Rechargeable lithium-sulfur batteries get a boost from graphene

Jul 13, 2011 by Lisa Zyga feature
Synthesis steps for a graphene-sulfur composite, which can be used as a cathode material for rechargeable lithium-sulfur batteries with a high energy density. Image copyright: Hailang Wang, et al. ©2011 American Chemical Society

(PhysOrg.com) -- By wrapping tiny sulfur particles in graphene sheets, researchers from Stanford University have synthesized a promising cathode material for rechargeable lithium-sulfur batteries that could be used for powering electric vehicles on a large scale. When combined with silicon-based anodes, the new graphene-sulfur cathodes could lead to rechargeable batteries with a significantly higher energy density than is currently possible.

The researchers, led by Yi Cui and Hongjie Dai from Stanford University, have published their study in a recent issue of .

As the researchers explain in their study, in order to that are competitive with gasoline-powered vehicles, one of the biggest challenges is improving the energy and power densities of rechargeable batteries. The batteries’ weak spot is currently the cathode materials, which have specific capacities that are much lower than those of the anode materials. (The specific capacities for cathode materials are about 150 mAh/g for layer oxides and 170 mAh/g for LiFe-PO4, while those for anode materials are 370 mAh/g for graphite and 4200 mAh/g for .)

In order to improve the cathode, the researchers turned to sulfur, which has a theoretical specific capacity of 1672 mAh/g, about five times higher than those of traditional cathode materials. Although sulfur has other advantages, such as low cost and a benign environmental impact, it also has some disadvantages. For instance, sulfur is a poor conductor, it expands during discharge, and the polysulfides dissolve in electrolyte. Together, these problems cause a low cycle life, low specific capacity, and low energy efficiency.

Previous research has shown that adding carbon to sulfur can increase sulfur’s electrical conductivity. But although various carbon-sulfur composites have achieved specific capacities of more than 1000 mAh/g, their cycle life is still low; it remains challenging to retain these high capacities for more than 100 cycles.

“We developed a strategy of graphene wrapping to overcome many issues related to using sulfur as lithium-ion battery cathodes,” Cui told PhysOrg.com. “We have shown excellent cycling performance.”

To achieve this high performance, the Stanford researchers made some adjustments to the sulfur. First, they coated submicrometer sulfur with poly(ethylene glycol) (PEG) to trap the polysulfides and prevent their dissolution. The flexible PEG coating also improves cycle life by accommodating the sulfur particles’ volume expansion during the discharge portion of each cycle. Next, the researchers wrapped the coated sulfur particles with graphene sheets decorated with carbon black nanoparticles, which improves the sulfur cathode’s conductivity. The loosely packed graphene layer also further traps polysulfides and accommodates the volume expansion of the sulfur.

“This is a very rational material design to overcome the issues of polysulfide dissolution,” said Hailiang Wang, lead author of the paper.

Rechargeable lithium-sulfur batteries get a boost from graphene
The cycling performance of the PEG-coated graphene-sulfur composite shows that it can maintain a specific capacity of close to 600 mAh/g for more than 100 cycles. Image copyright: Hailang Wang, et al. ©2011 American Chemical Society

The researchers demonstrated that the resulting graphene-sulfur cathode can achieve high specific capacities of 500- 600 mAh/g for more than 100 cycles. The new cathode material could be used to fabricate with a higher than that of other rechargeable batteries today.

“The capacity fading is only about 10-15% for 100 cycles, which is very exciting,” said coauthor Yuan Yang, who made electrodes and cells in the project.

However, before such batteries can be manufactured, the researchers have to address the large performance variability of the lithium-sulfur batteries that they tested in this study. For example, about 30-50% of the batteries had a 20-25% decay over 100 cycles. In the future, the researchers hope to continue improving the capping of sulfur to enable lossless cycling.

“Overall, the biggest challenges facing rechargeable batteries for electric vehicles are increasing the energy density and reducing the cost,” Cui said. “Using high-energy and low-cost materials such as is very attractive.”

Explore further: Thinnest feasible nano-membrane produced

More information: Hailiang Wang, et al. “Graphene-Wrapped Sulfur Particles as a Rechargeable Lithium-Sulfur Battery Cathode Material with High Capacity and Cycling Stability.” Nano Letters, DOI: 10.1021/nl200658a

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Eikka
1.6 / 5 (5) Jul 13, 2011
For practical electric cars, the cycle life must be at least 1000 cycles with insignificant loss of capacity.

