Agar-assisted sol-gel synthesis and electrochemical characterization of TiNb2O7 anode materials for lithium-ion batteries

Abstract TiNb2O7 powders are synthesized via a newly developed agar-assisted sol-gel process for the first time. Phase-pure TiNb2O7 powders are obtained upon calcination at 800 °C. On contrast, TiNb2O7 powders synthesized via the conventional solid-state method require high calcination temperature at 1100 °C for the complete compound formation. The samples synthesized with agar improve the morphology with submicron-sized particles. The formed porous structure is favorable for enhancing the electrochemical kinetics due to the large contact area between the electrode and the electrolyte. Based on the electrochemical active surface area analysis, the electrical double-layer capacitance of TiNb2O7 powders synthesized via both the agar-assisted and the solid-state method is 145 mF cm−2 and 22 mF cm−2, respectively. The electrochemical active surface area of the sample prepared via the agar-assisted method is higher than that of the sample prepared via the solid-state method. The TiNb2O7 sample synthesized via the agar-assisted process yields 284 mAh g−1 at 0.1 C, whereas the sample synthesized via the conventional solid-state method yields only 265 mAh g−1 at 0.1 C. The discharge capacities of the agar-assisted synthesized sample are 205 mAh g−1 and 174 mAh g−1 at 5 C and 10 C, respectively. Moreover, the sample exhibits high capacity retention of 91% after 100 discharge-charge cycles at 5 C. Based on the obtained results, the agar-assisted sol-gel process is inferred as one of the facile methods for preparing high performance anode materials for lithium-ion batteries.