Synthesis and Characterization of chitosan-based Aerogel membranes as separators in LiS batteries

Kurzfassung

The steady increase in energy demand around the world requires a lot of scientific attention. Up to this day, a large amount of energy is harnessed from fossil fuels, which are a great danger to earth and its inhabitants by e.g., polluting ecosystems during oil spills on the ocean[1] or releasing huge amounts of greenhouse gases like CO2 and methane into the atmosphere.[2] In order to prevent further global warming and ensure good living conditions for future generations, academic and industrial research shifted towards developing novel renewable energy sources such as wind, solar and tidal parks.[3] Unfortunately, renewable energy sources face a variety of challenges e.g., fluctuations in energy production due to varying weather conditions or seasonal changes, no close proximity of energy production facilities to the end user and lastly a surplus of energy produced at times where demand is exceeded.[4] Circumvention of this problem can ultimately be reached by using large-scale storage facilities such as stationary batteries that can readily release the energy whenever necessary. In recent years, Lithium-sulfur (LiS) batteries have seen considerable attention due to their advantages over commercial Lithium-ion batteries (LiB) e.g., higher specific capacity, higher energy density, environmental friendliness and low cost.[5] However, up until now practical application of this battery system remains limited due to severe problems like the dissolution and migration of polysulfides and the insulation and volume expansion during the cycling of sulfur in its elemental form.[5] Due to the many components in batteries, different approaches to solving these problems exist in literature. One approach is to design novel separator materials with drastically different properties compared to the commercially available polymer-based separators such as polyethylene and polypropylene.[6] In this regard, aerogels possess a variety of material properties, which are highly sought-after for separator application e.g., a highly-porous polymer network, mechanical as well as high temperature stability.[7] Additionally, aerogels can be made of a variety of chemical compositions e.g., organic, inorganic or hybrid organic/inorganic materials.[8] In keepsake of the environmental aspect, biopolymer-based aerogels as separator membranes developed increasing interest among the scientific research community. While various separator materials based on cellulose[9],[10],[11] have already been reported in literature, chitosan-based aerogel membranes have not and are therefore of great interest for further studies. Hence, during this masters’ thesis a chitosan-based aerogel film will be developed, synthesized and structurally characterized for future application in LiS battery systems.