dinitrile; preferably, the organic solvent is one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl propionate, ethyl methyl carbonate, propyl ether, butyl ether, glutaronitrile, sulfolane, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate; further preferably, the organic solvent is one or more of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate. The above lithium salts and organic solvents are all widely used and have better performance improvement effects on battery electrolytes and batteries.

[0016] Furthermore, the battery electrolyte additive is a compound of Formula I and Formula V, the organic solvent is glutaronitrile, and the lithium salt is lithium perchlorate; or, the battery electrolyte additive is a compound of Formula II and Formula III, the organic solvent is sulfolane, and the lithium salt is lithium difluoro(bisoxalate)phosphate; or, the battery electrolyte additive is a compound of Formula IV and Formula VI, the organic solvent is ethylene carbonate, and the lithium salt is lithium tetrafluoroborate; wherein the chemical structures of Formula I, Formula II, Formula III, Formula IV, Formula V and Formula VI are as follows:

[0017] The composite battery electrolyte additive can synergize with the corresponding lithium salt and organic solvent, which is more conducive to enhancing the stability and interface characteristics of the battery electrolyte and improving the cycle stability of the battery.

[0018] According to a third aspect of the present invention, a lithium-ion battery is provided, comprising the aforementioned battery electrolyte. Using the battery electrolyte containing the battery electrolyte additive of the present invention enables the lithium-ion battery to have not only good first-charge characteristics but also good capacity retention and maintain good performance in low-temperature environments.

[0019] Furthermore, the lithium-ion battery also includes a positive electrode containing a cathode active material, a negative electrode containing an anode active material, and a battery separator. Preferably, the cathode active material is a material capable of releasing lithium ions. Preferably, the cathode active material is one or more of transition metal phosphates, transition metal oxide lithium salts, and metal sulfides. Preferably, the anode active material is a material capable of receiving lithium ions. Preferably, the anode active material is one or more of graphite, silicon, silicon-carbon, graphite-silicon-carbon composites, silicon oxide-graphite composites, or silicon-carbon-silicon oxide composites. Preferably, the battery separator is at least one of a polyimide separator, a polyethylene separator, a polypropylene separator, and a polyethylene terephthalate separator. Preferably, the battery separator is a polyethylene separator or a polypropylene separator. By optimizing the crystal form of the positive electrode material, negative electrode material, and battery separator in the battery, the overall performance of the battery can be further improved.

[0020] The present invention provides a battery electrolyte additive, a battery electrolyte and its application. The battery electrolyte additive is an alkyl ether alkoxysilane compound, which not only contains Si-O ether groups and CO ether groups, but also contains a long chain structure composed of Si-O ether groups and CO ether groups and an alkyl chain ((CH2)n). Under the synergistic effect of the above-mentioned functional groups, the battery electrolyte additive has a lower viscosity, can greatly reduce the surface tension of the battery electrolyte, and improve the wettability of the battery electrolyte. In addition, the oxygen atoms in the Si-O ether group and the CO ether group contain two pairs of lone pairs of electrons. Under the further action of the electron donating effect of R1, R2, R3, R4 and the alkyl chain ((CH2)n), the electronic effect of the lone pairs of electrons around the oxygen atoms is increased. When the alkyl ether alkoxysilane battery electrolyte additive is used as one of the components in the battery electrolyte, it can more effectively react with Li in the lithium salt of the battery electrolyte. + The combination greatly increases the dissociation degree of lithium salts, thereby increasing the conductivity of the battery electrolyte, reducing battery impedance, and improving the battery's dynamic performance. Alkyl ether alkoxysilanes have the characteristics of low viscosity and the ability to enhance the dissociation degree of lithium salts. This prevents the lithium salts from precipitating out of the battery electrolyte additive at low temperatures due to excessively low temperatures, greatly improving the battery's low-temperature discharge and low-temperature cycling performance, and enabling the battery to maintain stable performance over a wide temperature range. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0022] As described in the background technology section, the main method for solving the problem of poor wettability of lithium-ion batteries is to add battery electrolyte additives to the battery electrolyte to change the liquid absorption speed and uniformity of the battery electrolyte. Although the commonly used fluorobenzene additives can improve wettability by reducing the surface tension of the battery electrolyte, fluorobenzene additives not only have relatively strict requirements on the amount of addition, but also have the disadvantages of relatively high acquisition cost and easy decomposition of fluorine-containing hazardous substances. It is also impossible to effectively prevent the precipitation of lithium salts under low temperature conditions. The above-mentioned shortcomings seriously limit the discharge performance and cycle stability of the battery under low temperature environment. Therefore, it is urgent to develop a battery electrolyte additive that can effectively improve wettability and improve conductivity, while also taking into account reasonable cost, environmental friendliness and the ability to maintain stable performance in a wide temperature range.

