Electrochemical device and electronic device

Abstract

An electrochemical device (100) and an electronic device. The electrochemical device (100) comprises an electrode assembly (10) and an electrolyte. The electrode assembly (10) comprises tabs (20); a tab sealing adhesive (30) is provided on each tab (20); and in a direction perpendicular to the extension direction of each tab (20), the maximum width of the portion of the corresponding tab sealing adhesive (30) extending beyond the tab (20) is A mm, wherein 1.8≤A≤2.6. The electrolyte comprises a linear ester; based on the mass of the electrolyte, the mass percentage content of the linear ester is B%; and A / B satisfies 0.0215≤A / B≤0.058. The electrolyte comprises the linear ester, and the values of A and A / B are adjusted and controlled within the ranges above, so that the problem of high solubility of the sealing adhesive on the tab (20) due to a high content of the linear ester can be ameliorated, the content of impurities in the electrolyte is reduced, the transmission of ions in the electrolyte is facilitated, and side reactions in the electrolyte are reduced, thereby improving the cycle performance and rate performance of the electrochemical device (100).

Description

Electrochemical device and electronic device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 1, 2023, with application number 202311125229.3 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 electrochemistry, and in particular to an electrochemical device and an electronic device. Background Art

[0003] Electrochemical devices, such as lithium-ion batteries, have the advantages of high energy storage density, high open-circuit voltage, low self-discharge rate, long cycle life and good safety. They are now widely used as power sources in electronic products such as cameras, mobile phones, drones, laptops and smart watches.

[0004] As the use of lithium-ion batteries continues to expand, the market has placed higher demands on lithium-ion batteries, such as requiring lithium-ion batteries to have good cycle performance. Therefore, developing lithium-ion batteries with good cycle performance has become a technical problem that needs to be solved urgently by those skilled in the art.

[0005] Summary of the Invention

[0006] The purpose of this application is to provide an electrochemical device and an electronic device to improve the cycle performance of the electrochemical device. The specific technical solution is as follows:

[0007] In a first aspect, the present application provides an electrochemical device comprising an electrode assembly, a tab, and an electrolyte. A tab sealant is disposed on the tab, and the tab sealant extends perpendicular to the tab by a maximum width of A mm, with 1.8 ≤ A ≤ 2.6 mm. The electrolyte comprises a linear ester, wherein the linear ester has a mass percentage of B% based on the mass of the electrolyte, and A / B satisfies 0.0215 ≤ A / B ≤ 0.058. The inclusion of the linear ester in the electrolyte, with the values ​​of A and A / B controlled within the aforementioned ranges, can alleviate the problem of high solubility of the tab sealant due to a high linear ester content, reduce the impurity content in the electrolyte, facilitate ion (e.g., lithium ion) transport in the electrolyte, and reduce side reactions in the electrolyte, thereby improving the cycling performance and rate capability of the electrochemical device.

[0008] In some embodiments of the present application, 0.03≤A / B≤0.05. By regulating the value of A / B within the above range, the electrochemical device can have good rate performance and better cycle performance.

[0009] In some embodiments of the present application, the melting point of the tab sealant is 110° C. to 250° C. By regulating the melting point of the tab sealant within the above range, the tab sealant is advantageously maintained in a stable structure during the preparation process of the electrochemical device, and the amount of tab sealant dissolved in the electrolyte is reduced, which can reduce the impurity content in the electrolyte, facilitate ion transport in the electrolyte, and reduce side reactions in the electrolyte, thereby improving the cycle performance and rate performance of the electrochemical device.

[0010] In some embodiments of the present application, the tab sealant includes at least one of polypropylene, polyethylene, polyethylene-propylene copolymer, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate, or polyethylene naphthalate. Selecting materials within the above range can reduce the amount of tab sealant dissolved in the electrolyte, reduce the impurity content in the electrolyte, facilitate ion transport in the electrolyte, and reduce side reactions in the electrolyte, thereby improving the cycle performance and rate performance of the electrochemical device.

[0011] In some embodiments of the present application, the electrochemical device further comprises a packaging bag having a cavity, wherein the electrode assembly and electrolyte are disposed within the cavity, and the packaging bag includes a top seal for sealing the cavity, wherein the tabs are connected to the electrode assembly and extend from the top seal; the top seal has a sealing width of 1.0 mm to 1.7 mm along the direction in which the tabs extend. By regulating the sealing width of the top seal within the above range, the risk of leakage caused by the dissolution of the linear ester can be reduced, thereby improving the safety performance of the electrochemical device; the impurity content in the electrolyte can also be reduced, further improving the cycling performance and rate performance of the electrochemical device.

[0012] In some embodiments of the present application, the electrochemical device satisfies at least one of the following characteristics: (1) 45 ≤ B ≤ 75; (2) the melting point of the tab sealant is 140° C. to 200° C. The electrochemical device having the above characteristics has good cycle performance and rate performance.

[0013] In some embodiments of the present application, the linear ester includes at least one of a non-fluorinated linear carbonate, a non-fluorinated linear carboxylate, a fluorinated linear carbonate, or a fluorinated linear carboxylate; the non-fluorinated linear carbonate includes at least one of dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate; the non-fluorinated linear carboxylate includes at least one of propyl propionate, ethyl propionate, ethyl acetate, or methyl propionate; the fluorinated linear carbonate includes at least one of bis(2,2,2-trifluoroethyl) carbonate, 2,2-difluoroethyl methyl carbonate, or 1,1,1-trifluoroethyl methyl ethyl carbonate; and the fluorinated linear carboxylate includes at least one of 2,2-difluoroethyl propionate or 2,2-difluoroethyl acetate. The electrolyte includes linear esters within the above range, which is beneficial to improving the ion transport capacity of the electrolyte, thereby further improving the cycle performance and rate performance of the electrochemical device.

[0014] In some embodiments of the present application, the electrolyte further comprises a compound represented by formula (I):

[0015] Among them, R 12 、R 13 、R 14 、R 15 Each independently selected from H, F, Cl to C 10 Fluorinated alkyl, C1 to C 10 Fluoroalkoxy or C1 to C 10 fluoroalkoxyalkyl, and R 12 、R 13 、R 14 、R 15 are not hydrogen atoms at the same time; and the mass percentage C% of the compound represented by formula (I) is 1% to 15% based on the mass of the electrolyte. The electrolyte comprising the compound represented by formula (I) and regulating its content within the above range can adjust the solvation structure in the electrolyte, reduce the binding force between the solvent (e.g., linear ester and the compound represented by formula (I)) in the electrolyte and ions, further enhance the ion transport capacity of the electrolyte, and thus improve the cycling performance and rate performance of the electrochemical device.

[0016] In some embodiments of the present application, the mass percentage C% of the compound represented by formula (I) is 2.5% to 8% based on the mass of the electrolyte. Controlling the content of the compound represented by formula (I) within the above range is more conducive to reducing the binding force between the solvent and ions, improving the ion transport capacity of the electrolyte, and thus improving the cycle performance and rate performance of the electrochemical device.

[0017] In some embodiments of the present application, the compound represented by formula (I) includes at least one of the following compounds:

[0018] The electrolyte comprising the compound represented by formula (I) within the above range is more conducive to reducing the binding force between the solvent and ions, improving the ion transport capacity of the electrolyte, and thus improving the cycle performance and rate performance of the electrochemical device.

