Shape-Controlled Guanine Self-Assemblies for Stable and Fast-Ion Solid-Electrolyte Interphases in Sustainable Li Metal Batteries

Abstract

Guanine (G) is a fascinating molecular tool because of its ability to create supramolecular self-assemblies; thus, G is usable in a wide range of applications. Although the shape of G self-assemblies is an important factor governing supramolecular structures and properties, its control is challenging. Herein, we demonstrate that the shapes of G self-assemblies can be tuned by introducing alkyl (G8), fluoroalkyl (G8f), and oligoether (G8g) side chains into the G moiety. Consequently, we observe an unordered scaffold for G and G8g, quartet-based assemblies for G8, and hexads-based assemblies for G8f, as evidenced by scanning tunneling microscopy and molecular mechanics calculations. In addition, the shape-varying G self-assemblies show promise as artificial solid-electrolyte interphases (SEI) for lithium (Li) metal battery electrodes, revealing enhanced mechanochemical stability and reduced SEI resistance and activation energy for charge transport, particularly for G8f-Li cells, which might result from favorable self-assembling ability and improved structural integrity. We expect the side-chain engineering of G self-assemblies may provide a useful strategy for designing artificial SEIs for Li metal batteries and related supramolecular systems because of its simplicity and versatility.