Secondary battery and electronic device

Abstract

A secondary battery and an electronic device, the secondary battery including a non-aqueous electrolyte, the non-aqueous electrolyte including a compound of formula I, where R 1 and R 2 are each independently selected from fluorine element, C1 to C10 alkyl substituted or unsubstituted by F, and C6 to C10 phenyl substituted or unsubstituted by F; at least one group in R 1 and R 2 is substituted by F; based on the mass of the non-aqueous electrolyte, the mass percentage of the compound of the formula I is 10%-80%. The interface reaction of the non-aqueous electrolyte on the positive electrode can be reduced and the cycle stability and interval cycle stability of the secondary battery under high voltage can be improved by regulating and controlling the non-aqueous electrolyte comprising the compound as shown in the formula I and the type and mass percentage content of the compound as shown in the formula I.

Description

Technical Field

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

[0002] Lithium-ion batteries are widely used in portable electronic products, electric vehicles, aerospace, energy storage and other fields due to their advantages such as high energy density, good cycle performance, safety, environmental protection and no memory effect. In order to meet the needs of social development, it has become an urgent problem to seek lithium-ion batteries with higher energy density and higher power density, which makes the cathode active material develop towards the direction suitable for high voltage. With the increase of voltage, the interfacial reaction of non-aqueous electrolyte at the cathode intensifies, resulting in the performance degradation of lithium-ion batteries.

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

[0004] The purpose of the present application is to provide a secondary battery and an electronic device that can reduce the interfacial reaction of non-aqueous electrolyte at the cathode and improve the cycle stability and intermittent cycle stability of the secondary battery at high voltage. The specific technical solutions are as follows:

[0005] In the first aspect of the present application, a secondary battery is provided, which includes a non-aqueous electrolyte, and the non-aqueous electrolyte includes a compound of Formula I.

[0006]

[0007] Wherein, R 1 and R 2 are each independently selected from a fluorine element, a C1-C10 alkyl group which is substituted or unsubstituted by F, and a C6-C10 phenyl group which is substituted or unsubstituted by F; at least one of R 1 and R 2 is substituted by F. Based on the mass of the non-aqueous electrolyte, the mass percentage content of the compound of Formula I is 10% to 80%, and preferably, the mass percentage content W1 of the compound of Formula I is 10% to 70%. By regulating that the non-aqueous electrolyte includes the compound of Formula I, and the type and mass percentage content of the compound of Formula I are within the scope of the present application, the interfacial reaction of the non-aqueous electrolyte at the cathode can be reduced, and the cycle stability and intermittent cycle stability of the secondary battery at high voltage can be improved.

[0008] In an embodiment of the present application, the compound of Formula I includes at least one of the following compounds:

[0009]

[0010]

[0011] Select the compound of Formula I above, and at least one of the R 1 and R 2 in the compound of Formula I is substituted by F, forming stable components such as LiSOxF on the negative electrode side, 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, reduces the continuous reaction on the positive electrode interface, and can further improve the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0012] In one embodiment of the present application, both R 1 and R 2 are substituted by F, and based on the mass of the non-aqueous electrolyte, the mass percentage content of the compound of Formula I is 10% to 30%. Both R 1 and R 2 in the compound of Formula I are substituted by F, and the mass percentage content of the compound of Formula I is within the scope of the present application. While effectively weakening the continuous reactions on the negative electrode side and the positive electrode side, it can also make the non-aqueous electrolyte have an appropriate viscosity, which is beneficial to the transport of lithium ions, and further improve the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0013] In one embodiment of the present application, only R 2 is substituted by F, and based on the mass of the non-aqueous electrolyte, the mass percentage content of the compound of Formula I is 10% to 60%. Only R 2 in the compound of Formula I is substituted by F, and the mass percentage content of the compound of Formula I is within the scope of the present application. While effectively weakening the continuous reactions 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, and further improve the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0014] In one embodiment of the present application, the non-aqueous electrolyte further includes a first lithium salt, and the first lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, or lithium difluorophosphate. The non-aqueous electrolyte further includes a first lithium salt, and the above first lithium salt is selected. The anions introduced into the first lithium salt can participate in the solvation of lithium ions and compete for coordination with the compound of Formula I and / or hexafluorophosphate anions (PF 6 - ) in the non-aqueous electrolyte, reducing the coordination and decomposition of the compound of Formula I and / or hexafluorophosphate anions in the first solvation layer; in addition, the first lithium salt has a relatively high reduction potential, and the first lithium salt can be reduced prior to the compound of Formula I, thereby reducing the reduction reaction activity of the compound of Formula I and further improving the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0015] In an embodiment of the present application, based on the mass of the non-aqueous electrolyte, the mass percentage of the first lithium salt is 0.1% to 5%. By regulating the mass percentage of the first lithium salt within the scope of the present application, the first lithium salt has a suitable mass percentage, and the first lithium salt can be preferentially reduced 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 transport of lithium ions, thereby further improving the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0016] In an 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, glutarodinitrile, adiponitrile, pimelonitrile, suberonitrile or 2-methylglutaronitrile. The non-aqueous electrolyte further includes a first nitrile compound, and the above-mentioned first nitrile compound is selected. The first nitrile compound can 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 generation of the secondary battery during the cycle, improve the interfacial contact, facilitate the transport of lithium ions, and further improve the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0017] In an embodiment of the present application, based on the mass of the non-aqueous electrolyte, the mass percentage of the first nitrile compound is 0.5% to 4%. By regulating the mass percentage of the first nitrile compound within the scope of the present application, the first nitrile compound has a suitable mass percentage, and the first nitrile compound can preferably 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 generation of the secondary battery during the cycle, improve the interfacial contact, facilitate the transport of lithium ions, and further improve the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0018] In an 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:

