Non-aqueous electrolyte and secondary battery

Abstract

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 non-aqueous organic solvent comprises ethylene carbonate, the additive comprises a first additive and a second additive, the first additive comprises a compound represented by a structural formula 1, and the second additive comprises a compound represented by a structural formula 2. The second additive comprises one or two of acetone and tert-butyl alcohol; the non-aqueous electrolyte satisfies the following conditions: a / c is greater than or equal to 1 and less than or equal to 100, # imgabs 1 # is greater than or equal to 0.1 and less than or equal to 2.5, a is greater than or equal to 0.001 and less than or equal to 1, and c is greater than or equal to 0.001 and less than or equal to 0.03; wherein a is the mass percentage content of the first additive in the non-aqueous electrolyte, and the unit is%; and c is the mass percentage content of the second additive in the non-aqueous electrolyte, and the unit is%. The lithium ion battery prepared from the non-aqueous electrolyte provided by the invention has relatively high cycle capacity retention ratio and high-temperature storage performance.

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] Lithium-ion batteries have excellent charge and discharge characteristics and are one of the electrochemical energy storage technologies favored by the new energy industry in recent years. Considering the cost of use and the convenience of application, users have higher requirements for the calendar life and service life of lithium-ion batteries. For the energy storage industry, due to the service life of more than ten years, the cycle charge and discharge life of the battery is usually thousands or even tens of thousands of times. At the same time, it is also necessary to meet the requirements of stable storage performance and slow enough calendar decay during the use cycle. The existing patent KR1020030033598A mentions that the addition of peroxide to the electrolyte can dissolve in the electrolyte by generating CO2 gas, and CO2 participates in the formation of a film on the surface of the cathode plate, thereby inhibiting the solvent decomposition of the electrolyte and improving the charge and discharge performance. However, this improvement in battery performance is not very obvious. The main reason is that peroxide will cause the acidity of the electrolyte to increase. It may be that the peroxide attacks the end group of the carbonate solvent at high temperature to produce protonated intermediates. At the same time, peroxide produces too much CO2 that dissolves in the electrolyte. The dissolved CO2 combines with the protonated intermediates to transform into acidic products, increasing the acidity of the electrolyte, deteriorating the electrolyte performance and battery interface performance, and also deteriorating the high-temperature performance of the battery, thereby offsetting its film-forming gain effect, and thus limiting the improvement in the overall battery performance. Summary of the invention

[0003] In view of the problems of insufficient cycle life and unstable performance at high temperatures of existing lithium-ion batteries, the present invention provides a non-aqueous electrolyte and a secondary battery.

[0004] 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 non-aqueous organic solvent comprises ethylene carbonate, the additive comprises a first additive and a second additive, the first additive comprises a compound represented by structural formula 1, and the second additive comprises one or both of acetone and tert-butyl alcohol; ; 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: 1≤a / c≤100,0.1≤ ≤2.5, and 0.001≤a≤1, 10≤b≤40, 0.001≤c≤0.03; Wherein, a is the mass percentage of the first additive in the non-aqueous electrolyte, in units of %; b is the mass percentage of ethylene carbonate in the non-aqueous electrolyte, unit is %; c is the mass percentage of the second additive in the non-aqueous electrolyte, in %.

[0005] Optionally, the non-aqueous electrolyte satisfies the following conditions: 5≤a / c≤70,0.2≤ ≤2.2.

[0006] Optionally, the mass percentage a% of the first additive in the non-aqueous electrolyte is 0.005% to 0.8%; and / or The mass percentage b% of ethylene carbonate in the non-aqueous electrolyte is 15% to 35%; The mass percentage c% of the second additive in the non-aqueous electrolyte is 0.001%-0.02%.

[0007] Optionally, the mass percentage b% of ethylene carbonate in the non-aqueous electrolyte is 50%~90%.

