Battery cell, battery device, electric device

Abstract

The battery monomer comprises a positive electrode sheet, a negative electrode sheet and a separator film, the positive electrode sheet comprises a positive electrode film layer, the positive electrode film layer comprises a lithium transition metal oxide, the lithium transition metal oxide comprises an element Ni, the mole percentage of the element Ni in the transition metal elements of the lithium transition metal oxide is above 80%, and the porosity of the positive electrode film layer is 13%-20%, the compaction density of the positive electrode film layer is 3.4 g / cm 3 -3.7 g / cm 3 ; the negative electrode sheet comprises a negative electrode film layer, the negative electrode film layer comprises a silicon-based material and a carbon-based material, the mass percentage of Si elements in the negative electrode film layer is 1%-10%, and the porosity of the negative electrode film layer is 25%-35%, the compaction density of the negative electrode film layer is 1.55 g / cm 3 -1.8 g / cm 3 . The battery monomer has high energy density and good low-temperature power performance.

Description

[0001] This application claims priority to patent application PCT / CN2025 / 107987, filed on July 10, 2025, entitled “Battery Cell, Battery Device, Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to a battery cell, a battery device, and an electrical device. Background Technology

[0003] In recent years, with the widespread application of lithium-ion battery cells, the energy density of existing lithium-ion battery cells using graphite as the negative electrode active material can no longer meet the growing technological demands. Furthermore, graphite is prone to lithium plating at low temperatures, which also affects the use of lithium-ion battery cells. Summary of the Invention

[0004] This disclosure provides a battery cell, a battery device, and an electrical device, wherein the battery cell has both high energy density and good low-temperature power performance.

[0005] In a first aspect, this disclosure provides a battery cell, including a casing and an electrode assembly. The electrode assembly is located within the casing and includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive active material, which includes a lithium transition metal oxide (LiMeO). The LiMeO includes Ni, and the molar percentage of Ni in the transition metal elements of the LiMeO is more than 80%. The porosity of the positive electrode film layer is 13%-20%, and the compaction density of the positive electrode film layer is 3.4 g / cm³. 3 -3.7g / cm 3 The negative electrode includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes silicon-based materials and carbon-based materials. The silicon-based materials include one or more of elemental silicon, silicon-carbon materials, silicon oxides, silicon nitrides, and silicon alloys. The carbon-based materials include one or more of natural graphite, artificial graphite, soft carbon, hard carbon, and mesophase carbon microspheres. The mass percentage of Si element in the negative electrode film layer is 1%-10%, and the porosity of the negative electrode film layer is 25%-35%. The compaction density of the negative electrode film layer is 1.55 g / cm³. 3 -1.8g / cm 3 .

[0006] This disclosure enables a single battery cell to possess both high energy density and good low-temperature power performance by adjusting the types of positive and negative electrode active materials, the compaction density of the positive and negative electrode films, and the porosity.

[0007] In some embodiments, the porosity of the positive electrode film is 15%-18%.

[0008] In some embodiments, the compaction density of the positive electrode film is 3.5 g / cm³. 3 -3.65g / cm 3 .

[0009] In some embodiments, the mass percentage of Si element in the negative electrode film layer is 3%-8%.

[0010] In some embodiments, the porosity of the negative electrode film is 28%-32%.

[0011] In some embodiments, the compaction density of the negative electrode film is 1.65 g / cm³. 3 -1.75g / cm 3 .

[0012] In some embodiments, the thickness of the positive electrode film is 30 μm-80 μm.

[0013] In some embodiments, the thickness of the negative electrode film is 35 μm-90 μm.

[0014] In some embodiments, the volumetric particle size Dv50 of the positive electrode active material is 1 μm-7 μm. A small volumetric particle size Dv50 of the positive electrode active material results in a short solid-phase diffusion path for lithium ions, which facilitates rapid insertion and extraction of lithium ions, helps reduce positive electrode polarization, and helps improve the low-temperature power performance of the battery cell.

[0015] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the positive electrode active material is 1-1.5. This can improve the processing of the positive electrode slurry, increase the compaction density of the positive electrode film, and improve the energy density of the battery cell.

[0016] In some embodiments, the volume distribution particle size Dv50 of the negative electrode active material is 10 μm-20 μm.

[0017] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the negative electrode active material is 1.2-2.5.

[0018] In some embodiments, the lithium transition metal oxide includes a single-crystal lithium transition metal oxide, and the total area of ​​the single-crystal lithium transition metal oxide is 60%-100% of the total area of ​​the positive electrode active material.

[0019] In some embodiments, the lithium transition metal oxide includes Ni and Co elements, and the Co content in the surface region of the lithium transition metal oxide is higher than the Co content in the core region of the lithium transition metal oxide; or, the lithium transition metal oxide includes Ni and Mn elements, and the Mn content in the surface region of the lithium transition metal oxide is lower than the Mn content in the core region of the lithium transition metal oxide; or, the lithium transition metal oxide includes Ni, Co, and Mn elements, and the Co content in the surface region of the lithium transition metal oxide is higher than the Co content in the core region of the lithium transition metal oxide, and the Mn content in the surface region of the lithium transition metal oxide is lower than the Mn content in the core region of the lithium transition metal oxide. The surface region of the lithium transition metal oxide is a region extending radially inward 100 nm from the outermost surface of the particle, and the core region of the lithium transition metal oxide is a region extending radially outward 300 nm from the center of the particle.

[0020] The resulting lithium transition metal oxide exhibits high surface stability and better resistance to overcharging and over-discharging. It can reduce side reactions with the electrolyte and decrease the dissolution of transition metal ions, thereby improving the cycle performance of the battery cell. Furthermore, it can enhance the thermal stability of the lithium transition metal oxide and reduce the risk of thermal runaway in the battery cell.

[0021] In some embodiments, the lithium transition metal oxide includes Ni and doping elements, the doping elements including cation doping elements and / or anion doping elements, the cation doping elements including one or more of Al, Y, Zr, Zn, Cr, Mg, V, Ti and B, and the anion doping elements including one or more of N, F, S and Cl.

[0022] The aforementioned doping elements can enhance the structural stability of lithium transition metal oxides, improve their ability to withstand overcharge and over-discharge, reduce the volume change of lithium transition metal oxides during charge and discharge, reduce the dissolution of transition metal ions, and improve the chemical stability and cycle stability of battery cells; they can also enhance the thermal stability of lithium transition metal oxides and reduce the risk of thermal runaway of battery cells.

[0023] In some embodiments, the positive electrode film layer includes a positive electrode conductive agent, and the mass percentage of the positive electrode conductive agent in the positive electrode film layer is 0.5%-2.5%.

[0024] In some embodiments, the positive electrode conductive agent includes one or more of carbon nanotubes, carbon black, acetylene black, carbon fiber, and graphene, and the carbon nanotubes include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0025] In some embodiments, the positive electrode conductive agent includes carbon nanotubes, and at least a portion of the carbon nanotubes are located on the surface of the positive electrode active material.

[0026] In some embodiments, the positive electrode conductive agent includes an agglomerated positive electrode conductive agent, wherein the number density of the agglomerated positive electrode conductive agent in the positive electrode film layer is 1 to 5 atoms / 1000 μm. 2 It can be selected as 1 to 3 per 1000μm 2 This not only helps to improve the electronic conductivity of the positive electrode and reduce the electron transport resistance and polarization of the positive electrode, but also helps to improve the electrolyte wettability of the positive electrode film, thereby helping to further improve the low-temperature power performance of the battery cell.

[0027] In some embodiments, the agglomerated positive conductive agent satisfies that the maximum distance between any two points on the perimeter is greater than or equal to 2 μm.

[0028] In some embodiments, the porosity of the agglomerated positive conductive agent is 30%-65%.

[0029] In some embodiments, the agglomerated positive electrode conductive agent includes carbon nanotubes. Optionally, the agglomerated positive electrode conductive agent also includes one or more of carbon black and acetylene black.

[0030] In some embodiments, the average particle size of the silicon-based material is 2 μm-15 μm.

[0031] In some embodiments, the average particle size of the carbon-based material is 11 μm-21 μm.

[0032] In some embodiments, the negative electrode film layer includes a first negative electrode film layer away from the negative electrode current collector and a second negative electrode film layer close to the negative electrode current collector. The first negative electrode film layer includes a first negative electrode active material, and the second negative electrode film layer includes a second negative electrode active material. The first negative electrode active material includes a first carbon-based material and a first silicon-based material. The second negative electrode active material includes a second carbon-based material, and the second negative electrode film layer does not contain Si element, or the second negative electrode active material includes a second carbon-based material and a second silicon-based material, and the mass percentage of Si element in the first negative electrode film layer is greater than the mass percentage of Si element in the second negative electrode film layer.

[0033] The first negative electrode film is located in the surface region, and the second negative electrode film is located in the bottom region. By making the mass ratio of Si element in the surface region high, it helps to reduce the problem of lithium deposition at low temperature of the negative electrode. By making the bottom region free of Si element or making the mass ratio of Si element in the bottom region low, it helps to reduce the damage to the overall conductive network of the negative electrode film due to the volume expansion of silicon-based materials in the bottom region, thereby helping to improve the low temperature power performance of the battery cell.

[0034] In some embodiments, the mass percentage of Si element in the first negative electrode film layer is 2%-15%, and can be selected as 2%-10%.

[0035] In some embodiments, the mass percentage of Si element in the second negative electrode film layer is 0%-10%, and can be selected as 0%-8%.

[0036] In some embodiments, the volumetric particle size Dv50 of the first negative electrode active material is smaller than that of the second negative electrode active material. The first negative electrode active material is located in the surface region, and the second negative electrode active material is located in the bottom region. By making the volumetric particle size Dv50 of the first negative electrode active material smaller than that of the second negative electrode active material, the lithium-ion diffusion path of the first negative electrode active material in the surface region is shorter, the diffusion time of lithium ions from the surface to the interior is shorter, and lithium ions are more easily and quickly inserted and extracted. This can improve the overall ion transport kinetics of the negative electrode film, reduce negative electrode polarization, and improve the low-temperature power performance of the battery cell.

[0037] In some embodiments, the first carbon-based material includes one or more of natural graphite and artificial graphite.

[0038] Optionally, the first carbon-based material includes artificial graphite, and the surface of the artificial graphite has a carbon coating layer, which includes soft carbon and / or hard carbon. The carbon coating layer can improve the migration energy barrier of lithium ions at the interface, which is beneficial to improving the lithium ion diffusion capability and enhancing the low-temperature power performance of the battery cell.

[0039] In some embodiments, the second carbon-based material includes one or more of natural graphite and artificial graphite.

[0040] In some embodiments, the average particle size of the first carbon-based material is 11 μm-21 μm.

[0041] In some embodiments, the average particle size of the second carbon-based material is 11 μm-21 μm.

[0042] In some embodiments, the first silicon-based material includes one or more of silicon-carbon materials and pre-magnesium silicon oxide.

[0043] In some embodiments, the second negative electrode active material includes a second silicon-based material, which includes one or more of silicon-carbon materials and pre-magnesium silicon oxide.

[0044] In some embodiments, the average particle size of the first silicon-based material is 2 μm-15 μm.

[0045] In some embodiments, the second negative electrode active material includes a second silicon-based material, the average particle size of which is 2 μm-15 μm.

[0046] In some embodiments, the battery cell further includes an electrolyte, which comprises an organic solvent and an electrolyte salt, wherein the concentration of the electrolyte salt is 0.9 mol / L to 1.2 mol / L.

[0047] In some embodiments, the organic solvent includes ethylene carbonate and ethyl methyl carbonate, wherein the mass percentage of ethyl methyl carbonate in the organic solvent is greater than or equal to 55% and less than 100%.

[0048] In some embodiments, the organic solvent further includes one or more of the following: propylene carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0049] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0050] In some embodiments, the electrolyte further includes additives, including one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate.

[0051] In some embodiments, the separator includes a porous base membrane and a porous coating located on at least one side of the porous base membrane. The porous coating includes filler particles, which include one or more of inorganic particles, organic particles, and organic-inorganic composite particles.

[0052] In some embodiments, the porous coating further includes polymer binder particles, wherein the volume distribution particle size Dv50 of the polymer binder particles is greater than the volume distribution particle size Dv50 of the filler particles.

[0053] In some embodiments, the thickness of the porous coating is 0.5 μm-2 μm.

[0054] In some embodiments, the thickness of the porous base film is 5 μm-10 μm.

[0055] In some embodiments, the porosity of the separator is 35%-55%.

[0056] In some embodiments, the battery cell is a pouch cell, and the casing includes two packaging films, an 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 seal; the pouch cell also includes electrode leads that pass through the two packaging films and are electrically connected to the electrode assembly.

[0057] In some embodiments, the packaging film includes an insulating protective layer, a metal layer, and an insulating connecting layer, wherein 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.

[0058] In some embodiments, the battery cell is a hard-shell battery cell with a square-shaped casing made of metal.

[0059] In a second aspect, this disclosure provides a battery device comprising a plurality of battery cells according to the first aspect of this disclosure.

