Positive pole piece, electrode assembly, battery and electric equipment

Abstract

The invention discloses a positive pole piece, an electrode assembly, a battery and electric equipment. The positive pole piece comprises a positive active layer; the positive electrode active layer comprises a first positive electrode active part, a middle positive electrode active part and a second positive electrode active part which are arranged in sequence; wherein the surface capacity of the middle positive electrode active part is smaller than the surface capacity of the first positive electrode active part and / or smaller than the surface capacity of the second positive electrode active part in the charge-discharge cycle process after the first time of the positive electrode plate. According to the invention, the surface capacity of the middle part is lower than the surface capacity of the edge part and the expansion degree of the middle part is lower than the expansion degree of the edge part in the charge-discharge cycle process after the first time of the positive pole piece, so that the lithium precipitation condition of the corresponding negative pole piece is reduced and / or relieved; and the diving risk caused by lithium precipitation in the later period of battery circulation is reduced, and the safety performance of the single battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a positive electrode sheet, an electrode assembly, a battery, and an electrical device. Background Art

[0002] As a new generation of green energy storage and conversion devices, batteries are widely used in fields such as portable electronic devices, electric vehicles, and aerospace. With the development and progress of battery technology, improving the energy density and endurance of batteries has become an important task in the industry. Lithium-ion batteries have received wide attention due to their high energy density, low cost, and long cycle life. However, at present, lithium-ion batteries still have the problem that the electrode sheet is prone to expand during the cycling process, resulting in a sudden drop in battery power, which has a great impact on the cycling performance and safety of the battery. The above statements are only used to provide background technical information related to the present application, and do not necessarily constitute prior art. Summary of the Invention

[0003] The main technical problem to be solved by the present application is that lithium-ion batteries still have the problem that the electrode sheet is prone to expand during the cycling process, resulting in a sudden drop in battery power, which has a great impact on the cycling performance and safety of the battery.

[0004] In a first aspect, an embodiment of the present application provides a positive electrode sheet, including:

[0005] A positive electrode current collector;

[0006] A positive electrode active layer disposed on at least one side of the positive electrode current collector along the thickness direction of the positive electrode current collector; the positive electrode active layer includes a positive electrode active material; along the TD direction of the positive electrode current collector, the positive electrode active layer includes a first positive electrode active part, an intermediate positive electrode active part, and a second positive electrode active part arranged in sequence;

[0007] Wherein, during the charge and discharge cycling process after the first time, the areal capacity of the intermediate positive electrode active part is less than the areal capacity of the first positive electrode active part and / or less than the areal capacity of the second positive electrode active part.

[0008] In the embodiment of the present application, by making the areal capacity of the middle part lower than that of the edge part during the charge and discharge cycling process after the first time, the expansion degree of the middle part is lower than that of the edge part, reducing and / or alleviating the occurrence of lithium plating on the corresponding negative electrode sheet, reducing the diving risk caused by lithium plating in the later stage of battery cycling, and improving the safety performance of the battery cell.

[0009] In some embodiments, the positive electrode active layer further includes a positive electrode lithium supplement material. During the initial state and the first charge-discharge cycle of the positive electrode sheet, based on the total mass of the positive electrode active layer, the content of the positive electrode lithium supplement material in the middle positive electrode active part is different from the content of the positive electrode lithium supplement material in the first positive electrode active part.

[0010] In the embodiments of the present application, by regulating the content of the positive electrode lithium supplement material in the middle part and the edge part of the positive electrode active layer, during the charge-discharge cycle after the first time of the positive electrode sheet, the areal capacity of the middle part is lower than that of the edge part, so as to reduce and / or alleviate the occurrence of lithium plating on the corresponding negative electrode sheet, reduce the diving risk caused by lithium plating in the later stage of battery cycling, and improve the safety performance of the battery cell. In addition, after the positive electrode lithium supplement material is consumed during the cycling process, corresponding pores are generated on the positive electrode active layer, which is beneficial to the electrolyte reflux during the cycling process and reduces the polarization phenomenon of the battery.

[0011] In some embodiments, the first positive electrode active part, the middle positive electrode active part, and the second positive electrode active part are all single-layer structures in which a positive electrode active material and a positive electrode lithium supplement material are mixed.

[0012] In the embodiments of the present application, the above three parts of the positive electrode active layer supplement the lithium content of each part through the added positive electrode lithium supplement material, and while reducing and / or alleviating the lithium plating of the corresponding negative electrode sheet, the cycling performance of the battery is improved.

[0013] In some embodiments, based on the total mass of the positive electrode active layer, the content of the positive electrode lithium supplement material in the middle positive electrode active part is greater than the content of the positive electrode lithium supplement material in the first positive electrode active part and / or greater than the content of the positive electrode lithium supplement material in the second positive electrode active part; during the initial state and the first charge-discharge cycle of the positive electrode sheet, the areal capacity of the middle positive electrode active part is greater than the areal capacity of the first positive electrode active part and / or greater than the areal capacity of the second positive electrode active part.

[0014] In the embodiments of the present application, by regulating the content of the positive electrode lithium supplement material in the middle part of the positive electrode active layer to be greater than the content of the positive electrode lithium supplement material in the edge part, during the initial state and the first charge-discharge cycle of the positive electrode sheet, the areal capacity of the middle part is higher than that of the edge part, which improves the energy density. During the charge-discharge cycle after the first time, due to the continuous consumption of the positive electrode lithium supplement material, the areal capacity of the part with a higher content of the positive electrode lithium supplement material during the initial state and the first charge-discharge cycle decreases instead, so as to realize that the areal capacity of the middle part is lower than that of the edge part, and reduce and / or alleviate the occurrence of lithium plating on the corresponding negative electrode sheet.

[0015] In some embodiments, the first positive electrode active part, the middle positive electrode active part, and the second positive electrode active part are all bilayer structures; the first positive electrode active part, the middle positive electrode active part, and the second positive electrode active part each include a bottom positive electrode active layer close to the positive electrode current collector and a top positive electrode active layer far from the positive electrode current collector; in the initial state of the positive electrode sheet and during the first charge-discharge cycle, based on the total mass of the positive electrode active layer, the content of the positive electrode active material in the bottom positive electrode active layer and the top positive electrode active layer is different.

[0016] In the embodiments of the present application, through the setting of the bilayer structure, it is possible to only change one of the layer structures, so that the content of the positive electrode active material in this single layer structure is reduced, and the other layer structure can remain unchanged. When reducing the swelling degree of the positive electrode sheet and reducing and / or slowing down the lithium deposition on the corresponding negative electrode sheet, it is beneficial for the overall positive electrode sheet to have good capacity, energy density, and cycle performance.

[0017] In some embodiments, both the bottom positive electrode active layer and the top positive electrode active layer are single-layer structures in which the positive electrode active material and the positive electrode lithium supplement material are mixed; in the initial state of the positive electrode sheet and during the first charge-discharge cycle, based on the total mass of the positive electrode active layer, the content of the positive electrode lithium supplement material in the bottom positive electrode active layer is greater than the content of the positive electrode lithium supplement material in the top positive electrode active layer.

[0018] In the embodiments of the present application, through the setting of the bilayer structure, it is possible to design the content of the positive electrode active material and the positive electrode lithium supplement material in each layer and each region according to the actual situation, improving the flexibility of the design; it is also possible to coat in layers, and each single-layer structure can be formed integrally, which is beneficial to reducing the production difficulty and improving the production efficiency.

[0019] In some embodiments, the thickness of the bottom positive electrode active layer of the middle positive electrode active part is greater than the thickness of the bottom positive electrode active layer of the first positive electrode active part and the thickness of the bottom positive electrode active layer of the second positive electrode active part, respectively.

[0020] In the embodiments of the present application, by increasing the thickness of the bottom structure in the middle part, since the proportion of the positive electrode lithium supplement material in the bottom structure is high, the content of the positive electrode lithium supplement material in the middle part is greater than the content of the positive electrode lithium supplement material in the first part and the second part, so that the areal capacity of the middle part is greater than the areal capacity of the first part and the second part during the first charge-discharge cycle. During the second charge-discharge cycle and subsequent multiple charge-discharge cycles, due to the consumption of the positive electrode lithium supplement material, the capacity provided by the positive electrode lithium supplement material decreases, so that the areal capacity of the middle part is lower than the areal capacity of the first part and the second part, thereby reducing the swelling degree of the middle part of the positive electrode sheet and reducing and / or slowing down the occurrence of lithium deposition on the corresponding negative electrode sheet.

[0021] In some embodiments, during the initial state and the first charge-discharge cycle of the positive electrode sheet, based on the total mass of the positive electrode active layer, the content of the positive electrode lithium supplement material in the bottom positive electrode active layer of the middle positive electrode active part is greater than the content of the positive electrode lithium supplement material in the first positive electrode active part and the content of the positive electrode lithium supplement material in the second positive electrode active part, respectively.

[0022] In the embodiments of the present application, by increasing the content of the positive electrode lithium supplement material in the bottom structure of the middle part, the areal capacity of the middle part during the first charge-discharge cycle is improved. And during the second charge-discharge cycle and subsequent multiple charge-discharge cycles, the areal capacity of the middle part is lower than that of the first part and the second part, thereby reducing the swelling degree of the middle part of the positive electrode sheet and reducing and / or slowing down the occurrence of lithium plating on the corresponding negative electrode sheet.

[0023] In some embodiments, both the bottom positive electrode active layer and the top positive electrode active layer are single-layer structures in which the positive electrode active material and the positive electrode lithium supplement material are mixed; during the initial state and the first charge-discharge cycle of the positive electrode sheet, based on the total mass of the positive electrode active layer, the content of the positive electrode lithium supplement material in the bottom positive electrode active layer is less than the content of the positive electrode lithium supplement material in the top positive electrode active layer.

[0024] In the embodiments of the present application, through the setting of the double-layer structure, the content of the positive electrode active material and the positive electrode lithium supplement material in each layer and each region can be designed layer by layer according to the actual situation, improving the flexibility of the design; and it can also be coated layer by layer, and each single-layer structure can be formed integrally, which is beneficial to reducing the production difficulty and improving the production efficiency.

