A positive electrode material, a secondary battery, and an electric device

Abstract

The application provides a positive electrode material, a secondary battery and an electric device. The positive electrode material comprises a metal oxide containing Na, Ni, Fe and Mn elements, and the positive electrode material satisfies the following characteristics: 1.0x10 9 ≤BET / [π(D v50 x10 ‑6 ) 2 ]≤3.5x10 10 The application realizes the improvement of the overall performance of the battery, especially the improvement of the cycle performance, by reasonably controlling the BET and particle size distribution of the positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a positive electrode material, a secondary battery, and an electrical device. Background Technology

[0002] With the large-scale commercialization of lithium-ion batteries, the lithium resource problem has become increasingly prominent. The price of lithium sources for batteries continues to rise, and the contradiction between the explosive demand for power batteries and the limited availability of lithium resources will inevitably intensify. Therefore, finding and developing new energy storage systems and key materials to replace lithium is urgent. Sodium, as the closest element in the same group as lithium, has very similar chemical properties and is much cheaper than lithium mineral raw materials. Its huge cost advantage makes it a promising candidate to replace lithium-ion batteries as the next generation of electrochemical systems. However, the layered cathode active materials currently widely studied for sodium-ion batteries have low capacity, poor rate performance, and high gas production. In particular, their cycle performance is significantly inferior to that of currently commercialized lithium-ion batteries, which seriously hinders the commercialization process of these batteries.

[0003] Therefore, new technologies need to be developed to enable batteries to have higher capacity, better cycle performance, and lower gas production. Summary of the Invention

[0004] The purpose of this invention is to provide a cathode material to meet the need for further improvements in the cycle stability and capacity of batteries in the prior art. This invention, by rationally controlling the BET and particle size distribution of the cathode material to meet certain conditions, effectively reduces side reactions between the cathode material and the electrolyte, optimizes ion transport, electron transport, and electrolyte diffusion rates, and simultaneously reduces the gas production of the secondary battery, thereby improving the overall battery performance, especially the cycle performance.

[0005] To achieve the above objectives, a first aspect of the present invention provides a cathode material comprising a metal oxide containing Na, Ni, Fe, and Mn elements, and the cathode material satisfies the following conditions:

[0006] 1.0×10 9 ≤BET / [π(D v50 x10 -6 ) 2 ≤3.5×10 10 ,

[0007] Among them, D v50 The particle size, in μm, corresponds to a cumulative volume distribution percentage of the cathode material reaching 50%.

[0008] BET is the specific surface area of ​​the positive electrode material, in m². 2 / g.

[0009] As an embodiment of the present invention, the particle size of the positive electrode material further satisfies: 0.7 ≤ D v50 / D n50 ≤9.5, D n50 The particle size is defined as the particle size at which the cumulative percentage of the positive electrode material reaches 50%, expressed in μm.

[0010] As an embodiment of the present invention, the particle size of the positive electrode material satisfies: 3.0 μm ≤ D v50 ≤19.5m, and / or 0.4μm≤D n50 ≤13μm.

[0011] As an embodiment of the present invention, the specific surface area of ​​the positive electrode material satisfies: 0.3 m² / g. 2 / g≤BET≤3.5m 2 / g.

[0012] As an embodiment of the present invention, the positive electrode material further satisfies 2.5≤D FW ≤15.5, D FW The full width at half maximum (FWHM) D of the interval particle size distribution curve of the cathode material. FW The unit is μm.

[0013] As an embodiment of the present invention, the chemical formula of the metal oxide is Na. a M b Ni c Fe d Mn e O 2-f , 0.6≤a≤1.1, 0.05<b<0.15, 0.15<c<0.45, 0.05<d<0.40, 0.05<e<0.40, 0≤f≤0.1, and b+c+d+e=1; wherein, M includes at least one of Zr, Nb, B, Li, Mg, Al, Si, P, Ca, Ti, Cr, V, Zn, and Cu.

[0014] As an embodiment of the present invention, the oxide further has a coating layer, the coating layer comprising a metal oxide material, the metal oxide material comprising at least one of ZrO2, NbO, B2O3, Li2O, MgO, Al2O3, SiO2, P2O5, CaO, Ti2O3, Cr2O3, VO, ZnO, and CuO.

