Non-aqueous electrolyte, electrochemical device, and electronic device

Abstract

The application discloses a non-aqueous electrolyte, an electrochemical device and an electronic device. The non-aqueous electrolyte comprises vinylene carbonate and a dicyanocyclobutane sulfone compound. The dicyanocyclobutane sulfone compound comprises at least one of a compound of formula I or a compound of formula II, wherein n is selected from 0, 1 or 2, m is selected from 0, 1, 2 or 3, R 1 , R 2 , R 3 , R 4 , R 5 may be selected from a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, a cyano group or a keto group, R 6 and R 7 are selected from a carbon atom or an oxygen atom; the mass content of the dicyanocyclobutane sulfone compound is W1, and the mass content of the vinylene carbonate is W2, based on the total mass of the non-aqueous electrolyte, 0.05% <= W1 <= 3%, 0.25 <= W1 / W2 <= 50. By adding the dicyanocyclobutane sulfone compound and the vinylene carbonate in the non-aqueous electrolyte and controlling the mass content of the two within a suitable range, the high-temperature storage performance and the high-temperature cycle performance of the electrochemical device can be improved.

Description

Technical Field

[0001] This application relates to the field of electrochemistry, and more particularly to a non-aqueous electrolyte, an electrochemical device, and an electronic device. Background Technology

[0002] Lithium-ion batteries, with their high energy density, miniaturized design, and lightweight characteristics, have become a key energy storage technology in portable electronic devices, dominating in end products such as smartphones, laptops, and tablets. As market penetration continues to increase, the storage stability and cycle life of rechargeable batteries under high-temperature environments have gradually become a focus of industry attention. Currently, the industry commonly uses electrolyte additive technology to improve the storage and cycle performance of battery cells. However, due to the severe transition metal ion dissolution and electrolyte oxidation gas generation phenomena in high-nickel ternary cathode materials under high-temperature conditions, traditional additive systems struggle to overcome the inherent defects of the materials, resulting in a lack of substantial breakthroughs in the thermal stability bottleneck of high-nickel ternary lithium-ion batteries. To address this technical challenge, novel film-forming additives with interfacial chemical regulation functions are being developed to improve the structural integrity of high-nickel ternary systems under high-temperature conditions. Summary of the Invention

[0003] The purpose of this application is to provide a non-aqueous electrolyte, an electrochemical device, and an electronic device to improve the high-temperature storage performance and high-temperature cycling performance of the electrochemical device.

[0004] It should be noted that the invention description in this application uses lithium-ion batteries as an example of electrochemical devices to explain this application, but the electrochemical devices in this application are not limited to lithium-ion batteries.

[0005] The first aspect of this application provides a non-aqueous electrolyte comprising vinylene carbonate and a dicyanocyclobutane sulfone compound, wherein the dicyanocyclobutane sulfone compound comprises at least one of a compound of formula I or a compound of formula II.

[0006]

[0007] Where n is selected from 0, 1, or 2, m is selected from 0, 1, 2, or 3, and R 1 R 2 R 3 R 4 R 5 The atom can be selected from hydrogen, fluorine, methyl, trifluoromethyl, cyano, or ketone groups, R 6 and R 7Selected from carbon or oxygen atoms; based on the total mass of the non-aqueous electrolyte, the mass content of dicyanosulfone compound is W1, the mass content of vinylene carbonate is W2, 0.05%≤W1≤3%, preferably 0.05%≤W1≤2%, 0.25≤W1 / W2≤50, preferably 5≤W1 / W2≤20.

[0008] This application introduces a sulfolane dicyanocyclobutane compound into a non-aqueous electrolyte, controlling its mass content to meet the aforementioned range. The 3d orbitals of the sulfur atom in the S=O bond of the sulfolane dicyanocyclobutane compound overlap with the p orbitals of the oxygen atom, forming delocalized π bonds that are more readily accessible to the cathode interface than commonly used carbonate solvents. After electrochemical oxidation, a thermodynamically stable SO3-structured CEI film is formed. Furthermore, the cyano group in the sulfolane dicyanocyclobutane compound has a strong coordination ability with the transition metal elements at the cathode interface. Therefore, the sulfolane dicyanocyclobutane compound of this application not only improves the formation of the CEI film at the cathode interface but also deactivates catalytically active sites at the cathode interface, reduces metal ion dissolution at the cathode interface, and improves the stability of the cathode interface, resulting in good high-temperature storage performance of the electrochemical device. However, metal ion dissolution can cause the loss of the active structure of the cathode, affecting the high-temperature cycling performance of the electrochemical device.

[0009] Therefore, this application incorporates vinylene carbonate into the non-aqueous electrolyte. Vinylene carbonate has low solvation capability, and because it can participate in the solvation structure of sulfolane dicyanocyclobutane compounds, it can preferentially reduce them at the negative electrode interface. The polymer layer formed by its reduction product can inhibit the reaction of cyano compounds at the negative electrode interface, improving the stability of the negative electrode interface and thus improving the high-temperature cycling performance of the electrochemical device. Furthermore, vinylene carbonate migrates to the positive electrode interface along with the sulfolane dicyanocyclobutane compounds through solvation. Since it can improve the surface activity of the positive electrode interface, it can promote the oxidative film formation of the sulfolane dicyanocyclobutane compounds at the positive electrode interface, which is beneficial for maintaining the stability of the positive electrode interface structure and improving the high-temperature storage performance of the electrochemical device.

[0010] In one embodiment of this application, the compound of formula I includes at least one of the following compounds:

[0011]

[0012] In one embodiment of this application, the compound of formula II includes at least one of the following compounds:

[0013]

[0014] In one embodiment of this application, 0.01% ≤ W2 ≤ 2%.

[0015] Vinylene carbonate has low solvation ability, but it can preferentially reduce at the negative electrode interface by participating in the solvation structure of dicyanocyclobutane compound. The polymer layer formed by its reduction product can inhibit the reaction of the cyano group in dicyanocyclobutane compound at the negative electrode interface, improve the stability of the negative electrode interface, and thus improve the high-temperature cycling performance of the electrochemical device. In addition, vinylene carbonate migrates to the positive electrode interface together with dicyanocyclobutane compound through solvation. Since it can improve the surface activity of the positive electrode interface, it can promote the oxidation film formation of dicyanocyclobutane compound at the positive electrode interface, which is beneficial to maintaining the stability of the positive electrode interface structure and further improving the high-temperature storage performance of the electrochemical device.

