Brown seaweed-derived high-performance electrode prepared using DES as green solvent to serve as effective cathode in aqueous Zn-ion battery

In this study, we present a sustainable and cost-effective method for synthesizing a composite directly from brown seaweed Sargassum tenerrimum (SAR) along with a green solvent eutectic mixture. This innovative process resulted in the creation of β-MnO₂ integrated with carbon sourced from SAR, marking its inaugural application. The efficient conversion of seaweed into mesoporous β-MnO₂@SARC was accomplished through a direct pyrolysis technique performed under inert atmospheric conditions at various temperature ranges (700 °C–900 °C). Initially, granules of seaweed were utilized as the primary raw material, while a eutectic mixture formed from urea and manganese acetate was used as both the precursor and catalyst for the large-scale and straightforward fabrication of β-MnO₂@SARC (M-SARC) composites. These composites, designated as M-SARC@900 °C, M-SARC@ 800 °C, and M-SARC@700 °C, were specifically designed as manganese-based cathodes, optimized for use in aqueous Zinc ion batteries (AZIBs). In a coin cell configuration, the AZIB constructed with M-SARC @ 900 °C demonstrated an impressive specific capacity of 159 mAh/g (at 0.1 A/g), showcasing remarkable charge-storage efficiency. It also exhibited exceptional long-term stability, retaining 95 % of its capacity after 5000 charge-discharge cycles at 1 A/g, in contrast to M-SARC@800 °C and M-SARC@700 °C. Furthermore, the zinc-storage mechanism in the M-SARC@900 °C composite was comprehensively examined and analyzed through kinetic studies. This research ultimately lays the groundwork for the advancement of affordable and high-performance cathode materials for aqueous ZIBs.