Battery

Abstract

The battery comprises a membrane shell and a battery cell, the membrane shell is provided with a first groove used for containing the battery cell and a side sealing edge arranged on the side portion of the first groove in the first direction, the side sealing edge comprises a first bent portion and a first straight portion connected with the first bent portion, and the first straight portion extends in the second direction. The first direction is perpendicular to the first direction, the second direction is perpendicular to the first direction, the depth of the first groove is L1, the length of the first bent part in the first direction is L2, the length of the first straight part in the second direction is L3, and L1, L2 and L3 meet the relational expression that L3 / L1 is larger than or equal to 0.4 and smaller than or equal to 1; 0.1 < = L2 / L3 < = 0.4; and the width of the side sealing edge is 1.3 to 6.6 mm. By adjusting the relation among the L1, the L2 and the L3, the energy density and the sealing performance of the battery can be ensured, and the battery has high reliability and is not easy to leak while ensuring that the battery has high energy density.

Description

TECHNICAL FIELD

[0001] The utility model relates to battery structure technical field, more specifically, relate to a battery. BACKGROUND

[0002] Among various electric equipment, soft package battery has wide application. Soft package battery refers to the shell containing bag or containing high polymer, and the soft package battery includes battery cell and film shell, and the battery cell is packaged in the film shell.

[0003] The film shell includes side sealing edges located at the side of the battery cell in the width direction, the side sealing edges include bending parts and straight parts, the side sealing edges make the straight parts adhere to the side of the battery cell through the bending parts, and the quality of the side sealing edges will affect the performance of the battery, for example, when the distance from one end of the side sealing edge close to the battery cell to the other end of the side sealing edge away from the battery cell is long, the volume of the battery is increased, thereby affecting the energy density of the battery, and when the distance from one end of the side sealing edge close to the battery cell to the other end of the side sealing edge away from the battery cell is short, the sealing effect is affected, and liquid leakage caused by virtual sealing is prone to occur. Especially for the silicon negative electrode battery, the expansion of the battery cell is large, and the requirement for the film shell packaging is higher.

[0004] Therefore, how to ensure that the battery does not lose the energy density while having good reliability is a problem to be solved by the technical personnel in the field at present. CONTENT OF THE UTILITY MODEL

[0005] Therefore, the utility model aims at providing a battery which can improve the energy density of the battery and make the battery have higher reliability.

[0006] In order to realize the above-mentioned purpose, the utility model provides the following technical scheme:

[0007] A battery includes a film shell and a battery cell, the film shell is provided with a first recess for accommodating the battery cell and a side sealing edge provided on the side of the first recess in a first direction, the side sealing edge includes a first bending part and a first straight part connected with the first bending part, the first straight part extends in a second direction, the second direction is perpendicular to the first direction, the depth of the first recess is L1, the length of the first bending part in the first direction is L2, and the length of the first straight part in the second direction is L3, and the relationship between L1, L2 and L3 satisfies:

[0008] 0.4≤L3 / L1≤1;

[0009] 0.1≤L2 / L3≤0.4;

[0010] The width of the side sealing edge (14) is 1.3-6.6mm.

[0011] Optionally, the film shell is provided with a top sealing edge at one end thereof along a third direction perpendicular to the first direction and the second direction, a width of the top sealing edge from a side close to the electrode to a side away from the electrode is S1, a top sealing seal is provided between two ends of the top sealing edge, a width of the top sealing seal along the third direction is S2, a distance from a side of the top sealing seal away from the electrode to a side of the top sealing edge 15 away from the electrode along the third direction is S3, and the following conditions are met among the S1, the S2 and the S3:

[0012] 0.3≤S3 / S2≤0.84;

[0013] 0.25≤S2 / S1≤0.9.

[0014] Optionally, the L1 is 1-10 mm; the L2 is 0.3-0.8 mm; and the L3 is 1-5.8 mm.

[0015] Optionally, the S1 is 1.5-6 mm; the S2 is 1-2.6 mm; and the S3 is 0.5-3 mm.

[0016] Optionally, the electrode comprises a positive electrode sheet, a separator and a negative electrode sheet which are arranged in a stacked manner by winding, along a winding direction of the electrode, an end of the negative electrode sheet is beyond an end of the positive electrode sheet, and an end of the separator is beyond an end of the negative electrode sheet.

[0017] Optionally, along the winding direction, the starting end of the negative electrode sheet comprises a second flat portion, a second bending portion, a third flat portion, a third bending portion and a fourth flat portion which are connected in sequence, and the second flat portion, the third flat portion and the fourth flat portion are arranged in parallel along the second direction.

[0018] The outer side surface of the second flat portion, the second bending portion, the third flat portion, the third bending portion and the fourth flat portion is provided with a first coating, the outer side surface refers to a side away from a winding center of the electrode; an end of the second flat portion away from the second bending portion has an overhanging section beyond the first coating of the second flat portion, the overhanging section is not provided with an active layer, and the overhanging section is bent towards a side away from the first coating of the second flat portion; or,

[0019] Both sides of the second flat portion, the second bending portion, the third flat portion, the third bending portion and the fourth flat portion are provided with a second coating, and an end of the second flat portion away from the second bending portion is flush with an end of the second coating of the second flat portion.

[0020] Optionally, the tail end of the negative electrode sheet comprises, in sequence along the winding direction, a fifth flat section, a fourth bending section, a sixth flat section, a fifth bending section and a seventh flat section, the fifth flat section, the sixth flat section and the seventh flat section being arranged in parallel along the second direction.

[0021] The inner side surface of each of the fifth flat section, the fourth bending section, the sixth flat section, the fifth bending section and the seventh flat section is provided with a third coating, the inner side surface being the side close to the winding center of the electric core; or,

[0022] The two side surfaces of each of the fifth flat section, the fourth bending section, the sixth flat section, the fifth bending section and the seventh flat section are provided with a fourth coating.

[0023] Optionally, the head end of the negative electrode sheet is 1-10 mm beyond the head end of the positive electrode sheet; and / or,

[0024] The tail end of the negative electrode sheet is 5-20 mm beyond the tail end of the positive electrode sheet; and / or,

[0025] The head end of the separator is 20-150 mm beyond the head end of the negative electrode sheet; and / or,

[0026] The part of the tail end of the negative electrode sheet beyond the tail end of the positive electrode sheet contains at least two first winding bending sections, and the part of the tail end of the separator beyond the tail end of the negative electrode sheet contains at least 2-5 second winding bending sections.

[0027] Optionally, the negative electrode sheet comprises a negative electrode current collector, the positive electrode sheet comprises a positive electrode current collector, and the relationship between the gap G along the third direction perpendicular to the first direction and the second direction between the electric core and the film shell, the thickness H1 of the negative electrode current collector, the strength σ1 of the negative electrode current collector, the thickness H2 of the positive electrode current collector and the strength σ2 of the positive electrode current collector needs to satisfy the following relationship: 8000≤(H1×σ1+ H2×σ2)×G≤30000.

[0028] Optionally, the G is 0.8-4.6 mm; the σ1 is 300-800 MPa; the H1 is 4-15 μm; the σ2 is 100-300 MPa; and the H2 is 7-20 μm.

[0029] Optionally, the positive electrode sheet is provided with at least two positive electrode tabs, and all the positive electrode tabs are stacked. Each positive electrode tab includes a first transition portion, a sixth bend portion, and a first electrode tab connecting portion. The first transition portion is connected to the positive electrode sheet, and the sixth bend portion is connected between the first transition portion and the first electrode tab connecting portion. All the sixth bend portions are gathered in the middle region of the cell along the second direction. Any two adjacent first electrode tab connecting portions are in contact and parallel to the end face of the positive electrode tab of the cell.

[0030] The negative electrode sheet is provided with at least two negative electrode tabs, all of which are stacked. Each negative electrode tab includes a second transition portion, a seventh bend portion, and a second electrode tab connection portion. The second transition portion is connected to the negative electrode sheet, and the seventh bend portion is connected between the second transition portion and the second electrode tab connection portion. All the seventh bend portions are gathered in the middle region of the cell along the second direction. Any two adjacent second electrode tab connection portions are in contact with each other and are parallel to the end face of the end where the negative electrode tab of the cell is located.

