Coating method for cathode material, coating system, cathode composite material and use

Abstract

The application relates to a coating method and system of a positive electrode material, a positive electrode composite material and an application, and belongs to the technical field of lithium secondary batteries. The positive electrode composite material provided by the application comprises an inner core and an in-situ coating layer coated on the surface of the inner core, the inner core comprises a positive electrode material, the chemical formula of the positive electrode material is LiNi x M 1‑x O2, M is one or more of Mn, Co, Al, B, Ti, Zr, Sr, Nb, Ta and W, and 0.8<=x<=1; the material of the in-situ coating layer comprises one or more of Li2CO3, Li2SO3 and Li2SO4. The positive electrode composite material provided by the application can solve the problem of air corrosion during storage of the nickel-rich positive electrode material, and simultaneously improve the cycle life of the positive electrode composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium secondary batteries, in particular to a coating method and system of a positive electrode material, a positive electrode composite material and use. BACKGROUND

[0002] To promote the progress of carbon peak and carbon neutralization and improve the utilization rate of clean energy, the next generation of lithium ion batteries is developing towards higher energy density. High-nickel layered positive electrode materials have high energy density and low cost, so the development of high-nickel layered positive electrode materials can effectively promote the development of the next generation of high-specific-energy lithium ion batteries. However, high-nickel layered positive electrode materials face serious interface stability problems, mainly manifested in that the air contact of high-nickel layered positive electrode materials, the residual lithium oxide and the surface lattice lithium on the material surface in the solid-phase reaction will chemically react with water (H2O) and carbon dioxide (CO2) to produce lithium carbonate (Li2CO3), lithium bicarbonate (LiHCO3) and lithium hydroxide (LiOH) and other impurities. The presence of residual lithium compounds not only makes the storage environment of the nickel-rich positive electrode material more stringent, increasing the cost of the material, but also has many effects on the subsequent slurry preparation and the electrochemical performance of the positive electrode material, and even causes battery safety problems. SUMMARY

[0003] Therefore, it is necessary to provide a coating method and system of a positive electrode material, a positive electrode composite material and use to solve the problem of air corrosion during the storage of nickel-rich positive electrode materials and improve the cycle life of the positive electrode composite material.

[0004] To achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0005] The present application provides a positive electrode composite material, which comprises an inner core and an in-situ coating layer coated on the surface of the inner core, and the inner core comprises a positive electrode material.

[0006] In some embodiments, the chemical formula of the positive electrode material is LiNi x M 1-x O2, M is one or more of Mn, Co, Al, B, Ti, Zr, Sr, Nb, Ta and W, and 0.8≤x≤1.

[0007] In some embodiments, the material of the in-situ coating layer comprises one or more of Li2CO3, Li2SO3 and Li2SO4.

[0008] In some embodiments, the material of the in-situ coating layer comprises one or more of Li2CO3, Li2SO3 and Li2SO4, and Li2CO3, Li2SO3 and Li2SO4 are amorphous structures.

[0009] In some embodiments, the particle size D50 of the positive electrode composite material is 2-15 μm.

[0010] In some embodiments, the specific surface area of the positive electrode composite material is 0.2-2.0 m 2 / g.

[0011] In some embodiments, the pH value of the positive electrode composite material is < 12.5.

[0012] In some embodiments, the content of LiOH in the positive electrode composite material is < 3500 ppm.

[0013] In some embodiments, the content of water in the positive electrode composite material is < 1000 ppm.

[0014] The present application also provides a coating method of a positive electrode material, comprising the following steps:

[0015] The positive electrode material is subjected to airflow crushing treatment and coating treatment simultaneously using a mixed gas to obtain a crushing product;

[0016] The crushing product is subjected to grading treatment and screening treatment in sequence to obtain a positive electrode composite material, which comprises an inner core and an in-situ coating layer coated on the surface of the inner core, and the inner core comprises the positive electrode material.

[0017] In some embodiments, the chemical formula of the positive electrode material is LiNi x M 1-x O2, M is one or more of Mn, Co, Al, B, Ti, Zr, Sr, Nb, Ta and W, and 0.8≤x≤1.

[0018] In some embodiments, the mixed gas comprises one or more of air, O2, N2, O3, CO2 and SO2.

[0019] Optionally, the gas pressure of the airflow crushing treatment is 0.2-1.0 MPa.

[0020] In some embodiments, the material of the in-situ coating layer comprises one or more of Li2CO3, Li2SO3 and Li2SO4.

[0021] In some embodiments, the material of the in-situ coating layer comprises one or more of Li2CO3, Li2SO3 and Li2SO4, and Li2CO3, Li2SO3 and Li2SO4 are amorphous structures.

[0022] In some embodiments, before the airflow crushing treatment and the coating treatment, pre-crushing treatment and pre-screening treatment are further included in sequence.

[0023] In some embodiments, the maximum particle size D max <5mm.

[0024] In some embodiments, the content of LiOH in the positive electrode material is 3500-7000 ppm.

[0025] In some embodiments, the maximum particle size D max <5mm.

[0026] In some embodiments, the screen hole size of the screening treatment is 40-300 μm.

[0027] In some embodiments, the particle size D50 of the positive electrode composite material is 2-15 μm.

[0028] In some embodiments, the specific surface area of the positive electrode composite material is 0.2-2.0 m 2 / g.

[0029] In some embodiments, the pH value of the positive electrode composite material is <12.5.

[0030] In some embodiments, the content of LiOH in the positive electrode composite material is <3500 ppm.

[0031] In some embodiments, the content of water in the positive electrode composite material is <1000 ppm.

[0032] The application also provides a coating system for a positive electrode material, comprising an air flow mill and a gas delivery device, the gas delivery device comprising a first gas storage tank, a second gas storage tank, a first pressure regulating valve, a second pressure regulating valve, a third pressure regulating valve, a first flow meter, a second flow meter, a first branch pipe, a second branch pipe and a main pipe;

[0033] The first gas storage tank, the first pressure regulating valve and the first flow meter are connected in series through the first branch pipe, the second gas storage tank, the second pressure regulating valve and the second flow meter are connected in series through the second branch pipe, the first branch pipe and the second branch pipe are connected in parallel to form a parallel pipeline, the parallel pipeline is connected in series on the main pipe for forming a mixed gas, the main pipe is connected with the air flow mill, and the third pressure regulating valve is arranged on the main pipe.

