Battery monomer, pole piece, preparation method of pole piece, battery device and energy storage device

Abstract

The embodiment of the invention provides a battery monomer, a pole piece, a preparation method of the pole piece, a battery device and an energy storage device, and belongs to the technical field of batteries. The battery monomer comprises a shell and an electrode assembly, the electrode assembly is arranged in the shell, the electrode assembly comprises a pole piece, and the pole piece comprises a current collector, a pre-pressing layer arranged on at least one side of the current collector in the thickness direction and a gluing layer arranged between the pre-pressing layer and the current collector; wherein d1 is greater than d2, and d1 is greater than or equal to 1.8 g / cc; wherein d1 is the compaction density of the prepressing layer, and d2 is the compaction density of the current collector. The lithium ion battery is not limited by the ductility defect of the current collector, and the compaction density of the pole piece is improved, so that the energy density of the single battery is improved.

Description

Technical Field

[0001] This application relates to the field of battery technologies, and more particularly, to a battery cell, an electrode sheet, a method for preparing the electrode sheet, a battery device, and an energy storage device. Background Art

[0002] In the cold pressing process of the electrode sheet of a battery cell, the compaction density of the electrode sheet is positively correlated with the energy density of the battery cell. In related technologies, the strategy for increasing the compaction density of the electrode sheet often involves material modification, such as particle size structure design, etc., but the upper limit of the improvement in the compaction density of the electrode sheet is limited. Summary of the Invention

[0003] This application provides a battery cell, an electrode sheet, a method for preparing the electrode sheet, a battery device, and an energy storage device to increase the compaction density of the electrode sheet, thereby effectively increasing the energy density of the battery cell.

[0004] In a first aspect, an embodiment of this application provides a battery cell, including: A housing; An electrode assembly disposed inside the housing, the electrode assembly including an electrode sheet, and the electrode sheet including: A current collector; A pre-pressing layer disposed on at least one side of the current collector in the thickness direction; An adhesive layer disposed between the pre-pressing layer and the current collector; Satisfying: d1 > d2, d1 ≥ 1.8 g / cc; where d1 is the compaction density of the pre-pressing layer, and d2 is the compaction density of the current collector.

[0005] In the above technical solution, by setting the electrode sheet as a structure including a current collector, an adhesive layer, and a pre-pressing layer, after pre-pressing the pre-pressing layer and then stacking it with the current collector and performing pressing, the pre-pressing pressure is greater than the pressing pressure, so that the limitation of the ductility defect of the current collector can be overcome, the compaction density of the electrode sheet can be increased, and thus the energy density of the battery cell can be increased.

[0006] In some embodiments, when the electrode sheet is a positive electrode sheet, the compaction density d1 of the pre-pressing layer of the positive electrode sheet satisfies: d1 ≥ 1.8 g / cc; the compaction density D1 of the positive electrode sheet satisfies: D1 ≥ 1.6 g / cc.

[0007] In some embodiments, when the electrode sheet is a negative electrode sheet, the compaction density d1 of the pre-pressing layer of the negative electrode sheet satisfies: d1 ≥ 3 g / cc; the compaction density D2 of the negative electrode sheet satisfies: D2 ≥ 2.7 g / cc.

[0008] In some embodiments, the pre-pressing layers are respectively disposed on both sides of the current collector in the thickness direction.

[0009] In some embodiments, the melting point T1 of the crosslinking agent of the adhesive layer is less than the melting point T2 of the crosslinking agent of the pre-pressing layer.

[0010] In a second aspect, an electrode sheet provided by an embodiment of the present application includes: A current collector; A pre-pressing layer disposed on at least one side of the current collector in the thickness direction; An adhesive layer disposed between the pre-pressing layer and the current collector; Satisfying: d1 > d2, d1 ≥ 1.8 g / cc, where d1 is the compaction density of the pre-pressing layer and d2 is the compaction density of the current collector.

[0011] In a third aspect, a method for preparing an electrode sheet provided by an embodiment of the present application includes: Providing a current collector; Providing main and auxiliary materials, and performing pre-pressing treatment on the main and auxiliary materials with a pressure F1 to obtain a pre-pressing layer with a compaction density of d1; Providing an adhesive material, and coating the adhesive material on at least one side of the current collector in the thickness direction to obtain an adhesive layer; Placing the pre-pressing layer on the adhesive layer to obtain an electrode sheet that has not been pressed, and performing pressing treatment on the electrode sheet that has not been pressed with a pressure F2 to obtain an electrode sheet; Wherein, satisfying: d1 > d2, d1 ≥ 1.8 g / cc, F1 > F2, where d1 is the compaction density of the pre-pressing layer and d2 is the compaction density of the current collector.

[0012] In some embodiments, the pressure F1 of the pre-pressing treatment satisfies: 5 MPa ≤ F1 ≤ 50 Mpa.

[0013] In some embodiments, the pressure F2 of the pressing treatment satisfies: 5 MPa ≤ F2 ≤ 15 Mpa.

[0014] In some embodiments, after performing pressing treatment on the electrode sheet that has not been pressed to obtain an electrode sheet, it further includes: Performing re-pressing treatment on the pressed electrode sheet with a pressure F3, where F3 < F2.

[0015] In some embodiments, satisfying: 1 MPa ≤ F3 ≤ 8 Mpa.

[0016] In a fourth aspect, a battery device provided by an embodiment of the present application includes: a plurality of battery cells described in any one of the above embodiments.

[0017] Fifth aspect, an embodiment of the present application provides an energy storage device, including: a plurality of battery cells or a plurality of battery devices as described in any of the above embodiments, and the battery cells or the battery devices are used for storing or providing electric energy.

[0018] Sixth aspect, an embodiment of the present application provides an energy storage system, including: a power conversion device and the energy storage device as described in any of the above embodiments, and the power conversion device is used for electrically connecting a power generation device and the energy storage device. Description of the Drawings

[0019] To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0020] Figure 1 Structural schematic diagram of an energy storage system provided by some embodiments of the present application; Figure 2 Structural schematic diagram of a charging network provided by some embodiments of the present application; Figure 3 Structural schematic diagram of a vehicle provided by some embodiments of the present application; Figure 4 Exploded structural view of a battery device provided by some embodiments of the present application; Figure 5 One of the structural schematic diagrams of a pole piece provided by some embodiments of the present application; Figure 6 Another structural schematic diagram of a pole piece provided by some embodiments of the present application; Figure 7 Flow schematic diagram of a method for preparing a pole piece provided by some embodiments of the present application.

