Cation-Disordered High-Entropy Garnet Structures as Solid-State Electrolytes for All-Solid-State Batteries: Machine Learning-Driven Discovery

Exploring the vast chemical space of high-entropy (HE)
solid-state
electrolytes (SSEs) has become a highly active area of battery studies
owing to the exceptional performance of all-solid-state batteries
(ASSBs) with higher energy density and improved safety. The compositional
complexity and extensive chemical space inherent to HE SSEs pose significant
challenges for their investigation via conventional methodologies
such as experimental approaches and density functional theory (DFT)
calculations. In this study, we propose a novel material screening
methodology aimed at accelerating the exploration of promising HE
SSEs while maintaining reasonable computational costs and efficiency.
Specifically, we introduce a machine learning (ML)-based screening
framework to evaluate 4348 cation-disordered high-entropy (CDHE) garnet-type
SSE candidates derived from the well-known Li7La3Zr2O12 structure. First, the ML-based surrogate
model was incorporated to screen electron-conducting (bandgap (Eg) < 1 eV) and thermodynamically unfavorable
(energy above the convex hull (Ehull)
> 0.040 eV/atom). Second, the crystal Hamiltonian graph neural
network
(CHGNet), a recently developed machine learning interatomic potential,
was adapted to find the most stable atomic configuration of each composition
with the following further DFT relaxations. Third, the CHGNet potential
was fine-tuned on the CDHE garnet-type materials. Then, the elastic
properties were calculated with retrained CHGNet to confirm whether
the candidate materials could suppress dendrite formation and exhibit
interfacial stability. Finally, molecular dynamics (MD) simulations
equipped with fine-tuned CHGNet potential were conducted to investigate
the lithium diffusion characteristics of CDHE garnet-type materials,
resulting in the confirmation of three promising CDHE garnet-type
candidates with ionic conductivities exceeding 10–4 S/cm at room temperature.