High-pressure additive for capturing free radicals and non-aqueous electrolyte

Abstract

The invention provides a compound. The compound has a structure as shown in a formula (I). The invention also discloses a functional additive for the secondary battery electrolyte. The electrolyte additive can be preferentially combined with methoxyl / trifluoroethoxyl free radicals to terminate a chain reaction, further decomposition of CO3 <-> and other anions is inhibited through coordination or steric hindrance, in addition, a compact interface layer with high ionic conductance can be formed on the surface of an electrode, and continuous decomposition of the electrolyte is blocked. The functional additive and the FEC are combined for use and have a synergistic effect, so that the oxidation resistance of the solvent and the positive electrode material is improved, meanwhile, the attack of free radicals generated by decomposition of the FEC on carbonic ester is avoided, a composite SEI layer rich in inorganic Li3BO3 / LiF is formed, the interface ion conductivity and mechanical strength are improved, the rate and the cycling stability are improved, and particularly, the high-pressure and high-temperature cycling stability is improved. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and relates to a compound and its application in lithium-ion batteries, a non-aqueous electrolyte for lithium-ion batteries, and a lithium-ion battery, and in particular to a high-voltage additive for capturing free radicals and the non-aqueous electrolyte. Background Art

[0002] Lithium cobalt oxide (LCO), a common cathode material for lithium-ion batteries, is widely used in consumer electronics due to its high energy density and excellent cycling performance. However, when operating under high-voltage conditions, traditional electrolyte formulations often face numerous challenges, such as poor thermal stability, a narrow electrochemical window, and easy decomposition, which limit the battery's energy density and service life. Therefore, the development of electrolyte technology solutions suitable for high-voltage LCO batteries is crucial.

[0003] Improving the voltage window and capacity of LCO materials and pairing them with high-capacity silicon-carbon anodes is an effective approach to further increasing battery energy density. Researchers have modified LCO electrode materials to increase their voltage window and capacity, improve their oxidation resistance, and enhance their cycling stability. Besides protecting the electrode material, optimizing the electrolyte solvent and widening the electrochemical window are also crucial to battery performance.

[0004] In electrolyte improvements, conventional carbonate and carboxylate solvents have limited oxidation resistance and cannot meet the requirements of high-voltage electrolytes. Fluorine-substituted solvents can adjust the electrolyte solvation structure and improve oxidation resistance, forming a LiF-rich inorganic interface and improving ionic conductivity. Compared with fluoroethers, fluorocarbonates are easier to dissociate from lithium salts and have high conductivity, which is beneficial for rate performance. Compared with fluorocarboxylates, they have a wider energy level window, are more resistant to reduction and oxidation, and reduce interfacial side reactions. Currently, the most widely used fluorocarbonate is methyl trifluoroethyl carbonate (FEMC), but FEMC still has the phenomenon of interfacial side reactions that deteriorate battery performance. FEMC has two possible decomposition pathways: the first is decomposition to form CF3CH2 radicals and CO3CH3 anions, and methyl carbonate further decomposes into CO2 molecules and methoxy groups, which has the lowest reaction energy. The second pathway is the decomposition of FEMC molecules into CH3 radicals and CF3CH2CO3 anions, and trifluoroethyl carbonate can further decarboxylate to form CO2 and trifluoroethoxy groups. The methoxy and trifluoroethoxy radicals generated by decomposition attack the carbonate solvent with nucleophilicity to form different by-products, which destroy the stability of the SEI film.

[0005] Therefore, how to develop an electrolyte suitable for high-voltage LCO batteries and solve the above-mentioned problems of existing FEMC-containing electrolytes has become one of the focuses of widespread attention of many front-line scientific researchers and R&D companies in the field. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a compound and its application in lithium-ion batteries, a non-aqueous electrolyte for lithium-ion batteries, a lithium-ion battery, and in particular a high-voltage additive for capturing free radicals. The compound provided herein can be used as an electrolyte additive to preferentially bind methoxy / trifluoroethoxy free radicals, terminate the chain reaction, and inhibit CO3 by coordination or steric hindrance. - The further decomposition of anions such as ferrite and ferrite, and the formation of a dense, highly ionic conductive interface layer on the electrode surface, which blocks the continued decomposition of the electrolyte, the additive and FEMC work synergistically to improve high-voltage and high-temperature cycling stability. Furthermore, the preparation method is simple and easy, with mild conditions, strong controllability, and good stability, making it easier to promote and apply in industrial production.

[0007] The present invention provides a compound having a structure as shown in formula (I):

[0008]

[0009] The present invention provides a method for preparing the compound as described in the above technical solution, comprising the following steps:

[0010] Using dimethyl sulfoxide and tetrahydrofuran as a mixed solvent, 4-bromo-2,6-(trifluoromethyl)phenol, boric acid pinacol ester and potassium acetate are mixed with a mixed solvent, and then a catalyst dichlorobis(diphenylphosphinoferrocene)palladium is added, and the mixture is heated for reaction to obtain a compound.

