Electrochemical device and electronic device

Abstract

The present application provides an electrochemical device and an electronic device. The electrochemical device comprises an electrode assembly and an electrolyte. The electrode assembly is of a winding structure and comprises curved parts and a straight part, wherein the maximum length of the straight part is L mm, the maximum radius of each curved part is D mm, and 5≤L / D≤10. The electrolyte contains a compound represented by a formula (I), wherein, on the basis of the mass of the electrolyte, the content percentage by mass of the compound represented by the formula (I) is A%, and 30≤A≤80. By means of combining the regulation and control of L / D of the electrode assembly with the the regulation and control of components of the electrolyte, the present application improves the high-temperature cycle performance of the electrochemical device.

Description

Electrochemical device and electronic device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 22, 2023, with application number 202311785375.9 and invention name “An electrochemical device and electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Art

[0003] Electrochemical devices, such as lithium-ion batteries, offer advantages such as high energy storage density, high open-circuit voltage, low self-discharge rate, long cycle life, and excellent safety. They are widely used in various fields, including portable energy storage, electronic devices, and electric vehicles. With the rapid development of lithium-ion battery applications in consumer devices and other fields, market demands for lithium-ion battery performance, such as high-temperature cycling performance, are also increasing. As important components of lithium-ion batteries, electrode assemblies and electrolytes are in urgent need of improvement to achieve lithium-ion batteries with excellent high-temperature cycling performance.

[0004] Summary of the Invention

[0005] The purpose of this application is to provide an electrochemical device and an electronic device to improve the high-temperature cycle performance of the electrochemical device. The specific technical solution is as follows:

[0006] A first aspect of the present application provides an electrochemical device comprising an electrode assembly and an electrolyte, wherein the electrode assembly is a wound structure, wherein the electrode assembly comprises a curved portion and a straight portion, wherein the maximum length of the straight portion is L mm, the maximum radius of the curved portion is D mm, and 5≤L / D≤10; and the electrolyte comprises a compound represented by formula (I):

[0007] R 11 and R 12 Each independently selected from C1 to C 10 The alkyl group, R 11 and R 12At least one is substituted with fluorine; based on the mass of the electrolyte, the mass percentage of the compound represented by formula (I) is A%, 30≤A≤80. The present application adjusts the L / D value of the wound structure electrode assembly within the scope of the present application, and adds the compound represented by formula (I) to the electrolyte, and the content of the compound represented by formula (I) is within the scope of the present application, so that the curved portion in the electrode assembly has a suitable volume share, and the compound represented by formula (I) has strong antioxidant properties, which can reduce the oxidation reaction between the positive electrode active material and the electrolyte, widen the oxidation window of the electrolyte, enhance the positive electrode interface stability, reduce the consumption rate of the electrolyte, and delay the loss rate of the electrolyte in the curved portion of the electrode assembly, thereby improving the high-temperature cycle performance of the electrochemical device, and at the same time making the electrochemical device have a smaller DC impedance at a low state of charge (SOC).

[0008] In some embodiments of the present application, 5≤L≤30 or 1≤D≤5. By regulating the value of L or D within the above range, the value of L / D can be regulated within the range of the present application, which is beneficial to limiting the volume proportion of the curved portion in the electrode assembly, exerting the effect of the compound represented by formula (I), enhancing the positive electrode interface stability, reducing the consumption rate of the electrolyte, and delaying the loss rate of the electrolyte in the curved portion of the electrode assembly, thereby facilitating improving the high-temperature cycle performance of the electrochemical device and also facilitating the electrochemical device to have a smaller DC impedance at a low SOC.

[0009] In some embodiments of the present application, the electrochemical device satisfies any of the following: a) 40 ≤ A ≤ 75; b) 7 ≤ L / D ≤ ​​9; c) 10 ≤ L ≤ 20; d) 1.5 ≤ D ≤ 2.5. By regulating the above parameters, the volume proportion of the curved portion in the electrode assembly is appropriately adjusted, which is more conducive to the effect of the compound represented by formula (I), enhancing the positive electrode interface stability, reducing the consumption rate of the electrolyte, and delaying the loss rate of the electrolyte in the curved portion of the electrode assembly, thereby further improving the high-temperature cycle performance of the electrochemical device and further helping to further reduce the DC impedance of the electrochemical device at low SOC.

[0010] In some embodiments of the present application, the width of the electrode assembly is W mm, where W = L + 2D and 10 ≤ W ≤ 40. When the width W of the electrode assembly is within the above range, it is more beneficial to reduce the consumption rate of the electrolyte and delay the loss rate of the electrolyte in the curved portion of the electrode assembly, thereby improving the high-temperature cycling performance of the electrochemical device and also helping the electrochemical device to have a smaller DC impedance at a low SOC.

[0011] In some embodiments of the present application, the compound represented by formula (I) includes at least one of the following compounds:

[0012] In the electrochemical device of the present application, the electrolyte includes the compound represented by formula (I) within the above-mentioned range, which can better exert the antioxidant effect of the compound represented by formula (I), so that the electrochemical device has good positive electrode interface stability, reduces the consumption rate of the electrolyte, and delays the loss rate of the electrolyte in the bent part of the electrode assembly, thereby helping to improve the high-temperature cycle performance of the electrochemical device, and at the same time helps to make the electrochemical device have a smaller DC impedance at a low SOC.

[0013] In some embodiments of the present application, the electrolyte includes a non-fluorinated carboxylate, wherein the non-fluorinated carboxylate includes at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; the mass percentage of the non-fluorinated carboxylate is B%, based on the mass of the electrolyte, and 10≤B≤60. Further introducing the aforementioned non-fluorinated carboxylate into the electrolyte and regulating its mass percentage B% within the aforementioned range can impart an appropriate viscosity to the electrolyte, improve wettability at the positive and negative electrode interfaces, and reduce polarization, thereby facilitating improved high-temperature cycling performance of the electrochemical device and also facilitating a lower DC impedance of the electrochemical device at low SOC.

[0014] In some embodiments of the present application, the electrolyte includes a cyclic carbonate, and the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or vinyl ethylene carbonate; based on the mass of the electrolyte, the mass percentage of the cyclic carbonate is C%, and 0≤C≤10. Further introducing the cyclic carbonate into the electrolyte and regulating its mass percentage C% within the above range is beneficial to the dissociation of the lithium salt, improving the conductivity of the electrolyte, and also facilitating the anion film formation of the lithium salt, adjusting the electrolyte solvation structure, and enhancing the stability of the positive electrode interface and the negative electrode interface, thereby facilitating improving the high-temperature cycling performance of the electrochemical device and also facilitating the electrochemical device to have a smaller DC impedance at a low SOC.

[0015] In some embodiments of the present application, the electrolyte includes a nitrile additive, the nitrile additive including at least one of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, methylglutaronitrile, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, or 1,2,3-tris(2-cyanoethoxy)propane; based on the mass of the electrolyte, the mass percentage of the nitrile additive is E%, and 2≤E≤10. The electrolyte further introduces the above-mentioned type of nitrile additive and regulates its mass percentage E% within the above-mentioned range, which can further enhance the stability of the positive electrode interface, thereby facilitating improved high-temperature cycling performance of the electrochemical device, and also facilitating the electrochemical device to have a smaller DC impedance at a low SOC.

[0016] In some embodiments of the present application, the electrolyte includes a boron-containing compound, the boron-containing compound including at least one of lithium bis(1,1-trifluoromethyloxalato)borate, lithium bis(1-trifluoromethyloxalato)borate, lithium difluoro(1,1-trifluoromethyl)oxalatoborate, lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium bis(1,1-trifluoromethylmalonate)borate, lithium difluoromalonate borate, or lithium bis(fluoromalonate)borate; the mass percentage of the boron-containing compound is F%, based on the mass of the electrolyte, and 0.01≤F≤2. Including the above-mentioned boron-containing compound in the electrolyte and regulating its mass percentage F% within the above-mentioned range can synergistically enhance the stability of the positive electrode interface and the negative electrode interface with the compound represented by formula (I), thereby facilitating improved high-temperature cycling performance of the electrochemical device and also facilitating a smaller DC impedance of the electrochemical device at a low SOC.

[0017] A second aspect of the present application provides an electronic device, which includes the electrochemical device provided by the first aspect of the present application.

