Battery cell, battery apparatus, and electric device

Abstract

A battery cell, a battery apparatus, and an electric device, relating to the technical field of batteries. A battery cell, comprising: a positive electrode film layer, the positive electrode film layer comprising a positive electrode active material, a first additive and a second additive, the positive electrode active material comprising a lithium-containing phosphate, the first additive comprising a lithium-containing transition metal oxide, and the second additive comprising a nickel-containing metal oxide; a negative electrode film layer, the negative electrode film layer comprising a negative electrode active material, and the negative electrode active material comprising graphite; at least part of a surface of the graphite contains a first coating layer, and in an accumulation distribution curve of R values acquired for the negative electrode active material in an area scanning mode of a confocal laser micro-Raman spectrometer, an R value with an accumulation distribution of 50% is 0.05 to 0.15; or at least part of the surface of the graphite contains at least one element of Al, Ti, Zn, Zr, B, Si, and Ni, which helps to improve battery cell cycle life.

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 side of the positive current collector, the positive electrode film layer including a positive electrode active material, a first additive, and a second additive, the positive electrode active material including a lithium phosphate, the first additive including a lithium transition metal oxide, and the second additive including a nickel metal oxide; and 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 of the negative current collector, the negative electrode film layer including a negative electrode active material, the negative electrode active material including graphite; wherein...

[0007] At least a portion of the surface of the graphite contains a first coating layer, and in the cumulative distribution curve of the R-value obtained by laser microscopy confocal Raman spectroscopy in instrument scanning mode, the cumulative distribution of the R-value is 0.05 to 0.15 for 50% of the material, where R = 1. D / I G I D I represents the intensity of the D peak of the negative electrode active material. G This indicates the intensity of the G peak of the negative electrode active material; or,

[0008] The graphite has at least a portion of its surface containing at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni.

[0009] 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 first additive can provide active lithium ions to improve the cycle life of the battery cell, and the second additive can promote the conversion of oxygen free radicals generated by the delithiation of the first additive into oxygen, thereby reducing the risk of reduced cycle life of the battery cell due to side reactions of oxygen free radicals. The negative electrode active material in the negative electrode film layer includes graphite, at least a portion of the surface of the graphite contains a first coating layer, and the cumulative distribution of the negative electrode active material is 50% with an R value of 0.05 to 0.15. Thus, the negative electrode active material has lower surface defects, which reduces side reactions at the negative electrode. This reduces the risk of lithium-ion consumption and reduced cycle life due to the continuous formation of the SEI film caused by the dissolution of transition metals from nickel-containing metal oxides damaging the SEI film at the negative electrode. At least a portion of the graphite surface contains at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni. This facilitates the formation of an SEI film with inorganic components, improving its stability and further reducing the risk of lithium-ion consumption and reduced cycle life due to the continuous formation of the SEI film caused by the dissolution of transition metals from nickel-containing metal oxides damaging the SEI film at the negative electrode. Therefore, the battery cells of this embodiment have a longer cycle life.

[0010] In some embodiments, the first coating layer comprises at least one of amorphous carbon, graphene, natural graphite, and carbon nanotubes; optionally, the first coating layer comprises amorphous carbon. These materials are beneficial for reducing the surface defects of the negative electrode active material, reducing side reactions at the negative electrode and lithium ion consumption, thereby resulting in a longer cycle life for the battery cell.

[0011] In some embodiments, the thickness of the first coating layer is 20 nm to 70 nm. When the thickness of the first coating layer is greater than or equal to 20 nm, it is beneficial to reduce the risk of graphite exposure due to the first coating layer being too thin, and the negative electrode active material has lower surface defects, which is beneficial to improving the cycle life of the battery cell. When the thickness of the first coating layer is less than or equal to 70 nm, it is beneficial to reduce the risk of increased preparation difficulty and uneven coating caused by the first coating layer being too thick, and the negative electrode active material has lower surface defects, which is beneficial to improving the cycle life of the battery cell.

[0012] In some embodiments, at least a portion of the surface of the graphite contains at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni, and the cumulative R-value distribution curve of the negative electrode active material obtained in laser microscopy confocal Raman spectroscopy surface scanning mode shows an R-value of 0.28 to 0.31 for a cumulative distribution of 50%. Thus, while improving the stability of the SEI film, the negative electrode active material exhibits a low degree of surface defects, which is beneficial for further improving the cycle life of the battery cell.

[0013] In some embodiments, the volume average particle size Dv50 of the graphite is 9 μm to 11.5 μm. This provides the graphite with a suitable particle size, which is beneficial for reducing surface defects in the negative electrode active material and resulting in a longer cycle life for the battery cell.

[0014] In some embodiments, the volume average particle size Dv50 of the negative electrode active material is 9 μm to 12 μm. This results in a suitable particle size for the negative electrode active material, which helps reduce side reactions at the negative electrode, decreases lithium-ion consumption, and gives the battery cell a longer cycle life.

[0015] In some embodiments, the graphitization degree of the negative electrode active material is 93% to 97%, optionally 93% to 95%. This results in a higher graphitization degree in the negative electrode active material, which helps reduce surface defects and leads to a longer cycle life for the battery cell.

[0016] In some embodiments, the specific surface area of ​​the negative electrode active material is 1.0 m². 2 / g to 3.0m 2 / g, can be selected as 1.1m 2 / g to 1.5m 2 / g. In this way, the negative electrode active material has lower surface defects and a lower degree of side reactions between the negative electrode active material and the electrolyte, which is beneficial to improving the cycle life of the battery cell.

[0017] In some embodiments, the specific capacity of the negative electrode active material is between 345 mAh / g and 355 mAh / g. This provides a suitable specific capacity for the negative electrode active material, which helps reduce the expansion of both the negative electrode active material and the negative electrode sheet, thereby mitigating the adverse effects of negative electrode sheet expansion on cycle life.

[0018] In some embodiments, the tap density of the negative electrode active material at a frequency of 250±15 times / minute is 1.0 g / cm³. 3 Up to 1.3 g / cm 3 In this way, the negative electrode active material has good structural stability during charge-discharge cycles, which helps to reduce side reactions at the negative electrode and gives the battery cell a longer cycle life.

[0019] 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.

[0020] When the total mass of lithium-containing transition metal oxides is greater than or equal to 0.3% based on the positive electrode film, the lithium-containing transition metal oxides can release more lithium ions, which is beneficial to improving the cycle life of the battery cell. When the total mass of lithium-containing transition metal oxides is less than 4.5% based on the positive electrode film, the oxygen free radicals generated by the delithiation of lithium-containing transition metal oxides can be reduced, thereby reducing the adverse effect of oxygen free radicals on cycle life.

[0021] In some embodiments, the mass content of the lithium-containing transition metal oxide is 0.5% to 2% based on the total mass of the positive electrode film. This is beneficial for further improving the cycle life of the battery cell.

[0022] In some embodiments, the mass content of the nickel-containing metal oxide is from 0.03% to 2.5% based on the total mass of the positive electrode film.

[0023] When the mass content of nickel-containing metal oxides is greater than or equal to 0.03% based on the total mass of the positive electrode film, it is beneficial to promote the conversion of oxygen free radicals generated by lithium-containing transition metal oxides into oxygen, thereby reducing the adverse effects of oxygen free radicals on the cycle life of the battery cell. When the mass content of nickel-containing metal oxides is less than or equal to 2.5% based on the total mass of the positive electrode film, it is beneficial to reduce the content of dissolved transition metals, reduce the damage of dissolved transition metals to the SEI film, and thus help improve the cycle life of the battery cell.

[0024] In some embodiments, the mass content of the nickel-containing metal oxide is 0.05% to 1.5% based on the total mass of the positive electrode film. This is beneficial for further improving the cycle life of the battery cell.

[0025] In some embodiments, the lithium-containing transition metal oxide includes Fe element, and the ratio of the mass of Fe element in the lithium-containing transition metal oxide to the mass of Ni element in the nickel-containing metal oxide is 0.5 to 10 based on the total mass of the cathode film.

[0026] When the mass ratio of Fe in lithium-containing transition metal oxides to Ni in nickel-containing metal oxides is greater than or equal to 0.5, more active lithium ions can be provided to the battery cells, which is beneficial to improving the cycle life of the battery cells. When the mass ratio of Fe in lithium-containing transition metal oxides to Ni in nickel-containing metal oxides is less than or equal to 10, it is beneficial to fully catalyze the conversion of oxygen free radicals into oxygen, thereby reducing the adverse effects of oxygen free radicals on cycle life.

[0027] In some embodiments, the mass ratio of Fe in the lithium-containing transition metal oxide to Ni in the nickel-containing metal oxide is 1.5 to 5. This is beneficial for further improving the cycle life of the battery cell.

[0028] In some embodiments, the average longest diameter of the lithium-containing transition metal oxide is 3 μm to 20 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 3 μm, the rate at which oxygen free radicals are generated by lithium-containing transition metal oxides can be reduced, which is beneficial to reducing the adverse effects of oxygen free radicals on the cycle life of battery cells. When the average longest diameter of lithium-containing transition metal oxides is less than or equal to 20 μm, it is beneficial to the extraction of lithium ions from lithium-containing transition metal oxides, which is beneficial to improving the cycle life of battery cells.

[0030] In some embodiments, the average longest diameter of the lithium-containing transition metal oxide is 5 μm to 20 μm on a longitudinal section along the thickness direction of the positive electrode sheet. This results in a longer cycle life for 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, and thus improve 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 degree of side reactions of oxygen free radicals in battery cells, and reduce the adverse effects on the cycle life of battery cells.

[0033] In some embodiments, on the longitudinal section along the thickness direction of the positive electrode sheet, the average value of the longest diameter of the nickel-containing metal oxide is 10 μm to 30 μm. In this way, the battery cell has a long cycle life.