[0034] The air flow mill simultaneously performs air flow milling treatment and coating treatment on the positive electrode material by using the mixed gas.

[0035] In some embodiments, the coating system of the positive electrode material further comprises a classifier, a first sifter, a cyclone separator and a universal collector, the classifier and the first sifter are sequentially used for classifying and sieving the positive electrode material pulverized by the jet mill, and the cyclone separator and the universal collector are used for dust removal of the powder generated by the classifier.

[0036] In some embodiments, the coating system of the positive electrode material further comprises a communication pipe for communicating the jet mill, the classifier and the main pipe to recycle the mixed gas.

[0037] In some embodiments, the coating system of the positive electrode material further comprises a crushing device and a second sifter arranged in sequence, the crushing device is used for pre-crushing the positive electrode material, and the second sifter is used for pre-sieving the positive electrode material.

[0038] In some embodiments, the positive electrode material is obtained by calcining a lithium salt and a precursor mixture, and the calcining is performed in a sintering device.

[0039] In some embodiments, the process conditions of the calcining include a calcining temperature of 600-1000℃, a heating rate of 2-5℃ / min, a calcining time of 8-20h, and a calcining atmosphere comprising oxygen.

[0040] In some embodiments, the sintering device comprises one or more of a roller kiln, a push plate kiln and a bell jar kiln.

[0041] In some embodiments, the crushing device comprises one or more of a roller crusher, a jaw crusher and a disc crusher.

[0042] In some embodiments, the jet mill comprises one or more of a flat jet mill, a counter jet mill and a fluidized bed impingement jet mill.

[0043] The application also provides a positive electrode tab, comprising a positive electrode composite material, the positive electrode composite material being the above-mentioned positive electrode composite material, or being a positive electrode composite material obtained by coating a positive electrode material using the above-mentioned coating method, or being a positive electrode composite material obtained by coating a positive electrode material using the above-mentioned coating system.

[0044] The application also provides a battery comprising the above-mentioned positive electrode tab.

[0045] The application also provides an electric device comprising the above-mentioned battery.

[0046] Compared with the prior art, the coating method, the coating system, the positive electrode composite material and the use of the positive electrode material have the following advantages:

[0047] (1) The air stability of the positive electrode composite material is good, the problem of air corrosion during storage of the nickel-rich positive electrode material is solved, direct contact between the positive electrode material and the electrolyte is avoided, a more stable interface CEI layer is generated during the cycle process, and the cycle life of the positive electrode composite material is improved.

[0048] (2) The coating method and coating system of the positive electrode material are subjected to airflow crushing treatment and coating treatment at the same time, the positive electrode composite material obtained has an in-situ coating layer formed on the surface of the positive electrode material core, the specific modification of the surface of the positive electrode material is realized, the pH value of the positive electrode composite material is less than 12.5, the content of lithium hydroxide is less than 3500 ppm, the generation of harmful residual lithium compounds such as LiOH is reduced, the air stability of the positive electrode composite material is effectively improved, the problem of air corrosion during production and storage of the nickel-rich positive electrode material is solved, direct contact between the positive electrode material and the electrolyte is avoided, a more stable interface CEI layer is generated during the cycle process, and the cycle life of the positive electrode composite material is improved.

[0049] (3) In the coating method and coating system, mixed gas is used as the crushing gas source, so that the airflow crushing treatment and the coating treatment are carried out at the same time, the water washing process and the secondary coating calcination process are omitted, the production efficiency is improved, and the production cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 It is a schematic diagram of the coating system of the positive electrode material in some embodiments of the present application.

[0051] Figure 2 It is a structural schematic diagram of the gas conveying device in some embodiments of the present application.

[0052] Figure 3 It is an SEM image of the positive electrode composite material of Example 1 of the present application.

[0053] Figure 4 It is an EDS element distribution map of the positive electrode composite material of Example 1 of the present application.

[0054] Figure 5 It is an HRTEM image of the positive electrode composite material of Example 1 of the present application.

[0055] Figure 6 It is a cycle performance diagram of the positive electrode composite material of Example 1 and Comparative Examples 1-2 of the present application under 0.3C rate for 100 cycles.

[0056] Figure 2In the figure, 1-first gas storage tank, 2-first pressure regulating valve, 3-first flow meter, 4-first branch pipe, 5-second gas storage tank, 6-second pressure regulating valve, 7-second flow meter, 8-second branch pipe, 9-main pipe, 10-third pressure regulating valve, 11-airflow pulverizer, 12-communication pipe, 13-classifier. DETAILED DESCRIPTION

[0057] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application and not used to limit the present application.

[0058] In the description of the present application, unless otherwise defined, the professional terms and professional words not explicitly described are the same as the meanings commonly understood by the skilled in the art, and are the common knowledge of the skilled in the art, and the methods not explicitly described are the conventional methods known to the skilled in the art. The term "multiple" in the present application means at least two, for example, two, three, etc., unless otherwise specifically limited.

[0059] In the present application, the technical features described in an open manner include both the closed technical solution consisting of the listed features and the open technical solution containing the listed features.

[0060] An embodiment of the present application provides a positive electrode composite material, which comprises a core and an in-situ coating layer covering the surface of the core, and the core comprises a positive electrode material.

[0061] The positive electrode composite material provided by the present application has good air stability, can solve the problem of air erosion during storage of the nickel-rich positive electrode material, and can improve the cycle life of the positive electrode composite material.

[0062] In some embodiments, the chemical formula of the positive electrode material is LiNi x M 1-x O2, M is one or more of Mn, Co, Al, B, Ti, Zr, Sr, Nb, Ta and W, and 0.8≤x≤1. Understandably, x can be any value between 0.8 and 1, for example, x can be 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98 or 1, etc.

[0063] In some embodiments, the material of the in-situ coating layer comprises one or more of Li2CO3, Li2SO3 and Li2SO4.

[0064] In some embodiments, the material of the in-situ coating layer comprises one or more of Li2CO3, Li2SO3, and Li2SO4, which are in amorphous structure.

[0065] In some embodiments, the particle size D50 of the positive electrode composite material is 2-15 μm. It can be understood that the particle size D50 of the positive electrode composite material can be any value between 2-15 μm, for example, the particle size D50 of the positive electrode composite material can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm, etc.

