An electrolyte additive composition, electrolyte containing the same, method of preparation and use

Abstract

The application discloses an electrolyte additive composition, an electrolyte containing the same, a preparation method and application, and belongs to the technical field of lithium ion batteries. The technical problem to be solved is that an electrolyte system is accelerated to deteriorate and storage capacity is attenuated under high temperature, which seriously threatens the reliability of a battery system. The electrolyte additive composition comprises an alkoxy silane compound and an aluminum alcohol compound. The structural formula of the alkoxy silane compound is shown as formula I, wherein R1 is selected from C1-C6 saturated alkyl, unsaturated hydrocarbon or halogenated hydrocarbon; R2-R4 are each independently selected from a hydrogen atom, a halogen atom, C1-C6 saturated alkyl, unsaturated hydrocarbon, halogenated hydrocarbon, alkoxy or ether; the structural formula of the aluminum alcohol compound is shown as formula II, wherein R5-R7 are each independently selected from 1-8 carbon alkyl.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to an electrolyte additive composition, an electrolyte containing the same, a preparation method, and an application. Background Technology

[0002] Lithium-ion rechargeable batteries have become a core energy technology supporting portable electronic devices, electric vehicles, and large-scale energy storage systems due to their high energy density, long cycle life, and environmental compatibility. To overcome the durability bottleneck in high-temperature applications and eliminate the risk of corrosion failure, developing battery systems that combine long lifespan and high reliability is an urgent need for industrial development.

[0003] At high temperatures, the electrolyte system deteriorates rapidly: the hydrolysis side reaction of lithium hexafluorophosphate (LiPF6) continuously generates corrosive hydrogen fluoride (HF), which erodes the lattice of the positive electrode active material and dissolves the transition metal; the aluminum current collector undergoes pitting corrosion and perforation under the synergistic effect of HF and high-voltage polarization; simultaneously, the exothermic interface side reaction coupled with the flammability of organic solvents lowers the thermal runaway trigger temperature to below 150°C. These defects result in a high-temperature storage capacity decay rate exceeding 30% per month, seriously threatening the reliability of the battery system.

[0004] Electrolyte additives, as a key strategy for inhibiting HF corrosion, can capture acidic substances through molecular design, but they cannot block the thermodynamic spontaneous pathway of LiPF6 hydrolysis. Scavengers, represented by borate esters, form stable adducts with HF through BO bonds, effectively reducing the concentration of free HF. However, the equilibrium constant of this reversible reaction (K≈10) remains high. 2 At high temperatures, the HF generation chain shifts significantly to the left, and the water-driven hydrolysis of LiPF6 cannot be suppressed. This thermodynamic limitation leads to the failure of the scavenger after high-temperature cycling, and the transition metal ion catalytic effect remains unsuppressed, resulting in a dynamic imbalance of "scavenging-regeneration". To completely dismantle the HF generation chain, control corrosion at its source, and ensure the uniformity of ion transport and the integrity of the electrode interface at high temperatures, it is urgent to develop a novel additive system with molecular synergistic effects that simultaneously achieves irreversible HF removal and inhibits the hydrolysis process of LiPF6 that generates HF.

[0005] Breakthrough progress has been made in siloxane compounds through highly reactive silicon centers: the binding constant K between their ≡Si-OR bonds and HF is greater than 10. 6This process stabilizes the free HF concentration below 1 ppm, significantly reducing cathode corrosion (transition metal leaching < 2 ppm); the accompanying high bond energy of the Si-O bonds (452 ​​kJ / mol) imparts thermal stability to the system (initial decomposition temperature > 300℃); the silanol (≡Si-OH) generated by in-situ hydrolysis self-assembles into a repair layer, greatly reducing the high-temperature cycling capacity decay rate. However, this mechanism is still downstream scavenging and needs to be combined with aluminum alkoxides to construct a synergistic defense line—aluminum alkoxides preferentially capture trace moisture (Al(OR')3 + 3H2O → Al(OH)3↓ + 3R'OH), blocking the source of LiPF6 hydrolysis; at the same time, it forms an Al-O-Si coordination network with siloxanes, reducing the residual HF diffusion flux by 3 orders of magnitude, achieving sub-ppm HF concentration throughout the entire life cycle.

