High-capacity lithium-ion cells using graphitized mesophase-pitch-based carbon fiber anodes

We have developed high-capacity lithium-ion cells using graphitized mesophase-pitch-based carbon fiber (MCF) as an anode material, The graphitized MCF is a highly graphitized carbon fiber with a radial-like texture in the cross section. This structure contributes to the rapid diffusion of lithium ions inside the carbon fiber. The diffusion coefficient of lithium ions in the graphitized MCF was one order of magnitude larger than those for graphite, resulting in an excellent high-rate performance of the carbon electrode. The graphitized MCF anode showed larger capacity, a higher rate capability, and better reversibility than the graphite anode. The 863448 size (8.6 mm x 34 mm x 48 mm) prismatic cell with the graphitized MCF anode exhibited a large capacity of > 1000 mAh. At 3 A discharge, the prismatic cell had 95% of its capacity at 0.5 A discharge with a mid-discharge voltage of 3.35 V, The cell maintained > 85% of its initial capacity after 500 cycles and showed high capacity at -20 degrees C. It has thus been demonstrated that the prismatic cell using the graphitized MCF anode has excellent performance, and is an attractive choice for the power sources of cellular phones and other appliances. (C) 1997 Elsevier Science S.A.