Electrolyte, and electrochemical device and electronic apparatus comprising same

Abstract

The invention provides an electrolyte, and an electrochemical device and electronic equipment containing the electrolyte. The electrolyte comprises a compound as shown in a formula I and fluorocarboxylic ester, in the formula, R1, R2, R3 and R4 are independently selected from any one of a fluorine atom, a difluorophosphoryloxy group, a methanesulfonic acid group and a trifluoromethanesulfonic acid group respectively, and R1, R2, R3 and R4 are independently selected from any one of a fluorine atom, a difluorophosphoryloxy group, a methanesulfonic acid group and a trifluoromethanesulfonic acid group; based on the total mass of the electrolyte, the mass percentage of the compound shown in the formula I is A, the mass percentage of the fluorocarboxylate in the electrolyte is B, A is larger than or equal to 0.01% and smaller than or equal to 5%, and B is larger than or equal to 10% and smaller than or equal to 80%. According to the present invention, the compound represented by the formula I and the fluorocarboxylate are matched for use in the electrolyte, such that the cycle and the high-temperature storage performance of the electrochemical device are significantly improved.

Description

Technical Field

[0001] This application belongs to the technical field of batteries, particularly to the technical field of lithium-ion batteries, and specifically relates to an electrolyte and an electrochemical device and an electronic device comprising the electrolyte. Background Art

[0002] Electrochemical devices, especially lithium-ion batteries, are increasingly widely used in the field of portable electronic products because they have advantages such as high energy density, high working voltage, light weight, low self-discharge rate, long cycle life, no memory effect, and environmental friendliness. In addition to smart electronic products (including mobile phones, laptops, cameras, etc.) and energy storage products, there is an increasing demand in the fields of higher-power electronic products such as electric vehicles, power tools, drones, and electric ships. High-power electronic products also have higher requirements for the high-temperature gas generation and safety performance of electrochemical devices, especially lithium-ion batteries. Therefore, it is particularly important to develop electrochemical devices, especially lithium-ion batteries, that can balance high-temperature storage and cycling performance. Summary of the Invention

[0003] The purpose of this application is to provide an electrolyte, an electrochemical device, and an electronic device comprising the electrolyte to improve the high-temperature storage and cycling performance of the electrochemical device. The specific solutions are as follows:

[0004] According to the first aspect of this application, this application provides a non-aqueous electrolyte, and the electrolyte comprises: a compound of formula I and a fluorinated carboxylic acid ester;

[0005]

[0006] Wherein, R 1 , R 2 , R 3 and R 4 each independently selected from any one of a fluorine atom, a difluorophosphoryloxy group, a methylsulfonic acid group, and a trifluoromethylsulfonic acid group; based on the total mass of the electrolyte, the mass percentage of the compound of formula I is A, and the mass percentage of the fluorinated carboxylic acid ester is B, wherein, A satisfies: 0.01% ≤ A ≤ 5%, and B satisfies: 10% ≤ B ≤ 80%.

[0007] Electrolytes usually have the problem of cyclic gas generation, and the problem of gas generation mainly stems from the poor stability of the solvent, which is prone to side reactions with the positive and negative electrodes. When fluorinated carboxylic esters are used as solvents, due to their relatively high oxidation resistance, the decomposition of the electrolyte solvent can be reduced. However, the application of fluorinated carboxylic esters also has obvious drawbacks. As a solvent, fluorinated carboxylic esters will reduce the kinetic performance of the electrolyte, thereby affecting the cycle and impedance performance. Through research, it is found in this application that when Compound I is introduced as an additive into the electrolyte containing fluorinated carboxylic esters for combined use, the kinetics of the electrolyte can be improved, and while the cycle performance is improved, the high-temperature storage performance can also be significantly improved. When Compound I is introduced into the electrolyte containing fluorinated carboxylic esters, on the one hand, due to the relatively large anion radius of Compound I, it is more easily dissociated, which can improve the kinetics of the electrolyte and improve the cycle performance; on the other hand, Compound I can also form an interfacial film rich in boron and phosphorus, or boron and sulfur elements at the positive electrode interface, further improving the oxidation resistance of the positive electrode interface, reducing the probability of side reactions, and stabilizing the positive electrode interface, so as to improve the high-temperature storage performance of the electrochemical device. And by controlling the mass percentage A of Compound I and the mass percentage B of fluorinated carboxylic esters within the above ranges, the high-temperature storage of the electrochemical device can be further improved while having almost no impact on the impedance of the positive electrode interface. If it exceeds the above ranges, the performance such as cycle and high-temperature storage will deteriorate significantly. For example, if the dosage of fluorinated carboxylic esters is too high, the kinetics of the electrolyte will deteriorate severely, seriously affecting the improvement of performance such as cycle and high-temperature storage. If the dosage of fluorinated carboxylic esters is too low, no obvious improvement effect can be achieved.

[0008] In some embodiments of this application, the mass percentage A of Compound I satisfies: 0.1% ≤ A ≤ 5%. When the mass percentage A of Compound I is further controlled within the above range, the cycle and high-temperature storage performance can be further improved.

[0009] In some embodiments of this application, the ratio A / B of the mass percentage A of Compound I to the mass percentage B of fluorinated carboxylic esters satisfies: 0.002 ≤ A / B ≤ 0.2. When the ratio A / B of the mass percentage A of Compound I to the mass percentage B of fluorinated carboxylic esters is further controlled within the above range, the cycle and high-temperature storage performance can be further improved.

[0010] In some embodiments of the present application, the mass percentage B of the fluorinated carboxylic acid ester satisfies: 20% ≤ B ≤ 80%. In some embodiments of the present application, the mass percentage B of the fluorinated carboxylic acid ester satisfies: 30% ≤ B ≤ 70%. In some embodiments of the present application, the mass percentage B of the fluorinated carboxylic acid ester satisfies: 40% ≤ B ≤ 70%. The content of the fluorinated carboxylic acid ester will seriously affect the kinetics of the electrolyte. In the technical solution provided by the present application, when the compound of Formula I is used in combination with the fluorinated carboxylic acid ester, further regulating the mass percentage B of the fluorinated carboxylic acid ester within the above range can further improve the oxidation resistance of the electrolyte without causing the deterioration of the kinetics of the electrolyte, achieving a better improvement effect on the cycle performance.

