Coated ternary positive electrode material, preparation method and application thereof

Abstract

The application relates to the technical field of lithium ion batteries, in particular to a coated ternary positive electrode material and a preparation method and application thereof. The coated ternary positive electrode material comprises a ternary positive electrode material and a coating layer on the surface of the ternary positive electrode material, and the coating layer comprises an aluminum oxide chemically modified cobalt compound layer; in the coating layer, the molar ratio of aluminum oxide and the cobalt compound is (0.001-2):100. The provided coated ternary positive electrode material can improve the specific capacity and cycle performance of a battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a coated ternary cathode material and a preparation method and application thereof. BACKGROUND

[0002] The ternary cathode material has the advantages of traditional cathode materials LiNiO2, LiCoO2 and LiMnO2, and has a more stable structure and more excellent electrochemical performance, and has great commercial value. However, in practical application, the ternary cathode material still faces many problems, such as strong water absorption and poor storage performance, which seriously affect its industrial production, storage, transportation and battery preparation process. Taking electrode preparation as an example, the ternary cathode material is easy to absorb water and glue during the preparation of slurry, resulting in poor mechanical processing performance. In addition, due to the low lithium ion diffusion coefficient and electronic conductivity coefficient of the layered ternary cathode material, the rate performance of the material still needs to be improved. On the other hand, during the process of deintercalating lithium, Ni 4+ reacts with the electrolyte to cause phase transition from a layered structure to a molten salt structure, resulting in increased impedance of the ternary cathode material and deteriorated cycle performance. Moreover, the first irreversible capacity of the ternary cathode material is as high as 30 mAh / g to 40 mAh / g or even higher in the charge and discharge range of 2.7 V to 4.3 V, and the efficiency is generally lower than 85%.

[0003] At present, a simple oxide (such as TiO2, Al2O3, ZrO2, MnO2, MoO3 and CeO2, etc.) which is not electrochemically active is generally coated by a solid phase method to modify the ternary cathode material, but this method cannot fundamentally solve the problem of performance deterioration of the ternary cathode material during the cycle process. On the one hand, after coating the non-electrochemically active oxide material, the capacity of the ternary cathode material is reduced to a certain extent, and the cycle performance of the ternary cathode material is also reduced due to polarization during the cycle process. On the other hand, the coating layer formed by the solid phase coating of the ternary cathode material may not be uniform, and cannot effectively inhibit the interface reaction of the electrode / electrolyte. SUMMARY

[0004] Therefore, it is necessary to provide a coated ternary cathode material capable of improving the specific capacity and cycle performance of the battery, and a preparation method and application thereof.

[0005] In one aspect of the present application, a coated ternary cathode material is provided, which comprises a ternary cathode material and a coating layer on the surface of the ternary cathode material, and the coating layer comprises an aluminum oxide chemically modified cobalt oxide layer; in the coating layer, the molar ratio of aluminum oxide to cobalt oxide is (0.001-2):100.

[0006] In one embodiment, the cobalt compound is selected from one or more of cobalt sulfate, cobalt oxalate, cobalt acetate, cobalt carbonate, and cobalt oxide; and / or

[0007] The molar ratio of the coating layer to the ternary cathode material is (0.001-2):100.

[0008] In one aspect, this invention also provides a method for preparing a coated ternary cathode material as described above, comprising the following steps:

[0009] A cobalt compound raw material and an aluminum source are dispersed in a first solvent, reacted, dried, and calcined once to prepare a cobalt compound chemically modified with alumina. The molar ratio of the aluminum source to the cobalt compound raw material is (0.001–2):100.

[0010] The alumina-modified cobalt compound and the ternary cathode material are dispersed in a second solvent, dried after reaction, and then calcined a second time.

[0011] In one embodiment, the aluminum source is selected from one or more of aluminum hydroxide, aluminum oxide, aluminum sulfate, aluminum carbonate, and aluminum nitrate.

[0012] In one embodiment, the first solvent and the second solvent are each independently selected from anhydrous ethanol and / or anhydrous diethyl ether.

[0013] In one embodiment, the calcination temperatures for the primary calcination and the secondary calcination are independently 700°C to 900°C.

