New Anodes Could Increase Battery Life
Highly porous silicon anode
Current Lithium Batteries
Almost all portable devices we use today are powered by rechargeable lithium ion batteries. Cell phones, iPods, Laptops, Cameras, and more depend on them. Everyone that uses these devices, though, realizes the importance of making sure you have properly charged the battery so as to get the maximum amount of battery life. Otherwise, one is out of luck when it comes time for that all-important presentation or entertainment on the bike ride home.
These batteries work by transferring lithium ions from the anode (usually made of graphite) to the cathode during discharge and from the cathode to the anode during recharge. First proposed by Whittingham in the 70s, these have become vital in our everyday lives. Although many advances have already been made in safety and transportability, battery life is still a limiting factor.
High Efficiency Lithium Batteries
Researchers at Hanyang University in Korea, led by Jaephil Cho, have discovered a new usable material for the Anode that could increase battery life dramatically. This material is a highly porous silicon structure that could store more ions than the commonly-used graphite anode.
Silicon anodes have been avoided in the past due to expansion and contraction under recharge and discharge, respectively. This causes erosion that disables the anode after a few cycles. Cho and his team’s prospective material can withstand this erosion, though, given their new production method, outlined in their paper Three-Dimensional Porous Silicon Particles for Use in High-Performance Lithium Secondary Batteries, published in Angewandte Chemie Journal.
This process involved annealing SiO2 nanoparticles with plain Si particles at 900°C under Argon. They then chemically etched out all the SiO2, leaving behind “carbon-coated silicon crystals in a continuous, three-dimensional, highly porous structure.” These pore walls are estimated to have a thickness of less than 70nm. This structure was then used as a replacement anode, and shown to have a higher charge capacity, a faster charge movement, and a high overall specific capacity given large current.
They did not test the anode’s abilities to any significant boundaries, though, I think. After 100 cycles, though, they noted that stress/erosion was not noticeable. However, they did find that the first time they charged the anode an amorphous silicon mass formed around residual nanoparticles in the pore walls.
This discovery opens up a new avenue for research in Li-ion batteries, and will hopefully have a noticeable impact in the near future on our consumer electronic battery life. I know I would certainly appreciate it!
Sources:
http://www.sciencedaily.com /releases/2008/11/081120103802.htm
Three-Dimensional Porous Silicon Particles for Use in High-Performance Lithium Secondary Batteries. Angewandte Chemie International Edition, DOI: 10.1002/anie.200804355
This entry was posted on Saturday, November 29th, 2008 at 2:26 pm and is filed under Atomic, Molecular, and Optical. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
