Electrolyte, electrochemical device, and electronic device

Abstract

The application discloses an electrolyte, an electrochemical device and an electronic device. The electrolyte comprises a compound of formula I and a compound of formula II, the mass percentage of the compound of formula I is A, and the mass percentage of the compound of formula II is B, based on the total mass of the electrolyte, wherein 0.01%<=A<=80%, 0.1%<=B<=10%. By comprising the compound of formula I and the compound of formula II in the electrolyte, the compound of formula I and the compound of formula II are within the scope of the application, the addition of the compound of formula I in the electrolyte improves the low-temperature large-rate discharge capacity retention rate of the electrochemical device, meanwhile, the compound of formula I and the compound of formula II synergize to improve the stability of the positive and negative electrodes and reduce the negative electrode interface impedance, so that the high-temperature cycle capacity retention rate of the electrochemical device is improved.

Description

Technical Field

[0001] This application relates to the field of electrochemical device technology, and more particularly to an electrolyte, an electrochemical device, and an electronic device. Background Technology

[0002] Electrochemical devices (such as lithium-ion batteries) have advantages such as high energy 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 devices, and electric vehicles. However, this also puts forward higher requirements for the comprehensive performance of electrochemical devices. For example, there is a need to develop electrolytes that can simultaneously improve 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] This application provides an electrolyte, an electrochemical device, and an electronic device. By improving the composition of the electrolyte, an electrolyte that can improve both the high-temperature cycling performance and the low-temperature rate discharge performance of the electrochemical device can be obtained.

[0004] In a first aspect, this application provides an electrolyte comprising compounds of formula I and formula II;

[0005]

[0006] In Formula I, R1 is selected from unsubstituted or R0-substituted C2-C6 alkyl, unsubstituted or R0-substituted C2-C6 alkenyl, unsubstituted or R0-substituted C2-C6 alkynyl, unsubstituted or R0-substituted C3-C6 nitrogen-containing heteroaryl, and unsubstituted or R0-substituted C6-C 12 Any of the aryl groups, wherein 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;

[0007] In Formula II, R2 is selected from unsubstituted or fluorinated C3-C 10 The nitrogen-containing heteroaryl group, the unsubstituted or fluorinated C1-C5 phosphate ester group, and the unsubstituted or fluorinated C1-C5 carbonate group are all of the following: the atoms in R2 that are bonded to the B atom are the nitrogen atom in the nitrogen-containing heteroaryl group, the oxygen atom in the phosphate ester group that is connected to the phosphorus atom by a double bond, and the carbonyl oxygen atom in the carbonate group.

[0008] Based on the total mass of the electrolyte, the mass percentage of compound I is A, and the mass percentage of compound II is B, wherein 0.01% ≤ A ≤ 80%, and 0.1% ≤ B ≤ 10%. By including compound I and compound II in the electrolyte and ensuring that the contents of compound I and compound II are within the range of this application, compound I improves the low-temperature high-rate discharge capacity retention rate of the electrochemical device. Simultaneously, the synergistic effect of compound I and compound II improves the stability of the positive and negative electrodes and reduces the negative electrode interface impedance, thereby also improving the high-temperature cycling capacity retention rate of the electrochemical device.

[0009] In some embodiments, the electrolyte satisfies at least one of the following conditions: (1) 0.5% ≤ A ≤ 60%; (2) 3% ≤ B ≤ 5%.

[0010] In some embodiments, 2 ≤ A / B ≤ 15. This application selects the mass percentages of both Formula I and Formula II compounds in the electrolyte to satisfy the above range, so that the two can better cooperate to improve the stability of the positive and negative electrode interfaces and improve the positive and negative electrode impedance, thereby simultaneously improving the low-temperature high-rate discharge capacity retention rate and high-temperature cycling capacity retention rate of the electrochemical device.

[0011] In some embodiments, the compound of formula I includes at least one of the following compounds:

[0012]

[0013] By selecting the above-mentioned Formula I compound, the Formula I compound can form a positive electrode interface passivation layer of lithium-containing inorganic compound rich in S and F elements at the positive electrode interface, further reducing the positive electrode side impedance, thereby improving the low-temperature high-rate discharge capacity retention rate of the electrochemical device.

[0014] In some embodiments, the compound of formula II includes at least one of the following compounds:

[0015]

[0016] By selecting the above-mentioned compound II, compound II can better react with HF to consume HF, reduce the damage of HF to the positive electrode, and the synergistic effect of compound I and compound II can form a passivation layer at the negative electrode interface, improve the stability of the negative electrode, further reduce the negative electrode interface impedance, and thus further improve the high-temperature cycling capacity retention rate of the electrochemical device.

[0017] In some embodiments, the electrolyte further includes a first component, which includes at least one selected from vinylene carbonate, propylene carbonate, and fluoroethylene carbonate; the mass percentage of the first component is C based on the total mass of the electrolyte, where 0.2 ≤ C / (A+B) ≤ 1.6. By adjusting the mass percentage of the first component, the mass percentage of compound I, and the mass percentage of compound II in the electrolyte to satisfy the ranges of the above conditions, the viscosity of the electrolyte can be further improved, the ionic conductivity of the electrolyte can be increased, and this helps to improve the kinetic performance of the electrochemical device.

[0018] In some embodiments, the electrolyte further includes a second component, which includes at least one of diethyl carbonate, propyl propionate, and ethyl propionate; based on the total mass of the electrolyte, the mass percentage of the second component is D, where 0.8 ≤ D / (A+B) ≤ 1.5. By adjusting the mass percentage of the second component, the mass percentage of compound I, and the mass percentage of compound II in the electrolyte to satisfy the ranges of the above conditions, the conductivity of the electrolyte can be further improved, and the high-temperature cycling capacity retention rate and low-temperature high-rate discharge capacity retention rate of the electrochemical device can be improved.

