Battery cell and battery pack

Abstract

The application provides an electric core and a battery pack, and relates to the technical field of energy storage. The electric core comprises a shell and a pole piece arranged in the shell. The pole piece comprises four edge structures located at four edge portions, and each of the four edge structures comprises a second edge structure at a slitting position. The electric core further comprises a sealing structure. The sealing structure covers the side surface of the second edge structure and is arranged in the thickness direction to overlap the second edge structure. The side surface of the second edge structure is a side surface of the pole piece parallel to the thickness direction. The sealing structure covers the side surface of the second edge structure, so that burrs on the side surface and loose or possibly falling powder are covered, burrs on the side surface are prevented from piercing the pole piece to cause short circuit, and the powder on the side surface is prevented from falling off, so that the falling powder is prevented from remaining in the electric core to pierce the diaphragm and cause short circuit.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and more particularly to a battery cell and battery pack. Background Technology

[0002] In the manufacturing process of battery cells in related technologies, burrs and powder particles are generated at the slitting point of the electrode sheets during the electrode sheet cutting process. These burrs and powder particles can easily cause short circuits in the battery cells, posing a risk of thermal runaway.

[0003] In some related technologies, in order to avoid burrs, the burrs at the cutting point are polished after the electrode is cut to avoid the influence of burrs. However, polishing cannot effectively deal with the separated powder particles. Polishing will also increase the separated powder particles, so it still cannot effectively reduce or avoid the risk of thermal runaway of the battery cell. Utility Model Content

[0004] Embodiments of this application provide a battery cell and a battery pack to reduce the risk of thermal runaway of the battery cell.

[0005] In a first aspect, embodiments of this application provide a battery cell, which includes a housing and an electrode sheet disposed within the housing. The electrode sheet includes four edge structures located at four edges, each of the four edge structures including an active material layer, a current collector, and an active material layer sequentially stacked in the thickness direction of the electrode sheet. One of the four edge structures used to connect a tab is a first edge structure, and the edge structure adjacent to the first edge structure is a second edge structure. Specifically, the second edge structure also includes an active material layer, a current collector, and an active material layer sequentially stacked in the thickness direction of the electrode sheet, and the side surface of the second edge structure is the side surface of the electrode sheet parallel to the thickness direction. The battery cell also includes a sealing structure, a portion of which covers the side surface of the second edge structure, and a portion of the sealing structure is combined with the active material layers on both sides of the current collector. That is, a portion of the sealing structure overlaps with the second edge structure in the thickness direction. It can be understood that the combination of the partial sealing structure with the active material layers on both sides of the current collector can mean that the sealing structure is combined with the surface of the active material layer or with the interior of the active material layer. In this embodiment, since the electrode is typically cut along the side surface of the second edge structure during slitting, meaning the cutting surface is the side surface of the second edge structure, burrs are generally generated on the side surface of the second edge. The sealing structure covers the side surface of the second edge structure, thereby covering the burrs and loose or potentially detached powder on the side surface. This prevents the burrs on the side surface from puncturing the electrode and causing a short circuit, and also prevents powder from falling off the side surface, thus preventing detached powder from remaining inside the cell and puncturing the separator and causing a short circuit. Furthermore, the sealing structure overlaps with the second edge structure in the thickness direction to prevent powder from falling off, thereby preventing detached powder from puncturing the separator and causing a short circuit. Moreover, the sealing structure has ionic insulation properties, which can block abnormal lithium ion deposition at the edge and reduce the risk of dendrites puncturing the separator. The sealing structure can also prevent the exposed metal current collector on the cut surface from directly contacting the electrolyte or the opposite electrode, reducing the probability of micro-short circuits.

[0006] In some embodiments, the second edge structure further includes an upper surface and a lower surface opposite each other in the thickness direction, with a side surface connecting the upper and lower surfaces, and a closed structure covering the side surface, upper surface, and lower surface respectively. In this embodiment, since the upper and lower surfaces of the second edge structure are also prone to powder separation, in order to avoid thermal runaway of the battery cell caused by burrs and separated powder, the closed structure covers the side surface, upper surface, and lower surface respectively, thereby preventing powder from falling off in all directions, and reducing or avoiding the risk of thermal runaway of the battery cell caused by the falling powder.

[0007] In some embodiments, the closed structure includes a first portion covering the side surface, a second portion covering the upper surface, and a third portion covering the lower surface, with the second and third portions respectively connected to the first portion. In this embodiment, the closed structure includes a first portion covering the side surface, a second portion covering the upper surface, and a third portion covering the lower surface, with the second and third portions respectively connected to the first portion. That is, the closed structure is a U-shaped structure with its opening generally facing horizontally. By physically encapsulating the second edge structure through the closed structure, i.e., encapsulating the electrode cutting edge, burrs can be covered and powder shedding can be inhibited, preventing burrs and shed powder from piercing the diaphragm or contacting adjacent electrodes and causing a short circuit. Moreover, due to its U-shaped structure, the elasticity or rigidity of the closed structure can support and prevent the electrode from cracking or deforming at the edge due to mechanical stress during winding or charging / discharging.

