Compared with traditional metal-oxide lithium-ion battery
(LIB)
cathodes, nanocarbon-based cathode materials have received much attention
for potential application in LIBs because of their superior power
density and long-term cyclability. However, their lithium-ion storage
capacity needs further improvement for practical applications, and
the trade-off between capacity and conductivity, when oxygen functional
groups as lithium-ion storage sites are introduced to the nanocarbon
materials, needs to be addressed. Here, we report a sequential oxidation–reduction
process for the synthesis of single-walled carbon nanotubes (SWCNTs)
for LIB cathodes with fast charging, long-term cyclability, and high
gravimetric capacity. A LIB cathode based on highly exfoliated (d
bundle < 10 nm) and oxygen-functionalized
single-walled carbon nanotubes is obtained via the modified Brodie’s
method using fuming nitric acid and a mild oxidant (B-SWCNTs). Post
treatment including horn sonication and hydrogen thermal reduction
developed surface defects and removed the unnecessary C–O groups,
resulting in an increase in the Li-ion storage capacity. The B-SWCNTs
exhibit a high reversible gravimetric capacity of 344 mA h g–1 at 0.1 A g–1 without noticeable capacity fading
after 1000 cycles. Furthermore, it delivers a high gravimetric energy
density of 797 W h kgelectrode
–1 at a
low gravimetric power density of 300 W kgelectrode
–1 and retains its high gravimetric energy density of
∼100 W h kgelectrode
–1 at a high
gravimetric power of 105 W kgelectrode
–1. These results suggest that the highly exfoliated, oxygen-functionalized
single-walled carbon nanotubes can be applied to LIBs designed for
high-rate operations and long cycling.