Batteries and battery packs

Abstract

This invention relates to the field of battery technology and provides a battery and battery pack. The battery includes a casing, a cover plate, and a cell. The casing has a first side surface, at least one of which has a thickened portion. At least a portion of the thickened portion protrudes towards the cell. The cover plate is welded to the thickened portion. The cell is disposed in the receiving space formed by the casing and the cover plate. The cell includes a first electrode and a separator. The first electrode includes a current collector and an active material layer. The separator is at least partially disposed between the first electrode and the first side surface. In the height direction of the first side surface, the dimension of the thickened portion is h mm. In the direction perpendicular to the first side surface, the distance between the surface of the active material layer disposed on the first electrode and the outer end face of the cell is d μm. The puncture resistance of the separator is kgf, satisfying: 6.3 ≤ 291. This solution solves the problem in the prior art where lithium dendrites formed inside the cell easily puncture the separator, thus threatening battery safety.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a battery and a battery pack. Background Technology

[0002] A battery consists of a casing and cells housed inside the casing. To prevent electrical short circuits between the cells and the casing and to ensure mutual insulation, a separator is typically installed on the outermost layer of the cell as an insulating barrier; that is, the outermost electrode is separated from the inner wall of the casing by the separator. However, during battery charging and discharging, lithium dendrites can easily form inside the cell. These lithium dendrites can puncture the separator, causing insulation failure between the cell and the casing, resulting in an electrical short circuit, and thus threatening battery safety. Summary of the Invention

[0003] This invention provides a battery and battery pack to solve the problem in the prior art where lithium dendrites formed inside the battery cell can easily puncture the separator, thereby threatening battery safety.

[0004] According to an embodiment of the present invention, a battery is provided, the battery including a casing, a cover plate and a cell. The casing has an opening at at least one end and a first side. At least the first side has a thickened portion, at least a portion of which protrudes toward the cell. The cover plate seals the opening and is welded to the thickened portion. The casing and the cover plate form a receiving space. The cell is disposed in the receiving space. The cell includes a first electrode and a separator disposed near the first side. The first electrode includes a current collector and an active material layer disposed on at least one surface of the current collector. The separator is at least partially disposed between the first electrode and the first side.

[0005] In the height direction of the first side, the thickness of the thickened portion is h mm. In the direction perpendicular to the first side, the distance between the surface of the active material layer on the first electrode and the outer end face of the cell is d μm. The puncture resistance of the separator is k gf, satisfying: 6.3 ≤ ≤291.

[0006] Embodiments of the present invention also provide a battery pack comprising at least two of the above-described batteries.

[0007] Applying this technical solution, the outer casing provides installation space for the battery cell, preventing interference from the external environment. Furthermore, the first side of the casing has a thickened portion protruding towards the battery cell. The cover plate is welded to this thickened portion to form a sealed structure, preventing cracking at the connection between the cover plate and the casing due to the expansion of the battery cell volume during charging and discharging. This improves the welding strength between the cover plate and the casing, ensuring the stability and reliability of the device. Regardless of whether the battery cell is formed by winding or lamination, its outermost layer is typically a diaphragm to ensure insulation between the battery cell and the casing. The outer surface of the outermost diaphragm is the outer end face of the battery cell. The first electrode is the outermost electrode of the battery cell. The thickness h of the thickened portion, the distance d μm between the surface of the active material layer on the first electrode and the outer end face of the battery cell, and the puncture resistance of the diaphragm (kgf) are synergistically controlled to ensure that all three satisfy 6.3 ≤ The ≤291mm thickened section provides reliable welding support, improves the connection strength between the outer shell and the cover plate, and reserves expansion space for the cell, reducing the risk of the separator being punctured by lithium dendrites. This not only ensures the insulation performance of the battery and improves the battery's safety performance, but also ensures the rapid transport of ions within the cell, improving the overall charging and discharging efficiency of the battery and enhancing the battery's safety and cycle reliability.

[0008] when When the ratio is less than 6.3, if the proportions of d and k are too large, the electrolyte in the battery will have difficulty quickly wetting the inside of the cell. There will be dry areas inside the cell that are not wetted by the electrolyte, which will hinder ion transport, increase the overall resistance of the battery, and increase the heat generated inside the battery. In order to ensure battery safety, the battery thermal management system will automatically reduce the battery charging and discharging efficiency, and ultimately it will be difficult to guarantee the fast charging performance of the battery. If the proportion of h is too small, it will not be able to meet the requirements of increasing the welding size and thus enhancing the welding performance.

[0009] when When the ratio of d to k is greater than 291, if the proportion of d and k is too small, the cell will experience excessive local stress in the thickened part during battery charging and discharging, increasing the risk of material loss. After the electrode material is lost, the exposed foil area will easily form lithium dendrites due to the lack of lithium insertion sites, which will exacerbate the formation of lithium dendrites. At the same time, the puncture resistance k of the separator will also be small, making the separator more easily punctured by lithium dendrites, causing the electrode to overlap with the shell or positive and negative electrode sheets, increasing the risk of short circuit between the cell and the shell or positive and negative electrode sheets, and threatening battery safety. If the proportion of h is too large, the space reserved for cell expansion in the battery will be reduced, aggravating the situation of material loss due to compression, and increasing the risk of lithium dendrites puncturing the separator and causing a short circuit between the cell and the shell.

[0010] While ensuring the welding strength between the casing and the cover plate, each cell in the battery pack reduces the risk of active material shedding and lithium dendrite formation that could puncture the separator due to localized stress concentration during charging and discharging. This avoids insulation failure between the casing and the cell, and improves the overall safety and reliability of the battery. Attached Figure Description

[0011] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0012] Figure 1 A cross-sectional view of the battery provided by the present invention is shown;

[0013] Figure 2 A schematic diagram of the battery's structural dimensions is shown;

[0014] Figure 3 A partial structural cross-sectional view of the battery is shown from another angle;

[0015] Figure 4 A partial structural schematic diagram of the outer casing is shown;

[0016] Figure 5 A partial side view of the housing, including the thickened portion, is shown;

[0017] Figure 6 A schematic diagram of the battery structure is shown.

[0018] The above figures include the following reference numerals:

[0019] 10. Outer casing;

[0020] 11. First side view;

[0021] 12. Thickened section; 121. First region; 122. Second region;

[0022] 20. Cover plate; 21. Insulating component;

[0023] 30. Battery cells;

[0024] 31. First electrode; 311. Current collector; 312. Active material layer;

[0025] 32. Diaphragm; 321. Base membrane;

[0026] 33. Outer end face;

[0027] 40. Insulation layer. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] To address the issue of weld cracking at the connection between the casing and the cover plate, related technologies employ a thickened section at the casing opening to enhance the welding strength between the casing and the cover plate. However, this thickened section shortens the distance between the casing and the battery cell. During battery charging and discharging, the space reserved for cell expansion is reduced, causing stress compression on the electrode plates inside the cell, resulting in the shedding of active material from the electrode plates. The larger the protrusion of the thickened section, the greater the risk of material shedding. After the electrode plates shed material, the exposed foil area is prone to lithium dendrite formation due to the lack of lithium insertion sites. Lithium dendrites can easily puncture the separator, causing the electrode plates to overlap with the casing or the positive and negative electrode plates, resulting in an internal short circuit and threatening battery safety. Furthermore, the larger the protrusion of the thickened section, the greater the risk of material shedding.

