Designing a Graphene Coating-Based Supercapacitor with Lithium Ion Electrolyte: An Experimental and Computational Study via Multiscale Modeling

Abstract

Graphene electrodes are investigated for electrochemical double layer capacitors (EDLCs) with lithium ion electrolyte, the focus being the effect of the pore size distribution (PSD) of electrode with respect to the solvated and desolvated electrolyte ions. Two graphene electrode coatings are examined: a low specific surface area (SSA) xGNP-750 coating and a high SSA coating based on a-MWGO (activated microwave expanded graphene oxide). The study comprises an experimental and a computer modeling part. The experimental part includes fabrication, material characterization and electrochemical testing of an EDLC with xGNP-750 coating electrodes and electrolyte 1M LiPF6 in EC:DMC. The computational part includes simulations of the galvanostatic charge-discharge of each EDLC type, based on a continuum ion transport model taking into account the PSD of electrodes, as well as molecular modeling to determine the parameters of the solvated and desolvated electrolyte ions and their adsorption energies with each type of electrode pore surface material. Predictions, in agreement with the experimental data, yield a specific electrode capacitance of 110 F g−1 for xGNP-750 coating electrodes in electrolyte 1M LiPF6 in EC:DMC, which is three times higher than that of the high SSA a-MWGO coating electrodes in the same lithium ion electrolyte.

Continuous Production of Functionalized Graphene Inks by Soft Solution Processing

“…We expect that the solution processing method can be extended for continuous production of hybrid materials such as metal supported/N-FG, which may find potential application in the area of catalysis [ 63 , 64 , 65 , 66 , 67 , 68 , 69 ]. It is expected that these materials will have a wide range of surface area and pore size distribution, which can be useful for various applications such as catalysis and energy storage devices [ 70 ]. The bulk electrical conductivity of these N-FG materials may be comparable to parent graphene-based material, which can be optimized for the designing and development of electrodes [ 70 , 71 ].…”

The Challenge of Electrolyte Impregnation in the Fabrication and Operation of Li‐ion and Li−S Batteries

“…under the effect of convection and diffusion, with D S8,p being the diffusion coefficient of S 8 in the electrolyte solution in pore size p, expressed by the Stokes-Einstein relation: [11,12,37]…”

“…under the effect of convection and diffusion, with D S8,p being the diffusion coefficient of S 8 in the electrolyte solution in pore size p, expressed by the Stokes‐Einstein relation: [11,12, 37] $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr {D}_{S8,p}={{{k}_{B}T}\over{3\pi \mu {d}_{S8}}}\hfill\cr}}$$$ …”

Investigation and Determination of Electrochemical Reaction Kinetics in Lithium-Sulfur Batteries with Electrolyte LiTFSI in DOL/DME

“…Intensive research in lithium-sulfur (Li-S) batteries worldwide has been offering optimized electrolytes, 1 novel cathode materials that might trap soluble polysulfides via physical microstructural restriction, [2][3][4] adsorption effects 5 or high tortuosity of 2D materials, [6][7][8] and selective separators. 9,10 The complex and competing processes occurring in Li-S batteries and affecting their performance create the need for physicochemical models at continuum level for the design of materials and optimization of the operation conditions for the formation cycles, battery cycling and possibly recovery.…”

“…1 for each desolvated species s, expressing the fraction of desolvated species s depending on the relation between the electrochemical EDLC (electrochemical double layer capacitor) energy and the desolvation energy, as is given in. 7,16,17 D s , p denotes the diffusion coefficient of species s in the liquid electrolyte of pore p given by a modified Stokes-Einstein relation, equation (SI.12) 7,16,17 as a function of the electrolyte viscosity and species size, pore tortuosity for pore size p, and pore constrictivity relating the ion size to the pore size p. The species size is the size of the solvated species 19 if it fits the pore size p or the size of the desolvated species 19 if it is smaller than pore size p. 7,16,17 If the pore size p is smaller than the size of desolvated species s, no s species is transported in pore size p. The electrolyte viscosity and conductivity (Nernst-Einstein equation) change with time as a function of the local species concentrations as described in 7,16,17 and are given by equations (SI.14) and (SI.16), respectively. R s,p is the net rate between the rate of dissolution and the rate of precipitation of species s in pore size p, given as a function of the mass transfer coefficient, k s , and the concentration difference between C s,p and the saturation concentration C s-sat of species s in the electrolyte (data from 20,21 ) by the following equation:…”