Battery cell and electric device

Abstract

The present application provides a battery cell, which comprises an electrode assembly, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material comprises a first layered lithium transition metal oxide having a chemical composition of formula (1), Lia1Nix1Coy1Mnz1Ab1Bc1Cd1De1O2 formula (1), in which A, B, C and D each independently comprise any one of Ti, Nb, Mg, Mo, Ca, Sr, Ta, W, Zr, Zn and Al and are different from each other, and optionally comprise Ti, Nb, Mg and Mo, 0.60≤a1≤1.20, 0.80≤x1≤0.98, y1≥0, z1≥0, 0≤b1≤0.02, 0≤c1≤0.02, 0≤d1≤0.02, 0≤e1≤0.02, at least three of b1, c1, d1 and e1 are not 0 at the same time, and x1+y1+z1+b1+c1+d1+e1=1. Further provided is an electric device comprising the battery cell.

Description

Battery cells and electrical devices This application is based on and claims priority to Chinese patent application No. 202510029581.X, filed on January 8, 2025, the contents of which are incorporated herein by reference in their entirety. Technical Field

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

[0002] With the development of the battery industry, especially in the development of high-energy-density battery systems, ordinary high-nickel materials for cathodes can no longer meet energy density requirements, making the development and application of ultra-high-nickel materials urgent. However, the structural stability of currently used ultra-high-nickel NCM materials is poor, and their cycle performance deteriorates significantly compared to conventional high-nickel materials.

[0003] Currently, in the preparation of high-nickel materials, measures such as increasing coating to strengthen the material structure have been considered; alternatively, high-nickel materials with lower Ni content are selected to balance structural stability and system energy density. However, these approaches have significant shortcomings. Specifically, the structure may be damaged during the mechanical stirring of the powder, and the expansion and contraction of the battery cell during cyclic lithium insertion and extraction can still damage the coating layer, ultimately leading to structural collapse. Simple coating cannot fundamentally solve the problem of poor material structural stability.

[0004] Therefore, there is still a need in the field to provide high-nickel materials with improved structural stability, thereby improving battery performance, especially cycle performance, to achieve a balance between volumetric energy density and cycle performance. Summary of the Invention

[0005] This application provides a battery cell and an electrical device to improve the cycle performance of the battery cell, thereby achieving a balance between volumetric energy density and cycle performance.

[0006] The first aspect of this application relates to a battery cell, including an electrode assembly comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode comprises a positive active material, which comprises a first layered lithium transition metal oxide with the chemical composition of formula (1).

[0007] Li a1 Ni x1 Co y1 Mn z1 A b1 B c1 C d1 D e1 O2 formula (1)

[0008] Where A, B, C, and D each independently include any one of Ti, Nb, Mg, Mo, Ca, Sr, Ta, W, Zr, Zn, and Al, and they are all distinct. Optionally, they include Ti, Nb, Mg, and Mo. The following conditions must be met: 0.60 ≤ a1 ≤ 1.20, 0.80 ≤ x1 ≤ 0.98, y1 ≥ 0, z1 ≥ 0, 0 ≤ b1 ≤ 0.02, 0 ≤ c1 ≤ 0.02, 0 ≤ d1 ≤ 0.02, 0 ≤ e1 ≤ 0.02. At least three of b1, c1, d1, and e1 are not simultaneously 0, and x1 + y1 + z1 + b1 + c1 + d1 + e1 = 1. Optionally, b1, c1, d1, and e1 are all non-zero; more preferably, b1, c1, d1, and e1 are all equal.

[0009] According to a first aspect of the invention, b1, c1, d1, and e1 are all non-zero, and optionally, 0.001≤b1≤0.01, 0.001≤c1≤0.01, 0.001≤d1≤0.01, and 0.001≤e1≤0.01.

[0010] According to a first aspect of the invention, in the first layered lithium transition metal oxide, the difference between at least two of b1, c1, d1 and e1 is not more than 0.001, optionally the difference between at least three of b1, c1, d1 and e1 is not more than 0.001, and further optionally, the difference between any two of b1, c1, d1 and e1 is not more than 0.001.

