Battery cell, electrochemical device, and electronic device

Abstract

The utility model discloses a kind of electric core, electrochemical device and electronic equipment.The electric core includes first pole piece, second pole piece, diaphragm, diaphragm is between first pole piece, second pole piece, first pole piece, diaphragm and second pole piece are sequentially laminated and are wound to form electrode assembly, first pole piece includes current collector and the active material layer of coating on the at least one side of current collector;First pole piece includes the first pole piece segment and the second pole piece segment sequentially distributed along the winding direction of electrode assembly, first pole piece segment is close to winding center and is arranged;Active material layer includes first active material layer, second active material layer, first pole piece segment includes first active material layer, second pole piece segment includes second active material layer, the adhesion between first active material layer and current collector is greater than the adhesion between second active material layer and current collector.The utility model can be compatible with the energy density and safety performance of battery.

Description

Technical Field

[0001] This utility model relates to the field of energy storage devices, and in particular to a battery cell, an electrochemical device, and an electronic device. Background Technology

[0002] In recent years, the explosive growth of the new energy industry globally has made lithium-ion batteries a core component supporting portable electronics, electric transportation, and large-scale energy storage. The market's continued demand for longer range and higher energy density has prompted research and manufacturing to continuously reduce the proportion of inactive material layers.

[0003] As a crucial layer that simultaneously performs the functions of ion conduction and electronic isolation, the thickness of the separator has significantly decreased in the ever-developing lithium battery technology. The direct consequence of this reduction in thickness is a simultaneous weakening of mechanical strength and safety redundancy. Systems that were originally not sensitive to small-diameter dust particles are now significantly affected by them. Any foreign matter inclusions can become a source of subsequent dendrite precipitation, micro-short circuits, thermal runaway, and other issues, posing significant safety hazards during use. Utility Model Content

[0004] The main objective of this invention is to propose a battery cell, an electrochemical device, and an electronic device that can balance the energy density and safety performance of the electrochemical device.

[0005] To achieve the above objectives, some embodiments of this utility model propose a battery cell, including a first electrode, a second electrode, and a separator, with the separator located between the first electrode and the second electrode. The first electrode, the separator, and the second electrode are sequentially stacked and wound to form an electrode assembly. The first electrode includes a current collector and an active material layer coated on at least one side of the current collector. The first electrode includes a first electrode segment and a second electrode segment distributed sequentially along the winding direction of the electrode assembly, with the first electrode segment positioned close to the winding center; The active material layer includes a first active material layer and a second active material layer. The first electrode segment includes the first active material layer, and the second electrode segment includes the second active material layer. The adhesion between the first active material layer and the current collector is greater than the adhesion between the second active material layer and the current collector.

[0006] In some embodiments, the adhesion force between the first active material layer and the current collector is F1, and the adhesion force between the second active material layer and the current collector is F2, wherein 1.1≤F1:F2≤3.0.

[0007] In some embodiments, the electrode assembly includes a straight section and bent sections located on both sides of the straight section. Along the winding direction of the electrode assembly, the straight section has a straight length L and a first electrode segment length L1, and satisfies L1=c*L, where 1.2≤c≤4.5, and the first electrode segment includes at least one first straight section and a first bent section.

[0008] In some embodiments, the current collector has a first surface and a second surface opposite each other along the thickness direction, both the first surface and the second surface are coated with an active material layer, and the first active material layer on the first surface and the first active material layer on the second surface are offset from each other along the winding direction of the electrode assembly.

[0009] In some embodiments, the current collector has a first surface and a second surface opposite each other along the thickness direction, both the first surface and the second surface being coated with an active material layer; wherein... The adhesion force between the first active material layer on the first surface and the current collector is greater than the adhesion force between the second active material layer on the first surface and the current collector. And / or, the adhesion force between the first active material layer on the second surface and the current collector is greater than the adhesion force between the second active material layer on the second surface and the current collector.

[0010] In some embodiments, the second electrode segment is provided with a plurality of alternately distributed second straight segments and second bent segments along the winding direction of the electrode assembly, and the second active material layer includes a second straight active material layer disposed in the second straight segment and a second bent active material layer disposed in the second bent segment. The adhesion force between the second bent active material layer and the current collector is greater than the adhesion force between the second straight active layer and the current collector.

