Battery cells, battery devices, electrical equipment

Abstract

A battery cell, a battery device, and an electrical appliance belong to the field of battery technology. The battery cell includes: a positive electrode sheet comprising a positive current collector, a first positive electrode film, and a first insulating layer; the positive current collector includes a positive electrode tab protruding from the positive electrode body in a first direction; the first insulating layer and the first positive electrode film are disposed on the same side surface of the positive current collector along its thickness direction; the first insulating layer is close to the positive electrode tab relative to the first positive electrode film along the first direction; the first positive electrode film includes a lithium phosphate containing a carbon coating layer; and a negative electrode sheet comprising a negative electrode film; along the first direction, the edge of the negative electrode film extends beyond the edge of the first positive electrode film by a distance greater than or equal to 2 mm; along the first direction, the first insulating layer and the first positive electrode film have a first overlapping region; within the first overlapping region, along the thickness direction of the positive electrode sheet, the first positive electrode film is disposed between the positive current collector and the first insulating layer, which can improve the reliability of the battery cell.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery cell, a battery device, and an electrical appliance. Background Technology

[0002] The new energy industry is attracting increasing attention. Within this industry, battery technology is a crucial factor in its development.

[0003] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, lifespan, capacity, fast charging performance, and reliability. How to provide a highly reliable battery cell is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell with high reliability.

[0005] To achieve the above objectives, this application provides a battery cell, a battery device, and an electrical appliance.

[0006] In a first aspect, a battery cell is provided, comprising: a positive electrode sheet, the positive electrode sheet including a positive current collector, a first positive electrode film layer, and a first insulating layer; the positive current collector including a positive electrode body portion and a positive electrode tab, the positive electrode tab protruding from the positive electrode body portion along a first direction; the first insulating layer and the first positive electrode film layer being disposed on the same side surface of the positive current collector along its thickness direction; and, along the first direction, the first insulating layer being closer to the positive electrode tab than the first positive electrode film layer; the first positive electrode film layer including a positive electrode active material, the positive electrode active material including a lithium phosphate, the lithium phosphate being packaged... The device includes a lithium phosphate matrix and a carbon coating layer covering at least a portion of the surface of the lithium phosphate matrix; a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative electrode film layer disposed on at least one side surface of the negative current collector along the thickness direction, wherein, along the first direction, the edge of the negative electrode film layer extends beyond the edge of the first positive electrode film layer by a distance greater than or equal to 2 mm; wherein, along the first direction, the first insulating layer and the first positive electrode film layer have a first overlapping region, and within the first overlapping region, along the thickness direction of the positive electrode sheet, the first positive electrode film layer is disposed between the positive current collector and the first insulating layer.

[0007] In this embodiment, along the first direction, the edge of the negative electrode film extends beyond the edge of the first positive electrode film by a distance greater than or equal to 2 mm. This helps reduce the risk that errors in the manufacturing process may cause the edge of the negative electrode film to not extend beyond the edge of the first positive electrode film. By setting a first overlapping region between the first insulating layer and the first positive electrode film along the first direction, and within this first overlapping region, the first positive electrode film is disposed between the positive current collector and the first insulating layer along the thickness direction of the positive electrode sheet. This helps reduce the lithium ion extraction rate at the location corresponding to the first overlapping region of the first positive electrode film, thereby reducing the risk of lithium plating at the boundary between the region where the edge of the negative electrode film extends beyond the edge of the first positive electrode film and the overlapping region of the negative and first positive electrode films. This compensates for the deficiency of the increased reservoir effect caused by the distance of the negative electrode film edge extending beyond the edge of the first positive electrode film by a distance greater than or equal to 2 mm, and reduces the risk of lithium plating. Therefore, the battery cell of this embodiment has high reliability.

[0008] In some embodiments, the length of the first overlapping region along the first direction is 0.2 mm to 1 mm.

[0009] When the length of the first overlapping region along the first direction is greater than or equal to 0.2 mm, it helps to reduce the risk of lithium deposition at the boundary between the region where the edge of the negative electrode film extends beyond the edge of the first positive electrode film and the region where the negative electrode film and the first positive electrode film overlap, thereby improving the reliability of the battery cell. When the length of the first overlapping region along the first direction is less than or equal to 1 mm, it facilitates the extraction of lithium ions from the first positive electrode film, which helps to improve the power, capacity and other electrical performance of the battery cell.

[0010] In some embodiments, the length of the first overlapping region along the first direction is 0.2 mm to 0.6 mm. This provides a suitable length for the first overlapping region, reducing the risk of lithium plating and resulting in higher reliability for the battery cell.

[0011] In some embodiments, the thickness of the first insulating layer increases in the first overlapping region along the direction from the first positive electrode film layer to the positive electrode tab. This helps reduce the risk of lithium plating at the boundary between the region where the edge of the negative electrode film layer extends beyond the edge of the first positive electrode film layer and the overlapping region of the negative electrode film layer and the first positive electrode film layer, resulting in higher reliability of the battery cell.

[0012] In some embodiments, the length of the first insulating layer along the first direction is 1 mm to 3 mm.

[0013] When the length of the first insulating layer is greater than or equal to 1 mm, the first insulating layer can effectively block burrs, which helps reduce the risk of burrs on the positive electrode overlapping with the negative electrode or puncturing the separator, resulting in higher reliability of the battery cell. When the length of the first insulating layer is less than or equal to 3 mm, it helps to improve the energy density of the battery cell.

[0014] In some embodiments, the maximum thickness of the first insulating layer is 20 μm to 80 μm.

[0015] When the maximum thickness of the first insulating layer is greater than or equal to 20 μm, the first insulating layer can effectively block burrs, which helps reduce the risk of burrs on the positive electrode overlapping with the negative electrode or puncturing the separator, resulting in higher reliability of the battery cell. When the maximum thickness of the first insulating layer is less than or equal to 80 μm, it helps to improve the energy density of the battery cell.

[0016] In some embodiments, the thickness of the positive current collector is 13 μm to 16 μm.

[0017] When the thickness of the positive electrode current collector is greater than or equal to 13 μm, the positive electrode sheet has good conductivity, which is beneficial to improving electronic conductivity, reducing the impedance of the battery cell, and thus improving the dynamic performance of the battery cell. When the thickness of the positive electrode current collector is less than or equal to 16 μm, the positive electrode sheet has a more suitable thickness, which is beneficial to improving the energy density of the battery cell.

[0018] In some embodiments, the maximum thickness of the first positive electrode film is 85 μm to 135 μm. This results in a suitable thickness for the first positive electrode film and a higher energy density for the battery cell.

[0019] In some embodiments, the first positive electrode film layer is provided with a positive electrode main region and a positive electrode transition region. Along the first direction, the positive electrode transition region is disposed at at least one end of the positive electrode main region, and the thickness of the positive electrode transition region is less than the thickness of the positive electrode main region. The provision of the positive electrode transition region helps to reduce stress concentration during the winding or stacking process of the positive electrode sheet, and can make the thickness of the edge and center regions of the positive electrode sheet more uniform, which is beneficial to improving the reliability and lifespan of the battery cell.

[0020] In some embodiments, along the first direction, the projection of the positive electrode transition region near the positive electrode tab onto the positive electrode current collector overlaps the projection of the first overlapping region onto the positive electrode current collector. This helps reduce the risk of lithium plating at the boundary between the region where the edge of the negative electrode film extends beyond the edge of the first positive electrode film and the overlapping region of the negative electrode film and the first positive electrode film, resulting in higher reliability of the battery cell.

[0021] In some embodiments, the positive electrode further includes a second positive electrode film layer. The first and second positive electrode films are respectively disposed on both sides of the positive electrode body along the thickness direction. The first and second positive electrode films include a positive electrode active material, which includes lithium phosphate. The compaction density of the positive electrode is 2.2 g / cm³. 3 Up to 2.7 g / cm 3 Along the direction from the first positive electrode film layer to the positive electrode tab, the edge of the second positive electrode film layer near the positive electrode tab extends beyond the edge of the first positive electrode film layer near the positive electrode tab.

[0022] In this embodiment, the positive electrode active material includes lithium phosphate, and the positive electrode sheet has a compaction density of 2.2 g / cm³. 3 Up to 2.7 g / cm 3 The battery cell has a high energy density, but there is significant stress concentration at the interfaces between the first positive electrode film and the positive electrode tab, and between the second positive electrode film and the positive electrode tab. The first and second positive electrode films are respectively disposed on the two sides of the main body along the thickness direction. The first positive electrode film points towards the positive electrode tab, and the edge of the second positive electrode film near the positive electrode tab extends beyond the edge of the first positive electrode film near the positive electrode tab. This staggered arrangement of the first and second positive electrode films in the first direction reduces the risk of cracking of the positive electrode sheet due to severe stress concentration at the interfaces between the first and second positive electrode films and the positive electrode tab. Furthermore, it compensates for the problem of stress concentration and cracking of the positive electrode sheet caused by high compaction density, thus improving the reliability of the battery cell.

[0023] In some embodiments, along the first direction, the length of the first gap space is 0.05 mm to 0.5 mm, and the first gap space is the space between the edge of the second positive electrode film layer near the positive electrode tab and the edge of the first positive electrode film layer near the positive electrode tab.

[0024] When the length of the first gap space along the first direction is greater than or equal to 0.05 mm, the risk of cracking of the positive electrode sheet caused by stress concentration at the interface between the first positive electrode film layer and the positive electrode tab, and between the second positive electrode film layer and the positive electrode tab can be reduced, which is beneficial to improving the reliability of the battery cell. When the length of the first gap space along the first direction is less than or equal to 0.5 mm, it is beneficial to improve the energy density of the battery cell.

[0025] In some embodiments, the length of the first gap space along the first direction is 0.05 mm to 0.2 mm. This provides a more suitable length for the first gap space, which is beneficial for balancing the reliability and energy density of the battery cells.

[0026] In some embodiments, the positive electrode sheet includes a second insulating layer, the second insulating layer and the first positive electrode film layer are disposed on the same side surface of the positive current collector along the thickness direction, the first insulating layer and the second insulating layer are located at both ends of the first positive electrode film layer along the first direction, and the second insulating layer and the first positive electrode film layer have a first gap.

[0027] The second insulating layer helps to further reduce the impact of burrs, thereby improving the reliability of the battery cell; the second insulating layer and the first positive electrode film layer have a first gap, which helps to reduce the risk of positive electrode cracking caused by stress concentration, thereby improving the reliability of the battery cell.

[0028] In some embodiments, the positive electrode sheet includes a third insulating layer, the third insulating layer and the second positive electrode film layer are disposed on the same side surface of the positive electrode current collector along the thickness direction, and the third insulating layer and the second positive electrode film layer have a second gap along the first direction; the projection of the first insulating layer on the positive electrode current collector covers the projection of the third insulating layer on the positive electrode current collector. This helps reduce the risk of positive electrode sheet cracking caused by stress concentration, thereby improving the reliability of the battery cell.

[0029] The first insulating layer and the first positive electrode film layer are disposed on the same side surface of the positive electrode current collector along the thickness direction. Along the first direction, the first insulating layer and the first positive electrode film layer have a first overlapping region. The presence of this first overlapping region helps reduce the lithium-ion extraction rate at the location of the first positive electrode film layer corresponding to the first overlapping region. This reduces the risk of lithium plating at the boundary between the edge of the negative electrode film layer extending beyond the edge of the first positive electrode film layer and the overlapping region of the negative electrode film layer and the first positive electrode film layer, thereby further improving the reliability of the battery cell. Therefore, the battery cell of this embodiment can achieve both high energy density and high reliability.

[0030] In some embodiments, the positive electrode sheet includes a fourth insulating layer, the fourth insulating layer and the second positive electrode film layer are disposed on the same side surface of the positive electrode current collector along the thickness direction, the fourth insulating layer and the third insulating layer are located at both ends of the second positive electrode film layer along the first direction, the edge of the negative electrode film layer extends beyond the edge of the second positive electrode film layer by a distance greater than or equal to 2 mm along the first direction, the fourth insulating layer and the second positive electrode film layer have a second overlapping region, in the second overlapping region, the second positive electrode film layer is disposed between the positive electrode current collector and the fourth insulating layer along the thickness direction of the positive electrode sheet.

[0031] In this embodiment, the distance by which the edge of the negative electrode film extends beyond the edges of both the first and second positive electrode films is greater than or equal to 2 mm. Furthermore, because the first and fourth insulating layers have a staggered structure in the first direction, the risk of lithium plating due to the reservoir effect increases compared to a structure where the first and fourth insulating layers are aligned in the first direction. By setting a second overlapping region, and within this second overlapping region, the second positive electrode film is positioned between the positive current collector and the fourth insulating layer along the thickness direction of the positive electrode sheet. This helps to reduce the lithium ion extraction rate at the location corresponding to the second overlapping region of the second positive electrode film, thereby further reducing the risk of lithium plating and improving the reliability of the battery cell.

[0032] In some embodiments, the first insulating layer comprises inorganic particles and a binder. The inorganic particles include at least one of alumina, boehmite, and magnesium oxide. The binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and vinylidene fluoride-chlorotrifluoroethylene copolymer. The inorganic particles have a certain degree of insulation and can also block burrs. The binder can bond the inorganic particles to the surface of the positive electrode current collector, thereby facilitating the bonding of the first insulating layer to the positive electrode current collector and the first positive electrode film layer.

[0033] In some embodiments, the compaction density of the positive electrode sheet is 2.45 g / cm³. 3 Up to 2.6 g / cm 3 .

[0034] The compaction density of the positive electrode sheet is greater than or equal to 2.45 g / cm³. 3 Under these conditions, the battery cell has a high energy density; and the compaction density of the positive electrode is less than or equal to 2.6 g / cm³. 3 In this case, it facilitates the transport of lithium ions, which is beneficial to improving the fast charging performance of individual battery cells.

