Battery cell structure, electrochemical device and electronic equipment

Abstract

The invention discloses a cell structure which comprises a cathode piece, an anode piece and an isolating membrane, the isolating membrane is arranged between the cathode piece and the anode piece, the isolating membrane, the cathode piece and the anode piece are jointly wound to form an electrode assembly, the isolating membrane comprises a base material and a coating layer, and the coating layer is attached to the surface of the base material. The coating layer sequentially comprises a first part and a second part in the winding direction of the electrode assembly, the first part is located on the side, facing the winding center of the cell structure, of the second part, and the thickness of the coating layer in the first part is larger than that in the second part. The safety performance of the battery cell structure can be improved, and the energy density of the battery cell structure is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery, in particular to a battery cell structure, an electrochemical device and an electronic device. BACKGROUND

[0002] Lithium ion batteries are widely used in portable electronic devices and power systems due to their high energy density and long cycle life. With the increasing demand for energy density, battery safety issues have become increasingly prominent. In the winding type battery cell structure, due to the lack of effective support of the innermost layer area during winding, and the relatively thin thickness of the separator, this area becomes a high-risk area of thermal runaway under thermal, mechanical or electrical abuse conditions. Especially in extreme cases such as external mechanical impact or needle puncture, burrs generated at the edges of the positive and negative electrodes can easily pierce the separator in this area, causing internal short circuit, and then triggering thermal runaway, causing serious safety accidents. SUMMARY

[0003] The main purpose of the present application is to provide a battery cell structure, an electrochemical device and an electronic device, which can improve the safety performance of the battery cell structure and ensure the energy density of the battery cell structure.

[0004] To achieve the above-mentioned purpose, some embodiments of the present application provide a battery cell structure, comprising a cathode sheet, an anode sheet and a separator film, the separator film is arranged between the cathode sheet and the anode sheet, and the separator film and the cathode sheet and the anode sheet are laminated and wound to form an electrode assembly, the separator film comprises a substrate and a coating layer, the coating layer is attached to at least one surface of the substrate, the coating layer comprises a first part close to the winding center and a second part away from the winding center, and the thickness of the coating layer at the first part is greater than the thickness of the coating layer at the second part.

[0005] In some embodiments, along the winding direction of the electrode assembly, the second part comprises a transition zone and an outer ring zone connected in sequence, the thickness of the first part is T1, the thickness of the transition zone is T2, and the thickness of the outer ring zone is T3, and the relationship between T1, T2 and T3 satisfies: T1>T2≥T3.

[0006] In some embodiments, the thickness of the first part is T1, and T1 ranges from 4.5 μm to 30 μm.

[0007] In some embodiments, the relationship between T2 and T1 satisfies: T2=(50%-90%)*T1; and / or, The thickness of T3 ranges from 4 μm to 20 μm.

[0008] In some embodiments, the number of turns N1 corresponding to the first part satisfies: N1=max(3,[Ks*(1.02*(1+0.04tan(0.03*(W-60)))) / (β*tunit*α1) / 0.707]); Where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn group, α1 is the inner layer turn number correction coefficient, 0.95≤α1≤1.1, Ks is the small size compensation factor, when W<30, Ks=0.7+0.05*(W-8), when W≥30, Ks=1.0.

[0009] In some embodiments, the length L1 corresponding to the first part satisfies: L1=π / 2*[2*N1*d0+N1*(N1+1)*tunit]*T1(W); Where d0 is the needle diameter, T1(W) is the inner layer length correction factor, tunit is the thickness of a single-turn group, and N1 is the number of turns corresponding to the first part, N1 satisfies: N1=max(3,[Ks*(1.02*(1+0.04tan(0.03*(W-60)))) / (β*tunit*α1) / 0.707]); Where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn group, α1 is the inner layer turn number correction coefficient, 0.95≤α1≤1.1, Ks is the small size compensation factor, when W<30, Ks=0.7+0.05*(W-8), when W≥30, Ks=1.0.

[0010] In some embodiments, the number of turns N2 corresponding to the transition zone satisfies: N2=max(2,[Ks*(1.38*(0.85–0.0015*W+2*10^-5*W²)) / (β*tunit*1.414*(1+0.005*W))]); Where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn stage, and Ks is the small size compensation factor. When W < 30, Ks = 0.7 + 0.05 * (W - 8), and when W ≥ 30, Ks = 1.0.

[0011] In some embodiments, the length L2 corresponding to the transition region satisfies: L2=π / 2*[2*N2*(d0+2*N1*tunit)+N2*(N2+1)*tunit]*T2(W); Where d0 is the needle diameter, T1(W) is the inner layer length correction factor, N1 is the number of turns corresponding to the first part, T2(W) is the transition zone length correction factor, tunit is the single-turn group thickness, and N2 is the number of turns corresponding to the transition zone, where N2 satisfies: N2=max(2,[Ks*(1.38*(0.85–0.0015*W+2*10^-5*W²)) / (β*tunit*1.414*(1+0.005*W))]); Where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn stage, and Ks is the small size compensation factor. When W < 30, Ks = 0.7 + 0.05 * (W - 8); when W ≥ 30, Ks = 1.0. N1 satisfies: N1=max(3,[Ks*(1.02*(1+0.04tan(0.03*(W-60)))) / (β*tunit*α1) / 0.707]); Where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn group, α1 is the inner layer turn number correction coefficient, 0.95≤α1≤1.1, Ks is the small size compensation factor, when W<30, Ks=0.7+0.05*(W-8), when W≥30, Ks=1.0.