[0011] Preferably, in the mixed flux, the volume ratio of dimethyl sulfoxide to tetrahydrofuran is (0.9-1.1): (1.1-0.9);

[0012] The molar ratio of 4-bromo-2,6-(trifluoromethyl)phenol, pinacol borate and potassium acetate is 1.0:(1.3-1.8):(1.8-2.5);

[0013] The molar ratio of the catalyst dichlorobis(diphenylphosphinoferrocene)palladium to 4-bromo-2,6-(trifluoromethyl)phenol is 2% to 5%;

[0014] The temperature of the heating reaction is 80-100°C;

[0015] The heating reaction time is 12 to 24 hours.

[0016] The present invention provides the use of the compound described in the above technical solution or the compound prepared by the preparation method described in any one of the above technical solutions in lithium ion batteries.

[0017] Preferably, the lithium-ion battery is specifically an electrolyte of a lithium-ion battery;

[0018] The electrolyte includes a non-aqueous electrolyte;

[0019] The applications include applications as functional additives;

[0020] The application is specifically to improve one or more of the high-voltage stability, high-temperature storage performance and high-temperature cycle performance of lithium-ion batteries;

[0021] The lithium-ion battery comprises a high-voltage and high-temperature lithium-ion battery system with a charge cut-off voltage higher than 4.5V;

[0022] The application also includes the application of the compound in combination with methyl trifluoroethyl carbonate in lithium ion batteries;

[0023] The methyl trifluoroethyl carbonate is specifically used as an auxiliary solvent;

[0024] The added mass of the methyl trifluoroethyl carbonate is 5% to 20% of the total mass of the electrolyte.

[0025] The present invention provides a non-aqueous electrolyte for a lithium ion battery, comprising a lithium salt, an anhydrous organic solvent and an additive;

[0026] The additive includes the compound described in the above technical solution or the compound prepared by the preparation method described in any one of the above technical solutions.

[0027] Preferably, the added mass of the compound is 0.1% to 10% of the total mass of the non-aqueous electrolyte;

[0028] The non-aqueous electrolyte further includes an auxiliary solvent;

[0029] The auxiliary solvent is methyl trifluoroethyl carbonate;

[0030] The added mass of the auxiliary solvent is 5% to 20% of the total mass of the non-aqueous electrolyte;

[0031] The anhydrous organic solvent includes one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, 1,4-butyrolactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate and γ-butyrolactone.

[0032] Preferably, the lithium salt includes one or more of LiBF4, LiPF6, LiAsF6, LiB(C2O4)2, LiClO4, LiFSI and LiTFSI;

[0033] In the non-aqueous electrolyte, the concentration of lithium salt is 0.5 to 2.0 M;

[0034] The additives also include other functional additives;

[0035] The other functional additives include one or more of sulfonate compounds, sulfate compounds, unsaturated cyclic carbonate compounds, borate compounds, trimethylsilyl ester compounds, heterocyclic compounds and nitrile compounds;

[0036] The added mass of the other functional additives is 0.1% to 8% of the total mass of the non-aqueous electrolyte.

[0037] The present invention provides a lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte;

[0038] The non-aqueous electrolyte is the non-aqueous electrolyte described in any one of the above technical solutions.

[0039] Preferably, the positive electrode active material on the positive electrode sheet is one or more of lithium cobalt oxide, lithium nickel manganese cobalt oxide and lithium-rich manganese-based positive electrode materials;

[0040] The negative electrode active material on the negative electrode sheet is one or more of graphite, silicon, silicon-carbon composite material and metallic lithium;

[0041] The lithium-ion battery includes a lithium-ion battery with a charging cut-off voltage higher than 4.5V.

[0042] The present invention provides a compound having a structure as shown in formula (I). Compared with the prior art, the present invention creatively designs a compound with a specific structure and composition and uses it as a functional additive for secondary battery electrolytes. This electrolyte additive can preferentially bind methoxy / trifluoroethoxy free radicals, terminate the chain reaction, and inhibit CO3 through coordination or steric hindrance. - The further decomposition of anions such as ferrite and ferromagnetic acid (FEMC) can also form a dense, highly ionic conductive interface layer on the electrode surface, blocking the continued decomposition of the electrolyte. Furthermore, the functional additives and FEMC work synergistically to improve the oxidation resistance of the solvent and cathode material while avoiding the attack of carbonates by free radicals generated by FEMC decomposition, forming an inorganic Li3BO3 / LiF-rich composite SEI layer. This enhances the interfacial ionic conductivity and mechanical strength, and improves rate and cycling stability, especially high-pressure and high-temperature cycling stability.

