Study on dead-Li suppression mechanism of Li-hosting vapor-grown-carbon-nanofiber-based protective layer for Li metal anodes

Abstract

Li metal exhibits considerable morphological changes during its plating/stripping, and in particular, the formation of needle-like Li or “dead Li” during plating/stripping has limited the widespread the use of Li metal as a secondary battery anode material. In recent attempts to suppress dead-Li formation during Li plating/stripping, the method of hosting Li metal in a stable structure in plating process has attracted considerable attention. Although many types of conductive Li host materials have been introduced to improve the electrochemical properties of Li metal anodes, the mechanism by which conductive Li hosting materials inhibit dead Li in each system has not been precisely investigated. In this study, we introduce a vapor-grown carbon-nanofiber-based protective layer on the Li metal surface and investigate the effects of the protective layer on the formation of dead Li. To this end, we investigate the adhesion properties of the plated Li and the morphological changes of the Li metal anodes with the protective layer during plating. Furthermore, the effects of the protective layer on the electrochemical properties of Li metal anodes are investigated. The protective layer firmly holds the plated Li over entire area, which results in reduced amounts of dead Li during repeated cycling.