[0014] In another aspect, the present invention provides a positive electrode sheet, which includes a positive current collector and a positive active material layer located on one or both sides of the positive current collector, wherein the positive active material in the positive active material layer is the coated ternary positive electrode material described above.

[0015] In another aspect, the present invention provides a secondary battery comprising the positive electrode sheet described above.

[0016] In another aspect, the present invention provides an electrical device comprising the aforementioned secondary battery.

[0017] The aforementioned coated ternary cathode material includes electrochemically active cobalt compounds, thus avoiding a decrease in the electrochemical activity of the ternary cathode material after coating modification. Compared to traditional ternary cathode materials coated with electrochemically inert oxide layers, introducing cobalt compounds into the coating layer can improve the structural instability of the ternary cathode material, avoiding problems such as gas generation, structural collapse, and structural damage.

[0018] Furthermore, by modifying the cobalt compound coating layer with alumina, the direct contact between the active material and the electrolyte in the ternary cathode material can be isolated, delaying the side reactions between the active material and the electrolyte, stabilizing the material structure, and further improving the cycle performance and rate performance of the ternary cathode material.

[0019] In summary, the coated ternary cathode material prepared by the above method has a stable interface layer (coating layer), which reduces the interfacial reaction between the coated ternary cathode material and the electrolyte, improves its cycle performance, and reduces the battery internal resistance (DCR); moreover, it has high capacity and low metal dissolution. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 The discharge specific capacity diagrams are shown for the coated modified NCM ternary cathode material prepared in Example 1 of the present invention and the NCM ternary cathode materials prepared in Comparative Examples 1 to 4.

[0022] Figure 2 The graph shows the cycle performance of the coated modified NCM ternary cathode material prepared in Example 1 of the present invention and the NCM ternary cathode materials prepared in Comparative Examples 1 to 4 at 45°C and 0.5°C. Detailed Implementation

[0023] Reference will now be made to detailed embodiments of the present invention, one or more of which are described below. Each example is provided for explanation and not for limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0024] Therefore, this invention is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the invention are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] Terms and definitions:

[0027] "Chemical modification" refers to the process of attaching active groups or substances to the surface of a substrate using methods such as adsorption, coating, polymerization, and chemical reactions to protect or improve the substrate's characteristic functions. For example, in this invention, chemical modification refers to loading alumina onto a cobalt compound, where the alumina and cobalt compound form a solid solution.

[0028] In one aspect, the present invention provides a coated ternary cathode material, comprising a ternary cathode material and a coating layer located on the surface of the ternary cathode material, the coating layer comprising a cobalt compound layer chemically modified with alumina; in the coating layer, the molar ratio of alumina to cobalt compound is (0.001-2):100.

[0029] The aforementioned coated ternary cathode material includes electrochemically active cobalt compounds, thus avoiding a decrease in the electrochemical activity of the ternary cathode material after coating modification. Compared to traditional ternary cathode materials coated with electrochemically inert oxide layers, introducing cobalt compounds into the coating layer can improve the structural instability of the ternary cathode material, avoiding problems such as gas generation, structural collapse, and structural damage.

[0030] Furthermore, by modifying the cobalt compound coating layer with alumina, the direct contact between the active material and the electrolyte in the ternary cathode material can be isolated, delaying the side reactions between the active material and the electrolyte, stabilizing the material structure, and further improving the cycle performance and rate performance of the ternary cathode material.

[0031] In summary, the aforementioned coated ternary cathode materials have a stable interface layer (coating layer), which reduces the interfacial reaction between the coated ternary cathode material and the electrolyte, improves its cycle performance, and reduces the battery internal resistance (DCR); moreover, they have high capacity and low metal dissolution.

[0032] In some implementations, the ternary cathode material has the structural formula LiNi. x Co y Mn z O2, where 0.6≤x≤1, 0≤y≤0.5, 0≤z≤0.5, and x+y+z=1.