[0006] Relevant patent documents retrieved:

[0007] The document, published in the United States (publication number US12964870) on April 29, 2014, discloses an aonaqueous secondary battery including a lithium composite oxide as a positive electrode active material. According to claim 1, the nonaqueous secondary battery contains at least one selected from methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, hexytrimethoxysilane, and 3-acryloxypropyltrimethoxysilane; and according to claim 2, the nonaqueous secondary battery contains at least one selected from aluminum bisethylacetoacetate monoacetylacetonate, aluminum ethylacetoacetate diisopropylate, aluminum trisethylacetoacetate, and aluminum triacetylacetonate.An advantage of some aspects of the invention is to provide a nonaqueous secondary battery including a lithium composite oxide as a positive electrode active material, in which the amount of gas generated is small when the battery is stored at high temperature in a charged state, capacity efficiency is good, and charge load characteristics are good in alow temperature Environment. (Chinese definition: According to claim 1, the non-aqueous secondary battery is characterized in that the silane coupling agent comprises at least one of methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, hexyltrimethoxysilane, and 3-acryloyloxypropyltrimethoxysilane; according to claim 2, the non-aqueous secondary battery is characterized in that the coupling agent represented by general formula (I) is at least one of ethyl diacetoacetate monoacetylacetonate aluminum, ethyl acetoacetate diisopropoxy aluminum, ethyl triacetoacetate aluminum, and ethyl triacetylacetonate aluminum; the beneficial effects of some embodiments of the present invention are that a non-aqueous secondary battery with lithium composite oxide as the positive electrode active material is provided, which produces less gas and has excellent capacity efficiency when stored at high temperature in a charged state, and has good charging load characteristics in a low temperature environment.) The invention describes that the electrolyte of the battery includes a nitrile compound, a silane coupling agent, and an aluminum complex; the abstract describes that the battery produces less gas and has good capacity efficiency when stored at high temperature in a charged state, and has good charging load characteristics in a low temperature environment.

[0008] The document, published in China (CN107069088A) on August 18, 2017, discloses a linear siloxane additive and its application in a high-temperature electrolyte for lithium-ion batteries. The electrolyte comprises a linear siloxane additive, a lithium salt, and a solvent. In this invention, the electrolyte additive is characterized by coin cell testing using a ternary cathode material. Under a current density of 2C (1C = 160 mAh / g), it exhibits high reversible specific capacity and capacity retention after 200 high-temperature cycles, significantly improving high-temperature cycling stability and storage performance, and enhancing high-temperature rate performance.

[0009] The prior art represented by the aforementioned documents has at least the following unresolved technical problems or defects: 1. The implementation cost of US12964870 is high and the process control is difficult. In actual large-scale production, even a small deviation in any link may cause the synergistic effect to fail and the performance to fall short of expectations, making it unsuitable for large-scale industrial production.

[0010] 2. The hydrolysis-cleansing dynamic equilibrium mechanism of the complex system, the interface evolution behavior under long-term high-temperature storage, and its universality in wide temperature range conditions in CN107069088A still need to be systematically analyzed.

[0011] Therefore, it is necessary to deepen the research on the synergistic inhibition mechanism of alkoxysilane compounds and aluminum alkoxide compounds, and promote their large-scale application in high-temperature and long-life battery systems. Summary of the Invention

[0012] The purpose of this invention is to provide: An electrolyte additive composition, an electrolyte containing the same, a preparation method and an application thereof, and related technologies thereof, to solve technical problems such as accelerated degradation of electrolyte systems at high temperatures, storage capacity decay, and serious threats to the reliability of battery systems, or combinations thereof.

