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

Aqueous ammonium-ion (NH 4 + ) batteries are becoming the competitive energy storage candidate on account of their safety, affordability, sustainability, and intrinsically peculiar properties. Herein, an aqueous NH 4 + -ion pouch cell is investigated based on a tunneled manganese dioxide (α-MnO 2 ) cathode and a 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) anode. The MnO 2 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 (NH 4 ) 2 SO 4 , which outperforms the most reported ammonium-ion host materials. Besides, a solid-solution behavior is revealed about the migration of NH 4 + in the tunnel-like α-MnO 2 . 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 MnO 2 ). What is more, the flexible MnO 2 //PTCDA pouch cell based on the hydrogel electrolyte shows excellent flexibility and good electrochemical properties. The topochemistry results of MnO 2 //PTCDA point to the potential practicability of ammonium-ion energy storage.