[0023] In order to solve the above problems, the present invention provides a battery electrolyte additive, which is an alkyl ether alkoxysilane compound. The alkyl ether alkoxysilane compound has a structure shown in the following formula (A):

[0024] Wherein, R1, R2, R3 and R4 are each independently selected from one of C1 to C20 alkyl groups, 1≤n≤20, and n is an integer.

[0025] The alkyl ether alkoxysilane structure in the above-mentioned battery electrolyte additive contains not only Si-O ether group and CO ether group, but also an alkyl chain ((CH2)n) connecting the Si-O ether group and the CO ether group. The above-mentioned group structural characteristics make the alkyl ether alkoxysilane have a long-chain structure. Under the synergistic effect of the various functional groups and groups in the structure, the battery electrolyte additive has a lower viscosity, which can greatly reduce the surface tension of the battery electrolyte and improve the wettability of the battery electrolyte. In addition, the oxygen atoms in the Si-O ether group and the CO ether group in the structure contain two pairs of lone pairs of electrons, which can greatly enhance the electronic effect of the lone pair of electrons around the oxygen atoms under the further action of the electron donating effect of R1, R2, R3, R4 and the alkyl chain ((CH2)n), so that it can more effectively interact with Li in the battery electrolyte. +Combined with, increase the degree of lithium salt dissociation, improve the conductivity of the battery electrolyte, and reduce the battery impedance, thereby effectively improving the dynamic performance of the battery. Furthermore, R1, R2, R3 and R4 in the alkyl ether alkoxysilane structure are each independently selected from one of the C1 to C20 alkyl groups, 1≤n≤20, and n is an integer. The battery electrolyte additive proposed by the present invention is mainly used to improve the wettability of the battery electrolyte. By controlling the length of the side chain and the alkyl chain within the above range, the obtained battery electrolyte additive can have suitable viscosity and system compatibility, which is beneficial to improve the wettability and conductivity of the battery electrolyte, thereby playing a better role in improving the overall performance of the battery.

[0026] In summary, the alkyl ether alkoxysilane battery electrolyte additive with the above-mentioned structure proposed by the present invention, due to its unique structural characteristics, not only has a low viscosity, but also has the characteristic of enhancing the dissociation degree of lithium salts. This has a significant effect on reducing the surface tension of the battery electrolyte, improving the wettability and conductivity of the battery electrolyte, and reducing battery impedance. In addition, the battery electrolyte additive prevents lithium salt precipitation in the battery electrolyte due to excessively low temperatures, greatly improving the low-temperature discharge and low-temperature cycling performance of the battery.

[0027] In a preferred embodiment, R1, R2, R3, and R4 in the alkyl ether alkoxysilane compound are each independently selected from a C1-C5 alkyl group, with 1≤n≤5, and n being an integer. Further controlling the lengths of the R1, R2, R3, and R4 side chains and alkyl chains in the alkyl ether alkoxysilane structure within the aforementioned ranges can improve the physical and chemical properties of the battery electrolyte additive, such as viscosity and system compatibility.

[0028] In a preferred embodiment, R1, R2, R3, and R4 in the alkyl ether alkoxysilane compound are independently selected from methyl, ethyl, propyl, and butyl, with 3≤n≤4, and n being an integer. The battery electrolyte additive prepared by selecting the above-mentioned specific branched substituent groups and alkyl chain lengths is more effective in improving the wettability and conductivity of the battery electrolyte and enhancing the overall performance of the battery. Furthermore, selecting the above-mentioned branched and alkyl chains with lower carbon numbers can reduce the preparation cost and simplify the preparation process, making it more conducive to large-scale production after promotion.

[0029] By way of example but not limitation, the battery electrolyte additive is selected from one or more of the following structures:

[0030]

[0031]

[0032] Preferably, the battery electrolyte additive is a compound of one or more of Formula I, Formula II, Formula III, Formula IV, Formula V and Formula VI. The above-mentioned battery electrolyte additives having an alkyl ether alkoxysilane structure all show a good effect of improving the overall performance of the battery when applied to the battery. In addition, after a large number of experiments, the inventors creatively discovered that when the battery electrolyte additive is a compound of one or more of Formula I, Formula II, Formula III, Formula IV, Formula V and Formula VI, the effect of improving battery performance is better. This may be because when one or more battery electrolyte additives are compounded, the properties of different additives can complement each other, so that the viscosity, surface tension and dissociation degree of lithium salts can be optimally balanced, thereby achieving the purpose of further improving the overall performance of the battery. Preferably, the battery electrolyte additive is a mixture of Formula I and Formula V in a weight ratio of 2:(1-2); alternatively, the battery electrolyte additive is a mixture of Formula II and Formula III in a weight ratio of (3-4):1; alternatively, the battery electrolyte additive is a mixture of Formula IV and Formula VI in a weight ratio of 3:(1-3). The above-mentioned improvement effect will be further enhanced when the battery electrolyte additives are mixed and used in the above ratios.

