“The carbon nanotube technology that we’re adding to our IP portfolio has broad market implications,” said Dr. Simon Jones, director of research and development at Contour Energy Systems. “We will apply this game-changing material to our next-generation line of batteries designed to address the longevity and power density requirements for a wide range of applications in portable devices spanning automotive, industrial, medical, military and consumer electronics markets.”
Understanding the Carbon Nanotube Breakthrough
Three basic components make up lithium-ion batteries: two electrodes (the anode—or negative electrode—and the cathode, or positive electrode) and an electrolyte that allows charged ions to flow between the electrodes during charge or discharge.
In the new battery electrode being developed by Contour Energy Systems based on the MIT technology, carbon nanotubes—sheets of pure carbon atoms rolled up into tiny tubes—“self assemble” through a controlled deposition process driven by electrostatic interactions into a tightly bound structure that is porous at the nanometer scale (billionths of a meter).
“These carbon nanotubes contain numerous functional groups on their surfaces that can store a large number of lithium ions per unit mass,” says Professor Shao-Horn of Mechanical Engineering and Materials Science and Engineering at MIT. As a result, “for the first time, carbon nanotubes can serve as the cathode in lithium-ion batteries, instead of the traditional role that carbon materials have played as the anode in such systems. This lithium storage reaction on the surface of carbon nanotubes is much faster than conventional lithium intercalation reactions, so can deliver high power.”
“The ‘electrostatic self-assembly’ process is important,” says Dr. Paula Hammond, Bayer Chair Professor of Chemical Engineering at Massachusetts Institute of Technology. “Ordinarily, carbon nanotubes deposited on a surface tend to clump together in bundles leaving fewer exposed surfaces to undergo reactions. We’ve discovered that by integrating charged molecules on the nanotubes, they can assemble in a way that produces a highly porous electrode resulting in a greater number of nanotubes accessible for Li-ion storage and release.”
In terms of what this means for lithium-ion battery performance, the new material can produce very high power outputs in short bursts and steady, lower power for long periods. The energy output for a given weight of this new electrode material is over five times greater than for conventional electrochemical capacitors while the total power delivery capability approaches 10 times that of lithium-ion batteries.
In addition to their high power output, the carbon nanotube electrodes demonstrate very good stability over time. After 1,000 cycles of charging and discharging a test battery there was no detectable change in the material’s performance.
“It’s gratifying to see that the extensive research we’ve done on carbon nanotubes is being commercialized through our technical licensing agreement with Contour Energy Systems,” said Professor Shao-Horn. “By dramatically improving the power density of lithium-ion batteries, carbon nanotube technology will pave the way to new and improved portable power applications.”
Contour Energy Systems is an innovative portable power company commercializing customizable battery technologies for a wide range of cross-industry applications. Contour’s next-generation battery systems are designed to deliver unprecedented improvements in energy and power density, and are capable of performing in extreme operating conditions at significantly improved costs.
Founded through the collaboration of CalTech and CNRS, the French National Center for Scientific Research, the company combines expertise in nano-materials science, patented Fluorinetic™ technologies and proprietary manufacturing processes to significantly advance the state of portable power. Headquartered in Azusa, CA, Contour Energy is managed by a world-class team of battery industry leaders from CalTech, Energizer, Duracell, ConocoPhillips, Hewlett-Packard and Ultralife. The company is privately held with funding from CMEA Capital, Harris and Harris, Schlumberger and US Venture Partners.