CN117543095A - Electrochemical device and electronic device - Google Patents

Electrochemical device and electronic device Download PDF

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Publication number
CN117543095A
CN117543095A CN202311260329.7A CN202311260329A CN117543095A CN 117543095 A CN117543095 A CN 117543095A CN 202311260329 A CN202311260329 A CN 202311260329A CN 117543095 A CN117543095 A CN 117543095A
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China
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edge
positive electrode
electrochemical device
active material
width direction
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CN202311260329.7A
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Inventor
李巍巍
李春华
韩翔龙
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Xiamen Xinneng'an Technology Co ltd
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Xiamen Xinneng'an Technology Co ltd
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Priority to CN202311260329.7A priority Critical patent/CN117543095A/en
Publication of CN117543095A publication Critical patent/CN117543095A/en
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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
    • H01M10/42—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
    • 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
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/61—Types of temperature control
    • H01M10/613—Cooling or keeping cold
    • 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
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/65—Means for temperature control structurally associated with the cells
    • H01M10/653—Means for temperature control structurally associated with the cells characterised by electrically insulating or thermally conductive materials
    • 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
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/65—Means for temperature control structurally associated with the cells
    • H01M10/654—Means for temperature control structurally associated with the cells located inside the innermost case of the cells, e.g. mandrels, electrodes or electrolytes
    • 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
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/65—Means for temperature control structurally associated with the cells
    • H01M10/655—Solid structures for heat exchange or heat conduction
    • H01M10/6551—Surfaces specially adapted for heat dissipation or radiation, e.g. fins or coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/584—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries
    • H01M50/59—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries characterised by the protection means
    • H01M50/593—Spacers; Insulating plates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The application provides an electrochemical device and an electronic device, wherein the electrochemical device comprises an electrode assembly and is formed by sequentially laminating and winding a positive electrode plate, a diaphragm and a negative electrode plate. The positive pole piece comprises a first edge and a second edge, the diaphragm comprises a third edge and a fourth edge, and the negative pole piece comprises a fifth edge and a sixth edge. The positive pole piece sequentially comprises a first empty foil area, an insulating coating and a positive pole active material coating from a first edge to a second edge, the edge, close to the first edge, of the insulating coating is a coating edge, and along the direction from the first edge to the second edge, the third edge and the fifth edge are sequentially far away from the coating edge. The distance between the coating edge and the third edge is a, the distance between the third edge and the fifth edge is b, the width of the diaphragm is c, the shrinkage rate of the diaphragm in the width direction is d, and the requirements are satisfied: a is more than or equal to 0mm and less than or equal to 1.5mm, and c multiplied by d/2 is more than or equal to b and less than or equal to 1.5mm. The electrochemical device provided by the application has good safety performance and high energy density.

Description

Electrochemical device and electronic device
Technical Field
The present application relates to the field of electrochemistry, and in particular, to an electrochemical device and an electronic device.
Background
Electrochemical devices, such as lithium ion batteries, have many advantages of high specific energy density, long cycle life, high nominal voltage, low self-discharge rate, small volume, light weight, etc., and have wide application in the consumer electronics field.
The design of the high-power lithium ion battery at present generally adopts the design of a multipolar lug or an electrodeless lug without cutting the lug, and the design matched with the design comprises that the positive electrode lug and the negative electrode lug extend out from opposite directions, and the design is prepared by adopting a lug flattening or rubbing technology and a transfer piece welding technology. However, due to the fact that the welding phenomenon often occurs in the conventional transfer piece welding process, the diaphragm is burnt and contracted to cause the contact between the positive pole piece and the negative pole piece, and the lithium ion battery is short-circuited or even on fire, the problem not only reduces the production yield, but also brings potential safety hazards and influences the safety performance of the lithium ion battery. If the distance from the welding area is lengthened, the distance from the diaphragm to the welding area is increased, and although the influence of over-welding on the burnt diaphragm can be reduced, the energy density of the lithium ion battery is seriously influenced. That is, it is difficult to achieve both safety performance and energy density of the current high-power battery.
Disclosure of Invention
An object of embodiments of the present application is to provide an electrochemical device and an electronic device capable of achieving both safety performance and energy density of the electrochemical device.
In the context 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. The specific technical scheme is as follows:
a first aspect of the present application provides an electrochemical device including an electrode assembly formed by sequentially stacking and winding a positive electrode sheet, a separator, and a negative electrode sheet. Along the width direction after the positive pole piece is expanded, the positive pole piece comprises a first edge and a second edge which are opposite, the diaphragm comprises a third edge and a fourth edge which are opposite, and the negative pole piece comprises a fifth edge and a sixth edge which are opposite. The positive electrode plate sequentially comprises a first empty foil area, an insulating coating and a positive electrode active material coating from a first edge to a second edge along the width direction of the expanded positive electrode plate, the edge, close to the first edge, of the insulating coating is a coating edge, and the third edge and the fifth edge are sequentially far away from the coating edge along the direction from the first edge to the second edge. Along the width direction of the expanded positive electrode plate, the distance between the coating edge and the third edge is a, the distance between the third edge and the fifth edge is b, the width of the diaphragm is c, the shrinkage rate of the diaphragm in the width direction is d, and the electrochemical device meets the following conditions: a is more than or equal to 0mm and less than or equal to 1.5mm, and c multiplied by d/2 is more than or equal to b and less than or equal to 1.5mm. Preferably, a is more than or equal to 0.2mm and less than or equal to 1.5mm. According to the method, the edge positions and the lengths of the positive pole piece, the negative pole piece and the diaphragm are regulated, the diaphragm can be covered by the insulating coating of the positive pole piece along the width direction of the expanded positive pole piece, when slight overspray occurs, the heat can be absorbed and diffused by the insulating coating of the positive pole piece in time, the shrinkage of the diaphragm is reduced, and the safety performance is improved while the energy density loss of the electrochemical device is reduced.
In some embodiments of the present application, the first empty foil region has a width g in the width direction of the expanded positive electrode sheet 1 ，0.5mm≤g 1 Less than or equal to 2.5mm. Preferably 0.6 mm.ltoreq.g 1 Less than or equal to 2mm. By controlling g 1 The value of (2) is within the above range, which is advantageous in terms of subtractionThe safety performance of the electrochemical device is improved while the energy density loss of the electrochemical device is reduced.