[0015] Furthermore, the weight of the coating layer accounts for 0.1% to 3.5% of the metal oxide.

[0016] As an embodiment of the present invention, the surface of the positive electrode material has a lower NaOH content than the Na2CO3 content.

[0017] In a second aspect, the present invention provides a secondary battery, the secondary battery comprising a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode material layer disposed on the positive current collector, the positive electrode material layer comprising the aforementioned positive electrode material.

[0018] A third aspect of the present invention provides an electrical device comprising the secondary battery.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This invention achieves this by rationally controlling the morphology and size of the cathode material, particularly controlling the specific surface area (BET) and particle size (D) of the cathode material. v50 A proper combination of these elements can ensure that the positive electrode material has high structural stability, significantly reduce the gas production of the secondary battery, and improve the cycle stability of the battery. Detailed Implementation

[0021] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further describe the invention below. However, these embodiments do not limit the invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, all reagents and materials used in this invention are commercially available.

[0022] An embodiment of the present invention provides a cathode material comprising a metal oxide containing Na, Ni, Fe, and Mn elements, and the cathode material satisfies the following conditions:

[0023] 1.0×10 9 ≤BET / [π(D v50 x10 -6 ) 2 ≤3.5×10 10 ,

[0024] Among them, D v50 The particle size, in μm, corresponds to a cumulative volume distribution percentage of the cathode material reaching 50%.

[0025] BET is the specific surface area of ​​the positive electrode material, in m². 2 / g.

[0026] This invention achieves this by rationally controlling the morphology and size of the cathode material, particularly controlling the specific surface area (BET) and particle size (D) of the cathode material. v50With proper combination, the cathode material can optimize ion transport rate and electrolyte diffusion rate, thereby improving the capacity utilization of the cathode material. On the other hand, it can also enable the layered sodium active material particles to have a better coating effect, effectively reducing the side reactions between the cathode material and the electrolyte in the battery, reducing the gas production of the battery (especially the gas production under high temperature conditions). At the same time, the cathode material also has high structural stability, further improving the cycle stability of the battery.

[0027] Cathode material

[0028] It should be noted that the interval particle size distribution (also known as the differential particle size distribution) curve of the cathode material in this invention has a well-known meaning in the art. It is a curve plotted with particle size as the abscissa and volume percentage as the ordinate, which can accurately reflect the particle size distribution characteristics of the cathode material. The volume particle size distribution of the cathode material can be determined and the interval particle size distribution curve can be plotted using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0029] This invention also found through research that, for the particle size distribution of cathode materials, if 0.7 ≤ D v50 / D n50 ≤9.5, can further improve the cycle performance and rate performance of the prepared secondary battery, where D n50 The particle size is defined as the particle size at which the cumulative percentage of the positive electrode material reaches 50%, expressed in μm.

[0030] D v50 / D n50 The closer the value is to 1, the more concentrated the particle size distribution of the cathode material. When D v50 / D n50 When the value is in the range of 0.7 to 9.5, the ratio of large particles to small particles in the cathode material is more suitable. Large particles will reduce the transport distance of sodium ions, improve the kinetic performance of the material, and are conducive to improving the rate performance of the battery. In addition, large particles are not easy to crush during the processing of the cathode sheet, reducing the reaction between the cathode material and the electrolyte, which is conducive to improving the cycle performance of the battery. An appropriate amount of small particles can fill the gaps between large particles, increase the compaction density of the electrode sheet, and facilitate the utilization of battery capacity and energy density.

[0031] In some embodiments of the present invention, the D of the positive electrode material v50 The diameter is 3.0–19.5 μm, and / or the D of the cathode material is... n50The particle size ranges from 0.4 to 13 μm. This ensures a low content of tiny particles in the cathode material, reducing side reactions of the electrolyte on the cathode material surface, suppressing gas production, and improving the cycle performance of the secondary battery. The low content of tiny particles in the cathode material also helps to make the particles more uniformly distributed, increasing the compaction density of the cathode material, thereby giving the cathode sheet a higher compaction density and improving the energy density of the secondary battery.

