Battery cell, battery apparatus and electric device

Abstract

The present invention belongs to the technical field of batteries, and provides a battery cell, a battery apparatus and an electric device. The battery cell comprises: a positive electrode sheet, which comprises a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, wherein the positive electrode film layer comprises a lithium-containing phosphate positive electrode active material, a first additive and a second additive, the first additive comprises a lithium-containing transition metal oxide, and the second additive comprises a nickel-containing metal oxide; and a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector, wherein the negative electrode film layer comprises graphite, and a single negative electrode film layer has a thickness of 0.04-0.1 mm. The battery cell of the present application has a relatively high energy density, relatively good kinetic performance, and relatively low gas production.

Description

Battery cells, battery devices, electrical equipment Technical Field

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

[0002] With increasing environmental pollution, the new energy industry is attracting more and more attention. Within the new energy industry, battery technology is a crucial factor in its development.

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

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide a battery cell with high energy density and less gas production.

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

[0006] In a first aspect, a battery cell is provided, comprising: a positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a lithium phosphate positive electrode active material, a first additive and a second additive, the first additive including a lithium transition metal oxide and the second additive including a nickel metal oxide; and a negative electrode sheet including a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer including graphite, the thickness of a single layer of the negative electrode film layer being 0.04 mm to 0.1 mm.

[0007] In this embodiment, the negative electrode film layer comprises graphite, and the thickness of a single negative electrode film layer is 0.04 mm to 0.1 mm. This relatively large thickness of the negative electrode film layer is beneficial for improving the energy density of the battery cell. The positive electrode film layer comprises a lithium phosphate positive electrode active material, a first additive, and a second additive. The first additive comprises a lithium-containing transition metal oxide, and the second additive comprises a nickel-containing metal oxide. The first additive improves the kinetic performance of the SEI film at the negative electrode, facilitating lithium-ion transport at the negative electrode and compensating for the slow lithium-ion insertion rate at the negative electrode due to the thicker negative electrode film layer. The second additive promotes the conversion of oxygen free radicals generated from the delithiation of the first additive into oxygen, thereby reducing the risk of excessive gas production within the battery cell due to side reactions of oxygen free radicals. Therefore, the battery cell in this embodiment has a high energy density and low gas production.

[0008] In some embodiments, the thickness of the single-layer negative electrode film is 0.05 mm to 0.08 mm.

[0009] When the thickness of a single-layer negative electrode film is greater than or equal to 0.05 mm, the negative electrode film has a large thickness, thus the battery cell has a high energy density; when the thickness of a single-layer negative electrode film is less than or equal to 0.08 mm, the above negative electrode film, combined with the first additive and the second additive, allows the battery cell to have a high energy density while producing less gas.

[0010] In some embodiments, the mass content of the lithium-containing transition metal oxide is 0.3% to 4.5% based on the total mass of the positive electrode film.

[0011] When the total mass of the positive electrode film is greater than or equal to 0.3%, the kinetic performance of the SEI film at the negative electrode is improved, the lithium-ion insertion rate at the negative electrode is increased, and the kinetic performance of the battery cell is improved. Thus, the battery cell can have good kinetic performance while having high energy density. When the total mass of the positive electrode film is less than 4.5%, the oxygen free radicals generated by the delithiation of lithium-containing transition metal oxides can be reduced, thereby reducing the risk of increased gas production in the battery cell due to the side reactions of oxygen free radicals.

[0012] In some embodiments, the mass content of the lithium-containing transition metal oxide is 0.5% to 2% based on the total mass of the positive electrode film. This results in a single battery cell with higher energy density, less gas production, and better kinetic performance.

[0013] In some embodiments, the mass content of the nickel-containing metal oxide is from 0.03% to 2.5% based on the total mass of the positive electrode film.

[0014] When the total mass of the positive electrode film is greater than or equal to 0.03%, it is beneficial to promote the conversion of oxygen free radicals generated by lithium transition metal oxides into oxygen, thereby reducing the risk of increased gas production in the battery cell due to the side reactions of oxygen free radicals in the battery cell. When the total mass of the positive electrode film is less than or equal to 2.5%, the lithium phosphate positive electrode active material and the lithium transition metal oxide have a more suitable mass content, which is beneficial to improving the cycle life of the battery cell.

[0015] In some embodiments, the mass content of the nickel-containing metal oxide is 0.05% to 1.5% based on the total mass of the positive electrode film. This results in a longer cycle life and less gas production in the battery cell.

[0016] In some embodiments, the lithium-containing transition metal oxide includes Fe element, and the ratio of the mass of Fe element in the lithium-containing transition metal oxide to the mass of Ni element in the nickel-containing metal oxide is 0.5 to 10 based on the total mass of the cathode film.

[0017] When the ratio of the mass of Fe in lithium-containing transition metal oxide to the mass of Ni in nickel-containing metal oxide is greater than or equal to 0.5 based on the total mass of the positive electrode film, the risk of lithium plating at the negative electrode is low, which is beneficial to improving the cycle life of the battery cell. When the ratio of the mass of Fe in lithium-containing transition metal oxide to the mass of Ni in nickel-containing metal oxide is less than or equal to 10 based on the total mass of the positive electrode film, it is beneficial to fully catalyze the conversion of oxygen free radicals into oxygen, and reduce the gas generation in the battery cell caused by the side reactions of oxygen free radicals.

[0018] In some embodiments, based on the total mass of the positive electrode film, the ratio of the mass of Fe in the lithium-containing transition metal oxide to the mass of Ni in the nickel-containing metal oxide is 1.5 to 5. This results in a single battery cell with less gas production and a longer cycle life.

[0019] In some embodiments, the average longest diameter of the lithium-containing transition metal oxide is 3 μm to 30 μm on a longitudinal section along the thickness direction of the positive electrode sheet.

[0020] When the average longest diameter of lithium-containing transition metal oxides is greater than or equal to 3 μm, the rate of oxygen radical generation from lithium-containing transition metal oxides can be reduced, which is beneficial for reducing gas production in battery cells. When the average longest diameter of lithium-containing transition metal oxides is less than or equal to 30 μm, it is beneficial for the extraction of lithium ions and the generation of oxygen radicals from lithium-containing transition metal oxides, which is beneficial for improving the kinetic performance of the SEI film, reducing the risk of lithium plating at the negative electrode, and improving the cycle life of battery cells. Therefore, when the average longest diameter of lithium-containing transition metal oxides is between 3 μm and 30 μm, oxygen radicals in lithium-containing transition metal oxides have a suitable extraction rate, which is beneficial for both reducing gas production in battery cells and reducing the risk of lithium plating.

[0021] In some embodiments, the average longest diameter of the lithium-containing transition metal oxide is 5 μm to 20 μm on a longitudinal section along the thickness direction of the positive electrode sheet. This results in less gas generation and a longer cycle life for the battery cell.

[0022] In some embodiments, the average longest diameter of the nickel-containing metal oxide is 5 μm to 50 μm on a longitudinal section along the thickness direction of the positive electrode sheet.

[0023] When the average longest diameter of nickel-containing metal oxides is greater than or equal to 5 μm, it is beneficial to reduce the risk of side reactions in battery cells due to the small particle size and high reactivity of nickel-containing metal oxides, and to improve the cycle life of battery cells. When the average longest diameter of nickel-containing metal oxides is less than or equal to 50 μm, it is beneficial to catalyze the conversion of oxygen free radicals generated by lithium-containing transition metal oxides into oxygen, reduce the degree of side reactions of oxygen free radicals in battery cells, and reduce gas production in battery cells.

[0024] In some embodiments, the average longest diameter of the nickel-containing metal oxide is 8 μm to 30 μm on a longitudinal section along the thickness direction of the positive electrode sheet. This results in less gas generation and a longer cycle life for the battery cell.

[0025] In some embodiments, the average longest diameter of the nickel-containing metal oxide is less than the average longest diameter of the lithium-containing transition metal oxide. This results in a suitable size distribution between the nickel-containing metal oxide and the lithium-containing transition metal oxide particles, which is beneficial for the nickel-containing metal oxide to catalyze the conversion of oxygen free radicals generated by the lithium-containing transition metal oxide into oxygen, reducing the degree of side reactions of oxygen free radicals within the battery cell and decreasing gas production within the battery cell.

[0026] In some embodiments, the average longest diameter of the nickel-containing metal oxide is greater than or equal to the average longest diameter of the lithium-containing transition metal oxide. This results in particles of suitable size for both the nickel-containing metal oxide and the lithium-containing transition metal oxide, facilitating their preparation.

[0027] In some embodiments, the lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate, the substrate comprising Li a MO b , where 1≤a≤6, 1≤b≤6, and M includes at least one of Fe, Cu, Co, Mn, and Al.

[0028] The high molar content of lithium in the lithium-containing transition metal oxide matrix allows for the release of more lithium ions, providing more active lithium ions to the battery cells and improving their cycle performance. In addition, the coating layer helps to improve the stability of the lithium-containing transition metal oxide.

[0029] In some embodiments, the lithium-containing transition metal oxide includes a matrix and a coating layer located on at least a part of the surface of the matrix, and the matrix includes Li5FeO4. The above lithium-containing transition metal oxide can improve the kinetic performance of the SEI film while providing a relatively large number of active lithium ions, thereby being beneficial to further improving the cycle performance of the battery cell.

[0030] In some embodiments, the lithium-containing transition metal oxide includes a matrix and a coating layer located on at least a part of the surface of the matrix, and the matrix includes Li e FeO f , 0 ≤ e ≤ 5, 0 < f ≤ 4. During the formation process of the battery cell, the matrix decomposes, generating oxygen free radicals while generating lithium ions, and the molar contents of Li element and O element change.

[0031] In some embodiments, the lithium-containing transition metal oxide includes a matrix and a coating layer located on at least a part of the surface of the matrix, and the matrix includes Li m FeO n , 0 ≤ m ≤ 1, 0 < n ≤ 2. During the formation process of the battery cell, the matrix decomposes, generating oxygen free radicals while generating lithium ions, and the molar contents of Li element and O element change.

[0032] In some embodiments, at least a part of the surface of the matrix contains at least one of Al or Mg. In this way, it is beneficial to improve the stability of the lithium-containing transition metal oxide, reduce the side reaction between the lithium-containing transition metal oxide and the electrolyte, and thus be beneficial to improving the cycle life of the battery cell.

[0033] In some embodiments, the coating layer includes carbon element. The setting of the coating layer is beneficial to improving the stability of the lithium-containing transition metal oxide, and the inclusion of carbon element in the coating layer is beneficial to improving the conductivity of the lithium-containing transition metal oxide, and further beneficial to the exertion of the capacity of the battery cell.

[0034] In some embodiments, the thickness of the coating layer is 10 nm to 100 nm. In this way, the coating layer has a suitable thickness, which is beneficial to improving the stability of the lithium-containing transition metal oxide, and is convenient for the extraction of lithium ions and oxygen free radicals, beneficial to the insertion of lithium ions at the negative electrode, and the risk of lithium deposition at the negative electrode is relatively low.

[0035] In some embodiments, the nickel-containing metal oxide includes N c NiO d, where N includes at least one of Li, Na, and K, 0 ≤ c ≤ 2, and 1 ≤ d ≤ 2. The above nickel-containing metal oxide can promote the conversion of oxygen free radicals generated by lithium-containing iron oxide into oxygen, thereby reducing the risk of increased gas production in the battery cell caused by oxygen free radicals; in addition, when the molar content of lithium element in the nickel-containing metal oxide is greater than 1, it can also play a role in supplementing lithium ions, which is beneficial to improving the cycle life of the battery cell.

