I stumbled across some interesting research that's taken place as a collaboration between researchers from Clemson University and Georgia Tech. Unfortunately, i was unable to find the literature for it anywhere, so I was forced to scrounge around on ScienceDaily and New Scientiest-type sites for information.
Basically, a material called alginate has recently been extracted from fast growing brown algae for its property that it contains uniformly distributed carboxylic group, and has been used as a "binder" material in lithium ion battery electrodes. In short, binder materials suspend graphite (or possibly in future, silicon) particles in space so that they're able to interact with a liquid electrolyte.
Researchers decided that it was logical to study animals that inhabit highly ionic environments for possible new binding materials.
So far anodes are manufactured from carbon. There are hopes that silicon anodes may increase efficiency by up to ten times but so far no silicon anode has proven stable (as allowances must be made for expansion and contraction of Si particles (?)).
This research opens the door to many possibilities such as cheaper, longer lasting batteries for mobiles phones, notebooks etc, as well as more energy storage. The need for use of toxic materials in battery manufacture may also be eliminated.
Basically, a material called alginate has recently been extracted from fast growing brown algae for its property that it contains uniformly distributed carboxylic group, and has been used as a "binder" material in lithium ion battery electrodes. In short, binder materials suspend graphite (or possibly in future, silicon) particles in space so that they're able to interact with a liquid electrolyte.
Researchers decided that it was logical to study animals that inhabit highly ionic environments for possible new binding materials.
So far anodes are manufactured from carbon. There are hopes that silicon anodes may increase efficiency by up to ten times but so far no silicon anode has proven stable (as allowances must be made for expansion and contraction of Si particles (?)).
This research opens the door to many possibilities such as cheaper, longer lasting batteries for mobiles phones, notebooks etc, as well as more energy storage. The need for use of toxic materials in battery manufacture may also be eliminated.
Hi Wendy.
ReplyDeleteI am not at all familiar with how Li+ batteries work... why is the carbon suspended? What is it's purpose (if it forms one of the terminals presumably the binder must be conductive too).
James
Hey Wenxdy (your new nickname, it works well on a keyboard! (: ) and James,
ReplyDeleteIf I recall correctly, James, the carbon atoms act as one of the electrodes and so have to be suspended so as to increase their 'electron-gathering' capabilities. This is one of the reasons that Li+ batteries are so efficient, and it is also has something to do with the lithium bits needing to be spread out in the battery. Check out Chemistry (our first year chem text), I think it has a good (if basic, i.e. no quantum atom theory... :)) overview.
I wonder, Wendy, if the carboxylic groups interfere with the electron-transport at all? This would be an interesting biophysics/quantum discussion. I suspect that the alginate has a dendrimer-like structure (i.e. lots of sticy-out bits and electron-transporty bits in the middle). It would be interesting to probe the connection between highly ionic habitats and binder molecules. I also would be interested to see how this actually makes the battery more efficient (as in, the mechanism) and a comparison to other efficient batteries (hydrogen fuel cells come to mind).
The 'expansion' of 'Si particles' is probably not actual atomic expansion (the rare case of atomic inflammation only observed in movies without a science director) but rather the blobs of silicon that they use as particles expanding and contracting in different electrolytes; possibly due to small particle size, the Si interacts more with the solvent and the outer layer of the blob changes? One must look out for 'engineer-speak/device-scientist-speak', of course, with these things; not to suggest device scientists are subtly planning a coup d'etat of the English language, but rather that 'no silicon anode has proven stable' could refer to other things than what someone not in the research field would think of (like for my summer research project last summer, our devices wouldn't work because the organic films wouldn't spin coat properly due to surface adhesion problems. Doesn't sound very physicsy until you talk about the surface adhesion...).
I think that Si is more efficient because of the band gaps present; like with organic transistors versus silicon transistors, Si ones beat the stuffing out of C-based ones on efficiency levels. But then the flexible C-based transistors can take it, the Si ones (being crystals) cannot.... It could also be due to the ease of creating high-quality silicon in crystalline format, which might increase electron transport/flexibility of semiconductor electron bands.
I also suggest you look on reputable news sites (like Australian BC, e.g.) as they often have links to papers. This is not to suggest that you looked at dodgy, third-rate news sites that make up stuff...:) but rather that some other sites might have direct links like the rather good ABC science site. Also, the papers might not have been published yet, at least not in a big journal...
Usually, the site/s I frequent do provide the journal articles on the topics covered, but for this one, for some reason, the paper wasn't there. It also wasn't able to be found via UQ Library, so it may not be available at this point.
ReplyDeleteThe mechanism by which Li-ion batteries function is as follows. We're all aware that batteries have cathodes and anode and that upon discharging electrons move from anode to cathode. In Li-ion batteries, there are cathodes, anodes and an electrolyte which contains Li-ions (which are 'mobile guest ions').
ReplyDeleteThe anode and cathode in these batteries are basically what can be referred to as "Lithium-ion insertion hosts" (basically just ionic hosts). Usually, the cathode is comprised of LiCoO2 while the anode is graphite.
Upon charging, Li-ions move from the cathode and are inserted into the graphite coupling with electrons, and the overall charge of this process is therefore neutral. This whole ion extraction/insertion is a basic solid state redox process.
(Jiang et al, 2006).