”Synthesis and Application of Multifunctional Ionic Liquids for Lithium Ion Batteries”
Due to the Corona situation the defense will be held virtual.
If you wish to follow the defense you will have to sign up by sending an e-mail to Christian Carlsson cc@kt.dtu.dk at the latest 28 April at 12:00 hereafter you will receive an invitation to join the virtual defense.
Principal supervisor:
Associate Professor Kaj Thomsen
Co-supervisor:
Associate Professor Nicolas von Solms
Examiners:
Associate Professor Xiaodong Liang, DTU
Associate Professor Yansong Zhao, Western Norway University of Applied Sciences, Norway
Specialist Jørgen Peter Jensen, Cowi, Denmark
Chairperson at defence:
Associate Professor Hariklia Gavala, Chemical Engineering, DTU
“An electronic copy of the thesis can be requested from the department”
The electrolyte of lithium ion batteries affects the transport, specific energy density, electrochemical stability, thermal stability and safety properties of the battery.
The research and development of new types of electrolytes are focused on the special requirements of electric vehicles (EVs) and hybrid electric vehicles (HEVs).
Ionic liquids (ILs) are liquids containing solely ions and usually have melting points below 100 °C.
They have been widely used for various purposes because of their unique characteristics, such as non-flammability, non-volatility, thermostability, electrochemical stability, good conductivity, large electrochemical windows, and so on.
Functionally designed ILs have been considered as attractive additives in lithium ion batteries to improve the physicochemical and electrochemical properties of electrolytes and lithium ion batteries.
In this PhD study, two new types of multifunctional ionic liquids 3-(2-amino-2-oxoethyl)-1-vinylimidazolium bis(trifluoromethylsulfonyl) amide ([VAIM][TFSI]) and 3-(3-amino-3-oxoethyl)-1-vinylimidazolium bis(trifluoromethylsulfonyl)amide ([VPIM][TFSI]) are designed.
The two ionic liquids have two different functional groups, one functional group is unsaturated and is expected to be able to contribute to the formation of the Solid Electrolyte Interphase film.
The other group is the basic group which helps to decrease the content of water and HF in electrolytes. The physicochemical, thermodynamic, and electrochemical properties of pure ionic liquids show that the ionic liquids have large liquid ranges and high thermal stability. The conductivities of electrolytes increase by adding a certain amount of ionic liquid.
The applications of the two ionic liquids as additives of electrolytes are assembled in SiC/Li, LTO/Li, NCM622/Li, and LFP/Li half-cells.
The two ionic liquids were found to control the water and HF content of the electrolytes at a low level during a period of time.
They also improve the capacity, cycling and rate performances of lithium ion batteries due to the decomposition of ionic liquids on the surface of electrodes.
The content of ionic liquids should not be more than 1 wt %. In the future, these ionic liquids can be utilized in lithium ion batteries to improve their electrochemical properties.