Ligand-mediated manganese phosphonates with a variable morphological framework: efficient for energy storage application

Abstract

The current work focuses on the efficient method of employing multiple organophosphorus ligands to produce distinct morphological forms in manganese phosphonates. Also, it offers insight into the electrochemical performance of various structural architecture outcomes. Different morphologies, such as sheet-like layered, aggregated flakes, needle, and sphere structures, have resulted from implementing distinct organic ligands. The as-synthesized microporous phosphonates (MnBPA, MnPPA, MnDPA, and MnNAPH) have been thoroughly characterized, which signifies the proper incorporation of the organic ligands in the hybrid framework. The electrochemical performance in an alkaline medium has also been examined in a wide voltage window of 1 V. The regular microporous nature and large surface area, which facilitate faster ionic transport, display a maximum capacitance of 846 F g⁻¹ for MnBPA compared to other as-prepared electrode materials. A striking energy density (E.D.) of 156.6 W h kg⁻¹ and a power density (P.D.) of 1658 W kg⁻¹ were achieved by an asymmetric coin cell device using the best electrode MnBPA as the cathode component. Furthermore, moving toward contemporary technology, an asymmetric in-plane interdigital structured flexible micro-supercapacitor was fabricated using an inexpensive vacuum filtration technique. The strategically designed interdigital structure, which was used as a customized mask, effectively reduces the ion-diffusion path, resulting in a high areal capacitance of 105.2 mF cm⁻².