Sodium storage mechanism of a GeP 5 /C composite as a high capacity anode material for sodium-ion batteries.

The sodium storage mechanism of a GeP 5 /C composite electrode was revealed. Metallic Ge formed during discharge enhances the electronic conductivity of the electrode, while Na x P mitigates the agglomeration and volume change of Ge in the alloying process. The GeP 5 phase is regenerated after recharge along with elemental Ge and P, implying a reversible phase transition of GeP 5 during cycling.