Effect of pyrolysis temperature on lithium storage performance of pyrolitic-PVDF coated hard carbon derived from cellulose

The effect of pyrolysis temperature on the electrochemical performance of cellulose-derived hard carbon as anode material for lithium ion batteries was discussed in detail. Because of the presence of more oxygen-containing groups, the hard carbon pyrolyzed below 700 °C has larger irreversible capacity. The initial coulombic efficiency is low and the capacity decreases rapidly. X-ray photoelectron spectroscopy (XPS)results show that the ratio of CO to C–O bond becomes very small when higher than 800 °C, most of the oxygen-containing groups and hydrogen disappears. Hard carbon obtained at 1100 °C has higher initial coulombic efficiency and better cycle performance, no voltage hysteresis exists. The number of micropores of HC-1100 is much larger than that of mesopores, which reduces the irreversible deposition of lithium ions in mesopores. However, due to the decrease of interlayer space, lithium storage sites become less and the capacity is a bit lower than HC-800 and HC-950. The hard carbon obtained in 800–1000 °C range has the best comprehensive performance in charge-discharge capacity, initial coulombic efficiency and cycle performance.