The project has delivered results that clearly advance the state of the art in organic redox‑flow batteries and metal‑free electrolytes. Most existing organic flow‑battery systems require strict exclusion of oxygen and avoid molecular association, because dimerisation has been linked to capacity fade. In contrast, this project shows that associative, fully organic bis‑pyridinium electrolytes can be engineered to self‑assemble in solution and that this association can be harnessed to protect against oxygen, enabling stable operation in air. This overturns prevailing assumptions that organic electrolytes must be run under air‑free conditions and that association is necessarily detrimental to performance.
The optimised APE structures combine metal‑free composition, aqueous and near‑neutral pH operation, and tunable redox properties in a single platform. We demonstrate that these electrolytes can be synthesised on the multi‑10‑gram scale with reduced catalyst loadings and more efficient use of key reagents, indicating compatibility with future industrial production rather than remaining a purely academic curiosity. On the device side, long‑term cycling in flow‑cell hardware—with per‑cycle stability greater than 99.99%, low crossover and stable operation under exposure to air—shows that APE‑based systems can match or surpass the durability benchmarks of vanadium and other metal‑based technologies, while potentially offering advantages in safety and sustainability.
The potential impacts are substantial. If developed to industrial scale, APE electrolytes could enable lower‑cost, safer and more sustainable stationary energy storage, supporting higher penetrations of renewables and facilitating deployment in settings with weaker infrastructure or challenging environmental conditions. Because the chemistry avoids critical metals and uses precursors that can be sourced and manufactured in many regions, the technology also supports more resilient and geopolitically robust energy systems.
For further uptake and success, several needs have been identified. Additional research and demonstration at larger scale are required, in particular construction and testing of higher‑capacity demonstrators (100 Wh and beyond) and deeper study of long‑term degradation mechanisms and regeneration strategies. Access to markets and finance will be essential to support scale‑up of electrolyte production and integration into commercial flow‑battery products, alongside continued engagement with manufacturers and project developers. Ongoing commercialisation and IPR support are needed to consolidate the patent position, structure partnerships and licensing agreements, and refine the business model of the spin‑out company. As the technology matures, engagement with relevant standards and regulatory frameworks for grid‑scale storage will help ensure efficient deployment and formal recognition of safety and environmental benefits.
In summary, the project has: (i) established a scalable, cost‑aware synthetic route to associative, metal‑free bis‑pyridinium electrolytes; (ii) demonstrated long‑term, air‑stable operation of these electrolytes in aqueous flow‑battery hardware with very high per‑cycle stability and low crossover; and (iii) defined a credible commercial pathway, including creation and initial funding of a spin‑out, to advance this electrolyte platform towards real‑world deployment in stationary energy storage.
