Cylindrical battery and bare cell assembly thereof

Abstract

The utility model provides a kind of cylindrical battery and its bare cell assembly, bare cell assembly includes: positive pole piece, negative pole piece and the diaphragm being arranged between the positive pole piece and the negative pole piece, wherein, the side close to bare cell positive pole lug is first side, and the other side is second side;Along first direction, the first side of the diaphragm has diaphragm extension area beyond the negative pole piece;The insulating tape is at least covered in the diaphragm extension area towards the negative pole piece one side.The utility model significantly improves the structural stability and the short-circuit resistance of cylindrical battery under shoulder edge extrusion, and can prevent diaphragm from puncturing or wrinkling due to lack of negative support during winding and external extrusion, avoid positive and bare negative contact to cause internal short circuit.

Description

Technical Field

[0001] This utility model belongs to the field of battery technology, specifically relating to a cylindrical battery and its bare cell assembly. Background Technology

[0002] As the energy density of cylindrical batteries increases, the safety issue of the shoulder edge facing the positive electrode post of the cylindrical battery cracking under high pressure has become increasingly prominent. Research has found that the main reason is that the existing cylindrical batteries have a serious failure rate in the extrusion test due to the defective separator design, and there is also a risk of internal short circuit. Utility Model Content

[0003] In view of the shortcomings of the prior art, the purpose of this utility model is to provide a cylindrical battery and its bare cell assembly to solve the problem that the existing battery has a serious insufficient extrusion pass rate due to the defect of the separator design, and also has the risk of internal short circuit.

[0004] To achieve the above and other related objectives, this utility model proposes a bare cell assembly for cylindrical batteries, comprising: a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, wherein the side closer to the positive electrode tab of the bare cell is the first side, and the other side is the second side.

[0005] Along the first direction, the first side of the diaphragm has a diaphragm epitaxial region that extends beyond the negative electrode sheet;

[0006] The insulating tape covers at least the side of the diaphragm epitaxial region facing the negative electrode sheet.

[0007] In one embodiment of this utility model, the insulating tape has a puncture resistance greater than 100 g / µm, an elongation at break greater than 15%, a peel strength greater than 1 N / cm, and a resistivity greater than 5 × 10⁻⁶. 2 Ω·cm.

[0008] In one embodiment of the present invention, the insulating tape extends from the edge of the first side of the diaphragm to at most the edge of the first side of the negative electrode sheet in the opposite direction to the first direction.

[0009] In one embodiment of the present invention, along the first direction, the width W of the diaphragm satisfies: 0.5mm≤W≤1.05mm.

[0010] In one embodiment of this utility model, the thickness H of the insulating tape satisfies: 10μm≤H≤30μm.

[0011] In one embodiment of this utility model, the insulating tape is made of one of the following materials: polyimide, polyester film, polypropylene, silicone rubber, and fiberglass cloth.

[0012] In one embodiment of the present invention, the insulating tape also covers the epitaxial region of the diaphragm on the side of the diaphragm facing the positive electrode sheet.

[0013] In one embodiment of the present invention, the side of the diaphragm facing the positive electrode is further covered with a first ceramic layer.

[0014] In one embodiment of the present invention, the second surface is further covered with a second ceramic layer, which extends at least from the edge of the second side of the insulating tape to the edge of the first side of the positive electrode sheet in the opposite direction to the first direction.

[0015] In one embodiment of the present invention, the second surface is further covered with a third ceramic layer, and a thinned area is provided on the second side of the negative electrode sheet, and the third ceramic layer at least covers the thinned area.

[0016] In one embodiment of this utility model, the thickness of the third ceramic layer satisfies 2μm≤H2≤6μm.

[0017] The present invention also proposes a battery comprising a bare cell assembly for a cylindrical battery as described in any of the above embodiments.

[0018] This invention significantly improves the safety performance and interface stability of cylindrical batteries through innovative design of the separator in the bare cell structure, and has the following beneficial effects:

[0019] By attaching insulating tape to the epitaxial region of the separator on its non-ceramic surface, the structural stability and short-circuit withstand capability of the cylindrical battery under shoulder edge compression were significantly improved. Experiments show that the pass rate of the compression test increases significantly with the increase of tape width, and the safety performance is greatly improved compared to the design without tape.

