Exfoliation and reassembly of cobalt oxide nanosheets into a reversible lithium-ion battery cathode

An exfoliation–reassembly–activation (ERA) approach to lithium-ion battery cathode fabrication is introduced, demonstrating that inactive HCoO2 powder can be converted into a reversible Li1-xHxCoO2 thin-film cathode. This strategy circumvents the inherent difficulties often associated with the powder processing of the layered solids typically employed as cathode materials. The delamination of HCoO2 via a combination of chemical and mechanical exfoliation generates a highly processable aqueous dispersion of [CoO2]− nanosheets that is critical to the ERA approach. Following vacuum-assisted self-assembly to yield a thin-film cathode and ion exchange to activate this material, the generated cathodes exhibit excellent cyclability and discharge capacities approaching that of low-temperature-prepared LiCoO2 (~83 mAh g−1), with this good electrochemical performance attributable to the high degree of order in the reassembled cathode.