High-Energy Aqueous Ammonium-Ion Hybrid Supercapacitors.

Chen, Qiang; Jin, Jialun; Song, Mengda; Zhang, Xiangyong; Li, Hang; Zhang, Jianli; Hou, Guangya; Tang, Yiping et al. · Adv Mater · 2022

basic_science · Level V

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Abstract

The development of novel electrochemical energy storage devices is a grand challenge. Here, an aqueous ammonium-ion hybrid supercapacitor (A-HSC), consisting of a layered δ-MnO<sub>2</sub> based cathode, an activated carbon cloth anode, and an aqueous (NH<sub>4</sub> )<sub>2</sub> SO<sub>4</sub> electrolyte is developed. The aqueous A-HSC demonstrates an ultrahigh areal capacitance of 1550 mF cm<sup>-2</sup> with a wide voltage window of 2.0 V. An amenable peak areal energy density (861.2 μWh cm<sup>-2</sup> ) and a decent capacitance retention (72.2% after 5000 cycles) are also achieved, surpassing traditional metal-ion hybrid supercapacitors. Ex situ characterizations reveal that NH<sub>4</sub> <sup>+</sup> intercalation/deintercalation in the layered δ-MnO<sub>2</sub> is accompanied by hydrogen bond formation/breaking. This work proposes a new paradigm for electrochemical energy storage.