[0034] In some embodiments, the average value of the longest diameter of the nickel-containing metal oxide is less than the average value of the longest diameter of the lithium-containing transition metal oxide. In this way, the nickel-containing metal oxide and the lithium-containing transition metal oxide have a suitable size combination, which is conducive to the nickel-containing metal oxide catalyzing the oxygen free radicals generated by the lithium-containing transition metal oxide to be converted into oxygen, reducing the degree of side reactions of the oxygen free radicals in the battery cell, and improving the cycle life of the battery cell.

[0035] In some embodiments, the average value of the longest diameter of the nickel-containing metal oxide is greater than or equal to the average value of the longest diameter of the lithium-containing transition metal oxide. In this way, the nickel-containing metal oxide and the lithium-containing transition metal oxide have suitable sizes, which is convenient for the preparation of the nickel-containing metal oxide and the lithium-containing transition metal oxide.

[0036] In some embodiments, the lithium-containing transition metal oxide includes a matrix and a second coating layer located on at least a part of the surface of the matrix, and the matrix includes 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 lithium element in the matrix of the lithium-containing transition metal oxide has a relatively high molar content, and more lithium ions can be extracted to provide more active lithium ions to the battery cell, which is beneficial to improving the cycle life of the battery cell; in addition, the setting of the second coating layer is beneficial to improving the stability of the lithium-containing transition metal oxide. <00002*69>

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

[0039] In some embodiments, the lithium-containing transition metal oxide includes a matrix and a second coating layer located on at least a part of the surface of the matrix, and the matrix includes Li e FeO<* f , 0 ≤ e ≤ 5, 0 < f ≤ 4. During the formation process of the battery cell, the matrix decomposes, generating oxygen free radicals while generating lithium ions, and the molar contents of the Li element and the O element change.

[0040] It should be noted that there seems to be a formatting issue in the original text where the formula in ID=9 and ID=22 seems incomplete. I've translated it as accurately as possible based on the provided content. Also, in ID=25, it seems there might be a typo in the original text as <* f is not a standard tag format, but I've left it as is for translation.In some embodiments, the lithium-containing transition metal oxide includes a matrix and a second coating layer located on at least a part of the surface of the matrix, and the matrix includes Li m FeO n , where 0≤m≤1 and 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 a part of the surface of the matrix contains at least one of Al or Mg. In this way, it is beneficial to improve the stability of the lithium-containing transition metal oxide, reduce the side reaction between the lithium-containing transition metal oxide and the electrolyte, and thus is beneficial to improve the cycle life of the battery cell.

[0042] In some embodiments, the second coating layer includes carbon element. The setting of the second coating layer is beneficial to improve the stability of the lithium-containing transition metal oxide, and the inclusion of carbon element in the second coating layer is beneficial to improve the conductivity of the lithium-containing transition metal oxide, and further is beneficial to the performance of the capacity of the battery cell and to improve the cycle life of the battery cell.

[0043] In some embodiments, the thickness of the second coating layer is 10 nm to 100 nm. In this way, the second coating layer has a suitable thickness, which is beneficial to improve the stability of the lithium-containing transition metal oxide and facilitates the extraction of lithium ions, and the battery cell has a long cycle life.

[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, and thus can reduce the adverse effect of oxygen free radicals on 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 improve 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.

[0046] In some embodiments, the nickel-containing metal oxide includes Li g NiO h , where 0≤g≤2 and 0<h≤2. During the formation process of the battery cell, the nickel-containing metal oxide decomposes, and the molar contents of its lithium element and oxygen element will change to a certain extent.

[0047] In some embodiments, the nickel-containing metal oxide includes NiOq , 0 < q ≤ 2. During the formation process of the battery cell, the nickel-containing metal oxide decomposes, and the molar content of lithium element and the molar content of oxygen element will change to a certain extent.

[0048] In some embodiments, the de-lithiation potential of the lithium-containing transition metal oxide is greater than that of the lithium-containing phosphate, and the de-lithiation potential of the nickel-containing metal oxide is greater than that of the lithium-containing phosphate. Thus, during the formation process, the lithium-containing transition metal oxide and the nickel-containing metal oxide can release lithium ions to provide more active lithium ions to the battery cell.

[0049] In some embodiments, in the voltage range of 2V to 4.3V, the charging specific capacity of the lithium-containing transition metal oxide is 200 mAh / g to 1000 mAh / g, and optionally 600 mAh / g to 700 mAh / g.

[0050] The oxide of the lithium-containing transition metal has a high charging specific capacity, which is beneficial to improving the energy density and cycle life of the battery cell.

[0051] In some embodiments, the single-sided areal density of the negative electrode film layer is 0.12 g / 1540.25 mm 2 to 0.2 g / 1540.25 mm 2 , and optionally 0.13 g / 1540.25 mm 2 to 0.19 g / 1540.25 mm 2 .

[0052] In the above embodiments, the negative electrode film layer has a suitable areal density, and the battery cell has relatively suitable energy density and kinetic performance.

[0053] In some embodiments, the compaction density of the negative electrode film layer at 0% SOC is 1.3 g / cm 3 to 1.8 g / cm 3 , and optionally 1.35 g / cm 3 to 1.65 g / cm 3 .

[0054] In the above embodiments, the negative electrode film layer has a suitable compaction density, and the battery cell has relatively suitable energy density, kinetic performance and cycle life.

[0055] In some embodiments, the porosity of the negative electrode plate is 10% - 50%, and optionally 25% - 35%.

[0056] In the above embodiments, the negative electrode sheet has a suitable porosity, which is beneficial for electrolyte wetting, reducing polarization in the battery cell, reducing the degree of side reactions at the negative electrode, reducing lithium ion consumption, and improving the cycle life of the battery cell.

[0057] 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 .

[0058] 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.

[0059] 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 .

[0060] 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.

[0061] In some embodiments, the lithium phosphate comprises primary particles and secondary particles formed by the aggregation of the 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.

[0062] In this way, the lithium phosphate particles have a suitable size, which facilitates the extraction of lithium ions and helps to maximize the capacity of the battery cell.

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

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

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

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

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

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

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

[0070] In a second aspect, a battery device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof.

[0071] 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

[0072] 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.

[0073] Figure 1 is a schematic diagram of a vehicle according to an embodiment of this application;

[0074] Figure 2 is a schematic diagram of the structure of a battery device according to an embodiment of this application;

[0075] Figure 3 is a schematic diagram of the structure of a battery cell according to an embodiment of this application;

[0076] Figure 4 is a schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0077] Figure 5 is a schematic diagram of the negative electrode sheet according to an embodiment of this application.

[0078] Reference numerals: 1: Vehicle; 10: Battery unit; 30: Controller; 40: Motor; 11: Housing; 111: First housing section; 112: Second housing section; 3: Battery cell; 31: Housing; 32: End cap assembly; 33: Electrode assembly; 34: Connecting member; 331: Tab; 322: Electrode terminal; 50: Positive electrode sheet; 501: Positive current collector; 502: Positive electrode film; 60: Negative electrode sheet; 601: Negative current collector; 602: Negative electrode film.

[0079] The accompanying drawings are not drawn to scale. Detailed Implementation

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

[0081] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

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

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

[0084] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

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

[0086] This application aims to provide a battery cell with a long cycle life. 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 active material, a first additive, and a second additive; the positive active material includes a lithium phosphate; the first additive includes a lithium transition metal oxide; and the second additive includes a nickel metal oxide. It also includes a negative electrode sheet, which includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector; the negative electrode film layer includes a negative active material, which includes graphite.

[0087] At least a portion of the graphite surface contains a first coating layer, and in the cumulative distribution curve of the R-value obtained by laser microscopy confocal Raman spectroscopy in instrument scanning mode, the R-value for a cumulative distribution of 50% is 0.05 to 0.15, where R = I D / I G I D I represents the intensity of the D peak of the negative electrode active material. G This indicates the intensity of the G peak of the negative electrode active material; or,

[0088] At least a portion of the surface of graphite contains at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni.

[0089] Lithium-containing phosphates are widely used in the positive electrode active materials of battery cells due to their high structural stability. To further improve the initial efficiency and cycle life of battery cells, lithium-containing transition metal oxides as a first additive and nickel-containing metal oxides as a second additive are added to the positive electrode. This replenishes active lithium ions while reducing the reactive oxygen species generated by the lithium-containing transition metal oxides through the nickel-containing metal oxides, thereby reducing the side reactions between reactive oxygen species and the electrolyte and minimizing their impact on the cycle life of the battery cell. However, the addition of nickel-containing metal oxides increases the risk of transition metal dissolution within the battery cell. The dissolved transition metals can damage the SEI film at the negative electrode and the structure of graphite in the negative electrode, leading to the continuous formation of new SEI films at the negative electrode. This increases the consumption of active lithium and is detrimental to improving the cycle life of the battery cell.

[0090] This application further configures the graphite structure or optimizes the graphite composition, such that at least a portion of the graphite surface contains a first coating layer and the cumulative distribution of the negative electrode active material is 50%, with an R value set to 0.05 to 0.1. This results in lower surface defects in the negative electrode active material, reducing the risk of side reactions caused by direct contact between transition metals dissolved from nickel-containing metal oxides and defects on the surface of the negative electrode active material. This reduces the risk of lithium-ion consumption due to side reactions, thereby helping to reduce the risk of reduced cycle life of the battery cell. Alternatively, by configuring at least a portion of the graphite surface to contain at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni, it is beneficial to generate an inorganic-rich SEI film, increasing the content of inorganic components in the SEI film. Thus, the inorganic-rich SEI film has higher stability and density due to its high mechanical strength and more compact structure, which can reduce the degree of damage to the SEI film caused by transition metal dissolution. This further reduces the risk of increased lithium-ion consumption caused by the continuous formation of SEI film after SEI film damage, thus helping to improve the cycle life of the battery cell.

