Battery cell assembly and preparation method thereof, secondary battery and power utilization device

Abstract

The invention provides a battery cell assembly and a preparation method thereof, a secondary battery and a power utilization device, the battery cell assembly is of a winding type structure and comprises a positive pole piece and a negative pole piece which are arranged in a laminated manner, and each of the positive pole piece and the negative pole piece comprises a first tab part, a main body part and a second tab part, the main body part extends along a first direction and comprises a first end and a second end which are oppositely arranged in the first direction, the first end of the main body part is connected with the first tab part, the second end of the main body part is connected with the second tab part, and at least one of the first tab part and the second tab part is coated with a plurality of coating layers which are arranged at intervals along the winding direction of the first tab part and the second tab part; the winding direction is orthogonal to the first direction, and the coating layer and the main body part are arranged at intervals; and at least part of the coating layer on the positive pole piece is opposite to at least part of the coating layer on the negative pole piece. According to the battery cell assembly and the preparation method thereof, the secondary battery and the power utilization device provided by the invention, the energy density of the battery cell can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a battery cell assembly, a preparation method thereof, a secondary battery and a power utilization device. BACKGROUND

[0002] The positive and negative tabs of mainstream large cylindrical battery cells are generally processed by cutting and stacking process, rubbing and flattening process, etc. Both of the above processes will leave empty foil tabs at both ends in the axial direction of the battery cell, and will occupy a certain thickness, thereby forming a part of the invalid volume at both ends of the battery cell, affecting the energy density of the battery cell. In addition, the tabs processed by the above cutting and stacking process and rubbing and flattening process will also cause welding energy fluctuation due to the uneven thickness of the welding part when welding with the busbar, thereby causing problems such as tab area welding, damage to the internal separator of the winding core, etc., affecting the performance of the battery cell.

[0003] With the development of battery technology, the requirement for the energy density of the battery cell is gradually increasing. How to improve the energy density of the battery while ensuring the stability of the battery performance is a problem to be solved. SUMMARY

[0004] The present application aims to at least partially solve one of the technical problems in the related art.

[0005] To this end, the embodiments of the present application provide a battery cell assembly, a preparation method thereof, a secondary battery and a power utilization device. The battery cell assembly, the preparation method thereof, the secondary battery and the power utilization device can improve the energy density of the battery cell.

[0006] The battery cell assembly provided by an embodiment of the present application is of a winding type structure and includes a positive electrode tab and a negative electrode tab arranged in layers. The positive electrode tab and the negative electrode tab each include a first tab portion, a main body portion and a second tab portion. The main body portion extends along a first direction and includes a first end and a second end arranged opposite to each other in the first direction. The first end of the main body portion is connected to the first tab portion, and the second end of the main body portion is connected to the second tab portion. At least one of the first tab portion and the second tab portion is coated with a plurality of coating layers arranged at intervals along a winding direction thereof. The winding direction is orthogonal to the first direction, and the coating layers are arranged at intervals from the main body portion.

[0007] At least part of the coating layers on the positive electrode tab is arranged opposite to at least part of the coating layers on the negative electrode tab.

[0008] The electrode assembly of the embodiment of the application is provided with a plurality of coating layers arranged at intervals with the main body on at least one of the first tab and the second tab, at least part of the coating layers on the positive electrode tab can be arranged at least partially opposite to the coating layers on the negative electrode tab, thereby forming an energy storage structure capable of storing energy on at least one of the first tab and the second tab. The above structure design not only reduces the area of the empty foil area formed on at least one of the first tab and the second tab, but also effectively utilizes the space of at least one of the first tab and the second tab for energy storage, so that the electrode assembly can obtain higher energy density.

[0009] In some embodiments, one of the first tab of the positive electrode tab and the first tab of the negative electrode tab comprises a plurality of sub-tabs arranged at intervals in the circumferential direction of the electrode assembly, and the coating layer is coated on the sub-tabs; and the other comprises a coating area and a lamination area arranged at intervals in the circumferential direction of the electrode assembly, the coating area is coated with the coating layer, and the lamination area is not coated with the coating layer.

[0010] And / or, one of the second tab of the positive electrode tab and the second tab of the negative electrode tab comprises a plurality of sub-tabs arranged at intervals in the circumferential direction of the electrode assembly, and the coating layer is coated on the sub-tabs; and the other comprises a coating area and a lamination area arranged at intervals in the circumferential direction of the electrode assembly, the coating area is coated with the coating layer, and the lamination area is not coated with the coating layer.

[0011] In some embodiments, at least one of the first tab and the second tab is folded inwardly in the radial direction of the electrode assembly, and at least part of the lamination area is laminated outside the coating area.

[0012] In some embodiments, in the first direction, the projection of the coating layer on the positive electrode tab partially overlaps with the projection of the coating layer on the negative electrode tab.

[0013] In some embodiments, in the winding direction of the electrode assembly, the coating size of the coating layer in the first direction gradually increases or decreases in the same first tab or second tab;

[0014] And / or, in the winding direction of the electrode assembly, the interval size of the coating layer and the main body in the first direction gradually decreases or increases;

[0015] And / or, in the winding direction of the electrode assembly, the interval size between two adjacent coating layers gradually increases.

[0016] In some embodiments, the size of each adjacent coating layer in the first direction gradually increases or decreases in an arithmetic progression along the winding direction of the electrode assembly.

[0017] In some embodiments, the coating size of the coating layer in the first direction is not more than 13 mm, and the coating size of the coating layer in the winding direction is not more than 23 mm.

[0018] In some embodiments, the interval size of the coating layer and the main body part in the first direction is not less than 1 mm.

[0019] In some embodiments, at least one of the first tab part and the second tab part is symmetrically provided with the coating layer on both sides in the thickness direction.

[0020] In some embodiments, two bus bars are further included, one of the bus bars is connected to the first end of the main body part through the first tab part, and the other bus bar is connected to the second end of the main body part through the second tab part.

[0021] According to another embodiment of the present application, a preparation method of an electrode assembly is provided, the positive electrode tab and the negative electrode tab of the electrode assembly each include a first tab part, a main body part and a second tab part arranged in sequence along a first direction, and the preparation method includes the following steps:

[0022] Intervals of paste are coated on at least one of the first tab part and the second tab part along the length direction of the main body part to form coating layers arranged at intervals along the length direction of the main body part, and the coating layers are arranged at intervals with the main body part in the first direction;

[0023] The positive electrode tab, the separator and the negative electrode tab are arranged in layers, and at least part of the coating layers on the positive electrode tab are arranged opposite to at least part of the coating layers on the negative electrode tab to form a to-be-wound component;

[0024] The to-be-wound component is wound along the length direction of the main body part to form a wound structure.

[0025] The preparation method of the electrode assembly provided by the embodiments of the present application forms an energy storage structure with energy storage function in the tab part of the electrode assembly by coating paste on at least one of the first tab part and the second tab part of the electrode assembly to form coating layers arranged at intervals with the main body part and the coating layers are distributed in the corresponding positions of the oppositely arranged positive electrode tab and negative electrode tab, which utilizes the tab area of the empty foil to enable the tab part to also achieve energy storage, thereby effectively improving the energy density of the electrode assembly and enabling the electrode assembly to have better energy storage effect.

[0026] In some embodiments, the coating size of the coating layer in the first direction gradually increases or decreases along the winding direction of the battery cell assembly.

[0027] And / or, the interval size of the coating layer and the main body part in the first direction gradually decreases or increases along the winding direction of the battery cell assembly.

[0028] And / or, the interval size between two adjacent coating layers gradually increases along the winding direction of the battery cell assembly.

[0029] In some embodiments, the preparation method of the battery cell assembly further comprises coating slurry on both sides of at least one of the first tab part and the second tab part in the thickness direction thereof to achieve double-sided coating.

[0030] In some embodiments, the preparation method of the battery cell assembly further comprises:

[0031] cutting one of the first tab part of the positive electrode tab and the first tab part of the negative electrode tab to obtain a plurality of sub-tabs arranged at intervals, and the coating layer is coated on the sub-tabs;

[0032] And / or, cutting one of the second tab part of the positive electrode tab and the second tab part of the negative electrode tab to obtain a plurality of sub-tabs arranged at intervals, and the coating layer is coated on the sub-tabs.

