Lithium cobalt oxide positive electrode material based on nano-sol low-temperature coated O2 configuration and preparation method and application thereof

Abstract

The invention discloses a lithium cobalt oxide positive electrode material based on nano-sol low-temperature coated O2 configuration and a preparation method and application thereof, and belongs to the technical field of lithium ion battery positive electrode materials. An ion exchange method is adopted, firstly, a sodium-containing layered oxide is synthesized through a high-temperature calcination method, then the sodium-containing layered oxide and fused salt are fully mixed for ion exchange, and the lithium cobalt oxide positive electrode material based on the nano-sol low-temperature coated O2 configuration can be obtained after filtering, washing and drying. According to the preparation method, the nano sol is prepared by adopting a high-shear homogenizing technology, and the O2 lithium cobalt oxide positive electrode material is coated at low temperature to realize surface modification, so that a uniform nano coating is formed, and the electrochemical performance of the nano coating is improved. According to the method, the cycling stability and the rate capability of the material can be remarkably improved, and a new thought is provided for research and development of a high-energy-density lithium ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing cathode materials for lithium-ion batteries, and particularly relates to a lithium cobaltate cathode material with an O2 configuration coated at low temperature based on nano sol, and a preparation method and application thereof. Background Art

[0002] Lithium cobaltate (LiCoO 2 ) as the earliest commercially used cathode material for lithium-ion batteries has advantages such as high energy density, excellent rate performance, and large tap density. So far, it still plays an important role in the lithium-ion battery market. In the traditional O3 structure, the oxygen layer is arranged in the ABCABC manner, and LiO 6 shares edges with the TMO 6 octahedron, while the O2-type structure has an ABCBA arrangement, and the LiO 6 octahedron shares a face with the TMO 6 octahedron on one side and shares edges on the other side. The lithium cobaltate cathode material with an O2 configuration is an emerging cathode material for lithium-ion batteries and has received extensive attention due to its unique layered oxide structure and high energy density. In the O2 structure, due to the stronger electrostatic repulsion between the shared-face cations, the migration of TM from the middle site to the adjacent Li site is inhibited.

[0003] However, the application of lithium cobaltate still faces some challenges. Especially under high voltage and long-cycle conditions, problems such as its structure collapse and poor cycle performance are more significant. In addition, the side reaction between the surface of lithium cobaltate and the electrolyte will be aggravated, which not only affects the battery performance but may also shorten the service life of the battery.

[0004] To solve these problems, the surface coating technology has been used by researchers as an effective modification means. Existing research has adopted sol coating on lithium cobaltate cathode materials to improve the performance of the materials. For example, the Chinese invention patent with the application number 201710821143.2 discloses a preparation process for coating lithium cobaltate cathode materials with nano-aluminum sol, forming a nano-aluminum-containing compound coating layer on the surface of O3-type lithium cobaltate, and then obtaining a lithium cobaltate cathode material uniformly coated with nano-aluminum oxide through medium and high-temperature sintering, thereby improving the cycle performance and structural stability of lithium cobaltate. However, the preparation of the sol in this process is carried out by diluting the existing aluminum sol, lacking wide applicability. In addition, its coating temperature is relatively high, which not only leads to large energy consumption, but more importantly, it is not applicable to the lithium cobaltate cathode material with an O2 structure because the lithium cobaltate with an O2 structure will undergo a phase change at high temperatures. Summary of the Invention

[0005] In order to overcome the disadvantages of the above-mentioned existing technologies, the object of the present invention is to provide a method for preparing and applying a lithium cobalt oxide cathode material with an O2 configuration coated with a nano-sol at low temperature, so as to solve the technical problems of high coating temperature, large energy consumption and inapplicability to the lithium cobalt oxide cathode material with an O2-type structure in the existing technologies.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a preparation method of a lithium cobalt oxide cathode material with an O2 configuration coated with a nano-sol at low temperature, including: Synthesize a sodium-containing layered oxide Na m CoO 2 , where 0.70 ≤ m ≤ 1.00; then mix the sodium-containing layered oxide Na m CoO 2 with a lithium-containing molten salt for ion exchange, and then wash and dry to obtain a raw sample LiCoO 2 ; Prepare a nano-sol by high-shear homogenization method, and then coat the raw sample LiCoO 2 with the nano-sol at 150 - 200 °C to form a uniform nano-coating on the surface of the raw sample LiCoO 2 , thus obtaining a lithium cobalt oxide cathode material with an O2 configuration coated with a nano-sol at low temperature.

[0007] Furthermore, the above method for preparing a nano-sol by high-shear homogenization technology and using it to coat a lithium cobalt oxide cathode material with an O2 configuration specifically includes the following steps: Step 1. Weighing: Weigh a certain mass of precursor particles and sodium source according to the molar ratio Na m CoO 2 (0.70 ≤ m ≤ 1.00), and then place them in a high-speed mixer and mix well for 10 - 30 min.

[0008] Step 2. High-temperature calcination: Heat the mixture obtained in Step 1 at a heating rate of 5 - 10 °C / min to 400 - 500 °C, pre-calcine for 2 - 5 h, then calcine at 700 - 900 °C for 10 - 30 h, and then naturally cool to room temperature to obtain a sodium-containing intermediate product.