[0013] This invention provides an electrolyte additive composition comprising an alkoxysilane compound and an aluminum alkoxide compound; the structural formula of the alkoxysilane compound is shown in Formula I:

[0014] The structural formula of the aluminum alkoxide compound is shown in Formula II: , Wherein, R1 is selected from saturated alkyl, unsaturated hydrocarbon or haloalkyl groups of C1-C6; R2-R4 are each independently selected from hydrogen atom, halogen atom, saturated alkyl, unsaturated hydrocarbon, haloalkyl, alkoxy or ether group of C1-C6; R5-R7 are each independently selected from alkyl groups containing C1-C8. The mass ratio of the alkoxysilane compound to the aluminum alkoxide compound is 1-10:0.1-2.

[0015] Preferably, R1 is selected from C1-C3 saturated alkyl or haloalkyl groups.

[0016] Preferably, R2-R4 are each independently selected from hydrogen atoms, halogen atoms, C1-C3 saturated alkyl groups, unsaturated hydrocarbon groups, haloalkyl groups, alkoxy groups, and ether groups.

[0017] Preferably, each of R5-R7 is independently selected from C2-C5 alkyl groups.

[0018] Preferably, the alkoxysilane compound is selected from one or more of tetramethoxysilane (TMS), methyltrimethoxysilane (MTMS), trimethoxysilane (TMOS), triethoxysilane (TEOS), vinyltrimethoxysilane (VTMOS), and trifluoropropyltrimethoxysilane (TFPS).

[0019] Preferably, the aluminum alkoxide compound is selected from one or more of aluminum triethanolamine, aluminum isopropoxide, aluminum n-propoxide, aluminum sec-butoxide, aluminum tert-butoxide, and aluminum isoamyl alcohol.

[0020] More preferably, the aluminum alkoxide compound is aluminum triethanolamine or aluminum isopropoxide.

[0021] Preferably, the mass ratio of the alkoxysilane compound to the aluminum alkoxide compound is selected from any value or range between 1-10:0.1-2, specifically from: 1:0.1, 10:0.1, 5:0.5, 10:2 or a range between the two.

[0022] More preferably, the mass ratio of the alkoxysilane compound to the aluminum alkoxide compound is selected from any value or range between 1-5:0.1-0.5.

[0023] More preferably, the mass ratio of the alkoxysilane compound to the aluminum alkoxide compound is 5:0.5.

[0024] The interaction mechanism between aluminum alkoxides and siloxane compounds involves a nucleophilic attack on the electrophilic center, leading to a nucleophilic substitution reaction. Specifically, the electron-rich alkoxy oxygen atom in the siloxane compound acts as a nucleophile, attacking the aluminum atom in the aluminum alkoxide. Because the aluminum atom lacks electrons in its empty orbitals, it accepts the electron pair provided by the lone pair oxygen atom, resulting in the substitution of the alkoxy group in the aluminum alkoxide with the siloxy group in the siloxane compound, forming a new aluminum-oxy-silicon bond (Al-O-Si) covalently. Alternatively, the oxygen atom of the alkoxy group in the aluminum alkoxide initiates a nucleophilic attack on the silicon atom in the siloxane compound. The silicon atom, with its empty 3d orbitals exhibiting strong electrophilicity, promotes the elimination of the alkoxy group and the formation of a silicon-oxy-aluminum bond (Si-O-Al) structure. Through this nucleophilic substitution reaction, the two compounds achieve a close molecular-level connection via covalent bonding. During the HF removal process, siloxane compounds mainly undergo irreversible substitution with HF through the ≡Si-OR bond (≡Si-OR+HF→≡Si-F+ROH), effectively reducing the concentration of free HF. Meanwhile, aluminum alkoxide compounds mainly eliminate trace water molecules through efficient hydrolysis, reducing the hydrolysis of LiPF6 and the generation of HF. The two work synergistically to efficiently remove HF from the electrolyte.

