Non-aqueous electrolyte and secondary battery

Abstract

In order to overcome the problems of low initial coulombic efficiency and poor cycle performance caused by insufficient ionic conductivity and large lithium consumption of a solid electrolyte interface film formed by unsaturated carbonate, the invention provides a non-aqueous electrolyte and a secondary battery, the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive, the additives comprise a first additive, a second additive and a third additive, the first additive comprises a compound as shown in a structural formula 1, and the second additive comprises vinylene carbonate, vinylethylene carbonate, 1, 1, 1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3 the first additive comprises at least one unsaturated carbonate selected from 1, 2-divinyl ethylidene or 1-methyl-1-vinyl ethylidene carbonate, and the third additive comprises one or two selected from acetone or tert-butyl alcohol; the non-aqueous electrolyte satisfies the following conditions: 10 < = X / Y < = 500, 0.1 < = Z / X < = 30, 10 < = X < = 1000, 1 < = Y < = 5, and 10 < = Z < = 500. The non-aqueous electrolyte provided by the invention can regulate and control the film forming quality of unsaturated carbonate, and effectively improves the first coulombic efficiency and the cycle life of the secondary battery.

Description

Technical Field

[0001] The invention belongs to the technical field of battery materials, and in particular relates to a non-aqueous electrolyte and a secondary battery. Background Art

[0002] The increasing reliance on renewable energy around the world requires efficient and reliable energy storage solutions to balance supply and demand. Lithium-ion batteries have become the preferred technology for new energy vehicles, electric light vehicles, power tools, consumer electronics, and new energy storage industries due to their high energy conversion efficiency and comprehensive performance. The electrolyte is one of the four main materials of lithium-ion batteries and is the carrier for the movement of lithium ions between the positive and negative electrodes. The solvation behavior of the electrolyte has an important influence on the stability of the solid electrolyte interface film.

[0003] In existing studies, unsaturated ethylene carbonate containing unsaturated olefin groups has been proven to participate in the formation of solid electrolyte interface film on the negative electrode surface in battery formation before solvent, and the formed electrolyte interface film has a good effect on inhibiting the decomposition of electrolyte at the negative electrode interface. However, the activation energy required for the reaction of a single unsaturated ethylene carbonate is high, the thickness of the formed solid electrolyte interface film is large, and a large amount of active lithium is consumed while forming the solid electrolyte interface film, resulting in a decrease in battery capacity. Therefore, how to improve the film-forming performance of unsaturated ethylene carbonate is an urgent problem to be solved. Summary of the invention

[0004] Aiming at the problem that the existing solid electrolyte interface membrane formed by unsaturated carbonate has low initial coulombic efficiency and poor cycle performance due to insufficient ion conductivity and large lithium consumption, the present invention provides a non-aqueous electrolyte and a secondary battery.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows: In one aspect, the present invention provides a non-aqueous electrolyte, comprising a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises a first additive, a second additive and a third additive, wherein the first additive comprises a compound shown in Structural Formula 1, the second additive comprises at least one unsaturated carbonate selected from vinylene carbonate, vinylethylene carbonate, 1,2-divinylethylene carbonate or 1-methyl-1-vinylethylene carbonate, and the third additive comprises one or both of acetone or tert-butyl alcohol; Structural formula 1 wherein n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1 and R2 are not are hydrogen at the same time, R1 and R2 may be connected to each other to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-C12 alkenylene, substituted or unsubstituted C2-C12 alkynylene, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; when R1, R2, and R3 are substituted, the substituent is alkoxy, hydroxyl, acyl, ester, cyano or halogen; The non-aqueous electrolyte meets the following conditions: 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500; Wherein, X is the mass content of the first additive in the non-aqueous electrolyte, in ppm; Y is the mass percentage of the second additive in the non-aqueous electrolyte, in %; Z is the mass content of the third additive in the non-aqueous electrolyte, in ppm.

[0006] Optionally, the non-aqueous electrolyte satisfies the following conditions: 10≤X / Y≤200, 0.3≤Z / X≤10.

[0007] Optionally, the non-aqueous electrolyte satisfies at least one of the following conditions: (1) 20≤X≤500; (2) 1.5≤Y≤4; (3) 100≤Z≤300.

[0008] Optionally, the compound represented by structural formula 1 satisfies at least one of the following conditions: (1) R1 is selected from hydrogen, R2 is selected from , substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl; (2) R1 and R2 are each independently selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, or substituted or unsubstituted C6-C20 aryl; (3) R1 is selected from R2 is selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; (4) R1 is selected from , where R 12 R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 13 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl.

[0009] Optionally, the compound represented by structural formula 1 includes one or more of the following compounds: .

[0010] Optionally, the additive further includes one or more of a cyclic sulfate ester compound, a sultone compound, a silicon-containing compound, a phosphite compound, and an isocyanurate (or isocyanate) ester compound.

