Porous, one-dimensional and high aspect ratio nanofibric network of cobalt manganese oxide as a high performance material for aqueous and solid-state supercapacitor (2 V)

Porous nanofibric network of spinel CoMn₂O₄ (CMO) are fabricated by facile electrospinning process and characterized by XRD, BET, TGA, FTIR, FESEM, TEM, XPS techniques. CMO nanofibers are employed as supercapacitor electrode for first time which exhibits high specific capacitance (C_s) of 320(±5) F g⁻¹ and 270(±5) F g⁻¹ at 1 A g⁻¹ and 5 A g⁻¹, respectively in 1 M H₂SO₄. CMO nanofibers exhibit excellent cyclability (till 10,000 cycles @ 5 A g⁻¹). To examine practical performance, solid-state symmetric supercapacitor (SSSC) is also fabricated using PVA-H₂SO₄ as gel electrolyte. The SSSC evinces high energy density of 75 W h kg⁻¹ (comparable to Pb-acid and Ni-MH battery) along with high power density of 2 kW kg⁻¹. Furthermore, a red colored LED (1.8 V @ current 20 mA) was lit for 5 min using single SSSC device supporting its output voltage of 2 V. This high performance of CMO in both aqueous and SSSC is attributed to one dimensional nanofibers consisting of voids/gaps with minimum inter-particle resistance that facilitates smoother transportation of electrons/ions. These voids/gaps in CMO (structural as well as morphological) act as intercalation/de-intercalation sites for extra storage performance, and also works as buffering space to accommodate stress/strain produced while long term cyclings.