[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 non-aqueous organic solvent further comprises a linear carbonate, and the linear carbonate comprises one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluorine-substituted dimethyl carbonate, fluorine-substituted diethyl carbonate, and fluorine-substituted ethyl methyl carbonate; and / or The non-aqueous organic solvent also includes cyclic carboxylic acid esters and halogen-substituted products thereof and / or chain carboxylic acid esters and halogen-substituted products thereof.

[0011] Optionally, the mass ratio of the linear carbonate to the ethylene carbonate is (1~6):1.

[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 non-aqueous organic solvent includes ethylene carbonate, and a first additive and a second additive are added to the non-aqueous electrolyte, wherein the first additive is an organic peroxide shown in structural formula 1, and the second additive is one or two of acetone and tert-butyl alcohol; the inventors have found that in the above electrolyte system, when the mass percentage a of the first additive, the mass percentage b of ethylene carbonate and the mass percentage c of the second additive meet the conditions 1≤a / c≤100, 0.1≤ ≤2.5, and 0.001≤a≤1, 10≤b≤40, 0.001≤c≤0.03, the obtained lithium ion battery has a high cycle capacity retention rate and high temperature storage performance, indicating that the addition of the first additive, ethylene carbonate and the second additive has a mutual influence on the improvement of the performance of the lithium ion battery. The mechanism is speculated to be: in the battery formation stage, the compound shown in structural formula 1 reacts with ethylene carbonate to generate CO2, and CO2 participates in the formation of the solid electrolyte film on the electrode surface to increase the content of Li2CO3 in the solid electrolyte film, which is beneficial to improve the mechanical strength and high temperature resistance of the solid electrolyte film. At the same time, acetone and / or tert-butyl alcohol are added as the second additive, and the second additive can be adsorbed on the negative electrode surface, and at high temperature, it forms a carbon-oxygen double bond intermediate on the negative electrode surface with the first additive to participate in the electrode surface coating, consume part of the first additive and improve the interface stability, inhibit the first additive from excessively generating CO2 and acidic products, and thus eliminate the adverse effects of the first additive. 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 non-aqueous organic solvent comprises ethylene carbonate, the additive comprises a first additive and a second additive, the first additive comprises a compound represented by structural formula 1, and the second additive comprises one or both of acetone and tert-butyl alcohol; ; 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: 1≤a / c≤100,0.1≤ ≤2.5, and 0.001≤a≤1, 10≤b≤40, 0.001≤c≤0.03; Wherein, a is the mass percentage of the first additive in the non-aqueous electrolyte, in units of %; b is the mass percentage of ethylene carbonate in the non-aqueous electrolyte, unit is %; c is the mass percentage of the second additive in the non-aqueous electrolyte, in %.

[0018] The inventors have found that in the above electrolyte system, when the mass percentage a of the first additive, the mass percentage b of the ethylene carbonate and the mass percentage c of the second additive meet the conditions 1≤a / c≤100, 0.1≤ ≤2.5, and 0.001≤a≤1, 10≤b≤40, 0.001≤c≤0.03, the obtained lithium ion battery has a high cycle capacity retention rate and high temperature storage performance, indicating that the addition of the first additive, ethylene carbonate and the second additive has a mutual influence on the improvement of the performance of the lithium ion battery. The mechanism is speculated to be: in the battery formation stage, the compound shown in structural formula 1 reacts with ethylene carbonate to generate CO2, and CO2 participates in the formation of the solid electrolyte film on the electrode surface to increase the content of Li2CO3 in the solid electrolyte film, which is beneficial to improve the mechanical strength and high temperature resistance of the solid electrolyte film. At the same time, acetone and / or tert-butyl alcohol are added as the second additive, and the second additive can be adsorbed on the negative electrode surface, and at high temperature, it forms a carbon-oxygen double bond intermediate on the negative electrode surface with the first additive to participate in the electrode surface coating, consume part of the first additive and improve the interface stability, inhibit the first additive from excessively generating CO2 and acidic products, and thus eliminate the adverse effects of the first additive.

[0019] In a preferred embodiment, the non-aqueous electrolyte satisfies the following conditions: 5≤a / c≤70,0.2≤ ≤2.2.

