Aryl Viologen Polymers in High‐Voltage Full‐Organic Batteries

Anion-rocking chair batteries, functioning without any metals, are intriguing candidates as alternative, more sustainable energy storage systems. They can be operated by using two types of p-type organic electrode-active materials (OAMs) with low and high redox potentials for the negative and positive electrode, respectively. However, identifying compatible material pairs delivering a potential difference above 1.5 V is challenging. Viologens are promising candidates as low-potential OAMs, but they usually lack stability when cycled over both redox processes. Herein, we report on linear and crosslinked N-aryl viologen polymers with enhanced electrochemical stability over both redox processes in lithium half-cells. We employ these as negative electrodes in anion-rocking chair full-cells with a dimethoxyphenothiazine-polymer-based positive electrode, able to undergo two reversible oxidations. The full-cell, using 2 m LiClO$_4$ in PC as electrolyte, delivered a voltage of ca. 1.8 V and a capacity of up to 78 mAh g$^{−1}$ and could be cycled over 100 cycles with a capacity retention of 71%. We further demonstrate a metal-free all-organic full-cell using nBu$_4$NClO$_4$ as electrolyte salt that delivers an even higher specific discharge capacity of up to 88 mAh g$^{−1}$. ... mehrThis work constitutes a step forward toward anion-rocking chair batteries with attractive cell voltages exceeding 1.5 V.