[0031] The membrane shell is provided with a positive electrode post and a negative electrode post. The positive electrode post is connected to the side of the first electrode tab connection portion away from the battery cell, and the negative electrode post is connected to the side of the second electrode tab connection portion away from the battery cell.

[0032] Optionally, an adhesive layer is provided at the end of the diaphragm, and the adhesive layer is connected to the diaphragm. Along a third direction perpendicular to the first direction and the second direction respectively, the length T1 of the adhesive layer and the length T3 of the battery cell need to satisfy the following relationship: 0.8≤T1 / T3≤1.06; the width T2 of the adhesive layer along the first direction and the width T4 of the battery cell along the first direction need to satisfy the following relationship: 0.2≤T2 / T4≤0.5.

[0033] Optionally, the battery cell includes a negative electrode sheet, which includes a negative current collector, a first negative active layer, and a second negative active layer. At least one of the first negative active layer and the second negative active layer is a silicon-carbon layer. The first negative active layer is disposed on the surface of the negative current collector, and the second negative active layer is disposed on the side of the first negative active layer away from the negative current collector.

[0034] The battery provided by this utility model has the following beneficial effects:

[0035] By adjusting the width of the side seal within the range of 1.3~6.6mm, a suitable overall width is ensured, avoiding excessively long or short side seals. Excessive width can affect the overall battery thickness, while insufficient width can lead to leakage. Simultaneously, by adjusting the L3 / L1 ratio within the range of 0.4~1, the first straight portion extending along the second direction of the side seal has a suitable length relative to the depth L1 of the first groove, preventing the first straight portion from being too long or too short. An excessively large L3 / L1 ratio results in an overly long first straight portion, potentially affecting the overall battery thickness. If the value of L1 is too small, the first straight section will be too short, resulting in insufficient sealing length and a tendency for leakage. By adjusting the ratio of L2 / L3 within the range of 0.1 to 0.4, the first bent section of the side seal has a suitable size relative to the first straight section. It is understood that the length L2 of the first bent section along the first direction has a certain influence on the position of the first straight section and its angle relative to the second direction. When the ratio of L2 / L3 is appropriate, it helps ensure that the first straight section extends along the second direction. Otherwise, if the ratio of L2 / L3 is too large or too small, the first straight section may tilt relative to the second direction, making it difficult for it to fit snugly against the side of the battery and potentially affecting the overall width of the battery. In other words, by adjusting L1, L2, and L3, the membrane shell has suitable encapsulation parameters, thus ensuring both the energy density and sealing performance of the battery. This means that while ensuring high energy density, the battery also has good reliability and is less prone to leakage.

[0036] Through practical experiments and applications conducted by the inventors, it has been shown that under a certain L1, L2 and L3, satisfying the respective relationships of L3 / L1 and L2 / L3, can reduce the sealing edge size of the battery, thereby increasing the battery's energy density and reducing the edge voltage. Simultaneously, it can prevent issues such as incomplete sealing and leakage. However, when L2 and L3 are too large, exceeding the range defined by L3 / L1 or L2 / L3, it leads to an excessively long sealing edge. In this case, although there is a good sealing effect, the battery's space utilization is low, resulting in low energy density. Conversely, when L2 and L3 are too small, exceeding the range defined by L3 / L1 or L2 / L3, it leads to an excessively short sealing edge, affecting battery packaging performance, easily causing incomplete sealing, increasing the battery's edge voltage, worsening the internal sealing of the battery, and ultimately leading to leakage. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this utility model or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0038] Figure 1 A schematic diagram of the structure of the first groove 11 and the side sealing edge of the battery membrane shell provided in a specific embodiment of this utility model;

[0039] Figure 2 for Figure 1 A schematic diagram of the structure when the middle side edge banding is not bent;

[0040] Figure 3 This is a schematic diagram of the top sealing edge of the membrane shell;

[0041] Figure 4 This is a schematic diagram of the battery cell structure;

[0042] Figure 5 A schematic diagram of a structure in which a first coating is provided on the outer side of the starting end of the negative electrode along the winding direction;

[0043] Figure 6 A schematic diagram of a structure in which a second coating is provided on both the inner and outer sides of the starting end of the negative electrode along the winding direction;

[0044] Figure 7 A schematic diagram of a structure in which a third coating is provided on the inner side of the end of the negative electrode along the winding direction;

[0045] Figure 8 A schematic diagram showing that the negative electrode sheet has a fourth coating on both the inner and outer sides along the winding direction at its end;

[0046] Figure 9 This is a schematic diagram illustrating the bending of the electrode tabs in a battery cell in a related technology.

[0047] Figure 10 for Figure 9 The diagram shows the assembled battery cell and membrane housing.

[0048] Figure 11 A schematic diagram showing the bending of the electrode tabs of the battery cell provided in an embodiment of this utility model;

[0049] Figure 12 for Figure 11 The diagram shows the assembled battery cell and membrane housing.

[0050] Figure 13 This is a schematic diagram showing the location of the adhesive layer;

[0051] Figure 14 This is a structural diagram showing the length of the adhesive layer and the width of the battery cell along a third direction and along a first direction, respectively.

[0052] Figure label:

[0053] 1-Membrane shell; 11-First groove 11; 12-Second groove; 13-Electrical post; 14-Side seal; 141-First bend; 142-First straight section; 15-Top seal; 151-Top seal; 2-Cell; 21-Positive electrode; 22-Negative electrode; 221-Second straight section, 222-Second bend, 223-Third straight section, 224-Third bend; 225-Fourth straight section; 226-Fifth straight section, 227-Fourth bend, 228-Sixth straight section, 229-Fifth bend; 220-Seventh straight section; 23-Separator; 24-First coating; 25-Extended section; 26-Second coating; 27-Third coating; 28-Fourth coating; 29-Electrical tab; 291-Electrical tab connection; 3-Adhesive layer. Detailed Implementation

[0054] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0055] The core of this invention is to provide a battery that can improve the energy density of the battery and make the battery more reliable.

[0056] It should be noted that, in the embodiments of this utility model, the first direction refers to the thickness direction of the battery, that is, the Y-axis direction in the accompanying drawings; the second direction refers to the width direction of the battery, that is, the X-axis direction in the accompanying drawings; and the third direction refers to the length direction of the battery (also known as the height direction), that is, the Z-axis direction in the accompanying drawings.

[0057] Please refer to Figure 1 and Figure 2This utility model provides a battery, including a membrane shell 1 and a battery cell 2. The membrane shell 1 is provided with a first groove 11 and a side sealing edge 14. The battery cell 2 is disposed in the first groove 11. The side sealing edge 14 is disposed on the side of the outer side wall of the first groove 11 along a first direction. The side sealing edge 14 includes a first bent portion 141 and a first straight portion 142 connected to the first bent portion 141. The first straight portion 142 extends along a second direction, which is perpendicular to the first direction. The depth of the first groove 11 is L1, the length of the first bent portion 141 along the first direction is L2, and the length of the first straight portion 142 along the second direction is L3. The relationship between L1, L2, and L3 is: 0.4≤L3 / L1≤1; 0.1≤L2 / L3≤0.4. The width of the side sealing edge 14 is 1.3~6.6mm.

[0058] It should be noted that in some embodiments, only the first groove 11 may be provided on the membrane housing 1, and the battery cell 2 may be completely placed in the first groove 11. In other embodiments, such as... Figure 1 As shown, the membrane shell 1 is also provided with a second groove 12. The depth of the second groove 12 is less than the depth of the first groove 11. The depth of the second groove 12 is L4. A part of the battery cell 2 is disposed in the first groove 11 and the other part of the battery cell 2 is disposed in the second groove 12. Then the thickness of the battery cell 2 is L1 + L4. If the thickness of the membrane shell 1 is ignored, the thickness of the battery is L1 + L4.