[0020] This insulating tape effectively enhances the mechanical strength of the diaphragm's outer epitaxial region, preventing punctures or wrinkles during winding and external extrusion due to lack of negative electrode support, and avoiding internal short circuits caused by contact between the positive and exposed negative electrodes. By rationally controlling the tape's width and thickness, it ensures protective effectiveness without covering the negative electrode's active area, thus not affecting electrolyte wetting and ion transport, balancing safety and electrochemical performance.

[0021] Multiple ceramic coatings are applied to the second side of the diaphragm to form a synergistic reinforcement structure. Applying a second ceramic layer to the side where the insulating tape is applied can further enhance the support and prevent the diaphragm from being punctured during the extrusion process, which could lead to a short circuit between the positive and negative electrodes. Applying a third ceramic layer to the corresponding position in the thinned area of ​​the negative electrode can compensate for the thickness difference and improve the interface contact. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0023] Figure 1 This is a front view of the bare battery cell assembly after it has been unfolded in one embodiment of the present invention.

[0024] Figure 2 This is a side view of the separator in a bare cell assembly according to one embodiment of the present invention.

[0025] Figure 3 This is a side view of the separator in a bare cell assembly according to another embodiment of the present invention.

[0026] Label Explanation:

[0027] 10. Positive electrode sheet; 20. Negative electrode sheet; 30. Separator; 31. First side; 32. Second side; 33. First ceramic layer; 34. Second ceramic layer; 35. Third ceramic layer; 40. Insulating tape. Detailed Implementation

[0028] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0029] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0030] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the present invention.

[0031] With the continuous pursuit of longer driving range and higher power performance in electric vehicles and energy storage systems, the energy density and single-cell capacity of cylindrical lithium-ion batteries are constantly improving. However, high energy density also brings higher safety risks, especially in scenarios such as external compression and collisions, where internal short circuits can easily occur inside the battery, leading to thermal runaway, fire, or even explosion. To assess battery structural safety, the industry widely adopts shoulder edge compression testing, requiring the battery to produce no smoke, fire, or explosion after the test. However, current mainstream cylindrical batteries perform poorly in this test, with an actual pass rate generally below 50%, and approximately 20% of the samples exhibiting internal short circuits after compression, exposing serious structural safety hazards. Disassembly analysis revealed that internal short circuits mainly occur in the shoulder area of ​​the cell winding structure on the side facing the positive electrode post of the cylindrical battery. Specifically, the problems manifest in two ways: First, in the area where the separator extends beyond the negative electrode membrane, the lack of support makes it susceptible to punctures from positive electrode burrs or current collector edges. Second, in the same area, uneven stress causes wrinkles in the separator, preventing it from completely covering the negative electrode and creating a core deformation zone, resulting in direct contact between the positive and negative electrodes. The root cause of these problems lies in the significant shortcomings of existing separators in terms of mechanical strength, puncture resistance, and ductility, especially in the high-stress area where the separator extends beyond the negative electrode membrane, becoming a weak point. Therefore, a novel separator structure or bare cell design is urgently needed to effectively enhance the mechanical stability and insulation reliability of the shoulder area, meeting the stringent intrinsic safety requirements of high-energy-density batteries.

[0032] Please see Figure 1 and Figure 2 As shown, this utility model proposes a cylindrical battery and its bare cell assembly to solve the problem of insufficient extrusion throughput and internal short circuit risk in existing batteries due to separator design defects. The bare cell assembly includes a positive electrode 10, a negative electrode 20, and a separator 30 disposed between the two. In the cell structure, the side closer to the positive electrode tab of the bare cell is defined as the first side (i.e., the side closer to the positive electrode post of the cylindrical battery), and the other side is defined as the second side. The direction from the second side to the first side is defined as the first direction X. Along the first direction X, the separator 30 has a region extending beyond the edge of the negative electrode 20 on the first side, called the separator area-overhang (SA-OH). The separator 30 has a first surface 31 and a second surface 32. The first surface 31 faces the positive electrode 10, and the second surface 32 faces the negative electrode 20. In the separator area, at least the second surface 32 of the separator 30 is covered with an insulating tape 40. The insulating tape 40 is applied only to the outer region of the diaphragm on the first side, without covering the positive electrode 10 and the negative electrode 20, so as to avoid affecting the electrolyte wetting and ion transport.

