离子大小对固态电解质中离子交换过程中的热力学,动力学和机械性能的影响
Harsh D Jagad1, Stephen J Harris2, Brian W Sheldon1
1School of Engineering, Brown University, Providence, Rhode Island 02912, United States.
概括
在固态电解质中交换离子,如中氧化物 (LLZO) 与较大的离子,如Na+或Ag+,可以提高断裂强度. 离子大小极大地影响应力,扩散和电子特性,优化电池性能.
科学领域:
- 材料科学 材料科学 材料科学
- 电化学 电化学 电化学
- 固态物理 固态物理
背景情况:
- 固态电解质容易发生电化学机械裂变.
- 离子交换是一种引入压缩应力的方法,增强机械稳定性.
研究的目的:
- 研究交换离子大小对固态电解质应力,扩散,断裂性和电子性质的影响.
- 建立一个框架,通过离子交换优化固态电池性能.
主要方法:
- 结合多尺度建模:密度函数理论 (DFT),分子动力学 (MD) 和连续建模.
- 在兰氧化 (LLZO) 中与较大的同价离子 (Na+,Ag+,K+) 进行离子交换的分析.
主要成果:
- DFT证实,较大的离子更喜欢八面体位点,其大小与化学自由膨胀系数相关.
- 模拟MD显示Na+和Ag+保持良好的流动性,而K+集群;表面压力应力达到~1.0GPa与Ag+.
- 在室温下,Ag+交换降低了Li+扩散率~40%,而Na+的影响微不足道. 没有观察到带隙变化,但Ag+引入了缺陷状态.
结论:
- 离子大小是调整LLZO特性和减轻裂纹的关键参数.
- 优化的离子交换可以显著提高断裂强度和固态电池性能.
- +交换为增强LLZO稳定性提供了一个有前途的途径,对Li+扩散性影响最小.
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