Secondary battery and electronic device

Abstract

A secondary battery and an electronic device. The secondary battery comprises a non-aqueous electrolyte, the non-aqueous electrolyte comprises a compound as represented by formula I, wherein R1 and R2 are each independently selected from a fluorine element, an F-substituted or unsubstituted C1-C10 alkyl group, and an F-substituted or unsubstituted C6-C10 phenyl group; at least one of R1 and R2 is substituted by F; and on the basis of the mass of the non-aqueous electrolyte, the mass percentage content of the compound as represented by formula I is 10%-80%. By regulating and controlling the non-aqueous electrolyte to comprise the compound as represented by formula I, and the type and mass percentage content of the compound as represented by formula I, the interfacial reaction of the non-aqueous electrolyte on a positive electrode can be reduced, and the cycle stability under high voltage and the interval cycle stability of the secondary battery can be improved.

Description

Secondary battery and electronic device Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a secondary battery and an electronic device. Background Art

[0002] Lithium-ion batteries are widely used in portable electronics, electric vehicles, aerospace, energy storage, and other fields due to their high energy density, excellent cycle performance, safety, environmental friendliness, and lack of memory effect. To meet the demands of society, the search for lithium-ion batteries with higher energy density and power density has become a pressing issue, driving the development of cathode active materials suitable for high voltages. As voltage increases, non-aqueous electrolyte reactions at the cathode interface intensify, causing lithium-ion battery performance degradation.

[0003] Therefore, there is an urgent need to provide a lithium-ion battery that can reduce the interfacial reaction of the non-aqueous electrolyte at the positive electrode and improve the cycle stability and inter-cycle stability of the lithium-ion battery at high voltage.

[0004] Summary of the Invention

[0005] The purpose of this application is to provide a secondary battery and electronic device that can reduce the interfacial reaction of the non-aqueous electrolyte at the positive electrode and improve the cycle stability and inter-cycle stability of the secondary battery at high voltage. The specific technical solution is as follows:

[0006] The first aspect of the present application provides a secondary battery comprising a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a compound of formula I,

[0007] Wherein, R1 and R2 are each independently selected from fluorine, a C1 to C10 alkyl group substituted or unsubstituted by F, or a C6 to C10 phenyl group substituted or unsubstituted by F; and at least one of R1 and R2 is substituted by F. Based on the mass of the non-aqueous electrolyte, the mass percentage of the compound of formula I is 10% to 80%, preferably, the mass percentage W1 of the compound of formula I is 10% to 70%. By regulating the non-aqueous electrolyte to include the compound of formula I, and the type and mass percentage of the compound of formula I within the scope of this application, the interfacial reaction of the non-aqueous electrolyte at the positive electrode can be reduced, thereby improving the cycle stability and inter-cycle stability of the secondary battery at high voltage.

[0008] In one embodiment of the present application, the compound of formula I comprises at least one of the following compounds:

[0009] The compound of formula I is selected, and at least one of the groups R1 and R2 of the compound of formula I is replaced by F, forming stable components such as LiSOxF on the negative electrode side, thereby alleviating the continuous reaction of the electrolyte on the negative electrode side; at the same time, the fluorine substitution improves the oxidation resistance of the electrolyte and reduces the continuous reaction at the positive electrode interface, which can further improve the cycle stability and inter-cycle stability of the secondary battery at high voltage.

[0010] In one embodiment of the present application, R1 and R2 are both substituted with F, and the mass percentage of the compound of Formula I is 10% to 30% based on the mass of the non-aqueous electrolyte. When R1 and R2 of the compound of Formula I are both substituted with F and the mass percentage of the compound of Formula I is within the range of the present application, while effectively reducing the sustained reaction on the negative electrode side and the positive electrode side, the non-aqueous electrolyte can also have a suitable viscosity, which is beneficial for lithium ion transport and further improves the cycle stability and inter-cycle stability of the secondary battery at high voltage.

[0011] In one embodiment of the present application, only R2 is substituted with F, and the mass percentage of the compound of Formula I is 10% to 60% based on the mass of the non-aqueous electrolyte. In the compound of Formula I, only R2 is substituted with F, and the mass percentage of the compound of Formula I is within the range of the present application. This effectively reduces the sustained reaction on the negative and positive electrode sides while also facilitating the dissociation of the lithium salt, thereby improving the liquid phase homogeneity of the non-aqueous electrolyte and further enhancing the cycling stability and inter-cycling stability of the secondary battery at high voltage.

[0012] In one embodiment of the present application, the non-aqueous electrolyte further comprises a first lithium salt, and the first lithium salt comprises at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium dioxalatoborate or lithium difluorophosphate. The non-aqueous electrolyte further comprises a first lithium salt, and the above-mentioned first lithium salt is selected to introduce an anion in the first lithium salt, and the above-mentioned anion can participate in lithium ion solvation and react with the compound of formula I and / or hexafluorophosphate anion (PF6 - ) competes for coordination, reducing the coordination and decomposition of the compound of formula I and / or the hexafluorophosphate anion in the first solvation layer; in addition, the first lithium salt has a higher reduction potential, and the first lithium salt can be reduced preferentially over the compound of formula I, thereby reducing the reduction reaction activity of the compound of formula I, further improving the cycle stability and inter-cycle stability of the secondary battery at high voltage.

[0013] In one embodiment of the present application, the mass percentage of the first lithium salt is 0.1% to 5% based on the mass of the non-aqueous electrolyte. By regulating the mass percentage of the first lithium salt within the scope of the present application, the first lithium salt has an appropriate mass percentage, and the first lithium salt can be reduced preferentially over the compound of Formula I, thereby effectively reducing the reduction reaction activity of the compound of Formula I. In addition, an appropriate amount of active lithium is consumed during the reaction on the positive electrode side or the negative electrode side, which is beneficial for reducing interfacial impedance and facilitating lithium ion transmission, thereby further improving the cycle stability and inter-cycle stability of the secondary battery at high voltage.

[0014] In one embodiment of the present application, the non-aqueous electrolyte further includes a first nitrile compound, and the first nitrile compound includes at least one of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, or 2-methylglutaronitrile. The non-aqueous electrolyte further includes a first nitrile compound, and the first nitrile compound is selected. The first nitrile compound can adsorb and complex transition metals on the surface of the positive electrode, reduce the reaction between the non-aqueous electrolyte and the positive electrode active material, reduce the gas production of the secondary battery during the cycle, improve the interfacial contact, facilitate the transmission of lithium ions, and further improve the cycle stability and interval cycle stability of the secondary battery at high voltage.

