Pole piece, electrode assembly, battery monomer, battery and electric device

Abstract

The invention provides a pole piece, an electrode assembly, a battery monomer, a battery and a power utilization device, and belongs to the technical field of batteries. The pole piece comprises a current collector and an active substance layer, the active substance layer is arranged on the surface of the current collector and comprises N subareas which are sequentially arranged in the preset direction, N is larger than or equal to 2, and the electrochemical performance of the adjacent subareas is different.

Description

Technical Field

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

[0002] Energy conservation and emission reduction are the key to the sustainable development of the automobile industry. Electric vehicles have become an important part of the sustainable development of the automobile industry due to their advantages of energy conservation and environmental protection. For electric vehicles, battery technology is an important factor related to their development. How to improve the phenomenon of metal precipitation inside the battery (such as lithium precipitation in lithium-ion batteries) and improve battery safety are technical problems that technicians in this field need to solve urgently. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems existing in the background technology. To this end, one purpose of the present application is to provide a pole piece, an electrode assembly, a battery cell, a battery and an electrical device to improve / mitigate / solve the problems in the related technology.

[0004] An embodiment of the first aspect of the present application provides a pole piece, comprising: a current collector; and an active material layer, which is arranged on the surface of the current collector and comprises N partitions arranged sequentially along a preset direction, wherein N≥2, and the electrochemical properties of adjacent partitions are different.

[0005] The technical solution of the embodiment of the present application can specifically adjust the kinetic properties of the active material layer on the positive electrode sheet and / or the active material layer on the negative electrode sheet in different areas, thereby improving the phenomenon of metal element precipitation in the end area of ​​the active material layer of the negative electrode sheet in the battery cell, thereby improving the safety of the battery.

[0006] In some embodiments, the impedances of adjacent partitions are different. When designing multiple partitions of the active material layer, impedance is used as a factor to evaluate the electrochemical performance of different partitions. The evaluation method is simple and the measurement results are highly accurate.

[0007] In some embodiments, at least two of the N partitions have different sizes along the preset direction. When the material properties of multiple partitions are designed with differentiation, further combining the size difference design can more flexibly and accurately adjust the dynamic performance of different regions.

[0008] In some embodiments, N≥3, wherein the pole piece is a negative pole piece, and the impedances of the N partitions first increase and then decrease in sequence along a preset direction; or, the pole piece is a positive pole piece, and the impedances of the N partitions first decrease and then increase in sequence along a preset direction.

[0009] For the active material layer of the negative electrode, the impedance of the partition adjacent to the end of the active material layer is designed to be relatively small, which is conducive to improving its ability to embed metal ions. For the active material layer of the positive electrode, the impedance of the partition adjacent to the end of the active material layer is designed to be relatively large, which is conducive to weakening its ability to release metal ions.

[0010] In some embodiments, N≥3, wherein, among the N partitions, the size of the 1st partition along the preset direction is smaller than the size of any partition among the 2nd to the N-1th partitions along the preset direction, and the size of the Nth partition along the preset direction is smaller than the size of any partition among the 2nd to the N-1th partitions along the preset direction.

[0011] The electrochemical properties of the materials in the first and Nth partitions can be mainly used to improve the metal element precipitation phenomenon, and their proportion is designed to be relatively small to minimize the impact on other aspects of the battery performance. In addition, the design can compensate for the impedance deviation caused by process limitations through targeted design of the first and Nth partitions, which can be achieved by adjusting the electrochemical properties of the first and Nth partitions.

[0012] In some embodiments, N≥3, wherein along the preset direction, the sizes of the N partitions along the preset direction first increase in sequence and then decrease in sequence.

[0013] The electrochemical properties of the materials in the first and Nth partitions can be mainly used to improve the metal element precipitation phenomenon, and their proportion is designed to be relatively small to minimize the impact on other aspects of the battery performance. In addition, since the electrochemical properties of adjacent partitions are different, the size along the preset direction is designed to change in sections, which can more gently compensate for the impedance deviation caused by process limitations.

[0014] In some embodiments, the active material layer is rectangular or parallelogram-shaped, so that it is convenient to design the electrochemical performance of each partition and also easy to implement in terms of process.

[0015] In some embodiments, the active material layer is a single-layer film layer, and the material ratios of adjacent partitions in the N partitions are different. The active material layer is a single-layer film layer, which is simple in process and easy to implement.

[0016] In some embodiments, the active material layer includes a first film layer and a second film layer arranged in sequence along a direction away from the surface of the current collector, wherein the material ratios of the first film layer and the second film layer are different; the thickness ratio of the first film layer and the second film layer first increases uniformly and then decreases uniformly along a preset direction, or the thickness ratio of the first film layer and the second film layer first decreases uniformly and then increases uniformly along the preset direction.

[0017] In these embodiments, the electrochemical performance of the partitions can be adjusted by combining chemical differences and physical differences, that is, by designing the material ratio differences and thickness ratio differences of the two membrane layers. The adjustment scheme is flexible in design and easy to implement.

