Modified Separator with a Composite Layer of LLZTO-PEO/PVDF-HFP/LiTFSI for Lithium-Ion Batteries

Functionalized separator is more competitive than commercial polyolefin separator for rechargeable lithium-ion batteries. In this work, we design the separator modified by a composite coating layer, which is composed of Li6.75La3Zr1.75Ta0.25O12 (LLZTO), poly(ethylene oxide) (PEO), poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and lithium bis(triuoromethanesulfonyl) imide (LiTFSI) (LLZTO-PEO/PVDF-HFP/LiTFSI, LLZTO-PPL). The LLZTO-PPL composite coating layer gives an impressive effect on dendrite inhibition of lithium metal. In comparison with commercial polyolefin separator, smaller overpotential value and better Coulombic efficiency are observed for the Li/LLZTO-PPL/Li symmetric cells and the Li/LLZTO-PPL/Cu asymmetric cells at various current densities of 0.2, 0.5, and 1 mA cm–2. Moreover, the LLZTO-PPL composite coating layer modified separator exhibits better high-rate capability and cycle performance for these cells assembled with different kinds of cathode materials (LiFePO4, LiCoO2, and LiNi0.8Co0.1Mn0.1O2) and their counterpart of a lithium metal anode. The functionalized composite coating layer modified separator may be a more attractive candidate material for commercial lithium-ion batteries.