WO2023245826A1 - Positive electrode plate, battery cell, battery, and electric device - Google Patents

Abstract

The present application relates to the field of batteries. Provided in the present application are a positive electrode plate, a battery cell, a battery, and an electric device. The positive electrode plate comprises a positive electrode current collector and two positive electrode film layers coated onto both surfaces of the positive electrode current collector, wherein at least one positive electrode film layer is provided with a film layer body and a filling portion that is soluble in an electrolyte solution, the filling portion is embedded in the film layer body, some of the surface of the filling portion is not covered by the film layer body, the filling portion and the positive electrode current collector are separated by the film layer body, the filling portion is located at a turning portion formed by the winding of the positive electrode plate, and the filling portion is used for being at least partially dissolved in the electrolyte solution so as to form a groove in the surface of the positive electrode film layer. When the positive electrode plate is used in a wound battery cell, not only can the problem of a negative electrode plate at a turning portion being prone to lithium plating be alleviated, but also the preparation difficulty of the positive electrode plate is low and the yield of the obtained positive electrode plate is high.

Description

Positive electrode sheet, battery cells, batteries and electrical devices

cross reference

This application claims priority to Chinese patent application No. 2022215396374, titled "Cathode Sheets, Battery Cells, Batteries and Electrical Devices" submitted on June 20, 2022. The entire content of this application is incorporated herein by reference. middle.

Technical field

The present application relates to the field of batteries, specifically, to a positive electrode sheet, a battery cell, a battery and an electrical device.

Background technique

Lithium-ion batteries have been widely used in consumer electronics markets such as mobile phones and computers due to their excellent properties such as high operating voltage and high energy density, and have achieved great commercial success. Due to technological progress and environmental protection requirements, lithium-ion batteries as a power source are currently making rapid progress in the field of new energy vehicles. Many companies and their researchers have invested huge resources to continuously optimize and improve their performance and manufacturing processes to meet the needs of new energy vehicles. Urgent needs. At present, most lithium-ion batteries are assembled in a winding method, but the negative electrode sheet in the winding corner is prone to lithium precipitation, which affects its safety performance.

Contents of the invention

The present application provides a positive electrode sheet, a battery cell, a battery and an electrical device, which can improve the technical problem that the negative electrode sheet in the corner is prone to lithium precipitation and affects its safety performance.

In a first aspect, embodiments of the present application provide a cathode sheet, including a cathode current collector and two cathode film layers coated on both sides of the cathode current collector, wherein at least one cathode film layer has a film body and is soluble in the electrolyte. The filling part is embedded in the film body. Part of the surface of the filling part is not covered by the film body, and the filling part is separated from the positive electrode current collector by the film body. The filling part is located at the turning part after the positive electrode sheet is wound. The filling part It is used to at least partially dissolve in the electrolyte to form grooves on the surface of the positive electrode film layer.

In the technical solution of the embodiment of the present application, part of the surface of the filling part that is soluble in the electrolyte is not covered by the film layer body, and the filling part is separated from the positive electrode current collector by the film layer body, so as to facilitate the use of the positive electrode sheet when it is used in a roll-up type In the electrode assembly, when the filling part is made to correspond to the turning part after winding, the filling part can be in contact with the electrolyte at this time so that at least part of the filling part can be dissolved in the electrolyte to form grooves on the surface of the positive electrode film layer. On the one hand, Effectively reduces the active material capacity of the positive electrode film layer on the turning part, thereby increasing the ratio of the active material capacity of the negative electrode sheet in the turning part to the active material capacity of the corresponding positive electrode, preventing lithium deposition from the negative electrode sheet in the turning part, and on the other hand, dissolution of the filling part The interface between the groove formed later and the film body will not bulge. Compared with the method of directly forming the groove with less coating on the turning part of the corresponding positive electrode film layer, not only the preparation process is less difficult, but also Avoid the problems of easy material bulging and capacity loss caused by using local sparse coating to directly form grooves.

In some embodiments, the ratio of the thickness of the filling part to the thickness of the positive electrode film layer is H, 0.05<H≤0.95. The thickness of the filling part within the above range is reasonable, which can alleviate the problems of lithium deposition in the negative electrode sheet at the turning part and easy breakage of the positive electrode sheet in the turning part, and has better battery energy density. Excessive thickness will reduce the battery energy density, and too small thickness will lead to final dissolution. The depth of the formed groove is too small and cannot effectively improve the lithium deposition of the negative electrode sheet in the turning part.

In some embodiments, the tabs of the positive electrode sheet are located in the first direction of the positive electrode current collector, and the two ends of the filling portion respectively extend along the first direction to the edge of the positive electrode film layer. Under the above setting conditions, the corresponding groove structure formed in the filling part is in the shape of a groove with both ends penetrating the edge of the positive electrode film layer in the first direction. At this time, the groove can not only provide a path for the migration of electrolyte, but also improve the migration of lithium ions. The speed is conducive to alleviating the insufficient supply of electrolyte in the middle of the electrode assembly, and is conducive to the expansion and release of the positive electrode sheet, thereby reducing the risk of breakage of the positive electrode sheet due to expansion in the turning portion, and can further effectively prevent lithium precipitation from the negative electrode sheet in the turning portion.

In some embodiments, the length of the filling part in the second direction is 0.01%-1% of the length of the positive electrode sheet in the second direction, the second direction and the first direction are perpendicular to each other, and the second direction is the roll of the positive electrode sheet. around direction. The length of the filling part in the second direction is set reasonably, which can not only alleviate the problems of lithium deposition of the negative electrode sheet in the turning part and the easy breakage of the positive electrode sheet in the turning part, but also has better energy density. If the length of the filling part in the second direction is If it is too small, the effect of improving lithium deposition in the turning portion will be poor. If the length of the filling portion in the second direction is too large, the energy density of the battery will be affected.

