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, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer provided on at least one side surface of the positive electrode current collector. The positive electrode film layer comprises a positive electrode active material, a first additive, a second additive and a binder, wherein the positive electrode active material comprises a lithium-containing phosphate, the first additive comprises a lithium-containing transition metal oxide, and the additive comprises a nickel-containing metal oxide; and the binder comprises an F element, and the mass content of the F element in the binder is 0.25% to 0.75% on the basis of the total mass of the positive electrode film layer. The technical solution of the present application is beneficial for improving the cycle life of the battery cell.

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, service life, capacity, fast charging performance, and reliability. How to provide a battery cell with a long cycle life is a technical problem that urgently needs to be solved. Summary of the Invention

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

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

[0006] In a first aspect, a battery cell is provided, comprising: a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material, a first additive, a second additive, and a binder; wherein the positive electrode active material includes a lithium phosphate, the first additive includes a lithium transition metal oxide, and the additive includes a nickel metal oxide; the binder includes element F, and the mass content of element F in the binder is 0.25% to 0.75% based on the total mass of the positive electrode film layer.

[0007] In this embodiment, the positive electrode film layer includes a positive electrode active material, a first additive, and a second additive. The positive electrode active material includes a lithium-containing phosphate, the first additive includes a lithium-containing transition metal oxide, and the second additive includes a nickel-containing metal oxide. The lithium-containing transition metal oxide can release lithium ions to provide active lithium ions to the battery cell, thereby improving the cycle life of the battery cell containing the lithium phosphate. The nickel-containing metal oxide can catalyze the conversion of oxygen free radicals generated by the delithiation of the lithium-containing transition metal oxide into oxygen, thereby reducing the damage of oxygen free radicals to the chemical bonds in the binder and reducing the risk of the positive electrode film layer detaching from the positive electrode current collector, thus improving the cycle life of the battery cell. Furthermore, the addition of the lithium-containing transition metal oxide makes the positive electrode slurry alkaline. The alkaline positive electrode slurry causes the binder to decompose and generate HF. HF will damage the SEI film at the negative electrode, leading to an increase in lithium ion consumption in the battery cell. By setting the F element mass content in the binder to 0.25% to 0.75%, the generation of HF can be reduced, thereby reducing damage to the SEI film and lithium ion consumption, further improving the cycle life of the battery cell.

[0008] In some embodiments, the F element content in the binder is 0.3% to 0.65% based on the total mass of the positive electrode film. This helps to further reduce HF generation, thereby further reducing damage to the SEI film and lithium ion consumption, resulting in a longer cycle life for the battery cell.

[0009] In some embodiments, the binder comprises a first fluoropolymer with a weight-average molecular weight of 1.8 million to 5 million. The first fluoropolymer has a high molecular weight and good bonding properties, thus achieving bonding between the positive electrode film and the positive electrode current collector with a relatively small mass content of the first fluoropolymer. In this way, the presence of the first fluoropolymer results in a lower F element mass content in the positive electrode film, making the positive electrode film less prone to detachment and leading to a longer cycle life for the battery cell.

[0010] In some embodiments, the first fluoropolymer is a polymer containing structural units as shown in Formula I and Formula II, wherein R1 includes one or more of fluorine and trifluoromethyl.

[0011] The fluorine groups in the structural units shown in Formula I and Formula II can form hydrogen bonds or other interactions with the polar groups in the solvent of the positive electrode slurry to achieve a bonding effect. However, excessive fluorine content in high molecular weight binders can easily cause the slurry to become gel-like. The mass content of F element in the structural unit shown in Formula I is lower than that in the structural unit shown in Formula II. By selecting the structural unit shown in Formula I, the degree of gelation of the positive electrode slurry can be reduced, making it easier for the positive electrode slurry to be coated on the positive electrode current collector. In addition, the higher the mass content of F element, the better it is to improve the adhesion between the positive electrode film layer and the positive electrode current collector. By selecting the structural unit shown in Formula II, the mass ratio of the binder in the positive electrode slurry can be appropriately reduced, achieving a good adhesion effect with a lower fluorine content and reducing the risk of the positive electrode film layer detaching from the positive electrode current collector. Therefore, the first fluoropolymer includes the structural units shown in Formula I and Formula II, which not only helps to reduce the risk of the positive electrode film layer falling off from the positive electrode current collector and improve the cycle life of the battery cell, but also helps to reduce the gelation degree of the positive electrode slurry and facilitate the coating of the positive electrode slurry.

[0012] In some embodiments, the mass content of the structural unit represented by Formula II is 0.5% to 15% based on the total mass of the first fluoropolymer.

[0013] When the mass content of the structural unit shown in Formula II is greater than or equal to 0.5% based on the total mass of the first fluoropolymer, the risk of the positive electrode film layer falling off from the positive electrode current collector is low, which is beneficial to improving the cycle life of the battery cell. When the mass content of the structural unit shown in Formula II is less than or equal to 15% based on the total mass of the first fluoropolymer, it is beneficial to reduce the gelation degree of the positive electrode slurry and facilitate the coating of the positive electrode slurry.

[0014] In some embodiments, the F element has a mass content of 50% to 65% in the first fluoropolymer.

[0015] When the mass content of element F in the first fluorinated polymer is greater than or equal to 50%, it is beneficial to improve the adhesion of the first fluorinated polymer, and the risk of the positive electrode film layer falling off from the positive electrode current collector is lower, which is beneficial to improving the cycle life of the battery cell. When the mass content of element F in the first fluorinated polymer is less than or equal to 65%, it is beneficial to reduce the gelation degree of the positive electrode slurry, which is convenient for the coating of the positive electrode slurry.

[0016] In some embodiments, the adhesive further includes a second fluoropolymer with a weight-average molecular weight of 800,000 to 1,100,000.

[0017] The second fluoropolymer has a smaller weight-average molecular weight than the first fluoropolymer. The addition of the second fluoropolymer helps to reduce the gelation degree of the positive electrode slurry and facilitates the coating of the positive electrode slurry.

[0018] In some embodiments, the mass ratio of the first fluoropolymer to the second fluoropolymer is 7:3 to 9:1 based on the total mass of the positive electrode film.

[0019] When the mass ratio of the first fluoropolymer to the second fluoropolymer is greater than or equal to 7:3 based on the total mass of the positive electrode film, it is beneficial to improve the adhesion of the binder, reduce the risk of the positive electrode film falling off from the positive electrode current collector, and improve the cycle life of the battery cell. When the mass ratio of the first fluoropolymer to the second fluoropolymer is less than or equal to 9:1 based on the total mass of the positive electrode film, it is beneficial to reduce the gelation degree of the positive electrode slurry and facilitate the coating of the positive electrode slurry.

[0020] 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.

[0021] When the total mass of the positive electrode film is greater than or equal to 0.3%, the lithium transition metal oxide can release more lithium ions, which is beneficial to improving the cycle life of the battery cell. When the total mass of the positive electrode film is less than 4.5%, the oxygen free radicals generated by the delithiation of the lithium transition metal oxide can be reduced, thereby reducing the damage of oxygen free radicals to the chemical bonds in the binder, reducing the risk of positive electrode film peeling off, and thus improving the cycle performance of the battery cell.

[0022] In some embodiments, the mass content of the lithium-containing transition metal oxide is 0.3% to 3% based on the total mass of the positive electrode film. This is beneficial for improving the cycle performance of the battery cell while also considering the volumetric energy density of the battery cell.

[0023] In some embodiments, the mass content of the nickel-containing metal oxide is 0.01% to 3% based on the total mass of the positive electrode film.

