title: Nano "Koosh Balls" of Mesoporous MnO2: Improved Supercapacitor Performance through Superior Ion Transport.
abstract: Manganese dioxide nanomaterials with "Koosh-ball"-like morphology (MnO2-KBs) as well as worm-like nanotubes (MnO2-NWs) are obtained by employing Tween 20 as the reducing and structure-directing agent, and KMnO4as a MnO2precursor. Whereas the MnO2-KBs are interconnected through tubular extensions, the MnO2-NWs are largely disconnected. Both MnO2-KBs and MnO2-NWs have large BET surface areas (>200 m2g-1), and are thermally robust up to 300 °C. Electrochemical studies reveal that the highest specific capacitance (Csp) obtained for MnO2-KBs (272 F g-1) is significantly higher than that of MnO2-NWs (129 F g-1). The Cspvalues correlate well with the electroactive surface areas of the materials: MnO2-KBs have a significantly higher electrolyte-accessible surface area. Electrochemical impedance spectroscopy (EIS) reveals a higher electron-transfer rate at the electrode/electrolyte interface for MnO2-KBs than for MnO2-NWs. The multiple tubular interconnections between individual MnO2-KBs allow improved ion penetration and act as conduits for their propagation, shortening the diffusion distances of the ions from external electrolytes to the interior of the MnO2framework. Thus, this work exemplifies the importance of interconnections for enhancing the electrochemical performance of nanomaterials employed for energy storage.
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal-Bypass Road, Bhauri, Bhopal, 462066, Madhya Pradesh, India.
authors.forename: Qysar
authors.initials: Q
authors.lastname: Maqbool
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal-Bypass Road, Bhauri, Bhopal, 462066, Madhya Pradesh, India.
authors.forename: Chanderpratap
authors.initials: C
authors.lastname: Singh
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal-Bypass Road, Bhauri, Bhopal, 462066, Madhya Pradesh, India.
authors.forename: Priyajit
authors.initials: P
authors.lastname: Jash
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal-Bypass Road, Bhauri, Bhopal, 462066, Madhya Pradesh, India.
authors.forename: Amit
authors.initials: A
authors.lastname: Paul
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal-Bypass Road, Bhauri, Bhopal, 462066, Madhya Pradesh, India.
authors.forename: Aasheesh
authors.initials: A
authors.lastname: Srivastava
keywords: electrochemistry; interconnected MnO2; ion transport; nanostructures; supercapacitors