Positive electrode material and preparation method therefor, positive electrode, secondary battery, and electric device

Abstract

A positive electrode material and a preparation method therefor, a positive electrode, a secondary battery, and an electric device. The positive electrode material comprises a core and a shell layer covering the core, wherein the core comprises (LiaAd)1+x(M1-bEb)1-x(O1-cL2c)2, 0<x≤0.33, 0<a≤1, 0≤b<1, 0≤c<1, 0≤d<1, M comprises at least one of Ni, Co and Mn, A comprises at least one of Na, K and Mg, E comprises at least one of Al, Mg, Cr, Co, Ce, Zr, Mo, Nb, W, Ta, B, Y, Sr, V and Ti, L comprises at least one of F, Cl and Br, the shell layer comprises WO2.72, and the mass ratio of WO2.72 in the shell layer is greater than or equal to 90%. The positive electrode material has high charge / discharge energy and excellent electronic conductivity and ionic conductivity, can exhibit good structural stability during battery charge / discharge cycles, and can be used for providing a secondary battery having high capacity, good cycle stability and good rate performance.

Description

Positive Electrode Material, Preparation Method Thereof, Positive Electrode, Secondary Battery, and Electrical Equipment

[0001] This disclosure claims the priority of a Chinese patent application filed with the Chinese Patent Office on December 20, 2023, with an application number of 202311767571.3 and an application title of "Positive Electrode Material, Preparation Method Thereof, Positive Electrode, Secondary Battery, and Electrical Equipment", the entire content of which is incorporated herein by reference. Technical Field

[0002] This disclosure relates to the field of battery technologies, and particularly to positive electrode materials, preparation methods thereof, positive electrodes, secondary batteries, and electrical equipment. Background Art

[0003] Rich lithium transition metal layered oxides, which have both high charge-discharge capacities and low costs, are one of the next-generation positive electrode materials with broad application prospects. However, during the battery cycling process, they are extremely prone to irreversible oxidation of oxygen atoms. The oxygen atoms in the material will generate oxygen and escape, which not only reduces the first-cycle efficiency of the battery but also causes structural rupture and phase transformation of the material, further leading to gradual inactivation of the material and rapid attenuation of the battery capacity, severely restricting the large-scale application of rich lithium transition metal layered oxides.

[0004] Summary of the Invention

[0005] In view of this, embodiments of this disclosure provide a positive electrode material that has high charge-discharge energy, excellent electron conductivity and ion conductivity performance, and can exhibit good structural stability during the battery charge-discharge cycling process, and can be used to provide a secondary battery with a relatively high capacity, good cycle stability, and good rate performance.

[0006] In a first aspect of the embodiments of this disclosure, a positive electrode material is provided, including a core and a shell layer coated on the core; wherein, the material of the core includes (Li a A d ) 1+x (M 1-b E b [[ID=�2]]) 1-x (O 1-c L 2c )2, where 0 < x ≤ 0.33, 0 < a ≤ 1, 0 ≤ b < 1, 0 ≤ c < 1, 0 ≤ d < 1; M includes at least one of Ni, Co, and Mn; A includes at least one of Na, K, and Mg; E includes at least one of Cr, Al, Mg, Co, Ce, Zr, Mo, Nb, W, Ta, B, Y, Sr, V, and Ti; L includes at least one of F, Cl, and Br;

[0007] The material of the shell layer includes WO2.72, and the mass percentage of the WO2.72 in the shell layer is ≥90%.

[0008] In one implementation, the shell layer (12) further includes a doping element, and the doping element includes at least one of Ni, Co and Mn.

[0009] In one implementation, the mass percentage of the doping element in the shell layer (12) is 0.05%-10%.

[0010] In one implementation, the thickness of the shell layer (12) is in the range of 5 nm to 200 nm.

[0011] In one implementation, based on the mass of the positive electrode material (10), the mass proportion of the tungsten element in the shell layer (12) is in the range of 0.05%-5%.

[0012] In one implementation, the kernel (11) includes the (Li a A d ) 1+x (M 1-b E b ) 1-x (O 1-c L 2c )2 single crystal particles.

[0013] Based on the inherent properties of the core material, the positive electrode material has a high charge and discharge capacity; at the same time, the shell material with a high WO2.72 mass content has more oxygen vacancies and a stable structure, which can effectively inhibit (Li a A d ) 1+x (M 1-b E b ) 1-x (O 1-c L 2c )2, improving the structural stability of the cathode material and optimizing its interface, thereby enhancing the battery's cycling performance. Furthermore, WO2.72 exhibits both good electronic and ionic conductivity, effectively enhancing the rate performance of the cathode material. Therefore, this cathode material can be used to provide a secondary battery with high capacity, excellent cycling performance, and superior rate performance.

[0014] A second aspect of the embodiments of the present disclosure provides a method for preparing a positive electrode material, comprising the following operations.

[0015] A lithium source, an A source, an M source, an E source, and an L source are mixed according to the molar ratio of each element in the (LiaAd)1+x(M1-bEb)1-x(O1-cL2c)2 to be prepared, and a first calcination is performed under an air atmosphere to obtain a first material; wherein, M includes at least one of Ni, Co, and Mn; A includes at least one of Na, K, and Mg; E includes at least one of Al, Mg, Cr, Co, Ce, Zr, Mo, Nb, W, Ta, B, Y, Sr, V, and Ti; and L includes at least one of F, Cl, and Br; the first material, a tungsten source, oxalic acid, and a solvent are mixed to obtain a mixture; the mixture is heated to react, and the obtained solid is subjected to a second calcination under a protective atmosphere to obtain a positive electrode material.

[0016] The positive electrode material includes a core and a shell layer coated on the core. The core includes (LiaAd)1+x(M1-bEb)1-x(O1-cL2c)2, wherein 0 <x≤0.33,0<a≤1,0≤b<1,0≤c<1,0≤d<1。

[0017] The material of the shell layer includes WO2.72, and the mass percentage of the WO2.72 in the shell layer is ≥90%.

