Advancing Particle Dispersion/Interface Design in Composite Solid Electrolytes for Solid-State Batteries

Composite solid electrolytes (CSEs) are promising materials owing to the synergistic effects of solid polymers and inorganic solid electrolytes. CSEs using an inorganic solid electrolyte as an active filler require a small particle size, and dry-milling processes limit the performance of CSEs owing to particle aggregation and surface layer resistance. Herein, we introduce a solvent-assisted ultrasonication process to effectively disperse agglomerated particles and suppress the surface resistive layer while inhibiting Li+/H+ exchange. Ultrasonicated Li6.4La3Zr1.4Ta0.6O12 (LLZTO) provides a high ionic conductivity of 4.4 × 10–4 S/cm in poly(ethylene oxide) (PEO)-based CSE and an Li transference number twice that of dry-milled LLZTO. In addition, it can be confirmed that the LFP/CSE/Li cell has a high initial discharge capacity of 159.9 mAh/g and a capacity retention rate of 89.9% for 150 cycles.