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

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

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

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

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

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

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

[0098] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

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

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

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

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

[0103] [Battery cell]

[0104] One embodiment of this application provides a battery cell, which includes a positive electrode and a negative electrode.

[0105] Figure 3 is a schematic diagram of the structure of a battery cell according to an embodiment of this application. As an example, referring to Figure 3, 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.

[0106] Figure 4 is a schematic diagram of a positive electrode sheet in one embodiment of this application. For example, as shown in Figure 4, the positive electrode sheet 50 includes a positive current collector 501 and a positive electrode film layer 502 disposed on at least one side of the positive current collector 501.

[0107] The positive electrode current collector 501 has two side surfaces along its own thickness direction (e.g., the z-direction in Figure 4). 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. As an example, as shown in Figure 4, the positive electrode film layer 502 is disposed on both side surfaces of the positive electrode current collector 501.

[0108] The positive electrode film 502 includes a positive electrode active material, a first additive, and a second additive. 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.

[0109] Lithium-containing phosphates are used as positive electrode active materials, allowing lithium ions to be reversibly extracted and inserted.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] Nickel-containing metal oxides include nickel and oxygen. In some embodiments, nickel-containing metal oxides may also include lithium.

[0116] Lithium-containing transition metal oxides can decompose to generate lithium ions within a certain voltage range, while also producing oxygen free radicals (also known as reactive oxygen species). These oxygen free radicals react with the electrolyte to produce carbonate fragments. These fragments diffuse to the negative electrode and participate in the formation of the SEI film, leading to an increase in the porous organic components of the SEI film. This increased porous organic component in the SEI film is detrimental to its stability. Nickel-containing metal oxides can promote or catalyze the conversion of oxygen free radicals into oxygen, thereby reducing the generation of carbonate fragments. This reduces the porous organic components in the SEI film at the negative electrode, resulting in a more stable SEI film. With a more stable SEI film, the risk of continuously consuming lithium ions to repair or generate the SEI film is reduced, which is beneficial for improving the cycle life of individual battery cells.

[0117] Figure 5 is a schematic diagram of a negative electrode sheet in one embodiment of this application. For example, as shown in Figure 5, the negative electrode sheet 60 includes a negative current collector 601 and a negative electrode film layer 602 disposed on at least one side of the negative current collector 601.

[0118] The negative electrode current collector 601 has two side surfaces along its own thickness direction (e.g., the z-direction in FIG. 5). 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. As an example, as shown in FIG. 5, the negative electrode film layer 602 is disposed on both side surfaces of the negative electrode current collector 601.

[0119] In some embodiments, the negative electrode active material comprises graphite, at least a portion of the surface of the graphite having a first coating layer, and in the cumulative distribution curve of the R-value obtained by laser microscopy confocal Raman spectroscopy in surface scanning mode, the R-value for a cumulative distribution of 50% is 0.05 to 0.25, where R = 1. D / I G I D I represents the intensity of the D peak of the negative electrode active material. G This indicates the intensity of the G peak of the negative electrode active material.

[0120] The R-value can be controlled by adjusting the material and thickness of the first coating layer; it can also be controlled by adjusting the particle size, specific surface area, graphitization degree, and particle size distribution of the negative electrode active material. Furthermore, negative electrode active materials with different specific capacities and tap densities may also have different R-values.

[0121] The material in the first coating layer can be a carbon material, such as amorphous carbon, graphene, etc.

[0122] In this application, the R-value of the negative electrode active material can be obtained using a laser microconfocal Raman spectrometer in surface scanning mode. As an example, a laser microconfocal Raman spectrometer (e.g., a high-precision Renishaw laser microconfocal Raman spectrometer) can be used, selecting a laser wavelength of 532 nm. An appropriate amount of sample is taken and its surface is scanned in all directions. The scanning area is 100 μm × 100 μm, the step size is 2 μm, and the total number of scanning points is multiple (e.g., 100 points). This yields the R-values ​​at different sites and the cumulative distribution curve of the R-values ​​over the surface scanning area. The negative electrode active material in this application can be either a prepared negative electrode active material or a negative electrode active material obtained by scraping powder from a negative electrode sheet.

[0123] When at least a portion of the graphite surface contains a first coating layer, the cumulative distribution curve of the R value obtained by the negative electrode active material in the laser microscopy confocal Raman spectroscopy instrument scanning mode, the R value with a cumulative distribution of 50% can be 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15 or any value range between the two.

[0124] The R-value of a negative electrode active material refers to the ratio of the peak heights of the D-band and G-band peaks in its Raman spectrum. The D-band peak is located at 1350 ± 50 cm⁻¹. -1 The position of peak G is 1585±50cm. -1 The R-value characterizes the degree of defect and disorder in the negative electrode active material. A larger R-value indicates a greater degree of surface defect and higher surface disorder, while a smaller R-value indicates fewer surface defects. Surface defects in the negative electrode active material can serve as deposition sites for transition metals dissolved from nickel-containing metal oxides and as active sites for side reactions. By controlling these surface defects, the risk of side reactions at the negative electrode and the risk of damage to the SEI film from dissolved transition metals are reduced, resulting in less lithium ion consumption. This can compensate for the damage to the SEI film at the negative electrode caused by the dissolution of transition metals from nickel-containing metal oxides, leading to continuous repair of the SEI film and subsequent lithium ion consumption. This, in turn, helps reduce lithium ion consumption and improves the cycle performance of the battery cell.

[0125] In the embodiments of this application, by setting at least a portion of the surface of graphite to contain a first coating layer, and the cumulative distribution of the negative electrode active material is 50% with an R value of 0.05 to 0.15, the negative electrode active material has low surface defects, which can reduce side reactions at the negative electrode and compensate for the defects caused by the dissolution of transition metals in nickel-containing metal oxides damaging the SEI film at the negative electrode, resulting in continuous formation of the SEI film at the negative electrode, leading to lithium ion consumption and reduced cycle life of the battery cell. This is beneficial to further improve the cycle life of the battery cell.

[0126] In some embodiments, the negative electrode active material includes graphite, and at least a portion of the surface of the graphite contains at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni.

[0127] By ensuring that at least a portion of the graphite surface contains at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni, it is beneficial to generate an SEI film rich in inorganic components, thereby increasing the content of inorganic components in the SEI film. Compared to SEI films rich in organic components, SEI films rich in inorganic components exhibit higher stability and density due to their high mechanical strength and good density. This reduces the damage to the SEI film caused by the dissolution of transition metals from nickel-containing metal oxides, lowering the risk of SEI film destruction. Furthermore, it reduces the risk of increased lithium-ion consumption due to the continuous formation of SEI films after SEI film destruction, thus improving the cycle life of individual battery cells.

[0128] In some embodiments, at least a portion of the surface of the graphite contains a first coating layer, the first coating layer comprising at least one of amorphous carbon, graphene, natural graphite, and carbon nanotubes.

[0129] The aforementioned materials help reduce the surface defects of the negative electrode active material, reduce side reactions at the negative electrode and the consumption of lithium ions, thereby compensating for the adverse effects of transition metal dissolution on lithium ion consumption and improving the cycle life of the battery cell.

[0130] In some embodiments, the first coating layer comprises amorphous carbon.

[0131] Amorphous carbon refers to carbon materials with a very low degree of graphitization, exhibiting an approximately amorphous morphology (or lacking a fixed shape and periodic structural regularity). The carbon atoms in amorphous carbon structures are not arranged in a regular pattern; therefore, amorphous carbon can be characterized by transmission electron microscopy (TEM). By using focused ion beam (FIB) to cut a thin slice approximately 100 nm thick from the middle of the negative electrode active material particles, and then performing TEM on the slice, it can be observed that the surface region includes a coating layer. The lattice fringes in the coating layer exhibit long-range disorder and short-range order, and the electron diffraction pattern shows a halo-like appearance, indicating that the coating layer contains amorphous carbon.

[0132] The first coating layer includes amorphous carbon, which helps to reduce the specific surface area of ​​the negative electrode active material, reduce surface defects of the negative electrode active material, reduce side reactions at the negative electrode and lithium ion consumption, and give the battery cell a longer cycle life.

[0133] In some embodiments, the thickness of the first coating layer is 20 nm to 70 nm.

[0134] The thickness of the first coating layer can be 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm or any value within the above range.

[0135] When the thickness of the first coating layer is greater than or equal to 20 nm, it helps to reduce the risk of graphite exposure due to the first coating layer being too thin, and the negative electrode active material has lower surface defects, which helps to improve the cycle life of the battery cell. When the thickness of the first coating layer is less than or equal to 70 nm, it helps to reduce the risk of increased preparation difficulty and uneven coating caused by the excessive thickness of the first coating layer, and the negative electrode active material has lower surface defects, which helps to improve the cycle life of the battery cell.

[0136] In some embodiments, at least a portion of the surface of the graphite contains at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni, and the cumulative distribution curve of the R value obtained by the negative electrode active material in the laser microscopy confocal Raman spectroscopy instrument scanning mode shows that the cumulative distribution of 50% of the R value is 0.28 to 0.31.

[0137] When at least a portion of the surface of graphite contains at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni, the value of R can be 0.28, 0.29, 0.3, 0.31, or any value within the range described above.

[0138] In some embodiments, at least a portion of the surface of the graphite contains Al, Ti, Zn, or Zr.

[0139] As an example, Al, Ti, Zn, or Zr exists in the form of inorganic metal oxides on at least a portion of the surface of graphite. For instance, at least a portion of the surface of graphite contains Al2O3 or Ti2O3.

[0140] In some embodiments, the volume average particle size Dv50 of graphite is from 9 μm to 11.5 μm.

[0141] The volume average particle size (Dv50) of a material represents the particle size corresponding to a cumulative volume distribution percentage of 50%, and can be determined using instruments and methods known in the art. For example, it can be conveniently determined using a laser particle size analyzer, referring to GB / T19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0142] The volume average particle size Dv50 of graphite can be 9 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm or any value within the above range.