[0018] Beneficial effects of this application:

[0019] The present application provides an electrochemical device and an electronic device. The electrochemical device includes an electrode assembly and an electrolyte. The electrode assembly is a wound structure, wherein the electrode assembly includes a curved portion and a straight portion, the straight portion has a maximum length of L mm, the curved portion has a maximum radius of D mm, and 5≤L / D≤10; the electrolyte includes a compound represented by formula (I), wherein the mass percentage of the compound represented by formula (I) is A%, based on the mass of the electrolyte, and 30≤A≤80. The present application regulates the L / D value of the wound structure electrode assembly within the scope of the present application, and adds the compound represented by formula (I) to the electrolyte, and the content of the compound represented by formula (I) is within the scope of the present application, so that the curved portion in the electrode assembly has a suitable volume share, and the compound represented by formula (I) has strong antioxidant properties, which can reduce the oxidation reaction between the positive electrode active material and the electrolyte, broaden the oxidation window of the electrolyte, enhance the positive electrode interface stability, reduce the consumption rate of the electrolyte, and delay the loss rate of the electrolyte in the curved portion of the electrode assembly, thereby improving the high-temperature cycle performance of the electrochemical device, and at the same time making the electrochemical device have a smaller DC impedance at a low SOC.

[0020] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0022] FIG1 is a schematic structural diagram of an electrode assembly according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0024] It should be noted that, in the specific embodiments of the present application, a lithium-ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to a lithium-ion battery.

[0025] A first aspect of the present application provides an electrochemical device comprising an electrode assembly and an electrolyte. As shown in FIG1 , the electrode assembly is a wound structure, wherein the electrode assembly comprises a curved portion and a straight portion, the maximum length of the straight portion is L mm, the maximum radius of the curved portion is D mm, 5≤L / D≤10, preferably 7≤L / D≤9; and the electrolyte comprises a compound represented by formula (I):

[0026] R 11 and R 12 Each independently selected from C1 to C 10 The alkyl group, R 11 and R 12 At least one is substituted by fluorine. In some embodiments of the present application, R 11 and R 12 are each independently selected from the following groups which may be substituted or unsubstituted by fluorine: methyl, ethyl or propyl, R 11 and R 12 At least one is substituted with fluorine. Based on the mass of the electrolyte, the mass percentage of the compound represented by formula (I) is A%, 30≤A≤80, preferably, 40≤A≤75. For example, L / D can be 5, 6, 6.4, 7, 7.6, 8, 8.3, 9, 10, or a range consisting of any two of the above values. For example, A can be 30, 40, 44, 50, 53, 60, 66, 70, 80, or a range consisting of any two of the above values.

[0027] In this application, the maximum radius D of the "bend" and the maximum length L of the "straight portion" are obtained based on testing of the outermost electrode of the wound electrode assembly (i.e., the electrode directly opposite the packaging of the encapsulated electrode assembly). The outermost edges of the bend and the outermost edges of the straight portions are alternately connected to form the outermost electrodes of the wound electrode assembly. The outermost edge of the bend refers to the arcuate portion of the outermost electrode of the wound electrode assembly, which includes a first bend formed by a first arc line and a second bend formed by a second arc line. The outermost edge of the straight portion refers to the straight portion of the outermost electrode of the wound electrode assembly, i.e., the electrode portion between the first bend and the second bend, which includes the first straight portion and the second straight portion. The "radius of the bend" refers to the distance between the line segment between the two endpoints of the first (or second) arc of the first (or second) curved portion and the intersection of the perpendicular bisector of the line segment and the first (or second) arc. Since the electrode assembly has two outermost edges of the bend, the larger of the two radiuses is taken as the maximum radius D of the bend of the electrode assembly. "The length of the straight portion" refers to the length of the first straight portion and the length of the second straight portion. Since one of the first straight portion and the second straight portion is the winding end of the electrode assembly, the larger value of the straight portion length is taken as the maximum length L of the straight portion.

[0028] FIG1 is a schematic diagram of the structure of an electrode assembly according to an embodiment of the present application. The electrode assembly 100 includes a stacked positive electrode sheet 101, a negative electrode sheet 102, and a separator 103 between the positive electrode sheet 101 and the negative electrode sheet 102. The wound electrode assembly is flat, wherein in the width (W) direction of the electrode assembly, the outermost electrode of the electrode assembly includes a first curved portion (left side), a second curved portion (right side), a first straight portion (upper side), and a second straight portion (lower side), wherein the second curved portion, the first straight portion, the first curved portion, and the second straight portion are connected in sequence to form the outermost electrode of the electrode assembly. The first curved portion is formed by a first arc line along points A, C, and B, wherein point A is the intersection of the first curved portion and the first straight portion, and point B is the intersection of the first curved portion and the second straight portion. The second curved portion is formed by a second arc along points A', C', and B', where point A' is the intersection of the second curved portion and the first straight portion, and point B' is the intersection of the second curved portion and the straight portion of the sub-outer electrode corresponding to the second straight portion. The first straight portion is formed by the line segment between point A and point A', and the second straight portion is formed by the line segment between point B and point B" (point B" is the end point of the outermost electrode). Points A and B are the endpoints of the first arc, point C is the intersection of the perpendicular bisector of the line segment between points A and B and the first arc, and the distance between the line segment between points A and B and point C is the radius D1 of the first curved portion. Points A' and B' are the endpoints of the second arc, point C' is the intersection of the perpendicular bisector of the line segment between points A' and B' and the second arc, and the distance between the line segment between points A' and B' and point C' is the radius D2 of the second curved portion. The larger of the curved portion (D1) and (D2) is recorded as the maximum radius (D) of the curved portion (i.e., the radius (D1) of the first curved portion in Figure 1). The length of the line segment between points A and A' is the length (L1) of the first straight portion, and the length of the line segment between points B and B" is the length (L2) of the second straight portion. The larger of L1 and L2 is recorded as the maximum length (L) of the straight portion (i.e., the length (L1) of the first straight portion in Figure 1).

[0029] In the electrochemical device of this application, the electrode assembly is a wound structure. During cycling, the electrolyte is easily squeezed out of the curved portion of the electrode assembly due to the rebound of the electrode sheet. In addition, as the electrolyte is continuously consumed, it leads to electrolyte depletion, which affects the transport of lithium ions and thus the high-temperature cycling performance of the electrochemical device. In addition, at a low state of charge (SOC), such as 20% SOC, the DC impedance of the electrochemical device is too high, thus affecting the normal operation of the electrochemical device. The present application limits the volume ratio of the curved portion in the electrode assembly to a certain range, that is, limits the ratio of the maximum length L of the straight portion to the maximum radius D of the curved portion in the electrode assembly to a certain range, and introduces a compound represented by formula (I) into the electrolyte and controls its mass percentage A% within the above range. Due to the strong antioxidant properties of the compound represented by formula (I), it can reduce the oxidation reaction between the positive electrode active material and the electrolyte, widen the oxidation window of the electrolyte, and provide the electrochemical device with good positive electrode interface stability, reduce the electrolyte consumption rate, and delay the electrolyte loss rate in the curved portion of the electrode assembly, thereby improving the high-temperature cycling performance of the electrochemical device. At the same time, the electrochemical device has a low DC impedance at low SOC and can operate normally. When the value of L / D is too small, for example, less than 5, the volume ratio of the curved portion in the electrode assembly is large, electrolyte extrusion is large, and the probability of electrolyte loss in the curved portion is high. The effect of the compound represented by formula (I) is limited, and the effect of reducing the electrolyte consumption rate and delaying the electrolyte loss rate is weak, thereby improving the high-temperature cycling performance of the electrochemical device. When the value of L / D is too large, for example, greater than 10, the volume of the curved portion in the electrode assembly accounts for a small proportion, the electrolyte is less squeezed out, the probability of electrolyte loss in the curved portion is small, and the effect of adding the compound represented by formula (I) to the electrolyte to improve the high-temperature cycle performance of the electrochemical device is weak, which easily increases the impedance of the electrochemical device and increases the polarization. When A is too small, for example, less than 30, the content of the compound represented by formula (I) is too low, the effect of enhancing the stability of the positive electrode interface is weak, and the effect of reducing the electrolyte consumption rate and delaying the electrolyte loss rate is also weak, which is not conducive to improving the high-temperature cycle performance of the electrochemical device. When A is too large, for example, greater than 80, the content of the compound represented by formula (I) is too high, the impedance of the electrochemical device increases, the polarization increases, which is not conducive to improving the high-temperature cycle performance of the electrochemical device. At the same time, the DC impedance of the electrochemical device at low SOC is also too high, affecting the normal operation of the electrochemical device.The present application regulates the L / D value of the wound structure electrode assembly within the scope of the present application, and adds the compound represented by formula (I) to the electrolyte, and regulates the mass percentage A% of the compound represented by formula (I) within the scope of the present application, so that the curved portion in the electrode assembly has a suitable volume share, and can exert the antioxidant effect of the compound represented by formula (I), enhance the positive electrode interface stability, reduce the consumption rate of the electrolyte, and delay the loss rate of the electrolyte in the curved portion of the electrode assembly, thereby improving the high-temperature cycle performance of the electrochemical device, and at the same time making the electrochemical device have a smaller DC impedance at a low SOC.