[0036] In some embodiments, the nickel-containing metal oxide includes Li2NiO2. In this way, it is beneficial to increase the cycle life of the battery cell while reducing gas production in the battery cell.

[0037] In some embodiments, the nickel-containing metal oxide includes Li g NiO h , 0 ≤ g ≤ 2, 0 < h ≤ 2. During the formation process of the battery cell, the nickel-containing metal oxide decomposes, and the molar contents of its lithium element and oxygen element will change to a certain extent.

[0038] In some embodiments, the nickel-containing metal oxide includes NiO q , 0 < q ≤ 2. During the formation process of the battery cell, the nickel-containing metal oxide decomposes, and the molar contents of its lithium element and oxygen element will change to a certain extent.

[0039] In some embodiments, the deintercalation potential of the lithium-containing transition metal oxide is greater than the deintercalation potential of the lithium-containing phosphate, and the deintercalation potential of the nickel-containing metal oxide is greater than the deintercalation potential of the lithium-containing phosphate. In this way, during the formation process, the lithium-containing transition metal oxide and the nickel-containing metal oxide can deintercalate lithium ions to provide more active lithium ions to the battery cell.

[0040] In some embodiments, in the voltage range of 2V to 4.3V, the charging specific capacity of the lithium-containing transition metal oxide is 200 mAh / g to 1000 mAh / g, and can be optionally 600 mAh / g to 700 mAh / g.

[0041] The oxide of the lithium-containing transition metal has a high charging specific capacity, which is beneficial to improving the energy density and cycle life of the battery cell.

[0042] In some embodiments, the single-sided areal density of the negative electrode film layer is 0.12 g / 1540.25 mm 2 to 0.2 g / 1540.25 mm 2 , and can be optionally 0.13 g / 1540.25 mm 2 to 0.19 g / 1540.25 mm 2 .

[0043] In the above embodiments, the negative electrode film layer has a suitable areal density, and the battery cell has a relatively suitable energy density and kinetic performance.

[0044] In some embodiments, the compaction density of the negative electrode film at 0% SOC is 1.3 g / cm³. 3 Up to 1.8 g / cm 3 The option is 1.35g / cm³. 3 Up to 1.65 g / cm 3 .

[0045] In the above embodiments, the negative electrode film layer has a suitable compaction density, and the battery cell has a relatively suitable energy density and kinetic performance.

[0046] In some embodiments, the negative electrode film layer includes a first negative electrode sub-film layer and a second negative electrode sub-film layer. Along the thickness direction of the negative electrode sheet, the first negative electrode sub-film layer is farther away from the negative electrode current collector than the second negative electrode sub-film layer. The first negative electrode sub-film layer includes a first negative electrode active material, and the second negative electrode sub-film layer includes a second negative electrode active material. The first negative electrode active material includes artificial graphite, and the second negative electrode active material includes natural graphite or a combination of natural graphite and artificial graphite.

[0047] During the drying process of the negative electrode film after coating with the negative electrode slurry, the binder in the negative electrode film layer tends to float to the surface. Compared to setting a single, integral negative electrode film layer, the arrangement of a first and a second negative electrode sub-film layer facilitates a more uniform distribution of the binder within the negative electrode film layer, reducing concentrated distribution of the binder on the surface of the negative electrode film layer (the side away from the negative electrode current collector). This promotes the insertion and diffusion of lithium ions within the negative electrode film layer, thereby improving the kinetic performance of the battery cell. Furthermore, the more uniform distribution of the binder within the negative electrode film layer also facilitates adhesion between the negative electrode film layer and the negative electrode current collector, reducing the risk of the negative electrode film layer detaching from the negative electrode current collector, thus contributing to improved cycle life of the battery cell.

[0048] Natural graphite particles have a larger particle size than artificial graphite particles. By placing artificial graphite in the first negative electrode film layer away from the negative electrode current collector and placing natural graphite or a mixture of natural and artificial graphite in the second negative electrode film layer near the negative electrode current collector, it is beneficial to form pores of different sizes in the negative electrode film layer. The pore sizes vary along the thickness direction of the negative electrode film layer, which facilitates the diffusion of lithium ions and thus improves the kinetic performance of the battery cell. In addition, the above-mentioned negative electrode film layer, combined with the first and second additives of the embodiments of this application, also helps to compensate for the problem of increased lithium ion consumption caused by the larger electrochemically active specific surface area of ​​artificial graphite compared to natural graphite. Therefore, the battery cell can have a longer cycle life while maintaining good kinetic performance.

[0049] In some embodiments, the thickness ratio of the first negative electrode film layer to the second negative electrode film layer is 4:6 to 6:4. This facilitates the insertion and diffusion of lithium ions in the negative electrode film layer, reduces the risk of lithium plating at the negative electrode, and helps improve the cycle life of the battery cell.

[0050] In some embodiments, the volume average particle size Dv50 of the natural graphite is 8 μm to 20 μm, and / or the volume average particle size Dv50 of the artificial graphite is 6 μm to 17 μm.

[0051] The difference in volume average particle size between natural graphite and artificial graphite is beneficial for forming a porous structure in the negative electrode film, which facilitates the wetting of electrolyte and the diffusion of lithium ions, thereby improving the dynamic performance of the battery cell.

[0052] In some embodiments, the negative electrode film layer includes a negative electrode active material, which further includes a silicon-based material. This is beneficial for further improving the energy density of the battery cell.

[0053] In some embodiments, based on the total mass of the negative electrode active material, the mass content of silicon element in the silicon-based material is from 0.01% to 10%, optionally from 0.05% to 3%.

[0054] When the mass content of silicon in the silicon-based material is greater than or equal to 0.01% based on the total mass of the negative electrode active material, it is beneficial to improve the energy density of the battery cell. When the mass content of silicon in the silicon-based material is less than 10% based on the total mass of the negative electrode active material, it can reduce the risk of deterioration in the cycle life of the battery cell caused by excessive silicon content. In addition, by combining silicon-based materials and the first additive, the battery cell can also have a higher initial efficiency.

[0055] In some embodiments, the porosity of the negative electrode sheet is 10% to 50%, optionally 25% to 35%. This provides a suitable range of porosity for the negative electrode sheet, which is beneficial for electrolyte wetting, improving lithium-ion insertion and transport rates at the negative electrode, enhancing the kinetic performance of the battery cell, reducing polarization in the battery cell, and also helping to reduce the degree of side reactions.

[0056] In some embodiments, the thickness of the single-layer positive electrode film is 0.06 mm to 0.13 mm, optionally 0.07 mm to 0.1 mm.

[0057] When the thickness of the single-layer positive electrode film is between 0.06 mm and 0.13 mm, the lithium ions and oxygen free radicals generated by the first additive in the positive electrode film have a suitable desorption rate, which is beneficial to improving the kinetic performance of the SEI film, facilitating the insertion and transport of lithium ions in the negative electrode, and also helps to reduce the risk of excessive gas generation in the battery cell due to excessive desorption of oxygen free radicals in a short period of time. In addition, a larger thickness of the positive electrode film is beneficial to improving the energy density of the battery cell.

[0058] In some embodiments, the one-sided density of the positive electrode film is 0.25 g / 1540.25 mm². 2 Up to 0.45g / 1540.25mm 2 Available in 0.28g / 1540.25mm. 2 Up to 0.4g / 1540.25mm 2 .

[0059] In the above embodiments, the positive electrode film has a suitable areal density, and the battery cell has a suitable energy density and kinetic performance.

[0060] In some embodiments, the compaction density of the positive electrode film at 0% SOC is 2.1 g / cm³. 3 Up to 2.9 g / cm 3 2.4g / cm³ is an optional value. 3 Up to 2.7 g / cm 3 .

[0061] In the above embodiments, the positive electrode film layer has a suitable compaction density, and the battery cell has a relatively suitable energy density and kinetic performance.

[0062] In some embodiments, the lithium phosphate-containing cathode active material comprises primary particles and secondary particles formed by the agglomeration of the primary particles. The average longest diameter of the primary particles is 100 nm to 500 nm, and the average longest diameter of the secondary particles is 1 μm to 2 μm. This ensures that the lithium phosphate particles have a suitable size, facilitating the extraction of lithium ions and contributing to the full utilization of the battery cell's capacity.

[0063] In some embodiments, the lithium phosphate-containing positive electrode active material includes materials with the general formula Li x D y Me a1 M b1 P 1-c1 X c1 Y zCompounds wherein 0.5≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, and 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z≤5; D includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; Y includes one or more of O and F.

[0064] During the charging and discharging process of a single battery cell, the molar content of lithium, oxygen, and other elements in the lithium phosphate cathode active material changes within a certain range.

[0065] In some embodiments, the lithium phosphate-containing cathode active material includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The aforementioned lithium phosphate-containing cathode active materials exhibit high structural stability, which helps to improve the cycle life of individual battery cells.

[0066] In some embodiments, at least a portion of the surface of the lithium phosphate-containing positive electrode active material has carbon elements. This helps to improve the conductivity of the lithium phosphate, facilitating the utilization of the battery cell's capacity.

[0067] In some embodiments, the carbon content is 1% to 2% based on the total mass of the lithium phosphate cathode active material. This results in the lithium phosphate cathode active material having good conductivity, facilitating the utilization of the battery cell's capacity.

[0068] In some embodiments, the positive electrode film layer satisfies at least one of the following conditions: the volume average particle size of the lithium-containing transition metal oxide is 3 μm to 30 μm; the volume average particle size of the nickel-containing metal oxide is 5 μm to 50 μm; and the volume average particle size of the lithium phosphate-containing positive electrode active material is 0.5 μm to 8 μm.

[0069] In the above embodiments, the lithium phosphate positive electrode active material, the lithium transition metal oxide, and the nickel metal oxide have suitable particle sizes, and the battery cells have good energy density and less gas production.

[0070] In some embodiments, the battery cell further includes an electrolyte comprising additives, the additives including at least one of FEC, PS, VC, and DTD. This helps reduce lithium-ion consumption at the negative electrode, and improves the initial efficiency and cycle life of the battery cell.

[0071] In a second aspect, a battery device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof.

[0072] Thirdly, an electrical device is provided, including the battery device described in the second aspect. Attached Figure Description

[0073] 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.

[0074] Figure 1 is a schematic diagram of a vehicle according to an embodiment of this application;

[0075] Figure 2 is a schematic diagram of a battery device according to an embodiment of this application;

[0076] Figure 3 is a schematic diagram of the negative electrode sheet according to an embodiment of this application;

[0077] Figure 4 is a schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0078] Figure 5 is a schematic diagram of the negative electrode sheet according to an embodiment of this application;

[0079] Figure 6 is a schematic diagram of a battery cell according to an embodiment of this application. Detailed Implementation

[0080] Embodiments of the battery cell, battery device, and electrical appliance of this application have been described in detail with appropriate reference to the accompanying drawings; however, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0081] 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.

[0082] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0083] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0084] 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.

[0085] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0086] This application aims to develop a battery cell that balances dynamic performance, long cycle life, and high safety. The battery cell includes a positive electrode sheet, comprising a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer comprises a lithium phosphate positive electrode active material, a first additive, and a second additive. The first additive comprises a lithium-containing transition metal oxide, and the second additive comprises a nickel-containing metal oxide. The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer comprises graphite, and the thickness of a single negative electrode film layer is 0.04 mm to 0.1 mm.

