Computational Design of Cathode Coating Materials for All-Solid-State Lithium Ion Batteries with on-the-Fly Machine Learning

Abstract

All-solid-state lithium-ion batteries have attracted significant research interest in recent years. Solid-state electrolytes have emerged as an appealing alternative to flammable organic liquid electrolytes, with the potential to accommodate higher-voltage cathode materials and a metallic lithium anode. Despite the discoveries of solid electrolyte materials exhibiting superionic conductivities, capacity loss and rate performance degradation has been commonly observed due to the prevailing issue of electrolyte/electrode interface reactivity, which originates from abrupt electrochemical potential changes at the electrode-electrolyte interface. The cycling stability of solid-state lithium ion batteries can be improved through the use of interfacial coating materials, but computationally identifying materials with sufficiently high lithium-ion conductivity can be challenging. Methods such as ab initio molecular dynamics that work well for superionic conductors can be prohibitively expensive when used on materials that conduct lithium ions less well but are still suitable for use as interfacial coatings. We demonstrate a way to address this problem using machine-learned interatomic potentials models in the form of moment tensor potentials. To prevent the potentials from significantly deviating from density functional theory (DFT) calculations we use molecular dynamics simulations coupled with on-the-fly machine learning. The efficiency of the calculations is increased by seven orders of magnitude compared to pure DFT, allowing for significantly improved prediction accuracy relative to experimental benchmarks. Using this approach, we have identified two particularly promising materials, Li3B7O12 and Li3Sc2(PO4)3, that are predicted to enhance long-term cyclability. The top candidate, Li3B7O12, has outstanding interface stability and to our knowledge has not previously been investigated as a lithium-ion conductor.