Battery monomer, battery device, power utilization device and preparation method of electrode assembly

Abstract

The invention relates to a battery monomer, a battery device, a power utilization device and a preparation method of an electrode assembly, and the preparation method of the electrode assembly comprises the following steps: providing a positive plate, a diaphragm and a negative plate, each of the positive plate and the negative plate comprises a main body part and a tab part located on at least one side of the main body part along the width direction; the positive plate and the negative plate are respectively coated with a protective layer, and the protective layers are positioned at the junctions of the main body parts and the tab parts; sequentially laminating the positive plate, the diaphragm and the negative plate along the thickness direction, and winding to obtain an electrode assembly; and performing die cutting on a position, corresponding to the tab part, on the electrode assembly to form the tab. According to the invention, the tab is subjected to die cutting after winding, so that the toughness of the tab part is relatively high during winding, the problems of folding, damage and the like of the tab part are not easy to occur, and the efficiency of the winding process can be effectively improved; and during die cutting, the protective layer can reduce the probability that burrs on the die cutting edge are inserted into the electrode assembly, so that the use performance of the battery monomer can be effectively improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method for preparing a battery cell, a battery device, an electrical device, and an electrode assembly. Background Art

[0002] In the process of preparing the electrode assembly, it is necessary to die-cut the tabs, which can be electrically connected to the electrode terminals on the shell, so that the battery cell can smoothly realize output and input. However, in the current die-cutting process of the tabs, the die-cutting precision is required to be high, and the tabs after die-cutting are prone to dislocation, folding and damage, which affects the structure and performance of the battery cell. Summary of the invention

[0003] Based on this, it is necessary to provide a method for preparing a battery cell, a battery device, an electrical device and an electrode assembly in view of the fact that the current die-cutting process of the tabs has high precision requirements and the tabs after die-cutting are prone to dislocation, folding and breakage, which affects the structure and performance of the battery cell.

[0004] In a first aspect, the present application provides a method for preparing an electrode assembly, comprising the following steps:

[0005] A positive electrode sheet, a separator and a negative electrode sheet are provided, wherein the positive electrode sheet and the negative electrode sheet each include a main body and an ear portion located at at least one side of the main body along a width direction, and the main body is coated with an active material layer;

[0006] A protective layer is coated on the positive electrode sheet and the negative electrode sheet respectively, and the protective layer is located at the junction of the main body and the pole ear;

[0007] The positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence along the thickness direction, and are wound to obtain an electrode assembly;

[0008] Die-cutting is performed at positions corresponding to the pole ears on the electrode assembly to form pole ears.

[0009] It should be noted that if the current method of first die-cutting the tabs and then winding is adopted, the tabs of the positive electrode sheet and the negative electrode sheet are die-cut separately. At this time, the positive electrode sheet or the negative electrode sheet is placed on the corresponding die-cutting platform, and the die-cutting platform can provide a support force for the positive electrode sheet or the negative electrode sheet to prevent the tab from winding or bending at the die-cutting edge. That is, the die-cutting edge is made smoother. Therefore, in the current method of first die-cutting the tabs and then winding, it is only necessary to set a corresponding insulating layer on the positive electrode sheet, and the insulating layer can prevent the burrs on the positive electrode sheet or the negative electrode sheet during the winding process from causing a short circuit between the positive and negative electrodes.

[0010] However, when the method of first winding and then die-cutting the pole ears is adopted, a gap will be generated between the pole ears of the positive electrode sheet and the pole ears of the negative electrode sheet along the stacking direction. At this time, the pole ears are die-cut for the electrode assembly after winding, and the die-cut edges of the pole ears are prone to winding or bending, causing the wound or bent parts to puncture the diaphragm and cause the positive and negative electrodes to overlap and short-circuit; in addition, the main bodies of the negative and positive electrodes are coated with active material layers, resulting in thickness differences between the main bodies and the pole ears of the positive and negative electrodes, and these thickness differences can cause tearing when the pole ears are die-cut.

[0011] Based on this, when winding first and then die-cutting the pole ear, a protective layer needs to be coated on both the positive electrode sheet and the negative electrode sheet respectively. The protective layer can fill the gap between the positive electrode sheet and the negative electrode sheet, reduce the probability of bending of the die-cut edge, and improve the tear strength of the pole ear.

