2D-Nanofiller-Based Polymer Nanocomposites for Capacitive Energy Storage Applications

High-energy-density storage devices play a major role in modern electronics from traditional lithium-ion batteries to supercapacitors for a variety of applications from rechargeable devices to advanced military equipment. Despite the mass adoption of polymer capacitors, their application is limited by their low energy densities and low-temperature tolerance. Polymer nanocomposites based on 2D nanomaterials have superior capacitive energy densities, higher thermal stabilities, and higher mechanical strength as compared to the pristine polymers and nanocomposites based on 0D or 1D nanomaterials, thus making them ideal for high-energy-density dielectric energy storage applications. Here, the recent advances in 2D-nanomaterial-based nanocomposites and their implications for energy storage applications are reviewed. Nanocomposites based on conducting 2D nanofillers such as graphene, reduced graphene oxide, MXenes, semiconducting 2D nanofillers including transition metal dichalcogenides such as MoS₂, dielectric 2D nanofillers including hBN, Mica, Al₂O₃, TiO₂, Ca₂Nb₃O₁₀ and MMT, and their effects on permittivity, dielectric strength, capacitive energy density, efficiency, thermal stability, and the mechanical strength, are discussed. Also, the theory and machine-learning-guided design of polymer 2D nanomaterial composites is learnt and the challenges and opportunities for developing ultrahigh-capacitive-energy-density devices based on these nanofiller polymer composites are presented.