Graphene-coated high-nickel positive electrode material based on cooperation of oxygen vacancy and covalent interface and preparation method of graphene-coated high-nickel positive electrode material
By forming oxygen vacancy on the surface of high-nickel ternary cathode material and covalently coated with functionalized graphene, the thermal stability and cycle life of high-nickel ternary materials are solved, and efficient interface thermal management and electrochemical performance improvement are achieved.
Patent Information
- Application Number
- CN202510683217.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-26
- Publication Date
- 2025-08-26
AI Technical Summary
High-nickel layered nickel cobalt manganese ternary layered materials have problems in lithium-ion batteries with poor thermal conductivity, high interface thermal resistance and heat accumulation caused by interfacial side reactions during circulation, which affects its stability and safety performance.
By forming oxygen vacancy on the surface of high-nickel ternary positive electrode material and covalently coated with functionalized graphene, the interface structure and thermal electron transmission are regulated by oxygen vacancy, the bridge cladding between functionalized graphene and high-nickel material is achieved to form a stable interface bridge structure.
It improves the thermal stability and cycle life of the material, reduces the risk of local heat accumulation, enhances the interface thermal management capabilities, prevents structural phase change and lattice oxygen loss caused by overheating, and improves electrochemical cycling performance.
Smart Images
Figure CN120545334A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium-ion battery positive electrode materials, and in particular to a graphene-coated high-nickel positive electrode material based on the synergy of oxygen vacancies and covalent interfaces and a preparation method thereof. Background Art
[0002] High nickel layered nickel-cobalt-manganese ternary layered materials (LiNi x Co y Mn 1-x-y Nickel-nickel ternary cathode materials (NCM, x ≥ 0.8) are core cathode materials for next-generation high-energy-density lithium-ion batteries. They offer advantages such as high energy density, a high voltage platform, and a long lifespan, and hold broad application prospects in power batteries and energy storage systems. However, in practical applications, high-nickel ternary cathode materials suffer from poor intrinsic thermal conductivity, high interfacial thermal resistance, and heat accumulation caused by interfacial side reactions during cycling, severely limiting their stability and safety.
[0003] In the existing technology, fillers such as graphene and carbon nanotubes that have both conductive and thermal conductive functions are used to construct a composite structure. Although the conductive / thermal conductive properties of the electrode can be improved to a certain extent, the traditional mechanical mixing method is difficult to achieve close interfacial bonding between the filler and the active material, resulting in scattering during phonon heat transfer, forming a high interfacial thermal resistance, and local heat accumulation can easily lead to thermal runaway. Conventional surface coating strategies (such as oxides, carbon materials, etc.) can alleviate interfacial side reactions to a certain extent, but due to weak interfacial bonding and high thermal resistance, it is difficult to significantly improve the interfacial heat transfer efficiency and overall thermal management capabilities. At the same time, surface defect engineering (such as the introduction of oxygen vacancies) is an effective means to regulate the surface chemical activity of high-nickel materials and promote lithium ion diffusion. Current research focuses on its improvement of electrochemical kinetic performance, but lacks attention to the potential synergistic effect of oxygen vacancies in interfacial molecular coordination and heat transfer regulation. The above-mentioned deficiencies have led to the fact that high-nickel ternary positive electrode materials still face prominent problems such as poor thermal safety and cycle life attenuation in high energy density applications.
[0004] Therefore, it is urgent to develop a new strategy that can achieve strong interfacial bonding at the molecular scale and synergistically utilize oxygen vacancies to regulate the interface structure and thermal electron transport, so as to achieve efficient coupling of high-nickel ternary positive electrode materials and thermal conductive functional fillers, thereby fundamentally improving their structural stability, interfacial thermal management capabilities and cycle reliability, effectively inhibiting local heat accumulation, and preventing structural phase changes and lattice oxygen loss caused by overheating. Summary of the Invention
[0005] The purpose of the present invention is to provide a method for preparing graphene-coated high-nickel positive electrode materials based on the synergy of oxygen vacancies and covalent interfaces to address the problems of high-nickel ternary positive electrode materials (NCMs) causing structural phase transition and lattice oxygen loss due to surface heat accumulation, thereby leading to cycle life degradation and insufficient thermal stability.
