Sunday, May 25, 2014

Durable and safe cathode material enabled by ALD for the next-generation electric vehicles

Researchers at University of Colorado at Boulder, Brookhaven National Laboratory, and Seoul National University, has shown that a Al2O3 coating deposited by Atomic Layer Deposition (ALD) dramatically reduces the degradation in cell conductivity and reaction kinetics of commercially available cathode material used in today's state-of-art Li-ion batteries, lithium nickel–manganese–cobalt oxide Li[Ni1/3 Mn1/3Co1/3]O2 a.k.a. NMC.
 
According to the researchers the use of NMC cathodes for plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs), have not been possible so far because of: 
  • limited power performance (rate capability)
  • degradation in their capacity and cycle-life at high operation temperatures and voltages
The researches have developed a new durable ultra-thin Al2O3-ALD coating layer that also improves stability for the NMC at an elevated temperature. Furthermore, the experimental results suggest that a highly durable and safe cathode material enabled by atomic-scale surface modification can meet the demanding performance and safety requirements of next-generation electric vehicles.
 

The University of Colorado Boulder (also commonly referred to as CU-Boulder, CU, Boulder, or Colorado) is a public research university located in Boulder, Colorado, United States. It is the flagship university of the University of Colorado system and was founded five months before Colorado was admitted to the union in 1876. According to The Public Ivies: America's Flagship Public Universities (2001), it is considered one of the thirty "Public Ivy League" schools. (Source: Wikipedia, Picture :  The  Campus of University of Colorado Boulder, http://www.colorado.edu/).
 
The work has been funded by by National Science Foundation (USA), Department of Energy (USA), and Ministry of Knowledge Economy (KOR).
 
Results have been published in the article below in the Journal of Power Sources:
 
Ji Woo Kim, Jonathan J. Travis, Enyuan Hu, Kyung-Wan Nam, Seul Cham Kim, Chan Soon Kang, Jae-Ha Woo, Xiao-Qing Yang, Steven M. George, Kyu Hwan Oh, Sung-Jin Cho, Se-Hee Lee
Journal of Power Sources, Volume 254, 15 May 2014, Pages 190–197
 
Abstract: Electric-powered transportation requires an efficient, low-cost, and safe energy storage system with high energy density and power capability. Despite its high specific capacity, the current commercially available cathode material for today's state-of-art Li-ion batteries, lithium nickel–manganese–cobalt oxide Li[Ni1/3 Mn1/3Co1/3]O2 (NMC), suffers from poor cycle life for high temperature operation and marginal rate capability resulting from irreversible degradation of the cathode material upon cycling. Using an atomic-scale surface engineering, the performance of Li[Ni1/3Mn1/3Co1/3]O2 in terms of rate capability and high temperature cycle-life is significantly improved. The Al2O3 coating deposited by atomic layer deposition (ALD) dramatically reduces the degradation in cell conductivity and reaction kinetics. This durable ultra-thin Al2O3-ALD coating layer also improves stability for the NMC at an elevated temperature (55 °C). The experimental results suggest that a highly durable and safe cathode material enabled by atomic-scale surface modification could meet the demanding performance and safety requirements of next-generation electric vehicles.
 
More interesting publications from The Electrochemical Energy Laboratory at University of Colorado at Boulder  on high performance materials for sustainable energy applications :  batteries, supercapacitors, fuel cells, electrochromic winodws, and photoelectrochemical devices can be found here: http://www.colorado.edu/mechanical/ecel/publication.html
  

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