The high price of the batteries means that they will remain small, and for a car that gets 100 kilometers per charge, 1000 cycles means just 100 000 km, which for modern gasoline engine cars is considered merely a "break-in".

If the battery is shot by 100 000 km, the car is worthless, because you or the next owner will have to buy a new battery, which is almost as expensive as buying a completely new car. Hence, you can't sell the car because it has no resale value, and you can't drive the car properly without buying a new battery.

Who would buy such a car in the first place? Put down something like 30 000 for a new car and that's 30 cents a kilometer if you're the first and last owner of it. Gasoline only costs about 10 cents a kilometer.
lengould100
3.4 / 5 (5) Jul 13, 2011
Gasoline only costs about 10 cents a kilometer.
This year...
SteveL
4.3 / 5 (4) Jul 13, 2011
Preferrably we should expect 5,000 or more charge/discharge cycles from an electric car battery.

You only mention the purchase cost for the electric vehicle and are comparing it to only the energy (fuel) cost of the petroleum powered vehicle. There isn't enough reliability or long term expense information on all-electric cars to honestly compare the two in vehicular lifetime cost per distance.
Eikka
2.3 / 5 (6) Jul 13, 2011
Gasoline only costs about 10 cents a kilometer.
This year...

Well, I used my car as the reference point. You could get a hybrid and use half as much. And remove the gasoline tax and VAT, which are responsible for more than half of the price anyways.

Point is, regular cars are cheaper on the get-go, and you can easily drive one 3-5 times further, which means gasoline prices can easily double and it still doesn't make sense to buy an electric car that has a battery that won't last a thousand cycles.
Eikka
1.3 / 5 (7) Jul 13, 2011
You only mention the purchase cost for the electric vehicle and are comparing it to only the energy (fuel) cost of the petroleum powered vehicle.


Taking two equally priced cars, driving the electric car 100 000 kilometers makes it worthless, while the petroleum powered car will likely sell for a bit less than half its original price. At that point, neither vehicle is likely to have required any major maintenance besides normal checkups for the brakes, shocks, joints etc.

Half the price of a car in the price range of things like Mitsubishi MiEV buys you a lot of gasoline. Much much more than what is needed to drive 100 000 kilometers.

And you get a much better car because 80% of the cost isn't in the battery.
HeloMenelo
2.8 / 5 (9) Jul 13, 2011
Maybe true for now, however the stove stoker's time is ticking away, in the end electric cars will prevail above all else.
Battery technology is changing, it only takes time.
yoatmon
3.9 / 5 (7) Jul 13, 2011
@Eikka:
I'd like to point out a similarity in behaviour among yeasts, bacteria and humans.
The classical method of ethanol (alcohol) production via fermentation is based on yeasts or bacteria. In a normal fermentation process, fermentation stops when an alcohol concentration (temperature dependent)of 12 to 15 % is achieved. Neither the yeasts nor the bacteria can exist in an environment that they pollute with their waste product, alcohol. Once this concentration limit is reached, they have virtually done their best to eliminate themselves - brainless as they are.
Humans are much more clever and intelligent than stupid yeasts and bacteria; they have devised more than just one method of polluting their environment to extinguish their own existence.
I have the impression that some individuals are capable of making only economic decisions but fail bitterly when making decisions to their own welfare or utter existence.
fmfbrestel
4 / 5 (4) Jul 13, 2011
@Eikka -- then dont buy one. But dont use economics to tell car makers what to make. SUV's in the 90s were much more expensive and burned twice the gas as an economy car, and yet people bought them. The market exists. People want electric cars, and there's nothing wrong with that. Are they some panacea invention that will save the planet tomorrow? -- of course not. Maybe they never will either, but it doesn't matter. We don't live in a command economy where you make all the decisions. Get over it.
bishop
3.8 / 5 (5) Jul 13, 2011
One thing:
GO GRAPHENE!!!!

This material will change everything in our everyday lifes!
SemiNerd
5 / 5 (3) Jul 13, 2011
Just a note about the life cycles and current carrying capacity. These experiments are showing that the cathode has about 650 ma/g capacity after > 150 cycles. I have high confidence they could get that to 1000 cycles with the same or a bit higher.