[0024] When the total mass of the positive electrode film is greater than or equal to 0.01%, it is beneficial to promote the conversion of oxygen free radicals generated by lithium transition metal oxides into oxygen, thereby reducing the damage of chemical bonds of the binder by oxygen free radicals, reducing the risk of positive electrode film detachment, and improving the cycle performance of the battery cell. When the total mass of the positive electrode film is less than or equal to 3%, the lithium phosphate positive electrode active material and lithium transition metal oxide have a more suitable mass content, which is beneficial to improving the cycle life of the battery cell.

[0025] In some embodiments, based on the total mass of the positive electrode film, the mass ratio of the lithium-containing transition metal oxide to the nickel-containing metal oxide is 50:50 to 95:5.

[0026] When the ratio of the mass content of lithium transition metal oxides to the mass content of nickel metal oxides is greater than or equal to 50:50 based on the total mass of the positive electrode film, more active lithium ions can be provided to the battery cell, which is beneficial to improving the cycle life of the battery cell. When the ratio of the mass content of lithium transition metal oxides to the mass content of nickel metal oxides is less than or equal to 95:5 based on the total mass of the positive electrode film, it is beneficial to fully catalyze the conversion of oxygen free radicals into oxygen, reduce the damage of oxygen free radicals to the chemical bonds of the binder, reduce the risk of positive electrode film peeling, and improve the cycle performance of the battery cell.

[0027] In some embodiments, based on the total mass of the positive electrode film, the mass ratio of the lithium-containing transition metal oxide to the nickel-containing metal oxide is 80:20 to 90:10. This is beneficial for further improving the cycle performance of the battery cell.

[0028] In some embodiments, the average longest diameter of the lithium-containing transition metal oxide is 2 μm to 15 μm on a longitudinal section along the thickness direction of the positive electrode sheet.

[0029] When the average longest diameter of lithium-containing transition metal oxides is greater than or equal to 2 μm, the rate at which oxygen free radicals are generated can be reduced, which helps to reduce the damage of chemical bonds of binders by oxygen free radicals, reduce the risk of cathode film shedding, and thus help to improve the cycle life of battery cells. When the average longest diameter of lithium-containing transition metal oxides is less than or equal to 15 μm, it is beneficial to the extraction of lithium ions from lithium-containing transition metal oxides, which helps to improve the cycle life of battery cells.

[0030] In some embodiments, the average longest diameter of the lithium-containing transition metal oxide is 4 μm to 12 μm on a longitudinal section along the thickness direction of the positive electrode sheet. This is beneficial for further improving the cycle life of the battery cell.

[0031] In some embodiments, the average longest diameter of the nickel-containing metal oxide is 5 μm to 30 μm on a longitudinal section along the thickness direction of the positive electrode sheet.

[0032] 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, thus improving the cycle life of battery cells. When the average longest diameter of nickel-containing metal oxides is less than or equal to 30 μm, it is beneficial to catalyze the conversion of oxygen free radicals generated by lithium-containing transition metal oxides into oxygen, reduce the damage of chemical bonds of binders by oxygen free radicals, reduce the risk of positive electrode film peeling, and thus improve the cycle life of battery cells.

[0033] In some embodiments, the average longest diameter of the nickel-containing metal oxide is 8 μm to 20 μm on a longitudinal section along the thickness direction of the positive electrode sheet. This is beneficial for further improving the cycle life of the battery cell.

[0034] 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 provides a suitable size match 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 damage of oxygen free radicals to the chemical bonds of the binder, lowering the risk of cathode film detachment, and thus improving the cycle life of the battery cell.

[0035] 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.

[0036] 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.

[0037] The molar content of lithium element in the matrix of the lithium-containing transition metal oxide is relatively high, and more lithium ions can be released to provide more active lithium ions to the battery cell, which is beneficial to improving the cycling performance of the battery cell; in addition, the setting of the coating layer is beneficial to improving the stability of the lithium-containing transition metal oxide.

[0038] In some embodiments, the lithium-containing transition metal oxide includes a matrix and a coating layer located on at least part of the surface of the matrix, and the matrix includes Li5FeO4. The above lithium-containing transition metal oxide can provide more active lithium ions, which is thus beneficial to further improving the cycling performance of the battery cell.

[0039] In some embodiments, the lithium-containing transition metal oxide includes a matrix and a coating layer located on at least 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.

[0040] In some embodiments, the lithium-containing transition metal oxide includes a matrix and a coating layer located on at least 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.

[0041] In some embodiments, at least part of the surface of the matrix contains at least one of Al or Mg. In this way, it is beneficial to improving the stability of the lithium-containing transition metal oxide, reducing the risk of metal ion dissolution in the matrix, thereby reducing the risk that the dissolved metal ions move to the negative electrode and become metal单质, and thus reducing the influence of the metal单质 on the intercalation of lithium ions at the negative electrode, and reducing the risk of lithium deposition at the negative electrode and the reduction of the cycle life caused by lithium deposition.

[0042] 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 reducing the risk of metal ion dissolution in the matrix, thereby being beneficial to improving the cycle life of the battery cell.

[0043] 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 facilitating the release of lithium ions, and is beneficial to improving the cycle life of the battery cell.

[0044] 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 the lithium-containing iron oxide into oxygen, thereby reducing the damage of oxygen free radicals to the chemical bonds of the binder and reducing the risk of shedding of the positive electrode film layer, which is beneficial to improving the cycle life of the battery cell; 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.

[0045] In some embodiments, the nickel-containing metal oxide includes Li2NiO2. In this way, it is beneficial to improve the cycle life of the battery cell. <00002​​​​​​​​​​​​​​​​​​​​​​​​​​Available in 0.28g / 1540.25mm. 2 Up to 0.4g / 1540.25mm 2 .

[0052] 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.

[0053] 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 .

[0054] 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.

[0055] 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.

[0056] In the above embodiments, the positive electrode film layer has a large thickness, and the battery cell has a high energy density.

[0057] In some embodiments, the battery cell further includes a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative electrode film layer disposed on at least one side surface of the negative current collector, the negative electrode film layer including a negative electrode active material, the negative electrode active material including at least one of natural graphite, artificial graphite, soft carbon, and hard carbon.

[0058] In some embodiments, the negative electrode active material comprises natural graphite or a mixture of natural and artificial graphite. Graphite-based materials have high stability, which is beneficial for improving the cycle life of individual battery cells.

[0059] In some embodiments, the negative electrode active material comprises a mixture of natural graphite and artificial graphite, wherein the mass ratio of artificial graphite to natural graphite is 5:5 to 9:1 based on the total mass of the negative electrode active material. This combination results in a negative electrode active material with a suitable electrochemically active specific surface area, which helps reduce lithium-ion consumption and improve the cycle life of the battery cell.

[0060] In some embodiments, the thickness of the single-layer negative electrode film is 0.04 mm to 0.1 mm, optionally 0.05 mm to 0.08 mm. This results in a relatively large thickness of the negative electrode film, which is beneficial for improving the energy density of the battery cell.

[0061] In some embodiments, the one-sided density of the negative electrode film 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 .

[0062] In the above embodiments, the negative electrode film layer has a suitable areal density, and the battery cell has a suitable energy density, cycle life, and kinetic performance.

[0063] 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 .

[0064] In the above embodiments, the negative electrode film layer has a suitable compaction density, and the battery cell has a relatively suitable energy density, cycle life, and kinetic performance.

