IDENTIFYING THE ROLE OF ELECTROLYTE ADDITIVES FOR LITHIUM PLATING ON GRAPHITE ELECTRODE BY OPERANDO X‐RAY TOMOGRAPHY

The plating of lithium on the graphite electrode is a major degradation mechanism in lithium-ion batteries (LIBs) and brings safety concerns and leads to short cycle life. Understanding how and when plating occurs is crucial for the development of mitigation strategies, e.g. tuning the electrolyte composition. We present an operando X-ray tomographic microscopy study to monitor the plating of lithium on a graphite electrode. XTM enables non-destructive, quantitative operando characterization of lithium deposition and allows us to probe the role of the electrolyte additives vinylene carbonate and lithium bis(fluorosulfonyl)imide in the standard electrolyte LP57. The additives show a better performances in terms of delayed onset of lithium plating, important to utilise the full capacity of the graphite, since  once lithium plating is initiated this rapidly becomes dominating and hinders further intercalation. For the base electrolyte a homogeneous and dense morphology of plated lithium is found, whereas a more dendritic morphology is observed in the presence of additives. During delithiation, there is a rapid stripping of some of the plated lithium followed by deintercalation. In addition, our work provides a general methodology to track the morphology of plated lithium, which is crucial for fundamental research about battery safety.