Electrolyte solution, electrochemical device, and electronic apparatus

Abstract

The invention discloses an electrolyte, an electrochemical device and electronic equipment. The electrolyte comprises a compound # imgabs0 # shown in a formula I and a compound # imgabs1 # shown in a formula II, based on the mass of the electrolyte, the mass percentage A of the compound shown in the formula I is more than or equal to 0.01% and less than or equal to 70%, and the mass percentage B of the compound shown in the formula II is more than or equal to 2.0% and less than or equal to 20%. According to the present invention, the electrolyte comprises the compound represented by the formula I and the compound represented by the formula II, the compound represented by the formula I and the compound represented by the formula II are in the range of the present application, the compound represented by the formula I can improve the low-temperature high-rate discharge capacity retention rate of the electrochemical device, and the compound represented by the formula II can improve the stability of the positive electrode and the negative electrode so as to improve the high-temperature cycle capacity retention rate of the electrochemical device.

Description

Technical Field

[0001] The present application relates to the technical field of electrochemical devices, and in particular to an electrolyte, an electrochemical device and an electronic device. Background Art

[0002] Electrochemical devices (e.g., lithium-ion batteries) have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, and good safety. They are widely used in various fields such as portable energy storage, electronic equipment, and electric vehicles. However, they also place higher requirements on the comprehensive performance of electrochemical devices, such as the need to develop electrolytes that can improve both the high-temperature cycle capacity retention rate and the low-temperature high-rate discharge capacity retention rate of electrochemical devices. Summary of the invention

[0003] The embodiments of the present application provide an electrolyte, an electrochemical device, and an electronic device. By improving the components of the electrolyte, an electrolyte that improves both the high-temperature cycle performance and the low-temperature rate discharge performance of the electrochemical device can be obtained.

[0004] In a first aspect, the present application provides an electrolyte, comprising a compound of formula I and a compound of formula II;

[0005]

[0006] Wherein, in Formula I, R is selected from C2-C6 alkyl which is unsubstituted or substituted by R0, C2-C6 alkenyl which is unsubstituted or substituted by R0, C2-C6 alkynyl which is unsubstituted or substituted by R0, C3-C6 nitrogen-containing heteroaryl which is unsubstituted or substituted by R0, C6-C 12 Any of the aryl groups, the substituents R0 of each group are independently selected from any of the unsubstituted or substituted C1-C6 alkyl groups, and when substituted, the substituent is fluorine;

[0007] In formula II, R1 to R5 are each independently selected from any one of fluorine, unsubstituted or substituted C1-C5 alkyl, unsubstituted or substituted C1-C5 phosphate, unsubstituted or substituted C1-C5 sulfonic acid, and unsubstituted or substituted C1-C5 ester. When substituted, the substituent is fluorine;

[0008] Based on the mass of the electrolyte, the mass percentage of the compound of formula I is A, and the mass percentage of the compound of formula II is B, wherein 0.01%≤A≤70%, and 2.0%≤B≤20%. By making the electrolyte include the compound of formula I and the compound of formula II, the compound of formula I and the compound of formula II are within the scope of the present application, while the compound of formula I improves the low-temperature high-rate discharge capacity retention rate of the electrochemical device, the compound of formula II can take into account the improvement of the positive and negative electrode stability, thereby improving the high-temperature cycle capacity retention rate of the electrochemical device.

[0009] In some embodiments, 0.17≤A / B≤18. By selecting the mass percentages of the compound of formula I and the compound of formula II in the electrolyte to meet the above range, the two can be better matched to improve the positive electrode impedance and the positive and negative electrode interface stability, thereby improving the low-temperature high-rate discharge capacity retention rate and high-temperature cycle capacity retention rate of the electrochemical device.

[0010] In some embodiments, the electrolyte satisfies at least one of the following conditions:

[0011] (1) 0.5% ≤ A ≤ 50%;

[0012] (2)4%≤B≤8%.

[0013] In some embodiments, the compound of Formula I includes at least one of the following compounds:

[0014]

[0015] By selecting the above-mentioned compound of formula I, the compound of formula I can form a positive electrode interface passivation layer of lithium-containing inorganic compounds rich in S and F elements at the positive electrode interface, further reducing the positive electrode side impedance, thereby improving the low-temperature and high-rate discharge capacity retention rate of the electrochemical device.

[0016] In some embodiments, the compound of Formula II includes at least one of the following compounds:

[0017]

[0018]

[0019] By selecting the above-mentioned compound of formula II, the compound of formula II has good antioxidant properties, which can further improve the overall antioxidant capacity of the electrolyte, inhibit the compound of formula I from accelerating the oxidative decomposition of components in the electrolyte to generate HF, protect the positive electrode, and improve the high-temperature cycle capacity retention rate of the electrochemical device.

[0020] In some embodiments, the electrolyte further includes a first component, the first component including at least one of difluoroethylene carbonate, propylene carbonate or vinylene carbonate; based on the mass of the electrolyte, the mass percentage of the first component is C, 0.8≤C / (A+B)≤1.15. By adjusting the mass percentage of the first component in the electrolyte, the mass percentage of the compound of formula I and the mass percentage of the compound of formula II to meet the above conditional formula, the viscosity of the electrolyte can be further improved, the ionic conductivity of the electrolyte can be improved, and the kinetic performance of the electrochemical device can be improved.

