Overcoming the Technical Challenges in Al Anode–Based Electrochromic Energy Storage Windows

Abstract A new variant of electrochromic energy storage (EES) windows is introduced recently by pairing an electrochromic cathode with an Al anode. Electrochromism in this case is driven by the built‐in potential difference and chemical recharging (via oxidation by O 2 or H 2 O 2 ) without the need for an external power source. However, the Al anode–based EES windows are adversely affected by the irreversibility of the Al anode reaction, the inconvenience of chemical recharging, and a short cycle life. An electrically rechargeable alternative based on a prelithiated Al anode and a WO 3 −x cathode is presented here, which not only overcomes the operational difficulties of Al anode–based EES windows, but also allows for spectrally selective modulation of visible light and near‐infrared and efficient energy recycling. This dual‐band electrochromic energy storage (DEES) window upon assembly is able to self‐colorize by its high built‐in cell voltage (≈2.59 V) without any energy input, and to recycle a large fraction of the energy consumed in the bleaching operation. The DEES window, with its impressive dual‐band electrochromic performance and low energy consumption in a round‐trip electrochromic operation, can be an energy‐saving technology for buildings.