Timothy Arthur1

1, Toyota Research Inst, Ann Arbor, Michigan, United States

To meet the future demands of future hybrid, plug-in hybrid, and all electric vehicles, advances in energy storage for transportation is indispensable. Additionally, energy diversification is vital to tailor electrification requirements to optimize the cost, range and size of the application. Recently, post Li-ion batteries, such as Li-O2, multivalent and anion batteries, have garnered much attention. The lithium metal sulfur (Li-S) battery is an exciting system due to its high theoretical capacity (1673 mAh/g-S) and the potential of low cost.1 However, realizing Li-S batteries relies on solving key challenges such as dissolution and shuttling of polysulfides, low sulfur utilization at high-areal loading levels, lithium metal dendrite formation, and continuous electrolyte decomposition on the Li metal surface.
The potential benefits of solid-state electrolytes, such as polymer electrolytes, gel electrolytes and ion-conducting ceramics electrolytes, are wide-operating windows, active material dissolution prevention and metal dendrite inhibition. However, low ionic conductivity and interfacial stability require continued development to achieve a viable energy storage system. Recently, ionic conductivities rivaling liquid based-systems have been observed for the sulfide-based, glass-ceramic L10GeP2S12 (LGPS),2 encouraging continued research into solid-state batteries using sulfide-based solid-electrolytes. Tatsumisago et al.3 illustrated and impressive initial cycling results using lithium-indium alloy anode, a lithium iodide/lithium sulfide solid-solution cathode, and a solid sulfide electrolyte: over 1000 mAh/g at 2C cycling for over 2000 cycles. Inspired by the results, developing all solid Li-S batteries presents hope for a high-energy density battery.
Here, we will present the electrochemical discharge mechanism of solid state Li-S batteries using glass-ceramic, sulfide-based solid-electrolyte and a lithium metal anode. The solid-state reactions of the active materials with the solid-electrolyte are evidenced through X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and thermal analysis. Our results reveal that the electrochemical properties are closely tied to the fabrication of the solid-state cathodes. Additionally, researchers have recently observed the decomposition of sulfide electrolytes in contact with lithium metal4,5. We will discuss protection strategies to inhibit undesired reactions at the anode-electrolyte interface as potential solutions to further improve all-solid Li-S batteries for vehicle electrification.

[1] Manthiram, A. et al. Chem. Rev. 2014, 114, 11751-11787.
[2] Kanno, R. et al. Nat. Mater. 2011, 10, 682-686.
[3] Tatsumisago, M. et al. Adv. Sustainable Syst. 2017, 1700017, 1-6.
[4] Sakamoto, J. et al. Electrochimica Acta 2017, 237, 144-151.
[5] Janek et al. Solid-State Ionics 2016, 286, 24-33.