Twist-Angle Engineering of Moiré Potentials for High-Performance Ionics in Bilayer Graphene

Controlling ion transport is a fundamental challenge for advanced energy storage systems, including lithium-ion batteries. In this context, bilayer graphene has emerged as a unique platform for investigating and modulating ion diffusion, owing to the highly tunable local atomic environments introduced by twist-angle-dependent moiré superlattices. However, conventional stacking configurations face a fundamental trade-off: AA stacking provides relatively stable Li intercalation but high diffusion barriers, while AB stacking enables fast diffusion but less favorable intercalation stability. Twisted bilayer graphene (tBLG), with twist-angle-dependent moiré structures, offers potential to overcome this limitation, yet systematic understanding of Li intercalation properties across different twist angles remains limited. Here, we systematically investigate Li intercalation in tBLG using first-principles density functional theory calculations, evaluating both intercalation energies and diffusion barriers across multiple twist angles through detailed potential energy surface (PES) mapping. We identify a twisted structure that simultaneously achieves the most favorable intercalation energy and the lowest diffusion barrier among the tBLG structures examined, resolving the trade-off inherent to conventional stacking configurations. 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 a limited set of structures can predict the PES of untested twist angles with high accuracy. This transferability enables efficient screening of optimal tBLG configurations without exhaustive first-principles calculations. Our findings provide design guidelines for tBLG-based battery anodes and demonstrate the effectiveness of twist angle control in optimizing Li intercalation properties.