替代对Na2Fe2F7韦伯石阴极的结构,稳定性和性能的影响
Hanna Z Porter1,2, Emily E Foley1,2, Wen Jin1,2
1Materials Department, University of California Santa Barbara, California 93106, United States.
ACS materials Au
|January 13, 2025
概括
在电化学循环过程中,替代增强了离子阴极 (Na2Fe2F7) 的结构稳定性. 然而,这种替代可以限制提取动力学,并降低总体容量.
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
- 固态化学 固态化学
背景情况:
- 离子 (Na-ion) 阴极对于下一代能源存储至关重要.
- Na2Fe2F7显示出有希望的结果,但在循环过程中遭受结构不稳定和相变.
- 了解结构属性关系是提高Na-ion阴极性能的关键.
研究的目的:
- 研究 (Mg) 替代对Na2Fe2F7.7的结构稳定性和电化学性能的影响.
- 探索用Mg替代的韦伯固体溶液,以提高热力学稳定性.
- 为改进的离子电池阴极确定最佳组成.
主要方法:
- 预测Mg替代韦伯的热力学稳定性的第一原则计算.
- 优化了合成协议以分离特定的多态 (Na2Fe2F7和Na2Mg0.125Fe1.875F7).
- 在狭窄和宽的电压窗口上进行电化学循环测试,以评估稳定性和性能.
主要成果:
- 替代增强了韦伯阶段的热力学稳定性,特别是在较高的含量 (例如,x=0.125) 时.
- 在循环期间,维贝里特相在狭窄的电压窗口 (2.8-4.0 V) 中保持.
- 与未被替换的Na2Fe2F7 (Mg0) 相比,用Mg替换的Na2Fe2F7 (Mg0.125) 显示出更好的循环可逆性和减少相位转换,在更广泛的电压范围 (1.9-4.0 V) 上,尽管动力上有限的Na提取和减少容量.
结论:
- 替代提供了一种提高Na2Fe2F7阴极结构稳定的策略.
- 在增强的稳定性和电化学性能 (容量和动力学) 之间存在一种权衡.
- 进一步的组成优化是必要的,以平衡实际的离子电池应用的结构完整性和能量密度.
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