A lithium replenishment device

Abstract

This application relates to the field of battery technology and provides a lithium replenishment device, which includes a first roller, a second roller, a third roller, a fourth roller, and a fifth roller. The first and second rollers are used to roll a lithium strip to make the lithium strip adhere to the second roller to form a lithium layer. The second and third rollers are used to roll the lithium layer and the negative electrode sheet, coating the negative electrode sheet with the lithium layer; the fourth and fifth rollers jointly perform a secondary roll pressing on the negative electrode sheet coated with the lithium layer. By performing a secondary roll pressing on the negative electrode sheet coated with the lithium layer by the fourth and fifth rollers, the lithium layer is embedded in the negative electrode sheet. Since the lithium layer on the negative electrode sheet has already achieved solid-phase lithium intercalation through the secondary roll pressing before winding, the difference in the degree of lithium intercalation between the corner area and the straight area formed after the negative electrode sheet is wound is greatly reduced, which can improve the problem of uneven lithium intercalation, and thus improve the lithium plating and lifespan problems caused by the difference in solid-phase lithium intercalation.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing technology, and in particular to a lithium replenishment device. Background Technology

[0002] Battery cells can be used to store or provide electrical energy and are widely used in many fields such as vehicles and electronic products.

[0003] In related technologies, during the first charging process of a battery cell, some lithium is consumed due to the formation of the SEI film (solid electrolyte interface film), which in turn causes the loss of lithium in the negative electrode material and reduces the battery capacity. Therefore, there is a need to provide a lithium replenishment device that can coat metallic lithium onto the negative electrode and improve the problem of uneven lithium intercalation. Utility Model Content

[0004] This application provides a lithium replenishment device that uses a fourth roller and a fifth roller to perform secondary rolling on a negative electrode sheet coated with a lithium layer, thereby embedding the lithium layer into the negative electrode sheet and improving the problem of uneven lithium intercalation.

[0005] The technical solution of this application embodiment is implemented as follows:

[0006] This application provides a lithium replenishment device, the lithium replenishment device comprising:

[0007] First roller;

[0008] The second roller, the first roller and the second roller are used to roll the lithium strip so that the lithium strip adheres to the second roller to form a lithium layer;

[0009] The third roller, the second roller, and the third roller are used to roll the lithium layer and the negative electrode sheet, and to coat the lithium layer onto the negative electrode sheet;

[0010] Fourth roller;

[0011] The fifth roller, together with the fourth roller, performs secondary rolling on the negative electrode sheet coated with the lithium layer.

[0012] The lithium replenishment device provided in this application embodiment includes a first roller and a second roller for performing a rolling process. The second roller cooperates with the first roller to roll the lithium strip, causing the lithium metal on the lithium strip to adhere to the second roller and form a lithium layer. The second roller and a third roller are used to perform a lamination process. The third roller cooperates with the second roller to roll the negative electrode sheet, causing the lithium layer adhered to the second roller to be laminated onto the negative electrode sheet. A fourth roller and a fifth roller jointly perform a second rolling process on the negative electrode sheet with the lithium layer laminated, embedding the lithium layer into the negative electrode sheet. Thus, solid-phase lithium intercalation of the lithium layer is achieved before the winding process. After solid-phase lithium intercalation treatment, the negative electrode sheet, separator, and positive electrode sheet are stacked and wound. The wound electrode assembly then undergoes shaping, casing, and baking processes. Since the lithium layer on the negative electrode sheet has already achieved solid-phase lithium intercalation through secondary rolling before winding, the difference in the degree of lithium intercalation between the corner area and the straight area formed after winding the negative electrode sheet is greatly reduced. This can improve the problem of uneven lithium intercalation, thereby improving the lithium plating and lifespan problems caused by differences in solid-phase lithium intercalation. This improves the performance of the battery cell, increases the cycle life of the battery cell, and also improves the utilization rate of the lithium layer, reducing the need for additional metallic lithium, thus reducing costs and enhancing the competitiveness of the product.

[0013] In some embodiments, the fourth roller is provided with a first channel through which a cooling medium flows.

[0014] In this embodiment, since the solid-phase lithium intercalation speed of the lithium layer and the negative electrode sheet is accelerated by the secondary rolling, heat is generated during the process of lithium metal intercalation into the negative electrode sheet. The cooling medium flows through the first channel of the fourth roller and absorbs the heat generated during the secondary rolling process, thus avoiding the harm caused by heat accumulation.

[0015] In some embodiments, a second channel is provided inside the fifth roller, through which a cooling medium flows.

[0016] In this embodiment, since the solid-phase lithium intercalation speed of the lithium layer and the negative electrode sheet is accelerated by the secondary rolling, heat is generated during the process of lithium metal intercalation into the negative electrode sheet. The cooling medium flows through the second channel of the fifth roller, and the cooling medium absorbs the heat generated during the secondary rolling process, thus avoiding the harm caused by heat accumulation.

[0017] In some embodiments, the lithium replenishment device includes:

[0018] An air-cooling mechanism is located downstream of the fourth and fifth rollers. The air-cooling mechanism blows cooling airflow to air-cool the negative electrode sheet coated with the lithium layer after secondary rolling.

[0019] In this embodiment, since the solid-phase lithium intercalation speed of the lithium layer and the negative electrode sheet is accelerated by the secondary rolling, heat is generated during the process of lithium metal intercalation into the negative electrode sheet. The air cooling mechanism is located downstream of the fourth and fifth rollers. After the negative electrode sheet coated with the lithium layer is rolled twice by the fourth and fifth rollers, it is then air-cooled by the air cooling mechanism. The cooling airflow generated by the air cooling carries away the heat accumulation caused by solid-phase lithium intercalation, thereby achieving the purpose of heat dissipation and cooling.

[0020] In some embodiments, the cooling gas flow is carbon dioxide gas.

[0021] In this embodiment, carbon dioxide has advantages such as stable properties and low cost. Using carbon dioxide gas to cool the lithium layer can reduce the risk of lithium metal undergoing chemical reactions at high temperatures, and the temperature is uniform and controllable.

[0022] In some embodiments, the lithium replenishment device includes:

[0023] The sixth roller is located downstream of the third roller and upstream of the fourth roller, and the roller surface of the sixth roller abuts against the negative electrode sheet coated with the lithium layer.

[0024] In this embodiment, the roller surface of the sixth roller abuts against the negative electrode sheet coated with lithium layer, providing guidance and transition function for the negative electrode sheet coated with lithium layer, so that the negative electrode sheet passing through the second and third rollers can be more smoothly transported to the fourth and fifth rollers, thereby facilitating the fourth and fifth rollers to jointly perform secondary rolling on the negative electrode sheet coated with lithium layer.

[0025] In some embodiments, the lithium replenishment device includes:

[0026] The seventh roller is located downstream of the sixth roller and upstream of the fourth roller. The roller surface of the seventh roller abuts against and tensions the negative electrode sheet covered with the lithium layer.

[0027] In this embodiment, the sixth roller smoothly conveys the negative electrode sheet that has passed through the second and third rollers to the seventh roller. The roller surface of the seventh roller abuts against and tensions the negative electrode sheet coated with the lithium layer, so as to provide guidance, transition and tension functions for the negative electrode sheet coated with the lithium layer, so that the negative electrode sheet coated with the lithium layer can be in a roughly straight state, thereby facilitating the fourth and fifth rollers to jointly perform secondary rolling on the negative electrode sheet coated with the lithium layer, reducing the generation of wrinkles and other problems.

[0028] In some embodiments, the diameter of the seventh roller is larger than the diameter of the sixth roller.

