Lithium-coordinated polyaromatic anions such as tetrareduced corannulene, C 20 H 10 4- (1 4- ), are useful substrates to model and ultimately improve the graphitic electrodes in lithium-ion (Li + ) batteries. Previous studies suggested that 1 4- forms dimers encasing four Li + ions in solution. Here, we report a single-crystal x-ray diffraction analysis confirming the formation of a sandwich-type supramolecular aggregate with a high degree of alkali metal intercalation. In contrast to the prior model, our data reveal that five Li + ions are sandwiched between the two tetrareduced corannulene decks, and 7 Li nuclear magnetic resonance spectroscopy delineates a conserved structure in tetrahydrofuran solution. Remarkably, the sandwich is robust in both solution and solid states even in the presence of crown ethers that compete for Li + coordination. These results should help elucidate Li + intercalation motifs between curved carbon surfaces more broadly.