Oral Defense Examination : Design And Synthesis Of Advanced Cathode Materials For Alkali (Na, K) Ion Batteries

Speaker Jiang Xi (Supervisor: Prof Lee Jim Yang)

Host Department of Chemical and Biomolecular Engineering

Date/Time 21 Nov - 21 Nov, 2.00PM

Venue E5-02-06 , Faculty of Engineering, National University of Singapore

Synopsis

The increase in the number of electrical vehicles and large-scale energy storage systems based on the lithium-ion batteries is expected to significantly raise the battery cost due to the limited and uneven distribution of Li reserves. The need for finding low-cost, earth abundant and alternative battery chemistries has resurrected the development of sodium ion batteries where the charge carriers are based on a more ubiquitous element (sodium). Similar to the lithium ion batteries, the development of sodium ion batteries is strongly dependent on the development of the electrode materials. The lower cost of sodium naturally renders the sodium-ion batteries more suitable for large deployments, for which the electrode materials must possess such desirable attributes as strong safety, high rate performance and long cycle life. The cathode material is usually the limiting factor because of its higher cost, more complex synthesis process and lower specific capacity. Recent research has nonetheless identified Na3V2(PO4)3 as a promising cathode material for sodium ion batteries because of its high thermal stability, high rate capability (after carbon coating) and fast sodium insertion/extraction chemistry. However, many of the research done to date on Na3V2(PO4)3 has focused mostly on improving the material overall rate performance by nanosizing and carbon coating. Cycle life improvement, which weighs in heavily on the life-cycle cost of the sodium ion batteries, has not received the same attention. Nanosizing and surface coating can also result in excess carbon dead weight and low packing density to reduce the Na3V2(PO4)3 energy density. This thesis therefore examines methodologies which can improve the practical use of Na3V2(PO4)3 used as a sodium ion battery cathode material. It also examines other alternative battery technologies based on the alkali-metal ions such as the potassium ion batteries.

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