In some embodiments of the present application, the coating edge is spaced from the fifth edge by a distance h in the width direction of the expanded positive electrode sheet 1 ，0.4mm≤h 1 Less than or equal to 2.5mm. Preferably 0.5 mm.ltoreq.h 1 Less than or equal to 2mm. By regulating and controlling h 1 The value of (2) is within the above range, which is advantageous in improving the safety performance of the electrochemical device while reducing the energy density loss of the electrochemical device.
In some embodiments of the present application, along the width direction of the expanded positive electrode sheet, the negative electrode sheet sequentially includes a negative electrode active material coating layer and a second empty foil region from a fifth edge to a sixth edge, and a fourth edge is disposed between the edge where the negative electrode active material coating layer and the second empty foil region meet and the second edge, a distance between the edge where the second empty foil region and the negative electrode active material coating layer meet and the fourth edge is e, a distance between the second edge and the fourth edge is f,0 mm.ltoreq.e.ltoreq.1.5 mm, and c×d/2.ltoreq.f.ltoreq.1.5 mm. Preferably, e is 0.2 mm.ltoreq.e.ltoreq.1.5 mm. By regulating the values of e and f within the above ranges, the risk of short circuit and thermal runaway of the electrochemical device is reduced, and the safety performance of the electrochemical device is improved while the energy density loss of the electrochemical device is reduced.
In some embodiments of the present application, the second empty foil region has a width g in the width direction of the expanded positive electrode sheet 2 ，0.5mm≤g 2 Less than or equal to 2.5mm. Preferably 0.6 mm.ltoreq.g 2 Less than or equal to 2mm. By controlling g 2 The value of (2) is within the above range, which is advantageous in improving the safety performance of the electrochemical device while reducing the energy density loss of the electrochemical device.
In some embodiments of the present application, the distance between the edge where the second empty foil region meets the anode active material coating layer and the second edge in the width direction after the cathode sheet is unfolded is h 2 ，0.4mm≤h 2 Less than or equal to 2.5mm. Preferably 0.5 mm.ltoreq.h 2 Less than or equal to 2mm. By regulating and controlling h 2 The value of (2) is within the above range, which is advantageous in improving the safety of the electrochemical device while reducing the energy density loss of the electrochemical deviceFull performance.
In some embodiments of the present application, 10 mm.ltoreq.c.ltoreq.600 mm, 0%.ltoreq.d.ltoreq.5%. By regulating the values of e and f within the above range, it is advantageous to reduce the risk of short circuit and thermal runaway of the electrochemical device, thereby improving the safety performance of the electrochemical device.
A second aspect of the present application provides an electronic device comprising an electrochemical device in any of the foregoing embodiments. The electrochemical device can give consideration to safety performance and energy density, so that the electronic device provided by the application has longer service life.
The beneficial effects of the embodiment of the application are that:
the embodiment of the application provides an electrochemical device and an electronic device, wherein the electrochemical device comprises an electrode assembly, and the electrode assembly is formed by sequentially laminating and winding a positive electrode plate, a diaphragm and a negative electrode plate. Along the width direction after the positive pole piece is expanded, the positive pole piece comprises a first edge and a second edge which are opposite, the diaphragm comprises a third edge and a fourth edge which are opposite, and the negative pole piece comprises a fifth edge and a sixth edge which are opposite. The positive electrode plate sequentially comprises a first empty foil area, an insulating coating and a positive electrode active material coating from a first edge to a second edge along the width direction of the expanded positive electrode plate, the edge, close to the first edge, of the insulating coating is a coating edge, and the third edge and the fifth edge are sequentially far away from the coating edge along the direction from the first edge to the second edge. Along the width direction of the expanded positive electrode plate, the distance between the coating edge and the third edge is a, the distance between the third edge and the fifth edge is b, the width of the diaphragm is c, the shrinkage rate of the diaphragm in the width direction is d, and the electrochemical device meets the following conditions: a is more than or equal to 0mm and less than or equal to 1.5mm, and c multiplied by d/2 is more than or equal to b and less than or equal to 1.5mm. Through regulating and controlling above-mentioned parameter in this application scope, the insulating coating of positive pole piece can cover the diaphragm, when slight overseld appears, and the insulating coating of positive pole piece can in time absorb and spread the heat dissipation capacity, reduces the thermal contraction of diaphragm, reduces electrochemical device short circuit and thermal runaway's risk, when reducing electrochemical device energy density loss, has improved electrochemical device's security performance, through above-mentioned setting, can compromise electrochemical device's security performance and energy density.
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 an expanded schematic view of an electrode assembly in some embodiments of the present application;
FIG. 2 is an expanded schematic view of an electrode assembly according to further embodiments of the present application;
fig. 3 is a schematic view of a negative current collecting plate in some embodiments of the present application.
Reference numerals: a positive electrode sheet 10; a first empty foil area 11; an insulating coating 12; a positive electrode active material coating layer 13; a positive electrode flattening region 14; a diaphragm 20; a negative electrode tab 30; a negative electrode active material coating layer 31; a second empty foil area 32; a negative electrode flattening area 33; a negative current collecting plate 34; a negative electrode bonding wire 35; a first edge 101; a second edge 102; a coating edge 103; a third edge 201; a fourth edge 202; a fifth edge 301; sixth edge 302.
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. Based on the embodiments herein, a person of ordinary skill in the art would be able to obtain all other embodiments based on the disclosure herein, which are within the scope of the disclosure herein.
