In-situ Characterizations of the Dynamics of Cathode Electrolyte Interfaces at Different Current Densities

LiNi0.8Mn0.1Co0.1O2 with high nickel content plays a critical role in enabling lithium metal batteries (LMBs) to achieve high specific energy density, making it a prominent choice for electric vehicles (EVs). However, ensuring the long-term cycling stability of the cathode electrolyte interfaces (CEIs), particularly at fast-charge conditions, remains an unsolved challenge. The decay mechanism associated with CEIs and electrolyte in LMB at high current densities is still not fully understood. To address this issues, in-situ Fourier transform infrared (FTIR) is employed to observe the dynamic process of formation/disappearance/regeneration of CEIs during charge and discharge cycles. These dynamic processes further exacerbate the instability of CEIs as current density increases, leading to rupture and dissolution of CEIs and subsequent deterioration in battery performance because of continuous electrolyte reactions. Additionally, the dynamic changes occurring within individual components of CEIs at different cycling stages and various current densities are also discussed. The results demonstrate that excellent capacity retention at small current density is attributed to the enrichment of inorganic compounds (Li2CO3, LiF, etc.) and rendering better stability and smaller expansion of CEIs. This study aims to provide insights into modifying the CEIs under high current densities for achieving stable and sustainable cycling performance of LMBs.

LiNi0.8Mn0.1Co0.1O2高镍含量材料在实现锂金属电池（LMBs）的高比能量密度方面发挥着至关重要的作用，因而成为电动汽车（EVs）领域的一个优选材料。然而，确保正极电解质界面（CEIs）的长期循环稳定性，尤其是在快速充电条件下，仍然是一个尚未解决的难题。在高电流密度下，锂金属电池中与CEIs和电解质相关的衰减机制尚不完全明了。为了解决这一问题，本研究采用了原位傅里叶变换红外光谱（FTIR）技术，以观察充电和放电循环过程中CEIs的形成、消失及再生动态过程。随着电流密度的增加，这些动态过程进一步加剧了CEIs的不稳定性，导致CEIs的破裂和溶解，并因电解质持续反应而引起电池性能的下降。此外，还讨论了CEIs在不同循环阶段和不同电流密度下各个组分所发生的动态变化。研究结果表明，在低电流密度下优异的容量保持率归因于无机化合物（如Li2CO3、LiF等）的富集，从而提高了CEIs的稳定性和减小了其膨胀。本研究旨在为在高电流密度下对CEIs进行改性，以实现锂金属电池的稳定和可持续循环性能提供洞见。