[0065] In some embodiments, the lithium phosphate 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 results in lithium phosphate particles of a suitable size, facilitating lithium ion extraction, which helps to maximize the capacity of the battery cell and thus improves the cycle life of the battery cell.

[0066] In some embodiments, the lithium-containing phosphate includes those 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.

[0067] During the charging and discharging process of a single battery cell, the molar content of lithium, oxygen, and other elements in lithium phosphate varies within a certain range.

[0068] In some embodiments, the lithium-containing phosphate includes at least one selected from LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. These lithium-containing phosphates exhibit high structural stability, which helps to improve the cycle life of battery cells.

[0069] In some embodiments, at least a portion of the surface of the lithium phosphate contains carbon. This helps to improve the conductivity of the lithium phosphate, facilitating the utilization of the battery cell's capacity.

[0070] In some embodiments, the carbon content is 1% to 2% based on the total mass of the lithium phosphate. This gives the lithium phosphate good conductivity, facilitating the utilization of the battery cell's capacity.

[0071] 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 2 μm to 15 μm; the volume average particle size of the nickel-containing metal oxide is 5 μm to 30 μm; and the volume average particle size of the lithium-containing phosphate is 0.5 μm to 8 μm.

[0072] 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 long cycle life.

[0073] In a second aspect, a battery device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof.

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

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

[0076] Figure 1 is a schematic diagram of a vehicle according to an embodiment of this application;

[0077] Figure 2 is a schematic diagram of a battery device according to an embodiment of this application;

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

[0079] Figure 4 is a schematic diagram of the negative electrode sheet according to an embodiment of this application;

[0080] Figure 5 is a schematic diagram of a battery cell according to an embodiment of this application. Detailed Implementation

[0081] 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.

[0082] 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.

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

[0084] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0085] 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.

[0086] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0087] This application aims to develop a battery cell that balances long cycle life and high safety. The battery cell includes a positive electrode sheet, which 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 positive electrode active material, a first additive, a second additive, and a binder. The positive electrode active material includes a lithium phosphate, the first additive includes a lithium transition metal oxide, and the second additive includes a nickel metal oxide. The binder includes element F, and the mass content of element F in the binder is 0.25% to 0.75% based on the total mass of the positive electrode film layer.

[0088] Lithium-containing phosphates are widely used as positive electrode active materials in battery cells due to their high structural stability. To further improve the cycle life of battery cells containing lithium-containing phosphates, adding lithium-containing transition metal oxide (LMO) lithium supplementers to the positive electrode is a relatively effective method. However, LMOs generate oxygen free radicals during lithium ion release. These free radicals disrupt the chemical bonds of the binder in the positive electrode film, leading to a decrease in the molecular weight of the binder. This, in turn, reduces the adhesion between the positive electrode film and the current collector, accelerating the degradation of the battery cell's cycle life. Furthermore, positive electrode slurries containing LMOs are alkaline. Alkaline slurries more easily cause the binder (generally containing sulfur) to decompose and release HF. HF has a destructive effect on the SEI film. After the SEI film is damaged, the battery cell continuously repairs the damaged SEI film, leading to increased lithium ion consumption and hindering the improvement of the battery cell's cycle life.

[0089] This application adds a nickel-containing metal oxide to the positive electrode film containing lithium transition metal oxides. The nickel-containing metal oxide can promote the conversion of oxygen free radicals generated by lithium transition metal oxides into oxygen, reduce the damage of oxygen free radicals to the chemical bonds of the binder, reduce the risk of the positive electrode film falling off from the positive electrode current collector, and help improve the cycle life of the battery cell. Furthermore, by controlling the mass content of F element in the binder to 0.25% to 0.75%, the side reaction of generating a large amount of HF caused by the inclusion of lithium transition metal oxides in the slurry is reduced, thereby reducing the damage of HF to the negative electrode SEI film, reducing lithium ion consumption, and further improving the cycle life of the battery cell.

[0090] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0091] In some embodiments, the positive electrode can be a positive electrode sheet, which can include a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0092] In some embodiments, the negative electrode may be a negative electrode sheet, which may include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0093] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

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

[0095] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride, and ceramic.

[0096] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0097] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel, or solid.

[0098] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0099] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as electrode assemblies and electrolytes. The housing may be made of steel, aluminum, plastic (such as polypropylene), composite metal (such as copper-aluminum composite), or aluminum-plastic film, etc. The housing includes a shell and end caps.

[0100] The battery mentioned in the embodiments of this application may be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed via a busbar.

[0101] In some embodiments, the battery device may be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0102] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0103] In some embodiments, the battery device may be located within an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0104] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery devices.

[0105] 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.

[0106] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] The battery cells can be lithium-ion batteries or lithium metal batteries.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] [Battery cell]

[0117] This application provides a battery cell including a positive electrode.

[0118] Figure 3 is a schematic diagram of a positive electrode sheet according to an embodiment of this application. For example, as shown in Figure 3, the positive electrode sheet 50 includes a positive current collector 501 and a positive electrode film layer 502 disposed on at least one side surface of the positive current collector 501.

[0119] 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.

[0120] The positive electrode film layer 502 includes a positive electrode active material, a first additive, a second additive, and a binder. The positive electrode active material includes a lithium phosphate, the first additive includes a lithium transition metal oxide, and the second additive includes a nickel metal oxide. The binder includes element F, and the mass content of element F in the binder is 0.25% to 0.75% based on the total mass of the positive electrode film layer.

[0121] Lithium-containing phosphates are used as positive electrode active materials, allowing lithium ions to be reversibly extracted and inserted.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] Nickel-containing metal oxides include nickel and oxygen. In some embodiments, nickel-containing metal oxides may also include lithium.

[0128] The binder includes the element F; as an example, the binder includes polyvinylidene fluoride (PVDF).

[0129] Based on the total mass of the positive electrode film, the mass content of F element in the binder can be 0.25%, 0.28%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, or any value within the above range.

[0130] 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). Nickel-containing metal oxides can catalyze the conversion of oxygen free radicals generated from the delithiation of lithium-containing transition metal oxides into oxygen, thereby reducing the damage of oxygen free radicals to the chemical bonds in the binder, lowering the risk of the positive electrode film detaching from the positive electrode current collector, and thus improving the cycle life of the battery cell. The fluorine (F) content in the binder is in the range of 0.25% to 0.75%, which is relatively low. This reduces the HF generated by the decomposition of the binder, reducing the damage of HF to the solid electrolyte interface (SEI) membrane at the negative electrode, thereby reducing lithium ion consumption and contributing to improved cycle life of the battery cell.

[0131] Furthermore, the alkalinity of the cathode slurry is enhanced when lithium is included in the nickel-containing metal oxide. Controlling the F content within the range of 0.25% to 0.75% also helps reduce the impact of the cathode slurry's alkalinity on the binder, facilitates control of HF content, reduces HF's damage to the SEI film and lithium-ion consumption, and results in a longer cycle life for the battery cells.

[0132] In this embodiment, the positive electrode film layer includes a positive electrode active material, a first additive, and a second additive. The positive electrode active material includes a lithium-containing phosphate, the first additive includes a lithium-containing transition metal oxide, and the second additive includes a nickel-containing metal oxide. The lithium-containing transition metal oxide can release lithium ions to provide active lithium ions to the battery cell, thereby improving the cycle life of the battery cell containing the lithium phosphate. The nickel-containing metal oxide can catalyze the conversion of oxygen free radicals generated by the delithiation of the lithium-containing transition metal oxide into oxygen, thereby reducing the damage of oxygen free radicals to the chemical bonds in the binder and reducing the risk of the positive electrode film layer detaching from the positive electrode current collector, thus improving the cycle life of the battery cell. Furthermore, by setting the mass content of F element in the binder to 0.25% to 0.75%, the F element content in the positive electrode film layer binder is reduced, thereby reducing the amount of HF caused by the addition of alkaline substances containing lithium-containing transition metal oxides or nickel-containing metal oxides. This reduces the damage to the negative electrode SEI film and the consumption of lithium ions, further improving the cycle life of the battery cell.

