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 a dicyanosulfolane compound, the dicyanosulfolane 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 dicyanosulfolane compound is W1, 0.05% <= W1 <= 3% based on the total mass of the non-aqueous electrolyte. By adding the dicyanosulfolane compound in the non-aqueous electrolyte and controlling the mass content in a suitable range, the high-temperature storage performance and the hot box 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 outstanding advantages of high energy density, compact size, and lightweight design, have become the core power solution in the field of portable electronic devices, widely used in terminal products such as mobile phones, laptops, and tablets. With increasing market penetration, the high-temperature performance of rechargeable batteries, especially their high-temperature storage stability, has become increasingly prominent. Currently, the industry commonly uses electrolyte additives to improve battery storage performance and thermal safety. However, due to the severe transition metal ion dissolution and gas generation behavior of high-nickel ternary cathode materials at high temperatures, existing additive systems still struggle to overcome the limitations of the material's intrinsic properties, resulting in the inadequate thermal stability of high-nickel ternary lithium-ion batteries remaining unresolved. Therefore, to improve the application of high-nickel ternary lithium-ion batteries, it is necessary to further develop a novel film-forming additive that can simultaneously improve both high-temperature storage performance and high-temperature cycle performance. 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 thermal box performance (thermal safety 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 a dicyanocyclobutane compound, wherein the dicyanocyclobutane 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 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, 0.05% ≤ W1 ≤ 3%, preferably 0.05% ≤ W1 ≤ 2%.

[0008] This application introduces a sulfolane dicyanocyclobutane compound into a non-aqueous electrolyte. The 3d orbitals of the sulfur atom in the S=O bond of the sulfolane 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, thereby reducing the decomposition of the non-aqueous electrolyte and helping to maintain the stability of the cathode interface. This results in the electrochemical device exhibiting excellent high-temperature storage performance and thermal box performance (thermal safety performance).

[0009] In one embodiment of this application, the compound of formula I includes at least one of the following compounds:

[0010]

[0011]

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

[0013]

[0014]

[0015] In one embodiment of this application, the non-aqueous electrolyte further includes a lithium salt, which includes at least one of lithium bis(fluorosulfonyl)imide (LiDFSI), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2), or lithium hexafluorophosphate (LiPF6). Based on the total mass of the non-aqueous electrolyte, the mass content of the lithium salt is W2, where 0.003 ≤ W1 / W2 ≤ 0.3.

[0016] This application, by adding the aforementioned lithium salt to a non-aqueous electrolyte and controlling the ratio W1 / W2 of the mass content of dicyanocyclobutane compound to the mass content of the aforementioned lithium salt to meet the aforementioned range, improves the desolvation ability of the dicyanocyclobutane compound due to the participation of lithium salt anions in the solvation structure, promotes the uniform film formation of the dicyanocyclobutane compound at the positive electrode interface, improves the stability of the positive electrode interface, and further improves the high-temperature storage performance and thermal box performance of the electrochemical device.

[0017] In one embodiment of this application, 8% ≤ W2 ≤ 20%.

[0018] This application further controls the mass content of the lithium salt to meet the above range. The anions in the lithium salt can greatly reduce the desolvation energy of the dicyanocyclobutane compound, promote the uniform film formation of the dicyanocyclobutane compound at the interface of the positive electrode, and further improve the high-temperature storage performance and thermal box performance of the electrochemical device.

[0019] In one embodiment of this application, the non-aqueous electrolyte further includes compound A, which includes at least one of 1,3-propanesulfonate lactone (PSL), vinyl sulfate (VS), or methanedisulfonate methylene (MSA); based on the total mass of the non-aqueous electrolyte, the mass content of compound A is W3, and 0.2 ≤ W1 / W3 ≤ 10.

[0020] This application improves the stability of the negative electrode interface by adding compound A and controlling its mass content in the non-aqueous electrolyte. Since the decomposition products of compound A at the negative electrode interface can reduce the reduction and decomposition of the cyano structure in the dicyanocyclobutane compound at the negative electrode interface, it can also reduce the content of organic matter SEI (solid electrolyte interphase) at the negative electrode interface, thereby further improving the high-temperature storage performance and thermal box performance of the electrochemical device.