[0012] Therefore, through the above steps, the positive electrode sheet, the separator and the negative electrode sheet are wound and then the pole ears are die-cut, which can not only improve the efficiency of the winding process, but also reduce the probability of the pole ears being folded or damaged during the winding process. In addition, the die-cut pole ears after winding are more neat and less likely to have the problem of pole ear misalignment.

[0013] According to one or more embodiments, the protective layer is configured as an insulating layer, so that the insulating layer can not only well cover the burrs formed by die cutting, but also play a good insulation effect, thereby improving the performance of the battery cell.

[0014] According to one or more embodiments, the protection layer includes a first portion overlapping the body portion and a second portion overlapping the tab portion.

[0015] Through the above structure, the protective layer is divided into the first part and the second part, so that the protective layer can better cover the main body and the pole ear. In this way, when the pole ear is die-cut, the protective layer can better cover the burrs and reduce the probability of the burrs being inserted into the electrode assembly.

[0016] According to one or more embodiments, die-cutting is performed at a position corresponding to the pole ear portion on the electrode assembly, and before the step of forming the pole ear, the width of the protective layer along the width direction is less than or equal to half the width of the pole ear portion.

[0017] Through the above structure, the influence on the welding of the tab can be reduced while ensuring a good covering effect on the burrs.

[0018] According to one or more embodiments, die cutting is performed at a position corresponding to the pole ear portion on the electrode assembly, and before the step of forming the pole ear, the width of the protective layer along the width direction ranges from 5 mm to 15 mm. In this way, the protective layer can better cover and protect the pole ear portion.

[0019] According to one or more embodiments, after die-cutting at a position corresponding to the pole ear portion on the electrode assembly to form the pole ear, the width of the first portion along the width direction ranges from 2 mm to 5 mm. Thus, the first portion can better cover the connection position between the pole ear portion and the main body portion and cover the burrs at the connection position.

[0020] According to one or more embodiments, after die-cutting at a position corresponding to the pole ear portion on the electrode assembly to form the pole ear, the width of the second portion along the width direction accounts for 5% to 30% of the width of the pole ear portion. Based on this, setting the width of the second portion to the above range can not only improve the covering effect of the protective layer on the burrs, but also improve the welding quality of the pole ear.

[0021] According to one or more embodiments, the thickness of the protective layer in the thickness direction ranges from 30 μm to 120 μm. In this way, the protective layer can better cover the burrs during the die-cutting process.

[0022] According to one or more embodiments, die-cutting is performed at a position corresponding to the pole ear portion on the electrode assembly to form the pole ear, and the steps specifically include the following steps:

[0023] Die cutting is performed on opposite sides of the electrode assembly along the width direction to form a positive electrode tab and a negative electrode tab, respectively.

[0024] As a result, the positive and negative tabs can be better distinguished during the die-cutting process, making the operation easier.

[0025] According to one or more embodiments, before the step of performing die cutting at a position corresponding to the pole ear portion on the electrode assembly to form the pole ear, the step further includes:

[0026] The wound electrode assembly is hot pressed and shaped.

[0027] Therefore, the structure of the electrode assembly is made more compact through hot pressing and shaping, the tab die-cutting can be performed better, and the electrode assembly after die-cutting can be smoothly assembled into the shell to form a battery cell.

[0028] In a second aspect, the present application further provides a battery cell, comprising a shell and an electrode assembly disposed inside the shell, wherein the electrode assembly is manufactured by the preparation method described above.

[0029] In a third aspect, the present application also provides a battery device, comprising the battery cell as described above.

[0030] In a fourth aspect, the present application also provides an electrical device, comprising the battery device as described above.

[0031] The preparation method of the above-mentioned battery cell, battery device, electrical device and electrode assembly is firstly to coat a protective layer on the positive electrode sheet and the negative electrode sheet respectively, the protective layer can cover the junction between the main body and the pole ear portion, and then the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound to form an electrode assembly. In this process, since there is no die-cut pole ear, the pole ear portion has strong toughness at this time, and the pole ear portion is not prone to folding, breakage and other problems during the winding process, which can effectively improve the efficiency of the winding process; after the winding is completed, the electrode assembly is die-cut to form the pole ear. At this time, the protective layer can reduce the probability of burrs on the die-cut edge inserting into the electrode assembly, and the pole ear size error formed by the die-cutting is smaller, and it is not easy to be misaligned, which can effectively improve the performance of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The figure is a schematic flow chart of a method for preparing a battery cell according to one or more embodiments.

