Positive electrode active material, positive electrode sheet, battery cell, battery, and power using device

Abstract

The application relates to a positive electrode active material, a positive electrode sheet, a battery monomer, a battery and a power utilization device, the positive electrode active material comprising a core part and a coating layer, the core part comprising a compound with a molecular formula of LiNi a Co b M( 1‑a‑b )O2, 0.9<=a<1.0, 0 The coating layer is coated on at least part of the surface of the core part, the coating layer comprises bismuth elements and titanium elements, and the ratio of the molar percentage content of the bismuth elements to the molar percentage content of the titanium elements is (0.1 to 2.0):1.

Description

Technical Field

[0001] This application relates to a positive electrode active material, a positive electrode sheet, a battery cell, a battery, and an electrical device. Background Technology

[0002] Battery cells are widely used due to their reliable performance, lack of pollution, and absence of memory effect. For example, with increasing emphasis on environmental protection and the growing popularity of new energy vehicles, the demand for power battery cells will experience explosive growth.

[0003] As battery cells are used in a wider range of applications, the requirements for their performance are becoming increasingly stringent. Positive electrode active materials are a crucial component of battery cells; however, the rapid capacity decay of these materials leads to short cycle life and storage life for the battery cells. Summary of the Invention

[0004] This application provides a positive electrode active material, a positive electrode sheet, a battery cell, a battery, and an electrical device. The cycle performance and storage performance of the battery cell described in this application can be improved.

[0005] In a first aspect, embodiments of this application propose a positive electrode active material, the positive electrode active material comprising a core and a coating layer, the core comprising a material with the molecular formula LiNi. a Co b The compound M(1-ab)O2 has 0.9 ≤ a < 1.0, 0 < b < 0.1, and a + b < 1.0, where M includes at least one of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, La, and Nb; a coating layer covers at least a portion of the surface of the core, the coating layer comprising bismuth and titanium, and the molar percentage of bismuth to the molar percentage of titanium is (0.1 to 2.0):1.

[0006] Therefore, in this embodiment, a layered transition metal oxide is used as the core, and a coating layer is applied to at least a portion of the outer surface of the core, forming a core-shell structure. The coating layer protects the core, reducing the risk of side reactions from direct contact between the layered transition metal oxide and the electrolyte, thus improving cycle life and storage life. Furthermore, the coating layer includes bismuth and titanium elements, and by controlling the molar percentage of bismuth to titanium to be (0.1 to 2.0):1, bismuth and titanium elements more readily form a perovskite structure, which is beneficial for lithium-ion insertion and extraction. During lithium-ion insertion and extraction, the coating layer structure is relatively stable with minimal volume change, reducing structural changes in the positive electrode active material and effectively improving the overall structural stability of the positive electrode active material, thereby enhancing its cycle life and storage life when applied to battery cells. The perovskite structure formed by the above materials has high ionic conductivity, which is beneficial for improving the rate performance of the positive electrode active material.

[0007] In some embodiments, the molar percentage of bismuth to the molar percentage of titanium is (0.1 to 1.0):1. A molar percentage of titanium that is the same as or even higher than that of bismuth is more conducive to the formation of perovskite structures, such as bismuth titanate.

[0008] In some embodiments, the coating layer includes at least one of bismuth titanate, lithium titanate, and lithium bismuthate; optionally, the coating layer includes bismuth titanate. The coating layer containing the above materials can improve cycle life and storage life, and also provide capacity to the positive electrode active material, thereby increasing the overall capacity of the positive electrode active material.

[0009] In some embodiments, 0.9 < a ​​< 0.98; alternatively, 0.92 ≤ a < 0.98. The relatively high molar amount of nickel can significantly improve the capacity of the layered transition metal oxide, and in combination with the above-mentioned coating layer, it can improve the overall structural stability of the positive electrode active material.

[0010] In some implementations, b ≥ 1-ab. The molar amount of cobalt (Co) is greater than that of element M, which is beneficial for further stabilizing the structure of layered transition metal oxides and can reduce the risk of cation mixing, thereby improving the cycling performance of the material; moreover, Co can participate in charge-discharge reactions in the operating voltage range of 2.8V to 4.25V, which is beneficial for improving capacity.

[0011] In some embodiments, the core comprises a material with the molecular formula LiNi. 0.91 Co 0.05 M 0.04 O2, LiNi 0.92 Co 0.04M 0.04 O2, LiNi 0.92 Co 0.05 M 0.03 O2, LiNi 0.92 Co 0.06 M 0.02 O2, LiNi 0.93 Co 0.03 M 0.02 O2 and LiNi 0.93 Co 0.025 M 0.025 At least one compound in O2.

[0012] In some embodiments, based on the total mass of the positive electrode active material, the mass percentage of the core is A%, the mass percentage of the coating layer is B%, and 99 ≤ A / B < 1000; alternatively, 99 ≤ A / B < 300. When the embodiments of this application satisfy the above range, the protective effect of the coating layer on the core can be improved, the risk of the core being corroded by the electrolyte can be reduced, and the energy density can be increased.

[0013] In some embodiments, 99 ≤ A < 100; and / or 0 < B ≤ 1. When the embodiments of this application satisfy the above ranges, the protective effect of the coating layer on the core can be improved, the risk of the core being corroded by the electrolyte can be reduced, and the energy density can be increased.

[0014] In some embodiments, the thickness of the coating layer is from 1 nm to 100 nm. When the thickness of the coating layer is within this range, it can provide good protection for the core, improve the overall structural stability of the positive electrode active material, and the coating layer does not occupy too much space, which is beneficial to improving energy density.

[0015] In some embodiments, the positive electrode active material satisfies at least one of the following conditions:

[0016] (1) The volume distribution particle sizes Dv10, Dv50 and Dv90 of the positive electrode active material satisfy the following: 0.5≤(Dv90-Dv10) / Dv50≤1.5; optionally, 0.8≤(Dv90-Dv10) / Dv50≤1.4;

[0017] (2) The volume distribution particle size Dv50 of the positive electrode active material satisfies: 2.0μm≤Dv50≤15μm; optionally, 3μm≤Dv50≤12μm;

[0018] (3) The specific surface area BET of the positive electrode active material satisfies 0.34m². 2 / g≤BET≤1.2m 2 / g; optionally, 0.5m 2 / g≤BET≤1.0m2 / g.

[0019] When the embodiments of this application satisfy the above-mentioned scope, the structure of the positive electrode active material can be made more stable, and the overall structural stability of the positive electrode active material is higher during cycling.

[0020] In some embodiments, the positive electrode active material comprises polycrystalline aggregate particles; optionally, the primary particle size D1 of the polycrystalline aggregate particles satisfies: 0.1 μm ≤ D1 ≤ 0.4 μm; and / or the volume distribution particle size Dv50 of the polycrystalline aggregate particles satisfies: 4.0 μm ≤ Dv50 ≤ 15.0 μm. When the volume distribution particle size Dv50 of the positive electrode active material is within the above range, its particle size is relatively large, but not excessively large, which is beneficial for capacity utilization and can improve its structural stability.

