Pole piece and manufacturing method, electrode assembly, secondary battery and electrical device

Abstract

A pole piece (10) and a manufacturing method thereof, an electrode assembly, a battery (100), and an electrical device. A lithium replenishing space (13) is provided on a current collecting structure (11), so that the lithium replenishing space (13) is in communication with an active layer (12) on one side. A lithium replenishing agent in the lithium replenishing space (13) is used to replenish lithium into the battery (100), offsetting the irreversible lithium loss during the cycle, thereby improving the total capacity and energy density of the battery (100). Since the average weight Ma of active material per unit area corresponding to different distribution areas (14) on the active layer (12) is different, the sum V0 of the volume of the lithium replenishing space (13) corresponding to each distribution area (14) is positively correlated with the change in the average weight of active material per unit area in the different distribution areas (14). That is, when Ma in the first distribution area (14a) is smaller than Ma in the second distribution area (14b), V0 corresponding to the first distribution area (14a) is smaller than V0 corresponding to the second distribution area (14b). In this way, different amounts of lithium are replenished for different distribution areas (14), achieving quantitative and precise lithium replenishment, which is beneficial to improving the energy density and life of the battery (100).

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a pole piece and a manufacturing method thereof, an electrode assembly, a secondary battery and an electrical device. Background Art

[0002] With the ever-increasing demand for energy, the demands on the endurance and lifespan of lithium-ion batteries are becoming increasingly stringent. Silicon anodes typically have low initial coulombic efficiency, so to be used in battery products, they must be supplemented with lithium to increase energy density and lifespan.

[0003] To avoid edge thickening during the coating process, the electrode edges are thinned. However, in some cases, lithium replenishment methods such as lithium ribbon rolling can result in excessive lithium replenishment in the thinned areas, leading to lithium plating, or insufficient lithium replenishment in the central, large area, resulting in capacity loss or less-than-expected lifespan improvement. Summary of the Invention

[0004] Based on this, it is necessary to provide an electrode and its manufacturing method, an electrode assembly, a secondary battery and an electrical device to achieve quantitative and precise lithium replenishment and improve the battery energy density and life.

[0005] In the first aspect, the present application provides a pole piece, comprising: a current collecting structure; two active layers, respectively provided on opposite sides of the current collecting structure along the thickness direction of the current collecting structure; the current collecting structure is provided with a plurality of lithium replenishing spaces for accessing the active layer on one side, wherein the lithium replenishing spaces contain a lithium replenishing agent; in the distribution area on the active layer connected to the lithium replenishing spaces, the average weight of the active material per unit area of ​​the active layer is recorded as M A The sum of the internal volumes of the lithium replenishment space covered by the projection of the distribution area along the thickness direction of the current collecting structure is recorded as V0, and the distribution area includes at least the first distribution area and the second distribution area; wherein, M in the first distribution area A Smaller than M in the second distribution area A , and the V0 corresponding to the first distribution area is smaller than the V0 corresponding to the second distribution area.

[0006] The above-mentioned electrode is provided with a lithium replenishing space on the current collecting structure so that the lithium replenishing space is connected to the active layer on one side; the lithium replenishing agent in the lithium replenishing space is used to replenish lithium into the battery to offset the irreversible lithium loss during the cycle, thereby improving the total capacity and energy density of the battery. ATherefore, the present application controls the sum of the pore volumes V0 of the lithium replenishment spaces corresponding to each distribution area in a positive correlation according to the change in the average weight of the active material in different distribution areas, that is, the sum of the volumes of the corresponding lithium replenishment spaces in the second distribution area is larger, and the sum of the volumes of the corresponding lithium replenishment spaces in the first distribution area is smaller. In this way, different lithium is replenished in different distribution areas to achieve quantitative and precise lithium replenishment, avoiding the problem of lithium precipitation caused by too much lithium replenishment in the first distribution area under the premise of the same lithium replenishment amount, or the problem of capacity loss or less-than-expected life improvement in the second distribution area due to too little lithium replenishment in the second distribution area, which is beneficial to improving the energy density and life of the battery.

[0007] In some embodiments, the depth of the lithium replenishment space is denoted as d, and the thickness of the active layer corresponding to the location of the lithium replenishment space is denoted as h. Here, h in the first distribution region is smaller than h in the second distribution region, and d corresponding to the first distribution region is smaller than d corresponding to the second distribution region. This not only achieves quantitative and precise lithium replenishment, but also simplifies the processing of the lithium replenishment space and improves electrode manufacturing efficiency.

[0008] In some embodiments, the depth d of the lithium replenishing space satisfies the following relationship:

[0009]

[0010] Among them, C A is the initial lithium insertion capacity of the negative electrode active material in milliampere hours per gram (mAh / g), C C is the first lithium removal capacity of the positive electrode active material mAh / g, M C The average weight of the active material per unit area of ​​the positive electrode is g / cm2 (g / cm 2 ), where P is the ratio of the open area of ​​all lithium-replenishing spaces per unit area on the current collecting structure. By setting an upper limit on the depth of the lithium-replenishing space, excessive lithium replenishment, which can lead to lithium plating during cycling on the negative electrode, can be avoided, improving battery safety.

[0011] In some embodiments, the ratio P of the opening area of ​​all lithium replenishment spaces per unit area satisfies the following relationship: 10% ≤ P ≤ 50%. Thus, while ensuring sufficient space for the lithium replenishment agent, the pore area ratio of the lithium replenishment space is rationally controlled to ensure stable electronic conduction function of the current collecting structure.

[0012] In some embodiments, the depth d of the lithium replenishing space satisfies the following relationship:

[0013]

[0014] Among them, CE C is the first coulombic efficiency of the positive electrode active material, CE Ais the first coulombic efficiency of the negative electrode active material, C A The initial lithium insertion capacity of the negative electrode active material is expressed in mAh / g. By setting a lower limit for the depth of the lithium replenishment space, the lithium replenishment agent can be fully filled into the lithium replenishment space, thereby fully utilizing the capacity of the positive electrode active material and effectively improving energy density.

[0015] In some embodiments, the lithium replenishment spaces are spaced apart in at least one side of the active layer, and the spacing between any two adjacent lithium replenishment spaces is equal. This evenly distributes the lithium replenishment spaces, facilitating uniform lithium diffusion and improving battery performance.

[0016] In some embodiments, the current collecting structure includes at least one current collector along its thickness. Within the current collector having the active layer, at least one lithium-replenishing space is provided. This not only facilitates electron conduction but also facilitates the creation of pores in the current collecting structure, allowing the lithium-replenishing agent to be stably deposited within the lithium-replenishing space.

[0017] In some embodiments, the current collection structure includes two current collectors, with two active layers disposed on opposite sides of the current collectors, each with a lithium replenishment space extending through it. The lithium replenishment spaces provided through each current collector allow for effective lithium replenishment in the active layers on both sides, further improving the battery's energy density and cycle life.

[0018] In some embodiments, the current collecting structure further includes at least one lithium replenishment layer, which is located between the two current collectors. Providing at least one lithium replenishment layer between the two current collectors increases the amount of lithium replenishment and can effectively improve the cycle life of the battery.

[0019] In some embodiments, the lithium replenishment space is a lithium replenishment hole, which extends along the thickness of the current collecting structure into the active layer on either side. Designing the lithium replenishment space as a lithium replenishment hole, with one end of the lithium replenishment hole extending into the active layer, not only simplifies the electrode manufacturing process but also facilitates controlling the corresponding lithium replenishment dosage in different distribution areas, achieving more precise lithium replenishment.

[0020] In some embodiments, the first distribution area extends around the periphery of the second distribution area. A Less than the average weight M of the active material near the middle of the electrode A Such a design is helpful to solve the problem of bulging edges due to excessive thickness of the electrode edges.

[0021] In a second aspect, the present application provides a method for manufacturing an electrode, comprising the following steps: step S100, providing two single-sided electrode sheets, wherein the single-sided electrode sheets include a current collector and an active layer provided on one side of the current collector; step S200, on at least one single-sided electrode sheet, opening lithium replenishment holes extending into the active layer in the current collector, and controlling the average weight M of the active material per unit area in at least two distribution areas on the active layer. A The sum of the pore volume V0 of the corresponding lithium-replenishing pores satisfies: M in the first distribution area A Smaller than M in the second distribution area A , and the V0 corresponding to the first distribution area is smaller than the V0 corresponding to the second distribution area, wherein the distribution area includes the first distribution area and the second distribution area; step S300, depositing a lithium replenishing agent in the lithium replenishing hole; step S400, bonding the side surfaces of the two single-sided pole pieces facing away from the active layer to each other.

