Development of 2D Framework Structures-Based Solid-State Electrolytes with Fast Ion-Transport Channels Using Ionic Liquids Encapsulated in 2D-LiMNT Frameworks

The use of three-dimensional (3D) framework materials to encapsulate ionic liquids is a novel method for the preparation of solid-state electrolytes (SSEs). However, these types of SSEs face problems such as unstable framework structures, narrow pore sizes that restrict organic macromolecules while hindering Li⁺ migration, and the high viscosity of ionic liquids. Herein, a two-dimensional (2D) lithium-montmorillonite (LiMNT) framework was used to encapsulate ionic liquids containing a propylene carbonate (PC) solvent. The PC solvent reduced the viscosity of the ionic liquids and activated Li⁺ in LiMNT, and an efficient 2D Li⁺ transport channel was formed inside the SSE. The ionic conductivity of the prepared lithium-based ionic liquid (LiIL)-PC@LiMNT SSE was as high as 6.2 × 10^-4 S·cm^-1, and a Li⁺ mobility number of 0.35 was observed. At a current density of 0.2 mA·cm^-2, the lithium dissolution-deposition experiment of lithium symmetric batteries operated stably for 1000 h. Solid-state lithium metal batteries prepared with LiFePO₄ cathodes were able to achieve a reversible capacity of 121.1 mAh·g^-1 after 120 cycles at 0.3C, with a capacity retention of 87.4%. This demonstrated the excellent performance of the LiIL-PC@LiMNT SSE. This work provides a novel design idea for the development of solid-state electrolytes based on 2D framework structures using ionic liquids encapsulated in 2D materials and for the construction of fast ion-transport channels.