[0021] In one embodiment of this application, 0.05% ≤ W3 ≤ 2.5%.

[0022] This application further controls the mass content of compound A to meet the above range. Since the decomposition products of compound A at the negative electrode interface can reduce the reduction and decomposition of the cyano structure in the dicyanocyclobutane compound at the negative electrode interface, the stability of the negative electrode interface is improved. It can also reduce the content of organic matter SEI (solid electrolyte interphase) at the negative electrode interface, further improving the high-temperature storage performance and hot box performance of the electrochemical device.

[0023] In one embodiment of this application, the non-aqueous electrolyte further includes a boron-containing lithium salt, which includes at least one of lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiDFBOC), or lithium oxalate borate (LiBOC2O4); based on the total mass of the non-aqueous electrolyte, the mass content of the boron-containing lithium salt is W4, where 0.05 ≤ W1 / W4 ≤ 100.

[0024] This application introduces boron-containing lithium salt into a non-aqueous electrolyte and controls the ratio W1 / W4 of the mass content of sulfolane dicyanocyclobutane compound to that of the boron-containing lithium salt within the scope of this application. Since the cyano group exhibits poor stability at the negative electrode interface due to its reduction and decomposition products, the introduced boron-containing lithium salt anion participates in the solvation structure of the sulfolane dicyanocyclobutane compound. This adjusts the contact between the sulfolane dicyanocyclobutane compound and the negative electrode interface. Due to steric hindrance, the boron-containing lithium salt anion is located within the solvation shell and preferentially contacts the negative electrode interface to undergo a reduction reaction, generating an interfacial film that covers the active sites at the negative electrode interface. This reduces the decomposition of the sulfolane dicyanocyclobutane compound at the negative electrode interface, improves the stability of the negative electrode interface, and further enhances the high-temperature storage performance and thermal performance of the electrochemical device.

[0025] In one embodiment of this application, 0.01% ≤ W4 ≤ 3%.

[0026] This application, by further controlling the mass content of boron-containing lithium salt in the non-aqueous electrolyte to meet the above-mentioned range, can achieve the effect of adjusting the solvation structure of dicyanocyclobutane compound. At the same time, it reduces and forms a film at the negative electrode interface to cover the active sites of graphite, inhibits the decomposition of cyano groups in dicyanocyclobutane compound at the negative electrode interface, improves the stability of the negative electrode interface, and further improves the high-temperature storage performance and thermal box performance of the electrochemical device.

[0027] 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 performance and thermal performance.

[0028] 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 onto the positive electrode interface, and is beneficial to the positive electrode film formation reaction, thus giving the electrochemical device good high-temperature storage performance and thermal performance.

[0029] 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 thermal performance, which is beneficial for extending the lifespan of the electronic device.

[0030] The beneficial effects of this application are:

[0031] This application provides a non-aqueous electrolyte, an electrochemical device, and an electronic device. The electrochemical device includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The non-aqueous electrolyte contains a dicyanocyclobutane compound. In the dicyanocyclobutane compound, the 3d orbitals of the sulfur atoms in the S=O bonds overlap with the p orbitals of the oxygen atoms, forming delocalized π bonds that are more easily accessible to the positive electrode interface than commonly used carbonate solvents. After electrochemical oxidation, a CEI film with a thermodynamically stable SO3 structure is formed. Furthermore, the cyano group in the dicyanocyclobutane compound has a strong coordination ability with the transition metal elements at the positive electrode interface. Therefore, the dicyanocyclobutane compound of this application not only improves the formation of the CEI film at the positive electrode interface but also deactivates catalytically active sites at the positive electrode interface, thereby reducing the decomposition of the non-aqueous electrolyte and helping to maintain the stability of the positive electrode interface. This results in the electrochemical device having good high-temperature storage performance and thermal box performance (thermal safety performance). Detailed Implementation

[0032] 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.

[0033] 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.