[0019] In some embodiments, 1 ≤ D / C ≤ 2. By selecting the mass percentage ratio of the first component and the second component within the above range, it is convenient to control the conductivity and viscosity of the electrolyte within a suitable range, so as to further improve the high-temperature cycling capacity retention rate and low-temperature high-rate discharge capacity retention rate of the electrochemical device.

[0020] In some embodiments, the electrolyte further includes a first lithium salt, which comprises at least one of lithium hexafluorophosphate or lithium bis(fluorosulfonyl)imide; the mass percentage of the first lithium salt is E based on the total mass of the electrolyte, wherein 10% ≤ E ≤ 20%. By adjusting the mass percentage of the first lithium salt in the electrolyte to meet the above range, the first lithium salt dissociates, giving the electrolyte good conductivity. The compound of formula I is polar and has a good dissociation effect on lithium salt, helping to dissolve lithium salt. Even when the lithium salt content in the electrolyte is high, the compound of formula I still has a good dissociation effect on lithium salt, further improving the conductivity of the electrolyte.

[0021] In some embodiments, the electrolyte further includes a second lithium salt, which includes at least one of lithium tetrafluoroborate, lithium difluorooxalate borate, and lithium dioxalate borate; the mass percentage of the second lithium salt is F based on the total mass of the electrolyte, wherein 0.1% ≤ F ≤ 10%. The second lithium salt can improve gas generation during high-temperature storage of the electrochemical device. By adjusting the mass percentage of the second lithium salt in the electrolyte to meet the above range, the high-temperature storage performance of the electrochemical device can be further improved.

[0022] Secondly, this application provides an electrochemical device comprising the electrolyte as described above.

[0023] Thirdly, this application provides an electronic device including the electrochemical device described above.

[0024] Based on the electrolyte, electrochemical device, and electronic device of this application, by including a compound of formula I and a compound of formula II in the electrolyte, wherein the mass percentage A of compound I satisfies 0.01% ≤ A ≤ 80%, and the mass percentage B of compound II satisfies 0.1% ≤ B ≤ 10%, compound I can form a passivation layer at the positive electrode interface rich in lithium-containing inorganic compounds rich in S and F elements, reducing the positive electrode side impedance and thereby improving the low-temperature high-rate discharge capacity retention rate of the electrochemical device. Compound II can consume HF generated by the accelerated oxidative decomposition of components in the electrolyte by compound I, preventing HF from damaging the positive electrode and improving the stability of the positive electrode. Furthermore, the compounds of Formula I and Formula II can work synergistically to form a passivation layer at the negative electrode interface rich in lithium-containing inorganic compounds with S and F elements, thereby improving the stability of the negative electrode, mitigating the increase in negative electrode impedance caused by the compound of Formula II, and reducing the negative electrode interface impedance. Therefore, while adding the compound of Formula I to the electrolyte improves the low-temperature high-rate discharge capacity retention rate of the electrochemical device, the synergistic effect of the compounds of Formula I and Formula II can improve the stability of the positive and negative electrodes and reduce the negative electrode interface impedance, thus improving the high-temperature cycling capacity retention rate of the electrochemical device. Detailed Implementation

[0025] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0026] This application provides an electrolyte comprising a compound of formula I and a compound of formula II. Based on the total mass of the electrolyte, the mass percentage of compound I is A and the mass percentage of compound II is B, wherein 0.01% ≤ A ≤ 80% and 0.1% ≤ B ≤ 10%. By configuring the electrolyte as described above, this application can simultaneously improve the low-temperature high-rate discharge capacity retention rate and high-temperature cycling capacity retention rate of the electrochemical device.

[0027] The electrolyte includes compounds of formula I, which are as follows:

[0028]

[0029] In Formula I, R1 is selected from unsubstituted or R0-substituted C2-C6 alkyl, unsubstituted or R0-substituted C2-C6 alkenyl, unsubstituted or R0-substituted C2-C6 alkynyl, unsubstituted or R0-substituted C3-C6 nitrogen-containing heteroaryl, and unsubstituted or R0-substituted C6-C 12 Any of the aryl groups, wherein 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.

[0030] Based on the total mass of the electrolyte, the mass percentage of compound I is A, where 0.01% ≤ A ≤ 80%. In some embodiments, 0.5% ≤ A ≤ 60%. In some embodiments, 1% ≤ A ≤ 30%. In some embodiments, 3% ≤ A ≤ 20%. In some embodiments, 5% ≤ A ≤ 25%. In some embodiments, the value of A is 0.01%, 0.5%, 2.0%, 6.0%, 16.0%, 35.0%, 40.0%, 55.0%, 65.0%, 80.0%, or a value within the range of any two of these values.

[0031] The electrolyte also includes compounds of formula II, which are as follows:

[0032]

[0033] In formula II, R2 is selected from unsubstituted or fluorinated C3-C. 10 The R2 group comprises any one of the following: nitrogen-containing heteroaryl group, unsubstituted or fluorinated C1-C5 phosphate ester group, and unsubstituted or fluorinated C1-C5 carbonate group, wherein the atoms bonded to the B atom in R2 are any one of the following: nitrogen atom in nitrogen-containing heteroaryl group, oxygen atom in phosphate ester group connected to phosphorus atom by double bond, and carbonyl oxygen atom in carbonate group.

