Rechargeable batteries based on metallic anodes are of interest for fundamental and application-focused studies of chemical and physical kinetics of liquids at solid interfaces. Approaches that allow facile creation of uniform coatings on these metals to prevent physical contact with liquid electrolytes, while enabling fast ion transport, are essential to address chemical instability of the anodes.H ere,w er eport as imple electroless ion-exchange chemistry for creating coatings of indium on lithium. By means of joint density functional theory and interfacial characterization experiments,w es howt hat In coatings stabilizeL ib ym ultiple processes,i ncluding exceptionally fast surface diffusion of lithium ions and high chemical resistance to liquid electrolytes.I ndium coatings also undergo reversible alloying reactions with lithium ions,f acilitating design of high-capacity hybrid In-Li anodes that use both alloying and plating approaches for charge storage.Bymeans of direct visualization, we further show that the coatings enable remarkably compact and uniform electrodeposition. The resultant In-Li anodes are shown to exhibit minimal capacity fade in extended galvanostatic cycling when paired with commercial-grade cathodes.Secondary batteries comprising of metallic anodes (e.g.L i, Na, Al) have drawn significant recent attention due to their promise for enabling large (as high as ten-fold) increases in the anodic capacity,incomparison to state-of-art lithium-ion anode chemistry. [1,2] Am ajor barrier to the successful implementation of such anodes is the uneven electrodeposition of the metal in the charging process,w hich leads to formation of rough, so-called dendritic structures.T hese structures are diffusion-limited and as such under extended battery operation can grow to fill the inter-electrode space, short-circuiting the battery. [3][4][5] Previously,u sing continuum modeling,T ikekar et al. [6,7] proposed that dendrite-induced short-circuits can be prevented using electrolytes with moderate mechanical modulus (10 MPa) if afraction of the anions are tethered to prevent cell polarization at high current densities and to maintain electrolyte conductivity in the region near the anode.T here is also al arge body of experimental work showing that dendrite growth can be regulated using solid-state electrolytes, [8] nanoporous polymers or ceramics that host liquids in their pores, [9][10][11] crosslinked polymers, [12,13] as well as with high transference number gel-like electrolytes. [14][15][16][17] Although researchers are now able to address safety concerns associated with Li and Na metal anodes by av ariety of means,t his progress has uncovered difficult challenges associated with uncontrolled parasitic reactions between liquid electrolytes and ar eactive metal electrode. [18,19] In rechargeable batteries that employ metallic anodes, particularly those based on Li and Na, the electrolyte would ideally react with the metal surface to form astable and selflimiting passivation layer termed the solid-electrolyt...