[0018] In some embodiments, N≥3, wherein the active material layer includes a first film layer and a second film layer sequentially arranged in a direction away from the surface of the current collector, wherein the material ratios of the first film layer and the second film layer are different; the thickness of the first film layer is the same everywhere in the same partition, the thickness of the second film layer is the same everywhere in the same partition, and the ratio of the thickness of the first film layer to the second film layer first increases gradually and then decreases gradually along a preset direction, or the ratio of the thickness of the first film layer to the second film layer first decreases gradually and then increases gradually along a preset direction.

[0019] In these embodiments, the electrochemical performance of the partitions can be adjusted by combining chemical differences and physical differences, that is, by designing the material ratio difference and thickness ratio difference of the two film layers. The adjustment scheme is flexible and easy to implement. The thickness of the first film layer is the same everywhere in the same partition, and the thickness of the second film layer is the same everywhere in the same partition, which is convenient for controlling the process and reducing the process cost.

[0020] In some embodiments, the active material layer includes a first film layer and a second film layer arranged in sequence in a direction away from the surface of the current collector, wherein the thickness of the first film layer is the same everywhere, and the thickness of the second film layer is the same everywhere; the material ratio of the first film layer in adjacent partitions among N partitions is different, and / or the material ratio of the second film layer in adjacent partitions among N partitions is different.

[0021] In these embodiments, the electrochemical performance of the partitions can be adjusted by adjusting the material ratio differences of the first film layer and / or the second film layer in different partitions. Since the first film layer and the second film layer are designed with equal thickness, the process is relatively simple.

[0022] The second aspect of the present application provides a battery cell, which includes the pole piece in the above embodiment. Based on the design of the pole piece, the dynamic performance of the positive electrode active material layer and / or the negative electrode active material layer in different regions of the battery cell can be specifically adjusted, thereby improving the phenomenon of metal single substance precipitation in the end region of the negative electrode active material layer, thereby improving the safety of the battery.

[0023] The second aspect of the present application provides a battery, which includes the battery cell in the above embodiment. Based on the design of the pole piece, the phenomenon of metal element precipitation in the battery is improved, and the safety of the battery is improved.

[0024] The third aspect of the present application provides an electrical device, which includes the battery in the above embodiment, and the battery is used to provide electrical energy. Based on the design of the above pole piece, it is beneficial to improve the phenomenon of metal element precipitation inside the battery of the electrical device, and improve the stability of battery performance, life and safety of use.

[0025] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0027] Figure 1 A schematic diagram of the structure of a vehicle according to some embodiments of the present application;

[0028] Figure 2 A schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0029] Figure 3 A schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0030] Figure 4 This is a schematic diagram of the main structure of the pole piece of some embodiments of the present application;

[0031] Figure 5 It is a schematic diagram of the main structure of the pole pieces of other embodiments of the present application;

[0032] Figure 6 For some embodiments of the present application, the pole piece Figure 4 Schematic diagram of the cross-sectional structure cut along the AA direction;

[0033] Figure 7 For other embodiments of the present application, the pole piece edge Figure 4 A schematic diagram of the cross-sectional structure cut along the AA direction; and

[0034] Figure 8 For some other embodiments of the present application, the pole piece edge Figure 4 Schematic diagram of the cross-sectional structure cut along the AA direction.

[0035] Description of reference numerals:

[0036] Vehicles 1000;

[0037] Battery 100, controller 200, motor 300;

[0038] Box body 10, first part 11, second part 12;

[0039] Battery cell 20, end cover 21, electrode terminal 21a, housing 22, battery cell assembly 23, and tab 23a;

[0040] Pole piece 300, current collector 30, active material layer 40, partitions 401-405, first film layer 410, second film layer 420, and ends 40a and 40b. DETAILED DESCRIPTION

[0041] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0043] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0044] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0045] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0046] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0047] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0048] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0049] In the related art, the battery includes a plurality of battery cells combined in series and / or in parallel, and the battery cell is the smallest unit in the battery that provides an energy source. The battery cell includes an electrode assembly and an electrolyte, wherein the electrode assembly mainly includes a positive electrode sheet, a negative electrode sheet and a separator. The battery cell mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer, the positive electrode active material layer is coated on the surface of the positive electrode collector, and the positive electrode collector not coated with the positive electrode active material layer is stacked as a positive electrode ear. Taking lithium-ion batteries as an example, the material of the positive electrode collector can be aluminum, and the material of the positive electrode active material layer can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide, etc. The negative electrode sheet includes a negative electrode collector and a negative electrode active material layer, the negative electrode active material layer is coated on the surface of the negative electrode collector, and the negative electrode collector not coated with the negative electrode active material layer is stacked as a negative electrode ear. The material of the negative electrode collector can be copper, and the material of the negative electrode active material layer can be carbon or silicon, etc. The material of the separator may be PP (polypropylene) or PE (polyethylene), etc. In addition, the electrode assembly may be a winding structure or a laminated structure.