[0034] Based on the total mass of the electrolyte, the mass percentage of compound II is B, where B satisfies: 0.1% ≤ B ≤ 10%. In some embodiments, 3.0% ≤ B ≤ 10.0%. In some embodiments, 4.0% ≤ B ≤ 8.0%. In some embodiments, 5.0% ≤ B ≤ 10.0%. In some embodiments, 6.0% ≤ B ≤ 10.0%. In some embodiments, the value of B is 0.1%, 0.5%, 1.5%, 4.8%, 5.8%, 7.0%, 7.8%, 8.6%, 9.5%, 10.0%, or a value within the range of any two of these values.

[0035] This application improves the low-temperature, high-rate discharge capacity retention of the electrochemical device by adding a compound of formula I to the electrolyte. Compound I can form a passivation layer at the positive electrode interface, rich in lithium-containing inorganic compounds rich in S and F elements, thereby reducing the positive electrode impedance. In the fully charged state or high-temperature storage state of the electrochemical device, components in the electrolyte are prone to oxidative decomposition reactions to generate HF. HF can damage the positive electrode structure, leading to a deterioration in positive electrode impedance. For example, to improve the viscosity of the electrolyte and enhance the kinetic performance of the electrochemical device, related technologies add carbonate compounds and carboxylic acid ester compounds to the electrolyte. Compound I accelerates the oxidative decomposition reaction between carbonate compounds and carboxylic acid ester compounds and fluorine-containing compounds in the electrolyte to generate HF. By adding a compound of formula II, which can react with HF to consume it, HF is prevented from damaging the positive electrode, thus improving the positive electrode stability. Furthermore, while Compound II itself can form a protective film at the negative electrode interface to improve its stability, it also tends to increase the interface impedance. Through the synergistic effect of Compound I and Compound II, a passivation layer rich in S and F elements (containing lithium inorganic compounds) can be formed at the negative electrode interface, improving stability and reducing interface impedance. Therefore, adding Compound I to the electrolyte improves the low-temperature, high-rate discharge capacity retention of the electrochemical device. The synergistic effect of Compound I and Compound II also improves the stability of both the positive and negative electrodes and reduces the interface impedance, thus simultaneously improving the high-temperature cycling capacity retention of the electrochemical device. When the mass percentage A of Compound I exceeds the upper limit of 80%, it accelerates the oxidative decomposition of the remaining electrolyte components to produce hydrofluoric acid, which can easily damage the positive electrode structure. When the mass percentage A of Compound I is below the lower limit of 0.01%, its effect on improving the positive electrode impedance is limited, thus limiting its improvement on the low-temperature, high-rate discharge capacity retention of the electrochemical device. When the mass percentage B of compound II exceeds the upper limit of 10%, the negative electrode interface impedance will be too large, and the high-temperature cycling capacity retention rate of the electrochemical device will be reduced. When the mass percentage B of compound II is lower than the lower limit of 0.1%, the ability to capture HF is limited. HF damages the positive electrode and causes the structure to be damaged, resulting in a decrease in the charge capacity that the electrochemical device can release.

[0036] In some embodiments, A and B satisfy: 2 ≤ A / B ≤ 15. In some embodiments, 3.0 ≤ A / B ≤ 14%. In some embodiments, 4.0 ≤ A / B ≤ 12.0. 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 within the range of any two of these values. This application selects the mass percentage content of both Formula I and Formula II compounds in the electrolyte to satisfy the above ranges, enabling them to better cooperate to improve the stability of the positive and negative electrode interfaces and improve the positive and negative electrode impedance, thereby simultaneously improving the low-temperature high-rate discharge capacity retention rate and high-temperature cycling capacity retention rate of the electrochemical device.

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

[0038]

[0039] By selecting the above-mentioned Formula I compound, the Formula I compound can form a positive electrode interface passivation layer of lithium-containing inorganic compound rich in S and F elements at the positive electrode interface, further reducing the positive electrode side impedance, thereby improving the low-temperature high-rate discharge capacity retention rate of the electrochemical device.

[0040] In some embodiments, the compound of formula II comprises at least one of the following compounds;

[0041]

[0042] By selecting the above-mentioned compound II, compound II can better react with HF to consume HF, reduce the damage of HF to the positive electrode, and the synergistic effect of compound I and compound II can form a passivation layer at the negative electrode interface, improve the stability of the negative electrode, further reduce the negative electrode interface impedance, and thus further improve the high-temperature cycling capacity retention rate of the electrochemical device.

[0043] In some embodiments, the electrolyte further includes a first component, which is at least one selected from vinylene carbonate, propylene carbonate, and fluoroethylene carbonate. Based on the total mass of the electrolyte, the mass percentage of the first component is C, where C satisfies 5% ≤ C ≤ 40%, and in some embodiments, 8% ≤ C ≤ 30%. In some embodiments, 10% ≤ C ≤ 30%. In some embodiments, 15% ≤ C ≤ 30%. In some embodiments, the value of C is within the range of 5%, 7%, 13%, 16%, 19%, 27%, 30%, 35%, 40%, or any combination thereof. By adjusting the mass percentage of the first component in the electrolyte to meet the above ranges, the first component can improve the ion conductivity of the electrolyte. Furthermore, the first component has a relatively high viscosity, while both compounds of formula I and formula II have relatively low viscosities. Adding the first component, compound I, and compound II to the electrolyte can improve the viscosity of the electrolyte.

[0044] In some embodiments, C satisfies the following relationship with A and B: 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 within the range of 0.80, 0.88, 0.94, 0.98, 1.01, 1.06, 1.10, 1.12, 1.14, 1.15, or any combination of these values. By adjusting the mass percentage of the first component, the mass percentage of compound I, and the mass percentage of compound II in the electrolyte to satisfy the above conditions, the viscosity of the electrolyte can be further improved, the ionic conductivity of the electrolyte can be increased, and thus the kinetic performance of the electrochemical device can be improved.

