Ultra‐Uniform Lithium‐Ion Transport Enabled by Supramolecular Polymeric Networks as Artificial Solid Electrolyte Interphase Layers for Highly Stable Lithium‐Ion Battery Anodes

Polymer-based artificial solid electrolyte interphase (SEI) layers have emerged as a promising solution to address the inherent limitations of silicon-carbon nanocomposite (SCN) anodes. However, their practical implementation remains hindered by the inherent trade-off between achieving complete surface coverage and maintaining a thin, uniform coating. This trade-off often compromises either the electrolyte-blocking capability or the Li-ion transport efficiency. To overcome these challenges, we aim to enhance the ionic conductivity of the artificial SEI layer to levels comparable to liquid electrolytes, while simultaneously improving Li-ion dissociation properties. To this end, we developed a polymer-based supramolecular artificial SEI layer incorporating p-phenylenediamine (pPD) as a bridging agent. The supramolecular network formed via pPD introduces robust hydrogen bonding and facilitates the formation of Li-ion hopping channels through its benzenoid-quinoid transition. As a result, the incorporation of pPD significantly increases the ionic conductivity of PEO and PMMA polymers to 0.215 and 0.106 mS cm^-1, respectively. Furthermore, SCN anodes coated with this supramolecular SEI exhibited over fourfold improvement in cycling stability under ultra-lean electrolyte conditions, closely mimicking commercial operating environments, compared to uncoated SCN in full-cell configurations. This study offers a robust platform for the design of advanced artificial SEI layers tailored for high-performance anode materials.