The first aspect of the present application provides an electrochemical device, including an electrode assembly, the electrode assembly is formed by sequentially laminating and winding a separator, a positive electrode sheet, a separator and a negative electrode sheet according to a winding direction, or the electrode assembly is formed by sequentially laminating and winding a positive electrode sheet, a separator, a negative electrode sheet and a separator according to a winding direction. For convenience of understanding, the width direction of the positive electrode sheet after being unfolded is the Y direction, and it can be understood that the width direction of the wound electrode assembly, the negative electrode sheet and the separator is the same as the width direction of the positive electrode sheet after being unfolded. As shown in fig. 1 to 2, in the width direction Y direction of the expanded positive electrode sheet 10, the positive electrode sheet 10 includes opposite first and second edges 101 and 102, the separator 20 includes opposite third and fourth edges 201 and 202, and the negative electrode sheet 30 includes opposite fifth and sixth edges 301 and 302. Along the width direction Y direction of the expanded positive electrode sheet 10, the positive electrode sheet 10 sequentially comprises a first empty foil region 11, an insulating coating 12 and a positive electrode active material coating 13 from a first edge 101 to a second edge 102, wherein the edge of the insulating coating 12 close to the first edge 101 is a coating edge 103, and along the direction from the first edge 101 to the second edge 102, a third edge 201 and a fifth edge 301 are sequentially far away from the coating edge 103. Along the width direction Y direction of the expanded positive electrode sheet 10, the distance between the coating edge 103 and the third edge 201 is a, the distance between the third edge 201 and the fifth edge 301 is b, the width of the separator 20 is c, the shrinkage ratio of the separator 20 in the width direction is d, and the electrochemical device satisfies: a is more than or equal to 0mm and less than or equal to 1.5mm, and c multiplied by d/2 is more than or equal to b and less than or equal to 1.5mm. Preferably, a is more than or equal to 0.2mm and less than or equal to 1.5mm. For example, a is 0mm, 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm or a range of any two values therein. When a is smaller than 0mm, that is, the second edge 102 is located between the first edge 101 and the coating edge 103, when slight overselding occurs, the insulating edge of the positive electrode sheet is difficult to absorb and timely spread heat, resulting in thermal shrinkage of the separator. When a is greater than 1.5mm, although the influence of the overselding on the separator may be reduced, the energy density of the electrochemical device may be lost, resulting in a decrease in the energy density of the electrochemical device. When b is smaller than c×d/2, overspray heating is easy to occur, and the electrode is easy to shrink to the inner side of the positive electrode plate and the inner side of the negative electrode plate at high temperature, so that the risks of short circuit and thermal runaway of the electrochemical device exist; when b is greater than 1.5mm, although the influence of the overselding on the separator may be reduced, the energy density of the electrochemical device may be lost, resulting in a decrease in the energy density of the electrochemical device. According to the method, the edge positions and the lengths of the positive pole piece, the negative pole piece and the diaphragm are regulated, the diaphragm can be covered by the insulating coating of the positive pole piece along the width direction of the expanded positive pole piece, when slight overspray occurs, the heat can be absorbed and diffused by the insulating coating of the positive pole piece in time, the shrinkage of the diaphragm is reduced, and the safety performance is improved while the energy density loss of the electrochemical device is reduced.
In some embodiments of the present application, as shown in fig. 1, the width of the insulating coating 12 is 1mm to 6mm in the width direction Y direction after the positive electrode sheet 10 is developed. When the width of the insulating coating is controlled within the range, the insulating coating of the positive electrode plate can cover the diaphragm, and when slight overselding occurs, the insulating coating can timely absorb and spread heat, so that the shrinkage of the diaphragm is reduced, and the safety performance of the electrochemical device is improved.
In some embodiments of the present application, as shown in fig. 1, the first empty foil region 11 has a width g in the width direction Y direction after the positive electrode sheet 10 is stretched 1 ，0.5mm≤g 1 Less than or equal to 2.5mm. Preferably 0.6 mm.ltoreq.g 1 Less than or equal to 2mm. For example g 1 Is 0.5mm, 0.6mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm or a range of any two values therein. Width g of first empty foil region 1 In the above range, when the energy density loss of the electrochemical device is reduced and slight overselding occurs, the edge of the positive electrode plate is favorable for timely absorbing and diffusing heat, and the heated shrinkage of the diaphragm is reduced, so that the safety performance of the electrochemical device is improved.
In some embodiments of the present application, as shown in fig. 1, the coating edge 103 is spaced from the fifth edge 301 by a distance h in the width direction Y of the expanded positive electrode sheet 10 1 ，0.4mm≤h 1 Less than or equal to 2.5mm. Preferably 0.5 mm.ltoreq.h 1 Less than or equal to 2mm. For example, h 1 Is 0.4mm, 0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm or a range of any two values therein. Distance h of the coating edge from the fifth edge 1 In the above range, the separator is beneficial to position adjustment between the positive pole piece and the negative pole piece while reducing energy density loss of the electrochemical deviceIs favorable for improving the production rate.
In some embodiments of the present application, as shown in fig. 2, in the width direction Y direction of the positive electrode tab 10 after being expanded, the negative electrode tab 30 includes a negative electrode active material coating 31 and a second empty foil region 32 in this order from a fifth edge 301 to a sixth edge 302, and a fourth edge 202 is disposed between the edge where the negative electrode active material coating 31 and the second empty foil region 32 meet and the second edge 102, the distance between the edge where the second empty foil region 32 meets the negative electrode active material coating 31 and the fourth edge 202 is e, the distance between the second edge 102 and the fourth edge 202 is f,0mm < e < 1.5mm, c×d/2 < f < 1.5mm. Preferably, e is 0.2 mm.ltoreq.e.ltoreq.1.5 mm. For example, e is 0mm, 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm or ranges of any two values therein. The distance e between the edge where the second empty foil area is connected with the anode active material coating and the fourth edge and the distance f between the second edge and the fourth edge are regulated and controlled within the range, so that the energy density loss of the electrochemical device is reduced, and when slight overselding occurs, the separator is favorable for reducing the thermal shrinkage of the separator, and the risks of short circuit and thermal runaway of the electrochemical device are reduced, so that the safety performance of the electrochemical device is improved.
In some embodiments of the present application, as shown in fig. 2, the second empty foil region 32 has a width g in the width direction Y direction after the positive electrode sheet 10 is stretched 2 ，0.5mm≤g 2 Less than or equal to 2.5mm. Preferably 0.6 mm.ltoreq.g 2 Less than or equal to 2mm. For example g 2 Is 0.5mm, 0.6mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm or a range of any two values therein. Width g of second empty foil region 2 In the above range, when the energy density loss of the electrochemical device is reduced and slight overselding occurs, the edge of the negative electrode plate is favorable for timely absorbing and diffusing heat, and the heated shrinkage of the diaphragm is reduced, so that the safety performance of the electrochemical device is improved.
