Metal-free boron-doped carbon microspheres as excellent cathode catalyst for rechargeable Li-O-2 battery

摘要

Rechargeable Li-O-2 batteries are attracting more and more interest due to their high energy density. Meanwhile, the replacement of high-cost and scarce precious-metal catalysts has attracted more and more attention. Currently, many academic researchers have paid attention to find highly efficient metal-free catalysts as air cathode material. Herein, the boron-doped carbon microspheres (B-CMs) were prepared through a novel and facile static calcination method and showed high electrocatalytic activity as a cathode material. The battery with a B-CM cathode delivered a high initial discharge capacity of 13,757.2 mAh g(-1) and outstanding coulombic efficiency of 90.1 % at 100 mA g(-1). In addition, stable cyclability (151 cycles with stable discharge voltage of similar to 2.60 V with a cutoff capacity of 1000 mAh g(-1) at 200 mA g(-1)) has been exhibited. These performances are due to three main points: boron carbide compound changed the surface area of the CMs and formed the mesopore architectures as well as the large surface area of 683.738 m(2) g(-1); the reduce of boron atom can slow down the oxidation of the CMs during the cyclings; and finally, the electron-deficient boron atom introduction greatly facilitated Li+ diffusion and electrolyte immersion and enhanced the oxygen reduction and evolution reaction kinetics.