[0018] In one implementation, the mixture is subjected to a heating reaction to obtain a solidified product, and the obtained solidified product is subjected to a second calcination under a protective atmosphere to obtain a positive electrode material, which includes: heating the mixture to react; performing solid-liquid separation and drying on the heated mixture in sequence to obtain a solidified product; and performing a second calcination on the solidified product obtained after solid-liquid separation and drying under a protective atmosphere.

[0019] In one implementation, the method further includes adding a compound containing a doping element to the mixture, wherein the doping element includes at least one of Ni, Co, and Mn.

[0020] In one implementation, the second calcination is carried out under a protective atmosphere at 300° C. to 700° C. for 3 to 8 hours.

[0021] In one implementation, the heating reaction conditions are: keeping the mixture at 130° C.-180° C. for 18 h-36 h.

[0022] The preparation method is simple and easy to implement, has strong process reliability, high production efficiency, and can be used for large-scale industrial production.

[0023] In the third aspect of the embodiments of the present disclosure, a positive electrode is provided, including the positive electrode material provided in the first aspect of the embodiments of the present disclosure. Due to the positive electrode material provided in the embodiments of the present disclosure, this positive electrode can be used to provide a secondary battery with both high capacity, excellent cycle performance, and good rate performance.

[0024] In the fourth aspect of the embodiments of the present disclosure, a secondary battery is provided, including the positive electrode provided in the third aspect of the embodiments of the present disclosure. This secondary battery can have both high capacity, excellent cycle performance, and good rate performance.

[0025] In the fifth aspect of the embodiments of the present disclosure, an electrical device is provided, including the secondary battery provided in the embodiments of the present disclosure. Due to being powered by the secondary battery provided in the embodiments of the present disclosure, this electrical device can have good battery life, high charging efficiency, and good market prospects. Description of the Drawings

[0026] FIG. 1 is a schematic diagram of a positive electrode material according to an embodiment of the present disclosure.

[0027] FIG. 2 is a flowchart of a method for preparing a positive electrode material according to an embodiment of the present disclosure.

[0028] FIG. 3 is a schematic block diagram of a positive electrode according to an embodiment of the present disclosure.

[0029] FIG. 4 is a schematic block diagram of a secondary battery according to an embodiment of the present disclosure.

[0030] FIG. 5 is a schematic block diagram of an electrical device according to an embodiment of the present disclosure.

[0031] Reference Numerals: Positive electrode material 10; Core 11; Shell layer 12; Secondary battery 20; Positive electrode 22; Negative electrode 24, Separator 26, Electrical device 30. [[ID=''28]]Detailed Description of the Embodiments

[0032] The lithium-rich transition metal layered oxide (Li 1+x M 1-x O2, 0 < x ≤ 0.33) not only has a high capacity, but also can have a certain lithium supplement effect by increasing the proportion of the lithium-rich phase in the material. Therefore, the lithium-rich transition metal layered oxide is a very promising positive electrode material. However, during the high-voltage formation process of the battery, Li 1+x M 1-x O2 is extremely easy to oxidize and release oxygen at high voltage, and the oxygen atoms on the surface of the material are also relatively easy to escape during the cycling process. This process will be accompanied by phase transformation (from layered structure to spinel phase, rock salt phase transformation) and material structure rupture, and even induce cation mixing, affecting the performance of the battery. In addition, Li 1+x M<00**********30>O2 has poor electrical conductivity, and a relatively thick interfacial film is likely to form on its surface under high-voltage formation conditions, reducing the rate performance of the battery. Therefore, the large-scale application of lithium-rich transition metal layered oxides, whether as cathode materials or lithium supplement materials, will be subject to certain limitations. Although it is common knowledge in the industry to solve the above problems through ion doping or material nanosizing, the improvement effect is limited.

[0033] To solve the above technical problems, an embodiment of the present disclosure provides a cathode material. Figure 1 is a schematic diagram of the cathode material 10 provided by an embodiment of the present disclosure. As shown in Figure 1, the cathode material 10 includes a core 11 and a shell layer 12 coated on the core; wherein, the material of the core includes (Li a A d ) 1+x (M 1-b E b ) 1-x (O 1-c L 2c )2, where 0 < x ≤ 0.33, 0 < a ≤ 1, 0 ≤ b < 1, 0 ≤ c < 1, 0 ≤ d < 1. M includes at least one of Ni, Co, and Mn; A includes at least one of Na, K, and Mg; E includes at least one of Cr, Al, Mg, Co, Ce, Zr, Mo, Nb, W, Ta, B, Y, Sr, V, and Ti; L includes at least one of F, Cl, and Br. It can be understood that when b, c, and d are all 0 at the same time, the material of the above core is Li 1+x M 1-x O2.

[0034] The material of the shell layer includes WO 2.72 , and the mass percentage of WO 2.72 in the shell layer ≥ 90%.

[0035] Based on the inherent properties of the core material, the cathode material has a high charge-discharge capacity. Further, doping Li 1+x M 1-x O2 can further improve the structural stability and / or electrical conductivity of Li 1+x M 1-x O2, thereby further improving the cycle performance and / or rate performance of the final secondary battery. More importantly, WO 2.72 with oxygen vacancies in the molecular structure has good structural stability and electrochemical stability. Therefore, the shell layer material with a high WO 2.72 mass content has more oxygen vacancies and a stable structure, which can effectively inhibit (Li a A d ) 1+x (M 1-b E b ) 1-x (O1-c L 2c )2, and the physical barrier effect of the shell can also reduce the risk of oxygen atoms escaping due to side reactions between the core and the electrolyte (e.g., electrolyte), thereby significantly improving the structural stability of the positive electrode material and optimizing its interface, thereby improving the cycle performance of the battery. In addition, WO 2.72 The combination of good electronic and ionic conductivity can effectively improve the rate performance of the positive electrode material. Therefore, the above-mentioned positive electrode material can be used to provide a secondary battery with high capacity, good cycle performance and excellent rate performance.