[0025] Furthermore, aluminum alkoxides act as crosslinking agents, promoting the crosslinking of the aluminum-oxy-silicon and silicon-oxy-aluminum structural units formed in the above reactions into a three-dimensional network polymer through aluminum-oxy-aluminum bonds (Al-O-Al). This allows the inorganic products generated during cycling (such as SiO2, Al2O3, etc.) to be uniformly distributed in the solid electrolyte interface (SEI) and cathode electrolyte interface (CEI), significantly reducing the activation energy of lithium-ion transport. In addition, this network can also suppress HF diffusion through size exclusion effect; at the same time, its high elastic modulus can effectively buffer the stress of electrode volume change, ensuring the consistency of lithium-ion flux spatial distribution and suppressing the propagation of microcracks and structural degradation of cathode materials caused by abrupt changes in lattice parameters at high temperatures.

[0026] Preferably, an aluminum alkoxide compound and an alkoxysilane compound are mixed to obtain an electrolyte additive composition.

[0027] The present invention provides an electrolyte comprising the above-described electrolyte additive composition or the electrolyte additive composition prepared by the above-described preparation method, an electrolyte solute, and a non-aqueous solvent.

[0028] Preferably, the electrolyte solute is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium dioxolaneborate (LiBOB), lithium difluorooxolaneborate (LiDFOB), lithium difluorodioxolane phosphate (LiDFOP), lithium trifluoromethanesulfonate (LiCF3SO3), lithium perchlorate (LiClO4), lithium difluorophosphate (LiPO2F2), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), and lithium tetrafluorooxolane phosphate (LiTFOP).

[0029] More preferably, the electrolyte solute is lithium hexafluorophosphate.

[0030] Preferably, the non-aqueous solvent is selected from one or more of carbonate solvents, carboxylic acid ester solvents, ether solvents, nitrile solvents, and sulfone solvents.

[0031] Preferably, the carbonate solvent is selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), diethyl carbonate (DEC), ethyl propyl carbonate (EPC), and dipropyl carbonate (DPC).

[0032] Preferably, the carboxylic acid ester solvent is selected from one or more of methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate, butyl acetate, methyl propionate, ethyl propionate (EP), propyl propionate (PP), butyl propionate, methyl butyrate, methyl isobutyrate, ethyl butyrate, methyl trimethylacetate, ethyl trimethylacetate, and 1,4-butyrolactone.

[0033] Preferably, the ether solvent is selected from one or more of 1,3-dioxane (DOL), 1,4-dioxane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), 2-trifluoromethyltetrahydrofuran (2-CF3-THF), diethyl ether, dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), and diethylene glycol dimethyl ether (TEGDME).

[0034] Preferably, the nitrile solvent is selected from one or more of acetonitrile (AN), malononitrile, succinic anionyl (SN), glutaronitrile, and adiponitrile (ADN).

[0035] Preferably, the sulfone solvent is selected from one or more of dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, and sulfolane.

[0036] Preferably, the non-aqueous solvent is a carbonate solvent.

[0037] Preferably, the carbonate solvent is a mixture of ethylene carbonate and diethyl carbonate.

[0038] Preferably, the amount of the electrolyte additive composition is any value or range between 1% and 15% of the total mass of the electrolyte, specifically selected from: 1%, 1.1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 8%, 8.5%, 10%, 10.5%, 12%, 12.5%, 13%, 13.5%, 14%, 15%, or a range between two of these.

[0039] More preferably, the amount of the electrolyte additive composition is selected from any value or range between 1.1% and 12% of the total mass of the electrolyte, specifically from: 1.1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 8%, 8.5%, 10%, 10.5%, 12% or a range between the two.

[0040] More preferably, the amount of the electrolyte additive composition is selected from 5.5% of the total mass of the electrolyte.

[0041] Preferably, the amount of alkoxysilane compound in the electrolyte additive composition is selected from any value or range between 1% and 10% of the total mass of the electrolyte, specifically from: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range between the two.

[0042] More preferably, the amount of alkoxysilane compound in the electrolyte additive composition is selected from any value or range between 1% and 5% of the total mass of the electrolyte.

[0043] More preferably, the amount of alkoxysilane compound in the electrolyte additive composition is 5% of the total mass of the electrolyte.

