doktorska disertacija
Nejc Pavlin (Author), Robert Dominko (Mentor), Boštjan Genorio (Thesis defence commission member), Marjan Marinšek (Thesis defence commission member), Karin Stana-Kleinschek (Thesis defence commission member)

Abstract

Litij žveplovi akumulatorji so eden najobetavnejših kandidatov za prevzem primata litij ionskim akumulatorjem na področju shranjevanja energije,saj jih odlikujejo številne zaželene lastnosti, kot so nizka cela aktivnih materialovin majhen vpliv na okolje. Poleg tega je njihova teoretična gostota energije veliko višja od komercialnih litij ionskih akumulatorjev, ki temeljijo na interkalacijskih materialih. Kljub tem prednostim množično uporabo Li-S akumulatorjev ovirajo številni izzivi, povezanis hitro izgubo kapacitete večinoma zaradi izgube aktivnega materiala in elektrokemijsko nestabilnega pasivnega sloja med kovinski litijem in različnimi vrstami elektrolitov. Celuloza je najbolj razširjen polimer na Zemlji in zaradi svojih dobrih mehanskih lastnosti, enostavne modifikacije ter biorazgradljivosti primeren kandidat za naslovitev problemov Li-S akumulatorjev, če se uporabi kot separacijski sloj med žveplovo katodo in anodo iz kovinskega litija. Primarna vloga separatorja v akumulatorskih celicah je preprečitev kontakta med anodo in katodo, s primerno modifikacijo in izdelavo pa je z njim mogoče vplivati tudi na procese v akumulatorski celici. Primerne lastnosti celuloze in zmožnost njenega vpliva na procese v akumulatorski celici so bile glavne smernice te doktorske disertacije. V našem delu smo najprej iz nanofibrilirane celuloze (NFC) izdelali samostoječe NFC-separatorje in dokazali, da se izboljša delovanje Li-S akumulatorjev v primerjavi s komercialnimi separatorji. Z uporabo XPS-spektroskopije in SEM-FIB-mikroskopije smo pokazali, da NFC-separator še posebno dobro vpliva na kovinsko litijevo elektrodo. Za naslovitev problema difuzije in migracije topnih polisulfidnih zvrsti iz žveplaste katode smo sintetizirali dva različna celulozna materiala: fluoro NFC in s polianilinom oplaščeno NFC ter jih implementirali v Li-S akumulator. Oba materiala sta imela pozitiven učinek na migracijo topnih polisulfidnih zvrsti po Li-S akumulatorski celici, nista pa v celoti odpravila problema hitre izgube kapacitete Li-S akumulatorjev. Pozitivni vpliv NFC materialov na kovinsko litijevo elektrodo smo z izdelavo zaščitnih preverili slojev direktno na litijevi površini z uporabo trimetilsilil celuloze. Rezultati analiz so pokazali, da tanek zaščitni sloj na osnovi NFC uspešno zavre dendritsko rast litija, prepreči korozivne reakcije med kovinskim litijem in elektrolitom tertako stabilizira kovinsko litijevo elektrodo.

Keywords

baterije;akumulatorski sistemi;Li-žveplov akumulator;kovinska litijeva elektroda;celuloza;celulozni separator;modifikacija nanofibrilirane celuloze;litijevi dendriti;celulozni zaščitni sloj;optimizacija;elektrokemijska karakterizacija;FIB-SEM;doktorske disertacije;

Data

Language: Slovenian
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UL FKKT - Faculty of Chemistry and Chemical Technology
Publisher: [N. Pavlin]
UDC: 621.355:661.728(043.3)
COBISS: 1538552259 Link will open in a new window
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Other data

Secondary language: English
Secondary title: Modified cellulose separators in lithium-sulphur batteries
Secondary abstract: Lithium sulphur batteries are one of the most promising candidates to take primacy of the lithium-ion batteries in the field of energy storage due to their desirable features, such as competitive cost of production and low environmental impact. In addition, their exceptional theoretical energy density is much higher than commercial Li-ion batteries based on intercalation materials. Despite of these advantages, the mass commercialization of Li-S batteries is still hampered by the many challenges associated with rapid loss of capacity, mainly due to the loss of active material and the electrochemically unstable passive layer between lithium metal and various types of electrolytes. Cellulose is the most abonded polymer material on the Earth and, due to its good mechanical properties, easy modification and biodegradability, is a suitable candidate for addressing Li-S battery problems and it can be used as separation layer between sulphur cathode and lithium metal anode. The primary role of the separator in the battery cell is to prevent contact between the anode and the cathode, with appropriate modification and fabrication; it can also affect the processes in the battery cell. Appropriate cellulose properties and the ability to influence processes through separator has been the main focus of this doctoral dissertation. In presented work, we first constructed self-standing separator membranes from nano-fibrillated cellulose (NFC) and proved that they improve the performance of Li-S batteries compared to commercial separator membranes. Using XPS spectroscopy and FIB-SEM microscopy, we showed that the separator membranes from NFC has, in particular, good effect on the lithium metal electrode. To address the problem associated to the diffusion and migration of soluble polysulphides species from the sulphur cathode, two different NFC materials were synthesized: fluoro NFC and polyaniline coated NFC, and implemented in a Li-S battery. Both materials had a positive effect on the migration of soluble polysulphides species across the Li-S battery cell, but did not completely solved the problem of rapid capacity loss of Li-S batteries. Positive effect of NFC materials on the metal lithium electrode was verified with implementation of protective layers based on cellulose directly on the lithium metal surface using trimethylsilyl cellulose. The results of the analyses showed that a thin NFC based protective layer successfully inhibits dendritic growth of lithium, preventing corrosive reaction between the lithium metal and the electrolyte, thus stabilizing the lithium metal electrode.
Secondary keywords: Li-sulphur battery;cellulose separator;nanofibrillated cellulose modification;lithium dendrites;cellulose protective layer;optimization;FIB-SEM;Litij žveplovi akumulatorji;Disertacije;
Type (COBISS): Doctoral dissertation
Study programme: 1000381
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo
Pages: XVI, 129 f.
ID: 11431406