Wood, salt and air: key ingredients in next gen ‘eco’ batteries

Posted on 19 Sep 2013 by Tim Brown

The next generation of batteries could be made using sodium with Korean scientists having designed a Na-ion battery which has delivered a high energy density rivalling some Lithium ion batteries.

The scientists have designed a new cathode for the Sodium (Na-ion) batteries that provides an energy density of 600 Wh kg-1, the highest reported so far for Na-ion batteries and provides greatly improved cycle life.

The group, which has published their findings in the Journal of the American Chemical Society, says the new cathode material had the potential to meet and even exceed the performance of today’s Lithium ion batteries.

“We are currently searching for more new electrode materials that can outperform the material that was reported this time,” co-author Kisuk Kang, Professor of Materials Science and Engineering at Seoul National University said. “We have both computational and experimental tools to search for them, which will accelerate the identification of this new material.”

In June this year scientists at the University of Maryland developed a battery using using only wood, tin and sodium as raw materials and can be charged over 400 times.

The scientists built the battery by using a very thin piece of wood, which they say is “a thousand times thinner than a piece of paper,” coated with tin. And, instead of lithium, which is found in many rechargeable batteries, they chose to use sodium to make it eco-friendly.

“Sodium [Na]-ion batteries offer an attractive option for low-cost grid scale storage due to the abundance of Na. Tin (Sn) is touted as a high-capacity anode for Na-ion batteries with a high theoretical capacity of 847 mAh/g,” scientists said in a research paper that appeared in ACS Publications.

Companies such as IBM are also working with sodium batteries to create  ‘metal-air’ batteries which, rather than reacting with a liquid, such as in a conventional battery, metal-air batteries react metal electrodes (such as lithium, sodium or even zinc) with the oxygen in the air to produce a current.

Metal-air batteries have the potential to reduce the weight, and thus increase the energy density, of traditional batteries. Zinc-air batteries are already commonplace in hearing aids, and IBM is aiming to produce an all-electric car with a range of 1000 miles using the technology.