Electrodeposited manganese oxide supercapacitor microelectrodes with enhanced performance in neutral aqueous electrolyte

• Published in: Electrochimica acta Vol. 335; p. 135564
• Main Authors: Tran, C.C.H., Santos-Peña, J., Damas, C.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.03.2020; Elsevier BV; Elsevier
• Subjects: Activated carbon; Aluminum oxide; Aqueous electrolytes; Carbonaceous materials; Chemical Sciences; Electrodeposition; Electrodes; Electrolytic cells; Flux density; Inorganic chemistry; Manganese dioxide; Manganese oxide; Manganese oxides; Material chemistry; Microelectrodes; Microsupercapacitors; Nanowires; Nickel nanowires; or physical chemistry; Performance enhancement; Sodium sulfate; Theoretical and; Time constant; Microelectrodes; Electrodeposition; Nickel nanowires; Manganese oxide; Microsupercapacitors
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2019.135564

1.6–4 μm thick microelectrodes of manganese oxide MnO2 were produced by electrolytic deposition on nickel nanowires Ninw previously electrodeposited on Anodized Aluminium Oxide (AAO). MnO2/Ninw electrodes prepared under optimized pressure, obtained by application of a torque of 0.2–1.5 N m between the electrolytic cell blocks, show significant electrochemical capacities without addition of conductive additive or binder and can compete with current microsupercapacitor electrodes. Thus, MnO2/Ninw microelectrodes provide a large and reproducible capacitance of 51.8 mF cm−2 (per MnO2 electrode surface) at a scan rate of 200 mV s−1 in a three-electrode configuration in neutral aqueous 0.5 M Na2SO4. Time constant for the electrochemical process is in the 1.4–2.0 s range, which compares quite well with other microelectrodes. After 3400 cycles, two-electrode devices containing activated carbon negative electrode provide a capacity of 12.76 mF cm−2 and an energy density of 4.17 μWh·cm−2 per total surface area of both electrodes at a cycling rate of 0.05 A g−1 per MnO2 electrode mass which turns into a power density of 3.75 μW cm−2 per total surface of an electrode. Ragone plot shows a high energy density of 5.4 Wh·kg−1 (2.14 μWh·cm−2) for a power exceeding 0.7 kWh·kg−1 (0.31 mW cm−2). These results are, overall, significantly higher than those found in the literature for symmetrical or asymmetric devices based on manganese oxide (with or without carbonaceous materials), and even comparable with some 3D microdevices. •A reliable, fast and cost-saving method for the preparation of supercapacitor manganese oxide microelectrodes without conductive or binder additives is reported.•2D AC/MnO2 devices working in non-corrosive electrolytic solution provide a long-term capacity of 12.76 mF cm−2 and an energy density of 4.17 μWh·cm−2 per total surface area of both electrodes at a power density of 3.75 μW cm−2 per total surface of an electrode.•2D AC/MnO2 devices furnish an energy density of 5.4 Wh·kg−1 (2.14 μWh·cm−2) for a power exceeding 0.7 kWh·kg−1 (0.31 mW cm−2).•The energetic parameters provided by these new devices exceed that of several micro-supercapacitors working in aqueous solutions and approach those obtained with expensive 3D configurations or ionic liquid electrolytes.