High breakdown strength and outstanding piezoelectric performance in flexible PVDF based percolative nanocomposites through the synergistic effect of topological-structure and composition modulations

Over decades, the fabrication of flexible poly(vinylidene fluoride) (PVDF) based percolative nanocomposites with high piezoelectric performance is of great concern from both academia and industry. However, the issue of sharply declined breakdown strength in percolative nanocomposites poses an obstacle to realizing the full potential of conductive nanofillers in enhancing piezoelectricity. Herein, we demonstrated that through proper topological structure and composition modulations, notably improved breakdown strength and piezoelectric performance can be achieved in PVDF based percolative nanocomposites. By constructing a sandwiched structure where a layer of high breakdown strength is intercalated between layers containing high content (near percolation threshold) of conductive nanofillers, the breakdown strength of overall nanocomposites is significantly strengthened and thus allows for sufficient poling of outer layers, fulfilling the great potential of conductive nanofillers in yielding piezoelectricity enhancement. A super high piezoelectric coefficient d33 of 48 pC/N is obtained in the optimized sandwich nanocomposites.