Sol-gel synthesis of porous Na 3 Fe 2 (PO 4 ) 3 with enhanced sodium-ion storage capability
Institute for Ionics
School of Engineering
Porous Na 3 Fe 2 (PO 4 ) 3 has been synthesized via a sol-gel method using citric acid as a metal ion complexing agent and polyvinyl alcohol as a structure-guiding agent. The obtained porous Na 3 Fe 2 (PO 4 ) 3 with particle size distribution of 40–60 nm has a typical NASICON structure in a space group of C2/c and the specific surface area is 40.2 m 2 g −1 . Electrochemical measurement results indicate that the initial discharge-specific capacity of porous Na 3 Fe 2 (PO 4 ) 3 is up to 92.5 mAh g −1 and maintains at 86 mAh g −1 after 200 cycles at 20 mA g −1 (92% of theoretical capacity) and the corresponding coulombic efficiency is up to 100% as well as high rate capability performance (71.5 mAh g −1 after 1000 cycles under 500 mA g −1 ). The excellent electrochemical properties are attributed to its particular [Fe 2 (PO 4 ) 3 ] “lantern units” stacked crystal structure and porous morphology, which significantly improves intercalation/de-intercalation kinetic of sodium ions. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.