[0033] In some embodiments, the molar ratio of aluminum oxide to cobalt compound in the coating layer can be any value between (0.001 to 2):100, for example, it can also be 0.001:100, 0.005:100, 0.008:100, 0.01:100, 0.02:100, 0.05:100, 0.05:100, 0.08:100, 0.1:100, 0.3:100, 0.5:100, 0.7:100, 0.9:100, 1:100, 1.1:100, 1.2:100, 1.4:100, 1.5:100, 1.8:100, or 2:100. Controlling the molar ratio of aluminum oxide to cobalt oxide within the above range ensures the electrochemical performance of the coated ternary cathode material. When the alumina content is too low, it cannot effectively isolate the direct contact between the active material in the ternary cathode material and the electrolyte, thus failing to effectively suppress the side reactions between the electrode active material and the electrolyte; while when the alumina content is too high, it will affect the formation of lithium-ion transport and diffusion channels, which will lead to a significant reduction in its capacity and affect its use.

[0034] In some embodiments, the molar ratio of the coating layer to the ternary cathode material can be any value between (0.001 and 2):100, for example, it can also be 0.001:100, 0.005:100, 0.008:100, 0.01:100, 0.02:100, 0.05:100, 0.05:100, 0.08:100, 0.1:100, 0.3:100, 0.5:100, 0.7:100, 0.9:100, 1:100, 1.1:100, 1.2:100, 1.4:100, 1.5:100, 1.8:100, or 2:100. When the coating content is too low, it cannot form an effective coating and it is difficult to effectively inhibit the corrosion of the positive electrode material by the electrolyte; while when the coating content is too high and the coating is too thick, it will affect the formation of lithium-ion transport and diffusion channels, which will lead to a significant reduction in its capacity and affect its use.

[0035] In some embodiments, the choice of cobalt compound is not limited, and any cobalt compound commonly used in the art can be selected, such as, but not limited to, one or more of cobalt sulfate, cobalt oxalate, cobalt acetate, cobalt carbonate, and cobalt oxide. Preferably, the cobalt compound is cobalt oxide.

[0036] In one aspect, the present invention also provides a method for preparing a coated ternary cathode material as described above, comprising steps S100 to S200:

[0037] Step S100: Disperse the cobalt compound raw material and aluminum source in a first solvent, dry after reaction, and calcine once to prepare a cobalt compound chemically modified with alumina, wherein the molar ratio of aluminum source to cobalt compound raw material is (0.001~2):100.

[0038] Understandably, dispersing the cobalt compound raw material and the aluminum source in the first solvent can be achieved by dispersing the cobalt compound raw material and the aluminum source separately in the first solvent to form their respective solutions, and then mixing the respective solutions; alternatively, the cobalt compound raw material and the aluminum source can be dispersed together in the first solvent; furthermore, the cobalt compound raw material can be first dispersed in the first solvent to form a solution, and then the aluminum source can be added. Specifically, the cobalt compound raw material can be dispersed in a mixed solution of water and anhydrous diethyl ether, and then the aluminum source and anhydrous ethanol can be added.

[0039] In some embodiments, the particle size of the cobalt compound can be any value between 50 nm and 300 nm, for example, it can also be 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 250 nm, or 280 nm.

[0040] In some embodiments, the aluminum source may be selected from one or more of aluminum hydroxide, aluminum oxide, aluminum sulfate, aluminum carbonate, and aluminum nitrate.

[0041] Preferably, the particle size of the aluminum source can be any value between 20nm and 40nm, for example, it can also be 25nm, 30nm, or 35nm.

[0042] In some embodiments, in order to fully disperse the cobalt compound and the aluminum source in the first solvent, a dispersion process commonly used in the art, such as mechanical stirring, can be used during the dispersion process. The stirring speed is not limited, for example, it can be 500 r / min to 1000 r / min.

[0043] In some embodiments, the first solvent may be a solvent commonly used in the art, such as anhydrous ethanol, anhydrous diethyl ether, or a mixture thereof. It is understood that water may be present in the first solvent.

[0044] In some embodiments, the temperature and time of a single calcination are not limited; for example, the temperature can be 700°C to 900°C and the time can be 8 hours to 12 hours.