[0021] In some embodiments, the electrolyte further includes a second component, the second component includes at least one of diethyl carbonate, propyl propionate or ethyl propionate; based on the mass of the electrolyte, the mass percentage of the second component is D, 0.9≤D / (A+B)≤2. The compound of formula I and the compound of formula II both have good dissociation ability for lithium salts, and when used in combination with the second component, they can make up for the lack of dissociation ability of the second component for lithium salts, improve the conductivity of the electrolyte, and help to further improve the high temperature cycle capacity retention rate and low temperature high rate discharge capacity retention rate of the electrochemical device.

[0022] In some embodiments, the electrolyte further comprises a nitrile compound, wherein the nitrile compound comprises at least one of a dinitrile compound and a trinitrile compound; based on the mass of the electrolyte, the mass percentage of the nitrile compound is E, wherein 2%≤E≤10%. By making the mass percentage of the nitrile compound in the electrolyte meet the above range, the nitrile compound can synergize with the compound of formula I to form a positive electrode interface passivation layer rich in LiF and cyano groups, which can improve the positive electrode interface stability, and can also further enhance the oxidation resistance of the electrolyte, thereby further improving the high temperature storage performance of the electrochemical device.

[0023] In some embodiments, the dinitrile compound includes at least one of adiponitrile, succinonitrile, glutaronitrile, and 1,4-dicyano-2-butene; and the trinitrile compound includes at least one of 1,3,6-hexanetrinitrile and 1,3,5-pentanetricarboxynitrile.

[0024] In a second aspect, the present application provides an electrochemical device, comprising the electrolyte as described above.

[0025] In a third aspect, the present application provides an electronic device comprising the electrochemical device as described above.

[0026] Based on the electrolyte, electrochemical device and electronic device of the embodiment of the present application, by making the electrolyte include a compound of formula I and a compound of formula II, and making the mass percentage A of the compound of formula I satisfy 0.01%≤A≤70%, and the mass percentage B of the compound of formula II satisfy 2.0%≤B≤20%, the compound of formula I can form a positive electrode interface passivation layer of a lithium-containing inorganic compound rich in S and F elements at the positive electrode interface, reduce the positive electrode side impedance, thereby improving the low temperature and high rate discharge capacity retention rate of the electrochemical device. The compound of formula II has good antioxidant ability, and the addition of the compound of formula II can enhance the antioxidant ability of the electrolyte as a whole, prevent the compound of formula I from accelerating the oxidation and decomposition of the components in the electrolyte to generate HF, thereby preventing HF from damaging the positive electrode, improving the stability of the positive electrode, and at the same time, the compound of formula II can also be preferentially adsorbed on the negative electrode to form a protective film, improving the stability of the negative electrode. Therefore, while adding the compound of formula I to the electrolyte to improve the low temperature and high rate discharge capacity retention rate of the electrochemical device, the compound of formula II can take into account the improvement of the stability of the positive and negative electrodes, thereby improving the high temperature cycle capacity retention rate of the electrochemical device. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0028] The present application provides an electrolyte, the electrolyte comprising a compound of formula I and a compound of formula II, based on the mass of the electrolyte, the mass percentage of the compound of formula I is A, the mass percentage of the compound of formula II is B, wherein 0.01%≤A≤70%, 2.0%≤B≤20%. The present application can improve both the low-temperature high-rate discharge capacity retention rate and the high-temperature cycle capacity retention rate of the electrochemical device by performing the above-mentioned configuration on the electrolyte.

[0029] The electrolyte includes a compound of formula I, which is as follows:

[0030]

[0031] Wherein, in Formula I, R is selected from C2-C6 alkyl which is unsubstituted or substituted by R0, C2-C6 alkenyl which is unsubstituted or substituted by R0, C2-C6 alkynyl which is unsubstituted or substituted by R0, C3-C6 nitrogen-containing heteroaryl which is unsubstituted or substituted by R0, C6-C 12 Any of the aryl groups, the substituent R0 of each group is independently selected from any of the unsubstituted or substituted C1-C6 alkyl groups, and when substituted, the substituent is fluorine.

[0032] Based on the mass of the electrolyte, the mass percentage of the compound of formula I is A, 0.01%≤A≤70%. In some embodiments, 0.5%≤A≤50%. In some embodiments, 1%≤A≤30%. In some embodiments, 3%≤A≤20%. In some embodiments, 5%≤A≤15%. In some embodiments, the value of A is 0.01%, 2.0%, 6.0%, 16.0%, 35.0%, 40.0%, 45.0%, 55.0%, 60.0%, 70.0% or a value within the range of any two of these values.

[0033] The electrolyte also includes a compound of formula II, which is as follows:

[0034]

[0035] Wherein, R1 to R5 in Formula II are each independently selected from any one of fluorine, unsubstituted or substituted C1-C5 alkyl, unsubstituted or substituted C1-C5 phosphate, unsubstituted or substituted C1-C5 sulfonic acid, and unsubstituted or substituted C1-C5 ester. When substituted, the substituent is fluorine.

[0036] Based on the mass of the electrolyte, the mass percentage of the compound of formula II is B, and B satisfies: 2.0%≤B≤20%. In some embodiments, 3.0%≤B≤18.0%. In some embodiments, 4.0%≤B≤8.0%. In some embodiments, 5.0%≤B≤12.0%. In some embodiments, 5.0%≤B≤10.0%. In some embodiments, the value of B is 2.0%, 5.5%, 6.8%, 9.8%, 11.0%, 13.4%, 14.5%, 15.0%, 18.0%, 20.0%, or a value in the range of any two of these values.