[0033] Understandably, by attaching insulating tape 40 to the epitaxial region of the second side 32 of the separator 30, the mechanical support capability is enhanced. The insulating tape 40 provides additional structural strength to the epitaxial region of the separator, which originally had no negative electrode support, effectively resisting lateral stress during external compression or collision, preventing the separator 20 from wrinkling or collapsing due to uneven stress, thereby avoiding short circuits caused by negative electrode exposure; at the same time, it also improves puncture resistance. During battery assembly or use, there may be tiny burrs or current collector folds at the edges of the electrode sheets. Traditional separators rely solely on the base film to resist puncture in the epitaxial region, while in this embodiment, the insulating tape 30 acts as an additional barrier, significantly improving the overall puncture resistance of this area, blocking the physical damage path of the positive electrode to the separator; and improving width direction stability. The insulating tape 40 enhances the dimensional stability of the separator 30 during the winding process, reduces offset or twisting caused by uneven tension, and improves the overall alignment accuracy of the cell.

[0034] Please see Figure 1 and Figure 2 As shown, in this embodiment, in the opposite direction to the first direction X, the insulating tape 40 extends from the edge of the first side of the separator 30 to at most the edge of the first side of the negative electrode 20, that is, the end of the insulating tape 40 does not exceed the end position of the negative electrode 20 on the first side. This design ensures that the insulating tape 40 only covers the outer epitaxial region of the separator and does not extend to the active material coating area of ​​the negative electrode 20. By controlling the second side edge of the insulating tape 40 to be outside the first side edge of the negative electrode 20, it avoids contact with the negative electrode active material, which can ensure smooth ion transport. If the insulating tape 40 covers the negative electrode coating area, it may hinder the wetting of the electrolyte at the end of the electrode, causing local lithium ion transport to be blocked, increasing polarization, and affecting the battery rate performance and cycle life.

[0035] Please see Figure 1 and Figure 2 As shown, in this embodiment, the width of the insulating tape 40 along the first direction is W, specifically the total width from the first side edge to the second side edge. In this embodiment, the width W satisfies: 0.5mm ≤ W ≤ 1.05mm. When the diaphragm width W is less than 0.5mm, its coverage margin in the axial direction is insufficient, making it difficult to form an effective coverage area, failing to provide sufficient support strength for the diaphragm's epitaxial region, and preventing offset or twisting due to uneven tension during winding. When the insulating tape 40 is greater than 1.05mm, although mechanical coverage safety is improved, it significantly increases the volume ratio of inactive materials inside the cell, leading to a decrease in the battery's energy density. Furthermore, the excessive width of the insulating tape 40 may cause it to cover part of the active material during adhesion, affecting the passage of lithium ions between the positive and negative electrodes.

[0036] Please see Figure 1 and Figure 2As shown, in this embodiment, the thickness H of the insulating tape 40 satisfies: 10μm ≤ H ≤ 30μm. When the thickness H of the insulating tape 40 is less than 10μm, its mechanical strength is insufficient, making it difficult to effectively resist external extrusion or puncture from positive electrode burrs, and failing to significantly improve the puncture resistance of the epitaxial region of the separator; simultaneously, excessively thin tapes are prone to tensile deformation or breakage during application, affecting process stability. When the thickness H of the insulating tape 40 is greater than 30μm, obvious local protrusions will form on the separator surface, leading to stress concentration during cell winding, easily causing separator wrinkles, electrode slippage, or end warping, and in severe cases, potentially damaging the internal structure. Setting the thickness within a suitable range ensures that it provides sufficient puncture resistance and structural support without negatively impacting the winding process.

