Battery cell and battery cell manufacturing method

Abstract

The invention relates to the technical field of batteries, and discloses a battery cell and a battery cell manufacturing method. The battery cell comprises a pole group; the packaging film comprises a main body part and a sealing edge connected to the peripheral side of the main body part, the main body part wraps the outer side of the pole group, the sealing edge connected to at least one side of the main body part is bent to form an edge folding structure, the edge folding structure is provided with a buffer part, the buffer part and the side face, connected with the edge folding structure, of the main body part are oppositely arranged, and the buffer part is of an elastic structure. The sealing edge, connected to at least one side of the main body part, in the packaging film is bent to form the folded edge structure, the buffer part is constructed on the folded edge structure, the folded edge structure in the bent state has certain elastic deformation capacity, and the buffer part is of an elastic structure and has a buffer function; and the folding edge structure and the buffer part can effectively absorb external impact and reduce direct damage of the external impact to the pole group in the main body part, so that the safety of the battery cell is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to an electrode core and a method for manufacturing the electrode core. Background Art

[0002] The electrode core mainly consists of a tab, an electrode group, and a packaging film. The packaging film encapsulates the electrode group and the tab, and the four peripheral edges of the packaging film are sealed by hot pressing to protect the electrode group by sealing. However, during the handling of the electrode core or during the operation of the electrode core in a vehicle, the electrode core is prone to external impact or extrusion. When the electrode core is subjected to external impact or extrusion, it is easy to damage the internal electrode group, resulting in situations such as the electrode core being deformed under pressure and short circuit inside the electrode core, leading to a decline or failure of the performance of the electrode core, which is relatively dangerous. Summary of the Invention

[0003] In view of this, the present invention provides an electrode core and a method for manufacturing the electrode core to solve the problem that the electrode core is easily damaged when subjected to external impact.

[0004] In a first aspect, the present invention provides an electrode core, comprising: an electrode group; a packaging film, including a main body portion and a sealing edge connected to the outer peripheral side of the main body portion. The main body portion wraps around the outside of the electrode group, and the sealing edge connected to at least one side of the main body portion is bent to form a folded edge structure. A buffer portion is provided on the folded edge structure, and the buffer portion is disposed opposite to the side surface of the main body portion where the folded edge structure is connected. The buffer portion is an elastic structure.

[0005] Beneficial effects: By setting the sealing edge connected to at least one side of the main body portion in the packaging film to be bent to form a folded edge structure and constructing a buffer portion on the folded edge structure, the folded edge structure in a bent state has a certain elastic deformation ability, and the buffer portion is an elastic structure, both of which have a buffering effect. Then, the folded edge structure and the buffer portion can effectively absorb external impact, reduce the direct damage of the external impact to the electrode group located inside the main body portion, thereby improving the safety of the electrode core. Moreover, the folded edge structure formed by bending can reduce the occupied space of the sealing edge, thereby facilitating the stacking of the electrode cores in the battery pack, improving the space utilization rate inside the battery pack, and the folded edge structure is formed by the sealing edge of the packaging film itself without connecting additional components to the packaging film, with a simple structure and easy to manufacture.

[0006] In an optional embodiment, along the thickness direction of the main body portion, the size of the main body portion is T, and the size of the buffer portion is W2, where 2 mm ≤ W2 ≤ T - 1 mm;

[0007] And / or, along the width direction of the main body portion, the size of the buffer portion is t, where the value range of t is: 1 mm ≤ t ≤ 5 mm; the plane where the width direction of the main body portion is located is perpendicular to the thickness direction of the main body portion.

[0008] Beneficial effects: By setting the dimension W2 of the buffer portion along the thickness direction of the main body portion to be in the range of 2 mm to T - 1 mm, a reasonable design dimension of the buffer portion along the height direction is obtained. This can not only ensure the smooth forming of the buffer portion and guarantee a good buffering effect to play a role in preventing mechanical shock, but also avoid the buffer portion occupying too much space and affecting the stacking of the battery cells in the battery pack, thus achieving a balance between the buffering effect and space utilization rate.

[0009] By setting the dimension t of the buffer portion along the width direction of the main body portion to be in the range of 1 mm to 5 mm, the dimension of the buffer portion along the width direction is controlled within a reasonable range. This can not only avoid the buffer portion failing under external impact, ensure that the buffer portion can effectively absorb external impact force, reduce the direct impact on the main body portion, thereby protecting the main body portion and the electrode group inside it from damage and improving the reliability of the overall structure, but also ensure the smooth forming of the buffer portion and avoid unnecessary space occupation, making the overall structure more compact.

[0010] In an optional implementation manner, the encapsulation film is formed by buckling a first film body and a second film body. Along the thickness direction of the encapsulation film, the total dimension of the first film body is greater than the total dimension of the second film body. The buffer portion corresponds to the side surface of the first film body, the second film body is located below the first film body, and the vertical distance between the lower surface of the sealing edge and the lower surface of the second film body is h0, where 0 ≤ h0 / T ≤ 1 / 3.

[0011] Beneficial effects: By setting the ratio h0 / T of the vertical distance h0 between the lower surface of the sealing edge and the lower surface of the second film body to the dimension T of the main body portion along the thickness direction to be in the range of 0 to 1 / 3, it can be ensured that the buffer portion can protect the electrode group as much as possible along the thickness direction, avoid too many electrode sheets on the electrode group not being protected by the buffer portion due to the excessive proportion of the dimension of the second film body along the thickness direction on the main body portion, and avoid the misalignment of the electrode sheets when being impacted, thereby avoiding the short circuit of the battery cell and improving the safety of the battery cell.

[0012] In an optional implementation manner, the folding edge structure includes a first folding section, a second folding section, and a third folding section. The third folding section is connected to the main body portion and extends along the height direction of the encapsulation film. The buffer portion is located on the third folding section. The second folding section is located on the side of the third folding section facing the main body portion along the width direction of the main body portion, and the first folding section is located between the third folding section and the second folding section.

[0013] Beneficial effects: By arranging the buffer part on the third folding section farthest from the main body part, when the battery cell is subjected to an external impact, the impact can be effectively absorbed through the buffering of the buffer part and each folding section in sequence, reducing the damage to the electrode group inside the main body part. Moreover, the buffer part is in direct contact with the external impact force first, and the buffer part has a good buffering effect, and also has a certain protective effect on each folding section, avoiding the direct damage of the folding section by the external impact force and causing the direct breakage of the encapsulation film. In addition, the first folding section located at the end of the sealing edge is received in the spaced space formed between the second folding section and the third folding section, which can prevent the end of the first folding section from scratching the main body part, further improving the safety performance.