[0011] In some embodiments of the present application, the compound of Formula I includes at least one of the following compounds of Formula I-1 to Formula I-9:

[0012]

[0013] In the technical solution provided by the present application, when at least one of the above compounds is selected as the compound of Formula I, the combination with the fluorinated carboxylic acid ester in the electrolyte has a better effect, and can further improve the cycle and high-temperature storage performance.

[0014] In some embodiments of the present application, the fluorinated carboxylic acid ester includes at least one of the following compounds of Formula 1 to Formula 8:

[0015]

[0016] In the technical solution provided by the present application, when at least one of the above compounds is selected as the fluorinated carboxylic acid ester, the combination with the compound of Formula I in the electrolyte has a better effect, and can further improve the cycle and high-temperature storage performance.

[0017] In some embodiments of the present application, the electrolyte further includes fluoroethylene carbonate. In the technical solution provided by the present application, when the compound of Formula I is used in combination with the fluorinated carboxylic acid ester in the electrolyte, a SEI film containing boron, phosphorus and fluorine can be formed at the negative electrode interface for the compound of Formula I and the fluorinated carboxylic acid ester. However, due to the content limitation, it cannot completely cover the entire negative electrode interface. When fluoroethylene carbonate is further introduced into the electrolyte containing the compound of Formula I and the fluorinated carboxylic acid ester, fluoroethylene carbonate can form a structure rich in LiF and poly-VC at the negative electrode interface, uniformly wrap and cover elements such as boron and phosphorus at the negative electrode interface, and form a stable SEI film, achieving the effect of further improving the cycle performance.

[0018] In some embodiments of the present application, the electrolyte further includes fluoroethylene carbonate. Based on the total mass of the electrolyte, the mass percentage of fluoroethylene carbonate is F, and F satisfies 0.3% ≤ F ≤ 5%. When the mass percentage F of fluoroethylene carbonate is adjusted within the above range, further improvement effects can be achieved.

[0019] In some embodiments of the present application, the ratio F / (A + B) between the mass percentage F of fluoroethylene carbonate, the mass percentage A of the compound of formula I, and the mass percentage B of the fluorocarboxylate satisfies the following relationship: 0.005 ≤ F / (A + B) ≤ 0.49; preferably, F / (A + B) satisfies the following relationship: 0.005 ≤ F / (A + B) ≤ 0.2. In the further technical solution provided by the present application, when the ratio relationship F / (A + B) between the mass percentage F of fluoroethylene carbonate, the mass percentage A of the compound of formula I, and the mass percentage B of the fluorocarboxylate is adjusted within the above range, excessive decomposition can be reduced, and a better improvement effect on the cycle performance can be achieved. When the ratio relationship F / (A + B) between fluoroethylene carbonate and the compound of formula I and the fluorocarboxylate is lower than the above range, with respect to the contents of the compound of formula I and the fluorocarboxylate, if the content of fluoroethylene carbonate is too low, effective protection cannot be formed on the negative electrode interface. When the ratio relationship F / (A + B) between fluoroethylene carbonate and the compound of formula I and the fluorocarboxylate is higher than the above range, with respect to the contents of the compound of formula I and the fluorocarboxylate, the content of fluoroethylene carbonate is too high. At this time, too much fluoroethylene carbonate participates in reduction, which will cause excessive accumulation of carbonates on the negative electrode. At high temperatures, the decomposition of carbonates generates CO2, resulting in deterioration of the high-temperature storage performance.

[0020] In some embodiments of the present application, the electrolyte further includes a sulfur-oxygen compound. In some embodiments of the present application, the electrolyte includes a sulfur-oxygen compound, and the sulfur-oxygen compound includes at least one of 1,3-propane sultone, 1,3-propene sultone, and ethylene sulfate. In a further solution of the present application, when a sulfur-oxygen compound is further introduced into the electrolyte containing the compound of formula I and the fluorocarboxylate, the solvation structure jointly participated by the cyclic sulfur-oxygen double bond compound, the compound of formula I, the fluorocarboxylate, and the lithium salt can improve the migration ability of lithium ions, improve the conductivity of the electrolyte, and at the same time participate in redox reactions at the positive and negative electrode interfaces to form an interface film rich in sulfur elements. These sulfur-containing structures can reduce the influence of transition metal ions in the electrolyte on the SEI, thereby further improving the high-temperature storage performance of the electrochemical device.

[0021] In some embodiments of the present application, the electrolyte further includes a sulfur-oxide compound. Based on the total mass of the electrolyte, the mass percentage of the sulfur-oxide compound is S, and S satisfies: 0.1% ≤ S ≤ 3%. Controlling the mass percentage S of the sulfur-oxide compound in the electrolyte within the above range can further improve the conductivity of the electrolyte and the high-temperature storage performance of the electrochemical device.

[0022] In some embodiments of the present application, the ratio S / (A + B) between the mass percentage S of the sulfur-oxide compound, the mass percentage A of the compound of Formula I, and the mass percentage B of the fluorinated carboxylate satisfies the following relationship: 0.002 ≤ S / (A + B) ≤ 0.1. In the further technical solution provided by the present application, when the ratio relationship S / (A + B) between the mass percentage S of the sulfur-oxide compound, the mass percentage A of the compound of Formula I, and the mass percentage B of the fluorinated carboxylate is controlled within the above range, the high-temperature storage performance of the electrochemical device can be further improved. If the ratio S / (A + B) is too high, the content of the sulfur-oxide compound is too high relative to the compound of Formula I and the fluorinated carboxylate, and more organic SEI layers will be formed by reduction at the negative electrode. The excessive organic SEI layers have poor high-temperature resistance, which will lead to a decline in the high-temperature storage performance of the electrochemical device. If the ratio S / (A + B) is too low, the content of the sulfur-oxide compound is too low relative to the compound of Formula I and the fluorinated carboxylate, and no improvement effect can be achieved.

[0023] According to the second aspect of the present application, the present application also provides an electrochemical device, and the electrochemical device includes the electrolyte according to any one of the first aspect of the present application. The electrochemical device containing the above electrolyte has good cycling and high-temperature storage performance.

[0024] In some embodiments of the present application, the electrochemical device further includes a positive electrode, and the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material of the positive electrode active material layer is a lithium nickel cobalt manganese oxide ternary positive electrode material. Using the above electrolyte system provided by the present application in combination with a positive electrode whose positive electrode active material is a lithium nickel cobalt manganese oxide ternary positive electrode material can enable the electrochemical device to have better high-temperature storage and cycling performance.

