Mesoporous yolk-shell CoS2/nitrogen-doped carbon dodecahedron nanocomposites as efficient anode materials for lithium-ion batteries

Abstract

Transition metal sulfides with a high theoretical capacity have been widely regarded as ideal electrode materials for lithium-ion batteries (LIBs). However, their poor cycling stability, caused by large volume expansion during the discharge-charge process, hinders their practical application. Yolk-shell structures have great potential for addressing the huge volume change of anode materials for LIBs. In this work, we report a facile, two-step heat-treatment method to synthesize unique mesoporous yolk-shell CoS2/nitrogen-doped carbon dodecahedron (CoS2/NC) nanocomposites using Co-ZIF-67 as a self-sacrificing precursor. In the composites, the CoS2 nanoparticles (15–20 nm) are anchored homogenously onto a yolk-shell nitrogen-doped mesoporous carbon skeleton. The NC mesoporous yolk-shell matrix acts as a highly conductive skeleton for rapid electron/ion transfer and alleviates the volume expansion during charge-discharge processes. The CoS2 nanoparticles provide more active reaction sites for Li ions. Due to the synergistic interaction of CoS2 and NC, the composites exhibit excellent electrochemical performance. When used as anode materials for LIBs, the CoS2/NC exhibits superior capacity, good rate capability and long cycling stability. A reversible capacity of 1083 mAh·g−1 is attained at a current density of 0.1 A g−1 after 200 cycles, and even at a high current rate of 2 A g−1, a reversible capacity of 696 mAh·g−1 is achieved.