[0033] The present invention prepares a battery electrolyte additive by adding an alkenyl ether and an alkoxysilane corresponding to the target product in a molar ratio of 1:(8-20) to anhydrous ethanol, using CuCl as a reaction catalyst, and reacting the mixture at 45-75°C for 5-16 hours. After the reaction is complete, the anhydrous ethanol and unreacted alkoxysilane are removed by vacuum rotary evaporation to obtain the corresponding battery electrolyte additive. This method is simple to operate and highly efficient, making it a preferred preparation method.

[0034] According to another aspect of the present invention, a battery electrolyte is also provided, comprising a lithium salt, an organic solvent, and the aforementioned battery electrolyte additive. Applying the battery electrolyte additive of the present invention to the battery electrolyte can significantly reduce the viscosity and surface tension of the battery electrolyte, and improve the wettability and conductivity of the battery electrolyte. Furthermore, the battery electrolyte containing the aforementioned battery electrolyte additive is less susceptible to low temperatures, and lithium salt precipitation will not occur due to excessively low temperatures. This can significantly improve the low-temperature discharge performance and low-temperature cycle performance of the battery, allowing the battery to maintain an efficient and stable operating state over a wider temperature range, thus having significant economic benefits and application prospects.

[0035] In a preferred embodiment, the battery electrolyte contains 8-15% lithium salt, 0.5-10% battery electrolyte additive, and the balance is an organic solvent. By controlling the relative proportions of lithium salt, battery electrolyte additive, and organic solvent in the battery electrolyte, the battery performance can be optimized. By controlling the proportions of each component in the battery electrolyte within the above range, the obtained battery electrolyte can have better performance during use, which is beneficial to improving the comprehensive performance of the battery. Preferably, by weight percentage, the battery electrolyte contains 9-14% lithium salt, 0.5-3% battery electrolyte additive, and the balance is an organic solvent. Controlling the relative proportions of lithium salt, battery electrolyte additive, and organic solvent within the above preferred range will have a better effect on improving the battery electrolyte and battery performance.

[0036] By way of example but not limitation, the lithium salt is one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium perchlorate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium trifluoromethanesulfonate, lithium bis(pentafluoroethylsulfonylimide), lithium bis(trifluoromethylsulfonylimide), lithium bis(fluorosulfonylimide), lithium difluoro(bisoxalato)phosphate and lithium tetrafluoro(oxalato)phosphate; preferably, the lithium salt is lithium hexafluorophosphate and / or lithium hexafluoroarsenate; preferably, the organic solvent is an organic carbonate, an ionic liquid, One or more of polyether, aromatic ether, C1-C30 alkyl ether, cyclic ether, carboxylate, sulfone, nitrile and dinitrile; preferably, the organic solvent is one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl propionate, ethyl methyl carbonate, propyl ether, butyl ether, glutaronitrile, sulfolane, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate; further preferably, the organic solvent is one or more of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate. The battery electrolyte provided by the present invention has multiple properties such as improving the wettability of the battery electrolyte, increasing the dissociation degree of the lithium salt, and improving the stability of the battery electrolyte over a wide temperature range. There is no strict limitation on the specific types of lithium salts and organic solvents. The above-mentioned types of lithium salts and organic solvents are all widely used and have better performance improvement effects on the battery electrolyte and battery.

[0037] In a preferred embodiment, the battery electrolyte additive is a compound of Formula I and Formula V, the organic solvent is glutaronitrile, and the lithium salt is lithium perchlorate; or, the battery electrolyte additive is a compound of Formula II and Formula III, the organic solvent is sulfolane, and the lithium salt is lithium difluoro(bisoxalato)phosphate; or, the battery electrolyte additive is a compound of Formula IV and Formula VI, the organic solvent is ethylene carbonate, and the lithium salt is lithium tetrafluoroborate; wherein the chemical structures of Formula I, Formula II, Formula III, Formula IV, Formula V, and Formula VI are as follows:

[0038] Through extensive experiments, the inventors discovered that when the battery electrolyte additive, lithium salt, and organic solvent are combined in the aforementioned manner during the preparation of the battery electrolyte, the resulting battery electrolyte exhibits improved overall performance. This is likely because the composite battery electrolyte additive can synergize with the corresponding lithium salt and organic solvent, further enhancing the stability and interfacial properties of the battery electrolyte and improving the battery's cycling stability.

