Lithium (Li) metal anodes promise to provide high energy density for Li-ion batteries, but are limited by poor cycle life. Among many strategies reported for extending Li metal lifetime for commercial application, polymeric coatings have been investigated as a low-cost and scalable method. So far, viscoelasticity, self-healability, and single-ion conductivity have been proposed as beneficial properties for polymer coatings, but a systematic study of these properties is lacking. Furthermore, previous works exploring coatings with such properties utilize synthetically complex and expensive polymers. In this work, we report the synthesis of a new class of low-cost and scalable coordination polymers based on anionic crosslinking centers that form dynamic bonds with connector ligands. By controlling the chemical nature of the crosslinking center in these coordination polymers, networks with self-healability, viscoelasticity, and single-ion conductivity can be created. By systematically tuning the coordination chemistry, we found that the properties of self-healability and singe-ion-conductivity both drastically improve the life of Li metal anodes, and that these properties are synergistic. The final structure for use as a Li metal coating is a self-healable, single-ion-conducting network (SSN) with room temperature Li ion conductivity of 3.5 * 10-5 S cm-1. When cut, the material self-heals at room temperature in 12 hours. Molecular dynamics simulations combined with DFT calculations show that the labile bonding between the anionic centers and the coordination ligands impart the self-healability and high ionic conductivity. When used as a coating on Li metal, 1 mAh cm-2 of lithium can be reversibly plated and stripped at rate of 0.5 mA cm-2 for a record high 300 cycles with a high coulombic efficiency of 96.5%. In contrast to other lithium coatings, synthesis of SSN emerges from a facile, scalable, one-pot process with only hydrogen gas as the by-product. Furthermore, the coating can be directly applied to Li metal via a dip-coating process at a cost of only 0.02 $ cm-2. Using this scalable approach, a SSN-coated Li metal anode was used in a high-voltage NMC-532 full-cell with all commercial components. The coated Li metal anodes show dramatically increased cycle life (160+ cycles) over uncoated Li (&lt;100 cycles). The rational design of these scalable coordination polymers offers a promising approach to enable next-generation batteries with Li metal anodes.

Scalable and facile preparation of SSNs for lithium metal stabilization

2019 Fall National Meeting

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