Battery cell

Abstract

The invention relates to the technical field of batteries. By arranging the first colloid, on one hand, a barrier layer is formed between the tail end of the Nth fold of the first pole piece and the surface of the (N-2) th fold, and the overall strength of the opposite region of the tail ends of the (N-2) th fold and the Nth fold of the first pole piece is improved, so that the opposite region of the tail ends of the (N-2) th fold and the Nth fold of the first pole piece is effectively prevented from being pulled and fractured when the battery cell falls off and is impacted; even if the area is torn, the first colloid forms a barrier layer, so that the short circuit between the tail end of the Nth fold of the first pole piece and the second pole piece is avoided, and the safety is improved; on the other hand, the tail end of the Nth fold of the first pole piece, the surface of the (N-2) th fold of the first pole piece and the second colloid are bonded at the same time, namely, the first bonding surface of the second colloid fixes the three parts at the same time, and in addition, the second bonding surface of the second colloid is bonded with the membrane shell, so that the connection stability between the roll core and the membrane shell is greatly improved; and the safety of the battery is improved through the cooperation of the three parts.

Description

Technical Field

[0001] The present invention relates to the field of new energy technologies, and particularly to battery cells. Background Art

[0002] Rechargeable batteries have been widely used in the fields of portable electronic devices and electric vehicles due to their high energy density. With the increase in the functions and power consumption of smart phones, the demand for the energy density of mobile phone batteries is getting higher and higher, resulting in easier contact between the positive and negative electrodes of the battery cells during safety tests such as dropping, increasing the risk of thermal runaway and reducing the battery safety performance. Summary of the Invention

[0003] In view of this, the present invention provides a battery cell to solve the problems of high risk of thermal runaway of the existing wound core and low battery safety performance.

[0004] The present invention provides a battery cell, comprising: a wound core and a film shell. An accommodation cavity is formed in the film shell, and the wound core is located in the accommodation cavity. The wound core includes a straight section and arc sections located on both sides of the straight section.

[0005] The wound core includes a first pole piece, a separator, and a second pole piece that are stacked and wound. The first pole piece and the second pole piece have opposite polarities. The first pole piece is located outside the second pole piece. Along the winding direction, the tail end of the first pole piece exceeds the tail end of the second pole piece. The total number of turns of the first pole piece is N, where N is a positive integer. A first colloid is provided on the outer surface of the (N - 2)-th turn of the first pole piece away from the winding center, and the first colloid is located on the straight section. The tail end of the first pole piece covers part of the first colloid. The wound core further includes a second colloid, which has a first bonding surface and a second bonding surface. The first bonding surface bonds the outer surface of the N-th turn of the first pole piece away from the winding center, the outer surface of the (N - 2)-th turn of the first pole piece away from the winding center, and the first colloid, and the second bonding surface bonds the inner wall surface of the accommodation cavity.

[0006] In an optional embodiment, along the winding direction, the total width of the first colloid is L, and the bonding width of the first colloid and the second colloid is L1; wherein, L and L1 satisfy: L1 ≥ 3 mm and / or L1 / L > 1 / 3.

[0007] In an optional embodiment, along the width direction of the first pole piece, the two side edges of the second pole piece exceed the two side edges of the first pole piece, and the two side edges of the separator exceed the two side edges of the second pole piece; at least one side edge of the first colloid exceeds the adjacent side edge of the adjacent second pole piece and bonds with the separator.

[0008] In an alternative embodiment, along the height direction of the core, at least one first tab is provided at the top end of the first pole piece; in the orthographic projection in the thickness direction of the core, the first colloid at least partially overlaps with at least one of the first tabs, and the ratio of the width of the overlapping portion of the first colloid and the first tab to the width of the first tab is 50% to 100%.

[0009] In an alternative embodiment, along the height direction of the core, at least one first tab is provided at the top end of the first pole piece; along the thickness direction of the core, the first tab is bent towards the (N - 1)-th fold of the first pole piece to form a first bending portion; a third colloid is provided on the outer surface of the (N - 1)-th fold of the first pole piece away from the winding center, the third colloid is disposed close to the side edge of the first pole piece extending beyond the first tab, and the third colloid is arranged to extend along the winding direction; along the height direction of the core, the side edge of the third colloid extends beyond the side edge of the second pole piece and is bonded to the separator.

[0010] In an alternative embodiment, along the height direction of the core, at least one second tab is provided at the top end of the second pole piece; in the orthographic projection in the thickness direction of the core, along the width direction of the core, the two side edges of all the first tabs and the second tabs do not exceed the two side edges of the third colloid.

[0011] In an alternative embodiment, the core further includes a fourth colloid, the fourth colloid is adhesively disposed at the bottom ends of the first pole piece and the second pole piece and extends along the thickness direction of the core; along the thickness direction of the core, one end of the fourth colloid is attached to the outer surface of the (N - 1)-th fold of the first pole piece away from the winding center, and the other end of the fourth colloid is attached to the outer surface of the N-th fold of the first pole piece away from the winding center and / or the outer surface of the (N - 2)-th fold of the first pole piece away from the winding center; the fourth colloid is spaced apart from the second colloid; and / or, the fourth colloid is spaced apart from the tail end of the N-th fold of the first pole piece.

[0012] In an alternative embodiment, along the height direction of the core, at least one first tab is provided at the top end of the first pole piece, and at least one second tab is provided at the top end of the second pole piece; the first pole piece includes a first current collector and a first active layer coated on at least one surface of the first current collector; along the winding direction, the first tab or the second tab closest to the tail end of the first pole piece is located at the i-th fold, and at least a part of the surface of the first active layer of the first pole piece from the 1st fold to the i-th fold is provided with a recess; and / or, at least a part of the surface of the first active layer of the first pole piece from the (i + 1)-th fold to the (i + k)-th fold is formed with a recess, and the surface of the first active layer of the first pole piece from the (i + k + 1)-th fold to the N-th fold is not provided with the recess, where 2 ≤ k ≤ 5 and k is a positive integer; and / or, the number of folds of the first pole piece from the (i + k + 1)-th fold to the N-th fold without the recess satisfies: 0.1 ≤ (N - (i + k)) / N ≤ 0.4.

[0013] In an alternative embodiment, the peeling force between the second colloid and the first colloid is F1, and the peeling force between the first colloid and the first pole piece is F2, where F1 and F2 satisfy: 0.1 N / mm ≤ F1 ≤ 1 N / mm; and / or, 0.05 N / mm ≤ F2 ≤ 0.8 N / mm; and / or, F1 > F2.

