CN219591429U

CN219591429U - Cathode pole piece, electrode assembly, battery cell, battery and electricity utilization device

Info

Publication number: CN219591429U
Application number: CN202320112403.XU
Authority: CN
Inventors: 杜香龙
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-01-16
Filing date: 2023-01-16
Publication date: 2023-08-25
Anticipated expiration: 2033-01-16

Abstract

The utility model relates to the technical field of secondary batteries, in particular to a cathode pole piece, an electrode assembly, an electric core, a battery monomer, a battery and an electric device. The cathode pole piece comprises a current collector and a coating arranged on at least one side surface of the current collector, the coating comprises a first coating and a second coating, the first coating is arranged on the current collector, the second coating and the first coating are arranged on the same surface of the current collector, and the second coating is arranged at a position, close to the edge, of the current collector; the second coating has a lower capacitance per unit area than the first coating. The thinning area of the anode pole piece is easy to generate the phenomenon of lithium precipitation, a second coating with low unit area coating capacitance is arranged on the surface of the current collector of the cathode pole piece near the edge, when the second coating corresponds to the thinning area of the anode pole piece, the unit area coating capacitance of the second coating is low, and in the process of lithium ion circulation, the quantity of lithium ions reaching the thinning area of the anode pole piece from the second coating is small, so that the phenomenon of lithium precipitation is avoided.

Description

Cathode pole piece, electrode assembly, battery cell, battery and electricity utilization device

Technical Field

The utility model relates to the technical field of secondary batteries, in particular to a cathode pole piece, an electrode assembly, an electric core, a battery monomer, a battery and an electric device.

Background

Lithium ion batteries are widely used as power batteries, and the cycle performance is one of the main interesting performances of the lithium ion batteries. In the design and use process of the lithium ion battery, different factors influencing the cycle performance of the lithium ion battery exist. Lithium ion battery manufacturers need to discover the reasons that affect the cycling performance of lithium ion batteries and provide solutions.

Disclosure of Invention

The utility model mainly aims to provide a cathode plate, which aims to solve the problem of lithium precipitation of an electrode in a thinned area and improve the use safety of a battery.

In order to achieve the above object, the present utility model provides a cathode sheet, which includes a current collector and a coating layer disposed on at least one side surface of the current collector, the coating layer including:

the first coating is arranged on the current collector; and

the second coating and the first coating are arranged on the same surface of the current collector, and the second coating is arranged at a position, close to the edge, of the current collector;

Wherein the second coating has a lower capacitance per unit area than the first coating.

Optionally, the second coating layer includes at least two sub-coating layers, and at least two sub-coating layers are stacked on the current collector.

The second coating comprises at least two layers of sub-coatings, namely the second coating is composed of two or more layers of coatings, the at least two layers of sub-coatings form the second coating, and the capacitance of the whole unit area coating of the at least two layers of sub-coatings is equal to that of the unit area coating of the second coating.

Optionally, the at least two layers of sub-coatings comprise a first sub-coating and a second sub-coating, the first sub-coating is arranged on the current collector, and the second sub-coating is arranged on one side of the first sub-coating away from the current collector;

or, the at least two layers of sub-coatings comprise a first sub-coating and a second sub-coating, the second sub-coating is arranged on the current collector, and the first sub-coating is arranged on one side of the second sub-coating, which is away from the current collector.

It will be appreciated that the location of each sub-coating in the second coating is not limited, and that when at least two sub-coatings include a first sub-coating and a second sub-coating, the first sub-coating is disposed on the current collector, and the second sub-coating is disposed on a side of the first sub-coating facing away from the current collector; or, the at least two layers of sub-coatings comprise a first sub-coating and a second sub-coating, the second sub-coating is arranged on the current collector, and the first sub-coating is arranged on one side of the second sub-coating, which is away from the current collector.

Optionally, the first subcoat has a coating capacitance per unit area that is less than the coating capacitance per unit area of the first subcoat.

In at least two layers of the second coating layer, the coating capacitance per unit area of at least one layer of the sub-coating layer is required to be lower than the coating capacitance per unit area of the first coating layer so as to satisfy that the coating capacitance per unit area of the second coating layer is lower than the coating capacitance per unit area of the first coating layer, and for this purpose, the coating capacitance per unit area of the first sub-coating layer is smaller than the coating capacitance per unit area of the first coating layer.

Optionally, the coating capacitance per unit area of the second sub-coating layer is greater than or equal to the coating capacitance per unit area of the first sub-coating layer, the thickness of the second coating layer is defined as D, and the thickness of the first sub-coating layer is D, so that the relation is satisfied: the D is more than or equal to 0.3 and less than or equal to 1.

Since the second coating layer is composed of the first sub-coating layer and the second sub-coating layer, the unit area coating layer capacitance of the first sub-coating layer is smaller than the unit area coating layer capacitance of the first coating layer according to the foregoing description, when the unit area coating layer capacitance of the second sub-coating layer is larger than or equal to the unit area coating layer capacitance of the first coating layer, theoretically, the thicker the first sub-coating layer is, the lower the unit area coating layer capacitance of the second coating layer is, and under the condition that the unit area coating layer capacitance of the second coating layer is lower, the more obvious the phenomenon of lithium precipitation at the cutting position of the anode electrode sheet is, the phenomenon of lithium precipitation is even disappeared, therefore, the thickness of the second coating layer is D, and the thickness of the first sub-coating layer is D, and the following relation is satisfied: the D is more than or equal to 0.3 and less than or equal to 1.

Optionally, the second coating has a width in the range of 20mm to 40mm.

The unit area coating capacitance of the second coating layer is smaller than the unit area coating capacitance of the first coating layer, in theory, the larger the width of the second coating layer is, the more favorable the width range of the second coating layer is for covering the width range of the skived area of the anode pole piece, however, if the width of the second coating layer is too large, although the skived area of the anode pole piece can be covered, the reduction of the unit area coating capacitance of the cathode pole piece can also affect the whole capacity of the battery, so the width of the second coating layer needs to be in a proper range to ensure that the width range of the second coating layer is for covering the width range of the skived area of the anode pole piece, wherein the width range value of the second coating layer is 20mm-40mm.

Optionally, defining the capacitance of the coating layer in unit area of the first coating layer as M, the gram volume of the active substance in the first coating layer as a, and the mass of the active substance in the first coating layer as b, wherein M=a×b is satisfied, wherein, a is more than or equal to 135mAh/g and less than or equal to 200mAh/g, b is more than or equal to 150mg and less than or equal to 400mg;

defining the capacitance of the coating layer in unit area of the second coating layer as N, the gram volume of the active substance in the second coating layer as c, and the mass of the active substance in the second coating layer as d, N=c×d is satisfied, wherein 125mAh/g is less than or equal to c and less than or equal to 195mAh/g, and 150mg is less than or equal to d and less than or equal to 400mg.