[0133] In some embodiments, the F element content in the binder is 0.3% to 0.65% based on the total mass of the positive electrode film. This results in a lower fluorine content in the binder, which helps to further reduce HF generation, thereby further reducing damage to the SEI film and lithium-ion consumption, leading to a longer cycle life for the battery cell.

[0134] In some embodiments, the binder comprises a first fluoropolymer with a weight-average molecular weight of 1.8 million to 4 million.

[0135] The weight-average molecular weight of the first fluoropolymer can be 1.8 million, 1.9 million, 2 million, 2.1 million, 2.5 million, 2.8 million, 3 million, 3.2 million, 3.5 million, 3.8 million, 4 million, or any value within the above range.

[0136] The bonding performance of an adhesive is related to its weight-average molecular weight. Within a certain range, the higher the weight-average molecular weight of the adhesive, the better its bonding performance.

[0137] In the above embodiments, the first fluoropolymer has a high molecular weight and good adhesion properties, thus achieving bonding between the positive electrode film and the positive electrode current collector with a relatively small mass content of the first fluoropolymer. This results in a lower F element mass content in the positive electrode film, and the positive electrode film is less prone to detachment, leading to a longer cycle life for the battery cell.

[0138] In some embodiments, the first fluoropolymer is a polymer containing structural units as shown in Formula I and Formula II, wherein R1 includes one or more of fluorine, chlorine, and trifluoromethyl.

[0139] The fluorine groups in the structural units shown in Formula I and Formula II can form hydrogen bonds or other interactions with the polar groups in the solvent of the positive electrode slurry to achieve a bonding effect. However, excessive fluorine content in high molecular weight binders can easily cause the slurry to become gel-like. The mass content of F element in the structural unit shown in Formula I is lower than that in the structural unit shown in Formula II. By selecting the structural unit shown in Formula I, the degree of gelation of the positive electrode slurry can be reduced, making it easier for the positive electrode slurry to be coated on the positive electrode current collector. In addition, the higher the mass content of F element, the better it is to improve the adhesion between the positive electrode film layer and the positive electrode current collector. By selecting the structural unit shown in Formula II, the mass ratio of the binder in the positive electrode slurry can be appropriately reduced, achieving a good adhesion effect with a lower fluorine content and reducing the risk of the positive electrode film layer detaching from the positive electrode current collector. Therefore, the first fluoropolymer includes the structural units shown in Formula I and Formula II, which not only helps to reduce the risk of the positive electrode film layer falling off from the positive electrode current collector and improve the cycle life of the battery cell, but also helps to reduce the gelation degree of the positive electrode slurry and facilitate the coating of the positive electrode slurry.

[0140] In some embodiments, the mass content of the structural unit represented by Formula II is 0.5% to 15% based on the total mass of the first fluoropolymer.

[0141] Based on the total mass of the first fluoropolymer, the mass content of the structural unit shown in Formula II can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, or any value within the above range.

[0142] When the mass content of the structural unit shown in Formula II is greater than or equal to 0.5% based on the total mass of the first fluoropolymer, the risk of the positive electrode film layer falling off from the positive electrode current collector is low, which is beneficial to improving the cycle life of the battery cell. When the mass content of the structural unit shown in Formula II is less than or equal to 15% based on the total mass of the first fluoropolymer, it is beneficial to reduce the gelation degree of the positive electrode slurry and facilitate the coating of the positive electrode slurry.

[0143] In some embodiments, the mass content of element F in the first fluoropolymer is 50% to 65%.

[0144] The mass content of element F in the first fluoropolymer can be 50%, 52%, 55%, 58%, 60%, 63%, 65%, or any value within the above range.

[0145] When the mass content of element F in the first fluorinated polymer is greater than or equal to 50%, it is beneficial to improve the adhesion of the first fluorinated polymer, and the risk of the positive electrode film layer falling off from the positive electrode current collector is lower, which is beneficial to improving the cycle life of the battery cell. When the mass content of element F in the first fluorinated polymer is less than or equal to 65%, it is beneficial to reduce the gelation degree of the positive electrode slurry, which is convenient for the coating of the positive electrode slurry.

[0146] In some embodiments, the binder further includes a second fluoropolymer with a weight-average molecular weight of 800,000 to 1,100,000.

[0147] The weight-average molecular weight of the second fluoropolymer can be 800,000, 850,000, 900,000, 950,000, 1,000,000, 1,050,000, 1,100,000 or any value within the above range.

[0148] Fluoropolymers with higher weight-average molecular weight have better bonding properties, but the higher the weight-average molecular weight, the greater the risk of gelation in the cathode slurry.

[0149] In the above embodiments, the second fluoropolymer has a smaller weight-average molecular weight than the first fluoropolymer. The inclusion of the second fluoropolymer helps to reduce the gelation degree of the positive electrode slurry and facilitates the coating of the positive electrode slurry.

[0150] In some embodiments, the mass ratio of the first fluoropolymer to the second fluoropolymer is 7:3 to 9:1 based on the total mass of the positive electrode film.

[0151] Based on the total mass of the positive electrode film, the mass ratio of the first fluoropolymer to the second fluoropolymer can be 7:3, 8:2, 9:1, or any value within the above range.

[0152] When the mass ratio of the first fluoropolymer to the second fluoropolymer is greater than or equal to 7:3 based on the total mass of the positive electrode film, it is beneficial to improve the adhesion of the binder, reduce the risk of the positive electrode film falling off from the positive electrode current collector, and improve the cycle life of the battery cell. When the mass ratio of the first fluoropolymer to the second fluoropolymer is less than or equal to 9:1 based on the total mass of the positive electrode film, it is beneficial to reduce the gelation degree of the positive electrode slurry and facilitate the coating of the positive electrode slurry.

[0153] 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.

[0154] Based on the total mass of the positive electrode film, 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.

[0155] As an example, when the lithium-containing transition metal oxide includes Fe, the mass content of the lithium-containing transition metal oxide can be calculated based on the mass ratio of Fe to P in the cathode film.

[0156] When the total mass of the positive electrode film is greater than or equal to 0.3%, the lithium transition metal oxide can release more lithium ions, which is beneficial to improving the cycle life of the battery cell. When the total mass of the positive electrode film is less than 4.5%, the oxygen free radicals generated by the delithiation of the lithium transition metal oxide can be reduced, thereby reducing the damage of oxygen free radicals to the chemical bonds in the binder, reducing the risk of positive electrode film peeling off, and thus improving the cycle performance of the battery cell.

[0157] In some embodiments, the mass content of lithium transition metal oxide is 0.3% to 3% based on the total mass of the positive electrode film. This is beneficial for improving the cycle performance of the battery cell while also taking into account the volumetric energy density of the battery cell.

[0158] In some embodiments, the mass content of nickel metal oxide is 0.01% to 3% based on the total mass of the positive electrode film.

[0159] Based on the total mass of the positive electrode film, the mass content of nickel metal oxide can be 0.01%, 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%, 2.8%, 3%, or any value within the above range.

[0160] The mass content of nickel-containing metal oxides can be calculated based on the mass content of Ni element in the positive electrode film.

