A Novel Layered WO₃ Derived from An Ion Etching Engineering for Ultrafast Proton Storage in Frozen Electrolyte

Aqueous proton batteries/pseudocapacitors are promising candidates for next-generation electrochemical energy storage. However, their development is impeded by the lack of suitable electrode materials that facilitate rapid transport and storage of protons. Herein, an open-layered hydrous tungsten oxide (WO3 center dot nH(2)O) with larger layer spacing from Aurivillius Bi2WO6 via ion etching is proposed. Particularly, the WO3 center dot nH(2)O electrode possesses a unique multi-level nanostructure and presents superior rate performance (254 F g(-1) at 1000 mV s(-1), surpassing most carbon-based electrode materials known). In situ X-ray Diffraction combined with crystallography study demonstrate that the open layered structure with negligible structural strain enables fast and reversible (de)intercalation of protons during electrochemical reaction. Furthermore, a full proton pseudocapacitor (Prussian blue analogues//WO3 center dot nH(2)O) operating in a wide temperature range from -40 to 25 degrees C is fabricated. This device can deliver 70% of the room-temperature capacitance and stably cycle with negligible capacitance fading over 5000 cycles even in the solid-phase electrolyte at -20 degrees C. This study provides a valuable strategy to design electrode materials with layered structures for the development of high-performance aqueous proton batteries/pseudocapacitors at low temperatures.