But this is still greater than 4 times the capacity of current batteries. You would have to degrade the battery more than 80% just to reach what current batteries provide (on the order of 150 ma/g). It's quite likely that at least 10000 cycles could be achieved before the battery degrades to that amount.

This is all speculation of course, but history well demonstrates that the first prototypes are never the last word on capability.
CapitalismPrevails
1 / 5 (3) Jul 13, 2011
Now combine this new battery with 'in-wheel' electric car and we're golden!

http://www.physor...car.html
Eikka
2.4 / 5 (5) Jul 13, 2011
@Eikka -- then dont buy one. But dont use economics to tell car makers what to make.


I am not, on both cases.

I'm merely pointing out that it's not nearly enough to have a battery last two-three hundred cycles. It might work for the lastest iPhone due to planned obsolescence, but electric cars shouldn't be even mentioned in the same article if they aren't talking a thousand cycles to start with.

The car makers can make whatever they think they can sell. There's always some doofus who will buy the electric car even though it won't actually make any difference for the next two or three decades to come. That's because it takes at least that long to change our current energy infrastructure in ways that would actually make the electric car pollute less than any other car. In the mean while, you're just wasting your money.
Eikka
3.2 / 5 (5) Jul 13, 2011
In fact, if you wanted to slash your CO2 output in half, rather than waiting for the pie in the sky electrics, you should get a LPG car.

It even has the potential to run on biomethane, which would be almost totally carbon neutral, unlike electricity.

And no. When you buy "green energy" from your power co. you are actually getting the output of the nearest coal plant. You turn the lights on, they turn the heat up.
Eikka
3 / 5 (5) Jul 13, 2011

But this is still greater than 4 times the capacity of current batteries. You would have to degrade the battery more than 80% just to reach what current batteries provide (on the order of 150 ma/g).


You think they would put four times as much capacity in the car, when the main problem is that the current batteries weight ten times too much, cost ten times too much and take ten times too much space as they are?

Gasoline gives you the energy equivalent of 2.8 kWh per kilogram at the engine output. Reliable lithium batteries give you 0.1 kWh per kilogram. You need to do more than 4x to get the practical problems solved.
SemiNerd
not rated yet Jul 13, 2011
Eikka - so what your saying is that the energy equivalent of gasoline is 28x that of current day batteries? I find that figure dubious, but I am unwilling to look it up. That means that either the batteries make up for that horrible difference somewhere, or that cars using batteries couldn't really run at all. Since we have cars right now with (in round numbers) 1/8 the range of gasoline equivalents, I cant make your numbers work.
DamienS
5 / 5 (1) Jul 13, 2011
Since we have cars right now with (in round numbers) 1/8 the range of gasoline equivalents, I cant make your numbers work.

I'm guessing that with an IC car there are all kinds of mechanical and parasitic losses (belts, drivetrain, etc) which would reduce the ideal 28x multiplier, To what, I don't know...
RealScience
3.7 / 5 (3) Jul 13, 2011
SemiNerd - The energy density of gasoline is ~28x that of current batteries. However the electric motor uses the energy ~3x or 4x more efficiently, which reduces the energy-to-the-wheel to a 'mere' ~8x. The Tesla roadster overcomes this by providing a lot more battery weight than a tank of gas weighs.

Eikka - The battery is not the bulk of the car price. Even in the battery-rich Tesla roadster, the battery pack is only 1/3 of the cost. For a commuter-range car the battery would currently be about 20% of the car cost. However I agree that below 1000 cycles the economics degrade fast unless the cost drops more.

yoatmon - yeast produce alcohol to poison competitors and lock up the nutrients for themselves, and in a normal (in-the-wild) process fermenting fruit doesn't get high enough to hurt the yeast.
Humans just trick the yeast by denying them oxygen to stop the yeast from using their alcohol, and then rob the yeast of their hard-earned alcohol.
quasi44
not rated yet Jul 13, 2011
SemiNerd - The energy density of gasoline is ~28x that of current batteries. However the electric motor uses the energy ~3x or 4x more efficiently, which reduces the energy-to-the-wheel to a 'mere' ~8x. The Tesla roadster overcomes this by providing a lot more battery weight than a tank of gas weighs.

Eikka - The battery is not the bulk of the car price. Even in the battery-rich Tesla roadster, the battery pack is only 1/3 of the cost. For a commuter-range car the battery would currently be about 20% of the car cost. However I agree that below 1000 cycles the economics degrade fast unless the cost drops more.