[0032] In some embodiments of the present invention, the cathode material further satisfies 2.5 ≤ D FW ≤15.5, D FW The full width at half maximum (FWHM) D of the interval particle size distribution curve of the cathode material. FW The unit is μm. Further, if the full width at half maximum (FWHM) D of the particle size distribution curve of the positive electrode active material is simultaneously calculated... FW Within a predetermined range, the positive electrode sheet is guaranteed to have a high compaction density, thereby enabling the battery to have a high energy density. The full width at half maximum (FWHM) D of the curve is... FW This refers to the difference between two particle size values ​​corresponding to half the maximum height of the particle size distribution curve in the aforementioned interval.

[0033] In some embodiments of the present invention, the compaction density PD of the positive electrode sheet prepared by the positive electrode material satisfies: 2.5 g / cm³. 3 ≤PD≤4.0g / cm 3 If the compaction density of the cathode material is too low, the particles will not make close contact and will lose their connection, which is detrimental to the capacity. Furthermore, too low a compaction density will result in a thicker electrode, increasing the migration path of sodium ions and leading to poor rate performance. Conversely, too high a compaction density will cause the particles to be too close together, making the electrode prone to breakage and hindering electrolyte wetting, thus reducing conductivity. A suitable compaction density allows the secondary battery to achieve high energy density while also ensuring excellent processing performance.

[0034] In some embodiments of the present invention, the specific surface area (BET) of the positive electrode material is 0.3–3.5 m². 2 / g. When the specific surface area of ​​the cathode material is within this range, the resulting secondary battery exhibits superior performance.

[0035] The metal oxide in the cathode material of this invention is an O3 phase layered metal oxide, and the chemical formula of the O3 phase layered metal oxide is Na. a M b Ni c Fe d Mn e O 2-fThe following conditions apply: 0.6 ≤ a ≤ 1.1, 0 < b < 0.15, 0.15 < c < 0.45, 0.05 < d < 0.40, 0.05 < e < 0.40, 0 ≤ f ≤ 0.1, and b + c + d + e = 1; where M is a doping element selected from at least one of Zr, Nb, B, Li, Mg, Al, Si, P, Ca, Ti, Cr, V, Zn, and Cu. It can be seen that this invention uses a material with a low Ni content as the cathode material, reducing the sodium-nickel mixing ratio and further improving the battery's cycle performance.

[0036] The invention achieves this by rationally controlling the morphology and size of the cathode material, particularly controlling the specific surface area (BET) and particle size (D) of the cathode material. v50 The appropriate combination of these elements, while controlling the particle size distribution of the cathode material (the half-width at half-maximum D of the particle size distribution curve), is crucial. FW This method can significantly improve the capacity utilization of cathode materials, and can further enhance the performance of the prepared secondary batteries under conditions of low nickel content, thereby reducing production costs.

[0037] In some embodiments, the metal oxide further comprises a coating layer, wherein the coating layer includes a metal oxide material, and the metal oxide material includes at least one selected from ZrO2, NbO, B2O3, Li2O, MgO, Al2O3, SiO2, P2O5, CaO, Ti2O3, Cr2O3, VO, ZnO, and CuO. In some embodiments, the weight of the coating layer may be 0.1% to 3.5% of the weight of the metal oxide, and the coating layer thickness is 10 nm to 500 nm. Within the above-mentioned content and thickness range, the corrosion of the positive electrode material by the electrolyte is effectively reduced, the gas production is reduced, and the energy density of the positive electrode material is not reduced.

[0038] In some embodiments of the present invention, the NaOH content on the surface of the positive electrode material is lower than the Na2CO3 content, and the NaOH content is ≤4000ppm.

[0039] The cathode material in this invention can be prepared by a method including the following steps:

[0040] S1. Add nickel source, iron source and manganese source to water according to a certain mass ratio and mix evenly to obtain a precursor solution. Adjust the pH of the precursor solution to 11-13 in an inert atmosphere and react at 25-60℃. The precipitate obtained is the nickel-manganese-iron metal salt precursor.

[0041] S2. After mixing the nickel-manganese-iron metal salt precursor, sodium source, and M source obtained in step S1, the mixture is sintered in an oxygen atmosphere at 600–1000°C to obtain the cathode material.

[0042] In some embodiments, after step S2, the method further includes:

[0043] S3. Combine the positive electrode material with optional M y The source is sintered in air at 400–1000°C for 1–9 hours to obtain a positive electrode material with a coating layer.