In some embodiments, the number of filling parts is multiple, and the plurality of filling parts are spaced apart along the second direction of the positive electrode sheet. There are multiple turning parts after winding, and the actually used winding direction is the second direction. Multiple filling parts are arranged at intervals along the second direction of the positive electrode sheet to provide filling in each turning part according to actual needs. part to reduce the problem of lithium precipitation in the negative electrode sheet at the turning part after winding.

In some embodiments, both positive electrode film layers are provided with filling portions. The above settings can further improve the problem of lithium deposition from the negative electrode sheet in the turning part.

In a second aspect, the present application provides a battery cell, which includes an electrolyte, a negative electrode sheet, the positive electrode sheet provided in the above embodiment, and a separator arranged between the positive electrode sheet and the negative electrode sheet. The negative electrode sheet, the separator and the positive electrode The sheets are rolled to form an electrode assembly, and the filling portion is in contact with the electrolyte so that the filling portion can be at least partially dissolved in the electrolyte. The filling portion is located at the turning portion after the positive electrode sheet is rolled.

In the technical solutions of the embodiments of the present application, the filling part is used to contact the electrolyte so that the filling part can be at least partially dissolved in the electrolyte to form grooves on the surface of the positive electrode film layer. On the one hand, the positive electrode film on the turning part is effectively reduced. The active material capacity of the layer, thereby increasing the ratio of the active material capacity of the negative electrode sheet in the turning part to the active material capacity of the corresponding positive electrode, and mitigating lithium deposition from the negative electrode sheet in the turning part. On the other hand, the grooves and film layer bodies formed after the filling part is dissolved The interface will not produce bulges caused by piles of materials. Compared with the method of directly forming grooves with less coating at the turning portion of the corresponding positive electrode film layer, not only is the preparation process less difficult, but it also avoids the use of local less coating. The problem of easy stacking and capacity loss caused by directly forming grooves.

In some embodiments, the number of turns of the positive electrode sheet after winding is n+1, and at least one of the first to nth turns of the positive electrode sheet from the inside to the outside is provided with a filling portion. The above arrangement can not only avoid lithium deposition on the negative electrode sheet at the corner during charging, but also because the inner ring will become very tight when the electrode piece is expanded and released, but will have little effect on the outer ring, so the outermost layer does not need to be provided with a filling part, which reduces the battery life. Preparation costs are reduced while avoiding impact on battery energy.

In some embodiments, n≥10. The energy density of the battery can be further improved while avoiding lithium precipitation at the corners.

In a third aspect, the present application provides a battery, which includes the battery cell in the above embodiment.

In a third aspect, the present application provides an electrical device, which includes the battery in the above embodiment, and the battery is used to provide electrical energy.

The above description is only an overview of the technical solutions of the present application. In order to have a clearer understanding of the technical means of the present application, they can be implemented according to the content of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and understandable. , the specific implementation methods of the present application are specifically listed below.

Description of the drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating preferred embodiments only and are not to be construed as limiting the application. Also, the same parts are represented by the same reference numerals throughout the drawings. In the attached picture:

Figure 1 is a schematic structural diagram of a vehicle according to some embodiments of the present application;

Figure 2 is a schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

Figure 3 is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

Figure 4 is a schematic structural diagram of an electrode assembly according to some embodiments of the present application;

Figure 5 is a schematic cross-sectional structural diagram of the positive electrode sheet before winding in some embodiments of the present application;

Figure 6 is a schematic top view of the positive electrode sheet before winding according to some embodiments of the present application;

Figure 7 is a schematic cross-sectional structural diagram of a positive electrode sheet before winding according to some embodiments of the present application;

Figure 8 is a schematic cross-sectional structural diagram of the positive electrode sheet before winding according to some embodiments of the present application;

Figure 9 is a schematic structural diagram of the positive electrode sheet and the negative electrode sheet in some embodiments of the present application when they are rolled together but not in contact with the electrolyte;

Figure 10 is a schematic structural diagram of some embodiments of the present application in which the positive electrode sheet and the negative electrode sheet are rolled together and contacted with the electrolyte to be dissolved to form a groove.

The reference numbers in the specific implementation are as follows:

1000-vehicle;

100-battery; 200-controller; 300-motor;

10-box; 11-first part; 12-second part;

20-battery cell; 21-end cover; 21a-electrode terminal; 22-casing; 23-electrode assembly; 23a-pole lug;

231-straight part; 233-turn part; 24-positive electrode piece; 25-negative electrode piece; 26-separator;

241-positive electrode current collector; 243-positive electrode film layer; 245-film layer body; 2451-first film layer; 2455-second film layer; 247-filling part; 248-groove.

Detailed ways

The embodiments of the technical solution of the present application will be described in detail below with reference to the accompanying drawings. The following examples are only used to illustrate the technical solution of the present application more clearly, and are therefore only used as examples and cannot be used to limit the protection scope of the present application.

Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the technical field belonging to this application; the terms used herein are for the purpose of describing specific embodiments only and are not intended to be used in Limitation of this application; the terms "including" and "having" and any variations thereof in the description and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion.

In the description of the embodiments of this application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying the relative importance or implicitly indicating the quantity or specificity of the indicated technical features. Sequence or priority relationship. In the description of the embodiments of this application, "plurality" means two or more, unless otherwise explicitly and specifically limited.

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 appearances of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art understand, both explicitly and implicitly, that the embodiments described herein may be combined with other embodiments.

In the description of the embodiments of this application, the term "and/or" is only an association relationship describing associated objects, indicating that there can be three relationships, such as A and/or B, which can mean: A exists alone, and A exists simultaneously and B, there are three cases of B alone. In addition, the character "/" in this article generally indicates that the related objects are an "or" relationship.

In the description of the embodiments of this application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to It is more than two pieces (including two pieces).