[0030] To improve the welding strength between the outer casing and the cover plate, a thickened area is incorporated into the outer casing. However, this thickened area reduces the space reserved for cell expansion within the battery, increasing the risk of material breakage due to pressure. Reducing the height h of the thickened area can decrease the space it occupies within the battery, reducing the risk of material breakage under pressure and preventing lithium dendrites from piercing the separator, thus avoiding short circuits between the cell and the outer casing. However, if the height h is too small, it cannot achieve the desired effect of increasing the welding dimensions and enhancing welding performance. Therefore, the puncture resistance k of the separator is introduced. By reducing the value of k, the electrolyte's wetting performance of the cell can be improved, allowing the electrolyte to fully wet the cell and reducing the energy loss during charging and discharging. To prevent side reactions from generating gases that could lead to excessive internal pressure in the battery and cracking of the weld seam at the connection between the casing and the cover plate, a further increase in the distance d between the outermost electrode active material region and the side of the cell is introduced. Increasing the value of d can prevent lithium dendrites from piercing the separator, avoid direct contact between the cell and the casing leading to a short circuit, and ensure insulation. However, if d is too large, it will occupy too much internal space in the battery, making the battery too large. It will also lengthen the ion transport path, reduce the number and size of pores in the separator, making it difficult for the electrolyte to quickly wet the inside of the cell, reducing ion transport efficiency, and making it difficult to guarantee the fast charging performance of the battery.

[0031] Therefore, in order to enhance the connection strength between the casing and the cover plate, reduce the risk of puncture of the outermost separator of the cell, improve the insulation performance between the casing and the cell, and reduce the risk of active material loss, it is necessary to comprehensively control the height h of the thickened area, the distance d from the active material area of ​​the outermost electrode to the side of the cell, and the puncture resistance k of the separator. This requires controlling these three factors to meet the following conditions. This range ensures the battery's insulation performance while improving the overall charge and discharge rate of the battery.

[0032] like Figures 1 to 6 As shown, an embodiment of the present invention provides a battery, which includes a casing 10, a cover plate 20, and a battery cell 30. The casing 10 has an opening at at least one end and a first side 11. At least the first side 11 has a thickened portion 12, and at least a portion of the thickened portion 12 protrudes toward the battery cell 30. The cover plate 20 seals the opening and is welded to the thickened portion 12. The casing 10 and the cover plate 20 form a receiving space. The battery cell 30 is disposed in the receiving space. The battery cell 30 includes a first electrode 31 disposed near the first side 11 and a separator 32. The first electrode 31 includes a current collector 311 and an active material layer 312 disposed on at least one surface of the current collector 311. The separator 32 is at least partially disposed between the first electrode 31 and the first side 11.

[0033] In the height direction of the first side surface 11, the size of the thickened portion 12 is h mm. In the direction perpendicular to the first side surface 11, the distance between the surface of the active material layer 312 disposed on the first electrode 31 and the outer end face 33 of the battery cell 30 is d μm. The puncture resistance of the separator 32 is k gf, satisfying: 6.3 ≤ ≤291. Among them, This refers to taking the square root of (d×k) / h, i.e., ((d×k) / h). 1 / 2 .

[0034] The aforementioned battery can store chemical energy and controllably convert chemical energy into electrical energy. Recyclable batteries can be recharged after discharge to activate the active materials and continue to be used. Batteries typically include a casing and battery cells housed within the casing.

[0035] In the direction perpendicular to the first side 11, the end of the thickened portion 12 away from the cell 30 may be flush with the edge of the opening, or the end of the thickened portion 12 away from the cell 30 may be spaced apart from the edge of the opening, that is, there is another area between the thickened portion 12 and the edge of the opening where no thickened portion is provided (not shown in the figure).

[0036] By applying this technical solution, the outer casing 10 provides installation space for the battery cell 30, avoiding interference from the external environment. Furthermore, the first side 11 of the outer casing 10 has a thickened portion 12 protruding towards the battery cell 30. The cover plate 20 is welded to the thickened portion 12 to form a sealed structure, which avoids the problem of cracking at the connection between the cover plate 20 and the outer casing 10 due to the volume expansion of the battery cell 30 during charging and discharging. This improves the welding strength between the cover plate 20 and the outer casing 10, ensuring the stability and reliability of the device. Regardless of whether the battery cell 30 is formed by winding or lamination, its outermost side is usually set as a separator 32 to ensure insulation between the battery cell 30 and the outer casing 10. The outer surface of the outermost separator 32 is the outer end face 33 of the battery cell 30. The first electrode 31 is the outermost electrode of the battery cell 30. The thickness h of the thickened part 12, the distance d μm between the surface of the active material layer 312 on the first electrode 31 and the outer end face 33 of the battery cell 30, and the puncture resistance of the separator 32 are synergistically controlled so that the three together satisfy 6.3 ≤ The thickened portion 12, with a thickness of ≤291, provides reliable welding support, improving the connection strength between the outer shell 10 and the cover plate 20. At the same time, it provides expansion space for the cell 30, reducing the risk of the separator 32 being punctured by lithium dendrites. This not only ensures the insulation performance of the battery and improves its safety performance, but also ensures the rapid transport of ions within the cell 30, improving the overall charging and discharging efficiency of the battery and enhancing its safety and cycle reliability.

[0037] Among them, the distance between the surface of the active material layer 312 disposed on the first electrode 31 and the outer end face 33 of the cell 30 is one of the factors affecting the puncture resistance of the diaphragm 32. Other factors affecting the puncture resistance of the diaphragm 32 include diaphragm porosity, density, and material.

[0038] when When the ratio is less than 6.3, if the proportions of d and k are too large, the electrolyte in the battery will have difficulty quickly wetting the inside of the cell 30. There will be dry areas inside the cell 30 that are not wetted by the electrolyte, which will hinder ion transport, increase the overall resistance of the battery, and increase the heat generated inside the battery. In order to ensure battery safety, the battery thermal management system will automatically reduce the battery charging and discharging efficiency, and ultimately it will be difficult to guarantee the fast charging performance of the battery. If the proportion of h is too small, it will not be able to meet the requirements of increasing the welding size and thus enhancing the welding performance.

[0039] when When the ratio of d and k is greater than 291, if the proportion of d and k is too small, the cell 30 will be subjected to excessive local stress in the thickened part 12 during the charging and discharging process, which increases the risk of material loss. After the electrode material is lost, the empty foil area is exposed. Due to the lack of lithium intercalation sites, lithium dendrites are easily formed, which aggravates the formation of lithium dendrites. At the same time, the puncture resistance k of the separator 32 is also small, and the separator 32 is more easily punctured by lithium dendrites, causing the electrode to overlap with the shell 10 or the positive and negative electrode sheets, which increases the risk of short circuit between the cell 30 and the shell 10 or the positive and negative electrode sheets, threatening battery safety. If the proportion of h is too large, the space reserved for the expansion of the cell 30 in the battery will be reduced, which aggravates the situation of material loss due to compression, and increases the risk of lithium dendrites puncturing the separator 32 and causing a short circuit between the cell 30 and the shell 10.