[0035] In some embodiments, the density of one side of the positive electrode sheet is 0.33 g / 1540.25 mm. 2 Up to 0.45g / 1540.25mm 2 .

[0036] The density on one side of the positive electrode sheet is greater than or equal to 0.33 g / 1540.25 mm. 2 Under these conditions, it is beneficial to improve the energy density of the battery cell; when the density of one side of the positive electrode is less than or equal to 0.45g / 1540.25mm. 2 Under these conditions, it is beneficial for lithium-ion transport and helps improve the fast-charging performance of individual battery cells.

[0037] In some embodiments, the projection of the negative electrode film layer onto the positive electrode current collector covers at least a portion of the projection of the first insulating layer onto the positive electrode current collector. This helps to reduce the risk of lithium plating.

[0038] In some embodiments, the negative electrode film layer includes a negative electrode body region and a negative electrode transition region. Along the first direction, the negative electrode transition region is disposed at at least one end of the negative electrode body region, and the thickness of the negative electrode transition region is less than the thickness of the negative electrode body region. The presence of the negative electrode transition region helps reduce stress concentration during the winding or stacking process of the negative electrode sheet, and can make the thickness of the negative electrode sheet more uniform between the edge and center regions, thus improving the reliability and lifespan of the battery cell.

[0039] In some embodiments, the density of the negative electrode sheet on one side is 0.15 g / 1540.25 mm. 2 Up to 0.22g / 1540.25mm 2 .

[0040] The density on one side of the negative electrode sheet is greater than or equal to 0.15 g / 1540.25 mm. 2 Under these conditions, it is beneficial to improve the energy density of the battery cell; when the density of one side of the negative electrode is less than or equal to 0.22g / 1540.25mm. 2 Under these conditions, it is beneficial for lithium-ion transport and helps improve the fast-charging performance of individual battery cells.

[0041] In some embodiments, the compaction density of the negative electrode sheet is 1.3 g / cm³. 3 Up to 1.52 g / cm 3 .

[0042] The compaction density of the negative electrode sheet is greater than or equal to 1.3 g / cm³. 3 Under these conditions, the battery cell has a high energy density; and the compaction density of the negative electrode sheet is less than or equal to 1.52 g / cm³. 3 In this case, it facilitates the transport of lithium ions, which is beneficial to improving the fast charging performance of individual battery cells.

[0043] In some embodiments, the compaction density of the negative electrode sheet is 1.35 g / cm³. 3 Up to 1.5g / cm 3 In this way, the negative electrode sheet has a suitable compaction density, which is beneficial for balancing the energy density and fast charging performance of the battery cell.

[0044] In some embodiments, the battery cell includes an electrode assembly and a packaging bag. The electrode assembly includes a positive electrode and a negative electrode, and is housed within the packaging bag. The packaging bag includes two packaging films, with the electrode assembly located between the two packaging films. The edges of the two packaging films are connected to each other to form a seal. The battery cell also includes an electrode lead that passes between the two packaging films and is electrically connected to the electrode assembly.

[0045] The battery cell with this structure is a pouch cell. The connection of two packaging films can form a sealed space inside the battery cell to accommodate the positive electrode, negative electrode and electrolyte. By electrically connecting the electrode leads to the electrode assembly, it is easy to draw out the current.

[0046] In some embodiments, the packaging film includes an insulating protective layer, a metal layer, and an insulating connecting layer. The insulating connecting layer is disposed on the surface of the metal layer facing the electrode assembly, and the insulating protective layer is disposed on the surface of the metal layer away from the electrode assembly. This design not only seals the electrode assembly and electrolyte for protection but also provides a degree of flexibility to cushion the battery cells when subjected to compression or vibration.

[0047] In some embodiments, the battery cell is a cylindrical battery cell. Cylindrical battery cells have better uniformity, which is beneficial for achieving more balanced control under the management of the battery management system, thereby ensuring the overall performance of the battery device; in addition, it is also beneficial for forming a better heat dissipation space within the battery device, facilitating heat dissipation of the battery cells.

[0048] In some embodiments, the diameter of the cylindrical battery cell is greater than or equal to 40 mm. This results in a battery cell with a large capacity and high energy density.

[0049] In some embodiments, along the first direction, the edge of the negative electrode film extends beyond the edge of the first positive electrode film by a distance greater than or equal to 2 mm and less than or equal to 7 mm. This is advantageous in ensuring that the edge of the negative electrode film extends beyond the edge of the positive electrode film while maintaining a high energy density.

[0050] In some embodiments, the average longest diameter of the primary particles containing lithium phosphate is between 300 nm and 800 nm. This provides a suitable distance for the lithium ion extraction path, which is beneficial for improving the power performance of the battery cell.

[0051] In some embodiments, the lithium phosphate matrix comprises lithium iron phosphate, which is doped with at least one of Al, V, and Ti. These doping elements are beneficial for improving the conductivity and other properties of the lithium phosphate, thereby improving the capacity of the battery cell. Furthermore, these doping elements also help increase the compaction density of the positive electrode, thus improving the energy density of the battery cell.

[0052] In some embodiments, the negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprising graphite, and at least a portion of the surface of the graphite having a coating layer comprising amorphous carbon. This facilitates the rapid intercalation of lithium ions into the graphite, thereby improving the fast-charging performance of the battery cell.

[0053] In some embodiments, the thickness of the coating layer is between 100 nm and 500 nm. This coating layer has a suitable thickness, facilitating lithium-ion insertion and transport, and improving the fast-charging performance of the battery cell.

[0054] In some embodiments, the graphite comprises secondary particles. This facilitates lithium-ion transport and improves the fast-charging performance of individual battery cells.

[0055] In some embodiments, the graphite has a graphitization degree of 90% to 94%. This results in graphite with a suitable graphitization degree, which is beneficial for achieving a suitable specific capacity and for controlling side reactions within the battery cell within a suitable range, thereby enabling the battery cell to have a suitable capacity and cycle life.

[0056] In some embodiments, the volume average particle size Dv50 of the graphite is 15 μm to 25 μm. This appropriate range of graphite particle size is beneficial for increasing the compaction density of the negative electrode sheet, thereby improving the energy density of the battery cell.

[0057] In some embodiments, the volume average particle size Dv50 of the graphite is 16 μm to 20 μm. This appropriate range of graphite particle size is beneficial for increasing the compaction density of the negative electrode sheet, thereby improving the energy density of the battery cell.

[0058] In some embodiments, the electrolyte has an ionic conductivity of 9.5 ms / cm to 20 ms / cm. This high ionic conductivity facilitates lithium-ion transport, reduces the risk of lithium plating, and improves the cycle performance and lifespan of the battery cells.

[0059] In some embodiments, the electrolyte has an ionic conductivity of 12 ms / cm to 16 ms / cm. This high ionic conductivity facilitates lithium-ion transport, reduces the risk of lithium plating, and improves the cycle performance and lifespan of the battery cells.

[0060] In some embodiments, the electrolyte includes a solvent, which includes at least one of linear carbonates and linear carboxylic acid esters. The solvent has a low viscosity, and the electrolyte including the solvent has a low viscosity, which is beneficial for lithium-ion transport, thereby improving the fast-charging performance of the battery cell.

[0061] In some embodiments, the linear carbonate comprises dimethyl carbonate, and the linear carboxylic acid ester comprises at least one of ethyl acetate and methyl acetate. The solvents described above have low viscosity, and the electrolyte comprising these solvents has low viscosity, which is beneficial for lithium-ion transport, thereby improving the fast-charging performance of the battery cells.

[0062] In some embodiments, the sum of the mass contents of the linear carbonate and the linear carboxylic acid ester is 10% to 90% based on the total mass of the electrolyte.

[0063] When the total mass content of linear carbonate and linear carboxylic acid ester is greater than or equal to 10% based on the total mass of the electrolyte, the electrolyte has a lower viscosity, which is beneficial for lithium-ion transport, and the battery cell has better fast-charging performance. When the total mass content of linear carbonate and linear carboxylic acid ester is less than or equal to 90% based on the total mass of the electrolyte, the gas production of linear carbonate and linear carboxylic acid ester in the battery cell can be reduced, thereby reducing the risk of gas accumulation between the separator and the positive and negative electrode plates, reducing the risk of lithium plating, and improving the cycle performance of the battery cell.

[0064] In some embodiments, the sum of the mass contents of the linear carbonate and the linear carboxylic acid ester is 40% to 80% based on the total mass of the electrolyte. This provides a suitable range for the sum of the mass contents of the linear carbonate and the linear carboxylic acid ester, allowing the battery cell to achieve both good fast-charging performance and good cycle performance.

[0065] In some embodiments, the battery cell further includes an electrolyte comprising additives, including at least one selected from vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sulpholactone. These additives facilitate film formation at the negative electrode, reduce side reactions at the negative electrode, and thus improve the cycle life, kinetics, and other performance characteristics of the battery cell.

[0066] In some embodiments, the mass content of the additive is less than or equal to 5% based on the total mass of the electrolyte. The appropriate mass content of the additive is beneficial for improving the cycle life, kinetics, and other performance characteristics of the battery cells.

[0067] In some embodiments, the additive content is 0.5% to 3% by mass, based on the total mass of the electrolyte. The appropriate mass content of the additive is beneficial for improving the cycle life, kinetics, and other performance characteristics of the battery cells.

[0068] In a second aspect, a battery device is provided, comprising the battery cell of the first aspect and any of the embodiments thereof.

[0069] In some embodiments, the battery device includes: a housing; a plurality of battery cells housed within the housing, the plurality of battery cells being stacked along a third direction, each battery cell having a rated capacity greater than or equal to 100 Ah, each battery cell having a surface including a first surface and a second surface, the area of ​​the first surface being greater than the area of ​​the second surface, the first surfaces of the plurality of battery cells being disposed opposite to each other along the third direction; and a thermal management component for regulating the temperature of the plurality of battery cells, the thermal management component being disposed opposite to the second surfaces of the plurality of battery cells along a fourth direction, the fourth direction being perpendicular to the third direction.

[0070] In this embodiment, the rated capacity of each battery cell is greater than or equal to 100Ah. During the charging and discharging process of the battery cell, a lot of heat will be generated. By matching the thermal management component with the battery cell, it is beneficial to control the temperature of the battery cell and reduce the risk of the battery cell temperature being too high.

[0071] In some embodiments, the battery device further includes a fixing adhesive disposed between the thermal management component and the battery cell, the fixing adhesive being used to fix the battery cell to the thermal management component. This facilitates the fixing of the battery cell to the thermal management component.

[0072] In some embodiments, the battery cell includes a packaging bag and an electrode assembly, the electrode assembly being housed within the packaging bag, and the adhesive being directly attached to the packaging bag. This facilitates an increase in the energy density of the battery device.

[0073] In some embodiments, the battery device further includes a housing containing at least one of the battery cells, the adhesive being directly attached to the wall of the housing. The housing facilitates better heat dissipation from the battery cells, thus helping to reduce the temperature of the battery cells.

[0074] Thirdly, an electrical device is provided, comprising a battery cell as described in the first aspect and any of the embodiments thereof, or a battery device as described in the second aspect and any of the embodiments thereof, wherein the battery cell or battery device is used to store or provide electrical energy. Attached Figure Description

[0075] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0076] Figure 1 This is a schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0077] Figure 2 This is a schematic diagram of one side surface of the positive electrode sheet according to an embodiment of this application;

[0078] Figure 3 This is a schematic diagram of the other side surface of the positive electrode sheet according to an embodiment of this application;

[0079] Figure 4 This is a schematic diagram of the positive and negative electrode plates in accordance with an embodiment of this application.

[0080] Figure 5 This is a schematic diagram of the positive and negative electrode plates in conjunction, from another perspective, according to an embodiment of this application.

[0081] Figure 6 This is a schematic diagram of the negative electrode sheet according to an embodiment of this application;

[0082] Figure 7 This is a schematic diagram of a battery cell according to an embodiment of this application;

[0083] Figure 8 This is a schematic diagram of a battery cell according to an embodiment of this application;

[0084] Figure 9 This is a schematic diagram of a battery device according to an embodiment of this application;

[0085] Figure 10 This is a schematic diagram illustrating the interaction between a battery cell and a thermal management component according to an embodiment of this application;

[0086] Figure 11 This is a schematic diagram illustrating the interaction between a battery cell and a thermal management component according to another embodiment of this application;

[0087] Figure 12 This is a schematic diagram of a battery module according to an embodiment of this application;

[0088] Figure 13 This is a schematic diagram of a vehicle according to an embodiment of this application.

