(401c) Enhancing the Dielectric Breakdown Strength of Solid-State Polymer Capacitors By Chain End Manipulations

The need for high power density, flexible, pulsed power, and lightweight energy storage devices requires the use of polymer film-based dielectric capacitors. The maximum energy storage density of a linear dielectric capacitor is directly proportional to the square of the maximum voltage (dielectric breakdown voltage) that can be applied to the dielectric without causing the breakdown. Theoretically, it has been shown that chain ends contribute adversely to the electrical breakdown of polymer dielectrics at high electric fields, resulting in low energy density in polymer capacitors. In this work, we enhanced the dielectric breakdown voltage and hence the energy density of the polymer capacitor by using well-ordered high molecular weight block copolymers (BCP), in which the chain ends are segregated to narrow zones. The well-ordered and easily processable BCP-based capacitors exhibit an energy density of more than 5 J/cm³, which is higher than that of industrial used biaxially oriented polypropylene. Furthermore, we tested the role of chain ends in the dielectric breakdown of polymer films by comparing the linear polymers with cyclic polymers (no chain ends). The cyclic polymer films demonstrated ~50% enhancement in dielectric breakdown strength and as a result, the capacitive energy density in the cyclic polymer films increased by ~80% as compared to their linear counterparts. These novel insights into manipulating chain end distribution such as in BCPs and with molecular topology to increase the energy density of polymers will help fulfill next-generation energy demands.