[0019]

[0020]

[0021]

[0022] The non-aqueous electrolyte includes a second nitrile compound, and by selecting the above-mentioned second nitrile compound, on the one hand, the second nitrile compound can preferably 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 generation of the secondary battery during the cycle, improve the interfacial contact, and be beneficial to the transmission of lithium ions; on the other hand, the second nitrile compound will occupy the first solvation layer of lithium ions, reduce the coordination between the compound of formula I and lithium ions, and reduce the decomposition reaction of the compound of formula I, thereby further improving the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0023] In an embodiment of the present application, based on the mass of the non-aqueous electrolyte, the mass percentage content of the second nitrile compound is 0.5% to 5%. By controlling the mass percentage content of the second nitrile compound within the scope of the present application, the second nitrile compound has an appropriate mass percentage content. On the one hand, the second nitrile compound can preferably 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 generation of the secondary battery during the cycle, improve the interfacial contact, and be beneficial to the transmission of lithium ions; on the other hand, the second nitrile compound will occupy the first solvation layer of lithium ions, further reduce the coordination between the compound of formula I and lithium ions, and reduce the decomposition reaction of the compound of formula I, thereby further improving the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0024] The second aspect of the present application provides an electronic device, which includes the secondary battery in any of the foregoing embodiments. Therefore, the electronic device provided by the present application has good cycle stability and intermittent cycle stability at high voltages.

[0025] Advantages of the present application:

[0026] The present application provides a secondary battery and an electronic device. The secondary battery includes a non-aqueous electrolyte, and the non-aqueous electrolyte includes a compound of formula I, wherein R 1 and R 2 are each independently selected from a fluorine element, a C1-C10 alkyl group which is substituted or unsubstituted by F, and a C6-C10 phenyl group which is substituted or unsubstituted by F; at least one of R 1 and R 2 is substituted by F; based on the mass of the non-aqueous electrolyte, the mass percentage content of the compound of formula I is 10% to 80%. By controlling that the non-aqueous electrolyte includes the compound of formula I, and the type and mass percentage content of the compound of formula I are within the scope of the present application, the interfacial reaction of the non-aqueous electrolyte at the positive electrode can be reduced, and the cycle stability and intermittent cycle stability of the secondary battery at high voltages can be improved. Detailed embodiments

[0027] To make the objectives, technical solutions, and advantages of this application more clearly understood, the following examples are provided to further elaborate on this application in detail. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of them. All other embodiments obtained by those skilled in the art based on this application fall within the scope of protection of this application.

[0028] It should be noted that in the specific implementation manner of this application, a lithium-ion battery is used as an example of a secondary battery to explain this application. However, the secondary battery of this application is not limited to lithium-ion batteries.

[0029] This application provides a secondary battery, which includes a non-aqueous electrolyte. The non-aqueous electrolyte includes a compound of Formula I,

[0030]

[0031] wherein, R 1 , R 2 are each independently selected from a fluorine element, a C1-C10 alkyl group that is either F-substituted or unsubstituted, and a C6-C10 phenyl group that is either F-substituted or unsubstituted; at least one of R 1 , R 2 is F-substituted. Based on the mass of the non-aqueous electrolyte, the mass percentage content W1 of the compound of Formula I is 10% to 80%. Preferably, the mass percentage content 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 composed of any two of the above values. In this application, the compound of Formula I is a sulfonic acid group compound; the C1-C10 alkyl group can be methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, or decyl; the C6-C10 phenyl group can be benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, trimethylbenzene, methylethylbenzene, propylbenzene, butylbenzene, diethylbenzene, or dimethylethylbenzene.

[0032] In one embodiment of this application, both R 1 and R 2 are F-substituted. Based on the mass of the non-aqueous electrolyte, the mass percentage content W1 of the compound of Formula I is 10% to 80%.

[0033] In one embodiment of this application, only R 2 is F-substituted. Based on the mass of the non-aqueous electrolyte, the mass percentage content W1 of the compound of Formula I is 10% to 80%.

[0034] In one embodiment of the present application, only R 1 is replaced by F, and based on the mass of the non-aqueous electrolyte, the mass percentage content W1 of the compound of formula I is 10% to 80%.

[0035] The inventors have found through research that conventional (unsubstituted) sulfonic acid group compounds react on the negative electrode side to form unstable interfacial components, and continuous reactions occur during the cycling process, continuously consuming lithium, resulting in rapid decay during high-voltage cycling. After fluorine substitution 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, alleviating the continuous reaction of the electrolyte on the negative electrode side; at the same time, fluorine substitution improves the oxidation resistance and reduces the continuous reaction on the positive electrode interface, which can enhance the cycling stability and intermittent cycling stability of the secondary battery at high voltages. When the mass percentage content of the compound of formula I is too low, for example, less than 10%, it cannot effectively weaken the continuous reactions on the negative electrode side and the positive electrode side, resulting in poor cycling stability and intermittent cycling stability of the secondary battery at high voltages; when the mass percentage content of the compound of formula I is too high, for example, higher than 80%, it will cause an increase in the viscosity of the non-aqueous electrolyte, making it difficult for lithium ions to diffuse in the liquid phase, and the interfacial impedance will also increase, resulting in poor cycling stability and intermittent cycling stability of the secondary battery at high voltages. By regulating the non-aqueous electrolyte to include the compound of formula I, and the type and mass percentage content of the compound of formula I are within the scope of the present application, the interfacial reaction of the non-aqueous electrolyte on the positive electrode can be reduced, and the cycling stability and intermittent cycling stability of the secondary battery at high voltages can be enhanced. In the present application, "high voltage" means a voltage ≥ 4.5V.

