An electrolyte additive composition, electrolyte, and preparation method and application thereof

Abstract

The application discloses an electrolyte additive composition, an electrolyte and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The technical problem to be solved is the sharp capacity decline of the battery after long-term high-temperature storage. The electrolyte additive composition comprises an amine / amide compound and an alcohol aluminum compound; the structural formula of the amine / amide compound is at least one of the structural formulas shown in formula I and formula II, wherein R1, R2 and R3 are each independently selected from a hydrogen atom, a substituted or unsubstituted C1-C12 alkyl, a substituted or unsubstituted C2-C12 unsaturated hydrocarbon group, a substituted or unsubstituted C3-C12 cycloalkyl and a substituted or unsubstituted C6-C14 aryl; and the structural formula of the alcohol aluminum compound is shown in formula III, wherein R4, R5 and R6 are alkyl groups containing 1-8 carbons. Formula I, formula II and formula III.

Description

Technical Field

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

[0002] Lithium-ion rechargeable batteries, due to their high energy density, long cycle life, and environmental compatibility, have become a core energy technology supporting portable electronic devices, electric vehicles, and large-scale energy storage systems. To overcome the challenges of capacity retention degradation and safety reliability under high-temperature conditions, developing battery systems that combine long-term stability with intrinsic safety is an urgent need for industrial development.

[0003] Under high-temperature conditions, battery systems are highly susceptible to systemic failures: the hydrolysis reaction of LiPF6 continuously generates corrosive HF, which erodes the active materials of the electrodes and catalyzes the dissolution of transition metal ions; the aluminum current collector undergoes localized perforation under the synergistic effect of HF corrosion and electrochemical polarization; and the exothermic reaction coupled with the flammability of the solvent significantly lowers the thermal runaway trigger threshold. These associated failures lead to a sharp decline in battery capacity retention after prolonged high-temperature storage and pose safety risks, seriously threatening system reliability.

[0004] Electrolyte additives are an economical and effective modification strategy for addressing high-temperature failure issues. However, traditional additives are often designed with a single function in mind, making it difficult to synergistically solve multiple interfacial failure problems at high temperatures. For example, some additives can form a protective layer on the electrode surface, but cannot effectively suppress the continued occurrence of interfacial side reactions at high temperatures; other additives may improve initial interfacial kinetics, but are insufficient in protecting the stability of the current collector during long-term high-temperature storage. This functional disconnect creates a bottleneck in improving the overall performance of batteries under harsh high-temperature conditions.

[0005] Amine compounds, due to their unique molecular structure, are considered promising multifunctional additives. The nitrogen-rich interfaces produced by their decomposition can effectively improve the ionic conductivity of the solid electrolyte interphase (SEI) / cathode electrolyte interphase (CEI) layer, thereby enhancing the battery's high-temperature storage life. To further improve the uniformity and stability of the interface, enhance scavenging persistence, and expand corrosion resistance, they need to be compounded with trace amounts of aluminum alkoxides to construct a synergistic defense line—the Al in the aluminum alkoxides... 3+ It forms Al-N coordination bonds with amine groups, inducing the formation of a dense AlN / Al2O3 composite film on the aluminum foil surface to block corrosion pathways. At the same time, it catalyzes the cross-linking of amine molecules into a thermally stable network, thereby enabling the battery to operate or be stored safely and reliably at high temperatures.

[0006] Relevant patent documents retrieved:

[0007] This document, published in China (CN108832175A) on November 16, 2018, discloses a method for preparing a polymer electrolyte. The method involves dissolving ethylene glycol and a first deacidifying agent in a first organic solvent to prepare an ethylene glycol solution. Under ice bath conditions, 2-chloro-2-oxo-1,3,2-dioxophosphazenecyclopentane is added dropwise to the ethylene glycol solution to obtain a ring-opening monomer. This monomer, along with a catalyst, is dissolved in a second organic solvent under an anhydrous inert atmosphere. Then, ethylene glycol monomethyl ether, a ring-opening polymerization initiator, is added to the solvent. After reacting, separation, and drying, an ion-conducting agent is obtained. Finally, a crosslinking agent, lithium salt, thermal initiator, and ion-conducting agent are mixed and poured into a mold for in-situ polymerization to obtain the final product.

