Single-Wall Carbon Nanotubes Embedded in Active Masses for High-Performance Lead-Acid Batteries

This work reports on successful attempts to improve the performance of lead-acid batteries by the use of carbon nanotubes as additives to the active mass of both positive and negative electrodes. Both single-wall carbon nanotubes (SWCNT) and multi-wall carbon nanotubes (MWCNT) from commercial sources were tested. The use of SWCNT seems to be very advantageous based on this work. Lead-acid prototype cells which electrodes contained SWCNT showed superior performance in terms of high specific capacity, improved cycle-life, low resistivity, better kinetics and higher rate capability. Post mortem analysis by electron microscopy and Raman spectroscopy indicated their stability in both electrodes during prolonged cycling. Morphological, structural and surface area analyses seemed to prove that the presence of SWCNT mitigates pronouncedly the detrimental sulfation phenomena, namely, formation of large, inaccessible PbSO4 particles upon discharge. We suggest that their presence in both positive and negative electrodes of these batteries increases the effective electronic conductivity and improves the contact among the particles, thus leading to homogeneous current distribution throughout the electrodes. We achieved specific electrodes capacities around 120 mAh g−1 and could demonstrate 950 cycles with cells operating at 25% depth-of-discharge by adding SWCNT, while CNT-free cells could exhibit only 90 mAh g−1 and reach only 200 cycles at the same experimental conditions.