Boosted sodium storage of GeS2/GeO2/ZnS composite via heterostructure engineering

Transition metal dichalcogenides exhibit tremendous potential for sodium ion batteries (SIBs), owing to the outstanding specific capacity and aboundant reserves. However, the large ionic radius of sodium and poor conductivity often result in the fast decaying performance and inferior reaction kinetics. Herein, the GeS2/GeO2/ZnS@rGO (GGZ/C) ternary metal-based composite is fabricated as an anode material for SIBs. Notably, the GGZ/C composite is derived from the phase transformation of Zn2GeO4 precursor, which is beneficial for the heterostructure engineering. In this hierarchical structure, the metal phases ZnS and GeO2 are used to form the heterogeneous framework, while graphene is applied to build a conductive network and anchor the host nanoparticles. Therefore, the great Na+ diffusion channels are achieved by the rational design of the huge exquisite interfaces among the heterogeneous mixed phases. Notably, it can almost completely relieve the volume expansion and restrain the internal stress of GGZ/C composite, providing the excellent structural tolerance. As expected, the GGZ/C composite exhibits excellent rate capability, with an impressive reversible capacity of 548 mAh g−1 at a high rate of 5.0 A g−1. Meanwhile, the GGZ/C also displays outstanding cycling performance with a specific capacity of 519 mAh g−1 after 650 cycles at high rate of 5.0 A g−1. This strategy offers the inspiration for rational heterostructure engineering for the energy storage materials with excellent reversible capacity and large volume variation.