Improving Energy Storage Density and Efficiency of Polymer Dielectrics by Adding Trace Biomimetic Lysozyme-Modified Boron Nitride

Dielectric materials can store and release electrical energy quickly and efficiently and have potential applications in the fields of rail transportation, air and space detection, and electromagnetic weapons. However, the most promising dielectric polymer composites under research suffer either from unsatisfactory energy density (Ue) or from increasing the Ue at the cost of energy efficiency (η). Herein, by the solution casting method, a nanocomposite film is fabricated by introducing trace self-assembly phase-transitioned lysozyme (PTL) modified boron nitride nanosheets (mBNNS) into a blend matrix consisting of poly(vinylidene fluoride–hexafluoropropylene) P(VDF–HFP) and poly(methyl methacrylate) (PMMA). The results suggest that PTL helps improve the interfacial compatibility of the corresponding nanocomposites via hydrogen-bonding interaction effectively. The nanocomposite film with 5 wt % mBNNS shows remarkably enhanced breakdown strength (Eb) of ∼500 MV/m and Ue of 14.9 J/cm3, which are 166% and 244% of the blend matrix, respectively. Meanwhile, η of the nanocomposite film reaches ∼71% because of the clipping effect of linear PMMA on the large ferroelectric crystal phase of P(VDF–HFP) and the barrier effect of the highly insulating two-dimensional (2D) mBNNS, which effectively reduces the relaxation and leakage losses. Our research results show that by using a low-loss matrix and trace high-insulation 2D nanosheets, it is possible to achieve dielectric materials with high η and high Ue at the same time.