Boosting the Performance of Aqueous Ammonium-Ion Batteries by Mitigating Side Reactions Using Polymer Additive

Abstract

Aqueous ammonium ion battery (AAIB) is a sustainable and highly safer energy storage technology than traditional metal-ion batteries owing to the low-cost, good diffusion kinetics, and abundant charge carrier ability. Besides, AAIBs suffer from less-cyclic stability to meet the practical applications due to the undesired side reactions and low electrochemical stable potential window. Herein, for the first time, the role of a molecular crowding agent, i.e., poly(ethylene oxide) (PEO) as an organic polymer-based electrolyte additive was tested to achieve high-performance AAIBs. The addition of PEO molecules improves the ammonium ion (NH4+) kinetics and regulates the hydrogen bond behavior in the water through the interactions between oxygen (−O) groups in the ethylene oxide units of PEO and water. Such a strong interaction between the PEO-water network effectively suppresses hydrogen (HER) and oxygen evolution reactions (OER) and increases the potential window. Further, the weak interaction between PEO-NH4+ facilitates the topotactic binding mechanism and eventually leads to increased ionic conductivity. In addition, the full cell is fabricated using 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) as an anode and ammoniated nickel hexacyanoferrate (N-NiHCF) as a cathode. The assembled device shows a maximum capacity of 42.51 mAh/g at 0.3 A/g with a rate capability of 99.7%. The device shows negligible performance deterioration after 1000 charge-discharge cycles. Hence, this strategy sheds light on the effective utilization of polymer additives for the design and development of highly stable and sustainable ammonium ion batteries for stationary grid-scale applications. © 2023 American Chemical Society.