Electrochemically Exfoliating Graphite Cathode to N-Doped Graphene Analogue and Its Excellent Al Storage Performance

In this work, we have developed a facile and catalyst-free synthesis method to obtain nitrogen-doped graphene analogue (NGA) by electrolyzing graphite cathode in molten AlCl3-urea under a constant voltage of 2.1 V at 120°C. With continuous electrolysis in high temperature, the coordination ions in the electrolyte are ceaselessly intercalated into the graphite flake, which is further exfoliated to graphene analogue. Meanwhile, nitrogen is successfully doped into the exfoliated graphene by substituting partial C atoms in electrolysis process. The electrochemical performance of NGA is tested in an aluminum-ion battery based on room temperature ionic liquid electrolyte containing AlCl3 and 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl). The initial specific discharge capacity is as high as 110.8 mA h g−1 at a current density of 0.4 A g−1. Moreover, the battery shows an excellent cyclic stability with the discharge capacity of 66.8 mA h g−1 at a higher current density of 1.0 A g−1 over 2500 cycles, delivering a Coulombic efficiency above 99%.