Au包覆的LiMn2O4中锂插入减少的Operando观测和第一性原理计算,Advanced Materials Interfaces

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Au包覆的LiMn2O4中锂插入减少的Operando观测和第一性原理计算
Advanced Materials Interfaces ( IF 4.3 ) Pub Date : 2019-01-16 , DOI: 10.1002/admi.201801923
Kimberly L. Bassett ₁ , Robert E. Warburton ₂ , Siddharth Deshpande ₂ , Timothy T. Fister ₃ , Kim Ta ₁ , Jennifer L. Esbenshade ₁ , Alper Kinaci ₄ , Maria K. Y. Chan ₄ , Kamila M. Wiaderek ₅ , Karena W. Chapman ₅ , Jeffrey P. Greeley ₂ , Andrew A. Gewirth ₁

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在尖晶石LiMn ₂ O ₄（LMO）锂离子电池阴极上沉积保护涂层可有效减少Mn从电极表面的溶解。尽管保护性涂层对LMO循环寿命有积极影响，但关于这些涂层与LMO之间形成的界面，仍有许多待理解之处。使用Rietveld精修的操作性粉末X射线衍射表明，与裸露的LMO相比，Au涂层的LMO模型阴极的晶格参数在重塑后显着降低。与裸露的LMO相比，流经Au涂层的LMO的电荷更少，这表明降低的晶格参数与Li ⁺在Au涂层的LMO中的溶解度降低有关。密度泛函理论计算表明⁺缺陷的近表面在存在Au涂层的情况下在热力学上是有利的，这可以通过抑制在表面形成Jahn–Teller扭曲的Li ₂ Mn ₂ O ₄相来进一步稳定这些阴极。电子结构和化学键合分析表明，Au和LMO之间对去石化表面的杂化作用增强，导致去石化时Au发生部分氧化。这项研究表明，除了过渡金属从电极表面溶解外，保护涂层的设计还必须平衡由电极-涂层界面处的电荷转移引起的势能效应。

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Operando Observations and First‐Principles Calculations of Reduced Lithium Insertion in Au‐Coated LiMn2O4

The deposition of protective coatings on the spinel LiMn₂O₄ (LMO) lithium‐ion battery cathode is effective in reducing Mn dissolution from the electrode surface. Although protective coatings positively affect LMO cycle life, much remains to be understood regarding the interface formed between these coatings and LMO. Using operando powder X‐ray diffraction with Rietveld refinement, it is shown that, in comparison to bare LMO, the lattice parameter of a model Au‐coated LMO cathode is significantly reduced upon relithiation. Less charge passes through Au‐coated LMO in comparison to bare LMO, suggesting that the reduced lattice parameter is associated with decreased Li⁺ solubility in the Au‐coated LMO. Density functional theory calculations show that a more Li⁺‐deficient near‐surface is thermodynamically favorable in the presence of the Au coating, which may further stabilize these cathodes through suppressing formation of the Jahn–Teller distorted Li₂Mn₂O₄ phase at the surface. Electronic structure and chemical bonding analyses show enhanced hybridization between Au and LMO for delithiated surfaces leading to partial oxidation of Au upon delithiation. This study suggests that, in addition to transition metal dissolution from electrode surfaces, protective coating design must also balance potential energy effects induced by charge transfer at the electrode‐coating interface.

更新日期：2019-01-16

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