Past and Present Research Systems on Green Chemistry

Biography

Biography: Lingzi Sang

Abstract

The long-lasting environmental concerns arising from the use of fossil fuels and the rapid growth of renewable energy demand requires safe, large-scale, and reliable nextgeneration energy storage systems. All-solid-state lithium-ion batteries potentially offer enhanced energy and power density, and improved battery safety compared to the liquid electrolyte-based Li-ion batteries that are currently in use. Solid lithium-ion conductors such as thiophosphates are potential electrolyte materials for all-solid Li batteries because of their high Li+ ion conductivity, which is close to its liquid counterparts. Current challenges to achieving high performance all-solid-state batteries with long cycle life include shorting resulting predominantly from Li dendrite formation and infiltration through the solid electrolyte (SE), and increases in cell impedance induced by SE decomposition at the SE/electrode interface. In this work, we evaluate the electrochemical properties of two interlayer materials, Si and LiXAl(2-x/3)O3 (LiAlO), at the Li7P3S11 (LPS)/Li interface. Compared to the Li/LPS/Li symmetric cells in absence of interlayers, the presence of Si and LiAlO both significantly enhance the cycle number and total charge passing through the interface before failures resulting from cell shorting. In both cases, the noted improvements were accompanied by cell impedances that had increased substantially. The data reveal that both interlayers prevent the direct exposure of LPS to the metallic Li, and therefore eliminate the intrinsic LPS decomposition that occurs at Li surfaces before electrochemical cycling. After cycling, a reduction of LPS to Li2S at the interface when a Si interlayer is present; LiAlO, which functions to drop the potential between Li and LPS, suppresses LPS decomposition processes. The relative propensities towards SE decomposition follows from the electrochemical potentials at the interface which are dictated by the identities of the interlayer materials. This work provides new insights into the phase dynamics associated with specific choices for SE/electrode interlayer materials and the requirements they impose for realizing high efficiency, long lasting all-solid batteries.