[0040] Optionally, It can be any value between 7, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280 or 6.3 mm to 291 mm.

[0041] Optionally, the outer casing 10 may also include other sides such as a second side and a third side. In addition to the first side 11, the thickened portion 12 may be provided on the second side, the third side, and other sides simultaneously, or the thickened portion 12 may be provided continuously along the circumference of the outer casing 10, or the thickened portion 12 may be provided at intervals along the circumference of the outer casing 10.

[0042] Optionally, the thickened portion 12 is located on the outer casing 10 and includes a first thickened portion and a second thickened portion. The first thickened portion protrudes toward the battery cell 30, and the second thickened portion protrudes toward a side away from the battery cell 30. In a direction perpendicular to the first side surface 11, the first thickened portion and the second thickened portion are at least partially corresponding.

[0043] Optionally, the thickened portion 12 is located on the housing 10 and includes a first thickened portion that protrudes toward the battery cell 30.

[0044] In some embodiments, the orthographic projection of the first electrode 31 on the first side 11 at least partially overlaps with the orthographic projection of the thickened portion 12 on the first side 11.

[0045] This design ensures that the thickened part 12 has a larger dimension along the height direction of the first side 11, which guarantees the welding strength between the outer shell 10 and the cover plate 20, improves the stability and reliability of the connection between the two, avoids the problem of welding cracks between the outer shell 10 and the cover plate 20 during battery charging and discharging, and improves the overall safety and stability of the battery.

[0046] like Figure 1 and Figure 2As shown, the thickened portion 12 has an upper end and a lower end. The upper end is the end of the thickened portion 12 that is close to the cover plate 20, and the lower end is the end of the thickened portion 12 that is away from the cover plate 20. In the direction perpendicular to the first side surface 11, the size of the upper end is larger than the size of the lower end.

[0047] In this embodiment, the thickened portion 12 has an upper end and a lower end, and in the direction perpendicular to the first side 11, the size of the upper end is larger than the size of the lower end. The larger upper end increases the weld line size between the outer shell 10 and the cover plate 20, thereby enhancing the welding strength. The smaller lower end provides more expansion space for the cell 30, reducing the risk of the active material layer 312 on the first electrode 31 falling off due to compression during battery charging and discharging, and ensuring the insulation performance between the outer shell 10 and the cell 30.

[0048] like Figure 1 , Figure 5 As shown, the thickened portion 12 includes a first region 121 and a second region 122 connected in sequence. The first region 121 is disposed near the cover plate 20. In the direction perpendicular to the first side 11, the size of the first region 121 is the thickness of the first region 121, and the size of the second region 122 is the thickness of the second region 122. The thickness of the second region 122 gradually decreases along the direction away from the cover plate 20 from the first side 11, and the thickness of the first region 121 is greater than the maximum thickness of the second region 122.

[0049] In this embodiment, the thicker first region 121 can be stably connected to the cover plate 20 to ensure the reliability of the weld. The thickness of the second region 122 gradually decreases along the first side 11 away from the cover plate 20, forming a buffer transition structure. This avoids stress concentration caused by a sudden change in thickness at the junction of the thickened part 12 and the outer shell 10, preventing breakage at this point when the cell expands. This ensures the integrity of the battery structure and function and improves the safety of use.

[0050] In some embodiments, the orthographic projection of the first pole piece 31 onto the first side surface 11 at least partially overlaps with the orthographic projection of the second region 122 onto the first side surface 11.

[0051] With this configuration, the larger upper part of the second region 122 enhances the welding strength and the tightness of the connection. The thickness of the second region 122 gradually decreases along the direction away from the cover plate 20 on the first side 11, reserving more expansion space for the cell 30. This reduces the risk of the active material layer 312 on the first electrode 31 falling off due to compression during battery charging and discharging, suppresses the formation of lithium dendrites, and ensures the insulation performance between the outer casing 10 and the cell 30.

[0052] like Figure 1 and Figure 3As shown, the thickness of the first region 121 is equal everywhere. One end of the first region 121 is welded to the cover plate 20, and the other end of the first region 121 is connected to the second region 122.

[0053] In this embodiment, after eliminating measurement errors and processing errors, the thickness of the first region 121 is equal everywhere, which ensures the weld line size between the outer shell 10 and the cover plate 20, improves the uniformity and stability of the weld, reduces the mechanical stress in the weld area, and enhances the weld strength between the outer shell 10 and the cover plate 20.

[0054] In an embodiment not shown, the thickened portion 12 protrudes from the first side surface 11 by an amount of c1 mm in the direction perpendicular to the first side surface 11, satisfying: 0.05 mm ≤ c1 mm ≤ 1.2 mm.

[0055] Setting the size range of 0.05mm≤c1mm≤1.2mm ensures the weld line size between the cover plate 20 and the outer shell 10, improving the welding strength, while also ensuring that the battery cell 30 has sufficient expansion space. This avoids the battery cell 30 being squeezed against the outer shell 10 due to volume expansion during charging and discharging, reduces the risk of material loss from the active material layer 312, suppresses the formation of lithium dendrites, and ensures the insulation performance between the outer shell 10 and the battery cell 30.

[0056] If c1 mm < 0.05 mm, the contact area between the cover plate 20 and the thickened part 12 will be insufficient, the weld wire size will be too small, the welding strength will be reduced, and the risk of weld wire cracking will be increased. If c1 mm > 1.2 mm, the reserved expansion space of the cell 30 will be excessively occupied, causing the cell 30 to be under pressure, increasing the risk of the active material layer 312 on the first electrode 31 falling off due to compression, thereby causing the insulation between the outer shell 10 and the cell 30 to fail.

[0057] Optionally, c1 can be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.2, or other values ​​between 0.05mm and 1.2mm. Among these, c1mm is best selected between 0.05mm and 0.5mm.

[0058] In an embodiment not shown, in the first electrode 31, an active material layer 312 is disposed on the side of the current collector 311 facing the outer end face 33 of the cell 30, and d μm > 5 μm.

[0059] The active material layer 312 is disposed on the side of the current collector 311 facing the outer end face 33 of the cell 30. When the battery is charged and discharged, the volume of the cell 30 expands, and the active material layer 312 will come into contact with the outer casing 10 under pressure, which will aggravate the shedding of the active material layer 312 and promote the formation of lithium dendrites. However, by setting d μm > 5 μm, the thickness of the separator 32 disposed between the first electrode 31 and the outer casing 10 is ensured, the risk of lithium dendrite puncture is reduced, the insulation performance between the outer casing 10 and the cell 30 is ensured, and the safety of the battery is improved.

[0060] like Figure 2 As shown, in the direction perpendicular to the first side 11, the distance between the surface of the active material layer 312 of the first electrode 31 and the thickened portion 12 is L1 mm, which satisfies: 0.05 mm ≤ L1 mm ≤ 0.5 mm.

