Ultrathin Nanotube/Nanowire Electrodes by Spin-Spray Layer-by-Layer Assembly: A Concept for Transparent Energy Storage

Fully integrated transparent devices require versatile architectures for energy storage, yet typical battery electrodes are thick (20-100 μm) and composed of optically absorbent materials. Reducing the length scale of active materials, assembling them with a controllable method and minimizing electrode thickness should bring transparent batteries closer to reality. In this work, the rapid and controllable spin-spray layer-by-layer (SSLbL) method is used to generate high quality networks of 1D nanomaterials: single-walled carbon nanotubes (SWNT) and vanadium pentoxide (V₂O₅) nanowires for anode and cathode electrodes, respectively. These ultrathin films, deposited with 2 nm/bilayer precision are transparent when deposited on a transparent substrate (>87% transmittance) and electrochemically active in Li-ion cells. SSLbL-assembled ultrathin SWNT anodes and V₂O₅ cathodes exhibit reversible lithiation capacities of 23 and 7 μAh/cm², respectively at a current density of 5 μA/cm². When these electrodes are combined in a full cell, they retain 5 μAh/cm² capacity over 100 cycles, equivalent to the prelithiation capacity of the limiting V₂O₅ cathode. The SSLbL technique employed here to generate functional thin films is uniquely suited to the generation of transparent electrodes and offers a compelling path to realize the potential of fully integrated transparent devices.