Intermolecular π-π stacking of oligomeric naphthalene cathodes facilitate high performance aluminum ion battery

Π-conjugated organic compounds (π-COCs), as a potential electrode material, mainly emphasized the effects of functional groups and intramolecular π-conjugated system on charge storage in the past studies. In this work, we discovered a brand-new two step energy storage mechanism for π-COCs using oligomeric naphthalene (ONA) with intermolecular π-π stacking structure as electrode material in Al ion battery system. The electrochemical reaction of ONA is identified as the synergistic work of the chemical-adsorption of AlCl4- anions at low potential and the π···[AlCl4]···π interaction at high potential. Based on this, the Al-ONA battery exhibits an excellent electrochemical performance (high specific capacity of 450 mAh/g at 0.1 A/g, long cycle life without attenuation for 4000 cycles at 1 A/g). This discovery of the energy storage mechanism, especially for the π···anion···π interaction, for π-COCs materials opens the door to exploring high performance organic electrode materials in energy storage field.