High Rate Discharge Performance and Thermal Stability of Heat-Treated Carbon Nanobeads

With the commercialization of lithium-ion batteries, these batteries, taking advantage of higher energy density than other batteries, are now being used as power sources for portable devices. Recently, lithium-ion batteries have attracted attention as energy storage devices for load leveling or a hybrid energy conversion systems, e.g., for leveling of wind-mill generation or hybrid electric vehicle. To satisfy the demands of these applications, a high rate charge and discharge performance is required. These applications need large input current and large output current because input and output power varies rapidly. But the high rate ability of lithium-ion batteries is inferior to Ni–Cd or Ni–MH batteries. One of the key factors influencing rapid charge/discharge is the carbon negative electrode. Graphite has been used extensively as a negative electrode. The graphite electrode has many advantages such as flat potentials as low as Li metal, small volume expansion, and high reversibility of lithium-ion intercalation and deintercalation. However, lithium-ion diffusion in graphite can be the ratedetermining step in intercalation or deintercalation.