Electrode tab, battery cell, and secondary battery

Abstract

The application relates to an electrode tab, an electric core and a secondary battery. A ductile material pattern is constructed in a current collector empty foil area, which is composed of a plurality of ductile material strips and space gaps. The ductile material pattern can be further provided with a gradient buffer. The width / thickness of the ductile material strip is designed to be gradually reduced along the direction away from the electrode material layer, a three-dimensional stress buffer network is formed, the current collector double-sided ductile material pattern is distributed in mirror symmetry, an edge connection or a through-hole connection structure is matched, a reinforcing frame is formed at the edge of the empty foil area, the width of the space gap is 40%-75% of the width of the ductile material strip, the buffer space is balanced, the thickness of the ductile material strip is smaller than that of the electrode material layer, the active material layer is prevented from being crushed, and the adjacent ductile material strips are partially connected to form a continuous buffer network. The technical scheme can improve the tensile strength of the current collector, reduce the breakage rate of the ultra-thin copper foil, and reduce the tension fluctuation amplitude of high-speed rolling.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrode sheet, a battery cell, and a secondary battery. Background Technology

[0002] In the electrode manufacturing process of lithium-ion or sodium-ion batteries, strip breakage during rolling has become a key bottleneck restricting the improvement of production line yield. According to industry statistics, the resulting high material loss rate directly drives up the production cost of power batteries. This problem is particularly prominent in the preparation of ultra-thin electrodes. As the thickness of the copper foil substrate decreases, the risk of strip breakage increases exponentially, affecting the large-scale mass production process of high-energy-density batteries.

[0003] Existing technical analysis indicates that the breakage phenomenon mainly stems from three core contradictions: First, the lack of active material coating support in the non-material area (blank foil area) leads to stress concentration zones during the rolling process, causing the substrate to wrinkle or break at the interface between the material and non-material areas; Second, the micron-level edge cracks generated by the current collector slitting process will rapidly expand under high pressure, forming a fracture source; Third, the thickness difference between the material and non-material areas caused by the traditional zebra coating process leads to dynamic tension mismatch during the rolling process.

[0004] Current industry-standard reinforcement methods, such as edge coating and tape application, can improve edge tensile strength, but they have limitations: First, localized reinforcement measures do not change the inherent uneven stress distribution within the substrate, and the risk of tape breakage still exists in the entire non-material area; second, incompatibility differences between the adhesive layer and electrode materials lead to new interface defects, and abrupt thickness changes further affect the accuracy of subsequent winding processes. Therefore, developing a full-width, irregularly shaped coating technology that forms a composite coating with ductile buffering function in the non-material area is a solution to the problem of tape breakage during roll forming. This technology requires high interfacial bonding strength with the substrate, high elongation at break of the buffer layer, and precise coating control to achieve uniform stress distribution reconstruction. Utility Model Content

[0005] The purpose of this application is to form a buffer layer in the empty foil area to uniformly disperse the rolling stress, thereby solving the problem of strip breakage caused by stress concentration, edge damage, and abrupt thickness changes in the prior art, improving the electrode manufacturing yield, and ensuring compatibility with ultra-thin current collector processes. This purpose is achieved through the following technical solution: the electrode sheet includes a current collector, and the current collector includes a coating area and an empty foil area; The electrode material is completely coated on the coating area to form an electrode material layer, and the empty foil area includes an extended material pattern, which includes a plurality of extended material strips extending from one side of the empty foil area to the other side and the space gaps between the extended material strips; The current collector includes empty foil areas on both its front and back sides. The extended material patterns on the front and back sides are mirror-symmetrical with respect to the current collector, and the extended material strips in the extended material patterns have the same thickness.

[0006] In one embodiment, the width of the extended material strip gradually decreases in the direction away from the electrode material layer.

[0007] In one embodiment, the thickness of the extended material strip gradually decreases in the direction away from the electrode material layer.

[0008] In one embodiment, the extended material strips on the front and back sides of the current collector are connected at the edges or connected through through holes in the current collector.

[0009] In one embodiment, the extended material patterns on both sides of the electrode material region on the coated area are symmetrical.

[0010] In one embodiment, the width of the gap is 40%-75% of the width of the extended material strip.

[0011] In one embodiment, the thickness of the extended material strip is less than the thickness of the electrode material layer.