[0009] Step 3. Molten salt ion exchange: Mix the sodium-containing intermediate product obtained in Step 2 with a lithium-containing molten salt in a molar ratio of 1 - 10 times the molar amount, heat it in a muffle furnace at 180 - 280 °C for 1 - 8 h, and then filter, wash and dry the product to obtain an uncoated raw sample LiCoO2 。

[0010] Step 4. Preparation of nano sol by high-shear homogenization: First, add an appropriate amount of water to a beaker, and gradually add the particulate powder under low-speed stirring (300 - 500 rpm) to prevent powder agglomeration or floating. At the same time, add a surfactant to improve stability. Subsequently, gradually increase the rotation speed to 6000 - 10000 rpm and continuously stir for 10 - 30 min to fully disperse the powder and form a uniform sol.

[0011] Step 5. Coating of nano sol: Disperse the material obtained in Step 3 into the sol solution obtained in Step 4, heat and stir at 80 - 100 °C. When only a little water remains, stop heating and use the remaining heat to evaporate the remaining water. Subsequently, react at 150 - 200 °C for 2 - 5 h to obtain the surface-modified material M-LiCoO 2 (M is the coating element).

[0012] Furthermore, the cobalt source of the precursor particles described in Step 1 is any one of Co(NO 3 ) 2 ·6H 2 O, Co(CH 3 COO) 2 ·4H 2 O, Co 3 O 4 , Co(OH) 2 , CoCO 3 and CoC 2 O 4 among others.

[0013] Furthermore, the sodium source of the precursor particles described in Step 1 is any one of Na 2 CO 3 , NaOH, NaNO 3 and CH 3 COONa among others.

[0014] Furthermore, the high-temperature calcination atmosphere in Step 2 is an air atmosphere or an oxygen atmosphere.

[0015] Furthermore, the lithium-containing molten salt in Step 3 is a combination of LiCl and LiNO 3 , or a combination of LiCl and LiNO 3 , NaNO 3 , NaCl, KCl and KNO 3 in any one or several combinations.

[0016] Further, during the ion exchange treatment operation, starting from room temperature, the temperature is raised to 180 - 280 °C at a heating rate of 5 - 10 °C / min, and the ion exchange treatment time is 1 - 8 h.

[0017] Further, the particulate powder described in step 4 is CuO, Fe 2 O 3 , MnO 2 , Al 2 O 3 , Nb 2 O 5 , Y 2 O 3 , WO 3 , CeO 2 , TiO 2 , ZnO, ZrO 2 , LiNbO 3 , Li 2 WO 4 and Li 3 BO 3 any one of them.

[0018] Further, in step 4, the specific operation of the high - shear homogenization treatment is as follows: At a rotation speed of 300 - 500 rpm, the coated particulate powder is added to water, and at the same time, a surfactant is added, and then the rotation speed is gradually increased to 6000 - 10000 rpm, and the continuous stirring treatment is carried out for 10 - 30 min.

[0019] Further, the surfactant is selected from any one of cetyltrimethylammonium bromide (CTAB), polyvinylpyrrolidone (PVP), and polyacrylic acid (PAA).

[0020] Even further, the mass ratio of CTAB to the coating is 1:100 - 1:10, the mass ratio of PVP to the coating is 1:100 - 1:20, and the mass ratio of PAA to the coating is 1:100 - 1:10.

[0021] Further, in step 5, the temperature is raised to 150 - 200 °C at a heating rate of 5 - 10 °C / min, and the reaction time is 2 - 5 h.

[0022] Further, in step 5, the coating amount is 500 - 5000 ppm (mass ratio of the coating element to lithium cobaltate), and the mass ratio of the metal element in the coated particulate powder to the original sample LiCoO 2 is 500 - 5000 ppm.

[0023] The present invention also discloses a lithium cobaltate cathode material with an O2 configuration coated with a nano-sol at low temperature prepared by the above preparation method. The lithium cobaltate cathode material with an O2 configuration coated with a nano-sol at low temperature is a micron-sized particle, and at 3 - 4.65 V and 1C conditions, the capacity retention rate reaches over 93% after 50 cycles.

[0024] The present invention also discloses the application of the lithium cobaltate cathode material with an O2 configuration coated with a nano-sol at low temperature prepared above in the preparation of lithium ion batteries.

