Method for manufacturing battery cell, manufacturing apparatus, and battery cell

Abstract

The application relates to the technical field of energy storage, and provides a manufacturing method and manufacturing equipment of a battery monomer and the battery monomer. The manufacturing method of the battery monomer comprises the following steps: performing a winding treatment according to the sequence of a first diaphragm, a negative electrode sheet, a second diaphragm and a positive electrode sheet to obtain an electrode assembly; the electrode assembly comprises a main body part and a bent part arranged at intervals; the electrode assembly comprises a plurality of inner rings and a plurality of outer rings; a lithium sheet is arranged between the bent part corresponding to the negative electrode sheet and the first diaphragm and / or the second diaphragm; the plurality of inner rings comprise a first ring layer, a second ring layer and a third ring layer; the thickness of the lithium sheet arranged in the second ring layer is greater than the thickness of the lithium sheet arranged in the first ring layer or the third ring layer; a box body is obtained, and the electrode assembly is arranged in the box body to obtain the battery monomer. Therefore, the probability that dendrites are formed in the R corner area and cause the risk of micro-short circuit or short circuit of the battery core is reduced, meanwhile, the overlarge lithium supplement amount of the negative electrode sheet can be avoided to cause the imbalance of the N / P ratio of the lithium battery, and the performance of the lithium battery is ensured.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a method for manufacturing a battery cell, manufacturing equipment, and a battery cell. Background Technology

[0002] In lithium battery manufacturing, the winding process is a highly automated method that involves stacking positive and negative electrode sheets with a separator and then winding them into a tightly packed cell. The rounded corner area at the edge of the wound cell is the arc transition zone formed at the bend. This corner area concentrates most of the failure risk of the wound cell and is a key factor affecting battery performance.

[0003] However, current lithium battery manufacturing processes have the risk of dendrite formation in the R-corner region at the edge of the core, which can lead to micro-short circuits or short circuits in the cell and affect the performance of the lithium battery. Summary of the Invention

[0004] This application provides a method, equipment, and battery cell for manufacturing a single cell, which avoids wrinkling and deformation of the negative electrode sheet, reduces the probability of dendrite formation in the R-corner region that could lead to micro-short circuits or short circuits in the cell, and minimizes the amount of lithium added to the negative electrode sheet to avoid excessive lithium added to the negative electrode sheet, which could cause an imbalance in the N / P ratio of the lithium battery and ensure the performance of the lithium battery.

[0005] According to some embodiments of this application, one aspect of this application provides a method for manufacturing a battery cell, comprising: obtaining a first separator, a negative electrode sheet, a second separator, and a positive electrode sheet; and performing a winding process in the order of the first separator, the negative electrode sheet, the second separator, and the positive electrode sheet to obtain an electrode assembly; the electrode assembly includes a main body and spaced-apart bent portions, the bent portions being connected to the end of the main body; the electrode assembly includes a plurality of inner rings and a plurality of outer rings arranged sequentially from the inside to the outside; a lithium sheet is placed between the negative electrode sheet corresponding to the bent portion of the inner ring and the first separator and / or the second separator; wherein the plurality of inner rings include a first ring layer, a second ring layer, and a third ring layer arranged sequentially from the inside to the outside, the thickness of the lithium sheet disposed in the second ring layer being greater than the thickness of the lithium sheet disposed in the first ring layer or the third ring layer; obtaining a housing, and placing the electrode assembly in the housing to obtain a battery cell.

[0006] According to some embodiments of this application, another aspect of this application provides a battery cell manufacturing apparatus, comprising: a winding module, the winding module being used to obtain a first separator, a negative electrode sheet, a second separator, and a positive electrode sheet, and to perform a winding process in the order of the first separator, the negative electrode sheet, the second separator, and the positive electrode sheet to obtain an electrode assembly; the electrode assembly includes a main body and spaced-apart bent portions, the bent portions being connected to the end of the main body; the electrode assembly includes a plurality of inner rings and a plurality of outer rings sequentially arranged from the inside to the outside; a lithium sheet is placed between the negative electrode sheet corresponding to the bent portion of the inner ring and the first separator and / or the second separator; wherein, the plurality of inner rings include a first ring layer, a second ring layer, and a third ring layer sequentially arranged from the inside to the outside, the thickness of the lithium sheet disposed in the second ring layer being greater than the thickness of the lithium sheet disposed in the first ring layer or the third ring layer; and an assembly module, the assembly module being used to obtain a housing, and to place the electrode assembly in the housing to obtain a battery cell.

[0007] According to some embodiments of this application, another aspect of this application also provides a battery cell, which is prepared by the above-described battery cell manufacturing method.

[0008] The technical solution provided in this application has at least the following advantages: This embodiment of the application places a lithium sheet between the negative electrode sheet corresponding to the bend in the inner ring and the first and / or second separator during the winding process. This allows the lithium sheet to provide support for the negative electrode sheet when winding to the bend. During subsequent liquid injection and formation processes, the lithium sheet embeds into the graphite layer of the negative electrode sheet, releasing corresponding space and allowing the negative electrode sheet to expand and contract freely. This avoids wrinkling and deformation of the negative electrode sheet, reduces the probability of dendrite formation in the R-corner region, which could lead to micro-short circuits or short circuits in the cell, and improves the performance of the lithium battery. Furthermore, due to the R-corner region of the inner ring during hot pressing... The high stress in the region causes porosity in the R-corner area, resulting in different deformations in the R-corner areas of different inner rings. The R-corner area in the second ring has the greatest deformation. Therefore, in this embodiment, the thickness of the lithium sheet in the second ring is greater than that in the first or third ring. This provides different support and space for the negative electrode sheets in different rings, solving the wrinkling problem in the R-corner area while minimizing the amount of lithium added to the negative electrode sheet. This avoids excessive lithium added to the negative electrode sheet, which could lead to an imbalance in the N / P ratio of the lithium battery and ensure the performance of the lithium battery. Attached Figure Description

[0009] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 This is a schematic diagram of the structure of the first diaphragm, negative electrode, second diaphragm, and positive electrode in Embodiment 1 of this application; Figure 2 This is a schematic diagram of the electrode assembly obtained by the winding process in Embodiment 1 of this application; Figure 3 This is a schematic diagram of a CT scan of a lithium battery after existing winding processing. Figure 4 A schematic diagram showing the structure in which the first lithium sheet is set between the first separator and the negative electrode sheet; Figure 5 A schematic diagram showing the structure in which a second lithium sheet is provided between the second separator and the negative electrode sheet; Figure 6 A comparison diagram showing the thickness of the R-corner region after full filling and the thickness of the R-corner region after hot pressing. Figure 7 This is a schematic diagram of the structure of a single battery cell obtained in Embodiment 1 of this application; Figure 8 This is a disassembly diagram of a battery cell obtained in Embodiment 1 of this application; Figure 9 This is a partial structural schematic diagram of the electrode assembly obtained by the winding process in Embodiment 2 of this application; Figure 10 This is a partial structural schematic diagram of the electrode assembly according to Embodiment 3 of this application; Figure 11 This is a schematic diagram of the structure of multiple inner rings in the electrode assembly of Embodiment 4 of this application; Figure 12 This is a schematic diagram of the structure of the battery cell manufacturing equipment according to an embodiment of this application. Detailed Implementation

[0011] As can be seen from the background technology, current lithium battery manufacturing processes have the risk of forming dendrites in the R-corner region at the edge of the lithium battery core, which could lead to micro-short circuits or short circuits in the cell.

[0012] Analysis revealed that the formation of dendrites in the R-corner region of the core edge of lithium batteries is due to the tendency of wrinkles to occur in this region. The main causes of wrinkle formation include: material deformation after charging and discharging; insufficient gap at the inner layer corners to release stress concentration and deformation; the positive and negative electrodes being inserted at the corners; stress concentration at the hot pressing and charging / discharging winding steps; and the release of the winding needles after winding, resulting in changes in the flatness and distortion of the inner separator and electrode sheets.

