Positive pole piece, battery, power utilization device and pole piece preparation method

Abstract

The invention discloses a positive pole piece (230), a battery, a power utilization device and a pole piece preparation method, the positive pole piece (230) comprises a supporting layer and an active material layer (232), the active material layer (232) is provided with a concave part (2321), the concave part (2321) is provided with a filling layer (234), and the height of the filling layer (234) is smaller than the depth of the concave part (2321). The filling layer (234) is formed by converting a supplementary material layer, and can form a pore between the positive pole piece (230) and the negative pole piece (240), thereby facilitating the outflow of gas and the infiltration of electrolyte, alleviating the phenomena of lithium precipitation and black spots, and improving the cycle performance and dynamic performance of the battery. The supplementary materials comprise a lithium supplementing material and a sodium supplementing material, and the capacity of the battery can be improved.

Description

Positive electrode sheet, battery, electrical device and electrode sheet preparation method Technical Field

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

[0002] Energy conservation and emission reduction are key to the sustainable development of the automotive industry. Electric vehicles, due to their energy-saving and environmentally friendly advantages, have become an important component of the sustainable development of the automotive industry. For electric vehicles, battery technology is a key factor in their development.

[0003] Currently, lithium-ion batteries still experience irreversible capacity loss during the charge and discharge process, resulting in low initial coulombic efficiency and low capacity. Lithium supplementation is an effective means to solve this problem. Sodium-ion batteries also have a similar problem.

[0004] Summary of the Invention

[0005] The inventors of the present application have discovered that current lithium replenishment methods may cause the adhesion between the active material layer and the current collector to deteriorate, the active material layer to collapse, or even fall off from the current collector, thereby deteriorating the battery cycle performance.

[0006] In view of the above problems, the inventors of this application have designed a new lithium replenishment method, that is, coating the active material layer on the support layer, and setting a recess on the surface of the active material layer, filling the lithium replenishment material layer in the recess of the active material layer to form a lithium replenishment material layer. The positive electrode plate is used to assemble a battery. After formation or charge and discharge, the lithium replenishment material is consumed, resulting in a reduction in the thickness of the lithium replenishment material layer. The lithium replenishment material layer forms a filling layer. The upper surface of the filling layer has a certain height difference with the upper surface of the active material layer. This height difference creates a gap between the positive and negative electrodes. The gas generated when the lithium replenishment material is consumed can be discharged through the gap, slowing down the appearance of purple spots on the electrode plate and improving the battery's cycle performance. In addition, the electrolyte can effectively infiltrate the electrode plate, improving the battery's kinetic performance. It should be noted that this lithium replenishment method is also suitable for sodium replenishment, that is, when sodium ion batteries are replenished with sodium, the solution of this application can also be applied. In this application, the lithium replenishment material layer or the sodium replenishment material layer is collectively referred to as the replenishment material layer, and the lithium replenishment material or the sodium replenishment material is collectively referred to as the replenishment material.

[0007] The present application provides a positive electrode plate, a battery, an electrical device and a method for preparing the plate, which can alleviate the problem of deterioration of battery cycle performance.

[0008] In a first aspect, the present application provides a positive electrode plate, comprising: a support layer and an active material layer, wherein the active material layer is provided with a recess, and the recess is provided with a filling layer, wherein the height of the filling layer is less than the depth of the recess.

[0009] In the technical solution of the embodiment of the present application, a lithium-supplementing material layer or a sodium-supplementing material layer is arranged in a concave portion of the active material layer, which can replenish lithium or sodium while improving the cycle performance of the battery. The lithium-supplementing material layer or the sodium-supplementing material layer forms a filling layer after being consumed, so that in a battery using the positive electrode sheet, there is a gap between the positive electrode sheet and the negative electrode sheet, that is, the upper surface of the filling layer is a certain distance away from the upper surface of the active material layer. This distance creates a gap channel between the positive and negative electrode sheets of the battery (in places where there are no pits, the contact interface between the positive and negative electrode sheets of the battery is relatively tight). The presence of the gap channel facilitates the infiltration of the electrolyte and improves the dynamic performance of the battery.

[0010] In some embodiments, the filling layer includes a conductive agent, preferably comprising 5% to 21% of the filling layer's mass. Below the filling layer is the active material layer, and the presence of the conductive agent can improve the conductivity of the active material layer below the filling layer. In some embodiments, the filling layer includes an adhesive, preferably comprising 6% to 25% of the filling layer's mass. The presence of the adhesive can securely bond the inert material remaining after the supplemental material is consumed, as well as the conductive agent, to the active material layer.

[0011] In some embodiments, the porosity of the filling layer is greater than that of the active material layer. Preferably, the porosity of the filling layer is 50%-91%. Consumption of the supplementary material increases the porosity of the filling layer, which facilitates faster infiltration of the electrolyte into the active material layer, thereby improving the battery's dynamic performance.

[0012] In some embodiments, the surface roughness of the filling layer is greater than that of the active material layer. The consumption of the supplementary material makes the filling layer loose and porous, and the surface is relatively rough, which is also conducive to the infiltration of the electrolyte.

[0013] In some embodiments, the filling layer contains an inert substance. Preferably, the mass of the inert substance is 55%-80% of the mass of the filling layer.

[0014] In some embodiments, the filling layer contains an inert substance and a positive electrode material, with the combined mass of the inert substance and the positive electrode material accounting for 55%-80% of the filling layer's mass. Adding an appropriate amount of positive electrode material to the filling layer can simultaneously replenish lithium and increase the battery's capacity. In lithium-ion batteries, the positive electrode material includes a lithium-containing positive electrode material, while in sodium-ion batteries, the positive electrode material includes a sodium-containing positive electrode material.

[0015] Preferably, the mass of the inert substance accounts for 0-8% of the mass of the total positive electrode material. In some embodiments, the inert substance is formed by converting the lithium-supplementing material or the sodium-supplementing material. The inert substance is converted after the lithium-supplementing material or the sodium-supplementing material is consumed, that is, some types of lithium-supplementing materials or sodium-supplementing materials will leave inert substances after consumption. In some embodiments, the ratio of the depth of the recess to the thickness of the active material layer is 0.05-0.2. In some embodiments, there are multiple recesses, the sum of the widths of the multiple recesses is k, the width of the active material layer is b, and k / b is 0.05-0.5. By controlling the depth and width of the recess, the lithium-supplementing effect can be improved while increasing the capacity of the battery.

[0016] In some embodiments, the filling layer is formed by converting a lithium-supplementing material layer. After the lithium-supplementing material is consumed, the lithium-supplementing material layer is converted into a filling layer, at which point the filling layer is located in the recessed portion of the active material layer. In some embodiments, the filling layer is formed by converting a sodium-supplementing material layer. After the sodium-supplementing material is consumed, the sodium-supplementing material layer is converted into a filling layer, at which point the filling layer is located in the recessed portion of the active material layer.

[0017] The present application also provides a positive electrode sheet, comprising a support layer and an active material layer, wherein the active material layer has a recess, and the recess has a supplementary material layer, wherein the height of the supplementary material layer is no greater than the depth of the recess. After the positive electrode sheet is assembled into a battery and undergoes charge and discharge cycles, the supplementary material layer undergoes changes, forming the positive electrode sheet provided in the above embodiments.

[0018] In some embodiments, the supplementary material layer includes at least one of a lithium supplementary material layer or a sodium supplementary material layer. The lithium supplementary material or the sodium supplementary material can be beneficial for improving the battery capacity.

[0019] In some embodiments, the lithium-supplementing material layer includes a lithium-supplementing material whose mass accounts for 92%-98.5% of the mass of the lithium-supplementing material layer. Including this range of lithium-supplementing material in the lithium-supplementing material layer can improve the lithium-supplementing effect while also increasing the battery capacity. In some embodiments, the sodium-supplementing material layer includes a sodium-supplementing material whose mass accounts for 92%-98.5% of the mass of the sodium-supplementing material layer. Including this range of sodium-supplementing material in the sodium-supplementing material layer can improve the sodium-supplementing effect while also increasing the battery capacity.

