Non-aqueous electrolyte and secondary battery

Abstract

To overcome the storage issues of existing electrolytes containing organic peroxides, the present 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, wherein the additive comprises a compound represented by Structural Formula 1 and a compound represented by Structural Formula 2; #imgabs0# Structural Formula 1; #imgabs1# Structural Formula 2. The non-aqueous electrolyte provided by the present invention exhibits good property consistency after long-term storage, thus preventing quality degradation after long-term storage.

Description

Technical Field

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

[0002] In recent years, as the application technology of secondary batteries has gradually matured, the demand for electric vehicles and large-scale energy storage markets has exploded. In cutting-edge research on battery technology, high energy density and long cycle life have always been the common goals pursued by the industry. From a technical perspective, the core of lithium-ion battery long-cycle technology lies in regulating and optimizing the electrochemical stability of the solid electrolyte interface film (SEI) through electrolyte design. Among them, in the existing technology, different film-forming additives are usually added to the electrolyte to change the properties of the SEI in the hope of obtaining a more stable SEI component. Effective electrolyte additives will play a key role in the formation of the SEI. However, the SEI formed by existing conventional additives has defects. It constantly dissolves and reorganizes during the charge and discharge process, which not only makes the interface film thicker and increases the impedance, but also consumes active substances and causes capacity decay.

[0003] Organic peroxides are unstable compounds. The -OO- group in their molecular structure is highly chemically active and heat-sensitive, subjecting them to self-accelerating decomposition at specific temperatures. Heat-induced decomposition readily produces primary oxygen free radicals. Consequently, they are typically used as initiators in gel electrolytes in secondary batteries, where they are consumed before the battery's initial charge / discharge cycle. While there are also reports of their use as additives in liquid electrolytes, their limited stability requires a relatively short timeframe after formulation for battery filling and charge / discharge formation. Decomposition during long-term storage can lead to a significant decrease in the effective content, making such electrolytes generally unstorable and unsuitable for commercial applications. Summary of the Invention

[0004] In order to solve the problem that existing electrolytes containing organic peroxides are not resistant to storage, the present invention provides a non-aqueous electrolyte and a secondary battery.

[0005] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0006] 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 compound represented by Structural Formula 1 and a compound represented by Structural Formula 2:

[0007] ;

[0008] 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, R 2 are not hydrogen at the same time, R1 and R2 are connected to each other to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-12 alkenylene, substituted or unsubstituted C2-12 alkynylene, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; when R1, R2, and R3 are substituted, the substituent is alkoxy, hydroxy, acyl, ester, cyano, or halogen;

[0009] ;

[0010] Wherein, R4, R5, and R6 are each independently selected from a C1-C6 hydrocarbon group, a C6-C20 aryl group, a C3-C6 silicon-containing group, or a C1-C6 fluorinated hydrocarbon group.

[0011] Optionally, in the compound shown in 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.

[0012] Optionally, in the compound shown in 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.

[0013] Optionally, in the compound shown in structural formula 1, 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 11Selected 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.

[0014] Optionally, in the compound shown in 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.

[0015] Optionally, the compound represented by structural formula 1 includes one or more of the following compounds:

[0016] .

[0017] Optionally, the compound represented by structural formula 2 includes one or more of the following compounds:

[0018] .

[0019] Optionally, based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by structural formula 1 is 0.01% to 1%; and / or

[0020] Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by structural formula 2 is 0.005% to 0.1%; and / or

[0021] The mass ratio of the compound represented by Structural Formula 1 to the compound represented by Structural Formula 2 is 0.2-40.

[0022] Optionally, the non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerizing a polymerizable monomer.

[0023] 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.