[0050] When the battery cell is charging, metal ions escape from the positive active material layer of the positive electrode sheet and embed into the negative active material layer of the negative electrode sheet. During this process, some abnormal situations may occur, leading to the precipitation of metal single substance. Taking lithium-ion battery cells as an example, due to insufficient lithium embedding space in the negative active material layer, too much resistance of lithium ions embedding into the negative active material layer, or lithium ions escaping from the positive active material layer too quickly, the escaped lithium ions cannot be embedded in the negative active material layer of the negative electrode sheet in equal amounts. These lithium ions can only obtain electrons on the surface of the negative electrode sheet, thereby forming metallic lithium single substance. This is the lithium precipitation phenomenon. The lithium precipitation phenomenon is more obvious in the end area of ​​the negative active material layer (i.e., the area close to the positive and negative electrodes of the battery cell). Lithium precipitation not only reduces the performance of the battery cell and significantly shortens the cycle life, but also limits the fast charging capacity of the battery cell. In addition, when lithium is deposited in the battery cell, the deposited lithium metal is very active and can react with the electrolyte at a relatively low temperature, causing the battery cell's self-heating starting temperature (Tonset) to decrease and the self-heating rate to increase, thus seriously endangering the safety of the battery cell.

[0051] For batteries made of other materials, such as sodium-ion batteries (which mainly rely on the movement of sodium ions between the positive and negative electrodes to work, similar to the working principle of lithium-ion batteries), similar technical problems exist as mentioned above, and metallic sodium is easily precipitated in the end area of ​​the negative electrode active material layer.

[0052] Based on the above considerations, the embodiments of the present application design a pole piece, an electrode assembly, a battery cell, a battery and an electrical device, wherein the active material layer of the pole piece includes a plurality of partitions arranged in sequence along a preset direction, and the electrochemical properties of adjacent partitions are different. Based on this design, the kinetic properties of the active material layer on the positive pole piece and / or the active material layer on the negative pole piece in different areas can be adjusted in a targeted manner, thereby improving the phenomenon of metal element precipitation in the end area of ​​the active material layer of the negative pole piece in the battery cell, thereby improving the safety of the battery.

[0053] The battery cell disclosed in the embodiment of the present application can be used in, but not limited to, electrical devices such as vehicles, ships or aircraft. A power supply system comprising the battery cell and battery disclosed in the present application can be used to form the electrical device, which is conducive to improving the phenomenon of metal precipitation inside the battery, and improving the stability of battery performance, life and safety of use.

[0054] The embodiment of the present application provides an electric device using a battery as a power source, and the electric device may be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, etc. Among them, the electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, etc., and the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, etc.

[0055] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0056] Reference Figure 1 , Figure 1 A schematic diagram of the structure of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0057] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0058] Reference Figure 2 , Figure 2 An exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a box 10 and a battery cell 20, and the battery cell 20 is contained in the box 10. Among them, the box 10 is used to provide a storage space for the battery cell 20, and the box 10 can adopt a variety of structures. In some embodiments, the box 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 may be a hollow structure with one end open, the first part 11 may be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 may also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 may be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0059] 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 mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for realizing electrical connection between the multiple battery cells 20.

[0060] Each battery cell 20 may be a secondary battery or a primary battery, or a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0061] Reference Figure 3 , Figure 3 The schematic diagram of the exploded structure of the battery cell 20 provided in some embodiments of the present application. The battery cell 20 refers to the smallest unit that constitutes the battery. Figure 3 The battery cell 20 includes an end cover 21, a shell 22, a battery cell assembly 23 and other functional components.

[0062] The end cap 21 refers to a component that covers the opening of the shell 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 shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect to the battery cell assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating member may be provided inside the end cap 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be plastic, rubber, or the like.

[0063] The shell 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 battery cell assembly 23, electrolyte and other components. The shell 22 and the end cap 21 can be independent components, and an opening can be set on the shell 22, and the internal environment of the battery cell 20 is formed by covering the opening with the end cap 21 at the opening. Without limitation, the end cap 21 and the shell 22 can also be integrated. Specifically, the end cap 21 and the shell 22 can form a common connection surface before other components are put into the shell, and when the interior of the shell 22 needs to be encapsulated, the end cap 21 covers the shell 22. The shell 22 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the battery cell assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.

[0064] The cell assembly 23 is a component in the battery cell 20 where electrochemical reactions occur. One or more cell assemblies 23 may be contained in the housing 22. The cell assembly 23 is mainly formed by winding or stacking the positive electrode sheet and the negative electrode sheet, and a separator is usually provided between the positive electrode sheet and the negative electrode sheet. The parts of the positive electrode sheet and the negative electrode sheet with active materials constitute the main body of the cell assembly, and the parts of the positive electrode sheet and the negative electrode sheet without active materials each constitute a tab 23a. The positive tab and the negative tab may be located together at one end of the main body or respectively 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 tab 23a connects the electrode terminals to form a current loop.

[0065] According to some embodiments of the present application, reference Figure 4 As shown, a pole piece 300 is provided, which includes a current collector 30 and an active material layer 40, wherein the active material layer 40 is arranged on the surface of the current collector 30 and includes N partitions (such as partitions 401, 402, 403, 404, 405) arranged in sequence along a preset direction, wherein N≥2, and the electrochemical properties of adjacent partitions are different.

[0066] N can be an odd number or an even number, and the electrochemical properties of the N partitions can be different from each other, or some of them can be the same, as long as the electrochemical properties of adjacent partitions are different. Figure 4As shown, as an example, in this embodiment, the active material layer 40 includes five partitions, wherein, in the arrangement order along the preset direction, the electrochemical properties of the first partition 401, the second partition 402, and the third partition 403 are different from each other, the electrochemical properties of the fourth partition 404 can be the same as the electrochemical properties of the second partition 402, the electrochemical properties of the fifth partition 405 can be the same as the electrochemical properties of the first partition 401, and the first partition 401 and the fifth partition 405 are adjacent to the ends 40a, 40b of the active material layer 40 in a one-to-one correspondence.

