CN116845357A

CN116845357A - Electrochemical device and electronic device

Info

Publication number: CN116845357A
Application number: CN202311013424.7A
Authority: CN
Inventors: 蔡鑫; 崔辉; 刘建; 唐超
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2023-08-11
Filing date: 2023-08-11
Publication date: 2023-10-03

Abstract

The application provides an electrochemical device and an electronic device. The electrochemical device comprises an electrolyte, an electrode assembly and a tab, wherein the electrolyte comprises a compound shown in a formula (I) and a compound shown in a formula (II). Based on the mass of the electrolyte, the mass percentage of the compound shown in the formula (I) is p percent, the mass percentage of the compound shown in the formula (II) is q percent, p is more than or equal to 0.01 and less than or equal to 3, and p/q is more than or equal to 0.002 and less than or equal to 60. By regulating the values of p and p/q within the above ranges, the inorganic component content in the solid electrolyte interface film can be increased, which is beneficial to reducing the impedance of the solid electrolyte interface film, improving the ion transmission rate at low temperature, and improving the toughness of the solid electrolyte interface film and the stability thereof at high temperature, thereby improving the cycle performance of the electrochemical device at low temperature and high temperature.

Description

Electrochemical device and electronic device

Technical Field

The present application relates to the field of electrochemical technology, and in particular, to an electrochemical device and an electronic device.

Background

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, good safety and the like, and are widely used as power sources for electronic products such as cameras, mobile phones, unmanned aerial vehicles, notebook computers, smart watches and the like.

With the continuous expansion of the application range of lithium ion batteries, the market has set higher requirements for lithium ion batteries. Lithium ion batteries are required to have a wide operating temperature window, to exhibit excellent electrochemical properties not only at normal temperature but also at high or low temperatures. The electrolyte is an important component in lithium ion batteries, and the operating temperature range of the electrolyte can affect the cycle performance of an electrochemical device.

Disclosure of Invention

The present application provides an electrochemical device and an electronic device for improving the cycle performance of the electrochemical device at low and high temperatures. The specific technical scheme is as follows:

a first aspect of the present application provides an electrochemical device comprising an electrolyte, an electrode assembly, and a tab, the electrolyte comprising a compound represented by formula (I) and a compound represented by formula (II):

wherein R is ₁ Selected from O or-CH (Ra) -, ra is selected from H, F, C ₁ To C ₅ Alkyl or C of (2) ₁ To C ₅ Alkoxy groups of (a); r is R ₂ And R is ₃ Each independently selected from H, F, C ₁ To C ₅ Alkyl, C of (2) ₁ To C ₅ Alkoxy or C of (2) ₂ To C ₅ Alkenyl, C ₂ To C ₅ Alkynyl of (a); r is R ₄ Selected from H, F, C unsubstituted or substituted by F ₁ To C ₅ Alkyl, C of (2) ₁ To C ₅ Alkoxy, C ₂ To C ₅ Alkenyl or C of (2) ₂ To C ₅ Is an alkynyl group of (c).

Wherein n is 0, 1 or 2, M is selected from C or O, and X is selected fromR ₂₁ 、R ₂₂ Each independently selected from H, & gt>R ₂₁ And R is ₂₂ Not simultaneously selected from H, and X, R ₂₁ And R is ₂₂ Contains at least one sulfur atom; based on the mass of the electrolyte, the mass percentage of the compound shown in the formula (I) is p percent, the mass percentage of the compound shown in the formula (II) is q percent, p is more than or equal to 0.01 and less than or equal to 3, and p/q is more than or equal to 0.002 and less than or equal to 60. The electrolyte comprises a compound shown in a formula (I) and a compound shown in a formula (II) and regulates the values of p and p/q within the range, so that the synergistic effect of the compound shown in the formula (I) and the compound shown in the formula (II) can be exerted, the inorganic component content in a solid electrolyte interface film (SEI film) can be increased, the impedance of the SEI film can be reduced, the transmission rate of ions (such as lithium ions) at low temperature can be improved, the toughness of the SEI film can be improved to reduce the risk of cracking the SEI film, the stability of the SEI film at high temperature can be improved, the side reaction between the SEI film and the electrolyte can be reduced, and the cycle performance and the low-temperature discharge performance of an electrochemical device at low temperature can be improved.

In some embodiments of the application, 0.05.ltoreq.q.ltoreq.5. The value of q is regulated within the range, so that the synergistic effect of the compound shown in the formula (I) and the compound shown in the formula (II) is exerted, and the compound form inorganic components rich in sulfur together, so that the impedance of the SEI film is further reduced, the ion transmission rate at low temperature is improved, the side reaction between the SEI film and electrolyte can be reduced, and the cycle performance, the low-temperature discharge performance and the safety performance of the electrochemical device at low temperature and high temperature are improved.

In some embodiments of the application, 0.1.ltoreq.p.ltoreq. 1,0.003.ltoreq.p/q.ltoreq.2. By regulating the values of p and p/q within the above range, the synergistic effect of the compound shown in the formula (I) and the compound shown in the formula (II) can be better exerted, the ion transmission rate at low temperature is further improved, the toughness of the SEI film is improved to reduce the risk of SEI film rupture, the stability of the SEI film at high temperature is improved, the side reaction between the SEI film and the electrolyte is reduced, and the cycle performance, the low-temperature discharge performance and the safety performance of the electrochemical device at low temperature and high temperature are further improved.

In some embodiments of the present application, the compound of formula (I) comprises at least one of the following compounds:

the electrolyte comprises the compound shown in the formula (I) in the range, can better exert the synergistic effect of the compound shown in the formula (I) and the compound shown in the formula (II), is beneficial to reducing the impedance of the SEI film, improving the ion transmission rate at low temperature, improving the stability of the SEI film at high temperature, reducing the side reaction between the SEI film and the electrolyte, and further improving the cycle performance, the low-temperature discharge performance and the safety performance of the electrochemical device at low temperature and high temperature.

In some embodiments of the present application, the compound of formula (II) comprises at least one of the following compounds:

the electrolyte comprises the compound shown in the formula (II) in the range, and can better exert the synergistic effect of the compound shown in the formula (I) and the compound shown in the formula (II), and the compound shown in the formula (II) are combinedForming inorganic components rich in sulfur, further reducing the impedance of the SEI film and improving the ion transmission rate at low temperature; is more beneficial to increasing Li in SEI film ₂ CO ₃ And alkyl lithium content, improve toughness of SEI film in order to reduce SEI film rupture risk, and improve SEI film stability under high temperature, reduce side reaction between SEI film and electrolyte, thus improve electrochemical device cycle performance, low-temperature discharge performance and security performance under low temperature and high temperature.