[0034] The first aspect of this application provides a non-aqueous electrolyte comprising a dicyanocyclobutane compound, wherein the dicyanocyclobutane compound comprises at least one of a compound of formula I or a compound of formula II.

[0035]

[0036] 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 7The compound is selected from carbon or oxygen atoms; based on the total mass of the non-aqueous electrolyte, the mass content of the dicyanocyclobutane compound is W1, 0.05% ≤ W1 ≤ 3%, preferably 0.05% ≤ W1 ≤ 2%. For example, the mass content of the dicyanocyclobutane 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, thereby deteriorating the hot box 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 hot box 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 positive electrode 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 positive electrode interface. Therefore, the dicyanocyclobutane compound of this application, while improving the formation of a CEI film at the positive electrode interface, can also deactivate the catalytically active sites at the positive electrode interface, thereby reducing the decomposition of non-aqueous electrolytes and helping to maintain the stability of the positive electrode interface. This results in the electrochemical device having good high-temperature storage performance and thermal box performance (thermal safety performance).

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

[0038]

[0039]

[0040] 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, thereby reducing the decomposition of non-aqueous electrolytes and helping to maintain the stability of the cathode interface, so that the electrochemical device has good high-temperature storage performance and thermal box performance (thermal safety performance).

[0041] In one embodiment of this application, the compound of formula II includes at least one of the following compounds:

[0042]

[0043]

[0044] 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, thereby reducing the decomposition of non-aqueous electrolytes and helping to maintain the stability of the cathode interface, so that the electrochemical device has good high-temperature storage performance and thermal box performance (thermal safety performance).

[0045] In one embodiment of this application, the non-aqueous electrolyte further includes a lithium salt, which includes at least one of lithium bis(fluorosulfonyl)imide (LiDFSI), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2), or lithium hexafluorophosphate (LiPF6). Based on the total mass of the non-aqueous electrolyte, the mass content of the lithium salt is W2, where 0.003 ≤ W1 / W2 ≤ 0.3. For example, W1 / W2 is 0.003, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, or a range 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 lithium salt is low, which cannot effectively adjust the solvation structure of sulfolane cyanocyclobutane compound and reduce its desolvation ability, thereby reducing the film formation efficiency of sulfolane cyanocyclobutane compound at the cathode interface and reducing the stability of the cathode interface, which has a deteriorating effect on the high-temperature storage performance and thermal box performance of the electrochemical device. When W1 / W2 is too low, for example, below the lower limit of this application, the relative content of lithium salt is too high, resulting in a small proportion of sulfolane cyanocyclobutane compound in the solvation layer. A large amount of sulfolane cyanocyclobutane compound can only act on the cathode interface by adsorption, resulting in poor film uniformity and weak protection of the cathode interface. Therefore, the improvement effect on the high-temperature storage performance and thermal box performance of the electrochemical device is limited. Without being limited to any theory, the inventors of this application have discovered that when W1 / W2 is within the above range, the participation of lithium salt anions in the solvation structure improves the desolvation ability of sulfolane cyanocyclobutane compounds, promotes the uniform film formation of sulfolane cyanocyclobutane compounds at the positive electrode interface, improves the stability of the positive electrode interface, and further improves the high-temperature storage performance and thermal box performance of the electrochemical device.

[0046] In one embodiment of this application, 8% ≤ W2 ≤ 20%. For example, the mass content of the lithium salt is 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or a range of any two of these values. When the mass content of the lithium salt is too high, for example, higher than the upper limit of this application, the proportion of sulfolane cyanocyclobutane compound in the solvation structure will decrease, resulting in reduced film formation efficiency and weaker protection of the positive electrode interface, thus having limited effect on improving the high-temperature storage performance and thermal box performance of the electrochemical device. When the mass content of the lithium salt is too low, for example, lower than the lower limit of this application, the solvation structure involving sulfolane cyanocyclobutane compound cannot be effectively adjusted, and the improvement on reducing the desolvation energy of sulfolane cyanocyclobutane compound at the positive electrode is not significant. Without being limited to any theory, the inventors of this application have discovered that when the mass content of lithium salt is within the above-mentioned range, the solvation structure of sulfolane cyanocyclobutane compound can be effectively adjusted, and the desolvation efficiency of sulfolane cyanocyclobutane compound at the positive electrode interface can be improved, thereby further improving the high-temperature storage performance and thermal box performance of the electrochemical device.