[0039] According to a third aspect of the present invention, a lithium-ion battery is also provided, comprising the aforementioned battery electrolyte. Using a battery electrolyte containing the battery electrolyte additive proposed by the present invention enables the resulting lithium-ion battery to exhibit not only good first-charge characteristics but also good capacity retention, excellent cycling stability and safety, and good performance in low-temperature environments, providing new insights into the development of lithium-ion batteries suitable for use in cold environments.

[0040] In a preferred embodiment, the lithium-ion battery further comprises a positive electrode containing a cathode active material, a negative electrode containing an anode active material, and a battery separator; preferably, the cathode active material is a material capable of releasing lithium ions; by way of example but not limitation, the cathode active material is one or more of a transition metal phosphate, a transition metal oxide lithium salt, and a metal sulfide; preferably, the anode active material is a material capable of receiving lithium ions; preferably, the anode active material is one or more of a graphite material, a silicon material, a silicon-carbon material, a graphite-silicon-carbon composite, a silicon oxide-graphite composite, or a silicon-carbon-silicon oxide composite; preferably, the battery separator is at least one of a polyimide separator, a polyethylene separator, a polypropylene separator, and a polyethylene terephthalate separator; preferably, the battery separator is a polyethylene separator or a polypropylene separator. By optimizing the crystal form of the positive electrode material, negative electrode material, and battery separator in the battery, the overall performance of the battery can be further improved, achieving optimal conditions in terms of high energy density, high power density, long cycle life, and a wide temperature operating range. The above materials have a significant effect on further improving the comprehensive performance of the battery.

[0041] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0042] Example 1

[0043] (1) Preparation of battery electrolyte additives

[0044] Vinyl n-butyl ether and ethyltrimethoxysilane were added to anhydrous ethanol in a molar ratio of 1:8, and CuCl was used as a reaction catalyst. After the reaction was carried out at 50°C for 12 hours, the anhydrous ethanol and unreacted ethyltrimethoxysilane were removed from the reaction mixture by vacuum rotary evaporation to obtain the battery electrolyte additive A1 shown in Formula I. The reaction formula for the above reaction is:

[0045]

[0046] (2) Preparation of battery electrolyte

[0047] In an argon-filled glove box, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are uniformly mixed in a mass ratio of 3:5:2, wherein the water content in the glove box is less than 0.1 ppm and the oxygen content is less than 0.1 ppm. Lithium hexafluorophosphate (LiPF6) is then added. After the lithium salt is completely dissolved, the battery electrolyte additive represented by Formula I is added and uniformly mixed to obtain a battery electrolyte. The battery electrolyte comprises, by weight, 12% lithium salt, 1% battery electrolyte additive, and 87% organic solvent.

[0048] (3) Preparation of batteries

[0049] Positive electrode sheet: 95% NCM811, 2% acetylene black and 3% PVDF binder were added to N-methylpyrrolidone to prepare a slurry by weight. The obtained slurry was coated on a 12-micron thick aluminum foil, dried and rolled to obtain a positive electrode sheet.

[0050] Negative electrode sheet: According to the weight percentage, 91% artificial graphite, 4% acetylene black and 5% SBR binder are added with deionized water to prepare a mixed slurry. The obtained slurry is coated on an 8-micron copper foil, dried and rolled to obtain the negative electrode sheet.

[0051] Lithium-ion battery: In a dry environment with a leak point below -50°C, the positive electrode, separator, and negative electrode are stacked in sequence to form a battery cell. During the stacking process, ensure that the separator completely separates the positive electrode and that the negative electrode completely covers the positive electrode. The tabs are then encapsulated in aluminum-plastic film of a fixed size using adhesive, forming a soft-pack battery ready for liquid injection. The prepared battery electrolyte is then injected into the soft-pack battery. The battery is then sealed, formed, aged, and then sealed and capped to produce a lithium-ion battery.

[0052] Example 2

[0053] The difference between Example 2 and Example 1 is that the prepared battery electrolyte additives are different, and the addition ratios of the battery electrolyte additives, lithium salt and organic solvent are different during the process of preparing the battery electrolyte.

[0054] (1) Preparation of battery electrolyte additives

[0055] Propylene n-butyl ether and methyltripropoxysilane were added to anhydrous ethanol in a molar ratio of 1:10, and CuCl was used as a reaction catalyst. After the reaction was carried out at 60°C for 8 hours, the anhydrous ethanol and unreacted methyltripropoxysilane were removed from the reaction mixture by vacuum rotary evaporation to obtain the battery electrolyte additive A2 shown in Formula II. The reaction formula of the above reaction is:

[0056]

[0057] (2) Preparation of battery electrolyte

[0058] The battery electrolyte preparation process is the same as that in Example 1, but the battery electrolyte prepared in this example contains 12% lithium salt, 0.5% battery electrolyte additive, and 87.5% organic solvent by weight.

