Redox Targeting of Prussian Blue: Toward Low-Cost and High Energy Density Redox Flow Battery and Solar Rechargeable Battery

The ever-increasing penetration of solar energy demands high energy density, safe and affordable energy storage systems. We demonstrated a redox flow battery on the basis of the redox targeting reactions of a bifunctional redox mediator – ethyl viologen diiodide (EVI2) with a low-cost pigment material – Prussian blue (PB). Sharing the same I–/I3– based electrolyte, this new battery system can be feasibly integrated with a dye-sensitized TiO2 photoelectrode for photoassisted charging process. The introduction of PB not only increases the energy density up to 117 Wh/L with good cycling performance and capacity retention, also instantaneously regenerates I– ensuring a stable I–/I3– concentration which is crucial to the operation of the photoelectrode. We anticipate that the work presented here may open an intriguing and credible way for the development of integrated all-in-one solar energy conversion and storage devices for large-scale applications.