[0020] When the mass percentage a of the first additive, the mass percentage b of ethylene carbonate and the mass percentage c of the second additive further meet the above conditions, it is beneficial to further improve the high temperature resistance of the solid electrolyte membrane, thereby improving the high temperature storage performance of the secondary battery.

[0021] In a specific embodiment, the mass percentage a% of the first additive in the non-aqueous electrolyte can be 0.001%, 0.002%, 0.005%, 0.008%, 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.18%, 0.2%, 0.22%, 0.28%, 0.3%, 0.32%, 0.38%, 0.4%, 0.42%, 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range consisting of any two of these values.

[0022] In a preferred embodiment, the mass percentage a% of the first additive in the non-aqueous electrolyte is 0.005%-0.8%.

[0023] The first additive is used to regulate the formation quality of the solid electrolyte membrane on the electrode surface. If the content of the first additive is too little, it is difficult to substantially improve the high-temperature stability of the solid electrolyte membrane; if the content of the first additive is too much, due to the active nature of the first additive, it will increase the occurrence of undesirable side reactions in the non-aqueous electrolyte, and at the same time lead to excessive production of CO2, affecting the acidity of the non-aqueous electrolyte.

[0024] In a specific embodiment, the mass percentage b% of ethylene carbonate in the non-aqueous electrolyte can be 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, 27.5%, 30%, 32.5%, 35%, 37.5%, 40% or a range consisting of any two of these values.

[0025] In a preferred embodiment, the mass percentage b% of ethylene carbonate in the non-aqueous electrolyte is 15%-35%.

[0026] In the non-aqueous electrolyte, the carbonate solvent dissociates the lithium salt through solvation, and the lithium salt exists in the form of free ions, loose ion pairs, and tight ion pairs, thereby providing the transmission of charge inside the battery. When the content of the carbonate solvent is within the above range, it is beneficial to cooperate with the first additive to increase the content of Li2CO3 in the solid electrolyte membrane, and at the same time, it is beneficial to improve the ionic conductivity of the non-aqueous electrolyte.

[0027] In a specific embodiment, the mass percentage c% of the second additive in the non-aqueous electrolyte can be 0.001%, 0.002%, 0.005%, 0.008%, 0.01%, 0.02%, 0.03% or a range consisting of any two of these values.

[0028] In a preferred embodiment, the mass percentage c% of the second additive in the non-aqueous electrolyte is 0.001%-0.02%.

[0029] The second additive is used to reduce the adverse effects of the first additive and cooperates with the first additive to form a film on the electrode surface. If the content of the second additive is too low, it is difficult to suppress the generation of acidic substances in the non-aqueous electrolyte; if the content of the second additive is too high, the probability of side reactions in the electrolyte increases, which is not conducive to improving the stability of the non-aqueous electrolyte.

[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 alkyl, branched-chain alkyl and cycloalkyl. The term "C2-C12 alkenylene" includes straight-chain alkenyl, branched-chain alkenyl and cycloalkenyl. The term "C2-C12 alkynylene" includes straight-chain alkynyl, branched-chain alkynyl and cycloalkynyl.

[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 and R 15 Each is independently selected from C1-C11 alkyl groups.

[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 is 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 12R2 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 some embodiments, the non-aqueous organic solvent further comprises a linear carbonate, and the linear carbonate comprises one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluorine-substituted dimethyl carbonate, fluorine-substituted diethyl carbonate, and fluorine-substituted ethyl methyl carbonate.

[0052] In some embodiments, the mass ratio of the linear carbonate to the ethylene carbonate is (1-6): 1. In a preferred embodiment, the mass ratio of the linear carbonate to the ethylene carbonate is (1.5-5): 1. Specifically, the mass ratio of the linear carbonate to the ethylene carbonate is 1: 1, 1.5: 1, 2: 1, 2.5: 1, 3: 1, 3.2: 1, 4: 1, 4.5: 1, 5: 1, 5.5: 1, 6: 1, or a range consisting of any two of these values.

