An electric cell

Abstract

The utility model discloses an electric core, including pole piece and diaphragm, and diaphragm is stacked with pole piece and is wound and is arranged, and pole piece has the most inside circle and the most outside circle, and the most outside circle of pole piece includes empty foil section, and the surface of empty foil section is constructed with a plurality of recesses at intervals, and the surface of empty foil section in recess and between recess is coated with insulating layer. The utility model discloses, sets up empty foil section to replace the traditional coating end structure, can avoid the expansion stress concentration problem of the most outside circle active material in the charge and discharge process, and through the surface of empty foil section interval construction a plurality of recesses and forms the grid -like structure, provides the release passage and shift path for the expansion stress of electric core inside, reduces the internal stress accumulation caused by volume change, and simultaneously, the surface of empty foil section in recess and between recess is coated with insulating layer, ensures the electrical insulation safety between the most outside circle and other pole piece.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a battery cell. Background Technology

[0002] In terms of anode materials, the theoretical specific capacity of traditional graphite anodes is only 372 mAh / g, which is insufficient to meet the requirements of high-energy-density batteries. In contrast, silicon, with its extremely high theoretical specific capacity (4200 mAh / g), has become a highly anticipated next-generation anode material and is considered one of the ideal choices for improving the performance of lithium-ion batteries.

[0003] Silicon anode materials have significant advantages over graphite anodes, particularly their higher lithium insertion / extraction potential. This characteristic effectively prevents lithium deposition during high-rate charge / discharge processes, thereby improving battery safety.

[0004] However, the irreversible expansion of silicon during charge-discharge cycles leads to the accumulation of mechanical stress inside the cell. The expansion force is greatest at the outermost edge of the cell, causing the positive and negative current collectors to break due to metal fatigue. Utility Model Content

[0005] The main purpose of this invention is to propose a battery cell that aims to solve the problem of mechanical stress accumulation inside the battery cell caused by the irreversible expansion of silicon-based electrodes.

[0006] To achieve the above objectives, this utility model proposes a battery cell, comprising: an electrode sheet and a separator, wherein the separator and the electrode sheet are stacked and wound together, the electrode sheet has an innermost ring and an outermost ring, the outermost ring of the electrode sheet includes a hollow foil segment, the surface of the hollow foil segment is configured with a plurality of grooves at intervals, and an insulating layer is coated on the surface of the hollow foil segment in the grooves and between the grooves.

[0007] In some embodiments, the groove is circular and the radius of curvature of the groove is from 10 μm to 100 μm.

[0008] In some embodiments, the radius of curvature of the groove is 30 μm to 70 μm.

[0009] In some embodiments, the groove is polygonal, and the side length of the groove is from 10 μm to 100 μm.

[0010] In some embodiments, the side length of the groove is 30 μm to 70 μm.

[0011] In some embodiments, the thickness of the insulating layer is h1, and the thickness of the empty foil segment is h2, satisfying the following relationship:

[0012] 5≤100h1 / h2≤50.

[0013] In some embodiments, the spacing between adjacent grooves is 200 μm to 500 μm.

[0014] In some embodiments, the spacing between adjacent grooves is 300 μm to 400 μm.

[0015] In some embodiments, the depth of the groove is h3, and the thickness of the empty foil segment is h2, satisfying the following relationship:

[0016] 8≤100h3 / h2≤80;

[0017] 5≤h2≤20.

[0018] In some embodiments, the electrode includes a positive electrode and a negative electrode. The outermost empty foil segment of the negative electrode is a first empty foil segment, and the outermost empty foil segment of the positive electrode is a second empty foil segment. The first empty foil segment, the second empty foil segment, and the separator are stacked and wound together. The length of the first empty foil segment is D1, the length of the second empty foil segment is D2, and the length of the separator is D3, satisfying D1>D3>D2.

[0019] The beneficial effects of this utility model are as follows: by setting empty foil segments on the outermost ring of the electrode instead of the traditional coating end structure, the problem of expansion stress concentration of the outermost active material during charging and discharging can be avoided; furthermore, by constructing multiple grooves at intervals on the surface of the empty foil segments to form a grid structure, a release channel and transfer path are provided for the expansion stress inside the cell, reducing the accumulation of internal stress caused by volume changes; at the same time, an insulating layer is applied to the surface of the empty foil segments inside and between the grooves, ensuring the electrical insulation safety between the outermost ring and other electrodes, while maintaining good mechanical strength and structural stability, thereby effectively improving the cycle life and safety reliability of the cell, and achieving an organic unity of structural optimization and performance improvement. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the battery cell structure in one embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of the hollow foil in one embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the structure of the hollow foil in one embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the structure of the empty foil in another embodiment of the present invention.

