Highly boron-doped holey graphene for lithium oxygen batteries with enhanced electrochemical performance

Abstract

The development of advanced catalyst cathode with high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities, low cost and rich natural resource is a key to improve the electrochemical performance of rechargeable lithium oxygen batteries (LOBs). Heteroatoms-doped carbon nanomaterials as cathodes for LOBs with improved electrochemical performance have attracted great attentions. Herein, we report an approach to synthesize holey graphene and a boron doped holey graphene (B-hG) with plenty of holey structure and high B doping level of 6 at. %. Benefiting from plenty of holey structures and B related active sites to accelerate the ORR and OER kinetics, the B-hGs (e.g., B-hG-700) cathode displays an extremely high capacity of 19698 mA h g−1 at 100 mA g−1 and long cycling stability over 120 cycles. Both experimental results and density functional theory calculations indicate that the discharge products (e.g., Li2O2) prefer to nucleate and vertically grow near holes/edges sites, which facilitates the formation of relatively isolated and uniformly distributed Li2O2. Such formation process significantly reduces the agglomeration of Li2O2 and effectively provides many spaces to accommodate Li2O2, thus leading to the enhanced ORR and OER kinetic.