[0016] In one embodiment of this application, the non-aqueous electrolyte further includes fluoroethylene carbonate, and the mass content of fluoroethylene carbonate is W3 based on the total mass of the non-aqueous electrolyte, where 0.05 ≤ W1 / W3 ≤ 100.

[0017] This application adds fluoroethylene carbonate to a non-aqueous electrolyte and controls the ratio W1 / W3 of the mass content of sulfolane dicyanocyclobutane compound to meet the above-mentioned range. Due to the strong solvation effect of fluorocarbonate, the content of carbonate solvent in the solvation structure can be reduced, thus reducing the decomposition of carbonate solvent. At the same time, the solvation structure of sulfolane dicyanocyclobutane compound is adjusted, reducing its desolvation energy at the positive electrode interface, improving the decomposition ability of sulfolane dicyanocyclobutane compound at the positive electrode interface, and improving the stability of the positive electrode interface. In addition, it has excellent reducing ability and can stably reduce and decompose at the negative electrode interface to generate an inorganic layer rich in LiF, further reducing the reduction and decomposition of sulfolane dicyanocyclobutane compound at the negative electrode interface, improving the stability of the negative electrode interface, and thus improving the high-temperature cycling and high-temperature storage performance of the electrochemical device.

[0018] In one embodiment of this application, 0.01% ≤ W3 ≤ 5%.

[0019] This application controls the mass content of fluoroethylene carbonate added to the non-aqueous electrolyte to meet the above-mentioned range. Since it can adjust the desolvation ability of sulfolane dicyanocyclobutane compound at the positive electrode interface, improve the film-forming ability of sulfolane dicyanocyclobutane compound at the positive electrode interface, and inhibit the decomposition of sulfolane dicyanocyclobutane compound at the negative electrode interface, it can improve the stability of the positive and negative electrode interfaces, and further improve the high-temperature storage performance and high-temperature cycling performance of the electrochemical device.

[0020] In one embodiment of this application, the non-aqueous electrolyte further includes lithium difluorophosphate, and the mass content of lithium difluorophosphate is W4 based on the mass of the non-aqueous electrolyte, with 0.01% ≤ W4 ≤ 2%.

[0021] This application improves the high-temperature storage performance of the electrochemical device by adding lithium difluorophosphate to a non-aqueous electrolyte and controlling its mass content to meet the above-mentioned range. Since the difluorophosphate anion can participate in the solvation structure of the electrolyte, it further reduces the desolvation ability of the dicyanocyclobutane compound and promotes the oxidative decomposition of the dicyanocyclobutane compound. At the same time, the difluorophosphate anion can be oxidized at the positive electrode interface to form an inorganic component rich in phosphates, which fills the voids after the dicyanocyclobutane compound forms a film, maintaining the stability of the positive electrode interface.

[0022] The second aspect of this application provides an electrochemical device comprising a positive electrode, a negative electrode, a separator, and the non-aqueous electrolyte provided in the first aspect of this application. The electrochemical device of this application exhibits excellent high-temperature storage and high-temperature cycling performance.

[0023] In one embodiment of this application, the positive electrode includes a positive electrode material comprising lithium nickel cobalt manganese oxide. Based on the total amount of nickel, cobalt, and manganese in the lithium nickel cobalt manganese oxide, the molar content of nickel is 79% to 85%. When the molar content of nickel is within the above range, it has a suitable NiO6 octahedral structure, which is beneficial to the adsorption of the sulfolane structure in the dicyanocyclobutane compound at the interface, and is beneficial to the positive electrode film formation reaction, thus giving the electrochemical device good high-temperature storage performance and high-temperature cycling performance.

[0024] A third aspect of this application provides an electronic device, including the electrochemical device provided in the second aspect of this application. The electrochemical device exhibits excellent high-temperature storage and high-temperature cycling performance, which is beneficial for extending the service life of the electronic device.

[0025] The beneficial effects of this application are:

[0026] This application introduces a sulfolane dicyanocyclobutane compound into a non-aqueous electrolyte, controlling its mass content to meet the aforementioned range. The 3d orbitals of the sulfur atom in the S=O bond of the sulfolane dicyanocyclobutane compound overlap with the p orbitals of the oxygen atom, forming delocalized π bonds that are more readily accessible to the cathode interface than commonly used carbonate solvents. After electrochemical oxidation, a thermodynamically stable SO3-structured CEI film is formed. Furthermore, the cyano group in the sulfolane dicyanocyclobutane compound has a strong coordination ability with the transition metal elements at the cathode interface. Therefore, the sulfolane dicyanocyclobutane compound of this application not only improves the formation of the CEI film at the cathode interface but also deactivates catalytically active sites at the cathode interface, reduces metal ion dissolution at the cathode interface, and improves the stability of the cathode interface, resulting in good high-temperature storage performance of the electrochemical device. However, metal ion dissolution can cause the loss of the active structure of the cathode, affecting the high-temperature cycling performance of the electrochemical device. Therefore, this application adds vinylene carbonate to the non-aqueous electrolyte. Vinylene carbonate has a low solvation ability, and because it can participate in the solvation structure of dicyanocyclobutane compound, it can achieve preferential reduction at the negative electrode interface. The polymer layer formed by its reduction product can inhibit the reaction of the cyano group in dicyanocyclobutane compound at the negative electrode interface, improve the stability of the negative electrode interface, and thus improve the high-temperature cycling performance of the electrochemical device. In addition, vinylene carbonate migrates to the positive electrode interface together with dicyanocyclobutane compound through solvation. Since it can improve the surface activity of the positive electrode interface, it can promote the oxidation film formation of dicyanocyclobutane compound at the positive electrode interface, which is beneficial to maintaining the stability of the positive electrode interface structure and improving the high-temperature storage performance of the electrochemical device. Detailed Implementation

[0027] 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.

[0028] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the chemical devices of this application are not limited to lithium-ion batteries.

[0029] The first aspect of this application provides a non-aqueous electrolyte comprising vinylene carbonate and a dicyanocyclobutane sulfone compound, wherein the dicyanocyclobutane sulfone compound comprises at least one of a compound of formula I or a compound of formula II.