[0021] In some embodiments, the positive electrode active material comprises single-crystal particles or quasi-single-crystal particles. Optionally, the primary particle size D2 of the single-crystal particles or quasi-single-crystal particles satisfies: 0.7 μm ≤ D2 ≤ 2.0 μm; and / or the volume distribution particle size Dv50 of the single-crystal particles or quasi-single-crystal particles satisfies: 2.0 μm ≤ Dv50 ≤ 4.0 μm. When the volume distribution particle size Dv50 of the positive electrode active material is within the above range, its particle size is relatively large, but not excessively large, which is beneficial for capacity utilization and can improve its structural stability.

[0022] Secondly, this application also proposes 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 as described in any embodiment of the first aspect of this application.

[0023] Thirdly, this application also proposes a battery cell, which includes a positive electrode as described in any embodiment of the second aspect of this application.

[0024] Fourthly, this application also proposes a battery comprising a battery cell as described in any embodiment of the third aspect of this application.

[0025] Fifthly, this application also proposes an electrical device comprising a battery as described in any embodiment of the fourth aspect of this application. Attached Figure Description

[0026] 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.

[0027] Figure 1 This is a schematic diagram of one embodiment of the battery cell of this application.

[0028] Figure 2 yes Figure 1 An exploded view of the implementation method of the battery cell.

[0029] Figure 3 This is a schematic diagram of one embodiment of the battery module of this application.

[0030] Figure 4 This is a schematic diagram of one embodiment of the battery pack of this application.

[0031] Figure 5 yes Figure 4 An exploded view of an embodiment of the battery pack shown.

[0032] Figure 6 This is a schematic diagram of one embodiment of an electrical device that uses the battery cell of this application as a power source.

[0033] Figure 7 This is one of the SEM (Scanning Electron Microscopy) schematic diagrams of the positive electrode active material in Example A.

[0034] Figure 8 This is the second schematic diagram of the scanning electron microscope (SEM) of the positive electrode active material in Example A.

[0035] Figure 9 This is the X-ray diffraction (XRD) pattern of the positive electrode active material in Example A.

[0036] The accompanying drawings may not be drawn to scale.

[0037] The annotations in the attached figures are explained as follows:

[0038] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module;

[0039] 5. Battery cell; 51. Housing; 52. Electrode assembly;

[0040] 53. Cover plate;

[0041] 6. Electrical appliances. Detailed Implementation

[0042] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, positive electrode sheet, battery cell, battery, and power device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0043] 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.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0045] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0046] 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.

[0047] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0048] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0049] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The positive electrode includes a positive active material that can provide active ions, and the negative electrode includes a negative active material. The separator is located between the positive and negative electrodes to isolate them. Active ions, such as sodium ions and lithium ions, migrate between the positive and negative electrodes via the electrolyte, thereby enabling the charging and discharging of the battery cell.

[0050] The interface between the active material and the electrolyte is a solid-liquid interface, where side reactions are prone to occur, leading to the consumption or even destruction of the active material, which may shorten the cycle life of the battery cell. To improve the cycle life of battery cells, related technologies aim to add film-forming additives to the electrolyte, allowing these additives to participate in film-forming reactions on the surface of the active material, thereby protecting it. However, some film-forming additives have low solubility in the electrolyte, making it difficult to utilize them by simply adding them to the electrolyte, thus failing to effectively improve the cycle life of the battery cell.

[0051] In view of the above problems, the embodiments of this application add a metal salt to the negative electrode active material layer of the negative electrode sheet. During the cycle charging and discharging process of the battery cell, the metal salt can dissolve in the electrolyte to a certain extent and participate in the film-forming reaction on the surface of the active material to form an interface film on the surface of the active material, thereby playing a good protective role for the active material and improving the cycle life of the battery cell.

[0052] As a crucial component of battery cells, the performance of the positive electrode active material largely determines the overall performance of the battery cell. During the cyclic charging and discharging process of a battery cell, the positive electrode active material primarily provides the active ions (e.g., at least one of sodium ions and lithium ions) required for the repeated insertion and extraction between the positive and negative electrode lithium-ion compounds. Layered transition metal oxide materials possess advantages such as high energy density, high reversible capacity, and environmental friendliness, and are therefore widely used in the battery field. Layered transition metal oxides contain nickel, and because Ni... 2+ / Ni 3+ Ni 3+ / Ni 4+ The redox couple potential is low, with more Li at 4.2V. + The nickel content increases the energy released, thus storing more electricity; therefore, increasing the nickel content can effectively improve the material's capacity. However, increasing the nickel content will also increase the oxidation and depletion of lithium. + There is a risk that mixed storage can lead to a decrease in cycle life and storage life.

[0053] In view of the above-mentioned technical problems, this application proposes a positive electrode active material, which includes a core and a coating layer. The core includes a layered transition metal oxide material, and the coating layer includes bismuth and titanium. The coating layer can provide good protection for the core, and the coating layer has good structural stability during the cycle of the battery cell, thereby improving the overall structural stability of the positive electrode active material and enhancing the cycle life and storage life.

[0054] Positive electrode active material

[0055] In a first aspect, embodiments of this application propose a positive electrode active material, the positive electrode active material comprising a core and a coating layer, the core comprising a material with the molecular formula LiNi. a Co b M( 1-a-b The compound of O2, 0.9≤a<1.0, 0<b<0.1, and a+b<1.0, M includes at least one of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, La and Nb; the coating layer covers at least a portion of the surface of the core, the coating layer includes bismuth and titanium, and the molar percentage of bismuth to the molar percentage of titanium is (0.1 to 2.0):1.

[0056] The core includes molecules with the molecular formula LiNi a Co b M( 1-a-b Compounds of O2, which are layered transition metal oxides with high nickel content, 0.9≤a<1.0. When layered transition metal oxides are used in battery cells, volume changes may occur during the cyclic charging and discharging of the battery cells, leading to lattice collapse. The volume changes are more pronounced when the nickel content is high, which makes the material risky of pulverization.

[0057] To improve the performance of layered transition metal oxides, this application proposes a coating layer on their outer surface. The layered transition metal oxide serves as the core, and the coating layer covers at least a portion of the outer surface of the core, forming a core-shell structure. The coating layer protects the core, reducing the risk of side reactions from direct contact between the layered transition metal oxide and the electrolyte, thus improving cycle life and storage life. Furthermore, the coating layer includes bismuth and titanium. By controlling the molar percentage of bismuth to titanium to be (0.1 to 2.0):1, bismuth and titanium more readily form a perovskite structure, which is beneficial for lithium-ion insertion and extraction. During lithium-ion insertion and extraction, the coating layer structure remains relatively stable with minimal volume change, reducing structural changes in the positive electrode active material and effectively improving the overall structural stability of the positive electrode active material. This enhances the cycle life and storage life when the positive electrode active material is used in a battery cell. The perovskite structure formed by the above materials exhibits high ionic conductivity, which is beneficial for improving the rate performance of the positive electrode active material.

