Insights into the Solubility of Poly(vinylphenothiazine) in Carbonate-Based Battery Electrolytes.

Organic materials are promising candidates for next-generation battery systems. However, many organic battery materials suffer from high solubility in common battery electrolytes. Such solubility can be overcome by introducing tailored high-molecular-weight polymer structures, for example, by cross-linking, requiring enhanced synthetic efforts. We herein propose a different strategy by optimizing the battery electrolyte to obtain insolubility of non-cross-linked poly(3-vinyl-N-methylphenothiazine) (PVMPT). Successive investigation and theoretical insights into carbonate-based electrolytes and their interplay with PVMPT led to a strong decrease in the solubility of the redox polymer in ethylene carbonate/ethyl methyl carbonate (3:7) with 1 M LiPF6. This allowed accessing its full theoretical specific capacity by changing the charge/discharge mechanism compared to previous reports. Through electrochemical, spectroscopic, and theoretical investigations, we show that changing the constituents of the electrolyte significantly influences the interactions between the electrolyte molecules and the redox polymer PVMPT. Our study demonstrates that choosing the ideal electrolyte composition without chemical modification of the active material is a successful strategy to enhance the performance of organic polymer-based batteries.

Phenothiazine-Functionalized Poly(norbornene)s as High-Rate Cathode Materials for Organic Batteries.

Organic cathode materials are handled as promising candidates for new energy-storage solutions based on their transition-metal-free composition. Phenothiazine-based polymers are attractive owing to their redox potential of 3.5 V vs. Li/Li+ and high cycling stabilities. Herein, three types of poly(norbornene)s were investigated, functionalized with phenothiazine units through either a direct connection or ester linkages, as well as their crosslinked derivatives. The directly linked poly(3-norbornylphenothiazine)s demonstrated excellent rate capability and cycling stability with a capacity retention of 73 % after 10 000 cycles at a C-rate of 100 C for the crosslinked polymer. The polymer network structure of the crosslinked poly(3-norbornylphenothiazine) was beneficial for its rate performance.