[0013] There are currently several methods to address wrinkles in the R-angle region, including: increasing the expandable space (e.g., reducing tension, circular coiled needle structure, semi-automatic winding insert), reducing expansion (e.g., low-expansion negative electrode, applying adhesive-coated diaphragm, negative pressure fixture formation), and reducing process deformation (e.g., reducing tension fluctuations, reducing baking time to reduce diaphragm thermal shrinkage, changing the liquid injection method to reduce impact through three-stage liquid injection).

[0014] However, the control effect of tension adjustment and product preparation process is poor. As the cell size increases, the inhibitory effect of the coating separator is also limited. The inventors discovered that pre-lithiation technology can also increase the internal space of lithium battery. When applied to the cell preparation process, it can not only achieve lithium replenishment, but also reduce the wrinkles in the inner ring of the core during the cell preparation process.

[0015] This application provides a method for preparing a battery cell, comprising: obtaining a first separator, a negative electrode sheet, a second separator, and a positive electrode sheet; and winding the first separator, negative electrode sheet, second separator, and positive electrode sheet in that order to obtain an electrode assembly; the electrode assembly includes a main body and spaced-apart bent portions, the bent portions being connected to the end of the main body; the electrode assembly includes a plurality of inner rings and a plurality of outer rings arranged sequentially from the inside to the outside; a lithium sheet is placed between the negative electrode sheet corresponding to the bent portion of the inner ring and the first separator and / or the second separator; wherein the plurality of inner rings include a first ring layer, a second ring layer, and a third ring layer arranged sequentially from the inside to the outside, the thickness of the lithium sheet disposed in the second ring layer being greater than the thickness of the lithium sheet disposed in the first ring layer or the third ring layer; obtaining a housing, and placing the electrode assembly inside the housing to obtain a battery cell.

[0016] This embodiment of the application places a lithium sheet between the negative electrode sheet corresponding to the bend in the inner ring and the first and / or second separator during the winding process. This allows the lithium sheet to provide support for the negative electrode sheet when winding to the bend. During subsequent liquid injection and formation processes, the lithium sheet embeds into the negative electrode active material, releasing corresponding space and allowing the negative electrode sheet to freely expand and contract. This avoids wrinkling and deformation of the negative electrode sheet, reduces the probability of dendrite formation in the R-corner region, and thus reduces the risk of micro-short circuits or short circuits in the cell, improving the performance of the lithium battery. Furthermore, due to the R-corner region during hot pressing... The corner region experiences greater stress, resulting in porosity and varying deformations in the corner regions of different inner rings. The deformation is greatest in the corner region located in the second ring. Therefore, in this embodiment, the thickness of the lithium sheet in the second ring is greater than that in the first or third ring. This provides different support forces for the negative electrode sheets in different rings, solving the wrinkling problem in the corner region while minimizing the amount of lithium replenishment to the negative electrode sheet. This avoids excessive lithium replenishment to the negative electrode sheet, which could lead to an imbalance in the N / P ratio of the lithium battery and ensure the performance of the lithium battery.

[0017] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined. Similarly, "multiple sets" refers to two or more sets (including two sets), and "multiple pieces" refers to two or more pieces (including two pieces).

[0018] In this document, the term "embodiment" means that a particular 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 throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0019] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0020] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application. For example, if the device or element in the illustration is inverted, then the element described as "below," "under," "below," or "bottom" of other elements or features will be oriented "above" or "top" of other elements or features. Therefore, the term "below" may cover both above and below orientation depending on the context in which the term is used, which will be obvious to those skilled in the art. Materials may be oriented in other ways (e.g., rotated 90 degrees, inverted, flipped), and the spatial relative descriptive terms used herein may be interpreted accordingly.

[0021] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0022] In the description of embodiments of this application, the terms "about," "approximately," "roughly," or "about" for referring to a specific parameter include numerical values, and those skilled in the art will understand that the deviation from the numerical value is within the acceptable tolerance of the specific parameter. For example, "about" or "about" for a numerical value may include additional numerical values ​​that are in the range of 90.0% to 110.0% of the numerical value, such as in the range of 95.0% to 105.0%, 97.5% to 102.5%, 99.0% to 101.0%, 99.5% to 100.5%, or 99.9% to 100.1%.

[0023] In the accompanying drawings corresponding to the embodiments of this application, the thickness and / or area of ​​layers, films, panels, regions, etc., are enlarged for better understanding and ease of description. Throughout the specification, the same reference numerals denote the same elements. Furthermore, when describing a component as being "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0024] In the description of embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and may be further included. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be an intermediate component between the two components. Conversely, when describing a component on the surface of another component, or a component "directly" on another component, or a component surface on which another component is formed or disposed, it indicates that there is no intermediate component between the two components. For simplicity and clarity, various components may be drawn at any scale. In the drawings, some components may be omitted for simplicity.

[0025] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "component" is also intended to include the plural form unless the context clearly indicates otherwise.

[0026] The “components” mentioned above can refer to layers, membranes, regions, parts, plates, or structures, etc.

[0027] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0028] Embodiment 1 of this application provides a method for preparing a single battery cell, comprising: obtaining a first separator, a negative electrode, a second separator, and a positive electrode, and performing a winding process in the order of the first separator, the negative electrode, the second separator, and the positive electrode to obtain an electrode assembly.

[0029] like Figure 1 The diagram shown is a structural schematic of the first diaphragm, the negative electrode, the second diaphragm, and the positive electrode.

[0030] This application embodiment first provides a first diaphragm 10, a negative electrode 20, a second diaphragm 30, and a positive electrode 40. Before the first diaphragm 10, the negative electrode 20, the second diaphragm 30, and the positive electrode 40 are wound, they are arranged in the order of the first diaphragm 10, the negative electrode 20, the second diaphragm 30, and the positive electrode 40 to provide a material basis for the subsequent winding process.

[0031] The positive electrode 40 includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material. As an example, the positive current collector has two opposing surfaces, and the positive electrode film layer is disposed on either or both of the opposing surfaces of the positive current collector.

[0032] The positive electrode current collector can be a metal foil or a composite current collector. For example, the metal foil may include, but is not limited to, aluminum foil. The composite current collector may include a base layer and a metal layer located on at least one surface of the base layer. For example, the base layer may be a polymer material base layer, including but not limited to polypropylene (PP) base layer, polyethylene terephthalate (PET) base layer, polybutylene terephthalate (PBT) base layer, polystyrene (PS) base layer, or polyethylene (PE) base layer. The material of the metal layer may include, but is not limited to, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy.

[0033] The positive electrode active material includes lithium salts, such as lithium-containing phosphates. Lithium-containing phosphates refer to phosphate materials containing lithium elements and can be detected by any method known in the art. For example, they can be detected by combining X-ray diffraction with energy dispersive spectroscopy (EDS) or inductively coupled plasma mass spectrometry (ICP-MS). As examples, lithium-containing phosphates include, but are not limited to, lithium iron phosphate, lithium iron phosphate doped and modified materials, or lithium iron phosphate coated and modified materials.

[0034] For example, the positive electrode active material can also be a high-voltage system with a working voltage greater than or equal to 4.3V, such as high-nickel ternary materials, high-voltage spinel materials, lithium manganese phosphate, or lithium-rich manganese-based materials.

[0035] For example, high-nickel ternary materials such as LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.15 Al 0.05 O2 (NCA) and other compounds possess operating voltages of 4.3V~4.6V and high specific capacity, making them ideal cathode choices for high-voltage lithium metal batteries. High-voltage spinel LiNi...0.5 Mn 1.5 O4 operates at a voltage up to 4.7V, perfectly matching its high voltage stability. Lithium manganese iron phosphate, a type of lithium manganese phosphate, is an emerging high-voltage phosphate material that combines safety and high-voltage characteristics.