[0058] The coating layer in this application, by controlling the molar percentages of bismuth and titanium, can form perovskite materials, such as bismuth titanate, a bismuth-type perovskite. It may also form lithium titanate, lithium bismuthate, etc. The coating layer containing these materials improves cycle life and storage life, and also provides capacity to the positive electrode active material, thereby increasing the overall capacity of the positive electrode active material. Since bismuth titanate has better coating performance and is more conducive to improving the structural stability of the positive electrode active material, in some embodiments, the molar percentage of bismuth to the molar percentage of titanium is (0.1 to 1.0):1. A molar percentage of titanium that is the same as or even higher than that of bismuth is more conducive to forming perovskite structures such as bismuth titanate.

[0059] For example, the molar percentage ratio of bismuth to titanium can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 4 / 3:1, 1.35:1, 1.40:1, 1.45:1, 1.50:1, 1.55:1, 1.60:1, 1.65:1, 1.70:1, 1.75:1, 1.80:1, 1.85:1, 1.90:1, 1.95:1, 2.00:1, or a range of any two of the above values.

[0060] In the embodiments of this application, the material and content of each element in the coating layer are as known in the art and can be detected using equipment and methods known in the art. For example, referring to EPA6010D-2014, inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400) is used for testing. First, 0.4g of the positive electrode active material is weighed and 10ml (50% concentration) of aqua regia is added. Then, it is placed on a plate at 180℃ for 30min. After digestion on the plate, the volume is adjusted to 100mL, and quantitative testing is performed using the standard curve method.

[0061] The embodiments of this application, through further selection of the core material, enable the core material and the coating layer to play a better synergistic role, thereby improving the cycle life and storage life of the battery cell.

[0062] In some embodiments, 0.9 < a ​​< 0.98; alternatively, 0.92 ≤ a < 0.98. The relatively high molar amount of nickel can significantly improve the capacity of the layered transition metal oxide, and in combination with the above-mentioned coating layer, it can improve the overall structural stability of the positive electrode active material.

[0063] For example, 'a' can be 0.9, 0.905, 0.91, 0.915, 0.92, 0.925, 0.93, 0.935, 0.94, 0.945, 0.95, 0.955, 0.96, 0.965, 0.97, 0.975, 0.98, or a range of any two of the above values.

[0064] In some implementations, b ≥ 1-ab. The molar amount of cobalt (Co) is greater than that of element M, which is beneficial for further stabilizing the structure of layered transition metal oxides and can reduce the risk of cation mixing, thereby improving the cycling performance of the material; moreover, Co can participate in charge-discharge reactions in the operating voltage range of 2.8V to 4.25V, which is beneficial for improving capacity.

[0065] In some implementations, M includes at least one of Mn, Al, XX, XX, and XX.

[0066] For example, the core includes a molecular formula of LiNi 0.91 Co 0.05 M 0.04 O2, LiNi 0.92 Co 0.04 M 0.04 O2, LiNi 0.92 Co 0.05 M 0.03 O2, LiNi 0.92 Co 0.06 M 0.02 O2, LiNi 0.93 Co 0.03 M 0.02 O2 and LiNi 0.93 Co 0.025 M 0.025 At least one compound in O2.

[0067] The coating layer possesses ion-conducting properties, but may lack electrochemical activity. Its addition amount has a certain impact on coating performance. For example, if the coating layer addition amount is too small, the protective effect on the core is poor. As the coating layer addition amount increases, the protective effect on the core is enhanced. However, if the coating layer addition amount is too large, it may occupy too much space because it lacks electrochemical activity. To improve the protective effect of the coating layer on the core, reduce the risk of core corrosion by the electrolyte, and increase energy density, in some embodiments, based on the total mass of the positive electrode active material, the mass percentage of the core is A%, the mass percentage of the coating layer is B%, and 99 ≤ A / B < 1000. Optionally, 99 ≤ A / B < 300.

[0068] For example, the ratio of the mass percentage of the core to the mass percentage of the coating layer can be 99, 99.01, 99.05, 99.1, 99.15, 99.2, 99.25, 99.3, 99.35, 99.4, 99.45, 99.5, 99.55, 99.6, 99.65, 99.7, 99.75, 99.8, 99.85, 99.9, 99.95, 100, 200, 300, 400, 500, 600, 700, 800, 900, 950, 990, or a range of any two of the above values.

[0069] In some implementations, 99 ≤ A < 100. Exemplarily, the mass percentage of the core can be 99%, 99.01%, 99.05%, 99.1%, 99.15%, 99.2%, 99.25%, 99.3%, 99.35%, 99.4%, 99.45%, 99.5%, 99.55%, 99.6%, 99.65%, 99.7%, 99.75%, 99.8%, 99.85%, 99.9%, 99.95%, or a range of any two of the above values.

[0070] In some implementations, 0 < B ≤ 1. Exemplarily, the mass percentage content of the coating layer can be 0.01%, 0.02%, 0.05%, 0.08%, 0.10%, 0.12%, 0.15%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45%, etc. 0.48%, 0.50%, 0.52%, 0.55%, 0.58%, 0.60%, 0.62%, 0.65%, 0.68%, 0.70%, 0.72%, 0.75%, 0.80%, 0.85%, 0.90%, 0.92%, 0.95%, 0.98%, 0.99%, 1%, or a range consisting of any two of the above values.

[0071] In some embodiments, the thickness of the coating layer is between 1 nm and 100 nm. When the thickness of the coating layer is within this range, it can provide good protection for the core, improve the overall structural stability of the positive electrode active material, and the coating layer does not occupy too much space, which is beneficial to improving energy density.

[0072] In the embodiments of this application, the thickness of the coating layer has a meaning known in the art and can be detected using commonly used equipment and methods in the art, such as ion polishing cross-sectional morphology analysis (CP) of the sample.

[0073] To further improve cycle life and storage life, the embodiments of this application select relevant parameters such as particle size of the positive electrode active material, which can make the structure of the positive electrode active material more stable and the overall structural stability of the positive electrode active material is higher during cycling.

[0074] In some embodiments, the volume distribution particle sizes Dv10, Dv50, and Dv90 of the positive electrode active material satisfy the following: 0.5 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.5; optionally, 0.8 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.4. (Dv90 - Dv10) / Dv50 can be represented as the particle size distribution span, which can be understood as the width of the particle size distribution. When the span is within the above range, the particle size distribution of the positive electrode active material is relatively concentrated. During the coating of the positive electrode slurry to form the positive electrode film layer, the positive electrode slurry is more stable and less prone to gelation. Furthermore, during the compaction process of forming the positive electrode film layer, the structure of the positive electrode active material is more stable and less prone to crushing. Moreover, the positive electrode active material is less likely to fail during cycling.

[0075] For example, span can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50 or a range of any two of the above values.

