Nanotechnology gives a boost to next-generation batteries

Oct 25, 2013
Schematic views (top) and transmission electron microscopy images (bottom) showing rigid crystals that form on bare carbon nanotubes (left) and amorphous deposits on carbon nanotube cathodes with ruthenium oxide (RuO2) nanoparticles (right) after discharge of lithium–oxygen (Li–O2) batteries. Credit: Reproduced, with permission, from Ref. 1 © 2013 American Chemical Society

Non-aqueous lithium–oxygen (Li–O2) batteries could store energy at densities rivaling gasoline. Commercializing this emerging technology, however, will require breakthroughs that will allow the batteries to be recharged efficiently. Hye Ryung Byon and Eda Yilmaz at the RIKEN Byon Initiative Research Unit have taken a major stride toward this goal by significantly enhancing the recharge efficiency of Li–O2 batteries through judicious application of catalytic ruthenium oxide (RuO2) nanoparticles.

Li–O2 batteries eliminate the heavy metal oxide cathodes used in conventional lithium-ion batteries to let lithium react directly with atmospheric oxygen on cathodes made from light, porous materials such as carbon nanotubes. When the battery discharges, lithium ions and oxygen gas react to form lithium peroxide (Li2O2) crystals on the cathode. To recharge the battery, the insulating Li2O2 crystals must be decomposed—a reaction that requires significant recharge potentials, which can shorten battery life.

Byon and Yilmaz tried to improve the battery recharge efficiency by adding RuO2 nanoparticles to the cathodes. "RuO2 has an optimal surface energy for oxygen adsorption and is a good catalyst for oxidation reactions," explains Yilmaz. However, because most ruthenium-based catalyses are performed in aqueous solutions, the team had to tread carefully to understand what would happen when RuO2 was surrounded by solid Li2O2.

Experiments revealed that the new RuO2/carbon nanotube composite considerably lowered the potential compared to cathodes made from nanotubes alone. To understand why, the researchers collaborated with the Synchrotron Radiation Center at Ritsumeikan University in Kyoto to characterize the discharge products using a number of techniques, including x-ray absorption spectroscopy and electron microscopy. These tests revealed that the Li2O2 deposits on the RuO2-loaded nanotubes had an amorphous morphology quite unlike that seen in any other Li–O2 battery system.

The electron microscopy images showed that Li2O2 particles that formed on the bare nanotube cathodes had large, halo-shaped crystals. On the RuO2/carbon nanotube cathodes, however, a formless layer of Li2O2 coated the entire nanotube (Fig. 1). The team notes that this Li2O2 layer has a large contact area with the conducting carbon nanotube cathode. Consequently, Li2O2 decomposition can be achieved with less energy, resulting in improved battery efficiency.

"This is one of the first studies showing how catalysts affect non-aqueous Li–O2 batteries; until now there has been little focus on the impact of Li2O2 structure on performance," says Byon. "This research might act as a guideline for future alternative approaches."

Explore further: A nanoscale glimpse of batteries in action

More information: Yilmaz, E., Yogi, C., Yamanaka, K., Ohta, T. & Byon, H. R. Promoting formation of noncrystalline Li2O2 in the Li–O2 battery with RuO2 nanoparticles. Nano Letters 13, 4679–4684 (2013). dx.doi.org/10.1021/nl4020952

Related Stories

A nanoscale glimpse of batteries in action

Sep 13, 2013

Lithium–oxygen (Li–O2) batteries are a new type of experimental battery that electric car manufacturers are hoping will address the issue of limited driving range. Unlike the lithium-ion batteries used ...

For better batteries, just add water

Jul 04, 2013

Lithium-ion batteries are now found everywhere in devices such as cellular phones and laptop computers, where they perform well. In automotive applications, however, engineers face the challenge of squeezing ...

Progress made in building rechargeable lithium-air battery

Jul 20, 2012

(Phys.org) -- Researchers in the United Kingdom have taken another step towards proving that so named lithium-air (Li-O2) batteries might one day become practical. Up to now the problem has been using the technology to build a ...

Inexpensive material boosts battery capacity

Oct 23, 2013

Battery-powered cars offer many environmental benefits, but a car with a full tank of gasoline can travel further. By improving the energy capacity of lithium-ion batteries, a new electrode made from iron ...

Recommended for you

A new way to make microstructured surfaces

10 hours ago

A team of researchers has created a new way of manufacturing microstructured surfaces that have novel three-dimensional textures. These surfaces, made by self-assembly of carbon nanotubes, could exhibit a ...

Tough foam from tiny sheets

Jul 29, 2014

Tough, ultralight foam of atom-thick sheets can be made to any size and shape through a chemical process invented at Rice University.

Graphene surfaces on photonic racetracks

Jul 28, 2014

In an article published in Optics Express, scientists from The University of Manchester describe how graphene can be wrapped around a silicon wire, or waveguide, and modify the transmission of light through it.

User comments : 0