[0030]

[0031] Where n is selected from 0, 1, or 2, m is selected from 0, 1, 2, or 3, and R 1 R 2 R3 R 4 R 5 The atom can be selected from hydrogen, fluorine, methyl, trifluoromethyl, cyano, or ketone groups, R 6 and R 7 Selected from carbon or oxygen atoms; based on the total mass of the non-aqueous electrolyte, the mass content of dicyanosulfone compound is W1, the mass content of vinylene carbonate is W2, 0.05%≤W1≤3%, preferably 0.05%≤W1≤2%, 0.25≤W1 / W2≤50, preferably 5≤W1 / W2≤20. For example, the mass content of the dicyanosulfone compound is 0.05%, 0.07%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.24%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.3%, 1.5%, 1.7%, 2%, 2.3%, 2.5%, 2.7%, 2.9%, 3%, or a range of any two of these values. When the mass content of sulfolane dicyanobutylene compound is too high, for example, above the upper limit of this application, excessive sulfolane dicyanobutylene compound will migrate to the negative electrode interface to participate in the reduction reaction, generating unstable interfacial film components, resulting in instability of the negative electrode interface and deteriorating the high-temperature storage performance of the electrochemical device; when the mass content of sulfolane dicyanobutylene compound is too low, for example, below the lower limit of this application, its effect on improving the high-temperature storage performance and high-temperature cycling performance of the electrochemical device is relatively limited. Without being limited to any particular theory, the inventors of this application have discovered that when the mass content of the dicyanocyclobutane compound is within the aforementioned range, the 3d orbitals of the sulfur atoms in the S=O bonds of the dicyanocyclobutane compound overlap with the p orbitals of the oxygen atoms, forming delocalized π bonds that are more likely to contact the cathode interface than commonly used carbonate solvents. After electrochemical oxidation, a CEI film with a thermodynamically stable SO3 structure is formed. In addition, the cyano group in the dicyanocyclobutane compound has a strong coordination ability with the transition metal elements at the cathode interface. Therefore, the dicyanocyclobutane compound of this application can not only improve the formation of a CEI film at the cathode interface, but also deactivate the catalytically active sites at the cathode interface, reduce the dissolution of metal ions at the cathode interface, and improve the stability of the cathode interface. However, the dissolution of metal ions will cause the loss of the active structure of the cathode, which will affect the high-temperature cycling performance of the electrochemical device.

[0032] Therefore, this application also adds vinylene carbonate to the non-aqueous electrolyte and controls the ratio W1 / W2 of the mass content of sulfolane dicyanosulfate and the mass content of vinylene carbonate to satisfy the above-mentioned range. For example, W1 / W2 is 0.25, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 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, 48, 49, 50, or a range consisting of any two of these values. When W1 / W2 is too high, for example, above the upper limit of this application, the relative content of vinylene carbonate is low, which cannot effectively inhibit the reductive decomposition of compound I at the negative electrode interface, resulting in little improvement in the stability of the negative electrode interface and thus little effect on improving the high-temperature cycling performance of the electrochemical device. When W1 / W2 is too low, for example, below the lower limit of this application, the relative content of vinylene carbonate is too high. Excessive vinylene carbonate will participate in the reductive decomposition of the negative electrode interface to generate too much organic layer, resulting in a decrease in the stability of the negative electrode interface and failing to effectively promote the uniform decomposition of dicyanosulfone compound at the positive electrode interface, thereby affecting the stability of the positive and negative electrode interfaces and thus deteriorating the high-temperature storage performance of the electrochemical device. Without being limited to any theory, the inventors of this application have discovered that when W1 / W2 is within the above range, vinylene carbonate can be electrochemically reduced and polymerized at the negative electrode interface to obtain polyvinyl carbonate (VC) structures adsorbed at the active sites of the negative electrode interface. This reduces the interfacial instability caused by the reduction of cyano groups in the dicyanosulfone compound at the negative electrode interface, thereby improving the high-temperature cycling performance of the electrochemical device. In addition, vinylene carbonate migrates to the positive electrode interface together with the dicyanosulfone compound through solvation. Since it can improve the surface activity of the positive electrode interface, it can promote the oxidation film formation of the dicyanosulfone compound at the positive electrode interface, which is beneficial to maintaining the stability of the positive electrode interface structure, thereby improving the high-temperature storage performance of the electrochemical device.

[0033] In one embodiment of this application, the compound of formula I includes at least one of the following compounds:

[0034]

[0035]

[0036] When the compound of Formula I is selected from the compounds within the above range, the 3d orbitals of the sulfur atom in the S=O bond of the compound of Formula I overlap with the p orbitals of the oxygen atom to form delocalized π bonds, which are easier to contact the cathode interface than commonly used carbonate solvents. After electrochemical oxidation, a CEI film with a thermodynamically stable SO3 structure will be formed. In addition, the cyano group in the dicyanocyclobutane compound has a strong coordination ability with the transition metal element at the cathode interface. Therefore, the dicyanocyclobutane compound of this application can not only improve the formation of CEI film at the cathode interface, but also deactivate the catalytically active sites at the cathode interface, reduce the dissolution of metal ions at the cathode interface, and improve the stability of the cathode interface, so that the electrochemical device has good high-temperature storage performance.

[0037] In one embodiment of this application, the compound of formula II includes at least one of the following compounds:

[0038]

[0039]

[0040] When the compound of formula II is selected from the compounds within the above range, the 3d orbitals of the sulfur atom in the S=O bond of the compound of formula II overlap with the p orbitals of the oxygen atom to form delocalized π bonds, which are easier to contact the cathode interface than commonly used carbonate solvents. After electrochemical oxidation, a CEI film with a thermodynamically stable SO3 structure will be formed. In addition, the cyano group in the dicyanocyclobutane compound has a strong coordination ability with the transition metal element at the cathode interface. Therefore, the dicyanocyclobutane compound of this application can not only improve the formation of CEI film at the cathode interface, but also deactivate the catalytically active sites at the cathode interface, reduce the dissolution of metal ions at the cathode interface, and improve the stability of the cathode interface, so that the electrochemical device has good high-temperature storage performance.