[0076] In some embodiments, the volumetric particle size Dv50 of the positive electrode active material satisfies: 2.5 μm ≤ Dv50 ≤ 15 μm; optionally, 3 μm ≤ Dv50 ≤ 12 μm. When the volumetric particle size Dv50 of the positive electrode active material is within the above range, the structural stability of the positive electrode active material during cycling is improved, and the positive electrode active material is less prone to cracking. This reduces the risk of battery cell failure due to corrosion at the boundaries of the positive electrode active material caused by cracking, leading to the formation of a rock salt phase. Furthermore, it reduces the risk of accelerated corrosion caused by excessive contact between the positive electrode active material and the electrolyte.

[0077] In the embodiments of this application, Dv10, Dv50, and Dv90 of the particles have well-known meanings in the art. For example, Dv10 refers to the particle size corresponding to 10% of the volume distribution, Dv50 refers to the particle size corresponding to 50% of the volume distribution, and Dv90 refers to the particle size corresponding to 90% of the volume distribution. The above particle sizes can all be detected using commonly used equipment and methods in the art. For example, according to the test standard GB / T 19077-2016, a certain amount of positive electrode active material sample is taken, and the particle size distribution of the positive electrode active material is measured by a Mastersizer 2000E laser particle size analyzer to obtain Dv10, Dv90, and Dv50, and (Dv90-Dv10) / Dv50 is calculated.

[0078] For example, the volume distribution particle size Dv50 of the positive electrode active material can be 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10.0 μm, 10.5 μm, 11.0 μm, 11.5 μm, 12.0 μm, 12.5 μm, 13.0 μm, 13.5 μm, 14.0 μm, 14.5 μm, 15 μm, or a range of any two of the above values.

[0079] In some embodiments, the specific surface area (BET) of the positive electrode active material satisfies 0.34 m². 2 / g≤BET≤1.2m 2 / g; optionally, 0.5m 2 / g≤BET≤1.0m 2 / g. When the specific surface area of ​​the positive electrode active material is within the above range, the positive electrode active material can expose a relatively large active specific surface area, which is beneficial to the capacity of the positive electrode active material.

[0080] For example, the specific surface area (BET) of the positive electrode active material can be 0.34 m². 2 / g, 0.35m 2 / g, 0.38m 2 / g, 0.40m 2 / g, 0.42m 2 / g, 0.45m 2 / g, 0.50m 2 / g, 0.55m 2 / g, 0.60m 2 / g, 0.65m 2 / g, 0.70m 2 / g, 0.75m 2 / g, 0.80m 2 / g, 0.85m 2 / g, 0.90m 2 / g, 0.95m 2 / g, 1.00m 2 / g, 1.05m 2 / g, 1.10m 2 / g, 1.15m 2 / g, 1.20m 2 / g or a range consisting of any two of the above values.

[0081] In this application, the specific surface area (BET) of the positive electrode active material is a well-known concept in the art and can be detected using commonly used equipment and methods. According to the testing standard GB / T 19587-2017, the specific surface area is calculated using the BET (Brunauer-Emmett-Teller) method. A certain amount of positive electrode active material sample is taken, and the specific surface area is tested using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0082] To further improve cycle life and storage life, the embodiments of this application improve the structural stability of the positive electrode active material by selecting relevant parameters such as particle morphology, thereby making the positive electrode active material have higher structural stability during cycling.

[0083] In some embodiments, the positive electrode active material includes polycrystalline aggregate particles. In order to improve the structural stability of the positive electrode active material, the volume distribution particle size Dv50 of the positive electrode active material is optionally 4.0 μm to 15.0 μm. When the volume distribution particle size Dv50 of the positive electrode active material is within the above range, its particle size is relatively large, but not too large, which is beneficial to the capacity utilization and can improve its structural stability.

[0084] For example, the volume distribution particle size Dv50 of the positive electrode active material can be 4.0 μm, 4.5 μm, 5.0 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10.0 μm, 10.5 μm, 11.0 μm, 11.5 μm, 12.0 μm, 12.5 μm, 13.0 μm, 13.5 μm, 14.0 μm, 14.5 μm, 15 μm, or a range of any two of the above values.

[0085] Optionally, the primary particle size D1 of the polycrystalline agglomerates satisfies: 0.1 μm ≤ D1 ≤ 0.4 μm. A relatively small primary particle size D1 is beneficial for agglomeration into spherical or near-spherical positive electrode active materials, thereby improving the structural stability of the positive electrode active material.

[0086] For example, the primary particle size D1 of the polycrystalline aggregate particles can be 0.20 μm, 0.21 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.27 μm, 0.28 μm, 0.29 μm, 0.30 μm, 0.31 μm, 0.32 μm, 0.33 μm, 0.34 μm, 0.35 μm, 0.36 μm, 0.37 μm, 0.38 μm, 0.39 μm, 0.40 μm, or a range of any two of the above values.

[0087] In some embodiments, the positive electrode active material includes single crystal particles or quasi-single crystal particles. The particle size of the single crystal particles or quasi-single crystal particles is relatively small, and the structural stability during cycling is improved. To further improve the structural stability of the positive electrode active material, the volume distribution particle size Dv50 of the positive electrode active material may optionally satisfy: 2.0 μm ≤ Dv50 ≤ 4.0 μm.

[0088] For example, the volume distribution particle size Dv50 of the positive electrode active material can be 2.0 μm, 2.2 μm, 2.3 μm, 2.5 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm or any range of two of the above values.

[0089] Optionally, the primary particle size D2 of the single-crystal particles or quasi-single-crystal particles satisfies: 0.7 μm ≤ D2 ≤ 2.0 μm. A relatively small primary particle size D2 of single-crystal particles or quasi-single-crystal particles is beneficial for improving the structural stability of the cathode active material.

[0090] For example, the primary particle size D2 of a single crystal particle or a quasi-single crystal particle can be 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, or a range of any two of the above values.

[0091] In this embodiment, the primary particle size D1 of the positive electrode active material has a well-known meaning in the art and can be detected using commonly used equipment and methods in the art. For example, the sample can be detected by scanning electron microscopy (SEM), and the particle size of the sample can be obtained intuitively based on the obtained SEM image. Multiple samples can be detected by SEM, and the average particle size can be calculated by averaging the multiple measured particle sizes to obtain the average particle size.

[0092] Methods for preparing positive electrode active materials

[0093] Secondly, this application proposes a method for preparing positive electrode active materials, which can be prepared by co-precipitation.

[0094] The method includes:

[0095] Step S100: Weigh the lithium source, nickel source, cobalt source and M source according to the target composition and their corresponding stoichiometric ratios.

[0096] Step S200: The lithium source, nickel source, cobalt source and M source are mixed evenly to obtain a raw material mixture;

[0097] Step S300: The above raw material mixture is successively ground, calcined, cooled and crushed to obtain a layered transition metal oxide intermediate;

[0098] In step S400, the layered transition metal oxide intermediate is mixed with the coating material, and then calcined and cooled to obtain the positive electrode active material.

[0099] In step S100, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium oxalate.

[0100] In some embodiments, the nickel source includes at least one of nickel sulfate, nickel nitrate, or nickel chloride.

