Functionally modified high-nickel positive electrode composite material and method for preparing the same

Abstract

The application belongs to the technical field of materials, and particularly relates to a functionally modified high-nickel positive electrode composite material and a preparation method thereof, the preparation method comprising: (1) dissolving tetraethyl orthosilicate in a mixed solution of ethanol and ammonia water, and then adding a high-nickel positive electrode material and stirring for a period of time; (2) dispersing fluorine-containing silane in ethanol, and then adding the solution in step (1) and stirring for a period of time, and then evaporating the solvent to obtain a composite material. Through a simple solution reaction technology, the hydroxyl groups on the surface of the high-nickel ternary are reacted with silane coupling agents and chemically bonded, a three-dimensional conductive network coating is first formed on the surface of the material, and then reactive silane is added to graft fluorine-containing groups to the surface of the coating. The fluorine-containing groups on the surface of the coating are beneficial to forming lithium fluoride with high mechanical strength in the battery cycle process, and accelerate the transmission of lithium ions.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a functionally modified high-nickel cathode composite material and its preparation method. Background Technology

[0002] With the pursuit of high energy density, the nickel content of ternary cathode materials is constantly increasing. However, the higher nickel content leads to an exponential increase in the activity of the surface and interface, ultimately resulting in a rapid decline in cycle performance. Traditional metal oxides can only isolate electrolyte corrosion, while deposits on the material surface and interface continue to increase.

[0003] Recently, fluorine has been widely used in material modification schemes. For example, patent CN112186190A discloses a high-voltage lithium-ion battery. In this battery, the positive electrode uses a high-voltage fluorinated positive electrode material, and the electrolyte consists of a co-solvent of fluorinated ether and additives composed of fluorinated carbonate and boron-containing substances. The high-voltage positive electrode material initially establishes a fluorine-containing interface layer through fluorination treatment, and then the interface layer is modified and consolidated using a fluorinated electrolyte, thereby effectively improving the high-voltage cycle performance of the lithium-ion battery. Patent CN118738560A discloses a fluorocarbon electrolyte additive, which can help form a fluorine-rich CEI film on the material surface through fluorocarbon chains. This not only improves ionic conductivity but also inhibits interfacial side reactions. Therefore, fluorine-containing substances, whether used as a modifying material for positive electrode materials or as an additive for electrolytes, significantly contribute to improving the various performance characteristics of positive electrode materials. However, current fluorine-modified materials are limited to fluorine doping or fluoride coating, failing to fully utilize the advantages of high-nickel positive electrode materials. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a functionally modified high-nickel cathode composite material, which includes the following steps:

[0005] (1) Dissolve tetraethyl orthosilicate in a mixed solution of ethanol and ammonia, then add high-nickel cathode material and stir for a period of time;

[0006] The high-nickel cathode material is LiNi. 1-x-y Co x Mn y O2 (x≤0.1, y≤0.1).

[0007] The molar ratio of ethanol to ammonia is 10–20:1.

[0008] The concentration of tetraethyl orthosilicate is 0.005–0.5 g / ml.

[0009] The mass ratio of tetraethyl orthosilicate to high-nickel cathode material is 0.01 to 0.5:1.

[0010] The stirring time is 0.5 to 10 hours.

[0011] (2) Disperse the fluorinated silane in ethanol, then add it to the solution in step (1), stir for a period of time and then evaporate the solvent to obtain the composite material.

[0012] Among them, the fluorinated silanes are: 1H,1H,2H,2H-perfluorodecyltrichlorosilane PFDTS, 3,3,3-trifluoropropyltrimethoxysilane TFTMS, or trifluoromethyltrimethylsilane TFMTMS.

[0013] The mass ratio of fluorinated silane to tetraethyl orthosilicate is 0.005 to 0.02:1.

[0014] The stirring temperature is 60-70℃, and the stirring time is 0.5-10h.

[0015] The volatilization temperature is 60–100℃, and the volatilization time is 6–12 hours.

[0016] This invention preferentially constructs a three-dimensional Si-O-Si network coating on the surface of a high-nickel cathode material through the hydrolytic condensation of tetraethyl orthosilicate. Subsequently, a fluorinated silane is added to graft its fluorine-containing groups onto the Si-O-Si three-dimensional network coating, resulting in a coating rich in fluorine-containing groups on its outer surface. During battery cycling, these fluorine-containing groups combine with lithium ions to form a LiF-containing CEI film, inhibiting electrolyte decomposition and enhancing the interfacial diffusion capacity of lithium ions, which greatly benefits the long-term operation of the battery.