[0011] In some embodiments, the side of the first electrode sheet closest to the winding center of the electrode assembly is defined as the inner side, and the side furthest from the winding center is defined as the outer side. In the second bend of the same fold of the electrode assembly, the adhesion force between the second bend active material layer located on the inner side of the second bend and the current collector is greater than the adhesion force between the second bend active material layer located on the outer side and the current collector.

[0012] In some embodiments, the first electrode is a negative electrode and the second electrode is a positive electrode; And / or, the battery cell also includes a positive tab and a negative tab, with the positive tab electrically connected to the second electrode and the negative tab electrically connected to the first electrode.

[0013] An embodiment of the second aspect of the utility model provides an electrochemical device comprising a battery cell according to any of the above claims, and a housing or aluminum-plastic film for encapsulating the battery cell.

[0014] A third aspect of the utility model provides an electronic device including the electrochemical device described above, the electronic device further including a receiving cavity for accommodating the electrochemical device.

[0015] According to the above embodiments, the beneficial effects of this utility model are: This invention proposes a battery cell, including an electrode assembly formed by a single-layer winding of a first electrode, a separator, and a second electrode. The first electrode includes a current collector and an active material layer coated on the current collector. The current collector carries the active material layer and conducts current. The active material layer includes a binder and other components, and is used to store and release lithium ions to provide the energy storage capacity of the electrochemical device. Along the length of the first electrode, the first electrode includes a first electrode segment and a second electrode segment connected in sequence, with the first electrode segment positioned close to the winding center. The active material layer includes a first active material layer and a second active material layer. The first electrode segment includes the first active material layer, and the second electrode segment includes the second active material layer. The adhesion between the first active material layer and the current collector is greater than the adhesion between the second active material layer and the current collector.

[0016] The first electrode segment, located in the innermost circle, has the smallest bending radius and the most severe stress concentration, making it extremely prone to dust shedding. This invention increases the amount of binder only in the first electrode segment, significantly enhancing the adhesion between the active material layer and the current collector. This effectively reduces debris during winding and coating detachment during subsequent cycles, reducing the risk of dust puncturing the ultra-thin diaphragm from the source and avoiding safety hazards such as micro-short circuits, increased self-discharge, and thermal runaway. Because the increased binder is concentrated only in this localized area of ​​the first electrode segment, the outer circle formed by the second electrode segment maintains a low binder ratio. The overall energy density loss is limited to an acceptable range, and its ion / electron transport impedance does not increase significantly. The rate performance and cycle life of the cell are maintained. Therefore, this application can balance the energy density and safety performance of the electrochemical device.

[0017] Furthermore, this invention achieves the effect of increasing the amount of adhesive used through segmented coating, while maintaining low cost.

[0018] In summary, this application can balance the energy density and safety performance of electrochemical devices, and is low in cost, easy to implement, and applicable to actual production.

[0019] Additional aspects and advantages of this 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

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a three-dimensional structural diagram of the battery cell in one embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the first electrode in one embodiment of the present invention, wherein the upper part is a top view of the first electrode and the lower part is a side view of the first electrode. Figure 3 This is a three-dimensional structural diagram of the electrochemical device in one embodiment of the present invention.

[0022] Explanation of icon numbers: 10 battery cells; 20 electrochemical devices; First electrode 100; current collector 110; active material layer 120; first electrode segment 130; second electrode segment 140; bent segment 150; straight segment 160; negative electrode tab 170; Second electrode 200; Positive electrode tab 210.

[0023] 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

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] It should be noted that if the embodiments of this utility model 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.

[0026] Furthermore, if the embodiments of this utility model 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 A and B are simultaneously satisfied. 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 utility model.

[0027] In related technologies, the dust sources of battery cell 10 can be divided into two main categories: external and internal. External dust refers to suspended particles in the environment, equipment wear debris, particles carried by the human body, and fiber debris from packaging materials. Currently, leading companies have reduced the concentration of environmental particles to only a few 0.1μm particles per cubic foot through multiple engineering methods such as cleanroom upgrading, electrostatic dust suppression, and ion air showers. The marginal cost of further improvement increases exponentially. In contrast, the generation mechanism of internal dust is more insidious and difficult to eradicate: during the coating, rolling, slitting, and winding processes of the electrode sheet, microcracks are generated at the interface between the active coating and the current collector 110 due to repeated bending, shearing, and stretching. After the cracks expand, free particles are formed, and the swelling difference during electrolyte wetting further aggravates coating peeling. These internal particles often carry highly active surfaces, making them more likely to react with the electrolyte, forming conductive pathways, leading to a deterioration of the K value (self-discharge rate). Even more challenging is the inherent contradiction between the generation of endogenous dust and the improvement of energy density: in order to increase specific capacity, the industry generally adopts silicon-based or high-nickel electrode materials with higher compaction density and greater brittleness, while reducing the amount of binder. This results in a decrease in coating toughness and a significant increase in the tendency of dust shedding.

