Enhancing Energy Storage—A Novel Approach Using 2D/3D/2D Heterostructures

Managing high energy density is increasingly critical for applications ranging from electric power systems to portable electronic devices. Electrostatic capacitors, renowned for their ultrafast charge and discharge rates, are pivotal in these applications. However, their performance is constrained by the low maximum polarization of conventional dielectric materials. In contrast, ferroelectric materials like HfO₂, ZrO₂, and BaTiO₃ (BTO) exhibit higher maximum polarization due to their higher electric susceptibilities, related to dielectric constants. Unfortunately, their high remnant polarization hampers effective energy storage and release during the discharging process.<br/>We propose a strategy to precisely control the relaxation time of polarization with minimal energy loss, utilizing monolayer two-dimensional (2D) materials produced through the layer-splitting technique. This is achieved by creating 2D/single-crystalline 3D/2D (2D/C-3D/2D) heterostructures using a layer-transfer technique to produce freestanding single-crystalline BTO (C-BTO), allowing for manipulation at both interfaces. Unlike previous methods that degrade ferroelectric materials via structural changes, our approach preserves the single-crystal nature of BTO. In our design, a C-BTO layer is sandwiched between 2D materials in a freestanding membrane configuration. This setup leverages the Maxwell-Wagner effect—relaxation by charge accumulation at heterogeneous interfaces—to modulate the relaxation time. By controlling the thickness of 2D materials with atomic precision through layer-resolved splitting, we achieve minimal energy loss and dielectric loss while managing relaxation time. This innovative approach effectively suppresses the remnant polarization of ferroelectric materials while maintaining maximum polarization. Consequently, we achieved an energy density of 191.7 J/cm³ with an efficiency exceeding 90%. Our method has the potential to significantly enhance the performance of dielectric materials, making it suitable for a variety of applications requiring high-energy storage systems.