[0024] According to the non-aqueous electrolyte provided by the present invention, the compound shown in structural formula 1 and the compound shown in structural formula 2 are added to the non-aqueous electrolyte as additives, wherein the compound shown in structural formula 1 is an organic peroxide, which can participate in the formation of the solid electrolyte interface film (SEI) on the surface of the negative electrode during the first charge and discharge formation of the battery, thereby reducing the irreversible capacity loss of the negative electrode during the battery cycle. However, the inventors have found in practice that although the compound shown in structural formula 1 can be used as a film-forming additive, the non-aqueous electrolyte containing the compound shown in structural formula 1 needs to complete the filling and formation of the battery in a relatively short period of time. During conventional storage or transportation, the hydrolysis of lithium salts (such as LiPF6) in the electrolyte will inevitably produce components such as HF and PF5. , these components will accelerate the decomposition of the -OO- group in the compound represented by Structural Formula 1. Therefore, the non-aqueous electrolyte containing the compound represented by Structural Formula 1 is not resistant to storage. To solve this problem, the inventors added the compound represented by Structural Formula 2 to the non-aqueous electrolyte and unexpectedly found that after the introduction of the compound represented by Structural Formula 2, the long-term storage performance of the compound represented by Structural Formula 1 was improved, indicating that the compound represented by Structural Formula 2 plays a role in stabilizing the compound represented by Structural Formula 1. The mechanism is: the compound represented by Structural Formula 2 can inhibit the decomposition of lithium salts to produce HF and PF5, thereby inhibiting the continuous decomposition of the compound represented by Structural Formula 1, ensuring the consistency of the properties of the non-aqueous electrolyte after long-term storage, and avoiding the quality deterioration problem after long-term storage. DETAILED DESCRIPTION

[0025] 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 intended to limit the present invention.

[0026] An embodiment of the present invention provides a non-aqueous electrolyte solution comprising a non-aqueous organic solvent, an electrolyte salt, and an additive, wherein the additive comprises a compound represented by Structural Formula 1 and a compound represented by Structural Formula 2:

[0027] ;

[0028] 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, R 2 are not hydrogen at the same time, R1 and R2 are connected to each other to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-12 alkenylene, substituted or unsubstituted C2-12 alkynylene, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; when R1, R2, and R3 are substituted, the substituent is alkoxy, hydroxy, acyl, ester, cyano, or halogen;

[0029] ;

[0030] Wherein, R4, R5, and R6 are each independently selected from a C1-C6 hydrocarbon group, a C6-C20 aryl group, a C3-C6 silicon-containing group, or a C1-C6 fluorinated hydrocarbon group.

[0031] The compound shown in structural formula 1 and the compound shown in structural formula 2 are added as additives to the non-aqueous electrolyte, wherein the compound shown in structural formula 1 is an organic peroxide, which can participate in the formation of the solid electrolyte interface film (SEI) on the surface of the negative electrode during the first charge and discharge formation of the battery, thereby reducing the irreversible capacity loss of the negative electrode during the battery cycle. However, the inventors have found in practice that although the compound shown in structural formula 1 can be used as a film-forming additive, the non-aqueous electrolyte containing the compound shown in structural formula 1 needs to complete the filling and formation of the battery in a relatively short period of time. During the normal storage or transportation process, the hydrolysis of the lithium salt (such as LiPF6) in the electrolyte will inevitably produce HF, PF5 and other components, which will increase the capacity of the battery. The -OO- group in the compound represented by Structural Formula 1 decomposes rapidly, and therefore, the non-aqueous electrolyte containing the compound represented by Structural Formula 1 is not resistant to storage. To solve this problem, the inventors added the compound represented by Structural Formula 2 to the non-aqueous electrolyte, and unexpectedly found that after the introduction of the compound represented by Structural Formula 2, the long-term storage performance of the compound represented by Structural Formula 1 was improved, indicating that the compound represented by Structural Formula 2 played a role in stabilizing the compound represented by Structural Formula 1. The mechanism is as follows: the compound represented by Structural Formula 2 can inhibit the decomposition of lithium salts to produce HF and PF5, and thus inhibit the continuous decomposition of the compound represented by Structural Formula 1, thereby ensuring the consistency of the properties of the non-aqueous electrolyte after long-term storage and avoiding the quality deterioration problem after long-term storage.

[0032] In the description of the present invention, the term "C3-C6 silicon-containing group" includes C3-C6 silane groups and fluorinated C3-C6 silane groups.

[0033] 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.

[0034] 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 as a C1-C12 alkyl group in which a single or multiple carbon atoms 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.

[0035] 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 a 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.

[0036] 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 group connecting two adjacent carbon atoms in a C2-C12 alkyl group. The number of oxygen atoms in the resulting group may be single or multiple.

