Aluminum alkoxide-phosphate / phosphite electrolyte and preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion batteries, and provides an aluminum alkoxide-phosphate / phosphite electrolyte as well as a preparation method and application thereof. The aluminum alkoxide-phosphate ester / phosphite ester electrolyte comprises aluminum triethoxide, a phosphate ester / phosphite ester compound, an electrolyte solute and a non-aqueous solvent; the phosphate ester / phosphite ester compound is trimethyl phosphate, triethyl phosphate, triisobutyl phosphate, triphenyl phosphate, tripropargyl phosphate, tris (trimethylsilyl) phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, trimethyl phosphite, triethyl phosphite and triisopropyl phosphite, and the solvent is a solvent. The catalyst is one or more of triphenyl phosphite and tri (trimethylsilyl) phosphite. The electrolyte has good thermal stability and flame retardance under high voltage, and the safety of the battery is greatly improved; in addition, the electrolyte additive composition can inhibit the corrosion of the aluminum current collector, so that the side effect of the corrosion of the current collector on the battery is reduced.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and provides an aluminum alkoxide-phosphate / phosphite electrolyte, its preparation method and application. Background Technology

[0002] Lithium-ion rechargeable batteries, with their excellent energy density, cycle life, and environmental friendliness, have become an ideal energy carrier for portable electronic devices, electric vehicles, and large-scale energy storage. To overcome current energy density bottlenecks and eliminate safety hazards, developing battery systems that combine high specific energy with high reliability is the core objective of the industry's development.

[0003] While increasing the charging cutoff voltage can effectively improve the specific capacity and operating voltage platform of the cathode material, commercial LiPF6 / carbonate electrolytes face severe challenges under high voltage conditions above 4.5V: the oxidative decomposition of solvent molecules triggers the continuous dissolution of transition metal ions, leading to the collapse of the cathode structure; the decomposition products of lithium hexafluorophosphate corrode the aluminum current collector, causing local perforation and inducing current distribution distortion; at the same time, the flammability of organic solvents and the exothermic side reactions work together to significantly increase the risk of thermal runaway. These defects severely restrict the practical application of high-voltage batteries.

[0004] Electrolyte additives, as a key means of interface optimization, can cause imbalances in the spatial distribution of lithium-ion flux due to the heterogeneous interface layer formed by their simple chemical decomposition. This non-uniformity leads to localized concentration of lithium deposition on the negative electrode side, accelerating dendrite penetration into the separator; abnormally high current density at corrosion sites of the aluminum current collector on the positive electrode side, causing potential micro-short circuits; and violent decomposition of the electrolyte in the interfacial hot zone causes gas expansion, further amplifying safety risks. To ensure uniform lithium-ion flow, balanced electrode stress distribution, and interfacial thermal stability under high voltage, it is urgent to develop novel additive systems with molecular synergistic effects to construct multifunctional composite interface layers through chemical interactions.

[0005] Chinese invention patent application CN112164825A discloses a high-voltage phosphate ester electrolyte additive and a lithium-ion battery electrolyte containing the additive. It proposes phosphate esters as additives for lithium-ion battery electrolytes because they can stabilize LiPF6 and form a uniform and dense CEI and SEI film on the surfaces of the positive and negative electrodes, thus stabilizing the electrode-electrolyte interface and protecting the positive and negative electrode materials from byproduct attacks, resulting in a significant improvement in battery performance. However, the interface reconstruction law of the composite system under high-voltage long-cycle conditions, its safety in high-temperature thermal runaway scenarios, and its interaction mechanism in complex electrolyte environments still require in-depth exploration.

[0006] Chinese invention patent application CN119601770A discloses a non-flammable electrolyte for lithium-ion batteries and its preparation method. The electrolyte comprises an organic solvent, a lithium salt, a fluorophosphate ester, and a film-forming additive, wherein the film-forming additive is aluminum isopropoxide. This meets the current market requirements for non-flammable and high-safety performance of electrolytes. However, when used in lithium-ion batteries, its electrical performance and stability under high voltage still need further improvement. Furthermore, under high temperature or high pressure conditions, the fluorophosphate ester may decompose to produce fluorine-containing gases (such as HF), corroding electrode materials and current collectors and causing gas generation problems. It may also negatively affect the interfacial stability of positive and negative electrode materials (such as graphite and high-nickel cathodes), leading to uneven SEI film (solid electrolyte interphase) and accelerated battery capacity decay.

[0007] Therefore, it is necessary to deepen the research on the synergistic mechanism of phosphate esters / phosphites and aluminum alkoxides to promote their application in high-energy-density battery systems above 4.6V. Summary of the Invention

[0008] This invention addresses the problems existing in the prior art by providing an aluminum alkoxide-phosphate / phosphite electrolyte and its preparation method.

