Facile synthesis of hollow Cu₃P for sodium-ion batteries anode

Combining metal to form metal phosphide is a promising strategy to address the fast capacity decay of P rooted from its low electronic conductivity and large volume changes upon cycling. Cu₃P, which possesses a high theoretical gravimetric and volumetric capacity of 363 mAh·g⁻¹ and 1028 Ah·L⁻¹ and reasonable volume expansion of 156% during sodiation, was investigated as anode material in SIBs. Hollow-structured Cu₃P electrode delivers an initial de-sodiation capacity of ~ 159.0 mAh·g⁻¹ with high capacity retention of ~ 85.1% over 50 cycles at 0.2C rate and exhibits good rate performance, retaining 70% of the capacity when the current density increases from 0.2C to 1.6C. A 3 V-class full cell consisting of P2-Na_2/3Ni_1/3Mn_1/2Ti_1/6O₂ cathode and Cu₃P anode was also assembled, which could achieve an energy density of ~ 189.3 Wh·kg⁻¹ (based on the mass of both electrode materials) and average discharge voltage of ~ 2.91 V when cycled in 1.0–4.3 V at 0.1C. 
Graphic abstract: Facile synthesis of hollow Cu₃P as a good anode candidate for sodium-ion batteries [Figure not available: see fulltext.]