[0037] In some embodiments, in the compound represented by 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 10is 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.

[0038] In this case, the compound represented by Structural Formula 1 is a hydroperoxide or an organic peracid. When the compound represented by Structural Formula 1 is a hydroperoxide or an organic peracid, the high oxygen content can preemptively remove reducing impurities in the electrolyte, thereby reducing the amount of gas produced by the formation, improving the initial coulombic efficiency, and increasing the initial discharge capacity of the secondary battery.

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

[0040] .

[0041] 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.

[0042] In this case, the compound represented by the structural formula 1 is a dialkyl peroxide. When the compound represented by the structural formula 1 is a dialkyl peroxide, it is beneficial to inhibit the co-embedding of solvent molecules and improve the interface compatibility between the electrolyte and the negative electrode.

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

[0044] .

[0045] 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.

[0046] In some embodiments, in the compound represented by structural formula 1, R1 is selected from ; R2 is selected from , where R 11Selected 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.

[0047] In this case, the compound represented by Structural Formula 1 is a diacyl peroxide. When the compound represented by Structural Formula 1 is a diacyl peroxide, in addition to improving the battery cycle life, it can also decompose to form inert carbon dioxide during thermal runaway to dilute the explosion limit of the combustible gas, thereby improving battery safety.

[0048] As an example, the compound represented by the structural formula 1 can be selected from the following compounds:

[0049] .

[0050] 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.

[0051] In this case, the compound represented by the structural formula 1 is a peroxy ester. When the compound represented by the structural formula 1 is a peroxy 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.

[0052] As an example, the compound represented by the structural formula 1 can be selected from the following compounds:

[0053] .

[0054] 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 13is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl.

[0055] In this case, the compound represented by the structural formula 1 is a peroxycarbonate or a peroxydicarbonate. When the compound represented by 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.

[0056] As an example, the compound represented by the structural formula 1 can be selected from the following compounds:

[0057] .

[0058] In some embodiments, the compound represented by Structural Formula 1 includes one or more of the following compounds:

[0059] .

[0060] In some embodiments, the compound represented by Structural Formula 2 includes one or more of the following compounds:

[0061] .

[0062] In some embodiments, based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by Structural Formula 1 is 0.01% to 1%.

[0063] In a specific embodiment, based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of the compound represented by Structural Formula 1 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%, 0.24%, 0.25%, 0.28%, 0.3%, 0.32%, 0.34%, 0.35%, 0.38%, 0.4%, 0.42%, 0.44%, 0.45%, 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range consisting of any two of these values.

[0064] In a preferred embodiment, based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by Structural Formula 1 is 0.02% to 0.5%.

[0065] The compound represented by Structural Formula 1 participates in the formation of the solid electrolyte interface film (SEI) on the surface of the negative electrode. The solid electrolyte interface film (SEI) formed by the compound represented by Structural Formula 1 can block direct contact between the non-aqueous electrolyte and the negative electrode, thereby reducing the decomposition and gas production of the non-aqueous electrolyte on the surface of the negative electrode, and is used to improve the cycle capacity retention rate and high-temperature storage performance of the secondary battery. If the content of the compound represented by Structural Formula 1 is too low, the performance improvement effect on the secondary battery is limited; if the content of the compound represented by Structural Formula 1 is too high, the probability of side reactions in the electrolyte is increased, and the storage performance of the non-aqueous electrolyte is also degraded.

[0066] In some embodiments, based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by Structural Formula 2 is 0.005% to 0.1%.

[0067] In a specific embodiment, based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of the compound represented by Structural Formula 2 can be 0.005%, 0.008%, 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1% or a range consisting of any two of these values.

[0068] In a preferred embodiment, based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by Structural Formula 2 is 0.005% to 0.05%.

[0069] The compound represented by structural formula 2 and the compound represented by structural formula 1 jointly participate in the formation of the solid electrolyte interface film (SEI) on the surface of the negative electrode. More importantly, the compound represented by structural formula 2 inhibits the decomposition of the compound represented by structural formula 1 in the non-aqueous electrolyte, thereby extending the storage life of the non-aqueous electrolyte. If the content of the compound represented by structural formula 2 is too low, the storage performance of the non-aqueous electrolyte will not be significantly improved; if the content of the compound represented by structural formula 2 is too high, the film thickness of the solid electrolyte interface film (SEI) on the surface of the negative electrode will be too large, thereby increasing the impedance of the secondary battery.