[0020] In some embodiments, the lithium-supplementing material layer includes a positive electrode material, and the combined mass of the lithium-supplementing material and the positive electrode material accounts for 92%-98.5% of the mass of the lithium-supplementing material layer. In some embodiments, in the lithium-supplementing material layer, the mass ratio of the lithium-supplementing material to the positive electrode material is 1:1-10:1. Adding an appropriate amount of positive electrode material to the lithium-supplementing material layer can increase the capacity of the battery. In some embodiments, the sodium-supplementing material layer includes a sodium-containing positive electrode material, and the combined mass of the sodium-supplementing material and the positive electrode material accounts for 92%-98.5% of the mass of the sodium-supplementing material layer. In some embodiments, in the sodium-supplementing material layer, the mass ratio of the sodium-supplementing material to the positive electrode material is 1:1-10:1. Adding an appropriate amount of sodium-containing positive electrode material to the sodium-supplementing material layer can increase the capacity of the battery.

[0021] In some embodiments, the mass ratio of the lithium-supplementing material to the total mass ratio of the positive electrode material is 0.5%-10%, preferably 3%-7%. Within this range, the lithium-supplementing material can enhance the lithium-supplementing effect while also increasing the battery capacity. In some embodiments, the mass ratio of the sodium-supplementing material to the total mass ratio of the positive electrode material is 0.5%-10%, preferably 3%-7%. Within this range, the sodium-supplementing material can enhance the sodium-supplementing effect while also increasing the battery capacity.

[0022] In some embodiments, the lithium-supplementing material layer includes a binder, the mass of which accounts for 0.05%-3% of the mass of the lithium-supplementing material layer. Within this binder content range, the lithium-supplementing material layer can be better bonded to the recessed portion of the active material layer, while also achieving a higher lithium-supplementing effect. In some embodiments, the sodium-supplementing material layer includes a binder, the mass of which accounts for 0.05%-3% of the mass of the sodium-supplementing material layer. Within this binder content range, the sodium-supplementing material layer can be better bonded to the recessed portion of the active material layer, while also achieving a higher sodium-supplementing effect.

[0023] In some embodiments, the lithium-supplementing material layer includes a conductive agent, the mass of which accounts for 0.5%-5% of the mass of the lithium-supplementing material layer. A conductive agent content within this range can improve the conductivity of the active material layer and the lithium-supplementing material layer, while also achieving a high lithium-supplementing effect. In some embodiments, the sodium-supplementing material layer includes a conductive agent, the mass of which accounts for 0.5%-5% of the mass of the sodium-supplementing material layer. A conductive agent content within this range can improve the conductivity of the active material layer and the sodium-supplementing material layer, while also achieving a high sodium-supplementing effect.

[0024] In some embodiments, the porosity of the lithium-supplementing material layer is 25%-44%. A porosity within this range facilitates electrolyte infiltration and promotes lithium replenishment. In some embodiments, the porosity of the sodium-supplementing material layer is 25%-44%. A porosity within this range facilitates electrolyte infiltration and promotes sodium replenishment.

[0025] In some embodiments, the ratio of the depth of the recess to the thickness of the active material layer is 0.05-0.2. In some embodiments, there are multiple recesses, the sum of the widths of the multiple recesses is k, the width of the active material layer is b, and k / b is 0.05-0.5. By controlling the size of the recesses, the amount of lithium replenishment material can be controlled, thereby improving the lithium replenishment effect and increasing the battery capacity.

[0026] In a second aspect, the present application provides a battery comprising the positive electrode sheet in the above embodiment.

[0027] In some embodiments, a battery includes a negative electrode sheet, and a positive electrode sheet includes a support layer and an active material layer. The active material layer has a recessed portion, and the recessed portion has a filling layer. The height of the filling layer is less than the depth of the recessed portion. A gap is formed between the negative electrode sheet and the positive electrode sheet in the recessed portion. The presence of the gap facilitates gas discharge and electrolyte infiltration.

[0028] 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.

[0029] In a fourth aspect, the present application provides a method for preparing an electrode, wherein an active material layer is coated on a support layer, a recess is formed on the surface of the active material layer, and a lithium supplement material layer is coated on the recess.

[0030] In some embodiments, the lithium-supplementing material layer is coated on the recessed portions while the recessed portions are formed on the surface of the active material layer, thereby improving coating efficiency.

[0031] In some embodiments, a concave portion is formed on the surface of the active material layer, and the lithium-replenishing material layer is applied to the concave portion at the same time. The active material layer and the lithium-replenishing material layer are applied simultaneously, which can improve the coating efficiency.

[0032] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0034] FIG1 is a schematic structural diagram of a vehicle according to some embodiments of the present application;

[0035] FIG2 is a schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0036] FIG3 is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0037] FIG4 is a schematic diagram of the cross-sectional structure of a positive electrode sheet before cold pressing in some embodiments of the present application;

[0038] FIG5 is a schematic diagram of the cross-sectional structure of a positive electrode sheet after cold pressing in some embodiments of the present application;

[0039] FIG6 is a schematic diagram of a top view of the structure of a cold-pressed positive electrode sheet in some embodiments of the present application;

[0040] FIG7 is a schematic diagram of a cell structure before charging and discharging in some embodiments of the present application;

[0041] FIG8 is a schematic diagram of the battery cell structure after charge and discharge in some embodiments of the present application;

[0042] FIG9 is a schematic diagram of cold pressing a battery cell structure according to some embodiments of the present application;

[0043] FIG10 is a schematic diagram of a localized magnification of a positive electrode plate after charge and discharge in some embodiments of the present application;

[0044] FIG11 is a schematic diagram of the coating gasket structure of some embodiments of the present application;

[0045] FIG12 is a schematic diagram of the coating gasket structure of other embodiments of the present application;

[0046] FIG13 is a schematic structural diagram of a coating device according to some embodiments of the present application;

[0047] FIG14 is a schematic diagram of a partial structure of a coating device according to some embodiments of the present application. DETAILED DESCRIPTION

[0048] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0050] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0051] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0052] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0053] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0054] In the description of the embodiments of the present application, the technical 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., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the 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 embodiments of the present application.

[0055] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0056] Currently, market developments indicate that power batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As power battery applications continue to expand, market demand is also growing.

[0057] The battery has irreversible capacity loss, resulting in low battery capacity. The most widely used graphite negative electrode has an irreversible capacity loss of >6%, and the silicon-based and tin-based alloy negative electrodes have irreversible capacity losses of up to 10% to 20%. Lithium replenishment can effectively alleviate or solve this problem. There are currently many lithium replenishment methods on the market. For example, in the process of coating the active material layer, the active material layer and the lithium replenishment material layer are coated on the current collector in steps and intervals. This method will produce the following phenomenon. After the active material layer and the lithium replenishment material layer are rolled, the active material layer will cover the lithium replenishment material layer. After the lithium replenishment layer is consumed, holes are formed, the adhesion between the active material layer and the current collector deteriorates, and the electrode structure may collapse, causing the active material to fall off from the electrode and deteriorating the battery cycle performance.

[0058] Through research, the inventors of this application have designed a new lithium replenishment method, which has resulted in a pole piece. Specifically, an active material layer is applied to a current collector, a recess is provided on the surface of the active material layer, and a lithium replenishment material layer is placed in the recess. The pole pieces undergo a winding or lamination process and are assembled into a finished battery. Using this lithium replenishment method, the active material layer is less likely to collapse. Furthermore, after the battery is charged and discharged, the lithium replenishment material decomposes, and the lithium replenishment material layer can no longer completely fill the recess in the active material layer, resulting in gaps between the pole pieces. The lithium replenishment material generates gas during consumption. In the prior art, the pole pieces are tightly bonded to each other. As gas is released from between the pole pieces, gaps form between the positive and negative pole pieces, hindering lithium ion transmission and making the pole pieces susceptible to purple or black spots, which in turn reduces battery capacity or causes lithium plating. In this application, the gaps formed between the pole pieces facilitate gas discharge, significantly alleviating the occurrence of purple spots or wrinkling in the battery, thereby reducing battery capacity deterioration and improving battery cycle life. In addition, after the lithium supplement material decomposes, the concave portion of the active material layer can also facilitate the infiltration of the electrolyte into the electrode, thereby improving the dynamic performance of the battery.

[0059] To prepare the electrode described above, this application also designs a coating gasket, a coating device containing the coating gasket, and a coating method. The main body of the coating gasket is provided with an upper discharge port and a lower discharge port. The lower discharge port is used for coating the active material, and the upper discharge port is used for coating the lithium-replenishing material. Using this coating gasket, coating device, and coating method, it is possible to simultaneously coat the active material and the lithium-replenishing material. This is simple, convenient, and highly efficient.