[0161] When the total mass of the positive electrode film is greater than or equal to 0.01%, it is beneficial to promote the conversion of oxygen free radicals generated by lithium transition metal oxides into oxygen, thereby reducing the damage of chemical bonds of the binder by oxygen free radicals, reducing the risk of positive electrode film detachment, and improving the cycle performance of the battery cell. When the total mass of the positive electrode film is less than or equal to 3%, the lithium phosphate positive electrode active material and lithium transition metal oxide have a more suitable mass content, which is beneficial to improving the cycle life of the battery cell.

[0162] In some embodiments, the ratio of the mass content of lithium transition metal oxide to the mass content of nickel metal oxide is 50:50 to 95:5 based on the total mass of the positive electrode film.

[0163] Based on the total mass of the positive electrode film, the ratio of the mass content of lithium transition metal oxide to the mass content of nickel metal oxide can be 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, 90:10, 95:5 or any value within the above range.

[0164] As an example, the ratio of the mass content of lithium-containing transition metal oxides to the mass content of nickel-containing metal oxides can be calculated based on the mass content of P, Fe, and Ni elements in the cathode film.

[0165] When the ratio of the mass content of lithium transition metal oxides to the mass content of nickel metal oxides is greater than or equal to 50:50 based on the total mass of the positive electrode film, more active lithium ions can be provided to the battery cell, which is beneficial to improving the cycle life of the battery cell. When the ratio of the mass content of lithium transition metal oxides to the mass content of nickel metal oxides is less than or equal to 95:5 based on the total mass of the positive electrode film, it is beneficial to fully catalyze the conversion of oxygen free radicals into oxygen, reduce the damage of oxygen free radicals to the chemical bonds of the binder, reduce the risk of positive electrode film peeling, and improve the cycle performance of the battery cell.

[0166] In some embodiments, based on the total mass of the positive electrode film, the mass ratio of lithium transition metal oxide to nickel metal oxide is 80:20 to 90:10. This is beneficial for further improving the cycle performance of the battery cell.

[0167] In some embodiments, the average longest diameter of the lithium-containing transition metal oxide is 2 μm to 15 μm on a longitudinal section along the thickness direction of the positive electrode sheet.

[0168] The average longest diameter of lithium-containing transition metal oxides can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 13 μm, 15 μm, or a value within the range obtained by any combination of the above two values.

[0169] 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 its outer periphery. The average longest diameter of lithium-containing transition metal oxides can be measured as follows: Take 30 lithium-containing transition metal oxide particles from a longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 particles, and take the average value to obtain the average longest diameter of lithium-containing iron oxides.

[0170] When the average longest diameter of lithium-containing transition metal oxides is greater than or equal to 2 μm, the rate at which oxygen free radicals are generated can be reduced, which helps to reduce the damage of chemical bonds of binders by oxygen free radicals, reduce the risk of cathode film shedding, and thus help to improve the cycle life of battery cells. When the average longest diameter of lithium-containing transition metal oxides is less than or equal to 15 μm, it is beneficial to the extraction of lithium ions from lithium-containing transition metal oxides, which helps to improve the cycle life of battery cells.

[0171] 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 sheet is 4 μm to 12 μm. This is beneficial for further improving the cycle life of the battery cell.

[0172] In some embodiments, the average longest diameter of the nickel-containing metal oxide is 5 μm to 30 μm on a longitudinal section along the thickness direction of the positive electrode sheet.

[0173] 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, or a value within the range obtained by any combination of the above two values.

[0174] 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.

[0175] 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, thus improving the cycle life of battery cells. When the average longest diameter of nickel-containing metal oxides is less than or equal to 30 μm, it is beneficial to catalyze the conversion of oxygen free radicals generated by lithium-containing transition metal oxides into oxygen, reduce the damage of chemical bonds of binders by oxygen free radicals, reduce the risk of positive electrode film peeling, and thus improve the cycle life of battery cells.

[0176] In some embodiments, the average longest diameter of the nickel-containing metal oxide on the longitudinal section along the thickness direction of the positive electrode sheet is 8 μm to 20 μm. This is beneficial for further improving the cycle life of the battery cell.

[0177] 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 provides a suitable size match 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 damage of oxygen free radicals to the chemical bonds of the binder, lowering the risk of cathode film detachment, and thus improving the cycle life of the battery cell.

[0178] 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.

[0179] In some embodiments, 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 2 μm to 15 μm, and the average longest diameter of the nickel-containing metal oxide is 5 μm to 30 μm. The combination of lithium-containing transition metal oxide particles and nickel-containing metal oxide particles of the aforementioned particle sizes is beneficial for increasing the compaction density of the positive electrode sheet and facilitates the release of lithium ions and the catalytic conversion of oxygen free radicals into oxygen, resulting in a battery cell with higher energy density and longer cycle life.

[0180] 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.

[0181] The coating layer can cover part of the substrate surface or the entire substrate surface.

[0182] 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.

[0183] 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.

[0184] 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 provide a greater number of active lithium ions, thereby contributing to further improvements in the cycle performance of the battery cell.

[0185] 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。

[0186] In Li e FeO fIn 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.

[0187] 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.

[0188] 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.

[0189] 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。

[0190] 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.

[0191] 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.

[0192] In some embodiments, at least a portion of the surface of the substrate contains at least one of Al or Mg.

[0193] As an example, Al on at least a portion of the substrate surface is present in the form of aluminum oxide or nitride, and Mg on at least a portion of the substrate surface is present in the form of magnesium oxide or nitride.

[0194] The presence of at least one of Al or Mg on at least part of the substrate surface is beneficial to improving the stability of lithium-containing transition metal oxides and reducing the risk of metal ion dissolution in the substrate. This reduces the risk of dissolved metal ions migrating to the negative electrode and becoming elemental metals, thereby reducing the impact of elemental metals on lithium ion intercalation at the negative electrode and reducing the risk of lithium plating at the negative electrode and the resulting reduction in cycle life.

[0195] In some embodiments, the coating layer includes carbon. The coating layer improves the stability of lithium-containing transition metal oxides, and the inclusion of carbon in the coating layer enhances the conductivity of the lithium-containing transition metal oxides and reduces the risk of metal ion dissolution from the matrix, thereby improving the cycle life of the battery cell.

[0196] In some embodiments, the thickness of the coating layer is 10 nm to 100 nm.

[0197] 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.

[0198] In the above embodiments, the coating layer has a suitable thickness, which is beneficial to improving the stability of lithium-containing transition metal oxides and facilitating the extraction of lithium ions, thereby improving the cycle life of the battery cell.

[0199] In some embodiments, the thickness of the coating layer is 20 nm or 50 nm. This allows the coating layer to have a more suitable thickness, which is beneficial for improving the cycle life of the battery cell.

[0200] 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.

[0201] 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.

[0202] 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.

[0203] The aforementioned nickel-containing metal oxides can promote the conversion of oxygen free radicals generated by lithium-containing iron oxides into oxygen, thereby reducing the damage of oxygen free radicals to the chemical bonds of the binder and reducing the risk of positive electrode film detachment, which is beneficial to improving the cycle life of the battery cell. 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.

[0204] In some embodiments, the nickel-containing metal oxide includes Li2NiO2. This is beneficial for improving the cycle life of the battery cell.

[0205] In some embodiments, nickel-containing metal oxides include Li g NiO h ,0≤g≤2,0 <h≤2。

[0206] In China 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 any of the above values. 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 any of the above values.

