(Digital Presentation) Aqueous Zn Batteries and Capacitors Working Under Extreme Conditions

Abstract

Aqueous zinc-based energy storage devices hold great promise for grid-level energy storage yet are challenged by dendritic growth and low Coulombic efficiency under both normal and extreme conditions. In the past years, we have developed Zn batteries and capacitors working under extreme conditions through engineering electrode, electrolyte, and binder. The first project is the development of Zn-free polymer anode that enables ultrafast rates (100 A g-1), ultralong life (1 million cycles), and ultrahigh-loadings (50 mg cm-2) through DFT calculation, polymer preparation, and electrolyte optimization. The optimal polymer possesses suitable electronic structure and a large π-conjugated structure and its storage mechanism involves reversible Zn2+/proton co-storage at the carbonyl site. The polymer-based full cells demonstrate ultrahigh power densities and ultralong lifespans, far surpassing those of corresponding Zn-metal-based devices. The second project is the making of ultrafast, stable, high-loading and wide-temperature zinc ion supercapacitors 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.