[0011] According to a first aspect of the invention, in the first layered lithium transition metal oxide, 0.80≤a1≤1.10, 0.82≤x1≤0.98, y1>0, z1>0; optionally, 0.85≤a1≤1.10, 0.85≤x1≤0.97, 0.01≤y1≤0.1, 0.005≤z1≤0.05.

[0012] According to a first aspect of the invention, the first layered lithium transition metal oxide satisfies at least one of the following conditions: (1) 0.002≤b1≤0.01; (2) 0.002≤c1≤0.01; (3) 0.002≤d1≤0.01; (4) 0.002≤e1≤0.01; (5) 0.005≤b1+c1+d1+e1≤0.05, optionally 0.02≤b1+c1+d1+e1≤0.05.

[0013] According to a first aspect of the invention, the first layered lithium transition metal oxide has the chemical formula Li a1 Ni x1 Co y1 Mn z1 Ti b1 Nb c1 Mg d1 Moe1 O2, 0.001≤b1≤0.003, 0.001≤c1≤0.003, 0.001≤d1≤0.003, 0.001≤e1≤0.003.

[0014] According to a first aspect of the present invention, the particles of the first layered lithium transition metal oxide are in a secondary particle morphology, and the average particle size of the first layered lithium transition metal oxide satisfies 7 μm to 10 μm.

[0015] According to a first aspect of the present invention, the positive electrode active material further comprises a second layered lithium transition metal oxide with a chemical composition of formula (2), and the composition of the second layered lithium transition metal oxide is different from that of the first layered lithium transition metal oxide: Li a2 Ni x2 Co y2 Mn z2 M b2 O2 formula (2), wherein M includes at least one of Al, Zr, Mg, Zn, Y, Fe, Nb, W, Zn, Mo, Ba, Ca, Ta and Ti, 0.60≤a2≤1.20, 0.80≤x2≤0.98, y2>0, z2>0, 0.002≤b2≤0.02, x2+y2+z2+b2=1.

[0016] According to a first aspect of the present invention, the second layered lithium transition metal oxide is in the form of secondary or primary particles, and the average particle size of the second layered lithium transition metal oxide satisfies 1 μm-3.5 μm; optionally, the primary particles of the second layered lithium transition metal oxide are spherical or near-spherical.

[0017] According to a first aspect of the present invention, in the positive electrode active material, the mass ratio of the first layered lithium transition metal oxide to the second layered lithium transition metal oxide is in the range of 5:5 to 9:1.

[0018] According to a first aspect of the invention, the positive electrode has a unit area capacity of 15.3 mWh / cm². 2 ~35.7mWh / cm 2 .

[0019] According to a first aspect of the present invention, the negative electrode sheet comprises a negative electrode active material, the negative electrode active material comprises a silicon-carbon composite material, and the mass percentage of silicon in the negative electrode active material is 9wt% to 35wt%.

[0020] According to a first aspect of the present invention, the silicon-carbon composite material comprises a porous carbon matrix and a silicon-based material dispersed in the pores and surface of the porous carbon matrix; optionally, the silicon-based material comprises silicon nanocrystals of 0.2 nm to 20 nm, and optionally the silicon nanocrystals are distributed within the pores of the porous carbon matrix.

[0021] According to a first aspect of the invention, the electrolyte comprises a lithium salt, the lithium salt comprising one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium dioxaborate, lithium difluorooxaborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide; optionally, the lithium salt comprises at least three of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium fluorosulfonate.

[0022] According to a first aspect of the invention, the total concentration of lithium salt in the electrolyte is 0.5 mol / L to 1.5 mol / L, and optionally 0.8 mol / L to 1.2 mol / L.

[0023] According to a first aspect of the present invention, the volumetric energy density of the battery cell is in the range of 750Wh / L to 870Wh / L.

[0024] A second aspect of the present invention relates to an electrical device, characterized in that the electrical device comprises the battery cell described in the first aspect above. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0026] Figure 1 is a schematic diagram of a battery cell according to one embodiment of this application.

[0027] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1.

[0028] Figure 3 is a schematic diagram of a battery module according to one embodiment of this application.

