Understanding and Mitigating Mechanical Degradation in Li-S Batteries: Lithium Sulfide Particle Compressions and Additive Manufacturing of Lithium Sulfide-Carbon Composites

Li-S batteries are poised to outcompete Li-ion batteries in key sectors such as transportation and grid storage. Improving energy density and mitigating degradation in Li-S batteries could unlock immense impacts such as gigaton-order annual CO2 reduction. Well-designed electrolyte systems can mitigate the degradation mechanisms of electrolyte reactivity, polysulfide shuttling, and lithium dendrite growth. The most significant remaining degradation mechanism is mechanical failure and detachment of insulating Li2S from the conductive matrix in the cathode, causing irreversible capacity fade. We measure the yet unknown material properties and deformation mechanisms of Li2S powders via in situ SEM mechanical experiments. Understanding these basic properties is a first step towards rational design of high energy density, long-cycling, and mechanically robust sulfur cathodes. We also describe the development of a novel technique for additive manufacturing of Li2S composites to fabricate such rationally designed cathodes and demonstrate a 3D printed Li2S cathode with feature sizes 3x smaller than previously attainable via additive manufacturing methods for Li-S cathode materials . This work represents the most fundamental mechanical study of Li-S batteries to date and will pioneer a new design strategy for 3D-structured Li-S cathodes. Figure 1