[0036] However, this application is not limited to the materials listed above, and other materials that can be used as positive electrode active materials in battery cells may also be used. These positive electrode active materials may be used alone, or two or more may be used in combination.

[0037] The positive electrode film may also include a binder and / or a conductive agent.

[0038] The binder may be selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), or polyacrylic acid (PAA). The conductive agent may be selected from one or more of conductive carbon black, superconducting carbon, Ketjen black, carbon dots, acetylene black, graphene, carbon nanotubes, carbon nanofibers, or graphite.

[0039] The negative electrode 20 includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer comprising a negative electrode active material. As an example, the negative current collector has two opposing surfaces, and the negative electrode film layer is disposed on either or both of the opposing surfaces of the negative current collector.

[0040] The negative electrode current collector can be a metal foil or a composite current collector. For example, the metal foil may include, but is not limited to, copper foil. The composite current collector may include a base layer and a metal layer located on at least one surface of the base layer. For example, the base layer may be a polymer material base layer, including but not limited to polypropylene (PP) base layer, polyethylene terephthalate (PET) base layer, polybutylene terephthalate (PBT) base layer, polystyrene (PS) base layer, or polyethylene (PE) base layer. The material of the metal layer may include, but is not limited to, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy.

[0041] The negative electrode active material can be any negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material can be at least one of the following materials, including but not limited to: graphite, carbon materials, silicon-based materials, tin-based materials, or lithium titanate. Graphite can be artificial graphite or natural graphite. Carbon materials can be soft carbon or hard carbon. Silicon-based materials can be selected from at least one of elemental silicon, silicon oxide, silicon-carbon compounds, silicon-nitrogen compounds, and silicon alloys. Tin-based materials can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other materials that can be used as negative electrode active materials for battery cells can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0042] Optionally, the negative electrode film may also include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0043] Optionally, the negative electrode film layer may also include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0044] Optionally, the negative electrode film may also include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0045] The materials of the first diaphragm 10 and the second diaphragm 30 can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. This application does not impose any particular limitation on the types of the first diaphragm 10 and the second diaphragm 30; for example, porous membranes with chemical and mechanical stability can be selected.

[0046] The first diaphragm 10 and the second diaphragm 30 can be single-layer thin films or multi-layer composite thin films, without particular restrictions. When the first diaphragm 10 and the second diaphragm 30 are multi-layer composite thin films, the materials of each layer can be the same or different, without particular restrictions.

[0047] In some specific examples, the first separator 10 and the second separator 30 may include polypropylene (PP) separators, polyethylene (PE) separators, PP / PE / PP three-layer composite separators, ceramic-coated separators, high-strength polymer separators, or functionalized composite separators. PP and PE separators typically have a thickness of 12 to 25 micrometers and a porosity of 30% to 50%, exhibiting good mechanical strength and chemical stability. Ceramic-coated separators, with a coating of ceramic materials such as Al2O3, SiO2, and TiO2 (coating thickness 2 to 5 micrometers) on a polyolefin-based membrane, improve high-temperature resistance (thermal shut-off temperature > 160°C) and puncture resistance. High-strength polymer separators (such as polyimide PI, polyethylene terephthalate PET, and aramid nanofiber separators) possess excellent mechanical properties and high-temperature resistance. Functionalized composite separators (such as separators containing solid electrolyte coatings or lithiophilic coatings) can further enhance lithium deposition stability.

[0048] In the winding process, the embodiments of this application wind the electrode assembly in the following order: first separator 10, negative electrode 20, second separator 30, and positive electrode 40. A lithium sheet is placed between the negative electrode 20 and the first separator 10 and / or the second separator 30, providing support for the negative electrode 20 during winding. During subsequent liquid injection and formation processes, the lithium sheet embeds into the negative electrode active material, releasing corresponding space and allowing the negative electrode 20 to expand and contract freely, preventing wrinkles. Simultaneously, the lithium sheet can also replenish lithium to the negative electrode 20, improving lithium battery performance by adding additional active lithium to the battery.

[0049] like Figure 2 The diagram shown is a schematic diagram of the electrode assembly obtained by the winding process.

[0050] The electrode assembly includes a main body 101 and spaced-apart bent portions 102, the bent portions 102 being connected to the ends of the main body 101; the electrode assembly includes a plurality of inner rings 1 and a plurality of outer rings 2 arranged sequentially from the inside to the outside; a lithium sheet is placed between the negative electrode 20 corresponding to the bent portion 102 of the inner ring 1 and the first separator 10 and / or the second separator 30 (see below) Figure 4 , Figure 5 , Figure 9 ); wherein, the multiple inner rings 1 include a first ring 11, a second ring 12 and a third ring 13 arranged sequentially from the inside to the outside, and the thickness of the lithium sheet arranged in the second ring 12 is greater than the thickness of the lithium sheet arranged in the first ring 11 or the third ring 13.

[0051] The reason for wrinkles in the inner circle's R-corner region is that the radius of curvature of the inner circle is extremely small. The sharp bending at this region, with its tiny radius of curvature, generates enormous stress on the brittle electrode sheet, especially on the high-density negative electrode sheet 20, causing wrinkles in the R-corner region. Furthermore, during the winding process from the innermost circle outwards, due to the stress accumulation effect, the winding of the outer electrode sheets exerts continuous circumferential pressure and compression on the already wound inner negative electrode sheet 20. The negative electrode sheet 20 not only has to withstand its own bending stress but also the superimposed pressure from all the outer layers. As the number of turns increases, this superimposed pressure accumulates rapidly, causing the total compressive stress on the negative electrode sheet 20 in the R-corner region of the second layer 12 to reach its maximum, resulting in the most severe wrinkling. Therefore, the degree of wrinkling in the negative electrode sheet 20 in the R-corner region from the first layer 11 to the second layer 12 increases first. Subsequently, when winding to the third layer 13, the radius of curvature of the R-angle region gradually increases, the degree of bending of the negative electrode 20 gradually decreases, the bending stress generated by the negative electrode 20 in the R-angle region also decreases, and the wrinkles also gradually decrease.

[0052] By performing CT scans on existing wound lithium batteries, the following results were obtained: Figure 3 The schematic diagram of a CT scan of a lithium battery after existing winding process shows that the stress in the R-corner region of the inner ring 1 is relatively large during hot pressing, which leads to certain porosity in the R-corner regions of different inner rings 1, and the negative electrode sheet 20 undergoes certain deformation during hot pressing. By... Figure 3 The various layers are divided into inner circle 1 and outer circle 2. Inner circle 1 includes first layer 11, second layer 12 and third layer 13. It can be seen that the negative electrode plate of the second layer 12 has the largest deformation in the R-angle region, while the negative electrode plates of the first layer 11 and the third layer 13 have smaller deformation in the R-angle region.

[0053] Therefore, in this embodiment, lithium sheets are provided at the R-corner regions of the negative electrode 20 of the first layer 11, the second layer 12, and the third layer 13 to provide corresponding support for the R-corner regions of each layer. This prevents the first layer 11, the second layer 12, and the third layer 13, which have small radii of curvature, from bending sharply at the R-corner regions. At the same time, it can also support the already wound negative electrode 20 of the first layer 11, the second layer 12, and the third layer 13 when the outer electrode is wound, reducing the continuous circumferential pressure and compression on the wound negative electrode 20.

[0054] Furthermore, since the second ring 12 has the largest wrinkles in the R-corner region, and the negative electrode sheets of the first ring 11, second ring 12, and third ring 13 require different support forces, this embodiment sets the thickness of the lithium sheet in the second ring 12 to be the largest, that is, the thickness of the lithium sheet in the second ring 12 is greater than the thickness of the lithium sheet in the first ring 11 or the third ring 13. This provides greater support force for the R-corner region of the second ring 12 with larger wrinkles, avoids wrinkles in the R-corner region of each inner ring 1, and minimizes the amount of lithium replenished to the negative electrode sheet 20. This prevents excessive lithium replenishment to the negative electrode sheet 20 from causing an imbalance in the N / P ratio of the lithium battery, thus ensuring the performance of the lithium battery.

