RECHARGEABLE LITHIUM-ION CELLS USING GRAPHITIZED MESOPHASE-PITCH-BASED CARBON-FIBER ANODES

The electrochemistry of lithium intercalation into a graphitized mesophase-pitch-based carbon fiber with a radial-like texture used as the anode material in rechargeable lithium-ion cells was characterized. The radial-like texture in the cross section of the carbon fiber contributed to the rapid diffusion of lithium ions, resulting in the high rate capability. The anode performance of the graphitized carbon fiber was superior to that of the graphite. Experimental flat-plate C/LiCoO2 lithium-ion cells using the graphitized carbon fiber anode exhibited a high mid-discharge voltage of 3.7 V, a high rate capability, and a long cycle life of more than 400 cycles at 2 mA/cm(2) during charge-discharge cycling between 4.2 and 2.7 V. The long cycle Life obtained for the cell was due to no significant change in resistance associated with the passivating films on the graphitized carbon fiber with extended cycles. It was also demonstrated that A size C/LiCoO2 cells using the graphitized carbon fiber anode have excellent rate performance at discharge currents between 0.25 and 3 A, a large discharge capacity of 0.95 Ah, and a high energy density of 310 Wh/dm(3) and 120 Wh/kg.