KTH Royal Institute of Technology in Stockholm is the largest and oldest technical university in Sweden. No less than one-third of Sweden’s technical research and engineering education capacity at university level is provided by KTH. Education and research spans from natural sciences to all branches of engineering and includes Architecture, Industrial Management and Urban Planning. There are a total of 13,400 first and second level students and almost 1,900 doctoral students. KTH has 4,900 employees.
The School of Chemical Science and Engineering includes the areas Chemistry, Chemical Engineering and Fibre and Polymer Technology. It encompasses both fundamental and applied Chemical sciences and seeks sustainable development through scientific excellence. Many research activities are interdisciplinary across the borders from Chemistry to Materials science, Environmental science, Biochemistry, Biology and Medicine. The School offers a Bachelor of Science in Engineering Chemistry, Degree Programs in Engineering Chemistry, Technical Preparatory Year and three international master programs: Chemical Engineering for Energy and the Environment, Macromolecular Materials and Molecular Science and Engineering. We also cooperate with the master programs Energy and Environment, Materials Design and Biotechnology.
Research subject
Since lithium-ion batteries were introduced to the market in the 1990’s the demand has increased enormously and today several billions of battery cells are produced yearly. However, realization of flexible and/or stretchable batteries would open up for an even larger array of applications, such as new electronic devices as flexible displays, printed and wearable electronics, where the stiff batteries of today are a limitation. More environmentally friendly materials than the petroleum-based polymers used now for electrode binders and separators is another important issue.
Nanofibrillated cellulose (NFC) is a class of high aspect ratio nanomaterial that can be prepared in bulk quantities and be used to address all of the above-presented challenges. Very thin and strong nanopapers with a controlled porosity can be made from NFC, with properties that well suit electrochemical devices. Indeed, composite papers with nanocellulose and nanoparticles have been tested as electrodes and separators in batteries and supercapacitors. Some of the attractive properties with such composites are their flexibility/bendability, the nano dimension compatible with the electroactive nanoparticles, the possibility to improve the ionic transport by functionalizing the NFC and/or tailoring the porosity, cellulose being a renewable material, the possibility to produce batteries more efficiently than today. Another remarkable feature of NFC is that at 5 wt.% (based on total dry electrode weight) it can be used to load as much as 95 wt.% of active material particles without losing mechanical integrity of the electrode. In fact, at this weight ratio even freestanding electrodes can be produced.
Project description
The project consists of three parts, all focused on improved cellulose-based Li-ion batteries.
First, the coulumbic efficiency obtained could be improved and is probably related to water bound to the cellulose. The water content in a Li-ion battery should not exceed 20-50 ppm, which is in contrast to the high moisture content of cellulose fibers. The issue of water is important for cellulose to be used in any non-aqueous electrochemical system. Second, the theoretical capacity of the negative electrode could be increased considerably if replacing graphite commonly used today, with nanoparticles of, for example, tin or silicon. A problem with such high capacity materials is the volume increase during insertion of lithium in the electrode reaction, which damages the active material as well as the porous structure. Cellulose nanofibrils could be route to increase the lifetime of such electrodes. Third, charging and discharging at high rates result in a low capacity and this is most likely due to poor transport of Li+ ions between the electrodes. A better understanding about how to tailor the pores in the nanopapers is needed, and also knowledge about the interactions between cellulose and the electrolyte components. Factors such as “dead end” pores, low wettability of pores as well as attraction forces between Li+ and cellulose may be responsible for the low capacity.
Placement: Department of Chemical Engineering and Technology, the School of Chemical Sciences and Engineering.
Eligibility and Assessment Criteria
Master of Science in Chemical Engineering, alternatively Engineering Physics, Mechanical Engineering, or a related field. This specific sub-project concerns electrochemical processes to a large extent why a good knowledge in electrochemistry is a merit. Previous experience and knowledge about cellulosic materials is a merit, as well as fundamental knowledge in chemical and electrical engineering. The research task is to a large extent experimental and previous experience with testing of materials and structures will be a merit. Good oral and written communication skills in English and Swedish are an advantage.
The candidate should be highly motivated for doing scientific research and should have well developed analytical and problem solving skills as well as an interest and curiosity for multi-disciplinary problems in the context of energy savings towards a sustainable society.
Employment
Form of employment: fixed term contract. The salary is set according to the current agreement on doctoral student employment. Within the employment, departmental work may be included, but to a maximum of 20%.
Start: To be agreed.
Application
Application deadline: 2014-07-07
Reference number: K-2014-0391
The application must include following documents:
- CV (maximum 2 pages) including education and relevant academic/work experience
- Cover letter (maximum 1 page)
- Official record of transcripts and copy of degree certificate
The application, with annexes, is sent by e-mail to: registrator-kf@che.kth.se.
Please indicate the reference number K-2014-0391 in the e-mail subject.
Contact
Göran Lindbergh, Professor
Phone: +46 (0)8 790 8143
E-mail: goeran.lindbergh@ket.kth.se
Trade union representative
Kristina Östman, SACO
Phone: +46 (0)8 790 6139
E-mail: kostm@kth.se
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