Figure 1.

Structural characterization and electrochemical performance analysis of Hard Carbon (carbonized switchgrass, GC-1000 and GC-2050) as an anode in Sodium ion batteries (SIBs): (a) Low magnification SEM image from a cross section of GC-1000. (b) Corresponding higher magnification SEM image of GC-1000. (c) Low magnification SEM image from longitudinal section of GC-2050 where vertical lines are showing the array structure. (d) Higher magnification SEM image of GC-2050 where dashed circles highlight the micro/nanoscale holes for ion transport. (e,f) HRTEM (High-resolution transmission electron microscopy) images of GC-1000 and GC-2050. (g) Digital photograph of switchgrass derived carbon under Joule heating. (h) Light emission spectra of the carbonized switchgrass, here the temperature was fitted according to blackbody radiation equation. (i) XRD patterns of the GC-1000 (black) and Gc-2050 (red). Samples show identical twin broad peaks around 2ϴ = 23.6° and 43.6°, corresponding to the diffraction of graphitic layered structure. (j) Raman spectra of GC-1000 (black) and GC-2050 (red) confirmed the progressively ordered structure in the samples. (k,l) N₂ adsorption/desorption isotherms and pore size distribution of GC-1000 and GC-2050, respectively. (m,n) Cyclic voltammogram (CV) curves for the first five cycles of GC-1000 and GC-2050, respectively at a scanning rate of 0.5 mV s⁻¹. (o,p) Voltage profiles of GC-1000 and GC-2050 respectively at a current density of 50 mA g⁻¹ in the potential range: (0.01–2 V). (q,r) Specific capacity, coulombic efficiency, and rate capability of GC-1000 and GC-2050 samples. Reprinted with permission from [48]. Copyright 2017 American Chemical Society.