[0043] The structural additive represented by formula (I) provided by the present invention is used in combination with FEMC auxiliary solvent to improve the high-voltage stability of the electrolyte and form a LiF-rich interface. However, there is a defect that methoxy and trifluoroethoxy radicals are decomposed to attack the carbonate solvent with nucleophilicity, forming different by-products and destroying the stability of the SEI film. The phenolic hydroxyl group in the phenol structure of the additive provided by the present invention can capture and react with ·OCH3 and ·CF3CH2O radicals, inhibiting the free radicals from attacking the carbonate solvent. The borate group and CO3 - Anions such as CF₃CH₂CO₃⁻ are coordinated through Lewis acid-base interactions, reducing their reactivity and inhibiting decarboxylation to produce CO₂ and free radicals. The electron-withdrawing effect of the trifluoromethyl group adjacent to the hydroxyl group reduces the acidity of the hydroxyl group and inhibits the dehydrogenation side reaction. The additive can be preferentially oxidized on the cathode surface to form a boron-phenol cross-linked polymer, forming an inorganic Li₃BO₃ / LiF-rich composite interface layer, improving the interface's ionic conductivity and mechanical strength.

[0044] The functional additives provided by the present invention are used in combination with heterocyclic additives, such as the compound of formula (I) and heterocyclic additives, and further in combination with the compound of formula (I), heterocyclic additives and FEMC, to effectively protect the positive electrode while inhibiting the electrolyte consumption and increased interfacial impedance caused by the expansion of the silicon negative electrode, thereby improving high-voltage cycling and high-temperature storage performance. DETAILED DESCRIPTION

[0045] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent claims of the present invention.

[0046] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0047] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure materials or materials with conventional purities in the field of secondary battery electrolyte additive preparation.

[0048] The present invention provides a compound having a structure as shown in formula (I):

[0049]

[0050] The present invention also provides a method for preparing the compound described in the above technical solution, comprising the following steps:

[0051] Using dimethyl sulfoxide and tetrahydrofuran as a mixed solvent, 4-bromo-2,6-(trifluoromethyl)phenol, boric acid pinacol ester and potassium acetate are mixed with a mixed solvent, and then a catalyst dichlorobis(diphenylphosphinoferrocene)palladium is added, and the mixture is heated for reaction to obtain a compound.

[0052] Furthermore, the above step can be performed by adding 4-bromo-2,6-(trifluoromethyl)phenol, pinacol diboron, dichlorobis(diphenylphosphinoferrocene)palladium, potassium acetate, and a dimethyl sulfoxide / tetrahydrofuran mixed solvent to a Schlenk tube, replacing the atmosphere with nitrogen, and heating and stirring to react. Filtering with celite, extracting with ethyl acetate, and performing column chromatography to obtain white crystals.

[0053] In the present invention, the volume ratio of dimethyl sulfoxide to tetrahydrofuran in the mixed flux is preferably (0.9-1.1):(1.1-0.9), more preferably (0.92-1.08):1, more preferably (0.95-1.05):1, more preferably (0.98-1.03):1, or 1:(0.92-1.08), or 1:(0.95-1.05), or 1:(0.98-1.03). Specifically, it can be 1:1.

[0054] In the present invention, the molar ratio of 4-bromo-2,6-(trifluoromethyl)phenol to boric acid pinacol ester is preferably 1.0:(1.3-1.8), more preferably 1.0:(1.4-1.7), and even more preferably 1.0:(1.5-1.6).

[0055] In the present invention, the molar ratio of 4-bromo-2,6-(trifluoromethyl)phenol to potassium acetate is preferably 1.0:(1.8-2.5), more preferably 1.0:(1.9-2.4), and even more preferably 1.0:(2-2.3).

[0056] In the present invention, the molar ratio of the catalyst dichlorobis(diphenylphosphinoferrocene)palladium to 4-bromo-2,6-(trifluoromethyl)phenol is preferably 2% to 5%, more preferably 2.5% to 4.5%, and even more preferably 3% to 4%.

[0057] In the present invention, the temperature of the heating reaction is preferably 80-100°C, more preferably 83-98°C, more preferably 85-95°C, and more preferably 87-93°C.

[0058] In the present invention, the heating reaction time is preferably 12 to 24 hours, more preferably 15 to 21 hours, and even more preferably 16 to 20 hours.

[0059] The present invention provides the use of the compound described in the above technical solution or the compound prepared by the preparation method described in any one of the above technical solutions in lithium ion batteries.

[0060] In the present invention, the lithium ion battery is preferably an electrolyte of a lithium ion battery.

[0061] In the present invention, the electrolyte preferably includes a non-aqueous electrolyte.

[0062] In the present invention, the application preferably includes application as a functional additive.

[0063] In the present invention, the lithium-ion battery is preferably a lithium-ion battery using a high-voltage positive electrode material.

[0064] In the present invention, the application is preferably to improve one or more of the high-voltage stability, high-temperature storage performance and high-temperature cycle performance of lithium-ion batteries, and more preferably to improve the high-voltage stability, high-temperature storage performance or high-temperature cycle performance of lithium-ion batteries.

[0065] In the present invention, the lithium-ion battery preferably comprises a high-voltage and high-temperature lithium-ion battery system with a charge cut-off voltage higher than 4.5V.

[0066] In the present invention, the added mass of the functional additive is preferably 0.1% to 10% of the total mass of the electrolyte, more preferably 2% to 8%, and even more preferably 4% to 6%.