[0066] In some embodiments, the specific surface area of the positive electrode composite material is 0.2-2.0 m2 / g. It can be understood that the specific surface area of the positive electrode composite material can be 0.2 m2 / g, 0.3 m2 / g, 0.4 m2 / g, 0.5 m2 / g, 0.6 m2 / g, 0.7 m2 / g, 0.8 m2 / g, 0.9 m2 / g, 1.0 m2 / g, 1.1 m2 / g, 1.2 m2 / g, 1.3 m2 / g, 1.4 m2 / g, 1.5 m2 / g, 1.6 m2 / g, 1.7 m2 / g, 1.8 m2 / g, 1.9 m2 / g, or 2.0 m2 / g. The specific surface area of the positive electrode composite material can also be other values between 0.2-2.0 m2 / g. 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 The specific surface area of the positive electrode composite material can also be other values between 0.2-2.0 m2 / g. x 1-x In some embodiments, the pH value of the positive electrode composite material is <12.5. It can be understood that the pH value of the positive electrode composite material can be 10, 10.2, 10.4, 10.6, 10.8, 11, 11.2, 11.4, 11.6, 12.0, or 12.5, etc. max max ​​​​​​​​​​​​​​​In some embodiments, the content of LiOH in the positive electrode composite is < 3500 ppm. Understandably, the content of LiOH in the positive electrode composite can be 1 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 2000 ppm, 2400 ppm, 2800 ppm, 3000 ppm, or 3500 ppm.

[0069] The pH value of the positive electrode composite is lower than 12.5, and the content of lithium hydroxide is lower than 3500 ppm, which reduces the generation of harmful residual lithium compounds such as LiOH, effectively improves the air stability of the positive electrode composite, solves the problem of air corrosion during storage of the nickel-rich positive electrode material, avoids the direct contact of the positive electrode material with the electrolyte, thereby generating a more stable interface CEI layer in the cycle process, and further improves the cycle life of the positive electrode composite.

[0070] In some embodiments, the content of water in the positive electrode composite is < 1000 ppm. Understandably, the content of water in the positive electrode composite can be 0.5 ppm, 1 ppm, 2 ppm, 3 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, 30 ppm, 50 ppm, 70 ppm, 90 ppm, 110 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 550 ppm, 650 ppm, 750 ppm, 850 ppm, 950 ppm, or 990 ppm.

[0071] Another embodiment of the present application provides a coating method of a positive electrode material, which comprises the following steps:

[0072] The positive electrode material is subjected to airflow crushing treatment and coating treatment simultaneously by using mixed gas to obtain a crushing product;

[0073] The crushing product is subjected to grading treatment and screening treatment in sequence to obtain a positive electrode composite, and the positive electrode composite comprises a core and an in-situ coating layer coated on the surface of the core, and the core comprises the positive electrode material.

[0074] On the one hand, the in-situ coating layer effectively improves the air stability of the positive electrode composite material, isolates the direct contact between the positive electrode material and the electrolyte, generates a more stable positive electrode material interface CEI layer in the cycle process, and improves the cycle life of the material. On the other hand, the mixed gas as a crushing gas source can simultaneously perform airflow crushing treatment and coating treatment on the positive electrode material, eliminating the need for traditional water washing and secondary coating calcination processes, improving production efficiency, reducing production costs by 15% per ton, and simultaneously solving the problem of air erosion during the production and storage of nickel-rich positive electrode materials.

[0075] In some embodiments, the positive electrode material has a chemical formula of LiNi x M 1-x O2, M is one or more of Mn, Co, Al, B, Ti, Zr, Sr, Nb, Ta and W, and 0.8≤x≤1. Understandably, x can be any value between 0.8 and 1, for example, x can be 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98 or 1, etc.

[0076] In some embodiments, the mixed gas includes one or more of air, O2, N2, O3, CO2 and SO2. It should be explained that the mixed gas includes a high-pressure gas and an auxiliary gas, wherein the high-pressure gas includes but is not limited to air, O2 and N2, etc., and the auxiliary gas includes but is not limited to O3, CO2 and SO2, etc. Both the high-pressure gas and the auxiliary gas can perform airflow crushing treatment on the positive electrode material, and the auxiliary gas provides raw materials for the in-situ coating layer.

[0077] In some embodiments, the material of the in-situ coating layer includes one or more of Li2CO3, Li2SO3 and Li2SO4.

[0078] It should be noted that the auxiliary gas CO2 reacts with the positive electrode material to generate Li2CO3, the auxiliary gas SO2 reacts with the positive electrode material to generate Li2SO3, and the auxiliary gas SO2, O3 and the positive electrode material react to generate Li2SO4.

[0079] In some embodiments, the material of the in-situ coating layer includes one or more of Li2CO3, Li2SO3 and Li2SO4, and Li2CO3, Li2SO3 and Li2SO4 are amorphous structures.

[0080] In some embodiments, before the airflow crushing treatment and the coating treatment, pre-crushing treatment and pre-screening treatment are sequentially performed. It should be noted that the equipment or device used for the pre-crushing treatment and the pre-screening treatment is not particularly limited in the present application, as long as the maximum particle size D max of the positive electrode material obtained by the pre-screening treatment is less than 5 mm.

[0081] In some embodiments, the maximum particle size D max of the positive electrode material is less than 5 mm. The maximum particle size D max may be, for example, 4.95 mm, 4.9 mm, 4.8 mm, 4.5 mm, 4 mm, 3.5 mm, 3 mm, 2.5 mm, 2 mm, 1.5 mm, 1 mm, 500 μm, 400 μm, 300 μm, 200 μm, 100 μm, 50 μm, 20 μm, or 10 μm, etc.

[0082] In some embodiments, the content of LiOH in the positive electrode material is 3500-7000 ppm. It can be understood that the content of LiOH in the positive electrode material can be any value between 3500-7000 ppm, for example, it can be 3500 ppm, 3600 ppm, 3700 ppm, 3800 ppm, 4000 ppm, 4200 ppm, 4500 ppm, 4700 ppm, 4900 ppm, 5000 ppm, 5500 ppm, 6000 ppm, 6500 ppm, or 7000 ppm, etc. Alternatively, the testing method of the content of LiOH in the positive electrode material can be: collecting the positive electrode material, sieving with a 325 mesh sieve, and taking the sieved product for testing.

