Zhixiao Xu1,Xiaolei Wang1
University of Alberta1
Zhixiao Xu1,Xiaolei Wang1
University of Alberta1
Aqueous energy storage devices require highly reversible Zn electrodes, but this has been impeded by challenges including dendrite growth, low efficiency, hydrogen evolution, and metal corrosion. Here, we report reversible Zn powder electrodes for aqueous batteries and supercapacitors. In the first part, through thermal reduction of spent anode in alkaline batteries, Zn powder anode was regenerated, which shows super-zincophilicity and low overpotentials even under fast rates (8 mA cm<sup>−2</sup>) and high depth-of-discharge (50 %), resulting from coating of hydroxyl-rich organic layer with abundant nucleation sites as well as high orientation of favorable (002) plane and induced horizontal plating behavior. On the other hand, through thermal oxidation, spent MnO<sub>2</sub>-based cathode was also regenerated to pair with the regenerated Zn powder anode. Under a low negative-to-positive (N/P) ratio of 3.8 and high loading of ~10 mg cm<sup>−2</sup>, the regenerated full cell demonstrates high energy and power densities (94 Wh kg<sup>−1</sup>, 1349 W kg<sup>−1</sup>), holding potential for practical applications. In the second part, guided by theoretical calculation, we further fabricated Zn powder anodes <i>via</i> engineering the growth of zinc crystals in different solvents. Theoretical calculations demonstrate that the adsorption energy gap of different solvents on the (002) or (100) facet of Zn metal varies and that a larger energy gap favors a higher orientation of Zn (002) plane. Highly oriented Zn (002) powder exhibits horizontal deposition, corrosion resistance, faster kinetics and longer life under deep discharge (60%) in symmetric cells compared with less oriented Zn. Under practical conditions including low N/P ratios (1-3), high-loading cathodes (10-18 mg cm<sup>-2</sup>), and lean electrolyte (5-9 µL mg<sup>-1</sup>), highly (002)-oriented Zn powder-based batteries and supercapacitors demonstrate large capacity (~3 mAh cm<sup>-2</sup>) and energy/power density (108 Wh kg<sup>-1</sup>/2317 W kg<sup>-1</sup>), showing promise for practical use.