[0070] In some embodiments, the mass ratio of the compound represented by Structural Formula 1 to the compound represented by Structural Formula 2 is 0.2-40.

[0071] In a specific embodiment, the mass ratio of the compound represented by Structural Formula 1 to the compound represented by Structural Formula 2 can be 0.2, 2.8, 5.4, 8.0, 10.6, 13.2, 15.8, 18.4, 21.0, 23.6, 26.2, 28.8, 31.4, 40.0 or a range consisting of any two of these values.

[0072] In a preferred embodiment, based on the total mass of the non-aqueous electrolyte being 100%, the mass ratio of the compound represented by Structural Formula 1 to the compound represented by Structural Formula 2 is 4-20.

[0073] The compound represented by Structural Formula 2 is a Lewis base that neutralizes Lewis acids such as HF and PF5 in the electrolyte, preventing the consumption of the compound represented by Structural Formula 1 by components such as HF and PF5. However, this can also lead to degradation of the battery's high-temperature storage performance. Combining the compound represented by Structural Formula 1 with the compound represented by Structural Formula 2 not only inhibits the decomposition and consumption of peroxides by the compound represented by Structural Formula 2, but also improves the storage degradation caused by the compound represented by Structural Formula 2, thereby balancing the battery's long-term cycle stability and storage capacity release.

[0074] Through extensive research, the inventors found that when the mass ratio of the compound represented by Structural Formula 1 to the compound represented by Structural Formula 2 is in the range of 0.2 to 40, the two have the best cooperation effect, which can significantly extend the battery's room temperature cycle life, solve the impedance growth of the battery during high-temperature storage, and improve the battery's high-temperature storage performance.

[0075] 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 participation of the compound shown in Structural Formula 1 and the compound shown in Structural Formula 2 in the formation of the solid electrolyte interface film (SEI) on the negative electrode surface during the charge and discharge formation stage of the battery, as well as the continuous repair of the damaged solid electrolyte interface film (SEI) by the compound shown in Structural Formula 1 and the compound shown in Structural Formula 2 remaining in the electrolyte during the long-term cycle of the battery. As a precursor of a gel electrolyte or a solid electrolyte, a polymerization reaction will occur to form a gel electrolyte before the charge and discharge formation of the battery. In this polymerization reaction, the organic peroxide shown in Structural Formula 1 reacts as an initiator with the polymerizable monomer, 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 charge and discharge cycle of the battery.

[0076] In some embodiments, the non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerizing a polymerizable monomer.

[0077] 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.

[0078] In some embodiments, the non-aqueous electrolyte does not undergo polymerization reaction under light or heating conditions.

[0079] In some embodiments, the non-aqueous electrolyte is in liquid state after formation.

[0080] In some embodiments, the additive further comprises at least one of a sultone compound, a cyclic carbonate compound, a phosphate compound, a nitrile compound, a lithium salt additive, or an alkane compound.

[0081] 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 methanedisulfonate.

[0082] In some embodiments, the cyclic carbonate compound includes at least one of vinylene carbonate, vinyl ethylene carbonate, methylene carbonate, or a compound represented by Structural Formula 3:

[0083] ;

[0084] In some embodiments, in the structural formula 3, 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.

[0085] In some embodiments, the phosphate compound includes a compound represented by structural formula 4:

[0086] ;

[0087] In the structural formula 4, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated hydrocarbon group, C1-C5 unsaturated hydrocarbon group, C1-C5 halogenated hydrocarbon group, C6-C12 aryl group, C6-C12 halogenated aryl group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3.

[0088] In a preferred embodiment, the phosphate compound shown in structural formula 4 may be at least one of triphenyl phosphate, trimethyl phosphate, triethyl 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.

[0089] In some embodiments, the nitrile compound includes at least one of succinonitrile, glutaronitrile, hexanetrionitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile, and sebacononitrile.

