SEMINAR: Two-Dimensional Transition Metal Carbides and Carbonitrides “MXenes” for Electrochemical Energy Storage Systems

Dr. Michael Naguib, Wigner Fellow, Materials Science and Technology Division, Oak Ridge National Laboratory, Tenn.
When Feb 22, 2016
from 01:00 PM to 02:00 PM
Where Sackett Hall, Room 200
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Abstract

Two-dimensional, 2D, materials, such as graphene, possess a unique morphology compared to their 3D counterparts, from which interesting and novel properties arise. Recently a new large family of 2D early transition metal carbides and carbonitrides, called MXenes, was discovered. The synthesis of MXenes is carried out by the selective etching of “A” atoms from MAX phases. The latter are a large family (more than 60 members) of hexagonal layered ternary metal carbides and nitrides with composition of Mn+1AXn, where “M” is an early transition metal, “A” is a group A element, “X” is carbon and/or nitrogen, and n = 1, 2, or 3. So far, more than 15 MXenes have been produced experimentally (e.g. Ti3C2, Nb2C, V2C, (V0.5,Cr0.5)3C2, Ti3CN, Ta4C3, and Nb4C3). In addition, many others were predicted by density functional theory calculations to be stable.

MXenes combine the metallic conductivity of transition metal carbide/nitrides with the hydrophilic nature of their hydroxyl or oxygen terminated surfaces. In essence, they behave as “conductive clays”. This unique combination suggests MXenes can be used in many applications from energy storage, to sensors to catalysts. They have already shown promising performance in electrochemical energy storage systems. For example, flexible binder-free electrodes of delaminated Mo2C showed a reversible capacity of 570 mAh/g at a specific current of 400 mA/g when tested as anode material in Li-ion batteries (LIBs). At very high specific currents such as 5 A/g and 10 A/g, reversible capacities of 250 mAh/g and 75 mAh/g, respectively, were found to be stable over 1000 cycles. MXenes also have been shown to be excellent electrodes for supercapacitors with exceptional volumetric capacitance (>900 F/cm3) in aqueous electrolytes. In this seminar, an overview for the synthesis, structure, properties, and applications of this new family of 2D materials will be presented. A special focus will be dedicated to the electrochemical performance of MXenes as electrode materials in LIBs and their lithiation and delithiation mechanisms.

Speaker's Biography

Michael Naguib is currently a Wigner Fellow at Oak Ridge National Laboratory. He earned his Ph.D. in Materials Science and Engineering at Drexel University in 2014 under the advising of Prof. Michel Barsoum and Prof. Yury Gogotsi. His research focuses on the synthesis and characterization of novel materials for electrochemical energy storage. He has published 38 papers in international journals and presented many invited talks at number of international conferences. He is also an inventor on the MXene discovery patent, and another recently filled patent on current collectors for improving the safety of Li-ion batteries. He has received many international awards, such as MRS Gold Graduate Student Award, Graduate Excellence in Materials Science (GEMS) Award, and Ross Coffin Purdy Award.