[0022] The above-mentioned electrode manufacturing method manufactures the required electrode by laminating the electrodes in a unidirectional manner, which greatly simplifies the manufacturing process. At the same time, it is also convenient to open holes in the electrode to ensure that the lithium replenisher is stably deposited in the lithium replenishment holes, so as to achieve a quantitative and accurate lithium replenishment effect.

[0023] In some embodiments, step S200 includes: step S210, obtaining the thickness h of the active layer in different distribution areas; step S220, uniformly creating a plurality of lithium-replenishing pores in the current collector; and step S230, controlling the depth d of the lithium-replenishing pores in the projection area of ​​each distribution area onto the current collector, such that h in the first distribution area is smaller than h in the second distribution area, and d in the first distribution area is smaller than d in the second distribution area. In this way, using the thickness of the active layer as a reference, the control of the sum of the intrapore volumes of the lithium-replenishing pores is converted into control of the depth of the lithium-replenishing pores. This not only achieves quantitative and precise lithium replenishment, but also simplifies the processing of the lithium-replenishing pores, improving electrode manufacturing efficiency.

[0024] In some embodiments, the depth d of the lithium replenishing pore satisfies the following relationship:

[0025]

[0026] Among them, C A is the initial lithium insertion capacity of the negative electrode active material mAh / g, C C is the first lithium removal capacity of the positive electrode active material mAh / g, M C is the average weight of the active material per unit area of ​​the positive electrode g / cm 2 , where P is the ratio of the total lithium-replenishing pore area per unit area of ​​the current collecting structure. This design, by setting an upper limit on the depth of the lithium-replenishing pores, prevents excessive lithium replenishment and the resulting lithium plating during cycling on the negative electrode, thereby improving battery safety.

[0027] In some embodiments, the depth d of the lithium replenishing pore satisfies the following relationship:

[0028]

[0029] Among them, CE C is the first coulombic efficiency of the positive electrode active material, CE A is the first coulombic efficiency of the negative electrode active material, C A The initial lithium insertion capacity of the negative electrode active material is expressed in mAh / g. By setting a lower limit for the depth of the lithium replenishment pores, the pores can be filled with the lithium replenishment agent, fully utilizing the capacity of the positive electrode active material and effectively improving energy density.

[0030] In a third aspect, the present application provides an electrode assembly, comprising a positive electrode sheet, a negative electrode sheet, and an isolating member disposed between the positive electrode sheet and the negative electrode sheet; wherein the positive electrode sheet and / or the negative electrode sheet is any one of the above electrode sheets.

[0031] The above-mentioned electrode assembly uses the above-mentioned pole pieces to supplement different lithium distribution areas, achieving quantitative and precise lithium supplementation, which is beneficial to improving the battery energy density and life.

[0032] In a fourth aspect, the present application provides a secondary battery comprising the above electrode assembly.

[0033] The above-mentioned secondary battery adopts the above-mentioned electrode to supplement different lithium distribution areas, thereby achieving quantitative and precise lithium supplementation, which is beneficial to improving the battery energy density and life.

[0034] In a fifth aspect, the present application provides an electrical device comprising the above secondary battery.

[0035] 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

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0037] Figure 1 A schematic diagram of a vehicle structure described in some embodiments of the present application;

[0038] Figure 2An exploded view of a battery described in some embodiments of the present application;

[0039] Figure 3 Schematic diagram of the partial structure of the pole piece described in some embodiments of the present application;

[0040] Figure 4 A cross-sectional view of the structure of the pole piece described in some embodiments of the present application;

[0041] Figure 5 The process of manufacturing the electrode described in some embodiments of this application Figure 1 ;

[0042] Figure 6 The process of manufacturing the electrode described in some embodiments of this application Figure 2 .

[0043] 1000, vehicle; 100, battery; 200, controller; 300, motor; 110, housing; 111, first part; 112, second part; 120, battery cell; 10, pole piece; 11, current collecting structure; 11a, current collector; 12, active layer; 13, lithium replenishment space; 13a, lithium replenishment hole; 14, distribution area; 14a, first distribution area; 14b, second distribution area; 15, lithium replenishment layer; 16, single-sided pole piece. DETAILED DESCRIPTION

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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).

[0050] 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.

[0051] 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.

[0052] 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.

[0053] The applicant has noticed that during the first charging process of a lithium-ion battery, the organic electrolyte will be reduced and decomposed on the surface of the negative electrode such as graphite, forming a solid electrolyte phase interface film, which permanently consumes a large amount of lithium from the positive electrode, resulting in a low coulombic efficiency in the first cycle, thereby reducing the capacity and energy density of the lithium-ion battery.

[0054] In order to solve the problem of reduced battery capacity and energy density due to irreversible loss of lithium during the cycle, the applicant has found that lithium replenishment methods such as lithium strip rolling can be used to add lithium to the battery to supplement lithium ions, thereby improving energy density and life. However, during the coating process, such as transfer coating, the slurry is transferred to the current collector, such as copper foil or aluminum foil, by a steel roller to form a coating area with uniform thickness; then it is baked in a tunnel drying oven. However, during the baking process, the solid content of the edge of the coating area on the current collector increases faster than that of the middle area. The surface tension of the slurry at the edge of the coating area is greater than the surface tension of the middle part. The slurry flows to the edge area, resulting in a "thick edge" phenomenon on the pole piece after baking.

[0055] In order to avoid thick edges on the electrode, it is usually necessary to thin the edges of the electrode, such as using a thinning device or a transfer coater to thin the edges. However, after thinning, the amount of active material in different distribution areas on the electrode will be different. For example, the amount of active material in the middle large area and the edge thinned area of ​​the electrode will be different. If the same amount of lithium replenishment is arranged on the electrode, since the amount of active material deintercalation in the edge thinned area and the amount of deintercalation in the middle large area are relatively small, under the same amount of lithium replenishment, the amount of lithium replenishment in the thinned area will be too much, resulting in lithium plating problems, or the amount of lithium replenishment in the middle large area will be too little, resulting in capacity loss or less-than-expected life improvement.

[0056] Based on the above considerations, in order to solve the problem of inaccurate lithium replenishment due to different amounts of active materials in different distribution areas, the inventors conducted in-depth research and designed a pole piece, where the average weight of the active material per unit area of ​​the active layer is recorded as M. A The sum of the pore volumes of the lithium-supplementing space covered by the projection of the distribution area along the thickness direction of the current collecting structure is recorded as V0. A Smaller than M in the second distribution area A , and the V0 corresponding to the first distribution area is smaller than the V0 corresponding to the second distribution area.

[0057] During the lithium replenishment space configuration, the sum of the pore volumes (V0) of the corresponding lithium replenishment spaces in each distribution area is positively correlated with the average weight change of the active material in at least two distribution areas. This means that the sum of the volumes of the corresponding lithium replenishment spaces in the second distribution area is larger, while the sum of the volumes of the corresponding lithium replenishment spaces in the first distribution area is smaller. This allows for quantitative and precise lithium replenishment by targeting different distribution areas. This avoids the problem of excessive lithium replenishment in the first distribution area, which could lead to lithium deposition, or insufficient lithium replenishment in the second distribution area, which could lead to capacity loss or less-than-expected lifespan improvement, all while maintaining the same lithium replenishment amount. This helps improve battery energy density and lifespan.

[0058] 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 system comprising the battery cells and batteries disclosed in this application can be used to construct such electrical devices. This allows for targeted lithium replenishment in different distribution areas, achieving quantitative and precise lithium replenishment, which in turn improves battery energy density and lifespan.

[0059] 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.

[0060] 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.

[0061] Please refer to Figure 1 , Figure 1 A schematic structural diagram of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000. The battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000. For example, the battery 100 may serve as an operating power source for the vehicle 1000. The vehicle 1000 may further 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, to meet the power requirements for starting, navigating and driving the vehicle 1000.

[0062] 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.

[0063] Please refer to Figure 2 , Figure 2 An exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a housing 110 and a battery cell 120, with the battery cell 120 being housed within the housing 110. The housing 110 is used to provide a storage space for the battery cell 120, and the housing 110 can adopt a variety of structures. In some embodiments, the housing 110 can include a first portion 111 and a second portion 112, the first portion 111 and the second portion 112 overlapping each other, and the first portion 111 and the second portion 112 jointly defining a storage space for accommodating the battery cell 120. The second portion 112 can be a hollow structure with one end open, and the first portion 111 can be a plate-like structure, with the first portion 111 overlapping the open side of the second portion 112, so that the first portion 111 and the second portion 112 jointly define a storage space; the first portion 111 and the second portion 112 can also be hollow structures with one side open, with the open side of the first portion 111 overlapping the open side of the second portion 112. Of course, the box body 110 formed by the first part 111 and the second part 112 can be in various shapes, such as a cylinder, a cuboid, etc.