[0090] 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 trioxalatophosphate, lithium difluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium dicyanamide, or a lower aliphatic lithium carboxylate having 4 or fewer carbon atoms.

[0091] 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).

[0092] In other embodiments, the additives may also include other additives that can improve battery performance: for example, additives that enhance battery safety, such as flame retardant additives such as fluorophosphates and cyclophosphazenes, or overcharge prevention additives such as tert-amylbenzene and tert-butylbenzene.

[0093] It should be noted that, unless otherwise specified, under normal circumstances, 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% to 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.

[0094] 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%.

[0095] 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%.

[0096] 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.

[0097] 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.

[0098] 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-dioxane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, and 2-trifluoromethyltetrahydrofuran; the chain ether may be, but is not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Since chain ethers have 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 a range that does not significantly impair 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 100% by volume of the non-aqueous solvent. In addition, the volume ratio is usually 30% or less, preferably 25% or less, and more preferably 20% or less.

[0099] In some embodiments, the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.

[0100] In some embodiments, the carbonate solvent includes a cyclic carbonate or a chain carbonate. The cyclic carbonate may be, but is not limited to, at least one of ethylene carbonate, propylene carbonate, γ-butyrolactone, and butylene carbonate; the chain carbonate may be, but is not limited to, at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and dipropyl carbonate. 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. However, when using one alone, the lower limit of its content is generally 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 caused by the decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, and it is easy to achieve good high-current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery. In addition, the upper limit is generally 90% or less by volume, preferably 85% or less by volume, and more preferably 80% or less by volume. By setting this range, the oxidation / reduction resistance of the non-aqueous electrolyte can be improved, thereby helping to improve stability during high-temperature storage. The content of linear carbonate is not particularly limited, and with respect to the total amount of solvent of nonaqueous electrolytic solution, is generally volume ratio and is more than 15%, preferred volume ratio and is more than 20%, more preferably volume ratio and is more than 25%.In addition, usually volume ratio is below 90%, preferred volume ratio and is below 85%, more preferably volume ratio and is below 80%.By making the content of linear carbonate in above-mentioned scope, easily make the viscosity of nonaqueous electrolytic solution 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 using in combination two or more linear carbonates, make the total amount of linear carbonate satisfy above-mentioned scope and get final product.

[0101] In certain embodiments, also can preferably use the linear carbonates with fluorine atoms (hereinafter referred to as " fluorinated linear carbonate ").The number of the fluorine atoms possessed by fluorinated linear carbonate is as long as being more than 1 then has no particular restrictions, but is generally below 6, preferably below 4.When fluorinated linear carbonate has a plurality of fluorine atoms, these fluorine atoms can be bonded on the same carbon, also can be bonded on different carbons.As fluorinated linear carbonate, can enumerate, fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, fluorinated diethyl carbonate derivatives etc.

[0102] Carboxylate solvents include cyclic carboxylates and / or chain carbonates. Examples of cyclic carboxylates include at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonates include at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propyl propionate, and butyl propionate.

[0103] In some embodiments, the sulfone solvent includes a cyclic sulfone and a chain sulfone. Preferably, in the case of a cyclic sulfone, it is generally a compound having 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms; in the case of a chain sulfone, it is generally a compound having 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 in the non-aqueous electrolyte, the volume ratio is generally 0.3% or more, preferably 0.5% or more, more preferably 1% or more. In addition, the volume ratio is generally 40% or less, preferably 35% or less, more preferably 30% or less. When two or more sulfone solvents are used 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.

[0104] In a preferred embodiment, the non-aqueous organic solvent comprises a mixture of cyclic carbonate and chain carbonate.

[0105] 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 lower aliphatic carboxylic acid lithium having 4 or less carbon atoms, or at least one of lithium tetraphenylborate.

[0106] 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 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, 1.0 mol / L, 1.1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.45 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, 2.5 mol / L or a range consisting of any two of these values.

[0107] 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.

[0108] In some embodiments, the secondary battery is a lithium-ion battery.

[0109] 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 nickelate), 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、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.

