CN117577959A - Electrochemical device and electronic device - Google Patents

Electrochemical device and electronic device Download PDF

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Publication number
CN117577959A
CN117577959A CN202311785375.9A CN202311785375A CN117577959A CN 117577959 A CN117577959 A CN 117577959A CN 202311785375 A CN202311785375 A CN 202311785375A CN 117577959 A CN117577959 A CN 117577959A
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electrolyte
electrochemical device
ltoreq
formula
mass
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刘建禹
崔辉
唐超
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)

Abstract

The application provides an electrochemical device and an electronic device. The electrochemical device comprises an electrode assembly and electrolyte, wherein the electrode assembly is of a winding structure, the electrode assembly comprises a bending part and a straight part, the maximum length of the straight part is L mm, the maximum radius of the bending part is D mm, and L/D is more than or equal to 5 and less than or equal to 10; the electrolyte comprises a compound shown in a formula (I), wherein the mass percentage of the compound shown in the formula (I) is A% which is more than or equal to 30 and less than or equal to 80 based on the mass of the electrolyte. The high-temperature cycle performance of the electrochemical device is improved by combining the L/D regulation and the electrolyte component regulation of the electrode assembly.

Description

Electrochemical device and electronic device
Technical Field
The present disclosure 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 applied to various fields of portable electric energy storage, electronic equipment, electric automobiles and the like. With the rapid development of applications of lithium ion batteries in consumer terminals and other fields, the performance requirements of the market on lithium ion batteries are also higher and higher, such as high-temperature cycle performance. As an important component of lithium ion batteries, there is an urgent need for improvement in the electrode assembly and the electrolyte to obtain lithium ion batteries having good high temperature cycle performance.
Disclosure of Invention
An object of the present application is to provide an electrochemical device and an electronic device to improve high-temperature cycle performance of the electrochemical device. The specific technical scheme is as follows:
the first aspect of the present application provides an electrochemical device comprising an electrode assembly and an electrolyte, the electrode assembly being of a wound structure, wherein the electrode assembly comprises a curved portion and a straight portion, the maximum length of the straight portion being L mm, the maximum radius of the curved portion being D mm, 5.ltoreq.L/D.ltoreq.10; the electrolyte comprises a compound shown as a formula (I):
R 11 and R is 12 Each independently selected from C substituted or unsubstituted with fluorine 1 To C 10 Alkyl of R 11 And R is 12 At least one of which is substituted with fluorine; based on the mass of the electrolyte, the mass percentage of the compound shown in the formula (I) is A, and A is more than or equal to 30 and less than or equal to 80. The L/D value of the electrode assembly with the winding structure is regulated and controlled within the application range, the compound shown in the formula (I) is added into the electrolyte, and the content of the compound shown in the formula (I) is within the application range, so that the bending part in the electrode assembly has a proper volume ratio, the oxidation resistance of the compound shown in the formula (I) is high, the oxidation reaction between the positive electrode active material and the electrolyte can be reduced, the oxidation window of the electrolyte is widened, the positive electrode interface stability is enhanced, the consumption rate of the electrolyte is reduced, the deletion rate of the electrolyte at the bending part in the electrode assembly is delayed, and the high electrochemical device is improved The temperature cycle performance, while allowing the electrochemical device to have a small direct current resistance at a low SOC.
In some embodiments of the present application, 5.ltoreq.L.ltoreq.30 or 1.ltoreq.D.ltoreq.5. By regulating the value of L or D within the range, the value of L/D can be regulated within the range of the application, which is favorable for limiting the volume ratio of the bending part in the electrode assembly, playing the role of the compound shown in the formula (I), enhancing the stability of the positive electrode interface, reducing the consumption rate of electrolyte, and delaying the rate of loss of the electrolyte at the bending part in the electrode assembly, thereby being favorable for improving the high-temperature cycle performance of the electrochemical device, and simultaneously being favorable for enabling the electrochemical device to have smaller direct current impedance at low SOC.
In some embodiments of the present application, the electrochemical device satisfies any one of the following: a) A is more than or equal to 40 and less than or equal to 75; b) L/D is more than or equal to 7 and less than or equal to 9; c) L is more than or equal to 10 and less than or equal to 20; d) D is more than or equal to 1.5 and less than or equal to 2.5. By regulating the parameters, the volume ratio of the bending part in the electrode assembly is proper, the compound shown in the formula (I) can be used more favorably, the stability of an anode interface is enhanced, the consumption rate of electrolyte is reduced, the rate of loss of the electrolyte at the bending part in the electrode assembly is delayed, the high-temperature cycle performance of the electrochemical device is further improved, and meanwhile, the electrochemical device has smaller direct current impedance at a low SOC.
In some embodiments of the present application, the width of the electrode assembly is W mm, W=L+2D and 10.ltoreq.W.ltoreq.40. The width W of the electrode assembly is in the above range, which is more advantageous in reducing the consumption rate of the electrolyte and retarding the rate of the electrolyte loss at the bent portion of the electrode assembly, thereby being advantageous in improving the high-temperature cycle performance of the electrochemical device and also in making the electrochemical device have a small direct current impedance at a low SOC.
In some embodiments of the present application, the compound of formula (I) includes at least one of the following compounds:
in the electrochemical device, the electrolyte comprises the compound shown in the formula (I) in the range, so that the antioxidation effect of the compound shown in the formula (I) can be better exerted, the electrochemical device has good positive electrode interface stability, the consumption rate of the electrolyte is reduced, and the rate of loss of the electrolyte at the bending part in the electrode assembly is delayed, thereby being beneficial to improving the high-temperature cycle performance of the electrochemical device, and simultaneously being beneficial to enabling the electrochemical device to have smaller direct current impedance under low SOC.
In some embodiments of the present application, the electrolyte comprises a non-fluorinated carboxylic ester comprising at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; based on the mass of the electrolyte, the mass percentage of the non-fluorinated carboxylic ester is B.ltoreq.B.ltoreq.60. The non-fluorinated carboxylic ester of the type is further introduced into the electrolyte, and the mass percent B% of the non-fluorinated carboxylic ester is regulated and controlled within the range, so that the electrolyte has proper viscosity, the wettability of an anode interface and a cathode interface is improved, polarization is reduced, the high-temperature cycle performance of the electrochemical device is improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC.
In some embodiments of the present application, the electrolyte comprises a cyclic carbonate comprising at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or ethylene carbonate; based on the mass of the electrolyte, the mass percentage of the cyclic carbonate is C.ltoreq.C.ltoreq.10. The cyclic carbonate is further introduced into the electrolyte, and the mass percent C% of the cyclic carbonate is regulated and controlled within the range, so that the dissociation of lithium salt is facilitated, the conductivity of the electrolyte is improved, the anion film formation of the lithium salt is facilitated, the solvation structure of the electrolyte is regulated, the stability of an anode interface and a cathode interface is enhanced, the high-temperature cycle performance of an electrochemical device is improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC.
In some embodiments of the present application, the electrolyte comprises a nitrile additive comprising at least one of succinonitrile, glutaronitrile, adiponitrile, pimelic acid dinitrile, xin Erjing, methylglutaronitrile, 1,3, 5-valeronitrile, 1,2, 3-propionitrile, 1,3, 6-hexanetrinitrile or 1,2, 3-tris (2-cyanoethoxy) propane; based on the mass of the electrolyte, the mass percentage of the nitrile additive is E.ltoreq.E.ltoreq.10. The electrolyte is further introduced with the nitrile additive of the type, and the mass percent E% of the nitrile additive is regulated and controlled within the range, so that the stability of an anode interface can be further enhanced, the high-temperature cycle performance of the electrochemical device is improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC.
