(606i) Ultrathin Gel Electrolytes for Lithium Ion Batteries

Lithium ion batteries reign supreme among commercial electrochemical energy storage technologies. However, the trade-off between energy and power densities inherent to lithium ion batteries often limits their feasibility in many applications. An important example is electric vehicles, where lithium ion batteries must be specifically designed for high power performance. The consequence is lower energy density and greater expense. As a first step to mitigating this trade-off, ultrathin gel electrolyte layers are being developed using a technique called initiated chemical vapor deposition (iCVD). iCVD provides exquisite control over composition and network structure in gel layers with thicknesses anywhere from 10 nm to several micrometers. Crosslinked poly(n-butyl acrylate) was synthesized directly on top of LiCoO₂ composite cathodes by iCVD. Adhesion promoters were used to covalently attach the polymer to the LiCoO₂ active material. The polymer layer imbibed standard liquid electrolyte (1M LiPF₆ in alkyl carbonate mixtures), and characterization by Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy and scanning electron microscopy showed that the gel remained attached to the electrode. The electrodes were assembled into half cells against Li metal and then cycled. The performance of the gel-coated electrodes compared to uncoated, state-of-the-art lithium ion battery electrodes will be presented.