Battery cell, battery device and power-consuming device

Abstract

Battery cell, comprising the following: a case; and an electrode assembly located in the housing, wherein the electrode assembly comprises a cathode foil, an anode foil and a separator, the separator being located between the cathode foil and the anode foil, where, the cathode foil comprises a cathode collector and a cathode film layer located on at least one side of the cathode collector, the cathode film layer comprising an active cathode material, the active cathode material comprising a lithium transition metal oxide, the lithium transition metal oxide comprising a nickel element, the molar fraction of the nickel element in the transition metal element of the lithium transition metal oxide being more than 80%, the lithium transition metal oxide comprising a lithium transition metal oxide with a single-crystal morphology, the total area of ​​the lithium transition metal oxide with the single-crystal morphology being 60% to 100% of the total area of ​​the active cathode material, and the porosity of the cathode film layer being 13% to 20%; wherein the anode foil comprises an anode collector and an anode film layer located on at least one side of the anode collector, wherein the anode film layer comprises an active anode material, the active anode material comprising a silicon-based material and a carbon-based material, wherein the mass fraction of the Si element in the anode film layer is 1% to 10%.

Description

Technical field

[0001] The present application relates to a battery cell, a battery device and a power-consuming device. State of the art

[0002] With the widespread adoption of lithium-ion battery cells in recent years, the energy density of existing lithium-ion battery cells that use graphite as the active anode material can no longer meet the growing technical demands. Furthermore, graphite tends to precipitate lithium at low temperatures, which also limits the use of lithium-ion battery cells. Registration content

[0003] The present application provides a battery cell, a battery device and a power-consuming device, wherein the battery cell exhibits both high energy density and good cycle performance at low temperature.

[0004] According to a first aspect, the present application provides for a battery cell comprising a housing and an electrode assembly, wherein the electrode assembly is located in the housing, wherein the electrode assembly comprises a cathode foil, an anode foil and a separator, wherein the separator is located between the cathode foil and the anode foil, wherein the cathode foil comprises a cathode collector and a cathode film layer located on at least one side of the cathode collector, wherein the cathode film layer comprises an active cathode material, wherein the active cathode material comprises a lithium transition metal oxide, wherein the lithium transition metal oxide comprises a nickel element, wherein the molar fraction of the nickel element in the transition metal element of the lithium transition metal oxide is more than 80%, and wherein the lithium transition metal oxide comprises a lithium transition metal oxide with a single-crystal morphology.wherein the total area of ​​the lithium transition metal oxide with single-crystal morphology is 60% to 100% of the total area of ​​the active cathode material, wherein the porosity of the cathode film layer is 13% to 20%; wherein the anode foil comprises an anode collector and an anode film layer located on at least one side of the anode collector, the anode film layer comprising an active anode material, the active anode material comprising a silicon-based material and a carbon-based material, wherein the mass fraction of the silicon element in the anode film layer is 1% to 10%. The present application enables the battery cell to combine high energy density and good cycle performance at low temperatures by matching the cathode and anode components of the battery cell.

[0005] In some embodiments, the mass fraction of the Si element in the anode film layer is 3% to 8%.

[0006] In some embodiments, the porosity of the cathode film layer is 15% to 18%.

[0007] In some embodiments, the porosity of the anode film layer is 25% to 35%.

[0008] In some embodiments, the density of the cathode film layer is 3.4 g / cm³. 3 up to 3.7 g / cm³ 3 .

[0009] In some embodiments, the compression density of the anode film layer is 1.55 g / cm³. 3 up to 1.8 g / cm³ 3 .

[0010] In some embodiments, the volume-distributed particle size Dv50 of the active cathode material is 1 µm to 7 µm.

[0011] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the active cathode material is 1 to 1.5.

[0012] In some embodiments, the volume-distributed particle size Dv50 of the active anode material is 10 µm to 20 µm.

[0013] In some embodiments, the lithium transition metal oxide comprises a nickel element and a cobalt element, wherein the cobalt content in a surface region of the lithium transition metal oxide is lower than the cobalt content in a core region of the lithium transition metal oxide; or the lithium transition metal oxide comprises a nickel element and a manganese element, wherein the manganese content in the surface region of the lithium transition metal oxide is lower than the manganese content in the core region of the lithium transition metal oxide;or the lithium transition metal oxide comprises a nickel element, a cobalt element, and a cobalt element, wherein the cobalt content in a surface region of the lithium transition metal oxide is greater than the cobalt content in a core region of the lithium transition metal oxide, and wherein the manganese content in a surface region of the lithium transition metal oxide is less than the manganese content in a core region of the lithium transition metal oxide. The surface region of the lithium transition metal oxide is a region extending radially inward from the outermost surface of the particle for 100 nm, and the core region of the lithium transition metal oxide is a region extending radially outward from the center of the particle for 300 nm.

[0014] In some embodiments, the lithium transition metal oxide comprises a Ni element and a dopant element, wherein the dopant element comprises a cationic dopant element and / or an anionic dopant element, wherein the cationic dopant element comprises one or more of the elements Al, Y, Zr, Zn, Cr, Mg, V, Ti and B, and wherein the anionic dopant element comprises one or more of the elements N, F, S and Cl.

[0015] The above-mentioned dopants can increase the structural stability of the lithium transition metal oxide and reduce its volume change during charging and discharging. This reduces the leaching of transition metal ions and improves the chemical and cycle stability of the battery cell; furthermore, it can increase the thermal stability of the lithium transition metal oxides and reduce the risk of thermal runaway in the battery cell.

[0016] In some embodiments, the cathode film layer comprises a conductive cathode medium, wherein the mass fraction of the conductive cathode medium in the cathode film layer is 0.5% to 2.5%.

[0017] In some embodiments, the conductive cathode medium comprises one or more carbon nanotubes, carbon black, acetylene black, carbon fibers, graphene, wherein the carbon nanotubes comprise one or more single-walled carbon nanotubes, thin-walled carbon nanotubes, multi-walled carbon nanotubes.

[0018] In some embodiments, the conductive cathode material comprises carbon nanotubes, wherein at least a portion of the carbon nanotubes are located on the surface of the active cathode material.

[0019] In some embodiments, the conductive cathode medium comprises an agglomerated conductive cathode medium, wherein the number density of the agglomerated conductive cathode medium in the cathode film layer is 1 to 5 per 1000 µm. 2 , optionally 2 to 4 per 1000 µm 2 This improves the electronic conductivity of the cathode, reduces the electron transfer resistance and cathode polarization, and enhances the wettability of the electrolyte solution in the cathode film layer, which in turn further improves the cycle performance of the battery cell at low temperatures. In some embodiments, the maximum distance between any two points on the circumference of the agglomerated conductive cathode medium is greater than or equal to 2 µm.

[0020] In some embodiments, the porosity of the agglomerated conductive cathode medium is 30% to 65%.

[0021] In some embodiments, the agglomerated conductive cathode material comprises carbon nanotubes. In some embodiments, the agglomerated conductive cathode material further comprises one or more carbon black and acetylene black.

[0022] In some embodiments, the silicon-based material comprises one or more of monomeric silicon, silicon-carbon material, silicon oxide, silicon nitride, or silicon alloy material.

[0023] In some embodiments, the carbon-based material comprises one or more of natural graphite, artificial graphite, soft carbon, hard carbon, and microspheres of interphase carbon.

[0024] In some embodiments, the average particle size of the silicon-based material is 2 µm to 15 µm.

[0025] In some embodiments, the average particle size of the carbon-based material is 11 µm to 21 µm.

[0026] In some embodiments, the anode film layer comprises a first anode film layer facing away from the anode collector and a second anode film layer facing the anode collector, wherein the first anode film layer comprises a first active anode material, and wherein the second anode film layer comprises a second active anode material; wherein the first active anode material comprises a first carbon-based material and a first silicon-based material; wherein the second active anode material comprises a second carbon-based material, and wherein the second anode film layer is free of silicon elements, or wherein the second active anode material comprises a second carbon-based material and a second silicon-based material, and wherein the mass fraction of the silicon element in the first anode film layer is greater than the mass fraction of the silicon element in the second anode film layer.

[0027] The first anode film layer is located in the surface region, and the second anode film layer is located in the bottom region. A high crude mass fraction of silicon in the surface region helps to reduce the problem of lithium precipitation from the anode at low temperatures. The bottom region contains no silicon or a low mass fraction of silicon, which can help to reduce damage to the overall conductive network of the anode film layer due to the volume expansion of the silicon-based material in the bottom region, thus helping to improve the low-temperature cycle performance of the battery cell.

[0028] In some embodiments, the mass fraction of the Si element in the first anode film layer is 2% to 15%, optionally 2% to 10%.

[0029] In some embodiments, the mass fraction of the Si element in the second anode film layer is 0% to 10%, optionally 0.5% to 8%.

[0030] In some embodiments, the volume-distributed particle size Dv50 of the first active anode material is smaller than the volume-distributed particle size Dv50 of the second active anode material. The first active anode material is located in the surface region, and the second active anode material is located in the bottom region, with the volume-distributed particle size Dv50 of the first active anode material being smaller than the volume-distributed particle size Dv50 of the second active anode material. The diffusion path of the lithium ions from the first active anode material in the surface region is short, the diffusion time of the lithium ions from the surface to the interior is short, and the lithium ions are more likely to be embedded and rapidly displaced.In this way, the overall ion transfer kinetics of the anode film layer can be improved, anode polarization reduced, and the low-temperature cycle performance and low-temperature multiplication performance of the battery cell improved.

[0031] In some embodiments, the first carbon-based material comprises one or more natural graphite or synthetic graphite.

[0032] In some embodiments, the second carbon-based material comprises one or more natural and synthetic graphites.

[0033] In some embodiments, the average particle size of the first carbon-based material is 11 µm to 21 µm.

[0034] In some embodiments, the average particle size of the second carbon-based material is 11 µm to 21 µm.

[0035] In some embodiments, the first silicon-based material comprises one or more silicon-carbon materials, a pre-magnesium-silicon-oxygen material.

[0036] In some embodiments, the second active anode material comprises a second silicon-based material, wherein the second silicon-based material comprises one or more silicon-carbon materials, pre-magnesium-silicon-oxygen materials.

[0037] In some embodiments, the average particle size of the first silicon-based material is 2 µm to 15 µm.

[0038] In some embodiments, the second active anode material comprises a second silicon-based material, wherein the average particle size of the second silicon-based material is 2 µm to 15 µm.

[0039] In some embodiments, the battery cell further comprises an electrolyte solution, wherein the electrolyte solution 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.

[0040] In some embodiments, the organic solvent comprises vinyl carbonate and methyl ethyl carbonate, wherein the mass fraction of the methyl ethyl carbonate in the organic solvent is greater than or equal to 55% and less than 100%.

[0041] In some embodiments, the organic solvent further comprises one or more of propylidene carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylenepropylene carbonate, ethylenepropylene carbonate, butylidene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0042] In some embodiments, the electrolyte salt comprises 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 borate dioxylic acid (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxylic acid phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). In some embodiments, the electrolyte solution further comprises an additive, wherein the additive comprises one or more of fluorinated vinyl carbonate, vinylidene carbonate, 1,3-propanesulfonic acid lactone, and vinyl sulfate.

[0043] In some embodiments, the separator comprises a porous base film and a porous coating located on at least one side of the porous base film, wherein the porous coating comprises filler particles, the filler particles comprising one or more of inorganic particles, organic particles, or organic-inorganic composite particles. In some embodiments, the porous coating further comprises polymer binder particles, wherein the volume-distributed particle size Dv50 of the polymer binder particles is larger than the volume-distributed particle size Dv50 of the filler particles.

[0044] In some embodiments, the thickness of the porous coating is 0.5 µm to 2 µm.

[0045] In some embodiments, the thickness of the porous coating is 5 µm to 10 µm.

[0046] In some embodiments, the porosity of the separator is 35% to 55%.

[0047] In some embodiments, the battery cell is a soft-pack battery cell, wherein the housing comprises two packaging films, the electrode assembly being located between the two packaging films, the edges of the two packaging films being connected to each other and forming a sealing section; wherein the soft-pack battery cell further comprises an electrode conductor, the electrode conductor running between the two packaging films and being electrically connected to the electrode assembly.

[0048] In some embodiments, the packaging film comprises an insulating protective layer, a metal layer and an insulating connecting layer, wherein the insulating connecting layer is provided on a surface of the metal layer facing the electrode assembly, while the insulating protective layer is provided on a surface of the metal layer facing away from the electrode assembly.

[0049] In some embodiments, the battery cell is a hard-case battery cell, wherein the case has a square shape and is made of metal.

[0050] According to a second aspect, the present application provides a battery device comprising a plurality of the battery cell according to the first aspect of the present application.

[0051] In some embodiments, the battery device includes the following: a box comprising a support plate and a frame provided around the circumference of the support plate, the support plate being firmly connected to the frame; a plurality of battery cells, wherein the battery cell is a soft-pack battery cell, wherein the plurality of battery cells is stacked in the first direction and received in the box, wherein the surface of the battery cell comprises a first surface and a second surface, wherein the area of ​​the first surface is larger than the area of ​​the second surface, wherein the first surfaces of a plurality of battery cells are arranged opposite each other along the first direction, wherein the support plate is arranged opposite the second surfaces of a plurality of battery cells along the second direction; wherein at least one connecting beam is provided in the box which extends in a third direction, wherein the connecting beam is firmly connected to the support plate and / or the frame; wherein at least one of the battery cells rests against the connecting beam along the first direction, wherein the first direction, the second direction and the third direction are perpendicular to each other.

[0052] In some embodiments, the battery device further comprises a thermal management component and a fastening adhesive.

[0053] The thermal management component is positioned between the support plate and the battery cell to regulate the temperature of the battery cell; the fastening adhesive is positioned between the thermal management component and the battery cell to secure the battery cell to the thermal management component.

[0054] In some embodiments, the adhesive is directly bonded to the battery cell housing.

[0055] In some embodiments, the battery device further comprises a receiving housing, wherein the receiving housing accommodates at least one of the battery cells, and wherein the fastening adhesive is directly bonded to a housing wall of the receiving housing.

[0056] In some embodiments, the nominal capacity of each battery cell is greater than or equal to 100 Ah.

[0057] According to a third aspect, the present application provides a power-consuming device comprising the battery cell according to the first aspect of the present application or the battery device according to the second aspect of the present application. Description of the drawings

[0058] To better illustrate the technical solutions of the embodiment of the present application, the attached drawings, which must be used for the embodiments of the present application, are briefly described below. Of course, the attached drawings described below are only some of the embodiments of the present application, and other attached drawings can be derived from the attached drawings by a person with normal technical knowledge without creative effort. Fig. Figure 1 shows a schematic representation of a battery device in an exemplary embodiment. Fig. Figure 2 shows a schematic decomposition representation of the battery device in an exemplary embodiment. Fig. Figure 3 shows a partially enlarged view of the battery device of Fig. 2. Fig.Figure 4 shows a schematic representation of a power-consuming device in some embodiments of the present application. Fig. Figure 5 shows a schematic decomposition representation of a soft-pack battery cell in an exemplary embodiment. Specific embodiments

[0059] The following sections disclose in detail embodiments of the battery cell, the battery device, and the power-consuming device of the present application with corresponding reference to the accompanying drawings. However, there will be instances where an unnecessarily detailed description is omitted. For example, detailed descriptions of things that are already well known and repeated descriptions of the same structure will be left out. This is to prevent the following description from becoming unnecessarily long and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description serve to ensure the complete understanding of the present application by those skilled in the art and are not intended to limit the subject matter specified in the claims.

