CN217719660U - Electrode assembly, battery cell, battery, and power consumption device - Google Patents
Electrode assembly, battery cell, battery, and power consumption device Download PDFInfo
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- CN217719660U CN217719660U CN202221330631.6U CN202221330631U CN217719660U CN 217719660 U CN217719660 U CN 217719660U CN 202221330631 U CN202221330631 U CN 202221330631U CN 217719660 U CN217719660 U CN 217719660U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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Abstract
The application relates to an electrode assembly, a battery monomer, a battery and an electric device, and belongs to the technical field of battery manufacturing. The application provides an electrode assembly, which comprises a positive electrode piece and a negative electrode piece, wherein the positive electrode piece comprises a positive electrode current collector and a positive electrode active substance layer coated on the surface of the positive electrode current collector, the positive electrode piece is provided with a plurality of straight areas and a plurality of corner areas, and the straight areas and the corner areas are alternately arranged along the winding direction of the positive electrode piece; the thickness of the positive active material layer in the first N corner regions is smaller than that of the positive active material layer in the straight region from the winding starting end of the positive pole piece, and N is larger than or equal to 1. The risk that lithium is separated out, the pole piece is broken and deformed is low, and the safety performance of the battery monomer is improved. The application also provides a battery monomer, a battery and an electric device, comprising the electrode component.
Description
Technical Field
The application relates to the technical field of battery manufacturing, in particular to an electrode assembly, a battery cell, a battery and an electric device.
Background
With the continuous prosperity of the new energy automobile market, the power battery industry is rapidly expanding and growing, the lithium battery technology is increasingly advanced, and the higher and higher requirements on the safety performance of the battery monomer are provided.
However, during the charging and discharging of the battery cell, the electrode assembly may be separated from lithium, the electrode sheet may be broken or deformed, and the safety of the battery cell may be reduced.
SUMMERY OF THE UTILITY MODEL
Therefore, the electrode assembly, the single battery, the battery and the power utilization device are provided, the risk that the electrode assembly is subjected to lithium precipitation, the pole piece is broken and deformation is low, and the safety performance of the single battery is improved.
An embodiment of a first aspect of the present application provides an electrode assembly, where the electrode assembly is a winding structure, the electrode assembly includes a positive electrode piece and a negative electrode piece, the positive electrode piece includes a positive electrode current collector and a positive electrode active material layer coated on a surface of the positive electrode current collector, the positive electrode piece has a plurality of straight regions and a plurality of corner regions, and the straight regions and the corner regions are alternately arranged along a winding direction of the positive electrode piece; the thickness of the positive active material layers of the first N corner regions from the winding starting end of the positive pole piece is smaller than that of the positive active material layers of the straight region, and N is larger than or equal to 1.
In the electrode subassembly of this application embodiment, from the coiling initiating terminal of positive pole piece, because the thickness on the positive pole active material layer in preceding N turning district is less than the thickness on the positive pole active material layer in straight district, can reduce the positive pole active material unit area capacity in preceding N turning district of positive pole piece, make and be in the unsaturated state of lotus all the time with its positive negative pole piece in charging process, not only reduce the risk that this department takes place to analyse lithium, can also reduce the great and its self fracture of negative pole piece inflation degree of this department or the risk that electrode subassembly takes place deformation, thereby make battery monomer have better security performance.
According to some embodiments of the present application, 1 ≦ N ≦ 10.
In the scheme, the radius of the first ten corner areas from the winding starting end of the positive pole piece is smaller, the possibility of lithium precipitation of the corresponding negative pole piece is higher, the thicknesses of the first ten corner areas of the positive pole piece are reduced, the safety performance of a battery monomer can be obviously improved, and the rest corner areas of the negative pole piece can be in a charge saturation state in the charging process, so that the energy density is better.
According to some embodiments of the present application, 1 ≦ N ≦ 4.
In the above scheme, the radius of the first four corner regions from the winding start end of the positive electrode piece is smaller, so that the possibility of lithium separation from the corresponding negative electrode piece is higher, the expansion stress is not easy to release, the thickness of the first four corner regions of the positive electrode piece is reduced, the risks of lithium separation, breakage, electrode assembly extrusion and the like of the corresponding negative electrode piece can be reduced, and the rest corner regions of the negative electrode piece can be in a charge saturation state in the charging process, so that the energy density is better.
According to some embodiments of the present application, the positive electrode active material layer includes a first positive electrode active material layer coated on an inner side surface of the positive electrode current collector and a second positive electrode active material layer coated on an outer side surface of the positive electrode current collector; from the winding starting end of the positive pole piece, the thickness of the first positive pole active material layers in the first N corner areas is smaller than that of the first positive pole active material layers in the straight area.
In the scheme, the first positive active material layer is coated on the inner side surface of the positive current collector, the first positive active material layer is thinned in the former N corner areas, the unit area capacity of the positive active material on the inner sides of the former N corner areas can be reduced, the negative pole piece opposite to the inner side of the positive active material layer is always in a charged unsaturated state in the charging process, and the expansion degree of the negative pole piece is further reduced. Because the radius of the negative pole piece just opposite to the inner side of the corner area is smaller than that of the negative pole piece just opposite to the outer side of the corner area, the charge saturation rate of the negative pole piece in the charging process is reduced, the risk of lithium precipitation at the position is reduced, and the risk of breakage of the negative pole piece or deformation of an electrode assembly caused by overlarge expansion amount of the negative pole piece at the position can be reduced, so that the single battery has better safety performance.
According to some embodiments of the present application, a thickness of the second positive electrode active material layer of the first N corner regions from a winding start end of the positive electrode sheet is smaller than a thickness of the second positive electrode active material layer of the straight region.
In the scheme, the second positive active material layer is coated on the outer side surface of the positive current collector, the thickness of the second positive active material layer in the front N corner areas is reduced, the unit area capacity of the positive active material outside the front N corner areas can be reduced, the negative pole piece opposite to the outer side of the second positive active material layer is always in a charged unsaturated state in the charging process, the expansion degree of the negative pole piece at the position is further reduced, and the charged saturation rate of the negative pole piece at the position in the charging process is reduced. Because the charges at the two sides of the first N corner regions of the negative pole piece are in an unsaturated state in the charging process, the expansion amount of the negative pole piece can be reduced better, and the safety performance of the battery monomer is improved.
According to some embodiments of the present application, the positive electrode active material layer includes a first positive electrode active material layer coated on an inner side surface of the positive electrode current collector and a second positive electrode active material layer coated on an outer side surface of the positive electrode current collector; in the first N corner regions, along the winding direction of the positive electrode sheet, the thickness of the first positive electrode active material layer in one of the two adjacent corner regions is smaller than the thickness of the first positive electrode active material layer in the straight region, and the thickness of the second positive electrode active material layer in the other one is smaller than the thickness of the second positive electrode active material layer in the straight region.