[0017] The beneficial effects of this invention are as follows:

[0018] This invention utilizes a simple solution reaction technique to react and chemically bond hydroxyl groups on the surface of a high-nickel ternary material with tetraethyl orthosilicate, first forming a three-dimensional network coating on the material surface. Subsequently, reactive silanes are added to graft fluorine-containing groups onto the coating surface. These fluorine-containing groups on the coating surface facilitate the formation of high-mechanical-strength lithium-rich fluorides during battery cycling, accelerating lithium-ion transport. Attached Figure Description

[0019] Figure 1 This is a SEM image of the composite cathode material provided in Embodiment 1 of the present invention;

[0020] Figure 2 This is a SEM image of the matrix material provided in Comparative Example 1 of the present invention;

[0021] Figure 3 The graph shows the cycling performance of the high-nickel cathode materials prepared in Example 1 and Comparative Example 1 of this invention at 0.5C. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] Example 1

[0024] (1) Dissolve 0.03 g of tetraethyl orthosilicate in a mixed solution of 100 ml ethanol and 58 ml ammonia, and add 2 g of LiNi after stirring for 30 min. 0.8 Co 0.1 Mn 0.1 O2 high-nickel cathode material was used, and the mixture was stirred again for 6 hours to obtain mixed solution A.

[0025] (2) Disperse 0.0015 g of PFDTS in 10 ml of ethanol to form solution B. Then, add solution B dropwise to solution A and stir at 65 °C for 6 h to obtain solution C. Finally, place solution C in a vacuum drying oven and dry at 70 °C for 12 h to obtain a high-nickel cathode material with functional coating modification.

[0026] Example 2

[0027] (1) Dissolve 0.015 g of tetraethyl orthosilicate in a mixed solution of 100 ml ethanol and 58 ml ammonia, and add 2 g of LiNi after stirring for 30 min. 0.8 Co 0.1 Mn 0.1 O2 high-nickel cathode material was used, and the mixture was stirred again for 6 hours to obtain mixed solution A.

[0028] (2) Disperse 0.0015 g of PFDTS in 10 ml of ethanol to form solution B. Then, add solution B dropwise to solution A and stir at 65 °C for 6 h to obtain solution C. Finally, place solution C in a vacuum drying oven and dry at 70 °C for 12 h to obtain a high-nickel cathode material with functional coating modification.

[0029] Example 3

[0030] (1) Dissolve 0.06 g of tetraethyl orthosilicate in a mixed solution of 100 ml ethanol and 58 ml ammonia, and add 2 g of LiNi after stirring for 30 min. 0.8 Co 0.1 Mn 0.1 O2 high-nickel cathode material was used, and the mixture was stirred again for 6 hours to obtain mixed solution A.

[0031] (2) Disperse 0.0015 g of PFDTS in 10 ml of ethanol to form solution B. Then, add solution B dropwise to solution A and stir at 65 °C for 6 h to obtain solution C. Finally, place solution C in a vacuum drying oven and dry at 70 °C for 12 h to obtain a high-nickel cathode material with functional coating modification.

[0032] Example 4

[0033] (1) Dissolve 0.03 g of tetraethyl orthosilicate in a mixed solution of 100 ml ethanol and 58 ml ammonia, and add 2 g of LiNi after stirring for 30 min. 0.8 Co 0.1 Mn 0.1 O2 high-nickel cathode material was used, and the mixture was stirred again for 6 hours to obtain mixed solution A.

[0034] (2) Disperse 0.001 g of PFDTS in 10 ml of ethanol to form solution B. Then, add solution B dropwise to solution A and stir at 65 °C for 6 h to obtain solution C. Finally, place solution C in a vacuum drying oven and dry at 70 °C for 12 h to obtain a high-nickel cathode material with functional coating modification.

[0035] Example 5

[0036] (1) Dissolve 0.03 g of tetraethyl orthosilicate in a mixed solution of 100 ml ethanol and 58 ml ammonia, and after stirring for 30 min, add 2 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 high-nickel cathode material was used, and the mixture was stirred again for 6 hours to obtain mixed solution A.

