A flexible and high voltage symmetric supercapacitor based on hybrid configuration of cobalt hexacyanoferrate/reduced graphene oxide hydrogels

Flexible solid-state supercapacitor (FSSC) holds great promise as power source to supply the next generation of portable and wearable electronics. Assembling asymmetric supercapacitor constructed with broadening cell voltage (V) is the promising way to increase the energy density. However, the imparity reaction kinetics between EDLC and pseudocapacitive materials will further lead to inferior power density. Hence, to pursue higher working voltage and energy density, a hybrid configuration of cobalt hexacyanoferrate/reduced graphene oxide hydrogels (PB-Co/rGOH) is prepared through a one-pot hydrothermal method. With highly interconnected 3D network structure, excellent mechanical robustness and the synergistic effects between the graphene and PB-Co, the resultant PB-Co/rGOH exhibits a high specific capacitance of 220 F g−1 and well cycle stability (83% capacitance retention after 10,000 cycles at 5 A g−1). Moreover, the assembled PB-Co/rGOH//PB-Co/rGOH symmetric flexibly solid-state supercapacitor exhibits an amazing higher working voltage of 2.0 V and a remarkable energy density of 57.5 Wh kg−1, which is comparable with that of Ni/MH batteries (60–120 Wh kg−1). These excellent electrochemical performances of the hybrid electrode provide a rational design strategy for developing supercapacitors with high energy density.