Abstract
AbstractIn recent years, organic battery cathode materials have emerged as an attractive alternative to metal oxide–based cathodes. Organic redox polymers that can be reversibly oxidized are particularly promising. A drawback, however, often is their limited cycling stability and rate performance in a high voltage range of more than 3.4 V versus Li/Li+. Herein, a conjugated copolymer design with phenothiazine as a redox‐active group and a bithiophene co‐monomer is presented, enabling ultra‐high rate capability and cycling stability. After 30 000 cycles at a 100C rate, >97% of the initial capacity is retained. The composite electrodes feature defined discharge potentials at 3.6 V versus Li/Li+ due to the presence of separated phenothiazine redox centers. The semiconducting nature of the polymer allows for fast charge transport in the composite electrode at a high mass loading of 60 wt%. A comparison with three structurally related polymers demonstrates that changing the size, amount, or nature of the side groups leads to a reduced cell performance. This conjugated copolymer design can be used in the development of advanced redox polymers for batteries.
Highlights
In recent years, organic battery cathode materials have emerged as an cell voltages of up to 4.1 V versus attractive alternative to metal oxide–based cathodes
We have shown that using a π-conjugated copolymer structure enabled ultra-high rate capability and cycling stability at 100C rate in phenothiazine-based polymers as cathode-active battery materials
Best results were achieved with P1a, possessing alternating phenothiazine and bithiophene units
Summary
Organic battery cathode materials have emerged as an cell voltages of up to 4.1 V versus attractive alternative to metal oxide–based cathodes. Organic cathode materials have been identified as promising times only low doping levels are accessible in a reversible candidates for next-generation battery systems.[1,2,3,4,5,6,7,8,9,10,11,12] Their fashion.[4,15,23,24] We present a combination of the benadvantages include a high structural diversity and design efits of both designs by using π-conjugated redox polymers P1 flexibility as well as a low toxicity They are acces- and P2 as cathode-active materials in a lithium organic batsible from less-limited resources compared to their inorganic tery (Figure 1). Esser Cluster of Excellence livMatS @ FIT—Freiburg Center for Interactive Materials and Bioinspired Technologies University of Freiburg Georges-Köhler-Allee 105, 79110 Freiburg, Germany
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