In some embodiments of the present application, the electrolyte comprises a boron-containing compound comprising at least one of lithium bis (1, 1-trifluoromethyl oxalic acid) borate, lithium bis (1-trifluoromethyl oxalic acid) borate, lithium difluoro (1, 1-trifluoromethyl) oxalate borate, lithium difluoro oxalate borate (LiDFOB), lithium bis (1, 1-trifluoromethyl malonic acid) borate, lithium fluoro malonic acid difluoro borate, or lithium bis (fluoro malonic acid) borate; based on the mass of the electrolyte, the mass percentage of the boron-containing compound is F.0.01-2. The electrolyte comprises the boron-containing compound of the type, and the mass percentage content F% of the boron-containing compound is regulated and controlled within the range, so that the stability of an anode interface and a cathode interface can be enhanced in cooperation with the compound shown in the formula (I), the high-temperature cycle performance of the electrochemical device can be improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC.
A second aspect of the present application provides an electronic device comprising the electrochemical device provided in the first aspect of the present application.
The beneficial effects of this application:
the application provides an electrochemical device and an electronic device. The electrochemical device comprises an electrode assembly and electrolyte, wherein the electrode assembly is of a winding structure, the electrode assembly comprises a bending part and a straight part, the maximum length of the straight part is L mm, the maximum radius of the bending part is D mm, and L/D is more than or equal to 5 and less than or equal to 10; the electrolyte comprises a compound shown in a formula (I), wherein the mass percentage of the compound shown in the formula (I) is A% which is more than or equal to 30 and less than or equal to 80 based on the mass of the electrolyte. According to the electrode assembly with the winding structure, the L/D value of the electrode assembly is regulated and controlled within the application range, the compound shown in the formula (I) is added into the electrolyte, the content of the compound shown in the formula (I) is within the application range, the bending part in the electrode assembly has a proper volume ratio, the oxidation resistance of the compound shown in the formula (I) is high, the oxidation reaction between the positive electrode active material and the electrolyte can be reduced, the oxidation window of the electrolyte is widened, the positive electrode interface stability is enhanced, the consumption rate of the electrolyte is reduced, the loss rate of the electrolyte at the bending part in the electrode assembly is delayed, and therefore the high-temperature cycle performance of an electrochemical device is improved, and meanwhile, the electrochemical device has smaller direct current impedance under a low SOC.
Of course, not all of the above-described advantages need be achieved simultaneously in practicing any one of the products or methods of the present application.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following description will briefly introduce the drawings that are required to be used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are only some embodiments of the present application, and other embodiments may also be obtained according to these drawings to those skilled in the art.
Fig. 1 is a schematic structural view of an electrode assembly according to an embodiment of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments obtained based on the present application by a person skilled in the art are within the scope of the protection of the present application.
In the specific embodiment of the present application, the present application is explained using 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.
A first aspect of the present application provides an electrochemical device comprising an electrode assembly and an electrolyte, as shown in fig. 1, the electrode assembly being of a wound structure, wherein the electrode assembly comprises a curved portion and a straight portion, the maximum length of the straight portion being L mm, the maximum radius of the curved portion being D mm, 5.ltoreq.l/d.ltoreq.10, preferably 7.ltoreq.l/d.ltoreq.9; the electrolyte comprises a compound shown as a formula (I):
R 11 and R is 12 Each independently selected from C substituted or unsubstituted with fluorine 1 To C 10 Alkyl of R 11 And R is 12 At least one of which is substituted with fluorine. In some embodiments of the present application, R 11 And R is 12 Each independently selected from the following groups substituted or unsubstituted with fluorine: methyl, ethyl or propyl, R 11 And R is 12 At least one of which is substituted with fluorine. The mass percentage of the compound shown in the formula (I) is A.ltoreq.A.ltoreq.80, preferably 40.ltoreq.A.ltoreq.75, based on the mass of the electrolyte. For example, L/D may be 5, 6, 6.4, 7, 7.6, 8, 8.3, 9, 10 or a range of any two of the foregoing values. For example, a may be 30, 40, 44, 50, 53, 60, 66, 70, 80 or a range of any two of the foregoing values.
In this application, the maximum radius D of the "bent portion" and the maximum length L of the "straight portion" are measured from the outermost electrode of the rolled electrode assembly (i.e., the electrode directly opposite the package in which the electrode assembly is packaged), and the outermost sides of the bent portion and the outermost sides of the straight portion are alternately connected to form the outermost electrode of the rolled electrode assembly. The outermost side of the bent portion refers to an arc-shaped portion of the outermost electrode of the wound electrode assembly, which includes a first bent portion formed by a first arc and a second bent portion formed by a second arc. The outermost side of the flat portion refers to a flat portion of the outermost electrode of the wound electrode assembly, i.e., an electrode portion between the first curved portion and the second curved portion, which includes the first flat portion and the second flat portion. The "radius of the curved portion" refers to the distance between a line segment between two end points of the first (or second) arc of the first (or second) curved portion and the intersection of the perpendicular bisector of the line segment and the first (or second) arc. Since the electrode assembly has the outermost sides of the two bent portions, a larger value of the radius of the two bent portions is taken as the maximum radius D of the bent portions of the electrode assembly. The "length of the straight portion" refers to the length of the first straight portion and the length of the second straight portion, and since one of the first straight portion and the second straight portion is the winding end of the electrode assembly, a larger value of the length of the straight portion is taken as the maximum length L of the straight portion.