[0025] According to the third aspect of the present application, the present application also provides an electronic device, and the electronic device includes the electrochemical device according to the second aspect of the present application. Detailed Embodiments

[0026] The technical solutions of the present application are further illustrated by the following specific embodiments. The specific embodiments do not represent a limitation on the protection scope of the present application. Some non-essential modifications and adjustments made by others based on the concept of the present application still fall within the protection scope of the present application.

[0027] 1. Electrolyte

[0028] According to the first aspect of the present application, the present application provides a non-aqueous electrolyte, and the electrolyte comprises: a compound of Formula I and a fluorinated carboxylic acid ester;

[0029]

[0030] wherein, R 1 , R 2 , R 3 and R 4 are each independently selected from any one of a fluorine atom, a difluorophosphoryloxy group, a methylsulfonic acid group, and a trifluoromethylsulfonic acid group; based on the total mass of the electrolyte, the mass percentage of the compound of Formula I is A, and the mass percentage of the fluorinated carboxylic acid ester is B, wherein, A satisfies: 0.01% ≤ A ≤ 5%, and B satisfies: 10% ≤ B ≤ 80%.

[0031] Specifically, the structural formula of the difluorophosphoryloxy group can be When R 1 , R 2 , R 3 or R 4 is selected from the difluorophosphoryloxy group, O in P-O in the structural formula of the difluorophosphoryloxy group is connected to B to form the compound of Formula I. Specifically, the structural formula of the methylsulfonic acid group can be When R 1 , R 2 , R 3 or R 4 is selected from the methylsulfonic acid group, O in S-O in the methylsulfonic acid group is connected to B to form the compound of Formula I. The structural formula of the trifluoromethylsulfonic acid group can be When R 1 , R 2 , R 3 or R 4 is selected from the trifluoromethylsulfonic acid group, O in S-O in the trifluoromethylsulfonic acid group is connected to B to form the compound of Formula I. Specifically, the fluorinated carboxylic acid ester used in the present application is a type of carboxylic acid ester compound containing fluorine atoms.

[0032] Specifically, in some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage A of the compound of Formula I may be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0% or a range composed of any two of the above values. Specifically, in some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage B of the fluorinated carboxylate may be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80% or a range composed of any two of the above values.

[0033] The electrolyte usually has the problem of cyclic gas generation, and the problem of gas generation mainly stems from the poor stability of the solvent, which is prone to side reactions with the positive and negative electrodes. When fluorinated carboxylic esters are used as solvents, due to their high oxidation resistance, the decomposition of the electrolyte solvent can be reduced. However, there are also obvious disadvantages in applying fluorinated carboxylic esters in the electrolyte. As a solvent, fluorinated carboxylic esters will reduce the kinetic performance of the electrolyte, thus affecting the cycle performance. Through research, it is found in this application that when a compound of Formula I is introduced as an additive and used in combination with the electrolyte containing fluorinated carboxylic esters, the kinetics of the electrolyte can be improved, and while improving the cycle performance, the high-temperature storage performance can also be significantly improved. Introducing the compound of Formula I into the electrolyte containing fluorinated carboxylic esters, on the one hand, due to the relatively large anion radius of the compound of Formula I, it is more easily dissociated, which can improve the kinetics of the electrolyte and improve the cycle performance; on the other hand, the compound of Formula I can also form an interfacial film rich in boron and phosphorus, or boron and sulfur elements at the positive electrode interface, further improving the oxidation resistance of the positive electrode interface, reducing the probability of side reactions, and stabilizing the positive electrode interface to achieve the improvement of the high-temperature storage performance of the electrochemical device. And through further research in this application, it is found that when the mass percentage A of the compound of Formula I and the mass percentage A of the compound of Formula I are adjusted within the above ranges, the high-temperature storage of the electrochemical device can be further improved while having almost no impact on the impedance of the positive electrode interface. If it exceeds the above range, the performance of the electrochemical device such as cycling and high-temperature storage will deteriorate significantly. For example, if the dosage of fluorinated carboxylic esters is too high, the kinetics of the electrolyte will deteriorate severely, seriously affecting the improvement of the performance of the electrochemical device such as cycling and high-temperature storage. If the dosage of fluorinated carboxylic esters is too low, there will be no obvious improvement effect.

[0034] In some embodiments of this application, the mass percentage A of the compound of Formula I satisfies: 0.1% ≤ A ≤ 5%. When the mass percentage A of the compound of Formula I in the electrolyte is further adjusted within the above range, the effect of further improving the cycle and high-temperature storage performance of the electrochemical device can be achieved.

[0035] In some embodiments of the present application, the ratio A / B of the mass percentage A of the compound of Formula I to the mass percentage B of the fluorinated carboxylate satisfies: 0.002 ≤ A / B ≤ 0.2. Specifically, in some embodiments of the present application, the ratio A / B between the mass percentage A of the compound of Formula I in the electrolyte and the mass percentage B of the fluorinated carboxylate in the electrolyte may be 0.002, 0.0025, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.0125, 0.02, 0.025, 0.03, 0.04, 0.05, 0.06, 0.0625, 0.07, 0.08, 0.09, 0.1, 0.125, 0.2 or a range composed of any two of the above values. When the ratio A / B of the mass percentage A of the compound of Formula I in the electrolyte to the mass percentage B of the fluorinated carboxylate in the electrolyte is further regulated within the above range, the effects of further improving the cycle and high-temperature storage performance of the electrochemical device can be achieved.

[0036] In some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage B of the fluorinated carboxylate satisfies: 20% - 80%. Preferably, the mass percentage B of the fluorinated carboxylate satisfies: 30% - 70%. Preferably, the mass percentage B of the fluorinated carboxylate satisfies: 40% - 70%. The content of the fluorinated carboxylate will seriously affect the kinetic performance of the electrolyte. In the technical solution provided by the present application, when the compound of Formula I and the fluorinated carboxylate are used in combination in the electrolyte, further regulating the mass percentage B of the fluorinated carboxylate in the electrolyte within the above range can achieve the effect of further significantly improving the oxidation resistance of the electrolyte without causing the deterioration of the kinetics of the electrolyte, and achieving a better improvement effect on the cycle performance. If the mass percentage B of the fluorinated carboxylate in the electrolyte is higher than the above range, it will cause serious deterioration of the kinetics of the electrolyte, seriously affecting the improvement of the performance of the electrochemical device such as cycle and high-temperature storage. If the mass percentage B of the fluorinated carboxylate in the electrolyte is lower than the above range, the obvious improvement effect cannot be achieved.

