Probing Pseudocapacitive response of MXene electrodes for energy storage from first principles

Pseudocapacitive devices are able to store and release electrical energy by virtue of the rapid and reversible redox reactions which occur at the electrode surfaces. The family of transition metal carbides and nitrides, MXenes, show promise as pseudocapacitive electrodes. As the performance, power and energy densities, of the pseudocapacitive device is predicated on the quantity of lithium-ion adsorption onto the surface of the MXene, we are interested in the effects of MXene composition and solution properties on this phenomenon. We perform voltage-dependent cluster expansions to study reversible lithium-ion adsorption in realistic environments. The cluster expansions are fit with semi-local density functional calculations in implicit solvent. Preliminary results show that lithium-ion pseudocapacitance is sensitive to the dielectric constant of the solution and extent of surface electrification through electrochemical double layer capacitance. Our results also suggest that solvents with higher lithium reduction potentials that stabilize the lithium-ions in solution can extend the potential window of the pseudocapacitive electrode.