[0060] The “range” disclosed in this application is defined in terms of a lower bound and an upper bound, whereby a particular range is defined by selecting a lower bound and an upper bound that establish the limits of the respective range. The ranges defined in this way may include or exclude end values ​​and may be combined in any way; that is, any lower bound can be combined with any upper bound to form a range. For example, if a range of 60 to 120 and 80 to 110 is specified for a particular parameter, a range of 60 to 110 and 80 to 120 is also to be expected. Furthermore, if the minimum values ​​1 and 2 and the maximum values ​​3, 4, and 5 are specified, the following ranges may be expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.Unless otherwise specified, the range of values ​​“ab” in this application denotes any combination of real numbers between a and b, where both a and b are real numbers. For example, the range of values ​​“0-5” means that all real numbers between 0 and 5 are listed here, and 0-5 is simply a shorthand representation of the combination of these values. Furthermore, stating that a parameter is an integer ≥ 2 is equivalent to stating that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0061] Unless expressly stated otherwise, all embodiments and optional embodiments of the present application may be combined to form new technical solutions, and such a technical solution should be considered to be covered by the disclosure of the present application.

[0062] Unless expressly stated otherwise, all technical features of the present application, as well as optional technical features, may be combined to form a new technical solution, and such a technical solution should be considered to be covered by the disclosure of the present application.

[0063] Unless expressly stated otherwise, all steps of the present application may be carried out sequentially or randomly, preferably sequentially. For example, the phrase "the method includes steps (a) and (b)" means that the method may include steps (a) and (b) carried out one after the other, or that it may include steps (b) and (a) carried out one after the other. The statement that the method may also include step (c) means, for example, that step (c) may be added to the method in any order; for instance, 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).

[0064] The terms “first”, “second”, etc. in the present application or in the drawings mentioned above are used to distinguish between different objects and not to describe a particular order or priority, unless otherwise stated.

[0065] In the present application, the terms "plural" and "multiple" refer to two or more.

[0066] In the description of embodiments of the present application, the first feature “above” or “below” the second feature can refer to direct contact between the first and second features or indirect contact between the first and second features via an intermediate medium, unless otherwise expressly stated. Furthermore, the first feature “above,” “above,” and “above” the second feature can mean that the first feature is located directly or obliquely above the second feature, or simply that the first feature is horizontally higher than the second feature. The first feature “below” and “below” the second feature can mean that the first feature is located directly or obliquely below the second feature, or simply that the first feature is horizontally lower than the second feature.

[0067] Unless otherwise specified, the test temperature for each parameter in this application is 25°C.

[0068] The battery cell referred to in the embodiments of the present application is alone capable of performing the charging and discharging function.

[0069] The battery cell referred to in the embodiments of the present application can be a soft-pack battery cell or a hard-case battery cell.

[0070] The battery apparatus in the embodiments of the present application can comprise one or more battery cell assemblies to provide a voltage and capacity. The battery cell assembly can comprise a plurality of battery cells, wherein the plurality of battery cells are connected by a converging element in series, parallel, or in a mixed configuration.

[0071] In some embodiments, a battery cell assembly is typically formed by arranging several battery cells.

[0072] For example, the battery cell assembly can be a battery module, wherein the battery module comprises a plurality of battery cells arranged and secured to form an independent module. For example, the battery module can be formed by bonding the multiple battery cells together.

[0073] In some embodiments, the battery device can be a battery pack, wherein the battery pack comprises a box and one or more battery cell assemblies, the battery cell assemblies being contained in the box.

[0074] For example, the battery cell assembly can be a battery module; the battery cell assembly can be accommodated in the box by securing the battery module in the box.

[0075] For example, the battery cell assembly can also be accommodated in the box by attaching a large number of battery cells directly inside the box.

[0076] For example, the enclosure can comprise a first enclosure and a second enclosure. The first and second enclosures are attached to each other in such a way that an enclosed space is formed inside the enclosure, which houses the battery cell assembly. "Enclosed" here means covered or sealed, and this space can be either sealed or unsealed. The first enclosure can be a top cover or a bottom plate.

[0077] For example, the box can comprise a top cover, a frame, and a base plate. The top cover and the base plate are each connected to the frame, creating an enclosed space inside the box to house the battery cell assembly.

[0078] In some embodiments, the box can be part of the vehicle's chassis structure. For example, parts of the box can be at least part of the vehicle's floor, or parts of the box can be at least part of a cross member and a longitudinal member of the vehicle.

[0079] Fig. Figure 1 shows a schematic representation of a battery device 100 in an exemplary embodiment. Fig. Figure 2 shows a schematic disassembly representation of the battery device 100 in an exemplary embodiment. Fig. Figure 3 shows a partially enlarged representation of the battery device 100 of Fig.2.

[0080] As in Fig. 1 to Fig. As shown in Figure 3, the battery device 100 comprises a box 10 and a plurality of battery cells 22. The box 10 comprises a first box 11 and a second box 12, wherein the first box 11 and the second box 12 snap together to form an enclosed space in the box 10 to accommodate the battery cells 22.

[0081] As in Fig. As shown in Figure 2, the first box 11 is an upper cover, and the second box 12 comprises a support plate 121 and a frame 122 which is provided around the perimeter of the support plate 121, and the support plate 121 is firmly connected to the frame 122.

[0082] The battery cell 22 is a soft-pack battery cell. A plurality of the battery cells 22 are stacked in a first direction X and received in the box 10, wherein the surface of the battery cell 22 comprises 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 plurality of battery cells 22 being arranged opposite each other along the third direction X, and the support plate 121 being arranged opposite the second surfaces of the plurality of battery cells 22 along a second direction Z.

[0083] Optionally, the nominal capacity of each battery cell 22 is greater than or equal to 100 Ah.

[0084] As in Fig.As shown in Figure 1, at least one connecting beam 13 is provided in the box 10, which extends in a third direction Y, wherein the connecting beam 13 is firmly connected to the support plate 121 and / or the frame 122; wherein at least one of the battery cells 22 rests against the connecting beam 13 along the first direction X.

[0085] The first direction X, the second direction Z, and the third direction Y are perpendicular to each other. In some embodiments, the battery device 100 further comprises a thermal management component 30, wherein the thermal management component 30 is provided between the support plate 121 and the battery cell 22 to regulate the temperature of the battery cell 22; the thermal management component 30 is arranged opposite the second surface of a plurality of battery cells 22 along the second direction Z.

[0086] In some embodiments, the battery device 100 further comprises a receiving housing 23, wherein the receiving housing 23 receives at least one of the battery cells 22. The receiving housing 23, together with the battery cell 22 received therein, forms the battery cell assembly 20.

[0087] In some embodiments, the battery device 100 further comprises a fastening adhesive 40, wherein the fastening adhesive 40 is provided between the thermal management component 30 and the battery cell 22 in order to fasten the battery cell 22 to the thermal management component 30.

[0088] For example, the fastening adhesive 40 can be directly bonded to the housing of the battery cell 22.

[0089] For example, the fastening adhesive 40 can be directly bonded to the housing wall of the receiving housing 23.

[0090] The technical solutions described in the embodiments of this application are all applicable to a wide variety of power-consuming devices that use battery cells or battery devices, for example, 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., but are not limited to these. Battery cells and battery devices are used for storing or providing electrical energy.

[0091] Fig. Figure 4 shows a schematic representation of the power-consuming device as an example. The power-consuming device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.

[0092] Graphite is a carbon-based active anode material commonly used in lithium-ion batteries. The embedded lithium potential of graphite is approximately 0.1 V (vs. Li / Li). + ), which is close to the precipitation potential of lithium (0V vs. Li / Li +As a result, lithium can easily precipitate onto the graphite surface during low-temperature charging. The precipitated lithium reacts with the electrolyte solution, leading to a reduction in active lithium, a decrease in battery cell capacity, and a deterioration in low-temperature cycle performance.Furthermore, the viscosity of the electrolyte solution increases, the ionic conductivity decreases, and the electrochemical reaction rate within the battery cell slows down, leading to a further decrease in the battery cell's capacity and cycle performance at low temperatures; in addition, the migration rate of lithium ions in the electrolyte solution slows down at low temperatures, and some lithium ions may not be able to be embedded in the graphite in time during charging, which can lead to precipitation on the graphite surface and thus also to a decrease in the battery cell's capacity and cycle performance at low temperatures.In view of this, the embodiments of the present application provide a battery cell, a battery device and a power-consuming device comprising the battery cell, by matching the cathode and the anode of the battery cell to each other, so that the battery cell can have both a high energy density and good cycle performance at low temperature.

[0093] The battery cell provided in the embodiments of the present application can be a lithium-ion battery.

[0094] The battery cell in the embodiments of the present application comprises a housing and an electrode assembly, wherein the electrode assembly is located in the housing, wherein the electrode assembly comprises a cathode foil, an anode foil and a separator, wherein the separator is located between the cathode foil and the anode foil.

[0095] The cathode foil comprises a cathode collector and a cathode film layer located on at least one side of the cathode collector, wherein the cathode film layer comprises an active cathode material, the active cathode material comprising a lithium transition metal oxide, the lithium transition metal oxide comprising a nickel element, the molar fraction of the nickel element in the transition metal element of the lithium transition metal oxide being more than 80%, the lithium transition metal oxide comprising a lithium transition metal oxide with a single-crystal morphology, the total area of ​​the lithium transition metal oxide with the single-crystal morphology being 60% to 100% of the total area of ​​the active cathode material, and the porosity of the cathode film layer being 13% to 20%.

[0096] The anode foil comprises an anode collector and an anode film layer located on at least one side of the anode collector, wherein the anode film layer comprises an active anode material, the active anode material comprising a silicon-based material and a carbon-based material, wherein the mass fraction of the Si element in the anode film layer is 1% to 10%.

[0097] The active cathode material in the present application comprises a lithium transition metal oxide with a high nickel content, wherein the molar fraction of nickel in the transition metal element of the lithium transition metal oxide is more than 80%. The higher the nickel content of the lithium transition metal oxide, the higher its theoretical specific capacity, thereby improving the energy density of the battery cell. However, the higher the nickel content in the lithium transition metal oxide, the more unstable its lattice structure, the higher its reactivity with the electrolyte solution, the more side reactions with the electrolyte solution, the greater the gas evolution during the cycling process, the greater the irreversible consumption of active lithium, and the accelerated decline in the cycle capacity maintenance rate of the battery cell.By comprising a lithium transition metal oxide with a single-crystal morphology in the present application, and by ensuring that the total area of ​​the lithium transition metal oxide with a single-crystal morphology comprises 60% to 100% of the total area of ​​the active cathode material, the present application enables the lithium transition metal oxide with a high Ni content to exhibit high structural stability, reduces side reactions with the electrolyte solution, reduces the amount of gas evolution during the cycling process, and reduces the irreversible consumption of the active lithium. This allows the advantage of the high capacity of the lithium transition metal oxide with a high Ni content to be fully utilized, so that the battery cell exhibits both high energy density and good cycle performance at low temperatures.

[0098] The silicon-based material is an active anode material that provides at least silicon. The silicon-based material can also provide other elements, such as carbon, or, of course, only silicon. The carbon-based material is also an active anode material that provides at least carbon. Compared to the carbon-based material, the silicon-based material has a higher theoretical specific capacity and a higher potential for embedded lithium, thus reducing the risk of lithium precipitation from the anode in low-temperature environments. Accordingly, the active anode material in the present application comprises a silicon-based material and a carbon-based material, which contributes to improving the energy density and cycle performance of the battery cell.

[0099] Compared to carbon-based materials, silicon-based materials typically have significant problems with volume expansion, resulting in large volume expansion of the anode foil. This expansion compresses the separator and forces out the electrolyte solution stored in its pores. Simultaneously, the expansion of the anode foil causes the separator and the cathode film layer to adhere more closely to each other. At this point, the separator generates strong capillary action on the electrolyte solution in the pores of the cathode film layer, resulting in poor wettability of the electrolyte solution within the cathode film layer. This reduces the electrolyte solution concentration, particularly in the bottom region near the cathode collector, or even interrupts the flow of the electrolyte solution along the thickness of the cathode film layer.In this case, the embedding / elimination of lithium ions from the active cathode material becomes difficult in a region of the cathode film layer where the electrolyte solution is lacking (e.g., a bottom region, a surface region, or an intermediate region). Furthermore, the embedding / elimination of lithium ions in the cathode during the charging / discharging process occurs primarily in the region of the cathode film layer where the electrolyte solution has good wettability. This leads to the problem of excessive lithium embedding and elimination in the region with good electrolyte solution wettability of the cathode film layer, which degrades the structural stability of the active cathode material in this region and causes particle fragmentation, while simultaneously rapidly reducing the cycle capacity of the battery cell.

[0100] In the present application, the mass fraction of the silicon element in the anode film layer is between 1% and 10%. Within this range, not only can the energy density of the battery cell be improved and the risk of lithium precipitation problems on the anode in a low-temperature environment be reduced, but it also enables the anode film to have a low volumetric expansion and reduces the adverse effects on the wettability of the electrolyte solution for the separator and the cathode film.The porosity of the cathode film layer in the present application is 13% to 20%. This high porosity improves the wettability of the electrolyte solution and the liquid retention of the cathode film layer, resulting in lower resistance to lithium ion transfer at the cathode. This improves the cycle performance of the battery cell at low temperatures, but is detrimental to increasing the energy density of the battery cell. The high porosity of the cathode film layer improves the wettability of the electrolyte solution in low-temperature environments and reduces the resistance to lithium ion transfer at the cathode. At the same time, the porosity of the cathode film layer should not be too high, as this leads to a reduction in the contact area between the particles of the active anode material, lengthens the electron transfer path in the cathode, and increases the internal resistance of the battery cell.Accordingly, the porosity of the cathode film layer is 13% to 20%, resulting in a battery cell with both high energy density and good cycle performance at low temperatures. Furthermore, the lithium transition metal oxide in the present application comprises a lithium transition metal oxide with a single-crystal morphology, and the total area of ​​the lithium transition metal oxide with the single-crystal morphology is 60% to 100% of the total area of ​​the active cathode material. The lithium transition metal oxide with the single-crystal morphology exhibits no or only a few grain boundaries, which are less prone to grain boundary fragmentation during cyclic charging and discharging and are more resistant to overcharging and over-discharging due to their higher structural stability and particle integrity.This can reduce the irreversible consumption of active lithium, reduce the decomposition of the electrolyte solution, and thus enable the battery cell to have better cycle performance at low temperatures.

[0101] Therefore, the present application enables the battery cell to combine high energy density and good cycle performance at low temperature by matching the cathode and anode summation of the battery cell to each other. [Anode foil]

[0102] The anode foil comprises an anode collector and an anode film layer located on at least one side of the anode collector, wherein the anode film layer comprises an active anode material, the active anode material comprising a silicon-based material and a carbon-based material, wherein the mass fraction of the Si element in the anode film layer is 1% to 10% and can be, for example, 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 value in a range between any two of these values.

[0103] The anode film layer of the present application can have a single-layer or a multi-layer structure. A multi-layer structure means that different sublayers of the anode film layer differ in their component types and / or contents. In the present application, the mass fraction of the silicon element in the anode film layer refers to the mass fraction of the silicon element in the entire anode film layer. Optionally, the mass fraction of the silicon element in the anode film layer is 3% to 8%, 3.5% to 6%, or 4% to 6%.

[0104] The mass fraction of the silicon element in the anode film layer can be measured using an inductively coupled plasma emission spectrometer (ICP). The test standard can be obtained from JY / T 015 1996.