[0101] In some embodiments, the cobalt source includes at least one of cobalt sulfate, cobalt nitrate, or cobalt chloride.

[0102] In some embodiments, the M source includes at least one of sulfates, nitrates, chlorides, oxidants, and carbonates containing M. The M source includes at least one of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, La, and Nb sources.

[0103] Nickel source, cobalt source and M source can be derived from the same material or from different materials.

[0104] Before step S100, the nickel source, cobalt source, and M source can be mixed in solution, and an appropriate precipitant can be added to the solution to co-precipitate the components that have been mixed evenly in the solution according to their stoichiometric ratio, forming a raw material intermediate. In step S100, the raw material intermediate and lithium source are mixed and then ground, calcined, cooled, and crushed to obtain a layered transition metal oxide intermediate.

[0105] In step S200, the mixing time for each raw material can be from 0.5h to 2h.

[0106] In step S300, the raw material mixture powder can be calcined in a pure oxygen atmosphere. Multiple calcinations can be performed: the first calcination temperature is 300℃ to 650℃, and the calcination time is 5 to 20 hours; the second calcination temperature is 600℃ to 900℃, and the calcination time is 5 to 20 hours. These two calcinations can perform pre-oxidation, eliminating internal defects in the material. Alternatively, a single calcination can be performed, for example, calcining at 600℃ to 900℃ for 6 to 30 hours.

[0107] In step S400, the coating material includes a bismuth source and a titanium source. Optionally, the bismuth source may include at least one of bismuth oxide, bismuth carbonate, and bismuth nitrate; optionally, the titanium source may include at least one of titanium oxide, titanium carbonate, and titanium nitrate.

[0108] In some embodiments, the calcination temperature of the layered transition metal oxide intermediate and the coating material can be lower than the calcination temperature of the raw material mixture powder. In step S400, the calcination temperature after mixing the layered transition metal oxide intermediate and the coating material can be from 400°C to 750°C.

[0109] battery cell

[0110] Thirdly, this application also provides a battery cell.

[0111] A battery cell, also known as a rechargeable battery or accumulator, is a battery that can be recharged after discharge to activate its active materials and continue to be used. Typically, a battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is positioned between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0112] 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 surface of the positive current collector. The positive electrode film layer includes a positive electrode active material prepared by the method described in any embodiment of the first aspect of this application or in any embodiment of the second aspect of this application. Therefore, the battery cell of this application can improve cycle life and storage life.

[0113] [Positive electrode plate]

[0114] In some embodiments, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0115] In some embodiments, the positive electrode film layer may optionally include a positive electrode conductive agent. This application does not impose any particular limitation on the type of positive electrode conductive agent; as an example, the positive electrode conductive agent includes at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent is ≤5 wt% based on the total weight of the positive electrode film layer.

[0116] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose any particular limitation on the type of positive electrode binder. As an example, the positive electrode binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, the mass percentage of the positive electrode binder is ≤5 wt% based on the total weight of the positive electrode film layer.

[0117] In some embodiments, the positive current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymeric material substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0118] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing a composite positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring until homogeneous. The solvent may be N-methylpyrrolidone (NMP), but is not limited to this.

[0119] [Negative electrode plate]

[0120] In some implementations, the battery cell also includes a negative electrode.

[0121] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0122] The negative electrode active material may be any negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy materials.

[0123] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent; as an example, the negative electrode conductive agent may include at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent is ≤5 wt% based on the total weight of the negative electrode film layer.

[0124] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), 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). In some embodiments, the mass percentage of the negative electrode binder is ≤5 wt% based on the total weight of the negative electrode film layer.

[0125] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass percentage of the other additives is ≤2 wt% based on the total weight of the negative electrode film.

[0126] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0127] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0128] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0129] Electrolyte

[0130] In some implementations, the battery cell also includes an electrolyte.

[0131] During the charging and discharging process of a single battery cell, active ions repeatedly insert and extract between the positive and negative electrode plates, while the electrolyte acts as a conductor for these active ions. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to actual needs.

[0132] The electrolyte comprises an electrolyte salt and a solvent. The types of electrolyte salt and solvent are not specifically limited and can be selected according to actual needs.

[0133] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0134] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ester carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0135] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0136] [Isolation membrane]

[0137] In some implementations, the battery cell also includes a separator.

[0138] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0139] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0140] In some embodiments, the positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process and / or a stacking process.

[0141] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0142] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a soft package, such as a pouch. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0143] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 1 The example shown is a square-structured battery cell 5.

[0144] In some implementations, such as Figure 2As shown, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process and / or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be adjusted according to requirements.

[0145] The method for preparing the battery cell of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0146] In some embodiments of this application, the battery cells according to this application can be assembled into a battery module. The number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0147] Figure 3 This is a schematic diagram of battery module 4 as an example. Figure 3 As shown, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0148] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0149] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0150] Figure 4 and Figure 5 This is a schematic diagram of battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0151] Electrical appliances

[0152] A fourth aspect of this application provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack described in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0153] The electrical device can be configured to use individual battery cells, battery modules, or battery packs according to its usage requirements.

[0154] Figure 6 This is a schematic diagram of an example electrical device 6. This electrical device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device 6, a battery pack or battery module can be used.

[0155] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0156] Example

[0157] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0158] Example A: Preparation of Positive Electrode Active Material

[0159] The precursor P0 for high-nickel ternary materials was prepared by co-precipitation.

[0160] A 2 mol / L solution (using water) was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 9.2:0.4:0.4. The solution was placed in a reaction vessel, and the particle size and micromorphology were adjusted by controlling the reaction time (12-24 h), reaction temperature (40-70 °C), pH (11-13), and ammonia concentration (0.2-0.6 mol / L). The final prepared P0(Ni) 0.92Co 0.04 Mn 0.04 (OH)2), with a volume distribution particle size Dv50 of 10 μm and a span of approximately 1.25.

[0161] Lithium hydroxide and PO were mixed evenly at a molar ratio of 1.03:1 and placed in a box furnace, where they were sintered at 800°C for 15 hours to obtain LiNi core. 0.92 Co 0.04 Mn 0.04 O2; after cooling and pulverizing, coating material (1200ppm Bi2O3 + 900ppm TiO2) is added, and then the mixture is placed in a high-speed mixer and mixed at 200r / min for 2h. The mixture is then sintered at 650℃ for 13h in an oxygen atmosphere to obtain the positive electrode active material.

[0162] Examples B-1 to B-4

[0163] The positive electrode active material was prepared using a method similar to that of Example A. The difference from Example A is that the amount of coating material added in Examples B-1 to B-4 was adjusted.

[0164] Examples C-1 to C-5

[0165] The positive electrode active material was prepared using a method similar to that in Example A. The difference from Example A is that the ratio of bismuth source and titanium source in the coating material was adjusted in Examples C-1 to C-5.

[0166] Examples D-1 to D-3

[0167] The positive electrode active material was prepared using a method similar to that of Example A. The difference from Example A is that the material type of the core was adjusted in Examples D-1 to D-3.

