Exploring the effect of interlayer distance of expanded graphite for sodium ion storage using first principles calculations,Physical Chemistry Chemical Physics

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Exploring the effect of interlayer distance of expanded graphite for sodium ion storage using first principles calculations
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2021-1-18 , DOI: 10.1039/d0cp06134d
R. M. N. M. Rathnayake _{1,

2,

3,

4} , Timothy T. Duignan _{1,

2,

3,

4} , Debra J. Searles _{2,

4,

5,

6,

7} , X. S. Zhao _{1,

2,

3,

4}

Affiliation

Expanded graphite (EG) has been shown to be able to store a significant amount of sodium ions. Understanding the alkali metal ion storage in EG is of importance for improving EG electrode performance. In this work, the effect of interlayer distance of pure EG on sodium ion storage was investigated using the density functional theory calculation method. EG structure models with interlayer distances ranging from 3.4 Å to 10.0 Å were simulated. It was found that EG can store a fairly large amount of sodium ions through an intercalation mechanism without any contributions from the co-intercalation mechanism or adsorption mechanism if the interlayer distance is larger than 4.4 Å and smaller than 6.0 Å. It was also found that an interlayer distance of 6.0 Å gives strong binding energy of sodium ions with EG forming thermodynamically stable sodium-graphite intercalation compound (Na-GIC). However, when the interlayer distance becomes larger than 6.0 Å, the binding energy between sodium ions and EG becomes weaker. Computational results have also shown that the enthalpy of formation of the Na-GIC of EG is energetically more favourable when the interlayer distance is increased. An optimal d-spacing of EG for sodium ion storage was identified in this work. These findings provide atomistic insights into sodium ion storage in EG, providing guidelines for the design of graphite-based anode materials for sodium-ion batteries.

中文翻译：

使用第一原理计算探索膨胀石墨的层间距离对钠离子存储的影响

膨胀石墨（EG）已被证明能够储存大量的钠离子。了解EG中的碱金属离子存储对于提高EG电极性能非常重要。在这项工作中，使用密度泛函理论计算方法研究了纯EG的层间距离对钠离子存储的影响。模拟了层间距离为3.4到10.0的EG结构模型。已经发现，如果层间距离大于4.4且小于6.0，则EG可以通过插层机理存储相当大量的钠离子，而没有来自共插层机理或吸附机理的任何贡献。还发现层间距离为6。0Å能使钠离子与EG形成强结合能，形成热力学稳定的钠-石墨插层化合物（Na-GIC）。但是，当层间距离大于6.0时，钠离子与EG之间的结合能变弱。计算结果还表明，当增加层间距离时，EG的Na-GIC的形成焓在能量上更加有利。最佳选择在这项工作中确定了d间隔用于钠离子存储的EG。这些发现提供了对EG中钠离子存储的原子学见解，为钠离子电池的石墨基负极材料的设计提供了指导。

更新日期：2021-01-25

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