[0064] In the battery 100, there may be multiple battery cells 120, and the multiple battery cells 120 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 120. The multiple battery cells 120 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery 120 may be housed within the housing 110. Of course, the battery 100 may also be in the form of a battery module 100, in which multiple battery cells 120 are first connected in series, in parallel, or in a hybrid connection, and then the multiple battery modules 100 are further connected in series, in parallel, or in a hybrid connection to form an entire battery 100, and then housed within the housing 110. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for electrically connecting the multiple battery cells 120.

[0065] Each battery cell 120 may be a secondary battery 100 or a primary battery 100; it may also be a lithium-sulfur battery 100, a sodium-ion battery 100, or a magnesium-ion battery 100, but is not limited thereto. The battery cell 120 may be cylindrical, flat, rectangular, or in other shapes.

[0066] According to some embodiments of this application, please refer to Figure 3The present application provides a pole piece 10. The pole piece 10 includes: a current collecting structure 11 and two active layers 12. The two active layers 12 are respectively arranged on the opposite side surfaces of the current collecting structure 11 along the thickness direction of the current collecting structure 11. The current collecting structure 11 is provided with a plurality of lithium replenishing spaces 13 for accessing the active layer 12 on one side. The lithium replenishing space 13 contains a lithium replenishing agent. In the distribution area 14 on the active layer 12 connected to the lithium replenishing space 13, the average weight of the active material per unit area of ​​the active layer 12 is recorded as M A The sum of the volumes of the lithium replenishing space 13 covered by the projection of the distribution area 14 along the thickness direction of the current collecting structure 11 is recorded as V0. The distribution area 14 includes at least a first distribution area 14a and a second distribution area 14b. A Smaller than M in the second distribution area 14b A , and the V0 corresponding to the first distribution area 14a is smaller than the V0 corresponding to the second distribution area 14b.

[0067] The current collecting structure 11 is a component or part that not only carries the active material but also collects and outputs the current generated by the electrode active material. This component or part can have one or more layers. The current collecting structure 11 can be made of a variety of materials, including but not limited to metals such as copper, aluminum, nickel, and stainless steel. Alternatively, it can be made of semiconductor materials such as carbon, as well as composite materials such as conductive resins, titanium-nickel shape memory alloys, and carbon-coated aluminum foil.

[0068] The active layer 12 is the active material coated on the current collecting structure 11. Its specific composition varies depending on the polarity of the electrode 10. For example, the active material on the positive electrode can be, but is not limited to, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium iron phosphate, or ternary materials. The active material on the negative electrode can be, but is not limited to, graphite, lithium titanate, or silicon oxide.

[0069] A lithium replenisher refers to a substance that can replenish lithium ions within the battery 100. For example, when the electrode 10 is a negative electrode, the lithium replenisher may be, but is not limited to, lithium foil, lithium powder, or lithium silicide powder. When the electrode 10 is a positive electrode, the lithium replenisher may be, but is not limited to, Li2NiO2, Li5FeO4, or Li2O. Furthermore, the lithium replenisher may be formed in the lithium replenishment space 13 by rolling or deposition, with the deposition method including, but not limited to, magnetron sputtering deposition.

[0070] The lithium replenishment space 13 refers to a space on the current collecting structure 11 that can accommodate the lithium replenisher, such as a hole-shaped or groove-shaped structure; or a concave structure, etc. When the lithium replenishment space 13 is a concave structure on the current collecting structure 11, the surface of the current collecting structure 11 may be wavy. The active layer 12 has a plurality of distribution areas 14 on the side facing away from the current collecting structure 11, and the average weight of the active material per unit area in at least two distribution areas 14 is different. For example: after the edge of the electrode 10 is thinned, the average weight of the active material per unit area in the edge is generally less than the average weight of the active material in the distribution area 14 in the middle of the electrode 10. Among them, the factors affecting the average weight of the active material per unit area may be but are not limited to the type of active material, the thickness of the active material, the density of the active material, etc. Therefore, when setting the lithium replenishment space 13, using the average weight of the active material per unit area as a reference basis can more comprehensively consider the situations that affect the lithium replenishment effect, so that the amount of lithium replenishment is more accurate. For ease of understanding, Figure 3 For example, the thickness direction of the current collecting structure 11 is Figure 3 The direction indicated by any arrow in S.

[0071] The sum of the intrapore volumes of the lithium-replenishing spaces 13 encompassed by the projections of the distribution areas 14 along the thickness direction of the current collecting structure 11 should be understood as follows: within the same active layer 12, each distribution area 14, when projected along the thickness direction of the current collecting structure 11, can enclose a portion of the lithium-replenishing spaces 13, and the sum of the intrapore volumes of this portion of the lithium-replenishing spaces 13 is denoted as V0. The size of the intrapore volume of the lithium-replenishing spaces 13 determines the total amount of lithium replenishment corresponding to the corresponding distribution area 14. It should be noted that the size of the sum of the intrapore volumes of the lithium-replenishing spaces 13 corresponding to each distribution area 14 may be influenced by, but not limited to, the depth of the lithium-replenishing spaces 13, the opening area of ​​the lithium-replenishing spaces 13, and the distribution density of the lithium-replenishing spaces 13.

[0072] The lithium-replenishing space 13 being accessible to the active layer 12 means that one end of the lithium-replenishing space 13 is in communication with the active layer 12, and the lithium-replenishing agent in the lithium-replenishing space 13 can penetrate into the active layer 12 to achieve a lithium-replenishing effect. The lithium-replenishing space 13 can be accessible to the active layer 12 by, for example, opening a space on the side of the current collecting structure 11 facing the active layer 12 or extending one end of the lithium-replenishing space 13 into the interior of the active layer 12.

[0073] The sum of the volumes within the lithium replenishment spaces 13 refers to the total internal volumes of the multiple lithium replenishment spaces 13 corresponding to a distribution area 14. The volume of a single lithium replenishment space 13 can be determined in a variety of ways, such as first obtaining the opening area of ​​the lithium replenishment space 13, then obtaining the depth of the lithium replenishment space 13, and finally multiplying the opening area by the depth to obtain the volume of the single lithium replenishment space 13.

[0074] The shape of the lithium replenishing space 13 can be designed in a variety of ways, for example, it can be any one or more of circular, square, diamond, triangular, etc. At the same time, the opening area of ​​all the lithium replenishing spaces 13 can be consistent or inconsistent, for example, the opening area of ​​all the lithium replenishing spaces 13 is different. In order to make the lithium replenishment diffusion as uniform as possible, the opening area of ​​the lithium replenishing space 13 should be as small as possible. For example, when the lithium replenishing space 13 is circular or square, its diameter or width can be 5 microns (um) to 1 millimeter (mm). In some embodiments, the diameter or width of the lithium replenishing space 13 can be 30um to 200um, for example, the diameter or width of the lithium replenishing space 13 can be but not limited to 30um, 50um, 70um, 90um, 100um, 120um, 150um, 180um, 200um.

[0075] In the electrode 10 of the present application, the lithium replenishment space 13 can be provided on one side of the current collecting structure 11, or on both sides of the current collecting structure 11. If the lithium replenishment space 13 is provided on only one side of the current collecting structure 11, the electrode 10 has a one-side lithium replenishment effect.

[0076] A lithium replenishing space 13 is provided on the current collecting structure 11, so that the lithium replenishing space 13 is adjacent to the active layer 12 on one side; the lithium replenishing agent in the lithium replenishing space 13 is used to replenish lithium into the battery 100, thereby offsetting the irreversible lithium loss during the cycle, thereby improving the total capacity and energy density of the battery 100. A Therefore, the present application controls the sum of the pore volumes V0 of the lithium replenishment spaces 13 corresponding to each distribution area 14 in a positive correlation based on the average weight change of the active material in different distribution areas 14. That is, the sum of the volumes of the lithium replenishment spaces 13 corresponding to the second distribution area 14b is larger, while the sum of the volumes of the lithium replenishment spaces 13 corresponding to the first distribution area 14a is smaller. This method replenishes different lithium in different distribution areas 14, achieving quantitative and precise lithium replenishment. This avoids the problem of excessive lithium replenishment in the first distribution area 14a, which may lead to lithium deposition, or insufficient lithium replenishment in the second distribution area 14b, which may lead to capacity loss or less-than-expected lifespan improvement, under the premise of the same lithium replenishment amount. This is beneficial to improving the energy density and lifespan of the battery 100.

[0077] According to some embodiments of this application, please refer to Figure 4 The depth of the lithium replenishment space 13 is denoted as d. The thickness of the active layer 12 corresponding to the location of the lithium replenishment space 13 is denoted as h. Here, h in the first distribution region 14a is smaller than h in the second distribution region 14b, and d corresponding to the first distribution region 14a is smaller than d corresponding to the second distribution region 14b.