Fig. 1 is a schematic structural view of an electrode assembly according to an embodiment of the present application. The electrode assembly 100 includes a positive electrode tab 101, a negative electrode tab 102, and a separator 103 between the positive electrode tab 101 and the negative electrode tab 102, which are stacked. The wound electrode assembly is flat, wherein in the width (W) direction of the electrode assembly, the outermost electrode of the electrode assembly includes a first bent portion (left side), a second bent portion (right side), a first straight portion (upper side), and a second straight portion (lower side), wherein the second bent portion, the first straight portion, the first bent portion, and the second straight portion are sequentially connected to form the outermost electrode of the electrode assembly. The first curved portion is formed by a first arc along points a, C and B, where point a is the intersection of the first curved portion and the first straight portion and point B is the intersection of the first curved portion and the second straight portion. The second curved portion is formed by a second arc line along a ' point, a C ' point and a B ' point, wherein the a ' point is an intersection of the second curved portion and the first straight portion, and the B ' point is an intersection of the second curved portion and the straight portion of the secondary outer electrode corresponding to the second straight portion. The first straight portion is formed by a line segment between the point a and the point a', and the second straight portion is formed by a line segment between the point B and the point B "(the point B is the end point of the outermost electrode). The point A and the point B are endpoints of a first arc line, the point C is an intersection point of a perpendicular bisector of a line segment between the point A and the point B and the first arc line, and the distance between the line segment between the point A and the point B and the point C is the radius D1 of the first bending part. The point A 'and the point B' are endpoints of a second arc line, the point C 'is an intersection point of a perpendicular bisector of a line segment between the point A' and the point B 'and the second arc line, and the distance between the line segment between the point A' and the point B 'and the point C' is the radius D2 of the second bending part. Both curved portions D1 and D2 take a larger value denoted as the maximum radius D of the curved portion (i.e., the radius D1 of the first curved portion in fig. 1). The length of the line segment between the point A and the point A 'is the length L1 of the first straight part, and the length of the line segment between the point B and the point B' is the length L2 of the second straight part. Both L1 and L2 take larger values to mark the maximum length L of the straight portion (i.e., the length L1 of the first straight portion in FIG. 1)
In the electrochemical device, the electrode assembly is of a winding structure, electrolyte is easy to extrude at the bending part of the electrode assembly due to rebound of the electrode pole piece in the circulation process, and the electrolyte is lost along with continuous consumption of the electrolyte, so that the transmission of lithium ions is influenced, and the high-temperature circulation performance of the electrochemical device is influenced. In addition, at a low state of charge (SOC), for example, 20% SOC, the direct current resistance is too high, thereby affecting the normal operation of the electrochemical device. According to the method, the volume ratio of the bending part in the electrode assembly is limited within a certain range, namely the ratio of the maximum length L of the straight part in the electrode assembly to the maximum radius D of the bending part is limited within a certain range, the compound shown in the formula (I) is introduced into the electrolyte, and the mass percentage content A% of the compound is regulated and controlled within the range, so that the oxidation reaction between the positive electrode active material and the electrolyte can be reduced, the oxidation window of the electrolyte is widened, the electrochemical device has good positive electrode interface stability, the consumption rate of the electrolyte is reduced, the deletion rate of the electrolyte at the bending part in the electrode assembly is delayed, the high-temperature cycle performance of the electrochemical device is improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC and can work normally. When the value of L/D is too small, for example, less than 5, the volume of the bent portion in the electrode assembly is relatively large, the electrolyte is more extruded, the probability of electrolyte deficiency in the bent portion is relatively large, the compound represented by the formula (I) has a limited effect, and the effects of reducing the consumption rate of the electrolyte and delaying the rate of electrolyte deficiency are weak, so that the effect of improving the high-temperature cycle performance of the electrochemical device is weak. When the value of L/D is too large, for example, greater than 10, the volume of the bent portion in the electrode assembly is small, the extrusion of the electrolyte is small, the loss probability of the electrolyte in the bent portion is small, and the effect of adding the compound shown in the formula (I) into the electrolyte to improve the high-temperature cycle performance of the electrochemical device is weak, so that the impedance of the electrochemical device is easily increased and the polarization is increased. When A is too small, for example, less than 30, the content of the compound represented by the formula (I) is too low, the effect of enhancing the stability of the positive electrode interface is weak, and the effect of reducing the electrolyte consumption rate and delaying the electrolyte deficiency rate is also weak, thereby being unfavorable for improving the high-temperature cycle performance of the electrochemical device. When a is excessively large, for example, more than 80, the content of the compound represented by formula (I) is excessively high, the impedance of the electrochemical device is increased, and polarization is increased, thereby being unfavorable for improving the high-temperature cycle performance of the electrochemical device, and simultaneously, the direct current impedance of the electrochemical device at a low SOC is also excessively high, which affects the normal operation of the electrochemical device. According to the method, the L/D value of the electrode assembly with the winding structure is regulated and controlled within the range of the application, the compound shown in the formula (I) is added into the electrolyte, and the mass percentage content A% of the compound shown in the formula (I) is regulated and controlled within the range of the application, so that the bending part in the electrode assembly has a proper volume ratio, the antioxidation effect of the compound shown in the formula (I) can be exerted, the stability of an interface of the positive electrode is enhanced, the consumption rate of the electrolyte is reduced, the loss rate of the electrolyte at the bending part in the electrode assembly is delayed, the high-temperature cycle performance of the electrochemical device is improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC.
In some embodiments of the present application, 5.ltoreq.L.ltoreq.30, preferably 10.ltoreq.L.ltoreq.20. For example, L may be 5, 10, 12, 15, 18, 20, 25, 30 or a range of any two of the foregoing values. By regulating the value of L within the range, the value of L/D can be regulated within the range of the application, which is favorable for limiting the volume ratio of the bending part in the electrode assembly, playing the role of the compound shown in the formula (I), enhancing the stability of the positive electrode interface, reducing the consumption rate of electrolyte, and delaying the rate of loss of the electrolyte at the bending part in the electrode assembly, thereby being favorable for improving the high-temperature cycle performance of the electrochemical device and simultaneously being favorable for enabling the electrochemical device to have smaller direct current impedance under low SOC.
In some embodiments of the present application, 1.ltoreq.D.ltoreq.5, preferably 1.5.ltoreq.D.ltoreq.2.5. For example, D may be 1, 1.5, 2, 2.5, 3, 3.4, 4, 5 or a range of any two of the foregoing values. The value of L/D can be regulated and controlled within the range by regulating and controlling the value of D, so that the volume ratio of the bending part in the electrode assembly is limited, the effect of the compound shown in the formula (I) is exerted, the stability of an anode interface is enhanced, the consumption rate of electrolyte is reduced, and the rate of loss of the electrolyte at the bending part in the electrode assembly is delayed, thereby being beneficial to improving the high-temperature cycle performance of an electrochemical device, and simultaneously being beneficial to enabling the electrochemical device to have smaller direct current impedance under low SOC.
In some embodiments of the present application, the width of the electrode assembly is W mm, W=L+2D and 10.ltoreq.W.ltoreq.40. For example, W may be 10, 15, 20, 23, 25, 28, 30, 35, 40 or a range of any two of the foregoing values. The width W of the electrode assembly is in the above range, and the electrode assembly is smaller in size and more suitable for small electronic devices such as watches, but the volume ratio of the bending part in the electrode assembly of small size is larger, the extrusion of electrolyte is more, and the electrolyte loss probability of the bending part is larger. The compound shown in the formula (I) is introduced into the electrolyte of the electrochemical device, and the mass percentage content A% of the compound is regulated and controlled within the scope of the application, and as the oxidation resistance of the compound shown in the formula (I) is high, the oxidation reaction between the positive electrode active material and the electrolyte can be reduced, the oxidation window of the electrolyte is widened, the electrochemical device has good positive electrode interface stability, the consumption rate of the electrolyte is more beneficial to reducing, the depletion rate of the electrolyte at the bending part in the electrode assembly is delayed, the high-temperature cycle performance of the electrochemical device is improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC.
In some embodiments of the present application, the compound of formula (I) includes at least one of the following compounds:
In the electrochemical device, the electrolyte comprises the compound shown in the formula (I) in the range, and the antioxidation effect of the compound shown in the formula (I) can be better exerted, so that the electrochemical device has good positive electrode interface stability, the consumption rate of the electrolyte is reduced, the loss rate of the electrolyte at the bending part in the electrode assembly is delayed, the high-temperature cycle performance of the electrochemical device is improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC.
In some embodiments of the present application, the electrolyte comprises a non-fluorinated carboxylic ester comprising at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; based on the mass of the electrolyte, the mass percentage of the non-fluorinated carboxylic ester is B.ltoreq.B.ltoreq.60. For example, B may be 10, 20, 26, 30, 38, 40, 44, 50, 60 or a range of any two of the foregoing values. The compound shown in the formula (I) has high viscosity, so that the electrolyte has poor wettability to a positive electrode interface and a negative electrode interface. The non-fluorinated carboxylic ester is similar to the compound shown in the formula (I) in structure, has good affinity and small viscosity, and the non-fluorinated carboxylic ester is further introduced based on the compound shown in the formula (I) and the mass percent B% of the non-fluorinated carboxylic ester is regulated and controlled in the range, so that the electrolyte has proper viscosity, the wettability of an anode interface and a cathode interface is improved, polarization is reduced, the high-temperature cycle performance of an electrochemical device is improved, and meanwhile, the electrochemical device has small direct current impedance under low SOC.
