Achieving ultrahigh charge-discharge efficiency and energy storage in high-temperature polar polymeric dielectrics...

Advancements in microelectronics and electrical power systems require dielectric polymeric materials capable of maintaining high discharged energy density and charge-discharge efficiency over a wide temperature range. Intrinsic polar polymers with enhanced dielectric constants are crucial for achieving high energy density and are extensively utilized at room temperature. However, the compatibility of high energy density and efficiency remains a significant challenge. Most polar polymer dielectric films suffer a considerable drop in capacitive performance as the temperature rises, with efficiency falling below 50%, and the waste Joule heat generated from conduction loss may lead to a vicious cycle. Herein, a new strategy of restraining dipole interactions in polar polymers is proposed to achieve optimal molecular chain stacking configurations, significantly decreased conductivity, and deeper charge trap sites, thus exhibiting enhanced energy density with outstanding efficiency at elevated temperatures. Remarkably, an energy density of 4.61 J cm^-3 at an ultra-high efficiency above 95% was achieved, as well as cycling stability exceeding 150 000 cycles with an energy density of 2.4 J cm^-3 at 150 °C, surpassing current high polar polymers and most advanced polymer composites. This discovery presents a promising solution for preserving high capacitive performance in polar polymeric materials at elevated temperatures.