Modulating the Li-Ion Transport Pathway of Succinonitrile-Based Plastic Crystalline Electrolytes for Solid-State Lithium Metal Batteries

Succinonitrile (SCN) based plastic crystal electrolytes (SPCEs) have attracted much attention for lithium metal batteries due to their considerable ionic conductivity and thermal stability. Insufficient mechanical properties, weak reductive stability, and the presence of free SCN molecules can result in adverse interfacial reactions. Polymer introduction has been explored to address these challenges. However, the introduction of polymer affects the SCN state, leading to reduced ionic conductivity, potentially due to limited segmental motion of the polymer at room temperature. Herein, a cross-linked network polymer strategy is proposed to modify the Li-ion transport pathway in SPCE, aiming to significantly improve the ionic conductivity. The strong interaction between the polymer matrix and SCN enhances their mutual solubility, reduces the crystallinity of SCN, and forms a rapid conduction pathway (polymer—[SCN—Li⁺]). The ionic conductivity of SPCE increases to 1.28 mS cm⁻¹, with the Li-ion migration number (t_Li+) also rising to 0.7. Electrochemical performances in Li symmetrical, Li||LiFePO₄ and Li||LiNi_0.8Co_0.1Mn_0.1O₂ cells show significant improvement at both room temperature and 0 °C. These findings suggest that designing polymer network structures in SPCEs holds promise for solid-state lithium metal battery applications.