High‐capacity anode derived from graphene oxide with lithium‐active functional groups

Summary Applications utilizing Li‐ion batteries (LIBs) have recently been broadened from portable electronic devices to electric vehicles. Graphite has been applied as an anode material for commercialized LIBs; however, there is a growing demand for application‐oriented LIBs with higher energy and power densities, and faster charging, compared with its limited electrochemical properties. Heteroatom‐doped graphene has been considered as a potential alternative to graphite, although its synthesis is complex and costly. In this study, we introduced a facile strategy to realize advanced anode materials through fine control of the sheet size and oxygen‐containing functional groups on the surface of graphene oxide (GO) as a raw material for heteroatom‐doped graphene. The sheet size of GO is inversely proportional to the amount of oxidizing agent, which affects the formation of various types of oxygen‐containing functional groups at the edges of GO. Mild annealing of GO selectively removes the functional groups with weak binding strength, leading to the formation of GO maximized with carbonyl groups, which can interact with Li ions quickly and reversibly. The GO with the average sheet size of 500 nm developed in this study exhibits capacities of up to 779 and 220 mAh g−1 at 0.1 and 2 A g−1, respectively. Therefore, decreasing the sheet size of GO with mild‐temperature annealing increases the number of carbonyl groups formed on the additional exposed edge of the sheets, resulting in facile Li‐ion interaction and a higher capacity as an anode material. We introduced a facile strategy to realize advanced anode materials through fine control of the sheet size and oxygen‐containing functional groups on the surface of graphene oxide (GO) exfoliated from graphite. Mild annealing of GO selectively removes the functional groups with weak binding strength, leading to the formation of GO maximized with carbonyl groups, which can interact with Li ions quickly and reversibly. GO‐based electrode exhibited improved Li‐ion interaction and a higher capacity even at high current densities.