[0105] In some embodiments, the porosity of the anode film layer is 25% to 35%, optionally 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% or any value in a range between two of these values.

[0106] The volume expansion of the silicon-based material is significant during charging, and it is easy to squeeze out some of the electrolyte solution stored in the anode film layer, resulting in poor wettability of the electrolyte solution within the anode film layer. In the present application, the porosity of the anode film layer is 25% to 35%, and the anode film layer has multiple pore structures that can provide a buffer space for the volume expansion of the silicon-based material. This can not only reduce the volume expansion of the anode film layer but also improve the wettability of the electrolyte solution within the anode film layer, which in turn helps to improve the low-temperature cycle performance of the battery cell.

[0107] Optionally, the porosity of the anode film layer is 28% to 32%.

[0108] In some embodiments, the compression density of the anode film layer is 1.55 g / cm³.3 up to 1.8 g / cm³ 3 and can, for example, be 1.55 g / cm² 3 , 1.6 g / cm³ 3 , 1.65 g / cm³ 3 , 1.7 g / cm³ 3 , 1.75 g / cm³ 3 , 1.8 g / cm³ 3 or any value within a range between two of these values.

[0109] The high compression density of the anode film layer contributes to improving the energy density of the battery cell, but at this point the pore space between the particles of the active anode material is reduced, which is unfavorable for the wettability of the electrolyte solution in the anode film layer. Furthermore, at a high compression density of the anode film layer, the volume expansion of the anode film layer during the charging and discharging process is large, which likely forces out some of the electrolyte solution stored in the anode film layer, leading to a deterioration in the wettability of the electrolyte solution in the anode film layer. In the present application, the compression density of the anode film layer is 1.55 g / cm³. 3 up to 1.8 g / cm³ 3This allows the battery cell to have a high energy density and the anode film layer to have a suitable pore structure and good wettability of the electrolyte solution, which in turn enables the battery cell to perform well at low temperatures.

[0110] Optionally, the compression density of the anode film layer is 1.65 g / cm³. 3 up to 1.7 g / cm³ 3 .

[0111] Adjusting parameters such as the volume-distributed particle size Dv50 and / or the particle size distribution (Dv90-Dv10) / Dv50 of the active anode material and adjusting the cold pressing pressure of the anode allows for the adjustment of the porosity and / or the pressing density of the anode film layer.

[0112] In some embodiments, the volume-distributed particle size Dv50 of the active anode material is 10 µm to 20 µm and can be, for example, 10 µm, 10.5 µm, 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 or any value in a range between two of these values.

[0113] Optionally, the volume-distributed particle size Dv50 of the active anode material is 11 µm to 15 µm.

[0114] The active anode material comprises a carbon-based material and a silicon-based material. The silicon-based material is an active anode material that provides at least silicon. It can also provide other elements, such as carbon, or, of course, only silicon. The carbon-based material is also an active anode material that provides at least carbon.

[0115] In some embodiments, the silicon-based material comprises one or more of monomeric silicon, silicon-carbon material, silicon oxide, silicon nitride, or silicon alloy material.

[0116] The silicon dioxide may contain alkali metal elements and / or alkaline earth metal elements, or it may contain neither. Optionally, the silicon dioxide may contain alkali metal elements and / or alkaline earth metal elements; for example, it may be used as a substrate to embed alkali metal elements and / or alkaline earth metal elements by chemical or physical means.

[0117] The silicon-carbon material may contain alkali metal elements and / or alkaline earth metal elements, or it may contain neither. Optionally, the silicon-carbon material may contain alkali metal elements and / or alkaline earth metal elements; for example, it may be used as a substrate to embed alkali metal elements and / or alkaline earth metal elements by chemical or physical means.

[0118] Optionally, the alkali metal element Li and the alkaline earth metal element Mg can be included.

[0119] Optionally, the silicon-carbon material can include porous carbon and silicon in the pores of the porous carbon.

[0120] In some embodiments, the carbon-based material comprises one or more of natural graphite, artificial graphite, soft carbon, hard carbon, and microspheres of interphase carbon.

[0121] Optionally, the carbon-based material includes one or more components of natural graphite and synthetic graphite.

[0122] In some embodiments, the average particle size of the silicon-based material is 2 µm to 15 µm, for example 2 µm, 2.5 µm, 3 µm, 3.5 µm, 4 µm, 4.5 µm, 5 µm, 5.5 µm, 6 µm, 6.5 µm, 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, 13.5 µm, 14 µm, 14.5 µm, 15 µm or any value in a range between any two of these values.

[0123] Optionally, the average particle size of the silicon-based material is 3 µm to 10 µm, 3 µm to 8 µm, 3 µm to 6 µm.

[0124] In some embodiments, the average particle size of the carbon-based material is 11 µm to 21 µm, for example 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 value in a range between any two of these values. Optionally, the average particle size of the carbon-based material is 12 µm to 18 µm, 12 µm to 16 µm.

[0125] The average particle size of the silicon-based material and the average particle size of the carbon-based material can be tested as follows: A scanning electron microscope in combination with an energy spectrometer (EDS) is used to obtain SEM-EDS images of the anode foil, and a test sample is randomly selected (e.g., 50 mm × 100 mm in length × width). Within the test sample, several test areas (e.g., 5) are randomly selected, and the number and particle size of the silicon-based and carbon-based materials in each test area are counted at a specific magnification (e.g., more than 500x).The arithmetic mean of the particle sizes of all silicon-based materials in each test area is determined as the average particle size of the silicon-based materials, and the arithmetic mean of the particle sizes of all carbon-based materials in each test area is determined as the average particle size of the carbon-based materials. To ensure the accuracy of the test results, a large number of test samples (e.g., 10) can be taken to perform the above test, and the average of each test sample is taken as the final test result. It should be noted that for irregularly shaped particles, the distance between the two most distant points on the particle is taken as the particle size.

[0126] In some embodiments, the anode film layer may further comprise a conductive anode material. For example, the conductive anode material may comprise, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dot, carbon nanotubes, graphene, and carbon nanofibers.

[0127] In some embodiments, the anode film layer may further comprise an anode binder. For example, the anode binder may comprise, but is not limited to, at least one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0128] In some embodiments, the anode film layer may include other additives. These additives may include, for example, thickening agents such as sodium carboxymethylcellulose (CMC), PTC thermistor materials, and the like.

[0129] The anode film layer is typically produced by applying an anode slurry to the anode collector, drying, and cold pressing. The anode slurry is usually prepared by dispersing the active anode material, a conductive anode compound, an anode binder, and other optional additives in a solvent and mixing thoroughly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0130] In some other embodiments, the anode film layer comprises a first anode film layer facing away from the anode collector and a second anode film layer facing the anode collector, wherein the first anode film layer comprises a first active anode material, and wherein the second anode film layer comprises a second active anode material. The active cathode material comprises a carbon-based material and a silicon-based material. The second active anode material comprises a second carbon-based material, and wherein the second anode film layer is free of silicon elements, or wherein the second active anode material comprises a second carbon-based material and a second silicon-based material, and wherein the mass fraction of the silicon element in the first anode film layer is greater than the mass fraction of the silicon element in the second anode film layer.The mass fraction of the Si element in the anode film layer (including the first and second anode film layers) is 1% to 10%.

[0131] Compared to carbon-based materials, silicon-based materials have a higher potential for embedded lithium and are less susceptible to low-temperature lithium precipitation. The first anode film layer is located in the surface region, and the second anode film layer is located in the bottom region. A high crude mass fraction of silicon in the surface region helps to reduce the problem of low-temperature lithium precipitation from the anode. The bottom region contains no silicon or a low mass fraction of silicon, which can help to reduce damage to the overall conductive network of the anode film layer due to the volume expansion of the silicon-based material in the bottom region, thus helping to improve the low-temperature cycle performance of the battery cell.

[0132] The anode film was sectioned along the direction perpendicular to the surface of the anode film layer, and a SEM cross-sectional image in the thickness direction of the anode film layer was acquired using a scanning electron microscope, or a SEM-EDS cross-sectional image in the thickness direction of the anode film layer was acquired using a scanning electron microscope in combination with an energy spectrometer (EDS). The first and second anode film layers can be easily distinguished from the images because the mass fraction of the silicon element differs between them. In some embodiments, the mass fraction of the Si element in the first anode film layer is 2% to 15%, for example 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 value in a range between two of these values.

[0133] Optionally, the mass fraction of the Si element in the first anode film layer is 2% to 10%, 3% to 9%, 3% to 8%.

[0134] In some embodiments, the mass fraction of the Si element in the second anode film layer is 0% to 10%, for example 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 value in a range between two of these values.

[0135] 0% means that the second anode film layer contains no Si elements.

[0136] Optionally, the mass fraction of the Si element in the second anode film layer is 0% to 8%, 0.5% to 8%, 0.5% to 5%.

[0137] In some embodiments, the volume-distributed particle size Dv50 of the first active anode material is smaller than the volume-distributed particle size Dv50 of the second active anode material.

[0138] The first active anode material is located in the surface region, and the second active anode material is located in the bottom region, with the volume-distributed particle size Dv50 of the first active anode material being smaller than that of the second active anode material. The diffusion path of the lithium ions from the first active anode material in the surface region is short, the diffusion time of the lithium ions from the surface to the interior is short, and the lithium ions are more likely to be embedded and rapidly displaced. This improves the overall ion transfer kinetics of the anode film layer, reduces anode polarization, and enhances the low-temperature cycle performance and multiplication performance of the battery cell.

[0139] The first carbon-based material is an active anode material that provides at least the carbon element. In some embodiments, the first carbon-based material comprises one or more of natural graphite, synthetic graphite, soft carbon, hard carbon, and microspheres of interphase carbon.

[0140] Optionally, the first carbon-based material includes one or more components of natural graphite and synthetic graphite.

[0141] Optionally, the first carbon-based material includes synthetic graphite.

[0142] Synthetic graphite has a denser structure and a more stable surface. When synthetic graphite is located in the first anode film layer, it helps to better reduce the side reactions of the electrolyte solution and the irreversible consumption of the electrolyte solution and active lithium, further improving the first coulometric efficiency and the cycle performance of the battery cell at low temperatures.

[0143] In some embodiments, the average particle size of the first carbon-based material is 11 µm to 21 µm, for example 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 value in a range between any two of these values. Optionally, the average particle size of the first carbon-based material is 12 µm to 18 µm, 12 µm to 16 µm.

[0144] The second carbon-based material is an active anode material that provides at least the carbon element. In some embodiments, the second carbon-based material comprises one or more of natural graphite, synthetic graphite, soft carbon, hard carbon, and microspheres of interphase carbon.

[0145] Optionally, the second carbon-based material includes one or more natural and synthetic graphites.

[0146] Optionally, the second carbon-based material includes natural graphite.

[0147] Natural graphite typically exhibits a certain number of pores, which make it more malleable and resistant to compression. When natural graphite is present in the second anode film layer, it can contribute to improving the compressive strength of the anode film layer and the volumetric energy density of the battery cell.

[0148] In some embodiments, the average particle size of the second carbon-based material is 11 µm to 21 µm, for example 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 value in a range between any two of these values. Optionally, the average particle size of the second carbon-based material is 12 µm to 18 µm, 12 µm to 16 µm.

[0149] The first silicon-based material is an active anode material that provides at least the silicon element. The first silicon-based material can also provide other elements, such as the carbon element, or, of course, only the silicon element. In some embodiments, the first silicon-based material comprises one or more monomeric silicon, silicon-carbon material, silicon oxide, silicon nitride, or silicon alloy material.

[0150] The second silicon-based material is an active anode material that provides at least the silicon element. The second silicon-based material can also provide other elements, such as the carbon element, or, of course, only the silicon element. In some embodiments, the second active anode material comprises a second silicon-based material, wherein the silicon-based material includes one or more of monomeric silicon, silicon-carbon material, silicon oxide, silicon nitride, or silicon alloy material.

[0151] The silicon dioxide may contain alkali metal elements and / or alkaline earth metal elements, or it may contain neither. Optionally, the silicon dioxide may contain alkali metal elements and / or alkaline earth metal elements; for example, it may be used as a substrate to embed alkali metal elements and / or alkaline earth metal elements by chemical or physical means.

[0152] The silicon-carbon material may contain alkali metal elements and / or alkaline earth metal elements, or it may contain neither. Optionally, the silicon-carbon material may contain alkali metal elements and / or alkaline earth metal elements; for example, it may be used as a substrate to embed alkali metal elements and / or alkaline earth metal elements by chemical or physical means.

[0153] Optionally, the alkali metal element Li and the alkaline earth metal element Mg can be included.

[0154] Optionally, the first silicon-based material includes one or more silicon-carbon materials, a pre-magnesium-silicon-oxygen material.

[0155] Optionally, the second active anode material comprises a second silicon-based material, wherein the second silicon-based material comprises one or more of a silicon-carbon material, a pre-magnesium-silicon-oxygen.

[0156] Optionally, the silicon-carbon material can include porous carbon and silicon in the pores of the porous carbon.

[0157] Pre-magnesium silicon-oxygen is a material obtained by embedding a magnesium element in silicon oxide as a substrate through chemical or physical processes.

[0158] The silicon-carbon material and the pre-magnesium silicon dioxide-oxygen have a high specific capacity, which contributes to improving the energy density of the battery cell. Compared to monomeric silicon (pure silicon), the silicon-carbon material and the pre-magnesium silicon dioxide-oxygen exhibit low volumetric expansion and high structural stability during charging and discharging. This allows the anode to form a stable SEI film, reducing the irreversible consumption of electrolyte solution and active lithium, thus improving the initial coulometric efficiency and cycle performance of the battery cell. The good thermal stability of the silicon-carbon material and the pre-magnesium silicon dioxide-oxygen also helps to reduce the risk of thermal runaway in the battery cell.

[0159] In some embodiments, the average particle size of the first silicon-based material is 2 µm to 15 µm, for example 2 µm, 2.5 µm, 3 µm, 3.5 µm, 4 µm, 4.5 µm, 5 µm, 5.5 µm, 6 µm, 6.5 µm, 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, 13.5 µm, 14 µm, 14.5 µm, 15 µm or any value in a range between any two of these values.

[0160] Optionally, the average particle size of the first silicon-based material is 3 µm to 10 µm, 3 µm to 8 µm, 3 µm to 6 µm.

[0161] In some embodiments, the second active anode material comprises a second silicon-based material, wherein the average particle size of the second silicon-based material is 2 µm to 15 µm and can be, for example, 2 µm, 2.5 µm, 3 µm, 3.5 µm, 4 µm, 4.5 µm, 5 µm, 5.5 µm, 6 µm, 6.5 µm, 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, 13.5 µm, 14 µm, 14.5 µm, 15 µm or any value in a range between any two of these values.

[0162] Optionally, the average particle size of the second silicon-based material is 3 µm to 10 µm, 3 µm to 8 µm, 3 µm to 6 µm.

