Na-ion anode based on Na(Li,Ti)O2 system: Effects of Mg addition

Abstract

This study involves enhancing the performance of the Na(Li,Ti)O2 system as an Na-ion battery anode with the addition of Mg, which partially replaces Li ions. We perform both computational and experimental approaches to achieve a higher reversible capacity and a faster transport of Na ions for the devised system. Computational results indicate that the Na(Li,Mg,Ti)O2 system can provide a lower-barrier path for Na-ion diffusion than can a system without the addition of Mg. Experimentally, we synthesize various Naz(Liy,Mgx,Ti)O2 systems and evaluate their electrochemical characteristics. In agreement with the theoretical study, Mg addition to such systems improves general cell performance. For example, the prepared Na0.646(Li0.207Mg0.013Ti0.78)O2 system displays an increase in reversible capacity of 8.5% and in rate performance of 13.5%, compared to those characteristics of a system without the addition of Mg. Computational results indicate that these improvements can be attributed to the slight widening of the Na-O6 layer in the presence of Mg in the (Li,Ti)O6 layer.