[0055] It is understood that the number of the first concentric circle 11, the second concentric circle 12, and the third concentric circle 13 can be set according to actual needs, and can be one layer or multiple layers. This application embodiment does not make specific limitations.

[0056] The N / P ratio of a lithium battery is the ratio of the negative electrode capacity to the positive electrode capacity. Optionally, the N / P ratio in the embodiments of this application ranges from 1.02 to 1.15, for example, 1.02, 1.05, 1.08, 1.1, 1.12, and 1.15. Optionally, the N / P ratio in the embodiments of this application ranges from 1.06 to 1.1, for example, 1.06, 1.07, 1.08, 1.09, and 1.1.

[0057] Lithium replenishment includes positive electrode lithium replenishment and negative electrode lithium replenishment. Positive electrode lithium replenishment often uses lithium replenishment additives, while negative electrode lithium replenishment uses lithium foil rolling, lithium bar rolling, or lithium powder oscillation for pre-lithiation. Therefore, the embodiments of this application combine negative electrode lithium replenishment technology with winding processing technology, reducing wrinkles in the R-corner area while achieving lithium replenishment of the negative electrode sheet 20, thereby improving lithium battery performance.

[0058] The negative electrode 20 of this application embodiment can be prepared by a dry electrode process, without using any solvent in the entire process. Based on this equipment, the difficulty of lithium replenishment can be greatly reduced, providing a safe and compatible environment for lithium replenishment. Alternatively, the negative electrode 20 can be directly prepared by solvent-assisted processing followed by drying to achieve a three-layer composite electrode thick sheet.

[0059] In some embodiments, the ratio of the number of inner rings 1 to the number of outer rings 2 is one-fifth to one-quarter. By setting the ratio of the number of inner rings 1 to outer rings 2 within this range, this application embodiment can effectively solve the problem of wrinkles in the inner rings 1 of the negative electrode 20 and improve the efficiency of the lithium sheet. On the other hand, it avoids the problem of excessive lithium replenishment caused by too many layers of the lithium sheet, which leads to an imbalance in the N / P ratio of the lithium battery, thus ensuring the performance of the lithium battery.

[0060] Optionally, the number of inner rings 1 is 8, and the number of outer rings 2 is 42.

[0061] Optionally, the number of inner rings 1 is 10, and the number of outer rings 2 is 50.

[0062] Optionally, the number of inner rings 1 is 10, and the number of outer rings 2 is 40.

[0063] Optionally, among the multiple inner rings 1, the first ring 11 has 2 rings, the second ring 12 has 1 ring, and the third ring 13 has 7 rings.

[0064] In some embodiments, a lithium sheet is placed only between the negative electrode 20 and the first separator 10. The lithium sheet placed between the first separator 10 and the negative electrode 20 at the bend 102 of the inner ring 1 is the first lithium sheet. Figure 4 The diagram shows a first lithium sheet disposed on the first separator and the negative electrode. The thickness of the first lithium sheet 52 disposed on the second ring layer 12 is greater than the thickness of the first lithium sheet 51 disposed on the first ring layer 11 or the first lithium sheet 53 disposed on the third ring layer 13.

[0065] In this embodiment, a first lithium sheet (including a first lithium sheet 51 in the first ring 11, a first lithium sheet 52 in the second ring 12, and a first lithium sheet 53 in the third ring 13) is disposed between the first separator 10 in the inner ring 1 and the negative electrode 20. That is, the first lithium sheet is disposed inside the negative electrode 20 in the inner ring 1. On the one hand, the first lithium sheet located inside the negative electrode 20 can provide support for the negative electrode 20 in the R-corner area during the winding process. On the other hand, the thickness of the first lithium sheet generally shows a trend of first increasing and then decreasing from the inside to the outside, thereby solving the wrinkling problem of the negative electrode 20 while minimizing the amount of lithium replenishment and improving the performance of the lithium battery.

[0066] Optionally, the thickness of the first lithium sheet (including the first lithium sheet 51 of the first ring 11, the first lithium sheet 52 of the second ring 12, and the first lithium sheet 53 of the third ring 13) is 1mm to 10mm, for example: 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm.

[0067] Optionally, the thickness of the first lithium sheet (including the first lithium sheet 51 of the first ring 11, the first lithium sheet 52 of the second ring 12, and the first lithium sheet 53 of the third ring 13) is 3mm to 8mm, for example: 3mm, 4mm, 5mm, 6mm, 7mm, 8mm.

[0068] Optionally, the number of inner rings 1 is 10, and the thickness of the first lithium sheet 51 of the first ring 11, the first lithium sheet 52 of the second ring 12, and the first lithium sheet 53 of the third ring 13 generally shows a trend of first increasing and then decreasing from the inside to the outside.

[0069] Optionally, the thicknesses of the first lithium sheet located inside the negative electrode 20 from the inside out are 3um, 5um, 10um, 9um, 8um, 7um, 6um, 5um, 4um, and 3um, respectively.

[0070] Optionally, the thicknesses of the first lithium sheet located inside the negative electrode 20 from the inside out are 2um, 4um, 9um, 8um, 7um, 6um, 5um, 4um, 3um, and 2um, respectively.

[0071] In some embodiments, a lithium sheet is placed only between the negative electrode 20 and the second separator 30. The lithium sheet placed between the negative electrode 20 and the second separator 30 at the bend 102 of the inner ring 1 is the second lithium sheet. Figure 5 The diagram shows a second lithium sheet disposed on the second separator and the negative electrode. The thickness of the second lithium sheet 62 disposed on the second ring 12 is greater than the thickness of the second lithium sheet 61 disposed on the first ring 11 or the second lithium sheet 63 disposed on the third ring 13.

[0072] In this embodiment, a second lithium sheet (including a second lithium sheet 61 in the first ring 11, a second lithium sheet 62 in the second ring 12, and a second lithium sheet 63 in the third ring 13) is disposed between the second separator 30 in the inner ring 1 and the negative electrode 20. That is, the second lithium sheet is disposed on the outside of the negative electrode 20 in the inner ring 1. On the one hand, the second lithium sheet located on the outside of the negative electrode 20 can provide support for the negative electrode 20 in the R-corner area of ​​the next ring during the winding process. On the other hand, the thickness of the second lithium sheet generally shows a trend of first increasing and then decreasing from the inside to the outside, thereby solving the wrinkling problem of the negative electrode 20 while minimizing the amount of lithium replenishment and improving the performance of the lithium battery.

[0073] Optionally, the thickness of the second lithium sheet (including the second lithium sheet 61 of the first ring 11, the second lithium sheet 62 of the second ring 12, and the second lithium sheet 63 of the third ring 13) is 1 mm to 10 mm, for example: 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm.

[0074] Optionally, the thickness of the second lithium sheet (including the second lithium sheet 61 of the first ring 11, the second lithium sheet 62 of the second ring 12, and the second lithium sheet 63 of the third ring 13) is 3mm to 8mm, for example: 3mm, 4mm, 5mm, 6mm, 7mm, 8mm.

[0075] Optionally, the number of inner rings 1 is 10, and the thickness of the second lithium sheet 61 of the first ring 11, the second lithium sheet 62 of the second ring 12, and the second lithium sheet 63 of the third ring 13 generally shows a trend of first increasing and then decreasing from the inside to the outside.

[0076] Optionally, the thicknesses of the second lithium sheet located on the outer side of the negative electrode sheet 20 from the inside to the outside are 3um, 5um, 10um, 9um, 8um, 7um, 6um, 5um, 4um, and 3um, respectively.

[0077] Optionally, the thicknesses of the second lithium sheet located on the outer side of the negative electrode sheet 20 from the inside to the outside are 2um, 4um, 9um, 8um, 7um, 6um, 5um, 4um, 3um, and 2um, respectively.