[0059] Example 3

[0060] The difference between Example 3 and Example 1 is that the prepared battery electrolyte additives are different, and the addition ratios of the battery electrolyte additives, lithium salt and organic solvent are different during the process of preparing the battery electrolyte.

[0061] (1) Preparation of battery electrolyte additives

[0062] Vinyl ethyl ether and methyltrimethoxysilane were added to anhydrous ethanol in a molar ratio of 1:15, and CuCl was used as a reaction catalyst. After the reaction was carried out at 45°C for 7 hours, the anhydrous ethanol and unreacted methyltrimethoxysilane were removed from the reaction mixture by vacuum rotary evaporation to obtain the battery electrolyte additive A3 shown in Formula III. The reaction formula for the above reaction is:

[0063]

[0064] (2) Preparation of battery electrolyte

[0065] The battery electrolyte preparation process is the same as that in Example 1, but the battery electrolyte prepared in this example contains 12% lithium salt, 3% battery electrolyte additive, and 85% organic solvent by weight.

[0066] Example 4

[0067] The difference between Example 4 and Example 1 is that the prepared battery electrolyte additives are different, and the addition ratios of the battery electrolyte additives, lithium salt and organic solvent are different during the process of preparing the battery electrolyte.

[0068] (1) Preparation of battery electrolyte additives

[0069] Vinyl propyl ether and methyltriethoxysilane were added to anhydrous ethanol in a molar ratio of 1:20, and CuCl was used as a reaction catalyst. After the reaction was carried out at 70°C for 5 hours, the anhydrous ethanol and unreacted methyltriethoxysilane were removed from the reaction mixture by vacuum rotary evaporation to obtain the battery electrolyte additive A4 shown in Formula IV. The reaction formula for the above reaction is:

[0070]

[0071] (2) Preparation of battery electrolyte

[0072] The battery electrolyte preparation process is the same as that in Example 1, but the battery electrolyte prepared in this example contains 12% lithium salt, 1.5% battery electrolyte additive, and 86.5% organic solvent by weight.

[0073] Example 5

[0074] The difference between Example 5 and Example 1 is that the prepared battery electrolyte additives are different, and the addition ratios of the battery electrolyte additives, lithium salt and organic solvent are different during the process of preparing the battery electrolyte.

[0075] (1) Preparation of battery electrolyte additives

[0076] Propylene n-butyl ether and methyltributoxysilane were added to anhydrous ethanol in a molar ratio of 1:18, and CuCl was used as a reaction catalyst. After the reaction was carried out at 65°C for 14 hours, the anhydrous ethanol and unreacted methyltributoxysilane were removed by vacuum rotary evaporation of the reaction mixture to obtain the battery electrolyte additive A5 shown in Formula V. The reaction formula of the above reaction is:

[0077]

[0078] (2) Preparation of battery electrolyte

[0079] The battery electrolyte preparation process is the same as that in Example 1, but the battery electrolyte prepared in this example contains 12% lithium salt, 2.5% battery electrolyte additive, and 85.5% organic solvent by weight.

[0080] Example 6

[0081] The difference between Example 6 and Example 1 is that the prepared battery electrolyte additives are different, and the addition ratios of the battery electrolyte additives, lithium salt and organic solvent are different during the process of preparing the battery electrolyte.

[0082] (1) Preparation of battery electrolyte additives

[0083] Vinyl methyl ether and methyltriethoxysilane were added to anhydrous ethanol in a molar ratio of 1:11, and CuCl was used as a reaction catalyst. After the reaction was carried out at 75°C for 16 hours, the anhydrous ethanol and unreacted methyltriethoxysilane were removed from the reaction mixture by vacuum rotary evaporation to obtain the battery electrolyte additive A6 represented by Formula VI. The reaction formula for the above reaction is:

[0084]

[0085] (2) Preparation of battery electrolyte

[0086] The battery electrolyte preparation process is the same as that in Example 1, but the battery electrolyte prepared in this example contains 12% lithium salt, 2% battery electrolyte additive, and 86% organic solvent by weight.

[0087] Example 7

[0088] The difference between Example 7 and Example 1 is that, in the battery electrolyte, by weight percentage, the lithium salt accounts for 8%, the battery electrolyte additive accounts for 0.5%, and the organic solvent accounts for 91.5%.

[0089] Example 8

[0090] The difference between Example 8 and Example 1 is that, in the battery electrolyte, by weight percentage, the lithium salt accounts for 15%, the battery electrolyte additive accounts for 10%, and the organic solvent accounts for 75%.