[0029] In this embodiment, the seventh roller is mainly used to apply tension to stabilize the operation of the lithium-coated negative electrode sheet. The seventh roller has a relatively larger diameter, which can increase the contact area with the lithium-coated negative electrode sheet, making the tension distribution more uniform, and thus enabling the lithium-coated negative electrode sheet to maintain a taut state better. The sixth roller is mainly used to guide the direction of travel of the lithium-coated negative electrode sheet. Its smaller diameter can meet the guidance requirements. Moreover, the relatively smaller diameter of the sixth roller occupies less installation space and can also reduce the overall volume and manufacturing cost of the lithium replenishment device.

[0030] In some embodiments, at least one of the fourth and fifth rollers has a hardness-enhancing layer on its roller surface.

[0031] In this embodiment, the hardness-enhancing layer can increase the hardness of the roller surface of at least one of the fourth and fifth rollers, thereby improving the wear resistance of the roller surface of at least one of the fourth and fifth rollers, reducing the risk of wear and deformation of the roller surface of at least one of the fourth and fifth rollers, and thus increasing the service life of at least one of the fourth and fifth rollers.

[0032] In some embodiments, the flatness Ra of the hardness-enhancing layer is not greater than 1.

[0033] In this embodiment, the flatness Ra of the hardness reinforcement layer is no greater than 1, the surface of the hardness reinforcement layer is relatively smooth, and it makes uniform contact with the negative electrode sheet coated with lithium layer. This reduces the risk of the negative electrode sheet coated with lithium layer being stretched, broken or misaligned due to excessive local contact pressure. It can also reduce the frictional resistance with the negative electrode sheet coated with lithium layer, reduce wear on both, and protect the negative electrode sheet coated with lithium layer from scratches. Attached Figure Description

[0034] Figure 1 These are schematic diagrams of the vehicle structure provided in some embodiments of this application;

[0035] Figure 2 This is a schematic diagram of the structure of a battery device provided in some embodiments of this application;

[0036] Figure 3 These are schematic diagrams of the structure of a single battery cell provided in some embodiments of this application;

[0037] Figure 4 This is a schematic diagram of the structure of a lithium replenishment device provided in some embodiments of this application;

[0038] Figure 5 This is a schematic diagram of the structure of the fourth roller, fifth roller and air cooling mechanism provided in other embodiments of this application for secondary rolling of the negative electrode sheet coated with lithium layer;

[0039] Figure 6It is a scanning electron microscope image of a cut surface of a lithium-coated negative electrode sheet that has not undergone secondary rolling in the related technology.

[0040] Figure 7 This is a scanning electron microscope image of a cut surface of a lithium-coated negative electrode sheet that has undergone secondary rolling, as provided in some embodiments of this application.

[0041] Explanation of reference numerals in the attached figures

[0042] 1000, Vehicle; 100, Battery Unit; 200, Controller; 300, Motor; 1, Battery Cell; 11, Electrode Assembly; 111, Negative Electrode Sheet; 101, Negative Electrode Current Collector; 102, Negative Electrode Active Layer; 112, Lithium Layer; 12, Shell; 121, End Cap; 122, Housing; 2, Box Body; 21, First Box Body; 22, Second Box Body; 10, First Roller; 20, Second Roller; 30, Third Roller; 40, Fourth Roller; 50, Fifth Roller; 60, Air Cooling Mechanism; 70, Sixth Roller; 80, Seventh Roller; 90, Winding Roller; 2000, Lithium Strip. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this application clearer, embodiments of the technical solutions of this application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0045] In the description of the embodiments of this application, the technical terms "first", "second", "third", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0046] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that combinations can be made in any suitable manner without contradiction; for example, different combinations of specific technical features / embodiments can form different implementations. To avoid unnecessary repetition, the various possible combinations of specific technical features / embodiments in this application will not be described separately.

[0047] It should be noted that in this application, "multiple" refers to two or more items. "At least two" refers to two or more items.

[0048] Please see Figures 1 to 3 First, let’s introduce some basic structures of the battery cell 1, battery device 100 and electrical equipment provided in the embodiments of this application.

[0049] In this embodiment of the application, the battery cell 1 can be a secondary battery, which refers to the battery cell 1 that can be used again after being discharged by recharging to activate the active materials.

[0050] The type of battery cell 1 in this application is not limited. For example, battery cell 1 may include, but is not limited to, lithium-ion batteries or sodium-ion batteries, etc.

[0051] Please see Figure 3 and Figure 5 The battery cell 1 includes an electrode assembly 11, which includes a negative electrode 111, a positive electrode, and a separator, with the separator disposed between the negative electrode 111 and the positive electrode.

[0052] The electrode assembly 11 is the core component that enables the battery cell 1 to achieve repeated charging and discharging. During the charging and discharging process of the battery cell 1, active ions, such as lithium ions, are inserted and extracted back and forth between the negative electrode 111 and the positive electrode. The separator is disposed between the negative electrode 111 and the positive electrode to prevent short circuits between the negative electrode 111 and the positive electrode, while allowing active ions to pass through.

[0053] In some embodiments, the positive electrode may include a positive current collector.

[0054] In some embodiments, the positive electrode sheet may include a positive active layer disposed on at least one surface of the positive current collector.

[0055] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0056] As an example, the positive current collector can be made of metal foil, conductive polymer material, carbon material, or composite current collector. For example, as a metal foil, pure metal, alloy, or surface-treated metal can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. Composite current collectors can be formed by forming a metallic material (aluminum, aluminum alloy, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, etc.).

[0057] As an example, the positive electrode active layer may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active layers of batteries may also be used. These positive electrode active layers may use only one type or a combination of two or more types. Examples of lithium phosphate include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium manganese phosphate (such as LiMnPO4), or lithium manganese iron phosphate, etc.

[0058] In some embodiments, please refer to Figure 5 The negative electrode 111 may include a negative electrode current collector 101.

[0059] As an example, the negative electrode current collector 101 can be made of metal foil, conductive polymer material, carbon material, or composite current collector. For example, as a metal foil, pure metal, alloy, or surface-treated metal can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material substrate and the negative electrode current collector 101. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a polypropylene or polyethylene terephthalate substrate, etc.).

[0060] In some embodiments, please refer to Figure 5 The negative electrode 111 may include a negative electrode active layer 102 disposed on at least one surface of the negative electrode current collector 101.

[0061] As an example, the negative electrode current collector 101 has two surfaces opposite each other in its own thickness direction, and the negative electrode active layer 102 is disposed on either or both of the two opposite surfaces of the negative electrode current collector 101.

[0062] As an example, the negative electrode active layer 102 may employ a type of negative electrode active layer 102 known in the art for use in battery cell 1. As an example, the negative electrode active layer 102 may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. However, this application is not limited to these materials, and other conventional materials that can be used as the negative electrode active layer 102 of battery cell 1 may also be used. These negative electrode active layers 102 may be used alone or in combination of two or more.

[0063] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector 101 can be made of copper.

[0064] This application does not impose any particular restrictions on the type of separator; any known porous membrane with good chemical and mechanical stability can be selected.

[0065] As an example, the main material of the separator can be selected from at least one of polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular restrictions. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular restrictions.

[0066] In some embodiments, the battery cell 1 further includes an electrolyte, which acts as a conductor of ions between the negative electrode 111 and the positive electrode. This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. The electrolyte can be liquid, gel-like, or solid.

[0067] Liquid electrolytes include electrolyte salts and solvents.

