Coupled reaction and diffusion governing interface evolution in solid-state batteries
This addresses the problem of battery degradation for energy storage applications by providing atomistic insights into SEI formation, though it appears incremental as it builds on existing simulation methods with new analysis techniques.
The researchers tackled the challenge of understanding solid-electrolyte interphase (SEI) formation in solid-state batteries by conducting large-scale reactive simulations with quantum accuracy, revealing a previously unreported crystalline disordered phase (Li₂S₀.₇₂P₀.₁₄Cl₀.₁₄) in the SEI that explains experimental observations and Li creep mechanisms critical to dendrite initiation.
Understanding and controlling the atomistic-level reactions governing the formation of the solid-electrolyte interphase (SEI) is crucial for the viability of next-generation solid state batteries. However, challenges persist due to difficulties in experimentally characterizing buried interfaces and limits in simulation speed and accuracy. We conduct large-scale explicit reactive simulations with quantum accuracy for a symmetric battery cell, {\symcell}, enabled by active learning and deep equivariant neural network interatomic potentials. To automatically characterize the coupled reactions and interdiffusion at the interface, we formulate and use unsupervised classification techniques based on clustering in the space of local atomic environments. Our analysis reveals the formation of a previously unreported crystalline disordered phase, Li$_2$S$_{0.72}$P$_{0.14}$Cl$_{0.14}$, in the SEI, that evaded previous predictions based purely on thermodynamics, underscoring the importance of explicit modeling of full reaction and transport kinetics. Our simulations agree with and explain experimental observations of the SEI formations and elucidate the Li creep mechanisms, critical to dendrite initiation, characterized by significant Li motion along the interface. Our approach is to crease a digital twin from first principles, without adjustable parameters fitted to experiment. As such, it offers capabilities to gain insights into atomistic dynamics governing complex heterogeneous processes in solid-state synthesis and electrochemistry.