Comparing a Tesla at current avg price of 109000 to the avg commuter gas powered car at 22000? And that just to get to a 200 mile range for the Tesla. If I'm not rich, what is the point of the comparison in the real sense? EPA has the Nissan Leaf at the equivalent of about 73mpg. That is the proper comparison vehicle, because we don't compare Ferrari's to Volkswagons
nickbish
not rated yet Jul 14, 2011
This development should be recognised for what it is, a significant step forward.

At the moment despite poor returns, deployment of solar PV panels is doubling every 2 years. If this continues in about 20-25 years we will have enough capacity to power everything.

Long before this, when the sun is shining brightly we will have a local energy surplus which could be used to make hydrogen to power cars and planes.

If you are going to compare liquid fuel and battery cars you should throw this one into the thinking too. It is arguably a far greener solution.
Duude
1 / 5 (1) Jul 14, 2011
The number of cycles needed in the life of the battery is totally dependent upon the full capacity of the battery after each recharge. If we can only get 50 miles between charges, we're going to need 4000 cycles. If we can get 300 miles, maybe 700 cycles.
Eikka
2.3 / 5 (3) Jul 14, 2011
S
Eikka - The battery is not the bulk of the car price. Even in the battery-rich Tesla roadster, the battery pack is only 1/3 of the cost. For a commuter-range car the battery would currently be about 20% of the car cost. However I agree that below 1000 cycles the economics degrade fast unless the cost drops more.


The Roadster isn't comparable to a regular vehicle. You don't compare $100k "sports cars" to $20k commuters. Of course the relative cost of the battery goes down when you put it in an already expensive car.

The battery in the i-MiEV costs $22 000. About as much as an entire new car.
Eikka
1 / 5 (1) Jul 14, 2011
The number of cycles needed in the life of the battery is totally dependent upon the full capacity of the battery after each recharge. If we can only get 50 miles between charges, we're going to need 4000 cycles. If we can get 300 miles, maybe 700 cycles.


Don't forget to account for the wear on the battery.

If you still want to get 50 miles after n-cycles, you need to start with a battery that gets you about 75 miles at start.

After the battery has fallen below 2/3rds of its capacity, it usually starts to go worse a lot faster due to accumulaton of damage which increases the effect of wear, which is why they hold 2/3rds as the point where the battery is considered dead.
Eikka
1 / 5 (1) Jul 14, 2011
Eikka - so what your saying is that the energy equivalent of gasoline is 28x that of current day batteries? I find that figure dubious, but I am unwilling to look it up.


It's actually quite a lot worse.

Gasoline contains 8.76 kWh per litre, with a density of 0.78 kg/l which gives it 11.2 kWh per kilogram in chemical energy.

The gasoline engine outputs roughly 25% of that, but with hybrid technology it can be pushed up to 35%.

Lithium-ion batteries can go up to 0.2 kWh/kg but if you want reliability, that figure drops down to about .15 kWh/kg for the bare cells, and once you figure in the other requirements such as bus bars, frames and casings, cooling and insulation, you're looking at 0.1 kWh/kg for the whole battery system.

Batteries really are about 28...39x worse than gasoline in terms of practical energy density. They're really pathetic - only just good enough that we can now build some sort of electric cars that aren't simply a joke.
RealScience
not rated yet Jul 14, 2011
Quasi44:
I used Tesla because the price of a replacement battery is documented. If you have an actual figure for Leaf battery price as a percentage of the car's price, please contribute it to the discussion rather than tossing out a "1" rating.

In sports car everything, including the batteries, is premium performance, so the 33% battery cost to car cost ratio for Tesla is a tolerable starting point. The main difference is range, with the Tesla having >2x the range a typical commuter vehicle will. Adjusting for an 80-mile range would put the battery cost at around 15%. However in a low-cost car the battery would be proportionately more, so I estimated 20% instead of 15%.

Eikka:
Thank you for the i-MiEV info. $22K MiEV battery price is at June 2009 launch (Goldman Sachs report). Mistubihi in July 2011 says battery cost has been more than halved since introduction, so <$10 now. At July 2011 price of $32K for the car, thats <30%. Probably still >20%, but nowhere near 100%.
RealScience
5 / 5 (1) Jul 14, 2011
Quasi44:
I used Tesla because the price of a replacement battery is documented. If you have an actual figure for Leaf battery price as a percentage of car price, please contribute it to the discussion rather than tossing out a 1 rating.

