Superior Polyaniline Cathode Material with Enhanced Capacity for Ammonium Ion Storage

High Resolution Image Download MS PowerPoint Slide A paradigm shift in aqueous rechargeable batteries has seen the development of nonmetal ammonium ions ( NH 4 + ) as charge carriers. NH 4 + ions have a molecular weight of 18 g mol –1 and hydrated ionic size of 3.31 Å, which are smaller than those of metal ions, leading to faster kinetics during charge transfer. Yet few electrode materials have been studied for this type of battery. This work is the first effort to show that polyaniline (PANI) is an excellent material for NH 4 + ion storage, and thus further proves that NH 4 + ions can be used as effective charge carriers in aqueous ion battery systems. A facile solution method is used to prepare emeraldine salt polyaniline (ES-PANI) on the carbon felts (CFs) as the cathode material. The battery cell based on the ES-PANI cathode material shows a good discharge capacity of 160 mAh g –1 at a specific current of 1 A g –1 . At 5 A g –1, it shows a good capacity retention of 82% after 100 cycles and also exhibits excellent rate capability. Furthermore, it is found that the ES-PANI/CFs washed with water deliver higher capacity than those washed with ethanol, because washing with ethanol causes the oligomers to dissolve in the solution and thus decreases the storage capacity of ES-PANI for NH 4 + ion storage. The intercalation/deintercalation of NH 4 + ion is shown to be highly reversible in the ES-PANI electrode doped with Cl - ions, due to the stable redox properties of nitrogen in ES-PANI polymer chains. As such, this work sheds new insight into the exploration of alternative electrode material for ammonium ion storage, which can lead to new electrochemical energy technology.