In the description of the embodiments of this application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right" and "vertical" The orientation or positional relationships indicated by "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on those shown in the accompanying drawings. The orientation or positional relationship is only for the convenience of describing the embodiments of the present application and simplifying the description. It 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 implementation of the present application. Example limitations.

In the description of the embodiments of this application, unless otherwise clearly stated and limited, technical terms such as "installation", "connection", "connection" and "fixing" should be understood in a broad sense. For example, it can be a fixed connection or a removable connection. It can be disassembled and connected, or integrated; it can also 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 an internal connection between two elements or an interaction between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

At present, judging from the development of the market situation, 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 are also widely used in electric vehicles such as electric bicycles, electric motorcycles and electric cars, as well as in many fields such as military equipment and aerospace. . As the application fields of power batteries continue to expand, their market demand is also constantly expanding.

The rolled flat electrode assembly has interconnected curved portions and straight portions. During actual use, the length of the positive electrode film layer inside the positive electrode sheet located in the curved portion is longer than the length of the negative electrode film layer outside the opposite negative electrode sheet. length, causing the ratio of the active material capacity of the negative electrode sheet to the active material capacity of the positive electrode sheet in the turning part to be smaller than the average design value, causing this part to be prone to lithium precipitation during the charging process, and in severe cases may even cause damage to the electrode assembly Safety issues such as large self-discharge or short circuit effects. Lithium precipitation means that if the lithium ions that have fallen off the positive electrode cannot be embedded in the negative electrode, then the lithium ions can only precipitate on the surface of the negative electrode, forming a layer of gray material, which is called lithium precipitation.

Although it is possible to apply less or no cathode active slurry on the positive electrode sheet at the turning part, so as to create grooves on the surface of the positive electrode film layer at the turning part to reduce the capacity of the positive electrode active material at the turning part, thereby alleviating the problem of lithium deposition from the negative electrode sheet at the turning part. Since the preparation method of the positive electrode sheet is usually coating first, then drying, and finally cold pressing, if the positive electrode sheet is directly coated with little or no positive active slurry on the turning part to form the groove, on the one hand, the preparation process needs to be optimized. Make improvements, such as making improvements to the cold pressing process or related equipment, to ensure that the positive electrode film layer has grooves of a preset shape after cold pressing, which is difficult to prepare. On the other hand, there are steps at the intersection of the less coated part and the normal coated part. , and the material at the junction is easy to bulge, affecting the appearance and yield of the positive electrode sheet.

In order to solve the above problem, the inventor found that a filling part soluble in the electrolyte can be provided in the positive electrode sheet in advance, and then it will be dissolved by the electrolyte when assembled in a single cell, thereby forming a groove. On the one hand, the above arrangement can directly use existing preparation equipment to produce positive electrode sheets with uniform thickness when preparing positive electrode sheets, effectively reducing the difficulty of preparation. On the other hand, the filling part can be at least partially soluble in the electrolyte to form a concave surface. In the tank, the interface between the tank wall of the groove and the positive electrode film layer that still exists on the positive electrode current collector after dissolution is smooth, no accumulation of materials will occur, and the product yield is high. And by selecting the position of the filling part during winding, for example, arranging it at the turning part after winding, the risk of breakage of the positive electrode sheet due to expansion can be reduced, and the lithium deposition of the negative electrode sheet corresponding to the turning part corresponding to the positive electrode sheet can be avoided, which is effective Solve the above technical problems.

Based on the above considerations, in order to alleviate the lithium precipitation of the negative electrode sheet in the turning part, and to reduce the processing difficulty of the positive electrode sheet and improve the product yield, the inventors conducted in-depth research and designed a positive electrode sheet, which includes a positive electrode current collector and a positive electrode current collector coated on the positive electrode collector. Two positive electrode film layers on both sides of the fluid, at least one of the positive electrode film layers has a film layer body and a filling part soluble in the electrolyte, the filling part is buried in the film layer body, part of the surface of the filling part is not covered by the film layer body, and The filling part is separated from the body of the positive electrode current collector film layer and is located at the turning part after the positive electrode sheet is rolled. The filling part is used to at least partially dissolve in the electrolyte to form grooves on the surface of the positive electrode film layer.

Part of the surface of the filling part that is soluble in the electrolyte is not covered by the film layer body, and the filling part is separated from the positive electrode current collector by the film layer body, so that when the positive electrode sheet is used in a wound electrode assembly, the filling part can be made to correspond When winding the turning part, the filling part can be in contact with the electrolyte at this time, so that at least part of the filling part can be dissolved in the electrolyte to form grooves on the surface of the positive electrode film layer. On the one hand, it effectively reduces the positive electrode on the turning part. The active material capacity of the film layer, thereby increasing the ratio of the active material capacity of the negative electrode sheet in the turning part to the active material capacity of the corresponding positive electrode, preventing lithium precipitation from the negative electrode sheet in the turning part, and on the other hand, the grooves and film layers formed after the filling part is dissolved The interface of the body is flat and will not cause bulges caused by piles of materials. Compared with using less coating to directly form grooves at the turning portion of the corresponding positive electrode film layer, not only the preparation process is less difficult, but also less coating is avoided. The problem of easy stacking and capacity loss caused by directly forming grooves.

The batteries disclosed in the embodiments of the present application can be used in, but are not limited to, electrical devices such as vehicles, ships, or aircrafts. The power supply system of the electrical device can be composed of battery cells, batteries, etc. disclosed in this application, which is beneficial to improving the stability of battery performance and battery life.

Embodiments of the present application provide an electrical device that uses a battery as a power source. The electrical device may be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric vehicle, a ship, a spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, spaceships, etc.

For the convenience of explanation in the following embodiments, an electric device 1000 according to an embodiment of the present application is used as an example.

