Vapor phase infiltration of ZnO quantum dots for all-solid-state PEO-based lithium batteries

Abstract Composite solid polymer electrolytes (CSPEs) have long been considered as one of the most promising candidates for all-solid-state lithium batteries owing to the merits of easy fabrication and low cost. However, the inorganic fillers physically mixed into the polymer matrix have weak polymer-filler interactions and tend to agglomerate, which limits the further improvement of the ionic conductivity and Li+ transference number of CSPEs. In this work, we demonstrated ZnO quantum dots can be chemically incorporated into the poly(ethylene oxide) (PEO) matrix by vapor phase infiltration (VPI), a special variant of atomic layer deposition (ALD). The ZnO quantum dots have strong chemical interactions with PEO polymer chains, which suppresses the crystallization of PEO and enhances the Li+ conduction. Due to the strong interactions, ZnO quantum dots distribute uniformly in the PEO-based solid electrolyte matrix as well as the top surface, which leads to a significant decrease of interfacial resistance with Li metal. As a result, the NCM811|Li half-cell with the VPI-ZnO/PEO/LiTFSI CSPE exhibit high discharge capacity at 50 ℃ (164.7 mAh g−1 at 0.5 C (1 C = 200 mA g−1), 2.8–4.25 V). This result could potentially serve as a model for a more general approach of using VPI to introduce strong polymer-filler interaction in CSPEs for high-performance lithium metal batteries.