[0068] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0069] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0070] In some embodiments, the electrolyte may optionally include additives. For example, additives may include positive electrode film-forming additives, negative electrode film-forming additives, and additives that can improve certain performance of the battery cell 1, such as additives that improve the overcharge / fast charge performance of the battery cell 1, additives that improve the high-temperature performance of the battery cell 1, additives that improve the low-temperature performance of the battery cell 1, etc.

[0071] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0072] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0073] As an example, the polymer of a polymeric solid electrolyte may include polyether (polyoxyethylene), polysiloxane, or polycarbonate, etc.

[0074] As an example, inorganic solid electrolytes can be one or more of oxide solid electrolytes (crystalline perovskite, amorphous LiPON thin films), sulfide solid electrolytes (crystalline lithium superion conductors (lithium germanium phosphate sulfide, silver sulfide germanium ore), amorphous sulfides), and halide solid electrolytes.

[0075] In some embodiments, the electrode assembly 11 is provided with tabs that can conduct current from the electrode assembly 11. The tabs include a negative tab and a positive tab. The negative tab is connected to the negative electrode plate 111, and the positive tab is connected to the positive electrode plate. The negative tab protrudes from one end of the negative electrode plate 111 in the width direction. The negative tab is made of the same material as the negative current collector 101, and the negative tab is not attached to the negative active layer 102. The positive tab protrudes from one end of the positive electrode plate in the width direction. The positive tab is made of the same material as the positive current collector, and the positive tab is not attached to the positive active layer.

[0076] In some embodiments, the battery cell 1 may include a casing 12. The casing 12 may be a steel casing, an aluminum casing, a plastic casing (such as polypropylene), a composite metal casing (such as a copper-aluminum composite casing 12), or an aluminum-plastic film, etc. In some embodiments, the casing 12 may be a sealed structure or a non-sealed structure. As an example, when the casing 12 is a non-sealed structure, the casing 12 serves to protect the electrode assembly 11, and a sealing bag is also included between the casing 12 and the electrode assembly 11. The sealing bag is used to encapsulate the electrode assembly 11 and the electrolyte. Specifically, the sealing bag may be a bag-shaped insulating structure or an aluminum-plastic film. When the casing 12 is a sealed structure, it is used to encapsulate the electrode assembly 11 and the electrolyte, etc.

[0077] As an example, the battery cell 1 can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic battery cells. Multi-prismatic battery cells are, for example, hexagonal prismatic battery cells. This application does not have any particular limitations.

[0078] In some embodiments, please refer to Figure 3 The outer casing 12 includes an end cap 121 and a housing 122. The housing 122 has an opening, and the end cap 121 covers the opening. The housing 122 may have one or more openings. The end cap 121 may also have one or more.

[0079] In some embodiments, at least one terminal post is provided on the housing 12, and the terminal post is electrically connected to the tab. The terminal post can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The terminal post can be provided on the end cap 121 or on the housing 122.

[0080] Please see Figure 2 The battery device 100 provided in this application includes a battery cell 1 as described in any one of the embodiments of this application. The battery cell 1 is used to provide voltage and capacity.

[0081] Multiple battery cells 1 can be connected in series, parallel, or mixed via a busbar. The busbar is used to achieve electrical connection between at least two battery cells 1.

[0082] For example, "hybrid connection" refers to at least two battery cells 1 that are connected in both series and parallel. At least two battery cells 1 can be directly connected in series, parallel, or hybrid connections; of course, at least two battery cells 1 can also be first connected in series, parallel, or hybrid connections to form a module, and then the module can be connected in series, parallel, or hybrid connections to form a whole.

[0083] In some embodiments, the battery cell assembly is typically formed by arranging multiple battery cells 1.

[0084] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells 1 together to form an independent module. As an example, a battery module can be formed by bundling multiple battery cells 1 together with cable ties.

[0085] In some embodiments, the battery device 100 may be a battery pack.

[0086] Please see Figure 2 The battery device 100 may include a housing 2. As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be housed in the housing 2 by fixing the battery module in the housing 2.

[0087] As an example, the battery cell assembly can also be housed in the housing 2 by directly fixing multiple battery cells 1 to the housing 2.

[0088] In some embodiments, the housing 2 can be part of the vehicle's chassis structure. For example, a portion of the housing 2 can be at least a portion of the vehicle's floor, or a portion of the housing 2 can be at least a portion of the vehicle's crossbeams and longitudinal beams.

[0089] In some embodiments, please refer to Figure 2The housing 2 may include a first housing body 21 and a second housing body 22, with the first housing body 21 and the second housing body 22 having openings opposite to each other, together forming a receiving cavity. The battery cell assembly can be housed within the receiving cavity.

[0090] The electrical equipment provided in this application includes the battery device 100 in any embodiment of this application. The battery device 100 is used to store or provide electrical energy.

[0091] Electrical equipment includes, but is not limited to, energy storage devices, mobile phones, tablets, laptops, electric toys, power tools, vehicles, ships, or spacecraft. Vehicles can include electric bicycles and electric cars; electric toys can include electric bicycle toys and electric car toys, etc., including stationary or mobile electric toys such as game consoles, electric car toys, electric boat toys, and electric airplane toys; spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0092] Energy storage devices include, but are not limited to, energy storage containers or energy storage cabinets.

[0093] In the following embodiments, for ease of explanation, a vehicle 1000 is used as an example of an electrical device according to an embodiment of this application. The description is as follows, with reference to the accompanying drawings.

[0094] Figure 1 The diagram illustrates the structure of a vehicle 1000 as provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Figure 1 As shown, a battery device 100 is installed inside the vehicle 1000. The battery device 100 can be located in the lower part, front, or rear of the vehicle 1000. The battery device 100 can be used to power the vehicle 1000; for example, the battery device 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery device 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during starting, navigation, and driving.

[0095] In some embodiments of this application, the battery device 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0096] In some embodiments, please refer to Figure 3 and Figure 5The battery cell 1 includes a lithium layer 112, a negative electrode 111, a separator, and a positive electrode wound into a wound structure. The negative electrode 111 has a lithium layer 112 disposed on at least one surface in the thickness direction. During the first charge and subsequent cycles, the lithium layer 112 can compensate for the irreversible lithium loss consumed in the formation of the SEI film, replenish the lost active lithium ions, thereby reducing the capacity loss of the battery cell 1 during the first charge and discharge process and improving the capacity and cycle life of the battery cell 1.

[0097] The lithium layer 112 is a layered structure formed of lithium metal. The lithium layer 112 can serve as a lithium replenishment layer.

[0098] The negative electrode 111, the separator, and the positive electrode are wound into a wound structure. This can be achieved by stacking the negative electrode 111, the separator, and the positive electrode, and then spirally winding them around the same axis from one end, layer by layer inwards or outwards. The wound electrode assembly 11 is shaped to be approximately flat. The wound negative electrode 111 includes at least two straight regions and at least two corner regions, with the corner regions connecting the two straight regions. The straight regions extend in a generally straight line, while the corner regions extend in a generally arc shape.