[0047] In one embodiment of this application, the non-aqueous electrolyte further includes compound A, which comprises at least one of 1,3-propanesulfonate lactone (PSL), vinyl sulfate (VS), or methanedisulfonate (MSA); the mass content of compound A is W3 based on the total mass of the non-aqueous electrolyte, and 0.2 ≤ W1 / W3 ≤ 10. For example, W1 / W3 is 0.2, 0.25, 0.3, 0.5, 0.7, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or a range consisting of any two of these values. When W1 / W3 is too high, for example, exceeding the upper limit specified in this application, it fails to inhibit the reduction of sulfolane dicyanocyclobutane compound at the negative electrode interface, affecting the stability of the negative electrode interface. When W1 / W3 is too low, for example, below the lower limit specified in this application, it deteriorates the cycling performance of the hot box. Without being limited to any theory, the inventors of this application have discovered that when W1 / W3 is within the above range, the decomposition products of compound A at the negative electrode interface can reduce the reduction and decomposition of the cyano structure in the sulfolane dicyanocyclobutane compound at the negative electrode interface, thereby improving the stability of the negative electrode interface. It can also reduce the content of organic matter SEI (solid electrolyte interphase) at the negative electrode interface, further improving the high-temperature storage performance and hot box performance of the electrochemical device.

[0048] In one embodiment of this application, 0.05% ≤ W3 ≤ 2.5%. For example, the mass content of compound A 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%, or a range of any two of these values. When the mass content of compound A is too high, for example, exceeding the upper limit specified in this application, it will lead to an excessive content of organic SEI (solid electrolyte interphase) at the negative electrode interface, which will deteriorate the heat box performance of the electrochemical device. When the mass content of compound A is too low, for example, below the lower limit specified in this application, it will not be able to inhibit the reduction and decomposition of the cyano structure in the dicyanosulfone compound at the negative electrode interface, which will deteriorate the high-temperature storage performance of the electrochemical device. Without being limited to any theory, the inventors of this application have discovered that when the mass content of compound A is within the above-mentioned range, the decomposition products of compound A at the negative electrode interface can reduce the reduction and decomposition of the cyano structure in the dicyanosulfone compound at the negative electrode interface, thereby improving the stability of the negative electrode interface and reducing the content of organic SEI (solid electrolyte interphase) at the negative electrode interface, further improving the high-temperature storage performance and heat box performance of the electrochemical device.

[0049] In one embodiment of this application, the non-aqueous electrolyte further includes a boron-containing lithium salt, which includes at least one of lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiDFBOC), or lithium oxalate borate (LiBOC2O4). Based on the total mass of the non-aqueous electrolyte, the mass content of the boron-containing lithium salt is W4, where 0.05 ≤ W1 / W4 ≤ 100. For example, W1 / W4 is 0.05, 0.1, 0.2, 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or a range consisting of any two of these values. When W1 / W4 is too high, for example, above the upper limit of this application, the relative content of boron-containing lithium salt is too low, and the anion steric hindrance effect cannot be effectively used to exclude the dicyanocyclobutane compound from the outer layer of the solvation structure, resulting in the reduction reaction of the dicyanocyclobutane compound at the negative electrode interface, leading to insufficient stability of the negative electrode interface. When W1 / W4 is too low, for example, below the lower limit of this application, the content of boron-containing lithium salt is relatively too high, and its reduction and decomposition at the negative electrode interface will lead to the generation of too many organic by-products at the negative electrode interface, which will deteriorate the thermal safety performance of the electrochemical device. At the same time, its solvation structure will occupy the solvation sites of the dicyanocyclobutane compound, resulting in a decrease in the film formation efficiency of the dicyanocyclobutane compound at the positive electrode interface. Without being limited to any theory, the inventors of this application have discovered that when W1 / W4 is within the above range, the boron-containing lithium salt anion can adjust the contact between the dicyanocyclobutane compound and the negative electrode interface by participating in the solvation structure of the dicyanocyclobutane compound. Due to steric hindrance, the boron-containing lithium salt anion structure is located in the inner layer of the solvation shell and preferentially contacts the negative electrode interface to undergo a reduction reaction to generate an interfacial film covering the active sites of the negative electrode interface. This can reduce the decomposition of the dicyanocyclobutane compound on the negative electrode interface, improve the stability of the negative electrode interface, and further improve the high-temperature storage performance and thermal box performance of the electrochemical device.

