Interface-modulated fabrication of hierarchical yolk–shell Co3O4/C dodecahedrons as stable anodes for lithium and sodium storage

Abstract

Transition-metal oxides (TMOs) have gradually attracted attention from researchers as anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because of their high theoretical capacity. However, their poor cycling stability and inferior rate capability resulting from the large volume variation during the lithiation/sodiation process and their low intrinsic electronic conductivity limit their applications. To solve the problems of TMOs, carbon-based metal-oxide composites with complex structures derived from metal–organic frameworks (MOFs) have emerged as promising electrode materials for LIBs and SIBs. In this study, we adopted a facile interface-modulated method to synthesize yolk–shell carbon-based Co3O4 dodecahedrons derived from ZIF-67 zeolitic imidazolate frameworks. This strategy is based on the interface separation between the ZIF-67 core and the carbon-based shell during the pyrolysis process. The unique yolk–shell structure effectively accommodates the volume expansion during lithiation or sodiation, and the carbon matrix improves the electrical conductivity of the electrode. As an anode for LIBs, the yolk–shell Co3O4/C dodecahedrons exhibit a high specific capacity and excellent cycling stability (1,100 mAh·g−1 after 120 cycles at 200 mA·g−1). As an anode for SIBs, the composites exhibit an outstanding rate capability (307 mAh·g−1 at 1,000 mA·g−1 and 269 mAh·g−1 at 2,000 mA·g−1). Detailed electrochemical kinetic analysis indicates that the energy storage for Li+ and Na+ in yolk–shell Co3O4/C dodecahedrons shows a dominant capacitive behavior. This work introduces an effective approach for fabricating carbonbased metal-oxide composites by using MOFs as ideal precursors and as electrode materials to enhance the electrochemical performance of LIBs and SIBs.