Achieving in-situ hybridization of NaTi2(PO4)3 and N-doped carbon through a one-pot solid state reaction for high performance sodium-ion batteries

The development of green, sustainable and low-cost energy storage materials through simple and environmental friendly routes is of great significance for futural large-scale energy storage systems. Due to its unique sodium super ionic conductor (NASICON) structure, polyanion-type NaTi2(PO4)3 (NTP) is regarded as one of the promising potential cathode materials for sodium-ion batteries (SIBs). However, its practical application has been impeded by its intrinsic poor conductivity for unmodified NTP. To resolve this issue, this work hybridizes the NTP with a N-doped carbon matrix (NC) through a facile one-pot solid state reaction, taking an organophosphonic acid (ethylenediamine tetramethylene phosphonic acid, EDTMPA) as source material providing carbon, nitrogen and phosphorous element at the same time. The as-prepared NTP@NC composite not only possesses improved electrical conductivity, but also mitigates particle agglomeration during prolonged charge-discharge cycles. As a result, the NTP@NC composite exhibits an outstanding sodium storage behavior, in terms of a high specific charge capacity (105.6 ​mA ​h ​g−1 at 0.2 ​C with 87.3% initial coulombic efficiency), an excellent cycle performance (101.2 ​mA ​h ​g−1 charge capacity after 100 cycles at 0.2 ​C with a charge capacity retention of 95.8%) and outstanding rate capabilities (103.6 ​mA ​h ​g−1 charge capacity at 1 ​C and 71.5 ​mA ​h ​g−1 at 5 ​C, respectively).