In the above scheme, in two adjacent corner regions, the thickness of the first positive electrode active material layer in one corner region is reduced, and the thickness of the second positive electrode active material layer in the other corner region is reduced, so that the reduced regions of the positive electrode active material layer can alternately appear on two sides of the thickness of the positive electrode plate along the winding direction of the positive electrode plate, so that the stress on two sides of the positive electrode plate is approximately uniform after the positive electrode plate is wound and bent, and the risk of breakage of the positive electrode plate can be reduced.
According to some embodiments of the present application, a ratio of a thickness of the positive electrode active material layer of the first N corner regions to a thickness of the positive electrode active material layer of the flat region ranges from 0.05 to 0.95.
In the above scheme, the thickness ratio range of the positive active material layer in the first N corner regions and the positive active material layer in the flat region of the positive electrode sheet is within the above range, so that the expansion degree of the negative electrode sheet opposite to the first N corner regions can be effectively reduced, and the safety performance of the battery cell is improved.
According to some embodiments of the present application, the ratio is in the range of 0.48-0.95.
In the above scheme, the thickness ratio range of the positive active material layer in the first N corner regions of the positive electrode sheet and the positive active material layer in the flat region is further limited to be within the above range, so that the charge saturation ratio of the negative electrode sheet corresponding to the first N corner regions can be improved as much as possible while the safety performance of the battery cell is ensured, and the battery cell has higher energy density.
According to some embodiments of the present application, the positive electrode active material layer includes a bottom layer and a surface layer, the bottom layer is continuously coated on the surface of the positive electrode current collector along the winding direction of the positive electrode sheet, and the surface layer is coated on the bottom layer at intervals.
In the above scheme, the thickness of the bottom layer is the minimum thickness of the positive electrode active material layer, the surface layers are coated on the bottom layer at intervals along the winding direction of the positive electrode sheet, and a concave portion is formed in the region between two adjacent surface layers, namely the region with the smaller thickness of the positive electrode active material layer in the first N corner regions. The positive active material layer in the form has the characteristic of easy manufacturing and forming, and can reduce the manufacturing cost of the positive pole piece.
According to some embodiments of the present application, the base layer and the surface layer are made of the same or different materials.
In the above scheme, by selecting the materials of the bottom layer and the surface layer, the thickness of the positive active material layer and the unit area capacity of the positive active material can be flexibly adjusted, so that the thicknesses of the corner region and the straight region of the positive pole piece and the unit area capacity of the positive active material meet the requirements.
In a second aspect, the present invention provides a battery cell including the electrode assembly according to the first aspect.
An embodiment of the third aspect of the present application provides a battery including the battery cell described in the embodiment of the second aspect of the present application.
An embodiment of a fourth aspect of the present application provides an electrical device, including the battery of the embodiment of the third aspect of the present application, where the battery is used to provide electrical energy.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 illustrates a simplified schematic diagram of a vehicle in an embodiment of the present application;
FIG. 2 is a schematic diagram of the battery of the vehicle of FIG. 1;
fig. 3 is a schematic diagram illustrating the structure of one battery cell 10 in the battery 100 of fig. 2;
fig. 4 illustrates a schematic view of the structure of an electrode assembly in a battery cell according to some embodiments of the present application;
FIG. 5 shows a partial enlarged view at A in FIG. 4;
FIG. 6 is a schematic structural view of a first form of positive and negative electrode tabs in an electrode assembly according to some embodiments of the present application;
FIG. 7 is an enlarged view of a portion of FIG. 6 at B;
FIG. 8 is an enlarged view of a portion of FIG. 6 at C;
FIGS. 9 and 10 are partial schematic views of the junction of a first corner region and two adjacent flat regions, respectively, in an electrode assembly according to some embodiments of the present application;
FIG. 11 is a schematic structural view of a second form of positive and negative electrode tabs in an electrode assembly according to some embodiments of the present application;
FIG. 12 shows an enlarged view of a portion of FIG. 11 at D;
FIG. 13 is a schematic illustration of the structure of a third form of positive and negative electrode tabs in an electrode assembly in accordance with certain embodiments of the present application;
FIG. 14 is an enlarged view of a portion of FIG. 13 at E;
FIG. 15 is an enlarged view of a portion of FIG. 13 at F;
fig. 16, 17 and 18 are schematic structural views illustrating three types of positive electrode sheets, respectively, in an electrode assembly according to some embodiments of the present application;
the figures are not provided to scale.
An icon: 1000-a vehicle; 100-a battery; 10-a battery cell; 11-a housing; 111-a housing; 112-an end cap; 12-an electrode assembly; 121-positive pole piece; 1211-positive current collector; 12111-medial side; 12112-lateral surface; 1212-positive electrode active material layer; 12121-first positive electrode active material layer; 12122-second positive electrode active material layer; 1213-straight area; 12131-first flat area; 12132-second flat region; 12133-a first body; 12134-first reduced thickness region; 12135-a second body; 12136-second reduced thickness region; 1214-corner region; 12141-first corner region; 12142-second corner region; 12143-third corner region; 12144-fourth corner region; 1215-winding the starting end; 1216-bottom layer; 1217-surface layer; 1218 — a first recess; 1219-second recess; 122-negative pole piece; 1221-negative current collector; 1222-a negative electrode active material layer; 123-a first membrane; 124-a second membrane; 125-straight portion; 1261-a first fold; 1262-a second bent portion; 127-a tab; 13-an electrode terminal; 20-a box body; 21-a first part; 22-a second part; 200-a controller; 300-motor.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "including" and "having," and any variations thereof, in the description and claims of this application and the description of the above figures are intended to cover non-exclusive inclusions. The terms "first," "second," and the like in the description and claims of this application or in the above-described drawings are used for distinguishing between different elements and not for describing a particular sequential or chronological order.
Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the specification. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.
Throughout the description of the present application, it is to be noted that unless otherwise expressly specified or limited the terms "mounted," "connected," and "attached" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
The appearances of "a plurality" in this application are intended to mean more than two (including two).
In the present application, the battery cell may include a lithium ion secondary battery, a lithium ion primary battery, a lithium sulfur battery, a sodium lithium ion battery, a sodium ion battery, a magnesium ion battery, or the like, which is not limited in the embodiments of the present application. The battery cell may be a cylinder, a flat body, a rectangular parallelepiped, or other shapes, which is not limited in the embodiments of the present application. The battery cells are generally divided into three types in an encapsulation manner: the battery pack comprises a cylindrical battery monomer, a square battery monomer and a soft package battery monomer.
