Nitrogen- and boron-doped carbon nanoparticles for lithium-ion storage

Usually, Lithium-ion batteries (LIBs) use graphite as anode material, due to its stability and good performance along charge and discharge cycles; even with these good characteristics, they lack in specific capacity (300 mAh/g). Because of this, diverse carbon forms are studied for their use as anodic materials (graphene, vitreous carbon, and carbon spheres), and not only their form but also their modifications at the molecular level have been studied to enhance the electrochemical performance of anodic electrodes.

This research presents a way to improve the specific capacity of the LIBs that use carbonaceous materials as anodes via doping carbon spheres. For the synthesis of the carbon spheres, we use pyrolysis, this technique allows us to obtain carbon spheres in a simple way. The spheres were observed using scanning electron microscopy. In this characterization, we observed that the high concentration of carbon shows more regular shapes and sizes of the spheres. The chemical composition analysis confirmed the presence of the doping agents in our synthesized material.

The carbon spheres with doping material in concentrations below 1% show a higher capacity than the ones with concentrations higher than 1%. Furthermore, theoretical calculations allow us to comprehend in a better way how this low concentration of heteroatoms allows the carbon spheres to have a higher number of active sites for the deposition of Li ions. Also, we analyzed diverse combinations and concentrations of these doping agents to determine their effect on the specific capacity of carbon-based materials. Our results show that doping carbon spheres with N and B in low concentrations exhibits a higher specific capacity compared to commercial LIBs.