[0037] Please see Figure 1 and Figure 2 As shown, in this embodiment, the insulating tape 40 is made of one of the following materials: polyimide, polyester film, polypropylene, silicone rubber, and fiberglass cloth. These materials all possess excellent electrical insulation, thermal stability, and mechanical properties, making them suitable for the harsh chemical and physical environment inside lithium batteries.

[0038] Please see Figure 1 and Figure 2 As shown, in this embodiment, the insulating tape 40 must meet the following performance indicators: puncture resistance greater than 100 g / μm, which reflects the tape's ability to resist penetration by sharp objects per unit thickness. For example, when the tape thickness is 20 μm, its puncture force must be greater than 2000 g. High puncture resistance can effectively prevent burrs, metal particles, or external foreign objects from piercing the separator, blocking internal short circuit paths. Elongation at break greater than 15%, indicating the material's maximum deformation capacity before breakage. A higher elongation means the tape has good flexibility, allowing it to deform synchronously with the separator during cell winding without breaking, especially maintaining integrity in areas with large curvature at the shoulder of cylindrical cells. Simultaneously, the tape can maintain adhesion even when the cell slightly expands during battery cycling, preventing delamination. Peel strength greater than 1 N / cm, indicating the strength of the bond between the tape and the separator base film, ensuring that the tape will not curl, slip, or fall off under cell winding tension, temperature changes, or long-term cycling conditions. Resistivity greater than 5×10 2 The Ω·cm indicates that the material has extremely strong electrical insulation capabilities, which can effectively block the electron conduction path and prevent leakage or local micro-short circuits from forming between the positive and negative electrodes through the tape surface. This high resistivity ensures that the insulation performance remains reliable even in high humidity and high voltage environments.

[0039] Please see Figure 1 , Figure 2 and Figure 3As shown, in this embodiment, a first ceramic layer 33 is covered on the first surface 31, that is, the first ceramic layer 33 is coated on the first surface 31 facing the positive electrode 10 to improve the heat resistance of the cell. It should be noted that the first ceramic layer 33 can cover the entire area of ​​the separator 30 facing the positive electrode 10; it can also cover the area of ​​the separator 30 facing the positive electrode 10 except for the epitaxial region of the separator. In this case, insulating tape 40 can also be covered on the epitaxial region of the separator 30 facing the positive electrode 10 to further improve the structural stability and short-circuit resistance of the cylindrical battery under the pressure of the shoulder edge on the side of the positive electrode post, and further enhance the mechanical strength of the epitaxial region of the separator, preventing the separator from being punctured or wrinkled due to lack of negative electrode support during winding and external extrusion, and avoiding internal short circuit caused by contact between the positive electrode and the exposed negative electrode.

[0040] Please see Figure 1 and Figure 2 As shown, in this embodiment, a second ceramic layer 34 is further covered on the second surface 32 of the separator. Specifically, in the opposite direction to the first direction X, the second ceramic layer 34 starts from the edge of the second side of the insulating tape 40 and extends at least to the edge of the first side of the positive electrode 10. In the outer region of the separator, the insulating tape 40 provides mechanical support and puncture resistance; while in the main body region of the cell, the second ceramic layer 34 can further enhance the support and reduce the probability of the separator being punctured during extrusion, resulting in a short circuit between the positive and negative electrodes. Setting the starting end of the second ceramic layer 34 at the edge of the second side of the insulating tape 40 can prevent the ceramic coating from directly contacting the tape layer and avoid adhesion failure due to material interface incompatibility. In this embodiment, the width W1 of the second ceramic layer 34 along the first direction satisfies: W1 ≥ 0.55 mm. When W1 < 0.55 mm, the coverage area of ​​the second ceramic layer 34 is too narrow and cannot effectively extend to the edge area of ​​the positive electrode 10. Under the condition of large winding alignment error, exposed areas are likely to occur, which can easily lead to the diaphragm being punctured during the extrusion process, resulting in a short circuit between the positive and negative electrodes.