[0009] The technical solution of the present invention is as follows: This invention provides an aluminum alkoxide-phosphate / phosphite electrolyte, wherein the aluminum alkoxide-phosphate / phosphite electrolyte comprises aluminum triethanolate, phosphate / phosphite compounds, electrolyte solutes, and non-aqueous solvents; The phosphate / phosphite compounds are one or more selected from the following: trimethyl phosphate, triethyl phosphate, triisobutyl phosphate, triphenyl phosphate, triargyl phosphate, tri(trimethylsilyl) phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, trimethyl phosphite, triethyl phosphite, triisopropyl phosphite, triphenyl phosphite, and tri(trimethylsilyl) phosphite.

[0010] Preferably, the phosphate / phosphite compound is one or more of trimethyl phosphate, trimethyl phosphite, dimethyl methylphosphonate, triethyl phosphate, and tris(trimethylsilyl)phosphite.

[0011] More preferably, the phosphate / phosphite compound is trimethyl phosphite.

[0012] In this invention, the interaction mechanism between aluminum triethanolamine and phosphate / phosphite compounds originates from a nucleophilic substitution reaction triggered by the directed attack of a nucleophile on an electrophilic center. On one hand, the oxygen atom of the phosphorus-oxygen double bond (P=O) in the phosphate ester acts as an electron-rich nucleophile, attacking the electron-deficient aluminum atom in aluminum triethanolamine. The aluminum atom accepts a lone pair of electrons in its empty orbital, leading to the substitution of its alkoxy group and the formation of an aluminum-oxygen-phosphorus bond (Al-OP) covalent connection. On the other hand, the oxygen atom of the alkoxy group in aluminum triethanolamine nucleophilically attacks the trivalent phosphorus center of the phosphite. The empty 3d orbital of the phosphorus atom significantly enhances its electrophilicity, promoting alkoxy elimination after nucleophilic addition and generating a phosphorus-oxygen-aluminum bond (PO-Al) bond structure.

[0013] Furthermore, aluminum triethanolamine acts as a crosslinking agent, promoting the crosslinking of Al-OP and PO-Al structural units generated through the two pathways via aluminum-oxygen bonds (Al-O-Al), forming a phosphoroaluminoxane polymer with a three-dimensional network characteristic. This polymer ensures that interfacial components (such as Li3P and Al2O3) generated during cycling are uniformly distributed in the solid electrolyte interface (SEI) and cathode electrolyte interface (CEI), thereby reducing the activation energy of lithium-ion transport and improving the consistency of ion migration during cycling. At the same time, it blocks the corrosion path of aluminum current collectors, reduces battery polarization at high voltages, and buffers the lattice stress of the cathode, suppressing the propagation of microcracks caused by deep delithiation at high voltages.

[0014] In some specific embodiments of the present invention, the amount of aluminum triethanolamine used is 0.1-2% of the total mass of the electrolyte; preferably 0.1-0.5%; more preferably 0.5%.

[0015] In some specific embodiments of the present invention, the amount of the phosphate ester / phosphite compound is 1-10% of the total mass of the electrolyte; preferably 2-6%; more preferably 5%.

[0016] In some specific embodiments of the present invention, the amount of the electrolyte additive composition is 0.1-15% of the total mass of the electrolyte; preferably 3-10%; more preferably 5.5%.

[0017] In some specific embodiments of the present invention, 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).

[0018] In some specific embodiments of the present invention, the non-aqueous solvent is selected from one or more of carbonate solvents, carboxylic acid ester solvents, ether solvents, nitrile solvents, and sulfone solvents.

[0019] In some specific embodiments of the present invention, carbonate solvents include, but are not limited to, at least one 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).

[0020] In some specific embodiments of the present invention, the carboxylic acid ester solvents include, but are not limited to, at least one 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.

[0021] In some specific embodiments of the present invention, the ether solvents include, but are not limited to, at least one of 1,3-dioxane (DOL), 1,4-dioxane (DX), crown ethers, 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).

[0022] In some specific embodiments of the present invention, nitrile solvents include, but are not limited to, at least one of acetonitrile (AN), malononitrile, succinic anionyl (SN), glutaronitrile, and adiponitrile (ADN).

[0023] In some specific embodiments of the present invention, sulfone solvents include, but are not limited to, at least one of dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, and sulfolane.