In some embodiments of the present application, as shown in fig. 2, the distance between the edge where the second empty foil region 32 meets the anode active material coating 31 and the second edge 102 in the width direction Y direction after the cathode sheet 10 is expanded is h 2 ，0.4mm≤h 2 Less than or equal to 2.5mm. Preferably 0.5 mm.ltoreq.h 2 Less than or equal to 2mm. For example, h 2 Is 0.4mm, 0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm or a range of any two values therein. Distance h between edge connecting second empty foil region and negative electrode active material coating layer and second edge 2 In the above range, the diaphragm is beneficial to position adjustment between the positive pole piece and the negative pole piece while reducing the energy density loss of the electrochemical device, and the adjustment is beneficial to the improvement of the production rate. In addition, the coating amount of the anode active material at the edge of the anode active material coating is smaller than that in the middle of the anode active material coating in general, and h is regulated 2 The regulation and control are in the range, so that the edge positions of the anode active material coating and the cathode active material coating with small coating amount are staggered, enough anode active materials are provided for absorbing lithium ions, the risk of changing lithium ions into lithium simple substance precipitation is reduced, the occurrence of lithium precipitation in the charging and discharging process of the electrochemical device is reduced, and the safety performance of the electrochemical device is improved.
In some embodiments of the present application, 10 mm.ltoreq.c.ltoreq.600 mm, 0%.ltoreq.d.ltoreq.5%. For example, c is 10mm, 100mm, 200mm, 300mm, 400mm, 500mm, 600mm or ranges of any two of the values therein, and d is 0%, 1%, 2%, 3%, 4%, 5% or ranges of any two of the values therein. As shown in fig. 1 and 2, regulating the width c of the separator 20 and the shrinkage rate d of the separator 20 in the width direction Y within the above-described ranges is advantageous in reducing the thermal shrinkage of the separator when slight overspray occurs, reducing the risk of short circuit and thermal runaway of the electrochemical device, and thus improving the safety performance of the electrochemical device. The shrinkage rate of the separator in the width direction in the present application may be controlled by means known to those skilled in the art, for example, by selecting separators of different thicknesses, the present application is not particularly limited as long as the object of the present application can be achieved.
The positive electrode plate in the application comprises a positive electrode current collector, an insulating coating layer and a positive electrode active material coating layer, wherein the insulating coating layer and the positive electrode active material coating layer are arranged on at least one surface of the positive electrode current collector. The above-mentioned "insulating coating layer and positive electrode active material coating layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode active material coating layer may be disposed on one surface of the positive electrode current collector in the thickness direction thereof, or may be disposed on both surfaces of the positive electrode current collector in the thickness direction thereof. The "surface" herein refers to a partial region of the surface 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, the positive electrode current collector may include an aluminum foil, an aluminum alloy foil, or a composite current collector (e.g., an aluminum carbon composite current collector), or the like.
The insulating coating layer of the present application includes an insulating material and a binder, and the present application is not particularly limited as long as the object of the present application can be achieved. For example, the insulating material may include aluminum oxide, boehmite, silicon oxide (SiO 2 ) Magnesium oxide (MgO), titanium oxide (TiO) 2 ) Hafnium oxide (HfO) 2 ) Tin oxide (SnO) 2 ) Cerium oxide (CeO) 2 ) Nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO) 2 ) Yttria (Y) 2 O 3 ) At least one of silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate, and the like. The kind of binder in the insulating coating layer is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.
The positive electrode active material coating layer of the present application contains a positive electrode active material, and the kind of the positive electrode active material is not particularly limited as long as the object of the present application can be achieved. For example, the positive electrode active material may contain at least one of lithium nickel cobalt manganate (NCM 811, NCM622, NCM523, NCM 111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium cobalt oxide, lithium manganate, lithium manganese iron phosphate, lithium titanate, or the like. In the present application, the positive electrode active material may further contain a non-metal element, for example, the non-metal element includes at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur. In the present application, the thicknesses of the positive electrode current collector and the positive electrode active material coating 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 5 μm to 20 μm, preferably 6 μm to 18 μm. The thickness of the single-sided positive electrode active material coating layer is 30 μm to 120 μm.
In the present application, the positive electrode active material coating layer may further include a conductive agent and a binder. The kind of the binder in the positive electrode active material coating layer is not particularly limited as long as the object of the present application can be achieved, and for example, the binder may include, but is not limited to, at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. The kind of the conductive agent in the positive electrode active material coating layer is not particularly limited as long as the object of the present application can be achieved, and for example, the conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon Nanotubes (CNTs), carbon fibers, crystalline graphite, ketjen black, graphene, a metal material, or a conductive polymer. The carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and/or multi-walled carbon nanotubes. The carbon fibers may include, but are not limited to, vapor Grown Carbon Fibers (VGCF) and/or nano carbon fibers. The above-mentioned metal material may include, but is not limited to, metal powder and/or metal fiber, and in particular, the metal may include, but is not limited to, at least one of copper, nickel, aluminum or silver. The conductive polymer may include, but is not limited to, at least one of a polyphenylene derivative, polyaniline, polythiophene, polyacetylene, or polypyrrole. The mass ratio of the positive electrode active material, the conductive agent and the binder in the positive electrode active material coating is not particularly limited, and can be selected by a person skilled in the art according to actual needs as long as the purpose of the application can be achieved.
In the present applicationThe negative electrode sheet comprises a negative electrode current collector and a negative electrode active material coating layer arranged on at least one surface of the negative electrode current collector. The above-mentioned "anode active material coating layer disposed on at least one surface of the anode current collector" means that the anode active material coating layer may be disposed on one surface of the anode current collector in the thickness direction thereof, or may be disposed on both surfaces of the anode current collector in the thickness direction thereof. The "surface" herein refers to a partial region of the surface 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, the negative electrode current collector may include a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, nickel foam, copper foam, or a composite current collector (e.g., a lithium copper composite current collector, a carbon copper composite current collector, a nickel copper composite current collector, a titanium copper composite current collector, etc.), or the like. The anode active material coating of the present application comprises an anode active material. The kind of the negative electrode active material is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the anode active material may contain natural graphite, artificial graphite, intermediate phase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon-carbon composite, siO x (0<x<2) Li-Sn alloy, li-Sn-O alloy, sn, snO, snO 2 Spinel-structured lithium titanate Li 4 Ti 5 O 12 At least one of Li-Al alloy or metallic lithium. In the present application, the thickness of the negative electrode current collector and the negative electrode active material coating layer is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 20 μm, and the thickness of the negative electrode active material coating layer is 30 μm to 130 μm. Optionally, the anode active material coating may further include at least one of a conductive agent, a stabilizer, and a binder. The kind of the conductive agent, the stabilizer, and the binder in the anode active material coating layer is not particularly limited as long as the object of the present application can be achieved. The mass ratio of the anode active material, the conductive agent, the stabilizer, and the binder in the anode active material coating layer is not particularly limited as long as the object of the present application can be achieved.