[0036] In the embodiment of the present disclosure, WO in the shell 2.72 The mass percentage of WO can be, but is not limited to, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 100%, etc. 2.72 If the mass ratio of WO is too low, the content of oxygen vacancies in the shell material will decrease, which will not only affect the stability of the shell material itself, but also weaken the inhibitory effect on the escape of oxygen atoms in the core, resulting in poor cycle performance of the final battery. If other components in the shell are low-conductivity materials, the rate performance of the final battery will also be reduced. In the embodiment of the present disclosure, the characterization of WO 2.72 The methods include X-ray diffraction test, transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS).

[0037] In the embodiment of the present disclosure, when WO 2.72 When the mass percentage of WO is less than 100%, the remaining components may be, but are not limited to, impurities adhering to the surface of the positive electrode material during the preparation process, and / or intentionally doped on WO 2.72 doping elements in .

[0038] In some embodiments of the present disclosure, the shell layer further comprises a doping element, and the doping element comprises at least one of Ni, Co or Mn. In some specific embodiments, the above doping element is doped in WO 2.72 The valence of the ions formed by the above three elements is lower than that of tungsten ions, and they are doped in WO 2.72 The lattice of WO can be improved 2.72 The ratio of oxygen vacancies in the core (Li a A d ) 1+x (M 1-b Eb ) 1-x (O 1-c L 2c )2 During the charge and discharge process, the oxygen atoms are released, which can further improve the structural stability of the positive electrode material during the charge and discharge process, and then further improve the cycle performance of the final battery. It can be understood that the above doping elements are doped into WO 2.72 The lattice may cause changes in the lattice parameters, which in turn causes WO 2.72 The molar quantity of O element in the WO 2.72 The doping is carried out in this specific crystal lattice, so even if the molar amount of the O element changes slightly, it should be considered as the scope of protection of the present disclosure.

[0039] In some embodiments of the present disclosure, the mass percentage of the doping element in the shell layer is 0.05%-10%. Controlling the mass percentage of the doping element within the above range can be done without affecting the WO 2.72 Under the condition of its own structural stability, it effectively improves WO 2.72 The proportion of oxygen vacancies in the shell can reduce the interface impedance; at the same time, it is also easier to prepare. For example, the mass percentage of the doping element in the shell can be 0.05%, 0.1%, 0.15%, 0.20%, 0.25%, 0.30%, 0.50%, 0.80%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 3.0%, 3.5%, 4.0%, 5.0%, 5.5%, 6.0%, 7.0%, 8.0%, 9.0%, 9.5%, etc. In some specific embodiments, the mass percentage of the doping element in the shell is 0.1%-3%. In this way, the WO in the shell can be effectively increased. 2.72 The ratio of oxygen vacancies can also ensure that WO 2.72 The structural stability is better, which is more conducive to the cycle performance of the battery. In the embodiment of the present disclosure, XPS can be used to test the mass ratio of the doping element in the shell layer.

[0040] In some embodiments of the present disclosure, the thickness of the shell is in the range of 5nm-200nm. In some specific embodiments, the thickness of the shell is in the range of 5nm-100nm. In this way, on the one hand, there is a good effect of fixing oxygen and improving the conductivity of the material, and on the other hand, it can effectively avoid the side reactions caused by direct contact between the positive electrode material and the electrolyte, thereby protecting the positive electrode material; illustratively, the thickness of the shell can be, but is not limited to, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 110nm, 120nm, 130nm, 150nm, 180nm, 200nm, etc.

[0041] In some embodiments of the present disclosure, based on the mass of the positive electrode material, the mass proportion of the tungsten element in the shell layer in the positive electrode material is in the range of 0.05%-5%. 2.72 The mass proportion of tungsten in the shell is at least 90%, which controls the mass proportion of tungsten in the shell in the positive electrode material to be within the above range, and can also represent that the proportion of the shell material in the positive electrode material is within a suitable range. In particular, when the thickness of the shell is constant, the mass proportion of tungsten in the shell in the positive electrode material can be further regulated to control the density or compactness of the shell material within a suitable range. In some specific embodiments, the mass proportion of tungsten in the shell in the positive electrode material is in the range of 0.2%-1%. Taking into account that there may be doping elements in the shell, the mass proportion of tungsten in the shell is controlled within the above range, and the remaining mass proportion, except for WO 2.72The O element in the shell does not contain too much doping elements by mass. In this way, the proportion of doping elements in the shell is controlled within a more appropriate range, which is more conducive to improving the structural stability, ionic conductivity and electronic conductivity of the positive electrode material. In some specific embodiments, the mass proportion of tungsten elements in the shell in the positive electrode material is in the range of 0.3%-0.6%. For example, the mass proportion of tungsten elements in the shell in the positive electrode material can be, but is not limited to, 0.05%, 0.10%, 0.15%, 0.20%, 0.30%, 0.50%, 0.80%, 1.00%, 1.50%, 2.00%, 2.50%, 3.00%, 3.50%, 4.00%, 4.50%, 5.00%, etc. In the embodiments of the present disclosure, an X-ray fluorescence spectrometer (XRF), an energy dispersive spectrometer (EDS), and an X-ray photoelectron spectroscopy (XPS) can be used to test the mass proportion of tungsten in the positive electrode material.

