Single cell, battery pack, and electronic device

Abstract

The utility model relates to battery manufacturing technical field especially relates to a single battery, battery pack and electronic equipment, single battery includes roll core, roll core includes the positive sheet, diaphragm and negative sheet of winding arrangement, diaphragm is located between adjacent positive sheet and negative sheet, along the winding direction of roll core, the part of negative sheet beyond the end of positive sheet is first extension section, along the axial direction perpendicular to roll core makes first cross section, the central angle corresponding to the span of first extension section along the circumference direction of roll core on first cross section is theta, and the range of central angle theta is 14~ 65 DEG. The utility model limits the range of the end of negative sheet beyond the first extension section of the end of positive sheet, considers the end allowance, avoids the problem that the tension distribution is uneven at the end, reduces the stress distribution at the end, improves the cycle life of electric core, and is favorable to guarantee the overall structure and performance of battery.

Description

Technical Field

[0001] This utility model relates to the field of battery manufacturing technology, and in particular to a single cell, a battery pack, and an electronic device. Background Technology

[0002] The electrode assembly of a cylindrical battery includes a core structure formed by winding a positive electrode, a negative electrode, and a separator between them. The design and process control of the core of a cylindrical battery at the end (i.e., the termination end of the positive electrode, negative electrode, and separator) are crucial, as they not only affect the battery assembly, capacity, and energy density, but are also closely related to the core performance of the cell, such as long-term safety and cycle life.

[0003] If the end allowance of the positive and negative electrode plates and the separator is not properly designed, uneven tension distribution can easily occur. In addition, excessive allowance can also cause changes in the core diameter, which can lead to problems such as winding rebound, resulting in failure to be encased or loose winding. Utility Model Content

[0004] This invention provides a single cell, a battery pack, and an electronic device to solve the technical problem in the prior art where uneven tension distribution and poor capacity retention of the cell are easily caused by improper design of the end allowance at the positive and negative electrode ends.

[0005] This utility model provides a single battery cell, which includes a core, and the core includes a positive electrode sheet, a separator and a negative electrode sheet wound together, with the separator located between adjacent positive electrode sheets and negative electrode sheets;

[0006] Along the winding direction of the core, the portion of the negative electrode sheet that extends beyond the end of the positive electrode sheet is the first extension segment; a first cross section is made along the axial direction perpendicular to the core, and the central angle corresponding to the span of the first extension segment along the circumference of the core on the first cross section is θ, and the range of the central angle θ is 14° to 65°.

[0007] In one embodiment of the present invention, the length of the first extension segment along the circumferential direction of the core is L1, where L1 = L ± 5; Where D is the diameter of the core, L is the designed length of the first extension section along the circumference of the core, and the units of L1, L and D are all mm.

[0008] In one embodiment of this utility model, the diameter D of the core, the group margin k, and the diameter M of the steel shell satisfy the following relationship: D = k × M, and the group margin k ranges from 95% to 98.5%.

[0009] In one embodiment of the present invention, the length L1 of the first extension segment along the circumferential direction of the core ranges from 5mm to 31mm, and the maximum value of the diameter D of the core is 46mm.

[0010] In one embodiment of the present invention, along the winding direction of the core, the portion of the diaphragm extending beyond the end of the negative electrode sheet is a second extension segment, and the length of the second extension segment along the circumferential direction of the core is L2, with L2 ranging from 3mm to 10mm.

[0011] In one embodiment of the present invention, in the opposite direction to the winding direction of the core, the negative electrode has an extended portion beyond the initial end of the positive electrode, the extended portion being wound around the winding needle more than 1.5 times, and the diameter of the winding needle being greater than or equal to 5 mm.

[0012] In one embodiment of the present invention, the portion of the diaphragm forming the outer peripheral surface of the core is adhered with finishing tape. At least one of the initial end and the final end of the finishing tape is located between a first extension line and a second extension line in the circumferential direction of the core. On the first cross-section, the first extension line is an extension line of the line connecting the final end of the negative electrode sheet and the center point of the core, extending away from the final end of the negative electrode sheet. The second extension line is an extension line of the line connecting the final end of the positive electrode sheet and the center point of the core, extending away from the final end of the positive electrode sheet.