[0025] Compared with the prior art, the present invention has the following beneficial effects: The preparation method of the lithium cobaltate cathode material with an O2 configuration coated with a nano-sol at low temperature disclosed by the present invention uses Li + / Na + ion exchange method. First, a sodium-containing layered oxide is synthesized by a high-temperature calcination method, and then it is fully mixed with a molten salt for ion exchange. After filtration, washing, and drying, the O2 configuration LiCoO 2 cathode material can be obtained. The present invention innovatively uses a high-shear homogenization technique to prepare a nano-sol, and coats the O2 lithium cobaltate cathode material at low temperature to achieve surface modification, thereby forming a uniform nano-coating to improve its electrochemical performance. On the one hand, due to its strong shearing force, the high-shear homogenization technique can effectively break the powder agglomeration, make the nano-particles uniformly dispersed in the solvent, and thus form a homogeneous and stable sol. Compared with traditional stirring or ultrasonic dispersion, this technique can achieve efficient dispersion in a shorter time and reduce particle agglomeration. On the other hand, the low-temperature sol coating treatment at 150 - 200 °C has the advantages of simple process, uniform coating, and strong controllability. This method can form a dense and uniform protective layer, effectively isolate the direct contact between the electrolyte and the cathode material, and reduce the occurrence of side reactions. In addition, the low-temperature coating can effectively inhibit the structural phase change, realize the precise control of the nano-scale coating layer, and significantly improve the cycle stability and rate performance of the material. Therefore, the core invention point of the present invention lies in using the high-shear homogenization technique to prepare a nano-sol and combining the low-temperature coating technique to modify the O2 configuration lithium cobaltate cathode material, which has important research value and application prospects. This method can significantly improve the cycle stability and rate performance of the material, provide a new idea for the research and development of high-energy density lithium ion batteries, and effectively solve the defective problems of high energy consumption caused by the relatively high coating temperature in the prior art and the inapplicability to the preparation of the lithium cobaltate cathode material with an O2 structure.

[0026] The lithium cobaltate cathode material with an O2 configuration coated with a nano-sol at low temperature prepared by the method of the present invention has excellent cycle performance. At 3 - 4.65 V and 1C conditions, the capacity retention rate of the material reaches as high as over 93% after 50 cycles. Description of the Drawings

[0027] Figure 1 X-ray diffraction pattern of the uncoated original sample LCO prepared in Example 1 of the present invention.

[0028] Figure 2 Scanning electron microscopy image of the uncoated original sample LCO prepared in Example 1 of the present invention.

[0029] Figure 3 First charge-discharge curve of the uncoated original sample LCO prepared in Example 1 of the present invention at a rate of 0.1C.

[0030] Figure 4 Nanometer Al 2 O 3 sol-gel coated O2-type lithium cobalt oxide cathode material at a rate of 1C.

[0031] Figure 5 Nanometer Fe 2 O 3 sol-gel coated O2-type lithium cobalt oxide cathode material prepared in Example 2 of the present invention.

[0032] Figure 6 X-ray diffraction pattern of the nanometer ZnO sol-gel coated O2-type lithium cobalt oxide cathode material prepared in Example 3 of the present invention.

[0033] Figure 7 Nanometer ZrO 2 sol-gel coated O2-type lithium cobalt oxide cathode material prepared in Example 4 of the present invention.

[0034] Figure 8 Scanning electron microscopy image of the nanometer CuO sol-gel coated O2-type lithium cobalt oxide cathode material prepared in Example 5 of the present invention.

[0035] Figure 9 Nanometer Y 2 O 3 sol-gel coated O2-type lithium cobalt oxide cathode material at a rate of 1C prepared in Example 6 of the present invention.

[0036] Figure 10 Nanometer TiO 2 sol-gel coated O2-type lithium cobalt oxide cathode material prepared in Example 7 of the present invention.

[0037] Figure 11 Nanometer LiNbO 3 sol-gel coated O2-type lithium cobalt oxide cathode material at a rate of 1C prepared in Example 8 of the present invention. Detailed implementation mode

[0038] To enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solution in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above accompanying drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0040] The following further describes the present invention in detail with reference to the accompanying drawings: Embodiment 1 In this embodiment, ingredients are prepared according to the chemical formula LiCoO 2 and nano-Al 2 O 3 sol is selected for coating.

[0041] Specifically, a preparation method for a low-temperature coated O2 configuration lithium cobalt oxide cathode material based on nano-Al 2 O 3 sol includes the following steps: Step 1. Weighing: Weigh a certain mass of Co 3 O 4 and Na 2 CO 3 according to the molar ratio, and then place them in a high-speed mixer and mix well for 30 minutes to obtain a mixture.

[0042] Step 2. High-temperature calcination: The mixture obtained in Step 1 is heated from room temperature to 500 °C at a heating rate of 5 °C / min, pre-calcined for 5 h, then calcined at 900 °C for 10 h, and then naturally cooled to room temperature to obtain a sodium-containing intermediate product NaCoO 2 .

[0043] Step 3. Molten salt ion exchange: Mix the sodium-containing intermediate obtained in Step 2 with 2 molar equivalents of LiNO 3 / LiCl molten salt and ball-mill them evenly. Heat and react in a muffle furnace at 180 °C for 8 h, then filter, wash, and dry the product to obtain the uncoated original sample LCO (LiCoO 2 ).

[0044] The X-ray diffraction pattern of the uncoated original sample LCO prepared in this example is shown in Figure 1 . It can be seen that all diffraction peaks are consistent with the characteristic peak positions of the O2-type layered structure, confirming the successful preparation of the O2-configured lithium cobalt oxide cathode material LCO. The corresponding morphology is shown in Figure 2 . The prepared LCO is mainly hexagonal in shape with a particle size of about 10 μm.

[0045] Step 4. Preparation of nano-sol by high-shear homogenization: First, add an appropriate amount of water to a beaker and gradually add Al 2 O 3 powder at a rotation speed of 300 rpm to prevent powder agglomeration or floating, and at the same time add 1 wt% surfactant CTAB. Subsequently, gradually increase the rotation speed to 6000 rpm and continuously stir for 10 min to fully disperse the Al 2 O 3 powder and form a uniform nano-Al 2 O 3 sol.