[0163] The average particle size of the first silicon-based material and the first carbon-based material can be tested as follows: A scanning electron microscope in combination with an energy spectrometer (EDS) is used to obtain SEM-EDS images on the surface of the first anode film layer facing away from the anode collector, and a test sample is randomly selected (e.g., 50 mm × 100 mm in length × width). Within the test sample, several test areas (e.g., 5) are randomly selected, and the number and particle size of the first silicon-based material and the second carbon-based material in each test area are counted at a specific magnification (e.g., more than 500x).The arithmetic mean of the particle sizes of all silicon-based first materials in each test area is determined as the average particle size of the silicon-based first materials, and the arithmetic mean of the particle sizes of all carbon-based first materials in each test area is determined as the average particle size of the carbon-based second materials. The average particle size of the silicon-based second material and the carbon-based second material can be tested as follows: A scanning electron microscope in combination with an energy spectrometer (EDS) is used to obtain SEM-EDS images on the surface of the second anode film layer facing the anode collector, and a test sample is arbitrarily selected (e.g., 50 mm × 100 mm in length × width). Several test areas (e.g.,5) Samples were randomly selected, and the number and particle size of the second silicon-based material and the second carbon-based material in each test area were counted under a specific magnification (e.g., more than 500 times). The arithmetic mean of the particle sizes of all the second silicon-based materials in each test area is determined as the average particle size of the second silicon-based materials, and the arithmetic mean of the particle sizes of all the second carbon-based materials in each test area is determined as the average particle size of the second carbon-based materials. To ensure the accuracy of the test results, a large number of test samples (e.g., 10) can be taken to perform the above test, and the average of each test sample is taken as the final test result.It should be noted that for irregularly shaped particles, the distance between the two furthest points on the particle is taken as the particle size.

[0164] In some embodiments, the first anode film layer and the second anode film layer may further comprise a conductive anode material. For example, the conductive anode material may comprise, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dot, carbon nanotubes, graphene, and carbon nanofibers.

[0165] In some embodiments, the first anode film layer and the second anode film layer may further comprise an anode binder. For example, the anode binder may comprise, but is not limited to, at least one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0166] In some embodiments, the first anode film layer and the second anode film layer may further comprise other additives. These other additives may include, for example, thickening agents such as sodium carboxymethylcellulose (CMC), PTC thermistor materials, and the like.

[0167] The anode film layer can be formed by applying a second slurry to the anode collector and a first slurry to the second slurry, then drying and cold pressing. The first slurry is dried to form a first anode film layer, and the second slurry is dried to form a second anode film layer.

[0168] The first slurry is typically prepared by dispersing the first active anode material, a conductive anode compound, an anode binder, and other optional additives, etc., in a solvent and mixing thoroughly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0169] The second slurry is typically prepared by dispersing the second active anode material, a conductive anode compound, an anode binder, and other optional additives, etc., in a solvent and mixing thoroughly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0170] The first and second coatings can be applied simultaneously in one or two operations. In some embodiments, the first and second coatings are applied simultaneously in a single operation. Simultaneous coating can reduce the resistance of the anode film layer, which can further improve the kinetic energy and performance of the battery cell.

[0171] The coating weights of the first and second slurry applications can be adjusted depending on the actual situation.

[0172] The anode collector has two surfaces that are opposite each other in its thickness direction, and the anode film layer is provided on one or both of the two surfaces opposite the anode collector.

[0173] The parameters of the anode film layer (e.g., packing density, surface density, etc.) of the present application are all parameters of the anode film layer for a single side of the anode collector. In some embodiments, the anode collector can be a metal foil or a composite collector. For example, a copper foil can be used as the metal foil. The composite collector can comprise a base layer of polymeric material and a metallic material layer formed on at least one surface of the polymeric base layer. For example, the metallic material layer can comprise, but is not limited to, one or more of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy.For example, the polymer base layer may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, polyethylene. [Cathode foil]

[0174] The cathode foil comprises a cathode collector and a cathode film layer located on at least one side of the cathode collector, wherein the cathode film layer comprises an active cathode material, the active cathode material comprising a lithium transition metal oxide, the lithium transition metal oxide comprising a nickel element, the molar fraction of the nickel element in the transition metal element of the lithium transition metal oxide being more than 80%, the lithium transition metal oxide comprising a lithium transition metal oxide with a single-crystal morphology, the total area of ​​the lithium transition metal oxide with the single-crystal morphology being 60% to 100% of the total area of ​​the active cathode material, and the porosity of the cathode film layer being 13% to 20%.

[0175] In some embodiments, the molar fraction of the Ni element in the transition metal element of the lithium transition metal oxide is more than 83%, more than 84%, more than 85%, more than 86%, more than 87%.

[0176] The proportion of the total area of ​​the lithium transition metal oxide with single-crystal morphology in the total area of ​​the active cathode material is 60% to 100% and, for example, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 99%, 100% or any value in a range between two of these values. In some embodiments, the lithium transition metal oxide comprises a lithium transition metal oxide in a single-crystal morphology, and wherein the total area of ​​the lithium transition metal oxide in a single-crystal morphology is 100% of the total area of ​​the active cathode material.

[0177] In some embodiments, the lithium transition metal oxide comprises a lithium transition metal oxide in a single-crystal morphology and a lithium transition metal oxide in a multi-crystal morphology, wherein the total area of ​​the lithium transition metal oxide in a single-crystal morphology is 60% to 99% of the total area of ​​the active cathode material, while the total area of ​​the lithium transition metal oxide in a multi-crystal morphology is 1% to 40% of the total area of ​​the active cathode material. For example, the proportion of the total area of ​​the lithium transition metal oxide in the single-crystal morphology in the total area of ​​the active cathode material is 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 99% or any value in a range between two of these values.For example, the proportion of the total surface area of ​​the lithium transition metal oxide in the multicrystal morphology in the total surface area of ​​the active cathode material is 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40% or any value in a range between two of these values.

[0178] Optionally, the total area of ​​the lithium transition metal oxide in a single-crystal morphology is 80% to 99% of the total area of ​​the active cathode material, while the total area of ​​the lithium transition metal oxide in a multi-crystal morphology is 1% to 20% of the total area of ​​the active cathode material.

[0179] Optionally, the total area of ​​the lithium transition metal oxide in a single-crystal morphology is 90% to 99% of the total area of ​​the active cathode material, while the total area of ​​the lithium transition metal oxide in a multi-crystal morphology is 1% to 10% of the total area of ​​the active cathode material.

[0180] In some embodiments, the average particle size of the lithium transition metal oxide with single-crystal morphology is 1 µm to 6 µm, for example 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 other value. in a range between two of these values.

[0181] In some embodiments, the average particle size of the lithium transition metal oxide with the multicrystal morphology is 7 µm to 13 µm, for example 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 value in a range between two of these values.

[0182] The terms "lithium transition metal oxides with a single-crystal morphology" and "lithium transition metal oxides with a multi-crystal morphology" have established meanings in engineering. The term "lithium transition metal oxides with a single-crystal morphology" also encompasses lithium transition metal oxides with a quasi-single-crystal (also referred to as single-crystal-like) morphology, and quasi-single-crystal (single-crystal-like) has the established meaning in engineering and generally refers to particles formed by the agglomeration of a small number of primary particles, for example, fewer than 10 primary particles. Typically, the primary particles comprising the lithium transition metal oxide with the quasi-single-crystal (single-crystal-like) morphology have a particle size of 500 nm or more.Lithium transition metal oxides with multicrystal morphology are lithium transition metal oxides exhibiting a morphology of secondary particles formed by the agglomeration of a large number of primary particles on the nanoscale. Lithium transition metal oxides with a single-crystal morphology and lithium transition metal oxides with a multicrystal morphology can be distinguished by scanning electron microscopy. The average particle size of lithium transition metal oxide with a single-crystal morphology and the average particle size of lithium transition metal oxide with a multi-crystal morphology can be tested as follows: A scanning electron microscope is used, with reference to JY / T 010-1996, to obtain SEM images of the cathode foil, and a test sample is arbitrarily selected (e.g., 50 mm × 100 mm in length × width). Several test areas were examined in the test sample (e.g.,5) Randomly selected, and the number and particle size of the lithium transition metal oxide with a single-crystal morphology and the lithium transition metal oxide with a multi-crystal morphology in each test area were counted under a specific magnification (e.g., more than 500x). The arithmetic mean of the particle sizes of all lithium transition metal oxides with a single-crystal morphology in each test area is determined as the average particle size of the lithium transition metal oxides with a single-crystal morphology, and the arithmetic mean of the particle sizes of all lithium transition metal oxides with a multi-crystal morphology in each test area is determined as the average particle size of the lithium transition metal oxides with a multi-crystal morphology. To ensure the accuracy of the test results, a large number of test samples (e.g.,10) are taken to perform the above test, and the average value of each test sample is taken as the final test result. The testing instrument can be a ZEISS Sigma 300. It should be noted that for irregularly shaped particles, the distance between the two furthest points on the particle is taken as the particle size.

[0183] The area fraction of lithium transition metal oxide with a single-crystal morphology and the area fraction of lithium transition metal oxide with a multi-crystal morphology in the active cathode material can be tested as follows: A scanning electron microscope is used, with reference to JY / T 010-1996, to obtain SEM images of the cathode foil, and a test sample is randomly selected (e.g., 50 mm × 100 mm in length × width). Several test areas (e.g., 5) are randomly selected within the test sample, and the sum of the areas of all lithium transition metal oxides with a single-crystal morphology, the sum of the areas of all lithium transition metal oxides with a multi-crystal morphology, and the sum of the areas of all active cathode materials in each test area are measured at a specific magnification (e.g.,The area fraction of lithium transition metal oxides with a single-crystal morphology and the area fraction of lithium transition metal oxides with a multi-crystal morphology are counted (more than 500 times). The average of the test results from the multiple test areas is then taken as the ratio of the area of ​​lithium transition metal oxides with a single-crystal morphology in the active cathode material to the ratio of the area of ​​lithium transition metal oxides with a multi-crystal morphology in the active cathode material. To ensure the accuracy of the test results, a large number of test samples (e.g., 10) can be used to perform the above test, and the average of each test sample is taken as the final test result. The test instrument can be a ZEISS Sigma 300.

[0184] The lithium transition metal oxide with single-crystal morphology exhibits few or no grain boundaries, making it less susceptible to particle fragmentation during charging and discharging and offering better resistance to overcharging and over-discharging due to its higher structural stability and particle integrity. This can reduce the irreversible consumption of active lithium and minimize electrolyte degradation. The total surface area of ​​the lithium transition metal oxide with single-crystal morphology comprises 60% to 100% of the total surface area of ​​the active cathode material, thus enabling the battery cell to achieve better cycle performance at low temperatures.

[0185] The lithium transition metal oxide with multi-crystal morphology exhibits higher electrochemical activity and a higher specific capacity at low temperatures, leading to improved multiplication performance and energy density of the battery cell. By incorporating a small amount of this multi-crystal lithium transition metal oxide into the active cathode material, the battery cell can achieve good cycle performance at low temperatures while simultaneously maintaining good multiplication performance.

[0186] The average particle size of the lithium transition metal oxide with multi-crystal morphology is larger than that of the lithium transition metal oxide with single-crystal morphology. The active cathode material, which contains a small amount of the lithium transition metal oxide with multi-crystal morphology, contributes to the cathode film layer having a higher porosity and a larger pore structure, while also having a higher packing density, thus contributing to the energy density of the battery cell.

[0187] In some embodiments, the volume-distributed particle size Dv50 of the active cathode material is 1 µm to 7 µm, for example 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, 6.2 µm, 6.4 µm, 6.6 µm, 6.8 µm, 7 µm or any value in a range between any two of these values.

[0188] A small volumetric particle size Dv50 of the active cathode material results in a short diffusion path for the lithium ions, thus contributing to rapid encapsulation and detachment of the lithium ions and improving the multiplication performance of the battery cell. The smaller volumetric particle size Dv50 also improves the specific surface area of ​​the active cathode material. This larger specific surface area, at high current densities in the surface layer of the cathode film, helps to reduce the current's impact on the surface layer and improves the structural stability of the active cathode material. Furthermore, a volumetric particle size Dv50 of the active cathode material ranging from 1 µm to 7 µm also reduces the micropowder content in the active cathode material, thereby improving the processing of the cathode slurry.

[0189] Optionally, the volume-distributed particle size Dv50 of the active cathode material is 2 µm to 7 µm, 2 µm to 6 µm.

[0190] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the active cathode material is 1 to 1.5, for example 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5 or any value in a range between two of these values.

[0191] The volume-distributed particle size Dv50 of the active cathode material is small and the particle size distribution (Dv90-Dv10) / Dv50 is narrow, which is unfavorable for improving the compaction density of the cathode film layer and thus unfavorable for achieving a battery cell with high energy density; The volume-distributed particle size Dv50 of the active cathode material is small and the particle size distribution (Dv90-Dv10) / Dv50 is wide, which is helpful for improving the compaction density of the cathode film layer and for improving the energy density of the battery cell, but at this point the micropowder content in the active cathode material should be higher, and a high micropowder content is likely to lead to difficulties in processing the cathode slurry, for example, the easy occurrence of the problem of gelation.The particle size distribution (Dv90-Dv10) / Dv50 of the active cathode material in the present application is 1 to 1.5, which can improve the processing problem of the cathode slurry as well as increase the compression density of the cathode film layer and the energy density of the battery cell.

[0192] Optionally, the particle size distribution (Dv90-Dv10) / Dv50 of the active cathode material is 1.2 to 1.4.

[0193] In some embodiments, the lithium transition metal oxide comprises a Ni element and a Co element, wherein the Co element content in a surface region of the lithium transition metal oxide is greater than the Co element content in a core region of the lithium transition metal oxide.

[0194] The lithium transition metal oxide has a high cobalt content in the surface region and a low cobalt content in the core region. The resulting lithium transition metal oxide exhibits high surface stability, which reduces side reactions with the electrolyte solution and can minimize the leaching of transition metal ions. This can improve the cycle performance of the battery cell at low temperatures; it can also enhance the thermal stability of the lithium transition metal oxide and reduce the risk of thermal runaway in the battery cell.

[0195] In some embodiments, the lithium transition metal oxide comprises a Ni element and a Mn element, wherein the content of the Mn element in a surface region of the lithium transition metal oxide is smaller than the content of the Mn element in a core region of the lithium transition metal oxide.

[0196] The lithium transition metal oxide has a low manganese content in the surface region and a high manganese content in the core region. The resulting lithium transition metal oxide exhibits high surface stability, which reduces side reactions with the electrolyte solution and can minimize the leaching of transition metal ions. This can improve the cycle performance of the battery cell at low temperatures; it can also enhance the thermal stability of the lithium transition metal oxide and reduce the risk of thermal runaway in the battery cell.

[0197] In some embodiments, the lithium transition metal oxide comprises a Ni element, a Co element and a Co element, wherein the Co element content in a surface region of the lithium transition metal oxide is greater than the Co element content in a core region of the lithium transition metal oxide, and wherein the Mn element content in a surface region of the lithium transition metal oxide is less than the Mn element content in a core region of the lithium transition metal oxide.

[0198] The surface region of the lithium transition metal oxide is a region extending radially inward from the outermost surface of the particle for 100 nm; the core region of the lithium transition metal oxide is a region extending radially outward from the center of the particle for 300 nm. The center of the particle is the midpoint of the longest straight line between any two points on the particle's circumference.

[0199] The content of individual elements in the surface and core regions of lithium transition metal oxide can be tested as follows: A particle section is prepared using an ion cutter, a suitable field of view is selected using a scanning electron microscope, and then a spot scan of the particle section within a 5k field of view is performed using an energy spectrometer (EDS). The content of each element is measured at more than 10 locations in the surface region of the particle section, and the average value is then taken as the test result for the corresponding element content in the surface region of the lithium transition metal oxide. The content of each element is measured at more than 10 locations in the core region of the particle section, and the average value is then taken as the test result for the corresponding element content in the core region of the lithium transition metal oxide.