[0008] The document, published in China (CN119419359A) on February 11, 2025, discloses a cyclophosphamide electrolyte additive, its electrolyte, and a lithium-ion battery. The electrolyte uses cyclophosphamide as the additive, and the decomposition products of cyclophosphamide participate in the construction of the SEI film. The cyclic structure improves the chemical stability of the SEI film, while the phosphoramide structure improves the thermal stability of the SEI film. Simultaneously, it enhances the flame retardancy of the electrolyte, thereby simultaneously improving the battery's cycle life and safety performance.

[0009] The prior art represented by the aforementioned documents has at least the following unresolved technical problems or defects: 1. The polymer electrolyte prepared by CN108832175A still exhibits low ionic conductivity at low temperatures, indicating that its conductivity needs further improvement. Moreover, in high-energy-density batteries, flame retardancy of the matrix alone may be insufficient to cope with extreme thermal runaway conditions. Furthermore, the preparation of this polymer electrolyte requires complex processes such as multi-step reactions, crosslinking, and in-situ polymerization, which is not conducive to large-scale industrial production.

[0010] 2. The lithium-ion battery prepared by CN119419359A, using cyclophosphamide as an electrolyte additive, still cannot completely solve the problems of lithium-ion desolvation and slow transport at extreme low temperatures, resulting in limited improvement in low-temperature performance. Moreover, the complex synthesis, high cost, and incompatibility with existing electrolyte systems are industrialization obstacles that make it unsuitable for large-scale industrial production. Summary of the Invention

[0011] The purpose of this invention is to provide: An electrolyte additive composition, an electrolyte, a method for preparing the electrolyte and its application, and related technologies, to solve technical problems such as the sharp decline in battery capacity after long-term high-temperature storage, or a combination thereof.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides an electrolyte additive composition comprising an amine / amide compound and an aluminum alkoxide compound; wherein the amine / amide compound has a structural formula selected from at least one of the formulas shown in Formula I and Formula II.

[0013] Formula I;

[0014] Formula II; R1, R2, and R3 are each independently selected from hydrogen atoms, substituted or unsubstituted C1-C12 alkyl groups, substituted or unsubstituted C2-C12 unsaturated hydrocarbon groups, substituted or unsubstituted C3-C12 cycloalkyl groups, and substituted or unsubstituted C6-C14 aryl groups.

[0015] Preferably, R1, R2, and R3 are each independently selected from one or more of the following: hydrogen atom, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxyalkyl, substituted or unsubstituted C1-C6 aminoalkyl, substituted or unsubstituted C3-C8 cycloalkyl, substituted or unsubstituted C6-C10 aryl, and substituted or unsubstituted C2-C6 unsaturated hydrocarbon group.

[0016] Preferably, the amine / amide compound is selected from one or more of N-(2-methoxyethyl)methylamine (MOEA), formamide (FM), benzamide (BZA), diethylenetriamine (DETA), 2-methoxyethylamine (MEA), p-phenylenediamine (PPD), cis-1,2-cyclohexanediamine (DACH), n-butylamine, and acrylamide.

[0017] Preferably, the aluminum alkoxide compound has the structural formula shown in Formula III:

[0018] Formula III; R4, R5, and R6 are each independently selected from alkyl groups containing C1-C8.

[0019] Preferably, R4, R5, and R6 are each independently selected from alkyl groups containing C2-C6. Preferably, the aluminum alkoxide compound is selected from one or more of aluminum triethanolamine, aluminum isopropoxide, aluminum n-propoxide, aluminum sec-butoxide, and aluminum isoamyl alcohol.