[0014] In an optional implementation manner, the folding edge structure further includes a connecting section, the connecting section is connected between the main body part and the third folding section, and the third folding section is located above the connecting section; in the height direction of the encapsulation film, the distance between the midpoint of the buffer part and the lower surface of the sealing edge is a, and the distance between the first folding section and the lower surface of the sealing edge is b, where a and b satisfy the relational expression: 0.6 ≤ b / a ≤ 3.

[0015] Beneficial effects: By setting the relational expression that 0.6 ≤ b / a ≤ 3 between a and b, it can not only prevent the tail of the first folding section from piercing the air bag during the impact of the battery cell, thus ensuring the safety of the battery cell, but also ensure that the buffer part has a sufficient proportion relative to the folding edge structure in the height direction, thereby ensuring the anti-collision effect and further improving the safety of the battery cell.

[0016] In an optional implementation manner, in the height direction of the encapsulation film, the value range of the distance a between the midpoint of the buffer part and the lower surface of the sealing edge is: 1mm < a ≤ 20mm;

[0017] And / or, the value range of the distance b between the first folding section and the lower surface of the sealing edge is: 1mm < b ≤ 40mm.

[0018] Beneficial effects: By setting the distance a in the thickness direction between the midpoint of the buffer part and the lower surface of the sealing edge to be within the range of 1mm to 20mm, it can not only ensure the smooth formation of the buffer part and ensure that the buffer part has a good buffering effect, but also avoid the buffer part occupying too much space and affecting the stacking of the battery cell in the battery pack;

[0019] By setting the distance b between the first folding section and the lower surface of the sealing edge to be within the range of 1mm to 40mm, it can not only prevent the first folding section from piercing the air bag, thus ensuring the safety of the battery cell, but also ensure the smooth bending and forming of the folding edge structure and improve the reliability of the structure.

[0020] In an alternative embodiment, along the height direction of the encapsulation film, the lower surface of the connecting section is the lowest point of the hem structure, and the distance between the lower surface of the connecting section and the lower surface of the main body is h2, where the value range of h2 is: h2 ≥ 0.1 mm;

[0021] And / or, the hem structure further includes a transition section, which is connected between the upper end of the third folding section and the upper end of the second folding section. Along the height direction of the encapsulation film, the highest point of the transition section is the highest point of the hem structure, and the distance between the highest point of the transition section and the upper surface of the main body is h1, where the value range of h1 is: h1 ≥ 0.1 mm.

[0022] Beneficial effects: By setting the distance h2 between the lower surface of the connecting section and the lower surface of the main body to be greater than or equal to 0.1 mm, it is ensured that there is a sufficient distance between the lowest point of the hem structure and the lowest point of the main body, avoiding the situation that the lowest point of the hem structure is too close to the lower surface of the main body and affecting the stacking of the battery cells in the whole package, thereby improving the space utilization rate inside the battery pack;

[0023] The third folding section and the second folding section are connected by a transition section, which ensures the smooth progress of the bending process of the second folding section relative to the third folding section. At the same time, by setting the distance h1 between the highest point of the transition section and the upper surface of the main body to be greater than or equal to 0.1 mm, it is ensured that there is a sufficient distance between the highest point of the hem structure and the highest point of the main body, avoiding the situation that the highest point of the hem structure is too close to the upper surface of the main body and affecting the stacking of the battery cells in the whole package, thereby further improving the space utilization rate inside the battery pack.

[0024] In an alternative embodiment, the buffer part is an air bag.

[0025] Beneficial effects: The structure is simple, easy to process, and has a low cost. The air bag has a good buffering effect, high reliability, and basically does not increase the weight of the battery cell, which is beneficial to realizing the lightweight of the battery cell.

[0026] In a second aspect, the present invention also provides a method for manufacturing a battery cell, which is used to manufacture the above-mentioned battery cell. The method for manufacturing a battery cell includes:

[0027] Welding the electrode group and the electrode tab, and placing them between the first plastic film and the second plastic film, where both the first plastic film and the second plastic film include a body area and an air bag area;

[0028] The first plastic film and the second plastic film are buckled to form a plastic film structure, and the edges of the plastic film structure are top-sealed and side-sealed on one side;

[0029] After injecting electrolyte into the inside of the plastic-sealed film structure and evacuating, the second side of the plastic-sealed film structure is side-sealed to form a first plastic seal on the plastic-sealed film structure to obtain a semi-finished battery cell;

[0030] The semi-finished battery cell is subjected to charge and discharge cycles to form an SEI film, and gas is generated inside the plastic-sealed film structure;

[0031] The gas inside the plastic-sealed film structure is driven to the air bag area, and a third plastic seal and a second plastic seal are sequentially processed in the air bag area. Among them, the third plastic seal is connected to the main body area, the second plastic seal is located between the third plastic seal and the first plastic seal, and a first air bag is formed between the second plastic seal and the third plastic seal;

[0032] The plastic-sealed film structure is cut from the side of the second plastic seal away from the first plastic seal to obtain a packaging film;

[0033] The edges of the packaging film with the second plastic seal and the third plastic seal are bent to obtain a folded edge structure.

[0034] Beneficial effects: By sequentially performing top-sealing, side-sealing, liquid injection, vacuum pumping, forming, etc. on the plastic-sealed film structure, the airtightness, consistency of the battery cell packaging, and the formation of the SEI film are ensured; after gas is generated inside the plastic-sealed film structure, by driving the gas to the air bag area, the accumulation of gas inside the battery cell is avoided, and the safety of the battery cell is improved; on the basis of the first plastic seal, the second plastic seal and the third plastic seal are processed on the plastic-sealed film structure, so that a part of the air bag area close to the main body part forms a first air bag, that is, a buffer part is formed by using the gas generated by the battery cell itself in combination with the structure of the packaging film. Finally, after bending and winding the edge where the buffer part is located, a folded edge structure with a buffer effect can be formed. The structure is simple, easy to process, has a low cost, and has a good buffer effect.

[0035] In an optional embodiment, along the width direction of the battery cell, the melting width of the third plastic seal is f, where the value range of f is: 3mm ≤ f ≤ 10mm;

[0036] And / or, along the width direction of the battery cell, the melting width of the second plastic seal is Z, where the value range of Z is: 2mm ≤ Z ≤ 10mm.

