Towards eco-friendly redox flow batteries with all bio-sourced cell components

Recent research and few pilot deployments have demonstrated promising aqueous organic redox flow battery (RFB) systems. However, the claim that these organic RFB systems are eco-friendlier energy storage than Lithium-ion batteries and aqueous inorganic metallic RFB counterparts needs reinforcement, primarily if cell components other than redox-active species are still based on unsustainable materials. This thesis of the present work presents the prospects of achieving future eco-friendly RFBs with higher consideration for sustainability by adopting significant amounts of abundant bio-sourced/based materials for all main cell components. As we highlight the promising sources of the energy materials from a review of previous studies, we infer that plant derived quinones and other organic polymers may continue to dominate the organic redox-active species space. Furthermore, a candidate methodology to accomplish porous electrodes and membranes/separators of the eco-friendly RFBs is to apply stand-alone bio-based/sourced fibrils derived from cellulose, lignin, chitin, among other materials. These materials can be combined with (un)carbonised biomass or food wastes & residues to impart conductivity, catalytic activity, and ion selectivity. We explore symmetric chemistry as an ideal system for the eco-friendly RFBs of the discourse, given interplay between the electrolyte, electrode material and membrane dictates energy efficiency and cycling stability. These strategies also need to be coupled with further improvements to achieve reliability.

Automated summary

Recent research suggests promising prospects for aqueous organic redox flow battery (RFB) systems, which can be more environmentally friendly by adopting sustainable materials. Plant-derived substances and bio-based fibers derived from cellulose, lignin, chitin, and other materials may be the dominant sources of organic redox-active species. Applying these materials to achieve eco-friendly electrodes and membranes can improve conductivity, catalytic activity, and ion selectivity.