[0059] This embodiment of the invention adjusts the width of the side sealing edge 14 within the range of 1.3~6.6mm to ensure that the side sealing edge 14 has a suitable overall width, avoiding it being too long or too short. If the side sealing edge 14 is too long, it can easily affect the overall thickness of the battery; if it is too short, leakage can easily occur due to insufficient sealing width. Simultaneously, by adjusting the L3 / L1 ratio within the range of 0.4~1, the first straight portion 142 extending along the second direction of the side sealing edge 14 has a suitable length relative to the depth L1 of the first groove 11, avoiding it being too long or too short. If the L3 / L1 value is too large, the first straight portion 142 will be too long, easily affecting the overall thickness of the battery. If the value of L1 is too small, the first straight portion 142 will be too short, resulting in insufficient sealing length and easy leakage. By adjusting the ratio of L2 / L3 within the range of 0.1 to 0.4, the first bent portion 141 of the side sealing edge 14 will have a suitable size relative to the first straight portion 142 of the side sealing edge 14. It can be understood that the length L2 of the first bent portion 141 along the first direction has a certain influence on the position of the first straight portion 142 and the angle of the first straight portion 142 relative to the second direction. When the ratio of L2 / L3 is appropriate, it is beneficial to ensure that the first straight portion 142 extends along the second direction. Otherwise, if the ratio of L2 / L3 is too large or too small, the first straight portion 142 will easily tilt relative to the second direction, which is not conducive to the first straight portion 142 fitting the side of the battery and may affect the overall width of the battery.

[0060] Through actual experiments and applications by the inventors, it has been shown that: when the depth L1 of the first groove 11 is determined, L2 and L3, which satisfy the above-mentioned relationship, can reduce the size of the side sealing edge 14 of the membrane shell 1, thereby increasing the energy density of the battery and reducing the side voltage; at the same time, it can prevent issues such as incomplete sealing and leakage of the battery cell. However, when L2 and L3 are too large, exceeding the range defined by the above-mentioned relationship, the width of the side sealing edge 14 along the second direction will be too long. In this case, although there is a good sealing effect, the space utilization of the battery is low, resulting in a low energy density. Conversely, when L2 and L3 are too small, exceeding the range defined by the above-mentioned relationship, the width of the side sealing edge 14 along the second direction will be too short, thereby affecting the battery sealing performance, easily causing incomplete sealing, increasing the battery side voltage, worsening the internal sealing of the battery, and ultimately leading to leakage.

[0061] Therefore, by adjusting L1, L2 and L3, the present invention can ensure both the energy density and sealing performance of the battery. That is, while ensuring that the battery has a high energy density, it also has good reliability and is not prone to leakage.

[0062] It should be noted that this embodiment does not limit the specific values ​​of L3 / L1 and L2 / L3, as long as the values ​​of L3 / L1 and L2 / L3 fall within their respective ranges. For example, in some embodiments, the value of L3 / L1 can be 0.4, 0.5, 0.8, or 1, etc.; the value of L2 / L3 can be 0.1, 0.2, 0.3, 0.4, etc.

[0063] Furthermore, in some embodiments, L1 ranges from 1 to 10 mm; L2 ranges from 0.3 to 0.8 mm; and L3 ranges from 1 to 5.8 mm. That is, this embodiment ensures better packaging performance by controlling L1 within the range of 1 to 10 mm, L2 within the range of 0.3 to 0.8 mm, and L3 within the range of 1 to 5.8 mm, while satisfying 0.4 ≤ L3 / L1 ≤ 1 and 0.1 ≤ L2 / L3 ≤ 0.4, thus ensuring both the energy density and the sealing performance of the battery. In some embodiments, L1 is 1 mm, 2.5 mm, 5 mm, 6.5 mm, 8 mm, or 10 mm, etc.; L2 is 0.3 mm, 0.45 mm, 0.5 mm, 0.65 mm, or 0.8 mm, etc.; and L3 is 1 mm, 1.6 mm, 2 mm, 2.5 mm, 3 mm, 3.8 mm, 4 mm, 5 mm, or 5.8 mm, etc.

[0064] Additionally, please refer to Figure 3 To further optimize the encapsulation parameters of the membrane shell 1, in some embodiments, the membrane shell 1 is provided with a top sealing edge 15 at one end along a third direction, the third direction being perpendicular to the first direction and the second direction respectively. The width of the top sealing edge 15 from the end near the battery cell 2 to the end away from the battery cell 2 is S1. A top sealing seal 151 is provided between the two ends of the top sealing edge 15. The width of the top sealing seal 151 along the third direction is S2. The distance from the end of the top sealing seal 151 away from the battery cell 2 to the end of the top sealing edge 15 along the third direction away from the battery cell 2 is S3. S1, S2 and S3 satisfy the following: 0.3≤S3 / S2≤0.84, 0.25≤S2 / S1≤0.9.

[0065] Understandably, the first groove 11, side sealing edge 14, and top sealing edge 15 of the battery housing 1 provide a sealed environment for the lithium insertion / extraction of the battery cell 2 located inside the housing 1. The side sealing edge 14 and top sealing edge 15 also function like a door, isolating the inside of the battery cell 2 from the outside. Therefore, the size of the top sealing edge 15 also affects the energy density and sealing performance of the battery. For example, a larger top sealing edge 15 will occupy too much space, reducing the energy density of the battery; a smaller top sealing edge 15 will affect the sealing performance of the battery, resulting in excessive edge voltage of the housing 1.

[0066] Therefore, this embodiment adjusts the relationship between S1, S2, and S3 to ensure the dimensions of the top sealing edge 15 are within acceptable limits, thereby further ensuring that the battery has high energy density and good reliability, and is not prone to leakage. It is understandable that when the ratio of S3 / S2 is too large, the distance S3 from the end of the top sealing seal 151 furthest from the cell 2 to the end of the top sealing edge 15 furthest from the cell 2 along a third direction is too large, which can easily lead to an excessively long overall width of the top sealing edge 15, affecting the battery height; when the ratio of S3 / S2 is too small, the risk of leakage increases. Furthermore, when the ratio of S2 / S1 is too large, the overall width of the top sealing edge 15 can easily become too long, affecting the battery height; when the ratio of S2 / S1 is too small, leakage is likely.

[0067] It should be noted that this embodiment does not limit the specific values ​​of S3 / S2 and S2 / S1, as long as the values ​​of S3 / S2 and S2 / S1 fall within their respective ranges. For example, in some embodiments, the value of S3 / S2 can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.54, etc.; the value of S2 / S1 can be 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc.

[0068] Furthermore, in some embodiments, S1 ranges from 1.5 to 6 mm; S2 ranges from 1 to 2.6 mm; and S3 ranges from 0.5 to 3 mm. That is, this embodiment ensures a more suitable top sealing edge 15 dimension by controlling S1 within the range of 1.5 to 6 mm, S2 within the range of 1 to 2.6 mm, and S3 within the range of 0.5 to 3 mm, while satisfying 0.3 ≤ S3 / S2 ≤ 0.84 and 0.25 ≤ S2 / S1 ≤ 0.9, thereby enabling the battery to have higher energy density and better sealing performance. In some embodiments, S1 is 1.5 mm, 2.1 mm, 3 mm, 3.8 mm, 4 mm, 5.5 mm, or 6 mm, etc.; S2 is 1 mm, 1.2 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2 mm, 2.5 mm, or 2.6 mm, etc.; and S3 is 0.5 mm, 0.6 mm, 1 mm, 1.6 mm, 2 mm, 2.5 mm, or 3 mm, etc.

[0069] In addition, the above embodiments do not limit the specific structure of the battery cell 2 disposed in the membrane shell 1, as long as the battery cell 2 can meet the performance requirements of the battery.

[0070] Understandably, in current related technologies, the structure of cell 2 typically involves the positive electrode 21 extending beyond the negative electrode 22 at its end. Along the winding direction of cell 2, the negative electrode 22 has coatings on both its inner and outer sides along a predetermined length near the beginning, while the positive electrode 21 has a coating on only one side along a predetermined length near its end. This cell 2 structure, during charging and discharging, repeatedly expands and compresses the positive electrode 21, easily leading to uneven stress on the single-sided and double-sided areas of the positive electrode 21. This ultimately causes the positive electrode 21 to break, resulting in decreased battery performance, especially noticeable in cells 2 with silicon negative electrodes.

[0071] To address the technical issue of positive electrode plate 21 breakage, please refer to... Figure 4 In some embodiments, the battery cell 2 includes a positive electrode 21, a separator 23 and a negative electrode 22 that are wound and stacked together. Along the winding direction of the battery cell 2, the end of the negative electrode 22 extends beyond the end of the positive electrode 21 and the end of the separator 23 extends beyond the end of the negative electrode 22.

