Plasma surface engineering of graphite and its effect on advancing the performance of aluminium battery

Abstract

Aluminium batteries, with high gravimetric capacities and cost-effective aluminium metal anodes, are a promising alternative to the existing energy storage devices. Graphite is a frontrunner among variously explored cathode active materials due to its high electrical conductivity and ability to accommodate chloroaluminate anions for non-aqueous aluminium batteries. However, the quality of graphite, surface chemistry, contamination, and various structures affect the performance differently. Particularly, the graphite surface significantly influences the fast intercalation of aluminium anions. Here, we put forward a fast and facile plasma-enabled surface engineering strategy to tailor the commercial graphite flakes to investigate their effect on the storage capabilities of chloroaluminate anions. A mild hydrogen and argon plasma was used to engineer the graphite surface and tailor the structural quality. Notably, the hydrogen plasma-treated graphite exhibits a significant increase in electrochemical performance by delivering a remarkable specific capacity (132.68 mAh/g at 50 mA/g) and excellent high-rate performance (83.94 mAh/g at 1000 mA/g) with good stability. Ex-situ Raman and X-ray photoelectron spectroscopy studies showed that plasma surface tailoring allows the fast intercalation of the chloroaluminate. The controlled plasma surface treatment on graphite directs the fundamental understanding of the basic principles of intercalation chemistry of chloroaluminate in graphite via the surface. The effect of the surface treatment on the ion intercalation and energy storage capability was confirmed and demonstrated by the density functional theory calculation. Such a finding would pave a new path to developing practical aluminium batteries using commercially available graphite.