Mechanistic understanding of Li metal anode processes in a model 3D conductive host based on vertically aligned carbon nanofibers
Mechanistic understanding of Li metal anode processes in a model 3D conductive host based on vertically aligned carbon nanofibers
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DOI：
10.1016/j.carbon.2023.118174
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发表时间：
2023-05-31
期刊：
影响因子：
10.9
通讯作者：
Li，Jun
中科院分区：
文献类型：
--
作者：
Rajendran，Sabari;Sekar，Archana;Li，Jun
三维（3D）导电主体的使用是减轻锂金属阳极中枝晶形成的有前景的策略。然而，与3D主机，如过量的固体电解质界面（SEI）和复杂的锂沉积形态的形成相关的基本问题，还没有得到很好的研究。本研究的重点是了解这些关键问题，使用垂直排列的碳纳米管（VACNF）阵列作为模型的3D主机。采用各种表征工具来阐明电沉积Li（e-Li）及其相关SEI的形态和组成。VACNFs上的电子锂具有两种不同的形貌-主要的微米级柱状渗透锂和少量的纳米级同轴锂鞘在VACNFs上的未填充的间隙区域之间的渗透颗粒。在嵌锂过程中，在VACNF阵列的顶部形成了富含有机物的松散的SEI膜，并且在单个VACNF周围形成了富含无机物的SEI鞘。锂电镀将它们转化为直接与e-Li表面接触的无机主导SEI。在剥离Li之后，渗透性Li上的SEI皮肤保持松散地附接到VACNF阵列，并且在Li镀覆/剥离循环期间不可逆地积累，而纳米级Li上的同轴SEI保持为稳定的弹性鞘。疏松的SEI表皮导致电解质消耗和增加的异质性，最终导致电池故障。
The use of three dimensional (3D) conductive hosts is a promising strategy to alleviate dendrite formation in lithium metal anodes. However, the fundamental issues associated with the 3D hosts, such as formation of excessive solid electrolyte interphase (SEI) and complicated Li deposition morphologies, have not been well studied. This study focuses on understanding these critical issues using vertically aligned carbon nanofiber (VACNF) array as a model 3D host. Various characterization tools are employed to elucidate the morphology and composition of electrodeposited Li (e-Li) and its associated SEI. The e-Li on VACNFs exhibits two different morphologies – a dominant micron-scale columnar infiltrative Li and a small amount of nanoscale coaxial Li sheath on VACNFs in the unfilled interstitial area between infiltrative grains. During Li intercalation, an organic-rich loose SEI film forms on the top of VACNF array and an inorganic-rich SEI sheath forms around individual VACNFs. Li plating transforms them into inorganic dominant SEIs directly in contact with the e-Li surface. The SEI skins on the infiltrative Li remain loosely attached to the VACNF array after stripping Li and irreversibly accumulate during Li plating/stripping cycling, while the coaxial SEI on the nanoscale Li remains as a stable elastic sheath. The loose SEI skins cause electrolyte consumption and increased heterogeneity, eventually leading to cell failure.