Hysteresis during Lithium Insertion in Hydrogen‐Containing Carbons

Abstract

We studied lithium insertion in hydrogen-containing carbons heated at temperatures near 700�C. High capacities with large hysteresis (lithium insertion into these carbons at nearly 0 V and removal at nearly 1 V) were shown to be proportional to the hydrogen content of the samples. It is believed that the lithium atoms may bind on hydrogen-terminated edges of hexagonal carbon fragments, causing a change in the bond from sp2 to sp3. We have carefully studied the electrochemical insertion of lithium in hydrogen-containing carbons using a variety of charge-discharge rates and cycling temperatures. These measurements allow the hysteresis to be quantified. A simple model, which treats the bonding change as an activated process, is used to model the hysteresis in the cells qualitatively.