[0037] (2) Disperse 0.002 g of PFDTS in 10 ml of ethanol to form solution B. Then, add solution B dropwise to solution A and stir at 65 °C for 6 h to obtain solution C. Finally, place solution C in a vacuum drying oven and dry at 70 °C for 12 h to obtain a high-nickel cathode material with functional coating modification.

[0038] Example 6

[0039] (1) Dissolve 0.03 g of tetraethyl orthosilicate in a mixed solution of 100 ml ethanol and 20 ml ammonia, and add 2 g of LiNi after stirring for 30 min. 0.8 Co 0.1 Mn 0.1 O2 high-nickel cathode material was used, and the mixture was stirred again for 6 hours to obtain mixed solution A.

[0040] (2) Disperse 0.0015 g of PFDTS in 10 ml of ethanol to form solution B. Then, add solution B dropwise to solution A and stir at 65 °C for 6 h to obtain solution C. Finally, place solution C in a vacuum drying oven and dry at 70 °C for 12 h to obtain a high-nickel cathode material with functional coating modification.

[0041] Example 7

[0042] (1) Dissolve 0.03 g of tetraethyl orthosilicate in a mixed solution of 100 ml ethanol and 100 ml ammonia, and add 2 g of LiNi after stirring for 30 min. 0.8 Co 0.1 Mn 0.1 O2 high-nickel cathode material was used, and the mixture was stirred again for 6 hours to obtain mixed solution A.

[0043] (2) Disperse 0.0015 g of PFDTS in 10 ml of ethanol to form solution B. Then, add solution B dropwise to solution A and stir at 65 °C for 6 h to obtain solution C. Finally, place solution C in a vacuum drying oven and dry at 70 °C for 12 h to obtain a high-nickel cathode material with functional coating modification.

[0044] Example 8

[0045] (1) Dissolve 0.03 g of tetraethyl orthosilicate in a mixed solution of 100 ml ethanol and 60 ml ammonia, and after stirring for 30 min, add 2 g of LiNi. 0.8 Co 0.1 Mn 0.1 O2 high-nickel cathode material was used, and the mixture was stirred again for 6 hours to obtain mixed solution A.

[0046] (2) 0.0015 g of 3,3,3-trifluoropropyltrimethoxysilane (TFTMS) was dispersed in 10 ml of ethanol to form solution B. Then, solution B was added dropwise to solution A and stirred at 65 °C for 6 h to obtain solution C. Finally, solution C was placed in a vacuum drying oven and dried at 70 °C for 12 h to obtain a high-nickel cathode material with functional coating modification.

[0047] Example 9

[0048] (1) Dissolve 0.03 g of tetraethyl orthosilicate in a mixed solution of 100 ml ethanol and 60 ml ammonia, and after stirring for 30 min, add 2 g of LiNi. 0.8 Co 0.1 Mn 0.1 O2 high-nickel cathode material was used, and the mixture was stirred again for 6 hours to obtain mixed solution A.

[0049] (2) Disperse 0.0015 g of trifluoromethyltrimethylsilane (TFMTMS) in 10 ml of ethanol to form solution B. Then, add solution B dropwise to solution A and stir at 65 °C for 6 h to obtain solution C. Finally, place solution C in a vacuum drying oven and dry at 70 °C for 12 h to obtain a high-nickel cathode material with functional coating modification.

[0050] Comparative Example 1

[0051] Untreated LiNi 0.8 Co 0.1 Mn 0.1 O2 high-nickel cathode material is used as Comparative Example 1.

[0052] Comparative Example 2

[0053] Dissolve 0.03 g of tetraethyl orthosilicate in a mixed solution of 100 ml ethanol and 58 ml ammonia. After stirring for 30 min, add 2 g of LiNi. 0.8 Co 0.1 Mn 0.1 The high-nickel cathode material was prepared by stirring O2 for another 6 hours to obtain a mixed solution. This mixed solution was then dried at 70°C for 12 hours to obtain a high-nickel cathode material modified only with SiO2.

[0054] The composite cathode material prepared in Example 1 and the matrix material in Comparative Example 1 were subjected to SEM tests. Figure 1-2 As shown, the surface of the composite cathode material prepared in Example 1 is relatively rough, while the surface of the substrate material prepared in Comparative Example 1 is very smooth, indicating that the surface of the high-nickel cathode material is covered with a functional coating.