[0061] This setting, limiting the thickness to 0.05mm≤L1mm≤0.5mm, provides sufficient expansion space for the cell 30 during charging and discharging, while ensuring the thickness of the separator 32 located between the first electrode 31 and the outer casing 10. This reduces the risk of lithium dendrite puncture, ensures the insulation performance between the outer casing 10 and the cell 30, and improves the safety of the battery.

[0062] Alternatively, L1 can be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.5 or other values ​​between 0.05 mm and 0.5 mm, among which, L1 mm between 0.07 mm and 0.3 mm is more effective.

[0063] In some embodiments, in the first electrode 31, the active material layer 312 is disposed on the side of the current collector 311 away from the outer end face 33 of the cell 30, and the current collector 311 is located between the first side face 11 and the active material layer 312.

[0064] The active material layer 312 is disposed on the side of the current collector 311 away from the outer end face 33 of the cell 30, and is spaced apart from the outer casing 10 through the current collector 311. This avoids the active material layer 312 being directly subjected to the extrusion pressure of the outer casing 10, reduces material loss, suppresses the generation of lithium dendrites, and ensures the insulation performance between the outer casing 10 and the cell 30.

[0065] In an embodiment not shown, the thickness of the active material layer 312 located on one side of the first electrode 31 in the direction perpendicular to the first side 11 is c2 μm, satisfying: 20 μm ≤ c2 μm ≤ 220 μm.

[0066] If c2 μm < 20 μm, meaning the thickness of the active material layer 312 is too small, it will lead to a decrease in the energy density of the battery and reduce battery performance. If c2 μm > 220 μm, meaning the thickness of the active material layer 312 is too large, when the cell 30 expands in volume, the active material layer 312 is more easily squeezed by the outer casing 10, which will aggravate material loss, promote the formation of lithium dendrites, increase the risk of the separator 32 being punctured, and easily lead to insulation failure between the outer casing 10 and the cell 30, threatening battery safety.

[0067] Optionally, c2 can be 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220 or other values ​​between 20μm and 220μm, among which c2 μm between 30μm and 210μm is more effective.

[0068] In some embodiments, at least two separators 32 are disposed between the first electrode 31 and the outer end face 33 of the cell 30. The outermost layer of the cell 30 is the separator 32, and the outer end face 33 is the outer surface of the outermost separator 32 disposed on the cell 30. Multiple separators 32 can be disposed between the first electrode 31 and the outer end face 33. This arrangement increases the overall thickness of the separator 32 between the first electrode 31 and the outer end face 33 of the cell 30, reduces the risk of lithium dendrite puncture, prevents electrical short circuit between the casing 10 and the cell 30, and ensures battery safety.

[0069] In an embodiment not shown, the diaphragm 32 includes a base film 321 and a ceramic layer coated on at least one surface of the base film 321. In a direction perpendicular to the first side surface 11, the ratio of the thickness of the base film 321 to the total thickness of the diaphragm 32 is A, which satisfies: 0.3≤A≤0.9.

[0070] The diaphragm 32 includes a base membrane 321 and a ceramic layer coated on at least one surface of the base membrane 321. The diaphragm 32 enables the flow and transport of ions but does not conduct electricity. Therefore, the diaphragm 32 ensures the insulation performance between the battery cell 30 and the outer casing 10 or adjacent electrodes. The base membrane 321 can be wetted by the electrolyte to enable the free transport of ions in the electrolyte. The ceramic layer cannot be wetted by the electrolyte and is used to enhance the structural strength of the diaphragm 32, avoiding the overall structural strength of the diaphragm 32 being low due to the relatively soft base membrane 321.

[0071] If A < 0.3, the wetting effect of the electrolyte will be worse, reducing the ion transport efficiency and increasing the battery resistance, thus affecting the fast charging performance of the battery. If A > 0.9, the overall structural strength of the separator 32 will decrease, increasing the risk of the separator 32 being punctured, which may lead to insulation failure between the outer shell 10 and the cell 30, threatening battery safety.

[0072] Optionally, A can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, or other values ​​between 0.3 and 0.9, with A between 0.38 and 0.8 generally yielding better results.

[0073] In some embodiments, the diaphragm 32 further includes an adhesive layer, and a ceramic layer is disposed on the side of the base membrane 321 facing the first side 11, with the adhesive layer being at least partially disposed between the ceramic layer and the base membrane 321.

[0074] With this configuration, when the cell 30 expands, the local stress applied by the thickened portion 12 to the separator 32 is first concentrated on the ceramic layer. Because the ceramic layer has high structural strength, it can improve the puncture resistance of the separator 32 in the stress concentration area, thereby preventing the active material layer 312 from falling off due to extrusion, and avoiding lithium dendrites piercing the separator 32 and causing an electrical short circuit between the cell 30 and the casing 10. At least a partial adhesive layer is provided between the ceramic layer and the base membrane 321 to firmly connect the ceramic layer and the base membrane 321, reduce the gap between the two, and enhance the supporting effect of the ceramic layer on the base membrane 321.

[0075] In an embodiment not shown, the diaphragm 32 further includes an adhesive layer, which is at least partially disposed between the first electrode 31 and the base film 321.

[0076] The separator 32 also includes an adhesive layer, which realizes a stable connection between the first electrode 31 and the base film 321, while reducing the gap between the first electrode 31 and the base film 321, shortening the ion transport channel, reducing the battery resistance, and improving the battery's charge and discharge efficiency.

[0077] Specifically, the adhesive layer can be used to bond the positive electrode and the negative electrode, so that the positive electrode and the negative electrode are bonded to both sides of the base film 321, reducing the gap between the positive electrode and the negative electrode, shortening the ion transport channel, reducing the battery resistance, and improving the battery's charging and discharging efficiency.

[0078] In some embodiments, the thickness of the adhesive layer in the direction perpendicular to the first side 11 is c3 μm, satisfying: 1μm≤c3 μm≤5μm.

[0079] If c3 μm < 1 μm, the thickness of the adhesive layer is too small, the bonding strength between the first electrode 31 and the base film 321 is small, and it is difficult to ensure a tight connection between the two, making it difficult to achieve the effect of reducing the gap between the first electrode 31 and the base film 321. If c3 μm > 5 μm, the thickness of the adhesive layer is too large, which expands the gap between the first electrode 31 and the base film 321, prolongs the ion transport channel, increases the battery resistance, and reduces the charging and discharging efficiency of the battery.

[0080] Optionally, c3 can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or other values ​​between 1 μm and 5 μm, among which c3 μm between 2 μm and 4 μm is better.

[0081] like Figure 1 and Figure 3 As shown, the battery also includes an insulating layer 40, which is located between the outer casing 10 and the cell 30. In the direction perpendicular to the first side 11, the thickness of the insulating layer 40 is greater than the thickness of the separator 32.

