Low‐Cost Self‐Assembled Oxide Separator for Rechargeable Batteries

Abstract

AbstractRechargeable battery cells having a liquid electrolyte require a separator permeable to the electrolyte between the two electrodes. Because the electrodes change their volume during charge and discharge, the porous separators are flexible polymers with an electronic energy gap Eg large enough for the Fermi levels of the two electrodes to be within it. In this work, a porous film of self‐assembled SiO2 nanoparticles is developed as the separator for a Li‐ion battery with a liquid electrolyte. This coating does not require the plasticity of a polymer membrane and has the required large Eg. If adsorbed water is removed from the SiO2 surface, the nanoparticles bond to one another and to an oxide cathode to form a plastic self‐assembling porous layer into which the liquid electrolyte can penetrate. The Li‐ion batteries with a LiCoO2 cathode coated with SiO2 as a separator show similar performance to cells with a traditional polypropylene separator and improved cyclability with a reduced volume of liquid electrolyte owing to the electrolyte wetting properties of the SiO2 nanoparticles. The SiO2 nanoparticles are easy to prepare, cheap, and environmentally friendly.