[0014] In an alternative embodiment, the second pole piece includes a second current collector and a second active layer coated on at least one surface of the second current collector, and a plurality of linear grooves are provided at intervals in the second active layer; and / or, the second active layer is made of a silicon-containing material with a silicon element content of more than 5%; and / or, along the height direction of the core, at least one first tab is provided at the top end of the first pole piece, and at least one second tab is provided at the top end of the second pole piece, and the total number of the first tab and the second tab is four, and / or, the first tab and / or the second tab is coated with tab glue, and the melting point range of the tab glue is 95°C to 130°C.

[0015] The technical solution of the present application has the following advantages:

[0016] Since the top winding glue on the side of the battery cell close to the tab is cancelled to reduce the overall thickness of the battery cell and increase the battery capacity, in this application, by setting the first colloid, on the one hand, a barrier layer is formed between the tail end of the Nth fold of the first pole piece and the surface of the (N - 2)th fold, and the overall strength of the relative area between the (N - 2)th fold and the tail end of the Nth fold of the first pole piece is increased. When the battery cell is subjected to a drop impact, it effectively avoids the tensile fracture of the relative area between the (N - 2)th fold and the tail end of the Nth fold of the first pole piece. And even if this area is torn, since the first colloid forms a barrier layer, it avoids the short circuit between the tail end of the Nth fold of the first pole piece and the second pole piece, improving the safety; on the other hand, by setting the second colloid that simultaneously bonds the tail end of the Nth fold of the first pole piece, the surface of the (N - 2)th fold and the first colloid, that is, the first bonding surface of the second colloid fixes three parts at the same time, and the second bonding surface of the second colloid is also bonded to the film shell, thus greatly improving the connection stability between the wound core and the film shell; that is, by simultaneously setting the first colloid and the second colloid, the relative displacement between the wound core and the film shell and the probability of short circuit between the first pole piece and the second pole piece when the battery cell is subjected to a drop impact are reduced, so as to jointly cooperate to improve the safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 Schematic structural diagram of one side of the wound core according to an embodiment of the present invention;

[0019] Figure 2 Schematic structural diagram of the other side of the wound core according to an embodiment of the present invention;

[0020] Figure 3 For Figure 2 The top view of the wound core shown;

[0021] Figure 4 For Figure 3 The sectional structural diagram in the X-X direction in

[0022] Figure 5 Schematic structural diagram of an arrangement of the first pole piece and the second pole piece according to an embodiment of the present invention;

[0023] Figure 6 Schematic structural diagram of another arrangement of the first pole piece and the second pole piece according to an embodiment of the present invention;

[0024] Figure 7Schematic diagram of the unfolded structure of the first pole piece according to an embodiment of the present invention;

[0025] Figure 8 Enlarged schematic diagram of the concave portion according to an embodiment of the present invention;

[0026] Figure 9 Schematic diagram of the unfolded structure of the second pole piece according to an embodiment of the present invention;

[0027] Figure 10 Enlarged schematic diagram of the linear groove according to an embodiment of the present invention;

[0028] Figure 11 is Figure 9 Schematic diagram of one side of the second pole piece in

[0029] Figure 12 is Figure 9 Schematic diagram of the other side of the second pole piece in

[0030] Explanation of reference numerals:

[0031] 1. First pole piece; 101. Concave portion; 102. First pole tab groove; 103. First current collector; 104. First active layer; 105. Tail end; 2. Separator; 3. Second pole piece; 301. Second pole tab groove; 302. Linear groove; 303. Second current collector; 304. Second active layer; 4. First colloid; 5. Second colloid; 6. First pole tab; 601. First bending portion; 7. Third colloid; 8. Fourth colloid; 9. Second pole tab; 10. Fifth colloid; 11. Sixth colloid; 12. Pole tab glue. Detailed implementation manners

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] The following combines Figures 1 to 12 to describe the embodiments of the present invention.

[0034] According to an embodiment of the present invention, a battery cell is provided, including: a wound core and a film case. A receiving cavity is formed in the film case, and the wound core is located in the receiving cavity. The wound core includes a straight section and arc sections located on both sides of the straight section. Among them, the wound core includes a first electrode tab 1, a separator 2, and a second electrode tab 3 that are stacked and wound. The first electrode tab 1 and the second electrode tab 3 have opposite polarities. The first electrode tab 1 is located outside the second electrode tab 3. Along the winding direction, the tail end 105 of the first electrode tab 1 exceeds the tail end of the second electrode tab 3. The total number of turns of the first electrode tab 1 is N, and N is a positive integer. A first colloid 4 is provided on the outer surface of the (N - 2)-th turn of the first electrode tab 1 away from the winding center. The first colloid 4 is located in the straight section, and the tail end 105 of the first electrode tab 1 covers a part of the first colloid 4. The wound core further includes a second colloid 5. The second colloid 5 has a first bonding surface and a second bonding surface. The first bonding surface is bonded to the outer surface of the N-th turn of the first electrode tab 1 away from the winding center, the outer surface of the (N - 2)-th turn of the first electrode tab 1 away from the winding center, and the first colloid 4. The second bonding surface is bonded to the inner wall surface of the receiving cavity.

[0035] In the battery cell of this embodiment, since the top winding glue on the side of the battery cell close to the tab is cancelled to reduce the overall thickness of the battery cell and improve the battery capacity, in this application, by setting the first colloid 4, on the one hand, a barrier layer is formed between the tail end 105 of the N-th turn and the surface of the (N - 2)-th turn of the first electrode tab 1, and the overall strength of the relative area between the (N - 2)-th turn and the tail end 105 of the N-th turn of the first electrode tab 1 is improved. When the battery cell is dropped and impacted, the relative area between the (N - 2)-th turn and the tail end 105 of the N-th turn of the first electrode tab 1 is effectively prevented from being pulled and broken. And even if this area is torn, since the first colloid 4 forms a barrier layer, the short circuit between the tail end 105 of the N-th turn of the first electrode tab 1 and the second electrode tab 3 is avoided, improving the safety. On the other hand, by setting the second colloid 5 that bonds the tail end 105 of the N-th turn of the first electrode tab 1, the surface of the (N - 2)-th turn, and the first colloid 4 at the same time, that is, the first bonding surface of the second colloid 5 fixes three parts at the same time, and the second bonding surface of the second colloid 5 is bonded to the film case, thereby greatly improving the connection stability between the wound core and the film case. That is, by setting the first colloid 4 and the second colloid 5 at the same time, the relative displacement between the wound core and the film case and the probability of short circuit between the first electrode tab 1 and the second electrode tab 3 when the battery cell is dropped and impacted are reduced, so as to jointly cooperate to improve the safety of the battery.

