Mesoporous and defective activated carbon cathode for AlCl4− anion storage in non-aqueous aluminium-ion batteries

Most commercial rechargeable battery types suffer from several drawbacks, including high cost, toxic and hazardous materials, poor performance and general non-sustainability. Aluminium-ion batteries (AIBs), with aluminium as the most common metal in the Earth's crust, can theoretically overcome almost all these shortcomings. However, the intercalation of large-sized chloroaluminate (AlCl4−) active ions into a host cathode, such as graphite, leads to poor capacity with volume expansion restricting practical applications. Finding a suitable cathode material for such large anions is a great challenge. We demonstrate a highly porous activated carbon derived from coconut shell chars as a promising cathode material. Activated carbon possesses a high mesoporosity and defect concentration with a specific area of 2686 m2 g−1. Its high surface area along with a great degree of mesoporosity and defects, activated carbon provides sufficient space and efficient transport channels for these active ions. Activated carbon cathodes show a specific discharge capacity of 150 mAh g−1 at 0.1 A g−1 with a good rate capability and cycling stability over 1500 cycles at 1 A g−1. This work illustrates that the mesoporosity and defect structures in this low-cost carbon material allow good AlCl4− anion storage capability, which supports the design principles for electrode materials storing large ion species.