[0042] Understandably, due to the WO in the shell 2.72 It has good electronic conductivity, which is reflected in the electrochemical performance as improving the rate performance of the positive electrode material, and can be manifested in the intrinsic parameters of the positive electrode material as reducing the powder resistivity of the positive electrode material. In some embodiments of the present disclosure, a powder resistivity tester is used to measure the powder resistivity of the positive electrode material. Under a test pressure of 12KN, the powder resistivity of the positive electrode material is in the range of 0.005Ω·cm-200Ω·cm. Exemplarily, under the above test conditions, the powder resistivity of the positive electrode material can be, but is not limited to, 0.005Ω·cm, 0.01Ω·cm, 0.05Ω·cm, 0.10Ω·cm, 0.5Ω·cm, 1.0Ω·cm, 2.5Ω·cm, 5.0Ω·cm, 10.0Ω·cm, 15.0Ω·cm, 20.0Ω·cm, 50.0Ω·cm, 100Ω·cm, 200Ω·cm, etc.

[0043] In some embodiments of the present disclosure, the kernel includes (Li a A d ) 1+x (M 1-b E b ) 1-x (O 1-c L 2c )2 single crystal particles. In some specific embodiments, the core is (Li a A d ) 1+x (M 1-b Eb ) 1-x (O 1-c L 2c Single crystal particles. Single crystal particles can overcome the problem of polycrystalline materials being prone to cracking at the grain boundaries. This prevents the uncoated interface from coming into contact with the electrolyte (e.g., electrolyte) in the battery due to grain boundary rupture, which can exacerbate material deoxidation. This allows the positive electrode material to remain stable during charge and discharge cycles, thereby improving the long-cycle performance of the final battery.

[0044] In some embodiments of the present disclosure, the D50 particle size of the positive electrode material is in the range of 3μm-5.5μm. By controlling the particle size of the positive electrode material within the above range, firstly, the transmission path of the active ions in the positive electrode material can be regulated to be shorter, which is beneficial to ensure the rate performance of the final battery; secondly, it is beneficial to achieve a higher compaction density, thereby improving the capacity of the final battery. For example, the D50 of the positive electrode material can be, but is not limited to, 3.0μm, 3.5μm, 4.0μm, 4.5μm, 5.0μm, 5.5μm, etc. In the embodiment of the present disclosure, the D50 particle size of the positive electrode material can be tested using a laser particle size analyzer.

[0045] The present disclosure also provides a method for preparing a positive electrode material, which can be used to prepare the aforementioned positive electrode material. As shown in FIG2 , the preparation method includes the following steps:

[0046] S01, according to the (Li a A d ) 1+x (M 1-b E b ) 1-x (O 1-c L 2c )2, and a lithium source, an A source, an M source, an E source, and an L source are mixed in a molar ratio of each element in )2, and a first calcination is performed under an air atmosphere to obtain a first material; wherein, M includes at least one of Ni, Co, and Mn; A includes at least one of Na, K, and Mg; E includes at least one of Al, Mg, Cr, Co, Ce, Zr, Mo, Nb, W, Ta, B, Y, Sr, V, and Ti; and L includes at least one of F, Cl, and Br.

[0047] S02. Mix the first material, tungsten source, oxalic acid and solvent to obtain a mixture; heat the mixture to react, and perform a second calcination on the obtained solidified material under a protective atmosphere to obtain a positive electrode material.

[0048] The positive electrode material includes a core and a shell layer coated on the core; wherein the core includes (Li a A d ) 1+x (M 1-b Eb ) 1-x (O 1-c L 2c )2, where 0 < x ≤ 0.33, 0 < a ≤ 1, 0 ≤ b < 1, 0 ≤ c < 1, 0 ≤ d < 1; the material of the shell layer includes WO 2.72 , and the mass percentage of WO 2.72 in the shell layer ≥ 90%.

[0049] The above preparation method is simple and easy to implement, with high production efficiency, and can achieve large-scale industrial production.

[0050] In the embodiment of the present disclosure, in step S01, according to common knowledge in the field, some raw materials can be in relative excess. For example, the lithium source and the A source can be in relative excess. In some embodiments of the present disclosure, the ratio of the sum of the molar amounts of lithium element and A element to the molar amount of M element is (1.4 - 1.65):1.

[0051] In the embodiment of the present disclosure, in step S01, the lithium source, the A source, the M source, the E source and the L source can each be selected from any compounds known in the field that are suitable for the preparation of lithium-rich transition metal oxides. For example, salts or hydroxides of lithium element or A element. Exemplarily, the lithium source includes but is not limited to at least one of lithium carbonate, lithium acetate, lithium hydroxide, etc.; when the A element is potassium element, the above A source includes but is not limited to at least one of potassium carbonate, potassium acetate, potassium hydroxide, etc. The above M source includes but is not limited to hydroxides or salts of manganese (such as manganese carbonate), hydroxides or salts of cobalt (such as cobalt carbonate), hydroxides or salts of nickel (such as nickel carbonate), (Mn 2 / 3 Co 1 / 6 Ni 1 / 6 )(OH)2, (Mn 2 / 3 Co 1 / 6 Ni 1 / 6 )CO3, etc., and those skilled in the art can select as needed. For the selection of other element sources, it will not be elaborated in the present disclosure.

[0052] In some embodiments of the present disclosure, the M source is a granular material with a D50 of 3 μm - 5 μm. In this way, it is easier to obtain the cathode material with the target D50 particle size. Exemplarily, the D50 of the M source can be but is not limited to 3.0 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4.0 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5.0 μm, etc.

[0053] In some embodiments of the present disclosure, in step S01, the first calcination is carried out at 950°C-1050°C for 8-15 hours. This promotes the formation of a single crystal structure in the core material. For example, the holding temperature for the first calcination may be, but is not limited to, 950°C, 975°C, 1000°C, 1025°C, 1050°C, etc. For example, the holding time for the first calcination may be, but is not limited to, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, etc.

[0054] In some embodiments of the present disclosure, step S01 further includes crushing and screening the product obtained by the first calcination to obtain the first material.