[0044] In some embodiments of the present invention, in step S1, ammonia solution with a concentration of 0.05 to 0.75 mol / L is used to adjust the pH of the precursor solution to 11 to 13; the reaction time in step S1 is 6 to 24 hours.

[0045] In some embodiments of the present invention, the heating rate during sintering in step S2 is 5–50 °C / min, and the sintering time is 6–30 h. The sintering in step S2 is further preferably performed using a two-stage sintering process: a first stage, sintering at 600–750 °C for 5–7 h; and a second stage, sintering at 800–1000 °C for 12–16 h.

[0046] Commonly used nickel sources, iron sources, manganese sources, sodium sources, M sources, and M sources in this field y All sources can be used in this invention. In step 3, M is added. y This is to enable the formation of a metal oxide coating layer on the surface of the cathode material after sintering.

[0047] The nickel source includes, but is not limited to, at least one of nickel sulfate, nickel acetate, and nickel nitrate; the iron source includes, but is not limited to, at least one of ferric nitrate, ferric chloride, ferric sulfate, ferric acetate, and ferric oxalate; the manganese source includes, but is not limited to, at least one of manganese nitrate, manganese chloride, manganese sulfate, manganese acetate, and manganese oxalate; the sodium source includes, but is not limited to, at least one of sodium hydroxide, sodium carbonate, sodium acetate, and sodium nitrate; the M source includes, but is not limited to, at least one of alumina, molybdenum oxide, and calcium oxide; the M y The source includes, but is not limited to, at least one of alumina, aluminum fluoride, silicon oxide, and boron oxide.

[0048] Sodium-ion secondary battery

[0049] Embodiments of the present invention also provide a secondary battery comprising the above-described positive electrode material.

[0050] The secondary battery of this invention is assembled by stacking positive electrode, separator, and negative electrode. After assembly, electrode tabs are welded on, and then the battery is placed in an aluminum-plastic film. Electrolyte is injected into the aluminum-plastic shell, and then the battery is finally formed through processes such as encapsulation, settling, formation, aging, and shaping.

[0051] Positive electrode sheet

[0052] The positive electrode sheet of the present invention includes a positive current collector and a positive electrode material layer disposed on the positive current collector. The positive electrode material layer includes the aforementioned positive electrode material and may also include a binder and a conductive agent.

[0053] The positive electrode sheet of the present invention is prepared by mixing the above-mentioned positive electrode material, binder and conductive agent in a solvent to form a positive electrode active slurry, which is then coated onto a positive electrode current collector and obtained by drying, compacting, slitting and die-cutting. The weight ratio of each component in the positive electrode active slurry is: positive electrode material: binder: conductive agent: dispersant = (95~99): (1~2): (1.5~2.5).

[0054] Conventional binders, conductive agents, and solvents used in this invention can all be used. The binder can be commonly used PVDF; the conductive agent can be at least one of conductive carbon black or carbon nanotubes; and the solvent can be NMP (N-methylpyrrolidone).

[0055] In some embodiments of the present invention, the positive electrode current collector is aluminum foil. The thickness of the aluminum foil is 10-15 μm, and in some embodiments, the thickness of the aluminum foil is 12 μm. A thinner aluminum foil can improve the energy density of the sodium-ion battery, while a thinner aluminum foil is prone to processing problems such as wrinkling and curling.

[0056] Conventional negative electrode sheets, separators, electrolytes, and assembly processes used in secondary batteries can all be used in this invention.

[0057] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on the negative current collector. The negative active material layer includes one or more of the following: natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, and soft carbon. The negative current collector is a copper foil, which can be 5-8 μm thick; in some embodiments, the thickness of the copper foil is 6 μm.

[0058] The diaphragm includes, but is not limited to, at least one of polyethylene, polypropylene, or polyvinylidene fluoride.

[0059] The electrolyte includes an electrolyte salt and an organic solvent: the electrolyte salt includes, but is not limited to, at least one of NaPF6, NaClO4, NaBCl4 and NaSO3CF3; the organic solvent includes, but is not limited to, at least one of cyclic carbonates and carboxylic acid esters.

[0060] Finally, the present invention also protects electrical devices that include the secondary battery.

[0061] The present invention provides the following embodiments to facilitate understanding of the invention. These embodiments are provided not to limit the scope of the claims.