[0024] Explanation of icon numbers:

[0025] 100. Electrode;

[0026] 102, Positive electrode sheet; 102a, Single-sided coated section; 201, First empty foil section;

[0027] 101. Negative electrode sheet; 202. Second empty foil section;

[0028] 200, Empty foil segment; 200a, Groove;

[0029] 300. Insulation layer;

[0030] 400. Diaphragm.

[0031] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0032] The solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0033] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0034] It should also be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component present. When a component is described as "connected to" another component, it can be directly connected to the other component or there may be an intervening component present.

[0035] Furthermore, the use of terms such as "first" and "second" in this utility model is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.

[0036] Silicon anode materials have significant advantages over graphite anodes, particularly their higher lithium insertion / extraction potential. This characteristic effectively prevents lithium deposition during high-rate charge / discharge cycles, thus improving battery safety. However, the irreversible expansion of silicon during charge / discharge cycles leads to the accumulation of mechanical stress within the cell, with the greatest expansion force at the outermost edge. Therefore, this invention proposes a cell in which a micron-sized mesh of ceramic-coated copper and aluminum foil is designed as the outermost ring of the core to replace the coated end electrode. Specifically, referring to... Figure 1 and Figure 2 This utility model proposes a battery cell, including an electrode 100 and a separator 400. The separator 400 and the electrode 100 are stacked and wound together. The electrode 100 has an innermost ring and an outermost ring. The outermost ring of the electrode 100 includes a hollow foil segment 200. The surface of the hollow foil segment 200 is constructed with a plurality of grooves 200a at intervals. An insulating layer 300 is coated on the surface of the hollow foil segment 200 in the grooves 200a and between the grooves 200a.

[0037] In this embodiment, the electrode 100 includes a positive electrode 100 and a negative electrode 100. The negative electrode 100 uses a silicon-based composite material as the active material, which has high specific capacity and excellent lithium storage performance. The separator 400 uses a polyolefin porous film material, which has good ion conductivity and mechanical strength. The separator 400 and the electrode 100 are stacked in a predetermined order and formed into the cell body by a winding process. The empty foil section 200 is the part of the electrode 100 that is not coated with the active material layer, that is, the exposed area of ​​the current collector. This area retains the original physical properties of the metal foil.

[0038] In this embodiment, the empty foil segment 200 can be set on the outermost ring of the positive electrode 100, or on the outermost ring of the negative electrode 100, or on both the outermost rings of the positive and negative electrode 100. The configuration can be selected according to the specific design requirements of the battery cell. The width of the empty foil segment 200 can be 2-10mm.

[0039] In this embodiment, the insulating layer 300 is formulated with a ceramic coating. Its main components may include inorganic ceramic powders such as alumina and zirconium oxide, along with appropriate amounts of organic binders and dispersants. During cell cycling, the ceramic coating provides protection and effectively prevents short circuits when the empty foil area breaks. The ceramic coating possesses a microporous structure with a pore size ranging from 0.1 to 2 μm, providing electrolyte storage space and improving ion transport channels, thereby optimizing the cell's cycling performance.

[0040] The grooves 200a on the empty foil segment 200 are formed by laser etching or chemical etching. Several regularly arranged grooves 200a are formed on the surface of the empty foil segment 200. The depth of each groove 200a is 30%-70% of the current collector thickness, the width of each groove 20-100 μm, and the spacing between the grooves 200a is 50-200 μm, forming a micron-scale mesh-like reinforcing rib structure. This mesh-like reinforcing rib is used to replace the traditional coated terminal electrode 100 structure, effectively releasing and transferring expansion stress, reducing capacity decay and safety degradation caused by the fracture of the coated electrode 100. The micron-scale mesh-like reinforcing ribs constructed on the surface of the empty foil area can significantly improve the tensile strength and structural stability of the foil, effectively disperse stress concentration, enhance the overall structural rigidity, significantly enhance stress resistance, and improve the problem of electrode breakage during cycling.

[0041] During the charge-discharge cycle of the battery cell, the silicon anode material undergoes significant volume changes. During charging, silicon and lithium form an alloy, causing the volume to expand by more than 300%. During discharging, the alloy decomposes and contracts. This repeated volume change generates enormous mechanical stress inside the battery cell, especially at the outermost winding position of the cell. Due to the geometric constraint effect, the expansion stress reaches its maximum value, which can easily lead to fatigue fracture of the electrode material.

[0042] Traditional coating termination structures create rigid constraint boundaries on the outermost ring, failing to effectively release accumulated internal expansion stress and leading to severe stress concentration. This embodiment eliminates the expansion source of the active material at this location by setting an empty foil segment 200 on the outermost ring of the electrode 100, fundamentally preventing expansion stress on the outermost ring. The mesh-like structure formed by the grooves 200a on the surface of the empty foil segment 200 plays a crucial stress regulation role. When expansion stress occurs inside the cell, the mesh-like grooves 200a provide multi-dimensional deformation space, allowing the foil to undergo moderate elastic deformation under stress, thereby releasing some of the stress. The reinforcing ribs between the grooves 200a act as stress transmission paths, dispersing concentrated point stress over a larger area, achieving a uniform stress distribution. Simultaneously, the geometric characteristics of the mesh-like structure allow stress to be transferred and redistributed along the direction of the grooves 200a, preventing excessive stress accumulation at a single location.

