Superionic conductor for fuel cells

August 5, 2015, Institut Laue-Langevin
Trajectories of the Li atoms obtained by Molecular Dynamics simulations at room temperatures (image extracted from the Lamp package). The white clouds represents the positions of the Li atoms (in red) during the simulations (carbon atoms in grey). They show interconnected paths allowing for a high mobility of the ions in the C60 framework. Low frequency vibrations of the fullerenes are believed to sustain this diffusion

An alternative material for use in fuel cells has been probed by the ILL, with the aim of understanding its peculiar bonding structure and complex behaviour.

Buckminsterfullerene, or C60 buckyballs, were first generated in the mid-80s, but despite a high research profile and the Nobel Prize in Chemistry that followed, few direct applications of the cage-like molecule have been found. However, when atoms of alkali-metals such as (Li) are added to the cage, the buckyballs undergo polymerisation, forming long chains that create a material with a range of new properties. Despite being a solid, Li4C60 displays an ionic conductivity comparable to that of liquid electrolytes, even at room temperature. And this has led to suggestions that this material could find use in future fuel-cells or batteries.

In this project, neutrons and magnetic resonance techniques were used to pinpoint the location of the carbon atoms involved in the intermolecular bonds, and to reveal the Li positions in the lattice. This process involved a series of neutron diffraction and spectroscopy experiments, carried out on the ILL Super D2B two-axis diffractometer, and the IN4C and IN1BeF spectrometers. In parallel with this, the team used theoretical lattice calculations to reveal the polymer structure, and to characterise its dynamic behaviour.

The agreement between structural models and the experimental data confirms the coexistence of unusual bonding among the buckyballs and suggests that charge transfer between lithium and the C60 cage is responsible for this behaviour. The information concerning the positioning of the lithium between the cages provides important insight into the origin of the high mobility of these ions. This mobility, in addition, seems tributary to the cage motion. In fact hybrid modes, i.e. modes for which lithium ions and adjacent buckyballs move in communion, could be identified at relatively low frequencies. This observation makes the team believe that the ion mobility may be highly dynamic with the motion of the buckyballs "pushing" the lithium ions along and thus playing an important role in the material's temperature-dependent ionic conductivity.

ILL Scientist Stephane Rols said "This work will help in understanding the role of the guest and plasticity in the material's high Li-ionic conductivity. Development of a full description of the phenomenon is a necessary first step to the design of solid material with controlled ionic conductivity. This would generate new generations of Li-batteries that integrate non-liquid ionic exchange membrane, potentially making them safer."

Explore further: Japanese team creates new lithium battery

More information: "Structure and dynamics of the fullerene polymer Li4C60 studied with neutron scattering", Physical Review B, 92, 014305 (2015). DOI: 10.1103/PhysRevB.92.014305

Related Stories

Japanese team creates new lithium battery

May 20, 2014

The long life of lithium ion batteries makes them the rechargeable of choice for everything from implantable medical devices to wearable consumer electronics. But lithium ion batteries rely on liquid chemistries involving ...

No more leakage of explosive electrolytes in batteries

June 27, 2013

( —A research team at Ulsan National Institute of Science and Technology (UNIST), S. Korea, found a new physical organogel electrolyte with two unique characteristics: an irreversible thermal gelation and a high ...

Buckle up for fast ionic conduction

June 15, 2015

ETH material engineers found that the performance of ion-conducting ceramic membranes that are so important in industry depends largely on their strain and buckling profiles. For the first time, scientists can now selectively ...

Recommended for you

Galactic center visualization delivers star power

March 21, 2019

Want to take a trip to the center of the Milky Way? Check out a new immersive, ultra-high-definition visualization. This 360-movie offers an unparalleled opportunity to look around the center of the galaxy, from the vantage ...

Ultra-sharp images make old stars look absolutely marvelous

March 21, 2019

Using high-resolution adaptive optics imaging from the Gemini Observatory, astronomers have uncovered one of the oldest star clusters in the Milky Way Galaxy. The remarkably sharp image looks back into the early history of ...

When more women make decisions, the environment wins

March 21, 2019

When more women are involved in group decisions about land management, the group conserves more—particularly when offered financial incentives to do so, according to a new University of Colorado Boulder study published ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.