[0067] In the present invention, the application also preferably includes the application of the compound described in the above technical solution or the compound prepared by the preparation method described in any one of the above technical solutions in combination with methyl trifluoroethyl carbonate in a lithium ion battery.

[0068] In the present invention, methyl trifluoroethyl carbonate is particularly preferably used as the auxiliary solvent.

[0069] In the present invention, the added mass of the methyl trifluoroethyl carbonate is preferably 5% to 20% of the total mass of the electrolyte, more preferably 8% to 17%, and even more preferably 11% to 14%.

[0070] The present invention provides a non-aqueous electrolyte for a lithium ion battery, comprising a lithium salt, an anhydrous organic solvent and an additive;

[0071] The additive includes the compound described in the above technical solution or the compound prepared by the preparation method described in any one of the above technical solutions.

[0072] In the present invention, the added mass of the compound is preferably 0.1% to 10% of the total mass of the non-aqueous electrolyte, more preferably 2% to 8%, and even more preferably 4% to 6%.

[0073] In the present invention, the non-aqueous electrolyte preferably further includes an auxiliary solvent.

[0074] In the present invention, the auxiliary solvent is preferably methyl trifluoroethyl carbonate;

[0075] In the present invention, the added mass of the auxiliary solvent is preferably 5% to 20% of the total mass of the non-aqueous electrolyte, more preferably 8% to 17%, and even more preferably 11% to 14%.

[0076] In the present invention, the anhydrous organic solvent preferably includes one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, 1,4-butyrolactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate and γ-butyrolactone, more preferably ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, 1,4-butyrolactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate or γ-butyrolactone.

[0077] In the present invention, the lithium salt preferably includes one or more of LiBF4, LiPF6, LiAsF6, LiB(C2O4)2, LiClO4, LiFSI and LiTFSI, and more preferably LiBF4, LiPF6, LiAsF6, LiB(C2O4)2, LiClO4, LiFSI or LiTFSI.

[0078] In the present invention, the concentration of the lithium salt in the non-aqueous electrolyte is preferably 0.5 to 2.0 M, more preferably 0.8 to 1.7 M, and even more preferably 1.1 to 1.4 M.

[0079] In the present invention, the additives preferably further include other functional additives.

[0080] In the present invention, the other functional additives preferably include one or more of sulfonate compounds, sulfate compounds, unsaturated cyclic carbonate compounds, borate compounds, trimethylsilyl ester compounds, heterocyclic compounds and nitrile compounds, more preferably sulfonate compounds, sulfate compounds, unsaturated cyclic carbonate compounds, borate compounds, trimethylsilyl ester compounds, heterocyclic compounds or nitrile compounds, more preferably heterocyclic compounds.

[0081] In the present invention, the other functional additives include but are not limited to 1,3-propane sultone (PS), 1,3-butane sultone (BS), methylene methanedisulfonate (MMDS), vinyl sulfate (DTD), vinyl sulfite (ES), 4,4'-disulfate (BDTD), pentaerythritol bicyclic sulfate (TDT), propylene sulfate (PSA), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), tripropynyl phosphate (TPP), trimethyl borate (TMB), triethyl borate (TEB), tris(trimethylsilyl) borate (TMSB), tris(trimethylsilyl) phosphate (TMSP), tris(trimethylsilyl) phosphite (TMSPi), 2-fluoropyridine, 2-propyn-1-yl 1H -imidazole-1-carboxylate, hexanetrinitrile (HTCN), adiponitrile (ADN), succinonitrile (SN) and ethylene glycol bis(propionitrile) ether (DENE), or one or more of 1,3-propane sultone, 1,3-butane sultone, methylene methanedisulfonate, vinyl sulfate, vinyl sulfite, 4,4'-vinyl bisulfate, pentaerythritol bicyclic sulfate, propylene sulfate, vinylene carbonate, vinyl ethylene carbonate, tripropynyl phosphate, trimethyl borate, triethyl borate, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, 2-fluoropyridine, 2-propyn-1-yl 1H-imidazole-1-carboxylate, 1,3,6-hexanetrinitrile, adiponitrile, succinonitrile and ethylene glycol bis(propionitrile) ether.

[0082] In the present invention, the added mass of the other functional additives is preferably 0.1% to 8% of the total mass of the non-aqueous electrolyte, more preferably 1% to 7%, more preferably 2% to 6%, more preferably 3% to 5%.

[0083] The present invention provides a lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte;

[0084] The non-aqueous electrolyte is the non-aqueous electrolyte described in any one of the above technical solutions.

[0085] In the present invention, the positive electrode active material on the positive electrode sheet is preferably one or more of lithium cobalt oxide, lithium nickel manganese cobalt oxide and lithium-rich manganese-based positive electrode materials, more preferably lithium cobalt oxide, lithium nickel manganese cobalt oxide or lithium-rich manganese-based positive electrode materials.

[0086] In the present invention, the negative electrode active material on the negative electrode sheet is preferably one or more of graphite, silicon, silicon-carbon composite material and metallic lithium, more preferably graphite, silicon, silicon-carbon composite material or metallic lithium.