[0072] In other words, this embodiment changes the structure of the cell 2 so that at the end of the cell 2, the end of the negative electrode 22 extends beyond the end of the positive electrode 21, so that the negative electrode 22 covers the outside of the positive electrode 21, and the end of the separator 23 extends beyond the end of the negative electrode 22, so that the separator 23 covers the outside of the negative electrode 22. In this way, the single-sided area of ​​the positive electrode 21 can be eliminated, so that the positive electrode 21 is coated on both the inner and outer sides along the winding direction, so that the positive electrode 21 is subjected to more uniform stress and the risk of the positive electrode 21 breaking can be reduced. In addition, a separator 23 is wrapped around the outermost side of the negative electrode 22. After the separator 23 is formed by hot pressing, it generates a strong adhesive force with the negative electrode 22. Therefore, the separator 23 can restrain the expansion of the negative electrode 22, thereby preventing the negative electrode 22 from expanding rapidly, which would lead to problems such as increased particle gaps, increased impedance and polarization, powder shedding, lithium plating, and extrusion of the outermost negative electrode 22. This helps to maintain the stability of the cell 2.

[0073] Further, please refer to Figure 5In some embodiments, along the winding direction of the battery cell 2, the starting end of the negative electrode 22 includes a second straight portion 221, a second bent portion 222, a third straight portion 223, a third bent portion 224, and a fourth straight portion 225 connected in sequence. The second straight portion 221, the third straight portion 223, and the fourth straight portion 225 are arranged parallel to each other along a second direction. The outer surfaces of the second straight portion 221, the second bent portion 222, the third straight portion 223, the third bent portion 224, and the fourth straight portion 225 are all provided with a first coating 24. The outer surface refers to the side away from the winding center of the battery cell 2. The second straight portion 221 has an overhanging section 25 extending beyond the first coating 24 of the second straight portion 221 at one end away from the second bent portion 222. The overhanging section 25 is not provided with an active layer and is bent toward the side away from the first coating 24 of the second straight portion 221; or, the second straight portion 221, the second bent portion 222, the third straight portion 223, the third bent portion 224 and the fourth straight portion 225 are all provided with a second coating 26 on both sides, and the end of the second straight portion 221 away from the second bent portion 222 is flush with the end of the second coating 26 of the second straight portion 221.

[0074] In other words, the preset length of the negative electrode 22 near the starting end (the sum of the lengths of the second straight portion 221, the second bent portion 222, the third straight portion 223, the third bent portion 224, and the fourth straight portion 225) can be a single-sided coating or a double-sided coating. When the preset length of the negative electrode 22 near the starting end is a single-sided coating, the thickness of the cell 2 can be reduced, saving coating, saving costs, and increasing the energy density of the cell 2. Moreover, the starting end of the negative electrode 22 extends beyond the starting end of the single-sided coating (i.e., the first coating 24). The extended portion (i.e., the extended section 25) is not provided with an active layer. That is, the extended section 25 is an empty foil. The extended section 25 is bent toward the side away from the first coating 24. The thickness of the coating is compensated by the bent extended section 25, which helps to improve the overall flatness of the cell 2 and make the overall thickness of the cell 2 more uniform. When the preset length of the negative electrode 22 near the starting end is double-sided coated, continuous coating can be achieved when coating the negative electrode 22, which is convenient for manufacturing and helps to improve the stability of the negative electrode 22 and reduce costs.

[0075] Additionally, please refer to Figure 7 and Figure 8In some embodiments, along the winding direction of the battery cell 2, the end of the negative electrode sheet 22 includes a fifth straight portion 226, a fourth bent portion 227, a sixth straight portion 228, a fifth bent portion 229, and a seventh straight portion 220 connected in sequence. The fifth straight portion 226, the sixth straight portion 228, and the seventh straight portion 220 are arranged parallel to each other along a second direction. The inner surface of each of the fifth straight portion 226, the fourth bent portion 227, the sixth straight portion 228, the fifth bent portion 229, and the seventh straight portion 220 is provided with a third coating 27. The inner surface refers to the side close to the winding center of the battery cell 2. Alternatively, the two side surfaces of each of the fifth straight portion 226, the fourth bent portion 227, the sixth straight portion 228, the fifth bent portion 229, and the seventh straight portion 220 are provided with a fourth coating 28.

[0076] In other words, in this embodiment, the preset length of the negative electrode 22 near its end (the sum of the lengths of the fifth straight portion 226, the fourth bent portion 227, the sixth straight portion 228, the fifth bent portion 229, and the seventh straight portion 220) can be either a single-sided coating or a double-sided coating. When the preset length of the negative electrode 22 near its end is a single-sided coating, the thickness of the battery cell 2 can be reduced, saving coating material, reducing costs, and increasing the energy density of the battery cell 2. When the preset length of the negative electrode 22 near its end is a double-sided coating, continuous coating can be achieved when applying the coating to the negative electrode 22, which is convenient for manufacturing and helps to improve the stability of the negative electrode 22 and reduce costs.

[0077] In some embodiments, the tip of the negative electrode 22 extends 1-10 mm beyond the tip of the positive electrode 21. That is, along the winding direction of the cell 2, the starting position of the tip of the positive electrode 21 is 1-0 mm behind the starting position of the tip of the negative electrode 22. This can prevent the positive electrode 21 from losing lithium during battery charging and discharging without the negative electrode 22 receiving it. This distance range is suitable, does not waste too much distance, and is conducive to ensuring the energy density of the battery. At the same time, it can prevent lithium loss, etc.

[0078] In some embodiments, the end of the negative electrode 22 extends 5-20 mm beyond the end of the positive electrode 21. That is, along the winding direction of the cell 2, the end of the negative electrode 22 is 5-20 mm behind the end of the positive electrode 21. Similarly, this prevents the positive electrode 21 from losing lithium during battery charging and discharging without the negative electrode 22 receiving it. This distance range is suitable, does not waste too much distance, helps ensure the energy density of the battery, and at the same time, prevents lithium loss.

[0079] In some embodiments, the tip of the separator 23 extends 20-150 mm beyond the tip of the negative electrode 22. That is, along the winding direction of the cell 2, the starting position of the tip of the separator 23 is 20-150 mm in front of the starting position of the tip of the negative electrode 22. This is beneficial for separating the positive electrode 21 and the negative electrode 22 of the battery at the tip of the cell 2, preventing short circuits caused by contact between the positive electrode 21 and the negative electrode 22.

[0080] In some embodiments, the portion of the negative electrode 22 extending beyond the end of the positive electrode 21 contains at least two first winding bends, and the portion of the separator 23 extending beyond the end of the negative electrode 22 contains at least 2 to 5 second winding bends. That is, the length of the negative electrode 22 extending beyond the end of the positive electrode 21 can be wound at least twice to form two first winding bends, which effectively solves the problem of positive electrode 21 breakage. The length of the separator 23 extending beyond the end of the negative electrode 22 can be wound at least 2 to 5 times to form 2 to 5 second winding bends, which helps to provide better binding of the negative electrode 22 and prevent the negative electrode 22 from expanding.

[0081] Additionally, it is understandable that during the charging and discharging process, the active material of the negative electrode 22 will repeatedly undergo lithium insertion and delithiation. That is, when the active material particles of the negative electrode 22 undergo lithium insertion, the particles will expand, and the expansion will occur in various directions of the plane of the current collector of the negative electrode 22. When the expansion occurs along the height direction (i.e., the third direction) of the current collector of the negative electrode 22, it will cause compression and stretching of the current collector of the negative electrode 22 along the height direction, and the current collector of the negative electrode 22 will extend in the height direction. When the active material of the negative electrode 22 undergoes delithiation and shrinks, the current collector of the negative electrode 22 does not shrink and remains in an extended state. Based on the above two situations, during the charging and discharging process, the active material particles of the negative electrode 22 repeatedly expand and contract, causing the current collector of the negative electrode 22 to extend little by little, eventually causing the current collector of the negative electrode 22 to contact the membrane shell 1, causing compression of the membrane shell 1. When the gap between the membrane shell 1 and the cell 2 along the third direction is small, the membrane shell 1 may rupture. Therefore, to prevent the membrane shell 1 from being squeezed or ruptured, sufficient space needs to be left between the cell 2 and the membrane shell 1 in a third direction. However, if this space is too large, it will reduce the width of the electrode, thus affecting the energy density of the battery. Based on this, it is necessary to have a suitable gap range between the height of the cell 2 and the height of the membrane shell 1 to balance the energy density of the battery and the ductility of the cell 2. In addition, the thickness and strength of the positive electrode 21 and the negative electrode 22 can limit the expansion and extension of the cell 2. Therefore, by rationally designing the thickness and strength of the positive electrode 21 and the negative electrode 22, it is beneficial to avoid the cell 2 squeezing the membrane shell 1.