[0078] The thickness of the active layer 12 corresponding to the location of the lithium replenishing space 13 can be understood as: the location of the lithium replenishing space 13 is extended along the thickness direction of the current collecting structure 11 to the surface of the active layer 12, and the length of the path penetrating the active layer 12 is the corresponding thickness of the active layer 12.

[0079] When the thickness of the active layer 12 is used as a reference for the open space, it should be ensured as much as possible that the active layer 12 on one side of the current collecting structure 11 is made of the same type of active material and has the same density on the current collecting structure 11.

[0080] In different distribution areas 14 , with the thickness of the active layer 12 as a reference, the control of the sum of the volume parameters within the lithium replenishment space 13 is converted into the control of the depth of the lithium replenishment space 13 , which not only can achieve quantitative and precise lithium replenishment effects, but also simplifies the processing technology of the lithium replenishment space 13 and improves the production efficiency of the electrode 10 .

[0081] According to some embodiments of the present application, the depth d of the lithium replenishing space 13 satisfies the following relationship: Among them, C A is the initial lithium insertion capacity of the negative electrode active material, mAh / g, C C is the first lithium removal capacity of the positive electrode active material mAh / g, M C is the average weight of the active material per unit area of ​​the positive electrode, g / cm2 (g / cm 2 ), P is the ratio of the area of ​​all lithium-replenishing spaces 13 per unit area.

[0082] In the inequality, 3860 is the theoretical specific capacity of lithium metal, its unit is mAh / g; 0.534 is the density of lithium metal, its unit is g / cm3 (g / cm 3 ); 10000 is the unit conversion value. In addition, the proportion of the hole area of ​​all lithium-replenishing spaces 13 per unit area should be understood as: the ratio between the sum of the cross-sectional areas of all lithium-replenishing spaces 13 per unit area and "1".

[0083] During the lithium replenishment process, excessive lithium replenishment can easily lead to lithium deposition during the negative electrode cycle. Therefore, an upper limit must be set when designing the depth of the lithium replenishment space 13. Furthermore, if the depth of the lithium replenishment space 13 does not satisfy the aforementioned inequality during manufacturing, the depth of the lithium replenishment space 13 can be adjusted to meet the aforementioned inequality by increasing the average weight of the active material per unit area of ​​the negative electrode, for example by coating the corresponding distribution area 14 with the active material.

[0084] By setting an upper limit for the depth of the lithium replenishment space 13 , it is possible to avoid excessive lithium replenishment that may cause lithium deposition during the negative electrode cycle, thereby improving the safety performance of the battery 100 .

[0085] According to some embodiments of the present application, the proportion P of the opening area of ​​all lithium replenishing spaces 13 per unit area satisfies the following relationship: 10%≤P≤50%.

[0086] The ratio of the open area of ​​the lithium replenishing space 13 to the unit area should not be too large. If the ratio of the lithium replenishing space 13 is too large, it will result in a large number of hollow portions in the current collecting structure 11, seriously affecting its own electron conduction function. In some embodiments, the ratio P of the open area of ​​all lithium replenishing spaces 13 to the unit area can be, but is not limited to, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0087] The proportion P of the opening area of ​​all lithium replenishing spaces 13 per unit area is controlled between 10% and 50%. While ensuring that there is enough space to accommodate the lithium replenishing agent, the proportion of the opening area of ​​the lithium replenishing space 13 is reasonably controlled to ensure the stability of the electronic conduction function of the current collecting structure 11.

[0088] According to some embodiments of the present application, the depth d of the lithium replenishing space 13 satisfies the following relationship:

[0089]

[0090] Among them, CE C is the first coulombic efficiency of the positive electrode active material, CE A is the first coulombic efficiency of the negative electrode active material, C A It is the initial lithium insertion capacity of the negative electrode active material in mAh / g.

[0091] The first coulombic efficiency of the positive electrode active material is the ratio of the first lithium insertion capacity of the positive electrode active material in mAh / g to the first lithium removal capacity of the positive electrode active material in mAh / g. The first coulombic efficiency of the negative electrode active material is the ratio of the first lithium removal capacity of the negative electrode active material in mAh / g to the first lithium insertion capacity of the negative electrode active material in mAh / g. The first lithium removal capacity can be tested by preparing a button battery, for example: the positive and negative electrodes are prepared into slurries according to conventional formulas, the electrode sheet 10 is coated on one side, and the small discs are cut into button batteries, which are then combined with a lithium metal sheet to form a button battery half-cell. The positive electrode plate is tested at a charge and discharge rate of 0.1C / 0.1C. The positive electrode material is charged first and then discharged. The first charge capacity is the first lithium de-lithiation capacity of the positive electrode active material, and the first discharge capacity is the first lithium insertion capacity of the positive electrode active material. The negative electrode plate is tested at a charge and discharge rate of 0.1C / 0.05C. The negative electrode material is discharged first and then charged. The first discharge capacity is the first lithium insertion capacity of the negative electrode active material, and the first charge capacity is the first lithium de-lithiation capacity of the negative electrode active material.

[0092] When the depth d of the lithium replenishing space 13 is greater than or equal to When the depth d is increased, the capacity of the positive electrode active material can be fully utilized, effectively improving the capacity and energy density of the battery 100. At the same time, as the depth d further increases, the amount of lithium replenishment also increases. Although the capacity of the positive electrode active material has reached its limit and will not increase further at this point, the cycle life can be effectively improved.

[0093] The depth d of the lithium replenishing space 13 satisfies the following conditions: and less than or equal to When the lithium replenishment effect of the battery 100 is better. If the depth d of the lithium replenishment space 13 cannot simultaneously meet the requirements of being greater than or equal to and less than or equal to When the depth d of the lithium replenishing space 13 is controlled to be less than or equal to Of course, in this case, the depth d of the lithium replenishing space 13 can be controlled to satisfy the above two inequalities at the same time by increasing the average weight of the active material per unit area of ​​the negative electrode.

[0094] By setting a lower limit value of the depth of the lithium replenishing space 13 , the lithium replenishing space 13 can be filled with a lithium replenishing agent (such as metallic lithium, etc.), thereby fully utilizing the capacity of the positive electrode active material and effectively improving the energy density.

[0095] According to some embodiments of this application, please refer to Figure 4 In the active layer 12 on at least one side, the lithium replenishing spaces 13 are arranged at intervals, and the distance between any two adjacent lithium replenishing spaces 13 is equal.

[0096] The spacing between any two adjacent lithium-supplementing spaces 13 is equal, which can be understood as follows: the lithium-supplementing spaces 13 on one side of the current collecting structure 11 are evenly spaced, that is, the distribution density of the lithium-supplementing spaces 13 is constant. At this time, the sum of the volumes of the lithium-supplementing spaces 13 corresponding to each distribution area 14 mainly depends on the depth of the lithium-supplementing spaces 13. In this way, when controlling V0 and M A The changing relationship between can be effectively converted into the changing relationship between d and h.

[0097] In at least one side of the active layer 12 , it means that in the electrode 10 of the present application, only one side of the active layer 12 may have a plurality of lithium replenishing spaces 13 ; of course, a plurality of lithium replenishing spaces 13 may also be provided on the active layers 12 on both sides.

[0098] In the active layer 12 on either side, the lithium replenishment spaces 13 are evenly distributed, so that quantitative and precise lithium replenishment can be achieved simply by controlling the depth of the lithium replenishment spaces 13. At the same time, the lithium replenishment spaces 13 are evenly arranged to facilitate uniform diffusion of lithium replenishment, thereby improving the performance of the battery 100.

[0099] According to some embodiments of this application, please refer to Figure 4The current collecting structure 11 includes at least one current collector 11a along the thickness direction of the current collecting structure 11. In the current collector 11a provided with the active layer 12, at least one lithium supplementing space 13 is provided through it.

[0100] The current collector 11a refers to a component or part that can not only carry active materials, but also collect and output the current generated by the electrode active materials. It is the core structure of the current collecting structure 11. The number of current collectors 11a can be one or more. When there is one current collector 11a, the two active layers 12 are arranged on the opposite sides of the same current collector 11a; when there are multiple current collectors 11a, the two active layers 12 are respectively arranged on the current collectors 11a located at the outermost ends in the thickness direction of the current collecting structure 11. In addition, when there are multiple current collectors 11a, the multiple current collectors 11a are stacked along the thickness direction of the current collecting structure 11.

