Lithium intercalation in graphites precipitated from pig iron melts

The structural and electrochemical properties of graphitic materials precipitated from supersaturated solutions of carbon in pig iron melts were investigated. Doping of the graphite with boron was accomplished by adding ferroboron to the iron melt. X-ray diffraction patterns showed that all the products were highly crystalline graphites, and that doping with boron generally reduced the d0 0 2 values, which indicated that boron was incorporated in the hexagonal graphite matrix. Boron incorporation also led to a break in the local symmetry of the graphitic structure, as evidenced by the evolution of the D-band of the Raman spectra with an increase in the boron content. Scanning electron micrographs revealed the presence of nanocarbon structures on the surface of the graphites. The first-cycle capacity of the graphites was found to increase as the boron content was increased. However, the capacities of the boron-free and 60 ppm boron-doped materials abruptly increased in the second cycle, while the capacity of the 300 ppm boron-doped graphite remained fairly steady. All the graphites cycled well. The boron-free, 60 ppm boron-doped and the 300 ppm boron-doped graphites, sustained 198, 203 and 180 cycles, respectively, before reaching a charge retention level of 80%.