BIAN-based durable polymer metal complex as a cathode material for Li–O2 battery applications

Abstract

Among several strategies employed to reduce overpotential and achieve reliable reversibility with Li–O2 batteries, the use of atomically dispersed bifunctional carbon catalysts is very attractive. However, most of the methods used to prepare these bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts require high temperatures and exhibit low yields, and it is therefore difficult to predetermine the active sites qualitatively and quantitatively. Here, we propose the use of atomically dispersed metal centers coordinated to diimine moieties of conjugated polymers as bifunctional catalysts without further modification (pyrolysis or composite formation) for Li–O2 battery applications. Poly(bisiminoacenaphthenequinone) (BIAN) iron complex (BP-Fe) catalysts showed high OER activities, which enabled 100% coulombic efficiency for 160 galvanostatic charge discharge cycles with a capacity limit of 500 mAh/g at a current density of 250 mA/g. The overpotential corresponding to charging was as low as ~1.0 V and exhibited almost no change in discharge overpotential across 160 cycles. Additionally, it showed a commendable rate capability with only a 170 mV increase in charge overpotential when the charge‒discharge rate was increased from 100 to 500 mA/g.