[0013] In one embodiment of this utility model, a positive electrode tape is attached to the end of the positive electrode sheet, and a negative electrode tape is attached to the end of the negative electrode sheet. The positive electrode tape and the negative electrode tape have a length L3 along the winding direction of the core, L3 = 0.5L, and L3 ranges from 5mm to 13mm. The length of the positive electrode tape along the winding direction is less than the length of the negative electrode tape along the winding direction. The positive electrode tape has a first covering portion attached to the two opposite sides of the positive electrode sheet along the radial direction of the core and a first fixing portion extending from the first covering portion along the winding direction. The negative electrode tape has a second covering portion attached to the two opposite sides of the negative electrode sheet along the radial direction and a second fixing portion extending from the second covering portion along the winding direction. The first fixing portion and the second fixing portion have a length L4 along the winding direction, and L4 ≥ 0.5L3.

[0014] Along the winding direction, the length of the first covering portion of the positive electrode tape is less than the length of the second covering portion of the negative electrode tape;

[0015] The positive electrode tape includes a thick positive electrode region and a thin positive electrode region. The thickness of the thick positive electrode region is greater than the thickness of the thin positive electrode region. The thin positive electrode region is close to the free end of the positive electrode tape. The thick positive electrode region is located in the first covering portion, and the thin positive electrode region is located in the first fixing portion.

[0016] The negative electrode tape includes a thick negative electrode region and a thin negative electrode region. The thickness of the thick negative electrode region is greater than the thickness of the thin negative electrode region. The thin negative electrode region is located near the free end of the negative electrode tape. The thick negative electrode region is located in the second covering portion, and the thin negative electrode region is located in the second fixing portion.

[0017] The positive electrode tape includes a substrate and an adhesive layer coated on one or both sides of the substrate. The substrate includes at least one thin film material, which is polyimide or polyvinyl fluoride.

[0018] The negative electrode tape includes a substrate and an adhesive layer coated on one or both sides of the substrate. The substrate includes at least one thin film material, which is polyethylene terephthalate.

[0019] Based on the same concept, this utility model also provides a battery pack, including the single battery cell as described above.

[0020] Based on the same concept, this utility model also provides an electronic device, including the single battery as described above.

[0021] The beneficial effects of this utility model are as follows: The single cell, battery pack and electronic device proposed by this utility model have a first extension section of the negative electrode sheet that extends beyond the end of the positive electrode sheet along the winding direction, and the central angle corresponding to the span of the first extension section in the circumferential direction of the winding core is θ, and the range of the central angle θ is set to 14° to 65°. This can avoid the problem of uneven tension distribution at the end, reduce the stress distribution at the end, improve the cycle life of the cell, and help ensure the overall structure and performance of the battery. 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] In the attached diagram:

[0024] Figure 1 A cross-sectional schematic diagram of a winding core provided in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram showing the position of the finishing tape on the roll core in one embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram showing the positions of the positive electrode tape and the negative electrode tape on the core in one embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the structure of the positive electrode tape provided in one embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of the structure of the negative electrode tape provided in one embodiment of the present invention.

[0029] The attached figures are labeled as follows:

[0030] 1-Positive electrode plate; 11-The end of the positive electrode plate; 12-The beginning of the positive electrode plate;

[0031] 2-Negative electrode sheet; 21-Tail end of negative electrode sheet; 22-Initial end of negative electrode sheet; 201-First extension segment;

[0032] 3-September; 31-Terminal end of septum; 301-Second extension section;

[0033] 4-Positive electrode tape; 401-First covering portion; 402-First fixing portion; 41-Thick positive electrode region; 42-Thin positive electrode region;

[0034] 5-Negative electrode tape; 501-Second covering portion; 502-Second fixing portion; 51-Thick negative electrode area; 52-Thin negative electrode area;

[0035] 6- Finishing tape; 61- Finishing end of the finishing tape; 62- Initial end of the finishing tape;

[0036] 701 - First extension line; 702 - Second extension line. Detailed Implementation

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Please see Figure 1 , Figure 1 The single-cell battery provided in one embodiment of the present invention includes a core, the core including a positive electrode 1, a separator 3 and a negative electrode 2 wound together, the separator 3 being located between adjacent positive electrode 1 and negative electrode 2; along the winding direction of the core, the portion of the negative electrode 2 extending beyond the end 11 of the positive electrode is a first extension 201; a first cross-section is made along the axial direction perpendicular to the core, and the central angle corresponding to the span of the first extension 201 along the circumferential direction of the core on the first cross-section is θ, the range of the central angle θ being 14° to 65°.

