Toyota developing LPG hybrid taxi for Japan market
Volkswagen Group brings in new Head of Group Strategy from GM

Technical review outlines challenges for both batteries and fuel cells as basis for electric vehicles

In an open-access invited review for the Journal of the Electrochemical Society, Oliver Gröger (earlier post), Volkswagen AG; Dr. Hubert A. Gasteiger, Chair of Technical Electrochemistry, Technische Universität München; and Dr. Jens-Peter Suchsland, SolviCore GmbH, delve into the technological barriers for all-electric vehicles—battery-electric or PEM fuel cell vehicles.

They begin by observing that the EU’s goal of 95 gCO2/km fleet average emissions by 2020 can only be met by means of extended range electric vehicles or all-electric vehicles in combination with the integration of renewable energy (e.g., wind and solar). Based on other studies, they note that without an increasing percentage of renewables in the European electricity generation mix, the only vehicle concept which could meet the 95 gCO2/km target is the pure battery electric vehicles. (Hydrogen produced via electrolysis using the EU mix or by natural gas reforming would exceed the target.)

Theoretically, with renewable electricity, the 95 gCO2/km target could also be met by extended range electric vehicles with 40 miles all-electric range if 50% of driving is powered by the battery, or by fuel cell electric vehicles (FECVs), with hydrogen produced by water electrolysis.

While these propulsion concepts look promising, their contribution to CO2 emission savings in the transportation sector would only be meaningful if their market penetration were substantial. In the absence of government regulations, the latter largely hinges on consumer acceptance, which in turn strongly depends on cost. In addition, in the case of BEVs, recent studies clearly showed that BEV driving range (closely followed by cost) are the predominant variables determining consumer acceptance.

Since vehicle cost and range largely control market penetration, we will first provide a rough estimate of the cost/range projected for BEVs and FCEVs. Next, we will briefly review the current status and the expected future progress in lithium ion battery (LiB) technology, which is currently used to power BEVs. This will be followed by an assessment of the perceived technological barriers and the potential energy density gains for so-called post-LiBs, namely lithium-oxygen and lithium-sulfur batteries. Last, we will discuss the materials development challenges for FCEVs, focusing on approaches to reduce platinum catalyst loadings and to improve fuel cell durability.

—Gröger et al.

(Volkswagen’s Gröger, who holds a number of battery patents, was responsible for the Li-sulfur section of the paper.)

Gröger
Factors influencing the needed/perceived range of all-electric vehicles: i) amount of storable energy (in units of Wh) either in (post-)lithium ion batteries or in hydrogen to power H2-fuel cells; ii) vehicle energy consumption (in units of Wh/mile); iii) the customer’s perceived range, strongly affected by the recharge rate; and, iv) novel integrated mobility concepts. Source: Gröger et al. Click to enlarge.

As others, including automakers such as Toyota, have done, Gröger and his colleagues suggest that that BEVs will be the preferred option for short-range vehicles, while FCEVs are more suitable for large driving distances. In explaining this, they note that:

Since the societal value of electromobility requires substantial market penetration, it hinges on consumer acceptance of all-electric vehicles. … the main obstacles to BEV consumer acceptance are driving range and cost. The observed paradox with regards to driving range is the difference between actually needed and preferred driving range, which is related to several factors: i) inaccurate understanding of needed driving range; ii) habitually large driving range of conventional vehicles; iii) so-called “range anxiety”, i.e., the fear of getting stranded; and, iv) lack of experience with limited-range vehicles.

… Since driving range is a critical factor determining market penetration, it is useful to briefly examine the options to increase the actual or the perceived range of all-electric vehicles… Quite clearly, increasing the gravimetric and volumetric energy density by means of advanced LiBs and so-called post-LiBs would be the most straightforward way toward long-range BEVs; alternatively, H2-powered FECVs would be another path toward long-range all-electric vehicles. Driving range could also be increased by reducing energy consumption per mile … which can be accomplished by the use of light-weight materials (e.g., carbon composite chassis explored by BMW), by improvements in electric-drive efficiency, and by advanced vehicle climatization concepts (e.g., for the UDDS (urban dynamometer drive schedule) drive cycle, BEV driving range reductions by ≈17 and ≈50% have been reported for cooling and heating, respectively).