[0060] In some embodiments, the battery device includes: The enclosure includes a support plate and a frame surrounding the outer periphery of the support plate, with the support plate and the frame fixedly connected. Multiple battery cells, which are soft-pack battery cells, are stacked in a first direction and housed in a box. The surface of each battery cell includes a first surface and a second surface. The area of ​​the first surface is larger than the area of ​​the second surface. The first surfaces of the multiple battery cells are arranged opposite each other in the first direction, and the support plate and the second surfaces of the multiple battery cells are arranged opposite each other in the second direction. The housing is provided with at least one connecting beam extending along a third direction. The connecting beam is fixedly connected to the support plate and / or the frame. At least one battery cell abuts against the connecting beam along a first direction. The first direction, the second direction, and the third direction are perpendicular to each other.

[0061] In some embodiments, the battery device further includes thermal management components and a fixing adhesive.

[0062] The thermal management component is located between the support plate and the battery cell to regulate the temperature of the battery cell; the fixing adhesive is located between the thermal management component and the battery cell to fix the battery cell to the thermal management component.

[0063] In some embodiments, the adhesive is directly attached to the casing of the battery cell.

[0064] In some embodiments, the battery device further includes a housing containing at least one battery cell, with adhesive directly attached to the wall of the housing.

[0065] In some embodiments, the rated capacity of each battery cell is greater than or equal to 100 Ah.

[0066] Thirdly, this disclosure provides an electrical device that includes a battery cell according to the first aspect of this disclosure or a battery device according to the second aspect of this disclosure. Attached Figure Description

[0067] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the drawings without any creative effort.

[0068] Figure 1 A schematic diagram of a battery device provided in one embodiment is shown.

[0069] Figure 2 An exploded view of a battery device provided in one embodiment is shown.

[0070] Figure 3 Show Figure 2 A partial enlarged view of the battery device shown.

[0071] Figure 4 A schematic diagram of an electrical device provided in some embodiments of this disclosure is shown.

[0072] Figure 5 An exploded view of a single pouch cell provided in one embodiment is shown. Detailed Implementation

[0073] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this disclosure. However, unnecessary detailed descriptions 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 disclosure and are not intended to limit the subject matter of the claims.

[0074] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the 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 expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​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 disclosure, 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.

[0075] Unless otherwise specified, all embodiments and optional embodiments of this disclosure may be combined with each other to form new technical solutions, and such technical solutions should be considered as included in the disclosure of this disclosure.

[0076] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions, and such technical solutions should be considered as included in the disclosure of this disclosure.

[0077] Unless otherwise specified, all steps in this disclosure 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 mention that the method may also include step (c) indicates 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.

[0078] Unless otherwise specified, in this disclosure, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0079] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0080] In the description of the embodiments of this disclosure, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0081] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0082] The individual battery cells mentioned in the embodiments of this disclosure are capable of charging and discharging independently.

[0083] The battery cells mentioned in the embodiments of this disclosure may be pouch cells or hard-shell cells.

[0084] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0085] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0086] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0087] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0088] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0089] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0090] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0091] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0092] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0093] Figure 1 A schematic diagram of a battery device 100 provided in one embodiment is shown. Figure 2 An exploded view of a battery device 100 provided in one embodiment is shown. Figure 3 Show Figure 2 A partial enlarged view of the battery device 100 shown.

[0094] like Figures 1 to 3 As shown, the battery device 100 includes a housing 10 and a plurality of battery cells 22. The housing 10 includes a first housing 11 and a second housing 12, which are fastened together to form a closed space inside the housing 10 to accommodate the battery cells 22.

[0095] like Figure 2 As shown, the first box 11 is the top cover, and the second box 12 includes a support plate 121 and a frame 122 arranged around the outer periphery of the support plate 121. The support plate 121 and the frame 122 are fixedly connected.

[0096] The battery cell 22 is a pouch battery cell. Multiple battery cells 22 are stacked in the first direction X and housed in the housing 10. The surface of the battery cell 22 includes a first surface and a second surface. The area of ​​the first surface is larger than the area of ​​the second surface. The first surfaces of the multiple battery cells 22 are arranged opposite to each other in the first direction X. The support plate 121 is arranged opposite to the second surfaces of the multiple battery cells 22 in the second direction Z.

[0097] Optionally, the rated capacity of each battery cell 22 is greater than or equal to 100Ah.

[0098] like Figure 1 As shown, at least one connecting beam 13 extending along the third direction Y is provided inside the housing 10. The connecting beam 13 is fixedly connected to the support plate 121 and / or the frame 122. At least one battery cell 22 abuts against the connecting beam 13 along the first direction X.

[0099] The first direction X, the second direction Z, and the third direction Y are all perpendicular to each other.

[0100] In some embodiments, the battery device 100 further includes a thermal management component 30 disposed between the support plate 121 and the battery cell 22 for regulating the temperature of the battery cell 22. The thermal management component 30 is disposed opposite to the second surfaces of the plurality of battery cells 22 along a second direction Z.

[0101] In some embodiments, the battery device 100 further includes a housing 23 that houses at least one battery cell 22. The housing 23 and the battery cell 22 therein together constitute a battery cell assembly 20.

[0102] In some embodiments, the battery device 100 further includes a fixing adhesive 40 disposed between the thermal management component 30 and the battery cell 22 for fixing the battery cell 22 to the thermal management component 30.

[0103] As an example, the adhesive 40 can be directly attached to the casing of the battery cell 22.

[0104] As an example, the adhesive 40 can be directly attached to the shell wall that houses the housing 23.

[0105] The technical solutions described in this disclosure are applicable to various electrical devices that use battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Battery cells and battery devices are used to store or provide electrical energy.

[0106] Figure 4 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0107] Electrolytes play a crucial role in ion transport within battery cells. At low temperatures, electrolyte viscosity increases, leading to increased resistance to ion migration and concentration polarization. This polarization causes a rapid drop in battery cell voltage, reducing usable capacity and impacting low-temperature power performance. Furthermore, increased electrolyte viscosity at low temperatures reduces the wettability of the positive and negative electrodes and the separator, potentially preventing some electrode active materials from participating in electrochemical reactions, thus also degrading low-temperature power performance. Additionally, the lithium intercalation potential of graphite-based carbon materials is approximately 0.1V (vs. Li / Li). +Its deposition potential with lithium (0V vs. Li / Li) + The lithium content is close to that of graphite-based carbon materials, and when charging at low temperatures, lithium tends to precipitate on the surface of these materials, which can lead to a decrease in the low-temperature power performance of individual battery cells.

[0108] In view of this, embodiments of the present disclosure provide a battery cell, as well as a battery device and an electrical device including the battery cell. By adjusting the positive and negative electrodes of the battery cell, the battery cell can have both high energy density and good low-temperature power performance.

[0109] The battery cells provided in the embodiments of this disclosure can be lithium-ion battery cells.

[0110] The battery cell provided in the embodiments of this disclosure includes a casing and an electrode assembly. The electrode assembly is located inside the casing and includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive active material, which includes a lithium transition metal oxide (LiMeO). The LiMeO includes Ni, and the molar percentage of Ni in the transition metal elements of the LiMeO is more than 80%. The porosity of the positive electrode film layer is 13%-20%, and the compaction density of the positive electrode film layer is 3.4 g / cm³. 3 -3.7g / cm 3 The negative electrode includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which may be a silicon-based material or a carbon-based material. The mass percentage of Si element in the negative electrode film layer is 1%-10%, and the porosity of the negative electrode film layer is 25%-35%. The compaction density of the negative electrode film layer is 1.55 g / cm³. 3 -1.8g / cm 3 .

[0111] The positive electrode active material disclosed herein includes a lithium transition metal oxide with a high Ni content. The molar proportion of Ni in the transition metal elements of the lithium transition metal oxide is more than 80%. The high Ni content of the lithium transition metal oxide results in a high theoretical specific capacity, a high voltage plateau, and a fast ion diffusion rate. It can provide more lithium ions at low temperatures, thereby providing higher power output.

[0112] Silicon-based materials are anode active materials that provide at least Si (silicon). They can also provide other elements, such as carbon (carbon), or even just Si. Carbon-based materials are anode active materials that provide at least carbon (carbon). Compared to carbon-based materials, silicon-based materials have a higher theoretical specific capacity and a higher lithium intercalation potential, which reduces lithium deposition at the anode in low-temperature environments. Therefore, by including both silicon-based and carbon-based materials in the anode active materials disclosed herein, it is beneficial to improve the energy density and low-temperature power performance of individual battery cells.

[0113] Compared to carbon-based materials, silicon-based materials suffer from severe volume expansion, leading to significant volume expansion in the negative electrode. This volume expansion disrupts the conductive network of the negative electrode, affecting its electron transport performance and the power performance of the battery cell. This disclosure reduces the mass percentage of Si in the negative electrode film to 1%-10%. Within this range, lithium deposition at low temperatures is reduced, while the negative electrode exhibits lower volume expansion and a better conductive network, resulting in improved low-temperature power performance for the battery cell.

[0114] The compaction density of the positive electrode film layer disclosed herein is 3.4 g / cm³. 3 -3.7g / cm 3 The compaction density of the negative electrode film is 1.55 g / cm³. 3 -1.8g / cm 3 The positive and negative electrode films disclosed herein employ relatively low compaction densities. This increases the distance between the electrode active material particles and the pore size, improving the electrolyte wettability of the positive and negative electrode films at low temperatures and reducing the lithium-ion transport resistance at both electrodes. This, in turn, helps improve the low-temperature power performance of the battery cell. However, the compaction density of the positive and negative electrode films cannot be too low, as this would reduce the contact area between the electrode active material particles, lengthen the electron transport path at both electrodes, increase the internal resistance of the battery cell, and consequently decrease the low-temperature power performance of the battery cell.

[0115] The porosity of the positive electrode film in this disclosure is 13%-20%, and the porosity of the negative electrode film is 25%-35%. The high porosity of both the positive and negative electrode films improves electrolyte wettability at low temperatures, reducing lithium-ion transport resistance at the positive and negative electrodes, thereby enhancing the low-temperature power performance of the battery cell. However, the porosity of the positive and negative electrode films cannot be too high, as this would reduce the contact area between the electrode active material particles, lengthen the electron transport path at the positive and negative electrodes, increase the internal resistance of the battery cell, and consequently decrease the low-temperature power performance of the battery cell.

[0116] Therefore, by adjusting the types of positive and negative electrode active materials, the compaction density and porosity of the positive and negative electrode films, this disclosure enables battery cells to possess both high energy density and good low-temperature power performance.

[0117] The mass percentage of Si in the negative electrode film can be measured using an inductively coupled plasma optical emission spectrometer (ICP). The testing standard can be found in JY / T 015 1996.

[0118] The porosity of the electrode film can be tested as follows: After fully disassembling the battery cell, remove the electrode sheets. Immerse the electrode sheets in an organic solvent (e.g., dimethyl carbonate) for a period of time (e.g., 2-10 hours). Then, remove the electrode sheets and dry them at a certain temperature and time (e.g., 60°C for more than 4 hours). After drying, remove the electrode sheets. Take a single-sided coated electrode sheet (if it is a double-sided coated electrode sheet, wipe off the electrode film layer on one side first), and cut it into small circular samples of a certain area. Calculate the apparent volume V1 of the electrode sheet. Referring to GB / T 24586-2009, use an inert gas (such as helium or nitrogen) as the medium and employ the gas displacement method to measure the true volume V2 of the electrode sheet using a true density meter. The porosity of the electrode film = (V1-V2) / V1×100%. Multiple samples (e.g., 30 pieces) with good appearance and no powder shedding at the edges can be tested, and the average value of the results can be taken to improve the accuracy of the test results. The testing instrument can be the Micromeritics AccuPyc II 1340 true density tester.

[0119] The compaction density of the electrode film is equal to the areal density of the electrode film divided by the thickness of the electrode film. The thickness of the electrode film can be measured using a micrometer; multiple measurements (e.g., more than 10) can be taken and the average value calculated. The areal density of the electrode film can be tested as follows: After fully disassembling the battery cell, remove the electrode plates. Immerse the electrode plates in an organic solvent (e.g., dimethyl carbonate) for a period of time (e.g., 2-10 hours). Then remove the electrode plates and dry them at a specific temperature and time (e.g., 60°C for more than 4 hours). After drying, remove the electrode plates. Take a single-sided coated electrode plate (if it is a double-sided coated electrode plate, wipe off the electrode film on one side first), cut it into small circular pieces with an area of ​​S1, weigh them, and record the weight as M1. Then wipe off the electrode film of the weighed electrode plate and weigh the current collector, recording the weight as M0. The areal density of the electrode film is equal to (M1-M0) / S1.

[0120] [Negative electrode plate] The negative electrode includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which may be a silicon-based material or a carbon-based material. The mass percentage of Si element in the negative electrode film layer is 1%-10%, and the porosity of the negative electrode film layer is 25%-35%. The compaction density of the negative electrode film layer is 1.55 g / cm³. 3 -1.8g / cm 3 .

[0121] The negative electrode film disclosed herein can be a single-layer structure or a multi-layer structure. A multi-layer structure refers to a negative electrode film where different sublayers differ in the types and / or contents of components.

[0122] In this disclosure, the mass percentage of Si in the negative electrode film layer refers to the mass percentage of Si in the entire negative electrode film layer.

[0123] The mass percentage of Si element in the negative electrode film layer is 1%-10%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any range of the above values. Optionally, the mass percentage of Si element in the negative electrode film layer is 3%-8%, 3%-7%, 3%-6%, 3.5%-6%, or 4%-6%.

[0124] The porosity of the negative electrode film layer is 25%-35%, for example, it can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or any range of the above values. Optionally, the porosity of the negative electrode film layer is 26%-32% or 28%-32%.