[0200] In some embodiments, the lithium transition metal oxide comprises a nickel element and a dopant, wherein the dopant comprises a cationic dopant and / or an anionic dopant, the cationic dopant comprising one or more of the elements aluminum, yen, zirconium, zinc, chromium, magnesium, vanadium, titanium, and boron, and the anionic dopant comprising one or more of the elements nitrogen, fluorine, sulfur, and chloride. The cationic dopant can be a lithium site dopant and / or a transition metal site dopant, and the anionic dopant can be an oxygen site dopant. The above dopant elements can increase the structural stability of the lithium transition metal oxide and reduce the volume change of the lithium transition metal oxide during charging and discharging.In this way, the leaching of transition metal ions is reduced and the chemical stability and cycle stability of the battery cell is improved; in addition, the thermal stability of lithium transition metal oxides can be increased and the risk of thermal runaway of the battery cell can be reduced.

[0201] In some embodiments, the active cathode material comprises a lithium transition metal oxide, wherein the lithium transition metal oxide is a composition of Li a Ni b Co c Mn d M e O f A g exhibits, wherein 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, where M comprises one or more of the elements Al, Y, Zr, Zn, Cr, Mg, V, Ti and B, where A comprises one or more of the elements N, F, S and Cl.

[0202] During charging and discharging, the battery cell undergoes both the deposition and consumption of lithium, and the molar lithium content of the battery cell varies depending on the discharge state. In the listing of active cathode materials in the present application, the molar lithium content represents an initial state of the material, i.e., the state before the material is added. The molar lithium content changes when the active cathode material is added to the battery cell after a charge and discharge cycle. In the listing of active cathode materials in the present application, the molar oxygen content is only a theoretical value; the release of oxygen from the lattice causes a change in the molar oxygen content, and in practice, the molar oxygen content will fluctuate.

[0203] In some embodiments, the cathode film layer also comprises a conductive cathode medium.

[0204] In some embodiments, the mass fraction of the conductive cathode medium in the cathode film layer is 0.5% to 2.5%, for example 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 value in a range between two of these values.

[0205] Optionally, the mass fraction of the positive conductive cathode medium in the cathode film layer is 0.6% to 1.5%, 0.8% to 1.5%.

[0206] In some embodiments, the conductive cathode material comprises one or more carbon nanotubes, carbon black, acetylene black, carbon fibers, graphene.

[0207] The carbon nanotubes comprise one or more single-walled carbon nanotubes, thin-walled carbon nanotubes, or multi-walled carbon nanotubes.

[0208] Single-walled carbon nanotubes are formed by rolling up a single-layer graphene, multi-walled carbon nanotubes are formed by concentrically aligning 2 to 3 graphene sheets rolled into a tube, and multi-walled carbon nanotubes are formed by concentrically arranging more than 4 graphene sheets rolled into a tube.

[0209] In some embodiments, the conductive cathode material comprises carbon nanotubes, wherein at least a portion of the carbon nanotubes are located on the surface of the active cathode material.

[0210] Carbon nanotubes possess excellent electronic conductivity, making it possible to reduce the mass fraction of conductive cathode material in the cathode film layer, increase the mass fraction of active cathode material, and thus improve the energy density of the battery cell. The use of carbon nanotubes also reduces the cathode impedance and contributes to improved high-rate charging and discharging performance of the battery cell. At least some of the carbon nanotubes located on the surface of the active cathode material can stabilize its crystal structure, increase its particle strength, and reduce its volume change during charging and discharging.This contributes to the formation of a stable SEI film on the surface of the active cathode material, reduces a side reaction between the lithium transition metal oxide and the electrolyte solution, and decreases the leaching of transition metal ions, thereby improving the initial coulometric efficiency and the cycle capacity maintenance rate of the battery cell. Simultaneously, at least some of the carbon nanotubes located on the surface of the active cathode material contribute to the formation of a uniform conductive network at the cathode. This helps to improve the electron transfer effect of the cathode, reduce the electron transfer resistance of the cathode, and decrease the cathode impedance and polarization, which in turn contributes to improving the cycle performance of the battery cell at low temperatures.

[0211] In some embodiments, the conductive cathode material comprises an agglomerated conductive cathode material.

[0212] The agglomerated conductive cathode medium can be formed by agglomerating a conductive cathode medium; for example, the agglomerated conductive cathode medium can consist of agglomerated carbon nanotubes. The agglomerated conductive cathode medium can also be formed by agglomerating several conductive cathode media; for example, the agglomerated conductive cathode medium can be formed by agglomerating carbon nanotubes and carbon black or by agglomerating carbon nanotubes and carbon black. Optionally, the conductive cathode medium also includes a non-agglomerated conductive cathode medium.

[0213] Optionally, the maximum distance between any two points on a circumference of the agglomerated conductive cathode medium is greater than or equal to 2 µm.

[0214] Optionally, the porosity of the agglomerated conductive cathode medium is 30% to 65%, for example 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 65% or any value in a range between two of these values.

[0215] Optionally, the agglomerated conductive cathode material comprises carbon nanotubes. In some embodiments, the agglomerated conductive cathode material further comprises one or more carbon black and acetylene black.

[0216] Optionally, the number density of the agglomerated conductive cathode medium in the cathode film layer is 1 to 5 per 1000 µm. 2 , for example 1 per 1000µm 2 , 2 per 1000µm 2 , 3 per 1000µm 2 , 4 per 1000µm 2 , 5 per 1000µm 2 or any value within a range between two of these values.

[0217] A non-agglomerated conductive cathode medium is a conductive cathode medium existing in an independent, dispersed form without significant aggregation or entanglement with other conductive cathode media. An agglomerated conductive cathode medium is a conductive cathode medium in the form of an agglomerate consisting of a number of conductive cathode media linked together by van der Waals forces or disordered entanglement. The number density of the agglomerated conductive cathode medium in the cathode film layer can be tested as follows: The cathode film is sectioned along the direction perpendicular to the surface of the cathode film layer, and a scanning electron microscope is used, with reference to JY / T 010-1996, to obtain a SEM section in the thickness direction of the cathode film layer, and a test sample is arbitrarily selected. A number of test areas (e.g.5) with an area of ​​1000 µm. 2 (20 µm × 50 µm) were randomly selected from the test sample, and the number of agglomerated conductive cathode medium particles in each test area was counted under a specific magnification (e.g., 1000×). The agglomerated conductive cathode medium must meet the condition that the maximum distance between any two points on the circumference is greater than or equal to 2 µm. The average of the counts across several test areas is then taken as the number density of the agglomerated conductive cathode medium in the cathode film layer. To ensure the accuracy of the test results, a large number of test samples (e.g., 10) can be used to perform the above test, and the average of each sample is taken as the final test result. The test instrument can be a ZEISS Sigma 300.

[0218] Current research suggests that agglomerated conductive cathode compound makes the conductive network of the cathode film layer uneven, reduces the electron transfer path, increases the electron transfer resistance, and intensifies polarization. Therefore, the use of agglomerated conductive cathode compound is generally avoided when applied to the cathode film layer. The inventor of the present application has found that the agglomerated conductive cathode compound has a loose and porous structure, and that by using an appropriate amount of the agglomerated conductive cathode compound in the cathode film layer, it can play a role in retaining the electrolyte solution. This helps to improve the wettability of the electrolyte solution in the cathode film layer, which in turn helps to improve the low-temperature cycle performance of the battery cell.At the same time, the number density of the agglomerated conductive cathode medium should be 5 / 1000 µm. 2 The mass of the conductive cathode medium must not be exceeded, and if the mass of the conductive cathode medium is the same, more agglomerated conductive cathode medium makes the conductive network of the cathode film layer uneven, the electron transfer path is reduced, the electron transfer resistance is increased, and the polarization is intensified. At the same time, the agglomerated conductive cathode medium can also penetrate the pores of the cathode film layer, leading to a blockage of the path for the electrolyte solution. Therefore, in the present application, the number density of the agglomerated conductive cathode medium in the cathode film layer is 1 to 5 per 1000 µm. 2In this way, both the electronic conductivity of the cathode is improved and the transmission resistance of the electrons and the polarization of the cathode are reduced, as well as the wettability of the electrolyte solution of the cathode film layer, which in turn contributes to a further improvement in the cycle performance of the battery cell at low temperature.

[0219] Optionally, the number density of the agglomerated conductive cathode medium is 2 to 4 per 1000 µm. 2 .

[0220] In some embodiments, the cathode film layer also includes a cathode binder.

[0221] For example, the cathode 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 fluorine-containing acrylate resin.

[0222] The porosity of the cathode film layer is 13% to 20%, optionally 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20% or any value in a range between two of these values.

[0223] Optionally, the porosity of the cathode film layer is 15% to 18.5%, 15% to 18%, 15.5% to 18%, 16% to 18%.

[0224] In some embodiments, the density of the cathode film layer is 3.4 g / cm³. 3 up to 3.7 g / cm³ 3 and can, for example, be 3.4 g / cm² 3 , 3.45 g / cm³ 3 , 3.5 g / cm³3 , 3.55 g / cm³ 3 , 3.6 g / cm³ 3 , 3.65 g / cm³ 3 , 3.7 g / cm³ 3 or any value within a range between two of these values.

[0225] The high density of the cathode film layer contributes to improving the energy density of the battery cell, but at this point the pore space between the particles of the active cathode material is reduced, which is unfavorable for the wettability of the electrolyte solution in the cathode film layer. In the present application, the density of the cathode film layer is 3.4 g / cm³. 3 up to 3.7 g / cm³ 3 This allows the battery cell to have a high energy density and the cathode film layer to have a suitable pore structure, which in turn enables the battery cell to perform well at low temperatures.

[0226] Optionally, the density of the cathode film layer is 3.5 g / cm³. 3 up to 3.65 g / cm³ 3 .

[0227] Adjusting parameters such as the volume-distributed particle size Dv50 and / or the particle size distribution (Dv90-Dv10) / Dv50 of the active cathode material and adjusting the cold pressing pressure of the cathode allows for the adjustment of the porosity and / or the pressing density of the cathode film layer.

[0228] The cathode film layer is typically produced by applying a cathode slurry to the cathode collector, drying, and cold pressing. The cathode slurry is usually prepared by dispersing the active cathode material, a conductive cathode compound, a cathode binder, and other components in a solvent and mixing thoroughly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP). The cathode collector has two surfaces opposite each other in its thickness direction, and the cathode film layer is applied to one or both of these surfaces opposite the cathode collector.

[0229] The parameters of the cathode film layer (e.g., compression density, surface density, etc.) of the present application are all parameters of the cathode film layer for a single side of the cathode collector.

[0230] In some embodiments, the cathode collector can be a metal foil or a composite collector. For example, an aluminum foil can be used as the metal foil. The composite collector can comprise a polymer base layer and a metallic layer formed on at least one surface of the polymer base layer. For example, the metallic layer can include, but is not limited to, one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. For example, the polymer base layer can include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0231] Electrode film layer density = surface density of the electrode film layer / thickness of the electrode film layer. The thickness of the electrode film layer can be measured with a universal measuring tape, and measurements can be taken at several points (e.g., 10 or more) and then averaged. The surface density of the electrode film layer can be tested as follows: After the battery cell has been completely discharged, the electrode foil is removed and soaked in an organic solvent (e.g., dimethyl carbonate) for a specific period of time (e.g., 2–10 hours). The electrode foil is then removed and dried at a specific temperature for a specific period of time (e.g., 60 °C for more than 4 hours). After drying, the electrode foil is removed.A single-sided coated electrode foil is taken (if the electrode foil is double-sided, the electrode foil can be wiped on one side first), punched out and cut into small round samples with an area of ​​S1, weighed and recorded as M1; the electrode film layer of the electrode foil weighed above was then wiped and the weight of the electrode collector was weighed and recorded as M0; the surface density of the electrode film layer = (M1-M0) / S1.

[0232] The porosity of the electrode film layer can be tested as follows: After the battery cell has been completely discharged, the electrode foil is removed and soaked in an organic solvent (e.g., dimethyl carbonate) for a specific period of time (e.g., 2–10 hours). The electrode foil is then removed and dried at a specific temperature for a specific period of time (e.g., 60°C for more than 4 hours). After drying, the electrode foil is removed. A single-sided coated electrode foil is taken (if the electrode foil is double-coated, one side can be wiped clean first), punched out, and cut into small round samples with a specific area. The apparent volume of the electrode foil, V1, is then calculated. According to GB / T 24586-2009, an inert gas (e.g., carbon dioxide) is introduced.Helium or nitrogen is used as the medium, the gas exchange method is applied, and the actual volume V2 of the electrode foil is measured with the true density tester. Electrode film porosity = (V1-V2) / V1 × 100%. For the test, several samples (e.g., 30 discs) with good appearance and no powder residue on the edges can be taken, and the results are averaged, thus improving the accuracy of the test results. The Micromeritics AccuPyc II 1340 true density tester can be used as the test instrument.

[0233] Dv10, Dv50, and Dv90 represent the particle size of the material when the percentage of cumulative volume distribution reaches 10%, 50%, and 90%, respectively, which can be tested using a laser particle size analyzer in accordance with GB / T 19077-2016. During the test, 1 g of the sample to be tested is placed in a small, clean beaker, 20 ml of deionized water is added, and the sample is sonicated for 5 minutes at 53 kHz / 120 W to ensure complete dispersion. The laser particle size analyzer is then switched on, the optical system is cleaned, and the automated test is started. The solution to be tested is stirred ultrasonically to ensure uniform dispersion, then transferred to the cuvette, and the particle size measurement begins. The test instrument can be the MasterSizer 3000 laser particle size analyzer.

[0234] The active electrode material (active cathode material, active anode material) can be obtained by the following procedure: After the battery cell has been completely discharged, the electrode foil is disassembled and soaked in an organic solvent (e.g., dimethyl carbonate) for a certain period of time (e.g., 2 to 10 hours). The electrode foil is then removed and dried at a specific temperature and time (e.g., 60°C for more than 4 hours). After drying, the electrode foil is removed and baked at a specific temperature and time (e.g., 400°C for more than 2 hours). A section of the baked electrode foil is selected, and the active electrode material is extracted as a sample (e.g., a blade can be used to scrape off the powder for sampling).

[0235] Samples of the first active anode material and the second active anode material can be obtained using the following procedure: After the battery cell has been completely discharged, the anode foil is disassembled and soaked in an organic solvent (e.g., dimethyl carbonate) for a certain period of time (e.g., 2 to 10 hours). The anode foil is then removed and dried at a specific temperature and time (e.g., 60°C for more than 4 hours). After drying, the anode foil is removed and baked at a specific temperature and time (e.g., 400°C for more than 2 hours). An area within the baked first anode film layer is selected, and the first active anode material is extracted as a sample. For example, a blade can be used to scrape off the powder for sampling.An area within the baked second anode film layer is selected, and a sample of the second active anode material is taken. For example, a blade can be used to scrape off the powder for sampling. To ensure the accuracy of the test results, the interface between the first and second anode film layers must be avoided during sampling. [Separator]

[0236] In a battery cell, the separator serves to separate the cathode and the anode from each other and to conduct the ions.

[0237] The present application does not impose any specific restrictions regarding the type of separator, and any known separator with a porous structure and good chemical and mechanical stability may be selected. For example, the separator material may be selected from one or more of the following: glass fiber, nonwoven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film without any particular restriction. If the separator is a multi-layer composite film, the materials of the layers may be the same or different without any particular restriction. The separator may be a separate component located between the cathode and the anode, or it may be attached to the surface of the cathode and the anode.

