Journal Entry #11: Nanowire Battery

Silicon nanowires before and after lithium absorption
http://news.stanford.edu/news/2008/january9/gifs/battery-nanowires.jpg

Introduction

For the grant proposal, my group’s idea is to make an efficient and reliable electric car while using various types of renewable energy to power the car (wind, solar, water). By doing this we wish significantly reduce the dependence on fossil fuels for transportation.
In order to increase the efficiency of the car, I decided to research upon a highly efficient battery that we could possibly use for our project. I came across a scientific journal in the journal Nature Nanotechnology, titled “High-performance lithium battery anodes using silicon nanowires.”
This journal is not available on the databases offered through the school’s library; therefore I decided to use the free abstract that was available as well as other online sources to gather more information.

Nanowire battery – What is it?

In 2007, Yi Cui, assistant professor of materials science and engineering at Stanford University, and his team of researchers discovered a way to use silicon nanowires to increase the capacity of regular lithium-ion batteries. This new silicon nanowire battery has ten times the capacity of a regular Li-ion battery. This means that if a laptop currently has a battery life of 2 hours; with the new silicon nanowire technology, its battery life would increase to 20 hours!
Naturally, this battery can be of use to my group’s grant proposal as this battery can greatly increase the efficiency of battery dependant electrical devices.

Li-ion batteries vs. Silicon nanowire batteries

The amount of lithium that an anode can hold determines the capacity of lithium-ion batteries. Lithium ion batteries usually use carbon for the anode, which has a lower capacity than carbon. Despite having a larger capacity, silicon anodes have a disadvantage. While charging and discharging of the battery, the silicon anode expands and contracts, causing the degradation of the silicon and, therefore, the battery. Yi Cui used nanotechnology to solve this problem in his battery. Instead of the regular anode shape, silicon nanowires are used instead. Although the silicon still expands, in its nanowire shape it does not fracture and degrade. This method solves the problem of degradation and makes them more efficient and reliable than current Li-ion batteries.

Battery life

According to the abstract of the full journal, Cui’s team were able to reach the theoretical charge capacity of the silicon anode. They observed little capacity fading during charge and discharge cycles and maintained a charge capacity of 75% of the maximum charge capacity.
Even if the practical charge capacity is 75% of the theoretical maximum, these batteries will still be able to last 7.5 times longer than Li-ion batteries (75% * theoretical charge capacity of 10 times Li-ion battery = 7.5 times Li-ion battery capacity). From these numbers, silicon nanowire batteries seem like a viable idea to include in our grant proposal.

Dr. Yi Cui
http://www.gm-volt.com/wp-
content/uploads/2007/12/yi.jpg

Cost

According to an interview with Dr. Yi Cui, conducted by Dr. Lyle Dennis, the cost of nanowire silicon batteries will not be very high. According to Dr. Yi Cui, silicon is a very common element in the world, and since the silicon industry is large; the cost of producing nanowire silicon batteries will be reduced dramatically. In addition to this, Cui states that battery applications don’t require “high purity silicon,” which can also help to reduce the cost of the battery.

Conclusion

Based on the research I have done on the nanowire battery, it is an efficient battery design which can increase the amount of electrical charge provided by the same battery volume and mass. If what Dr. Yi Cui says is true regarding the cost, and the cost of nanowire batteries becomes similar to, or even less than modern Li-ion batteries; then the silicon nanowire battery is definitely a realistic option, both economically and performance-wise.



Chan, Candace K., Hailin Peng, Gao Liu, Kevin McIlwrath, Xiao Feng Zhang, Robert A. Huggins, and Yi Cui. "High-performance Lithium Battery Anodes Using Silicon Nanowires." Nature Nanotechnology 3.1 (2007): 31-35. Nature Nanotechnology. Nature Publishing Group, 16 Dec. 2007. Web. 19 Nov. 2012. <http://www.nature.com/nnano/journal/v3/n1/abs/nnano.2007.411.html>.

Dennis, Lyle, Dr. "Interview with Dr. Cui, Inventor of Silicon Nanowire Lithium-ion Battery Breakthrough." GM-VOLT.com. GM-Volt.com, 21 Dec. 2007. Web. 20 Nov. 2012. <http://gm-volt.com/2007/12/21/gm-voltcom-interview-with-dr-cui-inventor-of-silicon-nanowire-lithium-ion-battery-breakthrough/>.

Stober, Dan. "Nanowire Battery Can Hold 10 times the Charge of Existing Lithium-ion Battery." Stanford News. Stanford University, 18 Dec. 2007. Web. 19 Nov. 2012. <http://news.stanford.edu/news/2008/january9/nanowire-010908.html>.