Using Polypyrrole Coating to Improve Cycling Stability of NaTi2(PO4)3 as an Aqueous Na-Ion Anode

Aqueous alkali - ion batteries offer an economical method for large-scale energy storage demanded by current sources of renewable energy. Although NASICON-type NaTi2(PO4)(3) is an attractive anode material with high capacity and a low redox potential allowing for high voltage cells, it suffers from considerable capacity fade when cycled slowly and deeply. In this work polypyrrole has been introduced as a coating for NaTi2(PO4)(3) through a high-energy ballmilling process. When an excessive coating was applied, no redox reactions from the NaTi2(PO4)(3) were visible due to the poor Na+ diffusion through the polypyrrole. However, the as-coated composites containing 5 wt% polypyrrole showed much better capacity retention compared to the uncoated material, retaining 57% of the initial discharge capacity after 50 cycles compared to the uncoated material, which retained only 10% of the initial discharge capacity. It is concluded that coating NaTi2(PO4)(3) with conducting polymers can be an effective strategy for promoting battery lifetime. (C) The Author(s) 2015. Published by ECS. All rights reserved.