[0033] In some embodiments, the preparation method of the battery cell assembly further comprises folding the first tab part and / or the second tab part:

[0034] folding the area coated with the coating layer inward along the radial direction of the battery cell assembly to form a coating area, and in the first direction, the projection of the coating layer on the positive electrode tab partially overlaps with the projection of the coating layer on the negative electrode tab;

[0035] folding the area not coated with the coating layer inward along the radial direction of the battery cell assembly to form a lamination area, and at least part of the lamination area is laminated on the outside of the coating area.

[0036] In some embodiments, the preparation method of the battery cell assembly further comprises installing bus bars outside the first tab part and the second tab part:

[0037] connecting a certain bus bar to the first tab part through the lamination area;

[0038] connecting another bus bar to the second tab part through the lamination area.

[0039] The battery cell assembly provided by the embodiment of the application is prepared by the preparation method.

[0040] The battery cell assembly provided by the embodiment of the application can be prepared by the preparation method, and the prepared battery cell assembly has a high energy density.

[0041] The secondary battery provided by the embodiment of the application comprises the battery cell assembly.

[0042] The power device provided by the embodiment of the application comprises the secondary battery.

[0043] Additional aspects and advantages of the application will be described in the following description and become apparent from the following description or will be learned by practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can be obtained from these drawings without creative labor.

[0045] Figure 1 is a front view of a positive electrode sheet in the battery cell assembly provided by the embodiment of the application;

[0046] Figure 2 is a front view of a negative electrode sheet in the battery cell assembly provided by the embodiment of the application;

[0047] Figure 3 is a cross-sectional view of the positive electrode sheet and the negative electrode sheet in the battery cell assembly provided by the embodiment of the application in an unfolded state;

[0048] Figure 4 is a side view of the battery cell assembly provided by the embodiment of the application in an unfolded state;

[0049] Figure 5 is a structure schematic view of a folding area of the battery cell assembly provided by the embodiment of the application in a folded state;

[0050] Figure 6 is a welding schematic view of a busbar in the battery cell assembly provided by the embodiment of the application.

[0051] Figure 7 is a flow chart of the preparation method of the battery cell assembly provided by the embodiment of the application.

[0052] In the drawings:

[0053] 10, cell assembly; 101, positive electrode tab; 102, negative electrode tab; 103, separator;

[0054] 1, first tab portion; 2, main body portion; 21, first end; 22, second end; 3, second tab portion; 4, coating layer; 5, sub-tab; 6, coating region; 7, lamination region; 8, busbar;

[0055] X, first direction;

[0056] Y, winding direction. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work under the premise that the embodiments in the present application belong to the scope of protection of the present application.

[0058] Unless otherwise defined, 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 specification herein is for describing particular embodiments only and is not intended to be limiting of the present application; the use of the terms "include," "have," or "comprise" and variations thereof herein are intended to be equivalent to the term "comprising"; the use of the term "about" in relation to a geographic location refers to a location within a 10 km radius of the geographic location.

[0059] In the description of the embodiments of the present application, the technical terms "first", "second", and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise explicitly and specifically limited. Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0060] Reference herein 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 present application. The appearance of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily independent or alternative embodiments to other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0061] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the same, wherein any statement of a range can be modified by the use of "sub ranges" to achieve those sub-ranges. For example, a range of "1 to 10" can include any and all sub-ranges between (and including) the minimum value of 1 and the maximum value of 10, that is, any value from 1 to 10, including 1 and 10. In addition, the phrase "a range of "a to b" means that the range includes any and all sub-ranges between (and including) the minimum value of a and the maximum value of b. For example, the phrase "a range of 1 to 10" means that the range includes any and all sub-ranges between (and including) the minimum value of 1 and the maximum value of 10. Further, a number of values and sub-ranges are stated herein. It is specifically intended that each of the range and sub-ranges be independently combinable with any other of the ranges or sub-ranges. For example, the range of "0 to 5" is intended to include any and all sub-ranges between (and including) the minimum value of 0 and the maximum value of 5, that is, any value from 0 to 5, including 0 and 5. In addition, the phrase "a range of "a to b" means that the range includes any and all sub-ranges between (and including) the minimum value of a and the maximum value of b. For example, the phrase "a range of 1 to 10" means that the range includes any and all sub-ranges between (and including) the minimum value of 1 and the maximum value of 10. Further, a number of values and sub-ranges are stated herein. It is specifically intended that each of the range and sub-ranges be independently combinable with any other of the ranges or sub-ranges. For example, the range of "0 to 5" is intended to include any and all sub-ranges between (and including) the minimum value of 0 and the maximum value of 5, that is, any value from 0 to 5, including 0 and 5.

[0062] In the description of the embodiments of the present application, the term "and / or" is only a description of association relationship of associated objects, that is, there can be three relationships, for example, A and / or B, which can represent the three cases of A existing alone, A and B existing together, and B existing alone. In addition, the character " / " in the present application generally represents that the front and rear associated objects have an "or" relationship.

[0063] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0064] In the description of the embodiments of the present application, unless specifically defined and limited otherwise, the terms "mount", "connected", "connection", "fixed", and the like should be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be direct connection, can also be indirect connection through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0065] In the present application, unless specifically defined and limited otherwise, the first feature is "on" or "under" the second feature. The first and second features can be in direct contact, or the first and second features can be in indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0066] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in the specification and the features of different embodiments or examples without contradiction.

[0067] The following will be described in conjunction with Figures 1-7 The following will be described in conjunction with

[0068] The secondary battery mentioned in the embodiments of the present application refers to a single physical module comprising one or more cell assemblies to provide higher voltage and capacity. Among them, multiple cell assemblies can be directly connected in series, parallel or mixed connection to form the secondary battery. Mixed connection means that there are both series and parallel connections among multiple cell assemblies. Multiple cell assemblies can also be connected in series, parallel or mixed connection to form a battery module, and multiple battery modules are connected in series, parallel or mixed connection to form the secondary battery. The secondary battery can also include a box for packaging one or more cell assemblies. The box can prevent liquid or other foreign matter from affecting the charging or discharging of the cell assembly.

[0069] The cell assembly comprises an electrode assembly and an electrolyte, and the electrode assembly is composed of a positive electrode sheet, a negative electrode sheet and a separator. The cell assembly mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work. The positive electrode sheet comprises a positive current collector and a positive active material layer, and the positive active material layer is coated on the surface of the positive current collector. The positive current collector without the positive active material layer protrudes from the positive current collector with the positive active material layer, and the positive current collector without the positive active material layer serves as the tab portion of the positive electrode sheet. Taking a lithium ion secondary battery as an example, the material of the positive current collector can be aluminum, and the positive active material can be lithium cobaltate, lithium iron phosphate, ternary lithium or lithium manganate, etc. The negative electrode sheet comprises a negative current collector and a negative active material layer, and the negative active material layer is coated on the surface of the negative current collector. The negative current collector without the negative active material layer protrudes from the negative current collector with the negative active material layer, and the negative current collector without the negative active material layer serves as the tab portion of the negative electrode sheet. The material of the negative current collector can be copper, and the negative active material can be carbon or silicon, etc. The material of the separator can be PP (polypropylene) or PE (polyethylene), etc.

[0070] At present, from the development of market situation, the application of power battery is more and more widely. The power battery is not only applied to the energy storage power supply system of hydropower, thermal power, wind power and solar power station, but also widely applied to electric vehicles such as electric scooter, electric bicycle, electric motorcycle, electric vehicle, electric transportation tool, military equipment and aerospace, etc. With the continuous expansion of the application field of power battery, the demand of its market is also increasing.

[0071] In the battery technology, how to improve the energy density of the battery while ensuring the stability of the battery performance is a problem to be solved.