[0041] Specifically, the core has a central axis, and a first cross-section is made along a direction perpendicular to the core's axial direction. The center point of the core is the projection point of the core's central axis onto the first cross-section. The positive electrode 1 has an initial end 12 near the core's central axis and a terminal end 11 away from the core's central axis. The negative electrode 2 has an initial end 22 near the core's central axis and a terminal end 21 away from the core's central axis. If the terminal end 21 of the negative electrode does not extend beyond the terminal end 11 of the positive electrode, lithium plating may occur, especially during charging, where excessive lithium ions deposit on the surface of the negative electrode 2, potentially leading to battery performance degradation and safety hazards. If the terminal end 21 of the negative electrode extends too far beyond the terminal end 11 of the positive electrode, it results in wasted active material, increases non-capacity-contributing mass, and thus limits the battery's energy density. Furthermore, a negative electrode 2 exceeding the design limits will occupy internal battery space, affecting the overall battery structure and performance.

[0042] Along the winding direction of the core, the portion of the negative electrode 2 that extends beyond the end 11 of the positive electrode is the first extension segment 201. The central angle corresponding to the span of the first extension segment 201 along the circumferential direction of the core on the first cross-section is θ, and the range of the central angle θ is 14° to 65°. The central angle θ can be 14°, 20°, 25°, 30°, 45°, 50°, 65°, etc. The fact that the end 21 of the negative electrode extends beyond the end 11 of the positive electrode can appropriately reduce the stress distribution at the end of the positive electrode 1, thereby improving the cycle life of the cell. If the extension of the end 21 of the negative electrode beyond the end 11 of the positive electrode is too small (θ < 14°), it is easy for the ends of the positive electrode 1 and the negative electrode 2 to be at the same position. This end is greatly affected by shear force, and stress concentration points are prone to appear, affecting the overall performance of the battery. If the end 21 of the negative electrode extends too far beyond the end 11 of the positive electrode (θ>65°), the cell cycle life of the battery will not be significantly improved, which will lead to waste of active materials and a continuous decrease in cell capacity.

[0043] By providing a first extension 201 in the negative electrode 2 that extends beyond the end 11 of the positive electrode along the winding direction, and setting the central angle θ corresponding to the span of the first extension 201 along the circumferential direction of the winding core, with the central angle θ ranging from 14° to 65°, lithium plating can be avoided, as can the waste of active material, reducing the production cost of the product. Furthermore, it can reduce the mass that does not contribute to capacity, ensuring the energy density of the battery. Simultaneously, the end 11 of the positive electrode and the end 21 of the negative electrode are located at different positions, which avoids uneven tension distribution at the end, reduces stress distribution at the end, avoids stress concentration, improves the cycle life of the cell, and helps ensure the overall structure and performance of the battery.

[0044] It should be noted that the length of the first extension segment 201 along the circumferential direction of the core is L1, where L1 = L ± 5; Where D is the diameter of the core, L is the designed length of the first extension segment 201 along the circumference of the core, and the units of L1, L, and D are all mm. The length L1 of the first extension segment 201 must at least satisfy L1≥1mm to avoid lithium plating. Based on the range of the central angle θ and the core diameter D, the corresponding range of L values ​​and the range of L1 values ​​for the first extension segment 201 can be calculated, with a tolerance of 5mm between L1 and L.

[0045] In the above embodiments, the core diameter D, group margin k, and steel shell diameter M satisfy the following relationship: D = k × M, and the group margin k ranges from 95% to 98.5%. Specifically, the core diameter D is usually related to the battery's energy density, thermal management performance, and mechanical strength. The choice of core diameter D affects the battery's charge / discharge efficiency, cycle life, and safety. Common cylindrical cell specifications include 18650 (diameter 18mm, height 65mm), 21700 (diameter 21mm, height 70mm), 26650 (diameter 26mm, height 65mm), 4695 (diameter 46mm, height 95mm), 46110 (diameter 46mm, height 110mm), and 46120 (diameter 46mm, height 120mm), etc. The diameter in the above specifications refers to the steel shell diameter, i.e., the common steel shell diameter M is 18mm, 21mm, 26mm, or 46mm. The coil needle diameter ranges from 4 to 6mm. In this example, the diameter of the coil needle is 5mm, the group margin k is 97%, and the diameter of the coil core D = group margin k × steel shell diameter M = 97% × 46mm = 44.62mm.