[0082] To prevent the membrane shell 1 from being squeezed or broken, in some embodiments, the negative electrode 22 includes a negative current collector, and the positive electrode 21 includes a positive current collector. The relationship between the gap G between the cell 2 and the membrane shell 1 along the height direction of the battery (i.e., the third direction), the thickness H1 of the negative current collector, the strength σ1 of the negative current collector, the thickness H2 of the positive current collector, and the strength σ2 of the positive current collector needs to satisfy is: 8000≤(H1×σ1+ H2×σ2)×G≤30000.

[0083] In other words, this embodiment defines the relationship between the gap G between the core 2 and the membrane shell 1 along the battery height direction, the thickness H1 of the negative electrode current collector, the strength σ1 of the negative electrode current collector, the thickness H2 of the positive electrode current collector, and the strength σ2 of the positive electrode current collector as described above. This allows G, H1, σ1, H2, and σ2 to work together to achieve a better matching effect. That is, the thickness and strength of the negative and positive electrode current collectors can effectively limit the cell 2. The expansion and extension allow for a suitable gap G between the cell 2 and the membrane shell 1 along the battery height direction (i.e., the third direction). This balances the battery's energy density with the cell 2's ductility, ensuring the battery has a high energy density while preventing the membrane shell 1 from being compressed or ruptured. Furthermore, it can be seen that G is inversely related to H1, σ1, H2, and σ2. When any one of H1, σ1, H2, and σ2 is large, the size of G can be appropriately reduced to satisfy 8000≤(H1×σ1+ H2×σ2)×G≤30000; when any one of H1, σ1, H2, and σ2 is small, the size of G can be appropriately increased to satisfy 8000≤(H1×σ1+ H2×σ2)×G≤30000. For example, in some embodiments, the value of (H1×σ1+ H2×σ2)×G can be 8000, 10000, 15000, 18000, 20000, 25000 or 30000, etc.

[0084] Furthermore, in some embodiments, the range of G is 0.8~4.6mm; the range of σ1 is 300~800MPa; the range of H1 is 4~15μm; the range of σ2 is 100~300MPa; and the range of H2 is 7~20μm. That is to say, this embodiment controls G within the range of 0.8~4.6mm, σ1 within the range of 300~800MPa, H1 within the range of 4~15μm, σ2 within the range of 100~300MPa, and H2 within the range of 7~20μm, and satisfies 8000≤(H1×σ1+ H2×σ2)×G≤30000, to ensure that the thickness and strength of the negative electrode current collector and the positive electrode current collector can effectively limit the expansion and extension of the cell 2, and to make the gap G between the cell 2 and the membrane shell 1 along the height direction of the battery more suitable. In some embodiments, G is 0.8 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 4.6 mm, etc.; σ1 is 300 MPa, 500 MPa, 550 MPa, 600 MPa, or 800 MPa, etc.; H1 is 4 μm, 6 μm, 8 μm, 10 μm, 15 μm, or 15 μm, etc.; σ2 is 100 MPa, 150 MPa, 200 MPa, 250 MPa, or 300 MPa, etc.; and H2 is 7 μm, 10 μm, 12 μm, 15 μm, 18 μm, or 20 μm, etc. Additionally, in some embodiments, both the positive electrode 21 and the negative electrode 22 are provided with at least two tabs 29, that is, the number of tabs 29 with the same polarity is at least two, such as... Figure 9 As shown, in the related technology, in order to connect the tab 29 to the pole post 13 of the membrane shell 1, multiple tabs 29 of the same polarity are gathered toward one side of the cell 2, and then the multiple tabs 29 of the same polarity are bent toward the other side to form a large bending arc, so that the multiple tabs 29 of the same polarity form a shape similar to a U or V. Then, the pole post 13 is inserted in the middle of the U or V shaped tabs 29, that is, the pole post 13 is located between the upper and lower sides of the multiple tabs 29 of the same polarity after bending. In this structural form, since all the tabs 29 with the same polarity converge towards one side of the cell 2, the tabs 29 farther away from the converged side are not long enough to make contact with the terminal 13, while the tabs 29 closer to the converged side are too long and tend to arch in the middle. In other words, the tabs 29 are prone to uneven distribution after bending. As a result, there is a risk of poor connection when the tabs 29 are connected to the terminal 13. For example, when the tabs 29 are soldered to the terminal 13, there is a risk of incomplete soldering or over-soldering.

[0085] To solve this technical problem, please refer to... Figure 10In some embodiments, the positive electrode 21 has at least two positive electrode tabs 29, all of which are stacked. Each positive electrode tab 29 includes a first transition portion, a sixth bend portion, and a first electrode tab connecting portion 291. The first transition portion is connected to the positive electrode 21, and the sixth bend portion connects the first transition portion and the first electrode tab connecting portion 291. All sixth bend portions converge in the middle region of the cell 2 along the second direction. Any two adjacent first electrode tab connecting portions 291 are in contact and parallel to the end face of the positive electrode tab 29 of the cell 2. The negative electrode 22 has at least two negative electrode tabs, all of which are stacked. The cells are stacked together, and the negative electrode tab includes a second transition portion, a seventh bend portion, and a second electrode tab connection portion. The second transition portion is connected to the negative electrode sheet 22, and the seventh bend portion is connected between the second transition portion and the second electrode tab connection portion. All seventh bend portions are gathered in the middle area of ​​the cell 2 along the second direction. Any two adjacent second electrode tab connection portions are in contact with each other and are parallel to the end face of the negative electrode tab 29 of the cell 2. The membrane shell 1 is provided with a positive electrode post 13 and a negative electrode post. The positive electrode post 13 is connected to the side of the first electrode tab connection portion 291 away from the cell 2, and the negative electrode post is connected to the side of the second electrode tab connection portion away from the cell 2.

[0086] In other words, in this embodiment, taking the positive electrode tab 29 as an example, all the positive electrode tabs 29 first move towards the middle position of the cell 2 along the second direction. After all the positive electrode tabs 29 move towards the middle position of the cell 2 along the second direction, all the positive electrode tabs 29 are bent as a whole towards one side of the cell 2 at the middle position of the cell 2 along the second direction. In this way, the length distribution of the positive electrode tabs 29 after bending can be more uniform. For example, after the positive electrode tabs 29 close to both sides of the cell 2 along the second direction are gathered towards the middle position, the length distribution of the positive electrode tabs 29 close to the cell 2 can be more uniform. The bending degree of the positive electrode tabs 29 on both sides along the second direction is the same or nearly the same, avoiding situations where all positive electrode tabs 29 are too long or too short after bending, thus reducing the likelihood of poor connection. Furthermore, the positive electrode post 13 is connected to the side furthest from the battery cell 2 at the first electrode tab connection portion 291 formed after bending the positive electrode tabs 29; that is, the positive electrode post 13 and the positive electrode tabs 29 are connected on the outer side along the third direction, facilitating connection and further reducing the risk of poor connection. Similarly, the negative electrode tab is bent in the same way as the positive electrode tab, achieving the same beneficial effects.

[0087] In addition, for the structure where the end of the separator 23 extends beyond the end of the negative electrode 22, an adhesive layer 3 is attached to the separator 23 at the end of the cell 2 to fix the separator 23. In this case, the adhesive layer 3 is in contact with the separator 23 but not in direct contact with the negative electrode 22 or the positive electrode 21. Therefore, when the battery is dropped, the negative electrode 22 or the positive electrode 21 at the end of the cell 2 is prone to instability, causing the negative electrode 22 or the positive electrode 21 to move or even bend. Therefore, the separator 23 needs to have a strong binding force on the negative electrode 22 and the positive electrode 21. That is, the tension of the separator 23 is needed to maintain the stability of the electrode. The tension of the separator 23 needs to be fixed by the adhesive layer 3. If the length and width of the adhesive layer 3 are short, resulting in a small area of ​​the adhesive layer 3, the fixed area of ​​the separator 23 will be small, which will make it easy for the separator 23 to move in places where there is no adhesive layer 3, thus affecting the stability of the electrode.