[0060] The battery cells disclosed in the embodiments of this application can be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft. A power supply system comprising the battery cells and batteries disclosed in this application can be used to construct such electrical devices. This can help alleviate or avoid the phenomenon of black or purple spots on the electrode due to obstructed lithium ion transmission, thereby improving the battery's capacity and cycle performance. Furthermore, it can facilitate electrolyte infiltration, promote lithium ion transmission, and enhance the battery's dynamic performance.

[0061] The present invention provides an electric device that uses a battery as a power source. The electric device may be, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery-powered vehicle, an electric car, a ship, a spacecraft, etc. The electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, etc. The spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, etc.

[0062] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0063] Please refer to Figure 1, which is a schematic structural diagram of a vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can 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 power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0064] In some embodiments of the present application, the battery 100 can serve not only as an operating power source for the vehicle 1000, but also 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.

[0065] Please refer to Figure 2, which is an exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a storage space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 can include a first portion 11 and a second portion 12, which overlap each other and together define a storage space for the battery cell 20. The second portion 12 can be a hollow structure with one end open. The first portion 11 can be a plate-like structure, with the first portion 11 overlapping the open side of the second portion 12, so that the first portion 11 and the second portion 12 together define a storage space. Alternatively, the first portion 11 and the second portion 12 can each be a hollow structure with one end open, with the open side of the first portion 11 overlapping the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0066] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 20 may be housed within the housing 10. Alternatively, the battery 100 may be constructed by first connecting multiple battery cells 20 in series, in parallel, or in a hybrid connection to form a battery module, which is then connected in series, in parallel, or in a hybrid connection to form a complete battery module, and then housed within the housing 10. The battery 100 may also include other structures, such as a busbar assembly for electrically connecting the multiple battery cells 20.

[0067] Each battery cell 20 may be a secondary battery or a primary battery, and may also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0068] Please refer to Figure 3, which is a schematic diagram of the exploded structure of a battery cell 20 provided in some embodiments of the present application. A battery cell 20 is the smallest unit that makes up a battery. As shown in Figure 3, a battery cell 20 includes an end cap 21, a housing 22, a cell assembly 23, and other functional components.

[0069] The end cap 21 is a component that covers the opening of the housing 22 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the end cap 21 can be adapted to the shape of the housing 22 to match the housing 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as an aluminum alloy). This prevents the end cap 21 from deforming when subjected to compression or collision, giving the battery cell 20 greater structural strength and improved safety. The end cap 21 can be provided with functional components such as electrode terminals 21a. The electrode terminals 21a can be used to electrically connect to the battery cell assembly 23 to output or input electrical energy to the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for relieving 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 a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application are not particularly limited in this regard. In some embodiments, an insulating member may be provided inside the end cap 21 to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be made of plastic, rubber, or the like.

[0070] The housing 22 is a component that cooperates with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can be used to accommodate the battery cell assembly 23, electrolyte, and other components. The housing 22 and end cap 21 can be separate components. An opening can be provided in the housing 22, and the end cap 21 is placed over the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and housing 22 can be integrated. Specifically, the end cap 21 and housing 22 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 22 needs to be enclosed, the end cap 21 is placed over the housing 22. The housing 22 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined based on the specific shape and size of the battery cell assembly 23. The housing 22 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any specific limitations on this.

[0071] The cell assembly 23 is a component in the battery cell 100 where electrochemical reactions occur. One or more cell assemblies 23 may be contained in the housing 22. The cell assembly 23 is mainly formed by winding or stacking a positive electrode sheet 230 and a negative electrode sheet 240, and a separator 250 is usually provided between the positive electrode sheet 230 and the negative electrode sheet 240. The parts of the positive electrode sheet 230 and the negative electrode sheet 240 with active materials constitute the main body 41 of the cell assembly, and the parts of the positive electrode sheet 230 and the negative electrode sheet 240 without active materials each constitute a tab 23a. The positive tab and the negative tab may be located together at one end of the main body 41 or respectively at both ends of the main body 41. During the charge and discharge process of the battery, 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.

[0072] According to some embodiments of the present application, the positive electrode plate 230 of the present application includes a supporting layer, an active material layer 232 and a filling layer 234. The active material layer 232 is provided with a recess 2321, and the filling layer 234 is arranged in the recess 2321. The supporting layer is used to support the active material layer 232, and is also often referred to as a current collector 231. The current collector 231 can be a metal foil or a composite foil composed of metal and non-metal. In the present application, a conventional current collector 231 can be used without special requirements. The technical solution of the present application can be applied to lithium-ion batteries and sodium-ion batteries. The following mainly takes lithium-ion batteries as an example to elaborate on the technical solution of the present application in detail.

[0073] According to some embodiments of the present application, the filling layer 234 is formed by converting the lithium-replenishing material layer 233. Specifically, the following steps are included: 1) coating the active material layer 232 on the support layer, the active material layer 232 having a concave portion 2321, and simultaneously coating the lithium-replenishing material layer 233 on the concave portion 2321 of the active material layer 232; 2) drying the layered structure composed of the support layer, the active material layer 232, and the lithium-replenishing material layer 233, and performing processes such as cold pressing, die-cutting, and slitting to obtain the positive electrode sheet 230; 3) assembling the obtained positive electrode sheet 230 with the negative electrode sheet 240 and the separator 250 into a battery; 4) after the battery is injected and formed, the lithium-replenishing material layer 233 is converted into the filling layer 234.

[0074] According to some embodiments of the present application, referring to Figures 4 and 5, a positive electrode sheet 230 includes a current collector 231, an active material layer 232 disposed on the upper surface of the current collector 231, a recess 2321 being provided on the active material layer 232, and a lithium replenishing material layer 233 disposed in the recess 2321 of the active material layer 232, thereby forming the positive electrode sheet 230 shown in Figure 4. After the positive electrode sheet 230 shown in Figure 4 is cold pressed, the positive electrode sheet 230 shown in Figure 5 is formed. After the positive electrode sheet 230 shown in Figure 5 is assembled into a battery and the battery is formed or charged and discharged, the lithium replenishing material layer 233 is consumed and converted into a filling layer 234.

[0075] It should be noted that other methods can also be used to prepare the positive electrode plate 230 of the present application, not limited to the above method. For example, the active material layer 232 and the lithium replenishing material layer 233 can be coated in steps, first coating the active material layer 232 on the current collector 231, and then coating the lithium replenishing material layer 233 on the active material layer 232.

[0076] In some embodiments of the present application, the lithium-supplementing material layer 233 includes a lithium-supplementing material and further includes a binder and a conductive agent. The lithium-supplementing material includes lithium oxide, lithium nitride, lithium sulfide, Li2C2O4, Li2C4O4, Li2M1O2, Li2M2O3, Li5FexM3(1-x)O4, and Li6MnyM4(1-y)O4, wherein M1 includes at least one of Ni, Mn, Cu, Fe, Cr, and Mo, M2 includes at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr, and Ru, M3 includes at least one of Al, Nb, Co, Mn, Ni, Mo, Ru, and Cr, and M4 includes at least one of Ni, Fe, Cu, and Ru, and x is less than or equal to 1. Among them, lithium oxide, lithium nitride, lithium sulfide, Li2C2O4, and Li2C4O4 are completely consumable lithium supplement materials, that is, when these lithium supplement materials are used for lithium supplementation, these lithium supplement materials will basically be converted into gas, and no residue will be left; among them, some lithium supplement materials are partially consumable lithium supplement materials, including Li2M1O2, Li2M2O3, Li5FexM3(1-x)O4, and Li6MnyM4(1-y)O4, wherein M1 includes at least one of Ni, Mn, Cu, Fe, Cr, and Mo, M2 includes at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr, and Ru, M3 includes at least one of Al, Nb, Co, Mn, Ni, Mo, Ru, and Cr, and M4 includes at least one of Ni, Fe, Cu, and Ru, and x is less than or equal to 1. Partially consumable lithium supplement materials mean that when these lithium supplement materials are used for lithium supplementation, these lithium supplement materials are partially converted into gas and partially converted into inert substances, and remain in the lithium supplement material layer 233.

[0077] In some embodiments, there are no specific requirements for the selection of adhesive and conductive agent; they can be selected according to conventional standards. For example, the adhesive includes at least one of conventional adhesives such as polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, and polyhexafluoroethylene. The conductive agent includes at least one of conventional conductive agents such as conductive carbon, graphene, carbon nanotubes, and acetylene black. The adhesive is used to bond the lithium-replenishing material layer 233 to the recess 2321 of the active material layer 232, and the conductive agent is used to improve the conductivity of the lithium-replenishing material layer 233.