[0008] In some embodiments, the dimensions of the first portion in the direction perpendicular to the side surface are 0.5mm-2mm, or the dimensions of the second portion in the thickness direction are 3μm-30μm, or the dimensions of the third portion in the thickness direction are 3μm-30μm. In this embodiment, the dimensions of the first portion in the direction perpendicular to the side surface are within this range. After the first portion covers the burrs, a safety margin can be reserved, and edge exposure caused by coating alignment errors can be avoided. In addition, when the dimensions of the first portion in the direction perpendicular to the side surface are >2mm, it will occupy the effective area of ​​the electrode sheet and reduce the capacity of the cell; when the dimensions of the first portion in the direction perpendicular to the side surface are <0.5mm, it cannot effectively cover the burrs. The dimensions of the second portion in the thickness direction are in the range of 3μm-30μm, which can effectively cover the active material layer of the second edge structure and prevent the material in the active material layer from falling off. Similarly, the dimensions of the third portion in the thickness direction are in the range of 3μm-30μm, which can effectively cover the active material layer of the second edge structure and prevent the material in the active material layer from falling off.

[0009] In some embodiments, the dimensions of the second portion and the third portion are both 1mm-2mm in the direction perpendicular to the side surface. In this embodiment, the size of the second portion is within this range, which substantially completely avoids the shedding of the active layer and the formation of burrs, preventing thermal runaway of the battery cell, and also minimizes the impact on energy density and process complexity. Similarly, the size of the third portion is within this range, which substantially completely avoids the shedding of the active layer and the formation of burrs, preventing thermal runaway of the battery cell, and also minimizes the impact on energy density and process complexity.

[0010] In some embodiments, the electrode further includes a central portion located between the four edge structures. The central portion includes an active material layer, a current collector, and another active material layer stacked sequentially in the thickness direction of the electrode. The current collector of the second edge structure and the current collector of the central portion have the same dimensions in the thickness direction. In the thickness direction, the dimensions of the active material layers on both sides of the current collector of the second edge structure are smaller than the dimensions of the active material layers on both sides of the current collector of the central portion. In this embodiment, in the thickness direction, the dimensions of the active material layers on both sides of the current collector of the second edge structure are smaller than the dimensions of the active material layers on both sides of the current collector of the central portion. Therefore, when the second part of the closed structure covers the upper surface of the second edge structure, it can effectively offset part of the thickness of the second part in the thickness direction. Similarly, when the third part of the closed structure covers the lower surface of the second edge structure, it can also effectively offset part of the thickness of the third part in the thickness direction. This can effectively reduce the thickness increase of the electrode edge and avoid affecting the tightness of the cell stacking or winding.

[0011] In some embodiments, the upper surface of the second portion in the thickness direction is flush with the upper surface of the middle portion in the thickness direction, the lower surface of the second portion in the thickness direction is disposed on the upper surface of the second edge structure, and the lower surface of the third portion in the thickness direction is flush with the lower surface of the middle portion in the thickness direction, while the upper surface of the third portion in the thickness direction is disposed on the lower surface of the second edge structure. In this embodiment, since the upper surface of the second portion in the thickness direction is flush with the upper surface of the middle portion in the thickness direction, a tight fit between the electrodes can be ensured during electrode stacking or winding, thereby effectively improving the energy density of the cell. Similarly, the lower surface of the third portion in the thickness direction is flush with the lower surface of the middle portion in the thickness direction, while the upper surface of the third portion in the thickness direction is disposed on the lower surface of the second edge structure. Because the lower surface of the third portion in the thickness direction is flush with the lower surface of the middle portion in the thickness direction, a tight fit between the electrodes can be ensured during electrode stacking or winding, thereby effectively improving the energy density of the cell.

[0012] In some embodiments, a portion of the closed structure is mixed within the active material layers on both sides of the current collector of the second edge structure. In this embodiment, because a portion of the closed structure penetrates into and combines with the active material layer of the second edge structure, the loose or soon-to-fall-off powder in the active material layer is stably fixed by the penetrated closed structure to prevent powder from falling off. Moreover, this method can also avoid the closed structure causing an increase in the thickness of the edge portion of the electrode sheet. Therefore, this embodiment can reduce the impact on the tightness of cell stacking or winding, that is, effectively reduce the impact on the energy density of the cell.

[0013] In some embodiments, the second edge structure is elongated, and the closed structure extends from one end of the second edge structure to the other along its length. In this embodiment, the closed structure can effectively cover most of the second edge structure, thereby effectively covering the burrs on the side surface of the second edge structure and inhibiting powder shedding from the second edge structure.

[0014] In some embodiments, the edge structure opposite to the first edge structure among the four edge structures is the third edge structure. The sealing structure is disposed on the side surface of the third edge structure and overlaps with the third edge structure in the thickness direction. The side surface of the third edge structure is the outer surface of the electrode sheet parallel to the thickness direction. In this embodiment, the sealing structure covers the side surface of the third edge structure, thereby covering the burrs and loose powder located on the side surface of the third edge structure. This prevents the burrs on the side surface of the third edge structure from puncturing the electrode sheet and causing a short circuit, and also prevents the powder on the side surface of the third edge structure from falling off, thus preventing the fallen powder from remaining inside the cell and puncturing the separator and causing a short circuit.

[0015] In some embodiments, the four edge structures include two second edge structures, both of which are provided with a closed structure. In this embodiment, the two slit surfaces of the electrode can be covered by the closed structure to effectively suppress burrs and powder on the two second edge structures, thereby reducing the risk of thermal runaway in the battery cell.