In some embodiments of the present application, the electrolyte comprises a cyclic carbonate comprising at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or ethylene carbonate; based on the mass of the electrolyte, the mass percentage of the cyclic carbonate is C.ltoreq.C.ltoreq.10. For example, C may be 0, 2, 3.4, 4, 5, 6, 8, 10 or a range of any two of the foregoing values. The compound shown in the formula (I) has poorer dissociation on lithium salt, and the cyclic carbonic ester is further introduced and the mass percent C% of the cyclic carbonic ester is regulated and controlled within the range on the basis of the compound shown in the formula (I), so that the dissociation of the lithium salt is facilitated, the conductivity of electrolyte is improved, the anion film formation of the lithium salt is facilitated, the solvation structure of the electrolyte is regulated, the stability of an anode interface and a cathode interface is enhanced, the high-temperature cycle performance of an electrochemical device is improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC.
In some embodiments of the present application, the electrolyte comprises a nitrile additive comprising at least one of succinonitrile, glutaronitrile, adiponitrile, pimelic acid dinitrile, xin Erjing, methylglutaronitrile, 1,3, 5-valeronitrile, 1,2, 3-propionitrile, 1,3, 6-hexanetrinitrile or 1,2, 3-tris (2-cyanoethoxy) propane; based on the mass of the electrolyte, the mass percentage of the nitrile additive is E.ltoreq.E.ltoreq.10, preferably 2.ltoreq.E.ltoreq.6. For example, E may be 2, 4, 5, 6, 6.5, 8, 10 or a range of any two of the foregoing values. The nitrile additive can be complexed with high-valence metal ions in the positive electrode active material to stabilize the positive electrode interface, the nitrile additive of the type is further introduced on the basis of the compound shown in the formula (I) and the mass percent E% of the nitrile additive is regulated and controlled in the range, so that the stability of the positive electrode interface can be further enhanced, the high-temperature cycle performance of the electrochemical device can be improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC.
In some embodiments of the present application, the electrolyte comprises a boron-containing compound comprising at least one of lithium bis (1, 1-trifluoromethyl oxalic acid) borate, lithium bis (1-trifluoromethyl oxalic acid) borate, lithium difluoro (1, 1-trifluoromethyl) oxalate borate, lithium difluoro oxalate borate, lithium bis (1, 1-trifluoromethyl malonic acid) borate, lithium fluoro malonic acid difluoro borate, or lithium bis (fluoro malonic acid) borate; the mass percentage of the boron-containing compound is F.ltoreq.F.ltoreq.2, preferably 0.01.ltoreq.F.ltoreq.1, based on the mass of the electrolyte. For example, F may be 0.01, 0.3, 0.4, 0.8, 1, 1.4, 1.8, 2 or a range of any two of the foregoing values. The compound shown in the formula (I) can enhance the stability of a positive electrode interface, and the boron-containing compound can form a stable Solid Electrolyte Interface (SEI) film on a negative electrode, so that the stability of the negative electrode interface is enhanced. The boron-containing compound of the type is further introduced on the basis of the compound shown in the formula (I) and the mass percentage content F% of the boron-containing compound is regulated and controlled within the range, so that the stability of an anode interface and a cathode interface can be synergistically enhanced, the high-temperature cycle performance of an electrochemical device is improved, and meanwhile, the electrochemical device has smaller direct current impedance under low SOC.
In this application, the electrolyte also includes other organic solvents and other additives. The kind of other organic solvents and other additives is not particularly limited in the present application, as long as the objects of the present application can be achieved. For example, the number of the cells to be processed, other organic solvents may include, but are not limited to, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl Propyl Carbonate (MPC), ethylene Propyl Carbonate (EPC), methyl Ethyl Carbonate (MEC), fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate at least one of trifluoromethyl ethylene carbonate, gamma-butyrolactone, decalactone, valerolactone, caprolactone, dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, dimethylsulfoxide, 1, 2-dioxolane, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. Other additives may include, but are not limited to, at least one of 1, 3-propane sultone, vinyl sulfate, vinylene carbonate.
In some embodiments of the present application, the sum of the mass percentages of other organic solvents and other additives is G.ltoreq.G.ltoreq.40, based on the mass of the electrolyte. For example, G may be 0, 10, 15, 20, 22, 25, 30, 33, 35, 40 or a range of any two of the foregoing values.
In the present application, the electrolyte further includes a lithium salt, and the kind of the lithium salt is not particularly limited as long as the object of the present application can be achieved. For example, the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate, lithium bis (fluorosulfonyl) imide, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluorooxalato borate, or lithium difluorophosphate. Preferably, the lithium salt comprises lithium hexafluorophosphate.
In some embodiments of the present application, the mass percent of lithium salt is H.ltoreq.H.ltoreq.20 based on the mass of the electrolyte. For example, H may be 10, 12, 14, 15, 16, 18, 20 or a range of any two of the foregoing values.
In some embodiments of the present application, the electrolyte may include a lithium salt, a compound of formula (I), a cyclic carbonate, other organic solvents, and other additives. The mass percentages of the lithium salt, the compound of formula (I), the cyclic carbonate, other organic solvents and other additives are as described above. The electrochemical device comprising the electrolyte has good high-temperature cycle performance and small direct current impedance at low SOC.
In some embodiments of the present application, the electrolyte may include any one of a lithium salt, a compound represented by formula (I), a cyclic carbonate, other organic solvents and other additives, and a non-fluorinated carboxylate, a nitrile additive, a boron-containing compound. The mass percentages of lithium salt, compound of formula (I), cyclic carbonate, other organic solvents and other additives, non-fluorocarboxylic acid ester, nitrile additive, and boron-containing compound are as described above. The electrochemical device comprising the electrolyte has good high-temperature cycle performance and small direct current impedance at low SOC.
In some embodiments of the present application, the electrolyte may include at least one of a lithium salt, a compound of formula (I), a cyclic carbonate, a non-fluorinated carboxylate, other organic solvents and other additives, and a nitrile additive, a boron-containing compound. The mass percentage of the compound shown in the formula (I) is 30-75%, the mass percentage of the non-fluorinated carboxylic ester is 10-55%, and the mass percentage of the lithium salt, the cyclic carbonate, other organic solvents and other additives, the nitrile additive and the boron-containing compound are as described above. The electrochemical device comprising the electrolyte has good high-temperature cycle performance and small direct current impedance at low SOC.
In some embodiments of the present application, the electrolyte may include lithium salts, compounds of formula (I), cyclic carbonates, nitrile additives, boron-containing compounds, other organic solvents, and other additives. The mass percentages of the lithium salt, the compound of formula (I), the cyclic carbonate, the nitrile additive, the boron-containing compound, the other organic solvent and the other additive are as described above. The electrochemical device comprising the electrolyte has good high-temperature cycle performance and small direct current impedance at low SOC.
In this application, electrode assembly includes positive pole piece, negative pole piece and barrier film, and the barrier film is used for separating positive pole piece and negative pole piece, prevents electrochemical device internal short circuit, allows electrolyte ion free passage, and does not influence the going on of electrochemical charge-discharge process.
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 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 present application 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 thickness of the positive electrode sheet is 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. The chemical formula of the lithium-rich manganese-based material is LiMnO.LiMO, and M can comprise Ni, co or Mn. In this 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, calcia, boria, 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, thereby improving the service life of the electrochemical device.