[0033] Figure 2 Schematic diagram of the structure of a pole piece according to one or more embodiments.

[0034] Figure 3 Schematic diagram of the structure of an electrode assembly after winding and die-cutting according to one or more embodiments.

[0035] Figure 4 for Figure 2 A partial enlarged view of point A in the middle.

[0036] Explanation of reference numerals: 100, electrode assembly; 10, main body; 20, pole ear; 30, protective layer; 40, pole ear; 31, first part; 32, second part; a, width direction. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0038] In the description of the present application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0039] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0040] In this application, unless otherwise clearly specified and limited, if the terms "installed", "connected", "connected", "fixed" and the like appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0041] In the present application, unless otherwise clearly specified and limited, if there is a description that a first feature is "above" or "below" a second feature, etc., or similar descriptions appear, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0042] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only implementation method.

[0043] At present, from the perspective of market development, the application of power batteries is becoming more and more extensive. Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars and other fields. With the continuous expansion of the application field of power batteries, the market demand is also constantly expanding.

[0044] The structure of a battery generally includes a box and a battery cell. The battery cell is placed in the box, so that the box provides a storage space for the battery cell and provides good protection for the battery cell.

[0045] A battery cell is the smallest unit that makes up a battery device. A battery cell usually includes a shell and an electrode assembly disposed inside the shell. The electrode assembly is the structure where the electrochemical reaction actually occurs. The electrode assembly is usually formed by stacking or winding a positive electrode sheet, a separator, and a negative electrode sheet. The portion of the positive electrode sheet coated with the positive electrode active material layer forms the main body, and the portion not coated with the positive electrode active material layer forms the pole ear portion. Similarly, the portion of the negative electrode sheet coated with the negative electrode active material layer forms the main body, and the portion not coated with the negative electrode active material layer forms the pole ear portion.

[0046] Currently, in the process of preparing battery cells, it is usually necessary to first die-cut the ear parts of the positive and negative electrode sheets to form the ear parts, and then stack and wind the die-cut positive and negative electrode sheets with the separator to form an electrode assembly, and then hot-press the electrode assembly and finally assemble it into a shell to form a battery cell.

[0047] However, in the above process, a plurality of pole ears are respectively formed by die-cutting on the positive electrode sheet and the negative electrode sheet. After winding, the pole ears on the positive electrode sheet need to overlap with each other and then welded to form a positive pole ear, and the pole ears on the negative electrode sheet need to overlap with each other and then welded to form a negative pole ear.

[0048] Therefore, the die-cutting precision is required to be high, and there may be misalignment between the pole ears after winding, and the pole ears are prone to folding and damage during the winding process. Based on this, during the winding process, the shape of the pole ears needs to be 100% inspected, resulting in low production efficiency.

[0049] Based on the above considerations, in order to solve the problem that the current die-cutting process of the pole ear has high precision requirements, and the pole ear after die-cutting is prone to dislocation, folding and breakage, which affects the structure and performance of the battery cell, one or more embodiments of the present application provide a method for preparing an electrode assembly, firstly, a protective layer is coated on the positive electrode sheet and the negative electrode sheet respectively, and the protective layer can cover the junction between the main body and the pole ear, and then the positive electrode sheet, the diaphragm and the negative electrode sheet are stacked and wound to form an electrode assembly. In this process, since there is no die-cut pole ear, the pole ear part has strong toughness at this time, and the pole ear part is not prone to folding, breakage and other problems during the winding process, which can effectively improve the efficiency of the winding process. After the winding is completed, the electrode assembly is die-cut and the pole ear is formed. At this time, the protective layer can reduce the probability of the burr on the die-cut edge inserting into the electrode assembly, and the pole ear formed by the die-cutting has a smaller size error, is not prone to dislocation, and can effectively improve the performance of the battery cell.

[0050] It should be noted that the battery apparatus mentioned in the embodiments of the present application may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include multiple battery cells, which are connected in series, in parallel or in mixed connection through a busbar.

[0051] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells. As an example, a battery cell assembly may be a battery module, which is formed by arranging and fixing a plurality of battery cells to form an independent module. As an example, a battery module may be formed by bundling a plurality of battery cells by a cable tie.

[0052] In some embodiments, the battery device may be a battery pack, which includes a case and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the case.

[0053] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the box by fixing the battery module in the box.