[0016] Secondly, embodiments of this application provide a battery pack, which includes a housing and a battery cell as described in any of the first aspects above, with the battery cell disposed within the housing.

[0017] Thirdly, embodiments of this application provide an energy storage device, which includes a cabinet and a battery pack as described in the second aspect above, with the battery pack housed within the cabinet. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0019] Figure 1 This is a schematic diagram of the structure of a battery pack provided in an embodiment of this application;

[0020] Figure 2A for Figure 1 A schematic diagram of the battery cell structure in the embodiment;

[0021] Figure 2B for Figure 1 A schematic diagram of the battery cell structure in the embodiment;

[0022] Figure 3 for Figure 2A or Figure 2BA schematic diagram of the combination of the electrode and the closed structure in the embodiment;

[0023] Figure 4 for Figure 3 A simplified schematic diagram of the electrode and the closed structure in the embodiment;

[0024] Figure 5 for Figure 3 A view of the structure in the embodiment from direction A;

[0025] Figure 6 for Figure 2A or Figure 2B A schematic diagram of the combination of the electrode and the closed structure in the embodiment;

[0026] Figure 7 for Figure 6 A view of the structure in the embodiment from direction A;

[0027] Figure 8 for Figure 2A or Figure 2B A schematic diagram of the combination of the electrode and the closed structure in the embodiment;

[0028] Figure 9 for Figure 8 A view of the structure in the embodiment from direction A;

[0029] Figure 10 This is a schematic diagram of another battery cell with a combination of electrode and enclosure structure, provided as an embodiment of this application.

[0030] Explanation of reference numerals in the attached figures:

[0031] M, thickness direction; A, direction

[0032] 1. Battery pack; 2. Casing; 3. Battery cell; 4. Outer casing; 5. Cover; 6. Electrode; 7. Tab;

[0033] 10. Active substance layer; 11. First active substance layer; 12. Second active substance layer;

[0034] 20. Current collector;

[0035] 30. Edge structure;

[0036] 31. First edge structure;

[0037] 32. Second edge structure; 321. Side surface of the second edge structure; 322. Upper surface of the second edge structure; 323. Lower surface of the second edge structure;

[0038] 33. Third edge structure;

[0039] 40. Middle part; 41. Upper surface of the middle part; 42. Lower surface of the middle part;

[0040] 50. Closed structure; 51. First part; 52. Second part; 521. Upper surface of the second part; 522. Lower surface of the second part; 53. Third part; 531. Upper surface of the third part; 532. Lower surface of the third part. Detailed Implementation

[0041] The following section will first explain some of the terms used in the embodiments of this application.

[0042] The terms "first," "second," "third," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0043] In this specification, the terms "vertical" and "parallel" are explained.

[0044] Perpendicularity: The perpendicularity defined in this application is not limited to an absolute perpendicular intersection (with an included angle of 90 degrees). It is permissible for non-absolute perpendicular intersections caused by factors such as assembly tolerances, design tolerances, and structural flatness. It is permissible for errors within a small angular range, such as an assembly error range of 80 to 100 degrees, which can all be understood as a perpendicular relationship.

[0045] Parallelism: The parallelism defined in this application is not limited to absolute parallelism. This definition of parallelism can be understood as basic parallelism, allowing for situations where the parallelism is not absolute due to factors such as assembly tolerances, design tolerances, and structural flatness. These situations may lead to the sliding mating part and the first door panel not being absolutely parallel, but this application also defines such situations as parallelism.

[0046] Modern society is filled with a large number of devices that rely on electricity, from small household appliances to large data centers and factory production lines. Electricity supply is one of the factors that maintain the normal operation of modern society. Therefore, energy storage devices have developed rapidly and are widely used. This application provides an energy storage device, such as an energy storage cabinet using battery packs, a power cabinet for a data center, or even a vehicle using battery packs. Energy storage devices can be used to store electrical energy and supply power to devices that require electricity. Energy storage devices can be applied in fields such as site energy, photovoltaics, residential energy storage, industrial and commercial energy storage, and large-scale ground-mounted power plant energy storage.

[0047] With the development of energy storage equipment, safety has become the top priority. As the core component of energy storage equipment, the safety performance of the battery pack determines the safety performance of the energy storage equipment. Preventing thermal runaway of the battery cells in the battery pack can effectively improve the safety performance of the battery pack.

[0048] The reason why some battery packs in related technologies experience thermal runaway is that during the manufacturing process of the cells inside the battery pack, burrs and separated powder are generated when the electrode sheets are cut. The burrs and separated powder can puncture the electrode sheets, causing short circuits between the electrode sheets, which leads to thermal runaway of the cells and increases the risk of thermal runaway of the battery pack.

[0049] To improve the safety of battery pack 1, refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a battery pack 1 provided in an embodiment of this application. Figure 1 The top cover of housing 2 is hidden and not shown; see reference [reference]. Figure 1 The battery pack 1 includes a housing 2 and multiple battery cells 3 disposed inside the housing 2. The multiple battery cells 3 are arranged inside the housing 2.

