Synthesis of NaTi2(PO4)3@C microspheres by an in situ process and their electrochemical properties

Sodium-ion batteries (SIBs) have broad applications in the field of power grid energy storage owing to their significant cost advantages. Although the 3D framework structure of NaTi2(PO4)3 with a sodium superionic conductor (NASICON) has recently been regarded as a promising anode material in SIBs, the low inherent electrical conductivity of NaTi2(PO4)3 has hindered its practical application to batteries. However, since a number of research studies have shown that the conductivities of composite materials can be improved by carbon doping or coating, the carbon-coated NaTi2(PO4)3@C (NTP@C) composite is expected to show excellent electrochemical performance in SIBs. In general, the production of NTP@C requires two steps (i.e. sample preparation and carbon coating), and the development of a one-step in situ preparation of NTP@C is desirable. In the present work, NTP@C microspheres with carbon concentrations of 1.4% and 4.95% were prepared in situ by a simple spray method followed by calcination. Of these, the NTP@C with a carbon content of about 4.95% displayed superior properties, delivering a high capacity of 105.26 mA h/g at a current rate of 5 C for the initial cycle, and presenting long-term cycling stability with a slow capacity decay of about 0.018% per cycle over 2000 cycles. The excellent electrochemical performance of the NTP@C microspheres can be attributed to the improved conductivity due to carbon coating and the enhanced stability provided by the microsphere structure. Thus, NTP@C is a promising alternative anode material for SIBs. [Display omitted] •A facile in-situ preparation of NaTi2(PO4)3@C was proposed via one-step method.•The obtained composite with various carbon content shows micro spherical morphology.•The composite with 5% carbon content has excellent electrochemical properties in SIBs.•The coated carbon of NaTi2(PO4)3@C enhanced the anodic conductivity and durability.