Microstructure regulation and electrochemical potassium storage properties of semi-coke based hard carbon

SU Fangle; KANG Weiwei; HUANG Guangxu; XING Baolin; LI Qiang; HU Han; ZENG Haitao; JIA Jianbo; ZHANG Chuanxiang

doi:10.13225/j.cnki.jccs.2024.0914

Abstract：The clean,low-carbon and high-value utilization of semi-coke powder can not only improve the utilization effi-ciency of resources,but also reduce environmental pollution,which is conducive to realizing the national strategic goal of"carbon peak carbon neutralization".Herein,hard carbon as anode active materials for potassium ion batteries was pre-pared by carbonizing the semi-coke powder.The effects of carbonization temperatures on the carbon phase(highly dis-ordered carbon,pseudo-graphite carbon and graphite-like carbon),carbon crystallite size,carbon layer spacing,defect con-centration,surface properties of semi-coke based hard carbon were researched,and the electrochemical potassium storage properties of semi-coke based hard carbon with different microstructures were also evaluated.It can be found that with the increase of carbonization temperature(600-1600℃),the highly disordered carbon in hard carbon can evolve into the pseudo-graphitic carbon and graphitic-like carbon,the lateral size together with stacked size of carbon crystallite gradu-ally increases.The content of sp3 hybridized carbon in hard carbon gradually decreases,which can evolve into sp2 hybrid-ized carbon,and the order degree of hard carbon gradually increases with elevating the temperature.In addition,the spe-cific surface area and total pore volume of hard carbon decrease with increasing the carbonization temperature,and the mean carbon layer spacing increases first and then decreases.The hard carbon(ZN-1000)prepared at 1000℃ has the area ratio of 31.2%of highly disordered carbon,34.5%of pseudo-graphite carbon and 34.3%of graphite-like carbon,and demonstrates the highest mesopore volume of 0.04 cm3/g,largest mean carbon layer distance of d002=0.375 nm and some oxygen-containing functional groups such as C=O,C—O and—OH.As anode active materials for potassium ion batter-ies,ZN-1000 delivers a high reversible specific capacity of 207 mAh/g at a current density of 20 mA/g,and 32 mAh/g at a higher current density of 1000 mA/g.The excellent electrochemical potassium storage performances are closely related to the microstructure of semi-coke based hard carbon.K+can be stored by adsorbing/desorbing on the highly disordered car-bon,defects,oxygen-containing functional groups as well as open pores,and embedding/stripping in ordered carbon lay-ers of semi-coke based hard carbon.The work can provide new ideas for the clean and high-value utilization of semi-coke powder and development of carbon anode materials for potassium ion batteries.