Na-Ion Anode Based on Na(Li,Ti)O-2 System: Effects of Mg Addition

This study involves enhancing the performance of the Na(Li,Ti)O-2 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) O-2 system can provide a lower-barrier path for Na-ion diffusion than can a system without the addition of Mg. Experimentally, we synthesize various Na-z(Li-y,Mg-x,Ti)O-2 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 Na-0.646(Li0.207Mg0.013Ti0.78)O-2 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-O-6 layer in the presence of Mg in the (Li,Ti)O-6 layer.