[0019] In some embodiments of the present application, the tab includes a positive tab and a negative tab; the electrode assembly includes a positive electrode sheet and a negative electrode sheet, the positive electrode sheet includes a positive current collector, a positive electrode active material layer and a positive electrode tab, the positive electrode active material layer is provided on at least one surface of the positive electrode collector, the positive electrode active material layer is provided with a first groove exposing the positive electrode collector, the positive electrode tab is provided in the first groove and is connected to the positive electrode collector, and the surface of the positive electrode tab and the area corresponding to the first groove on the surface of the positive electrode sheet away from the positive electrode tab are each provided with insulating tape; The electrode sheet includes a negative electrode current collector, a negative electrode active material layer and a negative electrode tab. The negative electrode active material layer is arranged on at least one surface of the negative electrode current collector. The negative electrode active material layer is provided with a second groove exposing the negative electrode current collector. The negative electrode tab is arranged in the second groove and connected to the negative electrode current collector. The area on the surface of the negative electrode sheet away from the negative electrode tab corresponding to the second groove is set as the tab protection area, and the area on the surface of the positive electrode sheet opposite to the second groove and the tab protection area is respectively provided with insulating tape; the melting point range of the insulating tape is 250°C to 600°C. By arranging insulating tape in each of the above-mentioned areas and selecting insulating tape with a melting point within the above-mentioned range, since the insulating tape has good high-temperature stability and low thermal shrinkage, when a large amount of heat is generated in the electrochemical device, the insulating tape can maintain its intact state when pasted, has a good protective effect on the electrode ear, reduces the risk of internal short circuit at high temperature of the electrochemical device, and thus improves the safety performance of the electrochemical device; it can also reduce the amount of insulating tape dissolved in the electrolyte, reduce the impurity content in the electrolyte, facilitate the transmission of ions in the electrolyte and reduce side reactions in the electrolyte, thereby further improving the cycle performance and rate performance of the electrochemical device.

[0020] In some embodiments of the present application, the insulating adhesive tape includes a substrate layer and an adhesive layer disposed on a surface of the substrate layer; the substrate layer includes at least one of polyethylene terephthalate or polyimide; and the adhesive layer includes at least one of polypropylene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, or polyethylene terephthalate. Insulating adhesive tape with the substrate layer and adhesive layer materials within the above-mentioned ranges has good high-temperature stability and low thermal shrinkage, can better exert its protective effect on the tabs, is more conducive to reducing the impurity content in the electrolyte, improving the ion transport capacity in the electrolyte, and reducing side reactions in the electrolyte, thereby further improving the safety performance, cycle performance, and rate performance of the electrochemical device.

[0021] The second aspect of the present application provides an electronic device, wherein the electronic device includes the electrochemical device provided in the first aspect of the present application. The electrochemical device provided in the present application has good cycle performance and rate performance, so that the electronic device of the present application has a long service life.

[0022] Beneficial effects of this application:

[0023] The present application provides an electrochemical device and an electronic device. The electrochemical device includes an electrode assembly and an electrolyte. The electrode assembly includes a tab, on which a tab sealant is disposed. The tab sealant extends perpendicular to the tab by a maximum width of A mm, with 1.8 ≤ A ≤ 2.6 mm. The electrolyte includes a linear ester, the mass percentage of the linear ester being B% based on the mass of the electrolyte, and A / B satisfying 0.0215 ≤ A / B ≤ 0.058. Including a linear ester in the electrolyte and regulating the values ​​of A and A / B within the above ranges can alleviate the problem of high solubility of the tab sealant due to a high linear ester content, reduce the impurity content in the electrolyte, facilitate ion transport in the electrolyte, and reduce side reactions in the electrolyte, thereby improving the cycling performance and rate capability of the electrochemical device.

[0024] 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

[0025] 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.

[0026] FIG1 is a schematic structural diagram of an electrochemical device according to an embodiment of the present application;

[0027] FIG2 is a schematic diagram of the pasting position of the insulating tape and the positive electrode tab in one embodiment of the present application;

[0028] FIG3 is a schematic diagram of the pasting position of the insulating tape and the negative electrode tab in one embodiment of the present application.

[0029] Reference numerals: electrochemical device 100, electrode assembly 10, tab 20, tab sealant 30, packaging bag 40, top seal 41, positive tab 21, negative tab 22, positive electrode sheet 11, positive electrode current collector 111, first positive electrode active material layer 112a, second positive electrode active material layer 112b, first surface 111a, second surface 111b, surface 11a of the positive electrode sheet opposite to the second groove, surface 11b of the positive electrode sheet opposite to the tab protection area, negative electrode sheet 12, negative electrode current collector 121, first negative electrode active material layer 122a , second negative electrode active material layer 122b, third surface 121a, fourth surface 121b, surface 12a of the negative electrode sheet opposite to the first groove, surface 12b of the negative electrode sheet opposite to the area corresponding to the first groove on the surface of the positive electrode sheet away from the positive electrode ear, first insulating tape 51, second insulating tape 52, third insulating tape 53, fourth insulating tape 54, first protective tape 61, second protective tape 62, third protective tape 63, fourth protective tape 64, first groove 71, second groove 72, third groove 73, fourth groove 74. DETAILED DESCRIPTION

[0030] 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.

[0031] 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.

[0032] Linear esters have low viscosity, good ion transport properties, and a low melting point. Using linear esters in electrolytes for electrochemical devices can improve their kinetic and low-temperature performance. However, linear esters have a certain solubility in the components of tab sealants. High levels of linear esters increase solubility in tab sealants, increasing the impurity content in the electrolyte and thus affecting the cycling performance of the electrochemical device.

[0033] In view of this, a first aspect of the present application provides an electrochemical device, comprising an electrode assembly, a tab, and an electrolyte. A tab sealant is provided on the tab, wherein the tab sealant extends perpendicular to the tab by a maximum width A mm, with 1.8 ≤ A ≤ 2.6. The electrolyte comprises a linear ester, wherein the weight percentage of the linear ester is B% based on the weight of the electrolyte, and A / B satisfies 0.0215 ≤ A / B ≤ 0.058, preferably 0.03 ≤ A / B ≤ 0.05. For example, the value of A can be 1.8, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, or a range consisting of any two thereof, and the value of A / B can be 0.0215, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.058, or a range consisting of any two thereof. When the value of A is too large, the impurity content in the electrolyte is too high, the side reactions in the electrolyte are too many and are not conducive to the transmission of ions (such as lithium ions) in the electrolyte, thereby affecting the cycle performance and rate performance of the electrochemical device. When the value of A is too small, the width of the tab sealant beyond the tab is small, and it cannot play a good sealing role. There is a risk of electrolyte leakage, which affects the safety performance of the electrochemical device. When the value of A / B is too large, the transmission ability of ions in the electrolyte will be reduced, thereby failing to improve the cycle performance and rate performance of the electrochemical device. When the value of A / B is too small, the tab sealant will not be able to play a good sealing role, the tab sealant will dissolve too much, the side reactions in the electrolyte will be too many, and the ion transmission resistance will be too large, thereby affecting the safety performance of the electrochemical device and not conducive to improving the cycle performance and rate performance of the electrochemical device. The electrolyte includes linear esters, and the values ​​of A and A / B are regulated within the above ranges. This can improve the problem of high solubility of the tab sealant due to the high linear ester content, reduce the impurity content in the electrolyte, and help reduce side reactions in the electrolyte. It also improves the transport capacity of ions (such as lithium ions) in the electrolyte, thereby improving the cycle performance and rate performance of the electrochemical device.

[0034] In Figures 1 to 3, for ease of understanding, a three-dimensional rectangular coordinate system is established with the length of the electrode assembly 10 as the X direction, the width of the electrode assembly 10 as the Y direction, and the thickness of the electrode assembly 10 as the Z direction. It is understood that the tab extends along the Y direction, the thickness of the tab is the Z direction, and the X direction is perpendicular to the plane formed by the Y and Z directions. The electrochemical device 100 includes the electrode assembly 10 and the tab 20. The tab 20 is provided with a tab sealant 30. Along the X direction, that is, perpendicular to the extension of the tab 20 within the plane formed by the X and Y directions, the tab sealant 30 extends beyond the maximum width of the tab 20 by A mm. Typically, an electrochemical device 100 includes two tabs 20, each of which is provided with a tab sealant 30. Along the X-direction, the width of the tab sealant 30 is greater than the width of the tab 20, and the width of the tab sealant 30 extends beyond both sides of the tab 20. The widths of the tab sealants 30 extending beyond both sides of the tab 20 are A1, A2, A3, and A4, respectively. These four widths may be the same or different. When they are the same, A = A1 = A2 = A3 = A4. When they are different, A is the maximum value among them. For example, if A1 < A2 < A3 < A4, then A = A4. The present application does not particularly limit the dimensions of the tabs, as long as they can achieve the objectives of this application. For example, the tab width along the X-direction may be 3 mm to 8 mm, the length along the Y-direction may be 30 mm to 45 mm, and the thickness along the Z-direction may be 0.2 μm to 0.6 μm. The present application does not particularly limit the size of the tab sealant, as long as the purpose of the present application can be achieved. For example, the width of the tab sealant along the X direction can be 6 mm to 13.2 mm, the length along the Y direction can be 7 mm to 13 mm, and the thickness along the Z direction can be 75 μm to 85 μm.

