Water-soluble salt-templated strategy to regulate mesoporous nanosheets-on-network structure with active mixed-phase CoO/Co3O4 nanosheets on graphene for superior lithium storage

Highlights: • A heterostructured hybrid constructed by vertically aligned CoO/Co₃O₄ nanosheets on graphene. • NaCl templates exert a vital role in determining the structure and performance of products. • The hierarchical structure greatly boosts the electron conduction and ion diffusion kinetics. • The mesoporous CoO/Co₃O₄/Gra hybrid delivers high reversible capacity and excellent cycle stability for Li-storage. -- Abstract: Facile construction of high-energy Li-ion batteries (LIBs) anode materials with robust heterostructure remains great challenges, especially for the fine integration of active materials with conductive carbon. Here, vertically aligned mixed-phase CoO/Co₃O₄ nanosheets anchored on wrinkled graphene (CoO/Co₃O₄/Gra) are controllably synthesized with the assistance of water-removable NaCl-templates through facile freeze-drying and calcination processes. In-depth investigations disclose that the wrinkled graphene induces the bonding with nucleating precursors, and the nanosheets vertically grow along the crystal planes of multilevel-NaCl. The as-formed mesoporous nanosheets-on-network structure endows the hybrids with efficient exposure of mixed-phase CoO/Co₃O₄ active sites and rapid charge-transfer channels. And the multiple composites can integrate the advantages of their long complements and fully exert their synergistic effects to solve the problems of the single metal oxide electrode. Furthermore, the electrochemical performance of hierarchically mesoporous architecture is beyond that of the single individual structure on account of the sufficient electrode/electrolyte interfaces, rapid Li⁺ diffusion and electron conduction, and stable structural integrity upon cycling. Accordingly, the capacitive kinetic of Li-storage behaviors is greatly enhanced by these synergistic effects. Serving as a LIBs anode material, the mesoporous CoO/Co₃O₄/Gra-4 hybrid yields superior reversible capacity (1390 mAh g⁻¹ at 0.1 A g⁻¹), high rate performance (1130 mAh g⁻¹ at 0.2 A g⁻¹), and impressive cycling stability (811 mAh g⁻¹ after 500 cycles at 1 A g⁻¹). This work may inspire the design of high-performance electrodes with advanced 3D hierarchical structures.