Polymer Dielectrics with Simultaneous Ultrahigh Energy Density and Low Loss

Polymer dielectrics are highly desirable in capacitor applications due to their low cost, high breakdown strength, and unique self-healing capability. However, existing polymer dielectrics suffer from either a low energy density or a high dielectric loss, thereby hindering the development of compact, efficient, and reliable power electronics. Here, a novel type of polymer dielectrics simultaneously exhibiting an extraordinarily high recoverable energy density of 35 J cm(-3) and a low dielectric loss is reported. It is synthesized by grafting zwitterions onto the short side chains of a poly(4-methyl-1-pentene) (PMP)-based copolymer, which increases its dielectric constant from approximate to 2.2 to approximate to 5.2 and significantly enhances its breakdown strength from approximate to 700 MV m(-1) to approximate to 1300 MV m(-1) while maintaining its low dielectric loss of 90%. Based on a combination of the phase-field method description of mesoscale structures, Maxwell equations, and theoretical analysis, it is demonstrated that the outstanding combination of high energy density and low dielectric loss of zwitterions-grafted copolymers is attributed to the covalent-bonding restricted ion polarization and the strong charge trapping by the zwitterions. This work represents a new strategy in polymer dielectrics for achieving simultaneous high energy density and low dielectric loss.