[0067] The ends 40a and 40b of the active material layer 40 can be understood as the two ends thereof distributed along the aforementioned preset direction. In a battery cell, the ends 40a and 40b of the active material layer 40 are closer to the positive and negative electrodes of the battery cell. For the negative electrode active material layer 40, the metal element is more likely to precipitate in the region close to the ends 40a and 40b (i.e., the end region).

[0068] In the embodiment of the present application, the pole piece 300 can be a positive pole piece or a negative pole piece.

[0069] In some examples, the pole piece 300 is a positive pole piece, and the substrate of its current collector 30 may be a metal foil or a composite current collector, wherein the metal foil may be, for example, aluminum foil, and the composite current collector may include, for example, a base layer and a metal layer (such as an aluminum layer) formed on at least one side surface of the base layer, and the active material layer 40 of the positive pole piece, that is, the positive active material layer (for example, the main material includes lithium cobalt oxide, conductive carbon black, polyvinylidene fluoride, etc.), may be arranged on at least one side surface of the above-mentioned metal foil or composite current collector, for example, may be formed on at least one side surface of the above-mentioned metal foil or composite current collector by a coating process.

[0070] In other examples, the pole piece 300 is a negative pole piece, and the substrate of its current collector 30 may be a metal foil or a composite current collector, wherein the metal foil may be, for example, a copper foil, and the composite current collector may include, for example, a base layer and a metal layer (such as a copper layer) formed on at least one side surface of the base layer, and the active material layer 40 of the negative pole piece, that is, the negative active material layer (for example, the main material includes graphite, conductive carbon black, styrene-butadiene rubber, etc.), may be arranged on at least one side surface of the above-mentioned metal foil or composite current collector, for example, may be formed on at least one side surface of the above-mentioned metal foil or composite current collector by a coating process.

[0071] The electrochemical performance of a material is related to its material properties, such as the crystal structure, lattice constant, crystal plane energy, carrier diffusion coefficient, particle size, surface area, microporous structure, etc. The evaluation of the electrochemical performance of a material generally considers chemical reaction kinetics, electrochemical activity, electrocatalytic activity, impedance, capacitance, etc. One or more aspects (such as impedance) can be selected as considerations for evaluating the electrochemical performance of different partitions.

[0072] In response to the technical problem that the negative electrode active material layer in the battery cell is prone to precipitate metal elements in the end area, in an embodiment of the present application, the active material layer is designed to include multiple partitions arranged in sequence along a preset direction, and the electrochemical properties of adjacent partitions are different. In this way, the kinetic properties of the positive electrode active material layer and / or the negative electrode active material layer in different areas can be adjusted in a targeted manner (the kinetic properties are mainly reflected in the rate at which electrochemical reactions occur), thereby weakening the ability of the positive electrode to release metal ions and / or enhancing the ability of the negative electrode to embed metal ions, thereby improving the phenomenon of metal element precipitation in the end area of ​​the negative electrode active material layer and improving the safety of the battery.

[0073] In some embodiments of the present application, in the N partitions of the active material layer 40, the impedances of adjacent partitions are different. Impedance is the amount that indicates the ability of a circuit to hinder the passage of current. In a battery, impedance can be used to characterize the ability of metal ions (such as lithium ions) to be deintercalated. For the positive active material layer, the greater the impedance of its end region, the weaker its ability to remove metal ions; for the negative active material layer, the smaller the impedance of its end region, the stronger its ability to embed metal ions. When designing multiple partitions of the active material layer 40, impedance is used as a consideration for evaluating the electrochemical performance of different partitions. The evaluation method is simple and the measurement results are highly accurate.

[0074] Impedance testing can be performed after the pole pieces of the battery cell are disassembled and the experimental samples are prepared. In some embodiments, the test steps include: first, using an electrochemical workstation (a measuring device commonly used in electrochemical research and teaching) to test the impedance values ​​of the active material layers in different partitions, and then, with the standard battery as the reference, the measured battery impedance value is fitted with a gradient data value, and then, based on the fitting results, the impedance of different partitions is calculated in Ω. In some embodiments, the perturbation voltage of the electrochemical impedance spectrum is set to 5mV, the frequency is set to 500KHz-30MHz (ambient temperature above 20°C), and the voltage is set to -1V~1V. The test result data can be used to analyze and review the parameter design of the active material layer in different partitions, such as structure, material, size, etc.

[0075] In some embodiments of the present application, at least two of the N partitions of the active material layer have different sizes along a preset direction. When the material properties of multiple partitions are designed with differentiation, further combining the difference in size design can more flexibly and accurately adjust the dynamic performance of different regions.

[0076] refer to Figure 4 As shown, in some examples of the present application, the number of partitions of the active material layer 40 is N ≥ 3 (this embodiment is illustrated by taking 5 as an example), so that the 1st partition (such as partition 401 in the figure) and the Nth partition (such as partition 405 in the figure) are adjacent to the ends 40a and 40b of the active material layer 40 one by one, and can be used as the end areas that need to be focused on to improve the problem of metal element precipitation.