[0072] Applicant notices that, taking cylindrical battery as an example, the electrode assembly is assembled, and the tab part needs to be cut and folded or flattened after being connected with the busbar to ensure the stable connection of the tab part. Since the electrode tab has a certain thickness, during the cutting and folding or flattening process of the tab, the thickness of each position of the tab part is not completely consistent, thereby causing energy fluctuation during welding, and the relatively thin part may be welded through, thereby burning the inner diaphragm of the winding core, causing short circuit of the battery, and seriously affecting the stability of the battery.

[0073] In order to improve the energy density of the electrode assembly under the premise of overcoming the above problems, the application provides an electrode assembly.

[0074] Specifically, as shown in Figures 1-6 The electrode assembly 10 is a winding type structure, which includes the positive electrode tab 101 and the negative electrode tab 102 arranged in layers. The positive electrode tab 101 and the negative electrode tab 102 each include a first tab part 1, a main body part 2, and a second tab part 3. The main body part 2 extends along a first direction X and includes a first end 21 and a second end 22 arranged opposite to each other in the first direction X. The first end 21 of the main body part 2 is connected with the first tab part 1, and the second end 22 of the main body part 2 is connected with the second tab part 3. At least one of the first tab part 1 and the second tab part 3 is coated with a plurality of coating layers 4 arranged at intervals along a winding direction Y thereof. The winding direction Y is orthogonal to the first direction X. The coating layers 4 are arranged at intervals from the main body part 2, as shown in Figure 1 and Figure 2 At least part of the coating layers 4 on the positive electrode tab 101 is arranged opposite to at least part of the coating layers 4 on the negative electrode tab 102, as shown in Figure 3 .

[0075] The electrode assembly 10 of the embodiment of the application is provided with a plurality of coating layers 4 arranged at intervals from the main body part 2 on at least one of the first tab part 1 and the second tab part 3. At least part of the coating layers 4 on the positive electrode tab 101 can be arranged opposite to at least part of the coating layers 4 on the negative electrode tab 102, thereby forming an energy storage structure capable of storing energy on at least one of the first tab part 1 and the second tab part 3. The above structure design not only reduces the area of the empty foil area formed on at least one of the first tab part 1 and the second tab part 3, but also effectively utilizes the space of at least one of the first tab part 1 and the second tab part 3 for energy storage, so that the electrode assembly 10 can obtain higher energy density.

[0076] It should be noted that the first tab portion 1 and the second tab portion 3 must have a part of the foil area not coated with the conductive active material, which is used to realize the tab function of the first tab portion 1 and the second tab portion 3. The first tab portion 1 and / or the second tab portion 3 with the coating layer 4 can realize the conductive function through the structure of the bus bar 8 corresponding to the structure of the foil area not coated with the conductive active material.

[0077] In some embodiments, the inner side of the bus bar 8 connected to the battery cell assembly 10 should be configured to be in a form not in contact with the coating layer 4 (which can be any one of the first tab portion 1 and the second tab portion 3). For example, the side of the inner side wall of the bus bar 8 opposite to the coating layer 4 can be recessed inwardly to avoid the coating layer 4; or the side of the inner side wall of the bus bar 8 opposite to the foil area not coated with the conductive active material can be protruded outwardly to ensure that the bus bar 8 can avoid the coating layer 4 when connected to the foil area not coated with the conductive active material, etc. The above structure can ensure that the bus bar 8 can realize its normal conduction function.

[0078] In some embodiments, at least one of the first tab portion 1 and the second tab portion 3 is symmetrically provided with the coating layer 4 on both sides in the thickness direction.

[0079] Based on the energy storage effect, the first tab portion 1 and the second tab portion 3 are both coated with the coating layer 4 by using a double-sided coating technology, for example, a double-sided coating process, or the two sides of the tab can be coated by using a single-sided coating process respectively. In addition, the separator 103 is necessarily arranged between the positive tab 101 and the negative tab 102. The material and arrangement of the separator 103 are prior art, which will not be described here.

[0080] Specifically, in some embodiments, the conductive active material constituting the coating layer 4 on the positive tab 101 is lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganese oxide, or sodium ion positive active material, etc., and the coating surface density is 35-45 mg / cm 2 ; the conductive active material constituting the coating layer 4 on the negative tab 102 is graphite, hard carbon, silicon-carbon, etc., and the coating surface density is 15-20 mg / cm 2 .

[0081] The coating surface density is affected by the coating material, coating process, and coating equipment, etc. The above numerical values are conventional data in the field, which are only used to illustrate the scheme and are not limited to the coating surface density data of the coating layer 4 in the embodiments.

[0082] The interval arrangement between the coating layer 4 and the main portion 2 means that there is a foil area not coated with the conductive active material between the coating layer 4 and the main portion 2, and the size of the foil area not coated with the conductive active material in the first direction X is not less than 1 mm, i.e., the interval between the main portion 2 and the coating layer 4 in the first direction X is not less than 1 mm.

[0083] The interval of the body part 2 and the coating layer 4 in the first direction X is selected based on comprehensive consideration of energy density and safety. Through reasonable size design, the distribution area of the coating layer 4 can be as large as possible, and the utilization rate of the tab area can be improved on the premise of reducing resource waste.

[0084] The positive electrode tab 101 comprises, from top to bottom in the first direction X (i.e. the height direction of the battery assembly 10, which is also the width direction of the positive electrode tab 101 itself), the first tab part 1, the body part 2 and the second tab part 3. When the positive electrode tab 101 is coated to form the coating layer 4, the coating layer 4 can be distributed in at least one of the first tab part 1 and the second tab part 3 according to the needs, and the same applies to the negative electrode tab 102.

[0085] When the coating layer 4 on the positive electrode tab 101 is only located in the first tab part 1, and correspondingly, the coating layer 4 on the negative electrode tab 102 is also only arranged in the first tab part 1, then the second tab part 3 of the positive electrode tab 101 and the negative electrode tab 102 can remain consistent with the tab part structure disclosed in the related art. Similarly, when the coating layer 4 on the positive electrode tab 101 is only located in the second tab part 3, and the negative electrode tab 102 also only has the coating layer 4 on the second tab part 3, then the first tab part 1 of the positive electrode tab 101 and the negative electrode tab 102 can remain consistent with the tab part structure disclosed in the related art. Alternatively, as shown in Figure 1 and Figure 2 At this time, the first tab part 1 and the second tab part 3 of the positive electrode tab 101 are both provided with the coating layer 4. When the battery assembly 10 is in a wound state, at least part of the coating layer 4 can overlap, thereby achieving the energy storage effect, as shown in Figure 3 .

[0086] Considering the size of the battery assembly 10, in order for the battery assembly 10 provided in the embodiment to achieve the effect of improving the energy density on the premise of basically unchanged size, the first tab part 1 and the second tab part 3 both need to be folded radially towards the axis relative to the body part 2, so as to shorten the size of the battery assembly 10 in the axis direction (i.e. the first direction X).

[0087] Specifically, at least one of the first tab part 1 and the second tab part 3 is folded inward along the radial direction of the battery assembly 10.

[0088] In order to ensure that the folded first tab part 1 and / or the second tab part 3 can still be used normally, the shape of at least one of the first tab part 1 and the second tab part 3 and the corresponding area of the diaphragm 103 needs to be adjusted appropriately.

[0089] In some embodiments, the coating layer 4 is arranged only on the first tab 1. In this case, the first tab 1 of the positive electrode tab 101 and the first tab 1 of the negative electrode tab 102 are both arranged with the coating layer 4 described above. One of the first tab 1 of the positive electrode tab 101 and the first tab 1 of the negative electrode tab 102 includes a plurality of sub-tabs 5 arranged circumferentially at intervals along the electric core assembly 10, and the coating layer 4 is coated on the sub-tabs 5. The other one includes a coating area 6 and a stacking area 7 arranged circumferentially at intervals along the electric core assembly 10, the coating area 6 is coated with the coating layer 4, and the stacking area 7 is not coated with the coating layer 4. The shape of the region corresponding to the first tab 1 of the separator 103 can also be adjusted as needed.

