MIT Researchers Develop Lithium Iron Phosphate Material with Charge/Discharge Rates Comparable to Supercapacitors
12 March 2009
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| Discharge capability at very high rate for LiFe0.9P0.95O42-δ. Full charge–discharge cycles at constant 197C and 397C current rates without holding the voltage. The first, fiftieth and hundredth discharges are shown for each rate. Source: Kang and Ceder (2009). Click to enlarge. |
Researchers at MIT have developed a lithium iron phosphate electrode material that achieves ultra-high discharge rates comparable to those of supercapacitors, while maintaining the high energy density characteristic of lithium-ion batteries. The new material has a rate capability equivalent to full battery discharge in 10–20 s. A paper on the work led by Gerbrand Ceder, the Richard P. Simmons Professor of Materials Science and Engineering, appeared online 12 March in the journal Nature.
The MIT team realized the fast-charge and discharge capability by creating a glassy lithium phosphate coating on the surface of nanoscale LiFePO4. Glassy lithium phosphates are known to be good, stable Li+ conductors.
Because the material involved is not new, the researchers, led by Gerbrand Ceder, the Richard P. Simmons Professor of Materials Science and Engineering, believe the work could make it into the marketplace within two to three years.
The ability to charge and discharge batteries in a matter of seconds rather than hours may make possible new technological applications and induce lifestyle changes. Such changes may first take place in the use of small devices, where the total amount of energy stored is small. Only 360 W is required to charge a 1 Wh cell phone battery in 10 s (at a 360C charging rate). On the other hand, the rate at which very large batteries such as those planned for plug-in hybrid electric vehicles can be charged is likely to be limited by the available power: 180 kW is needed to charge a 15 kWh battery (a typical size estimated for a plug-in hybrid electric vehicle) in 5 min.
Electrode materials with extremely high rate capability will blur the distinction between supercapacitors and batteries. The power density based on the measured volume of the electrode film, including carbon and binder, is around 65 kW l-1 in the 400C test. Assuming that the cathode film takes up about 40% of the volume of a complete cell, this will give a power density of ~25 kW l-1 at the battery level, which is similar to or higher than the power density in a supercapacitor, yet with a specific energy and energy density one to two orders of magnitude higher. The fact that our material can obtain power densities similar to those of supercapacitors is consistent with there being an exceedingly fast bulk process. For LiFePO4, bulk lithium transport is so fast that the charging is ultimately limited by the surface adsorption and surface transfer, which is also the rate-limiting step in supercapacitors.
—Kang and Ceder (2009)
Lithium-ion batteries absorb and release energy via the extraction and insertion of Li+ ions and electrons. The power capability of a lithium battery depends heavily on the rate at which the ions and electrons can move through the electrolyte and electrode structure into the active electrode material.
Much of the work on improving the power rate for lithium-ion batteries has focused on improving electron transport in the bulk or at the surface of the material, or on reducing the path length over which the electron and the Li+ ion have to move by using nano-sized materials, the researchers note.
However, about five years ago, Ceder and colleagues found that computer models of a lithium iron phosphate material predicted that the material’s lithium ions should actually be moving extremely quickly.
Further calculations showed that lithium ions can indeed move very quickly into the material but only through tunnels accessed from the surface. If a lithium ion at the surface is directly in front of a tunnel entrance, it proceeds efficiently into the tunnel. But if the ion isn’t directly in front, it is prevented from reaching the tunnel entrance because it cannot move to access that entrance.
To address that problem, Ceder and Byoungwoo Kang, a graduate student in materials science and engineering, created a new surface structure that allows the lithium ions to move quickly around the outside of the material. When an ion traveling across this material reaches a tunnel, it is instantly diverted into it. Kang is a coauthor of the Nature paper.
Ceder notes that further tests showed that unlike other battery materials, the new material does not degrade as much when repeatedly charged and recharged. This could lead to smaller, lighter batteries, because less material is needed for the same result.
This work was supported by the National Science Foundation through the Materials Research Science and Engineering Centers program and the Batteries for Advanced Transportation Program of the US Department of Energy. It has been licensed by two companies.
Resources
Byoungwoo Kang and Gerbrand Ceder (2009) Battery materials for ultrafast charging and discharging. Nature 458, 190-193 doi: 10.1038/nature07853
It sounds fantastic - even if you can't do a 5 minute 180KW charge, you do not need supercaps for regenerative braking, and if the number of discharge cycles is very high (no number is given) especially to a high level of discharge, you rally have something.
However, let's see what happens.
There are more false dawns in GCC than ... well ... a spinning asteroid.
If the number of charges / discharges is high, you could do V2G with a clear conscience. You could use a small battery and charge at work.
You could build charging stations with these batteries in them: charge the charging station at a reasonable rate, and charge cars really fast.
Pull in, hook up, get a coffee, etc. Ding, your car is ready and off you go.
You could pay extra for a 5 minute charge vs a 10 or 30 minute one.
But lets see what pans out.
Posted by: mahonj | 12 March 2009 at 10:10 AM
Don't try to have every car in town do a 180kwh charge in a few minutes all at once. There are limits to the quick charge idea and that is one of them.