[0011] Optionally, the cyclic sulfate compound includes at least one of vinyl sulfate, vinyl methyl sulfate, and 4,4'-vinyl sulfate; and / or The sultone compound includes at least one of 1,3-propane sultone, 1,3-propylene sultone and methylene methane disulfonate; and / or The silicon-containing compound comprises at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, hexamethyldisilazane, and heptamethyldisilazane; and / or The phosphite compound comprises at least one of trimethyl phosphite, triethyl phosphite, triphenyl phosphite and tricresyl phosphite; and / or The isocyanurate compound includes at least one of trimethyl isocyanurate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, toluene-2,4-diisocyanate, and trimethylsilyl isocyanate.

[0012] Optionally, the non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerizing a polymerizable monomer.

[0013] In another aspect, the present invention provides a secondary battery comprising a positive electrode, a negative electrode and the non-aqueous electrolyte as described above.

[0014] Optionally, the positive electrode includes a positive electrode active material, and the positive electrode active material includes LiFe 1-x’ M' x’ PO4、LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z At least one of O2, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0015] According to the non-aqueous electrolyte provided by the present invention, the compound shown in structural formula 1 is used as the first additive, the unsaturated carbonate is used as the second additive, and one or two of acetone or tert-butyl alcohol are used as the third additive. The inventors have found through research that when the mass content X of the first additive, the mass percentage content Y of the second additive, and the mass content Z of the third additive meet the conditions: 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500, the obtained non-aqueous electrolyte can effectively improve the first coulombic efficiency and cycle life of the secondary battery when applied to the secondary battery. It is speculated that this is due to the reduction potential of the first additive (vs Li / Li+) is lower than that of the second additive, so the intermediate product is preferentially formed after the reduction decomposition occurs at the negative electrode. The intermediate product reduces the activation energy required for the second additive to form a film at the negative electrode. The formed SEI film is denser and more uniform than the secondary battery containing only the second additive, and the thickness of the SEI film is reduced, thereby reducing the consumption of active lithium during the first charge and discharge process and improving the first coulomb efficiency of the battery. However, a small amount of harmful hydroxyl radicals will remain after the electrochemical reaction of the first additive, consuming the effective content of other additives and producing harmful by-products. The added third additive can react with the free radicals produced by the first additive, thereby rendering them harmless and improving the battery cycle life. Therefore, the first additive, the second additive and the third additive interact with each other. By regulating the mass content X of the first additive, the mass percentage Y of the second additive and the mass content Z of the third additive so that the three are in a synergistic state, it is beneficial to improve the comprehensive performance of the secondary battery. DETAILED DESCRIPTION

[0016] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] An embodiment of the present invention provides a non-aqueous electrolyte, comprising a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises a first additive, a second additive and a third additive, wherein the first additive comprises a compound shown in Structural Formula 1, the second additive comprises at least one unsaturated carbonate selected from vinylene carbonate, vinylethylene carbonate, 1,2-divinylethylene carbonate or 1-methyl-1-vinylethylene carbonate, and the third additive comprises one or both of acetone or tert-butyl alcohol; Structural formula 1 wherein n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1 and R2 are not are hydrogen at the same time, R1 and R2 may be connected to each other to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-C12 alkenylene, substituted or unsubstituted C2-C12 alkynylene, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; when R1, R2, and R3 are substituted, the substituent is alkoxy, hydroxyl, acyl, ester, cyano or halogen; The non-aqueous electrolyte meets the following conditions: 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500; Wherein, X is the mass content of the first additive in the non-aqueous electrolyte, in ppm; Y is the mass percentage of the second additive in the non-aqueous electrolyte, in %; Z is the mass content of the third additive in the non-aqueous electrolyte, in ppm.

[0018] The inventors have found through research that when the mass content X of the first additive, the mass percentage content Y of the second additive and the mass content Z of the third additive meet the conditions: 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500, the obtained non-aqueous electrolyte can effectively improve the first coulombic efficiency and cycle life of the secondary battery when applied to the secondary battery. It is speculated that this is due to the reduction potential of the first additive (vs Li / Li+) is lower than that of the second additive, so the intermediate product is preferentially formed after the reduction decomposition occurs at the negative electrode. The intermediate product reduces the activation energy required for the second additive to form a film at the negative electrode. The formed SEI film is denser and more uniform than the secondary battery containing only the second additive, and the thickness of the SEI film is reduced, thereby reducing the consumption of active lithium during the first charge and discharge process and improving the first coulomb efficiency of the battery. However, a small amount of harmful hydroxyl radicals will remain after the electrochemical reaction of the first additive, consuming the effective content of other additives and producing harmful by-products. The added third additive can react with the free radicals produced by the first additive, thereby rendering them harmless and improving the battery cycle life. Therefore, the first additive, the second additive and the third additive interact with each other. By regulating the mass content X of the first additive, the mass percentage Y of the second additive and the mass content Z of the third additive so that the three are in a synergistic state, it is beneficial to improve the comprehensive performance of the secondary battery.

[0019] In a preferred embodiment, the non-aqueous electrolyte satisfies the following conditions: 10≤X / Y≤200, 0.3≤Z / X≤10.

[0020] When the mass content X of the first additive, the mass percentage content Y of the second additive and the mass content Z of the third additive further meet the above conditions, it is beneficial to further improve the coulombic efficiency and cycle capacity retention rate of the secondary battery.

