Highly transparent electrostatic energy storage capacitors based on CeO2-doped BaTiO3 lead-free nanocomposite films

Abstract

This study presents the development of highly transparent and eco-friendly electrostatic energy storage capacitors using CeO2-doped BaTiO3 lead-free nanocomposite films [denoted as (1-x)BT-xC (0.0 ≤ x ≤ 0.5)]. Systematic optimization of CeO2 enabled precise control over optical transparency, energy storage performance, and the associated frequency and thermal stability. Optical measurements revealed that all film capacitors exhibited high optical transparency with a maximum transmittance of ~ 75%. By varying the CeO2 content, we achieved enhanced energy storage performance through compositional engineering, demonstrating an ultrahigh efficiency of ~ 90%, and a high energy storage density of 28.3 - 37.1 J/cm3. The proposed lead-free composition comprises only four elements (Ba, Ti, Ce, and O), making it both environmentally friendly and structurally simple. Additionally, the films exhibit remarkable operational stability, retaining superior frequency stability (5 Hz to 10 kHz) and thermal stability (25 °C - 140 °C), while maintaining consistent energy storage performance. These findings provide a practical strategy for designing compositionally optimized, eco-friendly and highly transparent energy storage systems.