[0168] Examples F-1 to F-5

[0169] The positive electrode active material was prepared using a method similar to that of Example A. The difference from Example A is that the sintering temperature and sintering time of the preparation process were adjusted in Examples F-1 to F-5 to regulate at least one of the particle size and morphology.

[0170] Example F-1

[0171] The preparation process conditions for the positive electrode active material were adjusted, specifically as follows:

[0172] The precursor P0 for high-nickel ternary materials was prepared by co-precipitation.

[0173] A 2 mol / L solution (using water) was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 9.2:0.4:0.4. The solution was placed in a reaction vessel, and the particle size and micromorphology were adjusted by controlling the reaction time (12-24 h), reaction temperature (40-70 °C), pH (11-13), and ammonia concentration (0.2-0.6 mol / L). The final prepared P0(Ni) 0.92 Co 0.04 Mn 0.04 (OH)2), with a volume distribution particle size Dv50 of 8 μm and a span of approximately 1.3.

[0174] Lithium hydroxide and PO were mixed uniformly at a molar ratio of 1.03:1 and placed in a box furnace, where they were sintered at 790°C for 15 hours to obtain LiNi core. 0.92 Co 0.04 Mn 0.04 O2; after cooling and pulverizing, coating material (1200ppm Bi2O3 + 900ppm TiO2) is added, and then the mixture is placed in a high-speed mixer and mixed at 200r / min for 2h. The mixture is then sintered at 650℃ for 13h in an oxygen atmosphere to obtain the positive electrode active material.

[0175] Example F-2

[0176] The preparation process conditions for the positive electrode active material were adjusted, specifically as follows:

[0177] The precursor P0 for high-nickel ternary materials was prepared by co-precipitation.

[0178] A 2 mol / L solution (using water) was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 9.2:0.4:0.4. The solution was placed in a reaction vessel, and the particle size and micromorphology were adjusted by controlling the reaction time (12-24 h), reaction temperature (40-70 °C), pH (11-13), and ammonia concentration (0.2-0.6 mol / L). The final prepared P0(Ni) 0.92 Co 0.04 Mn 0.04 (OH)2), with a volume distribution particle size Dv50 of 9.2 μm and a span of approximately 1.25.

[0179] Lithium hydroxide and PO were mixed evenly at a molar ratio of 1.03:1 and placed in a box furnace, where they were sintered at 800°C for 15 hours to obtain LiNi core. 0.92 Co 0.04 Mn 0.04 O2; after cooling and pulverizing, coating material (1200ppm Bi2O3 + 900ppm TiO2) is added, and then the mixture is placed in a high-speed mixer and mixed at 200r / min for 2h. The mixture is then sintered at 650℃ for 13h in an oxygen atmosphere to obtain the positive electrode active material.

[0180] Example F-3

[0181] The preparation process conditions for the positive electrode active material were adjusted, specifically as follows:

[0182] The precursor P0 for high-nickel ternary materials was prepared by co-precipitation.

[0183] A 2 mol / L solution (using water) was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 9.2:0.4:0.4. The solution was placed in a reaction vessel, and the particle size and micromorphology were adjusted by controlling the reaction time (12-24 h), reaction temperature (40-70 °C), pH (11-13), and ammonia concentration (0.2-0.6 mol / L). The final prepared P0(Ni) 0.92 Co 0.04 Mn 0.04 (OH)2), with a volume distribution particle size Dv50 of 9.8 μm and a span of approximately 1.33.

[0184] Lithium hydroxide and PO were mixed evenly at a molar ratio of 1.03:1 and placed in a box furnace, where they were sintered at 800°C for 15 hours to obtain LiNi core. 0.92 Co 0.04 Mn 0.04 O2; after cooling and pulverizing, coating material (1200ppm Bi2O3 + 900ppm TiO2) is added, and then the mixture is placed in a high-speed mixer and mixed at 200r / min for 2h. The mixture is then sintered at 650℃ for 13h in an oxygen atmosphere to obtain the positive electrode active material.

[0185] Example F-4

[0186] The preparation process conditions for the positive electrode active material were adjusted, specifically as follows:

[0187] The precursor P0 for high-nickel ternary materials was prepared by co-precipitation.

[0188] A 2 mol / L solution (using water) was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 9.2:0.4:0.4. The solution was placed in a reaction vessel, and the particle size and micromorphology were adjusted by controlling the reaction time (12-24 h), reaction temperature (40-70 °C), pH (11-13), and ammonia concentration (0.2-0.6 mol / L). The final prepared P0(Ni) 0.92 Co 0.04 Mn 0.04 (OH)2), with a volume distribution particle size Dv50 of 16 μm and a span of approximately 1.2.

[0189] Lithium hydroxide and PO were mixed uniformly at a molar ratio of 1.03:1 and placed in a box furnace, where they were sintered at 820°C for 15 hours to obtain LiNi core. 0.92 Co 0.04 Mn 0.04 O2; after cooling and pulverizing, coating material (1200ppm Bi2O3 + 900ppm TiO2) is added, and then the mixture is placed in a high-speed mixer and mixed at 200r / min for 2h. The mixture is then sintered at 650℃ for 13h in an oxygen atmosphere to obtain the positive electrode active material.

[0190] Example F-5

[0191] The preparation process conditions for the positive electrode active material were adjusted, specifically as follows:

[0192] The precursor P0 for high-nickel ternary materials was prepared by co-precipitation.

[0193] A 2 mol / L solution (using water) was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 9.2:0.4:0.4. The solution was placed in a reaction vessel, and the particle size and micromorphology were adjusted by controlling the reaction time (12-24 h), reaction temperature (40-70 °C), pH (11-13), and ammonia concentration (0.2-0.6 mol / L). The final prepared P0(Ni) 0.92 Co 0.04 Mn 0.04 (OH)2), with a volume distribution particle size Dv50 of 3.8 μm (similar to single crystal particles) and a span of approximately 1.4.

[0194] Lithium hydroxide and PO were mixed evenly at a molar ratio of 1.03:1 and placed in a box furnace, where they were sintered at 840℃ for 15 h to obtain LiNi core. 0.92 Co 0.04 Mn 0.04 O2; after cooling and pulverizing, coating material (1200ppm Bi2O3 + 900ppm TiO2) is added, and then the mixture is placed in a high-speed mixer and mixed at 200r / min for 2h. The mixture is then sintered at 650℃ for 13h in an oxygen atmosphere to obtain the positive electrode active material.

[0195] Comparative Example M

[0196] The precursor P0 for high-nickel ternary materials was prepared by co-precipitation.

[0197] A 2 mol / L solution (using water) was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 9.2:0.4:0.4. The solution was placed in a reaction vessel, and the particle size and micromorphology were adjusted by controlling the reaction time (12-24 h), reaction temperature (40-70 °C), pH (11-13), and ammonia concentration (0.2-0.6 mol / L). The final prepared P0(Ni) 0.92 Co 0.04 Mn 0.04 (OH)2), with a volume distribution particle size Dv50 of 10 μm and a span of approximately 1.25.