[0037] In some embodiments of the present application, the compound of Formula I includes at least one of the following compounds:

[0038]

[0039] In the technical solution provided by the present application, when at least one of the above compounds is selected as the compound of Formula I, the effect is better when used in combination with the fluorinated carboxylate in the electrolyte, and the performance of the electrochemical device such as cycle and high-temperature storage can be further improved.

[0040] In some embodiments of the present application, the fluorinated carboxylic acid ester includes at least one of the following compounds:

[0041]

[0042] In the technical solution provided by the present application, when at least one of the above compounds is selected as the fluorinated carboxylic acid ester, the effect is better when used in combination with the compound of Formula I in the electrolyte, and the performance of the electrochemical device such as cycle and high-temperature storage can be further improved.

[0043] In some embodiments of the present application, the electrolyte further includes fluoroethylene carbonate. In the technical solution provided by the present application, when the compound of Formula I and the fluorinated carboxylic acid ester are used in combination in the electrolyte, an SEI film containing boron, phosphorus and fluorine can be formed at the negative electrode interface of the compound of Formula I and the fluorinated carboxylic acid ester. However, due to content limitations, it cannot completely cover the entire negative electrode interface. When fluoroethylene carbonate is further introduced into the electrolyte containing the compound of Formula I and the fluorinated carboxylic acid ester, fluoroethylene carbonate can form a structure rich in LiF and poly-VC at the negative electrode interface, and evenly wrap and cover elements such as boron and phosphorus at the negative electrode interface to form a stable SEI film, achieving the effect of further improving the cycle performance of the electrochemical device.

[0044] In some embodiments of the present application, the electrolyte further includes fluoroethylene carbonate. Based on the total mass of the electrolyte, the mass percentage of fluoroethylene carbonate is F, and F satisfies 0.3% ≤ F ≤ 5%. Specifically, in some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage F of fluoroethylene carbonate can be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0% or a range composed of any two of the above values. When the mass percentage F of fluoroethylene carbonate is regulated within the above range, a further improvement effect can be achieved.

[0045] In some embodiments of the present application, the ratio F / (A + B) between the mass percentage F of the fluorinated ethylene carbonate, the mass percentage A of the compound of Formula I, and the mass percentage B of the fluorinated carboxylic acid ester satisfies the following relationship: 0.005 ≤ F / (A + B) ≤ 0.49. Specifically, in some embodiments of the present application, the ratio F / (A + B) between the mass percentage F of the fluorinated ethylene carbonate, the mass percentage A of the compound of Formula I, and the mass percentage B of the fluorinated carboxylic acid ester can be 0.005, 0.0055, 0.006, 0.00625, 0.0065, 0.007, 0.0075, 0.008, 0.0085, 0.009, 0.01, 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, 0.095, 0.1, 0.125, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5 or a range composed of any two of the above values. Preferably, the ratio F / (A + B) between the mass percentage F of the fluorinated ethylene carbonate, the mass percentage A of the compound of Formula I, and the mass percentage B of the fluorinated carboxylic acid ester satisfies the following relationship: 0.005 ≤ F / (A + B) ≤ 0.2. In the further technical solution provided by the present application, when the ratio relationship F / (A + B) between the mass percentage F of the fluorinated ethylene carbonate, the mass percentage A of the compound of Formula I, and the mass percentage B of the fluorinated carboxylic acid ester in the electrolyte is adjusted within the above range, the increase in interfacial impedance caused by excessive decomposition of the electrolyte can be reduced, achieving a better effect of improving the cycle performance of the electrochemical device. When the ratio relationship F / (A + B) between the fluorinated ethylene carbonate, the compound of Formula I, and the fluorinated carboxylic acid ester is lower than the above range, with respect to the contents of the compound of Formula I and the fluorinated carboxylic acid ester, if the content of the fluorinated ethylene carbonate is too low, effective protection of the negative electrode interface cannot be formed. When the ratio relationship F / (A + B) between the fluorinated ethylene carbonate, the compound of Formula I, and the fluorinated carboxylic acid ester is higher than the above range, with respect to the contents of the compound of Formula I and the fluorinated carboxylic acid ester, the content of the fluorinated ethylene carbonate is too high. At this time, too much fluorinated ethylene carbonate participates in reduction, which will cause too much carbonate to accumulate on the negative electrode. At high temperatures, the decomposition of the carbonate generates CO2, resulting in the deterioration of the high-temperature storage performance of the electrochemical device.

[0046] In some embodiments of the present application, the electrolyte further includes a sulfur-oxygen compound. In some embodiments of the present application, the electrolyte further includes a sulfur-oxygen compound, and the sulfur-oxygen compound includes at least one of 1,3-propane sultone, 1,3-propene sultone, and ethylene sulfate. In a further aspect of the present application, a sulfur-oxygen compound is further introduced into the electrolyte containing the compound of Formula I and the fluorinated carboxylate. The solvation structure in which the cyclic sulfur-oxygen double bond compound participates together with the compound of Formula I, the fluorinated carboxylate, and the lithium salt can improve the migration ability of lithium ions, improve the conductivity of the electrolyte, and at the same time participate in redox reactions at the positive and negative electrode interfaces to form an interfacial film rich in sulfur elements. These sulfur-containing structures can reduce the influence of transition metal ions in the electrolyte on the SEI, thereby further improving the cycle performance of the electrochemical device.

[0047] In some embodiments of the present application, the electrolyte further includes a sulfur-oxygen compound. Based on the total mass of the electrolyte, the mass percentage of the sulfur-oxygen compound is S, and S satisfies: 0.1% ≤ S ≤ 3%. Specifically, in some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage S of the sulfur-oxygen compound can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0% or a range composed of any two of the above values. Controlling the mass percentage S of the sulfur-oxygen compound in the electrolyte within the above range can further improve the conductivity of the electrolyte and the cycle performance of the electrochemical device.