[0050] In one embodiment of this application, 0.01% ≤ W4 ≤ 3%. For example, the mass content of the boron-containing lithium salt 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%, 2.3%, 2.5%, 2.7%, 2.9%, 3%, or a range of any two of these values. When the mass content of boron-containing lithium salt is too high, for example, exceeding the upper limit specified in this application, it significantly occupies the solvation sites of sulfolane dicyanocyclobutane compound, reducing the oxidative film formation of sulfolane dicyanocyclobutane compound at the positive electrode interface. Simultaneously, it forms a large amount of organic matter at the negative electrode interface, reducing the thermal stability of the negative electrode and deteriorating the high-temperature storage and thermal box performance of the electrochemical device. When the mass content of boron-containing lithium salt is too low, for example, below the lower limit specified in this application, it cannot effectively inhibit the reduction reaction of sulfolane dicyanocyclobutane compound at the negative electrode interface, thus having limited effect on improving the high-temperature storage and thermal box performance of the electrochemical device. Without being limited to any theory, the inventors of this application have discovered that when the mass content of boron-containing lithium salt is within the above-mentioned range, it can inhibit the reductive decomposition of sulfolane dicyanocyclobutane compound at the negative electrode interface, improve the stability of the negative electrode interface, and further improve the high-temperature storage and thermal box performance of the electrochemical device.

[0051] In one embodiment of this application, the non-aqueous electrolyte further includes a non-aqueous solvent.

[0052] 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.

[0053] 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 fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or 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.

[0054] This application does not impose any particular limitation on the content of non-aqueous solvents in non-aqueous electrolytes, 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 can be from 0% to 91.95%.

[0055] In one embodiment of this application, the non-aqueous electrolyte may include a sulfolane dicyanobutyl sulfone compound, a lithium salt, and a non-aqueous solvent. The mass content of the sulfolane dicyanobutyl sulfone compound and the lithium salt is as described above, and the mass content of the non-aqueous solvent is 77% to 91.95%. Electrochemical devices comprising the above-mentioned non-aqueous electrolyte exhibit good high-temperature storage performance and thermal performance.

[0056] In one embodiment of this application, the non-aqueous electrolyte may include a dicyanosulfone compound, compound A, a lithium salt, and a non-aqueous solvent. The mass content of the dicyanosulfone compound, compound A, and lithium salt is as described above, and the mass content of the non-aqueous solvent is 74.5% to 91.90%. Electrochemical devices comprising the above-mentioned non-aqueous electrolyte exhibit good high-temperature storage performance and thermal performance.

[0057] In one embodiment of this application, the non-aqueous electrolyte may include a sulfolane dicyanocyclobutane compound, compound A, a boron-containing lithium salt, a lithium salt, and a non-aqueous solvent. The mass content of the sulfolane dicyanocyclobutane compound, compound A, boron-containing lithium salt, and lithium salt is as described above, and the mass content of the non-aqueous solvent is 71.5% to 91.89%. Electrochemical devices comprising the above-mentioned non-aqueous electrolyte exhibit good high-temperature storage performance and thermal performance.

