Surface modification of Na₂Ti₃O₇ nanofibre arrays using N-doped graphene quantum dots as advanced anodes for sodium-ion batteries with ultra-stable and high-rate capability

Abstract

Both nanoscale surface modification and structural control play significant roles in enhancing the electrochemical properties of battery electrodes. Herein, we design a novel binder-free anode via N-doped graphene quantum dot (N-GQD) decorated Na₂Ti₃O₇ nanofibre arrays (Na₂Ti₃O₇ NFAs) directly grown on flexible carbon textiles (CTs) for high-performance sodium-ion batteries (SIBs). Three dimensional (3D) hierarchical Na₂Ti₃O₇ NFAs constructed from ultrathin Na₂Ti₃O₇ nanosheets provide a large specific surface area and shorter diffusion paths for both ions and electrons. More importantly, the unique N-GQD soft protection produces greatly increased surface conductivity and imparts stability to the nanofibre array structure, leading to fast Na-ion diffusion kinetics. As a result, the flexible 3D hierarchical Na₂Ti₃O₇@N-GQDs/CT electrode as a binder-free anode for a sodium half-battery delivers a high specific capacity of 158 mA h g⁻¹ after 30 cycles and retains ∼92.5% of this capacity after 1000 cycles at a high rate of 4C (1C = 177 mA g⁻¹). Furthermore, it can be assembled into a flexible full cell with Na₃V₂(PO₄)₃@NC/CTs as the cathode, which exhibits high levels of flexibility, excellent long-term cycling stability, and outstanding energy/power density. Our results open up a new approach for the surface modification strategy to enhance the performance of battery electrodes.