[0020] More preferably, the aluminum alkoxide compound is aluminum triethanolamine and / or aluminum sec-butoxide.

[0021] More preferably, the aluminum alkoxide compound is aluminum triethanolamine.

[0022] Preferably, the mass ratio of the amine / amide compound to the aluminum alkoxide compound is selected from any value or range between 0.1-3:0.1-2, specifically from: 0.1:0.1, 0.5:1, 0.5:2, 1:0.5, 2:0.5, 1:0.5, 3:2 or a range between the two.

[0023] More preferably, the mass ratio of the amine / amide compound to the aluminum alkoxide compound is selected from any value or range between 0.1-1:0.1-0.5.

[0024] More preferably, the mass ratio of the amine / amide compound to the aluminum alkoxide compound is 1:0.5.

[0025] Preferably, the preparation method of the electrolyte additive composition includes the following steps: The aluminum alkoxide compound and the amine / amide compound are mixed to obtain the product.

[0026] The present invention also provides an electrolyte comprising the above-described electrolyte additive composition, an electrolyte solute, and a non-aqueous solvent.

[0027] Preferably, the electrolyte solute is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxalateborate, lithium difluorooxalateborate, lithium difluorodioxalate phosphate, lithium trifluoromethanesulfonate, lithium perchlorate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, and lithium tetrafluorooxalate phosphate.

[0028] More preferably, the electrolyte solute is lithium hexafluorophosphate.

[0029] Preferably, the non-aqueous solvent is selected from one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0030] More preferably, the non-aqueous solvent is a mixture of diethyl carbonate and ethylene carbonate.

[0031] Preferably, the amount of the electrolyte additive composition is selected from any value or range between 0.2% and 5% of the total mass of the electrolyte, specifically from: 0.2%, 0.5%, 1%, 1.5%, 2.1%, 2.5%, 3.1%, 3.8%, 4%, 4.5%, 5% or a range between the two.

[0032] More preferably, the amount of the electrolyte additive composition is selected from any value or range between 0.2% and 1.5% of the total mass of the electrolyte.

[0033] More preferably, the amount of the electrolyte additive composition is selected from 1.5% of the total mass of the electrolyte.

[0034] Preferably, the amount of amine / amide compounds in the electrolyte additive composition is selected from any value or range between 0.1% and 3% of the total mass of the electrolyte, specifically from: 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% or a range between the two.

[0035] More preferably, the amount of amine / amide compounds in the electrolyte additive composition is selected from any value or range between 0.1% and 1% of the total mass of the electrolyte.

[0036] More preferably, the amount of amine / amide compounds in the electrolyte additive composition is 1% of the total mass of the electrolyte.

[0037] 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.

[0038] 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.

[0039] More preferably, the amount of aluminum alkoxide compound in the electrolyte additive composition is 0.5% of the total mass of the electrolyte.

[0040] The present invention also provides a method for preparing the above-mentioned electrolyte, characterized by 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.

[0041] The specific method for preparing the electrolyte described above is as follows: First, ethylene carbonate (EC) and diethyl carbonate (DEC) 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.

[0042] 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-ion secondary batteries.

[0043] The present invention also provides a lithium-ion secondary battery, comprising the electrolyte described above or the electrolyte prepared by the above preparation method, a positive electrode material, and a negative electrode material.

[0044] Preferably, the cathode material is selected from any one of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium nickel manganese oxide, and lithium-rich manganese.

[0045] More preferably, the positive electrode material is lithium nickel cobalt manganese oxide.

[0046] 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, 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.

[0047] 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 (NMP) 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.

[0048] Preferably, the negative electrode material is selected from any one of graphite, lithium metal, copper, silicon carbide, and silicon.

[0049] More preferably, the negative electrode material is lithium metal.