[0024] The present invention also provides a method for preparing an aluminum alkoxide-phosphate / phosphite electrolyte, specifically by dissolving the electrolyte solute, aluminum triethanolamine, and phosphate / phosphite compounds in a non-aqueous solvent to obtain the electrolyte.

[0025] The present invention also provides the application of the above-mentioned aluminum alkoxide-phosphate / phosphite electrolyte or the aluminum alkoxide-phosphate / phosphite electrolyte prepared by the above preparation method in the preparation of lithium-ion secondary batteries.

[0026] The present invention also provides a lithium-ion secondary battery, which is prepared by a positive electrode material, a negative electrode material and the above-mentioned aluminum alkoxide-phosphate / phosphite electrolyte.

[0027] In some specific embodiments of the present invention, 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 (LiNi x Co y Al 1-x-y O2), lithium cobalt oxide (LiCoO2), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4) and lithium-rich manganese (Li) 1+x [NiMnCo] 1-x One or more of the following (O2).

[0028] In some specific embodiments of the present invention, the negative electrode material is selected from any one of graphite, lithium metal, silicon carbide, and silicon.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) The lithium secondary battery made using the electrolyte of the present invention can operate stably at a high voltage of 4.7V or above, which is far greater than the charging cutoff voltage of 4.2V under the prior art, greatly improving the specific capacity and energy density of the battery, and having a high capacity retention rate.

[0030] (2) In the electrolyte of the present invention, triethanolamine and specific phosphate / phosphite compounds form a continuous passivation film on the aluminum foil surface through Al-OP coordination bonds, which greatly increases the breakdown potential of the current collector aluminum, suppresses the polarization current under high voltage to less than 1 / 10 of that of the conventional system, and completely blocks the high-pressure corrosion path.

[0031] (3) The specific phosphate / phosphite compounds of the present invention decompose at high temperature to generate phosphorus oxygen free radicals (PO·), which efficiently quench hydrogen free radicals (H·) and hydroxyl free radicals (HO·), making the electrolyte impossible to be ignited by open flame; the introduction of aluminum triethanolamine further catalyzes the formation of a three-dimensional phosphorus aluminum oxane cross-linking network, which has both flame retardant enhancement effect and interface stabilization function, so that the battery has no risk of fire and explosion, and pushes the electrolyte initial decomposition temperature to above 200°C, significantly delaying the thermal runaway triggering and greatly improving the safety of the battery. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It is worth noting that the raw materials used in the present invention are all common commercially available products, and their sources are not specifically limited.

[0033] The aluminum alkoxide additive (aluminum triethanolamine) used in the 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: (1) 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 LiAl alloy; (2) Take 0.115g of LiAl alloy and put it into 20mL of anhydrous ethanol. Place it at 60℃ for 30h and obtain uniform aluminum triethanolamine (its morphology is nanowires with a diameter of 20-200nm) through chemical desalting process.

[0034] Preparation of positive electrode sheet: positive electrode active material LiN i0.8 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.

[0035] The negative electrode sheet was purchased from Tianjin Zhongneng Lithium Industry Co., Ltd.

[0036] The negative electrode shell, positive electrode shell, stainless steel sheet, gasket, and spring were purchased from Dongguan Kelude Experimental Equipment Technology Co., Ltd., model number CR2032.

[0037] The diaphragm was purchased from Dongguan Kelude Experimental Equipment Technology Co., Ltd., model Celgard 2500.

[0038] Example 1 Preparation of electrolyte: 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; 0.5% by mass of aluminum triethanolamine and 5% by mass of trimethyl phosphite (YTMP) are added and mixed evenly.

[0039] Example 2 The only difference from Example 1 is that the electrolyte additive uses 0.5% aluminum triethanolamine and 5% trimethyl phosphate (TMP) by mass of the electrolyte.

[0040] Example 3 The only difference from Example 1 is that the electrolyte additive uses 0.5% aluminum triethanolamine and 5% triethyl phosphate (TEP) by mass percentage of the electrolyte.

[0041] Example 4 The only difference from Example 1 is that the electrolyte additive uses 0.5% aluminum triethanolamine and 5% dimethyl methylphosphonate (DMMP) by mass of the electrolyte.

[0042] Example 5 The only difference from Example 1 is that the electrolyte additive uses 0.5% aluminum triethanolamine and 5% tris(trimethylsilyl)phosphite (YP) by mass percentage of the electrolyte.

[0043] Example 6 The only difference from Example 1 is that the electrolyte additive uses 0.1% aluminum triethanolamine and 1% trimethyl phosphite (YTMP) by mass percentage of the electrolyte.

[0044] Example 7 The only difference from Example 1 is that the electrolyte additives used are 2% aluminum triethanolamine and 10% trimethyl phosphite (YTMP) by mass percentage of the electrolyte.

