Morphology-Tunable Binary Transition Metal Oxide Heterostructure@Carbon Composites for Lithium-Ion Batteries

Heterostructures of binary and unary transition metal oxides (B and UTMOs) have demonstrated excellent electrochemical performance in lithium-ion batteries (LIBs) due to synergistic effects; however, there remains a lack of research combining multiple strategies for synergy enhancement. Herein, we present the development of crystallinity-controlled heterostructures based on nickel and cobalt oxides (NiCo₂O₄/NiO and NiO/Co₃O₄) with different morphologies (urchin- and flower-like structures, e.g., U-NiCo₂O₄/NiO and F-NiCo₂O₄/NiO) to investigate the influence of heterostructure combinations and morphologies on electrochemical performance in LIBs. The morphologies of the heterostructures were controlled by adjusting the fluoride concentration during the synthesis of the nickel–cobalt (Ni–Co) precursor, while heterostructure combinations were regulated by heat treatment under specific conditions. When used as anodes for LIBs, electrochemical analyses revealed that the carbon-coated urchin-like U-NiCo₂O₄/NiO (U-NiCo₂O₄/NiO@C) sample provided more efficient charge transfer and a shorter Li-ion transport pathway compared to its counterpart (F-NiCo₂O₄/NiO@C) due to its high surface area and distinctive morphological features. In addition, U-NiCo₂O₄/NiO@C exhibited superior electrochemical performance as an anode in LIBs than U-NiO/Co₃O₄@C, indicating that the advantageous effects of BTMO over UTMO can effectively enhance LIB performance. This facile synthesis approach provides a foundation for morphology-controlled heterostructures in the development of high-performance anode materials for LIB applications.