In some embodiments of the application, the tab is provided with tab sealant, the width of the tab sealant exceeding the maximum width of the tab along the direction perpendicular to the extending direction of the tab is Amm, A is 1.8-2.6, and the thickness of the tab sealant is 75-85 μm. The value of A and the thickness of the tab sealant are regulated within the range, so that the risk of leakage of the electrochemical device can be reduced, the dissolution amount of the tab sealant in the electrolyte can be reduced, the impurity content in the electrolyte can be reduced, the transmission of ions in the electrolyte can be facilitated, and the safety performance of the electrochemical device can be improved, and the cycle performance and the low-temperature discharge performance of the electrochemical device at low temperature and high temperature can be improved.

In some embodiments of the application, 1.ltoreq.A/p.ltoreq.30. The dissolution amount of the tab sealant in the electrolyte can be reduced by regulating the value of A/p within the range, which is beneficial to further improving the transmission capability of ions in the electrolyte, thereby improving the safety performance of the electrochemical device and further improving the cycle performance and the low-temperature discharge performance at low temperature and high temperature.

In some embodiments of the application, the electrochemical device further comprises a package having a cavity, the electrode assembly and electrolyte disposed in the cavity, the package comprising a top seal for sealing the cavity, the tab being connected to the electrode assembly and extending from the top seal; along the extending direction of the electrode lugs, the sealing width of the top sealing edge is D mm, and D is more than or equal to 1.0 and less than or equal to 1.7. The sealing width of the top sealing edge is regulated and controlled within the range, so that the leakage risk caused by the dissolution of the packaging bag in the electrolyte can be reduced, and the safety performance of the electrochemical device is improved; the impurity content in the electrolyte can be reduced, and the cycle performance of the electrochemical device can be further improved.

In some embodiments of the application, 1.ltoreq.D/p.ltoreq.20. By regulating the value of D/p within the above range, the dissolution amount of the packaging bag in the electrolyte can be reduced, which is beneficial to further improving the transmission capability of ions in the electrolyte, thereby improving the safety performance of the electrochemical device and further improving the cycle performance and low-temperature discharge performance at low and high temperatures.

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 by the application has good low-temperature cycle performance, high-temperature cycle performance and low-temperature discharge performance, so that the electronic device provided by the application has longer service life.

The application has the beneficial effects that:

the application provides an electrochemical device and an electronic device. The electrochemical device comprises an electrolyte, an electrode assembly and a tab, wherein the electrolyte comprises a compound shown in a formula (I) and a compound shown in a formula (II). Based on the mass of the electrolyte, the mass percentage of the compound shown in the formula (I) is p percent, the mass percentage of the compound shown in the formula (II) is q percent, p is more than or equal to 0.01 and less than or equal to 3, and p/q is more than or equal to 0.002 and less than or equal to 60. By regulating the values of p and p/q within the above range, the inorganic component content in the SEI film can be increased, the impedance of the SEI film can be reduced, the ion transmission rate at low temperature can be improved, the toughness of the SEI film and the stability of the SEI film at high temperature can be improved, the side reaction between the SEI film and the electrolyte can be reduced, and the cycle performance and the low-temperature discharge performance of the electrochemical device at low temperature and high temperature can be improved; in addition, the electrochemical device may be provided with an SEI film having a proper thickness, thereby improving safety performance of the electrochemical device, such as heat box performance.

Of course, it is not necessary for any one product or method of practicing the application to achieve all of the advantages set forth above at the same time.

Drawings

In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the application, and other embodiments may be obtained according to these drawings to those skilled in the art.

Fig. 1 is a schematic structural view of an electrochemical device according to an embodiment of the present application in an XY plane;

fig. 2 is a schematic view showing the structure of an electrochemical device according to an embodiment of the present application in the YZ plane.

Reference numerals: electrochemical device 100, electrode assembly 10, tab 20, tab sealant 30, package bag 40, top seal 41.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments obtained by the person skilled in the art based on the present application fall within the scope of protection of the present application.

In the specific embodiment of the present application, the present application is explained by taking a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.

wherein R is ₁ Selected from O or-CH (Ra) -, ra is selected from H, F, C ₁ To C ₅ Alkyl or C of (2) ₁ To C ₅ Alkoxy groups of (a); r is R ₂ And R is ₃ Each independently selected from H, F, C ₁ To C ₅ Alkyl, C of (2) ₁ To C ₅ Alkoxy or C of (2) ₂ To C ₅ Alkenyl group of (C),C ₂ To C ₅ Alkynyl of (a); r is R ₄ Selected from H, F, C unsubstituted or substituted by F ₁ To C ₅ Alkyl, C of (2) ₁ To C ₅ Alkoxy, C ₂ To C ₅ Alkenyl or C of (2) ₂ To C ₅ Is an alkynyl group of (c).

Wherein n is 0, 1 or 2, M is selected from C or O, and X is selected fromR ₂₁ 、R ₂₂ Each independently selected from H, & gt>R ₂₁ And R is ₂₂ Not simultaneously selected from H, and X, R ₂₁ And R is ₂₂ Contains at least one sulfur atom; based on the mass of the electrolyte, the mass percentage of the compound shown in the formula (I) is p percent, the mass percentage of the compound shown in the formula (II) is q percent, p is more than or equal to 0.01 and less than or equal to 3, p/q is more than or equal to 0.002 and less than or equal to 60, and preferably p is more than or equal to 0.1 and less than or equal to 1,0.003 and p/q is more than or equal to 2. For example, the value of p may be 0.01, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8, 1, 1.5, 2, 2.5, 3 or a range of any two of these values, e.g., the value of p/q may be 0.002, 0.003, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 or a range of any two of these values. The electrolyte comprises a compound shown in a formula (I) and a compound shown in a formula (II) and regulates the values of p and p/q within the range, can exert the synergistic effect of the compound shown in the formula (I) and the compound shown in the formula (II), can increase the content of inorganic components in a solid electrolyte interface film (SEI film), is beneficial to reducing the impedance of the SEI film, improving the ion transmission rate at low temperature and can also increase Li in the SEI film ₂ CO ₃ And the content of alkyl lithium (e.g., methyl lithium, ethyl lithium), can improve the toughness of the SEI film to reduce the risk of SEI film cracking, and can improveThe stability of the SEI film at high temperature reduces side reactions between the SEI film and the electrolyte, thereby improving the cycle performance and low-temperature discharge performance of the electrochemical device at low temperature and high temperature; in addition, the electrochemical device may be provided with an SEI film having a proper thickness, thereby improving safety performance of the electrochemical device, such as heat box performance.