[0078] In some embodiments of the present application, the mass of the lithium-supplementing material in the lithium-supplementing material layer 233 accounts for 92% to 98.5% of the mass of the lithium-supplementing material layer 233. This can improve the lithium-supplementing effect and simultaneously increase the battery capacity. In some embodiments of the present application, the mass of the lithium-supplementing material accounts for 93%, 94%, 95%, 96%, 97%, 98%, etc., of the mass of the lithium-supplementing material layer 233.

[0079] In some embodiments of the present application, the lithium-replenishing material layer 233 also includes a positive electrode material. A mixture of the lithium-replenishing material and the positive electrode material is applied to the recess 2321, which can help increase the battery capacity. The positive electrode materials referred to herein are existing or future positive electrode materials that can be used in battery systems. The positive electrode materials may also be positive electrode materials that have undergone processes such as doping or coating. In some embodiments of the present application, the combined mass of the lithium-replenishing material and the positive electrode material in the lithium-replenishing material layer 233 accounts for 92% to 98.5% of the mass of the lithium-replenishing material layer 233. Specifically, the positive electrode materials include lithium nickel oxide, such as lithium nickelate; lithium cobalt oxide, such as lithium cobaltate; lithium titanium oxide, such as lithium titanate; nickel-cobalt multi-component oxides, such as lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide; lithium manganese oxide, such as lithium manganese oxide and lithium permanganate; lithium iron phosphorus oxide, such as lithium iron phosphate and lithium manganese iron phosphate; and modified materials of the above materials, including doping and coating of the positive electrode materials. In some embodiments of the present application, the lithium-replenishing material layer 233 includes a mixture of two or more positive electrode materials. In some embodiments of the present application, the total mass of the lithium-replenishing material and the positive electrode material accounts for 93%, 94%, 95%, 96%, 97%, 98%, etc., of the mass of the lithium-replenishing material layer 233.

[0080] In some embodiments of the present application, in the lithium replenishing material layer 233, the mass ratio of the lithium replenishing material to the mass ratio of the positive electrode material in the lithium replenishing material layer 233 is 1:1-10:1. Preferably, the positive electrode material in the lithium replenishing material layer 233 is the same as the positive electrode material in the active material layer 232. Of course, the positive electrode material in the lithium replenishing material can also be different from the positive electrode material in the active material layer 232, as long as it is beneficial to the improvement of the battery capacity. If the mass of the positive electrode material in the lithium replenishing material layer 233 is too large, it will affect the lithium replenishment effect, and if the mass of the positive electrode material is too small, it will be detrimental to the improvement of the battery capacity. In some embodiments of the present application, the mass ratio of the lithium replenishing material to the mass ratio of the positive electrode material in the lithium replenishing material layer 233 is 1:1-8:1, 1:1-6:1, 1:1-4:1, 1:1-2:1, etc.

[0081] In some embodiments of the present application, the positive electrode material in the lithium-supplementing material layer 233 is the same as the positive electrode material in the active material layer 232. The mass ratio of the lithium-supplementing material to the total positive electrode material (the sum of the positive electrode material in the lithium-supplementing material layer 233 and the positive electrode material in the active material layer 232) is 0.5%-10%, preferably 3%-7%. This can improve the lithium replenishment effect and simultaneously increase the battery capacity. In some embodiments of the present application, the lithium-supplementing material accounts for 1%, 2%, 4%, 5%, 6%, 8%, 9%, etc. of the total positive electrode material.

[0082] In some embodiments of the present application, the mass of the adhesive accounts for 1-3% of the mass of the lithium-supplementing material layer 233, which can improve adhesion and increase battery capacity. In some embodiments of the present application, the mass ratio of the conductive agent to the mass of the lithium-supplementing material layer 233 is 0.5-5%, which can improve conductivity, improve dynamic performance, and increase battery capacity.

[0083] In some embodiments of the present application, referring to FIG5 , after cold pressing of the positive electrode sheet 230, the porosity of the lithium-supplementing material layer 233 is 25%-44%. Using a lithium-supplementing material layer 233 with this porosity can improve electrolyte infiltration efficiency and lithium ion transmission rate, while also achieving a good lithium-supplementing effect. In some embodiments of the present application, the porosity of the lithium-supplementing material layer 233 is 27%, 29%, 31%, 33%, 35%, 37%, 39%, 41%, 43%, etc.

[0084] In some embodiments of the present application, as shown in Figures 5 and 6 , the active material layer 232 has a plurality of elongated recesses 2321, distributed on the surface of the active material layer 232. In some embodiments of the present application, multiple lithium replenishing material layers 233 are disposed in the plurality of recesses 2321, respectively.

[0085] In some embodiments of the present application, as shown in Figures 5 and 6, in the cold-pressed positive electrode sheet 230, the ratio of the depth of the recess 2321 formed on the surface of the active material layer 232 to the thickness of the active material layer 232, h / H, is 0.05-0.2. This is beneficial for increasing the battery capacity of the positive electrode sheet 230 and increasing the amount of lithium replenishment. In some embodiments of the present application, the ratio of the depth of the recess 2321 to the thickness of the active material layer 232, h / H, is 0.07, 0.09, 0.11, 0.13, 0.15, 0.17, or 0.19. In some embodiments of the present application, the ratio of the total width of the recess 2321 to the width of the active material layer 232, k / b, is 0.05-0.5. This is beneficial for improving the uniformity and efficiency of lithium replenishment. In some embodiments of the present application, the ratio of the total width of the recess 2321 to the width of the active material layer 232, k / b, is 0.1, 0.2, 0.3, or 0.4. In some embodiments of the present application, the recess 2321 is in the shape of an elongated strip and is evenly distributed on the surface of the active material layer 232. It should be further explained that the depth of the recess 2321 referred to herein refers to the distance from the lowest position of the recess 2321 to the surface of the active material layer 232, as specifically shown in FIG5 , where h is the depth of the recess 2321. The thickness of the active material layer 232 referred to herein refers to the distance from the plane where the contact surface of the active material layer 232 and the current collector 231 is located to the plane where the upper surface of the active material layer 232 is located, as specifically shown in FIG5 , H is the thickness of the active material layer 232. The total width of the recess 2321 referred to herein refers to the sum of the widths of all recesses 2321, and the width of the recess 2321 refers to the distance between the two upper edges in the width direction of the recess 2321, as specifically shown in FIG5 , where w is the width of a single recess 2321, and k is the width of a single recess 2321 multiplied by the number of recesses 2321. For example, Figure 5 shows four recesses 2321, where k = w * 4. The width of the active material layer 232 referred to herein refers to the width of the top surface of the active material layer 232, as shown in Figure 5, where b represents the width of the active material layer 232. If the active material layer 232 has inclined surfaces on both sides, the width of the active material layer 232 herein does not include these inclined surfaces.

[0086] In some embodiments of the present application, in the cold-pressed positive electrode sheet 230, the lithium replenishing material layer 233 completely fills the recess 2321, that is, the surface of the lithium replenishing material layer 233 is flush with the surface of the active material layer 232. This allows the space in the recess 2321 to be fully utilized for lithium replenishment.

[0087] In some embodiments of the present application, with reference to Figures 7 and 8, a cold-pressed positive electrode sheet 230, a negative electrode sheet 240, and a separator 250 are assembled into a battery, as shown in Figure 7. After several charge and discharge cycles, the lithium-supplementing material in the lithium-supplementing material layer 233 is consumed, and the lithium-supplementing material layer 233 is converted into a filling layer 234. The filling layer 234 cannot completely fill the recess 2321 of the active material layer. As shown in Figures 8 and 10, there is a height difference S between the upper surface of the filling layer 234 and the upper surface of the active material layer 232, resulting in a gap between the positive electrode sheet 230 and the negative electrode sheet 240. The formation of this gap facilitates the transmission of gas and electrolyte. Specifically, with reference to Figure 9, after the positive electrode sheet 230, the negative electrode sheet 240, and the separator 250 are assembled, they are wound to form a battery cell. The battery cell is usually cold-pressed, with the cold-pressing direction indicated by the arrow in Figure 9. After cold-pressing, the positive electrode sheet 230 and the negative electrode sheet 240 are tightly bonded. The lithium replenishing material will produce a lot of gas during the consumption process. Since the positive electrode sheet 230 and the negative electrode sheet 240 are tightly fitted, if there is no gap, the gas will be discharged between the positive electrode sheet 230 and the negative electrode sheet 240, resulting in poor contact between the positive electrode sheet 230 and the negative electrode sheet 240 in some areas, thereby causing problems such as purple spots. With the positive electrode sheet 230 of the present application, since a gap is formed between the positive electrode sheet 230 and the negative electrode sheet 240 in the recess 2321, the gas generated by the lithium replenishing material can be discharged from the gap, which can effectively alleviate the poor contact and purple spots between the positive electrode sheet 230 and the negative electrode sheet 240, thereby improving the battery capacity and the battery cycle performance. At the same time, the formation of the gap is also conducive to the infiltration of the electrolyte. The electrolyte can penetrate into the space between the positive electrode sheet 230 and the negative electrode sheet 240 through the gap, better penetrate into the active material layer 232 on the electrode sheet, and improve the dynamic performance of the battery.

