Ab Initio Study of the Sodium Intercalation and Intermediate Phases in Na0.44MnO2 for Sodium-Ion Battery

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• 作者：Heejin Kim ; Dong Jun Kim ; Dong-Hwa Seo ; Min Sun Yeom ; Kisuk Kang ; Do Kyung Kim ; Yousung Jung
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：March 27, 2012
• 年：2012
• 卷：24
• 期：6
• 页码：1205-1211
• 全文大小：437K
• 年卷期：v.24,no.6(March 27, 2012)
• ISSN：1520-5002

文摘

The Na_0.44MnO₂ structure is a promising cathode material for sodium ion batteries due to a high capacity (130 mAh/g) and good cycle performance. In this work, we present the results of density functional theory (DFT) calculations on the structural and electrochemical properties of Na_0.44MnO₂, combined with experiments. Seven intermediate phases and the two-phase reactions among them were found, where the calculated voltage profile agreed well with experiments. We found that the S-shaped tunnel is not empty in the deintercalated Na_0.22MnO₂ structure but has a partial occupancy of sodium ions. The new sodium sites were found in a limited sodium composition range (x = 0.44鈥?.55) which is attributed to the electrostatic interactions between sodium ions and manganese atoms. The asymmetric lattice evolution in Na_0.44MnO₂ as a function of sodium insertion/deinsertion is shown to be due to the Jahn鈥揟eller effects. On the basis of this interpretation, we suggest that the Cr substitution will reduce the volume change significantly.

Keywords:

sodium ion batteries; density functional theory; sodium manganese oxide; insertion/deinsertion mechanism; Jahn鈭扵eller distortion