Please refer to FIG. 1 , which is a schematic structural diagram of a vehicle 1000 provided by some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. The battery 100 is disposed inside the vehicle 1000 , and the battery 100 may be disposed at the bottom, head, or tail of the vehicle 1000 . The battery 100 may be used to power the vehicle 1000 , for example, the battery 100 may serve as an operating power source for the vehicle 1000 . The vehicle 1000 may also include a controller 200 and a motor 300 . The controller 200 is used to control the battery 100 to provide power to the motor 300 , for example, for starting, navigating and driving the vehicle 1000 .

In some embodiments of the present application, the battery 100 can not only be used as an operating power source for the vehicle 1000 , but also can be used as a driving power source for the vehicle 1000 , replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000 .

Please refer to FIG. 2 , which is an exploded view of the battery 100 provided by some embodiments of the present application. The battery 100 includes a case 10 and battery cells 20 , and the battery cells 20 are accommodated in the case 10 . Among them, the box 10 is used to provide an accommodation space for the battery cells 20, and the box 10 can adopt a variety of structures. In some embodiments, the box 10 may include a first part 11 and a second part 12 , the first part 11 and the second part 12 covering each other, the first part 11 and the second part 12 jointly defining a space for accommodating the battery cells 20 of accommodation space. The second part 12 may be a hollow structure with one end open, and the first part 11 may be a plate-like structure. The first part 11 covers the open side of the second part 12 so that the first part 11 and the second part 12 jointly define a receiving space. ; The first part 11 and the second part 12 may also be hollow structures with one side open, and the open side of the first part 11 is covered with the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 can be in various shapes, such as cylinder, rectangular parallelepiped, etc.

In the battery 100, there may be a plurality of battery cells 20, and the plurality of battery cells 20 may be connected in series, in parallel, or in mixed connection. Mixed connection means that the plurality of battery cells 20 are connected in series and in parallel. The plurality of battery cells 20 can be directly connected in series or in parallel or mixed together, and then the whole composed of the plurality of battery cells 20 can be accommodated in the box 10 ; of course, the battery 100 can also be a plurality of battery cells 20 First, the battery modules are connected in series, parallel, or mixed to form a battery module, and then multiple battery modules are connected in series, parallel, or mixed to form a whole, and are accommodated in the box 10 . The battery 100 may also include other structures. For example, the battery 100 may further include a bus component for realizing electrical connections between multiple battery cells 20 .

Each battery cell 20 may be a secondary battery or a primary battery. The battery cell 20 may be in the shape of a cylinder, a flat body, a rectangular parallelepiped or other shapes.

Please refer to FIG. 3 , which is an exploded structural diagram of a battery cell 20 provided in some embodiments of the present application. The battery cell 20 refers to the smallest unit that constitutes the battery 100 . As shown in FIG. 3 , the battery cell 20 includes an end cap 21 , a case 22 , an electrode assembly 23 , an electrolyte (not shown) and other functional components.

The end cap 21 refers to a component that covers the opening of the case 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the housing 22 to fit the housing 22 . Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy). In this way, the end cap 21 is less likely to deform when subjected to extrusion and collision, so that the battery cell 20 can have higher durability. Structural strength and safety performance can also be improved. The end cap 21 may be provided with functional components such as electrode terminals 21a. The electrode terminal 21a may be used to electrically connect with the electrode assembly 23 for outputting or inputting electrical energy of the battery cell 20 . In some embodiments, the end cap 21 may also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The end cap 21 can also be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which are not particularly limited in the embodiment of the present application. In some embodiments, an insulating member may also be provided inside the end cover 21 , and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cover 21 to reduce the risk of short circuit. For example, the insulating member may be plastic, rubber, etc.

The housing 22 is a component used to cooperate with the end cover 21 to form an internal environment of the battery cell 20 , wherein the formed internal environment can be used to accommodate the electrode assembly 23 , electrolyte, and other components. The housing 22 and the end cover 21 may be independent components, and an opening may be provided on the housing 22. The end cover 21 covers the opening at the opening to form the internal environment of the battery cell 20. Without limitation, the end cover 21 and the housing 22 can also be integrated. Specifically, the end cover 21 and the housing 22 can form a common connection surface before other components are put into the housing. When it is necessary to encapsulate the inside of the housing 22 At this time, the end cover 21 covers the housing 22 again. The housing 22 can be of various shapes and sizes, such as rectangular parallelepiped, cylinder, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23 . The housing 22 may be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which are not particularly limited in the embodiments of the present application.

The electrode assembly 23 is a component in the battery cell 20 where electrochemical reactions occur. One or more electrode assemblies 23 may be contained within the housing 22 .

Please refer to FIG. 4 . The electrode assembly 23 is formed by winding a positive electrode sheet 24 , a negative electrode sheet 25 , and a separator 26 disposed between the positive electrode sheet 24 and the negative electrode sheet 25 . Q in FIG. 4 represents the winding direction.

The wound electrode assembly 23 has a flat structure, which has a turning portion 233 and a straight portion 231 connected to each other. The turning portion 233 is provided at both ends of the straight portion 231 along the length direction, and the positive electrode sheet 24 and the negative electrode are located in the straight portion 231 . The sheet 25 and the separator 26 are parallel to each other and extend along a straight line. The positive electrode sheet 24, the negative electrode sheet 25 and the separator 26 located at the turning portion 233 all extend along a curve.

Please refer to FIGS. 3 and 4 . The portion of the positive electrode sheet 24 containing the positive electrode active material and the portion of the negative electrode sheet 25 containing the negative electrode active material constitute the main body of the electrode assembly 23 . The portions of the positive electrode sheet 24 and the negative electrode sheet 25 that do not contain active material are formed separately. The tabs 23a can be full tabs or split tabs. The tabs 23a of the positive electrode piece 24 and the tabs 23a of the negative electrode piece can be located together at one end of the main body or at both ends of the main body. During the charging and discharging process of the battery cell 20, the positive active material and the negative active material react with the electrolyte, and the tab 23a is connected to the electrode terminal 21a to form a current loop.