[0087] Lithium phosphates are widely used as positive electrode active materials in battery cells due to their high structural stability. To further improve the energy density of battery cells containing lithium phosphates, a higher thickness of the negative electrode film is required. However, with the increase in the thickness of the negative electrode film, the rate of lithium ion insertion into the negative electrode film slows down, leading to a decrease in the fast-charging performance and cycle performance of the battery cell.

[0088] This application introduces a lithium-containing transition metal oxide into the positive electrode film. During the formation stage, this lithium-containing metal oxide releases active lithium and oxygen free radicals. The generated active lithium helps increase the active lithium content in the battery cell, improving its cycle performance. The generated oxygen free radicals also help improve the kinetics of the SEI film on the surface of the negative electrode active material, accelerating the insertion and extraction of lithium ions. However, the oxygen free radicals generated by the lithium-containing transition metal oxide react with the electrolyte during the aging stage to produce RH+ (R being alkyl or alkoxy). These RH+ are reduced during the battery cell aging stage, which not only exacerbates gas production in the battery cell during aging, increasing the process cost of negative pressure extraction, but also increases the hydrogen content in the gas, significantly increasing the safety risk of the battery cell.

[0089] This application further incorporates a nickel-containing metal oxide, which can effectively catalyze the conversion of oxygen free radicals generated by lithium-containing transition metal oxides into oxygen, thereby reducing the oxygen free radical content in the battery cell. This reduces the RH+ generated by the electrolyte being attacked by oxygen free radicals, thereby reducing the gas production during the aging stage caused by RH+, thus reducing the amount of gas produced by the battery cell during the aging stage and optimizing the gas composition.

[0090] Therefore, when the thickness of the negative electrode film meets the above-mentioned range, the battery cell has a high energy density. Furthermore, the addition of the first additive can improve the kinetic performance and cycle life reduction caused by the increased thickness of the negative electrode film. The addition of the second additive can mitigate the increased gas production within the battery cell caused by oxygen free radicals generated during the delithiation of the first additive. Therefore, the battery cell of this embodiment has a high energy density and low gas production.

[0091] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery devices.

[0092] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical equipment.

[0093] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0094] For example, as shown in Figure 1, which is a structural schematic diagram of a vehicle 1 according to an embodiment of this application, vehicle 1 can be a gasoline vehicle, a natural gas vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A motor 40, a controller 30, and a battery device 10 can be installed inside vehicle 1. The controller 30 is used to control the battery device 10 to supply power to the motor 40. For example, the battery device 10 can be installed at the bottom, front, or rear of vehicle 1. The battery device 10 can be used to power vehicle 1. For example, the battery device 10 can serve as the operating power source for vehicle 1, for example, for the electrical system of vehicle 1, such as for the power requirements of vehicle 1's starting, navigation, and operation. In another embodiment of this application, the battery device 10 can not only serve as the operating power source for vehicle 1, but also as the driving power source for vehicle 1, replacing or partially replacing gasoline or natural gas to provide driving power for vehicle 1.

[0095] Figure 2 shows a partial structural schematic diagram of the battery device 10 according to an embodiment of this application. For example, as shown in Figure 2, the battery device 10 according to this application embodiment may include multiple battery cells 3 to meet different power usage requirements. The shape of the battery cell 3 according to this application embodiment can be set according to actual application. For example, the battery cell 3 can be cylindrical, or it can be cuboid or other shapes, and this application embodiment is not limited to this.

[0096] It should be understood that, as shown in FIG. 2, the battery device 10 of this embodiment may further include a housing 11, which can be used to accommodate multiple battery cells 3. The housing 11 of this embodiment has a hollow internal structure, and the multiple battery cells 3 are accommodated within the housing 11. The housing 11 may include two parts, referred to herein as a first housing portion 111 and a second housing portion 112, which are fastened together. The shapes of the first housing portion 111 and the second housing portion 112 can be determined according to the shape of the components accommodated internally, for example, according to the shape of the combination of the multiple battery cells 3 accommodated internally. At least one of the first housing portion 111 and the second housing portion 112 has an opening. For example, as shown in Figure 2, the first housing portion 111 and the second housing portion 112 can both be hollow cuboids with one open face. The openings of the first housing portion 111 and the second housing portion 112 are opposite to each other, and the first housing portion 111 and the second housing portion 112 are interlocked to form a housing 11 with a closed cavity, which can be used to accommodate multiple battery cells 3. The multiple battery cells 3 are connected in parallel, series, or mixed and placed inside the housing 11 formed by the interlocking of the first housing portion 111 and the second housing portion 112.

[0097] For example, unlike what is shown in Figure 2, only one of the first housing portion 111 and the second housing portion 112 may be a hollow cuboid with an opening, while the other is plate-shaped to cover the opening. Taking the second housing portion 112 as a hollow cuboid with one opening, and the first housing portion 111 as a plate-shaped example, then the first housing portion 111 covers the opening of the second housing portion 112 to form a housing 11 with a closed chamber, which can be used to accommodate multiple battery cells 3.

[0098] 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.

[0099] The battery cell can be a lithium-ion battery.

[0100] During the charging process of a single battery cell, lithium ions are released from the positive electrode active material, move and embed into the negative electrode; while during the discharging process, lithium ions are released from the negative electrode, move and embed into the positive electrode active material.

[0101] It should be understood that the “intercalation” process described in this application refers to the process by which lithium ions are intercalated in the positive electrode active material or the negative electrode due to an electrochemical reaction, and the “extraction” process described in this application refers to the process by which lithium ions are extracted from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0102] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. The following section describes the battery cell and its components provided in this application.

[0103] [Battery cell]

[0104] This application provides a battery cell including a negative electrode and a positive electrode.

[0105] Figure 3 is a schematic diagram of a negative electrode sheet according to an embodiment of this application. For example, as shown in Figure 3, the negative electrode sheet 60 includes a negative current collector 601 and a negative electrode film layer 602 disposed on at least one side of the negative current collector 601.

[0106] The negative electrode current collector 601 has two side surfaces along its own thickness direction. The negative electrode film layer 602 can be disposed on one side surface of the negative electrode current collector 601 or on both side surfaces of the negative electrode current collector 601.

[0107] The negative electrode film 602 includes graphite, and the thickness of a single negative electrode film 602 is 0.04 mm to 0.1 mm.

[0108] The negative electrode film layer 602 includes graphite, which may include natural graphite, artificial graphite, or a mixture of both.

[0109] For example, as shown in Figure 3, the thickness of the single-layer negative electrode film 602 can be represented by T1. The thickness of the single-layer negative electrode film 602 is 0.04 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.095 mm, 0.1 mm or any value within the above range.

[0110] The thickness of the negative electrode film 602 can be measured in the following way. For example, measurements can be taken at multiple locations (e.g., 10 locations), and the average of the multiple measurements can be taken as the thickness of the negative electrode film 602.

[0111] When the thickness of the single-layer negative electrode film 602 is 0.04 mm to 0.1 mm, the negative electrode film 602 can accommodate more negative electrode active materials, which is beneficial to increasing the number of lithium ions accommodated in the negative electrode film 602, thereby improving the energy density of the battery cell, while also avoiding excessive thickness that would reduce the dynamic performance of the battery cell.

[0112] Figure 4 is a schematic diagram of a positive electrode sheet according to an embodiment of this application. For example, as shown in Figure 4, the positive electrode sheet 50 includes a positive current collector 501 and a positive electrode film layer 502 disposed on at least one side of the positive current collector 501.

[0113] The positive electrode current collector 501 has two side surfaces along its own thickness direction. The positive electrode film layer 502 can be disposed on one side surface of the positive electrode current collector 501 or on both side surfaces of the positive electrode current collector 501.

[0114] The positive electrode film 502 includes a lithium phosphate positive electrode active material, a first additive, and a second additive. The first additive includes a lithium transition metal oxide, and the second additive includes a nickel metal oxide.

[0115] As a type of positive electrode active material, lithium ions can be reversibly extracted and inserted from lithium phosphate.

[0116] Lithium-containing phosphates can refer to lithium-containing transition metal phosphates with an olivine structure, such as lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their modified forms.

[0117] The first additive includes lithium-containing transition metal oxides. The first additive is different from the positive electrode active material. Lithium ions are irreversibly extracted from the first additive.

[0118] Lithium-containing transition metal oxides can decompose to generate lithium ions within a certain voltage range, while also producing oxygen free radicals (also known as reactive oxygen species). These oxygen free radicals migrate to the negative electrode and participate in the formation of the solid electrolyte interface (SEI) membrane. This changes the composition of the SEI membrane (e.g., the SEI membrane includes lithium oxide), which improves the kinetic performance of the SEI membrane and facilitates lithium ion insertion into the negative electrode. Thus, when the thickness of the negative electrode film layer 602 is 0.04 mm to 0.1 mm, the first additive can compensate for the slower lithium ion insertion rate at the negative electrode caused by a larger thickness of the negative electrode film layer 602, thereby reducing the risk of lithium plating at the negative electrode and consequently reducing the risk of reduced cycle life of the battery cells due to lithium plating at the negative electrode.

[0119] Lithium-containing transition metal oxides can be used as lithium replenishing agents, that is, lithium-containing transition metal oxides can generate active lithium ions to replenish the lithium ions consumed in the process of forming SEI film.

[0120] As an example, the lithium-containing transition metal oxide is Li5FeO4. During formation and subsequent charge-discharge processes, as lithium ions are released, Li5FeO4 decomposes into iron oxides or lithium-containing iron oxides.

[0121] The second additive includes nickel-containing metal oxides, and is distinct from the positive electrode active material. For example, in the case where the second additive includes lithium, lithium ions are irreversibly released from the second additive.

[0122] Nickel-containing metal oxides include nickel and oxygen. In some embodiments, nickel-containing metal oxides may also include lithium.

[0123] While lithium-containing transition metal oxides (LMOs) can improve the kinetic performance of the SEI film, the RH+ (where R is alkyl or alkoxy) generated by the side reaction of oxygen radicals produced during lithium delithiation with the electrolyte can lead to increased gas production during the aging stage of the battery cells after formation. This increases the complexity of battery cell fabrication (e.g., increased gas production during aging requires additional gas extraction equipment to remove excess gas from the battery cells). Nickel-containing metal oxides can promote or catalyze the conversion of oxygen radicals into oxygen, thereby reducing oxygen radicals, reducing the RH+ generated by the side reaction of oxygen radicals with the electrolyte, and reducing the gas production caused by RH+ during the aging stage of the battery cells. Furthermore, oxygen moving to the negative electrode can participate in the formation of the SEI film at the negative electrode, altering the SEI film composition and thus improving its kinetic performance.

[0124] In this embodiment, the negative electrode film 602 comprises graphite, and the thickness of a single negative electrode film 602 is 0.04 mm to 0.1 mm. This relatively large thickness of the negative electrode film 602 is beneficial for improving the energy density of the battery cell. The positive electrode film 502 comprises a lithium phosphate positive electrode active material, a first additive, and a second additive. The first additive comprises a lithium-containing transition metal oxide, and the second additive comprises a nickel-containing metal oxide. The first additive improves the kinetic performance of the SEI film at the negative electrode, facilitating lithium-ion transport at the negative electrode and compensating for the slow lithium-ion insertion rate at the negative electrode due to the thicker negative electrode film 602. The second additive promotes the conversion of oxygen free radicals generated from the delithiation of the first additive into oxygen, thereby reducing the risk of excessive gas production within the battery cell due to side reactions of oxygen free radicals. Therefore, the battery cell in this embodiment has a higher energy density and less gas production.