[0035] In some embodiments of the present application, the melting point of the tab sealant is 110°C to 250°C, preferably 140°C to 200°C. For example, the melting point of the tab sealant can be 110°C, 120°C, 130°C, 140°C, 145°C, 150°C, 160°C, 180°C, 200°C, 220°C, 250°C, or a range consisting of any two values ​​therein. By regulating the melting point of the tab sealant within the above range, it is beneficial to maintain a stable structure of the tab sealant during the preparation process of the electrochemical device, reduce the amount of the tab sealant dissolved in the electrolyte, reduce the impurity content in the electrolyte, facilitate ion transport in the electrolyte, and reduce side reactions in the electrolyte, thereby improving the cycle performance and rate performance of the electrochemical device.

[0036] In some embodiments of the present application, the tab sealant includes at least one of polypropylene, polyethylene, polyethylene-propylene copolymer, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate, or polyethylene naphthalate. Selecting materials within the above range can reduce the amount of tab sealant dissolved in the electrolyte, reduce the impurity content in the electrolyte, facilitate ion transport in the electrolyte, and reduce side reactions in the electrolyte, thereby improving the cycle performance and rate performance of the electrochemical device.

[0037] In the present application, the melting point of the tab sealant can be controlled by changing the material type of the tab sealant. Selecting different materials within the above range can make the melting point of the tab sealant within the range of the present application. For example, when the tab sealant includes polyethylene, its melting point is 110°C; when the tab sealant includes polystyrene, its melting point is 120°C; when the tab sealant includes polypropylene, its melting point is 150°C; when the tab sealant includes polyvinyl chloride, its melting point is 180°C; when the tab sealant includes acrylonitrile-butadiene-styrene copolymer, its melting point is 200°C; when the tab sealant includes polyethylene terephthalate, its melting point is 250°C.

[0038] In some embodiments of the present application, as shown in FIG1 , the electrochemical device 100 further includes a packaging bag 40, the packaging bag 40 having a cavity (not shown in FIG1 ), the electrode assembly 10 and the electrolyte (not shown in FIG1 ) being disposed in the cavity, the packaging bag 40 including a top seal 41 for sealing the cavity, the electrode tab 20 being connected to the electrode assembly 10 and extending from the top seal 41; the top seal 41 having a sealing width D along the direction in which the electrode tab 20 extends (the Y direction), where D is 1.0 mm to 1.7 mm, for example, the sealing width of the top seal can be 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, or a range consisting of any two of these values. Since linear esters in the electrolyte are soluble in packaging bags (e.g., aluminum-plastic film packaging bags), a narrow top seal width increases the risk of leakage during storage of the electrochemical device, while a wide top seal width increases the impurity content in the electrolyte. By regulating the sealing width of the top seal within the above range, the risk of leakage caused by the dissolution of linear esters can be reduced, thereby improving the safety performance of the electrochemical device; the impurity content in the electrolyte can also be reduced, and the cycle performance and rate performance of the electrochemical device can be further improved.

[0039] Typically, the top seal width is controlled by adjusting the width of the stamping when sealing the packaging bag. In this application, the packaging bag is used to accommodate the electrode assembly and electrolyte, as well as other components known in the field of electrochemical devices. This application does not limit these other components. The packaging bag in this application may include, but is not limited to, aluminum-plastic film packaging bags. The packaging bag may also include side seals. This application does not specifically limit the sealing width of the side seals, as long as the purpose of this application is achieved. For example, the sealing width of the side seals can be 1 mm to 3 mm.

[0040] In some embodiments of the present application, 45≤B≤75, for example, the value of B can be 45, 48, 50, 52, 55, 58, 60, 63, 65, 70, 75, or a range consisting of any two of these values. By regulating the mass percentage B% of the linear ester within the above range, the solvation structure can be regulated and the electrolyte viscosity and bulk impedance can be reduced, thereby improving the ion transport capacity of the electrolyte. It is also beneficial to reduce the impedance of the solid electrolyte interface film on the surface of the positive electrode and the negative electrode, thereby further improving the cycle performance and rate performance of the electrochemical device.

[0041] In some embodiments of the present application, the linear ester includes at least one of a non-fluorinated linear carbonate, a non-fluorinated linear carboxylate, a fluorinated linear carbonate, or a fluorinated linear carboxylate; the non-fluorinated linear carbonate includes at least one of dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate; the non-fluorinated linear carboxylate includes at least one of propyl propionate, ethyl propionate, ethyl acetate, or methyl propionate; the fluorinated linear carbonate includes at least one of bis(2,2,2-trifluoroethyl) carbonate, 2,2-difluoroethyl methyl carbonate, or 1,1,1-trifluoroethyl methyl ethyl carbonate; and the fluorinated linear carboxylate includes at least one of 2,2-difluoroethyl propionate or 2,2-difluoroethyl acetate. The electrolyte includes a linear ester within the above range, which is beneficial for reducing the viscosity and bulk impedance of the electrolyte, improving the ion transport capacity of the electrolyte, and further improving the cycle performance and rate performance of the electrochemical device.

[0042] In some embodiments of the present application, the electrolyte further comprises a compound represented by formula (I):

[0043] Among them, R 12 、R 13 、R 14 、R 15 Each independently selected from H, F, Cl to C 10 Fluorinated alkyl, C1 to C 10 Fluoroalkoxy or C1 to C 10 fluoroalkoxyalkyl, and R 12 、R 13、R 14 、R 15 are not hydrogen atoms at the same time; based on the mass of the electrolyte, the mass percentage C% of the compound represented by formula (I) is 1% to 15%, preferably 2.5% to 8%, for example, the value of C can be 1, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range consisting of any two values ​​therein. The electrolyte includes the compound represented by formula (I) and regulates its content within the above range, which can adjust the solvation structure in the electrolyte, reduce the binding force between the solvent (e.g., linear ester and the compound represented by formula (I)) in the electrolyte and ions, further improve the ion transport capacity of the electrolyte, and thus improve the cycle performance and rate performance of the electrochemical device.

[0044] In some embodiments of the present application, the compound represented by formula (I) includes at least one of the following compounds:

[0045] The electrolyte comprising the compound represented by formula (I) within the above range is more conducive to reducing the binding force between the solvent and ions, improving the ion transport capacity of the electrolyte, and thus improving the cycle performance and rate performance of the electrochemical device.

[0046] In some embodiments of the present application, the tab includes a positive tab and a negative tab; the electrode assembly includes a positive electrode sheet and a negative electrode sheet, 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, the positive electrode active material layer is provided with a first groove exposing the positive electrode current collector, the positive electrode tab is provided in the first groove and connected to the positive electrode current collector, and the surface of the positive electrode tab and the area corresponding to the first groove in the surface of the positive electrode sheet away from the positive electrode tab are each provided with insulating tape; the negative electrode sheet includes a negative electrode current collector and a negative positive electrode active material provided on at least one surface of the negative electrode current collector A layer, a second groove exposing the negative electrode current collector is provided in the negative electrode active material layer, the negative electrode tab is provided in the second groove and is connected to the negative electrode current collector, the area corresponding to the second groove on the surface of the negative electrode plate away from the negative electrode tab is set as the tab protection area, and the area on the surface of the positive electrode plate opposite to the second groove and the tab protection area is respectively provided with insulating tape; the melting point range of the insulating tape is 250°C to 600°C, for example, the melting point of the insulating tape can be 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C or a range consisting of any two values ​​therein. By arranging insulating tape in each of the above-mentioned areas and selecting insulating tape with a melting point within the above-mentioned range, since the insulating tape has good high-temperature stability and low thermal shrinkage, when a large amount of heat is generated in the electrochemical device, the insulating tape can maintain its intact state when pasted, has a good protective effect on the electrode ear, reduces the risk of internal short circuit at high temperature of the electrochemical device, and thus improves the safety performance of the electrochemical device; it can also reduce the amount of insulating tape dissolved in the electrolyte, reduce the impurity content in the electrolyte, facilitate the transmission of ions in the electrolyte, reduce side reactions in the electrolyte, and further improve the cycle performance and rate performance of the electrochemical device.

