Exploring multiphase conversion pathways in Li-S batteries through cryo-TEM and ML-assisted operando neutron scattering

Abstract Understanding the complex physicochemical processes in conversion-type batteries requires investigations across multiple length scales. Here, we present a novel approach to examine Li-S batteries at the nanoscale by combining cryogenic transmission electron microscopy (cryoTEM) with operando small-angle neutron scattering (SANS). CryoTEM revealed discharge products with a biphasic structure, consisting of nanocrystalline Li2S within an amorphous Li2Sx matrix. Data analysis of complementary operando SANS measurements was accelerated by a convolutional neural network trained to predict scattering curves based on plurigaussian random fields, enabling comprehensive parameter space exploration for model fitting. Our findings are in line with disproportionation-driven deposition of Li2S2 particles that agglomerate and partially reduce to Li2S via solid-state conversion. This challenges the conventional view of direct, step-wise electroreduction of polysulfides at the electrode-electrolyte interface. Overall, our multi-technique approach demonstrates the value of combining localized high-resolution imaging with time-resolved operando scattering measurements to understand complex electrochemical conversion pathways in next-generation energy storage systems.