[0088] Therefore, please refer to Figure 12 To prevent the diaphragm 23 from moving and improve the stability of the electrode fixing, in some embodiments, an adhesive layer 3 is provided at the end of the diaphragm 23. The adhesive layer 3 is connected to the diaphragm 23. Along a third direction that is perpendicular to the first direction and the second direction respectively, the relationship between the length T1 of the adhesive layer 3 and the length T3 of the cell 2 needs to satisfy the following formula: 0.8≤T1 / T3≤1.06; the relationship between the width T2 of the adhesive layer 3 along the first direction and the width T4 of the cell 2 along the first direction needs to satisfy the following formula: 0.2≤T2 / T4≤0.5.

[0089] In other words, this embodiment ensures that the adhesive layer 3 has sufficient area by reasonably designing the length of the adhesive layer 3 along the third direction and the width along the first direction, so that the adhesive layer 3 can fix the separator 23 more firmly and prevent the separator 23 from moving. In turn, the tension of the separator 23 can be used to maintain the stability of the electrode, so that the electrode remains in a fixed position and avoids the instability of the negative electrode 22 or positive electrode 21 at the end of the cell 2 when the battery is dropped, and avoids the negative electrode 22 or positive electrode 21 from moving or even bending.

[0090] In some embodiments, the negative electrode 22 includes a negative electrode current collector, a first negative electrode active layer, and a second negative electrode active layer. At least one of the first and second negative electrode active layers is a silicon-carbon layer. The first negative electrode active layer is disposed on the surface of the negative electrode current collector, and the second negative electrode active layer is disposed on the side of the first negative electrode active layer away from the negative electrode current collector. That is, the negative electrode 22 in this embodiment is a silicon negative electrode, which can enable the battery to have a larger lithium storage capacity and a higher energy storage density. Regarding the drawback of silicon negative electrode batteries being more prone to expansion compared to traditional graphite negative electrode batteries, the solution disclosed in the above embodiments can effectively solve the problem of easy expansion of cell 2. Moreover, by limiting the various parameters mentioned above, the silicon negative electrode battery can maintain good reliability while ensuring battery energy density.

[0091] The following comparison between embodiments of this utility model and comparative examples demonstrates the impact of parameter variations on battery performance testing. The battery performance testing indicators involved in the embodiments of this utility model include:

[0092] 1. Battery Energy Density: Obtained through battery energy testing. Battery energy testing involves using a Newway battery tester to charge the battery at a constant current of 0.2C to the upper limit voltage, then charging it at the upper limit voltage to the cutoff current of 0.02C / 0.2C to the lower limit voltage. This process is repeated three times, and the energy of the third discharge is taken as the battery energy Q. The battery width W and height H are measured using a 2.5D microscope, and the fully charged thickness L is measured using a PPG thickness meter. Therefore, the battery energy density is: Q / (W×H×L).

[0093] 2. Voltage drop after 30 days of storage at 60℃±2℃: This refers to the voltage internal resistance measured after the battery has been stored at 60℃±2℃ for 30 days and then left to stand at room temperature for 2 hours.

[0094] 3. Battery 25℃ Cycling Performance Test: This refers to cycling at 25℃, charging at 1C to the cutoff voltage, charging at constant voltage to the 0.05C cutoff current, discharging at 1C to the lower limit voltage, repeating the above charge and discharge steps 300 times, and obtaining the 25℃ cycle capacity retention rate.

[0095] 4. 25℃ Cyclic Expansion Rate: This refers to the battery thickness B1 before cycling, which is fully charged before cycling. After 500 cycles, the battery is fully charged and the thickness B2 is measured. The expansion rate is calculated as (B2-B1) / B1.

[0096] 5. Battery 45℃ Cycling Performance Test: This refers to cycling at 45℃, charging at 1C to the cutoff voltage, charging at constant voltage to the 0.05C cutoff current, discharging at 1C to the lower limit voltage, and repeating the above charge and discharge steps 300 times.

[0097] 6. 45℃ Cyclic Expansion Rate: Before cycling, fully charge the battery and measure its thickness B1. After 300 cycles, fully charge the battery and measure its thickness B2. Expansion rate = (B2 - B1) / B1.

[0098] 7. Voltage drop after drop test: This refers to fully charging the battery at 25±2℃, clamping the battery on the clamping arm, and dropping it. The specific parameters are: 1m height, concrete ground, dropping the battery on the front, back, left, right, top, and bottom (6 sides in total), and dropping it once at each of the four corners where the side and top / bottom meet, for a total of 10 drops. After the battery is removed from the clamping arm and left to stand for 30 minutes, the final voltage and internal resistance are tested.

[0099] 8. Side voltage test: Use a voltmeter to test the voltage between the positive tab of the battery and the 14 aluminum layer on the side seal.

[0100] Furthermore, this embodiment of the invention does not limit the specific methods for obtaining the values ​​of the parameters involved in Example 1 and the comparative examples below. The values ​​can be obtained by measurement means before testing and comparing Example 1 and each comparative example.

[0101] For example, the depth L1 of the first groove 11 of the membrane housing 1 can be measured using a 2.5D microscope. A baffle is fixed at the 0 mark, making the battery perpendicular to the horizontal plane, with the battery side seal 14 facing upwards. The outer wall of the first groove 11 of the membrane housing 1 is close to the baffle. The microscope is focused on the seal, and the scale line is moved to the bottom of the seal. The scale reading is recorded, which is the depth L1 of the first groove 11. The length L3 of the first straight portion 142 of the side seal 14 of the membrane housing 1 along the second direction can also be measured using a 2.5D microscope. The side seal 14 of the membrane housing 1 is unfolded to a horizontal position. The scale is moved to the junction of the side wall of the first groove 11 and the side seal 14, which is set as the 0 mark. The scale line is moved vertically to the edge of the first straight portion 142; the distance moved is L3. The length L2 of the first bend 141 of the side seal 14 of the membrane housing 1 along the first direction can be measured using a CT scanner to image the cross-section of the battery. Starting from the junction of the sidewall of the first groove 11 and the side seal 14, the horizontal measurement extends to the outermost edge of the first bend 141, which is L2. The width S1 of the top seal 15 of the membrane housing 1 can be measured using a 2.5D microscope. Starting from the junction of the top of the first groove 11 and the top seal 15, the vertical measurement extends to the outermost edge of the top seal 15, which is the width S1 of the top seal 15 of the membrane housing 1. The width S2 of the top seal 151 can be measured using a 2.5D microscope. At the tab 29, the distance between the two ends of the top seal 151 is measured perpendicularly to the top seal 151, which is the width S2 of the top seal 151. The outer edge width S3 of the top seal can be tested using a 2.5D microscope. The distance from the top seal 151 (closest to the top seal edge 15) to the edge of the top seal 15 is the outer edge width S3. The thickness H1 of the negative electrode current collector and the thickness H2 of the positive electrode current collector can be tested using a scanning electron microscope (SEM). The current collector without coating or the electrode sheet is cut into a cross-section using an argon ion milling instrument, and the thickness of the current collector is measured in backscatter mode of the SEM. The strength σ1 of the negative electrode current collector and the strength σ2 of the positive electrode current collector can be obtained as follows: The current collector is cut into strips of 15mm ± 0.2mm. Using a WD-D3 type electronic universal testing machine with a 50mm gap between the upper and lower clamps, both ends of the current collector are clamped in the clamps. The test is started at a speed of 100mm / min and continues until the equipment stops. The strength σ1 of the negative electrode current collector or the strength σ2 of the positive electrode current collector is recorded. The error of three tests should not exceed 10%, and the average value is taken. The gap G between cell 2 and membrane shell 1 along the battery height direction (third direction) can be determined by taking a cross-section of cell 2 using CT imaging, taking the innermost cross-section, and measuring the vertical length of the outermost negative electrode sheet 22 from the membrane shell 1. The sum of the lengths at the top and bottom is the gap G. The length T1 of adhesive layer 3 along the third direction, the width T2 of adhesive layer 3 along the first direction, the length T3 of cell 2 along the third direction, and the width T4 of cell 2 along the first direction can be measured using a digital caliper.