[0015] In one embodiment of the present application, the mass percentage of the first nitrile compound is 0.5% to 4% based on the mass of the non-aqueous electrolyte. By regulating the mass percentage of the first nitrile compound within the scope of the present application, the first nitrile compound has an appropriate mass percentage, and the first nitrile compound can better adsorb and complex transition metals on the surface of the positive electrode, reduce the reaction between the non-aqueous electrolyte and the positive electrode active material, reduce gas production of the secondary battery during cycling, improve interfacial contact, facilitate lithium ion transmission, and further enhance the cycle stability and inter-cycle stability of the secondary battery at high voltage.

[0016] In one embodiment of the present application, the non-aqueous electrolyte further includes a second nitrile compound, and the second nitrile compound includes at least one of the following compounds:

[0017] The non-aqueous electrolyte includes a second nitrile compound, and the above-mentioned second nitrile compound is selected. On the one hand, the second nitrile compound can better adsorb and complex the transition metal on the surface of the positive electrode, reduce the reaction between the non-aqueous electrolyte and the positive electrode active material, reduce the gas production of the secondary battery during the cycle, improve the interface contact, and facilitate the transmission of lithium ions; on the other hand, the second nitrile compound will occupy the first solvation layer of the lithium ion, reduce the coordination of the compound of formula I with the lithium ion, and reduce the decomposition reaction of the compound of formula I, thereby further improving the cycle stability and interval cycle stability of the secondary battery at high voltage.

[0018] In one embodiment of the present application, based on the mass of the non-aqueous electrolyte, the mass percentage of the second nitrile compound is 0.5% to 5%. By regulating the mass percentage of the second nitrile compound within the scope of the present application, the second nitrile compound has an appropriate mass percentage. On the one hand, the second nitrile compound can better adsorb and complex the transition metal on the surface of the positive electrode, reduce the reaction between the non-aqueous electrolyte and the positive electrode active material, reduce the gas production of the secondary battery during the cycle, improve the interface contact, and facilitate the transmission of lithium ions; on the other hand, the second nitrile compound will occupy the first solvation layer of the lithium ion, further reduce the coordination of the compound of formula I with the lithium ion, reduce the decomposition reaction of the compound of formula I, thereby further improving the cycle stability and interval cycle stability of the secondary battery at high voltage.

[0019] The second aspect of the present application provides an electronic device, which includes the secondary battery according to any one of the aforementioned embodiments. Therefore, the electronic device provided by the present application has good cycle stability under high voltage and inter-cycle stability.

[0020] Beneficial effects of this application:

[0021] The present application provides a secondary battery and an electronic device. The secondary battery includes a non-aqueous electrolyte, the non-aqueous electrolyte including a compound of formula I, wherein R1 and R2 are each independently selected from fluorine, a C1 to C10 alkyl group substituted or unsubstituted by F, or a C6 to C10 phenyl group substituted or unsubstituted by F; at least one of R1 and R2 is substituted by F; and the mass percentage of the compound of formula I is 10% to 80% based on the mass of the non-aqueous electrolyte. By regulating the inclusion of the compound of formula I in the non-aqueous electrolyte, and by adjusting the type and mass percentage of the compound of formula I within the scope of the present application, the interfacial reaction of the non-aqueous electrolyte at the positive electrode can be reduced, thereby improving the cycle stability and inter-cycle stability of the secondary battery at high voltage. DETAILED DESCRIPTION

[0022] To make the purpose, technical solutions, and advantages of this application more clearly understood, the following examples are given to further describe this application in detail. Obviously, the described examples are only some examples of this application, rather than all examples. All other examples obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0023] It should be noted that, in the specific embodiments of the present application, lithium-ion batteries are used as an example of secondary batteries to explain the present application, but the secondary batteries of the present application are not limited to lithium-ion batteries.

[0024] The present application provides a secondary battery comprising a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a compound of formula I,

[0025] Wherein, R1 and R2 are each independently selected from fluorine, a C1 to C10 alkyl group substituted or unsubstituted by F, or a C6 to C10 phenyl group substituted or unsubstituted by F; and at least one of R1 and R2 is substituted by F. Based on the mass of the non-aqueous electrolyte, the mass percentage W1 of the compound of Formula I is 10% to 80%. Preferably, the mass percentage W1 of the compound of Formula I is 10% to 70%. Exemplarily, the value of W1 can be 10%, 13%, 15%, 17%, 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, 53%, 55%, 57%, 60%, 63%, 65%, 67%, 70%, 73%, 75%, 77%, 80%, or a range consisting of any two of the foregoing values. In the present application, the compound of formula I is a sulfonic acid group compound; the alkyl group of C1 to C10 can be methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl or decyl; the phenyl group of C6 to C10 can be benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, trimethylbenzene, methylethylbenzene, propylbenzene, butylbenzene, diethylbenzene or dimethylethylbenzene.

[0026] In one embodiment of the present application, R1 and R2 are both substituted by F, and the mass percentage W1 of the compound of formula I is 10% to 80% based on the mass of the non-aqueous electrolyte.

[0027] In one embodiment of the present application, only R2 is substituted by F, and the mass percentage W1 of the compound of formula I is 10% to 80% based on the mass of the non-aqueous electrolyte.

[0028] In one embodiment of the present application, only R1 is substituted by F, and the mass percentage W1 of the compound of formula I is 10% to 80% based on the mass of the non-aqueous electrolyte.

[0029] The inventors have found that conventional (unsubstituted) sulfonic acid group compounds react to form unstable interface components on the negative electrode side, and the cycle process continues to react, lithium is continuously consumed, and the high-voltage cycle decays quickly. After fluorine substitution is performed on one or both sides of the sulfonic acid group of the corresponding compound, stable components such as LiSOxF are formed on the negative electrode side, which alleviates the sustained reaction of the electrolyte on the negative electrode side; at the same time, fluorine substitution improves oxidation resistance, reduces the sustained reaction on the positive electrode interface, and can improve the cycle stability and interval cycle stability of the secondary battery at high voltage. When the mass percentage of the compound of formula I is too low, for example, less than 10%, it is impossible to effectively weaken the sustained reaction of the negative electrode side and the positive electrode side, which will cause the cycle stability and interval cycle stability of the secondary battery at high voltage to be poor; when the mass percentage of the compound of formula I is too high, for example, higher than 80%, it will cause the viscosity of the non-aqueous electrolyte to increase, lithium ions will be difficult to diffuse in the liquid phase, and the interface impedance will also increase, resulting in the cycle stability and interval cycle stability of the secondary battery at high voltage to be poor. By regulating the non-aqueous electrolyte to include a compound of Formula I, and by controlling the type and weight percentage of the compound of Formula I within the scope of this application, the interfacial reaction of the non-aqueous electrolyte at the positive electrode can be reduced, thereby improving the cycle stability and inter-cycle stability of the secondary battery at high voltage. In this application, "high voltage" refers to a voltage ≥4.5V.