The separator in the electrochemical device of the present application is not particularly limited as long as the object of the present application can be achieved, and the separator substrate includes at least one of Polyethylene (PE), polypropylene (PP), polypropylene-coated separator, and the like. For example, the polyethylene includes at least one component selected from the group consisting of high density polyethylene, low density polyethylene, and ultra high molecular weight polyethylene. The separator of the present application may have a porous structure, and the size of the pore diameter of the porous structure of the separator is not particularly limited as long as the object of the present application can be achieved. For example, the pore size may be 0.01 μm to 1 μm. The thickness of the separator is not particularly limited as long as the object of the present application can be achieved, and for example, the thickness of the separator may be 5 μm to 500 μm.
The electrochemical device in this application includes a current collecting plate. In this application, "current collecting tray" includes a positive current collecting tray and/or a negative current collecting tray. The material and shape of the current collecting plate are not particularly limited as long as the object of the present application can be achieved. As shown in fig. 1 to 3, along the width direction Y direction of the expanded positive electrode sheet 10, the positive electrode sheet 10 further includes a positive electrode rubbing and flattening area 14 and a positive electrode current collecting disc (not shown in the figure), wherein no positive electrode active material coating 13 is provided on both surfaces of the positive electrode rubbing and flattening area 14, the positive electrode rubbing and flattening area 14 is close to the first empty foil area 11 and is connected with the first edge 101, and the positive electrode current collecting disc (not shown in the figure) is welded with the positive electrode rubbing and flattening area 14 to form a positive electrode welding line (not shown in the figure) and then is connected to the positive electrode post (not shown in the figure); the negative electrode sheet 30 further includes a negative electrode rubbing area 33, no negative electrode active material coating 31 is disposed on both surfaces of the negative electrode rubbing area 33, the negative electrode rubbing area 33 is close to the second hollow foil area 32 and is connected to the sixth edge 302, and the negative electrode current collecting disc 34 is welded to the negative electrode rubbing area 33 to form a negative electrode welding line 35 and then connected to a negative electrode post (not shown in the figure). The welding mode of the positive electrode current collecting disc and the positive electrode rubbing area and the welding mode of the negative electrode current collecting disc and the negative electrode rubbing area are not particularly limited, so long as the purpose of the application can be achieved. The positive electrode rubbing area is a blank area of the rubbed positive electrode current collector, and the negative electrode rubbing area is a blank area of the rubbed negative electrode current collector.
In the present applicationThe electrochemical device further includes an electrolyte including a lithium salt and a nonaqueous solvent. The lithium salt may include LiPF 6 、LiBF 4 、LiAsF 6 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 、LiSiF 6 At least one of LiBOB or lithium difluoroborate. The concentration of the lithium salt in the electrolyte is not particularly limited in the present application as long as the object of the present application can be achieved. The nonaqueous solvent is not particularly limited as long as the object of the present application can be achieved, and may include, for example, but not limited to, at least one of a carbonate compound, a carboxylate compound, an ether compound, or other organic solvents. The carbonate compound may include, but is not limited to, at least one of a chain carbonate compound, a cyclic carbonate compound, or a fluorocarbonate compound. The chain carbonate compound may include, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), or ethylmethyl carbonate (MEC). The above-mentioned cyclic carbonates may include, but are not limited to, at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC) or Vinyl Ethylene Carbonate (VEC). The fluorocarbonate compound may include, but is not limited to, at least one of 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, or trifluoromethyl ethylene carbonate. The above carboxylic acid ester compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, gamma-butyrolactone, decalactone, valerolactone, or caprolactone. The ether compounds may include, but are not limited to, dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxy ethane At least one of ethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1, 2-dioxolane, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.
The electrochemical device of the present application is not particularly limited, and may include any device in which an electrochemical reaction occurs. In one embodiment of the present application, the electrochemical device may include, but is not limited to: lithium ion secondary batteries (lithium ion batteries), lithium polymer secondary batteries, lithium ion polymer secondary batteries, and the like.
The process of preparing the electrochemical device of the present application is well known to those skilled in the art, and the present application is not particularly limited, and may include, for example, but not limited to, the following steps: cutting a required positive electrode plate, a diaphragm and a required negative electrode plate, stacking the positive electrode plate, the diaphragm and the negative electrode plate in sequence, determining the edge positions and the lengths of the positive electrode plate, the diaphragm and the negative electrode plate according to design requirements, winding, rubbing, encapsulating, welding a current collecting disc, assembling an insulating sheet and the like 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 the electrochemical device. The packaging bag is not limited in this application, and a person skilled in the art can select according to actual needs, so long as the purpose of this application can be achieved. For example, an aluminum plastic film package may be used.
A second aspect of the present application provides an electronic device comprising an electrochemical device in any of the foregoing embodiments. The electrochemical device can give consideration to safety performance and energy density, so that the electronic device provided by the application has longer service life.
The electronic device of the present application is not particularly limited, and may be any electronic device known in the art. 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.
Test method and apparatus:
length test:
discharging the lithium ion batteries of each example and comparative example to 0% at a rate of 1C, namely, in a full discharge state, removing the shell of the lithium ion battery, soaking for 20min with diethyl carbonate to remove electrolyte to obtain an electrode assembly, then placing the electrode assembly on a Charge Coupled Device (CCD) platform in parallel along the length direction, disassembling to obtain a positive pole piece, a negative pole piece and a diaphragm, and measuring a, b, e, f, g by using the CCD along the width direction of the positive pole piece 1 、g 2 、h 1 And h 2 . Each length was measured 5 times and averaged as the final result.
Width and shrinkage test of separator:
the lithium ion batteries of the examples and the comparative examples in each group were prepared two by two, and the number of charge and discharge times of each lithium ion battery was less than 5, i.e., the total discharge capacity was 5×standard capacity of lithium ion batteries. Discharging the lithium ion batteries of each example and comparative example to 0% at a multiplying power of 1C, namely, in a full discharge state, directly removing the shell of one lithium ion battery in each group, soaking for 20min with dimethyl ether to remove electrolyte, obtaining an electrode assembly, then placing the electrode assembly on a Charge Coupled Device (CCD) platform in parallel along the length direction, disassembling to obtain a diaphragm, measuring the width C of the diaphragm by using the CCD along the width direction of the diaphragm, measuring each width 5 times, and taking an average value as a final result. And (3) placing the other lithium ion battery in a baking oven at 130 ℃ for baking for 0.5h, removing the shell, soaking for 20min with dimethyl ether to remove electrolyte, obtaining an electrode assembly, then placing the electrode assembly on a Charge Coupled Device (CCD) platform in parallel along the length direction, disassembling to obtain a diaphragm, measuring the width i of the diaphragm after baking and shrinking by using the CCD along the width direction of the diaphragm, measuring each width for 5 times, and taking an average value as a final result.
