Transition-Metal-Substituted Nanoporous Manganese Ferrites Mn<sub>0.95</sub>M<sub>0.05</sub>Fe<sub>2</sub>O<sub>4</sub> (M: Co, Cu, and Zn) as Electrode Materials for High-Performance Supercapacitors in Redox-Active Nonaqueous Electrolytes
Arun Kumar, Bhisma Narayan Mahanty, Anuj Rawat, Raeesh Muhammad, Rajib Kumar Panigrahi, Debabrata Pradhan, Paritosh Mohanty
Abstract
Transition-metal-substituted manganese ferrites, Mn 0.95 M 0.05 Fe 2 O 4 (M: Co, Cu, and Zn), synthesized by the combustion method exhibit a single-phase cubic spinel structure. A maximum specific surface area (SA BET ) of 125 m 2 g –1 and a controlled pore size distribution (1.0 and 3.6 nm) and pore volume (0.17 cm 3 g –1 ) were estimated for Mn 0.95 Zn 0.05 Fe 2 O 4 . All of these ferrites are used as active electrode materials for electrochemical supercapacitor applications. The best specific capacitance ( C sp ) and areal capacitance ( C ar ) in nonaqueous electrolytes, i.e., 0.1 M lithium perchlorate/propylene carbonate (LiClO 4 /PC), were estimated for Mn 0.95 Zn 0.05 Fe 2 O 4 . Further, in order to understand the effect of redox additive electrolytes, the C sp and C ar for Mn 0.95 Zn 0.05 Fe 2 O 4 were measured in 0.1 M lithium perchlorate/propylene carbonate/tetraethylammonium tetrafluoroborate/potassium iodide (LiClO 4 /PC/TEA-BF 4 /KI) along with non-redox-active electrolytes (LiClO 4 /PC). The electrodes were fabricated using Mn 0.95 Zn 0.05 Fe 2 O 4 with optimized mass and exhibited high C sp and C ar of 829 F g –1 and 1277 mF cm –2, respectively, in a redox-active electrolyte as compared to lower values of 452 F g –1 and 696 mF cm –2, respectively, at 1 mV s –1, in a non-redox-active electrolyte. A symmetric pouch cell supercapacitor device (SPCSDR) fabricated using Mn 0.95 Zn 0.05 Fe 2 O 4 with a redox-active electrolyte (LiClO 4 /PC/TEA-BF 4 /KI) provides high energy ( E ) and power ( P ) densities of 77.5 W h kg –1 and 900 W kg –1, respectively, at 0.5 A g –1 . The SPCSDR has demonstrated stability up to 8000 charge–discharge cycles with an initial C sp retention of ∼80% and high Coulombic efficiencies of ∼97–100%, at 2 A g –1 .