[0089] Figure label:

[0090] 5: Positive electrode sheet; 50: Positive current collector; 501: Positive electrode body; 502: Positive electrode tab; 51: First positive electrode film layer; 52: Second positive electrode film layer; 531: First insulating layer; 532: Second insulating layer; 533: Third insulating layer; 534: Fourth insulating layer; 511: Positive electrode body region; 512: Positive electrode transition region; 6: Negative electrode sheet; 601: Negative electrode body; 602: Negative electrode tab; 61: Negative electrode film layer; 60: Negative electrode current collector; 611: Negative electrode body region; 612: Negative electrode transition region; 56: First... Overlapping area; 57: Second overlapping area; 3: Battery cell; 31: Packaging bag; 1: Vehicle; 10: Battery unit; 30: Controller; 40: Motor; 11: Housing; 111: First housing section; 112: Second housing section; 33: Electrode assembly; 310: Packaging film; 321: Electrode lead; 301: First surface; 302: Second surface; 91: Thermal management component; 92: Fixing adhesive; 80: Battery module; 801: Housing; 8011: First wall; 8012: Second wall; 8013: Third wall. Detailed Implementation

[0091] Embodiments of the battery cell, battery device, and electrical appliance of this application have been described in detail with appropriate reference to the accompanying drawings; however, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0092] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0093] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0094] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0095] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0096] This application aims to develop a highly reliable battery cell. The risk of lithium plating at the negative electrode plays a crucial role in the reliability of the battery cell. In a battery cell, to reduce the risk of lithium plating at the negative electrode, the edge of the negative electrode film layer, including the negative active material, typically extends beyond the edge of the positive electrode film layer, including the positive active material. The region where the edge of the negative electrode film layer extends beyond the edge of the positive electrode film layer can be called the overhang region, and the region where the negative and positive electrode films overlap can be called the main region of the negative electrode film layer. Due to various process issues (such as alignment errors between the positive and negative electrodes, expansion between the positive and negative electrodes, or other process fluctuations leading to incomplete edge coverage), the size of the overhang region is typically not less than 2 mm to ensure that the edge of the negative electrode film layer extends beyond the edge of the positive electrode film layer. However, when the size of the overhang region is greater than or equal to 2 mm, the "reservoir" effect intensifies, which also leads to the risk of lithium plating and is detrimental to improving the reliability of the battery cell. The "reservoir" effect can be explained as follows. Because the lithium intercalation amount in the overhang region is lower than that in the main region of the negative electrode film, a potential difference exists between the overhang region and the main region of the negative electrode film. Lithium ions in the main region of the negative electrode film spontaneously migrate to the overhang region, and the lithium concentration in the overhang region continuously increases with charge-discharge cycles. After multiple charge-discharge cycles, when the battery cell discharges again, all lithium ions in the main region of the negative electrode film are extracted, while not all lithium ions in the overhang region are extracted. The lithium ion concentration in the overhang region is higher than that in the main region of the negative electrode film. Lithium ions in the overhang region migrate to the boundary between the negative electrode film and the overhang region, resulting in an increase in the lithium ion concentration at the boundary. During recharging, the risk of lithium plating at the boundary increases, and the larger the overhang region, the greater the risk of lithium plating, which is detrimental to the reliability of the battery cell.

[0097] In view of this, embodiments of this application provide a battery cell, including: a positive electrode sheet, the positive electrode sheet including a positive current collector, a first positive electrode film layer and a first insulating layer, the positive current collector including a positive electrode body portion and a positive electrode tab, the positive electrode tab protruding from the positive electrode body portion along a first direction, the first insulating layer and the first positive electrode film layer being disposed on the same side surface of the positive current collector along the thickness direction, and, along the first direction, the first insulating layer being closer to the positive electrode tab relative to the first positive electrode film layer, the first positive electrode film layer including a positive electrode active material, the positive electrode active material including a lithium phosphate, the lithium phosphorus-containing... The acid salt includes a lithium phosphate matrix and a carbon coating layer covering at least a portion of the surface of the lithium phosphate matrix; the negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side surface of the negative current collector along the thickness direction, wherein the edge of the negative electrode film layer extends beyond the edge of the first positive electrode film layer by a distance greater than or equal to 2 mm along a first direction; wherein, along the first direction, the first insulating layer and the first positive electrode film layer have a first overlapping region, and within the first overlapping region, the first positive electrode film layer is disposed between the positive current collector and the first insulating layer along the thickness direction of the positive electrode.

[0098] In this embodiment, along the first direction, the edge of the negative electrode film extends beyond the edge of the first positive electrode film by a distance greater than or equal to 2 mm. This helps reduce the risk that errors in the manufacturing process may cause the edge of the negative electrode film to not extend beyond the edge of the first positive electrode film. By setting a first overlapping region between the first insulating layer and the first positive electrode film along the first direction, and within this first overlapping region, the first positive electrode film is disposed between the positive current collector and the first insulating layer along the thickness direction of the positive electrode sheet. This helps reduce the lithium ion extraction rate at the location corresponding to the first overlapping region of the first positive electrode film, thereby reducing the risk of lithium plating at the boundary between the region where the edge of the negative electrode film extends beyond the edge of the first positive electrode film and the overlapping region of the negative and first positive electrode films. This compensates for the deficiency of the increased reservoir effect caused by the distance of the negative electrode film edge extending beyond the edge of the first positive electrode film by a distance greater than or equal to 2 mm, and reduces the risk of lithium plating. Therefore, the battery cell of this embodiment has high reliability.

[0099] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0100] The battery cell can be a lithium-ion battery.

[0101] During the charging process of a single battery cell, lithium ions are released from the positive electrode active material, move and embed into the negative electrode; while during the discharging process, lithium ions are released from the negative electrode, move and embed into the positive electrode active material.

[0102] It should be understood that the “intercalation” process described in this application refers to the process by which lithium ions are intercalated in the positive electrode active material or the negative electrode due to an electrochemical reaction, and the “extraction” process described in this application refers to the process by which lithium ions are extracted from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0103] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. The following section describes the battery cell and its components provided in this application.

[0104] [Battery cell]

[0105] This application provides a battery cell including a positive electrode and a negative electrode.

[0106] Figure 1 This is a schematic diagram of the positive electrode sheet according to an embodiment of this application. Figure 2 This is a schematic diagram of one side surface of the positive electrode sheet according to an embodiment of this application. Figure 3 This is a schematic diagram of the other side surface of the positive electrode sheet according to an embodiment of this application. For example, combined with... Figures 1 to 3 As shown, the positive electrode includes a positive current collector 50, a first positive electrode film layer 51, and a first insulating layer 531.

[0107] The positive electrode current collector 50 includes a positive electrode body portion 501 and a positive electrode tab 502, the positive electrode tab 502 protruding from the positive electrode body portion 501 along a first direction. The first direction can be... Figure 1 and Figure 2 The x-direction in the middle.

[0108] The first insulating layer 531 and the first positive electrode film layer 51 are disposed on the same side surface of the positive electrode current collector 50 along the thickness direction, and along the first direction, the first insulating layer 531 is closer to the positive electrode tab 502 relative to the first positive electrode film layer 51.

[0109] The first positive electrode film layer 51 includes a positive electrode active material, and the first insulating layer 531 includes an insulating material. The first insulating layer 531 can reduce the adverse effects caused by burrs on the positive electrode sheet (such as burrs piercing the separator, causing positive and negative electrodes to overlap, which in turn causes the battery cell to self-discharge or even short circuit), which is beneficial to improving the reliability of the battery cell.

[0110] The first positive electrode film layer includes a positive electrode active material, which includes a lithium phosphate, and the lithium phosphate includes a lithium phosphate matrix and a carbon coating layer that covers at least a portion of the surface of the lithium phosphate matrix.

[0111] A carbon coating can be understood as a coating that includes carbon elements.

[0112] The carbon coating layer facilitates the formation of a continuous electron transport network on the lithium phosphate surface, which in turn improves the conductivity of the positive electrode active material.

[0113] In this embodiment, the positive electrode active material can be tested in the following way: After disassembling the battery cell, the positive electrode sheet is obtained. The positive electrode sheet is cut along the thickness direction to expose the longitudinal section of the positive electrode film. By performing SEM testing on the longitudinal section of the positive electrode film, after selecting lithium phosphate particles, it can be observed that the lithium phosphate particles have a core-shell structure, that is, the lithium phosphate has a coating layer. Furthermore, by combining energy dispersive spectroscopy (EDS) to test the elements in the carbon coating layer, the carbon element can be measured, that is, the lithium phosphate has a carbon coating layer.

[0114] Figure 4 This is a schematic diagram illustrating the combination of the positive and negative electrode plates according to an embodiment of this application. Figure 5 This is a schematic diagram showing the interaction of the positive and negative electrode plates from another perspective according to an embodiment of this application. Figure 6 This is a schematic diagram of the negative electrode sheet according to an embodiment of this application. (In conjunction with...) Figures 4 to 6 As shown, the negative electrode sheet 6 includes a negative electrode current collector 60 and a negative electrode film layer 61 disposed on at least one side surface of the negative electrode current collector 60.

[0115] As an example, a negative electrode film layer 61 is disposed on both sides of the negative electrode current collector 60 along the thickness direction. The negative electrode film layer 61 comprises a negative electrode active material.

[0116] Along the first direction, the distance by which the edge of the negative electrode film layer 61 extends beyond the edge of the first positive electrode film layer 51 is greater than or equal to 2 mm. The distance by which the edge of the negative electrode film layer 61 extends beyond the edge of the first positive electrode film layer 51 can be represented by H, which can be 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm or any value within the above range.

[0117] Along the first direction, the edge of the negative electrode film layer 61 extends beyond the edge of the first positive electrode film layer 51. This can be understood as the projection of the negative electrode film layer 61 onto the xoy plane covering and extending beyond the projection of the first positive electrode film layer 51 onto the xoy plane. This structural arrangement helps reduce the risk of lithium plating on the negative electrode, thereby improving the reliability of the battery cell.

[0118] Although the edge of the negative electrode film 61 extending beyond the edge of the first positive electrode film 51 helps reduce the risk of lithium plating, as the number of charge-discharge cycles of the battery cell increases, the above-mentioned setting, under the influence of the "reservoir" effect (for an explanation of the "reservoir" effect, please refer to the previous content, which will not be repeated here), also presents a risk of lithium plating at the boundary between the region where the edge of the negative electrode film 61 extends beyond the edge of the first positive electrode film 51 and the region where the negative electrode film 61 and the first positive electrode film 51 overlap; and the larger H is, the higher the risk of lithium plating, and when H is greater than or equal to 2 mm, the risk of lithium plating increases.

[0119] Combination Figures 1 to 6 As shown, along the first direction, the first insulating layer 531 and the first positive electrode film layer 51 have a first overlapping region 56. Within the first overlapping region 56, along the thickness direction of the positive electrode sheet, the first positive electrode film layer 51 is disposed between the positive current collector and the first insulating layer 531.

[0120] As an example, the positive electrode body 501 includes a first region and a second region. Along a first direction, the second region is located between the first region and the positive electrode tab 502. The first insulating layer 531 includes a first part, a second part, and a third part. The first part is disposed in a first overlapping region, the second part is disposed on the surface of the second region other than the first overlapping region, and the third part is disposed on the surface of a portion of the positive electrode tab 502. The first part, the second part, and the third part are connected sequentially in the first direction. The first positive electrode film layer is disposed on the surface of the first region.

[0121] As an example, the first insulating layer is a single-piece structure. As an example, the second and third portions are in direct contact with the positive current collector.

[0122] The setting of the first overlapping region 56 helps to reduce the lithium ion extraction rate at the position of the first positive electrode film 51 corresponding to the first overlapping region 56, thereby mitigating the risk of lithium plating caused by the slow lithium ion insertion at the position of the negative electrode sheet corresponding to the first overlapping region 56. This reduces the risk of lithium plating at the boundary between the area where the edge of the negative electrode film 61 extends beyond the edge of the first positive electrode film 51 and the overlapping area of ​​the negative electrode film 61 and the first positive electrode film 51, compensating for the deficiency of the aggravated reservoir effect caused by the distance of the edge of the negative electrode film extending beyond the edge of the first positive electrode film being greater than or equal to 2 mm, reducing the risk of lithium plating, and thus further improving the reliability of the battery cell.

[0123] As an example, the first overlapping region 56 can be formed in the following manner: After coating the slurry of the first positive electrode film layer onto the positive electrode current collector, a slurry of the first insulating layer is coated onto a portion of the surface of the first positive electrode film layer, a portion of the positive electrode body, and a portion of the positive electrode tab. After drying, a positive electrode sheet with the first overlapping region is obtained.

[0124] In this embodiment, a first positive electrode film layer 51 and a first insulating layer 531 are provided in the first overlapping region 56, and the first positive electrode film layer 51 is located between the positive current collector 50 and the first insulating layer 531 along the thickness direction of the positive electrode sheet.

[0125] As an example, after disassembling a battery cell, the positive electrode sheet can be observed. The first positive electrode film, the first insulating layer, and the first overlapping area can be different colors. The first positive electrode film, the first insulating layer, and the first overlapping area of ​​the first positive electrode film and the first insulating layer can be distinguished by different colors.

[0126] The first insulating layer 531 has a certain insulating function and may include organic insulating materials or inorganic insulating materials. As an example, the first insulating layer 531 includes inorganic insulating materials, such as aluminum oxide.

[0127] During the preparation of the positive electrode sheet, such as when preparing the positive electrode tab by cutting or when cutting a large positive electrode sheet into two positive electrode sheets, burrs are usually generated. The first insulating layer 531 can play a certain role in blocking burrs, for example, reducing the risk of burrs overlapping with the negative electrode sheet and reducing the risk of burrs puncturing the separator.

[0128] In this embodiment, along the first direction, the edge of the negative electrode film extends beyond the edge of the first positive electrode film by a distance greater than or equal to 2 mm. This helps reduce the risk that errors in the manufacturing process may cause the edge of the negative electrode film to not extend beyond the edge of the first positive electrode film. By setting a first overlapping region between the first insulating layer and the first positive electrode film along the first direction, and within this first overlapping region, the first positive electrode film is disposed between the positive current collector and the first insulating layer along the thickness direction of the positive electrode sheet. This helps reduce the lithium ion extraction rate at the location corresponding to the first overlapping region of the first positive electrode film, thereby reducing the risk of lithium plating at the boundary between the region where the edge of the negative electrode film extends beyond the edge of the first positive electrode film and the overlapping region of the negative and first positive electrode films. This compensates for the deficiency of the increased reservoir effect caused by the distance of the negative electrode film edge extending beyond the edge of the first positive electrode film by a distance greater than or equal to 2 mm, and reduces the risk of lithium plating. Therefore, the battery cell of this embodiment has high reliability.

[0129] In some embodiments, the length P1 of the first overlapping region along the first direction is 0.2 mm to 1 mm.

[0130] Along the first direction, the length P1 of the first overlapping region can be 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm or any value within the above range.

