Structural characterization of boron-doped submicron vapor-grown carbon fibers and their anode performance

Structural evolution of undoped and boron-doped submicron vapor-grown carbo n fibers (S-VGCFs) was monitored as a function of heat-treatment temperatur e (HTT). Based on x-ray and Raman data, over the range of HTT from 1800 to 2600 degrees C, it was found that boron atoms act as catalysts to promote g raphitization due to boron's higher diffusivity. For the range of HTT from 2600 to 2800 degrees C, the process of boron out-diffusion from the host ma terial induces defects, such as tilt boundaries; this process would be rela ted with the improved capacity and Coulombic efficiency of boron-doped S-VG CFs. When 10 wt% S-VGCFs was used as an additive to synthetic graphite, the cyclic efficiency of the capacities was improved to almost 100%.