Carbon sphere@Co₉S₈ yolk-shell structure with good morphology stability for improved lithium storage performance

The poor electronic conductivity and huge volume expansion of cobalt sulfides upon cycling would lead to their poor electrochemical performances for Lithium-ion batteries. Here, we rationally design a yolk-shell carbon sphere@Co₉S₈ (C@CS) composite, which demonstrates improved kinetics and excellent morphology stability during cycling. This structure can keep Co₉S₈ shell from collapse and aggregation. After cycling, a layer of thin solid electrolyte interphase is coated on the Co₉S₈ shells and prevented them from dissolving in electrolyte, which is helpful for the electrochemical performances. As a result, the C@CS electrodes exhibit good lithium storage performances, including excellent cyclic stability up to 300 cycles at 1000 and 2000 mA g^-1 and high-rate property of 4000 mA g^-1 with a capacity of 489 mA h g^-1.