[0131] When the length P1 of the first overlapping region along the first direction is greater than or equal to 0.2 mm, it helps to reduce the risk of lithium deposition at the boundary between the region where the edge of the negative electrode film layer 61 extends beyond the edge of the first positive electrode film layer 51 and the region where the negative electrode film layer 61 and the first positive electrode film layer 51 overlap, thereby improving the reliability of the battery cell. When the length of the first overlapping region along the first direction is less than or equal to 1 mm, it facilitates the extraction of lithium ions from the first positive electrode film layer 51, which helps to improve the power, capacity and other electrical performance of the battery cell.

[0132] In some embodiments, the length P1 of the first overlapping region along the first direction is 0.2 mm to 0.6 mm. This allows the first overlapping region to have a suitable length, reducing the risk of lithium plating and resulting in higher reliability of the battery cell.

[0133] In some embodiments, the thickness of the first insulating layer 531 increases in the direction from the first positive electrode film layer 51 to the positive electrode tab 502 in the first overlapping region 56. This helps to reduce the risk of lithium plating at the boundary between the region where the edge of the negative electrode film layer 61 extends beyond the edge of the first positive electrode film layer 51 and the region where the negative electrode film layer 61 and the first positive electrode film layer 51 overlap, resulting in higher reliability of the battery cell.

[0134] As an example, within the first overlapping region 56, at the end of the first overlapping region 56 away from the positive electrode tab along the first direction, the thickness of the first insulating layer 531 is the smallest, and the thickness of the first positive electrode film layer 51 is the largest.

[0135] In some embodiments, the maximum thickness d1 of the first insulating layer 531 is 20 μm to 80 μm.

[0136] The maximum thickness d1 of the first insulating layer 531 is the thickness on one side.

[0137] As an example, the first insulating layer 531 has approximately the same thickness in the region outside the first overlapping region 56. In this case, the maximum thickness of the first insulating layer 531 can also be understood as the average thickness of the first insulating layer 531 in the region outside the first overlapping region 56.

[0138] The maximum thickness d1 of the first insulating layer 531 can be 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm or any value within the above range.

[0139] As an example, along the first direction, the thickness of the first insulating layer at multiple locations (e.g., 10 locations) in the non-first overlapping region 56 is measured using a scanning electron microscope (SEM), and the average of the multiple thicknesses is taken as the maximum thickness d1 of the first insulating layer.

[0140] When the maximum thickness of the first insulating layer 531 is greater than or equal to 20 μm, the first insulating layer 531 can effectively block burrs, which helps reduce the risk of burrs on the positive electrode plate overlapping with the negative electrode plate or puncturing the separator, and the battery cell has high reliability; when the maximum thickness of the first insulating layer 531 is less than or equal to 80 μm, it helps to improve the energy density of the battery cell.

[0141] In some embodiments, the thickness of the positive current collector 50 is 13 μm to 16 μm, for example, it can be 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm or any value within the above range.

[0142] The thickness of the positive current collector is the average thickness. For example, after disassembling a battery cell to obtain the positive electrode sheet, the thickness of the positive current collector at multiple locations (e.g., 10 locations) along the length direction of the positive electrode sheet (e.g., the x-direction) is measured using SEM, and the average of the multiple thicknesses is taken as the thickness of the positive current collector.

[0143] When the thickness of the positive electrode current collector 50 is greater than or equal to 13 μm, the positive electrode sheet has good conductivity, which is beneficial to improving electronic conductivity, reducing the impedance of the battery cell, and thus improving the dynamic performance of the battery cell. When the thickness of the positive electrode current collector 50 is less than or equal to 16 μm, the positive electrode sheet has a more suitable thickness, which is beneficial to improving the energy density of the battery cell.

[0144] In some embodiments, the maximum thickness of the first positive electrode film 51 is 85 μm to 135 μm.

[0145] The maximum thickness of the first positive electrode film layer 51 is the thickness on one side only.

[0146] As an example, the first positive electrode film layer 51 has approximately the same thickness in the region outside the first overlapping region 56. In this case, the maximum thickness of the first positive electrode film layer 51 can also be understood as the average thickness of the first positive electrode film layer 51 in the region outside the first overlapping region 56.

[0147] The maximum thickness d2 of the first positive electrode film layer 51 can be 85μm, 90μm, 95μm, 100μm, 105μm, 110μm, 115μm, 120μm, 125μm, 130μm, 135μm or any value within the above range.

[0148] In the above embodiments, the first positive electrode film layer 51 has a suitable thickness, and the battery cell has a high energy density.

[0149] In some embodiments, the length of the first insulating layer 531 along the first direction is 1 mm to 3 mm.

[0150] Along the first direction, the length of the first insulating layer 531 can be 1 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3 mm or any value within the above range.

[0151] When the length of the first insulating layer 531 is greater than or equal to 1 mm, the first insulating layer 531 can effectively block burrs, which helps reduce the risk of burrs on the positive electrode plate overlapping with the negative electrode plate or puncturing the separator, and the battery cell has high reliability; when the length of the first insulating layer 531 is less than or equal to 3 mm, it helps to improve the energy density of the battery cell.

[0152] In some embodiments, the first positive electrode film layer 51 is provided with a positive electrode main body region 511 and a positive electrode transition region 512. Along the first direction, the positive electrode transition region 512 is disposed at at least one end of the positive electrode main body region 511, and the thickness of the positive electrode transition region 512 is less than the thickness of the positive electrode main body region 511.

[0153] The setting of the positive electrode transition region 512 helps to reduce stress concentration in the positive electrode sheet during the winding or stacking process, and can make the thickness of the edge and center regions of the positive electrode sheet more uniform, which is beneficial to improving the reliability and life of the battery cell.

[0154] As an example, along the first direction, positive electrode transition regions 512 are disposed at both ends of the positive electrode main body region 511, wherein one positive electrode transition region 512 is close to the positive electrode tab 502, and the other positive electrode transition region 512 is located at the end away from the positive electrode tab 502.

[0155] As an example, along the first direction, the positive electrode transition region 512 is disposed at one end of the positive electrode main body region 511. The positive electrode transition region 512 can be disposed at the end of the positive electrode main body region 511 closer to the positive electrode tab, or at the end of the positive electrode main body region 511 farther away from the positive electrode tab.

[0156] In some embodiments, along the first direction, the projection of the positive electrode transition region 512 near the positive electrode tab onto the positive electrode current collector 50 covers the projection of the first overlapping region onto the positive electrode current collector 50. This helps to reduce the risk of lithium plating at the boundary between the region where the edge of the negative electrode film layer 61 extends beyond the edge of the first positive electrode film layer 51 and the overlapping region of the negative electrode film layer 61 and the first positive electrode film layer 51, resulting in higher reliability of the battery cell.

[0157] In some embodiments, the positive electrode sheet further includes a second positive electrode film layer 52. The first positive electrode film layer 51 and the second positive electrode film layer 52 are respectively disposed on both sides of the positive electrode body portion along the thickness direction. The first positive electrode film layer and the second positive electrode film layer include a positive electrode active material, which includes lithium phosphate. The compaction density of the positive electrode sheet is 2.2 g / cm³. 3 Up to 2.7 g / cm 3 Along the direction from the first positive electrode film layer to the positive electrode tab, the edge of the second positive electrode film layer near the positive electrode tab extends beyond the edge of the first positive electrode film layer near the positive electrode tab.

[0158] Lithium-containing phosphates can refer to lithium-containing transition metal phosphates with an olivine structure, such as lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their modified forms. The modification can be either doping or surface modification. For example, in doping modification, elements such as titanium can be doped into lithium iron phosphate; in surface modification, a coating layer can be applied to the surface of lithium iron phosphate.

[0159] Lithium phosphates have high structural stability, and lithium phosphate battery cells have long cycle life.

[0160] The positive electrode current collector 50 has two opposing surfaces along its thickness direction. The first positive electrode film layer 51 and the second positive electrode film layer 52 are respectively disposed on the two side surfaces of the positive electrode body portion 501 along the thickness direction. In the direction from the first positive electrode film layer to the positive electrode tab, the edge of the second positive electrode film layer near the positive electrode tab extends beyond the edge of the first positive electrode film layer near the positive electrode tab. That is to say, in the first direction, the first positive electrode film layer 51 and the second positive electrode film layer 52 are not completely aligned, but are misaligned.

[0161] The compaction density of the positive electrode sheet is 2.2 g / cm³. 3 Up to 2.7 g / cm 3 Under these conditions, the battery cell has a high energy density. However, when the compaction density of the positive electrode sheet meets the aforementioned range, stress concentration is severe at the interface between the region of the positive current collector containing the positive active material and the positive electrode tab 502. This stress concentration increases the risk of cracking of the positive electrode sheet. In this embodiment, along the direction from the first positive electrode film layer to the positive electrode tab, the edge of the second positive electrode film layer near the positive electrode tab extends beyond the edge of the first positive electrode film layer near the positive electrode tab. This reduces the risk of cracking of the positive electrode sheet caused by severe stress concentration at the interfaces between the first positive electrode film layer 51 and the positive electrode tab, and between the second positive electrode film layer 52 and the positive electrode tab. This mitigates the problem of stress concentration and subsequent cracking of the positive electrode sheet due to high compaction density, thus improving the reliability of the battery cell.

[0162] In this embodiment, the compaction density of the positive electrode sheet is the compaction density when the state of charge (SOC) of the battery cell is 0%. The compaction density of the positive electrode sheet can be 2.2 g / cm³. 3 2.25g / cm 3 2.3g / cm 3 2.32 g / cm 3 2.35g / cm 3 2.36 g / cm 3 2.38g / cm 3 2.4g / cm 3 2.42 g / cm 3 2.45g / cm 3 2.48 g / cm 3 2.5g / cm 3 2.52g / cm 3 2.55g / cm 3 2.58g / cm 3 2.6g / cm 3 2.62 g / cm 3 2.65g / cm 3 2.7g / cm 3 Or any value within the above range.

[0163] The compaction density of the positive electrode sheet can be measured as follows: At 25°C, the battery cell is discharged at a constant current of 0.33C to 2.0V to obtain a battery cell with 0% SOC. Then, the positive and negative electrode sheets are removed from the battery cell, and the thickness of the electrode sheet and the current collector are measured respectively. The electrode sheet is then cut into small circular pieces with an area of ​​S1 (if it is a double-sided coated electrode sheet, the film layer on one side can be wiped off first), and its weight is recorded as M1. Then, the film layer of the weighed electrode sheet is wiped off, and the weight of the current collector is recorded as M0. The density of one side is calculated as (M1 - M0) / S1. The compaction density is calculated as: density of one side / (electrode sheet thickness - current collector thickness). Furthermore, the compaction density of the negative electrode sheet can also be measured using the same method.

[0164] In some embodiments, along the first direction, the length L1 of the first gap space is 0.05 mm to 0.5 mm, and the first gap space is the space between the edge of the second positive electrode film layer near the positive electrode tab and the edge of the first positive electrode film layer near the positive electrode tab.

[0165] Along the first direction, the length L1 of the first interval space can be 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm or any value within the above range.

[0166] When the length L1 of the first gap space along the first direction is greater than or equal to 0.05 mm, the risk of cracking of the positive electrode sheet caused by stress concentration at the junction between the first positive electrode film layer 51 and the positive electrode tab, and between the second positive electrode film layer 52 and the positive electrode tab can be reduced, which is beneficial to improving the reliability of the battery cell. When the length of the first gap space along the first direction is less than or equal to 0.5 mm, it is beneficial to improve the energy density of the battery cell.

[0167] In some embodiments, the length L1 of the first spacing space along the first direction is 0.05 mm to 0.2 mm. This provides a more suitable length for the first spacing space, which is beneficial for balancing the reliability and energy density of the battery cells.

[0168] In some embodiments, the positive electrode sheet includes a second insulating layer 532, the second insulating layer 532 and the first positive electrode film layer 51 are disposed on the same side surface of the positive current collector 50 along the thickness direction, the first insulating layer 531 and the second insulating layer 532 are located at both ends of the first positive electrode film layer 51 along the first direction, and the second insulating layer 532 and the first positive electrode film layer 51 have a first gap.

[0169] The provision of the second insulating layer 532 helps to further reduce the impact of burrs, thereby improving the reliability of the battery cell; the second insulating layer 532 and the first positive electrode film layer 51 have a first gap, which helps to reduce energy density loss, thereby improving the energy density of the battery cell.

[0170] As an example, the first insulating layer 531 and the second insulating layer 532 may have the same composition and the same maximum thickness.

[0171] In some embodiments, the positive electrode includes a third insulating layer 533, the third insulating layer 533 and the second positive electrode film layer 52 are disposed on the same side surface of the positive electrode current collector 50 along the thickness direction, and the third insulating layer 533 and the second positive electrode film layer 52 have a second gap along the first direction; the projection of the first insulating layer 531 on the positive electrode current collector 50 covers the projection of the third insulating layer 533 on the positive electrode current collector 50.

[0172] The projection of the first insulating layer 531 onto the positive current collector and the projection of the third insulating layer 533 onto the positive current collector 50 can be understood as the first insulating layer 531 and the third insulating layer 533 being aligned at the end closest to the positive electrode tab along the first direction.

[0173] As an example, the second insulating layer 532 and the third insulating layer 533 have the same shape, thickness, composition and length.

[0174] In some embodiments, the positive electrode includes a fourth insulating layer 534, the fourth insulating layer 534 and the second positive electrode film layer 52 are disposed on the same side surface of the positive current collector 50 along the thickness direction, the fourth insulating layer 534 and the third insulating layer 533 are located at both ends of the second positive electrode film layer 52 along the first direction, the edge of the negative electrode film layer extends beyond the edge of the second positive electrode film layer 52 by a distance greater than or equal to 2 mm along the first direction, and the fourth insulating layer 534 and the second positive electrode film layer 52 have a second overlapping region 57.

