Inducing an Amorphous Phase in Polymer Plastic Crystal Electrolyte for Effective Ion Transportation in Lithium Metal Batteries

Polymer plastic crystal electrolytes (PPCEs) have garnered significant attention for addressing the challenges associated with succinonitrile (SN), including its inadequate mechanical properties and side reactions with electrodes. However, a comprehensive investigation of the influence of the molecular structure of the polymer network on the states of SN within the network and its subsequent impact on ionic conductivities remains largely unexplored. To shed light on this critical aspect, the binding energy between SN and the polymer moiety is investigated as a determining factor in the conformation and crystallization behavior of SNs, through the dispersion-corrected density functional theory (DFT-D) simulations. These findings reveal that variations in miscibility resulting from the effects of binding energy significantly affected the formation of the amorphous phase in PPCEs. As a result, vinyl ethylene carbonate (VEC)-based PPCE exhibits high ionic conductivity at room temperature (2.6 × 10⁻³ S cm⁻¹ at 25 °C) and possesses a completely amorphous phase, which can be attributed to the optimized miscibility among its components. The feasibility of using a high-performance solid-state lithium-metal battery (LMB) configuration is also examined by combining the PPCE with LiFePO₄ (LFP) and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode materials.