[0037] The present application adds a compound of formula I to the electrolyte, and the compound of formula I can form a positive electrode interface passivation layer of a lithium-containing inorganic compound rich in S and F elements at the positive electrode interface, reduce the positive electrode side impedance, and thus improve the low-temperature high-rate discharge capacity retention rate of the electrochemical device. The compound of formula II has good oxidation resistance, and the addition of the compound of formula II can enhance the overall antioxidant capacity of the electrolyte, prevent the components in the electrolyte from oxidative decomposition to generate HF, and then prevent HF from damaging the positive electrode, and improve the positive electrode stability. For example, in order to improve the viscosity of the electrolyte and enhance the kinetic performance of the electrochemical device, carbonate compounds and carboxylate compounds are added to the electrolyte in the related art. However, in the fully charged state or high-temperature storage state of the electrochemical device, the compound of formula I will accelerate the oxidation and decomposition reaction of carbonate compounds and carboxylate compounds with the fluorine-containing compounds in the electrolyte to generate HF, and HF will damage the positive electrode structure, resulting in deterioration of the positive electrode impedance. At the same time, the compound of formula II can also be preferentially adsorbed on the negative electrode to form a protective film, improving the negative electrode stability. Therefore, while adding the compound of formula I to the electrolyte to improve the low-temperature high-rate discharge capacity retention rate of the electrochemical device, the compound of formula II can improve the stability of the positive and negative electrodes, thereby taking into account the improvement of the high-temperature cycle capacity retention rate of the electrochemical device. When the mass percentage content A of the compound of formula I exceeds the upper limit of 70%, the oxidative decomposition of the carbonate compound and the carboxylate compound in the electrolyte will be violently accelerated to generate HF, resulting in an increase in the positive electrode impedance. When the mass percentage content A of the compound of formula I is lower than the lower limit of 0.5%, the compound of formula I does not significantly improve the positive electrode interface impedance, and it is difficult to effectively improve the low-temperature high-rate discharge capacity retention rate of the electrochemical device. When the mass percentage content B of the compound of formula II exceeds the upper limit of 20.0%, the content of the compound of formula II is too high, resulting in insufficient conductivity of the electrochemical device, and then the kinetic performance of the electrochemical device is reduced. When B is lower than the lower limit of 2.0%, the content of the compound of formula II is too low, and the auxiliary ability of the compound of formula II to the compound of formula I is insufficient, resulting in the compound of formula I still being able to accelerate the oxidative decomposition of the components in the electrolyte to damage the positive electrode structure.

[0038] In some embodiments, A and B satisfy: 0.17≤A / B≤18. In some embodiments, 3.0≤A / B≤18.0. In some embodiments, 4.0≤A / B≤15.0. In some embodiments, 5.0≤A / B≤12.0. In some embodiments, 5.0≤A / B≤10.0. In some embodiments, the value of A / B is 2.0, 3.5, 5.5, 6.8, 9.8, 11.0, 12.7, 13.4, 14.5, 15.0 or a value in the range composed of any two of these values. The present application selects the mass percentage of both the compound of formula I and the compound of formula II in the electrolyte to meet the above range, so that the two can better cooperate to improve the positive electrode impedance and the positive and negative electrode interface stability, thereby taking into account the improvement of the low-temperature high-rate discharge capacity retention rate and the high-temperature cycle capacity retention rate of the electrochemical device.

[0039] In some embodiments, the compound of Formula I includes at least one of the following compounds:

[0040]

[0041] By selecting the above-mentioned compound of formula I, the compound of formula I can form a positive electrode interface passivation layer of lithium-containing inorganic compounds rich in S and F elements at the positive electrode interface, further reducing the positive electrode side impedance, thereby improving the low-temperature and high-rate discharge capacity retention rate of the electrochemical device.

[0042] In some embodiments, the compound of Formula II includes at least one of the following compounds:

[0043]

[0044] By selecting the above-mentioned compound of formula II, the compound of formula II has good antioxidant properties, which can further improve the overall antioxidant capacity of the electrolyte, inhibit the compound of formula I from accelerating the oxidative decomposition of components in the electrolyte to generate HF, protect the positive electrode, and improve the high-temperature cycle capacity retention rate of the electrochemical device.

[0045] In some embodiments, the electrolyte further comprises a first component, the first component comprising at least one of bisfluoroethylene carbonate, vinylene carbonate or propylene carbonate. Based on the mass of the electrolyte, the mass percentage of the first component is C, 5%≤C≤60%, in some embodiments, 8%≤C≤50%. In some embodiments, 10%≤C≤30%. In some embodiments, 15%≤C≤30%. In some embodiments, the value of C is 5%, 7%, 13%, 16%, 19%, 27%, 38%, 48%, 55%, 60% or a value in the range of any two of these values. By adjusting the mass percentage of the first component in the electrolyte to meet the above range, the first component can improve the ion conductivity of the electrolyte. In addition, the viscosity of the first component is relatively large, and the viscosity of the compound of formula I and the compound of formula II is relatively small. The first component, the compound of formula I and the compound of formula II are added to the electrolyte to improve the viscosity of the electrolyte.

