Cyclotriphosphonitrile-Based Electroactive Flame-Retardant Polymers for Electrochromic/Supercapacitor Devices

To mitigate the thermal runaway issue and thereby enhance the safety of electrochemical energy storage devices, designing electro-active materials with intrinsic flame-retardant and thermal insulation functions is considered an effective way. Herein, we propose an innovative molecular design strategy that amalgamated the cyclotriphosphonitrile derivative HCTP-BTDPBr with a conjugated polymer framework to construct intrinsic flame-retardant electro-active materials serving as dual function electrochromic/supercapacitor applications. Two series of donor-acceptor type copolymers, namely, PrOEG-BTDx-CTPy and PrOC12-BTDx-CTPy, were prepared by carefully modulating the ratio of HCTP-BTDPBr in the whole polymers. Systematic characterization of the electrochemical and flame-retardant performance revealed that PrOEG-BTD0.82-CTP0.18, PrOC12-BTD0.46-CTP0.54, and PrOC12-CTP showed obvious flame-retardant effects with the ignition times of 120, 108, and 80 s alongside heat release rates of 41.9, 27.5, and 31 KW m(-2) g(-1), respectively. The high specific capacitance of 87.34 mF cm(-2) (at 0.1 mA cm(-2)) was obtained from PrOEG-BTD0.82-CTP0.18. Meanwhile, those three copolymers showed excellent electrochromic performance with multiple color changes between blue/transparent, purple/gray, and red-orange/grass green and impressive coloration efficiencies of 258, 158, and 172 cm(2) C1-, respectively. Thus, we believe this molecular design strategy has great potential to improve the safety of electrochemical energy storage devices.

Automated summary

To enhance the safety of electrochemical energy storage devices, designing electro-active materials with flame-retardant and thermal insulation functions is considered effective. In this study, a molecular design strategy was proposed to construct intrinsic flame-retardant electro-active materials through the combination of a cyclotriphosphonitrile derivative with a conjugated polymer framework. These materials show dual function capabilities for electrochromic and supercapacitor applications.