[0110] 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 battery's energy density. The battery also has a charge cutoff voltage of up to 3.8V, a high discharge platform, and good cycling stability within a conventional voltage window. Furthermore, because iron is relatively abundant and inexpensive globally, the use of the above-mentioned positive electrode active material helps reduce costs and alleviate dependence on limited resources compared to rare and expensive metals such as cobalt, nickel, and manganese.

[0111] In a more preferred embodiment, the positive electrode active material is selected from LiFe 1-x’ Mn x’ PO4, where 0≤x'≤0.5.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] In some embodiments, the negative electrode includes a negative electrode material layer, the negative electrode material layer including 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. Carbon-based negative electrodes may include graphite, hard carbon, soft carbon, graphene, mesocarbon microbeads, and the like; silicon-based negative electrodes may include silicon materials, silicon oxides, silicon-carbon composites, and silicon alloys; tin-based negative electrodes may include tin, tin-carbon, tin-oxygen, and tin metal compounds; and lithium negative electrodes may include metallic lithium or a lithium alloy. Specifically, the lithium alloy may 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.

[0118] 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.

[0119] 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.

[0120] 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 an electron-conducting metal material, preferably comprising at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0121] In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductor, and the negative electrode active material, the negative electrode binder and the negative electrode conductor are blended to obtain the negative electrode material layer.

[0122] 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.

[0123] 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.

[0124] In some embodiments, the secondary battery further includes a separator, and the separator is located between the positive electrode and the negative electrode.

[0125] The diaphragm can be an existing conventional diaphragm, which can be 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.

[0126] The present invention is further described below with reference to the following examples.

[0127] Table 1

[0128]

[0129] Example 1

[0130] This example is used to illustrate the preparation method of the non-aqueous electrolyte disclosed in the present invention, which includes the following steps:

[0131] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of EC:EMC=3:7, and then 1M lithium hexafluorophosphate was added. Based on the total weight of the non-aqueous electrolyte being 100%, the components were added in the mass contents shown in Table 1 to obtain a non-aqueous electrolyte.

[0132] Examples 2 to 19

[0133] Examples 2 to 19 are used to illustrate the non-aqueous electrolyte for lithium ion batteries and the preparation method thereof disclosed in the present invention, and include most of the operating steps in Example 1, except that:

[0134] In the preparation steps of the non-aqueous electrolyte:

[0135] Based on the total mass of the non-aqueous electrolyte being 100%, the non-aqueous electrolyte is added with the components in the mass percentages shown in Examples 2 to 19 in Table 1.

[0136] Comparative Examples 1-11

[0137] Comparative Examples 1 to 11 are used to illustrate the non-aqueous electrolyte for lithium ion batteries and the preparation method thereof disclosed in the present invention, and include most of the operating steps in Example 1, except that:

[0138] In the preparation steps of the non-aqueous electrolyte:

[0139] Based on the total mass of the non-aqueous electrolyte being 100%, the non-aqueous electrolyte was added with the components in the mass percentages shown in Comparative Examples 1 to 11 in Table 1.

[0140] Performance Testing

[0141] The non-aqueous electrolytes prepared in Examples 1 to 19 and Comparative Examples 1 to 11 were stored at 25° C. for 30 days. The content of the compound represented by Structural Formula 1 after storage was detected, and the remaining percentage of the compound represented by Structural Formula 1 was calculated and recorded in Table 2. The acidity of the non-aqueous electrolytes before and after storage was detected, and the acidity growth rate was calculated based on the acidity of the non-aqueous electrolytes before and after storage and recorded in Table 2.

[0142] Table 2

[0143]

[0144] The test results of Examples 1-10 and Comparative Examples 1-8 show that by introducing the compound of Structural Formula 2 into a non-aqueous electrolyte containing the compound of Structural Formula 1, the long-term storage performance of the non-aqueous electrolyte is significantly improved. In contrast, in the non-aqueous electrolyte not containing the compound of Structural Formula 2, the compound of Structural Formula 1 showed a significant decrease after 30 days of storage. This indicates that the compound of Structural Formula 2 can effectively stabilize the compound of Structural Formula 1 and inhibit the HF and PF5 produced by the decomposition of lithium salts, thereby preventing the continued decomposition of the compound of Structural Formula 1. This mechanism ensures that the non-aqueous electrolyte maintains consistent properties after long-term storage, avoiding the problem of quality degradation caused by long-term storage.