[0087] In the present invention, the lithium-ion battery preferably includes a lithium-ion battery with a charge cut-off voltage higher than 4.5V.

[0088] The present invention is a complete and detailed overall technical solution that better improves the performance of the compound represented by the structure of formula (I) as an electrolyte additive in secondary batteries, especially improving the performance of lithium-ion batteries with high-voltage positive electrode materials. The above-mentioned high-voltage additive for capturing free radicals, a non-aqueous electrolyte for lithium-ion batteries, and a lithium-ion battery can specifically include the following:

[0089] Additive 1: 4-Borate-2,6-bis(trifluoromethyl)phenol, the structural formula is as follows:

[0090]

[0091] Auxiliary solvent: methyl trifluoroethyl carbonate (FEMC)

[0092]

[0093] The present invention also discloses the application of the lithium ion battery electrolyte additive: the lithium ion battery non-aqueous electrolyte contains at least the two electrolyte additives.

[0094] Specifically, the non-aqueous electrolyte for lithium-ion batteries includes lithium salt, an anhydrous organic solvent and additives, wherein the amount of the additives is 0.1% to 10% of the total weight of the non-aqueous electrolyte for lithium-ion batteries.

[0095] Specifically, the auxiliary solvent is 5% to 20% of the total weight of the lithium-ion battery non-aqueous electrolyte.

[0096] Specifically, the lithium salt is selected from at least one of LiBF4, LiPF6, LiAsF6, LiB(C2O4)2, LiClO4, LiFSI or LiTFSI, and the concentration of the lithium salt is 0.5 to 2.0M.

[0097] Specifically, the anhydrous organic solvent is selected from one or more mixtures of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, 1,4-butyrolactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate and γ-butyrolactone.

[0098] Specifically, the electrolyte contains other functional additives, and the basic additives are selected from at least one of sulfonate compounds, sulfate compounds, unsaturated cyclic carbonate compounds, borate compounds, trimethylsilyl ester compounds, heterocyclic compounds and nitrile compounds, and the added amount accounts for 0.1% to 8% of the total mass of the electrolyte.

[0099] The present invention also provides a lithium-ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the electrolyte is the lithium-ion battery high-voltage electrolyte provided above.

[0100] Specifically, the positive electrode active material is selected from lithium cobalt oxide, lithium nickel manganese cobalt oxide, and lithium-rich manganese-based positive electrode materials.

[0101] Specifically, the negative electrode active material is selected from one of graphite, silicon-carbon, silicon-carbon composite material, and metallic lithium.

[0102] Specifically, the lithium-ion battery of the present invention has a charging cut-off voltage higher than 4.5V and is suitable for high-voltage and high-temperature battery systems.

[0103] The present invention provides a high-voltage additive for capturing free radicals, a non-aqueous electrolyte for lithium-ion batteries, and a lithium-ion battery. The present invention designs a compound with a specific structure and composition and uses it as a functional additive for secondary battery electrolytes. The electrolyte additive preferentially binds to methoxy / trifluoroethoxy free radicals, terminates the chain reaction, and inhibits CO3 production through coordination or steric hindrance. - The further decomposition of anions such as ferrite and ferromagnetic acid (FEMC) can also form a dense, highly ionic conductive interface layer on the electrode surface, blocking the continued decomposition of the electrolyte. Furthermore, the functional additives and FEMC work synergistically to improve the oxidation resistance of the solvent and cathode material while avoiding the attack of carbonates by free radicals generated by FEMC decomposition, forming an inorganic Li3BO3 / LiF-rich composite SEI layer. This enhances the interfacial ionic conductivity and mechanical strength, and improves rate and cycling stability, especially high-pressure and high-temperature cycling stability.

[0104] The structural additive represented by formula (I) provided by the present invention is used in combination with FEMC auxiliary solvent to improve the high-voltage stability of the electrolyte and form a LiF-rich interface. However, there is a defect that methoxy and trifluoroethoxy radicals are decomposed to attack the carbonate solvent with nucleophilicity, forming different by-products and destroying the stability of the SEI film. The phenolic hydroxyl group in the phenol structure of the additive provided by the present invention can capture and react with ·OCH3 and ·CF3CH2O radicals, inhibiting the free radicals from attacking the carbonate solvent. The borate group and CO3 - CF3CH2CO3 - The anions coordinate via Lewis acid-base interactions, reducing their reactivity and inhibiting decarboxylation to generate CO2 and free radicals. The electron-withdrawing effect of the trifluoromethyl group adjacent to the hydroxyl group reduces the acidity of the hydroxyl group and inhibits the dehydrogenation side reaction. The additive preferentially oxidizes on the cathode surface to form a boron-phenol cross-linked polymer and an inorganic Li3BO3 / LiF-rich composite interface layer, improving interfacial ion conductivity and mechanical strength.