[0036] In one embodiment of the present application, the compound of formula I includes at least one of the following compounds:

[0037]

[0038]

[0039] When the above-mentioned compound of formula I is selected, at least one of the R 1 and R 2 in the compound of formula I is replaced by F, forming stable components such as LiSOxF on the negative electrode side, alleviating the continuous reaction of the electrolyte on the negative electrode side; at the same time, fluorine substitution improves the oxidation resistance and reduces the continuous reaction on the positive electrode interface, which can further enhance the cycling stability and intermittent cycling stability of the secondary battery at high voltages.

[0040] In one embodiment of the present application, R 1 and R 2are all replaced by F. Based on the mass of the non-aqueous electrolyte, the mass percentage content 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 composed of any two of the above numerical values. R of the compound of Formula I 1 and R 2 are all replaced by F. The mass percentage content 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 can also make the non-aqueous electrolyte have an appropriate viscosity, which is beneficial to the transport of lithium ions, and further improves the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0041] In one embodiment of this application, only R 2 is replaced by F. Based on the mass of the non-aqueous electrolyte, the mass percentage content 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 composed of any two of the above numerical values. Only R 2 in the compound of Formula I is replaced by F. The mass percentage content 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 the transport of lithium ions, and further improves the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0042] In one embodiment of this application, the non-aqueous electrolyte further includes a first lithium salt. The first lithium salt includes lithium bis(trifluoromethanesulfonyl)imide (LiN(CF 3 SO 2 ), LiTFSI), lithium tetrafluoroborate (LiBF 2 ), lithium difluoro(oxalato)borate (LiBF 4 (C 2 O 2 O 4 ), LiDFOB), lithium bis(oxalato)borate (LiB(C 2 O 4 ), LiBOB) or lithium difluorophosphate (LiPO 2 F 2 F 2 ), LiPO2F2), or at least one of them. The non-aqueous electrolyte further includes a first lithium salt, and the above first lithium salt is selected. The anions introduced into the first lithium salt can participate in the solvation of lithium ions and react with the compound of Formula I and / or hexafluorophosphate anions (PF 6 -)Competitive coordination reduces the coordination and decomposition of the compound of formula I and / or hexafluorophosphate anions in the first solvation layer; in addition, the first lithium salt has a relatively high reduction potential and can be preferentially reduced over the compound of formula I, thereby reducing the reduction reaction activity of the compound of formula I and further enhancing the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0043] 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%. Exemplarily, 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 composed of any two of the above values. By regulating the mass percentage content of the first lithium salt within the scope of the present application, the first lithium salt has a suitable mass percentage content, and the first lithium salt can be preferentially reduced 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 transport of lithium ions, thereby further enhancing the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0044] 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, glutarodinitrile, adiponitrile, pimelonitrile, suberonitrile or 2-methylglutaronitrile. The non-aqueous electrolyte further includes a first nitrile compound, and by selecting the above first nitrile compound, the first nitrile compound can 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 generation of the secondary battery during the cycle, improve the interfacial contact, facilitate the transport of lithium ions, and further enhance the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0045] In one embodiment of the present application, based on the mass of the non-aqueous electrolyte, the mass percentage content 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 composed of any two of the above values. By regulating the mass percentage content of the first nitrile compound within the scope of the present application, the first nitrile compound has a suitable mass percentage content, and the first nitrile compound can preferably 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 generation of the secondary battery during the cycle, improve the interfacial contact, facilitate the transport of lithium ions, and further enhance the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0046] 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:

[0047]

[0048]

[0049] The non-aqueous electrolyte further includes a second nitrile compound, and the above-mentioned second nitrile compound is selected. On the one hand, the second nitrile compound can preferably 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 generation of the secondary battery during the cycle, improve the interfacial contact, and be beneficial to the transmission of lithium ions; on the other hand, the second nitrile compound will occupy the first solvation layer of lithium ions, reduce the coordination between the compound of formula I and lithium ions, and reduce the decomposition reaction of the compound of formula I, thereby further improving the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0050] In one embodiment of the present application, based on the mass of the non-aqueous electrolyte, the mass percentage content W4 of the second nitrile compound is 0.5% to 5%. Exemplarily, 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 composed of any two of the above values. By adjusting the mass percentage content of the second nitrile compound within the scope of the present application, the second nitrile compound has a suitable mass percentage content. On the one hand, the second nitrile compound can preferably 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 generation of the secondary battery during the cycle, improve the interfacial contact, and be beneficial to the transmission of lithium ions; on the other hand, the second nitrile compound will occupy the first solvation layer of lithium ions, further reduce the coordination between the compound of formula I and lithium ions, and reduce the decomposition reaction of the compound of formula I, thereby further improving the cycle stability and intermittent cycle stability of the secondary battery at high voltages.

[0051] In the present application, the characteristics of different components included in the above non-aqueous electrolyte can be combined, and the embodiments covered by the above combination are all within the protection scope of the present application.