[0028] The following is for reference. Figures 1 to 3 This describes the battery cell 10 and the electrochemical device 20 according to embodiments of the present invention. (Refer to...) Figure 1 and Figure 2In some embodiments, the present invention provides a battery cell 10, including a first electrode 100, a second electrode 200, and a separator, wherein the separator is located between the first electrode 100 and the second electrode 200. The first electrode 100, the separator, and the second electrode 200 are sequentially stacked and wound to form an electrode assembly. The first electrode 100 includes a current collector 110 and an active material layer 120 coated on at least one side of the current collector 110. The current collector 110 is used to carry the active material layer 120 and conduct current. The active material layer 120 includes a binder and other components, and is used to store and release lithium ions to provide the energy storage capacity of the electrochemical device 20. The first electrode 100 includes a first electrode segment 130 and a second electrode segment 140 sequentially distributed along the winding direction of the electrode assembly, wherein the first electrode segment 130 is disposed near the winding center. The active material layer 120 includes a first active material layer and a second active material layer. The first electrode segment 130 includes the first active material layer, and the second electrode segment 140 includes the second active material layer. The adhesion between the first active material layer and the current collector 110 is greater than the adhesion between the second active material layer and the current collector 110.

[0029] It should be noted that, assuming the same type of adhesive is used, the bonding force between the active material layer 120 and the current collector 110 mainly depends on the amount of adhesive used. Therefore, the bonding force between the active material layer 120 and the current collector 110 is roughly equivalent to the amount of adhesive used. The bonding force between the first active material layer and the current collector 110 is greater than that between the second active material layer and the current collector 110, which can be understood as the amount of adhesive used between the first active material layer and the current collector 110 being greater than that between the second active material layer and the current collector 110.

[0030] As mentioned above, the first electrode segment 130 is located in the innermost circle, with the smallest bending radius and the most severe stress concentration, making the first electrode sheet 100 extremely prone to dust shedding at this location. This invention increases the amount of adhesive only in the first electrode segment 130, significantly enhancing the adhesion between the active material layer 120 and the current collector 110. This effectively reduces debris during the winding process and coating detachment during subsequent cycles, reducing the risk of dust puncturing the ultra-thin diaphragm from the source and avoiding safety hazards such as micro-short circuits, increased self-discharge, and thermal runaway. Since the increased adhesive is concentrated only in the localized area of ​​the first electrode segment 130, the outer circle formed by the winding of the second electrode segment 140 still maintains a relatively small amount of adhesive. The overall energy density loss is limited to an acceptable range, and its ion / electron transport impedance does not increase significantly. The rate performance and cycle life of the cell 10 are maintained. Therefore, this application can balance the energy density and safety performance of the electrochemical device 20.

[0031] Furthermore, this invention achieves the effect of increasing the amount of adhesive used through segmented coating, while maintaining low cost.

[0032] In summary, this application can balance the energy density and safety performance of the electrochemical device 20, and is low in cost, easy to implement, and applicable to actual production.

[0033] Furthermore, regarding the battery cell 10 of this application, the process only requires segmented adhesive bonding of the first electrode segment 130 at the coating station. No additional equipment or structural components are needed to directly introduce the second electrode segment 140 into existing production lines while maintaining the conventional amount of adhesive. The overall stiffness gradient of the first electrode 100 is smooth, and the winding wrinkles and electrolyte wetting resistance are simultaneously reduced. Thus, this application overcomes multiple bottlenecks related to dust, safety, energy, and process with minimal material increments and process modifications, achieving low-cost, high-yield large-scale manufacturing of the high-energy-density electrochemical device 20.

[0034] In some embodiments, the first electrode 100 is a negative electrode. Specifically, the first electrode 100 includes a current collector 110 and a negative electrode active material layer 120, which is composed of a negative electrode active material, a binder, and other additives. In the first electrode segment 130, the proportion of binder in the negative electrode active material layer 120 is increased.