[0062] Examples 1-29, Comparative Examples 1-2

[0063] Example 1

[0064] A secondary battery is provided, and the specific preparation process includes the following steps:

[0065] 1) Preparation of cathode materials

[0066] S1. Nickel sulfate, ferric sulfate, and manganese sulfate are added to water and mixed thoroughly to obtain a precursor solution. The molar ratio of nickel, iron, and manganese in the precursor solution is 32:28:33. Nitrogen gas is introduced as a protective gas, and then 0.1 mol / L ammonia solution is added to adjust the pH of the precursor solution to 12. The reaction is carried out at 30°C for 10 hours. The precipitate obtained is the nickel-manganese-iron metal salt precursor Ni. 0.32 Fe 0.28 Mn 0.33 (OH)2;

[0067] S2. The above nickel-manganese-iron metal salt precursor, sodium nitrate, and aluminum isopropoxide (dopant) were mixed in a molar ratio of 1:0.65:0.07. The mixture was then sintered at 600°C for 6 hours in an oxygen atmosphere, followed by sintering at 800°C for 15 hours at a heating rate of 5°C / min to obtain solid Na powder. 0.65 Al 0.07 Ni 0.32 Fe 0.28 Mn 0.33 O2;

[0068] S3. Mix 100 parts by weight of solid powder with 0.3 parts by weight of alumina (coating agent), sinter in air at 450°C for 8 hours, pulverize and sieve to obtain a cathode material coated with alumina.

[0069] 2) Preparation of a positive electrode sheet

[0070] The prepared positive electrode material, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black were mixed in a mass ratio of 96:2:2, and N-methylpyrrolidone solvent was added. The mixture was then stirred in a vacuum mixer until the system was homogeneous to obtain the positive electrode slurry. The positive electrode slurry was uniformly coated onto both surfaces of an aluminum foil. The coated electrode was dried in an oven and then cold-pressed and slit to obtain the positive electrode sheet.

[0071] 3) Preparation of a negative electrode sheet

[0072] The negative electrode active material hard carbon, thickener sodium carboxymethyl cellulose, binder styrene-butadiene rubber, and conductive agent acetylene black are mixed in a mass ratio of 97:1:1:1, deionized water is added, and a negative electrode slurry is obtained under the action of a vacuum stirrer. The negative electrode slurry is uniformly coated on both sides of the negative electrode current collector copper foil. The coated electrode sheet is transferred to an oven to dry, and then cold-pressed and slit to obtain the negative electrode sheet.

[0073] 4) Preparation of an electrolyte

[0074] The organic solvent is a mixture containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC, and DEC is 20:20:60. In an argon-atmospheric glove box, thoroughly dried electrolyte salt NaClO4 is dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0075] 5) Assembly of a secondary battery

[0076] The positive electrode, separator (polypropylene), and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. After being wound into a square bare cell, it is placed in an aluminum-plastic shell, baked at 80°C to remove water, injected with electrolyte, and sealed. After processes such as standing, hot and cold pressing, formation, clamping, and capacity testing, the secondary battery is obtained.

[0077] Examples 2-29, Comparative Examples 1-2

[0078] A secondary battery is provided, prepared using the same method as in Example 1, except that cathode materials with different parameter characteristics are obtained by changing the process parameters and other conditions of the cathode material (see Table 1 for details). Specifically, the coating material is adjusted by changing the type of coating agent, the type of dopant element is adjusted by changing the type of dopant, and the particle size distribution and specific surface area are adjusted by adjusting the crushing and sieving parameters of the pulverizer. Different full width at half maximum (FWHM) D... FW The cathode material can be obtained by adjusting the heating rate and sintering time in the preparation process, and the cathode material with different compaction densities can be adjusted by adjusting the pressure of cold pressing.

[0079] The specific surface area of ​​the cathode material was obtained by measuring the specific surface area.

[0080] Particle size distribution (D) v50 D n50 and D FW The test method (unit: μm) is as follows: Determination of the cathode by laser particle size analyzer The particle size distribution of the material is determined, and the interval particle size distribution curve is drawn, and finally D v50 , D n50 , and D FW The physical property parameters are determined.

