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 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 battery 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.