[0052] In the present application, the non-aqueous electrolyte further includes a second lithium salt and / or other organic solvents. The present application does not particularly limit the type of the second lithium salt, and lithium salts known in the art can be used. Exemplarily, 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 limitation on other organic solvents, as long as the object of the present application can be achieved. For example, the other organic solvents may include at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents. The above carbonate compounds may include, but are not limited to, at least one of linear carbonate compounds, cyclic carbonate compounds or fluorinated carbonate compounds. The above linear carbonate compounds may 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 cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinylene ethylene carbonate (VEC). The above fluorinated carbonate compounds may include, but are 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 trifluoromethyl ethylene carbonate. The above carboxylate compounds may include, but are 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 ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The above other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphate esters. When the non-aqueous electrolyte further includes a second lithium salt and other organic solvents, the present application has no particular limitation on the mass percentage content of the second lithium salt and other organic solvents in the non-aqueous electrolyte, as long as the object of the present application can be achieved. For example, based on the mass of the non-aqueous electrolyte, the mass percentage content W5 of the second lithium salt is 8% to 20%, and the mass percentage content W6 of the other organic solvents is 10% to 82%.

[0053] In an embodiment of the present application, the non-aqueous electrolyte may include a compound of Formula I and a second lithium salt. Based on the mass of the non-aqueous electrolyte, the mass percentage content W1 of the compound of Formula I is 10% to 80%, and the mass percentage content W5 of the second lithium salt is 20% to 90%. The secondary battery including the above non-aqueous electrolyte has good cycle stability and intermittent cycle stability under high voltage at the same time.

[0054] In an embodiment of the present application, the non-aqueous electrolyte may include a compound of Formula I, a second lithium salt, and other organic solvents. The mass percentage contents of the compound of Formula I and the second lithium salt are as described above, and the mass percentage content W6 of the other organic solvents is 10% to 82%. The secondary battery including the above non-aqueous electrolyte has good cycle stability and intermittent cycle stability under high voltage at the same time.

[0055] In an 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 other organic solvents. The mass percentage contents of the compound of Formula I, the second lithium salt, and the first lithium salt are as described above, and the mass percentage content W6 of the other organic solvents is 11.9% to 81.9%. The secondary battery including the above non-aqueous electrolyte has good cycle stability and intermittent cycle stability under high voltage at the same time.

[0056] In an 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 other organic solvents. The mass percentage contents of the compound of Formula I, the second lithium salt, and the first nitrile compound are as described above, and the mass percentage content W6 of the other organic solvents is 11.5% to 81.5%. The secondary battery including the above non-aqueous electrolyte has good cycle stability and intermittent cycle stability under high voltage at the same time.

[0057] In an 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 other organic solvents. The mass percentage contents of the compound of Formula I, the second lithium salt, and the second nitrile compound are as described above, and the mass percentage content W6 of the other organic solvents is 11.5% to 81.5%. The secondary battery including the above non-aqueous electrolyte has good cycle stability and intermittent cycle stability under high voltage at the same time.

[0058] In an 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 other organic solvents. The mass percentage contents 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 content W6 of the other organic solvents is 11.4% to 81.4%. The secondary battery including the above non-aqueous electrolyte has good cycle stability and intermittent cycle stability under high voltage at the same time.

[0059] In an 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 other organic solvents. The mass percentage contents 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 content W6 of the other organic solvents is 11% to 81%. The secondary battery including the above non-aqueous electrolyte has good cycle stability and intermittent cycle stability under high voltage at the same time.

[0060] In an 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 other organic solvents. The mass percentage contents 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 content W6 of the other organic solvents is 10.9% to 80.9%. The secondary battery including the above non-aqueous electrolyte has good cycle stability and intermittent cycle stability under high voltage at the same time.

[0061] In the present application, the secondary battery further includes a positive electrode plate, and the positive electrode plate includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector. The above "positive electrode material layer provided on at least one surface of the positive electrode current collector" means that the positive electrode material layer may be provided on one surface of the positive electrode current collector along its own thickness direction, or may be provided on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here may be the entire area of the positive electrode current collector or a partial area of the positive electrode current collector, and the present application has no special limitation as long as the purpose of the present application can be achieved. The present application has no special limitation on the positive electrode current collector as long as the purpose of the present application can be achieved. For example, it may include aluminum foil, aluminum alloy foil, or a composite current collector (such as an aluminum-carbon composite current collector), etc.

[0062] The positive electrode material layer of the present application includes a positive electrode active material, and the positive electrode active material includes a substance capable of reversibly inserting and extracting active ions such as lithium ions. The positive electrode material layer may be one layer or multiple layers, and each layer in the multiple positive electrode material layers may contain the same or different positive electrode active materials. The present application has no special limitation 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 may include, but is not limited to, lithium nickel cobalt manganate (such as NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobaltate (LiCoO 2) at least one of lithium manganate, lithium iron manganese phosphate or lithium titanate. The positive electrode material layer of the present application further includes a conductive agent and a binder. There are no particular limitations on the conductive agent and the binder in the positive electrode material layer of the present application, as long as the purpose of the present application can be achieved. For example, the conductive agent may 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 above-mentioned conductive carbon black may include, but is not limited to, Super P, acetylene black or Ketjen black. The above-mentioned carbon nanotubes may include, but is not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include, but is not limited to, vapor-grown carbon fibers (VGCF) and / or nanofibers. The above-mentioned metal materials may include, but is not limited to, metal powders and / or metal fibers. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymers may include, but is 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 polyacrylate, polyacrylic acid, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, styrene-acrylate copolymer, polystyrene butadiene copolymer (styrene-butadiene rubber, SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl ether, polyhexafluoropropylene, potassium carboxymethyl cellulose, sodium hydroxymethyl cellulose or potassium hydroxymethyl cellulose. There are no particular limitations on the mass ratio of the positive electrode active material, the conductive agent and the binder in the positive electrode material layer of the present application. 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 may be (91 to 99):(0.5 to 3):(0.5 to 6).