The inventors have found that the electrolyte solution including the compound of formula (I) can increase the content of inorganic components in the SEI film, which is advantageous for reducing the resistance of the SEI film, but increases the risk of cracking the SEI film, and that the electrolyte solution including the compound of formula (II) can further increase the content of inorganic components (sulfur-containing inorganic compounds) in the SEI film and also can increase Li in the SEI film ₂ CO ₃ And alkyl lithium content, improve the toughness of SEI film, reduce SEI film rupture risk. The electrolyte comprises a compound shown in a formula (I) and a compound shown in a formula (II), and the compound are synergistic, so that an SEI film with low impedance, high toughness and good stability at high temperature can be formed, thereby improving the ion transmission rate at low temperature, reducing side reactions between the SEI film and the electrolyte at high temperature, and further considering the cycle performance and low-temperature discharge performance of an electrochemical device at low temperature and high temperature. When p is too small, for example, less than 0.01, the compound represented by the formula (I) is too small in content to form a low-resistance SEI film, which is unfavorable for ion transport, and also makes the SEI film poor in stability at high temperature, thereby failing to improve the cycle performance and low-temperature discharge performance of an electrochemical device at low temperature and also unfavorable for improving the safety performance of an electrochemical device. When p is too large, for example, more than 3, the compound represented by the formula (I) is excessively contained to cause the thickness of the SEI film to be too large due to the strong reactivity of the compound, and also to be unfavorable for ion transport, thereby failing to compromise the cycle performance of the electrochemical device at low and high temperatures. When p/q is too small, for example, less than 0.002, it is not advantageous to exert the synergistic effect of the compound represented by the formula (I) and the compound represented by the formula (II), an SEI film having low resistance, high toughness and good stability at high temperature cannot be formed, and the formed SEI film has too large resistance, and is not advantageous to improve the low-temperature cycle performance and low-temperature discharge performance of an electrochemical device Electrical properties. When p/q is excessively large, for example, greater than 60, the formed SEI film is excessively thick, which is unfavorable for ion transmission, and also causes poor toughness of the SEI film, easy breakage, and poor stability at high temperature, thereby failing to improve the cycle performance and low-temperature discharge performance of the electrochemical device at low and high temperatures. The electrolyte comprises the compound shown in the formula (I) and the compound shown in the formula (II) and regulates the values of p and p/q within the range, so that the synergistic effect of the compound shown in the formula (I) and the compound shown in the formula (II) can be exerted, and the cycle performance and the low-temperature discharge performance of the electrochemical device at low temperature and high temperature can be realized.

In some embodiments of the application, 0.05.ltoreq.q.ltoreq.5, preferably 0.5.ltoreq.q.ltoreq.3. For example, q may have a value of 0.05, 0.1, 0.2, 0.3, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or a range of any two values therein. The value of q is regulated within the range, so that the synergistic effect of the compound shown in the formula (I) and the compound shown in the formula (II) is brought into play, and the compound form inorganic components rich in sulfur together, so that the impedance of the SEI film is further reduced, the ion transmission rate at low temperature is improved, the toughness of the SEI film and the stability of the SEI film at high temperature are improved, the side reaction between the SEI film and electrolyte is reduced, and the cycle performance, the low-temperature discharge performance and the safety performance of an electrochemical device at low temperature and high temperature are improved.

the electrolyte comprises the compound shown in the formula (I) in the range, can better play the synergistic effect of the compound shown in the formula (I) and the compound shown in the formula (II), increases the content of inorganic components in the SEI film, is beneficial to reducing the impedance of the SEI film, improves the ion transmission rate at low temperature, can also improve the stability of the SEI film at high temperature, reduces the side reaction between the SEI film and the electrolyte, and can further improve the cycle performance, the low-temperature discharge performance and the safety performance of an electrochemical device at low temperature and high temperature.

the electrolyte comprises the compound shown in the formula (II) in the range, so that the synergistic effect of the compound shown in the formula (I) and the compound shown in the formula (II) can be better exerted, and the compound together form an inorganic component rich in sulfur, so that the impedance of the SEI film is further reduced, and the ion transmission rate at low temperature is improved; is more beneficial to increasing Li in SEI film ₂ CO ₃ And alkyl lithium content, improve toughness of SEI film in order to reduce SEI film rupture risk, and improve SEI film stability under high temperature, reduce side reaction between SEI film and electrolyte, thus improve electrochemical device cycle performance, low-temperature discharge performance and security performance under low temperature and high temperature.

The electrolyte of the present application further comprises a lithium salt and an organic solvent. The lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium difluorophosphate, lithium tetrafluoroborate, lithium nitrate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (pentafluoroethylsulfonyl) imide, lithium tris (trifluoromethylsulfonyl) methyl, lithium difluorooxalato phosphate, or lithium tetrafluorooxalato phosphate. The present application is not particularly limited as long as the object of the present application can be achieved. Illustratively, the above-mentioned lithium salt may be 8 to 15% by mass based on the mass of the electrolyte, for example, the lithium salt may be 8%, 9%, 10%, 12%, 13%, 14%, 15% by mass or a range of any two values therein. The present application is not particularly limited as long as the object of the present application can be achieved, and may include, for example, but not limited to, at least one of a carbonate compound, a carboxylate compound, an ether compound, or other organic solvents. The carbonate compound may include, but is not limited to, at least one of a chain carbonate compound or a cyclic carbonate compound. The above chain carbonate compound may include, but is not limited to, at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, or methyl ethyl carbonate. The cyclic carbonate compound may include, but is not limited to, at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or ethylene carbonate. The above carboxylic acid ester compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, gamma-butyrolactone, decalactone, valerolactone, or caprolactone. The ether compound may include, but is not limited to, at least one of ethylene glycol dimethyl ether, dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The present application is not particularly limited as long as the object of the present application can be achieved. Illustratively, the above-mentioned organic solvent may be present in an amount of 62% to 91.94% by mass, based on the mass of the electrolyte, for example, the organic solvent may be present in an amount of 62%, 65%, 70%, 75%, 77%, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 91.94% by mass, or in a range of any two values therein. Optionally, the electrolyte includes an additive, which may include, but is not limited to, at least one of fluoroethylene carbonate, 1, 3-propane sultone, adiponitrile, or the like. The present application is not particularly limited as long as the object of the present application can be achieved. Illustratively, the above additives are present in an amount of 0% to 15% by mass based on the mass of the electrolyte, e.g., the additives may be present in an amount of 0%, 0.5%, 1%, 2%, 5%, 8%, 10%, 12%, 13%, 14%, 15% by mass or in a range of any two values therein. In some embodiments, the electrolyte may include a compound represented by formula (I), a compound represented by formula (II), a lithium salt, and an organic solvent, the mass percentage of the compound represented by formula (I), the compound represented by formula (II), and the lithium salt being 62 to 91.94% as described above. The electrochemical device comprising the electrolyte has good cycle performance at low temperature and high temperature, and has good low-temperature discharge performance and safety performance. In other embodiments, the electrolyte may include the compound of formula (I), the compound of formula (II), the lithium salt, the organic solvent, and the above-described additives, wherein the mass percentage of the compound of formula (I), the compound of formula (II), the lithium salt, and the additives is 77 to 91.94% of the mass percentage of the organic solvent as described above. The electrochemical device comprising the electrolyte has good cycle performance at low temperature and high temperature, and has good low-temperature discharge performance and safety performance.