[0078] In some embodiments, before placing the lithium sheet between the negative electrode 20 corresponding to the bend 102 of the inner ring 1 and the first separator 10 and / or the second separator 30, the output end of the lithium roll is rolled and cut to obtain the corresponding lithium sheet (including the first lithium sheet and the second lithium sheet). The lithium roll is a roll of high-purity metallic lithium strip or foil, which is the core raw material of the lithium replenishment process. By rolling and cutting the output end of the lithium roll, lithium sheets of corresponding thickness and length can be obtained, and the lithium sheets are placed at the corresponding positions of the negative electrode 20. This provides support for the negative electrode 20 in the R-corner area of ​​the inner ring 1 during the winding process, and releases the corresponding space during the subsequent liquid injection and formation processes, preventing the negative electrode 20 from deforming and wrinkling.

[0079] Optionally, the lithium roll is a narrow and long lithium roll or a narrow and long lithium roll with pores.

[0080] During the winding process, the first separator 10 and the second separator 30 are first wound around using clamping pins. Then, the negative electrode sheet 20 and the positive electrode sheet 40 are wound in sequence. At the same time, the lithium sheet is clamped by clamping rollers and wound along with one or both sides of the negative electrode sheet 20. The lithium roll is placed on the unwinding shaft. During the conveyor belt feeding process, the lithium roll is rolled by a roller press (the pressure is controlled by air pressure) to form the corresponding thickness at the output end of the lithium roll. After the roller press rolls it to the corresponding length, it is cut by a cutter to obtain lithium sheets of the corresponding thickness and length. The lithium sheets are then wound together with the negative electrode sheet 20 into the core.

[0081] Alternatively, when cutting lithium coils, small protrusions or small notches can be marked on the lithium coils, and the small protrusions or small notches can be identified by a CCD (Charge-Coupled Device) so that the cutting can be achieved by a cutter.

[0082] During the winding process, the inner ring 1 has a slower winding speed, less than or equal to 600 mm / s (e.g., 200 mm / s, 300 mm / s, 400 mm / s, 500 mm / s, 600 mm / s), while the outer ring 2 has a winding speed of 2000 mm / s to 2500 mm / s (e.g., 2000 mm / s, 2100 mm / s, 2200 mm / s, 2300 mm / s, 2400 mm / s, 2500 mm / s). Adding lithium sheets during the winding of the inner ring 1, with the lithium sheets sequentially wound along with one or both sides of the negative electrode 20, does not require changing the existing winding speed. This allows for a more efficient production process while maintaining the existing winding speed.

[0083] Optionally, the winding speed of the inner ring 1 is less than or equal to 500 mm / s, for example, 200 mm / s, 300 mm / s, 400 mm / s, or 500 mm / s, and the winding speed of the outer ring 2 is 2100 mm / s to 2400 mm / s, for example, 2100 mm / s, 2200 mm / s, 2300 mm / s, or 2400 mm / s.

[0084] Optionally, after cutting the lithium sheet to the corresponding thickness and length, a pre-lithiation section can be determined on the negative electrode 20, that is, the area of ​​the negative electrode 20 that needs pre-lithiation, i.e., multiple inner rings 1, can be identified. Then, the negative electrode 20 and the cut lithium sheet can be simultaneously fed into the laminating roller, and the lithium sheet can be transferred to the negative electrode surface under pressure. After that, the negative electrode 20 that has been re-lithiated is rewound and then enters the next winding process.

[0085] The embodiments of this application provide lithium sheets of different thicknesses for different inner rings 1, which can ensure that the battery cell does not deposit lithium.

[0086] Optionally, the pre-lithiation amount in this embodiment is 1.5% to 2.5%, that is, the active lithium capacity supplemented by all lithium sheets is 1.5% to 2.5% of the positive electrode design capacity, for example: 1.5%, 1.8%, 2%, 2.2%, 2.5%.

[0087] Optionally, the pre-lithiation amount in this application embodiment is 1.7% to 2.3%, that is, the active lithium capacity supplemented by all lithium sheets is 1.7% to 2.3% of the positive electrode design capacity, for example: 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%.

[0088] Optionally, the pre-lithiation amount can be determined to be 2%, meaning that the active lithium capacity supplemented by all lithium sheets is 2% of the positive electrode design capacity, thus determining the total amount of all lithium sheets. Then, ensuring no lithium deposition, the height of the lithium sheets is confirmed with a 2% pre-lithiation amount, and the maximum thickness of the lithium sheets can be confirmed as 10µm; and the pre-lithiation section of the negative electrode 20 is confirmed. Based on the cell disassembly after the introduction of adhesive coating and separator, the pre-lithiation range of the negative electrode 20 is confirmed, for example, the 1st to 10th turns from the inside out require pre-lithiation. Then, based on the cell deformation after expansion, the expansion space of the cell is calculated, such as... Figure 6 The figure shows a comparison of the thickness of the R-corner region after full charging and the thickness of the R-corner region after winding and hot pressing. The deformation of the cell can be denoted as d2-d1, where d2 is the thickness of the R-corner region after full charging, i.e., the thickness of the R-corner after expansion, and d1 is the thickness of the R-corner region after winding and hot pressing, i.e., the thickness of the R-corner before expansion.

[0089] Finally, the pre-lithiation thickness of multiple inner rings 1 was confirmed based on the thickness variation of d2-d1. The pre-lithiation thickness can be designed in a gradient according to the interlayer spacing and adjusted according to the ring in the negative electrode 20 range that needs pre-lithiation. The pre-lithiation height of the third inner ring with the most severe wrinkles is 10um. The lithium sheet thicknesses of the first to third inner rings are 3um, 5um, and 10um, respectively. The lithium sheet thicknesses of the fourth to tenth inner rings are 9um, 8um, 7um, 6um, 5um, 4um, and 3um, respectively.

[0090] Optionally, the thickness of the lithium sheet can be finely adjusted according to the folds of the corresponding inner ring 1 to achieve the optimal fold scheme. After locking the complete thickness chain, the lithium sheet of the corresponding thickness can be manufactured.

[0091] During the winding process, a lithium sheet is placed between the negative electrode 20 corresponding to the bend 102 of the inner ring 1 and the first separator 10 and / or the second separator 30. When the winding reaches the bend 102, the lithium sheet can provide support for the negative electrode 20. During the subsequent liquid injection and formation process, the lithium sheet is embedded in the negative electrode active material of the negative electrode, releasing the corresponding space, so that the negative electrode 20 can freely expand and contract, avoiding wrinkle deformation of the negative electrode 20, reducing the probability of dendrite formation in the R-corner area, which could lead to micro-short circuit or short circuit risk in the cell, and improving the performance of the lithium battery.

[0092] In this embodiment, the lithium sheet is disposed in the R-corner region of the inner ring 1. The N / P ratio of the inner ring 1 of the cell is relatively large. Since the temperature of the inner ring 1 of the cell is higher than that of the outer ring 2, the high temperature can improve the reversibility of lithium plating. Even if the lithium sheet is embedded into the negative electrode active material of the negative electrode during subsequent liquid injection and formation processes, it can be ensured that the risk of lithium plating in the inner ring 1 of the cell is low, thus guaranteeing the performance of the lithium battery.

[0093] like Figure 7 The diagram shown is a schematic representation of the obtained battery cell structure; as shown... Figure 8 The diagram shown is a disassembly diagram of the obtained battery cell.

[0094] After the electrode assembly 21 is obtained through winding, a housing is obtained, and the electrode assembly 21 is placed inside the housing to obtain a battery cell 200.

[0095] In some embodiments, the housing may include a cover plate 22 and a shell 23, with the cover plate 22 and the shell 23 covering each other, and the cover plate 22 and the shell 23 together defining a receiving space for accommodating the electrode assembly 21. The shell 23 may be a hollow structure with one end open, and the cover plate 22 may be a plate-like structure, with the cover plate 22 covering the open side of the shell 23 so that the cover plate 22 and the shell 23 together define the receiving space; or the cover plate 22 and the shell 23 may both be hollow structures with one side open, with the open side of the cover plate 22 covering the open side of the shell 23. Of course, the housing formed by the cover plate 22 and the shell 23 may be of various shapes, such as a cylinder, a cuboid, etc.