[0063] There are no particular limitations on the thickness of the positive electrode current collector of the present application, 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. There are no particular limitations on the thickness of the positive electrode material layer of the present application, 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.

[0064] Optionally, the positive electrode tab may further include a conductive layer, and the conductive layer is located between the positive electrode current collector and the positive electrode material layer. There are no particular limitations on the composition of the conductive layer of the present application, and it may be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. There are no particular limitations on the conductive agent and the binder in the conductive layer of the present application, and they may be at least one of the above-mentioned conductive agents and the above-mentioned binders. There are no particular limitations on the mass ratio of the conductive agent and the binder in the conductive layer of the present application. Those skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved.

[0065] In this application, the secondary battery further includes a negative electrode tab, which 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 "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 can be provided on both 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. There is no special limitation in this application, as long as the purpose of this application can be achieved. There is no special limitation on the negative electrode current collector in this application, 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, nickel foam, copper foam or composite current collector, etc.

[0066] The negative electrode material layer of this application includes negative electrode active materials. There is no special limitation on the negative electrode active materials in this application, as long as the purpose of this application can be achieved. For example, the negative electrode active materials can include at least one of natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0.5 < x < 1.6), silicon oxycarbide material, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , lithium titanate Li 4 Ti 5 O 12 , Li-Al alloy or metallic lithium, etc. The negative electrode material layer of this application further includes a binder. There is no special limitation on the binder in the negative electrode material layer of this application, as long as the purpose of this application can be achieved. For example, the binder can be at least one of the above-mentioned binders. The negative electrode material layer of this application further includes a conductive agent. There is no special limitation on the conductive agent in the negative electrode material layer of this application, as long as the purpose of this 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 this application further includes a thickener. There is no special limitation on the thickener in the negative electrode material layer of this application, as long as the purpose of this application can be achieved. For example, the thickener can be sodium carboxymethyl cellulose (CMC-Na). There is no special limitation on the mass ratio of the negative electrode active material, conductive agent, thickener, and binder in the negative electrode material layer of this application. Those skilled in the art can select according to actual needs, as long as the purpose of this application can be achieved. For example, the mass ratio of the negative electrode active material, conductive agent, thickener, and binder can be (78 to 98.5):(0.1 to 10):(0.1 to 10):(0.1 to 10).

[0067] The present application has no particular limitation on the thickness of the negative electrode current collector, as long as the object 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 has no particular limitation on the thickness of the negative electrode material layer, as long as the object 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.

[0068] Optionally, the negative electrode sheet may further include a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode material layer. The present application has no particular limitation on the composition of the conductive layer, and it may be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular limitation on the conductive agent and the binder in the conductive layer, and it may be at least one of the above-mentioned conductive agents and the above-mentioned binders. The present application has no particular limitation on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art can select according to actual needs as long as the object of the present application can be achieved.

[0069] In the present application, the secondary battery further includes a separator, and the separator is used to separate the positive electrode sheet and the negative electrode sheet, prevent internal short circuit of the secondary battery, allow electrolyte ions to pass freely, and does not affect the progress of the electrochemical charge and discharge process. The present application has no particular limitation on the separator, as long as the object of the present application can be achieved. For example, the material of the separator may include, but is not limited to, at least one of polyolefins (PO) mainly composed of polyethylene (PE) and polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; the type of the separator may include at least one of a woven film, a non-woven film, a microporous film, a composite film, a rolled film or a spun film.

[0070] 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. Selecting polyethylene and polypropylene as the materials of the substrate has a good effect on preventing short circuits and can improve the safety performance of the secondary battery through the shut-off 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. The surface treatment layer may be a polymer layer, an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a binder. The present application does not particularly limit the above-mentioned inorganic particles. For example, it may include at least one of alumina, silica, magnesia, titania, hafnium dioxide, tin dioxide, 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 does not particularly limit 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, antioxidant performance, and electrolyte infiltration performance of the separator and enhance the adhesion between the separator and the electrode sheet. The polymer layer contains a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyethylene ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0071] The secondary battery of the present application further includes a packaging bag for accommodating the positive electrode sheet, the separator, the negative electrode sheet, and the non-aqueous electrolyte, as well as other components known in the art in the secondary battery. The present application does not limit the above-mentioned other components. The present application does not particularly limit the packaging bag and may be a packaging bag well known in the art as long as the purpose of the present application can be achieved.

[0072] The present application does not particularly limit the type of the secondary battery, and it may include any device that undergoes an electrochemical reaction. In the present application, the secondary battery may include, but is 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.

[0073] The preparation process of the secondary battery of the present application is well-known to those skilled in the art, and the present application has no special limitations. For example, it may include but is not limited to the following steps: stacking the positive electrode sheet, separator, and negative electrode sheet in sequence, and winding, folding, etc. as needed to obtain a wound-structured electrode assembly, placing the electrode assembly into 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, separator, and negative electrode sheet in sequence, and then fixing the four corners of the entire laminated structure with tape to obtain a laminated-structured electrode assembly, placing the electrode assembly into a packaging bag, injecting a non-aqueous electrolyte into the packaging bag and sealing it to obtain a secondary battery. In addition, an overcurrent protection element, a guide plate, etc. can also be placed in the packaging bag as needed to prevent the pressure inside the secondary battery from rising and overcharging / discharging.