[0077] In some examples, reference Figure 4 As shown, if the electrode 300 is a negative electrode, the impedances of the N partitions along the preset direction can be designed to first increase and then decrease in sequence, for example, Figure 4 The impedance of the first partition 401, the impedance of the second partition 402, and the impedance of the third partition 403 increase in sequence, and the impedance of the third partition 403, the impedance of the fourth partition 404, and the impedance of the fifth partition 405 decrease in sequence. The impedance of the fourth partition 404 can be the same as the impedance of the second partition 402, and the impedance of the fifth partition 405 can be the same as the impedance of the first partition 401.

[0078] For the active material layer 40 of the negative electrode sheet, the impedance of the partitions adjacent to the ends 40a and 40b of the active material layer 40 is designed to be relatively small, which is beneficial to improving its ability to embed metal ions.

[0079] In some examples, reference Figure 4 As shown, if the electrode 300 is a positive electrode, the impedances of the N partitions can be designed to decrease first and then increase in sequence along a preset direction. For example, the impedance of the first partition 401, the impedance of the second partition 402, and the impedance of the third partition 403 in the figure decrease in sequence, and the impedance of the third partition 403, the impedance of the fourth partition 404, and the impedance of the fifth partition 405 increase in sequence. The impedance of the fourth partition 404 can be the same as the impedance of the second partition 402, and the impedance of the fifth partition 405 can be the same as the impedance of the first partition 401.

[0080] For the active material layer 40 of the positive electrode sheet, the impedance of the partitions adjacent to the ends 40a and 40b of the active material layer 40 is designed to be relatively large, which is beneficial to weakening its ability to release metal ions.

[0081] In some embodiments of the present application, Figure 4As shown, the number of partitions of the active material layer 40 is N≥3, and among the N partitions, the size of the first partition (such as partition 401 in the figure) along the preset direction is smaller than the size of any partition from the second to the N-1th partition (such as partitions 402, 403, and 404 in the figure) along the preset direction (such as S1 in the figure is smaller than any of S2, S3, and S4), and the size of the Nth partition (such as partition 405 in the figure) along the preset direction is smaller than the size of any partition from the second to the N-1th partition (such as partitions 402, 403, and 404 in the figure) along the preset direction (such as S5 in the figure is smaller than any of S2, S3, and S4). That is, the preset direction size of the partitions adjacent to the ends 40a and 40b of the active material layer 40 is designed to be smaller than that of other partitions. For example, Figure 4 Among the five partitions in the illustrated embodiment, the size S1 of the first partition 401 along the preset direction and the size S5 of the fifth partition 405 along the preset direction are designed to be smaller than the sizes S2, S3, S4 of the other partitions along the preset direction.

[0082] The electrochemical properties of the materials in the first and Nth partitions can be mainly used to improve the problem of metal element precipitation, and their proportion can be designed to be relatively small to minimize the impact on other aspects of the battery performance. In addition, for wound or laminated electrode assemblies, due to the limitations of the assembly process, the gap between the pole pieces is larger as it is closer to the end, and smaller as it is farther away from the end, resulting in a certain deviation between the actual impedance of the active material layer in the end area of ​​the battery and the impedance of the material itself. This design can compensate for the impedance deviation caused by process limitations through targeted design of the first and Nth partitions, which can be achieved by adjusting the electrochemical properties of the first and Nth partitions.

[0083] In some embodiments of the present application, the number of partitions N of the active material layer 40 is ≥ 3, such as Figure 4 As shown, along the preset direction, the sizes of the N partitions along the preset direction can also be designed to first increase in sequence and then decrease in sequence. Figure 4 Among the five partitions of the illustrated embodiment, the sizes of the first partition 401, the second partition 402, and the third partition 403 along the preset direction increase successively (i.e., S1, S2, and S3 increase successively), and the sizes of the third partition 403, the fourth partition 404, and the fifth partition 405 along the preset direction decrease successively (i.e., S3, S4, and S5 decrease successively).

[0084] The electrochemical properties of the materials in the first and Nth partitions can be used to improve the metal element precipitation problem, and their proportion is designed to be relatively small to minimize the impact on other aspects of the battery performance. In addition, since the electrochemical properties of adjacent partitions are different, the size of the partitions along the preset direction is designed to change step by step, which can more gently compensate for the impedance deviation caused by process limitations.

[0085] like Figure 4 As shown, in some embodiments of the present application, the active material layer 40 is rectangular, and each partition of the active material layer 40 is also rectangular. The dimensions of each partition in the length direction orthogonal to the preset direction are the same, for example, they can extend to the edge of the current collector, which makes it easy to design the electrochemical properties of each partition and is also easy to implement in terms of process.

[0086] like Figure 5 As shown, in some embodiments of the present application, the active material layer 40 is in the shape of a parallelogram, and each partition of the active material layer 40 is also in the shape of a parallelogram. The dimensions of each partition in the height direction orthogonal to the preset direction are the same, and each partition can extend to the edge of the current collector, which makes it easy to design the electrochemical properties of each partition and is also easy to implement in terms of process.