[0046] In this example, the positive electrode active material used in positive electrode 1 can be a lithium-containing composite oxide, and the negative electrode active material used in negative electrode 2 can be a material capable of lithium insertion and extraction, including but not limited to crystalline carbon (such as natural graphite and artificial graphite), amorphous carbon, carbon-coated graphite, and resin-coated graphite, or oxide materials such as indium oxide, silicon oxide, tin oxide, lithium titanate, zinc oxide, and lithium oxide. Furthermore, the negative electrode active material can also be lithium metal or a metal material that can form an alloy with lithium, such as Cu, Sn, Si, Co, Mn, Fe, Sb, and Ag. Binary or ternary alloys containing these metals and lithium can also be used as negative electrode active materials. These negative electrode active materials can be used alone or in combination of two or more forms. From the perspective of improving energy density, carbon materials such as graphite can also be combined with Si-based materials such as Si, Si alloys, and Si oxides.

[0047] Based on the central angle θ of the first extension segment 201, the battery capacity retention performance was tested to address the stress problem. The test results are as follows:

[0048] When the central angle θ of the first extension section 201 is 5°, the corresponding L value is 2mm. The stress at the end is relatively large, the cell capacity is 38.225Ah, and the capacity retention rate at 25℃ is 81.3%.

[0049] When the central angle θ of the first extension section 201 is 14°, the corresponding L value is 5mm. The stress at the end is relatively large, the cell capacity is 38.220Ah, and the capacity retention rate at 25℃ is 85.6%.

[0050] When the central angle θ of the first extension section 201 is 30°, the corresponding L value is 12mm, the stress at the end is moderate, the cell capacity is 38.210Ah, and the capacity retention rate at 25℃ is 87.7%.

[0051] When the central angle θ of the first extension section 201 is 65°, the corresponding L value is 26mm, the stress at the end is small, the cell capacity is 38.190Ah, and the capacity retention rate at 25℃ is 88.3%.

[0052] When the central angle θ of the first extension section 201 is 75°, the corresponding L value is 30mm. The stress at the end is small, the cell capacity is 38.185Ah, and the capacity retention rate at 25℃ is 88.3%.

[0053] Among them, the cycle capacity retention rate is the retention rate measured after 100 cycles under certain test conditions.

[0054] Based on the comparison of the above test data, it can be seen that when the central angle θ of the first extension section 201 is 14° to 65°, the range is appropriate, the stress at the end is small, and the cell capacity can be guaranteed while the cycle capacity retention rate will not increase too much.

[0055] The above description based on the test results of the central angle θ of the first extension segment 201 can be implemented in one embodiment by the following battery cycle capacity retention rate test method: At 25°C, the prepared battery is charged at a constant current of 1C to 3.7V, then charged at a constant voltage of 3.7V until the current drops to 0.05C, and then discharged at 3C to 2.5V. The resulting capacity is recorded as the initial capacity (C0). The above steps are repeated for the same battery, and the discharge capacity (Cn) of the battery after the nth cycle is recorded. Then, the battery capacity retention rate after each cycle is Pn = Cn / C0 × 100%. The battery capacity retention rate versus the number of cycles is obtained by plotting the 100 points P1, P2...100 on the vertical axis and the corresponding number of cycles on the horizontal axis. During this test, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 100th cycle corresponds to n=100. The battery capacity retention rate data corresponding to the above embodiment is the data measured after 100 cycles under the above test conditions, that is, the value of P100.

[0056] In some embodiments, the length L1 of the first extension 201 along the circumferential direction of the core ranges from 5 mm to 31 mm, and the maximum value of the core diameter D is less than 46 mm. Specifically, the range of L1 is between the lower limit and the upper limit, with the lower limit of L1 being 5 mm. During the winding process of the core, the tension of the winding needle, the winding speed, and the thickness of the material all affect the final degree of overlap, i.e., the actual effect of exceeding the length control. If the length L1 of the first extension 201, which extends beyond the end 21 of the negative electrode sheet to the end 11 of the positive electrode sheet, is designed with too small a margin (e.g., θ < 14°, L1 < 5 mm), it may cause the end 11 of the positive electrode sheet to extend beyond the end 21 of the negative electrode sheet after final winding, thereby affecting the overall performance of the battery. Furthermore, in actual production, the capabilities of the winding process and the precision of the equipment affect the degree of overlap between the negative electrode 2 and the positive electrode 1, often causing fluctuations in the dimension L1 at that location. This can easily lead to the positive electrode 1 and the negative electrode 2 ending at the same position, where they are more susceptible to shear forces, resulting in stress concentration, material particle breakage, or current collector breakage, thus affecting the overall performance of the battery. Therefore, L1 ≥ 5mm, i.e., the lower limit is 5mm.