[0046] In some embodiments, C and A, B satisfy the relationship: 0.8≤C / (A+B)≤1.15. In some embodiments, 0.8≤C / (A+B)≤1.10. In some embodiments, 0.9≤C / (A+B)≤1.05. In some embodiments, 0.95≤C / (A+B)≤1.10. In some embodiments, 1.0≤C / (A+B)≤1.15. In some embodiments, the value of C / (A+B) is 0.80, 0.88, 0.94, 0.98, 1.01, 1.06, 1.10, 1.12, 1.14, 1.15 or a value within the range of any two of these values. By adjusting the mass percentage of the first component in the electrolyte, the mass percentage of the compound of formula I and the mass percentage of the compound of formula II to meet the above conditional formula, the viscosity of the electrolyte can be further improved, the ionic conductivity of the electrolyte can be improved, and the kinetic performance of the electrochemical device can be improved.

[0047] In some embodiments, the electrolyte further comprises a second component, the second component comprising at least one of diethyl carbonate, propyl propionate or ethyl propionate. Based on the mass of the electrolyte, the mass percentage of the second component is D, 10%≤D≤60%, in some embodiments, 12%≤D≤50%. In some embodiments, 15%≤D≤30%. In some embodiments, 30%≤D≤50%. In some embodiments, the value of D is 5%, 7%, 13%, 16%, 19%, 27%, 38%, 48%, 55%, 60% or a value in the range composed of any two of these values. By adjusting the mass percentage of the second component in the electrolyte to meet the above range, the second component has a lower viscosity, which can improve the wetting ability of the electrolyte, and the compound of formula I and the compound of formula II both have good dissociation ability for lithium salts. When used in combination with the second component, it can make up for the lack of dissociation ability of the second component for lithium salts, improve the conductivity of the electrolyte, and help improve the high temperature cycle capacity retention rate and low temperature high rate discharge capacity retention rate of the electrochemical device.

[0048] In some embodiments, D and A, B satisfy the relationship: 0.90≤D / (A+B)≤2.00, in some embodiments, 1.00≤D / (A+B)≤1.80. In some embodiments, 0.90≤D / (A+B)≤1.20. In some embodiments, 0.95≤D / (A+B)≤1.10. In some embodiments, 1.50≤D / (A+B)≤2.0. In some embodiments, the value of D / (A+B) is 0.90, 0.95, 1.05, 1.23, 1.36, 1.55, 1.68, 1.79, 1.91, 2.00 or a value within the range of any two of these values. By adjusting the mass percentage of the second component in the electrolyte, the mass percentage of the compound of formula I and the mass percentage of the compound of formula II to meet the above conditional formula, the conductivity of the electrolyte can be further improved, and the high temperature cycle capacity retention rate and low temperature high rate discharge capacity retention rate of the electrochemical device can be improved.

[0049] In some embodiments, the electrolyte further comprises a nitrile compound, wherein the nitrile compound comprises at least one of a dinitrile compound and a trinitrile compound. In some embodiments, the dinitrile compound comprises at least one of adiponitrile, succinonitrile, glutaronitrile, and 1,4-dicyano-2-butene. In some embodiments, the trinitrile compound comprises at least one of 1,3,6-hexanetrinitrile and 1,3,5-pentanetricarbonitrile.

[0050] Based on the mass of the electrolyte, the mass percentage of the nitrile compound is E, 2%≤E≤10%. In some embodiments, 2%≤E≤8%. In some embodiments, 4%≤E≤8%. In some embodiments, 5%≤E≤10%. In some embodiments, the value of E is 2.2%, 3.4%, 4.6%, 5.5%, 6.8%, 7.2%, 8.5%, 9.7%, 10.0% or a value within the range of any two of these values. By making the mass percentage of the nitrile compound in the electrolyte meet the above range, the nitrile compound can synergize with the compound of formula I to form a positive electrode interface passivation layer rich in LiF and cyano, which can improve the positive electrode interface stability, and can also further enhance the oxidation resistance of the electrolyte, thereby further improving the high temperature storage performance of the electrochemical device.

[0051] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium difluorooxalatoborate, and lithium dioxalatoborate.

[0052] In some embodiments, based on the mass of the electrolyte, the mass percentage of the lithium salt is F, 5%≤F≤25%. In some embodiments, 5%≤F≤20%. In some embodiments, 8%≤F≤18%. In some embodiments, 10%≤F≤15%. In some embodiments, the value of F is 5%, 6%, 7%, 9%, 11%, 12%, 17%, 19%, 20%, 23% or a value in the range of any two of these values. The use of lithium salt in an electrochemical device can improve the ionic conductivity of the electrochemical device. By selecting the content of the lithium salt in the above range, the viscosity and conductivity of the electrolyte can be balanced, which helps to improve the low-temperature high-rate discharge capacity retention rate of the electrochemical device.

[0053] In the present application, the features of the different components contained in the above-mentioned electrolyte can be combined, and the implementation modes covered by the above-mentioned combination are all within the protection scope of the present application.

[0054] In the present application, the electrolyte also includes a non-aqueous organic solvent. The present application has no particular restrictions on the non-aqueous organic solvent, as long as the purpose of the present application can be achieved. For example, the non-aqueous organic solvent may contain at least one of a carbonate compound, a carboxylate compound, an ether compound or other organic solvents. The above-mentioned carbonate compound may include but is not limited to at least one of a chain carbonate compound and a cyclic carbonate compound. The above-mentioned chain carbonate compound may include but is not limited to at least one of dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC) or ethyl methyl carbonate (EMC). The above-mentioned cyclic carbonate compound may include but is not limited to at least one of ethylene carbonate (EC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The above-mentioned carboxylate compound may include but is not limited to at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate or methyl propionate. The above-mentioned ether compound may include but is 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-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, cyclopentane, methyl cyclopentane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphate. The present application has no particular restrictions on the mass percentage of the non-aqueous organic solvent in the electrolyte, as long as the purpose of the present application can be achieved. For example, based on the mass of the electrolyte, the mass percentage G of the non-aqueous organic solvent is 10% to 70%.