[0043] During cycling, the microporous structure of the insulating layer 300 can also accommodate a small amount of electrolyte, providing lubrication for local stress release, further reducing frictional resistance and stress peak, and ensuring the stability and integrity of the overall structure during long-term cycling.

[0044] The preparation process involves thoroughly mixing lithium cobalt oxide (positive electrode material), acetylene black (SP) (conductive agent), and polyvinylidene fluoride (PVDF) (binder) in an N-methylpyrrolidone solvent system at a mass ratio of 98:1.2:0.8. This mixture is then coated onto a 15 μm thick Al foil using a doctor blade coating process. After drying at 120°C for 12 hours, micron-scale mesh-like reinforcing ribs are constructed in the empty foil area using laser etching technology. The laser power is set to 50W, and the scanning speed is 1000 mm / min. The prepared ceramic slurry is then coated onto the reinforcing rib area using a roller coating process, with the coating thickness controlled at 5-8 μm. Finally, after rolling and slitting, the positive electrode sheet 100 is obtained.

[0045] The negative electrode sheet 100 can be prepared by thoroughly mixing silicon-based composite negative electrode material, conductive agent, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 98.1:0.5:0.7:0.7, coating it onto a 10μm thick Cu foil at 105℃ under vacuum, constructing micron-level mesh-like reinforcing ribs in the empty foil area using chemical etching technology, using ferric chloride solution as the etching solution, and controlling the etching time to 30-60 seconds, then rolling the prepared ceramic slurry onto the reinforcing rib area, and obtaining the negative electrode sheet 100 after rolling and slitting.

[0046] The beneficial effects of this utility model are as follows: by setting an empty foil segment 200 on the outermost ring of the electrode 100 instead of the traditional coating end structure, the problem of expansion stress concentration of the outermost active material during charging and discharging can be avoided; furthermore, by constructing multiple grooves 200a at intervals on the surface of the empty foil segment 200 to form a grid structure, a release channel and transfer path are provided for the expansion stress inside the cell, reducing the accumulation of internal stress caused by volume changes; at the same time, an insulating layer 300 is coated on the surface of the empty foil segment 200 inside and between the grooves 200a, ensuring the electrical insulation safety between the outermost ring and other electrode 100, while maintaining good mechanical strength and structural stability, thereby effectively improving the cycle life and safety reliability of the cell, and achieving an organic unity of structural optimization and performance improvement.

[0047] In some embodiments, in this embodiment, the groove 200a is circular, and the radius of curvature of the groove 200a is 10μm to 100μm.

[0048] In this embodiment, the grooves 200a formed on the surface of the empty foil segment 200 can adopt a circular geometric shape. Multiple circular grooves 200a are arranged in a regular array on the empty foil segment 200 to form a mesh reinforcing rib structure with specific curvature characteristics. The design of the circular grooves 200a takes into account the stress dispersion principle and material mechanical properties. By optimizing the curvature radius parameter, while forming an effective mesh reinforcing rib, the overall rigidity and structural integrity of the empty foil are ensured to the greatest extent.

[0049] Specifically, the radius of curvature of the circular groove 200a is limited to the range of 10μm to 100μm. This range is determined based on the thickness characteristics of the foil material, the stress transfer mechanism, and the feasibility of the manufacturing process. Compared with other shapes, the circular geometry has the advantages of uniform stress distribution and no sharp corner stress concentration points, which can achieve a smooth transition and effective release of expansion stress.

[0050] When the radius of curvature of groove 200a is set to 10μm, the geometric dimensions of a single groove 200a are relatively small, and the depth of groove 200a is controlled within the range of 30%-40% of the current collector thickness. For example, on an aluminum foil with a thickness of 15μm, the depth of groove 200a is approximately 4.5-6μm. At this time, the perimeter of the circular groove 200ac is approximately 62.8μm, and the spacing between grooves 200a is set to 25-30μm, which can form a high-density grid distribution within a unit area.

[0051] The smaller radius of curvature allows the mesh reinforcement to have a finer grid structure, enabling it to respond sensitively to minute stress changes. Simultaneously, the smaller geometry of the groove 200a ensures that most of the empty foil section 200 retains its original thickness, resulting in minimal overall rigidity loss, approximately 5%-8% of the original rigidity. This configuration is particularly suitable for high-capacity battery cell applications where structural stability is extremely critical.