[0125] The compaction density of the negative electrode film is 1.55 g / cm³. 3 -1.8g / cm 3 For example, it can be 1.55 g / cm³. 3 1.6g / cm 3 1.65g / cm 3 1.7g / cm 3 1.75g / cm 3 1.8g / cm 3 Or, a range of any of the above values. Optionally, the compaction density of the negative electrode film is 1.65 g / cm³. 3 -1.75g / cm 3 .

[0126] In some embodiments, the thickness of the negative electrode film is 35μm-90μm, for example, it can be 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, or any range of the above values.

[0127] Optionally, the thickness of the negative electrode film is 50μm-70μm.

[0128] Adjusting parameters such as the volume distribution particle size Dv50 and / or particle size distribution (Dv90-Dv10) / Dv50 of the negative electrode active material, as well as adjusting the negative electrode cold pressing pressure, can regulate the porosity and / or compaction density of the negative electrode film.

[0129] In some embodiments, the volume distribution particle size Dv50 of the negative electrode active material is 10μm-20μm, for example, it can be 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm, 19μm, 19.5μm, 20μm, or any range of the above values.

[0130] Optionally, the volume distribution particle size Dv50 of the negative electrode active material is 11μm-15μm.

[0131] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the negative electrode active material is 1.2-2.5, for example, it can be 1.2, 1.25, 1.3, 1.35, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, or any range of the above values.

[0132] Optionally, the particle size distribution (Dv90-Dv10) / Dv50 of the negative electrode active material is 1.35-2.

[0133] Negative electrode active materials include silicon-based materials and carbon-based materials. Silicon-based materials are negative electrode active materials that provide at least silicon (Si). Silicon-based materials can also provide other elements, such as carbon (C), or they can provide only silicon. Carbon-based materials are negative electrode active materials that provide at least carbon (C).

[0134] In some embodiments, silicon-based materials include one or more of elemental silicon, silicon-carbon materials, silicon oxides, silicon nitrides, and silicon alloy materials.

[0135] Silicon oxides may contain alkali metal elements and / or alkaline earth metal elements, or they may not contain alkali metal elements and alkaline earth metal elements. Optionally, silicon oxides may contain alkali metal elements and / or alkaline earth metal elements, for example, alkali metal elements and / or alkaline earth metal elements may be embedded in silicon oxide as a matrix by chemical or physical methods.

[0136] Silicon-carbon materials may contain alkali metal elements and / or alkaline earth metal elements, or they may not contain alkali metal elements and alkaline earth metal elements. Optionally, silicon-carbon materials may contain alkali metal elements and / or alkaline earth metal elements, for example, by embedding alkali metal elements and / or alkaline earth metal elements into a silicon-carbon material matrix through chemical or physical methods.

[0137] Alternatively, alkali metals may include Li, and alkaline earth metals may include Mg.

[0138] Optionally, the silicon-carbon material may include porous carbon and silicon located in the pores of the porous carbon.

[0139] In some embodiments, the carbon-based material includes one or more of natural graphite, artificial graphite, soft carbon, hard carbon, and mesophase carbon microspheres.

[0140] Optionally, carbon-based materials include one or more of natural graphite and artificial graphite.

[0141] In some embodiments, the average particle size of the silicon-based material is 2μm-15μm, for example, it can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, or any range of the above values.

[0142] Optionally, the average particle size of the silicon-based material is 3μm-10μm, 3μm-8μm, or 3μm-6μm.

[0143] In some embodiments, the average particle size of the carbon-based material is 11 μm-21 μm, for example, it can be 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm, 20.5 μm, 21 μm, or any range of the above values.

[0144] Optionally, the average particle size of the carbon-based material is 12μm-18μm or 12μm-16μm.

[0145] The average particle size of silicon-based materials and carbon-based materials can be tested as follows: Using a scanning electron microscope combined with energy dispersive spectroscopy (EDS), acquire SEM-EDS images of the negative electrode sheet. Randomly select a test sample (e.g., 50mm x 100mm). Randomly select multiple test regions (e.g., 5 regions) within the test sample. At a certain magnification (e.g., 500x or higher), count the quantity and particle size of silicon-based and carbon-based materials in each test region. Take the arithmetic mean of the particle sizes of all silicon-based materials in each test region as the average particle size of the silicon-based material, and take the arithmetic mean of the particle sizes of all carbon-based materials in each test region as the average particle size of the carbon-based material. To ensure the accuracy of the test results, multiple test samples (e.g., 10 samples) can be used for the above test, and the average value of each test sample can be taken as the final test result. It should be noted that when the particles are irregularly shaped, the distance between the two farthest points on the particle is taken as the particle size.

[0146] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0147] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), 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).

[0148] In some embodiments, the negative electrode film layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0149] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0150] In other embodiments, the negative electrode film layer includes a first negative electrode film layer away from the negative electrode current collector and a second negative electrode film layer close to the negative electrode current collector. The first negative electrode film layer includes a first negative electrode active material, and the second negative electrode film layer includes a second negative electrode active material. The first negative electrode active material includes a first carbon-based material and a first silicon-based material. The second negative electrode active material includes a second carbon-based material, and the second negative electrode film layer does not contain Si element; or, the second negative electrode active material includes a second carbon-based material and a second silicon-based material, and the mass percentage of Si element in the first negative electrode film layer is greater than the mass percentage of Si element in the second negative electrode film layer. The mass percentage of Si element in the negative electrode film layer (including the first negative electrode film layer and the second negative electrode film layer) is 1%-10%.

[0151] Compared to carbon-based materials, silicon-based materials have a higher lithium intercalation potential and are less prone to low-temperature lithium plating. The first negative electrode film is located in the surface region, and the second negative electrode film is located in the bottom region. By making the mass proportion of Si element in the surface region, it helps to reduce the problem of low-temperature lithium plating at the negative electrode. By making the bottom region free of Si element or having a low mass proportion of Si element in the bottom region, it helps to reduce the damage to the overall conductive network of the negative electrode film caused by the volume expansion of silicon-based materials in the bottom region, thereby helping to improve the low-temperature power performance of the battery cell.

[0152] Cut the negative electrode sheet along a direction perpendicular to the surface of the negative electrode film, and use a scanning electron microscope to obtain a cross-sectional SEM image of the negative electrode film in the thickness direction, or use a scanning electron microscope combined with an energy dispersive spectroscopy (EDS) to obtain a cross-sectional SEM-EDS image of the negative electrode film in the thickness direction. Since the mass ratio of Si element in the first negative electrode film and the second negative electrode film is different, the first negative electrode film and the second negative electrode film can be easily distinguished from the image.

[0153] In some embodiments, the mass percentage of Si element in the first negative electrode film layer is 2%-15%, for example, it can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 11%, 12%, 13%, 14%, 15%, or any range of the above values.

[0154] Optionally, the mass percentage of Si element in the first negative electrode film layer is 2%-10%, 3%-9%, or 3%-8%.

[0155] In some embodiments, the mass percentage of Si element in the second negative electrode film layer is 0%-10%, for example, it can be 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any range of the above values.

[0156] Optionally, the mass percentage of Si element in the second negative electrode film layer is 0%-8%, 0%-5%, 0.5%-8%, or 0.5%-5%.

[0157] In some embodiments, the mass percentage of Si in the second negative electrode film is 0%. 0% indicates that the second negative electrode film contains no Si.

[0158] In some embodiments, the volume distribution particle size Dv50 of the first negative electrode active material is smaller than the volume distribution particle size Dv50 of the second negative electrode active material.

[0159] The first negative electrode active material is located in the surface region, and the second negative electrode active material is located in the bottom region. By making the volume distribution particle size Dv50 of the first negative electrode active material smaller than that of the second negative electrode active material, the lithium ion diffusion path of the first negative electrode active material in the surface region is shorter, the diffusion time of lithium ions from the surface to the interior is shorter, and lithium ions are more likely to be inserted and extracted quickly. This can improve the overall ion transport dynamics of the negative electrode film, reduce negative electrode polarization, and improve the low-temperature power performance of the battery cell.

[0160] The first carbon-based material is a negative electrode active material that provides at least carbon. In some embodiments, the first carbon-based material includes one or more of natural graphite, artificial graphite, soft carbon, hard carbon, and mesophase carbon microspheres.

[0161] Optionally, the first carbon-based material includes one or more of natural graphite and artificial graphite.

[0162] Optionally, the first carbon-based material includes artificial graphite.

[0163] Artificial graphite has a dense structure and a more stable surface. Therefore, placing artificial graphite in the first negative electrode film layer helps to better reduce electrolyte side reactions and reduce irreversible consumption of electrolyte and active lithium, thereby further improving the first coulombic efficiency, low-temperature cycle performance and low-temperature power performance of the battery cell.

[0164] Optionally, the first carbon-based material includes artificial graphite, and the surface of the artificial graphite has a carbon coating layer, which includes soft carbon and / or hard carbon.

[0165] Carbon coating can improve the energy barrier for lithium ion migration at the interface, which is beneficial to improving lithium ion diffusion ability and enhancing the low-temperature power performance of battery cells.

[0166] In some embodiments, the average particle size of the first carbon-based material is 11 μm-21 μm, for example, it can be 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm, 20.5 μm, 21 μm, or any range of the above values.

[0167] Optionally, the average particle size of the first carbon-based material is 12μm-18μm or 12μm-16μm.

[0168] The second carbon-based material is a negative electrode active material that provides at least carbon. In some embodiments, the second carbon-based material includes one or more of natural graphite, artificial graphite, soft carbon, hard carbon, and mesophase carbon microspheres.

[0169] Optionally, the second carbon-based material includes one or more of natural graphite and artificial graphite.

[0170] Optionally, the second carbon-based material includes natural graphite.

[0171] Natural graphite typically has a certain amount of porosity, which makes it more ductile and pressure resistant. Therefore, placing natural graphite in the second negative electrode film layer helps to improve the compaction density of the negative electrode film layer and the volumetric energy density of the battery cell.

[0172] In some embodiments, the average particle size of the second carbon-based material is 11 μm-21 μm, for example, it can be 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, 20 μm, 20.5 μm, 21 μm, or any range of the above values.

[0173] Optionally, the average particle size of the second carbon-based material is 12μm-18μm or 12μm-16μm.

[0174] The first silicon-based material is a negative electrode active material that provides at least Si. The first silicon-based material may also provide other elements, such as C, or of course, only Si. In some embodiments, the first silicon-based material includes one or more of elemental silicon, silicon-carbon materials, silicon oxides, silicon nitrides, and silicon alloys.

[0175] The second silicon-based material is a negative electrode active material that provides at least Si. The second silicon-based material may also provide other elements, such as C, or of course, only Si. In some embodiments, the second negative electrode active material includes a second silicon-based material, which includes one or more of elemental silicon, silicon-carbon materials, silicon oxides, silicon nitrides, and silicon alloys.

[0176] Silicon oxides may contain alkali metal elements and / or alkaline earth metal elements, or they may not contain alkali metal elements and alkaline earth metal elements. Optionally, silicon oxides may contain alkali metal elements and / or alkaline earth metal elements, for example, alkali metal elements and / or alkaline earth metal elements may be embedded in silicon oxide as a matrix by chemical or physical methods.

[0177] Silicon-carbon materials may contain alkali metal elements and / or alkaline earth metal elements, or they may not contain alkali metal elements and alkaline earth metal elements. Optionally, silicon-carbon materials may contain alkali metal elements and / or alkaline earth metal elements, for example, by embedding alkali metal elements and / or alkaline earth metal elements into a silicon-carbon material matrix through chemical or physical methods.

[0178] Alternatively, alkali metals may include Li, and alkaline earth metals may include Mg.

[0179] Optionally, the first silicon-based material includes one or more of silicon-carbon materials and pre-magnesium silicon oxide.

[0180] Optionally, the second negative electrode active material includes a second silicon-based material, which includes one or more of silicon-carbon materials and pre-magnesium silicon oxide.

[0181] Optionally, the silicon-carbon material may include porous carbon and silicon located in the pores of the porous carbon.

[0182] Pre-magnesium silicate is a material obtained by embedding magnesium elements into a silicon oxide matrix through chemical or physical methods.

[0183] Silicon-carbon materials and pre-magnesium silicon-oxygen compounds have high specific capacity, which helps to improve the energy density of battery cells. Compared with elemental silicon (pure silicon), silicon-carbon materials and pre-magnesium silicon-oxygen compounds have small volume expansion and high structural stability during charge and discharge processes. This allows for the formation of a stable SEI film on the negative electrode, thereby reducing the irreversible consumption of electrolyte and active lithium, which in turn helps to improve the first coulombic efficiency and cycle performance of battery cells. Silicon-carbon materials and pre-magnesium silicon-oxygen compounds also have good thermal stability, which helps to reduce the risk of thermal runaway of battery cells.

[0184] In some embodiments, the average particle size of the first silicon-based material is 2μm-15μm, for example, it can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, or any range of the above values.

[0185] Optionally, the average particle size of the first silicon-based material is 3μm-10μm, 3μm-8μm, or 3μm-6μm.

[0186] In some embodiments, the second negative electrode active material includes a second silicon-based material, the average particle size of which is 2μm-15μm, for example, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, or any range of the above values.

[0187] Optionally, the average particle size of the second silicon-based material is 3μm-10μm, 3μm-8μm, or 3μm-6μm.