[0048] In some embodiments of the present application, the ratio S / (A + B) between the mass percentage S of the sulfur-oxygen compound, the mass percentage A of the compound of Formula I, and the mass percentage B of the fluorinated carboxylate satisfies the following relationship: 0.002 ≤ S / (A + B) ≤ 0.1. Specifically, in some embodiments of the present application, the ratio S / (A + B) between the mass percentage S of the sulfur-oxygen compound, the mass percentage A of the compound of Formula I, and the mass percentage B of the fluorinated carboxylate can be 0.002, 0.0025, 0.003, 0.0035, 0.004, 0.0045, 0.005, 0.0055, 0.006, 0.0065, 0.007, 0.0075, 0.008, 0.0085, 0.009, 0.0095, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, 0.095, 0.1 or a range composed of any two of the above values. In the further technical solution provided by the present application, when the ratio relationship S / (A + B) between the mass percentage S of the sulfur-oxygen compound in the electrolyte, the mass percentage A of the compound of Formula I in the electrolyte, and the mass percentage B of the fluorinated carboxylate in the electrolyte is adjusted within the above range, the high-temperature storage performance of the electrochemical device can be further improved. If the ratio S / (A + B) is too high, the content of the sulfur-oxygen compound is too high relative to the compound of Formula I and the fluorinated carboxylate, and more organic SEI layers will be formed by reduction at the negative electrode. Excessive organic SEI layers have poor high-temperature resistance, which will lead to a decline in high-temperature storage performance. If the ratio S / (A + B) is too low, the content of the sulfur-oxygen compound is too low relative to the compound of Formula I and the fluorinated carboxylate, and no improvement effect can be achieved.

[0049] In some embodiments of the present application, the electrolyte provided by the present application may further include, but is not limited to, at least one of carbonate compounds, carboxylate compounds, ether compounds, or other organic solvents. The above-mentioned carbonate compounds include, but are not limited to, at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, propylene carbonate, butylene carbonate, or bis(2,2,2-trifluoroethyl) carbonate. The above-mentioned carboxylate compounds include, but are not limited to, at least one of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, γ-butyrolactone, 2,2-difluoroethyl acetate, valerolactone, butyrolactone, 2-fluoroethyl acetate, 2,2-difluoroethyl acetate, or trifluoroethyl acetate. The above-mentioned ether compounds include, but are not limited to, at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, or bis(2,2,2-trifluoroethyl) ether. The above-mentioned 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, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.

[0050] In some embodiments of the present application, the electrolyte of the present application may further include an electrolyte salt. The present application has no particular limitation on the type of the electrolyte salt, as long as the object of the present application can be achieved. For example, the electrolyte salt may include, but is not limited to, lithium salts or sodium salts. The lithium salts may include, but are not limited to, at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methyl, lithium difluoro(oxalato)phosphate, or lithium tetrafluoro(oxalato)phosphate; the sodium salts may include, but are not limited to, at least one of sodium hexafluorophosphate, sodium perchlorate, sodium trifluoromethanesulfonate, sodium tetrachloroaluminate, sodium tetrachloroborate, sodium tetrafluoroborate, sodium nitrate, sodium tetrafluorophosphate, sodium hexafluoroarsenate, sodium hexafluoroarsenate, or sodium hexafluoroantimonate. The present application has no particular limitation on the mass percentage content of the electrolyte salt, as long as the object of the present application can be achieved. In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt in the electrolyte is 10% to 20%. Specifically, based on the total mass of the electrolyte, the mass percentage of the lithium salt in the electrolyte is 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or a range composed of any two of the above values.

[0051] In some embodiments of the present application, the method for preparing the electrolyte provided by the present application is not limited and can be prepared in the manner of a conventional electrolyte. In some embodiments, the electrolyte of the present application can be prepared by mixing various components.

[0052] II. Electrochemical Device

[0053] According to the second aspect of the present application, the present application further provides an electrochemical device, and the electrochemical device includes the electrolyte according to any one of the first aspect of the present application. The electrochemical device containing the above electrolyte has good high-temperature storage and cycling performance.

[0054] In some embodiments of the present application, the electrochemical device of the present application includes, but is not limited to: all kinds of primary batteries, secondary batteries, fuel cells, solar cells or capacitors. In some embodiments of the present application, the electrochemical device is a lithium secondary battery. In some embodiments of the present invention, the lithium secondary battery includes, but is not limited to: lithium metal secondary battery, lithium ion secondary battery, lithium polymer secondary battery or lithium ion polymer secondary battery. In some embodiments of the present application, the electrochemical device of the present application can also be a non-negative electrode battery system.

[0055] 1. Positive Electrode

[0056] In some embodiments of the present application, the electrochemical device further includes a positive electrode, and the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The specific type of the positive electrode active material of the positive electrode active material layer is not specifically limited and can be selected according to requirements. In some embodiments of the present application, the positive electrode active material includes a lithium transition metal composite oxide. In some embodiments, the positive electrode active material is selected from at least one of the following: lithium cobaltate, lithium nickel manganese cobalt ternary material, lithium manganate, lithium nickel manganate or lithium iron phosphate.

[0057] In some embodiments of the present application, the positive electrode active material of the positive electrode active material layer is a lithium nickel cobalt manganese ternary positive electrode material. Using the above electrolyte system provided by the present application in combination with a positive electrode whose positive electrode active material of the positive electrode active material layer is a lithium nickel cobalt manganese ternary positive electrode material can make the electrochemical device have better high-temperature storage and cycling performance.

[0058] In some embodiments of the present application, the positive electrode active material layer further includes a binder. The binder can improve the binding between the positive electrode active material particles and can also improve the binding between the positive electrode active material and the positive electrode current collector. In some embodiments, the binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0059] In some embodiments of the present application, the positive electrode active material layer further includes a conductive agent to endow the electrode with conductivity. The conductive agent can include any conductive material as long as it does not cause chemical changes. Non-limiting examples of the conductive material include carbon-based materials (such as carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (such as metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (such as polyphenylene derivatives), and mixtures thereof.

[0060] In some embodiments of the present application, the positive electrode current collector is a metal, such as aluminum foil.

[0061] In some embodiments of the present application, the structure of the positive electrode is a positive electrode structure known to those skilled in the art and can be used in an electrochemical device.