[0096] After obtaining the aforementioned battery cell 200, the battery cell 200 is injected with electrolyte using an injection pump, injecting a precisely measured amount of electrolyte into the battery cell. Optionally, the electrolyte injection is performed using a vacuum sealing and negative pressure impregnation method, that is, the gas inside the cell is extracted, further reducing the pressure inside the core. The negative pressure is then released or a positive pressure is applied, with the external pressure greater than the internal pressure, driving the electrolyte to penetrate deeper into the micropores of the electrode and separator. Through multiple cycles, the electrolyte is pumped deep into the core. During this process, lithium on the lithium sheet is embedded into the negative electrode active material, and the internal space of the battery cell 200 is released, improving the wrinkling problem of the negative electrode sheet in the R-corner region. Afterwards, the battery cell undergoes normal formation and capacity testing before being discharged from the production line.

[0097] The electrolyte acts as a conductor of ions between the positive electrode 40 and the negative electrode 20. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0098] For example, the electrolyte is an electrolyte solution. The electrolyte solution consists of an electrolyte salt and a solvent.

[0099] For example, 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.

[0100] For example, solvents may be selected from 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 At least one of butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.

[0101] For example, the electrolyte may also include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery cell, such as additives that improve the overcharge performance of the battery cell, additives that improve the high-temperature or low-temperature performance of the battery cell, etc.

[0102] Embodiment 2 of this application provides a method for preparing a battery cell. In this embodiment, lithium sheets are placed between the negative electrode and the first separator, and between the negative electrode and the second separator. The lithium sheets include a first lithium sheet and a second lithium sheet.

[0103] like Figure 9 The diagram shown is a partial structural schematic of the electrode assembly obtained by the winding process.

[0104] A first lithium sheet (including a first lithium sheet 51 in the first ring 11, a first lithium sheet 52 in the second ring 12, and a first lithium sheet 53 in the third ring 13) is placed between the first separator 10 and the negative electrode 20 corresponding to the bend of the inner ring 1. A second lithium sheet (including a second lithium sheet 61 in the first ring 11, a second lithium sheet 62 in the second ring 12, and a second lithium sheet 63 in the third ring 13) is placed between the negative electrode 20 and the second separator 30 corresponding to the bend of the inner ring 1. The thickness of the first lithium sheet 51 in the second ring 12 is greater than the thickness of the first lithium sheet 52 in the first ring 11 or the first lithium sheet 53 in the third ring 13. The thickness of the second lithium sheet 62 in the second ring 12 is greater than the thickness of the second lithium sheet 61 in the first ring 11 or the second lithium sheet 63 in the third ring 13.

[0105] During the winding process, the first separator 10 and the second separator 30 are first wound around using clamping pins. Then, the negative electrode 20 and the positive electrode 40 are wound in sequence. At the same time, the first lithium sheet and the second lithium sheet are clamped by clamping wheels, and the first lithium sheet is wound in sequence along the inner side of the negative electrode 20 (i.e., the side of the negative electrode 20 closest to the first separator 10) and the second lithium sheet is wound in sequence along the outer side of the negative electrode 20 (i.e., the side of the negative electrode 20 closest to the second separator 30). Since the winding speed of the inner ring 1 is relatively slow during the winding process, the addition of the first and second lithium sheets during this process, and their sequential winding along the inner and outer sides of the negative electrode 20, does not require changing the existing winding speed. This maintains the existing winding process flow and is more efficient.

[0106] Optionally, after obtaining lithium sheets of the corresponding thickness through rolling and cutting, the lithium sheets of the corresponding thickness can be placed into the corresponding slots according to their thickness. When the sheets are wound to the corresponding position, the lithium sheets of the corresponding thickness are inserted. Insertion is performed on both the inner and outer sides of each turn of the negative electrode sheet 20 to increase the expansion space and minimize the probability of wrinkles in the R-corner area of ​​the negative electrode sheet 20.

[0107] In this embodiment, a first lithium sheet (including a first lithium sheet 51 in a first ring 11, a first lithium sheet 52 in a second ring 12, and a first lithium sheet 53 in a third ring 13) and a second lithium sheet (including a second lithium sheet 61 in a first ring 11, a second lithium sheet 62 in a second ring 12, and a second lithium sheet 63 in a third ring 13) are added during the unwinding process. The first lithium sheet is located inside the negative electrode 20 of the inner ring 1, and the second lithium sheet is located outside the negative electrode 20 of the inner ring 1. The first and second lithium sheets provide support for the negative electrode 20 during the winding process. After subsequent liquid injection and formation processes, the first and second lithium sheets are embedded in the negative electrode active material of the negative electrode 20, so that gaps are formed on both the inner and outer sides of the bending area of ​​the negative electrode 20, and the negative electrode 20 can expand and contract in both directions, thus better solving the wrinkling problem in the inner ring R-corner area of ​​the negative electrode 20.

[0108] In some embodiments, for the bent portion of the inner ring 1, the thickness of the first lithium sheet located inside the negative electrode 20 is greater than the thickness of the second lithium sheet located outside the negative electrode 20. That is, for the negative electrode 20 of the same inner ring 1, the thickness of the first lithium sheet located inside the negative electrode 20 (i.e., the side of the negative electrode 20 closer to the first separator 10) is greater than the thickness of the second lithium sheet located outside the negative electrode 20 (i.e., the side of the negative electrode 20 closer to the second separator 30).

[0109] Optionally, the thickness of the first lithium sheet located inside the negative electrode 20 is 1 to 2 μm greater than the thickness of the second lithium sheet located outside the negative electrode 20. For example, 1 μm, 1.3 μm, 1.5 μm, 1.8 μm, and 2 μm. Specifically, the thickness of the first lithium sheet 51 in the first ring 11 is greater than the thickness of the second lithium sheet 61 in the first ring 11, the thickness of the first lithium sheet 52 in the second ring 12 is greater than the thickness of the second lithium sheet 62 in the second ring 12, and the thickness of the first lithium sheet 53 in the third ring 13 is greater than the thickness of the second lithium sheet 63 in the third ring 13.

[0110] Optionally, the number of inner rings 1 is 10.

[0111] Optionally, the thicknesses of the first lithium sheet (including the first lithium sheet 51 of the first ring 11, the first lithium sheet 52 of the second ring 12, and the first lithium sheet 53 of the third ring 13) located inside the negative electrode sheet 20 from the inside out are 3um, 5um, 10um, 9um, 8um, 7um, 6um, 5um, 4um, and 3um, respectively; and the thicknesses of the second lithium sheet (including the second lithium sheet 61 of the first ring 11, the second lithium sheet 62 of the second ring 12, and the second lithium sheet 63 of the third ring 13) located outside the negative electrode sheet 20 from the inside out are 2um, 4um, 9um, 8um, 7um, 6um, 5um, 4um, 3um, and 2um, respectively.

[0112] Optionally, the thicknesses of the first lithium sheet (including the first lithium sheet 51 of the first ring 11, the first lithium sheet 52 of the second ring 12, and the first lithium sheet 53 of the third ring 13) located inside the negative electrode sheet 20 from the inside out are 3um, 5um, 10um, 9um, 8um, 7um, 6um, 5um, 4um, and 3um, respectively; and the thicknesses of the second lithium sheet (including the second lithium sheet 61 of the first ring 11, the second lithium sheet 62 of the second ring 12, and the second lithium sheet 63 of the third ring 13) located outside the negative electrode sheet 20 from the inside out are 1um, 3um, 8um, 7um, 6um, 5um, 4um, 3um, 2um, and 1um, respectively.