[0099] In related technologies, a single battery cell forms an SEI film during its first charge and discharge cycle. This SEI film consumes some lithium, resulting in lithium loss. To mitigate the capacity loss caused by lithium consumption, a lithium layer is pre-added to the negative electrode during its production. However, after the lithium layer is deposited onto the negative electrode, no further processing is performed. Instead, it is directly stacked with the separator and positive electrode and wound. The wound electrode assembly then undergoes shaping, casing, and baking processes. Prior to these processes, there is no corresponding solid-state lithium intercalation scheme; the process relies solely on simple self-reactions of the electrode assembly, which is slow. On the one hand, during the shaping process, the large surface area of ​​the wound electrode assembly (corresponding to the flat area of ​​the negative electrode sheet) is subjected to pressure, while the corner area of ​​the negative electrode sheet is not subjected to pressure. However, a significant amount of metallic lithium remains on the surface of the corner area, resulting in a higher degree of solid-phase lithium intercalation on the large surface area compared to the corner area. The difference between the large surface area and the corner area is approximately 22%. This leads to differences in the SEI film between the flat area and the corner area during liquid-phase lithium intercalation, resulting in impedance differences. The impedance of the corner area is higher, and because of this higher impedance, the kinetic window is affected. In such cases, lithium intercalation becomes difficult, meaning that lithium intercalation at corners is more difficult than on larger surfaces, leading to problems such as lithium plating and high lithium consumption in corner areas. On the other hand, after lithium replenishment, the negative electrode sheet is directly stacked with the separator and positive electrode sheet and wound, and then shaped and packaged in sequence. Until the baking process, the lithium layer on the surface of the negative electrode sheet can come into contact with oxygen, nitrogen, and moisture in the air. It will react with oxygen and nitrogen in the air, causing some of the metallic lithium to be consumed, greatly reducing the utilization rate of metallic lithium and leading to increased costs.

[0100] In view of this, embodiments of this application provide a lithium replenishment device, which includes a first roller, a second roller, a third roller, a fourth roller, and a fifth roller. The first and second rollers are used to roll the lithium strip so that the lithium strip adheres to the second roller to form a lithium layer. The second and third rollers are used to roll the lithium layer and the negative electrode sheet, coating the negative electrode sheet with the lithium layer; the fourth and fifth rollers together perform a secondary rolling of the negative electrode sheet coated with the lithium layer.

[0101] The lithium replenishment device provided in this application embodiment includes a first roller and a second roller for performing a rolling process. The second roller cooperates with the first roller to roll the lithium strip, causing the lithium metal on the lithium strip to adhere to the second roller and form a lithium layer. The second roller and a third roller are used to perform a lamination process. The third roller cooperates with the second roller to roll the negative electrode sheet, causing the lithium layer adhered to the second roller to be laminated onto the negative electrode sheet. A fourth roller and a fifth roller jointly perform a second rolling process on the negative electrode sheet with the lithium layer laminated, embedding the lithium layer into the negative electrode sheet. Thus, solid-phase lithium intercalation of the lithium layer is achieved before the winding process. After solid-phase lithium intercalation treatment, the negative electrode sheet, separator, and positive electrode sheet are stacked and wound. The wound electrode assembly then undergoes shaping, casing, and baking processes. Since the lithium layer on the negative electrode sheet has already achieved solid-phase lithium intercalation through secondary rolling before winding, the difference in the degree of lithium intercalation between the corner area and the straight area formed after winding the negative electrode sheet is greatly reduced. This can improve the problem of uneven lithium intercalation, thereby improving the lithium plating and lifespan problems caused by differences in solid-phase lithium intercalation. This improves the performance of the battery cell, increases the cycle life of the battery cell, and also improves the utilization rate of the lithium layer, reducing the need for additional metallic lithium, thus reducing costs and enhancing the competitiveness of the product.

[0102] The lithium replenishment device provided in the embodiments of this application is further described below with reference to the accompanying drawings. Figure 4 and Figure 5 The lithium replenishment device provided in this application includes a first roller 10, a second roller 20, a third roller 30, a fourth roller 40, and a fifth roller 50. The first roller 10 and the second roller 20 are used to roll the lithium strip 2000 so that the lithium strip 2000 adheres to the second roller 20 to form a lithium layer 112. The second roller 20 and the third roller 30 are used to roll the lithium layer 112 and the negative electrode 111, coating the lithium layer 112 onto the negative electrode 111; the fourth roller 40 and the fifth roller 50 together perform a secondary roll pressing on the negative electrode 111 coated with the lithium layer 112.

[0103] The first roller 10 and the second roller 20 are used to carry out the rolling process. The second roller 20 is used to cooperate with the first roller 10 to roll the lithium strip 2000 together, so that the lithium metal on the lithium strip 2000 is adhered to the second roller 20 to form a lithium layer 112.

[0104] The first roller 10 and the second roller 20 are arranged in parallel, that is, the axis of the first roller 10 and the axis of the second roller 20 are parallel. In some embodiments, the axis of the first roller 10 and the axis of the second roller 20 are both parallel to the horizontal plane and located at the same height. After the lithium strip 2000 is fed between the first roller 10 and the second roller 20, the first roller 10 and the second roller 20 can cooperate with each other to achieve the rolling of the lithium strip 2000.

[0105] For example, the first roller 10 rotates in opposite directions to the second roller 20, and the gap between the first roller 10 and the second roller 20 is smaller than the thickness of the lithium strip 2000.

[0106] The lithium strip 2000 has a certain degree of plasticity. When it is fed between the first roller 10 and the second roller 20, the lithium strip 2000 is located in the gap between the first roller 10 and the second roller 20. The lithium strip 2000 will stretch due to the rolling pressure and form a thinner lithium layer 112, which is beneficial for its subsequent lamination onto the surface of the negative electrode sheet 111. Of course, the gap between the first roller 10 and the second roller 20 needs to be smaller than the thickness of the lithium strip 2000 to roll the lithium strip 2000 and make the lithium strip 2000 adhere to the roller surface of the second roller 20 under pressure. The first roller 10 and the second roller 20 rotate in opposite directions to facilitate the feeding of the lithium strip 2000.

[0107] The second roller 20 and the third roller 30 are used to implement the lithium replenishment technology bonding process. The third roller 30 is used to cooperate with the second roller 20 to roll the negative electrode 111 together, so that the lithium layer 112 adhering to the second roller 20 is bonded to the negative electrode 111.

[0108] The second roller 20 and the third roller 30 are arranged in parallel, that is, the axis of the second roller 20 and the axis of the third roller 30 are parallel. In some embodiments, the axes of the second roller 20 and the third roller 30 are both parallel to the horizontal plane and located at the same height. After the negative electrode sheet 111 is fed between the second roller 20 and the third roller 30, the second roller 20 and the third roller 30 can cooperate with each other to achieve the coating function of the lithium layer 112 and the negative electrode sheet 111.

[0109] For example, the second roller 20 rotates in the opposite direction to the third roller 30 in order to facilitate the conveying of the negative electrode sheet 111.

[0110] As the second roller 20 rotates, the lithium layer 112 on the second roller 20 is fed between the second roller 20 and the third roller 30. Since the negative electrode 111 is fed between the second roller 20 and the third roller 30, the lithium layer 112 and the negative electrode 111 are simultaneously located in the gap between the second roller 20 and the third roller 30. Due to the large surface roughness of the negative electrode 111, the adhesion between the lithium layer 112 and the negative electrode 111 is greater than the adhesion between the lithium layer 112 and the roller surface of the second roller 20. The adhesion between the lithium layer 112 and the negative electrode 111 is such that when they come into contact and are subjected to rolling pressure, the lithium layer 112 will adhere to the negative electrode 111. As the negative electrode 111 is conveyed, it will pull the lithium layer 112 and cause it to peel off from the roller surface of the second roller 20, thus achieving lithium coating on the negative electrode 111. In other words, the lithium layer 112 that is adhered to the roller surface of the second roller 20 is coated onto the surface of the negative electrode 111, realizing the lithium replenishment process of the negative electrode 111.