The positive electrode active material layer may further include a positive electrode conductive agent and a positive electrode binder, the kinds of which are not particularly limited as long as the objects of the present application can be achieved, and for example, the positive electrode binder may include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropylcellulose, diacetylcellulose, polyvinylchloride, carboxylated polyvinylchloride, polyvinylfluoride, an ethyleneoxy-containing polymer, 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. 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 positive electrode conductive agent and the positive electrode binder in the positive electrode active material layer is not particularly limited, and may be selected according to actual needs as long as the purposes 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, 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), li-Sn alloy, 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 an anode binder and an anode conductive agent, or the anode active material layer may further include an anode binder, an anode conductive agent, and a thickener. The types of the negative electrode binder and the negative electrode conductive agent are not particularly limited as long as the object of the present application can be achieved, and for example, the negative electrode binder may include, but is not limited to, at least one of the positive electrode binders described above, and the negative electrode conductive agent may include, but is not limited to, at least one of the positive electrode conductive agents described above. 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 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 inorganic particles are not particularly limited herein, and may include, for example, 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 is not particularly limited, and may be at least one of the positive electrode binders described above, for example. The polymer layer contains a polymer, and the polymer is not particularly limited herein, and includes, for example, at least one of polyamide, polyacrylonitrile, acrylate 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 50 μm.
The electrochemical device of the present application further includes a package for accommodating the positive electrode tab, the separator, the negative electrode tab, and the electrolyte, and other components known in the art in the electrochemical device, and the present application is not particularly limited. The packaging bag is not particularly limited, and may be a packaging bag known in the art as long as the object of the present application can be achieved. For example, an aluminum plastic film package may be used.
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 of the present application, the electrochemical device may include, but is not limited to: lithium ion batteries, sodium ion batteries, lithium polymer electrochemical devices, lithium ion polymer electrochemical devices, and the like.
The process of preparing the electrochemical device 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, winding and folding the positive electrode plate, the isolating film and the negative electrode plate 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, fixing four corners of the whole lamination structure by using adhesive tapes 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.
A 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 high-temperature cycle performance, so that the electronic device provided by the application has longer service life and good performance.
The electronic device of the present application is not particularly limited, and may be any electronic device known in the art. For example, 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 hand-held cleaner, a portable CD, a mini-compact disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flash, a camera, a household large-sized battery, and a lithium ion capacitor.
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:
testing of maximum length L of straight portion and maximum length D of curved portion of electrode assembly
And (3) adopting an electronic Computer Tomography (CT) to amplify to 300% multiplying power, and scanning the bent part and the straight part of the electrode assembly in the lithium ion battery to obtain a cross-sectional image. The length of the first straight portion is measured and denoted as L1, the length of the second straight portion is measured and denoted as L2, and the maximum value of the two is taken as the maximum length of the straight portion L. The radius of the first curved portion is measured and denoted as D1, the radius of the second curved portion is measured and denoted as D2, and the maximum value of the two is taken as the maximum radius D of the curved portion.
Testing of high temperature cycle performance
The test temperature was adjusted to 45℃constant temperature. The lithium ion battery is charged to 4.48V at a constant current of 1C, then charged to 0.05C at a constant voltage of 4.48V, and then discharged to 3.0V at a constant current of 1C, which is a charge-discharge cycle, and the first cycle is recorded as the discharge capacity of the first cycle. And (3) carrying out charge and discharge circulation on the lithium ion battery according to the method, recording the discharge capacity of each circulation until the discharge capacity of the lithium ion battery is reduced to 80% of the discharge capacity of the first circulation, and recording the charge and discharge circulation times, namely recording the circulation number of 45 ℃.
Testing of direct current impedance (DCR)
The test temperature was adjusted to 45℃constant temperature. The lithium ion battery is charged to 4.48V at a constant current of 0.2C, then charged to 0.05C at a constant voltage of 4.48V, and then discharged for 8 hours at a current of 0.1C, so that the state of charge (SOC) of the lithium ion battery is 20% of the SOC. Constant-current discharge at 0.1C for 10s, and recording voltage value as U 1 Then 1C constant current is used for discharging for 1s, and the recorded voltage value is U 2 。
20％SOC DCR＝(U 2 -U 1 )/(1C-0.1C)。
Example 1-1
< preparation of electrolyte >
In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF 6 ) And (3) uniformly mixing the compound shown in the formula (I) and the compound shown in the formula (I-3) to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percentage of the compound of the formula (I-3) is 12.5%, the mass percentage A% is 50%, and the rest is the basic solvent.
< preparation of Positive electrode sheet >
LiCoO as positive electrode active material 2 Conductive carbon black (Super P), positive electrode binder polyvinylidene fluoride (PVDF, weight average molecular weight mw=7×10) 6 ) Mixing according to the mass ratio of 97.5:1:1.5, adding N-methyl pyrrolidone (NMP) as a solvent, and stirring uniformly under the action of a vacuum stirrer to obtain the anode 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.
< preparation of negative electrode sheet >
Artificial graphite as a negative electrode active material, a negative electrode conductive agent Super P, and carboxymethyl cellulose as a thickener (CMC-Na, mw=7x10) 5 ) Negative electrode binder styrene-butadiene rubber (SBR, mw=5×10 6 ) Mixing according to the mass ratio of 97.5:1:0.5:1, adding deionized water as a solvent, and uniformly stirring under the action of a vacuum stirrer to obtain the cathode slurry with the solid content of 50 wt%. Cathode slurryThe material is uniformly coated on one surface of a negative electrode current collector copper foil with the thickness of 8 mu m, and is dried at the temperature of 85 ℃ to obtain a negative electrode plate with a single-side coated negative electrode active material layer with the thickness of 60 mu m. 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.
< preparation of isolation Membrane >
A porous polyethylene film (supplied by Celgard corporation) having a thickness of 7 μm was used as the separator.
< preparation of lithium ion Battery >
And sequentially stacking the prepared positive pole piece, the isolating film and the negative pole piece, wherein the isolating film is positioned between the positive pole piece and the negative pole piece to play a role of isolation, and then winding to obtain the electrode assembly, the maximum length L of the straight part is 9mm, the maximum radius D of the bending part is 1.8mm, the value of L/D is 5, and the width W of the electrode assembly is 12.6mm. And (3) placing the electrode assembly into an aluminum plastic film packaging bag, drying the electrode assembly in a vacuum oven at 85 ℃ for 12 hours to remove water, injecting the prepared electrolyte, and performing vacuum packaging, standing, formation (0.3C constant current is charged to 3.5V, and then 1C constant current is charged to 3.9V), shaping, capacity testing, secondary packaging and other procedures to obtain the lithium ion battery.
Examples 1-2 to 1-6
The procedure of example 1-1 was repeated except that the parameters were adjusted in accordance with Table 1 in < preparation of lithium ion battery >, wherein the positive electrode sheet and the negative electrode sheet were the same in size as in example 1-1 when L and D were changed.
Examples 1 to 7 to 1 to 10
The procedure of examples 1 to 3 was repeated, except that the mass percentage A% of the compound of the formula (I-3) was adjusted in accordance with Table 1 in < preparation of electrolyte >. When the mass percentage A% of the compound of formula (I-3) is changed, the mass percentage of the base solvent is changed, and the mass ratio of EC, PC, DEC and the mass percentage of the lithium salt are unchanged.
