基于机械力化学作用煤基石墨纳米片的制备及其电化学储能特性

Preparation of coal-based graphite nanoplatelets based on mechanochemistry and the characterization of their electrochemical energy storage performance

煤炭清洁高效转化是国家实施“碳达峰与碳中和”能源发展战略的重要内容,而煤的材料化是实现其低碳高值化洁净利用的有效途径。以自制煤基石墨为前驱体,借助高能机械球磨产生的机械力化学作用制备煤基石墨纳米片(CGNs),考察了球磨时间对CGNs微观结构的影响,并研究其用作锂离子电池负极材料的电化学储能特性,探索利用机械力化学作用制备负极材料用CGNs的可行性。研究表明,利用机械力化学作用可以从煤基石墨中剥离出富含纳米孔隙和含氧官能团等缺陷结构的CGNs,通过控制球磨时间可实现石墨纳米片微观结构的有效调控。当球磨时间为50 h时,CGNs具有由数层石墨微晶片层相互堆叠、交联而形成的三维网络结构,其石墨微晶层间距约为0.3455 nm,且富含1.5~20.0 nm的纳米孔隙和少量的含氧官能团,比表面积可达573 m^(2)/g。CGNs用作锂离子电池负极材料时表现出良好的电化学储能特性,其可逆容量最高达726 mAh/g,且具有良好的倍率特性和循环稳定性,在2.0 A/g大电流密度下的可逆容量仍可达252 mAh/g,经过200次循环容量保持率为88.1%。CGNs负极材料的锂离子存储由扩散插层电容和表面吸附电容共同控制,引入纳米孔隙和含氧官能团等缺陷结构有利于提高表面吸附电容对负极材料储能容量的贡献。为高性能石墨纳米片负极材料的研发和煤炭的材料化高附加值利用提供了新思路。

The clean and efficient conversion of coal is an important part of the national energy development strategy of“carbon emission peak and carbon neutrality”,and the materialization of coal is an effective way to realize its low car⁃bon,high value and clean utilization.In this paper,the coal⁃based graphite nanoplatelets(CGNs)were prepared from the pre⁃synthesized coal⁃based graphite with the help of mechanochemistry generated by high⁃energy mechanical ball⁃milling.The effect of ball⁃milling time on the microstructure of CGNs was investigated,and the electrochemical en⁃ergy storage properties of CGNs as anode in lithium⁃ion batteries(LIBs)were studied to explore the feasibility of using mechanochemical action to prepare CGNs anode materials.The results show that the CGNs with rich defective structures such as nanopores and oxygen⁃containing functional groups can be exfoliated from coal⁃based graphite by mechanochemical action,and the microstructure of graphite nanoplatelets can be effectively regulated by controlling ball⁃milling time.When the ball⁃milling time is 50 h,the CGNs exhibits a three⁃dimensional network structure formed by stacking and cross⁃linking of graphite microcrystal layers,and contains abundant nanopores with a pore size distri⁃bution of 1.5-20.0 nm and a small amount of oxygen⁃containing functional groups,and its layer spacing and specific surface area are 0.3455 nm and 573 m^(2)/g,respectively.The CGNs as anode in LIBs show some good electrochemical energy storage properties.The CGNs electrode delivers a high reversible capacity of 726 mAh/g,good rate performance and cycling stability,in which the CGNs electrode exhibits a reversible capacity of 252 mAh/g at a high current densi⁃ty of 2.0 A/g and a capacity retention rate of 88.1%after 200 cycles.The lithium ion storage of the CGNs anode is controlled by both diffusive intercalation capacitance and surface adsorption capacitance,and the introduction of de⁃fective structures such as nanopores and oxygen⁃containing functional groups is beneficial to improve the contribution of surface adsorption capacitance to the energy storage capacity of the CGNs anode.This study provides some new ideas for the development of high⁃performance graphite nanoplatelets anode,the materialization and high value⁃added utiliza⁃tion of coal.