[0012] In some embodiments, the cell structure further includes tabs connected to the cathode and anode plates, respectively. The inner layer length correction factor of the cell structure is T1(W), and the inner layer turn number correction factor is α1. The cell structure is configured as an inner tab welded structure. In the inner tab welded structure, the inner layer length correction factor T1(W) satisfies: T1(W)=1.15-0.0015*W+1.5*10^-5*W², The inner layer number correction factor α1 satisfies: α1 = 1.1; or, The cell structure can be configured as an external tab structure. In the external tab structure, the inner layer length correction factor T1(W) satisfies: T1(W) = 1.05 + 0.0008 * W, The inner layer number correction factor α1 satisfies: α1 = 0.95; or, The cell structure can be configured as a tab-centered structure. In the tab-centered structure, the inner layer length correction factor T1(W) satisfies: T1(W) = 11.10 + 0.0003 * W, The inner layer number correction factor α1 satisfies: α1 = 1.0; Where W is the cell width, W≥5mm.

[0013] An embodiment of the second aspect of this application provides an electrochemical device including the cell structure of any of the above embodiments, and the electrochemical device further includes a housing or aluminum-plastic film for encapsulating the cell structure.

[0014] An embodiment of the third aspect of this application provides an electronic device including the electrochemical device of the above embodiments, and the electronic device further includes a battery compartment for housing the electrochemical device.

[0015] According to the above embodiments, the beneficial effects of the present invention are: The battery cell structure of the present invention includes a cathode plate, an anode plate, and a separator. The separator is disposed between the cathode plate and the anode plate and is wound together with the cathode plate and the anode plate to form an electrode assembly. The separator includes a substrate and a coating layer. The coating layer is attached to the surface of the substrate. The coating layer has a first portion and a second portion sequentially arranged along the winding direction of the electrode assembly. The first portion is located on the side of the second portion facing the winding center of the battery cell structure. The thickness of the coating layer in the first portion is greater than the thickness in the second portion.

[0016] This application employs a gradient coating design with a thicker inner layer and a thinner outer layer. Without increasing the overall separator thickness, only the first part is locally thickened, improving the innermost separator's resistance to shrinkage and puncture under high temperature or mechanical puncture conditions. This effectively prevents short circuits between the positive and negative electrodes caused by separator melting or damage in the early stages of thermal runaway. Furthermore, the structure avoids the energy density loss and reduced flexibility issues associated with traditional full-width thickening solutions, balancing safety and electrical performance. Simultaneously, since the first part is close to the winding center, this area has concentrated heat and lacks electrode support, making it most susceptible to thermal runaway. Locally thickening the coating in this area can immediately hinder heat conduction, improving the reliability of the entire battery pack system. Moreover, the gradient coating design does not require the introduction of new components; it can be achieved simply by adjusting the coating head's output during the manufacturing process, exhibiting good mass production compatibility and facilitating compatibility with existing soft-pack, cylindrical, and square winding technologies.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0019] Figure 1 This is a three-dimensional structural diagram of a battery cell structure in one embodiment of the present invention, specifically an internally welded electrode structure; Figure 2 This is a three-dimensional structural diagram of a battery cell structure in one embodiment of the present invention, specifically a tab external welding structure; Figure 3 This is a three-dimensional structural diagram of a battery cell structure in one embodiment of the present invention, specifically a structure with the tabs placed in the middle; Figure 4 This is a schematic diagram of the structure of the isolation membrane in one embodiment of the present invention; Figure 5 To observe from another perspective Figure 4 The diagram shows the structure of the isolation membrane.

[0020] Explanation of icon numbers: Cell structure 10; 100; 110; 120; 121; 122; 123; 124; Cathode plate 200; Anode plate 300; JE400.

[0021] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention 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 the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0024] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are 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 with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or," "and / or," or "and / or" throughout the text implies three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0025] In existing technologies, to improve the thermal stability and mechanical strength of the separator, the overall coating thickness is typically increased or additional functional layers are introduced. However, while this full-width thickening strategy improves safety, it significantly increases the overall thickness of the battery cell, leading to a decrease in energy density and reduced separator flexibility, thus affecting the yield of the winding process.

[0026] The following is for reference. Figures 1 to 5 This describes the cell structure 10, electrochemical device, and electronic device according to embodiments of the present invention. (Refer to...) Figure 1 , Figure 4 and Figure 5 An embodiment of the first aspect of this application provides a battery cell structure 10, including a cathode sheet 200, an anode sheet 300, and a separator 100. The separator 100 is disposed between the cathode sheet 200 and the anode sheet 300, and is wound together with the cathode sheet 200 and the anode sheet 300 to form an electrode assembly. The separator 100 includes a substrate 110 and a coating layer 120. The coating layer 120 is attached to the surface of the substrate 110. The coating layer 120 has a first portion 121 and a second portion sequentially arranged along the winding direction of the electrode assembly. The first portion 121 is located on the side of the second portion facing the winding center of the battery cell structure 10. The thickness of the coating layer 120 in the first portion 121 is greater than the thickness in the second portion.