[0021] Reference Signs: Energy storage device 1, power conversion device 2, power generation device 3, charging pile 4, connector 5; Vehicle 1000; Battery device 100; Box body 10, first box body 11, second box body 12; Battery cell 20, pole piece 21, current collector 211, pre-pressing layer 212, adhesive layer 213; Controller 200; motor 300. Detailed Embodiments

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly describe the technical solutions in the embodiments of this application in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0023] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects and are not used to describe a specific order or primary-secondary relationship.

[0024] Referring to "embodiments" in this application 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 does not necessarily refer to the same embodiment when it appears in various positions in the specification, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0025] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" 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 directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0026] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally represents an "or" relationship between the associated objects before and after.

[0027] The term "multiple" as used in this application refers to two or more (including two). Similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to two or more pieces (including two pieces).

[0028] In the embodiments of the present application, the battery cell may be a secondary battery, which refers to a battery cell that can be activated by charging after discharging to continue to be used.

[0029] The battery cell may be a lithium-ion battery, a sodium-ion battery, a sodium-lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium-sulfur battery, a magnesium-ion battery, a nickel-metal hydride battery, a nickel-cadmium battery, a lead-acid battery, etc., and the embodiments of the present application are not limited thereto.

[0030] The battery cell may be in the shape of a cylinder, a flat body, a cuboid or other shapes, etc., and the embodiments of the present application are not limited thereto. Generally, the battery cells are divided into three types according to the encapsulation method: cylindrical battery cells, square battery cells and soft-pack battery cells, and the embodiments of the present application are not limited thereto.

[0031] The battery cell includes a housing, an electrode assembly and an electrolyte. The housing is used to accommodate the electrode assembly and the electrolyte. The electrode assembly is composed of a positive electrode plate, a negative electrode plate and a separator. The battery cell mainly works by the movement of metal ions between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive current collector and a positive active material layer. The positive current collector includes a positive current collector body and a positive tab. The positive active material layer is coated on the surface of the positive current collector body. The positive tab is not coated with the positive active material layer and protrudes from the positive current collector body. Taking a lithium-ion battery as an example, the material of the positive current collector can be aluminum, and the positive active material can be lithium cobaltate, lithium iron phosphate, ternary lithium or lithium manganate, etc. The negative electrode plate includes a negative current collector and a negative active material layer. The negative current collector includes a negative current collector body and a negative tab. The negative active material layer is coated on the surface of the negative current collector body. The negative tab is not coated with the negative active material layer and protrudes from the negative current collector body. The material of the negative current collector can be copper, and the negative active material can be carbon or silicon, etc. In order to ensure that a large current can pass through without fusing, the number of positive tabs is multiple and stacked together, and the number of negative tabs is multiple and stacked together.

[0032] The material of the separator can be PP (polypropylene) or PE (polyethylene), etc. In addition, the electrode assembly can be a wound structure or a stacked structure, and the embodiments of the present application are not limited thereto.

[0033] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using battery cells, such as mobile phones, portable devices, laptop computers, battery cars, electric toys, electric tools, vehicles, ships and spacecrafts, etc. For example, spacecrafts include airplanes, rockets, space shuttles and spaceships, etc. The battery cell is used to store or provide electrical energy.

[0034] The inventors found that during the cold pressing process of the electrode sheet of a battery cell, the compaction density of the electrode sheet is positively correlated with the energy density of the battery cell. In related technologies, the strategy for increasing the compaction density of the electrode sheet often involves material modification, such as particle size structure design, etc., but the upper limit for improving the compaction density of the electrode sheet is limited.

[0035] Based on the above considerations regarding the limited upper limit for improving the compaction density of the electrode sheet, through in-depth research, the inventors designed a battery cell, which includes a housing and an electrode assembly. The electrode assembly is disposed within the housing, and the electrode assembly includes an electrode sheet. The electrode sheet includes: a current collector, a pre-pressing layer provided on at least one side of the current collector in the thickness direction, and an adhesive layer provided between the pre-pressing layer and the current collector; wherein, d1 > d2 and d1 ≥ 1.8 g / cc are satisfied; where d1 is the compaction density of the pre-pressing layer and d2 is the compaction density of the current collector.

[0036] In the battery cell with this structure, by setting the electrode sheet as a structure of a current collector, an adhesive layer, and a pre-pressing layer, after pre-pressing the pre-pressing layer and then stacking it with the current collector and then performing pressing, the pre-pressing pressure is greater than the pressing pressure, so that it is not limited by the ductility defect of the current collector, the compaction density of the electrode sheet can be increased, and thus the energy density of the battery cell can be increased.

[0037] The battery apparatus mentioned in the embodiments of the present application may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include multiple battery cells, and the multiple battery cells are connected in series, parallel, or in a hybrid connection through a busbar component.

[0038] In some embodiments, the battery cell assembly is usually formed by arranging multiple battery cells.

[0039] As an example, the battery cell assembly can be a battery module, and the battery module is formed by arranging and fixing multiple battery cells into an independent module. As an example, the battery module can be formed by bundling multiple battery cells with cable ties.

[0040] In some embodiments, the battery apparatus can be a battery pack, and the battery pack includes a box body and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body.

[0041] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be accommodated in the box body by fixing the battery module in the box body.

[0042] As an example, the battery cell assembly can also be accommodated in the box body by directly fixing multiple battery cells to the box body.

[0043] As an example, the box body may include a first box body and a second box body. The first box body and the second box body are buckled together so that a closed space is formed inside the box body to accommodate the battery cell assembly. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first box body can be a top cover or a bottom plate.

[0044] As an example, the box body may include a top cover, a frame and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the box body to accommodate the battery cell assembly.