[0125] In some embodiments, the thickness of the monolayer negative electrode film 602 is 0.05 mm to 0.08 mm.

[0126] When the thickness of the single-layer negative electrode film 602 is greater than or equal to 0.05 mm, the negative electrode film 602 has a large thickness, thus the battery cell has a high energy density; when the thickness of the single-layer negative electrode film 602 is less than or equal to 0.08 mm, the above-mentioned negative electrode film 602, combined with the first additive and the second additive, allows the battery cell to have a high energy density while producing less gas.

[0127] In some embodiments, the mass content of lithium transition metal oxide is 0.3% to 4.5% based on the total mass of the positive electrode film 502.

[0128] Based on the total mass of the positive electrode film layer 502, the mass content of lithium transition metal oxide can be 0.3%, 0.4%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.3%, 4.5% or any value within the above range.

[0129] When the total mass of the positive electrode film layer 502 is greater than or equal to 0.3%, it is beneficial to improve the kinetic performance of the SEI film at the negative electrode, increase the lithium ion insertion rate at the negative electrode, reduce the risk of lithium plating at the negative electrode and the risk of a sharp drop in the cycle life of the battery cell caused by lithium plating. Thus, the battery cell can have a long cycle life while having a high energy density. When the total mass of the positive electrode film layer 502 is less than 4.5%, it can reduce the oxygen free radicals generated by the delithiation of lithium-containing transition metal oxides, thereby reducing the risk of increased gas production in the battery cell caused by the side reactions of oxygen free radicals in the battery cell.

[0130] In some embodiments, the mass content of lithium transition metal oxide is 0.5% to 2% based on the total mass of the positive electrode film 502. This results in a single battery cell with higher energy density, less gas generation, and a longer cycle life.

[0131] In some embodiments, the mass content of nickel metal oxide is from 0.03% to 2.5% based on the total mass of the positive electrode film 502.

[0132] Based on the total mass of the positive electrode film 502, the mass content of nickel metal oxide can be 0.03%, 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, or any value within the above range.

[0133] When the total mass of the positive electrode film 502 is greater than or equal to 0.03%, it is beneficial to promote the conversion of oxygen free radicals generated by lithium transition metal oxides into oxygen, thereby reducing the risk of increased gas production in the battery cell due to the side reaction of oxygen free radicals in the battery cell; when the total mass of the positive electrode film 502 is less than or equal to 2.5%, the lithium phosphate positive electrode active material has a more suitable mass content, and the battery cell has a higher energy density.

[0134] In some embodiments, the mass content of nickel metal oxide is 0.05% to 1.5% based on the total mass of the positive electrode film 502. This results in a single battery cell with higher energy density and less gas production.

[0135] In some embodiments, the lithium-containing transition metal oxide includes Fe element, and the ratio of the mass of Fe element in the lithium-containing transition metal oxide to the mass of Ni element in the nickel-containing metal oxide is 0.5 to 10 based on the total mass of the positive electrode film layer 502.

[0136] Based on the total mass of the positive electrode film layer 502, the ratio of the mass of Fe element in the lithium-containing transition metal oxide to the mass of Ni element in the nickel-containing metal oxide can be 0.5, 0.8, 1, 1.5, 2, 2.2, 2.5, 3, 3.2, 3.5, 3.8, 4, 4.5, 5, 5.5, 5.8, 6, 6.2, 6.5, 6.8, 7, 7.5, 8, 8.5, 9, 9.5, 10 or any value within the above range.

[0137] The ratio of the mass of Fe in the lithium-containing transition metal oxide to the mass of Ni in the nickel-containing metal oxide reflects the mass ratio of the first additive and the second additive. A larger ratio indicates a higher mass content of the first additive in the positive electrode film 502, which is more conducive to increasing the lithium insertion rate at the negative electrode and improving the kinetic performance of the battery cell. Conversely, a smaller ratio indicates a higher mass content of the second additive in the positive electrode film 502, which is more conducive to catalyzing the conversion of oxygen free radicals generated by the first additive into oxygen, reducing the risk of excessive gas production within the battery cell due to oxygen free radicals.

[0138] When the ratio of the mass of Fe in lithium-containing transition metal oxide to the mass of Ni in nickel-containing metal oxide is greater than or equal to 0.5 based on the total mass of the positive electrode film layer 502, it is beneficial to improve the kinetic performance of the battery cell. When the ratio of the mass of Fe in lithium-containing transition metal oxide to the mass of Ni in nickel-containing metal oxide is less than or equal to 10 based on the total mass of the positive electrode film layer 502, it is beneficial to fully catalyze the conversion of oxygen free radicals into oxygen, and reduce the gas generation in the battery cell caused by the side reaction of oxygen free radicals.

[0139] In this embodiment, based on the total mass of the positive electrode film 502, the mass ratio of Fe element in the lithium transition metal oxide to Ni element in the nickel metal oxide is 0.5 to 10, the first additive and the second additive have appropriate mass content, and the battery cell has a long cycle life and less gas production.

[0140] In some embodiments, based on the total mass of the positive electrode film 502, the ratio of the mass of Fe in the lithium-containing transition metal oxide to the mass of Ni in the nickel-containing metal oxide is 1.5 to 5. This results in a single battery cell exhibiting less gas production and a longer cycle life.

[0141] In some embodiments, the average length of the longest diameter of the lithium-containing transition metal oxide is 3 μm to 30 μm on a longitudinal section along the thickness direction of the positive electrode 50.

[0142] The average longest diameter of lithium-containing transition metal oxides can be 3μm, 4μm, 5μm, 6μm, 8μm, 10μm, 12μm, 13μm, 15μm, 16μm, 18μm, 20μm, 21μm, 22μm, 24μm, 26μm, 28μm, 30μm, or a value within the range obtained by any combination of the above two values.

[0143] The longest diameter of a particle can be defined as the longest straight line that passes through the center point of the particle and extends to the outer periphery of the particle. The average value of the longest diameter of lithium-containing transition metal oxides can be obtained by taking 30 lithium-containing transition metal oxide particles in a longitudinal section of the positive electrode film layer 502, measuring the longest diameter of each of the 30 particles, and then taking the average value to obtain the average value of the longest diameter of lithium-containing iron oxides.

[0144] When the average longest diameter of lithium-containing transition metal oxides is greater than or equal to 3 μm, the rate of oxygen radical generation from lithium-containing transition metal oxides can be reduced, which is beneficial for reducing gas production in battery cells. When the average longest diameter of lithium-containing transition metal oxides is less than or equal to 30 μm, it is beneficial for the extraction of lithium ions and the generation of oxygen radicals from lithium-containing transition metal oxides, which is beneficial for improving the kinetic performance of the SEI film, reducing the risk of lithium plating at the negative electrode, and improving the cycle life of battery cells. Therefore, when the average longest diameter of lithium-containing transition metal oxides is between 3 μm and 30 μm, oxygen radicals in lithium-containing transition metal oxides have a suitable extraction rate, which is beneficial for both reducing gas production in battery cells and reducing the risk of lithium plating.

[0145] In some embodiments, the average longest diameter of the lithium-containing transition metal oxide in a longitudinal section along the thickness direction of the positive electrode 50 is 5 μm to 20 μm. This results in less gas generation and a longer cycle life for the battery cell.

[0146] In some embodiments, the average longest diameter of the nickel-containing metal oxide is 5 μm to 50 μm on a longitudinal section along the thickness direction of the positive electrode 50.

[0147] The average longest diameter of the nickel-containing metal oxide can be 5μm, 6μm, 8μm, 10μm, 12μm, 13μm, 15μm, 16μm, 18μm, 20μm, 21μm, 22μm, 24μm, 26μm, 28μm, 30μm, 32μm, 34μm, 35μm, 36μm, 38μm, 40μm, 42μm, 44μm, 46μm, 48μm, 50μm, or a value within the range obtained by any combination of the above two values.

[0148] The average value of the longest diameter of nickel-containing metal oxide can be obtained by taking 30 nickel-containing metal oxide particles in the longitudinal section of the positive electrode film 502, measuring the longest diameter of each of the 30 particles, and then taking the average value to obtain the average value of the longest diameter of the nickel-containing metal oxide.

[0149] When the average longest diameter of nickel-containing metal oxides is greater than or equal to 5 μm, it is beneficial to reduce the risk of side reactions in battery cells due to the small particle size and high reactivity of nickel-containing metal oxides, and to improve the cycle life of battery cells. When the average longest diameter of nickel-containing metal oxides is less than or equal to 50 μm, it is beneficial to catalyze the conversion of oxygen free radicals generated by lithium-containing transition metal oxides into oxygen, reduce the degree of side reactions of oxygen free radicals in battery cells, and reduce gas production in battery cells.

[0150] In some embodiments, the average longest diameter of the nickel-containing metal oxide in a longitudinal section along the thickness direction of the positive electrode 50 is 8 μm to 30 μm. This results in less gas generation and a longer cycle life for the battery cell.

[0151] In some embodiments, the average longest diameter of the nickel-containing metal oxide is smaller than the average longest diameter of the lithium-containing transition metal oxide. This results in a suitable size distribution between the nickel-containing metal oxide and lithium-containing transition metal oxide particles, which is beneficial for the nickel-containing metal oxide to catalyze the conversion of oxygen free radicals generated by the lithium-containing transition metal oxide into oxygen, reducing the degree of side reactions of oxygen free radicals within the battery cell and decreasing gas production within the battery cell.

[0152] In some embodiments, the average longest diameter of the nickel-containing metal oxide is greater than or equal to the average longest diameter of the lithium-containing transition metal oxide. This results in particles of suitable size for both the nickel-containing metal oxide and the lithium-containing transition metal oxide, facilitating their preparation.

[0153] In some embodiments, the lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate, the substrate comprising Li a MO b , where 1≤a≤6, 1≤b≤6, and M includes at least one of Fe, Cu, Co, Mn, and Al.

[0154] The coating layer can cover part of the substrate surface or the entire substrate surface.

[0155] In Li a MO b In this context, 'a' can be a range of values ​​consisting of 1, 1.3, 1.5, 2, 2.3, 2.5, 2.8, 3, 3.5, 4, 4.5, 4.8, 5, 6, or any of the above values; 'b' can be a range of values ​​consisting of 1, 1.3, 1.5, 2, 2.3, 2.5, 2.8, 3, 3.5, 4, 4.5, 4.8, 5, 6, or any of the above values.

[0156] The high molar content of lithium in the lithium-containing transition metal oxide matrix allows for the release of more lithium ions, providing more active lithium ions to the battery cells and improving their cycle performance. In addition, the coating layer helps to improve the stability of the lithium-containing transition metal oxide.

[0157] In some embodiments, the lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate, wherein the substrate includes Li5FeO4. The aforementioned lithium-containing transition metal oxide can improve the kinetic performance of the SEI film while also providing a greater number of active lithium ions, thereby contributing to further improvements in the cycle performance of the battery cell.

[0158] In some embodiments, the lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate, the substrate comprising Li e FeO f ,0≤e≤5,0 <f≤4。

[0159] In Li e FeO f In this context, e can be 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.3, 1.5, 2, 2.3, 2.5, 2.8, 3, 3.5, 4, 4.5, 4.8, 5, or any of the above values. f can be 0.1, 0.5, 0.8, 1, 1.3, 1.5, 2, 2.3, 2.5, 2.8, 3, 3.5, 4, or any of the above values.

