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.