[0036] It should be noted that, please refer to Figure 1 , the first colloid 4 extends along the height direction of the wound core to the opposite ends of the first electrode tab 1; please refer to Figure 3 , the first colloid 4 extends out of the tail end 105 of the N-th turn of the first electrode tab 1 along the winding direction.

[0037] It should be noted that, please refer to Figure 3, taking the first pole piece 1 as an example, for each winding, the number of folds increases by two. Therefore, the difference in the number of folds between two adjacent folds on the same side is 2. It can be understood that the (N - 2)-th fold and the N-th fold of the first pole piece 1 are adjacent folds.

[0038] It should be noted that, please refer to Figure 1 and Figure 3 , the N-th fold of the first pole piece 1 is the last fold, and the end 105 of the N-th fold of the first pole piece 1 is the end 105 of the entire core. The N-th fold of the first pole piece 1 is usually formed by the extension of the current collector of the first pole piece 1.

[0039] It should be further noted that for the core, it includes a straight section and arc sections located on opposite sides of the straight section. One fold of the first pole piece 1 includes at least part located in the straight section and at least part located in one arc section. In this embodiment, the end 105 of the first pole piece 1 extends to the straight section.

[0040] It is worth noting that the first bonding surface of the second colloid 5 is the inner surface of the second colloid 5 close to the winding center, and the second bonding surface of the second colloid 5 is the outer surface of the second colloid 5 away from the winding center.

[0041] In one embodiment, please refer to Figure 1 and Figure 2 , along the height direction of the core, at least one first pole tab 6 is provided at the top end of the first pole piece 1. Correspondingly, the other end opposite to the top end is the bottom end; similarly, at least one second pole tab 9 is provided at the top end of the second pole piece 3. Correspondingly, the other end opposite to the top end is the bottom end.

[0042] In one embodiment, as Figure 2 shown, along the thickness direction of the core, the first pole tab 6 is bent towards the (N - 1)-th fold of the first pole piece 1 to form a first bending portion 601; a third colloid 7 is provided on the outer surface of the (N - 1)-th fold of the first pole piece 1 away from the winding center. The third colloid 7 is arranged close to one side edge of the first pole piece 1 where the first pole tab 6 extends (that is, the edge of the first pole piece 1 close to the top end), and the third colloid 7 extends along the winding direction; along the height direction of the core, the side edge of the third colloid 7 extends beyond the side edge of the second pole piece 3 and is bonded to the separator 2 (that is, the top edge of the third colloid 7 extends beyond the top edge of the second pole piece 3).

[0043] Exemplarily, in the C-PACK structure, due to the folded top edge sealing design, under the dual actions of bending the tab and extrusion, it is easy to cause short-circuiting between the positive and negative electrode plates or contact between the tab and the positive and negative electrode plates, thereby triggering safety problems. Therefore, in this embodiment, by providing the third colloid 7, it plays an isolating role for the positive and negative electrode plates and the tab, thereby improving the safety performance of the battery. It should be noted that in a soft-pack lithium-ion battery, the top edge seal is the sealed area at the top of the battery, usually formed by melting and bonding the aluminum-plastic film through a sealing head under high temperature and high pressure; the top edge seal connects the positive and negative electrode posts of the battery, playing a role of sealing and insulation, ensuring that the electrolyte inside the battery will not leak, and preventing external moisture and oxygen from entering.

[0044] However, due to the setting of the third colloid 7, considering the thickness of the core and the flatness of the core surface simultaneously, it is no longer possible to wind glue around the top of the core. Therefore, the current collector at the top of the core is not fixed, and it is easy to cause the tearing of the current collector during the drop test. In particular, it is easy for the (N - 2)-th fold of the first electrode plate 1 to be torn, resulting in a short circuit between the N-th fold of the first electrode plate 1 and the second electrode plate 3, triggering a safety problem. Therefore, in this embodiment, by providing the first colloid 4 between the (N - 2)-th fold and the N-th fold of the first electrode plate 1, the risk of the (N - 2)-th fold of the first electrode plate 1 being torn can be reduced. Moreover, if the (N - 2)-th fold of the first electrode plate 1 is torn, the first colloid 4 can isolate between the second electrode plate 3 and the N-th fold of the first electrode plate 1, avoiding short circuit and triggering safety problems.

[0045] Furthermore, in one embodiment, in the orthographic projection in the thickness direction of the core, along the width direction of the core, the two side edges of all the first tabs 6 and the second tabs 9 do not exceed the two side edges of the third colloid 7. That is, along the width direction of the core, the third colloid 7 covers all the first tabs 6 and the second tabs 9. Therefore, it can further ensure the isolation of the positive and negative electrode plates and the tabs, thereby further ensuring the safety performance of the battery.

[0046] In one embodiment, as Figure 1 shown, along the winding direction, the bonding width of the first colloid 4 and the second colloid 5 is L1, and L1 satisfies L1 ≥ 3 mm. With such a setting, it is ensured that the first colloid 4 and the second colloid 5 have a sufficient bonding width, ensuring the firmness of the connection between the first colloid 4 and the second colloid 5, thereby ensuring the stability of the fixation of the tail end 105 of the core.

[0047] It is worth noting that in this embodiment, the second colloid 5 is a hot melt adhesive. Please refer to Figure 1 , along the winding direction, the second colloid 5 is adhesively arranged with the N-th fold of the first electrode plate 1, the first colloid 4, and the (N - 2)-th fold of the first electrode plate 1.

[0048] Furthermore, please refer to Figure 1, along the winding direction, the total width of the first colloid 4 is L, and L and L1 satisfy L1 / L > 1 / 3. With such a setting, the peel strength of the hot melt adhesive can be improved, and the battery drop failure can be prevented.

[0049] In one embodiment, the peel strength between the second colloid 5 and the first colloid 4 is F1, and the peel strength between the first colloid 4 and the first pole piece 1 is F2. Among them, F1 and F2 satisfy F1 > F2. The adhesiveness between the hot melt adhesive and the colloid will be greater than the adhesiveness between the hot melt adhesive and the first pole piece 1. Therefore, the second colloid 5 and the first colloid 4 are directly bonded to avoid the loosening or even detachment of the tail end 105 of the core during the drop process and the tearing problem of the current collector.

