Flexible Ammonium-Ion Pouch Cells Based on a Tunneled Manganese Dioxide Cathode

Aqueous ammonium-ion (NH4+) batteries are becoming the competitive energy storage candidate on account of their safety, affordability, sustainability, and intrinsically peculiar properties. Herein, an aqueous NH4+-ion pouch cell is investigated based on a tunneled manganese dioxide (α-MnO2) cathode and a 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) anode. The MnO2 electrode possesses a high specific capacity of ∼190 mA h g-1 at 0.1 A g-1 and displays excellent long cycling performance after 50,000 cycles in 1 M (NH4)2SO4, which outperforms the most reported ammonium-ion host materials. Besides, a solid-solution behavior is revealed about the migration of NH4+ in the tunnel-like α-MnO2. The battery displays a splendid rate capacity of 83.2 mA h g-1 even at 10 A g-1. It also exhibits a high energy density of ∼78 W h kg-1 as well as a high power density of ∼8212 W kg-1 (based on the mass of MnO2). What is more, the flexible MnO2//PTCDA pouch cell based on the hydrogel electrolyte shows excellent flexibility and good electrochemical properties. The topochemistry results of MnO2//PTCDA point to the potential practicability of ammonium-ion energy storage.