[0055] The present application also provides an electrochemical device, which includes the electrolyte as described above, and further includes a positive electrode, a negative electrode and a separator.

[0056] The present application does not specifically limit the materials, structures and processing methods of the positive electrode, negative electrode and separator of the electrochemical device. The positive electrode, negative electrode and separator that can be used in the art are applicable to the present application.

[0057] Ⅰ Positive electrode

[0058] The positive electrode in the electrochemical device of the present application includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. The above-mentioned "positive electrode material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector along its own thickness direction, or on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the positive electrode current collector or a partial area of ​​the positive electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0059] The positive electrode material layer of the present application includes a positive electrode active material, and the positive electrode active material 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 multi-layer 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 may 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. At least one of.

[0060] The cathode 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 the binder in the cathode material layer, 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 are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal materials may include but are not limited to metal powders and / or metal fibers, and 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 are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. The binder may include, but is not limited to, polyacrylate, polyimide, polyamide, polyamide-imide, polyvinylidene fluoride, polystyrene butadiene copolymer (styrene-butadiene rubber, SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose (CMC-Na), 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.

[0061] The present application has no particular restrictions 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). The present application has no particular restrictions on 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 5μm to 20μm, preferably 6μm to 18μm. The present application has no particular restrictions on 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 30μm to 120μm.

[0062] Optionally, the positive electrode may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode material layer. The present application has no particular restrictions on the composition of the conductive layer, which may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, which may be at least one of the above conductive agent and the above binder. The present application has no particular restrictions on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art may select according to actual needs, as long as the purpose of the present application can be achieved.

[0063] In the present application, the electrochemical device also includes a negative electrode, which includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed 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.

[0064] 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), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithium titanate Li4Ti5O 12 , Li-Al alloy or metallic lithium, etc.

[0065] 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 present application has no special restrictions on the mass ratio of the negative electrode active material, the binder, and the conductive agent 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.

[0066] The present application has no particular restrictions on the negative electrode current collector, as long as the purpose of the present 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 composite current collector, etc. The present application has no particular restrictions on 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 5μm to 16μm. The present application has no particular restrictions on 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 30μm to 120μm.

[0067] Optionally, the negative electrode may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. The present application has no particular restrictions on the composition of the conductive layer, which may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, which may be at least one of the above conductive agent and the above binder. The present application has no particular restrictions on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art may choose according to actual needs, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the thickness of the conductive layer, as long as the purpose of the present application can be achieved, for example, the thickness of the conductive layer is 1 μm to 10 μm.

[0068] In the present application, the electrochemical device also includes a diaphragm, which is used to separate the positive electrode and the negative electrode, prevent the internal short circuit of the electrochemical device, 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 (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid at least one; the type of diaphragm may include woven membranes, non-woven membranes, microporous membranes, composite membranes, rolled membranes or spun membranes at least one. The present application has no special restrictions on the thickness of the diaphragm, as long as the purpose of the present application can be achieved, for example, the thickness of the diaphragm is 3μm to 30μm.

[0069] In the present application, the diaphragm 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. 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. Optionally, the thickness of the base film is 3 μm to 25 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 substance. For example, the inorganic layer includes inorganic particles and a binder, and 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 above-mentioned binder, for example, it can be at least one of the aforementioned binders. 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). Optionally, the thickness of the surface treatment layer is 1 μm to 10 μm.

[0070] The electrochemical device of the present application also includes a packaging bag for containing a positive electrode, a separator, a negative electrode and an electrolyte, as well as other components known in the art in the electrochemical device, and the present application does not limit the above-mentioned other components. The present application does not specifically limit the packaging bag, and it can be a packaging bag known in the art, as long as it can achieve the purpose of the present application.

[0071] The present application does not particularly limit the type of electrochemical device, which may include any device that undergoes an electrochemical reaction. In the present application, the electrochemical device may include, but is not limited to: a lithium metal electrochemical device, a lithium ion electrochemical device (lithium ion battery), a lithium polymer electrochemical device or a lithium ion polymer electrochemical device (lithium ion polymer battery), etc.

[0072] The preparation process of the electrochemical device of the present application is well known to those skilled in the art, and the present application has no particular limitation. For example, it may include but is not limited to the following steps: stacking the positive electrode, the separator and the negative electrode in order, and winding, folding and other operations as needed to obtain an electrode assembly of a wound structure, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag and sealing it to obtain an electrochemical device; or stacking the positive electrode, the separator and the negative electrode in order, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly of a stacked structure, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag and sealing it to obtain an electrochemical device. In addition, overcurrent protection elements, guide plates, etc. may also be placed in the packaging bag as needed to prevent pressure rise and overcharge and discharge inside the electrochemical device.

[0073] The present application also provides an electronic device, which includes the electrochemical device in any of the above embodiments. Therefore, the electronic device provided by the present application has good performance.

[0074] The present application does not particularly limit the type of electronic device, which can be any electronic device known in the prior art. In some embodiments, the electronic device can include but is not limited to a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo 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, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0075] The preparation of the electrochemical device is described below in conjunction with specific embodiments. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation method is within the scope of this application.

