锂沉积过程中固体电解质间相开裂与自愈合的原位观察

In situ observation of cracking and self-healing of solid electrolyte interphases during lithium deposition

锂金属电池由于其超高的理论容量,被誉为是电池的"圣杯".然而,锂金属电池循环过程中树枝状或苔藓状锂的生长会使电池容量下降、电解液消耗、内部短路甚至起火爆炸.而直接追踪锂枝晶的生长仍然是一个巨大的挑战.本文报道了在CO_(2)气氛下利用环境电镜实时地观察了电化学诱导的锂沉积.研究发现单个锂沉积的形态强烈地受到固体电解质界面(SEI)开裂和自愈合的竞争过程的影响.当SEI膜的开裂速度超过自愈合时,锂晶须的定向生长占主导地位.相反地,当自愈大于裂纹时,圆形锂颗粒的各向同性生长将占主导地位.并且当SEI层是Li2O时,锂沉积的形貌只有球形,没有晶须的生成.因此,可以通过调节锂沉积速率和SEI成分来控制锂的形貌.本文还揭示了锂枝晶生长的一种新的"弱点"模式,这主要是由于在晶须截面上的Bardeen-Herring生长机制的作用.本研究对控制锂电池中锂枝晶的生长具有重要意义.

The growth of lithium(Li)whiskers is detrimental to Li batteries.However,it remains a challenge to directly track Li whisker growth.Here we report in situ observations of electrochemically induced Li deposition under a CO_(2) atmosphere inside an environmental transmission electron microscope.We find that the morphology of individual Li deposits is strongly influenced by the competing processes of cracking and self-healing of the solid electrolyte interphase(SEI).When cracking overwhelms self-healing,the directional growth of Li whiskers predominates.In contrast,when self-healing dominates over cracking,the isotropic growth of round Li particles prevails.The Li deposition rate and SEI constituent can be tuned to control the Li morphologies.We reveal a new“weak-spot”mode of Li dendrite growth,which is attributed to the operation of the Bardeen-Herring growth mechanism in the whisker’s cross section.This work has implications for the control of Li dendrite growth in Li batteries.