Ni-Co MOF-derived rambutan-like NiCo2O4/NC composite anode materials for high-performance lithium storage

Abstract

Taking advantage of the large surface area and high porosity characteristic of metal-organic framework (MOF) materials, the synthesis of carbon-coated bimetallic transition metal oxides stands out as an effective strategy to reduce volume expansion, enhance cycling stability, and improve electronic conductivity at the active sites in lithium-ion batteries (LIBs). In this research, a novel rambutan-like Ni-Co MOF was successfully synthesized via a hydrothermal method followed by calcination to obtain nitrogen-doped carbon-stabilized hierarchical rambutan-like NiCo2O4 composites (NiCo2O4/NC). The resulting composites inherited the original rambutan-like structure of the Ni-Co MOF, which was characterized by uniform size, highly ordered porosity and large surface area, and showed excellent electrochemical Li+ storage performance. In particular, the NiCo2O4/NC-600 composite exhibited superior cyclic stability and rate capability, maintaining a remarkable reversible charge/discharge specific capacity of 1281.7/1292.7 mAh g−1 after 400 cycles at 0.5 A g−1. In addition, when paired with LiFePO4 in a full cell, it maintained a reversible discharge specific capacity of 143.9 mAh g−1 after 200 cycles at 0.1 A g−1, indicating commendable cyclic stability. Ex-situ analyses confirmed the pseudo-capacitive behavior of the NiCo2O4/NC composites. Furthermore, the nitrogen-doped carbon layer embedded in the NiCo2O4/NC composites effectively mitigated the volume expansion during repeated Li stripping/plating processes, thereby improving the structural integrity, conductivity, and specific capacitance. This study presents a practical approach for fabricating nitrogen-doped carbon-stabilized bimetallic oxide anodes in high-power LIBs through architectural engineering and compositional tailoring.