[0050] Furthermore, in one embodiment, the peel strength F1 between the second colloid 5 and the first colloid 4 satisfies 0.1 N / mm ≤ F1 ≤ 1 N / mm; the peel strength F2 between the first colloid 4 and the first pole piece 1 satisfies 0.05 N / mm ≤ F2 ≤ 0.8 N / mm.

[0051] It should be noted that if F1 < 0.1 N / mm, the adhesive force between the second colloid 5 and the first colloid 4 is too small, and it is easy to cause the separation of the second colloid 5 and the first colloid 4 during the drop of the battery cell, resulting in the detachment of the tail end 105 of the core and easily triggering the failure of the battery cell; if F1 > 1 N / mm, the adhesive force between the second colloid 5 and the first colloid 4 is too large, resulting in a mismatch between the adhesive force between the second colloid 5 and the first colloid 4 and the adhesive force between the first colloid 4 and the first pole piece 1, and it is easy to cause local tearing of the core and trigger battery failure.

[0052] Preferably, the peel strength F1 between the second colloid 5 and the first colloid 4 satisfies 0.3 N / mm ≤ F1 ≤ 0.8 N / mm. With such a setting, the battery cell can have better drop performance and stronger drop resistance.

[0053] Optionally, the value of F1 is any value among 0.1 N / mm, 0.2 N / mm, 0.3 N / mm, 0.4 N / mm, 0.5 N / mm, 0.6 N / mm, 0.7 N / mm, 0.8 N / mm, 0.9 N / mm, 1 N / mm or a value between any two of them.

[0054] It should be noted that if F2 < 0.05 N / mm, the adhesive force between the first colloid 4 and the first pole piece 1 is too small, and it is easy to cause the separation of the first colloid 4 and the first pole piece 1, and then it is easy to cause the detachment of the tail end 105 of the core and trigger the failure of the battery cell; if F2 > 0.8 N / mm, the adhesive force between the first colloid 4 and the first pole piece 1 is too large, resulting in a mismatch between the adhesive force between the first colloid 4 and the first pole piece 1 and the adhesive force between the second colloid 5 and the first colloid 4, and it is easy to cause local tearing of the core and trigger battery failure.

[0055] Preferably, the peeling force F2 between the first colloid 4 and the first pole piece 1 satisfies 0.2 N / mm ≤ F2 ≤ 0.6 N / mm. With such a setting, the battery cell can have better drop performance and stronger drop resistance.

[0056] Optionally, the value of F2 is any value among 0.05 N / mm, 0.1 N / mm, 0.2 N / mm, 0.3 N / mm, 0.4 N / mm, 0.5 N / mm, 0.6 N / mm, 0.7 N / mm, 0.8 N / mm or a value between any two of them.

[0057] It should be noted that the test processes for the peeling force F1 and the peeling force F2 are as follows: Discharge the battery to 3.0 V and disassemble it until the interface where the second colloid 5 is located. Peel the second colloid 5 with a universal tensile testing machine to separate it from other layers. During the peeling process, the running stroke of the universal tensile testing machine is 40 mm and the running speed is 100 mm / min. The average peeling force obtained during the test process is the peeling force F1 between the second colloid 5 and the first colloid 4; Discharge the battery to 3.0 V and disassemble it until the interface where the first colloid 4 is located. Peel the first colloid 4 with a universal tensile testing machine to separate it from other layers. During the peeling process, the running stroke of the universal tensile testing machine is 40 mm and the running speed is 100 mm / min. The average peeling force obtained during the test process is the peeling force F2 between the first colloid 4 and the first pole piece 1.

[0058] In one embodiment, as Figure 1 shown, along the width direction of the first pole piece 1, the two side edges of the second pole piece 3 extend beyond the two side edges of the first pole piece 1, and the two side edges of the separator 2 extend beyond the two side edges of the second pole piece 3; at least one side edge of the first colloid 4 extends beyond the adjacent side edge of the adjacent second pole piece 3 and is bonded to the separator 2. Further, the top end of the first colloid 4 covers the top end of the second pole piece 3 and is bonded to the separator 2, and the top end of the first colloid 4 does not exceed the top end of the separator 2. With such a setting, on the one hand, it can effectively cover the active layer of the second pole piece 3, prevent the end section of the first pole piece 1 from piercing the separator 2 during movement and coming into contact with the second pole piece 3, and ensure the isolation effect on the Nth fold of the second pole piece 3 and the first pole piece 1 after the (N - 2)th fold of the first pole piece 1 is torn, improving the battery safety performance; on the other hand, the bonding of the first colloid 4 to the separator 2 can further improve the connection stability between the wound core and the film case.

[0059] It should be noted that the width direction of the first pole piece 1 in the unfolded state before winding of the first pole piece 1 is the height direction of the wound core in the wound core winding and forming state.

[0060] In one embodiment, as Figure 1As shown, in the orthographic projection in the thickness direction of the core, the first colloid 4 and at least one first tab 6 at least partially overlap. At the tab position, the current density is high, generating more heat, which can easily cause the separator 2 to shrink and lead to short circuit between the positive and negative electrodes, triggering thermal runaway. Therefore, in this embodiment, by providing the first colloid 4, the positive and negative electrode plates can be isolated when the separator 2 shrinks, improving the battery safety performance.

[0061] Further, in one embodiment, along the winding direction, the ratio of the width of the overlapping portion of the first colloid 4 and the first tab 6 to the width of the first tab 6 is 50% to 100%.

[0062] It should be noted that if the ratio of the width of the overlapping portion of the first colloid 4 and the first tab 6 to the width of the first tab 6 is less than 50%, the isolation effect of the first colloid 4 on the positive and negative electrode plates is poor, and there is still a risk of short circuit between the positive and negative electrodes, triggering thermal runaway of the battery cell; if the ratio of the width of the overlapping portion of the first colloid 4 and the first tab 6 to the width of the first tab 6 is greater than 100%, the required width of the first colloid 4 is too large, resulting in waste of materials and increase in cost.

[0063] Preferably, the ratio of the width of the overlapping portion of the first colloid 4 and the first tab 6 to the width of the first tab 6 is 80% to 100%. Further, the ratio of the width of the overlapping portion of the first colloid 4 and the first tab 6 to the width of the first tab 6 is 100%. Therefore, the first colloid 4 can completely cover the first tab 6, thus completely avoiding the risk of thermal runaway caused by the shrinkage of the separator 2.