[0030] In some embodiments of the present application, 5≤L≤30, preferably, 10≤L≤20. For example, L can be 5, 10, 12, 15, 18, 20, 25, 30 or a range consisting of any two of the above values. By regulating the value of L within the above range, the value of L / D can be regulated within the scope of the present application, which is beneficial to limit the volume proportion of the curved portion in the electrode assembly, give play to the role of the compound represented by formula (I), enhance the positive electrode interface stability, reduce the consumption rate of the electrolyte, and delay the loss rate of the electrolyte in the curved portion of the electrode assembly, thereby helping to improve the high temperature cycle performance of the electrochemical device, and also helping to make the electrochemical device have a smaller DC impedance at low SOC.

[0031] In some embodiments of the present application, 1≤D≤5, preferably, 1.5≤D≤2.5. For example, D can be 1, 1.5, 2, 2.5, 3, 3.4, 4, 5 or a range consisting of any two of the above values. By regulating the value of D within the above range, the value of L / D can be regulated within the scope of the present application, which is beneficial to limit the volume proportion of the curved portion in the electrode assembly, give play to the role of the compound shown in formula (I), enhance the positive electrode interface stability, reduce the consumption rate of the electrolyte, and delay the loss rate of the electrolyte in the curved portion of the electrode assembly, thereby helping to improve the high temperature cycle performance of the electrochemical device, and also helping to make the electrochemical device have a smaller DC impedance at low SOC.

[0032] In some embodiments of the present application, the width of the electrode assembly is W mm, where W = L + 2D and 10 ≤ W ≤ 40. For example, W can be 10, 15, 20, 23, 25, 28, 30, 35, 40, or a range consisting of any two of the above values. When the width W of the electrode assembly is within the above range, the electrode assembly is smaller and more suitable for small electronic devices such as watches. However, in small-sized electrode assemblies, the volume of the curved portion accounts for a larger proportion, the electrolyte is squeezed out more, and the probability of electrolyte loss in the curved portion is greater. Introducing the compound represented by formula (I) into the electrolyte of the above-mentioned electrochemical device and regulating its mass percentage A% is within the scope of this application. Since the compound represented by formula (I) has strong antioxidant properties, it can reduce the oxidation reaction between the positive electrode active material and the electrolyte, widen the oxidation window of the electrolyte, and make the electrochemical device have good positive electrode interface stability, which is more conducive to reducing the consumption rate of the electrolyte and delaying the loss rate of the electrolyte in the bent part of the electrode assembly, thereby improving the high-temperature cycle performance of the electrochemical device, and at the same time, it is also beneficial to make the electrochemical device have a smaller DC impedance at a low SOC.

[0033] In some embodiments of the present application, the compound represented by formula (I) includes at least one of the following compounds:

[0034] In the electrochemical device of the present application, the electrolyte includes the compound represented by formula (I) within the above-mentioned range, which can better exert the antioxidant effect of the compound represented by formula (I), so that the electrochemical device has good positive electrode interface stability, which is beneficial to reducing the consumption rate of the electrolyte and delaying the loss rate of the electrolyte in the curved part of the electrode assembly, thereby helping to improve the high-temperature cycle performance of the electrochemical device, and at the same time, it is also beneficial to make the electrochemical device have a smaller DC impedance at a low SOC.

[0035] In some embodiments of the present application, the electrolyte includes a non-fluorinated carboxylate, and the non-fluorinated carboxylate includes at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; based on the mass of the electrolyte, the mass percentage of the non-fluorinated carboxylate is B%, and 10≤B≤60. For example, B can be 10, 20, 26, 30, 38, 40, 44, 50, 60, or a range consisting of any two of the above values. The viscosity of the compound represented by formula (I) is relatively large, resulting in poor wettability of the electrolyte to the positive electrode interface and the negative electrode interface. The non-fluorinated carboxylic acid ester has a similar structure to the compound represented by formula (I), has good affinity and low viscosity. On the basis of the compound represented by formula (I), the above-mentioned type of non-fluorinated carboxylic acid ester is further introduced and its mass percentage B% is controlled within the above-mentioned range. This can make the electrolyte have a suitable viscosity, improve the wettability of the positive electrode interface and the negative electrode interface, reduce polarization, and thus help improve the high-temperature cycle performance of the electrochemical device. At the same time, it is also beneficial for the electrochemical device to have a smaller DC impedance at a low SOC.

[0036] In some embodiments of the present application, the electrolyte includes a cyclic carbonate, and the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate or ethylene ethylene carbonate; based on the mass of the electrolyte, the mass percentage of the cyclic carbonate is C%, and 0≤C≤10. For example, C can be 0, 2, 3.4, 4, 5, 6, 8, 10 or a range consisting of any two of the above values. The compound represented by formula (I) has poor dissociation of lithium salts. On the basis of the compound represented by formula (I), a cyclic carbonate is further introduced and its mass percentage C% is regulated within the above range, which is beneficial to the dissociation of lithium salts, improves the conductivity of the electrolyte, and is also beneficial to the anion film formation of the lithium salt, adjusts the electrolyte solvation structure, and enhances the stability of the positive electrode interface and the negative electrode interface, thereby improving the high temperature cycle performance of the electrochemical device, and is also beneficial to making the electrochemical device have a smaller DC impedance at low SOC.

[0037] In some embodiments of the present application, the electrolyte includes a nitrile additive, the nitrile additive including at least one of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, methylglutaronitrile, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile or 1,2,3-tris(2-cyanoethoxy)propane; based on the mass of the electrolyte, the mass percentage of the nitrile additive is E%, 2≤E≤10, preferably, 2≤E≤6. For example, E can be 2, 4, 5, 6, 6.5, 8, 10 or a range consisting of any two of the above values. Nitrile additives can complex with high-valent metal ions in the positive electrode active material to stabilize the positive electrode interface. Further introducing the above-mentioned type of nitrile additive on the basis of the compound represented by formula (I) and regulating its mass percentage E% within the above range can further enhance the stability of the positive electrode interface, thereby facilitating the improvement of the high-temperature cycle performance of the electrochemical device, and also facilitating the electrochemical device to have a smaller DC impedance at a low SOC.

[0038] In some embodiments of the present application, the electrolyte includes a boron-containing compound, and the boron-containing compound includes at least one of lithium bis(1,1-trifluoromethyloxalato)borate, lithium bis(1-trifluoromethyloxalato)borate, lithium difluoro(1,1-trifluoromethyl)oxalatoborate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium bis(1,1-trifluoromethylmalonate)borate, lithium fluoromalonate difluoroborate, or lithium bis(fluoromalonate)borate; based on the mass of the electrolyte, the mass percentage of the boron-containing compound is F%, 0.01≤F≤2, preferably, 0.01≤F≤1. For example, F can be 0.01, 0.3, 0.4, 0.8, 1, 1.4, 1.8, 2, or a range consisting of any two of the above values. The compound shown in formula (I) can enhance the stability of the positive electrode interface, and the boron-containing compound can form a stable solid electrolyte interface (SEI) film at the negative electrode, thereby enhancing the stability of the negative electrode interface. Further introducing the above-mentioned type of boron-containing compound on the basis of the compound represented by formula (I) and regulating its mass percentage F% within the above-mentioned range can synergistically enhance the stability of the positive electrode interface and the negative electrode interface, thereby facilitating the improvement of the high-temperature cycle performance of the electrochemical device, and also facilitating the electrochemical device to have a smaller DC impedance at a low SOC.