[0041] Please see Figure 1 and Figure 2As shown, in this embodiment, the second surface 32 of the separator 30 is further covered with a third ceramic layer 35. The arrangement of the third ceramic layer 35 matches the structural features of the negative electrode 20. Specifically, a thinned area is provided on the second side of the negative electrode 20, and the third ceramic layer 35 is coated on the second surface 32 of the separator corresponding to the thinned area, and the third ceramic layer 35 at least completely covers the thinned area. By compensating for thickness differences on the separator side, a smoother transition structure is formed at the end of the cell, reducing local stress concentration caused by sudden changes in hardness, improving winding consistency, and also improving interface contact. The ceramic layer has a certain rigidity and surface flatness, which can improve the adhesion between the separator and the electrode, reduce micro-gaps, promote uniform electrolyte wetting, and reduce interface impedance. In this embodiment, along the first direction, the width W2 of the third ceramic layer 35 satisfies: W2 ≥ 7.5 mm, which ensures that it completely covers the thinned area and is slightly extended to compensate for alignment errors. If W2 < 7.5 mm, the thinned area 20 cannot be fully covered, weakening the compensation effect and increasing the probability of lithium plating in the thinned area of ​​the negative electrode. The thickness H2 of the third ceramic layer 35 satisfies 2 μm ≤ H2 ≤ 6 μm, which matches the gradient change of the negative electrode thinning. If it is too thin, the compensation effect will be insignificant; if it is too thick, it may cause local protrusions and affect the winding flatness.

[0042] Please see Figure 1 and Figure 2 As shown, in this embodiment, the third ceramic layer 35 also covers the portion of the second side of the separator 30 that extends beyond the edge of the negative electrode plate 20, so as to improve the puncture resistance of the separator in this area, effectively resist physical damage to the edge of the positive electrode current collector or metal particles, and the ceramic layer can delay the thermal shrinkage of the separator, maintain structural integrity, and prevent direct contact between the positive and negative electrodes.

[0043] In this embodiment, the ceramic layer includes one or more of alumina, boehmite, silicon dioxide, aluminum nitride, and silicon carbide.

[0044] Please see Figure 1 and Figure 2 As shown, this utility model also provides a battery, including a bare cell assembly as described in the above embodiments. This battery can be a cylindrical lithium-ion battery, suitable for high-power, high-energy-density applications such as electric vehicles, energy storage systems, and power tools. The battery includes a casing, a cover plate assembly, and a bare cell assembly 100, wherein the bare cell assembly 100 is wound or stacked and then installed in a metal casing.

[0045] Please see Figure 1 and Figure 2 As shown, in order to better understand the advantages of the proposed solution in this utility model, an analysis can be conducted through comparative embodiments and specific implementation methods:

[0046] Comparative Example 1: The compaction of concave negative electrode sheet and convex negative electrode sheet are both 1.62; the width W of insulating tape 40 is 0; the pass rate of M142 extrusion without internal short is 3 / 10, the probability of M142 extrusion with internal short is 2 / 10, and the total pass rate of M142 extrusion is 5 / 10.

[0047] Example 1: The compaction of concave negative electrode sheet and convex negative electrode sheet is 1.62; the width W of insulating tape 40 is 0.5mm; the pass rate of M142 extrusion without internal short is 6 / 10, the probability of M142 extrusion with internal short is 1 / 10, and the total pass rate of M142 extrusion is 7 / 10.

[0048] Example 2: The compaction of both the concave and convex negative electrode sheets is 1.62; the width W of the insulating tape 40 is 0.75 mm, and the puncture resistance of this insulating tape 400 is greater than 100 g / μm, the elongation at break is greater than 15%, the peel strength is greater than 1 N / cm, and the resistivity is greater than 5 × 10⁻⁶. 2 Ω·cm; The pass rate of M142 extrusion without internal short is 8 / 10, the probability of M142 extrusion with internal short is 1 / 10, and the total pass rate of M142 extrusion is 9 / 10; The pass rate of M142 extrusion without internal short is 8 / 10, the probability of M142 extrusion with internal short is 1 / 10, and the total pass rate of M142 extrusion is 9 / 10.

