Effect of the Activation Process on the Microstructure and Electrochemical Properties of N-Doped Carbon Cathodes in Li–O₂ Batteries

Lithium–oxygen (Li–O2) batteries have the potential to provide high energy densities; however, they suffer from low actual specific capacity and poor cycle performance. Hence, it is urgent to design a satisfactory oxygen electrode for a Li–O2 battery. In this study, carbonaceous materials, denominated CA, CB, and CC, from chitin were prepared by the three activators of H3PO4, KOH, and KHCO3 as oxygen electrode materials for Li–O2 batteries. The different carbon structural characteristics from the same precursor were regulated and controlled by different chemical reagents. Finally, the spherical particle cluster structure of CA has a high specific surface area, rich N doping, good connectivity, and uniform surface chemistry, so that CA acts as an oxygen electrode presenting excellent electron conductivity, providing sufficient, and stable electrochemical activity sites for oxygen reduction reaction and storing abundant discharge products. The electrochemical measurements indicate that at a current density of 0.02 mA/cm2, a CA-based battery delivers a high specific capacity of 16 600 mA h/g and a stable cycle performance of 210 cycles. This study proposes a functional carbonaceous material from chitin as a cathode oxygen electrode, which provides an economical and sustainable way for the improvement of oxygen electrodes and the application of Li–O2 batteries.