Electrochemical Properties and Crystal Structure of Li+/H+ Cation-Exchanged LiNiO2,ACS Applied Energy Materials

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Electrochemical Properties and Crystal Structure of Li+/H+ Cation-Exchanged LiNiO2
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2020-04-03 00:00:00 , DOI: 10.1021/acsaem.0c00602
Takahiro Toma _{1,

2} , Ryo Maezono _{2,

3} , Kenta Hongo _{3,

4,

5,

6}

Affiliation

LiNiO₂ has high energy density but readily reacts with moisture in the atmosphere and deteriorates. We performed qualitative and quantitative evaluations of the degraded phase of LiNiO₂ and the influence of the structural change on the electrochemical properties of the phase. The formation of the Li_1–xH_xNiO₂ phase with cation exchange between Li⁺ and H⁺ was confirmed by thermogravimetric analysis and Karl Fischer titration measurement. As the H concentration in Li_1–xH_xNiO₂ increased, the rate capability deteriorated, especially in the low-temperature range and under low state of charge. Experimental and density functional theory (DFT) calculation results suggested that this outcome was attributed to an increased activation energy of Li⁺ diffusion because of cation exchange. Rietveld analysis of X-ray diffraction and DFT calculation confirmed that the c lattice parameter and Li–O layer decreased because of the Li⁺/H⁺ cation exchange. These results indicate that LiNiO₂ reacting with moisture in the atmosphere has a narrowed Li–O layer, which is the Li diffusion path, and the rate characteristics are degraded.

中文翻译：

Li ⁺ / H ⁺阳离子交换的LiNiO _2的电化学性质和晶体结构

LiNiO ₂具有高能量密度，但是容易与大气中的水分反应并劣化。我们对LiNiO ₂的降解相进行了定性和定量评估，以及结构变化对该相的电化学性质的影响。通过热重分析和卡尔·费休滴定法确定了在Li ⁺和H ⁺之间发生阳离子交换的Li _{1– x} H _x NiO ₂相的形成。Li _1–_x H _x NiO _2中的H浓度增加，速率能力恶化，特别是在低温范围和低电荷状态下。实验和密度泛函理论（DFT）的计算结果表明，该结果归因于由于阳离子交换，Li ⁺扩散的活化能增加。Rietveld的X射线衍射分析和DFT计算证实，由于Li ⁺ / H ⁺阳离子交换，c晶格参数和Li–O层减少。这些结果表明，与大气中的水分反应的LiNiO ₂具有狭窄的Li–O层，这是Li的扩散路径，并且速率特性下降。

更新日期：2020-04-03

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