[0091] Example 9

[0092] The difference between Example 9 and Example 1 is that, in the battery electrolyte, by weight percentage, the lithium salt accounts for 9%, the battery electrolyte additive accounts for 0.5%, and the organic solvent accounts for 90.5%.

[0093] Example 10

[0094] The difference between Example 10 and Example 1 is that, in the battery electrolyte, by weight percentage, the lithium salt accounts for 14%, the battery electrolyte additive accounts for 3%, and the organic solvent accounts for 83%.

[0095] Example 11

[0096] The difference between Example 11 and Example 1 is that in the battery electrolyte, the battery electrolyte additive is a battery electrolyte additive A1 and a battery electrolyte additive A5 compounded in a weight ratio of 2:1, the lithium salt is lithium perchlorate (LiClO4), and the organic solvent is glutaronitrile.

[0097] Example 12

[0098] The difference between Example 12 and Example 1 is that in the battery electrolyte, the battery electrolyte additive is a battery electrolyte additive A1 and a battery electrolyte additive A5 compounded in a weight ratio of 1:1, the lithium salt is lithium perchlorate, and the organic solvent is glutaronitrile.

[0099] Example 13

[0100] The difference between Example 13 and Example 1 is that in the battery electrolyte, the battery electrolyte additive is a battery electrolyte additive A2 and a battery electrolyte additive A3 compounded in a weight ratio of 3:1, the lithium salt is lithium difluoro(bisoxalato)phosphate (Li2PF2(C2O4)), and the organic solvent is cyclopentane.

[0101] Example 14

[0102] The difference between Example 14 and Example 1 is that in the battery electrolyte, the battery electrolyte additive is a battery electrolyte additive A2 and a battery electrolyte additive A3 compounded in a weight ratio of 4:1, the lithium salt is lithium difluoro(bisoxalato)phosphate, and the organic solvent is sulfolane.

[0103] Example 15

[0104] The difference between Example 15 and Example 1 is that in the battery electrolyte, the battery electrolyte additive is a battery electrolyte additive A4 and a battery electrolyte additive A6 compounded in a weight ratio of 3:1, the lithium salt is lithium tetrafluoroborate (LiBF4), and the organic solvent is ethylene carbonate (EC).

[0105] Example 16

[0106] The difference between Example 16 and Example 1 is that in the battery electrolyte, the battery electrolyte additive is a mixture of battery electrolyte additive A4 and battery electrolyte additive A6 in a weight ratio of 1:1, the lithium salt is lithium tetrafluoroborate, and the organic solvent is ethylene carbonate.

[0107] Example 17

[0108] The difference between Example 17 and Example 3 is that, in the battery electrolyte, by weight percentage, the battery electrolyte additive is 0.2%, the lithium salt is 12%, and the organic solvent is 87.8%.

[0109] Example 18

[0110] The difference between Example 18 and Example 3 is that, in the battery electrolyte, by weight percentage, the battery electrolyte additive accounts for 12%, the lithium salt accounts for 12%, and the organic solvent accounts for 76%.

[0111] Comparative Example 1

[0112] The difference between Comparative Example 1 and Example 1 is that, in the prepared battery electrolyte, by weight percentage, the lithium salt is 12%, the battery electrolyte additive is 0.5%, the organic solvent is 87.5%, and the battery electrolyte additive is fluorobenzene.

[0113] Comparative Example 2

[0114] The difference between Comparative Example 1 and Example 1 is that, in the prepared battery electrolyte, by weight percentage, the lithium salt is 12%, the battery electrolyte additive is 1%, the organic solvent is 87%, and the battery electrolyte additive is fluorobenzene.

[0115] Comparative Example 3

[0116] The difference between Comparative Example 1 and Example 1 is that, in the prepared battery electrolyte, by weight percentage, the lithium salt is 12%, the battery electrolyte additive is 3%, the organic solvent is 85%, and the battery electrolyte additive is fluorobenzene.

[0117] Comparative Example 4

[0118] The difference between Comparative Example 1 and Example 1 is that, in the prepared battery electrolyte, the lithium salt accounts for 12% and the organic solvent accounts for 88% by weight, and no battery electrolyte additives are added.

[0119] The components and weight percentages of the battery electrolytes in the examples and comparative examples are summarized in Table 1. The proportions of the organic solvents and battery electrolyte additives mentioned in the table are all by mass.

[0120] Table 1

[0121]

[0122]

[0123] The battery electrolytes and batteries prepared in the examples and comparative examples were tested for relevant performance, and the results are shown in Table 2. The testing methods for the relevant data in the table are as follows:

[0124] Battery electrolyte surface tension test: The surface tension of the battery electrolytes prepared in the above examples and comparative examples was tested using a fully automatic surface tension tester at a temperature of 25±2°C.