[0039] In the present application, the electrolyte also includes other organic solvents and other additives. The present application is not particularly limited to the types of other organic solvents and other additives, as long as the purpose of the present application can be achieved. For example, other organic solvents may include but are not limited to dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), 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 At least one of -1-methylethylene ester, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, γ-butyrolactone, decanoic acid, valerolactone, caprolactone, dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, trimethyl phosphate, triethyl phosphate or trioctyl phosphate. Other additives may include but are not limited to at least one of 1,3-propane sultone, vinyl sulfate and vinylene carbonate.

[0040] In some embodiments of the present application, the sum of the mass percentages of other organic solvents and other additives based on the mass of the electrolyte is G%, and 0≤G≤40. For example, G can be 0, 10, 15, 20, 22, 25, 30, 33, 35, 40, or a range consisting of any two of the above values.

[0041] In the present application, the electrolyte further includes a lithium salt. The present application does not particularly limit the type of lithium salt, as long as the purpose of the present application can be achieved. For example, the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, or lithium difluorophosphate. Preferably, the lithium salt includes lithium hexafluorophosphate.

[0042] In some embodiments of the present application, the mass percentage of the lithium salt is H% based on the mass of the electrolyte, and 10≤H≤20. For example, H can be 10, 12, 14, 15, 16, 18, 20, or a range consisting of any two of the above values.

[0043] In some embodiments of the present application, the electrolyte may include a lithium salt, a compound represented by formula (I), a cyclic carbonate, other organic solvents, and other additives. The mass percentages of the lithium salt, the compound represented by formula (I), the cyclic carbonate, other organic solvents, and other additives are as described above. The electrochemical device including the above electrolyte has good high-temperature cycle performance and also has a small DC impedance at low SOC.

[0044] In some embodiments of the present application, the electrolyte may include any one of a lithium salt, a compound represented by formula (I), a cyclic carbonate, other organic solvents and other additives, and a non-fluorinated carboxylic acid ester, a nitrile additive, and a boron-containing compound. The mass percentages of the lithium salt, the compound represented by formula (I), the cyclic carbonate, other organic solvents and other additives, the non-fluorinated carboxylic acid ester, the nitrile additive, and the boron-containing compound are as described above. The electrochemical device including the above-mentioned electrolyte has good high-temperature cycle performance and also has a small DC impedance at a low SOC.

[0045] In some embodiments of the present application, the electrolyte may include at least one of a lithium salt, a compound shown in formula (I), a cyclic carbonate, a non-fluorinated carboxylic acid ester, other organic solvents and other additives, a nitrile additive, and a boron-containing compound. The mass percentage of the compound shown in formula (I) is 30% to 75%, the mass percentage of the non-fluorinated carboxylic acid ester is 10% to 55%, and the mass percentage of the lithium salt, the cyclic carbonate, other organic solvents and other additives, the nitrile additive, and the boron-containing compound is as described above. The electrochemical device including the above-mentioned electrolyte has good high temperature cycle performance and also has a small DC impedance at low SOC.

[0046] In some embodiments of the present application, the electrolyte may include a lithium salt, a compound represented by formula (I), a cyclic carbonate, a nitrile additive, a boron-containing compound, other organic solvents, and other additives. The mass percentages of the lithium salt, the compound represented by formula (I), the cyclic carbonate, the nitrile additive, the boron-containing compound, other organic solvents, and other additives are as described above. The electrochemical device including the above electrolyte has good high-temperature cycle performance and also has a small DC impedance at low SOC.

[0047] In the present application, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator. The separator is used to separate the positive electrode sheet and the negative electrode sheet to prevent internal short circuit of the electrochemical device, allow electrolyte ions to pass freely, and do not affect the electrochemical charge and discharge process.

[0048] This application has no special restrictions on the positive electrode sheet, as long as the purpose of this application can be achieved. For example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. In this application, the positive electrode active material layer can be provided on one surface of the positive electrode current collector along its own thickness direction, or on two surfaces in the thickness direction of the positive electrode current collector. It should be noted that the "surface" here can be the entire area of ​​the positive electrode current collector or a partial area of ​​the positive electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0049] The present application has no special restrictions on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector). The present application has no special restrictions on the thickness of the positive electrode current collector and the positive electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 6μm to 12μm, and the thickness of the positive electrode active material layer is 30μm to 120μm. The present application has no special restrictions on the thickness of the positive electrode sheet, as long as the purpose of the present application can be achieved, for example, the thickness of the positive electrode sheet is 50μm to 250μm.

[0050] The positive electrode active material layer of the present application includes a positive electrode active material, and the positive electrode active material includes a substance that can reversibly embed and extract active ions such as lithium ions. The positive electrode active material layer can be one layer or more layers, and each layer in the multi-layer positive electrode active material layer can contain the same or different positive electrode active materials. The present application has no particular restrictions on the positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include but is not limited to lithium nickel cobalt manganese oxide (such as NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. The chemical formula of the above-mentioned lithium-rich manganese-based material is LiMnO·LiMO, and M may include Ni, Co or Mn. In the present application, a substance having a different composition than that of the positive electrode active material may be attached to the surface of the positive electrode active material. For example, the surface-attached substance may include, but is not limited to, at least one of aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, aluminum sulfate, lithium carbonate, calcium carbonate, magnesium carbonate, or carbon. By attaching the above-mentioned substance to the surface of the positive electrode active material, the oxidation reaction of the electrolyte on the surface of the positive electrode active material can be suppressed, thereby improving the service life of the electrochemical device.

[0051] The positive electrode active material layer may also include a positive electrode conductive agent and a positive electrode binder. The present application does not particularly limit the types of the positive electrode conductive agent and the positive electrode binder, as long as the purpose of the present application can be achieved. For example, the positive electrode binder may include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon; the positive electrode conductive agent may include, but is not limited to, at least one of a carbon-based material, a metal-based material, or a conductive polymer. For example, the carbon-based material may include, but is not limited to, at least one of natural graphite, artificial graphite, conductive carbon black (Super P), or carbon fiber; the metal-based material may include, but is not limited to, at least one of metal powder, metal fiber, copper, nickel, aluminum, or silver; and the conductive polymer may include, but is not limited to, a polyphenylene derivative. The present application has no particular limitation on the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder in the positive electrode active material layer, and can be selected according to actual needs as long as the purpose of the present application can be achieved.

[0052] This application does not impose any particular restrictions on the negative electrode sheet, as long as the purpose of this application can be achieved. For example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. In this application, the negative electrode active material layer can be disposed on one surface in the thickness direction of the negative electrode current collector, or on two surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or a partial area of ​​the negative electrode current collector. This application does not impose any particular restrictions, as long as the purpose of this application can be achieved.

[0053] The present application has no special restrictions on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collector (such as carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, etc.). In the present application, there is no special restriction on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode current collector is 6μm to 12μm, and the thickness of the negative electrode active material layer is 30μm to 130μm. In the present application, there is no special restriction on the thickness of the negative electrode sheet, as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode sheet is 50μm to 280μm.

[0054] The negative electrode active material layer of the present application includes a negative electrode active material. The negative electrode active material layer can be one or more layers. Each layer in the multi-layer negative electrode active material layer can contain the same or different negative electrode active materials. The negative electrode active material is any substance that can reversibly embed and extract active ions such as lithium ions. The negative electrode active material can include but is not limited to graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO x (0.5<x<1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithium titanate lithiated TiO2-Li4Ti5O 12 , Li-Al alloy and at least one of metallic lithium.

[0055] The negative electrode active material layer in the present application may further include a negative electrode binder and a negative electrode conductor, or the negative electrode active material layer may further include a negative electrode binder, a negative electrode conductor and a thickener. The present application has no particular restrictions on the types of negative electrode binders and negative electrode conductors, as long as the purpose of the present application can be achieved. For example, the negative electrode binder may include but is not limited to at least one of the above-mentioned positive electrode binders, and the negative electrode conductor may include but is not limited to at least one of the above-mentioned positive electrode conductors. The present application has no particular restrictions on the type of thickener, as long as the purpose of the present application can be achieved. For example, the thickener may include but is not limited to at least one of sodium carboxymethyl cellulose or carboxymethyl cellulose.

