We report on a detailed structural versus electrochemical
property
investigation of the corncob-derived non-graphitizable carbons prepared
at different carbonization temperatures using a combination of structural
characterization methodology unique to this field. Non-graphitizable
carbons are currently the most viable option for the negative electrode
in sodium-ion batteries. However, many challenges arise from the strong
dependence of the precursor’s choice and carbonization parameters
on the evolution of the carbon matrix and its resulting electrochemistry.
We followed structure development upon the increase in carbonization
temperature with thorough structural characterization and electrochemical
testing. With the increase of carbonization temperature from 900 to
1600 °C, our prepared materials exhibited a trend toward increasing
structural order, an increase in the specific surface area of micropores,
the development of ultramicroporosity, and an increase in conductivity.
This was clearly demonstrated by a synergy of small- and wide-angle
X-ray scattering, scanning transmission electron microscopy, and electron-energy
loss spectroscopy techniques. Three-electrode full cell measurements
confirmed incomplete desodiation of Na
+
ions from the non-graphitizable
carbons in the first cycle due to the formation of a solid–electrolyte
interface and Na trapping in the pores, followed by a stable second
cycle. The study of cycling stability over 100 cycles in a half-cell
configuration confirmed the observed high irreversible capacity in
the first cycle, which stabilized to a slow decrease afterward, with
the Coulombic efficiency reaching 99% after 30 cycles and then stabilizing
between 99.3 and 99.5%. Subsequently, a strong correlation between
the determined structural properties and the electrochemical behavior
was established.
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