[0047] As shown in Figures 2 and 3, it can be understood that the length direction of the electrode assembly corresponds to the length direction of the positive electrode sheet, the width direction of the electrode assembly corresponds to the width direction of the positive electrode sheet, and the thickness direction of the electrode assembly corresponds to the thickness direction of the positive electrode sheet. That is, the length direction of the positive electrode sheet is the X direction, the width direction of the positive electrode sheet is the Y direction, and the thickness direction of the positive electrode sheet is the Z direction. It can be understood that the length, width, and thickness directions of the positive electrode current collector 111, the first positive electrode active material layer 112a, the second positive electrode active material layer 112b, the negative electrode sheet 12, the negative electrode current collector 121, the first negative electrode active material layer 122a, and the second negative electrode active material layer 122b are the same as those of the positive electrode sheet. The above-mentioned "positive electrode active material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode active material layer is disposed on one or both surfaces of the positive electrode current collector, where the above-mentioned "surface" can be a partial surface of the positive electrode collector or the entire surface of the positive electrode collector. For example, in some embodiments, as shown in FIG2 , the positive electrode current collector 111 includes a first surface 111a and a second surface 111b, and the positive electrode active material layer is disposed on both surfaces of the positive electrode current collector 111, namely, a first positive electrode active material layer 112a on the first surface 111a and a second positive electrode active material layer 112b on the second surface 111b. In other embodiments, the positive electrode active material layer is disposed on one surface of the positive electrode current collector, which may be the first surface or the second surface. The above-mentioned “negative electrode active material layer disposed on at least one surface of the negative electrode current collector” means that the negative electrode active material layer is disposed on one surface or both surfaces of the negative electrode current collector, wherein the above-mentioned “surface” may be a partial surface of the negative electrode current collector or the entire surface of the negative electrode current collector. For example, in some embodiments, as shown in FIG3 , the negative electrode current collector 121 includes a third surface 121a and a fourth surface 121b, and the negative electrode active material layer is disposed on both surfaces of the negative electrode current collector 121, namely, a first negative electrode active material layer 122a on the third surface 121a and a second negative electrode active material layer 122b on the fourth surface 121b. In other embodiments, the negative electrode active material layer is disposed on one surface of the negative electrode current collector, which may be the third surface or the fourth surface.

[0048] It should be noted that the term "relative" is based on the relative positional relationship between the surface of the positive electrode sheet and the second groove. The "area of ​​the positive electrode sheet surface opposite the second groove" refers to the area of ​​the positive electrode sheet surface adjacent to the second groove and corresponding to the position of the second groove. It should be noted that the positive electrode sheet in the "area of ​​the positive electrode sheet surface opposite the second groove" and the positive electrode sheet in the "area of ​​the positive electrode sheet surface opposite the tab protection area" are not the same layer of positive electrode sheets, but are two layers of positive electrode sheets adjacent to the negative electrode sheets.

[0049] As shown in Figure 2, the positive electrode plate 11 includes a positive electrode collector 111, and the positive electrode collector 111 includes a first surface 111a and a second surface 111b. The positive electrode plate 11 also includes a first positive electrode active material layer 112a arranged on the first surface 111a and a second positive electrode active material layer 112b arranged on the second surface 111b. The first positive electrode active material layer 112a is provided with a first groove 71 exposing the first surface 111a of the positive electrode collector 111. The positive electrode tab 21 is arranged in the first groove 71 and connected to the first surface 111a of the positive electrode collector 111. The surface of the positive electrode tab 21 and the area corresponding to the first groove 71 on the surface of the positive electrode plate 11 away from the positive electrode tab 21 are each provided with insulating tape. The above-mentioned “the surface of the positive electrode tab 21, and the area corresponding to the first groove 71 in the surface of the positive electrode sheet 11 away from the positive electrode tab 21 are respectively provided with insulating tape” means: a first insulating tape 51 is provided on the surface of the positive electrode tab 21, and a second insulating tape 52 is provided in the area corresponding to the first groove 71 in the surface of the positive electrode sheet 11 away from the positive electrode tab 21. It can be understood that the above-mentioned “first insulating tape 51 provided on the surface of the positive electrode tab 21” means: the first insulating tape 51 can be partially provided on the surface of the first positive active material layer 112a, and partially provided on the surface of the positive electrode tab 21, so that the first insulating tape 51 can cover the positive electrode tab 21 when it is provided on the surface of the positive electrode tab 21. The above “a second insulating tape 52 is provided in the area corresponding to the first groove 71 on the surface of the positive electrode sheet 11 away from the positive electrode tab 21” means: the second insulating tape 52 is provided in the area corresponding to the first groove 71 on the surface of the positive electrode sheet 11 away from the positive electrode tab 21. In some embodiments, the second positive active material layer 112b is provided with a third groove 73 that exposes the second surface 111b of the positive electrode current collector 111, and the orthographic projection of the third groove 73 on the positive electrode current collector 111 completely overlaps with the first groove 71. The second insulating tape 52 can be partially located on the surface of the second positive active material layer 112b and partially covers the third groove 73, so that along the Z' direction, the orthographic projections of the second insulating tape 52 and the first insulating tape 51 on the positive electrode current collector 111 completely overlap or partially overlap.

[0050] In some embodiments, as shown in FIG2 , a first protective tape 61 may be provided on the surface 12a of the negative electrode sheet 12 opposite the first groove 71, and a second protective tape 62 may be provided on the surface 12b of the negative electrode sheet 12 opposite the area corresponding to the first groove 71 on the surface of the positive electrode sheet 11 away from the positive electrode tab 21. The phrase "providing the first protective tape 61 on the surface 12a of the negative electrode sheet 12 opposite the first groove 71" means providing the first protective tape 61 on the surface 12a of the second negative electrode active material layer 122a opposite the first groove 71 and adjacent to the first positive electrode active material layer 112a. Along the Z direction, the orthographic projections of the first protective tape 61 and the first insulating tape 51 on the positive electrode current collector 111 completely or partially overlap. The above-mentioned “a second protective tape 62 is provided on the surface 12b of the negative electrode sheet 12 opposite to the area corresponding to the first groove 71 on the surface of the positive electrode sheet 11 away from the positive electrode tab 21” means: there is an area corresponding to the first groove 71 on the surface of the positive electrode sheet 11 away from the positive electrode tab 21, and a second protective tape 62 is provided on the surface 12b of the negative electrode sheet opposite to the area, and along the Z direction, the orthographic projections of the second protective tape 62 and the second insulating tape 52 on the positive electrode current collector 111 completely overlap or partially overlap.