[0125] Battery electrolyte viscosity test: The viscosity of the battery electrolytes prepared in the above examples and comparative examples was tested using a rotational viscometer at 25°C and -40°C, respectively. The rotor measurement range was 0.01-25 mPa / s, and the measurement speed was 60 rpm.

[0126] Conductivity test of battery electrolyte: The battery electrolytes prepared in the above examples and comparative examples were tested for conductivity using a benchtop conductivity tester at test temperatures of 25°C and -40°C, respectively. The test results were averaged over three measurements.

[0127] Battery performance test: The batteries prepared in the above examples and comparative examples are placed in a -40°C ultra-low temperature constant temperature box and connected to a charge and discharge tester. First, charge to 4.2V with a constant current and constant voltage of 1C, and set the cut-off current to 0.05C; after standing for 10 minutes, discharge to 2.8V with a constant current of 1C. Perform a cyclic charge and discharge test in this way, and record the discharge capacity each time. Based on the recorded data, calculate the cell capacity retention rate of the 100th, 150th, and 300th weeks of the battery cycle, respectively, where the cell capacity retention rate (%) of the Nth week of the battery cycle = discharge capacity of the Nth week / discharge capacity of the first week × 100%. -40°C discharge capacity retention rate (%) = -40°C constant capacity / constant capacity at room temperature × 100%.

[0128] Table 2

[0129]

[0130]

[0131] From the above description, it can be seen that in Examples 1 to 18, the addition of the alkyl ether alkoxysilane battery electrolyte additive provided by the present invention to the battery electrolyte can achieve the purpose of reducing the surface tension of the battery electrolyte and reducing the viscosity of the battery electrolyte, and can also significantly improve the conductivity of the battery, especially under low temperature conditions of -40°C, it can also have a good improvement effect on the viscosity and conductivity of the battery electrolyte, indicating that the addition of the alkyl ether alkoxysilane battery electrolyte additive of the present invention can effectively improve the wettability of the battery electrolyte. When the above battery electrolyte is applied to the battery, it still has good discharge capacity retention and cycle capacity retention under low temperature conditions of -40°C. In addition, controlling the addition amount of the battery electrolyte additive within the preferred range will have better effects on the above-mentioned improvement of the battery electrolyte and the battery. The battery prepared under the preferred conditions has a capacity retention rate of more than 80% after 100 cycles under low temperature conditions of -40°C, which greatly improves the low temperature cycle performance.

[0132] In Comparative Examples 1 to 3, conventional fluorobenzene battery electrolyte additives were added to the battery electrolyte, while in Comparative Example 4, no conventional additives were added during the preparation of the battery electrolyte. When the mass percentage of fluorobenzene added to the battery electrolyte in Comparative Examples 1 to 3 was 0.5%, 1%, and 3%, the improvements in the viscosity, surface tension, and conductivity of the battery electrolyte were not ideal, and even reduced the viscosity and surface tension of the battery electrolyte, thereby adversely affecting the conductive properties of the battery electrolyte. Similarly, when the corresponding battery electrolytes in the comparative examples were applied to batteries, the improvement in the discharge capacity retention rate and cycle capacity retention rate of the batteries at a low temperature of -40°C was significantly lower than that of the present invention, and even had adverse effects, making it impossible to continue the cycle process.

[0133] In summary, the application of the alkyl ether alkoxysilane battery electrolyte additive proposed in this invention to battery electrolytes significantly reduces the surface tension and viscosity of the battery electrolyte, improves the wettability and conductivity of the battery electrolyte, and reduces battery impedance. Furthermore, it significantly improves the low-temperature discharge and low-temperature cycling performance of the battery.

[0134] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A lithium ion battery electrolyte additive, characterized in that The lithium-ion battery electrolyte additive is an alkyl ether alkoxysilane compound, and the alkyl ether alkoxysilane compound has a structure shown in formula (A): Formula (A), Wherein, R1, R2, R3 and R4 are each independently selected from one of C1 to C20 alkyl groups, 1≤n≤20, and n is an integer.

2. The lithium-ion battery electrolyte additive according to claim 1, characterized in that In the alkyl ether alkoxysilane compound, R1, R2, R3 and R4 are independently selected from one of C1 to C5 alkyl groups, 1≤n≤5, and n is an integer.

3. The lithium-ion battery electrolyte additive according to claim 1, characterized in that In the alkyl ether alkoxysilane compound, R1, R2, R3 and R4 are independently selected from methyl, ethyl, propyl and butyl, 3≤n≤4, and n is an integer.