[0175] As an example, the fourth insulating layer 534 and the first insulating layer 531 have the same configuration. For example, they have the same length, maximum thickness, shape, and composition.

[0176] As an example, the dimension P2 of the second overlapping region 57 along the first direction is the same as the dimension P1 of the first overlapping region 56 along the first direction.

[0177] In this embodiment, the distance by which the edge of the negative electrode film extends beyond the edges of both the first and second positive electrode films is greater than or equal to 2 mm. Furthermore, because the first and fourth insulating layers have a staggered structure in the first direction, the risk of lithium plating due to the reservoir effect increases compared to a structure where the first and fourth insulating layers are aligned in the first direction. By setting a second overlapping region, and within this region, the second positive electrode film is positioned between the positive current collector and the fourth insulating layer along the thickness direction of the positive electrode sheet. This helps to reduce the lithium ion extraction rate at the position of the second positive electrode film 52 corresponding to the second overlapping region 57. This reduces the risk of lithium plating at the boundary between the region where the edge of the negative electrode film 61 extends beyond the edge of the second positive electrode film 52 and the overlapping region of the negative electrode film 61 and the second positive electrode film 52, thereby further improving the reliability of the battery cell.

[0178] In some embodiments, the first insulating layer 531 includes inorganic particles and a binder. The inorganic particles include at least one of alumina, boehmite, and magnesium oxide. The binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and vinylidene fluoride-trifluorochloroethylene copolymer.

[0179] Inorganic particles have a certain degree of insulation and can block burrs. The binder can bond the inorganic particles to the surface of the positive electrode current collector, thereby facilitating the bonding of the first insulating layer 531 with the positive electrode current collector and the first positive electrode film layer.

[0180] In some embodiments, the compaction density of the positive electrode sheet is 2.45 g / cm³. 3 Up to 2.6 g / cm 3 .

[0181] The compaction density of the positive electrode sheet is greater than or equal to 2.45 g / cm³. 3 Under these conditions, the battery cell has a high energy density; and the compaction density of the positive electrode is less than or equal to 2.6 g / cm³. 3 In this case, it facilitates the transport of lithium ions, which is beneficial to improving the fast charging performance of individual battery cells.

[0182] In some embodiments, the density of one side of the positive electrode is 0.33 g / 1540.25 mm. 2 Up to 0.45g / 1540.25mm 2 .

[0183] The density of a single side of the positive electrode sheet can be 0.33 g / 1540.25 mm. 2 0.34g / 1540.25mm 2 0.36g / 1540.25mm 2 0.38g / 1540.25mm 2 0.40g / 1540.25mm 2 0.41g / 1540.25mm 2 0.42g / 1540.25mm 2 0.43g / 1540.25mm 2 0.44g / 1540.25mm 2 0.45g / 1540.25mm 2 Or any value within the above range.

[0184] The density on one side of the positive electrode sheet is greater than or equal to 0.33 g / 1540.25 mm. 2 Under these conditions, it is beneficial to improve the energy density of the battery cell; when the density of one side of the positive electrode is less than or equal to 0.45g / 1540.25mm. 2 Under these conditions, it is beneficial for lithium-ion transport and helps improve the fast-charging performance of individual battery cells.

[0185] In some embodiments, the projection of the negative electrode film 61 onto the positive electrode current collector 50 covers at least a portion of the projection of the first insulating layer 531 onto the positive electrode current collector 50. This helps to reduce the risk of lithium plating.

[0186] As an example, the first insulating layer 531 includes a first portion, a second portion, and a third portion. The third portion is disposed on at least one side surface of a portion of the positive electrode tab 502, and the first and second portions are disposed on at least one side surface of a portion of the positive electrode body. The projection of the negative electrode film layer onto the positive electrode current collector 50 covers and extends beyond the projections of the first and second portions onto the positive electrode current collector 50. Alternatively, it can be understood that, along the first direction, the negative electrode film layer 61 extends beyond the first and second portions.

[0187] In some embodiments, the negative electrode film layer 61 includes a negative electrode main region 611 and a negative electrode transition region 612. Along a first direction, the negative electrode transition region 612 is disposed at at least one end of the negative electrode main region 611, and the thickness of the negative electrode transition region 612 is less than the thickness of the negative electrode main region 611.

[0188] The setting of the negative electrode transition region 612 helps to reduce stress concentration in the negative electrode sheet during the winding or stacking process, and can make the thickness of the edge and center areas of the negative electrode sheet more uniform, which is beneficial to improving the reliability and life of the battery cell.

[0189] In some embodiments, the density of the negative electrode sheet on one side is 0.15 g / 1540.25 mm. 2 Up to 0.22g / 1540.25mm 2 .

[0190] The density of the negative electrode sheet on one side can be 0.15g / 1540.25mm. 2 0.16g / 1540.25mm 2 0.17g / 1540.25mm 2 0.18g / 1540.25mm 2 0.19g / 1540.25mm 2 0.20g / 1540.25mm 2 0.21g / 1540.25mm 2 0.22g / 1540.25mm 2 Or any value within the above range.

[0191] The density on one side of the negative electrode sheet is greater than or equal to 0.15 g / 1540.25 mm. 2 Under these conditions, it is beneficial to improve the energy density of the battery cell; when the density of one side of the negative electrode is less than or equal to 0.22g / 1540.25mm. 2 Under these conditions, it is beneficial for lithium-ion transport and helps improve the fast-charging performance of individual battery cells.

[0192] In some embodiments, the compaction density of the negative electrode sheet is 1.3 g / cm³. 3 Up to 1.52 g / cm3 .

[0193] In this embodiment, the compaction density of the negative electrode sheet is the compaction density when the state of charge (SOC) of the battery cell is 0%. The compaction density of the negative electrode sheet can be 1.3 g / cm³. 3 1.32g / cm 3 1.35g / cm 3 1.38g / cm 3 1.4g / cm 3 1.42g / cm 3 1.45g / cm 3 1.48g / cm 3 1.5g / cm 3 1.52g / cm 3 Or any value within the above range.

[0194] The compaction density of the negative electrode sheet is greater than or equal to 1.3 g / cm³. 3 Under these conditions, the battery cell has a high energy density; and the compaction density of the negative electrode sheet is less than or equal to 1.52 g / cm³. 3 In this case, it facilitates the transport of lithium ions, which is beneficial to improving the fast charging performance of individual battery cells.

[0195] In some embodiments, the compaction density of the negative electrode sheet is 1.35 g / cm³. 3 Up to 1.5g / cm 3 In this way, the negative electrode sheet has a suitable compaction density, which is beneficial for balancing the energy density and fast charging performance of the battery cell.

[0196] In some embodiments, a single battery cell includes a plurality of positive electrode plates and a plurality of negative electrode plates, which are stacked to form an electrode assembly.

[0197] The battery cell may also include a separator, which is disposed between the positive electrode and the negative electrode to isolate the positive electrode and the negative electrode.

[0198] The battery cells described above are stacked battery cells, which have higher space utilization and higher energy density.

[0199] In some embodiments, a single battery cell includes a positive electrode and multiple negative electrode plates. The positive electrode includes multiple straight positive segments and multiple bent positive segments. The straight positive segments are connected to the bent positive segments, and the multiple straight positive segments and multiple negative electrode plates are stacked.

[0200] In some embodiments, a battery cell includes a plurality of positive electrode plates and a negative electrode plate. The negative electrode plate includes a plurality of straight negative electrode sections and a plurality of bent negative electrode sections. The straight negative electrode sections and the bent negative electrode sections are connected, and the plurality of bent negative electrode sections and the plurality of positive electrode plates are stacked.

[0201] In a battery cell with stacked negative and positive electrodes, the battery cell includes an electrode assembly, which includes a negative electrode, a positive electrode, and a separator. The electrode assembly has little or no bending area. This type of battery cell can also be called a stacked battery cell.

[0202] Figure 7 This is a schematic diagram of a battery cell according to an embodiment of this application. Figure 8 This is a schematic diagram of a battery cell according to an embodiment of this application. In some embodiments, such as... Figure 7 and Figure 8 As shown, the battery cell 3 includes an electrode assembly 33 and a packaging bag 31. The electrode assembly 33 includes a positive electrode and a negative electrode. The packaging bag 31 includes two packaging films 310. The electrode assembly is located between the two packaging films 310. The edges of the two packaging films 310 are connected to each other to form a sealing part. The battery cell 3 also includes an electrode lead 321, which passes through the two packaging films 310 and is electrically connected to the electrode assembly 33.

[0203] As an example, the battery cell includes two electrode leads: a positive lead for electrical connection to the positive tab 502 of the electrode assembly 33, and a negative lead for electrical connection to the negative tab 602 of the electrode assembly 33.

[0204] The battery cell with this structure is a pouch cell. The connection of two packaging films can form a sealed space inside the battery cell to accommodate the positive electrode, negative electrode and electrolyte. By electrically connecting the electrode leads to the electrode assembly, it is easy to draw out the current.

[0205] In some embodiments, the packaging film 310 includes an insulating protective layer, a metal layer, and an insulating connecting layer. The insulating connecting layer is disposed on the surface of the metal layer facing the electrode assembly, and the insulating protective layer is disposed on the surface of the metal layer away from the electrode assembly. In this way, the electrode assembly and electrolyte can be sealed for protection, while also having a certain degree of flexibility to provide cushioning when the battery cell is subjected to compression or vibration.

[0206] In some embodiments, the material of the insulating protective layer may include nylon, the material of the metal layer may include aluminum or steel, and the material of the insulating connecting layer may include polypropylene.

[0207] In some embodiments, the packaging bag 31 is made of an aluminum-plastic film, and the positive and negative electrode sheets are housed within the space formed by the aluminum-plastic film. The battery cell in this structure is a pouch cell.

[0208] Aluminum-plastic film is a multi-layered composite flexible packaging material, which can be formed by laminating an outer layer of polymer (such as nylon or polyester), an intermediate layer of aluminum film (such as aluminum foil), and an inner layer of polymer (such as polypropylene or polyethylene). Compared with aluminum or steel shells, the battery cells made from aluminum-plastic film are soft-pack battery cells.

[0209] In some embodiments, the battery cell may also be a rigid-cased battery cell, and the casing material may be steel or aluminum.

[0210] In some embodiments, the battery cell is a cylindrical battery cell.

[0211] Cylindrical battery cells have better uniformity, which is conducive to achieving more balanced control under the management of the battery management system, thereby ensuring the overall performance of the battery device; in addition, it is also conducive to forming a better heat dissipation space within the battery device, facilitating the heat dissipation of the battery cells.

[0212] In some embodiments, the diameter of the cylindrical battery cell is greater than or equal to 40 mm, for example, it can be 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm or any value within the above range.

[0213] When the diameter of a cylindrical battery cell is greater than or equal to 40 mm, the battery cell has a large capacity and a high energy density.

[0214] In some embodiments, along the first direction, the edge of the negative electrode film extends beyond the edge of the first positive electrode film by a distance greater than or equal to 2 mm and less than or equal to 7 mm. This is advantageous in ensuring that the edge of the negative electrode film extends beyond the edge of the positive electrode film while maintaining a high energy density.

[0215] In some embodiments, the average longest diameter of the primary particles containing lithium phosphate is between 300 nm and 800 nm, for example, it can be 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, or any value within the above range. This ensures that the lithium ion extraction path has a suitable distance, which is beneficial for improving the power performance of the battery cell.

[0216] In the embodiments of this application, a primary particle refers to the smallest unit of a particle within a certain observation range. A primary particle may contain defects of any form, but it is impossible to further define smaller particles within a primary particle. Primary particles may aggregate under physical forces such as van der Waals forces, but such aggregation is easily disaggregated under external forces such as ultrasound, stirring, and rolling, so that the main constituent morphology of the positive electrode active material in the film layer is still primary particles.

[0217] The longest diameter of a lithium phosphate is the longest straight line that passes through the center point of the lithium phosphate and extends to the outer periphery of the particle.

[0218] In the embodiments of this application, the average value of the longest diameter can be measured in the following manner.

[0219] The battery cell is disassembled to obtain the positive electrode sheet. The positive electrode sheet is cut along its thickness to expose the longitudinal section of the positive electrode film. The longest diameter of the lithium phosphate-containing particles is determined by scanning electron microscopy (SEM) of the longitudinal section of the positive electrode film. As an example, 30 lithium phosphate-containing particles are randomly selected from the longitudinal section image of the positive electrode film, and the longest diameter of each of the 30 particles is measured and averaged.

[0220] In some embodiments, the lithium phosphate matrix includes lithium iron phosphate, which is doped with at least one of Al, V, and Ti. These doping elements are beneficial for improving the conductivity and other properties of the lithium phosphate, thereby improving the capacity of the battery cell. Furthermore, these doping elements also help increase the compaction density of the positive electrode, thus improving the energy density of the battery cell.

[0221] In some embodiments, based on the total mass of lithium phosphate, the mass content of Al is 200 ppm to 2500 ppm, the mass content of V is 300 ppm to 2000 ppm, and the mass content of Ti is 1500 ppm to 3500 ppm. With suitable mass contents of the aforementioned doping elements, the battery cell exhibits high energy density, capacity, and cycle performance.

[0222] Based on the total mass of lithium phosphate, the mass content of Al can be 200ppm, 300ppm, 500ppm, 800ppm, 1000ppm, 1200ppm, 1500ppm, 1800ppm, 2000ppm, 2200ppm, 2400ppm, 2500ppm or any value within the above range; the mass content of V can be 300ppm, 500ppm, 800ppm, 1000ppm, 1200ppm, 1500ppm, 1800ppm, 2000ppm or any value within the above range; and the mass content of Ti can be 1500ppm, 1800ppm, 2000ppm, 2200ppm, 2400ppm, 2500ppm, 2800ppm, 3000ppm, 3200ppm, 3500ppm or any value within the above range.