[0045] In some embodiments, the box body can be part of the chassis structure of a vehicle. For example, part of the box body can become at least part of the floor of the vehicle, or part of the box body can become at least part of the cross beam and longitudinal beam of the vehicle.

[0046] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using battery devices, such as mobile phones, portable devices, laptop computers, battery cars, electric toys, electric tools, vehicles, ships and spacecrafts, etc. For example, spacecrafts include airplanes, rockets, space shuttles and spaceships, etc. The battery device is used to store or provide electrical energy.

[0047] The embodiments of the present application provide an energy storage device, including one or more battery clusters (Battery Cluster) to increase the voltage and capacity of the energy storage device. The battery cluster may include a plurality of battery devices, and the plurality of battery devices are connected in series through a busbar component to increase the voltage of the energy storage device. When the energy storage device includes a plurality of battery clusters, the plurality of battery clusters are connected in parallel to increase the capacity of the energy storage device.

[0048] The energy storage device can be used in energy storage power stations, wind power generation systems, solar power generation systems, mobile power systems or temporary power supply systems, etc. The energy storage device can store electrical energy as needed and output electrical energy at an appropriate time. For example, the energy storage device can store electrical energy during low electricity consumption periods, and provide electrical energy to relevant users or electrical devices during high electricity consumption periods. The energy storage system provided by the embodiments of the present application can be any power system that requires an energy storage device.

[0049] In some embodiments, the energy storage device is an energy storage container or an energy storage electric cabinet.

[0050] In some embodiments, the energy storage device may include a cabinet body and one or more battery clusters, and the battery clusters are accommodated in the cabinet body.

[0051] In some embodiments, the energy storage device may include modules such as a thermal management module, a main control module, a total control module, a power distribution module and a fire protection module, etc.

[0052] As an example, the thermal management module may include a liquid cooling unit, which supplies coolant for regulating the temperature of battery cells to each battery device through pipelines.

[0053] As an example, the master control module may serve as the battery management unit of the battery cluster for monitoring and managing the battery cluster. The master control module can monitor information such as the current, voltage, power, or temperature of the battery cluster. For example, it can control the charge and discharge current, voltage, etc. of the battery cluster. The master control module includes modules such as the auxiliary battery management unit SBMU (Slave Battery Management Unit), and the fusion switch.

[0054] As an example, the total control module may serve as the battery management unit of the energy storage device for monitoring and managing the energy storage device. The total control module can monitor information such as the current, voltage, power, state of charge, or temperature of the energy storage device. For example, it can control the charge and discharge current, voltage, etc. of the energy storage device. As an example, the total control module includes modules such as the insulation monitoring module IMM (Insulation Monitoring Module), the main battery management unit MBMU (Master Battery Management Unit), the Ethernet ETH (EtherNet), and the optical fiber conversion module.

[0055] As an example, the fire protection system includes a control panel, detectors, alarm devices, etc., for detecting, alarming, or extinguishing fires in the energy storage system.

[0056] As an example, the power distribution device can be used to distribute power to the power consumption modules of the energy storage device.

[0057] The technical solutions described in the embodiments of this application are applicable to various electrical devices using energy storage devices, such as mobile phones, portable devices, laptop computers, battery cars, electric toys, electric tools, vehicles, ships, and spacecrafts, etc. For example, spacecrafts include airplanes, rockets, space shuttles, and spaceships, etc. The energy storage device is used to store or provide electrical energy.

[0058] In some embodiments, as Figure 1 shown, the energy storage system may include one or more energy storage devices 1 and a power conversion device 2 (Power Converter System, abbreviated as PCS). The power conversion device 2 is used to connect between the power generation device 3 and the energy storage device 1. The power generation device 3 is used to generate electrical energy, and the electrical energy generated by the power generation device 3 can be stored in the energy storage device 1 through the power conversion device 2. As an example, the power generation device 3 may specifically be a solar panel, a hydroelectric power generation device, a thermal power generation device, a wind power generation device, etc. Among them, the specific type of the power generation device 3 is not limited in this application.

[0059] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using energy storage systems, such as mobile phones, portable devices, laptops, battery cars, electric toys, power tools, vehicles, ships, and spacecrafts, etc. For example, spacecrafts include airplanes, rockets, space shuttles, and spaceships, etc. The energy storage device is used to store or provide electrical energy.

[0060] Please refer to Figure 2 , an embodiment of the present application provides a charging network, including a charging pile 4 and an energy storage device 1. The charging pile 4 is electrically connected to the energy storage device 1, and the energy storage device 1 is used to provide electrical energy for the charging pile 4. The charging pile 4 and the battery device in the energy storage device 1 are electrically connected through a cable, and the battery device can provide the electrical energy stored in itself to the charging pile 4. The charging pile 4 has one or more connectors 5, and the connectors are used to connect with an electrical device (such as a vehicle), so as to replenish energy to the electrical device.

[0061] The energy storage device can be located inside the charging pile (such as an integrated charging and energy storage machine), or outside the charging pile.

[0062] An embodiment of the present application provides an electrical device using a battery cell or a battery device or an energy storage device or an energy storage system as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric vehicles, ships, and spacecrafts, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric airplane toys, etc. Spacecrafts can include airplanes, rockets, space shuttles, and spaceships, etc.

[0063] For the convenience of description in the following embodiments, a vehicle 1000 in an embodiment of the present application is taken as an example for description.

[0064] Please refer to Figure 3 , Figure 3 is a schematic structural diagram of the vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc. A battery device 100 is arranged inside the vehicle, and the battery device 100 can be arranged at the bottom, head, or tail of the vehicle. The battery device 100 can be used for power supply of the vehicle. For example, the battery device 100 can be used as the operating power source of the vehicle. The vehicle may further include a controller 200 and a motor 300. The controller 200 is used to control the battery device 100 to supply power to the motor 300. For example, it is used for the working power requirements during the start, navigation, and driving of the vehicle.

