Rational design and synthesis of yolk–shell ZnGa2O4@C nanostructure with enhanced lithium storage properties

Highlights: • Yolk–shell ZnGa₂O₄@C was synthesized through surface coating followed by thermal treatment and etching process. • Yolk–shell ZnGa₂O₄@C revealed superior capacity and cycling stability. • Carbon shell and void space were responsible to the enhanced property. The ability to create hybrid nanostructure with synergistic effect and confined morphology to achieve high performance and long-term stability is high desirable in lithium ion batteries. Although transition metal oxides as anode material reveal high theoretical capacities, the significant volume changes during repeated lithium insertion and extraction cause pulverization of electrode materials, resulting in rapid fade in capacity. Herein, yolk–shell nanostructure of ZnGa₂O₄ encapsulated by amorphous carbon is rationally designed and synthesized through two-step surface coating followed by thermal treatment and etching process. It is noteworthy that ZnGa₂O₄@C with yolk–shell structure is superior to pristine ZnGa₂O₄ and ZnGa₂O₄@C with core-shell structure in term of lithium storage. The stable reversible capacity of yolk–shell ZnGa₂O₄@C can be retained at 657.2 mAh g⁻¹ at current density of 1 A g⁻¹ after completion of 300 cycles, which also reveals superior rate performance. The appropriate carbon shell and void space involved in the yolk–shell structure are considered to be the crucial factor in accommodating volume expansion as well as preserving the structural integrity of yolk–shell ZnGa₂O₄@C.