[0056] The present application has no particular restrictions on the isolation membrane, as long as the purpose of the present application can be achieved. For example, the material of the isolation membrane may include, but is not limited to, polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (such as polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; the type of isolation membrane may include at least one of woven membrane, non-woven membrane, microporous membrane, composite membrane, rolled membrane or spun membrane. For example, the isolation membrane may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric, a membrane or a 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 non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a binder. The present application has no particular restrictions on the inorganic particles. For example, it may include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The present application has no particular restrictions on the binder. For example, it may be at least one of the above-mentioned positive electrode binders. The polymer layer contains a polymer. The present application has no particular restrictions on the polymer. For example, the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl ether or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene). In the present application, the thickness of the isolation membrane is not particularly limited, as long as the purpose of the present application can be achieved. For example, the thickness of the isolation membrane can be 5μm to 50μm.

[0057] The electrochemical device of the present application also includes a packaging bag for containing the positive electrode sheet, separator, negative electrode sheet, and electrolyte, as well as other components of the electrochemical device known in the art. This application does not particularly limit these other components. This application does not particularly limit the packaging bag and can be any packaging bag known in the art, as long as it can achieve the purpose of this application. For example, an aluminum-plastic film packaging bag can be used.

[0058] The electrochemical device of the present application is not particularly limited and may include any device that undergoes an electrochemical reaction. In some embodiments of the present application, the electrochemical device may include, but is not limited to, a lithium-ion battery, a sodium-ion battery, a lithium polymer electrochemical device, or a lithium-ion polymer electrochemical device.

[0059] The preparation process of an electrochemical device is well known to those skilled in the art and is not particularly limited in this application. For example, it may include, but is not limited to, the following steps: stacking the positive electrode sheet, separator, and negative electrode sheet in sequence, and performing winding, folding, and other operations as needed to obtain a wound electrode assembly; placing the electrode assembly into a packaging bag; injecting an electrolyte into the packaging bag and sealing it to obtain the electrochemical device. Furthermore, overcurrent protection components, guide plates, and the like may be placed in the packaging bag as needed to prevent pressure buildup and overcharging and discharging within the electrochemical device.

[0060] The second aspect of the present application provides an electronic device comprising the electrochemical device provided in the first aspect of the present application. The electrochemical device provided in the present application has good high-temperature cycle performance, thereby providing the electronic device provided in the present application with a long service life and good performance.

[0061] The electronic device of the present application is not particularly limited and can be any electronic device known in the art. For example, the electronic device can include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0062] Example

[0063] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0064] Test methods and equipment:

[0065] Test of the maximum length L of the straight part and the maximum radius D of the curved part of the electrode assembly

[0066] A computed tomography (CT) scanner, magnified to 300%, scans the curved and straight portions of the electrode assembly in a lithium-ion battery to obtain cross-sectional images. The length of the first straight portion is measured, recorded as L1, and the length of the second straight portion is measured, recorded as L2. The maximum value of the two is recorded as the maximum length L of the straight portion. The radius of the first curved portion is measured, recorded as D1, and the radius of the second curved portion is measured, recorded as D2. The maximum value of the two is recorded as the maximum radius D of the curved portion.

[0067] High temperature cycle performance test

[0068] Adjust the test temperature to a constant 45°C. Charge the lithium-ion battery at a constant current of 1C to 4.48V, then charge it at a constant voltage of 4.48V to 0.05C, and then discharge it at a constant current of 1C to 3.0V. This constitutes one charge-discharge cycle, which is the first cycle and is recorded as the discharge capacity of the first cycle. Repeat the charge-discharge cycle described above, recording the discharge capacity of each cycle until the discharge capacity of the lithium-ion battery decays to 80% of the discharge capacity of the first cycle. Record the number of charge-discharge cycles and record it as the number of cycles at 45°C.

[0069] DC resistance (DCR) test

[0070] The test temperature was maintained at a constant 45°C. The lithium-ion battery was charged at a constant current of 0.2C to 4.48V, then charged at a constant voltage of 4.48V to 0.05C. The battery was then discharged at a current of 0.1C for 8 hours, bringing the state of charge (SOC) of the lithium-ion battery to 20%. The battery was discharged at a constant current of 0.1C for 10 seconds, with the voltage value recorded as U1. The battery was then discharged at a constant current of 1C for 1 second, with the voltage value recorded as U2.

[0071] 20% SOC DCR=(U2-U1) / (1C-0.1C).

[0072] Example 1-1

[0073] <Preparation of Electrolyte>

[0074] In an argon atmosphere glove box with a water content of less than 10 ppm, the cyclic carbonate ethylene carbonate (EC), the cyclic carbonate propylene carbonate (PC), and another organic solvent diethyl carbonate (DEC) are mixed in a mass ratio of 10:10:80 to obtain a base solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) and the compound represented by formula (I) (Formula (I-3)) are added to the base solvent and mixed to obtain an electrolyte. The mass percentage of the lithium salt LiPF6 is 12.5% ​​based on the mass of the electrolyte, the mass percentage of the compound represented by formula (I-3) is 50%, and the remainder is the base solvent.

[0075] <Preparation of positive electrode sheet>

[0076] The positive electrode active material LiCoO2, the positive electrode conductive agent conductive carbon black (Super P), the positive electrode binder polyvinylidene fluoride (PVDF, weight average molecular weight Mw = 7×10 6) are mixed in a mass ratio of 97.5:1:1.5, N-methylpyrrolidone (NMP) is added as a solvent, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry with a solid content of 75wt%. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 85°C to obtain a positive electrode sheet with a single-sided coating of a positive electrode active material layer with a thickness of 50μm. Thereafter, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of a positive electrode active material layer. After cold pressing, cutting, and welding of the positive electrode aluminum tab, a positive electrode sheet with a specification of 74mm×851mm is obtained for standby use.

[0077] <Preparation of negative electrode sheet>

[0078] The negative electrode active material artificial graphite, negative electrode conductive agent Super P, thickener carboxymethyl cellulose (CMC-Na, Mw = 7 × 10 5 ), negative electrode binder styrene-butadiene rubber (SBR, Mw = 5 × 10 6 ) were mixed in a mass ratio of 97.5:1:0.5:1, and then deionized water was added as a solvent and stirred evenly in a vacuum mixer to obtain a negative electrode slurry with a solid content of 50 wt%. The negative electrode slurry was evenly coated on one surface of an 8 μm thick negative electrode current collector copper foil and dried at 85°C to obtain a negative electrode sheet coated on one side with a 60 μm thick negative electrode active material layer. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet coated on both sides with a negative electrode active material layer. The negative electrode sheet was then cold pressed, cut, and welded to the nickel tabs to obtain a negative electrode sheet measuring 76 mm x 867 mm for later use.

[0079] <Preparation of Separator>

[0080] A porous polyethylene film with a thickness of 7 μm (provided by Celgard) was used as the separator.

[0081] <Preparation of lithium-ion batteries>

[0082] The positive electrode sheet, separator, and negative electrode sheet prepared above are stacked in order, with the separator placed between the positive and negative electrode sheets to act as an insulator. The electrode assembly is then wound to obtain a maximum length L of the straight portion of 9 mm, a maximum radius D of the curved portion of 1.8 mm, an L / D ratio of 5, and a width W of 12.6 mm. The electrode assembly is placed in an aluminum-plastic film packaging bag, dried in an 85°C vacuum oven for 12 hours to remove moisture, and then injected with the prepared electrolyte. The battery undergoes vacuum packaging, standing, formation (charging to 3.5 V at a constant current of 0.3C, then to 3.9 V at a constant current of 1C), shaping, capacity testing, and secondary packaging to obtain a lithium-ion battery.

[0083] Example 1-2 to Example 1-6

[0084] Except for adjusting the parameters according to Table 1 in <Preparation of Lithium-ion Battery>, the rest is the same as Example 1-1. Among them, when L and D change, the size of the positive electrode sheet and the negative electrode sheet is the same as Example 1-1.

[0085] Example 1-7 to Example 1-10

[0086] The preparation was the same as in Example 1-3, except that the mass percentage A% of the compound of formula (I-3) in the "Electrolyte Preparation" was adjusted according to Table 1. When the mass percentage A% of the compound of formula (I-3) was changed, the mass percentage of the base solvent also changed, while the mass ratio of EC, PC, and DEC and the mass percentage of the lithium salt remained unchanged.

[0087] Example 1-11 to Example 1-13

[0088] Except that the type of the compound represented by formula (I) was adjusted according to Table 1 in <Preparation of Electrolyte>, the rest was the same as Example 1-3.

