Renewable Energy Global Innovations features: Polymeric Ionic Liquid Gel Electrolyte for Room Temperature Lithium Battery Applications

Significance Statement

Professor Bilal El-Zahab and doctoral students, Meer Safa, Amir Chamaani, and Neha Chawla from Florida International University (FIU) developed a free-standing gel polymer electrolyte (GPE) and evaluated its thermal and electrochemical properties in order to ascertain the overall performance of their synthesis in lithium battery applications. The new findings appeared in peer-reviewed journal, Electrochimica Acta.

The gel polymer electrolyte comprised of a pyrrolidinium-based polymeric ionic liquid (PIL), an imidazolium based ionic liquid [EMIM][TFSI], and the lithium salt [LiTFSI]. They compared two electrolytes: the gel polymer electrolyte and ionic liquid electrolyte to investigate stability and compatibility with lithium metal electrode using various electrochemical characterization techniques, including electrochemical impedance spectroscopy with further determination of their rate performance in a cell with LiFePO₄ cathode at room temperature.

Thermogravimetric analyses showed the prepared gel polymer electrolyte had a high thermal stability. The pair of polymeric ionic liquid and ionic liquid inside the gel polymeric electrolyte which contains ionic liquid and lithium salt content (LiTFSI) of about 80wt.% led to an improved ionic conductivity of approximately 3.35 mS×cm^-1 when measured at 25°C using electrochemical impedance spectroscopy.

The most notable improvement using the FIU team’s new gel polymer electrolyte was its improved cathodic limit and widened electrochemical stability window. The improved cathodic limit to below the plating potential of lithium made this gel polymer electrolyte a preferred choice in Li/LiFePO₄ cells. Moreover, the gel polymer electrolyte also showed higher lithium-ion transference number compared to the ionic liquid electrolyte indicating higher chemical affinity. This affinity was demonstrated using in Li/Li symmetrical cell that immensely outperformed the ionic liquid electrolyte.

The cyclic charge-discharge rate when observed at 40 cycles and 22°C showed that the gel polymer electrolyte batteries had a higher discharge capacity at higher C-rates compared to ionic liquid cells. The authors attribute this improved performance to the improved electrochemical and interfacial stability, and the increased Lithium transference number. The gel polymer electrolyte developed by the authors is an exciting development that can serve effectively as an electrolytic conductor with other lithium-ion electrodes.

About The Author

Mr. Meer Safa is a PhD candidate in Materials Science and Engineering at Florida International University working under the supervision of Dr. El-Zahab. He received his M.S. Materials Science and Engineering from Kungliga Tekniska Högskolan (KTH) in Sweden and his B.S. degree in Materials and Metallurgical Engineering from Bangladesh University of Engineering and Technology (BUET) in Bangladesh. His research concentrates on the synthesis of ionic liquids for the development of polymer electrolyte for lithium batteries and their electrochemical investigations. 

About The Author

Mr. Amir Chamaani is a Ph.D. candidate in Materials Science and Engineering at Florida International University. He received his M.S. in Nanomaterials Engineering from the Materials and Energy Research Center (MERC) in Tehran, Iran in 2011. He served as Research at MERC working on thin film anodes for Li-ion micro-batteries. He is currently a Dissertation Year fellow working under the supervision of Dr. El-Zahab on the development of polymer electrolytes, electrochemical, and materials characterizations of Lithium battery applications, especially Li-O₂ batteries. 

About The Author

Ms. Neha Chawla is a Ph.D. candidate in Materials Science and Engineering at Florida International University. She has received her M.S. in Materials Science and Engineering from Florida International University and her B.Eng. in Production Engineering from Mumbai University in India. She is currently working towards her Ph.D. under the supervision of Dr. El-Zahab developing cathodes for improved performance of lithium-oxygen batteries. 

About The Author

Dr. Bilal El-Zahab is an Assistant Professor of Mechanical and Materials Engineering at Florida International University (2012-present). He received in Ph.D. in Chemical Engineering from the University of Akron in Ohio and was a Postdoctoral Research Associate in Analytical Chemistry at Louisiana State University (2008-2010) and a Postdoctoral Associate in Chemical Engineering at Massachusetts Institute of Technology (2010-2012). His research interests include the development of advanced materials for energy storage and bioanaylical applications.  

Journal Reference

Meer Safa, Amir Chamaani, Neha Chawla, Bilal El-Zahab. Polymeric Ionic Liquid Gel Electrolyte for Room Temperature Lithium Battery Applications, Electrochimica Acta 213 (2016) 587-593.

Mechanical and Materials Engineering Department, Florida International University, Miami, Florida 33174, USA

 

 

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