[0223] The elements and their contents in the positive electrode active material can be determined using an argon ion cross-section polisher (model JEOLIB-19530CP) and a scanning electron microscope (model Zeiss Sigma 300) (equipped with an X-ray energy dispersive spectrometer (EDS, model OXFord X-Max-50mm2)).

[0224] As an example, the battery cell was discharged at a constant current of 0.33C to 2.0V at 25°C to obtain a battery cell with 0% SOC. Then, the positive electrode was removed from the battery cell, and a longitudinal cross-section of the positive electrode film was obtained using an ion section polisher. The cross-section of the positive electrode active material particles was then scanned using a scanning electron microscope to test the elements and their content.

[0225] In some embodiments, the lithium phosphate-containing cathode active material includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The aforementioned lithium phosphate-containing cathode active materials exhibit high structural stability, which helps to improve the cycle life of individual battery cells.

[0226] During the charging and discharging process, lithium (Li) undergoes insertion / extraction and consumption within a single battery cell. The molar content of Li in the positive electrode active material varies depending on the discharge state of the cell. In the examples of positive electrode active materials in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar content of Li changes when the positive electrode active material is applied to the battery system. Similarly, the molar content of O in the examples of positive electrode active materials in this application is only an ideal value. Oxygen release from the crystal lattice causes changes in the molar content of O, resulting in fluctuations in the actual molar content of O.

[0227] In some embodiments, the negative electrode film layer includes a negative electrode active material, which includes graphite, and at least a portion of the surface of the graphite has a coating layer comprising amorphous carbon. This facilitates the rapid intercalation of lithium ions into the graphite, thereby improving the fast-charging performance of the battery cell.

[0228] In some embodiments, the thickness of the coating layer is from 100 nm to 500 nm, for example, it can be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm or any value within the above range. This coating layer has a suitable thickness, facilitating lithium-ion insertion and transport, and improving the fast-charging performance of the battery cell.

[0229] In some embodiments, the graphite comprises secondary particles. This facilitates lithium-ion transport and improves the fast-charging performance of individual battery cells.

[0230] In some embodiments, the graphitization degree of graphite is 90% to 94%, for example, it can be 90%, 91%, 92%, 93%, 94% or any value within the above range. Thus, graphite with a suitable graphitization degree is beneficial for achieving a suitable specific capacity and for controlling side reactions in the battery cell within a suitable range, thereby resulting in a battery cell with suitable capacity and cycle life.

[0231] In some embodiments, the volume average particle size Dv50 of graphite is 15 μm to 25 μm. This appropriate range of graphite particle size is beneficial for increasing the compaction density of the negative electrode sheet, thereby improving the energy density of the battery cell.

[0232] The volume average particle size (Dv50) of graphite represents the particle size corresponding to a cumulative volume distribution percentage of 50%, and can be determined using instruments and methods known in the art. As an example, a battery cell is disassembled to obtain the negative electrode sheet. The negative electrode film layer is scraped off to obtain powder of the negative electrode film layer. This powder is then mixed with water, filtered, and dried to obtain graphite. Subsequently, the particle size is conveniently determined using a laser particle size analyzer according to GB / T19077-2016, Laser Diffraction Method for Particle Size Distribution. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0233] The volume average particle size Dv50 of graphite can be 115μm, 15.2μm, 15.5μm, 15.8μm, 16μm, 16.2μm, 16.5μm, 16.8μm, 17μm, 17.2μm, 17.5μm, 17.8μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm or any value within the above range.

[0234] In some embodiments, the volume average particle size Dv50 of graphite is 16 μm to 20 μm. This appropriate range of graphite particle size is beneficial for increasing the compaction density of the negative electrode sheet, thereby improving the energy density of the battery cell.

[0235] In some embodiments, the ionic conductivity of the electrolyte is from 9.5 ms / cm to 20 ms / cm, for example, it can be 9.5 ms / cm, 10 ms / cm, 11 ms / cm, 12 ms / cm, 12.5 ms / cm, 13 ms / cm, 14 ms / cm, 15 ms / cm, 15.5 ms / cm, 16 ms / cm, 17 ms / cm, 18 ms / cm, 19 ms / cm, 20 ms / cm, or any value within the above range. This results in a electrolyte with high ionic conductivity, facilitating lithium-ion transport, reducing the risk of lithium plating, and improving the cycle performance and lifespan of the battery cells.

[0236] In some embodiments, the electrolyte has an ionic conductivity of 12 ms / cm to 16 ms / cm. This high ionic conductivity facilitates lithium-ion transport, reduces the risk of lithium plating, and improves the cycle performance and lifespan of the battery cells.

[0237] In some embodiments, the electrolyte includes a solvent, which includes at least one of linear carbonates and linear carboxylic acid esters.

[0238] Linear carbonates and linear carboxylic acid esters have low viscosity, which is beneficial for improving the wettability of the electrolyte on the positive and negative electrode sheets, thereby improving the dynamic performance of the battery cells and giving the battery cells better fast charging performance.

[0239] Linear carbonates can have the general formula RO-CO-OR', where R and R' are substituted or unsubstituted alkyl groups.

[0240] As an example, linear carbonates may include at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0241] Linear carboxylic acid esters can have the general formula R1-COO-R2, where R1 and R2 can be substituted or unsubstituted alkyl groups.

[0242] As an example, linear carboxylic acid esters may include at least one of methyl acetate, ethyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

[0243] In some embodiments, the linear carbonate includes dimethyl carbonate, and the linear carboxylic acid ester includes at least one of ethyl acetate and methyl acetate. The solvents described above have low viscosity, and the electrolyte containing these solvents has low viscosity, which is beneficial for lithium-ion transport, thereby improving the fast-charging performance of the battery cells.

[0244] In some embodiments, the sum of the mass contents of linear carbonates and linear carboxylic acid esters, based on the total mass of the electrolyte, is 10% to 90%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any value within the range above.

[0245] When the total mass content of linear carbonate and linear carboxylic acid ester is greater than or equal to 10% based on the total mass of the electrolyte, the electrolyte has a lower viscosity, which is beneficial for lithium-ion transport, and the battery cell has better fast-charging performance. When the total mass content of linear carbonate and linear carboxylic acid ester is less than or equal to 90% based on the total mass of the electrolyte, the gas production of linear carbonate and linear carboxylic acid ester in the battery cell can be reduced, thereby reducing the risk of gas accumulation between the separator and the positive and negative electrode plates, reducing the risk of lithium plating, and improving the cycle performance of the battery cell.

[0246] In some embodiments, the sum of the mass contents of linear carbonate and linear carboxylic acid ester is 40% to 80% based on the total mass of the electrolyte. This provides a suitable range for the sum of the mass contents of linear carbonate and linear carboxylic acid ester, allowing the battery cell to achieve both good fast-charging performance and cycle performance.

[0247] In some embodiments, the electrolyte comprises an electrolyte salt, which includes lithium hexafluorophosphate and lithium bisfluorosulfonylimide. Lithium bisfluorosulfonylimide has a good ability to dissociate lithium ions, and by combining lithium hexafluorophosphate and lithium bisfluorosulfonylimide, the electrolyte has a high ionic conductivity.

[0248] In some embodiments, the total mass content of lithium hexafluorophosphate and lithium difluorosulfonylimide, based on the total mass of the electrolyte, is 12% to 20%, for example, it can be 12%, 13%, 15%, 16%, 18%, 19%, 20% or any value within the above range.

[0249] When the total mass content of lithium hexafluorophosphate and lithium difluorosulfonylimide is greater than or equal to 12% based on the total mass of the electrolyte, the electrolyte has a high ionic conductivity, which facilitates lithium-ion transport, helps reduce the risk of lithium plating, and improves the cycle performance of the battery cell. When the total mass content of lithium hexafluorophosphate and lithium difluorosulfonylimide is less than or equal to 20% based on the total mass of the electrolyte, the electrolyte has a suitable viscosity, which facilitates lithium-ion transport and helps improve the fast-charging performance of the battery cell.

[0250] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is 1.2 to 3, for example, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, or any value within the above range. This results in an electrolyte with high ionic conductivity, facilitating lithium-ion transport, reducing the risk of lithium plating, and improving the cycle performance of the battery cell.

[0251] In the embodiments of this application, the types and contents of organic components in the electrolyte can be detected using equipment and methods known in the art. For example, the organic solvents in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents".

[0252] In the embodiments of this application, the types and contents of inorganic components / lithium salt concentrations in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the concentrations of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis using the standard JY / T020-1996 "General Rules for Ion Chromatography Analysis".

[0253] In this embodiment of the application, the ionic conductivity of the electrolyte to be tested can be tested using a conductivity meter in accordance with HG / T 4067-2015: Take about 100 ml of the sample to be tested in a dry, clean, corrosion-resistant sample bottle, seal it and place it in a constant temperature water bath at 25±0.5 ℃. When the temperature of the sample to be tested is constant, replace the cap of the sample bottle with a rubber stopper with an electrode inserted. When the temperature is within the range of 25±0.5℃, read the data, which is the ionic conductivity of the sample to be tested.

[0254] In the embodiments of this application, a freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery cell can be used as a sample, or a battery cell that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell can be used as a sample.

[0255] In the embodiments of this application, after quantitative and qualitative detection of each component in the electrolyte, the composition and mass content of the solvent and lithium salt based on the electrolyte mass can be determined.

[0256] In some embodiments, the ratio of electrolyte mass to battery cell capacity is between 2.8 g / Ah and 3.5 g / Ah, for example, 2.8 g / Ah, 2.9 g / Ah, 3.0 g / Ah, 3.1 g / Ah, 3.2 g / Ah, 3.3 g / Ah, 3.4 g / Ah, 3.5 g / Ah, or any value within the above range. This provides good wettability of the electrolyte to the positive electrode 5 and the negative electrode 6, which is beneficial for lithium-ion transport, thereby reducing the risk of lithium plating and improving the cycle performance of the battery cell.

[0257] In some embodiments, the ratio of electrolyte mass to battery cell capacity is 3.0 g / Ah to 3.2 g / Ah. This provides good wettability of the electrolyte to the positive electrode 5 and negative electrode 6, which is beneficial for lithium-ion transport, thereby reducing the risk of lithium plating and improving the cycle performance of the battery cell.

[0258] In some embodiments, the electrolyte includes additives, including at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propane sulpholactone (PS). These additives facilitate film formation at the negative electrode, reduce side reactions at the negative electrode, and thus improve the cycle life, kinetics, and other performance characteristics of the battery cell.

[0259] In some embodiments, based on the total mass of the electrolyte, the mass content of the additive is less than or equal to 5%, for example, it can be 5%, 4.8%, 4.5%, 4.2%, 4%, 3.8%, 3.5%, 3%, 2.8%, 2.5%, 2%, 1.8%, 1.5%, 1.2%, 1%, 0.8%, 0.5%, or any value within the above range. The above-mentioned additives have suitable mass content, which is beneficial to improving the cycle life, kinetics, and other performance characteristics of the battery cells.

[0260] In some embodiments, the additive content is 0.5% to 3% by mass, based on the total mass of the electrolyte. The appropriate mass content of the additive is beneficial for improving the cycle life, kinetics, and other performance characteristics of the battery cells.

[0261] In some embodiments, the battery cell further includes a separator membrane disposed between the positive electrode 5 and the negative electrode 6. The separator membrane includes a base film with a thickness of 5 μm to 9 μm, for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 8.5 μm, 9 μm or any value within the above range.

[0262] When the thickness of the base film is greater than or equal to 5 μm, the separator has high strength, which can reduce the risk of lithium dendrites puncturing the separator and causing internal short circuits in the battery cell; when the thickness of the base film is less than or equal to 9 μm, it is beneficial to reduce the space occupied by the separator, and the battery cell has high energy density.

[0263] In some embodiments, the porosity of the separator is 40% to 55%, for example, it can be 40%, 42%, 45%, 48%, 50%, 52%, 55% or any value within the above range. This facilitates the wetting of the separator by the electrolyte, which is beneficial for lithium ion transport, thereby reducing the risk of lithium plating and resulting in better cycle performance of the battery cell.

[0264] [Battery Device]

[0265] This application provides a battery device, including the battery cell in any of the above embodiments.

[0266] Figure 9 This is a schematic diagram of a battery device according to an embodiment of this application. For example, such as... Figure 9 As shown, the battery device 10 of this application embodiment may include a plurality of battery cells 3 to meet different power usage requirements. The shape of the battery cell 3 in this application embodiment can be set according to actual application. For example, the battery cell 3 can be cylindrical, or it can be cuboid or other shapes, and this application embodiment is not limited to this.

[0267] The battery device 10 of this embodiment may further include a housing 11, which can be used to accommodate multiple battery cells 3. The housing 11 of this embodiment has a hollow interior, and the multiple battery cells 3 are accommodated within the housing 11. The housing 11 may include two parts, referred to herein as a first housing portion 111 and a second housing portion 112, which are fastened together. The shapes of the first housing portion 111 and the second housing portion 112 can be determined according to the shape of the components housed inside, for example, according to the shape of the combination of the multiple battery cells 3 housed inside. At least one of the first housing portion 111 and the second housing portion 112 has an opening. For example, as... Figure 9 As shown, the first housing portion 111 and the second housing portion 112 can both be hollow cuboids with one open side each. The openings of the first housing portion 111 and the second housing portion 112 are opposite to each other, and the first housing portion 111 and the second housing portion 112 are interlocked to form a housing 11 with a closed chamber, which can be used to accommodate multiple battery cells 3. The multiple battery cells 3 are connected in parallel, series, or mixed and placed inside the housing 11 formed by the interlocking of the first housing portion 111 and the second housing portion 112.

