Anode materials and processing technologies for modern lithium-ion battery cell concepts

Abstract: Lithium-ion batteries (LIBs) have become an integral part of our daily life and hold great promise to be a significant enabler toward a zero-emission society. For high energy batteries, the commonly used graphite anode can be complemented with silicon-based materials. However, the production of state-of-the-art (SOTA) graphite entails the emission of large quantities of CO2 and other greenhouse gases. In this thesis, the investigation and development of high-energy and sustainable anode materials are presented as the major topics, accompanied by research on additive manufacturing methods and a concept describing a novel gel polymer electrolyte.

- High-capacity silicon-carbon-graphite blend slurries were designed for a 3D-printed lithium-ion microbattery application. To custom-manufacture the slurries for an automated dispenser printing process, the binder content (carboxymethyl cellulose/styrene-butadiene rubber, CMC/SBR) was considered a significant variable and was assessed at 6wt%, 12wt%, 18wt%, and 24wt%. Subsequently, the electrochemical and rheological properties of slurries were systematically investigated. As a result, higher binder content leads to higher yield stresses and viscosities, promising printed structures with high aspect ratios (AR) but reduced electrochemical performance. In fact, printed anode structures showed the highest AR of 6.5 for slurries with 24wt% binder. On the other hand, a capacity of 484 mAh/g at a current rate of 0.25 C was achieved for anodes with 12wt%.

- Lithium-ion battery full-cells based on biomass-derived hard carbon anodes are presented as an environmentally friendly alternative to standard graphite. The hard carbon material was derived from spruce wood by pyrolysis at 1100 °C. To compensate initial lithium losses, in situ electrochemical pre-lithiation was applied in the same cell set-up as full-cell operation. Thus, full-cells based on pre-lithitated anodes were characterized by a significantly increased cycle life, capacity, and first-cycle coulombic efficiency relative to full-cells using untreated anodes (state of health (SOH) 80 after 150 cycles versus 70 cycles, 195 mAh/g versus 150 mAh/g, and 90% versus 65%). Finally, the lithiation state was determined by detailed investigation of the full-cell operation.

- Novel gel polymer electrolytes (GPEs) based on a cationic vinylimidazolium-terminated poly(2-ethyl-2-oxazoline) (PEtOx) macromonomer as the key component are presented for the application in LIBs. GPE production was performed by UV curing of the solution containing the macromonomer, polyfunctional acrylic comonomers, and organic electrolyte (LP30). As a result, electrolyte-swollen polymeric ionic liquid networks with PEtOx side chains were achieved. The GPE was characterized by intense electrolyte retention properties against evaporation. In fact, at 160 °C the overall mass loss was only 5%. For a comparable SOTA system, the same mass loss was already observed at 110 °C. Differential scanning calorimetry showed crystallization for the pure liquid electrolyte but not for the GPE. The same behavior was qualitatively confirmed by conductivity measurements. At room temperature, the GPE had a conductivity of 3.6 × 10-4 S/cm, outperforming that of the SOTA system. Finally, electrochemical half-cell measurement using an LFP cathode renders the GPE a promising candidate with respect to future and safter lithium battery operation.

In addition to the focus on sustainable and high-energy anodes, this thesis addresses selected topics which are highly relevant for current LIB research

Objekt anzeigen

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch
• Anmerkungen: Universität Freiburg, Dissertation, 2022

Klassifikation und Themen

• Klassifikation: Elektrotechnik, Elektronik
• Schlagwort: Lithium ; Materials ; Lithium-Ionen-Akkumulator

Beteiligte, Orts- und Zeitangaben

• Ereignis: Veröffentlichung
• (wo): Freiburg
• (wer): Universität
• (wann): 2022
• Urheber: Drews, Mathias
• Beteiligte Personen und Organisationen: Biró, Daniel ; Vierrath, Severin ; Glunz, Stefan ; Albert-Ludwigs-Universität Freiburg. Fakultät für Angewandte Wissenschaften

Weitere Informationen

• DOI: 10.6094/UNIFR/227124
• URN: urn:nbn:de:bsz:25-freidok-2271243
• Rechteinformation: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.