van der Waals gap modulation of graphene oxide through mono-Boc ethylenediamine anchoring for superior Li-ion batteries†

Abstract

Li-ion batteries stand out among energy storage systems due to their higher energy and power density, cycle life, and high-rate performance. Development of advanced, high-capacity anodes is essential for enhancing their performance, safety, and durability, and recently, two-dimensional materials have garnered extensive attention in this regard due to distinct properties, particularly their ability to modulate van der Waals gap through intercalation. Covalently intercalated Graphene oxide interlayer galleries with mono-Boc-ethylenediamine (GO-EnBoc) was synthesized via the ring opening of epoxide, forming an amino alcohol moiety. This creates three coordination sites for Li ion exchange on the graphene oxide nanosheets' surface. Consequently, the interlayer d-spacing expands from 8.47 Å to 13.17 Å, as anticipated. When explored as an anode, Li–GO–EnBoc shows a significant enhancement in the stable and reversible capacity of 270 mA h g⁻¹ at a current density of 25 mA g⁻¹ compared to GO (80 mA h g⁻¹), without compromising the mechanical or chemical stability. Through ¹³C, ⁷Li and ⁶Li MAS NMR, XPS, IR, Raman microscopy, and density functional theory (DFT) calculations, we confirm the positioning of Li⁺ ions at multiple sites of the interlayer gallery, which enhances the electrochemical performance. Our findings suggest that these novel systematically modulated van der Waals gap GO-engineered materials hold promise as efficient anodes for Li-ion batteries.