Two-step growth mechanism of the solid electrolyte interphase in argyrodyte/Li-metal contacts

The structure and growth of the Solid Electrolyte Interphase (SEI) region between an electrolyte and an electrode is one of the most fundamental, yet less-well understood phenomena in solid-state batteries. We present a parameter-free atomistic simulation of the SEI growth for one of the currently promising solid electrolytes (Li$_6$PS$_5$Cl), based on \textit{ab initio} trained machine learning (ML) interatomic potentials, for over 30,000 atoms during 10 ns, well-beyond the capabilities of conventional MD. This unveils a two-step growth mechanism: Li-argyrodite chemical reaction leading to the formation of an amorphous phase, followed by a kinetically slower crystallization of the reaction products into a 5Li$_2$SLi$_3$PLiCl solid solution. The simulation results support the recent, experimentally founded hypothesis of an indirect pathway of electrolyte reduction. These findings shed light on the intricate processes governing SEI evolution, providing a valuable foundation for the design and optimization of next-generation solid-state batteries

Multiscale CT-Based Computational Modeling of Alveolar Gas Exchange during Artificial Lung Ventilation, Cluster (Biot) and Periodic (Cheyne-Stokes) Breathings and Bronchial Asthma Attack

An airflow in the first four generations of the tracheobronchial tree was simulated by the 1D model of incompressible fluid flow through the network of the elastic tubes coupled with 0D models of lumped alveolar components, which aggregates parts of the alveolar volume and smaller airways, extended with convective transport model throughout the lung and alveolar components which were combined with the model of oxygen and carbon dioxide transport between the alveolar volume and the averaged blood compartment during pathological respiratory conditions. The novel features of this work are 1D reconstruction of the tracheobronchial tree structure on the basis of 3D segmentation of the computed tomography (CT) data; 1D−0D coupling of the models of 1D bronchial tube and 0D alveolar components; and the alveolar gas exchange model. The results of our simulations include mechanical ventilation, breathing patterns of severely ill patients with the cluster (Biot) and periodic (Cheyne-Stokes) respirations and bronchial asthma attack. The suitability of the proposed mathematical model was validated. Carbon dioxide elimination efficiency was analyzed in all these cases. In the future, these results might be integrated into research and practical studies aimed to design cyberbiological systems for remote real-time monitoring, classification, prediction of breathing patterns and alveolar gas exchange for patients with breathing problems

Enhancing first-principles simulations of complex solid-state ion conductors using topological analysis of procrystal electron density

Abstract Atomistic-level understanding of ion migration mechanisms holds the key to design high-performance solid-state ion conductors for a breadth of electrochemical devices. First-principles simulations play an important role in this quest. Yet, these methods are generally computationally-intensive, with limited access to complex, low-symmetry structures, such as interfaces. Here we show how topological analysis of the procrystal electron density can be applied to efficiently mitigate this issue. We discuss how this methodology goes beyond current state of the art capabilities and demonstrate this with two examples. In the first, we examine Li-ion transport across grain boundaries in Li3ClO electrolyte. Then we compute diffusion coefficients as a function of charge carrier concentration in spinel LiTiS2 electrode material. These two case studies do not exhaust the opportunities and might constitute motivations for still more complex applied materials.</jats:p

Unveiling Solid Electrolyte Interphase Formation at the Molecular Level: Computational Insights into Bare Li-Metal Anode and Li₆PS_5–<i>x</i>Se_<i>x</i>Cl Argyrodite Solid Electrolyte

The development of high-energy-dense, sustainable all-solid-state batteries faces a major challenge in achieving compatibility between the anode and electrolyte. A promising solution lies in the use of highly ion-conductive solid electrolytes, such as those from the argyrodite family. Previous studies have shown that the ionic conductivity of the argyrodite Li6PS5Cl can be significantly enhanced by partially substituting S with Se. However, there remains a lack of fundamental knowledge regarding the effect of doping on the interfacial stability. In this study, we employ long-scale ab initio molecular dynamics simulations, which allowed us to gain unprecedented insights into the process of solid electrolyte interface (SEI) formation. The study focuses on the stage of nucleation of crystalline products, enabling us to investigate in silico the SEI formation process of Se-substituted Li6PS5Cl. Our results demonstrate that kinetic factors play a crucial role in this process. Importantly, we discovered that selective anionic substitution can accelerate the formation of a stable interface, thus potentially resolving anode–electrolyte compatibility issues

A combined DFT/topological analysis approach for modeling disordered solid electrolytes

In the scope of this study, the Ag2S·CdS·3SnS2 solid electrolyte disordered in the Cd/Sn sublattice is explored by means of the approach involving configurational space (CS) setting and first-principles calculations. Within the density functional theory calculations on the CS, the absolute differences in Ag vacancy formation energies up to 2.6 eV/cell were obtained for possible Cd/Sn dispositions. Subsequently, silver ion migration was modeled using the nudged elastic band method. The migration energies in the range of 0.250 to 2.993 eV/cell were obtained. By application of topological descriptors, namely, the relative disposition of Cd atoms and the number of Cd atoms in the vicinity of Ag vacancy, the reliable correlations were obtained between the Cd/Sn relative disposition and the calculated energy characteristics

Molecular-Level Insight into the Interfacial Reactivity and Ionic Conductivity of a Li-Argyrodite Li₆PS₅Cl Solid Electrolyte at Bare and Coated Li-Metal Anodes

Sulfide glasses, with high room-temperature Li-ion conductivities, are a promising class of solid-state electrolytes for all-solid-state batteries. Yet, when in contact with Li metal, our current understanding of important interfacial phenomena such as electrolyte reduction and Li-ion transport is still quite limited, especially at the atomic scale. Here, using first-principles molecular dynamics simulations, we tackle these open questions head-on and examine key interfacial properties of Li-argyrodite Li6PS5Cl electrolyte at bare and coated Li-metal anodes. Specifically, we investigate the role of the interfacial composition and morphology in a number of Li-metal surfaces, including surfaces coated with thin films of Li2Sn5, MoS2, LiF, and Li3P. Our materials models are designed to gain insights into the early stages of interface formation and structural evolution. In addition, by employing a novel topological analysis of procrystal electron density distribution as applied to interfacial solid-state ionics, we thoroughly assess Li-ion conductivity through the investigated interfaces. Our results provide evidence of progressive breaking of P–S bonds in PS43– groups and eventual P–P recombination of intermediate species as the main reaction mechanisms of Li6PS5Cl reduction by Li metal. We also predict Li2Sn5 as the most suitable coating to partially prevent the electrolyte degradation while keeping a relatively low interfacial resistance. These findings shed light on the interface chemistry of sulfide-based electrolytes in contact with Li metal and pave the way for rationalizing further computational and experimental studies in the field