Zn₂GeO₄ rods/graphene supported on Ni foam as binder-free anode for enhanced Na ion storage performance

Given the abundance of sodium resources, sodium-ion batteries (SIBs) have been considered as one of the candidates for storing energy on a large scale. However, the slower sodium ion transport in the electrode limits its use. Here, we report a binder free Zn₂GeO₄-graphene Ni foam integrated anode for Na ion storage. The obtained integrated anode was supported by nickel foam without binder, the Zn₂GeO₄ exhibits nanotube structure, and the graphene was coating on the Zn₂GeO₄. The Zn₂GeO₄ nanorods are able to coalesce with each other to form porous structures. The binder free Zn₂GeO₄-graphene Ni foam integrated anode electrode delivered a discharge capacity of 427.7 mAh g⁻¹ at 0.1 A g⁻¹ after 200 cycles. And at a high current density of 2 A g⁻¹ a favorable rate capacity of 391.4 mAh g⁻¹ could be achieved, twice that of the Zn₂GeO₄-graphene powder electrode. The outstanding electrochemical performance can be attributed to the synergistic effect between in situ grown Zn₂GeO₄ nanorods and graphene sheets, which enhanced the conductivity and stabilized the electrode structure during the cycling process, as well as the improved electrochemical reaction kinetics due to in-situ growth. This work sheds light on the design of Ge-based ternary oxide anodes and provides a promising anode for high performance SIBs.