Lithium metal is an attractive anode for next-generation, high-energy batteries but it suffers from both capacity fading and safety problems associated with microstructural and dendritic growth. A detailed understanding of the fundamental processes that lead to an uneven Li deposition is necessary to develop new and effective strategies to mitigate dendrite growth. The morphology of Li deposits is highly dependent on the choice of electrolyte system with improved cycling performance attributed to a more uniform, robust and conductive solid electrolyte interphase (SEI). [1] In this work we use in situ nuclear magnetic resonance (NMR) spectroscopy in combination with electrochemical characterisation techniques and scanning electron microscopy (SEM). With in situ NMR we are able to monitor and quantify the microstructures that form during lithium deposition. As a result of the ‘skin depth issue’ of metals, that is the electromagnetic RF field excites only the surface of the Li metal, NMR is a sensitive and quantitative method for microstructure formation.[2] Furthermore, the resonance of the microstructural peak gives an indication of the morphology of the growing deposits. [3] This allows for an effective comparison of different electrolyte systems and lithium plating conditions. [2,3] Superconcentrated electrolytes are investigated in detail as their suppression of dendrite growth has been reported in many studies. [1,4] Different electrochemical cycling parameters are investigated including the relatively unexplored method of applying pulsed current as to ascertain the role of the concentration gradients in the SEI layer. Reference s : [1] Liu, B. et al. Joule 2, 833–845 (2018). [2] Bhattacharyya, R. et al. Nat. Mater. 9, 504–510 (2010). [3] S. Chandrashekar, et al. Nat. Mater. 11, 311-315 (2012). [4] Qian, J. et al. Nano Energy 15, 135–144 (2015).