V2O5 intercalated with polyaniline for improved kinetics in aqueous ammonium-ion batteries

The use of non-metal ammonium ions (NH4+) as effective charge carriers in battery systems is receiving wide-spread attention because of their light weight and small hydration shells in water as well as abundancy of the elements. The research concerning NH4+ ion redox chemistry in batteries is still in its infancy, mainly because the large ionic radius of NH4+ would require a host material to have a wider open structure and thus limits the choice of electrode materials. NH4+ ion redox chemistry is dominated by non-ionic chemical bonding such as hydrogen bonding with some covalent bonding in nature which plays a significant role in electrochemical performance of the battery. In this work, an in-situ intercalation technique is utilized to synthesize polyaniline-intercalated vanadium oxide with a nanoflower morphology for increased surface area and enhanced NH4+ ion (de)intercalation kinetics. Through this strategy, an interlayer spacing of 13.99 angstrom between V-O layers is reached, offering large diffusion channels to accommodate NH4+ ions which have an ionic radius of 1.48 angstrom and a hydrated radius of 3.31 angstrom . The diffusion kinetics of the NH4+ ions, influenced by the hydrogen bonds formed between NH4+ ion and O2- in the host structure, are thus effectively enhanced by the unique pi-conjugated structure of PANI, leading to high capacity, improved rate capability and improved cycle life. The as-prepared PANI-intercalated V2O5 (PVO) demonstrates stable, ultrafast NH4+ ion electrochemical storage based on hydrogen bond chemistry as elucidated by X-ray photoelectron spectroscopy and Raman spectroscopy characterizations. Additionally, the composition of the PVO electrode is optimized with respect to the amount of PANI between the V-O layers. The PVO with an optimal composition exhibits the best overall electrochemical performance, delivering a high capacity of 192.5 mA hg(-1) and 39 mA hg(-1) at specific currents of 1 and 20 A g(-1) respectively, as well as a stable cycle life with a capacity retention of 98% at a specific current of 10 and 20 A g(-1). As such, the present work provides critical insights into the design of promising electrode materials for emerging aqueous non-metal batteries with intrinsic safety and reduced cost.

Automated summary

The research focuses on the use of non-metal ammonium ions as effective charge carriers in battery systems and the synthesis of polyaniline-intercalated vanadium oxide to enhance NH4+ ion intercalation kinetics. By optimizing the composition of the PVO electrode, the study demonstrates excellent electrochemical performance for emerging aqueous non-metal batteries.