Physicochemical characterisation of ionic liquids and lactones binary mixtures and their application as electrolytes for lithium-ion batteries

Abstract

<p>U&nbsp; ovoj&nbsp; doktorskoj&nbsp; disertaciji&nbsp; ispitivani&nbsp; su&nbsp; elektroliti&nbsp; na&nbsp; bazi binarnih&nbsp; sme&scaron;a&nbsp; imidazolijumovih&nbsp; jonskih&nbsp; tečnosti&nbsp; i&nbsp; laktona&nbsp; koji su&nbsp; pogodni&nbsp; za&nbsp; primenu&nbsp; u&nbsp; litijum-jonskim&nbsp; baterijama.&nbsp; Fizičkohemijska&nbsp; svojstva&nbsp; binarnih&nbsp; sme&scaron;a&nbsp; jonskih&nbsp; tečnosti&nbsp; na&nbsp; bazi imidazolijum katjona i <em>bis </em>(trifluorometilsulfonil)imidnog anjona i laktona ispitana su u celom opsegu molskih udela i na različitim temperaturama.&nbsp; Na&nbsp; osnovu&nbsp; izmerenih&nbsp; gustina,&nbsp; viskoznosti&nbsp; i električne&nbsp; provodljivosti&nbsp; izračunati&nbsp; su&nbsp; različiti&nbsp; fizičko-hemijski parametri i diskutovane&nbsp; interakcije između komponenata sme&scaron;a. Ispitana&nbsp; je&nbsp; termička&nbsp; i&nbsp; elektrohemijska&nbsp; stabilnost&nbsp; odabranih elektrolita.&nbsp; Na&nbsp; osnovu&nbsp; dobijenih&nbsp; rezultata,&nbsp; prvo&nbsp; je&nbsp; odabran odgovarajući&nbsp; lakton&nbsp; koji&nbsp; je&nbsp; kasnije&nbsp; kombinovan&nbsp; sa&nbsp; jonskim<br />tečnostima&nbsp; na&nbsp; bazi&nbsp; imidazola,&nbsp; koje&nbsp; se&nbsp; međusobno&nbsp; razlikuju&nbsp; u dužini&nbsp; bočnog&nbsp; niza&nbsp; katjona.&nbsp; Na&nbsp; osnovu&nbsp; fizičko-hemijskih svojstava&nbsp; na&nbsp; različitim&nbsp; temperaturama&nbsp; i&nbsp; pri&nbsp; različitim&nbsp; sastavima binarnih&nbsp; sme&scaron;a&nbsp; diskutovan&nbsp; je&nbsp; način&nbsp; organizacije&nbsp; njihovih<br />komponenata.&nbsp; U&nbsp; binarne&nbsp; sme&scaron;e&nbsp; koje&nbsp; su&nbsp; se&nbsp; pokazale&nbsp; kao najperspektivnije&nbsp; sa&nbsp; stanovi&scaron;ta&nbsp; električne&nbsp; provodljivosti, viskoznosti,&nbsp; elektrohemijske&nbsp; stabilnosti&nbsp; i&nbsp; (ne)zapaljivosti&nbsp; dodata je litijumova so. Tako dobijeni ternarni sistemi su okarakterisani<br />u zavisnosti od koncentracije litijumove soli. Odabrani elektroliti upotrebljeni su za ispitivanje performansi litijum-jonske ćelije sa elektrodama&nbsp; na&nbsp; bazi&nbsp; anatas&nbsp; TiO₂&nbsp; nanocevi.&nbsp; Cikličnom voltametrijom&nbsp; i&nbsp; galvanostatskim&nbsp; cikliranjem&nbsp; ispitane&nbsp; su<br />performanse ćelije u toku 350 ciklusa punjenja i pražnjenja. Na osnovu&nbsp;&nbsp; ciklovoltametrijskih&nbsp; merenja&nbsp; izračunati&nbsp; su&nbsp; koeficijenti difuzije jona Li^{&nbsp; +}i energija aktivacije za difuziju.&nbsp; Kombinacijom jonskih&nbsp; tečnosti&nbsp; i&nbsp; laktona&nbsp; moguće&nbsp; je&nbsp; dobiti&nbsp; elektrolite&nbsp; smanjene viskoznosti,&nbsp; povećane&nbsp; električne&nbsp; provodljivosti,&nbsp; povećane<br />termičke&nbsp; stabilnosti&nbsp; usled&nbsp; međusobnog&nbsp; stabilizacionog&nbsp; efekta laktona na imidazolijumove jonske tečnosti.</p>