[0050] The housing 2 includes a bottom wall, a top cover, and multiple side walls located between the bottom wall and the top cover. The bottom wall, the top cover, and the multiple side walls enclose a cavity for accommodating the battery cell 3. For ease of description, the Z direction in the attached figures is the height direction Z of the battery pack 1, the X direction in the attached figures is the length direction X of the battery pack 1, and the Y direction in the attached figures is the width direction of the battery pack 1. The height direction Z is also the direction in which the top cover and the bottom wall are opposite each other.

[0051] The casing 2 is made of metal, such as aluminum.

[0052] Figure 2A for Figure 1 A schematic diagram of the structure of cell 3 in the embodiment. Figure 2A Cell 3 in the middle is a stacked cell 3. Figure 2B for Figure 1 A schematic diagram of the structure of cell 3 in the embodiment. Figure 2BThe battery cell 3 in the figure is a wound battery cell 3. Specifically, the battery cell 3 includes a housing 4 and a plurality of electrode plates 6 disposed within the housing 4. The plurality of electrode plates 6 include a positive electrode plate 6 and a negative electrode plate 6. The battery cell 3 also includes a separator (not shown in the figure) disposed between the positive electrode plate 6 and the negative electrode plate 6. Figure 2A The battery cell 3 is composed of a positive electrode 6, a separator, and a negative electrode 6 stacked together. Figure 2B The battery cell 3 is made up of a positive electrode 6, a separator, and a negative electrode 6 wound together.

[0053] Reference Figure 2A or Figure 2B The battery cell 3 also includes tabs 7, such as a positive tab 7 and a negative tab 7. The tabs 7 are located on the side of the battery cell 3 facing the cover 5 of the outer casing 4. The positive tab 7 is used for electrical connection to the positive terminal on the cover 5, and the negative tab 7 is used for electrical connection to the negative terminal on the cover 5. The positive tab 7 is electrically connected to the positive electrode plate 6, and the negative tab 7 is electrically connected to the negative electrode plate 6. In the attached diagram, the Z direction represents the height direction Z of the battery cell 3, the X direction represents the thickness direction X of the battery cell 3, and the Y direction represents the width direction of the battery cell 3.

[0054] Figure 2A and Figure 2B In the embodiment, the risk of short circuits in the electrode 6 caused by burrs and separated powder generated during the cutting process of the battery cell 3 in the battery pack 1 is effectively resolved through reasonable structural design. See the embodiments below for details.

[0055] Figure 3 for Figure 2A or Figure 2B A schematic diagram of the structure in which the electrode 6 is combined with the closed structure 50 in the embodiment. Figure 4 for Figure 3 A simplified schematic diagram of the electrode 6 and the closed structure 50 in the embodiment. For ease of illustration, the side surface 321 of the second edge structure 32 is shown. Figure 4 In the embodiment, part of the side surface 321 is not covered by the closed structure 50. In the actual product, the entire side surface 321 can be covered by the closed structure 50.

[0056] Reference Figure 3 In this embodiment, the electrode 6 comprises an active material layer 10, a current collector 20, and the active material layer 10 stacked sequentially in its thickness direction M. The current collector 20 can be made of materials such as aluminum foil or copper foil; for example, the positive electrode 6 is made of aluminum foil, and the negative electrode 6 is made of copper foil. The electrode 6 is used to collect and conduct current, directing the current generated by the active material layer 10 to an external circuit. The electrode 6 also serves as a carrier, supporting the active material layer 10 and other functional coatings.

[0057] The active material layer 10 of the positive electrode 6 and the active material layer 10 of the negative electrode 6 are also different. For example, the active material layer 10 of the positive electrode 6 can be made of materials such as lithium transition metal oxides, such as lithium cobalt oxide (LiCoO2), ternary materials (LiNiCoMnO2 / NCM), and lithium iron phosphate (LiFePO4). The active material layer 10 of the negative electrode 6 can be made of materials such as graphite (C), silicon-based materials (Si / SiO3), or lithium metal (Li). During charging and discharging, the active material layer 10 of the positive electrode 6 stores and releases energy through the insertion and extraction of lithium ions. The active material layer 10 of the negative electrode 6 is used to receive and store lithium ions to complete the electrochemical reaction.

[0058] For ease of description, the active material layers 10 on both sides of the current collector 20 are designated as the first active material layer 11 and the second active material layer 12, respectively.

[0059] The electrode 6 includes four edge structures 30 located at its four edges. For example, when the electrode 6 is unfolded into a rectangular sheet structure, it has four sides, and the four edge structures 30 are located at the positions of these four sides. These four edge structures 30 are three-dimensional structures, not simply referring to a single surface. Specifically, each of the four edge structures 30 includes an active material layer 10, a current collector 20, and another active material layer 10, which are sequentially stacked in the thickness direction M of the electrode 6. It can be understood that the active material layer 10, current collector 20, and the active material layer 10 included in the four edge structures 30 are also the four edges of the first active material layer 11, the current collector 20, and the second active material layer 12 of the electrode 6. It should be noted that the thickness direction M mentioned below refers to the thickness direction M of the electrode 6 when it is unfolded.