[0105] The functional additives provided by the present invention are used in combination with heterocyclic additives, such as the compound of formula (I) and heterocyclic additives, and further in combination with the compound of formula (I), heterocyclic additives and FEMC, to effectively protect the positive electrode while inhibiting the electrolyte consumption and increased interfacial impedance caused by the expansion of the silicon negative electrode, thereby improving high-voltage cycling and high-temperature storage performance.

[0106] To further illustrate the present invention, a compound provided by the present invention and its application in a lithium ion battery, a non-aqueous electrolyte for a lithium ion battery, and a lithium ion battery are described in detail below in conjunction with examples. However, it should be understood that these examples are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operating processes are provided only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. The scope of protection of the present invention is not limited to the following examples.

[0107] Preparation Example

[0108] Functional additives having the structure shown in synthetic formula (I):

[0109] A 50 mL Schlenk tube was vacuumed and filled with nitrogen three times. Then, 4-bromo-2,6-(trifluoromethyl)phenol (CAS No. 1026369-41-4) (1.0 eq, 3.0 g), diboronic acid pinacol ester (1.5 eq, 3.8 g), dichlorobis(diphenylphosphinoferrocene)palladium (3 mol%), potassium acetate (2.0 eq), and a super-dry dimethyl sulfoxide / tetrahydrofuran mixture (20 mL, 1:1) were added. Stirring was initiated and the mixture was heated to 90°C for 18 hours. After the reaction was complete, the mixture was cooled to room temperature and filtered through celite. The celite was then washed with 50 mL of ethyl acetate, and the organic phases were combined. The mixture was then washed three times with saturated brine (100 mL × 3), dried over anhydrous sodium sulfate, and then distilled under reduced pressure to remove the solvent. The residue was purified by column chromatography using a petroleum ether / ethyl acetate mixture (volume ratio 10:1) as the eluent. Finally, the solvent was removed by rotary evaporation and dried to obtain the functional additive compound represented by formula (I).

[0110] Preparation of electrolyte

[0111] Comparative Example 1

[0112] Preparation of electrolyte: In an argon-filled glove box (moisture <0.1ppm, oxygen <0.1ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), and fluoroethylene carbonate (FEC) were mixed in a mass ratio of EC:PC:PP:FEC = 5:10:52:13, and lithium hexafluorophosphate (LiPF6) was slowly added to the solution with a LiPF6 molar ratio of 1.25mol / L. 1,3-propane sultone was added with a content of 1.5%, 1% adiponitrile, and 2% hexanetrionitrile to prepare the electrolyte of Comparative Example 1.

[0113] Comparative Example 2

[0114] Preparation of electrolyte: In an argon-filled glove box (moisture <0.1ppm, oxygen <0.1ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), fluoroethylene carbonate (FEC), and methyl trifluoroethyl carbonate (FEMC) were mixed in a mass ratio of EC:PC:PP:FEC:FEMC = 5:10:42:13:10, and lithium hexafluorophosphate (LiPF6) was slowly added to the solution with a LiPF6 molar ratio of 1.25mol / L. 1,3-propane sultone content of 1.5%, 1% adiponitrile, and 2% hexanetrionitrile were added to serve as the electrolyte of Comparative Example 2.

[0115] Example 1

[0116] Preparation of the electrolyte: In an argon-filled glove box (moisture <0.1ppm, oxygen <0.1ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), and fluoroethylene carbonate (FEC) were mixed uniformly in a mass ratio of EC:PC:PP:FEC = 5:10:52:13, and lithium hexafluorophosphate (LiPF6) was slowly added to the solution with a LiPF6 molar ratio of 1.25mol / L. 1,3-propane sultone was added to have a content of 1.5%, 1% adiponitrile, 2% hexanetrionitrile, and 0.5% functional additive 1 to prepare the electrolyte of Example 1.

[0117] Example 2

[0118] Preparation of the electrolyte: In an argon-filled glove box (moisture <0.1ppm, oxygen <0.1ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), fluoroethylene carbonate (FEC), and methyl trifluoroethyl carbonate (FEMC) were mixed in a mass ratio of EC:PC:PP:FEC:FEMC = 5:10:42:13:10, and lithium hexafluorophosphate (LiPF6) was slowly added to the solution. The molar ratio of LiPF6 was 1.25mol / L, and 1,3-propane sultone content was 1.5%, 1% adiponitrile, 2% hexanetrionitrile, and 0.5% functional additive 1 were added to obtain the electrolyte of Example 2.

[0119] Example 3

[0120] Preparation of the electrolyte: In an argon-filled glove box (moisture <0.1ppm, oxygen <0.1ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), fluoroethylene carbonate (FEC), and methyl trifluoroethyl carbonate (FEMC) were mixed at a mass ratio of EC:PC:PP:FEC:FEMC = 5:10:42:13:10, and lithium hexafluorophosphate (LiPF6) was slowly added to the solution. The molar ratio of LiPF6 was 1.25mol / L, and 1,3-propane sultone content was 1.5%, 1% adiponitrile, 2% hexanetrionitrile, and 1% functional additive 1 were added to obtain the electrolyte of Example 3.

