Phase-Controllable Cobalt Phosphides Induced through Hydrogel for Higher Lithium Storages

Abstract

Transition metal phosphides (TMPs) have gained the increased attention in energy storage due to their potential to optimize electrochemical performances. However, their preparation routes usually require highly toxic and flammable phosphorus sources with strict reaction conditions. The existence of multiple energetically favorable stoichiometries also makes it a challenge to achieve phase-control of metal phosphides.In this work, we have been successfully realized the phase-controllable framework of cobalt phosphide from Co2P to CoP by employing semi-interpenetrating network (semi-IPN) hydrogel as precursor. Interestingly, the semi-IPN hydrogel could serve as a selfassembly/sacrificing template to accomplish 3D space confinement, where PVPA was identified as a prominent phosphorous source due to its strong metal complexation ability and high thermal stability. Furthermore, this route is successfully extended to the synthesis of other TMPs including Fe2P, Ni2P and Cu3P. The specific structure of cobalt phosphides give rise to superior lithium storage performance, showing superior cycling stability (495.2 mAh g -1 after 1000 cycles at 2.0 A g -1 ). This approach envisions a new outlook on exploitation of essential functional hydrogels for the creation of inorganic materials towards sustainable energy development.