Dual-Functional Molecular Design Enabling Conformal Electrodeposition of Polymer Networks (EPoN) as Electrolyte Interphases for 3D Solid-State Batteries

Interfaces between materials of various functionalities are omnipresent in solid-state energy-storage devices and partially determine the device performance and degradation due to interfacial incompatibility, instability, resistance, and loss of contact over cycling. Electrolyte-type interphases that bridge battery components and materials with disparate functions, such as the active electrode materials and electrolytes, could overcome some of these detriments. Additionally, 3D thin-film solid-state batteries as promising candidates for high-performance microscale power sources require 3D ultrathin solid electrolyte interphases, as they take advantage of both short ion diffusion distances for high rate and the third dimension for high material loading and energy density. Important characteristics of such electrolyte-type interphases are their capability of electronic insulation and the physical separation of incompatible materials while allowing for ion transport. However, a key challenge of obtaining such functional interphases in batteries is their conformal deposition as thin and uniform coatings on 3D electrode architectures.<br/>Here, we introduce the electrodeposition of polymer networks (EPoN) as a general approach to uniformly coat a wide range of polymers with varying functionalities on non-planar conductive materials. Conceptually, EPoN utilizes electrochemically activated crosslinkers as polymer end groups or pendant groups to confine their network formation exclusively to the material surface upon charge transfer, yielding a passivating and self-limiting growth of conformal and uniform coatings with tunable submicron thickness on conductive materials. Specifically, choosing poly(ethylene glycol) (PEO) as the Lithium-ion conducting backbone, we showed that our rational molecular design enables the conformal electrodeposition of ultrathin functional coatings with solid polymer electrolyte properties on 3D structured electrodes that allow designer interphases in various solid-state battery architectures and chemistries.