[0051] As shown in FIG3 , the negative electrode sheet 12 includes a negative electrode current collector 121, and the negative electrode current collector 121 includes a third surface 121a and a fourth surface 121b. The negative electrode sheet 12 also includes a first negative electrode active material layer 122a provided on the third surface 121a and a second negative electrode active material layer 122b provided on the fourth surface 121b. The first negative electrode active material layer 122a is provided with a second groove 72 exposing the third surface 121a of the negative electrode current collector 121. The negative electrode tab 22 is provided in the second groove 72 and is connected to the third surface 121a of the negative electrode current collector 121. The surface of the negative electrode sheet 12 away from the negative electrode tab 22 is connected to the second The area corresponding to the groove 72 is set as the tab protection area, and the areas on the surface of the positive electrode sheet 11 opposite the second groove 72 and the tab protection area are each provided with insulating tape. The above-mentioned "the areas on the surface of the positive electrode sheet 11 opposite the second groove 72 and the tab protection area are each provided with insulating tape" means that: a third insulating tape 53 is provided on the surface 11a of the positive electrode sheet 11 opposite the second groove 72, and the area on the surface of the negative electrode sheet 12 away from the negative electrode tab 22 corresponding to the second groove 72 is set as the tab protection area, and a fourth insulating tape 54 is provided on the surface 11b of the positive electrode sheet 11 opposite the tab protection area. It can be understood that the above-mentioned "the third insulating tape 53 is provided on the surface 11a of the positive electrode sheet 11 opposite the second groove 72" means that the third insulating tape 53 is provided on the surface 11a of the first positive electrode active material 112a opposite the second groove 72 and adjacent to the first negative electrode active material layer 122a. Along the Z direction, the orthographic projection of the third insulating tape 53 on the negative electrode current collector 121 can completely cover the negative electrode tab 22. The above-mentioned "a fourth insulating tape 54 is provided on the surface 11b of the positive electrode sheet 11 opposite the tab protection area" means: the fourth insulating tape 54 is provided on the surface 11b of the second positive electrode active material 112b opposite the tab protection area and adjacent to the second negative electrode active material layer 122b, and along the Z direction, the fourth insulating tape 54 completely overlaps or partially overlaps with the orthographic projection of the third insulating tape 53 on the negative electrode current collector 121.

[0052] In some embodiments, as shown in FIG3 , the second negative active material layer 122b is provided with a fourth groove 74 that exposes the fourth surface 121b of the negative current collector 121. The orthographic projection of the fourth groove 74 on the negative current collector 121 completely overlaps with the second groove 72. In some embodiments, protective tape may be provided on the surface of the negative electrode tab 22 and on the surface of the negative electrode sheet 12 away from the negative electrode tab 22 in an area corresponding to the second groove 72. The above “protective tape is provided on the surface of the negative electrode tab 22 and on the surface of the negative electrode sheet 12 away from the negative electrode tab 22 in an area corresponding to the second groove 72” means that a third protective tape 63 is provided on the surface of the negative electrode tab 22, and a fourth protective tape 64 is provided on the surface of the negative electrode sheet 12 away from the negative electrode tab 22 in an area corresponding to the second groove 72. It is understood that the phrase "a third protective tape 63 is provided on the surface of the negative electrode tab 22" means that the third protective tape 63 can be partially provided on the surface of the first negative electrode active material layer 122a and partially provided on the surface of the negative electrode tab 22, so that the third protective tape 63 can cover the negative electrode tab 22 when provided on the surface of the negative electrode tab 22. The phrase "a fourth protective tape 64 is provided on the surface of the negative electrode sheet 12 away from the negative electrode tab 22 in an area corresponding to the second groove 72" means that the fourth protective tape 64 is provided on the surface of the negative electrode sheet 12 away from the negative electrode tab 22 in an area corresponding to the second groove 72. The fourth protective tape 64 can be partially provided on the surface of the second negative electrode active material layer 122b and partially provided on the fourth groove 74 opposite the second groove 72, so that along the Z direction, the orthographic projections of the fourth protective tape 64 and the third protective tape 63 on the negative electrode current collector 121 completely overlap or partially overlap.

[0053] The insulating tape of the present application includes first insulating tape 51, second insulating tape 52, third insulating tape 53, and fourth insulating tape 54, as shown in Figures 2 and 3. The protective tape of the present application includes first protective tape 61, second protective tape 62, third protective tape 63, and fourth protective tape 64, as shown in Figures 2 and 3. The materials of the protective tape and the insulating tape can be the same or different, and this application does not particularly limit this, as long as the purpose of this application can be achieved.

[0054] In some embodiments of the present application, the insulating adhesive tape includes a substrate layer and an adhesive layer disposed on a surface of the substrate layer; the substrate layer includes at least one of polyethylene terephthalate or polyimide; and the adhesive layer includes at least one of polypropylene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, or polyethylene terephthalate. Insulating adhesive tape with the substrate layer and adhesive layer materials within the above-mentioned ranges has good high-temperature stability and low thermal shrinkage, can better exert its protective effect on the tabs, is more conducive to reducing the impurity content in the electrolyte, is conducive to reducing side reactions in the electrolyte, and improves the ion transport capacity in the electrolyte, thereby further improving the safety performance, cycle performance, and rate performance of the electrochemical device.

[0055] In the present application, the melting point of the insulating tape can be controlled by changing the material type of the substrate layer. By selecting different substrate layer materials within the above range, the melting point of the insulating tape can be adjusted within the range of the present application. For example, when the substrate layer includes polyethylene terephthalate, its melting point is 250°C; when the substrate layer includes polyimide, its melting point is 500°C. The present application does not particularly limit the size of the insulating tape, as long as the purpose of the present application can be achieved. For example, the size of the insulating tape along the X direction can be 9mm to 20mm, the size along the Y direction can be 20mm to 35mm, and the size along the Z direction can be 55μm to 100μm.

[0056] The electrolyte of the present application also includes a lithium salt. The lithium salt may include, but is not limited to, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluoroborate, lithium nitrate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, tris(trifluoromethylsulfonyl)methyllithium, lithium difluorooxalatophosphate or lithium tetrafluorooxalatophosphate. The present application has no particular restrictions on the percentage by mass of the lithium salt, as long as the purpose of the present application can be achieved. Exemplarily, based on the mass of the electrolyte, the mass percentage of the above-mentioned lithium salt is 8% to 15%, for example, the mass percentage of the lithium salt can be 8%, 9%, 10%, 12%, 13%, 14%, 15% or a range consisting of any two of the values.

[0057] The electrolyte of the present application can also be a non-fluorinated cyclic ester. The non-fluorinated cyclic ester can include but is not limited to at least one of ethylene carbonate, vinylene carbonate, propylene carbonate, hexyl carbonate or octyl carbonate. The present application has no particular restriction on the mass percentage of the non-fluorinated cyclic ester, as long as the purpose of the present application can be achieved. Exemplarily, based on the mass of the electrolyte, the mass percentage of the above-mentioned non-fluorinated cyclic ester is 0% to 45%, for example, the mass percentage of the non-fluorinated cyclic ester can be 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or a range consisting of any two of these values.

[0058] In some embodiments, the electrolyte includes a linear ester, a lithium salt, and a non-fluorinated cyclic ester, wherein the weight percentages of the linear ester and the lithium salt are as described above. The weight percentage of the non-fluorinated cyclic ester is 10% to 45% based on the weight of the electrolyte. An electrochemical device including this electrolyte has a high ion transport capacity, which can improve the cycling performance and rate performance of the electrochemical device.

[0059] In some embodiments, the electrolyte includes a linear ester, a lithium salt, and a compound represented by formula (I), and optionally includes a non-fluorinated cyclic ester. The weight percentages of the linear ester, the lithium salt, and the compound represented by formula (I) are as described above. The weight percentage of the non-fluorinated cyclic ester is 0% to 45% based on the weight of the electrolyte. The electrochemical device includes the above electrolyte, which can adjust the solvation structure in the electrolyte, reduce the binding force between the solvent and ions in the electrolyte, and further improve the ion transport capacity of the electrolyte, thereby further improving the cycle performance and rate performance of the electrochemical device.

[0060] The present application does not particularly limit the positive and negative electrode tabs, as long as the objectives of the present application can be achieved. For example, the positive electrode tabs may include aluminum tabs or aluminum alloy tabs, and the negative electrode tabs may include nickel tabs or copper-plated nickel tabs.

[0061] The present application has no particular 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. The present application has no particular 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 particular 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 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 de-embed 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 materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. In the present application, the surface of the positive electrode active material may be attached with a substance having a different composition from that 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 substances 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, and the service life of the electrochemical device can be increased.