[0045] In some embodiments, the drying method in step S100 is not limited. For example, it can be drying by heating or heating in a water bath, as long as the first organic solvent can be removed. The temperature and time of the water bath heating are not limited; for example, it can be heated in a water bath at 80°C to 90°C for 5 to 7 hours.

[0046] Step S200: The cobalt compound modified with alumina and the ternary cathode material are dispersed in a second organic solvent, dried after reaction, and then calcined once.

[0047] In some embodiments, in order to fully disperse the cobalt compound loaded with alumina and the ternary cathode material in the second solvent, a dispersion process commonly used in the art, such as mechanical stirring, can be used during the dispersion process. The stirring speed is not limited, for example, it can be 500 r / min to 1000 r / min.

[0048] In some embodiments, the second solvent may be a solvent commonly used in the art, such as anhydrous ethanol, anhydrous diethyl ether, or a mixture thereof. It is understood that water may be present in the second solvent.

[0049] In some embodiments, the temperature and time of the secondary calcination are not limited; for example, the temperature can be 700℃ to 900℃ and the time can be 8h to 12h.

[0050] In some embodiments, the drying method in step S200 is not limited. For example, it can be drying by heating or water bath heating, as long as the first organic solvent can be removed. Water bath heating is preferred. The temperature and time of water bath heating are not limited; for example, it can be water bath heating at 80°C to 90°C for 5 to 7 hours.

[0051] In some embodiments, after the secondary calcination, a grinding step is also included, wherein the grinding speed and method are not limited, and a grinding process commonly used in the art can be selected.

[0052] In another aspect, the present invention provides a positive electrode sheet, which includes a positive current collector and a positive active material layer located on one or both sides of the positive current collector, wherein the positive active material in the positive active material layer is the coated ternary positive electrode material described above.

[0053] In this application, the choice of the positive current collector is not limited; in some embodiments, the positive current collector is aluminum foil. The method for forming the positive active material layer on the positive current collector can be any method known in the art, such as coating processes, magnetron sputtering processes, etc. Furthermore, the parameters for coating processes and magnetron sputtering processes can also refer to process parameters known in the art.

[0054] In another aspect, the present invention provides a secondary battery comprising the positive electrode sheet described above.

[0055] In some implementations, the secondary battery is a lithium secondary battery.

[0056] It is understood that lithium secondary batteries may also include other necessary battery structures, such as negative electrode sheets, separators, and electrolytes. The specific material and type of the negative electrode sheet are not limited. For example, the negative electrode sheet may be composed solely of carbon-based negative electrode materials or of a combination of carbon-based negative electrode materials and a negative electrode current collector. The carbon-based negative electrode materials may include one or more of artificial graphite, natural graphite, graphitized carbon fibers, graphitized carbon microspheres, fullerenes, and amorphous carbon. The negative electrode current collector may be copper foil.

[0057] The separator can include any known separator, specifically selected from polyolefin-based polymer membranes. Polyolefin-based polymers can include polypropylene and polyethylene. It is understood that the polyolefin-based polymer membrane can be a multilayer membrane, a microporous membrane, a woven fabric, or a nonwoven fabric. The main function of the separator is to prevent short circuits between the positive and negative electrodes and to provide channels for lithium ions.

[0058] The electrolyte can be a solid electrolyte or an electrolyte solution. Specifically, it can be an electrolyte solution formed by lithium salt and organic solvent. The lithium salt can be one or more of LiPF6, LiBF4, LiSbF6 and LiAsF6. The organic solvent is mainly selected from carbonate solvents, such as ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC).

[0059] In another aspect, the present invention also provides an electrical device that uses the lithium-ion battery described above as a power source.

[0060] In some implementations, an electrical device refers to a device that uses a lithium secondary battery as its power supply. For example, an electrical device can be a small electronic device (mobile phone, PDA, laptop, camera, portable game console, etc.), a large transportation device such as a vehicle (hybrid vehicle, electric vehicle, etc.), or a power tool such as an electric drill, electric hammer, electric saw, or cutting machine.

