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Li-ion Silicon Anode Based on Virus-Enabled 3-D Current Collector Shows Strong Cycleability

Xchen
SEM images before and after the silicon deposition. Source: Chen et al.Click to enlarge.

Researchers at the University of Maryland have used a nickel-coated, genetically modified Tobacco mosaic virus (TMV1cys) as a 3-D current collector, combined with electrodeposition (ED), to fabricate a porous silicon anode for lithium-ion batteries.

Preliminary data shows that the porous silicon anode has very strong cycleability, with more than 1,000 mAh g-1 capacity retained after 170 cycles in the voltage range of 0-1.5V. The researchers attribute this performance to the porous silicon structure and the 3-D current collector. In both structures, the team notes, there is enough space to accommodate the silicon volume expansion during lithium insertion.

The high electronic conductivity of the nickel layer allows electrochemical deposition of silicon onto the coated virus to form nickel silicon core-shell nano-wires. In addition, the highly conductive nickel cores, which are attached to the current collector, enable all porous silicon shells to contribute to the total capacity.

Although silicon is a promising high-capacity anode material for lithium-ion batteries (3572 mAh g-1 and low charge/discharge voltage at room temperature) a silicon anode experiences a large volume expansion during lithium-ion insertion and a consequent shrinkage during extraction. This large volume change leads to severe particle pulverization, resulting in a quick electrode structure failure. Accordingly, a numerous efforts are underway to devise a structure and a material resistant to those changes, which result in a rapid capacity fade with cycling.

The virus-based material is one of several types of porous silicon anode materials members of the University of Maryland team have developed, including ones using polymer scaffold binders and carbon fiber as a current collector.

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Comments

HarveyD

Various improved electrodes will be used to progressively increase lithium batteries performances. By 2020, energy density will certainly be over 600 Wh/Kg and could even be close to 1,000 Wh/Kg. However, associated patent rights could delay worldwide mass production till 2030+ in USA, EU and many other countries with the exception of a few very large countries like China, India etc where lower cost generics will be mass produced for the local markets.

Treehugger

Harvey

nope, as Koshla mentioned it, current battery technology can at best double energy density but cost won't drop significantly with scaling, unfortunately. Battery industry need a breakthrough both in energy density and in cost of manufacturing, time will tell, but current electric car technology won't grab a significant share of car sales between now and 2020. There is no evidence today that we will ever reach power densities of 500Wh/kg, this a tremendous challenge. In the same given that most of the electricity is made from coal worldwide, putting too much electric cars on the road would be counter productive in our fight against global warming, so no hurry on this side...

clett

Lithium sulphur is already up to 600 Wh/kg (although still with poor cycle-life).

The theoretical capacity of lithium-air is 11,600 Wh/kg, and some think we'll be able to tap up to 3,000 Wh/kg of that realistically when the rechargeable LiAir formats are created (that would be equivalent to 400 miles range from a 27 kg battery).

SJC

The lithium air rechargeable batteries could change a lot of things in a hurry. What little I know of them, it is the recharging that is a major problem. If they can get over those problems then low cost, high range EVs might just be in our future.

sheckyvegas

All I know is, I started reading about "shrinkage" up there and had to quit the article.
Freaky....

Darius

Treehugger,

Coal issue you are referring to has no relevance because EV's basically use night electricity and electricity volumes needed for transportation are marginal and will be generated from efficiency gains by evening night/day demand. On other hand only 50% of electricity is generated by burning coal in US and decreasing. Other countries like Europe and Japan use of coal is limited. If you like to worry about global warming or cooling you should think about electricity generation sources. For transportation there is no other way making it sustainable than making it electrical.

HarveyD

Tree....: Some Electrovaya's batteries have already reached 400+ Wh/Kg and 600 Wh/Kg should be reached within 5 years or so. Cost will certainly come down with mass production and aggressive competition (by 2015/2020). Patent rights may have a negative effect on price reduction.

Arne

Treehugger,

In the same given that most of the electricity is made from coal worldwide, putting too much electric cars on the road would be counter productive in our fight against global warming, so no hurry on this side...

You're saying: What is the advantage of an electric car when it runs off coal-generated electricity?
I answer: "What use is all that renewable electricity if cars still run on hydrocarbon fuels?"

The roll-out of electric cars and renewable energy must take place in parallel.

The bulk of renewable energy will have to come from wind and solar, which are variable sources. As their part in the energy mix grows, more storage will be needed. The spin off of a shift to electric cars will be better and cheaper batteries. The more electric cars are sold, the more R&D money goes into batteries, speeding up their development. Add smart-charging, V2G and re-use of spent car batteries and I would say that the electric car is a huge factor in the success of renewable energy.

SJC

I could see batteries in the garage over V2G. If 10 million homes had batteries and inverters to help the grid, then vehicle charging with renewable energy should not be a problem.

I like the idea of having 4 kW of solar on my roof that gives my car enough energy to run 80 miles. That would do the commute without using any fossil fuels at all. That is one of those "sustainable" images that people can understand.

Bob Simpson

SJC is right on the money with personal solar.

With your own solar array on your home sized for your daily commute, many benefits arise:
1. No longer use fuel except for trips out of town (<5%)
2. Helps load-level the grid, putting the power on the grid when needed most. And power is always taken off the grid during off peak time (while sleeping)
3. Because of the time_of_use metering, the power company credits the account during peak times at peak value from the solar array. My electric vehicle is always charged during off-peak times for about half the cost per kWhr, helping pay down the home's power consumption as a side benefit of this time based value of energy.
4. Power companies pocket the money we pay them for the distribution of power since my array is avoiding the losses of distribution altogether. Power companines love this!

To Treehuggers comment:
We receive power without ANY coal sources involved. In Pacific NW, only a max of 15% of coal is used during peak conditions. We personally pay an extra 1.2 c/kWhr for renewable sources so no coal involved at all for us.
I am driving 41 miles/day with this renewable power source and have a 5kW solar array going up now to net zero my annual driving energy.

One last note about coal power:
I have done research into the details to determine the quantity of CO2 emitted if 100% of the power put into my EV (a converted BMW325i) came from coal (mostly because I keep hearing this assumption and am I am regularly asked this question). By comparing the electricity used in the converted vehicle travelling the same distance and route as the original fuel powered design, variables are minimized. A spreadsheet with terms accounting for the mining, delivery to the furnace, generation and distribution, the bottom line came to 27% less CO2 emitted with the electric version. (This does not even include the oil extraction, refining and distribution of the gasoline yet)
I can drive ~20 miles on the energy that is consumed in making one gallon of gasoline, without even using it!

I plan to post this data on my website for scrutiny by others and potentially improve its accuracy if I get any better data (with references of course) to make it as real as possible. You can see this full performance conversion in slide show form at www.evdrive.com

Conclusions drawn from assumptions are counterproductive in this quest for cleaner transportation.

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