## AQMD Plug-in Hybrid Vehicle Technical Forum: Li-Ion Technically Ready, Manufacturing a Big Barrier

##### 12 July 2006
 The relative importance of the charge-sustaining mode and the charge-depleting mode in a PHEV. The chart shows the total consumption benefit as a function of the improvement in charge-sustaining mode consumption for HEVs and PHEVs with several electric range capabilities. Source: NREL

The California South Coast Air Quality Management District (AQMD) today held a Plug-in Hybrid Electric Vehicle (PHEV) Forum and Technical Roundtable focused on the technical issues related to advanced batteries and their effect on the development and commercialization of PHEVs.

The mission was to accelerate the deployments of PHEVs and the goal for the meeting was threefold: to discuss and assess capabilities of advanced batteries; to identify requirements and issues; and to initiate dialogue between different participants in the market and to establish their respective roles.

AQMD’s focus on PHEVs comes more from the emissions control frame of reference. The four-county South Coast district has the worst air quality in the country. Although the progress has been made over the past years in reducing emissions, emissions have plateaued, and at levels above required standards.

With the most immediate gains being made, AQMD is looking for longer term changes—such as that represented by PHEVs—to alleviate the air quality issues. In March, the AQMD board directed staff to expand PHEV activities. This technical meeting was a first step in that direction.

Participating in the panel discussion were:

• Matt Miyasto, Technology Demonstrations Manager, AQMD
• Mark Duvall, Manager Technology Development, EPRI
• Tien Duong, Team leader Vehicle technologies, FreedomCAR (DOE)
• Ahmad Pesaran, Principal Engineer, NREL (DOE)
• Dan Doughty, Manager, Li-Ion Battery R&D, Sandia
• Michael Andrew, Johnson-Controls-SAFT
• Greg Hansen, Energy CS
• Loic Gaillac, Southern California Edison

The general sense of the panel was that from an electrochemistry point of view, lithium-ion cells note only were poised to become the predominant PHEV system in the short- to medium-terms, but that they were basically ready to go.

There exist, however, a number of significant barriers to the commercialization of Li-ion PHEV battery systems, among them being cost, cycle life, and safety management. While the chemistry may be ready, in other words, the barriers are primarily on the manufacturing side.

The other significant issue that emerged during the discussion was the question of the system design target, specifically whether or not the PHEV needed a pure electric mode, or whether it could use a blended approach.

Plug-in hybrids use a grid-rechargeable energy storage system to provide capabilities beyond those of conventional charge-sustaining hybrid systems. A PHEV essentially has two battery operating modes: a charge-sustaining mode [recharging the battery during operation via regenerative braking, for example] and a charge-depleting mode [drawing down the charge from the grid]. The total consumption benefits of a PHEV are a combination of the charge-depleting and charge-sustaining modes.

Characteristics of a PHEV battery pack include:

• Higher total energy capacity than those of HEVs;
• The cell design has lower power density but higher energy density than HEVs;
• The battery is deep discharged during driving to a lower minimum State of Charge than an HEV;
• The battery is grid-recharged;
• Total battery cost is higher than that of HEVs an represent a larger portion of the projected PHEV cost delta;
• Battery energy is directly related to the per mile electrical energy consumption and the desired range;
• Battery mass is greater but typically not to the extent that vehicle performance is significantly affected.

Tien Duong from the FreedomCAR project noted that the DOE has a draft goal of reducing the cost of PHEV batteries to $300 kWh by 2014. That would give a 10 kWh PHEV battery system a cost of about$3,000—about a quarter of the current cost. He also noted that the DOE is at work on a research roadmap for PHEVs, and that the draft roadmap should be ready by December.

Ahmad Pesaran from NREL pointed out that there is a broad spectrum of HEV-PHEV designs leading to different battery requirements. There are currently batteries that could meet the energy and power demands for PHEVs, he noted, but cost and the short cycle/calendar life are still major barriers.