[0037] Beneficial effects: By setting the melting width f of the third plastic seal to be between 3mm and 10mm, it can not only ensure that the third plastic seal has sufficient structural strength to avoid the third plastic seal peeling and failing during the impact of the battery cell, thereby avoiding the communication between the first air bag and the main body part and ensuring the safety of the battery cell, but also avoid wasting materials and space, improve space utilization rate, and reduce costs;

[0038] By setting the melting width Z of the second plastic encapsulation to take values between 2 mm and 10 mm, it can not only ensure that the second plastic encapsulation has sufficient structural strength to avoid peeling failure of the second plastic encapsulation during the impact on the battery cell, thereby ensuring the effectiveness of the buffer part, but also avoid wasting materials and space, and facilitate the forming and maintaining stability of the flanging structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] 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 the description of the specific embodiments or the prior art. Obviously, the drawings in the following description 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.

[0040] Figure 1 A top view of a battery cell according to an embodiment of the present invention;

[0041] Figure 2 is Figure 1 a cross-sectional view taken along the A-A direction in

[0042] Figure 3 is Figure 1 a side view of the battery cell shown;

[0043] Figure 4 is Figure 3 a partial enlarged schematic view of the side with the flanging structure in

[0044] Figure 5 a schematic structural view of a semi-finished battery cell after the first plastic encapsulation according to an embodiment of the present invention;

[0045] Figure 6 a schematic structural view of a semi-finished battery cell after the second plastic encapsulation and the third plastic encapsulation according to an embodiment of the present invention;

[0046] Figure 7 a schematic structural view of a battery cell before flanging according to an embodiment of the present invention.

[0047] Description of the reference numerals:

[0048] 1. Electrode group; 2. Encapsulation film; 201. Main body part; 202. Sealing edge; 203. Flanging structure; 204. First folding section; 205. Second folding section; 206. Third folding section; 207. Connection section; 208. Transition section; 210. First film body; 220. Second film body; 3. Buffer part; 4. Tab; 5. Plastic encapsulation film structure; 501. Body area; 502. Air bag area; 503. Second air bag; 601. First plastic encapsulation; 602. Second plastic encapsulation; 603. Third plastic encapsulation. Detailed Implementation Modes

[0049] 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. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0050] The following combines Figures 1 to 7 , to describe the embodiments of the present invention.

[0051] According to an embodiment of the present invention, on the one hand, a battery cell is provided. As Figures 1 to 4 shown, the battery cell includes: a pole group 1 and a packaging film 2. The packaging film 2 includes a main body portion 201 and a sealing edge 202 connected to the outer peripheral side of the main body portion 201. The main body portion 201 wraps around the outside of the pole group 1. The sealing edge 202 connected to at least one side of the main body portion 201 is bent to form a folded edge structure 203. A buffer portion 3 is provided on the folded edge structure 203. The buffer portion 3 is disposed opposite to the side surface of the main body portion 201 where the folded edge structure 203 is connected. The buffer portion 3 is an elastic structure. Among them, the main body portion 201 includes two large surfaces corresponding to the larger surfaces of the pole group 1, and four side surfaces connected between the two relatively arranged large surfaces. The sealing edge 202 is connected to the side surface of the main body portion 201. The outer peripheral side of the main body portion 201 refers to the side of the four side surfaces of the main body portion 201 that is away from the central position inside the main body portion 201.

[0052] When applying the battery cell of this embodiment, by setting the sealing edge 202 connected to at least one side of the main body portion 201 in the packaging film 2 to be bent to form a folded edge structure 203, and constructing a buffer portion 3 on the folded edge structure 203, the folded edge structure 203 in a bent state has a certain elastic deformation ability, and the buffer portion 3 is an elastic structure, both having a buffering effect. Then, the folded edge structure 203 and the buffer portion 3 can effectively absorb external impacts, reduce direct damage to the pole group 1 located inside the main body portion 201 caused by external impacts, thereby improving the safety of the battery cell. Moreover, the folded edge structure 203 formed by bending can reduce the occupied space of the sealing edge 202, thereby facilitating the stacking of the battery cells in the battery pack, improving the space utilization rate inside the battery pack, and the folded edge structure 203 is formed by the sealing edge 202 of the packaging film 2 itself without connecting additional components to the packaging film 2, with a simple structure and easy to manufacture.

[0053] It should be noted that the folded edge structure 203 and the buffer portion 3 are disposed opposite to the side surface of the main body portion 201, and the anti-collision effect is to absorb the impact force of the external force towards this side surface. Further combine Figure 3It is described that the hemming structure 203 and the buffer part 3 are located on the right side of the main body part 201 along the width direction of the main body part 201, so that the impact force from right to left can be buffered. Among them, the width direction refers to Figure 3 the "width direction" indicated by the arrow in Figure 3 and the left and right refer to the "left and right" indicated by the arrow in

[0054] Preferably, the battery cell is a soft-pack battery cell, the encapsulation film 2 is an aluminum-plastic film, and a sealing edge 202 is connected to each of the four sides of the main body part 201. The number of the sealing edges 202 is four, and at least one of the four sealing edges 202 forms the hemming structure 203. Taking the Figures 1 to 4 shown battery cell as an example, the tab ears are led out from both ends of the battery cell, and the sealing edge 202 connected to one side of the main body part 201 is bent to form the hemming structure 203. The number of the hemming structures 203 is one, that is, one of the sealing edges 202 corresponding to the two side edges without tab ears forms the hemming structure 203; as an alternative embodiment, when the battery cell has a structure with tab ears led out from one end, two of the three side edges without tab ears can also be configured as the hemming structure 203.

[0055] In one embodiment, the buffer part 3 is an airbag. It should be noted that during the production process of the battery cell, formation is an essential step. After the battery cell undergoes the formation step, gas is generated inside the battery cell. By dividing the area corresponding to the airbag on the encapsulation film 2 and using the gas generated by the battery cell to form the airbag, the buffer part 3 can be directly formed on the encapsulation film 2. The structure is simple, easy to process, and the cost is low. The airbag has a good buffering effect, high reliability, and basically does not increase the weight of the battery cell, which is beneficial to realizing the lightweight of the battery cell.