[0027] This application employs a gradient coating design with a thicker inner layer and a thinner outer layer. Without increasing the overall separator thickness, only the first portion 121 is locally thickened, improving the innermost separator's resistance to shrinkage and puncture under high temperature or mechanical puncture conditions. This effectively prevents short circuits between the positive and negative electrodes caused by separator melting or damage in the early stages of thermal runaway. Furthermore, the structure avoids the energy density loss and reduced flexibility issues associated with traditional full-width thickening schemes, balancing safety and electrical performance. Simultaneously, since the first portion 121 is close to the winding center, this area has concentrated heat and lacks electrode support, making it most susceptible to thermal runaway. Locally thickening the coating layer 120 in this area can immediately hinder heat conduction, improving the reliability of the entire battery pack system. Moreover, the gradient design of the coating layer 120 does not require the introduction of new components; it can be achieved simply by adjusting the coating head output during the manufacturing process, exhibiting good mass production compatibility and facilitating compatibility with existing soft-pack, cylindrical, and square winding technologies.

[0028] In some embodiments, the coating layer 120 of the first portion 121 has a uniform thickness; in some embodiments, the thickness of the coating layer 120 of the first portion 121 decreases towards the second portion; in some embodiments, the inner protective region has varying heights in the thickness direction, and the thickness of its thinnest point is greater than the thickness of the second portion. Similarly, the thickness of the coating layer 120 of the second portion can also be designed in this way.

[0029] Reference Figure 4 and Figure 5In some embodiments, along the winding direction of the electrode assembly, the second part includes a transition region 122 and an outer ring region 123 connected in sequence. The coating layer 120 has a thickness of T1 in the first part 121, a thickness of T2 in the transition region 122, and a thickness of T3 in the outer ring region 123. The relationship between T1, T2, and T3 satisfies: T1>T2≥T3. Specifically, the second part is further subdivided into the transition region 122 and the outer ring region 123, and it is clearly defined that the thicknesses of the first part 121, the transition region 122, and the outer ring region 123 decrease in a gradient, forming a continuous transition in thickness. This segmented gradient structure matches the mechanical strength and thermal shrinkage suppression capability of the separator with the actual risk distribution along the cell radius. Specifically, the innermost first section 121 bears the maximum bending stress and highest temperature, retaining maximum thickness to prevent short circuits. The intermediate transition zone 122, through moderate thinning, alleviates internal stress concentration caused by abrupt thickness changes while maintaining a stable mechanical structure, preventing separator wrinkles or coating peeling during cycling. The outermost outer ring 123 is thinned to its thinnest point, reducing energy density consumption and ensuring overall separator flexibility, making winding tension easier to control and reducing manufacturing defects such as edge collapse and wrinkles. Thus, the cell structure 10 avoids both the ED (energy density) loss caused by overall thickening and the potential weaknesses resulting from step-thinning, achieving a balance between safety and performance. Furthermore, the continuous gradient can be configured for linear thinning, ensuring a consistent process without additional composite or splicing steps, resulting in high production efficiency.

[0030] In some embodiments, gradient coatings are present in each region of the first part 121 and the second part. Specifically, within the several turns covered by the first part 121, the coating thickness decreases radially outward from the winding center, forming a continuous gradient from thick to thin. This allows heat to be gradually absorbed and dispersed during radial transfer, avoiding local hot spot concentration. In the second part, the transition region 122 and the outer ring region 123 can each be provided with independent roll-direction gradients. The thickness of the transition region 122 gradually decreases along the winding direction from the position bordering the first part 121, providing a rigid-flexible transition effect for the cell structure 10. The outer ring region 123 smoothly descends to adapt to the mechanical constraints of the shell sidewall, thereby eliminating stress concentration caused by abrupt thickness changes. By constructing continuous micro-gradients within the first part 121 and the second part respectively, the cell achieves multi-layer synergy of thermal protection, ion transport, and mechanical compliance without increasing the amount of additional coating material.

[0031] Reference Figure 4 and Figure 5In some embodiments, T1 ranges from 4.5 μm to 30 μm, for example, T1 is 4.5 μm, 10 μm, 15 μm, 20 μm, 25 μm, and 30 μm. By limiting the thickness T1 of the first portion 121 to the range of 4.5 μm to 30 μm, a sufficient and safe design window is provided for cell structures 10 with different energy densities, sizes, and material systems. The lower limit of this range ensures that the coating still has sufficient mechanical support and thermal barrier capabilities in the innermost ring, effectively suppressing separator shrinkage, melt-through, or burr puncture in the early stages of thermal runaway, thereby blocking direct contact between the positive and negative electrodes. The upper limit of this range avoids the problems of excessive thickness leading to a sudden increase in winding rigidity, stress concentration during electrode bending, and a significant decrease in ED, allowing the cell to maintain high energy density and good flexibility. Therefore, manufacturers can flexibly choose the coating thickness according to actual product requirements to achieve the best balance between safety and performance indicators without changing the substrate material or adding additional functional layers, thereby simplifying the process and reducing material costs.