Examples 1 to 11 to 1 to 13
The procedure of examples 1 to 3 was repeated except that the type of the compound represented by the formula (I) was changed as shown in Table 1 in the < preparation of electrolyte >.
Example 2-1
The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.
< preparation of electrolyte >
In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF 6 ) And uniformly mixing the compound shown in the formula (I) with the non-fluorinated carboxylic ester propyl propionate shown in the formula (I-3) to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percent of the compound of the formula (I-3) is 12.5%, the mass percent A% is 65%, the mass percent B% is 10%, and the rest is the basic solvent.
Example 2-2
The procedure of example 2-1 was repeated, except that the mass percentage A% of the compound of formula (I-3) and the mass percentage B% of the propyl propionate were adjusted in accordance with Table 2 in < preparation of electrolyte >. When the mass percentage of the compound of formula (I-3) a% and the mass percentage of the propyl propionate B% were varied, the mass ratio of EC, PC, DEC, the mass percentage of the base solvent, and the mass percentage of the lithium salt were unchanged.
Examples 2 to 3
The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.
< preparation of electrolyte >
In an argon atmosphere glove box with the water content being less than 10ppm, uniformly mixing a compound shown in a formula (I) in a formula (I-3) and propyl non-fluorinated carboxylate propionate according to a mass ratio of 30:57.5, and then adding lithium salt lithium hexafluorophosphate (LiPF 6 ) And (5) after uniformly mixing, obtaining the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percentage of (2) is as follows12.5% of the compound of formula (I-3) and the balance of propyl propionate.
Examples 2 to 4 to 2 to 5
The procedure of example 2-2 was repeated except that the type of the non-fluorocarboxylic acid ester was changed as shown in Table 2 in the following description of the electrolyte preparation.
Examples 2 to 6
The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.
< preparation of electrolyte >
In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF 6 ) And uniformly mixing the compound shown in the formula (I) in the formula (I-3) and the nitrile additive succinonitrile to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percent of the compound of the formula (I-3) is 12.5%, the mass percent A% is 50%, the mass percent E% is 2%, and the balance is the base solvent.
Examples 2 to 7 to 2 to 8
The procedure of examples 2 to 6 was repeated, except that the mass percentage E% of succinonitrile was adjusted in accordance with Table 2 in < preparation of electrolyte >. When the mass percentage content E% of succinonitrile is changed, the mass percentage content of the base solvent is changed, and the mass ratio of EC, PC, DEC, the mass percentage content of lithium salt and the mass percentage content A% of the compound of formula (I-3) are unchanged.
Examples 2 to 9
The procedure of examples 2 to 6 was repeated except that the types of the nitrile additives and the mass percentage content E% of the nitrile additives were adjusted in accordance with Table 2 in < preparation of electrolyte >. When the mass percent E% of the nitrile additive is changed, the mass percent of the basic solvent is changed, and the mass ratio of EC, PC, DEC, the mass percent of the lithium salt and the mass percent A% of the compound of the formula (I-3) are unchanged.
Examples 2 to 10
The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.
< preparation of electrolyte >
In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF 6 ) And uniformly mixing the compound shown in the formula (I) with the compound shown in the formula (I-3) and the boron-containing compound lithium dioxalate LiBOB to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percent of the compound of the formula (I-3) is 12.5%, the mass percent A% is 50%, the mass percent F% of LiBOB is 0.01%, and the rest is the base solvent.
Examples 2 to 11 to 2 to 12
The procedure of examples 2 to 10 was repeated except that the mass percentage F% of LiBOB was adjusted as shown in Table 2 in < preparation of electrolyte >. When the mass percentage F% of LiBOB is changed, the mass percentage of the base solvent is changed, and the mass ratio of EC, PC, DEC, the mass percentage of lithium salt and the mass percentage A% of the compound of formula (I-3) are unchanged.
Examples 2 to 13
The procedure of examples 2 to 10 was repeated except that the types of the boron-containing compounds and the mass percentage of the boron-containing compounds F% were adjusted as shown in Table 2 in < preparation of electrolyte >. When the mass percentage F% of the boron-containing compound is changed, the mass percentage of the base solvent is changed, and the mass ratio of EC, PC, DEC, the mass percentage of the lithium salt and the mass percentage A% of the compound of formula (I-3) are unchanged.
Examples 2 to 14
The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.
< preparation of electrolyte >
In an argon atmosphere glove box with a water content of less than 10ppmThe preparation method comprises the steps of uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to a mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF) serving as a lithium salt into the base solvent 6 ) And uniformly mixing the compound shown in the formula (I) with the formula (I-3), the non-fluorinated carboxylic ester propyl propionate and the nitrile additive succinonitrile to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percent of the compound of the formula (I-3) is 12.5%, the mass percent A% is 48%, the mass percent B% is 25%, the mass percent E% is 2%, and the balance is a base solvent.
Examples 2 to 15 to 2 to 16
The procedure of examples 2 to 14 was repeated, except that the mass% A% of the compound of the formula (I-3) and the mass% E% of succinonitrile were adjusted in accordance with Table 2 in < preparation of electrolyte >. When the mass percent A% of the compound of formula (I-3) and the mass percent E% of succinonitrile were varied, the mass ratio of EC, PC, DEC, the mass percent of the base solvent, the mass percent of the lithium salt, and the mass percent B% of the propyl propionate were unchanged.
Examples 2 to 17
The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.
< preparation of electrolyte >
In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF 6 ) And uniformly mixing the compound shown in the formula (I) with the formula (I-3), the non-fluorinated carboxylic acid ester propyl propionate and the boron-containing compound LiBOB to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 12.5% by mass, 50% by mass of the compound of the formula (I-3) A%, 25% by mass of the propyl propionate B% and 0.01% by mass F% of LiBOBThe balance being the base solvent.
Examples 2 to 18 to examples 2 to 19
The procedure of examples 2 to 17 was repeated except that the mass percentage F% of LiBOB was adjusted as shown in Table 2 in < preparation of electrolyte >. When the mass percentage F% of LiBOB is changed, the mass percentage of the basic solvent is changed, and the mass percentage of EC, PC, DEC, the mass percentage of lithium salt, the mass percentage A of the compound of the formula (I-3) and the mass percentage B of propyl propionate are unchanged.
Examples 2 to 20
The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.
< preparation of electrolyte >
In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF 6 ) And uniformly mixing the compound shown in the formula (I) with the formula (I-3), the nitrile additive succinonitrile and the boron-containing compound LiBOB to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percent of the compound of the formula (I-3) is 12.5%, the mass percent A% is 50%, the mass percent E% is 2%, the mass percent F% of LiBOB is 0.3%, and the rest is a base solvent.
Examples 2 to 21 to 2 to 22
The procedure of examples 2 to 20 was repeated, except that the mass percentage E% of succinonitrile was adjusted in accordance with Table 2 in < preparation of electrolyte >. When the mass percent E% of succinonitrile is changed, the mass percent of the basic solvent is changed, and the mass percent of EC, PC, DEC, the mass percent of lithium salt, the mass percent A of the compound of formula (I-3) and the mass percent F% of LiBOB are unchanged.
Examples 2 to 23
The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.
< preparation of electrolyte >
In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF 6 ) And uniformly mixing the compound shown in the formula (I) with the formula (I-3), non-fluorinated carboxylic acid ester propyl propionate, nitrile additive succinonitrile and boron-containing compound LiBOB to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percent of the compound of the formula (I-3) is 12.5%, the mass percent A% is 62.7%, the mass percent B% is 10%, the mass percent E% is 2%, the mass percent F% is 0.3%, and the balance is the base solvent.