Reference to a battery in embodiments of the present application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the battery referred to in the present application may include a battery module or a battery pack, etc. The battery generally includes a case for enclosing one or more battery cells, and the case prevents liquid or other foreign materials from affecting the charge or discharge of the battery cells.
The single battery comprises an electrode assembly and electrolyte, and the single battery mainly depends on metal ions to move between a positive pole piece and a negative pole piece to work. The positive pole piece includes anodal mass flow body and anodal active material layer, and anodal active material layer coats in anodal mass flow body surface, and the negative pole piece includes negative current collector and negative pole active material layer, and the negative pole active material layer coats in the surface of negative current collector. Wherein, the electrode assembly is in a flat winding structure.
In the related art, for a single battery using an electrode assembly having a flat winding structure, lithium deposition easily occurs at a bent portion of the innermost several turns of the electrode assembly during charging of the single battery, and a pole piece is easily broken and a winding center hole is easily pressed to deform the electrode assembly, which all results in a reduction in safety of the single battery.
The inventor finds that the negative electrode sheet expands during the charging process of the battery cell, and the negative electrode sheet at the corner part of the innermost turns of the electrode assembly has the defects that the stress is difficult to release, the adjacent positive electrode sheet is seriously pressed and the like under the same expansion degree due to the small radius of the negative electrode sheet at the corner part of the innermost turns of the electrode assembly. If the amount of expansion of the negative electrode tab at the corner portions of the innermost turns of the electrode assembly can be reduced, the risk of breakage of the tab itself and deformation of the electrode assembly can be reduced. Furthermore, the expansion amount of the negative pole piece is related to the charge saturation degree of the negative pole piece in the charging process, if the charge saturation degree of the negative pole piece of the bending part of the innermost circles can be reduced, namely the lithium intercalation degree of the negative pole piece is reduced, the expansion amount of the negative pole piece can be reduced, the risk of lithium precipitation of the negative pole piece due to charge saturation can be reduced, and the safety performance of the single battery is obviously improved.
Based on the above thought, the inventor of the present application has proposed a technical scheme that, from the winding start end of the positive electrode sheet, the thickness of the positive electrode active material layer in the first N corner regions is smaller than the thickness of the positive electrode active material layer in the straight region. The unit area capacity of the positive active materials in the first N corner areas of the positive pole piece is reduced, so that the negative pole piece opposite to the positive pole piece is always in a charged unsaturated state in the charging process, the risk of lithium precipitation at the position is reduced, the risk that the negative pole piece is broken due to large expansion degree or the risk that an electrode assembly deforms at the position is reduced, and the single battery has good safety performance.
It can be understood that the battery cell described in the embodiments of the present application may directly supply power to an electric device, or may form a battery in parallel or in series, so as to supply power to various electric devices in the form of a battery.
It is to be understood that the electric device using the battery cell or the battery described in the embodiments of the present application may be applied to various forms, for example, a mobile phone, a portable device, a notebook computer, a battery car, an electric car, a ship, a spacecraft, an electric toy, an electric tool, and the like, for example, a spacecraft including an airplane, a rocket, a space shuttle, a spacecraft, and the like, an electric toy including a stationary type or a mobile type electric toy, for example, a game machine, an electric car toy, an electric ship toy, an electric plane toy, and the like, and an electric tool including a metal cutting electric tool, a grinding electric tool, an assembly electric tool, and a railway electric tool, for example, an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator, and an electric planer.
The battery cell and the battery described in the embodiments of the present application are not limited to be applied to the above-described electric devices, but may be applied to all electric devices using the battery cell and the battery.
FIG. 1 illustrates a simplified schematic diagram of a vehicle in an embodiment of the present application; fig. 2 shows a schematic diagram of the battery of the vehicle in fig. 1.
As shown in fig. 1, a battery 100, a controller 200, and a motor 300 are provided inside a vehicle 1000, and the battery 100 may be provided, for example, at the bottom or the front or rear of the vehicle 1000. The vehicle 1000 may be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile may be a pure electric automobile, a hybrid electric automobile, or a range-extended automobile, etc.
In some embodiments of the present application, the battery 100 may be used for power supply of the vehicle 1000, for example, the battery 100 may serve as an operating power source of the vehicle 1000. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, for operation power demand at the start, navigation, and traveling of the vehicle 1000.
In other embodiments, the battery 100 may be used not only as an operating power source of the vehicle 1000, but also as a driving power source of the vehicle 1000, instead of or in part replacing fuel or natural gas to provide driving power for the vehicle 1000.
Here, the battery 100 referred to in the embodiments of the present application refers to a single physical module including one or more battery cells 10 to provide higher voltage and capacity. For example, the battery 100 is formed by connecting a plurality of battery cells 10 in series or in parallel.
The battery 100 includes a plurality of battery cells 10 and a case 20, the plurality of battery cells 10 are connected in parallel or in series-parallel combination to realize high voltage output, and the plurality of battery cells 10 are assembled and then placed inside the case 20.
The case 20 includes a first portion 21 and a second portion 22, the first portion 21 and the second portion 22 are covered with each other to form a battery cavity, and a plurality of battery 100 modules are placed in the battery cavity. The plurality of battery cells 10 are connected in parallel or in series-parallel combination and then placed in a box body 20 formed by buckling a first part 21 and a second part 22.
Fig. 3 is a schematic diagram showing the structure of one battery cell in the battery of fig. 2.
As shown in fig. 3, each battery cell 10 includes a case 11, an electrode assembly 12, and two electrode terminals 13. The case 11 may have a hexahedral shape or other shapes, and the case 11 has a receiving cavity formed therein for receiving the electrode assembly 12 and the electrolyte.
In some embodiments of the present application, the case 11 includes a case 111 and an end cap 112, and one end of the case 111 has an opening such that the electrode assembly 12 can be placed inside the case 111 through the opening. The housing 111 may be made of a metal material such as aluminum, aluminum alloy, or nickel-plated steel. The end cap 112 is provided with two electrode terminals 13. One of the two electrode terminals 13 is a positive electrode terminal 13, and the other is a negative electrode terminal 13. The housing 111 may be rectangular parallelepiped or elliptical cylinder. Both of the electrode terminals 13 may be provided on the end cap 112, or both may be provided on the case 111, or one may be provided on the end cap 112 and the other may be provided on the case 111.
In other embodiments, the single battery 10 may be a pouch battery 100, and the case 111 may be a packaging bag made of an aluminum plastic film.
The electrode assembly 12 is disposed inside the case 11, the electrode assembly 12 includes two tabs 127 having opposite polarities, the positive electrode terminal 13 is connected to the tab 127 of the positive electrode of the electrode assembly 12, and the negative electrode terminal 13 is connected to the tab 127 of the negative electrode of the electrode assembly 12.
