Monometallic and bimetallic metal-organic frameworks derived CoP embedded in porous carbon: Monodisperse CoP nanoparticles for highly reversible potassium ion storage

Abstract

Metal phosphides show promise as anode materials for high-energy potassium-ion batteries due to their high capacity. However, their cycling performance is hampered by volume changes. Although nanoparticle/carbon composites are commonly employed to tackle this issue, achieving uniform embedding within confined carbon structures still presents a challenge. In this study, we investigate the synthesis strategies of CoP/porous carbon composites using isostructural bimetallic and monometallic-zeolitic imidazolate framework (ZIF), and achieve uniform embedding of-4 nm CoP nanoparticles in porous carbon by utilizing a bimetallic Co/Zn ZIF. Conversely, monometallic ZIF-67 leads to substantial coarsening and non-uniform distribution of-25 nm CoP particles. The resulting bimetallic-ZIF-derived CoP/porous carbon composite exhibits a specific capacity of 490.5 mAh/g at 0.05 A/g for potassium-ion storage and remarkable cycling stability, retaining 100 % capacity over 500 cycles at 0.1 A/g. Differential capacity plots confirm improved reversibility of the CoP conversion reaction. Notably, the evaporation of Zn generates a pore structure that effectively confines CoP, preventing further ag-gregation during electrochemical cycling. This work showcases a unique synthesis strategy using a bimetallic ZIF for high-performance potassium-ion battery materials.