Kish Graphite Flakes as a Cathode Material for an Aluminum Chloride–Graphite Battery

Nonaqueous, ionic liquid-based aluminum chloride-graphite batteries (AlCl₃-GBs) are a highly promising post-Li-ion technology for low-cost and large-scale storage of electricity because these batteries feature exclusively highly abundant chemical elements and simple fabrication methods. In this work, we demonstrate that synthetic kish graphite, which is a byproduct of steelmaking, can be used as a cathode in AlCl₃-GB and exhibits high capacities of ≤142 mAh g^-1. The comprehensive characterization of kish graphite flakes and other forms of graphite by X-ray diffraction, Raman spectroscopy, and Brunauer-Emmett-Teller surface area analysis provides solid evidence that the exceptional electrochemical behavior of kish graphite flakes is mainly determined by the high structural order of carbon atoms, a low level of defects, and a unique "crater morphology". In view of the nonrocking chair operation mechanism of AlCl₃-GB, we have tested the achievable energy densities as a function of the composition of chloroaluminate ionic liquid (AlCl₃ content) and have obtained energy densities of up to 65 Wh kg^-1. In addition, the kish graphite flakes can rapidly charge and discharge, offering high power densities of up to 4363 W kg^-1.