<p>In&nbsp; this&nbsp; doctoral&nbsp; dissertation,&nbsp; binary&nbsp; mixtures&nbsp; based&nbsp; on&nbsp; imidazolium&nbsp; ionic&nbsp; liquids&nbsp; with&nbsp; lactones&nbsp; were&nbsp; tested&nbsp; for&nbsp; use&nbsp; in lithium-ion&nbsp; batteries.&nbsp; The&nbsp; physicochemical&nbsp; properties&nbsp; of&nbsp; binary&nbsp; mixtures&nbsp; of&nbsp; imidazolium&nbsp; based&nbsp; ionic&nbsp; liquids&nbsp; with&nbsp;<em> bis </em>(trifluoromethylsulfonyl)imide&nbsp; anions&nbsp; and&nbsp; lactones&nbsp; were&nbsp; examined&nbsp; throughout&nbsp; the&nbsp; whole&nbsp; composition&nbsp; range&nbsp; and&nbsp; at&nbsp; different temperatures. Based on the measured densities, viscosity&nbsp; and electrical conductivity, various physical chemical parameters&nbsp; and discrete interactions between the components of the mixture are&nbsp; calculated.&nbsp; Thermal&nbsp; and&nbsp; electrochemical&nbsp; stability&nbsp; of&nbsp; selected&nbsp; binary&nbsp; mixtures&nbsp; were&nbsp; examined.&nbsp; Based&nbsp; on&nbsp; obtained&nbsp; results&nbsp; was&nbsp; selected lactone&nbsp; which is later combined with imidazolium based&nbsp; ionic liquid,&nbsp; differing from each other in the length of the cation. Based&nbsp; on&nbsp; the&nbsp; physico-chemical&nbsp; properties&nbsp; at&nbsp; different&nbsp; temperatures and in the different compositions of binary mixtures, the way of organizing their components is discussed. Lithium salt&nbsp; is added to the binary mixtures that have been shown as the most perspective&nbsp; from&nbsp; the&nbsp; standpoint&nbsp; of&nbsp; electrical&nbsp; conductivity, viscosity,&nbsp; electrochemical&nbsp; stability&nbsp; and&nbsp; (non)flammability.&nbsp; The&nbsp; resulting&nbsp; ternary&nbsp; systems&nbsp; are&nbsp; characterized&nbsp; according&nbsp; to&nbsp; the concentration of lithium salt.&nbsp; The selected electrolytes were used to test the performance of the lithium-ion cell with anatase TiO₂ nanotubular&nbsp; electrodes.&nbsp; Cyclic&nbsp; voltammetry&nbsp; and&nbsp; galvanostatic&nbsp; cycling&nbsp; tested&nbsp; the&nbsp; cell&#39;s&nbsp; performance&nbsp; during&nbsp; the&nbsp; 350&nbsp; charge&nbsp; and discharge&nbsp; cycles.&nbsp; Based&nbsp; on&nbsp; cyclic&nbsp; voltammetric&nbsp; measurements, the&nbsp; Li ⁺ ion&nbsp; diffusion&nbsp; coefficients&nbsp; and&nbsp; activation&nbsp; energies&nbsp; for diffusion&nbsp; were&nbsp; calculated.&nbsp; Combination&nbsp; ionic&nbsp; liquid&nbsp; and&nbsp; lactone could&nbsp; be&nbsp; obtained&nbsp; electrolytes&nbsp; with&nbsp; lower&nbsp; viscosity,&nbsp; higher electrical&nbsp; conductivity,&nbsp; improved&nbsp; thermal&nbsp; stability&nbsp; due&nbsp; to stabilization effect of lactone on imidazolium based ionic liquids.</p>