Towards understanding the salt-intercalation exfoliation of graphite into graphene

Abstract

The preparation of graphene from graphite is critical for both theoretical studies and real-world applications. Herein, we present a systematic study to explore the fundamental factors that control the exfoliation of graphite into graphene in a salt-intercalation exfoliation system, using various inorganic salts as intercalators. The yields of the thin graphene sheets obtained, measured via UV-vis absorption spectrophotometry, suggest that both cations and anions significantly influence the exfoliation yields. Xray photoelectron spectroscopy and energy dispersive spectroscopy analysis showed that both anions and cations become inserted into the space between conjugated graphite layers during the intercalation process. X-ray diffraction spectra revealed that the anion can enhance the salt-intercalation exfoliation by expanding the interlayer spacing. Compared to lithium chloride, both potassium chloride and lithium sulfate can significantly enhance the exfoliation yields of graphene. Optimizing the cation and anion species can improve the yield of graphene, because co-intercalation with both anions and cations occurs during the intercalation process in the solution of inorganic salts. Our work provides a guide for rationally designing the salt-intercalation exfoliation procedure to obtain higher yields of exfoliated 2D materials.

Green Synthesis of Graphene from Graphite in Molten Salt Medium

“…The structure of the graphene products was also evaluated by UV analyses of CG, CGr, GGr500, GGr600, GGr700, and GGr800 given in Figure 3. As seen in the spec-trum, characteristic absorbance peaks at around 200 and 280 nm were observed for all samples, which is consistent with the previous studies [39][40][41]. Figure 4 illustrates the particle size analyses by the dynamic light scattering technique.…”

A Post-Mortem Study of Stacked 16 Ah Graphite//LiFePO4 Pouch Cells Cycled at 5 °C

“…The diffraction patterns of the anodes have been analysed for the shift of the first graphite peak at 26.8 • ( Figure S11). The shift towards lower angle of the 00l reflection is linked with graphite interlayer expansion upon lithium intercalation [12] The shift is larger in the Fresh Cell, while among the aged samples, Cell B showed the smallest shift, indicative of a lower amount of Li + remaining trapped into the graphite layers (the cells are opened in the fully discharged state, i.e., Li + ions should be fully removed). This translates into a higher lithiation of the cathode.…”

Origin of the catalytic activity at graphite electrodes in vanadium flow batteries

“…A VBM of 1.9 eV signifies an increase of occupied states close to EF (compare Figure 2d) due to increased electron transfer between layers of graphite, facilitated by intercalated electrolytic species such as water molecules, vanadium ions, or sulfuric acid. 85,86 The more active GF-980 exposes a lower number of defects (I(D)/I(G) = 2.06) compared to the less active GF (2.21) (Figure S16). The origin of defects on both electrodes, which are mainly edge sites, is not affected by the electrochemical cycling.…”