[0089] Example 2-1

[0090] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0091] <Preparation of Electrolyte>

[0092] In an argon atmosphere glove box with a water content of less than 10 ppm, cyclic carbonate ethylene carbonate (EC), cyclic carbonate propylene carbonate (PC), and other organic solvent diethyl carbonate (DEC) are mixed in a mass ratio of 10:10:80 to obtain a base solvent, and then lithium salt lithium hexafluorophosphate (LiPF6), compound represented by formula (I) (Formula (I-3), and non-fluorinated carboxylic acid ester propyl propionate are added to the base solvent and mixed to obtain an electrolyte. Wherein, based on the mass of the electrolyte, the mass percentage of lithium salt LiPF6 is 12.5%, the mass percentage A% of the compound represented by formula (I-3) is 65%, the mass percentage B% of propyl propionate is 10%, and the remainder is the base solvent.

[0093] Example 2-2

[0094] The preparation process was the same as in Example 2-1, except that the mass percentage A% of the compound of formula (I-3) and the mass percentage B% of propyl propionate were adjusted according to Table 2 in the "Preparation of Electrolyte Solution". When the mass percentage A% of the compound of formula (I-3) and the mass percentage B% of propyl propionate were changed, the mass ratio of EC, PC, and DEC, the mass percentage of the base solvent, and the mass percentage of the lithium salt remained unchanged.

[0095] Example 2-3

[0096] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0097] <Preparation of Electrolyte>

[0098] In an argon atmosphere glove box with a water content of less than 10 ppm, the compound represented by formula (I) (formula (I-3)) and the non-fluorinated carboxylic acid ester propyl propionate were mixed in a mass ratio of 30:57.5, and then lithium hexafluorophosphate (LiPF6) was added and mixed to obtain an electrolyte. The mass percentage of the lithium salt LiPF6, based on the mass of the electrolyte, was 12.5%, with the remainder being the compound represented by formula (I-3) and propyl propionate.

[0099] Example 2-4 to Example 2-5

[0100] Except for adjusting the type of non-fluorinated carboxylic acid ester according to Table 2 in <Preparation of Electrolyte>, the rest was the same as Example 2-2.

[0101] Examples 2-6

[0102] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0103] <Preparation of Electrolyte>

[0104] In an argon atmosphere glove box with a water content of less than 10 ppm, the cyclic carbonate ethylene carbonate (EC), the cyclic carbonate propylene carbonate (PC), and the other organic solvent diethyl carbonate (DEC) are mixed in a mass ratio of 10:10:80 to obtain a base solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6), the compound represented by formula (I) (Formula (I-3), and the nitrile additive succinonitrile are added to the base solvent and mixed to obtain an electrolyte. Based on the mass of the electrolyte, the mass percentage of the lithium salt LiPF6 is 12.5%, the mass percentage of the compound represented by formula (I-3) is 50%, the mass percentage of succinonitrile is 2%, and the remainder is the base solvent.

[0105] Example 2-7 to Example 2-8

[0106] The preparation was the same as in Example 2-6, except that the mass percentage E% of succinonitrile was adjusted according to Table 2 in the "Preparation of Electrolyte Solution". When the mass percentage E% of succinonitrile was changed, the mass percentage of the base solvent also changed, while the mass ratio of EC, PC, and DEC, the mass percentage of the lithium salt, and the mass percentage A% of the compound of formula (I-3) remained unchanged.

[0107] Examples 2-9

[0108] The preparation was the same as in Example 2-6, except that the type of nitrile additive and the weight percentage E% of the nitrile additive were adjusted according to Table 2 in "Preparation of Electrolyte". When the weight percentage E% of the nitrile additive was changed, the weight percentage of the base solvent was changed accordingly, while the mass ratio of EC, PC, and DEC, the weight percentage of the lithium salt, and the weight percentage A% of the compound of formula (I-3) remained unchanged.

[0109] Example 2-10

[0110] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0111] <Preparation of Electrolyte>

[0112] In an argon atmosphere glove box with a water content of less than 10 ppm, the cyclic carbonate ethylene carbonate (EC), the cyclic carbonate propylene carbonate (PC), and another organic solvent diethyl carbonate (DEC) were mixed in a mass ratio of 10:10:80 to obtain a base solvent. Then, lithium hexafluorophosphate (LiPF6), a compound represented by formula (I) (Formula (I-3), and a boron-containing compound lithium dioxalatoborate (LiBOB) were added to the base solvent and mixed to obtain an electrolyte. The electrolyte solution contained 12.5% ​​by mass of the lithium salt LiPF6, 50% by mass of the compound represented by formula (I-3), and 0.01% by mass of LiBOB, with the remainder being the base solvent.

[0113] Example 2-11 to Example 2-12

[0114] The preparation was identical to Example 2-10, except that the LiBOB mass percentage F% in "Electrolyte Preparation" was adjusted according to Table 2. Changing the LiBOB mass percentage F% also changed the base solvent mass percentage, while the mass ratio of EC, PC, and DEC, the lithium salt mass percentage, and the compound of Formula (I-3) mass percentage A% remained unchanged.

[0115] Example 2-13

[0116] The preparation process was the same as in Example 2-10, except that the type of boron-containing compound and the mass percentage F% of the boron-containing compound were adjusted according to Table 2 in the "Preparation of Electrolyte Solution". When the mass percentage F% of the boron-containing compound was changed, the mass percentage of the base solvent was also changed. The mass ratio of EC, PC, and DEC, the mass percentage of the lithium salt, and the mass percentage A% of the compound of Formula (I-3) remained unchanged.

[0117] Examples 2-14

[0118] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0119] <Preparation of Electrolyte>

[0120] In an argon atmosphere glove box with a water content of less than 10 ppm, cyclic carbonate ethylene carbonate (EC), cyclic carbonate propylene carbonate (PC), and other organic solvent diethyl carbonate (DEC) are mixed in a mass ratio of 10:10:80 to obtain a base solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6), compound (I-3) represented by formula (I), non-fluorinated carboxylic acid ester propyl propionate, and nitrile additive succinonitrile are added to the base solvent and mixed to obtain an electrolyte. Wherein, based on the mass of the electrolyte, the mass percentage of lithium salt LiPF6 is 12.5%, the mass percentage A% of the compound of formula (I-3) is 48%, the mass percentage B% of propyl propionate is 25%, the mass percentage E% of succinonitrile is 2%, and the remainder is the base solvent.

[0121] Example 2-15 to Example 2-16

[0122] The preparation process was the same as Example 2-14, except that the mass percentage A% of the compound of formula (I-3) and the mass percentage E% of succinonitrile in the electrolyte solution preparation were adjusted according to Table 2. When the mass percentage A% of the compound of formula (I-3) and the mass percentage E% of succinonitrile were changed, the mass ratio of EC, PC, and DEC, the mass percentage of the base solvent, the mass percentage of the lithium salt, and the mass percentage B% of propyl propionate remained unchanged.

[0123] Example 2-17

[0124] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0125] <Preparation of Electrolyte>

[0126] In an argon atmosphere glove box with a water content of less than 10 ppm, a cyclic carbonate ethylene carbonate (EC), a cyclic carbonate propylene carbonate (PC), and another organic solvent diethyl carbonate (DEC) were mixed uniformly in a mass ratio of 10:10:80 to obtain a base solvent. A lithium salt lithium hexafluorophosphate (LiPF6), a compound represented by formula (I) (Formula (I-3)), a non-fluorinated carboxylic acid ester propyl propionate, and a boron-containing compound LiBOB were then added to the base solvent and mixed uniformly to obtain an electrolyte. The electrolyte solution comprises, based on the mass of the electrolyte, 12.5% ​​by mass of the lithium salt LiPF6, 50% by mass of the compound represented by formula (I-3), 25% by mass of the propyl propionate, and 0.01% by mass of the LiBOB. The remainder is the base solvent.

[0127] Example 2-18 to Example 2-19

[0128] The preparation was identical to Example 2-17, except that the LiBOB mass percentage F% in "Electrolyte Preparation" was adjusted according to Table 2. Changing the LiBOB mass percentage F% also altered the base solvent mass percentage, while the mass ratio of EC, PC, and DEC, the lithium salt mass percentage, the compound of Formula (I-3) mass percentage A%, and the propyl propionate mass percentage B% remained unchanged.