In some embodiments of the present application, the tab is provided with a tab sealant, the width of the tab sealant exceeding the maximum width of the tab by a mm in a direction perpendicular to the direction in which the tab extends, 1.8.ltoreq.a.ltoreq.2.6, the thickness of the tab sealant being 75 μm to 85 μm, for example, the value of a may be 1.8, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6 or a range of any two of these values, and the thickness of the tab sealant may be 75 μm, 77 μm, 78 μm, 80 μm, 81 μm, 83 μm, 85 μm or a range of any two of these values. The value of A and the thickness of the tab sealant are regulated within the range, so that the risk of leakage of the electrochemical device can be reduced, the dissolution amount of the tab sealant in the electrolyte can be reduced, the impurity content in the electrolyte can be reduced, the transmission of ions in the electrolyte can be facilitated, and the safety performance of the electrochemical device can be improved, and the cycle performance and the low-temperature discharge performance of the electrochemical device at low temperature and high temperature can be improved.

As shown in fig. 1 and 2, for convenience of understanding, a three-dimensional rectangular coordinate system is established with the direction perpendicular to the extending direction of the tab as the X direction, the extending direction of the tab as the Y direction, and the thickness direction of the tab itself as the Z direction. The electrochemical device 100 includes an electrode assembly 10 and a tab 20, and a tab sealant 30 is provided on the tab 20, and a width of the tab sealant 30 exceeding a maximum width of the tab 20 is a mm in a direction (X direction) perpendicular to the extending direction of the tab 20. In general, the electrochemical device 100 includes two tabs 20, each of the two tabs 20 is provided with a tab sealant 30, the width of the tab sealant 30 is greater than the width of the tab 20 along the X direction, the width of the tab sealant 30 exceeds two sides of the tab 20, and the widths of the two tab sealants 30 exceeding two sides of the tab 20 are a in sequence ₁ 、A ₂ 、A ₃ 、A ₄ The four may be the same or different, when the four are the same, a=a ₁ ＝A ₂ ＝A ₃ ＝A ₄ . When the four are different, A is the maximum value, such as A ₁ ＜A ₂ ＜A ₃ ＜A ₄ A=a ₄ . The thickness of the tab sealant 30 is H μm (shown in fig. 2) in the Z direction, i.e., in the thickness direction of the tab 20 itself.

In the application, the tab comprises a positive electrode tab and a negative electrode tab. The positive electrode tab and the negative electrode tab are not particularly limited as long as the object of the present application can be achieved. For example, the positive electrode tab includes any one of an aluminum tab or an aluminum alloy tab, and the negative electrode tab includes any one of a nickel tab or a copper nickel-plated tab. The size of the tab is not particularly limited as long as the object of the present application can be achieved, for example, the width of the tab in the X direction may be 3mm to 8mm, the length in the Y direction may be 30mm to 45mm, and the thickness in the Z direction may be 0.2mm to 0.6mm. The width of the tab sealant in the X direction and the length of the tab sealant in the Y direction are not particularly limited as long as the object of the present application can be achieved, for example, the width of the tab sealant in the X direction may be 6.6mm to 13.2mm and the length in the Y direction may be 7mm to 13mm.

The material of the tab sealant is not particularly limited as long as the tab sealant can be realized The purpose of the application is just to do. Materials such as tab sealants may include, but are not limited to, at least one of polypropylene, polyethylene-propylene copolymer, polystyrene, polyvinyl chloride, acrylonitrile-styrene-butadiene copolymer, polyethylene terephthalate, or polyethylene naphthalate. The weight average molecular weight of the material is not particularly limited as long as the object of the present application can be achieved. For example, the weight average molecular weight of the above material may be 10 ³ To 10 ⁷ . The melting point of the tab sealant is not particularly limited as long as the object of the present application can be achieved. For example, the tab sealant may have a melting point of 110 ℃ to 250 ℃.

In some embodiments of the application, 1.ltoreq.A/p.ltoreq.30. The dissolution amount of the tab sealant in the electrolyte can be reduced by regulating the value of A/p within the range, which is beneficial to further improving the transmission capability of ions in the electrolyte, thereby improving the safety performance of the electrochemical device and further improving the cycle performance and the low-temperature discharge performance of the electrochemical device at low temperature and high temperature.

In some embodiments of the present application, as shown in fig. 1, the electrochemical device 100 further includes a packing bag 40, the packing bag 40 having a cavity in which the electrode assembly 10 and an electrolyte (not shown in fig. 1) are disposed, the packing bag 40 including a top sealing edge 41, the top sealing edge 41 sealing the cavity, and the tab 20 being connected to the electrode assembly 10 and protruding from the top sealing edge 41; along the extending direction (Y direction) of the tab 20, the sealing width of the top sealing edge 41 is D mm, and D is more than or equal to 1.0 and less than or equal to 1.7. For example, the seal width of the top seal may be 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, or a range of any two values therein. Because electrolyte has the solubility to wrapping bag (for example plastic-aluminum membrane wrapping bag), when the sealing width of top banding is too narrow, can increase the weeping risk in the electrochemical device storage process, when the sealing width of top banding is too wide, can increase impurity content in the electrolyte. The sealing width of the top sealing edge is regulated and controlled within the range, so that the leakage risk caused by the dissolution of the packaging bag in the electrolyte can be reduced, and the safety performance of the electrochemical device is improved; the impurity content in the electrolyte can be reduced, which is beneficial to further improving the transmission capability of ions in the electrolyte and further improving the cycle performance and low-temperature discharge performance of the electrochemical device at low temperature and high temperature.

Typically, the seal width of the top seal is controlled by controlling the width of the embossing when the package is sealed. In the present application, the packing bag is used to contain the electrode assembly and the electrolyte, and other components known in the art of electrochemical devices, and the present application is not limited to the above-mentioned other components. The package of the present application may include, but is not limited to, an aluminum plastic film package. The package may further include a side seal, and the sealing width of the side seal of the present application is not particularly limited as long as the object of the present application can be achieved, for example, the sealing width of the side seal may be 1mm to 3mm.

In some embodiments of the application, 1.ltoreq.D/p.ltoreq.20, e.g.the value of D/p may be 1, 2, 3, 5, 7, 9, 10, 12, 15, 17, 20 or a range of values consisting of any two of these. By regulating the value of D/p within the above range, the dissolution amount of the packaging bag in the electrolyte can be reduced, which is beneficial to further improving the transmission capability of ions in the electrolyte, thereby improving the safety performance of the electrochemical device and further improving the cycle performance and low-temperature discharge performance at low and high temperatures.

In the application, the electrode assembly comprises a positive electrode plate, a negative electrode plate and a separation film, wherein the separation film is used for separating the positive electrode plate and the negative electrode plate, preventing the internal short circuit of the electrochemical device, allowing electrolyte ions to pass freely and not influencing the electrochemical charging and discharging process.