[0021] In a specific embodiment, the mass content X of the first additive in the non-aqueous electrolyte can be 10ppm, 30ppm, 50ppm, 80ppm, 100ppm, 150ppm, 200ppm, 250ppm, 300ppm, 350ppm, 400ppm, 450ppm, 500ppm, 550ppm, 600ppm, 650ppm, 700ppm, 750ppm, 800ppm, 850ppm, 900ppm, 950ppm, 1000ppm or a range consisting of any two of these values.

[0022] In a preferred embodiment, 20≤X≤500.

[0023] The first additive is used to regulate the film-forming quality of the second additive on the negative electrode surface. If the content of the first additive is too little, it is difficult to effectively ensure the density and uniformity of the SEI film on the negative electrode surface, resulting in the SEI film being too thick and consuming more active lithium. If the content of the first additive is too much, it will promote the non-aqueous electrolyte to produce too many free radicals, increase the probability of side reactions with impurities in the non-aqueous electrolyte, and cause the instability of the properties of the non-aqueous electrolyte itself.

[0024] In a specific embodiment, the mass percentage Y of the second additive in the non-aqueous electrolyte can be 1%, 1.2%, 1.4%, 1.5%, 1.8%, 2%, 2.2%, 2.8%, 3%, 3.2%, 3.8%, 4%, 4.2%, 4.8%, 5% or a range consisting of any two of these values.

[0025] In a preferred embodiment, 1.5≤Y≤4.

[0026] The second additive is the main additive component involved in the negative electrode film formation. If the content of the second additive is too little, it is difficult to form a complete SEI film on the negative electrode surface, resulting in continuous consumption of active lithium during the battery cycle, affecting the battery cycle life; if the content of the second additive is too large, it is easy to cause the SEI film to be too thick and the battery impedance to increase, which is also not conducive to improving the battery cycle performance.

[0027] In a specific embodiment, the mass content Z of the third additive in the non-aqueous electrolyte can be 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 80ppm, 100ppm, 150ppm, 180ppm, 200ppm, 250ppm, 280ppm, 300ppm, 350ppm, 380ppm, 400ppm, 450ppm, 500ppm or a range consisting of any two of these values.

[0028] In a preferred embodiment, 100≤Z≤300.

[0029] The third additive is used to eliminate the damage to the non-aqueous electrolyte caused by the free radicals generated by the first additive. Therefore, if the content of the third additive is too small, it is difficult to suppress the degradation effect of the first additive on the non-aqueous electrolyte, resulting in an insignificant improvement in battery performance. However, the third additive is also prone to induce side reactions of the non-aqueous electrolyte under high voltage conditions when the content is high. Therefore, the content of the third additive should be added based on the content of the first additive.

[0030] In the description of the present invention, the term "C1-C12 alkyl" includes straight-chain alkyl, branched-chain alkyl and cycloalkyl. Similarly, the term "C2-C12 alkenyl" includes straight-chain alkenyl, branched-chain alkenyl and cycloalkenyl. The term "C2-C12 alkynyl" includes straight-chain alkynyl, branched-chain alkynyl and cycloalkynyl. The term "C1-C12 alkylene" includes straight-chain alkylene, branched-chain alkylene and cycloalkylene. The term "C2-C12 alkenylene" includes straight-chain alkenylene, branched-chain alkenylene and cycloalkenylene. The term "C2-C12 alkynylene" includes straight-chain alkynylene, branched-chain alkynylene and cycloalkynylene.

[0031] In the description of the present invention, the term "C1-C12 acyl group" should be understood in a broad sense. Specifically, it can be understood that a single or multiple carbon atoms in a C1-C12 alkyl group are replaced by a carbonyl group. The position of the substituted carbon atom is not particularly limited. In a preferred embodiment, the C1-C12 acyl group is selected from , where R 14 is selected from a single bond or a C1-C11 alkyl group, R 15 An alkyl group selected from C1-C11.

[0032] In the description of the present invention, the term "C2-C12 alkoxy acyl" should be understood in a broad sense. Specifically, it can be understood that a single or multiple carbon atoms in the C2-C12 alkyl group are replaced by The position of the substituted carbon atom is not particularly limited. In a preferred embodiment, the C2-C12 alkoxyacyl group is selected from , where R 16 is selected from a single bond or a C1-C11 alkyl group, R 17 An alkyl group selected from C1-C11.

[0033] In the description of the present invention, the term "C2-C12 ether group" should be understood in a broad sense. Specifically, it can be understood as a C2-C12 alkyl group connecting two adjacent carbon atoms. The number of oxygen atoms in the obtained group may be single or multiple.

[0034] In some embodiments, in the compound represented by the structural formula 1, R1 is selected from hydrogen, R2 is selected from , substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, and substituted or unsubstituted C6-C20 aryl.

[0035] At this time, the compound shown in the structural formula 1 is a hydroperoxide or an organic peracid. When the compound shown in the structural formula 1 is a hydroperoxide or an organic peracid, it has a higher oxygen content, which can remove reducing impurities in the electrolyte in advance, reduce the amount of gas produced during formation, improve the first coulomb efficiency, and increase the initial discharge capacity of the secondary battery.

