锂离子电池中正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故障中起主要作用。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,它们对阳极反应和结构的特定影响,如固体电解质中间相(SEI),由于在操作单元中研究此接口的复杂性,仍然知之甚少。在这项工作中,我们结合了操作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,以探测一系列过渡金属离子对形态的影响,机械,化学,和SEI的电性能。通过添加代表性浓度的Ni2+,Mn2+,和Co2+离子进入商业相关的电池电解质,揭示了每种对阳极界面层的形成和稳定性的影响;所有这些都表明对电池性能和稳定性构成威胁。Mn2+,特别是,被证明会诱发厚厚的,软,和不稳定的SEI层,已知会导致电池严重退化,Co2+和Ni2+显著影响界面电导率。当过渡金属离子混合时,SEI降解被放大,表明对细胞稳定性的协同作用。因此,通过揭示这些阴极降解产物在运行电池中的作用,我们为减轻或消除这些降解产物的策略提供了基础。
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 operando 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 Ni2+, Mn2+, and Co2+ 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. Mn2+, in particular, is shown to induce a thick, soft, and unstable SEI layer, which is known to cause severe degradation of batteries, while Co2+ and Ni2+ 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.