[0053] By controlling the ratio of chain carbonate to ethylene carbonate and regulating the polarity of the solvent to change the solvation structure, it is beneficial to reduce the generation of acidic substances, further improve the structure of the solid electrolyte membrane on the negative electrode surface, and improve the high-temperature storage performance of the battery.

[0054] In some embodiments, the non-aqueous organic solvent further comprises cyclic carboxylic acid esters and halogen substitutes thereof and / or chain carboxylic acid esters and halogen substitutes thereof.

[0055] The cyclic carboxylic acid esters include γ-butyrolactone, 4-methyl-γ-butyrolactone, δ-valerolactone, δ-hexanolactone, and δ-caprolactone.

[0056] The chain carboxylic acid esters include methyl formate, ethyl formate, methyl acetate, ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, butyl propionate, propyl butyrate, and butyl butyrate.

[0057] 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.

[0058] In some embodiments, the non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerizing a polymerizable monomer.

[0059] 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.

[0060] In some embodiments, the non-aqueous electrolyte does not undergo polymerization reaction under light or heating conditions.

[0061] In some embodiments, the non-aqueous electrolyte is in liquid state after formation.

[0062] In some embodiments, the additive further comprises at least one of cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, phosphate compounds, phosphite compounds, borate compounds, nitrile compounds, lithium salt additives or alkane compounds.

[0063] In some embodiments, the cyclic sulfate ester compound includes at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate.

[0064] In some embodiments, the sultone compound includes at least one of 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, and methylene disulfonate.

[0065] In some embodiments, the cyclic carbonate compound includes at least one of vinylene carbonate, ethylene carbonate, methylene carbonate, or a compound shown in Structural Formula 2: ; In the structural formula 2, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 Each is independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group.

[0066] In some embodiments, the phosphate compound includes at least one of tris(trimethylsilyl)phosphate, tris(triethylsilyl)phosphate, or a compound shown in formula 3: ; In the structural formula 3, R 31 , R 32 , R 33 Each is independently selected from a C1-C5 saturated hydrocarbon group, a C1-C5 unsaturated hydrocarbon group, a C1-C5 halogenated hydrocarbon group, a C6-C12 aryl group, a C6-C12 halogenated aryl group, a -Si(C m H 2m+1 )3, m is a natural number from 1 to 3.

[0067] In a preferred embodiment, the phosphate compound shown in the structural formula 3 can be at least one of triphenyl phosphate, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate.

[0068] In some embodiments, the phosphite compound includes at least one of trimethyl phosphite, triethyl phosphite, tributyl phosphite, triphenyl phosphite, tri-p-tolyl phosphite, tri-o-tolyl phosphite, tri(trimethylsilane)phosphite, and tri(triethylsilane)phosphite.

[0069] In some embodiments, the borate ester compound includes at least one of tris(trimethylsilyl)borate and tris(triethylsilyl)borate.

[0070] In some embodiments, the nitrile compound includes at least one of succinonitrile, glutaronitrile, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile, and sebacononitrile.

[0071] In some embodiments, the lithium salt additive includes at least one of lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorophosphate, lithium tetrafluorophosphate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethylsulfonyl imide, lithium bispentafluoroethylsulfonyl imide, lithium trifluoromethanesulfonate, lithium monofluorosulfonate, lithium trioxalate phosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium dicyanamide, or a lower aliphatic lithium carboxylate having 4 or less carbon atoms.

[0072] In some embodiments, the alkane compound includes at least one of cyclopentane, cyclohexane, cycloheptane, methylcyclopentane, ethylcyclopentane, 1,3-dimethylcyclopentane, 1,4-dimethylcyclopentane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, butylcyclohexane, pentylcyclohexane, cis-1-methyl-3-ethylcyclohexane, trans-1-methyl-3-ethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, 1,3,5-trimethylcyclohexane and perfluoro(ethylcyclohexane).

[0073] In other embodiments, the additives may also include other additives that can improve battery performance: for example, additives that enhance battery safety performance, such as flame retardant additives such as fluorophosphates and cyclophosphazenes, or overcharge prevention additives such as tert-amylbenzene and tert-butylbenzene.