[0012] In one embodiment, an extended material strip is interconnected with an adjacent extended material strip.

[0013] This application also provides a battery cell that includes the aforementioned electrode plates.

[0014] This application also provides a secondary battery comprising the aforementioned battery cell.

[0015] Compared with the prior art, this application has the following beneficial effects: This application effectively eliminates the abrupt thickness changes in traditional coatings by setting extended material patterns in the empty foil area, thereby improving the uniformity of roll stress distribution and solving the problem of stress concentration in non-material areas. The mirror-symmetrically distributed extended material strips form an integral buffer structure with the current collector. The gradually decreasing width / thickness design of the extended material strips away from the electrode material layer creates a stress gradient transition zone. Combined with the edge connection or through-hole connection structure of the extended material strips on both sides, the tensile strength of the current collector edge is improved, effectively suppressing the propagation of microcracks.

[0016] The design of the extended material layer being thinner than the electrode material layer ensures the overall thickness consistency of the electrode sheet, avoiding interference with subsequent winding processes. The connection structure between adjacent extended material strips enhances the structural integrity of the empty foil area, reducing the breakage rate of the ultra-thin copper foil. The symmetrically distributed extended patterns on both sides of the electrode material layer, combined with the smooth transition between the extended material strips and the electrode material layer, effectively balance the dynamic tension fluctuations during the rolling process, making it suitable for high-speed rolling processes. The design of the gaps between the extended material strips provides a buffer function while retaining sufficient ion transport channels, enabling secondary batteries using this electrode sheet to maintain energy density while improving cycle life, with a high capacity retention rate after 500 cycles. Attached Figure Description

[0017] Figure 1 This is a top view of the electrode sheet according to an embodiment of this application; Figure 2 This is a schematic cross-sectional view of an electrode sheet according to an embodiment of this application; Figure 3 This is a top view of the electrode sheet according to another embodiment of this application; Figure 4 This is a schematic cross-sectional view of the electrode sheet according to another embodiment of this application.

[0018] Explanation of reference numerals in the attached figures: 100, electrode sheet; 110, current collector; 120, coating area; 130, empty foil area; 140, electrode material layer; 150, extended material pattern; 151, extended material strip; 152, gap. Detailed Implementation

[0019] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0020] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0021] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] In the field of battery manufacturing, electrode sheets are core components, and their structural design and process precision directly affect battery energy density, cycle life, and production yield. As the industry rapidly evolves towards ultra-thin and high-energy-density materials, the limitations of traditional electrode sheet manufacturing processes are becoming increasingly apparent. Among these, the problem of strip breakage during rolling has become a key bottleneck restricting production line efficiency. This problem stems from structural defects in the empty foil area (non-material area). The lack of active material coating causes rolling stress to concentrate at the interface between the material and non-material areas, leading to substrate wrinkling or breakage. Simultaneously, microcracks generated by current collector slitting expand under high-pressure rolling, and the dynamic tension mismatch caused by thickness differences due to the coating process further increases the strip breakage rate. Although existing technologies attempt to strengthen the structure through edge coating or tape application, local reinforcement measures cannot solve the fundamental problem of uneven stress distribution within the substrate and are prone to introducing defects such as abrupt thickness changes and poor material compatibility. Based on this, this application proposes an irregular coating technology solution, which constructs a special patterned structure with extensible buffering function in the empty foil area. Please refer to [link to relevant documentation]. Figures 1 to 4 The electrode sheet 100 of this application includes a current collector 110, which includes a coating area 120 and an empty foil area 130. The coating area 120 is fully coated with electrode material to form an electrode material layer 140. The empty foil area 130 includes an extended material pattern 150. The extended material pattern 150 includes a plurality of extended material strips 151 extending from one side of the empty foil area 130 to the other side and space gaps 152 between the extended material strips 151. The empty foil area 130 is included on both the front and back sides of the current collector 110. The extended material pattern 150 on the front and back sides is mirror-symmetrical with respect to the current collector 110. The extended material strips 151 in the extended material pattern 150 have the same thickness.