[0238] In some embodiments, the separator comprises a porous base film and a porous coating located on at least one side of the porous base film, wherein the porous coating comprises filler particles, the filler particles comprising one or more of inorganic particles, organic particles, or organic-inorganic composite particles. The porous coating contains filler particles that can improve the thermal resistance of the separator and reduce the thermal contraction of the separator during the charging and discharging process, which in turn contributes to improving the thermal stability of the battery cell and reducing the risk of thermal runaway of the battery cell.The filler particles can improve the mechanical strength and puncture resistance of the separator, making it more durable during battery cell assembly and use, and also help reduce mechanical micro-short circuits. The filler particles can balance the ion flow, thus helping to form a well-functioning SEI film at the anode, reducing the irreversible consumption of electrolyte solution and active lithium, and improving the initial coulometric efficiency, cycle performance, and multiplication performance of the battery cell. If the current is too high, the filler particles can also help to block the current, preventing internal short circuits and overheating, and thus improving battery cell safety.

[0239] The filler particles can improve the wettability of the separator with the electrolyte solution and increase the ion transfer efficiency of the separator, thereby improving the low-temperature cycle performance and the low-temperature multiplication performance of the battery cell.

[0240] Optionally, the filler particles may include, but are not limited to, one or more of burmite, aluminum oxide, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, 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.

[0241] In some embodiments, the porous coating further comprises polymer binder particles, wherein the volume-distributed particle size Dv50 of the polymer binder particles is larger than the volume-distributed particle size Dv50 of the filler particles. The porous coating contains polymer binder particles, and these polymer binder particles can act as bonding agents between the separator, cathode, and anode during the cold-pressing or hot-pressing process of the battery cell. As a result, the separator, cathode, and anode can be firmly bonded together, the overall hardness and thickness consistency of the battery cells can be improved, the uneven distribution of internal resistance can be reduced, the consistency of the battery cells can be enhanced, and the volumetric energy density of the battery cells can also be improved.

[0242] The volume-distributed particle size Dv50 of the polymer binder particles is larger than the volume-distributed particle size Dv50 of the filler particles. As a result, the polymer binder particles can form a certain volume gap between the separator and the cathode and anode. This portion of the volume gap can act as a buffer against the volume expansion of the anode and cathode, thereby reducing the adverse effects of volume expansion on the separator and the wettability of the electrolytes at the anode and cathode, thus improving the battery's cycle performance at low temperatures.

[0243] The “polymer binder particles” play a role in the porous coating in improving the bond between the separator and the electrode foil and are generally not resistant to high temperatures.

[0244] Optionally, the polymer binder particles can comprise one or more of fluorine-containing polymer binder particles and non-fluorine-containing polymer binder particles.

[0245] Optionally, the fluorinated polymer binder particles may comprise vinylidene fluoride polymer particles, such as polyvinylidene fluoride (PVDF) particles, and / or copolymer particles consisting of vinylidene fluoride monomer and copolymer monomer. The copolymer monomer may comprise at least one olefinic monomer, one fluorinated olefinic monomer, one chlorinated olefinic monomer, one acrylate monomer, one acrylic monomer, and one fluorinated ether monomer. Optionally, the copolymer monomer may contain at least one of the following: trifluoroethylene, trifluoroethylene chloride, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ethers (e.g., perfluoro(methylene vinyl) ether, perfluoro(ethylene vinyl) ether, perfluoro(propylene vinyl) ether), perfluoro(1,3-methyldioxolane), and perfluoro(2,2-dimethyl-1,3-methyldioxolane).

[0246] Optionally, the non-fluorinated polymer binder particles can comprise an acrylate copolymer. The porous base film has two surfaces that face each other in its own thickness direction, and the porous coating is applied to one or both of these opposing surfaces of the porous base film.

[0247] Optionally, the porous coating is provided on at least one surface on one side of the porous base film facing the anode foil.

[0248] Since the anode film layer contains a silicon-based material, and silicon-based materials typically exhibit a large volumetric expansion, the resulting relative movement between the anode foil and the separator can lead to detachment of the anode film layer due to this expansion. This relative movement can be reduced by providing a porous coating on at least one surface on the side of the porous base film facing the anode foil, and by incorporating polymer binder particles into the porous coating. This ensures good electrical contact between the anode film layer and the anode collector, which in turn contributes to high capacity and good cycle stability of the battery cell.

[0249] In some embodiments, the thickness of the porous coating is 0.5 µm to 2 µm. The thickness of the porous coating is the thickness of the porous coating located on a single side of the porous base film.

[0250] In some embodiments, the thickness of the porous coating is 5 µm to 10 µm.

[0251] In a low-temperature environment, the viscosity of the electrolyte solution increases, and the wettability of the separator's electrolyte solution deteriorates. An appropriate thickness of the porous base film helps to improve the wettability of the separator's electrolyte solution and thus increase the separator's ion transfer efficiency. Furthermore, the appropriate thickness of the porous base film exhibits suitable heat resistance and mechanical strength, contributing to improved heat resistance, mechanical strength, and puncture resistance of the separator.

[0252] In some embodiments, the material of the porous base film can be selected from one or more glass fibers, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The porous base film can be a single-layer film or a multi-layer composite film without any particular restriction. If the porous base film is a multi-layer composite film, the materials of the layers can be the same or different without any particular restriction.

[0253] In some embodiments, the porosity of the separator is 35% to 55%.

[0254] In a low-temperature environment, the viscosity of the electrolyte solution increases, and the wettability of the separator deteriorates. High separator porosity improves electrolyte solution retention and increases the separator's ion transfer efficiency, which in turn improves low-temperature cycle performance and battery cell multiplication performance.

[0255] The porosity of the separator can be tested with reference to GB / T 36363-2018. [Electrolyte solution]

[0256] In some embodiments, the battery cell further comprises an electrolyte solution, wherein the electrolyte solution comprises an organic solvent and an electrolyte salt.

[0257] In some embodiments, the concentration of the electrolyte salt is 0.9 mol / L to 1.2 mol / L.

[0258] The concentration of the electrolyte salt is 0.9 mol / L to 1.2 mol / L, which helps to reduce the viscosity of the electrolyte solution, improve the ionic conductivity of the electrolyte solution, improve the wettability of the electrolyte solution of the electrode assembly in a low temperature environment, and improve the cycle performance of the battery cell at low temperatures.

[0259] In some embodiments, the organic solvent comprises vinyl carbonate (EC) and methyl ethyl carbonate (EMC), wherein the mass fraction of methyl ethyl carbonate (EMC) in the organic solvent is greater than or equal to 55% and less than 100%. Methyl ethyl carbonate (EMC) has a lower viscosity and a wider temperature range for liquids, so it remains free-flowing even at low temperatures. As a result, the wettability of the electrolyte solution in the electrode assembly can be improved at low temperatures, and the low-temperature performance of the battery cell can be enhanced.Furthermore, methyl ethyl carbonate (EMC) has a wide electrochemical window and high stability at high voltages, which contributes to improving the oxidative stability of the battery cell and also helps to fully exploit the properties of the active cathode material with high specific capacity, which in turn also contributes to improving the energy density of the battery cell.

[0260] Vinyl carbonate (EC) has a high dielectric constant and preferentially combines with lithium ions in the electrolyte solution to form a stable solvated structure, thus maintaining good ion mobility at low temperatures. Vinyl carbonate (EC) aids in the formation of a stable SEI film at the anode and also contributes to improving the high-pressure resistance of the electrolyte solution, thereby fully utilizing the high specific capacity of the active cathode material and improving the energy density of the battery cell.

[0261] Optionally, the organic solvent further comprises one or more of propylidene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylenepropylene carbonate (MPC), ethylenepropylene carbonate (EPC), butylidene 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), cyclobutane sulfone (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0262] In some embodiments, the electrolyte salt may comprise, but is not limited to, 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 borate dioxylic acid LiBOB, lithium difluorophosphate LiPO2F2, lithium difluorodioxylic acid phosphate LiDFOP and lithium tetrafluorooxalate phosphate LiTFOP.

[0263] Optionally, the electrolyte salt includes lithium hexafluorophosphate LiPF6.

[0264] LiPF6 has high ionic conductivity, which contributes to improved charging / discharging performance of the battery cell. LiPF6 aids in the formation of a stable passivation film on the surface of the cathode collector (e.g., aluminum foil), protecting it from further oxidation. LiPF6 contributes to the formation of a stable SEI film at the anode, thus helping to reduce the consumption of electrolyte solution and active lithium, and contributing to improved initial coulometric efficiency and cycle performance of the battery cell. LiPF6 exhibits good chemical stability and does not show harmful side reactions with the active electrode material, electrolyte solution, or separator, which contributes to improved battery cell lifetime.

[0265] In some embodiments, the electrolyte solution also includes an additive.

[0266] Optionally, the additive includes one or more of fluorinated vinyl carbonate (FEC), vinylidene carbonate (VC), 1,3-propanesulfonic acid lactone (PS) and vinyl sulfate (DTD).

[0267] Optionally, the additive includes fluorinated vinyl carbonate (FEC).

[0268] FEC contributes to the formation of a LiF-rich SEI film at the anode, resulting in a higher ionic conductivity of the SEI film, which can further improve the cycle performance of the battery cell at low temperatures.

[0269] The electrode assembly of the present application can be a wound structure or a stacked structure, and the embodiments of the present application are not limited thereto.

[0270] In some embodiments, the battery cell is a soft-pack battery cell.

[0271] Fig.Figure 5 shows a schematic decomposition representation of a soft-pack battery cell 22 in an exemplary embodiment.

[0272] As in Fig. As shown in Figure 5, the soft-pack battery cell 22 comprises an electrode assembly 221 and a housing, the housing comprising two packaging films 222, the electrode assembly 221 being located between the two packaging films 222, the edges of the two packaging films 222 being connected to each other and forming a sealing section. The soft-pack battery cell 22 further comprises an electrode lead 223, the electrode lead 223 running between the two packaging films 222 and being electrically connected to the electrode assembly 221.

[0273] The housing made of soft packing material has low hardness, and the reverse extrusion pressure exerted by the housing on the electrode assembly during expansion is low. This reduces the problem of electrolyte extrusion from the cathode, anode, and separator, allowing the electrode assembly to maintain good electrolyte wettability during charging and discharging. This, in turn, contributes to good low-temperature cycle performance of the battery cell.

[0274] In some embodiments, each packaging film comprises an insulating protective layer, a metal layer and an insulating compound layer, wherein the insulating compound layer is arranged on a surface of the metal layer facing the electrode assembly, while the insulating protective layer is arranged on a surface of the metal layer facing away from the electrode assembly.

[0275] Optionally, the insulating protective layer can be made of nylon.

[0276] Optionally, the metal layer can be made of aluminum or steel.

[0277] Optionally, the insulating connecting layer can be made of polypropylene.

[0278] In some embodiments, the housing of the soft pack battery is a pouch structure and consists of aluminum-plastic foil.

[0279] In some embodiments, the battery cell is a hard-cased battery cell.

[0280] The casing of the hard-case battery cell has a square shape and is made of metal; for example, the casing can be made of aluminum, steel, etc.

[0281] The methods for manufacturing the battery cell are generally known. In some embodiments, the battery cell can be formed by assembling the cathode foil, the separator, the anode foil, and the electrolyte solution. For example, an electrode assembly can be produced from the cathode foil, the separator, and the anode foil, and the electrode assembly is placed in a housing, dried, and injected with an electrolyte solution. After standing, forming, and other processes, the resulting battery cell is obtained. Example of implementation

[0282] The following embodiments describe in more detail what is disclosed in the embodiments of the present application, and these embodiments serve only for illustration, since various modifications and variations within the scope of disclosure of the embodiments of the present application will be obvious to the person skilled in the art. Unless otherwise stated, all parts, percentages, and ratios given in the following embodiments are based on mass counts, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the equipment used in the embodiments is commercially available. Example 1: Production of the cathode foil

[0283] The active cathode material LiNi 0,91 Co 0,07 Mn 0,02O2, the cathode binder polyvinylidene fluoride (PVDF), the conductive cathode material carbon nanotubes, and carbon black were added to N-methylpyrrolidone (NMP) in a mass ratio of 98:1.2:0.2:0.6 and prepared as a cathode slurry by thorough stirring and mixing. The cathode slurry was applied evenly to two surfaces of a 13 µm thick aluminum foil of the cathode collector and subsequently dried, cold-pressed, and slitted to obtain a cathode foil.

[0284] The active cathode material exhibits a single-crystal morphology.

[0285] The volume-distributed particle size Dv50 of the active cathode material in the cathode film layer is 2.5 µm, and (Dv90-Dv10) / Dv50 is 1.3.

[0286] The conductive cathode medium in the cathode film layer comprises an agglomerated conductive cathode medium and a non-agglomerated conductive cathode medium, and the number density of the agglomerated conductive cathode medium in the cathode film layer is 3 per 1000 µm 2 By adjusting the viscosity and dispersion of the cathode slurry, cathode film layers with different densities of the agglomerated conductive cathode medium can be produced. Production of the anode foil

[0287] The active anode material, the conductive anode medium acetylene black, the anode binder styrene-butadiene rubber, and the thickening agent sodium carboxymethylcellulose were added to the solvent of deionized water in a mass ratio of 96:0.4:2:1.6, and the anode slurry was prepared by thorough stirring and homogeneous mixing. The anode slurry was applied evenly to two surfaces of a 6 µm thick copper foil of the anode collector and subsequently dried, cold-pressed, and cut to obtain an anode foil.

[0288] The active anode material comprises silicon-carbon material and artificial graphite, whose mass ratio is 5:95, and the mass fraction of the Si element in the anode film layer is 4%.

[0289] The volume-distributed particle size Dv50 of the active anode material in the anode film layer is 13 µm. Separator production

[0290] The inorganic particles alumina, the dispersant sodium carboxymethylcellulose, and the binder polyacrylate were stirred uniformly in deionized water in a mass ratio of 90:2:8 to obtain a first slurry. The polymer binder particles commercially available polyvinylidene fluoride particles, the binder polyacrylate, the dispersant sodium carboxymethylcellulose, and the ether-based surfactant were stirred uniformly in deionized water in a solids mass ratio of 87:8:3:2 to obtain a second slurry. A commercially available polypropylene film with a thickness of 7 µm was used as a porous base film. The formulated first slurry was applied uniformly to both surfaces of the porous base film by micro-engraving. After drying, the second slurry was sprayed on. After drying and cutting, the separator was obtained. Preparation of the electrolyte solution

[0291] The organic solvent was obtained by mixing vinyl carbonate (EC) and methyl ethyl carbonate (EMC) in a mass ratio of 40:60 at 25°C. LiPF6 was then added and stirred homogeneously to obtain the electrolyte solution. The concentration of LiPF6 is 1 mol / L. Battery cell manufacturing

[0292] The cathode foil, separator, and anode foil are stacked sequentially to form the electrode assembly by winding. The electrode assembly is then inserted into the aluminum casing and filled with the electrolyte solution. After settling, formation, and other processes, the battery cell is obtained. Example 1-1

[0293] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the cathode foil

[0294] The active cathode material LiNi 0,91 Co 0,07 Mn 0,02 O2, the cathode binder polyvinylidene fluoride (PVDF), the conductive cathode material carbon nanotubes, and carbon black were added to N-methylpyrrolidone (NMP) in a mass ratio of 98:1.2:0.2:0.6 and prepared as a cathode slurry by thorough stirring and mixing. The cathode slurry was applied evenly to two surfaces of a 13 µm thick aluminum foil of the cathode collector and subsequently dried, cold-pressed, and slitted to obtain a cathode foil.

[0295] The active anode material is a mixture of single-crystal and multi-crystal morphology with a mass ratio of 80:20.