[0064] Optionally, the value of the ratio of the width of the overlapping portion of the first colloid 4 and the first tab 6 to the width of the first tab 6 is any value among 50%, 60%, 70%, 80%, 90%, 100% or a value between any two of them.

[0065] In one embodiment, please refer to Figure 7 , along the winding direction, a plurality of first tabs 6 are spaced on the first electrode plate 1, and the first colloid 4 at least has an overlapping portion with the first tab 6 close to the head end of the first electrode plate 1. The first tab 6 close to the head end of the first electrode plate 1 is the first first tab 6, and the current density of the first first tab 6 is relatively higher, so it is more likely to cause thermal runaway.

[0066] It should be noted that in this embodiment, the core can be two tabs (one first tab 6, one second tab 9), three tabs (one first tab 6, two second tabs 9, or two first tabs 6, one second tab 9), four tabs (two first tabs 6, two second tabs 9).

[0067] Specifically, when the width of the battery cell decreases or the number of tabs increases (for example, more than 2), since the tab glue 12 occupies too much of the top space of the battery cell, if the top winding glue is set (similar to the setting method of the fourth colloid 8), it may cause the projection of the top winding glue to overlap with the tab glue 12, thereby increasing the thickness of the battery cell.

[0068] By canceling the top winding glue in the embodiments of the present application, the thickness of the battery cell can be reduced.

[0069] In one embodiment, as Figure 1 and Figure 2 shown, the wound core further includes a fourth colloid 8 (i.e., the bottom winding glue of the wound core), and the fourth colloid 8 is adhesively disposed at the bottom ends of the first pole piece 1 and the second pole piece 3 and extends along the thickness direction of the wound core; along the thickness direction of the wound core, one end of the fourth colloid 8 adheres to the outer surface of the (N - 1)-th fold of the first pole piece 1 away from the winding center, and the other end of the fourth colloid 8 adheres to the outer surface of the N-th fold of the first pole piece 1 away from the winding center and / or the outer surface of the (N - 2)-th fold of the first pole piece 1 away from the winding center, and the fourth colloid 8 and the second colloid 5 are arranged at intervals. By providing the fourth colloid 8, the first pole piece 1, the separator 2, and the second pole piece 3 are fixed along the thickness direction at the bottom end of the wound core, and the fourth colloid 8 and the second colloid 5 are arranged at intervals to avoid the superposition of the colloids in the thickness direction, resulting in an overly thick wound core, thereby preventing the influence on the energy density of the battery.

[0070] Specifically, in this embodiment, as Figure 1 and Figure 2 shown, there are two fourth colloids 8 arranged at intervals, and the other end of one fourth colloid 8 adheres to the outer surface of the N-th fold of the first pole piece 1 away from the winding center, and the other end of the other fourth colloid 8 adheres to the outer surface of the (N - 2)-th fold of the first pole piece 1 away from the winding center.

[0071] Further, in one embodiment, as Figure 1 shown, the fourth colloid 8 and the tail end 105 of the N-th fold of the first pole piece 1 are arranged at intervals. That is, one fourth colloid 8 is arranged in this way to minimize the superposition of the fourth colloid 8 and the first colloid 4 in the thickness direction, further ensuring the energy density of the battery.

[0072] In one embodiment, as Figure 5 and Figure 6 shown, the first pole piece 1 includes a first current collector 103 and a first active layer 104 coated on at least one surface of the first current collector 103; the second pole piece 3 includes a second current collector 303 and a second active layer 304 coated on at least one surface of the second current collector 303.

[0073] In one embodiment, please refer to Figure 3, along the winding direction, the first tab 6 or the second tab 9 closest to the tail end 105 of the first electrode tab 1 is located at the i-th fold. At least part of the surface of the first active layer 104 of the first to i-th folds of the first electrode tab 1 is provided with recesses 101; at least part of the surface of the first active layer 104 of the (i + 1)-th to (i + k)-th folds of the first electrode tab 1 is formed with recesses 101, and no recesses 101 are provided on the surface of the first active layer 104 of the (i + k + 1)-th to N-th folds of the first electrode tab 1, where 2 ≤ k ≤ 5 and k is a positive integer. That is, the first active layer 104 of the k folds after the fold where the last tab (which can be the first tab 6 or the second tab 9) is located has recesses 101, and no recesses 101 are provided on the first active layer 104 from the (k + 1)-th fold after the fold where the last tab is located to the last fold. Please refer to Figure 3 , in Figure 3 , k = 2.

[0074] It should be noted that for the core, the electrolyte infiltration effect of the part near the head end is relatively poor, and the electrolyte infiltration effect of the part near the tail end 105 is relatively good. Therefore, by providing recesses 101 on the active layer of the first electrode tab 1 near the head end, the infiltration effect is improved. In order to prevent the first tab 6 from falling off and cracks from occurring in the current collector, generally no recesses 101 are provided on the active layer of the fold where the first tab 6 of the first electrode tab 1 is located; therefore, in order to balance the problem of poor infiltration effect of the fold where the first tab 6 is located, by providing recesses 101 on the active layer of the first electrode tab 1 in some folds before and after the fold where the first tab 6 is located, the force on the fold where the first tab 6 is located is made more uniform, the infiltration effect is better, the speed of lithium-ion insertion and extraction is faster, and the conductivity of the tab is improved. Moreover, during the winding process, the tension of the part near the head end is relatively large, and the tension of the part near the tail end 105 is relatively small. Therefore, by providing recesses 101 on the active layer of the first electrode tab 1 near the head end and not providing recesses 101 on the active layer of the first electrode tab 1 near the tail end 105, the tension of the first electrode tab 1 near the head end is reduced, so that it tends to be consistent with the tension of the first electrode tab 1 near the tail end 105, improving the deformation of the first electrode tab 1 and avoiding the occurrence of the problem of the electrode tab being folded.

[0075] It should be noted that if k < 2, the improvement degree of the infiltration effect of the fold where the first tab 6 is located is relatively low, and the force balance effect on the fold where the first tab 6 is located is relatively poor. There are still problems of uneven force and poor infiltration effect in the fold where the first tab 6 is located; if k > 5, the number of folds of the first electrode tab 1 provided with recesses 101 is too large, resulting in too large a loss of the energy density of the battery cell.

[0076] Optionally, the value of k is any one of 2, 3, 4, and 5.

