Construction of Zn₂GeO₄/Graphene Nanostructures with Dually-Protected Functional Nanoframes for Enhanced Lithium-Storage Performances

Application products moving from small-sized devices to large-scale energy storage systems have pushed the development of lithium-ion batteries towards high-energy densities, high-power densities, and long cycle life. Germanium-based anode materials with high theoretical capacities are expected as promising anode candidates to fulfill those requirements, but suffer from the huge volume expansion upon lithiation, leading to serious material pulverization and capacity fading. Herein, a convenient and cost-effective strategy was conceived focusing on construction of dually-protected Zn₂GeO₄/graphene composites. The rationally designed composite was composed of hollowed Zn₂GeO₄ nanostructures and flexible graphene layers, which acted as two functional nanoframes to synergistically alleviate the volume change during lithiation/delithiation. As a result, the Zn₂GeO₄/graphene composite exhibited high specific capacities, excellent cycling stability and desirable rate capability. Specifically, the Zn₂GeO₄/graphene composite electrode delivered specific capacity of 702 mA h g⁻¹ at 300 mA g⁻¹ after 600 cycles with capacity retention of 85%. In addition, a high reversible capacity of 600 mA h g⁻¹ was retained over 1000 cycles at a high current density of 800 mA g⁻¹. Those achieved-results suggested that rational design of electrode nanostructures offers an effective insight for obtaining high-performance batteries.