[0050] The beneficial effects of this invention are as follows: The present invention has at least the following beneficial effects: 1. This invention uses an aluminum alkoxide compound and an amine / amide compound to form an electrolyte additive composition for use in lithium-ion battery electrolytes. By utilizing the in-situ formed Al-N coordination structure to precisely control the lithium-ion solvation environment, the deposition / dissolution kinetics of lithium ions at the negative electrode interface are significantly optimized, and the nucleation overpotential is effectively reduced.

[0051] 2. This invention utilizes the preferential reaction and cross-linking characteristics of the aforementioned coordination complex at the electrode (especially the positive electrode) and aluminum current collector interface to induce the formation of an inorganic-organic composite interface film rich in high-ionic conductors such as Li3N and AlN. This synergistically constructed interface layer (SEI / CEI and current collector passivation layer) exhibits excellent structural density and thermal stability, thereby synergistically achieving high capacity retention, recovery rate, low voltage drop, and long cycle life after high-temperature storage. Detailed Implementation

[0052] 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.

[0053] 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.

[0054] The aluminum triethanolamine used in the embodiments and comparative examples of this invention 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, with 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 LiAl alloy. 0.115g of LiAl alloy was placed in 20mL of anhydrous ethanol and placed at 60℃ for 30h. Uniform aluminum triethanolamine (in the form of nanowires with a diameter of 20-200nm) was obtained through a chemical desalting process.

[0055] 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.

[0056] The negative electrode sheet was purchased from Tianjin Zhongneng Lithium Industry Co., Ltd.

[0057] 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.

[0058] The diaphragm was purchased from Dongguan Kelude Experimental Equipment Technology Co., Ltd., model Celgard 2500.

[0059] Aluminum sec-butoxide was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0060] Example 1: Preparation of Electrolyte The preparation method is as follows: Ethylene 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; electrolyte additive (0.5% aluminum triethanolamine and 1% formamide (FM) by mass percentage of electrolyte) is added and mixed evenly.

[0061] Example 2 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 0.5% aluminum triethanolamine and 1% benzamide (BZA) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0062] Example 3 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 0.5% aluminum triethanolamine and 1% diethylenetriamine (DETA) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0063] Example 4 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 0.5% aluminum triethanolamine and 1% 2-methoxyethylamine (MEA) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0064] Example 5 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 0.5% aluminum triethanolamine and 1% p-phenylenediamine (PPD) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0065] Example 6 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 0.5% aluminum triethanolamine and 1% N-(2-methoxyethyl)methylamine (MOEA) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0066] Example 7 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 0.5% aluminum triethanolamine and 1% cis-1,2-cyclohexanediamine (DACH) by mass of the electrolyte. All other steps and dosages are the same as in Example 1.

[0067] Example 8 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 0.1% aluminum triethanolamine and 0.1% formamide (FM) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0068] Example 9 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 2% aluminum triethanolamine and 3% formamide (FM) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0069] Example 10 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 0.5% aluminum triethanolamine and 1% n-butylamine (NBA) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0070] Example 11 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 0.5% aluminum triethanolamine and 1% acrylamide (AAM) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0071] Example 12 Preparation of Electrolyte Compared with Example 1, the only difference is that the electrolyte additive uses 0.5% aluminum sec-butoxide (ASB) and 1% formamide (FM) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0072] Comparative Example 1 Compared with Example 1, the only difference is that no electrolyte additive is added, while the other steps and dosages are the same as in Example 1.

[0073] Comparative Example 2 Compared with Example 1, the only difference is that the electrolyte additive uses only formamide (FM) at a mass percentage of 1% of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0074] Comparative Example 3 Compared with Example 1, the only difference is that the electrolyte additive uses only aluminum triethanolamine at a mass percentage of 0.5% of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0075] Comparative Example 4 Compared with Example 1, the only difference is that the electrolyte additive uses only aluminum triethanolamine at a mass percentage of 1.5% of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0076] Comparative Example 5 Compared with Example 1, the only difference is that the electrolyte additive uses only formamide (FM) at a mass percentage of 1.5% of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0077] Comparative Example 6 Compared with Example 1, the only difference is that the electrolyte additive uses 0.05% aluminum triethanolamine and 5% formamide (FM) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0078] Comparative Example 7 Compared with Example 1, the only difference is that the electrolyte additive uses 5% aluminum triethanolamine and 0.05% formamide (FM) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0079] Comparative Example 8 Compared with Example 1, the only difference is that the electrolyte additive uses 0.5% aluminum triethanolamine and 1% 2-pyridinecarboxamide (2-PA) by mass of the electrolyte, while the other steps and dosages are the same as in Example 1.