[0006] In order to achieve the above objectives, the present invention adopts the following technical solution: providing a method for preparing a graphene-coated high-nickel cathode material based on the synergy of oxygen vacancies and covalent interfaces, comprising the following steps:
[0007] (1) Oxygen vacancy control treatment: The high-nickel ternary cathode material powder is placed in a quartz boat and heated in a tube furnace with an inert gas to form oxygen vacancies on the surface of the high-nickel ternary cathode material. This process can induce the formation of a certain concentration of oxygen vacancies on the surface of the NCM material, accompanied by the breaking of local Ni–O bonds, exposing unsaturated Ni ion active sites, and providing binding sites for subsequent molecular coordination bonding.
[0008] (2) Preparation of functionalized graphene: Graphene is dispersed in an organic solvent, 4-aminophenol is added, isoamyl nitrite is slowly added dropwise under heating conditions, and a diazotization reaction is carried out in an inert atmosphere. After the reaction is completed, the product is centrifuged, washed, and dried to obtain phenol-functionalized graphene Gr-pAP; wherein 4-aminophenol realizes covalent bonding between phenol molecules and graphene through aminodiazotization reaction.
[0009] (3) Composite material construction and coating: The high nickel ternary cathode material with oxygen vacancies obtained in step (1) and the functionalized graphene Gr-pAP prepared in (2) are co-dispersed in ethanol or N-methylpyrrolidone in a certain mass ratio and ultrasonically mixed; then treated by solvent volatilization method to obtain the NCM cathode material Gr-pAP-NCM with functionalized graphene coated on the surface, that is, the graphene-coated high nickel cathode material based on the synergy of oxygen vacancies and covalent interface. During the formation of the interface structure of the graphene-coated high nickel cathode material, the phenolic hydroxyl group preferentially forms a stable coordination structure with the Ni site exposed on the NCM surface due to oxygen vacancies, thereby realizing the construction of the functionalized graphene bridging coating interface bridging structure.
[0010] Preferably, in the above preparation method, the inert gas introduced during the heat treatment in step (1) is argon, or a mixed gas of hydrogen and argon, wherein the volume fraction of hydrogen is 3-10%.
[0011] Preferably, in the above preparation method, the heat treatment temperature in step (1) is 300-500° C., and the treatment time is 0.5-2 h.
[0012] Preferably, in the above preparation method, the organic solvent in step (2) is ethanol, acetonitrile, N-methylpyrrolidone or N,N-dimethylformamide.
[0013] Preferably, in the above preparation method, in step (2), graphene and 4-aminophenol are added in a ratio of 0.01 mol 4-aminophenol per 0.1 g graphene.
[0014] Preferably, in the above preparation method, the heating temperature in step (2) is 60-80° C., and the reaction time is 16-20 h.
[0015] Preferably, in the above preparation method, the molar ratio of isoamyl nitrite to 4-aminophenol in step (2) is 1:1-1:2.
[0016] Preferably, in the above preparation method, the mass ratio of the high nickel ternary cathode material with oxygen vacancies to the functionalized graphene Gr-pAP in step (3) is 1:0.001–1:0.05.
[0017] Preferably, in the above preparation method, the solvent volatilization method in step (3) is carried out at 60-80° C., and the solvent volatilization method treatment time is 6-8 hours.
[0018] In addition, the present invention also provides a graphene-coated high-nickel cathode material based on oxygen vacancies and covalent interface synergy prepared by the above preparation method, wherein the graphene-coated high-nickel cathode material combines the amino group of 4-aminophenol with the sp 2 The carbon active sites are covalently bonded, and at the same time, their phenolic hydroxyl groups can coordinate with the low-coordination metal active sites induced by oxygen vacancies on the surface of high-nickel materials, thereby achieving uniform and stable bridging coating of high-nickel positive electrode material particles by functionalized graphene.
