Mitigation of the confinement-induced dielectric constant reduction via binary mixing strategy for energy storage applications

The dielectric constant of electrolytes, typically assumed constant at the macroscale, exhibits significant reduction under nanoscale confinement (<10 nm), as observed in confined liquids such as water. For supercapacitors employing MXene electrodes, understanding these variations is crucial for elucidating energy storage mechanisms at the solid–liquid interface. Here, we employ molecular dynamics simulations to investigate the reduction of the dielectric constant in organic solvents under confinement. By analyzing ethylene carbonate (EC), we reveal that confinement alters the charge density distribution of the electrolyte, enhancing local polarization correlation and causing an anomalous decrease in the dielectric constant near the surface. To address this issue, we propose a binary mixing strategy on EC-based. By balancing local and global polarization, this approach effectively mitigates the reduction of the dielectric constant. The optimized mixture not only maintains dielectric performance but also increases the diffusion coefficient fourfold compared to pure EC. Our findings provide a novel approach for designing high-performance electrolytes for supercapacitors operating under confined environments.