[0056] In one embodiment, further combined with Figure 4 shown, along the thickness direction of the main body part 201, the size of the main body part 201 is T, and the size of the buffer part 3 is W2. Among them, 2 mm ≤ W2 ≤ T - 1 mm. If W2 is less than 2 mm, the size of the buffer part 3 along the height direction is too small, making it difficult to form, and the anti-impact effect is not obvious; if W2 is greater than T - 1 mm, the size of the buffer part 3 along the height direction is too large, approaching the upper and lower surfaces of the main body part 201, which affects the stacking of the battery cells in the battery pack. Among them, the thickness direction refers to Figure 4 the "thickness direction" indicated by the arrow in Figure 4 and the upper and lower surfaces refer to the surfaces in the direction of "up and down" indicated by the arrow in

[0057] Therefore, by setting the dimension W2 of the buffer portion 3 in the thickness direction of the main body portion 201 to be within the range of 2 mm to T - 1 mm, a reasonable design dimension of the buffer portion 3 in the height direction is obtained. This can not only ensure the smooth molding of the buffer portion 3 and ensure that the buffer portion 3 has a good buffering effect to play a role in preventing mechanical shock, but also avoid the buffer portion 3 occupying too much space and affecting the stacking of the battery cells in the battery pack, thus achieving a balance between the buffering effect and space utilization rate.

[0058] In one embodiment, the value range of the dimension T of the main body portion 201 in the thickness direction is: 1.5 mm ≤ T ≤ 100 mm, which ensures that the battery cell has a reasonable dimension in the thickness direction. This can not only avoid insufficient energy of the battery cell due to too small a dimension of the main body portion 201 in the thickness direction, but also avoid problems such as too large a thickness of the battery cell and high heat generation due to too large a dimension of the main body portion 201 in the thickness direction. Therefore, by setting the dimension T of the main body portion 201 in the thickness direction to be within the range of 1.5 mm to 100 mm, it can not only ensure that the battery cell has sufficient energy, but also ensure the safety of the battery cell.

[0059] In one embodiment, along the width direction of the main body portion 201, the dimension of the buffer portion 3 is t, where the value range of t is: 1 mm ≤ t ≤ 5 mm; the plane where the width direction of the main body portion 201 is located is perpendicular to the height direction of the main body portion 201. Further combined with Figures 1 to 4 As shown, the flanging structure 203 is arranged on one side of the main body portion 201 along the width direction of the main body portion 201, and the width direction of the main body portion 201 refers to Figures 1 to 4 the "width direction" indicated by the arrow in

[0060] It should be noted that if t is less than 1 mm, the dimension of the buffer portion 3 in the width direction is too small, and the buffering effect on the external impact force is poor, and the anti-collision effect is not obvious, and it is easy to fail under the action of the external impact force; if t is greater than 5 mm, the dimension of the buffer portion 3 in the width direction is too large, occupying too much space and being difficult to process and form. Therefore, by setting the dimension t of the buffer portion 3 along the width direction of the main body portion 201 to be within the range of 1 mm to 5 mm, the dimension of the buffer portion 3 in the width direction is controlled within a reasonable range. This can not only avoid the failure of the buffer portion 3 under external impact, ensure that the buffer portion 3 can effectively absorb the external impact force, reduce the direct impact on the main body portion 201, thereby protecting the main body portion 201 and the electrode group 1 inside it from damage, and improving the reliability of the overall structure, but also ensure the smooth molding of the buffer portion 3, and at the same time avoid unnecessary space occupation, making the overall structure more compact.

[0061] In one embodiment, the encapsulation film 2 is formed by buckling a first film body 210 and a second film body 220. Along the thickness direction of the encapsulation film 2, the total size of the first film body 210 is larger than that of the second film body 220. The buffer portion 3 corresponds to the side surface of the first film body 210. The second film body 220 is located below the first film body 210. The vertical distance between the lower surface of the sealing edge 202 and the lower surface of the second film body 220 is h0, where 0 ≤ h0 / T ≤ 1 / 3. Here, the lower side refers to Figure 4 the side in the direction indicated by the "down" arrow in Figure 4 , and the lower surface refers to Figure 4 the surface in the direction indicated by the "down" arrow in Figure 4 ; the units of h0 and T are both mm. It should be noted that the first film body 210 includes a first pit and a first side edge surrounding and connecting to the edge of the opening end of the first pit. The second film body 220 includes a second pit and a second side edge surrounding and connecting to the edge of the opening end of the second pit. After the first film body 210 and the second film body 220 are buckled along the thickness direction, the first pit and the second pit are opposite to each other and form an accommodation space. The electrode group 1 is located in this accommodation space. The first side edge and the second side edge are opposite to each other and form a sealing edge 202 after heat sealing; the side surface of the first film body 210 refers to the surface where the side wall of the first pit is located; the depression depth of the first pit is greater than that of the second pit.

[0062] By setting the total size of the first film body 210 along the thickness direction to be larger than that of the second film body 220 along the thickness direction, after the first film body 210 and the second film body 220 are buckled to form the encapsulation film 2, the sealing edge 202 that is not bent is closer to the bottom surface of the second pit, that is, the connection position of the sealing edge 202 and the main body portion 201 is eccentrically arranged along the thickness direction. By setting the buffer portion 3 to correspond to the side surface of the first film body 210, the buffer portion 3 is arranged as close to the middle along the thickness direction of the main body portion 201 as possible, so as to ensure that when the buffer portion 3 is impacted in the direction towards the main body portion 201, the effective anti-collision buffer contact surface between the buffer portion 3 and the main body portion 201 is located as close to the middle position along the thickness direction of the main body portion 201 as possible, and the anti-collision effect is better.

[0063] It should be noted that along the thickness direction of the main body 201, the total dimension of the main body 201 includes the vertical distance h0 between the lower surface of the edge seal 202 and the lower surface of the second film body 220, the vertical distance between the upper surface of the edge seal 202 and the upper surface of the first film body 210, and the body thickness of the edge seal 202. Among them, the body thickness of the edge seal 202 is relatively small. By setting 0≤h0 / T≤1 / 3, the total thickness of the second film body 220 is made smaller than the total thickness of the first film body 210, ensuring that the connection position between the edge seal 202 and the main body 201 is eccentrically arranged along the thickness direction. If h0 / T is greater than 1 / 3, the ratio is too large, and the position of the buffer part 3 in the thickness direction is too high. Too much of the pole group 1 is located within the second film body 220, and this part cannot be protected by the buffer part 3. After the battery cell is subjected to an external impact, the pole pieces of the part of the pole group 1 located within the second film body 220 are easily impacted and displaced, resulting in an internal short circuit of the battery cell. Among them, when h0 / T = 0, there is no pit on the second film body 220.