[0052] When the radius of curvature of the groove 200a is set to 50 μm, the geometry of the groove 200a is moderate, and the depth of the groove 200a is controlled within the range of 40%-60% of the current collector thickness. For example, on an aluminum foil with a thickness of 15 μm, the depth of the groove 200a is approximately 6-9 μm. The perimeter of the circular groove 200a is approximately 314 μm, and the spacing of the groove 200a is set to 60-80 μm, achieving a good balance between grid density and the stress relief capability of a single groove 200a.

[0053] The moderate radius of curvature design provides each circular groove 200a with suitable deformation space, accommodating a greater degree of stress release, while the mesh density still ensures the continuity of stress transmission. The stiffness loss of the empty foil section 200 is controlled within the range of 10%-15%, ensuring sufficient structural strength while providing effective stress regulation capability. This configuration is suitable for most standard cell applications and has good versatility.

[0054] When the radius of curvature of the groove 200a is set to 100 μm, a single groove 200a has a relatively large geometric size, and the depth of the groove 200a can reach 50%-70% of the thickness of the current collector. For example, on an aluminum foil with a thickness of 15 μm, the depth of the groove 200a is approximately 7.5-10.5 μm. The perimeter of the circular groove 200a is approximately 628 μm, and the spacing between the grooves 200a is set to 120-150 μm, forming a relatively loose but large-unit-size mesh structure.

[0055] The larger radius of curvature gives each individual groove 200a a stronger stress release capability, allowing it to accommodate greater local deformation. Although the mesh density is relatively low, each mesh cell has a stronger load-bearing capacity, making it suitable for handling high-stress scenarios. The stiffness loss of the empty foil segment 200 is approximately 15%-20%, which is within an acceptable range. This configuration is particularly suitable for cell applications under high-rate charge / discharge or extreme operating conditions.

[0056] By designing the groove 200a as a circle and precisely controlling the radius of curvature within the range of 10 μm to 100 μm, the optimized configuration of the mesh reinforcing rib structure was achieved. The circular geometry eliminates stress concentration at sharp corners, resulting in a more uniform stress distribution; the reasonable range of curvature radius ensures sufficient stress release space while maintaining the basic rigidity requirements of the empty foil section 200.

[0057] Furthermore, the radius of curvature of the groove 200a is 30 μm to 70 μm.

[0058] In this embodiment, when the radius of curvature of the groove 200a is set to 30 μm, the depth of the groove 200a is controlled within the range of 35%-50% of the current collector thickness. For example, on an aluminum foil with a thickness of 15 μm, the depth of the groove 200a is approximately 5.2-7.5 μm. The circumference of the circular groove 200a is approximately 188 μm, and the spacing between the grooves 200a is set to 40-50 μm, forming a relatively dense grid distribution.

[0059] The mesh reinforcement at this radius of curvature has a fine mesh structure, enabling precise response to stress changes. The stiffness loss of the empty foil segment 200 is controlled within the range of 8%-12%, providing good stress adjustment capability while ensuring structural stability.

[0060] When the radius of curvature of groove 200a is set to 50 μm, the depth of groove 200a is controlled within the range of 40%-60% of the current collector thickness. For example, on an aluminum foil with a thickness of 15 μm, the depth of groove 200a is approximately 6-9 μm. The perimeter of the circular groove 200a is approximately 314 μm, and the spacing between grooves 200a is set to 60-80 μm, achieving a good balance between grid density and stress relief capability of individual grooves 200a.

[0061] The design with a moderate radius of curvature allows each circular groove 200a to have suitable deformation space, and the rigidity loss of the empty foil section 200 is controlled within the range of 10%-15%, which has good versatility and practicality.

[0062] When the radius of curvature of groove 200a is set to 70 μm, the depth of groove 200a is controlled within the range of 45%-65% of the current collector thickness. For example, on an aluminum foil with a thickness of 15 μm, the depth of groove 200a is approximately 6.7-9.7 μm. The perimeter of the circular groove 200a is approximately 440 μm, and the spacing between grooves 200a is set to 80-100 μm, forming a relatively loose but stress-relieving mesh structure.

[0063] The larger radius of curvature gives a single groove 200a a stronger stress release capability, and the rigidity loss of the empty foil section 200 is about 12%-18%, making it suitable for applications that require greater stress adjustment capabilities.

[0064] See Figure 3 and Figure 4 In this embodiment, the groove 200a is polygonal, and the side length of the groove 200a is 10μm to 100μm.

[0065] In this embodiment, the grooves 200a formed on the surface of the empty foil segment 200 adopt a polygonal geometry. Multiple polygonal grooves 200a are arranged in a regular array on the empty foil segment 200 to form a mesh-like reinforcing rib structure with specific geometric features. The design of the polygonal grooves 200a is based on discrete geometry theory and stress transfer mechanism. By optimizing the side length parameters and polygon type, effective mesh-like reinforcing ribs are formed while achieving directional stress transfer and effective stress release.