[0036] As an example, the compound represented by the structural formula 1 can be selected from the following compounds: .

[0037] In some embodiments, in the compound represented by structural formula 1, R1 and R2 are each independently selected from a substituted or unsubstituted C1-C12 alkyl, a substituted or unsubstituted C2-C12 alkenyl, a substituted or unsubstituted C2-C12 alkynyl, or a substituted or unsubstituted C6-C20 aryl.

[0038] At this time, the compound shown in the structural formula 1 is a dialkyl peroxide. When the compound shown in the structural formula 1 is a dialkyl peroxide, the co-embedding of solvent molecules is suppressed, and the interface compatibility between the electrolyte and the negative electrode is improved.

[0039] As an example, the compound represented by the structural formula 1 can be selected from the following compounds: .

[0040] In some embodiments, in the compound represented by structural formula 1, R1 is selected from R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether.

[0041] In some embodiments, in the compound represented by structural formula 1, R1 is selected from ; R2 is selected from , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether.

[0042] At this time, the compound shown in the structural formula 1 is a diacyl peroxide. When the compound shown in the structural formula 1 is a diacyl peroxide, in addition to having the characteristics of improving the battery cycle life, it can also decompose to form inert carbon dioxide to dilute the explosion limit of the combustible gas when the battery is thermally runaway, which is beneficial to improving the battery safety performance.

[0043] As an example, the compound represented by the structural formula 1 can be selected from the following compounds: .

[0044] In some embodiments, in the compound represented by structural formula 1, R1 is selected from R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether.

[0045] At this time, the compound shown in the structural formula 1 is a peroxy acid ester. When the compound shown in the structural formula 1 is a peroxy acid ester, the wettability of the electrolyte to the electrode can be improved, the ohmic internal resistance of the battery can be reduced, and the discharge performance of the battery can be improved.

[0046] As an example, the compound represented by the structural formula 1 can be selected from the following compounds: .

[0047] In some embodiments, in the compound represented by structural formula 1, R1 is selected from , where R 12 R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 13 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl.

[0048] At this time, the compound shown in the structural formula 1 is a peroxycarbonate or a peroxydicarbonate. When the compound shown in the structural formula 1 is a peroxycarbonate or a peroxydicarbonate, it has the effect of promoting the solvation of lithium ions and improving the lithium diffusion performance inside the battery.

[0049] As an example, the compound represented by the structural formula 1 can be selected from the following compounds: .

[0050] In some embodiments, the compound represented by structural formula 1 includes one or more of the following compounds: .

[0051] In the description of the present invention, the term "unsaturated carbonate" refers to a carbonate structure containing an unsaturated hydrocarbon group.

[0052] In some embodiments, the additive further comprises one or more of a cyclic sulfate compound, a sultone compound, a silicon-containing compound, a phosphite compound, and an isocyanurate compound.

[0053] In some embodiments, the cyclic sulfate ester compound includes at least one of vinyl sulfate, vinyl methyl sulfate, and 4,4'-vinyl bisulfate.

[0054] In some embodiments, the sultone compound includes at least one of 1,3-propane sultone, 1,3-propene sultone, and methylene methane disulfonate.

[0055] In some embodiments, the silicon-containing compound includes at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and hexamethyldisilazane.

[0056] In some embodiments, the phosphite compound includes at least one of trimethyl phosphite, triethyl phosphite, triphenyl phosphite, and tricresyl phosphite.

[0057] In some embodiments, the isocyanurate compound includes at least one of trimethyl isocyanurate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, toluene-2,4-diisocyanate, and trimethylsilyl isocyanate.

[0058] It should be noted that, unless otherwise specified, in general, the content of any one of the optional substances in the additives in the non-aqueous electrolyte is less than 10%, preferably, the content is 0.01-5%, and more preferably, the content is 0.1%~2%. Specifically, the content of any one of the optional substances in the additives can be 0.01%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10% or a range consisting of any two of these values.

[0059] In some embodiments, based on the total mass of the non-aqueous electrolyte being 100%, the mass content of the non-aqueous organic solvent is 65% to 90%.

[0060] Specifically, based on the total mass of the non-aqueous electrolyte as 100%, the mass content of the non-aqueous organic solvent can be 65%, 68%, 71%, 74%, 76%, 78%, 79%, 80%, 81.5%, 82%, 84%, 85%, 86%, 87%, 89%, 90% or a range consisting of any two of these values.

[0061] In some embodiments, the non-aqueous organic solvent includes at least one of an ether solvent, a nitrile solvent, a carbonate solvent, a carboxylate solvent, and a sulfone solvent.

[0062] In some embodiments, the ether solvent includes a cyclic ether or a chain ether, preferably a chain ether with 3 to 10 carbon atoms and a cyclic ether with 3 to 6 carbon atoms. The cyclic ether may be, but is not limited to, at least one of 1,3-dioxolane, 1,4-dioxolane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, and 2-trifluoromethyltetrahydrofuran; the chain ether may be, but is not limited to, dimethoxymethane, diethoxymethane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Since the chain ether has a high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. The ether compound can be used alone or in any combination and ratio. The content of the ether compound is not particularly limited and is arbitrary within the range that does not significantly damage the effect of the high-density lithium-ion battery of the present invention. The volume ratio is usually 1% or more, preferably 2% or more, and more preferably 3% or more, based on the volume ratio of the non-aqueous solvent being 100%. In addition, the volume ratio is usually 30% or less, preferably 25% or less, and more preferably 20% or less.