[0062] In some embodiments of the present application, the preparation method of the positive electrode is a preparation method of the positive electrode known to those skilled in the art and can be used in an electrochemical device. For example, the positive electrode can be obtained by the following method: mixing the positive electrode active material, the conductive agent, and the binder in a solvent to prepare a positive electrode active material slurry, and coating the positive electrode active material slurry on the positive electrode current collector, drying, and cold pressing to form a positive electrode active material layer. In some embodiments, the solvent can include water, N-methylpyrrolidone, etc., but is not limited thereto.

[0063] 2. Negative electrode

[0064] In some embodiments of the present application, the electrochemical device further includes a negative electrode. The negative electrode includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material is any material that can electrochemically occlude and release metal ions such as lithium ions. In some embodiments of the present application, the negative electrode active material includes carbonaceous materials (graphite), silicon materials, hard carbon materials, or lithium metal materials. In some embodiments of the present application, the negative electrode active material includes one or more of the above.

[0065] In some embodiments of the present application, the negative electrode active material layer further includes a conductive agent to improve the electrode conductivity. Any conductive material can be used as the conductive material as long as it does not cause chemical changes. Examples of the conductive agent include, but are not limited to: carbon-based materials, such as carbon black, acetylene black, Ketjen black, carbon fiber, etc.; metal-based materials, such as metal powders or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives, etc.; or mixtures thereof.

[0066] In some embodiments of the present application, the negative electrode active material layer further includes a thickening agent. The thickening agent can be selected from sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF).

[0067] In some embodiments of the present application, the negative electrode active material layer further includes a binder, and the binder can include various adhesive polymers, such as polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0068] In some embodiments of the present application, the negative electrode current collector includes, but is not limited to: copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metals, and any combination thereof. In some embodiments, the negative electrode current collector is copper foil.

[0069] In some embodiments of the present application, the structure of the negative electrode can be a negative electrode structure known to those skilled in the art and can be used in electrochemical devices.

[0070] In some embodiments of the present application, the preparation method of the negative electrode is a preparation method of the negative electrode known to those skilled in the art and can be used in electrochemical devices. Exemplarily, the negative electrode can be obtained by the following method: mixing the negative electrode active material, conductive agent, and binder in a solvent, and heating the thickening agent as needed to prepare a negative electrode active material slurry, and coating the negative electrode active material slurry on the negative electrode current collector, drying, and cold pressing to form a negative electrode active material layer. In some embodiments, the solvent can include, but is not limited to, water, N-methylpyrrolidone.

[0071] 3. Separator

[0072] In some embodiments of the present application, the electrochemical device further includes a separator membrane, which is used to prevent short circuits. There are no particular limitations on the material and shape of the separator membrane, and it can be any technology disclosed in the prior art. For example, in some embodiments of the present application, the separator membrane includes a substrate layer, which is a non-woven fabric, film or composite film with a porous structure. The material of the substrate layer can be selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, the material of the substrate layer can be selected from at least one of a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film. A surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer can be a polymer layer, an inorganic layer or a layer formed by a mixture of a polymer and an inorganic substance. Specifically, the inorganic layer includes inorganic particles and a binder. The inorganic particles can be selected from one or a combination of several of alumina, silica, magnesia, 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 binder can be selected from one or a combination of several of polyvinylidene fluoride, a polymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinyl pyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

[0073] In some embodiments of the present application, the preparation method of the electrochemical device provided in the present application is not limited, and it can be prepared in the manner of a conventional electrochemical device. In some embodiments, the electrochemical device of the present application can be prepared by the following method: stack the positive electrode, the separator membrane, and the negative electrode in sequence, so that the separator membrane is located between the positive and negative electrodes to play a role in isolation, and then wind it to obtain a bare battery cell; after welding the tabs, place the bare battery cell in an outer packaging foil-aluminum plastic film, and inject the prepared electrolyte, and then through processes such as vacuum packaging, standing, formation, shaping, and capacity testing, an electrochemical device is obtained.

[0074] III. Electronic Equipment

[0075] According to the third aspect of the present application, the present application also provides an electronic device, which includes the electrochemical device described in the second aspect of the present application. In some embodiments, the electronic devices of the present application include, but are not limited to: laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, minidiscs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc. In addition, the electrochemical device provided by the present application is applicable not only to the above-mentioned exemplified electronic devices, but also to energy storage power stations, marine vehicles, and air vehicles, and the air vehicles include air vehicles within the atmosphere and air vehicles outside the atmosphere.

[0076] Hereinafter, the present application will be described in more detail by specific examples and comparative examples.

[0077] I. Test methods used in examples and comparative examples:

[0078] (1) High-temperature storage performance test of lithium-ion batteries

[0079] Place the lithium-ion battery in a constant temperature environment of 25°C and let it stand for 30 minutes to make the lithium-ion battery reach a constant temperature state of 25°C. Charge it at a constant current of 0.5C to 4.5V and then charge it at a constant voltage of 4.5V until the current is 0.025C, and record the thickness of the lithium-ion battery at this time as the initial thickness H0. Transfer the lithium-ion battery to a constant temperature oven at 60°C for storage for 30 days. During this period, test and record the thickness of the lithium-ion battery every 6 days. The test thickness recorded after 30 days is the storage thickness H1. The high-temperature storage thickness expansion rate = (H1 - H0) / H0 × 100%. The high-temperature storage performance of the lithium-ion battery is evaluated by the high-temperature storage thickness expansion rate.

[0080] (2) Cycle performance test of lithium-ion batteries

[0081] Place the lithium-ion battery in a constant temperature environment of 25°C and let it stand for 30 minutes to make the lithium-ion battery reach a constant temperature state of 25°C. Charge it at a constant current of 0.5C to 4.5V and then charge it at a constant voltage of 4.5V until the current is 0.025C, and let it stand for 5 minutes. Discharge it at a constant current of 0.5C to 3.0V, and record the initial discharge capacity as C0. Repeat the above charge and discharge steps for 150 cycles, and record the discharge capacity after 150 cycles as C1. The cycle capacity retention rate = C1 / C0 × 100%. The cycle performance of the lithium-ion battery is evaluated by the cycle capacity retention rate.