[0082] The insulating layer 40 has insulating properties and is located between the outer shell 10 and the cell 30. The thickness of the insulating layer 40 is greater than that of the separator 32, which can prevent the separator 32 from being punctured by lithium dendrites due to local compression. This further improves the insulation performance between the outer shell 10 and the cell 30, reduces the risk of electrical short circuit, and ensures the safety and reliability of the battery.

[0083] like Figure 1 As shown, the battery also includes an insulating component 21, which is disposed between the cover plate 20 and the cell 30. In the height direction of the first side 11, the height of the insulating layer 40 is greater than the height of the cell 30, and one end of the insulating layer 40 is connected to the insulating component 21.

[0084] With this configuration, the height of the insulation layer 40 is greater than the height of the battery cell 30, and one end of the insulation layer 40 is connected to the insulating component 21 in the cover plate 20. The insulating component 21 is used to ensure insulation between the cover plate 20 and the battery cell 30. This configuration achieves complete physical isolation between the battery cell 30 and the outer casing 10, which can prevent the outer end face 33 of the battery cell 30 from directly contacting or overlapping with the outer casing 10 due to expansion or assembly stress. This further enhances the reliability of insulation between the end area of ​​the battery cell 30 and the outer casing 10, and solves the hidden danger of local short circuit caused by the lack of coverage of the height boundary.

[0085] In an embodiment not shown, in the height direction of the first side 11, the upper end face of the insulating layer 40 is L2 mm higher than the upper end face of the battery cell 30, satisfying: 0.1 mm ≤ L2 mm ≤ 5 mm.

[0086] If L2 mm < 0.1 mm, it cannot be guaranteed that the end of the cell 30 near the cover plate 20 is completely physically isolated from the outer casing 10. There is a risk that the cell 30 may come into direct contact or overlap with the outer casing 10 due to expansion, which may lead to a partial short circuit. If L2 mm > 5 mm, the end of the insulation layer 40 near the cover plate 20 is too close to the weld between the outer casing 10 and the cover plate 20. The high temperature at the weld will cause the insulation layer 40 to vaporize directly, resulting in small pores or tiny impurities in the weld wire, which reduces the strength of the weld wire. At the same time, the increased gas pressure inside the battery will also cause excessive pressure at the weld wire, which may lead to cracking of the weld wire.

[0087] Alternatively, L2 can be any value between 0.1 mm and 5 mm, such as 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, or 0.1 mm. Among these values, L2 mm between 0.3 mm and 4 mm is preferred.

[0088] In some embodiments, the insulating layer 40 is disposed at least around the outer peripheral surface of the battery cell 30, and the battery cell 30 is spaced apart from the housing 10 through the insulating layer 40.

[0089] With this configuration, the insulation layer 40 forms a continuous physical isolation around the outer periphery of the cell 30, avoiding insulation failure between the cell 30 and the outer casing 10 caused by the partial setting of the insulation layer 40, thus improving the overall safety and structural reliability of the battery under actual working conditions.

[0090] In an embodiment not shown, in the height direction of the first side 11, the overlap dimension of the first electrode 31 and the projection of the thickened portion 12 perpendicular to the first side 11 is L3 mm, satisfying: 0.1 mm ≤ L3 mm ≤ 10 mm.

[0091] If L3 mm < 0.1 mm, the size of the thickened part 12 is too small, resulting in a small weld line size between the outer shell 10 and the cover plate 20, which cannot guarantee the weld strength; if L3 mm > 10 mm, the size of the thickened part 12 is too large, which easily leads to a small expansion space reserved for the battery cell 30, which in turn leads to compression between the battery cell 30 and the outer shell 10, exacerbating the shedding of the active material layer 312, promoting the formation of lithium dendrites, and increasing the risk of local short circuit.

[0092] Optionally, L3 can be 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 or other values ​​between 0.1 mm and 10 mm. Among these, L3 mm between 0.4 mm and 8 mm is generally considered to be the best choice.

[0093] like Figure 2As shown, 1.8mm≤h mm≤20mm, and / or 3μm≤d μm≤110μm, and / or 200gf≤k gf≤1400gf.

[0094] If h mm < 1.8 mm, the size of the thickened part 12 is too small, resulting in a small weld line size between the outer shell 10 and the cover plate 20, which cannot guarantee the weld strength. During the charging and discharging process of the battery, the internal air pressure will increase significantly, and even if the explosion-proof valve is opened, it cannot meet the pressure relief requirements. If the weld line strength is small, cracks are likely to occur at the weld, and there is even a risk that the cover plate 20 will fly off. If L3 mm > 20 mm, the size of the thickened part 12 is too large, resulting in a reduction in the internal space of the battery, which makes it easier to squeeze the cell 30 and the active material layer 312 on it, causing material to fall off, promoting the formation of lithium dendrites, and increasing the risk of local short circuits.

[0095] If d μm < 3 μm, the risk of lithium dendrite puncture increases, which can easily cause insulation failure between the outer casing 10 and the cell 30. If d μm > 110 μm, the wetting performance of the electrolyte is reduced, resulting in excessive resistance inside the cell 30, which reduces the charging and discharging efficiency and affects the fast charging performance of the battery.

[0096] If k gf < 200 gf, the separator 32 is easily punctured by lithium dendrites, increasing the risk of local short circuits in the battery; if k gf > 1400 gf, the thickness of the separator 32 increases, resulting in a reduction in the internal space of the battery, making it easier to squeeze the cell 30 and the active material layer 312 on it, or increasing the manufacturing and processing cost of the separator 32 and increasing the production difficulty.

[0097] Optionally, h mm can be 2 mm, 5 mm, 8 mm, 11 mm, 14 mm, 17 mm, 20 mm, or other values ​​between 1.8 mm and 20 mm; d μm can be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, or other values ​​between 3 μm and 110 μm; k gf can be 200 gf, 300 gf, 400 gf, 500 gf, 600 gf, 700 gf, 800 gf, 900 gf, 1000 gf, 1100 gf, 1200 gf, 1300 gf, 1400 gf, or other values ​​between 200 gf and 1400 gf.

[0098] Furthermore, h mm can be 4mm-11mm, d μm can be 5μm-100μm, and k gf can be 300gf-1200gf.

[0099] The test methods for three parameters—the distance d μm between the surface of the active material layer 312 on the first electrode 31 and the outer end face 33 of the cell 30, the puncture resistance k gf of the separator 32, and the size h mm of the thickened part 12—and the adjustment method for k are as follows:

[0100] The test method for d is as follows: along the direction perpendicular to the first side 11, the distance between the surface of the active material layer 312 set on the first electrode 31 and the outer end face 33 of the battery cell 30 is measured using a microscope image measuring instrument and recorded as d mm.

[0101] Test method for k: Refer to "GBT37841-2019 Test method for puncture resistance of plastic films and sheets", measure the puncture resistance of diaphragm 32, and record it as k gf.

[0102] Test method for h: Measure the dimensions of the thickened part 12 along the height direction of the first side 11 using a micrometer (accuracy 0.1mm), measure 3 times, and take the average value as h mm.

[0103] Methods for adjusting k: Adjust parameters such as material, molecular weight, density and porosity of diaphragm 32 through the through hole, control the thickness of diaphragm 32, and increase coating (such as ceramic coating, aramid coating, etc.) to control the puncture resistance of the diaphragm.