Fig. 4 illustrates a schematic view of the structure of an electrode assembly in a battery cell according to some embodiments of the present application; fig. 5 shows a partial enlarged view of a point a in fig. 4.
As shown in fig. 4 and 5, the electrode assembly 12 includes a positive electrode tab 121, a negative electrode tab 122, a first separator 123 and a second separator 124, the first separator 123 and the second separator 124 are used for separating the adjacent positive electrode tab 121 and the negative electrode tab 122, and the positive electrode tab 121, the negative electrode tab 122, the first separator 123 and the second separator 124 are wound to form the electrode assembly 12. The winding axis of the electrode assembly 12 is a first axis P, and the winding directions of the positive electrode tab 121, the negative electrode tab 122, the first separator 123, and the second separator 124 are all a first direction Q.
As shown in fig. 5, the positive electrode tab 121 includes a positive electrode collector 1211 and a positive electrode active material layer 1212 coated on a surface of the positive electrode collector 1211, and the negative electrode tab 122 includes a negative electrode collector 1221 and a negative electrode active material layer 1222 coated on a surface of the negative electrode collector 1221. Taking the lithium ion battery 100 as an example, the material of the positive electrode current collector 1211 may be aluminum, and the positive electrode active material may be lithium cobaltate, lithium iron phosphate, ternary lithium, lithium manganate, or the like. Along the width direction of the positive electrode tab 121, the positive electrode collector 1211 not coated with the positive electrode active material layer 1212 protrudes from the positive electrode collector 1211 coated with the positive electrode active material layer 1212, and the positive electrode collector 1211 not coated with the positive electrode active material layer 1212 is used as the positive electrode tab 127 (see fig. 3). The material of the negative electrode collector 1221 may be copper, and the negative electrode active material may be carbon, silicon, or the like. Along the width direction of the negative electrode tab 122, the negative electrode current collector 1221 not coated with the negative electrode active material layer 1222 protrudes from the negative electrode current collector 1221 coated with the negative electrode active material layer 1222, and the negative electrode current collector 1221 not coated with the negative electrode active material layer 1222 serves as the negative electrode tab 127 (see fig. 3). In order to ensure that the fuse is not blown by a large current, the tab 127 of the positive electrode is stacked in plural, and the tab 127 of the negative electrode is stacked in plural. The material of the first diaphragm 123 and the second diaphragm 124 may be PP (polypropylene) or PE (polyethylene).
As shown in fig. 4, the electrode assembly 12 is flat, and the longitudinal direction of the electrode assembly 12 is the direction X and the thickness direction is the direction Y on a plane perpendicular to the winding axis (i.e., the first axis P) thereof. Specifically, the electrode assembly 12 includes a straight portion 125, a first bent portion 1261 and a second bent portion 1262, the first bent portion 1261 and the second bent portion 1262 are located at both sides of the straight portion 125 along the direction X, and the first bent portion 1261 and the second bent portion 1262 have an arc-shaped surface, respectively. The electrode assembly 12 may be directly wound in a flat shape, or may be wound in a circular or oval shape and then the middle portion thereof is compacted to form the flat portion 125 in the middle portion of the electrode assembly 12.
The positive electrode tab 121 and the negative electrode tab 122 have a flat shape at the flat portion 125 and a bent shape at the first bent portion 1261 and the second bent portion 1262. Taking the positive electrode tab 121 as an example, along the first direction Q, one end of the positive electrode tab 121 close to the first axis P is a winding start end 1215, and the other end is a winding end. From the winding start end 1215 of the positive electrode tab 121, the portion of the positive electrode tab 121 located at the straight portion 125 is a straight region 1213, and the portions of the positive electrode tab 121 located at the first bent portion 1261 and the second bent portion 1262 are corner regions 1214. It is understood that the positive electrode tab 121 includes a plurality of corner regions 1214 and a plurality of straight regions 1213 along the winding direction of the positive electrode tab 121, the corner regions 1214 and the straight regions 1213 being alternately arranged.
FIG. 6 is a schematic structural view of a first form of positive and negative electrode tabs in an electrode assembly according to some embodiments of the present application; FIG. 7 is a partial enlarged view of the portion B in FIG. 6; fig. 8 is a partially enlarged view of C in fig. 6.
As shown in fig. 6, fig. 7, and fig. 8, some embodiments of the present application provide an electrode assembly 12, where the electrode assembly 12 is a winding structure, the electrode assembly 12 includes a positive electrode sheet 121 and a negative electrode sheet 122, the positive electrode sheet 121 includes a positive electrode collector 1211 and a positive electrode active material layer 1212 coated on the surface of the positive electrode collector 1211, the positive electrode sheet 121 has a plurality of straight regions 1213 and a plurality of corner regions 1214, and the straight regions 1213 and the corner regions 1214 are alternately arranged along a winding direction of the positive electrode sheet 121. From the winding start end 1215 of the positive electrode sheet 121, the thickness of the positive electrode active material layer 1212 of the first N corner regions 1214 is less than that of the positive electrode active material layer 1212 of the straight region 1213, and N is greater than or equal to 1.
That is, from the winding start end 1215 of the positive electrode sheet 121, the positive electrode active material layer 1212 has a plurality of concave portions each corresponding to one corner region 1214.
Along the direction X, the two bent portions 126 are a first bent portion 1261 and a second bent portion 1262, and the positive electrode tab 121 passes through the first bent portion 1261 and the second bent portion 1262 in sequence from the winding start end 1215 of the positive electrode tab 121. As shown in fig. 6, a first corner region 12141 is a portion of the positive electrode tab 121 located at the first bent portion 1261, a second corner region 12142 is a portion of the positive electrode tab 121 located at the second bent portion 1262, a third corner region 1214 is a portion of the positive electrode tab 121 located at the first bent portion 1261, a fourth corner region 1214 is a portion of the positive electrode tab located at the second bent portion 1262, and so on. It will be appreciated that first corner regions 12141 and third corner regions 1214 are located at the first fold portion 1261 and that second corner regions 12142 and fourth corner regions 12144 are located at the second fold portion 1262.
As shown in fig. 7 and 8, the positive electrode active material layer 1212 has a thickness H1 in each of the flat regions 1213, a thickness H2 in the first N corner regions 1214, and a thickness H1 in each of the remaining corner regions 1214, which is the same as the thickness of the flat regions 1213, H1 > H2.