[0032] Reference Figure 4 and Figure 5 In some embodiments, the relationship between T2 and T1 satisfies: T2 = (50%~90%) * T1, for example, T2 is 50% * T1, 70% * T1, 80% * T1, 90% * T1, etc. In some embodiments, the thickness range of T3 is 4μm~20μm, for example, the thickness of T3 is 4μm, 10μm, 15μm, 20μm. By limiting the thickness T2 of the transition region 122 to 50% to 90% of the thickness T1 of the first part 121, and the thickness T3 of the outer ring region 123 to an independent range, a smooth and controllable thickness reduction gradient is designed. This proportional design allows the transition region 122 to inherit the high strength advantage of the inner layer while avoiding stress concentration caused by a sudden drop in thickness, effectively mitigating the risk of diaphragm wrinkles or coating cracking caused by differences in bending radius during winding. At the same time, the outer ring region 123 is thinned to a reasonable lower limit while maintaining basic insulation and puncture protection, thereby reducing the impact on energy density.

[0033] Reference Figure 4 and Figure 5In some embodiments, the number of turns N1 corresponding to the first part 121 satisfies: N1=max(3,[Ks*(1.02*(1+0.04tan(0.03*(W-60))))) / (β*tunit*α1) / 0.707]), where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn group (1 layer of cathode sheet 200 thickness + 1 layer of anode sheet 300 thickness + 1 layer of separator 100 thickness), α1 is the inner layer turn number correction coefficient, Ks is the small size compensation factor, when W<30, Ks=0.7+0.05*(W-8), when W≥30, Ks=1.0. By introducing an analytical formula based on cell width, thermal decay coefficient, single-turn stage thickness (1 layer of cathode sheet 200mm thick + 1 layer of anode sheet 300mm thick + 1 layer of separator 100mm thick), and inner layer correction coefficient, the minimum number of turns N1 for the first part 121 is dynamically determined, clarifying the specific number of turns corresponding to the thick coating layer 120. This formula smoothly captures the nonlinear effect of thermal accumulation caused by increased width, and the small-size compensation factor Ks provides additional turns to compensate for the heat concentration that easily occurs in narrow cells, thus ensuring that consecutive layers starting from the innermost turn are under thickened protection, avoiding the weakness of localized thinness leading to thermal runaway. Through a specific algorithm, R&D personnel only need to input basic physical parameters to obtain the optimal number of turns that balances safety and material usage, shortening the trial production cycle. Furthermore, according to this formula, the production line can quickly switch product specifications without changing the coating head by simply adjusting the winding cycle and coating weight, significantly improving manufacturing efficiency.

[0034] It should be noted that the number of turns N1 refers to the minimum number of complete winding turns of the separator 100 covered by the thickened coating layer 120 at the winding center. That is, the number of turns of the separator that are continuously wrapped around the electrode and maintain the thickness T1 from the start of the winding needle. This number of turns determines the radial depth of the thermal runaway protection zone.

[0035] It should be noted that Ks is a small size compensation factor. In some embodiments, when the cell width W is less than 30mm, Ks increases linearly with the width. This is used to add an extra 121 turns for narrow cells due to their short heat dissipation path and concentrated heat, ensuring that the thermal protection zone can adequately cover high-risk areas. In some embodiments, when W ≥ 30mm, Ks is taken as 1.0 to maintain calculation consistency.

[0036] It should be noted that W represents the cell width, which directly determines the lateral heat dissipation distance and thermal volume of the electrode assembly. The formula uses mm as the unit. The larger the width, the longer the heat diffusion path, and the required number of turns in the first part can be reduced accordingly. Conversely, narrower cells require more turns to compensate for the concentrated heat effect.

[0037] It should be noted that β is the thermal decay coefficient, which comprehensively reflects the influence of coating material, electrode thermal conductivity and winding density on radial heat decay. Its value is determined by experiments. The larger the value, the faster the heat decays radially and the smaller the calculated N1. Conversely, the protective area needs to be thickened.

[0038] It should be noted that tunit refers to the thickness of a single-turn electrode assembly, which is the sum of the thicknesses of a cathode sheet 200, an anode sheet 300, and a separator 100. It represents the radial increment of the electrode assembly per turn. The larger the tunit, the thicker the electrode assembly is for the same number of turns, and the heat capacity increases. N1 needs to be adjusted according to the formula to ensure the protection depth.

[0039] It should be noted that α1 is the inner layer turn number correction coefficient. In some embodiments, its value ranges from 0.95 to 1.1. It is set differently depending on whether the tab 400 is internally welded, externally welded, or centrally located. It is used to quantify the influence of the position of the tab 400 on the degree of heat concentration at the winding center, thereby correcting the number of turns required in the first part 121.