[0074] 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.

[0075] In some embodiments, the additive includes fluoroethylene carbonate, and based on the total mass of the non-aqueous electrolyte being 100%, the content of the fluoroethylene carbonate is 0.01% to 30%.

[0076] 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%.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] In some embodiments, the secondary battery is a lithium-ion battery.

[0082] 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 manganese oxide (such as lithium nickel manganese 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 phosphate, lithium cobalt oxide, and one or more of their doped / coated modified compounds. Preferably, 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.

[0083] 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 has a charge cut-off voltage of up to 3.8V, 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.

[0084] In a more preferred embodiment, the positive electrode active material is selected from LiFe 1-x’ Mn x’ PO4, where 0≤x'≤0.5.

[0085] 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 0.05 O2、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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] In some embodiments, the secondary battery further includes a separator, and the separator is located between the positive electrode and the negative electrode.

[0098] 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.

[0099] The present invention is further described below by way of examples.

[0100] Table 1

[0101] In Table 1, EC is ethylene carbonate, DMC is dimethyl carbonate, and EMC is ethyl methyl carbonate.

[0102] Example 1 This example is used to illustrate the preparation method of the lithium ion battery disclosed in the present invention, which includes the following steps: Preparation of non-aqueous electrolyte: mixing non-aqueous organic solvent, additives and lithium hexafluorophosphate, wherein the mass percentage of lithium hexafluorophosphate is 14.5%, the additives include 2wt% of vinylene carbonate and the first additive and the second additive in mass contents as shown in Table 1, the non-aqueous organic solvent includes a carbonate solvent, the composition and content of the carbonate solvent are shown in Table 1, and carboxylic acid ester is used to make up the balance in the non-aqueous organic solvent.

[0103] Preparation of positive electrode sheet: positive electrode active material LiFePO4, conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96:2:2, and then dispersed in N-methyl-2-pyrrolidone (NMP) to obtain positive electrode slurry. The slurry was evenly coated on both sides of aluminum foil, dried, rolled and vacuum dried, and aluminum lead wires were welded with an ultrasonic welder to obtain positive electrode sheets.

[0104] Preparation of negative electrode sheet: Mix the negative electrode active material artificial graphite, conductive carbon black Super-P, binder styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) in a mass ratio of 94:1:2.5:2.5, and then disperse them in deionized water to obtain negative electrode slurry. The slurry is coated on both sides of the copper foil, dried, rolled and vacuum dried, and the nickel lead wire is welded with an ultrasonic welder to obtain the negative electrode sheet.

[0105] Preparation of battery cells: Place three layers of isolation film between the positive electrode and the negative electrode, then wind the sandwich structure consisting of the positive electrode, the negative electrode and the separator, flatten the wound body and put it into an aluminum foil packaging bag, and vacuum bake it at 75°C for 48 hours to obtain the battery cell to be injected with liquid.

[0106] Injection and formation of the battery cell: Inject the electrolyte into the battery cell, seal it after standing for 1 hour, and age the battery at 35℃ for 48 hours after sealing. Then perform the conventional formation of the first charge according to the following steps: 0.05C constant current charge for 2 hours, 0.1C constant current charge for 2 hours, 0.2C constant current charge for 1 hour, stand for 1 hour, age at 50℃ for 48 hours, and then further charge to 3.65V at 0.33C constant current, and discharge to 2.5V at 0.33C constant current.

[0107] Embodiments 2 to 37 Examples 2 to 37 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: In the preparation steps of the non-aqueous electrolyte: The composition and content of the first additive, the second additive and the carbonate solvent are shown in Table 1.

[0108] Comparative Examples 1 to 15 Comparative Examples 1 to 15 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: In the preparation steps of the non-aqueous electrolyte: The composition and content of the first additive, the second additive and the carbonate solvent are shown in Table 1.