[0207] During the formation of a battery cell, nickel-containing metal oxides decompose, resulting in changes in the molar content of lithium and oxygen.

[0208] In some embodiments, nickel-containing metal oxides include NiO. q 0 <q≤2。

[0209] In NiO q In this context, q can be 0.1, 0.2, 0.5, 1, 1.2, 1.5, 1.8, 2, or any value within the above range.

[0210] During the formation of a battery cell, nickel-containing metal oxides decompose, resulting in changes in the molar contents of lithium and oxygen. For example, lithium may be completely released from the nickel-containing metal oxide, decomposing into nickel oxide. In the formed battery cell, the molar contents of lithium and oxygen in the nickel-containing metal oxide will fall within the aforementioned range.

[0211] It should be noted that, in the reverse stage, if Li5FeO4 and Li2NiO2 are not directly detected after disassembling the battery cell, but byproducts of Li5FeO4 (such as iron oxides) and byproducts of Li2NiO2 (such as nickel oxides) are detected, those skilled in the art can determine the presence of Li5FeO4 and Li2NiO2 in the battery cell before formation by the byproducts, and the battery cell is also within the scope of protection of this application.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] Lithium-containing transition metal oxides have high charge capacity, which is beneficial for improving the energy density and cycle life of individual battery cells.

[0218] 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 .

[0219] The single-sided density of the positive electrode film layer 502 can be 0.25 g / 1540.25 mm. 2 0.28g / 1540.25mm 2 0.3g / 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.

[0220] 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.

[0221] 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.

[0222] 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 .

[0223] 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.

[0224] 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 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.

[0225] 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.

[0226] 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.

[0227] In some embodiments, the thickness of the monolayer positive electrode film is 0.06 mm to 0.13 mm, and optionally 0.07 mm to 0.1 mm.

[0228] 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.

[0229] When the thickness of the single-layer positive electrode film 502 is between 0.06 mm and 0.13 mm, the lithium ions in the positive electrode film 502 have a suitable extraction rate, which is beneficial to improving the cycle life of the battery cell. In addition, a larger thickness of the positive electrode film 502 allows for the inclusion of more positive electrode active materials, which is beneficial to improving the energy density of the battery cell.

[0230] In the above embodiments, the positive electrode film layer has a large thickness, and the battery cell has a high energy density.

[0231] Figure 4 is a schematic diagram of a negative electrode sheet according to an embodiment of this application. In some embodiments, for example, as shown in Figure 4, the battery cell further includes a negative electrode sheet 60, which includes a negative current collector 601 and a negative electrode film layer 602 disposed on at least one side surface of the negative current collector 601. The negative electrode film layer 602 includes a negative electrode active material, which includes at least one of natural graphite, artificial graphite, soft carbon, and hard carbon.

[0232] 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.

[0233] In some embodiments, the negative electrode active material includes natural graphite or a mixture of natural and artificial graphite. Graphite-based materials have high stability, which is beneficial for improving the cycle life of individual battery cells.

[0234] In some embodiments, the negative electrode active material comprises a mixture of natural graphite and artificial graphite, wherein the mass ratio of artificial graphite to natural graphite is 5:5 to 9:1 based on the total mass of the negative electrode active material.

[0235] The mass ratio of artificial graphite to natural graphite can be 5:5, 6:4, 7:3, 8:2, 9:1 or any value within the above range.

[0236] With the above combination, the negative electrode active material has a suitable electrochemical active surface area, which is beneficial to reduce lithium ion consumption and improve the cycle life of the battery cell.

[0237] In some embodiments, the thickness of the monolayer negative electrode film is 0.04 mm to 0.1 mm, and optionally 0.05 mm to 0.08 mm.

[0238] The thickness of the single-layer negative electrode film is 0.04mm, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.095mm, 0.1mm or any value within the above range.

[0239] The thickness of the negative electrode film 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.

[0240] When the thickness of a single negative electrode film is 0.04 mm to 0.1 mm, the negative electrode film can accommodate more negative electrode active materials, which is beneficial to increasing the number of lithium ions accommodated in the negative electrode film, and thus improving the energy density of the battery cell.

[0241] In some embodiments, the one-sided density of the negative electrode film 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 .

[0242] The density of the negative electrode film on one side can be 0.12 g / 1540.25 mm. 2 0.13g / 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.

[0243] The unilateral density of the negative electrode film 602 is related to the kinetic performance and energy density of the battery cell. The higher the unilateral density of the negative electrode film 602, 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 unilateral density of the negative electrode film 602, the more conducive it is to lithium ion transport and insertion into the negative electrode, the better the kinetic performance of the battery cell, the lower the risk of lithium plating at the negative electrode, and the longer the cycle life of the battery cell.

[0244] In the above embodiments, the negative electrode film layer has a suitable areal density, and the battery cell has a suitable energy density, cycle life, and kinetic performance.

[0245] 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 .

[0246] 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 3 1.6g / 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.

[0247] 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, resulting in better kinetic performance of the battery cell. Furthermore, the risk of lithium plating at the negative electrode is lower, and the cycle life of the battery cell is longer.

[0248] In the above embodiments, the negative electrode film layer has a suitable compaction density, and the battery cell has a relatively suitable energy density, cycle life, and kinetic performance.

[0249] In some embodiments, the lithium phosphate includes primary particles and secondary particles formed by the aggregation of primary particles, wherein 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.

[0250] 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.

[0251] In the embodiments of this application, secondary particles refer to particles formed by the aggregation of primary particles.

[0252] 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.

[0253] In the above embodiments, the lithium phosphate particles have a suitable size, which facilitates the extraction of lithium ions, helps to maximize the capacity of the battery cell, and thus helps to improve the cycle life of the battery cell.

[0254] In some embodiments, lithium phosphates include those 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.

[0255] In the general formula for lithium phosphate, 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.

[0256] During the charging and discharging process of a single battery cell, the molar content of lithium, oxygen, and other elements in lithium phosphate varies within a certain range.

[0257] In some embodiments, the lithium phosphate includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The aforementioned lithium phosphates exhibit high structural stability, which helps to improve the cycle life of battery cells.

[0258] 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.

[0259] In some embodiments, at least a portion of the surface of the lithium phosphate contains carbon. This helps to improve the conductivity of the lithium phosphate, facilitating the utilization of the battery cell's capacity.

[0260] In some embodiments, the carbon content is 1% to 2% based on the total mass of lithium phosphate.

[0261] 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.

[0262] In the above embodiments, lithium phosphate has good conductivity, which facilitates the utilization of the capacity of the battery cell.

[0263] In some embodiments, the positive electrode film layer satisfies at least one of the following conditions: the volume average particle size of the lithium transition metal oxide is 2 μm to 15 μm; the volume average particle size of the nickel metal oxide is 5 μm to 30 μm; and the volume average particle size of the lithium phosphate is 0.5 μm to 8 μm.

[0264] 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 long cycle life.

[0265] Figure 5 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 5, 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.

[0266] In some embodiments, the end cap assembly 32 includes electrode terminals 322, as shown in FIG5. 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.

[0267] 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.

[0268] [Positive electrode plate]

[0269] 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.).

[0270] 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.

[0271] 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.

[0272] 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.

[0273] [Negative electrode plate]

[0274] 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.).

[0275] 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.

[0276] 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).

[0277] 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.

[0278] 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.

[0279] [Isolation Component]

[0280] 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.

[0281] 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.

[0282] This application provides a battery device, including the battery cell in any of the above embodiments.

[0283] 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.

[0284] 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.