Please refer to FIGS. 5 to 9 , wherein Y represents the thickness direction in FIGS. 5 to 7 , and X represents the direction in which the positive electrode sheet 24 will be wound in the future. According to some embodiments of the present application, the positive electrode sheet 24 includes a positive electrode current collector 241 and two positive electrode film layers 243 coated on both sides of the positive electrode current collector 241 , wherein at least one positive electrode film layer 243 has a film layer body 245 and is soluble in The filling part 247 of the electrolyte is embedded in the membrane body 245. Part of the surface of the filling part 247 is not covered by the membrane body 245, and the filling part 247 and the positive electrode current collector 241 are separated by the membrane body 245. The filling part 247 is located The turning portion 233 and the filling portion 247 of the positive electrode sheet 24 after being wound are used to at least partially dissolve in the electrolyte to form grooves 248 on the surface of the positive electrode film layer 243 .

Among them, the film layer body 245 refers to a film layer that contains a positive electrode active material, a conductive agent and a binder and is insoluble in the electrolyte. Exemplarily, the positive electrode active material includes but is not limited to lithium iron phosphate, lithium manganate, spinel lithium nickel manganate, nickel cobalt manganese ternary material LiNixMnyCozMO2 (0≤x≤1,0≤y≤1,0 ≤z≤1, x+y+z=1, M=Al, Zr, etc.), those skilled in the art can choose according to actual needs.

The filling part 247 that is soluble in the electrolyte means that the filling part 247 is composed of a substance that is soluble in the electrolyte. The solubility of the substance that is soluble in the electrolyte is >0.1%. Therefore, when the filling part 247 is in contact with the electrolyte When in contact with the electrolyte, it can at least partially dissolve in the electrolyte to form grooves 248 on the surface of the positive electrode film layer 243. It can be understood that the substances that are soluble in the electrolyte should not chemically react with the electrolyte and basically do not react with the electrolyte. The performance of the battery 100 may be adversely affected.

The fact that the filling part 247 and the positive electrode current collector 241 are separated by the film layer body 245 means that the thickness of the filling part 247 is smaller than the thickness of the positive electrode film layer 243, and when the filling part 247 contacts the electrolyte and is completely dissolved to form the groove 248, then The current collector portion corresponding to the groove 248 is still covered by the film body 245, thereby preventing the current collector from being exposed and preventing safety accidents caused by contact short circuit between the positive electrode current collector 241 and the negative electrode sheet 25.

In the technical solution of the embodiment of the present application, part of the surface of the filling part 247 that is soluble in the electrolyte is not covered by the film body 245, and the filling part 247 and the positive electrode current collector 241 are separated by the film body 245 to facilitate the use of the positive electrode sheet. 24 is applied to the wound electrode assembly 23, and when the filling part 247 is made to correspond to the turning part 233 after being rolled, the filling part 247 can be in contact with the electrolyte at this time so that at least part of the filling part 247 can be dissolved in the electrolyte to dissolve in the electrolyte. The groove 248 is formed on the surface of the positive electrode film layer 243, which effectively reduces the active material capacity of the positive electrode film layer 243 on the turning portion 233, thereby increasing the active material capacity of the negative electrode sheet 25 in the turning portion 233 and the positive electrode sheet 24 in the turning portion 233. The ratio of active material capacity prevents lithium deposition in the negative electrode sheet 25 in the turning part 233. On the other hand, the interface between the groove 248 formed after the filling part 247 of the groove 248 is dissolved and the film body 245 will not produce piles. Compared with The method of directly forming the groove 248 with less coating on the turning portion 233 of the corresponding positive electrode film layer 243 not only makes the preparation process less difficult, but also avoids the easy accumulation and capacity loss caused by less coating to directly form the groove 248. The problem.

It should be noted that the electrolyte solution includes electrolyte solution salt and solvent.

Among them, the electrolyte salt may include: lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethanesulfonic acid At least one of lithium, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate and lithium tetrafluoroxalate, but is not limited to any one of the above.

The solvent can be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluorinated Ethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4- At least one of butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

Optionally, the electrolyte also includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

Alternatively, substances soluble in the electrolyte include, but are not limited to, sodium chloride, lithium hexafluorophosphate or vinyl sulfate.

Optionally, the solubility of the substance soluble in the electrolyte in the electrolyte is >1%, and further optionally, >10%, thereby reducing the residual rate of the filling portion 247 after dissolution.

Among them, the junction between the filling part 247 and the film body 245 can be a cross-sectional type, a natural transition type, a parabola type or a semicircular type, and those skilled in the art can choose according to actual needs.

In order to facilitate production and reduce production costs, the film body 245 can be arranged in layers. Optionally, please refer to FIGS. 5 to 7 . The film body 245 has a stacked first film layer 2451 along its thickness direction. The second film layer 2455, the first film layer 2451 and the second film layer 2455 are all film layers that contain positive active materials and are insoluble in the electrolyte.

Among them, the first film layer 2451 is formed on the surface of the current collector, the second film layer 2455 is formed on the surface of the first film layer 2451, the number of the second film layers 2455 is multiple, and the multiple second film layers 2455 are along the positive electrode sheet. 24 are arranged at intervals in the winding direction, a gap is formed between any two adjacent second film layers 2455, the filling part 247 is filled in the gap, and the side of the filling part 247 away from the first film layer 2451 is in contact with the second film layer 2455 The side away from the first film layer 2451 is flush, that is, the thickness of the filling portion 247 is the same as the thickness of the second film layer 2455. At this time, the filling portion 247 and the positive electrode current collector 241 are separated by the first film layer 2451.