[0109] Performance Testing The lithium-ion battery prepared above was subjected to the following performance tests: 1. Normal temperature cycle capacity retention rate: Place the battery at room temperature, let it stand for 5 minutes, charge it to 3.65V at 0.5C constant current and constant voltage, let it stand for 5 minutes, discharge it to 2.5V at 0.5C constant current, and record the discharge capacity C1. Cycle this charge and discharge procedure, charge and discharge 4000 times, and record the discharge capacity C2. Record the initial acidity of the non-aqueous electrolyte after configuration and the acidity after 4000 cycles of charge and discharge.

[0110] Capacity retention rate after 4000 cycles at room temperature (%) = C2 / C1*100%.

[0111] Electrolyte acidity growth rate (%) = (acidity after cycle - initial acidity) / initial acidity * 100%.

[0112] 2. High temperature storage capacity retention rate: Place the battery at room temperature for 2 hours, charge it to 3.65V at 0.5C constant current and constant voltage, let it stand for 5 minutes, discharge it to 2.5V at 0.5C constant current and constant voltage, let it stand for 5 minutes, charge it to 3.65V at 0.5C constant current and constant voltage, let it stand for 5 minutes, and record the charge capacity C3. Place the battery at 60℃ and store it at a constant temperature for 30 days. Place the battery at room temperature for 2 hours, discharge it to 2.5V at 0.5C constant current, let it stand for 5 minutes, and record the discharge capacity C4. High temperature storage capacity retention rate (%) = C4 / C3*100%.

[0113] 3. High temperature storage internal resistance growth rate: The battery was placed at room temperature for 2 hours, charged to 50% SOC at 0.5C constant current and constant voltage, and left to stand for 40 minutes. The internal resistance R1 of the battery was tested. The battery was placed at 60°C and stored at a constant temperature for 30 days. The internal resistance R2 of the battery was tested using the internal resistance test. The internal resistance growth rate (%) during high temperature storage = R2 / R1*100%.

[0114] (1) The test results obtained in Examples 1 to 18 and Comparative Examples 1 to 15 are entered in Table 2.

[0115] Table 2

[0116] It can be seen from the test results of Examples 1 to 18 and Comparative Examples 1 to 15 that the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 are used as the first additive and the second additive in the non-aqueous electrolyte, ethylene carbonate is used as the non-aqueous organic solvent, and the mass percentage a of the first additive, the mass percentage b of ethylene carbonate, and the mass percentage c of the second additive satisfy the conditions 1≤a / c≤100, 0.1≤ ≤2.5, and 0.001≤a≤1, 10≤b≤40, 0.001≤c≤0.03, the obtained lithium ion battery has excellent room temperature cycle performance and high temperature storage performance. It is speculated that in the battery formation stage, the compound shown in structural formula 1 reacts with ethylene carbonate to generate CO2, and CO2 participates in the formation of the solid electrolyte film on the electrode surface to increase the content of Li2CO3 in the solid electrolyte film, which is beneficial to improve the mechanical strength and high temperature resistance of the solid electrolyte film. At the same time, acetone and / or tert-butyl alcohol are added as the second additive, and the second additive can be adsorbed on the negative electrode surface, and form a carbon-oxygen double bond intermediate with the first additive on the negative electrode surface at high temperature to participate in the electrode surface coating, consume part of the first additive and improve the interface stability, inhibit the first additive from excessively generating CO2 and acidic products, and then eliminate the adverse effects of the first additive, and then comprehensively regulate the relative proportions of the first additive, the second additive and ethylene carbonate, which is beneficial to achieve a synergistic state among the three and promote the improvement of the cycle performance and high temperature storage performance of the lithium ion battery.

[0117] It can be seen from the test results of Examples 1 to 18 that when the mass percentage a of the first additive, the mass percentage b of the ethylene carbonate and the mass percentage c of the second additive meet the conditions 5≤a / c≤70, 0.2≤ ≤2.2, and 0.005≤a≤0.8, 15≤b≤35, 0.001≤c≤0.02, it is beneficial to further improve the stability of the solid electrolyte membrane, inhibit the acidity growth of the non-aqueous electrolyte, improve the cycle capacity retention rate and high-temperature storage capacity retention rate of the lithium-ion battery, and reduce the high-temperature storage internal resistance growth rate.

