Study on sodium storage performance of zinc/sulfur co-doped hard carbon materials

To enhance the sodium storage capacity, cycling stability and rate performance of hard carbon (HC) materials, high-temperature pyrolysis was employed to achieve doping of various heteroatoms (Zn, S, and Zn/S co-doping) into the HC materials. Using the continuous etching of the carbon framework by ZnS particles, which were formed during the pyrolysis of carbon precursors, abundant pore structures were generated to increase the number of active sites. During Zn/S co-doping process, the pyrolysis temperature was adjusted to 1 050 ℃ and the H-Zn/S-HC-1050 carbon material was obtained after acid treatment. The composition and microstructure of the material were characterized, and its electrochemical performance was tested. The results indicate that the reversible discharge specific capacity of H-Zn/S-HC-1050 carbon material was 276.26 mA·h/g at a current density of 50 mA/g, which was 15.46% higher than the original Zn/S-HC carbon material with a specific capacity of 239.26 mA·h/g; After 100 charge-discharge cycles at a current density of 100 mA/g, reversible specific capacity still maintains at 201.65 mA·h/g. The modified H-Zn/S-HC-1050 carbon material can fully leverage the synergistic effect of Zn/S co-doping through optimizing carbonization and reducing impurity attachment, which provides some reference for the development of high-performance hard carbon materials.