[0063] In some embodiments, the nitrile solvent may specifically be but is not limited to at least one of acetonitrile, glutaronitrile, and malononitrile.

[0064] In some embodiments, the carbonate solvent includes a cyclic carbonate or a chain carbonate, and the cyclic carbonate may be, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC); the chain carbonate may be, but is not limited to, at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). The content of the cyclic carbonate is not particularly limited, and is arbitrary within the range that does not significantly damage the effect of the lithium ion battery of the present invention, but when one is used alone, the lower limit of its content is usually 3% or more by volume, preferably 5% or more by volume, relative to the total amount of solvent in the non-aqueous electrolyte. By setting this range, the decrease in conductivity due to the decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, and it is easy to make the large current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery reach a good range. In addition, the upper limit is usually 90% or less by volume, preferably 85% or less by volume, and more preferably 80% or less by volume. By setting this scope, the oxidation / reduction tolerance of nonaqueous electrolyte can be improved, thus contribute to the stability during high temperature storage. The content of linear carbonate is not particularly limited, and relative to the total amount of solvent of nonaqueous electrolyte, it is usually more than 15% by volume, preferably more than 20% by volume, and more preferably more than 25% by volume. In addition, usually the volume ratio is less than 90%, preferably less than 85% by volume, and more preferably less than 80% by volume. By making the content of linear carbonate in the above-mentioned scope, it is easy to make the viscosity of nonaqueous electrolyte reach appropriate range, suppress the reduction of ionic conductivity, and then contribute to make the output characteristics of nonaqueous electrolyte battery reach good scope. When two or more linear carbonates are used in combination, the total amount of linear carbonate is made to meet the above-mentioned scope.

[0065] In certain embodiments, it is also possible to preferably use chain carbonates with fluorine atoms (hereinafter referred to as "fluorinated chain carbonates"). The number of fluorine atoms possessed by the fluorinated chain carbonate is not particularly limited as long as it is more than 1, but is generally less than 6, preferably less than 4. When the fluorinated chain carbonate has a plurality of fluorine atoms, these fluorine atoms can be bonded to the same carbon or to different carbons. As the fluorinated chain carbonate, fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, fluorinated diethyl carbonate derivatives, etc. can be listed.

[0066] The carboxylate solvent includes cyclic carboxylate and / or chain carbonate. Examples of cyclic carboxylate include at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonate include at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propyl propionate, and butyl propionate.

[0067] In some embodiments, the sulfone solvent includes a cyclic sulfone and a chain sulfone. Preferably, in the case of a cyclic sulfone, it is usually a compound with 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and in the case of a chain sulfone, it is usually a compound with 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. The content of the sulfone solvent is not particularly limited, and is arbitrary within the range that does not significantly damage the effect of the lithium ion battery of the present invention. Relative to the total amount of solvent of the non-aqueous electrolyte, the volume ratio is usually 0.3% or more, preferably 0.5% or more, and more preferably 1% or more. In addition, the volume ratio is usually 40% or less, preferably 35% or less, and more preferably 30% or less. In the case of using two or more sulfone solvents in combination, the total amount of the sulfone solvent is sufficient to meet the above range. When the content of the sulfone solvent is within the above range, a non-aqueous electrolyte with excellent high temperature storage stability tends to be obtained.

[0068] In some embodiments, the electrolyte salt is selected from lithium salts, including LiPF6, LiODFP, LiODFB, LiBOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, LiSO3F, Li2B 10 Cl 10 , lithium chloroborane, lithium trioxalophosphate, a lithium lower aliphatic carboxylate having 4 or less carbon atoms, or at least one of lithium tetraphenylborate.

[0069] In some embodiments, the concentration of the lithium salt in the non-aqueous electrolyte is 0.1 mol / L to 4 mol / L. In a preferred embodiment, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol / L to 2.5 mol / L. Specifically, in the non-aqueous electrolyte, the concentration of the lithium salt can be 0.5mol / L, 0.55mol / L, 0.6mol / L, 0.65mol / L, 0.7mol / L, 0.8mol / L, 0.85mol / L, 0.9mol / L, 0.95mol / L, 1.0mol / L, 1.1mol / L, 1.15mol / L, 1.2mol / L, 1.3mol / L, 1.4mol / L, 1.45mol / L, 1.5mol / L, 1.6mol / L, 1.7mol / L, 1.8mol / L, 1.9mol / L, 2.0mol / L, 2.1mol / L, 2.2mol / L, 2.3mol / L, 2.4mol / L, 2.5mol / L or a range consisting of any two of these values.

