Towards Ultra-thick Battery Electrodes: Aligned Carbon Nanotube-Enabled Architecture

Increasing the specific capacity of Li-ion battery electrodes and minimizing the relative weight and volume of inactive components by increasing the electrode thickness are important for further improvements of Li-ion technology. Conventional electrodes contain active particles mixed with conductive additives and a polymer binder in a mixture typically limited by thickness and homogeneity, porosity control, tortuous diffusion paths, and high electrical and thermal resistances. We report the fabrication of ultra-thick (1 mm) electrodes composed of vertically aligned carbon nanotubes uniformly coated with Li-alloying materials (here, silicon) through vapor deposition techniques. The electrodes demonstrate a specific capacity much larger than standard graphitic anodes, high Coulombic efficiency, and stable performance for 250 cycles. With thermal conductivity >400 W upsilon .m-1K-1, the electrode provides a significantly lower thermal resistance than a densely packed nanoparticlebased electrode of similar thickness. Since most degradation processes in Li-ion batteries are temperature-dependent, the achieved results are of great practical significance.