While there are emission benefits with PHEVs, there are some differences between the emissions output of pure EV implementations and the blended EV range impacts that need to be understood. Specific points of discussion emerged around the current need for hybrids to fire up the engine to heat the catalytic converter at start-up. A PHEV with a robust EV mode would do so—but that in turn could confuse the existing testing regimens.

While NiMH systems have matured in power and energy, Li-ion systems support diverse chemistries and opportunities. Lithium-ion cells work basically on a shuttle mechanism, with the lithium ions moving back and for the between anode and cathode. Bsttery makers have an opportunity to change to the cathode and anode to improve characteristics such as recharge time or stability.

The lithium iron phosphate cathode chemistry used by Valence, for example, offers less potential watt output capacity than cobalt, but offers better safety characteristics. This is an exciting time for Li-ion, Pesaran noted, with new cathodes, new anodes and new electrolytes offering lower temperatures, better safety and lower cost.

All panel members agreed that one of the most pressing needs was larger demonstration PHEV fleets—on the order of several hundred vehicles in the aggregate.

I think what we heard today was that the best balance...is to put in a battery capable of only 20 kW rather than a full EV. Even in a vehicle like that (blended) you offer a lot of all-electric range. The evolution of the thing, if we have all electric range interspersed, or even just a Honda-type system where you are bleeding power into the system, will eventually evolve into more all-electric range, bigger and better all-electric range. If the automakers can get to the point where they can justify a 9 kWh battery or even 5 kWh on a car, then just as you saw with Toyota and Honda, you will see competition for providing more of that capability. And that will help all kinds of technologies.

—Greg Hansen

I think the technology is fanning out. I envision that in the future when you go buy a Ford Escape, you will have an option of Battery A, Battery B, Battery C with different cost-benefit ratios, etc. Customers will make the choices. I think it will diversify rather than narrow.

—Dan Doughty

Presentations and summary materials from the forum will be available on the AQMD website in several days.

Resources:

I am a little surprised by the comments on Lithium Ion battery safety and cycle life. The press releases I've read by Altair and A123 batteries seem to suggest that their batteries have passed safety tests with flying colors. I thought they had beat the overheating problem period. I've also read that the new Lithium Ion Nano-tech batteries are essentially good for the life of the car.

What gives.

There is a big difference between bench tests and field tests, and having a proof of technology versus a technology that can be commercialized successfully for transportation, including the reliable manufacturing and packaging of millions of units at an acceptable price point. Transportation is a tough application.

What Altair and A123—and others—have done and are doing are important steps along the way, but there is apparently still some distance to go before having mass-produced battery packs for PHEV vehicles...including not having a clear design target.

The A123 batteries are being tested in a plug-in hybrid Prius as we speak. 9 kWh pack made from 26650 type cells adding 60 kg to car weight.

http://hybrids-plus.com/

www.valence.com
Best battery, but to expensive.

I understand that Altair tests got a 9000 cycle life out of their batteries. But there was no indication of their calendar shelf life. Anyone heard?

Nice to see that there is some official desire to see PHEVs hit the road. The fuel savings look great! And thats not even including other possible savings such as lighter materials. (and death to SUVs!, sorry I digress)

PHEVs have promise, but they still cost at least an additional $10,000 for a very limited range and low top speed. Reasonable battery costs are always just around the corner. In the mean time, auto companies should be investing in ways that permit vehicles to get super mpg, i.e., at least 100 mpg without the necessity to charge heavy batteries from the grid. They could start with lighter materials such as carbon fiber and bigger battery capacities and larger electric motors as costs come down. It's kind of like solar PV for your home. The first thing to do is to make your home as efficient as possible. Only after you have maximized efficiency does it make sense to then install PV or solar thermal. Like the article implies, it also makes sense to have a wide range of options and price points or even the ability to upgrade one's vehicle as battery costs, longevity, recharge times, and weight come down. In the mean time, we can make tremendous strides in cutting oil use by fully utilizing the technologies we already have and the size vehicles we already have. As usual, changes in our value systems will have more impact than changes in our vehicle systems. "There is a big difference between bench tests and field tests " A123 batts are "on the field" in deWalt powertools. "PHEVs have promise, but they still cost at least an additional$10,000"

The next Prius is meant to have a 9 mile EV mode, rechargeable from the grid to its onboard lithium-ion battery (according to a senior Toyota engineer).

