Poly(vinylphenoxazine) as Fast-Charging Cathode Material for Organic Batteries
journal contributionposted on 06.12.2019 by Fabian Otteny, Verena Perner, Daniel Wassy, Martin Kolek, Peter Bieker, Martin Winter, Birgit Esser
Any type of content formally published in an academic journal, usually following a peer-review process.
Organic cathode materials are attractive for a new generation of more sustainable batteries due to their comparably low environmental footprint and toxicity. There is a continued quest for new compounds that meet the requirements of a competitive potential and a good cycling performance. We herein present phenoxazine-based polymers as cathode materials with good cycling stability, excellent rate performance, and a high discharge potential of 3.52 V vs Li|Li+ in composite electrodes. At the ultra-fast rate of 100C, a cross-linked phenoxazine poly(vinylene) showed only slow capacity decay over 10 000 cycles with a capacity retention of 74% in cycle 10 000. Mechanistic investigations using UV/vis/near-infrared (NIR) spectroscopy and density functional theory (DFT) calculations unveiled that unlike in the homologous phenothiazine polymers, π-interactions played a minor role in phenoxazine-based polymers. Our study is the first to present phenoxazine as a redox-active unit for cathode materials and shows that an elemental change of one atom (S vs O compared to known phenothiazine-based polymers) can have a profound effect on electrochemical performance.