A high strength hybrid separator with fast ionic conductor for dendrite-free lithium metal batteries

The inhomogeneous lithium deposition and dendrite formation hinder the practical application of lithium metal batteries (LMBs). Here, a hybrid separator combined with aramid nanofibers and solid-state fast ionic conductors of Li_6.75La₃Zr_1.75Ta_0.25O₁₂ (LLZTO) are fabricated by a simple casting method for dendrite-free LMBs. Compared with commercial polypropylene (PP) separator, this hybrid separator presents outstanding mechanical property and high thermal stability which is benefited for improving the safety of LMBs. Besides, the homogeneous distributed nanopores on the hybrid separator can uniformly adjust the movement of Li-ions for dendrite-free deposition. At the same time, LLZTO in the hybrid separator not only improve its mechanical stability but also anchor free anions and enhance Li-ions transportation. As expected, Li|LiFePO₄ full cells based on this hybrid separator show excellent performance at high rate (122 mAh g⁻¹ at 5C) and enhanced cycle stability (95.5% after 1000 cycles) with a high coulombic efficiency (99.5%) and can normally work even at a high temperature of 120 °C. These fascinating characteristics and facile preparation method make it a promising separator for large-scale production in LMBs with high safety.