The first coating and the second coating are existing positive electrode coatings, the active material in the first coating is selected from the existing active materials with high gram capacity, the active material in the second coating is selected from the existing active materials with low gram capacity, for example, the gram capacity of the active material in the first coating is 135mAh/g-200mAh/g, and the gram capacity of the active material in the second coating is 125mAh/g-195mAh/g. It is understood that the active material in the coating may be lithium iron phosphate, ternary materials, lithium manganate, lithium cobaltate, solid oxides, etc., for example, the gram capacity of lithium iron phosphate ranges from 135mAh/g to 140mAh/g; the gram capacity range value of the ternary material is 170mAh/g-200mAh/g, the unit area coating capacitance of the second coating is smaller than that of the first coating, and when the second coating and the second coating select the same kind of active materials, the unit area coating capacitance of the second coating can be smaller than that of the first coating by changing the mass of the active materials in unit area.

Optionally, the thickness of the second coating is equal to the thickness of the first coating.

To facilitate the preparation of the battery, the thickness of the second coating is equal to the thickness of the first coating.

Optionally, the type of positive electrode active material in the second coating layer is the same as the type of positive electrode active material in the first coating layer.

In theory, the types of the positive electrode active materials in the second coating layer and the first coating layer are not limited, so long as the capacitance of the positive electrode active materials in the second coating layer is lower than that of the first coating layer, and considering that the voltage platforms of the coating layers formed by different positive electrode active materials are different, in order to keep the voltage platforms of the cathode plate stable and improve the performance of the battery, the types of the positive electrode active materials in the second coating layer and the types of the positive electrode active materials in the first coating layer are the same, so as to reduce the difference of the voltage platforms, for example, the positive electrode active materials in the second coating layer and the positive electrode active materials in the first coating layer are one of lithium nickel oxide, lithium cobalt oxide, lithium titanium oxide and nickel cobalt multi-element oxide, and it can be understood that the second coating layer and the positive electrode active materials in the first coating layer have small differences under the condition of the same types, in order to further reduce the differences of the voltage platforms, the positive electrode active materials in the second coating layer and the first coating layer are the same types, and the content of elements in the second coating layer and the positive electrode active materials in the first coating layer are the same, for example, and the positive electrode active materials in the second coating layer and the first coating layer and the positive electrode active material are the same.

Optionally, the opposite ends of the cathode sheet are defined to include a cathode sheet skived region and a non-skived region, and the second coating is located in the non-skived region.

In theory, the thickness of the coating layer of the non-thinned area of the cathode pole piece is larger than that of the thinned area, so that the phenomenon of lithium precipitation is more serious when the thinned area of the anode pole piece corresponds to the non-thinned area of the cathode pole piece, and for this reason, the opposite ends of the cathode pole piece are defined to comprise the thinned area and the non-thinned area, and the second coating layer is positioned in the non-thinned area.

Optionally, the current collector is provided with a bottom coating, and the bottom coating is arranged on one surface of the bottom coating, which is away from the current collector.

For stable adhesion of the first and second coating layers to the current collector, a primer layer is provided on the current collector, the coating layer being provided on the side of the primer layer facing away from the current collector, i.e. a primer layer is provided between the coating layers and the current collector, the current collector and the coating layers being effectively bonded together by the adhesion of the primer layer.

The present application also provides an electrode assembly comprising an anode electrode sheet, a separator, and a cathode electrode sheet as described above.

Optionally, the cathode sheet comprises a current collector and a coating layer arranged on at least one side surface of the current collector;

The opposite ends of the anode pole piece are defined to comprise an anode pole piece skiving area and a non-skiving area, and the second coating of the cathode pole piece corresponds to the skiving area of the anode pole piece.

In order to avoid the phenomenon of lithium precipitation, coating layers with different coating capacities in unit area are arranged on a current collector of the cathode pole piece, a second coating layer with low coating capacity in unit area is arranged on the surface of the current collector of the cathode pole piece close to the edge, a first coating layer is arranged on other coating layer areas of the current collector, the coating capacity in unit area of the second coating layer is lower than that of the first coating layer, when the second coating layer of the cathode pole piece corresponds to the thinning area of the anode pole piece, the coating capacity in unit area of the second coating layer is low, and in the process of lithium ion circulation, the quantity of lithium ions released from the second coating layer is small, so that the quantity of lithium ions reaching the thinning area of the anode pole piece is also small, the enrichment of lithium ions in the thinning area of the anode pole piece is reduced, the phenomenon of lithium precipitation is avoided, and the use safety of the battery is improved.

Optionally, the thinned area of the anode pole piece is provided with a third coating, and the capacitance of the coating of the unit area of the third coating is larger than that of the coating of the unit area of the second coating.

The thinned area of the anode plate is provided with a third coating layer which is used for receiving lithium ions migrating from the cathode plate coating layer to the anode plate in the battery cycle process, and in order to avoid the phenomenon of lithium precipitation caused by enrichment of the lithium ions in the third coating layer, the capacitance of the coating layer per unit area of the third coating layer is larger than that of the coating layer per unit area of the second coating layer, so that the third coating layer has enough space for receiving the lithium ions and the phenomenon of lithium precipitation is avoided.

Optionally, the capacitance of all active materials per unit area of the third coating divided by the capacitance of all active materials per unit area of the second coating is defined to be equal to CB value, then: the CB value is more than or equal to 1.01 and less than or equal to 1.4, and alternatively, the CB value is more than or equal to 1.1 and less than or equal to 1.3.

As shown before, the third coating is opposite to the second coating, the capacitance of the coating in unit area of the third coating is larger than that of the coating in unit area of the second coating, the capacitance of all active substances in unit area of the third coating divided by the capacitance of all active substances in unit area of the second coating is equal to the CB value, the CB value is larger than 1, in order to better avoid the phenomenon of lithium precipitation, even eliminate the phenomenon of lithium precipitation, the CB value is satisfied: the CB value is more than or equal to 1.01 and less than or equal to 1.4, and alternatively, the CB value is more than or equal to 1.1 and less than or equal to 1.3.

Optionally, the width of the thinned area of the anode pole piece is smaller than or equal to the width of the second coating.

In order to effectively correspond the second coating of the cathode pole piece and the anode pole piece thinning area, the width of the anode pole piece thinning area is smaller than or equal to that of the second coating, so that the second coating of the cathode pole piece completely covers the anode pole piece thinning area.

