Zhang Zhenyu, Said Samia, Lovett Adam J, Jervis Rhodri, Shearing Paul R, Brett Daniel J L, Miller Thomas S
Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, Torrington Place, London, WC1E 7JE, U.K.
The Faraday Institution, Quad One, Becquerel Avenue, Harwell Campus, Didcot, OX11 ORA, U.K.
ACS Nano. 2024 Apr 2;18(13):9389-9402. doi: 10.1021/acsnano.3c10208. Epub 2024 Mar 20.
Degradation of cathode materials in lithium-ion batteries results in the presence of transition metal ions in the electrolyte, and these ions are known to play a major role in capacity fade and cell failure. Yet, while it is known that transition metal ions migrate from the metal oxide cathode and deposit on the graphite anode, their specific influence on anode reactions and structures, such as the solid electrolyte interphase (SEI), is still quite poorly understood due to the complexity in studying this interface in operational cells. In this work we combine electrochemical atomic force microscopy (EC-AFM), electrochemical quartz crystal microbalance (EQCM), and electrochemical impedance spectroscopy (EIS) measurements to probe the influence of a range of transition metal ions on the morphological, mechanical, chemical, and electrical properties of the SEI. By adding representative concentrations of Ni, Mn, and Co ions into a commercially relevant battery electrolyte, the impacts of each on the formation and stability of the anode interface layer is revealed; all are shown to pose a threat to battery performance and stability. Mn, in particular, is shown to induce a thick, soft, and unstable SEI layer, which is known to cause severe degradation of batteries, while Co and Ni significantly impact interfacial conductivity. When transition metal ions are mixed, SEI degradation is amplified, suggesting a synergistic effect on the cell stability. Hence, by uncovering the roles these cathode degradation products play in operational batteries, we have provided a foundation upon which strategies to mitigate or eliminate these degradation products can be developed.
锂离子电池中阴极材料的降解导致电解质中存在过渡金属离子，已知这些离子在容量衰减和电池失效中起主要作用。然而，虽然已知过渡金属离子从金属氧化物阴极迁移并沉积在石墨阳极上，但由于在运行电池中研究该界面的复杂性，它们对阳极反应和结构（如固体电解质界面（SEI））的具体影响仍知之甚少。在这项工作中，我们结合电化学原子力显微镜（EC-AFM）、电化学石英晶体微天平（EQCM）和电化学阻抗谱（EIS）测量，以探究一系列过渡金属离子对SEI的形态、机械、化学和电学性质的影响。通过向具有商业相关性的电池电解质中添加代表性浓度的镍、锰和钴离子，揭示了每种离子对阳极界面层形成和稳定性的影响；结果表明，所有这些离子都会对电池性能和稳定性构成威胁。特别是锰，它会诱导形成一层厚而软且不稳定的SEI层，已知这会导致电池严重降解，而钴和镍会显著影响界面电导率。当过渡金属离子混合时，SEI的降解会加剧，这表明对电池稳定性存在协同效应。因此，通过揭示这些阴极降解产物在运行电池中的作用，我们为开发减轻或消除这些降解产物的策略奠定了基础。