[0046] Step 5. Nano-sol coating: Disperse the original sample LCO obtained in Step 3 into a 5000 ppm nano-Al 2 O 3 sol solution, heat and stir at 80 °C. When only a little water remains, stop heating and use the remaining heat to evaporate the remaining water. Subsequently, heat-treat at 200 °C for 5 h to obtain the O2-configured lithium cobalt oxide cathode material coated with nano-Al 2 O 3 sol at low temperature, that is, the surface-modified material Al-LCO.

[0047] Perform charge-discharge performance tests on the O2-configured lithium cobalt oxide cathode material coated with nano-Al 2 O 3 sol at low temperature prepared in this example. The process is as follows: Weigh the nano-Al 2 O 3The lithium cobaltate cathode material with O2 configuration, acetylene black (SP), and polyvinylidene fluoride (PVDF) were sol-coated at low temperature, added to N-methylpyrrolidone (NMP) to form a slurry, uniformly coated on aluminum foil, dried in a vacuum drying oven at 80 °C for 12 h, then cut into electrode sheets with a diameter of 12 mm using a mold, and the electrode sheets were pressed at a pressure of 5 MPa to make the final positive electrode sheet; a lithium metal sheet was used as the negative electrode, and Celgard 2400 was used as the separator, and a CR2032 coin cell was assembled in a glove box filled with inert gas.

[0048] The electrochemical performance test of the battery was carried out in the voltage range of 3~4.65 V. The results showed that the initial discharge specific capacity of the uncoated original sample LCO prepared in this example was 254 mAh / g at a 0.1C rate, and the Coulombic efficiency was 94%, as Figure 3 shown. The initial discharge specific capacity at a 1C rate was 240 mAh / g, and the Coulombic efficiency was 95%. The initial discharge specific capacity of the lithium cobaltate cathode material with O2 configuration coated with nano-Al 2 O 3 sol at low temperature (Al-LCO) prepared in this example was 243 mAh / g at 1C, and the Coulombic efficiency was 96%, as shown in Figure 4 .

[0049] Example 2 In this example, the ingredients were prepared according to the chemical formula LiCoO 2 , and nano-Fe 2 O 3 sol was selected for coating.

[0050] Specifically, a preparation method of a lithium cobaltate cathode material with O2 configuration coated with nano-Fe 2 O 3 sol at low temperature includes the following steps: Step 1. Weighing: Weigh a certain mass of Co 3 O 4 and Na 2 CO 3 according to the molar ratio, and then put them in a high-speed mixer and mix well for 10 min to obtain a mixture.

[0051] Step 2. High-temperature calcination: The mixture obtained in Step 1 was heated from room temperature to 500 °C at a heating rate of 10 °C / min, pre-calcined for 2 h, then calcined at 800 °C for 20 h, and then naturally cooled to room temperature to obtain the sodium-containing intermediate product NaCoO 2 .

[0052] Step 3. Molten salt ion exchange: The sodium-containing intermediate obtained in step 2 was mixed with 5 times the molar amount of LiCl / NaNO 3 The molten salt was ball-milled and mixed evenly, and the mixture was heated in a muffle furnace at 200 °C for 4 h. The product was then filtered, washed, and dried to obtain the uncoated original sample LCO (LiCoO 2 ).

[0053] Step 4. Preparation of nanosol by high shear homogenization: First, add an appropriate amount of water into the beaker and gradually add Fe at a speed of 500 rpm. 2 O 3 The powder was stirred to prevent powder agglomeration or floating, and 5 wt% of the surfactant PVP was added. Then, the speed was gradually increased to 5000 rpm and stirred for 30 min to make Fe 2 O 3 The powder is fully dispersed and forms a uniform nano-Fe 2 O 3 Sol.

[0054] Step 5. Nanosol coating: The original sample LCO obtained in step 3 was dispersed to 2000 ppm nano-Fe 2 O 3 The sol solution was heated at 100°C while stirring. When only a small amount of water remained, the heating was stopped and the remaining water was evaporated using the residual heat. Then, the sol solution was heat treated at 180°C for 4 h to obtain a nano-Fe-based 2 O 3 Sol-coated O2-configuration lithium cobalt oxide positive electrode material at low temperature, that is, the surface-modified material Fe-LCO.

[0055] The nano-Fe prepared in this example 2 O 3 The scanning electron microscope image of the sol low temperature coated O2 configuration lithium cobalt oxide positive electrode material (Fe-LCO) is shown in Figure 5 , it can be seen that the material is evenly distributed and the particle size is about 10 μm.

[0056] Charge and discharge performance test: The test method is the same as that in Example 1. The experimental results show that the nano-Fe prepared in this example 2 O 3 The first discharge specific capacity of the sol-low temperature coated O2-configuration lithium cobalt oxide positive electrode material (Fe-LCO) at 1C reached 242mAh / g.

[0057] Example 3 In this embodiment, according to the chemical formula LiCoO 2 Ingredients: select nano ZnO sol for coating.