[0088] According to some embodiments of the present application, referring to FIG10 , the lithium-replenishing material layer 233 in the concave portion 2321 on the upper surface of the active material layer 232 is consumed to form a filling layer 234. The filling layer 234 cannot completely fill the concave portion 2321 of the active material layer 232, that is, the height of the filling layer 234 is less than the depth of the concave portion 2321, and the upper surface of the filling layer 234 is lower than the upper surface of the active material layer 232. As a result, after the positive electrode sheet 230 and the negative electrode sheet 240 are stacked, a gap can be formed between the positive electrode sheet 230 and the negative electrode sheet 240, thereby facilitating the infiltration of the electrolyte into the electrode sheets.

[0089] In some embodiments of the present application, after the lithium-replenishing material layer 233 is consumed, it becomes the filling layer 234. The dimensions of the recess 2321 do not change significantly. The ratio of the depth of the recess 2321 to the thickness of the active material layer 232, h / H, is 0.05-0.2, and the ratio of the total width of the recess 2321 to the width of the active material layer 232, k / b, is 0.05-0.5. In some embodiments of the present application, the ratio of the depth of the recess 2321 to the thickness of the active material layer 232, h / H, is 0.07, 0.09, 0.11, 0.13, 0.15, 0.17, or 0.19. In some embodiments of the present application, the ratio of the total width of the recess 2321 to the width of the active material layer 232, k / b, is 0.1, 0.2, 0.3, or 0.4.

[0090] In some embodiments of the present application, as shown in FIG10 , the lithium replenishing material layer 233 becomes the filling layer 234 after being consumed. Since the adhesive and the conductive agent are not consumed, the filling layer 234 also includes the adhesive and the conductive agent. The mass of the conductive agent is 5-21% of the mass of the filling layer 234, and the mass of the adhesive is 6%-25% of the mass of the filling layer 234. In some embodiments of the present application, the mass of the conductive agent is 16%, 17%, 18%, 19%, or 20% of the mass of the filling layer 234. In some embodiments of the present application, the mass of the adhesive is 8%, 10%, 12%, 14%, 16%, or 18% of the mass of the filling layer 234.

[0091] In some embodiments of the present application, after the lithium supplement material is consumed, some types of lithium supplement materials will disappear due to consumption, and some types of lithium supplement materials will leave some inert substances due to consumption. The true density of the inert substances is lower than that of the initial lithium supplement material. The adhesive can bond the inert substance to the active material layer 232. In addition, the adhesive can also bond the conductive agent to the active material layer 232. The presence of the conductive agent can improve the conductivity of the active material layer 232 at the recess 2321, reduce battery polarization, thereby reducing battery impedance and improving the dynamic performance of the battery. The inert substance is scattered in the filling layer 234 together with the conductive agent and the adhesive.

[0092] In some embodiments of the present application, the consumption of lithium-replenishing material also results in a larger porosity and roughness of the filling layer 234. The porosity of the filling layer 234 is generally 50%-91%. In some embodiments, the porosity of the filling layer 234 is 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%. A porosity within this range is beneficial for improving electrolyte wetting and electron transport. In some embodiments, the surface roughness of the filling layer 234 is significantly greater than the surface roughness of the active material layer 232.

[0093] The test method for porosity is:

[0094] Porosity = 1-compacted density / true density of material, where the true density of the material is equal to the true density of the lithium-supplementing material, positive electrode material, conductive agent, and binder in the formula multiplied by their respective proportions in the electrode.

[0095] The test method for roughness is:

[0096] The roughness test can be performed by directly using a roughness tester (needle tracing method) to scratch the surface of the sample to obtain the roughness Ra value.

[0097] In some embodiments of the present application, after the lithium-supplementing material is consumed, part of it generates gas and part of it generates inert substances, that is, inert substances remain in the filling layer 234, and the mass of the inert substances in the filling layer 234 accounts for 55%-80% of the mass of the filling layer 234. In some embodiments of the present application, the mass of the inert substances in the filling layer 234 accounts for 60%, 65%, 70%, and 75% of the mass of the filling layer 234. In other embodiments of the present application, the lithium-supplementing material layer 233 includes lithium-supplementing material and positive electrode material, and inert substances remain after the lithium-supplementing material is consumed. In this case, the filling layer 234 includes inert substances and positive electrode material, and the total mass of the inert substances and positive electrode material accounts for 10% of the mass of the filling layer 234.

[0098] In some embodiments of the present application, the total mass of the inert material and the positive electrode material accounts for 58%, 60%, 64%, 68%, 72%, 75%, or 78% of the mass of the filling layer 234. In some embodiments of the present application, the mass of the inert material accounts for 0-8% of the mass of the total positive electrode material. In some embodiments of the present application, the mass of the inert material accounts for 2%, 4%, or 6% of the mass of the total positive electrode material.

[0099] In some embodiments of the present application, the lithium-supplementing material used is completely converted into gas and discharged after consumption, and no inert material remains in the filling layer 234. In other embodiments of the present application, that is, when the lithium-supplementing material layer 233 includes both the lithium-supplementing material and the positive electrode material, and no inert material remains after the lithium-supplementing material is consumed, the positive electrode material remains in the filling layer 234. In this case, the filling layer 234 includes the positive electrode material, a binder, and a conductive agent.

[0100] In some embodiments of the present application, the active material layer 232 includes a positive electrode material, and the positive electrode material includes a lithium-containing positive electrode material commonly used in lithium-ion batteries.

[0101] In other embodiments of the present application, the positive electrode material includes a sodium-containing positive electrode material commonly used in sodium-ion batteries. In this case, the recess 2321 is configured as a sodium-supplementing material layer, which forms a filling layer 234 after being consumed. The sodium-supplementing material includes sodium carbonate, sodium nitride, sodium phosphide, sodium peroxide, sodium oxalate, sodium squarate, sodium chromate, and sodium nickelate. Among them, completely consumed sodium-supplementing materials include: sodium carbonate, sodium nitride, sodium phosphide, sodium peroxide, sodium oxalate, and sodium squarate. After the sodium-supplementing material is consumed, the filling layer 234 does not leave any residue of the sodium-supplementing material. Partially consumed sodium-supplementing materials include: sodium chromate and sodium nickelate. After the sodium-supplementing material is consumed, the filling layer 234 leaves inert substances that are residual in the sodium-supplementing material.

[0102] Sodium replenishment is similar to lithium replenishment. The mass ratios of the sodium replenishment material, conductive agent, and adhesive, as well as the dimensions of recess 2321 and active material layer 232, and other details are the same as those described above for lithium replenishment materials and are not repeated here. Lithium replenishment material layer 233 or sodium replenishment material layer can be collectively referred to as a replenishment material layer, and lithium replenishment material or sodium replenishment material can be collectively referred to as a replenishment material.

[0103] On the other hand, the present application also provides a battery, which includes a negative electrode plate 240 and a positive electrode plate 230 in any of the above embodiments. The positive electrode plate 230 includes a supporting layer and an active material layer 232. The active material layer 232 is provided with a recess 2321. The recess 2321 is provided with a filling layer 234. The height of the filling layer 234 is less than the depth of the recess 2321. The negative electrode plate 240 and the positive electrode plate 230 have a gap in the recess 2321. Because the recess 2321 of the positive electrode plate 230 contains lithium-supplementing material or sodium-supplementing material, the lithium-supplementing material or sodium-supplementing material can increase the battery capacity. After the lithium-supplementing material or sodium-supplementing material is consumed, a gap is formed between the positive electrode plate 230 and the negative electrode plate 240, which is conducive to the discharge of gas and the infiltration of the electrolyte, thereby improving the battery dynamics performance.

