Oxygen vacancies in NaTi2(PO4)3 nanoribbons to enhance low-temperature performance for Na storage

Sodium superionic conductor NaTi 2 (PO 4 ) 3 has attracted significant interest as an anode material for sodium-ion batteries (SIBs). However, its practical application is hindered by its low inherent electrical conductivity, particularly at low temperatures. In this study, oxygen vacancies (V O ) were introduced into NaTi 2 (PO 4 ) 3 nanoribbons to enhance sodium storage performance at low temperatures. X-ray diffraction with Rietveld refinement, electron paramagnetic resonance, and X-ray photoelectron spectroscopy confirm that NaTi 2 (PO 4 ) 3 -2 nanoribbons (NTP-2) exhibit the richest V O concentration. These V O , which bridge TiO 6 octahedra and PO 4 tetrahedra, significantly enhance the antibonding interactions of Ti1–O2 and P1–O1 bonds, while stabilizing the bonding in NaTi 2 (PO 4 ) 3 . The energy barrier for Na + migration is reduced to 0.40 eV involving the V O . The optimized NTP-2 anode demonstrates superior low-temperature performance, maintaining a capacity of 106.1 mAh g −1 (about 96.1 % of its initial capacity) at −20 °C after 300 cycles. Additionally, the NTP-2 anode exhibits a moderate Na + diffusion coefficient of 1.47 × 10 –11 cm 2 s −1 at −20 °C. Furthermore, the Na 3 V 2 (PO 4 ) 3 //NTP-2 full cell retains a capacity of 64 mAh g −1 at −20 °C after 250 cycles, highlighting its potential for low-temperature applications. By integrating oxygen vacancies and nanoengineering, both electronic and ionic conductivities are significantly enhanced in NaTi 2 (PO 4 ) 3 , positioning promising applications for SIBs in low-temperature environments.