[0030] In one embodiment of the present application, the compound of formula I comprises at least one of the following compounds:

[0031] The compound of formula I is selected, and at least one of the groups R1 and R2 of the compound of formula I is replaced by F, forming stable components such as LiSOxF on the negative electrode side, thereby alleviating the continuous reaction of the electrolyte on the negative electrode side; at the same time, fluorine substitution improves oxidation resistance and reduces the continuous reaction at the positive electrode interface, which can further improve the cycle stability and inter-cycle stability of the secondary battery at high voltage.

[0032] In one embodiment of the present application, R1 and R2 are both replaced by F, and based on the mass of the non-aqueous electrolyte, the mass percentage W1 of the compound of formula I is 10% to 30%. Exemplarily, the value of W1 can be 10%, 13%, 15%, 17%, 20%, 23%, 25%, 27%, 30% or a range consisting of any two of the above values. R1 and R2 of the compound of formula I are both replaced by F, and the mass percentage of the compound of formula I is within the scope of this application. While effectively weakening the sustained reaction on the negative electrode side and the positive electrode side, it can also enable the non-aqueous electrolyte to have a suitable viscosity, which is beneficial to lithium ion transmission and further improves the cycle stability and interval cycle stability of the secondary battery at high voltage.

[0033] In one embodiment of the present application, only R2 is replaced by F, and based on the mass of the non-aqueous electrolyte, the mass percentage W1 of the compound of formula I is 10% to 60%. Exemplarily, the value of W1 can be 10%, 13%, 15%, 17%, 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, 53%, 55%, 57%, 60% or a range consisting of any two of the above values. In the compound of formula I, only R2 is replaced by F, and the mass percentage of the compound of formula I is within the scope of this application. While effectively weakening the continuous reaction on the negative electrode side and the positive electrode side, it is also beneficial to the dissociation of the lithium salt, can improve the liquid phase homogeneity of the non-aqueous electrolyte, is beneficial to lithium ion transmission, and further improves the cycle stability and interval cycle stability of the secondary battery at high voltage.

[0034] In one embodiment of the present application, the non-aqueous electrolyte further comprises a first lithium salt, and the first lithium salt comprises at least one of lithium bis(trifluoromethanesulfonyl imide) (LiN(CF3SO2)2, LiTFSI), lithium tetrafluoroborate (LiBF4), lithium difluorooxalatoborate (LiBF2(C2O4), LiDFOB), lithium dioxalatoborate (LiB(C2O4)2, LiBOB) or lithium difluorophosphate (LiPO2F2). The non-aqueous electrolyte further comprises a first lithium salt, and the above-mentioned first lithium salt is selected to introduce an anion in the first lithium salt, and the above-mentioned anion can participate in lithium ion solvation and react with the compound of formula I and / or hexafluorophosphate anion (PF6 - ) competes for coordination, reducing the coordination and decomposition of the compound of formula I and / or the hexafluorophosphate anion in the first solvation layer; in addition, the first lithium salt has a higher reduction potential, and the first lithium salt can be reduced preferentially over the compound of formula I, thereby reducing the reduction reaction activity of the compound of formula I, further improving the cycle stability and inter-cycle stability of the secondary battery at high voltage.

[0035] In one embodiment of the present application, based on the mass of the non-aqueous electrolyte, the mass percentage content W2 of the first lithium salt is 0.1% to 5%. For example, the value of W2 can be 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range consisting of any two of the above values. By regulating the mass percentage content of the first lithium salt within the scope of this application, the first lithium salt has a suitable mass percentage content, and the first lithium salt can be reduced preferentially over the compound of formula I, thereby effectively reducing the reduction reaction activity of the compound of formula I; in addition, an appropriate amount of active lithium is consumed during the reaction on the positive electrode side or the negative electrode side, which is beneficial to reducing the interfacial impedance and facilitating the transmission of lithium ions, thereby further improving the cycle stability and inter-cycle stability of the secondary battery at high voltage.

[0036] In one embodiment of the present application, the non-aqueous electrolyte further includes a first nitrile compound, and the first nitrile compound includes at least one of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, or 2-methylglutaronitrile. The non-aqueous electrolyte further includes a first nitrile compound, and the first nitrile compound is selected. The first nitrile compound can adsorb and complex transition metals on the surface of the positive electrode, reduce the reaction between the non-aqueous electrolyte and the positive electrode active material, reduce the gas production of the secondary battery during the cycle, improve the interfacial contact, facilitate the transmission of lithium ions, and further improve the cycle stability and interval cycle stability of the secondary battery at high voltage.

[0037] In one embodiment of the present application, based on the mass of the non-aqueous electrolyte, the mass percentage W3 of the first nitrile compound is 0.5% to 4%. Exemplarily, the value of W3 can be 0.5%, 0.7%, 0.9%, 1%, 1.3%, 1.5%, 1.7%, 1.9%, 2%, 2.3%, 2.5%, 2.7%, 2.9%, 3%, 3.3%, 3.5%, 3.7%, 3.9%, 4% or a range consisting of any two of the above numerical values. By regulating the mass percentage of the first nitrile compound within the scope of this application, the first nitrile compound has a suitable mass percentage, and the first nitrile compound can better adsorb the transition metal on the surface of the complex positive electrode, reduce the reaction between the non-aqueous electrolyte and the positive electrode active material, reduce the gas production of the secondary battery during the cycle, improve the interface contact, and facilitate the transmission of lithium ions, further improving the cycle stability and interval cycle stability of the secondary battery at high voltage.

[0038] In one embodiment of the present application, the non-aqueous electrolyte further comprises a second nitrile compound, and the second nitrile compound comprises at least one of the following compounds:

[0039] The non-aqueous electrolyte also includes a second nitrile compound, and the above-mentioned second nitrile compound is selected. On the one hand, the second nitrile compound can better adsorb and complex the transition metal on the surface of the positive electrode, reduce the reaction between the non-aqueous electrolyte and the positive electrode active material, reduce the gas production of the secondary battery during the cycle, improve the interface contact, and facilitate the transmission of lithium ions; on the other hand, the second nitrile compound will occupy the first solvation layer of the lithium ion, reduce the coordination of the compound of formula I with the lithium ion, and reduce the decomposition reaction of the compound of formula I, thereby further improving the cycle stability and interval cycle stability of the secondary battery at high voltage.