[0045] In some embodiments, the electrolyte further includes a second component, which comprises at least two of diethyl carbonate, propyl propionate, or ethyl propionate. Based on the total mass of the electrolyte, the mass percentage of the second component is D, where D satisfies 20% ≤ D ≤ 60%, and in some embodiments, 22% ≤ D ≤ 50%. In some embodiments, 25% ≤ D ≤ 30%. In some embodiments, 30% ≤ D ≤ 50%. In some embodiments, the value of D is within the range of 25%, 27%, 33%, 36%, 39%, 43%, 48%, 50%, 55%, 60%, or any combination thereof. By adjusting the mass percentage of the second component in the electrolyte to meet the above ranges, the second component has a lower viscosity, which improves the wetting ability of the electrolyte. Both compounds of formula I and formula II have good dissociation ability for lithium salts; when used in combination with the second component, they can compensate for the insufficient dissociation ability of the second component for lithium salts, improve the conductivity of the electrolyte, and help improve the high-temperature cycling capacity retention rate and low-temperature high-rate discharge capacity retention rate of the electrochemical device.

[0046] In some embodiments, D satisfies the following relationship with A and B: 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 any combination of these values. By adjusting the mass percentage of the second component, the mass percentage of compound I, and the mass percentage of compound II in the electrolyte to satisfy the above conditions, the conductivity of the electrolyte can be further improved, and the high-temperature cycling capacity retention rate and low-temperature high-rate discharge capacity retention rate of the electrochemical device can be improved.

[0047] In some embodiments, the electrolyte may simultaneously contain a first component and a second component, in which case C and D satisfy: 1 ​​≤ D / C ≤ 2. In some embodiments, 1.1 ≤ D / C ≤ 1.20. In some embodiments, 1.3 ≤ D / C ≤ 1.90. In some embodiments, 1.50 ≤ D / C ≤ 2.0. In some embodiments, the value of D / C is 1.05, 1.23, 1.36, 1.55, 1.68, 1.79, 1.91, 2.00, or a value within any two of these ranges. By selecting the mass percentage ratio of the first component and the second component within the above range, it is convenient to control the conductivity and viscosity of the electrolyte within a suitable range, so as to further improve the high-temperature cycling capacity retention rate and low-temperature high-rate discharge capacity retention rate of the electrochemical device.

[0048] In some embodiments, the electrolyte further includes a first lithium salt, which is primarily used to provide lithium ions in the electrolyte. The first lithium salt comprises at least one of lithium hexafluorophosphate or lithium bisfluorosulfonylimide. Based on the total mass of the electrolyte, the mass percentage of the first lithium salt is E, where E satisfies 10% ≤ E ≤ 20%. In some embodiments, 17% ≤ E ≤ 18%. In some embodiments, 15% ≤ E ≤ 18%. In some embodiments, 15% ≤ E ≤ 17.5%. In some embodiments, the value of E is 10.0%, 13.4%, 16.6%, 16.5%, 17.8%, 18.2%, 19.5%, 19.7%, 20.0%, or a value within the range of any two of these values. By adjusting the mass percentage of the first lithium salt in the electrolyte to meet the above range, the first lithium salt dissociates, giving the electrolyte good conductivity. The compound of formula I is polar and has a good dissociation effect on lithium salt, which can help dissolve lithium salt. Even when the lithium salt content in the electrolyte is high, the compound of formula I still has a good dissociation effect on lithium salt, further improving the conductivity of the electrolyte.

[0049] In some embodiments, the electrolyte further includes a second lithium salt, which includes at least one of lithium tetrafluoroborate, lithium difluorooxalate borate, and lithium dioxalate borate. Based on the total mass of the electrolyte, the mass percentage of the second lithium salt is F, where F satisfies: 0.1% ≤ F ≤ 10%, and in some embodiments, 0.2% ≤ F ≤ 8.8%. In some embodiments, 0.5% ≤ F ≤ 5.8%. In some embodiments, 3.2% ≤ F ≤ 8.8%. In some embodiments, the value of F is 0.1%, 0.6%, 1.7%, 3.9%, 4.1%, 5.7%, 6.9%, 8.0%, 9.3%, 10.0%, or a value within the range of any two of these values. The second lithium salt can improve gas generation during high-temperature storage of the electrochemical device. By adjusting the mass percentage of the second lithium salt in the electrolyte to meet the above ranges, the high-temperature storage performance of the electrochemical device can be further improved.

[0050] In this application, the characteristics of the different components contained in the electrolyte can be combined, and the implementation methods covered by the above combinations are all within the protection scope of this application.

[0051] In this application, the electrolyte also includes a non-aqueous organic solvent. This application does not impose any particular limitation on the non-aqueous organic solvent, as long as it achieves the purpose of this application. For example, the non-aqueous organic solvent may include at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds and cyclic carbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (EMC). The aforementioned cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), or vinyl ethylene carbonate (VEC). The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, or propyl propionate. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The aforementioned 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-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters. This application does not impose any particular limitation on the mass percentage of non-aqueous organic solvents in the electrolyte, as long as the purpose of this application is achieved. For example, based on the total mass of the electrolyte, the mass percentage G of the non-aqueous organic solvent is 10% to 70%.

[0052] Secondly, this application provides an electrochemical device, which includes the electrolyte as described above, and further includes a positive electrode, a negative electrode, and a separating membrane.