[0066] The side length of the polygonal groove 200a is limited to the range of 10μm to 100μm. This range is determined based on a comprehensive consideration of the thickness characteristics of the foil material, the stress distribution characteristics of the geometry, and the precision of the manufacturing process. The polygon can be a regular polygon such as a triangle, square, rectangle, rhombus, regular hexagon, or regular octagon, or an irregular polygon such as a trapezoid. Different polygon shapes have different stress transfer characteristics: triangles have good structural stability; squares and rectangles are easy to arrange in a regular pattern; regular hexagons have the best space filling efficiency; and regular octagons have near-circular stress distribution characteristics.

[0067] For example, when using regular hexagonal grooves 200a with a side length of 20 μm, the circumscribed circle diameter of the groove 200a is approximately 40 μm, and the depth of the groove 200a is controlled within the range of 30%-45% of the current collector thickness. For instance, on an aluminum foil with a thickness of 15 μm, the depth of the groove 200a is approximately 4.5-6.7 μm. The spacing between the regular hexagonal grooves 200a is set to 25-35 μm, forming a high-density honeycomb-like grid distribution.

[0068] When a square groove 200a is used and its side length is set to 25 μm, the area of ​​groove 200a is 625 μm. 2 The depth of the groove 200a is controlled within 30%-40% of the thickness of the current collector. The spacing of the square grooves 200a is set to 30-40μm, forming a regular square grid structure.

[0069] The square groove 200a exhibits good geometric symmetry, with stress evenly distributed in four directions, facilitating array arrangement and batch processing. The rigidity loss is approximately 7%-11%.

[0070] In some embodiments, the side length of the groove 200a is 30 μm to 70 μm.

[0071] When using regular hexagonal grooves 200a with a side length of 50 μm, the circumscribed circle diameter of groove 200a is approximately 100 μm, and the depth of groove 200a is controlled within the range of 40%-60% of the current collector thickness. For example, on a 15 μm thick aluminum foil, the depth of groove 200a is approximately 6-9 μm. The spacing between the regular hexagonal grooves 200a is set to 60-80 μm, forming a moderately dense honeycomb grid distribution.

[0072] The 200a regular hexagonal groove of this size achieves the best balance between stress relief capability and structural stability, with rigidity loss controlled within the range of 10%-15%, and has good versatility and practicality.

[0073] When a square groove 200a is used and its side length is set to 40 μm, the area of ​​groove 200a is 1600 μm. 2 The depth of the groove 200a is controlled within the range of 35%-55% of the current collector thickness. The spacing of the square grooves 200a is set to 50-70μm, forming a medium-density grid structure.

[0074] When an equilateral triangular groove 200a is used and the side length is set to 60 μm, the area of ​​groove 200a is approximately 1559 μm². 2 The depth of groove 200a is controlled within the range of 40%-60% of the current collector thickness. The spacing of the equilateral triangular grooves 200a is set to 70-90μm, forming a triangular mesh structure.

[0075] When using regular octagonal grooves 200a with a side length of 80 μm, the circumscribed circle diameter of groove 200a is approximately 209 μm, and the depth of groove 200a is controlled within the range of 45%-65% of the current collector thickness. On a 15 μm thick aluminum foil, the depth of groove 200a is approximately 6.7-9.7 μm. The spacing of the regular octagonal grooves 200a is set to 100-120 μm, forming a relatively loose but stress-relieving mesh structure.

[0076] By designing the groove 200a as a polygon and precisely controlling the side length within the range of 10μm to 100μm, diverse configurations of the mesh reinforcing rib structure are achieved. The polygonal geometry offers a wider range of design options than a circle, allowing the selection of the most suitable geometry based on specific stress field characteristics and process requirements.

[0077] See Figure 2 In this embodiment, the thickness of the insulating layer 300 is h1, and the thickness of the empty foil segment 200 is h2, satisfying the following relationship:

[0078] 5≤100h1 / h2≤50.

[0079] In this embodiment, h1 is the thickness of the single-sided ceramic coating, and its value ranges from 5μm to 50μm; h2 is the thickness of the foil, and its value ranges from 5μm to 20μm.

[0080] When the thickness of the insulating layer 300 is less than 5% of the thickness of the empty foil segment 200, the ceramic coating is too thin to form a continuous and dense insulating layer 300, posing a risk of defects such as pinholes and cracks, leading to insulation failure and potential short circuit hazards. The minimum ratio of 5% ensures that the insulating layer 300 has sufficient thickness to completely cover the microscopic roughness and groove 200a structure of the surface of the empty foil segment 200, forming a smooth and continuous protective layer. An insulating layer 300 with a thickness of 5% can form a basic microporous structure, providing the necessary storage space for the electrolyte and maintaining the unobstructed ion conduction channels.