[0019] In summary, due to the adoption of the above technical solution, the present invention has the following beneficial effects:
[0020] 1. The present invention uses a diazotization reaction to connect the amino group of 4-aminophenol to the sp 2The carbon active sites are covalently bonded, while their phenolic hydroxyl groups coordinate with low-coordination metal active sites induced by oxygen vacancies on the surface of the high-nickel material, achieving a uniform and stable bridge-coating of the functionalized graphene onto the NCM cathode material particles. This bridge-coating structure helps disperse and transfer heat generated during operation, reducing the risk of localized heat accumulation. This inhibits high-temperature-induced crystal structure damage and reactive oxygen evolution, thereby improving the material's thermal stability and cycle life. Furthermore, the functionalized graphene firmly adheres to the surface of the NCM particles, strengthening the bond between the coating and the active material, effectively mitigating coating shedding and interfacial instability during cycling. Furthermore, oxygen vacancies play a dual role in this structural design: first, by exposing the metal active sites, they strengthen the chemical anchoring of the phenolic hydroxyl groups, inhibiting structural collapse and oxygen evolution during cycling; second, by optimizing lattice vibrational modes, they extend the phonon conduction path, reducing interfacial thermal resistance and improving overall thermal conductivity. This composite structure achieves breakthroughs in electrochemical cycle performance and thermal management capabilities simultaneously through the synergistic effect of chemical bond bridging and oxygen vacancy regulation, providing an innovative solution for improving the safety of high-energy-density batteries.
[0021] 2. Experimental data show that the graphene-coated high-nickel cathode material prepared by the present invention, which is based on the synergistic effect of oxygen vacancies and covalent interfaces, has an initial discharge capacity of 208.5-213.1 mAh / g. After 200 cycles, its discharge capacity is 140-149.5 mAh / g, with a cycle retention rate of approximately 67.2%-70.2%. In contrast, the battery made of pure NCM has an initial discharge capacity of 199.4 mAh / g, and after 200 cycles, its discharge capacity is 121.8 mAh / g, with a cycle retention rate of only 60.68%. The above data comparison demonstrates that the phenol-functionalized graphene-bridged high-nickel ternary cathode material has a stable structure, high specific capacity, and good cycle stability. In addition, the thermal diffusion coefficient of the graphene-coated high-nickel positive electrode material based on the synergy of oxygen vacancies and covalent interfaces prepared by the present invention is increased by 20.4%-24.3% compared with the pure phase NCM at 50°C, and the thermal diffusion coefficient at 100°C is increased by 40.5%-45.9% compared with the pure phase NCM; it can be seen that the composite structure of the graphene-coated high-nickel positive electrode material based on the synergy of oxygen vacancies and covalent interfaces prepared by the present invention is bridged by chemical bonds, and strong interface bonding is achieved at the molecular scale. It also synergistically utilizes oxygen vacancies to regulate the interface structure and thermal electron transport, thereby achieving efficient coupling of high-nickel ternary positive electrode materials and thermal conductive functional fillers, and simultaneously achieving breakthroughs in electrochemical cycle performance and thermal management capabilities, thereby improving its structural stability, interface thermal management capabilities and cycle reliability, effectively inhibiting local heat accumulation, and preventing structural phase changes and lattice oxygen loss caused by overheating, providing innovative solutions for improving the safety of high-energy density batteries. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is the SEM image of 0.5Gr-pAP-NCM in Example 1;
[0023] Figure 2 The electrochemical cycling performance diagram of 0.5Gr-pAP-NCM and NCM in Example 1;
[0024] Figure 3 This is a graph showing the thermal diffusion coefficient performance of 0.5Gr-pAP-NCM and NCM in Example 1;
[0025] Figure 4 The electrochemical cycling performance diagram of 1.0Gr-pAP-NCM and NCM in Example 2;
[0026] Figure 5 This is the thermal diffusion coefficient performance diagram of 1.0Gr-pAP-NCM and NCM in Example 2.
