Hydroxylated carbon black as improved deposition support for discharge products in lithium air(oxygen)batteries

Abstract

To date, compared with that of lithium oxygen batteries, the operation of lithium air batteries is still a great challenge due to the highly deteriorated cathode performances in air, including worse discharge capacities and OER/ORR dynamics. Herein, we propose hydroxylated carbon black as an improved deposition support, which not only functions as a conductive agent, but also improves the morphology of the discharge products. These improvements can significantly enhance the discharge properties and chargeability of the gas cathode, particularly in simulated air or ambient air. For example, the hydroxylated carbon black doubles the energy output of the air cathode in ambient air. It is believed that increased defects and hydroxyls on the hydroxylated carbon surface might play an important role. By the first principle calculation, it is revealed that a strong affinity between the hydroxyls and Li₂O₂ occurs, and this facilitates the nucleation of Li₂O₂. It is believed that the promoted nucleation can restrain the growth of the discharge products due to the competitive relationship between nucleation and growth of new phase in chemical reactions. Finally, smaller Li₂O₂ nanosheets formed on the hydroxylated carbon cathode instead of the dense discharge product layer, avoid the block of the porous cathode, thus benefiting the electrochemical performances. These results show that besides developing better catalysts, hydroxylation of carbon matrix is also an effective strategy to enhance the electrochemical performances of the lithium air battery.