Understanding the effect of structural compositions on electrochemical properties of titanium-based polyanionic compounds for superior sodium storage.

Titanium-based polyanionic compounds have gained wide attentions as anode materials for room-temperature sodium-ion batteries due to the robust structural framework, reversible redox chemistry, and compositional diversities. However, the effect of chemically-inserted cations on their structural and electrochemical properties is lack of being investigated to date. In this work, structural and electrochemical properties of ATi 2 (PO 4) 3 /C (A = Li, Na, Mg) compounds are comparatively studied by coupling X-ray diffraction, scanning electron microscope, cyclic voltammetry and galvanostatic measurements. Experimental results reveal that the structural composition is an important factor determining electrochemical properties of titanium-based polyanionic compounds, and the Li-containing composition shows the best charge/discharge performance with high specific capacities of 120.4 mAh g−1 at 20 mA g−1 and 89.7 mAh g−1 at 1000 mA g−1, and outstanding cycling stability without capacity fading after 1000 cycles. In particular, full battery assembled with it and Na 3 V 2 (PO 4) 3 cathode can deliver a specific energy of 124.5 Wh kg−1 at the power of 114.9 W kg−1, and a capacity retention of 84.9% after 100 cycles. • A x Ti 2 (PO 4) 3 /C (A = Li, Na, Mg) compositions are comparatively investigated. • LiTi 2 (PO 4) 3 composition shows the best sodium-storage performance. • Full battery with LiTi 2 (PO 4) 3 /C anode and Na 3 V 2 (PO 4) 3 /C cathode is studied. [ABSTRACT FROM AUTHOR]