[0188] The average particle size of the first silicon-based material and the first carbon-based material can be tested as follows: Using a scanning electron microscope combined with an energy dispersive spectroscopy (EDS) instrument, obtain a surface SEM-EDS image of the first negative electrode film layer far from the negative electrode current collector. Randomly select a test sample (e.g., 50mm x 100mm). Randomly select multiple test areas (e.g., 5) in the test sample. At a certain magnification (e.g., 500 times or more), count the quantity and particle size of the first silicon-based material and the second carbon-based material in each test area. Take the arithmetic mean of the particle size of all the first silicon-based materials in each test area as the average particle size of the first silicon-based material. Take the arithmetic mean of the particle size of all the first carbon-based materials in each test area as the average particle size of the second carbon-based material. The average particle size of the second silicon-based material and the second carbon-based material can be tested as follows: Using a scanning electron microscope combined with energy dispersive spectroscopy (EDS), acquire a surface SEM-EDS image of the second negative electrode film layer near the negative electrode current collector. Randomly select a test sample (e.g., 50mm x 100mm). Randomly select multiple test regions (e.g., 5 regions) within the test sample. At a certain magnification (e.g., 500x or higher), count the quantity and particle size of the second silicon-based material and the second carbon-based material in each test region. Take the arithmetic mean of the particle sizes of all second silicon-based materials in each test region as the average particle size of the second silicon-based material, and take the arithmetic mean of the particle sizes of all second carbon-based materials in each test region as the average particle size of the second carbon-based material. To ensure the accuracy of the test results, multiple test samples (e.g., 10 samples) can be used for the above test, and the average value of each test sample can be taken as the final test result. It should be noted that when the particles are irregularly shaped, the distance between the two farthest points on the particle is taken as the particle size.

[0189] In some embodiments, the first negative electrode film layer and the second negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0190] In some embodiments, the first negative electrode film layer and the second negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), 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).

[0191] In some embodiments, the first negative electrode film layer and the second negative electrode film layer may further include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0192] The negative electrode film can be formed by coating a second slurry onto the negative electrode current collector, coating a first slurry onto the second slurry, and then drying and cold pressing it. After the first slurry dries, a first negative electrode film is formed, and after the second slurry dries, a second negative electrode film is formed.

[0193] The first slurry is formed by dispersing the first negative electrode active material, negative electrode conductive agent, negative electrode binder, and other optional additives in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0194] The second slurry is formed by dispersing the second negative electrode active material, negative electrode conductive agent, negative electrode binder, and other optional additives in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0195] The first and second slurries can be coated simultaneously in one step or in two separate steps. In some embodiments, the first and second slurries are coated simultaneously in one step. Simultaneous coating in one step can reduce the negative electrode film resistance, thereby further improving the kinetic and cycle performance of the battery cell.

[0196] The coating weights of the first and second slurries can be adjusted according to actual conditions.

[0197] The negative electrode current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0198] The negative electrode film parameters disclosed herein (such as compaction density, areal density, thickness, etc.) are all negative electrode film parameters on one side of the negative electrode current collector.

[0199] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0200] [Positive electrode plate] The positive electrode sheet includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes a lithium transition metal oxide. The lithium transition metal oxide includes Ni element, and the molar percentage of Ni element in the transition metal element of the lithium transition metal oxide is more than 80%. The porosity of the positive electrode film layer is 13%-20%, and the compaction density of the positive electrode film layer is 3.4 g / cm³. 3 -3.7g / cm 3 .

[0201] Optionally, the molar percentage of Ni in the transition metal elements of lithium transition metal oxide is above 83%, above 84%, above 85%, above 86%, or above 87%.

[0202] The porosity of the positive electrode film is 13%-20%, for example, it can be 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, or any range of the above values. Optionally, the porosity of the positive electrode film is 15%-18.5%, 15%-18%, 15.5%-18%, or 16%-18%.

[0203] The compaction density of the positive electrode film is 3.4 g / cm³. 3 -3.7g / cm 3 For example, it can be 3.4 g / cm³. 3 3.45g / cm 3 3.5g / cm 3 3.55g / cm 3 3.6g / cm 3 3.65g / cm 3 3.7g / cm 3 Or, a range of any of the above values. Optionally, the compaction density of the positive electrode film is 3.5 g / cm³. 3 -3.65g / cm 3 .

[0204] In some embodiments, the thickness of the positive electrode film is 30 μm-80 μm, for example, it can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, or any range of the above values. Optionally, the thickness of the positive electrode film can be 45 μm-65 μm.

[0205] Adjusting parameters such as the volume distribution particle size Dv50 and / or particle size distribution (Dv90-Dv10) / Dv50 of the positive electrode active material, as well as adjusting the positive electrode cold pressing pressure, can regulate the porosity and / or compaction density of the positive electrode film.

[0206] In some embodiments, the volume distribution particle size Dv50 of the positive electrode active material is 1μm-7μm, for example, it can be 1μm, 1.5μm, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm, 3μm, 3.2μm, 3.4μm, 3.6μm, 3.8μm, 4μm, 4.2μm, 4.4μm, 4.6μm, 4.8μm, 5μm, 5.2μm, 5.4μm, 5.6μm, 5.8μm, 6μm, 6.2μm, 6.4μm, 6.6μm, 6.8μm, 7μm, or any range of the above values.

[0207] A small volumetric particle size (Dv50) in the positive electrode active material results in a short solid-phase diffusion path for lithium ions, which facilitates rapid lithium ion insertion and extraction, reduces positive electrode polarization, and improves the low-temperature power performance of the battery cell. Furthermore, a smaller Dv50 increases the specific surface area of ​​the positive electrode active material. This larger surface area helps reduce the current surge experienced by the positive electrode film surface when the current density is high, thus improving the structural stability of the positive electrode active material. Additionally, achieving a Dv50 of 1μm-7μm in the positive electrode active material helps reduce the content of fine powder, thereby improving the processing of the positive electrode slurry.

[0208] Optionally, the volume distribution particle size Dv50 of the positive electrode active material is 2μm-7μm or 2μm-6μm.

[0209] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the positive electrode active material is 1-1.5, for example, it can be 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, or any range of the above values.

[0210] A small volumetric particle size distribution (Dv50) and a narrow particle size distribution (Dv90-Dv10) / Dv50 in the positive electrode active material are detrimental to improving the compaction density of the positive electrode film, thus hindering the achievement of high energy density battery cells. Conversely, a small volumetric particle size distribution (Dv50) and a wide particle size distribution (Dv90-Dv10) / Dv50 in the positive electrode active material help improve the compaction density of the positive electrode film and thus the energy density of the battery cell. However, this approach tends to result in a higher content of microparticles in the positive electrode active material, which can lead to difficulties in processing the positive electrode slurry, such as gelation problems. This disclosure addresses these issues by setting the particle size distribution (Dv90-Dv10) / Dv50 of the positive electrode active material to 1-1.5, thereby improving both the processing of the positive electrode slurry and the compaction density of the positive electrode film, ultimately increasing the energy density of the battery cell.

[0211] Optionally, the particle size distribution (Dv90-Dv10) / Dv50 of the positive electrode active material is 1.2-1.4.

[0212] In some embodiments, the total area of ​​the single-crystal lithium transition metal oxide is 60%-100% of the total area of ​​the positive electrode active material, for example, it can be 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 99%, 100%, or any range of the above values.

[0213] In some embodiments, the lithium transition metal oxide includes a single-crystal lithium transition metal oxide, and the total area of ​​the single-crystal lithium transition metal oxide is 100% of the total area of ​​the positive electrode active material.

[0214] In some embodiments, the lithium transition metal oxide includes single-crystal lithium transition metal oxide and polycrystalline lithium transition metal oxide, wherein the total area of ​​the single-crystal lithium transition metal oxide is 60%-99% of the total area of ​​the cathode active material, and the total area of ​​the polycrystalline lithium transition metal oxide is 1%-40% of the total area of ​​the cathode active material. For example, the total area of ​​the single-crystal lithium transition metal oxide can be 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 99%, or any range of the above values, representing the total area of ​​the cathode active material. For example, the total area of ​​the polycrystalline lithium transition metal oxide can be 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, or any of the above values, which is the total area of ​​the cathode active material.

[0215] Optionally, the total area of ​​single-crystal lithium transition metal oxides is 80%-99% of the total area of ​​the positive electrode active material, and the total area of ​​polycrystalline lithium transition metal oxides is 1%-20% of the total area of ​​the positive electrode active material.

[0216] Alternatively, the total area of ​​single-crystal lithium transition metal oxides is 90%-99% of the total area of ​​the positive electrode active material, and the total area of ​​polycrystalline lithium transition metal oxides is 1%-10% of the total area of ​​the positive electrode active material.

[0217] In some embodiments, the average particle size of the single-crystal lithium transition metal oxide is 1 μm-6 μm, for example, it can be 1 μm, 1.5 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, 5 μm, 5.2 μm, 5.4 μm, 5.6 μm, 5.8 μm, 6 μm, or any range of the above values.

[0218] In some embodiments, the average particle size of the polycrystalline lithium transition metal oxide is 7 μm-13 μm, for example, it can be 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, or any range of the above values.

[0219] The terms "single-crystal lithium transition metal oxides" and "polycrystalline lithium transition metal oxides" have meanings well-known in the art. "Single-crystal lithium transition metal oxides" also include quasi-single-crystal (or near-single-crystal) lithium transition metal oxides. Quasi-single-crystal (or near-single-crystal) is a well-known term in the art, typically referring to particles composed of a small number, for example, less than 10 primary particles. Typically, the primary particles constituting quasi-single-crystal (or near-single-crystal) lithium transition metal oxides have a particle size greater than 500 nm. Polycrystalline lithium transition metal oxides refer to lithium transition metal oxides with a secondary particle morphology, formed by the aggregation of a large number of nanoscale primary particles. "Single-crystal lithium transition metal oxides" and "polycrystalline lithium transition metal oxides" can be distinguished using scanning electron microscopy.

[0220] The average particle size of single-crystal lithium transition metal oxides and polycrystalline lithium transition metal oxides can be tested as follows: Using a scanning electron microscope (SEM) according to JY / T 010-1996, obtain SEM images of the positive electrode sheet. Randomly select a test sample (e.g., 50mm x 100mm). Within the test sample, randomly select multiple test regions (e.g., 5 regions). At a certain magnification (e.g., 500x or higher), count the number and particle size of single-crystal and polycrystalline lithium transition metal oxides in each test region. Take the arithmetic mean of the particle sizes of all single-crystal lithium transition metal oxides in each test region as the average particle size of the single-crystal lithium transition metal oxides, and take the arithmetic mean of the particle sizes of all polycrystalline lithium transition metal oxides in each test region as the average particle size of the polycrystalline lithium transition metal oxides. To ensure the accuracy of the test results, multiple test samples (e.g., 10 samples) can be used for the above test, and the average value of each test sample can be taken as the final test result. The testing instrument can be a ZEISS Sigma 300. It should be noted that when the particles are irregularly shaped, the distance between the two farthest points on the particle is taken as the particle size.

[0221] The area ratio of single-crystal lithium transition metal oxides and the area ratio of polycrystalline lithium transition metal oxides in the positive electrode active material can be tested as follows: Using a scanning electron microscope (SEM) according to JY / T 010-1996, obtain the SEM image of the positive electrode sheet. Randomly select a test sample (e.g., 50mm x 100mm). Randomly select multiple test areas (e.g., 5) in the test sample. At a certain magnification (e.g., 500x or more), calculate the sum of the areas of all single-crystal lithium transition metal oxides, the sum of the areas of all polycrystalline lithium transition metal oxides, and the sum of the areas of all positive electrode active materials in each test area. Obtain the area ratio of single-crystal lithium transition metal oxides and the area ratio of polycrystalline lithium transition metal oxides. Then, take the average value of the test results of multiple test areas as the area ratio of single-crystal lithium transition metal oxides and the area ratio of polycrystalline lithium transition metal oxides in the positive electrode active material. To ensure the accuracy of the test results, multiple test samples (e.g., 10) can be taken for the above test, and the average value of each test sample can be taken as the final test result. The testing instrument can be a ZEISS Sigma 300.

[0222] Lithium transition metal oxides with single-crystal morphology have no grain boundaries or contain only a small number of grain boundaries. They are less prone to particle breakage during charging and discharging, and have better tolerance to overcharging and over-discharging. They also have higher structural stability and particle integrity, which helps to improve the low-temperature power performance of battery cells.

[0223] Polycrystalline lithium transition metal oxides exhibit higher electrochemical activity and higher specific capacity at low temperatures, which helps to improve the low-temperature power performance and energy density of battery cells.

[0224] The average particle size of polycrystalline lithium transition metal oxides is larger than that of single-crystal lithium transition metal oxides. By including a small amount of polycrystalline lithium transition metal oxides in the cathode active material, it is helpful for the cathode film to have high porosity and large pore structure while also having high compaction density, which in turn helps to improve the energy density of the battery cell.

[0225] In some embodiments, the lithium transition metal oxide includes Ni and Co elements, and the Co content in the surface region of the lithium transition metal oxide is higher than the Co content in the core region of the lithium transition metal oxide.

