A research group at the Tokyo University of Science, led by Associate Professor Shinichi Komaba, has confirmed that hard carbon obtained by pyrolyzing sucrose, the main constituent of sugar, is an effective anode material for sodium ion batteries.
Currently, most rechargeable batteries are lithium ion batteries. However, Japan relies on imports for its entire supply of lithium, a rare metal. Consequently lithium ion batteries are expensive. Sodium ion batteries are intended to overcome lithium’s disadvantages of high price and scarcity.
“In fact, the supply of sodium is unlimited. Also, sodium ion batteries can be made using iron, aluminum, and sodium, rather than cobalt or copper as before. What’s more, our results show that battery capacity can be increased simply by using carbon made from sugar as the anode. So high-performance batteries like expensive lithium batteries, which are an important type of rechargeable battery, may be achievable using cheaper, more abundant materials. We believe that, if the technology and performance can be improved, development may progress toward practical batteries that can replace lithium ion batteries.”
Hard carbon is very easy to manufacture, simply by heating sucrose in an electric furnace. The sucrose will burn if air gets in, but if sucrose powder is heated to 1,000-1,500 degrees C in a stream of inert atmosphere, such as argon or nitrogen, free from oxygen, the resultant product is black hard-carbon powder.
“Actually, we’ve spent about seven years researching sodium ion batteries. We’ve gained a lot of know-how regarding electrolytes and cells for such batteries. We have all the reagents needed right here.”
The Komaba Group has achieved a storage capacity of 300 mAh, 20% higher than that of conventional hard carbon. It’s expected that many researchers will work on making sodium ion batteries commercially viable. The Komaba Group anticipates it may take about five years to achieve a practical version.