[0074] The second aspect of the present application provides an electronic device, which includes the secondary battery in any of the foregoing embodiments. Therefore, the electronic device provided by the present application has good cycle stability and interval cycle stability under high voltage.

[0075] The present application does not particularly limit the type of the electronic device, and it can be any electronic device known in the prior art. In some embodiments, the electronic device may include but is not limited to a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset stereo, a video recorder, a liquid crystal TV, a portable cleaner, a portable CD player, a minidisc, 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 moped, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flash, a camera, a large household battery, and a lithium-ion capacitor, etc.

[0076] Examples

[0077] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments of the present application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0078] Testing methods and equipment:

[0079] Cycle stability test under high voltage:

[0080] The lithium-ion battery is placed in an incubator at 45 °C and charged at a constant current of 0.5C to 4.52V, then charged at a constant voltage of 4.52V until the current reaches 0.05C; it is left standing for 5 minutes, and then discharged at a constant current of 0.5C to 3.0V and left standing for 5 minutes. This is one charge-discharge cycle process. The charge-discharge cycle is carried out 500 times in the above manner. Record the discharge capacity of the lithium-ion battery after the first cycle, which is denoted as the initial capacity D0 of the lithium-ion battery cycle; record the discharge capacity of the lithium-ion battery after the 500th cycle, which is denoted as the remaining capacity Dz of the lithium-ion battery cycle.

[0081] The capacity retention rate (%) of the lithium-ion battery = Dz / D0×100%.

[0082] Interval cycle stability test:

[0083] The lithium-ion battery is placed in an incubator at 45 °C and charged at a constant current of 0.5C to 4.52V, then charged at a constant voltage of 4.52V until the current reaches 0.05C. After that, it is left standing for 19.5h, and then discharged at a constant current of 0.5C to 3.0V. Record the discharge capacity at this time, which is denoted as the initial discharge capacity D1. This is one charge-discharge cycle process. The charge-discharge cycle is carried out 23 times in the above manner; then it is charged at a constant current of 0.5C to 4.47V, charged at a constant voltage of 4.47V until the current reaches 0.05C, left standing for 19.5h, and then discharged at a constant current of 0.5C to 3.0V. This is another charge-discharge cycle process. The charge-discharge cycle is carried out 113 times in the above manner again. Record the discharge capacity at this time, which is denoted as the initial remaining capacity D2.

[0084] The interval capacity retention rate (%) of the lithium-ion battery = D2 / D1×100%.

[0085] Example 1-1

[0086] <Preparation of the positive electrode sheet>

[0087] The positive electrode active material lithium cobaltate (LiCoO 2 )), conductive agent (Super P), and 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%. After being stirred evenly by a vacuum mixer, the positive electrode slurry is obtained. 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 coated positive electrode material layer and a coating thickness of 110μm. Then, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coated positive electrode material layer. After coating, the positive electrode sheet is cold-pressed and cut into a size of 74mm×867mm for use. Among them, the compaction density of the positive electrode material layer after cold pressing is 4.15g / cm3 。

[0088] <Preparation of Negative Electrode Plate>

[0089] Mix artificial graphite as the negative electrode active material, conductive agent (Super P), thickening agent sodium carboxymethyl cellulose, and binder styrene-butadiene rubber according to a mass ratio of 96.4:1.5:0.5:1.6, add deionized water as a solvent, and formulate into a slurry with a solid content of 54 wt%. 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 10 μm, and dried at 90 °C to obtain a negative electrode plate with a single-sided coated negative electrode material layer with a coating thickness of 110 μm. Then, repeat the above steps on the other surface of the copper foil to obtain a negative electrode plate with a double-sided coated negative electrode material layer. After coating, the negative electrode plate is cold-pressed and cut into a specification of 76 mm × 851 mm for use. Among them, the compaction density of the negative electrode material layer after cold pressing is 1.70 g / cm 3 。

[0090] <Separator>

[0091] Mix alumina and PVDF according to a mass ratio of 95:5, add NMP as a solvent, formulate into a slurry with a solid content of 12 wt%, and stir evenly to obtain an inorganic layer slurry; evenly coat the inorganic layer slurry on one surface of a polyethylene substrate with a thickness of 9 μm, and after drying, obtain a separator with a single-sided coated inorganic layer with a coating thickness of 2 μm. Then, add PVDF to the NMP solvent and stir evenly to formulate a polymer layer slurry with a solid content of 25 wt%. Then, evenly coat the polymer layer slurry on the surface of the inorganic layer away from the substrate, and dry to obtain a separator with a single-sided coated inorganic layer and polymer layer; then evenly coat the polymer layer slurry on the other surface of the polyethylene substrate, and dry to obtain a separator with an inorganic layer and polymer layer coated on one side and only a polymer layer coated on the other side. Among them, the surface density of the coated polymer layer slurry is 0.15 mg / cm 2 。

[0092] <Preparation of Electrolyte>

[0093] In an argon atmosphere glove box with a water content of less than 10 ppm, mix EC, PC, and DEC to obtain a basic organic solvent, and then add a second lithium salt LiPF 6 , dissolve and mix evenly, and then add Compound I (Formula I-8) to obtain a non-aqueous electrolyte. Among them, based on the mass of the non-aqueous electrolyte, the mass percentage content W5 of the second lithium salt is 10%, the mass percentage content W1 of Compound I is 10%, 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%.