[0145] From the test results of Examples 1 to 6, it can be seen that as the content of the compound represented by Structural Formula 2 gradually increases, its decomposition inhibition effect on the compound represented by Structural Formula 1 first increases and then decreases, indicating that an appropriate amount of the compound represented by Structural Formula 2 can inhibit the decomposition of the compound represented by Structural Formula 1, but an excessive amount of the compound represented by Structural Formula 2 will affect its inhibitory effect. It is speculated that this is because the excessive amount of Structural Formula 2 itself will cause a reaction between it and the compound represented by Structural Formula 1.

[0146] It can be seen from the test results of Examples 4, 8 to 15 and Comparative Examples 1 to 7 that when the content of the compound represented by Structural Formula 2 is constant, as the content of the compound represented by Structural Formula 1 gradually increases, the storage decomposition inhibition effect on the compound represented by Structural Formula 1 also shows a trend of first increasing and then decreasing, indicating that the compound represented by Structural Formula 2 has a relatively poor decomposition inhibition effect on the excess or trace amount of the compound represented by Structural Formula 1.

[0147] It can be seen from the test results of Examples 16 to 19 and Comparative Examples 8 to 11 that when different types of compounds represented by Structural Formula 1 and different types of compounds represented by Structural Formula 2 are combined, they can all inhibit the decomposition of the compound represented by Structural Formula 1 to varying degrees.

[0148] Examples 20 to 38

[0149] Examples 20 to 38 are used to illustrate the preparation method of the lithium ion battery disclosed in the present invention, which includes the following steps:

[0150] 1) Electrolyte

[0151] Examples 20 to 38 respectively used the non-aqueous electrolytes of Examples 1 to 19 after being stored at 25° C. for 30 days.

[0152] 2) Preparation of positive electrode plate

[0153] The positive electrode active material, lithium iron phosphate, conductive carbon black (Super-P), and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 93:4:3 and then dispersed in N-methylpyrrolidone (NMP) to create a positive electrode slurry. The slurry is evenly coated on both sides of aluminum foil, dried, rolled, and vacuum-dried, and then cut using a mold to produce positive electrode plates with a thickness of 120-150μm.

[0154] 3) Preparation of negative plate

[0155] The negative electrode active materials, artificial graphite, conductive carbon black (Super-P), and binders, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC), are mixed in a mass ratio of 94:1:2.5:2.5 and dispersed in deionized water to create a negative electrode slurry. The slurry is then coated on both sides of copper foil, dried, rolled, and vacuum-dried, and then cut using a mold to produce negative electrode plates with a thickness of 120-150μm.

[0156] 4) Preparation of battery cells

[0157] A three-layer separator with a thickness of 20 μm is placed between the positive plate and the negative plate, and then the sandwich structure consisting of the positive plate, negative plate and separator is stacked. An ultrasonic welder is used to weld aluminum lead wires to the positive plate and nickel lead wires to the negative plate. The cells are placed in a punched aluminum foil packaging bag and sealed on the top and side. After vacuum baking at 75°C for 48 hours, the cells are completely encapsulated to obtain the battery cells ready for liquid injection.

[0158] 5) Battery filling and formation

[0159] In a glove box with a dew point controlled below -40°C, the prepared electrolyte was injected into the battery cell, vacuum-sealed, and left to stand for 24 hours before the first charge formation.

[0160] Comparative Examples 12-22

[0161] Comparative Examples 12 to 22 are used to compare and illustrate the method for preparing a lithium-ion battery disclosed in the present invention, and include most of the operating steps in Examples 20 to 38, except that:

[0162] As shown in Table 3, Comparative Examples 12 to 22 respectively use the non-aqueous electrolytes of Comparative Examples 1 to 11 after being stored at 25° C. for 30 days.

[0163] Performance Testing

[0164] The lithium-ion battery prepared above was subjected to the following performance tests:

[0165] (1) Battery first coulombic efficiency test: During the first charging and formation process of the battery, record the charging capacity. After formation, discharge the battery and record the discharge capacity. Calculate the first coulombic efficiency: First coulombic efficiency (%) = discharge capacity / charge capacity*100%.