[0040] Reference Figure 4 and Figure 5 In some embodiments, the length L1 corresponding to the first part 121 satisfies: L1=π / 2*[2*N1*d0+N1*(N1+1)*tunit]*T1(W), where d0 is the needle diameter, T1(W) is the inner layer length correction coefficient, and N1 is the number of turns corresponding to the first part 121. The formula in this embodiment further transforms the number of turns into the length of the coating. By multiplying the needle diameter, the single-turn stage thickness, and the inner layer length correction coefficient, the geometric parameters, structural characteristics, and thermal field distribution are mapped to the actual unfolded length of the first part 121 in one step. Through this formula, designers can quickly pinpoint the start and end points of the thickened coating. Simultaneously, this length can guide the start and stop timing and correction strategy of the coating equipment, avoiding endpoint drift caused by manual teaching, ensuring that each thickened area is closed from beginning to end without gaps, and preventing thermal runaway problems due to insufficient coating length.

[0041] In this embodiment, it should be noted that N1 is the number of turns corresponding to the first part 121, calculated by the formula in the previous embodiment. It represents the minimum number of complete turns that the separator 100 must maintain the maximum coating thickness T1 at the winding center. Its value directly determines the radial depth of the thermal protection zone, and the range varies dynamically with the cell width, thermal attenuation coefficient, and electrode tab 400 structure to ensure that the innermost layer receives sufficient mechanical and thermal protection. d0 is the diameter of the winding needle, referring to the outer diameter of the metal or plastic winding needle at the start of winding, in millimeters. Its size determines the initial radius of curvature of the innermost circle of the electrode group. The smaller d0 is, the greater the bending stress of the electrode group under the same number of turns. It needs to be used in the formula to calculate the unfolded length of the first part 121 to ensure the accurate position of the coating endpoint. T1(W) is the inner layer length correction coefficient, which is an empirical coefficient related to the cell width W. It is used to correct the difference in thermal field distribution when converting the number of geometric turns into the actual unfolded length. Different tab 400 structures correspond to different expressions. Its value changes monotonically as W increases. The range is determined by experimental regression to ensure that the length calculation results match the measured thermal runaway region.

[0042] Reference Figure 4 and Figure 5 In some embodiments, the number of turns N2 corresponding to the transition region 122 satisfies: N2=max(2,[Ks*(1.38*(0.85–0.0015*W+2*10^-5*W²)) / (β*tunit*1.414*(1+0.005*W))]), where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn group (1 layer of cathode sheet 200mm thickness + 1 layer of anode sheet 300mm thickness + 1 layer of separator 100mm thickness), and Ks is the small size compensation factor. When W<30, Ks=0.7+0.05*(W-8), and when W≥30, Ks=1.0. By introducing an analytical formula directly related to the cell width, thermal decay characteristics, and single-turn thickness, the minimum number of turns N2 required for the transition region 122 can be calculated, enabling a scientific and controllable step-like decrease in coating thickness from the first part 121 to the outer ring region 123. This formula fully considers the nonlinear characteristics of the extended heat diffusion path and slower heat accumulation as the width increases. It also utilizes a small-size compensation factor to compensate for the concentrated thermal effects of narrow cells with additional turns, ensuring that the transition region 122 is neither too short, resulting in an excessively steep thickness gradient, nor too long, wasting coating material. Consequently, the cell forms a continuous, smooth structure with decreasing mechanical strength and thermal stability in the radial direction, effectively mitigating potential problems such as diaphragm wrinkles and electrode microcracks caused by abrupt stiffness changes during winding, while simultaneously reducing internal stress concentration and improving cycle life.

[0043] Reference Figure 4 and Figure 5In some embodiments, the length L2 corresponding to the transition zone 122 satisfies: L2=π / 2*[2*N2*(d0+2*N1*tunit)+N2*(N2+1)*tunit]*T2(W), where d0 is the needle diameter, T1(W) is the inner layer length correction coefficient, N1 is the number of turns corresponding to the first part 121, N2 is the number of turns corresponding to the transition zone 122, T2(W) is the length correction coefficient of the transition zone 122, and tunit is the thickness of a single-turn group. By providing an analytical expression for the unfolded length of the transition zone 122, the transition zone 122 is geometrically formed as a predictable and reproducible gradient. The coupling terms of the needle diameter, the inner layer coating thickness, and the single-turn group thickness in the formula reflect the cumulative effect of the preceding thickened coating on the subsequent bending radius, avoiding steps or gaps that may occur when the coating is thickened first and then thinned. The width correction factor incorporates the subtle differences in thermal and stress fields caused by the lateral dimensions of the battery cell, ensuring a smooth gradient transition for products of varying widths. Using this formula, R&D personnel can pinpoint the start and end points of the transition zone (122) during the project initiation phase without repeated slicing and measurement, providing accurate start and stop coordinates for the coating machine and avoiding endpoint drift caused by manual teaching. Furthermore, during production line changeovers, only parameter updates are needed to complete the process migration for different battery cell specifications without hardware alterations. This shortens the new product introduction cycle, reduces trial production costs, and fundamentally improves batch-to-batch morphological consistency, providing a replicable and quantifiable engineering model for the large-scale, flexible manufacturing of high-energy-density electrochemical devices.