[0076] Example

[0077] Hereinafter, taking lithium-ion batteries as an example, examples and comparative examples are given to more specifically describe the implementation of the electrochemical device of the present application. Those skilled in the art will understand that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope 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] Test Method

[0079] 1. High temperature (45°C) cycle capacity retention rate test method

[0080] The test steps for high temperature (45°C) cycle capacity retention rate are as follows:

[0081] (1) Place the lithium-ion battery at 45°C for 60 minutes;

[0082] (2) Charge the lithium-ion battery at a constant current of 1.2C to 4.2V, and charge at a constant voltage until the current is less than 0.7C;

[0083] (3) Charge the lithium-ion battery at a constant current of 0.7C to 4.5V, charge at a constant voltage until the current is less than 0.05C, and let it stand for 5 minutes;

[0084] (4) Discharge the lithium-ion battery at 0.5C constant current to 3V and let it stand for 5 minutes;

[0085] Step (2) to step (4) is one charge-discharge cycle, and steps (2) to step (4) are repeated 600 times. The discharge capacity of the lithium-ion battery in the first charge-discharge cycle is recorded as C1, and the discharge capacity of the lithium-ion battery in the 600th charge-discharge cycle is recorded as C600.

[0086] High temperature (45°C) cycle capacity retention rate = C600 / C1*100%.

[0087] 2. Test method for high rate discharge capacity retention at low temperature (-20℃)

[0088] The low temperature (-20℃) rate discharge test steps are as follows:

[0089] (1) Place the lithium-ion battery at -20°C and leave it there for 30 minutes;

[0090] (2) Discharge the lithium-ion battery at a rate of 0.2C to 3V and let it stand for 10 minutes;

[0091] (3) Charge the lithium-ion battery at a constant current of 1.2C to 4.2V, and charge at a constant voltage until the current is less than 0.6C;

[0092] (4) Charge the lithium-ion battery at a constant current of 0.6C to 4.5V, charge at a constant voltage until the current is less than 0.05C, and let it stand for 10 minutes;

[0093] (5) Discharge to 3V at a constant current rate of Cx, Cx = 0.2C, 0.5C, 1C, 1.5C, 2C;

[0094] Step (2) to step (5) is a discharge process. The discharge process is repeated according to step (2) to step (5) until all Cx rate discharge processes are tested. The discharge capacity of the lithium-ion battery after the 0.2C discharge process is recorded as D1. After traversing all Cx rate discharge processes from low to high, the discharge capacity of the tested lithium-ion battery is recorded as Dmax.

[0095] Low temperature (-20°C) high rate discharge capacity retention rate = Dmax / D1*100%.

[0096] Example 1-1

[0097] (1) Preparation of positive electrode

[0098] The positive electrode active material lithium cobalt oxide LiCoO2, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride PVDF are mixed in a mass ratio of 97.9:0.9:1.2, N-methylpyrrolidone NMP is added as a solvent, and stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry with a solid content of 75wt%. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 9μm, and dried and cold pressed at 85°C to obtain a positive electrode with a single-sided coating of a positive electrode material layer with a thickness of 95μm. After that, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode with a double-sided coating of a positive electrode material layer. After cutting and welding the positive electrode aluminum pole ear, a positive electrode with a specification of 74mm×851mm is obtained for standby use, and the compaction density of the positive electrode material layer is 4.20g / cm 3 .

[0099] (2) Preparation of negative electrode

[0100] The negative electrode active material artificial graphite, the binder styrene butadiene rubber SBR, and the thickener sodium carboxymethyl cellulose CMC are mixed in a mass ratio of 97.4:1.4:1.2, and then deionized water is added as a solvent, and stirred evenly under the action of a vacuum mixer to obtain a negative electrode slurry with a solid content of 50wt%. 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 and cold pressed at 85°C to obtain a negative electrode with a negative electrode material layer coated on one side with a thickness of 130μm. After that, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode with a negative electrode material layer coated on both sides. After cutting and welding the negative electrode ear nickel ear, a negative electrode with a specification of 76mm×867mm is obtained for standby use, and the compaction density of the negative electrode material layer is 1.80g / cm 3 .

[0101] (3) Preparation of isolation membrane

[0102] The porous substrate layer adopts a 9 μm thick polypropylene film.

[0103] (4) Preparation of electrolyte

[0104] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1 is mixed to obtain a base solvent, and then the compound of formula I, the compound of formula II and lithium hexafluorophosphate (LiPF6) are dissolved in the above base solvent to obtain an electrolyte. Wherein, based on the mass of the electrolyte, the mass percentage of LiPF6 is 12.5%.

[0105] The mass percentages of the compound of formula I and the compound of formula II are shown in Table 1, and the rest is the base solvent.

[0106] (5) Assembly of lithium-ion electronics

[0107] The prepared positive electrode, separator, negative electrode and separator are stacked in order, so that the separator is between the positive electrode and the negative electrode to play a role of isolation, and then wound to obtain an electrode assembly. After welding the pole ear, the electrode assembly is placed in an aluminum plastic film packaging bag, placed in a vacuum oven at 85°C for 12 hours to remove moisture, and the prepared electrolyte is injected. After vacuum packaging, standing, formation, shaping, and capacity testing, a lithium-ion battery is obtained.

[0108] Examples 1-2 to 1-22 are the same as Example 1-1 except that the type and content A of the compound of formula I and the type and content B of the compound of formula II are adjusted in the preparation of the electrolyte as shown in Table 1. The mass percentage of the base solvent changes accordingly, and the mass percentage of the lithium salt remains unchanged.