[0049] Example 3: The compaction of both the concave and convex negative electrode sheets is 1.62; the width W of the insulating tape 40 is 1.05 mm, and the puncture resistance of this insulating tape 400 is greater than 100 g / μm, the elongation at break is greater than 15%, the peel strength is greater than 1 N / cm, and the resistivity is greater than 5 × 10⁻⁶. 2 The conditions are: Ω·cm; the pass rate of M142 extrusion without internal short is 10 / 10, the probability of M142 extrusion with internal short is 0 / 10, and the total pass rate of M142 extrusion is 10 / 10.

[0050] Example 4: The compaction of both the concave and convex negative electrode sheets is 1.62; the width W of the insulating tape 40 is 0.5 mm, and the puncture resistance of this insulating tape 400 is less than 100 g / μm, the elongation at break is less than 15%, the peel strength is less than 1 N / cm, and the resistivity is less than 5 × 10⁻⁶. 2 Ω·cm; The pass rate of M142 extrusion without internal short is 4 / 10, the probability of M142 extrusion with internal short is 2 / 10, and the total pass rate of M142 extrusion is 6 / 10.

[0051] As can be seen from the above comparative examples and Examples 1 to 3, the increase in the width of the insulating tape 40 significantly improves the pass rate and safety of the battery in the M142 extrusion test, and effectively reduces the probability of internal short circuit. As can be seen from Examples 2 and 4, the insulating tape 40 meeting certain puncture strength, elongation at break, peel strength and resistivity can effectively improve the pass rate and safety of the battery in the M142 extrusion test, and effectively reduce the probability of internal short circuit.

[0052] Comparative Example 2: The compaction of both concave and convex negative electrode sheets was 1.62; the width W of insulating tape 40 was 1.05 mm; the M142 extrusion with no internal shortness had a pass rate of 10 / 10. The width W1 of the second ceramic layer 34 was 0, and the width W2 of the third ceramic layer 35 was 0. At 100% SOC, slight lithium plating was observed in the thinned area of ​​the disassembly interface and in the area where the negative electrode extended beyond the positive electrode. Slight lithium plating was also observed in the thinned area and in the area where the negative electrode extended beyond the positive electrode at the ALP disassembly interface.

[0053] Example 5: The width W1 of the second ceramic layer 34 is 1.25 mm, and the rest is the same as Comparative Example 2. At 100% SOC, slight lithium plating is observed in the thinned area of ​​the disassembly interface and in the area where the negative electrode extends beyond the positive electrode. Slight lithium plating is also observed in the thinned area and in the area where the negative electrode extends beyond the positive electrode at the ALP disassembly interface.

[0054] Example 6: The width W2 of the third ceramic layer 35 is 10mm, and the rest is the same as in Example 4. Its disassembly interface is good at 100% SOC. Slight lithium plating is observed at the ALP disassembly interface in the thinned area and the area where the negative electrode exceeds the positive electrode.

[0055] Example 7: The width W1 of the second ceramic layer 34 is further increased to 1.95 mm, and the rest is the same as in Example 5. Its disassembly interface is good at 100% SOC. Slight lithium plating is observed at the ALP disassembly interface in the thinned area and the area where the negative electrode exceeds the positive electrode.

[0056] Example 8: The width W2 of the third ceramic layer 35 was further increased to 15 mm, and the rest was the same as in Example 6. The interface quality of the 100% SOC disassembly interface and the ALP disassembly interface remained good, and there was no obvious lithium plating phenomenon.

[0057] Example 9: The width W2 of the third ceramic layer 35 was further increased to 20 mm, and the rest was the same as in Example 7. The interface quality of the 100% SOC disassembly interface and the ALP disassembly interface remained good, and there was no obvious lithium plating phenomenon.

