Na2Ti3O7 nanowires with TiO2 and N-doped carbon dual-shells as binder-free electrodes for efficient sodium storage

Insufficient electronic/ionic conductivities and structural deformations upon sodiation/desodiation of layered Na 2 Ti 3 O 7 severely hinder its full application in sodium-ion batteries. Na 2 Ti 3 O 7 nanowires with TiO 2 and N-doped carbon dual-shells are synthesized by hydrothermal synthesis to construct conductive interpenetration network anode for efficient sodium storage. The Na 2 Ti 3 O 7 -based interpenetrating network is sequentially subjected to controllable H + -Na + ion exchange, dopamine/pyrrole modification, and thermal treatment to form the Na 2 Ti 3 O 7 @TiO 2 @N-doped carbon nanowires. Because of the rigid TiO 2 shell to protect the Na 2 Ti 3 O 7 core, the nitrogen-doped carbon shell with high specific surface area to enhance the conductivity, and the interpenetrating network to provide direct and fast diffusion pathways, the resultant NTO@TiO 2 @N-doped carbon electrode exhibits excellent electrochemical performances. Even at a high current density of 80 C (1 C = 177 mA g −1 ), the reversible capacity of the electrode is up to 78.3 mA h g −1 , 6.6 times that of bare Na 2 Ti 3 O 7 electrode. Further kinetic analyses of the CV curves at various scan rates reveal that the pseudocapacitive process contributes as high as 88.4% of the total capacity at the high scan rate of 10 mV s −1 .