[0054] As an example, the battery cell assembly may also be housed in the case by directly fixing a plurality of battery cells to the case.

[0055] Please also read Figure 1 , Figure 2 and Figure 3 , an embodiment of the present application provides a method for preparing an electrode assembly, comprising the following steps:

[0056] S10: providing a positive electrode sheet, a separator and a negative electrode sheet, wherein the positive electrode sheet and the negative electrode sheet each include a main body 10 and a tab 20 located at at least one side of the main body 10 along a width direction a, and the main body 10 is coated with an active material layer.

[0057] It should be noted that the positive electrode sheet refers to a structure formed by coating a positive electrode active material layer on a current collector, and the negative electrode sheet refers to a structure formed by coating a negative electrode active material layer on a current collector. The current collector is usually made of metal materials, such as aluminum foil or copper foil.

[0058] The separator is usually sandwiched between adjacent positive and negative electrodes. The separator refers to a porous plastic film that can ensure the free passage of lithium ions to form a circuit between the positive and negative electrodes, while preventing the two electrodes from contacting each other and playing an electronic insulation role. The types of separators can be, but are not limited to, polyethylene monolayer films, polypropylene monolayer films, etc.

[0059] During the production process, the electrode sheet is usually a whole sheet with a large size. It is necessary to cut the whole sheet of electrode sheet into strips to make it the size required for winding. Based on this, the width direction a refers to the width direction a of the positive electrode sheet or negative electrode sheet after cutting into strips.

[0060] Each positive electrode sheet and negative electrode sheet can be divided into a main body 10 and a tab 20, wherein the main body 10 refers to the portion of the current collector coated with a positive electrode active material layer or a negative electrode active material layer, and the tab 20 refers to the portion not coated with a positive electrode active material layer or a negative electrode active material layer. In other words, the tab 20 is actually a bare current collector.

[0061] Depending on the type of battery cell to be prepared, the pole ear portion 20 may be located only on one side of the main body portion 10 along the width direction a, or may be located on opposite sides of the main body portion 10 along the width direction a. When the pole ear portions 20 are located on opposite sides of the main body portion 10 along the width direction a, the pole ear portions 20 on the opposite sides are the positive pole ear 40 and the negative pole ear 40, respectively.

[0062] S30 : coating the protective layer 30 on the positive electrode sheet and the negative electrode sheet respectively, wherein the protective layer 30 is located at the junction of the main body 10 and the tab 20 .

[0063] The protective layer 30 refers to a structure that can protect the pole ear portion 20 . The protective layer 30 can reduce the probability that burrs generated at the edge of the pole ear 40 during subsequent die-cutting will be inserted into the electrode assembly 100 .

[0064] Specifically, when die-cutting the pole lug 40, the pole lug portion 20 is die-cut according to the design of the final shape and size of the pole lug 40. Among them, laser die-cutting or mechanical die-cutting can be used but is not limited to it. After die-cutting, burrs are easily generated on the edge of the pole lug 40, especially at the root of the pole lug 40. If these burrs are inserted into the electrode assembly 100, they will cause problems such as short circuits, affecting the safety of the battery cell.

[0065] It should be noted that if the current method of first die-cutting the tabs and then winding is adopted, the tabs of the positive electrode sheet and the negative electrode sheet are die-cut separately. At this time, the positive electrode sheet or the negative electrode sheet is placed on the corresponding die-cutting platform, and the die-cutting platform can provide a support force for the positive electrode sheet or the negative electrode sheet to prevent the tab from winding or bending at the die-cutting edge. That is, the die-cutting edge is made smoother. Therefore, in the current method of first die-cutting the tabs and then winding, it is only necessary to set a corresponding insulating layer on the positive electrode sheet, and the insulating layer can prevent the burrs on the positive electrode sheet or the negative electrode sheet during the winding process from causing a short circuit between the positive and negative electrodes.

[0066] However, when the method of first winding and then die-cutting the pole ears is adopted, a gap will be generated between the pole ears of the positive electrode sheet and the pole ears of the negative electrode sheet along the stacking direction. At this time, the pole ears are die-cut for the electrode assembly after winding, and the die-cut edges of the pole ears are prone to winding or bending, causing the wound or bent parts to puncture the diaphragm and cause the positive and negative electrodes to overlap and short-circuit; in addition, the main bodies of the negative and positive electrodes are coated with active material layers, resulting in thickness differences between the main bodies and the pole ears of the positive and negative electrodes, and these thickness differences can cause tearing when the pole ears are die-cut.

