(208e) Lyten’s Advancements in Lithium-Sulfur Batteries for Electric Vehicles

Among the ‘Beyond-Li-ion’ technologies, lithium-sulfur batteries have distinct advantages, including high specific energy, low cost, improved safety, abundant raw materials that are not plagued by supply chain issues, and low carbon footprint. Yet, their implementation has been challenging despite impressive results in academic environment, deterred mainly by the ‘polysulfide shuttle’ – a phenomenon attributed to the dissolution of polysulfides in electrolyte and formation of a redox shuttle. To address this, Lyten has developed a unique family of 3D Graphene materials from the cracking of hydrocarbons to produce hierarchical porous structure,[1] which has been reported to help mitigating the problem of polysulfide shuttle.[2] With its well-engineered nano/micro/meso porous structure, Lyten 3D graphene can physically retrain sulfur and the intermediate polysulfides. Furthermore, its mechanically flexible and electrically conductive framework counter the problems of volume change and poor conductivity of sulfur and polysulfides respectively, making it an ideal host for high-energy and long-life sulfur cathode in Li-S cells. In parallel, Lyten has been developing new cell components and materials, e.g., novel protected Li composite anodes including 3D architectures, advanced stable electrolytes that can function at low quantities (electrolyte/sulfur ratio) with adequate sulfation to support high rates of discharge, and multi-functional separators that can block polysulfide crossover to the anode. Integration of these advanced components resulted in Li-S cells with a specific energy comparable to current Li-ion cells (250-275 Wh/kg) and even exceeding for short-life applications. The cycle life is progressively improving, with the recent cells exhibiting 300 cycles at C/3 and 100% DOD and over 2200 cycles in a LEO (Low Earth Orbit) satellite cycling @ 20% DOD. There is expected to be further growth in the overall performance of Li-S cells, enabled by the ongoing tuning of the 3D graphene and advances in the cell components and materials, projected to be 325 Wh/kg and > 300 cycles by the end of this year. In parallel, various safety tests, including internal short through nail penetration, external short, overcharge and over-discharge and crush were performed on Li-S pouch and cylindrical 18650 cells, which showed impressive abuse tolerance without thermal runaway. Both the performance and safety results on the prototype cells have been corroborated by external 3^rd party testing. Using their semi-automatic assembly lines (2.4 MWh) commissioned recently, Lyten has been producing cylindrical 18650 (and soon 21700) and pouch cells of 2-10 Ah, and recently shipped samples to various auto OEMs and the DoD customers.

[1] Lyten patent on “Carbonaceous material for Li-S cells” US patent 11309 545 B2, April 19, 2022.

[2] X. Ji, K. Tae Lee and L. F. Nazar, “A highly ordered nanostructured carbon–sulfur cathode for lithium–sulfur batteries”, Nature Materials, Vol. 8, 500–506 (2009)