Understanding and mitigating mechanical degradation in lithium–sulfur batteries: additive manufacturing of Li₂S composites and nanomechanical particle compressions

Abstract

Lithium–sulfur batteries are poised to outcompete lithium-ion batteries in key sectors such as transportation and grid storage due to the low cost and high theoretical energy density of sulfur as a cathode material. Widespread implementation of this technology is hindered by significant degradation during cycling, including mechanical failure via cracking or detachment of insulating lithium sulfide (Li₂S) from the conductive matrix in the cathode, causing irreversible capacity fade. We developed a technique to additively manufacture Li₂S composites to fabricate rationally designed cathodes and demonstrate the utility of a three dimensionally architected Li₂S composite cathode in a battery. We additionally measure the yet unknown material properties and deformation mechanisms of Li₂S powders via in situ scanning electron microscope (SEM) nanomechanical experiments. Measuring these mechanical properties is a first step towards understanding the process of mechanical degradation and is necessary to enable the rational design of high energy density, long-cycling, and mechanically robust sulfur cathodes.