[0083] In some embodiments, the maximum particle size D max of the crushed product is less than 5 mm. It can be understood that the maximum particle size D max of the crushed product can be 4.95 mm, 4.9 mm, 4.85 mm, 4.8 mm, 4.75 mm, 4.5 mm, 4.2 mm, 4 mm, 3.7 mm, 3.5 mm, 3.2 mm, 3 mm, 2.5 mm, 2 mm, 1.5 mm, 1 mm, 500 μm, 400 μm, 300 μm, 200 μm, 100 μm, 50 μm, 20 μm, or 10 μm, etc.

[0084] In some embodiments, the sieve aperture size of the sieving treatment is 40-300 μm. It can be understood that the sieve aperture size of the sieving treatment can include but is not limited to 40 μm, 45 μm, 55 μm, 65 μm, 80 μm, 90 μm, 100 μm, 125 μm, 140 μm, 180 μm, 200 μm, or 300 μm.

[0085] In some embodiments, the particle size D50 of the positive electrode composite is 2-15 μm. It is appreciated that the particle size D50 of the positive electrode composite can be any value between 2-15 μm, for example, the particle size D50 of the positive electrode composite can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm, etc.

[0086] In some embodiments, the specific surface area of the positive electrode composite is 0.2-2.0 m 2 / g. It is appreciated that the specific surface area of the positive electrode composite can be 0.2 m 2 / g, 0.3 m 2 / g, 0.4 m 2 / g, 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1.0 m 2 / g, 1.2 m 2 / g, 1.4 m 2 / g, 1.6 m 2 / g, 1.8 m 2 / g, or 2.0 m 2 / g. The specific surface area of the positive electrode composite can also be other values between 0.2-2.0 m 2 / g.

[0087] In some embodiments, the pH value of the positive electrode composite is < 12.5. It is appreciated that the pH value of the positive electrode composite can be 10, 10.2, 10.4, 10.6, 10.8, 11, 11.2, 11.4, 11.6, 12.0, or 12.5, etc.

[0088] In some embodiments, the content of LiOH in the positive electrode composite is < 3500 ppm. It is appreciated that the content of LiOH in the positive electrode composite can be 1 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 2000 ppm, 2400 ppm, 2800 ppm, 3000 ppm, or 3500 ppm.

[0089] In some embodiments, the content of water in the positive electrode composite is <1000 ppm. It can be understood that the content of water in the positive electrode composite can be 0.5 ppm, 1 ppm, 2 ppm, 3 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, 30 ppm, 50 ppm, 70 ppm, 90 ppm, 110 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 550 ppm, 650 ppm, 750 ppm, 850 ppm, 950 ppm or 990 ppm.

[0090] In combination Figure 1 and Figure 2 , another embodiment of the present application provides a coating system of a positive electrode material, comprising an air flow mill 11 and a gas conveying device, the gas conveying device comprising a first gas storage tank 1, a second gas storage tank 5, a first pressure regulating valve 2, a second pressure regulating valve 6, a third pressure regulating valve 10, a first flow meter 3, a second flow meter 7, a first branch pipe 4, a second branch pipe 8 and a main pipe 9;

[0091] The first gas storage tank 1, the first pressure regulating valve 2 and the first flow meter 3 are connected in series through the first branch pipe 4, the second gas storage tank 5, the second pressure regulating valve 6 and the second flow meter 7 are connected in series through the second branch pipe 8, the first branch pipe 4 and the second branch pipe 8 are connected in parallel to form a parallel pipe, and the parallel pipe is connected in series on the main pipe 9 to form a mixed gas, the main pipe 9 is connected with the air flow mill 11, and the third pressure regulating valve 10 is arranged on the main pipe;

[0092] The air flow mill 11 utilizes the mixed gas to simultaneously perform air flow milling treatment and coating treatment on the positive electrode material.

[0093] The air flow mill 11 utilizes the mixed gas to simultaneously perform air flow milling treatment and coating treatment on the positive electrode material, and directly obtains or obtains a positive electrode composite through subsequent further processing, the positive electrode composite comprises an inner core and an in-situ coating layer coated on the surface of the inner core, and the inner core comprises a positive electrode material. The first gas storage tank 1 is used for storing high-pressure gas, and the high-pressure gas includes but is not limited to air, O2 and N2, etc., the second gas storage tank 5 is used for storing auxiliary gas, and the auxiliary gas includes but is not limited to O3, CO2 and SO2, etc., and adjusting the first pressure regulating valve 2, the second pressure regulating valve 6 and the third pressure regulating valve 10 can adjust the flow and gas pressure of the mixed gas in the main pipe 9. The high-pressure gas and the auxiliary gas can both perform air flow milling treatment on the positive electrode material, and the auxiliary gas provides raw materials for preparing the in-situ coating layer.

[0094] The airflow pulverizer 11 uses mixed gas as a pulverizing gas source, and realizes the simultaneous pulverization and coating of the positive electrode material in the airflow pulverizer 11, thereby eliminating the traditional water washing and secondary coating calcination process and improving the production efficiency. Moreover, the coating system can form an in-situ coating layer on the surface of the positive electrode material, effectively improving the air stability of the positive electrode composite material, isolating the direct contact between the positive electrode material and the electrolyte, generating a more stable positive electrode material interface CEI layer in the cycle process, improving the cycle life of the material, and solving the problem of air erosion during the production and storage of the nickel-rich positive electrode material.

[0095] In combination Figure 1 and Figure 2 In some embodiments, the coating system of the positive electrode material further includes a classifier 13, a first screen, a cyclone separator, and a universal collector, the classifier 13 and the first screen are used for grading and screening the positive electrode material pulverized by the airflow pulverizer 11, and the cyclone separator and the universal collector are used for dust removal of the powder generated by the classifier 13.

[0096] The fine powder generated by the classifier 13 is collected into the universal collector after being treated by the cyclone separator, and the gas is discharged after being dusted and filtered. The cyclone separator and the universal collector are provided for dust removal, thereby reducing environmental pollution caused by the coating process of the positive electrode material.

[0097] In combination Figure 1 and Figure 2 In some embodiments, the coating system of the positive electrode material further includes a communication pipe 12 for connecting the airflow pulverizer 11, the classifier 13, and the main pipe 9 to recycle the mixed gas.

[0098] In some embodiments, the coating system of the positive electrode material further includes a crushing device and a second screen arranged in sequence, the crushing device is used for pre-crushing the positive electrode material, and the second screen is used for pre-screening the positive electrode material.