N may be equal to 1, or may be another integer greater than 1. For example, N =1, from the winding start end 1215 of the positive electrode tab 121, the thickness of the positive electrode active material layer 1212 in the first corner region 12141 of the positive electrode tab 121 is H2, the thicknesses of the straight region 1213 of the positive electrode tab 121 and the positive electrode active material layer 1212 in the remaining corner regions 1214 are both H1, and H1 > H2; for another example, N =5, from the winding start end 1215 of the positive electrode tab 121, the positive electrode active material layer 1212 in the first five corner regions 1214 of the positive electrode tab 121 has a thickness H2, and the positive electrode active material layers 1212 in the straight regions 1213 and the remaining corner regions 1214 have thicknesses H1, H1 > H2.
The thickness of the positive electrode active material layer 1212 of each flat region 1213 is the same and H1, and the thickness of the positive electrode active material layer 1212 of the first N corner regions 1214 can be the same and H2, where H1 > H2; the thicknesses of the positive electrode active material layers 1212 in the first N corner regions 1214 may be different, and in the embodiment where the thicknesses of the positive electrode active material layers 1212 in the first two corner regions 1214 are smaller, the thickness of the positive electrode active material layer 1212 in the first corner region 12141 is H2a, the thickness of the positive electrode active material layer 1212 in the second corner region 12142 is H2b, and H2a < H2b < H1.
As shown in fig. 7 and 8, the positive electrode active material layers 1212 are applied to both sides of the positive electrode collector 1211 in the thickness direction, that is, the positive electrode active material layers 1212 include first positive electrode active material layers 12121 and second positive electrode active material layers 12122, the first positive electrode active material layers 12121 are applied to an inner side surface 12111 of the positive electrode collector 1211, that is, a side close to the first axis P, and the second positive electrode active material layers 12122 are applied to an outer side surface 12 of the positive electrode collector 1211, that is, a side away from the first axis P. In the first N corner regions 1214, the thickness of the first positive electrode active material layer 12121 of the first N corner regions 1214 may be smaller than the thickness of the first positive electrode active material layer 12121 of the straight region 1213 (as shown in fig. 7 and 8), the thickness of the second positive electrode active material layer 12122 of the first N corner regions 1214 may be smaller than the thickness of the second positive electrode active material layer 12122 of the straight region 1213, the thickness of the first positive electrode active material layer 12121 of the first N corner regions 1214 may be smaller than the thickness of the second positive electrode active material layer 12122 of the straight region 1213, and the thickness of the second positive electrode active material layer 12122 may be smaller than the thickness of the second positive electrode active material layer 12122 of the straight region 1213.
In the first N corner regions 1214, both ends of each corner region 1214 are respectively connected to a flat region 1213, and the thickness of the positive electrode active material layer 1212 may vary at the connection between the corner region 1214 and the flat region 1213, or the concave portion of the positive electrode active material layer 1212 formed in the corner region 1214 may slightly extend to the flat region 1213. Taking the first corner region 12141 and the adjacent two straight regions 1213 as an example, the straight region 1213 at one end of the first corner region 12141 near the winding start end 1215 is a first straight region 12131, and the straight region 1213 at the other end is a second straight region 12132.
As shown in fig. 7 and 8, in some embodiments of the present application, a step is formed between the first straight region 12131 and the first corner region 12141, and another step is formed between the positive electrode active material layer 1212 of the second straight region 12132 and the positive electrode active material layer 1212 of the first corner region 12141. In other embodiments of the present application, a transition portion is provided between the positive electrode active material layer 1212 of the first flat region 12131 and the positive electrode active material layer 1212 of the first corner region 12141, another transition portion is provided between the positive electrode active material layer 1212 of the second flat region 12132 and the positive electrode active material layer 1212 of the first corner region 12141, and the transition portion may be an arc surface or a plane surface, etc.
Fig. 9 and 10 are partial schematic views illustrating the junction of a first corner region and two adjacent flat regions, respectively, in an electrode assembly according to some embodiments of the present application.
As shown in fig. 9 and 10, in other embodiments of the present application, the positive active material layer 1212 of the first flat region 12131 includes a first body 12133 and a first reduced thickness region 12134, the first body 12133 has a thickness H1, and the first reduced thickness region 12134 is connected to the positive active material layer 1212 of the first corner region 12141 and has a thickness H2; the positive electrode active material layer 1212 of the second flat region 12132 includes a second body 12135 and a second reduced thickness region 12136, the second body 12135 has a thickness H1, and the second reduced thickness region 12136 is connected to the positive electrode active material layer 1212 of the first corner region 12141 and has a thickness H2.
In the electrode assembly 12 of the embodiment of the application, since H2 is less than H1 from the winding start end 1215 of the positive electrode tab 121, the unit area capacity of the positive active material in the first N corner regions 1214 of the positive electrode tab 121 can be reduced, so that the negative electrode tab 122 directly facing the positive electrode tab is always in a charge unsaturated state in the charging process, and thus the risk of lithium precipitation at the position is reduced, and the risk of the negative electrode tab 122 being broken due to a large expansion degree or deformation of the electrode assembly 12 can be reduced, so that the battery cell 10 has better safety performance.
In some embodiments of the present application, 1 ≦ N ≦ 10.
In the above scheme, the radius of the first ten corner regions 1214 from the winding start end 1215 of the positive electrode tab 121 is smaller, the probability of lithium precipitation of the corresponding negative electrode tab 122 is higher, and the thicknesses of the first ten corner regions 1214 of the positive electrode tab 121 are reduced, so that not only can the safety performance of the battery cell 10 be obviously improved, but also the remaining corner regions 1214 of the negative electrode tab 122 are in a charge saturation state in the charging process, and therefore, the battery cell has better energy density.
As shown in FIG. 6, in some embodiments of the present application, 1 ≦ N ≦ 4.
In the above scheme, the radius of the first four corner regions 1214 from the winding start end 1215 of the positive electrode tab 121 is smaller, which not only has a higher possibility of lithium precipitation with the corresponding negative electrode tab 122, but also has a difficulty in releasing the expansion stress, and the thickness of the first four corner regions 1214 of the positive electrode tab 121 is reduced, so that the risks of lithium precipitation, breakage, squeezing of the electrode assembly 12 and the like with the corresponding negative electrode tab 122 can be reduced, and the remaining corner regions 1214 of the negative electrode tab 122 can be ensured to be in a charge saturation state during the charging process, thereby having a better energy density.
As shown in fig. 5, 6, and 7, in some embodiments of the present application, the positive active material layer 1212 includes a first positive active material layer 12121 and a second positive active material layer 12122, the first positive active material layer 12121 is applied to an inner side surface 12111 of the positive current collector 1211, and the second positive active material layer 12122 is applied to an outer side surface 12112 of the positive current collector 1211. From the winding start end 1215 of the positive electrode sheet 121, the thickness of the first positive electrode active material layer 12121 of the first N corner regions 1214 is smaller than the thickness of the first positive electrode active material layer 12121 of the straight region 1213.
