9-13 July 2012
Africa/Johannesburg timezone
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First-Principle Study on Stabilities of Reactive Products of Sulphur and Oxygen in Lithium- and Sodium- air Batteries.

Presented by Mr. CLIFFTON MASEDI on 11 Jul 2012 from 08:00 to 08:20
Type: Oral Presentation
Session: DCMPM1
Track: Track A - Division for Condensed Matter Physics and Materials

Abstract

Lithium-air batteries are potentially viable ultrahigh energy density chemical power sources, which could potentially offer specific energy up to 3000 Wh/kg being rechargeable. However, the realization of Li-air batteries has a number of difficult problems to overcome, the biggest shortfall exhibited with these systems is the formation of lithium dendrite which raises safety issues. We suggest here to replace the metallic lithium anode by sodium and operate the sodium-air cell, which could enable the development of a new generation of high specific energy rechargeable batteries. We investigated the stabilities of insoluble discharge products of oxygen and sulphur in the Li-air and Na-air batteries(i.e.Li<sub>2</sub>O, Li<sub>2</sub>S, Li<sub>2</sub>O<sub>2</sub>, Li<sub>2</sub>S<sub>2</sub> , Na<sub>2</sub>O, Na<sub>2</sub>S, Na<sub>2</sub>O<sub>2</sub> and Na<sub>2</sub>S<sub>2</sub> structures) using density functional theory within the generalized gradient approximation. Their structural, mechanical and electronic properties were determined. The lattice parameters were well reproduced and agree to within 2% with the available experimental data. The heats of formation predicts Li<sub>2</sub>O and Na<sub>2</sub>O to be the most stable structures whereas Li<sub>2</sub>S<sub>2</sub> and Na<sub>2</sub>S<sub>2</sub> are the least stable which is in good agreement with calculated phonon dispersions. The elastic constants suggest that all the structures are mechanically stable.

Award

Yes

Level

MSc

Supervisor

Prof P.E NGOEPE phuti.ngoepe@ul.ac.za UNIVERSITY OF LIMPOPO MATERIALS MODELLING CENTRE

Paper

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