[0027] Figure 6 The electrochemical cycling performance diagram of 1.5Gr-pAP-NCM and NCM in Example 3
[0028] Figure 7 This is the thermal diffusion coefficient performance diagram of 1.5Gr-pAP-NCM and NCM in Example 3. DETAILED DESCRIPTION
[0029] The present invention provides a graphene-coated high-nickel cathode material based on the synergy of oxygen vacancies and covalent interfaces, wherein the graphene-coated high-nickel cathode material combines the amino group of 4-aminophenol with the sp 2 The carbon active sites are covalently bonded, and at the same time, their phenolic hydroxyl groups can coordinate with the low-coordination metal active sites induced by oxygen vacancies on the surface of high-nickel materials, thereby achieving uniform and stable bridging coating of high-nickel positive electrode material particles by functionalized graphene.
[0030] The method for preparing a graphene-coated high-nickel cathode material based on the synergy of oxygen vacancies and covalent interfaces comprises the following steps:
[0031] (1) Oxygen vacancy control treatment: The high-nickel ternary cathode material (NCM) powder is placed in a quartz boat, and high-purity Ar or 3-10% H2 / Ar mixed gas is introduced into a tube furnace, and heat treated at 300-500℃ for 0.5-2h. This process can induce the formation of a certain concentration of oxygen vacancies on the surface of the NCM material, accompanied by the local rupture of Ni–O bonds, exposing unsaturated Ni ion active sites, providing binding sites for subsequent molecular coordination bonding;
[0032] (2) Preparation of functionalized graphene: Graphene powder and 4-aminophenol are dispersed in ethanol, acetonitrile, N-methylpyrrolidone or N,N-dimethylformamide at a ratio of 0.01 mol 4-aminophenol per 0.1 g graphene; isoamyl nitrite is then slowly added dropwise at 60-80°C, with a molar ratio of isoamyl nitrite to 4-aminophenol of 1:1-1:2, and a diazotization reaction is carried out in an inert atmosphere for 16-20 hours. After the reaction is completed, the product is centrifuged, washed, and dried to obtain phenol-functionalized graphene Gr-pAP; wherein 4-aminophenol realizes covalent bonding between phenol molecules and graphene through aminodiazotization reaction.
[0033] (3) Composite material construction and coating: The high nickel ternary cathode material with oxygen vacancies obtained in step (1) and the functionalized graphene Gr-pAP prepared in (2) are co-dispersed in ethanol or N-methylpyrrolidone at a mass ratio of 1:0.001–1:0.05, and ultrasonically mixed for 1 hour; then, the mixture is dried at a low temperature of 60-80°C for 6-8 hours by a solvent volatilization method to obtain an NCM cathode material Gr-pAP-NCM with a surface coated with functionalized graphene, that is, the graphene-coated high nickel cathode material based on the synergy of oxygen vacancies and covalent interface; in the process of forming the interface structure of the graphene-coated high nickel cathode material, the phenolic hydroxyl group preferentially forms a stable coordination structure with the Ni site exposed on the NCM surface due to oxygen vacancies, thereby realizing the construction of the functionalized graphene bridging coating interface bridging structure.
[0034] In order to express the present invention more clearly, the present invention is further described below through specific examples.
[0035] Example 1:
[0036] This embodiment prepares a method for preparing a graphene-coated high-nickel cathode material based on the synergy of oxygen vacancies and covalent interfaces, which specifically includes the following steps:
[0037] (1) Oxygen vacancy regulation treatment: Commercial LiNi 0.8 Co 0.1 Mn 0.1 3g of O2(NCM811) powder was placed in a quartz boat, and argon was introduced into a tube furnace and heat treated at 300℃ for 1h. This process can induce the formation of a certain concentration of oxygen vacancies on the surface of NCM811 material.
[0038] (2) Preparation of functionalized graphene: 0.1 g of graphene powder was dispersed in 100 mL of acetonitrile (those skilled in the art can replace acetonitrile with ethanol, N-methylpyrrolidone or N,N-dimethylformamide according to actual operation needs. In this embodiment, acetonitrile is preferably used as the dispersion solvent). 4-aminophenol (1.092 g, 0.01 mol) was added, and isoamyl nitrite (1.34 mL, 0.01 mol) was slowly added dropwise at 80°C. The diazotization reaction was carried out in an inert atmosphere of N2 for 20 h. After the reaction was completed, the product was centrifuged, washed, and dried to obtain phenol-functionalized graphene Gr-pAP.
