Facile preparation of high-performance cobalt–manganese layered double hydroxide/polypyrrole composite for battery-type asymmetric supercapacitors

Cobalt–manganese layered double hydroxide/polypyrrole (CoMn LDH/PPy) composites were synthesized via facial in situ polymerization. Composites with an LDH/PPy mass ratio of 125:40 possess simultaneous enhancement in specific capacity (220 mA h g−1 at 2.5 A g−1), rate capability (71.2% retention at 10 A g−1), and cycling performance (97.4% retention after 2000 cycles). The strong electrochemical performance of CoMn LDH/PPy results from synergistic effects of spacing from conductive PPy particles and confinement from CoMn LDH layers. Electrochemical kinetics analysis indicates that the composite is more like a battery-type material. Finally, an asymmetric supercapacitor (ASC) was assembled using CoMn LDH/PPy as the positive electrode and multilayer graphene as the negative electrode. The ASC device with a potential of 1.53 V reaches an energy density of 29.6 Wh kg−1 at the power density of 0.5 kW kg−1. These favorable characteristics demonstrate that CoMn LDH/PPy is a promising battery-type electrode material for energy storage devices.