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: The latest fashion: Graphene edges can be tailor-made

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

The latest fashion: Graphene edges can be tailor-made

Jan 23, 2015

Theoretical physicists at Rice University are living on the edge as they study the astounding properties of graphene. In a new study, they figure out how researchers can fracture graphene nanoribbons to get ...

Nanotechnology changes behavior of materials

Jan 23, 2015

One of the reasons solar cells are not used more widely is cost—the materials used to make them most efficient are expensive. Engineers are exploring ways to print solar cells from inks, but the devices ...

Gold 'nano-drills'

Jan 22, 2015

Spherical gold particles are able to 'drill' a nano-diameter tunnel in ceramic material when heated. This is an easy and attractive way to equip chips with nanopores for DNA analysis, for example. Nanotechnologists ...

The importance of building small things

Jan 22, 2015

Strong materials, such as concrete, are usually heavy, and lightweight materials, such as rubber (for latex gloves) and paper, are usually weak and susceptible to tearing and damage. Julia R. Greer, professor ...

Graphene brings quantum effects to electronic circuits

Jan 22, 2015

Research by scientists attached to the EC's Graphene Flagship has revealed a superfluid phase in ultra-low temperature 2D materials, creating the potential for electronic devices which dissipate very little ...

User comments : 0

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.