[0104] The battery is manufactured as follows:

[0105] (1) Preparation of the positive electrode:

[0106] The prepared positive electrode active material, conductive agent (e.g., acetylene black), and binder (e.g., PVDF) are mixed, and NMP solvent is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, the foil is rolled and slit to obtain the positive electrode sheet. Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies the following conditions: .

[0107] (2) Preparation of negative electrode:

[0108] A negative electrode active material, a conductive agent (e.g., acetylene black), a thickener (e.g., carboxymethyl cellulose (CMC)), and a binder (e.g., styrene-butadiene rubber (SBR)) are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated onto both surfaces of a negative electrode current collector foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, the foil is rolled and slit to obtain a negative electrode sheet. Specifically, the ratio of negative electrode active material: conductive agent: thickener: binder meets the following requirements: .

[0109] (3) Preparation of electrolyte:

[0110] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0111] (4) Preparation of the diaphragm:

[0112] Polyethylene film is selected as the diaphragm.

[0113] (5) Preparation of lithium-ion batteries:

[0114] A thickened section is provided at the opening of the outer casing. The positive electrode, separator, and negative electrode are stacked in sequence and wound to form a battery cell. After welding the tabs of the battery cell to the terminal assembly, it is placed in the battery casing, and the cover plate is welded to the casing. The battery is dried, electrolyte is injected, and after encapsulation, settling, formation, and volume adjustment, a lithium-ion battery is obtained.

[0115] In the selection of materials for the aforementioned battery, this application may also select other materials, not limited to those limited by the above preparation method. The positive electrode active material may be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate. The conductive agent in the positive electrode sheet may also be selected from one or more of graphite, superconducting carbon, Ketjen black, SuperP, carbon nanotubes, graphene, and carbon nanofibers. The binder in the positive electrode sheet may also be selected from one or more of polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, and carboxymethyl chitosan. The positive electrode current collector may also be selected from one or more of stainless steel with silver plating, stainless steel, aluminum, nickel, carbon electrode, carbon, nickel, and titanium. The positive electrode current collector may also include a composite current collector, which may include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming metallic materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on a polymer substrate (such as a substrate of polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.).

[0116] The negative electrode active material can be selected from one or more of the following negative electrode active main materials: artificial graphite, natural graphite, silicon carbide, silicon oxide, lithium titanate, etc.; the conductive agent in the negative electrode sheet can be selected from one or more of the following: conductive carbon black, conductive graphite, carbon nanotubes, graphene, carbon fiber, etc.; the binder in the negative electrode sheet can be selected from one or more of the following: styrene-butadiene rubber, polyacrylic acid and its salts, sodium alginate, etc.; the thickener in the negative electrode sheet can be selected from one or more of the following: sodium carboxymethyl cellulose, polyacrylonitrile multi-component copolymer, etc.; the negative electrode current collector can also be selected from one or more of the following: stainless steel with silver plating, stainless steel, copper, nickel, carbon electrode, carbon, nickel, titanium, etc.; the negative electrode current collector can also include composite current collectors, which can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.). The negative electrode active layer includes the negative electrode active material, conductive components, adhesives, etc.

[0117] The battery needs to undergo the following performance tests:

[0118] Performance Test 1: Battery Short Circuit Test.

[0119] Following the battery preparation method described above, 200 batteries were prepared for each of the embodiments and comparative examples. The d, k, and h values ​​of the batteries in each embodiment are shown in Table 1 below. Apart from this, the other structures are the same.

[0120] The lithium-ion batteries prepared in the examples and comparative examples were subjected to cycle tests at 25°C according to the following procedure.

[0121] (1) Charge at a constant current of 1C to the upper limit voltage, and charge at a constant voltage until the current drops to 0.05C;

[0122] (2) Let stand for 10 minutes;

[0123] (3) Discharge the battery at a 1C rate to the lower limit voltage;

[0124] (4) Let stand for 10 minutes.

[0125] Perform 400 charge-discharge cycles according to steps (1) to (4).

[0126] Set the alarm current value of the withstand voltage tester to 0.1mA and the voltage value between the two output terminals to 1kV. Connect the two output terminals of the withstand voltage tester to the battery casing and the terminal assembly respectively, and apply the set voltage value. If the withstand voltage tester issues an alarm, it is determined that a short circuit has occurred between the terminal assembly and the casing. Record the number of batteries that have short-circuited, denoted as N. The battery short-circuit rate = (N / 200) × 100%. If the battery short-circuit rate is less than or equal to 1%, it is considered good. If the battery short-circuit rate is greater than 1% and less than or equal to 2%, it is considered qualified. If the battery short-circuit rate is greater than 2%, it is considered unqualified.

[0127] Different battery systems require corresponding adjustments to their upper and lower voltage limits: For cathode active materials including LFP (LiFePO4, lithium iron phosphate) – upper limit voltage 3.65V, lower limit voltage 2.5V; for cathode active materials including NCM (lithium nickel cobalt manganese oxide) – upper limit voltage 4.25V, lower limit voltage 2.5V; for cathode active materials including LFMP (lithium manganese iron phosphate) – upper limit voltage 4.25V, lower limit voltage 2.5V; for cathode active materials including lithium nickel manganese oxide – upper limit voltage 4.8V, lower limit voltage 3.5V.

[0128] The positive electrode active material used in this test was selected from LiNi. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, other positive electrode active materials all meet the above test requirements, and the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and other negative electrode active materials all meet the above test requirements, and the mass ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0129] Performance Test 2: Battery Internal Resistance Test.

[0130] Following the battery preparation method described above, 100 batteries were prepared for each of the embodiments and comparative examples. The d, k, and h values ​​of the batteries in each embodiment are shown in Table 1 below. Apart from this, the other structures are the same.

[0131] The lithium-ion batteries prepared in the examples and comparative examples were subjected to cycle tests at 25°C according to the following procedure.

[0132] (1) Charge at a constant current of 1C to the upper limit voltage, and charge at a constant voltage until the current drops to 0.05C;

[0133] (2) Let stand for 10 minutes;

[0134] (3) Discharge the battery at a 1C rate to the lower limit voltage;

[0135] (4) Let stand for 10 minutes;

[0136] Perform 200 charge-discharge cycles according to steps (1) to (4).

[0137] Use an AC resistance tester to measure the resistance between the positive and negative terminals. Determine if the measured resistance is greater than 0.6mΩ. If it is greater than 0.6mΩ, record the number of batteries that do not meet the battery internal resistance standard, denoted as N. The rate of batteries that do not meet the battery internal resistance standard is calculated as (N / 100) × 100%. If the rate of batteries that do not meet the battery internal resistance standard is less than or equal to 2%, it is considered good. If the rate of batteries that do not meet the battery internal resistance standard is greater than 2% and less than or equal to 5%, it is considered qualified. If the rate of batteries that do not meet the battery internal resistance standard is greater than 5%, it is considered unqualified.