[0039] (3) Composite material construction and coating: The high nickel ternary cathode material with oxygen vacancies obtained in step (1) and the functionalized graphene Gr-pAP prepared in step (2) were co-dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 1:0.005 and ultrasonically mixed for 1 hour; then, the mixture was dried at 80°C for 8 hours by solvent evaporation to obtain the NCM cathode material 0.5Gr-pAP-NCM coated with functionalized graphene on the surface, i.e., the graphene-coated high nickel cathode material based on the synergy of oxygen vacancies and covalent interface; the corresponding scanning electron microscope (SEM) image is shown in FIG. Figure 1 It can be clearly seen that the functionalized graphene is evenly coated on the surface of the NCM high nickel ternary cathode, and the coating effect is good.
[0040] Performance testing:
[0041] The positive electrode material 0.5Gr-pAP-NCM prepared in this example and the pure phase layered high nickel ternary positive electrode material NCM were mixed with conductive carbon black super P and binder PVDF in a mass ratio of 8:1:1, and N-methylpyrrolidone was added and stirred evenly. The resulting slurry was coated on a current collector aluminum foil and dried at 80°C to obtain a positive electrode sheet. A metal lithium sheet was used as the negative electrode, polypropylene was used as the separator, and LiPF6 was used as the electrolyte. A CR2025 button experimental battery was assembled in an argon-filled glove box, and the obtained battery was subjected to charge and discharge tests at a rate of 1.0C. The resulting cycle curve is shown in FIG. Figure 2 As shown by Figure 2It can be seen that the initial discharge specific capacity of 0.5Gr-pAP-NCM prepared in this example is 210.9mAh / g. After 200 cycles, its discharge specific capacity is 146mAh / g, and the cycle retention rate is about 69.2%. The initial discharge specific capacity of the battery made of pure phase NCM is 199.4mAh / g. After 200 cycles, its discharge specific capacity is 121.8mAh / g, and the cycle retention rate is only 60.68%. From the above results, it can be seen that the use of phenol-functionalized graphene bridge-coated high-nickel ternary positive electrode material has a stable structure, high specific capacity and good cycle stability. The positive electrode material 0.5Gr-pAP-NCM prepared in this example and the pure phase layered high nickel ternary positive electrode material NCM were pressed into sheets and their thermal conductivity was tested using a laser thermal conductivity meter. The thermal diffusion coefficient of 0.5Gr-pAP-NCM is increased by 20.4% at 50°C compared with pure phase NCM, and by 44.5% at 100°C. Figure 3 shown.
[0042] Example 2
[0043] This embodiment prepares a method for preparing a graphene-coated high-nickel cathode material based on the synergy of oxygen vacancies and covalent interfaces, which specifically includes the following steps:
[0044] (1) Oxygen vacancy control treatment: 3 g of commercial NCM811 powder was placed in a quartz boat, and a 5% H2 / Ar mixed gas was introduced into a tube furnace. The mixture was then heat treated at 300°C for 2 h. This process can induce the formation of a certain concentration of oxygen vacancies on the surface of the NCM811 material.
[0045] (2) Preparation of functionalized graphene: 0.1 g of graphene powder was dispersed in 100 mL of ethanol, 4-aminophenol (1.092 g, 0.01 mol) was added, and then isoamyl nitrite (2.67 mL, 0.02 mol) was slowly added dropwise at 80 °C. The diazotization reaction was carried out in an inert atmosphere of N2 for 18 h. After the reaction, the product was centrifuged, washed, and dried to obtain phenol-functionalized graphene Gr-pAP.
[0046] (3) Composite material construction and coating: The high nickel ternary cathode material with oxygen vacancies obtained in step (1) and the functionalized graphene Gr-pAP prepared in step (2) are co-dispersed in NMP at a mass ratio of 1:0.001 and ultrasonically mixed for 1 hour; then, the mixture is dried at 60°C for 8 hours by a solvent evaporation method to obtain an NCM cathode material 1.0Gr-pAP-NCM with a surface coated with functionalized graphene, i.e., the graphene-coated high nickel cathode material based on the synergy of oxygen vacancies and covalent interface.
