Dendrite-Free Lithium Deposition with Self-AlignedNanorod Structure.

Suppressing lithium (Li) dendritegrowth is one of the most critical challenges for the developmentof Li metal batteries. Here, we report for the first time the growthof dendrite-free lithium films with a self-aligned and highly compactednanorod structure when the film was deposited in the electrolyte consistingof 1.0 M LiPF6in propylene carbonate with 0.05 M CsPF6as an additive. Evolution of both the surface and the cross-sectionalmorphologies of the Li films during repeated Li deposition/strippingprocesses were systematically investigated. It is found that the formationof the compact Li nanorod structure is preceded by a solid electrolyteinterphase (SEI) layer formed on the surface of the substrate. Electrochemicalanalysis indicates that an initial reduction process occurred at ∼2.05V vs Li/Li+before Li deposition is responsible for theformation of the initial SEI, while the X-ray photoelectron spectroscopyindicates that the presence of CsPF6additive can largelyenhance the formation of LiF in this initial SEI. Hence, the smoothLi deposition in Cs+-containing electrolyte is the resultof a synergistic effect of Cs+additive and preformed SEIlayer. A fundamental understanding on the composition, internal structure,and evolution of Li metal films may lead to new approaches to stabilizethe long-term cycling stability of Li metal and other metal anodesfor energy storage applications. [ABSTRACT FROM AUTHOR]