The cathode active material in the first film layer 2451 and the cathode active material in the second film layer 2455 may be the same or different, for example, the cathode active material in the first film layer 2451 and the cathode active material in the second film layer 2455 Both are lithium iron phosphate or lithium manganate, or for example, the positive active material in the first film layer 2451 is lithium iron phosphate, and the positive active material in the second film layer 2455 is lithium manganate, etc. Those skilled in the art can The actual requirements are limited and will not be elaborated here.

The particle sizes of the cathode active material in the first film layer 2451 and the cathode active material in the second film layer 2455 may be the same or different. For example, the particle size of the cathode active material in the first film layer 2451 is larger than that of the second film layer 2455 . The particle size of the cathode active material in 2455, or the particle size of the cathode active material in the first film layer 2451, is smaller than the particle size of the cathode active material in the second film layer 2455, or the particle size of the cathode active material in the first film layer 2451 The particle size is equal to the particle size of the cathode active material of the second film layer 2455, which can be defined by those skilled in the art according to actual needs, and will not be described again here.

The unit capacity of the positive electrode sheet 24 can be flexibly adjusted to meet relevant requirements by selecting the positive active materials of the first film layer 2451 and the second film layer 2455 .

Wherein, the two positive electrode film layers 243 may both be provided with filling portions 247, or may be provided only on one side.

As shown in FIGS. 4 and 5 , among the two positive electrode film layers 243 , only one of the positive electrode film layers 243 is provided with a filling portion 247 , and the other positive electrode film layer 243 is entirely composed of a film layer body 245 of equal thickness. In practical applications, the positive electrode film layer 243 with the filling portion 247 is located inside the rolled positive electrode sheet 24 to better alleviate the risk of lithium deposition in the negative electrode sheet 25 in the turning portion 233 and the breakage of the positive electrode sheet 24 in the turning portion 233 after winding.

Optionally, the thickness of the positive electrode film layer 243 is 50 μm-100 μm.

For example, the thickness of the positive electrode film layer 243 is any one of 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm or between any two values.

Referring to FIG. 4 and FIG. 5 , according to some embodiments of the present application, optionally, the ratio of the thickness of the filling part 247 to the thickness of the positive electrode film layer 243 is H, 0.05<H≤0.95.

The thickness of the filling part 247 within the above range is reasonable, which can alleviate the problems of lithium deposition in the negative electrode sheet 25 in the turning part 233 and the easy breakage of the positive electrode sheet 24 in the turning part 233, and has better battery 100 energy density. Excessive thickness will reduce the battery energy density, and the thickness If it is too small, the groove 248 formed after final dissolution is too shallow and cannot effectively improve the lithium deposition on the negative electrode sheet 25 in the turning portion 233 .

For example, H can be any value among 0.055, 0.1, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95 or between any two values.

Optionally, 0.48≤H≤0.95. This range can not only improve the problems of lithium deposition on the negative electrode sheet 25 in the turning portion 233 and the breakage of the positive electrode sheet 24 in the turning portion 233, but also provide better battery energy density.

The tab 23a of the positive electrode sheet 24 is located in the first direction of the positive electrode current collector 241. At this time, both ends of the filling portion 247 extend along the first direction and at least one end is located in the positive electrode film layer 243. When both ends of the filling portion 247 When both ends are located in the positive electrode film layer 243, the corresponding groove 248 formed may be in the shape of a blind hole. When one end of the filling portion 247 is located in the positive electrode film layer 243, the corresponding formed groove 248 may be in the shape of one end penetrating the positive electrode film layer 243. In this case, the problem that the corresponding negative electrode sheet 25 is prone to lithium precipitation can be alleviated to a certain extent.

Please refer to Figure 6. In Figure 6, the Z direction represents the first direction. According to some embodiments of the present application, optionally, the tab 23a of the positive electrode sheet 24 is located in the first direction of the positive electrode current collector 241, and the filling portion 247 The two ends respectively extend along the first direction to the edge of the positive electrode film layer 243 .

The two ends of the filling part 247 respectively extending to the edge of the positive electrode film layer 243 along the first direction means that the two ends of the filling part 247 are respectively in contact with the edges of the positive electrode film layer 243, so that after the filling part 247 is dissolved in the electrolyte, a Grooves 248 penetrating both edges of the positive electrode film layer 243 in the first direction.

Under the above installation conditions, the structure of the groove 248 corresponding to the filling part 247 is in the shape of a groove with both ends penetrating the edge of the positive electrode film layer 243 along the first direction. At this time, the groove 248 can not only provide a path for the migration of the electrolyte, but also improve The migration rate of lithium ions is conducive to alleviating the insufficient supply of electrolyte in the middle of the electrode assembly 23, and is conducive to the expansion and release of the positive electrode sheet 24, thereby reducing the risk of fracture of the positive electrode sheet 24 in the turning portion 233 due to expansion, and can also effectively avoid the negative electrode sheet in the turning portion 233. 25 Lithium precipitation.

Referring to FIGS. 5 to 8 , according to some embodiments of the present application, optionally, the length of the filling portion 247 in the second direction is 0.01%-1% of the length of the positive electrode sheet 24 in the second direction. The direction is perpendicular to the first direction, and the second direction is the winding direction of the positive electrode sheet 24 .

Since the tabs 23 a of the positive electrode sheet 24 are located in the first direction of the positive electrode current collector 241 , during the actual winding process, the second direction is the winding direction of the positive electrode sheet 24 . In FIGS. 5 to 8 , X represents the second direction. direction.

The filling portion 247 has a reasonable length in the second direction, which can alleviate the problems of lithium deposition in the negative electrode sheet 25 in the turning portion 233 and breakage of the positive electrode sheet 24 in the turning portion 233, and has better energy density. If the filling portion 247 is in the second direction, If the length and width in the second direction are too small, the effect of improving lithium deposition will be poor. If the length and width of the filling portion 247 in the second direction are too large, the energy density of the battery 100 will be affected.