[0111] The fourth roller 40 and the fifth roller 50 are used to implement the solid-phase lithium intercalation process. The fifth roller 50 is used to cooperate with the fourth roller 40 to perform secondary rolling on the negative electrode 111 coated with lithium layer 112, so that the lithium layer 112 is embedded in the negative electrode 111.

[0112] The fourth roller 40 and the fifth roller 50 are arranged in parallel, that is, the axis of the fourth roller 40 and the axis of the fifth roller 50 are parallel. In some embodiments, the axes of the fourth roller 40 and the fifth roller 50 are both parallel to the horizontal plane and located at the same height. After the negative electrode sheet 111 coated with the lithium layer 112 is fed between the fourth roller 40 and the fifth roller 50, the fourth roller 40 and the fifth roller 50 can cooperate with each other to achieve secondary rolling of the lithium layer 112 and the negative electrode sheet 111, so that the lithium layer 112 is embedded in the negative electrode sheet 111 under pressure, playing the role of solid-phase lithium intercalation.

[0113] It is understandable that the axial height of the fourth roller 40 and the fifth roller 50 can be higher, lower, or equal to the axial height of the third roller 30.

[0114] For example, the fourth roller 40 rotates in the opposite direction to the fifth roller 50 in order to facilitate the transport of the negative electrode 111 coated with the lithium layer 112.

[0115] When the negative electrode sheet 111 coated with lithium layer 112 is fed between the fourth roller 40 and the fifth roller 50, the negative electrode sheet 111 coated with lithium layer 112 is located in the roll gap between the fourth roller 40 and the fifth roller 50, and the lithium layer 112 is embedded into the negative electrode sheet 111 due to the rolling pressure. The roll gap between the fourth roller 40 and the fifth roller 50 needs to be smaller than the thickness of the negative electrode sheet 111 coated with lithium layer 112 in order to roll the lithium layer 112 and embed it into the negative electrode sheet 111 under pressure. The fourth roller 40 and the fifth roller 50 rotate in opposite directions to facilitate the conveying of the negative electrode sheet 111 coated with lithium layer 112.

[0116] The negative electrode 111 coated with lithium layer 112 is subjected to secondary rolling by the fourth roller 40 and the fifth roller 50, so that the lithium layer 112 is embedded in the negative electrode 111. In this way, solid-phase lithium intercalation of lithium layer 112 is achieved before the winding process. Then, the negative electrode 111 treated with solid-phase lithium intercalation is stacked with the separator and the positive electrode and wound. The wound electrode assembly 11 is then subjected to shaping, shelling and baking processes in sequence. Since the lithium layer 112 on the negative electrode 111 has achieved solid-phase lithium intercalation through secondary rolling before winding, the difference in the degree of lithium intercalation between the corner area and the straight area formed after the negative electrode 111 is wound is greatly reduced, which can improve the problem of uneven lithium intercalation, and thus improve the lithium plating and lifespan problems caused by the difference in solid-phase lithium intercalation.

[0117] For example, the corner regions of the negative electrode sheet 111 coated with lithium layer 112 without secondary rolling and the corner regions of the negative electrode sheet 111 coated with lithium layer 112 after secondary rolling are respectively cut, and the differences in the degree of solid-state lithium intercalation on the cut surfaces are observed by scanning electron microscopy. Please refer to [link to relevant documentation]. Figure 6 and Figure 7 , Figure 6 This is a scanning electron microscope (SEM) image of a cut surface of a lithium-coated negative electrode sheet that has not undergone secondary rolling in the related technology. Figure 7 The scanning electron microscope image is a cross-section of the negative electrode 111 coated with lithium layer 112 after secondary rolling. The difference before and after secondary rolling can be clearly observed. The thickness of lithium layer 112 of negative electrode 111 coated with lithium layer 112 after secondary rolling is about 1 μm (micrometer) smaller than that of negative electrode 111 coated with lithium layer 112 without secondary rolling.

[0118] The lithium replenishment device provided in this application embodiment includes a first roller 10 and a second roller 20 for performing a rolling process. The second roller 20 cooperates with the first roller 10 to roll the lithium strip 2000 together, so that the lithium metal on the lithium strip 2000 adheres to the second roller 20 to form a lithium layer 112. The second roller 20 and a third roller 30 are used to perform a lamination process. The third roller 30 cooperates with the second roller 20 to roll the negative electrode sheet 111 together, so that the lithium layer 112 adhered to the second roller 20 is laminated onto the negative electrode sheet 111. A fourth roller 40 and a fifth roller 50 jointly perform a secondary rolling process on the negative electrode sheet 111 with the lithium layer 112 laminated thereon, so that the lithium layer 112 is embedded in the negative electrode sheet 111. Thus, during the winding process... Before the process, solid-phase lithium intercalation of the lithium layer 112 is achieved. Then, the negative electrode 111, which has undergone solid-phase lithium intercalation treatment, is stacked with the separator and the positive electrode and wound. The wound electrode assembly 11 is then subjected to shaping, casing, baking and other processes in sequence. Since the lithium layer 112 on the negative electrode 111 has already achieved solid-phase lithium intercalation through secondary rolling before winding, the difference in the degree of lithium intercalation between the corner area and the straight area formed after the negative electrode 111 is wound is greatly reduced. This can improve the problem of uneven lithium intercalation, thereby improving the lithium plating and lifespan problems caused by the difference in solid-phase lithium intercalation, thus improving the performance of the battery cell 1, increasing the cycle life of the battery cell 1, and also improving the utilization rate of the lithium layer 112, reducing the need for replenishing metallic lithium, thereby reducing costs and enhancing the competitiveness of the product.

[0119] A fourth roller 40 and a fifth roller 50 can form a group. In some embodiments, the lithium replenishment device can use a group of fourth rollers 40 and fifth rollers 50 to perform a single-stage secondary rolling process on the negative electrode 111 coated with the lithium layer 112. In some embodiments, the lithium replenishment device can use multiple groups of fourth rollers 40 and fifth rollers 50, which can be spaced apart to perform multi-stage secondary rolling process on the negative electrode 111 coated with the lithium layer 112.

[0120] It should be noted that "multiple groups" includes two or more groups.

[0121] In some embodiments, the negative electrode 111 includes a negative current collector 101 and a negative active layer 102. The lithium layer 112 can be disposed on the side of the negative active layer 102 away from the negative current collector 101, and the negative active layer 102 can be made of graphite. After being laminated by the second roller 20 and the third roller 30, most of the metallic lithium in the lithium layer 112 is on the graphite surface, and the LiCx layer is very small. The LiCx layer is the product of lithium metal intercalation with graphite. By applying pressure through the fourth roller 40 and the fifth roller 50, the metallic lithium can quickly combine with the graphite to form the LiCx layer, realizing solid-phase lithium intercalation. In this way, the metallic lithium is basically solid-phase intercalated into the graphite. For example, after solid-phase lithium intercalation, the thickness of the LiCx layer can be increased from 0 μm to about 2 μm (unit micrometer).

[0122] In some embodiments, a first channel is provided inside the fourth roller 40, through which a cooling medium flows.

[0123] The cooling medium flows through the first channel to absorb the heat generated during the secondary rolling process of the negative electrode 111 coated with the lithium layer 112.

[0124] It should be noted that there is no limit to the specific number of the first channel. There can be one or more.

[0125] The lithium layer 112 is embedded into the negative electrode active layer 102 through secondary rolling. Taking graphite as an example, the process of lithium metal embedding into graphite generates heat, and lithium metal (Li) is embedded into graphite to form LiCx. H2 is approximately equal to -15 kJ mol⁻¹, where, H2 represents the heat released during solid-phase lithium intercalation, and this heat needs to be dissipated promptly.

