All-gel Proton-conducting Batteries with BiOCl and VOSO₄ as Active Materials

Flexible, scalable, and low-cost energy storage solutions are required for the widespread use of renewable energy and the mitigation of climate change. State-of-the-art lithium-ion batteries provide high specific energy density; however, designing a safe and cost-effective grid-scale lithium-ion battery is still a major challenge. Redox flow batteries are scalable due to their ability to decouple power and energy; however, the commercial applications of these batteries are limited because of expensive ion-selective membranes. In this paper, we report a modified battery design approach in which Bi/BiOCl and V4+/V5+ reaction-based redox couples are utilized while employing a gel-based architecture. We show, for the first time, that Bi/BiOCl conversion reaction based redox couple can reversibly work against traditional vanadium-based redox pair in an aqueous electrolyte. Redox active materials in this cell design are in the gel form, and a traditional membrane or a separator is not required. This proof-of-concept battery delivers 0.9 V with a volumetric energy density of 22.14 Wh/L.