Unprecedented Dual Role of Polyaniline for Enhanced Pseudocapacitance of Cobalt-Iron Layered Double Hydroxide.

Creating nanosized pores in layered materials can increase the abundant active surface area and boost potential applications of energy storage devices. Herein, a unique synthetic strategy based on polyaniline (PANI) doped 2D cobalt-iron layered double hydroxide (CoFe-LDH/P) nanomaterials are designed, and the formation of pores at low temperature (80 °C) is developed. It is found that the optimized concentration of PANI creates the nanopores on the CoFe-LDH nanosheets among all other polymers. The well-ordered pores of CoFe-LDH/P allow the high accessibility of the redox-active sites and promote effective ion diffusion. The optimized CoFe-LDH/P2 cathode reveals a specific capacitance 1686 (1096 Cg -1 ) and 1200 Fg -1 (720 Cg -1 ) at 1 and 30 Ag -1 respectively, a high rate capability (71.2%), and a long cycle life (98% over 10 000 cycles) for supercapacitor applications. Charge storage analysis suggests that the CoFe-LDH/P2 electrode displays a capacitive-type storage mechanism (69% capacitive at 1 mV s -1 ). Moreover, an asymmetric aqueous supercapacitor (CoFe-LDH/P2//AC) is fabricated, delivering excellent energy density (75.9 Wh kg -1 at 1124 W kg -1 ) with outstanding stability (97.5%) over 10 000 cycles. This work opens a new avenue for designing porous 2D materials at low temperature for aqueous energy storage devices.