Solution
Assembled Single-Walled Carbon Nanotube Foams:
Superior Performance in Supercapacitors, Lithium-Ion, and Lithium–Air
Batteries
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Abstract
We demonstrate a surfactant-free,
solution processing route to
form three-dimensional freestanding foams of pristine single-walled
carbon nanotubes (SWCNTs) and explore the diverse electrochemical
energy storage applications of these materials. This route utilizes
SWCNT dispersions in organic <i>n</i>-methylpyrrolidone
solvents and subsequent electrophoretic assembly onto a metal foam
sacrificial template which can be dissolved to yield surfactant-free,
binder-free freestanding SWCNT foams. We further provide a comparison
between surfactant-free foams and conventional surfactant-based solvent
processing routes and assess performance of these foams in supercapacitors,
lithium-ion batteries, and lithium–air batteries. For pristine
SWCNT foams, we measure up to 83 F/g specific capacitance in supercapacitors,
specific capacity up to 2210 mAh/g for lithium-ion batteries with
up to 50% energy efficiency, and specific discharge capacity up to
8275 mAh/g in lithium–air batteries. For lithium–air
batteries, this corresponds to a total energy density of 21.2 and
3.3 kWh/kg for the active mass and total battery device, respectively,
approaching the 12.7 kWh/kg target energy density of gasoline. In
comparison, SWCNT foams prepared with surfactant exhibit poorer gravimetric
behavior in all devices and compromised Faradaic storage that leads
to depreciated amounts of usable, stored energy. This work demonstrates
the broad promise of SWCNTs as lightweight and highly efficient energy
storage materials but also emphasizes the importance of clean nanomanufacturing
routes which are critical to achieve optimized performance with nanostructures