Effect of oxygen contents in graphene like graphite anodes on their capacity for lithium ion battery

Graphene like graphite (GLG) samples containing various amounts of oxygen are prepared from the thermal reduction of graphite oxide (GO) and are used as anodes of lithium ion battery. The oxygen/carbon (O/C) ratios in GLG varied from 0 to 0.08, depending on the thermal reduction temperature, oxygen gas pressure during heat treatment and degree of oxidation of the starting GO. The cell voltage during discharge almost linearly increases below 1 V independent of the oxygen contents in them. The discharge capacity of GLG above 1 V increases with the increase in the oxygen content with a slope of lithium/oxygen ratio of 3 at lower O/C ratios. Then the slope becomes smaller and the discharge capacity reaches 673 mAhg−1 for GLG with O/C = 0.08. When GLG is treated with hydrogen gas, considerable amounts of oxygen atoms are substituted by hydrogen ones. The discharge capacity of the resulting GLG samples is larger than that expected form their oxygen contents and coulombic efficiency is slightly improved up to 59%. Introduction of oxygen atoms within carbon layers results in the large increase in the interlayer spacing during charging, which leads to accommodation of large amounts of lithium ions.