Raman probing carbon & aqueous electrolytes interfaces and molecular dynamics simulations towards understanding electrochemical properties under polarization conditions in supercapacitors

An evaluation of the capacitive behavior of supercapacitors as a function of the radius of cations using simulations with a constant potential method

“…Recently, our research group studied 12 the effect of H 2 SO 4 , Li 2 SO 4 , Na 2 SO 4 , and K 2 SO 4 into the electrochemical properties under polarisation conditions in a supercapacitor using operando Raman spectroscopy and molecular dynamics simulations. A decrease in the electrical double-layer capacitance as a function of the electrolyte composition (H 2 SO 4 4 Na 2 SO 4 4 Li 2 SO 4 4 K 2 SO 4 ) was observed for both cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge techniques.…”

“…The Stokes radii incorporating the hydration/solvation shell are Li + (2.39 Å) 4 Na + (1.83 Å) 4 K + (1.25 Å), while the crystal ionic radii for the bare ions are Li + (0.9 Å) o Na + (1.16 Å) o K + (1.52 Å). 12 Therefore, one can suggest that the Li + -ions partially lose their hydration shell, resulting in a facilitated intercalation process between the graphene layers accessible by the electrolyte, or the solvated Li + -ions resulted in a more drastic lattice displacement, leading to structural defects during the applied voltage. We also observed that the diffusion coefficient increases as observed (Li + o Na + o K + ).…”

New Insights on the Sodium Water-in-Salt Electrolyte and Carbon Electrode Interface from Electrochemistry and Operando Raman Studies

“…Another recent development in the study of energy storage devices is based on the operando ( in situ ) experimental approach where an external radiation source impinges the electrode material during the static or dynamic polarization of the electrode/solution interface. In this way, operando analyses using spectroscopy coupled to electrochemical techniques shed light on understanding the fundamental processes governing the charge-storage mechanism in SCs. ,− These analyses have been accomplished by several prominent authors for different energy storage materials. ,,, A very interesting example of a spectroscopic approach used in the operando analyses is based on the Raman technique, which can reveal during the cell polarization the chemical and near-surface structural effects on the electrode material incurred by intercalation and/or the solid-state redox processes …”

“…Because of the graphite anisotropy characteristics, electrolyte species could insert between its layers, causing charge-transfer reactions, which form the so-called intercalation phenomena. The adsorption/physical process and ionic intercalation/chemical process both can be observed through changes in Raman spectra of carbon-based electrodes under polarization conditions, i.e., operando Raman studies. , The Raman spectra of the ionic species intercalating between the graphite layers are assigned by the doublet structure formed close to the high-frequency phonon E 2g1 corresponding to the G-band. The presence of ionic species changes the environment, causing a reorganization of graphite interplanar spacing, which is detected by raising the second E 2g2 phonons observed for graphite .…”

Study of Peat Fillers for their Potential Use in Electric Energy Storage Devices

“…Accumulation and storage of charge in such capacitors occurs in a double electric layer [7], which appears in the "electrode -electrolyte" phase boundary. Thus, materials for these devices should possess the following properties: high electrical conductivity, developed specific surface area, availability of a porous structure for electrolyte ions, low density, ease of formation, and other properties that make it possible to substantiate the economic efficiency of their use.…”