[0029] Figure 4 is a schematic diagram of a battery pack according to one embodiment of this application.

[0030] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4.

[0031] Figure 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0032] The accompanying drawings are not drawn to scale.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Secondary battery cell; 51 Housing; 52 Electrode assembly; 53 End cap. Detailed Implementation

[0035] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0036] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0037] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0039] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0040] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0041] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0042] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0043] [Battery cell]

[0044] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0045] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0046] High-energy-density battery systems suffer from poor structural stability. Current solutions typically involve adding a coating layer to strengthen the material structure, or selecting high-nickel ternary materials with lower nickel content to balance structural stability and energy density. However, these approaches have significant shortcomings. Specifically, the mechanical stirring of the cathode active material powder can damage its structure during processing, and the expansion and contraction of individual cells during lithium insertion and extraction cycles can still damage the coating layer, ultimately leading to structural collapse. Therefore, simple coating cannot fundamentally solve the problem of poor material structural stability.

[0047] One embodiment of this application provides a battery cell including an electrode assembly, the electrode assembly including a positive electrode, a negative electrode, and an electrolyte, the positive electrode including a positive active material, the positive active material including a first layered lithium transition metal oxide with the chemical composition of formula (1): Li a1 Ni x1 Co y1 Mn z1 A b1 B c1 C d1 D e1 O2 formula (1), wherein A, B, C, and D each independently include any one of Ti, Nb, Mg, Mo, Ca, Sr, Ta, W, Zr, Zn, and Al, and are all different from each other. Optionally, they include Ti, Nb, Mg, and Mo, with 0.60≤a1≤1.20, 0.80≤x1≤0.98, y1≥0, z1≥0, 0≤b1≤0.02, 0≤c1≤0.02, 0≤d1≤0.02, and 0≤e1≤0.02. At least three of b1, c1, d1, and e1 are not simultaneously 0, and x1+y1+z1+b1+c1+d1+e1=1. Optionally, the total amount of b1+c1+d1+e1 ranges from 0.001 to 0.04. The elemental content in the technical solution of this application is determined by inductively coupled plasma spectrometry (ICP).

[0048] Although the mechanism is not yet clear, the applicant unexpectedly discovered that the aforementioned first-layered lithium transition metal oxide in Li + The material exhibits low volume change during insertion and extraction, achieving low strain and high capacity, resulting in a highly stable crystal structure; the capacity retention is significantly improved compared to commercial materials. The applicant believes that the superior structural stability can be attributed to three aspects: (1) reduced oxygen loss due to pinning effect of dopants; (2) reduced lattice expansion and contraction and defect generation; (3) improved structural stability by suppressing cation mixing and rock salt transformation through multi-component dopants, thereby improving battery performance, especially cycle performance. The technical solution of this application can improve the overall stability of the particles by adjusting the element content and utilizing the interaction between elements to optimize the surface and internal structure.

[0049] In some implementations, b1, c1, d1, and e1 are all non-zero. Optionally, 0.001≤b1≤0.01, 0.001≤c1≤0.01, 0.001≤d1≤0.01, and 0.001≤e1≤0.01.

[0050] In some embodiments, in the first layered lithium transition metal oxide, the molar content of at least two, and optionally at least three, of elements A, B, C, and D differs by no more than 0.001. Doping with these elements in similar amounts reduces oxygen loss and increases structural stability.

[0051] In some embodiments, in the first layered lithium transition metal oxide, 0.80 ≤ a1 ≤ 1.10, 0.82 ≤ x1 ≤ 0.98, y1 > 0, and z1 > 0. Optionally, 0.85 ≤ a1 ≤ 1.10, 0.85 ≤ x1 ≤ 0.97, 0.01 ≤ y1 ≤ 0.1, and 0.005 ≤ z1 ≤ 0.05. Multi-element doping schemes are particularly suitable for high-nickel layered transition metal oxides or ultra-high-nickel layered transition metal oxides, and can better maintain the structural stability of the aforementioned oxides.