[0061] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0062] Example 1

[0063] 1) According to cobalt oxide and ternary cathode material (LiNi 0.8 Co 0.1 Mn 0.1 The molar ratio of O2 is 1.5:100. A certain amount of cobalt hydroxide with a particle size of 200nm is weighed out, and 140g of deionized water and 60g of anhydrous diethyl ether are added. The mixture is then stirred at a rate of 800r / min for 1h to obtain an active slurry.

[0064] 2) Take the active slurry obtained in step 1), add aluminum hydroxide and anhydrous ethanol, wherein the particle size of aluminum hydroxide is 30 nm. Then disperse at a rate of 500 r / min for 10 min, continue to add anhydrous ethanol and aluminum hydroxide, and disperse at a rate of 1000 r / min for 30 min to obtain a first suspension with a solid content of 60%, wherein the molar ratio of aluminum hydroxide to cobalt hydroxide in the first suspension is 1:100. Subsequently, after drying the first suspension, sinter it at 700℃ for 10 h to obtain a cobalt oxide material uniformly modified with alumina;

[0065] 3) Take the ternary cathode material and the alumina-modified cobalt oxide material obtained in step 2), add anhydrous ethanol, and disperse at 500 r / min for 5 min. Then continue to add anhydrous ethanol and ternary cathode material, and stir at 1000 r / min for 30 min to obtain a second suspension with a solid content of 65%, wherein the molar ratio of cobalt oxide material obtained in step 2) to ternary cathode material in the second suspension is 1.5:100. Subsequently, reduce the stirring speed to 300 r / min and heat in a water bath at 80℃~90℃ for 6 h to remove anhydrous ethanol from the second suspension, obtaining a mixed powder. Then calcine the mixed powder at 750℃ for 10 h, cool, and grind to obtain the coated ternary cathode material.

[0066] The above-mentioned coated ternary cathode material was used to prepare CR2032 coin cells. The battery capacity was tested by constant current and constant voltage charging and constant current discharging. The test voltage range was 3.0 to 4.3V, and the charge and discharge current was 0.1C. The cycle degradation test method was as follows: (1) rest for 40 minutes; (2) fast charging - constant current charging at 0.5C, charging to 4.25V and then constant voltage charging, and charging ended when the current was less than 0.05C; (3) rest for 40 minutes; (4) constant current discharging at 0.5C, discharging ended when the terminal voltage was less than 2.5V; (5) repeat the above steps in cycles. The discharge specific capacity of the coated ternary cathode material obtained by the test was 213.0mAh / g, and the capacity retention rate after 50 cycles was 95.60%.

[0067] Example 2

[0068] The preparation method in this embodiment is basically the same as that in Example 1, except that the molar ratio of aluminum hydroxide to cobalt hydroxide is 0.005:100, and the molar ratio of cobalt oxide material to ternary cathode material is 1.5:100. The specific steps are as follows:

[0069] 1) According to cobalt oxide and ternary cathode material (LiNi 0.6 Co 0.2 Mn 0.2The molar ratio of O2 is 1.5:100. A certain amount of cobalt hydroxide with a particle size of 200nm is weighed out, and 140g of deionized water and 60g of anhydrous diethyl ether are added. The mixture is then stirred at a rate of 800r / min for 1h to obtain an active slurry.

[0070] 2) Take the active slurry obtained in step 1), add aluminum hydroxide and anhydrous ethanol, wherein the particle size of aluminum hydroxide is 30 nm. Then disperse at a rate of 500 r / min for 10 min, continue to add anhydrous ethanol and aluminum hydroxide, and disperse at a rate of 1000 r / min for 30 min to obtain a first suspension with a solid content of 60%, wherein the molar ratio of aluminum hydroxide to cobalt hydroxide in the first suspension is 0.005:100. Subsequently, after drying the first suspension, sinter it at 700℃ for 10 h to obtain a cobalt oxide material uniformly modified with alumina;

[0071] 3) Take the ternary cathode material and the modified cobalt oxide material obtained in step 2), add anhydrous ethanol, and disperse at 500 r / min for 5 min. Then continue to add anhydrous ethanol and ternary cathode material, and stir at 1000 r / min for 30 min to obtain a second suspension with a solid content of 65%, wherein the mass ratio of the cobalt oxide material obtained in step 2) to the ternary cathode material in the second suspension is 1.5:100. Subsequently, reduce the stirring speed to 300 r / min and heat in a water bath at 80℃~90℃ for 6 h to remove the anhydrous ethanol from the second suspension, obtaining a mixed powder. Then calcine the mixed powder at 750℃ for 10 h, cool, and grind to obtain the coated ternary cathode material.