[0044] Reference Figure 4 The cell structure 10 also includes tabs 400, which are connected to the cathode plate 200 and the anode plate 300 respectively. The cell structure 10 has a tab 400 inner soldered state, a tab 400 middle-positioned state and a tab 400 outer soldered state. The tab 400 in the inner soldered state is closer to the winding center of the cell structure 10 than the tab 400 in the middle-positioned state. The tab 400 in the outer soldered state is farther away from the winding center of the cell structure 10 than the tab 400 in the middle-positioned state.

[0045] Furthermore, referring to Figure 5 In some embodiments, with the tab 400 in the inner solder state, the inner layer length correction factor T1(W) satisfies: T1(W) = 1.15 - 0.0015*W + 1.5*10^-5*W², and the inner layer number correction factor α1 satisfies: α1 = 1.1; refer to Figures 1 to 5 In some embodiments, with the tab 400 externally soldered, the inner layer length correction factor T1(W) satisfies: T1(W) = 1.05 + 0.0008 * W, and the inner layer number correction factor α1 satisfies: α1 = 0.95; (Refer to...) Figure 1In some embodiments, with the tab 400 in the center position, the inner layer length correction factor T1(W) satisfies: T1(W) = 11.10 + 0.0003 * W, and the inner layer turn number correction factor α1 satisfies: α1 = 1.0. Wherein, W is the cell width, W ≥ 5mm, for example, W is 5mm, 10mm, 20mm, 30mm, or 40mm.

[0046] In the internal soldering structure of the tab 400, the soldering points of the cathode and anode tabs 400 are arranged on the winding start side, close to the center of the winding needle. The metal tab 400 is wound in synchronously with the innermost electrode sheet. The heat conduction path is short and heat is easily accumulated at the shaft center. Therefore, the formula increases α1 and T1(W) to add an extra 121 turns in the first part, so that the thickened coating covers the hot zone of the tab 400, suppressing the premature shrinkage of the diaphragm caused by the rapid heat conduction of the tab 400, and improving the safety margin for needle penetration and overcharge. The external soldering structure of the tab 400 places the soldering point on the winding end side, away from the center of the winding needle. The heat of the tab 400 needs to cross the entire electrode assembly to reach the shaft center. The heat effect is relatively dispersed. The formula correspondingly decreases α1 and reduces T1(W) to reduce the number of turns in the first part while ensuring safety, avoiding excessive thickening that squeezes out energy density, and balancing high capacity and reliable packaging. The 400-type electrode has a centrally located welding point in the middle of the electrode group. Its thermal characteristics are between those of inner and outer welding. α1 is set to the median value of 1.0 and T1(W) changes linearly and gradually. This provides moderate protection against heat concentration in the inner ring and avoids redundant thickening of the outer ring. This balances the cell's energy density, mechanical strength and thermal safety, making it suitable for most thin and light electronic products.

[0047] In summary, this application provides independent inner layer length correction coefficient T1(W) and turn number correction coefficient α1 for three typical arrangements of tab 400: inner welding, center placement, and outer welding. This allows the calculation method for the coating length and number of turns to be dynamically adjusted according to the position of tab 400, further improving safety and reducing material waste. When the tab 400 is in the inner welding state, i.e., the tab 400 is close to the winding center, the function automatically increases the inner layer length correction coefficient T1(W), giving the first part 121 additional length and turn number compensation, offsetting the risk of thermal shrinkage exacerbated by the rapid thermal conductivity and local temperature rise of the tab 400 metal. When the tab 400 moves outward, i.e., switching from the inner welding state to the center placement or outer welding state, the function is adjusted accordingly to avoid excessive thickening that encroaches on energy density. By incorporating the key structural variable of the tab 400 position into the analytical formula, cell designers can quickly generate coating schemes adapted to different tab 400 processes within the same material system without repeated prototyping, shortening the development cycle. Simultaneously, production line changes only require switching formula parameters to maintain a high degree of consistency in the coating machine's start / stop coordinates, number of revolutions, and length, fundamentally improving batch stability and manufacturing yield.

[0048] Reference Figure 2 The second aspect of this application provides an electrochemical device including a cell structure 10 as described in any of the above embodiments. The electrochemical device also includes a housing or aluminum-plastic film for encapsulating the cell structure 10. By encapsulating the cell structure 10 in any of the above embodiments within a housing or aluminum-plastic film, a complete electrochemical device is formed, allowing the local enhancement effect of the gradient-coated separator to be fully utilized at the system level. The encapsulation not only provides a barrier to isolate the device from the external environment, preventing the intrusion of moisture and oxygen, but also works in conjunction with the gradient coating to suppress heat diffusion. When the internal temperature rises, the first part 121 first blocks the radial spread of heat, while the encapsulation layer simultaneously withstands internal pressure and delays external impacts. Together, they limit thermal runaway to its initial stage. Since the cell itself has achieved a balance between energy density and safety performance through a thickness-reducing design, the encapsulation process does not require additional thickening or the addition of a metal armor, thus meeting stringent tests such as drop, puncture, and overcharge, reducing system weight and cost. At the same time, the flexible properties of the aluminum-plastic film retain the cell's expansion space, preventing leakage at the seal due to internal stress concentration in the later stages of cycling. Therefore, this electrochemical device maintains high energy density while possessing the advantages of higher reliability and lighter weight, providing a complete solution that balances safety and performance for the needs of thinner and lighter end products and longer battery life.