[0062] The positive electrode active material layer may further include a positive electrode conductive agent and a binder. The types of the positive electrode conductive agent and the binder are not particularly limited in this application, as long as the object of this application can be achieved. For example, the 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, polyvinylpyrrolidone, 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. Exemplarily, the carbon-based material may include at least one of natural graphite, artificial graphite, conductive carbon black (Super P) or carbon fiber, and the metal-based material may include, but is not limited to, at least one of metal powder, metal fiber, copper, nickel, aluminum or silver; the conductive polymer may include, but is not limited to, polyphenylene derivatives. The mass ratios of the positive electrode active material, the positive electrode conductive agent and the binder in the positive electrode active material layer are not particularly limited in this application and can be selected according to actual needs as long as the object of this application can be achieved.

[0063] The thickness of the negative electrode sheet is not particularly limited in this application as long as the object of this application can be achieved. For example, the thickness of the negative electrode sheet is 50 μm to 250 μm. The negative electrode current collector is not particularly limited in this application as long as the object of this 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 a composite current collector (such as a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.). In this application, the thicknesses of the negative electrode current collector and the negative electrode active material layer are not particularly limited as long as the object of this application can be achieved. For example, the thickness of the negative electrode current collector is 6 μm to 12 μm, and the thickness of the negative electrode active material layer is 30 μm to 120 μm. The negative electrode active material layer of this application includes a negative electrode active material. The negative electrode active material layer may be one layer or multiple layers, and each layer in the multiple negative electrode active material layers may contain the same or different negative electrode active materials. The negative electrode active material is any substance that can reversibly intercalate and deintercalate active ions such as lithium ions. The negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0.5 < x < 1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium titanate with a spinel structure, lithiated TiO2-Li4Ti5O 12 , Li-Al alloy and metallic lithium.

[0064] The negative electrode active material layer in the present application may also include a binder, a negative electrode conductor or a thickener. The present application has no special restrictions on the types of binders and negative electrode conductors, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of the optional substances for the above-mentioned positive electrode active material layer. The present application has no special restrictions on the types of thickeners, as long as the purpose of the present application can be achieved. For example, the thickener may include but is not limited to carboxymethyl cellulose and sodium carboxymethyl cellulose. The negative electrode sheet may also include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. There is no special restriction on the composition of the conductive layer, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application has no special restrictions on the types of binders and conductive agents in the conductive layer, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of the optional substances for the above-mentioned positive electrode active material layer.

[0065] The electrode assembly of the present application also includes a separator to separate the positive electrode plate and the negative electrode plate, prevent internal short circuits in the electrochemical device, allow electrolyte ions to pass freely, and do not affect the electrochemical charge and discharge process. The present application has no particular restrictions on the separator, as long as it can achieve the purpose of the present application. For example, the material of the separator 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 separator may include at least one of woven membranes, non-woven membranes, microporous membranes, composite membranes, rolled membranes or spun membranes. For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric, membrane or composite membrane with a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer can 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, and the application is not particularly limited to the inorganic particles, for example, it can 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 application is not particularly limited to the binder, for example, it can be at least one of the above-mentioned binders. Polymers are included in the polymer layer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene). In the present application, there is no particular limitation on the thickness of the isolation film, as long as the purpose of the present application can be achieved. For example, the thickness of the isolation film can be 5 μm to 500 μm.

[0066] The electrochemical device of the present application is not particularly limited and may include any device that undergoes an electrochemical reaction. In some embodiments, the electrochemical device may include but is not limited to a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0067] The preparation process of the electrochemical device of the present application is well known to those skilled in the art and is not particularly limited in the present application. For example, it may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, welding the tabs, attaching the tab sealant and insulating tape, and then winding, folding and other operations as needed to obtain a wound electrode assembly, placing the electrode assembly in a packaging bag, injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device; or stacking the positive electrode sheet, the separator and the negative electrode sheet in order, welding the tabs, attaching the tab sealant and insulating tape, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly, placing the electrode assembly in a packaging bag, injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device. In addition, an overcurrent protection element, a guide plate, etc. may also be placed in the packaging bag as needed to prevent pressure rise and overcharge and discharge inside the electrochemical device.

[0068] The second aspect of the present application provides an electronic device, wherein the electronic device includes the electrochemical device provided in the first aspect of the present application. The electrochemical device provided in the present application has good cycle performance and rate performance, so that the electronic device of the present application has a long service life.

[0069] The electronic device of the present application is not particularly limited and can be any electronic device known in the art. In some embodiments, the electronic device may 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.

[0070] Example

[0071] 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.

[0072] Test methods and equipment:

[0073] Cyclic performance test:

[0074] The cycling performance of lithium-ion batteries is evaluated by the capacity retention rate after 400 cycles at 45°C. A greater capacity retention rate after 400 cycles at 45°C indicates better cycling performance of the lithium-ion battery.

[0075] Place the lithium-ion battery in a 45°C constant temperature box and let it stand for 30 minutes to allow the lithium-ion battery to reach a constant temperature. Charge the lithium-ion battery that has reached a constant temperature at 45°C at a constant current of 0.2C to 4.5V, charge it at a constant voltage of 4.5V to 0.05C, let it stand for 5 minutes, then discharge it at a constant current of 0.2C to 3.0V, let it stand for 5 minutes, and test the initial discharge capacity C0 of the lithium-ion battery; then charge it at a constant current of 1.3C to 4.15V, charge it at a constant voltage of 4.15V to a current of 1C; then charge it at a constant current of 1C to 4.25V, then charge it at a constant voltage of 4.25V to a current of 0.8C; then charge it at a constant current of 0.8C to 4.5V, then charge it at a constant voltage of 4.5V to a current of 0.05C; let it stand for 5 minutes; then discharge it at a constant current of 1C to 3.0V, let it stand for 5 minutes. This is one charge and discharge cycle. The charge / discharge cycle was performed for 400 cycles according to the above steps, and the discharge capacity C' of the lithium-ion battery after 400 cycles was measured.

[0076] Capacity retention after 400 cycles at 45°C = C' / C0 x 100%.

[0077] Rate discharge capacity ratio test:

[0078] The lithium-ion battery was placed in a 25°C constant temperature box for 1 hour to allow the lithium-ion battery to reach a constant temperature; it was charged to 4.2V at a constant current of 0.5C, then charged to 4.5V at a constant current of 0.3C, and charged at a constant voltage of 4.5V until the current was 0.02C, and then allowed to stand for 30 minutes; it was then discharged to 3.0V at a constant current of 0.2C, and allowed to stand for 30 minutes. The capacity at this step (D0) was used as the benchmark. At 25°C, it was charged to 4.2V at a constant current of 0.5C, then charged to 4.5V at a constant current of 0.3C, and charged at a constant voltage of 4.5V until the current was 0.02C, and allowed to stand for 30 minutes; it was discharged to 3.0V at a constant current of 3.0V at a constant current of 0.5C, and allowed to stand for 30 minutes. The capacity at different rates was recorded as D x (x is 0.5, 1 or 2). Discharge capacity ratio at different rates = D x / D0×100%.

[0079] Test of the content of each component in the electrolyte:

[0080] The lithium-ion battery was discharged at a constant current of 1C to 3.0V and then disassembled to collect the electrolyte. The positive electrode sheet, negative electrode sheet, and separator were centrifuged, and the liquid obtained after centrifugation was mixed with the above electrolyte. Then, the components in the electrolyte were obtained and their contents were tested using a gas chromatography-mass spectrometer (model Agilent 8890) and an ion chromatography (model AQUION ion chromatograph).

[0081] Example 1-1

[0082] <Tab sealant>

[0083] The tab sealant is a single layer of glue, including polypropylene, and the melting point of the tab sealant is 150°C.

