Synthesis of a class of oxocarbons (C 4 O 4 , C 5 O 5 ) and the application as high-capacity cathode materials for lithium-ion batteries

Oxocarbons (C n O n , n =3, 4, 5, 6, …) are a series of compounds that are only composed of carbonyl groups. The highly electrophilic carbon atoms in C n O n make their poor stability toward H 2 O, and thus the synthesis of C n O n is very challenging. Here an oxidation-dehydration method is developed to successfully synthesize C 4 O 4 and C 5 O 5 . The combination of nuclear magnetic resonance ( 13 C NMR, 1 H NMR), mass spectra, and infrared spectra unambiguously proves the exact chemical structure of C 4 O 4 and C 5 O 5 . When used as a cathode material in lithium-ion batteries (LIBs), C 5 O 5 could deliver a high discharge capacity of 698 mAh g -1 (corresponding to an energy density of 1,256 Wh kg -1 C5O5 ). Furthermore, ex-situ infrared spectra and density functional theory (DFT) calculations demonstrate that the carbonyl groups are redox active sites during discharge and charge processes. This work paves the way to achieve the synthesis and battery application of oxocarbons.