Nanoporous hard carbon microspheres as anode active material of lithium ion battery

Nanoporous hard carbon microspheres (NHCSs) were prepared by combination of microemulsion and polymerization methods and using phenolic resin (resol) as precursor and ethanol and ethylene glycol (EG) as solvent and soft template, respectively, followed by carbonization process. Using different amounts of EG resulted in NHCSs with different crystalline structure, surface area and pore volumes, and Li ion storage capacity, as evidenced by physical and electrochemical measurements. Higher and lower polymerization rates were also tested on the starting resol solution with composition which led to the NHCS with the highest surface area and Li ion storage capacity. The sample polymerized at higher rate had the highest surface area and pore volume, as well as the best Li ion storage performance in terms of capacity and rate capability. for all of the NHCSs, the specific surface area and Li ion storage capacity were well correlated, and a good correlation was observed between total pore volume and rate capability. Furthermore, acceptable correlations were found between Li ion storage capacity and either surface area or microstructure of the NHCSs.