[0143] Within a certain range, the R-value for the cumulative distribution of the negative electrode active material at 50% is related to the volume average particle size of graphite. The smaller the volume average particle size of graphite, the larger the gaps and surface defects after the graphite powder is stacked, and the larger the R-value for the cumulative distribution of the negative electrode active material at 50%. By setting the volume average particle size Dv50 of graphite to 9μm to 11.5μm, the R-value for the cumulative distribution of the negative electrode active material at 50% is smaller, which is beneficial to reducing the surface defects of the negative electrode active material and resulting in a longer cycle life for the battery cell.

[0144] In some embodiments, the volume average particle size Dv50 of the negative electrode active material is 9 μm to 12 μm.

[0145] The volume average particle size Dv50 of graphite can be 9 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.6 μm, 11.7 μm, 11.8 μm, 11.9 μm, 12 μm or any value within the above range.

[0146] The volume average particle size of the negative electrode active material is the volume average particle size of the negative electrode active material particles. When the graphite surface contains a first coating layer, the volume average particle size of the negative electrode active material is the overall volume average particle size of the graphite and the first coating layer. Since the thickness of the first coating layer is at the nanometer level, the volume average particle size of the negative electrode active material particles is close to that of the graphite.

[0147] The volume average particle size of the negative electrode active material can also reflect the R-value of the cumulative distribution of the negative electrode active material at 50% to some extent. Within a certain range, the smaller the volume average particle size of the negative electrode active material, the larger the R-value of the cumulative distribution of the negative electrode active material at 50%.

[0148] In the above embodiments, the negative electrode active material has a suitable particle size and low surface defects, which helps to reduce side reactions at the negative electrode, reduce lithium ion consumption, and give the battery cell a longer cycle life.

[0149] In some embodiments, the graphitization degree of the negative electrode active material is 93% to 97%.

[0150] The graphitization degree of the negative electrode active material is 93%, 94%, 95%, 96%, 97%, or any value within the above range.

[0151] The higher the degree of graphitization of the negative electrode active material, the smaller the R value for the cumulative distribution of the negative electrode active material to 50%, and the smaller the surface defects of the negative electrode active material.

[0152] Specifically, the interlayer spacing of the (002) crystal plane of graphite was measured by X-ray diffraction (XRD), and the degree of graphitization was calculated using the Mering-Maire formula. The degree of graphitization g = [(3.440-d 002 ) / (3.440-3.354)]×100%, where d 002 denoted as the interlayer spacing of the (002) crystal plane of graphite.

[0153] By setting the graphitization degree of the negative electrode active material to 93% to 97%, the negative electrode active material has a high degree of graphitization, which is beneficial to reduce the surface defects of the negative electrode active material, reduce the side reactions at the negative electrode, reduce the consumption of lithium ions, and thus the battery cell has a longer cycle life.

[0154] In some embodiments, the graphitization degree of the negative electrode active material is 93% to 95%. This high graphitization degree of the negative electrode active material helps reduce side reactions at the negative electrode, decreases lithium-ion consumption, and improves the cycle life of the battery cell.

[0155] Furthermore, it should be noted that the R-value for a cumulative distribution of 50% of the anode active material is also related to the specific capacity and tap density of the anode active material. The relationship between specific capacity, tap density, and the R-value is not entirely positive or negative; parameters such as specific capacity, tap density, volume average particle size of the anode active material, and degree of graphitization of the anode active material all influence the R-value.

[0156] In some embodiments, the specific surface area of ​​the negative electrode active material is 1.0 m². 2 / g to 3.0m 2 / g.

[0157] The specific surface area of ​​the negative electrode active material can be 1.0 m². 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.8m 2 / g, 2.0m 2 / g、2.1m 2 / g, 2.2m 2 / g, 2.4m 2 / g, 2.6m 2 / g, 2.8m2 / g, 2.9m 2 / g, 3.0m 2 / g or any value within the above range.

[0158] The specific surface area of ​​the negative electrode active material is greater than or equal to 1.0 m². 2 At a specific surface area of ​​3.0 m² / g, the negative electrode active material has a suitable particle size, which facilitates the intercalation of lithium ions into the negative electrode active material, resulting in suitable kinetic performance of the battery cell; 2 At a rate of / g, the negative electrode active material has lower surface defects, which helps to reduce side reactions between the negative electrode active material and the electrolyte or other substances, reduce lithium ion consumption, and thus help to improve the cycle life of the battery cell.

[0159] In some embodiments, the specific surface area of ​​the negative electrode active material is 1.1 m². 2 / g to 1.5m 2 / g. In this way, the battery cells have both a long cycle life and good kinetic performance.

[0160] In some embodiments, different R values ​​can be achieved by adjusting the particle size of the graphite used to prepare the negative electrode active material, the degree of graphitization of the graphite, the elements on the graphite surface, the first coating layer on the graphite surface, and the thickness of the first coating layer.

[0161] As an example, negative electrode active materials can be obtained by the following preparation method.

[0162] A method is described: providing graphite; fusing the graphite with a coating agent; and carbonizing the fused product under a protective gas atmosphere to carbonize the coating agent into a coating layer at least covering the surface of the graphite, thereby obtaining a carbon-based material. The carbon-based material includes a core and a first coating layer at least partially covering the surface of the core, the core comprising graphite.

[0163] In some embodiments, the carbonization temperature is between 700°C and 1800°C. For example, the carbonization temperature is 700°C, 800°C, 900°C, 1000°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, 1700°C, 1800°C, or any range of the above values.

[0164] In some embodiments, the carbonization treatment time is from 1 hour to 6 hours. For example, the carbonization treatment time is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or any range of the above values.

[0165] In some embodiments, the volume average particle size of graphite is 9 μm to 11.5 μm.

[0166] In some embodiments, the coating agent includes liquid-phase coating agents, solid-phase coating agents, etc. Liquid-phase coating agents may include liquid-phase soft carbon coating agents, such as liquid-phase pitch, liquid tar, and other petroleum or coal-based byproducts. Liquid-phase coating agents may also include liquid-phase hard carbon coating agents, such as liquid resins.

[0167] In some embodiments, the solid content of the liquid resin may be from 50% to 88%.

[0168] As another example, negative electrode active materials are prepared by methods such as atomic layer deposition, where the surface of graphite contains aluminum (e.g., alumina), titanium, zinc, zirconium, boron, silicon, and nickel.

[0169] As an example, graphite is placed in a reaction chamber using trimethylaluminum as the aluminum source and water vapor as the oxygen source. The reaction chamber is heated to 120–160°C and the pressure increased to 15 Torr. Trimethylaluminum is pulsed into the reaction chamber and undergoes a chemisorption reaction on the exposed graphite surface. Nitrogen gas is used to remove excess trimethylaluminum and chemical reaction byproducts from the reaction chamber. The reaction chamber temperature is then adjusted to 100–120°C, and water vapor is pulsed into the reaction chamber to undergo a surface chemical reaction with the graphite after the trimethylaluminum precursor has been adsorbed. Nitrogen gas is used to remove excess water vapor and chemical reaction byproducts from the reaction chamber. This process is repeated to form an aluminum oxide atomic deposition layer of a certain thickness.

[0170] The specific steps for coating titanium trioxide onto the graphite surface using atomic layer deposition (ALD) are as follows: As an example, the graphite substrate is cleaned to remove surface impurities and placed in the ALD chamber; the reaction chamber is heated to 75°C, and titanium tetrachloride is introduced as a titanium precursor into the reaction chamber, causing it to undergo a chemical adsorption reaction on the graphite surface; the remaining unreacted titanium precursor is blown away using an inert carrier gas (such as nitrogen); water vapor is introduced to chemically react with the adsorbed titanium precursor, forming a titanium trioxide film; the byproducts and remaining precursor generated by the reaction are purged again with an inert gas; the above steps are repeated to achieve the desired titanium trioxide film; after deposition, the temperature of the ALD chamber is lowered to room temperature, and the graphite coated with titanium trioxide is removed.

[0171] Zinc, zirconium, boron, silicon, nickel, and other elements can also be prepared on the surface of graphite by atomic layer deposition, in which the temperature of the reaction chamber can be set to 60℃~200℃.

[0172] By adjusting the volume average particle size of graphite, negative electrode active materials with different particle sizes can be obtained. By adjusting the temperature or time of carbonization treatment, the degree of graphitization of graphite or negative electrode active materials can be adjusted. By adjusting the type and content of coating agent, the thickness of the first coating layer can be adjusted.

[0173] In some embodiments, the specific capacity of the negative electrode active material is from 345 mAh / g to 355 mAh / g.

[0174] The specific capacity of the negative electrode active material can be 345mAh / g, 346mAh / g, 348mAh / g, 349mAh / g, 350mAh / g, 351mAh / g, 352mAh / g, 353mAh / g, 354mAh / g, 355mAh / g or any value within the above range.

[0175] The degree of expansion of the negative electrode active material is related to its specific capacity. Within a certain range, the larger the specific capacity of the negative electrode active material, the greater the degree of expansion, the greater the risk of side reactions between the negative electrode active material or negative electrode sheet and the electrolyte or other substances, the greater the risk of dissolved metals damaging the structure of the negative electrode active material or negative electrode sheet, and the greater the impact on the cycle life of the battery cell.

[0176] In this embodiment, the specific capacity of the negative electrode active material is 345 mAh / g to 355 mAh / g. The negative electrode active material has a suitable specific capacity, which is beneficial to reducing the expansion of the negative electrode active material and the negative electrode sheet, and thus helps to reduce the adverse effect of the expansion of the negative electrode sheet on the cycle life.

[0177] In some embodiments, the tap density of the negative electrode active material at a frequency of 250±15 times / minute is 1.0 g / cm³. 3 Up to 1.3 g / cm 3 .