[0198] Lithium hydroxide and PO were mixed evenly at a molar ratio of 1.03:1 and placed in a box furnace. The mixture was sintered at 800℃ for 15 hours. After cooling and pulverizing, the core LiNi was obtained. 0.92 Co 0.04 Mn 0.04 O2.

[0199] Comparative Example N

[0200] The precursor PO of high-nickel ternary materials was prepared by co-precipitation. A 2 mol / L solution (using water) was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 89:11:10. The solution was placed in a reaction vessel, and the particle size and micromorphology were adjusted by controlling the reaction time (12-24 h), reaction temperature (40-70 °C), pH (11-13), and ammonia concentration (0.2 mol / L-0.6 mol / L). The final PO(Ni) precursor was obtained. 0.89 Co 0.10 Mn 0.1 (OH)2), with a volume distribution particle size Dv50 of 10 μm and a span of approximately 1.25.

[0201] Lithium hydroxide and PO were mixed evenly at a molar ratio of 1.03:1 and placed in a box furnace, where they were sintered at 850°C for 15 hours to obtain LiNi core. 0.89 Co 0.10 Mn 0.1 O2; after cooling and pulverizing, coating material (1200ppm Bi2O3 + 900ppm TiO2) is added, and then the mixture is placed in a high-speed mixer and mixed at 200r / min for 2h. The mixture is then sintered at 650℃ for 13h in an oxygen atmosphere to obtain the positive electrode active material.

[0202] Comparative example P

[0203] The precursor P0 for high-nickel ternary materials was prepared by co-precipitation.

[0204] A 2 mol / L solution (using water) was prepared by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 9.2:0.4:0.4. The solution was placed in a reaction vessel, and the particle size and micromorphology were adjusted by controlling the reaction time (12-24 h), reaction temperature (40-70 °C), pH (11-13), and ammonia concentration (0.2-0.6 mol / L). The final prepared P0(Ni) 0.92 Co 0.04 Mn 0.04 (OH)2), with a volume distribution particle size Dv50 of 10 μm and a span of approximately 1.25.

[0205] Lithium hydroxide and PO were mixed evenly at a molar ratio of 1.03:1 and placed in a box furnace, where they were sintered at 800°C for 15 hours to obtain LiNi core. 0.92 Co 0.04 Mn 0.04 O2; after cooling and pulverizing, 2000ppm of coating material (Bi2O3+TiO2, where the molar ratio of Bi to Ti is 0.08:1) is added, and then the mixture is placed in a high-speed mixer and mixed at 200r / min for 2h. The mixture is then sintered at 650℃ for 13h in an oxygen atmosphere to obtain the positive electrode active material.

[0206] Example 1: Preparation of Lithium-ion Batteries

[0207] 1. Preparation of positive electrode sheet

[0208] Aluminum foil with a thickness of 12μm was used as the positive electrode current collector.

[0209] The positive electrode active material prepared in Example A, conductive carbon black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were mixed evenly in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 96:2:2 to obtain a positive electrode slurry. The positive electrode slurry was coated onto a positive electrode current collector aluminum foil, and the positive electrode sheet was obtained through processes such as drying, cold pressing, slitting, and cutting.

[0210] 2. Preparation of negative electrode sheet

[0211] A copper foil with a thickness of 8μm was used as the negative electrode current collector.

[0212] Artificial graphite (as the negative electrode active material), conductive carbon black (as a conductive agent), and styrene-butadiene rubber (SBR) (as a binder) were uniformly mixed in deionized water to prepare a negative electrode slurry. The mass ratio of artificial graphite, conductive carbon black, and SBR in the solid components of the negative electrode slurry was 92:4:4. The negative electrode slurry was coated onto a copper foil current collector and dried at 85°C. After cold pressing, a negative electrode sheet containing a layer of negative electrode active material was obtained.

[0213] 3. Preparation of electrolyte

[0214] In an environment with a water content of less than 10 ppm, the organic solvents ethylene carbonate EC and diethyl carbonate DEC are mixed at a volume ratio of 3:7 to obtain the electrolyte solvent. Then, lithium hexafluorophosphate is mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0215] 4. Preparation of lithium-ion batteries

[0216] The positive electrode sheet, polyethylene (PE) separator, and negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0217] Other embodiments and comparative examples used a similar method to Example 1 to prepare lithium-ion batteries, except that some parameters were adjusted, as follows:

[0218] Comparative Example 1 uses the positive electrode active material of Comparative Example M.

[0219] Comparative Example 2 uses the positive electrode active material of Comparative Example N.

[0220] Comparative Example 3 uses the positive electrode active material of Comparative Example P.

[0221] Example 2-1 uses the positive electrode active material of Example B-1.

[0222] Example 2-2 uses the positive electrode active material of Example B-2.

[0223] Examples 2-3 use the positive electrode active material of Example B-3.

[0224] Examples 2-4 use the positive electrode active material of Example B-4.

[0225] Example 3-1 uses the positive electrode active material of Example C-1.

[0226] Example 3-2 uses the positive electrode active material of Example C-2.

[0227] Example 3-3 uses the positive electrode active material of Example C-3.

[0228] Examples 3-4 use the positive electrode active material of Example C-4.

[0229] Examples 3-5 use the positive electrode active material of Example C-5.

[0230] Example 4-1 uses the positive electrode active material of Example D-1.

[0231] Example 4-2 uses the positive electrode active material of Example D-2.

[0232] Example 4-3 uses the positive electrode active material of Example D-3.

[0233] Example 5-1 uses the positive electrode active material of Example F-1.

[0234] Example 5-2 uses the positive electrode active material of Example F-2.

[0235] Example 5-3 uses the positive electrode active material of Example F-3.

[0236] Examples 5-4 use the positive electrode active material of Example F-4.

[0237] Example 5-5 uses the positive electrode active material of Example F-5.

[0238] The relevant parameters for the embodiments and comparative examples are shown in Table 1.

[0239] Test section

[0240] 1. Cycle life test of lithium-ion batteries

[0241] At 25°C, the lithium-ion batteries prepared in each embodiment and comparative example were charged at a constant current rate of 0.5C to the charging cutoff voltage of 4.25V, then charged at a constant voltage until the current ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to the discharge cutoff voltage of 2V, allowed to stand for 5 minutes. This constitutes one charge-discharge cycle. The batteries were subjected to cyclic charge-discharge tests according to this method until the battery capacity decreased to 80%. The number of cycles at this point is the cycle life of the battery at 25°C.

[0242] 2. Storage life test of lithium-ion batteries

[0243] At 45°C, the capacitor is charged to 4.25V with a constant current of 1C, then charged to 0.05C with a constant voltage of 4.25V until the current drops to 0.05C, and then discharged to 2.8V with a constant current of 1C to obtain the first-cycle discharge specific capacity (Cd1). The capacitor is then charged to 4.25V with a constant current of 1C, then charged to 0.05C with a constant voltage of 4.25V until the current drops to 0.05C, and kept fully charged for 15 days. Then it is discharged to 2.8V with a constant current of 1C to obtain the discharge specific capacity after 15 days (Cd15). The storage retention rate after 15 days is obtained by (Cd15) / (Cd1).