[0113] Optionally, the thicknesses of the first lithium sheet (including the first lithium sheet 51 of the first ring 11, the first lithium sheet 52 of the second ring 12, and the first lithium sheet 53 of the third ring 13) located inside the negative electrode sheet 20 from the inside out are 2um, 4um, 9um, 8um, 7um, 6um, 5um, 4um, 3um, and 2um, respectively; and the thicknesses of the second lithium sheet (including the second lithium sheet 61 of the first ring 11, the second lithium sheet 62 of the second ring 12, and the second lithium sheet 63 of the third ring 13) located outside the negative electrode sheet 20 from the inside out are 1um, 3um, 8um, 7um, 6um, 5um, 4um, 3um, 2um, and 1um, respectively.

[0114] Optionally, the first lithium sheet is positioned at one-sixth or five-sixths of the height of the negative electrode 20; the second lithium sheet is positioned at one-sixth or five-sixths of the height of the negative electrode 20. By positioning the first lithium sheet at one-sixth or five-sixths of the height of the negative electrode 20 and the second lithium sheet at one-sixth or five-sixths of the height of the negative electrode 20, this embodiment ensures that the center of the negative electrode 20 is not obstructed. During electrolyte injection, the electrolyte can quickly penetrate to the center of the negative electrode 20, improving the wetting effect in the center of the negative electrode 20 and enhancing the performance of the lithium battery.

[0115] This application provides a method for preparing a single battery cell. In the electrode assembly of this application embodiment, the thickness of the negative electrode sheet of the inner ring 1 is greater than the thickness of the negative electrode sheet of the outer ring.

[0116] like Figure 10 The diagram shown is a partial structural schematic of the electrode assembly.

[0117] The electrode assembly includes multiple inner rings 1 and multiple outer rings 2 arranged sequentially from the inside to the outside. The thickness of the negative electrode sheet 20 of the multiple inner rings 1 is greater than the thickness of the negative electrode sheet 20 of the multiple outer rings 2. The inner ring 1 includes a first ring layer 11, a second ring layer 12, and a third ring layer 13.

[0118] Since the lithium sheets (including the first lithium sheet 51 of the first ring 11, the first lithium sheet 52 of the second ring 12, the first lithium sheet 53 of the third ring 13, the second lithium sheet 61 of the first ring 11, the second lithium sheet 62 of the second ring 12, and the second lithium sheet 63 of the third ring 13) will be embedded into the negative electrode active material of the negative electrode sheet 20 during the subsequent liquid injection and formation process, the embodiments of this application set the thickness of the negative electrode sheets 20 of the multiple inner rings 1 to be relatively thick, providing a sufficient thickness of negative electrode active material to embed the lithium sheets, reducing the probability of lithium deposition in the negative electrode sheet 20, and improving the performance of the lithium battery.

[0119] Meanwhile, since the embodiments of this application include lithium sheets (including a first lithium sheet and a second lithium sheet), during the liquid injection and formation process, the lithium atoms of the lithium sheets are mainly consumed, and the lithium atoms in the positive electrode 40 are consumed less. As a result, a large amount of lithium atoms are retained in the positive electrode 40. Therefore, when the lithium battery is used normally, the positive electrode 40 can release more lithium atoms, thereby increasing the total capacity of the lithium battery.

[0120] Optionally, the thickness of the negative electrode 20 of the inner ring 1 (including the first ring 11, the second ring 12, and the third ring 13) is 132 μm to 142 μm, for example, 132 μm, 134 μm, 136 μm, 138 μm, 140 μm, and 142 μm; the thickness of the negative electrode 20 of the outer ring 2 is 130 μm to 140 μm, for example, 130 μm, 132 μm, 134 μm, 136 μm, 138 μm, and 140 μm.

[0121] Optionally, the thickness of the negative electrode 20 of the inner ring 1 (including the first ring 11, the second ring 12, and the third ring 13) is 134 μm to 140 μm, for example, 134 μm, 135 μm, 136 μm, 137 μm, 138 μm, 139 μm, and 140 μm; the thickness of the negative electrode 20 of the outer ring 2 is 132 μm to 138 μm, for example, 132 μm, 133 μm, 134 μm, 135 μm, 136 μm, 137 μm, and 138 μm.

[0122] In some embodiments, the thickness of the negative electrode 20 located in the inner ring 1 (including the first ring 11, the second ring 12, and the third ring 13) is 1 μm to 2 μm thicker than the thickness of the negative electrode 20 located in the outer ring 2.

[0123] Optionally, the thickness of the negative electrode 20 of the inner ring 1 is 132 μm, and the thickness of the negative electrode 20 of the outer ring 2 is 130 μm; or, the thickness of the negative electrode 20 of the inner ring 1 is 134 μm, and the thickness of the negative electrode 20 of the outer ring 2 is 132 μm; or, the thickness of the negative electrode 20 of the inner ring 1 is 136 μm, and the thickness of the negative electrode 20 of the outer ring 2 is 134 μm; or, the thickness of the negative electrode 20 of the inner ring 1 is 138 μm, and the thickness of the negative electrode 20 of the outer ring 2 is 136 μm; or, the thickness of the negative electrode 20 of the inner ring 1 is 140 μm, and the thickness of the negative electrode 20 of the outer ring 2 is 138 μm; or, the thickness of the negative electrode 20 of the inner ring 1 is 142 μm, and the thickness of the negative electrode 20 of the outer ring 2 is 140 μm.

[0124] Embodiment 4 of this application provides a method for preparing a single battery cell. In the electrode assembly of this embodiment, the thickness of the negative electrode sheet located in the second layer is greater than the thickness of the negative electrode sheet located in the first or third layer.

[0125] like Figure 11 The diagram shown is a schematic representation of the structure of multiple inner rings in the electrode assembly.

[0126] In the electrode assembly, the inner ring 1 includes a first ring 11, a second ring 12 and a third ring 13 arranged sequentially from the inside to the outside. The thickness of the negative electrode 20 located in the second ring 12 is greater than the thickness of the negative electrode 20 located in the first ring 11 or the third ring 13.

[0127] In this embodiment, the thickness of the negative electrode 20 in the inner ring 1 matches the thickness of the lithium sheet. The first lithium sheet 52 and the second lithium sheet 62 corresponding to the bend in the second ring 12 are thicker, and the corresponding negative electrode 20 in the second ring 12 is also thicker. The first lithium sheet 51 and the second lithium sheet 61 corresponding to the bend in the first ring 11 are thinner, and the corresponding negative electrode 20 in the first ring 11 is also thinner. The first lithium sheet 53 and the second lithium sheet 63 corresponding to the bend in the third ring 13 are thinner, and the corresponding negative electrode 20 in the third ring 13 is also thinner. Thus, during the liquid injection and formation process, the negative electrode 20 of different thicknesses embeds lithium atoms of the corresponding thickness lithium sheet, reducing the probability of lithium deposition in the negative electrode 20, improving the performance of the lithium battery while ensuring the total capacity of the lithium battery.

[0128] Optionally, the number of inner rings 1 is 10, the number of first rings 11 is 2, the number of second rings 12 is 1, and the number of third rings 13 is 7.

[0129] Optionally, the thicknesses of the negative electrode plates 20 located in the inner ring 1 from the inside out are: 132.3 μm, 132.5 μm, 133 μm, 132.9 μm, 132.8 μm, 132.7 μm, 132.6 μm, 132.5 μm, 132.4 μm, and 132.3 μm; or, the thicknesses of the negative electrode plates 20 located in the inner ring 1 from the inside out are: 134.3 μm, 134.5 μm, 135 μm, 134.9 μm, 134.8 μm, 134.7 μm, 134.6 μm, 134.5 μm, 134.4 μm, and 134.3 μm; or, the thicknesses of the negative electrode plates 20 located in the inner ring 1 from the inside out are: 136.3 μm, 136.5 μm, 137 μm, and 136.9 μm. 136.8 um, 136.7 um, 136.6 um, 136.5 um, 136.4 um, 136.3 um; or, the thicknesses of the negative electrode plates 20 located in the inner ring 1 from the inside out are 138.3 um, 138.5 um, 139 um, 138.9 um, 138.8 um, 138.7 um, 138.6 um, 138.5 um, 138.4 um, 138.3 um respectively.