[0058] In one embodiment of this application, the non-aqueous electrolyte may include a sulfolane dicyanosulfate compound, a lithium salt, a non-aqueous solvent, and one of compound A and a boron-containing lithium salt. The mass content of the sulfolane dicyanosulfate compound, the lithium salt, and one of compound A and the boron-containing lithium salt is as described above, and the mass content of the non-aqueous solvent is 74.5% to 91.94%. Electrochemical devices comprising the above-mentioned non-aqueous electrolyte exhibit good high-temperature storage performance and thermal performance.

[0059] 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.

[0060] 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).

[0061] The positive electrode material layer may also include the positive electrode material, a conductive agent, and a binder.

[0062] 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 hot box performance.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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).

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] Example

[0085] 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.

[0086] Test methods and equipment

[0087] (1) High-temperature storage performance test:

[0088] 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 4.5V, and then charged at a constant voltage of 4.5V 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.

[0089] High-temperature storage thickness expansion rate = (H1-H0) / H0×100%.

[0090] (2) Thermal safety performance test

[0091] The lithium-ion battery was placed in a constant temperature environment of 25℃, discharged at a constant current of 0.5C to 2.8V, left to stand for 5 minutes, charged at a constant current of 0.5C to 4.5V, and charged at a constant voltage of 4.5V to a current of 0.025C. The temperature sensing wire was placed tightly against the surface of the battery, and the battery was placed vertically in the box. The temperature in the box was increased to 200±0.5℃ at a rate of 1±0.5℃. The temperature at which the battery caught fire or exploded was recorded.

[0092] (3) Content test of each element in the cathode material

[0093] 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.

[0094] Example 1-1

[0095] <Preparation of Non-Aqueous Electrolytes>

[0096] 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. The mass content of compound I-1 was 0.05%, the mass content of lithium salt was 6%, and the remainder was non-aqueous solvent, based on the mass of the non-aqueous electrolyte.

[0097] <Preparation of the positive electrode>

[0098] 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 .

[0099] <Preparation of Negative Electrode Sheets>

[0100] 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 .

[0101] <Preparation of the separating membrane>

[0102] A 5μm thick polyethylene (PE) porous membrane (supplied by Celgard) was used.

[0103] <Preparation of Lithium-ion Batteries>

[0104] 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.

[0105] Examples 1-2 to Examples 1-12

[0106] Except for adjusting the type and mass content of the dicyanocyclobutane compound in the <Preparation of Non-Aqueous Electrolyte>, the mass content of the non-aqueous solvent is changed accordingly, and the mass content of the lithium salt remains unchanged, the rest is the same as in Example 1-1.

[0107] Examples 2-1 to 2-12

[0108] Except for adjusting the type and mass content of lithium salt in <Preparation of Non-Aqueous Electrolyte>, the mass content of non-aqueous solvent is changed accordingly, otherwise it is the same as in Examples 1-3.

[0109] Examples 3-1 to 3-11

[0110] Except for the addition of compound A in the <Preparation of Non-Aqueous Electrolyte>, and the adjustment of the type and mass content of compound A, the mass content of the non-aqueous solvent is changed accordingly, while the mass content of the lithium salt remains unchanged, the rest is the same as in Examples 1-3.

[0111] Examples 4-1 to 4-14

[0112] Except for the addition of boron-containing lithium salt in the <Preparation of Non-Aqueous Electrolyte>, and the adjustment of the type and mass content of boron-containing lithium salt, the mass content of 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.

[0113] Examples 5-1 to 5-3

[0114] Except for the addition of compound A and boron-containing lithium salt in the <Preparation of Non-Aqueous Electrolyte>, and the adjustment of the type and mass content of compound A, the type and mass content of boron-containing lithium salt, and the change in the mass content of non-aqueous solvent, while keeping the mass content of lithium salt unchanged, the rest is the same as in Examples 1-3.

[0115] Examples 6-1 to 6-5

[0116] Except for changing the molar content of nickel in the <Preparation of Positive Electrode> section, the rest is the same as in Example 1-1.

[0117] Comparative Examples 1 to 2

[0118] Except for the addition of an excess of dicyanosulfone compound in the <Preparation of Non-Aqueous Electrolyte>, which changes 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.

[0119] Comparative Example 3

[0120] 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.