[0126] In this embodiment, since the solid-phase lithium insertion speed of the lithium layer 112 and the negative electrode 111 is accelerated by the secondary rolling, heat is generated during the process of lithium metal insertion into the negative electrode 111. The cooling medium flows through the first channel of the fourth roller 40, and the heat generated during the secondary rolling process is absorbed by the cooling medium, so as to avoid the harm caused by heat accumulation.

[0127] For example, the fourth roller 40 has a first input port and a first output port, both of which are connected to the first channel. The cooling medium enters the first channel through the first input port. After absorbing the heat generated during the secondary rolling process, the cooling medium flows out through the first output port to release the heat and complete the cooling and heat dissipation.

[0128] In some embodiments, the first input port and the first output port may be formed at the two ends of the fourth roller 40 in the axial direction.

[0129] In some embodiments, a second channel is provided inside the fifth roller 50, through which a cooling medium flows.

[0130] The cooling medium flows through the second channel to absorb the heat generated during the secondary rolling process of the negative electrode 111 coated with the lithium layer 112.

[0131] It should be noted that there is no limit to the specific number of second channels. There can be one or more.

[0132] In this embodiment, since the solid-phase lithium insertion speed of the lithium layer 112 and the negative electrode 111 is accelerated by the secondary rolling, heat is generated during the process of lithium metal insertion into the negative electrode 111. The cooling medium flows through the second channel of the fifth roller 50, and the heat generated during the secondary rolling process is absorbed by the cooling medium, so as to avoid the harm caused by heat accumulation.

[0133] For example, the fifth roller 50 has a second input port and a second output port, both of which are connected to the second channel. The cooling medium enters the second channel through the second input port. After absorbing the heat generated during the secondary rolling process, the cooling medium flows out through the second output port to release the heat and complete the cooling and heat dissipation.

[0134] In some embodiments, the second input port and the second output port may be formed at the two ends of the fifth roller 50 in the axial direction, respectively.

[0135] The specific type of cooling medium is not limited here, as long as it can absorb the heat generated by the secondary rolling process; for example, it can be gaseous or liquid. For instance, the cooling medium includes, but is not limited to, cooling oil.

[0136] In some embodiments, please refer to Figure 4 and Figure 5 The lithium replenishment device includes an air-cooling mechanism 60, which is located downstream of the fourth roller 40 and the fifth roller 50. The air-cooling mechanism 60 blows cooling airflow to air-cool the negative electrode sheet 111 coated with lithium layer 112 after secondary rolling.

[0137] For example, the temperature of the negative electrode 111 coated with lithium layer 112 after secondary rolling may reach about 60°C, which poses a risk of smoke. By using cooling airflow for air cooling, the temperature of the negative electrode 111 coated with lithium layer 112 can be reduced to about 25°C.

[0138] In this embodiment, since the solid-phase lithium intercalation speed of the lithium layer 112 and the negative electrode 111 is accelerated by secondary rolling, heat is generated during the process of lithium metal intercalation into the negative electrode 111. The air cooling mechanism 60 is located downstream of the fourth roller 40 and the fifth roller 50. After the negative electrode 111 coated with the lithium layer 112 is rolled twice by the fourth roller 40 and the fifth roller 50, it is then air-cooled by the air cooling mechanism 60. The cooling airflow generated by the air cooling carries away the heat accumulated from the solid-phase lithium intercalation 2000, thereby achieving the purpose of heat dissipation and cooling.

[0139] It should be noted that upstream and downstream refer to the sequential relationship in the process flow. In the embodiments of this application, such as... Figure 4As shown, the first roller 10, the second roller 20, and the third roller 30 are located upstream of the fourth roller 40 and the fifth roller 50, while the air-cooling mechanism 60 is located downstream of the fourth roller 40 and the fifth roller 50. During the conveying process, the negative electrode sheet 111 first passes through the second roller 20 and the third roller 30, then through the fourth roller 40 and the fifth roller 50, and finally through the air-cooling mechanism 60. In this way, the negative electrode sheet 111 first undergoes a lithium replenishment process, then a solid-phase lithium intercalation process, and finally an air-cooling process.

[0140] The number of air-cooling mechanisms 60 is unlimited; there can be one or more air-cooling mechanisms 60.

[0141] The arrangement of the air-cooling mechanism 60 is not limited. For example, multiple air-cooling mechanisms 60 can be arranged at intervals along the tape-carrying direction of the negative electrode sheet 111. For example, at least one air-cooling mechanism 60 can be arranged at one or both ends in the thickness direction of the negative electrode sheet 111.

[0142] In some embodiments, the air-cooling mechanism 60 includes an air knife, which may be located downstream of the rolling positions of the fourth roller 40 and the fifth roller 50, and the air knife can blow cooling airflow.

[0143] For example, the air knife may be located on one side of the negative electrode 111 coated with lithium layer 112 in the thickness direction.

[0144] In some embodiments, the cooling gas stream is carbon dioxide gas.

[0145] In this embodiment, carbon dioxide has advantages such as stable properties and low cost. Using carbon dioxide gas to cool the lithium layer 112 can reduce the risk of lithium metal undergoing chemical reactions at high temperatures, and the temperature is uniform and controllable.

[0146] The temperature of the cooling airflow can be set as needed; for example, the temperature of the cooling airflow can be no greater than 10°C. This facilitates rapid cooling of the negative electrode 111 coated with the lithium layer 112 after secondary rolling.

[0147] In some embodiments, please refer to Figure 4 The lithium replenishment device includes a sixth roller 70, which is located downstream of the third roller 30 and upstream of the fourth roller 40. The roller surface of the sixth roller 70 abuts against the negative electrode 111 coated with a lithium layer 112.

[0148] The sixth roller 70 can rotate, and the rotation of the sixth roller 70 causes the negative electrode sheet 111 coated with lithium layer 112 to be carried by the tape.

[0149] In this embodiment, the roller surface of the sixth roller 70 abuts against the negative electrode sheet 111 coated with the lithium layer 112, providing guidance and transition functions for the negative electrode sheet 111 coated with the lithium layer 112, so that the negative electrode sheet 111 passing through the second roller 20 and the third roller 30 can be transported more smoothly to the fourth roller 40 and the fifth roller 50, thereby facilitating the fourth roller 40 and the fifth roller 50 to jointly perform secondary rolling on the negative electrode sheet 111 coated with the lithium layer 112.

[0150] In some embodiments, please refer to Figure 4 The lithium replenishment device includes a seventh roller 80, which is located downstream of the sixth roller 70 and upstream of the fourth roller 40. The roller surface of the seventh roller 80 abuts against and tensions the negative electrode sheet 111 covered with a lithium layer 112.

[0151] The seventh roller 80 can rotate, and the rotation of the seventh roller 80 causes the negative electrode sheet 111 coated with lithium layer 112 to be carried by the tape.

[0152] In this embodiment, the sixth roller 70 smoothly conveys the negative electrode sheet 111 that has passed through the second roller 20 and the third roller 30 to the seventh roller 80. The roller surface of the seventh roller 80 abuts against and tensions the negative electrode sheet 111 coated with the lithium layer 112, so as to provide guidance, transition and tension functions for the negative electrode sheet 111 coated with the lithium layer 112, so that the negative electrode sheet 111 coated with the lithium layer 112 can be in a roughly taut state, thereby facilitating the fourth roller 40 and the fifth roller 50 to jointly perform secondary rolling on the negative electrode sheet 111 coated with the lithium layer 112, reducing the generation of wrinkles and other problems.