[0064] Therefore, by setting the ratio h0 / T of the vertical distance h0 between the lower surface of the edge seal 202 and the lower surface of the second film body 220 to the dimension T of the main body 201 along the thickness direction to take values between 0 and 1 / 3, it can be ensured that the buffer part 3 forms protection for the pole group 1 as much as possible along the thickness direction, avoiding that too many pole pieces of the pole group 1 cannot be protected by the buffer part 3 due to the excessive proportion of the dimension of the second film body 220 in the main body 201 along the thickness direction, avoiding the displacement of the pole pieces when impacted, and thus avoiding the short circuit of the battery cell and improving the safety of the battery cell.

[0065] Take different parameter values of h0 / T to manufacture battery cells, conduct impact tests on the battery cells, disassemble the battery cells after the impact tests are completed, and observe the damage conditions of the pole groups to experimentally verify the influence of different values of h0 / T on the battery cells.

[0066] Table 1 Influence of different values of h0 / T on battery cells

[0067]

[0068] As can be seen from Table 1, for the battery cells of Embodiment 1 to Embodiment 4, the values of h0 / T are all within the range defined in this application. After the impact tests, when disassembling the battery cells, it is found that the pole group inside the packaging film 2 is in good condition and the pole pieces are not displaced. For the battery cells of Comparative Case 1 to Comparative Case 2, the values of h0 / T are greater than 1 / 3 and are not within the range defined in this application. After the impact tests, when disassembling the battery cells, it is found that the pole pieces located in the impact pits of the second film body are displaced and the pole group is damaged.

[0069] In summary, when the ratio h0 / T of the vertical distance h0 between the lower surface of the edge seal 202 and the lower surface of the second film body 220 and the dimension T of the main body 201 along the thickness direction is set between 0 and 1 / 3, the buffer portion 3 can provide effective anti-collision protection for the pole group 1 to avoid dislocation of the pole piece when impacted.

[0070] In one embodiment, the vertical distance h0 between the lower surface of the edge seal 202 and the lower surface of the second film body 220 has a value range of: 0mm≤h0≤5mm. If h0 is greater than 5mm, the vertical distance between the lower surface of the edge seal 202 and the lower surface of the second film body 220 is too large, which will cause the size of the second film body 220 along the thickness direction to account for too large a proportion of the main body 201, resulting in the buffer part 3 not being able to provide a good buffer protection for the electrode group 1. Therefore, by setting h0 to a value within the range of 0 to 5mm, it is possible to avoid the size of the second film body 220 along the thickness direction to account for too large a proportion of the main body 201, and ensure that the buffer part 3 provides as much protection as possible to the electrode group 1 along the thickness direction.

[0071] In one embodiment, further combining Figure 4 As shown, the folding structure 203 includes a first folding segment 204, a second folding segment 205 and a third folding segment 206. The third folding segment 206 is connected to the main body 201 and extends along the height direction of the packaging film 2. The buffer portion 3 is located on the third folding segment 206. The second folding segment 205 is located on the side of the third folding segment 206 facing the main body 201 along the width direction of the main body 201. The first folding segment 204 is located between the third folding segment 206 and the second folding segment 205. The folded edge structure 203 is formed by bending and winding the first folded segment 204, the second folded segment 205 and the third folded segment 206 in sequence, so that the edge seal 202 is wound and gathered, which has a certain buffering effect. At the same time, by arranging the buffer part 3 on the third folded segment 206 located farthest from the main body 201, when the battery cell is subjected to external impact, it can be buffered by the buffer part 3 and each folded segment in sequence, which can effectively absorb the external impact and reduce the damage to the pole group 1 inside the main body 201. In addition, the buffer part 3 is first in direct contact with the external impact force. The buffer part 3 has a good buffering effect and a certain protective effect on each folded segment, thereby preventing the external impact force from directly damaging the folded segment and causing direct damage to the packaging film 2. In addition, the first folded segment 204 located at the tail end of the edge seal 202 is received in the interval space formed between the second folded segment 205 and the third folded segment 206, which can prevent the end of the first folded segment 204 from scratching the main body 201, thereby further improving safety.

[0072] Preferably, the folded edge structure 203 is bound by tape to increase stability.

[0073] In one embodiment, further combining Figure 4As shown, the hemming structure 203 further includes a connecting section 207. The connecting section 207 is connected between the main body section 201 and the third folding section 206, and the third folding section 206 is located above the connecting section 207. In the height direction of the encapsulation film 2, the distance between the midpoint of the buffer section 3 and the lower surface of the sealing edge 202 is a, and the distance between the first folding section 204 and the lower surface of the sealing edge 202 is b. Among them, the relationship between a and b satisfies the formula: 0.6 ≤ b / a ≤ 3. Here, the upper side refers to Figure 4 the side in the direction of "up" indicated by the arrow in Figure 4 and the lower surface refers to the surface in the direction of "down" indicated by the arrow in

[0074] It should be noted that the connecting section 207 and the unbent sealing edge 202 are in the same plane. By setting the third folding section 206 above the connecting section 207, it can be ensured that other parts of the hemming structure 203 except the connecting section 207 can correspond to the first film body 210 on the upper side, so as to ensure that the buffer section 3 is arranged as centrally as possible along the thickness direction of the main body section 201; a reflects the size of the buffer section 3 in the thickness direction, and b reflects the size of the first folding section 204 in the thickness direction. The buffer section 3 is an airbag, and the midpoint of the buffer section 3 in the height direction is the position with the largest size of the buffer section 3 in the width direction. If b / a is less than 0.6, in the thickness direction, the first folding section 204 is too small relative to the buffer section 3, and the end of the first folding section 204 far from its connection with the second folding section 205 is too close to the midpoint of the buffer section 3. Then, when the battery cell is impacted, the end of the first folding section 204 is likely to pierce the airbag. If b / a is greater than 3, the buffer section 3 is too small relative to the first folding section 204, resulting in too small a proportion of the buffer section 3 in the total size of the hemming structure 203 in the thickness direction, and the anti-collision effect is not obvious.

[0075] Therefore, by setting the relationship between a and b to satisfy 0.6 ≤ b / a ≤ 3, it can not only prevent the end of the first folding section 204 from piercing the airbag during the impact of the battery cell, thus ensuring the safety of the battery cell, but also ensure that the buffer section 3 has a sufficient proportion relative to the hemming structure 203 in the height direction, thereby ensuring the anti-collision effect and further improving the safety of the battery cell.

[0076] Battery cells are made by using different values of the ratio b / a between the distance b between the first folding section 204 and the lower surface of the sealing edge 202 and the distance a between the midpoint of the buffer section 3 and the lower surface of the sealing edge 202. The battery cells are subjected to impact tests, and the above test results are recorded to verify the influence of different parameters on the performance of the battery cells. Among them, the impact test of the battery cell is to apply an impact force to the hemming structure 203 from the outside of the battery cell, and observe the damaged condition of the battery cell after the experiment.