[0077] Further, in one embodiment, the number of folds from the (i + k + 1)-th fold to the N-th fold of the first pole piece 1 without the recess 101 satisfies: 0.1 ≤ (N - i - k) / N ≤ 0.4 with respect to the total number of folds of the first pole piece 1. That is, the ratio of the number of folds of the first pole piece 1 without the recess 101 after the (i + k)-th fold to the total number of folds of the first pole piece 1 ranges from 0.1 to 0.4. By setting it in this way, the infiltration effect of the core is ensured, thereby improving the battery energy density.

[0078] It should be noted that if (N - i - k) / N < 0.1, the number of folds of the first pole piece 1 without the recess 101 is too small, that is, the number of folds of the first pole piece 1 with the recess 101 is too large, resulting in too large a loss of the energy density of the battery cell; if (N - i - k) / N > 0.4, the number of folds of the first pole piece 1 without the recess 101 is too large, that is, the number of folds of the first pole piece 1 with the recess 101 is too small, which will lead to a poor infiltration effect of the core and affect the overall performance of the battery cell.

[0079] Optionally, the value of (N - i - k) / N is any one of 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 or a value between any two of them.

[0080] In one embodiment, as Figure 5 shown, for the first pole piece 1, the first active layer 104 of the fold where the first pole tab 6 is located does not have the recess 101, and the first active layers 104 of the two folds of the first pole piece 1 adjacent to the fold where the first pole tab 6 is located have the recess 101. By setting it in this way, the force on the fold where the first pole tab 6 is located can be made more uniform, thereby slowing down the problem of pole piece fracture caused by pulling due to uneven pressure, and moreover, improving the infiltration effect of the fold where the first pole tab 6 is located and increasing the battery energy density.

[0081] Further, in one embodiment, as Figure 5 shown, the first active layer 104 is provided with a first pole tab groove 102, the first pole tab 6 is located in the first pole tab groove 102, the sixth colloid 11 is attached to the second active layer 304, the sixth colloid 11 is disposed opposite to the first pole tab groove 102, and along the winding direction, the width of the sixth colloid 11 does not exceed the width of the first pole tab groove 102. By setting it in this way, the pressure on the first pole piece 1 at the first pole tab 6 is reduced, further avoiding problems such as pole piece fracture.

[0082] In one embodiment, as Figure 6As shown, for the second pole piece 3, the first active layers 104 of the two folds of the first pole piece 1 adjacent to the fold where the second tab 9 is located are not provided with recesses 101, and the first active layer 104 of one fold of the first pole piece 1 adjacent to the fold of the first pole piece 1 where the recess 101 is not provided has a recess 101. That is, the first active layer 104 of one fold of the first pole piece 1 before and adjacent to the fold where the second tab 9 is located is not provided with a recess 101, and the first active layer 104 of one fold of the first pole piece 1 adjacent to the above-mentioned fold of the first pole piece 1 where the recess 101 is not provided has a recess 101; the first active layer 104 of one fold of the first pole piece 1 after and adjacent to the fold where the second tab 9 is located is not provided with a recess 101, and the first active layer 104 of one fold of the first pole piece 1 adjacent to the above-mentioned fold of the first pole piece 1 where the recess 101 is not provided has a recess 101. With such a setting, the force on the fold where the second tab 9 is located can be made more uniform, thereby slowing down the problem of pole piece fracture caused by pulling due to uneven pressure, and improving the infiltration effect of the fold where the second tab 9 is located and the battery energy density.

[0083] Further, in one embodiment, as Figure 6 shown, the second active layer 304 is provided with a second tab groove 301, the second tab 9 is located in the second tab groove 301, the second pole piece 3 is attached with a fifth colloid 10, the fifth colloid 10 covers the second tab groove 301, and along the winding direction, the width of the fifth colloid 10 does not exceed the width of the second tab groove 301. With such a setting, the pressure on the second pole piece 3 at the second tab 9 is reduced, and further problems such as pole piece fracture are avoided.

[0084] In one embodiment, as Figure 8 shown, along the thickness direction of the first pole piece 1, the depression depth of the recess 101 is B, and 3μm ≤ B ≤ 30μm is satisfied.

[0085] It should be noted that the fold of the first pole piece 1 attached with the first colloid 4 and the third colloid 7 is not provided with a recess 101, that is, the first active layers 104 of the (N - 2)-th fold and the (N - 1)-th fold of the first pole piece 1 are not provided with recesses 101. With such a setting, the flatness of the fold where the first colloid 4 and the third colloid 7 are located is ensured, the bonding effect between the first colloid 4 and the third colloid 7 and the first pole piece 1 is improved, and the dropping of the first colloid 4 and the third colloid 7 is avoided.

[0086] In one embodiment, as Figures 9 to 12 shown, the second active layer 304 is provided with a plurality of linear grooves 302 at intervals. By providing the linear grooves 302, the infiltration effect of the electrolyte is improved, thereby enhancing the kinetic performance of the battery.

[0087] In one embodiment, as Figure 11 and Figure 12As shown, the linear grooves 302 extend along the width direction of the second pole piece 3 and are arranged at intervals along the winding direction.

[0088] It should be noted that the width direction of the second pole piece 3 is the same as that of the first pole piece 1.

[0089] Furthermore, as Figure 10 shown, in the cross-section perpendicular to the extension direction of the linear groove 302, the cross-section of the linear groove 302 is triangular, the depression depth of the linear groove 302 is A1, satisfying 5μm ≤ A1 ≤ 80μm; the maximum width of the linear groove 302 is A2, satisfying 30μm ≤ A2 ≤ 200μm.

[0090] It should be noted that if A1 < 5μm, the depression depth of the linear groove 302 is too small, the infiltration effect of the winding core is still poor, the improvement of the dynamic performance of the battery cell is too small, and the electrical performance requirements of the battery cell cannot be met; if A1 > 80μm, the depth of the linear groove 302 is too large, affecting the structural strength of the second active layer 304, and powder falling is likely to occur, affecting the safety performance of the battery cell.

[0091] Optionally, the value of A1 is any value among 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm or a value between any two of them.

[0092] It should be noted that if A2 < 30μm, the width of the linear groove 302 is too small, the infiltration effect of the winding core is still poor, the improvement of the dynamic performance of the battery cell is too small, and the electrical performance requirements of the battery cell cannot be met; if A2 > 200μm, the width of the linear groove 302 is too large, affecting the structural strength of the second active layer 304, and powder falling is likely to occur, affecting the safety performance of the battery cell.