[0072] Example 3

[0073] The preparation method in this embodiment is basically the same as that in Example 1, except that the molar ratio of aluminum hydroxide to cobalt hydroxide is 2:100, and the molar ratio of cobalt oxide material to ternary cathode material is 2:100. The specific steps are as follows:

[0074] 1) According to cobalt oxide and ternary cathode material (LiNi 0.9 Co 0.05 Mn 0.05 The molar ratio of O2 is 2:100. Weigh a certain amount of cobalt hydroxide with a particle size of 200 nm, add 140 g of deionized water and 60 g of anhydrous diethyl ether, and then stir at a rate of 800 r / min for 1 h to obtain an active slurry.

[0075] 2) Take the active slurry obtained in step 1), add aluminum hydroxide and anhydrous ethanol, wherein the particle size of aluminum hydroxide is 30 nm. Then disperse at a rate of 500 r / min for 10 min, continue to add anhydrous ethanol and aluminum hydroxide, and disperse at a rate of 1000 r / min for 30 min to obtain a first suspension with a solid content of 60%, wherein the molar ratio of aluminum hydroxide to cobalt hydroxide in the first suspension is 2:100. Subsequently, after drying the first suspension, sinter it at 700℃ for 10 h to obtain a cobalt oxide material uniformly modified with alumina;

[0076] 3) Take the ternary cathode material and the cobalt material obtained in step 2), add anhydrous ethanol, and disperse at 500 r / min for 5 min. Then continue to add anhydrous ethanol and ternary cathode material, and stir at 1000 r / min for 30 min to obtain a second suspension with a solid content of 65%, wherein the molar ratio of the cobalt material obtained in step 2) to the ternary cathode material in the second suspension is 2:100. Subsequently, reduce the stirring speed to 300 r / min and heat in a water bath at 80℃~90℃ for 6 h to remove the anhydrous ethanol from the second suspension, obtaining a mixed powder. Then calcine the mixed powder at 750℃ for 10 h, cool, and grind to obtain the coated ternary cathode material.

[0077] Comparative Example 1

[0078] The preparation method of this comparative example is basically the same as that of Example 1, except that the coating layer is a cobalt oxide layer without alumina modification. The specific steps are as follows:

[0079] 1) According to cobalt oxide and ternary cathode material (LiNi 0.8 Co 0.1 Mn 0.1 The molar ratio of O2 is 2:100. Weigh a certain amount of cobalt hydroxide with a particle size of 200 nm, add 140 g of deionized water and 60 g of anhydrous diethyl ether, and then stir at a rate of 800 r / min for 1 h to obtain an active slurry.

[0080] 2) The active slurry obtained in step 1) and the ternary cathode material were added to anhydrous ethanol and stirred at 1000 r / min for 30 min to obtain a second suspension with a solid content of 65%. The molar ratio of cobalt oxide material to ternary cathode material in the second suspension was 2:100. The stirring speed was then reduced to 300 r / min, and the mixture was heated in a water bath at 80℃~90℃ for 6 h to remove the anhydrous ethanol from the second suspension, obtaining a mixed powder. The mixed powder was then calcined at 750℃ for 10 h, cooled, and ground to obtain the coated ternary cathode material.

[0081] The ternary cathode material coated above was used to prepare a CR2032 coin cell, and the discharge specific capacity of the ternary cathode material was tested to be 206.7 mAh / g and the capacity retention rate after 50 cycles was 93.45%.

[0082] Comparative Example 2

[0083] The preparation method of this comparative example is basically the same as that of Example 1, except that the coating layer contains only alumina material. The specific steps are as follows:

[0084] 1) Weigh a certain amount of aluminum hydroxide with a particle size of 30 nm, add anhydrous ethanol, and disperse at a rate of 500 r / min for 10 min. Continue to add anhydrous ethanol and disperse at a rate of 1000 r / min for 30 min to obtain a first suspension with a solid content of 60%. Subsequently, dry the first suspension and sinter it at 700℃ for 10 h to obtain alumina material.