[0025] In some embodiments, the thickness of the bottom positive electrode active layer of the middle positive electrode active part is less than the thickness of the bottom positive electrode active layer of the first positive electrode active part and the thickness of the bottom positive electrode active layer of the second positive electrode active part.

[0026] In the embodiments of the present application, by reducing the thickness of the bottom structure of the middle part, the thickness of the top structure of the middle part is increased. Since the proportion of the positive electrode lithium supplement material in the top structure is high, the content of the positive electrode lithium supplement material in the middle part is greater than the content of the positive electrode lithium supplement material in the first part and the second part, making the areal capacity of the middle part greater than that of the first part and the second part during the first charge-discharge cycle. During the second charge-discharge cycle and subsequent multiple charge-discharge cycles, due to the consumption of the positive electrode lithium supplement material, the capacity provided by the positive electrode lithium supplement material decreases, and the areal capacity of the middle part is lower than that of the first part and the second part, thereby reducing the swelling degree of the middle part of the positive electrode sheet and reducing and / or slowing down the occurrence of lithium plating on the corresponding negative electrode sheet.

[0027] In some embodiments, during the initial state and the first charge-discharge cycle of the positive electrode sheet, based on the total mass of the positive electrode active layer, the content of the positive electrode lithium supplement material in the top positive electrode active layer of the middle positive electrode active part is greater than the content of the positive electrode lithium supplement material in the top positive electrode active layer of the first positive electrode active part and the content of the positive electrode lithium supplement material in the top positive electrode active layer of the second positive electrode active part, respectively.

[0028] In the embodiments of the present application, by increasing the content of the positive electrode lithium supplement material in the top layer structure of the middle part, the areal capacity of the middle part during the first charge-discharge cycle is improved, and during the second charge-discharge cycle and subsequent multiple charge-discharge cycles, the areal capacity of the middle part is lower than that of the first part and the second part, thereby reducing the swelling degree of the middle part of the positive electrode sheet and reducing and / or slowing down the occurrence of lithium plating on the corresponding negative electrode sheet.

[0029] In some embodiments, the surfaces of the first positive electrode active part, the middle positive electrode active part, and the second positive electrode active part away from the positive electrode current collector are flush.

[0030] In the embodiments of the present application, when achieving a reduction in the areal capacity of the middle part of the positive electrode active layer, by making the surfaces of the three parts of the positive electrode active layer away from the positive electrode current collector flush, the lithium ion transmission paths of each part are close, further reducing and / or slowing down the occurrence of lithium plating on the corresponding negative electrode sheet.

[0031] In some embodiments, along the TD direction of the positive electrode current collector, the ratio of the width of the middle positive electrode active part to the width of the positive electrode active layer is 0.02 - 0.20, and can be optionally 0.05 - 0.1.

[0032] In the embodiments of the present application, by regulating the width ratio of the middle part of the positive electrode active layer, while reducing the swelling degree of the middle part of the positive electrode sheet and reducing and / or alleviating lithium plating on the corresponding negative electrode sheet, the battery has good capacity, charge-discharge efficiency, cycle service life, and safety.

[0033] In some embodiments, the positive electrode current collector includes a body part and a tab part. Along the TD direction of the positive electrode current collector, the body part includes a first positive electrode active part, a middle positive electrode active part, and a second positive electrode active part; the first positive electrode active part is arranged on one side of the middle positive electrode active part close to the tab part, and the second positive electrode active part is arranged on one side of the middle positive electrode active part away from the tab part; wherein the ratio of the width of the second positive electrode active part to the width of the positive electrode active layer is 0.3 - 0.7, and can be optionally 0.4 - 0.6.

[0034] In the embodiments of the present application, by adjusting the width ratio of each part of the positive electrode active layer, while reducing the swelling degree of the middle part of the positive electrode sheet and reducing and / or alleviating lithium plating on the corresponding negative electrode sheet, the battery has good capacity, charge-discharge efficiency, cycle life, and safety.

[0035] In some embodiments, the specific capacity of the positive electrode lithium supplementing material is greater than that of the positive electrode active material.

[0036] In the embodiments of the present application, since the specific capacity of the positive electrode lithium supplementing material is greater than that of the positive electrode active material, it is beneficial to improve the capacity and energy density of the positive electrode sheet and beneficial to improve the cycle performance of the battery.

[0037] In some embodiments, the positive electrode active material includes one or more of lithium iron phosphate, lithium manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium cobaltate, lithium nickelate, and lithium iron manganese.

[0038] In the embodiments of the present application, by using one or more of the above materials as the active material of the positive electrode active layer, it is beneficial to make the positive electrode sheet have good capacity and energy density.

[0039] In some embodiments, the positive electrode lithium supplementing material includes: Li 2 C x O y 、Li 2 MO 2 、Li 2 MO 3 、Li 5 Fe x M 1-x O 4 and Li 6 Mn y M 1-y O 4 one or more of them; wherein, M includes at least one of Ni, Mn, Cu, Fe, Cr, Mo, Zr, Si, and Ru, x = 0.5 - 1, y = 0.5 - 1.

[0040] In the embodiments of the present application, by using one or more of the above materials as the lithium supplementing material of the positive electrode active layer, it is beneficial to make the positive electrode sheet have good capacity and energy density.

[0041] In some embodiments, the positive electrode active layer only includes the positive electrode active material. Based on the total mass of the positive electrode active layer, the lithium content of the positive electrode active material in the middle positive electrode active part is less than the lithium content of the positive electrode active material in the first positive electrode active part and / or less than the lithium content of the positive electrode active material in the second positive electrode active part.

[0042] In the embodiments of the present application, the lithium content of the cathode active material in the middle cathode active part is less than that of the cathode active material in the first cathode active part and / or less than that of the cathode active material in the second cathode active part, so that the areal capacity of the middle cathode active part is less than that of the first cathode active part and / or less than that of the second cathode active part, so that the areal capacity of the middle part of the cathode electrode sheet is lower than that of the edge part, and the swelling degree of the middle part is lower than that of the edge part, reducing and / or alleviating the occurrence of lithium deposition on the corresponding anode electrode sheet, reducing the diving risk caused by lithium deposition in the later stage of battery cycling, and improving the safety performance of the battery cell.

[0043] In some embodiments, the cathode active layer comprises a mixture of at least two cathode active materials.

[0044] In the embodiments of the present application, by forming the cathode active layer with a mixture of at least two cathode active materials and adjusting the mass ratio of each cathode active material in the mixture in each region, it is possible to achieve that the areal capacity of the middle cathode active part is less than and / or less than the areal capacities of the first cathode active part and the second cathode active part. The implementation means is simple and easy to operate, and the effects of alleviating lithium deposition on the corresponding anode electrode sheet and improving the battery safety performance are good.

[0045] In some embodiments, one of the at least two cathode active materials is a layered lithium-containing transition metal oxide; optionally, the cathode active material further comprises one or more of lithium iron phosphate, lithium manganate, lithium nickel manganate, and lithium manganese iron phosphate.

[0046] In the embodiments of the present application, by using a layered lithium-containing transition metal oxide in one of the mixtures, it is possible to reduce the content of the layered lithium-containing transition metal oxide in the middle cathode active part, so that the content of the layered lithium-containing transition metal oxide in the middle cathode active part is less than that of other cathode active materials, and the areal capacity of the cathode active material in the middle cathode active part is reduced, thereby alleviating lithium deposition on the corresponding anode electrode sheet and improving the safety performance of the battery.

[0047] In some embodiments, the cathode active material of the cathode active layer is the same cathode active material; based on the total mass of the cathode active layer, the content of the cathode active material in the middle cathode active part is less than and / or less than the content of the cathode active material in the first cathode active part and the content of the cathode active material in the second cathode active part.

[0048] In the embodiments of the present application, by using a positive electrode active layer with the same positive electrode active material, the content of the positive electrode active material in the middle positive electrode active part is less than the content of the positive electrode active material in the first positive electrode active part and / or less than the content of the positive electrode active material in the second positive electrode active part, so that the degree of swelling in the middle part is lower than that in the edge part, reducing and / or alleviating the occurrence of lithium deposition on the corresponding negative electrode tab, reducing the risk of voltage drop caused by lithium deposition in the later stage of battery cycling, and improving the safety performance of the battery cell.

[0049] In a second aspect, an embodiment of the present application provides a battery, including the positive electrode tab provided in the second aspect. Since the battery provided in the embodiment of the present application includes any one of the electrode tabs provided in the first aspect, it has at least the same advantages as the electrode assembly.

[0050] In a third aspect, an embodiment of the present application provides an electrical device, including the battery provided in the second aspect, and the battery is used to provide electrical energy. Since the electrical device provided in the embodiment of the present application includes any one of the batteries provided in the second aspect, it has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0052] Figure 1 Schematic structural diagram of a vehicle provided in an embodiment of the present application;

[0053] Figure 2 Schematic exploded view of a battery provided in an embodiment of the present application;

[0054] Figure 3 Schematic exploded view of a battery cell provided in an embodiment of the present application;

[0055] Figure 4 Schematic structural diagram of a positive electrode tab provided in some embodiments of the present application;

[0056] Figure 5 For Figure 4 The first schematic structural diagram of the positive electrode tab shown in the thickness direction;

[0057] Figure 6 For Figure 4 The second schematic structural diagram of the positive electrode tab shown in the thickness direction;

[0058] Figure 7 For Figure 4The third schematic diagram of the positive electrode plate along the thickness direction as shown;

[0059] Figure 8 is Figure 4 The fourth schematic diagram of the positive electrode plate along the thickness direction as shown;

[0060] Figure 9 is Figure 4 The fifth schematic diagram of the positive electrode plate along the thickness direction as shown;

[0061] Figure 10 is Figure 4 The sixth schematic diagram of the positive electrode plate along the thickness direction as shown.