[0296] In the cathode film layer, the average particle size of the active cathode material with single-crystal morphology is 2.5 µm, the average particle size of the active cathode material with multi-crystal morphology is 10 µm, the volume-distributed particle size Dv50 of the active cathode material is 4.5 µm, and (Dv90-Dv10) / Dv50 is 1.4.

[0297] The conductive cathode medium in the cathode film layer comprises an agglomerated conductive cathode medium and a non-agglomerated conductive cathode medium, and the number density of the agglomerated conductive cathode medium in the cathode film layer is 3 per 1000 µm 2 . Example 1-2

[0298] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the cathode foil

[0299] The active cathode material LiNi 0,91 Co 0,07Mn 0,02 O2, the cathode binder polyvinylidene fluoride (PVDF), the conductive cathode material carbon nanotubes, and carbon black were added to N-methylpyrrolidone (NMP) in a mass ratio of 98:1.2:0.2:0.6 and prepared as a cathode slurry by thorough stirring and mixing. The cathode slurry was applied evenly to two surfaces of a 13 µm thick aluminum foil of the cathode collector and subsequently dried, cold-pressed, and slitted to obtain a cathode foil.

[0300] The active anode material is a mixture of single-crystal and multi-crystal morphology with a mass ratio of 60:40.

[0301] In the cathode film layer, the average particle size of the active cathode material with single-crystal morphology is 2.5 µm, the average particle size of the active cathode material with multi-crystal morphology is 10 µm, the volume-distributed particle size Dv50 of the active cathode material is 6.7 µm, and (Dv90-Dv10) / Dv50 is 1.5.

[0302] The conductive cathode medium in the cathode film layer comprises an agglomerated conductive cathode medium and a non-agglomerated conductive cathode medium, and the number density of the agglomerated conductive cathode medium in the cathode film layer is 3 per 1000 µm 2 . Example 2-1

[0303] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the anode foil

[0304] The active anode material, the conductive anode medium acetylene black, the anode binder styrene-butadiene rubber, and the thickening agent sodium carboxymethylcellulose were added to the solvent of deionized water in a mass ratio of 96:0.4:2:1.6, and the anode slurry was prepared by thorough stirring and homogeneous mixing. The anode slurry was applied evenly to two surfaces of a 6 µm thick copper foil of the anode collector and subsequently dried, cold-pressed, and cut to obtain an anode foil.

[0305] The active anode material comprises silicon-carbon material and artificial graphite, and their mass ratio is adjusted based on embodiment 1 such that the mass fraction of the Si element in the anode film layer is 1.5%.

[0306] The volume-distributed particle size Dv50 of the active anode material in the anode film layer is 15 µm. Example 2-2

[0307] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the anode foil

[0308] The active anode material, the conductive anode medium acetylene black, the anode binder styrene-butadiene rubber, and the thickening agent sodium carboxymethylcellulose were added to the solvent of deionized water in a mass ratio of 96:0.4:2:1.6, and the anode slurry was prepared by thorough stirring and homogeneous mixing. The anode slurry was applied evenly to two surfaces of a 6 µm thick copper foil of the anode collector and subsequently dried, cold-pressed, and cut to obtain an anode foil.

[0309] The active anode material comprises silicon-carbon material and artificial graphite, and their mass ratio is adjusted based on embodiment 1 such that the mass fraction of the Si element in the anode film layer is 7.4%.

[0310] The volume-distributed particle size Dv50 of the active anode material in the anode film layer is 12 µm. Example 2-3

[0311] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the anode foil

[0312] The active anode material, the conductive anode medium acetylene black, the anode binder styrene-butadiene rubber, and the thickening agent sodium carboxymethylcellulose were added to the solvent of deionized water in a mass ratio of 96:0.4:2:1.6, and the anode slurry was prepared by thorough stirring and homogeneous mixing. The anode slurry was applied evenly to two surfaces of a 6 µm thick copper foil of the anode collector and subsequently dried, cold-pressed, and cut to obtain an anode foil.

[0313] The active anode material comprises silicon-carbon material and artificial graphite, and their mass ratio is adjusted based on embodiment 1 such that the mass fraction of the Si element in the anode film layer is 9.3%.

[0314] The volume-distributed particle size Dv50 of the active anode material in the anode film layer is 11 µm. Comparative example 1

[0315] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the cathode foil

[0316] The active cathode material LiNi 0,91 Co 0,07 Mn 0,02 O2, the cathode binder polyvinylidene fluoride (PVDF), and the conductive cathode medium carbon black were added to N-methylpyrrolidone (NMP) in a mass ratio of 98:1.2:0.8 and prepared as a cathode slurry by thorough stirring and mixing. The cathode slurry was applied evenly to two surfaces of a 13 µm thick aluminum foil of the cathode collector and subsequently dried, cold-pressed, and slitted to obtain a cathode foil.

[0317] The active cathode material exhibits a multi-crystal morphology.

[0318] The volume-distributed particle size Dv50 of the active cathode material in the cathode film layer is 10 µm, and (Dv90-Dv10) / Dv50 is 1.45.

[0319] The cathode film layer does not contain any agglomerated conductive cathode compound. Production of the anode foil

[0320] The active anode material, the conductive anode medium acetylene black, the anode binder styrene-butadiene rubber, and the thickening agent sodium carboxymethylcellulose were added to the solvent of deionized water in a mass ratio of 96:0.4:2:1.6, and the anode slurry was prepared by thorough stirring and homogeneous mixing. The anode slurry was applied evenly to two surfaces of a 6 µm thick copper foil of the anode collector and subsequently dried, cold-pressed, and cut to obtain an anode foil.

[0321] The active anode material comprises silicon-carbon material and artificial graphite, and their mass ratio is adjusted based on embodiment 1 such that the mass fraction of the Si element in the anode film layer is 14.5%.

[0322] The volume-distributed particle size Dv50 of the active anode material in the anode film layer is 10.5 µm. Comparative example 2

[0323] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the cathode foil

[0324] The active cathode material LiNi 0,91 Co 0,07 Mn 0,02 O2, the cathode binder polyvinylidene fluoride (PVDF), and the conductive cathode medium carbon black were added to N-methylpyrrolidone (NMP) in a mass ratio of 98:1.2:0.8 and prepared as a cathode slurry by thorough stirring and mixing. The cathode slurry was applied evenly to two surfaces of a 13 µm thick aluminum foil of the cathode collector and subsequently dried, cold-pressed, and slitted to obtain a cathode foil.

[0325] The active cathode material exhibits a single-crystal morphology.

[0326] The volume-distributed particle size Dv50 of the active cathode material in the cathode film layer is 2.5 µm, and (Dv90-Dv10) / Dv50 is 1.3.

[0327] The cathode film layer does not contain any agglomerated conductive cathode compound. Production of the anode foil

[0328] The active anode material, the conductive anode medium acetylene black, the anode binder styrene-butadiene rubber, and the thickening agent sodium carboxymethylcellulose were added to the solvent of deionized water in a mass ratio of 96:0.4:2:1.6, and the anode slurry was prepared by thorough stirring and homogeneous mixing. The anode slurry was applied evenly to two surfaces of a 6 µm thick copper foil of the anode collector and subsequently dried, cold-pressed, and cut to obtain an anode foil.

[0329] The active anode material comprises silicon-carbon material and artificial graphite, and their mass ratio is adjusted based on embodiment 1 such that the mass fraction of the Si element in the anode film layer is 14.5%.

[0330] The volume-distributed particle size Dv50 of the active anode material in the anode film layer is 10.5 µm. Performance test(1) Electrode film layer porosity test

[0331] The manufactured battery cell was disassembled after a constant current discharge of 0.5 C to a cutoff voltage of 2.5 V (i.e., complete discharge) at 25°C. The electrode foil was immersed in an organic solvent, dimethyl carbonate, for 2 hours, then removed and dried at 60°C for 4 hours. After drying, the electrode foil was removed. The electrode film layer on one side was wiped off to produce a single-sided coated electrode foil. The electrode foil was then punched and cut into small round samples with a specific area, and the apparent volume of the electrode foil, V1, was calculated. According to GB / T 24586-2009, an inert gas, helium, was used as the medium, the gas exchange method was applied, and the actual volume, V2, of the electrode foil was measured using a true density tester. The porosity of the electrode film layer is calculated as (V1-V2) / V1 × 100%.For the test, 30 slices of samples with good appearance and no powder residue on the edges can be taken, and the results are averaged. The Micromeritics AccuPyc II 1340 true density tester is used as the testing instrument. (2) Test of the electrode film layer pressure density

[0332] Electrode film layer density = surface density of the electrode film layer / thickness of the electrode film layer.

[0333] The thickness of the electrode film layer was measured with a universal measuring tape, and during the test 10 positions were taken and then the average value was determined.

[0334] The surface density of the electrode film layer is tested as follows: The manufactured battery cell was disassembled after a discharge at a constant current of 0.5 C down to a cutoff voltage of 2.5 V (i.e., complete discharge) at 25 °C. The electrode foil was immersed in an organic solvent, dimethyl carbonate, for 2 hours, then removed and dried at 60 °C for 4 hours. After drying, the electrode foil was removed. The electrode film layer on one side was wiped to produce a single-sided coated electrode foil. The electrode foil was then punched and cut into small round samples with a specific area S1, weighed, and recorded as M1. The electrode film layer of the weighed electrode foil was then wiped, and the weight of the electrode collector was weighed and recorded as M0. The surface density of the electrode film layer is calculated as (M1 - M0) / S1. (3) Low-temperature battery cell cycle performance test

[0335] At an ambient temperature of 25°C, the battery cell was charged to 80% SOC at a constant current of 0.5C, then charged to a cutoff voltage of 4.25V at a constant current of 0.33C, and subsequently charged to a current of ≤ 0.05C at a constant voltage. The ambient temperature was then set to -10°C, and the cell was kept warm for 30 minutes. During this time, the battery cell was discharged to a cutoff voltage of 2.5V at a constant current of 0.5C. The ambient temperature was then set to 25°C, the cell was kept warm for 30 minutes, and the charging process described above was repeated. This charging and discharging cycle was repeated until the battery cell's discharge capacity decreased to 80% of the discharge capacity of the first cycle. The test was then terminated, and the number of cycles completed by the battery cell was recorded. Table 1 number cathode film layer Anode film layer Number of cycles at low temperature (round) Morphology of inactive cathode material Number density of deagglomerated conductive cathode medium porosity Density (g / cm³) 3 ) Mass fraction of the Si element Dv50 of the active anode material (µm) porosity Density (g / cm³) 3 ) Example 1 single crystal 3 pro 1000 µm 2 18% 3,6 4,0% 13 30% 1,7 1210 Example 1-1 Single crystal:polycrystalline = 80:20 3 pro 1000 µm 2 16% 3,6 4,0% 13 30% 1,7 1020 Example 1-2 Single crystal:polycrystalline = 60:40 3 pro 1000 µm 2 13% 3,6 4,0% 13 30% 1,7 950 Example 2-1 single crystal 3 pro 1000 µm 2 18% 3,6 1,5% 15 32% 1,7 1130 Example 2-2 single crystal 3 pro 1000 µm 2 18% 3,6 7,4% 12 26% 1,7 920 Example 2-3 single crystal 3 pro 1000 µm 2 18% 3,6 9,3% 11 25% 1,7 850 Comparative example 1 polycrystal 0 18% 3,6 14,5% 10,5 30% 1,65 670 Comparative example 2 single crystal 0 18% 3,6 14,5% 10,5 30% 1,65 720

[0336] As can be seen from the test results above, the composition of the cathode and the composition of the anode in the present application are adapted such that the lithium transition metal oxide of the cathode comprises a lithium transition metal oxide with a single-crystal morphology, the total area of ​​the lithium transition metal oxide with the single-crystal morphology is 60% to 100% of the total area of ​​the active cathode material, the porosity of the cathode film layer is 13% to 20%, the active anode material in the anode comprises a silicon-based material and a carbon-based material, and the mass fraction of the Si element in the anode film layer is 1% to 10%, enabling the battery cell to have a high energy density and good cycle performance at low temperatures. Example 3-1

[0337] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the cathode foil

[0338] The conductive cathode medium in the cathode film layer comprises an agglomerated conductive cathode medium and a non-agglomerated conductive cathode medium, and the number density of the agglomerated conductive cathode medium in the cathode film layer is 1 per 1000 µm 2 . Example 3-2

[0339] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the cathode foil

[0340] The conductive cathode medium in the cathode film layer comprises an agglomerated conductive cathode medium and a non-agglomerated conductive cathode medium, and the number density of the agglomerated conductive cathode medium in the cathode film layer is 5 per 1000 µm 2 . Example 3-3

[0341] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the cathode foil

[0342] The cathode film layer does not contain any agglomerated conductive cathode compound. Example 3-4

[0343] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the cathode foil

[0344] The conductive cathode medium in the cathode film layer comprises an agglomerated conductive cathode medium and a non-agglomerated conductive cathode medium, and the number density of the agglomerated conductive cathode medium in the cathode film layer is 8 per 1000 µm 2 By adjusting the viscosity and dispersion of the cathode slurry, cathode film layers with different densities of the agglomerated conductive cathode medium can be produced. Table 2 number cathode film layer Number of cycles at low temperature (round) Number density of deagglomerated conductive cathode medium porosity Density (g / cm³) 3 ) Example 1 3 pro 1000µm 2 18% 3,6 1210 Example 3-1 1 pro 1000µm 2 18% 3,6 1150 Example 3-2 5 pro 1000µm 2 18% 3,6 1120 Example 3-3 0 18% 3,6 1060 Example 3-4 8 pro 1000µm 2 18% 3,6 980

[0345] As can be seen from the test results in Table 2, the production of the cathode film layer with an appropriate amount of agglomerated conductive cathode medium improves both the electronic conductivity of the cathode and reduces the electron transfer resistance and the polarization of the cathode, as well as improving the wettability of the electrolyte solution of the cathode film layer, which in turn contributes to a further improvement in the cycle performance of the battery cell at low temperature. Example 4-1

[0346] The method for manufacturing the battery cell is the same as in embodiment 1, except for the following differences. Production of the anode foil

[0347] The first active anode material, the conductive anode medium acetylene black, the anode binder styrene-butadiene rubber, and the thickening agent sodium carboxymethylcellulose, are added to the solvent of deionized water in a mass ratio of 96:0.4:2:1.6, and the first slurry is prepared by thorough stirring and homogeneous mixing. The second active anode material, the conductive anode medium acetylene black, the anode binder styrene-butadiene rubber, and the thickening agent sodium carboxymethylcellulose, are added to the solvent of deionized water in a mass ratio of 96:0.4:2:1.6, and the second slurry is prepared by thorough stirring and homogeneous mixing.The first and second slurries were simultaneously applied in a 1:1 ratio (solvent-free) to both surfaces of a 6 µm thick copper foil of the anode collector. The foil was then dried, cold-pressed, and cut to obtain the anode film. The second slurry faces the anode collector, and the first slurry faces away from it. The first slurry is dried to form a first anode film layer, and the second slurry is dried to form a second anode film layer.

[0348] The first active anode material comprises silicon-carbon material and artificial graphite, and their mass ratio is adjusted on the basis of embodiment 1 such that the mass fraction of the Si element in the first anode film layer is 5%.

[0349] The second active anode material comprises silicon-carbon material and artificial graphite, and their mass ratio is adjusted based on embodiment 1 such that the mass fraction of the Si element in the second anode film layer is 3%.

