High Performance TiP₂O₇Based Intercalation Negative Electrode for Aqueous Lithium-Ion Batteries via a Facile Synthetic Route

A composite TiP 2 O 7 /amorphous carbon material (C-TiP 2 O 7 ) was prepared by an intensive mechanical mixing/solid-state synthesis method at 800°C. Physical properties were characterized via powder X-ray diffraction, Rietveld refinement, SEM, BET and TGA. Electrochemical performance was evaluated in both a three electrode test setup and two electrode coin cells via cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic cycling tests. The C-TiP 2 O 7 composite demonstrated excellent cycling performance in 1 M Li 2 SO 4 when matched with LiMn 2 O 4 as a positive electrode: when cycled at C/2 for 150 cycles, the capacity retention is over 91% with coulombic efficiencies exceeding 99%. The initial discharge capacity obtained at a C/10 rate is 91 mAh/g which is about 75% of theoretical capacity 121 mAh/g. The apparent diffusion coefficient of C-TiP 2 O 7 composite calculated from cyclic voltammetry result is 3.5 * 10 −15 cm 2 /s.