That 9 mile range would require 2 kWh of storage, assume 2.5 kWh if cycling between 80% DOD.

How much would that cost? Well, since you can buy lithium-ion 18650s for $3 per cell, and each holds 9 Wh, that's$330 per kWh.

Remove the Prius NiMH battery (-$700) and add 2.5 kWh of 18650 LiIon (+$825) and you have a PHEV-Prius for $125 more than a standard Prius. It does not need to be anything like$10,000.

While PHEVs are a great transportation option I do believe the actual general consumer demand for PHEVs will be less than 1/4 the demand for a standard HEV. Then again I also feel every new car should at a minimum be a micro-hybrid capable of idle stop.

t-.

You have the proper approach. Let efficiency guide us for the purchase of new or replacement vehicles. This may have already started to some extend. The retailers lots are full of unsold Gas guzzlers in our city even with $8000 rebates. If we all refuse to buy a vehicle with less than 40 mpg or even 50 mpg efficiency this could do more for the reduction of fosill fuel consumption than a few thousand hybrids while promoting the purchase of more Hybrids and future PHEVs. Unfortunately, our love affair with 3-Ton dinosaurs is so strong that most of us will not give up those gas guzzlers until our pocket book is depleted. The switch to more efficient, lighter and probably more expensive vehicles will not occur on a massive scale until the price of liquid fuel (fossil or bio) goes up significantly. A$3+/gal progressive (over 3-5 years) carbon tax may be required to convince most of us. Are we mature enough to accept this inevitable tax? Would any politicians be re-elected after such a move?

Politicians would much prefer to see crude oil at $150+barrel/barrel so they could wash their hands of it and maintain that it is not their fault if the price at the pump has gone up from$3+ to $6+. Unfortunately, while the end objective may be attained with$150+/barrel, the green backs would be going to the wrong places unless we quickly divert food crops to the production of ethanol and n-butanol on a massive scale.

Mike,

While I accept that bankrupt transportation is a tough business and I lack an essential understanding of what it takes to go from successful field testing to viable commercialization, I do wonder if we are confusing marketing with politics.

In other word, it is okay for people to line up for gasoline a few cents cheaper than the norm, but if you are saying that with increasing gas prices and the potential for greater oil shortages, there is a lack of a market for PHEVs, then I question that assertion.

I would be more inclined to surmise that the people with the money who can give the nod to marketers to drop subtle hints about shifting to cleaner, cheaper electricity are disinclined to encourage "a clear design target" because so much of their money is in oil stocks and who would want oil stock with everyone running off the Grid?

clett.

If you what you say is true, then that means the current retrofitters are truly ripping people off. Why can't they do what you propose?

I drive 7 miles to work where I could plug in. I think that many drive that distance or less to work. Also I think that at some speed it makes sense to switch to drive directly by the ICE. Thus I think that a 5 or even less mile PHEV would make sense for some.

In fact I have thought that in the current Prius with a potential 1 mile all electric range could be plugged in would be cool. On average you might arrive with your battery half a mile low. If your average trip between charges was 7 topping off that ½ mile would improve your mile .5/7 = 7%. Some people might find it worth plugging in just to see how much they can push the mileage.

Having said that I agree with T. I think that MPG can greatly improved without resorting to PHEVs. In fact if the rumors are true that the Prius III (due out in 2008) will be a plug in hybrid, I think that it might be that only because they needed to add battery capacity to be able to capture more from regenerative braking systems and so why not add a plug.

Capital, capital, capital. That is the barrier to more efficient non-poluting cars and all new technologies. If state and local governments committed themselves to buy only PHEVs the capital would flow to the manufacturers quickly. Investors want customers before they invest.

t, you mention limited top speed and range. Are you referring to the electric drive alone? I suspect you must be. Because with the standard engine a plug in prius or any other plug in is *not* limited.