[0041] In one embodiment of this application, 0.01% ≤ W2 ≤ 2%. For example, the mass content of vinylene carbonate is 0.01%, 0.03%, 0.05%, 0.07%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.24%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.3%, 1.5%, 1.7%, 2%, or a range of any two of these values. For example, if the content of vinylene carbonate exceeds the upper limit specified in this application, the relative content of vinylene carbonate is too high. Excessive vinylene carbonate participates in the reduction and decomposition of the negative electrode interface to generate too much organic layer, resulting in a decrease in the stability of the negative electrode interface. Furthermore, it cannot effectively promote the uniform decomposition of dicyanocyclobutane compounds at the positive electrode interface, thereby affecting the stability of the positive and negative electrode interfaces and thus deteriorating the high-temperature storage performance of the electrochemical device. If the relative content of vinylene carbonate is too low, it cannot effectively inhibit the reduction and decomposition of dicyanocyclobutane compounds at the negative electrode interface, resulting in insignificant improvement in the stability of the negative electrode interface and thus little effect on improving the high-temperature cycling performance of the electrochemical device. Without being limited to any particular theory, the inventors of this application have discovered that vinylene carbonate has a low solvation ability, and because it can participate in the solvation structure of dicyanocyclobutane compound, it can achieve preferential reduction at the negative electrode interface. The polymer layer formed by its reduction product can inhibit the reaction of the cyano group in the dicyanocyclobutane compound at the negative electrode interface, improve the stability of the negative electrode interface, and thus improve the high-temperature cycling performance of the electrochemical device. In addition, vinylene carbonate migrates to the positive electrode interface together with the dicyanocyclobutane compound through solvation. Since it can improve the surface activity of the positive electrode interface, it can promote the oxidation film formation of the dicyanocyclobutane compound at the positive electrode interface, which is beneficial to maintaining the stability of the positive electrode interface structure and further improves the high-temperature storage performance of the electrochemical device.

[0042] In one embodiment of this application, the non-aqueous electrolyte further includes fluoroethylene carbonate, and the mass content of fluoroethylene carbonate is W3 based on the total mass of the non-aqueous electrolyte, where 0.05 ≤ W1 / W3 ≤ 100. For example, W1 / W3 is 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 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, 48, 49, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or a range of any two of these values. When W1 / W3 is too high, for example, above the upper limit of this application, the relative content of fluoroethylene carbonate is low, the ability to control solvation is weak, and the improvement effect on the high-temperature cycling and high-temperature storage performance of electrochemical devices is not obvious. When W1 / W3 is too low, for example, below the lower limit of this application, the relative content of fluoroethylene carbonate is too high, which will reduce the content of dicyanocyclobutane compound in the solvation structure and affect the film formation effect of dicyanocyclobutane compound on the cathode. Without being limited to any theory, the inventors of this application have discovered that when W1 / W3 is within the above range, due to the strong solvation effect of fluorocarbonate, the content of carbonate solvent in the solvation structure can be reduced, thus reducing the decomposition of carbonate solvent. At the same time, the solvation structure of dicyanocyclobutane compound is adjusted, reducing its desolvation energy at the positive electrode interface, improving the decomposition ability of dicyanocyclobutane compound at the positive electrode interface, and improving the stability of the positive electrode interface. In addition, fluoroethylene carbonate itself has excellent reducing ability and can stably reduce and decompose at the negative electrode interface to generate an inorganic layer rich in LiF, further reducing the reduction and decomposition of dicyanocyclobutane compound at the negative electrode interface, improving the stability of the negative electrode interface, and further improving the high-temperature cycling and high-temperature storage performance of electrochemical device.

[0043] In one embodiment of this application, 0.01% ≤ W3 ≤ 5%. For example, the mass content of fluoroethylene carbonate is 0.01%, 0.03%, 0.05%, 0.07%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.24%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0. The values ​​are 75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.3%, 1.5%, 1.7%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, or any two of these values. When the mass content of fluoroethylene carbonate is too high, for example, exceeding the upper limit of this application, the relative content of fluoroethylene carbonate is too high, which will reduce the content of dicyanocyclobutane compound in the solvation structure and affect the film-forming effect of dicyanocyclobutane compound at the positive electrode. When the mass content of fluoroethylene carbonate is too low, for example, below the lower limit of this application, the relative content of fluoroethylene carbonate is low, the ability to control solvation is weak, and the improvement effect on the high-temperature cycling and high-temperature storage performance of the electrochemical device is not obvious. Without being limited to any theory, the inventors of this application have discovered that when the mass content of fluoroethylene carbonate is within the above-mentioned range, due to the strong solvation effect of fluorocarbonate, the content of carbonate solvent in the solvation structure can be reduced, thus reducing the decomposition of carbonate solvent. At the same time, the solvation structure of dicyanocyclobutane compound is adjusted, its desolvation energy at the positive electrode interface is reduced, the decomposition ability of dicyanocyclobutane compound at the positive electrode interface is improved, and the stability of the positive electrode interface is improved. In addition, it has excellent reducing ability and can stably reduce and decompose at the negative electrode interface to generate an inorganic layer rich in LiF, further reducing the reduction and decomposition of dicyanocyclobutane compound at the negative electrode interface, improving the stability of the negative electrode interface, and further improving the high-temperature cycling and high-temperature storage performance of electrochemical devices.

[0044] In one embodiment of this application, the non-aqueous electrolyte further includes lithium difluorophosphate, wherein the mass content of lithium difluorophosphate is W4, 0.01% ≤ W4 ≤ 2%, based on the mass of the non-aqueous electrolyte. For example, the mass content of fluoroethylene carbonate is 0.01%, 0.03%, 0.05%, 0.07%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.24%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.3%, 1.5%, 1.7%, 2%, or a range of any two of these values. When the mass content of lithium difluorophosphate is too high, for example, exceeding the upper limit of this application, excessive inorganic components are formed at the positive electrode interface, leading to a decrease in the elasticity of the positive electrode, making it prone to breakage and detrimental to the stability of the positive electrode interface. This negatively impacts the high-temperature storage and high-temperature cycling performance of the electrochemical device. Conversely, when the mass content of lithium difluorophosphate is too low, for example, below the lower limit of this application, the improvement effect on the high-temperature cycling and high-temperature storage performance of the electrochemical device is not significant. Without being limited to any theory, the inventors of this application have discovered that when the mass content of lithium difluorophosphate is within the above range, the difluorophosphate anion can participate in the solvation structure of the non-aqueous electrolyte, further reducing the desolvation ability of the sulfolane dicyanobutyl compound and promoting the oxidative decomposition of the sulfolane dicyanobutyl compound. Simultaneously, the difluorophosphate anion can oxidize at the positive electrode interface to form phosphide-rich inorganic components that fill the voids in the sulfolane dicyanobutyl compound film, maintaining the stability of the positive electrode interface and thus further improving the high-temperature storage performance of the electrochemical device.