[0065] In some embodiments of the present application, the battery device 100 can not only serve as the operating power source of the vehicle, but also as the driving power source of the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0066] Please refer to Figure 4 , Figure 4 which is an exploded view of the structure of the battery device 100 provided in some embodiments of the present application. The battery device 100 includes a box body 10 and a plurality of battery cells 20, and the battery cells 20 are used to be accommodated in the box body 10. Among them, the box body 10 is used to provide an assembly 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 box body 11 and a second box body 12, the first box body 11 and the second box body 12 are covered with each other, and the first box body 11 and the second box body 12 jointly define an assembly space for accommodating the battery cells 20. The second box body 12 may be a hollow structure with one end open, and the first box body 11 may be a plate-like structure. The first box body 11 covers the open side of the second box body 12 so that the first box body 11 and the second box body 12 jointly define an assembly space; the first box body 11 and the second box body 12 may also both be hollow structures with one side open, and the open side of the first box body 11 covers the open side of the second box body 12. Of course, the box body 10 formed by the first box body 11 and the second box body 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0067] In the battery device 100, the plurality of battery cells 20 can be connected in series, in parallel or in a mixed connection. A mixed connection means that there are both series and parallel connections among the plurality of battery cells 20. The plurality of battery cells 20 can be directly connected in series, in parallel or in a mixed connection together, and then the whole formed by the plurality of battery cells 20 is accommodated in the box body 10; of course, the battery device 100 can also be that a plurality of battery cells 20 are first connected in series, in parallel or in a mixed connection to form a battery module form, and then a plurality of battery modules are connected in series, in parallel or in a mixed connection to form a whole and are accommodated in the box body 10. The battery device 100 may further include other structures. For example, the battery device 100 may further include a busbar component for realizing the electrical connection between the plurality of battery cells 20.

[0068] Please refer to Figure 4 , the battery device 100 includes multiple rows of battery cells 20, the multiple rows of battery cells 20 are arranged along a first direction, and each row of battery cells 20 includes a plurality of battery cells 20 arranged along a second direction. The first direction and the second direction are respectively the length direction and the width direction of the box body 10, and the first direction and the second direction are perpendicular to each other.

[0069] According to some embodiments of the present application, the present application provides a battery cell 20, including: a housing and an electrode assembly, the electrode assembly is disposed in the housing, and the electrode assembly includes a pole piece 21.

[0070] Among them, the electrode assembly can be a wound structure or a laminated structure.

[0071] In some embodiments, the electrode assembly is a laminated structure, reducing the processing difficulty in the cold pressing process.

[0072] Such as Figure 5 and Figure 6 As shown, the electrode tab 21 includes: a current collector 211, a pre-pressing layer 212, and an adhesive layer 213.

[0073] Among them, the electrode tab 21 includes a positive electrode tab and a negative electrode tab, and both the positive electrode tab and the negative electrode tab can include a current collector 211, a pre-pressing layer 212, and an adhesive layer 213.

[0074] Exemplarily, the positive electrode tab in the electrode assembly can include a current collector 211, a pre-pressing layer 212, and an adhesive layer 213; or, the negative electrode tab in the electrode assembly can include a current collector 211, a pre-pressing layer 212, and an adhesive layer 213; or, both the positive electrode tab and the negative electrode tab in the electrode assembly can include a current collector 211, a pre-pressing layer 212, and an adhesive layer 213.

[0075] Among them, the pre-pressing layer 212 is disposed on at least one side of the current collector 211 in the thickness direction; the adhesive layer 213 is disposed between the pre-pressing layer 212 and the current collector 211.

[0076] The pre-pressing layer 212 functions as the coating layer of the electrode tab 21. The pre-pressing layer 212 has the same function and material as the coating layer, but the pre-pressing layer 212 and the coating layer have different morphologies. The coating layer is a liquid slurry layer, and the pre-pressing layer 212 is a compacted solid layer.

[0077] Exemplarily, pre-pressing layers 212 are disposed on both sides of the current collector 211 in the thickness direction, as shown in FIG. 5; or, a pre-pressing layer 212 can be disposed on one side of the current collector 211 in the thickness direction, as shown in FIG. 6.

[0078] The adhesive layer melts in the hot pressing process to make the adhesive layer soft and adhesive. The softened adhesive layer 213 is used to bond the pre-pressing layer 212 and the current collector 211.

[0079] Among them, it satisfies: d1 > d2, where d1 is the compaction density of the pre-pressing layer 212 and d2 is the compaction density of the current collector 211.

[0080] In this embodiment, the compaction density d1 of the pre-pressing layer 212 is greater than the compaction density d2 of the current collector 211. After the pre-pressing layer 212 is pre-pressed and then stacked with the current collector 211, and then pressed, the pre-pressing pressure is greater than the pressing pressure, so that it can be unrestricted by the ductility defect of the current collector 211, improving the compaction density of the electrode tab 21, and thus improving the energy density of the battery cell 20.

[0081] Among them, the compaction density d1 of the pre-pressing layer 212 satisfies: d1 ≥ 1.8 g / cc.

[0082] Exemplarily, the compaction density d1 of the pre-pressing layer 212 can be 1.8 g / cc, 2 g / cc, 2.8 g / cc, 3.8 g / cc or a larger value.

[0083] Among them, the electrode sheet 21 can be a positive electrode sheet or a negative electrode sheet. For the positive electrode sheet, the compaction density d1 of the pre-pressing layer 212 satisfies d1 ≥ 1.8 g / cc, and for the negative electrode sheet, the compaction density d1 of the pre-pressing layer 212 satisfies d1 ≥ 1.8 g / cc.

[0084] In this embodiment, by increasing the compaction density d1 of the pre-pressing layer 212, the overall compaction density of the electrode sheet 21 can be increased.

[0085] In the related art, in the cold pressing process of the electrode sheet of the battery cell, limited by the ductility of the current collector (such as copper foil, aluminum foil), a higher compaction density may cause excessive extension of the current collector and result in belt breakage. Therefore, it is difficult to directly make an electrode sheet with a high compaction density, which further limits the energy density of the battery cell.

