Vacuum-Assisted Layer-by-Layer Nanocomposites for Self-Standing 3D Mesoporous Electrodes

Electrochemical energy storage devices will play a critical role for efficient storage and reliable on-demand supply to portable electronics, electric and/or plug-in-electric vehicles that entail rapid charging/discharging with long cycle life. The design and assembly of nanoscale materials is critical for developing high performance mesoporous electrodes for energy storage devices that can be scaled-up for manufacturing. To address the challenge of nanostructured electrode development, this work reports a layer-by-layer (LbL) fabrication technique based on electrostatic self-assembly coupled with vacuum assisted filtration. By combining electrostatic interactions with vacuum force, thick electrodes (4-50 mu m) of electroactive polyaniline (PANi) nanofibers and oxygen functionalized multiwalled carbon nanotubes (MWNT) are assembled in tens of minutes. The electronic conductivity and mechanical stability are further improved through controlled heat treatment of these electrodes that shows high surface area with interpenetrating networks of nanofibers and nanotubes. Electrochemical measurements reveal high specific capacity of 147 mAh/g originating from the MWNTs and redox active PANi nanofibers that store charges through both electrical double layer and faradaic mechanism with excellent charge/discharge stability over 10,000 cycles. The precise control over the electrode thickness and rapid assembly from this VA-LbL technique show promise for the development of binder-free mesoporous electrodes for next generation electrochemical energy storage devices.