[0040] In one embodiment of the present application, the weight percentage W4 of the second nitrile compound is 0.5% to 5% based on the weight of the non-aqueous electrolyte. For example, the value of W4 can be 0.5%, 0.7%, 0.9%, 1%, 1.3%, 1.5%, 1.7%, 1.9%, 2%, 2.3%, 2.5%, 2.7%, 2.9%, 3%, 3.3%, 3.5%, 3.7%, 3.9%, 4%, 4.3%, 4.5%, 4.7%, 4.9%, 5%, or a range consisting of any two of the above values. By regulating the mass percentage of the second nitrile compound within the scope of this application, the second nitrile compound has a suitable mass percentage. On the one hand, the second nitrile compound can better adsorb and complex the transition metal on the surface of the positive electrode, reduce the reaction between the non-aqueous electrolyte and the positive electrode active material, reduce the gas production of the secondary battery during the cycle, improve the interfacial contact, and facilitate the transmission of lithium ions; on the other hand, the second nitrile compound will occupy the first solvation layer of the lithium ion, further reduce the coordination of the compound of formula I with the lithium ion, reduce the decomposition reaction of the compound of formula I, thereby further improving the cycle stability and interval cycle stability of the secondary battery at high voltage.

[0041] In the present application, the features of the different components contained in the above-mentioned non-aqueous electrolyte can be combined, and the embodiments covered by the above-mentioned combination are all within the protection scope of the present application.

[0042] In the present application, the non-aqueous electrolyte further includes a second lithium salt and / or other organic solvents. The present application has no particular restrictions on the type of the second lithium salt, and lithium salts known in the art can be used. For example, the second lithium salt can include but is not limited to lithium hexafluorophosphate (LiPF6) or lithium bis(fluorosulfonyl)imide (LiFSI). The present application has no particular restrictions on other organic solvents, as long as the purpose of the present application can be achieved. For example, other organic solvents can include at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents. The above-mentioned carbonate compounds can include but are not limited to at least one of chain carbonate compounds, cyclic carbonate compounds or fluorocarbon compounds. The above-mentioned chain carbonate compounds can include but are not limited to at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC) or ethyl methyl carbonate (EMC). The above-mentioned cyclic carbonate compounds can include but are not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The fluorocarbonate compound may include, but is not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The carboxylate compound may include, but is not limited to, at least one of methyl formate, ethyl formate, propyl formate, n-butyl formate, isobutyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, or propyl propionate. The above-mentioned ether compound may include, but is not limited to, at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The above-mentioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or a phosphate ester. When the non-aqueous electrolyte further includes a second lithium salt and other organic solvents, the present application does not particularly limit the mass percentage of the second lithium salt and other organic solvents in the non-aqueous electrolyte, as long as the purpose of the present application can be achieved. For example, based on the mass of the non-aqueous electrolyte, the mass percentage W5 of the second lithium salt is 8% to 20%, and the mass percentage W6 of the other organic solvents is 10% to 82%.

[0043] In one embodiment of the present application, the non-aqueous electrolyte may include a compound of Formula I and a second lithium salt, wherein the mass percentage W1 of the compound of Formula I is 10% to 80%, and the mass percentage W5 of the second lithium salt is 20% to 90%, based on the mass of the non-aqueous electrolyte. A secondary battery including the non-aqueous electrolyte has both good high-voltage cycling stability and intermittent cycling stability.

[0044] In one embodiment of the present application, the non-aqueous electrolyte may include a compound of Formula I, a second lithium salt, and an organic solvent. The mass percentages of the compound of Formula I and the second lithium salt are as described above, and the mass percentage W6 of the other organic solvent is 10% to 82%. A secondary battery including the non-aqueous electrolyte has both good high-voltage cycling stability and intermittent cycling stability.

[0045] In one embodiment of the present application, the non-aqueous electrolyte may include a compound of Formula I, a second lithium salt, a first lithium salt, and another organic solvent. The mass percentages of the compound of Formula I, the second lithium salt, and the first lithium salt are as described above, and the mass percentage W6 of the other organic solvent is 11.9% to 81.9%. A secondary battery including the non-aqueous electrolyte has both good high-voltage cycling stability and intermittent cycling stability.

[0046] In one embodiment of the present application, the non-aqueous electrolyte may include a compound of Formula I, a second lithium salt, a first nitrile compound, and another organic solvent. The weight percentages of the compound of Formula I, the second lithium salt, and the first nitrile compound are as described above, and the weight percentage W6 of the other organic solvent is 11.5% to 81.5%. A secondary battery including the non-aqueous electrolyte has both good high-voltage cycling stability and intermittent cycling stability.

[0047] In one embodiment of the present application, the non-aqueous electrolyte may include a compound of Formula I, a second lithium salt, a second nitrile compound, and another organic solvent. The weight percentages of the compound of Formula I, the second lithium salt, and the second nitrile compound are as described above, and the weight percentage W6 of the other organic solvent is 11.5% to 81.5%. A secondary battery including the non-aqueous electrolyte has both good high-voltage cycling stability and intermittent cycling stability.

[0048] In one embodiment of the present application, the non-aqueous electrolyte may include a compound of Formula I, a second lithium salt, a first lithium salt, a first nitrile compound, and another organic solvent. The mass percentages of the compound of Formula I, the second lithium salt, the first lithium salt, and the first nitrile compound are as described above, and the mass percentage W6 of the other organic solvent is 11.4% to 81.4%. A secondary battery including the non-aqueous electrolyte has both good high-voltage cycling stability and intermittent cycling stability.

[0049] In one embodiment of the present application, the non-aqueous electrolyte may include a compound of Formula I, a second lithium salt, a first nitrile compound, a second nitrile compound, and another organic solvent. The mass percentages of the compound of Formula I, the second lithium salt, the first nitrile compound, and the second nitrile compound are as described above, and the mass percentage W6 of the other organic solvent is 11% to 81%. A secondary battery including the non-aqueous electrolyte has both good high-voltage cycling stability and intermittent cycling stability.

[0050] In one embodiment of the present application, the non-aqueous electrolyte may include a compound of Formula I, a second lithium salt, a first lithium salt, a first nitrile compound, a second nitrile compound, and another organic solvent. The mass percentages of the compound of Formula I, the second lithium salt, the first lithium salt, the first nitrile compound, and the second nitrile compound are as described above, and the mass percentage W6 of the other organic solvent is 10.9% to 80.9%. A secondary battery including the above non-aqueous electrolyte has good high-voltage cycle stability and intermittent cycle stability.

