Empowering Metal Phosphides Anode with Catalytic Attribute toward Superior Cyclability for Lithium-Ion Storage

Due to high capacity, moderate redox voltage, and relatively low polarization, metal phosphides (MPs) attract much attention as viable anode materials for lithium-ion storage. However, severe capacity decay induced by the poor reversibility of discharge product (Li3P) in these anodes suppresses their practical applications. Herein, it is first revealed that N-doped carbon can effectively catalyze the oxidation of Li3P by density functional theory calculations and activation experiments. By anchoring Ni2P nanoparticles on N-doped carbon sheets (Ni2P@N-C) via a facile method, an MP-based anode rendered with a catalytic attribute is successfully fabricated for improving the reversibility of Li3P during lithium-ion storage. Benefiting from this design, not only can high capacity and rate performance be reached, but also an extraordinary cyclability and capacity retention be realized, which is the best among all other phosphides reported so far. By employing such a Ni2P@N-C composite and a commercialized active carbon as the anode and cathode, respectively, hybrid lithium-ion capacitors can be fabricated with an ultrahigh energy density of 80 Wh kg(-1) at a power density of 12.5 kW kg(-1). This strategy of designing electrodes may be generalized to other energy storage systems whose cycling performance needs to be improved.