Efficient Utilization of Macropores as Artificial Solid–Electrolyte Interphase Channels for High-Capacity Silicon/Graphite Anode Materials

Abstract

Porous architectures for silicon/graphite (Si/Gr) composites can buffer the massive volume expansion of Si particles during electrochemical cycling. However, the large surface area derived from the high porosity leads to unavoidable side reactions at the electrode–electrolyte interface, leading to the formation of thick resistive natural solid–electrolyte interphase (SEI). Herein, a simple and scalable route is developed for coating a polymeric artificial SEI (A-SEI) inside the porous architecture for the Si/Gr composite via a facile incipient wetness impregnation (IWI) method. Cross-sectional focused ion beam microscopic results infer that the polymer coating is successful. Polymer coating for the porous matrix as A-SEI induces sufficient porosity as well as prevents excessive electrolyte penetration into the highly porous matrix. Furthermore, it prevents the direct contact of active materials with electrolytes, minimizing the parasitic reactions that form natural SEIs. Consequently, the polymer coating obtained by IWI enables remarkable enhancement in the long-cycle stability of the porous Si/Gr electrode, in contrast to the nonimpregnated electrode displaying capacity roll-over due to excessive SEI formation. Moreover, it is demonstrated that the coating effectively prevents the formation of dendritic lithium plating on the surface of the Si/Gr electrode, thereby enhancing the safety of the battery.