In some studies it has been noted that the adequate BEV range perceived by the customer could be lower if the recharging time would be sufficiently short. Therefore, companies have been establishing fast-charging stations (ranging, e.g., from 24 kW by BMW to 120 kW by Tesla). For a 100 mile-range BEV requiring ≈21 kWhnet, complete recharge could be accomplished within ≈60 min. using a 24 kW charging station and within ≈12 min. using a 120 kW charging station (assuming 90% charging efficiency). … On the other hand, FCEVs requiring ≈5 kg H2 for 300 miles range can be refilled within conventional filling times (≈8 min. acc. to the 0.6 kgH2 /min. filling rate reported by DoE, and only 3.5 min. from 20 to 95% fill-level for Toyota’s Mirai vehicle), so that they would have similar range and refilling attributes as conventional vehicles.

—Gröger et al.

In either case, however, cost and durability challenges still remain and at least evolutionary technology advances are still required, the authors go on to explain. Some of their main points, backed up by references to the literature, with respect to major technology options include:

  • Despite the enormous amount of research and development efforts put into Li-ion batteries, specific energies significantly larger than 0.25 kWhname-plate/kgbattery-system are not yet on the horizon. As a result, lithium-ion battery-based BEVs with 200 miles range or more will probably be out of scope for mid-size car market/pricing that would be attractive for mass adoption.

  • With respect to one of the targeted post-LiB systems, the Li-air or Li-O2 battery, no stable electrode components and electrolytes which would result in a demonstrated/reproducible 100% O2-recovery over a Li-O2 battery charge/discharge cycle have yet been confirmed. Therefore, the authors note, further fundamental research and materials development is required to determine the viability of Li-O2 batteries.

    If successful, the expected gains in specific energy of a practical battery-system would likely be not better than ≈1.5–fold compared to advanced lithium-ion batteries (Si/C-composite anodes with HE-NMC, NMC811, or NCA cathodes), they suggest.

  • On the Li-sulfur side, it is difficult to achieve the expected gravimetric energy density from a lithium sulfur battery-system. Along with that, the requirements of the automotive industry have also changed over the years, with increased focus on volumetric energy density rather than only gravimetric energy density. The achievable volumetric energy densities for lithium—sulfur batteries, independent of the anode, will always be substantially lower than that of lithium ion batteries, the authors observe.

    To deliver cell-level gravimetric energy densities competitive with advanced LiBs (Si-anode and HE-NMC, nickel-rich NMC811, or NCA), lithium-sulfur batteries would require relatively large areal capacities (≥4 mAh/cm2) and high cathode sulfur content (≥60 %wt). Such Li-S batteries with silicon anodes could reach 350–400 Wh/kgcell—at best ≈1.3-fold larger than the values projected for advanced LiBs.

    450– 500 Wh/kgcell could be obtained using a Li-metal anode—assuming the issues of safety and durability were dealt with successfully. This is ≈1.3-fold larger than the gravimetric energy densities for advanced LiB cathode materials coupled with lithium anodes.

    In terms of volumetric energy density, lithium-sulfur battery cells are definitively inferior to LiBs. However, with regards to cost, lithium-sulfur batteries might be superior, if the additional components which might be needed to improve cycle-life and safety (diffusion barriers, etc.) can be realized at low cost, the authors suggest.

    Further using silicon anodes instead of metallic lithium might enable higher power densities and longer cycle-life, if SEI-stabilizing electrolytes/additives can be developed which prevent the continuous consumption of electrolyte during cycling. One open issue with silicon anodes in lithium-sulfur batteries is the incorporation of lithium by either industrially feasible pre-lithiation procedures or by the use of LiS- rather than S-cathodes.

  • For hydrogen fuel cells, they note that much progress has been made over the last 10 years. Concepts for platinum-based cathode catalysts with high mass activity catalysts are putting the targeted Pt loading reduction to the 10 g/FCEV in reach. The new class of Pt-alloy catalysts formed by dealloying also shows improved voltage-cycling stability, reaching the targets set by the DOE.

    The challenge is now to combine these catalyst concepts with support materials with higher durability in order to ensure fuel cell performance over FCEV service life. In addition, the origin of the yet unassigned mass transport losses at low Pt loadings must be understood and mitigated, they write.

    The main challenge in fuel cell membrane research seems to be to identify materials suited for higher operating temperatures and at low relative humidity in order to simplify system design, improve heat rejection, and reduce energy losses by the air compressor.

