KOH-assisted aqueous synthesis of bimetallic metal-organic frameworks and their derived selenide composites for efficient lithium storage

To solve low efficiency, environmental pollution, and toxicity for synthesizing zeolitic imidazolate frameworks (ZIFs) in organic solvents, a KOH-assisted aqueous strategy is proposed to synthesize bimetallic ZIFs polyhedrons, which are used as precursors to prepare bimetallic selenide and N-doped carbon (NC) composites. Among them, Fe–Co–Se/NC retains the three-dimensional (3D) polyhedrons with mesoporous structure, and Fe–Co–Se nanoparticles are uniform in size and evenly distributed. When assessed as anode material for lithium-ion batteries, Fe–Co–Se/NC achieves an excellent initial specific capacity of 1165.9 mAh·g⁻¹ at 1.0 A·g⁻¹, and the reversible capacity of Fe–Co–Se/NC anode is 1247.4 mAh·g⁻¹ after 550 cycles. It is attributed to that the uniform composite of bimetallic selenides and N-doped carbon can effectively tune redox active sites, the stable 3D structure of Fe–Co–Se/NCs guarantees the structural stability and wettability of the electrolyte, and the uniform distribution of Fe–Co–S nanoparticles in size esuppresses the volume expansion and accelerates the electrochemical reaction kinetics.