[0049] Reference Figure 3 The third aspect of this application proposes an electronic device including the electrochemical device described above. The electronic device also includes a battery compartment for housing the electrochemical device. Specifically, by integrating the electrochemical device into the battery compartment of the electronic device, the high safety and high energy density advantages of the gradient-coated separator are directly extended to the end-application level. The battery compartment provides mechanical positioning and heat dissipation channels for the electrochemical device, while utilizing its own structural rigidity to suppress the relative displacement of the battery cell during drops or vibrations, reducing the risk of fatigue cracking of the encapsulation film due to repeated bending. The first part 121 inside the battery cell has already blocked the spread of thermal runaway, and the battery compartment further directs the local temperature rise to the device casing, achieving dual thermal management from point to surface, and preventing heat accumulation inside the compartment. Since the electrochemical device does not require additional reinforced casing, the battery compartment design can reduce wall thickness and increase volume, leaving more space for terminal manufacturers to arrange larger capacity battery cells or add functional modules, thereby extending the overall battery life and improving the user experience. At the same time, the lightweight compartment reduces the overall weight of the device, meeting the needs of handheld, wearable, and drone applications that are sensitive to weight down to the gram level. Head Office, the electronic device of this application achieves higher reliability and longer battery life while maintaining a slim and lightweight appearance, providing an ideal power solution that balances performance and safety for products such as smart terminals, mobile computing, and portable energy storage.

[0050] The following describes the battery cell structure 10, electrochemical device, and electronic device of this application systematically using a specific embodiment. (Refer to...) Figures 1 to 5 Figures 1 to 5 Figures 1 to 5In this invention, the separator 100 of the battery cell structure 10 is gradient coated. The innermost layers of the separator in the bare battery cell have three continuous coating layers 120 of thick, medium, and thin thicknesses, forming a first portion 121, a transition region 122, and an outer region 123 sequentially along the winding direction. The thickness relationship of these three regions satisfies T1>T2≥T3, where the thickness T1 of the first portion 121 is between 4.5μm and 30μm, the thickness T2 of the transition region 122 is 50% to 90% of T1, and the thickness T3 of the outer region 123 is only 4μm to 20μm. This distribution provides the highest mechanical strength and thermal shrinkage suppression at the most dangerous winding center, while the transition region 122 smooths the stiffness gradient, avoiding stress concentration. Finally, the outer ring retains basic insulation with minimal thickness, balancing energy density and flexibility.

[0051] To accurately quantify the dimensions of each zone, this invention provides a series of analytical formulas based on the cell width W, the winding needle diameter d0, the single-turn group thickness tunit, the thermal attenuation coefficient β, and the position of the tab 400: the number of inner layer turns N1 and length L1, the number of transition zone turns N2 and length L2 are all calculated using closed-loop formulas, and a small-size compensation factor Ks and tab 400 shape correction coefficients α1 and T1(W) are introduced. When W < 30 mm, Ks = 0.7 + 0.05(W - 8); when W ≥ 30 mm, Ks = 1.0. The three structures of the tab 400—inner soldering, center placement, and outer soldering—correspond to different expressions for α1 and T1(W), allowing the coating length and number of turns to automatically scale with the position of the tab 400, completely eliminating the need for experience-based trial production.

[0052] The substrate uses a conventional PE or PP porous membrane. The coating layer 120 consists of at least one inorganic filler such as alumina, boehmite, magnesium hydroxide, or magnesium oxide, along with binders such as PVDF, polyacrylate, and styrene-butadiene rubber. The wet film weight can be adjusted online and formed in one step at the same coating head, eliminating the need for additional lamination processes. When changing production lines, only parameter updates are required to migrate the process for different cell specifications, thereby shortening the new product introduction cycle, reducing prototyping costs, and fundamentally improving batch-to-batch morphological consistency and manufacturing yield.

[0053] Because this application only thickens the inner layer locally, the overall cell thickness remains almost unchanged, minimizing energy loss. Simultaneously, the first part 121 proactively blocks the spread of thermal runaway, while the encapsulation layer simultaneously withstands internal pressure and delays external impacts. Together, these two elements limit thermal runaway to its nascent stage. This structure maintains high energy density while offering higher reliability and a lighter system weight, providing a complete solution that balances safety and performance for the requirements of thinner, lighter, and longer-lasting end-products. This allows electronic devices to achieve higher reliability and longer battery life while maintaining a slim and lightweight appearance.

[0054] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural transformations made using the contents of the specification and drawings of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of patent protection of the present invention.

Claims

1. A battery cell structure, characterized in that, The electrode assembly includes a cathode sheet, an anode sheet, and a separator. The separator is disposed between the cathode sheet and the anode sheet and is stacked and wound with the cathode sheet and the anode sheet to form an electrode assembly. The separator includes a substrate and a coating layer. The coating layer is attached to at least one surface of the substrate. The coating layer includes a first portion near the winding center and a second portion away from the winding center. The thickness of the coating layer in the first portion is greater than the thickness in the second portion.