An analysis of the system-level energy density of lithium ion batteries (LiBs) suggests that the gravimetric energy density of advanced LiBs is unlikely to exceed 0.25 kWhname-plate/kgbattery-system, which would limit the range of BEVs for the compact car market/pricing to ca. 200 miles, with recharging times substantially larger than that of conventional vehicles. Whether this will suffice for a large market penetration will depend not only on the needed but also on the perceived range requirement by customers. Higher energy densities would only be possible, if one were able to develop durable and safe metallic lithium anodes. While the so-called post-LiBs, viz., lithium-air and lithium-sulfur batteries have been assumed to revolutionize battery energy storage, cell- and system-level gravimetric energy densities are not expected to substantially exceed that of advanced LiBs; volumetric energy densities will most definitely be lower.

In contrast to BEVs, H2-powered FCEVs are capable of large driving ranges (>300 miles) and can be refilled within several minutes. Besides the need for a hydrogen infrastructure based on hydrogen produced from renewable energy, a reduction of the platinum requirement per vehicle (currently ≈20–40 gPt/FCEV) still requires further development. Nevertheless, current data suggest that advanced catalysts (dealloyed Pt-alloys) are able to meet the long-term DOE activity and durability targets, but their integration into MEAs which can operate at high current densities and low Pt loadings still needs to be demonstrated.

—Gröger et al.

Resources

  • Oliver Gröger, Hubert A. Gasteiger, and Jens-Peter Suchsland (2015) “Review—Electromobility: Batteries or Fuel Cells?”, J. Electrochem. Soc. volume 162, issue 14, A2605-A2622 doi: 10.1149/2.0211514jes

Comments

usbseawolf2000

"They begin by observing that the EU’s goal of 95 gCO2/km fleet average emissions by 2020 can only be met by means of extended range electric vehicles or all-electric vehicles in combination with the integration of renewable energy (e.g., wind and solar)."
I am surprised nobody pointed this out.

Gen3 Prius achieved 89g/km 5 years ago. Gen4 should be 18% lower.

Auris HSD emission is similar.

TM

@SJC - where do you get your numbers that 85 KWh batteries will cost $20-30,000 in the year 2025? I'd like to see the assumptions you made.

William Stockwell

MIT is doing work on SOFCs that can work with gasoline or other hydrocarbon fuels- of course last I heard was a 2013 report that stated they got the working temp down from 900c to 600c and had increased power density 10 fold and were well on their way to a 350c working temp- I picture a 100mile battery range with a SOFC range extender providing 60-70mpg efficiency after.

Davemart

EP argued:

'There are ways to "refuel" a BEV while it is in motion. If one could squeeze as little as 10 kW through the road, a Tesla Model S could run all day at 60 MPH and a Leaf could run well beyond human endurance at that speed.'

I am a big supporter of through the road charging, as I have said several times on this forum.

If you are evaluating according to radically new technology, then to be even handed you have to look at possible breakthroughs for both sides, and in the case of fuel cell cars that includes everything from solar direct to hydrogen to intermediate temperature solid oxide fcs, which could run on just about any hydrocarbon including synthetic guarantee.

Since you have argued many times that the cost of rolling out a hydrogen infrastructure is not reasonably affordable, and would not happen, you suddenly seem to have changed your tune, as whatever its benefits rolling out enough electric highways to make a difference for through the road charging would certainly cost huge amounts.

It does not bother me if the technology works, as I have never held the cost of infrastructure to be a show stopper, but you have certainly argued to that effect in the case of the far cheaper hydrogen infrastructure.

And if you want a 10kw addition in power, then there is a far less capital intensive answer.

Nissan for the Leaf could simply turn to its partner, Renault, and use the technology already in the Kangoo ZE range extended van, of which they together with Michelin and Symbio are putting 1000 on the road in 2016.

Their 10 kw version of the fuel cell would do the job very nicely, and presumably for the Tesla too.

That is using off the shelf technology.

Davemart

William:

Intermediate temperature fuel cells are down to a lot lower temperature than the 600C you spotted in 2013:

'Researchers at Korea University in Seoul have developed high-performance, low-temperature solid-oxide fuel cells (SOFCs) using silver cathodes surface-treated with yttria-stabilized zirconia (YSZ) nano-particulates fabricated by atomic layer deposition (ALD).