[0062] Explanation of the reference numerals in the drawings:

[0063] 1000 - vehicle, 100 - battery, 200 - controller, 300 - motor, 10 - box body, 20 - battery cell, 11 - first part, 12 - second part, 21 - end cover, 22 - housing, 23 - electrode assembly, 21a - electrode terminal, 23a - tab, 30 - positive electrode plate, 31 - positive current collector, 32 - positive active layer, 311 - body part, 312 - tab part, 321 - first positive active part, 323 - intermediate positive active part, 322 - second positive active part, 32a - bottom positive active layer, 32b - top positive active layer, W - width of the positive active layer, W 1 - width of the intermediate positive active part, W 2 - width of the second positive active part. Detailed implementation manners

[0064] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0065] The terms "first", "second", and "third" in this application are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", and "third" may explicitly or implicitly include at least one of such features. In the description of this application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined. All directional indications (such as up, down, left, right, front, back...) in the embodiments of this application are only used to explain the relative positional relationship, movement conditions, etc. between components in a specific posture (as shown in the drawings). If the specific posture changes, then the directional indication also changes accordingly. In addition, the terms "comprise" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that comprises a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0066] Referring to "embodiments" herein means that specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0067] Currently, most of the positive electrode plates adopt one-piece coating, and the same material is coated at each position of the electrode plate. During the cycling process of the battery, the expansion force received in the middle part of the positive electrode plate is large, and the electrolyte reflux is not timely, and the corresponding negative electrode plate is prone to lithium deposition, resulting in voltage drop or even safety risks, deteriorating the cycle life. In order to increase the battery capacity, in some solutions, a lithium supplement agent is also added to the positive electrode active layer. Since the specific capacity of the lithium supplement agent is relatively high and the deviation is greater than that of the conventional positive electrode active material, it is easy to cause instability of the CB (cell Balance, which refers to the excess capacity of the negative electrode over the positive electrode on the opposite side under the same conditions in the same stage) in the middle part of the electrode plate, further deteriorating the lithium deposition situation of the negative electrode plate.

[0068] In the embodiments of this application, by making the areal capacity of the middle part lower than that of the edge part and the expansion degree of the middle part lower than that of the edge part during the charge and discharge cycling process after the first time of the positive electrode plate, the occurrence of lithium deposition on the corresponding negative electrode plate is reduced and / or alleviated, the voltage drop risk caused by lithium deposition in the later stage of battery cycling is reduced, and the safety performance of the battery cell is improved.

[0069] The following will describe this application in detail with reference to the drawings and embodiments.

[0070] The battery disclosed in the embodiments of the present application can be used in electrical devices powered by the battery or various energy storage systems using the battery as an energy storage element. The electrical device can be, but is not limited to, a mobile phone, a tablet computer, a laptop computer, an electric toy, an electric tool, a battery car, an electric vehicle, a ship, a spacecraft, etc. Among them, the electric toy can include stationary or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric airplane toys, etc. The spacecraft can include airplanes, rockets, space shuttles, and spaceships, etc.

[0071] For the convenience of description in the following embodiments, a vehicle 1000, which is an electrical device in an embodiment of the present application, is taken as an example for illustration.

[0072] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of the vehicle provided by the embodiment of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc. A battery 100 is disposed inside the vehicle 1000. The battery 100 can be disposed at the bottom, head, or tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000. For example, the battery 100 can be used as the operating power source of the vehicle 1000. The vehicle 1000 can further include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, for the working power requirements during the start, navigation, and driving of the vehicle 1000.

[0073] In some embodiments of the present application, the battery 100 can not only be used as the operating power source of the vehicle 1000, but also be used as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0074] Please refer to Figure 2 , Figure 2Schematic exploded view of the battery provided by the embodiment of the present application. The battery 100 includes a box body 10 and battery cells 20, and the battery cells 20 are accommodated in the box body 10. Among them, the box body 10 is used to provide an accommodation space for the battery cells 20, and the box body 10 can adopt various structures. In some embodiments, the box body 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 are covered with each other, and the first part 11 and the second part 12 jointly define an accommodation space for accommodating the battery cells 20. The second part 12 may be a hollow structure with one end open, and the first part 11 may be a plate-like structure. The first part 11 is covered on the open side of the second part 12 so that the first part 11 and the second part 12 jointly define an accommodation space; the first part 11 and the second part 12 may also both be hollow structures with one side open, and the open side of the first part 11 is covered on the open side of the second part 12. Of course, the box body 10 formed by the first part 11 and the second part 12 may be in various shapes, such as a cylinder, a cuboid, etc.

[0075] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection means that there are both series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection together, and then the whole formed by the multiple battery cells 20 is accommodated in the box body 10; of course, the battery 100 may also be that multiple battery cells 20 are first connected in series, in parallel, or in a hybrid connection to form a battery module form, and then multiple battery modules are connected in series, in parallel, or in a hybrid connection to form a whole and are accommodated in the box body 10. The battery 100 may further include other structures. For example, the battery 100 may further include a busbar component for realizing electrical connection among the multiple battery cells 20.

[0076] Among them, each battery cell 20 may be a secondary battery or a primary battery; it may also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be in the shape of a cylinder, a flat body, a cuboid, or other shapes, etc.

[0077] Please refer to Figure 3 , Figure 3 Schematic exploded view of the battery cell provided by the embodiment of the present application. The battery cell 20 refers to the smallest unit that makes up the battery. As Figure 3 shown, the battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0078] The end cap 21 refers to a component that covers the opening of the housing 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the housing 22 to fit the housing 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy). In this way, the end cap 21 is not easily deformed when subjected to extrusion and collision, enabling the battery cell 20 to have higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used for electrical connection with the electrode assembly 23 to output or input the electrical energy of the battery cell 20. In some embodiments, a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold can also be provided on the end cap 21. The material of the end cap 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special restrictions on this. In some embodiments, an insulating member can also be provided on the inner side of the end cap 21. The insulating member can be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. Exemplarily, the insulating member can be plastic, rubber, etc.

[0079] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, the electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 is covered at the opening to form the internal environment of the battery cell 20. Without limitation, the end cap 21 and the housing 22 can also be integrated. Specifically, the end cap 21 and the housing 22 can first form a common connection surface before other components are inserted into the housing. When it is necessary to encapsulate the inside of the housing 22, the end cap 21 is then covered on the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the housing 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special restrictions on this.

[0080] The electrode assembly 23 is a component in the battery cell 100 where electrochemical reactions occur. The housing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or laminating a positive electrode sheet and a negative electrode sheet, and a separator is usually provided between the positive electrode sheet and the negative electrode sheet. The portions of the positive electrode sheet and the negative electrode sheet having active materials constitute the main body of the battery cell assembly, and the portions of the positive electrode sheet and the negative electrode sheet without active materials respectively constitute the electrode tabs. The positive electrode tab and the negative electrode tab may be located together at one end of the main body or separately at both ends of the main body. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the electrode tabs are connected to the electrode terminals to form a current loop.

[0081] Please refer to Figures 4 - 6 , Figure 4 which is a schematic structural diagram of the positive electrode sheet provided by some embodiments of the present application. Figure 5 It is Figure 4 the first schematic structural diagram of the positive electrode sheet shown in the thickness direction. Figure 6 It is Figure 4 the second schematic structural diagram of the positive electrode sheet shown in the thickness direction.

[0082] Refer to Figures 4 - 6 , embodiments of the present application provide a positive electrode sheet 30. The positive electrode sheet 30 includes a positive electrode current collector 31 and a positive electrode active layer 32. The positive electrode active layer 32 is provided on at least one side of the positive electrode current collector 31 along the thickness direction of the positive electrode current collector 31. The positive electrode active layer 32 includes a positive electrode active material. Along the TD direction of the positive electrode current collector 31, the positive electrode active layer 32 includes a first positive electrode active portion 321, an intermediate positive electrode active portion 323, and a second positive electrode active portion 322 arranged in sequence. Among them, during the charge and discharge cycles after the first time of the positive electrode sheet 30, the areal capacity of the intermediate positive electrode active portion 323 is less than the areal capacity of the first positive electrode active portion 321 and / or less than the areal capacity of the second positive electrode active portion 322.

[0083] Among them, the positive electrode plate 30, as an important component of the secondary battery, contains an active material that undergoes a reduction reaction during discharge. The positive electrode current collector 31 represents the metal substrate in the positive electrode plate 30 for attaching the active material. Taking a lithium-ion battery as an example, the positive electrode current collector 31 can be made of aluminum metal. The positive electrode active layer 32 represents a layered structure formed mainly of the positive electrode active material. In some embodiments, the positive electrode current collector 31 has a first surface and a second surface oppositely disposed along its thickness direction. In some embodiments, the positive electrode plate 30 may be provided with the positive electrode active layer 32 only on one side of the first surface or the second surface of the positive electrode current collector 31, or may be provided with a layer of the positive electrode active layer 32 on both sides of the first surface and the second surface of the positive electrode current collector 31. In some embodiments, the positive electrode active layer 32 can be directly provided on the surface of the positive electrode current collector 31. In some other embodiments, other functional layers may also be provided between the positive electrode active layer 32 and the positive electrode current collector 31. The positive electrode active material represents the active material that undergoes a reduction reaction during discharge. The positive electrode active material can be any known positive electrode active material for secondary batteries in the art. In some embodiments, in addition to the positive electrode active material, the positive electrode active layer 32 may further contain other additives, such as a binder, a conductive agent, etc., which are specifically set according to needs. The TD direction (Transverse Direction) represents the width direction of the positive electrode current collector 31. The areal capacity represents the discharge capacity of the active material layer per unit area, which is equal to the discharge capacity of the positive electrode active material layer divided by the area of the positive electrode active material layer. In some embodiments, the numerical unit of the areal capacity is mAh / cm 2 . In some embodiments, the lithium element content can be obtained by ICP (ICP, Inductive Coupled Plasma Emission Spectrometer) testing. In some embodiments, the surface of the positive electrode current collector 31 is flat, and the surfaces of the first positive electrode active portion 321, the intermediate positive electrode active portion 323, and the second positive electrode active portion 322 away from the surface of the positive electrode current collector 31 are also flat, which is beneficial to simplifying the manufacturing process and reducing the risk of battery performance deterioration. It can be understood that at least one of the surface of the positive electrode current collector 31 and the surfaces of the first positive electrode active portion 321, the intermediate positive electrode active portion 323, and the second positive electrode active portion 322 away from the surface of the positive electrode current collector 31 may be undulating, and can be specifically set according to the actual situation, and this application does not make any restrictions. In some embodiments, such as Figure 5As shown, by making the surface of the intermediate positive electrode active part 323 away from the positive electrode current collector 31 recessed with respect to the surface of the first positive electrode active part 321 away from the positive electrode current collector 31 and the surface of the second positive electrode active part 322 away from the positive electrode current collector 31, the areal capacity of the intermediate positive electrode active part 323 can be made smaller. In some embodiments, by increasing the proportion of other additives in the intermediate positive electrode active part 323, the surfaces of the first positive electrode active part 321, the intermediate positive electrode active part 323, and the second positive electrode active part 322 away from the positive electrode current collector 31 can be made flush (as Figure 6 shown), which is beneficial to reducing the active ion transport path and reducing the occurrence of lithium deposition on the corresponding negative electrode tab. In some embodiments, the additive can be a positive electrode lithium supplement material, a binder, a conductive agent, etc., which are specifically set according to needs. The lithium element in the positive electrode tab participates in the formation of the solid electrolyte interphase film of the negative electrode tab during the first charge-discharge cycle, resulting in irreversible lithium element consumption.

