Spiral-structured Dielectric Polymers Exhibiting Ultra-High Energy Density And Charge-Discharge Efficiency at High Temperatures.

The growing need for high-power and compact-size energy storage in modern electronic and electrical systems demands polymer film capacitors with excellent temperature capability. However, conventional polymer dielectrics feature dramatic deterioration in capacitive performance under concurrent high temperature and electric field, because the high thermal stability traditionally relies on the conjugated, planar molecular segments in the polymer chains. Herein, inspired by the stable double helix structures of deoxyribonucleic acid, we demonstrate spiral-structured dielectric polymers that exhibit simultaneous high thermal stability and great capacitive performance. Both the experimental results and computational simulations confirm that the spiral groups serve to weaken the electrostatic molecular interaction, induce proper molecular chain stacking structure, and regulate the charge transfer process by breaking the conjugated planes and introducing deep trap sites. The resultant polymer exhibits the maximum discharged energy densities of 7.29 and 6.13 J/cm 3 with the charge-discharge efficiency above 90% at 150 and 200 °C, respectively, more than 10 times those of the original dielectric at the same conditions. The present work offers a completely new dimension for the molecular design of polymers, giving rise to well-balanced thermal and dielectric properties, and ultimately the desired capacitive energy storage performance at high temperatures. This article is protected by copyright. All rights reserved.