[0081] Upper limit control (100h1 / h2≤50): When the 300mm insulation layer thickness exceeds 50% of the 200mm blank foil thickness, excessive ceramic coating thickness significantly increases the overall thickness and weight of the battery cell, reducing its volumetric energy density and gravimetric energy density. Optimal range effect (5%-50%): This ratio range establishes an optimal balance between insulation protection and manufacturing economics, ensuring reliable insulation performance while controlling cost and complexity. The 300mm insulation layer thickness (5-50μm) corresponding to this ratio range matches the precise control capabilities of existing coating processes, exhibiting good process operability and quality controllability.

[0082] For general applications, a moderate ratio of 100h1 / h2 = 15-25 can be selected, such as a configuration of h1 = 8μm and h2 = 15μm, achieving a good balance between performance and cost. For applications with extremely high safety requirements, a configuration close to the upper limit can be selected, such as 100h1 / h2 = 40-50, providing stronger insulation protection. For energy density-sensitive applications, a configuration close to the lower limit can be selected, such as 100h1 / h2 = 5-10, minimizing the thickness increment while ensuring basic insulation.

[0083] By defining this relationship, the design of the insulation layer 300 is standardized and regulated, avoiding arbitrariness and uncertainty in the design.

[0084] In some embodiments, the depth of the groove 200a is h3, and the thickness of the empty foil segment 200 is h2, satisfying the following relationship:

[0085] 8≤100h3 / h2≤80;

[0086] 5≤h2≤20.

[0087] Furthermore, the spacing between adjacent grooves 200a is 200 μm to 500 μm, and the spacing between adjacent grooves 200a is 300 μm to 400 μm. Wherein, the depth of groove 200a (h3) ranges from 8 μm to 80 μm, and h2 is the thickness of the foil material, where 5 μm ≤ h2 ≤ 20 μm. The core limitation of the relationship in this embodiment lies in controlling the penetration ratio of the groove 200a depth relative to the thickness of the empty foil segment 200, ensuring that the groove 200a provides an effective stress relief channel without excessively weakening the structural integrity and mechanical strength of the empty foil segment 200.

[0088] Lower limit control (100h3 / h2≥8): Ensure that the depth of the groove 200a is at least 8% of the thickness of the empty foil section 200 to avoid insufficient stress release capacity due to an excessively shallow groove 200a. An excessively shallow groove 200a cannot provide enough deformation space, and expansion stress will still accumulate on the surface of the empty foil section 200, defeating the original design purpose of the mesh reinforcement.

[0089] Upper limit control (100h3 / h2≤80): The depth of groove 200a is limited to no more than 80% of the thickness of the empty foil section 200 to prevent excessive etching from severely damaging the structural strength of the empty foil section 200. When the depth of groove 200a exceeds 80%, the remaining foil thickness is insufficient to withstand cyclic stress, and breakage failure is likely to occur.

[0090] Specific parameter examples (based on experimental data);

[0091] Minimum permeability ratio (100h³ / h² = 8-15);

[0092] Example 1: 100h³ / h² = 8, stiffener spacing 200μm;

[0093] When the depth ratio of the groove 200a is set to 8%, it provides basic stress relief capability, and the spacing of the reinforcing ribs is set to 200μm, forming a relatively sparse grid structure. This configuration mainly forms micro-stress adjustment channels on the surface of the empty foil segment 200, maximizing the preservation of the original strength of the empty foil segment 200.

[0094] Example 2: 100h³ / h² = 15, stiffener spacing 300μm;

[0095] When the depth ratio of the groove 200a is increased to 15%, the stress release capability is significantly enhanced, and the spacing of the reinforcing ribs is increased to 300μm. While ensuring the stress dispersion effect, the impact on the overall continuity of the foil is reduced.

[0096] Equilibrium permeability ratio (100h³ / h² = 20-50);

[0097] Example 3: 100h3 / h2 = 20, stiffener spacing 400μm. When the depth ratio of the groove 200a reaches 20%, a relatively obvious stress release channel is formed. The stiffener spacing is set to 400μm to achieve a preliminary balance between stress release effect and structural stability.

[0098] Example 4: 100h3 / h2 = 30, stiffener spacing 500μm. When the groove depth ratio of 200a reaches 30%, the stress release capability is further improved, and the stiffener spacing is increased to 500μm, which is suitable for application scenarios with medium expansion stress.

[0099] Comparative example: 100h³ / h² = 0, stiffener spacing 0 μm;

[0100] The traditional 200a structure without grooves lacks stress relief channels, and the expansion stress acts directly on the foil, which can easily lead to structural failure. This structure is used to compare and verify the superiority of the technical solution of this utility model.