[0067] Based on this, when winding first and then die-cutting the pole ear, it is necessary to coat the protective layer 30 on both the positive electrode sheet and the negative electrode sheet respectively. The protective layer 30 can fill the gap between the positive electrode sheet and the negative electrode sheet, reduce the probability of bending of the die-cut edge, and improve the tear strength of the pole ear part 20.

[0068] Therefore, the protective layer 30 is disposed at the junction of the main body portion 10 and the electrode ear portion 20 , so as to cover the burrs generated during die cutting and reduce the probability of the burrs being inserted into the electrode assembly 100 .

[0069] S50: stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence along the thickness direction (not shown in the figure), and winding them to obtain the electrode assembly 100 .

[0070] It should be noted that the thickness direction refers to the thickness direction of the positive electrode sheet, the separator or the negative electrode sheet, that is, the stacking direction of the positive electrode sheet, the separator and the negative electrode sheet. The positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence and then wound to obtain the electrode assembly 100.

[0071] The electrode assembly 100 obtained at this time does not have the die-cut pole ear 40, and the pole ear portion 20 is a whole. Therefore, the pole ear portion 20 has strong toughness, and it is not easy for the pole ear 40 to fold, break, or bend during the winding process, which can also effectively improve the winding efficiency.

[0072] Furthermore, during the winding process, there is no need to fully inspect the shape and size of the tab 40 using a detection device, which can simplify the preparation process of the battery cell and improve production efficiency.

[0073] S70 : performing die cutting at a position corresponding to the electrode lug portion 20 on the electrode assembly 100 to form the electrode lug 40 .

[0074] After winding is completed, the electrode assembly 100 is die-cut, and the die-cutting position corresponds to the position of the pole ear portion 20 . After die-cutting, the pole ear 40 is formed on the electrode assembly 100 , and the complete structure of the electrode assembly 100 is formed.

[0075] The electrode tabs 40 formed after die-cutting include a positive electrode tab 40 and a negative electrode tab 40 , and the die-cutting method may be, but is not limited to, laser die-cutting or mechanical die-cutting.

[0076] Since the die-cutting is performed on the electrode assembly 100 after winding, the electrode tabs 40 formed by the die-cutting are more neat, which can effectively reduce the probability of misalignment of the electrode tabs 40 .

[0077] In addition, the insulating layer coated on the positive electrode sheet and the negative electrode sheet can cover the burrs generated during die cutting, effectively reducing the probability of the burrs being inserted into the electrode assembly 100 .

[0078] Through the above steps, the positive electrode sheet, the separator and the negative electrode sheet are wound and then the pole ear 40 is die-cut, which can not only improve the efficiency of the winding process, but also reduce the probability of the pole ear 40 being folded or damaged during the winding process. In addition, the die-cut pole ear 40 after winding is more neat and less likely to have the problem of misalignment of the pole ear 40.

[0079] In some embodiments, the protection layer 30 is configured as an insulating layer.

[0080] Specifically, the protective layer 30 can be, but is not limited to, a ceramic insulating layer, namely, an AT11 insulating layer. In this way, the insulating layer can not only well cover the burrs formed by die cutting, but also play a good insulation effect, thereby improving the performance of the battery cell.

[0081] like Figure 4 As shown, in some embodiments, the protection layer 30 includes a first portion 31 overlapping the main body portion 10 and a second portion 32 overlapping the tab portion 20 .

[0082] Specifically, the protective layer 30 can be divided into a first portion 31 and a second portion 32. The protective layer 30 is disposed at the junction of the main body 10 and the pole ear 20, that is, one portion of the protective layer 30 covers the main body 10, and the other portion covers the pole ear 20. Therefore, the portion of the protective layer 30 covering the main body 10 is the first portion 31, and the portion of the protective layer 30 covering the pole ear 20 is the second portion 32.

[0083] Through the above structure, the protective layer 30 is divided into a first part 31 and a second part 32, so that the protective layer 30 can better cover the main body 10 and the pole ear 20. In this way, when the pole ear 40 is die-cut, the protective layer 30 can better cover the burrs and reduce the probability of the burrs being inserted into the electrode assembly 100.

[0084] In some embodiments, before step S70 , the width D1 of the protection layer 30 along the width direction a is less than or equal to half of the width D2 of the electrode tab portion 20 .

