NiFe2O4 nanocubes anchored on reduced graphene oxide cryogel to achieve a 1.8 V flexible solid-state symmetric supercapacitor.

Highlight • A two-step hydrothermal strategy is adopted to transform Ni 3 [Fe(CN) 6 ] 2 to NiFe 2 O 4. • NiFe 2 O 4 @rGO slice is prepared as electrode for flexible symmetric supercapacitor. • NiFe 2 O 4 @rGO electrode shows excellent specific capacitance and cycling stability. Abstract A high working voltage and specific capacitance are vital for flexible solid-state symmetric supercapacitor (FSSC) devices to achieve decent energy densities with high power. In this paper, we report a 1.8 V FSSC based on NiFe 2 O 4 nanocubes anchored on reduced graphene oxide (rGO) cryogel electrode. Through surface protection by a free-standing three-dimensional cross-linked network structure, NiFe 2 O 4 converted from Ni 3 [Fe(CN) 6 ] 2 inhibits the original nanocube structure. Benefiting from the synergistic effects between NiFe 2 O 4 nanocubes and graphene nanosheets, the newly synthesized NiFe 2 O 4 @rGO hybrid electrode delivers a high charge storage capacity (488 F g−1 at a constant current density of 1 A g−1), excellent rate ability and cycling performance (89.8% of the initial capacitance value after 10,000 cycles). In addition, NiFe 2 O 4 @rGO FSSC has been assembled and exhibits stable behavior at bend state, as well as high energy density of 62.5 Wh kg−1, and long cycle life (93.2% of the initial capacitance value after 6000 cycles). The proposed strategy for controlling the design and synthesis of NiFe 2 O 4 @rGO nanostructures provides promise for the development of high performance electrode in advanced energy storage devices. [ABSTRACT FROM AUTHOR]