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 °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 °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%.