[0090] Specifically, the sub-tab 5 can be obtained by cutting the first tab 1. The coating area 6 and the stacking area 7 on the other first tab 1 arranged opposite to the first tab 1 composed of a plurality of sub-tabs 5 are arranged at intervals and connected in sequence, thereby forming a strip-shaped structure connected to the main body 2. That is, the structures of the two first tabs 1 located at the first end 21 of the main body 2 are necessarily different, thereby effectively avoiding the short circuit problem that may occur when the first tab 1 is folded.

[0091] In the arrangement, any one of the first tabs 1 formed on the negative electrode tab 102 and the positive electrode tab 101 respectively can be composed of a plurality of sub-tabs 5, and the other one can be composed of a coating area 6 and a stacking area 7 connected in sequence, the stacking area 7 being an empty foil area without coated conductive active material. The stacking area 7 can be directly connected to two adjacent coating areas 6, or can be connected to all coating areas 6 located at one end of the same tab.

[0092] In some embodiments, the coating layer 4 is arranged only on the second tab 3. In this case, the second tab 3 of the positive electrode tab 101 and the second tab 3 of the negative electrode tab 102 are both arranged with the coating layer 4 described above. One of the second tab 3 of the positive electrode tab 101 and the second tab 3 of the negative electrode tab 102 includes a plurality of sub-tabs 5 arranged circumferentially at intervals along the electric core assembly 10, and the coating layer 4 is coated on the sub-tabs 5. The other one includes a coating area 6 and a stacking area 7 arranged circumferentially at intervals along the electric core assembly 10, the coating area 6 is coated with the coating layer 4, and the stacking area 7 is not coated with the coating layer 4. The shape of the region corresponding to the second tab 3 of the separator 103 can also be adjusted as needed.

[0093] In some embodiments, the coating layer 4 is arranged on both the first tab 1 and the second tab 3. In this case, the first tab 1 and the second tab 3 of the positive electrode tab 101 and the negative electrode tab 102 are both arranged with the coating layer 4 described above. The arrangement of at least one of the two opposite first tab 1 and second tab 3 is as described above, and will not be described here.

[0094] Specifically, in some cases, the first pole ear portion 1 and the second pole ear portion 3 on the positive electrode plate 101 may have the same structure, both consisting of a plurality of spaced-apart sub-pole ears 5, or consisting of a coating area 6 and a stacking area 7 connected in sequence. In this case, the first pole ear portion 1 and the second pole ear portion 3 on the negative electrode plate 102 may also have the same structure, both consisting of a coating area 6 and a stacking area 7 connected in sequence, or separated by a plurality of spaced-apart sub-pole ears 5; in another case, as Figure 1 and Figure 2 As shown, at this time, the structures of the first pole ear portion 1 and the second pole ear portion 3 in the positive pole sheet 101 and the negative pole sheet 102 are exactly opposite. Taking the positive pole sheet 101 as an example, at this time, the structures of the first pole ear portion 1 and the second pole ear portion 3 of the positive pole sheet 101 are different, and the structure of the first pole ear portion 1 of the positive pole sheet 101 remains basically consistent with the structure of the second pole ear portion 3 of the negative pole sheet 102.

[0095] All of the above structures can be used to achieve the functions to be achieved in this embodiment. This solution does not limit the structures of the first pole lug portion 1 and the second pole lug portion 3, as long as the following conditions are met:

[0096] When the tab portion of the battery cell assembly 10 is not folded, Figure 4 As shown, at this time, the projections of the coating layer 4 on the ear portion of the positive electrode sheet 101 and the coating layer 4 on the negative electrode sheet 102 in the radial direction can be kept substantially coincident (it can also be understood that the projection of the coating layer 4 on the positive electrode sheet 101 in the radial direction can fall within the projection of the coating layer 4 on the negative electrode sheet 102 in the radial direction); when the ear portion is folded, as shown in FIG. Figure 5 As shown, the coating layer 4 in the folded state is affected by the thickness of the pole piece and the diaphragm 103, and the two coating layers 4 arranged radially at intervals will have a certain degree of misalignment, but at this time the above-mentioned coating layers 4 can still maintain at least a partial relative arrangement, that is, the projections of the two in the first direction X overlap.

[0097] In order to further ensure that the pole ear can still be relatively stably connected to the busbar 8 in the folded state, thereby effectively overcoming the problem of easy welding through of the pole ear, in some embodiments, at least part of the overlapping area 7 is overlapped on the outside of the coating area 6.

[0098] Since the stacking area 7 is composed of a portion of the electrode sheet that is not coated with the conductive active material, this area can better perform the conductive function. When folding, the positive electrode sheet 101, the negative electrode sheet 102, and the separator 103 in the battery cell assembly 10 can be folded sequentially according to the winding direction Y. After the winding is completed, the folding can also be performed by folding the coating area 6 with the coating layer 4, the sub-electrode tab 5, and the stacking area 7 separately.

[0099] In some embodiments, the tab part with the coating layer 4 is folded in a double-fold manner, which is as follows:

[0100] First, the coating area 6 with the coating layer 4 and the sub-tab 5 are folded. After the folding is completed, the coating layer 4 on the positive electrode tab 101 and the coating layer 4 on the negative electrode tab 102 are arranged oppositely, thereby forming a new energy storage structure similar to the main body 2 in the tab part. Then, the overlapping area 7 formed in a certain tab part on the positive electrode tab 101 or the negative electrode tab 102 is folded. After the folding is completed, the overlapping area 7 can cover the part with the coating layer 4, as shown in FIG. 6, so as to improve the interface tightness between the coating layers 4. In addition, the overlapping area 7 can be directly connected to the bus bar 8 by welding. Figure 5

[0101] The overlapping area 7 in the folded state has a certain thickness, which can effectively avoid the welding-through defect caused by the too thin metal sheet when welding with the bus bar 8, thereby avoiding the possibility of short circuit of the battery cell assembly 10 due to the damage of the diaphragm 103, and effectively improving the stability of the battery cell assembly 10.

[0102] In some embodiments, in the first direction X, the projection of the coating layer 4 on the positive electrode tab 101 partially overlaps with the projection of the coating layer 4 on the negative electrode tab 102.

[0103] It can be understood that, in order to ensure the overhang of the battery cell assembly 10 and avoid the occurrence of lithium precipitation, it is necessary to ensure that the size of the coating layer 4 coated on the negative electrode tab 102 is greater than the size of the coating layer 4 coated on the positive electrode tab 101.

[0104] overhang refers to the part of the negative electrode tab that exceeds the positive and negative electrode tabs in the length and width directions of the battery cell assembly. The overhang will cause lithium ions to diffuse thereto and remain to cause capacity loss, especially if it is stored for a long time in the charged state.

[0105] The overhang will affect the electrochemical performance of the battery to some extent. From the working principle of the battery, the battery with complete overlap of the positive and negative electrodes and no overhang design has the best performance, but due to the limitation of engineering precision, it cannot be realized in actual processing, which will instead cause the battery to have a "lithium precipitation" phenomenon during use, affecting the performance of the battery. Therefore, in actual processing, the overhang design of the battery cell assembly 10 is generally adopted.

[0106] Specifically, the width and height of the coating layer 4 on the negative electrode tab 102 should be 0.3-1.0 mm greater than the width and height of the coating layer 4 on the positive electrode tab 101.

[0107] ​The above method is a common technical means in the industry, and will not be described here.

[0108] Considering that the radial size of the cell assembly 10 gradually increases as the winding operation proceeds, in order to further ensure that the coating layers 4 arranged in sequence along the winding direction Y can always be relatively arranged as the winding operation proceeds, in some embodiments, the spacing between the adjacent two coating layers 4 along the winding direction Y of the cell assembly 10 gradually increases.

[0109] As shown in Figure 1 and Figure 2 , the spacing between the adjacent two coating layers 4 gradually increases along the winding direction Y to overcome the influence of the thickness of the stack of the positive electrode plate 101, the negative electrode plate 102 and the separator 103, and to ensure that the coating layers 4 on the positive electrode plate 101 and the negative electrode plate 102 can be relatively arranged as the winding operation proceeds.

