(Invited) Lyten’s High Energy Li-S Batteries for a Sustainable and Circular EV Economy

Abstract

Li-ion batteries (LIB), though widely used in EV batteries will be unable to meet the demands of the rapidly expanding vehicular market, mainly due to the challenges of cost and availability of key materials globally with limited resources, complicated by geopolitical factors. Li-S batteries promise significant advantages over Li-ion batteries with potentially higher specific energy, lower cost, and enhanced safety. However, their implementation has been hampered by poor cycle life due mainly to polysulfide shuttle caused by the soluble polysulfide intermediates. Lyten, an advanced materials company, has developed a family of new 3D Graphene™ materials for various applications including lithium-sulfur batteries. The mechanically flexible and electrically conductive framework of 3D graphene and its hierarchical porous structure make it an ideal host for potentially confining sulfur intermediates and mitigate the polysulfide shuttle. Lyten 3D Graphene™ materials have already shown enhanced sulfur utilization in Li-S cells far superior to the commercial nanocarbons (Fig. 1), even while their further fine-tuning is on-going. Lyten has established environmentally friendly 3D graphene-sulfur cathode fabrication methodology with high sulfur loadings using an aqueous binder.In parallel, Lyten has been developing new protected Li anodes, advanced stable electrolytes that can function at low quantities (electrolyte/sulfur ratio), and multi-functional separators with an ability to block polysulfide crossover. Integration of these cell components resulted in Li-S cells with specific energy comparable to current Li-ion cells (250-275 Wh/kg). The cycle life is, however, relatively modest with 300 cycles @ 100% DOD, C/3 in coin cells, and ~150 cycles@100% DOD and over one thousand cycles @ 50% DOD in multi-layer pouch cells and 18650 cylindrical cells. There is a steady growth in both these categories enabled by further tuning of 3D graphene and advances in other materials.Recently, Lyten has set up semi-automatic assembly lines for both multi-layer pouch and 18650 cylindrical cells, targeting an annual capacity of 2.4 MWh. These cells have started showing excellent consistency in specific energy in both cell formats. Fig.2 shows the narrow variability in the performance of 35 pouch and 18650 cells made recently for a customer.Finally, preliminary safety tests performed on the recent prototype cells have yielded surprisingly good results for the Li-S cells containing Li metal anode. Tolerance to usual abuse conditions, e.g., internal and external shorts, overcharge and overdischarge, as demonstrated in our ARC tests will be an additive advantage of Lyten Li-S cells. Figure 1