The
electrochemical performance of aluminum-sulfur batteries is beset
by poor stability and sluggish charge-storage properties. To address
these issues, carbon allotropes have been used as electrode fillers,
but successful outcomes remain inexplicably elusive. Here, a composite
of sulfur and small-diameter single-walled carbon nanotubes was studied
as a cathode for AlCl3:[EMIM]-based aluminum batteries.
The presence of carbon nanotubes, while enabling a high capacity (1024
mAh g–1) with slower decay and reducing the electrolyte-to-sulfur
ratio, is insufficient to fully stabilize the cell’s performance.
In fact, the main obstacle is in the interaction between sulfur and
chloroaluminate ions. As we show, there is a gradual buildup of insoluble
and poorly conductive discharge products that inhibit the diffusion
of electroactive ions and, ultimately, cause capacity decay. Overall,
this work sheds light on the carbon–sulfur–electrolyte
interactions and their role on the underlying charge-storage mechanism
of aluminum-sulfur batteries.