[0053] This application does not impose any particular limitations on the materials, structure, and processing methods of the positive electrode, negative electrode, and separator of the electrochemical device. Any positive electrode, negative electrode, and separator that can be used in this field is applicable to this application.

[0054] I Positive electrode

[0055] The positive electrode in this electrochemical device 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 phrase "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 thickness direction, or on two surfaces of the positive electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of ​​the positive electrode current collector or only a portion of it; this application has no particular limitation, as long as the purpose of this application is achieved.

[0056] The cathode material layer of this application includes a cathode active material, which comprises a substance capable of reversibly inserting and extracting active ions such as lithium ions. The cathode material layer can be one or more layers, and each layer in a multilayer cathode material layer can contain the same or different cathode active materials. This application does not impose any particular limitation on the cathode active material, as long as it can achieve the purpose of this application. For example, the cathode active material can include, but is not limited to, at least one of lithium nickel cobalt manganese oxide (e.g., 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 manganese iron phosphate, or lithium titanate.

[0057] The positive electrode material layer of this application also includes a conductive agent and a binder. This application does not impose any particular limitations on the conductive agent and binder in the positive electrode material layer, as long as they can achieve the purpose of this application. 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, metallic materials, or conductive polymers. The aforementioned conductive carbon black may include, but is not limited to, Super P, acetylene black, or Ketjen black. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. The binder may include, but is not limited to, at least one of polyacrylate, 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 carboxymethyl cellulose, or potassium carboxymethyl cellulose. This application does not impose any particular limitation on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer; those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0058] This application does not impose any particular limitation on the positive electrode current collector, as long as it achieves the purpose of this application. For example, it may include aluminum foil, aluminum alloy foil, or composite current collectors (such as aluminum-carbon composite current collectors). This application does not impose any particular limitation on the thickness of the positive electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. This application does not impose any particular limitation on the thickness of the positive electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of a single-sided positive electrode material layer is 30 μm to 120 μm.

[0059] 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. This application does not impose any particular limitation on the composition of the conductive layer, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer, and it can be at least one of the aforementioned conductive agents and binders. This application does not impose any particular limitation on the mass ratio of the conductive agent and binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved.

[0060] In this application, the electrochemical device further includes a negative electrode, which comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The phrase "a 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 thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or only a portion thereof; this application does not have any particular limitation, as long as the purpose of this application is achieved.

[0061] The negative electrode material layer of this application includes a negative electrode active material. This application does not impose any particular limitation on the negative electrode active material, as long as it can achieve the purpose of this application. For example, the negative electrode active material may include natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO₂, etc. x (0.5 < x < 1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li4Ti5O 12 At least one of Li-Al alloys or metallic lithium.

[0062] The negative electrode material layer of this application also includes a binder. This application does not impose any particular limitation on the binder in the negative electrode material layer, as long as it achieves the purpose of this application. For example, the binder can be at least one of the binders described above. The negative electrode material layer of this application also includes a conductive agent. This application does not impose any particular limitation on the conductive agent in the negative electrode material layer, as long as it achieves the purpose of this application. For example, the conductive agent can be at least one of the conductive agents described above. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, binder, and 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 this application is achieved.

[0063] This application does not impose any particular limitation on the negative electrode current collector, as long as it achieves the purpose of this application. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collectors. This application does not impose any particular limitation on the thickness of the negative electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode current collector may be 5 μm to 16 μm. This application does not impose any particular limitation on the thickness of the negative electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of a single-sided negative electrode material layer may be 30 μm to 120 μm.

[0064] 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. This application does not impose any particular limitation on the composition of the conductive layer, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer, and it can be at least one of the aforementioned conductive agents and binders. This application does not impose any particular limitation on the mass ratio of the conductive agent to the binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved. This application does not impose any particular limitation on the thickness of the conductive layer, as long as the purpose of this application is achieved; for example, the thickness of the conductive layer is 1 μm to 10 μm.

[0065] In this application, the electrochemical device also includes a diaphragm, which separates the positive and negative electrodes, prevents short circuits within the electrochemical device, allows electrolyte ions to pass freely, and does not affect the electrochemical charging and discharging process. This application does not impose any particular limitation on the diaphragm, as long as it achieves the purpose of this application. For example, the diaphragm material may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid; the diaphragm type may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0066] In this application, the diaphragm may include a substrate and a surface treatment layer. The substrate may be a nonwoven fabric or composite membrane with 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 membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials. For example, the inorganic layer includes inorganic particles and a binder. This application does not have any particular limitation on the aforementioned inorganic particles, and may include at least one of alumina, 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. This application does not have any particular limitation on the aforementioned binders, and may include at least one of the aforementioned binders. The polymer layer contains a polymer, the polymer material of which includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0067] The electrochemical device of this application also includes a packaging bag for containing the positive electrode, diaphragm, negative electrode, and electrolyte, as well as other components known in the art in the electrochemical device. This application does not limit the aforementioned other components. This application does not have any particular limitation on the packaging bag; it can be any packaging bag known in the art, as long as it can achieve the purpose of this application.

[0068] This application does not impose any particular limitation on the type of electrochemical device, which may include any device in which an electrochemical reaction occurs. In this application, the electrochemical device may include, but is not limited to: lithium metal electrochemical device, lithium-ion electrochemical device (lithium-ion battery), lithium polymer electrochemical device, or lithium-ion polymer electrochemical device (lithium-ion polymer battery), etc.

[0069] The preparation process of the electrochemical device of this application is well known to those skilled in the art, and this application has no particular limitations. For example, it may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device; or stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the packaging bag as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device.