Optionally, the opposite ends of the anode pole piece are defined to include a skived area and a non-skived area, the opposite ends of the cathode pole piece include a skived area and a non-skived area, the second coating is located in the non-skived area of the cathode pole piece, and the skived area of the anode pole piece corresponds to the non-skived area of the cathode pole piece.

In theory, the lithium precipitation phenomenon is more serious when the non-skived region of the cathode sheet corresponds to the skived region of the anode sheet, and for this purpose, it is defined that the opposite ends of the anode sheet include a skived region and a non-skived region, the opposite ends of the cathode sheet include a skived region and a non-skived region, the second coating layer is located in the non-skived region of the cathode sheet, the skived region of the anode sheet corresponds to the non-skived region of the cathode sheet, that is, the second coating layer having a low coating capacitance per unit area is disposed in the non-skived region of the cathode sheet to improve the lithium precipitation phenomenon when the non-skived region of the cathode sheet corresponds to the skived region of the anode sheet.

The application also provides a battery cell comprising the electrode assembly.

The application also provides a battery cell, which comprises the electric core.

The application also provides a battery, which comprises the electric core or the battery cell.

The application also provides an electric device, which comprises the battery.

The cathode plate comprises a current collector and a coating arranged on at least one side surface of the current collector, wherein the coating comprises the following components: the first coating and the second coating are arranged on the same surface of the current collector, and the second coating and the first coating are arranged at a position, close to the edge, of the current collector; wherein the second coating has a lower capacitance per unit area than the first coating. In order to avoid the phenomenon of lithium precipitation, coating layers with different coating capacities in unit area are arranged on a current collector of the cathode pole piece, specifically, a second coating layer with low coating capacity in unit area is arranged on the surface of the current collector of the cathode pole piece close to the edge, a first coating layer is arranged on other coating areas of the current collector, the coating capacity in unit area of the second coating layer is lower than that of the first coating layer, when the second coating layer of the cathode pole piece corresponds to the thinning area of the anode pole piece, the coating capacity in unit area based on the second coating layer is low, and in the process of lithium ion circulation, the quantity of lithium ions reaching the thinning area of the anode pole piece from the second coating layer is small, so that the enrichment of lithium ions in the thinning area of the anode pole piece is reduced, the phenomenon of lithium precipitation is avoided, and the use safety of the battery is improved.

Drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present utility model, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic view of an embodiment of a cathode sheet according to the present utility model;

FIG. 2 is a schematic view of another embodiment of a cathode sheet according to the present utility model;

FIG. 3 is a schematic view of the structure of an electrode assembly according to the present utility model;

FIG. 4 is a schematic view showing an assembled structure of an electrode assembly according to the present utility model;

fig. 5 is a schematic view of a secondary battery according to an embodiment of the present utility model;

fig. 6 is an exploded view of the secondary battery according to an embodiment of the present utility model shown in fig. 5;

fig. 7 is a schematic view of a battery module according to an embodiment of the present utility model;

fig. 8 is a schematic view of a battery pack according to an embodiment of the present utility model;

fig. 9 is an exploded view of the battery pack of the embodiment of the present utility model shown in fig. 8;

fig. 10 is a schematic view of an electric device in which a secondary battery according to an embodiment of the present utility model is used as a power source.

Reference numerals illustrate:

reference numerals	Name of the name	Reference numerals	Name of the name
				1000	Electrode assembly	21	Anode pole piece thinning area
100	Cathode pole piece	30	Diaphragm
				10	Current collector	1	Battery pack
11	Tab	2	Upper box body
				12	Cathode pole piece thinning area	3	Lower box body
13	First coating layer	4	Battery module
				15	Second coating	5	Secondary battery
151	First sub-coating	51	Shell body
				153	Second sub-coating	52	Electrode assembly
17	Primer coating	53	Top cover assembly
				200	Anode piece

The achievement of the objects, functional features and advantages of the present utility model will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

Detailed Description

The following description of the embodiments of the present utility model 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 embodiments of the utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

Hereinafter, embodiments of the cathode sheet, the electrode assembly, the battery cell, the battery and the power utilization device of the present utility model are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present utility model by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with the given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments of the application and alternative embodiments may be combined with each other to form new solutions, unless otherwise specified.

All technical features and optional technical features of the application may be combined with each other to form new technical solutions, unless specified otherwise.

All the steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise specified. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

The terms "comprising" and "including" as used herein mean open ended or closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

The batteries mentioned in the art can be classified into disposable batteries and rechargeable batteries according to whether they are rechargeable or not. The types of rechargeable batteries that are currently common are: lead acid batteries, nickel hydrogen batteries, and lithium ion batteries. The lithium ion battery is widely applied to pure electric vehicles and hybrid electric vehicles at present, and the capacity of the lithium ion battery used for the application is slightly lower, but the lithium ion battery has larger output and charging current, longer service life and higher cost.

The battery described in the embodiments of the present application refers to a rechargeable battery. Hereinafter, the disclosed embodiments of the present application will be mainly described by taking a lithium ion battery as an example. It should be appreciated that the disclosed embodiments are applicable to any other suitable type of rechargeable battery. The batteries according to the embodiments disclosed in the present application may be directly or indirectly used in a suitable device to power the device.

Reference to a battery in the presently disclosed embodiments refers to a single physical module that includes one or more battery cells to provide a predetermined voltage and capacity. The battery cells are basic units in the battery, and can be generally divided into: cylindrical battery cells, cuboid battery cells and soft package battery cells. Hereinafter, it will be mainly developed around the rectangular parallelepiped battery cells. It should be understood that the embodiments described hereinafter are also applicable in certain respects to cylindrical battery cells or pouch battery cells.

The battery cell comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm. The lithium ion battery cell mainly relies on movement of lithium ions between the positive electrode sheet and the negative electrode sheet.

The secondary battery pole piece is coated with slurry, dried and rolled to form a multilayer composite structure of a current collector and at least one surface coating of the current collector.

In order to avoid the problems of thick edges, bulging edges and the like of the pole pieces in the coating process, the coating of the edges of the pole pieces is thinned to form a thinned area, the thickness of the coating of the thinned area is thinner than that of the coating of a normal area, and the coating of the normal area is a non-thinned area. The thinning area of the pole piece can cause gaps between adjacent cathode and anode pole pieces at the position of the thinning area, so that the problem of lithium precipitation of the battery caused by bridge cutoff of electrolyte is caused, and the safety of the battery is influenced.

In order to solve the problem of lithium separation at the thinning position of an anode plate, the application provides a cathode plate, which comprises a current collector and a coating arranged on at least one side surface of the current collector, wherein the coating comprises the following components: the first coating and the second coating are arranged on the same surface of the current collector, and the second coating and the first coating are arranged at a position, close to the edge, of the current collector; wherein the second coating has a lower capacitance per unit area than the first coating.