[0052] In some embodiments, the first layered lithium transition metal oxide satisfies at least one of the following conditions: (1) 0.002 ≤ b1 ≤ 0.01; (2) 0.002 ≤ c1 ≤ 0.01; (3) 0.002 ≤ d1 ≤ 0.01; (4) 0.002 ≤ e1 ≤ 0.01; (5) 0.005 ≤ b1 + c1 + d1 + e1 ≤ 0.05, which can be optionally 0.02 ≤ b1 + c1 + d1 + e1 ≤ 0.05. Further preferred embodiments are used to increase stability.

[0053] In some embodiments, A, B, C, and D each independently comprise any one of Ti, Nb, Mg, and Mo and are distinct from each other, with 0.001 ≤ b1 ≤ 0.003, 0.001 ≤ c1 ≤ 0.003, 0.001 ≤ d1 ≤ 0.003, and 0.001 ≤ e1 ≤ 0.003. More preferred doping schemes are used to increase stability.

[0054] In some embodiments, the particles of the first layered lithium transition metal oxide are in a secondary particle morphology, and the average particle size of the first layered lithium transition metal oxide satisfies 7 μm to 10 μm. In some embodiments, the particles of the first layered lithium transition metal oxide are spherical or near-spherical. This increases the compaction density of the electrode.

[0055] In this application, the average particle size of the first layered lithium transition metal oxide can be tested using equipment and methods known in the art. For example, scanning electron microscope (SEM) images of the positive electrode sheet can be obtained using a scanning electron microscope (e.g., ZEISS Sigma 300), referring to JY / T010-1996. As an example, the test can be performed as follows: Randomly select a test sample with dimensions of 50mm x 100mm on the positive electrode. Randomly select multiple test areas (e.g., 5) within the test sample. At a certain magnification (e.g., 1000x when measuring the first layer of lithium transition metal oxide), read the particle size of each first layer of lithium transition metal oxide particle in each test area (i.e., take the distance between the two farthest points on the first layer of lithium transition metal oxide particle as the particle size). Count the number and particle size of the first layer of lithium transition metal oxide particles in each test area. Take the arithmetic mean of the particle size in each test area; this is the average particle size of the first layer of lithium transition metal oxide particles in the test sample. To ensure the accuracy of the test results, the above test can be repeated with multiple test samples (e.g., 10), and the average value of each test sample can be taken as the final test result.

[0056] In some embodiments, the positive electrode active material further includes a second layered lithium transition metal oxide with the chemical composition of formula (2), and the composition of the second layered lithium transition metal oxide is different from that of the first layered lithium transition metal oxide: Li a2 Ni x2 Co y2 Mn z2 M b2 O2, wherein M includes at least one of Al, Zr, Mg, Zn, Y, Fe, Nb, W, Zn, Mo, Ba, Ca, Ta, and Ti, 0.60≤a≤1.20, 0.80≤x≤0.98, y>0, z>0, 0.002≤b2≤0.02. In this application, different composition refers to any difference in the type or content of any one element in the molecular formula, which is considered to be different composition. The first layered oxide is a polycrystalline large particle with high specific capacity but low compaction density, while the second layered oxide is a single crystal or polycrystalline small particle with relatively low specific capacity but high compaction density. In order to improve the energy density, a material with high specific capacity and good rolling performance is required, and the large and small particles are mixed.

[0057] In some embodiments, the second layered lithium transition metal oxide is in the form of secondary or primary particles, and the average particle size of the second layered lithium transition metal oxide is 1 μm to 3.5 μm. Secondary particles are aggregates of primary particles. The second layered transition metal oxide has a smaller particle size than the first layered lithium transition metal oxide, achieving a size distribution. Larger particles form large voids, which are filled by smaller particles, thereby increasing the compaction density of the positive electrode sheet.

[0058] In this application, the average particle size test method for the second layered lithium transition metal oxide can be performed by referring to the method described above for testing the first layered lithium transition metal oxide.

[0059] In some embodiments, the mass ratio of the first layered lithium transition metal oxide to the second layered lithium transition metal oxide in the positive electrode active material is in the range of 5:5 to 9:1. A higher proportion of large particles and fewer small particles results in better specific capacity of the active material, as large particles have higher specific capacity.