[0035] In some embodiments, to further improve the reliability of the cell 10, the surface of the current collector 110 can be pretreated, such as by surface roughening, which increases the contact area between the surface of the current collector 110 and the active material layer 120, thereby enhancing the adhesion. For example, the surface of the aluminum foil can be treated by chemical etching to form a micro-uneven structure, which increases the mechanical locking force between the adhesive and the current collector 110, thereby further reducing the risk of the active material layer 120 falling off.

[0036] In some embodiments, different combinations of adhesives are used to optimize performance. For example, in the region of the first pole segment 130, in addition to increasing the proportion of adhesive, two or more different types of adhesives can be introduced in combination. For example, some components provide excellent adhesion properties, while others are used to improve the flowability and smoothness of the slurry, thereby working together to improve the adhesion of the active material layer 120.

[0037] Reference Figure 1 and Figure 2In some embodiments, the adhesion force between the first active material layer and the current collector 110 is F1, and the adhesion force between the second active material layer and the current collector 110 is F2, wherein 1.1 ≤ F1:F2 ≤ 3.0, for example, F1:F2 is 1.1, 1.8, 2.2, 2.6, 3.0. By increasing the amount of adhesive used in the first electrode segment 130, the adhesion force between the current collector 110 and the first active material layer is enhanced, which can effectively suppress the shedding of active material in areas with large bending curvature of the inner ring of the electrode sheet during winding and subsequent processes, thereby avoiding poor K-value caused by powder shedding from the electrode sheet material area and significantly improving the production yield of the battery cell 10. Experiments show that when the ratio of the amount of binder a in the first electrode segment 130 to the amount of binder b in the second electrode segment 140 is a:b < 1.1, the inner negative electrode is still prone to powder shedding. However, when a:b > 3.0, the first electrode segment 130 will have an excessively high proportion of binder, which will cause a decrease in energy density in this area, an increase in the internal resistance of the electrochemical device 20, and affect the charge and discharge efficiency.

[0038] In some embodiments, the specific values ​​of a and b can be adjusted appropriately for specific application scenarios, but the a:b ratio should always be kept within a specified range. For example, if the target market is more sensitive to cost control, a lower value of a, such as 20%, can be selected, while the value of b can be set to 10%, which can both meet technical requirements and effectively reduce costs.

[0039] Reference Figure 1 and Figure 2 In some embodiments, the electrode assembly includes a straight section 160 and bent sections 150 located on both sides of the straight section 160. Along the winding direction of the electrode assembly, the straight section 160 has a straight length L and the length of the first electrode segment 130 is L1, satisfying L1=c*L, where 1.2≤c≤4.5, and the first electrode segment 130 includes at least one first straight section and a first bent section.

[0040] For example, L1 equals 1.2L, L1 equals 3L, and L1 equals 4.5L. Specifically, when L is set to 10 mm, according to the above relationship, L1 can range from 12 to 45 mm. This design takes into account the characteristic of bending stress concentrating in the first electrode segment 130 during winding. By designing a reasonable length for the first electrode segment 130, it ensures that it has sufficient material allowance to disperse stress during bending, thereby reducing the risk of active material shedding. When the coefficient c is less than 1.2, the length of the first electrode segment 130 is too short, resulting in the area with a high proportion of binder failing to cover the inner bend segment 150 with a large curvature of the negative electrode sheet after winding. When the coefficient c is greater than 4.5, the length of the first electrode segment 130 is too large, resulting in an excessively high proportion of the area with a high proportion of binder in the electrode sheet, which not only reduces energy density but also significantly increases the cost of the cell 10.

[0041] Regarding the straight section 160 mentioned above, it is understood that the battery cell 10 itself has a certain degree of curvature. The straight section 160 here is not completely straight, but means a part with a lower curvature. For example, compared with the bent section 150, the curvature of the straight section 160 is significantly lower.

[0042] In some embodiments, a more complex structural design can be introduced in the region of the first pole segment 130, such as adding a layer of reinforcing fiber mesh, which can not only improve mechanical strength but also further disperse stress.

[0043] In some embodiments, a segmented strategy for controlling the binder content is employed. For example, the binder content is highest at the beginning of the first electrode segment 130, and then gradually decreases to the standard value of the second electrode segment 140. This gradient design effectively prevents the active material from detaching while avoiding the impact of excessively high binder content on the overall performance of the electrochemical device 20.