[0070] This application also provides an electronic device that includes the electrochemical device in any of the foregoing embodiments. Therefore, the electronic device provided by this application has good performance.

[0071] This application does not specifically limit the type of electronic device, which can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0072] The preparation of the electrochemical device is described below with reference to specific embodiments. Those skilled in the art will understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0073] Example

[0074] The following examples, using lithium-ion batteries as an example, provide more specific illustrations of the implementation methods of the electrochemical device of this application. Those skilled in the art will understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" refer to mass measurements.

[0075] Test methods

[0076] 1. High-temperature (45℃) cycling capacity retention test method

[0077] The high-temperature (45℃) cycling capacity retention test procedure is as follows:

[0078] (1) Place the lithium-ion battery at 45°C and let it stand for 60 minutes;

[0079] (2) Charge the lithium-ion battery at a constant current rate of 1.2C to 4.2V, and then charge it at a constant voltage rate until the current is less than 0.7C;

[0080] (3) Charge the lithium-ion battery at a constant current rate of 0.7C to 4.5V, charge it at a constant voltage rate until the current is less than 0.05C, and let it stand for 5 minutes.

[0081] (4) Discharge the lithium-ion battery at a constant current of 0.5C to 3V and let it stand for 5 minutes;

[0082] Steps (2) to (4) constitute one charge-discharge cycle. The cycle is repeated 600 times. The discharge capacity of the lithium-ion battery in the first charge-discharge cycle is denoted as C1, and the discharge capacity of the lithium-ion battery in the 600th charge-discharge cycle is denoted as C600.

[0083] High temperature (45℃) cycle capacity retention rate = C600 / C1*100%.

[0084] 2. Test method for capacity retention at high discharge rates at low temperatures (-20℃)

[0085] The low-temperature (-20℃) rate discharge test procedure is as follows:

[0086] (1) Place the lithium-ion battery at -20℃ and let it stand for 30 minutes;

[0087] (2) Discharge the lithium-ion battery to 3V at a rate of 0.2C and let it stand for 10 minutes;

[0088] (3) Charge the lithium-ion battery at a constant current rate of 1.2C to 4.2V, and then charge it at a constant voltage rate until the current is less than 0.6C;

[0089] (4) Charge the lithium-ion battery at a constant current rate of 0.6C to 4.5V, charge it at a constant voltage rate until the current is less than 0.05C, and let it stand for 10 minutes.

[0090] (5) Discharge to 3V at a constant current rate of Cx, where Cx = 0.2C, 0.5C, 1C, 1.5C, 2C;

[0091] Steps (2) to (5) constitute one discharge process. Repeat the discharge process according to steps (2) to (5) until all Cx rate discharge processes are tested. The discharge capacity of the lithium-ion battery after undergoing 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 lithium-ion battery is recorded as Dmax.

[0092] Low-temperature (-20℃) high-rate discharge capacity retention rate = Dmax / D1*100%.

[0093] Example 1-1

[0094] (1) Preparation of the positive electrode

[0095] Lithium cobalt oxide (LiCoO2) as the positive electrode active material, conductive carbon black as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder were mixed at a mass ratio of 97.9:0.9:1.2. N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 75 wt%. The positive electrode slurry was uniformly coated onto one surface of a 9 μm thick aluminum foil current collector. The foil was then dried at 85°C and cold-pressed to obtain a positive electrode with a single-sided coating thickness of 95 μm. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode with a double-sided coating. After cutting and welding the positive electrode tabs, a positive electrode with dimensions of 74 mm × 851 mm was obtained for use. The compaction density of the positive electrode material layer was 4.20 g / cm³. 3 .

[0096] (2) Preparation of negative electrode

[0097] Artificial graphite (anode active material), styrene-butadiene rubber (SBR) binder, and sodium carboxymethyl cellulose (CMC) thickener were mixed at a mass ratio of 97.4:1.4:1.2. Deionized water was then added as a solvent, and the mixture was stirred evenly under vacuum to obtain a cathode slurry with a solid content of 50 wt%. The cathode slurry was uniformly coated onto one surface of a 10 μm thick copper foil current collector. The foil was then dried at 85°C and cold-pressed to obtain a cathode with a single-sided coating thickness of 130 μm. The above steps were repeated on the other surface of the same copper foil to obtain a cathode with a double-sided coating. After cutting and welding of cathode tabs and nickel tabs, a cathode with dimensions of 76 mm × 867 mm was obtained for use. The compaction density of the cathode material layer was 1.80 g / cm³. 3 .

[0098] (3) Preparation of the separating membrane

[0099] The porous substrate layer is made of a 9μm thick polypropylene film.

[0100] (4) Preparation of electrolyte

[0101] In an argon-atmospheric glove box with a water content of less than 10 ppm, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were mixed in a 1:1:1 ratio to obtain a base solvent. Then, compounds of formula I and II, and lithium hexafluorophosphate (LiPF6) were dissolved in the base solvent to obtain an electrolyte. The mass percentage of LiPF6 in the electrolyte was 12.5%.

[0102] The mass percentages of compounds of formula I and formula II are shown in Table 1, with the remainder being the base solvent.

[0103] (5) Assembly of lithium-ion electrons

[0104] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. This is then wound to obtain a bare battery cell. The bare cell is placed in a packaging bag, injected with electrolyte, and sealed. After processes including formation, degassing, edge trimming, and capacity testing, a lithium-ion battery is obtained.

[0105] Examples 1-2 to 1-23 are identical to Example 1-1, except that the types and contents of compounds of formula I (A) and compounds of formula II (B) are adjusted according to Table 1 in the preparation of the electrolyte. The mass percentage of the base solvent is changed accordingly, while the mass percentage of the lithium salt remains unchanged.

