Nanostructuring of 尾-MnO2: The Important Role of Surface to Bulk Ion Migration

详细信息    查看全文

• 作者：David A. Tompsett ; Steve C. Parker ; Peter G. Bruce ; M. Saiful Islam
• 刊名：Chemistry of Materials
• 出版年：2013
• 出版时间：February 26, 2013
• 年：2013
• 卷：25
• 期：4
• 页码：536-541
• 全文大小：361K
• 年卷期：v.25,no.4(February 26, 2013)
• ISSN：1520-5002

文摘

Manganese oxide materials are attracting considerable interest for clean energy storage applications such as rechargeable Li ion and Li鈥揳ir batteries and electrochemical capacitors. The electrochemical behavior of nanostructured mesoporous 尾-MnO₂ is in sharp constrast to the bulk crystalline system, which can intercalate little or no lithium; this is not fully understood on the atomic scale. Here, the electrochemical properties of 尾-MnO₂ are investigated using density functional theory with Hubbard U corrections (DFT+U). We find good agreement between the measured experimental voltage, 3.0 V, and our calculated value of 3.2 V. We consider the pathways for lithium migration and find a small barrier of 0.17 eV for bulk 尾-MnO₂, which is likely to contribute to its good performance as a lithium intercalation cathode in the mesoporous form. However, by explicit calculation of surface to bulk ion migration, we find a higher barrier of >0.6 eV for lithium insertion at the (101) surface that dominates the equilibrium morphology. This is likely to limit the practical use of bulk samples, and demonstrates the quantitative importance of surface to bulk ion migration in Li ion cathodes and supercapacitors. On the basis of the calculation of the electrostatic potential near the surface, we propose an efficient method to screen systems for the importance of surface migration effects. Such insight is valuable for the future optimization of manganese oxide nanomaterials for energy storage devices.

Keywords:

lithium battery; surface; supercapacitor; DFT; cathode; manganese oxides