The inner side surface 12111 of the positive electrode collector 1211 refers to a surface of the positive electrode collector 1211 facing the first axis P in the thickness direction thereof; the outer side 12112 of the positive electrode current collector 1211 refers to a direction in which the positive electrode current collector 1211 faces away from the first axis P.
From the winding start end 1215 of the positive electrode tab 121, the thicknesses of the first positive electrode active material layers 12121 of the first N corner regions 1214 are all H2, and the thicknesses of the first positive electrode active material layers 12121 of the remaining corner regions 1214 and the first positive electrode active material layers 12121 of all the straight regions 1213 are all H1, with H1 > H2.
In the above scheme, the first positive electrode active material layer 12121 is coated on the inner side surface 12111 of the positive electrode current collector 1211, and the thickness of the first positive electrode active material layer 12121 in the first N corner regions 1214 is reduced, so that the unit area capacity of the positive electrode active material inside the first N corner regions 1214 can be reduced, the negative electrode sheet 122 facing inside can be always in a charge unsaturated state in the charging process, and the expansion degree of the negative electrode sheet 122 at this position can be further reduced. Because the radius of the negative electrode plate 122 facing the inner side of the corner area 1214 is smaller than that of the negative electrode plate 122 facing the outer side, the charge saturation degree of the negative electrode plate 122 in the charging process is reduced, the risk of lithium precipitation at the position is reduced, and the risk of fracture of the negative electrode plate 122 itself or deformation of the electrode assembly 12 due to too large expansion of the negative electrode plate 122 is also reduced, so that the single battery 10 has better safety performance.
FIG. 11 is a schematic structural view of a second form of positive and negative electrode tabs in an electrode assembly according to some embodiments of the present application; fig. 12 shows a partial enlarged view at D in fig. 11.
As shown in fig. 11 and 12, in some embodiments of the present application, the thickness of the second positive electrode active material layer 12122 of the first N corner regions 1214 is smaller than the thickness of the second positive electrode active material layer 12122 of the straight region 1213 from the winding start end 1215 of the positive electrode tab 121.
From the winding start end 1215 of the positive electrode tab 121, the thicknesses of the first positive electrode active material layer 12121 and the second positive electrode active material layer 12122 of the first N corner regions 1214 are both H2, and the thicknesses of the first positive electrode active material layer 12121 and the second positive electrode active material layer 12122 of the remaining corner regions 1214 and all of the straight regions 1213 are both H1, H1 > H2. As shown in fig. 12, the thickness of the first positive electrode active material layer 12121 and the thickness of the second positive electrode active material layer 12122 in the first corner region 12141 are both H2, and the thickness of the first positive electrode active material layer 12121 and the thickness of the second positive electrode active material layer 12122 in the first straight region 12131 are H1, H1 > H2.
In the above scheme, the second positive electrode active material layer 12122 is coated on the outer side surface 12112 of the positive electrode current collector 1211, and the thickness of the second positive electrode active material layer 12122 in the first N corner regions 1214 is reduced, so that the unit area capacity of the positive electrode active material layer 1212 in the outer sides of the first N corner regions 1214 can be reduced, the negative electrode sheet 122 facing the outer sides of the positive electrode active material layer is always in a charge unsaturation state in the charging process, and the expansion degree of the negative electrode sheet 122 in the position is further reduced, thereby reducing the charge saturation degree of the negative electrode sheet 122 in the charging process. Because the charges at the two sides of the first N corner regions 1214 of the negative electrode plate 122 are all in an unsaturated state during the charging process, the expansion amount of the negative electrode plate 122 can be better reduced, and the safety performance of the battery cell 10 is improved.
FIG. 13 is a schematic illustration of the structure of a third form of positive and negative electrode tabs in an electrode assembly in accordance with certain embodiments of the present application; FIG. 14 is an enlarged view of a portion of FIG. 13 at E; fig. 15 is a partial enlarged view at F in fig. 13.
As shown in fig. 13, 14, and 15, in some embodiments of the present application, the positive electrode active material layer 1212 includes a first positive electrode active material layer 12121 and a second positive electrode active material layer 12122, the first positive electrode active material layer 12121 is applied to the inner side surface 12111 of the positive electrode collector 1211, and the second positive electrode active material layer 12122 is applied to the outer side surface 12112 of the positive electrode collector 1211. In the first N corner regions 1214, along the winding direction (i.e., the first direction Q) of the positive electrode sheet 121, the thickness of the first positive electrode active material layer 12121 of one of the two adjacent corner regions 1214 is smaller than the thickness of the first positive electrode active material layer 12121 of the straight region 1213, and the thickness of the second positive electrode active material layer 12122 of the other one is smaller than the thickness of the second positive electrode active material layer 12122 of the straight region 1213.
In the adjacent two corner regions 1214, the first positive electrode active material layer 12121 of one corner region 1214 is reduced in thickness, and the second positive electrode active material layer 12122 of the other corner region 1214 is reduced in thickness.
For example, as shown in fig. 13, 14, and 15, N =4, the thickness of the first positive electrode active material layer 12121 is H2 in the first corner region 12141 and the third corner region 12143, and the thickness is H1 in the remaining corner regions 1214, H1 > H2; the second positive electrode active material layers 12122 of the second corner region 12142 and the fourth corner region 12144 have a thickness H2, and the second positive electrode active material layers 12122 of the remaining corner regions 1214 have a thickness H1, H1 > H2.
In the above configuration, since the thinned regions of the positive electrode active material layer 1212 are alternately present on both sides of the thickness of the positive electrode sheet 121 in the winding direction thereof, the stress on both sides of the positive electrode sheet 121 after winding and bending can be made substantially uniform, and the risk of breakage of the positive electrode sheet 121 can be reduced.
In some embodiments of the present application, a ratio of a thickness of the positive electrode active material layer 1212 of the first N corner regions 1214 to a thickness of the positive electrode active material layer 1212 of the straight region 1213 ranges from 0.05 to 0.95.
As shown in fig. 15, the thicknesses of the positive electrode active material layers 1212 in the first N corner regions 1214 are H2, the thicknesses of the positive electrode active material layers 1212 in the straight regions 1213 and the remaining corner regions 1214 are H1, and H2/H1 is 0.05 ≦ H2/H1 ≦ 0.95. That is, the ratio of the groove depth of the recessed portion of the positive electrode active material layer 1212 in the first N corner regions 1214 to the thickness of the remaining region is a, and satisfies 0.05 a 0.95.