[0086] According to the battery cell 20 provided by the embodiment of the present application, by setting the electrode sheet 21 as a structure including a current collector 211, an adhesive layer 213 and a pre-pressing layer 212, after pre-pressing the pre-pressing layer 212 and then stacking it with the current collector 211, and then performing pressing, the pre-pressing pressure is greater than the pressing pressure, so that it can be not limited by the ductility defect of the current collector 211, increase the compaction density of the electrode sheet 21, and thus increase the energy density of the battery cell 20.

[0087] In some embodiments, as shown in FIG. 5, the pre-pressing layer 212 is respectively provided on both sides of the current collector 211 in the thickness direction, the adhesive layer 213 is respectively provided on both sides of the current collector 211 in the thickness direction, and is respectively located between the pre-pressing layer 212 and the current collector 211 to bond the two sides of the pre-pressing layer 212 and the current collector 211 in the thickness direction respectively.

[0088] In some embodiments, the melting point T1 of the cross-linking agent of the adhesive layer 213 is less than the melting point T2 of the cross-linking agent of the pre-pressing layer 212. During the heating and pressing process, the adhesive layer 213 and the pre-pressing layer 212 are heated simultaneously, which can melt the cross-linking agent in the adhesive layer 213 to make the adhesive layer 213 soften and have adhesiveness, while not affecting the performance of the pre-pressing layer 212.

[0089] Exemplarily, in the positive electrode sheet, examples of the types of the cross-linking agent of the adhesive layer 213 and the cross-linking agent of the pre-pressing layer 212 are shown in Table 1.

[0090] Table 1 Examples of the types of the cross-linking agent of the adhesive layer 213 and the cross-linking agent of the pre-pressing layer 212 in the positive electrode sheet

[0091] As shown in Table 1, the softening temperatures of the crosslinking agents in the adhesive layer 213 are all lower than those of the crosslinking agents in the pre-pressing layer 212. This can not only melt the crosslinking agents in the adhesive layer 213 to soften the adhesive layer 213 and make it adhesive, but also not affect the performance of the pre-pressing layer 212.

[0092] Exemplarily, in the positive electrode tab, examples of the types of the crosslinking agents in the adhesive layer 213 and the crosslinking agents in the pre-pressing layer 212 are shown in Table 2.

[0093] Table 2 Examples of the types of the crosslinking agents in the adhesive layer 213 and the crosslinking agents in the pre-pressing layer 212 in the negative electrode tab

[0094] As shown in Table 2, the softening temperatures of the crosslinking agents in the adhesive layer 213 are all lower than those of the crosslinking agents in the pre-pressing layer 212. This can not only melt the crosslinking agents in the adhesive layer 213 to soften the adhesive layer 213 and make it adhesive, but also not affect the performance of the pre-pressing layer 212.

[0095] It should be noted that considering that the materials of the current collectors 211 of the positive electrode tab and the negative electrode tab are different, under the same compaction pressure, the compaction densities of the pre-pressing layer 212 of the positive electrode tab and the pre-pressing layer 212 of the negative electrode tab are different, so the compaction densities of the positive electrode tab and the negative electrode tab are different.

[0096] In some embodiments, when the tab 21 is a positive electrode tab, the compaction density d1 of the pre-pressing layer 212 of the positive electrode tab satisfies: d1≥1.8 g / cc; the compaction density D1 of the positive electrode tab satisfies: D1≥1.6 g / cc.

[0097] In this embodiment, by increasing the compaction density of the pre-pressing layer 212 in the positive electrode tab, the overall compaction density of the positive electrode tab can be increased, thereby increasing the energy density of the battery cell 20.

[0098] It can be understood that the overall compaction density of the positive electrode tab is the average value of the compaction densities of the current collector 211, the adhesive layer 213 and the pre-pressing layer 212. The overall compaction density of the positive electrode tab should be less than the compaction density of the pre-pressing layer 212, and the overall compaction density of the positive electrode tab should be greater than the compaction density of the current collector 211.

[0099] Exemplarily, the compaction density d1 of the pre-pressing layer 212 of the positive electrode sheet can be 1.8 g / cc, 2 g / cc, 2.1 g / cc, 2.5 g / cc, 3 g / cc or a greater compaction density, which can be specifically determined according to the usage scenario of the positive electrode sheet and the material of the pre-pressing layer 212. The compaction density D1 of the positive electrode sheet is determined according to the compaction density d1 of the pre-pressing layer 212 of the positive electrode sheet.

[0100] In some embodiments, a re-pressing process is added to the pressing step of the positive electrode sheet. In the re-pressing process, the compaction density D1 of the positive electrode sheet satisfies: D1 ≥ 1.7 g / cc.

[0101] In some embodiments, the compaction density D1 of the positive electrode sheet satisfies: D1 ≥ 2 g / cc.

[0102] In this embodiment, after the current collector 211 and the pre-pressing layer 212 of the positive electrode sheet are pressed together, and then through a low-pressure re-pressing process, the compaction density of the positive electrode sheet can be further increased, and the energy density of the battery cell 20 can be further improved.

[0103] In some embodiments, when the electrode sheet 21 is a negative electrode sheet, the compaction density d1 of the pre-pressing layer 212 of the negative electrode sheet satisfies: d1 ≥ 3 g / cc; the compaction density D2 of the negative electrode sheet satisfies: D2 ≥ 2.7 g / cc.

[0104] In this embodiment, by increasing the compaction density of the pre-pressing layer 212 in the negative electrode sheet, the overall compaction density of the negative electrode sheet can be increased, thereby improving the energy density of the battery cell 20.

[0105] It can be understood that the overall compaction density of the negative electrode sheet is the average value of the compaction densities of the current collector 211, the adhesive layer 213 and the pre-pressing layer 212. The overall compaction density of the negative electrode sheet should be less than the compaction density of the pre-pressing layer 212, and the overall compaction density of the negative electrode sheet should be greater than the compaction density of the current collector 211.

[0106] Exemplarily, the compaction density d1 of the pre-pressing layer 212 of the negative electrode sheet can be 3 g / cc, 3.2 g / cc, 3.5 g / cc, 4 g / cc, 4.5 g / cc or a greater compaction density, which can be specifically determined according to the usage scenario of the negative electrode sheet and the material of the pre-pressing layer 212. The compaction density D2 of the negative electrode sheet is determined according to the compaction density d1 of the pre-pressing layer 212 of the negative electrode sheet.