In sports car everything, including the batteries, is premium performance, so the 33% battery cost to car cost ratio for Tesla is a not-reasonable starting point. The main difference is range, with the Tesla having >2x the range a typical commuter vehicle will. Adjusting for an 80-mile range would put the battery cost at around 15%. However in a low-cost car the battery would be proportionately more, so I estimated 20% instead of 15%.

Eikka:
Thank you for the i-MiEV info. $22K MiEV battery price is as of June 2009 launch (Goldman Sachs report). Mistubihi in July 2011 says battery cost has been more than halved since introduction, so <$10K now. At July 2011 price of $32K for the car, thats <30%. Probably >20%, but nowhere near 100%.
J-n
5 / 5 (1) Jul 14, 2011
I wonder how often you have to get your oil changed in an electirc car -bet it's less than gas

I wonder how often you have to get your breaks changed in an electric car -bet it's less than gas

Fewer moving parts means to me less maintenance overall. An electric car is a much simpler, easy to understand thing than an internal combustion engine. EVs are not much different than Electric Wheelchairs, and even a kid can service those.

From what i've been able to find, the Leaf and Volt have 8 year 100k mile warranties on their batteries.

luongxuanduy
not rated yet Jul 14, 2011
You guys are talking about cars but it's the least concern with environment. Still near 90% of using energy is from fossil fuel. And that cars is not the worst problem. When You buy a car, you also help to burn some oil for making the car and produce some carbon dioxide from manufacturing. If you buy a car about 1 ton weight. The energy used to make it will be about 20000 MJ. It is equilavent with 5000l gasonline. And with 5000l gasonline your car can run for about 50000km. It means that when you buy a car, your car has already ran about more than 1 round of the world. The meat industry produce even more carbon dioxide than the running cars. Still a lot of meat are wasted, you know that. All of that I mean we are wasting a lot of energy to make thing rather than running it. 
luongxuanduy
not rated yet Jul 14, 2011
The fossil fuel is running out soon. Some people say there is plenty more fuel under the ocean that we don't know yet. But let me say we human are just like a mostique sucking blood from our mother earth. Some ways the mostique will bring diseases for her. And even if the mostique garuantee not to bring diseases we are sucking an amount of blood that she cannot produce at a time. And sooner later she will run out of blood and our race will die. Worse, we kill all lifeform on earth.
This is the big step to make a new life not depend on fossil fuel. And this is our future, not oil or coal we have suck from the earth for a long time.
CapitalismPrevails
1 / 5 (2) Jul 15, 2011
The fossil fuel is running out soon. Some people say there is plenty more fuel under the ocean that we don't know yet. But let me say we human are just like a mostique sucking blood from our mother earth. Some ways the mostique will bring diseases for her. And even if the mostique garuantee not to bring diseases we are sucking an amount of blood that she cannot produce at a time. And sooner later she will run out of blood and our race will die. Worse, we kill all lifeform on earth.
This is the big step to make a new life not depend on fossil fuel. And this is our future, not oil or coal we have suck from the earth for a long time.


Not really. I've got five words for you. Coal, Tar sands, natural gas. Everybody and there dog knows there's plethora of coal in the world. First 2 can liquefy into oil and w/ recent breakthroughs in microwaves and solvents, the cost shouldn't be a problem. The real problem is the facilities to do these things aren't being built fast enough.
Spenders
5 / 5 (2) Jul 15, 2011
If we are talking about batteries,application will have to
be considered. There are 6 ton lead asid batteries working daily under ground. Golf carts, wheel chairs, fork lifts and the battery in that gasoline car are vertally all lead asid.
Few mobil robots have cords or generators. Scores of devices
are waiting for a better battery. Many of us will be thank full for any improvement or atempt at a better battery. Win or loose we thank you for trying.
Eikka
1 / 5 (1) Jul 17, 2011

In sports car everything, including the batteries, is premium performance, so the 33% battery cost to car cost ratio for Tesla is a not-reasonable starting point. The main difference is range, with the Tesla having >2x the range a typical commuter vehicle will.