[0077] Table 2 Influence of different values of b / a on the battery cell

[0078] b / a Test results Implementation case 5 0.6 No abnormality in the cell impact test Implementation case 6 3 No abnormality in the cell impact test Implementation case 7 1 No abnormality in the cell impact test Comparison case 3 0.58 Abnormality in the cell impact test, the folded edge tail pierces the airbag Comparison case 4 0.55 Abnormality in the cell impact test, the folded edge tail pierces the airbag

[0079] As can be seen from Table 2, for the battery cells of Embodiment 5 to Embodiment 7, the value of b / a is within the range defined in the present application, and there is no abnormality in the impact test of the battery cells; while for the battery cells of Comparative Case 3 to Comparative Case 4, the value of b / a is less than 0.6, which is not within the range defined in the present application, and the impact test of the battery cells is abnormal, and the airbag of the buffer part 3 is punctured at the folded edge tail.

[0080] Experiments show that under the same impact conditions, the battery cell of the present embodiment can avoid the airbag of the buffer part 3 being punctured at the folded edge tail and significantly improve the impact resistance of the battery cell.

[0081] In addition, if b / a is greater than 3, the buffer part 3 is too small relative to the first folded section 204, and the proportion of the buffer part 3 in the total size of the folded edge structure 203 in the thickness direction is too small, and the anti-collision effect is not obvious.

[0082] In summary, by setting the relationship between a and b to satisfy 0.6 ≤ b / a ≤ 3, it is possible to avoid the tail of the first folded section 204 puncturing the airbag during the impact of the battery cell, thereby ensuring the safety of the battery cell, and it is also possible to ensure that the buffer part 3 has a sufficient proportion relative to the folded edge structure 203 in the height direction, thereby ensuring the anti-collision effect and further improving the safety of the battery cell.

[0083] In one embodiment, in the height direction of the packaging film 2, the value range of the distance a between the midpoint of the buffer part 3 and the lower surface of the sealing edge 202 is: 1 mm < a ≤ 20 mm. If a is less than or equal to 1 mm, the size of the buffer part 3 in the thickness direction is too small, making it difficult to form, and the anti-impact effect is not obvious; if a is greater than 20 mm, the size of the buffer part 3 in the height direction is too large, too close to the surfaces on both sides of the main body part 201 in the thickness direction, and even the size of the buffer part 3 in the thickness direction is greater than the size of the main body part 201 in the thickness direction, affecting the stacking of the battery cells in the battery pack. Therefore, by setting the distance a between the midpoint of the buffer part 3 and the lower surface of the sealing edge 202 in the thickness direction to be within the range of 1 mm to 20 mm, it is possible to ensure the smooth formation of the buffer part 3, ensure that the buffer part 3 has a good buffer effect, and avoid the buffer part 3 occupying too much space and affecting the stacking of the battery cells in the battery pack.

[0084] In one embodiment, the value range of the distance b between the first folded segment 204 and the lower surface of the sealing edge 202 is: 1 mm < b ≤ 40 mm. If b is less than or equal to 1 mm, the dimension of the first folded segment 204 in the thickness direction is too small, and the end of the first folded segment 204 is likely to pierce the airbag during the external impact on the battery cell. If b is greater than 40 mm, the dimension of the first folded segment 204 in the thickness direction is too large, which may interfere with the connecting segment 207 connected between the second folded segment 205 and the third folded segment 206, resulting in difficulty in bending and forming the folded edge structure 203. Therefore, by setting the distance b between the first folded segment 204 and the lower surface of the sealing edge 202 within the range of 1 mm to 40 mm, it is possible to avoid the first folded segment 204 from piercing the airbag, thus ensuring the safety of the battery cell, and at the same time ensuring the smooth bending and forming of the folded edge structure 203, improving the reliability of the structure.

[0085] In one embodiment, further in combination with Figure 4 As shown, along the height direction of the packaging film 2, the lower surface of the connecting segment 207 is the lowest point of the folded edge structure 203, and the distance between the lower surface of the connecting segment 207 and the lower surface of the main body portion 201 is h2, where the value range of h2 is: h2 ≥ 0.1 mm. Herein, the lower surface refers to the Figure 4 surface in the direction indicated by the arrow "down" in

[0086] In one embodiment, the folded edge structure 203 further includes a transition segment 208, and the transition segment 208 is connected between the upper end of the third folded segment 206 and the upper end of the second folded segment 205. Along the height direction of the packaging film 2, the highest point of the transition segment 208 is the highest point of the folded edge structure 203, and the distance between the highest point of the transition segment 208 and the upper surface of the main body portion 201 is h1, where the value range of h1 is: h1 ≥ 0.1 mm. Herein, the highest point refers to along Figure 4The middle arrow points to the uppermost position in the "up and down" direction; the highest point of the transition section 208 is the position on the folding structure 203 that is closest to the upper surface of the main body 201 in the height direction. The third folding section 206 is connected to the second folding section 205 through the transition section 208 to ensure that the second folding section 205 is smoothly bent relative to the third folding section 206. At the same time, by setting the distance h1 between the highest point of the transition section 208 and the upper surface of the main body 201 to be greater than or equal to 0.1 mm, it is ensured that there is a sufficient distance between the highest point of the folding structure 203 and the highest point of the main body 201, avoiding the highest point of the folding structure 203 being too close to the upper surface of the main body 201 and affecting the stacking of the battery cells in the whole package, thereby further improving the space utilization inside the battery pack.

[0087] According to an embodiment of the present invention, on the other hand, a method for manufacturing a battery cell is provided. The method for manufacturing a battery cell is used to manufacture the above-mentioned battery cell. Figures 5 to 7 The battery cell manufacturing method comprises the following steps:

[0088] Step S101 : welding the electrode group 1 and the electrode tab 4 , and placing them between a first plastic film and a second plastic film, wherein the first plastic film and the second plastic film both include a body region 501 and an air pocket region 502 .

[0089] Step S102: the first plastic film and the second plastic film are buckled together to form a plastic film structure 5, and the edge of the plastic film structure 5 is top-sealed and the first side is side-sealed.

