Electrochemical characterization of alkali metal salt based non-aqueous electrolytes for supercapacitors
Date
2013-06-26
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Abstract
Superkondensaatorid (SK) on kõrge võimsusega energiasalvestusseadmed, milles energia salvestamine toimub elektrolüüdi ioonide pöörduval füüsikalisel adsorptsioonil polariseeritud suure eripinnaga elektroodi ning elektrolüüdi piirpinnale. SK-de karakteristikute parendamiseks uuritakse mitmesuguseid poorseid materjale, elektrolüütide koostisi ning separaatori materjale. Kommertsiaalselt rakendatud kahjulikule atseetonitriilile ning viskoossele propüleenkarbonaadile asenduse leidmine on oluline etapp SK-de laiemas kasutuselevõtus. Lisaks solvendi vahetamisele tuleb uurida alternatiivseid elektrolüüdi soolasid optimeerimaks solvendi/soola kombinatsiooni.
Antud doktoritöö eesmärgiks oli uurida uudseid elektrolüüte, mis koosnevad leelismetallide katioonil ning erinevatel anioonidel põhinevatest sooladest (LiPF6, LiClO4, LiCF3SO3, LiB(C2O4)2, NaPF6, NaClO4, CsCB11H12) keskkonnasõbralikus etüleenkarbonaadi ja dimetüülkarbonaadi solvendisegus. Kõige laiem ideaalse polariseeritavuse ala (3.4 V) kehtestati NaPF6 korral. Identsetel tingimustel arvutatud energiatiheduse väärtused varieerusid elektrokeemiliselt stabiilsete elektrolüütidega testsüsteemide vahel 20% ulatuses (35–42 Wh kg-1), kuid võimsustihedus sõltus märkimisväärselt kasutatud elektrolüüdist, mille suurim väärtus 95 kW kg-1 arvutati NaPF6 elektrolüüdi korral.
Supercapacitors (SC) are high-power energy storage devices, where energy is stored through reversible physical adsorption of electrolyte ions on the interface between large surface area polarized electrode and electrolyte. Various porous materials, electrolyte compositions and separator materials are being studied and electrochemically characterized to improve the performance of SCs. Finding a replacement for commercially applied harmful acetonitrile and viscous propylene carbonate based electrolytes is an important step for wider commercialization of SCs. In addition to changing solvent, possible electrolyte salt candidates have to be studied to optimize solvent/salt combination. The aim of this thesis was to study novel electrolytes consisting of alkali metal cation and different anion based salts (LiPF6, LiClO4, LiCF3SO3, LiB(C2O4)2, NaPF6, NaClO4, CsCB11H12) in an environmentally friendly mixed solvent system of ethylene carbonate and dimethyl carbonate. The widest region of ideal polarizability (3.4 V) was established in case of NaPF6. Energy density values, calculated at identical conditions, varied only by 20% between the test systems with electrochemically stable electrolytes (35–42 Wh kg-1), but power densities depended remarkably on the electrolyte, with the highest value of 95 kW kg-1 calculated for NaPF6 based electrolyte.
Supercapacitors (SC) are high-power energy storage devices, where energy is stored through reversible physical adsorption of electrolyte ions on the interface between large surface area polarized electrode and electrolyte. Various porous materials, electrolyte compositions and separator materials are being studied and electrochemically characterized to improve the performance of SCs. Finding a replacement for commercially applied harmful acetonitrile and viscous propylene carbonate based electrolytes is an important step for wider commercialization of SCs. In addition to changing solvent, possible electrolyte salt candidates have to be studied to optimize solvent/salt combination. The aim of this thesis was to study novel electrolytes consisting of alkali metal cation and different anion based salts (LiPF6, LiClO4, LiCF3SO3, LiB(C2O4)2, NaPF6, NaClO4, CsCB11H12) in an environmentally friendly mixed solvent system of ethylene carbonate and dimethyl carbonate. The widest region of ideal polarizability (3.4 V) was established in case of NaPF6. Energy density values, calculated at identical conditions, varied only by 20% between the test systems with electrochemically stable electrolytes (35–42 Wh kg-1), but power densities depended remarkably on the electrolyte, with the highest value of 95 kW kg-1 calculated for NaPF6 based electrolyte.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
superkondensaatorid, elektrolüüdid, elektrokeemia, supercapacitors, electrolytes, electrochemistry