[0044] Preferably, the amount of aluminum alkoxide compound in the electrolyte additive composition is selected from any value or range between 0.1% and 2% of the total mass of the electrolyte, specifically from: 0.1%, 0.5%, 1%, 1.5%, 2% or a range between the two.

[0045] More preferably, the amount of aluminum alkoxide compound in the electrolyte additive composition is selected from any value or range between 0.1% and 0.5% of the total mass of the electrolyte.

[0046] More preferably, the amount of aluminum alkoxide compound in the electrolyte additive composition is 0.5% of the total mass of the electrolyte.

[0047] The present invention also provides a method for preparing the above-mentioned electrolyte, comprising the following steps: The electrolyte solute and electrolyte additive composition are dissolved in a non-aqueous solvent and mixed well to obtain the final product.

[0048] The specific method for preparing the electrolyte described above is as follows: First, ethylene carbonate and diethyl carbonate are mixed evenly in a volume ratio of 1:1 as a non-aqueous solvent; then, LiPF6 electrolyte solute is added to a concentration of 1M and mixed evenly; finally, an electrolyte additive composition is added and mixed evenly to obtain the final product.

[0049] The present invention also provides the application of the above-described electrolyte or the electrolyte prepared by the above-described preparation method in the preparation of lithium secondary batteries.

[0050] The present invention also provides a lithium-ion secondary battery, which is prepared from the electrolyte described above or the electrolyte prepared by the above preparation method, a positive electrode material and a negative electrode material.

[0051] Preferably, the positive electrode material is selected from lithium nickel cobalt manganese oxide (LiNi). x Co y Mn 1-x-y O2), lithium iron phosphate (LiFePO4), lithium nickel cobalt aluminum oxide (LiNix Co y Al 1-x-y O2), lithium cobalt oxide (LiCoO2), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4), lithium-rich manganese (Li) 1+x [NiMnCo] 1-x Any of the following (O2).

[0052] More preferably, the positive electrode material is lithium nickel cobalt manganese oxide.

[0053] Preferably, the method for preparing the positive electrode material includes the following steps: adding positive electrode active material, conductive agent, and binder to N-methyl-2-pyrrolidone (NMP), stirring to obtain a positive electrode slurry, coating the positive electrode slurry onto a positive electrode current collector aluminum foil, and then baking, rolling, and cutting to obtain the final product.

[0054] Preferably, the method for preparing the cathode material specifically comprises: Lithium nickel cobalt manganese oxide (LiNi) positive electrode active material was mixed in a mass ratio of 94:3:3. 0.8 Co 0.1 Mn 0.1 O2, NCM811), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are added to N-methyl-2-pyrrolidone and stirred evenly to form a positive electrode slurry. The positive electrode slurry is then evenly coated on the current collector aluminum foil, and after baking, rolling, and cutting, a positive electrode sheet is obtained.

[0055] Preferably, the negative electrode material is selected from any one of graphite, lithium metal, copper, silicon-carbon, and silicon.

[0056] More preferably, the negative electrode material is lithium metal.

[0057] The beneficial effects of this invention are as follows: The present invention has at least the following beneficial effects: (1) The aluminum alkoxide compound and siloxane compound in the compound additive system of the present invention construct an Al-O-Si three-dimensional network, forming a stable interface layer with high elastic modulus, reducing the side reaction between the electrode and the electrolyte, and filling the SEI crack generated by charging and discharging in real time.

[0058] (2) The compound additive system of the present invention improves the thermal safety and cycle life of the battery: the high bond energy characteristics of Si-O bond greatly increase the initial decomposition temperature of the electrolyte and significantly improve the high temperature storage life; the in-situ generated nano silica fills the interface defects, greatly reducing the capacity decay rate of the battery under high temperature cycling, and greatly improving the safety and environmental adaptability of the battery.

[0059] (3) The compound additive system of the present invention completely removes HF through irreversible bonding mechanism and inhibits the generation of HF, suppresses the concentration of free HF in the electrolyte to below 1 ppm, completely blocks the corrosion chain of HF on the electrode, greatly reduces the dissolution of transition metal ions, and significantly improves the stability of the positive electrode structure. Detailed Implementation

[0060] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0061] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all instruments, devices, equipment, reagents, products, etc., used in the embodiments of the present invention are obtained through conventional commercial means.

