Alkali metal insertion into hard carbon – the full picture

Abstract

<p> <italic>In operando</italic> Raman scattering during Li insertion into hard carbon, including the D-band (left) and the explanation for its disappearance (right).</p>

Sodiation Of Hard Carbon: How Separating Enthalpy And Entropy Contributions Can Find Transitions Hidden In The Voltage Profile

“…The operando Raman measurements of Euchner et al. combined with DFT calculations of phonon spectra, suggest a downwards shift in the G‐band as more sodium is added in the sloping region, [38] which was also observed experimentally by Weaving et al [13] . Both groups attributed this shift to charge transfer from the metal atoms to the carbon matrix [13,38] .…”

“…This results in rapid changes of the point term of lithium in graphite at low lithium occupation, resulting in additional electrochemical features [23] . Similarly, the local structure of hard carbons approximates to curved bilayer graphene, which also presents a low DOS at the Fermi level (Dirac cone at the Γ point minimum) when no sodium is in the lattice [10,38] . In fact, Stratford et al.…”

Alkaline Water Splitting Enhancement by MOF‐Derived Fe–Co–Oxide/Co@NC‐mNS Heterostructure: Boosting OER and HER through Defect Engineering and In Situ Oxidation

“…[ 43 ] Further analysis of XPS spectra in the binding energy region of 291–997 eV (Figure S5, Supporting Information), showed two peaks at the binding energies of 293 and 295 eV corresponding to K 2p 3/2 and K 2p 1/2 of K 2p, respectively (Figure S5, Supporting Information), which are attributed to K remained on the surface after electrochemical evaluations in KOH electrolyte, in agreement with the occurrence of the peak around 3.5 keV in the EDX spectra (Figure 2C 2 ). [ 44 ]…”

Regulating the Interlayer Spacings of Hard Carbon Nanofibers Enables Enhanced Pore Filling Sodium Storage

“…Previous studies indicate that the intercalation of Li + /Na + in the graphitic layers of HC would cause the electron occupation in the π* antibonding band, which weakens the C–C bond and elongates the bond length, thus leading to a redshift of the G‐band. [ 39,42–44 ] The recorded in‐situ Raman spectra with the corresponding initial discharge/charge curves are displayed in Figure a. Upon discharging in the slope region, the G‐band gradually splits into two bands and shifts to lower wavenumbers, corresponding to the intercalation of Na + into the interlayers of graphitic carbon.…”

“…The structural model used in the DFT calculations was based on the reported model. [ 43,49 ] The energy cost of Na inserted into carbon was calculated by the following equation: Δ E (cost) = [ E (total) – E (graphite) – 2 E (Na)]/2.…”