4. The lithium-ion battery electrolyte additive according to any one of claims 1 to 3, characterized in that The lithium-ion battery electrolyte additive is selected from one or more of the following structures: ， ， ， ， ， 。 5. The lithium-ion battery electrolyte additive according to claim 4, characterized in that The lithium-ion battery electrolyte additive is a combination of one or more of the formulas I, II, III, IV, V and VI.

6. The lithium-ion battery electrolyte additive according to claim 5, characterized in that The lithium-ion battery electrolyte additive is a mixture of the formula I and the formula V in a weight percentage of 2: (1-2); Alternatively, the lithium-ion battery electrolyte additive is a compound of the formula II and the formula III in a weight percentage ratio of (3-4):1; or the lithium-ion battery electrolyte additive is a compound of the formula IV and the formula VI in a weight percentage ratio of 3:(1-3).

7. A lithium ion battery electrolyte, characterized in that: The lithium-ion battery electrolyte comprises a lithium salt, an organic solvent, and the lithium-ion battery electrolyte additive according to any one of claims 1 to 6.

8. The lithium-ion battery electrolyte according to claim 7, characterized in that In terms of weight percentage, the lithium salt in the lithium ion battery electrolyte is 8-15%, the lithium ion battery electrolyte additive is 0.5-10%, and the balance is the organic solvent.

9. The lithium-ion battery electrolyte according to claim 8, characterized in that In terms of weight percentage, the lithium salt in the lithium ion battery electrolyte is 9-14%, the lithium ion battery electrolyte additive is 0.5-3%, and the balance is the organic solvent.

10. The lithium-ion battery electrolyte according to claim 7, characterized in that The lithium salt is one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium trifluoromethanesulfonate, lithium bis(pentafluoroethylsulfonylimide), lithium bis(trifluoromethylsulfonylimide), lithium bis(fluorosulfonylimide), lithium difluoro(bisoxalato)phosphate and lithium tetrafluoro(oxalato)phosphate.

11. The lithium-ion battery electrolyte according to claim 10, characterized in that The lithium salt is lithium hexafluorophosphate and / or lithium hexafluoroarsenate.

12. The lithium-ion battery electrolyte according to claim 7, characterized in that The organic solvent is one or more of organic carbonate, ionic liquid, polyether, aromatic ether, C1-C30 alkyl ether, cyclic ether, carboxylate, sulfone, nitrile and dinitrile.

13. The lithium-ion battery electrolyte according to claim 12, characterized in that The organic solvent is one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl propionate, ethyl methyl carbonate, propyl ether, butyl ether, glutaronitrile, sulfolane, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate.

14. The lithium-ion battery electrolyte according to claim 13, characterized in that The organic solvent is one or more of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate.

15. The lithium-ion battery electrolyte according to claim 7, characterized in that The lithium-ion battery electrolyte additive is a compound of Formula I and Formula V, the organic solvent is glutaronitrile, and the lithium salt is lithium perchlorate; or The lithium-ion battery electrolyte additive is a compound of Formula II and Formula III, the organic solvent is sulfolane, and the lithium salt is lithium difluoro(bisoxalato)phosphate; or The lithium-ion battery electrolyte additive is a compound of formula IV and formula VI, the organic solvent is ethylene carbonate, and the lithium salt is lithium tetrafluoroborate; Wherein, the chemical structures of Formula I, Formula II, Formula III, Formula IV, Formula V and Formula VI are as follows: ， ， ， ， ， 。 16. A lithium ion battery, characterized in that: The lithium-ion battery comprises the lithium-ion battery electrolyte according to any one of claims 7 to 15.

17. The lithium-ion battery according to claim 16, characterized in that The lithium-ion battery also includes a positive electrode containing a cathode active material, a negative electrode containing an anode active material, and a battery separator.

18. The lithium-ion battery according to claim 17, wherein: The cathode active material is a material capable of releasing lithium ions.

19. The lithium-ion battery according to claim 18, wherein The cathode active material is one or more of transition metal phosphates, transition metal oxide lithium salts and metal sulfides.

20. The lithium-ion battery according to claim 17, wherein The anode active material is a material capable of accepting lithium ions.

21. The lithium-ion battery according to claim 20, characterized in that The anode active material is one or more of graphite material, silicon material, silicon-carbon material, graphite and silicon-carbon composite material, silicon oxide and graphite composite material, silicon carbon and silicon oxide composite material.

22. The lithium-ion battery according to claim 17, wherein The battery separator is at least one of a polyimide separator, a polyethylene separator, a polypropylene separator and a polyethylene terephthalate separator.

23. The lithium-ion battery according to claim 22, wherein: The battery separator is a polyethylene separator or a polypropylene separator.

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