[0044] Reference Figure 1 and Figure 2 In some embodiments, the current collector 110 has a first surface and a second surface opposite each other along the thickness direction, both of which are coated with an active material layer 120. The adhesion between the first active material layer on the first surface and the current collector 110 is greater than the adhesion between the second active material layer on the first surface and the current collector 110; similarly, the adhesion between the first active material layer on the second surface and the current collector 110 is greater than the adhesion between the second active material layer on the second surface and the current collector 110. Specifically, by simultaneously increasing the adhesive ratio on both the first and second surfaces of the current collector 110 located in the first electrode segment 130, a symmetrical reinforcing layer can be formed in the innermost bending area, significantly enhancing the overall bonding force between the active material layer 120 and the foil, avoiding stress imbalance and peeling cracks that may result from unilateral adhesion. This design effectively suppresses double-sided powder shedding even when both sides of the electrode are simultaneously subjected to maximum winding tension, further reducing the risk of dust puncturing the separator, while maintaining balanced capacity on both sides, balancing safety redundancy and energy density.

[0045] Reference Figure 1 and Figure 2In some embodiments, the current collector 110 has a first surface and a second surface opposite each other along the thickness direction, both of which are coated with an active material layer 120. The adhesion between the first active material layer on the first surface and the current collector 110 is greater than the adhesion between the second active material layer on the first surface and the current collector 110; or, the adhesion between the first active material layer on the second surface and the current collector 110 is greater than the adhesion between the second active material layer on the second surface and the current collector 110. Specifically, by locally increasing the adhesive ratio only on the first electrode segment 130 of the first or second surface of the current collector 110, a single-sided reinforcing layer can be formed in the most critical bending area, significantly suppressing dust shedding on that side with minimal adhesive usage. The other side, without adhesive enhancement, maintains the original ratio, resulting in a limited increase in overall electrode stiffness. This makes it easier to adapt to curvature changes during winding and avoids cracking, reducing dust risk without sacrificing energy density. Furthermore, the process is simple, materials are reduced, and costs are further compressed.

[0046] In some embodiments, the current collector 110 has a first surface and a second surface opposite each other along the thickness direction. Both the first and second surfaces are coated with an active material layer 120, and the first active material layer on the first surface and the first active material layer on the second surface are staggered along the winding direction of the electrode assembly. By staggering the first active material layers along the length direction of the first and second surfaces of the current collector 110, the overall anti-powdering capability of the first electrode segment 130 can be maintained while avoiding the superposition of the first active material layers on both sides in the same cross section. This reduces the peak stiffness and bending stress concentration in this area, prevents creases or cracks from appearing on the electrode sheet during winding, and reduces the impact of this area on the thickness of the cell 10 after winding. In addition, the staggered design also reduces the amount of adhesive used, further controlling costs and taking energy density into account, while still covering all high-risk bending sections 150, achieving a balance between safety, performance, and economy.

[0047] Reference Figure 1 and Figure 2In some embodiments, the first electrode segment 130 is configured as the bending segment 150 (i.e., the innermost bending segment 150) that is closest to the winding center along the radial direction of the cell 10. In the cylindrical or flat core formed by winding the first electrode 100, the diaphragm, and the second electrode 200 layer by layer, the innermost bending segment 150 has the smallest radius of curvature (typically only equivalent to the radius of the winding needle). The material completes a 180° reverse bend within a very short unfolding length, generating the maximum alternating tensile and compressive stress. At the same time, the electrode at this location is always under the most severe constraint environment during subsequent hot pressing, liquid injection, formation, and cyclic expansion. The interface between the coating and the current collector 110 is most prone to microcracks that propagate outward, becoming the primary source of powder and debris. If the high-adhesion binder region is misplaced in the second or outermost bend 150, the radius of curvature at these locations has significantly increased, and the mechanical stress decreases exponentially. The anti-powdering benefit from the high-adhesion binder rapidly diminishes, while the side effects of excessive binder, such as decreased energy density, thickened electrode, and hindered electrolyte wetting, still occur, resulting in an uneconomical situation of low returns and high costs. Therefore, strictly anchoring the first electrode segment 130 in the innermost bend 150 ensures that the high-adhesion binder is precisely applied at the highest-risk failure point, maximizing safety margin by minimizing material increment. Simultaneously, it allows the outer bend 150 to retain the conventional formulation, maintaining overall energy density and process window, achieving compatibility between safety, performance, and cost.

