Surface-Based Li+ Complex Enables Uniform Lithium Deposition for Stable Lithium Metal Anodes
Uncontrollable Li dendrites growth and low Coulombic efficiency (CE) have severely prevented the practical applications of Li metal anode. Here, we propose to use poly(ethylene glycol) (PEG) as an electrolyte additive for suppressing dendritic growth and improving the cycling stability of Li metal anode. The PEG molecule can be absorbed on the surface of Li metal and complex with the Li+ ions effectively, which ensures a homogeneous diffusion of Li+ near the electrode surface and fundamentally avoids dendrite formation. Thus, full cells with LiFePO4|Li configuration can even maintain ∼100% capacity with CE > 99.5% after 250 cycles at 5.0 C.
Single crystals of tin iodide (SnI2) have been grown in silica gels. A detailed microtopographical study of {100} faces have been described. Horizontal striations are predominant on these faces for most of the crystals, while few of them show vertical striations. The horizontal striations are associated with the two-dimensional nucleation theory whereas the vertical striations relate to the growth fronts. Growth layers modified by the presence of misaligned microcystals have been illustrated. The natural etch pits on {100} faces of the crystal are attributed to the dissolution of crystals in the acid set gel. In the light of these observations, the mechanism of the development and growth of these faces have been assessed and the implications are discussed.