Design strategies for composite cathode to realize the high energy density and productivity in sulfide-based all-solid-state-batteries

Abstract

To realize a high energy density in all-solid-state batteries with outstanding fire safety in practical industries, it is essential to simultaneously satisfy various conditions. First, to ensure productivity, the electrode fabrication process would proceed with a wet slurry process, with a focus on minimizing the drying process that consumes a lot of times and cost. Based on this process, thickening of composite cathode should be achieved with the introduction Li-metal anode or anode less to maximize the available capacity per volume. At the same time, internal resistance must be minimized by constructing a uniform microstructure in the composite cathode and forming an intact interfacial SE-SE and AM-SE contact. While all these conditions need to be achieved concurrently, the increase in electrode drying speed to enhance productivity may act as a factor in increasing tortuosity by migrating and accumulating the low-density sulfide solid electrolyte to the electrode surface.

In this study, we try to deal with this problem by adjusting the particle size of the solid electrolyte in the composite cathode. To do this, thick composite cathode with an areal capacity of approximately 7mAh/cm2 was manufactured with small particle size of solid electrolyte (0.6𝜇m SE) and large particle size of solid electrolyte (3𝜇m SE), respectively, based wet electrode fabrication process. The drying of electrode was carried out at temperature of 60oC, 90oC, 120oC, and 150oC. We investigate the electrochemical performance for 0.6𝜇m SE electrode and 3𝜇m SE electrode by the impact of increasing drying temperature. Through this analysis, the advantages and disadvantages of the small and large particle sized SE were examined, and strategy to achieve synergetic effect by combining advantages of each were introduced. Using this strategy, it was possible to minimize tortuosity by suppressing SE migration under fast drying rate while achieving intact SE-SE and AM-SE interface formation. This result would help to realize high energy density with excellent productivity in sulfide based all solid-state batteries.