[0268] For example, unlike Figure 9 As shown, either the first housing portion 111 or the second housing portion 112 may have only one hollow cuboid with an opening, while the other is plate-shaped to cover the opening. Taking the second housing portion 112 as a hollow cuboid with one opening and the first housing portion 111 as a plate-shaped example, then the first housing portion 111 covers the opening of the second housing portion 112 to form a housing 11 with a closed chamber, which can be used to accommodate multiple battery cells 3.

[0269] Figure 10 This is a schematic diagram illustrating the interaction between a single battery cell and a thermal management component according to an embodiment of this application. Figure 11 This is a schematic diagram illustrating the interaction between a battery cell and a thermal management component according to another embodiment of this application. In some embodiments, combined with Figures 9 to 11 As shown, the battery device includes: a housing 11; a plurality of battery cells 3, which are housed within the housing 11 and stacked along a third direction, each battery cell having a rated capacity greater than or equal to 100 Ah, each battery cell having a surface including a first surface 301 and a second surface 302, the area of ​​the first surface being greater than the area of ​​the second surface, the first surfaces of the plurality of battery cells being arranged opposite each other along a third direction; and a thermal management component 91 for regulating the temperature of the plurality of battery cells, the thermal management component being arranged opposite to the second surfaces of the plurality of battery cells along a fourth direction, the fourth direction being perpendicular to the third direction.

[0270] The third direction can be Figure 10 and Figure 11 In the X direction, the fourth direction can be Figure 10 and Figure 11 The Z direction in the equation.

[0271] Each battery cell 3 may include two first surfaces 301 and two second surfaces 302, with the two first surfaces 301 facing each other along the X direction and the two second surfaces 302 facing each other along the second direction.

[0272] As an example, the first surface 301 is the surface with the largest surface area of ​​the battery cell.

[0273] As an example, the electrode terminals of the battery cell 3 are disposed on the first surface 301.

[0274] In this embodiment, the rated capacity of each battery cell is greater than or equal to 100Ah. During the charging and discharging process of the battery cell, a lot of heat will be generated. By matching the thermal management component with the battery cell, it is beneficial to control the temperature of the battery cell and reduce the risk of the battery cell temperature being too high.

[0275] In some embodiments, the battery device further includes a retaining adhesive 92 disposed between the thermal management component and the battery cell, which is used to fix the battery cell to the thermal management component. This facilitates the fixation between the battery cell and the thermal management component.

[0276] In some embodiments, such as Figure 10 As shown, the battery cell includes a packaging bag and an electrode assembly. The electrode assembly is housed inside the packaging bag, and the fixing adhesive 92 is directly connected to the packaging bag. In other words, the fixing adhesive 92 is directly connected to the packaging bag of the battery cell 3, which helps to improve the energy density of the battery device.

[0277] In this embodiment, the adhesive 92 is directly attached to the packaging bag, and the battery cells in the battery device are arranged one on top of the other, which eliminates the need for a component that fixes multiple battery cells together.

[0278] Figure 12 This is a schematic diagram of a battery module according to an embodiment of this application. In some embodiments, such as... Figure 11 and Figure 12 As shown, the battery device also includes a housing 801, which houses at least one battery cell, and adhesive 92 is directly attached to the wall of the housing 801. The housing 801 facilitates better heat dissipation from the battery cell, which helps to reduce the temperature of the battery cell.

[0279] In this embodiment, the battery device includes at least one battery module 80, which includes a housing 801 and a plurality of battery cells.

[0280] As an example, the housing 801 has a U-shaped form. For instance, the housing 801 includes a first wall 8011, a second wall 8012, and a third wall 8013, with the two ends of the second wall 8012 extending in the direction of extension connected to the first wall 8011 and the third wall 8013, respectively. As an example, the first wall 8011 and the third wall 8013 extend in the Z direction, and the second wall 8012 extends in the X direction.

[0281] As an example, the adhesive 92 is directly attached to the first wall 8011 and the third wall 8013 of the housing 801.

[0282] [Electrical Equipment]

[0283] This application provides an electrical device, including a battery cell or a battery device as described in any of the above embodiments, wherein the battery cell or battery device is used to store or provide electrical energy.

[0284] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery devices.

[0285] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical equipment.

[0286] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0287] For example, such as Figure 13 The diagram shown is a schematic representation of a vehicle according to one embodiment of this application. Vehicle 1 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A motor 40, a controller 30, and a battery device 10 can be installed inside vehicle 1. The controller 30 controls the battery device 10 to supply power to the motor 40. For example, the battery device 10 can be installed at the bottom, front, or rear of vehicle 1. The battery device 10 can be used to power vehicle 1. For example, the battery device 10 can serve as the operating power source for vehicle 1, for example, to meet the electrical system requirements of vehicle 1, such as for starting, navigation, and operation. In another embodiment of this application, the battery device 10 can not only serve as the operating power source for vehicle 1 but also as the driving power source for vehicle 1, replacing or partially replacing gasoline or natural gas to provide driving power for vehicle 1.

[0288] [Positive electrode plate]

[0289] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0290] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As an example, the positive electrode active material may include one or more of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.1 Al 0.05 One or more of the following: O2) and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0291] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption. The molar content of Li in the positive electrode active material varies depending on the discharge state. In the examples of positive electrode active materials in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar content of Li changes when the positive electrode active material is applied to the battery system. Similarly, the molar content of O in the examples of positive electrode active materials in this application is only an ideal value. Oxygen release from the crystal lattice causes changes in the molar content of O, and the actual molar content of O will fluctuate.

[0292] In some embodiments, the first positive electrode film layer and the second positive electrode film layer further include an adhesive. As an example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0293] In some embodiments, the first positive electrode film layer and the second positive electrode film layer further include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0294] [Negative electrode plate]

[0295] In some embodiments, the negative electrode current collector can be a metal foil or a composite negative electrode current collector. The negative electrode current collector can be a copper foil. The composite negative electrode current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0296] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material includes graphite, and may also include at least one of the following materials: soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0297] The negative electrode film layer may also optionally include a binder. As an example, the binder may include at least one of styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0298] The negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0299] In one embodiment, the negative electrode sheet can be prepared by forming a negative electrode slurry using the components described above. For example, the negative electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., deionized water) to form the negative electrode slurry. The negative electrode slurry is then coated onto a negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained.

[0300] [Isolation Component]

[0301] The separator is used to separate the positive electrode and the negative electrode. This application does not impose any particular restrictions on the type of separator; for example, any known porous membrane with good chemical and mechanical stability can be selected.

[0302] In one embodiment, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0303] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0304] [Example]

[0305] Example 1

[0306] (1) Preparation of negative electrode sheet

[0307] Artificial graphite (anode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) (thickener) were thoroughly stirred in a deionized water solvent system at a mass ratio of 96.5:0.5:2:1 to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto both sides of the copper foil (anode current collector) along its thickness direction. After drying, cold pressing, and slitting, the negative electrode sheet was obtained. The volume average particle size (Dv50) of the artificial graphite was 18 μm, and the compaction density of the negative electrode film was 1.4 g / cm³ when the battery cell was at 0% SOC. 3 The single-sided density of the negative electrode film is 0.17 g / 1540.25 mm. 2 .

[0308] (2) Preparation of positive electrode sheet

[0309] Lithium iron phosphate, the positive electrode active material, is mixed thoroughly in an N-methylpyrrolidone (NMP) solvent system with a carbon coating layer, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) at a mass ratio of 97:1.0:2.0 to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated on both sides of the main body of the positive electrode current collector aluminum foil along the thickness direction to obtain the first positive electrode film layer and the second positive electrode film layer, respectively.

[0310] The positive current collector includes a main body and a positive electrode tab. The positive electrode tab protrudes from the main body in a first direction. In the direction from the first positive electrode film layer to the positive electrode tab, the edge of the second positive electrode film layer near the positive electrode tab extends beyond the edge of the first positive electrode film layer near the positive electrode tab (that is, in the first direction, the edge of the first positive electrode film layer near the positive electrode tab and the edge of the second positive electrode film layer near the positive electrode tab have a first gap space). The length L1 of the first gap space is 0.15 mm.

[0311] Inorganic particles Al2O3 and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an N-methylpyrrolidone (NMP) solvent system to obtain an insulating slurry. The insulating slurry is then coated onto the corresponding positions to obtain a first insulating layer, a second insulating layer, a third insulating layer, and a fourth insulating layer.

[0312] The first insulating layer, the second insulating layer, and the first positive electrode film layer are disposed on the same side surface of the positive electrode current collector along the thickness direction. Along the first direction, the first insulating layer and the first positive electrode film layer have a first overlapping area, and the second insulating layer and the first positive electrode film layer have a first gap. Along the first direction, the length P1 of the first overlapping area is 0.5 mm, and the dimension L2 of the first gap is 0.05 mm.

[0313] The third insulating layer, the fourth insulating layer, and the second positive electrode film layer are disposed on the same side surface of the positive electrode current collector along the thickness direction. Along the first direction, the third insulating layer and the second positive electrode film layer have a second gap, and the fourth insulating layer and the second positive electrode film layer have a second overlapping area.

[0314] Along the first direction, the length P1 of the first overlapping region and the length P2 of the second overlapping region are the same, and the dimensions L2 of the first gap and the dimensions L3 of the second gap are the same. The maximum thickness d2 of the first positive electrode film is 105 μm, the maximum thickness d1 of the first insulating layer is 80 μm, the first positive electrode film and the second positive electrode film have the same maximum thickness, and the first insulating layer, the second insulating layer, the third insulating layer and the fourth insulating layer have the same maximum thickness.

[0315] With the battery cell at 0% SOC, the compaction density of the positive electrode film is 2.5 g / cm³. 3 The single-sided density of the positive electrode film is 0.38 g / 1540.25 mm. 2.

[0316] (3) Preparation of electrolyte

[0317] In an argon atmosphere glove box (H2O content <10ppm, O2 content <1ppm), organic solvents dimethyl carbonate (DMC), ethyl acetate (EA), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) were mixed evenly. Then, lithium hexafluorophosphate (LiPF6) and lithium difluorosulfonyl imide (LiFSI) were added to dissolve them in the organic solvents. Finally, ethylene carbonate (VC) was added and stirred evenly to obtain the electrolyte of Example 1.

[0318] Based on the total mass of the electrolyte, the mass content of LiPF6 is 9.6%, the mass content of LIFSI is 4.8%, the mass content of DMC is 16.3%, the mass content of EA is 33.4%, the mass content of EMC is 8.6%, the mass content of EC is 24.8%, and the mass content of VC is 2.5%.

[0319] (4) Separating membrane

[0320] The separator includes a base film, which is a polyethylene (PE) film with a thickness of 7 μm.

[0321] (5) Preparation of battery cells

[0322] The positive electrode, separator, and negative electrode are stacked according to the stacking process, with the separator positioned between the positive and negative electrodes to isolate them. The electrode assembly is placed in an aluminum-plastic film, and electrolyte is injected. After vacuum sealing, settling, formation, and shaping, a single battery cell is obtained.

[0323] In the first direction, the distance H from the edge of the negative electrode film layer to the edge of the first positive electrode film layer is 4 mm.

[0324] Examples 2-4

[0325] The difference between Examples 2-4 and Example 1 is that the length of the overlapping area is different along the first direction.

[0326] Example 5

[0327] The difference between Example 5 and Example 1 is that the distance H by which the edge of the negative electrode film extends beyond the edge of the first positive electrode film along the first direction is different.

[0328] Examples 6-8

[0329] The difference between Examples 6-8 and Example 1 is that the length of the first interval space along the first direction is different.

[0330] Example 9

[0331] The difference between Example 9 and Example 1 is that: along the direction from the first positive electrode film layer to the positive electrode tab, the edge of the second positive electrode film layer near the positive electrode tab does not extend beyond the edge of the first positive electrode film layer near the positive electrode tab, that is, the projections of the first positive electrode film layer and the second positive electrode film layer on the positive electrode current collector coincide.

[0332] Comparative Example 1

[0333] The difference between Comparative Example 1 and Example 1 is that: there is no overlapping region between the first positive electrode film layer and the first insulating layer, nor between the second insulating layer and the third insulating layer, nor between the second positive electrode film layer and the fourth insulating layer. That is, the first positive electrode film layer is connected to the first insulating layer and the first insulating layer, and to the second insulating layer, but they do not overlap; the second positive electrode film layer is connected to the third insulating layer and the second insulating layer, and to the fourth insulating layer, but they do not overlap. It should be noted that the overlapping regions here do not include the cases where, due to the flow of the insulating slurry and the positive electrode slurry during the preparation process, there are fused portions between the first positive electrode film layer and the first insulating layer, the second insulating layer, the second positive electrode film layer and the third insulating layer, the fourth insulating layer, etc.

[0334] Table 1. Data from the Examples and Comparative Examples

[0335]

[0336] Table 2 Data from some embodiments

[0337]

[0338] Table 3 Data from some embodiments

[0339]

[0340] In Tables 1, 2 and 3, H represents the distance from the edge of the negative electrode film layer to the edge of the first positive electrode film layer along the first direction, P1 represents the length of the first overlapping region along the first direction, and L1 represents the length of the first gap space along the first direction.

[0341] In this embodiment, the reliability of a single battery cell can be demonstrated through a self-discharge test. In the self-discharge test, a smaller value indicates higher reliability of the battery cell. The results of the self-discharge test can reflect the lithium plating status of the negative electrode; the less lithium plating in the negative electrode, the smaller the self-discharge value.

[0342] In conjunction with Examples 1-5 and Comparative Example 1, when the distance between the edge of the negative electrode film layer and the edge of the first positive electrode film layer along the first direction is greater than or equal to 2 mm, by setting a first overlapping area between the first insulating layer and the first positive electrode film layer along the first direction, and within the first overlapping area, the first positive electrode film layer is disposed between the positive current collector and the first insulating layer along the thickness direction of the positive electrode sheet, which helps to reduce the risk of lithium plating and improve the reliability of the battery cell.

