Electrical double layer structure and energy storage characteristics of ionic liquid based capacitors
Date
2018-07-05
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Abstract
Elektrokeemilised energia salvestamise ja muundamise seadmed on aluseks tuleviku jätkusuutlikule energiamajandusele. Olgu selleks siis elektromagnet kiirgust elektrienergiaks muundavad päikesepatareid, autotranspordis kasutatavad kütuseelemendid, veest kütust tootvad elektrolüüserid, sekundaar-akumulaatorid iga-päeva elektroonikaseadmetes, superkondensaatorid, mis säästavad energiat kõrge võimsusega rakendustes või dielektrilised kondensaatorid elektroonilistes muundurites, kõrgtehnoloogilised elektrokeemilised seadmed on kõikjal meie ümber. Kõikide eelpool nimetatud seadmete puhul on aktiivseks osaks kahe erineva materjali vaheline piirpind, kus toimuvad elektrokeemilised reaktsioonid ja salvestub elektrienergia. Uute, kõrge effektiivusega elektrokeemiliste seadmete loomiseks on aga ülimalt oluline arusaam vastavat piirpinda mõjutavatest teguritest. Antud doktoritöö keskendub just mahtuvuslikele energia salvestamise seadmetele ja erinevustele elektrostaatiliste, dielektriliste ja pseudomahtuvuslike kondensaatorite vahel ioonse vedeliku ja elektroodi piirpinna vaheliste mõjude karakteriseerimise toel. Selle saavutamiseks rakendati ülitundlikke elektrokeemilisi, füüsikalisi ja spektroskoopilisi piirpinna analüüsi meetodeid, et reaalajas vaadelda muutuseid, mis leiavad aset elektrokeemilisel piirpinnal. Teadmised vastavatest fundametaaluuringutest on aidanud luua kõrgema spetsiifilise energiaga superkondensaatoreid ning viinud uudse dielektrilise kondensaatori tehnoloogia arendamiseni.
Electrochemical energy storage and conversion devices are the basis of a sustainable energy economy of the future. Whether it is solar cells that convert electromagnetic radiation into electrical energy, fuel cells that consume chemical energy to power transportation, electrolysis cells that convert water into fuel, secondary batteries powering consumer electronics, supercapacitors that deliver considerable energy savings for high-power applications or dielectric capacitors that allow for efficient conversion between AC and DC signals, we are surrounded by advanced electrochemical devices. The active part of all of these devices is the interface between two dissimilar phases, where all the electrochemical reactions take place and energy is stored. In order to design more efficient electrochemical devices, however, detailed knowledge of this interface is of vital importance. This thesis focuses specifically on capacitive energy storage devices and the difference between purely electrostatic-, dielectric- and pseudo-capacitors from the perspective of their interfacial behaviour in ionic liquid electrolytes. This is achieved via advanced electrochemical, physical and spectroscopic analysis techniques that permit one to probe the properties of an electrochemical interface in real time. The knowledge from the fundamental studies has been applied to produce supercapacitors with higher specific energy and has led to the development of a new dielectric capacitor technology.
Electrochemical energy storage and conversion devices are the basis of a sustainable energy economy of the future. Whether it is solar cells that convert electromagnetic radiation into electrical energy, fuel cells that consume chemical energy to power transportation, electrolysis cells that convert water into fuel, secondary batteries powering consumer electronics, supercapacitors that deliver considerable energy savings for high-power applications or dielectric capacitors that allow for efficient conversion between AC and DC signals, we are surrounded by advanced electrochemical devices. The active part of all of these devices is the interface between two dissimilar phases, where all the electrochemical reactions take place and energy is stored. In order to design more efficient electrochemical devices, however, detailed knowledge of this interface is of vital importance. This thesis focuses specifically on capacitive energy storage devices and the difference between purely electrostatic-, dielectric- and pseudo-capacitors from the perspective of their interfacial behaviour in ionic liquid electrolytes. This is achieved via advanced electrochemical, physical and spectroscopic analysis techniques that permit one to probe the properties of an electrochemical interface in real time. The knowledge from the fundamental studies has been applied to produce supercapacitors with higher specific energy and has led to the development of a new dielectric capacitor technology.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
capacitors, electric double layer, energy storage, ionic liquids