High Structural Stability and Reaction Mechanism of Porous Carbon Nanobox Encapsulated Monodisperse CoP Nanoparticles for High-Performance Lithium-Ion Battery

Transition metal phosphides (TMPs) are perplexed by the low electronic/ionic conductivity, volume variations, and unstable reaction interfaces. To tackle these issues, herein, we have proposed a low-temperature phosphorization strategy by reactions between Co-based metal-organic frameworks (MOF) and sodium dihydric hypophosphite to encapsulate monodisperse CoP nanoparticle (similar to 12 nm) into MOF-derived hollow and porous carbon nanobox (CoP@PCB). Compared to bare CoP, such CoP@PCB electrode has shown remarkable electrochemical performance, which is highly ascribed to its robust structural feature, pre-reserved voids, monodisperse CoP nanoparticles, and stable reaction interfaces, as well as fast reaction kinetics. Moreover, the good electrochemical properties of CoP@PCB//LiFePO4 full cells have demonstrated practical possibility. The formation of Co and Li3P as discharged products has corroborated the redox conversion reaction mechanism, as assessed by in-situ X-ray diffractions. The favorable function of the carbon shell in boosting both electronic conductivity and lowering diffusion energy barriers has been confirmed by theoretical calculations, demonstrating an important synergistic effect.