Oxygen defect enriched hematite nanorods @ reduced graphene oxide core-sheath fiber for superior flexible asymmetric...

The development of flexible asymmetric supercapacitors with high operating potential, superior energy density, and exceptional rate performance holds significant implications for the advancement of flexible electronics. Herein, oxygen-deficient hematite nanorods @ reduced graphene oxide (Fe₂O_3-x@RGO) core-sheath fiber was rationally designed and fabricated. The introduction of oxygen defects can simultaneously enhance the conductivity, create a mesoporous crystalline structure, increase active surface area and sites. This leads to a significantly improved electrochemical performance, exhibiting a high specific capacitance of 525.2F cm^-3 at 5 mV s^-1 and remarkable rate capability (53.7 % retention from 5 to 100 mV s^-1). Additionally, a flexible asymmetric supercapacitor was assembled employing Fe₂O_3-x@RGO fibers as anode and MnO₂/RGO fibers as cathode. This design achieved a maximum operating voltage of 2.35 V, high energy density of 71.4 mWh cm^-3, and outstanding cycling stability with 97.1 % retention after 5000 cycles. This study proposes a straightforward and efficient strategy to substantially enhance the electrochemical performances of transition metal oxide anodes, thereby promoting their practical application in asymmetric supercapacitors.