[0085] Specifically, the width of the protective layer 30 will affect the covering effect on the burrs and the welding quality of the pole lug 40. Based on this, before die-cutting, the width of the protective layer 30 is set to be less than or equal to half the width of the pole lug portion 20, which can reduce the impact on the welding of the pole lug 40 while ensuring a good covering effect on the burrs.

[0086] In some embodiments, before step S70, the width of the protective layer 30 along the width direction a ranges from 5 mm to 15 mm. That is, the width of the protective layer 30 before die-cutting the tab is set to range from 5 mm to 15 mm. In this way, the protective layer 30 can better cover and protect the tab portion 20.

[0087] In some embodiments, after step S70, the width of the first portion 31 along the width direction a ranges from 2 mm to 5 mm. That is, after die-cutting the tab, the width of the first portion 31 is set to range from 2 mm to 5 mm. Thus, the first portion 31 can better cover the connection position between the tab portion 20 and the main body portion 10, and cover the burrs at the connection position.

[0088] In some embodiments, after step S70 , the width D3 of the second portion 32 along the width direction a accounts for 5% to 30% of the width D2 of the tab portion 20 .

[0089] Specifically, the second portion 32 covers the pole lug portion 20 , and therefore, the width of the second portion 32 will directly affect the covering effect of the burrs and the welding quality of the pole lug 40 .

[0090] Based on this, setting the width of the second portion 32 to the above range can not only improve the covering effect of the protective layer 30 on the burrs, but also improve the welding quality of the tab 40 .

[0091] In some embodiments, the thickness of the protective layer 30 in the thickness direction ranges from 30 μm to 120 μm. In this way, the protective layer 30 can better cover the burrs during the die-cutting process.

[0092] In some embodiments, in step S70, the following steps are specifically included:

[0093] Die cutting is performed on opposite sides of the electrode assembly 100 along the width direction a to form a positive electrode tab 40 and a negative electrode tab 40 , respectively.

[0094] Specifically, when the active material layer is applied to the electrode sheet, the active material layer is applied to the middle area of ​​the electrode sheet so that the electrode ear portion 20 is formed on opposite sides of the main body portion 10 along the width direction a. During the die-cutting process, the electrode ear portion 20 on one side is die-cut to obtain the positive electrode ear 40, and the electrode ear portion 20 on the other side is die-cut to obtain the negative electrode ear 40.

[0095] That is, the positive tab 40 and the negative tab 40 are located at opposite ends of the electrode assembly 100 along the width direction a of the electrode sheet. The junction between each tab portion 20 and the main body portion 10 is coated with a protective layer 30 to better cover the burrs formed by die cutting.

[0096] In some embodiments, before step S70, the process further includes the following steps:

[0097] S60: hot pressing and shaping the wound electrode assembly 100.

[0098] In the structure of the electrode assembly 100 formed after winding, the gaps between the positive electrode sheet, the separator and the negative electrode sheet are large, and the shape is cylindrical or nearly cylindrical. Based on this, it is necessary to perform hot pressing shaping on the wound electrode assembly 100 so that the positive electrode sheet, the separator and the negative electrode sheet fit closely together and the shape of the electrode assembly 100 is rectangular, so that the electrode assembly 100 can be placed in the shell.

[0099] Therefore, the structure of the electrode assembly 100 is made more compact by hot pressing and shaping, the electrode tab 40 can be die-cut better, and the die-cut electrode assembly 100 can be smoothly assembled into the shell to form a battery cell.

[0100] In some embodiments, after step S70, the die-cut electrode assembly 100 can be assembled into a shell (not shown in the figure), the tabs 40 are electrically connected to the electrode terminals on the shell, and the shell is packaged to form a battery cell.

[0101] Specifically, the shell generally includes a shell body and a top cover, one end of the shell body is open, and the die-cut electrode assembly 100 is placed into the shell body through the opening. The top cover is provided with electrode terminals, wherein the electrode terminals include a positive terminal and a negative terminal, the tabs 40 are electrically connected to the electrode terminals through a connecting structure such as an adapter, and the top cover is sealed and arranged at the opening of the shell body, and the top cover and the shell body are welded to finally form a battery cell.

[0102] Thus, the output and input of the battery cell can be smoothly realized through the connection between the electrode terminal and the tab 40 .

[0103] Based on the same concept as the above-mentioned preparation method, the present application also provides a battery cell, including a shell and an electrode assembly arranged inside the shell, and the electrode assembly is manufactured by the above-mentioned preparation method.

