Mechanochemical Preparation of Activated Carbon–Carbon Nanotube Composite Electrode for Zn-Air Battery

Enhancement of the carbon-based air electrodes is crucial for improving Zn-air battery performance. In this work, composite air electrodes combining activated carbon (AC) and carbon nanotubes (CNTs) are prepared via a simple process using a mechanochemical cogrinding process and tested as the cathode in a Zn-air battery cell. The cogrinding step produces the AC–CNT networks, in which CNT bundles bridge between AC particles with close contact. X-ray photoelectron spectroscopy (XPS) analysis of the N 1s spectra suggested a change in the relative distribution of nitrogen-containing functional groups after the mixture. Oxidized N observed in raw AC was no longer detected in the composites, while the relative contributions of pyridinic N, pyrrolic N, and graphitic N changed. These changes may be associated with interfacial interactions during mechanochemical processing, accompanied by defect formation in CNTs and the cracking of AC. As a result, the power generation performance of the Zn-air battery using the composite cathode was maximized at an AC/CNT weight ratio of 50:50. The power density obtained in this way was approximately three times higher than that obtained with a pristine CNT cathode. This improvement would be achieved by the combined effect of the high surface area contributed by AC, the high electrical conductivity of CNTs, and the favorable distribution of nitrogen functional groups mechanochemically created. The result shows that the tuning of AC–CNT interfacial interactions via mechanochemical processing is an effective strategy for enhancing carbon-based air electrodes in Zn-air batteries.