The positive electrode sheet of the present application is not particularly limited as long as the object of the present application can be achieved. For example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. In the present application, the positive electrode active material layer may be provided on one surface of the positive electrode current collector in the thickness direction thereof, or may be provided on both surfaces of the positive electrode current collector in the thickness direction thereof. The "surface" here may be the entire region of the positive electrode current collector or may be a partial region of the positive electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved.

The positive electrode current collector is not particularly limited as long as the object 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 (e.g., an aluminum carbon composite current collector). The thicknesses of the positive electrode current collector and the positive electrode active material layer are not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector is 6 μm to 12 μm, and the thickness of the positive electrode active material layer is 30 μm to 120 μm. The thickness of the positive electrode sheet is not particularly limited as long as the object of the present application can be achieved, for example, the positive electrode sheet has a thickness of 50 μm to 250 μm.

The positive electrode active material layer of the present application includes a positive electrode active material including a substance capable of reversibly intercalating and deintercalating active ions such as lithium ions. The positive electrode active material layer may be one or more layers, and each of the multiple positive electrode active material layers may contain the same or different positive electrode active materials. The positive electrode active material is not particularly limited as long as the object of the present application can be achieved, and for example, the positive electrode active material may include, but is not limited to, lithium nickel cobalt manganate (e.g., NCM811, NCM622, NCM523, NCM 111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO) ₂ ) At least one of lithium manganate, 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 composition different from that of the positive electrode active material, and illustratively, the surface-attached substance may include, but is not limited to, at least one of alumina, silica, titania, zirconia, magnesia, 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 improved.

The positive electrode active material layer may further include a conductive agent and a binder, the kind of which is not particularly limited as long as the object of the present application can be achieved, and for example, the binder may include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (esterified) styrene-butadiene rubber, epoxy resin, or nylon; the 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. Illustratively, 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, a polyphenylene derivative. The mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode active material layer is not particularly limited in the present application, and may be selected according to actual needs as long as the object of the present application can be achieved.

The negative electrode sheet is not particularly limited as long as the object of the present application can be achieved. For example, the negative electrode tab 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 the present application, the anode active material layer may be provided on one surface in the anode current collector thickness direction, or may be provided on both surfaces in the anode current collector thickness direction. The "surface" here may be the entire region of the negative electrode current collector or may be a partial region of the negative electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved.

The negative electrode current collector is not particularly limited as long as the object 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 (e.g., carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, etc.), and the like. In the present application, the thicknesses of the anode current collector and the anode active material layer are not particularly limited as long as the object of the present application can be achieved, for example, the anode current collector has a thickness of 6 μm to 12 μm and the anode active material layer has a thickness of 30 μm to 130 μm. In the present application, the thickness of the negative electrode sheet is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the negative electrode sheet is 50 μm to 280 μm.

The anode active material layer of the present application includes an anode active material, and the anode active material layer may be one or more layers, and each of the multiple anode active material layers may contain the same or different anode active materials. The negative electrode active material is any substance capable of reversibly intercalating and deintercalating active ions such as lithium ions. The negative electrode active material may include, but is not limited to, graphite, mesophase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon-carbon composite, siO _x (0.5<x<1.6 A) Li-Sn alloy, a Li-Sn-O alloy, sn, snO, snO ₂ Spinel structured lithiated TiO ₂ -Li ₄ Ti ₅ O ₁₂ At least one of Li-Al alloy and metallic lithium. The anode active material layer in the present application may further include a binder, a conductive agent, or a thickener. The kind of the binder and the conductive agent is not particularly limited as long as the object of the present application can be achieved, and for example, the binder and the conductive agent may include, but are not limited to, at least one of the above-mentioned optional substances of the positive electrode active material layer. The kind of the thickener is not particularly limited as long as the object of the present application can be achieved, and for example, the thickener may include, but is not limited to, at least one of sodium carboxymethyl cellulose or carboxymethyl cellulose. The present application is not particularly limited as long as the object of the present application can be achieved, and the anode tab may further include a conductive layer between the anode current collector and the anode material layer. The composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder.

The separator is not particularly limited as long as the object of the present application can be achieved. For example, the material of the separator film may include, but is not limited to, at least one of Polyethylene (PE), polypropylene (PP) -based Polyolefin (PO), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid; the type of separator film may include at least one of a woven film, a nonwoven film, a microporous film, a composite film, a laminate film, or a spun film. For example, the release film may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, a film or a composite film having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is disposed on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic material. For example, the inorganic layer includes inorganic particles and a binder, and the present application is not particularly limited, and for example, may include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder of the present application is not particularly limited, and may be at least one of the above binders, for example. The polymer layer contains a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylic polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene). In the present application, the thickness of the separator is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the separator may be 5 μm to 500 μm.

The electrochemical device of the present application is not particularly limited, and may include any device in which an electrochemical reaction occurs. 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, etc.

The process of preparing the electrochemical device of the present application is well known to those skilled in the art, and the present application is not particularly limited, and may include, for example, but not limited to, the following steps: sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, welding the electrode lugs, attaching the electrode lug sealant, winding and folding the electrode lugs according to the need to obtain an electrode assembly with a winding structure, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag, and sealing to obtain an electrochemical device; or sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, welding the electrode lugs, adhering the electrode lug sealant, fixing four corners of the whole lamination structure by using an adhesive tape to obtain an electrode assembly of the lamination structure, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag, and sealing to obtain the electrochemical device. In addition, an overcurrent prevention element, a guide plate, or the like may be placed in the package as needed, thereby preventing the pressure inside the electrochemical device from rising and overcharging and discharging.

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 by the application has good low-temperature cycle performance and high-temperature cycle performance, so that the electronic device provided by the application has longer service life.

The electronic device of the present application is not particularly limited, and may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copier, a portable printer, a headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-compact disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable audio recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a household large-sized battery, a lithium ion capacitor, and the like.

Examples

Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. The various tests and evaluations were carried out according to the following methods. Unless otherwise specified, "parts" and "%" are mass references.

Test method and apparatus:

high temperature cycle performance test:

the high temperature cycle performance of the lithium ion battery was evaluated by the capacity retention rate and the thickness expansion rate after 400 cycles at 45 ℃. The larger the capacity retention rate after 400 circles of 45 ℃ circulation, the better the high-temperature circulation performance of the lithium ion battery is. And placing the lithium ion battery in a 45 ℃ incubator, and standing for 30 minutes to keep the lithium ion battery at a constant temperature. Charging the lithium ion battery with constant temperature to 4.5V at 45 ℃ under constant current of 0.2C, charging to 0.05C under constant voltage of 4.5V, standing for 5 minutes, discharging to 3.0V under constant current of 0.2C, standing for 5 minutes, and testing initial discharge capacity C of the lithium ion battery ₀ The method comprises the steps of carrying out a first treatment on the surface of the Then charging to 4.15V with a constant current of 1.3C, and charging to 1C with a constant voltage of 4.15V; then charging to 4.25V with 1C constant current, and then charging to 0.8C with 4.25V constant voltage; charging to 4.5V with constant current of 0.8C, and charging to 0.05C with constant voltage of 4.5V; standing for 5 minutes; then, the mixture was discharged to 3.0V at a constant current of 1C and allowed to stand for 5 minutes, which was a charge-discharge cycle. The discharge capacity C' of the lithium ion battery after 400 cycles was tested by cycling 400 cycles according to the above charge/discharge cycling steps.

