Robust CoP<sub>2</sub>-C hollow nanoboxes: Superior anodes for Li- and Na-ion batteries

Abstract

Metal phosphides are attractive candidates for use as anodes in high-performance Li/Na-ion batteries (LIBs/ NIBs) owing to their high theoretical capacities and low operating potentials. In this study, CoP2-C hollow nanoboxes (HNBs), that is, CoP2 nanocrystallites (-5-10 nm) embedded in N -doped carbon HNBs, were produced using a simple two-step method and utilized as LIB/NIB anodes. Various cutting -edge ex situ techniques were used to analyze the phase transition mechanism of the CoP2-C HNBs during the Li/Na reaction. The CoP2-C HNBs anode exhibited high initial reversible capacities (LIB: 1082 mAh g-1, NIB: 507 mAh g-1), high -rate capabilities (LIB: 926 mAh g-1 at 3C, NIB: 370 mAh g-1 at 2C), and excellent cycling performance at a high 1C rate (LIB: -91 % capacity retention over 100 cycles, NIB: -100 % capacity retention over 100 cycles), respectively. The excellent anode performance of LIBs/NIBs was attributed to the uniformly embedded CoP2 nanocrystallites in the robust N -doped carbon HNBs and the electrochemically driven recombination reaction of CoP2. Therefore, we believe that CoP2-C HNBs are promising high -capacity anodes for LIBs/NIBs, and that this unique HNBs architecture is highly suitable for various energy storage and conversion systems.