[0058] Specifically, a preparation method of a cathode material of lithium cobaltate with an O2 configuration coated with nano-ZnO sol at low temperature includes the following steps: Step 1. Weighing: Weigh a certain mass of Co 3 O 4 and Na 2 CO 3 according to the molar ratio, and then put them in a high-speed mixer and mix well for 20 min to obtain a mixture.

[0059] Step 2. High-temperature calcination: Heat the mixture obtained in Step 1 from room temperature to 400 °C at a heating rate of 5 °C / min, pre-calcine for 5 h, then calcine at 850 °C for 15 h, and then naturally cool to room temperature to obtain a sodium-containing intermediate product Na 0.8 CoO 2 .

[0060] Step 3. Molten salt ion exchange: Mix the sodium-containing intermediate product obtained in Step 2 with 10 times the molar amount of LiCl / KCl molten salt by ball milling until uniform, heat and react in a muffle furnace at 240 °C for 5 h, and then filter, wash, and dry the product to obtain the uncoated original sample LCO (LiCoO 2 ).

[0061] Step 4. Preparation of nano sol by high-shear homogenization: First, add an appropriate amount of water to a beaker, and gradually add ZnO powder at a rotation speed of 300 rpm to prevent powder agglomeration or floating, and at the same time add 10 wt% surfactant CTAB. Subsequently, gradually increase the rotation speed to 6000 rpm and continuously stir for 20 min to fully disperse the ZnO powder and form a uniform nano-ZnO sol.

[0062] Step 5. Coating with nano sol: Disperse the original sample LCO obtained in Step 3 into a 3000 ppm nano-ZnO sol solution, heat and stir at 80 °C. When only a little water remains, stop heating and use the remaining heat to evaporate the remaining water. Subsequently, perform heat treatment at 150 °C for 5 h to obtain a cathode material of lithium cobaltate with an O2 configuration coated with nano-ZnO sol at low temperature, that is, the surface-modified material Zn-LCO.

[0063] The X-ray diffraction pattern of the cathode material of lithium cobaltate with an O2 configuration coated with nano-ZnO sol at low temperature (Zn-LCO) prepared in this example is shown in Figure 6 , and it can be seen from the figure that all diffraction peaks belong to the O2-type structure.

[0064] Charge and discharge performance test: The test method is the same as that in Example 1. The results show that the initial discharge specific capacity of the LiCoO₂ cathode material (Zn-LCO) based on nano-ZnO sol prepared in this example reaches 245 mAh / g at 1C.

[0065] Example 4 In this example, according to the chemical formula LiCoO 2 ingredients, nano-ZrO 2 sol is selected for coating.

[0066] Specifically, a preparation method of a LiCoO₂ cathode material based on nano-ZrO 2 sol low-temperature coating includes the following steps: Step 1. Weighing: Weigh a certain mass of Co 3 O 4 and Na 2 CO 3 according to the molar ratio, and then put them in a high-speed mixer and mix well for 15 min to obtain a mixture.

[0067] Step 2. High-temperature calcination: Heat the mixture obtained in Step 1 from room temperature to 450°C at a heating rate of 5°C / min, pre-calcine for 4 h, then calcine at 700°C for 30 h, and then naturally cool to room temperature to obtain the sodium-containing intermediate product Na 0.7 CoO 2 .

[0068] Step 3. Molten salt ion exchange: Mix the sodium-containing intermediate product obtained in Step 2 with 1-fold molar amount of LiCl / KNO 3 molten salt by ball milling, heat and react in a muffle furnace at 280°C for 2 h, and then filter, wash and dry the product to obtain the uncoated original sample LCO (LiCoO 2 ).

[0069] Step 4. Preparation of nano sol by high-shear homogenization: First, add an appropriate amount of water to a beaker, and gradually add ZrO 2 powder at a rotation speed of 400 rpm to prevent the powder from agglomerating or floating, and at the same time add 1 wt% surfactant PAA. Subsequently, gradually increase the rotation speed to 10000 rpm and continuously stir for 10 min to fully disperse the ZrO 2 powder and form a uniform nano-ZrO 2 sol.

[0070] Step 5. Nano sol coating: The original sample LCO obtained in step 3 was dispersed into 1000 ppm nano ZrO 2 The sol solution was heated at 90°C while stirring. When only a small amount of water remained, the heating was stopped and the remaining water was evaporated using the residual heat. Then, the sol solution was heat treated at 180°C for 4 hours to obtain a nano ZrO-based 2 Sol-coated O2-configuration lithium cobalt oxide positive electrode material at low temperature, that is, the surface-modified material Zr-LCO.

[0071] Rate performance test: The nano ZrO prepared in this example 2 The rate performance of the sol-coated O2-structured lithium cobalt oxide cathode material (Zr-LCO) is shown in Figure 7 It can be clearly seen that at a current density of 10C, the discharge capacity of Zr-LCO is as high as 199 mAh / g, while the discharge capacity of the uncoated original sample LCO is only 75 mAh / g.

[0072] Example 5 In this embodiment, according to the chemical formula LiCoO 2 Ingredients: select nano CuO sol for low temperature coating.

