Stress-Dispersed Nanoconstruction of CoMoP Anode: Improved Na-Storage Stability and Reversibility.

Abstract

Metal phosphide anode materials encounter poor reversibility of the discharge product (metal and Na3P) and large volume variation, resulting in low initial Coulombic efficiency (ICE) and severe capacity degradation. Herein, a bimetallic phosphide (CoMoP) with three-dimensional ordered porous (3DOP) nanoconstruction was fabricated, which presents a reduced Gibbs free energy change (ΔG) of redox reaction between Co-Mo/Na3P and CoMoP and improved conductivity compared to CoP and MoP. Additionally, the 3DOP architecture could disperse stress and reduce strain during cycling, thus improving structural stability of CoMoP. In situ and ex situ characterizations and electrochemical measurements suggest that 3DOP CoMoP exhibits highly reversible sodium storage with an ICE of 58% at 0.1 A g-1, enhanced reaction dynamics, and good cycling stability with around 0.04% capacity decay per cycle at 1 A g-1 after 1000 cycles. Consequently, this work offers a new perspective to solve issues of reversibility of redox chemistry and volume expansion for secondary batteries.