Posted by: SJC | 12 March 2009 at 11:48 AM
mahonj:
Like the idea of charging storage batteries and then fast charging a BEV from them. A good way to store power for usage by the grid.
I also see this as an answer to electric race cars running 25 minute sprints. With a fast discharge rate for power and a fast recharge capability with regen braking, problem solve...watch out all you heavy weight freak V8s, here come the EVR(Electric Vehicle Racer).
Posted by: Lad | 12 March 2009 at 03:44 PM
I think this is more for very tiny mild hybrid designs where they are trying to get a very tiny battery to belch out enough current to move the car.
This also likely would make it easier to use a smaller pack to catch all the power in a stop and gfling it out again in a start thus allowing full hybrids with .4 and under kwh packs stuffed under a seat.
Duno if the typical battery of say a plug in like the volt could handle being charged fast even if you could get the power to go in.
Posted by: wintermane2000 | 12 March 2009 at 04:14 PM
Mahonj,
Thanks for the tip I now know to invest in coffee plantations and developing an ultra fast esspesso machine!
Will this need to be added to the carbon footprint?
Thinks solar powered coffe maker (brain cells go into overdive) Oil co's "Golden Arches " replaced by solar thermal towers for ready to go steam. Hmm... could double up as "Sar wars" Missile defense laser or...
What was the question again?
Posted by: arnold | 12 March 2009 at 04:28 PM
The magnetic battery of the future has just been invented. Check it out:
http://www.rdmag.com/ShowPR.aspx?PUBCODE=014&ACCT=1400000101&ISSUE=0903&RELTYPE=MS&PRODCODE=00000000&PRODLETT=FQ&CommonCount=0
Posted by: Mannstein | 12 March 2009 at 06:42 PM
LiFePO4 is cathode material. What about anode? How Li titanate anode of Altair compares in speed of discharge?
Posted by: Andrey Levin | 13 March 2009 at 12:45 AM
A 10 minute charge for a 30 kWh pack (150 mile range) would require 180 kW input.
Aerovironment have already demonstrated to the public that their 180 kW chargers work easily and only require a standard 440-volt 3-phase industrial connection (available everywhere across the country).
As for charging multiple cars simultaneously at a charging station, I agree with Mahonj that they will have a 2-3 MWh buffer battery under the forecourt to smooth out the peak charge rates and store cheap night-time rate electricity.
Posted by: clett | 13 March 2009 at 02:43 AM
It could be a long wait for the fruition of this (good things are wort waiting for)
cletts 'battery' incorporating large storage caps? are
feasible today.
On the other hand I fear Manns's battery could be mostly 'spin'
Meanwhile I've already had an enquiry from a large retail oil co re the coffee maker.
Posted by: arnold | 13 March 2009 at 03:13 AM
Interesting idea for charging stations with large buffer battery.
It's all going to depend on price of batteries, their efficiency, cycle life.
It would also help stabilize the grid, especially with V2G capable stations.
If this solution proves viable, then it would make alot of sense to standardize car charging sockets so they can accept both AC and DC inputs - simple and inexpensive modification. The inductively coupled ones couldn't be used (the one on GM's EV1 was such, I guess).
With cars accepting DC input, double conversion (DC-AC-DC) would be avoided, saving 3+ % of power, and also reducing initial investment in station.
Also DC is less harmfull if touched.
In sunny areas it would be convenient to build a solar farm not too far from the charging station with batteries to recharge at daylight. All power transmission could be done in DC domain without need for inverters and grid connection. Reduced costs and better efficiency.
In unpopulated areas would be much easier to draw power cables. The price of photovoltaics should further go down for this to be economical.
Posted by: MG | 13 March 2009 at 10:15 AM
I assume DC grid needs the return unlike AC.
This would be both an expense in cable? and ensuring the opposite polarities don't make contact.
I gather some use of DC grid is practised in the US and special case long distance applications globally with the merit and potential well understood in in the area of (very) high voltage capability related efficiency and low noise.
I am unaware of the retail supply situation and would be interested to hear more of any experience with such (retail) infrastructure issues.
Posted by: arnold | 13 March 2009 at 11:15 AM
For the solar-powered car charging station...let's suppose that a typical corner "gas" station is 20 meters by 30 meters, and that your PV canopy manages to cover 500 square meters with useful PV panels. We will fiat the zoning approvals and assume average efficiencies, conversions and such. How many KwH of power would such a PV system produce in Los Angeles in the course of a year? How many recharges would that be?
I'm not trying to be a naysayer...I really wonder how good the business model gets for the service station owner who produces a lot of his product on site, and who gets a boost to his brand for having the PV. Such a vendor would definitely not pay retail power rates to his local utility for the power he uses on cloudy days and to meet demand that exceeds his PV system's output.
Posted by: HealthyBreeze | 13 March 2009 at 11:48 AM
Buffer batteries add cost and have limited life. It would be nice to have quick charge, but that means contact not inductive and it would be a bit risky in the rain.
Posted by: SJC | 13 March 2009 at 12:40 PM
I think that if these batteries do what they hope, they will be a revolutionary boost to BEVs.