[0099] In some embodiments, the positive electrode material is obtained by calcining a lithium salt and a precursor mixture. The calcination process is carried out in a sintering device. The lithium salt and the precursor mixture are not particularly limited in the present application, as long as the lithium salt and the precursor mixture commonly used in the technical field can be used to prepare the positive electrode material by calcination process.

[0100] In some embodiments, the process conditions of the calcination treatment include: a calcination temperature of 600-1000℃, a heating rate of 2-5℃ / min, a calcination time of 8-20h, and a calcination atmosphere including oxygen. The calcination treatment of the positive electrode material before the jet milling treatment and the coating treatment can control the content of LiOH in the positive electrode material. Understandably, the calcination temperature can be 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 725℃, 750℃, 775℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, and the calcination temperature can also be other values between 600-1000℃; the heating rate can be 2℃ / min, 2.2℃ / min, 2.5℃ / min, 2.7℃ / min, 3℃ / min, 3.2℃ / min, 3.5℃ / min, 3.8℃ / min, 4℃ / min, 4.5℃ / min or 5℃ / min, and the heating rate can also be other values between 2-5℃ / min; the calcination time can include but is not limited to 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 16h, 17h, 18h, 19h or 20h, etc.

[0101] In some embodiments, the sintering device includes one or more of a roller kiln, a push plate kiln and a bell jar kiln.

[0102] In some embodiments, the crushing device includes one or more of a roller crusher, a jaw crusher and a disc crusher.

[0103] In some embodiments, the jet mill includes one or more of a flat jet mill, a counter jet mill and a fluidized bed counter jet mill.

[0104] Another embodiment of the present application provides a positive electrode tab, including a positive electrode composite material, the positive electrode composite material being the above-mentioned positive electrode composite material, or being a positive electrode composite material obtained by coating a positive electrode material using the above-mentioned coating method, or being a positive electrode composite material obtained by coating a positive electrode material using the above-mentioned coating system.

[0105] It should be noted that the positive electrode tab includes a current collector and a coating material arranged on the current collector, the coating material including a conductive agent, a binder and the above-mentioned composite material, the conductive agent can be selected from one or more of acetylene black, graphene, carbon black and carbon nanotubes, and the binder can use a binder commonly used in the lithium secondary battery technology field, such as PVDF, etc.

[0106] Another embodiment of the present application provides a battery comprising the positive electrode sheet. It should be noted that the present application does not have special restrictions on the assembly method of the battery, and a commonly used assembly method in the lithium secondary battery technical field can be used, for example, the positive electrode sheet, the separator and the negative electrode sheet can be assembled into a battery shell in a winding or stacking manner, and an electrolyte is injected to form a battery.

[0107] Another embodiment of the present application provides an electric device comprising the battery. It should be noted that the battery can be used as a power supply or an energy storage unit of the electric device, and the electric device of the present application can include, but is not limited to, an electric vehicle, an electric bicycle, a mobile phone, a computer or a smart home appliance.

[0108] The present application will be further described in detail below in combination with specific examples and comparative examples.

[0109] Example 1

[0110] The coating method of the positive electrode material comprises the following steps:

[0111] S1, a roller kiln is used to calcine the lithium salt and the precursor mixture to obtain a high-nickel layered positive electrode material LiNi 0.83 Co 0.06 Mn 0.11 O2, the calcination temperature is 800℃, the heating rate is 3℃ / min, the calcination time is 12h, and the calcination atmosphere is oxygen. The high-nickel layered positive electrode material LiNi 0.83 Co 0.06 Mn 0.11 O2 obtained by calcination is conveyed to a roller crusher for pre-crushing treatment, and a second screen is used for pre-screening treatment to obtain a positive electrode material after pre-screening treatment, wherein the D max <5mm, and the LiOH content is 4250ppm;

[0112] S2, the positive electrode material after pre-screening treatment is conveyed to an air jet crusher by air, and a mixed gas of N2 and SO2 is used to perform air jet crushing and coating treatment on the positive electrode material after pre-screening treatment in the crushing chamber of the air jet crusher to obtain a crushing product, wherein the D50 of the crushing product is 10.5μm, and the D max <35μm, wherein the flow ratio of N2 and SO2 gas is 60:40, and the air jet crushing pressure is 0.3MPa;

[0113] S3, the pulverized product is transported to the classifier and the first screen by the mixed gas of N2 and SO2, the first screen is 325 mesh, the aperture is 45 μm, the qualified product is collected into the collector and discharged for packaging, the fine powder is collected into the universal collector through the cyclone separator, the gas is discharged after dust removal and filtration, and the qualified product is the positive electrode composite material, which is the high-nickel layered positive electrode material LiNi 0.83 Co 0.06 Mn 0.11 O2.

[0114] Example 2

[0115] The coating method of the positive electrode material comprises the following steps:

[0116] S1, the lithium salt and the precursor mixture are calcined by using a roller kiln to obtain a calcined high-nickel layered positive electrode material LiNi 0.90 Co 0.05 Mn 0.05 O2, the calcination temperature is 780 DEG C, the heating rate is 4 DEG C / min, the calcination time is 15 h, and the calcination atmosphere is oxygen, and the calcined high-nickel layered positive electrode material LiNi 0.90 Co 0.05 Mn 0.05 O2 is transported to a roller crusher for pre-crushing treatment, and a second screen is used for pre-screening treatment to obtain the positive electrode material after pre-screening treatment, the D max <5mm, and the LiOH content is 4680 ppm;

[0117] S2, the positive electrode material after pre-screening treatment is transported to an air jet crusher by air, and the mixed gas of air and CO2 is used in the crushing chamber of the air jet crusher to perform air jet crushing treatment on the positive electrode material after pre-screening treatment, thereby obtaining a pulverized product, the D50 of the pulverized product is 6 μm, and the D max <15 μm, wherein the flow ratio of air and CO2 gas is 50:50, and the air jet crushing pressure is 0.4 MPa;

[0118] S3, the pulverized product is transported to the classifier and the first screen by the mixed gas of N2 and SO2, the first screen is 325 mesh, the aperture is 45 μm, the qualified product is collected into the collector and discharged for packaging, the fine powder is collected into the universal collector through the cyclone separator, the gas is discharged after dust removal and filtration, and the qualified product is the positive electrode composite material, which is the high-nickel layered positive electrode material LiNi 0.90 Co 0.05 Mn 0.05 O2.

