Boosting the high-rate performance and cycling life of NaTi2(PO4)3 anode by forming N-doped carbon coating derived from polyacrylonitrile

Abstract

Poor electron conductivity is the key issue influencing the rate capability of NaTi₂(PO₄)₃ (NTP). Hence, herein, polyacrylonitrile (PAN) was utilized as a NTP modifier by simply mixing NTP in a liquid PAN suspension, followed by sintering at 850 °C for 5 h. The product with a PAN/NTP mass ratio of 0.3 delivered splendid rate capabilities (achieving lithiation capacities of 282.9, 243.0, 207.1, 173.1, 133.5, and 257.5 mAh g⁻¹ at 0.1, 0.2, 0.4, 0.8, 1.6, and 0.1 A⁻¹, respectively) and excellent long cycling life (capacity retention of 165.5 mAh g⁻¹ after 1200 cycles at 0.5 A g⁻¹). Based on detailed structural and compositional characterizations, as well as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the uniform N-doped carbon coating stemming from PAN carbonization around the NTP particles promoted electron transfer, while the oxygen vacancies induced by N-doping in NTP facilitated Li⁺ diffusion. The boosted and well matched electronic and ionic conductivities give rise to the optimized electrochemical performance.