And regarding some of what has been said here, why can't we have both a more conserative lifestyle AND a plug-in-hybrid?? I want both, and we can have both, and I do believe we will get both, eventually. It shouldn't be a toss-up between the two, even initially. But I am being a little idealistic here. Money does talk loudly.

A Li-ion battery like the 18650 lacks the deep-discharge cycle life required for EV or strong PHEV applications. But it's manufacturing cost observed by Kert should be representative of that which will be achieved using the improved power/life-cycle technologies that are just becoming available (eg. A123, Altair-nano). While the energy density of these new formulations is lower than that of the 18650 and the initial cost/KW-Hr will be higher, observing the cost of these widely available cells provides a good perspective.

here's what i never got. people keep talking about how the catalytic converter has to be heated. but why the hell does it have to be heated with the ICE? wouldn't it be a lot more efficient to just have an electric heater, dedicated to catalytic converter heating, that would take its power from the main (traction) battery? no?

Clett, those $3 18650 Li-ion cells don't put out nearly enough power for the Prius and only last about 500 hundred cycles (4500 EV miles). They also have problems with flammability and explosiveness, especially in large size automotive packs. I don't know of any serious manufacturer considering regular Li-ion (lithium cobalt) cells. Newer chemistries, such as lithium iron phosphate (Valence, A123) and lithium mangenese oxide (several vendors) promise to solve the power, safey and cycle life issues. But the few that are in production are still very expensive. I hope to see acceptable price/performance in 2-3 years. Actually, AC Propulsion did make an EV full of cobalt-oxide based Li-ion sells, but they weren't selling it as a commodity vehicle either. LA to Las Vegas on one charge ain't half bad. The AC Propulsion work is very neat, but with no firm production date, and an expected price "somewhere between a Porsche and a Ferrari," it seems as if their designs are at least a few years away from the mainstream. All the same, downsizing the battery pack from an all-electric range of 100-200 miles to a PHEV-style 20-40 miles (and adapting it for a vehicle somewhat larger than a two-seat roadster) should bring the price down from the stratospheric to the merely unaffordable. The Li-Ion lifespan issues (calendar/discharge cycle) also need to be addressed. A very near car, though. That is, a very "neat" car. And somewhat near, though not yet arrived. Hybrid Technologies has a$125K all electric supercar ( LiX-75 ) full of lithium batteries for sale now.
Thats merely unaffordable, not stratospheric.

NiMh batteries used in HEV are totally unsuitable to PHEV because of high rate of self-discharge, highly elevated at high temperatures. Household NiMh battery looses about 3% of the charge daily, and any one who put it into, say, TV remote control know that it need recharging in about a month. If you leave NiMh battery powered flashlight in glove compartment of a car parked at summer heat, the battery charge is gone in 3 hours.

Li batteries are not nearly developed enough to rugged vehicle applications at summer heat. Current failure of Valence Li batteries due to high level of self-discharge indicates just that. There is no wonder that Toyota, the highest authority in HEV, placed appearance of PHEV vehicles in about 8 years frame. Chill down, folks.

Unfortunately, while the end objective may be attained with \$150+/barrel, the green backs would be going to the wrong places unless we quickly divert food crops to the production of ethanol and n-butanol on a massive scale.
Harvey,
Let's do the math: In 2005, it is estimated that about 14% of the US corn harvest (total harvest: about 10 billion bushels) was used to produce 4 billion gallons of ethanol. Sounds like a lot? It's only 260,000 bpd. To put that in perspective, it is enough to replace almost 1% of the US crude demand, after factoring in that ethanol does not pack the same punch as gasoline. You don't have to be an economist to know that long before you make a dent in crude imports, you are going to cause corn shortages and affect the price American families pay for food.

For those who are slow: converting 100% of the US corn harvest into ethanol would allow us to produce ~7% of our oil needs.

So, if "we quickly divert food crops to the production of ethanol" we would not be achieving much ito energy independence. The food shortages would be quite noticeable, though!

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