[0107] In some embodiments, a re-pressing process is added to the pressing step of the negative electrode sheet. In the re-pressing process, the compaction density D2 of the negative electrode sheet satisfies: D2 ≥ 2.8 g / cc.

[0108] In some embodiments, the compaction density D2 of the negative electrode sheet satisfies: D2 ≥ 3 g / cc.

[0109] In this embodiment, after the current collector 211 and the pre-pressing layer 212 of the negative electrode tab are pressed together, through a low-pressure re-pressing process, the compaction density of the negative electrode tab can be further increased, and the energy density of the battery cell 20 can be further improved.

[0110] This application embodiment also provides an electrode tab 21. Referring to FIGS. 5 and Figure 6 , including: a current collector 211, a pre-pressing layer 212, and an adhesive layer 213.

[0111] Among them, the electrode tab 21 can be a positive electrode tab or a negative electrode tab. Both the positive electrode tab and the negative electrode tab can include a current collector 211, a pre-pressing layer 212, and an adhesive layer 213.

[0112] The pre-pressing layer 212 functions as the coating layer of the electrode tab 21. The pre-pressing layer 212 has the same function and material as the coating layer. The coating layer is a liquid slurry layer, and the pre-pressing layer 212 is a compacted solid layer.

[0113] The adhesive layer melts in the heating and pressing process to make the adhesive layer soft and adhesive. The softened adhesive layer 213 is used to bond the pre-pressing layer 212 and the current collector 211.

[0114] Among them, it satisfies: d1 > d2, d1 ≥ 1.8 g / cc, where d1 is the compaction density of the pre-pressing layer 212, and d2 is the compaction density of the current collector 211.

[0115] In the related art, in the cold pressing process of the electrode tab 21 of the battery cell 20, limited by the ductility of the current collector 211 (such as copper foil, aluminum foil), a relatively high compaction density may cause excessive extension of the current collector 211 and result in breakage of the strip. Therefore, it is difficult to directly make an electrode tab 21 with a high compaction density, which further limits the energy density of the battery core.

[0116] According to the electrode tab 21 provided by this application embodiment, the electrode tab 21 is set as a structure of a current collector 211, an adhesive layer 213, and a pre-pressing layer 212. After the pre-pressing layer 212 is pre-pressed and then stacked with the current collector 211, and then pressed, the pre-pressing pressure is greater than the pressing pressure, so that it can be not limited by the ductility defect of the current collector 211, the compaction density of the electrode tab 21 is increased, and thus the energy density of the battery cell 20 is improved.

[0117] In some embodiments, the compaction density d1 of the pre-pressing layer 212 satisfies: d1 ≥ 1.8 g / cc.

[0118] Exemplarily, the compaction density d1 of the pre-pressing layer 212 can be 1.8 g / cc, 2 g / cc, 2.8 g / cc, 3.8 g / cc or a larger value.

[0119] The electrode sheet 21 can be a positive electrode sheet or a negative electrode sheet. For the positive electrode sheet, the compaction density d1 of the pre-pressing layer 212 satisfies d1≥1.8 g / cc. For the negative electrode sheet, the compaction density d1 of the pre-pressing layer 212 satisfies d1≥1.8 g / cc.

[0120] In some embodiments, when the electrode sheet 21 is a positive electrode sheet, the compaction density d1 of the pre-pressing layer 212 of the positive electrode sheet satisfies d1≥1.8 g / cc; the compaction density D1 of the positive electrode sheet satisfies D1≥1.6 g / cc.

[0121] In some embodiments, when the electrode sheet 21 is a negative electrode sheet, the compaction density d1 of the pre-pressing layer 212 of the negative electrode sheet satisfies d1≥3 g / cc; the compaction density D2 of the negative electrode sheet satisfies D2≥2.7 g / cc.

[0122] Such as Figure 5 、 Figure 6 and 7 As shown in

[0123] The embodiments of the present application further provide a method for preparing the electrode sheet 21, including: step 110 to step 140.

[0124] Step 110, providing a current collector 211.

[0125] In this step, when preparing the positive electrode sheet, the current collector 211 can be aluminum foil; when preparing the negative electrode sheet, the current collector 211 can be copper foil.

[0126] Step 120, providing main and auxiliary materials, and performing pre-pressing treatment on the main and auxiliary materials with a pressure F1 to obtain a pre-pressing layer 212 with a compaction density of d1.

[0127] In this step, when preparing the positive electrode sheet, the main and auxiliary materials are positive electrode active materials, and the positive electrode active materials can be lithium cobaltate, lithium iron phosphate, ternary lithium, lithium manganate, etc.; when preparing the negative electrode sheet, the main and auxiliary materials are negative electrode active materials, and the negative electrode active materials can be carbon or silicon, etc.

[0128] The pre-pressing layer 212 functions as the coating layer of the electrode sheet 21. The pre-pressing layer 212 has the same function and material as the coating layer. The coating layer is a liquid slurry layer, and the pre-pressing layer 212 is a compacted solid layer.

[0129] Step 130, providing an adhesive material, and coating the adhesive material on at least one side of the current collector 211 in the thickness direction to obtain an adhesive layer 213.

[0130] Exemplarily, an adhesive layer 213 may be provided on one side of the current collector 211 in the thickness direction; alternatively, adhesive layers 213 may be provided on both sides of the current collector 211 in the thickness direction.

[0131] In this step, the adhesive layer melts during the hot pressing process to soften the adhesive layer and make it adhesive. The softened adhesive layer 213 is used to bond the pre-pressed layer 212 and the current collector 211.

[0132] Step 140: Place the pre-pressed layer 212 on the adhesive layer 213 to obtain the unpressed electrode sheet 21, and press the unpressed electrode sheet 21 with a pressure F2 to obtain the electrode sheet 21. In this step, when the adhesive layer 213 is provided on one side of the current collector 211, the pre-pressed layer 212 is placed on the side of the current collector 211 where the adhesive layer 213 is provided; when the adhesive layers 213 are provided on both sides of the current collector 211 in the thickness direction, the pre-pressed layer 212 is placed on both sides of the current collector 211 in the thickness direction.