[0109] Comparative Example 1-1 is the same as Example 1-6 except that the compound of Formula I is not added to the electrolyte, wherein the mass percentage of the base solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged.

[0110] Comparative Example 1-2 is the same as Example 1-6 except that the compound of Formula II is not added to the electrolyte, wherein the mass percentage of the base solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged.

[0111] Comparative Examples 1-3 to Comparative Examples 1-6 are the same as Examples 1-6 except that the content A of the compound of Formula I and the content B of the compound of Formula II are adjusted as shown in Table 1 in the preparation of the electrolyte. The mass percentage of the base solvent changes accordingly, and the mass percentage of the lithium salt remains unchanged.

[0112] Examples 2-1 to 2-8 are the same as Example 1-6 except that the type and content C of the first component in the preparation of the electrolyte are adjusted as shown in Table 2. The mass percentage of the base solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged.

[0113] Examples 3-1 to 3-6 are the same as Examples 1-6 except that the type and content D of the second component in the preparation of the electrolyte are adjusted as shown in Table 3. The mass percentage of the base solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged.

[0114] Example 3-7 is the same as Example 1-6 except that the first component and the second component are added in the preparation of the electrolyte as shown in Table 3. The mass percentage of the base solvent changes accordingly, while the mass percentage of the lithium salt remains unchanged.

[0115] Examples 4-1 to 4-5 are the same as Examples 1-6 except that nitrile compounds are added in the preparation of the electrolyte as shown in Table 4. The mass percentage of the base solvent changes accordingly, while the mass percentage of the lithium salt remains unchanged.

[0116] Example 4-6 is the same as Example 1-6 except that the nitrile compound and the first component are added in the preparation of the electrolyte as shown in Table 4. The mass percentage of the base solvent changes accordingly, while the mass percentage of the lithium salt remains unchanged.

[0117] Example 4-7 is the same as Example 1-6 except that the nitrile compound and the second component are added in the preparation of the electrolyte as shown in Table 4. The mass percentage of the base solvent is changed accordingly, and the mass percentage of the lithium salt remains unchanged.

[0118] Example 4-8 is the same as Example 1-6 except that the nitrile compound, the first component and the second component are added in the preparation of the electrolyte as shown in Table 4. The mass percentage of the base solvent changes accordingly, while the mass percentage of the lithium salt remains unchanged.

[0119] The preparation parameters and performance parameters of Examples 1-1 to 1-22 and Comparative Examples 1-1 to 1-6 are shown in Table 1.

[0120] Table 1

[0121]

[0122]

[0123] Note: “ / ” in Table 1 means there is no corresponding parameter.

[0124] In this application, regarding the performance parameters, the greater the high-temperature 45°C cycle capacity retention rate, the better the high-temperature 45°C cycle capacity retention rate of the lithium-ion battery, and the greater the low-temperature -20°C high-rate discharge capacity retention rate, the better the high-rate discharge capacity retention rate of the electrochemical device in a low-temperature -20°C environment.

[0125] It can be seen from Comparative Example 1-1, Comparative Example 1-3 to Comparative Example 1-4, and Example 1-1 to Example 1-13 that the compound of formula I and the compound of formula II are added to the electrolyte, and the content of the compound of formula I satisfies 0.01%≤A≤70%, and from Comparative Example 1-2, Comparative Example 1-5 to Comparative Example 1-6, and Example 1-14 to Example 1-22 that when the compound of formula I and the compound of formula II are added to the electrolyte, and the content B of the compound of formula II satisfies 2.0%≤B≤20%, the high temperature 45°C cycle capacity retention rate and the low temperature -20°C high rate discharge capacity retention rate are both increased, indicating that the compound of formula I and the compound of formula II can take into account the improvement of the high temperature 45°C cycle capacity retention rate and the high rate discharge capacity retention rate under a low temperature -20°C environment of the lithium ion battery.

[0126] It can be seen from Comparative Examples 1-3 to Comparative Examples 1-4 and Examples 1-1 to Examples 1-10 that when the content A of the compound of formula I is less than 0.01%, the amount of the compound of formula I added is too small, and there is almost no improvement effect on the low temperature (-20°C) high rate discharge capacity retention rate of the lithium ion battery. When the content A of the compound of formula I is greater than 70%, the content of the compound of formula I is too high, which will accelerate the oxidative decomposition of the electrolyte to generate HF, and the antioxidant capacity of the compound of formula II is insufficient, resulting in a decrease in the high temperature 45°C cycle capacity retention rate of the lithium ion battery.

[0127] It can be seen from Comparative Examples 1-3 to Comparative Examples 1-4 and Examples 1-14 to Examples 1-19 that when the content B of the compound of formula II is less than 2.0%, the content of the compound of formula II is too little, the antioxidant capacity of the electrolyte is insufficient, and it is difficult to inhibit the adverse reactions caused by the compound of formula I accelerating the oxidative decomposition of components in the electrolyte, resulting in the deterioration of the low-temperature -20°C high-rate discharge capacity retention rate of the electrochemical device; when the content B of the compound of formula II is greater than 20.0%, the content of the compound of formula II is too high, the conductivity of the electrolyte is insufficient, and the high-temperature 45°C cycle capacity retention rate and the low-temperature -20°C high-rate discharge capacity retention rate of the electrochemical device are both reduced.

[0128] The preparation parameters and performance parameters of Example 2-1 to Example 2-8 are shown in Table 2.