The extension length of the first N corner regions 1214 of the positive pole piece 121 along the first direction Q is W, and W is more than or equal to 1 and less than or equal to 100. The above range of H2/H1 is applied to the above range of W, and can preferably reduce the risk of lithium deposition, breakage, and deformation of the pressed electrode assembly 12 of the negative electrode tab 122 disposed opposite to the first N corner regions 1214 of the positive electrode tab 121.
In the above scheme, the thickness ratio range of the positive active material layer 1212 of the first N corner regions 1214 of the positive electrode tab 121 to the positive active material layer 1212 of the flat region 1213 is within the above range, so that the expansion degree of the negative electrode tab 122 directly opposite to the first N corner regions 1214 can be effectively reduced, and the safety performance of the battery cell 10 can be improved.
In some embodiments of the present application, the ratio ranges from 0.48 to 0.95.
0.48. Ltoreq. H2/H1. Ltoreq.0.95, that is to say, 0.05. Ltoreq. A. Ltoreq.0.52.
As a preferred embodiment, along the first direction Q, the range W of the extending length of the first N corner regions 1214 of the positive electrode tab 121 satisfies W =76mm, which can well reduce the risks of lithium deposition, breakage and deformation of the pressing electrode assembly 12 of the negative electrode tab 122 disposed opposite to the first N corner regions 1214 of the positive electrode tab 121.
In the above scheme, the ratio range of the thickness of the positive active material layer 1212 of the positive electrode tab 121 at the first N corner regions 1214 and the flat region 1213 is further limited to be within the above range, so that the charge saturation degree of the negative electrode tab 122 corresponding to the first N corner regions 1214 can be increased as much as possible while the safety performance of the battery cell 10 is ensured, and the battery cell 10 has a higher energy density.
Fig. 16, 17 and 18 are schematic views illustrating structures of three forms of positive electrode sheets, respectively, in an electrode assembly according to some embodiments of the present application.
As shown in fig. 16, 17 and 18, in some embodiments of the present application, the positive active material layer 1212 includes a primer layer 1216 and a surface layer 1217, the primer layer 1216 is continuously applied to the surface of the positive current collector 1211 along the winding direction of the positive electrode sheet 121, and the surface layer 1217 is applied to the primer layer 1216 at intervals.
The thickness of the underlayer 1216 is the minimum thickness of the positive electrode active material layer 1212, the surface layers 1217 are coated on the underlayer 1216 at intervals along the winding direction (i.e., the first direction Q) of the positive electrode sheet 121, and a concave portion is formed in a region between two adjacent surface layers 1217, that is, a region of the positive electrode active material layer 1212 with a smaller thickness in the first N corner regions 1214.
As shown in fig. 16, based on the aforementioned embodiment that the thickness of the first positive electrode active material layer 12121 is reduced in the first N corner regions 1214, the thickness of the bottom layer 1216 is H2, the bottom layer 1216 is continuously applied to the inner side surface 12111 of the positive electrode current collector 1211, the surface layers 1217 are applied to the bottom layer 1216 at intervals along the first direction Q, each surface layer 1217 corresponds to a flat region 1213, a portion of the bottom layer 1216 exposed between two adjacent surface layers 1217 forms a first concave portion 1218, the first concave portion 1218 corresponds to one corner region 1214, and the thickness of the surface layer 1217 is H1-H2.
As shown in fig. 17, based on the aforementioned embodiment in which the thicknesses of the first positive electrode active material layer 12121 and the second positive electrode active material layer 12122 of the same corner region 1214 are both reduced in the first N corner regions 1214, the first positive electrode active material layer 12121 and the second positive electrode active material layer 12122 each include the base layer 1216 and the surface layer 1217, and the surface layers 1217 are coated at intervals in the first direction Q. The first concave portion 1218 is formed by the portion between two adjacent surface layers 1217 of the first positive electrode active material layer 12121, the second concave portion 1219 is formed by the portion between two adjacent surface layers 1217 of the second positive electrode active material layer 12122, and the first concave portion 1218 and the second concave portion 1219 are symmetrically distributed on two sides of the positive electrode current collector 1211 and both correspond to the same corner region 1214.
As shown in fig. 18, based on the aforementioned embodiment in which the first positive electrode active material layer 12121 of one of the two adjacent corner regions 1214 is thinned and the second positive electrode active material layer 12122 of the other one is thinned, the first positive electrode active material layer 12121 and the second positive electrode active material layer 12122 each include a primer layer 1216 and a surface layer 1217, and the surface layers 1217 are coated at intervals in the first direction Q. A portion between two adjacent surface layers 1217 of the first positive electrode active material layer 12121 forms a first concave portion 1218, and a portion between two adjacent surface layers 1217 of the second positive electrode active material layer 12122 forms a second concave portion 1219. The first concave portions 1218 and the second concave portions 1219 are staggered on two sides of the positive electrode collector 1211 and correspond to two adjacent corner regions 1214.
In the above scheme, the positive electrode active material layer 1212 in this form has a characteristic of being easy to manufacture and mold, and the manufacturing cost of the positive electrode tab 121 can be reduced.
In some embodiments of the present application, the bottom layer 1216 and the top layer 1217 may be the same or different materials.
For example, the underlayer 1216 and the surface layer 1217 are made of the same material, and are both large-particle-size lithium iron phosphate materials, D50=10 μm; for another example, the material of the underlayer 1216 is different from that of the surface layer 1217, the underlayer 1216 is made of a small-particle-size lithium iron phosphate material with D50=1.2 μm, and the surface layer 1217 is made of a large-particle-size lithium iron phosphate material with D50=5 μm.
In the above scheme, by selecting the materials of the bottom layer 1216 and the surface layer 1217, the thickness of the positive active material layer 1212 and the active material unit area capacity can be flexibly adjusted, so that the thicknesses of the corner region 1214 and the flat region 1213 of the positive electrode tab 121 and the active material unit area capacity meet the requirements.
Some embodiments of the present application provide a battery cell 10 including an electrode assembly 12 of embodiments of the present application.
Some embodiments of the present application provide a battery 100 including the battery cell 10 of the embodiments of the present application.
Some embodiments of the present application provide an electric device, including the battery 100 of the embodiments of the present application, the battery 100 being used to provide electric energy.
As shown in fig. 1 to fig. 15, some embodiments of the present application provide a battery cell 10, including an electrode assembly 12 in a winding structure, where the electrode assembly 12 includes a positive electrode sheet 121 and a negative electrode sheet 122, and the positive electrode sheet 121 includes a positive electrode collector 1211 and a positive electrode active material layer 1212 coated on the surface of the positive electrode collector 1211. The positive electrode tab 121 has a plurality of straight regions 1213 and a plurality of corner regions 1214, the straight regions 1213 and the corner regions 1214 being alternately arranged along the winding direction of the positive electrode tab 121. Wherein, the positive electrode active material layer 1212 of the first N corner regions 1214 has a concave part from the winding start end 1215 of the positive electrode sheet 121, and N is more than or equal to 1. The recesses may be provided in pairs on both sides of the positive electrode collector 1211, or may be alternately provided on both sides of the positive electrode collector 1211 along the first direction Q.