[0055] In some embodiments of the present disclosure, in step S02, the ratio of the amount of tungsten element in the tungsten source to the amount of oxalic acid is 1:(6-10). 2.72 , which is also beneficial to further enhance the WO 2.72 For example, the molar ratio of tungsten element in the tungsten source to oxalic acid may be, but is not limited to, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, etc. In some embodiments of the present disclosure, in step S02, the tungsten source includes, but is not limited to, WCl6, Na2WO4, K2WO4, and (NH4)2WO4.

[0056] In some embodiments of the present disclosure, step S02 further includes adding a compound containing a doping element to the mixture, wherein the doping element includes but is not limited to at least one of Ni, Co and Mn. The compound containing the doping element is added to the mixture, and during the second calcination process, the doping element can be doped into the shell material, thereby preparing a shell with the doping element. The above-mentioned compound containing the doping element includes but is not limited to at least one of manganese oxide, hydroxide or salt (e.g., manganese carbonate), cobalt tungsten oxide, hydroxide or salt (e.g., cobalt carbonate), nickel tungsten oxide, hydroxide or salt (e.g., nickel carbonate).

[0057] In some embodiments of the present disclosure, in step S02, the first material, the tungsten source, and the oxalic acid are added to a solvent and stirred for 10 minutes to 30 minutes to obtain a mixture.

[0058] In some embodiments of the present disclosure, the above-mentioned solvent includes but is not limited to at least one of isopropyl alcohol and ethylene glycol.

[0059] In some embodiments of the present disclosure, in step S02, the conditions for the heating treatment are: keeping the mixture at 130°C-180°C for 18h-36h, that is, performing hydrothermal insulation at 130°C-180°C for 18h-36h.

[0060] In step S02, considering that the mixture after the heating reaction may still contain solvent, in some embodiments, the mixture after the heating reaction is sequentially subjected to solid-liquid separation and drying, and then the resulting solidified material is subjected to a second calcination under a protective atmosphere. In some specific embodiments, the solid-liquid separation is performed by filtration.

[0061] In some embodiments of the present disclosure, in step S02, the conditions for the second calcination are: keeping warm at 300°C-700°C for 3h-8h under a protective atmosphere. In this way, a stable shell layer can be formed on the surface of the first material, thereby obtaining a positive electrode material, and the structure of the core material will not be destroyed. In this process, the M element on the surface of the first material can also be partially doped into the shell layer. It can be understood that when the mixture includes a compound containing a doping element, the doping element will be doped into the shell layer during the second calcination process. Exemplarily, the temperature of the second calcination can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, etc. Exemplarily, the duration of the second calcination can be 3h, 4h, 5h, 6h, 7h, 8h, etc.

[0062] In the embodiment of the present disclosure, the protective atmosphere includes but is not limited to nitrogen atmosphere, argon atmosphere, a mixed atmosphere of nitrogen and argon, etc.

[0063] As shown in Figure 3, the present disclosure also provides a positive electrode 22, which includes the positive electrode material provided in the present disclosure. Due to the positive electrode material provided in the present disclosure, the positive electrode can be used to provide a secondary battery with high capacity, good cycle performance, and good rate performance.

[0064] In some embodiments, the positive electrode includes a positive electrode current collector and a positive electrode material layer disposed on at least one side of the positive electrode current collector. The positive electrode material layer includes a positive electrode active material, a binder, and an optional conductive agent.

[0065] In the embodiment of the present disclosure, all the positive electrode active materials in the positive electrode material layer may be the aforementioned positive electrode materials provided in the embodiment of the present disclosure; or the positive electrode active materials may include the positive electrode materials provided in the embodiment of the present disclosure and other positive electrode active materials. Among them, the other positive electrode active materials can be selected from any well-known positive electrode active materials of lithium-ion batteries, for example, at least one of phosphate-based positive electrode active materials, oxide positive electrode active materials, and polyanion-type positive electrode active materials. Among them, the phosphate-based positive electrode active materials include but are not limited to modified or unmodified lithium iron phosphate. The oxide positive electrode active materials include but are not limited to one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, and lithium manganese oxide. Polyanion-type positive electrode active materials include but are not limited to modified or unmodified lithium vanadium phosphate, etc.

[0066] In the embodiments of the present disclosure, the material of the positive electrode current collector can be any material known in the art. The binder and conductive agent can also be selected from any conductive agent and binder known in the art that are suitable for positive electrodes.

[0067] The present disclosure also provides a secondary battery. Figure 4 is a schematic block diagram of a secondary battery according to an embodiment of the present disclosure. As shown in Figure 4, the secondary battery 20 (referred to as battery 20) includes a positive electrode 22 provided by an embodiment of the present disclosure. This secondary battery can combine high capacity, excellent cycle performance, and good rate performance.

[0068] In some embodiments of the present disclosure, the secondary battery 20 includes the positive electrode 22, the negative electrode 24, and an electrolyte located between the positive electrode and the negative electrode. In the embodiments of the present disclosure, the negative electrode can be any negative electrode known in the art.

[0069] In the embodiments of the present disclosure, the secondary battery may be a solid-state battery using a solid electrolyte, a liquid battery using a liquid electrolyte, or a semi-solid-state battery.

[0070] In some embodiments of the present disclosure, the secondary battery 20 includes a positive electrode 22 , a negative electrode 24 , and a separator 26 and an electrolyte located between the positive electrode and the negative electrode.

[0071] The present disclosure also provides an electrical device. Figure 5 is a schematic block diagram of an electrical device according to the present disclosure. As shown in Figure 5, the electrical device 30 includes, but is not limited to, the aforementioned secondary battery 20 provided in the present disclosure. The secondary battery 20 includes a positive electrode 22, which is, for example, made from the positive electrode material 10 according to the present disclosure. Because it is powered by the secondary battery provided in the present disclosure, the electrical device can have good battery life and high charging efficiency, and has good market prospects.

