Regulating Lithium-Ion Transport in PEO-Based Solid-State Electrolytes through Microstructures of Clay Minerals

Abstract

Clay minerals show significant potential as fillers in polymer composite solid electrolytes (CSEs), whereas the influence of their microstructures on lithium-ion (Li⁺) transport properties remains insufficiently understood. Herein, we design advanced poly(ethylene oxide) (PEO)-based CSEs incorporating clay minerals with diverse microstructures including 1D halloysite nanotubes, 2D Laponite (Lap) nanosheets, and 3D porous diatomite. These minerals form distinct Li⁺ transport pathways at the clay-PEO interfaces due to their varied structural configurations. Among them, 2D Lap nanosheets exhibit the most significant improvements in Li⁺ conductivity (1.67 × 10^–4 ± 0.02 × 10^–4 S cm^–1 at 30 °C), Li⁺ transference number (0.72), and oxidative stability (4.7 V). Consequently, a solid-state Li|LiFePO₄ battery with the PEO/Lap CSE exhibits high reversible capacity and superior cycling stability (with 90.2% capacity retention after 250 cycles at 1.0 and 30 °C). Furthermore, pouch batteries with an integrated LiFePO₄ cathode and PEO/Lap CSE show superior safety performance, even under extreme damage. This work provides valuable theoretical insights for the design and application of clay mineral fillers in CSEs.