On the cycle behavior of various graphitic negative electrodes in a propylene carbonate-based electrolyte for lithium ion batteries

We investigated the negative electrode behaviors of several mesocarbon microbeads (MCMB) heat-treated over 2000 °C in 1 M LiPF6/propylene carbonate (PC) electrolyte under various charge–discharge current densities. A higher current density provided improved (a highly graphitized MCMB)/Li cell cycle stability as lower graphitized MCMB electrode was used. In addition, two pre-cycles at a higher current density also provided better cycle stability in subsequent cycles at a lower current density. For example, MCMB 6 μm in diameter and heat-treated at 2800 °C cycled stably at a current density of 0.2 mA cm−2 after 2 pre-cycles at 0.5 mA cm−2. A higher current density may provide an adequate surface film at the first charging.