[0060] exist Figure 3 In this embodiment, the electrode 6 further includes a central portion 40 located between the four edge structures 30, that is, the four edge structures 30 are located around the central portion 40. It is understood that the central portion 40 is also a three-dimensional structure. The central portion 40 also includes an active material layer 10, a current collector 20, and another active material layer 10 stacked sequentially in the thickness direction M of the electrode 6. It is understood that the active material layer 10, current collector 20, and the active material layer 10 included in the central portion 40 are also the central portion 40 of the first active material layer 11, the current collector 20, and the second active material layer 12 of the electrode 6. Furthermore, the current collector 20 of the central portion 40 is integrally formed with the current collectors 20 of the four edge structures 30, and the active material layers 10 on both sides of the current collector 20 of the central portion 40 are also integrally formed with the active material layers 10 on both sides of the current collectors 20 of the four edge structures 30.

[0061] Reference Figure 3In this embodiment, for ease of description, one of the four edge structures 30 used to connect the tab 7 is designated as the first edge structure 31, the edge structure 30 adjacent to the first edge structure 31 is designated as the second edge structure 32, and the edge structure 30 opposite to the first edge structure 31 is designated as the third edge structure 33. That is, the second edge structure 32 is connected between the first edge structure 31 and the third edge structure 33. The number of second edge structures 32 can be two, and the two second edge structures 32 are arranged opposite to each other.

[0062] Reference Figure 3 and Figure 4 In this embodiment, the second edge structure 32 includes an upper surface 322 and a lower surface 323 opposite to each other in the thickness direction M, and a side surface 321 connecting the upper surface 322 and the lower surface 323. The upper surface 322 is the outer surface of the active material layer 10 on one side of the current collector 20 of the second edge structure 32 in the thickness direction M; that is, the upper surface 322 is the outer surface of the first active material layer 11 of the second edge structure 32 facing away from the outer surface of the current collector 20 in the thickness direction M. The lower surface 323 is the outer surface of the active material layer 10 on the other side of the current collector 20 of the second edge structure 32 in the thickness direction M; that is, the lower surface 323 is the outer surface of the second active material layer 12 of the second edge structure 32 facing away from the outer surface of the current collector 20 in the thickness direction M. The side surface 321 is parallel to the thickness direction M when the electrode 6 is unfolded. That is, the side surface 321 is the side surface of the electrode 6 parallel to the thickness direction M. It can be understood that the side surface of the electrode 6 is the surface connecting the top and bottom surfaces of the electrode 6 in the thickness direction M. The side surface of the electrode 6 is formed by the current collector 20 of the electrode 6 on the side surface, the side surface of the first active material layer 11, and the side surface of the second active material layer 12.

[0063] Since the electrode sheet 6 is typically cut along the side surface 321 of the second edge structure 32, meaning the cutting surface is the side surface 321 of the second edge structure 32, burrs are generally generated on the side surface 321 of the second edge structure 32. Furthermore, powder not only separates from the side surface 321 of the second edge structure 32, but also easily separates from the upper surface 322 and lower surface 323 of the second edge structure 32. To avoid thermal runaway of the cell 3 caused by burrs and separated powder, refer to... Figure 3 and Figure 4 In this embodiment, the battery cell 3 also includes a sealing structure 50, which is used to fix the separated powder on the second edge structure 32 and to cover the burrs, thereby preventing the burrs from puncturing the electrode 6 and causing a short circuit. The sealing structure 50 also prevents the powder from falling off and prevents the fallen powder from remaining inside the battery cell 3 and puncturing the separator and causing a short circuit.

[0064] Specifically, the sealing structure 50 covers the side surface 321 of the second edge structure 32, thereby covering the burrs and loose or potentially detached powder on the side surface 321. This prevents the burrs on the side surface 321 from puncturing the electrode 6 and causing a short circuit, and also prevents the powder on the side surface 321 from falling off, thus preventing the detached powder from remaining inside the cell 3 and puncturing the separator and causing a short circuit. Furthermore, the sealing structure 50 overlaps with the second edge structure 32 in the thickness direction M to prevent powder from falling off, thereby preventing the detached powder from puncturing the separator and causing a short circuit. For example... Figure 3 In this embodiment, a closed structure 50 can be used to cover the upper surface 322 or the lower surface 323 to prevent powder from falling off, thereby preventing the falling powder from puncturing the diaphragm and causing a short circuit. Or as... Figure 8 In the embodiment, the sealing structure 50 may also be inserted into the active material layer 10 of the second edge structure 32 to fix the active material layer 10 of the second edge structure 32, increase the integrity of the active material layer 10 of the second edge structure 32, prevent the powder from falling off, and thus avoid the falling powder from piercing the diaphragm and causing a short circuit.

[0065] The closed structure 50 can be made of insulating material, such as polyurethane, epoxy resin, silicone, acrylic or fluororubber.

[0066] Reference Figure 3 In this embodiment, the closed structure 50 includes a first portion 51 covering the side surface 321, a second portion 52 covering the upper surface 322, and a third portion 53 covering the lower surface 323. The second portion 52 and the third portion 53 are respectively connected to the first portion 51. That is, the closed structure 50 is a U-shaped structure with its opening facing horizontally. By physically covering the second edge structure 32 with the closed structure 50, that is, covering the cut edge of the electrode 6, burrs can be covered and powder shedding can be suppressed, so as to prevent burrs and shed powder from piercing the separator or contacting adjacent electrodes 6 and causing short circuits. Moreover, since the closed structure 50 is U-shaped, the elasticity or rigidity of the closed structure 50 can support and prevent the electrode 6 from cracking or deforming at the edge due to mechanical stress during winding or charging and discharging. In addition, the closed structure 50 has ionic insulation, which can block abnormal deposition of lithium ions at the edge and reduce the risk of dendrites piercing the separator. The enclosed structure 50 can also prevent the exposed metal current collector 20 on the cut surface from directly contacting the electrolyte or the opposite electrode, reducing the probability of micro short circuits.

