Lotus-stalk Bi4Ge3O12 as binder-free anode for lithium and sodium ion batteries

Alloyed-type anode materials with high-energy density for lithium and sodium ion batteries attracted much attention of the researchers. However, substantial volume expansion of these materials in the devices during repeated electrochemical process leads to fast capacity fading and hinders their further practical application. Nanotechnology could act as a useful tool to effectively address the issue. Herein, lotus-stalk Bi₄Ge₃O₁₂ nanosheets vertically grown on the nickel foam (denoted as Bi₄Ge₃O₁₂ NSs@NF) were prepared via a straight-forward solvothermal method. Benefiting from their three dimensional (3D) conductive framework and two dimensional (2D) lotus-stalk Bi₄Ge₃O₁₂ nanosheet structure, as anode materials of lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs), the electrochemical performances of Bi₄Ge₃O₁₂ NSs@NF were greatly enhanced as a result of mitigating the huge volume variations during cycles. The Bi₄Ge₃O₁₂ NSs@NF electrodes delivered a high reversible capacity of 1033.1 mAh/g for the first cycle and exhibited 68.6% capacity retention of after 88 cycles at 0.10 A/g in the voltage window of 0.01~3.0 V versus Li/Li⁺. In the test of NIBs, the lotus-stalk Bi₄Ge₃O₁₂ composite electrodes still stored Na⁺ as high as 332.3 mAh/g at 0.10 A/g over 100 sodiation/desodiation repeating cycles.