[0051] In the present application, the secondary battery also includes a positive electrode plate, which includes a positive electrode collector and a positive electrode material layer arranged on at least one surface of the positive electrode collector. The above-mentioned "positive electrode material layer arranged on at least one surface of the positive electrode collector" means that the positive electrode material layer can be arranged on one surface of the positive electrode collector along the thickness direction of itself, or on two surfaces of the positive electrode collector along the thickness direction of itself. It should be noted that the "surface" here can be the entire area of ​​the positive electrode collector or a partial area of ​​the positive electrode collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the positive electrode collector, as long as the purpose of this application can be achieved. For example, it can include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector).

[0052] The positive electrode material layer of the present application includes a positive electrode active material, which includes a substance that can reversibly embed and extract active ions such as lithium ions. The positive electrode material layer can be one or more layers, and each layer in the multilayer positive electrode material layer can contain the same or different positive electrode active materials. The present application has no particular restrictions on the positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material can include but is not limited to lithium nickel cobalt manganese oxide (such as NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. The positive electrode material layer of the present application also includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and binder in the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the conductive agent can include but is not limited to at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metal materials or conductive polymers. The conductive carbon black may include but is not limited to Super P, acetylene black or Ketjen black. The carbon nanotubes may include but is not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nanofibers. The metal materials may include but are not limited to metal powder and / or metal fibers, specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The conductive polymers may include but are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. The binder may include but is not limited to at least one of polyacrylates, polyacrylic acid, polyimides, polyamides, polyamide-imide, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymers, styrene-acrylate copolymers, polystyrene butadiene copolymers (styrene-butadiene rubber, SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl ether, polyhexafluoropropylene, potassium carboxymethyl cellulose, sodium hydroxymethyl cellulose or potassium hydroxymethyl cellulose. The present application does not particularly limit the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer. Those skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved. For example, the mass ratio of the positive electrode active material, the conductive agent, and the binder can be (91 to 99): (0.5 to 3): (0.5 to 6).

[0053] The present application does not particularly limit the thickness of the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 1 μm to 20 μm. The present application does not particularly limit the thickness of the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the single-sided positive electrode material layer is 30 μm to 120 μm.

[0054] Optionally, the positive electrode sheet may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode material layer. The present application does not particularly limit the composition of the conductive layer, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application does not particularly limit the conductive agent and binder in the conductive layer, and it can be at least one of the above-mentioned conductive agents and binders. The present application does not particularly limit the mass ratio of the conductive agent and binder in the conductive layer, and those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved.

[0055] In the present application, the secondary battery also includes a negative electrode plate, and the negative electrode plate includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode material layer provided on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be provided on one surface of the negative electrode current collector along its own thickness direction, or on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or a partial area of ​​the negative electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the negative electrode current collector, as long as the purpose of this application can be achieved. For example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper or a composite current collector, etc.

[0056] The negative electrode material layer of the present application includes a negative electrode active material. The present application has no particular limitation on the negative electrode active material, as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0.5<x<1.6), silicon-oxygen-carbon materials, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithium titanate Li4Ti5O 12, Li-Al alloy or metallic lithium, etc. The negative electrode material layer of the present application also includes a binder. The present application has no special restrictions on the binder in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the binder can be at least one of the above-mentioned binders. The negative electrode material layer of the present application also includes a conductive agent. The present application has no special restrictions on the conductive agent in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the conductive agent can be at least one of the above-mentioned conductive agents. The negative electrode material layer of the present application also includes a thickener. The present application has no special restrictions on the thickener in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickener can be sodium carboxymethyl cellulose (CMC-Na). The present application has no special restrictions on the mass ratio of the negative electrode active material, conductive agent, thickener and binder in the negative electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved. For example, the mass ratio of the negative electrode active material, the conductive agent, the thickener, and the binder may be (78 to 98.5):(0.1 to 10):(0.1 to 10):(0.1 to 10).

[0057] The present application does not particularly limit the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 5 μm to 16 μm. The present application does not particularly limit the thickness of the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the single-sided negative electrode material layer is 30 μm to 120 μm.

[0058] Optionally, the negative electrode plate may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. The present application does not particularly limit the composition of the conductive layer, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application does not particularly limit the conductive agent and binder in the conductive layer, and it can be at least one of the above-mentioned conductive agents and binders. The present application does not particularly limit the mass ratio of the conductive agent and binder in the conductive layer, and those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved.

[0059] In the present application, the secondary battery also includes a diaphragm, which is used to separate the positive electrode plate and the negative electrode plate, prevent the internal short circuit of the secondary battery, allow the electrolyte ions to pass freely, and do not affect the electrochemical charge and discharge process. The present application has no special restrictions on the diaphragm, as long as the purpose of the present application can be achieved. For example, the material of the diaphragm may include but is not limited to polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; the type of diaphragm may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane.

[0060] In the present application, the separator may include a substrate and a surface treatment layer. The substrate may be a non-woven fabric or a composite film having a porous structure, and the material of the substrate may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. For example, the polyethylene may be selected from at least one of high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. Preferably, the material of the substrate may include polyethylene and polypropylene. The use of polyethylene and polypropylene as the substrate material has a good effect on preventing short circuits and can improve the safety performance of the secondary battery through the shutdown effect. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used. The present application does not particularly limit the thickness of the substrate, as long as the purpose of the present application can be achieved. For example, the thickness of the substrate may be 4 μm to 20 μm. Optionally, a surface treatment layer is provided on at least one surface of the substrate, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic material. For example, the inorganic layer includes inorganic particles and a binder. The present application has no particular restrictions on the above-mentioned inorganic particles. For example, it may include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The present application has no particular restrictions on the binder in the inorganic layer. For example, it may be at least one of the aforementioned binders. The inorganic layer can improve the heat resistance, oxidation resistance and electrolyte wetting performance of the diaphragm, and enhance the adhesion between the diaphragm and the electrode. The polymer layer contains a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinyl pyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0061] The secondary battery of this application also includes a packaging bag for containing the positive electrode sheet, separator, negative electrode sheet, non-aqueous electrolyte, and other components of the secondary battery known in the art. This application does not limit these other components. This application does not specifically limit the packaging bag and can be any packaging bag known in the art as long as it can achieve the purpose of this application.

[0062] The present application does not particularly limit the type of secondary battery, which may include any device that undergoes an electrochemical reaction. In the present application, secondary batteries may include, but are not limited to: lithium metal secondary batteries, lithium ion secondary batteries (lithium ion batteries), lithium polymer secondary batteries or lithium ion polymer secondary batteries (lithium ion polymer batteries), etc.