[0087] In the embodiment of the present application, the active material layer 40 can be either a single-layer film layer or a composite film layer.

[0088] In some embodiments, the active material layer 40 is a single-layer film layer, and the material ratios of adjacent partitions are different, so that the material properties and impedances of adjacent partitions are different, and thus the electrochemical properties of adjacent partitions are different.

[0089] The material ratio refers to the ratio of the material formula. In some embodiments, adjacent partitions may include different material components. In other embodiments, adjacent partitions may also include the same material components but in different proportions. By setting different material ratios in different partitions, the mass proportion of active materials in different partitions can be different, so that adjacent partitions have different impedances. The active material layer adopts a single-layer film layer, which is simple in process and easy to implement.

[0090] like Figure 6 As shown, in some embodiments, the active material layer 40 is a composite film layer, which includes a first film layer 410 and a second film layer 420 sequentially arranged in a direction away from the surface of the current collector 30, wherein the material ratios of the first film layer 410 and the second film layer 420 are different, and the thickness ratio c1 / c2 of the first film layer 410 and the second film layer 420 first increases uniformly and then decreases uniformly along the preset direction. In some embodiments, the thickness ratio c1 / c2 of the first film layer 410 and the second film layer 420 may also first decrease uniformly and then increase uniformly along the preset direction.

[0091] In these embodiments, the electrochemical performance of the partitions can be adjusted by combining chemical differences and physical differences, that is, by designing the material ratio difference and thickness ratio difference of the two film layers, and the adjustment scheme is flexible and easy to implement. The thickness ratio c1 / c2 of the first film layer 410 and the second film layer 420 changes gently along the preset direction, which also facilitates the gentle transition of electrochemical performance between adjacent partitions, thereby facilitating the stability of battery performance.

[0092] The variation trend of the thickness ratio c1 / c2 of the first film layer 410 and the second film layer 420 along a preset direction needs to take into account the polarity of the pole piece 300 and the material ratio of the first film layer 410 and the second film layer 420 .

[0093] For example, in some embodiments, Figure 6 As shown, if the electrode is a negative electrode, the mass proportion of active materials (referring to materials that have a significant effect on improving the electrochemical reaction rate, such as active substances or additives, etc.) in the first film layer 410 is less than the mass proportion of active materials in the second film layer 420, then the thickness ratio c1 / c2 of the first film layer 410 and the second film layer 420 can be designed to first increase uniformly and then decrease uniformly along a preset direction, so that the partitions adjacent to the ends 40a and 40b of the active material layer 40 have relatively more active materials and relatively smaller impedance, which is beneficial to improving its ability to embed metal ions.

[0094] For example, in some embodiments, Figure 6 As shown, if the pole piece is a positive pole piece, the mass proportion of the active material in the first film layer 410 is greater than the mass proportion of the active material in the second film layer 420, then the thickness ratio c1 / c2 of the first film layer 410 and the second film layer 420 can be designed to first increase uniformly and then decrease uniformly along a preset direction, so that the active material in the partition adjacent to the end portions 40a and 40b of the active material layer 40 is relatively less and the impedance is relatively larger, which is beneficial to weakening its ability to release metal ions.

[0095] For example, in some embodiments, the pole piece is a negative pole piece, and the mass proportion of the active material in the first film is greater than the mass proportion of the active material in the second film layer. Then, the thickness ratio of the first film layer and the second film layer can be designed to first decrease uniformly and then increase uniformly along a preset direction, so that the active material in the partition adjacent to the end of the active material layer is relatively more and the impedance is relatively small, which is beneficial to improving its ability to embed metal ions.

[0096] For example, in some embodiments, the pole piece is a positive pole piece, and the mass proportion of the active material in the first film layer is less than the mass proportion of the active material in the second film layer. Then the thickness ratio of the first film layer and the second film layer can be designed to first decrease uniformly and then increase uniformly along a preset direction, so that the active material in the partition adjacent to the end of the active material layer is relatively small and the impedance is relatively large, which is beneficial to weaken its ability to release metal ions.

[0097] like Figure 7 As shown, in some embodiments, the number of partitions N of the active material layer 40 is ≥ 3 (this embodiment is illustrated by taking 5 as an example), and the active material layer 40 is a composite film layer, which includes a first film layer 410 and a second film layer 420 sequentially arranged in a direction away from the surface of the current collector 30, wherein the material ratios of the first film layer 410 and the second film layer 420 are different, the thickness of the first film layer 410 is the same everywhere in the same partition, the thickness of the second film layer 420 is the same everywhere in the same partition, and the ratio c1 / c2 of the thickness of the first film layer 410 and the second film layer 420 increases first and then decreases in a gradient along a preset direction. In some embodiments, the ratio c1 / c2 of the thickness of the first film layer 410 and the second film layer 420 may also decrease first and then increase in a gradient along a preset direction.

[0098] In these embodiments, the electrochemical performance of the partitions can be adjusted by combining chemical differences and physical differences, that is, by designing the material ratio difference and thickness ratio difference of the two film layers, and the adjustment scheme is flexible and easy to implement. The thickness of the first film layer 410 is the same everywhere in the same partition, and the thickness of the second film layer 420 is the same everywhere in the same partition, which is convenient for controlling the process and reducing the process cost.

