Investigation and comparison of the energy storage performance of MXenes in dilute aqueous electrolytes and highly concentrated water-in-salt electrolytes

Abstract

In this thesis, the pseudocapacitive performance of MXene in different aqueous and acidic electrolytes was investigated. was found to have the highest capacitance, even greater than , with and . The two pairs of pseudocapacitive peaks of observed in windows A (from to vs Ag/AgCl) and B (from to vs Ag/AgCl) were studied, and conclusions were made about the stability of these two electrochemical processes. Dilute aqueous electrolytes based on nitrate, chloride, sulphate anion salts were studied, and among these, was found to perform the best in the lithium and potassium ion salts at higher scan-rates. At very low scan rates we examined a peculiar pseudocapacitive storage from some magnesium ion salts. Further, suitable and salts are chosen with high enough solubility, to prepare cheap, non-toxic water in salt electrolytes (WiSE). A remarkable cyclic stability of is observed in some WiSE, particularly the lithium ion based WiSE display an electrochemical stability window (ESW) larger than . Enhancing ESW along with good capacity allowed to improve energy density of MXene.