[0057] Furthermore, the upper limit of L1 is 31mm. Extending the negative electrode tip 21 beyond the positive electrode tip 11 can appropriately reduce the stress distribution at the positive electrode tip, thereby improving the cell's cycle life. However, if the negative electrode tip 21 extends too far beyond the positive electrode tip 11, it will lead to a decrease in cell capacity. According to an example, when the central angle θ of the first extension segment 201 of the negative electrode tip 21 beyond the positive electrode tip 11 exceeds 65°, the improvement in cell cycle life is not significant, but the cell capacity continues to decrease.

[0058] In some embodiments, along the winding direction of the core, the portion of the separator 3 extending beyond the end 21 of the negative electrode sheet is a second extension 301. The length of the second extension 301 along the circumferential direction of the core is L2, and the range of L2 is 3mm to 10mm. Specifically, the range of L2 is between the lower limit and the upper limit, and the fluctuation range between the upper limit and the lower limit is 5mm. The lower limit of L2 is 3mm to 5mm. Too little separator 3 will affect the tightness of the core. It is necessary to ensure that the separator 3 can effectively cover the negative electrode sheet 2 to avoid short circuits caused by stress and separator 3 shrinkage. The upper limit of L2 is 8mm to 10mm, which can avoid wasting the internal space of the cell due to too much separator 3.

[0059] It is worth mentioning that, in the opposite direction to the winding direction of the core, the negative electrode 2 has a portion extending beyond the initial end 12 of the positive electrode. This extended portion is wound around the winding needle more than 1.5 times, and the diameter of the winding needle is greater than or equal to 5 mm. Specifically, the core has a central axis, and a first cross-section is taken along a direction perpendicular to the axial direction of the core. The center point of the core is the projection point of the central axis of the core onto this first cross-section. The initial end 12 of the positive electrode is the projection point of the starting position of the winding of the positive electrode 1 onto this cross-section, and the initial end 22 of the negative electrode is the projection point of the starting position of the winding of the negative electrode 2 onto this cross-section.

[0060] Continue reading Figure 1 Understandably, the number of turns the initial end 22 of the negative electrode sheet extends beyond the initial end 12 of the positive electrode sheet when wound around the winding needle can be 1.5 turns, 2 turns, or 2.5 turns, etc. That is, the initial end 22 of the negative electrode sheet is wound around the winding needle an additional set number of turns before the positive electrode sheet 1 begins to be wound (shown in the figure as 1.5 turns). In this way, by winding the inner ring of the negative electrode sheet 2 an additional 2.5 turns, compared to 1.5 turns, stronger support can be provided to the center of the core, reducing the collapse of the inner hole of the core and lowering the risk of lithium plating.

[0061] It should be noted that, for reference Figure 2 The outer circumferential surface of the diaphragm 3 forming core is covered with finishing tape 6. At least one of the initial end 62 and the final end 61 of the finishing tape is located between the first extension line 701 and the second extension line 702 in the circumferential direction of the core. In the first cross section, the first extension line 701 is an extension line of the line connecting the final end 21 of the negative electrode sheet and the center point of the core, extending away from the final end 21 of the negative electrode sheet. The second extension line 702 is an extension line of the line connecting the final end 11 of the positive electrode sheet and the center point of the core, extending away from the final end 11 of the positive electrode sheet.

[0062] Specifically, during the winding process, the positive electrode sheet 1 is first cut to form the tail end 11 of the positive electrode sheet; then, the negative electrode sheet 2 is wound, and after the negative electrode sheet 2 extends beyond the first extension section 201 of the tail end 11 of the positive electrode sheet in the winding direction, the negative electrode sheet 2 is cut to form the tail end 21 of the negative electrode sheet; next, the separator 3 is wound, and after the separator 3 extends beyond the second extension section 301 of the tail end 21 of the negative electrode sheet, the two layers of separator 3 are cut; wherein, the tail tape 6 is pasted on the outer peripheral surface of the separator 3 before the separator 3 is cut (that is, the initial end 62 of the tail tape is located before the separator 3 is cut), the initial end 62 of the tail tape is pasted on the outermost separator 3, and the tail tape 6 is cut after being pasted for one circle to form the tail end 61 of the tail tape. Before the diaphragm 3 is cut, the finishing tape 6 is attached tightly to the outer periphery of the diaphragm 3; after the diaphragm 3 is cut, the finishing tape 6 provides tension and tightens the diaphragm 3 by winding the finishing tape 6, so as to ensure that the cell can still be tightened after the diaphragm 3 is cut, and to avoid loosening.

