Vertically aligned interlayer-nanoconfined channels for fast lithium-ion transport in solid-state batteries

Poly (vinylidene fluoride)-based solid polymer electrolytes (SPEs) with high mechanical strength and large-scale processability have attracted increasing attention for solid-state lithium (Li) batteries, but their practical application is still hampered by low effective ionic conductivity and poor interfacial compatibility due to chaotic ion transport pathways and reactive-solvent-involved ionic conducting mechanism. Herein, vertically aligned Li ion transport channels composed of BMIM⁺ cation-intercalated montmorillonite nanosheets (BMMT) were fabricated via a stacking-slicing approach. The interlayer nanoconfinement of BMMT significantly enhances Li⁺ transport kinetics, while the vertically aligned structure further provides shortened ion diffusion pathways. Altered Li⁺ solvation structure within the confined space of BMMT effectively reduces the content of reactive solvent molecules below 2.8 wt%, thereby enhancing the interfacial compatibility of the electrolyte. As a result, the optimized electrolyte achieved much enhanced ionic conductivity (1.17 mS/cm) and Li⁺ transference number (0.62), which enabled a high limiting current density of 5 mA/cm² and stable Li plating/stripping for 8000 h at 0.1 mA/cm² and 0.1 mAh/cm². The assembled LiNi_0.8Mn_0.1Co_0.1O₂ (6 mg/cm²) full cell demonstrated a cycling life of 190 cycles at 1C with a capacity retention of 91%. Meanwhile, the pouch cell exhibited stable cycling for over 200 cycles at 1C (0.2 mA/cm²).