[0130] This application provides a manufacturing apparatus for a single battery cell, such as... Figure 12 The diagram shown is a structural schematic of equipment for manufacturing battery cells. The equipment for manufacturing battery cells includes the following modules: The winding module 31 is used to obtain a first separator, a negative electrode sheet, a second separator, and a positive electrode sheet, and to wind them in the order of the first separator, the negative electrode sheet, the second separator, and the positive electrode sheet to obtain an electrode assembly. The electrode assembly includes a main body and bends spaced apart, with the bends connected to the ends of the main body. The electrode assembly includes multiple inner rings and multiple outer rings arranged sequentially from the inside to the outside. A lithium sheet is placed between the negative electrode sheet corresponding to the bend of the inner ring and the first separator and / or the second separator. The multiple inner rings include a first layer, a second layer, and a third layer arranged sequentially from the inside to the outside. The thickness of the lithium sheet in the second layer is greater than the thickness of the lithium sheet in the first layer or the third layer.

[0131] Assembly module 32 is used to obtain a housing and place the electrode assembly inside the housing to obtain a battery cell.

[0132] In some embodiments, the battery cell manufacturing equipment further includes a rolling module 33, which is used to roll and cut the discharge end of the lithium roll before placing the lithium sheet between the negative electrode sheet corresponding to the bend of the inner ring and the first and / or second separator, so as to obtain the corresponding lithium sheet.

[0133] In the battery cell manufacturing equipment of this application embodiment, during the winding process, a lithium sheet is placed between the negative electrode sheet corresponding to the inner bend and the first and / or second separator. When winding to the bend corresponding to the inner ring, the lithium sheet provides support for the negative electrode sheet. During subsequent liquid injection and formation processes, the lithium sheet is embedded into the negative electrode active material of the negative electrode sheet, thereby releasing the corresponding space, increasing the free expansion and contraction space of the negative electrode sheet, reducing the probability of wrinkling deformation of the negative electrode sheet, reducing the chance of dendrite formation in the R-corner region leading to micro-short circuits or short circuits in the cell, and improving the performance of the lithium battery. Furthermore, in this application embodiment, the thickness of the lithium sheet in the second ring is greater than the thickness of the lithium sheet in the first or third ring, thereby providing different support forces and spaces for the negative electrode sheets in different rings. This solves the wrinkling problem in the R-corner region of the negative electrode sheet while minimizing the amount of lithium replenishment to the negative electrode sheet, avoiding excessive lithium replenishment to the negative electrode sheet leading to an imbalance in the N / P ratio of the lithium battery, and ensuring the performance of the lithium battery.

[0134] This application provides a single battery cell, such as... Figure 7 The diagram shown is a structural schematic of a single battery cell; as shown... Figure 8 The diagram shown is a disassembly diagram of a single battery cell.

[0135] The battery cell 200 includes an electrode assembly 21 and a housing. The housing includes a cover plate 22 and a shell 23. The cover plate 22 and the shell 23 cover each other and together define a space for accommodating the electrode assembly 21.

[0136] The battery cell 200 provided in this application embodiment can be widely used in battery fields requiring high energy density and long cycle life, including high-end electric vehicle battery systems, portable electronic devices, and large-scale energy storage power stations. The battery cell 200 provided in this application embodiment can achieve large-capacity energy storage, comprehensively improving energy density, cycle life, and safety performance. It can meet the needs of long-term energy storage, achieving long-term energy storage of 4 hours or more, for example, it can be applied to energy storage scenarios such as 5 hours, 6 hours, and 8 hours. Long-term energy storage refers to the ability to continuously discharge at rated power for 4 hours or even longer, or to achieve large-scale, low-cost energy storage for several days or months.

[0137] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A method for preparing a single battery cell, characterized in that, include: A first separator, a negative electrode, a second separator, and a positive electrode are obtained, and then wound in the order of the first separator, the negative electrode, the second separator, and the positive electrode to obtain an electrode assembly. The electrode assembly includes a main body and spaced-apart bent portions, which are connected to the ends of the main body. The electrode assembly includes multiple inner rings and multiple outer rings arranged sequentially from the inside to the outside. A lithium sheet is placed between the negative electrode corresponding to the bent portion of the inner ring and the first separator and / or the second separator. The multiple inner rings include a first ring, a second ring, and a third ring arranged sequentially from the inside out, wherein the thickness of the lithium sheet arranged in the second ring is greater than the thickness of the lithium sheet arranged in the first ring or the third ring. Obtain the housing, place the electrode assembly inside the housing to obtain a single battery cell.

2. The method for preparing a single battery cell according to claim 1, characterized in that, The method further includes: Before placing the lithium sheet between the negative electrode corresponding to the bent portion of the inner ring and the first diaphragm and / or the second diaphragm, the discharge end of the lithium roll is rolled and cut to obtain the corresponding lithium sheet.

3. The method for preparing a single battery cell according to claim 1, characterized in that, The lithium sheet includes a first lithium sheet and a second lithium sheet; The first lithium sheet is placed between the first diaphragm corresponding to the bend in the inner ring and the negative electrode sheet, and the second lithium sheet is placed between the negative electrode sheet corresponding to the bend in the inner ring and the second diaphragm. The thickness of the first lithium sheet disposed in the second ring is greater than the thickness of the first lithium sheet disposed in the first ring or the third ring; the thickness of the second lithium sheet disposed in the second ring is greater than the thickness of the second lithium sheet disposed in the first ring or the third ring.

4. The method for preparing a single battery cell according to claim 3, characterized in that, For the bent portion of the inner ring, the thickness of the first lithium sheet located inside the negative electrode sheet is greater than the thickness of the second lithium sheet located outside the negative electrode sheet.

5. The method for preparing a battery cell according to any one of claims 1 to 4, characterized in that, The thickness of the negative electrode sheet in the inner ring is greater than the thickness of the negative electrode sheet in the outer ring.

6. The method for preparing a battery cell according to any one of claims 1 to 4, characterized in that, The thickness of the negative electrode sheet located in the inner ring is 1µm to 2µm thicker than the thickness of the negative electrode sheet located in the outer ring.

7. The method for preparing a battery cell according to any one of claims 1 to 4, wherein the thickness of the negative electrode sheet located in the second ring layer is greater than the thickness of the negative electrode sheet located in the first ring layer or the third ring layer.

8. The method for preparing a battery cell according to any one of claims 1 to 4, characterized in that, The length of the first lithium sheet is 1 mm to 10 mm, and the length of the second lithium sheet is 1 mm to 10 mm.

9. The method for preparing a battery cell according to claim 1, characterized in that, The ratio of the number of the plurality of inner rings to the number of the plurality of outer rings is one-fifth to one-quarter.

10. A manufacturing apparatus for a single battery cell, characterized in that, include: A winding module is used to obtain a first separator, a negative electrode sheet, a second separator, and a positive electrode sheet, and to wind them in the order of the first separator, the negative electrode sheet, the second separator, and the positive electrode sheet to obtain an electrode assembly. The electrode assembly includes a main body and spaced-apart bent portions, which are connected to the ends of the main body. The electrode assembly includes multiple inner rings and multiple outer rings arranged sequentially from the inside to the outside. A lithium sheet is placed between the negative electrode sheet corresponding to the bent portion of the inner ring and the first separator and / or the second separator. The multiple inner rings include a first layer, a second layer, and a third layer arranged sequentially from the inside to the outside. The thickness of the lithium sheet disposed in the second layer is greater than the thickness of the lithium sheet disposed in the first layer or the third layer. An assembly module is used to obtain a housing and place the electrode assembly inside the housing to obtain a battery cell.

11. A single battery cell, characterized in that, The battery cell is prepared by the manufacturing method of any one of claims 1 to 9.

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