Compositional Study of Ti-Nb Oxide (TiNb2O7, Ti2Nb10O29, Ti2Nb14O39, and TiNb24O62) Anode for High Power Li Ion Batteries
Abstract
Titanium niobium oxides (TNOs) are attractive anode materials for high power density Li-ion batteries. However, the details of capacity storage in TNOs is not fully understood today as it depends on the Ti and Nb composition and their changes in oxidation state. This is further complicated by a wide variation in gravimetric capacities reported in literature for TNO anodes. Therefore, in this work, we systematically synthesise TiNb2O7, Ti2Nb10O29, Ti2Nb14O39, and TiNb24O62 particles using the same solid state reaction approach, and report their electrochemical properties via galvanostatic cycling, cyclic voltammetry, galvanostatic intermittent titration technique (GITT). Further we use operando X-ray absorption spectroscopy (XAS) to investigate the redox reactions taking place in each of these compositions, which provides new insights in their charge storage mechanisms. We found that of the materials tested, TiNb2O7 anodes have the best cycling and rate performance, which could be related to the higher utilization of Nb redox revealed via operando XAS analysis.