[0073] Specifically, a method for preparing an O2-structured lithium cobalt oxide positive electrode material based on nano-CuO sol low temperature coating comprises the following steps: Step 1. Weighing: Weigh a certain mass of Co according to the molar ratio 3 O 4 with Na 2 CO 3 , and then put it in a high mixer and mix it thoroughly for 10 minutes to obtain a mixture.

[0074] Step 2. High temperature calcination: The mixture obtained in step 1 was heated from room temperature to 450°C at a heating rate of 10°C / min, pre-calcined for 3 h, and then calcined at 800°C for 20 h, and then naturally cooled to room temperature to obtain a sodium-containing intermediate product Na 0.9 CoO 2 .

[0075] Step 3. Molten salt ion exchange: The sodium-containing intermediate obtained in step 2 was mixed with 4 times the molar amount of LiNO 3 / KNO 3 The molten salt was ball-milled and mixed evenly, and the mixture was heated in a muffle furnace at 250 °C for 3 h. The product was then filtered, washed, and dried to obtain the uncoated original sample LCO (LiCoO 2 ).

[0076] Step 4. Preparation of nanosol by high shear homogenization: First, add an appropriate amount of water to the beaker and gradually add CuO powder at a speed of 300 rpm to prevent powder agglomeration or floating, and add 1wt% surfactant PVP. Then, gradually increase the speed to 8000 rpm and continue stirring for 20 min to fully disperse the CuO powder and form a uniform nano-CuO sol.

[0077] Step 5. Nanosol coating: The original sample LCO obtained in step 3 was dispersed into a 500 ppm nano-CuO sol solution, heated and stirred at 80°C, and when only a small amount of water remained, the heating was stopped and the remaining water was evaporated using the residual heat. Subsequently, the nano-CuO sol-based low-temperature coated O2-configured lithium cobalt oxide cathode material was obtained, i.e., the surface-modified material Cu-LCO.

[0078] The morphology of the O2-structured lithium cobalt oxide positive electrode material (Cu-LCO) prepared in this example based on nano-CuO sol low-temperature coating is shown in Figure 8 The material morphology is mainly hexagonal, and the particle size is about 10 μm.

[0079] Charge and discharge performance test: The test method is the same as that in Example 1. The results show that the first discharge specific capacity of the O2-structured lithium cobalt oxide positive electrode material based on nano-CuO sol low-temperature coating prepared in this example is 240 mAh / g at 1C.

[0080] Example 6 In this embodiment, according to the chemical formula LiCoO 2 Ingredients, choose Nano Y 2 O 3 Sol coating.

[0081] Specifically, a nano-Y 2 O 3 The preparation method of the sol low temperature coating O2 structure lithium cobalt oxide positive electrode material comprises the following steps: Step 1. Weighing: Weigh a certain mass of Co according to the molar ratio 3 O 4 with Na 2 CO 3 , and then put it in a high mixer and mix it thoroughly for 30 minutes to obtain a mixture.

[0082] Step 2. High temperature calcination: The mixture obtained in step 1 was heated from room temperature to 500°C at a heating rate of 5°C / min, pre-calcined for 3 h, and then calcined at 900°C for 15 h, and then naturally cooled to room temperature to obtain a sodium-containing intermediate product Na 0.9CoO 2 。

[0083] Step 3. Molten salt ion exchange: Mix the sodium-containing intermediate obtained in Step 2 with 2-fold molar amount of LiCl / KCl / NaCl molten salt by ball milling until homogeneous. Heat and react in a muffle furnace at 180 °C for 8 h, then filter, wash, and dry the product to obtain the uncoated original sample LCO (LiCoO 2 ).

[0084] Step 4. High-shear homogenization to prepare nano-sol: First, add an appropriate amount of water to a beaker, and gradually add Y 2 O 3 powder at a rotation speed of 500 rpm to prevent powder agglomeration or floating, and at the same time add 2 wt% surfactant CTAB. Subsequently, gradually increase the rotation speed to 9000 rpm and continuously stir for 30 min to fully disperse the Y 2 O 3 powder and form a uniform nano Y 2 O 3 sol.

[0085] Step 5. Nano-sol coating: Disperse the original sample LCO obtained in Step 3 into a 5000 ppm nano Y 2 O 3 sol solution, heat and stir at 100 °C. When only a little water remains, stop heating and use the residual heat to evaporate the remaining water. Subsequently, perform heat treatment at 150 °C for 5 h to obtain the O2 configuration lithium cobalt oxide cathode material coated with nano Y 2 O 3 sol at low temperature, that is, the surface-modified material Y-LCO.

[0086] Charge and discharge performance test: The test method is the same as that in Example 1. The results show that the LCO prepared in this example has an initial discharge specific capacity of 232 mAh / g at 1C and a Coulomb efficiency of 95%. The O2 configuration lithium cobalt oxide cathode material (Y-LCO) coated with nano Y 2 O 3 sol at low temperature has an initial discharge specific capacity of 242 mAh / g and a Coulomb efficiency of 96%, as shown in Figure 9 .

[0087] Example 7 In this example, formulate according to the chemical formula LiCoO 2 and select nano TiO 2 sol for coating.