Examples 2 to 24
The procedure of examples 2 to 23 was repeated, except that the mass% A% of the compound of the formula (I-3) and the mass% B% of the propyl propionate were adjusted in accordance with Table 2 in < preparation of electrolyte >. When the mass percent A% of the compound of formula (I-3) and the mass percent B% of the propyl propionate were varied, the mass ratio of EC, PC, DEC, the mass percent of the base solvent, the mass percent of the lithium salt, the mass percent E% of succinonitrile, and the mass percent F% of LiBOB were unchanged.
Examples 2 to 25
The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.
< preparation of electrolyte >
In an argon atmosphere glove box with the water content being less than 10ppm, uniformly mixing a compound shown in a formula (I) in a formula (I-3) and non-fluorinated carboxylic ester propyl propionate according to a mass ratio of 50:37.5, and then adding lithium salt lithium hexafluorophosphate (LiPF 6 ) And (5) after uniformly mixing, obtaining the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percent of the (B) is 12.5%, and the rest is the compound of the formula (I-3) and propyl propionate.
Comparative examples 1 to 2
The procedure of example 1-1 was repeated except that the parameters were adjusted in accordance with Table 1 in < preparation of lithium ion battery >. Wherein, when L and D are changed, the sizes of the positive electrode plate and the negative electrode plate are the same as those of the embodiment 1-1.
Comparative example 3
The procedure of examples 1 to 3 was repeated except that the electrolyte was prepared.
< preparation of electrolyte >
In an argon atmosphere glove box with the water content of less than 10ppm, uniformly mixing cyclic Ethylene Carbonate (EC), cyclic Propylene Carbonate (PC) and diethyl carbonate (DEC) serving as other organic solvents according to the mass ratio of 10:10:80 to obtain a base solvent, and then adding lithium hexafluorophosphate (LiPF 6 ) And (5) uniformly mixing to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percentage of the solvent is 12.5 percent, and the rest is basic solvent.
Comparative examples 4 to 5
The procedure of examples 1 to 3 was repeated, except that the mass percentage A% of the compound of the formula (I-3) was adjusted in accordance with Table 1 in < preparation of electrolyte >. When the mass percentage A% of the compound of formula (I-3) is changed, the mass percentage of the base solvent is changed, and the mass ratio of EC, PC, DEC and the mass percentage of the lithium salt are unchanged.
The preparation parameters and performance parameters of each example and comparative example are shown in tables 1 and 2.
TABLE 1
Note that: the "\" in table 1 indicates that there is no corresponding parameter.
As can be seen from examples 1-1 to 1-13 and comparative examples 1 to 5, the electrochemical device of the examples of the present application has a larger number of cycles at 45 ℃ and a smaller 20% soc DCR by controlling the value of L/D of the electrode assembly of the winding structure within the range of the present application and adding the compound represented by formula (I) to the electrolyte, and the mass percentage a% of the compound represented by formula (I) is within the range of the present application. The electrochemical device has better high-temperature cycle performance and smaller direct current impedance at low SOC. Whereas the electrochemical devices of comparative examples 1 and 2, the values of L/D of the electrode assemblies thereof were not within the scope of the present application; the electrochemical device of comparative example 3, in which the compound represented by the formula (I) was not included in the electrolyte; the electrochemical devices of comparative examples 4 and 5, in which the mass percentage content a% of the compound represented by formula (I) in the electrolyte is not within the range of the present application, the electrochemical devices of comparative examples 1 to 5, although the electrochemical device has a smaller 20% SOC DCR, have a smaller number of cycles at 45 ℃, indicating that the high temperature cycle performance of the electrochemical device is worse, and cannot have both good high temperature cycle performance and smaller direct current resistance at low SOC.
The value of L/D of the electrode assembly generally affects the high temperature cycle performance of the electrochemical device. As can be seen from examples 1-1 to 1-6, comparative examples 1 to 2, when the value of L/D is too small, for example, comparative example 1, the number of 45 ℃ cycles of the electrochemical device is smaller; when the value of L/D is too large, for example, comparative example 2, the number of 45℃cycles of the electrochemical device is smaller. Indicating that the electrochemical device has poorer high-temperature cycle performance, and cannot have both good high-temperature cycle performance and smaller direct current impedance at low SOC. When the value of L/D is regulated within the scope of the present application, the compound of formula (I) is advantageous to function, retarding the rate of loss of electrolyte at the bend in the electrode assembly, and thus the electrochemical device has a greater number of cycles at 45 ℃ and a smaller 20% soc DCR. This indicates that the electrochemical device has better high-temperature cycle performance and also has smaller direct current impedance at low SOC.
The mass percent A% of the compound of formula (I) generally affects the high temperature cycle performance of the electrochemical device. It can be seen from examples 1 to 3, examples 1 to 7 to examples 1 to 10, and comparative examples 3 to 5 that when the value of a is too small, for example, comparative examples 3 and 4, the compound represented by formula (I) has a limited effect, and the number of 45 ℃ cycles of the electrochemical device is smaller; when the value of a is too large, for example, comparative example 5, too much of the compound represented by formula (I) increases the direct current resistance of the electrochemical device at low SOC, increases polarization, and the electrochemical device has a smaller number of 45 ℃ cycles and a larger 20% SOC DCR. Indicating that the electrochemical device has poorer high-temperature cycle performance, and cannot have both good high-temperature cycle performance and smaller direct current impedance at low SOC. When the value of A is regulated within the scope of the application, the compound shown in the formula (I) can be used for acting, so that the electrochemical device has larger cycle number at 45 ℃ and smaller 20% SOC DCR. This indicates that the electrochemical device has better high-temperature cycle performance and also has smaller direct current impedance at low SOC.
The kind of the compound represented by formula (I) generally affects the high-temperature cycle performance of the electrochemical device. It can be seen from examples 1 to 3, examples 1 to 7 to examples 1 to 13 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) within the scope of the present application, it is advantageous to exert the effect of the compound represented by formula (I), and the electrochemical device has a large cycle number of 45 ℃ and a small 20% soc DCR. This indicates that the electrochemical device has good high-temperature cycle performance and also has a small direct current resistance at a low SOC.
TABLE 2
/>
Note that: the "\" in table 2 indicates that there is no corresponding parameter.
The mass percent B% of the non-fluorinated carboxylic acid esters generally affects the high temperature cycle performance of the electrochemical device. It can be seen from examples 1-3, 2-1 to 2-3 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) and the cyclic carbonate, and the non-fluorinated carboxylate is further introduced and the mass percentage B% thereof is regulated to be within the scope of the present application, the electrochemical device has a larger number of cycles at 45 ℃ and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance, and also has a smaller direct current resistance at a low SOC. The viscosity of the non-fluorinated carboxylic ester is small, the non-fluorinated carboxylic ester is further introduced into the electrolyte, and the B% is regulated and controlled within the scope of the application, so that the problem of large viscosity of the compound shown in the formula (I) can be solved, the electrolyte has proper viscosity, the wettability of an anode interface and a cathode interface is improved, and polarization is reduced.