[0048] In some embodiments, an additional protective layer is added to the first electrode segment 130. For example, a thin ceramic coating is applied over the active material layer 120, which not only increases the physical barrier but also further disperses bending stress and reduces the possibility of active material shedding. This composite structure can significantly improve the stability of key areas without affecting the overall performance of the electrochemical device 20, making it suitable for manufacturing lithium-ion electrochemical devices 20 in applications with high bending curvature.

[0049] In some embodiments, the first electrode 100 includes a plurality of first electrode segments 130 and a plurality of second electrode segments 140. Along the winding direction, the first electrode segments 130 include alternating first bent segments 150 and first straight segments 160, and the second electrode segments 140 include a plurality of alternating second bent segments and second straight segments. The second active material layer includes a second straight active material layer 120 disposed in the second straight segment and a second bent active material layer 120 disposed in the second bent segment. The adhesion between the second bent active material layer 120 and the current collector 110 is greater than the adhesion between the second straight active material layer 120 and the current collector 110. In the second electrode segment 140 located on the outer winding ring, the amount of adhesive used in the second bent segment is increased, thereby ensuring that the second bent segment is less prone to wrinkles or cracks during the winding process, further improving the manufacturing yield, and achieving a balanced optimization of safety, energy density, and cost. Meanwhile, keeping the amount of adhesive used in the second straight section at the normal setting can avoid the problems of decreased energy density, thickened electrode, and increased electrolyte wetting resistance caused by increasing the amount of adhesive used in the second straight section.

[0050] In some embodiments, the side of the first electrode 100 closest to the winding center of the electrode assembly is defined as the inner side, and the side furthest from the winding center is defined as the outer side. In the second bend of the electrode assembly within the same fold, the adhesion between the second bent active material layer 120 on the inner side of the second bend and the current collector 110 is greater than the adhesion between the second bent active material layer 120 on the outer side and the current collector 110. Specifically, compared to the outer side of the second bend, the inner side has a greater curvature. Therefore, increasing the amount of adhesive between the second bent active material layer 120 on the inner side and the current collector 110 can prevent wrinkles or cracks caused by excessive winding curvature on the inner side, which could lead to powder shedding and other problems. Simultaneously, it can ensure that the amount of adhesive on the outer side is smaller, avoiding the problems of decreased energy density, electrode thickness, and increased electrolyte wetting resistance caused by increasing the amount of adhesive.

[0051] Reference Figures 1 to 3The second aspect of this application provides an electrochemical device 20, wherein a first electrode 100 is a negative electrode and a second electrode 200 is a positive electrode; and / or, the battery cell 10 further includes a positive electrode tab 210 and a negative electrode tab 170, wherein the positive electrode tab 210 is electrically connected to the second electrode 200 and the negative electrode tab 170 is electrically connected to the first electrode 100. Exemplarily, the electrochemical device 20 may specifically be an energy storage device such as a battery. By increasing the proportion of binder only in the first electrode segment 130 of the negative electrode, the pain points of the negative electrode graphite (or silicon-carbon) layer being most prone to powdering, having the sharpest fragments, and exhibiting high conductivity at the minimum radius of curvature are specifically addressed. Specifically, high binder content significantly enhances the adhesion between graphite particles and copper foil, inhibits coating cracking and powdering caused by volume expansion and contraction cycles, and prevents hard graphite fragments from piercing the ultra-thin separator to form micro-short circuits. Meanwhile, the positive electrode maintains the original low binder ratio, which not only prevents the capacity from being reduced due to excessive binder blocking lithium-ion diffusion, but also maintains the positive electrode energy density and rate performance. This achieves a synergy between the negative electrode's anti-powdering safety redundancy and the positive electrode's capacity advantage, ensuring that the whole battery achieves the optimal balance between high energy density, high cycle life and low cost.

[0052] The electrochemical device 20 of this application locally increases the binder content in the first electrode segment 130 of the negative electrode, precisely covering the bending area with the smallest radius of curvature, forming a point-like reinforcement. This design significantly suppresses the shedding of active material from the inner ring of the electrode due to high stress without changing the overall electrode formulation or adding additional structural components, reducing dust at the source, preventing puncture of the ultra-thin separator, and lowering the probability of micro-short circuits and thermal runaway. Simultaneously, the outer ring maintains a low binder content, compressing energy density loss to an acceptable range, with almost no impact on rate performance and cycle life, achieving a balance between safety, energy density, and cost.

