Co₃O₄ Nanospheres Embedded in a Nitrogen-Doped Carbon Framework: An Electrode with Fast Surface-Controlled Redox Kinetics for Lithium Storage

Herein, we develop a Co₃O₄-based anode material with a hierarchical structure similar to that of a lotus pod, where single yolk–shell-structured Co₃O₄@Co₃O₄ nanospheres are well embedded in a nitrogen-doped carbon (N–C) conductive framework (Co₃O₄@Co₃O₄/N–C). This distinctive architecture contains multiple advantages of both the yolk–shell structure and conductive N–C framework to improve the Li ion storage performance. Especially, the doping of the N atom in N–C increases the interaction between the carbon and adsorbents, which is confirmed by the theoretical calculations in this work, making the carbon framework much more electrochemically active. As a result, the Co₃O₄@Co₃O₄/N–C exhibits fast surface-controlled kinetics, which corroborate the high counterion mobility and the ultrafast electron-transfer kinetics of the electrode. Due to these synergetic effects, desired capacity stability (1169.6 mAh g^–1 at 200 mA g^–1 after 100 cycles) and superior rate performance (633.4 mAh g^–1 at 10 A g^–1) have been realized in this Co₃O₄@Co₃O₄/N–C electrode.