[0099] The variation trend of the thickness ratio c1 / c2 of the first film layer 410 and the second film layer 420 along a preset direction needs to take into account the polarity of the electrode piece and the material ratio of the first film layer 410 and the second film layer 420 .

[0100] For example, in some embodiments, Figure 7 As shown, if the electrode is a negative electrode, the mass proportion of the active material in the first film layer 410 is less than the mass proportion of the active material in the second film layer 420, then the thickness ratio c1 / c2 of the first film layer 410 and the second film layer 420 can be designed to first increase with a gradient and then decrease with a gradient along a preset direction, so that the partitions adjacent to the ends 40a and 40b of the active material layer 40 have relatively more active materials and relatively smaller impedance, which is beneficial to improving its ability to embed metal ions.

[0101] For example, in some embodiments, Figure 7As shown, if the pole piece is a positive pole piece, the mass proportion of the active material in the first film layer 410 is greater than the mass proportion of the active material in the second film layer 420, then the thickness ratio c1 / c2 of the first film layer 410 and the second film layer 420 can be designed to first increase in a gradient and then decrease in a gradient along a preset direction, so that the active material in the partition adjacent to the end portions 40a and 40b of the active material layer 40 is relatively less and the impedance is relatively larger, which is beneficial to weakening its ability to release metal ions.

[0102] For example, in some embodiments, the pole piece is a negative pole piece, and the mass proportion of the active material in the first film layer is greater than the mass proportion of the active material in the second film layer. Then, the thickness ratio of the first film layer and the second film layer can be designed to first decrease in a gradient and then increase in a gradient along a preset direction, so that the active material in the partition adjacent to the end of the active material layer is relatively more and the impedance is relatively small, which is beneficial to improving its ability to embed metal ions.

[0103] For example, in some embodiments, the pole piece is a positive pole piece, and the mass proportion of the active material in the first film layer is less than the mass proportion of the active material in the second film layer. Then the thickness ratio of the first film layer and the second film layer can be designed to first decrease in a gradient and then increase in a gradient along a preset direction, so that the active material in the partition adjacent to the end of the active material layer is relatively small and the impedance is relatively large, which is beneficial to weaken its ability to release metal ions.

[0104] like Figure 8 As shown, in some embodiments, the active material layer 40 is a composite film layer, which includes a first film layer 410 and a second film layer 420 sequentially arranged in a direction away from the surface of the current collector 30, wherein the thickness of the first film layer 410 is the same everywhere, the thickness of the second film layer 420 is the same everywhere, the first film layer 410 has different material ratios in adjacent partitions, and / or the second film layer 420 has different material ratios in adjacent partitions. This embodiment shows that the material ratios of the first film layer 410 in adjacent partitions are the same, and the material ratios of the second film layer 420 in adjacent partitions are different.

[0105] In these embodiments, the electrochemical performance of the partitions can be adjusted by adjusting the material ratio differences of the first film layer 410 and / or the second film layer 420 in different partitions. Since the first film layer 410 and the second film layer 420 are designed with equal thickness, the process is relatively simple.

[0106] like Figure 4 As shown, some embodiments of the present application provide a pole piece 300, which includes a current collector 30 and an active material layer 40, wherein the active material layer 40 is disposed on the surface of the current collector 30 and includes 5 partitions arranged sequentially along a preset direction, wherein adjacent partitions have different electrochemical properties.

[0107] In some examples, the electrode sheet 300 is a negative electrode sheet, and the impedance of the first partition 401, the impedance of the second partition 402, and the impedance of the third partition 403 in the figure increase in sequence, and the impedance of the third partition 403, the impedance of the fourth partition 404, and the impedance of the fifth partition 405 decrease in sequence, and the impedance of the fourth partition 404 is the same as the impedance of the second partition 402, and the impedance of the fifth partition 405 is the same as the impedance of the first partition 401. For the active material layer 40 of the negative electrode sheet, the impedance of the partition adjacent to the end 40a, 40b of the active material layer 40 is designed to be relatively small, which is conducive to improving its ability to embed metal ions.

[0108] In some examples, the electrode sheet 300 is a positive electrode sheet, and the impedance of the first partition 401, the impedance of the second partition 402, and the impedance of the third partition 403 in the figure decrease in sequence, and the impedance of the third partition 403, the impedance of the fourth partition 404, and the impedance of the fifth partition 405 increase in sequence, the impedance of the fourth partition 404 is the same as the impedance of the second partition 402, and the impedance of the fifth partition 405 is the same as the impedance of the first partition 401. For the active material layer 40 of the positive electrode sheet, the impedance of the partition adjacent to the end 40a, 40b of the active material layer 40 is designed to be relatively large, which is conducive to weakening its ability to escape metal ions.

[0109] For the above-mentioned positive electrode sheet or negative electrode sheet, in terms of size design, the sizes of the first partition 401, the second partition 402, and the third partition 403 along the preset direction are increased successively, and the sizes of the third partition 403, the fourth partition 404, and the fifth partition 405 along the preset direction are decreased successively, so that the electrochemical properties of the materials of the first partition 401 and the fifth partition 405 can be mainly used to improve the metal element precipitation phenomenon, and their proportion is designed to be relatively small to minimize the impact on other aspects of the battery performance. In addition, since the electrochemical properties of adjacent partitions are different, the size along the preset direction is designed to change gradually, which can more gently compensate for the impedance deviation caused by process limitations.