[0138] Different battery systems require corresponding adjustments to their upper and lower voltage limits: For cathode active materials including LFP (LiFePO4, lithium iron phosphate) – upper limit voltage 3.65V, lower limit voltage 2.5V; for cathode active materials including NCM (lithium nickel cobalt manganese oxide) – upper limit voltage 4.25V, lower limit voltage 2.5V; for cathode active materials including LFMP (lithium manganese iron phosphate) – upper limit voltage 4.25V, lower limit voltage 2.5V; for cathode active materials including lithium nickel manganese oxide – upper limit voltage 4.8V, lower limit voltage 3.5V.

[0139] In this test, the positive electrode active material of the battery was selected as LiNi0.6Co0.2Mn0.2O2. Other positive electrode active materials all met the above test requirements. The mass ratio of positive electrode active material: conductive agent: binder met 96:2:2. The negative electrode active material was selected as artificial graphite. Other negative electrode active materials all met the above test requirements. The mass ratio of negative electrode active material: conductive agent: thickener: binder met 95:2:1:2.

[0140] Table 1

[0141]

[0142] As can be seen from Table 1, in Examples 1 to 20, The values ​​all ranged from 6.3 to 291. The battery resistance test results were either qualified or good, and the battery short-circuit test results were either qualified or good. In Comparative Examples 1 to 4, The values ​​are all outside the range of 6.3-291. Among them, the battery short circuit test results of Comparative Example 1 and Comparative Example 3 are both unqualified, and the battery resistance test results of Comparative Example 2 and Comparative Example 4 are both unqualified.

[0143] In an embodiment not shown, when the thickness of the first electrode 31 is c4 in the direction perpendicular to the first side 11, it satisfies the following condition: c4 mm ≥ 20 mm, k gf < 1200 gf.

[0144] When c4 mm≥20mm, the thickness of the first electrode 31 is relatively large, and the limit k gf<1200gf ensures that the electrolyte has good wetting performance, improves the ion transport efficiency, reduces the internal resistance of the cell 30, and improves the charging and discharging efficiency of the battery.

[0145] In some embodiments, the first electrode 31 is a negative electrode.

[0146] This configuration ensures that the outermost electrode of the cell 30 is the negative electrode, resulting in a greater number of negative electrode plates than positive electrode plates in the cell 30. This provides more lithium insertion sites, reduces the risk of lithium dendrite formation, and prevents the formed lithium dendrites from piercing the separator 32 and causing a short circuit between the casing 10 and the cell 30, thus improving the overall safety of the battery.

[0147] This invention also provides a battery pack comprising at least two of the aforementioned batteries.

[0148] While ensuring the welding strength between the outer casing 10 and the cover plate 20, each battery in the battery pack reduces the risk of the active material layer 312 falling off and lithium dendrites forming and piercing the separator 32 due to local stress concentration during the charging and discharging process. This avoids insulation failure between the outer casing 10 and the battery cell 30, and improves the overall safety and reliability of the battery.

[0149] The battery in this application is a secondary battery, also known as a rechargeable battery or accumulator, which refers to a battery that can be recharged after discharge to activate the active materials and continue to be used. Typically, a secondary battery includes a cell, an electrolyte, and a casing. The cell includes a positive electrode, a negative electrode, and a separator. The cell and electrolyte are assembled inside the casing. During the charging and discharging process, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes.

[0150] As an example, the preparation process of a secondary battery is as follows: the positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. Then, the electrodes are wound or stacked to obtain a cell. The cell is placed in a casing, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0151] The positive electrode is one of the core components of a battery that carries the positive electrode active material. During charging, metal ions (e.g., lithium ions) are released from the crystal lattice of the positive electrode active material (oxidation reaction), migrate through the electrolyte, and embed into the negative electrode. During discharging, metal ions (e.g., lithium ions in a lithium battery) are released from the negative electrode and embed into the crystal lattice of the positive electrode active material (reduction reaction), thus achieving the storage and release of lithium ions. A positive electrode generally includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is coated on at least one surface of the positive electrode current collector and includes: positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes, but is not limited to, at least one of the following: lithium phosphates, lithium transition metal oxides and their respective modified compounds, or other conventional materials that can be used as positive electrode active materials in batteries. These positive electrode active materials can be used alone or in combination of two or more. The lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. The lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds.

[0152] The positive electrode conductive agent includes, but is not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, SuperP, etc.), carbon nanotubes, graphene, and carbon nanofibers. The positive electrode binder includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0153] The negative electrode includes a negative current collector and a negative active layer disposed on at least one surface of the negative current collector. During battery charging, active ions (e.g., lithium ions) from the positive electrode are embedded in the negative electrode, while electrons from the positive electrode are transferred to the negative electrode through an external circuit to maintain charge balance. During discharge, the active ions (e.g., lithium ions) previously embedded in the negative electrode can be released, while electrons on the negative electrode are transferred to the negative electrode through an external circuit to maintain charge balance, thus achieving energy storage and release.

[0154] The negative electrode current collector is a conductive metal foil, which can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium with a silver-plated surface. Composite current collectors may include a polymer base layer and a metal layer. Composite current collectors can be formed by forming metal materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0155] The negative electrode active layer includes the negative electrode active material, conductive agent, binder, etc. The negative electrode active material can be carbon-based materials such as graphite, porous carbon, hard carbon, soft carbon, mesophase carbon microspheres, or silicon-based materials such as elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, etc. The conductive agent can be conductive carbon black, carbon nanotubes, etc., and the binder can be styrene-butadiene rubber, polyacrylic acid, etc.

[0156] A separator is positioned between the positive and negative electrode plates to separate them, primarily preventing short circuits and allowing active ions to pass through. The separator can be made of at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF). A coating can also be applied to the separator surface. This coating can be inorganic or organic, with inorganic coating materials including at least one of alumina, silicon dioxide, titanium dioxide, magnesium oxide, zirconium oxide, and boehmite; and organic coatings including at least one of aramid coatings and PVDF coatings.

[0157] The electrolyte, located between the positive and negative electrodes, primarily serves to conduct active ions.

[0158] The battery pack of this application is formed by connecting multiple batteries of similar capacity and internal resistance in series or in parallel.

[0159] The battery cell, as used in this application, is the component in a battery where electrochemical reactions occur; it is the smallest unit in a battery capable of performing electrochemical reactions such as charging / discharging. A battery cell is the basic unit of a battery and typically includes a positive electrode, a negative electrode, and a separator. Lithium-ion battery cells primarily function by the movement of lithium ions between the positive and negative electrodes. In cylindrical battery cells, the three-layer thin-film structure is wound into a cylindrical electrode assembly, while in cuboid battery cells, the thin-film structure is wound or stacked into an electrode assembly with a generally cuboid shape.

[0160] The aforementioned casing is a component used to provide a space to house the battery cell and other components and isolate them from the external environment. The casing generally includes a body with an opening at at least one end and a housing space. The opening of the casing can be closed by a cover plate, sealing and isolating the internal environment of the battery from the external environment. Casing materials include, but are not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, and aluminum-plastic film.