[0160] Li5FeO4 is the chemical formula of the matrix before delithiation. During the formation of the battery cell, Li5FeO4 decomposes to produce lithium ions and oxygen free radicals. The molar content of lithium and oxygen in the matrix will change depending on the degree of decomposition.

[0161] In the battery cell of this embodiment, the molar content of Li and O elements in the lithium transition metal oxide satisfies the above-mentioned range.

[0162] In some embodiments, the lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate, the substrate comprising Li m FeO n ,0≤m≤1,0 <n≤2。

[0163] In Li m FeO n In this context, m can be a range of values ​​consisting of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or any of the above values, and n can be a range of values ​​consisting of 0.1, 0.5, 0.8, 1, 1.3, 1.5, 2, or any of the above values.

[0164] During the formation of a battery cell, the matrix decomposes, generating oxygen free radicals along with lithium ions, and the molar contents of Li and O elements change. In the battery cell of this embodiment, the molar contents of Li and O elements in the lithium-containing transition metal oxide meet the above-mentioned ranges.

[0165] In some embodiments, at least a portion of the substrate surface contains at least one of Al or Mg. This is beneficial for improving the stability of lithium-containing transition metal oxides and reducing side reactions between lithium-containing transition metal oxides and the electrolyte, thereby improving the cycle life of the battery cells.

[0166] In some embodiments, the coating layer includes carbon. The coating layer improves the stability of the lithium-containing transition metal oxide, and the inclusion of carbon in the coating layer enhances the conductivity of the lithium-containing transition metal oxide, thereby maximizing the capacity of the battery cell.

[0167] In some embodiments, the thickness of the coating layer is 10 nm to 100 nm.

[0168] The thickness of the coating layer can be 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm or any combination of the above values.

[0169] In this embodiment, the coating layer has a suitable thickness, which is beneficial to improving the stability of lithium-containing transition metal oxides and facilitates the extraction of lithium ions and oxygen free radicals. It is also beneficial to the insertion of lithium ions at the negative electrode, and the risk of lithium plating at the negative electrode is low.

[0170] In some embodiments, nickel-containing metal oxides include N c NiO d , where N includes at least one of Li, Na, and K, 0≤c≤2, 1≤d≤2.

[0171] In nickel-containing metal oxides, c can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 or any of the above values, and d can be 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 or any of the above values.

[0172] When c is 0, the nickel-containing metal oxide can be nickel oxide; when c is greater than 0, the nickel-containing metal oxide can be a lithium-containing nickel metal oxide; when c is greater than 1, the nickel-containing metal oxide has a higher molar content of lithium, and can also provide active lithium ions to the battery cells to replenish the consumed active lithium ions.

[0173] The above nickel-containing metal oxide can promote the conversion of oxygen free radicals generated by lithium-containing iron oxide into oxygen, thereby reducing the risk of increased gas production in the battery cell caused by oxygen free radicals; in addition, when the molar content of lithium element in the nickel-containing metal oxide is greater than 1, it can also play a role in supplementing lithium ions, which is beneficial to improving the cycle life of the battery cell.

[0174] In some embodiments, the nickel-containing metal oxide includes Li2NiO2. In this way, it is beneficial to reduce the gas production in the battery cell while improving the cycle life of the battery cell.

[0175] Before the battery cell is formed, the nickel-containing metal oxide in the positive electrode film layer 502 of the battery cell can be Li2NiO2. During the formation process, Li2NiO2 decomposes, lithium ions are released, and the oxygen content may also change accordingly.

[0176] In some embodiments, the nickel-containing metal oxide includes Li g NiO h , 0≤g≤2, 0<h≤2.

[0177] In Li g NiO h , g can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 or a range composed of any of the above values, and h can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 or a range composed of any of the above values.

[0178] During the formation process of the battery cell, the nickel-containing metal oxide decomposes, and the molar content of its lithium element and oxygen element will change to a certain extent. For example, the lithium in the nickel-containing metal oxide is completely released and becomes nickel oxide after decomposition. In the formed battery cell, the molar content of the lithium element and oxygen element of the nickel-containing metal oxide is within the above range.

[0179] In some embodiments, the nickel-containing metal oxide includes NiO q , 0<q≤2. During the formation process of the battery cell, the nickel-containing metal oxide decomposes, and the molar content of its lithium element and oxygen element will change to a certain extent. For example, the lithium in the nickel-containing metal oxide is completely released and becomes nickel oxide after decomposition.

[0180] In some embodiments, the delithiation potential of lithium-containing transition metal oxides is greater than that of lithium-containing phosphates, and the delithiation potential of nickel-containing metal oxides is greater than that of lithium-containing phosphates.

[0181] The delithiation potential refers to the potential at which lithium ions are extracted from a material. For example, the upper limit of the voltage range during the formation of a battery cell is greater than the upper limit of the voltage range during the charging and discharging of the battery cell in a battery device. This facilitates the extraction of lithium from lithium-containing iron oxides and nickel-containing metal oxides, thereby increasing the number of active lithium ions in the battery cell and improving its initial efficiency.

[0182] In the above embodiments, during the formation process, lithium-containing transition metal oxides and nickel-containing metal oxides can release lithium ions to provide more active lithium ions to the battery cells.

[0183] In some embodiments, the charge capacity of the lithium transition metal oxide is 200 mAh / g to 1000 mAh / g, optionally 600 mAh / g to 700 mAh / g, in a voltage range of 2V to 4.3V.

[0184] Within a voltage range of 2V to 4.3V, the chargeable capacity of lithium-containing iron oxides can be 200mAh / g, 250mAh / g, 280mAh / g, 300mAh / g, 320mAh / g, 350mAh / g, 380mAh / g, 400mAh / g, 420mAh / g, 450mAh / g, 480mAh / g, 500mAh / g, 550mAh / g, 580mAh / g, 600mAh / g, 650mAh / g, 700mAh / g, 750mAh / g, 800mAh / g, 850mAh / g, 880mAh / g, 900mAh / g, 1000mAh / g, or any of the above values.

[0185] Lithium-containing transition metal oxides have high charge capacity, which is beneficial for improving the energy density and cycle life of individual battery cells.

[0186] In some embodiments, the one-sided density of the negative electrode film layer 602 is 0.12 g / 1540.25 mm². 2 Up to 0.2g / 1540.25mm 2 Available in 0.13g / 1540.25mm. 2 Up to 0.19g / 1540.25mm 2 .

[0187] The single-sided density of the negative electrode film layer 602 can be 0.12 g / 1540.25 mm. 20.13g / 1540.25mm 2 0.14g / 1540.25mm 2 0.15g / 1540.25mm 2 0.16g / 1540.25mm 2 0.17g / 1540.25mm 2 0.18g / 1540.25mm 2 0.19g / 1540.25mm 2 0.20g / 1540.25mm 2 Or a range between any of the above values.

[0188] The density of the negative electrode film 602 on one side is related to the kinetic performance and energy density of the battery cell. The higher the density of the negative electrode film 602 on one side, the greater the coating weight of the negative electrode film 602, which is more conducive to improving the energy density of the battery cell. Within a certain range, the lower the density of the negative electrode film 602 on one side, the more conducive it is to the transport and insertion of lithium ions into the negative electrode, and the better the kinetic performance of the battery cell.

[0189] In the above embodiments, the negative electrode film layer 602 has a suitable areal density, and the battery cell has a relatively suitable energy density and kinetic performance.

[0190] In some embodiments, the compaction density of the negative electrode film 602 at 0% SOC is 1.3 g / cm³. 3 Up to 1.8 g / cm 3 The option is 1.35g / cm³. 3 Up to 1.65 g / cm 3 .

[0191] As an example, a battery cell with 0% SOC can be obtained using the following method. Specifically, the battery cell is first charged to 3.65V at a constant current of 0.33C, then charged to 0.05C at a constant voltage of 3.65V, and finally discharged to 2.5V at a constant current of 0.33C to obtain a battery cell with 0% SOC. Afterwards, the battery cell is disassembled to obtain the electrode sheets (e.g., negative electrode sheet 60 or positive electrode sheet 50), and the compaction density is tested.

[0192] The compaction density of the 602 negative electrode film layer at 0% SOC can be 1.3 g / cm³. 3 1.32g / cm 3 1.35g / cm 3 1.4g / cm 3 1.45g / cm 3 1.5g / cm 3 1.55g / cm 31.6g / cm 3 1.62g / cm 3 1.65g / cm 3 1.7g / cm 3 1.75g / cm 3 1.8g / cm 3 Or a range between any of the above values.

[0193] The compaction density of the negative electrode film 602 is related to the kinetic performance and energy density of the battery cell. The higher the compaction density of the negative electrode film 602, the better it is for improving the energy density of the battery cell; within a certain range, the lower the compaction density of the negative electrode film 602, the better it is for lithium ion transport and insertion into the negative electrode, and the better the kinetic performance of the battery cell.

[0194] In the above embodiments, the negative electrode film layer 602 has a suitable compaction density, and the battery cell has a relatively suitable energy density and kinetic performance.

[0195] Figure 5 is a schematic diagram of a negative electrode sheet 60 according to an embodiment of this application. In some embodiments, as shown in Figure 5, the negative electrode film layer 602 includes a first negative electrode sub-film layer 6021 and a second negative electrode sub-film layer 6022. Along the thickness direction of the negative electrode sheet 60, the first negative electrode sub-film layer 6021 is farther away from the negative electrode current collector 601 than the second negative electrode sub-film layer 6022. The first negative electrode film layer 6021 includes a first negative electrode active material, and the second negative electrode film layer 6022 includes a second negative electrode active material. The first negative electrode active material includes artificial graphite, and the second negative electrode active material includes natural graphite and / or artificial graphite.

[0196] The thickness direction of the negative electrode sheet 60 can be the z-direction in Figure 5.

[0197] During the drying process of the negative electrode film 602 after coating with the negative electrode slurry, the binder in the negative electrode film 602 is more likely to float to the surface. Compared to setting a single, integral negative electrode film 602, the arrangement of the first negative electrode sub-film 6021 and the second negative electrode sub-film 6022 helps to achieve a more uniform distribution of the binder in the negative electrode film 602, reducing the concentrated distribution of the binder on the surface of the negative electrode film 602 (the side of the surface away from the negative electrode current collector 601). This facilitates the insertion and diffusion of lithium ions in the negative electrode film 602, thereby improving the kinetic performance of the battery cell. Furthermore, the more uniform distribution of the binder in the negative electrode film 602 also facilitates the adhesion between the negative electrode film 602 and the negative electrode current collector 601, reducing the risk of the negative electrode film 602 detaching from the negative electrode current collector 601, thus improving the cycle life of the battery cell.

[0198] In some embodiments, the first negative electrode active material includes artificial graphite, and the second negative electrode active material includes natural graphite or a mixture of natural graphite and artificial graphite.

[0199] Natural graphite particles have a larger particle size than artificial graphite particles. By setting artificial graphite in the first negative electrode film layer away from the negative electrode current collector 601 and setting natural graphite or a mixture of natural and artificial graphite in the second negative electrode film layer near the negative electrode current collector 601, it is beneficial to form pores of different sizes in the negative electrode film layer 602. The pore sizes vary along the thickness direction of the negative electrode film layer 602, which facilitates the diffusion of lithium ions and thus improves the kinetic performance of the battery cell. In addition, the above-mentioned negative electrode film layer 602, combined with the first and second additives of the present application embodiment, also helps to compensate for the problem of increased lithium ion consumption caused by the larger electrochemically active specific surface area of ​​artificial graphite compared to natural graphite. Therefore, the battery cell can have a longer cycle life while maintaining good kinetic performance.