[0094] <Preparation of Lithium-Ion Battery>

[0095] Stack the above-prepared positive electrode sheet, separator, negative electrode sheet, and separator in sequence, with the separator placed in the middle of the positive electrode sheet and the negative electrode sheet to play an isolation role, and then wind them to obtain an electrode assembly; place the electrode assembly in an outer packaging aluminum-plastic film, remove the moisture at 80 °C, inject the above-prepared non-aqueous electrolyte and seal it, and obtain a lithium-ion battery through the processes of standing, forming, degassing, trimming, shaping, and capacity testing.

[0096] Examples 1-2 to Examples 1-18

[0097] Except for adjusting the relevant preparation parameters according to Table 1, the rest are the same as Example 1-1.

[0098] Examples 2-1 to Examples 2-10

[0099] Except for further adding a first lithium salt in <Preparation of Electrolyte> and adjusting the relevant preparation parameters according to Table 2, the rest are the same as Example 1-3.

[0100] Examples 3-1 to Examples 3-16

[0101] Except for further adding a first nitrile compound and / or a second nitrile compound in <Preparation of Electrolyte> and adjusting the relevant preparation parameters according to Table 3, the rest are the same as Example 1-8. Among them, when the mass percentage content of at least one of the first nitrile compound or the second nitrile compound changes, the mass percentage content of DEC changes accordingly, and the mass percentage contents of the compound of Formula I, the second lithium salt, EC, and PC remain unchanged.

[0102] Example 3-17

[0103] Except for further adding a first nitrile compound in <Preparation of Electrolyte> and adjusting the relevant preparation parameters according to Table 3, the rest are the same as Example 2-9. Among them, 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 2.8%, the mass percentage content W2 of the first lithium salt is 0.2%, and the mass percentage content W3 of the first nitrile compound is 2%.

[0104] Example 3-18

[0105] Except for further adding a second nitrile compound in the <Preparation of electrolyte> and adjusting the relevant preparation parameters according to Table 3, the rest is the same as in Examples 2-9. Among them, 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 3.3%, the mass percentage content W2 of the first lithium salt is 0.2%, and the mass percentage content W4 of the second nitrile compound is 1.5%.

[0106] Examples 3-19

[0107] Except for further adding a first nitrile compound and a second nitrile compound in the <Preparation of electrolyte> and adjusting the relevant preparation parameters according to Table 3, the rest is the same as in Examples 2-9. Among them, 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%.

[0108] Comparative Examples 1 to 3

[0109] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1.

[0110] The preparation parameters and performance parameters of each example and comparative example are shown in Tables 1 to 3.

[0111] Table 1

[0112]

[0113]

[0114] Note: (1) In Table 1, " / " indicates no relevant preparation parameters; (2) Taking Examples 1-17 as an example, the "type of Compound I" is "Compound I-7 + Compound I-1", and the "mass percentage content W1 of Compound I" is "50 + 20", indicating that Compound I includes Compound I-7 and Compound I-1. Based on the mass of the non-aqueous electrolyte, the mass percentage content of Compound I-7 is 50%, and the mass percentage content of Compound I-1 is 20%. The same applies to other examples; (3) Taking Example 1-1 as an example, the "mass percentage content W6 of the basic organic solvent" is "17.5 + 17.5 + 45", indicating that the basic organic solvents include EC, PC, and DEC in sequence. 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%. The same applies to other examples.

[0115] 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 Compound I, and the type and mass percentage content of Compound I are within the scope of this application, the capacity retention rate of the lithium-ion battery is higher, and 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 Compound I, and the capacity retention rate of the lithium-ion battery is lower, and the interval capacity retention rate is lower, indicating that the cycle stability and interval cycle stability of the lithium-ion battery under high voltage are poor. In Comparative Example 2, the mass percentage content of Compound I is too low to effectively weaken the continuous reaction on the negative electrode side and the positive electrode side, resulting in a lower capacity retention rate and a lower interval capacity retention rate of the lithium-ion battery, and thus poor cycle stability and interval cycle stability of the lithium-ion battery under high voltage. In Comparative Example 3, the mass percentage content of Compound I is too high, which will lead to an increase in the viscosity of the non-aqueous electrolyte, making it difficult for lithium ions to diffuse in the liquid phase, and the interfacial impedance will also increase, resulting in a reduction in the cycle improvement effect.

[0116] It can be seen from Examples 1-1 to 1-6 that Compound I is selected as Compound I-8, and only R 2 is replaced by F. The mass percentage content of Compound I is within the scope of this application, and the capacity retention rate of the lithium-ion battery is relatively high, and the interval capacity retention rate is relatively high, indicating that the lithium-ion battery has good cycle stability and interval cycle stability under high voltage. In Examples 1-5 and 1-6, the mass percentage content of Compound I is relatively high, which will lead to a relatively high viscosity of the non-aqueous electrolyte, thereby affecting the lithium-ion transmission and ultimately affecting the cycle stability and interval cycle stability of the lithium-ion battery under high voltage.

[0117] As can be seen from Examples 1-7, the non-aqueous electrolyte includes the compound of Formula I. LiFSI is selected as the second lithium salt, and no other organic solvents are added. The lithium-ion battery has a high capacity retention rate and an interval capacity retention rate, indicating that the lithium-ion battery has good cycle stability and interval cycle stability at high voltages.

