Construction of silica-oxygen-borate hybrid networks on Al2O3-coated polyethylene separators realizing multifunction for high-performance lithium ion batteries

Abstract The separator, an essential component in lithium ion batteries, faces more challenges with the increasing diversification of electrode materials towards higher energy density and longer life. Herein we report the performance improvements of lithium ion batteries enabled by the multifunctional separator, which is fabricated by constructing the silica-oxygen-borate (Si–O–B) thin layer on Al2O3-coated polyethylene separators through surface engineering. This separator inherits the advantage of Al2O3-coated polyethylene separators in terms of excellent thermal stability and puncture strength, and no obvious dimensional change at 200 °C. The Si–O–B thin layer provides abundant Lewis acid sites and excellent electrolyte uptake to desolvate Li+ ions and traps anions, and therefore favors excellent lithium ion transport properties and lithium/electrolyte interfacial stability. More importantly, the Si–O–B hybrid thin layer endows an additional function of scavenging HF and H2O molecules. The benefits offered by this separator are demonstrated by the enhanced C-rates capability and cycling performance of both LiCoO2/Li half-cell and NCM/graphite full cell, which lies far beyond those achievable with commercial polyethylene separators and Al2O3-coated polyethylene separators. This work presents a simple and efficient strategy to construct multifunctional separators with excellent comprehensive properties, and provides inspiration for the rational design of advanced separators towards next-generation high-performance batteries.