[0060] In some embodiments, the positive electrode has a capacity per unit area of ​​15.3 mWh / cm². 2 ~35.7mWh / cm 2 This is to improve the energy density of individual battery cells.

[0061] In some embodiments, the volumetric energy density of the battery cell ranges from 750Wh / L to 870Wh / L.

[0062] A positive electrode typically includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0063] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0064] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0065] In some embodiments, the positive electrode active material may further include at least one of the following materials: lithium phosphate with an olivine structure. Examples of lithium phosphate with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0066] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0067] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0068] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0069] [Negative electrode plate]

[0070] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0071] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0072] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0073] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0074] In some embodiments, the negative electrode sheet includes a negative electrode active material, which is a silicon-carbon composite material, and the mass percentage of silicon in the negative electrode active material is 9wt% to 35wt%. Utilizing silicon increases the specific capacity of the negative electrode sheet, thereby improving the volumetric energy density of the battery cell.

[0075] In some embodiments, the silicon-carbon composite material comprises a porous carbon matrix and a silicon-based material dispersed in the pores and surface of the porous carbon matrix. Optionally, the silicon-based material comprises silicon nanocrystals of 0.2 nm to 20 nm, and optionally, the silicon nanocrystals are distributed within the pores of the porous carbon matrix. The silicon-based material dispersed within the pores of the porous carbon matrix provides space for the volume expansion of the silicon-based material during cyclic charging, thereby effectively mitigating the shortened cycle life and safety risks caused by the expansion of the negative electrode sheet due to the expansion of the silicon-based material. Furthermore, the silicon nanocrystals have a more stable structure and a smaller volume change rate during cyclic charging and discharging, thus further improving the cycle life of the battery cell.

[0076] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0077] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0078] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0079] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0080] [Electrolytes]

[0081] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0082] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0083] In some embodiments, the electrolyte comprises a lithium salt, specifically one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium dioxalate borate, lithium difluorooxalate borate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide; optionally, the lithium salt comprises at least three of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium fluorosulfonate. This can improve the interfacial stability of the cathode material and enhance the cycle life of the battery.

[0084] In some embodiments, the total concentration of lithium salt in the electrolyte is 0.5 mol / L to 1.5 mol / L, optionally 0.8 mol / L to 1.2 mol / L. This can improve the interfacial stability of the cathode material and enhance the cycle life of the battery.

[0085] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0086] In some embodiments, the electrolyte may optionally include additives. As examples, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0087] In some embodiments, the gel electrolyte comprises a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0088] In some embodiments, the solid electrolyte includes polymer solid electrolyte, inorganic solid electrolyte, and composite solid electrolyte.

[0089] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0090] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium-germanium-phosphorus-sulfur, sulfosilium-germanium), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0091] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0092] [Isolation Component]

[0093] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0094] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0095] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0096] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and isolate the positive and negative electrodes. In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0097] [Electrode Assembly]

[0098] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0099] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative electrode are wound into a wound structure.

[0100] In some implementations, the electrode assembly is a stacked structure.

[0101] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0102] As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0103] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0104] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0105] As an example, the separator can be continuously arranged between any adjacent positive or negative electrode plates by folding or rolling.

[0106] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0107] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0108] shell

[0109] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0110] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0111] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also have one or more.

[0112] Figure 1 shows a square-structured battery cell 5 as an example.

[0113] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and an end cap 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the end cap 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0114] electrode terminals

[0115] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0116] Pressure relief mechanism

[0117] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0118] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby forming an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0119] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0120] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0121] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0122] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0123] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0124] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0125] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0126] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0127] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other arbitrary way. Furthermore, these multiple secondary battery cells 5 can be fixed in place using fasteners.

[0128] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0129] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0130] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0131] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0132] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0133] As an example, the housing may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, forming a closed space inside the housing to accommodate individual battery modules. Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0134] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0135] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0136] As the electrical device, a single secondary battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0137] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0138] [Example]

[0139] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0140] Preparation Example 1

[0141] Step S1: Weigh lithium hydroxide and dried high-nickel ternary precursor, mix the mixture evenly in a high-speed mixer and then sinter it in an oxygen furnace. Adjust the sintering temperature and sintering time, and use oxygen as the sintering atmosphere. After cooling, the matrix material can be obtained.