[0067] Reference Figure 3In this embodiment, the second edge structure 32 is an elongated strip extending along direction A, and the closing structure 50 extends from one end of the second edge structure 32 along its length to the other end; that is, the closing structure 50 is also elongated and extends along direction A. Thus, the closing structure 50 effectively covers most of the second edge structure 32, effectively covering the burrs on the side surface 321 of the second edge structure 32 and suppressing powder shedding from the second edge structure 32. It is understood that in some other embodiments, the closing structure 50 may cover only a portion of the second edge structure 32, rather than completely covering it. Furthermore, the closing structure 50 may completely cover the upper surface 322 of the second edge structure 32, or it may only cover a portion of the upper surface 322 of the second edge structure 32. Similarly, the closing structure 50 may completely cover the lower surface 323 of the second edge structure 32, or it may only cover a portion of the lower surface 323 of the second edge structure 32.

[0068] Figure 5 for Figure 3 The structure in the embodiment is viewed along direction A. Direction A is parallel to the Z direction mentioned earlier.

[0069] Reference Figure 3 and Figure 5 In this embodiment, the dimension L1 of the first portion 51 in the direction perpendicular to the side surface 321 is 0.5mm-2mm. For example, L1 can be 0.5mm, 1mm, or 2mm. Since the length of the burrs generated after the electrode sheet 6 is cut is usually 50-500μm, the dimension L1 of the first portion 51 in the direction perpendicular to the side surface 321 is within this range. After the first portion 51 covers the burrs, a safety margin can be reserved, and edge exposure caused by coating alignment errors can be avoided. In addition, when the dimension L1 of the first portion 51 in the direction perpendicular to the side surface 321 is greater than 2mm, it will occupy the effective area of ​​the electrode sheet 6 and reduce the capacity of the cell 3; when the dimension L1 of the first portion 51 in the direction perpendicular to the side surface 321 is less than 0.5mm, it cannot effectively cover the burrs.

[0070] The second part 52 has a dimension L2 in the thickness direction M of 3μm–30μm, for example, L2 can be 3μm–5μm. When the dimension L2 of the second part 52 in the thickness direction M is within the range of 3μm–30μm, it can effectively cover the first active material layer 11 of the second edge structure 32, preventing material from falling out of the first active material layer 11. When the dimension L2 of the second part 52 in the thickness direction M is greater than 30μm, it will cause the edge of the electrode 6 to thicken too much, affecting the tightness of the stacking or winding of the cell 3. Furthermore, a dimension L2 of the second part 52 in the thickness direction M greater than 30μm will reduce flexibility and make it prone to cracking during winding.

[0071] Similarly, the dimension L2 of the third part 53 in the thickness direction M is 3μm–30μm. For example, L2 can be 3μm–5μm. When the dimension L2 of the third part 53 in the thickness direction M is within the range of 3μm–30μm, it can effectively cover the second active material layer 12 of the second edge structure 32, preventing the material in the second active material layer 12 from falling off. When the dimension L2 of the third part 53 in the thickness direction M is greater than 30μm, it will cause the edge of the electrode 6 to thicken too much, affecting the tightness of the stacking or winding of the cell 3. In addition, when the dimension L2 of the third part 53 in the thickness direction M is greater than 30μm, it will reduce the flexibility and make it easy to crack during winding.

[0072] In the direction perpendicular to the side surface 321, the dimension L3 of the second portion 52 is 1mm-2mm. Within this range, the shedding of the active layer and the covering burrs can be essentially completely avoided, preventing thermal runaway of the cell 3, and minimizing the impact on energy density and process complexity. Similarly, in the direction perpendicular to the side surface 321, the dimension L3 of the third portion 53 is 1mm-2mm. Within this range, the shedding of the active layer and the covering burrs can be essentially completely avoided, preventing thermal runaway of the cell 3, and minimizing the impact on energy density and process complexity.

[0073] It is understandable that the size of the second edge structure 32 in the direction perpendicular to the side surface 321 can be the same as that of the second part 52, so that the upper surface 322 of the second edge structure 32 can be completely covered by the second part 52. Alternatively, the size of the second edge structure 32 in the direction perpendicular to the side surface 321 can be smaller than that of the second part 52, in which case the upper surface 322 of the second edge structure 32 cannot be completely covered by the second part 52.

[0074] It should be noted that, in the direction perpendicular to the side surface 321, the dimensions of the second part 52 and the third part 53 can be the same or different. Furthermore, the dimensions of the second part 52 and the third part 53 in the thickness direction M can also be the same or different. Additionally, the dimensions of the closed structures 50 provided at the two second edge structures 32 of the electrode 6 can be exactly the same or not exactly the same.

[0075] Figure 6 for Figure 2A or Figure 2B A schematic diagram of the structure in which the electrode 6 is combined with the closed structure 50 in the embodiment. Figure 7 for Figure 6 The structure in the embodiment is viewed along direction A. Direction A is parallel to the Z direction mentioned earlier. Figure 3 The difference in the embodiments is that, Figure 6 and Figure 7 The second edge structure 32 in the embodiment has a smaller dimension in the thickness direction M.

