Lithium Insertion into Titanium Phosphates, Silicates, and Sulfates

TiIV phosphates, sulfates, and silicates were investigated as positive electrodes in lithium batteries. We present the lithium insertion into TiSO5, LiTiPO5, Li2TiSiO5, TiP2O7, and ATi2(PO4)3 (A = Li, Na). The SO42-, PO43-, and SiO44- groups alter significantly the operating voltage due to the inductive effect on the Ti4+/Ti3+ redox couple lying around 2.5 V vs Li+/Li, i.e., ∼1 V higher than for “simple” titanium oxides such as spinel Li4Ti5O12 or LiTiCrO4. Galvanostatic (GITT) and potentiostatic (PITT) intermittent titration techniques coupled with in situ X-ray diffraction were used to understand the lithium insertion mechanisms into these materials. Chemical lithiation was also performed on TiP2O7 and ATi2(PO4)3 (A = Li, Na) to isolate new TiIII-based compositions.