[0101] The lithium-replenishing space 13 can be designed in various ways on the current collector 11a. For example, when there is only one current collector 11a, the lithium-replenishing space 13 extending through the current collector can extend toward a single side. Alternatively, a portion of the lithium-replenishing space 13 can extend toward one active layer 12, while another portion can extend toward the other active layer 12. When there are multiple current collectors 11a, only one current collector 11a can be provided with the lithium-replenishing space 13 extending toward the corresponding active layer 12. Alternatively, both outermost current collectors 11a can be provided with the lithium-replenishing space 13.

[0102] Designing the current collecting structure 11 to be at least one current collector 11 a not only facilitates electron conduction but also makes it easy to open holes in the current collecting structure 11 so that the lithium replenishing agent can be stably deposited in the lithium replenishing space 13 .

[0103] According to some embodiments of this application, please refer to Figure 4 The current collectors 11a include two active layers 12, which are respectively disposed on opposite sides of the two current collectors 11a. A lithium replenishing space 13 is provided through each of the two current collectors 11a.

[0104] When the lithium-replenishing spaces 13 extend through the two current collectors 11a, one end of the lithium-replenishing spaces 13 on each current collector 11a extends into the interior of the corresponding active layer 12. The lithium-replenishing spaces 13 can be distributed in various ways on the current collectors 11a. For example, the lithium-replenishing spaces 13 can be evenly distributed on the current collectors 11a. Alternatively, the distribution density of the lithium-replenishing spaces 13 can be varied based on the thickness of the active layer 12, e.g., more lithium-replenishing spaces 13 can be distributed under a thick active layer 12, while fewer lithium-replenishing spaces 13 can be distributed under a thin active layer 12.

[0105] There are various distribution correspondences between the lithium-replenishing spaces 13 on the two current collectors 11a. For example, the distribution of the lithium-replenishing spaces 13 on one current collector 11a is completely staggered with that on the other current collector 11a, meaning the lithium-replenishing spaces 13 on one side are not connected to the lithium-replenishing spaces 13 on the other side. Alternatively, the distribution of the lithium-replenishing spaces 13 on one current collector 11a is completely aligned with that on the other current collector 11a, meaning the lithium-replenishing spaces 13 on one side remain connected to the lithium-replenishing spaces 13 on the other side. When the lithium-replenishing spaces 13 on the two current collectors 11a remain connected to each other, the lithium-replenishing agent in the lithium-replenishing spaces 13 on the two current collectors 11a can be shared, meaning the lithium-replenishing agent in the lithium-replenishing spaces 13 on one side can be used to replenish lithium in the active layer 12 on the other side.

[0106] The connection between the two current collectors 11a can be, but is not limited to, welding or bonding. For example, during the manufacturing process, two current collectors 11a coated with the active layer 12 are bonded together with their sides having the lithium replenishment space 13. After bonding, the circumferential edges of the two current collectors 11a are connected by welding or bonding.

[0107] A lithium replenishment space 13 is provided through each of the two current collectors 11 a , so that the active layers 12 on both sides can be effectively replenished with lithium, further improving the energy density and cycle life of the battery 100 .

[0108] According to some embodiments of this application, please refer to Figure 4 The current collecting structure 11 further includes at least one lithium replenishing layer 15. The lithium replenishing layer 15 is located between the two current collectors 11a.

[0109] The lithium replenishing layer 15 refers to a material that can replenish lithium ions into the battery 100. For example, when the electrode 10 is a negative electrode, the lithium replenishing layer 15 can be, but is not limited to, a metal lithium layer. When the electrode 10 is a positive electrode, the lithium replenishing layer 15 can be, but is not limited to, Li2NiO2, Li5FeO4, Li2O, etc.

[0110] There can be one or more lithium replenishing layers 15 between the two current collectors 11a. When there are two lithium replenishing layers 15, one lithium replenishing layer 15 is attached to the side of one current collector 11a facing away from the active layer 12; and the other lithium replenishing layer 15 is attached to the side of the other current collector 11a facing away from the active layer 12.

[0111] At least one lithium replenishing layer 15 is provided between the two current collectors 11 a to increase the amount of lithium replenishment, thereby effectively improving the cycle life of the battery 100 .

[0112] According to some embodiments of this application, please refer to Figure 4 The lithium replenishing space 13 is a lithium replenishing hole 13 a. The lithium replenishing hole 13 a extends along the thickness direction of the current collecting structure 11 into the active layer 12 on either side.

[0113] The lithium replenishing hole 13a extends into the active layer 12 along the thickness direction of the current collecting structure 11. It should be understood that one end of the lithium replenishing hole 13 is located inside the active layer 12 and does not penetrate the active layer 12, that is, it is similar to a blind hole structure.

[0114] The lithium replenishment space 13 is designed as a lithium replenishment hole 13a, and one end of the lithium replenishment hole 13a is extended into the interior of the active layer 12. This not only helps to simplify the manufacturing process of the electrode 10, but also helps to control the corresponding lithium replenishment dosage under different distribution areas 14, thereby achieving more accurate lithium replenishment.

[0115] According to some embodiments of this application, please refer to Figure 4 The first distribution area 14a extends around the periphery of the second distribution area 14b.

[0116] The first distribution area 14a is relatively close to the edge of the pole piece 10, and the second distribution area 14b is relatively close to the middle of the pole piece 10; at the same time, the first distribution area 14a is a linear ring structure.

[0117] The average weight M of the active material near the edge of the electrode 10 A Less than the average weight M of the active material near the middle of the electrode 10 A Such a design is helpful in solving the problem of bulging edges of the pole piece 10 due to excessive thickness.

[0118] According to some embodiments of this application, please refer to Figure 5 A method for manufacturing a pole piece 10 comprises the following steps:

[0119] S100 , providing two single-sided pole pieces 1610 , wherein the single-sided pole piece 1610 includes a current collector 11 a and an active layer 12 provided on one side of the current collector 11 a ;

[0120] S200, on at least one single-sided electrode 1610, a lithium replenishing hole 13a extending into the active layer 12 is opened in the current collector 11a, and the average weight M of the active material per unit area in at least two distribution areas 14 on the active layer 12 is controlled. A The sum of the volume V0 of the corresponding lithium supplement pores 13a satisfies: M in the first distribution area 14a A Smaller than M in the second distribution area 14b A , and V0 corresponding to the first distribution area 14a is smaller than V0 corresponding to the second distribution area 14b, wherein the distribution area 14 includes the first distribution area 14a and the second distribution area 14b;

[0121] S300, depositing lithium replenishing agent in all lithium replenishing holes 13a;

[0122] S400 , attaching the two single-sided electrode pieces 1610 , whose sides are facing away from the active layer 12 , to each other.

[0123] In step S100, the single-sided pole piece 1610 can be roughly understood as half of the structure of the pole piece 10, that is, it includes a current collector 11a and an active layer 12 coated on one side of the current collector 11a. At this time, the other side of the current collector 11a is not coated with the active layer 12. The manufacturing process of the single-sided pole piece 1610 may not be included in the pole piece 10 manufacturing method of the present application, and may be directly completed by the supplier or by other processes; of course, the manufacturing process of the single-sided pole piece 1610 may also be included in the pole piece 10 manufacturing method of the present application, for example: an active material is coated on one side of the current collector 11a; after coating, the current collector 11a is rolled (cold pressed) to compact the powder to rearrange and densify it. In addition, in order to avoid thick edges at the edges of the single-sided pole piece 1610, the edges of the single-sided pole piece 1610 are thinned. At this time, the average weight of the active material in different distribution areas 14 on the active layer 12 is different.

[0124] In step S200 , there are many ways to punch holes in the current collector 11 a , such as laser drilling, roller pinning, etc.

[0125] In step S300, when depositing the lithium replenishing agent in the lithium replenishing pores 13a, the lithium replenishing agent should be deposited completely within the pores 13a, i.e., the lithium replenishing agent in the pores should be flush with the end of the pores 13a on the current collector 11a. The lithium replenishing agent can be deposited by, but is not limited to, lithium ribbon rolling, magnetron sputtering, and other methods.

[0126] In step S400, the two single-sided electrode sheets 1610 are bonded together on one side facing away from the active layer 12. This can be understood as the perforated single-sided electrode sheets 1610 being bonded together on one side. Thus, during subsequent electrode assembly fabrication, the active layers 12 on the single-sided electrode sheets 1610 face the isolation member (e.g., diaphragm).