[0085] 2) Take ternary cathode material (LiNi) 0.8 Co 0.1 Mn 0.1 The alumina material obtained in step 1) and step O2 was mixed with anhydrous ethanol and dispersed at 500 rpm for 5 min. Then, anhydrous ethanol and ternary cathode material were added, and the mixture was stirred at 1000 rpm for 30 min to obtain a second suspension with a solid content of 65%, wherein the molar ratio of alumina material to ternary cathode material in the second suspension was 1.5:100. The stirring speed was then reduced to 300 rpm, and the mixture was heated in a water bath at 80℃–90℃ for 6 h to remove the anhydrous ethanol from the second suspension, yielding a mixed powder. The mixed powder was then calcined at 750℃ for 10 h, cooled, and ground to obtain the coated ternary cathode material.

[0086] The above-mentioned coated ternary cathode material was used to prepare a CR2032 coin cell, and the discharge specific capacity of the ternary cathode material was tested to be 207.5 mAh / g and the capacity retention rate after 50 cycles was 94.88%.

[0087] Comparative Example 3

[0088] The preparation method of this comparative example is basically the same as that of Example 1, except that iron oxide is used instead of aluminum hydroxide. The specific steps are as follows:

[0089] 1) According to cobalt oxide and ternary cathode material (LiNi 0.8 Co 0.1 Mn 0.1The molar ratio of O2 is 1.5:100. A certain amount of cobalt hydroxide with a particle size of 200nm is weighed out, and 140g of deionized water and 60g of anhydrous diethyl ether are added. The mixture is then stirred at a rate of 800r / min for 1h to obtain an active slurry.

[0090] 2) Take the active slurry obtained in step 1), add iron oxide and anhydrous ethanol, wherein the particle size of the iron oxide is 30 nm. Then disperse at a rate of 500 r / min for 10 min, continue to add anhydrous ethanol and cobalt hydroxide, and disperse at a rate of 1000 r / min for 30 min to obtain a first suspension with a solid content of 60%, wherein the mass ratio of iron oxide to cobalt hydroxide in the first suspension is 1:100. Subsequently, after drying the first suspension, sinter it at 700℃ for 10 h to obtain a cobalt oxide material uniformly modified with iron oxide;

[0091] 3) Take the ternary cathode material and the iron oxide-modified cobalt oxide material obtained in step 2), add anhydrous ethanol, and disperse at 500 r / min for 5 min. Then continue to add anhydrous ethanol and ternary cathode material, and stir at 1000 r / min for 30 min to obtain a second suspension with a solid content of 65%, wherein the molar ratio of cobalt oxide material obtained in step 2) to ternary cathode material in the second suspension is 1.5:100. Subsequently, reduce the stirring speed to 300 r / min and heat in a water bath at 80℃~90℃ for 6 h to remove anhydrous ethanol from the second suspension, obtaining a mixed powder. Then calcine the mixed powder at 750℃ for 10 h, cool, and grind to obtain the coated ternary cathode material.

[0092] The above-mentioned coated ternary cathode material was used to prepare a CR2032 coin cell, and the discharge specific capacity of the ternary cathode material was tested to be 203.5 mAh / g and the capacity retention rate after 50 cycles was 91.67%.

[0093] Comparative Example 4

[0094] The preparation method of this comparative example is basically the same as that of Example 1, except that the molar ratio of aluminum hydroxide to cobalt hydroxide is 4:100, and the molar ratio of cobalt oxide material to ternary cathode material is 1.5:100. The specific steps are as follows:

[0095] 1) According to cobalt oxide and ternary cathode material (LiNi 0.8 Co 0.1 Mn 0.1 The molar ratio of O2 is 1.5:100. A certain amount of cobalt hydroxide with a particle size of 200nm is weighed out, and 140g of deionized water and 60g of anhydrous diethyl ether are added. The mixture is then stirred at a rate of 800r / min for 1h to obtain an active slurry.

