The rapid rise of electric drive vehicles has accelerated research aimed at developing viable energy storage technologies. Lithium metal batteries (LMB) are considered particularly important in this aspect, but are not available today primarily because the lithium metal anode poses multiple challenges. Among them, the most difficult are the metal’s propensity to form rough electrodeposits at current densities below the diffusion limit and to react with species in its surroundings to initiate thermal runaway. It is noted that because these challenges arise from coupling of chemical reactivity of Li and the out-of-equilibrium transport phenomena that drive morphological and hydrodynamic instabilities at a metal/electrolyte interface, developing the principles to achieve stability in an LMB is as scientifically interesting as it is technologically important.<br/>We report that the multi-scale challenge of achieving stable electrodeposition at a metal electrode may have one elegant solution in the form of crosslinked polymer electrolytes. Motivated by a recent theoretical study by Tikekar et al. which predicted that confining electrodeposition to small length scales is effective in suppressing the morphological instability, we create polymeric electrolytes with hyperuniform pore size distributions. Performing the synthesis using PEO-based co-monomers yields novel materials with exceptional ability to stabilize a Li anode against the full set of chemical, morphological, and hydrodynamic instabilities. We confirm the effectiveness of the materials in galvanostatic ‘strip-plate’ experiments and find that the voltage responses achievable in these materials are exceptional. Additionally, we confirm that these traits can be extrapolated to hybrid crosslinked polymer electrolytes which combine beneficial transport properties of liquids, but at the same time retain the nanostructure of the polymeric network. By means of direct visualization experiments of the Li interphase using optical microscopy, we further show that the cross-linked electrolytes promote uniform electrodeposition of Li at both high and low current densities. At low currents, the behavior is attributable to nanostructuring of transport pathways in the electrolytes, while at high currents it is shown to be a consequence of the electrolyte's ability to completely arrest electroconvective instabilities above the diffusion limit.

Lithium electrodeposition in crosslinked polymer electrolytes

2019 Spring National Meeting

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