[0082] II. Specific Examples and Comparative Examples

[0083] Example 1-1

[0084] (1) Preparation of the positive electrode

[0085] The positive electrode active material LiCoO2, the conductive agent Super P, and the binder polyvinylidene fluoride were mixed at a weight ratio of 97:1.4:1.6, and added to the N-methylpyrrolidone (NMP) solvent. After being stirred evenly under the action of a vacuum mixer, a positive electrode slurry was obtained. Among them, the solid content of the positive electrode slurry was 72 wt%; the positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil; the coated aluminum foil was dried at 85°C, and then after cold pressing, slicing, and slitting, it was dried under vacuum conditions at 85°C for 4 h to obtain the positive electrode.

[0086] (2) Preparation of the negative electrode

[0087] The negative electrode active material artificial graphite, the conductive agent Super P, the thickening agent sodium carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) were mixed at a weight ratio of 96:2:0.8:1.2, and deionized water was added. After being stirred under the action of a vacuum mixer, a negative electrode slurry was obtained. Among them, the solid content of the negative electrode slurry was 54 wt%; the negative electrode slurry was evenly coated on the negative electrode current collector copper foil according to the areal density of the negative electrode active material of 7.8 mg / cm 2 ; the coated copper foil was dried at 85°C, and then after cold pressing, slicing, and slitting, it was dried under vacuum conditions at 120°C for 12 h to obtain the negative electrode.

[0088] (3) Preparation of the electrolyte

[0089] In a dry (water content < 10 ppm) argon atmosphere glove box, the solvents were mixed according to the mass ratio EC:DEC:EMC = 30:40:30. Then, the fully dried lithium salt LiPF6 (1 mol / kg, abbreviated as 1M) was added. After dissolution and sufficient stirring, the compound of formula I (formula I-1) and the fluorinated carboxylic acid ester (formula 1) were added. After being mixed evenly, an electrolyte was obtained; among them, based on the total mass of the electrolyte, the mass percentage of the compound of formula I (formula I-1) was 1%, the mass percentage of the fluorinated carboxylic acid ester (formula 1) was 80%, the mass percentage of LiPF6 was 12.5%, and the balance was the mixed solvent composed of EC, DEC, and EMC.

[0090] (4) Preparation of the separator

[0091] A 9-μm thick polyethylene (PE) separator is selected. After being coated with PVDF slurry and inorganic particle (the mass ratio of flaky boehmite to Al2O3 is 70:30) slurry and dried, the final separator is obtained. The coating thickness is 3 μm, and the porosity of the separator is 55%.

[0092] (5) Preparation of Lithium-Ion Batteries

[0093] Stack the positive electrode, separator, and negative electrode in sequence, with the separator placed between the positive and negative electrodes to play an insulating role, and then wind them to obtain a bare battery cell. After welding the electrode tabs, place the bare battery cell in an outer packaging foil aluminum-plastic film, and inject the prepared electrolyte mentioned above. Then, through processes such as vacuum packaging, standing, formation (constant current charging at 0.02C to 3.3V, and then constant current charging at 0.1C to 3.8V), shaping, and capacity testing, a soft-pack lithium-ion battery is obtained.

[0094] Examples 1-2 to 1-33

[0095] Except for adjusting the specific categories and content parameters of the Compound of Formula I and fluorinated carboxylic acid esters according to Table 1, the other parameters are the same as those in Example 1-1.

[0096] Comparative Examples 1-1 to 1-11

[0097] Except for adjusting the specific categories and content parameters of the Compound of Formula I and fluorinated carboxylic acid esters according to Table 1, the other parameters are the same as those in Example 1-1.

[0098] According to the above test methods, the high-temperature storage performance (high-temperature storage thickness expansion rate, %) and cycle performance (cycle capacity retention rate, %) of the lithium-ion batteries prepared through Examples 1-1 to 1-33 and Comparative Examples 1-1 to 1-11 are tested respectively. The results are shown in Table 1:

[0099] Table 1

[0100]

[0101]

[0102] According to the results presented in Table 1, referring to Comparative Examples 1-1 to 1-8 and Examples 1-1 to 1-33, adding the compound of Formula I and fluorinated carboxylate ester to the electrolyte simultaneously can further improve the high-temperature storage performance and cycling performance of lithium-ion batteries. Further referring to Comparative Examples 1-10 to 1-11 and Examples 1-1 to 1-33, as the contents of the compound of Formula I and fluorinated carboxylate ester increase, the corresponding high-temperature storage performance and cycling performance of the battery are gradually improved. However, when the dosage of the compound of Formula I or fluorinated carboxylate ester is too high or too low, the improvement effect of the high-temperature storage performance and cycling performance of the lithium-ion battery decreases instead of increasing. It can be seen that although the synergistic combination of the compound of Formula I and fluorinated carboxylate ester can improve the high-temperature storage performance and cycling performance of lithium-ion batteries, the dosages of the two also have a great influence on the improvement effect of the corresponding performance. Therefore, using the compound of Formula I and fluorinated carboxylate ester in a synergistic combination in the electrolyte and further controlling the dosages of the compound of Formula I and fluorinated carboxylate ester within the scope of this application can achieve a better improvement effect on high-temperature storage performance and cycling performance.

[0103] Examples 2-1 to 2-11

[0104] Based on the results in Table 1, in these corresponding examples, the effects of other components and dosages on improving the high-temperature cycling, storage and other performances of lithium-ion batteries were further explored. Except for adjusting the content A / % of the compound of Formula I (Formula I-1), the content B / % of the fluorinated carboxylate ester (Formula 1) and the type and content F / % of the carbonate ester according to Table 2, the other parameters were the same as those in Example 1-17.

[0105] According to the above test methods, the high-temperature storage performance (high-temperature storage thickness expansion rate, %) and cycling performance (cycle capacity retention rate, %) of the lithium-ion batteries prepared by Examples 2-1 to 2-11 were tested respectively, and the results are shown in Table 2:

[0106] Table 2

[0107]

[0108] The results presented in Table 2 show that, referring to Examples 1-17 and Examples 2-1 to 2-5, further adding vinylene carbonate fluoride in combination with the compound of Formula I and fluorinated carboxylate ester to the electrolyte can further improve the high-temperature storage performance and cycling performance of lithium-ion batteries; and further referring to Examples 2-1 to 2-8, as the content of vinylene carbonate fluoride in the electrolyte increases, the high-temperature storage performance and cycling performance of lithium-ion batteries are gradually improved. However, when the dosage of vinylene carbonate fluoride is too much or too little, the corresponding high-temperature storage performance and cycling performance of lithium-ion batteries do not increase but decrease. That is, although the addition of vinylene carbonate fluoride can further improve the high-temperature storage performance and cycling performance of lithium-ion batteries, its dosage will also have a greater impact on the improvement effect of the corresponding performance. Therefore, further controlling the dosage of vinylene carbonate fluoride within the scope of this application can achieve a better improvement effect on cycling performance and high-temperature storage performance.

