Nanostrukturované materiály pro uchovávání elektrické energie
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Tato diplomová práce se zabývá možnostmi aplikace nanostrukturovaných materiálů v problematice uchovávání elektrické energie. Z širokého portfolia aplikačních směrů je práce zaměřena zejména na uplatnění nanovlákenných materiálů v elektrochemických článcích a superkapacitorech s elektrickou dvojvrstvou. Tyto dvě oblasti byly zvoleny z důvodu jejich konstrukční a materiálové podobnosti. V teoretické části byla uskutečněna recenze vědeckých článků a publikací zabývajících se přípravou a aplikací nanostruktur, zejména pak nanovlákenných vrstev a porézních uhlíkových nanovláken v lithium iontovém článku a superkapacitoru s elektrickou dvojvrstvou. V návaznosti na tuto rešeršní činnost byly v praktické části práce připraveny nanovlákenné materiály pro separátory a modifikovaná uhlíková nanovlákna jako potenciální materiály elektrod. Morfologie takto připravených materiálů byla studována metodou skenovací i transmisní elektronové mikroskopie a energiově disperzní rentgenové spektroskopie. Měrný povrch vzorků byl stanoven metodou dusíkové adsorpce. Pro studium termicko-chemických vlastností byly použity metody infračervené spektroskopie, diferenční skenovací kalorimetrie a termogravimetrická analýza. Dále byly testovány elektrochemické vlastnosti materiálů elektrod a separátorů metodami galvanostatického cyklování a cyklické voltametrie ve spolupráci s VUT v Brně.Vývoj nanovlákenných vrstev pro separátory vedl k výrazné optimalizaci a zkrácení procesu přípravy polyimidových nanovláken s chemickou odolností nutnou pro tuto aplikaci. Na připravených separátorech bylo provedeno 30 nabíjecích cyklů v modelovém článku a jejich vlastnosti byly porovnány s komerčními separátory. Jako materiály elektrod byly připraveny dva typy modifikovaných uhlíkových nanovláken. První z nich se vyznačuje relativně velkým aktivním povrchem 93 m2/g, druhý pak rovnoměrným rozptýlením křemíku v nanovlákenné vrstvě. Provedené experimenty nabízí několik potenciálních směrů výzkumu, které jsou definovány v závěru práce.
This diploma thesis deals with possibilities of application of nanostructured materials in energy storage. From this wide field of potential applications is is focused mainly on the use of nanofibrous materials in electrochemical cells and electric double-layer capacitors. These two fields were chosen because of their similarities in construction as well as material requirements.The theoretical part of this thesis contains a review of scientific articles and publications dealing with preparations and applications of nanostructures, especially nanofibers and porous carbon nanofibers in lithium-ion cells and electric double layer capactitors. Following this review, nanofibrous structures for separators and porous carbon nanofibers for electrodes were prepared in the experimental part of this thesis. The morphology of these materials was studied using transmission electron microscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The surface area of these samples was studied using nitrogen adsorption. Thermal and physical properties were analyzed using infrared spectroscopy, differential scanning calorimetry and thermogravimetric measurements. Furthermore, electrochemical properties of samples were studied using galvanostatic cycling and cyclic voltammetry in cooperation with Brno University of Technology.The process of imidization was greatly optimized during the preparation of nanofibrous layers for separators made from polyamic acid, because of the key effect of this process on the resulting material polyimide. 30 discharge cycles were performed in a model cell with the sample separators and their performance was compared with commercial products. Two types of modified carbon nanofibers were produced as potential materials for electrodes. The first of them exhibited a relatively high surface area of 93 m2/g while the second had silicon evenly disperssed troughout its volume. The conducted experiments open several potential research possibilities, which are discussed at the end of the thesis.
This diploma thesis deals with possibilities of application of nanostructured materials in energy storage. From this wide field of potential applications is is focused mainly on the use of nanofibrous materials in electrochemical cells and electric double-layer capacitors. These two fields were chosen because of their similarities in construction as well as material requirements.The theoretical part of this thesis contains a review of scientific articles and publications dealing with preparations and applications of nanostructures, especially nanofibers and porous carbon nanofibers in lithium-ion cells and electric double layer capactitors. Following this review, nanofibrous structures for separators and porous carbon nanofibers for electrodes were prepared in the experimental part of this thesis. The morphology of these materials was studied using transmission electron microscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The surface area of these samples was studied using nitrogen adsorption. Thermal and physical properties were analyzed using infrared spectroscopy, differential scanning calorimetry and thermogravimetric measurements. Furthermore, electrochemical properties of samples were studied using galvanostatic cycling and cyclic voltammetry in cooperation with Brno University of Technology.The process of imidization was greatly optimized during the preparation of nanofibrous layers for separators made from polyamic acid, because of the key effect of this process on the resulting material polyimide. 30 discharge cycles were performed in a model cell with the sample separators and their performance was compared with commercial products. Two types of modified carbon nanofibers were produced as potential materials for electrodes. The first of them exhibited a relatively high surface area of 93 m2/g while the second had silicon evenly disperssed troughout its volume. The conducted experiments open several potential research possibilities, which are discussed at the end of the thesis.
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elektroda, elektrochemický článek, imidizace, polyimid, separátor, uhlíková nanovlákna, superkapacitor, electrode, electrochemical cell, imidization, polyimide, separator, carbon nanofiber, supercapacitor