[0070] It should be emphasized that the non-aqueous electrolyte provided in the present application is not a precursor of a gel electrolyte or a solid electrolyte, nor is it suitable as a precursor of a gel electrolyte or a solid electrolyte. The reason is that the improvement of the electrochemical performance of the secondary battery in the present application requires the compound shown in Structural Formula 1 to participate in the formation of the solid electrolyte interface film (SEI) on the negative electrode surface during the battery charge and discharge formation stage, and the compound shown in Structural Formula 1 remaining in the electrolyte to continuously repair the damaged solid electrolyte interface film (SEI) during the long-term cycle of the battery. As a precursor of a gel electrolyte or a solid electrolyte, there is a polymerization operation to form a gel electrolyte before the battery charge and discharge formation. In the polymerization operation, the organic peroxide shown in Structural Formula 1 reacts with the polymerizable monomer as an initiator, resulting in the consumption of the compound shown in Structural Formula 1, and thus cannot play a corresponding role in the charge and discharge formation and the battery charge and discharge cycle process.

[0071] In some embodiments, the non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerizing a polymerizable monomer.

[0072] In some embodiments, the polymerizable monomers include one or more of acrylate monomers (such as methyl acrylate, ethyl acrylate, butyl acrylate), acrylamide monomers (such as acrylamide, N,N'-methylenebisacrylamide), vinyl compound monomers (such as polyvinyl alcohol, vinyl pyrrolidone, vinyl imidazole), epoxy resin monomers (such as bisphenol A epoxy resin), polyethylene oxide monomers, polyacrylonitrile monomers, and siloxane monomers.

[0073] In some embodiments, the non-aqueous electrolyte does not undergo polymerization reaction under light or heating conditions.

[0074] In some embodiments, the non-aqueous electrolyte is in liquid state after formation.

[0075] Another embodiment of the present invention provides a secondary battery including a positive electrode, a negative electrode, and the non-aqueous electrolyte as described above.

[0076] In some embodiments, the secondary battery is a lithium-ion battery.

[0077] In some embodiments, the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, the positive electrode active material includes lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel oxide (such as lithium nickel oxide), lithium manganese oxide (such as spinel lithium manganese oxide, layered structure lithium manganese oxide, etc.), lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, and one or more of their doping / coating modified compounds. Preferably, the positive electrode active material includes LiFe 1-x’ M' x’ PO4、LiMn2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z At least one of O2, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0078] In a preferred embodiment, the positive electrode active material is selected from LiFe 1-x’ M' x’ PO4, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and 0≤x'<1. The lithium-ion battery has a high gram capacity, which can effectively improve the energy density of the battery, and the battery's charge cut-off voltage can reach 3.8V, has a high discharge platform, and shows good cycle stability under the conventional voltage window; and because the iron element is relatively abundant and low in price worldwide, compared with rare and high-priced metals such as cobalt, nickel, and manganese, the use of the above-mentioned positive electrode active material helps to reduce costs and reduce dependence on limited resources.

[0079] In a more preferred embodiment, the positive electrode active material is selected from LiFe 1-x’ Mn x’ PO4, where 0≤x'≤0.5.

[0080] In some specific embodiments, the positive electrode active material may include LiCoO2, LiFePO4, LiFe 0.4 Mn 0.6 PO4, LiMn2O4, LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.7 Co 0.1 Mn 0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.8 Co 0.15 Al 0.05O2、LiNi 0.9 Co 0.05 Mn 0.05 O2、LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O2、LiNi 0.5 Co 0.2 Al 0.3 One or more of O2.

[0081] In some embodiments, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductor, and the positive electrode active material, the positive electrode binder and the positive electrode conductor are blended to obtain the positive electrode material layer.

[0082] The positive electrode binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, a thermoplastic resin such as polyethylene and polypropylene; an acrylic resin; and at least one of styrene butadiene rubber.

[0083] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene or reduced graphene oxide.

[0084] In some embodiments, the positive electrode current collector includes a metal material that can conduct electrons. Preferably, the positive electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.

[0085] In some embodiments, the negative electrode includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode. The carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.; the silicon-based negative electrode may include silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials, etc.; the tin-based negative electrode may include tin, tin carbon, tin oxygen, and tin metal compounds; the lithium negative electrode may include metallic lithium or a lithium alloy. The lithium alloy may specifically be at least one of a lithium silicon alloy, a lithium sodium alloy, a lithium potassium alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.

[0086] In a more preferred embodiment, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, graphene, and silicon-carbon composite materials.

[0087] In some embodiments, the silicon material is one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon thin films, 3D porous silicon, and hollow porous silicon.

[0088] In some embodiments, the negative electrode further comprises a negative electrode current collector, and the negative electrode material layer covers the surface of the negative electrode current collector. The negative electrode current collector comprises a metal material that can conduct electrons, preferably, the negative electrode current collector comprises at least one of Al, Ni, tin, copper, and stainless steel, and in a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0089] In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer.

[0090] The negative electrode binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, a thermoplastic resin such as polyethylene and polypropylene; an acrylic resin; and at least one of styrene butadiene rubber.

[0091] The negative electrode conductive agent includes at least one of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene or reduced graphene oxide.

[0092] In some embodiments, the secondary battery further includes a separator, and the separator is located between the positive electrode and the negative electrode.

