在一维线性链四可充电离子阴极中探索阴离子氧化过程
Sunita Dey1, Jeongjae Lee1, Sylvia Britto1,2
1Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, U.K.
Journal of the American Chemical Society
|October 27, 2020
概括
离子电池需要新的阴极. VS4是有前途的,但其Mg间隔机制涉及合的V和S氧化还原,形成新的中间和竞争性途径,限制可逆性.
科学领域:
- 材料科学
- 电化学
- 电池技术
背景情况:
- 离子电池 (MIB) 需要稳定的阴极材料来实现商业可行性.
- 由于其1D结构和大链间距,VS4是一个有前途的MIB阴极.
- 在VS4中,Mg间隔/脱间隔过程中的详细氧化还原过程和结构变化尚不清楚.
研究的目的:
- 阐明VS4阴极中Mg间隔和脱间隔的反应机制.
- 在VS4的电化学循环过程中形成的任何新型中间体.
- 了解影响MIB中VS4可逆性和容量的因素.
主要方法:
- 用于表面化学分析的X射线光电子光谱 (XPS).
- 电子结构的V和SX射线吸收近边光谱 (XANES).
- 哈恩回声和MATPASS核磁共振用于局部结构洞察.
- 密度函数理论 (DFT) 与结构预测的进化算法.
- 用于实验结构验证的X射线对分布函数 (PDF) 分析.
主要成果:
- 在VS4中,Mg的间隙涉及离子-离子氧化还原:V4+氧化为V5+,[S2]2-还原为S2-.
- 一种新的中间体,Mg3V2S8,含有[VS4]3-四面体单位,被发现并进行了结构特征.
- 观察到两个相互竞争的反应途径:中间形成和直接转化为MgS和V金属.
- 充电部分改变了V5+/S2-的中间体,而不是原来的VS4,表明了有限的可逆性.
结论:
- 在VS4阴极中的反应机制是一个复杂的离子-离子氧化还原过程.
- 新的中间体和竞争反应途径的形成显著影响了可逆性.
- 过渡金属聚化物通过类似的氧化还原机制提供了更高容量的MIB.
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