[0088] Specifically, a kind of O2 configuration lithium cobalt oxide cathode material based on nano TiO 2Preparation method of sol low-temperature coated O2 configuration lithium cobaltate cathode material, comprising the following steps: Step 1. Weighing: Weigh a certain mass of Co 3 O 4 and Na 2 CO 3 according to the molar ratio, and then place them in a high-speed mixer and mix well for 25 min to obtain a mixture.

[0089] Step 2. High-temperature calcination: Heat the mixture obtained in Step 1 from room temperature to 450 °C at a heating rate of 10 °C / min, pre-calcine for 5 h, then calcine at 750 °C for 25 h, and then naturally cool to room temperature to obtain the sodium-containing intermediate product NaCoO 2 .

[0090] Step 3. Molten salt ion exchange: Mix the sodium-containing intermediate product obtained in Step 3 with 4 times the molar amount of LiNO 3 / NaNO 3 molten salt by ball milling to be uniformly mixed, heat and react in a muffle furnace at 280 °C for 1 h, and then filter, wash and dry the product to obtain the uncoated original sample LCO (LiCoO 2 ).

[0091] Step 4. Preparation of nano sol by high-shear homogenization: First, add an appropriate amount of water to a beaker, and gradually add TiO 2 powder at a rotation speed of 350 rpm to prevent powder agglomeration or floating, and at the same time add 10 wt% surfactant PAA. Subsequently, gradually increase the rotation speed to 7000 rpm and continuously stir for 20 min to fully disperse the TiO 2 powder and form a uniform nano TiO 2 sol.

[0092] Step 5. Nano sol coating: Disperse the original sample LCO obtained in Step 3 into 2000 ppm nano TiO 2 sol solution, heat and stir at 85 °C. When only a little water remains, stop heating and use the remaining heat to evaporate the remaining water. Subsequently, perform heat treatment at 160 °C for 4 h to obtain the O2 configuration lithium cobaltate cathode material low-temperature coated with nano TiO 2 sol, that is, the surface-modified material Ti-LCO.

[0093] Charge and discharge performance test: The test method is the same as that in Example 1, and the results show that the nano TiO 2The capacity retention rate of the sol-coated O2-type lithium cobalt oxide cathode material (Ti-LCO) is 93% after 50 cycles, while that of the uncoated original sample LCO is only 83%, as Figure 10 shown.

[0094] Example 8 In this example, ingredients are prepared according to the chemical formula LiCoO 2 and a nano-LiNbO 3 sol is selected for coating.

[0095] Specifically, a preparation method of a sol-coated O2-type lithium cobalt oxide cathode material based on nano-LiNbO 3 sol at low temperature includes the following steps: Step 1. Weighing: Weigh a certain mass of Co 3 O 4 and Na 2 CO 3 according to the molar ratio, and then place them in a high-speed mixer and mix well for 10 min to obtain a mixture.

[0096] Step 2. High-temperature calcination: Heat the mixture obtained in Step 1 from room temperature to 400 °C at a heating rate of 5 °C / min, pre-calcine for 5 h, then calcine at 900 °C for 15 h, and then naturally cool to room temperature to obtain a sodium-containing intermediate product Na 0.95 CoO 2 .

[0097] Step 3. Molten salt ion exchange: Mix the sodium-containing intermediate product obtained in Step 2 with 1.5 times the molar amount of LiCl / KCl molten salt by ball milling, heat and react in a muffle furnace at 220 °C for 5 h, and then filter, wash and dry the product to obtain the uncoated original sample LCO (LiCoO 2 ).

[0098] Step 4. Preparation of nano sol by high-shear homogenization: First, add an appropriate amount of water to a beaker, and gradually add LiNbO 3 powder at a rotation speed of 500 rpm to prevent powder agglomeration or floating, and at the same time add 3 wt% surfactant PVP. Subsequently, gradually increase the rotation speed to 6000 rpm and continuously stir for 10 min to fully disperse the LiNbO 3 powder and form a uniform nano-LiNbO 3 sol.

[0099] Step 5. Coating with nano sol: Disperse the raw sample LCO obtained in Step 3 into a 1000 ppm nano-LiNbO 3 sol solution, heat and stir at 95 °C. When only a little water remains, stop heating and use the remaining heat to evaporate the remaining water. Subsequently, heat-treat at 190 °C for 3 h to obtain a nano-LiNbO 3 sol low-temperature coated O2 configuration lithium cobalt oxide cathode material, that is, the surface-modified material Nb-LCO.

[0100] Charge and discharge performance test: The test method is the same as that in Example 1. The results show that the initial discharge specific capacity of the LCO prepared in this example is 235 mAh / g at 1C, and the Coulomb efficiency is 95%. Based on nano-LiNbO 3 sol low-temperature coated O2 configuration lithium cobalt oxide cathode material (Nb-LCO) has an initial discharge specific capacity of 243 mAh / g and a Coulomb efficiency of 94%. See Figure 11 .

[0101] In summary, the advantages of the method of the present invention are as follows: 1. The nano-sol is prepared by using high-shear homogenization technology. With its strong shear force, efficient dispersion can be achieved in a shorter time, reducing particle agglomeration and preparing a uniform and stable nano-sol; 2. The surface-modified O2 lithium cobalt oxide cathode material is prepared by low-temperature nano-sol coating. The method has good consistency, a uniform coating, a simple process, uniform and sufficient reactions, and effectively avoids the problem that the material is prone to phase change at high temperatures; 3. The cycle performance of the nano-sol low-temperature coated O2 configuration lithium cobalt oxide cathode material prepared by the method of the present invention is excellent. Under the conditions of 3 - 4.65 V and 1C, the capacity retention rate of the material is as high as over 93% after 50 cycles.

