The Electrochemical Investigation of Lithium-Oxygen (Li-O2) Battery utilizing an
innovative Perfluorocarbon-Based Electrolyte.
OR
Li-O2 Battery: From Oxygen to Gold.
Instructor: Balaish Moran Department of Material Science and Engineering.
Abstract:
The worldwide interest in high energy density batteries has increased due to the development
of electrical vehicles. The current state-of-art batteries can hardly provide sufficient energy to
meet the challenges of the next generation technologies, including transportation. Metal–
Oxygen batteries, utilizing the reduction of ambient oxygen, have the highest energy density
because most of the cell volume is occupied by the anode while the cathode active material is
not stored in the battery. Among all available metal-oxygen systems there is a good reason to
place more emphasis on development of Lithium-Oxygen (Li-O2) system on the ground of
its outstanding specific capacity derived from lithium chemistry. Unfortunately, current
configurations, mostly based on a non-aqueous organic liquid electrolyte, suffer from
numerous challenges, hindering the actualization of a lithium oxygen (Li–O2) battery as a
high-energy storage device, namely low oxygen availability at the cathode of the cell as most
organic electrolyte easily wet all cathodes pores while flooding air channels. This
circumstance substantially reduces the Li-O2 cell performance. In addition the highly
oxidative environment leads to electrolyte decomposition, low cycle-life, low discharge rates
and high discharge/charge over-potential. One potential method for increasing oxygen
mobility in the Li-air system is through the use of perfluorocarbons. Perfluorocarbons (PFCs)
are organo-fluorine compounds that contain only carbon and fluorine bonded together in
strong carbon-fluorine bonds. Perfluorocarbons are well known for their chemical stability
and their potential to dissolve large quantities of gases.
PFC solvents have long been studied as the liquid media for oxygen respiration of mammals
due to fast dissolution kinetics and the high solubility of oxygen in these compounds. Due to
their low polarity, PFC solvents neither dissolve lithium salt nor are they miscible with polar
electrolyte solvents. The solubility of oxygen in PFCs is three to ten times as large as that
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observed in the parent hydrocarbons or in water, respectively. The current research is
addressing the low oxygen solubility and diffusion of oxygen in common Li-O2 electrolytes
by developing an advantageous electrolyte system composed of common organic electrolyte
in Li-O2 batteries mixed with a PFC liquid.
The objective of this research is to enhance the performances of the Lithium – air system and
also explore the basic science behind organic electrolyte/PFC electrolyte system.
Li-O2 battery operation scheme. Upon discharging, Lithium metal is oxidized at the anode to lithium ions (red) which transport to the carb
where oxygen (blue) is being reduced producing lithium peroxide (Li2O2). Upon charging, Li2O2 is oxidized back to produce molecular oxyg
back to lithium metal at the anode side.
Student mission / Objective:
1. Acquire knowledge about the constituents and electrochemical operation of batteries.
2. Prepare the mixed electrolyte with different volume ratios of perfluorocarbon and
common organic electrolyte.
3. Be exposed to different surface characterization methods such as High Resolution
Scanning Electron Microscopy (HRSEM) and X-ray.
4. The mixed electrolytes will be fully characterized by electrochemical methods, such as
cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using a
Potentiostat; the electrochemical window will be determined at different electrolytes
volume ratios.
5. Mixed electrolytes Li-O2 batteries will be constructed and tested with a battery cycler at
different mixed electrolytes ratios and at different current densities.
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Requirements:
1.
2.
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4.
Basic knowledge on battery's component and electrochemical reactions.
Basic knowledge about Perfluorocarbons and their key features.
The willing to work and assemble the batteries in a glove box.
Respecting the rules and restrictions of working in a lab.
Paper name:
Paper name: Realization of an Artificial Three-Phase Reaction Zone in a Li-air Battery
Questions about the paper:
1. Write a brief summary about the key components of the non-aqueous Li-air battery (anode,
cathode, electrolyte, and separator), explain their main role and elaborate on the electrochemical
reactions occurring on each electrode.
2. Explain the challenges in the non-aqueous Li-O2 system concerning the anode, cathode and
electrolyte.
3. In the article, we demonstrated the use of Perfluorocarbon which are immiscible in the organic
electrolyte and thus are able to increase the oxygen solubility at the cathode side. In the current
research we are planning to use Perfluorocarbons which are miscible in the organic electrolyte.
What are the pros and cons of using miscible electrolytes?
4. Write a short summary about Perfluorocarbon liquids emphasizing their main features.
5. Write a brief summary about the key parameters in electrolyte optimization.
In order to answer these questions, you are free to use scientific papers and scientific websites
including Wikipedia. And write your references at the end of each answer.
We will discuss the answers when we meet at the dinner in the opening ceremony.
Please fill free to contact me with questions regarding the project at: [email protected]
or [email protected]
Recommended reading material:
1. Realization of an Artificial Three-Phase Reaction Zone in a Li-air Battery.
2. A review of cathode materials and structures for rechargeable lithium–air batteries.
3. Oxygen-enriched electrolytes based on perfluorochemicals for high-capacity lithium–
oxygen batteries.
4. A gamma fluorinated ether as an additive for enhanced oxygen activity in Li–O2
batteries.
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