[0119] Example 3

[0120] A coating method of a positive electrode material, comprising the following steps:

[0121] S1, a roller kiln is used to calcine a lithium salt and a precursor mixture, to obtain a high-nickel layered positive electrode material LiNi 0.92 Co 0.04 Mn 0.04 O2, the calcination temperature is 820℃, the heating rate is 2.5℃ / min, the calcination time is 15h, and the calcination atmosphere is oxygen, and the high-nickel layered positive electrode material LiNi 0.92 Co 0.04 Mn 0.04 O2 obtained by calcination is conveyed to a roller crusher for pre-crushing treatment, and a second screen is used for pre-screening treatment, to obtain a positive electrode material after pre-screening treatment, wherein the D max <5mm, and the LiOH content is 5060ppm;

[0122] S2, the positive electrode material after pre-screening treatment is conveyed to an air flow crusher by air, a mixed gas of N2, O3 and SO2 is used to perform air flow crushing treatment on the positive electrode material after pre-screening treatment in a crushing chamber of the air flow crusher, to obtain a crushing product, wherein the D50 of the crushing product is 3μm, and the D max <10μm, wherein the flow ratio of N2, O3 and SO2 gas is 40:5:35, and the air flow crushing pressure is 0.4MPa;

[0123] S3, the crushing product is conveyed to a classifier and a first screen by the above-mentioned mixed gas of N2, O3 and SO2 for classification and screening, the first screen is 325 mesh, and the aperture is 45μm, the particle size qualified product enters a collector for collection and discharging and packaging, the fine powder enters a universal collector through a cyclone separator, the gas is discharged after dust removal and filtration, and the particle size qualified product is a positive electrode composite material, which is a high-nickel layered positive electrode material LiNi 0.92 Co 0.04 Mn 0.04 O2 coated by Li2SO3 and Li2SO4.

[0124] Example 4

[0125] A coating method of a positive electrode material, comprising the following steps:

[0126] S1, a roller kiln is used to calcine a lithium salt and a precursor mixture, to obtain a high-nickel layered positive electrode material LiNi 0.92 Co 0.06 Mn 0.02 O2, the calcination temperature is 820℃, the heating rate is 2.5℃ / min, the calcination time is 15h, and the calcination atmosphere is oxygen, and the high-nickel layered positive electrode material LiNi0.92 Co 0.06 Mn 0.02 O2 is sent to a roller crusher for pre-crushing treatment, and a second screen is used for pre-screening treatment to obtain a pre-screening treated positive electrode material with a D max <5mm, and the LiOH content is 5140 ppm;

[0127] S2, the pre-screening treated positive electrode material is sent to an air flow crusher by air, and a mixed gas of N2, CO2 and SO2 is used to crush the pre-screening treated positive electrode material in the crushing chamber of the air flow crusher to obtain a crushing product, the D50 of the crushing product is 3.2 μm, and the D max <10 μm, wherein the flow ratio of N2, CO2 and SO2 gas is 60:25:15, and the air flow crushing pressure is 0.8 MPa;

[0128] S3, the crushing product is sent to a classifier and a first screen using the above-mentioned mixed gas of N2, CO2 and SO2 for classification and screening, the first screen is 200 mesh with a pore size of 75 μm, the particle size qualified product enters the collector for collection and is discharged and packaged, the fine powder enters the universal collector through the cyclone separator, the gas is discharged after dust removal and filtration, and the particle size qualified product is a positive electrode composite material, which is a high-nickel layered positive electrode material LiNi 0.92 Co 0.06 Mn 0.02 O2.

[0129] Example 5

[0130] A coating method of a positive electrode material, comprising the following steps:

[0131] S1, a roller kiln is used to calcine a lithium salt and a precursor mixture to obtain a high-nickel layered positive electrode material LiNi 0.89 Co 0.10 Al 0.01 O2, the calcination temperature is 740°C, the heating rate is 4°C / min, the calcination time is 15 h, and the calcination atmosphere is oxygen, and the obtained high-nickel layered positive electrode material LiNi 0.89 Co 0.10 Al 0.01 O2 is sent to a roller crusher for pre-crushing treatment, and a second screen is used for pre-screening treatment to obtain a pre-screening treated positive electrode material with a D max <5mm, and the LiOH content is 5140 ppm;

[0132] S2, the pre-screening treated positive electrode material is transported by air to an air flow crusher, and the pre-screening treated positive electrode material is subjected to air flow crushing treatment in a crushing chamber of the air flow crusher using a mixed gas of N2, O3, CO2 and SO2 to obtain a crushing product, the D50 of the crushing product is 12 μm, and the D max <35 μm, wherein the flow ratio of N2, O3, CO2 and SO2 is 80:5:5:10, and the air flow crushing pressure is 0.4 MPa;

[0133] S3, the crushing product is transported to a classifier and a first screen using the above-mentioned mixed gas of N2, O3, CO2 and SO2 for classification and screening, the first screen is 325 mesh with a pore size of 45 μm, the particle size qualified product enters a collector for collection and is discharged and packaged, the fine powder enters a universal collector through a cyclone separator, the gas is discharged after dust removal and filtration, and the particle size qualified product is a positive electrode composite material, which is a high-nickel layered positive electrode material LiNi 0.89 Co 0.10 Al 0.01 O2 coated with Li2CO3 and Li2SO4.

[0134] Comparative Example 1

[0135] The difference between Comparative Example 1 and Example 1 is that the mixed gas of N2 and SO2 in steps S2 and S3 is replaced with air, and the positive electrode composite material obtained in step S3 is not coated.

