Unraveling the De-/Lithiation Mechanism of different (Bismuth-doped) Niobium Oxides via ex situ and operando X-ray Absorption Spectroscopy

We aim to elucidate the Li storage mechanism of Nb2O5 when de-/lithiated in the range of 0.01-3.0 V, which offers almost twice the capacity compared to the common range of 1.0-3.0 V. Interestingly, Bi doping increases the initial capacity even further. Previously, we have performed an ex situ study on Bi-doped and neat orthorhombic Nb2O5 at selected potentials of the 1st and 2nd cycle, and the results show that the storage mechanism is very complex. Since ex situ samples are single data points, the operando measurements are highly complementary. In particular, we aim to answer the following questions: (i) Are the ex situ results confirmed by the operando results? (ii) How do the species change in-between the ex situ data points and (iii) what is the exact role of Bi? In addition to the 1st cycle, we will also perform an operando analysis of the 200th cycle. The results will (iv) shed light on the fading mechanisms and are, thus, essential for the further improvement of such materials.