[0072] In some embodiments of the present disclosure, the aforementioned electrical equipment includes, but is not limited to, vehicles and consumer electronic products, wherein vehicles include, but are not limited to, new energy vehicles and power-assisted electric vehicles.

[0073] The technical solution of the present disclosure is further illustrated below with multiple embodiments.

[0074] Example 1

[0075] (1) Lithium source (specifically Li2CO3), M source with D50=3.5μm (specifically Mn 0.54 Co 0.13 Ni 0.13 (OH) 1.6), E source (specifically ZrO2 nanopowder, V2O5 nanopowder) are evenly mixed according to the proportion of the core material to be prepared, wherein the molar ratio of Li:(Mn+Co+Ni+Zr+V) is 1.58:1; and in an air atmosphere, it is kept at 995°C for 12 hours, and then crushed and sieved in sequence to obtain the first material.

[0076] (2) The first material is added to an isopropanol solution and stirred, and a tungsten source (specifically WCl6), a compound containing a doping element (specifically Ni(NO3)2) and oxalic acid are added, wherein the molar ratio of WCl6 to oxalic acid is 1:10. After stirring for 30 minutes, the solution is transferred to a reactor, hydrothermally kept at 160°C for 24 hours, filtered, vacuum-dried, and calcined at 350°C for 5 hours in a nitrogen atmosphere to obtain a positive electrode material.

[0077] Example 2-Example 5

[0078] The difference between Example 2 to Example 5 and Example 1 is that in step (2), the amount of WCl6 added is fine-tuned. The parameters of the obtained positive electrode materials are summarized in Table 1.

[0079] Example 6

[0080] (1) Lithium source (specifically Li2CO3), M source with D50=3.5μm (specifically Mn 0.54 Co 0.13 Ni 0.13 (OH) 1.6 ), E source (specifically ZrO2 nanopowder and WO3 nanopowder) are evenly mixed according to the proportion of the core material to be prepared, wherein the molar ratio of Li:(Mn+Co+Ni+Zr+W) is 1.59:1; and in an air atmosphere, it is kept warm at 990°C for 13 hours, and then crushed and sieved in sequence to obtain the first material.

[0081] (2) The first material is added to an isopropanol solution and stirred, and a tungsten source (specifically WCl6), a compound containing a doping element (specifically Ni(NO3)2) and oxalic acid are added, wherein the molar ratio of WCl6 to oxalic acid is 1:10. After stirring for 30 minutes, the solution is transferred to a reactor, hydrothermally kept at 160°C for 24 hours, filtered, vacuum-dried, and calcined at 450°C for 3 hours in a nitrogen atmosphere to obtain a positive electrode material.

[0082] Example 7

[0083] (1) Lithium source (specifically Li2CO3), M source with D50=3.8μm (specifically Mn 0.54 Co 0.13 Ni 0.13 (OH) 1.6), E source (specifically ZrO2 nanopowder and Al2O3 nanopowder) are mixed evenly according to the proportion of the core material to be prepared, wherein the molar ratio of Li:(Mn+Co+Ni+Zr+Al) is 1.58:1; and in an air atmosphere, it is kept at 1000°C for 12 hours, and then crushed and sieved in sequence to obtain the first material.

[0084] (2) The first material is added to an isopropanol solution and stirred, and a tungsten source (specifically WCl6), a compound containing a doping element (specifically Ni(NO3)2) and oxalic acid are added, wherein the molar ratio of WCl6 to oxalic acid is 1:10. After stirring for 30 minutes, the solution is transferred to a reactor, hydrothermally kept at 160°C for 24 hours, filtered, vacuum-dried, and calcined at 550°C for 3 hours in a nitrogen atmosphere to obtain a positive electrode material.

[0085] Example 8 and Example 9

[0086] The difference from Example 1 is that in step (2), the amount of WCl6 added is fine-tuned.

[0087] Example 10

[0088] The difference from Example 1 is that in step (1), the M source is a large-particle precursor with D50=10.5 μm, and in step (2), the amount of WCl6 added is fine-tuned.

[0089] Example 11

[0090] The difference from Example 1 is that in step (1), the molar ratio of Li:(Mn+Co+Ni+Zr+V) is 1.56:1, and in step (2), the amount of WCl6 added is slightly adjusted.

[0091] Example 12-Example 15

[0092] The difference from Example 1 is that in step (2), the amount of Ni(NO3)2 added is fine-tuned.

[0093] Example 16

[0094] (1) Lithium source (specifically Li2CO3), M source with D50=3.5μm (specifically Mn 0.54 Co 0.13 Ni 0.13 (OH) 1.6 ) bodies are uniformly mixed according to the proportion of the core material to be prepared, wherein the molar ratio of Li:(Mn+Co+Ni) is 1.58:1; and are kept warm at 995°C for 12 hours in an air atmosphere, and are successively crushed and sieved to obtain a first material.

[0095] (2) The first material is added to an isopropanol solution and stirred, and a tungsten source (specifically WCl6), a compound containing a doping element (specifically Ni(NO3)2) and oxalic acid are added, wherein the molar ratio of WCl6 to oxalic acid is 1:10. After stirring for 30 minutes, the solution is transferred to a reactor, hydrothermally kept at 160°C for 24 hours, filtered, vacuum-dried, and calcined at 350°C for 5 hours in a nitrogen atmosphere to obtain a positive electrode material.

[0096] Example 17

[0097] (1) Lithium source (specifically Li2CO3), M source with D50=3.5μm (specifically Mn 0.54 Co 0.13 Ni 0.13 (OH) 1.6 ), E source (specifically ZrO2 nanopowder, V2O5 nanopowder) are evenly mixed according to the proportion of the core material to be prepared, wherein the molar ratio of Li: (Mn + Co + Ni + Zr + V) is 1.58:1; and in an air atmosphere, they are kept warm at 995°C for 12 hours, and then crushed and sieved in sequence to obtain the first material.