The type of non-fluorinated carboxylic acid ester generally affects the high temperature cycle performance of the electrochemical device. As can be seen from examples 1-3, 2-1 to 2-5, when the electrolyte of the electrochemical device includes the compound represented by formula (I) and the cyclic carbonate, the non-fluorinated carboxylate is further introduced, and the non-fluorinated carboxylate within the scope of the present application is selected, the electrochemical device has a larger number of cycles at 45 ℃ and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance while also having a smaller direct current impedance at a low SOC. This is because the viscosity of the non-fluorinated carboxylic ester is small, and the non-fluorinated carboxylic ester in the scope of the application is further introduced into the electrolyte, so that the problem of the large viscosity of the compound shown in the formula (I) can be solved, the electrolyte has proper viscosity, the wettability of the positive electrode interface and the negative electrode interface is improved, and the polarization is reduced.
The mass percent E% of the nitrile additive generally affects the high temperature cycle performance of the electrochemical device. It can be seen from examples 1-3, examples 2-6 to examples 2-8 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) and the cyclic carbonate, the nitrile additive is further introduced and the mass percentage content E% thereof is regulated to be within the scope of the present application, the electrochemical device has a larger number of cycles at 45 ℃ and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance, and also has a smaller direct current resistance at a low SOC. This is because the nitrile additive can stabilize the positive electrode interface, and further introducing the nitrile additive into the electrolyte and controlling E% within the scope of the present application can further enhance the stability of the positive electrode interface.
The type of nitrile additive generally affects the high temperature cycle performance of the electrochemical device. It can be seen from examples 1-3, examples 2-6 to examples 2-9 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) and the cyclic carbonate, the nitrile additive is further introduced, and the nitrile additive within the scope of the present application is selected, the electrochemical device has a larger cycle number of 45 ℃ and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance while also having a smaller direct current resistance at a low SOC. This is because the nitrile additive can stabilize the positive electrode interface, and the nitrile additive within the scope of the present application can be further incorporated into the electrolyte solution, which can further enhance the stability of the positive electrode interface.
The mass percentage f% of the boron-containing compound generally affects the high temperature cycle performance of the electrochemical device. As can be seen from examples 1 to 3, examples 2 to 10 to examples 2 to 12, when the electrolyte of the electrochemical device includes the compound represented by formula (I) and the cyclic carbonate, the boron-containing compound is further introduced and the mass percentage content F% thereof is regulated to be within the scope of the present application, the electrochemical device has a larger number of cycles at 45 ℃ and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance while also having a smaller direct current resistance at a low SOC. This is because the boron-containing compound can form a stable Solid Electrolyte Interface (SEI) film at the anode, enhance the stability of the anode interface, further introduce the boron-containing compound into the electrolyte and regulate F% within the scope of the application, and can synergistically enhance the stability of the anode interface and the anode interface.
The kind of the boron-containing compound generally affects the high temperature cycle performance of the electrochemical device. As can be seen from examples 1 to 3, examples 2 to 10 to examples 2 to 13, when the electrolyte of the electrochemical device includes the compound represented by formula (I) and the cyclic carbonate, the boron-containing compound is further introduced, and the boron-containing compound within the scope of the present application is selected, the electrochemical device has a larger number of cycles at 45 ℃ and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance while also having a smaller direct current resistance at a low SOC. This is because the boron-containing compound can form a stable Solid Electrolyte Interface (SEI) film at the anode, enhance the stability of the anode interface, and further introduce the boron-containing compound within the scope of the present application into the electrolyte, and can synergistically enhance the stability of the cathode interface and the anode interface.
It can be seen from examples 1 to 3, examples 2 to 14 to examples 2 to 24 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) and the cyclic carbonate, at least two of the non-fluorocarboxylic acid ester, the nitrile additive or the boron-containing compound are further introduced, the electrochemical device has a larger cycle number of 45 ℃ and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance while also having a smaller direct current resistance at a low SOC. The compound shown in the formula (I) has good compatibility and superposition property with cyclic carbonate, nitrile additive or boron-containing compound, and the combination of the substances is applied to an electrochemical device, so that the electrochemical device has good high-temperature cycle performance and small direct current impedance under low SOC.
It can be seen from examples 1 to 3, examples 2 to 3 and examples 2 to 25 that when the electrolyte of the electrochemical device includes the compound represented by formula (I) and the non-fluorinated carbonate, but does not include the cyclic carbonate, the electrochemical device has a larger cycle number of 45 ℃ and a smaller 20% SOC DCR, indicating that the electrochemical device has good high-temperature cycle performance while also having a smaller direct current impedance at a low SOC.
It should be noted that 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 present invention is not intended to limit the invention to the particular embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, alternatives, and alternatives falling within the spirit and scope of the invention.

Claims (10)

1. An electrochemical device comprising an electrode assembly and an electrolyte, the electrode assembly being of a rolled structure, wherein,
the electrode assembly comprises a bending part and a straight part, the maximum length of the straight part is L mm, the maximum radius of the bending part is D mm, and L/D is more than or equal to 5 and less than or equal to 10;
the electrolyte comprises a compound shown in a formula (I):
R 11 and R is 12 Each independently selected from C substituted or unsubstituted with fluorine 1 To C 10 Alkyl of R 11 And R is 12 At least one of which is substituted with fluorine;
based on the mass of the electrolyte, the mass percentage of the compound shown in the formula (I) is A.ltoreq.A.ltoreq.80.
2. The electrochemical device of claim 1, wherein 5.ltoreq.l.ltoreq.30 or 1.ltoreq.d.ltoreq.5.
3. The electrochemical device of claim 1, wherein the electrochemical device satisfies any one of the following:
a)40≤A≤75；
b)7≤L/D≤9；
c)10≤L≤20；
d)1.5≤D≤2.5。
4. the electrochemical device of claim 1, wherein the width of the electrode assembly is W mm, W = l+2d and 10+.w+.40.
5. The electrochemical device of claim 1, wherein the compound of formula (I) comprises at least one of the following compounds:
6. the electrochemical device of claim 1, wherein the electrolyte comprises a non-fluorinated carboxylic ester comprising at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate;
Based on the mass of the electrolyte, the mass percentage of the non-fluorinated carboxylic ester is B.ltoreq.B.ltoreq.60.
7. The electrochemical device of claim 1, wherein the electrolyte comprises a cyclic carbonate comprising at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or ethylene carbonate;
based on the mass of the electrolyte, the mass percentage of the cyclic carbonate is C.ltoreq.C.ltoreq.10.
8. The electrochemical device of claim 1, wherein the electrolyte comprises a nitrile additive comprising at least one of succinonitrile, glutaronitrile, adiponitrile, pimelic acid dinitrile, xin Erjing, methylglutaronitrile, 1,3, 5-valeronitrile, 1,2, 3-propionitrile, 1,3, 6-hexanetrinitrile, or 1,2, 3-tris (2-cyanoethoxy) propane;
based on the mass of the electrolyte, the mass percentage of the nitrile additive is E.ltoreq.E.ltoreq.10.
9. The electrochemical device of claim 1, wherein the electrolyte comprises a boron-containing compound comprising at least one of lithium bis (1, 1-trifluoromethyl oxalate) borate, lithium bis (1-trifluoromethyl oxalate) borate, lithium difluoro (1, 1-trifluoromethyl) oxalate borate, lithium difluoro oxalate borate, lithium dioxalate borate, lithium bis (1, 1-trifluoromethyl malonate) borate, lithium fluoro malonate difluoroborate, or lithium bis (fluoro malonate) borate;
Based on the mass of the electrolyte, the mass percentage of the boron-containing compound is F.0.01-2.
10. An electronic device comprising the electrochemical device of any one of claims 1 to 9.
CN202311785375.9A 2023-12-22 2023-12-22 Electrochemical device and electronic device Pending CN117577959A (en)

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