Construction of Cationic Vacancy-Rich Mulberry-Like MnCo<sub>2</sub>O<sub>4.5</sub> Nanostructures with High Surface Area for High-Performance Hybrid Supercapacitors
K. Prasad, Thupakula Venkata Madhukar Sreekanth, Kisoo Yoo, Jonghoon Kim
Abstract
Incorporating cationic vacancies into high surface area mesoporous structured materials is a viable strategy for improving the electrochemical performance of electrochemical energy storage/conversion devices. We successfully developed a mesoporous mulberry-like MnCo 2 O 4.5 (MCO–DMF) with cation metal vacancies via a solvothermal route using dimethylformamide (DMF) as the solvent. The large surface area of the mulberry-like morphology offers numerous electroactive sites and a high permeation of electrolyte ions, giving rise to an excellent electrochemical performance. For comparison, spheres like MnCo 2 O 4.5 (MCO-IPA) were prepared without cationic vacancies using isopropyl alcohol (IPA) as a solvent. The cationic vacancies (Mn) in MCO–DMF were identified by employing various analytical techniques such as energy-dispersive X-ray spectroscopy, scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy. The cation vacancies accelerated the charge transfer kinetics over the electrode–electrolyte interface in MCO–DMF with abundant electroactive sites. In the backdrop of supercapacitor application, the MCO–DMF electrode established a high specific capacity of 628.2 C g –1 at 0.75 A g –1 than the MCO-IPA electrode (380.6 C g –1 ) with a greater cycling performance of 95.1% retention at 5 A g –1 after 10,000 cycles. The MCO–DMF||AC hybrid supercapacitor (HSC) device exhibited a specific capacity of 165.5 C g –1 at 0.75 A g –1 within a potential window of 0.0–1.5 V. The HSC device also has a noteworthy energy and power densities of 58.5 Wh kg –1 and 1026.7 W kg –1, respectively, with a remarkable cycle stability of 91.4% capacity retention after 10,000 cycles.