updated 02:50 pm EDT, Fri May 4, 2012
New tech could lead to cheaper, more capacious batteries
New research shows that sodium rechargeable batteries could replace lithium-ion batteries in electronics and some electric vehicles, Nature reported. This would require using a new electrode material that contains iron rather than nickel and cobalt. Sodium and iron is widely available, and using them would drive costs down while creating similar energy density to electrodes in lithium batteries.
But batteries would need to be redesigned in order to house the different chemical reactivity and the larger sodium atoms. The positive electrode in the sodium battery needs to hold more ions in order to match a lithium ion battery's density.
Researchers at the Tokyo University of Science, headed up by Shinichi Komaba, made such a material by grinding together iron oxide, sodium oxide, and manganese oxide. The powder was then put into a pellet and heated at 900 degrees Celsius for 12 hours. The resulting material's formula was Na2/3[Fe1/2Mn1/2]O2 and it was used to make the positive electrode on a battery, with sodium metal on the negative electrode.
The capacity was 190milliAmp-hours/gram, with an average voltage of 2.75V. Carbon or titanium dioxide for the negative electrode could boost this to 3V, or about the same as in two AA batteries. [via ArsTechnica]