The cathode pole piece comprises a current collector and a positive electrode material arranged on the current collector.

The current collector refers to a structure or a part for collecting current, and the current collector mainly refers to metal foils such as copper foil and aluminum foil on the lithium ion battery. The current collector is used as a base material for attaching an anode or a cathode active material, and plays a role in collecting current generated by the active material and outputting large current. Generally, aluminum foil is used as a positive current collector, and copper foil is used as a negative current collector.

A coating layer including a positive electrode material disposed on the current collector, wherein the coating layer generally includes a conductive agent and a binder in addition to the positive electrode material.

Coating capacitance per unit area, coating capacitance per unit area = active material gram capacity x coating active material mass per unit area, capacitance per unit area of the coating is positively correlated to the gram capacity of active material in the coating and the mass of active material per unit area, active material refers to positive electrode materials capable of releasing lithium ions, e.g., lithium nickelate, lithium cobaltate, lithium titanate, ternary materials, lithium-rich materials, etc. In the case where the gram capacity of the active material in the coating layer is unchanged, when the mass of the active material per unit area in the coating layer increases, the capacitance per unit area of the coating layer also increases, and in the case where the mass of the active material per unit area in the coating layer is unchanged, when the gram capacity of the active material increases, the capacitance per unit area of the coating layer also increases.

As shown in fig. 1 and 3, a second coating 15 with a low coating capacitance per unit area is disposed on the surface of the cathode plate current collector 10 near the edge, a first coating 13 is disposed on other coating regions of the current collector 10, the coating capacitance per unit area of the second coating 15 is lower than that of the first coating 13, when the second coating 15 of the cathode plate 100 corresponds to the skiving region of the anode plate, the coating capacitance per unit area of the second coating 15 is low, and during the lithium ion cycle, the amount of lithium ions reaching the skiving region 21 of the anode plate from the second coating 15 is small, thereby reducing the enrichment of lithium ions in the skiving region 21 of the anode plate, avoiding the phenomenon of lithium precipitation, and improving the use safety of the battery.

As shown in fig. 3, the distance between the anode pole piece skiving area 21 and the cathode pole piece 100 is larger than the distance between the anode pole piece non-skiving area and the cathode pole piece, that is, a larger gap is formed between the anode pole piece skiving area and the cathode pole piece, when the battery is horizontally laid down, as shown in fig. 4, the electrode assembly 1000 is located on the ground, the area below the dotted line represents the electrolyte wetting area, the area above the dotted line represents the area without electrolyte wetting, the edge structure of the anode pole piece 200 is partially located at the upper side of the dotted line, the edge skiving area at the upper side is free of electrolyte, the edge skiving area at the lower side is wetted by electrolyte, so that the edge skiving area at the upper side of the anode pole piece 200 has electrolyte bridge breaking, during the process of transmitting lithium ions by the anode and the cathode, the concentration of the edge skiving area at the lower side of the anode pole piece 200 is transmitted, the lithium ions are enriched, the lithium precipitation is easy to occur, when the lithium precipitation is excessive, the edge is partially loaded and the phenomenon of cracking of the upper side is caused.

That is, when the battery is subjected to a horizontal lying test, the electrolyte is unevenly distributed, so that lithium is easily separated from a thinned area of a part of the anode pole piece, and the thinned area is easily broken due to the fact that the separated lithium is too thick, so that the safety risk of the battery is further caused. In order to avoid the problem of lithium precipitation when the battery is in a horizontal state, the second coating with low unit area coating capacitance is arranged at the position of the cathode pole piece corresponding to the anode pole piece thinning area, so that the quantity of lithium ions reaching the anode pole piece thinning area in the battery cycle process is reduced, the enrichment of lithium in the anode pole piece thinning area is reduced or avoided, the problem of lithium precipitation is reduced or eliminated, and the use safety of the battery is improved.

Because the use scene of battery is diversified, the battery can be unavoidable to appear lying the setting, when the aforesaid setting of lying appears in the battery, produces foretell problem easily.

It is understood that the battery may be a cylindrical battery, a square battery, a pouch battery, or the like.

Further, the second coating layer includes at least two sub-coating layers, and the at least two sub-coating layers are stacked on the current collector.

The second coating comprises at least two layers of sub-coatings, namely the second coating is composed of two or more layers of coatings, the at least two layers of sub-coatings form the second coating, and the average number of the capacitance of the whole coating per unit area of the at least two layers of sub-coatings is equal to the capacitance of the coating per unit area of the second coating.

In the process of setting a coating on a current collector, slurry is usually coated on the current collector, the slurry is dried to form the coating, different slurries are required to be coated in order to obtain different coatings, the slurries generally comprise active substances, binders, conductive agents and solvents, and the types and the contents of the active substances in the different slurries are regulated to obtain the coatings with different coating capacitance per unit area finally. The second coating layer is composed of at least two layers of sub-coating layers, at least two layers of sizing agents need to be coated in the coating process, and the capacitance of the coating layer per unit area of the second coating layer is reduced through the application of different sizing agents.

The stacking arrangement refers to the situation that at least two layers of structures are stacked along a certain direction, and the direction of the stacking arrangement is defined as the up-down direction, so that at least one layer of structure is located above and at least another layer of structure is located below. As shown in fig. 2, the first sub-coating 151 and the second sub-coating 153 are stacked on the current collector.

The second coating layer has a smaller coating capacitance per unit area than the first coating layer, and the second coating layer has a structure of, but not limited to, a layer structure having a lower coating capacitance per unit area than the first coating layer, as shown in fig. 1, for example, a coating capacitance per unit area of 150mAh/g×200mg of the second coating layer 15, a coating capacitance per unit area of 161mAh/g×200mg of the first coating layer 13, wherein 161mAh/g is a gram volume of the active material, and 200mg is a mass of the active material per unit area, as shown in fig. 1. As shown in fig. 2, the second coating layer 15 includes two layers of sub-coating layers (151 and 153), and the first sub-coating layer 151 and the second sub-coating layer 153 are stacked on the current collector 10, for example, in one embodiment, the coating capacitance per unit area of the first sub-coating layer 151 is 100mAh/g×100mg, the coating capacitance per unit area of the second sub-coating layer 153 is 160mAh/g×100mg, and the overall coating capacitance per unit area of the second coating layer 15 formed by the first sub-coating layer 151 and the second sub-coating layer 153 is (100 mAh/g×100 mg) + (160 mAh/g×100 mg) =130 mAh/g×200mg. It is also understood that the second coating may also include a third subcoat disposed on the second subcoat or a fourth subcoat disposed on the third subcoat. The number of layers of the second coating layer is not particularly limited, and the coating capacitance per unit area of each sub-coating layer is not particularly limited, as long as the total coating capacitance per unit area of the second coating layer formed by each sub-coating layer is lower than the coating capacitance per unit area of the first coating layer.