Shrinkage rate d=1 of the separator in the width direction-width i of the separator after baking shrinkage/width c of the separator.
Failure rate test:
the lithium ion batteries in each example and comparative example are welded in the assembly process, a positive current collecting disc aluminum strip is placed on a positive electrode rubbing area, a laser welding process is adopted in a central area where the positive current collecting disc aluminum strip and the positive electrode rubbing area are overlapped, welding power is increased to 400W, so that a special overspray sample is manufactured, when the positive current collecting disc is penetrated in the welded central area and the bottom electrode assembly or the electrode assembly is exposed by burning trace, namely overspray, the overspray electrode assembly is disassembled, if a diaphragm of the lithium ion battery is contracted to the edge where an insulating coating is connected with a positive electrode active material coating or is contracted to the inside of the positive electrode active material coating in the width direction of a positive electrode plate, failure is represented, if the diaphragm of the lithium ion battery is not contracted to the edge where the insulating coating is connected with the positive electrode active material coating in the width direction of the positive electrode plate and is not contracted to the inside of the positive electrode active material coating, the diaphragm is not contracted to the inside of the positive electrode active material coating, the number of the lithium ion battery is represented, the failure caused by direct contact of the positive electrode plate and the negative electrode plate due to the diaphragm contraction is repeated 10 times each group, and the failure is detected.
The step of testing the overselding failure rate of the negative electrode current collecting disc in the negative electrode rubbing zone is the same as the overselding failure rate of the positive electrode current collecting disc in the positive electrode rubbing zone.
The overselding failure rate of the positive electrode current collecting disc in the positive electrode flattening area/the overselding failure rate of the negative electrode current collecting disc in the negative electrode flattening area=the number/total number of the failed lithium ion batteries.
Test of significant increase rate of leakage current after high temperature:
the lithium ion batteries of each of the examples and comparative examples were charged to a full charge voltage of 4.2V at a constant current rate of 0.5C at 25℃and then charged to 0.05C at a constant voltage of 4.2V, and left standing for 48 hours, and the voltage V at this time was measured 1 The method comprises the steps of carrying out a first treatment on the surface of the Continuing to stand for 48h, recording the standing time at the moment as t 1 The voltage V at this time is measured 2 Leakage current I of lithium ion battery 1 Is (V) 2 -V 1 )/t。
Discharging the lithium ion battery to 0% at a rate of 1C at 25deg.C, baking in an oven at 130deg.C for 30min, and measuring leakage current I of the baked lithium ion battery 2 。
If the leakage current of the lithium ion battery after the high-temperature test is increased by 50% compared with the leakage current before the high-temperature test, the leakage current of the lithium ion battery after the high-temperature test is considered to be obviously increased.
Each group was repeated 10 times, and the number of lithium ion batteries with significantly increased leakage current after high temperature was measured.
Significant increase rate of leakage current after high temperature = number/total number of lithium ion batteries with significant increase of leakage current after high temperature.
Energy density testing:
in an environment of 25 ℃, the lithium ion batteries prepared in each example and comparative example are charged according to the following operation procedures, and then discharged, so as to obtain the discharge capacity of the lithium ion battery. The lithium ion battery is charged to the full charge voltage of 4.2V at the constant current of 0.5C, is charged to the full charge voltage of 0.05C at the constant voltage of 4.2V, is kept stand for 5min, is discharged to the full discharge voltage of 3.0V at the constant current of 1C, and the discharge capacity C of the lithium ion battery in the first cycle is recorded ap . And after the lithium ion battery is charged to 3.8V at a constant current, charging to 0.05C at a constant voltage of 3.8V, and testing the length L, the width W and the height H of the lithium ion battery by using a laser thickness gauge to obtain the volume V=L×W×H of the lithium ion battery. Its Energy Density (ED) =c ap V in Wh/L.
Example 1
< preparation of Positive electrode sheet >
Active substances of nickel cobalt lithium manganate, conductive carbon black and binder polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 97.8:0.8:1.4Mixing, adding N-methyl pyrrolidone (NMP) as a solvent, fully and uniformly stirring to prepare positive electrode active material coating slurry with the solid content of 75wt%, and uniformly coating the positive electrode active material coating slurry on one surface of a positive electrode current collector aluminum foil with the thickness of 10 mu m to obtain a positive electrode active material coating. Mixing aluminum oxide and a binder polyvinylidene fluoride according to a mass ratio of 90:10, adding N-methyl pyrrolidone (NMP) as a solvent, fully and uniformly stirring and preparing into insulating coating slurry with a solid content of 50wt%, uniformly coating the insulating coating slurry on an insulating coating 12 area along the width direction of the expanded positive electrode plate 10, wherein the edge connected with a positive electrode active coating 13 is a coating edge 103, and the width of the insulating coating is 2mm, as shown in figure 1. Wherein the area where the positive electrode active material coating and the insulating coating are not coated is a first empty foil area, the width g of the first empty foil area 1 The width of the positive electrode rubbing area is 0.3mm and is 1.3 mm; and (3) drying at 90 ℃ and then cold pressing to obtain the positive electrode active material coating with the single-sided coating thickness of 48 mu m and the positive electrode plate with the single-sided coating thickness of 20 mu m. And repeating the steps on the other surface of the aluminum foil of the positive electrode current collector to obtain the double-sided coated positive electrode plate. After the coating is completed, the positive electrode plate is cut into the specification of 66mm multiplied by 1250mm for standby.
