Asian Scientist (Jul. 8, 2013) – Researchers have developed a lithium-iodine battery system that has double the energy density of conventional lithium-ion batteries. This was achieved by replacing the organic electrolyte in conventional lithium-ion electrochemical cells with water.
Lithium-ion batteries are common in devices such as mobile phones and laptop computers but efforts to use them in electric vehicles have not taken off because of the low energy density of conventional batteries.
This meant that engineers face the challenge of squeezing enough batteries onto a vehicle to provide the desired power and range without introducing storage and weight issues.
To overcome this challenge, researchers have now developed a lithium-iodine battery system with twice the energy density of conventional lithium-ion batteries.
In their research, published in Nature Communications, the team of researchers improved the performance of lithium-based batteries by turning to an ‘aqueous’ system. In this system, the organic electrolyte used in conventional lithium-ion cells is replaced with water.
Such aqueous lithium battery technologies have the advantage of greatly reducing fire risk and environmental hazard. Aqueous solutions also have inherently high ionic conductivities.
After an extensive search in which they tested various new materials, the researchers produced the first-ever lithium battery that incorporates aqueous iodine. Iodine was chosen as it had high water solubility and a pair of ions that readily undergo aqueous electrochemical reactions.
Using this aqueous system, the researchers were able to develop a new lithium-iodine battery that had an energy density nearly double that of a conventional lithium-ion battery.
This battery had high and near-ideal power storage capacities and could be successfully recharged hundreds of times, avoiding a problem that plagues other alternative high-energy-density lithium-ion batteries.
The researchers are now seeking to raise energy densities even further by using a flowing-electrode configuration that stores aqueous ‘fuel’ in an external reservoir – a modification that should make this low-cost, heavy metal-free design more amenable to electric vehicle specifications.
Source: RIKEN; Photo: AndyArmstrong/Flickr.
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