[0121] Example 4

[0122] Preparation of the electrolyte: In an argon-filled glove box (moisture <0.1ppm, oxygen <0.1ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), fluoroethylene carbonate (FEC), and methyl trifluoroethyl carbonate (FEMC) were mixed in a mass ratio of EC:PC:PP:FEC:FEMC = 5:10:42:13:10, and lithium hexafluorophosphate (LiPF6) was slowly added to the solution. The molar ratio of LiPF6 was 1.25mol / L, and 1,3-propane sultone content was 1.5%, 1% adiponitrile, 2% hexanetrionitrile, and 2% functional additive 1 were added to obtain the electrolyte of Example 4.

[0123] Example 5

[0124] Preparation of the electrolyte: In an argon-filled glove box (moisture <0.1ppm, oxygen <0.1ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), fluoroethylene carbonate (FEC), and methyl trifluoroethyl carbonate (FEMC) were mixed in a mass ratio of EC:PC:PP:FEC:FEMC = 5:10:42:13:10, and lithium hexafluorophosphate (LiPF6) was slowly added to the solution. The molar ratio of LiPF6 was 1.25mol / L, and 1,3-propane sultone content was 1.5%, 1% adiponitrile, 2% hexanetrionitrile, 1% functional additive 1, and 0.3% imidazole carboxylate were added to prepare the electrolyte of Example 5.

[0125] Battery production and performance testing

[0126] The lithium-ion battery electrolytes of the above-mentioned embodiments and comparative examples were respectively made into lithium-ion batteries with a soft-pack capacity of 2500mAh. The lithium-ion batteries included a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and battery auxiliary materials. The positive electrode active material was a 4.55V high-voltage LiCoO2 material, and the negative electrode active material was graphite mixed with 10% SiC.

[0127] (1) Preparation of positive electrode: High-voltage LiCoO2, conductive carbon black, carbon nanotubes and polytetrafluoroethylene were evenly coated on 12 μm aluminum foil in a mass ratio of 97:1.2:0.8:1, with a double-sided coating density of 375 g / m 2 , compacted density is 4.2g / cm 3 .

[0128] (2) Preparation of negative electrode sheet: The negative electrode active material is graphite and artificial graphite, silicon carbon, conductive carbon black, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, and carbon nanotubes are evenly coated on a 6 μm copper foil in a mass ratio of 85.5:10:0.6:0.8:1.5:1.5:0.1. The double-sided coating density is 167 g / m 2 , compacted density is 1.6g / cm 3 .

[0129] (3) Preparation of batteries: The positive electrode sheet, separator and negative electrode sheet are wound together into a core, sealed with aluminum plastic film and then baked to ensure that the electrode moisture meets the requirements. After baking, the battery cell is injected with electrolyte at a rate of 2.5Ah / g, and then subjected to formation, aging and capacity separation processes to obtain a finished soft-pack battery cell; wherein, the formation conditions are: charging at 0.1C for 3h, leaving for 5min; charging at 0.2C for 2h, leaving for 5min; the aging conditions are: aging at 45℃ for 48h; and capacity separation is carried out at a rate of 0.2C.

[0130] Battery Test

[0131] 1. Cycle test

[0132] Xinwei test program settings: At a specific temperature, charge at a constant current of 1C to a charge cut-off voltage of 4.55V, then charge at a constant voltage until the current drops to 0.05C, and then discharge at a constant current of 1C to 3.0V to obtain the capacity retention rate of different formulas.

[0133] Capacity retention rate = discharge capacity in the last week / initial discharge capacity * 100%

[0134] 2. High temperature storage performance test

[0135] The battery was charged and discharged at a rate of 1C for one week at 25°C, and the discharge capacity was recorded. The battery was placed in a high-temperature explosion-proof box and stored at 60°C for one week. It was discharged to 3V at 1C at 25°C, and then charged and discharged at 1C for one week. The capacity retention rate and capacity recovery rate were calculated.

[0136] Capacity recovery rate = discharge capacity in the second cycle after high-temperature storage / discharge capacity in the last week before high-temperature storage * 100%

[0137] 3. Rate performance

[0138] Charge and discharge the battery at different rates, take 0.2C as the basic capacity, and calculate the capacity retention rate at different rates.

[0139] The test results are shown in Table 1, which shows the performance data of lithium-ion batteries prepared with the electrolytes obtained in the examples of the present invention and the comparative examples.

[0140] Table 1

[0141]

[0142] According to the data results of Example 1 and Comparative Example 1, the functional additives of the present invention can be preferentially oxidized on the positive electrode surface to form a boron-phenol cross-linked polymer and an inorganic Li3BO3 / LiF-rich composite interface layer, thereby enhancing the interfacial ion conductivity and mechanical strength, effectively improving the high-voltage stability of the battery, and improving high-temperature cycling and high-temperature storage performance. At the same time, the appropriate addition amount can help form a low-impedance, highly stable interface, thereby improving the battery's rate performance. The data results of Examples 2 to 4 and Comparative Example 2 show that the functional additives used in combination with FEMC can capture free radicals generated by FEMC side reactions, inhibit free radical attack on carbonate solvents, and reduce battery side reactions.

