Polypyrrole intercalated into the interlayer of vanadium oxide hydration boosts NH4+ storage for aqueous ammonium ion batteries

Non -metallic ammonium ion (NH4+) carrier has attracted great interest in aqueous energy storage due to its light molar mass, small hydration radius, mild reaction and unique topological chemical structure. The exploration of cathode materials for aqueous ammonium ion batteries (AAIBs) has become a hot research topic recently. In this work, we design and synthesize polypyrrole-inserted hydrated vanadium pentoxide (PPy/VOH) with boosted NH4+-storage and use it as a cathode material to produce AAIBs in the first time. By inserting PPy between the layers, the interlayer spacing is enlarged, and the interlayer forces are weakened, and structure of vanadium oxide is stabilized, all greatly improving the NH4+-storage performance. As expected, PPy/VOH can reach the specific capacity of 169.1 mAh g-1 at 0.5 A g-1, and the specific capacity is maintained at 69 % of the initial value after 5000 cycles. The 3,4,9,10-Perylene-bis(dicarboximide) (PTCDI)//PPy/VOH full cell delivers the specific capacity of 55 mAh g-1 at 0.2 A g-1. This work not only demonstrates the PPy intercalation VOH can improve the NH4+-storage performance, but also provides a new attempt at the practical application of cathode materials for AAIBs through the intercalation strategy.