[0063] The preparation process of the secondary battery of the present application is well known to those skilled in the art and is not particularly limited in the present application. For example, it may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly with a wound structure, placing the electrode assembly in a packaging bag, injecting a non-aqueous electrolyte into the packaging bag and sealing it to obtain a secondary battery; or stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly with a stacked structure, placing the electrode assembly in a packaging bag, injecting a non-aqueous electrolyte into the packaging bag and sealing it to obtain a secondary battery. In addition, as needed, overcurrent protection elements, guide plates, etc. may be placed in the packaging bag to prevent pressure rise and overcharge and discharge inside the secondary battery.

[0064] The second aspect of the present application provides an electronic device, which includes the secondary battery according to any one of the aforementioned embodiments. Therefore, the electronic device provided by the present application has good cycle stability under high voltage and inter-cycle stability.

[0065] The present application does not particularly limit the type of electronic device, and the electronic device may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0066] Example

[0067] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0068] Test methods and equipment:

[0069] Cyclic stability test at high voltage:

[0070] The lithium-ion battery was placed in a constant temperature box at 45°C, charged to 4.52V at a constant current of 0.5C, and then charged to 0.05C at a constant voltage at 4.52V; allowed to stand for 5 minutes, and then discharged to 3.0V at a constant current of 0.5C, and allowed to stand for 5 minutes. This is a charge and discharge cycle process. 500 charge-discharge cycles were performed in the above manner, and the discharge capacity of the lithium-ion battery after completing the first cycle was recorded, which was recorded as the initial capacity D0 of the lithium-ion battery cycle; the discharge capacity of the lithium-ion battery after completing the 500th cycle was recorded, which was recorded as the residual capacity Dz of the lithium-ion battery cycle;

[0071] Capacity retention rate (%) of lithium-ion battery = Dz / D0×100%.

[0072] Interval Cycling Stability Test:

[0073] The lithium-ion battery was placed in a constant temperature box at 45°C, charged to 4.52V at a constant current of 0.5C, charged to 0.05C at a constant voltage at 4.52V, then allowed to stand for 19.5h, and then discharged to 3.0V at a constant current of 0.5C. The discharge capacity at this time was recorded and recorded as the initial discharge capacity D1. This was a charge and discharge cycle process. 23 charge-discharge cycles were performed in the above manner. The battery was then charged to 4.47V at a constant current of 0.5C, charged to 0.05C at a constant voltage at 4.47V, and then allowed to stand for 19.5h. The battery was then discharged to 3.0V at a constant current of 0.5C. This was another charge and discharge cycle process. 113 charge-discharge cycles were performed in the above manner. The discharge capacity at this time was recorded and recorded as the initial residual capacity D2.

[0074] The interval capacity retention rate (%) of the lithium ion battery = D2 / D1×100%.

[0075] Example 1-1

[0076] <Preparation of positive electrode sheet>

[0077] The positive electrode active material lithium cobalt oxide (LiCoO2), the conductive agent (Super P), and the binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:1.4:1.6, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 72wt%. The positive electrode slurry is evenly stirred with a vacuum mixer to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm and dried at 85°C to obtain a positive electrode sheet with a single-sided positive electrode material layer coated with a coating thickness of 110μm. Thereafter, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer coated. After coating, the positive electrode sheet is cold pressed and cut into a size of 74mm×867mm for standby use. Among them, the compaction density of the positive electrode material layer after cold pressing is 4.15g / cm 3.

[0078] <Preparation of negative electrode sheet>

[0079] The negative electrode active material artificial graphite, conductive agent (Super P), thickener sodium carboxymethyl cellulose, and binder styrene-butadiene rubber are mixed in a mass ratio of 96.4:1.5:0.5:1.6, and deionized water is added as a solvent to prepare a slurry with a solid content of 54wt%. After stirring evenly with a vacuum mixer, a negative electrode slurry is obtained. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 10μm and dried at 90°C to obtain a negative electrode sheet with a single-sided negative electrode material layer coated with a coating thickness of 110μm. Thereafter, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided negative electrode material layer coated. After coating, the negative electrode sheet is cold pressed and cut into a size of 76mm×851mm for use. Among them, the compaction density of the negative electrode material layer after cold pressing is 1.70g / cm 3 .

[0080] <Diaphragm>

[0081] Alumina and PVDF were mixed in a mass ratio of 95:5, NMP was added as a solvent, and a slurry with a solid content of 12 wt% was prepared. The mixture was stirred evenly to obtain an inorganic layer slurry. The inorganic layer slurry was evenly coated on one surface of a polyethylene substrate with a thickness of 9 μm, and dried to obtain a diaphragm with a single-sided inorganic layer coating having a coating thickness of 2 μm. PVDF was then added to the NMP solvent and stirred evenly to obtain a polymer layer slurry with a solid content of 25 wt%. The polymer layer slurry was then evenly coated on the surface of the inorganic layer away from the substrate, and dried to obtain a diaphragm with a single-sided inorganic layer and a polymer layer coating. The polymer layer slurry was then evenly coated on the other surface of the polyethylene substrate, and dried to obtain a diaphragm with an inorganic layer and a polymer layer coated on one side and only a polymer layer coated on the other side. The surface density of the coated polymer layer slurry is 0.15 mg / cm 2 .

[0082] <Preparation of Electrolyte>

[0083] In an argon atmosphere glove box with a water content of less than 10 ppm, EC, PC, and DEC are mixed to obtain a base organic solvent, and then a second lithium salt, LiPF6, is added to the base organic solvent, dissolved and mixed uniformly, and then a compound of Formula I (Formula I-8) is added to obtain a non-aqueous electrolyte. Based on the mass of the non-aqueous electrolyte, the mass percentage W5 of the second lithium salt is 10%, the mass percentage W1 of the compound of Formula I is 10%, the mass percentage of EC is 17.5%, the mass percentage of PC is 17.5%, and the mass percentage of DEC is 45%.

[0084] <Preparation of lithium-ion batteries>

[0085] The positive electrode sheet, separator, negative electrode sheet and separator prepared above are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer packaging aluminum-plastic film, after dehydration at 80°C, the above-prepared non-aqueous electrolyte is injected and packaged, and a lithium-ion battery is obtained after standing, forming, degassing, trimming, shaping and capacity testing steps.

[0086] Example 1-2 to Example 1-18

[0087] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0088] Example 2-1 to Example 2-10

[0089] Except for further adding the first lithium salt in <Preparation of Electrolyte> and adjusting the relevant preparation parameters according to Table 2, the rest is the same as Example 1-3.

[0090] Example 3-1 to Example 3-16

[0091] The process was the same as in Examples 1-8, except that the first nitrile compound and / or the second nitrile compound were further added in the preparation of the electrolyte solution and the relevant preparation parameters were adjusted according to Table 3. When the mass percentage of at least one of the first nitrile compound or the second nitrile compound changes, the mass percentage of DEC changes accordingly, while the mass percentages of the compound of Formula I, the second lithium salt, EC, and PC remain unchanged.

