Significantly improved energy storage performance of polyetherimide based composite materials by introducing Na _0.5 Bi _0.5 TiO ₃ filler surface-modified with organic molecular semiconductors

The advancement of dielectric capacitors necessitates dielectric materials that exhibit high energy storage density and superior performance at high temperature. However, current dielectric polymer materials fall short of meeting these criteria. This work pioneers the use of an organic molecular semiconductor as a surface modifier for inorganic fillers. In this work, the inorganic high-ε filler Na_0.5Bi_0.5TiO₃ (NBT) was surface-modified with [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM), an organic molecule semiconductor exhibiting high electron affinity, and subsequently introduced into a polyetherimide (PEI) matrix to fabricate NBT@PCBM/PEI composites. The high-ε NBT enhances the polarization capability of the composites. Meanwhile, the PCBM not only mitigates the problems existing at the interface between inorganic NBT and organic PEI but also acts as a charge trap to restrict charge carrier migration, thereby improving the performance degradation of the composites at high temperature. The results indicate that at room temperature, the 0.2 vol% NBT@PCBM/PEI composites achieved a high energy storage density of 15.17 J cm^-3, exhibiting an improvement of 60% compared to pure PEI. At 150 °C, the 0.2 vol% NBT@PCBM/PEI composites achieved an energy storage density of 9.29 J cm^-3, exhibiting an improvement of 59% compared to pure PEI. It is worth noting that the energy efficiency of the composites in both cases reached more than 90%, which is very beneficial for practical applications. This work provides a feasible way to develop high quality dielectric materials at high temperature.