Physical confinement and chemical adsorption of porous C/CNTmicro/nano-spheres for CoS and Co9S8 as advanced lithium batteries anodes

Metal sulfides have been drawing more and more attention as electrode materials in batteries due to their high theoretical capacities. However, the volume expansion and loss of active materials are two major problems, hindering further improvement in their electrochemical performances. Herein, a strategy based on physical confinement/ chemical adsorption is proposed to fabricate CoS and Co9S8 electrodes for advanced lithium batteries. Via a facile two-step method, porous C/CNT micro/nanospheres embedding cobalt sulfide nanoparticles are successfully fabricated, in which sulfur is immobilized by C-S bonds. Physically, the porous C/CNT micro/nano-spheres well accommodate the volume change and inhibit the loss of active materials. Chemically, the sulfur species are anchored by C-S bonds to alleviate the migration and loss. Assembled as lithium battery anodes, the porous cobalt sulfide/carbon composites, particularly the CoS/C/CNT (CoS-0.4C) and Co9S8/C/CNT (Co9S8-0.8C), exhibit superior lithium storage properties to those without any complexing or any C-S bonding. Furthermore, an in-situ electrochemical measurement is proposed to detect the existence of Li2S, which is helpful to understand the mechanism of conversion reaction-based metal sulfides. (C) 2019 Elsevier Ltd. All rights reserved.