USC team develops new porous silicon nanoparticle material for high-performance Li-ion anodes
12 February 2013
|A new USC-developed process produces porous silicon nanoparticles for high-performance Li-ion anodes. Click to enlarge.|
Researchers at the University of Southern California (USC) have developed a new nanostructured silicon material for use as high performance lithium-ion battery anodes. The porous silicon nanoparticles, prepared using a novel two-step process combining controlled boron doping and facile electroless etching, have achieved capacities around 1,400 mA·h/g at a current rate of 1 A/g, and 1,000 mA·h/g at 2 A/g, with stable operation when combined with reduced graphene oxide and tested over up to 200 cycles.
In a paper published in the journal Nano Research, the team attributed the overall good performance to the combination of porous silicon that can accommodate large volume change during cycling and provide large surface area accessible to electrolyte, and reduced graphene oxide that can serve as an elastic and electrically conductive matrix for the porous silicon nanoparticles.
The design, currently under a provisional patent, could be commercially available within two to three years.
Silicon is one of the most promising anode candidates because of its high theoretical capacity of approximately 3,600 mA·h/g at room temperature. However, the drawbacks of silicon anodes are equally obvious. The large volume change during the insertion and extraction of lithium in silicon leads to severe pulverization and capacity fading, which has limited the use of silicon in real battery applications.
...Recently, we have reported [Ge et al. 2012] that a porous silicon nanowire anode can achieve a capacity of over 1,000 mA·h/g at a current rate of 4 A/g for 2,000 cycles when using commercially available alginate as the binder. We note that while porous silicon nanowires may find broad applications including in lithium-ion batteries, biomedical imaging, and thermoelectric devices, the preparation of porous silicon nanowires and similar nanostructures is usually achieved by wet etching of doped silicon wafers, and therefore is limited in quantity. A more scalable method is highly desirable for the preparation of porous silicon nanostructures.
Here, we introduce a new and simple synthetic route for the preparation of porous silicon nanoparticles. By doping and then etching of commercially available silicon nanoparticles, porous silicon nanoparticles can be synthesized in bulk quantities. Our approach represents a quantum leap from traditional porous silicon nanowires...—Ge et al.
In their process, they started with silicon nanoparticles with a size of <200nm. They first doped the silicon with boron, then etched the boron-doped silicon in an etchant containing silver nitrate (AgNO3) and hydrofluoric acid (HF) to obtain a porous structure.
Future research by the group will focus finding a new cathode material with a high capacity that will pair well with the porous silicon nanowires and/or porous silicon nanoparticles to create a completely redesigned battery.
The work was funded by the USC Viterbi School of Engineering.
Mingyuan Ge, Jiepeng Rong, Xin Fang, Anyi Zhang, Yunhao Lu, Chongwu Zhou (2013) Scalable preparation of porous silicon nanoparticles and their application for lithium-ion battery anodes. Nano Research doi: 10.1007/s12274-013-0293-y
Mingyuan Ge, Jiepeng Rong, Xin Fang, and Chongwu Zhou (2012) Porous Doped Silicon Nanowires for Lithium Ion Battery Anode with Long Cycle Life. Nano Lett. 12 (5), pp 2318–2323 doi: 10.1021/nl300206e
There is a lot of battery research going on. Seems each day someone in a lab somewhere discovers how to increase the energy density of battery electrodes twice as much as is available today, with a promise of mass production three years hence. Of course this has been the standard promise that justifies their continued research and their contining pay check. And, it's been working for many years.
What we really need is to coordinate all this lab activity and to direct all this research in the same direction, i.e., to upscale the devices to production. DOE is attempting to do this with the newly created JCESR project and I see it as the only group that will be able to produce a "better battery" any time soon.
Posted by: Lad | 12 February 2013 at 01:43 PM
Yes...one may wonder where all the battery breakthroughs of the last 5+ years ended up? Since none have been mass produced, can we conclude the they were ALL false claims or that they were put in the bottom drawer for some obscure reasons?
Something is going up, but what?
Posted by: HarveyD | 12 February 2013 at 04:46 PM
This sounds so encouraging and would be a great leap forward.
Now can someone please stop promising us the moon and simply show a good battery similar to the Toshiba SCiB in all respects except with 250Wh/kg that we could buy for somewhere below $300/kWh?
Posted by: DaveD | 12 February 2013 at 04:48 PM
The energy density of the SCiB is certainly attractive but the power density is less alluring. Personally, I prefer the new Panasonic 4 Ah cell with a volumetric energy density of 800 Wh/L. A single cell has the energy equivalent of 13.6 Wh. The power density is higher than that of the SCiB cells. This will more than likely be the next building block in Tesla's newest battery innovation.
Posted by: yoatmon | 13 February 2013 at 06:29 AM
Yes, Tesla could re-enforce its JV with Toyota and Panasonic to come out with various size improved battery packs by 2014 or so?
The large and very large size units could be used for BEVs.
The mid-size unit could be used for PHEVs
The small size unit could be used for HEVs.
Who knows, it is probably in the making.
Posted by: HarveyD | 13 February 2013 at 07:24 AM
yoatman, We must be talking about two different batteries. The power density was the reason I used the SCiB as a good example:
"Toshiba has improved the discharge density of its SCiB Li-ion battery to 3,900 W/kg. Last year, Toshiba described the development of a 3.0 Ah high-power version of the SCiB with 3,600 W/kg output specifically for hybrid electric vehicle (HEV) applications." http://www.greencarcongress.com/2009/04/scib-20090413.html
Their power density is so good that they can be rapid charged to 90% capacity within 5 minutes....literally thousands of times with only about 10% loss in energy storage. That is fantastic and all we could ever want really.
But they have very low energy density (177 Wh/L) and specific energy (90 Wh/kg) which are the areas I'd like to see improved...along with cost.
Posted by: DaveD | 13 February 2013 at 12:50 PM
It's only when they make a full cell in a format that is a commercial package that you can truely claim a breakthrough. I can make dirt an excellent anode if you let me run it under the right conditions in a half cell. All these professors know pork is pork and all their politicians need is some superficial evidence to justify the pork. Yes, our professors are dishonest people who just want money.
Posted by: Brotherkenny4 | 27 February 2013 at 09:10 AM