[0244] Test Results

[0245] The test results are shown in Table 1.

[0246] Table 1

[0247]

[0248] In Table 1, the mass content A% refers to the mass percentage of the core relative to the total mass of the positive electrode active material.

[0249] The mass content B% refers to the percentage of the coating layer by mass relative to the total mass of the positive electrode active material.

[0250] As shown in Table 1, the positive electrode active material in Comparative Example 1 is the high-nickel ternary material LiNi. 0.92 Co 0.04 Mn 0.04 O2 exhibits poor structural stability; compared to Comparative Example 1, Comparative Example 3 shows better performance in the high-nickel ternary material LiNi. 0.92 Co 0.04 Mn 0.04 The surface of O2 is coated with a layer in which the molar ratio of Bi to Ti is 0.08:1. The molar amount of Bi is relatively low, making it difficult for Bi to form a perovskite structure. The surface layer can only form a fast ion conductor of lithium titanate, which has a weak effect on improving the structural stability of high-nickel ternary materials.

[0251] The ternary material of the positive electrode active material in Comparative Example 2 has a lower nickel content (LiNi). 0.89 Co 0.10 Mn 0.1 O2) has a relatively low overall capacity, but its lifespan is better than that of 9-series ternary materials. Although its lifespan can be further improved by coating, the improvement is not significant because its structure is more stable than that of high-nickel materials.

[0252] The embodiments of this application, by setting a coating layer on the surface of the high-nickel ternary material, can protect the core, reduce the risk of side reactions caused by direct contact between the layered transition metal oxides of the core and the electrolyte, and thus improve cycle life and storage life. Furthermore, the coating layer includes bismuth and titanium elements, and by controlling the molar percentage of bismuth to titanium to be (0.1 to 2.0):1, bismuth and titanium elements are more likely to form a perovskite structure, which is beneficial for the insertion or extraction of lithium ions into or out of the perovskite structure. During the process of lithium ion insertion or extraction, the structure of the coating layer is relatively stable, and the volume change is small, reducing the structural changes of the positive electrode active material. This can effectively improve the overall structural stability of the positive electrode active material and enhance the cycle life and storage life when the positive electrode active material is applied to a battery cell.

[0253] Figure 7 and Figure 8 A schematic diagram of the positive electrode active material of Example A is shown. Figure 7 and Figure 8This is a SEM image of the positive electrode active material, showing that the core surface is coated with a coating layer.

[0254] Figure 9 The XRD pattern of the positive electrode active material shows that the sharp peaks indicate good crystallinity. The ratio of the (003) and (104) peaks is above 4.9, and the (108) and (110) peaks are well split. All of this indicates that the coating layer has not destroyed the layered structure of the material.

[0255] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A positive electrode active material, comprising: a core comprising a compound of formula LiNi a Co b M( 1-a-b )O2, 0.9≤a<1.0, 0 M comprises at least one of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, La, and Nb; and a coating layer coated on at least part of a surface of the core portion, the coating layer comprising a bismuth element and a titanium element, and a ratio of a molar percentage content of the bismuth element to a molar percentage content of the titanium element being (0.1 to 2.0):

1.

2. The positive electrode active material according to claim 1, wherein a ratio of a molar percentage content of the bismuth element to a molar percentage content of the titanium element being (0.1 to 1.0):

1.

3. The positive electrode active material according to claim 1 or 2, wherein the coating layer comprising at least one of bismuth titanate, lithium titanate, and lithium bismuthate.

4. The positive electrode active material according to claim 3, wherein the coating layer comprising bismuth titanate.

5. The positive electrode active material according to claim 1, wherein 0.9＜a＜0.98。 6. The positive electrode active material according to claim 5, wherein 0.92≤a＜0.98。 7. The positive electrode active material according to claim 1, wherein b ≥ 1 - a - b.

8. The positive electrode active material according to claim 1, wherein The core includes at least one compound of the formula LiNi 0.91 Co 0.05 M 0.04 O2, LiNi 0.92 Co 0.04 M 0.04 O2, LiNi 0.92 Co 0.05 M 0.03 O2, LiNi 0.92 Co 0.06 M 0.02 O2, LiNi 0.93 Co 0.03 M 0.02 O2, and LiNi 0.93 Co 0.025 M 0.025 O2.

9. The positive electrode active material according to claim 1, wherein a mass percentage content of the core portion being A%, and a mass percentage content of the coating layer being B% based on a total mass of the positive electrode active material, 99 ≤ A / B < 1000.

10. The positive electrode active material according to claim 9, wherein 99 ≤ A / B < 300.

11. The positive electrode active material according to claim 9, wherein 99 ≤ A < 100; and / or 0 < B ≤ 1.

12. The positive electrode active material according to claim 1, wherein a thickness of the coating layer being 1 nm to 100 nm.

13. The positive electrode active material according to claim 1, wherein the positive electrode active material satisfying at least one of the following conditions: (1) a volume distribution particle size Dv10, Dv50, and Dv90 of the positive electrode active material satisfy: 0.5 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.5; (2) a volume distribution particle size Dv50 of the positive electrode active material satisfies: 2.0 μm ≤ Dv50 ≤ 15 μm; (3) the specific surface area BET of the positive electrode active material satisfies 0.34 m 2 / g ≤ BET ≤ 1.2 m 2 / g.

14. The positive electrode active material according to claim 13, wherein 0.8 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.

4.

15. The positive electrode active material according to claim 13, wherein 3 μm ≤ Dv50 ≤ 12 μm.

16. The positive electrode active material according to claim 13, wherein 0.5 m 2 / g ≤ BET ≤ 1.0 m 2 / g.

17. The positive electrode active material according to claim 1, wherein the positive electrode active material comprising polycrystalline agglomerate particles.

18. The positive electrode active material according to claim 17, wherein a primary particle size D1 of the polycrystalline agglomerate particles satisfies: 0.1 μm ≤ D1 ≤ 0.4 μm; and / or a volume distribution particle size Dv50 of the polycrystalline agglomerate particles satisfies: 4.0 μm ≤ Dv50 ≤ 15.0 μm.

19. The positive electrode active material according to claim 1, wherein the positive electrode active material comprising single crystal particles or single crystal-like particles.

20. The positive electrode active material according to claim 19, wherein a primary particle size D2 of the single crystal particles or single crystal-like particles satisfies: 0.7 μm ≤ D2 ≤ 2.0 μm; and / or a volume distribution particle size Dv50 of the single crystal particles or single crystal-like particles satisfies: 2.0 μm ≤ Dv50 ≤ 4.0 μm. 21.A positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, the positive electrode film layer comprising the positive electrode active material according to any one of claims 1 to 20. 22.A battery cell, comprising the positive electrode sheet according to claim 21. 23.A battery, comprising the battery cell according to claim 22. 24.An electric device, comprising the battery according to claim 23.

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