[0142] In step S2, the matrix material prepared in S1 is washed with water at a mass ratio of 1:51 for 30 minutes, centrifuged, filtered, and then subjected to vibration drying at a vibration frequency of 30 Hz for 5 hours to obtain the washed matrix material.

[0143] In step S3, the water-washed matrix material prepared in S2 is mixed with the dopant and sintered. During this sintering process, the particle size of the primary particles is adjusted by adjusting the sintering temperature and sintering time, and the size of the secondary particles is adjusted by adjusting the precursor particle size, finally obtaining the first layered lithium transition metal oxide.

[0144] The composition of the high-nickel ternary precursor and dopant, the sintering temperature and time in step S1, and the sintering temperature and time in step S3 are specifically recorded in Table 1. Based on the molar percentages of each element in the first layered lithium transition metal oxide in Table 2, the dopant to be added in step S3 and its amount are selected. For other preparation examples, refer to the preparation process of Preparation Example 1; the specific processes and required materials are shown in Tables 1 and 2.

[0145] Table 1

[0146] Table 2

[0147] Example 1

[0148] Positive electrode sheet: The first layered lithium transition metal oxide synthesized in Preparation Example 1 was used as the positive electrode active material, and the conductive agent carbon black and the binder polyvinylidene fluoride (PVDF) were added in a mass ratio of 97:1:2. N-methylpyrrolidone was added and the mixture was stirred for 3 hours to obtain a positive electrode slurry. Then, it was uniformly coated on the positive electrode current collector, dried, cold-pressed and cut to obtain the positive electrode sheet.

[0149] Negative electrode sheet: Anode active material 1 artificial graphite, anode active material 2 silicon-based material, conductive agent carbon black, carbon nanotubes (CNT), binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC) are added to deionized water in a weight ratio of 60.48:34.02:1:0.375:2.8:1.325 and mixed and stirred for 2 hours to obtain a slurry; the slurry is uniformly coated on the negative electrode current collector and dried to obtain the negative electrode sheet.

[0150] Separator membrane: Polypropylene membrane is used as the separator membrane.

[0151] Electrolyte: LiPF6 was dissolved in a solvent of ethylene carbonate, methyl ethyl carbonate and diethyl carbonate in a volume ratio of 1:1:1 to prepare an electrolyte with a LiPF6 concentration of 1 mol / L. Then, lithium difluorophosphate was dissolved in the above electrolyte to obtain an electrolyte with a lithium difluorophosphate concentration of 0.01 mol / L.

[0152] Assembly: The above-mentioned positive electrode sheet, separator, and negative electrode sheet are wound or stacked in sequence to obtain a bare cell; the bare cell is placed in a packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0153] The compositions of the positive and negative electrode active materials in the remaining embodiments are recorded in Table 3, and the types and molar concentrations of lithium salts in the electrolyte are recorded in Table 4. In Examples 11-14, the positive electrode active material, in addition to the first layered lithium transition metal oxide obtained according to the above preparation examples, also includes a component of LiNi. 0.926 Co 0.057 Mn 0.014 Zr 0.003 O2 and a second layered lithium transition metal oxide with a particle morphology of individual primary particles, wherein the mass ratio of the first layered lithium transition metal oxide to the second layered lithium transition metal oxide is 7:3.

[0154] Table 3

[0155] Performance testing

[0156] Energy density test:

[0157] 1) Measurement of the discharge energy of a single battery cell: The method is as follows: Place the single battery cell at 25℃ for 2 hours to ensure that the temperature of the single battery cell is 25℃; charge the single battery cell at 0.1C at 25℃ to the charging cutoff voltage of 4.25V, and continue to charge at this charging cutoff voltage under constant voltage until the current is 0.05C, and the charging is cut off (where C represents the rated capacity of the single battery cell); place the single battery cell at 25℃ for 1 hour; discharge the single battery cell at 0.1C at 25℃ to the discharge cutoff voltage of 2.5V, and record the total discharge capacity C0 and the total discharge energy E0 of the single battery cell, in Wh.