[0110] The active material layer 40 may be designed to be in a rectangular shape. The active material layer 40 may be a single-layer film layer or a composite film layer.

[0111] Based on the design of the above-mentioned pole piece 300, the dynamic performance of the positive electrode active material layer and / or the negative electrode active material layer in different areas of the battery cell can be specifically adjusted, thereby improving the phenomenon of metal element precipitation in the end area of ​​the negative electrode active material layer, thereby improving the safety of the battery.

[0112] The battery cell manufactured according to the pole pieces of the above embodiments can refer to the aforementioned method and perform impedance testing after disassembling the pole pieces of the battery cell and preparing experimental samples. The test result data can be used to analyze and review the parameter design of the active material layer in different partitions, such as structure, material, size, etc., so as to more effectively improve the phenomenon of metal single substance precipitation in the end area of ​​the active material layer of the negative electrode.

[0113] According to one aspect of the present application, some embodiments of the present application further provide an electrode assembly, comprising a pole piece in any of the aforementioned embodiments.

[0114] According to one aspect of the present application, some embodiments of the present application further provide a battery cell, comprising the electrode assembly in any of the aforementioned embodiments.

[0115] According to one aspect of the present application, some embodiments of the present application further provide a battery, comprising a battery cell according to any of the aforementioned embodiments.

[0116] According to one aspect of the present application, some embodiments of the present application further provide an electrical device, comprising a battery cell in any of the aforementioned embodiments or a battery in any of the aforementioned embodiments, wherein the battery cell or the battery is used to provide electrical energy.

[0117] Based on the above improvements to the electrode, the phenomenon of metal element precipitation inside the battery can be effectively improved, thereby improving the safety of the battery.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A pole piece, characterized in that: include: current collector; as well as The active material layer is disposed on the surface of the current collector and comprises N partitions arranged in sequence along a preset direction, wherein N≥2, and the electrochemical properties of adjacent partitions are different.

2. The pole piece according to claim 1, characterized in that: The impedances of adjacent partitions are different.

3. The pole piece according to claim 1 or 2, characterized in that: Among the N partitions, at least two partitions have different sizes along the preset direction.

4. The pole piece according to any one of claims 1 to 3, characterized in that: N ≥ 3, where The electrode is a negative electrode, and along the preset direction, the impedances of the N partitions first increase and then decrease in sequence; or The pole piece is a positive pole piece, and along the preset direction, the impedances of the N partitions first decrease and then increase in sequence.

5. The pole piece according to any one of claims 1 to 4, characterized in that: N ≥ 3, where Among the N partitions, the size of the 1st partition along the preset direction is smaller than the size of any partition from the 2nd to the N-1th partitions along the preset direction, and the size of the Nth partition along the preset direction is smaller than the size of any partition from the 2nd to the N-1th partitions along the preset direction.

6. The pole piece according to any one of claims 1 to 5, characterized in that: N ≥ 3, where Along the preset direction, the sizes of the N partitions along the preset direction first increase in sequence and then decrease in sequence.

7. The pole piece according to any one of claims 1 to 6, characterized in that: The active material layer is rectangular or parallelogram-shaped.

8. The pole piece according to any one of claims 1 to 7, characterized in that: The active material layer is a single-layer film layer, and the material ratios of adjacent partitions in the N partitions are different.

9. The pole piece according to any one of claims 1 to 7, characterized in that: The active material layer includes a first film layer and a second film layer sequentially arranged in a direction away from the surface of the current collector, wherein: The material ratios of the first film layer and the second film layer are different; The thickness ratio of the first film layer to the second film layer first increases uniformly and then decreases uniformly along the preset direction, or the thickness ratio of the first film layer to the second film layer first decreases uniformly and then increases uniformly along the preset direction.

10. The pole piece according to any one of claims 1 to 7, characterized in that: N≥3, wherein the active material layer comprises a first film layer and a second film layer sequentially arranged in a direction away from the surface of the current collector, wherein: The material ratios of the first film layer and the second film layer are different; The thickness of the first film layer is the same everywhere in the same partition, the thickness of the second film layer is the same everywhere in the same partition, and, The thickness ratio of the first film layer to the second film layer first increases gradually and then decreases gradually along the preset direction, or the thickness ratio of the first film layer to the second film layer first decreases gradually and then increases gradually along the preset direction.

11. The pole piece according to any one of claims 1 to 7, characterized in that: The active material layer includes a first film layer and a second film layer sequentially arranged in a direction away from the surface of the current collector, wherein: The thickness of the first film layer is the same everywhere, and the thickness of the second film layer is the same everywhere; The material ratios of the first film layer in adjacent subareas among the N subareas are different, and / or the material ratios of the second film layer in adjacent subareas among the N subareas are different.

12. An electrode assembly, characterized in that: include: A pole piece according to any one of claims 1 to 11.

13. A battery cell, characterized in that: include: The electrode assembly according to claim 12.

14. A battery, characterized in that: include: The battery cell according to claim 13.

15. An electrical device, characterized in that: include: The battery according to claim 14, wherein the battery is used to provide electrical energy.

Images