Further, the at least two layers of sub-coatings include a first sub-coating 151 and a second sub-coating 153, the first sub-coating 151 being disposed on the current collector 10, the second sub-coating 153 being disposed on a side of the first sub-coating 151 facing away from the current collector 10; or, the at least two layers of sub-coatings include a first sub-coating 151 and a second sub-coating 153, the second sub-coating 153 being disposed on the current collector 10, the first sub-coating 151 being disposed on a side of the second sub-coating 153 facing away from the current collector 10.

In the application, the unit area coating capacitance of the second coating layer is required to be lower than that of the first coating layer, namely, the whole unit area coating capacitance formed by each sub-coating layer in the second coating layer is required to be lower than that of the first coating layer, so long as the whole unit area coating capacitance of the second coating layer formed by each sub-coating layer is required to be lower than that of the first coating layer, and the unit area coating capacitance of each sub-coating layer is not limited.

Further, the first subcoat has a coating capacitance per unit area that is less than the coating capacitance per unit area of the first subcoat.

For example, as shown in fig. 2, the coating capacitance per unit area of the first sub-coating layer 151 is smaller than the coating capacitance per unit area of the first coating layer 13, the coating capacitance per unit area of the second sub-coating layer 153 is equal to the coating capacitance per unit area of the first coating layer 13, and the coating capacitance per unit area of the first sub-coating layer 151 and the second sub-coating layer 153 is smaller than the coating capacitance per unit area of the first coating layer 13. For example, in one embodiment, the first coating layer 13 has a coating capacitance per unit area of 160mAh/g×200mg, where 160mAh/g is the gram volume of the active material, 200mg is the mass of the active material per unit area, the first sub-coating layer 151 has a coating capacitance per unit area of 100mAh/g×100mg, and the second sub-coating layer 153 has a coating capacitance per unit area of 160mAh/g×100mg, so that the overall coating capacitance per unit area of the second coating layer 15 formed by the first sub-coating layer 151 and the second sub-coating layer 153 is (100 mAh/g×100 mg) + (160 mAh/g×100 mg) =130 mAh/g×200mg.

Further, the capacitance of the coating layer in unit area of the second sub-coating layer is larger than or equal to that of the coating layer in unit area of the first coating layer, the thickness of the second coating layer is defined as D, the thickness of the first sub-coating layer is defined as D, and the relation is satisfied: the D is more than or equal to 0.3 and less than or equal to 1.

Since the second coating layer is composed of the first sub-coating layer and the second sub-coating layer, the unit area coating layer capacitance of the first sub-coating layer is smaller than the unit area coating layer capacitance of the first coating layer according to the foregoing description, when the unit area coating layer capacitance of the second sub-coating layer is larger than or equal to the unit area coating layer capacitance of the first coating layer, theoretically, the thicker the first sub-coating layer, the lower the unit area coating layer capacitance of the second coating layer is, the more obvious the phenomenon of lithium precipitation at the cutting position of the anode electrode sheet is, and even the phenomenon of lithium precipitation can disappear.

Defining the thickness of the second coating layer as D, and the thickness of the first sub-coating layer as D, the relation: the D is more than or equal to 0.3 and less than or equal to 1.

As shown in fig. 2, the thickness D of the second coating layer 15 and the thickness D of the first sub-coating layer 151 are defined, and the relationship is satisfied: the D is more than or equal to 0.3 and less than or equal to 1.

In the above-mentioned 0.3.ltoreq.d.ltoreq.1, values include the minimum value and the maximum value of the range, and each value between such minimum value and maximum value, and specific examples include, but are not limited to, point values in the examples and 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, and the like.

Further, the width of the second coating layer ranges from 20mm to 40mm.

The width of a coating refers to the width of the current collector that a certain coating occupies in the direction in which the different coatings are juxtaposed along the current collector, e.g., m is the width of the second coating 15 as shown in fig. 1.

The larger the width of the second coating 15 is, theoretically, more advantageous for covering the width of the anode tab skiving area 21 of the anode tab 200, but if the width of the second coating 15 is too large, although it can be ensured that the anode tab skiving area 21 of the anode tab 200 is covered, the reduction of the coating capacitance per unit area of the cathode tab will also affect the overall capacity of the battery, and therefore, the width of the second coating 15 needs to be within a suitable range to ensure that the width of the second coating 15 covers the width of the anode tab skiving area 21 of the anode tab 200, wherein the width of the second coating is 20mm-40mm.

Among the above 20mm-40mm, values include the minimum and maximum values of the range, and each value between such minimum and maximum values, specific examples include, but are not limited to, dot values in the examples and 20mm, 50mm, 30mm, 35mm, 40mm, etc.

Further, defining the coating capacitance per unit area of the first coating layer 13 as M, the gram capacity of the active material in the first coating layer 13 as a, and the mass of the active material per unit area of the first coating layer 13 as b, m=a×b is satisfied, wherein 135mAh/g is less than or equal to a and less than or equal to 200mAh/g, and 150mg is less than or equal to b and less than or equal to 400mg; defining the coating capacitance per unit area of the second coating layer 15 as N, the gram-volume of the active material in the second coating layer 15 as c, and the mass of the active material per unit area in the second coating layer 15 as d, n=c×d is satisfied, where 125 mAh/g.ltoreq.c.ltoreq.195 mAh/g,150 mg.ltoreq.d.ltoreq.400 mg.

The values of 135mAh/g-200mAh/g include the minimum and maximum values of the range, and each value between such minimum and maximum values, specific examples include, but are not limited to, point values in the embodiment and 135mAh/g, 140mAh/g, 145mAh/g, 150mAh/g, 155mAh/g, 160mAh/g, 165mAh/g, 170mAh/g, 175mAh/g, 180mAh/g, 185mAh/g, 190mAh/g, 195mAh/g, 200mAh/g, etc.

The values of 125mAh/g-195mAh/g include the minimum and maximum values of the range, and each value between such minimum and maximum values, specific examples include, but are not limited to, point values in the embodiment and 125mAh/g, 135mAh/g, 140mAh/g, 145mAh/g, 150mAh/g, 155mAh/g, 160mAh/g, 165mAh/g, 170mAh/g, 175mAh/g, 180mAh/g, 185mAh/g, 190mAh/g, 195mAh/g, etc.