[0136] Comparative Example 2

[0137] The coating method of the positive electrode material comprises the following steps:

[0138] S1, a roller kiln is used to calcine a lithium salt and a precursor mixture to obtain a calcined high-nickel layered positive electrode material LiNi 0.83 Co 0.06 Mn 0.11 O2, the calcination temperature is 800°C, the heating rate is 3°C / min, the calcination time is 12 h, and the calcination atmosphere is oxygen, and the obtained high-nickel layered positive electrode material LiNi 0.83 Co 0.06 Mn 0.11 O2 is transported to a roller crusher for pre-crushing treatment, and a second screen is used for pre-screening treatment to obtain a pre-screening treated positive electrode material with a D max <5 mm, and the LiOH content is 4250 ppm;

[0139] S2, the pre-screening treated positive electrode material is transported by air to an air flow crusher, air is used to perform air flow crushing treatment on the pre-screening treated positive electrode material in a crushing chamber of the air flow crusher, a crushing product is obtained, the D50 of the crushing product is 10.5 μm, and the D max <35 μm, wherein the air flow crushing pressure is 0.3 MPa;

[0140] S3, the crushing product is transported by air to a classifier and a first screen to perform classification and screening, the first screen is a 325 mesh screen with a pore size of 45 μm, the particle size qualified product is collected and discharged for packaging in a collector, and the fine powder is collected in a universal collector through a cyclone separator, the gas is discharged after dust removal and filtration, and the particle size qualified product is the sintered material;

[0141] S4, the sintered material is transported to a water washing kettle, pure water is added, the mass ratio of the pure water to the sintered material is 1:1, the water washing time is 5 min, the water washing material is transferred to a double-cone vacuum drying machine after pressure filtration, and is dried at 150 ℃ for 3 h to obtain a water washing and drying material;

[0142] S5, the water washing and drying material is uniformly mixed with 1.0 wt% of boric acid, and is calcined at 300 ℃ for 5 h to obtain a positive electrode composite material, the positive electrode composite material is a Li2O-B2O3 coated high-nickel layered positive electrode material LiNi 0.83 Co 0.06 Mn 0.11 O2.

[0143] Test Example 1: SEM, EDS, HRTEM and storage performance test

[0144] The positive electrode composite material obtained in Example 1 is subjected to SEM test, EDS test and HRTEM test, respectively as shown in Figures 3-5 .

[0145] It can be seen from Figures 3-4 that the positive electrode composite material is spherical, and the elements of Ni, Co, Mn and S are uniformly distributed on the surface of the positive electrode composite material, and in combination with Figure 5 , it can be shown that the high-nickel layered positive electrode material LiNi 0.83 Co 0.06 Mn 0.11 O2 in Example 1 is coated with amorphous structure Li2SO3 on the surface.

[0146] Examples 2-5 also undergo the above-mentioned SEM test, EDS test and HRTEM test, and the test results are similar to those of Example 1, indicating that the high-nickel layered positive electrode material LiNi 0.90 Co 0.05 Mn 0.05 O2 in Example 2 is uniformly coated with Li2CO3 on the surface, the high-nickel layered positive electrode material LiNi 0.92 Co0.04 Mn 0.04 O2surface is uniformly coated with Li2SO3and Li2SO4, the high-nickel layered positive electrode material LiNi 0.92 Co 0.06 Mn 0.02 O2surface is uniformly coated with Li2CO3and Li2SO3, the high-nickel layered positive electrode material LiNi 0.89 Co 0.10 Al 0.01 O2surface is uniformly coated with Li2CO3and Li2SO4.

[0147] The positive electrode composite materials of Examples 1-5 and Comparative Examples 1-2 were stored at room temperature (25°C) and a relative humidity of 60% for 7 days, and the pH value and LiOH content of the positive electrode composite materials before and after storage were tested, as shown in Table 1.

[0148] Table 1 Performance test results before and after storage

[0149]

[0150] Note: Change rate of pH value after storage = (pH value of positive electrode composite material after storage - pH value of positive electrode composite material before storage) / pH value of positive electrode composite material before storage;

[0151] Change rate of LiOH content after storage = (LiOH content of positive electrode composite material after storage - LiOH content of positive electrode composite material before storage) / LiOH content of positive electrode composite material before storage.

[0152] Test Example 2 Electrochemical performance test

[0153] The electrochemical performance of the positive electrode composite materials in Examples 1-5 and Comparative Examples 1-2 was tested in a button lithium secondary battery.

[0154] Specific manufacturing method of lithium secondary battery and positive electrode sheet thereof: the prepared positive electrode composite material powder was mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 92:4:4, an appropriate amount of N-methyl pyrrolidone was added as a dispersant, and the mixture was ground into a slurry; then the slurry was uniformly coated on an aluminum foil, vacuum dried at 120°C for 10h, the dried sheet was rolled using a roll machine, the aluminum foil was cut using a slicing machine, and the aluminum foil was cut into a circular sheet with a diameter of 1.3cm, and the loading amount of active material was controlled at 15mg / cm 2The half battery was assembled in an argon atmosphere glove box, the water partial pressure was ≤0.1 ppm, and the oxygen partial pressure was ≤0.1 ppm; a metal lithium was used as a counter electrode, a 1M LiPF6(FEC / EC / DMC, volume ratio of 1:1:1) solution was used as an electrolyte, a CR2032 type button cell was assembled, and the charge and discharge were performed at room temperature in a constant current charge and discharge mode, the voltage range was 2.5-4.3 V, the current density was 60 mA / g (0.3C rate), and the charge and discharge cycle was 100 weeks.

[0155] The first cycle charge specific capacity, the first cycle discharge specific capacity, the first cycle coulombic efficiency, and the capacity retention rate after 100 weeks of the lithium secondary battery of the positive electrode composite material in examples 1-5 and comparative examples 1-2 are shown in table 2.

[0156] Table 2: Electrochemical performance test results

[0157]

[0158] It can be seen from the data in table 1 that, compared with comparative examples 1-2, the pH value and the LiOH content of the positive electrode composite material in examples 1-5 are lower, and the change rate of the pH value and the change rate of the LiOH content of the positive electrode composite material in examples 1-5 after storage are smaller. The pH value and the LiOH content of the positive electrode composite material obtained in examples 1-5 before and after storage are lower than those obtained by the traditional crushing process (comparative example 1) and the traditional water washing coating process (comparative example 2), which indicates that the coating method provided in the application effectively improves the air stability of the positive electrode composite material.

[0159] It can be seen from table 2 and Figure 6 It can be seen from table 2 and

[0160] The capacity retention rate of the positive electrode composite material in example 1 after 100 cycles is obviously higher than that of comparative example 1 (traditional crushing process), and compared with comparative example 2 using the traditional water washing coating process, the positive electrode composite material in example 1 also has a relatively advantageous electrochemical performance, and the process route is more concise and the production cost is lower.

[0161] Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, as long as the combination of the technical features does not exist in contradiction, it shall be considered within the scope of the present disclosure.

[0162] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it shall not be understood as a limitation on the patent scope of the present application. It shall be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these shall be within the protection scope of the present application. Therefore, the protection scope of the present application patent shall be subject to the appended claims.

