Amorphous mesoporous GeO(x) anode for Na-ion batteries with high capacity and long lifespan

It is recently demonstrated that amorphous Ge anode shows higher reversible Na-ion storage capacity (590 mA h g(−1)) than crystallized Ge anode (369 mA h g(−1)). Here, amorphous GeO(x) anode is prepared by a simple wet-chemistry reduction route at room temperature. The obtained amorphous GeO(x) shows a porous hierarchical architecture, accompanied with a Brunauer–Emmett–Teller surface area of 159 m(2) g(−1) and an average pore diameter of 14 nm. This unique structure enables the GeO(x) anode to enhance the Na-ion/electron diffusion rate, and buffer the volume change. As anode for Na-ion battery, high reversible capacity over 400 mA h g(−1), fine rate capability with a capacity of 200 mA h g(−1) maintained at 3.0 A g(−1) and long-term cycling stability with 270 mA h g(−1) even over 1000 cycles at 1.0 A g(−1) are obtained.