1. In "Prius service" batteries last years (5? 15?) so let's say $200K of batteries lasting 4 years at a "gas" station
That's 50K per year - sounds fine; and the station batteries do not need high power or energy per size and weight (only per dollar). And the grid can use them during off peak and contribute some cash or batteries to the station and so increase it's total energy capacity.
But I worry that we will need few, if any stations by the time BEVs are populous.
2. Charging in the rain just cannot be a problem. Can't be as bad as letting untrained 16 year olds, movie starlets, old ladies, GCC contributors and politicians handle their own petrol - "that will never be allowed".
3. AC or DC makes no difference, conversion is common and more affordable every day (a hybrid makes AC-to-DC-to-battery-to-AC-to motor all day long.
AC power lines and your home appliances require a return also - the 2 wires just change polarity 60 times a second so that transformers will work.
If these batteries have anywhere near the life of todays BEV batteries and the power density of super caps we are IN.
Right mahonj "lets see what pans out."
Posted by: ToppaTom | 13 March 2009 at 08:57 PM
To get 100 mile range, you would need about 400 square feet of solar panels per car. If you want to service 100 cars per day, it would take 40,000 square feet of solar panels or about an acre of surface area. The solar panels would cost about $400,000 installed and might last 30 years. I can be profitable. You are trading off the cost of fuel for the cost of hardware. It all depends on how much the customer is willing to pay for a kilowatt hour of electricity. Ten cents, maybe not. Twenty cents...well maybe.
Posted by: SJC | 13 March 2009 at 10:48 PM
I don't think buffer batteries are needed in charging stations, you could simply place them near the power substations that transform electricity to lower voltage for city use. I am sure these are able to cope with more than a couple of cars charging at the same time.
Posted by: Alessio | 14 March 2009 at 04:33 AM
The great thing about these batteries is that any reasonable amount of energy storage comes with enough power capacity to provide sprightly performance. The image of hybrids as "penalty cars" and electric propulsion as a "sacrifice" could change overnight.
Posted by: Engineer-Poet | 14 March 2009 at 08:20 AM
Smaller battery packs for lower car costs.
The "gas station" model for charging up is old-school. Most charging will be at home and work where charging can take hours.
What about a charging lane on the freeway for long distance trips? Charge transfer strips every 100 feet.
Posted by: Economy Of Nature | 14 March 2009 at 03:33 PM
In many parts of the world people park on the street and cannot charge at home (they live in high-rise etc).
So they'll need charging stations. Often people who can charge at home will have to top-up to get back home.
Even very fast charging (of 50+ % of battery) will take 10+ minutes, which means that the charging and waiting cars won't be allowed to block one another because of very different individual charging times (gas refueling is usually done in just 2-5 minutes).
Because of that electric charging stations will probably have charging cars parked paralel to one another with front or rear end facing a wall with charging outlets and cables. All that space covered for rain.
Posted by: MG | 14 March 2009 at 10:46 PM
In charging stations, you don't only need high current, but you also need (unlike in your car) a very high capacity(MJoules). So, in that case, you don't need to focus on high discharge rates, since you can easily get high currents by placing lots of cheap Pb-batteries (firefly ?) in parallel. The weight is irrelevant, and you need to have an amount of energy of many cars anyway. Fast charging of the car (in % of total capacity) is important. Fast decharging of the charging station is only important in Watt, not in % of total capacity.
Posted by: Alain | 15 March 2009 at 05:46 AM
@MG "All that space covered for rain."
Well yes and no; Yes - because I would love to get in and out of my car without getting wet, and no - because modern circuits make it perfectly safe to charge in the rain.
The truth is there are already scores of EV charging stations in place in cities across Europe and few (if any) are under cover.
Posted by: ai_vin | 15 March 2009 at 08:20 AM
Um folks they wont be able to put these things anywhere near the gas pumps..... And as most gas stations are rather small....
Posted by: wintermane2000 | 15 March 2009 at 10:47 AM
"they wont be able to put these things anywhere near the gas pumps"
That is both debatable and irrelevent. The city is full of parking meters, use THEM. Park your ICE car, put in your coin and leave it there for __hours: Park your EV, put in two coins, pull out the cord, plug it in and leave it there for __hours.
OTOH if a city is too crowded to have enough parking spaces the chances are it has some kind of mass transit system in place, use THAT.
Posted by: ai_vin | 15 March 2009 at 11:14 AM
People have all kinds of good ideas for EVs in the cities and suburbs. I think a lot of people just want to get going on it. A car, truck or bus that uses CNG or electric or both (dual fuel PHEV) uses NO imported oil and that suits me just fine :)
Posted by: SJC | 15 March 2009 at 11:27 AM
Ai vin.. its more a matter of insurance. Unless they can prove it wont cause an explosion they arnt gona get insured wich nixes the possiblity of it happening at all. Gas plus bev chargers anywhere near each other is a given lawsuit factory. Any station owner would have to be an inbred batpoo crazy nitwit to even think of having them anywhere near each other.
Also a bit of a problem is that much power would require its own substation nearby.
Posted by: wintermane2000 | 15 March 2009 at 12:48 PM