Quantifying the search for solid Li-ion electrolyte materials by anion: a data-driven perspective

TL;DR

This study uses data-driven models to analyze and predict solid Li-ion electrolyte performance, highlighting promising material families and suggesting pathways for future solid-state battery development.

Contribution

It provides the first quantitative performance trends of solid electrolytes using machine learning, guiding future materials discovery efforts.

Findings

Sulfides may be more promising than oxides for fast ionic conductivity and stability.

Chlorides and bromides are potential candidates for Li-ion electrolytes.

Nitrides and phosphides are promising against Li-metal anodes.

Abstract

We compile data and machine learned models of solid Li-ion electrolyte performance to assess the state of materials discovery efforts and build new insights for future efforts. Candidate electrolyte materials must satisfy several requirements, chief among them fast ionic conductivity and robust electrochemical stability. Considering these two requirements, we find new evidence to suggest that optimization of the sulfides for fast ionic conductivity and wide electrochemical stability may be more likely than optimization of the oxides, and that the oft-overlooked chlorides and bromides may be particularly promising families for Li-ion electrolytes. We also find that the nitrides and phosphides appear to be the most promising material families for electrolytes stable against Li-metal anodes. Furthermore, the spread of the existing data in performance space suggests that fast conducting materials that are stable against both Li metal and a >4V cathode are exceedingly rare, and that a multiple-electrolyte architecture is a more likely path to successfully realizing a solid-state Li metal battery by approximately an order of magnitude or more. Our model is validated by its reproduction of well-known trends that have emerged from the limited existing data in recent years, namely that the electronegativity of the lattice anion correlates with ionic conductivity and electrochemical stability. In this work, we leverage the existing data to make solid electrolyte performance trends quantitative for the first time, building a roadmap to complement material discovery efforts around desired material performance.