Twist-Angle Engineering of Moir\'e Potentials for High-Performance Ionics in Bilayer Graphene

TL;DR

This study demonstrates how twist-angle engineering in bilayer graphene can optimize ion intercalation and diffusion, overcoming traditional trade-offs, through first-principles calculations and machine learning models.

Contribution

It systematically analyzes Li intercalation across various twist angles in bilayer graphene, identifying optimal angles and developing transferable models for ion transport prediction.

Findings

Sigma 37 structure (9.43°) has the best intercalation energy and lowest diffusion barrier.

PES governed by local atomic environments, enabling accurate transferability.

Transferable models reduce computational cost for screening twist-angle effects.

Abstract

Controlling ion transport is a fundamental challenge for advanced energy storage. Bilayer graphene offers a unique platform for modulating ion diffusion via twist-angle-dependent moire superlattices, yet conventional stacking configurations face an inherent trade-off: AA stacking provides stable Li intercalation but high diffusion barriers, while AB stacking enables fast diffusion but poor intercalation stability. Twisted bilayer graphene (tBLG) offers potential to overcome this limitation, yet systematic understanding across different twist angles remains limited. Here, we investigate Li intercalation in tBLG using first-principles density functional theory, evaluating intercalation energies and diffusion barriers across multiple twist angles through potential energy surface (PES) mapping. The Sigma 37 structure (9.43 degrees) simultaneously achieves the most favorable intercalation energy (-2.39 eV) and the lowest diffusion barrier (0.14 eV) among all structures examined, resolving the conventional stacking trade-off. Furthermore, using the Smooth Overlap of Atomic Positions (SOAP) descriptor, we demonstrate that the PES is governed by local atomic environments and that a model trained on limited structures predicts the PES of untested configurations with high accuracy. This transferability enables efficient screening without exhaustive first-principles calculations, establishing a systematic framework for twist-angle engineering of ion transport in two-dimensional layered materials.