[0090] It should be noted that the plastic film structure 5 is the structure of the packaging film 2 before cutting, the first plastic film is the structure of the first film body 210 before cutting, the second plastic film is the structure of the second film body 220 before cutting, the main body area 501 corresponds to the main body 201 on the packaging film 2 after cutting, the air pocket area 502 is connected to one side of the main body area 501, and the air pocket area 502 is connected to the main body area 501. Figure 5 The middle dotted line is the dividing line; the top seal refers to the edge of the plastic film structure 5. Figure 5 The two sides of the longitudinal direction are plastic-sealed, and the side of the top seal is provided with a pole ear 4; the first side refers to the side along Figure 5 A side edge closer to the electrode group 1 on both sides of the "width direction" indicated by the middle arrow; after the top sealing and the side sealing of the first side of the edge of the plastic film structure 5 are performed. The second side of the plastic film structure 5 is the opening side, wherein the second side refers to the side of the plastic film structure 5 opposite to the first side along the width direction.

[0091] Step S103: After injecting electrolyte into the plastic film structure 5 and evacuating the inside, side-sealing the second side of the plastic film structure 5 is performed, and a first plastic sealing 601 is formed on the plastic film structure 5 to obtain a semi-finished battery cell.

[0092] Specifically, electrolyte is injected into the second side of the plastic-sealed film structure 5 and evacuated; after side-sealing the second side of the plastic-sealed film structure 5, the plastic-sealed film structure 5 forms a closed bag-like structure as shown in Figure 5 and the electrode assembly 1 is encapsulated in the bag.

[0093] Step S104: Perform charge and discharge cycles on the semi-finished battery cell to form the SEI film and generate gas inside the plastic-sealed film structure 5.

[0094] It should be noted that the above step S104 is the formation process of the battery cell; the SEI film (Solid Electrolyte Interface membrane) is an important component in a lithium-ion battery, with the characteristics of a solid electrolyte. The SEI film is formed during the first charge and discharge process and covers the surface of the electrode plate. Gas is generated during the formation of the SEI film. To ensure the safety of the battery cell, the generated gas needs to be discharged.

[0095] Step S105: Drive the gas inside the plastic-sealed film structure 5 to the airbag area 502, and successively process the third plastic seal 603 and the second plastic seal 602 in the airbag area 502. Among them, the third plastic seal 603 is connected to the body area 501, the second plastic seal 602 is located between the third plastic seal 603 and the first plastic seal 601, and a first airbag is formed between the second plastic seal 602 and the third plastic seal 603.

[0096] It should be noted that by driving the gas inside the plastic-sealed film structure 5 to the airbag area 502, it can be ensured that there is no gas in the area where the electrode assembly 1 is located, and the safety of the battery cell after forming is guaranteed. After successively passing through the third plastic seal 603 and the second plastic seal 602, a semi-finished battery cell structure as shown in Figure 6 is formed. Further, as shown in Figure 6 , the first plastic seal 601, the second plastic seal 602, and the third plastic seal 603 all extend along the length direction of the plastic-sealed film structure 5 and are all vacuum plastic seals. The first airbag formed between the second plastic seal 602 and the third plastic seal 603 is the airbag serving as the buffer part 3. Among them, the length direction refers to the Figure 6 "length direction" indicated by the arrow in Figure 1 and is the same as the length direction of the battery cell shown in

[0097] In addition, a second airbag 503 is formed between the second plastic seal 602 and the first plastic seal 601. The second airbag 503 stores gas, and part of the area of the second airbag 503 is cut off during subsequent processes.

[0098] It should be noted that the entire plastic-sealed film structure 5 is vacuum plastic-sealed in the order of the first plastic seal 601, then the third plastic seal 603, and finally the second plastic seal 602 to obtain as shown inFigure 6 The semi-finished battery cell structure shown, where the third plastic sealing 603 is processed before the second plastic sealing 602. The third plastic sealing 603 separates the airbag area 502 from the body area 501, which can ensure that during the process of forming the first airbag, the gas in the airbag area 502 will not enter the body area 501 again, thereby avoiding secondary gas evacuation of the body area 501, simplifying the processing technology, and ensuring the reliability and safety of the battery cell.

[0099] Step S106: Cut the plastic sealing film structure 5 from the side of the second plastic sealing 602 away from the first plastic sealing 601 to obtain the encapsulation film 2.

[0100] Among them, the cutting line is located on the second airbag 503. When cutting, the part on the second airbag 503 away from the second plastic sealing 602 is cut off, and a part of the section of the second airbag 503 close to the second plastic sealing 602 is not cut off, and the unplastic-sealed area of this section is reserved for hemming; after cutting, the battery cell structure shown in Figure 7 is obtained. At this time, the sealing edges 202 on the battery cell are all in a flattened state.

[0101] Step S107: Bend the sealing edges of the encapsulation film 2 with the second plastic sealing 602 and the third plastic sealing 603 to obtain a hem structure 203. By forming the hem structure 203, the battery cell shown in Figure 1 can be obtained.

[0102] Applying the battery cell manufacturing method of this embodiment, by successively performing steps such as top sealing, side sealing, liquid injection, vacuum pumping, and formation on the plastic sealing film structure 5, the airtightness and consistency of the battery cell encapsulation and the formation of the SEI film are ensured; after generating gas inside the plastic sealing film structure, by driving the gas to the airbag area, the accumulation of gas inside the battery cell is avoided, and the safety of the battery cell is improved; the second plastic sealing 602 and the third plastic sealing 603 are processed on the basis of the first plastic sealing 601 of the plastic sealing film structure 5, so that a part of the airbag area close to the main body part 201 forms the first airbag, that is, a buffer part 3 is formed by using the gas generated by the battery cell itself in combination with the structure of the plastic sealing film structure 5. Finally, after bending and winding the sealing edge 202 where the buffer part 3 is located, a hem structure 203 with a buffer effect can be formed. The structure is simple, easy to process, has a low cost, and has a good buffer effect.

[0103] In one embodiment, further in combination with Figure 6 shown, along the width direction of the battery cell, the melting width of the third plastic sealing 603 is f, where the value range of f is: 3 mm ≤ f ≤ 10 mm. Among them, the width direction of the battery cell refers to the Figure 6 "width direction" indicated by the arrow in Figure 6The dimension in the "width direction" indicated by the arrow. It should be noted that the third plastic seal 603 is connected between the buffer part 3 and the main body part 201. If f is less than 3 mm, the width of the third plastic seal 603 is too small, resulting in insufficient sealing isolation strength between the first airbag as the buffer part 3 and the inner cavity of the battery cell. During the impact on the battery cell, the third plastic seal 603 is easily peeled off to form a through cavity, and the battery cell is damaged and fails. If f is greater than 10 mm, the width of the third plastic seal 603 is too large, wasting materials and space.

