Tannic acid-polypyrrole multifunctional coating layer enhancing the interface effect and efficient Li-ion transport of a phosphorus anode.

Phosphorus has been considered a promising anode material for lithium-ion batteries because of its high specific capacity of 2596 mA h g and safe lithiation voltage of 0.7 V. However, the practical application of the phosphorus anode is challenged by its poor cyclability associated with the dissolution of phosphorus intermediates, the enormous volume expansion and the sluggish lithiation reaction kinetics during the cycling process. Herein, a multifunctional coating layer is designed and fabricated on the surface of a phosphorus-carbon nanotube (P-CNT) electrode the facile polymerization of plant-derived tannic acid (TA) and pyrrole (Py). This coating layer shows strong adsorption of phosphorus and its derivatives, buffers the volumetric expansion of phosphorus and facilitates efficient Li-ion transport, thus enhancing phosphorus utilization during the cycling process. As a result, the P-CNT@TA-PPy hybrid exhibits a stable coulombic efficiency of 99.0% at 520 mA g after 100 cycles and a reduced volumetric expansion of 50% at 260 mA g, superior to P-CNT with its unstable coulombic efficiency and large electrode expansion of 329%. This study sheds light on the rational design of advanced phosphorus-based anodes for alkali metal-ion batteries.