Coal-derived synthetic graphite with high specific capacity and excellent cyclic stability as anode material for lithium-ion batteries

Abstract The synthetic graphite with higher specific capacity and superior cyclic lifespan is prepared by high temperature graphitization of anthracite coupled with effective catalyst. In the process of graphitization, the thermodynamically unstable carbon atoms orderly convert from disordered structure to graphite crystal structure by thermal activation. However, it is necessary for the graphitization process at high temperature above 2800 °C. The slow reaction speed, low conversion rate, and unmanageable temperature result in a low graphitization degree. Also, B2O3 as catalyst is beneficial to the directional growth of the aromatic layer in graphite structure, which reduces the cross-linking of the aromatic layer and enhances its coplanarity, as well as reduces energy barrier of graphitization and accelerates the formation of graphite phase. When served as anode material for lithium-ion batteries, the material delivers high delithiation capacity of 369 mA h g−1 with first coulomb efficiency (FCE) of 85.3% at 0.05C and even 160 mA h g−1 at 3C. Moreover, at the current density of 0.5 C, the initial capacity still maintains more than 300 mA h g−1 accompanied with almost 98% capacity after 500 cycles. Often, more than 80% of capacity retention at 2 C enables it more competitive and attractive in the fields of anode materials. By matching the graphite as anode and commercial LiFePO4 as cathode, a full battery is assembled, which still remains the capacity of 93% after nearly 400 cycles, showing cyclic stability of the material. The research provides a direction for the mass production of graphite with coal.