Redox Targeting of Anatase TiO₂ for Redox Flow Lithium‐Ion Batteries

Anatase TiO 2 is an extensively studied anode material for lithium‐ion batteries because of its superior capability of storing Li + electrochemically. Here reversible lithium storage of TiO 2 is achieved chemically using redox targeting reactions. In the presence of a pair of redox mediators, bis(pentamethylcyclopentadienyl)cobalt (CoCp * 2 ) and cobaltocene (CoCp 2 ) in an electrolyte, TiO 2 and its lithiated form Li x TiO 2 can be reduced and oxidized by CoCp * 2 and CoCp 2 + , respectively, which accompany Li + insertion and extraction, albeit without attaching the TiO 2 onto the electrode. The reversible chemical lithiation/delithiation and the involved phase transitions are unambiguously confirmed using density functional theory (DFT) calculations, UV‐vis spectroscopy, X‐ray photoelectron spectoscopy (XPS), and Raman spectroscopy. A redox flow lithium‐ion battery (RFLB) half‐cell is assembled and evaluated, which is a critical step towards the development of RFLB full cells.