[0121] Table 1

[0122]

[0123]

[0124] Note: (1) “ / ” in Table 1 indicates that there is no corresponding preparation parameter or substance. (2) Taking Examples 1-9 as examples, “type of dicyanocyclobutane compound” is “I-1+I-2”, and “mass content of dicyanocyclobutane compound” is “0.25+0.25”, indicating that dicyanocyclobutane compound includes compound I-1 and compound I-2. Based on the total mass of the electrolyte, the mass content of compound I-1 is 0.25%, and the mass content of compound I-2 is 0.25%. Other examples follow the same principle.

[0125] As can be seen from Examples 1-1 to 1-12 and Comparative Examples 1 to 3, when the type and mass content of the dicyanocyclobutane compound are within the scope of this application, the lithium-ion battery exhibits a lower storage thickness expansion rate and a higher battery ignition and explosion temperature, indicating that the high-temperature storage performance and thermal box performance (thermal safety performance) of the lithium-ion battery are improved. When the type and mass content of the dicyanocyclobutane compound in Comparative Examples 1 to 3 are not within the scope of this application, the lithium-ion battery exhibits a higher storage thickness expansion rate and a lower battery ignition and explosion temperature, indicating that the lithium-ion battery has lower high-temperature storage performance and thermal box performance (thermal safety performance). As can be seen from Examples 1-1 to 1-12, the lithium-ion battery of this application exhibits a lower storage thickness expansion rate and a higher battery ignition and explosion temperature, indicating that the lithium-ion battery of this application has good high-temperature storage performance and thermal box performance (thermal safety performance).

[0126] Table 2

[0127]

[0128]

[0129] Note: (1) “ / ” in Table 2 indicates that there is no corresponding preparation parameter or substance. (2) Taking Examples 2-9 as an example, “type of lithium salt” is “lithium hexafluorophosphate (LiPF6) + lithium bisfluorosulfonylimide (LiDFSI)”, and “mass content of lithium salt” is “7.5+2.5”, indicating that the lithium salt includes lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiDFSI). Based on the total mass of the electrolyte, the mass content of lithium hexafluorophosphate (LiPF6) is 7.5%, and the mass content of lithium bisfluorosulfonylimide (LiDFSI) is 2.5%. Other examples follow the same principle.

[0130] The type and mass content of lithium salts, as well as the W1 / W2 ratio, typically affect the high-temperature storage performance and thermal box performance (thermal safety performance) of electrochemical devices. Examples 1-3 and 2-1 to 2-12 demonstrate that when the type and mass content of lithium salts, and the W1 / W2 ratio, are within the range specified in this application, the storage thickness expansion rate of the lithium-ion battery is further reduced, and the battery ignition and explosion temperature is further increased, indicating that the high-temperature storage performance and thermal box performance (thermal safety performance) of the lithium-ion battery are improved.

[0131] Table 3

[0132]

[0133]

[0134] Note: (1) “ / ” in Table 3 indicates that there is no corresponding preparation parameter or substance. (2) Taking Examples 3-10 as an example, “the type of compound A” is “1,3-propanesulfonate lactone (PSL) + vinyl sulfate (VS)”, and “the mass content of lithium salt” is “0.5+0.5”, indicating that compound A includes 1,3-propanesulfonate lactone (PSL) and vinyl sulfate (VS). Based on the total mass of the electrolyte, the mass content of 1,3-propanesulfonate lactone (PSL) is 0.5%, and the mass content of vinyl sulfate (VS) is 0.5%. Other examples follow the same principle.

[0135] The type and mass content of compound A, as well as the W1 / W3 ratio, typically affect the high-temperature storage performance and thermal box performance (thermal safety performance) of electrochemical devices. Examples 1-3, 3-1 to 3-11 demonstrate that when the type and mass content of compound A, and the W1 / W3 ratio, are within the range specified in this application, the storage thickness expansion rate of the lithium-ion battery is further reduced, and the battery ignition and explosion temperature is further increased, indicating that the high-temperature storage performance and thermal box performance (thermal safety performance) of the lithium-ion battery are improved.