Optionally, the length of the filling portion 247 in the second direction is 1-100 mm.

Exemplarily, the length of the filling portion 247 in the second direction is 1 mm, 5 mm, 10 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 76 mm, 80 mm, 85 mm, 90 mm, 95 mm , 100mm, or between any two values.

The number of filling parts 247 may be one or more.

Referring to FIGS. 5 to 8 , according to some embodiments of the present application, optionally, the number of filling portions 247 is multiple, and the plurality of filling portions 247 are spaced apart along the second direction of the positive electrode sheet 24 .

The number of the rolled turning portions 233 is multiple, and the actually used winding direction is the second direction. A plurality of filling portions 247 are used to arrange them at intervals along the second direction of the positive electrode sheet 24, and can also be arranged in each direction according to actual needs. A filling portion 247 is provided in the turning portion 233 to reduce the problem of lithium deposition in the negative electrode sheet 25 in the turning portion 233 after winding.

Referring to FIG. 7 and FIG. 8 , according to some embodiments of the present application, optionally, both cathode film layers 243 are provided with filling portions 247 .

The above arrangement can effectively improve the degree of lithium deposition on the negative electrode sheet 25 in the turning portion 233.

When both positive electrode film layers 243 are provided with filling portions 247, the filling portions 247 located on the two film layers can be arranged one-to-one as shown in Figure 7, or can be arranged staggered as shown in Figure 8, but it is necessary It should be noted that, whether arranged in a one-to-one correspondence or in a staggered manner, the filling portions 247 are arranged corresponding to the rolled turning portions 233 .

Please refer to Figures 3, 4, 9 and 10. According to some embodiments of the present application, the present application also provides a battery cell 20, including an electrolyte, a negative electrode sheet 25, and a positive electrode sheet 24 provided in the above embodiments. , and the separator 26 spaced between the positive electrode sheet 24 and the negative electrode sheet 25. The negative electrode sheet 25, the separator 26 and the positive electrode sheet 24 are rolled to form the electrode assembly 23. The filling part 247 is in contact with the electrolyte so that the filling part 247 can at least partially Dissolved in the electrolyte, the filling portion 247 is located at the turning portion 233 of the positive electrode sheet 24 after being wound.

With the arrangement of the filling part 247 that is soluble in the electrolyte, after actual assembly, the filling part 247 is at least partially dissolved in the electrolyte to form a groove 248 in the film layer. On the one hand, it effectively reduces the stress of the positive electrode film layer 243 on the turning part 233. Active material capacity, thereby increasing the ratio of the active material capacity of the negative electrode sheet in the turning portion 233 to the active material capacity of the positive electrode sheet, preventing lithium deposition from the negative electrode sheet 25 in the turning portion 233, and on the other hand, the groove 248 and film formed after the filling portion 247 is dissolved The interface of the layer body 245 is flat and will not cause accumulation of materials. Compared with the method of directly forming the groove 248 with less coating on the turning portion 233 of the corresponding positive electrode film layer 243, not only the preparation process is less difficult, but also it can avoid Directly forming grooves 248 causes problems such as easy stacking and capacity loss.

As shown in FIGS. 9 and 10 , in some embodiments, the number of turns of the positive electrode sheet 24 after winding is n+1 turns, and at least one of the first to nth turns of the positive electrode sheet 24 from the inside to the outside is provided with Filling part 247.

The above arrangement can not only avoid lithium deposition on the negative electrode piece 25 in the turning portion 233 during the charging process, but also because the inner ring will become very tight when the electrode piece is expanded and released, but will have little effect on the outer ring, so the outermost layer does not need to be provided with a filling portion. 247, to avoid affecting the battery 100 energy.

In some embodiments, n≥10.

At this time, a filling portion 247 is formed in at least one of the first to tenth turns of the positive electrode sheet 24 from the inside to the outside. The above arrangement can further prevent lithium deposition in the turning portion 233 of the negative electrode sheet 25 during charging. Increase battery energy density by 100.

Optionally, n≥10, at least one of the first to fourth turns from the inside to the outside of the positive electrode sheet 24 is formed with a filling portion 247 .

According to some embodiments of the present application, the present application also provides an electrical device, including the battery 100 of any of the above solutions, and the battery 100 is used to provide electrical energy for the electrical device.

The power-consuming device may be any of the aforementioned devices or systems using the battery 100 .

According to some embodiments of the present application, referring to Figures 3, 4, 6 to 10, the present application provides a battery cell 20, which includes an electrolyte, a negative electrode sheet 25, a positive electrode sheet 24, and a positive electrode sheet disposed on the positive electrode sheet. The separator 26 between 24 and the negative electrode sheet 25, the negative electrode sheet 25, the separator 26 and the positive electrode sheet 24 are wound to form the electrode assembly 23. The positive electrode sheet 24 includes a positive electrode current collector 241 and two positive electrode film layers 243 coated on both sides of the positive electrode current collector 241. Each positive electrode film layer 243 has a film layer body 245 and a filling part 247 that is soluble in electrolyte, located at The filling portions 247 on the two positive electrode film layers 243 are located at the turning portion 233 of the positive electrode sheet 24 after being wound. The filling portions 247 are embedded in the film layer body 245. Part of the surface of the filling portion 247 is not covered by the film layer body 245 and is filled. The portion 247 is separated from the positive electrode current collector 241 by the film body 245 .

Some specific examples are listed below to better illustrate this application.

Example 1

Add lithium iron phosphate with D50 = 1.2 μm, acetylene black and polyvinylidene fluoride into the stirring tank at a mass ratio of 97.2:1.5:1.3, add N-methylpyrrolidone solvent, stir, pass through a 200 mesh screen, and configure the first membrane Layer slurry; add D50=5μm lithium iron phosphate, acetylene black and polyvinylidene fluoride into the mixing tank at a mass ratio of 97.2:1.5:1.3, add N-methylpyrrolidone solvent, stir and pass through a 200 mesh screen to configure as follows The second film layer slurry is prepared by mixing lithium hexafluorophosphate and N-methylpyrrolidone solvent to form a filling part slurry.