[0129] Table 2

[0130]

[0131]

[0132] Note: “ / ” in Table 2 means there is no corresponding parameter.

[0133] Adding the first component to the electrolyte can improve the ion conductivity of the electrolyte. The compound of formula I, the compound of formula II and the first component are added to the electrolyte together to improve the problem of high viscosity of the electrolyte due to the presence of the first component. It can be seen from Examples 1-6 and 2-1 to 2-8 that when the first component is added to the electrolyte, the high temperature 45°C cycle capacity retention rate and the low temperature -20°C high rate discharge capacity retention rate of the lithium ion battery are increased, indicating that the high temperature 45°C cycle capacity retention rate and the low temperature -20°C high rate discharge capacity retention rate of the lithium ion battery are improved.

[0134] The preparation parameters and performance parameters of Examples 3-1 to 3-7 are shown in Table 3.

[0135] Table 3

[0136]

[0137] Note: “ / ” in Table 3 means there is no corresponding parameter.

[0138] The second component has a lower viscosity and can improve the wetting ability of the electrolyte. Both the compound of formula I and the compound of formula II have good dissociation ability for lithium salts. When used in combination with the second compound, the second compound can make up for the lack of dissociation ability of the second compound for lithium salts and improve the conductivity of the electrolyte. It can be seen from Examples 1-6 and 3-1 to 3-7 that when the second component is added to the electrolyte, the high-temperature 45°C cycle capacity retention rate and the low-temperature -20°C high-rate discharge capacity retention rate of the lithium-ion battery are increased, indicating that the high-temperature 45°C cycle capacity retention rate and the low-temperature -20°C high-rate discharge capacity retention rate of the lithium-ion battery are improved.

[0139] The preparation parameters and performance parameters of Example 4-1 to Example 4-8 are shown in Table 4.

[0140] Table 4

[0141]

[0142] Note: “ / ” in Table 4 means there is no corresponding parameter.

[0143] The nitrile compound can act synergistically with the compound of formula I to form a positive electrode interface passivation layer rich in LiF and cyano groups, which can improve the positive electrode interface stability. It can be seen from Examples 1-6 and 4-1 to 4-8 that when nitrile compounds are added to the electrolyte, the high temperature 45°C cycle capacity retention rate and the low temperature -20°C high rate discharge capacity retention rate of the lithium ion battery are increased, indicating that nitrile compounds have an improvement effect on the high temperature 45°C cycle capacity retention rate and the low temperature -20°C high rate discharge capacity retention rate of the lithium ion battery.

[0144] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method or article.

[0145] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0146] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, 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. An electrolyte, characterized in that: Including compounds of formula I and compounds of formula II; Wherein, in Formula I, R is selected from C2-C6 alkyl which is unsubstituted or substituted by R0, C2-C6 alkenyl which is unsubstituted or substituted by R0, C2-C6 alkynyl which is unsubstituted or substituted by R0, C3-C6 nitrogen-containing heteroaryl which is unsubstituted or substituted by R0, C6-C 12 Any of the aryl groups, the substituents R0 of each group are independently selected from any of the unsubstituted or substituted C1-C6 alkyl groups, and when substituted, the substituent is fluorine; In formula II, R1 to R5 are each independently selected from any one of fluorine, unsubstituted or substituted C1-C5 alkyl, unsubstituted or substituted C1-C5 phosphate, unsubstituted or substituted C1-C5 sulfonic acid, and unsubstituted or substituted C1-C5 ester. When substituted, the substituent is fluorine; Based on the mass of the electrolyte, the mass percentage of the compound of formula I is A, and the mass percentage of the compound of formula II is B, wherein 0.01%≤A≤70%, and 2.0%≤B≤20%.

2. The electrolyte according to claim 1, characterized in that The electrolyte satisfies at least one of the following conditions: (1)0.5％≤A≤50％； (2)4％≤B≤8％； (3)0.17≤A / B≤18.

3. The electrolyte according to claim 1, characterized in that The compounds of formula I include at least one of the following compounds:

4. The electrolyte according to claim 1, characterized in that The compound of formula II includes at least one of the following compounds:

5. The electrolyte according to claim 1, characterized in that The electrolyte further includes a first component, the first component including at least one of bisfluoroethylene carbonate, propylene carbonate, or ethylene carbonate; Based on the mass of the electrolyte, the mass percentage of the first component is C, wherein 0.8≤C / (A+B)≤1.

15.

6. The electrolyte according to claim 1, characterized in that The electrolyte further includes a second component, the second component including at least one of diethyl carbonate, propyl propionate or ethyl propionate; Based on the mass of the electrolyte, the mass percentage of the second component is D, wherein 0.9≤D / (A+B)≤2.

7. The electrolyte according to claim 1, characterized in that The electrolyte further includes a nitrile compound, wherein the nitrile compound includes at least one of a dinitrile compound and a trinitrile compound; Based on the mass of the electrolyte, the mass percentage of the nitrile compound is E, wherein 2%≤E≤10%.

8. The electrolyte according to claim 7, characterized in that The dinitrile compound includes at least one of adiponitrile, succinonitrile, glutaronitrile, and 1,4-dicyano-2-butene; The trinitrile compound includes at least one of 1,3,6-hexanetrinitrile and 1,3,5-pentanetricarboxynitrile.

9. An electrochemical device, characterized in that: The invention comprises the electrolyte according to any one of claims 1 to 8.

10. An electronic device, characterized in that: The electrochemical device according to claim 9 is included.

Images