[0285] [Example]

[0286] Example 1

[0287] (1) Preparation of positive electrode sheet

[0288] Lithium iron phosphate (LiFePO4) as the positive electrode active material, Li5FeO4 as the first additive, Li2NiO2 as the second additive, Super P as the positive electrode conductive agent, and a first and second fluoropolymer as the positive electrode binder, were mixed in a mass ratio of 96:2:0.5:0.4:0.9:0.2. N-methylpyrrolidone (NMP) was added as a solvent, 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 current collector coated with the slurry was dried and cold-pressed to obtain the positive electrode sheet. The single-sided thickness of the positive electrode film was 0.075 mm, and the single-sided density was 0.31 g / 1540.25 mm². 2 The compaction density of the positive electrode sheet is 2.7 g / cm³. 3 .

[0289] The first fluoropolymer includes structural unit I and structural unit II, wherein structural unit I is... Structural Unit II is R1 is F.

[0290] The first fluoropolymer has a weight-average molecular weight of 250W, and based on the total mass of the first fluoropolymer, the mass content of structural unit II is 10%; the second fluoropolymer has a weight-average molecular weight of 90W, and the mass ratio of the first fluoropolymer to the second fluoropolymer is 82:18; based on the total mass of the positive electrode film, the mass content of F element in the binder is 0.42%.

[0291] Based on the total mass of the positive electrode film, the mass content of the first additive is 2%, the mass content of the second additive is 0.5%, the average length of the first additive is 5 μm, and the average length of the second additive is 8 μm.

[0292] (2) Preparation of negative electrode sheet

[0293] 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 96.7:0.4:1.1:1.8. 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 for the negative electrode. After drying and cold pressing, the negative electrode sheet was obtained. The volume average particle size (Dv50) of the negative electrode active material was 9.5 μm, and the areal density of the negative electrode film was 0.155 g / 1540.25 mm. 2The thickness of the negative electrode film is 0.063 mm, and the compaction density of the negative electrode film is 1.6 g / cm³. 3 .

[0294] (3) Separating membrane

[0295] The separator is a 5μm PE base film.

[0296] (4) Electrolyte

[0297] 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.

[0298] (5) Assembly of battery cells

[0299] The negative electrode, separator, and positive electrode are wound into an electrode assembly; the electrode assembly is placed in the housing, electrolyte is injected, and after standing and formation processes, a single battery cell is obtained.

[0300] Examples 2-5

[0301] The difference between Examples 2-5 and Example 1 is that the mass content of element F is different.

[0302] Examples 6-8

[0303] The difference between Examples 6-8 and Example 1 is that the mass content of the first additive is different.

[0304] Examples 9-11

[0305] The difference between Examples 9-11 and Example 1 is that the mass content of the second additive is different.

[0306] Examples 12-13

[0307] The difference between Examples 12-13 and Example 1 is that the average value of the longest diameter of the first additive and the second additive is different from the average value of the longest diameter of the additive.

[0308] Comparative Example 1

[0309] 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.

[0310] Comparative Example 2

[0311] 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.

[0312] Comparative Example 3

[0313] The difference between Comparative Example 3 and Example 1 is that the F content in the positive electrode film is too high.

[0314] Table 1. Test results of Examples 1-5 and Comparative Examples 1-3

[0315] Table 2 Test results of Examples 1 and 6-13

[0316] In this embodiment of the application, the cycle life of a battery cell is reflected by the capacity retention rate after 1200 cycles at 45°C. The higher the capacity retention rate, the longer the cycle life of the battery cell.

[0317] In this embodiment, no comparative example based on the total mass of the positive electrode film layer was provided, and the mass content of F element in the binder was less than 0.25%. The reason is that in binders containing F element, if the mass content of F element is too low, the mass content of the binder in the positive electrode slurry will also be too low, making it easy for the positive electrode film layer to detach, and making it difficult to prepare a positive electrode sheet with a mass content of F element less than 0.25%.

[0318] As shown in Example 1 and Comparative Examples 1-2, adding the first additive is beneficial to improving the cycle life of the battery cell, and adding the first additive and the second additive helps to further improve the cycle life of the battery cell.

[0319] In conjunction with Examples 1-5 and Comparative Example 3, when the mass content of F element in the binder is 0.25% to 0.75% based on the total mass of the positive electrode film, the battery cell has a longer cycle life; furthermore, when the mass content of F element in the binder is 0.3% to 0.65%, it is beneficial to further improve the cycle life of the battery cell.

[0320] As shown in Examples 1-5, different F element mass contents in the binder can be achieved by adjusting the mass ratio of the first fluoropolymer and the second fluoropolymer, and the mass ratio of structural unit I and structural unit II in the first fluoropolymer. When the mass content of the structural unit shown in Formula II is 0.5% to 15% based on the total mass of the first fluoropolymer, the battery cell exhibits a longer cycle life; when the mass content of F element in the first fluoropolymer is 50% to 65%, the battery cell exhibits a longer cycle life; and when the mass ratio of the first fluoropolymer to the second fluoropolymer is 7:3 to 9:1 based on the total mass of the positive electrode film, the battery cell exhibits a longer cycle life.

[0321] As shown in Examples 6-8, when the mass content of lithium transition metal oxide is between 0.3% and 4.5%, the battery cell exhibits a longer cycle life. Furthermore, when the mass content of lithium transition metal oxide is between 0.3% and 3%, the battery cell exhibits both a longer cycle life and a higher volumetric energy density. This is because, although lithium transition metal oxide can replenish lithium ions, its delithiation is irreversible. Therefore, with an increase in the lithium transition metal oxide content, the discharge capacity and volumetric energy density of the battery cell are slightly lower.

[0322] As shown in Examples 9-11, the mass content of nickel metal oxide is 0.01% to 3%, and the battery cell has a longer cycle life. As shown in Examples 10 and 11, increasing the content of lithium transition metal oxide is more beneficial to improving the cycle life of the battery cell than increasing the content of nickel metal oxide.

[0323] As shown in Examples 1 and 12-13, the average longest diameter of the lithium-containing transition metal oxide is 2 μm to 15 μm, and the average longest diameter of the nickel-containing metal oxide is 5 μm to 30 μm, which allows the battery cell to have good cycle performance. Furthermore, the average longest diameter of the lithium-containing transition metal oxide is 4 μm to 12 μm, and the average longest diameter of the nickel-containing metal oxide is 8 μm to 20 μm, which also allows the battery cell to have good cycle performance.

[0324] 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.

[0325] 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.

[0326] 1. Cycle life test method

[0327] At 25℃, the battery cell was charged at a constant current rate of 0.33C to 3.65V, then charged at a constant voltage rate until the current was less than or equal to 0.05C. After resting for 5 minutes, it was discharged at a constant current rate of 1C to 2.5V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is recorded as the discharge capacity of the battery cell in the first cycle. The battery cell was subjected to 1200 charge-discharge cycles using the above method, and the discharge capacity of each cycle was recorded.

[0328] The capacity retention rate of a single battery cell after 1200 cycles at 25℃ and 0.33C / 1C = discharge capacity of the 1200th cycle / discharge capacity of the 1st cycle × 100%.

[0329] 2. Testing of specific components in the positive electrode film.

[0330] Test of F element in the positive electrode film:

[0331] The positive electrode film layer of the positive electrode sheet is scraped off, ground, and the powder is passed through a 300-400 mesh sieve to form a smooth sample with a diameter of 3 cm and a thickness of >5 mm. The prepared sample is then added to an Epsilon 4ED-XRF (energy-dispersive X-ray fluorescence) spectrometer to analyze the intensity of the fluorine element and compare it with the intensity curve of a standard sample. This allows for the determination of the fluorine element content in the positive electrode film layer. The measurement error is approximately 0.04% to 0.25%.

