Specialties of the structure and conductivity of the non-aqueous electrolytes based on alkali metal bis (salicyl) borates and bis (oxalate) borates

Abstract

The structure and coordination environment of non-aqueous electrolytes based on bis(salicyl)borates of lithium, sodium, potassium, tetramethylammonium (MeBSB) and bis(oxalato)borates from lithium to cesium (MeBOB) using NMR spectroscopy have been investigated. Bis(salicyl)borates (BSB) and bis(oxalate)borates (BOB) of alkali metals and organic cations are considered as promising electroconductive components of electrolytes of modern chemical sources of current (lithium, sodium ion batteries and super-capacitors). The salts were synthesized by the microwave radiation method. The 13C and 11B NMR spectra analysis determined the presence of symmetric structure in BOB anion and the presence of two optical conformations of the BSB anion with labile coordination environment of boron. The conformations of the BSB are the result of the ion contact pairs formation. In the case of tetramethylammonium cation the presence of conformations are depended on the reactive medium. The conformational lability of the coordination sphere of NaBSB dissolved in DMAA is connected with increasing of the integral intensity of carboxyl group singles relatively signals of carbon atoms in fragments of another functional affiliation when the time delay between radio frequencies varies within 2-15 seconds. The difference in the structure of these anions leads to a change in the thermal dependence of the electrical conductivity of BSB and the transport of ions in non-aqueous solvents. Maximum electrical conductivity of salt solutions in DMFA is achieved at close concentrations of 0.75 m for KBSB and 0.77-1 m for NaBSB. The solubility of BSB is better than the BOB. Based on the measurements of the conductivity and the data of electrochemical impedance spectroscopy (the angle of inclination of spectra in the Nyquist coordinates in the low frequency range, the phase angle shift at a frequency) it was proposed the existence of two ways of ions and charge transfer in the electrolytes: diffusion and relay transport. The possibility of formation of a labile salt complex with a solvent due to hydrogen bonds is established.

Novel Non-Aqueous Electrolytes Based on Coordination Boron Compounds

“…For ionic liquids in the formation of polymer structures or in the formation of zwitterion, the characteristic Grotthuss (relay) mechanism of charge transport with the formation of free volume is realized [34][35]. The presence of apseudopolymer structure in the salt-solvent system changes the transport function of electrolytes due to a change in dielectric properties and conductivity [36][37][38][39][40].…”

Synthesis of sodium (oxalate) difluoro borate-based hybrid electrolyte salts with enhanced interfacial properties for NaNi0.3Fe0.4Mn0.3O2 cathodes

“…21–23 Consequently, there arises a compelling need to develop new sodium salts characterized by low cost, optimal safety, robust thermal stability, and a broad electrochemical window. In response to this imperative, researchers have tirelessly endeavored to discover novel sodium salts including sodium (oxalate) difluoro borate (NaODFB), 24–26 sodium bis(oxalate)borate (NaBOB), 27–29 sodium bis[salicylato(2-)]-borate (NaBSB), 30,31 sodium salicylic benzylic acid borate (NaBDSB), 32 sodium 4,5-dicyano-2-(trifluoromethyl)imidazolate (NaTDI) 33–35 and sodium 4,5-dicyano-2-(pentafluoroethyl)imidazolate (NaPDI). 33–35 Despite their unique properties such as low conductivity, low solubility, the requirement for in-house synthesis, or cost, many of these salts have not been extensively employed.…”

MODERN RESEARCH METHODS OF PHYSICOCHEMICAL AND ELECTROCHEMICAL PROPERTIES OF ELECTROLYTES IN FOR Li-ION BATTERIES AND HYBRID SUPERCAPACITIES

“…The secondary power sources need a higher electrochemical (operating potential range) and thermal (operating temperature range) resistance to ensure high operating life. Modern electrolytes have sufficiently high values of the potentials operating range (3.5-5.1 V) [33][34][35][36][37][38][39][40]. Salt components have significant thermal stability (100-400 °C) (Table 1) [33][34][35][36][37][38][39][40].…”

“…Modern electrolytes have sufficiently high values of the potentials operating range (3.5-5.1 V) [33][34][35][36][37][38][39][40]. Salt components have significant thermal stability (100-400 °C) (Table 1) [33][34][35][36][37][38][39][40]. Nowadays, the industry samples contained mainly lithium compounds that have some ope rational problems.…”