[0129] Example 2-20

[0130] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0131] <Preparation of Electrolyte>

[0132] In an argon atmosphere glove box with a water content of less than 10 ppm, the cyclic carbonate ethylene carbonate (EC), the cyclic carbonate propylene carbonate (PC), and another organic solvent diethyl carbonate (DEC) were mixed uniformly in a mass ratio of 10:10:80 to obtain a base solvent. Then, lithium hexafluorophosphate (LiPF6), a compound represented by formula (I) (Formula (I-3)), a nitrile additive succinonitrile, and a boron-containing compound LiBOB were added to the base solvent and mixed uniformly to obtain an electrolyte. The electrolyte solution contained 12.5% ​​by mass of the lithium salt LiPF6, 50% by mass of the compound represented by formula (I-3), 2% by mass of succinonitrile, and 0.3% by mass of LiBOB, with the remainder being the base solvent.

[0133] Example 2-21 to Example 2-22

[0134] The preparation process was the same as in Example 2-20, except that the mass percentage E% of succinonitrile was adjusted according to Table 2 in the "Electrolyte Preparation". When the mass percentage E% of succinonitrile was changed, the mass percentage of the base solvent also changed, while the mass ratio of EC, PC, and DEC, the mass percentage of the lithium salt, the mass percentage A% of the compound of formula (I-3), and the mass percentage F% of LiBOB remained unchanged.

[0135] Example 2-23

[0136] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0137] <Preparation of Electrolyte>

[0138] In an argon atmosphere glove box with a water content of less than 10 ppm, a cyclic carbonate ethylene carbonate (EC), a cyclic carbonate propylene carbonate (PC), and another organic solvent diethyl carbonate (DEC) were mixed uniformly in a mass ratio of 10:10:80 to obtain a base solvent. Then, a lithium salt lithium hexafluorophosphate (LiPF6), a compound represented by formula (I) (Formula (I-3)), a non-fluorinated carboxylic acid ester propyl propionate, a nitrile additive succinonitrile, and a boron-containing compound LiBOB were added to the base solvent and mixed uniformly to obtain an electrolyte. The electrolyte solution comprises, based on the mass of the electrolyte, 12.5% ​​by mass of the lithium salt LiPF6, 62.7% by mass of the compound represented by formula (I-3), 10% by mass of the propyl propionate, 2% by mass of the succinonitrile, and 0.3% by mass of the LiBOB. The remainder is the base solvent.

[0139] Examples 2-24

[0140] The process was the same as Example 2-23, except that the mass percentage A% of the compound of formula (I-3) and the mass percentage B% of propyl propionate in "Electrolyte Preparation" were adjusted according to Table 2. When the mass percentage A% of the compound of formula (I-3) and the mass percentage B% of propyl propionate were changed, the mass ratio of EC, PC, and DEC, the mass percentage of the base solvent, the mass percentage of the lithium salt, the mass percentage E% of succinonitrile, and the mass percentage F% of LiBOB remained unchanged.

[0141] Example 2-25

[0142] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0143] <Preparation of Electrolyte>

[0144] In an argon atmosphere glove box with a water content of less than 10 ppm, the compound represented by formula (I) (formula (I-3)) and the non-fluorinated carboxylic acid ester propyl propionate were mixed in a mass ratio of 50:37.5, and then lithium hexafluorophosphate (LiPF6) was added and mixed to obtain an electrolyte. The mass percentage of the lithium salt LiPF6, based on the mass of the electrolyte, was 12.5%, with the remainder being the compound represented by formula (I-3) and propyl propionate.

[0145] Comparative Example 1 to Comparative Example 2

[0146] Except for adjusting the parameters in <Preparation of Lithium-ion Battery> according to Table 1, the rest is the same as Example 1-1. When L and D are changed, the sizes of the positive and negative electrode sheets are the same as those in Example 1-1.

[0147] Comparative Example 3

[0148] Except for <Preparation of Electrolyte>, the rest is the same as Example 1-3.

[0149] <Preparation of Electrolyte>

[0150] In an argon atmosphere glove box with a water content of less than 10 ppm, the cyclic carbonates ethylene carbonate (EC), cyclic carbonate propylene carbonate (PC), and another organic solvent diethyl carbonate (DEC) were mixed in a mass ratio of 10:10:80 to obtain a base solvent. The lithium salt lithium hexafluorophosphate (LiPF6) was then added to the base solvent and mixed to obtain an electrolyte. The mass percentage of the lithium salt LiPF6, based on the mass of the electrolyte, was 12.5%, with the remainder being the base solvent.

[0151] Comparative Example 4 to Comparative Example 5

[0152] The preparation was the same as in Example 1-3, except that the mass percentage A% of the compound of formula (I-3) in the "Electrolyte Preparation" was adjusted according to Table 1. When the mass percentage A% of the compound of formula (I-3) was changed, the mass percentage of the base solvent also changed, while the mass ratio of EC, PC, and DEC and the mass percentage of the lithium salt remained unchanged.

[0153] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Table 1 and Table 2.

[0154] Table 1 Note: “\” in Table 1 indicates no corresponding parameter.

[0155] As can be seen from Examples 1-1 to 1-13 and Comparative Examples 1 to 5, the electrochemical devices of the embodiments of the present application, by regulating the L / D value of the wound structure electrode assembly within the range of the present application, and adding the compound represented by formula (I) to the electrolyte, and the mass percentage A% of the compound represented by formula (I) within the range of the present application, the electrochemical devices have a greater number of cycles at 45°C and a smaller 20% SOC DCR. This indicates that the electrochemical device has better high-temperature cycling performance and also has a smaller DC resistance at low SOC. However, the L / D values ​​of the electrode assemblies of the electrochemical devices of Comparative Examples 1 and 2 are not within the scope of the present application; the electrochemical device of Comparative Example 3 does not contain the compound represented by formula (I) in its electrolyte; the mass percentage A% of the compound represented by formula (I) in the electrochemical devices of Comparative Examples 4 and 5 is not within the scope of the present application. Although the 20% SOC DCR of the electrochemical devices of Comparative Examples 1 to 5 is small, the number of cycles at 45°C is even smaller, indicating that the high-temperature cycle performance of the electrochemical devices is worse, and they cannot simultaneously have good high-temperature cycle performance and a small DC impedance at low SOC.

[0156] The L / D value of the electrode assembly usually affects the high-temperature cycle performance of the electrochemical device. It can be seen from Examples 1-1 to 1-6 and Comparative Examples 1 to 2 that when the L / D value is too small, such as Comparative Example 1, the number of 45°C cycles of the electrochemical device is smaller; when the L / D value is too large, such as Comparative Example 2, the number of 45°C cycles of the electrochemical device is smaller. This shows that the high-temperature cycle performance of the electrochemical device is worse, and it cannot have both good high-temperature cycle performance and a smaller DC impedance at low SOC. When the L / D value is regulated within the range of this application, it is beneficial for the compound represented by formula (I) to play a role, delaying the loss rate of the electrolyte in the curved portion of the electrode assembly, so that the electrochemical device has a larger 45°C cycle number and a smaller 20% SOCDCR. This shows that the electrochemical device has better high-temperature cycle performance and also has a smaller DC impedance at low SOC.

[0157] The mass percentage A% of the compound represented by formula (I) generally affects the high-temperature cycling performance of the electrochemical device. As can be seen from Examples 1-3, 1-7, and 1-10, and Comparative Examples 3 to 5, when the value of A is too small, such as in Comparative Examples 3 and 4, the compound represented by formula (I) has limited effect, and the electrochemical device has a smaller 45°C cycle number. When the value of A is too large, such as in Comparative Example 5, an excess of the compound represented by formula (I) increases the DC impedance of the electrochemical device at low SOC, increases polarization, and results in a smaller 45°C cycle number and a larger 20% SOC DCR. This indicates that the high-temperature cycling performance of the electrochemical device is poorer, and it cannot simultaneously achieve good high-temperature cycling performance and a small DC impedance at low SOC. When the value of A is controlled within the range of this application, the compound represented by formula (I) is beneficially exerted, resulting in the electrochemical device having a larger 45°C cycle number and a smaller 20% SOC DCR. This indicates that the electrochemical device has better high-temperature cycling performance and also has a smaller DC impedance at low SOC.