[0045] In one embodiment of this application, the non-aqueous electrolyte further includes lithium salt and non-aqueous solvent.

[0046] This application does not impose any particular limitation on the lithium salt, as long as it achieves the purpose of this application. For example, the lithium salt may include, but is not limited to, at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. This application does not impose any particular limitation on the content of the lithium salt in the electrolyte, as long as it achieves the purpose of this application. For example, based on the mass of the non-aqueous electrolyte, the mass content of the lithium salt may be 8% to 15%.

[0047] This application does not impose any particular restrictions on non-aqueous solvents, as long as they can achieve the purpose of this application. For example, non-aqueous solvents may include, but are not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents.

[0048] The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorocarbonate 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 (MEC). The aforementioned cyclic carbonates 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). Fluorocarbonate compounds may include, but are not limited to, at least one of 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The 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, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. 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, 1-ethoxy-1-methoxyethane, 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, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.

[0049] This application does not impose any particular limitation on the content of non-aqueous solvents in the non-aqueous electrolyte, as long as the purpose of this application can be achieved. For example, based on the mass of the non-aqueous electrolyte, the mass content of non-aqueous solvents is 0% to 91.94%.

[0050] In one embodiment of this application, the non-aqueous electrolyte may include a sulfolane dicyanocyclobutane compound, vinylene carbonate, lithium salt, and a non-aqueous solvent. The mass content of the sulfolane dicyanocyclobutane compound, vinylene carbonate, and lithium salt is as described above, and the mass content of the non-aqueous solvent is 80% to 91.94%. Electrochemical devices comprising the above-mentioned non-aqueous electrolyte exhibit good high-temperature storage performance and high-temperature cycling performance.

[0051] In one embodiment of this application, the non-aqueous electrolyte may include a sulfolane dicyanosulfate compound, vinylene carbonate, fluoroethylene carbonate, lithium salt, and a non-aqueous solvent. The mass content of the sulfolane dicyanosulfate compound, vinylene carbonate, fluoroethylene carbonate, and lithium salt is as described above, and the mass content of the non-aqueous solvent is 75% to 91.93%. Electrochemical devices comprising the above-mentioned non-aqueous electrolyte exhibit good high-temperature storage performance and high-temperature cycling performance.

[0052] In one embodiment of this application, the non-aqueous electrolyte may include a sulfolane dicyanosulfate compound, vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium salt, and a non-aqueous solvent. The mass content of the sulfolane dicyanosulfate compound, vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, and lithium salt is as described above, and the mass content of the non-aqueous solvent is 73% to 91.92%. Electrochemical devices comprising the above-mentioned non-aqueous electrolyte exhibit good high-temperature storage performance and high-temperature cycling performance.

[0053] In one embodiment of this application, the non-aqueous electrolyte may include a sulfolane dicyanosulfate compound, vinylene carbonate, lithium salt, a non-aqueous solvent, and one of fluoroethylene carbonate and lithium difluorophosphate. The mass content of the sulfolane dicyanosulfate compound, vinylene carbonate, lithium salt, and one of fluoroethylene carbonate and lithium difluorophosphate is as described above, and the mass content of the non-aqueous solvent is 75% to 91.93%. Electrochemical devices comprising the above-mentioned non-aqueous electrolyte exhibit good high-temperature storage performance and high-temperature cycling performance.

[0054] The second aspect of this application provides an electrochemical device comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte provided in the first aspect of this application.

[0055] In one embodiment of this application, the electrochemical device further includes a positive electrode sheet, which comprises a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The phrase "positive electrode material layer disposed on at least one surface of the positive current collector" means that the positive electrode material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the positive current collector, or only a portion of the surface area; this application does not have any particular limitation, as long as the purpose of this application is achieved. This application does not have any particular limitation on the positive current collector, as long as the purpose of this application is achieved, it can include, for example, aluminum foil, aluminum alloy foil, or composite current collectors (e.g., aluminum-carbon composite current collectors).

[0056] The positive electrode material layer may also include the positive electrode material, a conductive agent, and a binder.

[0057] In one embodiment of this application, the cathode material comprises lithium nickel cobalt manganese oxide metal oxide, wherein the molar content of nickel is 79% to 85% based on the total amount of nickel, cobalt, and manganese in the lithium nickel cobalt manganese oxide metal oxide. For example, the molar content of nickel can be 79%, 79.2%, 79.4%, 79.6%, 79.8%, 80%, 80.2%, 80.4%, 80.6%, 80.8%, 81%, 81.2%, 81.4%, 81.6%, 81.8%, 82%, 82.2%, 82.4%, 82.6%, 82.8%, 83%, 83.2%, 83.4%, 83.6%, 83.8%, 84%, 84.2%, 84.4%, 84.6%, 84.8%, 85%, or a range consisting of any two of these values. When the molar content of nickel is within the above range, it has a suitable NiO6 octahedral structure, which is conducive to the adsorption of the sulfolane structure in the dicyanosulfone compound with the interface, and is conducive to the positive electrode film formation reaction, so that the electrochemical device has good high-temperature storage performance and high-temperature cycling performance.

[0058] The cathode material in the cathode material layer of this application may include, but is not limited to, at least one of lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel manganese aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganese oxide, spinel-type lithium nickel manganese oxide, and lithium titanate.

[0059] This application does not impose any particular limitation on the adhesive, as long as it can achieve the purpose of this application. For example, the adhesive may include, but is not limited to, adhesive polymers, such as at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified SBR rubber, or polyurethane, wherein polyolefin adhesives include at least one of polyethylene, polypropylene, polyolefin ester, polyolefin alcohol, or polyacrylic acid.

[0060] This application does not impose any particular limitation on conductive agents, as long as they can achieve the purpose of this application. For example, conductive agents may include, but are not limited to, carbon-based materials, metal-based materials, conductive polymers, or mixtures thereof; wherein carbon-based materials include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, or carbon fiber; metal-based materials include, for example, metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; and conductive polymers include polyphenylene derivatives.

[0061] This application does not impose any particular limitations on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector can be 5 μm to 20 μm, and the thickness of the single-sided positive electrode material layer can be 30 μm to 120 μm.

[0062] Optionally, the positive electrode may further include a conductive layer located between the positive current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited and can be any 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; for example, it can be at least one of the aforementioned conductive agents and binders.