Claims

1. A positive electrode composite material, characterized in that, The positive electrode composite material comprises an inner core and an in-situ coating layer coated on the surface of the inner core, and the inner core comprises a positive electrode material; LiNi x M 1-x O2, M is one or more of Mn, Co, Al, B, Ti, Zr, Sr, Nb, Ta and W, and 0.8≤x≤1; the material of the in-situ coating layer comprises one or more of Li2CO3, Li2SO3 and Li2SO4, Li2CO3, Li2SO3 and Li2SO4 are amorphous structure; the pH value of the positive electrode composite material is <12.5; the content of LiOH in the positive electrode composite material is <3500 ppm; The preparation method of the positive electrode composite material comprises a process of forming an in-situ coating layer on the surface of the inner core by simultaneously performing airflow crushing and coating treatment on the positive electrode material by using a mixed gas; and the process of forming the in-situ coating layer on the surface of the inner core does not comprise a secondary coating calcination process; The mixed gas comprises multiple kinds of air, O2, N2, O3, CO2 and SO2, and the mixed gas comprises a high-pressure gas and an auxiliary gas, wherein the high-pressure gas comprises one or more of air, O2 and N2, and the auxiliary gas comprises one or more of the following: (1) CO2; (2) SO2; and (3) a combination of SO2 and O3.

2. The positive electrode composite according to claim 1, characterized by At least one of the following features (1) to (3) is included: (1) The particle size D50 of the positive electrode composite material is 2 to 15 μm; (2) the specific surface area of the positive electrode composite is 0.2-2.0 m 2 / g; (3) The content of moisture in the positive electrode composite material is less than 1000 ppm.

3. The method of coating a positive electrode composite according to claim 1 or 2, characterized by, The following steps are included: The positive electrode material is simultaneously subjected to airflow crushing treatment and coating treatment by using a mixed gas to obtain a crushing product; The crushing product is sequentially subjected to classification treatment and screening treatment to obtain a positive electrode composite material, and the positive electrode composite material comprises an inner core and an in-situ coating layer coated on the surface of the inner core, and the inner core comprises the positive electrode material; The mixed gas comprises multiple kinds of air, O2, N2, O3, CO2 and SO2, and the mixed gas comprises a high-pressure gas and an auxiliary gas, wherein the high-pressure gas comprises one or more of air, O2 and N2, and the auxiliary gas comprises one or more of the following: (1) CO2; (2) SO2; and (3) a combination of SO2 and O3. The chemical formula of the positive electrode material is LiNi x M 1-x O2, M is one or more of Mn, Co, Al, B, Ti, Zr, Sr, Nb, Ta and W, and 0.8≤x≤1; the material of the in-situ coating layer comprises one or more of Li2CO3, Li2SO3 and Li2SO4, and Li2CO3, Li2SO3 and Li2SO4 are in amorphous structure; the pH value of the positive electrode composite material is <12.5; the content of LiOH in the positive electrode composite material is <3500 ppm.

4. The coating method according to claim 3, characterized in that, The gas pressure of the airflow crushing treatment is 0.2 to 1.0 MPa.

5. The coating method according to claim 3, characterized by Before the airflow crushing treatment and the coating treatment, pre-crushing treatment and pre-screening treatment are sequentially performed.

6. The coating method according to any one of claims 3 to 5, characterized in that, At least one of the following features (1) to (7) is included: (1) the maximum particle size D max <5 mm; (2) The content of LiOH in the positive electrode material is 3500 to 7000 ppm; (3) the maximum particle diameter D of the pulverized product max < 5 mm; (4) The screen aperture of the screening treatment is 40 to 300 μm; (5) The particle size D50 of the positive electrode composite material is 2 to 15 μm; (6) the specific surface area of the positive electrode composite is 0.2-2.0 m 2 / g; (7) The content of moisture in the positive electrode composite material is less than 1000 ppm.

7. The coating method according to any one of claims 3 to 5, characterized in that, The coating method uses a coating system of the positive electrode material, and the coating system comprises an airflow crusher and a gas conveying device, and the gas conveying device comprises a first gas storage tank, a second gas storage tank, a first pressure regulating valve, a second pressure regulating valve, a third pressure regulating valve, a first flow meter, a second flow meter, a first branch pipe, a second branch pipe and a main pipe. The first gas storage tank, the first pressure regulating valve and the first flow meter are sequentially connected in series through the first branch pipe, the second gas storage tank, the second pressure regulating valve and the second flow meter are sequentially connected in series through the second branch pipe, the first branch pipe and the second branch pipe are connected in parallel to form a parallel pipeline, and the parallel pipeline is connected in series on the main pipe to form a mixed gas, the main pipe is communicated with the jet mill, and the third pressure regulating valve is arranged on the main pipe. The jet mill simultaneously performs jet milling and coating treatment on the positive electrode material by using the mixed gas.

8. The coating method according to claim 7, characterized in that, Further comprising a classifier, a first sifter, a cyclone separator and a universal collector, the classifier and the first sifter are sequentially used for classifying and screening the positive electrode material pulverized by the jet mill, and the cyclone separator and the universal collector are used for dust removal of the powder generated by the classifier.

9. The coating method according to claim 8, characterized in that, Further comprising a communication pipe for communicating the jet mill, the classifier and the main pipe to recycle the mixed gas.

10. The coating method according to any one of claims 7 to 9, characterized in that, Further comprising a crushing device and a second sifter arranged in sequence, the crushing device is used for pre-crushing the positive electrode material, and the second sifter is used for pre-screening the positive electrode material.

11. The coating method according to claim 10, characterized in that The coating system satisfies at least one of the following conditions: (1) The crushing device comprises one or more of a roller crusher, a jaw crusher and a disc crusher; (2) The jet mill comprises one or more of a flat jet mill, a counter-jet mill and a fluidized bed counter-jet mill.

12. A positive electrode sheet characterized by comprising: The positive electrode composite material is the positive electrode composite material according to any one of claims 1-2, or is a positive electrode composite material obtained by coating the positive electrode material by using the coating method according to any one of claims 3-11.

13. A battery, characterized by The positive electrode sheet comprises the positive electrode composite material according to claim 12.

14. An electrical device, comprising: The battery comprises the positive electrode sheet according to claim 13. The battery comprises the positive electrode sheet according to claim 13.

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