[0200] In some embodiments, the thickness ratio of the first negative electrode film layer 6021 to the second negative electrode film layer 6022 is 4:6 to 6:4.

[0201] The thickness ratio of the first negative electrode film layer 6021 to the second negative electrode film layer 6022 can be 4:6, 5:5, 6:4 or any value within the above range.

[0202] In the above embodiments, the first negative electrode film layer 6021 and the second negative electrode film layer 6022 have suitable thicknesses, which facilitates the insertion and diffusion of lithium ions in the negative electrode film layer 602, reduces the risk of lithium plating at the negative electrode, and helps to improve the cycle life of the battery cell.

[0203] In some embodiments, the volume average particle size Dv50 of natural graphite is 8 μm to 20 μm, and / or the volume average particle size Dv50 of artificial graphite is 6 μm to 17 μm.

[0204] The volume average particle size (Dv50) of a material represents the particle size corresponding to a cumulative volume distribution percentage of 50%, and can be determined using instruments and methods known in the art. For example, it can be conveniently determined using a laser particle size analyzer, referring to GB / T19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0205] The volume average particle size Dv50 of natural graphite can be 8μm, 8.5μm, 9μm, 10μm, 11μm, 12μm, 12.5μm, 13μm, 14μm, 15μm, 15.6μm, 16μm, 17μm, 18μm, 19μm, 20μm or any value within the above range.

[0206] The volume average particle size Dv50 of artificial graphite can be 6μm, 7μm, 8μm, 9μm, 9.5μm, 10μm, 11μm, 12μm, 12.5μm, 13μm, 14μm, 15μm, 15.6μm, 16μm, 17μm or any value within the above range.

[0207] The difference in volume average particle size between natural graphite and artificial graphite is beneficial for forming a porous structure in the negative electrode film layer 602, which facilitates the wetting of electrolyte and the diffusion of lithium ions, and helps to improve the dynamic performance of the battery cell.

[0208] In some embodiments, the negative electrode film layer includes a negative electrode active material, which further includes a silicon-based material. This is beneficial for further improving the energy density of the battery cell.

[0209] In some embodiments, the silicon content in the silicon-based material is 0.01% to 10% by mass, and optionally 0.05% to 3%, based on the total mass of the negative electrode active material.

[0210] Based on the total mass of the negative electrode active material, the mass content of silicon element in the silicon-based material can be 0.01%, 0.02%, 0.03%, 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value within the above range.

[0211] When the mass content of silicon in the silicon-based material is greater than or equal to 0.01% based on the total mass of the negative electrode active material, it is beneficial to improve the energy density of the battery cell. When the mass content of silicon in the silicon-based material is less than 10% based on the total mass of the negative electrode active material, it can reduce the risk of deterioration in the cycle life of the battery cell caused by excessive silicon content. In addition, by combining silicon-based materials and the first additive, the battery cell can also have a higher initial efficiency.

[0212] In some embodiments, the porosity of the negative electrode 60 is 10% to 50%, optionally 25% to 35%.

[0213] The porosity of the negative electrode 60 is 10%, 20%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 45%, 50%, or any value within the above range.

[0214] In the above embodiments, the porosity of the negative electrode sheet 60 is within a suitable range, which is beneficial for electrolyte wetting, improving the lithium ion insertion and transport rate at the negative electrode, improving the kinetic performance of the battery cell and reducing polarization in the battery cell, and also helps to reduce the degree of side reactions.

[0215] In some embodiments, the thickness of the monolayer positive electrode film 502 is from 0.06 mm to 0.13 mm.

[0216] As an example, the thickness of a single-layer positive electrode film can be shown as T2 in Figure 4.

[0217] The thickness of the single-layer positive electrode film 502 can be 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.11mm, 0.12mm, 0.13mm or any value within the above range.

[0218] When the thickness of the single-layer positive electrode film 502 is between 0.06 mm and 0.13 mm, the lithium ions and oxygen free radicals generated by the first additive in the positive electrode film 502 have a suitable desorption rate, which is beneficial to improving the kinetic performance of the SEI film, facilitating the insertion and transport of lithium ions in the negative electrode, and also helps to reduce the risk of excessive gas generation in the battery cell due to excessive desorption of oxygen free radicals in a short period of time. In addition, the positive electrode film 502 has a larger thickness, and can include more positive electrode active materials, which is beneficial to improving the energy density of the battery cell.

[0219] In some embodiments, the thickness of the monolayer positive electrode film 502 is 0.07 mm to 0.1 mm. This results in a battery cell with good kinetic performance and less gas production, while also exhibiting a high energy density.

[0220] In some embodiments, the single-sided density of the positive electrode film layer 502 is 0.25 g / 1540.25 mm². 2 Up to 0.45g / 1540.25mm 2 Available in 0.28g / 1540.25mm. 2 Up to 0.4g / 1540.25mm 2 .

[0221] The single-sided density of the positive electrode film layer 502 can be 0.25 g / 1540.25 mm. 2 0.28g / 1540.25mm 20.3g / 1540.25mm 2 0.32g / 1540.25mm 2 0.35g / 1540.25mm 2 0.38g / 1540.25mm 2 0.4g / 1540.25mm 2 0.42g / 1540.25mm 2 0.43g / 1540.25mm 2 0.44g / 1540.25mm 2 0.45g / 1540.25mm 2 Or a range between any of the above values.

[0222] The unilateral density of the positive electrode film layer 502 is related to the kinetic performance and energy density of the battery cell. The higher the unilateral density of the positive electrode film layer 502, the greater the coating weight of the positive electrode film layer 502, which is more conducive to improving the energy density of the battery cell. Within a certain range, the lower the unilateral density of the positive electrode film layer 502, the more conducive it is to lithium-ion transport, and the better the kinetic performance of the battery cell.

[0223] In the above embodiments, the positive electrode film layer 502 has a suitable areal density, and the battery cell has a relatively suitable energy density and kinetic performance.

[0224] In some embodiments, the compaction density of the positive electrode film 502 at 0% SOC is 2.1 g / cm³. 3 Up to 2.9 g / cm 3 2.4g / cm³ is an optional value. 3 Up to 2.7 g / cm 3 .

[0225] The compaction density of the positive electrode film layer 502 at 0% SOC can be 2.1 g / cm³. 3 2.2g / cm 3 2.3g / cm 3 2.35g / cm 3 2.4g / cm 3 2.45g / cm 3 2.5g / cm 3 2.55g / cm 3 2.6g / cm 3 2.65g / cm 3 2.7g / cm 3 2.75g / cm 3 2.8g / cm 3 2.9g / cm 3 Or a range between any of the above values.

[0226] The compaction density of the positive electrode film 502 is related to the kinetic performance and energy density of the battery cell. The higher the compaction density of the positive electrode film 502, the better it is for improving the energy density of the battery cell; within a certain range, the lower the compaction density of the positive electrode film 502, the better it is for lithium-ion transport, and the better the kinetic performance of the battery cell.

[0227] In some embodiments, the lithium phosphate positive electrode active material includes primary particles and secondary particles formed by the agglomeration of primary particles. The average longest diameter of the primary particles is 100 nm to 500 nm, and the average longest diameter of the secondary particles is 1 μm to 2 μm.

[0228] In the embodiments of this application, a primary particle refers to the smallest unit of a particle within a certain observation range. A primary particle may contain defects of any form, but it is impossible to further define smaller particles within a primary particle. Primary particles may aggregate under physical forces such as van der Waals forces, but such aggregation is easily disaggregated under external forces such as ultrasound, stirring, and rolling, so that the main constituent morphology of the positive electrode active material in the film layer is still primary particles.

[0229] In the embodiments of this application, secondary particles refer to particles formed by the aggregation of primary particles.

[0230] The average longest diameter of the primary particles of the lithium iron phosphate cathode active material is 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 480nm, 500nm or any value within the above range, and the average longest diameter of the secondary particles can be 1μm, 1.5μm, 2μm or any value within the above range.

[0231] In the above embodiments, the lithium phosphate particles have a suitable size, which facilitates the extraction of lithium ions and helps to maximize the capacity of the battery cell.

[0232] In some embodiments, lithium phosphate cathode active materials include those with the general formula Li x D y Me a1 M b1 P 1- c1 X c1 Y zCompounds wherein 0.5≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, and 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z≤5; D includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; Y includes one or more of O and F.

[0233] In the general formula of lithium phosphate positive electrode active material, x can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3 or any of the above values; y can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3 or any of the above values; a1 can be 0.9, 1, 1.2, 1.3, 1.4, 1.5 or any of the above values; b1 can be 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any of the above values; c1 can be 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any of the above values; and z can be 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5 or any of the above values.

[0234] During the charging and discharging process of a single battery cell, the molar content of lithium, oxygen, and other elements in the lithium phosphate cathode active material changes within a certain range.

[0235] In some embodiments, the lithium phosphate-containing cathode active material includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The aforementioned lithium phosphate-containing cathode active materials exhibit high structural stability, which helps to improve the cycle life of individual battery cells.

[0236] During the charging and discharging process, lithium (Li) undergoes insertion / extraction and consumption within a single battery cell. The molar content of Li in the positive electrode active material varies depending on the discharge state of the cell. In the examples of positive electrode active materials in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar content of Li changes when the positive electrode active material is applied to the battery system. Similarly, the molar content of O in the examples of positive electrode active materials in this application is only an ideal value. Oxygen release from the crystal lattice causes changes in the molar content of O, resulting in fluctuations in the actual molar content of O.

[0237] In some embodiments, at least a portion of the surface of the lithium phosphate-containing positive electrode active material has carbon elements. This helps to improve the conductivity of the lithium phosphate, facilitating the utilization of the battery cell's capacity.

[0238] As an example, at least a portion of the surface of the lithium phosphate is provided with a coating layer, which includes carbon elements. The inclusion of a carbon-containing coating layer improves the conductivity of the positive electrode active material, facilitating the full utilization of the battery cell's capacity.

[0239] In some embodiments, the carbon content is 1% to 2% based on the total mass of the lithium phosphate cathode active material.

[0240] Based on the total mass of the lithium phosphate cathode active material, the mass content of carbon can be 1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any of the above values.

[0241] In the above embodiments, the lithium phosphate-containing positive electrode active material has good conductivity, which facilitates the utilization of the capacity of the battery cell.

[0242] In some embodiments, the positive electrode film 502 satisfies at least one of the following conditions: the volume average particle size of the lithium transition metal oxide is 3 μm to 30 μm; the volume average particle size of the nickel metal oxide is 5 μm to 50 μm; and the volume average particle size of the lithium phosphate positive electrode active material is 0.5 μm to 8 μm.

[0243] In the above embodiments, the lithium phosphate positive electrode active material, the lithium transition metal oxide, and the nickel metal oxide have suitable particle sizes, and the battery cells have good energy density and less gas production.

[0244] In some embodiments, the battery cell further includes an electrolyte, which includes additives, including at least one of fluoroethylene carbonate (FEC), 1,3-propane sulpholactone (PS), vinylene carbonate (VC), and ethylene sulfate (DTD).

[0245] The aforementioned additives help form a film at the negative electrode, thereby reducing the side reactions between the negative electrode active material and the electrolyte, reducing lithium ion consumption, and improving the initial efficiency and cycle life of the battery cell.

