Synergistic enhancement of ion/electron transport by ultrafine nanoparticles and graphene in Li2FeTiO4/C/G nanofibers for symmetric Li-ion batteries

Abstract

Low-cost Fe-based disordered rock salt (DRX) Li₂FeTiO₄ is capable of providing high capacity (295 mA h g⁻¹) by redox activity of cations (Fe²⁺/Fe⁴⁺ and Ti³⁺/Ti⁴⁺) and anionic oxygen. However, DRX structures lack transport channels for ions and electrons, resulting in sluggish kinetics, poor electrochemical activity, and cyclability. Herein, graphene conductive carbon network permeated Li₂FeTiO₄ (LFT/C/G) nanofibers are successfully prepared by a facile sol-gel assisted electrospinning method. Ultrafine Li₂FeTiO₄ nanoparticles (2 nm) and one-dimensional (1D) structure provide abundant active sites and unobstructed diffusion channels, accelerating ion diffusion. In addition, introducing graphene reduces the band gap and Li⁺ diffusion barrier and improves the dynamic properties of Li₂FeTiO₄, thus achieving a relatively mild interfacial reaction and reversible redox reaction. As expected, the LFT/C/1.0G cathode delivers a remarkable discharge capacity (238.5 mA h g⁻¹), high energy density (508.8 Wh kg⁻¹), and excellent rate capability (51.2 mA h g⁻¹ at 1.0 A g⁻¹). Besides, the LFT/C/1.0G anode also displays a high capacity (514.5 mA h g⁻¹ at 500 mA g⁻¹) and a remarkable rate capability (243.9 mA h g⁻¹ at 8 A g⁻¹). Moreover, the full batteries based on the LFT/C/1.0G symmetric electrode demonstrate a reversible capacity of 117.0 mA h g⁻¹ after 100 cycles at 50 mA g⁻¹. This study presents useful insights into developing cost-effective DRX cathodes with durable and fast lithium storage.