[0178] The tap density of the negative electrode active material at a frequency of 250±15 times / minute can be 1.0 g / cm³. 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 Or any value within the above range.

[0179] The structural stability of the negative electrode active material is related to its tap density. The better the structural stability of the negative electrode active material, the more beneficial it is to reduce side reactions at the negative electrode and improve the cycle life of the battery cell.

[0180] The tap density of the negative electrode active material was set to 1.0 g / cm³ at a frequency of 250 ± 15 times / minute. 3 Up to 1.3 g / cm 3 The negative electrode active material has good structural stability during charge-discharge cycles, which helps to reduce side reactions at the negative electrode and gives the battery cell a longer cycle life.

[0181] 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.

[0182] 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.

[0183] When the total mass of lithium-containing transition metal oxides is greater than or equal to 0.3% based on the positive electrode film, the lithium-containing transition metal oxides can release more lithium ions, which is beneficial to improving the cycle life of the battery cell. When the total mass of lithium-containing transition metal oxides is less than 4.5% based on the positive electrode film, the oxygen free radicals generated by the delithiation of lithium-containing transition metal oxides can be reduced, thereby reducing the adverse effect of oxygen free radicals on cycle life.

[0184] In some embodiments, the mass content of lithium transition metal oxide is 0.5% to 2% based on the total mass of the positive electrode film. This is beneficial for further improving the cycle life of the battery cell.

[0185] In some embodiments, the mass content of nickel metal oxide is 0.03% to 2.5% based on the total mass of the positive electrode film.

[0186] Based on the total mass of the positive electrode film, the mass content of nickel metal oxide can be 0.03%, 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, or any value within the above range.

[0187] When the mass content of nickel-containing metal oxides is greater than or equal to 0.03% based on the total mass of the positive electrode film, it is beneficial to promote the conversion of oxygen free radicals generated by lithium-containing transition metal oxides into oxygen, thereby reducing the adverse effects of oxygen free radicals on the cycle life of the battery cell. When the mass content of nickel-containing metal oxides is less than or equal to 2.5% based on the total mass of the positive electrode film, it is beneficial to reduce the content of dissolved transition metals, reduce the damage of dissolved transition metals to the SEI film, and thus help improve the cycle life of the battery cell.

[0188] In some embodiments, the mass content of nickel metal oxide is 0.05% to 1.5% based on the total mass of the positive electrode film. This is beneficial for further improving the cycle life of the battery cell.

[0189] In some embodiments, the lithium-containing transition metal oxide includes Fe element, and the ratio of the mass of Fe element in the lithium-containing transition metal oxide to the mass of Ni element in the nickel-containing metal oxide is 0.5 to 10 based on the total mass of the cathode film.

[0190] Based on the total mass of the positive electrode film, the ratio of the mass of Fe in the lithium-containing transition metal oxide to the mass of Ni in the nickel-containing metal oxide can be 0.5, 0.8, 1, 1.5, 2, 2.2, 2.5, 3, 3.2, 3.5, 3.8, 4, 4.5, 5, 5.5, 5.8, 6, 6.2, 6.5, 6.8, 7, 7.5, 8, 8.5, 9, 9.5, 10 or any value within the above range.

[0191] The ratio of the mass of Fe in lithium-containing transition metal oxides to the mass of Ni in nickel-containing metal oxides reflects the mass ratio of the first additive and the second additive. A larger ratio indicates a higher mass content of the first additive in the cathode film; a smaller ratio indicates a higher mass content of the second additive in the cathode film.

[0192] When the mass ratio of Fe in lithium-containing transition metal oxides to Ni in nickel-containing metal oxides is greater than or equal to 0.5, more active lithium ions can be provided to the battery cells, which is beneficial to improving the cycle life of the battery cells. When the mass ratio of Fe in lithium-containing transition metal oxides to Ni in nickel-containing metal oxides is less than or equal to 10, it is beneficial to fully catalyze the conversion of oxygen free radicals into oxygen, thereby reducing the adverse effects of oxygen free radicals on cycle life.

[0193] In some embodiments, the mass ratio of Fe in the lithium-containing transition metal oxide to Ni in the nickel-containing metal oxide is 1.5 to 5. This is beneficial for further improving the cycle life of the battery cell.

[0194] In some embodiments, the average longest diameter of the lithium-containing transition metal oxide is 3 μm to 20 μm on a longitudinal section along the thickness direction of the positive electrode sheet.

[0195] The average longest diameter of lithium-containing transition metal oxides can be 3μm, 4μm, 5μm, 6μm, 8μm, 10μm, 12μm, 13μm, 15μm, 16μm, 18μm, 20μm, or a value within the range obtained by any combination of the above two values.

[0196] 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.

[0197] When the average longest diameter of lithium-containing transition metal oxides is greater than or equal to 3 μm, the rate at which oxygen free radicals are generated by lithium-containing transition metal oxides can be reduced, which is beneficial to reducing the adverse effects of oxygen free radicals on the cycle life of battery cells. When the average longest diameter of lithium-containing transition metal oxides is less than or equal to 20 μm, it is beneficial to the extraction of lithium ions from lithium-containing transition metal oxides, which is beneficial to improving the cycle life of battery cells.

[0198] 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 5 μm to 20 μm. This results in a longer cycle life for the battery cell.

[0199] 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.

[0200] 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.

[0201] The average length of the longest diameter of nickel-containing metal oxides can be measured as follows: Take 30 nickel-containing metal oxide particles from the 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 length of the longest diameter of the nickel-containing metal oxides.

[0202] When the average longest diameter of nickel-containing metal oxides is greater than or equal to 5 μm, it is beneficial to reduce the risk of side reactions in battery cells due to the small particle size and high reactivity of nickel-containing metal oxides, and thus improve 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 degree of side reactions of oxygen free radicals in battery cells, and reduce the adverse effects on the cycle life of battery cells.

[0203] In some embodiments, the average longest diameter of the nickel-containing metal oxide in a longitudinal section along the thickness direction of the positive electrode sheet is 10 μm to 30 μm. This results in a longer cycle life for the battery cell.

[0204] In some embodiments, the average longest diameter of the nickel-containing metal oxide is less than the average longest diameter of the lithium-containing transition metal oxide. This results in a suitable size distribution between the nickel-containing metal oxide and lithium-containing transition metal oxide particles, which is beneficial for the nickel-containing metal oxide to catalyze the conversion of oxygen free radicals generated by the lithium-containing transition metal oxide into oxygen, reducing the degree of side reactions of oxygen free radicals within the battery cell and improving the cycle life of the battery cell.

[0205] 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.

[0206] In some embodiments, the lithium-containing transition metal oxide includes a substrate and a second 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.

[0207] The second coating layer can cover part of the substrate surface or the entire substrate surface.

[0208] 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.

[0209] The lithium content in the lithium-containing transition metal oxide matrix is ​​relatively high, which can release more lithium ions to provide more active lithium ions to the battery cells, thus improving the cycle life of the battery cells. In addition, the setting of the second coating layer helps to improve the stability of the lithium-containing transition metal oxide.

[0210] In some embodiments, the lithium-containing transition metal oxide includes a substrate and a second coating layer located on at least a portion of the surface of the substrate, the substrate comprising 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 life of the battery cell.

[0211] In some embodiments, the lithium-containing transition metal oxide includes a substrate and a second 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。

[0212] In Li e FeO f In this context, e can be 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.3, 1.5, 2, 2.3, 2.5, 2.8, 3, 3.5, 4, 4.5, 4.8, 5, or any of the above values. f can be 0.1, 0.5, 0.8, 1, 1.3, 1.5, 2, 2.3, 2.5, 2.8, 3, 3.5, 4, or any of the above values.

[0213] 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.

[0214] 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.

[0215] In some embodiments, the lithium-containing transition metal oxide includes a substrate and a second 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。

[0216] 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.

[0217] 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.

[0218] In some embodiments, at least a portion of the substrate surface contains at least one of Al or Mg. This is beneficial for improving the stability of lithium-containing transition metal oxides and reducing side reactions between lithium-containing transition metal oxides and the electrolyte, thereby improving the cycle life of the battery cells.

[0219] In some embodiments, the second coating layer includes carbon. The inclusion of a second coating layer improves the stability of the lithium-containing transition metal oxide, and the inclusion of carbon in the second coating layer enhances the conductivity of the lithium-containing transition metal oxide, thereby facilitating the utilization of the battery cell's capacity and improving its cycle life.

[0220] In some embodiments, the thickness of the second coating layer is 10 nm to 100 nm.

[0221] The thickness of the second 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.

[0222] In this embodiment, the second coating layer has a suitable thickness, which is beneficial to improving the stability of lithium-containing transition metal oxides and facilitates the extraction of lithium ions, resulting in a longer cycle life for the battery cell.

[0223] 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.

[0224] 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.

[0225] 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.

[0226] 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 adverse effects of oxygen free radicals on the cycle life of battery cells. In addition, when the molar content of lithium in the nickel-containing metal oxides is greater than 1, it can also play a role in supplementing lithium ions, which is beneficial to improving the cycle life of battery cells.

[0227] In some embodiments, the nickel-containing metal oxide includes Li2NiO2. This is beneficial for improving the cycle life of the battery cell.

[0228] Before the formation of the battery cell, the nickel-containing metal oxide of the positive electrode film 502 in the battery cell can be Li2NiO2. During the formation process, Li2NiO2 decomposes, lithium ions are released, and the oxygen content may also change accordingly.

[0229] In some embodiments, nickel-containing metal oxides include Li g NiO h ,0≤g≤2,0 <h≤2。

[0230] 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.

[0231] During the formation of a battery cell, the nickel-containing metal oxide decomposes, 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 remain within the aforementioned range.

[0232] In some embodiments, nickel-containing metal oxides include NiO. q 0 <q≤2。

[0233] In NiO q In this context, q can be 0.1, 0.2, 0.3, 0.5, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, or any value within the above range.