[0158] 2) Battery cell volume measurement: Use vernier calipers to measure the thickness, width, and height of the battery cell respectively. Measure 3 times in each direction and take the average value to obtain the thickness T1, width W1, and height H1. Calculate the volume of the battery cell V0 = T1 * W1 * H1, in L.

[0159] 3) Energy density calculation: The volumetric energy density of a battery cell is calculated as E0 / V0.

[0160] Cyclic performance test:

[0161] 1) First, measure the initial discharge capacity of the battery cell as follows: Let the battery cell stand at 25℃ for 2 hours to ensure that the temperature of the battery cell is 25℃; charge the battery cell at 0.33C at 25℃ to the charging cutoff voltage of 4.25V, and continue to charge at this charging cutoff voltage until the current is 0.05C, and the charging is cut off (where C represents the rated capacity of the battery cell); let the battery cell stand at 25℃ for 1 hour; discharge the battery cell at 0.33C at 25℃ to the discharge cutoff voltage of 2.5V, and record the total discharge capacity C0 and the total discharge energy E0 of the battery cell;

[0162] 2) Place the battery cell in a constant temperature environment of 25℃ and charge the battery cell at 0.33C to the charging cutoff voltage of 4.25V. Let it stand for 30 minutes, and then discharge the battery cell at 0.33C to the discharge cutoff voltage of 2.5V. Let it stand for 30 minutes to obtain the discharge capacity C1 of the first cycle. Repeat this step to obtain the discharge capacity Cn of the nth cycle.

[0163] 3) Capacity retention calculation: Cn / C0. The capacity retention rate after 1500 cycles is C1500 / C0.

[0164] The test results are recorded in Table 4.

[0165] Table 4

[0166] As shown in Table 4, Examples 1-14 of the present invention improve both the single-cell energy density and the capacity retention rate after 1500 cycles by employing the multi-element doped positive electrode active material of the present invention. In particular, Example 2 of the present invention achieves superior results in terms of both single-cell energy density and capacity retention rate after 1500 cycles. Building upon this, Example 12 further improves both single-cell energy density and capacity retention rate after 1500 cycles by introducing a second layered lithium transition metal oxide into the positive electrode sheet. In contrast, comparative examples cannot simultaneously achieve improvements in both single-cell energy density and capacity retention rate after 1500 cycles. For example, Comparative Example 1 achieves a high capacity retention rate after 1500 cycles but has a low single-cell energy density, while Comparative Example 2 achieves a high single-cell energy density but has a low capacity retention rate after 1500 cycles.

[0167] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising an electrode assembly, the electrode assembly comprising a positive electrode, a negative electrode, and an electrolyte, the positive electrode comprising a positive active material, the positive active material comprising a first layered lithium transition metal oxide having the chemical composition of formula (1). Li a1 Ni x1 Co y1 Mr z1 A b1 B c1 C d1 D e1 O2 type(1) in, A, B, C, and D each independently include any one of Ti, Nb, Mg, Mo, Ca, Sr, Ta, W, Zr, Zn, and Al, and they are all different from each other. Optionally, they include Ti, Nb, Mg, and Mo. 0.60≤a1≤1.20, 0.80≤x1≤0.98, y1≥0, z1≥0, 0≤b1≤0.02, 0≤c1≤0.02, 0≤d1≤0.02, 0≤e1≤0.02, at least three of b1, c1, d1, and e1 are not simultaneously 0, and x1+y1+z1+b1+c1+d1+e1=1.

2. The battery cell according to claim 1, wherein, b1, c1, d1, and e1 are all non-zero. Optionally, 0.001≤b1≤0.01, 0.001≤c1≤0.01, 0.001≤d1≤0.01, and 0.001≤e1≤0.

01.

3. The battery cell according to any one of claims 1 or 2, wherein, In the first layered lithium transition metal oxide, the difference between at least two of b1, c1, d1, and e1 does not exceed 0.001, and optionally the difference between at least three of b1, c1, d1, and e1 does not exceed 0.

001. Further optionally, the difference between any two of b1, c1, d1 and e1 shall not exceed 0.

001.