[0084] In the embodiments of the present application, by making the areal capacity of the middle part lower than that of the edge part and the expansion degree of the middle part lower than that of the edge part during the charge-discharge cycles after the first cycle of the positive electrode tab 30, the occurrence of lithium deposition on the corresponding negative electrode tab is reduced and / or alleviated, the diving risk caused by lithium deposition in the later stage of the battery charge-discharge cycle is reduced, and the safety performance of the battery cell is improved.

[0085] In some embodiments, the positive electrode active layer 32 further includes a positive electrode lithium supplement material. During the initial state and the first charge-discharge cycle of the positive electrode tab 30, based on the total mass of the positive electrode active layer 32, the content of the positive electrode lithium supplement material in the intermediate positive electrode active part 323 is different from the content of the positive electrode lithium supplement material in the first positive electrode active part 321.

[0086] Among them, the positive electrode lithium supplement material refers to a lithium-containing high specific capacity material added to the positive electrode active layer 32. In some embodiments, the positive electrode lithium supplement material can be mixed with the positive electrode active material, and among them, the positive electrode lithium supplement material can be uniformly mixed with the positive electrode active material. In some embodiments, the positive electrode lithium supplement material and the positive electrode active material can be arranged in layers. In some embodiments, the positive electrode lithium supplement material can be arranged in a layer close to the positive electrode current collector 31, and the positive electrode active material can be arranged in a layer away from the positive electrode current collector 31 with respect to the positive electrode lithium supplement material, which is beneficial to shortening the lithium ion transport path and improving the battery performance. Since the positive electrode lithium supplement material has a high specific capacity, it participates in the formation of the solid electrolyte interphase film of the negative electrode tab during the first charge-discharge cycle of the battery, reducing the loss of the positive electrode active material and being beneficial to the improvement of the electrode tab capacity. During the charge-discharge cycles after the first cycle, the positive electrode lithium supplement material is continuously consumed, resulting in a decrease in the areal capacity of the part with a higher content of the positive electrode lithium supplement material during the initial state and the first charge-discharge cycle.

[0087] In the embodiments of the present application, by regulating the content of the lithium - supplementing material for the positive electrode in the middle part and the edge part of the positive - electrode active layer 32, the areal capacity of the middle part is lower than that of the edge part during the charge - discharge cycles after the first cycle of the positive - electrode sheet 30, reducing and / or alleviating the occurrence of lithium deposition on the corresponding negative - electrode sheet, reducing the risk of voltage drop caused by lithium deposition in the later stage of the battery charge - discharge cycle, and improving the safety performance of the battery cell. In addition, after the lithium - supplementing material is consumed during the charge - discharge cycle, corresponding pores are generated on the positive - electrode active layer 32, which is beneficial to the electrolyte reflux during the cycle process and reduces the polarization phenomenon of the battery.

[0088] In some embodiments, referring to Figures 5 - 6 , the first positive - electrode active part 321, the middle positive - electrode active part 323, and the second positive - electrode active part 322 are all single - layer structures mixed with positive - electrode active material and lithium - supplementing material for the positive electrode.

[0089] Among them, the thicknesses of the three parts can be the same. By regulating the content of the positive - electrode active material in the middle part, the reduction of the areal capacity of the middle part is realized, which is beneficial to shortening the lithium - ion transport path in the middle part and reducing and / or slowing down the occurrence of lithium deposition on the corresponding negative - electrode sheet. In some cases, the positive - electrode active material and the lithium - supplementing material in the middle part can be reduced in the same proportion. In some cases, the content of the lithium - supplementing material can also be increased while reducing the content of the positive - electrode active material in the middle part.

[0090] In the embodiments of the present application, the above - mentioned three parts of the positive - electrode active layer 32 supplement the lithium content of each part through the added lithium - supplementing material for the positive electrode, reduce and / or alleviate the lithium deposition on the corresponding negative - electrode sheet, and improve the cycle performance of the battery.

[0091] In some embodiments, based on the total mass of the positive - electrode active layer 32, the content of the lithium - supplementing material for the positive electrode in the middle positive - electrode active part 323 is greater than the content of the lithium - supplementing material for the positive electrode in the first positive - electrode active part 321 and / or greater than the content of the lithium - supplementing material for the positive electrode in the second positive - electrode active part 322; during the initial state and the first charge - discharge cycle of the positive - electrode sheet 30, the areal capacity of the middle positive - electrode active part 323 is greater than the areal capacity of the first positive - electrode active part 321 and / or greater than the areal capacity of the second positive - electrode active part 322.

[0092] In the embodiments of the present application, by controlling the content of the positive electrode lithium supplement material in the middle part of the positive electrode active layer 32 to be greater than that in the edge part, during the initial state of the positive electrode sheet 30 and the first charge-discharge cycle, the areal capacity of the middle part is higher than that of the edge part, improving the energy density. During the charge-discharge cycles after the first one, due to the continuous consumption of the positive electrode lithium supplement material, the areal capacity of the part with a higher content of the positive electrode lithium supplement material during the initial state and the first charge-discharge cycle decreases instead, so that the areal capacity of the middle part is lower than that of the edge part, reducing and / or alleviating the occurrence of lithium deposition on the corresponding negative electrode sheet.

[0093] Please refer to Figure 7 , Figure 7 is Figure 4 the third schematic structural view of the positive electrode sheet along the thickness direction as shown.

[0094] In some embodiments, referring to Figure 7 , the first positive electrode active part 321, the middle positive electrode active part 323, and the second positive electrode active part 322 are all bilayer structures; the first positive electrode active part 321, the middle positive electrode active part 323, and the second positive electrode active part 322 all include a bottom positive electrode active layer 32a close to the positive electrode current collector 31 and a top positive electrode active layer 32b far from the positive electrode current collector 31; during the initial state of the positive electrode sheet 30 and the first charge-discharge cycle, based on the total mass of the positive electrode active layer 32, the contents of the positive electrode active materials in the bottom positive electrode active layer 32a and the top positive electrode active layer 32b are different.

[0095] Among them, the positive electrode active materials in each single-layer structure of the bilayer structure can be evenly distributed, and the contents of the positive electrode active materials in the two-layer structures are different. The contents of the positive electrode active materials in the bottom structures of the three parts can be the same or different, and the contents of the positive electrode active materials in the top structures of the three parts can be the same or different.

[0096] In the embodiments of the present application, through the setting of the bilayer structure, it is possible to only change one of the layer structures, so that the content of the positive electrode active material in this single-layer structure decreases, and the other layer structure can remain unchanged. While reducing the swelling degree of the positive electrode sheet 30 and reducing and / or slowing down lithium deposition on the corresponding negative electrode sheet, it is beneficial for the positive electrode sheet 30 to have good capacity, energy density, and cycle performance as a whole.

[0097] In some embodiments, the bottom positive electrode active layer 32a and the top positive electrode active layer 32b are both single-layer structures mixed with positive electrode active materials and positive electrode lithium replenishing materials; in the initial state of the positive electrode plate 30 and during the first charge and discharge cycle, based on the total mass of the positive electrode active layer 32, the content of positive electrode lithium replenishing materials in the bottom positive electrode active layer 32a is greater than the content of positive electrode lithium replenishing materials in the top positive electrode active layer 32b.

[0098] Wherein, the positive electrode active material and the positive electrode lithium replenishing material are uniformly mixed in each single layer structure of the double-layer structure, and the contents of the positive electrode active material and the positive electrode lithium replenishing material of the two layers are different. Wherein, the contents of the positive electrode lithium replenishing material of the bottom structure of the three parts can be the same, or the contents of the positive electrode lithium replenishing material of the bottom structure of the middle part can be greater than the contents of the positive electrode lithium replenishing material of the bottom structure of the first part and the second part, respectively. Wherein, the contents of the positive electrode lithium replenishing material of the top structure of the three parts can be the same, or the contents of the positive electrode lithium replenishing material of the bottom structure of the middle part can be greater than the contents of the positive electrode lithium replenishing material of the bottom structure of the first part and the second part, respectively. Wherein, the bottom structure can be a positive electrode lithium replenishing material layer, and the top structure can be a positive electrode active material layer. Since the content of the positive electrode lithium replenishing material in the bottom positive electrode active layer 32a is greater than the content of the positive electrode lithium replenishing material in the top positive electrode active layer 32b, during the first charge and discharge cycle of the battery, the surface capacity of the bottom positive electrode active layer 32a is greater than the surface capacity of the top positive electrode active layer 32b. During the charge and discharge cycles after the first time, due to the continuous consumption of the positive electrode lithium replenishing material, the surface capacity of the bottom positive electrode active layer 32a is smaller than the surface capacity of the top positive electrode active layer 32b.

