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

Structural evolution of undoped and boron-doped submicron vapor-grown carbon fibers (S-VGCFs) was monitored as a function of heat-treatment temperature (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 graphitization 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 material induces defects, such as tilt boundaries; this process would be related with the improved capacity and Coulombic efficiency of boron-doped S-VGCFs. When 10 wt% S-VGCFs was used as an additive to synthetic graphite, the cyclic efficiency of the capacities was improved to almost 100%.