[0098] (2) The first material was added to an isopropanol solution and stirred, and a tungsten source (specifically WCl6) and oxalic acid were added, wherein the molar ratio of WCl6 to oxalic acid was 1:10. After stirring for 30 minutes, the solution was transferred to a reactor, hydrothermally kept at 160°C for 24 hours, filtered, vacuum-dried, and calcined at 350°C for 5 hours under a nitrogen atmosphere to obtain a positive electrode material.

[0099] Example 18

[0100] (1) Lithium source (specifically Li2CO3), M source (specifically Mn 0.54 Co 0.13 Ni 0.13 (OH) 1.6 ), E source (specifically ZrO2 nanopowder, V2O5 nanopowder) are uniformly mixed according to the proportion of the core material to be prepared, wherein the molar ratio of Li:(Mn+Co+Ni+Zr+V) is 1.58:1; and in an air atmosphere, they are kept at 945°C for 12 hours, and then crushed and sieved in sequence to obtain the first material.

[0101] (2) The first material is added to an isopropanol solution and stirred, and a tungsten source (specifically WCl6), a compound containing a doping element (specifically Ni(NO3)2) and oxalic acid are added, wherein the molar ratio of WCl6 to oxalic acid is 1:10. After stirring for 30 minutes, the solution is transferred to a reactor, hydrothermally kept at 160°C for 24 hours, filtered, vacuum-dried, and calcined at 350°C for 5 hours in a nitrogen atmosphere to obtain a positive electrode material.

[0102] In order to highlight the beneficial effects of the embodiments of the present disclosure, the following comparative examples are provided.

[0103] Comparative Example 1

[0104] The lithium source (specifically Li2CO3), the M source with D50=3.8μm (specifically Mn 0.54 Co 0.13 Ni 0.13 (OH) 1.6 ), E source (specifically ZrO2 nanopowder, V2O5 nanopowder) were mixed uniformly in the same proportion as in Example 1, wherein the molar ratio of Li:(Mn+Co+Ni+Zr+V) was 1.58:1; and in an air atmosphere, they were kept warm at 1000°C for 12 hours, and then crushed and sieved in sequence to obtain the positive electrode material.

[0105] Comparative Example 2

[0106] The lithium source (specifically Li2CO3), the M source with D50=10.5μm (specifically Mn 0.54 Co 0.13 Ni 0.13 (OH) 1.6 ), E source (specifically ZrO2 nanopowder, Al2O3 nanopowder) are mixed uniformly in the same proportion as in Example 7, wherein the molar ratio of Li:(Mn+Co+Ni+Zr+Al) is 1.58:1; and in an air atmosphere, they are kept warm at 940°C for 12 hours, and then crushed and sieved in sequence to obtain the positive electrode material.

[0107] Comparative Example 3

[0108] (1) Lithium source (specifically Li2CO3), M source with D50=3.5μm (specifically Mn 0.54 Co 0.13 Ni 0.13 (OH) 1.6 ), E source (specifically ZrO2 nanopowder, V2O5 nanopowder) are evenly mixed according to the proportion of the core material to be prepared, wherein the molar ratio of Li:(Mn+Co+Ni+Zr+V) is 1.6:1; and in an air atmosphere, they are kept at 995°C for 12 hours, and then crushed and sieved in sequence to obtain the first material.

[0109] (2) The first material, β-WO 2.9 , WO 2.72 Nanopowders are mixed evenly, including β-WO 2.9、 WO 2.72 The mass ratio of the two materials is 9:1, and then the finished positive electrode material is obtained by calcining at 450 °C for 5 h.

[0110] Table 1

[0111] Performance Testing

[0112] (1) The positive electrode material, binder (specifically PVDF) and conductive agent (specifically conductive carbon black) of each embodiment and comparative example were mixed in a mass ratio of 95:2:3, dispersed in a solvent (specifically N-methylpyrrolidone), and mixed evenly to obtain a positive electrode slurry; the solid content of each positive electrode slurry was the same.

[0113] The positive electrode slurry was coated on two opposite surfaces of a positive electrode current collector (specifically, aluminum foil), dried, roll-pressed, and cut to obtain the positive electrodes of various examples and comparative examples.

[0114] The positive electrodes, separators, and lithium metal sheets were stacked and assembled in a glove box. The electrolyte was injected to produce a button cell. The electrolyte consisted of an organic solvent containing a lithium salt at a concentration of 1 mol / L. The organic solvent was a 3:6:1 ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate to 1% vinylene carbonate.

[0115] (2) First Discharge Gram Capacity and First Cycle Efficiency Test: Each test battery prepared in the above steps was connected to a battery cabinet and charged to 4.8V at a constant current of 0.1C. Then, it was charged at a constant voltage to a current of ≤0.02C. The battery was allowed to rest for 30 minutes, and then discharged to 3V at a constant current of 0.1C. The first charge capacity was recorded to calculate the first charge gram capacity of the battery. The first cycle efficiency = first discharge capacity / first charge capacity × 100%. The results are summarized in Table 2.

[0116] Cycling performance test: At 25±2°C, charge the battery at a constant current of 1C to 4.6V, then charge it at a constant voltage to a current of ≤0.02C. After 10 minutes of rest, discharge it at a constant current of 1C to 3.0V. The battery capacity retention after 100 cycles was recorded and the results are summarized in Table 2.

[0117] Rate performance test: The discharge capacity of each battery was tested at 2C and 0.1C at 25±2℃, with a voltage range of 2.5V-4.3V. The test results are summarized in Table 2.

[0118] AC impedance: The AC impedance of each battery was measured at 25°C in the frequency range of 100 kHz to 0.05 Hz with an amplitude of 5 mV. Rs and Rct were then fitted using Zview software. The ohmic impedance (Rs) and charge transfer impedance (Rct) are summarized in Table 2.