[0234] During the formation of a battery cell, nickel-containing metal oxides decompose, resulting in changes in the molar content of lithium and oxygen. For example, lithium may be completely released from the nickel-containing metal oxide, decomposing into nickel oxide.

[0235] 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.

[0236] 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.

[0237] 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.

[0238] 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.

[0239] Within a voltage range of 2V to 4.3V, the charge capacity of lithium-containing transition metal 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.

[0240] Lithium-containing transition metal oxides have high charge capacity, which is beneficial for improving the energy density and cycle life of individual battery cells.

[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. 2Up 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 is related to the kinetic performance and energy density of the battery cell. The higher the unilateral density of the negative electrode film, the greater the coating weight of the negative electrode film, 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, the more conducive it is to lithium ion transport and insertion into the negative electrode, and the better the kinetic performance 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 relatively suitable energy density 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] As an example, a battery cell with 0% SOC can be obtained using the following method. Specifically, the battery cell is first charged to 3.65V at a constant current of 0.33C, then charged to 0.05C at a constant voltage of 3.65V, and finally discharged to 2.5V at a constant current of 0.33C to obtain a battery cell with 0% SOC. Afterwards, the battery cell is disassembled to obtain the electrode sheets (e.g., negative or positive electrode sheets), and the compaction density is tested.

[0247] The compaction density of the negative electrode film at 0% SOC can be 1.3 g / cm³. 3 1.32g / cm 3 1.35g / cm 3 1.4g / cm3 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.

[0248] The compaction density of the negative electrode film is related to the kinetic performance and energy density of the battery cell. The higher the compaction density of the negative electrode film, 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, the better it is for lithium ion transport and insertion into the negative electrode, and the better the kinetic performance of the battery cell.

[0249] Furthermore, the compaction density of the negative electrode film is also related to the negative electrode active material. If the compaction density of the negative electrode film is too high, the risk of the negative electrode active material being crushed and cracked is greater. Crushed negative electrode active material will exhibit more pronounced side reactions, leading to increased lithium-ion consumption and negatively impacting the cycle life of the battery cell. Therefore, setting the compaction density of the negative electrode film to less than or equal to 1.8 g / cm³ is recommended. 3 This helps reduce the risk of the negative electrode active material being crushed, reduces side reactions and lithium ion consumption at the negative electrode, and gives the battery cell a longer cycle life.

[0250] In the above embodiments, the negative electrode film layer has a suitable compaction density, and the battery cell has a relatively suitable energy density, kinetic performance, and cycle life.

[0251] In some embodiments, the porosity of the negative electrode sheet is 10% to 50%, optionally 25% to 35%.

[0252] The porosity of the negative electrode sheet is 10%, 20%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 45%, 50%, or any value within the above range.

[0253] In the above embodiments, the negative electrode sheet has a suitable porosity, which is beneficial for electrolyte wetting, reducing polarization in the battery cell, reducing the degree of side reactions at the negative electrode, reducing lithium ion consumption, and improving the cycle life of the battery cell.

[0254] 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 2Available in 0.28g / 1540.25mm. 2 Up to 0.4g / 1540.25mm 2 .

[0255] 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.

[0256] The unilateral density of the positive electrode film is related to the kinetic performance and energy density of the battery cell. The higher the unilateral density of the positive electrode film, the greater the coating weight of the positive electrode film, 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, the more conducive it is to lithium-ion transport, and the better the kinetic performance of the battery cell.

[0257] 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.

[0258] 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 .

[0259] 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 32.6g / 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.

[0260] 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.

[0261] 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.

[0262] In some embodiments, the lithium phosphate includes primary particles and secondary particles formed by the aggregation of the 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.

[0263] 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.

[0264] In the embodiments of this application, secondary particles refer to particles formed by the aggregation of primary particles.

[0265] 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.

[0266] In the above embodiments, the lithium phosphate particles have a suitable size, which facilitates the extraction of lithium ions and helps to maximize the capacity of the battery cell.

[0267] In some embodiments, lithium phosphate cathode active materials include those with the general formula Li x D y Me a1 Mb1 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.

[0268] 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.

[0269] During the charging and discharging process of a single battery cell, the molar content of lithium, oxygen, and other elements in the lithium phosphate cathode active material changes within a certain range.

[0270] In some embodiments, the lithium phosphate-containing cathode active material includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The aforementioned lithium phosphate-containing cathode active materials exhibit high structural stability, which helps to improve the cycle life of individual battery cells.

[0271] 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.

[0272] In some embodiments, at least a portion of the surface of the lithium phosphate-containing positive electrode active material has carbon elements. This helps to improve the conductivity of the lithium phosphate, facilitating the utilization of the battery cell's capacity.

[0273] As an example, at least a portion of the surface of the lithium phosphate-containing material is provided with a third coating layer, which includes carbon elements. The inclusion of a carbon-containing third coating layer improves the conductivity of the positive electrode active material, facilitating the full utilization of the battery cell's capacity.

[0274] In some embodiments, the carbon content is 1% to 2% based on the total mass of the lithium phosphate cathode active material.

[0275] 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.

[0276] In the above embodiments, the lithium phosphate-containing positive electrode active material has good conductivity, which facilitates the utilization of the capacity of the battery cell.

[0277] 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 3 μm to 30 μm; the volume average particle size of the nickel metal oxide is 5 μm to 50 μm; and the volume average particle size of the lithium phosphate positive electrode active material is 0.5 μm to 8 μm.

[0278] In the above embodiments, the lithium phosphate positive electrode active material, the lithium transition metal oxide, and the nickel metal oxide have suitable particle sizes, and the battery cells have good energy density and less gas production.

[0279] In some embodiments, the end cap assembly 32 includes electrode terminals 322, as shown in FIG3. 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.

[0280] 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.

[0281] [Positive electrode plate]

[0282] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0283] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0284] 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.).

[0285] 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.

[0286] 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.

[0287] 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.

[0288] [Negative electrode plate]

[0289] The negative electrode includes a negative current collector and a negative electrode film layer disposed on the negative current collector.

[0290] The negative electrode current collector can be a metal foil or a composite negative electrode current collector. The negative electrode current collector can be copper foil. Composite negative electrode current collectors can be formed by depositing metallic materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) onto a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0291] 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).

[0292] 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.

[0293] 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.

[0294] [Isolation Component]

[0295] 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.

[0296] 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.

[0297] This application provides a battery device, including the battery cell in any of the above embodiments.

[0298] 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.

[0299] 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.

[0300] [Example]

[0301] Example 1

[0302] (1) Preparation of positive electrode sheet

[0303] Lithium iron phosphate (LiFePO4), the positive electrode active material, Li5FeO4 (first additive), Li2NiO2 (second additive), Super P (positive electrode conductive agent), and polyvinylidene fluoride (PVDF) (positive electrode binder) were mixed in a mass ratio of 95.26:1.79:0.45:0.5:2. N-methylpyrrolidone (NMP) solvent was added, and the mixture was stirred under vacuum until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto both surfaces of an aluminum foil current collector. The coated current collector was dried and cold-pressed to obtain the positive electrode sheet. The single-sided density of the positive electrode film was 0.3110 g / 1540.25 mm². 2 The compaction density of the positive electrode sheet is 2.7 g / cm³. 3 .

[0304] In the positive electrode film layer, based on the total mass of the positive electrode film layer, the mass content of the positive electrode active material is 95.26%, the mass content of the first additive is 1.79%, the mass content of the second additive is 0.45%, the average length of the first additive is 10 μm, and the average length of the second additive is 15 μm.

[0305] (2) Preparation of negative electrode sheet

[0306] The negative electrode active material, negative electrode conductive agent Super P, thickener sodium carboxymethyl cellulose, and negative electrode binder styrene-butadiene rubber (SBR) 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 the negative electrode current collector copper foil. After drying and cold pressing, the negative electrode sheet was obtained. The areal density of the negative electrode film was 0.155 g / 1540.25 mm². 2The compaction density of the negative electrode film is 1.6 g / cm³. 3 .

[0307] The negative electrode active material includes artificial graphite, the surface of which contains a first coating layer, which includes amorphous carbon, and the cumulative distribution of the negative electrode active material is 50%, with an R value of 0.06.

[0308] The R value of 50% cumulative distribution of negative electrode active material is related to the volume average particle size of artificial graphite used to prepare negative electrode active material, the thickness of the first coating layer, the volume average particle size of negative electrode active material, the degree of graphitization of negative electrode active material, the specific capacity of negative electrode active material, the specific surface area of ​​negative electrode active material, and the tap density of negative electrode active material.

[0309] The artificial graphite used to prepare the negative electrode active material has a volume average particle size (Dv50) of 10.3 μm, a first coating layer thickness of 50 nm, a volume average particle size of 10.5 μm, a graphitization degree of 94.17%, a specific capacity of 349.2 mAh / g, and a specific surface area of ​​1.12 m². 2 The tap density of the negative electrode active material is 1.19 g / cm³. 3 .

[0310] (3) Separating membrane

[0311] The separator is a 5μm PE base film.

[0312] (4) Electrolyte

[0313] 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.

[0314] (5) Assembly of battery cells

[0315] 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.

[0316] Examples 2-7

[0317] The difference between Examples 2-7 and Example 1 is that the R50 of the negative electrode active material is different.

[0318] Different R50 values ​​can be achieved by adjusting the thickness of the coating layer, the volume average particle size of the artificial graphite, and the degree of graphitization.

[0319] Examples 8-9

[0320] The difference between Examples 8-9 and Example 1 is that the surface of the artificial graphite does not include the first coating layer, and the surface of the artificial graphite includes Al or Ti elements.