[0133] Among them, it satisfies: d1 > d2, F1 > F2, where d1 is the compaction density of the pre-pressed layer 212 and d2 is the compaction density of the current collector 211.

[0134] In this embodiment, the compaction density d1 of the pre-pressed layer 212 is greater than the compaction density d2 of the current collector 211. After pre-pressing the pre-pressed layer 212 and then stacking it with the current collector 211, the pressure F1 for pressing the pre-pressed layer 212 is greater than the pressure F2 for pressing the unpressed electrode sheet 21, which can reduce the risk of fracture of the current collector 211, improve the compaction density of the electrode sheet 21, and thus improve the energy density of the battery cell 20.

[0135] In some embodiments, the pressure F1 of the pre-pressing process satisfies: 5 MPa ≤ F1 ≤ 50 Mpa.

[0136] Exemplarily, the pressure F1 of the pre-pressing process may be 5 MPa, 15 MPa, 25 MPa, 35 MPa, or 50 MPa, and can be specifically determined according to the application scenario of the electrode sheet 21 and the types of the main and auxiliary materials.

[0137] In this embodiment, the range of the pressure F1 of the pre-pressing process is applicable to both the positive electrode sheet and the negative electrode sheet. By setting the range of the pressure F1 of the pre-pressing process, a reasonable pressure range can be used to press the main and auxiliary materials to obtain a high-compaction-density pre-pressed layer 212.

[0138] In some embodiments, the working temperature T1 of the pre-pressing process satisfies: 10 °C ≤ T1 ≤ 60 °C.

[0139] Among them, the working temperature range T1 of the pre-pressing treatment is applicable to both the positive electrode sheet and the negative electrode sheet. The working temperature T1 of the pre-pressing treatment can be 10°C, 20°C, 30°C, 40°C, 50°C or 60°C, and can be specifically determined according to the types of the main and auxiliary materials.

[0140] In this embodiment, by setting the working temperature range T1 of the pre-pressing treatment, the influence on the cross-linking agent in the pre-pressing layer 212 can be reduced, and the influence on the performance of the pre-pressing layer 212 can be reduced.

[0141] In some embodiments, the pressure F2 of the pressing treatment satisfies: 5 MPa ≤ F2 ≤ 15 Mpa.

[0142] Exemplarily, the pressure F2 of the pressing treatment can be 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa or 15 MPa, and can be specifically determined according to the application scenario of the electrode sheet 21 and the type of the base material.

[0143] In this embodiment, the pressure F2 range of the pressing treatment is applicable to both the positive electrode sheet and the negative electrode sheet. By setting the pressure F2 range of the pressing treatment, the current collector 211 can be protected, and the fracture risk caused by the ductility problem of the current collector 211 can be reduced.

[0144] In some embodiments, the working temperature T2 of the pressing treatment satisfies: 10°C ≤ T2 ≤ 60°C.

[0145] Among them, the working temperature range T2 of the pre-pressing treatment is applicable to both the positive electrode sheet and the negative electrode sheet. The working temperature T2 of the pressing treatment can be 10°C, 20°C, 30°C, 40°C, 50°C or 60°C, and can be specifically determined according to the material types of the pre-pressing layer 212 and the adhesive layer 213.

[0146] In this embodiment, by setting the working temperature range T2 of the pressing treatment, the cross-linking agent in the adhesive layer 213 can be melted, so that the adhesive layer 213 is softened and has adhesiveness, and at the same time, the performance of the pre-pressing layer 212 is not affected.

[0147] In some embodiments, after the electrode sheet 21 that has not been subjected to the pressing treatment is subjected to the pressing treatment to obtain the electrode sheet 21, it further includes: performing a re-pressing treatment on the pressed electrode sheet 21 with a pressure F3, where F3 < F2.

[0148] In this step, performing a re-pressing treatment on the pressed electrode sheet 21 can further increase the compaction density of the electrode sheet 21, and at the same time, does not affect the performance of the current collector 211.

[0149] Among them, the re-pressing treatment is applicable to both the positive electrode sheet and the negative electrode sheet.

[0150] In some embodiments, it is satisfied that 1 MPa ≤ F3 ≤ 8 MPa.

[0151] Exemplarily, the repressing pressure F3 can be 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa or 8 MPa.

[0152] According to some embodiments of the present application, as shown in Table 3, the present application provides a plurality of embodiments for preparing a negative electrode sheet.

[0153] Table 3 Preparation parameters of the negative electrode sheet

[0154] As shown in Table 3, in Comparative Example 1, the entire electrode sheet 21 is pressed once, and the compaction density of the electrode sheet 21 is small; in Comparative Example 2, the entire electrode sheet 21 is pressed and repressed. Due to the limitation of the ductility of the current collector 211, the compaction density of the electrode sheet 21 is small; in Embodiments 1 to 5, after the pre-pressing layer 212 is pre-pressed and then stacked with the current collector 211, and then pressed and repressed, an electrode sheet 21 with a larger compaction density can be obtained; in Comparative Examples 3 and 4, the pre-pressing pressure F1 is greater than 50 MPa, but the compaction density of the electrode sheet 21 decreases.

[0155] In summary, after the pre-pressing layer 212 is pre-pressed and then stacked with the current collector 211 and then pressed and repressed, the compaction density of the negative electrode sheet can be increased. Pressing the pre-pressing layer 212 within a reasonable pressure range can further increase the compaction density of the negative electrode sheet.

[0156] Table 4 Preparation parameters of the positive electrode sheet

[0157] As shown in Table 4, in Comparative Example 1, the entire electrode sheet 21 is pressed once, and the compaction density of the electrode sheet 21 is small; in Comparative Example 2, the entire electrode sheet 21 is pressed and repressed. Due to the limitation of the ductility of the current collector 211, the compaction density of the electrode sheet 21 is small; in Embodiments 1 to 5, after the pre-pressing layer 212 is pre-pressed and then stacked with the current collector 211, and then pressed and repressed, an electrode sheet 21 with a larger compaction density can be obtained; in Comparative Examples 3 and 4, the pre-pressing pressure F1 is greater than 50 MPa, but the compaction density of the electrode sheet 21 decreases; in Comparative Example 4, although the compaction density of the electrode sheet 21 exceeds 1.6 g / cc, the pre-pressing pressure is too large and the processing difficulty is high.