[0104] On the other hand, the present application also provides a coating method, wherein the active material layer 232 is coated on the support layer, a concave portion 2321 is formed on the surface of the active material layer 232 , and the lithium supplement material layer 233 or the sodium supplement material layer is coated on the concave portion 2321 .

[0105] In some embodiments of the present application, a concave portion 2321 is formed on the surface of the active material layer 232, and a lithium-supplementing material layer 233 or a sodium-supplementing material layer is simultaneously applied to the concave portion 2321. Simultaneous application of the active material layer 232 and the lithium-supplementing material layer 233 or the sodium-supplementing material layer can improve coating efficiency.

[0106] This application also provides a coating spacer 400 that can simultaneously coat the active material layer 232 with recesses 2321 on the current collector 231 and the lithium-supplementing material layer 233 or sodium-supplementing material layer on the recesses 2321. This improves coating efficiency. The lithium-supplementing material layer 233 or the sodium-supplementing material layer are collectively referred to as the supplementary material layer.

[0107] In some embodiments of the present application, as shown in FIG11 , the coating gasket 400 includes a main body 41, and the main body 41 is provided with an upper discharge port 411 and a lower discharge port 412. The upper discharge port 411 and the lower discharge port 412 are arranged alternately, and the upper discharge port 411 and the lower discharge port 412 can be used for discharging materials at the same time. Specifically, the lower discharge port 412 can be used for coating the active material layer 232, and the upper discharge port 411 can be used for coating the lithium-supplementing material layer 233 or the sodium-supplementing material layer. Of course, in some cases, the upper discharge port 411 can also be controlled not to discharge material, in which case a wave-like active material layer 232 can be formed. The slurry flows out of the upper discharge port 411 and the lower discharge port 412 at the same time, and the slurry flowing out of the lower discharge port 412 diffuses to the periphery. The slurry flowing out of the upper discharge port 411 will be formed above the slurry flowing out of the lower discharge port 412, forming a double-layer coating in some areas.

[0108] In some embodiments of the present application, there are multiple lower discharge ports 412 and upper discharge ports 411, and the upper discharge ports 411 and the lower discharge ports 412 are staggered in the length direction of the gasket. There is a certain gap between two adjacent lower discharge ports 412. After the adjacent discharge ports discharge the material, the slurries coming out diffuse with each other. After the slurry solidifies, a wavy coating is formed. Among them, the area where the slurries of adjacent discharge ports diffuse with each other forms a concave portion 2321 of the coating. The upper discharge port 411 is arranged between two adjacent lower discharge ports 412. The slurry coming out of the upper discharge port 411 is formed in the area where the slurry coming out of the lower discharge port 412 diffuses with each other, that is, the slurry coming out of the upper discharge port 411 is formed in the concave portion 2321 area. For details, please refer to the lithium replenishing material layer 233 shown in Figure 4. The length direction of the gasket described here refers to the direction perpendicular to the coating direction.

[0109] In some embodiments of the present application, the coating gasket 400 is further provided with an upper discharge channel 413 communicating with the upper discharge port 411 and a lower discharge channel 414 communicating with the lower discharge port 412. The upper discharge channel 413 and the lower discharge channel 414 are used to transport the slurry to the upper discharge port 411 and the lower discharge port 412, respectively.

[0110] In some embodiments of the present application, the upper discharge channel 413 is arranged on the upper surface of the main body 41, and the lower discharge channel 414 is arranged on the lower surface of the main body 41. This is conducive to the efficient transmission of the slurry and the setting of the feeding mechanism.

[0111] In some embodiments of the present application, the coating gasket 400 is further provided with a crossbeam 42, an upper discharge channel 413 is provided on the upper surface of the crossbeam 42, and a lower discharge channel 414 is provided on the lower surface of the crossbeam 42. In some embodiments of the present application, the length of the upper discharge channel 413 is less than the width of the crossbeam 42, which is conducive to the transmission of the slurry.

[0112] The length of the upper discharge channel 413 referred to herein refers to the size of the discharge channel in the direction of slurry transmission. The width of the crossbeam referred to herein refers to the size of the crossbeam in the width direction of the coating gasket 400.

[0113] In some embodiments of the present application, referring to Figures 11 and 12 , the coating gasket 400 further includes a connecting cavity 43, which is connected to a lower discharge channel 414. The connecting cavity 43 is located on one side of the crossbeam, with the connecting cavity 43 and the lower discharge port 412 located at either end of the crossbeam. Because the connecting cavity 43 is connected to the lower discharge channel 414, and the length of the upper discharge channel 413 is less than the width of the crossbeam, a partition is formed between the upper and lower discharge channels 413 and 414, effectively preventing the upper and lower slurries from mixing.

[0114] In some embodiments of the present application, referring to Figure 11, both the upper discharge port 411 and the lower discharge port 412 are provided with a chamfer 415, which is conducive to guiding the stable outflow of the slurry and improving the consistency of the coating. It is also conducive to the formation of a recess 2321 in the slurry flowing out of the lower discharge port 412. The upper discharge port 411 is provided with a chamfer 415, which means that a chamfer 415 is provided at the upper discharge channel 413 near the upper discharge port 411, and the slurry flowing out of the upper discharge channel 413 can flow out along the chamfer 415 and diffuse outward. The lower discharge port 412 is provided with a chamfer 415, which means that a chamfer 415 is provided at the lower discharge channel 414 near the lower discharge port 412, and the slurry flowing out of the lower discharge channel 414 can flow out along the chamfer 415 and diffuse outward. In some embodiments of the present application, the form of the chamfer 415 is not particularly limited, and the chamfer 415 can be a plane, or it can be other forms such as a curved surface.

[0115] In some embodiments of the present application, as shown in Figure 12, there are multiple upper discharge channels 413, and the coating gasket 400 is also provided with a connecting channel 416. The multiple upper discharge channels 413 are connected by the connecting channel 416. In this way, the slurry in the upper discharge channels 413 can flow with each other. During the discharge process, when the slurry in the multiple upper discharge channels 413 becomes consistent, the slurry flows out from the upper discharge port 411, which helps to ensure the uniformity and consistency of discharge from each discharge port, thereby improving the uniformity and consistency of coating.

[0116] On the other hand, the present application also provides a coating device, which uses the coating gasket 400 described above, so that the coating device can simultaneously coat two slurries, one slurry forming a coating located in the lower layer and having a recess 2321, and the other slurry forming a coating located in the recess 2321.

[0117] In some embodiments of the present application, as shown in FIG12 , the ratio (W1 / W2) of the width W1 of the lower discharge channel 414 to the width W2 of the upper discharge channel 413 is 1.2-5. The width of the lower discharge channel 414 refers to the distance between the two side walls of the lower discharge channel 414, and the width of the upper discharge channel 413 refers to the distance between the two side walls of the upper discharge channel 413, as specifically indicated in the accompanying drawings. Within this range, W1 / W2 can facilitate the formation of recess 2321 by the slurry from the lower discharge port 412, and the coating of the slurry from the upper discharge port 411 in the recess 2321. This also facilitates the flow of the slurry and reduces damage to the gasket.

[0118] In some embodiments of the present application, as shown in FIG12 , the distance between the lower discharge channel 414 and the upper discharge channel 413 is W3, and W3 / W2 is 0.01-0.5. The distance between the lower discharge channel 414 and the upper discharge channel 413 refers to the horizontal distance between the nearest sidewalls of the lower discharge channel 414 and the upper discharge channel 413, as specifically indicated in the figure. Within this range, W3 / W2 facilitates the formation of a coating structure having a recessed portion 2321 while also improving the strength of the gasket.

[0119] In some embodiments of the present application, as shown in FIG12 , the ratio H1 / H of the depth of the lower discharge channel 414 to the thickness of the coating gasket 400 is 0.3-0.7. The depth of the lower discharge channel 414 refers to the height of the sidewall of the lower discharge channel 414, that is, the vertical distance from the top wall of the lower discharge channel 414 to the lower surface of the coating gasket 400. The thickness of the coating gasket 400 refers to the vertical distance from the upper surface to the lower surface of the coating gasket 400. When H1 / H is within this range, it is conducive to the outflow of the slurry, while increasing the strength of the coating gasket 400 and improving the stability of the slurry outflow.