[0047] Performance testing:
[0048] The positive electrode material 1.0Gr-pAP-NCM and the pure phase layered high nickel ternary positive electrode material NCM prepared in this example were mixed with conductive carbon black super P and binder PVDF in a mass ratio of 8:1:1, and N-methylpyrrolidone was added and stirred evenly. The resulting slurry was coated on the current collector aluminum foil and dried at 80°C to obtain a positive electrode sheet. A metal lithium sheet was used as the negative electrode, polypropylene was used as the separator, and LiPF6 was used as the electrolyte. A CR2025 button experimental battery was assembled in an argon-filled glove box. The obtained battery was charged and discharged at a rate of 1.0C. The resulting cycle curve is shown in FIG. Figure 4 As shown by Figure 4 It can be seen that the initial discharge capacity of the 1.0Gr-pAP-NCM prepared in this example is 213.1mAh / g. After 200 cycles, its discharge capacity is 149.5mAh / g, and the cycle retention rate is about 70.2%. The initial discharge capacity of the battery made of pure phase NCM is 199.4mAh / g. After 200 cycles, its discharge capacity is 121.8mAh / g, and the cycle retention rate is only 60.68%. From the above results, it can be seen that the use of phenol-functionalized graphene bridge-coated high-nickel ternary positive electrode material has a stable structure, high specific capacity, and good cycle stability. The positive electrode material 1.0Gr-pAP-NCM prepared in this example and the pure phase layered high-nickel ternary positive electrode material NCM were pressed into sheets and their thermal conductivity was tested using a laser thermal conductivity meter. The thermal diffusivity of 1.0Gr-pAP-NCM is increased by 24.3% at 50℃ and 45.9% at 100℃ compared with pure NCM. Figure 5 shown.
[0049] Example 3:
[0050] This embodiment prepares a method for preparing a graphene-coated high-nickel cathode material based on the synergy of oxygen vacancies and covalent interfaces, which specifically includes the following steps:
[0051] (1) Oxygen vacancy regulation treatment: Commercial LiNi 0.8 Co 0.1 Mn 0.1 3g of O2(NCM811) powder was placed in a quartz boat, and argon was introduced into a tube furnace. The mixture was heat treated at 500℃ for 0.5h. This process can induce the formation of a certain concentration of oxygen vacancies on the surface of NCM811 material.
[0052] (2) Preparation of functionalized graphene: 0.1 g of graphene powder was dispersed in 100 mL of N,N-dimethylformamide (those skilled in the art can replace N,N-dimethylformamide with acetonitrile, ethanol or N-methylpyrrolidone according to actual operation requirements. In this embodiment, N,N-dimethylformamide is preferably used as the dispersion solvent), 4-aminophenol (1.092 g, 0.01 mol) was added, and then isoamyl nitrite (2.67 mL, 0.02 mol) was slowly added dropwise at 80°C. The diazotization reaction was carried out in an inert atmosphere of N2 for 16 h. After the reaction, the product was centrifuged, washed and dried to obtain phenol-functionalized graphene Gr-pAP.
[0053] (3) Composite material construction and coating: The high nickel ternary cathode material with oxygen vacancies obtained in step (1) and the functionalized graphene Gr-pAP prepared in step (2) are co-dispersed in ethanol at a mass ratio of 1:0.015 and ultrasonically mixed for 1 hour; then, the mixture is dried at 80°C for 6 hours by a solvent evaporation method to obtain an NCM cathode material 1.5Gr-pAP-NCM with a surface coated with functionalized graphene, i.e., the graphene-coated high nickel cathode material based on the synergy of oxygen vacancies and covalent interface.