[0063] The core has a central axis. A first cross-section is made along the axial direction perpendicular to the core, and the center point of the core is the projection point of the central axis of the core onto the first cross-section. The end 11 of the positive electrode sheet is the projection point of the cut position of the positive electrode sheet 1 onto this cross-section, and the end 21 of the negative electrode sheet is the projection point of the cut position of the negative electrode sheet 2 onto this cross-section. The first extension line 701 and the second extension line 702 are both straight lines that need to pass through the center point of the core. At least one of the initial end 62 and the end 61 of the finishing tape is located between the first extension line 701 and the second extension line 702 in the circumferential direction of the core. For example, the initial end 62 of the finishing tape is located between the first extension line 701 and the second extension line 702, or the end 61 of the finishing tape is located between the first extension line 701 and the second extension line 702, or both the initial end 62 and the end 61 of the finishing tape 6 are located between the first extension line 701 and the second extension line 702. In this way, by setting the initial end 62 and the final end 61 of the finishing tape in the circumferential direction of the core, their distribution relative to the cutting positions of the final end 11 of the positive electrode and the final end 21 of the negative electrode is more dispersed, which plays a role in uniform stress distribution, reduces the risk of stress concentration, and solves the problem of lithium plating caused by stress distribution during expansion.

[0064] See Figure 3 In some embodiments, a positive electrode tape 4 is attached to the end 11 of the positive electrode sheet, and a negative electrode tape 5 is attached to the end 21 of the negative electrode sheet. The positive electrode tape 4 and the negative electrode tape 5 have a length L3 along the winding direction, where L3 = 0.5L and L3 ranges from 5mm to 13mm. The length of the positive electrode tape 4 along the winding direction is less than the length of the negative electrode tape 5 along the winding direction. Thus, the separator 3 covers the negative electrode sheet 2 once and extends beyond the second extension 301 of the end 21 of the negative electrode sheet before being cut to complete the full coverage of the negative electrode sheet 2. Therefore, at the end 21 of the negative electrode sheet, it needs to withstand greater winding internal stress; therefore, the negative electrode tape 5 needs to have a larger winding length than the positive electrode tape 4. In this example, the length of the positive electrode tape 4 along the winding direction is 7mm, and the length of the negative electrode tape 5 along the winding direction is 11mm.

[0065] In the above embodiment, the positive electrode tape 4 has a first covering portion 401 adhered to two opposite sides of the positive electrode sheet 1 along the radial direction of the core, and a first fixing portion 402 extending from the first covering portion 401 along the winding direction. The negative electrode tape 5 has a second covering portion 501 adhered to two opposite sides of the negative electrode sheet 2 along the radial direction, and a second fixing portion 502 extending from the second covering portion 501 along the winding direction. The first fixing portion 402 and the second fixing portion 502 have a length L4 along the winding direction, where L4 ≥ 0.5L3. Specifically, in this example, L4 ranges from 3mm to 6mm (tolerance ±1mm). Thus, by setting the length ratio of the first fixing portion 402 and the second fixing portion 502 relative to the lengths of the positive electrode tape 4 and the negative electrode tape 5, the length of the thickness gradient of the first fixing portion 402 and the second fixing portion 502 is increased, thereby enhancing the stress buffering effect and improving the stress distribution.

[0066] It is worth mentioning that, along the winding direction, the length of the first covering portion 401 of the positive electrode tape 4 is less than the length of the second covering portion 501 of the negative electrode tape 5. Specifically, in this example, the length of the first covering portion 401 is 4 mm (tolerance ±1 mm), and the length of the second covering portion 501 is 5 mm (tolerance ±1 mm). Since the end portion 11 of the positive electrode sheet is located closer to the front side of the winding direction, and the end portion 21 of the negative electrode sheet is located closer to the rear side of the winding direction and directly contacts the subsequently cut separator 3, the negative electrode sheet 2 also needs to bear the constraint force of the separator 3. This arrangement can disperse the radial stress of the positive electrode tape 4 and the negative electrode tape 5 at the end, avoiding stress concentration.

