Co9S8 confined in bifunctional N/S co-doped carbon/carbon with high electrochemical performance for lithium-ion batteries

The lithium storage performance of Co₉S₈ suffers from the poor cycling performance due to the inferior electron conductivity, huge volume expansion and structure deterioration during cycling. Herein, we develop a new approach to prepare the Co₉S₈ embedded in bifunctional N/S co-doped carbon/carbon (Co₉S₈/NSC@C) via the pyrolysis of S- and Co(II)-containing polypyrrole precursor accompanied by Ethanol Steam Reforming. The process simultaneously restricted the Co₉S₈ grains growth and conducted carbon deposition on the outer surface of Co₉S₈ nanoparticles. Such unique structure of the Co₉S₈/NSC@C electrode material exhibits superior lithium storage performance, delivering a high reversible specific capacity of 580 mAh g⁻¹ after 200 cycles at 0.1 A g⁻¹ for half-cell and a good rate capability with a reversible capacity of 159 mAh g⁻¹ at various current densities after 60 cycles for full-cell. The function-oriented design of Co₉S₈/NSC@C might open new avenues for the preparation of similar electrode materials.