Glass-ceramic Li2S-GeS2-P2S5 electrolytes were prepared by a single step ball milling (SSBM) process. Various compositions of Li4-xGe1-xPxS4 from x = 0.70 to x = 1.00 were systematically investigated. Structural analysis by X-ray diffraction (XRD) showed gradual increase of the lattice constant followed by significant phase change with increasing GeS2. All-solid-state LiCoO2/Li cells were tested by constant-current constant-voltage (CCCV) charge-discharge cycling at a current density of 50 μA cm-2 between 2.5 and 4.3 V (vs. Li/Li+). In spite of the high conductivity of the solid-state electrolyte (SSE), LiCoO2/Li cells showed a large irreversible reaction especially during the first charging cycle. Limitation of instability of Li2S-GeS2-P 2S5 in contact with Li was solved by using double layer electrolyte configuration: Li/(Li2S-P2S 5/Li2S-GeS2-P2S5)/ LiCoO2. LiCoO2 with SSEs heat-treated with elemental sulfur at elevated temperature exhibited a discharge capacity of 129 mA h g -1 at the second cycle and considerably improved cycling stability.
Bibliographical noteFunding Information:
This work has been supported by DARPA/DSO. Dr. Yoon Seok Jung acknowledges the Korea Research Foundation Grant funded by the Korean Government [KRF-2008-357-D00066].
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)