[0092] Example 3-17

[0093] Except for further adding the first nitrile compound in the "Preparation of Electrolyte" and adjusting the relevant preparation parameters according to Table 3, the rest is the same as Example 2-9. In particular, based on the mass of the non-aqueous electrolyte, the mass percentage W1 of the compound of Formula I is 50%, the mass percentage W5 of the second lithium salt is 10%, the mass percentage of EC is 17.5%, the mass percentage of PC is 17.5%, the mass percentage of DEC is 2.8%, the mass percentage W2 of the first lithium salt is 0.2%, and the mass percentage W3 of the first nitrile compound is 2%.

[0094] Example 3-18

[0095] The process was the same as in Example 2-9, except that a second nitrile compound was further added in the preparation of the electrolyte and relevant preparation parameters were adjusted according to Table 3. Based on the mass of the non-aqueous electrolyte, the mass percentage W1 of the compound of Formula I was 50%, the mass percentage W5 of the second lithium salt was 10%, the mass percentage of EC was 17.5%, the mass percentage of PC was 17.5%, the mass percentage of DEC was 3.3%, the mass percentage W2 of the first lithium salt was 0.2%, and the mass percentage W4 of the second nitrile compound was 1.5%.

[0096] Example 3-19

[0097] Except for further adding the first nitrile compound and the second nitrile compound in the "Preparation of Electrolyte" and adjusting the relevant preparation parameters according to Table 3, the rest is the same as Example 2-9. Wherein, based on the mass of the non-aqueous electrolyte, the mass percentage content W1 of the compound of Formula I is 50%, the mass percentage content W5 of the second lithium salt is 10%, the mass percentage content of EC is 17.5%, the mass percentage content of PC is 17.5%, the mass percentage content of DEC is 0.8%, the mass percentage content W2 of the first lithium salt is 0.2%, the mass percentage content W3 of the first nitrile compound is 2%, and the mass percentage content W4 of the second nitrile compound is 2%.

[0098] Comparative Examples 1 to 3

[0099] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0100] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 to 3.

[0101] Table 1

[0102] Note: (1) In Table 1, “ / ” indicates no relevant preparation parameters; (2) Taking Example 1-17 as an example, “Type of compound of formula I” is “Formula I-7 + Formula I-1”, and “Mass percentage content W1 of compound of formula I” is “50+20”, indicating that the compound of formula I includes Formula I-7 and Formula I-1, and based on the mass of the non-aqueous electrolyte, the mass percentage content of Formula I-7 is 50%, and the mass percentage content of Formula I-1 is 20%, and the same applies to other examples; (3) Taking Example 1-1 as an example, “Mass percentage content W6 of basic organic solvent” is “17.5+17.5+45”, indicating that the basic organic solvent includes EC, PC and DEC in sequence, and based on the mass of the non-aqueous electrolyte, the mass percentage content of EC is 17.5%, the mass percentage content of PC is 17.5%, and the mass percentage content of DEC is 45%, and the same applies to other examples.

[0103] Referring to Table 1, it can be seen from Examples 1-1 to 1-18 and Comparative Examples 1 to 3 that by regulating the non-aqueous electrolyte to include the compound of Formula I, the type and mass percentage of the compound of Formula I are within the scope of this application, the capacity retention rate of the lithium ion battery is higher, the interval capacity retention rate is higher, indicating that the lithium ion battery has good cycle stability and interval cycle stability under high voltage. In Comparative Example 1, the non-aqueous electrolyte does not include the compound of Formula I, the capacity retention rate of the lithium ion battery is low, the interval capacity retention rate is low, indicating that the cycle stability and interval cycle stability under high voltage of the lithium ion battery are poor. In Comparative Example 2, the mass percentage of the compound of Formula I is too low, and the sustained reaction of the negative electrode side and the positive electrode side cannot be effectively weakened. The capacity retention rate of the lithium ion battery is low, the interval capacity retention rate is low, resulting in poor cycle stability and interval cycle stability under high voltage of the lithium ion battery. In Comparative Example 3, the mass percentage of the compound of Formula I is too high, which will cause the viscosity of the non-aqueous electrolyte to increase, lithium ions to diffuse difficultly in the liquid phase, and the interfacial impedance will also increase, resulting in a reduced cycle improvement effect.

[0104] As can be seen from Examples 1-1 to 1-6, the compound of Formula I is selected from Formula I-8, in which only R2 is replaced by F. The mass percentage of the compound of Formula I is within the scope of this application, and the capacity retention rate of the lithium ion battery is high and the interval capacity retention rate is high, indicating that the lithium ion battery has good high-voltage cycle stability and interval cycle stability. In Examples 1-5 and 1-6, the mass percentage of the compound of Formula I is relatively high, which will lead to a relatively high viscosity of the non-aqueous electrolyte, thereby affecting lithium ion transmission and ultimately affecting the high-voltage cycle stability and interval cycle stability of the lithium ion battery.

[0105] As can be seen from Examples 1-7, the non-aqueous electrolyte includes the compound of Formula I, the second lithium salt is LiFSI, and no other organic solvent is added. The lithium-ion battery has a high capacity retention rate and interval capacity retention rate, indicating that the lithium-ion battery has good cycle stability and interval cycle stability under high voltage.

[0106] It can be seen from Examples 1-3, 1-8 to 1-12, 1-17, and 1-18 that the use of the compound of Formula I above results in a higher capacity retention rate and a higher interval capacity retention rate for the lithium-ion battery, indicating that the lithium-ion battery has good cycle stability and interval cycle stability under high voltage.

[0107] As can be seen from Examples 1-13 to 1-16, the compound of Formula I is selected from Formula I-1, R1 and R2 are both substituted by F, and the mass percentage of the compound of Formula I within the scope of this application, the capacity retention rate of the lithium ion battery is high and the interval capacity retention rate is high, indicating that the lithium ion battery has good high-voltage cycle stability and interval cycle stability. In Examples 1-16, the mass percentage of the compound of Formula I is relatively high, which makes it more difficult for the non-aqueous electrolyte to dissociate the lithium salt, and the liquid phase homogeneity of the non-aqueous electrolyte is poor, ultimately affecting the high-voltage cycle stability and interval cycle stability of the lithium ion battery.