[0080] Detection example 1. Experimental Methods: (1) Assembly and cycle test of the full cell: The coin cell was assembled in the following order: negative electrode shell, negative electrode plate, 15μL electrolyte, separator, 15μL electrolyte, positive electrode plate, gasket, spring, and positive electrode shell. The cell was left to stand at 30°C for 6 hours, then charged at 1C to 4.4V and discharged at 1C to 3.0V to obtain the specific capacity and initial coulombic efficiency of the cell in the first cycle. The cell was cycled for 50 cycles under the above conditions to obtain the specific capacity of the cell in the 50th cycle and the capacity retention rate after 50 cycles was calculated. The capacity retention rate after 50 cycles = specific capacity of the cell in the 50th cycle / specific capacity of the cell in the first cycle.

[0081] (2) Full-cell high-temperature storage performance test: At 30℃, the battery was left to stand for 6 hours, and then charged to 4.4V and discharged to 3.0V at a current density of 0.1C to obtain the initial specific capacity of the battery at 0.1C; the battery was charged to 4.4V and the initial open-circuit voltage at this time was recorded (denoted as V1). After that, the battery was placed in an oven at 85℃ for 24 hours. After storage, its open-circuit voltage was measured and recorded (denoted as V2). The voltage drop (ΔV) during storage was calculated using the formula ΔV=V1-V2. Then, the battery was discharged to 3V at 30℃ to obtain the remaining specific capacity and capacity retention rate after high-temperature storage (capacity retention rate = remaining specific capacity / initial specific capacity); the battery was charged to 4.4V and discharged to 3.0V at 30℃ to obtain the recovered specific capacity and capacity recovery rate of the battery (capacity recovery rate = recovered specific capacity / initial specific capacity).

[0082] (3) Nucleation overpotential test: Assemble the Li||Li symmetric coin cell in a glove box in the following order: negative electrode shell, lithium negative electrode sheet, 15μL electrolyte, separator, 15μL electrolyte, lithium negative electrode sheet, gasket, spring sheet, and positive electrode shell. The electrolyte is the prepared aluminum alkoxide-amine composite electrolyte. After assembly, the battery is left to stand at 30℃ for 6 hours to ensure that the electrolyte fully wets the electrode sheet and separator. For the Li-Li symmetric battery, constant current charging is performed at 30℃ with a constant current density (e.g., 1mA / cm²). Record the charging curve and take the highest voltage point (V). max ) and the lowest voltage point (V min ), calculate the nucleation overpotential Δη=V max -V min .

[0083] 2. Experimental Results The performance test results of the batteries assembled with the electrolytes prepared in Examples 1-13 and Comparative Examples 1-8 are shown in Table 1.