[0226] The lithium transition metal oxide has a high Co content in the surface region and a low Co content in the core region. As a result, the lithium transition metal oxide has high surface stability and better resistance to overcharge and over-discharge. It can reduce side reactions with the electrolyte and reduce the dissolution of transition metal ions, thereby improving the cycle performance of the battery cell. It can also enhance the thermal stability of the lithium transition metal oxide and reduce the risk of thermal runaway of the battery cell.

[0227] In some embodiments, the lithium transition metal oxide includes Ni and Mn elements, and the Mn content in the surface region of the lithium transition metal oxide is lower than the Mn content in the core region of the lithium transition metal oxide.

[0228] The lithium transition metal oxide has a low Mn content in the surface region and a high Mn content in the core region. As a result, the lithium transition metal oxide has high surface stability and better resistance to overcharge and over-discharge. It can reduce side reactions with the electrolyte and reduce the dissolution of transition metal ions, thereby improving the cycle performance of the battery cell. It can also enhance the thermal stability of the lithium transition metal oxide and reduce the risk of thermal runaway of the battery cell.

[0229] In some embodiments, the lithium transition metal oxide includes Ni, Co, and Mn elements, and the Co content in the surface region of the lithium transition metal oxide is higher than the Co content in the core region of the lithium transition metal oxide, while the Mn content in the surface region of the lithium transition metal oxide is lower than the Mn content in the core region of the lithium transition metal oxide.

[0230] The surface region of the lithium transition metal oxide is a region extending radially inward from the outermost surface of the particle, about 100 nm in diameter. The core region of the lithium transition metal oxide is a region extending radially outward from the center of the particle, about 300 nm in diameter. The center of the particle is the midpoint of the longest straight line between any two points on the particle's circumference.

[0231] The content of each element in the surface and core regions of lithium transition metal oxide can be tested as follows: A particle cross-section sample is prepared using an ion cutter. A suitable field of view is selected using a scanning electron microscope, and an energy dispersive spectroscopy (EDS) instrument is used to scan the particle cross-section within a 5k field of view. The content of each element at more than 10 locations in the surface region of the particle cross-section is measured, and the average value is taken as the test result for the corresponding element content in the surface region of the lithium transition metal oxide. Similarly, the content of each element at more than 10 locations in the core region of the particle cross-section is measured, and the average value is taken as the test result for the corresponding element content in the core region of the lithium transition metal oxide.

[0232] In some embodiments, the lithium transition metal oxide includes Ni element and doping elements. The doping elements include cation doping elements and / or anion doping elements. The cation doping elements include one or more of Al, Y, Zr, Zn, Cr, Mg, V, Ti, and B, and the anion doping elements include one or more of N, F, S, and Cl. The cation doping elements can be doping at the lithium site and / or at the transition metal site, and the anion doping elements can be doping at the oxygen site.

[0233] The above doping elements can enhance the structural stability of the lithium transition metal oxide, improve the ability of the lithium transition metal oxide to withstand overcharge and over-discharge, reduce the volume change of the lithium transition metal oxide during charge and discharge, reduce the dissolution of transition metal ions, and improve the chemical stability and cycle stability of the battery cell; they can also enhance the thermal stability of the lithium transition metal oxide and reduce the risk of thermal runaway of the battery cell.

[0234] In some embodiments, the positive electrode active material includes a lithium transition metal oxide, and the composition of the lithium transition metal oxide is Li a Ni b Co c Mn d M e O f A g , 0.8 ≤ a ≤ 1.2, 0.8 ≤ b < 1, 0 < c < 0.2, 0 < d < 0.2, 0 < e < 0.2, 1 ≤ f ≤ 2, 0 ≤ g ≤ 1, M includes one or more of Al, Y, Zr, Zn, Cr, Mg, V, Ti, and B, and A includes one or more of N, F, S, and Cl.

[0235] During the charge and discharge process of the battery cell, the deintercalation and consumption of Li will occur, and the molar content of Li is different when the battery cell is discharged to different states. In the listing of the positive electrode active material in the present disclosure, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery cell, after charge and discharge cycles, the molar content of Li will change. In the listing of the positive electrode active material in the present disclosure, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of O to change, and the actual molar content of O will also fluctuate.

[0236] In some embodiments, the positive electrode film layer further includes a positive electrode conductive agent.

[0237] In some embodiments, the mass percentage of the positive electrode conductive agent in the positive electrode film layer is 0.5%-2.5%, for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, or any range of the above values.

[0238] Optionally, the positive electrode conductive agent has a mass percentage of 0.6%-1.5% or 0.8%-1.5% in the positive electrode film.

[0239] In some embodiments, the positive electrode conductive agent includes one or more of carbon nanotubes, carbon black, acetylene black, carbon fiber, and graphene.

[0240] Carbon nanotubes include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0241] Single-walled carbon nanotubes are formed by rolling up a single layer of graphene, while few-walled carbon nanotubes are formed by rolling up two to three layers of graphene sheets concentrically, and multi-walled carbon nanotubes are formed by rolling up four or more layers of graphene sheets concentrically.

[0242] In some embodiments, the positive electrode conductive agent includes carbon nanotubes, and at least a portion of the carbon nanotubes are located on the surface of the positive electrode active material.

[0243] Carbon nanotubes have good electronic conductivity, which can reduce the mass ratio of the positive electrode conductive agent in the positive electrode film, increase the mass ratio of the positive electrode active material, and improve the energy density of the battery cell. The use of carbon nanotubes can also reduce the positive electrode impedance and help improve the high-rate charge and discharge performance of the battery cell.

[0244] By placing at least some carbon nanotubes on the surface of the cathode active material, the crystal structure of the cathode active material can be stabilized, the particle strength of the cathode active material can be improved, and the volume change of the cathode active material during charge and discharge can be reduced. This helps to form a stable SEI film on the surface of the cathode active material, reduces side reactions between lithium transition metal oxides and electrolytes, and reduces the dissolution of transition metal ions, thereby helping to improve the initial coulombic efficiency and cycle capacity retention of the battery cell. At the same time, placing at least some carbon nanotubes on the surface of the cathode active material also helps to form a uniform conductive network in the cathode, thereby improving the electron transport effect of the cathode, reducing the electron transport resistance of the cathode, and also helping to reduce the cathode impedance and polarization, which in turn helps to improve the low-temperature cycle performance and low-temperature power performance of the battery cell.

[0245] In some embodiments, the positive electrode conductive agent includes an aggregated positive electrode conductive agent.

[0246] Agglomerated positive electrode conductive agents can be formed by agglomerating one type of positive electrode conductive agent, such as agglomerated carbon nanotubes; or they can be formed by agglomerating multiple types of positive electrode conductive agents, such as agglomerated carbon nanotubes and acetylene black, or agglomerated carbon nanotubes and carbon black.

[0247] Optionally, the positive electrode conductive agent may also include a non-agglomerated positive electrode conductive agent.

[0248] Optionally, the agglomerated positive conductive agent satisfies that the maximum distance between any two points on the perimeter is greater than or equal to 2 μm.

[0249] Optionally, the porosity of the agglomerated positive electrode conductive agent is 30%-65%, for example, it can be 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 65%, or any range of the above values.

[0250] Optionally, the agglomerated positive electrode conductive agent includes carbon nanotubes. Optionally, the agglomerated positive electrode conductive agent also includes one or more of carbon black and acetylene black.

[0251] Optionally, the number density of agglomerated positive electrode conductive agents in the positive electrode film is 1 to 5 per 1000 μm. 2 For example, it can be 1 per 1000μm 2 2 per 1000μm 2 3 per 1000μm 2 4 per 1000μm 2 5 per 1000μm 2 Or a range consisting of any of the above values.

[0252] Non-agglomerated positive electrode conductive agents refer to positive electrode conductive agents that exist independently and dispersedly, without significant aggregation or entanglement with other positive electrode conductive agents. Agglomerated positive electrode conductive agents refer to positive electrode conductive agents that are aggregated together by several positive electrode conductive agents through van der Waals forces or disordered entanglement, forming an aggregate morphology.

[0253] The number density of agglomerated positive electrode conductive agent in the positive electrode film can be tested as follows: Cut the positive electrode sheet along a direction perpendicular to the surface of the positive electrode film. Using a scanning electron microscope (SEM) according to JY / T 010-1996, obtain a cross-sectional SEM image of the positive electrode film in the thickness direction. Randomly select a test sample, and then randomly select multiple samples with an area of ​​1000 μm from the test sample. 2Five test regions (20μm × 50μm) are used. At a certain magnification (e.g., 1000x), the number of agglomerated positive electrode conductive agents in each test region is counted. The agglomerated positive electrode conductive agents satisfy the condition that the maximum distance between any two points on the perimeter is greater than or equal to 2μm. The average number of agglomerated positive electrode conductive agents in multiple test regions is then taken as the number density of agglomerated positive electrode conductive agents in the positive electrode film. To ensure the accuracy of the test results, multiple test samples (e.g., 10) can be used, and the average value of each sample is taken as the final test result. The testing instrument can be a ZEISS Sigma 300.

[0254] Current research suggests that agglomerated positive electrode conductive agents lead to uneven conductive networks in the positive electrode film, reduced electron transport paths, increased electron transport resistance, and increased polarization. Therefore, their use in positive electrode films is generally avoided. However, the inventors of this disclosure have discovered that agglomerated positive electrode conductive agents possess a loose, porous structure. By applying an appropriate amount of agglomerated positive electrode conductive agent to the positive electrode film, it can effectively retain electrolyte, thereby improving the electrolyte wettability of the positive electrode film and enhancing the cycle performance of the battery cell. Furthermore, the number density of agglomerated positive electrode conductive agents should not exceed 5 particles / 1000 μm. 2 When the mass of the positive electrode conductive agent is the same, a large amount of agglomerated positive electrode conductive agent will result in an uneven conductive network in the positive electrode film, reducing electron transport paths, increasing electron transport resistance, and increasing polarization. Simultaneously, agglomerated positive electrode conductive agent may also fill the pores of the positive electrode film, leading to blockage of the electrolyte pathway. Therefore, this disclosure achieves a number density of agglomerated positive electrode conductive agent of 1 to 5 particles / 1000 μm in the positive electrode film. 2 This not only helps to improve the electronic conductivity of the positive electrode and reduce the electron transport resistance and polarization of the positive electrode, but also helps to improve the electrolyte wettability of the positive electrode film, thereby helping to further improve the low-temperature power performance of the battery cell.

[0255] Alternatively, the number density of agglomerated positive electrode conductive agents in the positive electrode film is 1 to 3 per 1000 μm. 2 .

[0256] In some embodiments, the positive electrode film layer further includes a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0257] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0258] The positive electrode current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0259] The positive electrode film parameters disclosed herein (such as compaction density, areal density, thickness, etc.) are all positive electrode film parameters on one side of the positive electrode current collector.

[0260] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0261] Dv10, Dv50, and Dv90 represent the particle sizes corresponding to a cumulative volumetric distribution percentage of 10%, 50%, and 90%, respectively. These values ​​can be determined using a laser particle size analyzer, referring to GB / T 19077-2016. During testing, add 1g of the sample to a clean small beaker and 20ml of deionized water. Sonicate at 53kHz / 120W for 5 minutes to ensure complete dispersion. Turn on the laser particle size analyzer, clean the optical path system, and automatically test the background. Stir the sonicated solution to ensure uniform dispersion, place it in the sample cell as required, and begin measuring the particle size. A MasterSizer 3000 laser particle size analyzer can be used as the testing instrument.

[0262] Electrode active materials (positive electrode active materials and negative electrode active materials) can be obtained by the following method: After fully disassembling the battery cell, the electrode sheets are removed and immersed in an organic solvent (e.g., dimethyl carbonate) for a period of time (e.g., 2h-10h). Then, the electrode sheets are removed and dried at a certain temperature and time (e.g., 60°C for more than 4h). After drying, the electrode sheets are removed. The dried electrode sheets are baked at a certain temperature and time (e.g., 400°C for more than 2h). A sample of the electrode active material is taken from a random area of ​​the baked electrode sheet (e.g., a blade can be used to scrape off the powder for sampling).

[0263] The first and second negative electrode active material samples can be obtained by the following method: After fully disassembling the battery cell, remove the negative electrode sheet. Immerse the negative electrode sheet in an organic solvent (e.g., dimethyl carbonate) for a period of time (e.g., 2-10 hours). Then, remove the negative electrode sheet and dry it at a certain temperature and time (e.g., 60°C for more than 4 hours). After drying, remove the negative electrode sheet. Bake the dried negative electrode sheet at a certain temperature and time (e.g., 400°C for more than 2 hours). Select any region in the baked first negative electrode film layer and sample the first negative electrode active material, such as by scraping powder with a blade. Select any region in the baked second negative electrode film layer and sample the second negative electrode active material, such as by scraping powder with a blade. To ensure the accuracy of the test results, the interface region between the first and second negative electrode film layers should be avoided during sampling.

[0264] [Isolation membrane] In a single battery cell, the separator acts as a barrier between the positive and negative electrodes and a conductor for ions.

[0265] This disclosure does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected. As an example, the separator material can be selected from one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can 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 can be the same or different, without particular limitation. The separator can be a separate component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes.

[0266] In some embodiments, the separator includes a porous base membrane and a porous coating located on at least one side of the porous base membrane. The porous coating includes filler particles, which include one or more of inorganic particles, organic particles, and organic-inorganic composite particles.