[0321] In Example 8, the negative electrode active material was prepared by the following method:

[0322] Graphite is placed in a reaction chamber, using trimethylaluminum as the aluminum source and water vapor as the oxygen source. The reaction chamber is heated to 150°C and the pressure is increased to 15 Torr. Trimethylaluminum is pulsed into the reaction chamber and undergoes a chemical adsorption reaction on the exposed graphite surface. Nitrogen gas is used to remove excess trimethylaluminum and chemical reaction byproducts from the reaction chamber. The reaction chamber temperature is then adjusted to 120°C, and water vapor is pulsed into the reaction chamber to undergo a surface chemical reaction with the graphite after the trimethylaluminum precursor is adsorbed. Nitrogen gas is used to remove excess water vapor and chemical reaction byproducts from the reaction chamber. The above steps are repeated to form a graphite layer of aluminum oxide atoms with a certain thickness.

[0323] In Example 9, the negative electrode active material was prepared by the following method:

[0324] Graphite is placed in an atomic layer deposition chamber; the chamber is heated to 75°C, and titanium tetrachloride is introduced into the reaction chamber as a titanium precursor, causing it to undergo a chemical adsorption reaction on the graphite surface; the remaining unreacted titanium precursor is purged away using an inert carrier gas (such as nitrogen); water vapor is introduced to react chemically with the adsorbed titanium precursor to form a titanium trioxide film; the byproducts and remaining precursor generated by the reaction are purged again with an inert gas; the above steps are repeated to achieve the desired titanium trioxide film; after deposition, the temperature of the atomic layer deposition chamber is lowered to room temperature, and the graphite with the titanium trioxide deposited layer is removed.

[0325] Examples 10-11

[0326] The difference between Examples 10-11 and Example 1 is that the specific capacity of the negative electrode active material is different.

[0327] Examples 12-13

[0328] The difference between Examples 12-13 and Example 1 is that the tap density of the negative electrode active material is different.

[0329] Examples 14-21

[0330] The difference between Examples 14-21 and Example 1 is that the mass content of the first additive or the second additive changes.

[0331] Examples 22-24

[0332] The difference between Examples 22-24 and Example 1 is that the average value of the longest diameter of the first additive or the second additive is different.

[0333] Comparative Example 1

[0334] The difference between Comparative Example 1 and Example 1 is that the negative electrode active material is graphite, and the surface of the graphite does not have a first coating layer, nor does it include elements such as Al or Ti.

[0335] Comparative Example 2

[0336] The difference between Comparative Example 2 and Example 1 is that the negative electrode active material includes artificial graphite, the surface of which contains a first coating layer, but the R50 of the negative electrode active material is too large.

[0337] In Tables 1, 2, and 3, R50 represents the R value with a cumulative distribution of 50% in the cumulative distribution curve of the R value obtained by laser microscopy confocal Raman spectroscopy instrument scanning mode, and Dv50 represents the volume average particle size of the negative electrode active material.

[0338] Table 1. Test results of Examples 1-7 and Comparative Examples 1-2

[0339] Table 2 Test results of Examples 8-9 and Comparative Example 1

[0340] Table 3 Test results of Examples 1 and 10-24

[0341] In this application embodiment, the cycle life is reflected by the capacity retention rate; the higher the capacity retention rate, the longer the cycle life.

[0342] It should be noted that in this application, at least a portion of the surface of the graphite is not provided with a first coating layer, but the R50 of the negative electrode active material is less than that of the comparative example of 0.05. This is because the structural characteristics of graphite itself cause certain defects on the surface of the negative electrode active material containing graphite, which limits the further reduction of R50.

[0343] In conjunction with Examples 1-9 and Comparative Examples 1-2, compared to graphite, by setting at least a portion of the surface of the graphite to contain a first coating layer and the cumulative distribution of the negative electrode active material to 50% with an R value in the range of 0.05 to 0.15, or by setting at least a portion of the surface of the graphite to contain elements such as Al and Ti, the consumption of lithium ions can be reduced and the cycle life of the battery cell can be improved.

[0344] As shown in Examples 1-3, the volume average particle size of the artificial graphite used to prepare the negative electrode active material is between 9 μm and 11.5 μm, the volume average particle size of the negative electrode active material is between 9 μm and 12 μm, and the specific surface area of ​​the negative electrode active material is 1.0 m². 2 / g to 3.0m 2 At a rate of / g, the negative electrode active material has a lower R50 value, and the battery cell has a longer cycle life.

[0345] In conjunction with Examples 1 and 4-5, when the graphitization degree of the negative electrode active material is 93% to 97%, the negative electrode active material has a lower R50 value and the battery cell has a longer cycle life.

[0346] In conjunction with Examples 1 and 6-7, when the thickness of the first coating layer is 20nm to 70nm, the negative electrode active material has a lower R50 value, and the battery cell has a longer cycle life.

[0347] In conjunction with Examples 1 and 10-11, when the specific capacity of the negative electrode active material is between 345 mAh / g and 355 mAh / g, the battery cell has a long cycle life.

[0348] In conjunction with Examples 1 and 12-13, the tap density of the negative electrode active material is 1.0 g / cm³. 3 Up to 1.3 g / cm 3 Under these conditions, individual battery cells have a long cycle life.

[0349] As shown in Examples 14-21, when the mass content of lithium transition metal oxide is 0.3% to 4.5%, the battery cell has a longer cycle life; further, when the mass content of lithium transition metal oxide is 0.5% to 2%, the battery cell has a better cycle life; when the mass content of nickel metal oxide is 0.03% to 2.5%, the battery cell has a longer cycle life; further, when the mass content of nickel metal oxide is 0.05% to 1.5%, the battery cell can have a better cycle life.

[0350] As shown in Examples 1 and 22-24, the average longest diameter of the lithium-containing transition metal oxide is 3 μm to 20 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 a longer cycle life. Furthermore, the average longest diameter of the lithium-containing transition metal oxide is 5 μm to 30 μm, and the average longest diameter of the nickel-containing metal oxide is 10 μm to 30 μm, which allows the battery cell to have an even better cycle life.

[0351] 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.

[0352] 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.

[0353] 1. Cycle life test method

[0354] At 45℃, the battery cell was charged at a constant current rate of 1C 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 1000 charge-discharge cycles using the above method, and the discharge capacity of each cycle was recorded.

[0355] The capacity retention rate of a single battery cell after 1000 cycles at 45℃ and 1C / 1C = discharge capacity of the 1000th cycle / discharge capacity of the 1st cycle × 100%.

[0356] 2. Test method for R-value when the cumulative distribution of negative electrode active material is 50%.

[0357] The negative electrode active material in this application can be either a prepared negative electrode active material or a negative electrode material obtained by scraping powder from a negative electrode sheet.

[0358] As an example, the battery cell is disassembled to obtain the negative electrode sheet, and the negative electrode film layer on the negative electrode sheet is scraped off, washed with anhydrous ethanol and dried to separate the negative electrode active material.

[0359] The R-value R50 of the negative electrode active material can be obtained using a laser confocal Raman spectroscopy instrument in surface scanning mode. Specifically, using a laser confocal Raman spectroscopy instrument (e.g., a high-precision Renishaw laser confocal Raman spectroscopy instrument), a laser wavelength of 532 nm is selected. An appropriate amount of sample is taken and its surface is scanned in all directions. The scanning area is 100 μm × 100 μm, the step size is 2 μm, and the total number of scanning points is 100. This yields the R-values ​​at different sites and the cumulative distribution curve of the R-values ​​across the surface scanned area.

[0360] The R-value of a negative electrode active material refers to the ratio of the peak heights of the D-band and G-band peaks in its Raman spectrum. The D-band peak is located at 1350 ± 50 cm⁻¹. -1 The position of peak G is 1585±50cm. -1 .

[0361] 3. Methods for testing specific surface area

[0362] As an example, the specific surface area was tested by the gas adsorption method according to the GB / T19587 2017 test standard.

[0363] Specifically, the negative electrode active material was used as a sample, and the sample tube was immersed in liquid nitrogen at -196℃. The amount of nitrogen adsorbed on the solid surface under different pressures of 0.05-0.30 was measured. Based on the BET multilayer adsorption theory and its formula, the amount of monolayer adsorption of the sample was obtained, and the specific surface area was calculated.

[0364] 4. Test method for volume average particle size

[0365] 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 (e.g., positive electrode active material, negative 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.

[0366] 5. Test method for graphitization degree

[0367] Crystal cell parameters were calculated using X-ray polycrystalline diffraction. The peak positions of C004 and Si311 in two parallel samples were obtained by centroid method. The interlayer spacing d002 of graphite (002) was calculated by substituting it into the interplanar spacing formula. The obtained d002 was then substituted into the Mering-Maire formula: g = [(3.440-d002) / (3.440-3.354)] × 100% to obtain the degree of graphitization g.

[0368] In the embodiments of this application, the degree of graphitization G of the negative electrode active material can be determined by XRD diffraction using the lattice parameters of the carbon crystal, with reference to standards JB / T4220-2011 and JISK0131-1996.

[0369] 6. Methods for testing gram capacity

[0370] The disassembled negative electrode sheets were cut to specific sizes, and then assembled with lithium sheets into coin cells. The cells were tested at 25°C and 0.33C. The specific capacity of the negative electrode active material = discharge capacity / mass of the negative electrode active material.

[0371] 7. Test method for tap density

[0372] The tap density of the negative electrode active material is a well-known concept in the art and can be determined using instruments and methods known in the art. For example, it can be determined using a powder tap density tester, referring to GB / T 5162-2006. The testing instrument can be the Dandong Baite BT-301.

[0373] The test parameters are as follows: vibration frequency 250±15 times / minute, amplitude 3±0.2mm, vibration count 5000 times, and graduated cylinder 25mL. This test is based on the results obtained from disassembled batteries that have undergone formation or cycling.