Use a coater to apply the first film layer slurry to the positive electrode current collector 241 (aluminum foil), dry it at 120°C, and then apply the second film layer slurry. After drying, apply the filler slurry and dry. Then, the positive electrode sheet 24 with the structure shown in Figure 7 is obtained by rolling. The length of the positive electrode sheet 24 in the second direction (X direction in Figure 6) is 10m, and the filling portion 247 is in the second direction (X direction in Figure 6). The length of the filling portion 247 is 76 mm. Both ends of the filling portion 247 in the first direction extend to both edges of the positive electrode film layer 243 . The thickness of the positive electrode film layer 243 is 100 μm. The thickness of the filling portion 247 is 70% of the thickness of the positive electrode film layer 243 .

Negative electrode sheet: The negative electrode coating composed of 97wt% graphite, 1wt% conductive carbon black and 2wt% styrene-butadiene rubber is applied to the negative electrode current collector with a coater, and the negative electrode sheet is obtained by drying and rolling.

Assemble the battery cell: The negative electrode sheet prepared above is rolled together with the positive electrode sheet and separator to form a roll core. The filling part is located at the corresponding corner of the first turn from the inside to the outside of the wound positive electrode sheet, and is covered with aluminum plastic film. After packaging, baking to remove moisture, electrolyte is injected, and hot-pressed to obtain battery cells.

Example 2

The only difference from Embodiment 1 is that the filling portion is located at the corresponding corner portion of the 1-4 turns from the inside to the outside of the wound positive electrode sheet.

Example 3

The only difference from Embodiment 1 is that, as shown in FIG. 8 , the filling portions 247 located on the two positive electrode film layers 243 are arranged in a staggered manner.

Example 4

The only difference from Embodiment 1 is that, as shown in FIG. 5 , the filling portion 247 is provided on one of the positive electrode film layers 243 , which is located on the side of the wound positive electrode sheet 24 facing the inner ring.

Example 5

The only difference from Example 1 is that the D50 of the lithium iron phosphate of the first film layer slurry is 5 μm, and the D50 of the lithium iron phosphate of the second film layer slurry is 1.2 μm.

Comparative example 1

The difference from Example 1 is that the second film layer slurry is used to replace the filler slurry, and the second film layer slurry is directly coated on the dried first film layer, and the second film layer slurry is Completely cover the first film layer.

Test example

The battery cells obtained in Examples 1-5 and Comparative Example 1 were fully charged, and the inside of the negative electrode sheet at the turning portion was observed to see whether lithium was deposited. The results are shown in Table 1.

Test method: Charge and discharge the assembled battery 20 times, then fully charge the battery and disassemble it to confirm whether there is lithium precipitation at the anode corner of the inner ring.

Table 1 test results

It can be seen from Table 1 that the embodiments provided in this application can effectively improve the lithium deposition on the inside of the negative electrode sheet at the turning part.

In summary, through structural improvements, the positive electrode sheet provided in this application, when used in a rolled battery cell, can not only improve the problem of easy lithium precipitation in the negative electrode sheet at the corner, but also has low preparation difficulty and the obtained positive electrode sheet has excellent High yield rate.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features can be equivalently replaced; and these modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present application. The scope shall be covered by the claims and description of this application. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any way. The application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims (11)

1. A positive electrode sheet, including a positive electrode current collector and two positive electrode film layers coated on both sides of the positive electrode current collector, wherein at least one of the positive electrode film layers has a film layer body and a filling part soluble in electrolyte, The filling part is embedded in the film body, part of the surface of the filling part is not covered by the film body, and the filling part and the positive electrode current collector are separated by the film body, The filling part is located at the turning part of the positive electrode sheet after being rolled, and the filling part is used to at least partially dissolve in the electrolyte to form grooves on the surface of the positive electrode film layer.
2. The positive electrode sheet according to claim 1, wherein the ratio of the thickness of the filling portion to the thickness of the positive electrode film layer is H, 0.05<H≤0.95.
3. The positive electrode sheet according to claim 1 or 2, wherein the tabs of the positive electrode sheet are located in the first direction of the positive electrode current collector, and both ends of the filling part respectively extend to the first direction along the first direction. The edge of the positive electrode film layer.
4. The positive electrode sheet according to claim 3, wherein the length of the filling portion in the second direction is 0.01%-1% of the length of the positive electrode sheet in the second direction, and the second direction is The first directions are perpendicular to each other, and the second direction is the winding direction of the positive electrode sheet.
5. The positive electrode sheet according to claim 4, wherein the number of the filling portions is multiple, and the plurality of filling portions are spaced apart along the second direction of the positive electrode sheet.
6. The positive electrode sheet according to any one of claims 1 to 5, wherein both of the positive electrode film layers are provided with the filling portion.
7. A battery cell, which includes an electrolyte, a negative electrode sheet, the positive electrode sheet according to any one of claims 1 to 6, and a separator disposed between the positive electrode sheet and the negative electrode sheet, the negative electrode The sheet, the separator and the positive electrode sheet are rolled to form an electrode assembly, the filling part is in contact with the electrolyte so that the filling part can be at least partially dissolved in the electrolyte, and the filling part is located on the The turning part after the positive electrode sheet is wound.
8. The battery cell according to claim 7, wherein the number of turns of the positive electrode sheet after winding is n+1 turns, and at least one of the first to nth turns of the positive electrode sheet from the inside to the outside is provided with The filling part.
9. The battery cell according to claim 8, wherein n≥10.
10. A battery, including the battery cell according to any one of claims 7-9.
11. An electric device, wherein the electric device includes the battery according to claim 10, and the battery is used to provide electric energy.

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