Novel Non-Aqueous Electrolytes Based on Coordination Boron Compounds

Abstract

The review provides a classification of electrolytes for modern chemical power sources, supercapacitors, sodium and lithium-ion batteries depending on changes in the physicochemical properties of salts and the products of their interaction with the solvent. A comparative analysis of physicochemical properties of salts depending on the structure of the cation and anion, and the influence of these properties on the properties of final solutions of electrolytes on the example of different classes of ionic liquids and chelatoborates of alkali metals and ammonium was conducted. The dependence of the physicochemical properties of electrolytes (solubility, electrical conductivity of solutions and the range of potentials of electrochemical stability) on the nature of the chelate ligand, electron donor and electroacceptor substituents in the bis (chelate) borate anion is analyzed. The electrical conductivity of salt solutions and ranges of potentials of electrochemical stability of the corresponding electrolytes containing other anions and used for a long time in chemical current sources are carried out. The advantages and disadvantages of using liquid electrolytes compared to solid and polymer electrolytes in terms of similarity of their structures have been detected. It is shown that the nature of the chelate ligand, electro-donor and electro-acceptor substituents in the bis (chelato) borate anion is an important factor in regulating the interaction with aprotic dipolar solvents. Mixed salts with two different chelate ligands typically combine the best characteristics of the corresponding monochelate compounds, but the methods for their preparation and purification are technologically significantly more complex compared to monochelate compounds. The analysis of the mechanism of formation of a protective film on a surface of electrode materials, dependence of potential on its formation and on the chemical nature of ligands is made. It is noted that bis (chelato) borate salts are more environmentally friendly compared to fluorine-containing complex salts. Emphasis is placed on the physicochemical properties of solutions of the most promising chelatoborate salts for use in lithium and sodium ion batteries, supercapacitors and electrolytic capacitors, and it is shown that bis (oxalate) borates and bis (salicylate gold) borates occupy ) borates in terms of electrical conductivity, solubility and potential range of electrochemical stability.