Operando investigations of lithiation and delithiation processes in a BiVO₄ anode material

BiVO4 undergoes a series of conversion and alloying reactions as an anode material in lithium ion batteries. The current work demonstrates a charge capacity of 485 mA h g-1 after 50 cycles in a voltage range of 0-2.00 V (graphite has a capacity of 372 mA h g-1 theoretically). An exceptionally high volumetric capacity makes BiVO4 suitable for compact applications (volumetric capacity of 3984 mA h cm-3 for BiVO4 in comparison to 756 mA h cm-3 for graphite theoretically). Reaction steps and electronic transformations have been identified by operando quasi simultaneous synchrotron X-ray diffraction and absorption spectroscopy studies. An irreversible reaction step occurs for the Bi3+/Bi0 redox pair, whereas reversible mechanisms are found for the V5+/V3+ and Bi0/Bi3- redox pairs. The proposed mechanisms are supported by density functional theory (DFT) calculations.