Encapsulated hollow Na2Ti3O7 spheres in reduced graphene oxide films for flexible sodium-ion batteries

Abstract

The binder-free films of hollow Na2Ti3O7 (NTO) spheres and reduced graphene oxide were employed as anodes for sodium ion batteries. The films were assembled by vacuum filtration of the pre-prepared hollow NTO spheres and reduced graphene oxide nanosheets (NTO-rGO). The ultrathin nanosheets, as the building blocks of hollow spheres, optimize the sodium ion transportation at the particle level. Furthermore, the hollow spheres were employed to prevent the restacking of reduced graphene oxide nanosheets and optimize the sodium ion transportation at electrode level. Thanks to the optimized ion transportation on both particle and electrode levels, the as-prepared NTO-rGO film showed enhanced rate performance of a high capacity of 135 mA h g−1 under the current density of 500 mA g−1 and over 650 cycles, demonstrating the superiority of this unique structure.