[0093] Optionally, the value of A2 is any value among 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm or a value between any two of them.

[0094] Furthermore, as Figure 11 shown, along the winding direction, the distance between two adjacent linear grooves 302 is A3, satisfying 0.3mm ≤ A3 ≤ 3mm.

[0095] It should be noted that if A3 < 0.3 mm, the distance between adjacent two linear grooves 302 is too close, resulting in easy powder dropping of the active layer, which affects the safety performance of the battery cell; if A3 > 3 mm, the distance between adjacent two linear grooves 302 is too far, and the infiltration effect of the wound core is still poor, with too little improvement in the dynamic performance of the battery cell to meet the electrical performance requirements of the battery cell.

[0096] Optionally, the value of A3 is any value among 0.3 mm, 0.5 mm, 0.8 mm, 1 mm, 1.5 mm, 1.8 mm, 2 mm, 2.5 mm, 2.8 mm, 3 mm or a value between any two of them.

[0097] Furthermore, as Figure 11 shown, along the width direction of the second pole piece 3, the linear grooves 302 are discontinuously arranged, that is, there is a discontinuity. In this way, the processing efficiency of the pole piece can be improved. Along the width direction of the second pole piece 3, the height of the discontinuity is A4, satisfying 0.5 mm ≤ A4 ≤ 4 mm.

[0098] It should be noted that if A4 < 0.5 mm, the discontinuity height of the linear groove 302 is too small, and it is difficult to ensure the processing accuracy of the equipment; if A4 > 4 mm, the discontinuity height of the linear groove 302 is too large, resulting in a decrease in the height of the linear groove 302 itself, and further resulting in a still poor infiltration effect of the wound core, with too little improvement in the dynamic performance of the battery cell to meet the electrical performance requirements of the battery cell.

[0099] Optionally, the value of A4 is any value among 0.5 mm, 0.8 mm, 1 mm, 1.5 mm, 1.8 mm, 2 mm, 2.5 mm, 2.8 mm, 3 mm, 3.5 mm, 3.8 mm, 4 mm or a value between any two of them.

[0100] Furthermore, as Figure 11 and Figure 12 shown, along the winding direction, no linear grooves 302 are provided on both side edges of the second active layer 304.

[0101] Specifically, the width of the area where no linear grooves 302 are provided on the second active layer 304 is A5, satisfying 2 mm ≤ A5 ≤ 10 mm.

[0102] In this way, it is prevented that powder dropping occurs at the edge of the active layer of the second pole piece 3, causing safety problems.

[0103] It should be noted that if A5 < 2 mm, the linear groove 302 is likely to hit the edge of the pole piece during processing, and powder dropping is likely to occur during pole piece cutting, affecting the safety performance of the battery cell; if A5 > 10 mm, the area where no linear grooves 302 are provided is too large, resulting in a still poor infiltration effect of the wound core, with too little improvement in the dynamic performance of the battery cell to meet the electrical performance requirements of the battery cell.

[0104] Optionally, the value of A5 is any value among 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm or a value between any two of them.

[0105] In one embodiment, as Figure 1 shown, the first tab 6 and / or the second tab 9 is coated with tab glue 12, and the melting point range of the tab glue 12 is from 95 °C to 130 °C. Therefore, the melting point of the tab glue 12 is relatively low.

[0106] With such a setting, when the battery cell is in a high-temperature / high-pressure state, the tab glue 12 can quickly melt, thereby creating a movable space for the tabs, effectively avoiding the tabs pulling the current collector when the high-temperature electrode sheet expands, and preventing the problem of current collector breakage.

[0107] It should be noted that, in this embodiment, the first electrode sheet 1 is a positive electrode sheet, and the second electrode sheet 3 is a negative electrode sheet. Further, the active layer of the negative electrode sheet (i.e., the second active layer 304) uses a silicon-containing material, and the silicon element content is above 5%.

[0108] It should be further noted that by processing the concave portion 101 of the first electrode sheet 1 and the linear groove 302 of the second electrode sheet 3, the expansion of the battery is reduced.

[0109] The battery of this embodiment can be prepared according to the following method:

[0110] First step, preparation of the positive electrode sheet: Prepare the positive electrode active material slurry. After mixing the conductive agent and the PVDF adhesive solution evenly, then add lithium cobaltate and stir evenly to obtain the positive electrode active material layer slurry. Coat the positive electrode active material on the surface of the aluminum foil, and obtain the positive electrode sheet through baking, rolling, and slitting.

[0111] Among them, the positive electrode active material layer is composed of 97.6% by mass of lithium cobaltate, 1.05% by mass of PVDF, and 1.35% by mass of the conductive agent. The conductive agent is composed of conductive carbon black, single-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0112] Second step, preparation of the negative electrode sheet: Prepare the negative electrode active material slurry. After mixing 0.5% by mass of the conductive agent and 97% by mass of graphite powder evenly, then add deionized water, 1.3% by mass of carboxymethyl cellulose, and 1.2% by mass of styrene-butadiene rubber binder and stir evenly to obtain the negative electrode active material layer slurry. Coat the negative electrode active material slurry on the copper foil with carbon coating, and obtain the negative electrode sheet through baking, rolling, and slitting.

[0113] Third step, the positive and negative electrode sheets are rolled, slit, and wound to obtain a wound core.

[0114] Step 4: The aluminum-plastic film is punched by the die core to obtain a film shell. Among them, the thickness of the aluminum-plastic film shell is 30 μm - 200 μm.

[0115] Step 5: After the battery cell is put into the film shell, it undergoes encapsulation, baking, liquid injection (electrolyte), formation, sorting, secondary sealing, OCV (open circuit voltage), and packaging to obtain a lithium-ion battery. Among them, the electrolyte is a commercially available conventional electrolyte, and the lithium salt therein is LiFP6.

