Graphite-coated ZnO nanosheets as high-capacity, highly stable, and binder-free anodes for lithium-ion batteries

ZnO is one of the materials of choice as anode for lithium batteries, due to its high theoretical capacity, natural abundance, low toxicity, and low cost. At present, however, its industrial exploitation is impeded by massive capacity fading, and by cycling instability due to the drastic volume expansions during the electrochemical lithiation/delithiation process. Herein, we present a novel graphite coated-ZnO anode for LiBs based on films of nanosheets, coated with graphite. The electrode is obtained by a simple and inexpensive solution hydrothermal synthesis, whereas the graphite is deposited by thermal evaporation, which is easier to perform than a wet chemistry technique. Our approach leads to a substantial increase of the permanent specific capacity, obtaining values of 600 mAhg-1 after 100 cycles at a high specific current of 1 Ag-1. This represents the best performance for long-cycled, ZnO-based anodes obtained so far. Such result derives from the peculiar porous structure of the nanosheets film (pore diameter < 1 nm), as well as by the graphite coating that works as a dimensional buffer and preserves its morphology during cycling. This appears a very promising strategy for designing more stable ZnO-based anodes for Li batteries and microbatteries.