[0246] Figure 6 is a schematic diagram of the structure of a battery cell according to an embodiment of this application. In one embodiment of this application, for example, referring to Figure 6, the battery cell 3 includes a housing 31, an end cap assembly 32, and an electrode assembly 33. The housing 31 has an opening for accommodating the electrode assembly 33, and the end cap assembly 32 is used to close the opening. The electrode assembly 33 may include a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode.

[0247] In some embodiments, the end cap assembly 32 includes electrode terminals 322, as shown in FIG6. The end cap assembly 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0248] The battery cell 3 also includes a connecting member 34 for connecting the tab 331 and the electrode terminal 322 of the electrode assembly 33. For example, one connecting member 34 is used to connect the tab of the positive electrode and the positive electrode terminal, and another connecting member 34 is used to connect the tab of the negative electrode and the negative electrode terminal.

[0249] [Positive electrode plate]

[0250] 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.).

[0251] In some embodiments, the positive electrode film layer further includes a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0252] In some embodiments, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0253] In one embodiment, the positive electrode sheet can be prepared by forming a positive electrode slurry using the components described above. For example, the positive electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form the positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained.

[0254] [Negative electrode plate]

[0255] In some embodiments, the negative electrode current collector can be a metal foil or a composite negative electrode current collector. The negative electrode current collector can be a copper foil. The composite negative electrode current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0256] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from one or more 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.

[0257] The negative electrode film layer may also optionally include a binder. As an example, the binder may include one or more of the following: styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0258] The negative electrode film may optionally include a conductive agent. The conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0259] In one embodiment, the negative electrode sheet can be prepared by forming a negative electrode slurry using the components described above. For example, the negative electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., deionized water) to form the negative electrode slurry. The negative electrode slurry is then coated onto a negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained.

[0260] [Isolation Component]

[0261] The separator is used to separate the positive electrode and the negative electrode. This application does not impose any particular restrictions on the type of separator; for example, any known porous membrane with good chemical and mechanical stability can be selected.

[0262] In one embodiment, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0263] This application provides a battery device, including the battery cell in any of the above embodiments.

[0264] This application provides an electrical device including a battery cell or battery device as described in any of the above embodiments, wherein the battery cell or battery device is used to store or provide electrical energy.

[0265] 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.

[0266] [Example]

[0267] Example 1

[0268] (1) Preparation of positive electrode sheet

[0269] Lithium iron phosphate (LiFePO4), the positive electrode active material, Li5FeO4 (first additive), Li2NiO2 (second additive), Super P (positive electrode conductive agent), and polyvinylidene fluoride (PVDF) (positive electrode binder) were mixed in a mass ratio of 95:2:0.5:0.5:2. N-methylpyrrolidone (NMP) solvent was added, and the mixture was stirred under vacuum until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto both surfaces of an aluminum foil current collector. The slurry-coated current collector was dried and cold-pressed to obtain the positive electrode sheet. The single-sided thickness of the positive electrode film was 0.077 mm, and the single-sided density was 0.31 g / 1540.25 mm². 2 The compaction density of the positive electrode sheet is 2.6 g / cm³. 3 .

[0270] In the positive electrode film, the average length of the longest diameter of the first additive is 5 μm, and the average length of the longest diameter of the second additive is 8 μm.

[0271] (2) Preparation of negative electrode sheet

[0272] Artificial graphite (negative electrode active material), Super P (negative electrode conductive agent), sodium carboxymethyl cellulose (thickener), and styrene-butadiene rubber (SBR) (negative electrode binder) were mixed in a mass ratio of 96.7:0.5:1:1.8. Deionized water was added as a solvent, and the mixture was stirred evenly under vacuum to prepare a slurry. The slurry was then uniformly coated onto both surfaces of a copper foil current collector. After drying and cold pressing, the negative electrode sheet was obtained. The artificial graphite (negative electrode active material) had a volume average particle size (Dv50) of 9.5 μm and a surface density of 0.155 g / 1540.25 mm². 2 The thickness of the single-layer negative electrode film is 0.063 mm, and the compaction density of the negative electrode film is 1.6 g / cm³. 3 .

[0273] (3) Separating membrane

[0274] The separator is a 5μm PE base film.

[0275] (4) Electrolyte

[0276] The electrolyte consists of a solvent and an electrolyte salt. The solvent is ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1. The electrolyte salt is LiPF6, and the concentration of the electrolyte salt is 1 mol / L.

[0277] (5) Assembly of battery cells

[0278] The negative electrode, separator, and positive electrode are wound into an electrode assembly; the electrode assembly is placed in a housing, electrolyte is injected, and after standing and formation processes, a secondary battery is obtained.

[0279] Examples 2-5

[0280] The difference between Examples 2-5 and Example 1 is that the mass content of the first additive is different.

[0281] Examples 6-10

[0282] The difference between Examples 6-10 and Example 1 is that the mass content of the second additive is different.

[0283] Examples 11-13

[0284] The difference between Examples 11-13 and Example 1 is that the average value of the longest diameter of the first additive and the average value of the longest diameter of the second additive are different.

[0285] Examples 14-15

[0286] The difference between Examples 14-15 and Example 1 is that the thickness D1 of the negative electrode film is different.

[0287] Comparative Example 1

[0288] The difference between Comparative Example 1 and Example 1 is that the positive electrode film layer includes positive electrode active material, but does not include the first additive and the second additive.

[0289] Comparative Example 2

[0290] The difference between Comparative Example 2 and Example 1 is that the positive electrode film layer includes a positive electrode active material and a first additive, but does not include a second additive.

[0291] Table 1. Aging gas production test results of the examples and comparative examples.

[0292] Table 2 shows the test results of charging time for the examples and comparative examples.

[0293] Table 3 shows the test results of cycle life in Examples 1, 7, and 9-10.

[0294] In this embodiment, the kinetic performance of a single battery cell is reflected by the charging time from 0% SOC to 100% SOC, and the gas production during the aging stage within the battery cell is reflected by the amount of gas produced during that stage. The shorter the charging time from 0% SOC to 100% SOC, the faster the lithium ion transport rate at the negative electrode, resulting in better kinetic performance of the battery cell, a lower risk of lithium plating at the negative electrode, and a lower risk of a significant drop in cycle life due to lithium plating.

[0295] As shown in Example 1 and Comparative Example 1, the addition of the first additive is beneficial to improving the kinetic performance of the battery cell. This means that the addition of the first additive helps to compensate for the problem that the lithium ion insertion and transport rate at the negative electrode is affected by the excessive thickness of the negative electrode film. By adding the first additive, the energy density and kinetic performance of the battery cell can be balanced.

[0296] As shown in Example 1 and Comparative Example 2, the combination of the first additive and the second additive can reduce gas production in the battery cell while taking into account both the energy density and kinetic performance of the battery cell.

[0297] As shown in Examples 1-2, with the increase of the mass content of the first additive, the charging time of the battery cell from 0% SOC to 100% SOC becomes shorter, and the kinetic performance of the battery cell is improved. As shown in Examples 1-5, when the mass content of lithium transition metal oxide is 0.3% to 4.5%, the battery cell has suitable kinetic performance and less gas production; furthermore, when the mass content of lithium transition metal oxide is 0.5% to 2%, the battery cell has even better kinetic performance and less gas production.

[0298] As shown in Examples 1 and 6-10, the gas production within the battery cell decreases with increasing mass content of the second additive. As shown in Examples 1 and 6-10, when the mass content of nickel metal oxide is 0.03% to 2.5%, the battery cell exhibits less gas production and better kinetic performance; furthermore, when the mass content of nickel metal oxide is 0.05% to 1.5%, the battery cell can exhibit both less gas production and better cycle performance.

[0299] In conjunction with Examples 1 and 11-13, the average longest diameter of the lithium-containing transition metal oxide is 3 μm to 30 μm, and the average longest diameter of the nickel-containing metal oxide is 5 μm to 50 μm. The battery cell can have less gas production while also having better cycle performance. Furthermore, the average longest diameter of the lithium-containing transition metal oxide is 5 μm to 20 μm, and the average longest diameter of the nickel-containing metal oxide is 8 μm to 30 μm. The battery cell can have less gas production while also having better cycle performance.

[0300] As shown in Examples 14-15, different negative electrode film layers can be configured with different mass contents of the first additive. By combining the thickness of the negative electrode film layer with different mass contents of the first and second additives, the battery cell can have less gas production while also having better kinetic performance.

[0301] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

[0302] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0303] 1. Charging time test method

[0304] The battery cell was disassembled to obtain the positive electrode, separator, and negative electrode. The positive electrode, negative electrode, separator, and lithium titanate were then assembled into a three-electrode battery, and the maximum charge rate was measured at different SOC ranges.

[0305] As an example, the maximum charge rate of a single battery cell was tested when the lithium titanate electrode potential reached -1.562V in different charging ranges. The maximum charge rates at 0%–10% SOC, 10%–20% SOC, 20%–30% SOC, 30%–40% SOC, 40%–50% SOC, 50%–60% SOC, 60%–70% SOC, 70%–80% SOC, 80%–90% SOC, and 90%–100% SOC were recorded and denoted as C1, C2, C3, C4, C5, C6, C7, C8, C9, and C10.

[0306] The charging time of a single battery cell from 0% to 100% SOC is = 1 / 10C1 + 1 / 10C2 + 1 / 10C3 + 1 / 10C4 + 1 / 10C5 + 1 / 10C6 + 1 / 10C7 + 1 / 10C8 + 1 / 10C9 + 1 / 10C10.

[0307] 2. Gas production during the aging stage of individual battery cells

[0308] Specifically, the battery cells were held in a clamp (with a clamping force of 0.2 MPa) and formed at 0.05°C and 4.2V under conditions of 25°C and -30 kPa. Afterward, the battery cells were placed at 25°C, normal pressure (approximately 0.1 MPa), and humidity <20% for 48 hours to test the gas production. The gas production was measured using an in-situ gas production analyzer.

[0309] 3. Test of the average value of the longest diameter

[0310] The positive electrode sheet, which includes the first additive particles and lithium iron phosphate material, is cut along the thickness direction to expose the longitudinal section of the positive electrode film. The longest diameter of the first additive, the second additive, and the lithium iron phosphate material is determined by scanning electron microscopy (SEM) testing of the longitudinal section of the positive electrode film.

[0311] Specifically, the longest diameter of the first additive refers to the longest straight line that passes through the center point of the first additive and extends to the outer periphery of the particle; the longest diameter of the lithium iron phosphate material refers to the longest straight line that passes through the center point of the lithium iron phosphate material and extends to the outer periphery of the particle; and the longest diameter of the second additive refers to the longest straight line that passes through the center point of the second additive and extends to the outer periphery of the particle.

[0312] As an example, arbitrarily select 30 first additive particles in the longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 first additive particles, and take their average value; arbitrarily select 30 lithium iron phosphate material particles in the longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 lithium iron phosphate material particles, and take their average value; arbitrarily select 30 second additive particles in the longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 second additive particles, and take their average value.

[0313] 4. Test method for coating thickness

[0314] Cut the positive electrode sheet along its thickness to expose the longitudinal section of the positive electrode film. By performing SEM testing on the longitudinal section of the positive electrode film, after selecting the first additive particle, it can be observed that the first additive particle has a core-shell structure. The thickness of the shell layer is the thickness of the coating layer.

[0315] 5. Testing of specific components in the positive and negative electrode films.