[0084] <Preparation of positive electrode sheet>

[0085] The positive electrode active material, lithium cobalt oxide (LiCoO2), the positive electrode conductive agent, conductive carbon black (Super P), and the binder, polyvinylidene fluoride (PVDF), were mixed in a mass ratio of 97.5:1:1.5. NMP was added as a solvent and stirred evenly in a vacuum mixer to obtain a positive electrode slurry with a solid content of 75 wt%. The positive electrode slurry was evenly coated on one surface of a 10 μm thick positive electrode current collector aluminum foil and dried at 85°C to obtain a positive electrode sheet coated with a 50 μm thick positive electrode active material layer on one side. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. The sheet was then cold pressed, cut, and welded to the positive electrode tabs, resulting in a 74 mm × 851 mm positive electrode sheet ready for use. Among them, the above-mentioned tab sealant is pasted on the positive electrode tab, and the size of the positive electrode tab is 5mm×40mm×0.4mm (X direction×Y direction×Z direction), and the size of the tab sealant pasted on the positive electrode tab is 9.4mm×10mm×80μm (X direction×Y direction×Z direction). As shown in Figure 1, the width of the tab sealant exceeding the two sides of the positive electrode tab is A1mm and A2mm respectively, A1=2.2, A2=2.2.

[0086] <Preparation of negative electrode sheet>

[0087] The negative electrode active material graphite, the negative electrode conductive agent Super P, the thickener carboxymethyl cellulose, and the binder styrene-butadiene rubber (SBR) were mixed in a mass ratio of 97.5:1:0.5:1. Deionized water was then added as a solvent and the mixture was stirred evenly in a vacuum mixer to produce 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 produce a negative electrode sheet coated on one side with a 60 μm thick layer of negative electrode active material. The above steps were then repeated on the other surface of the copper foil to produce a negative electrode sheet coated on both sides with a negative electrode active material layer. The sheet was then cold pressed, cut, and welded to the nickel tabs, resulting in a negative electrode sheet measuring 76 mm x 867 mm for later use. Among them, the above-mentioned tab sealant is pasted on the negative electrode tab. The size of the negative electrode tab is 5mm×40mm×0.4mm (X direction×Y direction×Z direction), and the size of the tab sealant is 9.4mm×10mm×80μm (X direction×Y direction×Z direction). As shown in Figure 1, the width of the tab sealant exceeding the two sides of the negative electrode tab is A3mm and A4mm respectively, A3=2.2, A4=2.2.

[0088] <Preparation of Electrolyte>

[0089] In an environment with a water content of less than 10 ppm, the solvent linear ester diethyl carbonate (DEC), propyl acetate (EP), propyl propionate (PP) and non-fluorinated cyclic ester propylene carbonate (PC), ethylene carbonate (EC) are mixed, and then lithium salt LiPF6 is added to the solvent to dissolve and mix evenly to obtain an electrolyte. Based on the mass of the electrolyte, the mass percentage of DEC is N DEC =20%, mass percentage of EP N EP =20%, PP mass percentage N PP =20%, PC mass percentage N PC =20%, EC mass percentage N EC =10%, the mass percentage of LiPF6 is 10%; among them, the mass ratio of DEC:EP:PP is 1:1:1, the mass ratio of PC:EC is 2:1, the mass percentage B% of linear ester is 60%, and the mass percentage of non-fluorinated cyclic ester is 30%.

[0090] <Isolation Film>

[0091] A polyethylene film with a thickness of 15 μm (manufacturer: Hunan Zhongli New Materials Co., Ltd.) was used.

[0092] <Preparation of lithium-ion batteries>

[0093] The negative electrode sheet, separator, and positive electrode sheet prepared above are stacked and wound in sequence to form a wound electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dried, injected with electrolyte, and subjected to vacuum packaging, static standing, formation, capacity measurement, degassing, and trimming to obtain a lithium-ion battery.

[0094] As shown in FIG1 , along the X direction, the width of the tab sealant exceeds the maximum width of the tab A by 2.2 mm, and the sealing width D of the top seal is 1.4 mm.

[0095] In the locations where the insulating tape is applied as shown in Figures 2 and 3, tapes with a base layer of polyethylene terephthalate and an adhesive layer of polypropylene, with a melting point of 250°C, are used as the insulating tape and protective tape, respectively. These tapes are applied to the locations indicated by the first insulating tape 51, second insulating tape 52, first protective tape 61, and second protective tape 62 in Figure 2, and the third insulating tape 53, fourth insulating tape 54, third protective tape 63, and fourth protective tape 64 in Figure 3. The dimensions of the insulating tape and protective tape are each 10 mm × 30 mm × 75 μm (X × Y × Z), with a base layer thickness of 40 μm and an adhesive layer thickness of 35 μm.

[0096] Example 1-2 to Example 1-3

[0097] Except for changing the width of the tab sealant along the X direction and keeping the width of the tab along the X direction unchanged so that the value of A is as shown in Table 1, the rest is the same as Example 1-1.

[0098] Example 1-4 to Example 1-8

[0099] Except that the value of A and the mass percentage of the linear ester B% are adjusted according to Table 1, the mass percentage of the non-fluorinated cyclic ester is changed accordingly, and the mass ratio of the linear ester DEC:EP:EC, the mass ratio of the non-fluorinated cyclic ester PC:EC and the mass percentage of the lithium salt remain unchanged, the rest is the same as Example 1-1.

[0100] Example 2-1 to Example 2-5

[0101] Except for adjusting the material of the tab sealant according to Table 2 so that the melting point of the tab sealant is as shown in Table 2, the rest is the same as Example 1-1.

[0102] Example 3-1 to Example 3-4

[0103] Except for adjusting the sealing width of the top seal according to Table 3, the rest is the same as Example 1-1.

[0104] Example 4-1 to Example 4-4

[0105] Except for adjusting the type and mass percentage of the linear ester according to Table 4, the rest is the same as Example 1-1.

[0106] Example 5-1 to Example 5-11

[0107] The same as in Example 1-1 except that the compound represented by formula (I) was further introduced and the type of the compound represented by formula (I) and its mass percentage C% were adjusted according to Table 5, the mass percentage of the non-fluorinated cyclic ester was changed accordingly, the mass ratio of the non-fluorinated cyclic ester PC:EC, the mass ratio of the linear ester DEC:EP:EC, the mass percentage of the linear ester B% and the mass percentage of the lithium salt remained unchanged.

[0108] Example 6-1

[0109] Except for adjusting the material of the base material layer according to Table 6 so that the melting point of the insulating tape is as shown in Table 6, the rest is the same as Example 1-1.

[0110] Comparative Example 1-1

[0111] Except for adjusting the value of A according to Table 1, the rest is the same as Example 1-1.

[0112] Comparative Example 1-2 to Comparative Example 1-3

[0113] Except that the value of A and the mass percentage of the linear ester B% are adjusted according to Table 1, the mass percentage of the non-fluorinated cyclic ester is changed accordingly, and the mass ratio of the linear ester DEC:EP:EC, the mass ratio of the non-fluorinated cyclic ester PC:EC and the mass percentage of the lithium salt remain unchanged, the rest is the same as Example 1-1.

[0114] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 to 6.

[0115] Table 1

[0116] It can be seen from Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-3 that by regulating the values ​​of A and A / B within the scope of this application, the lithium-ion battery can have a higher capacity retention rate and a 0.5C / 1C / 2C rate discharge capacity ratio, thereby indicating that the lithium-ion battery has better cycle performance and rate performance.

[0117] The value of A usually affects the cycle performance and rate performance of the lithium-ion battery. It can be seen from Example 1-1 to Example 1-3 and Comparative Example 1-1 that when the value of A is too large, such as Comparative Example 1-1, the capacity retention rate and 0.5C / 1C / 2C rate discharge capacity ratio of the lithium-ion battery are too low. When the value of A is too small, the risk of leakage of the lithium-ion battery increases. This shows that when the value of A is too large or too small, it is impossible to take into account the cycle performance, rate performance and safety performance of the lithium-ion battery. When A satisfies 1.8≤A≤2.6, the lithium-ion battery can have a higher capacity retention rate and 0.5C / 1C / 2C rate discharge capacity ratio, which shows that regulating the value of A within the scope of this application can reduce the risk of leakage of the lithium-ion battery while making the lithium-ion battery have better cycle performance and rate performance.