[0158] The type of compound represented by formula (I) usually affects the high-temperature cycle performance of the electrochemical device. It can be seen from Examples 1-3, 1-7 to 1-13 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) within the scope of this application, it is beneficial to play the role of the compound represented by formula (I), and the electrochemical device has a larger 45°C cycle number and a smaller 20% SOC DCR. This shows that the electrochemical device has good high-temperature cycle performance and also has a smaller DC impedance at low SOC.

[0159] Table 2 Note: “\” in Table 2 indicates no corresponding parameter.

[0160] The mass percentage B% of non-fluorinated carboxylates usually affects the high-temperature cycle performance of electrochemical devices. It can be seen from Examples 1-3 and 2-1 to 2-3 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) and a cyclic carbonate, and the non-fluorinated carboxylates are further introduced, and the mass percentage B% thereof is regulated within the scope of this application, the electrochemical device has a greater number of cycles at 45°C and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance and also has a smaller DC impedance at low SOC. This is because the viscosity of the non-fluorinated carboxylates is relatively low. Further introducing the non-fluorinated carboxylates into the electrolyte and regulating B% within the scope of this application can improve the problem of the high viscosity of the compound represented by formula (I) so that the electrolyte has a suitable viscosity, improve the wettability of the positive electrode interface and the negative electrode interface, and reduce polarization.

[0161] The type of non-fluorinated carboxylic acid ester usually affects the high-temperature cycle performance of the electrochemical device. It can be seen from Examples 1-3 and 2-1 to 2-5 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) and a cyclic carbonate, a non-fluorinated carboxylic acid ester is further introduced, and a non-fluorinated carboxylic acid ester within the scope of the present application is selected, the electrochemical device has a larger number of cycles at 45°C and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance and also has a smaller DC impedance at low SOC. This is because the viscosity of the non-fluorinated carboxylic acid ester is relatively small. Further introducing a non-fluorinated carboxylic acid ester within the scope of the present application into the electrolyte can improve the problem of the large viscosity of the compound represented by formula (I) so that the electrolyte has a suitable viscosity, improves the wettability of the positive electrode interface and the negative electrode interface, and reduces polarization.

[0162] The mass percentage E% of nitrile additives usually affects the high-temperature cycle performance of electrochemical devices. It can be seen from Examples 1-3, 2-6 to 2-8 that when the electrolyte of the electrochemical device includes a compound represented by formula (I) and a cyclic carbonate, a nitrile additive is further introduced, and its mass percentage E% is regulated within the scope of this application, the electrochemical device has a greater number of cycles at 45°C and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance and also has a smaller DC impedance at low SOC. This is because nitrile additives can stabilize the positive electrode interface. Further introducing nitrile additives into the electrolyte and regulating E% within the scope of this application can further enhance the stability of the positive electrode interface.

[0163] The type of nitrile additive usually affects the high temperature cycle performance of the electrochemical device. It can be seen from Examples 1-3, 2-6 to 2-9 that when the electrolyte of the electrochemical device includes a compound represented by formula (I) and a cyclic carbonate, a nitrile additive is further introduced, and the nitrile additive within the scope of this application is selected, the electrochemical device has a greater number of cycles at 45°C and a smaller 20% SOC DCR, indicating that the electrochemical device has good high temperature cycle performance and also has a smaller DC impedance at low SOC. This is because nitrile additives can stabilize the positive electrode interface, and further introducing nitrile additives within the scope of this application into the electrolyte can further enhance the stability of the positive electrode interface.

[0164] The mass percentage F% of the boron-containing compound usually affects the high-temperature cycle performance of the electrochemical device. It can be seen from Examples 1-3, 2-10 to 2-12 that when the electrolyte of the electrochemical device includes the compound shown in formula (I) and the cyclic carbonate, the boron-containing compound is further introduced, and its mass percentage F% is regulated within the scope of this application, the electrochemical device has a larger 45°C cycle number and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance and also has a smaller DC impedance at low SOC. This is because the boron-containing compound can form a stable solid electrolyte interface (SEI) film at the negative electrode, enhance the stability of the negative electrode interface, and further introduce the boron-containing compound into the electrolyte and regulate F% within the scope of this application, which can synergistically enhance the stability of the positive electrode interface and the negative electrode interface.

[0165] The type of boron-containing compound usually affects the high-temperature cycle performance of the electrochemical device. It can be seen from Examples 1-3, 2-10 to 2-13 that when the electrolyte of the electrochemical device includes a compound shown in formula (I) and a cyclic carbonate, a boron-containing compound is further introduced, and a boron-containing compound within the scope of this application is selected, the electrochemical device has a larger 45°C cycle number and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance and also has a smaller DC impedance at low SOC. This is because the boron-containing compound can form a stable solid electrolyte interface (SEI) film at the negative electrode, enhance the stability of the negative electrode interface, and further introduce the boron-containing compound within the scope of this application into the electrolyte, which can synergistically enhance the stability of the positive electrode interface and the negative electrode interface.

[0166] It can be seen from Examples 1-3, 2-14 to 2-24 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) and a cyclic carbonate, and further introduces at least two of non-fluorinated carboxylic acid esters, nitrile additives or boron-containing compounds, the electrochemical device has a greater number of cycles at 45°C and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance and also has a smaller DC impedance at low SOC. The compound represented by formula (I) has good compatibility and superposition with the cyclic carbonate, nitrile additive or boron-containing compound. The above combination of substances is applied to the electrochemical device, which is more conducive to making the electrochemical device have both good high-temperature cycle performance and a smaller DC impedance at low SOC.

[0167] It can be seen from Examples 1-3, 2-3, and 2-25 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) and the non-fluorinated carboxylic acid ester but does not include the cyclic carbonate, the electrochemical device has a greater number of cycles at 45°C and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycling performance and also has a smaller DC impedance at low SOC.

[0168] It should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method or article.

[0169] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0170] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An electrochemical device comprising an electrode assembly and an electrolyte, wherein the electrode assembly is a wound structure, wherein: The electrode assembly includes a curved portion and a straight portion, the maximum length of the straight portion is L mm, the maximum radius of the curved portion is D mm, and 5≤L / D≤10; The electrolyte comprises a compound represented by formula (I): R 11 and R 12 are independently selected from C1 to C 10 The alkyl group, R 11 and R 12 At least one is substituted with fluorine; Based on the mass of the electrolyte, the mass percentage of the compound represented by formula (I) is A%, 30≤A≤80.

2. The electrochemical device according to claim 1, wherein: 5≤L≤30 or 1≤D≤5.

3. The electrochemical device according to claim 1, wherein The electrochemical device satisfies any one of the following: a)40≤A≤75; b) 7≤L / D≤9; c) 10≤L≤20; d)1.5≤D≤2.

5.

4. The electrochemical device according to claim 1, wherein The width of the electrode assembly is W mm, W=L+2D and 10≤W≤40.

5. The electrochemical device according to claim 1, wherein The compound represented by formula (I) includes at least one of the following compounds:

6. The electrochemical device according to claim 1, wherein The electrolyte includes a non-fluorinated carboxylate, and the non-fluorinated carboxylate includes at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate or propyl propionate; Based on the mass of the electrolyte, the mass percentage of the non-fluorinated carboxylic acid ester is B%, and 10≤B≤60.

7. The electrochemical device according to claim 1, wherein: The electrolyte includes a cyclic carbonate, and the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate or vinyl ethylene carbonate; Based on the mass of the electrolyte, the mass percentage of the cyclic carbonate is C%, and 0≤C≤10.

8. The electrochemical device according to claim 1, wherein The electrolyte includes a nitrile additive, and the nitrile additive includes at least one of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, methylglutaronitrile, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile or 1,2,3-tris(2-cyanoethoxy)propane; Based on the mass of the electrolyte, the mass percentage of the nitrile additive is E%, 2≤E≤10.

9. The electrochemical device according to claim 1, wherein: The electrolyte includes a boron-containing compound, and the boron-containing compound includes at least one of lithium bis(1,1-trifluoromethyloxalate)borate, lithium bis(1-trifluoromethyloxalate)borate, lithium difluoro(1,1-trifluoromethyl)oxalateborate, lithium difluorooxalateborate, lithium dioxalateborate, lithium bis(1,1-trifluoromethylmalonate)borate, lithium fluoromalonatedifluoroborate or lithium bis(fluoromalonate)borate; Based on the mass of the electrolyte, the mass percentage of the boron-containing compound is F%, and 0.01≤F≤2.

10. An electronic device comprising the electrochemical device according to any one of claims 1 to 9.

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