Capacity retention after 400 cycles at 45 ℃ = C'/C ₀ ×100％。

Low temperature cycle performance test:

and placing the lithium ion battery in a constant temperature box at the temperature of minus 10 ℃, and standing for 30 minutes to ensure that the lithium ion battery achieves constant temperature. Charging the constant-temperature lithium ion battery to 4.5V at-10deg.C under constant current of 0.2C, charging to 0.05C under constant voltage of 4.5V, standing for 5 min, discharging to 3.0V under constant current of 0.2C, standing for 5 min, and testing initial capacity C ₁₁ The method comprises the steps of carrying out a first treatment on the surface of the Then charging to 4.2V with constant current of 0.5C, and charging to 0.3C with constant voltage of 4.2V; charging to 4.5V with constant current of 0.3C, and charging to 0.05C with constant voltage of 4.5V; standing for 5 minutes; then discharging to 3.0V at constant current of 0.2C, and standing for 5 minutes;this is a charge-discharge cycle. The discharge capacity C of the lithium ion battery after 200 circles of circulation is measured according to 200 circles of the charge/discharge circulation steps ₁₂ And calculating the capacity retention rate of the lithium ion battery after 200 cycles.

Capacity retention after 200 cycles at-10 ℃ = C ₁₂ /C ₁₁ ×100％。

And (3) hot box test:

the lithium ion battery is discharged to 3.0V at 25 ℃ under constant current of 0.5C, then is charged to 4.5V under constant current of 0.5C, and is charged to 0.05C under constant voltage of 4.5V. And (3) placing the lithium ion battery in a high-temperature furnace at 130 ℃, 132 ℃ or 134 ℃ for storage for 1 hour, and after the 1 hour is finished, observing whether the lithium ion battery catches fire or not, and judging that the lithium ion battery passes through the fire when the lithium ion battery catches fire is not caught. The passing rate recording mode is N/10, which means that 10 lithium ion batteries are tested, and N lithium ion batteries pass the test.

Low temperature discharge capacity ratio test:

standing the lithium ion battery in a constant temperature box at 25 ℃ for 1 hour to keep the lithium ion battery constant temperature; charging to 4.2V with 0.5C constant current, charging to 4.5V with 0.3C constant current, charging to 0.02C with 4.5V constant voltage, and standing for 30 min; then discharging to 3.4V with constant current of 0.2C, standing for 30 min, and discharging to obtain the final product (D ₀ ) As a reference. Charging to 4.2V at 25deg.C under constant current of 0.5C, charging to 4.5V under constant current of 0.3C, charging to 0.02C under constant voltage of 4.5V, and standing for 30 min; the temperature in the incubator is adjusted to be minus 10 ℃, and the lithium ion battery is kept stand in the incubator at minus 10 ℃ for 1 hour, so that the lithium ion battery is kept at a constant temperature; discharging to 3.4V with constant current of 0.2C, recording the capacity at this time as D ₁ . -10 ℃ discharge capacity ratio = D ₁ /D ₀ ×100％。

Testing the content of each component in the electrolyte:

discharging the lithium ion battery to 3.0V with a constant current of 1C, then disassembling, collecting electrolyte, centrifuging the disassembled positive pole piece, negative pole piece and isolating film, uniformly mixing the liquid obtained after centrifuging with the electrolyte, and then testing by adopting a gas chromatography-mass spectrometer (model is Agilent 8890) and an ion chromatograph (model is AQUION ion chromatograph) to obtain each component in the electrolyte and testing the content of each component.

Example 1-1

< preparation of tab sealant >

The tab sealant is a single-layer adhesive and comprises polypropylene (weight average molecular weight is 20000) and polyethylene (weight average molecular weight is 20000), and the mass ratio of the polypropylene to the polyethylene is 2:1. The melting point of the tab sealant was 140 ℃.

< preparation of Positive electrode sheet >

LiCoO as positive electrode active material ₂ Mixing conductive carbon black (Super P) serving as a positive electrode conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 97.5:1:1.5, adding N-methylpyrrolidone (NMP) serving as a solvent, and uniformly stirring under the action of a vacuum stirrer to obtain positive electrode slurry with the solid content of 75 wt%. And uniformly coating the positive electrode slurry on one surface of a positive electrode current collector aluminum foil with the thickness of 10 mu m, and drying at the temperature of 85 ℃ to obtain the positive electrode plate with the single-sided coating thickness of the positive electrode active material layer with the thickness of 50 mu m. And repeating the steps on the other surface of the aluminum foil to obtain the positive electrode plate with the double-sided coating positive electrode active material layer. And then cold pressing, cutting and welding the aluminum tab of the positive electrode tab to obtain the positive electrode sheet with the specification of 74mm multiplied by 851mm for standby. Wherein the above-mentioned tab sealant is adhered to the positive electrode tab, the size of the positive electrode tab is 5mm×40mm×0.4mm (X direction×y direction×z direction), the size of the tab sealant adhered to the positive electrode tab is 9.4mm×10mm×80 μm (X direction×y direction×z direction), and the widths of the tab sealant beyond both sides of the positive electrode tab are A respectively as shown in FIG. 1 ₁ mm、A ₂ mm，A ₁ ＝2.2，A ₂ ＝2.2。

< preparation of negative electrode sheet >

Mixing negative electrode active material graphite, a negative electrode conductive agent Super P, a thickener carboxymethyl cellulose and a binder styrene-butadiene rubber (SBR) according to a mass ratio of 97.5:1:0.5:1, then adding deionized water as a solvent, and uniformly stirring under the action of a vacuum stirrer to obtain the negative electrode slurry with the solid content of 50 wt%. Uniformly coating the anode slurry on one surface of an anode current collector copper foil with the thickness of 8 mu m, and drying at the temperature of 85 ℃ to obtain an anode active material layer with the single-side coating thickness of 60 mu mAnd a negative pole piece. And repeating the steps on the other surface of the copper foil to obtain the negative electrode plate with the double-sided coating negative electrode active material layer. And cold pressing, cutting and welding the nickel tab of the negative electrode tab to obtain the negative electrode tab with the specification of 76mm multiplied by 867mm for standby. Wherein the above-mentioned tab sealant is adhered to the negative electrode tab, the size of the negative electrode tab is 5mm×40mm×0.4mm (X direction×y direction×z direction), the size of the tab sealant adhered to the negative electrode tab is 9.4mm×10mm×80 μm (X direction×y direction×z direction), and the widths of the tab sealant beyond both sides of the negative electrode tab are A respectively as shown in FIG. 1 ₃ mm、A ₄ mm，A ₃ ＝2.2，A ₄ ＝2.2。

< preparation of electrolyte >

Mixing organic solvents of Ethylene Carbonate (EC), propylene Carbonate (PC) and Propyl Propionate (PP) according to a mass ratio of 1:1:3 in an environment with a water content of less than 10ppm, and then adding a compound shown in a formula (I) and a compound shown in a formula (I-1) and a formula (II-4) into the solvent, and lithium hexafluorophosphate (LiPF) ₆ ) Dissolving and mixing uniformly to obtain the electrolyte. LiPF based on electrolyte mass ₆ The mass percentage of (2) is 10%; the mass percent p% of the compound shown in the formula (I) is 0.4%, the mass percent q% of the compound shown in the formula (II) is 2%, and the balance is an organic solvent.