[0099] In the embodiments of the present application, by setting up a double-layer structure, the content of positive electrode active materials and positive electrode lithium supplement materials in each layer and each region can be designed in layers according to actual conditions, thereby improving the flexibility of the design; it can also be coated in layers, and each single-layer structure can be formed as an integral whole, which is conducive to reducing production difficulty and improving production efficiency.

[0100] In some embodiments, see Figure 7 The thickness of the bottom positive electrode active layer 32a of the intermediate positive electrode active portion 323 is greater than the thickness of the bottom positive electrode active layer 32a of the first positive electrode active portion 321 and the thickness of the bottom positive electrode active layer 32a of the second positive electrode active portion 322.

[0101] Among them, the surface of the positive electrode current collector 31 can be flat. The thickness of the bottom layer structure in the middle part is greater than that of the bottom layer structures on both sides, increasing the areal capacity of the middle part, which is beneficial to improving the capacity and energy density of the middle part and enhancing the overall cycle performance of the battery. In addition, since the positive electrode lithium supplement material does not intercalate lithium after consumption, the capacity of the middle part is lower than that of the parts on both sides, further reducing and / or slowing down the occurrence of lithium deposition on the corresponding negative electrode tab. In some embodiments, during the process of coating to form a double-layer structure, the nuts in the central area of the lower layer of the double-layer coater can be appropriately raised so that the thickness of the bottom layer structure in the middle part is greater than that of the bottom layer structures on both sides. After double-layer coating, the surfaces of the top layer structures of the three parts away from the positive electrode current collector 31 are flush. Since each single-layer structure can be coated in one pass, the production difficulty is reduced. In some embodiments, the thicknesses of the bottom layer structures of the first part and the second part can be the same or different, as long as the thicknesses of both are less than the thickness of the bottom layer structure in the middle part.

[0102] In the embodiments of the present application, by increasing the thickness of the bottom layer structure in the middle part, since the proportion of the positive electrode lithium supplement material in the bottom layer structure is high, the content of the positive electrode lithium supplement material in the middle part is greater than the content of the positive electrode lithium supplement material in the first part and the second part, making the areal capacity of the middle part greater than that of the first part and the second part during the first charge-discharge cycle. During the second charge-discharge cycle and subsequent multiple charge-discharge cycles, due to the consumption of the positive electrode lithium supplement material, the capacity provided by the positive electrode lithium supplement material decreases, making the areal capacity of the middle part lower than that of the first part and the second part, thereby reducing the swelling degree of the middle part of the positive electrode tab 30 and reducing and / or slowing down the occurrence of lithium deposition on the corresponding negative electrode tab.

[0103] Please refer to Figure 8 , Figure 8 for Figure 4 the fourth schematic structural view of the positive electrode tab along the thickness direction shown in

[0104] In some embodiments, during the initial state and the first charge-discharge cycle of the positive electrode tab, based on the total mass of the positive electrode active layer 32, the content of the positive electrode lithium supplement material in the bottom positive electrode active layer 32a of the middle positive electrode active part 323 is greater than the content of the positive electrode lithium supplement material in the first positive electrode active part 321 and the content of the positive electrode lithium supplement material in the second positive electrode active part 322, respectively.

[0105] Among them, in some embodiments, referring to Figure 8 , the surfaces of each single-layer structure of the double-layer structure away from the positive electrode current collector 31 are all flush.

[0106] In an embodiment of the present application, by increasing the areal capacity of the middle part during the first charge-discharge cycle, and during the second and subsequent multiple charge-discharge cycles, the areal capacity of the middle part is lower than that of the first part and the second part, thereby reducing the swelling degree of the middle part of the positive electrode sheet 30 and reducing and / or alleviating the occurrence of lithium plating on the corresponding negative electrode sheet.

[0107] In some embodiments, both the bottom positive electrode active layer 32a and the top positive electrode active layer 32b are single-layer structures in which a positive electrode active material and a positive electrode lithium supplement material are mixed; during the initial state and the first charge-discharge cycle of the positive electrode sheet 30, based on the total mass of the positive electrode active layer 32, the content of the positive electrode lithium supplement material in the bottom positive electrode active layer 32a is less than the content of the positive electrode lithium supplement material in the top positive electrode active layer 32b.

[0108] Among them, in each single-layer structure of the double-layer structure, the positive electrode active material and the positive electrode lithium supplement material are uniformly mixed, and the contents of the positive electrode active material and the positive electrode lithium supplement material in the two layers are different. Among them, the contents of the positive electrode lithium supplement material in the bottom structures of the three parts can be the same or different, and it is necessary to satisfy that the content of the positive electrode lithium supplement material in the bottom structure of each part is less than the content of the positive electrode lithium supplement material in its top structure. Among them, the contents of the positive electrode lithium supplement material in the top structures of the three parts can be the same, or the content of the positive electrode lithium supplement material in the bottom structure of the middle part is respectively greater than the content of the positive electrode lithium supplement material in the bottom structures of the first part and the second part.

[0109] In an embodiment of the present application, through the setting of the double-layer structure, the contents of the positive electrode active material and the positive electrode lithium supplement material in each layer and each region can be designed in layers according to the actual situation, improving the flexibility of the design; it can also be coated in layers, and each single-layer structure can be integrally formed, which is beneficial to reducing the production difficulty and improving the production efficiency.

[0110] Please refer to Figure 9 , Figure 9 which is Figure 4 the fifth schematic structural diagram of the positive electrode sheet shown along the thickness direction.

[0111] In some embodiments, referring to Figure 9 , the thickness of the bottom positive electrode active layer 32a of the middle positive electrode active part 323 is less than the thickness of the bottom positive electrode active layer 32a of the first positive electrode active part 321 and the thickness of the bottom positive electrode active layer 32a of the second positive electrode active part 322.

[0112] Among them, the surface of the positive electrode current collector 31 can be flat, and the top layer structures of the three parts can also be flat away from the surface of the positive electrode current collector 31. The content of the positive electrode lithium supplement material in the bottom layer structure of each part is less than that in the top layer structure thereof, and the thickness of the bottom layer structure of the middle part is less than the thickness of the bottom layer structures on both sides thereof. That is to say, the proportion of the thickness of the top layer structure of the middle part is larger than the proportion of the thickness of the top layer structures of the first part and the second part. That is, the content of the positive electrode lithium supplement material in the middle part is greater than that in the first part and the second part, which is beneficial to improving the first charge-discharge capacity and energy density of the middle part and improving the overall cycle performance of the battery. In addition, since the positive electrode lithium supplement material does not intercalate lithium after consumption, the capacity of the middle part is lower than that of its two sides, further reducing and / or slowing down the occurrence of lithium deposition on the corresponding negative electrode tab. In some embodiments, during the process of coating to form a double-layer structure, the nuts in the central area of the lower layer of the double-layer coater can be appropriately lowered so that the thickness of the bottom layer structure of the middle part is less than the thickness of the bottom layer structures on both sides thereof. After double-layer coating, the surfaces of the top layer structures of the three parts away from the positive electrode current collector 31 are flush. Since each single-layer structure can be coated in one pass, the production difficulty is reduced. In some embodiments, the thicknesses of the bottom layer structures of the first part and the second part can be the same or different, as long as the thicknesses of both are greater than the thickness of the bottom layer structure of the middle part.

[0113] In the embodiments of the present application, reducing the thickness of the bottom layer structure of the middle part increases the thickness of the top layer structure of the middle part. Since the proportion of the positive electrode lithium supplement material in the top layer structure is high, the content of the positive electrode lithium supplement material in the middle part is greater than the content of the positive electrode lithium supplement material in the first part and the second part, so that the areal capacity of the middle part is greater than the areal capacity of the first part and the second part during the first charge-discharge cycle. In the second charge-discharge cycle and subsequent multiple charge-discharge cycles, due to the consumption of the positive electrode lithium supplement material, the capacity provided by the positive electrode lithium supplement material decreases, and the areal capacity of the middle part is lower than the areal capacity of the first part and the second part, thereby reducing the swelling degree of the middle part of the positive electrode tab 30 and reducing and / or slowing down the occurrence of lithium deposition on the corresponding negative electrode tab.

[0114] In some embodiments, referring to Figure 8 , during the initial state and the first charge-discharge cycle of the positive electrode tab 30, based on the total mass of the positive electrode active layer 32, the content of the positive electrode lithium supplement material in the top layer positive electrode active layer 32b of the middle positive electrode active part 323 is greater than the content of the positive electrode lithium supplement material in the top layer positive electrode active layer 32b of the first positive electrode active part 321 and the content of the positive electrode lithium supplement material in the top layer positive electrode active layer 32b of the second positive electrode active part 322, respectively.

[0115] Among them, in some embodiments, the surfaces of each single-layer structure of the double-layer structure away from the positive current collector 31 may be flush.

[0116] In the embodiments of the present application, by increasing the content of the positive electrode lithium supplement material in the top-layer structure of the middle part, the areal capacity of the middle part during the first charge and discharge cycle is improved, and during the second charge and discharge cycle and subsequent multiple charge and discharge cycles, the areal capacity of the middle part is lower than that of the first part and the second part, thereby reducing the degree of swelling of the middle part of the positive electrode plate 30 and reducing and / or slowing down the occurrence of lithium deposition on the corresponding negative electrode plate.

[0117] Please refer to Figure 10 , Figure 10 for Figure 4 the sixth schematic structural view of the positive electrode plate shown in the thickness direction.