You forget that the Roadster is a smaller car than a typical hatchback, fitted with special tires and suspensions. It actually uses 3/4 the energy a typical commuter vehicle would. Tests on the i-MiEV point out that it uses about 20-21 kWh per 100km in real world traffic, which is 330 Wh/mi as compared to the Tesla Roadster's 250 Wh/mi.

Another problem is that Tesla's batteries are made of standard laptop cells. They cost less than things like LiFEPO4 cells which would last longer, but would offer lower energy density. It isn't built to the same requirements as you'd expect form a commuter vehicle.

And some would argue that the Roadster just looks like a sports car, for PR purposes, but isn't really one.
Eikka
1 / 5 (1) Jul 17, 2011
To illustrate the point, the Roadster is guaranteed to 100,000 mi for a 53 kWh battery pack. The Leaf etc. promise to do the same with a 16-24 kWh battery pack.

The Roadster battery has to do less than half the cycles, because it's big, which means it can be made of considerably cheaper cells. Unfortunately having a battery pack that large is infeasible in a commuter car, because it would cost and weigh too much.
Eikka
1 / 5 (1) Jul 17, 2011
I wonder how often you have to get your oil changed in an electirc car -bet it's less than gas


Beats me, but I would have the brakes and fluids checked yearly anyways, simply because of road safety. Especially the brakes, which don't get used so much and tend to rust.

Much of the same mechanisms are still there, including the water pumps, coolers, heaters, hydraulic brake assists etc.


From what i've been able to find, the Leaf and Volt have 8 year 100k mile warranties on their batteries.


The Volt is an interesting case. They have 16 kWh in the battery, but will only use 9 kWh so the battery can wear out 7 kWh before it shows. That means again, that they can use cheaper batteries.
RealScience
5 / 5 (1) Jul 17, 2011
Eikka - 0-60 mph in 3.9 seconds says sports car to me.
Following your i-MiEV data produced more relevant results of <30% (making the Roadster-based ~20% moot), and this is still <<80%.
However your answer was better than mine on the energy density difference - I applied the efficiencies to your ~28x number not realizing that you had already included them.

But an EV can also devote more mass to batteries because EV electric motors have a higher power density than internal combustion engines. For example the Roadster 248 HP motor (data available) is only 70 lbs, so the battery motor is 1062 lbs, which is not far from a 250 hp gasoline engine plus a tank of gas.
This helps a short-range EV a lot, and is the other major factor in bringing EV range to ~1/8 the range of gasoline equivalents (as SemiNerd put it).

If the cost doesn't quadruple, the article's 4x energy density would thus become practical at several hundred cycles (although I hope for your 1000 cycles).
Eikka
1 / 5 (1) Jul 18, 2011
Eikka - 0-60 mph in 3.9 seconds says sports car to me.


Nope. That's just the gimmick. I can make a Lada Niva go 0-60 in under four seconds with electric motors, and that doesn't make it a sports car because it isn't built to match the purpose otherwise. It just goes fast.

The Roadster's steering, suspension, drive geometry is built for economy, not for sport. Let's pop some proper fat tires underneath and see how far it goes?
Eikka
2 / 5 (3) Jul 18, 2011

But an EV can also devote more mass to batteries because EV electric motors have a higher power density than internal combustion engines. For example the Roadster 248 HP motor...


The Roadster's motor is a high-speed permanent magnet motor that revs up to 14 krpm, which is why it is so light, and expensive. Ordinary commuter cars can't afford that.

And you can't compare 250 HP engines to these new electrics. You're talking about a 1.6 litre four-banger with 100-150 HP instead, which weighs next to nothing. That's the class of cars we're talking about with the Leaf and i-MiEV and the like.

Regarding the price, the 2010 May estimates for the Nissan Leaf was $18,000 for the battery, $32,500 for the entire car. For the price of the battery alone, you could buy an entire Nissan Versa. In fact, the price of a new Versa is pretty much what is left over after you subtract the battery out of the Leaf.

The price of electrics seems to be basic car plus a battery.
Eikka
2.3 / 5 (3) Jul 18, 2011
bringing EV range to ~1/8 the range of gasoline equivalents (as SemiNerd put it).


My car has a 40 litre fuel tank. It goes about 600 km.
The Nissan Leaf actually goes about 73 miles according to the EPA. That's about 1/6 to a typical 20 year old Japanese sedan.

If I had a new hybrid car, or a diesel car, it would go 1000 km on the same tank, leaving the Leaf behind at 1/10th the distance.

