| AVS 56th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Wednesday Sessions |
| Session NS-WeA |
| Session: | Nanotubes - Electronics and Functionalization |
| Presenter: | X. Gu, University of Washington |
| Authors: | X. Gu, University of Washington D.B. Knorr, University of Washington G. Wang, Tongji University, China R.M. Overney, University of Washington |
| Correspondent: | Click to Email |
Lithium batteries offer high energy density, a flexible, lightweight design and longer lifespan than competing battery technologies. Poly(ethylene oxide) (PEO) is a polymeric material which has extensively been adopted as an electrolyte component in solid state rechargeable lithium batteries. PEO exhibits good complexation properties and high flexibility and retains good mechanical stability at temperatures up to its melting point. Recently, a layer-by-layer (LBL) technique was introduced to prepare battery thin films. This method offers fine control and tunability of material properties and architecture at the nanometer scale, and is a relatively simple method to implement. Films were fabricated by alternating deposition of PEO and poly(acrylic acid) (PAA) layers from aqueous solutions, However, PEO/PAA layer-by-layer (LBL) films exhibit low ionic conductivity when dry, and thus the inhibition of PEO crystallinity alone is not sufficient to improve the ionic conductivity. To achieve more enhanced conductivity in PEO films, various methods have been introduced. The exceptional electronic properties of carbon nanotubes (CNTs) have prompted intensive studies of PEO/CNTs composites. However, at present, these composites have shown only a moderate conductivity enhancement. LBL assembly has shown for other polymers to allow for excellent control of thickness and composition and diminished phase segregation compared with other methods of construction of CNT composites.
In this work, we demonstrate that fabrication of LBL films with carbon nanotubes is possible in a complex tricomponent film of PEO, PAA, and carboxy-functionalized multiwall carbon nanotubes (MWNT-COOH). Successful incorporation of carbon nanotubes layers and excellent surface coverage was observed by AFM topography images and lateral force microscopy. Our system displayed fast growth of LBL assembled films in the deposition process with film thicknesses reaching 1 mm for films composed of 10 cycles of layers. Rapid growth of the films affords fast preparation of PEO/PAA LBL films with incorporated carbon nanotubes which is essential for battery application. Impedance measurements and electrostatic force microscopy (EFM) were used to analyze the differences in ionic conductivity before and after incorporation of MWNT-COOH in to PEO/PAA assemblies. As expected, conductivity improved with the incorporation of the MWNT-COOH treatment. To this end we also employed thermomechanical characterization techniques including shear-modulation force microscopy (SM-FM) to investigate molecular mobility in the tricomponent systems.