[0343] As shown in Examples 1-4, setting the length P1 of the first overlapping region in the first direction to 0.2mm to 1mm allows the battery cell to achieve both high energy density and high reliability; setting P1 to 0.2mm to 0.6mm further helps to balance the energy density and reliability of the battery cell; as shown in Examples 1 and 5, increasing H will increase the risk of lithium plating.

[0344] In conjunction with Embodiment 1 and 6-8, setting the size L1 of the first gap space in the first direction to 0.05mm to 0.5mm allows the battery cell to achieve both high energy density and high reliability; setting L1 to 0.05mm to 0.2mm further helps to balance the energy density and reliability of the battery cell.

[0345] As shown in Examples 1 and 9, the direction of the first positive electrode film layer pointing towards the positive electrode tab is set such that the edge of the second positive electrode film layer near the positive electrode tab extends beyond the edge of the first positive electrode film layer near the positive electrode tab. This is beneficial to improve the energy density of the battery cell and at the same time reduce the risk of positive electrode cracking. The battery cell can also maintain high reliability.

[0346] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

[0347] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0348] 1. Self-discharge test

[0349] At 25±2℃, the battery cells were adjusted to 30% SOC by discharging. After standing for 12 hours, the initial voltage V0 was recorded. At the same temperature, the cells were left to stand for another 48 hours, and the final voltage V1 was recorded. The self-discharge K value = (V0-V1) / 48, with the unit being mV / h.

[0350] 2. Energy density testing

[0351] At 25±2℃, charge the battery cell at a constant current of 0.33C to the cutoff voltage of 3.65V, then charge it at a constant voltage to ≤0.05C, and then discharge it at a constant current of 0.33C to the cutoff voltage of 2.0V. Record the discharge energy E0 and discharge capacity C0. Weigh the battery cell (generally weigh the battery cell with the casing) M0. The energy density of the battery cell is E0 / M0, and the unit can be Wh / kg.

[0352] 3. Testing for cracks in the positive electrode sheet.

[0353] By using CT scans to photograph individual battery cells, it is possible to observe whether there are cracks in the positive electrode plate.

Claims

1. A battery cell, characterized in that, include: A positive electrode sheet, comprising a positive current collector, a first positive electrode film layer, and a first insulating layer, wherein the positive current collector comprises a positive electrode body portion and a positive electrode tab, the positive electrode tab protruding from the positive electrode body portion along a first direction, the first insulating layer and the first positive electrode film layer being disposed on the same side surface of the positive current collector along the thickness direction, and, along the first direction, the first insulating layer being closer to the positive electrode tab relative to the first positive electrode film layer, the first positive electrode film layer comprising a positive electrode active material, the positive electrode active material comprising a lithium phosphate, the lithium phosphate comprising a lithium phosphate matrix and a carbon coating layer at least covering a portion of the surface of the lithium phosphate matrix; The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector along its thickness direction. Along the first direction, the edge of the negative electrode film layer extends beyond the edge of the first positive electrode film layer by a distance greater than or equal to 2 mm. Along the first direction, the first insulating layer and the first positive electrode film layer have a first overlapping area. In the first overlapping area, along the thickness direction of the positive electrode sheet, the first positive electrode film layer is disposed between the positive current collector and the first insulating layer. The positive electrode sheet further includes a second positive electrode film layer. The first and second positive electrode film layers are respectively disposed on both sides of the positive electrode body along the thickness direction. The first and second positive electrode film layers include a positive electrode active material, which includes lithium phosphate. The compaction density of the positive electrode sheet is 2.2 g / cm³. 3 Up to 2.7 g / cm 3 ; Along the direction from the first positive electrode film layer to the positive electrode tab, the edge of the second positive electrode film layer near the positive electrode tab extends beyond the edge of the first positive electrode film layer near the positive electrode tab.

2. The battery cell according to claim 1, characterized in that, Along the first direction, the length of the first overlapping region is 0.2 mm to 1 mm.

3. The battery cell according to claim 2, characterized in that, Along the first direction, the length of the first overlapping region is 0.2 mm to 0.6 mm.

4. The battery cell according to claim 1, characterized in that, Along the direction from the first positive electrode film layer to the positive electrode tab, the thickness of the first insulating layer in the first overlapping region tends to increase.

5. The battery cell according to claim 1, characterized in that, The maximum thickness of the first insulating layer is 20 μm to 80 μm.

6. The battery cell according to claim 1, characterized in that, The thickness of the positive current collector is 13 μm to 16 μm.

7. The battery cell according to claim 1, characterized in that, The maximum thickness of the first positive electrode film is 85 μm to 135 μm.

8. The battery cell according to claim 1, characterized in that, Along the first direction, the length of the first insulating layer is 1 mm to 3 mm.

9. The battery cell according to claim 1, characterized in that, The first positive electrode film layer is provided with a positive electrode main body region and a positive electrode transition region. Along the first direction, the positive electrode transition region is provided at at least one end of the positive electrode main body region, and the thickness of the positive electrode transition region is less than the thickness of the positive electrode main body region.

10. The battery cell according to claim 9, characterized in that, Along the first direction, the projection of the positive transition region near the positive electrode tab onto the positive current collector overlaps the projection of the first overlapping region onto the positive current collector.

11. The battery cell according to claim 1, characterized in that, Along the first direction, the length of the first gap space is 0.05 mm to 0.5 mm, and the first gap space is the space between the edge of the second positive electrode film layer near the positive electrode tab and the edge of the first positive electrode film layer near the positive electrode tab.

12. The battery cell according to claim 11, characterized in that, Along the first direction, the length of the first interval space is 0.05 mm to 0.2 mm.

13. The battery cell according to claim 1, characterized in that, The positive electrode sheet includes a second insulating layer. The second insulating layer and the first positive electrode film layer are disposed on the same side surface of the positive electrode current collector along the thickness direction. Along the first direction, the first insulating layer and the second insulating layer are located at both ends of the first positive electrode film layer, and the second insulating layer and the first positive electrode film layer have a first gap.

14. The battery cell according to claim 1, characterized in that, The positive electrode sheet includes a third insulating layer, and the third insulating layer and the second positive electrode film layer are disposed on the same side surface of the positive current collector along the thickness direction. Along the first direction, the third insulating layer and the second positive electrode film layer have a second gap. The projection of the first insulating layer onto the positive current collector overlaps the projection of the third insulating layer onto the positive current collector.

15. The battery cell according to claim 14, characterized in that, The positive electrode sheet includes a fourth insulating layer, the fourth insulating layer and the second positive electrode film layer are disposed on the same side surface of the positive electrode current collector along the thickness direction, and along the first direction, the fourth insulating layer and the third insulating layer are located at both ends of the second positive electrode film layer; Along the first direction, the distance by which the edge of the negative electrode film extends beyond the edge of the second positive electrode film is greater than or equal to 2 mm; The fourth insulating layer and the second positive electrode film have a second overlapping region. Within the second overlapping region, along the thickness direction of the positive electrode sheet, the second positive electrode film is disposed between the positive current collector and the fourth insulating layer.

16. The battery cell according to claim 1, characterized in that, The first insulating layer comprises inorganic particles and a binder. The inorganic particles include at least one of alumina, boehmite, and magnesium oxide. The binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and vinylidene fluoride-trifluorochloroethylene copolymer.

17. The battery cell according to claim 1, characterized in that, The compaction density of the positive electrode sheet is 2.45 g / cm³. 3 Up to 2.6 g / cm 3 .

18. The battery cell according to claim 1, characterized in that, The density of the positive electrode sheet on one side is 0.33 g / 1540.25 mm. 2 Up to 0.45g / 1540.25mm 2 .

19. The battery cell according to claim 1, characterized in that, The projection of the negative electrode film layer onto the positive electrode current collector covers at least a portion of the projection of the first insulating layer onto the positive electrode current collector.

20. The battery cell according to claim 1, characterized in that, The negative electrode film layer includes a negative electrode main region and a negative electrode transition region. Along the first direction, the negative electrode transition region is disposed at at least one end of the negative electrode main region, and the thickness of the negative electrode transition region is less than the thickness of the negative electrode main region.

21. The battery cell according to claim 1, characterized in that, The density of the negative electrode sheet on one side is 0.15 g / 1540.25 mm. 2 Up to 0.22g / 1540.25mm 2 .

22. The battery cell according to claim 1, characterized in that, The compaction density of the negative electrode sheet is 1.3 g / cm³. 3 Up to 1.52 g / cm 3 .

23. The battery cell according to claim 22, characterized in that, The compaction density of the negative electrode sheet is 1.35 g / cm³. 3 Up to 1.5g / cm 3 .

24. The battery cell according to claim 1, characterized in that, The battery cell includes an electrode assembly and a packaging bag. The electrode assembly includes a positive electrode and a negative electrode, and the electrode assembly is housed in the packaging bag. The packaging bag includes two packaging films, the electrode assembly is located between the two packaging films, and the edges of the two packaging films are connected to each other to form a sealing portion; The battery cell also includes electrode leads that pass between the two packaging films and are electrically connected to the electrode assembly.

25. The battery cell according to claim 24, characterized in that, The packaging film includes an insulating protective layer, a metal layer, and an insulating connecting layer. The insulating connecting layer is disposed on the surface of the metal layer facing the electrode assembly, and the insulating protective layer is disposed on the surface of the metal layer away from the electrode assembly.

26. The battery cell according to claim 1, characterized in that, The battery cell is a cylindrical battery cell.

27. The battery cell according to claim 26, characterized in that, The diameter of the cylindrical battery cell is greater than or equal to 40 mm.

28. The battery cell according to claim 1, characterized in that, Along the first direction, the distance by which the edge of the negative electrode film extends beyond the edge of the first positive electrode film is greater than or equal to 2 mm and less than or equal to 7 mm.

29. The battery cell according to claim 1, characterized in that, The average longest diameter of the primary particles containing lithium phosphate is between 300 nm and 800 nm.

30. The battery cell according to claim 1, characterized in that, The lithium-containing phosphate matrix includes lithium iron phosphate, which is doped with at least one of Al, V, and Ti.

31. The battery cell according to claim 1, characterized in that, The negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite, and at least a portion of the surface of the graphite has a coating layer, the coating layer including amorphous carbon.

32. The battery cell according to claim 31, characterized in that, The thickness of the coating layer is 100 nm to 500 nm.

33. The battery cell according to claim 31, characterized in that, The graphite comprises secondary particles.

34. The battery cell according to claim 31, characterized in that, The graphite has a graphitization degree of 90% to 94%.

35. The battery cell according to claim 31, characterized in that, The volume average particle size Dv50 of the graphite is 15 μm to 25 μm.

36. The battery cell according to claim 35, characterized in that, The volume average particle size Dv50 of the graphite is 16 μm to 20 μm.

37. The battery cell according to claim 1, characterized in that, The battery cell includes an electrolyte with an ionic conductivity of 9.5 ms / cm to 20 ms / cm.

38. The battery cell according to claim 37, characterized in that, The electrolyte has an ionic conductivity of 12 ms / cm to 16 ms / cm.

39. The battery cell according to claim 37, characterized in that, The electrolyte includes a solvent, which includes at least one of linear carbonates and linear carboxylic acid esters.

40. The battery cell according to claim 39, characterized in that, The linear carbonate includes dimethyl carbonate, and the linear carboxylic acid ester includes at least one of ethyl acetate and methyl acetate.

41. The battery cell according to claim 39, characterized in that, Based on the total mass of the electrolyte, the sum of the mass contents of the linear carbonate and the linear carboxylic acid ester is 10% to 60%.

42. The battery cell according to claim 41, characterized in that, Based on the total mass of the electrolyte, the sum of the mass contents of the linear carbonate and the linear carboxylic acid ester is 15% to 35%.

43. The battery cell according to claim 1, characterized in that, The battery cell also includes an electrolyte, which includes additives, including at least one of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sulpholactone.

44. The battery cell according to claim 43, characterized in that, Based on the total mass of the electrolyte, the mass content of the additive is less than or equal to 5%.

45. The battery cell according to claim 44, characterized in that, The additive has a mass content of 0.5% to 3% based on the total mass of the electrolyte.

46. ​​A battery device, characterized in that, include: Multiple battery cells according to any one of claims 1-45.

47. The battery device according to claim 46, characterized in that, The battery device includes: Box; A plurality of battery cells are housed in the housing and stacked along a third direction. The rated capacity of each battery cell is greater than or equal to 100Ah. The surface of each battery cell includes a first surface and a second surface. The area of ​​the first surface is greater than the area of ​​the second surface. The first surfaces of the plurality of battery cells are arranged opposite to each other along the third direction. A thermal management component for regulating the temperature of a plurality of battery cells, the thermal management component being disposed opposite to the second surface of the plurality of battery cells along a fourth direction, the fourth direction being perpendicular to the third direction.

48. The battery device according to claim 47, characterized in that, The battery device further includes a fixing adhesive disposed between the thermal management component and the battery cell, the fixing adhesive being used to fix the battery cell to the thermal management component.

49. The battery device according to claim 48, characterized in that, The battery cell includes a packaging bag and an electrode assembly, the electrode assembly being housed within the packaging bag, and the adhesive being directly attached to the packaging bag.

50. The battery device according to claim 48, characterized in that, The battery device further includes a housing containing at least one of the battery cells, and the adhesive is directly attached to the wall of the housing.

51. An electrical appliance, characterized in that, include: A plurality of battery cells according to any one of claims 1-45, or a battery device according to any one of claims 46-50, wherein the battery cells or battery devices are used to store or provide electrical energy.

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