Ultrafast, long-life, high-loading, and wide-temperature zinc ion supercapacitors

Abstract

Aqueous zinc ion capacitors (ZICs) are promising for electric vehicles and stationary grid storage. To meet extreme needs, we here developed ZICs working under harsh conditions including ultrafast rates, sub-million cycles, high loadings, and wide temperatures through the incorporation of activated carbon (AC), aqueous binder, and concentrated electrolyte. AC exhibits large surface area, hierarchical porous structures, and abundant heteroatom dopants, aqueous binder enhances electrode-electrolyte wettability enabling high-mass-loading electrode, and concentrated electrolyte gives high Zn stripping/plating efficiency, high ionic conductivity as well as suppressed hydrogen bonding interaction in water realizing ultralow frozen temperature. Three keys combined unlock unprecedented ZICs with a large capacitance of 436 F g−1 (capacity: 200 mAh g−1), ultrahigh rate up to 200 Ag−1, ultralong cycles (0.3 million), ultrahigh loadings (10 mg cm−2) under lean electrolyte (8.8 µL mg−1), and wide-temperature operation (-60∼60 °C), leading to a maximal energy density of 134.8 Wh kg−1 and power density of 118.4 kW kg−1. A proton/Zn2+ ion co-interaction mechanism was revealed in the AC electrode. With low cost and extreme functionalities, this work opens an avenue towards practical supercapacitors beyond normal conditions.