[0118] It can be seen from Examples 1-3, Examples 1-8 to Examples 1-12, Examples 1-17, and Examples 1-18 that when the above-mentioned compound of Formula I is selected, the lithium-ion battery has a high capacity retention rate and a high interval capacity retention rate, indicating that the lithium-ion battery has good cycle stability and interval cycle stability at high voltages.

[0119] It can be seen from Examples 1-13 to Examples 1-16 that the compound of Formula I is selected as Formula I-1, and both R 1 and R 2 are replaced by F. When the mass percentage content of the compound of Formula I is within the scope of this application, the lithium-ion battery has a high capacity retention rate and a high interval capacity retention rate, indicating that the lithium-ion battery has good cycle stability and interval cycle stability at high voltages. In Example 1-16, the relatively high mass percentage content of the compound of Formula I will make it 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 cycle stability and interval cycle stability of the lithium-ion battery at high voltages.

[0120] Table 2

[0121]

[0122] Note: (1) In Table 2, " / " indicates no relevant preparation parameters; (2) In Example 2-10, the "type of the first lithium salt" is "LiPO 2 F 2 +LiBF 4 ", and the "mass percentage content W2 of the first lithium salt" is "0.1 + 0.1", indicating that the first lithium salt includes LiPO 2 F 2 and LiBF 4 . Based on the mass of the non-aqueous electrolyte, the mass percentage content of LiPO 2 F 2 is 0.1%, and the mass percentage content of LiBF 4 is 0.1%.

[0123] The non-aqueous electrolyte further includes a first lithium salt, and the type of the first lithium salt usually affects the cycle stability and intermittent cycle stability of the lithium-ion battery at high voltages. It can be seen from Examples 1-3, Example 2-1, and Examples 2-6 to 2-10 that when the non-aqueous electrolyte further includes a first lithium salt and the type of the first lithium salt is within the scope of this application, the capacity retention rate and intermittent capacity retention rate of the lithium-ion battery are relatively high, indicating that the lithium-ion battery has good cycle stability and intermittent cycle stability at high voltages.

[0124] The mass percentage content of the first lithium salt usually affects the cycle stability and intermittent cycle stability of the lithium-ion battery at high voltages. It can be seen from Examples 2-1 to 2-5 that when the mass percentage content of the first lithium salt is within the scope of this application, the capacity retention rate and intermittent capacity retention rate of the lithium-ion battery are relatively high, indicating that the lithium-ion battery has good cycle stability and intermittent cycle stability at high voltages.

[0125] Table 3

[0126]

[0127]

[0128] Note: (1) In Table 3, " / " indicates no relevant preparation parameters; (2) In Example 3-8, the "type of the first nitrile compound" is "succinonitrile + adiponitrile", and the "mass percentage content W3 of the first nitrile compound" is "2 + 2", indicating that the first nitrile compound includes succinonitrile and adiponitrile. 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, the "type of the second nitrile compound" is "Formula II-4 + Formula II-9 + Formula II-13", and the "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. 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%.

[0129] The non-aqueous electrolyte further includes a first nitrile compound, and the type of the first nitrile compound usually affects the cycle stability and intermittent cycle stability of the lithium-ion battery at high voltages. It can be seen from Examples 1-8, Example 3-1, and Examples 3-6 to 3-8 that when the non-aqueous electrolyte further includes a first nitrile compound and the type of the first nitrile compound is within the scope of this application, the capacity retention rate and intermittent capacity retention rate of the lithium-ion battery are relatively high, indicating that the lithium-ion battery has good cycle stability and intermittent cycle stability at high voltages.

[0130] The mass percentage content of the first nitrile compound usually affects the cycle stability and intermittent cycle stability of the lithium-ion battery at high voltages. It can be seen from Examples 3-1 to 3-5 that when the mass percentage content of the first nitrile compound is within the scope of this application, the capacity retention rate and intermittent capacity retention rate of the lithium-ion battery are relatively high, indicating that the lithium-ion battery has good cycle stability and intermittent cycle stability at high voltages.

[0131] The non-aqueous electrolyte further includes a second nitrile compound. The type of the second nitrile compound usually affects the cycle stability and intermittent cycle stability of the lithium-ion battery at high voltages. It can be seen from Examples 1-8, 3-9, 3-13 to 3-15 that when the non-aqueous electrolyte further 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 intermittent capacity retention rate of the lithium-ion battery are relatively high, indicating that the lithium-ion battery has good cycle stability and intermittent cycle stability at high voltages.

[0132] The mass percentage content of the second nitrile compound usually affects the cycle stability and intermittent cycle stability of the lithium-ion battery at high voltages. It can be seen from Examples 3-9 to 3-12 that when the mass percentage content of the second nitrile compound is within the scope of this application, the capacity retention rate and intermittent capacity retention rate of the lithium-ion battery are relatively high, indicating that the lithium-ion battery has good cycle stability and intermittent cycle stability at high voltages.

[0133] In Examples 3-16 to 3-19, the capacity retention rate and intermittent capacity retention rate of the lithium-ion battery are relatively high, indicating that the lithium-ion battery has good cycle stability and intermittent cycle stability at high voltages.

[0134] It should be noted that in this text, relational terms such as first and second are only used 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 term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method or article.

[0135] Each embodiment in this specification is described in a related manner. The same or similar parts among the embodiments can be referred to each other, and the differences between each embodiment and other embodiments are emphasized.

[0136] The above are only the preferred embodiments of the present application and are 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 within 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, and 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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