[0054] Performance testing:
[0055] The positive electrode material 1.5Gr-pAP-NCM prepared in this example and the pure phase layered high nickel ternary positive electrode material NCM were mixed with conductive carbon black super P and binder PVDF in a mass ratio of 8:1:1, and N-methylpyrrolidone was added and stirred evenly. The resulting slurry was coated on the current collector aluminum foil and dried at 80°C to obtain a positive electrode sheet. A metal lithium sheet was used as the negative electrode, polypropylene was used as the separator, and LiPF6 was used as the electrolyte. A CR2025 button experimental battery was assembled in an argon-filled glove box. The obtained battery was charged and discharged at a rate of 1.0C. The results are shown in FIG. Figure 6 As shown by Figure 6 It can be seen that the initial discharge capacity of 1.5Gr-pAP-NCM is 208.5mAh / g. After 200 cycles, its discharge capacity is 140mAh / g, and the cycle retention rate is about 67.2%. The initial discharge capacity of the battery made of pure phase NCM is 199.4mAh / g. After 200 cycles, its discharge capacity is 121.8mAh / g, and the cycle retention rate is only 60.68%. From the above results, it can be seen that the use of phenol-functionalized graphene bridge-coated high-nickel ternary positive electrode material has a stable structure, high specific capacity and good cycle stability. The positive electrode material 1.5Gr-pAP-NCM prepared in this example and the pure phase layered high-nickel ternary positive electrode material NCM were pressed into sheets and their thermal conductivity was tested using a laser thermal conductivity meter. The results are as follows Figure 7 As shown by Figure 7It can be seen that the thermal diffusion coefficient of 1.5Gr-pAP-NCM is increased by 22.1% at 50°C and 40.5% at 100°C compared with pure NCM.
[0056] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.
Claims
1. A method for preparing a graphene-coated high-nickel cathode material based on the synergy of oxygen vacancies and covalent interfaces, characterized in that: The following steps are involved: (1) Oxygen vacancy control treatment: The high nickel ternary cathode material powder is placed in a quartz boat and heated in a tube furnace with an inert gas to form oxygen vacancies on the surface of the high nickel ternary cathode material; (2) Preparation of functionalized graphene: Graphene is dispersed in an organic solvent, 4-aminophenol is added, isoamyl nitrite is added dropwise under heating conditions, and a diazotization reaction is carried out in an inert atmosphere. After the reaction is completed, the product is centrifuged, washed, and dried to obtain phenol-functionalized graphene Gr-pAP; (3) Composite material construction and coating: The high nickel ternary cathode material with oxygen vacancies obtained in step (1) and the functionalized graphene Gr-pAP prepared in (2) are co-dispersed in ethanol or N-methylpyrrolidone in a certain mass ratio and ultrasonically mixed; then treated by solvent evaporation method to obtain the NCM cathode material Gr-pAP-NCM with functionalized graphene coated on the surface, that is, the graphene-coated high nickel cathode material based on the synergy of oxygen vacancies and covalent interface.
2. The preparation method according to claim 1, characterized in that The inert gas introduced during the heat treatment in step (1) is argon, or a mixed gas of hydrogen and argon, wherein the volume fraction of hydrogen is 3-10%.
3. The preparation method according to claim 1, characterized in that The heat treatment temperature in step (1) is 300-500° C., and the treatment time is 0.5-2 h.
4. The preparation method according to claim 1, characterized in that The organic solvent in step (2) is ethanol, acetonitrile, N-methylpyrrolidone or N,N-dimethylformamide.
5. The preparation method according to claim 1, characterized in that In step (2), graphene and 4-aminophenol are added in a ratio of 0.01 mol 4-aminophenol per 0.1 g graphene.
6. The preparation method according to claim 1, characterized in that The heating temperature in step (2) is 60-80° C., and the reaction time is 16-20 h.
7. The preparation method according to claim 1, characterized in that In step (2), the molar ratio of isoamyl nitrite to 4-aminophenol is 1:1-1:
2.
8. The preparation method according to claim 1, characterized in that In step (3), the mass ratio of the high nickel ternary cathode material with oxygen vacancies to the functionalized graphene Gr-pAP is 1:0.001–1:0.
05.
9. The preparation method according to claim 1, characterized in that The solvent volatilization method in step (3) is carried out at 60-80° C., and the solvent volatilization method treatment time is 6-8 hours.
10. A graphene-coated high-nickel cathode material based on the synergy of oxygen vacancies and covalent interfaces, prepared by the preparation method according to any one of claims 1 to 9.