[0076] Reference Figure 6 and Figure 7 In this embodiment, the current collector 20 of the second edge structure 32 and the current collector 20 of the middle portion 40 have the same dimensions in the thickness direction M. That is, the two side surfaces of the current collector 20 of the second edge structure 32 in the thickness direction M and the two side surfaces of the current collector 20 of the middle portion 40 in the thickness direction M are flush. Based on this, in the thickness direction M, the dimensions of the active material layers 10 on both sides of the current collector 20 of the second edge structure 32 are smaller than the dimensions of the active material layers 10 on both sides of the current collector 20 of the middle portion 40. That is, the dimension of the first active material layer 11 of the second edge structure 32 in the thickness direction M is smaller than the dimension of the first active material layer 11 of the middle portion 40 in the thickness direction M, and the dimension of the second active material layer 12 of the second edge structure 32 in the thickness direction M is smaller than the dimension of the middle portion 40. The second active material layer 12 of portion 40 has a dimension in the thickness direction M, thereby forming a stepped groove between the second active material layer 12 of the second edge structure 32 and the second active material layer 12 of the middle portion 40. When the second part 52 of the closed structure 50 covers the upper surface 322 of the second edge structure 32, it is equivalent to being placed in the stepped groove, thereby effectively offsetting part of the thickness of the second part 52 in the thickness direction M. Similarly, when the third part 53 of the closed structure 50 covers the lower surface 323 of the second edge structure 32, it is equivalent to being placed in the stepped groove, thereby effectively offsetting part of the thickness of the third part 53 in the thickness direction M. This effectively reduces the edge thickening of the electrode 6 and avoids affecting the tightness of the stacking or winding of the battery cell 3.

[0077] Reference Figure 6 and Figure 7In this embodiment, the upper surface 521 of the second part 52 in the thickness direction M is flush with the upper surface 41 of the middle part 40 in the thickness direction M, and the lower surface 522 of the second part 52 in the thickness direction M covers the upper surface 322 of the second edge structure 32. Since the upper surface 521 of the second part 52 in the thickness direction M is flush with the upper surface 41 of the middle part 40 in the thickness direction M, the tight fit between the electrode sheets 6 can be ensured when the electrode sheets 6 are stacked or wound, so as to effectively improve the energy density of the cell 3. Similarly, the lower surface 532 of the third part 53 in the thickness direction M is flush with the lower surface 42 of the middle part 40 in the thickness direction M, and the upper surface 531 of the third part 53 in the thickness direction M is provided on the lower surface 323 of the second edge structure 32. Since the lower surface 532 of the third part 53 in the thickness direction M is flush with the lower surface 42 of the middle part 40 in the thickness direction M, the tight fit between the electrode sheets 6 can be ensured when the electrode sheets 6 are stacked or wound, so as to effectively improve the energy density of the cell 3.

[0078] It is understood that in some other embodiments, the upper surface 521 of the second part 52 in the thickness direction M and the upper surface 41 of the middle part 40 in the thickness direction M may not be flush. For example, the upper surface 521 of the second part 52 in the thickness direction M may be slightly higher or slightly lower than the upper surface 41 of the middle part 40 in the thickness direction M.

[0079] Figure 6 and Figure 7 In this embodiment, after the electrode 6 is cut, a layer of active material layer 10 at the edge of the electrode 6 needs to be removed to form a stepped groove. Specifically, the stepped groove can be formed by physical means, such as pressing, cutting, scraping, grinding or shaving, or by chemical means. After the stepped groove is formed, the sealing structure 50 is covered on the second edge structure 32, for example, by coating.

[0080] Figure 8 for Figure 2A or Figure 2B A schematic diagram of the structure in which the electrode 6 is combined with the closed structure 50 in the embodiment. Figure 9 for Figure 8 A view of the structure in the embodiment from direction A. Figure 3 The difference in the embodiments is that, Figure 8 and Figure 9 The closed structure 50 in this embodiment is configured differently from the second edge structure 32. It should be noted that... Figure 8 and Figure 9 The shaded area is not a sectional symbol, but is used to more clearly show the connection between the electrode 6 and the closed structure 50.

[0081] Reference Figure 8 and Figure 9 In this embodiment, a portion of the closed structure 50 is mixed within the active material layers 10 on both sides of the current collector 20 of the second edge structure 32. Specifically, the first portion 51 and the second portion 52 of the closed structure 50 are respectively incorporated into and combined with the first active material layer 11 and the second active material layer 12 of the second edge structure 32. This stabilizes and fixes any loose or about-to-fall-off powder in the first active material layer 11 and the second active material layer 12 by incorporating the first portion 51 and the second portion 52, thereby preventing the powder from falling off. Furthermore, this method also avoids the closed structure 50 causing an increase in the thickness of the edge portion of the electrode 6. Thus, this embodiment can reduce the impact on the tightness of the stacking or winding of the battery cells 3, that is, effectively reduce the impact on the energy density of the battery cells 3.

[0082] Specifically, the sealing mechanism in this embodiment has a certain penetration capability, enabling part of the sealing structure 50 to penetrate into the active material layer 10 of the second edge structure 32. Furthermore, after the sealing structure 50 solidifies, it also needs to cover the side surface 321 of the second edge structure 32 to address the impact of burrs on the safety of the battery cell 3.