[0053] Furthermore, localized adhesion enhancement can be achieved through segmented coating, which is a simple process that requires no additional equipment; staggered or single-sided adhesion enhancement can further reduce the amount of high-viscosity material used and lower material costs; the tabs are welded to the straight section of 160° to avoid the thickened area, reducing the risk of poor soldering, and the overall manufacturing yield and long-term reliability are improved simultaneously, enabling large-scale, low-cost mass production.

[0054] An embodiment of the third aspect of this application provides an electronic device including the electrochemical device 20 described above and a receiving cavity for accommodating the electrochemical device 20.

[0055] The above are merely preferred embodiments of this utility model and do not limit the patent scope of this utility model. Any equivalent structural transformations made based on the inventive concept of this utility model and the contents of this utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this utility model.

Claims

1. A battery cell, comprising a first electrode, a second electrode, and a separator, wherein the separator is located between the first electrode and the second electrode, and the first electrode, the separator, and the second electrode are sequentially stacked and wound to form an electrode assembly, characterized in that, The first electrode includes a current collector and an active material layer coated on at least one side of the current collector; The first electrode includes a first electrode segment and a second electrode segment distributed sequentially along the winding direction of the electrode assembly, wherein the first electrode segment is disposed close to the winding center; The active material layer includes a first active material layer and a second active material layer. The first electrode segment includes the first active material layer, and the second electrode segment includes the second active material layer. The adhesion between the first active material layer and the current collector is greater than the adhesion between the second active material layer and the current collector.

2. The battery cell according to claim 1, characterized in that, The bonding force between the first active material layer and the current collector is F1, and the bonding force between the second active material layer and the current collector is F2, wherein 1.1≤F1:F2≤3.

0.

3. The battery cell according to claim 1, characterized in that, The electrode assembly includes a straight section and bent sections located on both sides of the straight section. Along the winding direction of the electrode assembly, the straight section has a straight length L and the length of the first electrode segment is L1, and L1 = c * L, where 1.2 ≤ c ≤ 4.5, and the first electrode segment includes at least one first straight section and one first bent section.

4. The battery cell according to claim 1, characterized in that, The current collector has a first surface and a second surface opposite each other along the thickness direction. Both the first surface and the second surface are coated with the active material layer, and the first active material layer on the first surface and the first active material layer on the second surface are offset from each other along the winding direction of the electrode assembly.

5. The battery cell according to claim 1, characterized in that, The current collector has a first surface and a second surface opposite each other along its thickness direction, and both the first surface and the second surface are coated with the active material layer; wherein... The adhesion force between the first active material layer on the first surface and the current collector is greater than the adhesion force between the second active material layer on the first surface and the current collector. And / or, the adhesion between the first active material layer on the second surface and the current collector is greater than the adhesion between the second active material layer on the second surface and the current collector.

6. The battery cell according to claim 1, characterized in that, The second electrode segment has a plurality of alternately distributed second straight segments and second bent segments along the winding direction of the electrode assembly. The second active material layer includes a second straight active material layer disposed in the second straight segment and a second bent active material layer disposed in the second bent segment. The adhesion force between the second bent active material layer and the current collector is greater than the adhesion force between the second straight active layer and the current collector.

7. The battery cell according to claim 6, characterized in that, The side of the first electrode sheet closest to the winding center of the electrode assembly is defined as the inner side, and the side furthest from the winding center is defined as the outer side. In the second bending segment of the same fold of the electrode assembly, the adhesion force between the second bending active material layer located on the inner side of the second bending segment and the current collector is greater than the adhesion force between the second bending active material layer located on the outer side and the current collector.

8. The battery cell according to claim 1, characterized in that, The first electrode is a negative electrode, and the second electrode is a positive electrode; And / or, the battery cell further includes a positive tab and a negative tab, the positive tab being electrically connected to the second electrode and the negative tab being electrically connected to the first electrode.

9. An electrochemical device, characterized in that, The electrochemical device includes the battery cell according to any one of claims 1 to 8, and further includes a housing or aluminum-plastic film for encapsulating the battery cell.

10. An electronic device, characterized in that, The electronic device, including the electrochemical device of claim 9, further includes a receiving cavity for accommodating the electrochemical device.

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