[0153] In some embodiments, please refer to Figure 4 The diameter of the seventh roller 80 is greater than the diameter of the sixth roller 70.

[0154] It should be noted that the diameter of the seventh roller 80 refers to the outer diameter of the seventh roller 80 in the radial direction; the diameter of the sixth roller 70 refers to the outer diameter of the sixth roller 70 in the radial direction.

[0155] In this embodiment, the seventh roller 80 is mainly used to apply tension to stabilize the operation of the negative electrode 111 coated with lithium layer 112. The diameter of the seventh roller 80 is relatively larger, which can increase the contact area with the negative electrode 111 coated with lithium layer 112, making the tension distribution more uniform, and thus enabling the negative electrode 111 coated with lithium layer 112 to better maintain a taut state. The sixth roller 70 is mainly used to guide the travel direction of the negative electrode 111 coated with lithium layer 112. A smaller diameter can meet the guidance requirements. Moreover, the diameter of the sixth roller 70 is relatively small, occupying less installation space, and can also reduce the overall volume and manufacturing cost of the lithium replenishment device.

[0156] In some embodiments, the lithium replenishment device includes a first adjustment mechanism for adjusting the position of the sixth roller 70.

[0157] In some embodiments, the lithium replenishment device includes a second adjustment mechanism for adjusting the position of the seventh roller 80.

[0158] In some embodiments, the lithium replenishment device may include a control mechanism and a detection mechanism. The detection mechanism detects the position of the negative electrode 111 coated with the lithium layer 112 between the sixth roller 70 and the fourth roller 40. The control mechanism controls the second adjustment mechanism to adjust the position of the seventh roller 80 based on the position of the negative electrode 111 coated with the lithium layer 112 detected by the detection mechanism. In this way, the position of the seventh roller 80 can be adjusted in real time according to the position change of the negative electrode 111 between the fourth roller 40 and the sixth roller 70, so that the seventh roller 80 can tension the negative electrode 111 coated with the lithium layer 112, keeping the negative electrode 111 coated with the lithium layer 112 between the sixth roller 70 and the fourth roller 40 in a taut state.

[0159] In some embodiments, the detection mechanism can be a CCD (Charge) sensor. Charge-coupled device (CCD) cameras are small in size and light in weight, and are not affected by magnetic fields. They have strong anti-vibration and anti-impact characteristics. CCD cameras can be used to acquire image information of the negative electrode 111 coated with lithium layer 112, thereby determining the position of the negative electrode 111 coated with lithium layer 112.

[0160] The pressure of the fourth roller 40 and the fifth roller 50 during the secondary rolling can be adjusted according to the amount of lithium replenishment. For example, the fourth roller 40 and the fifth roller 50 can use a linear pressure of 0.6 MPa to 2 MPa. The pressure of the fourth roller 40 and the fifth roller 50 is approximately 2 to 3 tons.

[0161] The diameters of the fourth roller 40 and the fifth roller 50 can be equal, and the size of the diameters of the fourth roller 40 and the fifth roller 50 is not limited. For example, the diameters of the fourth roller 40 and the fifth roller 50 can be adjusted according to the thickness of the electrode sheet.

[0162] In some embodiments, at least one of the fourth roller 40 and the fifth roller 50 has a hardness-enhancing layer on its roller surface.

[0163] In some embodiments, at least a portion of the surface of the fourth roller 40 may be provided with a hardness-reinforcing layer, while the surface of the fifth roller 50 may not be provided with a hardness-reinforcing layer. Exemplarily, the surface of the fourth roller 40 may not be provided with a hardness-reinforcing layer, while at least a portion of the surface of the fifth roller 50 may be provided with a hardness-reinforcing layer. Exemplarily, at least a portion of the surface of both the fourth roller 40 and the fifth roller 50 may be provided with a hardness-reinforcing layer.

[0164] The hardness reinforcement layer is a layered structure used to increase the hardness of the roller surface. The hardness of the hardness reinforcement layer can be greater than the hardness of the roller surface of the fourth roller 40 and the fifth roller 50.

[0165] In this embodiment, the hardness-enhancing layer can increase the hardness of the roller surface of at least one of the fourth roller 40 and the fifth roller 50, thereby improving the wear resistance of the roller surface of at least one of the fourth roller 40 and the fifth roller 50, reducing the risk of wear and deformation of the roller surface of at least one of the fourth roller 40 and the fifth roller 50, and thus increasing the service life of at least one of the fourth roller 40 and the fifth roller 50.

[0166] It is understood that the roller surface is the surface on which the roller is used to roll the object being rolled, and the roller surface is typically a circumferential surface surrounding its axis. For example, the roller is generally cylindrical in shape, and the roller surface is the circumferential surface of the cylindrical structure. Taking the fourth roller 40 and the fifth roller 50 as examples, the roller surface of the fourth roller 40 is the surface on which the negative electrode 111 coated with the lithium layer 112 is rolled, and the roller surface of the fifth roller 50 is the surface on which the negative electrode 111 coated with the lithium layer 112 is rolled.

[0167] In some embodiments, the hardness-enhancing layer is a chromium layer.

[0168] The chromium layer is a layered structure formed by chromium metal.

[0169] In this embodiment, the chromium layer has extremely high hardness, which can greatly improve the wear resistance and scratch resistance of the roller surface and resist the wear caused by friction and impact on the negative electrode 111 coated with lithium layer 112. At the same time, the surface of the chromium layer is smooth and dense, and it is not easy to adhere to debris, dust and other impurities, making it easy to clean and maintain. In addition, the chromium layer also has good corrosion resistance and high temperature resistance.

[0170] In some embodiments, the flatness Ra of the hardness-enhancing layer is no greater than 1.

[0171] Smoothness Ra refers to the arithmetic mean deviation of the micro-profile of the surface of the hardening layer. It is an indicator for measuring the smoothness of the surface. If Ra is not greater than 1, it means that the average difference between the micro-protrusions and depressions on the surface of the hardening layer does not exceed 1 μm.

[0172] In this embodiment, the flatness Ra of the hardness reinforcement layer is no greater than 1, and the surface of the hardness reinforcement layer is relatively smooth, so that it has uniform contact with the negative electrode 111 coated with lithium layer 112. This reduces the risk of excessive local contact pressure causing the negative electrode 111 coated with lithium layer 112 to be stretched, broken or misaligned. It can also reduce the frictional resistance with the negative electrode 111 coated with lithium layer 112, reduce the wear of both, and protect the negative electrode 111 coated with lithium layer 112 from scratches.

[0173] The method for detecting the flatness Ra of the hardening reinforcement layer is not limited. For example, a surface roughness tester can be used. The probe of the surface roughness tester is brought into stable contact with the surface of the hardening reinforcement layer, allowing for multi-point sampling of the hardening reinforcement layer. The surface roughness tester can automatically calculate and display the Ra value, which is simple to operate, highly accurate, and allows for direct data reading. Of course, the flatness Ra of the hardening reinforcement layer can also be detected using other known detection methods, which will not be elaborated on in this application.

[0174] In some embodiments, the lithium replenishment device includes a lithium strip unwinding roller for unwinding lithium strip 2000; the lithium strip 2000 can be wound onto the lithium strip unwinding roller, and when the lithium strip unwinding roller unwinds the lithium strip 2000, it can provide lithium strip 2000 between the first roller 10 and the second roller 20.

[0175] In some embodiments, the lithium replenishment device includes an electrode unwinding roller for unwinding a negative electrode 111. The negative electrode 111 can be disposed on the electrode unwinding roller by winding, and when the electrode unwinding roller unwinds the negative electrode 111, it can provide the negative electrode 111 between the second roller 20 and the third roller 30.