[0136] Table 4

[0137]

[0138]

[0139] Note: (1) “ / ” in Table 4 indicates that there is no corresponding preparation parameter or substance. (2) Taking Examples 4-13 as an example, “type of boron-containing lithium salt” is “lithium tetrafluoroborate (LiBF4) + lithium difluorooxalate borate (LiDFBOC)”, and “mass content of boron-containing lithium salt” is “0.5+0.5”, indicating that the boron-containing lithium salt includes lithium tetrafluoroborate (LiBF4) and lithium difluorooxalate borate (LiDFBOC). Based on the total mass of the electrolyte, the mass content of lithium tetrafluoroborate (LiBF4) is 0.5%, and the mass content of lithium difluorooxalate borate (LiDFBOC) is 0.5%. Other examples follow the same principle.

[0140] The type and mass content of boron-containing lithium salts, as well as the W1 / W4 ratio, typically affect the high-temperature storage performance and thermal box performance (thermal safety performance) of electrochemical devices. Examples 1-3 and 4-1 to 4-14 demonstrate that when the type and mass content of boron-containing lithium salts, and the W1 / W4 ratio, are within the ranges specified in this application, the storage thickness expansion rate of the lithium-ion battery is further reduced, and the ignition and explosion temperature of the lithium-ion battery is further increased, indicating that the high-temperature storage performance and thermal box performance (thermal safety performance) of the lithium-ion battery are improved.

[0141] Table 5

[0142]

[0143] Note: " / " in Table 5 indicates that the corresponding preparation parameters or substances do not exist.

[0144] Different types of non-aqueous electrolytes typically affect the high-temperature storage performance and thermal box performance (thermal safety performance) of electrochemical devices. As can be seen from Examples 1-3 and Examples 5-1 to 5-3, 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 battery ignition and explosion temperature is further increased, indicating that the high-temperature storage performance and thermal box performance (thermal safety performance) of the lithium-ion battery are improved.

[0145] Table 6

[0146]

[0147] The molar content of nickel in lithium nickel cobalt manganese oxide (NiCoMnO) metal oxide, the cathode material, typically affects the high-temperature storage performance and thermal box performance (thermal safety performance) of electrochemical devices. As can be seen from Examples 1-1, 6-1 to 6-5, when the molar content of nickel is within the range specified in this application, the storage thickness expansion rate of the lithium-ion battery is further reduced, and the battery ignition and explosion temperature is further increased, indicating that the high-temperature storage performance and thermal box performance (thermal safety performance) of the lithium-ion battery are improved.

[0148] 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.

[0149] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0150] 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 compound includes dicyanocyclobutane sulfone compounds, said dicyanocyclobutane sulfone compounds comprising 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, where 0.05% ≤ W1 ≤ 3%.

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, The non-aqueous electrolyte also includes a lithium salt, which includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium hexafluorophosphate. Based on the total mass of the non-aqueous electrolyte, the mass content of the lithium salt is W2, where 0.003 ≤ W1 / W2 ≤ 0.

3.

6. The non-aqueous electrolyte according to claim 5, characterized in that, 8％≤W2≤20％。 7. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte further includes compound A, which includes at least one of 1,3-propanesulfonate lactone, vinyl sulfate, or methanedisulfonate; based on the total mass of the non-aqueous electrolyte, the mass content of compound A is W3, 0.2≤W1 / W3≤10.

8. The non-aqueous electrolyte according to claim 7, characterized in that, 0.05％≤W3≤2.5％。 9. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous electrolyte also includes boron-containing lithium salt, which includes at least one of lithium tetrafluoroborate, lithium difluorooxalate borate, or lithium oxalate borate; based on the total mass of the non-aqueous electrolyte, the mass content of the boron-containing lithium salt is W4, where 0.05 ≤ W1 / W4 ≤ 100.

10. The non-aqueous electrolyte according to claim 9, characterized in that, 0.01％≤W4≤3％。 11. 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 10.

12. The electrochemical device according to claim 11, 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%.

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

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