[0083] It is understandable that after the closed structure 50 solidifies, it can either cover the upper surface 322 and the lower surface 323 of the second edge structure 32, or it can leave the upper surface 322 and the lower surface 323 of the second edge structure 32 uncovered.

[0084] Figure 10 This is a schematic diagram showing the combination of the electrode 6 and the closed structure 50 in another battery cell 3 according to an embodiment of this application. Figure 3 The difference in the embodiments is that, Figure 10 In this embodiment, the closed structure 50 is not only located at the second edge structure 32, but also at the third edge structure 33.

[0085] Reference Figure 10 In this embodiment, the sealing structure 50 is disposed on the side surface of the third edge structure 33, which is the outer surface of the electrode 6 parallel to the thickness direction M. Specifically, the sealing structure 50 covers the side surface of the third edge structure 33, thereby covering the burrs and loose powder on the side surface of the third edge structure 33, so as to prevent the burrs on the side surface of the third edge structure 33 from puncturing the electrode 6 and causing a short circuit. It can also prevent the powder on the side surface of the third edge structure 33 from falling off, thereby preventing the fallen powder from remaining inside the cell 3 and puncturing the separator and causing a short circuit.

[0086] Furthermore, the closed structure 50 overlaps with the third edge structure 33 in the thickness direction M, which can prevent powder from falling off and thus prevent the falling powder from piercing the diaphragm and causing a short circuit. For example, similar to the principle of covering the second edge structure 32, the closed structure 50 can cover the upper or lower surface of the third edge structure 33 to prevent powder from falling off and thus prevent the falling powder from piercing the diaphragm and causing a short circuit. Alternatively, the closed structure 50 can also be... Figure 8 The same principle applies to the embodiment. The active material layer 10 of the third edge structure 33 is penetrated into the active material layer 10 to fix the active material layer 10 of the third edge structure 33, increase the integrity of the active material layer 10 of the third edge structure 33, prevent the powder from falling off, and thus avoid the falling powder from piercing the diaphragm and causing a short circuit.

[0087] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A battery cell, characterized in that, The battery cell includes a housing and electrode plates disposed within the housing; The electrode includes four edge structures located at four edge portions. One of the four edge structures used to connect the electrode tab is a first edge structure. The edge structure adjacent to the first edge structure is a second edge structure. The second edge structure includes an active material layer, a current collector, and an active material layer stacked sequentially in the thickness direction of the electrode. The side surface of the second edge structure is the side surface of the electrode parallel to the thickness direction. The cell also includes a closed structure, part of which covers the side surface of the second edge structure, and part of which is combined with the active material layers on both sides of the current collector.

2. The battery cell according to claim 1, characterized in that, The second edge structure also includes an upper surface and a lower surface opposite each other in the thickness direction, the side surface is connected between the upper surface and the lower surface, and the closing structure covers the side surface, the upper surface and the lower surface respectively.

3. The battery cell according to claim 2, characterized in that, The enclosed structure includes a first portion covering the side surface, a second portion covering the upper surface, and a third portion covering the lower surface, wherein the second portion and the third portion are respectively connected to the first portion.

4. The battery cell according to claim 3, characterized in that, The first part has a dimension of 0.5mm-2mm in the direction perpendicular to the side surface, or the second part has a dimension of 3μm-30μm in the thickness direction, or the third part has a dimension of 3μm-30μm in the thickness direction.

5. The battery cell according to claim 3, characterized in that, In the direction perpendicular to the side surface, the second part has a size of 1mm-2mm, and the third part has a size of 1mm-2mm.

6. The battery cell according to claim 3, characterized in that, The electrode also includes a central portion located between the four edge structures, the central portion comprising an active material layer, a current collector, and an active material layer sequentially stacked in the thickness direction of the electrode. In the thickness direction, the size of the active material layer on both sides of the current collector of the second edge structure is smaller than the size of the active material layer on both sides of the current collector of the middle part.

7. The battery cell according to claim 6, characterized in that, The upper surface of the second part in the thickness direction is flush with the upper surface of the middle part in the thickness direction, the lower surface of the second part in the thickness direction is disposed on the upper surface of the second edge structure, the lower surface of the third part in the thickness direction is flush with the lower surface of the middle part in the thickness direction, and the upper surface of the third part in the thickness direction is disposed on the lower surface of the second edge structure.

8. The battery cell according to claim 1, characterized in that, The portion of the closed structure is mixed within the active material layers on both sides of the current collector of the second edge structure.

9. The battery cell according to any one of claims 1-5, characterized in that, The second edge structure is elongated, and the closed structure extends from one end of the second edge structure along its length to the other end.

10. The battery cell according to any one of claims 1-8, characterized in that, The edge structure opposite to the first edge structure among the four edge structures is the third edge structure. The closed structure is disposed on the side surface of the third edge structure and overlaps with the third edge structure in the thickness direction. The side surface of the third edge structure is the outer surface of the electrode that is parallel to the thickness direction.

11. The battery cell according to any one of claims 1-8, characterized in that, The four edge structures include two second edge structures, and each of the two second edge structures is provided with the closed structure.

12. A battery pack, characterized in that, The battery pack includes a housing and a battery cell as described in any one of claims 1-11, wherein the battery cell is disposed within the housing.

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