But I fail to see the point of comparing ranges, since I can always pop in for a refill, while the Leaf cannot. Mine is effectively infinite, or limited to how long it takes for my butt to fall asleep.
Eikka
1 / 5 (1) Jul 18, 2011
And as for the price difference, you got cars like Nissan Leaf and Versa, one of which is a battery's worth more expensive but otherwise similiar. Which one is cheaper to drive?

For $18,000 and 100,000 miles, you get 18 cents a mile, plus the cost of electricity which we presume to be 328 Wh/mi (EPA), at 11 c/kWh which equals $3,508.

So, 21.5 cents a mile, and at the end of 100,000 miles you're left with a car with no resale value. You might as well count it all and say it's 36 cents a mile.

Meanwhile the gasoline car costs $15,000 and lasts for 200,000 miles with ease. Let's say you add $5000 for maintenance over the life of it. That's 10 cents a mile. You can spend 26 cents a mile on gasoline and still come up even.

26 cents buys you 0.0727 gallons at the current price point, which means a gasoline car will only have to do 14 miles to the gallon to be cheaper. Any modern small car will do at least 30-40 mpg.

Gasoline prices can double and it still makes no sense to buy electric
tahrey
5 / 5 (1) Jul 18, 2011
Let's attack this with more real-world figures.

My car has an approx 60-litre tank, weighing (if we assume it's roughly 2x that of a 45 litre alloy racing type) 15-20kg empty, and approx 60kg full (with 720g/L density petroleum). Using 50~55 of those litres, I can get better than a 400 mile range - this with it being an old car, with fairly short gearing and an engine that's arguably oversized... and I drive pretty hard.

At 400 miles for 55 litres, that's almost exactly 100g of fuel per mile for a slightly disappointing 33mpg UK (generally i'm mid-high 30s).

Tesla battery pack weighs a full 450kg, with a supposed EPA combined range of 227 miles (however, similar tests say my car gets 39.8mpg, and that's full to empty, aka 60 litres for me... so, correcting with the same 82.4% and 55/60 "real world" factors = 172 miles). Or in other words, 2616g per mile. 26x more.

I did not work any of this out beforehand or fudge the figures to make them fit that close, its just how the cards fell
tahrey
not rated yet Jul 18, 2011
Also, this car? It's coming up on 100,000 miles (160,000 km), having passed the 150 mega-metre mark some time ago - never mind 100,000km. I bought it at about 115kkm, for the equivalent of about $1600 - the first owners having got their money's worth of the $16~20000 purchase price. It still drives beautifully, the engine is a work of art in terms of solidity and maintained performance & reliability. All I've had to do with it are occasional oil/filter changes ($50 or so, DIY) and some ignition components ($100 all-in).

The original transmission, admittedly, was made out of glass, and so I spent about $500 overall replacing that about 10kkm ago - but it was still driveable despite missing a gear & having an iffy clutch. But that's still not a HUGE total expense. Other things like brakes, tyres, mounting bushes aren't a huge drain overall, & would be common to electrics.

I'd happily keep it going to 200kkm - IF I wasn't just planning to replace it for ~$2000 at the next serious fault!
Eikka
1 / 5 (1) Jul 18, 2011
Of course, it makes even less sense to drive electric if you live in places that use wind and solar and shun nuclear power, like in Germany where the prices are triple to that of the US average.

So you'd pay 10 cents a mile for the electricity alone.

This is why the current battery technology just doesn't cut it. It has to be durable and cheap - otherwise people will just choose the more sensible option that costs less and gives them more utility than just 1/8th of ordinary car.

It isn't even saving the environment in any way until we actually overhaul our energy infrastructure, which won't happen for decades, which means every electric car bought until then is just a net loss on all counts.
tahrey
5 / 5 (1) Jul 18, 2011
((Though I suppose - how much am I spending on the fuel? It's about $2 per litre right now. So, about $110 to fill up, vs maybe $5 max for an electric. If I will ultimately have kept it for about 30,000 miles, at 400 miles per tank, that's 75 fill ups, or $8250 over 3 years. Hmm. Is that enough of a difference to make an electric with comparable range/performance a sensible choice, if I arrange suitable financing for the purchase (and a savings trust fund for battery replacement) ??? Not well versed enough in THOSE maths to say either way, but right now, the speed and convenience is worth whatever small extra overall outlay I'm losing out by. If I was driving a turbodiesel of similar performance, and moderating my speed just slightly, I could halve the fuel costs. Instead, for city or shorter rural trips, I have a small motorcycle that gets 3x my car's economy, and cost less than $1500 - electric cars certainly can't match THAT value, yet.)
Eikka
1 / 5 (1) Jul 18, 2011

If the cost doesn't quadruple, the article's 4x energy density would thus become practical at several hundred cycles (although I hope for your 1000 cycles).


