Energy Density Boosted Vanadium Colloid Flow Batteries Realized by a Reversible Nanoparticle Suspension‐Dissolution Strategy

Abstract Vanadium redox flow batteries (VRFBs) hold great promise for large‐scale energy storage, but their performance requires further improvement. Herein, a design is proposed for vanadium colloid flow batteries (VCFBs) that integrates the redox chemistry of polyvalent vanadium‐based colloid suspensions with dispersed conductive agents into traditional vanadium electrolytes. The redox‐active colloids combine the advantages of nanoparticle suspensions and dissolved electrolytes, exhibiting good dispersibility, fluidity, conductivity, redox reversibility, and electrochemical kinetics. By leveraging a reversible dissolution/suspension process of high‐concentration vanadium‐based colloids, the VCFBs achieved an energy density of 48 Wh L −1 , nearly double that of conventional VRFBs. This work presents a rational design for homologous active material colloids to enhance the energy density of aqueous redox flow batteries, thereby advancing the potential for grid‐scale and renewable energy storage.