[0067] See Figure 4 and Figure 5 In the above embodiment, the positive electrode tape 4 includes a thick positive electrode region 41 and a thin positive electrode region 42. The thickness of the thick positive electrode region 41 is greater than the thickness of the thin positive electrode region 42. The thin positive electrode region 42 is close to the free end of the positive electrode tape 4. The thick positive electrode region 41 is located in the first covering portion 401, and the thin positive electrode region 42 is located in the first fixing portion 402. The negative electrode tape 5 includes a thick negative electrode region 51 and a thin negative electrode region 52. The thickness of the thick negative electrode region 51 is greater than the thickness of the thin negative electrode region 52. The thin negative electrode region 52 is close to the free end of the negative electrode tape 5. The thick negative electrode region 51 is located in the second covering portion 501, and the thin negative electrode region 52 is located in the second fixing portion 502. Specifically, the adhesive layer of the positive electrode tape 4 can be configured with a combination of a thick positive electrode region 41 and a thin positive electrode region 42, and the adhesive layer of the negative electrode tape 5 can be configured with a combination of a thick negative electrode region 51 and a thin negative electrode region 52. In this way, sufficient adhesive strength can be provided while avoiding stress concentration, and the thin positive electrode region 42 and the thin negative electrode region 52 can also be used to reduce the interference ratio.

[0068] Understandably, the positive electrode tape 4 and negative electrode tape 5 possess the following characteristics: High adhesion: Both positive electrode tape 4 and negative electrode tape 5 must possess high adhesion to prevent material loss and burr formation, ensuring the stability and safety of the core. High temperature resistance: Positive electrode tape 4 and negative electrode tape 5 must maintain their performance in high-temperature environments to prevent adhesive failure due to temperature increases. Electrolyte corrosion resistance: The materials of positive electrode tape 4 and negative electrode tape 5 must be resistant to electrolyte corrosion to prevent the electrolyte from eroding the tape and ensuring its long-term stability. Oxidation-reduction resistance: Positive electrode tape 4 and negative electrode tape 5 must resist oxidation-reduction reactions to protect the performance of the core. Strong mechanical properties: Positive electrode tape 4 and negative electrode tape 5 must possess good mechanical strength to withstand certain tensile and tearing forces, ensuring stability during use.

[0069] However, based on the above performance, it is also necessary to consider the differentiated treatment of positive electrode tape 4 and negative electrode tape 5 to meet their specific requirements. Among them, the heat resistance of positive electrode tape 4 is higher than that of negative electrode tape 5.

[0070] In the above embodiments, the positive electrode tape 4 includes a substrate and an adhesive layer coated on one or both sides of the substrate. The substrate of the positive electrode tape 4 includes at least one thin film material, which is polyimide or polyvinyl fluoride. Specifically, the positive electrode tape 4 is made of polyimide (PI) or polyvinyl fluoride (PTFE). PI material has excellent high temperature resistance (long-term temperature resistance >250℃) and high chemical stability. PTFE material has high and low temperature resistance, and can be used in a wide temperature range from -200℃ to 260℃, as well as good chemical corrosion resistance and electrical insulation.

[0071] The positive electrode tape 4 should possess oxidation resistance to prevent oxidation at the end 11 of the positive electrode sheet, which could lead to failure and affect cell performance. Simultaneously, the positive electrode tape 4 should also be heat-resistant, maintaining adhesion under high-temperature conditions and acting as a "thermal pad" during subsequent hot pressing to prevent micro-cracks from forming at the cut edges due to localized overheating. Furthermore, the positive electrode tape 4 should be resistant to electrolyte corrosion to prevent erosion and ensure long-term stability. Finally, the positive electrode tape 4 should possess strong mechanical properties, capable of withstanding certain tensile and tearing forces to ensure stability during use.

[0072] The negative electrode tape 5 comprises a substrate and an adhesive layer coated on one or both sides of the substrate. The substrate of the negative electrode tape 5 includes at least one thin film material, which is polyethylene terephthalate (PET). Specifically, the negative electrode tape 5 uses polyethylene terephthalate (PET) to ensure that it has electrical insulation properties and mechanical protection capabilities, thus ensuring the safety and stability of the battery cell. PET material has good dimensional stability, thermal stability, chemical stability, insulation, adhesion, initial tack, and adhesion. Since there is no similar oxidation resistance requirement on the negative electrode side, a lower-cost conventional insulating tape can be selected.

[0073] This utility model also provides a battery pack, including the single battery cells described in the above embodiments.

[0074] This invention also provides an electronic device, including a single battery as described in the above embodiments.

[0075] In summary, the single cell, battery pack, and electronic device provided by this utility model embodiment, by having the negative electrode 2 have a first extension segment 201 that extends beyond the end 11 of the positive electrode along the winding direction, and the central angle corresponding to the span of the first extension segment 201 in the circumferential direction of the winding core is θ, and setting the range of the central angle θ to 14°~65°, can avoid the problem of uneven tension distribution at the end, reduce the stress distribution at the end, improve the cycle life of the cell, and help ensure the overall structure and performance of the battery.