< separation Membrane >

Polyethylene film (manufacturer: lithium New Material Co., ltd. In lake south) having a thickness of 15 μm was used.

< preparation of lithium ion Battery >

And stacking and winding the prepared negative electrode plate, the separator and the positive electrode plate in sequence to obtain the electrode assembly with a winding structure. And placing the electrode assembly in an aluminum plastic film packaging bag, drying, injecting electrolyte, and performing vacuum packaging, standing, formation, capacity, degassing, trimming and other procedures to obtain the lithium ion battery.

As shown in fig. 1, in the X direction, the width of the tab sealant 30 exceeds the maximum width of the tab 20 by a mm, a=2.2, and the sealing width of the top seal 41 by D mm, d=1.4. As shown in fig. 2, in the Z direction, the thickness of the tab sealant 30 is H μm, h=80.

Examples 1-2 to 1-25

The procedure of example 1-1 was repeated, except that the compound represented by the formula (I) and the mass percentage p% thereof were changed as shown in Table 1, the compound represented by the formula (II) and the mass percentage q% thereof were changed, and the mass percentage of the organic solvent and the mass percentage of the lithium salt were unchanged.

Examples 2-1 to 2-7

The procedure of example 1-1 was repeated except that the width of the tab paste in the X direction was changed and the width of the tab in the X direction was kept constant so that the value of A was as shown in Table 2 and the mass percentage of the compound represented by the formula (I) was adjusted to p% in accordance with Table 2.

Examples 2 to 8 to 2 to 9

The procedure of example 1-1 was repeated except that the thickness H of the tab sealant was adjusted in accordance with Table 2.

Examples 3-1 to 3-10

The procedure of example 1-1 was repeated except that the value of the seal width D of the top-seal edge and the mass percentage p% of the compound represented by the formula (I) were adjusted as shown in Table 3.

Comparative examples 1 to 1

The procedure of example 1-1 was repeated except that the compound represented by the formula (I) and the compound represented by the formula (II) were not added in the < preparation of an electrolyte solution >, the mass percentage of the organic solvent was changed, and the mass percentage of the lithium salt was not changed.

Comparative examples 1 to 2

The procedure of example 1-1 was repeated, except that the compound represented by the formula (I) was not added in the < preparation of electrolyte >, the mass percentage of the organic solvent was changed, and the mass percentage of the lithium salt was not changed.

Comparative examples 1 to 3

The procedure of example 1-1 was repeated, except that the compound represented by the formula (II) was not added in the < preparation of electrolyte solution >, the mass percentage of the organic solvent was changed, and the mass percentage of the lithium salt was not changed.

Comparative examples 1 to 4 to 1 to 7

The procedure of example 1-1 was repeated, except that in < preparation of electrolyte > p% by mass of the compound represented by the formula (I) and q% by mass of the compound represented by the formula (II) were adjusted as shown in Table 1, the mass percentage of the organic solvent was changed and the mass percentage of the lithium salt was not changed.

The preparation parameters and performance parameters of each example and comparative example are shown in tables 1 to 3.

TABLE 1

/>

Note that: in Table 1 "/" the table does not add the substance or does not have the substance or parameter to be applied

As can be seen from examples 1-1 to 1-25 and comparative examples 1-1 to 1-7, the electrolyte including the compound represented by formula (I) and the compound represented by formula (II) within the scope of the present application was applied to a lithium ion battery, and simultaneously the values of p, p/q were controlled within the scope of the present application, the lithium ion battery had a higher 45 ℃ cycle capacity retention, -10 ℃ discharge capacity ratio, and hot box test pass rate, thereby demonstrating that the lithium ion battery had better high temperature cycle performance, low temperature discharge performance, and safety performance.

The mass percentage x% of the compound represented by formula (I) generally affects the high temperature cycle performance, the low temperature discharge performance and the safety performance of the lithium ion battery. It can be seen from examples 1-1 to 1-10, comparative examples 1-4 to comparative examples 1-5 that when p is too small, for example, smaller than comparative examples 1-4, the 45 ℃ cycle capacity retention, -10 ℃ discharge capacity ratio, and hot box test passing rate of the lithium ion battery are too small. As the p content increases, the SEI film thickness increases to some extent, and since the SEI film conductivity is too poor, the SEI film thickness does not increase any more. When p is too large, for example, greater than 3, the hot box test passing rate of the lithium ion battery can be made larger due to the larger SEI film thickness of comparative examples 1-5, but the 45 ℃ cycle capacity retention rate, -10 ℃ cycle capacity retention rate and-10 ℃ discharge capacity ratio of the lithium ion battery are too small due to the large SEI film thickness; when p is too large or too small, the high-temperature cycle performance, the low-temperature discharge performance and the safety performance of the lithium ion battery cannot be considered. When p is more than or equal to 0.01 and less than or equal to 3, the lithium ion battery has higher 45 ℃ cycle capacity retention rate, 10 ℃ discharge capacity ratio and hot box test passing rate, and when p is more than or equal to 0.1 and less than or equal to 1, the lithium ion battery has higher 45 ℃ cycle capacity retention rate, 10 ℃ discharge capacity ratio and hot box test passing rate, and when the value of p is regulated and controlled within the range of the application, the lithium ion battery has better high-temperature cycle performance, low-temperature discharge performance and safety performance.

The p/q value generally affects the high temperature cycle performance, low temperature discharge performance, and safety performance of the lithium ion battery. As can be seen from examples 1-1 to 1-14, comparative examples 1-6 to comparative examples 1-7, when p/q is too small, for example, comparative examples 1-7, the 45 ℃ cycle capacity retention, -10 ℃ discharge capacity ratio, and hot box test passing rate of the lithium ion battery are small; when p/q is too large, for example, comparative examples 1 to 6, the lithium ion battery has a 45 ℃ cycle capacity retention rate, -10 ℃ discharge capacity ratio, and a hot box test passing rate smaller; when p/q is too large or too small, the high-temperature cycle performance, the low-temperature discharge performance and the safety performance of the lithium ion battery cannot be considered. When p/q is more than or equal to 0.002 and less than or equal to p/q and less than or equal to 60, the lithium ion battery has higher 45 ℃ cycle capacity retention rate, 10 ℃ discharge capacity ratio and hot box test passing rate, and when p/q is more than or equal to 0.003 and less than or equal to p/q and less than or equal to 2, the lithium ion battery has higher 45 ℃ cycle capacity retention rate, 10 ℃ discharge capacity ratio and hot box test passing rate, and when the value of p/q is regulated and controlled in the range of the application, the lithium ion battery has better high-temperature cycle performance, low-temperature discharge performance and safety performance.