[0316] After disassembling the battery cells, positive and negative electrode sheets are obtained. The positive electrode film layer of the positive electrode sheet is scraped off, and the scraped material is added to aqua regia and digested under mechanical stirring for 30 minutes. The digested solution is then added to an ICAP7400 spectrometer for elemental analysis. For example, for the positive electrode sheet, the contents of Ni, Fe, and P elements can be measured. Specifically, by detecting Ni, it can be determined whether the positive electrode film layer before formation contains Li₂NiO₂ and its mass content. By detecting the ratio of P to Fe elements, it can be determined whether the positive electrode film layer before formation contains Li₅FeO₄ and its mass content.

[0317] The negative electrode film layer of the negative electrode sheet is scraped off, and the scraped material is added to concentrated nitric acid and digested under mechanical stirring for 30 minutes. The digested solution is then added to an ICAP7400 spectrometer to analyze the elemental composition, and the contents of Si and C elements can be determined.

[0318] 6. Testing of the mass content of electrolyte salts

[0319] The concentration of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography, referring to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte from a fresh battery can be used as a sample, or a fully discharged battery (discharged to the lower cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection by ion chromatography.

[0320] 7. Test methods for areal density and compacted density

[0321] The positive and negative electrode sheets are removed from the lithium-ion battery cell, and their thicknesses and current collector thicknesses are measured respectively. A certain area of ​​the electrode sheet is taken, its area is measured, and the mass of the film layer on the current collector after removing the current collector is measured. The electrode surface density is calculated based on this area and mass. Therefore, the compaction density PD of the electrode sheet is calculated as: electrode surface density / (electrode thickness - current collector thickness).

[0322] 8. Test of volume average particle size

[0323] Volumetric particle size distribution can be determined using a particle size analyzer-laser diffraction method. Specifically, refer to standard GB / T19077-2016, using a laser diffraction scattering particle size analyzer, and perform measurements according to the manufacturer's instructions. For example, take an appropriate amount of sample. The sample can be obtained directly from powder (e.g., self-made or purchased) or from powder obtained through disassembly of battery products. Use a Malvern 2000 (MasterSizer 2000) laser particle size analyzer to test the average volumetric particle size of the sample material. Take an appropriate amount of the sample to be tested (the sample concentration should be 8-12% opacity), add 20 ml of deionized water, and simultaneously incubate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0324] 9. Cycle life testing

[0325] Under 45℃ conditions, the battery cells were subjected to charge-discharge tests using a stepped charging method, and the capacity retention rate was tested after 1000 cycles. Specifically, the battery cells were charged from 0% SOC to 50% SOC at a rate of 1.1C, from 50% SOC to 70% SOC at a rate of 0.9C, from 70% SOC to 90% SOC at a rate of 0.5C, and from 90% SOC to 100% or 3.65V at a rate of 0.33C. Then, the battery cells were discharged to 2.5V with a constant current of 0.33C.

Claims

1. A battery cell, characterized in that, include: A positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a lithium phosphate positive electrode active material, a first additive, and a second additive. The first additive includes a lithium transition metal oxide, and the second additive includes a nickel metal oxide. The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer including graphite, and the thickness of a single negative electrode film layer is 0.04 mm to 0.1 mm.

2. The battery cell according to claim 1, characterized in that, The thickness of the single-layer negative electrode film is 0.05 mm to 0.08 mm.

3. The battery cell according to claim 1 or 2, characterized in that, Based on the total mass of the positive electrode film, the mass content of the lithium-containing transition metal oxide is 0.3% to 4.5%, optionally 0.5% to 2%.

4. The battery cell according to any one of claims 1 to 3, characterized in that, Based on the total mass of the positive electrode film, the mass content of the nickel-containing metal oxide is from 0.03% to 2.5%, and optionally from 0.05% to 1.5%.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The lithium-containing transition metal oxide includes Fe element. Based on the total mass of the positive electrode film, the mass ratio of Fe element in the lithium-containing transition metal oxide to the mass of Ni element in the nickel-containing metal oxide is 0.5 to 10, and optionally 1.5 to 5.

6. The battery cell according to any one of claims 1 to 5, characterized in that, On the longitudinal section along the thickness direction of the positive electrode sheet, the average longest diameter of the lithium-containing transition metal oxide is 3 μm to 30 μm, and can be selected as 5 μm to 20 μm.

7. The battery cell according to any one of claims 1 to 6, characterized in that, On the longitudinal section along the thickness direction of the positive electrode sheet, the average longest diameter of the nickel-containing metal oxide is 5 μm to 50 μm, and can be selected as 8 μm to 30 μm.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The average length of the longest diameter of the nickel-containing metal oxide is less than the average length of the longest diameter of the lithium-containing transition metal oxide.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The average length of the longest diameter of the nickel-containing metal oxide is greater than or equal to the average length of the longest diameter of the lithium-containing transition metal oxide.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate, the substrate comprising Li a MO b , where 1≤a≤6, 1≤b≤6, and M includes at least one of Fe, Cu, Co, Mn, and Al.

11. The battery cell according to any one of claims 1 to 9, characterized in that, The lithium-containing transition metal oxide includes a matrix and a coating layer located on at least a portion of the surface of the matrix, wherein the matrix includes Li5FeO4.

12. The battery cell according to any one of claims 1 to 9, characterized in that, The lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate, the substrate comprising Li e FeO f ,0≤e≤5,0 <f≤4。 13. The battery cell according to any one of claims 1 to 9, characterized in that, The lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate, the substrate comprising Li m FeO n ,0≤m≤1,0 <n≤2。 14. The battery cell according to any one of claims 10 to 13, characterized in that, At least a portion of the surface of the substrate contains at least one of Al or Mg.

15. The battery cell according to any one of claims 10 to 14, characterized in that, The coating layer includes carbon.

16. The battery cell according to any one of claims 10 to 15, characterized in that, The thickness of the coating layer is 10 nm to 200 nm.

17. The battery cell according to any one of claims 1 to 16, characterized in that, The nickel-containing metal oxide includes N c NiO d , where N includes at least one of Li, Na, and K, 0≤c≤2, 1≤d≤2.

18. The battery cell according to any one of claims 1 to 16, characterized in that, The nickel-containing metal oxide includes Li2NiO2.

19. The battery cell according to any one of claims 1 to 16, characterized in that, The nickel-containing metal oxide includes Li g NiO h ,0≤g≤2,0 <h≤2。 20. The battery cell according to any one of claims 1 to 16, characterized in that, The nickel-containing metal oxide includes NiO. q 0 <q≤2。 21. The battery cell according to any one of claims 1 to 20, characterized in that, The delithiation potential of the lithium-containing transition metal oxide is greater than that of the lithium-containing phosphate, and the delithiation potential of the nickel-containing metal oxide is greater than that of the lithium-containing phosphate.

22. The battery cell according to any one of claims 1 to 21, characterized in that, In a voltage range of 2V to 4.3V, the charging capacity of the lithium-containing transition metal oxide is 200mAh / g to 1000mAh / g, optionally 600mAh / g to 700mAh / g.

23. The battery cell according to any one of claims 1 to 22, characterized in that, The single-sided density of the negative electrode film is 0.12 g / 1540.25 mm. 2 Up to 0.2g / 1540.25mm 2 Available in 0.13g / 1540.25mm. 2 Up to 0.19g / 1540.25mm 2 .

24. The battery cell according to any one of claims 1 to 23, characterized in that, The compaction density of the negative electrode film at 0% SOC is 1.3 g / cm³. 3 Up to 1.8 g / cm 3 The option is 1.35g / cm³. 3 Up to 1.65 g / cm 3 .

25. The battery cell according to any one of claims 1 to 24, characterized in that, The negative electrode film layer includes a first negative electrode sub-film layer and a second negative electrode sub-film layer. Along the thickness direction of the negative electrode sheet, the first negative electrode sub-film layer is farther away from the negative electrode current collector than the second negative electrode sub-film layer. The first negative electrode film layer includes a first negative electrode active material, and the second negative electrode film layer includes a second negative electrode active material. The first negative electrode active material includes artificial graphite; the second negative electrode active material includes natural graphite or a combination of natural graphite and artificial graphite.

26. The battery cell according to claim 25, characterized in that, The thickness ratio of the first negative electrode film layer to the second negative electrode film layer is 4:6 to 6:

4.

27. The battery cell according to claim 25 or 26, characterized in that, The natural graphite has a volume average particle size Dv50 of 8 μm to 20 μm, and / or the artificial graphite has a volume average particle size Dv50 of 6 μm to 17 μm.

28. The battery cell according to any one of claims 1 to 27, characterized in that, The negative electrode film layer includes a negative electrode active material, which includes a silicon-based material.

29. The battery cell according to claim 28, characterized in that, Based on the total mass of the negative electrode active material, the silicon content in the silicon-based material is from 0.01% to 10%, and optionally from 0.05% to 3%.

30. The battery cell according to any one of claims 1 to 29, characterized in that, The porosity of the negative electrode sheet is 10% to 50%, and can be selected as 25% to 35%.

31. The battery cell according to any one of claims 1 to 30, characterized in that, The thickness of the single-layer positive electrode film is 0.06 mm to 0.13 mm, and can be selected as 0.07 mm to 0.1 mm.

32. The battery cell according to any one of claims 1 to 31, characterized in that, The single-sided density of the positive electrode film is 0.25 g / 1540.25 mm. 2 Up to 0.45g / 1540.25mm 2 Available in 0.28g / 1540.25mm. 2 Up to 0.4g / 1540.25mm 2 .

33. The battery cell according to any one of claims 1 to 32, characterized in that, The compaction density of the positive electrode film at 0% SOC is 2.1 g / cm³. 3 Up to 2.9 g / cm 3 2.4g / cm³ is an optional value. 3 Up to 2.7 g / cm 3 .

34. The battery cell according to any one of claims 1 to 33, characterized in that, The lithium phosphate positive electrode active material includes primary particles and secondary particles formed by the aggregation of the primary particles. The average longest diameter of the primary particles is 100 nm to 500 nm, and the average longest diameter of the secondary particles is 1 μm to 2 μm.

35. The battery cell according to any one of claims 1 to 34, characterized in that, The lithium phosphate-containing positive electrode active material includes materials with the general formula Li x D y Me a1 M b1 P 1-c1 X c1 Y z Compounds wherein 0.5≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, and 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z≤5; D includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; Y includes one or more of O and F.

36. The battery cell according to any one of claims 1 to 35, characterized in that, The lithium phosphate positive electrode active material includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

37. The battery cell according to any one of claims 1 to 36, characterized in that, At least a portion of the surface of the lithium phosphate-containing positive electrode active material has carbon elements.

38. The battery cell according to claim 37, characterized in that, Based on the total mass of the lithium phosphate positive electrode active material, the carbon content is 1% to 2% by mass.

39. The battery cell according to any one of claims 1 to 38, characterized in that, The positive electrode film layer satisfies at least one of the following conditions: The volume average particle size of the lithium-containing transition metal oxide is 3 μm to 30 μm; The volume average particle size of the nickel-containing metal oxide is 5 μm to 50 μm; The volume average particle size of the lithium phosphate positive electrode active material is 0.5 μm to 8 μm.

40. The battery cell according to any one of claims 1 to 39, characterized in that, The battery cell also includes an electrolyte, which includes additives, including at least one of FEC, PS, VC, and DTD.

41. A battery device, characterized in that, include: Multiple battery cells according to any one of claims 1 to 40.

42. An electrical appliance, characterized in that, include: A plurality of battery cells according to any one of claims 1 to 40, or a battery device according to claim 41, wherein the battery cells or battery devices are used to store or provide electrical energy.

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