Sodium storage mechanism of a GeP5/C composite as a high capacity anode material for sodium-ion batteries.

The sodium storage mechanism of a GeP5/C composite electrode was revealed. Metallic Ge formed during discharge enhances the electronic conductivity of the electrode, while NaxP mitigates the agglomeration and volume change of Ge in the alloying process. The GeP5 phase is regenerated after recharge along with elemental Ge and P, implying a reversible phase transition of GeP5 during cycling.