Design of Localized High-Concentration Electrolytes via Donor Number

Abstract

Salt-concentrated electrolytes offer properties beyond conventional dilute electrolytes yet suffer from high cost and viscosity which hinder their practical applications. Introducing a secondary solvent as a diluent could reduce the salt content while maintaining the local solution structure of salt-concentrated electrolytes, giving rise to localized high-concentration electrolytes (LHCEs). Through a comprehensive investigation involving over 500 samples, we find that the dielectric constant of solvent, a widely used parameter for electrolyte design, does not serve as a useful screening criterion for diluents; instead, donor number (DN) is an effective design parameter to achieve LHCE structure�i.e., the primary solvent must have DN > 10 and the diluent must have DN ≤ 10. Based on this simple rule, a new LHCE using lowcost m-fluorotoluene diluent is formulated, enabling high-voltage (>4.6 V) and wide-temperature (−40−100 °C) operation of lithium batteries.

Liquid electrolyte chemistries for solid electrolyte interphase construction on silicon and lithium-metal anodes

“…14e). 175,184 Moreover, currently reported uorinated ethers are expensive and not commercially available, and their large-scale production is hindered by the lack of correspondingly optimized synthetic methods. 245 As the price of conventional carbonate-based solvents has decreased aer decades of synthesis optimization for mass production, the price of various recently developed uorinated solvents could also decrease aer the optimization of the production process for electrolyte design.…”

Multi-constraint molecular generation using sparsely labelled training data for localized high-concentration electrolyte diluent screening

“…Overall, within the set of 27 838 unique molecules, only 3049 molecules have more than 8 F atoms, 2472 molecules have any S atoms, and 283 molecules have any P atoms. We note that some of the simpler known fluorocarbon-based diluent molecules such as m -fluorotoluene ( m FT) 37 and benzotrifluoride (BTF) 38 are not within the intended generative target range of our query (they contain no O atoms and have ≤3 F atoms), and correspondingly they are not generated. In future iterations, it will be ideal to further augment the training dataset with fluoro-phosphazene and fluoro-sulfonate families, as well as molecules with large number of F atoms to further diversify the generative model's output.…”

Customized Electrolyte and Host Structures Enabling High-Energy-Density Anode-Free Potassium–Metal Batteries

“…26 1,1,2,2-Tetrafluoroethyl-2,2,3,3-tetrafluoro-propyl ether (TTE), a hydrofluoroether diluent, earns attention for its low viscosity and donor number (DN = 1.9). 27,28 TTE transforms solvation structure without coordinating to K + , enabling a low K salt dissociation degree. 29 This strategy endows DHCE with favorable CIP or AGG structures, not only ensuring an anion-derived passivating SEI and wide electrochemical window but also preserving high ionic conductivity as well as low viscosity and K salt content.…”

“…On this basis, localized HCE (LHCE) or diluted HCE (DHCE) is prospering for its similar solvation structure to that of HCE while possessing lower salt content as well as viscosity and higher ionic conductivity by the participation of noncoordinative diluent . 1,1,2,2-Tetrafluoroethyl-2,2,3,3-tetrafluoro-propyl ether (TTE), a hydrofluoroether diluent, earns attention for its low viscosity and donor number (DN = 1.9). , TTE transforms solvation structure without coordinating to K + , enabling a low K salt dissociation degree . This strategy endows DHCE with favorable CIP or AGG structures, not only ensuring an anion-derived passivating SEI and wide electrochemical window but also preserving high ionic conductivity as well as low viscosity and K salt content. − Though DHCE has demonstrated its advantage in KIBs, high-energy-density K metal batteries based on anode-free configurations are necessary, and DHCE’s compatibility toward these batteries remains unknown.…”