As reported in a paper in the Journal of Power Sources, the fuel cell performance of the SOFCs with an optimized ALD YSZ surface treatment is close to that of SOFCs with porous Pt, which is known as the best performing catalyst in the low-temperature regime (250–450 °C).'

http://www.greencarcongress.com/2015/07/20150713-sofc.html

As in many things to do with fuel cells and hydrogen production and even storage, the rate of progress is remarkable, whilst increases in battery energy density are far from that.

electric-car-insider.com

SJC, I've already pointed out, with supporting numbers from industry reported here on GCC, why the price of a replacement S 85 pack is very unlikely to be anything close to $20k that far down the road.

Battery costs are declining 8% per year, and GM has said they'll hit $100 kWh by 2020. Tesla's public statements about their cost are in line with that number, or better. Your estimate of $20k replacement cost in 2025 and beyond is the same retail cost per kWh as Nissan charges for the Leaf in 2015. What evidence supports that wild claim?

Tesla Models S owners routinely report on their battery capacity loss in Tesla forums. It's typically only a few percent after 35-50k miles. My own is less than 2% at 40,000 miles. Tesla says they will replace under warranty any battery that loses more than 30% within 8 years. So those figures give you a reasonable bracket.

A Tesla Model S 85 that lost as much as 25% capacity would still have 199 miles of range. That still offers plenty of utility, especially considering that the density of the supercharger network will probably be double by that time.

Expensive battery replacement is a canard for most EVs except for the Nissan Leaf, which is one of the few EVs with an air cooled battery.

Even if I did have to replace a Model S battery, the cost would be more than covered by my fuel cost savings, which I conservatively estimate at $42,222 over 10 years (I drive about 20k miles a year).

ai_vin

For me the question of FCEVs vs BEVs is one of where the primary energy comes from. If my future FCV has to be refueled at a corner gas station run by a rebranded EXXON you can count me out. Those lying, cheating SOBs have gotten rich enough destroying the world, they don't deserve to get richer saving it.

BEVs at least could be recharged at home from the solar panels on your roof.

Davemart

ai vin:

Another nightworker speaks.

TM

@ electric-car-insider.com
How do you save $42,222 of fuel with 200,000 miles driven in 10 yrs? A prius would get you there at 50 mpg in 4000 gallons of gas. at $3 / gallon, this is $12,000 total in fuel. OK - maybe you are comparing it to a 20 mpg car but then that is still $30,000. I'll bet you didn't include the electricity cost either. Model S gets about 3.3 miles per KWh - That means 200,000 miles needs 66,000 KWh at 10 cents per KWh that is $6600 in electricity - say you get half of that from superchargers, that is still $3300 unaccounted for. How is $42222 a conservative number?

TM

oops 60,000 KWh not 66,000 KWh.
Still, I can't see anyway to get to $42K in fuel savings.

SJC

The first Model S were sold five years ago, so 2020 is the ten year point. We know the LEAF loses capacity within five years and costs about $8000 with labor to replace.

$300 per kWh installed at the pack level is a fair assumption. So the 70 kWH pack would cost over $20,000 installed. We have seen examples of packs having to be replaced, there is no reason to believe the Model S packs will last forever.

By the way, I bet the Model S pack is PRORATED, if it is covered for ten years but you need to replace it after eight years you get 20% towards a new pack. This is Total Cost of Operation.

Davemart

Even assuming the battery lasts for the life of the car, it still needs to be depreciated, and subsidies aside the battery in the 85 kWh Tesla costs maybe $30k.

Take that away from the petrol cost and don't forget to add in the cost of the electricity, and in the case of Europe very substantial taxes, and the savings on EVs are negligible.

That does not mean that they should not be done, but there is little if any cost saving at present prices.

That is why electric cars are a percent or two, and not 30% or whatever, save in places like Norway where the taxes are massively weighted.

TM

@SJC - you think that in 10 yrs from now the battery is going to be 2x higher than prices today? No, not a fair assumption at all - way off the mark.

electric-car-insider.com

@SJC, comparing the operating cost of a Prius to a Tesla Model S is a dodge. Compare the Tesla Model S to an equivalent full size premium car, say a BMW 7 series which gets 16 mpg City, 19 mpg combined.

Where I live, average gas prices have been above $3.80 per gallon for all but four months over the past five years. It's possible that they'll go down over the next ten years, but very unlikely. Other areas of the country might pay less, but probably won't forever.