[0102] The embodiments of this utility model are based on the following example, referred to as Example 1: L1 is 3.3mm, L2 is 0.5mm, L3 is 2.05mm, S1 is 3.8mm, and S2 is 1.6mm. S3 is 0.8mm. Both the positive electrode 21 and the negative electrode 22 of the cell 2 are coated on both sides, with no single-sided coating. The negative current collector of the negative electrode 22 is copper foil, and the positive current collector of the positive electrode 21 is aluminum foil. The thickness H1 of the copper foil is 6μm, and the strength σ1 of the copper foil is 550Mpa. The thickness H2 of the aluminum foil is 10μm, and the strength σ2 of the aluminum foil is 180Mpa. The gap G between the cell 2 and the membrane shell 1 along the height direction of the battery is 3.6mm. The connection between the tab 29 of the cell 2 and the terminal 13 of the membrane shell 1 is such that the terminal 13 and the tab 29 are connected at the outermost point of the cell 2. The length T3 of the cell 2 along the third direction is 73.2mm, and the width T4 of the cell 2 along the first direction is 43.1mm. The length T1 of the adhesive layer 3 along the third direction is 70mm, and the width T2 of the adhesive layer 3 along the first direction is 20mm.

[0103] Comparative Example 1: The difference from Example 1 is that L2 and L3 are different. In Comparative Example 1, L2 is 0.2 and L3 is 6 mm. Therefore, L3 / L1 = 1.81 and L2 / L3 = 0.03. In Example 1, L3 / L1 = 0.62 and L2 / L3 = 0.24.

[0104] Comparative Example 2: The difference from Example 1 is that L2 and L3 are different. In Comparative Example 2, L2 is 0.9 mm and L3 is 0.8 mm. Therefore, L3 / L1 = 0.24 and L2 / L3 = 1.13.

[0105] The comparison results of Example 1 with Comparative Example 1 and Comparative Example 2 are shown in Table 1 below:

[0106] Table 1

[0107]

[0108] As shown in Table 1, compared with Example 1, L2 and L3 in Comparative Example 1 exceed their respective ranges, causing the values ​​of L3 / L1 and L2 / L3 to exceed the maximum values ​​of the formula range. This significantly impacts the battery's energy density, resulting in a noticeable decrease in energy density. Similarly, compared with Example 1, L2 and L3 in Comparative Example 2 exceed their respective ranges, causing the values ​​of L3 / L1 and L2 / L3 to be outside their respective formula ranges. This results in a significant increase in the battery's side voltage, a large drop in battery voltage after a voltage drop, and a slight decrease in other performance characteristics. In other words, inappropriate values ​​of L3 / L1 and L2 / L3 will affect either the battery's energy density or its side voltage and drop voltage. Therefore, L3 / L1 and L2 / L3 need to meet suitable ranges. A battery with optimal overall performance is achieved when 0.4 ≤ L3 / L1 ≤ 1 and 0.1 ≤ L2 / L3 ≤ 0.4.

[0109] Comparative Example 3: The difference from Example 1 is that S1 is different. In Comparative Example 3, S1 is 1.5 mm. Therefore, S3 / S2 = 0.5 and S2 / S1 = 1.1. In Example 1, S3 / S2 = 0.5 and S2 / S1 = 0.42.

[0110] Comparative Example 4: The difference from Example 1 is that S2 is different. In Comparative Example 4, S2 is 0.8 mm. Therefore, S3 / S2=1 and S2 / S1=0.21.

[0111] The comparison results of Example 1 with Comparative Examples 3 and 4 are shown in Table 2 below:

[0112] Table 2

[0113]

[0114] As shown in Table 2, compared with Example 1, Comparative Example 3 has a lower S1 value than Example 1, causing S2 / S1 to exceed the formula range. This results in a significant increase in the battery's side voltage, a substantial decrease in the storage voltage, and a slight reduction in other performance characteristics. Comparative Example 4, compared with Example 1, has an S2 value exceeding its required range, causing both S3 / S2 and S2 / S1 values ​​to exceed the formula range. This leads to a significant increase in the battery's side voltage and a substantial decrease in the storage voltage. In other words, when the values ​​of S3 / S2 and S2 / S1 are inappropriate, the battery's side voltage is likely to increase significantly, and the storage voltage will decrease substantially. Therefore, S3 / S2 and S2 / S1 need to meet appropriate ranges. When 0.3 ≤ S3 / S2 ≤ 0.84 and 0.25 ≤ S2 / S1 ≤ 0.9, the battery's overall performance is better.

[0115] Comparative Example 5: The difference from Example 1 lies in the structure of cell 2. In Comparative Example 5, the structure of cell 2 is such that the positive electrode 21 is wrapped around the negative electrode 22 at the tail. The comparison results between Example 1 and Comparative Example 5 are shown in Table 3 below:

[0116] Table 3

[0117]

[0118] As shown in Table 3, the cell structure of Comparative Example 5 is different from that of Example 1, and its cycle capacity retention and expansion performance are significantly lower than those of Example 1. That is, the structure of cell 2 will affect the battery's cycle capacity retention and expansion performance.

[0119] Comparative Example 6: The difference from Example 1 is that σ1 and G are different. In Comparative Example 6, σ1 is 280MPa and G is 2mm, so (H1×σ1+ H2×σ2)×G=6960, while in Example 1 (H1×σ1+ H2×σ2)×G=18360.

[0120] Comparative Example 7: The difference from Example 1 is that σ1, σ2 and G are different. In Comparative Example 7, σ1 is 500MPa, σ2 is 250MPa and G is 6mm, so that (H1×σ1+ H2×σ2)×G=33000.

[0121] The comparison results between Example 1 and Comparative Examples 6 and 7 are shown in Table 4 below:

[0122] Table 4

[0123]

[0124] As shown in Table 4, compared with Example 1, Comparative Example 6 has a smaller gap G between the cell 2 and the membrane shell 1, and a smaller copper foil strength σ1, which is lower than the minimum value of its range. This results in a decrease in the battery's cycle capacity retention rate and a significant increase in expansion. Compared with Example 1, Comparative Example 7 has a larger gap G between the cell 2 and the membrane shell 1, which is higher than the maximum value of its formula range. This results in a significant decrease in the battery's energy density. In other words, a smaller copper foil strength σ1 and a smaller gap G between the cell 2 and the membrane shell 1 will affect the battery's cycle capacity retention rate and expansion performance. Conversely, a larger copper foil strength σ1, aluminum foil strength σ2, and a larger gap G between the cell 2 and the membrane shell 1 will affect the battery's energy density. Therefore, when the relationship between G, H1, σ1, H2, and σ2 satisfies the above-mentioned relationship 8000≤(H1×σ1+ H2×σ2)×G≤30000, the battery exhibits better overall energy density, cycle capacity retention rate, and expansion performance.

[0125] Comparative Example 8: The difference from Example 1 lies in the method of bending the tab 29. In Comparative Example 8, the tab 29 is bent such that the pole post 13 is located between the upper and lower sides of the bent tab 29. The comparison results between Example 1 and Comparative Example 8 are shown in Table 5 below:

[0126] Table 5

[0127]

[0128] As shown in Table 5, Comparative Example 8 exhibits reduced energy density, decreased cycle capacity retention, and increased expansion, resulting in poorer expansion performance. In other words, the way the tabs are folded affects the battery's energy density, cycle capacity retention, and expansion performance.

[0129] Comparative Example 9: The difference from Example 1 lies in the values ​​of T1 and T3. In Comparative Example 9, T1 is 10 mm and T3 is 30 mm. The comparison results between Example 1 and Comparative Example 9 are shown in Table 6 below:

[0130] Table 6

[0131]

[0132] As shown in Table 6, the drop voltage of Comparative Example 9 decreased significantly. This means that when the width of the adhesive layer 3 along the first direction and its length along the third direction are too small, the area of ​​the adhesive layer 3 is small, making the separator 23 not securely fixed and affecting the drop voltage drop performance of the battery. Therefore, when the length T1 of the adhesive layer 3 along the third direction and the length T3 of the cell 2 along the third direction satisfy the relationship 0.8≤T1 / T3≤1.06, and the width T2 of the adhesive layer 3 along the first direction and the width T4 of the cell 2 along the first direction satisfy the relationship 0.2≤T2 / T4≤0.5, the battery can be ensured to have better drop performance.