[0350] The mass fraction of the Si element in the entire anode film layer is 4%. Example 4-2

[0351] The method for manufacturing the battery cell is the same as in embodiment 4-1, except for the following differences. Production of the anode foil

[0352] The first active anode material comprises silicon-carbon material and artificial graphite, and their mass ratio is adjusted on the basis of embodiment 1 such that the mass fraction of the Si element in the first anode film layer is 8%.

[0353] The second active anode material comprises synthetic graphite, and the mass fraction of the Si element in the second anode film layer is 0%.

[0354] The mass fraction of the Si element in the entire anode film layer is 4%. Example 4-3

[0355] The method for manufacturing the battery cell is the same as in embodiment 4-1, except for the following differences. Production of the anode foil

[0356] The first active anode material comprises artificial graphite, and the mass fraction of the Si element in the first anode film layer is 0%.

[0357] The second active anode material comprises silicon-carbon material and artificial graphite, and their mass ratio is adjusted based on embodiment 1 such that the mass fraction of the Si element in the second anode film layer is 8%.

[0358] The mass fraction of the Si element in the entire anode film layer is 4%. Table 3 number First anode film layer Second anode film layer Anode film layer Number of cycles at low temperature (round) Mass fraction of the Si element Mass fraction of the Si element Mass fraction of the Si element porosity Density (g / cm³) 3 ) Example 4-1 5% 3% 4,0% 30% 1,7 1295 Example 4- 8% 0% 4,0% 30% 1,7 1242 2 Example 4-3 0% 8% 4,0% 30% 1,7 1110

[0359] As can be seen from the test results in Table 3, the first anode film layer is located in the surface region and the second anode film layer in the base region. The mass fraction of the silicon element in the surface region is high, while the base region contains no silicon element or a low mass fraction of silicon element. This helps to reduce damage to the overall conductive network of the anode film layer due to the volume expansion of the silicon-based material in the base region, which in turn helps to improve the low-temperature cycle performance of the battery cell. Example 5-1

[0360] The method for manufacturing the battery cell is the same as in embodiment 4-1, except for the following differences. Production of the anode foil

[0361] The first active anode material comprises silicon-carbon material and natural graphite, and their mass ratio is adjusted so that the mass fraction of the Si element in the first anode film layer is 5%.

[0362] The second active anode material comprises silicon-carbon material and artificial graphite, and their mass ratio is adjusted based on embodiment 1 such that the mass fraction of the Si element in the second anode film layer is 3%.

[0363] The mass fraction of the Si element in the entire anode film layer is 4%. Table 4 number First anode film layer Second anode film layer Anode film layer Number of cycles at low temperature (round) First active anode material Second active anode material Mass fraction of the Si element porosity Density (g / cm³) 3 ) Example 4-1 Silicon-carbon material + synthetic graphite Silicon-carbon material + artificial graphite 4,0% 30% 1,7 1295 Example 5-1 Silicon-carbon material + natural graphite Silicon-carbon material + artificial graphite 4,0% 29% 1,7 1065

[0364] As can be seen from the test results in Table 4, synthetic graphite has a denser structure and a more stable surface. When synthetic graphite is located in the first anode film layer, it helps to better reduce the side reaction of the electrolyte solution and the irreversible consumption of the electrolyte solution and active lithium, which further improves the cycle life of the battery cell at low temperatures.

[0365] It should be noted that this disclosure is not limited to the embodiments mentioned above. The embodiments mentioned above are only examples, and embodiments within the scope of the technical solution of this disclosure that have essentially the same composition as the technical idea and have the same effect are included within the technical scope of this disclosure. Furthermore, within the scope of this disclosure, it also includes other ways of constructing the embodiments by combining some of the constituent elements of the embodiments and applying various deformations to the embodiments, which a person skilled in the art can imagine without departing from the subject matter of this disclosure.

Claims

[1] Battery cell comprising the following: a case; and an electrode assembly located in the housing, wherein the electrode assembly comprises a cathode foil, an anode foil and a separator, the separator being located between the cathode foil and the anode foil, where, the cathode foil comprises a cathode collector and a cathode film layer located on at least one side of the cathode collector, the cathode film layer comprising an active cathode material, the active cathode material comprising a lithium transition metal oxide, the lithium transition metal oxide comprising a nickel element, the molar fraction of the nickel element in the transition metal element of the lithium transition metal oxide being more than 80%, the lithium transition metal oxide comprising a lithium transition metal oxide with a single-crystal morphology, the total area of ​​the lithium transition metal oxide with the single-crystal morphology being 60% to 100% of the total area of ​​the active cathode material, and the porosity of the cathode film layer being 13% to 20%; wherein the anode foil comprises an anode collector and an anode film layer located on at least one side of the anode collector, wherein the anode film layer comprises an active anode material, the active anode material comprising a silicon-based material and a carbon-based material, wherein the mass fraction of the Si element in the anode film layer is 1% to 10%. [2] Battery cell according to claim 1, wherein the mass fraction of the Si element in the anode film layer is 3% to 8%; and / or, wherein the porosity of the cathode film layer is 15% to 18%. [3] Battery cell according to claim 1 or 2, characterized by that the porosity of the anode film layer is 25% to 35%. [4] Battery cell according to any one of claims 1 to 3, wherein, The density of the cathode film layer is 3.4 g / cm³. 3 up to 3.7 g / cm³ 3 is; and / or, The compression density of the anode film layer is 1.55 g / cm³. 3up to 1.8 g / cm³ 3 . [5] Battery cell according to any one of claims 1 to 4, wherein, the volume-distributed particle size Dv50 of the active cathode material is 1 µm to 7 µm; and / or, where the particle size distribution (Dv90-Dv10) / Dv50 of the active cathode material is 1 to 1.5; and / or, where the volume-distributed particle size Dv50 of the active anode material is 10 µm to 20 µm. [6] Battery cell according to any one of claims 1 to 5, wherein, the lithium transition metal oxide comprises a nickel element and a cobalt element, wherein the cobalt content in a surface region of the lithium transition metal oxide is greater than the cobalt content in a core region of the lithium transition metal oxide; or, wherein the lithium transition metal oxide comprises a nickel element and a manganese element, wherein the manganese content in a surface region of the lithium transition metal oxide is lower than the manganese content in a core region of the lithium transition metal oxide; or, wherein the lithium transition metal oxide comprises a nickel element, a cobalt element and a manganese element, wherein the cobalt content in a surface region of the lithium transition metal oxide is greater than the cobalt content in a core region of the lithium transition metal oxide, wherein the manganese content in a surface region of the lithium transition metal oxide is less than the manganese content in a core region of the lithium transition metal oxide, wherein the surface region of the lithium transition metal oxide is a region extending radially inwards from the outermost surface of the particle over 100 nm, wherein the core region of the lithium transition metal oxide is a region extending radially outwards from the center of the particle over 300 nm. [7] Battery cell according to any one of claims 1 to 6, wherein the lithium transition metal oxide comprises a Ni element and a doping element, wherein the doping element comprises a cationic doping element and / or an anionic doping element, wherein the cationic doping element comprises one or more of the elements Al, Y, Zr, Zn, Cr, Mg, V, Ti and B, and wherein the anionic doping element comprises one or more of the elements N, F, S and Cl. [8] Battery cell according to one of claims 1 to 7, wherein the cathode film layer comprises a conductive cathode medium, wherein the mass fraction of the conductive cathode medium in the cathode film layer is 0.5% to 2.5%. [9] Battery cell according to claim 8, wherein the conductive cathode means comprises one or more of carbon nanotubes, carbon black, acetylene black, carbon fibers, graphene, wherein the carbon nanotubes comprise one or more of single-walled carbon nanotubes, thin-walled carbon nanotubes, multi-walled carbon nanotubes. [10] Battery cell according to claim 8, wherein the conductive cathode material comprises carbon nanotubes, wherein at least a part of the carbon nanotubes are located on the surface of the active cathode material. [11] Battery cell according to one of claims 8 to 10, wherein the conductive cathode material comprises an agglomerated conductive cathode material, wherein the number density of the agglomerated conductive cathode material in the cathode film layer is 1 to 5 per 1000 µm 2 amounts. [12] Battery cell according to claim 11, wherein the number density of the agglomerated conductive cathode material is 2 to 4 per 1000 µm 2 amounts. [13] Battery cell according to claim 11 or 12, wherein, the maximum distance between any two points on a circumference of the agglomerated conductive cathode medium is greater than or equal to 2 µm; and / or, wherein the porosity of the agglomerated conductive cathode medium is 30% to 65%; and / or, wherein the agglomerated conductive cathode medium comprises carbon nanotubes. [14] Battery cell according to claim 13, wherein the agglomerated conductive cathode material further comprises one or more carbon black and acetylene black. [15] Battery cell according to any one of claims 1 to 14, wherein the active anode material satisfies one or more of the following conditions (1) to (4): (1) the silicon-based material comprises one or more of monomeric silicon, silicon-carbon material, silicon oxide, silicon nitride, silicon alloy material; (2) the carbon-based material comprises one or more of natural graphite, artificial graphite, soft carbon, hard carbon and microspheres of intermediate-phase carbon; (3) the average particle size of the silicon-based material is 2 µm to 15 µm; (4) the average particle size of the carbon-based material is 11 µm to 21 µm. [16] Battery cell according to one of claims 1 to 15, wherein the anode film layer comprises a first anode film layer facing away from the anode collector and a second anode film layer facing the anode collector, wherein the first anode film layer comprises a first active anode material, and wherein the second anode film layer comprises a second active anode material; wherein the first active anode material comprises a first carbon-based material and a first silicon-based material; wherein the second active anode material comprises a second carbon-based material, and wherein the second anode film layer is free of Si elements, or wherein the second active anode material comprises a second carbon-based material and a second silicon-based material, and wherein the mass fraction of the Si element in the first anode film layer is greater than the mass fraction of the Si element in the second anode film layer. [17] Battery cell according to claim 16, wherein, the mass fraction of the silicon element in the first anode film layer is 2% to 15%; and / or, where the mass fraction of the Si element in the second anode film layer is 0% to 10%. [18] Battery cell according to claim 17, wherein, the mass fraction of the silicon element in the first anode film layer is 2% to 10%; and / or, where the mass fraction of the Si element in the second anode film layer is 0.5% to 8%. [19] Battery cell according to one of claims 16 to 18, wherein the volume distributed particle size Dv50 of the first active anode material is smaller than the volume distributed particle size Dv50 of the second active anode material. [20] Battery cell according to one of claims 16 to 19, wherein the anode film layer satisfies one or more of the following conditions (1) to (8): (1) the first carbon-based material comprises one or more of natural graphite, artificial graphite; (2) the second carbon-based material comprises one or more of natural graphite and artificial graphite; (3) the average particle size of the first carbon-based material is 11 µm to 21 µm; (4) the average particle size of the second carbon-based material is 11 µm to 21 µm; (5) the first silicon-based material comprises one or more of a silicon-carbon material, a pre-magnesium-silicon-oxygen material; (6) the second active anode material comprises a second silicon-based material, wherein the second silicon-based material comprises one or more silicon-carbon materials, a pre-magnesium-silicon-oxygen material; (7) the average particle size of the first silicon-based material is 2 µm to 15 µm; (8) the second active anode material comprises a second silicon-based material, wherein the average particle size of the second silicon-based material is 2 µm to 15 µm. [21] Battery cell according to any one of claims 1 to 20, wherein the battery cell further comprises an electrolyte solution, wherein the electrolyte solution 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. [22] Battery cell according to claim 21, wherein the organic solvent comprises vinyl carbonate and methyl ethyl carbonate, wherein the mass fraction of the methyl ethyl carbonate in the organic solvent is greater than or equal to 55% and less than 100%. [23] Battery cell according to claim 22, wherein the organic solvent further comprises one or more of propylidene carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylenepropylene carbonate, ethylenepropylene carbonate, butylidene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. [24] Battery cell according to one of claims 21 to 23, wherein the electrolyte salt comprises 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 borate dioxylic acid LiBOB, lithium difluorophosphate LiPO2F2, lithium difluorodioxylic acid phosphate LiDFOP and lithium tetrafluorooxalate phosphate LiTFOP. [25] Battery cell according to one of claims 21 to 24, wherein the electrolyte solution further comprises an additive, the additive comprising one or more of fluorinated vinyl carbonate, vinylidene carbonate, 1,3-propanesulfonic acid lactone and vinyl sulfate. [26] Battery cell according to one of claims 1 to 25, wherein the separator comprises a porous base film and a porous coating located on at least one side of the porous base film, wherein the porous coating comprises filler particles, wherein the filler particles comprise one or more of inorganic particles, organic particles, or organo-inorganic composite particles. [27] Battery cell according to claim 26, wherein the porous coating further comprises polymer binder particles, wherein the volume distributed particle size Dv50 of the polymer binder particles is larger than the volume distributed particle size Dv50 of the filler particles. [28] Battery cell according to claim 26 or 27, wherein, the thickness of the porous coating is 0.5 µm to 2 µm; and / or, wherein the thickness of the porous base film is 5 µm to 10 µm; and / or, where the porosity of the separator is between 35% and 55%. [29] Battery cell according to any one of claims 1 to 28, wherein the battery cell is a soft-pack battery cell, wherein the housing comprises two packaging films, wherein the electrode assembly is located between the two packaging films, wherein the edges of the two packaging films are connected to each other and form a sealing section; wherein the soft-pack battery cell further comprises an electrode conductor, wherein the electrode conductor runs between the two packaging films and is electrically connected to the electrode assembly. [30] Battery cell according to claim 29, characterized by, that the packaging film comprises an insulating protective layer, a metal layer and an insulating connecting layer, wherein the insulating connecting layer is provided on a surface of the metal layer facing the electrode assembly, while the insulating protective layer is provided on a surface of the metal layer facing away from the electrode assembly. [31] Battery cell according to any one of claims 1 to 28, wherein the battery cell is a hard-case battery cell, the case having a square shape and being made of metal. [32] Battery device comprising a plurality of battery cells according to any one of claims 1 to 31. [33] Battery device according to claim 32, wherein the battery device comprises: a box comprising a support plate and a frame provided around the circumference of the support plate, the support plate being firmly connected to the frame; a plurality of battery cells, wherein the battery cell is a soft-pack battery cell, wherein the plurality of battery cells is stacked in the first direction and received in the box, wherein the surface of the battery cell comprises a first surface and a second surface, wherein the area of ​​the first surface is larger than the area of ​​the second surface, wherein the first surfaces of a plurality of battery cells are arranged opposite each other along the first direction, wherein the support plate is arranged opposite the second surfaces of a plurality of battery cells along the second direction; wherein at least one connecting beam is provided in the box which extends in a third direction, wherein the connecting beam is firmly connected to the support plate and / or the frame; wherein at least one of the battery cells rests against the connecting beam along the first direction, wherein the first direction, the second direction and the third direction are perpendicular to each other. [34] Battery device according to claim 33, wherein the battery device further comprises: a thermal management component that is provided between the support plate and the battery cell to regulate the temperature of the battery cell; a fastening adhesive provided between the thermal management component and the battery cell to secure the battery cell to the thermal management component. [35] Battery device according to claim 34, wherein the fastening adhesive is directly connected to the housing of the battery cell. [36] Battery device according to claim 34 or 35, wherein the battery device further comprises a receiving housing, wherein the receiving housing accommodates at least one of the battery cells, wherein the fastening adhesive is directly bonded to a housing wall of the receiving housing. [37] Battery cell according to any one of claims 33 to 36, wherein the nominal capacity of each battery cell is greater than or equal to 100Ah. [38] Power consumption device comprising a battery cell according to any one of claims 1 to 31 or a battery device according to claims 32 to 37.

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