[0106] Comparative Example 1-1 was identical to Examples 1-6 except that no compound of Formula I was added to the electrolyte. The mass percentage of the base solvent was changed accordingly, while the mass percentage of the lithium salt remained unchanged.

[0107] Comparative Examples 1-2 were identical to Examples 1-6, except that no compound of Formula II was added to the electrolyte. The mass percentage of the base solvent was varied, while the mass percentage of the lithium salt remained unchanged.

[0108] Comparative Examples 1-3 to 1-6 were identical to Examples 1-6, except that the content of compound A of Formula I and the content of compound B of Formula II were adjusted according to Table 1 in the preparation of the electrolyte. The mass percentage of the base solvent was changed accordingly, while the mass percentage of the lithium salt remained unchanged.

[0109] Examples 2-1 to 2-8 are identical to Examples 1-6, except that the type and content C of the first component are adjusted according to Table 2 in the preparation of the electrolyte. The mass percentage of the base solvent is changed accordingly, while the mass percentage of the lithium salt remains unchanged.

[0110] Examples 3-1 to 3-5 are identical to Examples 1-6, except that the type and content D of the second component are adjusted according to Table 3 in the preparation of the electrolyte. The mass percentage of the base solvent changes accordingly, while the mass percentage of the lithium salt remains unchanged.

[0111] Examples 3-6 to 3-8 are identical to Examples 1-6, except that the first and second components are added as shown in Table 3 during the preparation of the electrolyte. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0112] Examples 4-1 to 4-5 are the same as those in Examples 1-6, except that the type and content of the first lithium salt are adjusted according to Table 4 in the preparation of the electrolyte.

[0113] Examples 4-6 to 4-10 are the same as those in Examples 1-6, except that a first lithium salt and a second lithium salt are added in the preparation of the electrolyte as shown in Table 4.

[0114] Examples 4-11 are the same as Examples 1-6 except that the first component, the second component, the first lithium salt and the second lithium salt are added in the preparation of the electrolyte as shown in Table 4. The mass percentage of the base solvent is changed accordingly.

[0115] The preparation parameters and performance parameters of Examples 1-1 to 1-23 and Comparative Examples 1-1 to 1-6 are shown in Table 1.

[0116] Table 1

[0117]

[0118]

[0119] Note: " / " in Table 1 indicates that there is no corresponding parameter.

[0120] In this application, regarding the performance parameters, a higher high-temperature (45°C) cycle capacity retention rate indicates a better high-temperature (45°C) cycle capacity retention rate for lithium-ion batteries, and a higher low-temperature (-20°C) high-rate discharge capacity retention rate indicates a better high-rate discharge capacity retention rate for electrochemical devices in a low-temperature (-20°C) environment.

[0121] As can be seen from Comparative Examples 1-1, 1-3 to 1-4, and 1-1 to 1-13, when Compound I and Compound II are added to the electrolyte, and the content of Compound I satisfies 0.01% ≤ A ≤ 80%, and as can be seen from Comparative Examples 1-2, 1-5 to 1-6, and 1-14 to 1-23, when Compound I and Compound II are added to the electrolyte, and the content B of Compound II satisfies 0.1% ≤ B ≤ 10%, both the high-temperature (45°C) cycle capacity retention rate and the low-temperature (-20°C) high-rate discharge capacity retention rate increase, indicating that Compound I and Compound II can simultaneously improve the high-temperature (45°C) cycle capacity retention rate and the low-temperature (-20°C) high-rate discharge capacity retention rate of lithium-ion batteries.

[0122] As can be seen from Comparative Examples 1-3 to 1-4 and Examples 1-1 to 1-10, when the content A of Compound I is less than 0.01%, the addition of Compound I is too small and has almost no effect on improving the capacity retention rate of lithium-ion batteries at low temperature (-20°C) high-rate discharge. When the content A of Compound I is greater than 80%, the content of Compound I is too high and will accelerate the oxidative decomposition of other components in the electrolyte to generate HF. Compound II has insufficient ability to consume HF, resulting in a decrease in the capacity retention rate of lithium-ion batteries at high temperature (45°C).

[0123] As can be seen from Comparative Examples 1-5 to 1-6 and Examples 1-14 to 1-20, when the content of compound B of Formula II is less than 0.1%, the content of compound II is too low, and the ability of compound II to consume HF is insufficient. When the content of compound B of Formula II is greater than 10.0%, the content of compound II is too high, and excessive compound II leads to an increase in negative electrode impedance and a decrease in the low-temperature -20°C high-rate discharge capacity retention rate of the electrochemical device.

[0124] The preparation parameters and performance parameters of Examples 2-1 to 2-8 are shown in Table 1.

[0125] Table 2

[0126]

[0127] Note: " / " in Table 2 indicates that there is no corresponding parameter.

[0128] The mass percentages of the first component, compound I, and compound II satisfy the condition 0.8≤C / (A+B)≤1.15, which can improve the viscosity of the electrolyte and increase its ionic conductivity. As can be seen from Examples 1-6 and Examples 2-1 to 2-8, the addition of the first component to the electrolyte increases the high-temperature (45°C) cycle capacity retention rate and low-temperature (-20°C) high-rate discharge capacity retention rate of the lithium-ion battery, indicating that the high-temperature (45°C) cycle capacity retention rate and low-temperature (-20°C) high-rate discharge capacity retention rate of the lithium-ion battery are both improved.

[0129] The preparation parameters and performance parameters of Examples 3-1 to 3-8 are shown in Table 3.