[0062] In the comparative examples of this invention, the aluminum triethanolamine used was prepared according to the method disclosed in "Transformation of bulk alloys to oxide nanowires" (Lei, D. et al. Science. 355: 267-271 (2017)). The specific preparation process is as follows: First, lithium powder and aluminum powder were used as materials for synthesizing LiAl alloy. 0.085g of lithium powder and 0.3g of aluminum powder (atomic ratio Li:Al = 1:1, 10% excess Li) were added to a graphite crucible lined with graphite paper. After heating at 800℃ for 30min, the graphite crucible was removed from the muffle furnace, and the graphite plunger was immediately pressed down to obtain the LiAl alloy. 0.115g of the LiAl alloy was placed in 20mL of anhydrous ethanol and left at 60℃ for 30h. A homogeneous aluminum triethanolamine (in the form of nanowires with a diameter of 20-200nm) was obtained through a chemical desalting process.

[0063] Preparation of the positive electrode: positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are added to N-methyl-2-pyrrolidone (NMP) in a mass ratio of 94:3:3 and stirred evenly to form a positive electrode slurry. The positive electrode slurry is then evenly coated onto the positive electrode current collector aluminum foil, and after baking, rolling, and cutting, a positive electrode sheet is obtained.

[0064] The negative electrode sheet was purchased from Tianjin Zhongneng Lithium Industry Co., Ltd.

[0065] The negative electrode shell, positive electrode shell, stainless steel sheet, gasket, and spring were all purchased from Dongguan Kelude Experimental Equipment Technology Co., Ltd., model number CR2032.

[0066] The diaphragm was purchased from Dongguan Kelude Experimental Equipment Technology Co., Ltd., model Celgard 2500.

[0067] Example 1: Preparation of Electrolyte The preparation method is as follows: Ethyl carbonate (EC) and diethyl carbonate (DEC) are mixed evenly in a volume ratio of 1:1 as the electrolyte solvent; LiPF6 is added to a concentration of 1M and mixed evenly; an electrolyte additive composition (0.5% aluminum triethanolamine and 5% tetramethoxysilane (TMS) by mass percentage of electrolyte) is added and mixed evenly.

[0068] Example 2 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive composition uses 0.5% aluminum triethanolamine and 5% methyltrimethoxysilane (MTMS) by mass of the electrolyte, while the other steps and amounts are the same as in Example 1.

[0069] Example 3 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive composition uses 0.5% aluminum triethanolamine and 5% trimethoxysilane (TMOS) by mass of the electrolyte, while the other steps and amounts are the same as in Example 1.

[0070] Example 4 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive composition uses 0.5% aluminum triethanolamine and 5% triethoxysilane (TEOS) by mass of the electrolyte, while the other steps and amounts are the same as in Example 1.

[0071] Example 5 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive composition uses 0.5% aluminum triethanolamine and 5% vinyltrimethoxysilane (VTMOS) by mass of electrolyte, while the other steps and amounts are the same as in Example 1.

[0072] Example 6 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive composition uses 0.5% aluminum triethanolamine and 5% trifluoropropyltrimethoxysilane (TFPS) by mass of electrolyte, while the other steps and amounts are the same as in Example 1.

[0073] Example 7 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive composition uses 0.5% aluminum isopropoxide and 5% tetramethoxysilane (TMS) by mass of the electrolyte, while the other steps and amounts are the same as in Example 1.

[0074] Example 8 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive composition uses 0.1% aluminum triethanolamine and 1% tetramethoxysilane (TMS) by mass of electrolyte, while the other steps and amounts are the same as in Example 1.

[0075] Example 9 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive composition uses 2% aluminum triethanolamine and 10% tetramethoxysilane (TMS) by mass of the electrolyte, while the remaining steps and amounts are the same as in Example 1.