[0110] In order to overcome the influence of folding on the arrangement of the coating layer 4, in some embodiments, the coating size of the coating layer 4 in the first direction X located at the same first tab portion 1 or second tab portion 3 along the winding direction Y of the cell assembly 10 can be any one of remaining unchanged, gradually increasing and gradually decreasing.

[0111] When the size of the coating layer 4 in the first direction X can be adjusted along the winding direction Y of the cell assembly 10, any one of the coating layers 4 is set to be rectangular or other shapes.

[0112] Specifically, the size of the coating layer 4 is set to be rectangular, for example, according to the size of the cell assembly 10 and the thickness of the plate and the separator 103 and other parameters, the coating layer 4 is arranged immediately adjacent to the main body portion 2 and spaced apart from the main body portion 2, or the coating layer 4 is arranged on the side of the corresponding tab portion away from the main body portion 2, and then the spacing is adjusted and the coating size of the coating layer 4 in the first direction X is gradually increased or decreased.

[0113] As shown in Figure 1 and Figure 2 , at this time, the coating layer 4 is arranged on the side of the corresponding tab portion away from the main body portion 2 and the coating size of the coating layer 4 in the first direction X gradually increases.

[0114] The adjustment of the coating size of the coating layer 4 in the first direction X can be made according to actual needs, and the main purpose is to ensure that the coating layers 4 respectively located on the positive electrode plate 101 and the negative electrode plate 102 can be arranged in the first direction X and the projection in the first direction X can be at least partially overlapped in the folded state.

[0115] When the size of the plurality of coating layers 4 in the first direction X gradually increases or decreases along the winding direction Y of the battery cell assembly 10, the size of the first tab portion 1 and / or the second tab portion 3 for forming the coating layer 4 in the first direction X can be adjusted synchronously along the winding direction Y of the battery cell assembly 10 to adapt to the changing size of the coating layer 4; or the size of the first tab portion 1 and / or the second tab portion 3 for forming the coating layer 4 in the first direction X can be kept constant, and the size of the plurality of coating layers 4 in the first direction X can be changed by adjusting the interval size between the coating layer 4 and the main body portion 2.

[0116] In some embodiments, the coating size of the coating layer 4 in the first direction X is not more than 13 mm, and the coating range of the coating layer 4 in the first direction X is 1-13 mm.

[0117] In some embodiments, the size of each adjacent coating layer 4 in the first direction X gradually increases or decreases in the form of an arithmetic sequence along the winding direction Y of the battery cell assembly 10.

[0118] Taking the case that the size of each adjacent coating layer 4 in the first direction X gradually increases in the form of an arithmetic sequence along the winding direction Y of the battery cell assembly 10, the specific data of the size change are described as follows:

[0119] Defining the number of the coating layers 4 located on a certain first tab portion 1 or second tab portion 3 as N (N is a positive integer and not less than two), the size of the first coating layer 4 in the first direction X is d1, and the size of the Nth coating layer 4 in the first direction X is dN, dN=d1+N*0.125, wherein the units of d1 and dN are millimeters (mm).

[0120] When the size of each adjacent coating layer 4 in the first direction X gradually decreases in the form of an arithmetic sequence, the size of the Nth coating layer 4 in the first direction X should be dN=d1-N*0.125.

[0121] In some embodiments, the coating size of the coating layer 4 in the winding direction Y is not more than 23 mm, and the specific coating range is 1-23 mm.

[0122] In some embodiments, the size of each coating area 6 in the winding direction Y can be the same; or the size of each coating area 6 in the winding direction Y can be different. When the size of each coating area 6 in the winding direction Y is different, the size of each coating area 6 in the winding direction Y can gradually increase.

[0123] Specifically, the straight line where the outer side edges of the plurality of coating layers 4 in the winding direction Y are located coincides with the straight line where a certain radial direction of the battery cell assembly 10 is located.

[0124] Specifically, in the case where the sizes of the first tab portion 1 and / or the second tab portion 3 used to form the coating layer 4 do not change, the interval size of the coating layer 4 and the main body portion 2 in the first direction X gradually decreases or increases along the winding direction Y of the battery cell assembly 10.

[0125] That is, the size change trend of the coating layer 4 in the first direction X is exactly opposite to the size change trend of the interval size of the coating layer 4 and the main body portion 2 in the first direction X along the winding direction Y of the battery cell assembly 10.

[0126] When the interval size of the coating layer 4 and the main body portion 2 in the first direction X gradually decreases or increases along the winding direction Y of the battery cell assembly 10, at this time, the size of the first tab portion 1 and / or the second tab portion 3 used to form the coating layer 4 in the first direction X can be adjusted synchronously along the winding direction Y of the battery cell assembly 10 to adapt to the changing interval size, or the size of the first tab portion 1 and / or the second tab portion 3 used to form the coating layer 4 in the first direction X can be kept constant, and the size change of the interval in the first direction X can be realized by adjusting the size of the coating layer 4 in the first direction X.

[0127] In some embodiments, the size of the first tab portion 1 and / or the second tab portion 3 of the coating layer 4 in the first direction X can be kept constant, and when the size of the interval formed between the coating layer 4 and the main body portion 2 in the first direction X changes, the size of the corresponding coating layer 4 in the first direction X also changes accordingly.

[0128] In some embodiments, the battery cell assembly 10 further includes two bus bars 8 located at both ends of the first direction X of the battery cell assembly 10, and the shape of the bus bar 8 is as shown in Figure 6 .

[0129] Specifically, one bus bar 8 is connected to the first end 21 of the main body portion 2 through the first tab portion 1, and the other bus bar 8 is connected to the second end 22 of the main body portion 2 through the second tab portion 3.

[0130] The certain bus bar 8 can be connected to the lamination area 7 formed outside the first end 21 of the main body portion 2, thereby being connected to the first end 21 of the main body portion 2; similarly, the other bus bar 8 can be connected to the lamination area 7 formed outside the second end 22 of the main body portion 2, thereby being connected to the second end 22 of the main body portion 2, and finally realizing the electrical connection of the bus bar with the positive tab 101 and the negative tab 102.

[0131] The two busbars 8 have substantially the same shape, or are mirror-symmetrical.

[0132] The above connection mode can also avoid the busbar 8 directly contacting the coating layer 4, thereby improving the stability of the battery cell assembly 10.

[0133] In the case of no conflict, the features in the above embodiments can be combined with each other.

[0134] The following table lists the capacity data of the battery cell assembly 10 provided in the present embodiment and the conventional battery cell assembly. The battery cell assemblies in group A are conventional battery cell assemblies, and the battery cell assemblies 10 in group B are battery cell assemblies 10 in which the tab portions at both ends in the first direction include the coating layer 4. The battery cell assemblies in the two groups have the same size, and are cylindrical battery cells with a diameter of 46 mm and a height of 95 mm.

[0135] The following describes the assembly and preparation process of the battery cell assemblies in the two groups.

[0136] The five different battery cell assemblies in group A are prepared in the same manner, and the preparation manner is a prior art. Group A is a parallel control group. The five different battery cell assemblies 10 in group B are prepared by using the structure provided in the present application, and group B is an experimental group.

[0137] Any one of the battery cell assemblies in group A is formed by stacking and winding a positive electrode tab, a separator and a negative electrode tab. The positive electrode tab and the negative electrode tab each have a strip-shaped structure, and the first tab portion and the second tab portion have the same structure. The tab portions of the wound core structure can be processed by cutting or flattening.

[0138] In some embodiments, the first tab portion and the second tab portion are each processed by die cutting to form a plurality of small tabs. After the positive electrode tab, the separator and the negative electrode tab are sequentially stacked and wound, the tabs are flattened, so that the small tabs are bent towards the axial direction of the battery cell assembly. Finally, the small tabs are connected to the busbar by welding to complete the preparation of the battery cell assembly. Alternatively, in other embodiments, the first tab portion and the second tab portion are not cut, and the ends of the wound core are directly flattened, and the tabs are connected to the busbar by welding to complete the preparation of the battery cell assembly. Any one of the above methods can be used to prepare the battery cell assemblies in group A.