[0102] 4. The operation of preparing the nano-sol coated O2 configuration lithium cobalt oxide cathode material by the method of the present invention is simple, which is conducive to mass production.

[0103] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a positive electrode material of lithium cobalt oxide with O2 structure based on nano-sol low temperature coating, characterized in that: include: The sodium-containing layered oxide Na was synthesized by high temperature calcination. m CoO2, where 0.70 ≤ m ≤1.00; then the sodium-containing layered oxide Na m CoO2 is mixed with lithium-containing molten salt for ion exchange, and then washed and dried to obtain the original sample LiCoO2; The nanosol is prepared by a high shear homogenization method, and then the original sample LiCoO2 is coated with the nanosol at 150-200°C to form a uniform nano coating on the surface of the original sample LiCoO2, thereby obtaining a nanosol-based low-temperature coated O2-configuration lithium cobalt oxide positive electrode material.

2. The method for preparing the O2-structured lithium cobalt oxide positive electrode material based on nanosol low-temperature coating according to claim 1, characterized in that: The following steps are involved: 1) Take the cobalt source precursor particles and the sodium source in molar ratio, mix them evenly to obtain a mixture, and calcine the mixture at high temperature to obtain a sodium-containing layered oxide Na m CoO2, 0.70 ≤ m ≤1.00; 2) The sodium-containing layered oxide Na m CoO2 and lithium-containing molten salt are uniformly mixed, and ion exchange treatment is performed at 180-280°C. The product is washed and dried to obtain the original sample LiCoO2. 3) subjecting the coated particle powder, water and surfactant to high shear homogenization to form a uniform nanosol; 4) The original sample LiCoO2 is dispersed in the nanosol, heated and stirred at 80-100°C to remove moisture, and then reacted at 150-200°C for 2-5 hours to obtain a nanosol-based low-temperature coated O2-configured lithium cobalt oxide positive electrode material.

3. The method for preparing the O2-structured lithium cobalt oxide positive electrode material based on nanosol low-temperature coating according to claim 2, characterized in that: In step 1), the cobalt source precursor particles are selected from any one of Co(NO3)2·6H2O, Co(CH3COO)2·4H2O, Co3O4, Co(OH)2, CoCO3 and CoC2O4; the sodium salt is selected from any one of Na2CO3, NaOH, NaNO3 and CH3COONa.

4. The method for preparing the O2-structured lithium cobalt oxide positive electrode material based on nanosol low-temperature coating according to claim 2, characterized in that: In step 1), the mixture is pre-calcined at 400-500°C for 2-5 h, then calcined at 700-900°C for 10-30 h, and then naturally cooled to room temperature to obtain a sodium-containing layered oxide.

5. The method for preparing the O2-structured lithium cobalt oxide positive electrode material based on nanosol low-temperature coating according to claim 2, characterized in that: In step 2), the lithium-containing molten salt is a combination of LiCl and LiNO3, or a combination of LiCl and any one or more of LiNO3, NaNO3, NaCl, KCl and KNO3; during the ion exchange treatment operation, the temperature is increased from room temperature to 180-280°C at a heating rate of 5-10°C / min, and the ion exchange treatment time is 1-8 h.

6. The method for preparing the O2-structured lithium cobalt oxide positive electrode material based on nanosol low-temperature coating according to claim 2, characterized in that: In step 3), the specific operation of high shear homogenization is as follows: At a rotation speed of 300-500 rpm, add the coated particle powder to the water, add the surfactant at the same time, then gradually increase the rotation speed to 6000-10000 rpm, and continue stirring for 10-30 min.

7. The method for preparing the O2-structured lithium cobalt oxide positive electrode material based on nanosol low-temperature coating according to claim 2, characterized in that: In step 3), the coated particle powder is selected from any one of CuO, Fe2O3, MnO2, Al2O3, Nb2O5, Y2O3, WO3, CeO2, TiO2, ZnO, ZrO2, LiNbO3, Li2WO4 and Li3BO3; the surfactant is selected from any one of hexadecyltrimethylammonium bromide, polyvinylpyrrolidone and polyacrylic acid.

8. The method for preparing the O2-structured lithium cobalt oxide positive electrode material based on nanosol low-temperature coating according to claim 2, characterized in that: In step 4), the mass ratio of the metal element in the coated particle powder to the original sample LiCoO2 is 500~5000 ppm.

9. A nano-sol low-temperature coated O2-structured lithium cobalt oxide positive electrode material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The nano-sol-based low-temperature coated O2-configured lithium cobalt oxide positive electrode material is a micron-sized particle. Under the conditions of 3-4.65 V and 1C, the capacity retention rate reaches more than 93% after 50 cycles.

10. Use of the nano-sol-based low-temperature coated O2-configuration lithium cobalt oxide positive electrode material according to claim 9 in the preparation of lithium-ion batteries.

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