[0267] The porous coating includes filler particles, which enhance the heat resistance of the separator and reduce its thermal shrinkage during charge and discharge, thereby improving the thermal stability of the battery cell and reducing the risk of thermal runaway. Filler particles also improve the mechanical strength and puncture resistance of the separator, making it more durable during battery cell assembly and use, and helping to reduce mechanical micro-short circuits. They promote uniform ion flow, facilitating the formation of a high-performance SEI film at the negative electrode, reducing irreversible consumption of electrolyte and active lithium, and improving the initial coulombic efficiency, cycle performance, and rate performance of the battery cell. Under excessive current, filler particles can also block current, prevent internal short circuits and overheating, thus contributing to improved battery cell safety. Finally, filler particles improve the wettability of the separator to the electrolyte and enhance its ion transport efficiency, thereby improving the low-temperature power performance of the battery cell.

[0268] Optionally, the filler particles may include, but are not limited to, one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, and magnesium fluoride.

[0269] In some embodiments, the porous coating further includes polymer binder particles, wherein the volume distribution particle size Dv50 of the polymer binder particles is greater than the volume distribution particle size Dv50 of the filler particles.

[0270] The porous coating includes polymer binder particles. During the cold or hot pressing of the battery cell, the polymer binder particles in the porous coating can play a role in bonding the separator and the positive and negative electrodes. This allows the separator and the positive and negative electrodes to be tightly bonded, improving the overall hardness and thickness uniformity of the battery cell, reducing the uneven distribution of internal resistance, thereby improving the uniformity of the battery cell and also increasing the volumetric energy density of the battery cell.

[0271] The volume distribution particle size Dv50 of the polymer binder particles is larger than that of the filler particles. As a result, the polymer binder particles can form a certain volume gap between the separator and the positive and negative electrodes. This volume gap can provide a buffer space for the volume expansion of the positive and negative electrodes, thereby reducing the adverse effects of volume expansion on the separator and the wettability of the electrolyte, and improving the low-temperature cycle performance and low-temperature power performance of the battery cell.

[0272] The "polymer binder particles" in the porous coating play a role in improving the adhesion between the separator and the electrode sheet, but they have virtually no high-temperature resistance.

[0273] Optionally, the polymer binder particles may include one or more of fluoropolymer binder particles and non-fluoropolymer binder particles.

[0274] Optionally, the fluoropolymer binder particles may include vinylidene fluoride polymer particles, such as polyvinylidene fluoride (PVDF) particles and / or copolymer particles of vinylidene fluoride monomer and comonomer. The comonomer may include at least one of olefin monomers, fluorinated olefin monomers, chlorinated olefin monomers, acrylate monomers, acrylic monomers, and fluoroether monomers. Optionally, the comonomer may include at least one of the following: trifluoroethylene, trifluorochloroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers (e.g., perfluoro(methyl vinyl) ether, perfluoro(ethyl vinyl) ether, perfluoro(propyl vinyl) ether), perfluoro(1,3-m-dioxacyclopentene), and perfluoro(2,2-dimethyl-1,3-m-dioxacyclopentene).

[0275] Alternatively, the non-fluoropolymer binder particles may include acrylate copolymers.

[0276] The porous base film has two surfaces opposite each other in its thickness direction, and the porous coating is disposed on one or both of the two opposite surfaces of the porous base film.

[0277] Optionally, the porous coating is located at least on the surface of the porous base film facing the negative electrode sheet.

[0278] Because the negative electrode film contains silicon-based materials, which typically exhibit significant volume expansion, the relative movement between the negative electrode and the separator under expansion can lead to the detachment of the negative electrode film. By ensuring that a porous coating is present at least on the surface of the porous base film facing the negative electrode and including polymer binder particles, the relative movement between the negative electrode and the separator can be reduced. This allows for good electrical contact between the negative electrode film and the negative current collector, thereby contributing to higher capacity and better cycle stability in the battery cell.

[0279] In some embodiments, the thickness of the porous coating is 0.5 μm-2 μm. The thickness of the porous coating refers to the thickness of the porous coating on one side of the porous base film.

[0280] In some embodiments, the thickness of the porous base film is 5 μm-10 μm.

[0281] At low temperatures, the viscosity of the electrolyte increases, leading to poorer electrolyte wettability of the separator. A suitable porous base membrane thickness helps improve the electrolyte wettability of the separator, thus enhancing its ion transport efficiency. Simultaneously, a suitable porous base membrane thickness also provides appropriate heat resistance and mechanical strength, contributing to improved heat resistance, mechanical strength, and puncture resistance of the separator.

[0282] In some embodiments, the porous base membrane can be made of one or more of the following materials: glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The porous base membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the porous base membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0283] In some embodiments, the porosity of the separator is 35%-55%.

[0284] At low temperatures, the viscosity of the electrolyte increases, and the electrolyte wettability of the separator deteriorates. Improving the separator's porosity helps enhance its electrolyte retention and ion transport efficiency, thereby improving the low-temperature power performance of the battery cell.

[0285] The porosity of the separator can be tested in accordance with GB / T 36363-2018.

[0286] Electrolyte In some embodiments, the battery cell further includes an electrolyte, which comprises an organic solvent and an electrolyte salt.

[0287] In some embodiments, the concentration of the electrolyte salt is 0.9 mol / L to 1.2 mol / L.

[0288] By setting the concentration of electrolyte salt to 0.9 mol / L-1.2 mol / L, it is helpful to reduce the viscosity of the electrolyte, increase the ionic conductivity of the electrolyte, improve the electrolyte wettability of the electrode assembly at low temperatures, and improve the low-temperature power performance of the battery cell.

[0289] In some embodiments, the organic solvent includes ethylene carbonate (EC) and ethyl methyl carbonate (EMC), wherein the mass percentage of ethyl methyl carbonate (EMC) in the organic solvent is greater than or equal to 55% and less than 100%.

[0290] Ethyl methyl carbonate (EMC) has low viscosity and a wide liquid temperature range, which allows it to maintain good fluidity at low temperatures. This improves the electrolyte wettability of electrode components at low temperatures, thereby enhancing the low-temperature cycle performance and power performance of individual battery cells. Furthermore, EMC has a wide electrochemical window and high stability at high voltages, which helps improve the oxidation stability of individual battery cells. It also helps to fully utilize the high specific capacity of the positive electrode active material, further contributing to an increase in the energy density of the individual battery cells.

[0291] Ethylene carbonate (EC) has a high dielectric constant and can preferentially combine with lithium ions in the electrolyte to form a stable solvation structure, thus maintaining good ion migration ability even at low temperatures. Ethylene carbonate (EC) helps to form a stable SEI film on the negative electrode and also helps to improve the high voltage resistance of the electrolyte, thereby helping to fully utilize the high specific capacity of the positive electrode active material and improve the energy density of the battery cell.

[0292] Optionally, the organic solvent also includes one or more of the following: propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0293] In some embodiments, the electrolyte salt may be one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0294] Alternatively, the electrolyte salt may include lithium hexafluorophosphate (LiPF6).

[0295] LiPF6 exhibits high ionic conductivity, which helps improve the charge and discharge performance of individual battery cells. LiPF6 also helps form a stable passivation film on the surface of the positive electrode current collector (e.g., aluminum foil), protecting it from further oxidation. Furthermore, LiPF6 helps form a stable SEI film on the negative electrode, thereby reducing electrolyte and active lithium consumption and improving the initial coulombic efficiency and cycle performance of the battery cells. Finally, LiPF6 possesses excellent chemical stability, avoiding harmful side reactions with electrode active materials, electrolytes, and separators, thus contributing to extended battery cell lifespan.

[0296] In some embodiments, the electrolyte may also include additives.

[0297] Optionally, the additive may include one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), and vinyl sulfate (DTD).

[0298] Alternatively, the additive may include fluoroethylene carbonate (FEC).

[0299] FEC helps form a LiF-rich SEI film on the negative electrode, giving the SEI film higher ionic conductivity, which in turn helps to further improve the low-temperature power performance of the battery cell.

[0300] The electrode assembly disclosed herein can be a wound structure or a stacked structure, and the embodiments disclosed herein are not limited to this.

[0301] In some embodiments, the battery cell is a pouch cell.

[0302] Figure 5 An exploded view of a pouch cell 22 provided in one embodiment is shown.

[0303] like Figure 5 As shown, the pouch cell 22 includes an electrode assembly 221 and a housing. The housing includes two packaging films 222, with the electrode assembly 221 located between the two packaging films 222. The edges of the two packaging films 222 are connected to each other to form a seal. The pouch cell 22 also includes electrode leads 223, which pass through the two packaging films 222 and are electrically connected to the electrode assembly 221.

[0304] The soft-pack battery cell has a low-hardness outer shell, which reduces the reverse extrusion force exerted on the electrode assembly during the expansion process. This reduces the problem of electrolyte being squeezed out from the positive and negative electrodes and the separator, thus allowing the electrode assembly to maintain good electrolyte wettability during charging and discharging. This, in turn, helps the battery cell to have good low-temperature cycle performance and low-temperature power performance.

[0305] In some embodiments, each packaging film includes an insulating protective layer, a metal layer, and an insulating connecting layer, wherein 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.

[0306] Alternatively, the insulating protective layer can be nylon.

[0307] Alternatively, the metal layer can be aluminum or steel.

[0308] Alternatively, the insulating bonding layer can be polypropylene.

[0309] In some embodiments, the outer casing of the pouch battery cell is a pouch structure made of aluminum-plastic film.

[0310] In some embodiments, the battery cell is a hard-cased battery cell.

[0311] The casing of a hard-shell battery cell is square in shape and made of metal, such as aluminum or steel.

[0312] The methods for preparing battery cells are well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be made into an electrode assembly, which is then placed in a housing, dried, and injected with electrolyte. After standing and formation processes, a battery cell is obtained.

[0313] Example The following examples describe the contents of this disclosure in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0314] Example 1 Preparation of positive electrode sheet LiNi, the positive electrode active material 0.91 Co 0.07 Mn 0.02 O2, positive electrode binder polyvinylidene fluoride (PVDF), positive electrode conductive agent carbon nanotubes and carbon black are added to N-methylpyrrolidone (NMP) in a mass ratio of 98:1.2:0.2:0.6 and mixed thoroughly to prepare a positive electrode slurry. The positive electrode slurry is then uniformly coated on both surfaces of a 13μm thick positive electrode current collector aluminum foil, and then dried, cold-pressed and slit to obtain the positive electrode sheet.

[0315] The positive electrode active material has a single crystal morphology. The volume distribution particle size Dv50 of the positive electrode active material in the positive electrode film is 2.5 μm, and (Dv90-Dv10) / Dv50 is 1.3.

[0316] The positive electrode conductive agent in the positive electrode film includes agglomerated positive electrode conductive agent and non-agglomerated positive electrode conductive agent. The number density of agglomerated positive electrode conductive agent in the positive electrode film is 3 per 1000 μm. 2 By adjusting the viscosity and dispersibility of the positive electrode slurry, positive electrode films with different agglomerated positive electrode conductive agent number densities can be obtained.

[0317] The thickness of the positive electrode film layer on one side of the positive current collector is 50 μm.

[0318] Preparation of negative electrode sheet The negative electrode active material, negative electrode conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were added to deionized water in a mass ratio of 96:0.4:2:1.6 and thoroughly mixed to prepare a negative electrode slurry. The negative electrode slurry was then uniformly coated on both surfaces of a 6μm thick negative electrode current collector copper foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0319] The negative electrode active material includes silicon-carbon material and artificial graphite, with a mass ratio of 5:95, and the mass percentage of Si element in the negative electrode film is 4.5%.

[0320] The volume distribution particle size Dv50 of the negative electrode active material in the negative electrode film layer is 13 μm, and (Dv90-Dv10) / Dv50 is 1.35.

[0321] The thickness of the negative electrode film layer on one side of the negative electrode current collector is 60 μm.

[0322] Preparation of the separating membrane Inorganic alumina particles, sodium carboxymethyl cellulose dispersant, and polyacrylate binder were mixed evenly in deionized water at a solid mass ratio of 90:2:8 to obtain a first slurry. Commercially available polyvinylidene fluoride (PVDF) polymer binder particles, polyacrylate binder, sodium carboxymethyl cellulose dispersant, and ether-based surfactants were mixed evenly in deionized water at a solid mass ratio of 87:8:3:2 to obtain a second slurry. A commercially available 7μm thick polypropylene membrane was used as the porous base membrane. The prepared first slurry was uniformly coated onto both surfaces of the porous base membrane using a microgravure process. After drying, the second slurry was sprayed onto the membrane, followed by further drying and slitting to obtain the release membrane.

[0323] Preparation of electrolyte At 25°C, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of 40:60 to obtain an organic solvent. Then, LiPF6 was added and stirred until homogeneous to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L.

[0324] Preparation of battery cells The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain an electrode assembly. The electrode assembly is placed in an aluminum shell, and electrolyte is injected. After standing and formation processes, a single battery cell is obtained.

[0325] Examples 2 to 4 The preparation process of the battery cell is similar to that of Example 1. Compared with Example 1, at least the volume distribution particle size Dv50 and (Dv90-Dv10) / Dv50 of the positive electrode active material in the positive electrode film layer are adjusted. In order to obtain the positive electrode film layer with the required porosity and compaction density, the positive electrode cold pressing pressure can also be adjusted.

[0326] Example 5 The preparation process of the battery cell is similar to that of Example 1. Compared with Example 1, at least the mass ratio of silicon-carbon material and artificial graphite, the mass percentage of Si element in the negative electrode film, and the volume distribution particle size Dv50 and (Dv90-Dv10) / Dv50 of the negative electrode active material in the negative electrode film were adjusted.

