Schematic of electrode process design: (a) Components mixing under ultrasonic irradiation, (b) an optical image of the as-fabricated electrode made of SiNP, SG and PAN, (c) the electrode after SHT, (d) Schematic of the atomic scale structure of the electrode. (Source: Nature Communications 6, article 8597).
Current lithium-ion batteries normally use graphite anodes. Engineers at the University of Waterloo have found that silicon anode materials have a much higher capacity for lithium and are capable of producing batteries with almost 10 times more energy.
Zhongwei Chen, a chemical engineering professor at Waterloo, and a team of graduate students created a low-cost battery using silicon that boosts the performance and life of lithium-ion batteries. Their findings are published in the current issue of Nature Communications.
The most critical challenge the Waterloo researchers faced when they began producing batteries using silicon was the loss of energy that occurs when silicon contracts and then expands by as much as 300 per cent with each charge cycle. The resulting increase and decrease in silicon volume forms cracks that reduce battery performance, create short circuits, and eventually cause the battery to stop operating. To overcome this problem, Professor Chen’s team along with the General Motors Global Research and Development Center developed a flash heat treatment for fabricated silicon-based lithium-ion electrodes that is said to minimize volume expansion while boosting the performance and cycle capability of lithium-ion batteries. Professor Chen stated that the economical flash heat treatment created uniquely structured silicon anode materials that delivered extended cycle life to more than 2000 cycles with increased energy capacity of the battery.
The researchers say the new anode can bring about a 40 to 60 percent increase in energy density of lithium ion batteries and that type of advance could see electric cars driven up to 500 km (310 mi) per charge. They also note a Coulombic efficiency of 99.9 percent-- pertaining to the charge transferred to and from the electrode—which had been seen as a weakness of silicon anodes.
Professor Chen expects to commercialize this technology and expects to see new batteries on the market within the next year.