[0023] The electrode sheet 100 proposed in this application has a buffer layer composed of multiple extended material strips 151 and space gaps 152 in the empty foil area 130. Compared with traditional reinforcement schemes, the technical solution of this application improves the uniformity of rolling stress distribution and eliminates the problem of stress concentration in non-material areas. The extended material strips 151 on both sides of the current collector 110 are distributed in a mirror symmetry, with the thickness difference controlled within ±1μm. By forming an overall buffer system, the tensile strength of the edge of the current collector 110 is improved, which can effectively suppress the propagation of microcracks. The width / thickness of the extended material strips 151 decreases in the direction away from the electrode material layer 140, which reduces the breakage rate of the ultra-thin copper foil. Combined with the smooth transition between the extended material strips 151 and the electrode material layer 140, it effectively balances the dynamic tension fluctuations during the rolling process. It is suitable for high-speed rolling processes, and the tension fluctuation amplitude can be significantly reduced. While solving the problem of rolling breakage, it also achieves compatibility with the ultra-thin current collector 110 process.

[0024] The width of the extended material strip 151 gradually decreases in the direction away from the electrode material layer 140. The width of the extended material strip 151 exhibits a linear / non-linear decreasing design in the direction away from the electrode material layer 140. Specifically, along the transverse direction of the current collector 110 (perpendicular to the rolling direction), the width of the extended material strip 151 at the starting end (adjacent to the electrode material layer 140) is W1, and the width at the ending end (away from the electrode material layer 140) is W2, satisfying W2 = (0.4~0.75)W1, and the width change rate (ΔW / ΔL) ≥ 5 μm / mm. This gradient change is achieved through a coating mold, and combined with the mirror-symmetric structure of the front and back extended material strips 151, forms a three-dimensional stress buffer network. The decreasing width design causes the rolling stress to exhibit a gradient distribution along the longitudinal direction (rolling direction) of the extended material strip 151. The wider structure at the starting end can withstand the initial high pressure stress (≥80MPa), and the narrower design at the ending end reduces stress concentration at the edge of the empty foil area 130.

[0025] The narrowing design at the termination end, combined with the edge connection or through-hole connection structure of the front and back extended material strips 151, forms a reinforced frame at the edge of the empty foil area 130, increasing the tensile strength of the current collector 110 edge and effectively suppressing the propagation of microcracks during slitting. Tests show that the risk of edge breakage of ultra-thin copper foil (≤6μm) is reduced by more than 60%. The gradient width variation and the decreasing thickness design of the extended material strip 151 work synergistically to form a dynamic tension buffer during rolling. This structure significantly reduces the tension fluctuation amplitude, ensuring dimensional stability under high-speed production. This structure is compatible with existing irregular-shaped coating equipment, and the gradient width can be controlled by adjusting the slit size of the coating die.

[0026] Furthermore, the thickness of the extended material strip 151 is designed to decrease linearly / non-linearly in the direction away from the electrode material layer 140. Specifically, along the transverse direction of the current collector 110 (perpendicular to the rolling direction), the thickness of the extended material strip 151 at the starting end (adjacent to the electrode material layer 140) is T1, and the thickness at the ending end (away from the electrode material layer 140) is T2, satisfying T2 = (0.5~0.9)T1. This thickness gradient is achieved through thickness control coating technology. An adjustable slit size coating head is used, and the coating pressure and speed are adjusted in real time to achieve continuous thickness reduction. A laser thickness gauge is integrated to provide feedback control of coating parameters. Combined with rheological simulation and rolling process parameters, a thickness-stress mapping model is established to guide the gradient design. The thickness reduction design creates a gradient distribution of rolling stress along the longitudinal direction of the extended material strip 151. The thicker structure at the beginning can withstand the initial high pressure stress, while the narrower design at the end reduces stress concentration at the edge of the empty foil area 130. This structure reduces the stress concentration coefficient compared to traditional structures and improves the uniformity of stress distribution. The thickness gradient change and the width reduction design of the extended material strip 151 work together to form a dynamic tension buffer during the rolling process, ensuring dimensional stability under high-speed production.

[0027] The front and back extended material strips 151 achieve physical contact at the edge of the current collector 110 through a coating process, forming a continuous closed frame structure. Specific implementation methods include: adjusting the slit angle of the coating mold to allow the front and back materials to naturally converge at the edge; employing double-sided synchronous coating technology to control edge alignment accuracy; or setting a laser-drilled array on the current collector 110, allowing the front and back extended material strips 151 to interpenetrate through the through holes, forming a three-dimensional network. This through-hole connection structure forms a three-dimensional stress transmission network, dispersing and extending the rolling stress from a single plane to a three-dimensional space. During high-speed rolling, the front and back connection structure can further effectively suppress the warping deformation of the current collector 110.