[0055] Figure 3 The cycling performance graphs of Example 1 and Comparative Example 1 at 0.5C are shown. It can be seen that Example 1 has a capacity retention of 97% after 100 cycles, while Comparative Example 1 has a retention of only 92%, indicating that the functional coating effectively improves the cycling performance of the high-nickel cathode material.

[0056] The composite cathode materials corresponding to Examples 1-9 and the matrix materials corresponding to Comparative Examples 1 and 2 were used as cathode active materials to prepare cathode sheets. Next, coin cells were assembled using lithium sheets as anodes, and the electrochemical performance of all cells was tested in the voltage range of 2.75-4.3V. The test results are shown in Table 1.

[0057] Table 1

[0058]

[0059] Table 1 shows that, according to Comparative Examples 1 and 2, constructing an O-Si-O functional coating on the material surface can effectively improve the material's first-efficiency and cycle performance. Comparative Example 2 and Example 1 show that grafting fluorine-containing functional groups onto the SiO2 coating surface slightly reduces the first-efficiency but improves cycle stability. Examples 1, 2, and 3 show that an appropriate SiO2 coating thickness can improve the material's interface stability. Examples 1, 4, and 5 show that a small amount of fluorine-containing groups can improve the first-efficiency and cycle stability; however, when the number of fluorine-containing groups increases, the first-efficiency decreases due to the consumption of a large amount of active lithium to form the CEI film. Examples 1, 6, and 7 show that adding too little ammonia will affect the hydrolysis and condensation rate of tetraethyl orthosilicate, potentially affecting the incompleteness of the coating on the surface of the high-nickel cathode material. However, adding too much ammonia will accelerate the hydrolysis and condensation rate of tetraethyl orthosilicate, causing it to agglomerate and fail to coat the high-nickel cathode material. As demonstrated in Examples 1, 8, and 9, different fluorinated silanes can assist in the formation of fluorinated groups on the coating surface. As demonstrated in Examples 1 and Comparative Example 1, functional coating modification can effectively protect the material, and the lithium-ion diffusion capability can be improved by constructing an inorganic CEI film of LiF.

[0060] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0061] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a functionally modified high-nickel cathode composite material, characterized in that, The preparation method steps are as follows: (1) Dissolve tetraethyl orthosilicate in a mixed solution of ethanol and ammonia, and then add high-nickel cathode material and stir. (2) Disperse the fluorinated silane in ethanol, then add it to the solution in step (1), stir and evaporate the solvent to obtain the composite material.

2. The method for preparing the functionally modified high-nickel cathode composite material according to claim 1, characterized in that, The high-nickel cathode material mentioned in step (1) is: LiNi 1-x-y Co x Mn y O2, where x≤0.1, y≤0.

1.

3. The method for preparing the functionally modified high-nickel cathode composite material according to claim 1, characterized in that, The molar ratio of ethanol and ammonia in step (1) is 10-20:1, and the stirring time is 0.5-10h.

4. The method for preparing the functionally modified high-nickel cathode composite material according to claim 1, characterized in that, The concentration of tetraethyl orthosilicate in step (1) is 0.005 to 0.5 g / ml.

5. The method for preparing the functionally modified high-nickel cathode composite material according to claim 1, characterized in that, The mass ratio of tetraethyl orthosilicate to high-nickel cathode material in step (1) is 0.01 to 0.5:

1.

6. The method for preparing the functionally modified high-nickel cathode composite material according to claim 1, characterized in that, The fluorinated silane in step (2) is: 1H,1H,2H,2H-perfluorodecyltrichlorosilane PFDTS, 3,3,3-trifluoropropyltrimethoxysilane TFTMS, or trifluoromethyltrimethylsilane TFMTMS.

7. The method for preparing the functionally modified high-nickel cathode composite material according to claim 1, characterized in that, The mass ratio of the fluorinated silane to tetraethyl orthosilicate in step (2) is 0.005 to 0.02:

1.

8. The method for preparing the functionally modified high-nickel cathode composite material according to claim 1, characterized in that, The stirring temperature in step (2) is 60-70℃, and the stirring time is 0.5-10h.

9. The method for preparing the functionally modified high-nickel cathode composite material according to claim 1, characterized in that, The evaporation temperature of the solvent in step (2) is 60-100℃, and the evaporation time is 6-12h.

10. A functionally modified high-nickel cathode composite material prepared according to the method of claim 1.

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