[0327] The mass ratio of silicon-carbon material to artificial graphite is 3:97, the mass percentage of Si element in the negative electrode film is 2.7%, the volume distribution particle size Dv50 of the negative electrode active material in the negative electrode film is 15μm, and (Dv90-Dv10) / Dv50 is 1.38.

[0328] Examples 6 and 7 The manufacturing process of the battery cell is similar to that of Example 1. At least the cold pressing pressure of the negative electrode was adjusted compared with Example 1 so that the porosity and compaction density of the negative electrode film are different from those of Example 1.

[0329] Comparative Example 1 Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0330] Preparation of positive electrode sheet LiNi, the positive electrode active material 0.91 Co 0.07 Mn 0.02 O2, positive electrode binder polyvinylidene fluoride (PVDF), and positive electrode conductive agent carbon black are added to N-methylpyrrolidone (NMP) in a mass ratio of 98:1.2:0.8 and thoroughly mixed to prepare a positive electrode slurry. The positive electrode slurry is then uniformly coated on both surfaces of a 13μm thick positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0331] The positive electrode active material has a single crystal morphology. The volume distribution particle size Dv50 of the positive electrode active material in the positive electrode film is 2.5 μm, and (Dv90-Dv10) / Dv50 is 1.3.

[0332] The positive electrode film does not contain agglomerated positive electrode conductive agents.

[0333] The thickness of the positive electrode film layer on one side of the positive current collector is 50 μm.

[0334] Preparation of negative electrode sheet The negative electrode active material, negative electrode conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were added to deionized water in a mass ratio of 96:0.4:2:1.6 and thoroughly mixed to prepare a negative electrode slurry. The negative electrode slurry was then uniformly coated on both surfaces of a 6μm thick negative electrode current collector copper foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0335] The negative electrode active material includes silicon-carbon material and artificial graphite. Based on Example 1, the mass ratio of the two is adjusted so that the mass ratio of Si element in the negative electrode film is 15%.

[0336] The thickness of the negative electrode film layer on one side of the negative electrode current collector is 48 μm.

[0337] Performance testing (1) Porosity test of electrode film At 25℃, the prepared battery cells were discharged at a constant current of 0.5C to a cutoff voltage of 2.5V (i.e., fully discharged), and the electrode sheets were then disassembled. The electrode sheets were immersed in the organic solvent dimethyl carbonate for 2 hours, then removed and dried at 60℃ for 4 hours. After drying, the electrode sheets were removed, and one side of the electrode film was wiped off to create a single-sided coated electrode sheet. These were then cut into small circular samples of a certain area, and the apparent volume V1 of the electrode sheet was calculated. Referring to GB / T 24586-2009, using inert helium as the medium, the true volume V2 of the electrode sheet was measured using a gas displacement method and a true density meter. The porosity of the electrode film is calculated as (V1-V2) / V1×100%. Thirty samples with good appearance and no powder shedding at the edges were tested, and the average value was taken. The testing instrument used was a Micromeritics AccuPyc II 1340 true density meter.

[0338] (2) Test of compaction density of electrode film layer The compaction density of the electrode film = the areal density of the electrode film / the thickness of the electrode film.

[0339] The thickness of the electrode film was measured using a micrometer (10 locations were measured during the test), and the average value was taken.

[0340] The areal density of the electrode film was tested as follows: At 25°C, the prepared battery cell was discharged at a constant current of 0.5C to a cutoff voltage of 2.5V (i.e., fully discharged), and the electrode sheet was disassembled. The electrode sheet was soaked in the organic solvent dimethyl carbonate for 2 hours, and then the electrode sheet was taken out and dried at 60°C for 4 hours. After drying, the electrode sheet was taken out; the electrode film layer on one side was wiped off to make a single-sided coated electrode sheet, which was then punched into a small circular piece with an area of ​​S1, and its weight was recorded as M1; then the electrode film layer of the above-weighed electrode sheet was wiped off, and the weight of the electrode current collector was weighed and recorded as M0; the areal density of the electrode film layer = (M1-M0) / S1.

[0341] (3) Energy density test of individual battery cells At 25℃, the battery cell is charged at a constant current of 0.33C to a cutoff voltage of 4.25V, then charged at a constant voltage to a current of 0.05C, left to stand for 10 minutes, and then discharged at a constant current of 0.33C to a cutoff voltage of 2.5V. The battery cell capacity C0 and average discharge voltage V0 are obtained. The product of the two is the discharge energy E0 of the battery cell. The volume V0 of the battery cell is calculated. The volumetric energy density of the battery cell = E0 / V0, in Wh / L.

[0342] (3) Power performance test of individual battery cells At 25℃, a single battery cell is charged at a constant current of 0.33C to a cutoff voltage of 4.25V, then charged at a constant voltage to a current of 0.05C, allowed to stand for 10 minutes, and then discharged at a constant current of 0.33C to a cutoff voltage of 2.5V. The battery cell capacity C0 and average discharge voltage V0 are obtained; their product is the discharge energy E0 of the battery cell. The battery cell is then charged at a constant current of 0.33C to a cutoff voltage of 4.25V, then charged at a constant voltage to a current of 0.05C, allowed to stand for 10 minutes, and then discharged at a constant current of 0.33C to 50% of its capacity. C0 is cut off, and the cutoff voltage V1 is recorded. The battery cell is placed in a 0℃ environment and left to stand for 30 minutes, then discharged at 0.36C for 10 seconds to obtain the DCR of the battery cell. DCR = voltage drop before and after discharge / discharge current. Continue to charge the battery cell at a constant current of 0.05C to the cutoff voltage V1 in a 0℃ environment, let it stand for 10 minutes, then discharge at 0.5C for 10 seconds, and record the discharge capacity C1 and cutoff voltage V2 at this time. Then charge the battery cell at a constant current of 0.05C to the capacity C1, then discharge at 1C for 10 seconds, and record the cutoff voltage V3.

[0343] The current I corresponding to a cutoff voltage of 2.5V was obtained by fitting (0.5C, V2) and (1C, V3). max .

[0344] The power of a single battery cell is P = [(V1 - I)] max ×DCR)×Imax ] / E0.

[0345] Table 1 The test results above show that, by adjusting the composition of the positive and negative electrodes, this disclosure achieves a molar ratio of Ni in the lithium transition metal oxide of the positive electrode of over 80%, a porosity of 13%-20% in the positive electrode film, and a compaction density of 3.4 g / cm³. 3 -3.7g / cm 3 The anode active material includes silicon-based and carbon-based materials; the mass percentage of Si in the anode film is 1%-10%; the porosity of the anode film is 25%-35%; and the compaction density of the anode film is 1.55 g / cm³. 3 -1.8g / cm 3 This enables battery cells to possess both high energy density and good low-temperature power performance.

[0346] Example 1-1 The preparation process of the battery cell is similar to that of Example 1. Compared with Example 1, at least the mass ratio of silicon-carbon material and artificial graphite, the mass percentage of Si element in the negative electrode film, and the volume distribution particle size Dv50 and (Dv90-Dv10) / Dv50 of the negative electrode active material in the negative electrode film were adjusted.

[0347] The mass ratio of silicon-carbon material to artificial graphite is 2:98, the mass percentage of Si element in the negative electrode film is 1.8%, the volume distribution particle size Dv50 of the negative electrode active material in the negative electrode film is 15μm, and (Dv90-Dv10) / Dv50 is 1.42.

[0348] Examples 1-2 The preparation process of the battery cell is similar to that of Example 1. Compared with Example 1, at least the mass ratio of silicon-carbon material and artificial graphite, the mass percentage of Si element in the negative electrode film, the volume distribution particle size Dv50 and (Dv90-Dv10) / Dv50 of the negative electrode active material in the negative electrode film, and the thickness of the negative electrode film on one side of the negative electrode current collector are adjusted.

[0349] The mass ratio of silicon-carbon material to artificial graphite is 8.5:91.5, the mass percentage of Si element in the negative electrode film is 7.7%, the volume distribution particle size Dv50 of the negative electrode active material in the negative electrode film is 12μm, (Dv90-Dv10) / Dv50 is 1.46, and the thickness of the negative electrode film on one side of the negative electrode current collector is 55μm.

[0350] Examples 1-3 The preparation process of the battery cell is similar to that of Example 1. Compared with Example 1, at least the mass ratio of silicon-carbon material and artificial graphite, the mass percentage of Si element in the negative electrode film, the volume distribution particle size Dv50 and (Dv90-Dv10) / Dv50 of the negative electrode active material in the negative electrode film, and the thickness of the negative electrode film on one side of the negative electrode current collector are adjusted.

[0351] The mass ratio of silicon-carbon material to artificial graphite is 11:89, the mass percentage of Si element in the negative electrode film is 9.9%, the volume distribution particle size Dv50 of the negative electrode active material in the negative electrode film is 11 μm, (Dv90-Dv10) / Dv50 is 1.5, and the thickness of the negative electrode film on one side of the negative electrode current collector is 53 μm.

[0352] Table 2 The test results above show that further adjusting the mass ratio of Si in the negative electrode film helps the battery cell to better combine high energy density and good low-temperature power performance.

[0353] Example 2-1 Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0354] Preparation of positive electrode sheet The positive electrode conductive agent in the positive electrode film includes agglomerated positive electrode conductive agent and non-agglomerated positive electrode conductive agent. The number density of agglomerated positive electrode conductive agent in the positive electrode film is 1 per 1000 μm. 2 .

[0355] Example 2-2 Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0356] Preparation of positive electrode sheet The positive electrode conductive agent in the positive electrode film includes agglomerated and non-agglomerated positive electrode conductive agents. The number density of agglomerated positive electrode conductive agents in the positive electrode film is 5 per 1000 μm. 2 .

[0357] Example 2-3 Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0358] Preparation of positive electrode sheet The positive electrode film does not contain agglomerated positive electrode conductive agents.

[0359] Examples 2-4 Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0360] Preparation of positive electrode sheet The positive electrode conductive agent in the positive electrode film includes agglomerated and non-agglomerated positive electrode conductive agents. The number density of agglomerated positive electrode conductive agents in the positive electrode film is 8 per 1000 μm. 2 .

[0361] By adjusting the viscosity and dispersibility of the positive electrode slurry, positive electrode films with different agglomerated positive electrode conductive agent number densities can be obtained.

[0362] Table 3 As shown in Table 3, by incorporating an appropriate amount of agglomerated positive electrode conductive agent into the positive electrode film, it is possible to improve the electronic conductivity of the positive electrode, reduce the electron transport resistance and polarization of the positive electrode, and also improve the electrolyte wettability of the positive electrode film, thereby further improving the low-temperature power performance of the battery cell.

[0363] Example 3-1 Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0364] Preparation of negative electrode sheet A first slurry was prepared by mixing the first negative electrode active material, the negative electrode conductive agent acetylene black, the negative electrode binder styrene-butadiene rubber, and the thickener sodium carboxymethyl cellulose in a mass ratio of 96:0.4:2:1.6 with deionized water and stirring thoroughly. A second slurry was prepared by mixing the second negative electrode active material, the negative electrode conductive agent acetylene black, the negative electrode binder styrene-butadiene rubber, and the thickener sodium carboxymethyl cellulose in a mass ratio of 96:0.4:2:1.6 with deionized water and stirring thoroughly. The first and second slurries were simultaneously coated onto the two surfaces of a 6 μm thick copper foil negative electrode current collector at a coating weight ratio (excluding solvent) of 1:1. After drying, cold pressing, and slitting, the negative electrode sheets were obtained. The second slurry was placed closer to the negative electrode current collector, and the first slurry was placed further away. After drying, the first slurry formed the first negative electrode film layer, and the second slurry formed the second negative electrode film layer.

[0365] The first negative electrode active material comprises silicon-carbon material and artificial graphite, with a hard carbon coating layer on the surface of the artificial graphite. The mass ratio of silicon-carbon material to artificial graphite is 6:94, and the mass percentage of Si in the first negative electrode film is 5.4%. The volumetric particle size distribution (Dv50) of the negative electrode active material in the first negative electrode film is 13 μm, and the (Dv90-Dv10) / Dv50 ratio is 1.45. The second negative electrode active material comprises silicon-carbon material and artificial graphite, with a mass ratio of 4:96. The mass percentage of Si in the second negative electrode film is 3.6%. The volumetric particle size distribution (Dv50) of the negative electrode active material in the second negative electrode film is 13 μm, and the (Dv90-Dv10) / Dv50 ratio is 1.43. The mass percentage of Si in the entire negative electrode film is 4.5%.

[0366] The thickness of the negative electrode film layer on one side of the negative electrode current collector is 60 μm.

[0367] Example 3-2 Except for the following differences, the manufacturing process of the battery cells is the same as in Example 3-1.

[0368] Preparation of negative electrode sheet The first negative electrode active material comprises silicon-carbon material and artificial graphite, with a hard carbon coating layer on the surface of the artificial graphite. The mass ratio of silicon-carbon material to artificial graphite is 10:90, and the mass percentage of Si in the first negative electrode film is 9%. The volumetric particle size distribution (Dv50) of the negative electrode active material in the first negative electrode film is 12 μm, and the ratio of (Dv90-Dv10) to Dv50 is 1.5. The second negative electrode active material comprises artificial graphite, and the mass percentage of Si in the second negative electrode film is 0%. The volumetric particle size distribution (Dv50) of the negative electrode active material in the second negative electrode film is 16 μm, and the ratio of (Dv90-Dv10) to Dv50 is 1.2. The mass percentage of Si in the entire negative electrode film is 4.5%.

