Amorphous germanium oxide nanobubbles for lithium-ion battery anode

Germanium (Ge) is a promising anode material for lithium-ion batteries (LIBs) due to its large theoretical specific capacity (1600 mA h g⁻¹), high Li diffusivity and large intrinsic electrical conductivity. Despite these merits, its large volumetric change during lithiation/delithiation process and relatively high production cost make it difficult to use in commercial batteries. In this paper, we report a facile, easy to scale up, and environmentally friendly method to prepare an amorphous phase GeO_x (x < 1) hollow composite at a hydrothermal condition using an aqueous precursor solution containing GeO₂ particles, and citric acid. The citric acid induces gas bubble templates and frameworks to improve the structural strain for Li⁺ ion conduction during cycling. The resulting GeO_x-C hallow composite anode shows enhanced cyclability with a reversible capacity of 930 mA h g⁻¹ after 100 cycles at a current density of 0.3 C.