[0028] Furthermore, the extended material patterns 150 on both sides of the electrode material region on the coating area 120 are symmetrical.

[0029] The width of the space gap 152 is 40%-75% of the width of the extended material strip 151. While providing sufficient buffer space to disperse the rolling stress, it exposes the current collector 110 of the empty foil area 130, so that the rolling stress presents a gradient distribution in the empty foil area 130, avoiding local stress concentration.

[0030] The thickness of the extended material strip 151 is less than the thickness of the electrode material layer 140. The design that the thickness of the extended material strip 151 is less than that of the electrode material layer 140 reduces the pressure on the active material layer during the rolling process and avoids the electrode material layer 140 from being crushed due to the excessive thickness of the buffer layer. The thickness difference design makes the rolling stress form a gradient transition at the junction of the extended material strip 151 and the electrode material layer 140, avoiding sudden stress changes.

[0031] In a further embodiment, an extended material strip 151 is interconnected with an adjacent extended material strip 151. The interconnection of adjacent extended material strips 151 forms a continuous buffer network, enhancing the tear resistance of the empty foil area 130, while dispersing stress during rolling and avoiding localized stress concentration. Specifically, a partial connection design can be adopted, with the width of the connection area being 20%-50% of the width of the extended material strip 151, ensuring structural strength while maintaining sufficient clearance space.

[0032] This application also provides a battery cell that includes the aforementioned electrode plates 100.

[0033] This application also provides a secondary battery comprising the aforementioned battery cell.

[0034] As mentioned above, this application proposes a solution based on irregular coating technology to address the problem of strip breakage during the rolling process in electrode manufacturing. The core of this solution lies in constructing an extended material pattern with gradient buffering function in the current collector empty foil area. This pattern consists of multiple extended material strips and spatial gaps. Through the synergistic optimization of the structure, stress dispersion, edge strengthening, and process adaptation are achieved.

[0035] The width / thickness of the extended material strip decreases along the direction away from the electrode material layer, forming a three-dimensional stress buffer network. The current collector has a mirror-symmetrical pattern of extended material on both sides, which, together with the edge connection or through-hole connection structure, forms a reinforcing framework at the edge of the empty foil area, improving the tensile strength of the current collector and reducing the risk of edge breakage. The gradient structure and connection design work together to reduce the tension fluctuation amplitude during high-speed rolling, thereby improving the overall efficiency of the equipment.

[0036] The above is only one specific implementation of this application, and any other improvements made based on the concept of this application shall be considered within the scope of protection of this application.

Claims

1. An electrode sheet, characterized in that, The current collector includes a coating area and an empty foil area. The electrode material is completely coated on the coating area to form an electrode material layer, and the empty foil area includes an extended material pattern, which includes a plurality of extended material strips extending from one side of the empty foil area to the other side and the space gaps between the extended material strips; The current collector includes empty foil areas on both its front and back sides. The extended material patterns on the front and back sides are mirror-symmetrical with respect to the current collector, and the extended material strips in the extended material patterns have the same thickness.

2. The electrode sheet according to claim 1, characterized in that, The width of the extended material strip gradually decreases in the direction away from the electrode material layer.

3. The electrode sheet according to claim 2, characterized in that, The thickness of the extended material strip gradually decreases in the direction away from the electrode material layer.

4. The electrode sheet according to claim 1, characterized in that, The extended material strips on the front and back of the current collector are connected at the edges or connected through through holes in the current collector.

5. The electrode sheet according to claim 1, characterized in that, The extended material patterns on both sides of the electrode material region on the coated area are symmetrical.

6. The electrode sheet according to claim 5, characterized in that, The width of the gap is 40%-75% of the width of the extended material strip.

7. The electrode sheet according to claim 1, characterized in that, The thickness of the extended material strip is less than the thickness of the electrode material layer.

8. The electrode sheet according to claim 1, characterized in that, An extended material strip is connected to an adjacent extended material strip.

9. A battery cell, characterized in that, Includes the electrode sheet as described in any one of claims 1-8.

10. A secondary battery, characterized in that, Including the battery cell as described in claim 9.

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