[0127] The required electrode 10 is produced by laminating the electrode 10 in a unidirectional manner, which greatly simplifies the production process. At the same time, it is also convenient to open holes in the electrode 10 to ensure that the lithium replenisher is stably deposited in the lithium replenishing holes 13a, so as to achieve a quantitative and accurate lithium replenishing effect. ATherefore, the present application controls the sum of the intrapore volumes (V0) of the lithium-replenishing pores 13a corresponding to each distribution region 14 in a positive correlation with the average weight change of the active material in each distribution region 14. Specifically, the sum of the intrapore volumes (V0) of the lithium-replenishing pores 13a corresponding to the second distribution region 14b is relatively large, while the sum of the intrapore volumes of the lithium-replenishing pores 13a corresponding to the first distribution region 14a is relatively small. This allows for quantitative and precise lithium replenishment of different lithium-replenishing amounts in different distribution regions 14. This avoids the problem of excessive lithium replenishment in the first distribution region 14a (e.g., thinned areas) and lithium deposition, or insufficient lithium replenishment in the second distribution region 14b (e.g., large surface areas) under the same lithium replenishment amount, resulting in capacity loss or less-than-expected lifespan improvement. This helps improve the energy density and lifespan of the battery 100.

[0128] According to some embodiments of this application, please refer to Figure 6 S200, controlling the average weight M of active material per unit area in different distribution areas 14 on the active layer 12 A The step of changing in a positive correlation with the sum V0 of the pore volumes of the corresponding lithium replenishing pores 13a comprises:

[0129] S210, obtaining the thickness h of the active layer 12 in different distribution areas 14,

[0130] S220, uniformly forming a plurality of lithium replenishing holes 13a on the current collector 11a;

[0131] S230, controlling the depth d of the lithium replenishing pores 13a in the projected area of ​​each distribution area 14 on the current collector 11a, so that h in the first distribution area 14a is smaller than h in the second distribution area 14b, and the corresponding d in the first distribution area 14a is smaller than the corresponding d in the second distribution area 14b.

[0132] In step S220, the uniform distribution of the lithium supplement pores 13a should be understood as: the distance between any two adjacent lithium supplement pores 13a is equal. Since the sum of the pore volumes of the lithium supplement pores 13a corresponding to each distribution area 14 is affected by factors such as, but not limited to, the depth of the lithium supplement pores 13a and the distribution density of the lithium supplement pores 13a, the distribution density of the lithium supplement pores 13a is controlled to be constant. In this case, the sum of the pore volumes of the lithium supplement pores 13a corresponding to each distribution area 14 mainly depends on the depth of the lithium supplement pores 13a. In this way, when controlling V0 and M A The changing relationship between can be effectively converted into the changing relationship between d and h.

[0133] Taking the thickness of the active layer 12 as a reference, the control of the sum of the pore volumes of the lithium replenishing pores 13a is converted into the control of the pore depth of the lithium replenishing pores 13a. This not only achieves a quantitative and precise lithium replenishment effect, but also simplifies the processing technology of the lithium replenishing pores 13a and improves the manufacturing efficiency of the electrode 10.

[0134] According to some embodiments of the present application, the depth d of the lithium replenishing hole 13a satisfies the following relationship:

[0135]

[0136] Among them, C A is the initial lithium insertion capacity of the negative electrode active material mAh / g, C C is the first lithium removal capacity of the positive electrode active material mAh / g, M C is the average weight of the active material per unit area of ​​the positive electrode g / cm 2 , P is the proportion of the pore area of ​​all lithium replenishing pores 13a per unit area on the current collecting structure 11.

[0137] During the lithium replenishment process, excessive lithium replenishment can easily lead to lithium deposition during the negative electrode cycle. Therefore, an upper limit must be set when designing the depth of the lithium replenishment pores 13a. Furthermore, if the depth of the lithium replenishment pores 13a does not satisfy the aforementioned inequality during manufacturing, the depth of the lithium replenishment pores 13a can be adjusted to satisfy the aforementioned inequality by increasing the average weight of the active material per unit area of ​​the negative electrode, for example by coating the corresponding distribution area 14 with the active material.

[0138] By setting an upper limit for the depth of the lithium replenishing hole 13 a , it is possible to avoid excessive lithium replenishment that may cause lithium deposition during the negative electrode cycle, thereby improving the safety performance of the battery 100 .

[0139] According to some embodiments of the present application, the depth d of the lithium replenishing hole 13a satisfies the following relationship:

[0140]

[0141] Among them, CE C is the first coulombic efficiency of the positive electrode active material, CE A is the first coulombic efficiency of the negative electrode active material, C A It is the initial lithium insertion capacity of the negative electrode active material in mAh / g.

[0142] When the depth d of the lithium replenishing hole 13a is greater than or equal to When the depth d is increased, the capacity of the positive electrode active material can be fully utilized, effectively improving the capacity and energy density of the battery 100. At the same time, as the depth d further increases, the amount of lithium replenishment also increases. Although the capacity of the positive electrode active material has reached its limit and will not increase further at this point, the cycle life can be effectively improved.

[0143] The depth d of the lithium replenishing hole 13a satisfies the following conditions: and less than or equal to When the lithium replenishment effect of the battery 100 is better. and less than or equal to When the depth d of the lithium replenishing hole 13a is controlled to be less than or equal to Of course, in this case, the depth d of the lithium replenishing pores 13 a can be controlled to simultaneously satisfy the above two inequalities by increasing the average weight of the active material per unit area of ​​the negative electrode.

[0144] By setting a lower limit of the depth of the lithium replenishing pores 13a, the lithium replenishing pores 13a can be filled with a lithium replenishing agent (such as metallic lithium), thereby fully utilizing the capacity of the positive electrode active material and effectively improving the energy density.

[0145] In order to make the purpose, technical solutions and advantages of this application more concise and clear, this application is illustrated with the following specific examples, but this application is by no means limited to these examples. The embodiments described below are only preferred embodiments of this application and can be used to describe this application. They should not be understood as limiting the scope of this application. It should be pointed out that any modifications, equivalent replacements and improvements made within the spirit and principles of this application should be included in the scope of protection of this application.

[0146] In order to better illustrate the present application, the present application is further described below in conjunction with the embodiments. The following are specific embodiments.

[0147] Under the same chemical system (ie, the current collector 11a of the positive and negative electrodes is of the same type), the influence of the depth d of the lithium replenishing hole 13a on the cycle number of the battery 100 is shown.

[0148] Comparative Example 1

[0149] Negative plate:

[0150] With high silicon as the negative electrode current collector 11a, the average weight of active material per unit area in the first distribution area 14a at the edge of the negative electrode is M A 0.0075g / cm 2 The average weight of active material per unit area in the second distribution area 14b at the edge of the negative electrode is M A 0.0100g / cm 2 , the initial lithium insertion capacity of the active material (charge gram capacity) C A It is 800mAh / g, and the first efficiency of the negative electrode (first discharge capacity / first charge capacity) is 80%.

[0151] The pore area ratio P of the lithium supplement pore 13a per unit area is set to 50%, according to According to the inequality, it is calculated that the depth d of the lithium replenishing hole 13a corresponding to the second distribution area 14b ranges from 7.8um to 13.6um, and the depth d of the lithium replenishing hole 13a corresponding to the first distribution area 14a ranges from 5.8um to 7.0um.

[0152] In this embodiment, the hole depth corresponding to the second distribution area 14b is designed to be 0 μm (i.e., no hole is punched), and the hole depth corresponding to the first distribution area 14a is designed to be 0 μm (i.e., no hole is punched). However, for the sake of comparison, the hole area proportion P of the lithium replenishment hole 13a in Comparative Example 1 is still recorded as 50%.

[0153] Positive electrode:

[0154] Taking NCM (ternary material composed of nickel, cobalt and manganese) as the positive electrode current collector 11a, the average weight of active material per unit area in the first distribution area 14a at the edge of the positive electrode is M C 0.0240g / cm 2 The average weight of active material per unit area in the second distribution area 14b at the edge of the positive electrode is M C 0.0300g / cm 2 , the initial lithium insertion capacity of the active material (charge gram capacity) C C It is 220mAh / g, and the first efficiency of the positive electrode (first discharge capacity / first charge capacity) is 90%.

[0155] Example 1

[0156] It is basically the same as Comparative Example 1, except that: in the negative electrode sheet, the case depth d of the lithium replenishing hole 13a corresponding to the second distribution area 14b is designed to be 10um, and the case depth d of the lithium replenishing hole 13a corresponding to the first distribution area 14a is designed to be 10um.

[0157] Example 2

[0158] It is basically the same as Comparative Example 1, with the only difference being that in the negative electrode sheet, the case depth d of the lithium replenishing hole 13a corresponding to the second distribution area 14b is designed to be 6.5um, and the case depth d of the lithium replenishing hole 13a corresponding to the first distribution area 14a is designed to be 6.5um.

[0159] Example 3

[0160] It is basically the same as Comparative Example 1, except that: in the negative electrode sheet, the case depth d of the lithium replenishing hole 13a corresponding to the second distribution area 14b is designed to be 10um, and the case depth d of the lithium replenishing hole 13a corresponding to the first distribution area 14a is designed to be 6.5um.