[0101] Furthermore, the precise control of the groove depth 200a is achieved using laser etching technology, through precise adjustment of laser power, scanning speed, and pulse frequency, for example:

[0102] Shallow etching (h3 = 1-5μm): laser power 20-35W, scanning speed 1500-1200mm / min;

[0103] Intermediate layer etching (h3 = 5-12μm): laser power 35-50W, scanning speed 1200-800mm / min;

[0104] Deep etching (h3 = 12-20μm): laser power 50-65W, scanning speed 800-500mm / min.

[0105] The design parameters can be found in the table below:

[0106]

[0107] Table 1

[0108] The performance of the examples and comparative examples in RT cycling tests is as follows:

[0109]

[0110] Table 2

[0111] The double-sided groove 200a structure is suitable for applications in high-capacity silicon anode cells, fast-charging cells, or extreme operating conditions, where expansion stress is greater and stress relief capabilities are more critical. This structure provides more reliable structural support for the stable cycling of silicon anode materials through enhanced stress regulation capabilities.

[0112] In another embodiment, the empty foil segment includes opposing first and second surfaces, both of which are formed with grooves 200a; both the first and second surfaces are coated with an insulating layer 300.

[0113] In this embodiment, the empty foil segment adopts a double-sided symmetrical structure design, with the first surface and the second surface located on the upper and lower sides of the empty foil segment, forming opposing parallel surfaces. Both surfaces are constructed with grooves 200a according to the same design specifications. The geometry, size parameters, and arrangement of the grooves 200a are consistent with or symmetrically distributed on the first and second surfaces.

[0114] The grooves 200a on the first and second surfaces can adopt the same layout pattern to form a mesh reinforcing rib structure with corresponding upper and lower parts; or they can adopt a staggered layout so that the grooves 200a on the first surface and the grooves 200a on the second surface are arranged alternately on the plane projection to further optimize the stress dispersion effect.

[0115] Both surfaces are coated with an insulating layer 300. The thickness and material composition of the insulating layer 300 are consistent with those of the single-sided structure, ensuring that the empty foil segment has reliable electrical insulation protection in both the top and bottom directions.

[0116] See Figure 1In this embodiment, the electrode 100 includes a positive electrode 102 and a negative electrode 101. The outermost empty foil segment of the positive electrode 102 is the first empty foil segment 201, and the outermost empty foil segment of the negative electrode 101 is the second empty foil segment 202. The first empty foil segment 201, the second empty foil segment 202 and the separator 400 are stacked and wound together. The length of the first empty foil segment 201 is D1, the length of the second empty foil segment 202 is D2, and the length of the separator 400 is D3, and D1>D3>D2 are satisfied.

[0117] In this embodiment, the winding structure of the battery cell adopts a stepped end design. By precisely controlling the length relationship between the first empty foil segment 201, the second empty foil segment 202, and the separator 400, a gradient layered structure is formed. The first empty foil segment 201, as the outermost part of the positive electrode 102, has the largest length D1; the length D3 of the separator 400 is in the middle; and the second empty foil segment 202, as the outermost part of the negative electrode 101, has the smallest length D2.

[0118] This length relationship ensures that during the winding process, the layers of material do not end at the same location simultaneously, but rather form a stepped finish from the inside out. The second empty foil segment 202 ends first, followed by the diaphragm 400, and the first empty foil segment 201 ends last, serving as the outermost layer finish, forming a smooth thickness transition.

[0119] Traditional designs with the same length at the winding end create a sudden change in thickness, resulting in significant stress concentration points. When the battery cell expands during charging and discharging, these stress concentration points can easily become the starting points for structural failure.

[0120] The stepped termination, through the length relationship D1>D3>D2, disperses the thickness variation originally concentrated at a single location to multiple locations, reducing the magnitude of thickness variation at each location and effectively lowering local stress peaks. After the second empty foil segment 202 terminates first, the stress at that location is mainly borne by the diaphragm 400 and the first empty foil segment 201; after the diaphragm 400 terminates, all remaining stress is transferred to the first empty foil segment 201. This gradual stress transfer process avoids sudden stress redistribution, making stress release more gradual and orderly.

[0121] For example, with D1 = 50mm, D3 = 40mm, and D2 = 30mm, the first empty foil segment 201 is 10mm longer than the separator 400, and the separator 400 is 10mm longer than the second empty foil segment 202, forming a uniform stepped transition. This design is suitable for standard-sized cells and provides good stress dispersion. The stepped termination design (D1 > D3 > D2) effectively disperses and gently releases the stress on the outermost ring of the cell. This structural design avoids the stress concentration problem caused by traditional terminations of the same length, and, combined with the mesh reinforcing rib structure of the first empty foil segment 201, provides reliable final termination protection.

