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过渡金属溶解机制和对复合材料LiNi_0.5Mn_1.5O₄阴极膜中的电子导电性的影响

Julia C Hestenes¹, Jerzy T Sadowski², Richard May³

¹Program of Materials Science and Engineering, Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York10027, United States.

ACS materials Au

|December 13, 2023

概括

使用LiNi0.5Mn1.5O4阴极的高压电池由于过渡金属溶解而降解. 这项研究揭示了与循环性能差相关的酸驱动反应和表面变化,需要改善电解质以保持稳定性.

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
电池技术电池技术

背景情况:

像LiNi0.5Mn1.5O4 (LNMO) 这样的高压螺旋阴极材料在没有的情况下提供高能量密度.
由于高电压下的电解质氧化和过渡金属溶解相结合,LNMO电池的循环运行不佳.

研究的目的:

阐明LNMO阴极中过渡金属溶解背后的机制.
用先进的光谱技术研究电解质氧化和金属溶解之间的联系.

主要方法:

运行电子磁共振 (EPR) 和核磁共振 (NMR) 光谱仪.
在现场溶液NMR和X射线光发射电子显微镜 (XPEEM) 与X射线吸收光谱 (XAS) 和X射线光电子光谱 (XPS).
电子导电性测量. 电子导电性测量.

主要成果:

在LNMO中过渡金属溶解与HF形成相结合,表明在充电过程中发生了酸驱动的不成比例反应.
LNMO加速LiPF6分解和Mn2+溶解,可能是由于酸性Mn-OH基.
充电期间的表面重建会产生不成比例的Mn3+位点,形成溶解的Mn2+和固体的Mn4+.
放电导致阴极电解质介相 (CEI) 中的MnF2形成,显著降低薄膜导电性.

结论:

酸驱动的不成比例和表面重建是LNMO中过渡金属溶解的关键机制.
在CEI中形成的MnF2阻碍了电池的性能.
开发具有增强阳极稳定性和减少酸性副产品形成的电解质对于改善LNMO阴极寿命至关重要.

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