[0116] It can be understood that the active material in the positive active material layer may include one or more of lithium cobaltate, lithium iron phosphate, lithium nickel cobalt manganese, lithium nickel cobalt aluminum, lithium manganate, and lithium-rich manganese-based lithium. The negative active material layer may include one or more of natural graphite, artificial graphite, mesocarbon microbeads, lithium titanate, silicon negative electrode, silicon-carbon negative electrode, and alloy negative electrode. The positive electrode binder is mainly a polyvinylidene fluoride (PVDF)-type binder, and the negative electrode binder is mainly styrene-butadiene rubber. The conductive agent includes at least one of conductive carbon black, Ketjen black, single-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0117] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A battery cell, characterized in that: include: A winding core and a film shell, wherein a receiving cavity is formed in the film shell, the winding core is located in the receiving cavity, and the winding core comprises a straight section and arc sections located on both sides of the straight section; The winding core comprises a first pole piece (1), a diaphragm (2) and a second pole piece (3) which are stacked and wound, the first pole piece (1) and the second pole piece (3) having opposite polarities, the first pole piece (1) being located outside the second pole piece (3), and along the winding direction, the tail end (105) of the first pole piece (1) exceeds the tail end of the second pole piece (3), and the total number of folds of the first pole piece (1) is N, where N is a positive integer; A first colloid (4) is provided on the outer surface of the N-2 fold of the first pole piece (1) away from the winding center, the first colloid (4) is located in the straight section, and the tail end (105) of the first pole piece (1) covers a portion of the first colloid (4); The winding core also includes a second colloid (5), the second colloid (5) having a first bonding surface and a second bonding surface, the first bonding surface being bonded to the outer surface of the Nth fold of the first pole piece (1) away from the winding center, the outer surface of the N-2nd fold of the first pole piece (1) away from the winding center and the first colloid (4), and the second bonding surface being bonded to the inner wall surface of the accommodating cavity.

2. The battery cell according to claim 1, characterized in that: Along the winding direction, the total width of the first colloid (4) is L, and the bonding width between the first colloid (4) and the second colloid (5) is L1; Among them, L and L1 satisfy: L1 ≥ 3 mm and / or L1 / L>1 / 3.

3. The battery cell according to claim 1, characterized in that: Along the width direction of the first pole piece (1), the two side edges of the second pole piece (3) exceed the two side edges of the first pole piece (1), and the two side edges of the diaphragm (2) exceed the two side edges of the second pole piece (3); At least one side edge of the first colloid (4) extends beyond the adjacent side edge of the second pole piece (3) and is bonded to the diaphragm (2).

4. The battery cell according to claim 1, characterized in that: At least one first pole lug (6) is provided at the top of the first pole piece (1) along the height direction of the winding core; In the orthographic projection in the thickness direction of the winding core, the first colloid (4) at least partially overlaps with at least one of the first pole tabs (6), and the ratio of the width of the overlapping portion of the first colloid (4) and the first pole tab (6) to the width of the first pole tab (6) is 50% to 100%.

5. The battery cell according to claim 1, characterized in that: At least one first pole lug (6) is provided at the top of the first pole piece (1) along the height direction of the winding core; Along the thickness direction of the winding core, the first pole lug (6) is bent toward the first pole piece (1) at the N-1th bend to form a first bend portion (601); A third colloid (7) is provided on the outer surface of the N-1th fold of the first pole piece (1) away from the winding center, the third colloid (7) is arranged close to the edge of one side of the first pole piece (1) extending beyond the first pole ear (6), and the third colloid (7) is arranged extending along the winding direction; Along the height direction of the winding core, the side edge of the third colloid (7) exceeds the side edge of the second pole piece (3) and is bonded to the diaphragm (2).

6. The battery cell according to claim 5, characterized in that: At least one second pole lug (9) is provided at the top of the second pole piece (3) along the height direction of the winding core; In the orthographic projection of the winding core in the thickness direction, along the width direction of the winding core, both side edges of all the first pole tabs (6) and the second pole tabs (9) do not exceed both side edges of the third colloid (7).

7. The battery cell according to claim 1, characterized in that: The winding core further comprises a fourth colloid (8), wherein the fourth colloid (8) is adhered to the bottom ends of the first pole piece (1) and the second pole piece (3) and extends along the thickness direction of the winding core; Along the thickness direction of the winding core, one end of the fourth colloid (8) is attached to the outer surface of the N-1 fold of the first pole piece (1) away from the winding center, and the other end of the fourth colloid (8) is attached to the outer surface of the N-1 fold of the first pole piece (1) away from the winding center and / or the outer surface of the N-2 fold of the first pole piece (1) away from the winding center; The fourth colloid (8) is spaced apart from the second colloid (5); and / or the fourth colloid (8) is spaced apart from the Nth folded tail end (105) of the first pole piece (1).

8. The battery cell according to claim 1, characterized in that: Along the height direction of the winding core, at least one first pole lug (6) is provided at the top of the first pole piece (1), and at least one second pole lug (9) is provided at the top of the second pole piece (3); the first pole piece (1) comprises a first current collector (103) and a first active layer (104) coated on at least one side surface of the first current collector (103); Along the winding direction, the first pole lug (6) or the second pole lug (9) closest to the tail end (105) of the first pole piece (1) is located at the i-th fold, and at least part of the surface of the first active layer (104) from the first fold to the i-th fold of the first pole piece (1) is provided with a recess (101); and / or, A concave portion (101) is formed on at least part of the surface of the first active layer (104) from the i+1th fold to the i+kth fold of the first pole piece (1), and the concave portion (101) is not provided on the surface of the first active layer (104) from the i+k+1th fold to the Nth fold of the first pole piece (1), wherein 2≤k≤5, and k is a positive integer; and / or, The number of folds from the i+k+1th fold to the Nth fold of the first pole piece (1) without the recess (101) and the total number of folds of the first pole piece (1) satisfy the following: 0.1≤(Nik) / N≤0.

4.

9. The battery cell according to claim 1, characterized in that: The peeling force between the second colloid (5) and the first colloid (4) is F1, and the peeling force between the first colloid (4) and the first electrode (1) is F2, wherein F1 and F2 satisfy: 0.1N / mm≤F1≤1N / mm; and / or, 0.05N / mm≤F2≤0.8N / mm; and / or, F1>F2.

10. The battery cell according to claim 1, characterized in that: The second pole piece (3) comprises a second current collector (303) and a second active layer (304) coated on at least one side of the second current collector (303), wherein the second active layer (304) is provided with a plurality of linear grooves (302) at intervals; and / or, The second active layer (304) is made of silicon-containing material, with a silicon content of more than 5%; and / or, Along the height direction of the winding core, at least one first pole ear (6) is provided at the top of the first pole piece (1), and at least one second pole ear (9) is provided at the top of the second pole piece (3), the total number of the first pole ears (6) and the second pole ears (9) is four, and / or the first pole ears (6) and / or the second pole ears (9) are coated with pole ear glue (12), and the melting point range of the pole ear glue (12) is 95°C to 130°C.

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