[0108] Table 2

[0109] Note: (1) In Table 2, “ / ” indicates no relevant preparation parameters; (2) In Examples 2-10, “Type of first lithium salt” is “LiPO2F2+LiBF4” and “Mass percentage content W2 of first lithium salt” is “0.1+0.1”, indicating that the first lithium salt includes LiPO2F2 and LiBF4, and based on the mass of the non-aqueous electrolyte, the mass percentage content of LiPO2F2 is 0.1%, and the mass percentage content of LiBF4 is 0.1%.

[0110] The non-aqueous electrolyte also includes a first lithium salt. The type of the first lithium salt generally affects the high-voltage cycling stability and inter-cycling stability of the lithium-ion battery. As can be seen from Examples 1-3, 2-1, 2-6, and 2-10, when the non-aqueous electrolyte also includes a first lithium salt and the type of the first lithium salt is within the scope of this application, the lithium-ion battery has a higher capacity retention rate and a higher inter-cycling capacity retention rate, indicating that the lithium-ion battery has good high-voltage cycling stability and inter-cycling stability.

[0111] The mass percentage of the first lithium salt generally affects the high-voltage cycling stability and inter-cycling stability of a lithium-ion battery. As can be seen from Examples 2-1 to 2-5, when the mass percentage of the first lithium salt is within the range of this application, the lithium-ion battery has a high capacity retention rate and a high inter-cycling capacity retention rate, indicating that the lithium-ion battery has good high-voltage cycling stability and inter-cycling stability.

[0112] Table 3

[0113] Note: (1) In Table 3, “ / ” indicates no relevant preparation parameters; (2) In Example 3-8, “type of the first nitrile compound” is “succinonitrile + adiponitrile”, and “mass percentage content W3 of the first nitrile compound” is “2+2”, indicating that the first nitrile compound includes succinonitrile and adiponitrile, and based on the mass of the non-aqueous electrolyte, the mass percentage content of succinonitrile is 2%, and the mass percentage content of adiponitrile is 2%; (3) In Example 3-15, “type of the second nitrile compound” is “Formula II-4 + Formula II-9 + Formula II-13”, and “mass percentage content W4 of the second nitrile compound” is “3+1+1”, indicating that the second nitrile compound includes Formula II-4, Formula II-9 and Formula II-13, and based on the mass of the non-aqueous electrolyte, the mass percentage content of Formula II-4 is 3%, the mass percentage content of Formula II-9 is 1%, and the mass percentage content of Formula II-13 is 1%.

[0114] The non-aqueous electrolyte also includes a first nitrile compound. The type of the first nitrile compound generally affects the high-voltage cycling stability and inter-cycling stability of the lithium-ion battery. As can be seen from Examples 1-8, 3-1, 3-6, and 3-8, when the non-aqueous electrolyte also includes a first nitrile compound and the type of the first nitrile compound is within the scope of this application, the lithium-ion battery has a higher capacity retention rate and a higher inter-cycling capacity retention rate, indicating that the lithium-ion battery has good high-voltage cycling stability and inter-cycling stability.

[0115] The mass percentage of the first nitrile compound generally affects the high-voltage cycling stability and inter-cycle stability of the lithium-ion battery. As can be seen from Examples 3-1 to 3-5, when the mass percentage of the first nitrile compound is within the range of this application, the lithium-ion battery has a high capacity retention rate and a high inter-cycle capacity retention rate, indicating that the lithium-ion battery has good high-voltage cycling stability and inter-cycle stability.

[0116] The non-aqueous electrolyte also includes a second nitrile compound. The type of the second nitrile compound generally affects the high-voltage cycling stability and inter-cycling stability of the lithium-ion battery. As can be seen from Examples 1-8, 3-9, 3-13, and 3-15, when the non-aqueous electrolyte also includes a second nitrile compound and the type of the second nitrile compound is within the scope of this application, the capacity retention rate and inter-cycling capacity retention rate of the lithium-ion battery are higher, indicating that the lithium-ion battery has good high-voltage cycling stability and inter-cycling stability.

[0117] The mass percentage of the second nitrile compound generally affects the high-voltage cycling stability and inter-cycle stability of the lithium-ion battery. As can be seen from Examples 3-9 to 3-12, when the mass percentage of the second nitrile compound is within the range of this application, the lithium-ion battery has a high capacity retention rate and a high inter-cycle capacity retention rate, indicating that the lithium-ion battery has good high-voltage cycling stability and inter-cycle stability.

[0118] In Examples 3-16 to 3-19, the capacity retention rate and the interval capacity retention rate of the lithium-ion battery are high, indicating that the lithium-ion battery has good cycle stability at high voltage and interval cycle stability.

[0119] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, or article.

[0120] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0121] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A secondary battery comprising a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a compound of formula I, in, R1 and R2 are each independently selected from fluorine, a C1 to C10 alkyl group substituted or unsubstituted by F, or a C6 to C10 phenyl group substituted or unsubstituted by F; at least one of R1 and R2 is substituted by F; Based on the mass of the non-aqueous electrolyte, the mass percentage of the compound of formula I is 10% to 80%.

2. The secondary battery according to claim 1, wherein The compound of formula I includes at least one of the following compounds:

3. The secondary battery according to claim 1, wherein Based on the mass of the non-aqueous electrolyte, the mass percentage of the compound of formula I is 10% to 70%.

4. The secondary battery according to claim 1, wherein R1 and R2 are both substituted by F, and the mass percentage of the compound of formula I is 10% to 30% based on the mass of the non-aqueous electrolyte.

5. The secondary battery according to claim 1, wherein Only R2 is substituted by F, and the mass percentage of the compound of formula I is 10% to 60% based on the mass of the non-aqueous electrolyte.

6. The secondary battery according to any one of claims 1 to 5, wherein The non-aqueous electrolyte further includes a first lithium salt, wherein the first lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium dioxalatoborate, or lithium difluorophosphate.

7. The secondary battery according to claim 6, wherein Based on the mass of the non-aqueous electrolyte, the mass percentage of the first lithium salt is 0.1% to 5%.

8. The secondary battery according to any one of claims 1 to 5, wherein The non-aqueous electrolyte further includes a first nitrile compound, wherein the first nitrile compound includes at least one of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile or 2-methylglutaronitrile.

9. The secondary battery according to claim 8, wherein Based on the mass of the non-aqueous electrolyte, the mass percentage of the first nitrile compound is 0.5% to 4%.

10. The secondary battery according to any one of claims 1 to 5, wherein The non-aqueous electrolyte further includes a second nitrile compound, wherein the second nitrile compound includes at least one of the following compounds:

11. The secondary battery according to claim 10, wherein Based on the mass of the non-aqueous electrolyte, the mass percentage of the second nitrile compound is 0.5% to 5%. 12 . An electronic device comprising the secondary battery according to claim 1 .

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