[0130] Table 3

[0131]

[0132]

[0133] Note: " / " in Table 3 indicates that there is no corresponding parameter.

[0134] The second component has a lower viscosity, which can improve the wetting ability of the electrolyte. Both Formula I and Formula II compounds have good dissociation ability for lithium salts. 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 and improve the conductivity of the electrolyte. As can be seen from Examples 1-6 and Examples 3-1 to 3-5, the addition of the second component to the electrolyte increases 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. This indicates that the low-temperature (-20°C) high-rate discharge capacity retention rate and the high-temperature (45°C) cycle capacity retention rate of the lithium-ion battery are both improved.

[0135] As can be seen from Examples 3-6 to 3-8, the simultaneous addition of the first component and the second component to the electrolyte increases the high-temperature (45°C) cycle capacity retention rate and the low-temperature (-20°C) high-rate discharge capacity retention rate. This indicates that the simultaneous addition of the first component and the second component can further improve the high-temperature (45°C) cycle capacity retention rate and the low-temperature (-20°C) high-rate discharge capacity retention rate of lithium-ion batteries.

[0136] The preparation parameters and performance parameters of Examples 4-1 to 4-11 are shown in Table 4.

[0137] Table 4

[0138]

[0139]

[0140] Note: " / " in Table 4 indicates that there is no corresponding parameter.

[0141] As can be seen from Examples 1-6 and Examples 4-1 to 4-5, when the content of the first lithium salt in the electrolyte increases from 10.0% to 20%, the high-temperature 45°C cycle capacity retention rate and the low-temperature (-20°C) high-rate discharge capacity retention rate are both maintained at a high level. This indicates that the addition of compounds of formula I and formula II to the electrolyte of this application has a good dissociation ability for lithium salt, enabling the lithium-ion battery to still have a good high-temperature 45°C cycle capacity retention rate and a low-temperature -20°C high-rate discharge capacity retention rate even under high-concentration lithium salt conditions.

[0142] As can be seen from Examples 1-6, 4-6 to 4-11, the simultaneous addition of a first lithium salt, a second lithium salt, a first component, and a second component to the electrolyte can further improve the high-temperature 45°C cycle capacity retention rate and the low-temperature -20°C high-rate discharge capacity retention rate of lithium-ion batteries.

[0143] In this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this application, it should be understood that if there are terms such as "upper", "lower", "left", "right" indicating the orientation or positional relationship, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships are only for illustrative purposes and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0144] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrolyte, characterized by, The compound of formula I includes at least one of the following compounds: wherein R1in formula I is selected from the group consisting of unsubstituted or R0-substituted C2-C6alkyl, unsubstituted or R0-substituted C2-C6alkenyl, unsubstituted or R0-substituted C2-C6alkynyl, unsubstituted or R0-substituted C3-C6nitrogen-containing heteroaryl, unsubstituted or R0-substituted C6-C 12 each substituent R0of each group is independently selected from the group consisting of unsubstituted or substituted C1-C6alkyl, and when substituted, the substituent is fluorine; R2in formula II is selected from the group consisting of unsubstituted or fluorine-substituted C3-C 10 any one of a nitrogen-containing heteroaryl group, a C1-C5 phosphate group unsubstituted or substituted with fluorine, a C1-C5 carbonate group unsubstituted or substituted with fluorine, the atom in R2to which the B atom is bonded being any one of a nitrogen atom in the nitrogen-containing heteroaryl group, an oxygen atom in the phosphate group that is double-bonded to the phosphorus atom, a carbonyl oxygen atom in the carbonate; The mass percentage content of the compound of formula I is A, and the mass percentage content of the compound of formula II is B, based on the total mass of the electrolyte, wherein 0.01%≤A≤80%, 0.1%≤B≤10%.

2. The electrolyte according to claim 1, characterized in that, The electrolyte satisfies at least one of the following conditions: (1) 2≤A / B≤15; (2)0.5％≤A≤60％； (3)3％≤B≤5％。 3. The electrolyte of claim 1, wherein The compound of formula I includes at least one of the following compounds:

4. The electrolyte of claim 1, wherein The compound of formula II includes at least one of the following compounds:

5. The electrolyte of claim 1, wherein The electrolyte further includes a first component, and the first component includes at least one of vinylene carbonate, propylene carbonate, and fluoroethylene carbonate; The mass percentage content of the first component is C, based on the total mass of the electrolyte, and 0.2≤C / (A+B)≤1.

6.

6. The electrolyte of claim 1, wherein The electrolyte further includes a second component, and the second component includes at least one of diethyl carbonate, propyl propionate, and ethyl propionate; The mass percentage content of the second component is D, based on the total mass of the electrolyte, and 0.8≤D / (A+B)≤1.

5.

7. The electrolyte according to claim 6, characterized in that 1≤D / C≤2.

8. The electrolyte of claim 1, wherein, The electrolyte further includes a first lithium salt, and the first lithium salt includes at least one of lithium hexafluorophosphate or lithium bisfluorosulfonylimide; The mass percentage content of the first lithium salt is E, based on the total mass of the electrolyte, and 10%≤E≤20%.

9. The electrolyte of claim 1, wherein, The electrolyte further includes a second lithium salt, and the second lithium salt includes at least one of lithium tetrafluoroborate, lithium difluoro(oxalato)borate, and lithium bis(oxalato)borate; The mass percentage content of the second lithium salt is F, based on the total mass of the electrolyte, and 0.1%≤F≤10%.

10. An electrochemical device, characterized by, The electrolyte includes any one of claims 1-9.

11. An electronic device, comprising: The electrochemical device includes the electrolyte of claim 10.

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