2. The cell structure according to claim 1, characterized in that, Along the winding direction of the electrode assembly, the second part includes a transition region and an outer ring region connected in sequence. The thickness of the first part is T1, the thickness of the transition region is T2, and the thickness of the outer ring region is T3. The relationship between T1, T2, and T3 satisfies: T1>T2≥T3.

3. The cell structure according to claim 1 or 2, characterized in that, The thickness of the first part is T1, and the range of T1 is 4.5μm to 30μm.

4. The cell structure according to claim 2, characterized in that, The relationship between T2 and T1 satisfies: T2 = (50%~90%) * T1; and / or, The thickness of T3 ranges from 4μm to 20μm.

5. The cell structure according to claim 2, characterized in that, The number of revolutions N1 corresponding to the first part satisfies: N1=max(3,[Ks*(1.02*(1+0.04tan(0.03*(W-60)))) / (β*tunit*α1) / 0.707]); Where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn group, α1 is the inner layer turn number correction coefficient, 0.95≤α1≤1.1, Ks is the small size compensation factor, when W<30, Ks=0.7+0.05*(W-8), when W≥30, Ks=1.

0.

6. The cell structure according to claim 2, characterized in that, The length L1 corresponding to the first part satisfies: L1=π / 2*[2*N1*d0+N1*(N1+1)*tunit]*T1(W); Where d0 is the needle diameter, T1(W) is the inner layer length correction factor, tunit is the thickness of a single-turn group, and N1 is the number of turns corresponding to the first part, wherein N1 satisfies: N1=max(3,[Ks*(1.02*(1+0.04tan(0.03*(W-60)))) / (β*tunit*α1) / 0.707]); Where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn group, α1 is the inner layer turn number correction coefficient, 0.95≤α1≤1.1, Ks is the small size compensation factor, when W<30, Ks=0.7+0.05*(W-8), when W≥30, Ks=1.

0.

7. The cell structure according to claim 2, characterized in that, The number of cycles N2 corresponding to the transition zone satisfies: N2=max(2,[Ks*(1.38*(0.85–0.0015*W+2*10^-5*W²)) / (β*tunit*1.414*(1+0.005*W))]); Where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn stage, and Ks is the small size compensation factor. When W < 30, Ks = 0.7 + 0.05 * (W - 8), and when W ≥ 30, Ks = 1.

0.

8. The cell structure according to claim 2, characterized in that, The length L2 corresponding to the transition region satisfies: L2=π / 2*[2*N2*(d0+2*N1*tunit)+N2*(N2+1)*tunit]*T2(W); Where d0 is the needle diameter, T1(W) is the inner layer length correction factor, N1 is the number of turns corresponding to the first part, T2(W) is the transition zone length correction factor, tunit is the single-turn group thickness, and N2 is the number of turns corresponding to the transition zone, wherein N2 satisfies: N2=max(2,[Ks*(1.38*(0.85–0.0015*W+2*10^-5*W²)) / (β*tunit*1.414*(1+0.005*W))]); Where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn stage, and Ks is the small size compensation factor. When W < 30, Ks = 0.7 + 0.05 * (W - 8); when W ≥ 30, Ks = 1.

0. The N1 satisfies: N1=max(3,[Ks*(1.02*(1+0.04tan(0.03*(W-60)))) / (β*tunit*α1) / 0.707]); Where W is the cell width, β is the thermal decay coefficient, tunit is the thickness of a single-turn group, α1 is the inner layer turn number correction coefficient, 0.95≤α1≤1.1, Ks is the small size compensation factor, when W<30, Ks=0.7+0.05*(W-8), when W≥30, Ks=1.

0.

9. The cell structure according to any one of claims 4 to 8, characterized in that, The cell structure also includes tabs, which are respectively connected to the cathode plate and the anode plate. The inner layer length correction factor of the cell structure is T1(W), and the inner layer turn number correction factor is α1. The cell structure is configured as an inner tab welded structure, wherein the inner layer length correction coefficient T1(W) of the inner tab welded structure satisfies: T1(W)=1.15-0.0015*W+1.5*10^-5*W², The inner layer number correction coefficient α1 satisfies: α1 = 1.1; or, The cell structure can be configured as an external tab structure, wherein in the external tab structure, the inner layer length correction coefficient T1(W) satisfies: T1(W) = 1.05 + 0.0008 * W, The inner layer number correction coefficient α1 satisfies: α1 = 0.95; or, The cell structure can be configured as a tab-centered structure, wherein in the tab-centered structure, the inner layer length correction coefficient T1(W) satisfies: T1(W) = 11.10 + 0.0003 * W, The inner layer number correction coefficient α1 satisfies: α1=1.0； Where W is the cell width, W≥5mm.

10. An electrochemical device, characterized in that, The electrochemical device includes the cell structure according to any one of claims 1 to 9, and further includes a housing or aluminum-plastic film for encapsulating the cell structure.

11. An electronic device, characterized in that, The electronic device, including the electrochemical device of claim 10, further includes a battery compartment for housing the electrochemical device.

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