[0120] In some embodiments of the present application, as shown in FIG12 , the ratio H2 / H of the depth of the upper discharge channel 413 to the thickness of the coating gasket 400 is 0.6-0.9. The depth of the upper discharge channel 413 refers to the vertical distance between the bottom wall of the upper discharge channel 413 and the upper surface of the coating gasket 400. The thickness of the coating gasket 400 refers to the vertical distance from the upper surface to the lower surface of the coating gasket 400. When H2 / H is within this range, it can facilitate the outflow of the slurry, while increasing the strength of the coating gasket 400 and improving the stability of the slurry outflow.

[0121] In some embodiments of the present application, as shown in FIG12 , the ratio W4 / L2 of the width of the communication channel 416 to the length of the upper discharge channel 413 is 0-0.5. Within this range, W4 / L2 can improve the consistency of the slurry and increase the cavity pressure of the upper discharge channel 413, thereby facilitating the flow of the slurry.

[0122] In some embodiments of the present application, as shown in reference figure 13, the coating device further includes an upper die head 500 and a lower die head 600, and the coating gasket 400 is located between the upper die head 500 and the lower die head 600. The upper die head 500 and the lower die head 600 can provide slurry for the coating gasket 400, and the upper die head 500 provides the upper side slurry to the upper discharge channel 413, and then the upper side slurry flows out from the upper discharge port 411, and the lower die head 600 provides the lower side slurry to the lower discharge channel 414, and then the lower side slurry flows out from the lower discharge port 412.

[0123] In some embodiments of the present application, the upper die head 500 is provided with a storage mechanism 51, which is connected to the upper discharge channel 413. The storage mechanism 51 is used to store the upper slurry. The upper slurry flows out from the storage mechanism 51 and is transferred to the upper discharge channel 413, and then flows out from the upper discharge port 411.

[0124] In some embodiments of the present application, the storage mechanism 51 is fixed to the upper die head by a fixing member. In this way, the storage mechanism 51 can be removed from the upper die head. Furthermore, the storage mechanism 51 includes a first shell 511 and a second shell 512, which form an upper storage cavity 513. The first shell 511 and the second shell 512 are sealed to prevent slurry leakage.

[0125] In some embodiments of the present application, the storage mechanism 51 is provided with a feed port 514 and a leakage port 515. The feed port 514 is provided at the lower portion of the storage mechanism 51, and the leakage port 515 is provided at the upper portion of the storage mechanism 51. In this way, after the slurry fills the storage mechanism 51, it flows out from the leakage port 515, which is conducive to improving the consistency of the distribution of the slurry in the storage mechanism 51, thereby improving the consistency of the coating. Furthermore, the upper die head 500 is also provided with a discharge pipe 516, and the leakage port 515 is connected to the upper discharge channel 413 through the discharge pipe 516. The lower portion of the storage mechanism 51 referred to here refers to the portion located below one-half of the height of the storage mechanism 51, including the bottom of the storage mechanism 51, and the upper portion of the storage mechanism refers to the portion located above one-half of the height of the storage mechanism 51, including the top of the storage mechanism 51.

[0126] In some embodiments of the present application, the upper discharge port 411 of the upper discharge channel 413 is defined as the front, the other end of the upper discharge channel 413 opposite the upper discharge port 411 is defined as the rear, and the discharge pipe 516 is located in front of the other end of the upper discharge channel 413 opposite the upper discharge port 411. This can improve the stability of the pressure chamber in the discharge channel, thereby improving the stability of the slurry.

[0127] In some embodiments of the present application, the upper die head is provided with a movable cover plate, and the feed pipe passes through the movable cover plate and is fixedly connected to the movable cover plate. In this way, the feed pipe or the gasket can be easily replaced and cleaned.

[0128] In some embodiments of the present application, referring to Figures 13 and 14, the lower die head 600 is provided with a storage box 61, which is connected to the connecting cavity 43 of the coating gasket 400, and the connecting cavity 43 is connected to the lower discharge channel 414 to supply slurry to the lower discharge channel 414.

[0129] The present application also provides a coating method, employing the coating pad 400 or coating device described above. In one embodiment of the present application, the active material and the lithium-replenishing material are applied simultaneously, and the active material layer 232 is formed into a wavy shape, i.e., the active material layer 232 is formed with recesses 2321, and the lithium-replenishing material layer 233 is applied to the recesses 2321. This improves coating efficiency, produces a battery with a higher capacity, and also improves the battery's cycle life and dynamic performance.

[0130] In some embodiments of the present application, the active material layer 232 and the lithium-replenishing material layer 233 are formed from an active material slurry and a lithium-replenishing material slurry. The viscosity of the active material slurry is 7,000-20,000, preferably 9,000-13,000, and the viscosity of the lithium-replenishing material slurry is 3,000-10,000, preferably 5,000-7,000. In some embodiments of the present application, the viscosity of the lithium-replenishing material slurry is lower than the viscosity of the active material slurry. This allows the lithium-replenishing material layer 233 to be more evenly coated on the concave portion 2321 of the active material layer 232, minimizing the impact on the morphology of the active material layer 232 itself.

[0131] The following describes the technical effects of the present application through specific examples and comparative examples. It should be noted that the following examples are only a specific implementation of the technical solution of the present application, which are used to illustrate that the technical solution of the present application can improve battery performance compared with the technical solutions in the prior art, and cannot be used to limit the scope of protection of the present application.

[0132] Example 1

[0133] Preparation of positive electrode sheet: Preparation of positive electrode active material slurry: The positive electrode active material lithium iron phosphate LFP, the conductive carbon black SP and the binder PVDF are dispersed in the solvent NMP in a weight ratio of 97:0.8:2.2 to obtain a mixed material, and the mixed material is stirred and mixed evenly to obtain the positive electrode active material slurry.

[0134] Preparation of lithium supplement material slurry: The lithium supplement material Li5FeO4, the positive electrode active material LiFePO4, the conductive carbon black SP, and the binder PVDF are dissolved in the solvent NMP in a weight ratio of 86.3:9.5:2.0:2.2, and a uniform lithium supplement material slurry is obtained by stirring.

[0135] The positive electrode slurry and lithium-replenishing material are simultaneously coated onto the upper and lower surfaces of the current collector according to the method described herein, forming an active material layer and a lithium-replenishing material layer. The active material layer has a recessed portion, and the lithium-replenishing material layer is disposed within the recessed portion. After drying, cold pressing, slitting, and cutting, a positive electrode sheet is obtained, wherein H is 78 μm, k is 52.2 mm, b is 174 mm, h / H = 0.1, k / b = 0.3, and g = 0.1.

[0136] Preparation of negative electrode sheets: Disperse the negative electrode active material graphite, conductive carbon black, thickener CMC and binder SBR in a solvent deionized water according to a weight ratio of 96:1:1:2, stir evenly to obtain a negative electrode slurry; evenly apply the negative electrode slurry on the negative electrode current collector copper foil; after drying, cold pressing, slitting and cutting, the negative electrode sheet is obtained.

[0137] electrolyte

[0138] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed to obtain an organic solvent. 1 mol / L LiPF6 is dissolved in the organic solvent and mixed to obtain an electrolyte.

[0139] The positive electrode sheet, negative electrode sheet, electrolyte and separator obtained above were assembled into a battery by winding, and capacity test, rate test and cycle life test were carried out.

[0140] Example 2

[0141] The difference from Example 1 is the preparation of the lithium supplement material slurry: the lithium supplement material Li5FeO4, the conductive carbon black SP, and the binder PVDF are dissolved in the solvent NMP in a weight ratio of 95.8:2.0:2.2, and a uniform lithium supplement material slurry is obtained by stirring.

[0142] Example 3

[0143] The difference from Example 1 is the preparation of the lithium supplement material slurry: the lithium supplement material Li2C2O4, the positive electrode active material LiFePO4, the conductive carbon black SP, and the binder PVDF are dissolved in the solvent NMP in a weight ratio of 90.3:5.5:2.0:2.2.

[0144] Example 14

[0145] The difference from Example 1 is the preparation of the lithium supplement material slurry: the lithium supplement material Li5FeO4, the positive electrode active material LiFePO4, the conductive carbon black SP, and the binder PVDF are dissolved in the solvent NMP in a weight ratio of 80.3:15.5:2.0:2.2, and a uniform lithium supplement material slurry is obtained by stirring.

[0146] Example 19

[0147] The difference from Example 1 is the preparation of the lithium supplement material slurry: the lithium supplement material Li2NiO2, the positive electrode active material LiFePO4, the conductive carbon black SP, and the binder PVDF are dissolved in the solvent NMP in a weight ratio of 90.3:5.5:2.0:2.2.