[0166] (2) Battery room temperature cycle performance test: The divided batteries were subjected to room temperature cycle test in a constant temperature environment at 25°C with the following steps: 1C constant current and constant voltage charging to 3.65 V, cut-off current 0.05C, after standing, 1.5C constant current discharge to 2.5 V, standing for 5 minutes, and so on for 2000 cycles. The discharge capacity of each cycle was recorded, and the cycle capacity retention rate (%) = 2000th cycle discharge capacity / first cycle discharge capacity * 100%, and the average value of the parallel test samples was calculated.

[0167] The test results are entered in Table 3.

[0168] Table 3

[0169]

[0170] The test results of Examples 20 to 38 and Comparative Examples 12 to 22 show that after 30 days of storage, when a non-aqueous electrolyte containing both the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 is used in a lithium-ion battery, it can effectively improve the initial coulombic efficiency and cycle capacity retention rate of the lithium-ion battery, while the non-aqueous electrolyte containing only the compound represented by Structural Formula 1 shows a significant decrease in battery performance. Moreover, combined with the test results in Table 2, it can be seen that the initial coulombic efficiency and cycle capacity retention rate of the lithium-ion battery are related to the content of the compound represented by Structural Formula 1 in the non-aqueous electrolyte, indicating that the compound represented by Structural Formula 2 can inhibit the decomposition of the compound represented by Structural Formula 1 during storage, thereby improving the storage stability of the non-aqueous electrolyte, ensuring that a sufficient amount of the compound represented by Structural Formula 1 remains in the non-aqueous electrolyte after a certain storage period, and thus improving the cycle performance of the lithium-ion battery through the compound represented by Structural Formula 1.

[0171] It can be seen from the test results of Examples 1 to 15 that when the mass ratio of the compound represented by Structural Formula 1 to the compound represented by Structural Formula 2 is 4 to 20, the cycle performance and the first coulombic efficiency of the obtained lithium-ion battery are optimal, indicating that at this ratio, the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 show a synergistic effect, which can not only inhibit the decomposition and consumption of peroxides by using the compound represented by Structural Formula 2, but also improve the storage degradation caused by the compound represented by Structural Formula 2 by using the compound represented by Structural Formula 1, taking into account the long-cycle stability and storage capacity release of the battery.

[0172] 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 scope of protection of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that The method comprises a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises a compound represented by structural formula 1 and a compound represented by structural formula 2: 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, R 2 are not hydrogen at the same time, R1 and R2 are connected to each other to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-12 alkenylene, substituted or unsubstituted C2-12 alkynylene, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C2-C12 ether; when R1, R2, and R3 are substituted, the substituent is alkoxy, hydroxy, acyl, ester, cyano, or halogen; Structural Formula 2 wherein R4, R5, and R6 are each independently selected from a C1-C6 hydrocarbon group, a C6-C20 aryl group, a C3-C6 silicon-containing group, or a C1-C6 fluorinated hydrocarbon group; Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by structural formula 1 is 0.01% to 1%; Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of the compound represented by structural formula 2 is 0.005% to 0.1%; The mass ratio of the compound represented by Structural Formula 1 to the compound represented by Structural Formula 2 is 0.2-40.

2. The non-aqueous electrolyte according to claim 1, characterized in that In the compound shown in 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.

3. The non-aqueous electrolyte according to claim 1, characterized in that In the compound represented by structural formula 1, R1 and R2 are each independently selected from a substituted or unsubstituted C1-C12 alkyl group, a substituted or unsubstituted C2-C12 alkenyl group, a substituted or unsubstituted C2-C12 alkynyl group, or a substituted or unsubstituted C6-C20 aryl group.

4. The non-aqueous electrolyte according to claim 1, wherein In the compound shown in the structural formula 1, 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.

5. The non-aqueous electrolyte according to claim 1, characterized in that In the compound shown in the 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.

6. 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: 。 7. The non-aqueous electrolyte according to claim 1, characterized in that The compound represented by structural formula 2 includes one or more of the following compounds: 。 8. The non-aqueous electrolyte according to claim 1, wherein 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: The invention comprises a positive electrode, a negative electrode and the non-aqueous electrolyte according to any one of claims 1 to 8.

Images