Among the above 150mg to 400mg, values include the minimum and maximum values of the range, and each value between such minimum and maximum values, specific examples include, but are not limited to, dot values in the examples and 150mg, 180mg, 200mg, 220mg, 250mg, 280mg, 300mg, 330mg, 350mg, 380mg, 400mg, etc.

Further, the thickness of the second coating layer is equal to the thickness of the first coating layer.

Further, the type of the positive electrode active material in the second coating layer 15 is the same as the type of the positive electrode active material in the first coating layer 13.

The types of the positive electrode active materials are classified into different types according to the elemental composition of the positive electrode active material, for example, lithium nickel oxide (including lithium nickelate), lithium cobalt oxide (including lithium cobaltate), lithium titanium oxide (including lithium titanate), nickel cobalt multi-element oxide (including ternary material), and the like.

In theory, the types of the positive electrode active materials in the second coating 15 and the first coating 13 are not limited, so long as the condition that the coating capacitance per unit area of the second coating 15 is lower than that of the first coating 13 is satisfied, and in consideration of the fact that the voltage platforms of the coatings formed by different positive electrode active materials are different, in order to keep the voltage platforms of the cathode plate stable so as to improve the performance of the battery, the types of the positive electrode active materials in the second coating 15 are the same as those of the positive electrode active materials in the first coating 13, so that the difference of the voltage platforms is reduced, for example, the positive electrode active materials in the second coating 15 and the positive electrode active materials in the first coating 13 are lithium nickel oxide, lithium cobalt oxide, lithium titanium oxide and nickel cobalt multi-element oxide, and in order to further reduce the difference of the voltage platforms, the content of the positive electrode active materials in the second coating 15 and the positive electrode active materials in the first coating 13 is the same as that the positive electrode active materials in the first coating 13 is different, for example, the mass of the positive electrode active materials in the second coating 13 is adjusted to be the same, and the mass of the positive electrode active materials in the first coating 13 is the same, and the mass of the active materials in the second coating 13 is adjusted to be the same, and the mass of the positive electrode active materials in the same as the first coating 13 is the same, and the active materials in the unit volume is adjusted.

Further, the opposite ends of the cathode sheet are defined to include a skived region and a non-skived region, the second coating being located in the non-skived region.

It can be understood that in the process of arranging the coating on the current collector, after the materials are uniformly stirred, the materials are coated on the surface of the copper/aluminum foil to form an active substance layer, then rolling is carried out, wherein the rolling is carried out by carrying out double-roll compaction on the coated and dried pole piece, and then cutting the pole piece to obtain a finished pole piece with a proper size. It will be appreciated that during the coating process, the second coating paste of low specific area coating capacitance is applied substantially near the cut of the current collector so that after subsequent cuts, the second coating 15 is at the end of the finished pole piece, and therefore, it will be appreciated that defining the cut side of the finished pole piece as the slit side, it is considered that the low specific area coating capacitance coating is provided on the slit side.

As shown in fig. 3, the second coating layer 15 is disposed in the non-skived region of the cathode sheet 100, and the non-skived region corresponds to the anode sheet skived region 21 of the anode sheet 200, at this time, the coating capacitance per unit area of the second coating layer 15 is low, and the lithium precipitation phenomenon of the anode sheet skived region 21 of the anode sheet 200 is improved.

Further, the current collector is provided with a bottom coating, and the bottom coating is arranged on one surface of the bottom coating, which is away from the current collector.

As shown in fig. 1 and 2, in order to stably adhere the first coating layer 13 and the second coating layer 15 to the current collector 10, an undercoat layer 17 is provided on the current collector 10, and the coating layers (the first coating layer 13 and the second coating layer 15) are provided on the side of the undercoat layer 17 facing away from the current collector 10, that is, a layer of undercoat layer 17 is provided between the coating layers and the current collector 10, and the current collector 10 and the coating layers are effectively bonded together by the adhesion of the undercoat layer 17.

It is understood that in the process of applying a coating to a current collector, a high-viscosity primer layer is applied to the current collector, and then the first coating layer and the second coating layer are applied to enhance the adhesion between the active material and the current collector.

The application also provides an electrode assembly, which comprises an anode pole piece, a diaphragm and a cathode pole piece.

As shown in fig. 3, the electrode assembly 1000 includes an anode tab 200, a separator 30, and a cathode tab 100.

The cathode plate adopts all the technical schemes of all the embodiments, so that the cathode plate has at least all the beneficial effects brought by the technical schemes of the embodiments, and the description is omitted.

Further, the cathode plate comprises a current collector and a coating arranged on at least one side surface of the current collector, the coating comprises a first coating and a second coating, the first coating is arranged on the current collector, the second coating and the first coating are arranged on the same surface of the current collector, and the second coating is arranged at a position, close to the edge, of the current collector; wherein the second coating has a lower capacitance per unit area than the first coating; the opposite ends of the anode electrode sheet are defined to include a skived region and a non-skived region, and the second coating of the cathode electrode sheet corresponds to the skived region of the anode electrode sheet.

It will be appreciated that the skived region of the anode electrode may correspond to the skived region of the cathode electrode or may correspond to the non-skived region of the cathode electrode, the second coating being disposed in the skived region of the cathode electrode when the skived region of the anode electrode corresponds to the skived region of the cathode electrode, and the second coating being disposed in the non-skived region of the cathode electrode when the skived region of the anode electrode corresponds to the non-skived region of the cathode electrode.

Further, the thinned area of the anode plate is provided with a third coating, and the unit area coating capacitance of the third coating is larger than that of the second coating.

As shown in fig. 3, the third coating layer of the anode pole piece skiving area 21 of the anode pole piece 200 is opposite to the second coating layer 15 of the cathode pole piece 100, during the battery cycle, lithium ions in the second coating layer 15 can migrate to the third coating layer, the capacitance of the coating layer in unit area of the second coating layer 15 is low, and meanwhile, the capacitance of the coating layer in unit area of the third coating layer is high, so that the problem of lithium precipitation is avoided.

Further, defining the capacitance of all active materials per unit area of the third coating layer divided by the capacitance of all active materials per unit area of the second coating layer to be equal to the CB value, satisfies: the CB value is more than or equal to 1.01 and less than or equal to 1.4, and alternatively, the CB value is more than or equal to 1.1 and less than or equal to 1.3.

CB value, which is the ratio of the capacitance of all active materials per unit area of the third coating layer to the capacitance of all active materials per unit area of the second coating layer, is the ratio of the total capacitance of all active materials per unit area of the anode electrode sheet to the total capacitance of all active materials per unit area of the cathode electrode sheet, i.e., specifically to the coating layer.