[0076] Comparative Example 1 Compared with Example 1, the only difference is that no electrolyte additive composition is added, while the other steps and dosages are the same as in Example 1.

[0077] Comparative Example 2 Compared with Example 1, the only difference is that the electrolyte additive composition uses only 0.5% aluminum triethanolamine by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0078] Comparative Example 3 Compared with Example 1, the only difference is that the electrolyte additive composition uses only 5% tetramethoxysilane (TMS) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0079] Comparative Example 4 Compared with Example 1, the only difference is that the electrolyte additive composition uses only aluminum triethanolamine at a mass percentage of 5.5% of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0080] Comparative Example 5 Compared with Example 1, the only difference is that the electrolyte additive composition uses only tetramethoxysilane (TMS) at a mass percentage of 5.5% of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0081] Comparative Example 6 Compared with Example 1, the only difference is that the electrolyte additive composition uses 0.5% aluminum triethanolamine and 5% γ-glycidoxypropyltrimethoxysilane by mass of electrolyte, while the other steps and dosages are the same as in Example 1.

[0082] Comparative Example 7 Compared with Example 1, the only difference is that the electrolyte contains 0.05% aluminum triethanolamine and 12% tetramethoxysilane (TMS) by mass, while the other steps and amounts are the same as in Example 1.

[0083] Comparative Example 8 Compared with Example 1, the only difference is that the electrolyte contains 3.5% aluminum triethanolamine and 0.5% tetramethoxysilane (TMS) by mass, while the other steps and amounts are the same as in Example 1.

[0084] Detection Example 1 1. Experimental Methods: (1) Assembly and high-temperature storage performance test of the full cell: The coin cell was assembled in the following order: negative electrode shell, negative electrode sheet, 30 μL electrolyte, separator, 30 μL electrolyte, positive electrode sheet, gasket, spring sheet, and positive electrode shell. The cell was left to stand for 8 hours at 45°C and activated for 3 cycles at a current density of 0.5C. Then it was charged to 4.3V at 1C and discharged to 3.0V to obtain the first discharge specific capacity and first coulombic efficiency of the cell at 1C. The cell was cycled for 50 cycles under the above conditions to obtain the discharge specific capacity of the cell at the 50th cycle and the capacity retention rate of the cell after 50 cycles was calculated. The capacity retention rate of the cell after 50 cycles = discharge specific capacity of the cell at the 50th cycle / discharge specific capacity of the cell at the first cycle.

[0085] (2) High temperature storage performance test: Assemble the button cell in the following order: negative electrode shell, negative electrode sheet, 30μL electrolyte, separator, 30μL electrolyte, positive electrode sheet, gasket, spring sheet, and positive electrode shell. At 30℃, the battery was left to stand for 8 hours, then charged to 4.3V at a current density of 0.2C, and then charged at a constant voltage until the current rate was less than 0.02C. It was then discharged at 0.2C to 3.0V to obtain the initial specific capacity at 0.2C. The battery was then charged to 4.3V, charged at a constant voltage until the current rate was less than 0.02C, and then stored in an 85℃ oven for 6 hours. It was then discharged at 30℃ at 0.2C to 3V to obtain the remaining specific capacity and capacity retention rate after high-temperature storage (capacity retention rate = remaining specific capacity / initial specific capacity). Finally, the battery was charged to 4.3V at 30℃, charged at a constant voltage until the current rate was less than 0.02C, and then discharged at 0.2C to 3.0V to obtain the recovered specific capacity and capacity recovery rate (capacity recovery rate = recovered specific capacity / initial specific capacity).