[0063] In one embodiment of this application, the electrochemical device preferably includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The phrase "the negative electrode material layer is 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 term "surface" here can refer to the entire surface area of ​​the negative electrode current collector, or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved.

[0064] This application does not impose any particular restrictions on the negative electrode current collector, as long as it can achieve 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 collector. For example, the composite current collector may be lithium copper composite current collector, carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, etc.

[0065] Anode materials may include, but are not limited to, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO, lithium-tin alloys, Sn, SnO, SnO2, and spinel-structured Li4Ti5O. 12 At least one of lithium-aluminum alloys.

[0066] The negative electrode material layer of this application may further include a conductive agent, a binder, and a thickener. This application does not impose any particular restrictions on the types of conductive agents, binders, and thickeners, as long as they achieve the purpose of this application. For example, the binder may include, 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 fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc. The conductive agent may include, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. Specifically, carbon-based materials are selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof; metal-based materials are selected from metal powder, metal fiber, copper, nickel, aluminum, or silver; and the conductive polymer is a polyphenylene derivative. This application does not impose any particular restrictions on the mass ratio of the negative electrode material, conductive agent, and binder in the negative electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved. Thickeners include, but are not limited to, sodium carboxymethyl cellulose.

[0067] This application does not impose any particular limitations on the thickness of the negative electrode current collector or the negative electrode active material layer, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode current collector can be 4 μm to 12 μm, and the thickness of the negative electrode material layer can be 30 μm to 130 μm.

[0068] Optionally, the negative electrode sheet may further include a conductive layer 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, which can be a conductive layer commonly used in the art. For example, the conductive layer may include a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer, which may be at least one of the aforementioned conductive agents and binders.

[0069] In one embodiment of this application, the electrochemical device further includes a separator membrane. This application does not impose any particular limitation on the separator membrane, as long as it achieves the purpose of this application. For example, the material of the separator membrane 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 type of separator membrane may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0070] In some embodiments of this application, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer 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.

[0071] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic substances.

[0072] In one embodiment of this application, the inorganic layer comprises inorganic particles and a binder. This application does not particularly limit the inorganic particles; for example, the inorganic particles may include at least one selected from 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 particularly limit the binder; for example, the binder may be at least one of the binders described above. In some embodiments of this application, the polymer layer comprises a polymer, the polymer material of which includes at least one selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0073] The inorganic layer may also include thickeners and wetting agents. This application does not have any particular restrictions on the types of thickeners and wetting agents, as long as they can achieve the purpose of this application. For example, the thickener may include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose; the wetting agent may include, but is not limited to, at least one of dimethylsiloxane, sodium dodecyl sulfate, trialkyl phosphate, methyl decanoate, and dodecyl acetate.

[0074] This application does not impose any particular limitation on the thickness of the separator, as long as it can achieve the purpose of this application. For example, the thickness of the separator can be from 4 μm to 30 μm.

[0075] The electrochemical device also includes a housing for accommodating the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of electrochemical devices. This application does not limit the scope of these other components. This application does not impose any particular limitation on the housing; it can be a housing known in the art, as long as it achieves the purpose of this application. For example, the housing can be a rigid housing or a flexible housing. The material of the rigid housing can be metal; this application does not limit the type of metal and can use known metal rigid housings, as long as they achieve the purpose of this application. The flexible housing can be a metal-plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0076] The preparation process of the electrochemical device described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, the preparation process of the electrochemical device 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 into a housing; injecting electrolyte into the housing and sealing it to obtain a secondary battery. Alternatively, 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 into a housing; injecting electrolyte into the housing and sealing it to obtain a secondary battery. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the secondary battery.

[0077] A third aspect of this application provides an electronic device, wherein the electronic device includes the electrochemical device provided in the second aspect of this application.

[0078] The electronic device described in this application is not particularly limited and 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.

[0079] Example

[0080] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0081] (1) High-temperature storage performance test:

[0082] The lithium-ion battery was placed in a constant temperature environment of 25℃ and left to stand for 30 minutes to allow it to reach the 25℃ constant temperature state. The lithium-ion battery was then charged at a constant current of 0.5C to 4.3V, and then charged at a constant voltage of 4.3V to a current of 0.025C. The thickness of the lithium-ion battery at this point was recorded as the initial thickness H0. The lithium-ion battery was then transferred to a constant temperature chamber at 60℃ and stored for 30 days. During this period, the thickness of the lithium-ion battery was measured and recorded every 6 days. The measured thickness recorded after 30 days was recorded as the storage thickness H1.

[0083] High-temperature storage thickness expansion rate = (H1-H0) / H0×100%.

[0084] (2) High-temperature cycling performance test

[0085] The lithium-ion battery was placed in a constant temperature environment of 45°C and left to stand for 30 minutes to allow it to reach the 45°C constant temperature state. It was then charged at a constant current of 0.5C to 4.3V, and then charged at a constant voltage of 4.3V to a current of 0.025C. After standing for 5 minutes, it was discharged at a constant current of 0.5C to 2.8V. The initial discharge capacity was recorded as C0. This charge-discharge cycle was repeated 200 times, and the discharge capacity after 200 cycles was recorded as C1.

[0086] Cyclic capacity retention rate = C1 / C0 × 100%.

[0087] (3) Component content test in non-aqueous electrolyte

[0088] After discharging the lithium-ion battery, centrifuge it, and then test the mass content of each substance in the electrolyte by GC-MS.

[0089] (4) Content test of each element in the cathode material

[0090] At least 1g of the active material layer powder of the positive electrode sheet, after being cleaned with DMC (dimethyl carbonate), is scraped off with a scraper. 0.4g of the positive electrode active material layer powder is dissolved in aqua regia and the solution is brought to a final volume of 100mL. Then, the mass content of elements such as Ni, Co, and Mn in the solution is tested using an ICP analyzer. The mass content of Ni, Co, and Mn is measured, and then each is divided by its respective molar mass. The molar amount of Ni is calculated by dividing the molar amount of Ni by the sum of the molar amounts of Ni, Co, and Mn, thus obtaining the molar percentage of Ni in the active material.