[0118] In some embodiments, referring to Figure 10 , both the first positive electrode active part 321 and the second positive electrode active part 322 are single-layer structures; the middle positive electrode active part 323 is a double-layer structure, and the middle positive electrode active part 323 includes a bottom-layer positive electrode active layer 32a close to the positive current collector 31 and a top-layer positive electrode active layer 32b away from the positive current collector 31; based on the total mass of the positive electrode active layer 32, the contents of the positive electrode active materials in the bottom-layer positive electrode active layer 32a and the top-layer positive electrode active layer 32b are different.

[0119] In the embodiments of the present application, by only modifying the middle part of the positive electrode active layer 32 and keeping the formulations of the first part and the second part unchanged, it is beneficial for the battery to have good capacity.

[0120] In some embodiments, both the bottom-layer positive electrode active layer 32a and the top-layer positive electrode active layer 32b are single-layer structures mixed with positive electrode active materials and positive electrode lithium supplement materials; during the initial state and the first charge and discharge cycle of the positive electrode plate 30, based on the total mass of the positive electrode active layer 32, the content of the positive electrode active material in the top-layer positive electrode active layer 32b is less than that in the bottom-layer positive electrode active layer 32a; the content of the positive electrode lithium supplement material in the top-layer positive electrode active layer 32b is greater than that in the bottom-layer positive electrode active layer 32a.

[0121] In the embodiments of the present application, by only modifying the top-layer structure of the middle part of the positive electrode active layer 32, the first part, the bottom-layer structure of the middle part, and the second part can have the same formulation and can be integrally formed, which is beneficial for simplifying the manufacturing process and reducing the process difficulty.

[0122] In some embodiments, the surfaces of the first positive electrode active part 321, the middle positive electrode active part 323, and the second positive electrode active part 322 away from the positive current collector 31 are flush.

[0123] Among them, in some embodiments, the surface of the positive current collector 31 is flat, and the three parts of the positive active layer 32 away from the surface of the positive current collector 31 are flat, so that the three parts have the same thickness.

[0124] In the embodiments of the present application, when reducing the areal capacity of the middle part of the positive active layer 32, by making the surfaces of the three parts of the positive active layer 32 away from the positive current collector 31 flush, the lithium ion transmission paths of each part are close, further reducing and / or slowing down the occurrence of lithium deposition on the corresponding negative electrode tab.

[0125] In some embodiments, referring to Figure 4 , along the TD direction of the positive current collector 31, the width W of the middle positive active part 1 The ratio to the width W of the positive active layer is 0.02 to 0.20, and can be optionally 0.05 to 0.10.

[0126] In any implementation manner, along the TD direction of the positive current collector 31, the width W of the middle positive active part 1 The ratio to the width W of the positive active layer can be 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, or a range composed of any two of the above values. For example, along the TD direction of the positive current collector 31, the width W of the middle positive active part 1 The ratio to the width W of the positive active layer can be 0.02 - 0.05, 0.05 - 0.10, 0.10 - 0.15, or 0.15 - 0.20, etc.

[0127] In the embodiments of the present application, by adjusting the width ratio of the middle part of the positive active layer 32, while reducing the swelling degree of the middle part of the positive electrode tab 30 and reducing and / or alleviating lithium deposition on the corresponding negative electrode tab, the battery has good capacity, charge and discharge efficiency, cycle life, and safety.

[0128] In some embodiments, the positive current collector 31 includes a body part 311 and a tab part 312. Along the TD direction of the positive current collector 31, the body part 311 includes a first positive active part 321, a middle positive active part 323, and a second positive active part 322; the first positive active part 321 is arranged on one side of the middle positive active part 323 close to the tab part 312, and the second positive active part 322 is arranged on one side of the middle positive active part 323 away from the tab part 312; wherein the width W of the second positive active part 2 The ratio to the width W of the positive active layer is 0.3 - 0.7, and can be optionally 0.4 - 0.6.

[0129] In any embodiment, along the TD direction of the positive current collector 31, the width W of the second positive active part 2 The ratio to the width W of the positive active layer can be 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, or a range composed of any two of the above values. For example, along the TD direction of the positive current collector 31, the width W of the second positive active part 2 The ratio to the width W of the positive active layer can be 0.3 - 0.4, 0.4 - 0.6, or 0.6 - 0.7, etc. It can be understood that the width of the first positive active part 321 along the TD direction of the positive current collector 31 can be obtained by subtracting the width W of the middle positive active part and the width W of the second positive active part from the width W of the positive active layer 1 And the width W of the second positive active part 2 Calculated. In some embodiments, along the TD direction of the positive current collector 31, the width of the body part 311 is greater than the width W of the positive active layer. In some embodiments, an insulating layer is provided on one side edge of the body part 311, and the insulating layer is provided on the side of the positive active layer close to the tab part 312

[0130] In the embodiments of the present application, by regulating the width ratio of each part of the positive active layer 32, while reducing the swelling degree of the middle part of the positive electrode plate 30 and reducing and / or alleviating the lithium deposition on the corresponding negative electrode plate, the battery has good capacity, charge and discharge efficiency, cycle service life, and safety

[0131] In some embodiments, the specific capacity of the positive lithium supplement material is greater than the specific capacity of the positive active material

[0132] Wherein, the specific capacity represents the ratio of the capacitance released by the active substance inside the battery to the mass of the active substance

[0133] In the embodiments of the present application, since the specific capacity of the positive lithium supplement material is greater than the specific capacity of the positive active material, it is beneficial to improve the capacity and energy density of the positive electrode plate 30 and beneficial to improve the cycle performance of the battery

[0134] In some embodiments, the positive active material includes lithium iron phosphate (LiFePO 4 ), lithium manganate (LiMn 2 O 4 ), lithium nickel cobalt manganate (LiNi x Co y Mn1-x-y O 2 )), lithium nickel cobalt aluminate (LiNi x Co y Al 1-x-y O 2 ), lithium cobalt oxide (Lithium oxido(oxo)cobalt, LiCoO 2 ), lithium nickel oxide (LithiumNickel Oxide, LiNiO 2 ), lithium manganate (Lithium Manganate, LiMn 2 O 4 ), or one or more of them.

[0135] In the embodiments of the present application, by using one or more of the above materials as the active material of the positive electrode active layer 32, it is beneficial to make the positive electrode sheet 30 have good capacity and energy density.

[0136] In some embodiments, the positive electrode lithium supplement material includes: Li 2 C x O y , Li 2 MO 2 , Li 2 MO 3 , Li 5 Fe x M 1-x O 4 , and Li 6 Mn y M 1-y O 4 , or one or more of them; wherein, M includes at least one of Ni, Mn, Cu, Fe, Cr, Mo, Zr, Si, and Ru, x = 0.5 - 1, y = 0.5 - 1.

[0137] Among them, M in Li 2 MO 2 can be at least one of Ni, Mn, Cu, Fe, Cr, and Mo; M in Li 2 MO 3 can be at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr, and Ru; M in Li 5 Fe x M 1-x O 4 can be at least one of Al, Nb, Co, Mn, Ni, Mo, Ru, and Cr; M in Li 6 Mn y M 1-y O 4 can be at least one of Ni, Fe, Cu, and Ru.

[0138] In the embodiments of the present application, by using one or more of the above materials as the lithium supplement material of the positive electrode active layer 32, it is beneficial to enable the positive electrode sheet 30 to have good capacity and energy density.

[0139] In some embodiments, the positive electrode active layer 32 only includes the positive electrode active material. Based on the total mass of the positive electrode active layer 32, the lithium content of the positive electrode active material in the middle positive electrode active part 323 is less than the lithium content of the positive electrode active material in the first positive electrode active part 321 and / or less than the lithium content of the positive electrode active material in the second positive electrode active part 322.

[0140] In the embodiments of the present application, since the lithium content of the positive electrode active material in the middle positive electrode active part 323 is less than the lithium content of the positive electrode active material in the first positive electrode active part 321 and / or less than the lithium content of the positive electrode active material in the second positive electrode active part 322, the areal capacity of the middle positive electrode active part 323 is less than the areal capacity of the first positive electrode active part 321 and / or less than the areal capacity of the second positive electrode active part 322. The swelling degree of the middle part is lower than that of the edge part, reducing and / or alleviating the occurrence of lithium deposition on the corresponding negative electrode sheet, reducing the diving risk caused by lithium deposition in the later stage of the battery charge-discharge cycle, and improving the safety performance of the battery cell.

[0141] In some embodiments, the positive electrode active layer 32 includes a mixture of at least two positive electrode active materials.

[0142] Among them, the mixture means that the respective positive electrode active material particles included are uniformly mixed together and uniformly distributed in the positive electrode active material setting area of the positive electrode current collector 31.

[0143] In the embodiments of the present application, by forming the positive electrode active layer 32 from a mixture including at least two positive electrode active materials and adjusting the mass ratio of each positive electrode active material in the mixture in each region, it is possible to achieve that the areal capacity of the middle positive electrode active part is less than the areal capacity of the first positive electrode active part and / or less than the areal capacity of the second positive electrode active part. The implementation means is simple and easy to operate, and the effects of alleviating lithium deposition on the corresponding negative electrode sheet and improving the battery safety performance are good.

[0144] In some embodiments, one of the at least two positive electrode active materials is a layered lithium-containing transition metal oxide; optionally, the positive electrode active material further includes any one or more of lithium iron phosphate, lithium manganate, lithium nickel manganate, and lithium manganese iron phosphate.

[0145] Among them, the specific capacity of the layered lithium-containing transition metal oxide is higher than that of other positive electrode active materials (any one or more of lithium iron phosphate, lithium manganate, lithium nickel manganate, and lithium manganese iron phosphate). In some embodiments, the layered lithium-containing transition metal oxide can be lithium nickel cobalt manganate.

[0146] In an embodiment of the present application, one of the mixtures uses a layered lithium-containing transition metal oxide. By reducing the content of the layered lithium-containing transition metal oxide in the intermediate positive electrode active part 323, the content of the layered lithium-containing transition metal oxide in the intermediate positive electrode active part 323 is made less than the content of other positive electrode active materials, so that the areal capacity of the intermediate positive electrode active part 323 is reduced, thereby alleviating lithium plating on the corresponding negative electrode sheet and improving the safety performance of the battery.