[0045] Comparative Example 1 The only difference from Example 1 is that no electrolyte additive is added.

[0046] Comparative Example 2 The only difference from Example 1 is that the electrolyte additive uses 0.5% by mass of aluminum triethanolamine.

[0047] Comparative Example 3 The only difference from Example 1 is that the electrolyte additive uses 5% by weight of trimethyl phosphite (YTMP) in the electrolyte.

[0048] Comparative Example 4 The only difference from Example 1 is that the electrolyte additive uses 5.5% aluminum triethanolamine by mass of the electrolyte.

[0049] Comparative Example 5 The only difference from Example 1 is that the electrolyte additive uses 5.5% by mass of trimethyl phosphite (YTMP).

[0050] Comparative Example 6 The only difference from Example 1 is that the electrolyte additive uses 0.5% aluminum triethanolamine and 5% tri(2,2,2-trifluoroethyl) phosphate (TFEP) by mass percentage of the electrolyte.

[0051] Comparative Example 7 The only difference from Example 1 is that the electrolyte additive uses 0.5% aluminum triethanolamine and 5% tris(2,2,2-trifluoroethyl) phosphite (TTFP) by mass percentage of the electrolyte.

[0052] Comparative Example 8 The only difference from Example 1 is that the electrolyte additive uses 0.5% aluminum isopropoxide and 5% trimethyl phosphite (YTMP) by mass percentage of the electrolyte.

[0053] Test case Assembly and testing of the full-cell Li||NCM811: The coin cell was assembled in the following order: negative electrode shell, negative electrode sheet, 30μL electrolyte, separator, 30μL electrolyte, positive electrode sheet, gasket, spring contact, and positive electrode shell. The cell was left to stand at 30°C for 8 hours and activated for 3 cycles at a current density of 0.1C. It was then charged to 4.7V (or 4.2V) at 1C and discharged to 3.0V to obtain the first-cycle discharge specific capacity and initial coulombic efficiency at 1C. The cell was cycled 50 times under the same conditions to obtain the discharge specific capacity at the 50th cycle, and the capacity retention rate was calculated as: capacity retention rate = discharge specific capacity at the 50th cycle / discharge specific capacity at the first cycle.

[0054] Aluminum breakdown potential test: A coin cell was assembled in the following order: negative electrode shell, negative electrode plate, 30 μL electrolyte, separator, 30 μL electrolyte, current collector aluminum foil, gasket, spring contact, and positive electrode shell. The cell was left to stand at 30°C for 8 hours. Then, a linear sweep voltammetry (LSV) method was used to scan from the open circuit voltage to 6 V at a scan rate of 1 mV / s to obtain the current-potential curve. The potential corresponding to the point where the slope of the curve first shows a significant change was taken as the aluminum breakdown potential. The magnitude of the aluminum breakdown potential reflects the corrosion of the aluminum current collector in the electrolyte.

[0055] Assembly and Electrochemical Window Testing of Li||SS Batteries: A coin cell was assembled in the following order: negative electrode shell, lithium sheet, 30 μL electrolyte, separator, 30 μL electrolyte, stainless steel sheet, gasket, spring contact, and positive electrode shell. The battery was left to stand at 30°C for 8 hours. Then, a linear sweep voltammetry (LSV) method was used to scan from the open-circuit voltage to 6 V at a scan rate of 1 mV / s to obtain the current-potential curve. The potential corresponding to the point where the slope of the curve changes significantly was taken as the decomposition potential of the electrolyte, and the electrochemical window of the electrolyte was determined.

[0056] Electrolyte flame retardancy test: Take 1g of electrolyte into the battery case, ignite the electrolyte with an ignition device for 5s, then remove the ignition device and record the time from when the ignition device is removed until the flame is automatically extinguished. The extinguishing time corresponding to a unit mass of electrolyte is the electrolyte self-extinguishing time (SET).

[0057] The test results of high-voltage full cell cycle performance, aluminum breakdown potential, electrochemical window and flame retardant performance of different electrolytes in the above embodiments are shown in Table 1.

[0058] Table 1. Battery and electrolyte performance test results

[0059] As shown in Table 1, without electrolyte additives, the battery capacity rapidly decays at high charging cutoff voltages, and the electrolyte continues to burn after ignition until all electrolyte is consumed. Adding only aluminum triethanolamine to the electrolyte improves the high-voltage cycle stability to some extent, but does not improve the flame retardancy; the electrolyte continues to burn after ignition. Adding only phosphate / phosphite compounds improves the flame retardancy of the electrolyte, preventing continuous burning, and improves the high-voltage cycle stability, but capacity decay remains rapid. Adding both aluminum triethanolamine and phosphate / phosphite compounds to the electrolyte expands the electrochemical window to varying degrees. The cycle stability at a high charging cutoff voltage of 4.7V is significantly improved compared to the control group without additives and the control group using only one additive. The specific capacity also increases by 31.7% compared to 4.2V, while corrosion resistance and flame retardancy are further improved.

