Achieving Uniform Lithium Electrodeposition in Cross-Linked Poly(ethylene oxide) Networks: "soft" Polymers Prevent Metal Dendrite Proliferation

The propensity of lithium to form nonplanar, mossy, or dendritic electrodeposits at current densities below the diffusion limit is a well-known, fundamental barrier to commercialization of energy-dense storage in lithium metal batteries. It has been proposed that proliferation of Li dendrites can be eliminated by controlling the uniformity and size of the deposits to levels where surface tension and other small-scale interfacial forces are able to planarize the deposition. Herein, we investigate lithium electrodeposition in uniformly porous, nanostructured media formed in cross-linked poly(ethylene oxide) polymer networks enabled by thiol-ene click chemistry. Using galvanostatic strip-plate experiments along with scanning electron microscopy and operando visualization techniques, we critically assess the effectiveness of these materials in enabling uniform, planar deposition of lithium. We report that thiol-ene click networks that host a liquid electrolyte in their pores are more effective than their liquid electrolyte or solid polymer network components in regulating Li deposition at both the nucleation and growth phases. It is shown further that compressive interfacial stresses imparted by the networks during electrodeposition may serve to augment surface tension to enable uniform Li electrodeposition. The practical relevance of these electrolytes is demonstrated in full-cell battery configurations with excellent long-term stability