[0093] The diaphragm may be an existing conventional diaphragm, such as a ceramic diaphragm, a polymer diaphragm, a non-woven fabric, an inorganic-organic composite diaphragm, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP and triple-layer PP / PE / PP diaphragms.

[0094] The present invention is further described below by way of examples.

[0095] Table 1 Example 1 This embodiment is used to illustrate the lithium ion battery and the preparation method thereof disclosed in the present invention, and includes the following steps: (1) Preparation of non-aqueous electrolyte: The solvents ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 5:2:5:8, and then 1 mol / L lithium hexafluorophosphate (LiPF6) is added as an electrolyte salt. Based on the total weight of the non-aqueous electrolyte being 100%, the first additive, the second additive, and the third additive are added in weight percentage as shown in Table 1, and the mixture is shaken and homogenized, filtered, and allowed to stand for use.

[0096] (2) Battery filling and formation: In a glove box with a water content of <10ppm and an oxygen content of <50ppm, the non-aqueous electrolyte prepared above was injected into a dry battery cell with a positive electrode of lithium iron phosphate and a negative electrode of artificial graphite, and maintained at a vacuum of 20 kPa for 10min. The packaged battery was aged at 45°C for 48h. Then, the conventional formation for the first charge was carried out according to the following steps: 0.05C constant current charging for 2h, 0.1C constant current charging for 1h, 0.2C constant current charging for 1h, and shelving for 24h. After the formation, the vacuum exhaust was evacuated and sealed, and then further charged at 0.2C constant current to 100% SOC, and constant voltage charged to 0.03C cut-off, and then discharged at 0.2C constant current to 0% SOC to obtain a secondary battery.

[0097] Embodiments 2 to 23 Examples 2 to 23 are used to illustrate the lithium ion battery and the preparation method thereof disclosed in the present invention, and include most of the operating steps in Example 1, except that: The first additive, the second additive and the third additive composition shown in Table 1 were used.

[0098] Comparative Examples 1 to 14 Comparative Examples 1 to 14 are used to illustrate the lithium ion battery and the preparation method thereof disclosed in the present invention, and include most of the operation steps in Example 1, except that: The first additive, the second additive and the third additive composition shown in Table 1 were used.

[0099] Performance Testing The lithium-ion battery prepared above was subjected to the following performance tests: 1. During the battery formation process, record the first discharge capacity and the first charge capacity, and calculate the first coulomb efficiency; the first coulomb efficiency (%) = first discharge capacity / first charge capacity*100%, and calculate the median of the parallel samples.

[0100] 2. Charging DC internal resistance test: 1) 0.5C constant current constant voltage charging to 100% SOC (cut-off current 0.05 C), 0.5C constant current discharge to 50% SOC, set aside for 30 min, 2) 0.1C constant current charging for 10s, set aside for 40s, 0.1C constant current discharge for 10s, set aside for 40s; 0.5C constant current charging for 10s, set aside for 40s, 0.5C constant current discharge for 10s, set aside for 40s; 1C constant current charging for 10s, set aside for 40s, 1C constant current discharge for 10s, set aside for 40s. According to Ohm's law, the three-point method is used to calculate the battery discharge process DCIR and obtain the battery impedance.

[0101] 3. Battery room temperature cycle test: The divided battery is placed in a constant temperature environment of 25℃, and after a short period of time, it is charged to 100% SOC at a constant current and constant voltage of 1C, with a cut-off current of 0.05C. After a short period of time, it is discharged to 0% SOC at a constant current of 1.5C, and the charge and discharge cycle is repeated for 2000 cycles. The discharge capacity of each cycle is recorded, and the capacity retention rate (%) = 2000th cycle discharge capacity / first cycle discharge capacity * 100%, and the average value between parallel samples is calculated.

[0102] (1) The test results obtained in Examples 1 to 17 and Comparative Examples 1 to 14 are entered in Table 2.

[0103] Table 2 It can be seen from the test results of Examples 1 to 17 and Comparative Examples 1 to 14 that in a non-aqueous electrolyte system using the compound shown in Structural Formula 1 as the first additive, an unsaturated carbonate as the second additive, and one or both of acetone or tert-butyl alcohol as the third additive, by controlling the mass content X of the first additive, the mass percentage content Y of the second additive, and the mass content Z of the third additive so that the conditions of 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500 are satisfied, the obtained lithium ion battery has a higher first coulombic efficiency, a lower impedance, and a higher cycle capacity retention rate, which is presumably due to the reduction potential (vs) of the first additive. Li / Li+) is lower than that of the second additive, so the intermediate product is preferentially formed after the reduction decomposition occurs at the negative electrode. The intermediate product reduces the activation energy required for the second additive to form a film at the negative electrode. The formed SEI film is denser and more uniform than the secondary battery containing only the second additive, and the thickness of the SEI film is reduced, thereby reducing the consumption of active lithium during the first charge and discharge process and improving the first coulomb efficiency of the battery. However, a small amount of harmful hydroxyl radicals will remain after the electrochemical reaction of the first additive, consuming the effective content of other additives and producing harmful by-products. The added third additive can react with the free radicals produced by the first additive, thereby rendering them harmless and improving the battery cycle life. Therefore, the first additive, the second additive and the third additive interact with each other. By regulating the mass content X of the first additive, the mass percentage Y of the second additive and the mass content Z of the third additive so that the three are in a synergistic state, it is beneficial to improve the comprehensive performance of the secondary battery.