[0104] Based on the same concept as the above-mentioned battery cell, the present application also provides a battery device, including the above-mentioned battery cell.

[0105] Based on the same concept as the above-mentioned battery, the present application also provides an electrical device, including the battery device as described above.

[0106] As a specific embodiment, the current collector is first coated, wherein the current collector may include a metal substrate such as aluminum foil, copper foil, etc., and the active material layer is coated at a corresponding position on the current collector according to calculations based on the size of the electrode piece.

[0107] Furthermore, after the active material layer is applied, a protective layer is applied at the junction of the main body and the ear of the positive electrode sheet and the negative electrode sheet. After the coating is completed, the positive electrode sheet and the negative electrode sheet are respectively sent to an oven for drying to form a dried positive electrode sheet and a dried negative electrode sheet.

[0108] Secondly, the dried positive and negative electrode sheets are transferred to the cold pressing equipment and cold pressed under a preset pressure to reach a preset thickness.

[0109] Next, the cold-pressed positive and negative electrodes are cut to a preset width. After cutting, the positive electrode, separator, and negative electrode are stacked in sequence and wound by a winding machine to form a fluffy electrode assembly, which is then hot-pressed and integrated to a preset thickness.

[0110] After the hot pressing and shaping is completed, the electrode assembly is fixed by a fixture, and then the tabs of a preset size are cut out by mechanical stamping or stamping die cutting to form the final electrode assembly. The electrode assembly is placed in the housing to form a complete battery cell.

[0111] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0112] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for preparing an electrode assembly, characterized in that: The following steps are involved: Providing a positive electrode sheet, a separator and a negative electrode sheet, wherein the positive electrode sheet and the negative electrode sheet each include a main body and an ear portion located at at least one side of the main body along a width direction, and the main body is coated with an active material layer; Coating protective layers on the positive electrode sheet and the negative electrode sheet respectively, wherein the protective layers are located at the junction of the main body and the tab portion; The positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence along the thickness direction, and are wound to obtain an electrode assembly; Die cutting is performed on the electrode assembly at a position corresponding to the pole ear portion to form a pole ear.

2. The preparation method according to claim 1, characterized in that: The protective layer is designed as an insulating layer.

3. The preparation method according to claim 1 or 2, characterized in that: The protection layer includes a first portion overlapping the main body portion and a second portion overlapping the tab portion.

4. The preparation method according to claim 3, characterized in that: Before the step of die-cutting at a position corresponding to the pole ear portion on the electrode assembly to form the pole ear, the width of the protective layer along the width direction is less than or equal to half the width of the pole ear portion.

5. The preparation method according to claim 4, characterized in that: Before die-cutting is performed on the electrode assembly at a position corresponding to the pole ear portion to form the pole ear, the width of the protective layer along the width direction ranges from 5 mm to 15 mm.

6. The preparation method according to claim 3, characterized in that: After the step of die-cutting the electrode assembly at a position corresponding to the pole ear portion to form the pole ear, the width of the first portion along the width direction ranges from 2 mm to 5 mm.

7. The preparation method according to claim 3, characterized in that: After the step of die-cutting the electrode assembly at a position corresponding to the pole ear portion to form the pole ear, the width of the second portion along the width direction accounts for 5% to 30% of the width of the pole ear portion.

8. The preparation method according to claim 1 or 2, characterized in that: In the thickness direction, the thickness of the protective layer ranges from 30 μm to 120 μm.

9. The preparation method according to claim 1, characterized in that: The step of performing die cutting at a position corresponding to the pole ear portion on the electrode assembly to form the pole ear specifically includes the following steps: Die cutting is performed on opposite sides of the electrode assembly along the width direction to form a positive electrode tab and a negative electrode tab respectively.

10. The preparation method according to claim 1, characterized in that: Before the step of die-cutting the electrode assembly at a position corresponding to the electrode ear to form the electrode ear, the step further includes: The wound electrode assembly is hot pressed and shaped.

11. A battery cell, characterized in that: It comprises a shell and an electrode assembly arranged inside the shell, and the electrode assembly is manufactured by the preparation method according to any one of claims 1 to 10.

12. A battery device, characterized in that: Comprising the battery cell as claimed in claim 11.

13. An electrical device, characterized in that: Comprising the battery device as claimed in claim 12.

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