4. The battery cell according to any one of claims 1 to 3, wherein, In the first layered lithium transition metal oxide, 0.80≤a1≤1.10, 0.82≤x1≤0.98, y1>0, z1>0; Optionally, 0.85≤a1≤1.10, 0.85≤x1≤0.97, 0.01≤y1≤0.1, and 0.005≤z1≤0.

05.

5. The battery cell according to any one of claims 1 to 4, wherein, The first layered lithium transition metal oxide satisfies at least one of the following conditions: (1)0.002≤b1≤0.01； (2)0.002≤c1≤0.01； (3)0.002≤d1≤0.01； (4)0.002≤e1≤0.01； (5) 0.005≤b1+c1+d1+e1≤0.05, can be selected as 0.02≤b1+c1+d1+e1≤0.

05.

6. The battery cell according to any one of claims 1 to 5, wherein, The chemical formula of the first layer of lithium transition metal oxide is Li a1 Ni x1 Co y1 Mn z1 Ti b1 Nb c1 Mg d1 Mo e1 O2, 0.001≤b1≤0.003, 0.001≤c1≤0.003, 0.001≤d1≤0.003, 0.001≤e1≤0.

003.

7. The battery cell according to any one of claims 1 to 6, wherein, The first layered lithium transition metal oxide particles are in a secondary particle morphology, and the average particle size of the first layered lithium transition metal oxide satisfies 7μm~10μm.

8. The battery cell according to any one of claims 1 to 7, wherein, The positive electrode active material further includes a second layered lithium transition metal oxide with the chemical composition of formula (2), and the composition of the second layered lithium transition metal oxide is different from that of the first layered lithium transition metal oxide. Li a2 Ni x2 Co y2 Mr z2 M b2 O2 formula(2) Wherein, M includes at least one of Al, Zr, Mg, Zn, Y, Fe, Nb, W, Zn, Mo, Ba, Ca, Ta and Ti, 0.60≤a2≤1.20, 0.80≤x2≤0.98, y2>0, z2>0, 0.002≤b2≤0.02, and x2+y2+z2+b2=1.

9. The battery cell according to claim 8, wherein, The second layered lithium transition metal oxide is in the form of secondary or primary particles, and the average particle size of the second layered lithium transition metal oxide satisfies 1μm-3.5μm; Optionally, the primary particles of the second layered lithium transition metal oxide are spherical or near-spherical.

10. The battery cell according to claim 8 or 9, wherein, In the positive electrode active material, the mass ratio of the first layered lithium transition metal oxide to the second layered lithium transition metal oxide is in the range of 5:5 to 9:

1.

11. The battery cell according to any one of claims 1 to 10, wherein, The positive electrode has a capacity per unit area of ​​15.3 mWh / cm². 2 ~35.7mWh / cm 2 .

12. The battery cell according to any one of claims 1 to 11, wherein, The negative electrode sheet includes a negative electrode active material, which includes a silicon-carbon composite material, and the mass percentage of silicon in the negative electrode active material is 9wt% to 35wt%.

13. The battery cell according to claim 12, wherein, The silicon-carbon composite material includes a porous carbon matrix and a silicon-based material dispersed in the pores and surface of the porous carbon matrix; optionally, the silicon-based material includes silicon nanocrystals of 0.2 nm to 20 nm, and optionally the silicon nanocrystals are distributed in the pores of the porous carbon matrix.

14. The battery cell according to any one of claims 1 to 13, wherein, The electrolyte comprises a lithium salt, which includes one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium dioxaborate, lithium difluorooxaborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide. Optionally, the lithium salt comprises at least three of lithium hexafluorophosphate, lithium difluorophosphate, lithium bisfluorosulfonylimide, and lithium fluorosulfonate.

15. The battery cell according to claim 14, wherein, The total concentration of lithium salt in the electrolyte is 0.5 mol / L to 1.5 mol / L, and can be selected as 0.8 mol / L to 1.2 mol / L.

16. The battery cell according to any one of claims 1 to 15, wherein, The volumetric energy density of the battery cells ranges from 750Wh / L to 870Wh / L.

17. An electrical appliance, characterized in that, Includes the battery cell described in any one of claims 1-16.

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