[0084] As can be seen from the test results in Table 1, the electrolyte additive composition provided by this invention can significantly improve the overall electrochemical performance of lithium-ion batteries, completely solving the technical problem of sharp capacity decline after long-term high-temperature storage. In the 50-cycle test at room temperature, the capacity retention rate of each embodiment generally remained at an excellent level of about 88% to 93% (e.g., the battery assembled with the electrolyte prepared in Example 1 reached 93.68%), while the retention rate of each comparative example decreased significantly to between 43% and 67%. Moreover, the nucleation overpotential of the embodiments was generally lower than that of the comparative examples, indicating that the dual additive combination can synergistically construct a stable interface protective layer at room temperature. In the more stringent high-temperature storage test, the embodiments further demonstrated excellent resistance to high-temperature degradation, with a high-temperature capacity retention rate of up to 93.75% and a capacity recovery rate as high as 98.99% (battery assembled with the electrolyte prepared in Example 10), which is far superior to the performance of conventional comparative examples (e.g., the recovery rate of Comparative Example 1 was only 75.09%). Furthermore, the voltage drop after high-temperature storage in each embodiment was significantly reduced, as low as 180.3 mV in Example 1 and as high as 329.7 mV in Comparative Example 8. The nucleation overpotential of the embodiments was effectively suppressed, which further confirms that the composite additive system can effectively regulate lithium-ion transport and form a dense and low-resistance passivation film on the electrode surface, thereby significantly suppressing the decomposition of the electrolyte and the occurrence of parasitic side reactions under high-temperature conditions. It should be noted that the battery assembled with the electrolyte prepared in Comparative Example 7 could not be assembled and tested because the amount of aluminum alkoxide compound added was too high (reaching 5%), which prevented it from dissolving with amine compounds to form a clear electrolyte system. This not only confirms the absolute necessity of rationally controlling the ratio of the two additives to maintain the thermodynamic stability of the electrolyte, but also fully highlights the irreplaceable critical technical significance of the range of compound types and mass ratios defined in this invention.

[0085] Table 1 Test Results

[0086] In Table 1, " / " indicates that measurement could not be performed, i.e., no measurement data is available.

[0087] 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 amine / amide compounds and aluminum alkoxide compounds; the structural formula of the amine / amide compounds is selected from at least one of the formulas shown in Formula I and Formula II: Formula I; Formula II; R1, R2, and R3 are each independently selected from hydrogen atoms, substituted or unsubstituted C1-C12 alkyl groups, substituted or unsubstituted C2-C12 unsaturated hydrocarbon groups, substituted or unsubstituted C3-C12 cycloalkyl groups, and substituted or unsubstituted C6-C14 aryl groups. The structural formula of the aluminum alkoxide compound is shown in Formula III: Formula III; R4, R5, and R6 are each independently selected from alkyl groups containing C1-C8.

2. The electrolyte additive composition according to claim 1, characterized in that, R1, R2, and R3 are each independently selected from one or more of the following: hydrogen atom, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxyalkyl, substituted or unsubstituted C1-C6 aminoalkyl, substituted or unsubstituted C3-C8 cycloalkyl, substituted or unsubstituted C6-C10 aryl, and substituted or unsubstituted C2-C6 unsaturated hydrocarbon group; R4, R5, and R6 are each independently selected from alkyl groups containing C2-C5.

3. The electrolyte additive composition according to claim 1, characterized in that, The amine / amide compounds are selected from one or more of formamide, benzamide, diethylenetriamine, 2-methoxyethylamine, p-phenylenediamine, N-(2-methoxyethyl)methylamine, cis-1,2-cyclohexanediamine, n-butylamine, and acrylamide; The aluminum alkoxide compound is selected from one or more of aluminum triethanolamine, aluminum isopropoxide, aluminum n-propoxide, aluminum sec-butoxide, and aluminum isoamyl alcohol.

4. The electrolyte additive composition according to claim 1, characterized in that, The mass ratio of the amine / amide compound to the aluminum alkoxide compound is 0.1-3:0.1-2; The preparation method of the electrolyte additive composition includes the following steps: The aluminum alkoxide compound and the amine / amide compound are mixed to obtain the product.

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 ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.

7. The electrolyte according to claim 5, characterized in that, The amount of the electrolyte additive composition used is 0.2-5% of the total mass of the electrolyte; The amount of amine / amide compounds in the electrolyte additive composition is 0.1-3% 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.

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, Includes the electrolyte as described in any one of claims 5-7 or the electrolyte, positive electrode material, and negative electrode material prepared by the preparation method described in claim 8.

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