[0143] From the data of Example 5 and Example 3, it can be seen that the use of functional additives in combination with heterocyclic additives can effectively protect the positive electrode, inhibit the electrolyte consumption and increase in interface impedance caused by the expansion of the silicon negative electrode, and improve the high-voltage cycle and high-temperature storage performance.

[0144] The above describes in detail a high-pressure additive and non-aqueous electrolyte for capturing free radicals, as well as a lithium-ion battery provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above examples is intended only to facilitate understanding of the methods and core concepts of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combined method. It should be noted that, without departing from the principles of the present invention, a person skilled in the art may make several improvements and modifications to the present invention, and such improvements and modifications fall within the scope of protection of the claims of the present invention. The scope of patent protection for the present invention is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those described in the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims, then these other embodiments are also intended to be included within the scope of the claims.

Claims

1. A compound, characterized in that The compound has a structure as shown in formula (I):

2. A method for preparing the compound according to claim 1, characterized in that: The following steps are involved: Using dimethyl sulfoxide and tetrahydrofuran as a mixed solvent, 4-bromo-2,6-(trifluoromethyl)phenol, boric acid pinacol ester and potassium acetate are mixed with a mixed solvent, and then a catalyst dichlorobis(diphenylphosphinoferrocene)palladium is added, and the mixture is heated for reaction to obtain a compound.

3. The preparation method according to claim 2, characterized in that In the mixed flux, the volume ratio of dimethyl sulfoxide to tetrahydrofuran is (0.9-1.1): (1.1-0.9); The molar ratio of 4-bromo-2,6-(trifluoromethyl)phenol, pinacol borate and potassium acetate is 1.0:(1.3-1.8):(1.8-2.5); The molar ratio of the catalyst dichlorobis(diphenylphosphinoferrocene)palladium to 4-bromo-2,6-(trifluoromethyl)phenol is 2% to 5%; The temperature of the heating reaction is 80-100°C; The heating reaction time is 12 to 24 hours.

4. Use of the compound according to claim 1 or the compound prepared by the preparation method according to any one of claims 2 to 3 in lithium-ion batteries.

5. The use according to claim 4, characterized in that The lithium-ion battery is specifically an electrolyte of a lithium-ion battery; The electrolyte includes a non-aqueous electrolyte; The applications include applications as functional additives; The application is specifically to improve one or more of the high-voltage stability, high-temperature storage performance and high-temperature cycle performance of lithium-ion batteries; The lithium-ion battery comprises a high-voltage and high-temperature lithium-ion battery system with a charge cut-off voltage higher than 4.5V; The application also includes the application of the compound in combination with methyl trifluoroethyl carbonate in lithium ion batteries; The methyl trifluoroethyl carbonate is specifically used as an auxiliary solvent; The added mass of the methyl trifluoroethyl carbonate is 5% to 20% of the total mass of the electrolyte.

6. A non-aqueous electrolyte for a lithium ion battery, characterized in that: including lithium salt, anhydrous organic solvent and additives; The additive includes the compound according to claim 1 or the compound prepared by the preparation method according to any one of claims 2 to 3.

7. The non-aqueous electrolyte according to claim 6, characterized in that The added mass of the compound is 0.1% to 10% of the total mass of the non-aqueous electrolyte; The non-aqueous electrolyte further includes an auxiliary solvent; The auxiliary solvent is methyl trifluoroethyl carbonate; The added mass of the auxiliary solvent is 5% to 20% of the total mass of the non-aqueous electrolyte; The anhydrous organic solvent includes one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, 1,4-butyrolactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate and γ-butyrolactone.

8. The non-aqueous electrolyte according to claim 6, characterized in that The lithium salt includes one or more of LiBF4, LiPF6, LiAsF6, LiB(C2O4)2, LiClO4, LiFSI and LiTFSI; In the non-aqueous electrolyte, the concentration of lithium salt is 0.5 to 2.0 M; The additives also include other functional additives; The other functional additives include one or more of sulfonate compounds, sulfate compounds, unsaturated cyclic carbonate compounds, borate compounds, trimethylsilyl ester compounds, heterocyclic compounds and nitrile compounds; The added mass of the other functional additives is 0.1% to 8% of the total mass of the non-aqueous electrolyte.

9. A lithium-ion battery, characterized in that: Including positive electrode sheet, negative electrode sheet, separator and electrolyte; The non-aqueous electrolyte is the non-aqueous electrolyte according to any one of claims 6 to 8.

10. The lithium-ion battery according to claim 9, characterized in that The positive electrode active material on the positive electrode sheet is one or more of lithium cobalt oxide, lithium nickel manganese cobalt oxide and lithium-rich manganese-based positive electrode materials; The negative electrode active material on the negative electrode sheet is one or more of graphite, silicon, silicon-carbon composite material and metallic lithium; The lithium-ion battery includes a lithium-ion battery with a charging cut-off voltage higher than 4.5V.

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