[0104] It can be seen from the test results of Examples 1 to 17 that when the mass content X of the first additive, the mass percentage content Y of the second additive and the mass content Z of the third additive further satisfy the conditions 10≤X / Y≤200, 0.3≤Z / X≤10, and 20≤X≤500, 1.5≤Y≤4, 100≤Z≤300, the obtained lithium ion battery has higher coulombic efficiency and cycle capacity retention rate.

[0105] From the test results of Comparative Examples 1 to 14, it can be seen that when the X value, Y value and Z value do not meet the restrictions of 10≤X / Y≤500, 0.1≤Z / X≤30, or when the X value, Y value and Z value are too high or too low, the cycle performance of the lithium ion battery will be deteriorated, indicating that the mass content X of the first additive, the mass percentage content Y of the second additive and the mass content Z of the third additive have a mutual influence on each other. When and only when the three reach a better balance, the ionic conductivity and cycle stability of the negative electrode solid electrolyte interface membrane can be significantly improved.

[0106] (2) The test results obtained in Examples 1-6 and 18-23 are entered in Table 3.

[0107] Table 3 It can be seen from the test results of Examples 1 to 6 and 18 to 23 that in the electrolyte system provided by the present invention, when different first additives, different second additives or different third additives are used, and the mass content X of the first additive, the mass percentage content Y of the second additive and the mass content Z of the third additive satisfy the conditions: 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500, it also plays a positive role in improving the coulombic efficiency and cycle performance of the lithium-ion battery, indicating that the battery system provided by the present invention is suitable for different first additives, second additives and third additives.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that: The invention comprises a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises a first additive, a second additive and a third additive, wherein the first additive comprises a compound shown in structural formula 1, the second additive comprises at least one unsaturated carbonate selected from vinylene carbonate, vinyl ethylene carbonate, 1,2-divinylethylene carbonate or 1-methyl-1-vinylethylene carbonate, and the third additive comprises one or both of acetone and tert-butyl alcohol; Structural formula 1 wherein n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1 and R2 are not are hydrogen at the same time, R1 and R2 may be connected to each other to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-C12 alkenylene, substituted or unsubstituted C2-C12 alkynylene, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; when R1, R2, and R3 are substituted, the substituent is alkoxy, hydroxyl, acyl, ester, cyano or halogen; The non-aqueous electrolyte meets the following conditions: 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500; Wherein, X is the mass content of the first additive in the non-aqueous electrolyte, in ppm; Y is the mass percentage of the second additive in the non-aqueous electrolyte, in %; Z is the mass content of the third additive in the non-aqueous electrolyte, in ppm.

2. The non-aqueous electrolyte according to claim 1, characterized in that The non-aqueous electrolyte meets the following conditions: 10≤X / Y≤200, 0.3≤Z / X≤10.

3. The non-aqueous electrolyte according to claim 1, characterized in that The non-aqueous electrolyte satisfies at least one of the following conditions: （1）20≤X≤500； （2）1.5≤Y≤4； （3）100≤Z≤300。 4. The non-aqueous electrolyte according to claim 1, characterized in that The compound represented by the structural formula 1 satisfies at least one of the following conditions: (1) R1 is selected from hydrogen, R2 is selected from , substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl; (2) R1 and R2 are each independently selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, or substituted or unsubstituted C6-C20 aryl; (3) R1 is selected from R2 is selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; (4) R1 is selected from , where R 12 R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl or , where R 13 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl.

5. The non-aqueous electrolyte according to claim 1, characterized in that The compound represented by the structural formula 1 includes one or more of the following compounds: 。 6. The non-aqueous electrolyte according to claim 1, characterized in that The additives further include one or more of cyclic sulfate compounds, sultone compounds, silicon-containing compounds, phosphite compounds, and isocyanurate compounds.

7. The non-aqueous electrolyte according to claim 6, characterized in that The cyclic sulfate compound includes at least one of vinyl sulfate, vinyl methyl sulfate, and 4,4'-vinyl sulfate; and / or The sultone compound includes at least one of 1,3-propane sultone, 1,3-propylene sultone and methylene methane disulfonate; and / or The silicon-containing compound comprises at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, hexamethyldisilazane, and heptamethyldisilazane; and / or The phosphite compound comprises at least one of trimethyl phosphite, triethyl phosphite, triphenyl phosphite and tricresyl phosphite; and / or The isocyanurate compound includes at least one of trimethyl isocyanurate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, toluene-2,4-diisocyanate, and trimethylsilyl isocyanate.

8. The non-aqueous electrolyte according to claim 1, characterized in that The non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerizing a polymerizable monomer.

9. A secondary battery, characterized in that: It comprises a positive electrode, a negative electrode and the non-aqueous electrolyte as claimed in any one of claims 1 to 8.

10. The secondary battery according to claim 9, characterized in that: The positive electrode includes a positive electrode active material, wherein the positive electrode active material includes LiFe 1-x’ M' x’ PO4、LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z At least one of O2, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

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