[0161] Some parameters of the embodiments and comparative examples are shown in Tables 1-1 and 1-2 below.

[0162] The battery 100 prepared in the comparative example and the embodiment was subjected to a room temperature cycle performance test, and the results are shown in Table 1-2. The specific test steps are as follows:

[0163] At 25°C, battery 100 is charged to 4.25V at a constant current of 1C, then charged to a current of 0.05C at a constant voltage, and then discharged to 2.8V at a constant current of 1C. This is the first cycle. Cyclic charge / discharge is performed according to the above conditions. The number of cycles of battery 100 is calculated when the capacity retention rate of battery 100 decays to 80%.

[0164] Table 1-1

[0165]

[0166] Table 1-2

[0167]

[0168] As shown in Tables 1-2, the battery 100 with lithium replenishment holes 13a in the electrode 10 significantly improves the positive electrode specific capacity compared to the battery 100 without holes in Comparative Example 1. Furthermore, the number of cycles to achieve 80% capacity retention is increased in Examples 2 and 3 compared to the battery 100 in Comparative Example 1. However, the number of cycles in Example 1 is reduced. This indicates that the depth of the lithium replenishment holes 13a is not necessarily greater as it increases; it must be less than or equal to the maximum depth of the different distribution regions 14. Excessive depth can easily lead to lithium deposition during cycling.

[0169] Comparison between Examples 1 and 2 and Example 3 shows that when the depth d of the lithium supplement hole 13a satisfies When the inequality is satisfied, the performance of the positive electrode capacity and the number of cycles of the battery 100 is optimal.

[0170] In addition, when the depth d of the lithium replenishing pores 13a changes in a positive correlation with different distribution areas 14, for example, the depth d in the second distribution area 14b is designed to be larger, and the depth d in the first distribution area 14a is designed to be smaller, the positive electrode capacity and cycle number of the battery 100 are the best.

[0171] In different chemical systems (ie, the current collector 11a of the positive and negative electrodes is of the same type), the influence of the depth d of the lithium replenishing hole 13a on the cycle number of the battery 100 is shown.

[0172] Comparative Example 2

[0173] It is basically the same as Comparative Example 1, with at least the following differences: in the negative electrode sheet, the pore area ratio P of the lithium replenishing pores 13a per unit area is recorded as 50%; the case depth d of the lithium replenishing pores 13a corresponding to the second distribution area 14b is designed to be 5um, and the case depth d of the lithium replenishing pores 13a corresponding to the first distribution area 14a is designed to be 4um.

[0174] Comparative Example 3

[0175] It is basically the same as Comparative Example 2, except that the case depth d of the lithium replenishing holes 13a corresponding to the second distribution area 14b is designed to be 20um, and the case depth d of the lithium replenishing holes 13a corresponding to the first distribution area 14a is designed to be 10um.

[0176] Comparative Example 4

[0177] It is basically the same as Comparative Example 1, with at least one difference being that in the negative electrode sheet, the negative electrode current collector 11a is low in silicon.

[0178] Comparative Example 5

[0179] It is basically the same as Comparative Example 1, with at least one difference being that in the negative electrode sheet, the negative electrode current collector 11a is graphite.

[0180] Comparative Example 6

[0181] It is basically the same as Comparative Example 1, with at least one difference: in the positive electrode sheet, the positive electrode current collector 11a is LFP (LiFePO4 lithium iron phosphate).

[0182] Example 4

[0183] It is basically the same as the above-mentioned embodiment 3, with at least the following differences: in the negative electrode sheet, the pore area ratio P of the lithium replenishing pores 13a per unit area is recorded as 30%; the case depth d of the lithium replenishing pores 13a corresponding to the second distribution area 14b is designed to be 15um, and the case depth d of the lithium replenishing pores 13a corresponding to the first distribution area 14a is designed to be 10.5um.

[0184] Example 5

[0185] It is basically the same as the above-mentioned embodiment 3, with at least the following differences: in the negative electrode sheet, the pore area ratio P of the lithium replenishing pores 13a per unit area is recorded as 10%; the case depth d of the lithium replenishing pores 13a corresponding to the second distribution area 14b is designed to be 40μm, and the case depth d of the lithium replenishing pores 13a corresponding to the first distribution area 14a is designed to be 31μm.

[0186] Example 6

[0187] It is basically the same as the above-mentioned embodiment 3, with at least the following differences: in the negative electrode sheet, the pore area ratio P of the lithium replenishing pores 13a per unit area is recorded as 70%; the case depth d of the lithium replenishing pores 13a corresponding to the second distribution area 14b is designed to be 7 μm, and the case depth d of the lithium replenishing pores 13a corresponding to the first distribution area 14a is designed to be 4.5 μm.

[0188] Example 7

[0189] The same as the above embodiment 3, the difference is at least that: the average weight of active material per unit area M in the first distribution area 14a at the edge of the negative electrode is A 0.0068g / cm 2 The average weight of active material per unit area in the second distribution area 14b at the edge of the negative electrode is M A 0.0090g / cm 2 The case depth d of the lithium replenishing holes 13a corresponding to the second distribution area 14b is designed to be 5 μm, and the case depth d of the lithium replenishing holes 13a corresponding to the first distribution area 14a is designed to be 1.0 μm.

[0190] Example 8

[0191] The same as the above embodiment 3, the difference is at least that: the average weight of active material per unit area M in the first distribution area 14a at the edge of the negative electrode is A 0.0120g / cm 2 The average weight of active material per unit area in the second distribution area 14b at the edge of the negative electrode is M A 0.0150g / cm 2 The case depth d of the lithium replenishing holes 13a corresponding to the second distribution area 14b is designed to be 25 μm, and the case depth d of the lithium replenishing holes 13a corresponding to the first distribution area 14a is designed to be 20.0 μm.

[0192] Example 9

[0193] It is basically the same as Comparative Example 4, with at least the following differences: in the negative electrode sheet, the pore area ratio P of the lithium replenishing pores 13a per unit area is recorded as 50%, the case depth d of the lithium replenishing pores 13a corresponding to the second distribution area 14b is designed to be 8 μm, and the case depth d of the lithium replenishing pores 13a corresponding to the first distribution area 14a is designed to be 5.0 μm.

[0194] Example 10

[0195] It is basically the same as Comparative Example 5, with at least the following differences: in the negative electrode sheet, the pore area ratio P of the lithium replenishing pores 13a per unit area is recorded as 50%, the case depth d of the lithium replenishing pores 13a corresponding to the second distribution area 14b is designed to be 7 μm, and the case depth d of the lithium replenishing pores 13a corresponding to the first distribution area 14a is designed to be 4.0 μm.

[0196] Example 11

[0197] It is basically the same as Comparative Example 6, with at least the following differences: in the negative electrode sheet, the pore area ratio P of the lithium replenishing pores 13a per unit area is recorded as 50%, the case depth d of the lithium replenishing pores 13a corresponding to the second distribution area 14b is designed to be 4.0 μm, and the case depth d of the lithium replenishing pores 13a corresponding to the first distribution area 14a is designed to be 3.0 μm.

[0198] Some parameters of the embodiments and comparative examples are shown in Table 2-1 and Table 2-2 below.

[0199] The battery 100 prepared in the above comparative example and embodiment was subjected to a room temperature cycle performance test, and the results are shown in Table 2-2.

[0200] Table 2-1

[0201]

[0202] As can be seen from Table 2-2, by comparing Examples 3 to 6 with Comparative Example 2, under the same chemical system, when the pore depth of the lithium-replenishing pore 13a satisfies the above two inequalities at the same time and the depth d varies with the thickness of the different distribution areas 14, the increase in the pore area ratio P of the lithium-replenishing pore 13a per unit area has little effect on the positive electrode gram capacity (that is, the positive electrode gram capacity has reached its limit and will not be increased any further), but will increase the number of cycles, that is, it can improve the cycle life of the battery 100.

[0203] Comparison of Examples 7 to 8 with Comparative Example 3 shows that when the depth of the lithium supplementing hole 13a cannot satisfy the above two inequalities at the same time, it is necessary to prioritize that the depth d of the lithium supplementing hole 13a satisfy less than or equal to At the same time, by increasing the average weight of active material per unit area of ​​the negative electrode M A , the pore depth d can be adjusted to satisfy the above two inequalities at the same time, and the positive electrode capacity and cycle number will be significantly improved.