[0139] Any one of the battery cell assembly 10 in group B is formed by stacking and winding the positive electrode sheet 101, the separator 103 and the negative electrode sheet 102, the positive electrode sheet 101 and the negative electrode sheet 102 are both in strip structure and the structure of the first tab 1 and the second tab 3 of any one of the two is different: the first tab 1 of the positive electrode sheet 101 is in strip structure, the strip structure is formed by the interval arrangement of the coating area 6 and the overlapping area 7, the coating layer 4 is arranged on the coating area 6, the adjacent two coating areas 6 are connected by the overlapping area 7, the second tab 3 of the positive electrode sheet 101 is formed by cutting into a plurality of interval arranged sub-tabs 5, the coating layer 4 is arranged on the sub-tab 5, the coating layer 4 formed on the first tab 1 and the coating layer 4 formed on the second tab 3 are arranged above and below in the first direction X and the above-mentioned coating layer 4 is separated from the main body 2 by the empty foil area; the structure of the first tab 1 of the negative electrode sheet 102 is exactly opposite to that of the first tab 1 of the positive electrode sheet 101, which is formed by cutting into a plurality of interval arranged sub-tabs 5, the coating layer 4 is arranged on the sub-tab 5, the structure of the second tab 3 of the negative electrode sheet 102 is also exactly opposite to that of the second tab 3 of the positive electrode sheet 101, which is formed by the interval arrangement of the coating area 6 and the overlapping area 7, the coating layer 4 is arranged on the coating area 6, the adjacent two coating areas 6 are connected by the overlapping area 7, the coating layer 4 formed on the first tab 1 and the coating layer 4 formed on the second tab 3 are arranged above and below in the first direction X and the above-mentioned coating layer 4 is separated from the main body 1 by the empty foil area.

[0140] After the positive electrode sheet 101, the separator 103 and the negative electrode sheet 102 are sequentially stacked and wound, the coating layer 4 formed in any one of the first end 21 and the second end 22 of the main body 2 is folded, then the overlapping area 7 formed on the certain first tab 1 and the certain second tab 3 is folded to make the overlapping area 7 overlap the coating layer 4, finally the overlapping area 7 is connected with the corresponding bus bar 8 by welding, the preparation of the battery cell assembly 10 in group B is completed.

[0141] The capacity test results of the above two groups of battery cell assemblies are as follows:

[0142] Label A1 A2 A3 A4 A5 B1 B2 B3 B4 B5 Capacity (Ah) 20.3 20.2 20.2 20.3 20.2 21.2 21.1 21.3 21.2 21.3

[0143] From the above table, it can be reflected that the energy density of the battery cell assembly 10 provided in the embodiment is about 5%-8% higher than that of the traditional battery cell assembly.

[0144] It can be understood that, compared with the traditional battery cell assembly, the battery cell assembly 10 provided by the embodiment can effectively utilize the empty foil area formed in the tab part, and has energy storage effect by adding the coating layer 4 in this part to form a local battery cell structure, thereby effectively improving the energy density of the battery cell assembly 10 without changing the overall size of the battery cell assembly 10, and improving the stability and safety of the battery cell assembly 10 to a certain extent.

[0145] The application also provides a preparation method of the battery cell assembly 10. The positive electrode tab 101 and the negative electrode tab 102 of the battery cell assembly 10 each include the first tab part 1, the main body part 2 and the second tab part 3 arranged in sequence along the first direction X. The specific preparation process is as shown in the figure Figure 7 The preparation process includes the following steps:

[0146] Step S1, coating slurry

[0147] The slurry is coated on at least one of the first tab part 1 and the second tab part 3 along the length direction of the main body part 2 to form the coating layer 4 arranged in the length direction of the main body part 2, and the coating layer 4 is arranged in the first direction X with the main body part 2;

[0148] Step S2, laminating arrangement

[0149] The positive electrode tab 101, the diaphragm 103 and the negative electrode tab 102 are laminated and arranged, and at least part of the coating layer 4 on the positive electrode tab 101 is arranged opposite to at least part of the coating layer 4 on the negative electrode tab 102 to form a winding component;

[0150] Step S3, winding

[0151] The winding component is wound along the length direction of the main body part 2 to form a winding structure.

[0152] Through the above steps, the coating layer 4 is arranged and the coating layer 4 formed on the positive electrode tab 101 and the negative electrode tab 102 is arranged opposite to each other, so that the battery cell assembly 10 forms an energy storage structure with energy storage function in the tab part (at least one of the first tab part 1 and the second tab part 3). This method realizes the utilization of the empty foil tab area, so that the tab part can also realize energy storage, thereby making the battery cell assembly 10 have better energy storage effect and helping to improve the energy density of the battery cell assembly 10.

[0153] It should be noted that the shape of the coating layer 4 can be flexibly adjusted as needed, as long as the corresponding coating layers 4 arranged on the positive electrode sheet 101 and the negative electrode sheet 102 can maintain their relative arrangement after winding. This embodiment does not limit the shape and size of the coating layer 4. The coating layer 4 can be any one or more of various structures such as circular, elliptical, rectangular, and trapezoidal. In addition, the thickness of the coating layer 4 is affected by the material and coating process, and this embodiment does not limit it.

[0154] Taking into account that the radial dimension of the battery cell assembly 10 will gradually increase as the winding action proceeds, in order to further ensure that the coating layers 4 arranged in sequence along the winding direction Y can always maintain a relative arrangement as the winding action proceeds, in some embodiments, the spacing size between two adjacent coating layers 4 is gradually increased along the winding direction Y of the battery cell assembly 10, so as to overcome the influence of the thickness generated by the stacking of the positive electrode sheet 101, the negative electrode sheet 102 and the diaphragm 103, and ensure that the coating layers 4 on the positive electrode sheet 101 and the negative electrode sheet 102 can be arranged relative to each other as the winding action proceeds.

[0155] In order to overcome the influence of folding on the arrangement of the coating layer 4, in some embodiments, along the winding direction Y of the battery cell assembly 10, the coating size of the coating layer 4 located at the same first pole ear portion 1 or second pole ear portion 3 in the first direction X can be any one of remaining unchanged, gradually increasing and gradually decreasing.

[0156] In order to overcome the influence of folding on the arrangement of the coating layer 4, in some embodiments, along the winding direction Y of the battery cell assembly 10, the coating size of the coating layer 4 located at the same first pole ear portion 1 or second pole ear portion 3 in the first direction X can be any one of remaining unchanged, gradually increasing and gradually decreasing.

[0157] When the size of the coating layer 4 in the first direction X can be adjusted along the winding direction Y of the battery cell assembly 10 , any one of the coating layers 4 is set to be rectangular or in other shapes.

[0158] Specifically, the size of the coating layer 4 is set to be rectangular. For example, based on the size of the battery cell assembly 10 and parameters such as the thickness of the electrode and the diaphragm 103, it can be determined that the coating layer 4 is adjacent to the main body 2 and spaced apart from the main body 2, or the coating layer 4 is arranged on the side of the corresponding electrode ear away from the main body 2, and then the corresponding spacing is adjusted and the coating size of the above-mentioned coating layer 4 in the first direction X is set to gradually increase or decrease.

[0159] like Figure 1 and Figure 2 As shown, at this time, the coating layer 4 is arranged on the side of the corresponding pole ear portion away from the main body portion 2 and the coating size of the coating layer 4 in the first direction X gradually increases.

[0160] The coating size of the coating layer 4 in the first direction X can be adjusted according to actual needs, and the main purpose is to ensure that the coating layers 4 respectively located on the positive electrode tab 101 and the negative electrode tab 102 can be arranged in a stacked manner in the first direction X and the projections in the first direction X can be kept at least partially overlapped in the folded state.

[0161] When the size of the plurality of coating layers 4 in the first direction X gradually increases or decreases along the winding direction Y of the battery cell assembly 10, the size of the first tab portion 1 and / or the second tab portion 3 for forming the coating layer 4 in the first direction X can be adjusted synchronously along the winding direction Y of the battery cell assembly 10 to adapt to the changing size of the coating layer 4, or the size of the first tab portion 1 and / or the second tab portion 3 for forming the coating layer 4 in the first direction X can be kept unchanged, and the size of the plurality of coating layers 4 in the first direction X can be changed by adjusting the interval size between the coating layer 4 and the main body portion 2.