[0058] Example 10: The width W of the insulating tape 40 was increased to 1.3 mm, and the rest was the same as in Example 9. The main interfaces of the 100% SOC disassembly interface and the ALP disassembly interface were good, but lithium plating appeared in the film area corresponding to the edge of the insulating tape 40.

[0059] As can be seen from the above comparative examples and embodiments, the increase in the width of the ceramic layer significantly improves the interface quality and lithium plating phenomenon of the battery under high SOC state, especially in the thinned area and the area where the negative electrode exceeds the positive electrode. Excessively wide insulating tape 40 will cause lithium plating on the corresponding film at its edge, affecting the battery quality.

[0060] This invention proposes a cylindrical battery and its bare cell assembly. By attaching insulating tape to the epitaxial region of the separator on the non-ceramic surface, the structural stability and short-circuit withstand capability of the cylindrical battery under shoulder edge compression are significantly improved. Experiments show that as the tape width increases, the M142 test pass rate increases significantly, and the safety performance is greatly improved compared to the design without tape.

[0061] This invention proposes a cylindrical battery and its bare cell assembly. The insulating tape effectively enhances the mechanical strength of the separator's epitaxial region, preventing punctures or wrinkles in the separator due to lack of negative electrode support during winding and external extrusion, and avoiding internal short circuits caused by contact between the positive electrode and the exposed negative electrode. By reasonably controlling the width and thickness of the tape, the protective effect is ensured while not covering the active area of ​​the negative electrode, thus not affecting electrolyte wetting and ion transport, balancing safety and electrochemical performance.

[0062] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A bare cell assembly for cylindrical batteries, characterized in that, include: A positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the side closer to the positive electrode tab of the bare cell is the first side, and the other side is the second side; Along the first direction, the first side of the diaphragm has a diaphragm epitaxial region that extends beyond the negative electrode sheet; The insulating tape covers at least the side of the diaphragm epitaxial region facing the negative electrode sheet.

2. The bare cell assembly for cylindrical batteries according to claim 1, characterized in that, The insulating tape has a puncture resistance greater than 100 g / µm, an elongation at break greater than 15%, a peel strength greater than 1 N / cm, and a resistivity greater than 5 × 10⁻⁶. 2 Ω·cm.

3. The bare cell assembly for cylindrical batteries according to claim 1, characterized in that, In the opposite direction to the first direction, the insulating tape extends from the edge of the first side of the diaphragm to at most the edge of the first side of the negative electrode sheet.

4. The bare cell assembly for cylindrical batteries according to claim 1, characterized in that, Along the first direction, the width W of the diaphragm satisfies: 0.5mm≤W≤1.05mm.

5. The bare cell assembly for cylindrical batteries according to claim 1, characterized in that, The thickness H of the insulating tape satisfies: 10μm≤H≤30μm.

6. The bare cell assembly for cylindrical batteries according to claim 1, characterized in that, The insulating tape is made of one of the following materials: polyimide, polyester film, polypropylene, silicone rubber, and fiberglass cloth.

7. The bare cell assembly for cylindrical batteries according to claim 1, characterized in that, The insulating tape also covers the epitaxial region of the diaphragm on the side of the diaphragm facing the positive electrode.

8. The bare cell assembly for cylindrical batteries according to claim 1, characterized in that, The side of the diaphragm facing the positive electrode is also covered with a first ceramic layer.

9. The bare cell assembly for cylindrical batteries according to claim 1, characterized in that, The second surface is also covered with a second ceramic layer, which extends at least from the edge of the second side of the insulating tape to the edge of the first side of the positive electrode sheet in the opposite direction to the first direction.

10. The bare cell assembly for cylindrical batteries according to claim 1, characterized in that, The second surface is also covered with a third ceramic layer, and a thinned area is provided on the second side of the negative electrode sheet, with the third ceramic layer at least covering the thinned area.

11. The bare cell assembly for cylindrical batteries according to claim 10, characterized in that, The thickness of the third ceramic layer satisfies 2μm≤H2≤6μm.

12. A cylindrical battery, characterized in that, Includes bare cell assemblies for cylindrical batteries as described in any one of claims 1 to 11.

Images