[0096] 2) Take the active slurry obtained in step 1), add aluminum hydroxide and anhydrous ethanol, wherein the particle size of aluminum hydroxide is 30 nm. Then disperse at a rate of 500 r / min for 10 min, continue to add anhydrous ethanol and aluminum hydroxide, and disperse at a rate of 1000 r / min for 30 min to obtain a first suspension with a solid content of 60%, wherein the molar ratio of aluminum hydroxide to cobalt hydroxide in the first suspension is 4:100. Subsequently, after drying the first suspension, sinter it at 700℃ for 10 h to obtain a cobalt oxide material uniformly modified with alumina;

[0097] 3) Take the ternary cathode material and the alumina-modified cobalt oxide material obtained in step 2), add anhydrous ethanol, and disperse at 500 r / min for 5 min. Then continue to add anhydrous ethanol and ternary cathode material, and stir at 1000 r / min for 30 min to obtain a second suspension with a solid content of 65%, wherein the molar ratio of cobalt oxide material obtained in step 2) to ternary cathode material in the second suspension is 1:100. Subsequently, reduce the stirring speed to 300 r / min and heat in a water bath at 80℃~90℃ for 6 h to remove anhydrous ethanol from the second suspension, obtaining a mixed powder. Then calcine the mixed powder at 750℃ for 10 h, cool, and grind to obtain the coated ternary cathode material.

[0098] The above-mentioned coated ternary cathode material was used to prepare a CR2032 coin cell, and the discharge specific capacity of the ternary cathode material was tested to be 203.5 mAh / g and the capacity retention rate after 50 cycles was 91.67%.

[0099] The electrochemical performance of the ternary cathode materials prepared in Example 1 and Comparative Examples 1-4 is shown in Table 1:

[0100] Table 1

[0101]

[0102] As can be seen from the table above, the coated ternary cathode material provided in this application exhibits superior electrochemical performance after being coated with cobalt oxide and modified with alumina.

[0103] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0104] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A coated ternary cathode material, characterized in that, It includes a ternary cathode material and a coating layer located on the surface of the ternary cathode material, wherein the coating layer includes a cobalt compound layer chemically modified with alumina; In the coating layer, aluminum oxide is loaded onto a cobalt compound, and the aluminum oxide and the cobalt compound form a solid solution. The molar ratio of aluminum oxide to cobalt compound is (0.001~2):100, and the cobalt compound is selected from cobalt oxide.

2. The coated ternary cathode material according to claim 1, characterized in that, The molar ratio of the coating layer to the ternary cathode material is (0.001~2):

100.

3. A method for preparing a coated ternary cathode material as described in claim 1 or 2, characterized in that, Includes the following steps: A cobalt compound raw material and an aluminum source are dispersed in a first solvent, reacted, dried, and calcined once to prepare a cobalt compound chemically modified with alumina. The molar ratio of the aluminum source to the cobalt compound raw material is (0.001~2):

100. The alumina-modified cobalt compound and the ternary cathode material are dispersed in a second solvent, dried after reaction, and then calcined a second time.

4. The method for preparing the coated ternary cathode material according to claim 3, characterized in that, The aluminum source is selected from one or more of aluminum hydroxide, aluminum oxide, aluminum sulfate, aluminum carbonate, and aluminum nitrate.

5. The method for preparing the coated ternary cathode material according to claim 3, characterized in that, The first solvent and the second solvent are each independently selected from anhydrous ethanol and / or anhydrous diethyl ether.

6. The method for preparing the coated ternary cathode material according to any one of claims 3 to 5, characterized in that, The calcination temperatures for the first and second calcinations are independently 700℃~900℃.

7. A positive electrode plate, characterized in that, It includes a positive current collector and a positive active material layer located on one or both sides of the positive current collector, wherein the positive active material in the positive active material layer is the coated ternary positive electrode material as described in claim 1 or 2.

8. A secondary battery, characterized in that, Includes the positive electrode sheet as described in claim 7.

9. An electrical device, characterized in that, Includes the secondary battery as described in claim 8.

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