Sodium Titanium Phosphate as Anode Materials for Aqueous Sodium-ion Batteries.

摘要

Renewable energy technology has become one of the promising energy solutions in the future. However, limited by their cyclic behavior, large scale energy storage devices are needed to boost their adoptions in the market. The existing energy storage technologies have limitations that inhibit their adoptions for large scale applications. Our group suggests that one reasonable technology that might overcome these issues is the neutral pH aqueous electrolyte sodium-ion battery. One potential anode material is NaTi2(PO4)3, which has a relatively flexible NASICON skeleton structure and is known in general to have stable performance characteristics in extreme environments. In this work, there are four objectives to study this potential anode material:;NaTi2(PO4)3 has been successfully synthesized via a rapid microwave method. The highest specific capacity is around 85mAh/g has been demonstrated. The effect of different carbon materials (namely graphite and carbon nanotubes) and different processes of adding them (pre and post- synthesis) on the electrochemical performance for sodium titanium phosphate has been extensively studied. Graphite coated NaTi2(PO4) 3 with carbon nanotubes composite electrode has demonstrated a specific capacity of 130mAh/g around theoretical value at 0.1C rate.;The effect of the electrolyte (with different salt concentrations) and the oxygen dissolved in the electrolyte on Na0.44MnO2/NaTi 2(PO4)3 sodium-ion battery system has been studied. High rate performance with an increased salt concentration electrolyte has been discovered and the oxygen effect has been extensively studied. Different charge methods have been tested on the aqueous sodium-ion battery systems and the capacity fading mechanisms have been studied.;1) Develop a rapid method to synthesize electrochemically functional NaTi2(PO4)3. In this case "Electrochemically functional" means the material can store usable capacity for practical application in a composite electrode. 2) Quantify the effect of intimate carbon on NaTi2(PO4)3 electrochemical functionality. (Electrochemical functionality regards the capacity and rate capability of electrode materials) 3) Investigate the stability of NaTi2(PO 4)3 in pH and thermal extremes and the mechanism of capacity fading under different cycling conditions. 4) Examine the performance of NaTi 2(PO4)3 in high salt concentration electrolyte and Li+ electrolyte.