[0104] Therefore, by setting the melting width f of the third plastic seal 603 to be between 3 mm and 10 mm, it can not only ensure that the third plastic seal 603 has sufficient structural strength, avoid the third plastic seal 603 peeling off and failing during the impact on the battery cell, thereby preventing the first airbag from communicating with the main body part 201 and ensuring the safety of the battery cell, but also avoid wasting materials and space, improve space utilization rate, and reduce costs.

[0105] In one embodiment, along the width direction of the battery cell, the melting width of the second plastic seal 602 is Z, where the value range of Z is: 2 mm ≤ Z ≤ 10 mm. It should be noted that the second plastic seal 602 is located at the tail section of the sealing edge 202, corresponding to the formation of the second folding section 205 and the third folding section 206. Therefore, the second plastic seal 602 is relatively longer and has more folding edges compared to the third plastic seal 603. So when the airbag is impacted, the second plastic seal 602 is less stressed and not easily damaged, and the gas is not easily discharged. However, if the value of Z is too small, the second plastic seal 602 will still be peeled off when the airbag is impacted, resulting in the failure of the airbag seal. If Z is too large, it will waste materials, be too hard to fold during folding, and is prone to bounce back.

[0106] Therefore, by setting the melting width Z of the second plastic seal 602 to be between 2 mm and 10 mm, it can not only ensure that the second plastic seal 602 has sufficient structural strength, avoid the second plastic seal 602 peeling off and failing during the impact on the battery cell, thereby ensuring the effectiveness of the buffer part 3, but also avoid wasting materials and space, and facilitate the forming and maintaining stability of the folding edge structure 203.

[0107] 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: Pole group; The packaging film includes a main body and a sealing edge connected to the outer peripheral side of the main body, the main body is wrapped around the outside of the pole group, the sealing edge connected to at least one side of the main body is bent to form a folded edge structure, the folded edge structure is provided with a buffer portion, the buffer portion is arranged opposite to the side of the main body connected to the folded edge structure, and the buffer portion is an elastic structure.

2. The battery cell according to claim 1, characterized in that: Along the thickness direction of the main body, the size of the main body is T, and the size of the buffer portion is W2, wherein 2mm≤W2≤T-1mm; And / or, along the width direction of the main body, the size of the buffer portion is t, wherein the value range of t is: 1mm≤t≤5mm; and the plane where the width direction of the main body is located is perpendicular to the thickness direction of the main body.

3. The battery cell according to claim 2, characterized in that: The packaging film is formed by buckling a first film body and a second film body. Along the thickness direction of the packaging film, the total size of the first film body is larger than the total size of the second film body. The buffer portion corresponds to the side surface of the first film body. The second film body is located on the lower side of the first film body. The vertical distance between the lower surface of the edge seal and the lower surface of the second film body is h0, wherein 0≤h0 / T≤1 / 3.

4. The battery cell according to claim 1, characterized in that: The folding structure includes a first folding segment, a second folding segment and a third folding segment, the third folding segment is connected to the main body and extends along the height direction of the packaging film, the buffer portion is located on the third folding segment, the second folding segment is located on the side of the third folding segment facing the main body along the width direction of the main body, and the first folding segment is located between the third folding segment and the second folding segment.

5. The battery cell according to claim 4, characterized in that: The folding structure further includes a connecting section, wherein the connecting section is connected between the main body and the third folding section, and the third folding section is located on the upper side of the connecting section; In the height direction of the packaging film, the distance between the midpoint of the buffer portion and the lower surface of the edge seal is a, and the distance between the first fold segment and the lower surface of the edge seal is b, wherein a and b satisfy the relationship: 0.6≤b / a≤3.

6. The battery cell according to claim 5, characterized in that: In the height direction of the packaging film, the distance a between the midpoint of the buffer portion and the lower surface of the edge seal is in the range of: 1 mm < a ≤ 20 mm; And / or, a distance b between the first folded section and the lower surface of the edge seal has a value range of: 1 mm < b ≤ 40 mm.

7. The battery cell according to claim 5, characterized in that: Along the height direction of the packaging film, the lower surface of the connecting section is the lowest point of the folding structure, and the distance between the lower surface of the connecting section and the lower surface of the main body is h2, wherein the value range of h2 is: h2 ≥ 0.1 mm; And / or, the folding structure also includes a transition section, which is connected between the upper end of the third folding section and the upper end of the second folding section. Along the height direction of the packaging film, the highest point of the transition section is the highest point of the folding structure, and the distance between the highest point of the transition section and the upper surface of the main body is h1, where the value range of h1 is: h1≥0.1mm.

8. The battery cell according to any one of claims 1 to 7, characterized in that: The buffer portion is an air bag.

9. A method for manufacturing a battery cell, characterized in that: The battery cell manufacturing method is used to manufacture the battery cell according to any one of claims 1 to 8, and the battery cell manufacturing method comprises: Welding the electrode group and the electrode tab, and placing them between a first plastic film and a second plastic film, wherein the first plastic film and the second plastic film both include a body area and an air bag area; The first plastic sealing film and the second plastic sealing film are buckled together to form a plastic sealing film structure, and the edge of the plastic sealing film structure is top-sealed and the first side is side-sealed; After injecting electrolyte into the plastic film structure and evacuating the vacuum, side-sealing the second side of the plastic film structure is performed, and a first plastic sealing is formed on the plastic film structure to obtain a semi-finished battery cell; Performing charge and discharge cycles on the semi-finished battery cell to form a SEI film and generate gas inside the plastic film structure; The gas inside the plastic film structure is driven to the air pocket area, and the third plastic sealing and the second plastic sealing are sequentially processed in the air pocket area, wherein the third plastic sealing is connected to the body area, the second plastic sealing is located between the third plastic sealing and the first plastic sealing, and a first air pocket is formed between the second plastic sealing and the third plastic sealing; Cutting the plastic film structure from a side of the second plastic sealing away from the first plastic sealing to obtain a packaging film; The sealed edges of the packaging film having the second plastic sealing layer and the third plastic sealing layer are bent to obtain a folded edge structure.

10. The method for manufacturing a battery cell according to claim 9, characterized in that: Along the width direction of the battery core, the third plastic sealing weld width is f, wherein the value range of f is: 3mm≤f≤10mm; And / or, along the width direction of the battery core, the weld width of the second plastic sealing layer is Z, wherein the value range of Z is: 2mm≤Z≤10mm.

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