[0161] A cover is a component that seals the opening of the casing to isolate the internal environment of the battery from the external environment. Its materials include, but are not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, etc. The material of the cover can be the same as that of the casing.

[0162] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0163] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0164] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0165] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0166] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0167] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A battery, characterized in that, The battery includes a casing (10), a cover plate (20), and a battery cell (30). At least one end of the casing (10) is provided with an opening. The casing (10) has a first side surface (11). At least the first side surface (11) has a thickened portion (12). At least a portion of the thickened portion (12) protrudes toward the battery cell (30). The cover plate (20) blocks the opening and is welded to the thickened portion (12). The casing (10) and the cover plate (20) form a receiving space. The battery cell (30) is disposed in the receiving space. The battery cell (30) includes a first electrode (31) disposed near the first side surface (11) and a separator (32). The first electrode (31) includes a current collector (311) and an active material layer (312) disposed on at least one surface of the current collector (311). The separator (32) is at least partially disposed between the first electrode (31) and the first side surface (11). In the height direction of the first side surface (11), the size of the thickened portion (12) is h mm. In the direction perpendicular to the first side surface (11), the distance between the surface of the active material layer (312) disposed on the first electrode (31) and the outer end face (33) of the battery cell (30) is d μm. The puncture resistance of the separator (32) is k gf, satisfying: 6.3 ≤ ≤291.

2. The battery according to claim 1, characterized in that, The orthographic projection of the first electrode (31) on the first side (11) at least partially overlaps with the orthographic projection of the thickened portion (12) on the first side (11).

3. The battery according to claim 1, characterized in that, The thickened portion (12) has an upper end and a lower end. The upper end is the end of the thickened portion (12) that is close to the cover plate (20), and the lower end is the end of the thickened portion (12) that is away from the cover plate (20). In the direction perpendicular to the first side surface (11), the size of the upper end is larger than the size of the lower end.

4. The battery according to claim 2, characterized in that, The thickened portion (12) includes a first region (121) and a second region (122) connected in sequence. The first region (121) is disposed close to the cover plate (20). In a direction perpendicular to the first side surface (11), the size of the first region (121) is the thickness of the first region (121), and the size of the second region (122) is the thickness of the second region (122). The thickness of the second region (122) gradually decreases along the direction away from the cover plate (20) from the first side surface (11), and the thickness of the first region (121) is greater than the maximum thickness of the second region (122).

5. The battery according to claim 4, characterized in that, The orthographic projection of the first electrode (31) onto the first side (11) at least partially overlaps with the orthographic projection of the second region (122) onto the first side (11).

6. The battery according to claim 4, characterized in that, The thickness of the first region (121) is equal everywhere. One end of the first region (121) is welded to the cover plate (20), and the other end of the first region (121) is connected to the second region (122).

7. The battery according to claim 1, characterized in that, In the direction perpendicular to the first side surface (11), the thickened part (12) protrudes from the first side surface (11) by a dimension of c1 mm, satisfying: 0.05 mm ≤ c1 mm ≤ 1.2 mm.

8. The battery according to any one of claims 1 to 7, characterized in that, In the first electrode (31), the active material layer (312) is disposed on the side of the current collector (311) facing the outer end face (33) of the cell (30), and dμm>5μm.

9. The battery according to claim 8, characterized in that, In the direction perpendicular to the first side (11), the distance between the surface of the active material layer (312) on the first electrode (31) and the thickened portion (12) is L1 mm, satisfying: 0.05 mm ≤ L1 mm ≤ 0.5 mm.

10. The battery according to any one of claims 1 to 7, characterized in that, In the first electrode (31), the active material layer (312) is disposed on the side of the current collector (311) away from the outer end face (33) of the cell (30), and the current collector (311) is located between the first side face (11) and the active material layer (312).

11. The battery according to any one of claims 1 to 7, characterized in that, In the direction perpendicular to the first side surface (11), the thickness of the active material layer (312) located on one side of the first electrode (31) is c2 μm, satisfying: 20μm≤c2 μm≤220μm.

12. The battery according to any one of claims 1 to 7, characterized in that, At least two diaphragms (32) are provided between the first electrode (31) and the outer end face (33) of the battery cell (30).

13. The battery according to any one of claims 1 to 7, characterized in that, The diaphragm (32) includes a base film (321) and a ceramic layer coated on at least one surface of the base film (321). In a direction perpendicular to the first side surface (11), the ratio of the thickness of the base film (321) to the total thickness of the diaphragm (32) is A, which satisfies: 0.3≤A≤0.

9.

14. The battery according to claim 13, characterized in that, The diaphragm (32) further includes an adhesive layer, the ceramic layer is disposed on the side of the base membrane (321) facing the first side (11), and the adhesive layer is at least partially disposed between the ceramic layer and the base membrane (321).

15. The battery according to claim 13, characterized in that, The diaphragm (32) further includes an adhesive layer, which is at least partially disposed between the first electrode (31) and the base film (321).

16. The battery according to claim 15, characterized in that, In the direction perpendicular to the first side surface (11), the thickness of the adhesive layer is c3 μm, satisfying: 1μm≤c3 μm≤5μm.

17. The battery according to any one of claims 1 to 7, characterized in that, The battery also includes an insulating layer (40) located between the outer casing (10) and the battery cell (30). In a direction perpendicular to the first side surface (11), the thickness of the insulating layer (40) is greater than the thickness of the separator (32).

18. The battery according to claim 17, characterized in that, The battery also includes an insulating component (21), which is disposed between the cover plate (20) and the battery cell (30). In the height direction of the first side surface (11), the height of the insulating layer (40) is greater than the height of the battery cell (30), and one end of the insulating layer (40) is connected to the insulating component (21).

19. The battery according to claim 18, characterized in that, In the height direction of the first side surface (11), the upper end face of the insulating layer (40) is L2 mm higher than the upper end face of the battery cell (30), satisfying: 0.1 mm ≤ L2 mm ≤ 5 mm.

20. The battery according to claim 17, characterized in that, The insulating layer (40) is disposed at least around the outer peripheral surface of the battery cell (30), and the battery cell (30) is disposed at a distance from the outer casing (10) through the insulating layer (40).

21. The battery according to any one of claims 1 to 7, characterized in that, In the height direction of the first side (11), the overlap dimension of the projection of the first electrode (31) and the thickened part (12) perpendicular to the first side (11) is L3 mm, which satisfies: 0.1 mm ≤ L3 mm ≤ 10 mm.

22. The battery according to any one of claims 1 to 7, characterized in that, 1.8mm≤h mm≤20mm, and / or 3μm≤d μm≤110μm, and / or 200gf≤k gf≤1400gf.

23. The battery according to any one of claims 1 to 7, characterized in that, When the thickness of the first electrode (31) is c4 mm in the direction perpendicular to the first side (11), it satisfies the following condition: when c4 mm ≥ 20 mm, k gf < 1200 gf.

24. The battery according to any one of claims 1 to 7, characterized in that, The first electrode (31) is the negative electrode.

25. A battery pack, characterized in that, The battery pack comprises at least two batteries as described in any one of claims 1 to 24.

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