All-Solid-State Lithium Batteries Using Ti-based Cathode Materials with Sulfide Solid Electrolyte

Abstract

The electrochemical performances of LiTi2(PS4)3 (LTPS), TiS¬2 with a 75Li2S-25P2S5 glass-ceramic solid electrolyte (SE) are investigated. In spite of irreversibility of structural changes, LTPS exhibits a high first discharge capacity of 455 mAh g-1 with good cycling retention of 76% at the 25th cycle between 1.5-3.5 V at 0.12C at 30 oC. In sharp contrast, LTPS with a liquid electrolyte (LE) in a conventional cell loses half of its initial capacity after only 14 cycles. The much poorer performance of LTPS in the LE compared to that in the SE is believed to be associated with dissolution of LTPS into the LE. The results highlight the prospects of exploring electrode materials that are compatible with SEs for all-solid-state batteries. The performances of composite electrodes prepared by controlled ball-milling (BM) of TiS2 and SE for all-solid-state lithium batteries are also investigated, where evolution of the microstructures is focused. Hand-mixed electrodes (HMe) exhibit ~240 mA h g-1 in the voltage ranges of 1.5–3.0 V and 1.0–3.0 V. In contrast, the ball-milled electrodes (BMe) exhibit exceedingly high first charge capacities of 416 mAh g-1 and 837 mA h g-1 in the voltage ranges of 1.5–3.0 V and 1.0–3.0 V, respectively. Excellent capacity retention of 95% in the 1.5–3.0 V range after 60 cycles for the BMe is also demonstrated as well as not losing the rate performance as compared to the HMe. More importantly, a variety of characterization techniques show that origin of the excess Li+ storage is associated with an amorphous (Li)-Ti-P-S phase formed during the controlled BM process.