[0119] Table 2

[0120] Combining the data in Tables 1 and 2, it can be seen that the positive electrode material provided in the embodiment of the present disclosure has both a high first discharge capacity and good first cycle discharge efficiency. More importantly, compared with the positive electrode material in the comparative example, the room temperature cycle capacity retention rate of the positive electrode material in the embodiment is significantly improved, indicating that the positive electrode material in the embodiment of the present disclosure exhibits high structural stability during the long cycle process of the battery; at the same time, the positive electrode material in the embodiment of the present disclosure can reduce the Rs and Rct of the battery, showing good rate performance, and the comprehensive electrochemical performance of the embodiment materials is better than that of the comparative example materials.

[0121] Comparing the data between Example 2 and Example 18, it is not difficult to see that when the material of the kernel is a single crystal (Example 2), the cycle performance of the material can be further improved, and it is also more conducive to improving the rate performance of the battery. Comparing the results of Example 2 and Examples 12-15, it can be found that when the content of the doping element is within the range further suggested in the embodiments of the present disclosure, the overall performance of the final battery is better. Comparing the data between Example 2 and Example 17, it can be seen that when the shell layer of the positive electrode material has a doping element (Example 2), it is more conducive to improving the electronic / ionic conductivity of the positive electrode material, and can further improve the structural stability of the positive electrode material during the charge and discharge process, thereby significantly improving the cycle performance of the battery.

[0122] The above is an exemplary embodiment of the present disclosure. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present disclosure. These improvements and modifications are also considered to be within the scope of protection of the present disclosure.

Claims

1. A positive electrode material (10), characterized in that: It includes a core (11) and a shell layer (12) coated on the core (11); wherein, the core (11) includes (Li a A d ) 1+x (M 1-b E b ) 1-x (O 1-c L 2c )2, 0 < x ≤ 0.33, 0 < a ≤ 1, 0 ≤ b < 1, 0 ≤ c < 1, 0 ≤ d < 1; M includes at least one of Ni, Co, and Mn; A includes at least one of Na, K, and Mg; E includes at least one of Al, Mg, Cr, Co, Ce, Zr, Mo, Nb, W, Ta, B, Y, Sr, V, and Ti; L includes at least one of F, Cl, and Br; The shell layer (12) comprises WO 2.72 , and the WO 2.72 The mass proportion in the shell layer (12) is ≥90%.

2. The positive electrode material (10) according to claim 1, characterized in that: The shell layer (12) further comprises a doping element, wherein the doping element comprises at least one of Ni, Co and Mn.

3. The positive electrode material (10) according to claim 2, characterized in that: The mass percentage of the doping element in the shell layer (12) is 0.05%-10%.

4. The positive electrode material (10) according to any one of claims 1 to 3, characterized in that: The thickness of the shell layer (12) is in the range of 5nm-200nm.

5. The positive electrode material (10) according to any one of claims 1 to 4, characterized in that: Based on the mass of the positive electrode material (10), the mass proportion of the tungsten element in the shell layer (12) is in the range of 0.05%-5%.

6. The positive electrode material (10) according to any one of claims 1 to 5, characterized in that: The kernel (11) includes the (Li a A d ) 1+x (M 1-b E b ) 1-x (O 1-c L 2c )2 single crystal particles.

7. A method for preparing a positive electrode material, characterized in that: include: According to the (Li a A d ) 1+x (M 1-b E b ) 1-x (O 1-c L 2c )2, and performing a first calcination (S01) in an air atmosphere to obtain a first material; wherein M includes at least one of Ni, Co and Mn; A includes at least one of Na, K and Mg; E includes at least one of Al, Mg, Cr, Co, Ce, Zr, Mo, Nb, W, Ta, B, Y, Sr, V and Ti; and L includes at least one of F, Cl and Br; mixing the first material, a tungsten source, oxalic acid and a solvent to obtain a mixture; The mixed material is heated to react to obtain a solidified product, and the solidified product is subjected to a second calcination (S02) under a protective atmosphere to obtain a positive electrode material; The positive electrode material comprises a core and a shell layer coated on the core; wherein the core comprises (Li a A d ) 1+x (M 1-b E b ) 1-x (O 1-c L 2c )2, where 0 <x≤0.33,0<a≤1,0≤b<1,0≤c<1,0≤d<1; The material of the shell layer includes WO 2.72 , and WO 2.72 The mass percentage in the shell layer is ≥ 90%.

8. The method for preparing the positive electrode material according to claim 7, characterized in that: The mixed material is heated to react to obtain a solidified product, and the solidified product is subjected to a second calcination under a protective atmosphere to obtain a positive electrode material comprising: heating the mixture to react; Sequentially performing solid-liquid separation and drying on the heated mixture to obtain a solidified material; and The solidified product obtained after solid-liquid separation and drying is subjected to a second calcination under a protective atmosphere.

9. The method for preparing the positive electrode material according to claim 7, characterized in that: The method further comprises adding a compound containing a doping element into the mixture, wherein the doping element comprises at least one of Ni, Co and Mn.

10. The method for preparing a positive electrode material according to any one of claims 7 to 9, characterized in that: The second calcination conditions are: in a protective atmosphere, keeping the temperature at 300° C.-700° C. for 3 h-8 h.

11. The method for preparing a positive electrode material according to any one of claims 7 to 9, characterized in that: The conditions of the heating reaction are: keeping the mixture at 130° C.-180° C. for 18 h-36 h.

12. A positive electrode (22), characterized in that: The invention comprises the positive electrode material (10) as described in any one of claims 1 to 6, or the positive electrode material prepared by the method for preparing the positive electrode material as described in any one of claims 7 to 8.

13. A secondary battery (20), characterized in that: The secondary battery (20) includes the positive electrode (22) according to claim 12.

14. An electrical device (30), characterized in that: The electric device (30) comprises the secondary battery (20) according to claim 13.

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