[0076] 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 single-cell battery, characterized in that, The device includes a core, which comprises a positive electrode sheet, a separator, and a negative electrode sheet wound together, wherein the separator is located between adjacent positive and negative electrode sheets. Along the winding direction of the core, the portion of the negative electrode sheet that extends beyond the end of the positive electrode sheet is the first extension segment; a first cross section is made along the axial direction perpendicular to the core, and the central angle corresponding to the span of the first extension segment along the circumference of the core on the first cross section is θ, and the range of the central angle θ is 14°~65°.

2. The single-cell battery according to claim 1, characterized in that, The length of the first extension segment along the circumferential direction of the core is L1. ; Where D is the diameter of the core, L is the designed length of the first extension section along the circumference of the core, and the units of L1, L and D are all mm.

3. The single-cell battery according to claim 2, characterized in that, The diameter D of the core, the group margin k, and the diameter M of the steel shell satisfy the following relationship: D = k × M, and the group margin k ranges from 95% to 98.5%.

4. The single-cell battery according to claim 3, characterized in that, The length L1 of the first extension segment along the circumference of the core ranges from 5mm to 31mm, and the maximum value of the diameter D of the core is 46mm.

5. The single-cell battery according to claim 1, characterized in that, Along the winding direction of the core, the portion of the diaphragm that extends beyond the end of the negative electrode sheet is a second extension segment. The length of the second extension segment along the circumferential direction of the core is L2, and the range of L2 is 3mm to 10mm.

6. The single-cell battery according to claim 1, characterized in that, In the opposite direction to the winding direction of the core, the negative electrode has an overhang beyond the initial end of the positive electrode, the overhang being wound around the winding needle more than 1.5 times, and the diameter of the winding needle is greater than or equal to 5 mm.

7. The single-cell battery according to claim 1, characterized in that, The portion of the diaphragm forming the outer circumferential surface of the core is covered with finishing tape. At least one of the initial end and the final end of the finishing tape is located between a first extension line and a second extension line in the circumferential direction of the core. In the first cross-section, the first extension line is an extension of the line connecting the final end of the negative electrode sheet and the center point of the core, extending away from the final end of the negative electrode sheet. The second extension line is an extension of the line connecting the final end of the positive electrode sheet and the center point of the core, extending away from the final end of the positive electrode sheet.

8. The single-cell battery according to claim 2, characterized in that, The positive electrode sheet has a positive electrode tape attached to its end, and the negative electrode sheet has a negative electrode tape attached to its end. The positive electrode tape and the negative electrode tape have a length L3 along the winding direction of the core, where L3 = 0.5L and L3 ranges from 5mm to 13mm. The length of the positive electrode tape along the winding direction is less than the length of the negative electrode tape along the winding direction. The positive electrode tape has a first covering portion attached to the two opposite sides of the positive electrode sheet along the radial direction of the core and a first fixing portion extending from the first covering portion along the winding direction. The negative electrode tape has a second covering portion attached to the two opposite sides of the negative electrode sheet along the radial direction and a second fixing portion extending from the second covering portion along the winding direction. The first fixing portion and the second fixing portion have a length L4 along the winding direction, where L4 ≥ 0.5L3. Along the winding direction, the length of the first covering portion of the positive electrode tape is less than the length of the second covering portion of the negative electrode tape; The positive electrode tape includes a thick positive electrode region and a thin positive electrode region. The thickness of the thick positive electrode region is greater than the thickness of the thin positive electrode region. The thin positive electrode region is close to the free end of the positive electrode tape. The thick positive electrode region is located in the first covering portion, and the thin positive electrode region is located in the first fixing portion. The negative electrode tape includes a thick negative electrode region and a thin negative electrode region. The thickness of the thick negative electrode region is greater than the thickness of the thin negative electrode region. The thin negative electrode region is close to the free end of the negative electrode tape. The thick negative electrode region is located in the second covering part, and the thin negative electrode region is located in the second fixing part. The positive electrode tape includes a substrate and an adhesive layer coated on one or both sides of the substrate. The substrate includes at least one thin film material, which is polyimide or polyvinyl fluoride. The negative electrode tape includes a substrate and an adhesive layer coated on one or both sides of the substrate. The substrate includes at least one thin film material, which is polyethylene terephthalate.

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

10. An electronic device, characterized in that, Includes the single-cell battery as described in any one of claims 1-8.

Images