[0109] Examples 3-1 to 3-7 and Examples 3-9 to 3-12

[0110] Based on the results in Table 2, in these corresponding examples, further exploration was carried out on the effects of other components and dosages on improving the high-temperature cycling, storage and other performances of lithium-ion batteries. Except for adjusting the content A / % of the compound of Formula I (Formula I-1), the content B / % of the fluorinated carboxylate ester (Formula 1), and the type and content S / % of the sulfur-oxygen compound according to Table 3, the remaining parameters are the same as those in Example 2-3.

[0111] Example 3-8

[0112] Based on Example 3-3, the positive electrode active material used in the preparation of the lithium-ion battery was replaced with a lithium nickel cobalt manganese oxide 811 ternary positive electrode material, and the remaining parameters are the same as those in Example 3-3.

[0113] According to the above test methods, the high-temperature storage performance (high-temperature storage thickness expansion rate, %) and cycling performance (cycling capacity retention rate, %) of the lithium-ion batteries prepared by Examples 3-1 to 3-12 were tested respectively, and the results are shown in Table 3:

[0114] Table 3

[0115]

[0116] The results presented in Table 3 show that, referring to Examples 2-3 and Examples 3-1 to 3-8, further adding sulfur-oxygen compounds in combination with substances such as compounds of Formula I and fluorinated carboxylates to the electrolyte can further improve the high-temperature storage performance and cycling performance of lithium-ion batteries; further referring to Examples 3-1 to 3-8 and Examples 3-9 to 3-10, as the content of sulfur-oxygen compounds in the electrolyte increases, although the high-temperature storage performance and cycling performance of lithium-ion batteries are gradually improved, when the dosage of sulfur-oxygen compounds is too much or too little, the corresponding high-temperature storage performance and cycling performance of lithium-ion batteries will not increase but decrease. That is, although the addition of sulfur-oxygen compounds can further improve the high-temperature storage performance and cycling performance of lithium-ion batteries, its dosage will also have a greater impact on the improvement effect of the corresponding performance. Therefore, further regulating the dosage of sulfur-oxygen compounds within the scope of this application can achieve a better improvement effect on cycling performance and high-temperature storage performance.

[0117] It can be understood that this application is described through some embodiments. Those skilled in the art know that, without departing from the scope of this application, various changes or equivalent substitutions can be made to these features and embodiments. Additionally, under the teaching of this application, these features and embodiments can be modified to adapt to specific situations and materials without departing from the scope of this application. Therefore, this application is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by this application.

Claims

1. A non-aqueous electrolyte, characterized in that: The electrolyte comprises: a compound of formula I and a fluorocarboxylic acid ester; Among them, R 1 , R 2 , R 3 and R 4 Each is independently selected from any one of a fluorine atom, a difluorophosphoryloxy group, a methylsulfonic acid group, and a trifluoromethylsulfonic acid group; based on the total mass of the electrolyte, the mass percentage of the compound of formula I is A, and the mass percentage of the fluorocarboxylic acid ester is B, wherein A satisfies: 0.01%≤A≤5%, and B satisfies: 10%≤B≤80%.

2. The electrolyte according to claim 1, characterized in that The electrolyte satisfies at least one of the following conditions: (1) A satisfies: 0.1% ≤ A ≤ 5%; (2) A / B satisfies: 0.002≤A / B≤0.2; (3) B satisfies: 20% ≤ B ≤ 80%; (4) B satisfies: 30% ≤ B ≤ 70%; (5) B satisfies: 40% ≤ B ≤ 70%.

3. The electrolyte according to claim 1, characterized in that The compound of formula I includes at least one of the following compounds of formula I-1 to formula I-9:

4. The electrolyte according to claim 1, characterized in that The fluorocarboxylate comprises at least one of the following compounds of Formula 1 to Formula 8:

5. The electrolyte according to claim 1, characterized in that The electrolyte also includes fluoroethylene carbonate; the electrolyte also includes fluoroethylene carbonate, and based on the total mass of the electrolyte, the mass percentage of the fluoroethylene carbonate is F, and F satisfies 0.3%≤F≤5%.

6. The electrolyte according to claim 5, characterized in that The ratio F / (A+B) of the mass percentage F of the fluoroethylene carbonate to the mass percentage A of the compound of formula I and the mass percentage B of the fluorocarboxylic acid ester satisfies the following relationship: 0.005≤F / (A+B)≤0.

49.

7. The electrolyte according to claim 5, characterized in that The ratio F / (A+B) of the mass percentage F of the fluoroethylene carbonate to the mass percentage A of the compound of formula I and the mass percentage B of the fluorocarboxylic acid ester satisfies the following relationship: 0.005≤F / (A+B)≤0.

2.

8. The electrolyte according to any one of claims 1 to 7, characterized in that: The electrolyte also includes a sulfur-oxygen compound; the sulfur-oxygen compound includes at least one of 1,3-propane sultone, 1,3-propylene sultone, and vinyl sulfate; based on the total mass of the electrolyte, the mass percentage of the sulfur-oxygen compound is S, and S satisfies: 0.1%≤S≤3%.

9. The electrolyte according to claim 8, characterized in that The ratio S / (A+B) of the mass percentage S of the sulfur-oxygen compound to the mass percentage A of the compound of formula I and the mass percentage B of the fluorocarboxylic acid ester satisfies the following relationship: 0.002≤S / (A+B)≤0.

1.

10. An electrochemical device, characterized in that: The electrochemical device comprises a positive electrode and an electrolyte as described in any one of claims 1 to 9; the positive electrode comprises a positive electrode collector and a positive electrode active material layer arranged on at least one surface of the positive electrode collector, and the positive electrode active material of the positive electrode active material layer is a nickel cobalt lithium manganese oxide ternary positive electrode material.

11. An electronic device, characterized in that: The electronic device comprises the electrochemical device according to claim 10.

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