[0332] Testing of other elements in the positive electrode film:

[0333] The positive electrode film layer of the positive electrode sheet can be scraped off, and the scraped material is added to aqua regia for digestion under mechanical stirring for 30 minutes. The digested solution is then added to an ICAP7400 spectrometer for elemental analysis. For example, the contents of Ni, Fe, and P 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, it can be determined whether the positive electrode film layer before formation contains Li₅FeO₄ and its mass content.

[0334] 3. Test of the average value of the longest diameter

[0335] 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 additive, and the lithium iron phosphate material is determined by scanning electron microscopy (SEM) testing of the longitudinal section of the positive electrode film.

[0336] 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 additive refers to the longest straight line that passes through the center point of the additive and extends to the outer periphery of the particle.

[0337] 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 additive particles in the longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 additive particles, and take their average value.

[0338] 4. Test method for coating thickness

[0339] 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.

[0340] Elemental mapping tests using SEM can detect elements on the surface of the core, such as Al or Mg.

[0341] 5. Test methods for areal density and compacted density

[0342] The positive and negative electrode sheets are removed from the 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 compacted density of the electrode sheet PD = electrode surface density / (electrode thickness - current collector thickness).

[0343] 6. Test of volume average particle size

[0344] The 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 (first metal oxide, second metal oxide, or positive electrode active material). 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.

[0345] 7. Test of weight-average molecular weight

[0346] The first and second fluorinated compounds used in the examples were dissolved in polar solvents such as NMP, and the weight-average molecular weight of the polymers was determined by gel permeation chromatography (GPC).

Claims

1. A battery cell, characterized in that, include: A positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer disposed on at least one side surface of the positive current collector, the positive electrode film layer comprising a positive electrode active material, a first additive, a second additive and a binder; The positive electrode active material includes lithium phosphate, the first additive includes lithium transition metal oxide, and the additive includes nickel metal oxide. The binder includes element F, and the mass content of element F in the binder is 0.25% to 0.75% based on the total mass of the positive electrode film.

2. The battery cell according to claim 1, characterized in that, Based on the total mass of the positive electrode film, the F element content in the binder is 0.3% to 0.65% by mass.

3. The battery cell according to claim 1 or 2, characterized in that, The binder comprises a first fluoropolymer with a weight-average molecular weight of 1.8 million to 4 million.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The first fluoropolymer is a polymer containing structural units as shown in Formula I and Formula II, wherein R1 includes one or more of fluorine, chlorine, and trifluoromethyl.

5. The battery cell according to claim 4, characterized in that, Based on the total mass of the first fluoropolymer, the mass content of the structural unit shown in Formula II is 0.5% to 15%.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The F element has a mass content of 50% to 65% in the first fluoropolymer.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The binder also includes a second fluoropolymer with a weight-average molecular weight of 800,000 to 1,100,000.

8. The battery cell according to claim 7, characterized in that, Based on the total mass of the positive electrode film, the mass ratio of the first fluoropolymer to the second fluoropolymer is 7:3 to 9:

1.

9. The battery cell according to any one of claims 1 to 8, 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 0.3% to 3%.

10. The battery cell according to any one of claims 1 to 9, characterized in that, Based on the total mass of the positive electrode film, the mass content of the nickel-containing metal oxide is from 0.01% to 3%.

11. The battery cell according to any one of claims 1 to 10, characterized in that, Based on the total mass of the positive electrode film, the mass content of the lithium-containing transition metal oxide to the mass content of the nickel-containing metal oxide is 50:50 to 95:5, and can be selected as 80:20 to 90:

10.

12. The battery cell according to any one of claims 1 to 11, 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 2 μm to 15 μm, and optionally 4 μm to 12 μm.

13. The battery cell according to any one of claims 1 to 12, 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 30 μm, and can be selected as 8 μm to 20 μm.

14. The battery cell according to any one of claims 1 to 13, 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.

15. The battery cell according to any one of claims 1 to 14, 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.

16. The battery cell according to any one of claims 1 to 15, 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.

17. The battery cell according to any one of claims 1 to 15, 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.

18. The battery cell according to any one of claims 1 to 15, 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。 19. The battery cell according to any one of claims 1 to 15, 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。 20. The battery cell according to any one of claims 16 to 19, characterized in that, At least a portion of the surface of the substrate contains at least one of Al or Mg.

21. The battery cell according to any one of claims 16 to 20, characterized in that, The coating layer includes carbon.

22. The battery cell according to any one of claims 16 to 21, characterized in that, The thickness of the coating layer is 10 nm to 200 nm.

23. The battery cell according to any one of claims 1 to 22, 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.

24. The battery cell according to any one of claims 1 to 22, characterized in that, The nickel-containing metal oxide includes Li2NiO2.

25. The battery cell according to any one of claims 1 to 22, characterized in that, The nickel-containing metal oxide includes Li g NiO h ,0≤g≤2,0 <h≤2。 26. The battery cell according to any one of claims 1 to 22, characterized in that, The nickel-containing metal oxide includes NiO. q 0 <q≤2。 27. The battery cell according to any one of claims 1 to 26, 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.

28. The battery cell according to any one of claims 1 to 27, 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.

29. The battery cell according to any one of claims 1 to 28, 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 .

30. The battery cell according to any one of claims 1 to 29, 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 .

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 battery cell further includes a negative electrode sheet, which includes a negative current collector and a negative electrode film layer disposed on at least one side surface of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes at least one of natural graphite, artificial graphite, soft carbon, and hard carbon.

33. The battery cell according to claim 32, characterized in that, The negative electrode active material includes natural graphite or a mixture of natural graphite and artificial graphite.

34. The battery cell according to claim 33, characterized in that, The negative electrode active material comprises a mixture of natural graphite and artificial graphite, and the mass ratio of artificial graphite to natural graphite is 5:5 to 9:1 based on the total mass of the negative electrode active material.

35. The battery cell according to any one of claims 32 to 34, characterized in that, The thickness of the single-layer negative electrode film is 0.04 mm to 0.1 mm, and can be selected as 0.05 mm to 0.08 mm.

36. The battery cell according to any one of claims 32 to 35, 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 .

37. The battery cell according to any one of claims 32 to 36, 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 .

38. The battery cell according to any one of claims 1 to 37, characterized in that, The lithium phosphate comprises 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.

39. The battery cell according to any one of claims 1 to 38, characterized in that, The lithium-containing phosphate includes those 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.

40. The battery cell according to any one of claims 1 to 39, characterized in that, The lithium-containing phosphate includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

41. The battery cell according to any one of claims 1 to 40, characterized in that, At least a portion of the surface of the lithium phosphate contains carbon.

42. The battery cell according to claim 41, characterized in that, Based on the total mass of the positive electrode active material, the mass content of the carbon element on the lithium phosphate surface is 1% to 2%.

43. The battery cell according to any one of claims 1 to 42, 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 2 μm to 15 μm; The volume average particle size of the nickel-containing metal oxide is 5 μm to 30 μm; The volume average particle size of the lithium phosphate is 0.5 μm to 8 μm.

44. A battery device, characterized in that, include: Multiple battery cells according to any one of claims 1-43.

45. An electrical appliance, characterized in that, include: Multiple battery cells according to any one of claims 1-43, or battery devices according to claim 44, wherein the battery cells or battery devices are used to store or provide electrical energy.

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