[0122] See Figure 1 In this embodiment, the positive electrode 102 also has an inner ring covered by its outermost ring. The inner ring includes a single-sided coated section 102a, which is connected to the first empty foil section 200 along the winding direction of the positive electrode 102.

[0123] In this embodiment, the single-sided coating on the single-sided coating section 102a is an active material layer, which includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material is selected from one or more of lithium iron phosphate, ternary materials, lithium manganese oxide, or lithium cobalt oxide; the conductive agent is selected from one or more of conductive carbon black, graphene, and carbon nanotubes; and the binder is selected from one or more of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC). The active material layer is formed on the foil substrate through a coating process to provide electrochemical activity for the battery.

[0124] Furthermore, the inner ring of the positive electrode 102, which is covered by its outermost ring, is a ring adjacent to the outermost ring, and the foil of this ring is a single-sided coated section 102a. Specifically, the single-sided coated section 102a is disposed on the side of the foil that faces away from the outermost ring, that is, coated on the inner surface of the inner ring, while the surface of the foil facing the outermost ring is an empty foil.

[0125] It should be noted that in this embodiment, the outermost surface of the foil is provided with a plurality of grooves 200a with an intermittent structure, and these grooves 200a form a mesh-like reinforcing rib structure.

[0126] In conjunction with the outermost empty foil segment 200 in the aforementioned embodiments, when the battery cell expands during charging and discharging, the inner single-sided coated segment 102a and the outermost empty foil segment 200 form a dual buffer mechanism, working together to absorb and disperse expansion stress. Specifically, the mesh reinforcing rib structure provides multi-directional stress transmission paths, dispersing the expansion force over a wider area and preventing stress concentration in localized regions. Simultaneously, the insulating layer 300 not only provides electrical insulation but also possesses a certain degree of elastic deformation capability, further absorbing some of the expansion stress.

[0127] When cracks or fractures occur in the outermost ring, the active material layer on the single-sided coated section 102a of the inner ring can still withstand the expansion force. The binder component provides the necessary bonding strength and flexibility, while the conductive agent component maintains the structural integrity, thereby preventing further crack propagation and deterioration. In addition, the mesh reinforcing rib structure can prevent the rapid propagation of cracks, controlling the damage within a localized area, significantly improving the overall reliability of the positive electrode 102 and the safety performance of the battery.

[0128] The above description is only a part or preferred embodiment of this utility model. Neither the text nor the drawings should limit the scope of protection of this utility model. All equivalent structural transformations made using the content of this utility model specification and drawings under the overall concept of this utility model, or direct / indirect applications in other related technical fields, are included within the scope of protection of this utility model.

Claims

1. An electric cell comprising a jelly-roll of a positive electrode sheet and a separator, the jelly-roll being wound and stacked with the positive electrode sheet and the separator, the positive electrode sheet having an outermost winding, characterized in that, The outermost ring of the electrode includes an empty foil segment, the surface of which is constructed with a plurality of grooves at intervals, and an insulating layer is coated on the surface of the empty foil segment within and between the grooves.

2. The electric cell of claim 1, wherein, The groove is circular and has a radius of curvature of 10 μm to 100 μm.

3. The battery cell according to claim 2, characterized in that, The radius of curvature of the groove is 30 μm to 70 μm.

4. The battery cell according to claim 1, characterized in that, The groove is polygonal in shape, and the side length of the groove is 10μm to 100μm.

5. The battery cell according to claim 4, characterized in that, The side length of the groove is 30μm to 70μm.

6. The battery cell according to claim 1, characterized in that, The thickness of the insulating layer is h1, and the thickness of the empty foil segment is h2, satisfying the following relationship: 5≤100h1 / h2≤50.

7. The battery cell according to claim 1, characterized in that, The spacing between adjacent grooves is 200 μm to 500 μm.

8. The battery cell according to claim 7, characterized in that, The spacing between adjacent grooves is 300 μm to 400 μm.

9. The battery cell according to any one of claims 1 to 6, characterized in that, The depth of the groove is h3, and the thickness of the empty foil segment is h2, satisfying the following relationship: 8≤100h3 / h2≤80: 5≤h2≤20。 10. The battery cell according to claim 1, characterized in that, The electrode includes a positive electrode and a negative electrode. The outermost empty foil segment of the positive electrode is the first empty foil segment, and the outermost empty foil segment of the negative electrode is the second empty foil segment. The first empty foil segment, the second empty foil segment, and the separator are stacked and wound together. The length of the first empty foil segment is D1, the length of the second empty foil segment is D2, and the length of the separator is D3, satisfying D1>D3>D2.

11. The battery cell according to claim 10, characterized in that, The positive electrode sheet also has an inner ring covered by its outermost ring, the inner ring including a single-sided coated section, the single-sided coated section being connected to the first empty foil section along the winding direction of the positive electrode sheet.

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