Graphene foam
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Graphene foam is a solid, open-cell foam made of single-layer sheets of graphene. It is a candidate substrate for the electrode of lithium-ion batteries.
Synthesis
The foam can be manufactured using vapor deposition to coat a metal foam, a three-dimensional mesh of metal filaments. The metal is then removed.
Applications
Electrode
A physically flexible battery was created using the foam for electrodes. The anode was made by coating the foam with a lithium-titanium compound (Li4Ti5O12) and the cathode by coating the foam with LiFePO4. Both electrodes were lightweight and their large surface area provided high energy density of 110 Wh/kg, comparable to commercial batteries.
Power density was much greater than a typical battery. At a rate that completely discharged the material in 18 seconds, power delivered was 80 percent of what it produced during an hour-long discharge. Performance remained stable through 500 charge/discharge cycles.
Support
In 2017 researchers used carbon nanotubes to reinforce a foam. The latter material supports 3,000 times its own weight and can return to its original shape when unweighted. Nanotubes, a powdered nickel catalyst and sugar were mixed. Dried pellets of the substance were then compressed in a steel die in the shape of a screw. The nickel was removed, leaving a screw-shaped piece of foam. The nanotubes' outer layers split and bonded with the graphene.