< preparation of negative electrode sheet >
Mixing graphite powder serving as a cathode active material, carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) serving as a binder according to a weight ratio of 97.7:1.3:1.0, adding deionized water serving as a solvent, preparing into slurry with a solid content of 70wt%, and uniformly stirring. Uniformly coating slurry on one surface of a negative current collector copper foil with the thickness of 5 mu m along the width direction of the unfolded negative electrode plate, wherein the area without the coating of the negative active material is a second empty foil area, and the width g of the second empty foil area 2 The width of the negative electrode rubbing area is 0.3mm and is 1.3 mm; and (3) drying at 110 ℃ and then cold pressing to obtain the negative electrode plate with the coating thickness of 130 mu m and the single-sided coated negative electrode active material. And repeating the steps on the other surface of the negative current collector copper foil to obtain the double-sided coated negative electrode plate. After coating is completed And cutting the negative electrode plate into a specification of 68mm multiplied by 1300mm for later use.
< preparation of separator >
A Polyethylene (PE) film with the thickness of 15 μm is arranged between the positive pole piece and the negative pole piece to serve as a diaphragm, wherein the length of the diaphragm is 1350mm, the width c is 63mm, and the shrinkage rate d of the diaphragm in the width direction is 0.5%.
< preparation of electrolyte >
In a glove box with a dry argon atmosphere, a basic solvent dimethyl ether (DME) is used as a basic solvent, and then lithium hexafluorophosphate is added into an organic solvent to be dissolved and uniformly mixed, so that an electrolyte is obtained. Based on the mass of the electrolyte, the mass percentage of lithium hexafluorophosphate is 21%, and the balance is the basic solvent.
< preparation of lithium ion Battery >
Sequentially stacking the positive pole piece, the diaphragm and the negative pole piece, enabling the diaphragm to be positioned between the positive pole piece and the negative pole piece to play a role in isolation, and designing the distance between the edges of the positive pole piece, the negative pole piece and the diaphragm: a=0 mm, b=1.3 mm, g 1 ＝1.3mm、e＝0.5mm、f＝0.8mm、g 2 The electrode assembly with the winding structure is obtained by the processes of winding, rubbing, encapsulation, current collecting disc welding, insulating sheet assembling and the like, the electrode assembly is put into an aluminum plastic film packaging bag, moisture is removed at 80 ℃, the prepared electrolyte is injected, and the lithium ion battery is obtained through the procedures of vacuum packaging, high-temperature standing, formation, capacity and the like. The upper limit voltage of the formation is 4.15V, the formation temperature is 60 ℃, and the formation standing time is 2h.
Examples 2 to 38
Except that the relevant preparation parameters were adjusted according to Table 1, when a, b, e, f, h 1 、g 1 、h 2 Or g 2 When the change occurs, the cutting size of the positive electrode sheet and the negative electrode sheet is kept unchanged, and the rest is the same as in example 1 except that the width of the positive electrode active material coating and/or the width of the negative electrode active material coating is changed accordingly. Wherein the polyethylene film having a thickness of 12 μm was selected in examples 6 to 8 and examples 15 to 18 so that the separator contracted in the width directionThe ratio d is shown in the table, and the length and width of the separator are the same as those of example 1-1.
Comparative examples 1 to 4
The procedure of example 1 was repeated except that the preparation parameters were adjusted as shown in Table 1, and the cut sizes of the positive electrode sheet and the negative electrode sheet were maintained as they were when a or b was changed, and the width of the positive electrode active material coating layer and/or the width of the negative electrode active material coating layer was changed accordingly. Among them, the polyethylene films having a thickness of 12 μm were selected in comparative examples 3 to 4 so that the shrinkage d of the separator in the width direction was as shown in the table, and the length and width of the separator were the same as those of example 1-1.
The preparation parameters and performance parameters of each example and comparative example are shown in table 1.
TABLE 1
As can be seen from examples 1 to 38 and comparative examples 1 to 4, when the distance a between the coating edge and the third edge is less than 0mm, as can be seen from comparative example 1, the overspray failure rate of the positive electrode current collecting plate and the overspray failure rate of the negative electrode current collecting plate of the lithium ion battery in the welding region of the first empty foil region and the welding region of the second empty foil region are too high, and the leakage current significantly increases at high temperature, and the energy density is low. When a is greater than 1.5mm, it can be seen from comparative example 2 that although the overselding failure rate of the positive electrode current collecting plate in the positive electrode rolling region and the overselding failure rate of the negative electrode current collecting plate in the negative electrode rolling region of the lithium ion battery are lower, the leakage current significantly increases at a low rate after high temperature, but the high energy density cannot be considered, and the energy density of the lithium ion battery is greatly reduced. When the distance b between the third edge and the fifth edge is smaller than c×d/2, it can be seen from comparative example 3 that although the over-welding failure rate of the positive electrode current collecting plate in the positive electrode rolling area and the over-welding failure rate of the negative electrode current collecting plate in the negative electrode rolling area of the lithium ion battery are lower, the energy density is higher, but the significant increase rate of the leakage current after high temperature is higher, and the safety performance of the lithium ion battery cannot be fully considered. When b is greater than 1.5mm, it can be seen from comparative example 4 that although the overselding failure rate of the positive electrode current collecting plate in the positive electrode rolling region and the overselding failure rate of the negative electrode current collecting plate in the negative electrode rolling region of the lithium ion battery are low, the leakage current significantly increases at a low rate after high temperature, but the high energy density cannot be considered, and the energy density of the lithium ion battery is greatly reduced. From embodiment 1 to embodiment 38, it can be seen that, by adjusting and controlling the edge positions and lengths of the positive pole piece, the negative pole piece and the diaphragm, the over-welding failure rate of the positive electrode current collecting disc in the positive electrode rubbing area and the over-welding failure rate of the negative electrode current collecting disc in the negative electrode rubbing area of the lithium ion battery are lower, the leakage current obviously increases at a lower rate after high temperature, and meanwhile, the high energy density is considered, so that the lithium ion battery in the embodiment of the application has better safety performance and simultaneously has high energy density.
The distance e between the edge where the second empty foil region meets the anode active material coating and the second edge affects the safety performance and energy density of the lithium ion battery. As can be seen from examples 9 to 14, when the value of e is within the range of the present application, the overselding failure rate of the positive electrode current collecting plate in the positive electrode rolling area and the overselding failure rate of the negative electrode current collecting plate in the negative electrode rolling area of the lithium ion battery are lower, and the significant increase rate of the leakage current after high temperature is lower, and meanwhile, the energy density is higher, which indicates that the lithium ion battery has good safety performance and energy density.
