Free-standing electrodes composed of carbon-coated Li₄Ti₅O₁₂ nanosheets and reduced graphene oxide for advanced sodium ion batteries

A free-standing electrode composed of carbon-coated Li₄Ti₅O₁₂ nanosheets and reduced graphene oxide (designated as LTO-C/RGO) is fabricated for Na storage by modified vacuum filtration and subsequent annealing. In this process, graphene oxide with negative charges and LTO-C nanosheets with abundant charged ions are self-assembled into the nanocomposite based on the screening effect of electrostatic repulsion. The unique structure of the confined LTO-C nanosheets in a highly conductive interconnected RGO network not only promotes the reaction kinetics and structural stability of the electrodes during Na⁺ insertion/extraction, but also provides plenty of interfacial sites for Na⁺ adsorption giving rise to additional interfacial Na storage. The free-standing LTO-C/RGO anode for sodium ion battery exhibits a high capacity of 166 mAhg⁻¹ at 1 C, good rate capability of 98.7 mAhg⁻¹ at 5 C, and superior cyclic performance of 114 mAhg⁻¹ at 2 C after 600 cycles. The materials boasting superior Na storage have large potential in high-performance sodium ion batteries in portable, flexible and wearable electronics.