Improvement of graphite interfacial stability in all-solid-state cells adopting sulphide glassy electrolytes

A study on the interfacial properties between a solid glassy electrolyte, LiI-Li3PS4 (LPSI), and graphite (MAG) composite electrodes was carried out with the aim of reducing or even eliminating the irreversible capacity during the 1st chargedischarge cycle. The performances of all-solid-state MAG|LPSI|Li cells were compared with those of conventional liquid cells. To reinforce a well-distributed conductive path in MAG as well as at the MAG/LPSI interface, the type of electron conducting additive and the pressure during cell preparation were optimized. Specific functions of the conducting additive were demonstrated, where the sub-micrometric carbon fibers allowed better galvanostatic performance in the solid-state configuration by virtue of their high aspect ratio. The coulombic efficiency of solid-state cells was improved from 46 to 99% and the reversible capacity value from 100 to 270 mAhg-1, by increasing the pressure from 2 to 4 ton. The interfacial stability of LPSI was also evaluated by impedance spectroscopy of MAGj MAG and Li j Li cells over time. Although ionic resistance of LPSI was higher than a conventional liquid electrolyte, LPSI exhibited controlled interfacial resistance.