[0091] Example 1-1

[0092] <Preparation of Electrolyte>

[0093] In an argon-atmospheric glove box with a water content of less than 10 ppm, dimethyl carbonate, diethyl carbonate, and ethylene carbonate were mixed in a mass ratio of 1:1:1 to obtain a non-aqueous solvent. Then, compound I-1 and lithium salt lithium hexafluorophosphate (LiPF6) were added to the non-aqueous solvent and stirred until homogeneous to obtain a non-aqueous electrolyte. Based on the total mass of the non-aqueous electrolyte, the mass content of compound I-1 was 0.05%, the mass content of fluoroethylene carbonate was 0.01%, the mass content of lithium salt was 12.5%, and the remainder was non-aqueous solvent.

[0094] <Preparation of the positive electrode>

[0095] The positive electrode active material NCM811, conductive agent Super P, and binder polyvinylidene fluoride were mixed in a mass ratio of 97.7:0.9:1.4. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%. After vacuum stirring, the slurry was obtained. The positive electrode slurry was uniformly coated onto one surface of a 9 μm thick aluminum foil current collector and dried at 120°C to obtain a single-sided coated positive electrode sheet with a coating weight of 208 mg / 1540 mm². The above steps were repeated on the other surface of the aluminum foil to obtain a double-sided coated positive electrode sheet. After drying at 120°C, the sheet was cold-pressed, cut, and had tabs welded to obtain a 74 mm × 867 mm positive electrode sheet for later use. The thickness of the single-sided positive electrode layer was 43 μm; the compaction density of the positive electrode layer after cold pressing was 3.5 g / cm³. 3 .

[0096] <Preparation of Negative Electrode Sheets>

[0097] Artificial graphite (negative electrode active material), styrene-butadiene rubber (binder), and acetylene black (conductive agent) were mixed in a mass ratio of 97.4:1.4:1.2. Deionized water was added as a solvent to prepare a slurry with a solid content of 45 wt%. The slurry was stirred evenly in a vacuum mixer to obtain the negative electrode slurry. The negative electrode slurry was uniformly coated onto one surface of a 6 μm thick copper foil used as a negative electrode current collector and dried at 120°C to obtain a negative electrode sheet with a single-sided negative electrode material layer. The coating weight of the negative electrode material layer was 142 mg / 1540 mm². 2 The above steps are then repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of negative electrode material. After drying at 120℃ and cold pressing, the sheet is cut and tabs are welded to obtain a negative electrode sheet with dimensions of 78mm × 875mm for later use. The thickness of the single-sided negative electrode material layer is 54.5μm; the compaction density of the negative electrode material layer after cold pressing is 1.70g / cm³. 3 .

[0098] <Preparation of the separating membrane>

[0099] A 5μm thick polyethylene (PE) porous membrane (supplied by Celgard) was used.

[0100] <Preparation of Lithium-ion Batteries>

[0101] The prepared positive electrode, separator, negative electrode, and separator are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. The electrodes are then wound to obtain the electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag and dried in an 85°C vacuum oven for 12 hours to remove moisture. The prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation (charged at a constant current of 0.2C to 3.9V), shaping, and capacity testing.

[0102] Examples 1-2 to Examples 1-16

[0103] Except for adjusting the type and mass content of dicyanopyridine compound and the mass content of vinylene carbonate in the <Preparation of Non-Aqueous Electrolyte>, the mass content of non-aqueous solvent is changed accordingly, and the mass content of lithium salt remains unchanged, the rest is the same as in Example 1-1.

[0104] Examples 2-1 to 2-10

[0105] Except for the addition of fluoroethylene carbonate in the <Preparation of Non-Aqueous Electrolyte>, and the adjustment of the mass content of fluoroethylene carbonate, the mass content of the non-aqueous solvent is changed accordingly, while the mass content of lithium salt remains unchanged, the rest is the same as in Examples 1-3.

[0106] Examples 3-1 to 3-9

[0107] Except for the addition of lithium difluorophosphate in the <Preparation of Non-Aqueous Electrolyte>, and the adjustment of the mass content of lithium difluorophosphate, the mass content of the non-aqueous solvent is changed accordingly, while the mass content of lithium salt remains unchanged, the rest is the same as in Examples 1-3.

[0108] Examples 4-1 to 4-3

[0109] Except for the addition of fluoroethylene carbonate and lithium difluorophosphate in the <Preparation of Non-Aqueous Electrolyte>, and the adjustment of the mass content of fluoroethylene carbonate and lithium difluorophosphate, the mass content of the non-aqueous solvent is changed accordingly, while the mass content of lithium salt remains unchanged, the rest is the same as in Examples 1-3.

[0110] Examples 5-1 to 5-2 and Examples 5-5 to 5-6

[0111] Except for the change in the molar content of nickel in the lithium nickel cobalt manganese oxide metal oxide of the positive electrode material in the <Preparation of Positive Electrode Sheet>, the rest is the same as in Example 1-1.

[0112] Comparative Examples 1 to 3

[0113] Except for the addition of excess of compound I-1 and vinylene carbonate in the <Preparation of Non-Aqueous Electrolyte>, which alters the mass content of the non-aqueous solvent, and the unchanged mass content of the lithium salt, the rest is the same as in Examples 1-3.

[0114] Comparative Example 4

[0115] Except that dicyanosulfone compound is not added in the <Preparation of Non-Aqueous Electrolyte>, the mass content of the non-aqueous solvent is changed accordingly, and the mass content of lithium salt remains unchanged, the rest is the same as in Examples 1-3.

[0116] Comparative Example 5

[0117] Except that vinylene carbonate is not added in the <Preparation of Non-Aqueous Electrolyte>, the mass content of the non-aqueous solvent is changed accordingly, and the mass content of lithium salt remains unchanged, the rest is the same as in Examples 1-3.

[0118] Comparative Example 6

[0119] Except that dicyanosulfone and vinylene carbonate are not added in the <Preparation of Non-Aqueous Electrolyte>, the mass content of the non-aqueous solvent is changed accordingly, and the mass content of lithium salt remains unchanged, the rest is the same as in Examples 1-3.

[0120] Table 1

[0121]

[0122]

[0123] Note: (1) “ / ” in Table 1 indicates that there is no corresponding preparation parameter or substance. (2) Taking Examples 1-13 as an example, “type of dicyanopyridine compound” is “I-1+I-4”, and “mass content of dicyanopyridine compound” is “0.25+0.25”, indicating that the dicyanopyridine compound includes compound I-1 and compound I-4. Based on the total mass of the non-aqueous electrolyte, the mass content of compound I-1 is 0.25%, and the mass content of compound I-4 is 0.25%. Other examples follow the same principle.