The mass percentage q% of the compound represented by formula (II) generally affects the high temperature cycle performance, the low temperature discharge performance and the safety performance of the lithium ion battery. It can be seen from examples 1-1, 1-10 to 1-14 that by adjusting the value of q within the scope of the present application, the lithium ion battery can have a higher 45 ℃ cycle capacity retention rate, -10 ℃ discharge capacity ratio and hot box test passing rate, and when the value of p is adjusted within the scope of the present application, the lithium ion battery has good high temperature cycle performance, low temperature discharge performance and safety performance.

The kind of the compound represented by formula (I) generally affects the high temperature cycle performance, the low temperature discharge performance and the safety performance of the lithium ion battery. As can be seen from examples 1-1, 1-15 to 1-20, the application of the electrolyte including the compound represented by formula (I) within the scope of the present application to a lithium ion battery can make the lithium ion battery have a higher 45 ℃ cycle capacity retention rate, -10 ℃ discharge capacity ratio and hot box test passing rate, indicating that the lithium ion battery has good high temperature cycle performance, low temperature discharge performance and safety performance.

The kind of the compound represented by formula (II) generally affects the high temperature cycle performance, the low temperature discharge performance and the safety performance of the lithium ion battery. As can be seen from examples 1-1, 1-21 to 1-25, the application of the electrolyte including the compound represented by formula (I) within the scope of the present application to a lithium ion battery can make the lithium ion battery have a higher 45 ℃ cycle capacity retention rate, -10 ℃ discharge capacity ratio and hot box test passing rate, indicating that the lithium ion battery has good high temperature cycle performance, low temperature discharge performance and safety performance.

TABLE 2

A. The value of a/p generally affects the high temperature cycle performance, low temperature discharge performance, and safety performance of the lithium ion battery. It can be seen from examples 1-1, 1-5 and 2-1 to 2-7 that by adjusting the values of A and A/p within the scope of the application, the leakage risk of the lithium ion battery can be reduced, and meanwhile, the lithium ion battery has higher 45 ℃ cycle capacity retention rate, -10 ℃ discharge capacity ratio and hot box test passing rate, thus indicating that the lithium ion battery has good high-temperature cycle performance, low-temperature discharge performance and safety performance.

The thickness of the tab sealant generally affects the high temperature cycle performance, low temperature discharge performance and safety performance of the lithium ion battery. From examples 1-1, 2-8 to 2-9, it can be seen that by adjusting the thickness of the tab sealant within the scope of the application, the lithium ion battery has a higher 45 ℃ cycle capacity retention rate, a-10 ℃ discharge capacity ratio and a hot box test passing rate, which indicates that the lithium ion battery has good high temperature cycle performance, low temperature discharge performance and safety performance.

TABLE 3 Table 3

D. The value of D/p generally affects the high temperature cycle performance, low temperature discharge performance, and safety performance of the lithium ion battery. It can be seen from examples 1-1, 3-1 to 3-10 that by adjusting the values of D and D/p within the range of the application, the lithium ion battery can have a higher 45 ℃ cycle capacity retention rate, -10 ℃ discharge capacity ratio and hot box test passing rate while the leakage risk of the lithium ion battery can be reduced, and the lithium ion battery has good high-temperature cycle performance, low-temperature discharge performance and safety performance.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, or article that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, or article.

In this specification, each embodiment is described in a related manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments.

The foregoing description of the preferred embodiments of the application is not intended to limit the application to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the application are intended to be included within the scope of the application.

Claims

1. An electrochemical device comprising an electrolyte, an electrode assembly, and a tab, the electrolyte comprising a compound represented by formula (I) and a compound represented by formula (II):

wherein R is ₁ Selected from O or-CH (Ra) -, ra is selected from H, F, C ₁ To C ₅ Alkyl or C of (2) ₁ To C ₅ Alkoxy groups of (a); r is R ₂ And R is ₃ Each independently selected from H, F, C ₁ To C ₅ Alkyl, C of (2) ₁ To C ₅ Alkoxy or C of (2) ₂ To C ₅ Alkenyl, C ₂ To C ₅ Alkynyl of (a); r is R ₄ Selected from the group consisting ofH. F, C which is unsubstituted or substituted by F ₁ To C ₅ Alkyl, C of (2) ₁ To C ₅ Alkoxy, C ₂ To C ₅ Alkenyl or C of (2) ₂ To C ₅ Alkynyl of (a);

wherein n is 0, 1 or 2, M is selected from C or O, and X is selected fromR ₂₁ 、R ₂₂ Each independently selected from H,R ₂₁ And R is ₂₂ Not simultaneously selected from H, and X, R ₂₁ And R is ₂₂ Contains at least one sulfur atom;

based on the mass of the electrolyte, the mass percentage of the compound shown in the formula (I) is p percent, the mass percentage of the compound shown in the formula (II) is q percent, p is more than or equal to 0.01 and less than or equal to 3, and p/q is more than or equal to 0.002 and less than or equal to 60.

2. The electrochemical device according to claim 1, wherein 0.05.ltoreq.q.ltoreq.5.

3. The electrochemical device of claim 1, wherein 0.1.ltoreq.p.ltoreq. 1,0.003.ltoreq.p/q.ltoreq.2.

4. The electrochemical device of claim 1, wherein the compound of formula (I) comprises at least one of the following compounds:

5. the electrochemical device of claim 1, wherein the compound of formula (II) comprises at least one of the following compounds:

6. the electrochemical device according to claim 1, wherein a tab sealant is provided on the tab, a width of the tab sealant exceeding a maximum width of the tab in a direction perpendicular to an extending direction of the tab is Amm, a is 1.8.ltoreq.a.ltoreq.2.6, and a thickness of the tab sealant is 75 μm to 85 μm.

7. The electrochemical device according to claim 6, wherein 1.ltoreq.A/p.ltoreq.30.

8. The electrochemical device of claim 1, wherein the electrochemical device further comprises a pouch having a cavity, the electrode assembly and the electrolyte being disposed in the cavity, the pouch comprising a top seal for sealing the cavity, the tab being connected to the electrode assembly and protruding from the top seal;

along the extending direction of the electrode lug, the sealing width of the top sealing edge is D mm, and D is more than or equal to 1.0 and less than or equal to 1.7.

9. The electrochemical device according to claim 8, wherein 1.ltoreq.d/p.ltoreq.20.

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