[0369] Example 3-3 Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0370] Preparation of negative electrode sheet The first negative electrode active material includes artificial graphite with a hard carbon coating layer on its surface. The mass percentage of Si in the first negative electrode film is 0%. The volumetric particle size distribution (Dv50) of the negative electrode active material in the first negative electrode film is 16 μm, and the (Dv90-Dv10) / Dv50 ratio is 1.2. The second negative electrode active material includes silicon-carbon material and artificial graphite, with a mass ratio of silicon-carbon material to artificial graphite of 10:90. The mass percentage of Si in the second negative electrode film is 9%. The volumetric particle size distribution (Dv50) of the negative electrode active material in the second negative electrode film is 12 μm, and the (Dv90-Dv10) / Dv50 ratio is 1.5. The total mass percentage of Si in the entire negative electrode film is 4.5%.

[0371] Table 4 As shown in Table 4, the first negative electrode film is located in the surface region and the second negative electrode film is located in the bottom region. By making the mass ratio of Si element in the surface region high and the bottom region contain no Si element or has a low mass ratio of Si element, it helps to improve the low-temperature power performance of the battery cell.

[0372] Example 4-1 Except for the following differences, the manufacturing process of the battery cells is the same as in Example 3-1.

[0373] Preparation of negative electrode sheet The first negative electrode active material comprises silicon-carbon material and natural graphite in a mass ratio of 6:94, with Si accounting for 5.4% of the total mass. The volumetric particle size distribution (Dv50) of the active material in the first negative electrode layer is 13 μm, and the ratio of (Dv90-Dv10) to Dv50 is 1.45. The second negative electrode active material comprises silicon-carbon material and artificial graphite in a mass ratio of 4:96, with Si accounting for 3.6% of the total mass. The volumetric particle size distribution (Dv50) of the active material in the second negative electrode layer is also 13 μm, and the ratio of (Dv90-Dv10) to Dv50 is 1.43. The total mass percentage of Si in the entire negative electrode layer is 4.5%.

[0374] Table 5 As can be seen from the test results in Table 5, artificial graphite has a dense structure and a more stable surface. Therefore, placing artificial graphite in the first negative electrode film layer helps to better reduce electrolyte side reactions and reduce the irreversible consumption of electrolyte and active lithium, thereby further improving the low-temperature power performance of the battery cell.

[0375] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same essential structure and achieving the same effect as the technical concept within the scope of this disclosure are included in the technical scope of this disclosure. 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, are also included in the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A single battery cell, comprising: shell; as well as An electrode assembly, located within the housing, includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrode. Its features are, The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes a lithium transition metal oxide. The lithium transition metal oxide includes Ni, and the molar percentage of Ni in the transition metal elements of the lithium transition metal oxide is more than 80%. The porosity of the positive electrode film layer is 13%-20%, and the compaction density of the positive electrode film layer is 3.4 g / cm³. 3 -3.7g / cm 3 ; The negative electrode includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes silicon-based materials and carbon-based materials. The silicon-based material includes one or more of elemental silicon, silicon-carbon materials, silicon oxides, silicon nitrides, and silicon alloys. The carbon-based material includes one or more of natural graphite, artificial graphite, soft carbon, hard carbon, and mesophase carbon microspheres. The mass percentage of Si element in the negative electrode film layer is 1%-10%, and the porosity of the negative electrode film layer is 25%-35%. The compaction density of the negative electrode film layer is 1.55 g / cm³. 3 -1.8g / cm 3 .

2. The battery cell according to claim 1, characterized in that, The battery cell satisfies one or more of the following conditions (1) to (5): (1) The porosity of the positive electrode film is 15%-18%; (2) The compaction density of the positive electrode film is 3.5 g / cm³. 3 -3.65g / cm 3 ; (3) The mass percentage of Si element in the negative electrode film is 3%-8%; (4) The porosity of the negative electrode film is 28%-32%; (5) The compaction density of the negative electrode film is 1.65 g / cm³. 3 -1.75g / cm 3 .

3. The battery cell according to claim 1, characterized in that, The thickness of the positive electrode film is 30μm-80μm; and / or, The thickness of the negative electrode film is 35μm-90μm.

4. The battery cell according to claim 1, characterized in that, The volumetric particle size Dv50 of the positive electrode active material is 1μm-7μm; and / or, The particle size distribution (Dv90-Dv10) / Dv50 of the positive electrode active material is 1-1.5; and / or, The volumetric particle size Dv50 of the negative electrode active material is 10μm-20μm; and / or, The particle size distribution (Dv90-Dv10) / Dv50 of the negative electrode active material is 1.2-2.

5.

5. The battery cell according to claim 1, characterized in that, The lithium transition metal oxide includes single-crystal lithium transition metal oxide, and the total area of ​​the single-crystal lithium transition metal oxide is 60%-100% of the total area of ​​the positive electrode active material.

6. The battery cell according to claim 1, characterized in that, The lithium transition metal oxide includes Ni and Co elements, and the Co content in the surface region of the lithium transition metal oxide is higher than the Co content in the core region of the lithium transition metal oxide; or, The lithium transition metal oxide includes Ni and Mn elements, and the Mn content in the surface region of the lithium transition metal oxide is lower than the Mn content in the core region of the lithium transition metal oxide; or, The lithium transition metal oxide includes Ni, Co, and Mn elements, with a higher Co content in the surface region than in the core region, and a lower Mn content in the surface region than in the core region. The surface region of the lithium transition metal oxide is a region extending 100 nm radially inward from the outermost surface of the particle, and the core region of the lithium transition metal oxide is a region extending 300 nm radially outward from the center of the particle.

7. The battery cell according to claim 1, characterized in that, The lithium transition metal oxide includes Ni and doping elements, wherein the doping elements include cation doping elements and / or anion doping elements, wherein the cation doping elements include one or more of Al, Y, Zr, Zn, Cr, Mg, V, Ti and B, and the anion doping elements include one or more of N, F, S and Cl.

8. The battery cell according to claim 1, characterized in that, The positive electrode film layer includes a positive electrode conductive agent, and the mass percentage of the positive electrode conductive agent in the positive electrode film layer is 0.5%-2.5%.

9. The battery cell according to claim 8, characterized in that, The positive electrode conductive agent includes one or more of carbon nanotubes, carbon black, acetylene black, carbon fiber, and graphene, and the carbon nanotubes include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

10. The battery cell according to claim 8, characterized in that, The positive electrode conductive agent includes carbon nanotubes, and at least a portion of the carbon nanotubes are located on the surface of the positive electrode active material.

11. The battery cell according to claim 8, characterized in that, The positive electrode conductive agent includes an agglomerated positive electrode conductive agent, and the number density of the agglomerated positive electrode conductive agent in the positive electrode film layer is 1 to 5 per 1000 μm. 2 .

12. The battery cell according to claim 11, characterized in that, The agglomerated positive electrode conductive agent has a number density of 1 to 3 per 1000 μm in the positive electrode film. 2 .

13. The battery cell according to claim 11, characterized in that, The agglomerated positive electrode conductive agent satisfies the following condition: the maximum distance between any two points on the perimeter is greater than or equal to 2 μm; and / or, The porosity of the agglomerated positive electrode conductive agent is 30%-65%; and / or, The agglomerated positive electrode conductive agent includes carbon nanotubes.

14. The battery cell according to claim 13, characterized in that, The agglomerated positive electrode conductive agent also includes one or more of carbon black and acetylene black.

15. The battery cell according to claim 1, characterized in that, The negative electrode active material satisfies one or more of the following conditions (1) to (2): (1) The average particle size of the silicon-based material is 2μm-15μm; (2) The average particle size of the carbon-based material is 11μm-21μm.

16. The battery cell according to any one of claims 1-15, characterized in that, The negative electrode film layer includes a first negative electrode film layer away from the negative electrode current collector and a second negative electrode film layer close to the negative electrode current collector. The first negative electrode film layer includes a first negative electrode active material, and the second negative electrode film layer includes a second negative electrode active material. The first negative electrode active material includes a first carbon-based material and a first silicon-based material; The second negative electrode active material includes a second carbon-based material, and the second negative electrode film does not contain Si element; or, the second negative electrode active material includes a second carbon-based material and a second silicon-based material, and the mass percentage of Si element in the first negative electrode film is greater than the mass percentage of Si element in the second negative electrode film.

17. The battery cell according to claim 16, characterized in that, The mass percentage of Si in the first negative electrode film is 2%-15%; and / or, The mass percentage of Si element in the second negative electrode film is 0%-10%.

18. The battery cell according to claim 17, characterized in that, The mass percentage of Si in the first negative electrode film is 2%-10%; and / or, The mass percentage of Si element in the second negative electrode film is 0%-8%.

19. The battery cell according to claim 16, characterized in that, The volume distribution particle size Dv50 of the first negative electrode active material is smaller than that of the second negative electrode active material.

20. The battery cell according to claim 16, characterized in that, The negative electrode film layer satisfies one or more of the following conditions (1) to (8): (1) The first carbon-based material includes one or more of natural graphite and artificial graphite; (2) The second carbon-based material includes one or more of natural graphite and artificial graphite; (3) The average particle size of the first carbon-based material is 11 μm-21 μm; (4) The average particle size of the second carbon-based material is 11 μm-21 μm; (5) The first silicon-based material includes one or more of silicon-carbon materials and pre-magnesium silicon oxide; (6) The second negative electrode active material includes a second silicon-based material, which includes one or more of silicon-carbon materials and pre-magnesium silicon oxide; (7) The average particle size of the first silicon-based material is 2μm-15μm; (8) The second negative electrode active material includes a second silicon-based material, wherein the average particle size of the second silicon-based material is 2μm-15μm.

21. The battery cell according to claim 20, characterized in that, The first carbon-based material includes artificial graphite, and the surface of the artificial graphite has a carbon coating layer, which includes soft carbon and / or hard carbon.

22. The battery cell according to claim 1, characterized in that, The battery cell also includes an electrolyte, which comprises an organic solvent and an electrolyte salt, wherein the concentration of the electrolyte salt is 0.9 mol / L to 1.2 mol / L.

23. The battery cell according to claim 22, characterized in that, The organic solvent includes ethylene carbonate and ethyl methyl carbonate, wherein the ethyl methyl carbonate accounts for more than or equal to 55% and less than 100% of the organic solvent by mass.

24. The battery cell according to claim 23, characterized in that, The organic solvent also includes one or more of the following: propylene carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

25. The battery cell according to claim 22, characterized in that, The electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

26. The battery cell according to claim 22, characterized in that, The electrolyte also includes additives, which include one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate.

27. The battery cell according to claim 1, characterized in that, The isolation membrane includes a porous base membrane and a porous coating located on at least one side of the porous base membrane. The porous coating includes filler particles, which include one or more of inorganic particles, organic particles, and organic-inorganic composite particles.

28. The battery cell according to claim 27, characterized in that, The porous coating also includes polymer binder particles, the volume distribution particle size Dv50 of which is greater than that of the filler particles.

29. The battery cell according to claim 27, characterized in that, The thickness of the porous coating is 0.5 μm-2 μm; and / or, The thickness of the porous base film is 5μm-10μm; and / or, The porosity of the isolation membrane is 35%-55%.

30. The battery cell according to claim 1, characterized in that, The battery cell is a pouch cell, and the outer casing 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 part. The pouch cell also includes electrode leads that pass between the two packaging films and are electrically connected to the electrode assembly.

31. The battery cell according to claim 30, 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.

32. The battery cell according to claim 1, characterized in that, The battery cell is a hard-shell battery cell, and the outer shell is square in shape and made of metal.

33. A battery device, characterized in that, It includes the battery cells described in any one of claims 1-32.

34. The battery device according to claim 33, characterized in that, The battery device includes: The housing includes a support plate and a frame surrounding the outer periphery of the support plate, wherein the support plate is fixedly connected to the frame. The battery cells are multiple pouch cells, which are stacked in a first direction and housed in the housing. The surface of each battery cell includes a first surface and a second surface, the area of ​​the first surface being larger than the area of ​​the second surface. The first surfaces of the multiple battery cells are arranged opposite to each other along the first direction, and the support plate is arranged opposite to the second surfaces of the multiple battery cells along a second direction. The housing is provided with at least one connecting beam extending along a third direction. The connecting beam is fixedly connected to the support plate and / or the frame. At least one battery cell abuts against the connecting beam along the first direction. The first direction, the second direction, and the third direction are perpendicular to each other.

35. The battery device according to claim 34, characterized in that, The battery device also includes: A thermal management component is disposed between the support plate and the battery cell, for regulating the temperature of the battery cell; A fixing adhesive is disposed between the thermal management component and the battery cell to fix the battery cell to the thermal management component.

36. The battery device according to claim 35, characterized in that, The adhesive is directly attached to the outer casing of the battery cell.

37. The battery device according to claim 35, 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.

38. The battery device according to claim 34, characterized in that, Each battery cell has a rated capacity of 100Ah or greater.

39. An electrical appliance, characterized in that, Includes the battery cell as described in any one of claims 1-32 or the battery device as described in any one of claims 33-38.

Images