High‐Energy Aqueous Ammonium‐Ion Hybrid Supercapacitors
Qiang Chen, Jialun Jin, Mengda Song, Xiangyong Zhang, Hang Li, Jianli Zhang, Guangya Hou, Yiping Tang, Liqiang Mai, Liang Zhou
Abstract
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 2 based cathode, an activated carbon cloth anode, and an aqueous (NH 4 ) 2 SO 4 electrolyte is developed. The aqueous A‐HSC demonstrates an ultrahigh areal capacitance of 1550 mF cm −2 with a wide voltage window of 2.0 V. An amenable peak areal energy density (861.2 μWh cm −2 ) 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 4 + intercalation/deintercalation in the layered δ‐MnO 2 is accompanied by hydrogen bond formation/breaking. This work proposes a new paradigm for electrochemical energy storage.