[0124] As can be seen from Examples 1-1 to 1-16 and Comparative Examples 1 to 6, when the type and mass content of dicyanopyridine compound, and the ratio of the mass content of dicyanopyridine compound to the mass content of vinylene carbonate, W1 / W2, are within the scope of this application, the lithium-ion battery exhibits a lower storage thickness expansion rate and a higher cycle capacity retention rate, indicating that the high-temperature storage performance and high-temperature cycle performance of the lithium-ion battery are improved. When the type and mass content of dicyanopyridine compound, and the ratio of the mass content of dicyanopyridine compound to the mass content of vinylene carbonate, W1 / W2, are not within the scope of this application in Comparative Examples 1 to 6, the lithium-ion battery exhibits a higher storage thickness expansion rate and a lower cycle capacity retention rate, indicating that the lithium-ion battery has lower high-temperature storage performance and high-temperature cycle performance. As can be seen from Examples 1-1 to 1-16, the lithium-ion battery of this application has a lower storage thickness expansion rate and a higher cycle capacity retention rate, indicating that the lithium-ion battery of this application has good high-temperature storage performance and high-temperature cycle performance.

[0125] Table 2

[0126]

[0127] Note: " / " in Table 2 indicates that the corresponding preparation parameters or substances do not exist.

[0128] The mass content of fluoroethylene carbonate typically affects the high-temperature storage and high-temperature cycling performance of electrochemical devices. As can be seen from Examples 1-3 and Examples 2-1 to 2-10, when the mass content of fluoroethylene carbonate is within the range specified in this application, the lithium-ion battery exhibits a lower storage thickness expansion rate and a higher cycle capacity retention rate, indicating that the high-temperature storage and high-temperature cycling performance of the lithium-ion battery are improved.

[0129] The value of W1 / W3 typically affects the high-temperature storage performance and high-temperature cycling performance of electrochemical devices. As can be seen from Examples 1-3 and Examples 2-1 to 2-10, when the value of W1 / W3 is within the range of this application, the lithium-ion battery has a lower storage thickness expansion rate and a higher cycle capacity retention rate, indicating that the high-temperature storage performance and high-temperature cycling performance of the lithium-ion battery are improved.

[0130] Table 3

[0131]

[0132]

[0133] Note: " / " in Table 3 indicates that the corresponding preparation parameters or substances do not exist.

[0134] The mass content of lithium difluorophosphate typically affects the high-temperature storage performance and high-temperature cycling performance of electrochemical devices. As can be seen from Examples 1-3 and Examples 3-1 to 3-9, when the mass content of lithium difluorophosphate is within the range specified in this application, the lithium-ion battery exhibits a lower storage thickness expansion rate and a higher cycle capacity retention rate, indicating that the high-temperature storage performance and high-temperature cycling performance of the lithium-ion battery are improved.

[0135] Table 4

[0136]

[0137] Note: " / " in Table 4 indicates that the corresponding preparation parameters or substances do not exist.

[0138] Different types of non-aqueous electrolytes can affect the high-temperature storage performance and high-temperature cycling performance of electrochemical devices. As can be seen from Examples 1-3 and Examples 4-1 to 4-3, when the non-aqueous electrolyte combination within the scope of this application is used, the storage thickness expansion rate of the lithium-ion battery is further reduced and the cycle capacity retention rate of the lithium-ion battery is further improved, indicating that the high-temperature storage performance and high-temperature cycling performance of the lithium-ion battery are improved.

[0139] Table 5

[0140]

[0141] The molar content of nickel in lithium nickel cobalt manganese oxide cathode material typically affects the high-temperature storage performance and high-temperature cycling performance of electrochemical devices. As can be seen from Examples 1-1 and Examples 5-1 to 5-4, when the molar content of nickel in lithium nickel cobalt manganese oxide cathode material is within a suitable range, the use of dicyanosulfone compound can result in a lower storage thickness expansion rate and a higher cycle capacity retention rate for lithium-ion batteries, indicating that the high-temperature storage performance and high-temperature cycling performance of lithium-ion batteries are improved.

[0142] The terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such a process, method, or article.

[0143] The various embodiments in this specification are described in a related manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

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

Claims

1. A non-aqueous electrolyte, characterized in that, The compounds include vinylene carbonate and dicyanocyclobutane sulfone, wherein the dicyanocyclobutane sulfone includes at least one of a compound of formula I or a compound of formula II: Where n is selected from 0, 1, or 2, m is selected from 0, 1, 2, or 3, and R 1 R 2 R 3 R 4 R 5 The atom can be selected from hydrogen, fluorine, methyl, trifluoromethyl, cyano, or ketone groups, R 6 and R 7 Selected from carbon or oxygen atoms; Based on the total mass of the non-aqueous electrolyte, the mass content of the dicyanosulfone compound is W1, the mass content of the vinylene carbonate is W2, 0.05% ≤ W1 ≤ 3%, and 0.25 ≤ W1 / W2 ≤ 50.

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

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

4. The non-aqueous electrolyte according to claim 1, characterized in that, 0.05％≤W1≤2％。 5. The non-aqueous electrolyte according to claim 1, characterized in that, 0.01％≤W2≤2％。 6. The non-aqueous electrolyte according to claim 1, characterized in that, 5≤W1 / W2≤20.

7. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte also includes fluoroethylene carbonate, and based on the total mass of the non-aqueous electrolyte, the mass content of the fluoroethylene carbonate is W3, where 0.05 ≤ W1 / W3 ≤ 100.

8. The non-aqueous electrolyte according to claim 7, characterized in that, 0.01％≤W3≤5％。 9. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte also includes lithium difluorophosphate, and based on the mass of the non-aqueous electrolyte, the mass content of the lithium difluorophosphate is W4, 0.01% ≤ W4 ≤ 2%.

10. An electrochemical device, characterized in that, It includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte as described in any one of claims 1 to 9.

11. The electrochemical device according to claim 10, characterized in that, The positive electrode includes a positive electrode material, which includes lithium nickel cobalt manganese oxide metal oxide. Based on the total amount of nickel, cobalt and manganese in the lithium nickel cobalt manganese oxide metal oxide, the molar content of nickel is 79% to 85%.

12. An electronic device, characterized in that, Includes the electrochemical device as described in any one of claims 10 to 11.

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