We
report here the fabrication of large-area continuous graphene
films on different substrates via inkjet printing using “solvent-exfoliated”
graphene nanosheets and associated printable ink prepared with the
nanosheets in “green solvent” (i.e., ethanol) and ethyl-cellulose
(as a stabilizer). The printed film was thermally annealed in Ar to
improve the electrical conductivity and embed well-defined porosity.
Sheet resistance decreased with an increase in the number of printed
layers, attaining a low value of ∼0.15 kΩ/sq after 8
printing cycles. When printed on Cu foil and directly tested as a
potential anode for Li-ion batteries, a high reversible Li storage
capacity of ∼942 mAh/g could be obtained at 0.1C based on dual
contributions from “classical” Li-intercalation/deintercalation
and surface charge storage. The nanoscaled dimension and porous nature
aided the latter, which also resulted in good rate capability, leading
to ∼40% of the above reversible capacity at 5C. Furthermore,
the electrode could retain ∼87% of the initial reversible capacity
after 100 cycles, even at a fairly high current density equivalent
to 2C. Overall, the inkjet-printed graphene film, by itself, is a
promising anode for Li-ion batteries, with the development likely
to aid a variety of important applications, including flexible devices
and energy storage systems.
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