[0204] It can be seen from Example 9 and Comparative Example 4, Example 10 and Comparative Example 5, and Example 11 and Comparative Example 6 that, regardless of the chemical system, when the depth d of the lithium replenishing pores 13a satisfies both of the above inequalities and the depth d varies positively with the thickness of the negative electrode active layer 12 in different distribution areas 14, the number of cycles of the battery 100 will be significantly improved, that is, the cycle life of the battery 100 can be effectively improved.

[0205] Table 2-2

[0206]

[0207] According to some embodiments of the present application, an electrode assembly is provided, comprising a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet and / or the negative electrode sheet is the electrode sheet 10 in any of the above solutions.

[0208] According to some embodiments of the present application, the present application provides a secondary battery 100 , which includes the electrode assembly in the above solution.

[0209] According to some embodiments of the present application, the present application provides an electric device, including the secondary battery 100 in the above solution.

[0210] According to some embodiments of the present application, the present application also provides a long-life negative electrode and a battery 100, which can achieve quantitative and accurate lithium replenishment and effectively control the amount of lithium replenishment to prevent mistakes. The specific implementation methods are as follows:

[0211] 1. Coating and cold pressing of single-sided negative electrode sheets;

[0212] 2. The single-sided negative electrode sheet is punched with holes of different depths in different areas by laser drilling, roller pinning, etc.

[0213] 3. Directed deposition of metallic lithium in the pores by lithium ribbon rolling or magnetron sputtering deposition;

[0214] 4. The above-mentioned negative electrode sheets are stacked or wound in the order of "positive electrode / separator / single-sided negative electrode sheet / single-sided negative electrode sheet / separator / positive electrode" to form a battery 100, wherein between every two single-sided negative electrode sheets, the punched lithium-supplemented side is assembled together, and the side of the negative electrode active material faces the separator.

[0215] To achieve precise lithium replenishment control, the pore depth d in different areas of the negative electrode sheet must be designed to meet the following relationship:

[0216]

[0217] When the pore depth d meets the minimum value of formula 1-1, the lithium replenishment pore 13a is filled with metallic lithium, which can fully utilize the positive electrode's specific capacity and effectively improve the energy density. As the pore depth d further increases, the amount of lithium replenishment increases, and the positive electrode's specific capacity has reached its limit and will no longer increase, but the cycle life can be effectively improved.

[0218] At the same time, in order to avoid excessive lithium supplementation and lithium plating during the negative electrode cycle, the hole depth d in different areas of the negative electrode sheet must be designed to meet the following relationship:

[0219]

[0220] The pore depth d must satisfy both Equation 1-1 and Equation 1-2. When Equation 1-1 and Equation 1-2 cannot be satisfied at the same time, the pore depth d must first satisfy Equation 1-2 to avoid safety risks caused by lithium plating. In addition, by increasing the average weight of active material per unit area of ​​the negative electrode M A , the hole depth d can be adjusted to satisfy both Equation 1-1 and Equation 1-2.

[0221] 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 pole piece, characterized in that: include: Current collecting structure; Two active layers are respectively provided on two opposite sides of the current collecting structure along the thickness direction of the current collecting structure, and the current collecting structure is provided with a plurality of lithium replenishing spaces for accessing the active layer on one side, wherein the lithium replenishing spaces contain a lithium replenishing agent; In the distribution area on the active layer communicating with the lithium supplement space, the average weight of the active material per unit area of ​​the active layer is recorded as M A The sum of the volumes of the lithium replenishing space covered by the projection of the distribution area along the thickness direction of the current collecting structure is recorded as V0, and the distribution area includes at least the first distribution area and the second distribution area; M in the first distribution area A Less than M in the second distribution area A , and the V0 corresponding to the first distribution area is smaller than the V0 corresponding to the second distribution area, so that the lithium supplement dosage in the first distribution area is smaller than the lithium supplement dosage in the second distribution area.

2. The pole piece according to claim 1, characterized in that: The depth of the lithium replenishing space is recorded as d, and the thickness of the active layer corresponding to the position of the lithium replenishing space is recorded as h; h in the first distribution area is smaller than h in the second distribution area, and d corresponding to the first distribution area is smaller than d corresponding to the second distribution area.

3. The pole piece according to claim 2, characterized in that: The depth d of the lithium replenishing space satisfies the following relationship: ， is the initial lithium insertion capacity of the negative electrode active material mAh / g, is the first delithiation capacity of the positive electrode active material mAh / g, is the average weight of the active material per unit area of ​​the positive electrode g / cm 2 , P is the ratio of the opening area of ​​all lithium replenishing spaces per unit area on the current collecting structure.

4. The pole piece according to claim 3, characterized in that: The ratio P of the opening area of ​​all lithium replenishment spaces per unit area satisfies the following relationship: 10%≤P≤50%。 5. The pole piece according to claim 2, characterized in that: The depth d of the lithium replenishing space satisfies the following relationship: ， is the first coulombic efficiency of the positive electrode active material, is the first coulombic efficiency of the negative electrode active material, It is the initial lithium insertion capacity of the negative electrode active material in mAh / g.

6. The pole piece according to claim 2, characterized in that: In the active layer on at least one side, the lithium replenishing spaces are arranged at intervals, and the distance between any two adjacent lithium replenishing spaces is equal.

7. The pole piece according to claim 1, characterized in that: The current collecting structure includes at least one current collector along the thickness direction of the current collecting structure. Among the current collectors provided with the active layer, at least one is provided with the lithium replenishing space penetrating therethrough.

8. The pole piece according to claim 7, characterized in that: The current collecting structure includes two current collectors, the two active layers are respectively arranged on two side surfaces of the two current collectors facing away from each other, and the lithium replenishing space is penetrated through the two current collectors.

9. The pole piece according to claim 7, characterized in that: The current collecting structure further includes at least one lithium replenishing layer, and the lithium replenishing layer is located between the two current collectors.

10. The pole piece according to any one of claims 1 to 9, characterized in that: The lithium replenishing space is a lithium replenishing hole, and the lithium replenishing hole extends into the active layer on either side along the thickness direction of the current collecting structure.

11. The pole piece according to any one of claims 1 to 9, characterized in that: The first distribution area is extended around the periphery of the second distribution area.

12. A method for manufacturing a pole piece, characterized in that: The steps include: Step S100: providing two single-sided pole pieces, wherein the single-sided pole pieces include a current collector and an active layer provided on one side of the current collector; Step S200: On at least one of the single-sided electrodes, a lithium replenishing hole is formed on the current collector extending into the active layer, and the average weight M of the active material per unit area in at least two distribution areas on the active layer is controlled. A The sum of the pore volume V0 of the corresponding lithium-replenishing pores satisfies: M in the first distribution area A Smaller than M in the second distribution area A , and V0 corresponding to the first distribution area is smaller than V0 corresponding to the second distribution area, wherein the distribution area includes the first distribution area and the second distribution area; Step S300, depositing a lithium supplement agent in the lithium supplement holes so that the lithium supplement dosage in the first distribution area is smaller than the lithium supplement dosage in the second distribution area; Step S400: Laminating the two single-sided electrode sheets with their sides facing away from the active layer to each other.

13. The electrode manufacturing method according to claim 12, characterized in that: Step S200 includes: Step S210, obtaining the thickness h of the active layer in different distribution areas; Step S220, uniformly opening a plurality of lithium replenishing holes in the current collector; Step S230: Control the depth d of the lithium replenishing holes in the projected area of ​​each distribution area on the current collector so that h in the first distribution area is smaller than h in the second distribution area, and d corresponding to the first distribution area is smaller than d corresponding to the second distribution area.

14. The pole piece manufacturing method according to claim 13, characterized in that: The depth d of the lithium supplementation hole satisfies the following relationship: ， is the initial lithium insertion capacity of the negative electrode active material mAh / g, is the first delithiation capacity of the positive electrode active material mAh / g, is the average weight of the active material per unit area of ​​the positive electrode g / cm 2 , P is the proportion of the area of ​​all lithium-supplementing pores per unit area on the current collecting structure, and the current collecting structure includes the current collectors of the two single-sided pole pieces.

15. The pole piece manufacturing method according to claim 13 or 14, characterized in that: The depth d of the lithium supplementation hole satisfies the following relationship: ， is the first coulombic efficiency of the positive electrode active material, is the first coulombic efficiency of the negative electrode active material, It is the initial lithium insertion capacity of the negative electrode active material in mAh / g.

16. An electrode assembly, characterized in that: It includes a positive electrode sheet, a negative electrode sheet and a separator provided between the positive electrode sheet and the negative electrode sheet; The positive electrode sheet and / or the negative electrode sheet is the electrode sheet according to any one of claims 1 to 11.

17. A secondary battery, characterized in that: Comprising the electrode assembly according to claim 16.

18. An electrical device, characterized in that: The secondary battery according to claim 17 is included.

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