[0118] From the test results of Comparative Examples 1 to 15, it can be seen that when the mass percentage a of the first additive, the mass percentage b of the ethylene carbonate and the mass percentage c of the second additive do not meet the range limits, even if the conditions 1≤a / c≤100, 0.1≤ ≤2.5, the lithium-ion battery still does not have good high-temperature storage performance and room-temperature cycle performance, indicating that the a value, b value or c value has a strong correlation in improving the performance of the passivation film on the positive and negative surfaces of lithium-ion batteries. Similarly, when the a value, b value and c value meet their range limits, but the a / c value or When the value does not meet the above preset conditions, the improvement of battery performance is not obvious.

[0119] (2) The test results obtained in Examples 1 and 19 to 27 are entered in Table 3.

[0120] Table 3

[0121] It can be seen from the test results of Examples 1 and 19 to 27 that in the electrolyte system provided by the present invention, when different compounds represented by Structural Formula 1 or Structural Formula 2 are used, the mass percentage a of the first additive, the mass percentage b of ethylene carbonate, and the mass percentage c of the second additive satisfy the conditions: 1≤a / c≤100, 0.1≤ ≤2.5, and 0.001≤a≤1, 10≤b≤40, 0.001≤c≤0.03, it also plays a positive role in improving the high temperature performance and cycle life of the lithium ion battery, indicating that the battery system provided by the present invention is suitable for different compounds represented by structural formula 1 and compounds represented by structural formula 2.

[0122] (3) The test results obtained in Examples 1, 28 to 37 are entered in Table 4.

[0123] Table 4

[0124] It can be seen from the test results of Examples 1 and 28 to 37 that, compared with Examples 28 and 37 in which the mass ratio of the chain carbonate to the ethylene carbonate exceeds the range of 1 to 6, by controlling the ratio of the chain carbonate to the ethylene carbonate within the range of 1 to 6, it is beneficial to reduce the generation of acidic substances, further improve the structure of the solid electrolyte membrane on the negative electrode surface, and improve the high temperature storage performance of the battery.

[0125] 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: It includes a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the non-aqueous organic solvent includes ethylene carbonate, the additive includes a first additive and a second additive, the first additive includes a compound shown in structural formula 1, and the second additive includes one or both of acetone and tert-butyl alcohol; ； 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: 1≤a / c≤100,0.1≤ ≤2.5, and 0.001≤a≤1, 10≤b≤40, 0.001≤c≤0.03; Wherein, a is the mass percentage of the first additive in the non-aqueous electrolyte, in units of %; b is the mass percentage of ethylene carbonate in the non-aqueous electrolyte, unit is %; c is the mass percentage of the second additive in the non-aqueous electrolyte, in %.

2. The non-aqueous electrolyte according to claim 1, characterized in that The non-aqueous electrolyte meets the following conditions: 5≤a / c≤70,0.2≤ ≤2.2。 3. The non-aqueous electrolyte according to claim 1, characterized in that The mass percentage a% of the first additive in the non-aqueous electrolyte is 0.005% to 0.8%; and / or The mass percentage b% of ethylene carbonate in the non-aqueous electrolyte is 15% to 35%; and / or The mass percentage c% of the second additive in the non-aqueous electrolyte is 0.001%-0.02%.

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 non-aqueous organic solvent further comprises a chain carbonate, and the chain carbonate comprises one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluorine-substituted dimethyl carbonate, fluorine-substituted diethyl carbonate, and fluorine-substituted ethyl methyl carbonate; and / or The non-aqueous organic solvent also includes cyclic carboxylic acid esters and halogen-substituted products thereof and / or chain carboxylic acid esters and halogen-substituted products thereof.

7. The non-aqueous electrolyte according to claim 6, characterized in that The mass ratio of the linear carbonate to the ethylene carbonate is (1-6):

1.

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.

Images