[0118] The value of A / B usually affects the cycle performance and rate performance of the lithium-ion battery. It can be seen from Examples 1-1 to 1-8 and Comparative Examples 1-2 to 1-3 that when the value of A / B is too small, such as Comparative Example 1-2, although the 0.5C / 1C / 2C rate discharge capacity of the lithium-ion battery is relatively high, the capacity retention rate of the lithium-ion battery is low. When the value of A / B is too large, such as Comparative Example 1-3, the capacity retention rate and 0.5C / 1C / 2C rate discharge capacity ratio of the lithium-ion battery are both too low. This shows that when the value of A / B is too large or too small, it is impossible to take into account both the cycle performance and rate performance of the lithium-ion battery. When A / B satisfies 0.0215≤A / B≤0.058, the lithium-ion battery can have a higher capacity retention rate and 0.5C / 1C / 2C rate discharge capacity ratio, indicating that the lithium-ion battery has better cycle performance and rate performance.

[0119] The mass percentage of linear ester, B%, generally affects the cycling and rate performance of lithium-ion batteries. As can be seen from Examples 1-1 to 1-8, regulating the value of B within the range of this application can result in lithium-ion batteries with high capacity retention and 0.5C / 1C / 2C rate discharge capacity ratios, demonstrating excellent cycling and rate performance.

[0120] Table 2

[0121] The melting point and material type of the tab sealant typically affect the cycling and rate performance of lithium-ion batteries. As can be seen from Examples 1-1, 2-1, and 2-5, selecting the tab sealant material and adjusting the tab sealant's melting point within the scope of this application can result in lithium-ion batteries with high capacity retention and 0.5C / 1C / 2C rate discharge capacity ratios, demonstrating good cycling and rate performance.

[0122] Table 3

[0123] The seal width of the top seal typically affects the cycle performance and rate performance of lithium-ion batteries. As can be seen from Examples 1-1, 3-1, and 3-4, adjusting the seal width of the top seal within the scope of this application can reduce the risk of lithium-ion battery leakage while enabling the lithium-ion battery to have a higher capacity retention rate and a 0.5C / 1C / 2C rate discharge capacity ratio, indicating that the lithium-ion battery has good cycle performance and rate performance.

[0124] Table 4

[0125] The type of linear ester generally affects the cycling and rate performance of lithium-ion batteries. As can be seen from Examples 1-1, 4-1, and 4-4, selecting linear esters within the scope of this application can result in lithium-ion batteries with high capacity retention and 0.5C / 1C / 2C rate discharge capacity ratios, demonstrating good cycling and rate performance.

[0126] Table 5

[0127] Note: “ / ” in Table 5 indicates that there is no corresponding parameter or substance.

[0128] The type and mass percentage C% of the compound represented by formula (I) generally affect the cycle performance and rate performance of lithium-ion batteries. As can be seen from Examples 1-1, 5-1, and 5-11, the electrolyte includes a linear ester and further introduces the compound represented by formula (I). Selecting the compound represented by formula (I) within the scope of this application and regulating its mass percentage C% within the scope of this application can enable the lithium-ion battery to have a high capacity retention rate and a 0.5C / 1C / 2C rate discharge capacity ratio, indicating that the lithium-ion battery has good cycle performance and rate performance.

[0129] Table 6

[0130] The melting point of insulating tape typically affects the cycling and rate performance of lithium-ion batteries. As shown in Examples 1-1 and 6-1, adjusting the melting point of insulating tape within the scope of this application can result in a lithium-ion battery with a high capacity retention rate and a 0.5C / 1C / 2C rate discharge capacity ratio, demonstrating good cycling and rate performance.

[0131] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, or article.

[0132] 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.

[0133] 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, a tab and an electrolyte, wherein a tab sealant is disposed on the tab, and along a direction perpendicular to the extension of the tab, the width of the tab sealant exceeds the maximum width of the tab by A mm, 1.8≤A≤2.6; The electrolyte includes a linear ester, and based on the mass of the electrolyte, the mass percentage of the linear ester is B%, and A / B satisfies 0.0215≤A / B≤0.

058.

2. The electrochemical device according to claim 1, wherein: 0.03≤A / B≤0.

05.

3. The electrochemical device according to claim 1, wherein The melting point of the tab sealant is 110°C to 250°C.

4. The electrochemical device according to claim 1, wherein The tab sealant includes at least one of polypropylene, polyethylene, polyethylene-propylene copolymer, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate or polyethylene naphthalate.

5. The electrochemical device according to any one of claims 1 to 4, wherein: The electrochemical device further comprises a packaging bag, wherein the packaging bag has a cavity, wherein the electrode assembly and the electrolyte are arranged in the cavity, wherein the packaging bag comprises a top sealing edge, wherein the top sealing edge is used to seal the cavity, and wherein the electrode tab is connected to the electrode assembly and extends from the top sealing edge; Along the extension direction of the pole ear, the sealing width of the top sealing edge is 1.0 mm to 1.7 mm.

6. The electrochemical device according to claim 1, which satisfies at least one of the following characteristics: (1)45≤B≤75； (2) The melting point of the tab sealant is 140°C to 200°C.

7. The electrochemical device according to any one of claims 1 to 4, wherein: The linear ester comprises at least one of a non-fluorinated linear carbonate, a non-fluorinated linear carboxylate, a fluorinated linear carbonate or a fluorinated linear carboxylate; The non-fluorinated linear carbonate comprises at least one of dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate; The non-fluorinated linear carboxylic acid ester comprises at least one of propyl propionate, ethyl propionate, ethyl acetate or methyl propionate; The fluorinated linear carbonate includes at least one of di(2,2,2-trifluoroethyl) carbonate, 2,2-difluoroethyl methyl carbonate or 1,1,1-trifluoroethyl methyl ethyl carbonate; The fluorinated linear carboxylic acid ester includes at least one of 2,2-difluoroethyl propionate or 2,2-difluoroethyl acetate.

8. The electrochemical device according to any one of claims 1 to 7, wherein: The electrolyte further comprises a compound represented by formula (I), Among them, R 12 , R 13 , R 14 , R 15 Each independently selected from H, F, Cl to C 10 Fluorinated alkyl, C1 to C 10 Fluorinated Alkoxy or C1 to C 10 A fluoroalkoxyalkyl group, and R 12 , R 13 , R 14 , R 15 Not all hydrogen atoms at the same time; Based on the mass of the electrolyte, the mass percentage C% of the compound represented by formula (I) is 1% to 15%.

9. The electrochemical device according to claim 8, wherein: Based on the mass of the electrolyte, the mass percentage C% of the compound represented by formula (I) is 2.5% to 8%.

10. The electrochemical device according to claim 8, wherein The compound represented by formula (I) includes at least one of the following compounds:

11. The electrochemical device according to any one of claims 1 to 10, wherein: The electrode tabs include a positive electrode tab and a negative electrode tab; the electrode assembly includes a positive electrode sheet and a negative electrode sheet, The positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer is provided with a first groove exposing the positive electrode current collector, the positive electrode tab is disposed in the first groove and connected to the positive electrode current collector, and the surface of the positive electrode tab and the area of ​​the surface of the positive electrode plate away from the positive electrode tab corresponding to the first groove are each provided with insulating tape; The negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer is provided with a second groove exposing the negative electrode current collector, the negative electrode tab is disposed in the second groove and connected to the negative electrode current collector, the area of ​​the surface of the negative electrode plate away from the negative electrode tab corresponding to the second groove is set as a tab protection area, and the area of ​​the surface of the positive electrode plate opposite to the second groove and the tab protection area is respectively provided with the insulating tape; The melting point of the insulating tape ranges from 250°C to 600°C.

12. The electrochemical device according to claim 11, wherein The insulating adhesive tape comprises a base material layer and an adhesive layer arranged on one surface of the base material layer; The substrate layer includes at least one of polyethylene terephthalate or polyimide; the adhesive layer includes at least one of polypropylene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer or polyethylene terephthalate.

13. An electronic device, wherein: The electronic device comprises the electrochemical device according to any one of claims 1 to 12.

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