[0148] For Examples 4 to 13 and 15 to 18, refer to Example 1, and the differences are shown in Table 1.

[0149] Comparative Example 1

[0150] In the preparation of the positive electrode sheet, the active material layer and the lithium supplement layer are alternately coated on the upper surface of the current collector, and the rest is the same as in Example 1. The thickness of the active material layer is 78 μm.

[0151] The obtained positive electrode sheet, negative electrode sheet, electrolyte and separator are assembled into a battery, and capacity test, rate test and cycle life test are carried out.

[0152] Table 1

[0153] In Table 1, the ratio of the mass of lithium-replenishing material and positive electrode material to the mass of lithium-replenishing material layer is w1, the ratio of the mass of lithium-replenishing material to the mass of all positive electrode materials is w2, the ratio of the mass of inert substance and positive electrode material to the mass of filling layer is w3, and the ratio of the mass of inert substance to the mass of all positive electrode materials is w4.

[0154] The test results of the batteries of the above embodiments and comparative examples are shown in Table 2.

[0155] Table 2

[0156] The capacity test method is as follows: maintain the ambient temperature at 25°C, charge and discharge the battery at a rate of 0.33C, record the discharge capacity, where the charge and discharge current is 16A, the voltage range is 2.5~3.65V, cycle 3 cycles, and take the discharge capacity of the third cycle as the capacity test value.

[0157] The cycle life test method is as follows:

[0158] (1) At 45°C, charge the battery at a constant current of 1C to 3.65V, then charge it at a constant voltage of 3.65V to a current of 0.05C, let it rest for 30 minutes, and then discharge it at 1C to 2.5V. Record the discharge capacity C0.

[0159] (2) Repeat the above step (1) 2000 times, and record the discharge capacity C2000 of the lithium-ion battery after the 2000th cycle, and the capacity retention rate P2000 = C2000 / C0×100%.

[0160] The DCR test method is as follows: At 25°C, charge to 50% SOC at 1 / 3C0 (C0 is the standard capacity obtained from the capacity test, unit is Ah), then discharge at 4C0 for 30s, and record the voltage difference before and after. DCR = voltage difference / current.

[0161] From the above experimental data, it can be seen that the provision of the lithium-supplementing material layer can increase the capacity of the battery. At the same time, the lithium-supplementing material layer is provided in the recessed portion of the active material layer, which can increase the cycle life of the battery and reduce the DCR of the battery.

[0162] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A positive electrode sheet, comprising a support layer and an active material layer, characterized in that: The active material layer is provided with a concave portion, and the concave portion is provided with a filling layer, and the height of the filling layer is smaller than the depth of the concave portion.

2. The positive electrode sheet according to claim 1, characterized in that: The filling layer includes a conductive agent. Preferably, the mass of the conductive agent is 5%-21% of the mass of the filling layer.

3. The positive electrode sheet according to claim 1, characterized in that: The filling layer includes an adhesive. Preferably, the mass of the adhesive is 6%-25% of the mass of the filling layer.

4. The positive electrode sheet according to claim 2, characterized in that: The porosity of the filling layer is greater than the porosity of the active material layer.

5. The positive electrode sheet according to claim 4, characterized in that: The porosity of the filling layer is 50%-91%.

6. The positive electrode sheet according to claim 1, characterized in that: The surface roughness of the filling layer is greater than the surface roughness of the active material layer.

7. The positive electrode sheet according to claim 1, characterized in that: The filling layer contains inert substances. Preferably, the mass of the inert substances accounts for 55%-80% of the mass of the filling layer.

8. The positive electrode sheet according to claim 1, characterized in that: The filling layer contains inert substances and positive electrode materials, and the total mass of the inert substances and the positive electrode materials accounts for 55%-80% of the mass of the filling layer.

9. The positive electrode sheet according to claim 7 or 8, characterized in that: The mass of the inert substance accounts for 0-8% of the mass of the entire positive electrode material.

10. The positive electrode sheet according to claim 7 or 8, characterized in that: The inert substance is formed by converting a lithium-supplementing material or a sodium-supplementing material.

11. The positive electrode sheet according to any one of claims 1 to 8, characterized in that: The ratio of the depth of the concave portion to the thickness of the active material layer is 0.05-0.

2.

12. The positive electrode sheet according to any one of claims 1 to 8, characterized in that: There are a plurality of recesses, the sum of the widths of the plurality of recesses is k, the width of the active material layer is b, and k / b is 0.05-0.

5.

13. The positive electrode sheet according to claim 1, characterized in that: The filling layer is formed by converting a lithium-supplementing material layer or a sodium-supplementing material layer.

14. A positive electrode sheet, comprising a support layer and an active material layer, characterized in that: The active material layer is provided with a concave portion, and the concave portion is provided with a supplementary material layer, and the height of the supplementary material layer is not greater than the depth of the concave portion.

15. The positive electrode sheet according to claim 14, characterized in that: The supplementary material layer includes at least one of a lithium supplementary material layer or a sodium supplementary material layer.

16. The positive electrode sheet according to claim 15, characterized in that: The lithium supplement material layer includes lithium supplement material, the mass of which accounts for 92%-98.5% of the mass of the lithium supplement material layer, or the sodium supplement material layer includes sodium supplement material, the mass of which accounts for 92%-98.5% of the mass of the sodium supplement material layer.

17. The positive electrode sheet according to claim 16, characterized in that: The lithium supplement material layer includes a lithium-containing positive electrode material, and the total mass of the lithium supplement material and the lithium-containing positive electrode material accounts for 92%-98.5% of the mass of the lithium supplement material layer, or the sodium supplement material layer includes a sodium-containing positive electrode material, and the total mass of the sodium supplement material and the sodium-containing positive electrode material accounts for 92%-98.5% of the mass of the sodium supplement material layer.

18. The positive electrode sheet according to claim 17, characterized in that: In the lithium supplement material layer, the mass ratio of the lithium supplement material to the lithium-containing positive electrode material is 1:1-10:1, or in the sodium supplement material layer, the mass ratio of the sodium supplement material to the sodium-containing positive electrode material is 1:1-10:

1.

19. The positive electrode sheet according to claim 16 or 17, characterized in that: The mass of the lithium supplement material accounts for 0.5%-10% of the mass of the total lithium-containing positive electrode material, preferably 3%-7%, or the mass of the sodium supplement material accounts for 0.5%-10% of the mass of the total sodium-containing positive electrode material, preferably 3%-7%.

20. The positive electrode sheet according to claim 15, characterized in that: The lithium supplement material layer includes an adhesive, the mass of which accounts for 0.5%-3% of the mass of the lithium supplement material layer, or the sodium supplement material layer includes an adhesive, the mass of which accounts for 0.5%-3% of the mass of the sodium supplement material layer.

21. The positive electrode sheet according to claim 15, characterized in that: The lithium supplement material layer includes a conductive agent, the mass of which accounts for 0.5%-5% of the mass of the lithium supplement material layer, or the sodium supplement material layer includes a conductive agent, the mass of which accounts for 0.5%-5% of the mass of the sodium supplement material layer.

22. The positive electrode sheet according to claim 15, characterized in that: The porosity of the lithium supplementing material layer is 25%-44%, or the porosity of the sodium supplementing material layer is 25%-44%.

23. The positive electrode sheet according to claim 15, characterized in that: The ratio of the depth of the concave portion to the thickness of the active material layer is 0.05-0.

2.

24. The positive electrode sheet according to claim 15, characterized in that: There are a plurality of recesses, the sum of the widths of the plurality of recesses is k, the width of the active material layer is b, and k / b is 0.05-0.

5.

25. A battery, characterized in that: include: A positive electrode sheet as claimed in any one of claims 1 to 24.

26. The battery according to claim 25, characterized in that include: The negative electrode sheet, the positive electrode sheet comprises a support layer and an active material layer, the active material layer is provided with a recess, the recess is provided with a filling layer, the height of the filling layer is less than the depth of the recess, and the negative electrode sheet and the positive electrode sheet have a gap in the recess.

27. An electrical device, characterized in that: The electrical device comprises the battery as claimed in claim 25 or 26, and the battery is used to provide electrical energy.

28. A method for preparing a pole piece, characterized in that: The active material layer is coated on the support layer, and recessed portions are formed on the surface of the active material layer, and the lithium supplementing material layer is coated on the recessed portions.

29. The method for preparing a pole piece according to claim 28, characterized in that: The recessed portions are formed on the surface of the active material layer and the lithium supplementing material layer is applied to the recessed portions.

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