[0147] Exemplarily, the positive electrode active layer 32 includes a mixture of lithium nickel cobalt manganese oxide and lithium iron phosphate, and a mixture of a layered lithium-containing transition metal oxide and lithium iron phosphate is uniformly coated in the respective regions of the first positive electrode active part 321, the intermediate positive electrode active part 323, and the second positive electrode active part 322, and the layered lithium-containing transition metal oxide and lithium iron phosphate in the mixture are uniformly mixed. Among them, the content of the layered lithium-containing transition metal oxide in the intermediate positive electrode active part 323 is lower than the content of lithium iron phosphate, the content of the layered lithium-containing transition metal oxide in the first positive electrode active part 321 is higher than the content of lithium iron phosphate, and the content of the layered lithium-containing transition metal oxide in the second positive electrode active part 322 is higher than the content of lithium iron phosphate, achieving that the areal capacity of the intermediate positive electrode active part 323 is less than the areal capacity of the first positive electrode active part 321 and / or less than the areal capacity of the second positive electrode active part 322, so that the degree of swelling of the middle part of the positive electrode sheet 30 is lower than that of the edge part, reducing and / or alleviating the occurrence of lithium plating on the corresponding negative electrode sheet, reducing the diving risk caused by lithium plating in the later stage of battery charge and discharge cycles, and improving the safety performance of the battery cell.

[0148] In some embodiments, the positive electrode active material of the positive electrode active layer 32 is the same positive electrode active material; based on the total mass of the positive electrode active layer 32, the content of the positive electrode active material in the intermediate positive electrode active part 323 is less than the content of the positive electrode active material in the first positive electrode active part 321 and / or less than the content of the positive electrode active material in the second positive electrode active part 322.

[0149] In an embodiment of the present application, by using the positive electrode active layer 32 with the same positive electrode active material, the content of the positive electrode active material in the intermediate positive electrode active part 323 is less than the content of the positive electrode active material in the first positive electrode active part 321 and / or less than the content of the positive electrode active material in the second positive electrode active part 322, so that the degree of swelling of the middle part is lower than that of the edge part, reducing and / or alleviating the occurrence of lithium plating on the corresponding negative electrode sheet, reducing the diving risk caused by lithium plating in the later stage of battery cycling, and improving the safety performance of the battery cell.

[0150] The beneficial effects of the present application are further described below in conjunction with embodiments.

[0151] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of the present application clearer, the following will further elaborate in detail in conjunction with the embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of them. The following description of at least one exemplary embodiment is actually only illustrative and in no way constitutes any limitation to the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present application.

[0152] Embodiment 1:

[0153] Mix the positive electrode active material (lithium iron phosphate), conductive agent (CNT), and binder (PVDF) evenly according to a mass ratio of 96.8:1:2.2. Then add NMP as a solvent and stir under a vacuum mixer until the system becomes homogeneous to obtain the positive electrode paste. Directly coat the positive electrode paste on the surface of the positive electrode current collector 31 and cold press to obtain the positive electrode plate 30. During the forming process, the middle part of the positive electrode plate 30 is recessed inward from both sides (the first part and the second part) of this middle part. Its configuration is shown in Figure 5 , and along the TD direction, the width W 1 of the middle positive electrode active part to the width W of the positive electrode active layer has a ratio of 0.1; the width W 2 of the second positive electrode active part to the width W of the positive electrode active layer has a ratio of 0.45; the areal capacity of the middle part is 4.17 mAh / cm 2 , and the areal capacity of the other parts is 4.22 mAh / cm 2 . Stack the positive electrode plate 30, separator, and negative electrode plate in sequence, with the separator placed in the middle of the positive and negative electrodes to play a role in isolation, and wind them to obtain a bare battery cell. Place the bare battery cell in an outer package, inject electrolyte, and encapsulate to obtain a battery monomer.

[0154] Embodiment 2:

[0155] The difference between this embodiment and Embodiment 1 is that: the positive electrode plate 30 further includes a positive electrode lithium supplement material (Li 5 FeO 4 ), and its mass ratio to the positive electrode active material (lithium iron phosphate) is 5.1:94.9, and the rest are the same as in Embodiment 1.

[0156] Embodiment 3:

[0157] The difference between this embodiment and Embodiment 2 is that: the areal capacity of the middle part is 4.05 mAh / cm 2 , and the rest are the same as in Embodiment 2.

[0158] Embodiment 4:

[0159] The difference between this embodiment and Embodiment 2 is that the areal capacity of the middle part is 4.19 mAh / cm 2 , and the rest are the same as Embodiment 2.

[0160] Embodiment 5:

[0161] The difference between this embodiment and Embodiment 2 is that the ratio of the width W of the middle positive electrode active part 1 to the width W of the positive electrode active layer is 0.2, and the ratio of the width W of the second positive electrode active part 2 to the width W of the positive electrode active layer is 0.4, and the rest are the same as Embodiment 2.

[0162] Embodiment 6:

[0163] The difference between this embodiment and Embodiment 5 is that the surfaces of the three parts of the positive electrode tab 30 away from the positive electrode current collector 31 are flush, and the content of the positive electrode active material in the middle part of the positive electrode tab 30 is less than that in the first part and the second part respectively. During the first charge-discharge cycle, the content of the positive electrode lithium supplement material in the middle part is greater than that in the first part and the second part respectively. For its configuration, see Figure 6 , and the rest are the same as Embodiment 5.

[0164] Embodiment 7:

[0165] The difference between this embodiment and Embodiment 5 is that as Figure 7 shown, the three parts of the positive electrode tab 30 are all double-layer structures, and the formulations of the bottom-layer structures of the three parts are the same, the formulations of the top-layer structures of the three parts are the same, and the thickness of the bottom-layer structure of the middle part is greater than that of the bottom-layer structures of the first part and the second part respectively, and the areal capacity of the positive electrode lithium supplement material in the bottom-layer structure is greater than that of the positive electrode lithium supplement material in its respective top-layer structure, and the rest are the same as Embodiment 5.

[0166] Embodiment 8:

[0167] The difference between this embodiment and Embodiment 5 is that as Figure 9 shown, the three parts of the positive electrode tab 30 are all double-layer structures, and the formulations of the bottom-layer structures of the three parts are the same, the formulations of the top-layer structures of the three parts are the same, and the thickness of the bottom-layer structure of the middle part is less than that of the bottom-layer structures of the first part and the second part respectively, and the areal capacity of the positive electrode lithium supplement material in the bottom-layer structure is less than that of the positive electrode lithium supplement material in its respective top-layer structure, and the rest are the same as Embodiment 5.

[0168] Embodiment 9:

[0169] The difference between this embodiment and Embodiment 5 is that as Figure 8As shown, the three parts of the positive electrode plate 30 are all double-layer structures, and the formulations of the bottom-layer structures of the three parts are the same. The content of the positive active material in the top-layer structure of the middle part is less than that in the first part and the second part. During the first charge-discharge cycle, the content of the positive lithium supplement material in the top-layer structure of the middle part is greater than that in the first part and the second part, and the rest are the same as in Example 5.

[0170] Comparative Example 1:

[0171] The difference between this comparative example and Example 1 is that in this comparative example, the positive active layer is not partitioned, the formulations of all parts are the same, and the thicknesses of all parts are the same, and the rest are the same as in Example 1.

[0172] The battery monomers 20 prepared in each example and comparative example were tested:

[0173] The positive electrode plate was cut along the boundary between the middle part and the edge part of the positive electrode plate 30 to cut out the middle part and the edge part of the positive electrode plate 30, and small round pieces of the same size were punched out in the corresponding areas of the middle part and the edge part respectively, and the mass, area and thickness of the corresponding areas were measured. Then the small round pieces punched out from the middle part and the edge part were assembled into batteries respectively. In a constant temperature environment of 25°C, discharge at 1 / 3C to 2.5V; stand for 5 minutes, charge at 1 / 3C to 4.35V, and then perform constant voltage charging at 4.35V until the current ≤ 0.05C; stand for 5 minutes, and then discharge at 1 / 3C to 2.5V, and the electric quantity during this discharge process is the discharge capacity. The compaction density is obtained by dividing the mass of the corresponding area by the product of the area and the thickness; the areal capacity is obtained by dividing the discharge capacity by the area of the corresponding area.

[0174] The battery monomers 20 in the examples and comparative examples were taken, and at least 2 parallel samples were ensured for each example. First, the battery monomers 20 were placed in a constant temperature environment of 25°C and left for 1 hour. Then, the battery monomers 20 were charged at a constant current at a charging rate of 2C. After charging to 3.65V, the charging was changed to constant voltage charging, and the charging was stopped when the charging current was lower than 0.05C. After standing for 5 minutes, the battery was discharged at a constant current at a discharge rate of 1C to 2.5V, and after standing for 5 minutes, the above process was charged and discharged 1000 cycles. The calculation of the cycle retention rate: The capacity retention rate of the 1000th cycle = the discharge capacity of the 1000th cycle / the discharge capacity of the second cycle * 100%. After the battery monomers were subjected to 1000-cycle charge-discharge tests in the above manner, the battery monomers 20 were disassembled, the negative electrode plates were taken out, and whether lithium deposition occurred in the middle part of the negative electrode plates was observed.

[0175] Table 1 Performance test results of the battery monomers in the examples and comparative examples

[0176]

[0177] Note: The areal capacity of the middle part and the areal capacity of the edge part of the electrode sheet in Table 1 both refer to the areal capacity of the second circle.

[0178] It can be seen from the results that:

[0179] (1) From the test data of Comparative Example 1 and Example 1, it can be seen that the areal capacity of the middle part of the positive electrode sheet is lower than that of the edge part. For the corresponding negative electrode sheet, no central lithium deposition occurs, and the cycle performance of the battery is significantly improved.

[0180] (2) From the test data of Examples 1-2, it can be seen that: by adding a lithium supplement material to the positive electrode sheet, the cycle performance of the battery is significantly improved.