[0162] In some embodiments, the coating size of the coating layer 4 in the first direction X is not more than 13 mm, and the coating range of the coating layer 4 in the first direction X is 1-13 mm.

[0163] In some embodiments, the size of each adjacent coating layer 4 in the first direction X gradually increases or decreases in the form of an arithmetic sequence along the winding direction Y of the battery cell assembly 10.

[0164] Taking the example that the size of each adjacent coating layer 4 in the first direction X gradually increases in the form of an arithmetic sequence along the winding direction Y of the battery cell assembly 10, the specific data of the size change is described as follows:

[0165] Defining the number of the coating layers 4 located on a certain first tab portion 1 or second tab portion 3 as N (N is a positive integer and not less than two), the size of the first coating layer 4 in the first direction X is d1, and the size of the Nth coating layer 4 in the first direction X is dN, dN=d1+N*0.125, the units of d1 and dN are both millimeters (mm).

[0166] When the size of each adjacent coating layer 4 in the first direction X gradually decreases in the form of an arithmetic sequence, the size of the Nth coating layer 4 in the first direction X should be dN=d1-N*0.125.

[0167] In some embodiments, the coating size of the coating layer 4 in the winding direction Y is not more than 23 mm, and the specific coating range is 1-23 mm.

[0168] In some embodiments, the size of each of the coating regions 6 in the winding direction Y can be set to be the same, or the size of each of the coating regions 6 in the winding direction Y can be set to be different. When the size of each of the coating regions 6 in the winding direction Y is different, the size of each of the coating regions 6 in the winding direction Y can be set to gradually increase.

[0169] Specifically, after the winding of the battery cell is completed, the straight line on which the outer side of the coating layer 4 in the winding direction Y is located coincides with the straight line on which a certain radial direction of the battery cell assembly 10 is located.

[0170] Specifically, in the case where the size of the first tab portion 1 and / or the second tab portion 3 used to form the coating layer 4 is constant, the interval size of the coating layer 4 and the main body portion 2 in the first direction X gradually decreases or increases along the winding direction Y of the battery cell assembly 10.

[0171] That is, along the winding direction Y of the battery cell assembly 10, the size change trend of the coating layer 4 in the first direction X is exactly opposite to the size change trend of the interval size of the coating layer 4 and the main body portion 2 in the first direction X.

[0172] When the interval size of the coating layer 4 and the main body portion 2 in the first direction X gradually decreases or increases along the winding direction Y of the battery cell assembly 10, at this time, the size of the first tab portion 1 and / or the second tab portion 3 used to form the coating layer 4 in the first direction X can be set to be adjusted synchronously along the winding direction Y of the battery cell assembly 10 to adapt to the constantly changing interval, or the size of the first tab portion 1 and / or the second tab portion 3 used to form the coating layer 4 in the first direction X can be set to be constant all the time, and the size change of the interval in the first direction X is realized by adjusting the size of the coating layer 4 in the first direction X.

[0173] In some embodiments, the size of the first tab portion 1 and / or the second tab portion 3 of the coating layer 4 in the first direction X can be set to be constant all the time, and when the size of the interval formed between the coating layer 4 and the main body portion 2 in the first direction X changes, the size of the corresponding coating layer 4 in the first direction X also adjusts accordingly.

[0174] In some embodiments, the method for preparing the battery cell assembly 10 further comprises:

[0175] In step S11, the two side surfaces of at least one of the first tab portion 1 and the second tab portion 3 in the thickness direction are coated with paste respectively to realize double-sided coating.

[0176] In step S1, at least one of the first tab portion 1 and the second tab portion 3 can be subjected to single-sided slurry coating (i.e., coating of the conductive active material on the relevant region), or can be subjected to the double-sided coating provided in step S11 to achieve the purpose of double-sided coating.

[0177] In the slurry coating process, any coating technology disclosed in the prior art can be used to achieve slurry coating, for example, double-sided coating technology.

[0178] In some embodiments, the method for preparing the battery cell assembly 10 further comprises:

[0179] In step S12, one of the first tab portion 1 of the positive electrode tab 101 and the first tab portion 1 of the negative electrode tab 102 is cut to obtain a plurality of sub-tabs 5 arranged at intervals, and the coating layer 4 is coated on the sub-tabs 5.

[0180] In step S12, one of the first tab portion 1 of the positive electrode tab 101 and the first tab portion 1 of the negative electrode tab 102 is cut to obtain a plurality of sub-tabs 5 arranged at intervals, and the coating layer 4 is coated on the sub-tabs 5.

[0181] Through the above cutting process, the first tab portion 1 and / or the second tab portion 3 composed of a plurality of sub-tabs 5 can be obtained. Taking the cutting of a certain first tab portion 1 as an example, the shapes of the two first tab portions 1 arranged oppositely are different, which can effectively avoid the short circuit problem that may occur when the first tab portion 1 is folded.

[0182] In some embodiments, the method for preparing the battery cell assembly 10 further comprises:

[0183] In step S4, the first tab portion 1 and / or the second tab portion 3 are folded:

[0184] The region coated with the coating layer 4 is folded inward along the radial direction of the battery cell assembly 10 to form a coating area 6, and in the first direction X, the projection of the coating layer 4 on the positive electrode tab 101 partially overlaps the projection of the coating layer 4 on the negative electrode tab 102.

[0185] The region not coated with the coating layer 4 is folded inward along the radial direction of the battery cell assembly 10 to form a lamination area 7, and at least part of the lamination area 7 is laminated on the outer side of the coating area 6.

[0186] The folding mode of the tab portion with the coating layer 4 is as follows:

[0187] (1) First, the coating area 6 and the sub-tab 5 with the coating layer 4 are folded

[0188] The coating area 6 and the sub-tab 5 should be folded along the radial direction towards the position where the axis of the battery cell assembly 10 is located. After the folding is completed, the coating layer 4 on the positive electrode tab 101 and the coating layer 4 on the negative electrode tab 102 are arranged oppositely, thereby forming a new energy storage structure similar to the main body 2 in the tab area.

[0189] (2) Subsequently, the lamination area 7 formed on one of the positive electrode tab 101 and the negative electrode tab 102 is folded

[0190] The lamination area 7 should be folded along the radial direction towards the position where the axis of the battery cell assembly 10 is located and be pressed above the coating layer 4. After the folding is completed, the lamination area 7 can be pressed on the part with the coating layer 4 to improve the interface tightness between the coating layers 4.

[0191] The conventional flattening method can generate metal scraps during the processing, which can fall into the battery cell and affect the safety of the battery cell. Compared with the flattening method, the folding of the tab can avoid the generation of metal scraps and, to some extent, improve the thickness of the lamination area 7 after the folding, thereby further improving the safety of the battery cell assembly 10. In addition, this processing method can effectively reduce the manufacturing cost of the battery cell assembly 10.

[0192] In some embodiments, the method for preparing the battery cell assembly 10 further comprises installing the bus bars 8 outside the first tab part 1 and the second tab part 3.

[0193] In step S5, the bus bars 8 are installed, one bus bar 8 is connected to the first tab part 1 through the lamination area 7 at the corresponding position, and the other bus bar 8 is connected to the second tab part 3 through the lamination area 7 at the corresponding position.

[0194] The lamination area 7 can be directly connected to the bus bar 8 by welding.

[0195] The lamination area 7 in the folded state has a certain thickness, which can effectively avoid the welding-through defect caused by the too-thin metal sheet when welding with the bus bar 8, thereby avoiding the possibility of short circuit of the battery cell assembly 10 due to the damage of the separator 103, and effectively improving the stability of the battery cell assembly 10.

[0196] It can be understood that the method for preparing the battery cell assembly 10 provided in the embodiment can effectively utilize the tab area of the battery cell, and the tab area can form a local battery cell structure by increasing the coating layer 4 in the area and improving the structure of the coating layer 4, thereby effectively improving the energy density of the battery cell without changing the overall size of the battery cell assembly 10, and improving the stability and safety of the battery cell to some extent.