[0086] 2. Experimental Results As shown in Table 1, without electrolyte additives, the battery's cycle capacity rapidly decays at high temperatures, and both voltage and capacity drop sharply after high-temperature storage. When only aluminum alkoxide compounds or siloxane compounds are added to the electrolyte, the battery's high-temperature storage performance improves, voltage drop decreases, and capacity retention increases, but the high-temperature cycle performance remains poor, with rapid capacity decay. However, when both aluminum alkoxide compounds and specific siloxane compounds are added to the electrolyte, the battery's cycle stability at 45°C is significantly improved compared to the control group without additives and the control group using only one additive. The high-temperature storage performance is also significantly improved. Furthermore, in Control Group 6, when γ-glycidoxypropyltrimethoxysilane was used as an additive, its high-temperature cycle capacity retention was even lower than that of Control Group 1 without additives, and the voltage drop after high-temperature storage was also larger, resulting in lower capacity retention. This indicates that aluminum alkoxide compounds only have a synergistic effect with specific siloxane compounds, effectively improving the electrolyte's thermal stability, the battery's high-temperature cycle stability, and high-temperature storage life, which will greatly enhance the battery's safety and stability.

[0087] Table 1. Battery and electrolyte performance test results

[0088] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. An electrolyte additive composition, characterized in that, This includes alkoxysilane compounds and aluminum alkoxide compounds; the structural formula of the alkoxysilane compounds is shown in Formula I: ； The structural formula of the aluminum alkoxide compound is shown in Formula II: ， Wherein, R1 is selected from saturated alkyl, unsaturated hydrocarbon or haloalkyl groups of C1-C6; R2-R4 are each independently selected from hydrogen atom, halogen atom, saturated alkyl, unsaturated hydrocarbon, haloalkyl, alkoxy or ether group of C1-C6; R5-R7 are each independently selected from alkyl groups containing C1-C8. The mass ratio of the alkoxysilane compound to the aluminum alkoxide compound is 1-10:0.1-2.

2. The electrolyte additive composition according to claim 1, characterized in that, R1 is selected from C1-C3 saturated alkyl or haloalkyl groups; The R2-R4 are each independently selected from hydrogen atoms, halogen atoms, C1-C3 saturated alkyl groups, unsaturated hydrocarbon groups, haloalkyl groups, alkoxy groups, and ether groups.

3. The electrolyte additive composition according to claim 1, characterized in that, The alkoxysilane compound is selected from one or more of tetramethoxysilane, methyltrimethoxysilane, trimethoxysilane, triethoxysilane, vinyltrimethoxysilane, and trifluoropropyltrimethoxysilane; The aluminum alkoxide compound is selected from one or more of aluminum triethanolamine, aluminum isopropoxide, aluminum n-propoxide, aluminum sec-butoxide, aluminum tert-butoxide, and aluminum isopentoxide.

4. The electrolyte additive composition according to claim 1, characterized in that, An electrolyte additive composition is obtained by mixing an aluminum alkoxide compound and an alkoxysilane compound.

5. An electrolyte, characterized in that, Includes the electrolyte additive composition, electrolyte solute and non-aqueous solvent as described in any one of claims 1-4.

6. The electrolyte according to claim 5, characterized in that, The electrolyte solute is selected from one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, lithium trifluoromethanesulfonate, lithium perchlorate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, and lithium tetrafluorooxalate phosphate. The non-aqueous solvent is selected from one or more of carbonate solvents, carboxylic acid ester solvents, ether solvents, nitrile solvents, and sulfone solvents.

7. The electrolyte according to claim 5, characterized in that, The amount of the electrolyte additive composition used is 1-15% of the total mass of the electrolyte; The amount of alkoxysilane compound in the electrolyte additive composition is 1-10% of the total mass of the electrolyte; The amount of aluminum alkoxide compound in the electrolyte additive composition is 0.1-2% of the total mass of the electrolyte; Preferably, the amount of the electrolyte additive composition is 1.1-12% of the total mass of the electrolyte.

8. The method for preparing the electrolyte according to any one of claims 5-7, characterized in that, Includes the following steps: The electrolyte solute and electrolyte additive composition are dissolved in a non-aqueous solvent and mixed well to obtain the final product.

9. The application of the electrolyte according to any one of claims 5-7 or the electrolyte prepared by the preparation method according to claim 8 in the preparation of lithium secondary batteries.

10. A lithium-ion secondary battery, characterized in that, The electrolyte, positive electrode material, and negative electrode material are prepared using the electrolyte according to any one of claims 5-7 or the preparation method according to claim 8.

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