[0081] The performance of the secondary batteries prepared in the above embodiments and comparative examples was tested. The specific test items, test methods, and results are as follows (see Table 2):

[0082] 1. First-cycle discharge specific capacity (mAh / g): At 25℃, the prepared secondary battery is charged at a constant current rate of 0.1C to the upper limit of voltage 3.9V, left to stand for 5 minutes, and then discharged at a constant current rate of 0.1C to the lower limit of voltage 1.5V, left to stand for 5 minutes. This is the first cycle of charge and discharge. The discharge specific capacity of this cycle is the first-cycle discharge specific capacity of the secondary battery.

[0083] 2.500-cycle room temperature (25℃) 1C cycle retention rate (%): At 25℃, the secondary battery is charged at a constant current of 1C to 3.9V and then left to stand for 5 minutes. It is then discharged to a voltage of 1.5V. This is one charge-discharge cycle. The ratio of the discharge specific capacity of the first cycle to that after 500 cycles, multiplied by 100%, is the 500-cycle room temperature (25℃) cycle retention rate.

[0084] 3.15d storage gas production volume expansion rate (%): 3.9V fully charged, the initial volume V0 of the battery was tested using the water displacement method. After storage in a 70℃ constant temperature chamber for 15 days, the battery volume V was tested using the water displacement method. t Gas production volume expansion rate (%) = [(V t -V0) / V0]*100%.

[0085] 4. Cycle retention rate at 4C rate after 300 cycles (%): At 25°C, the sodium-ion battery is charged at a constant current of 4C to 3.9V and then left to stand for 5 minutes. It is then discharged to a voltage of 1.5V. This is one charge-discharge cycle. The ratio of the discharge specific capacity of the first cycle to that after 300 cycles, multiplied by 100%, is the cycle retention rate at 4C rate after 300 cycles.

[0086] Table 1

[0087]

[0088] Table 2

[0089]

[0090] The results above show that:

[0091] Reasonable control of the morphology and size of cathode materials, especially the specific surface area (BET) and particle size (D) of cathode materials. v50 A proper combination of these elements can significantly improve battery performance.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A positive electrode material, characterized in that, The positive electrode material includes a metal oxide, which contains Na, Ni, Fe and Mn elements; The chemical formula of the metal oxide is Na. a M b Ni c Fe d Mn e O 2-f , 0.6≤a≤0.75, 0.05<b<0.15, 0.15<c<0.45, 0.05<d<0.40, 0.05<e<0.40, 0≤f≤0.1, and b+c+d+e=1; wherein, M includes at least one of Zr, Nb, B, Li, Mg, Al, Si, P, Ca, Ti, Cr, V, Zn, Cu; Furthermore, the positive electrode material satisfies the following conditions: 1.0×10 9 ≤BET / [π(D v50 ×10 -6 ) 2 ]≤3.5×10 10 ,0.7≤D v50 / D n50 ≤9.5,2.5≤D FW ≤15.5; Among them, D v50 The particle size, in μm, corresponds to a cumulative volume distribution percentage of the cathode material reaching 50%. D n50 The particle size, in μm, corresponds to a cumulative percentage distribution of the positive electrode material reaching 50%. BET is the specific surface area of ​​the positive electrode material, in m². 2 / g; D FW The full width at half maximum (FWHM) D of the interval particle size distribution curve of the cathode material. FW The unit is μm.

2. The cathode material according to claim 1, characterized in that, The particle size of the positive electrode material satisfies: 3.0 μm ≤ D v50 ≤19.5μm, and / or 0.4μm≤D n50 ≤13μm.

3. The cathode material according to claim 1, characterized in that, The specific surface area of ​​the positive electrode material satisfies: 0.3 m² / g. 2 / g≤BET≤3.5m 2 / g.

4. The cathode material according to claim 1, characterized in that, The metal oxide further has a coating layer comprising a metal oxide material, wherein the metal oxide material comprises at least one selected from ZrO2, NbO, B2O3, Li2O, MgO, Al2O3, SiO2, P2O5, CaO, Ti2O3, Cr2O3, VO, ZnO, and CuO.

5. The positive electrode material according to claim 4, characterized in that, The coating layer accounts for 0.1% to 3.5% of the weight of the metal oxide.

6. A secondary battery, comprising a positive electrode, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on the positive current collector, wherein the positive electrode material layer includes the positive electrode material according to any one of claims 1 to 5.

7. An electrical device, characterized in that, It includes the secondary battery as described in claim 6.

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