As shown before, the third coating is opposite to the second coating, the capacitance of the coating in unit area of the third coating is larger than that of the coating in unit area of the second coating, and the capacitance of all active substances in unit area of the third coating divided by the capacitance of all active substances in unit area of the second coating is equal to the CB value, the CB value is larger than 1, so that in order to better avoid the phenomenon of lithium precipitation, even eliminate the phenomenon of lithium precipitation, the following conditions are satisfied: the CB value is more than or equal to 1.01 and less than or equal to 1.4, and alternatively, the CB value is more than or equal to 1.1 and less than or equal to 1.3.

Among the above-mentioned values of 1.01.ltoreq.CB.ltoreq.1.4, values include the minimum and maximum values of the range, and each value between such minimum and maximum values, specific examples include, but are not limited to, point values in the examples and 1.01, 1.1, 1.2, 1.25, 1.3, 1.35, 1.4, etc.

Further, the width of the thinned area of the anode plate is smaller than or equal to the width of the second coating.

Further, the opposite ends of the anode pole piece are defined to comprise a skived area and a non-skived area, the opposite ends of the cathode pole piece comprise a skived area and a non-skived area, the second coating is positioned in the non-skived area of the cathode pole piece, and the skived area of the anode pole piece corresponds to the non-skived area of the cathode pole piece.

The application also provides a battery cell, which comprises the electrode assembly.

The electrode assembly adopts all the technical schemes of all the embodiments, so that the electrode assembly has at least all the beneficial effects brought by the technical schemes of the embodiments, and the description is omitted herein.

The application also provides a battery cell, which comprises the battery cell.

The application also provides a battery, which comprises the battery cell or the battery cell.

The battery cell adopts all the technical schemes of all the embodiments, so that the battery cell has at least all the beneficial effects brought by the technical schemes of the embodiments, and the description is omitted herein.

The application also provides an electric device which comprises the battery.

The battery adopts all the technical schemes of all the embodiments, so that the battery has at least all the beneficial effects brought by the technical schemes of the embodiments, and the description is omitted herein.

The battery (secondary battery, battery module, battery pack) and the electric device according to the present application will be described below with reference to the drawings.

In one embodiment of the present application, a secondary battery is provided.

In general, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The diaphragm is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and can enable ions to pass through. The separator is the improved separator of the present application described above.

The positive pole piece comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, when the secondary battery is a lithium ion battery, the positive electrode active material may be a positive electrode active material for a lithium ion battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (e.g. LiNiO) ₂ ) Lithium manganese oxide (e.g. LiMnO ₂ 、LiMn ₂ O ₄ ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) _1/3 Co _1/ ₃ Mn _1/3 O ₂ (also referred to as NCM) ₃₃₃ )、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also referred to as NCM) ₅₂₃ )、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also referred to as NCM) ₂₁₁ )、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM) ₆₂₂ )、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxide (e.g. LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) At least one of modified compounds thereof and the likeA kind of module is assembled in the module and the module is assembled in the module. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO ₄ (also abbreviated as LFP)), composite material of lithium iron phosphate and carbon, and manganese lithium phosphate (such as LiMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, and a composite material of lithium manganese phosphate and carbon.

In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.

The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode current collector.

In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the negative electrode film layer further optionally includes a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the negative electrode film layer may optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The application is not particularly limited in the kind of electrolyte, and may be selected according to the need.

In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.

In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability may be used.

In some embodiments, the material of the separator may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.

In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The exterior package of the secondary battery may also be a pouch type pouch, for example. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 5 is a secondary battery 5 of a square structure as one example.

In some embodiments, referring to fig. 6, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the receiving chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to specific practical requirements.

In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.

Fig. 7 is a battery module 4 as an example. Referring to fig. 7, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.

In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

Fig. 8 and 9 are battery packs 1 as an example. Referring to fig. 8 and 9, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

In addition, the application also provides an electric device which comprises at least one of the secondary battery, the battery module or the battery pack. The secondary battery, the battery module, or the battery pack may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The power utilization device may include, but is not limited to, mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, and the like.

As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 10 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.

Examples

Example 1

(1) Preparation of cathode pole piece

The positive electrode active material lithium iron phosphate (charging gram capacity is 150 mAh/g), the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 97:0.8:2.2 dissolving in a solvent N-methyl pyrrolidone (NMP), fully stirring and uniformly mixing to obtain positive electrode slurry 1, and mixing a positive electrode active material lithium iron phosphate (charging gram capacity is 161 mAh/g), a conductive agent acetylene black and a binder polyvinylidene fluoride (PVDF) according to a mass ratio of 97:0.8:2.2 dissolving in solvent N-methyl pyrrolidone (NMP), stirring thoroughly, mixing well, and obtaining positive electrode slurry 2.

Defining the area of the current collector for coating the first coating as a first coating area, the area for coating the second coating as a second coating area, coating the positive electrode slurry 1 on the second coating area of the aluminum foil (current collector), coating the positive electrode slurry 2 on the first coating area and the second coating area of the aluminum foil (current collector) to obtain the coating structure as shown in fig. 2, and obtaining the first sub-coating 151 and the second sub-coating 153 with low coating capacitance per unit area in the non-thinned area, wherein the thickness ratio of the first sub-coating 151 to the second sub-coating 153 is 1:1, and the width of the second coating 15 is 25mm.

It is understood that the coating is to uniformly stir the materials and then coat the materials on the surface of copper/aluminum foil to form an active material layer; the rolling is to carry out double-roller compaction on the coated and dried pole piece, and then cut the pole piece to obtain a finished pole piece with proper size. It will be appreciated that during the coating process, the positive electrode slurry 1 described above is applied substantially near the cut of aluminum foil (current collector) so that after subsequent cuts, the second coating 15 is at the end of the finished pole piece.

(2) Preparation of anode pole piece

Artificial graphite as a cathode active material, acetylene black as a conductive agent, styrene-butadiene rubber (SBR) as a binder and sodium carboxymethylcellulose (CMC) as a thickener according to the mass ratio of 96.5:0.7:1.8:1, dissolving the mixture in deionized water serving as a solvent, uniformly mixing the mixture to obtain negative electrode slurry, and coating the slurry on a copper foil of a negative electrode current collector to obtain a negative electrode plate.

(3) Assembly of battery cells

Stacking the cathode pole piece, the diaphragm and the anode pole piece in sequence, so that the diaphragm is positioned between the cathode pole piece and the anode pole piece and can isolate the cathode pole piece from the anode pole piece; then winding the stacked components to obtain an electrode assembly; the electrode assembly was placed in a case, and after drying, 11% LiPF was injected ₆ An electrolyte; and obtaining the battery monomer after the processes of formation, standing and the like.