[0133] It should also be noted that in this specification, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0134] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0135] The battery provided by this utility model has been described in detail above. Specific examples have been used to illustrate the principle and implementation of this utility model. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core idea of ​​this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made to this utility model without departing from the principle of this utility model, and these improvements and modifications also fall within the protection scope of this utility model.

Claims

1. A battery, characterized by, The application relates to a film shell (1) and a battery core (2), the film shell (1) is provided with a first groove (11) for accommodating the battery core (2) and a side sealing edge (14) arranged on the side of the first groove (11) along a first direction, the side sealing edge (14) comprises a first bending part (141) and a first flat part (142) connected with the first bending part (141), the first flat part (142) extends along a second direction, the second direction is perpendicular to the first direction, the depth of the first groove (11) is L1, the length of the first bending part (141) along the first direction is L2, the length of the first flat part (142) along the second direction is L3, and the relationship between L1, L2 and L3 satisfies the following formula: 0.4<=L3 / L1<=1; 0.1<=L2 / L3<=0.4; The width of the side sealing edge (14) is 1.3-6.6 mm.

2. The battery of claim 1, wherein, The film shell (1) is provided with a top sealing edge (15) at one end along a third direction which is perpendicular to the first direction and the second direction, the width of the top sealing edge (15) from one end close to the battery core (2) to one end far away from the battery core (2) is S1, a top sealing seal (151) is arranged between the two ends of the top sealing edge (15), the width of the top sealing seal (151) along the third direction is S2, and the distance from one end of the top sealing seal (151) far away from the battery core (2) to one end of the top sealing edge (15) far away from the battery core (2) along the third direction is S3, and the relationship between S1, S2 and S3 satisfies the following formula: 0.3<=S3 / S2<=0.84; 0.25<=S2 / S1<=0.

9.

3. The battery of claim 1, wherein, L1 is 1-10 mm, L2 is 0.3-0.8 mm, and L3 is 1-5.8 mm.

4. The battery of claim 2, wherein, S1 is 1.5-6 mm, S2 is 1-2.6 mm, and S3 is 0.5-3 mm.

5. The battery according to any one of claims 1 to 4, characterized in that, The battery core (2) comprises a positive electrode sheet (21), a diaphragm (23) and a negative electrode sheet (22) which are arranged in a winding mode, the end of the negative electrode sheet (22) is beyond the end of the positive electrode sheet (21), and the end of the diaphragm (23) is beyond the end of the negative electrode sheet (22).

6. The battery of claim 5, wherein, The starting end of the negative electrode sheet (22) comprises a second flat part (221), a second bending part (222), a third flat part (223), a third bending part (224) and a fourth flat part (225) which are sequentially connected along the winding direction, and the second flat part (221), the third flat part (223) and the fourth flat part (225) are arranged in parallel along the second direction. The outer side surface of the second flat section (221), the second bending section (222), the third flat section (223), the third bending section (224) and the fourth flat section (225) is provided with a first coating layer (24), the outer side surface refers to the side away from the winding center of the battery cell (2); one end of the second flat section (221) away from the second bending section (222) has an overhanging section (25) beyond the first coating layer (24) of the second flat section (221), the overhanging section (25) is not provided with an active layer, and the overhanging section (25) is bent towards the side away from the first coating layer (24) of the second flat section (221); or, The two side surfaces of the second flat section (221), the second bending section (222), the third flat section (223), the third bending section (224) and the fourth flat section (225) are provided with a second coating layer (26), and one end of the second flat section (221) away from the second bending section (222) is flush with the end of the second coating layer (26) of the second flat section (221).

7. The battery of claim 5, wherein, In the winding direction, the tail end of the negative plate (22) comprises a fifth flat section (226), a fourth bending section (227), a sixth flat section (228), a fifth bending section (229) and a seventh flat section (220) connected in sequence, and the fifth flat section (226), the sixth flat section (228) and the seventh flat section (220) are arranged in parallel along the second direction; The inner side surface of each of the fifth flat section (226), the fourth bending section (227), the sixth flat section (228), the fifth bending section (229) and the seventh flat section (220) is provided with a third coating layer (27), and the inner side surface refers to the side close to the winding center of the battery cell (2); or, The two side surfaces of each of the fifth flat section (226), the fourth bending section (227), the sixth flat section (228), the fifth bending section (229) and the seventh flat section (220) are provided with a fourth coating layer (28).

8. The battery of claim 5, wherein, The head end of the negative plate (22) is 1-10mm beyond the head end of the positive plate (21); and / or, The tail end of the negative plate (22) is 5-20mm beyond the tail end of the positive plate (21); and / or, The head end of the diaphragm (23) is 20-150mm beyond the head end of the negative plate (22); and / or, The part of the tail end of the negative plate (22) beyond the tail end of the positive plate (21) contains at least two first winding bending sections, and the part of the tail end of the diaphragm (23) beyond the tail end of the negative plate (22) contains at least 2-5 second winding bending sections.

9. The battery of claim 5, wherein, The negative electrode sheet (22) comprises a negative electrode current collector, the positive electrode sheet (21) comprises a positive electrode current collector, and a relationship between a gap G along a third direction perpendicular to the first direction and the second direction between the cell (2) and the film shell (1), a thickness H1 of the negative electrode current collector, a strength σ1 of the negative electrode current collector, a thickness H2 of the positive electrode current collector, and a strength σ2 of the positive electrode current collector needs to satisfy: 8000 ≤ (H1 × σ1 + H2 × σ2) × G ≤ 30000.

10. The battery of claim 9, wherein, The G is 0.8-4.6 mm; the σ1 is 300-800 MPa; the H1 is 4-15 μm; the σ2 is 100-300 MPa; and the H2 is 7-20 μm.

11. The battery of claim 5, wherein, The positive electrode sheet (21) is provided with at least two positive electrode tabs (29), all of which are arranged in layers, and the positive electrode tab (29) comprises a first transition portion, a sixth bending portion, and a first tab connecting portion (291), the first transition portion is connected with the positive electrode sheet (21), the sixth bending portion is connected between the first transition portion and the first tab connecting portion (291), all of the sixth bending portions are gathered in the middle region of the cell (2) along the second direction, and any two adjacent first tab connecting portions (291) are in contact and parallel to the end face of the end where the positive electrode tab (29) of the cell (2) is located. The negative electrode sheet (22) is provided with at least two negative electrode tabs, all of which are arranged in layers, and the negative electrode tab comprises a second transition portion, a seventh bending portion, and a second tab connecting portion, the second transition portion is connected with the negative electrode sheet (22), the seventh bending portion is connected between the second transition portion and the second tab connecting portion, all of the seventh bending portions are gathered in the middle region of the cell (2) along the second direction, and any two adjacent second tab connecting portions are in contact and parallel to the end face of the end where the negative electrode tab of the cell (2) is located. The film shell (1) is provided with a positive electrode post (13) and a negative electrode post, the positive electrode post (13) is connected with the side of the first tab connecting portion (291) away from the cell (2), and the negative electrode post is connected with the side of the second tab connecting portion away from the cell (2).

12. The battery of claim 5, wherein, The end of the separator (23) is provided with an adhesive layer (3), the adhesive layer (3) is connected with the separator (23), and a relationship between the length T1 of the adhesive layer (3) and the length T3 of the cell (2) along a third direction perpendicular to the first direction and the second direction needs to satisfy: 0.8 ≤ T1 / T3 ≤ 1.06; and a relationship between the width T2 of the adhesive layer (3) along the first direction and the width T4 of the cell (2) along the first direction needs to satisfy: 0.2 ≤ T2 / T4 ≤ 0.

5.

13. The battery of claim 1, wherein, The electric core (2) comprises a negative electrode sheet (22), the negative electrode sheet (22) comprises a negative electrode current collector, a first negative electrode active layer and a second negative electrode active layer, at least one of the first negative electrode active layer and the second negative electrode active layer is a silicon-containing carbon layer, the first negative electrode active layer is arranged on the surface of the negative electrode current collector, and the second negative electrode active layer is arranged on the side of the first negative electrode active layer away from the negative electrode current collector.

Images