[0060] However, in Comparative Examples 6 and 7, when 5% tris(2,2,2-trifluoroethyl) phosphate or 5% tris(2,2,2-trifluoroethyl) phosphite and 0.5% aluminum triethanolamine were used as additives, the capacity retention rate was even lower than that of Comparative Example 2, which only added 0.5% aluminum triethanolamine. The aluminum breakdown potential and electrochemical window of the electrolyte were also smaller. It can be seen that only specific phosphate / phosphite compounds combined with aluminum triethanolamine can ensure excellent flame retardant properties while achieving high voltage cycle stability, improved aluminum breakdown potential and electrochemical window.

[0061] In addition, when aluminum isopropoxide was used instead of aluminum triethanolamine as an additive in Comparative Example 8, its capacity retention rate was even lower than that of Comparative Example 1, which did not use the additive. This indicates that only aluminum triethanolamine has a synergistic effect with specific phosphate / phosphite compounds, which effectively improves the high-voltage stability of the electrolyte and reduces the corrosion of aluminum current collectors under high voltage. At the same time, the flame retardant properties of the electrolyte are also significantly improved, which will greatly improve the safety of the battery.

[0062] 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 aluminum alkoxide-phosphate / phosphite electrolyte, characterized in that, Including aluminum triethanolamine, phosphate / phosphite compounds, electrolyte solutes and non-aqueous solvents; The phosphate / phosphite compounds are one or more selected from the following: trimethyl phosphate, triethyl phosphate, triisobutyl phosphate, triphenyl phosphate, triargyl phosphate, tri(trimethylsilyl) phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, trimethyl phosphite, triethyl phosphite, triisopropyl phosphite, triphenyl phosphite, and tri(trimethylsilyl) phosphite.

2. The aluminum alkoxide-phosphate / phosphite electrolyte according to claim 1, characterized in that, The phosphate / phosphite compounds are one or more of trimethyl phosphate, trimethyl phosphite, dimethyl methylphosphonate, triethyl phosphate, and tris(trimethylsilyl)phosphite.

3. The aluminum alkoxide-phosphate / phosphite electrolyte according to claim 2, characterized in that, The phosphate / phosphite compound is trimethyl phosphite.

4. The aluminum alkoxide-phosphate / phosphite electrolyte according to claim 1, characterized in that, The amount of aluminum triethanolamine used is 0.1-2% of the total mass of the electrolyte; preferably 0.1-0.5%; more preferably 0.5%.

5. The aluminum alkoxide-phosphate / phosphite electrolyte according to claim 1, characterized in that, The amount of the phosphate / phosphite compound is 1-10% of the total mass of the electrolyte; preferably 2-6%; more preferably 5%.

6. The aluminum alkoxide-phosphate / phosphite electrolyte according to any one of claims 1-5, characterized in that, The amount of the electrolyte additive composition used is 0.1-15% of the total mass of the electrolyte; preferably 3-10%; more preferably 5.5%.

7. The aluminum alkoxide-phosphate / phosphite electrolyte according to any one of claims 1-5, characterized in that, 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); and / or the non-aqueous solvent is selected from one or more of carbonate solvents, carboxylic acid ester solvents, ether solvents, nitrile solvents, and sulfone solvents.

8. The method for preparing the electrolyte according to any one of claims 1-7, characterized in that, The electrolyte is obtained by dissolving the electrolyte solute, aluminum triethanolamine, and phosphate / phosphite compounds in a non-aqueous solvent.

9. The application of the electrolyte as described in any one of claims 1-7 or the aluminum alkoxide-phosphate / phosphite electrolyte prepared by the preparation method described in claim 8 in the preparation of lithium-ion secondary batteries.

10. A lithium-ion secondary battery, characterized in that, It is prepared from a positive electrode material, a negative electrode material, and an electrolyte, wherein the electrolyte is the aluminum alkoxide-phosphate / phosphite electrolyte according to any one of claims 1-7 or the preparation method according to claim 8. The aluminum alkoxide-phosphate / phosphite electrolyte was prepared by the following method; 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. The negative electrode material is selected from any one of graphite, lithium metal, copper, silicon-carbon, and silicon.

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