[0176] In some embodiments, please refer to Figure 4 The lithium replenishment device includes a winding roller 90, which can feed the negative electrode 111 coated with lithium layer 112, the separator and the positive electrode after secondary rolling into the winding roller 90, and form a winding structure by winding the winding roller 90.

[0177] The negative electrode 111 of the first preset length, the separator of the second preset length, and the positive electrode 111 of the third preset length are cut to form a single-roll electrode assembly 11.

[0178] In this embodiment, the negative electrode sheet 111 coated with a lithium layer 112, the separator, and the positive electrode sheet, which have undergone secondary rolling, can be directly wound into shape. Then, the negative electrode sheet 111 of a first preset length, the separator of a second preset length, and the positive electrode sheet of a third preset length are cut to form a single-wound electrode assembly 11. The negative electrode sheet 111 coated with a lithium layer 112, which has undergone secondary rolling, is a continuous strip structure. It is cut according to the first preset length to divide it into multiple segments of the first preset length of negative electrode sheet 111, thereby manufacturing the negative electrode sheet 111 required for a single wound structure.

[0179] In some embodiments, after the negative electrode 111, the separator, and the positive electrode 111 coated with lithium layer 112, which have undergone secondary rolling, are wound, the cylindrical wound structure can be extruded and shaped into a flat structure before subsequent processes such as casing and baking are performed. These processes can all adopt known production processes, and will not be described in detail in this application.

[0180] The following specific embodiment further illustrates the lithium replenishment device provided in this application. Please refer to [link / reference]. Figures 3 to 5 The lithium replenishment device includes a first roller 10, a second roller 20, a third roller 30, a fourth roller 40, a fifth roller 50, a sixth roller 70, a seventh roller 80, and an air-cooling mechanism 60. The first roller 10 and the second roller 20 are used to roll the lithium strip 2000, causing the lithium strip 2000 to adhere to the second roller 20 to form a lithium layer 112. The second roller 20 and the third roller 30 are used to roll the lithium layer 112 and the negative electrode sheet 111, coating the lithium layer 112 onto the negative electrode sheet 111; the fourth roller 40 and the fifth roller 50 together perform a secondary roll forming on the negative electrode sheet 111 coated with the lithium layer 112. The fourth roller 40 has a first channel through which a cooling medium flows. The fifth roller 50 has a second channel through which a cooling medium flows. A cooling mechanism 60 is located downstream of the fourth roller 40 and the fifth roller 50. The cooling mechanism 60 blows cooling air to cool the negative electrode sheet 111 coated with lithium layer 112 after secondary rolling. A sixth roller 70 is located downstream of the third roller 30 and upstream of the fourth roller 40. The roller surface of the sixth roller 70 abuts against the negative electrode sheet 111 coated with lithium layer 112. A seventh roller 80 is located downstream of the sixth roller 70 and upstream of the fourth roller 40. The roller surface of the seventh roller 80 abuts against and tensions the negative electrode sheet 111 coated with lithium layer 112.

[0181] In this embodiment, the first roller 10 and the second roller 20 are used to perform a rolling process. The second roller 20 cooperates with the first roller 10 to roll the lithium strip 2000 together, so that the lithium metal on the lithium strip 2000 adheres to the second roller 20 to form a lithium layer 112. The second roller 20 and the third roller 30 are used to perform a lamination process. The third roller 30 cooperates with the second roller 20 to roll the negative electrode sheet 111 together, so that the lithium layer 112 adhered to the second roller 20 is laminated onto the negative electrode sheet 111. The negative electrode sheet 111 with the lithium layer 112 is rolled a second time by the fourth roller 40 and the fifth roller 50, so that the lithium layer 112 is embedded in the negative electrode sheet 111. In this way, solid-phase lithium intercalation of the lithium layer 112 is achieved before the winding process. Then, the solid-phase intercalation process is performed on the negative electrode sheet 111. The lithium-treated negative electrode 111 is stacked with the separator and positive electrode and then wound. The wound electrode assembly 11 is then subjected to shaping, casing, and baking processes. Since the lithium layer 112 on the negative electrode 111 has already achieved solid-phase lithium intercalation through secondary rolling before winding, the difference in the degree of lithium intercalation between the corner area and the straight area formed after winding the negative electrode 111 is greatly reduced. This can improve the problem of uneven lithium intercalation, thereby improving the lithium plating and lifespan problems caused by the difference in solid-phase lithium intercalation, thus improving the performance of the battery cell 1, increasing the cycle life of the battery cell 1, and also improving the utilization rate of the lithium layer 112, reducing the need for lithium metal replenishment. For example, according to single-factor verification, the utilization rate of lithium metal can be increased by about 5%, and the cost can be reduced by about 0.6%, thereby reducing costs and improving the competitiveness of the product. Because the secondary rolling process accelerates the solid-phase lithium intercalation speed of the lithium layer 112 and the negative electrode 111, heat is generated during the lithium metal intercalation process. Cooling media circulate through the first channel of the fourth roller 40 and the second channel of the fifth roller 50, absorbing the heat generated during the secondary rolling process. The heat is then cooled by the air-cooling mechanism 60, preventing damage caused by heat accumulation. The sixth roller 70 and the seventh roller 80 ensure that the negative electrode 111, after passing through the second roller 20 and the third roller 30, is more smoothly transported to the fourth roller 40 and the fifth roller 50, facilitating the joint secondary rolling of the lithium-coated negative electrode 111 by the fourth roller 40 and the fifth roller 50.

[0182] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way.

Claims

1. A lithium replenishment device, characterized in that, The lithium replenishment device includes: First roller; The second roller, the first roller and the second roller are used to roll the lithium strip so that the lithium strip adheres to the second roller to form a lithium layer; The third roller, the second roller, and the third roller are used to roll the lithium layer and the negative electrode sheet, and to coat the lithium layer onto the negative electrode sheet; Fourth roller; The fifth roller, together with the fourth roller, performs secondary rolling on the negative electrode sheet coated with the lithium layer.

2. The lithium supplementing device according to claim 1, wherein The fourth roller is provided with a first channel through which a cooling medium flows.

3. The lithium supplementing device according to claim 1, wherein The fifth roller is provided with a second channel through which a cooling medium flows.

4. The lithium supplementing device according to claim 1, wherein The lithium replenishment device includes: An air-cooling mechanism is located downstream of the fourth and fifth rollers. The air-cooling mechanism blows cooling airflow to air-cool the negative electrode sheet coated with the lithium layer after secondary rolling.

5. The lithium replenishment device according to claim 4, characterized in that, The cooling airflow is carbon dioxide gas.

6. The lithium supplementing device according to claim 1, wherein The lithium replenishment device includes: The sixth roller is located downstream of the third roller and upstream of the fourth roller, and the roller surface of the sixth roller abuts against the negative electrode sheet coated with the lithium layer.

7. The lithium supplementing device according to claim 6, characterized in that The lithium replenishment device includes: The seventh roller is located downstream of the sixth roller and upstream of the fourth roller. The roller surface of the seventh roller abuts against and tensions the negative electrode sheet covered with the lithium layer.

8. The lithium supplementing device according to claim 7, characterized in that The diameter of the seventh roller is larger than the diameter of the sixth roller.

9. The lithium supplementing device according to claim 1, wherein At least one of the fourth and fifth rollers has a hardness-enhancing layer on its roller surface.

10. The lithium replenishment device according to claim 9, characterized in that, The flatness Ra of the hardness-enhancing layer is no greater than 1.

Images