Advanced materials | 2021
Constructing Li-Rich Artificial SEI Layer in Alloy-Polymer Composite Electrolyte to Achieve High Ionic Conductivity for All Solid-State Lithium Metal Batteries.
Abstract
To achieve high ionic conductivity for solid electrolyte, an artificial Li-rich interface layer of about 60\xa0nm thick has been constructed in polymer-based poly(ethylene oxide)-lithium bis(trifluoromethanesulfonyl)imide composite solid electrolyte (briefly noted as PEOm ) by adding Li-based alloys. As revealed by high-resolution transmission electron microscopy and electron energy loss spectroscopy, an artificial interface layer of amorphous feature is created around the Li-based alloy particles with the gradient distribution of Li across it. Electrochemical analysis and theoretical modeling demonstrate that the interface layer provides fast ion transport path and plays a key role in achieving high and stable ionic conductivity for PEOm -Li21 Si5 composite solid electrolyte. The PEOm -5%Li21 Si5 composite electrolyte exhibits an ionic conductivity of 3.9 × 10-5 \xa0S\xa0cm-1 at 30\xa0°C and 5.6 × 10-4 \xa0S\xa0cm-1 at 45\xa0°C. The LiFePO4 | PEOm -5%Li21 Si5 | Li all-solid-state batteries could maintain a stable capacity of 129.2\xa0mA\xa0h\xa0g-1 at 0.2 C and 30\xa0°C after 100 cycles, and 111.3\xa0mA\xa0h\xa0g-1 after 200 cycles at 0.5 C and 45\xa0°C, demonstrating excellent cycling stability and high-rate capability.