In some embodiments of the present application, N =10, lithium deposition is likely to occur in the first ten corner regions 1214, and by providing the concave portions in the positive electrode active material layers 1212 in the first ten corner regions 1214, the risk of lithium deposition occurring in the bent portion 126 of the inner ring of the electrode assembly 12 can be effectively reduced, and the safety performance of the battery cell 10 can be improved.
Preferably, N =4, the radius of the negative electrode pole piece 122 opposite to the first four corner regions 1214 is small, and stress is not easily released when expansion occurs. The positive active material layer 1212 of the first four corner regions 1214 is provided with the concave portion, so that the risks of the negative electrode piece 122 of the inner ring of the electrode assembly 12 breaking and the electrode assembly 12 deforming can be effectively reduced, and the safety performance of the battery cell 10 is improved.
As shown in fig. 16 to 18, in some embodiments of the present application, the positive active material layer 1212 includes a bottom layer 1216 and surface layers 1217, the bottom layer 1216 is continuously coated on the surface of the positive current collector 1211, the surface layers 1217 are coated on the surface of the bottom layer 1216 at intervals, and a concave portion is formed between two adjacent surface layers 1217 and corresponds to one corner region 1214. In the coating of the positive electrode active material layer 1212, two coating processes may be provided, a first coating process for continuously coating the primer layer 1216 and a second coating process for intermittently coating the surface layer 1217 downstream of the first coating process. The barrier can be placed on the bottom layer 1216 after the first coating pass is completed and removed after the second coating pass is completed to form a recess where the barrier is placed. The process for coating and molding the positive electrode active material layer 1212 is simple and feasible, and can mold the concave portion.
In the electrode assembly 12 of the embodiment of the present application, the thickness of the first N corner regions 1214 of the positive electrode tab 121 is relatively thin, so that the lithium insertion degree of the negative electrode tab 122 corresponding to the corner regions 1214 can be reduced, the risk of lithium precipitation of the negative electrode tab 122 corresponding to the corner regions 1214 and the risk of tab fracture due to expansion are significantly reduced, and the safety performance of the battery cell 10 including the electrode assembly 12 is greatly improved.
It should be noted that the features of the embodiments in the present application may be combined with each other without conflict.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (13)
1. An electrode assembly is characterized in that the electrode assembly is of a winding structure and comprises a positive electrode piece and a negative electrode piece, wherein the positive electrode piece comprises a positive electrode current collector and a positive electrode active substance layer coated on the surface of the positive electrode current collector, the positive electrode piece is provided with a plurality of straight areas and a plurality of corner areas, and the straight areas and the corner areas are alternately arranged along the winding direction of the positive electrode piece;
the thickness of the positive active material layers of the first N corner regions from the winding starting end of the positive pole piece is smaller than that of the positive active material layers of the straight region, and N is larger than or equal to 1.
2. The electrode assembly of claim 1, wherein 1 ≦ N ≦ 10.
3. The electrode assembly of claim 2, wherein 1 ≦ N ≦ 4.
4. The electrode assembly according to claim 1, wherein the positive electrode active material layer includes a first positive electrode active material layer coated on an inner side surface of the positive electrode current collector and a second positive electrode active material layer coated on an outer side surface of the positive electrode current collector;
from the winding starting end of the positive pole piece, the thickness of the first positive pole active material layer in the first N corner areas is smaller than that of the first positive pole active material layer in the straight area.
5. The electrode assembly according to claim 4, wherein the thickness of the second positive electrode active material layer of the first N corner regions from the winding start end of the positive electrode tab is smaller than the thickness of the second positive electrode active material layer of the flat region.
6. The electrode assembly according to claim 1, wherein the positive electrode active material layer includes a first positive electrode active material layer coated on an inner side surface of the positive electrode current collector and a second positive electrode active material layer coated on an outer side surface of the positive electrode current collector;
in the first N corner regions, along the winding direction of the positive electrode sheet, the thickness of the first positive electrode active material layer in one of the two adjacent corner regions is smaller than the thickness of the first positive electrode active material layer in the flat region, and the thickness of the second positive electrode active material layer in the other one is smaller than the thickness of the second positive electrode active material layer in the flat region.
7. The electrode assembly according to claim 1, wherein the ratio of the thickness of the positive electrode active material layer of the first N corner regions to the thickness of the positive electrode active material layer of the flat region is in the range of 0.05 to 0.95.
8. The electrode assembly of claim 7, wherein the ratio is in the range of 0.48-0.95.
9. The electrode assembly according to claim 1, wherein the positive active material layer includes a primer layer and a surface layer, the primer layer is continuously applied to the surface of the positive current collector along a winding direction of the positive electrode sheet, and the surface layer is applied to the primer layer at intervals.
10. The electrode assembly of claim 9, wherein the base layer and the skin layer are the same or different materials.
11. A battery cell comprising an electrode assembly according to any one of claims 1 to 10.
12. A battery comprising the battery cell of claim 11.
13. An electrical device comprising a battery as claimed in claim 12 for providing electrical energy.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117790684A (en) * | 2024-02-27 | 2024-03-29 | 武汉星纪魅族科技有限公司 | Lithium ion battery and preparation method thereof, and preparation method of electrode plate |
| WO2024092726A1 (en) * | 2022-11-04 | 2024-05-10 | 宁德时代新能源科技股份有限公司 | Electrode assembly, battery cell, battery and electrical device |
| WO2024174061A1 (en) * | 2023-02-20 | 2024-08-29 | 宁德时代新能源科技股份有限公司 | Electrode assembly, battery cell, battery, powered device, positive electrode plate, and preparation method therefor |
-
2022
- 2022-05-30 CN CN202221330631.6U patent/CN217719660U/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024092726A1 (en) * | 2022-11-04 | 2024-05-10 | 宁德时代新能源科技股份有限公司 | Electrode assembly, battery cell, battery and electrical device |
| WO2024174061A1 (en) * | 2023-02-20 | 2024-08-29 | 宁德时代新能源科技股份有限公司 | Electrode assembly, battery cell, battery, powered device, positive electrode plate, and preparation method therefor |
| CN117790684A (en) * | 2024-02-27 | 2024-03-29 | 武汉星纪魅族科技有限公司 | Lithium ion battery and preparation method thereof, and preparation method of electrode plate |
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