You are correct, most people would have to pay for electricity, but mine is free since my solar panels are paid off and I am on a net metering Time of Use rate plan - even after charging my 3 EVs, I pay only for gas service, I'm a net producer of electricity.

As you point out, even if I didn't have solar and net metering, the cost of electricity is a small fraction of what I used to pay for gas. The savings are quite substantial.

My girlfriend, who drives a lot for work, saves over $400 per month in fuel costs (used to drive a Lexus RX350. Says she's never going back to gas, ever).

SJC

"Under the Model S warranty, Tesla covers factory defects on the battery for eight years or 125,000 miles on the 60 kilowatt-hours (kwh) battery. The larger 85-kwh battery is covered for the eight years without a mileage cap. However, the warranty doesn’t cover range loss."

http://www.hybridcars.com/studies-suggest-tesla-batteries-lose-little-range/

electric-car-insider.com

30% loss claim is from owner correspondence withTesla, it has been posted on owners forum.

Nissan has a similar approach. I know someone who got a replacement Leaf battery based on range loss. It was not prorated, no charge.

No doubt these policies will be updated over time. I personally would expect to pay a prorata charge if my battery was swapped due to range loss.

SJC

Tesla Roadster battery pack replacement will cost $29,000

http://www.autoblog.com/2015/09/01/tesla-roadster-battery-pack-replacement/

SJC

"..the standard 85 kW version Model S would be a safe bet to have battery costs at “less than a quarter” – that translates to a total maximum cost of about $20,250 or $238/kWh."

http://insideevs.com/tesla-battery-in-the-model-s-costs-less-than-a-quarter-of-the-car-in-most-cases/

So a Model S bought 4 years ago runs another 3 years and has 70% range. The range loss is not covered by the warranty, so out of pocket will be $20,000+ with labor. That is over $2000 per year, which offsets electricity/gasoline savings.

TM

@SJC - Roadster pack upgrade (small volume) today is $29,000. OK fine, but has no bearing on what a model S pack will cost in 10 yrs. Tesla aims for $100 / KWh by 2020. Cost = 8500 in 2020. Price should fall further by 2025. I can't see it being above $10,000 - and it will most likely be a 100 KWh pack in 2025. Don't apply static logic to a dynamic situation.

SJC

We are talking 3 years away, not 10. When you keep changing the goal posts anything is possible.

electric-car-insider.com

We are three years away from what?

The roadster pack is not relevant to this discussion not only because, as TM points out, the Roadster is a very low volume exotic, but Tesla upgraded the battery from 53 kWh to 70 kWh.

330 miles range, 33% more than the original pack. That's a significant upgrade, a lot of engineering effort to support these original owners. Go check out pricing at your typical exotic aftermarket shop sometime. A set of HRE wheels can run $12,000.

I will concede your point that EV batteries are life limited, and we do not have perfect information about replacement and lifecycle costs.

So are hydrogen fuel tanks and fuel cell stacks. And ICE engines and transmissions btw.

We'll omit from consideration your favored on-board methanol reforming fuel cell stacks, which no one is actually producing and selling. Those are apparently priceless.

Engineer-Poet

FWIW, the cells available in 2020 will probably put 100 kWh in the Model S package.  That would be $10k for a battery which makes the car substantially better than new.

The Roadster refit also makes the car substantially better than new.

ai_vin

Everybody here is focusing on the replacement costs of a BEV's pack but what about a FCV's stack? Will a fuel cell last the life of the car or have to be replaced after 100,000 miles? Does it lose output over that time? How much is the replacement cost of an automotive fuel cell stack? If you're going to compare one against the other lets see both sides of the same arguments.

electric-car-insider.com

H2 fuel tank is about $3,500 each OEM cost. There are two per vehicle. Approximately 15 year life.

Previous generation fuel cell staks lasted about 70k miles. Toyota warranties the fuel cell components for 8 years or 100,000 miles, whichever comes first.

HarveyD

H2 versus quick e-chargers capital cost:

Since a single H2 dispenser point currently cost about 4X as much as a single quick e-charge point, but can refill 13 times more FCEVs than BEVs, the relative effective initial capital cost is 3X times in favour of H2 dispensers.

OTOH, H2 dispenser/electrolysers currently use (60%) more electricity than quick e-chargers. Near term more efficient electrolysers and compressors will reduce that differential to about 30% by 2020/2025. Being able to store H2 to avoid H2 generation during peak hours will offset most of the extra cost.

The comments to this entry are closed.