[0374] 8. Test method for the first coating layer

[0375] A thin slice of approximately 100 nm thickness was cut from the middle of the negative electrode active material particles using focused ion beam (FIB), and then TEM testing was performed on the slice. It was observed that the surface region included a first coating layer. The lattice fringes in the first coating layer exhibited long-range disorder and short-range order, and the electron diffraction pattern showed a halo-like appearance, indicating that the first coating layer contained amorphous carbon.

[0376] The thickness of the first coating layer can be characterized by transmission electron microscopy (TEM). By observing the negative electrode active material with TEM, the first coating layer covering the surface of the core (e.g., artificial stone chips) can be clearly observed based on the differences in lattice fringes. Five locations in the first coating layer are randomly selected for testing, and the average value is calculated as the average thickness of the first coating layer.

[0377] 9. Test of compacted density

[0378] For example, it can be tested using an electronic pressure testing machine (e.g., UTM7305 model) according to standard GB / T24533-2009. An exemplary test method is as follows: Weigh 1g of material and add it to a container with a base area of ​​1.327cm². 2In the mold, the pressure is increased to 5000 kg (equivalent to 50000 N), held for 30 seconds, then depressurized and held for 10 seconds. The compaction density of the powder under a force of 50000 N is then recorded and calculated.

[0379] 10. Porosity Testing

[0380] The sample was cut into 3mm × 3mm pieces, and its apparent volume V0 was measured (the apparent volume of the sample is the sample thickness × sample area). Then, the true volume of the sample was measured using a true density meter. Specifically, the sample was placed in the sample testing chamber, nitrogen gas was introduced into the chamber, and the sample testing chamber was connected to a reference chamber. The pressure after stabilization was recorded. The pore volume was calculated based on the pressure before the reference chamber and sample chamber were connected, the pressure after stabilization, and Bohr's law PV = nRT. The porosity of the sample = pore volume / apparent volume.

[0381] 11. Test of the average value of the longest diameter

[0382] The positive electrode sheet, which includes the first additive particles and lithium iron phosphate material, is cut along the thickness direction to expose the longitudinal section of the positive electrode film. The longest diameter of the first additive, the second additive, and the lithium iron phosphate material is determined by scanning electron microscopy (SEM) testing of the longitudinal section of the positive electrode film.

[0383] Specifically, the longest diameter of the first additive refers to the longest straight line that passes through the center point of the first additive and extends to the outer periphery of the particle; the longest diameter of the lithium iron phosphate material refers to the longest straight line that passes through the center point of the lithium iron phosphate material and extends to the outer periphery of the particle; and the longest diameter of the second additive refers to the longest straight line that passes through the center point of the second additive and extends to the outer periphery of the particle.

[0384] As an example, arbitrarily select 30 first additive particles in the longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 first additive particles, and take their average value; arbitrarily select 30 lithium iron phosphate material particles in the longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 lithium iron phosphate material particles, and take their average value; arbitrarily select 30 second additive particles in the longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 second additive particles, and take their average value.

[0385] 12. Test method for the thickness of the second coating layer of the first additive in the positive electrode film.

[0386] 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 second coating layer.

[0387] 13. Testing of specific components in the positive and negative electrode films.

[0388] The positive electrode film layer of the positive electrode or the negative electrode film layer of the negative electrode 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 to analyze the elemental composition. For example, for the positive electrode, the contents of Ni, Fe, and P can be measured; for the negative electrode, the contents of Si can be measured.

[0389] Specifically, the presence and mass content of Li2NiO2 in the cathode film before formation can be determined by detecting the Ni element, and the presence and mass content of Li5FeO4 in the cathode film before formation can be determined by detecting the ratio of the P and Fe elements.

[0390] 14. Test methods for areal density and compacted density

[0391] The positive and negative electrode sheets are removed from the lithium-ion battery cell, and their thicknesses and current collector thicknesses are measured respectively. A certain area of ​​the electrode sheet is taken, its area is measured, and the mass of the film layer on the current collector after removing the current collector is measured. The electrode surface density is calculated based on this area and mass. Therefore, the compaction density PD of the electrode sheet is calculated as: electrode surface density / (electrode thickness - current collector thickness).

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 of the positive current collector, the positive electrode film layer comprising a positive electrode active material, a first additive and a second additive, the positive electrode active material comprising a lithium phosphate, the first additive comprising a lithium transition metal oxide, and the second additive comprising a nickel metal oxide; A negative electrode sheet, comprising a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material, and the negative electrode active material comprises graphite; wherein, At least a portion of the surface of the graphite contains a first coating layer, and in the cumulative distribution curve of the R-value obtained by laser microscopy confocal Raman spectroscopy in instrument scanning mode, the cumulative distribution of the R-value is 0.05 to 0.15 for 50% of the material, where R = 1. D / I G I D I represents the intensity of the D peak of the negative electrode active material. G This indicates the intensity of the G peak in the negative electrode active material; or, The graphite has at least a portion of its surface containing at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni.

2. The battery cell according to claim 1, characterized in that, The first coating layer includes at least one of amorphous carbon, graphene, natural graphite, and carbon nanotubes; optionally, the first coating layer includes amorphous carbon.

3. The battery cell according to claim 1 or 2, characterized in that, The thickness of the first coating layer is 20 nm to 70 nm.

4. The battery cell according to claim 1, characterized in that, The graphite has at least a portion of its surface containing at least one element selected from Al, Ti, Zn, Zr, B, Si, and Ni, and the cumulative distribution curve of the R value obtained by the negative electrode active material in the laser microscopy confocal Raman spectroscopy instrument scanning mode shows that the cumulative distribution of 50% of the R value is between 0.28 and 0.

31.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The volume average particle size Dv50 of the graphite is 9 μm to 11.5 μm.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The volume average particle size Dv50 of the negative electrode active material is 9 μm to 12 μm.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The graphitization degree of the negative electrode active material is 93% to 97%, and can be selected as 93% to 95%.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The specific surface area of ​​the negative electrode active material is 1.0 m². 2 / g to 3.0m 2 / g, can be selected as 1.1m 2 / g to 1.5m 2 / g.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The specific capacity of the negative electrode active material is from 345 mAh / g to 355 mAh / g.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The tap density of the negative electrode active material at a frequency of 250±15 times / minute is 1.0 g / cm³. 3 Up to 1.3 g / cm 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 is 0.3% to 4.5%, optionally 0.5% to 2%.

12. The battery cell according to any one of claims 1 to 11, characterized in that, Based on the total mass of the positive electrode film, the mass content of the nickel-containing metal oxide is from 0.03% to 2.5%, and optionally from 0.05% to 1.5%.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The lithium-containing transition metal oxide includes Fe element. Based on the total mass of the positive electrode film, the mass ratio of Fe element in the lithium-containing transition metal oxide to the mass of Ni element in the nickel-containing metal oxide is 0.5 to 10, and optionally 1.5 to 5.

14. The battery cell according to any one of claims 1 to 13, characterized in that, On the longitudinal section along the thickness direction of the positive electrode sheet, the average longest diameter of the lithium-containing transition metal oxide is 3 μm to 20 μm, and can be selected as 5 μm to 20 μm.

15. The battery cell according to any one of claims 1 to 14, 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 10 μm to 30 μm.

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

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

18. The battery cell according to any one of claims 1 to 17, characterized in that, The lithium-containing transition metal oxide includes a substrate and a second 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.

19. The battery cell according to any one of claims 1 to 17, characterized in that, The lithium-containing transition metal oxide includes a matrix and a second coating layer located on at least a portion of the surface of the matrix, wherein the matrix includes Li5FeO4.

20. The battery cell according to any one of claims 1 to 17, characterized in that, The lithium-containing transition metal oxide includes a substrate and a second 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。 21. The battery cell according to any one of claims 1 to 17, characterized in that, The lithium-containing transition metal oxide includes a substrate and a second 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。 22. The battery cell according to any one of claims 18 to 21, characterized in that, At least a portion of the surface of the substrate contains at least one of Al or Mg.

23. The battery cell according to any one of claims 18 to 22, characterized in that, The second coating layer includes carbon.

24. The battery cell according to any one of claims 18 to 23, characterized in that, The thickness of the second coating layer is 10 nm to 200 nm.

25. The battery cell according to any one of claims 1 to 24, 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.

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

27. The battery cell according to any one of claims 1 to 24, characterized in that, The nickel-containing metal oxide includes Li g NiO h ,0≤g≤2,0 <h≤2。 28. The battery cell according to any one of claims 1 to 24, characterized in that, The nickel-containing metal oxide includes NiO. q 0 <q≤2。 29. The battery cell according to any one of claims 1 to 28, 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.

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

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

32. The battery cell according to any one of claims 1 to 31, 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 .

33. The battery cell according to any one of claims 1 to 32, characterized in that, The porosity of the negative electrode sheet is 10% to 50%, and can be selected as 25% to 35%.

34. The battery cell according to any one of claims 1 to 33, 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 .

35. The battery cell according to any one of claims 1 to 34, 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 .

36. The battery cell according to any one of claims 1 to 35, 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.

37. The battery cell according to any one of claims 1 to 36, characterized in that, The lithium phosphate-containing positive electrode active material includes materials with the general formula Li x D y Me a1 M b1 P 1-c1 X c1 Y z Compounds wherein 0.5≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, and 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z≤5; D includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; Y includes one or more of O and F.

38. The battery cell according to any one of claims 1 to 37, characterized in that, The lithium-containing phosphate includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

39. The battery cell according to any one of claims 1 to 38, characterized in that, At least a portion of the surface of the lithium phosphate contains carbon.

40. The battery cell according to claim 39, 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%.

41. The battery cell according to any one of claims 1 to 40, characterized in that, The positive electrode film layer satisfies at least one of the following conditions: The volume average particle size of the lithium-containing transition metal oxide is 3 μm to 30 μm; The volume average particle size of the nickel-containing metal oxide is 5 μm to 50 μm; The volume average particle size of the lithium phosphate positive electrode active material is 0.5 μm to 8 μm.

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

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

Images