Mechanism of charge transport in lithium thiophosphate

Lithium ortho-thiophosphate (Li₃PS₄) has emerged as a promising candidate for solid-state-electrolyte batteries, thanks to its highly conductive phases, cheap components, and large electrochemical stability range. Nonetheless, the microscopic mechanisms of Li-ion transport in Li₃PS₄ are far to be fully understood, the role of PS₄ dynamics in charge transport still being controversial. We build machine learning potentials targeting state-of-the-art DFT references (PBEsol, r²SCAN, and PBE0) to tackle this problem in all known phases of Li₃PS₄ (α, β and γ), for large system sizes and timescales. We discuss the physical origin of the observed superionic behavior of Li₃PS₄: the activation of PS₄ flipping drives a structural transition to a highly conductive phase, characterized by an increase of Li-site availability and by a drastic reduction in the activation energy of Li-ion diffusion. We also rule out any paddle-wheel effects of PS₄ tetrahedra in the superionic phases–previously claimed to enhance Li-ion diffusion–due to the orders-of-magnitude difference between the rate of PS₄ flips and Li-ion hops at all temperatures below melting.
This archive provides all the relevant data and input files that were used to fit the ML interatomic potentials used in this work, along with the relevant Density-Functional Theory calculations that were used for the training set construction, the validation of the ML models and the calculation of the electronic band structure of the β and γ structure. Furthermore, it provides input files of all the molecular dynamics trajectories needed to investigate Li-ion diffusion properties of Li₃PS₄ and the rotational dynamics of PS₄ tetrahedra. Finally, it provides the raw data to reproduce the figures of the manuscript associated with this archive.

锂正硫代磷酸盐（Li₃PS₄）凭借其高导电相、低成本成分和广阔的电化学稳定性范围，已成为固态电解质电池的极具潜力的候选材料。然而，Li₃PS₄中锂离子传输的微观机制尚待充分理解，PS₄动态在电荷传输中的作用仍存在争议。本研究构建了针对最先进密度泛函理论参考（PBEsol、r²SCAN和PBE0）的机器学习势能，旨在解决Li₃PS₄（α、β和γ）所有已知相态中，对于大规模系统和时间尺度的问题。我们探讨了Li₃PS₄所观测到的超离子行为的物理起源：PS₄翻转的激活驱动了结构向高导电相的转变，这一转变以锂位点的可用性增加和锂离子扩散活化能的显著降低为特征。此外，我们还排除了在所有低于熔点的温度下，由于PS₄翻转速率与锂离子跳跃速率的数量级差异，PS₄四面体在超离子相中的桨轮效应——先前声称可增强锂离子扩散——的可能性。此档案提供了用于拟合本研究中使用的机器学习原子间势能的所有相关数据和输入文件，以及用于训练集构建、验证机器学习模型和计算β和γ结构的电子能带结构的相应密度泛函理论计算。此外，它还提供了所有所需分子动力学轨迹的输入文件，以研究Li₃PS₄的锂离子扩散特性和PS₄四面体的旋转动力学。最后，它提供了用于重现与该档案相关的论文图示的原始数据。