[0158] In summary, after the pre-pressing layer 212 is pre-pressed and then stacked with the current collector 211 and then pressed and repressed, the compaction density of the positive electrode sheet can be increased. Pressing the pre-pressing layer 212 within a reasonable pressure range can further increase the compaction density of the positive electrode sheet.

[0159] According to some embodiments of the present application, the present application further provides a battery device 100, and the battery device 100 includes a plurality of battery cells 20.

[0160] According to some embodiments of the present application, the present application further provides an energy storage device 1. The energy storage device 1 includes a plurality of battery cells 20 according to any of the above solutions, and the battery cells 20 are used to store or provide electric energy; or the energy storage device 1 includes a plurality of battery devices 100 according to any of the above solutions, and the battery devices 100 are used to store or provide electric energy.

[0161] According to some embodiments of the present application, the present application further provides an energy storage system, and the energy storage system includes: a power conversion device 2 and the energy storage device 1 according to any of the above solutions, and the power conversion device 2 is used to electrically connect a power generation device 3 and the energy storage device 1.

[0162] According to some embodiments of the present application, the present application further provides an electrical device. The electrical device includes a plurality of battery cells 20 according to any of the above solutions, and the battery cells 20 are used to store or provide electric energy; or the electrical device includes a plurality of battery devices 100 according to any of the above solutions, and the battery devices 100 are used to store or provide electric energy; or the electrical device includes the energy storage device 1 according to any of the above solutions, and the battery cells 20 or the battery device 100 are used to store or provide electric energy; or the electrical device includes the energy storage system according to any of the above solutions, and the battery cells 20 or the battery device 100 are used to store or provide electric energy.

[0163] The electrical device may be any of the aforementioned devices or systems that apply the battery device 100.

[0164] According to some embodiments of the present application, the present application further provides a charging network, and the charging network includes a charging pile 4 and the energy storage device 1 according to any of the above solutions or the energy storage system according to any of the above solutions, and the energy storage device 1 is used to provide electric energy for the charging pile 4.

[0165] The energy storage device 1 may be located inside the charging pile 4 (such as an integrated charging and energy storage machine), or may be located outside the charging pile 4.

[0166] If there is no special description, all the embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0167] If there is no special description, all the technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0168] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A battery cell, characterized in that: include: shell; An electrode assembly is disposed in the housing, wherein the electrode assembly comprises a pole piece, and the pole piece comprises: current collector; A pre-pressed layer disposed on at least one side of the current collector along the thickness direction; An adhesive layer disposed between the pre-pressed layer and the current collector; Satisfies: d1>d2, d1≥1.8g / cc; wherein d1 is the compaction density of the pre-pressed layer, and d2 is the compaction density of the current collector.

2. The battery cell according to claim 1, characterized in that: In the case where the electrode sheet is a positive electrode sheet, the compaction density d1 of the pre-compression layer of the positive electrode sheet satisfies: d1≥1.8 g / cc; and the compaction density D1 of the positive electrode sheet satisfies: D1≥1.6 g / cc.

3. The battery cell according to claim 1, characterized in that: In the case where the electrode sheet is a negative electrode sheet, the compaction density d1 of the pre-pressed layer of the negative electrode sheet satisfies: d1≥3g / cc; and the compaction density D2 of the negative electrode sheet satisfies: D2≥2.7g / cc.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The pre-pressing layers are arranged on both sides of the current collector along the thickness direction.

5. The battery cell according to any one of claims 1 to 3, characterized in that: The melting point T1 of the cross-linking agent of the adhesive layer is lower than the melting point T2 of the cross-linking agent of the pre-pressing layer.

6. A pole piece, characterized in that: include: current collector; A pre-pressed layer disposed on at least one side of the current collector along the thickness direction; An adhesive layer disposed between the pre-pressed layer and the current collector; Satisfies: d1>d2, d1≥1.8g / cc, wherein d1 is the compaction density of the pre-pressed layer, and d2 is the compaction density of the current collector.

7. A method for preparing a pole piece, characterized in that: include: providing a current collector; Providing main and auxiliary materials, and pre-pressing the main and auxiliary materials with a pressure F1 to obtain a pre-pressed layer with a compaction density of d1; Providing an adhesive material, and coating the adhesive material on at least one side of the current collector along the thickness direction to obtain an adhesive layer; Placing the pre-pressed layer on the adhesive layer to obtain an unpressed electrode, and pressing the unpressed electrode with a pressure of F2 to obtain an electrode; Wherein, the following conditions are satisfied: d1>d2, d1≥1.8 g / cc, F1>F2, wherein d1 is the compaction density of the pre-pressed layer, and d2 is the compaction density of the current collector.

8. The method for preparing a pole piece according to claim 7, characterized in that: The pressure F1 of the pre-pressing treatment satisfies: 5MPa≤F1≤50Mpa.

9. The method for preparing a pole piece according to claim 7, characterized in that: The pressure F2 of the pressing process satisfies: 5MPa≤F2≤15Mpa.

10. The method for preparing a pole piece according to claim 7, characterized in that: After the unpressed pole piece is pressed to obtain the pole piece, the method further comprises: The pressed pole piece is subjected to re-pressing treatment with a pressure F3, wherein F3 < F2.

11. The method for preparing a pole piece according to claim 10, characterized in that: Meet: 1MPa≤F3≤8Mpa.

12. A battery device, characterized in that: include: A plurality of battery cells according to any one of claims 1-5.

13. An energy storage device, characterized in that: include: A plurality of battery cells according to any one of claims 1 to 5 or a plurality of battery devices according to claim 12, wherein the battery cells or the battery devices are used to store or provide electrical energy.

14. An energy storage system, characterized in that: include: A power conversion device and an energy storage device as claimed in claim 13, wherein the power conversion device is used to electrically connect a power generation device and the energy storage device.

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