Enhanced Electrochemical Performance of NTP/C with Rutile TiO2 Coating, as Anode Material for Sodium-Ion Batteries

NaTi2(PO4)3 (NTP) is known as a promising insertion-type anode material for aqueous and non-aqueous sodium-ion batteries (SIBs), due to its NASICON-type open 3D framework which makes a zero-strain insertion mechanism possible. NTP is considered to be an environmentally friendly, low-cost and high safety material. However, the electrochemical performance of NTP is limited due to its poor electrical conductivity. In this work a solvothermal synthesis method is used to synthesize NTP with a nanocube (NC) morphology. In a one-step synthesis rutile titanium dioxide (TiO2) and carbon coating of NTP are achieved (NTP/C-RT), simultaneously, which significantly improves the poor electrical conductivity of NTP. Additional rutile coating is used to further improve the electrochemical performance compared to simple carbon coating. Rate capabilities of 301 mAh/g are achieved for NTP/C-RT compared to 248 mAh/g for NTP/C at 0.1 C. That is, to the best of our knowledge, the highest gravimetric capacity reported for SIBs using NTP as anode material up to now. The results prove that NTP, which is itself already a promising anode material for SIBs, can be further enhanced with a combined approach of NC morphology, carbon and rutile coating, leading to superior capacities, higher than anywhere else reported in literature.