Interfacial covalent bonding enables transition metal phosphide superior lithium storage performance

Abstract

High theoretical capacity and moderate redox potential enable transition metal phosphide (TMP) sparkle under a spotlight as viable anode materials for lithium-ion batteries (LIBs). However, TMP suffers from severe voltage hysteresis and poor reversibility due to the breaking and formation of TM-P and Li-P bonds during lithiation/delithiation processes, resulting in significant energy dissipation and rapid capacity decay. Besides, traditional thermal phosphorization involves generation of toxic PH3, which contradicts green chemistry concept. Herein, Ni2P@C composite is successfully achieved under plasma activation with Ni MOF-74 and red phosphide as the starting materials. The monodispersed Ni2P nanoparticles are uniformly anchored within carbon matrix through covalent chemical bonding of C-O-Ni and C-P. Systematic experimental analysis and theoretical calculation indicates that such efficient interfacial chemical linkage could weaken TM-P bonds and bridge the gap between Ni2P nanoparticles and carbon matrix, thus promoting the conversion reversibility during charge/discharge reactions. Benefited from the unique structure, voltage hysteresis of Ni2P@C is significantly suppressed, the reversible lithium storage capacity and cycling stability is greatly enhanced. By employing Ni2P@C and commercial LiFePO4 as anode and cathode, the full LIBs delivers a high reversible capacity of 0.6 mAh cm−2 after 300 cycles at 1.7 mA cm−2. This strategy is expected to shed more light on interfacial chemical linkage towards rational design of advanced materials for LIBs.