Conquering the Adverse Polarization‐Breakdown Coupling in Heat‐Resistant Polymer Nanocomposites by Liquid Metals

The inevitable electrical-thermal-mechanical mismatch at the interface of traditional organic-inorganic nanocomposite dielectrics has long hindered the synergistic enhancement of polarization, voltage resistance, and heat dissipation capacity. To address this challenge, a liquid metal-polymer nanocomposite strategy is put forward to achieve excellent energy storage performance at high temperatures. By introducing EGaIn nanodroplets into a polyetherimide (PEI) matrix, the coupling effect among electricity, heat and force can be on-demand regulated. Simulated results demonstrate that the addition of liquid metals in polymer-based nanocomposites can effectively enhance the overall polarization, strengthen heat conduction and alleviate local stress concentration. Experimental results further indicate that the inverted coupling between the polarization and breakdown strength can be successfully disrupted even at 150 °C. Especially, a high electric displacement of up to 2.83 µC cm^-2 can be attained at 500 MV m^-1 with only 0.2 vol% of liquid metal fillers. Consequently, the nanocomposite film exhibits an enhanced energy density U_e of 6.0 J cm^-3 with an efficiency η of 90% at 150 °C and 500 MV m^-1. The present work not only reveals the physical mechanisms of complex electrical-thermal-mechanical interactions but also offers new perspectives on the design of energy storage nanocomposites to break the inverse polarization-breakdown relationship at high temperatures.