Example 2

Unlike example 1, in the coating process, the above-described positive electrode slurry 1 was coated on the second coating region of the aluminum foil (current collector), and the positive electrode slurry 2 was coated on the first coating region of the aluminum foil (current collector), resulting in the coating structure as in fig. 1, and the non-thinned region was provided with the second coating layer 15 having low coating capacitance per unit area.

Comparative example 1

Unlike example 1, the above-described positive electrode slurry 2 was applied to the first and second application regions of the aluminum foil (current collector) during the application process.

Cycle life test

Five battery cells of each of the above examples and comparative examples were respectively taken for parallel test, each of which was charged to a voltage of 4.2V at a rate of 0.33C at normal temperature, and then discharged to a voltage of 2.0V at a rate of 0.33C, and the reversible capacity was measured as C0. The charge and discharge are continuously repeated until the discharge capacity Cn/C0 of a certain cycle is less than or equal to 80 percent. Then the total number of cycles is noted as X-Cycle.

Table 1 list of experimental data

As can be seen from table 1, the lithium precipitation phenomenon in the skived area of the anode electrode sheet can be eliminated by providing the non-skived area of the cathode electrode sheet with a coating having a low coating capacitance per unit area, so that the cycle life and the use safety of the battery can be improved.

The foregoing description of the preferred embodiments of the present utility model should not be construed as limiting the scope of the utility model, but rather as utilizing equivalent structural changes made in the description of the utility model and the accompanying drawings, or as directly/indirectly employed in other related technical fields, are included in the scope of the utility model.

Claims

1. A cathode sheet, characterized in that it comprises a current collector (10) and a coating layer arranged on at least one side surface of the current collector (10), the coating layer comprising:

a first coating (13), the first coating (13) being provided to the current collector (10); and

a second coating (15), wherein the second coating (15) and the first coating (13) are arranged on the same surface of the current collector (10), and the second coating (15) is arranged at a position of the current collector (10) close to the edge;

wherein the second coating (15) has a lower coating capacitance per unit area than the first coating (13).

2. Cathode pole piece according to claim 1, characterized in that the second coating (15) comprises at least two sub-coatings, at least two sub-coatings being arranged in a stack on the current collector (10).

3. The cathode pole piece according to claim 2, characterized in that the at least two layers of subcoat-coated layers comprise a first subcoat-coated layer (151) and a second subcoat-coated layer (153), the first subcoat-coated layer (151) being arranged on the current collector (10), the second subcoat-coated layer (153) being arranged on the side of the first subcoat-coated layer (151) facing away from the current collector (10);

or, the at least two layers of sub-coatings comprise a first sub-coating (151) and a second sub-coating (153), the second sub-coating (153) is arranged on the current collector (10), and the first sub-coating (151) is arranged on one side, away from the current collector (10), of the second sub-coating (153).

4. A cathode sheet according to claim 3, characterized in that the coating capacitance per unit area of the first subcoat (151) is smaller than the coating capacitance per unit area of the first coating (13).

5. The cathode sheet according to claim 4, wherein a coating capacitance per unit area of the second sub-coating layer (153) is equal to or larger than a coating capacitance per unit area of the first sub-coating layer (151), a thickness D of the second coating layer (15) is defined, and a thickness D of the first sub-coating layer (151) satisfies the relationship: the D is more than or equal to 0.3 and less than or equal to 1.

6. Cathode pole piece according to any of claims 1 to 5, characterized in that the width of the second coating layer (15) ranges from 20mm to 40mm.

7. Cathode pole piece according to any of claims 1 to 5, characterized in that a coating capacitance per unit area of the first coating layer (13) is defined as M, the gram volume of active substance in the first coating layer (13) is a, the mass of active substance per unit area in the first coating layer (13) is b, M = a x b is satisfied, wherein 135mAh/g ∈a ∈200mAh/g,150mg ∈b ∈400mg;

defining the coating capacitance per unit area of the second coating layer (15) as N, the gram volume of the active substance in the second coating layer (15) as c, and the mass of the active substance per unit area in the second coating layer (15) as d, N=c×d is satisfied, wherein 125mAh/g is less than or equal to c is less than or equal to 195mAh/g, and 150mg is less than or equal to d is less than or equal to 400mg.

8. Cathode pole piece according to any of claims 1 to 5, characterized in that the thickness of the second coating layer (15) is equal to the thickness of the first coating layer (13).

9. Cathode pole piece according to any of claims 1 to 5, characterized in that the type of positive active material in the second coating layer (15) is the same as the type of positive active material in the first coating layer (13).

10. Cathode pole piece according to any of the claims 1 to 5, characterized in that the opposite ends defining the cathode pole piece comprise a cathode pole piece skived area (12) and a non-skived area, the second coating (15) being located in the non-skived area.

11. Cathode pole piece according to any of claims 1 to 5, characterized in that the current collector (10) is provided with a primer layer (17), which is arranged on the side of the primer layer (17) facing away from the current collector (10).

12. An electrode assembly comprising an anode electrode sheet, a separator, and the cathode electrode sheet of any one of claims 1 to 11.

13. The electrode assembly of claim 12, wherein the cathode sheet comprises a current collector and a coating disposed on at least one side surface of the current collector;

the opposite ends of the anode sheet (200) are defined to include an anode sheet skived region (21) and a non-skived region, and the second coating (15) of the cathode sheet corresponds to the anode sheet skived region (21) of the anode sheet.

14. The electrode assembly of claim 13, wherein the skived region of the anode electrode sheet is provided with a third coating having a greater capacitance per unit area of coating than the second coating.

15. The electrode assembly of claim 14, wherein the capacitance of all active materials per unit area of the third coating divided by the capacitance of all active materials per unit area of the second coating is equal to CB value is defined to satisfy: the CB value is more than or equal to 1.01 and less than or equal to 1.4, and alternatively, the CB value is more than or equal to 1.1 and less than or equal to 1.3.

16. The electrode assembly of any one of claims 12 to 14, wherein the width of the anode pole piece skived region is equal to or less than the width of the second coating layer.

17. The electrode assembly of any one of claims 13 to 15, wherein the opposite ends defining the anode electrode sheet include a skived region and a non-skived region, the opposite ends of the cathode electrode sheet include a skived region and a non-skived region, the second coating is located in the non-skived region of the cathode electrode sheet, and the skived region of the anode electrode sheet corresponds to the non-skived region of the cathode electrode sheet.

18. A cell comprising an electrode assembly according to any one of claims 12 to 17.

19. A battery cell comprising the cell of claim 18.

20. A battery comprising the cell of claim 18 or the cell of claim 19.

21. An electrical device comprising the battery of claim 20.