[0197] A further embodiment of the present application provides an electric core assembly 10 prepared by the method of preparing an electric core assembly 10 described in any of the above embodiments.

[0198] The electric core assembly 10 of the embodiments of the present application can be prepared by the method described above, and the prepared electric core assembly 10 has a high energy density.

[0199] A further embodiment of the present application provides a secondary battery comprising the electric core assembly 10 described above.

[0200] The secondary battery further comprises a housing, and the busbar 8 is connected to the housing, so that the structure formed by winding the positive electrode tab 101, the negative electrode tab 102 and the separator 103 is wrapped in the housing.

[0201] A further embodiment of the present application provides an electric device comprising the secondary battery described above, and the secondary battery is used to provide electric energy.

[0202] The electric device described above can be any device or system using the secondary battery.

[0203] In the case of no conflict, the features in each of the above embodiments can be combined with each other.

[0204] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. An electrochemical cell assembly, comprising: The electrode assembly (10) is of a winding type and comprises positive electrode tabs (101) and negative electrode tabs (102) arranged in a stack, each of the positive electrode tabs (101) and the negative electrode tabs (102) comprising a first tab portion (1), a main body portion (2) extending in a first direction and comprising a first end (21) and a second end (22) oppositely arranged in the first direction, the first end (21) of the main body portion (2) being connected with the first tab portion (1), the second end (22) of the main body portion (2) being connected with the second tab portion (3), at least one of the first tab portion (1) and the second tab portion (3) being coated with a plurality of coating layers (4) arranged at intervals in a winding direction thereof, the winding direction being orthogonal to the first direction, the coating layers (4) being arranged at intervals from the main body portion (2); At least part of the coating layers (4) on the positive electrode tabs (101) are oppositely arranged with at least part of the coating layers (4) on the negative electrode tabs (102).

2. The cell assembly of claim 1, wherein, One of the first tab portion (1) of the positive electrode tabs (101) and the first tab portion (1) of the negative electrode tabs (102) comprises a plurality of sub-tab portions (5) arranged at intervals in a circumferential direction of the electrode assembly (10), the coating layers (4) being coated on the sub-tab portions (5), and the other comprises coating regions (6) and overlapping regions (7) arranged at intervals in the circumferential direction of the electrode assembly (10), the coating regions (6) being coated with the coating layers (4), and the overlapping regions (7) being uncoated with the coating layers (4); And / or, one of the second tab portion (3) of the positive electrode tabs (101) and the second tab portion (3) of the negative electrode tabs (102) comprises a plurality of sub-tab portions (5) arranged at intervals in a circumferential direction of the electrode assembly (10), the coating layers (4) being coated on the sub-tab portions (5), and the other comprises coating regions (6) and overlapping regions (7) arranged at intervals in the circumferential direction of the electrode assembly (10), the coating regions (6) being coated with the coating layers (4), and the overlapping regions (7) being uncoated with the coating layers (4).

3. The cell assembly of claim 2, wherein, At least one of the first tab portion (1) and the second tab portion (3) is folded inwardly in a radial direction of the electrode assembly (10), and at least part of the overlapping regions (7) is overlapped outside the coating regions (6).

4. The cell assembly of claim 3, wherein, In the first direction, a projection of the coating layers (4) on the positive electrode tabs (101) partially coincides with a projection of the coating layers (4) on the negative electrode tabs (102).

5. The cell assembly of claim 1, wherein, In a winding direction of the electrode assembly (10), a coating size of the coating layers (4) in the first direction gradually increases or decreases along the same first tab portion (1) or the same second tab portion (3); And / or, in the winding direction of the electrode assembly (10), an interval size of the coating layers (4) and the main body portion (2) in the first direction gradually decreases or increases; And / or, the interval size between two adjacent coating layers (4) gradually increases along the winding direction of the battery cell assembly (10).

6. The cell assembly of claim 5, wherein, Along the winding direction of the battery cell assembly (10), the size of each adjacent coating layer (4) in the first direction gradually increases or decreases in the form of an arithmetic sequence.

7. The cell assembly of claim 1, wherein, The coating size of the coating layer (4) in the first direction is not more than 13mm, and the coating size of the coating layer (4) in the winding direction is not more than 23mm. And / or, the interval size of the coating layer (4) and the main body part (2) in the first direction is not less than 1mm.

8. The cell assembly of claim 1, wherein, At least one of the first tab part (1) and the second tab part (3) is symmetrically provided with the coating layer (4) on both sides in the thickness direction.

9. The cell assembly of any one of claims 1-8, wherein, Further comprising two bus bars (8), one of the bus bars (8) is connected with the first end (21) of the main body part (2) through the first tab part (1), and the other bus bar (8) is connected with the second end (22) of the main body part (2) through the second tab part (3).

10. A method of making an electrochemical cell assembly, the method comprising: The positive electrode tab (101) and the negative electrode tab (102) of the battery cell assembly (10) each comprises a first tab part (1), a main body part (2) and a second tab part (3) arranged in sequence along the first direction, and the preparation method comprises the following steps: At least one of the first tab part (1) and the second tab part (3) is coated with slurry along the length direction of the main body part (2) to form a coating layer (4) arranged in sequence along the length direction of the main body part (2), and the coating layer (4) is arranged in sequence with the main body part (2) in the first direction; The positive electrode tab (101), the separator (103) and the negative electrode tab (102) are arranged in layers, and at least part of the coating layer (4) on the positive electrode tab (101) is arranged opposite to at least part of the coating layer (4) on the negative electrode tab (102) to form a winding component; The winding component is wound along the length direction of the main body part (2) to form a winding structure.

11. The method of claim 10, wherein the method further comprises: Along the winding direction of the battery cell assembly (10), the coating size of the coating layer (4) in the first direction gradually increases or decreases on the same first tab part (1) or second tab part (3); And / or, the interval size of the coating layer (4) and the main body part (2) in the first direction gradually decreases or increases along the winding direction of the battery cell assembly (10); And / or, the interval size between two adjacent coating layers (4) gradually increases along the winding direction of the battery cell assembly (10).

12. The method of claim 10, wherein the method further comprises: The two sides in the thickness direction of at least one of the first tab part (1) and the second tab part (3) are respectively coated with slurry to realize double-sided coating.

13. The method of claim 10-12, wherein, Further comprising: One of the first tab part (1) of the positive electrode tab (101) and the first tab part (1) of the negative electrode tab (102) is cut to obtain a plurality of sub-tabs (5) arranged in sequence, and the coating layer (4) is coated on the sub-tab (5); and / or, one of the second tab part (3) of the positive electrode tab (101) and the second tab part (3) of the negative electrode tab (102) is cut to obtain a plurality of sub-tabs (5) arranged at intervals, and the coating layer (4) is coated on the sub-tabs (5).

14. The method of claim 13, wherein It also includes folding the first tab part (1) and / or the second tab part (3): The area coated with the coating layer (4) is folded inward along the radial direction of the battery cell assembly (10) to form a coating area (6), and in the first direction, the projection of the coating layer (4) on the positive electrode tab (101) partially overlaps the projection of the coating layer (4) on the negative electrode tab (102); The area not coated with the coating layer (4) is folded inward along the radial direction of the battery cell assembly (10) to form a lamination area (7), and at least part of the lamination area (7) is laminated on the outside of the coating area (6).

15. The method of claim 14, wherein the method further comprises: It also includes installing a bus bar (8) outside the first tab part (1) and the second tab part (3): One of the bus bars (8) is connected to the first tab part (1) through the lamination area (7); Another bus bar (8) is connected to the second tab part (3) through the lamination area (7).

16. An electrochemical cell assembly, comprising: According to any one of claims 10-15.

17. A secondary battery characterized by comprising: It includes the battery cell assembly (10) according to any one of claims 1-9 and 16.

18. An electrical device, comprising: It includes the secondary battery according to claim 17, which is used to provide electrical energy. It includes the secondary battery according to claim 17, which is used to provide electrical energy.

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