The distance f between the second edge and the fourth edge affects the safety performance and energy density of the lithium ion battery. As can be seen from examples 7, 15 to 18, when the value of f is within the range of the present application, the overseld failure rate of the positive electrode current collecting plate in the positive electrode rubbing zone and the overseld failure rate of the negative electrode current collecting plate in the negative electrode rubbing zone of the lithium ion battery are lower, and the leakage current significantly increases at a low rate after high temperature, and the energy density is higher, which indicates that the lithium ion battery has good safety performance and energy density.
Width g of first empty foil region 1 The safety performance and energy density of the lithium ion battery are affected. From the reality As can be seen from examples 19 to 25, when g 1 When the value of (2) is within the range of the application, the overselding failure rate of the positive electrode current collecting disc in the positive electrode flattening area and the overselding failure rate of the negative electrode current collecting disc in the negative electrode flattening area of the lithium ion battery are lower, the leakage current obviously increases at a lower rate after high temperature, and meanwhile, the energy density is higher, so that the lithium ion battery has good safety performance and energy density.
Width g of second empty foil region 2 The safety performance and energy density of the lithium ion battery are affected. As can be seen from examples 26 to 32, when g 2 When the value of (2) is within the range of the application, the overselding failure rate of the positive electrode current collecting disc in the positive electrode flattening area and the overselding failure rate of the negative electrode current collecting disc in the negative electrode flattening area of the lithium ion battery are lower, the leakage current obviously increases at a lower rate after high temperature, and meanwhile, the energy density is higher, so that the lithium ion battery has good safety performance and energy density.
Distance h of the coating edge from the fifth edge 1 The safety performance and energy density of the lithium ion battery are affected. It can be seen from examples 6 to 8 and examples 33 to 35 that when h 1 When the value of (2) is within the range of the application, the overselding failure rate of the positive electrode current collecting disc in the positive electrode flattening area and the overselding failure rate of the negative electrode current collecting disc in the negative electrode flattening area of the lithium ion battery are lower, the leakage current obviously increases at a lower rate after high temperature, and meanwhile, the energy density is higher, so that the lithium ion battery has good safety performance and energy density.
Distance h between the edge where the second empty foil region meets the anode active material coating and the second edge 2 The safety performance and energy density of the lithium ion battery are affected. It can be seen from examples 7, 16 to 17 and 36 to 38 that when h 2 When the value of (2) is within the range of the application, the overselding failure rate of the positive electrode current collecting disc in the positive electrode flattening area and the overselding failure rate of the negative electrode current collecting disc in the negative electrode flattening area of the lithium ion battery are lower, the leakage current obviously increases at a lower rate after high temperature, and meanwhile, the energy density is higher, so that the lithium ion battery has good safety performance and energy density.
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 is only of the preferred embodiments of the present application and is not intended to limit the scope of the present application. Any modifications, equivalent substitutions, improvements, etc. that are within the spirit and principles of the present application are intended to be included within the scope of the present application.

Claims (14)

1. An electrochemical device comprises an electrode assembly, wherein the electrode assembly is formed by sequentially laminating and winding a positive electrode plate, a diaphragm and a negative electrode plate;
the positive electrode plate comprises a first edge and a second edge which are opposite to each other along the width direction of the positive electrode plate after being unfolded, the diaphragm comprises a third edge and a fourth edge which are opposite to each other, and the negative electrode plate comprises a fifth edge and a sixth edge which are opposite to each other;
the positive electrode plate sequentially comprises a first empty foil area, an insulating coating and a positive electrode active material coating from the first edge to the second edge along the width direction of the expanded positive electrode plate, wherein the edge, close to the first edge, of the insulating coating is a coating edge, and the third edge and the fifth edge are sequentially far away from the coating edge along the direction from the first edge to the second edge;
along the width direction after the positive electrode plate is unfolded, the distance between the coating edge and the third edge is a, the distance between the third edge and the fifth edge is b, the width of the diaphragm is c, the shrinkage rate of the diaphragm in the width direction is d, and the electrochemical device meets the following conditions: a is more than or equal to 0mm and less than or equal to 1.5mm, and c multiplied by d/2 is more than or equal to b and less than or equal to 1.5mm.
2. The electrochemical device according to claim 1, wherein 0.2 mm.ltoreq.a.ltoreq.1.5 mm.
3. The electrochemical device according to claim 1, wherein the first empty foil region has a width g in a width direction of the positive electrode tab after being developed 1 ，0.5mm≤g 1 ≤2.5mm。
4. The electrochemical device according to claim 3, wherein 0.6 mm.ltoreq.g 1 ≤2mm。
5. The electrochemical device according to claim 1, wherein the coating edge is spaced from the fifth edge by a distance h in a width direction of the positive electrode sheet after being developed 1 ，0.4mm≤h 1 ≤2.5mm。
6. The electrochemical device according to claim 5, wherein 0.5 mm.ltoreq.h 1 ≤2mm。
7. The electrochemical device according to any one of claims 1 to 6, wherein the anode tab includes a anode active material coating layer and a second empty foil region in this order from the fifth edge to the sixth edge in a width direction of the anode tab after being developed, and the fourth edge is provided between an edge where the anode active material coating layer and the second empty foil region meet and the second edge, a distance between an edge where the second empty foil region and the anode active material coating layer meet and the fourth edge is e, a distance between the second edge and the fourth edge is f,0mm +.e +.1.5 mm, and c x d/2 +.f +.1.5 mm.
8. The electrochemical device according to claim 7, wherein 0.2 mm.ltoreq.e.ltoreq.1.5 mm.
9. The electrochemical device of claim 7, wherein the electrode is stretched along the positive electrode sheetThe width direction of the second empty foil area after opening is g 2 ，0.5mm≤g 2 ≤2.5mm。
10. The electrochemical device according to claim 7, wherein 0.6 mm.ltoreq.g 2 ≤2mm。
11. The electrochemical device according to claim 7, wherein a distance between an edge at which the second empty foil region meets the anode active material coating layer and the second edge in a width direction of the expanded cathode sheet is h 2 ，0.4mm≤h 2 ≤2.5mm。
12. The electrochemical device according to claim 11, wherein 0.5 mm.ltoreq.h 2 ≤2mm。
13. The electrochemical device of any one of claims 1 to 12, wherein 10mm +.c +.600 mm,0% +.d +.5%.
14. An electronic device comprising the electrochemical device of any one of claims 1 to 13.
CN202311260329.7A 2023-09-27 2023-09-27 Electrochemical device and electronic device Pending CN117543095A (en)

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