Boosting energy storage performances in Ni(OH)₂ /polymer composites via gradient multilayer structure

High energy storage in multilayer composites is pivotal for the progress of advanced electronic and power device systems, however, the uneven distribution of electric fields caused by significant dielectric contrast between adjacent layers limits its potential gaining in energy density . Through incorporating transition layers into multilayer composites to mitigate interlayer dielectric contrast, herein, four-layer matrix gradient-structured composites ( x vol% PMMA/(100- x ) vol% P(VDF-HFP) have been designed and fabricated. The results demonstrate that the transition layers play a crucial role in hindering the breakdown process and homogenizing the electric field distribution. In addition, the linear PMMA as well as horizontally oriented nanoplates are also beneficial in enhancing their energy storage performances. The gradient-structured composite ultimately achieved an energy density of 24.3 J/cm³ and a charge-discharge efficiency of 86.6 % at 676.8 MV/m, significantly surpassing that of traditional multilayer nanocomposites . The strategies proposed here may represent a universal approach to further enhance energy storage performances of multilayer composites. • Gradient nanocomposites with improved dielectric properties were designed. • Transition layers smooth electric field variations, stopping early breakdown. • Enhanced U d of 24.3 J/cm³ and η of 86.6 % at 676.8 MV/m are obtained. • Finite element analysis confirms the mechanism of performance improvements. • The nanocomposite with x = 60 shows reliability for practical applications.