[0181] (3) From the test data of Examples 2-4, it can be seen that: as the areal capacity of the middle part of the positive electrode sheet decreases, the capacity of the battery decreases accordingly, and the cycle performance first increases and then decreases. Therefore, when processing the positive electrode sheet, the areal capacity of the middle part of the positive electrode sheet should be regulated to balance the capacity and cycle performance of the battery to a greater extent.

[0182] (4) From the test data of Example 2 and Example 5, it can be seen that: within the set range, the width of the middle part of the positive electrode sheet has little effect on the capacity and cycle performance of the battery.

[0183] (5) From the test data of Examples 5-6, it can be seen that: the surface of the positive electrode sheet far from the positive current collector is flat. Compared with the scheme where the middle part of the positive electrode sheet is sunken, the cycle performance of the battery is significantly improved.

[0184] (6) From the test data of Example 5 and Example 7, it can be seen that: the thickness of the bottom layer structure of the middle part of the positive electrode sheet is greater than the thickness of the bottom layer structures on both sides. Compared with the scheme where the middle part of the positive electrode sheet is sunken, the cycle performance of the battery is significantly improved.

[0185] (7) From the test data of Example 5 and Example 8, it can be seen that: the thickness of the bottom layer structure of the middle part of the positive electrode sheet is less than the thickness of the bottom layer structures on both sides. Compared with the scheme where the middle part of the positive electrode sheet is sunken, the cycle performance of the battery is significantly improved.

[0186] (8) From the test data of Example 5 and Example 9, it can be seen that: the areal capacity of the top layer structure of the middle part is less than the areal capacity of both sides. During the first charge-discharge cycle, the content of the positive lithium supplement material in the middle part is greater than the content of the positive lithium supplement materials on both sides. Compared with the scheme where the middle part of the positive electrode sheet is sunken, the cycle performance of the battery is significantly improved.

[0187] In several embodiments provided by the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces, and the indirect couplings or communication connections of devices or units can be in electrical, mechanical, or other forms.

[0188] In addition, each functional unit in various embodiments of the present application can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0189] The above is only the implementation manner of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A positive electrode plate, characterized in that, it includes: a positive electrode current collector; a positive electrode active layer disposed on at least one side of the positive electrode current collector along the thickness direction of the positive electrode current collector; the positive electrode active layer includes a positive electrode active material; along the TD direction of the positive electrode current collector, the positive electrode active layer includes a first positive electrode active part, an intermediate positive electrode active part, and a second positive electrode active part arranged in sequence; wherein, during the charge-discharge cycle after the first time of the positive electrode plate, the areal capacity of the intermediate positive electrode active part is less than the areal capacity of the first positive electrode active part and / or less than the areal capacity of the second positive electrode active part.

2. The positive electrode plate according to claim 1, characterized in that, the positive electrode active layer further includes a positive electrode lithium supplement material; in the initial state and during the first charge-discharge cycle of the positive electrode plate, based on the total mass of the positive electrode active layer, the content of the positive electrode lithium supplement material in the intermediate positive electrode active part is different from the content of the positive electrode lithium supplement material in the first positive electrode active part.

3. The positive electrode plate according to claim 2, characterized in that, the first positive electrode active part, the intermediate positive electrode active part, and the second positive electrode active part are all single-layer structures mixed with a positive electrode active material and a positive electrode lithium supplement material.

4. The positive electrode plate according to claim 3, characterized in that, based on the total mass of the positive electrode active layer, the content of the positive electrode lithium supplement material in the intermediate positive electrode active part is greater than the content of the positive electrode lithium supplement material in the first positive electrode active part and / or greater than the content of the positive electrode lithium supplement material in the second positive electrode active part; in the initial state and during the first charge-discharge cycle of the positive electrode plate, the areal capacity of the intermediate positive electrode active part is greater than the areal capacity of the first positive electrode active part and / or greater than the areal capacity of the second positive electrode active part.

5. The positive electrode plate according to claim 2, characterized in that, the first positive electrode active part, the intermediate positive electrode active part, and the second positive electrode active part are all double-layer structures; the first positive electrode active part, the intermediate positive electrode active part, and the second positive electrode active part all include a bottom positive electrode active layer close to the positive electrode current collector and a top positive electrode active layer far from the positive electrode current collector; in the initial state and during the first charge-discharge cycle of the positive electrode plate, based on the total mass of the positive electrode active layer, the content of the positive electrode lithium supplement material in the bottom positive electrode active layer and the top positive electrode active layer is different.

6. The positive electrode plate according to claim 5, characterized in that, the bottom positive electrode active layer and the top positive electrode active layer are both single-layer structures mixed with a positive electrode active material and a positive electrode lithium supplement material; in the initial state and during the first charge-discharge cycle of the positive electrode plate, based on the total mass of the positive electrode active layer, the content of the positive electrode lithium supplement material in the bottom positive electrode active layer is greater than the content of the positive electrode lithium supplement material in the top positive electrode active layer.

7. The positive electrode plate according to claim 6, characterized in that, the thickness of the bottom positive electrode active layer of the intermediate positive electrode active part is respectively greater than the thickness of the bottom positive electrode active layer of the first positive electrode active part and the thickness of the bottom positive electrode active layer of the second positive electrode active part.

8. The positive electrode sheet according to claim 6, wherein, during the initial state and the first charge-discharge cycle of the positive electrode sheet, based on the total mass of the positive electrode active layer, the content of the lithium supplement material in the bottom positive electrode active layer of the intermediate positive electrode active part is greater than the content of the lithium supplement material in the positive electrode active part of the first positive electrode active part and the content of the lithium supplement material in the positive electrode active part of the second positive electrode active part, respectively.

9. The positive electrode sheet according to claim 5, wherein, both the bottom positive electrode active layer and the top positive electrode active layer are single-layer structures in which a positive electrode active material and a lithium supplement material are mixed; during the initial state and the first charge-discharge cycle of the positive electrode sheet, based on the total mass of the positive electrode active layer, the content of the lithium supplement material in the bottom positive electrode active layer is less than the content of the lithium supplement material in the top positive electrode active layer.

10. The positive electrode sheet according to claim 9, wherein, the thickness of the bottom positive electrode active layer of the intermediate positive electrode active part is less than the thickness of the bottom positive electrode active layer of the first positive electrode active part and the thickness of the bottom positive electrode active layer of the second positive electrode active part.

11. The positive electrode sheet according to claim 9, wherein, during the initial state and the first charge-discharge cycle of the positive electrode sheet, based on the total mass of the positive electrode active layer, the content of the lithium supplement material in the top positive electrode active layer of the intermediate positive electrode active part is greater than the content of the lithium supplement material in the top positive electrode active layer of the first positive electrode active part and the content of the lithium supplement material in the top positive electrode active layer of the second positive electrode active part, respectively.

12. The positive electrode sheet according to any one of claims 1-11, wherein, the surfaces of the first positive electrode active part, the intermediate positive electrode active part, and the second positive electrode active part away from the positive electrode current collector are flush.

13. The positive electrode sheet according to any one of claims 1-11, wherein, along the TD direction of the positive electrode current collector, the ratio of the width of the intermediate positive electrode active part to the width of the positive electrode active layer is 0.02 to 0.20, and can be selected as 0.05 to 0.

1.

14. The positive electrode sheet according to any one of claims 1-11, wherein, the positive electrode current collector includes a main body part and a tab part. Along the TD direction of the positive electrode current collector, the main body part includes the first positive electrode active part, the intermediate positive electrode active part, and the second positive electrode active part; the first positive electrode active part is arranged on one side of the intermediate positive electrode active part close to the tab part, and the second positive electrode active part is arranged on one side of the intermediate positive electrode active part away from the tab part; wherein the ratio of the width of the second positive electrode active part to the width of the positive electrode active layer is 0.3 to 0.7, and can be selected as 0.4 to 0.

6.

15. The positive electrode sheet according to any one of claims 2-11, wherein, the specific capacity of the lithium supplement material is greater than the specific capacity of the positive electrode active material.

16. The positive electrode sheet according to any one of claims 1-11, wherein, The positive electrode active material includes one or more of lithium iron phosphate, lithium manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium cobaltate, lithium nickelate, and lithium iron manganese.

17. The positive electrode sheet according to any one of claims 2-11, characterized in that, The positive electrode lithium supplement material includes: Li 2 C x O y , Li 2 MO 2 , Li 2 MO 3 , Li 5 Fe x M 1-x O 4 and Li 6 Mn y M 1-y O 4 or more of them; wherein, M includes at least one of Ni, Mn, Cu, Fe, Cr, Mo, Zr, Si and Ru, x = 0.5 - 1, y = 0.5 - 1.

18. The positive electrode sheet according to claim 1, characterized in that, The positive electrode active layer only includes the positive electrode active material. Based on the total mass of the positive electrode active layer, the lithium content of the positive electrode active material in the middle positive electrode active part is less than the lithium content of the positive electrode active material in the first positive electrode active part and / or less than the lithium content of the positive electrode active material in the second positive electrode active part.

19. The positive electrode sheet according to claim 18, characterized in that, The positive electrode active layer includes a mixture of at least two positive electrode active materials.

20. The positive electrode sheet according to claim 19, characterized in that, One of the at least two positive electrode active materials is a layered lithium-containing transition metal oxide; optionally, the positive electrode active material further includes one or more of lithium iron phosphate, lithium manganate, lithium nickel manganate, and lithium iron manganese phosphate.

21. The positive electrode sheet according to claim 18, characterized in that, The positive electrode active material is the same positive electrode active material; based on the total mass of the positive electrode active layer, the content of the positive electrode active material in the middle positive electrode active part is less than the content of the positive electrode active material in the first positive electrode active part and / or less than the content of the positive electrode active material in the second positive electrode active part.

22. A battery, characterized in that, including a positive electrode sheet, and the positive electrode sheet is the positive electrode sheet according to any one of claims 1-21.

23. An electrical device, characterized in that, including the battery according to claim 22, and the battery is used to provide electrical energy.

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