The car manufacturer's are going to put the least amount of batteries possible in the car, because the car itself sans the batteries already costs as much as an ordinary car.

So the total energy capacity in the car will remain the same. They are not going to put 4x the batteries in the car, which means the batteries will have to put up with at least a thousand cycles anyways to make sense.

If you put in a battery that does only 500 cycles, like an ordinary laptop battery, then it's dead at 50,000 miles. Even if the new battery manages to halve the price per kWh of storage, the total range is also halved and so the net result is the same.
Eikka
1.7 / 5 (3) Jul 18, 2011
$8250 over 3 years. Hmm. Is that enough of a difference to make an electric with comparable range/performance a sensible choice


Except $8250 isn't enough to buy you half a battery for a comparable performance.

At the cheapest end at $600/kWh, you could get about 13 kWh or 40 miles of range with that sort of money, which would shrink to about 25 miles after 3-4 years, after which you'd need a replacement. Your average range over about 500 cycles is 32 miles, which gives you a total of 16,250 miles.

That puts the price at 49 cents a mile.

You'd have to be stark raving mad to even consider it.
antialias_physorg
5 / 5 (1) Jul 18, 2011
Of course, it makes even less sense to drive electric if you live in places that use wind and solar and shun nuclear power, like in Germany where the prices are triple to that of the US average.

It makes as much sense here (in germany) as anywhere else, since our gas prices are also more than double those in the US. Additionally distances are a lot shorter due to a very high population density (80 million people living in an area of 350000km^2 - which is about half the size of Texas).
So especialy for commuters electric cars - even those with extremely short ranges like 40km - make a lot of sense.

However, the number of recharge cycles is the crucial factor here since people will likely not recharge when the batteries are empty but simply every day when they get home (or to work if the have the ability to recharge there)
Eikka
1 / 5 (1) Jul 18, 2011

However, the number of recharge cycles is the crucial factor here since people will likely not recharge when the batteries are empty but simply every day when they get home (or to work if the have the ability to recharge there)


That is where I can ease your pain, because lithium batteries don't count the number of recharges, just the amount of charge that has gone through the battery which is contrasted to the capacity of the battery to derive one "cycle".

Lithium batteries are also never overcharged like NiCD or NiMH batteries typically are, because they would simply catch fire.
Eikka
1 / 5 (1) Jul 18, 2011

It makes as much sense here (in germany) as anywhere else, since our gas prices are also more than double those in the US.


What is your gasoline price? 1.50 a litre?

For an ordinary car that does 7 litres to the 100, that would be 10.5 c/km.

Battery price of $18,000 translates to 12,0000 for 160,000 kilometers. The electricity cost, which we assume to be 200 Wh/km and 22 c/kWh gives us 7040 and a total of 12 c/km.

Then we do the cost analysis for the car itself, which start at the same price but the electric car only goes half the distance before it's worthless... etc. etc. you get the point.

It's still more expensive to drive electric, and you get less utility for it.
Eikka
2 / 5 (3) Jul 18, 2011
Though of course, if you don't actually drive all that much, getting to 100,000 miles or 160.000 kilometers may be impossible to achieve.

Because the battery is only going to last 6-8 calendar years (3-4 cheap ones). That would mean you have to do 39 miles each and every day or you won't get all of the miles out of the battery before it wears itself out just by age.

That's another factor to consider.
antialias_physorg
5 / 5 (1) Jul 18, 2011
What is your gasoline price? 1.50 a litre?

A few weeks ago I paid 1,79 Euros per liter (which would be about 4,83 $/gal.)
That was peak, though. Today we're back to 'normal' (about 1,62 Euros per liter which is about 4.37 $/gal.)

Then we do the cost analysis for the car itself, which start at the same price but the electric car only goes half the distance before it's worthless...

Depends on the model you use. Some car manufacturers are planning to rent out the battery pack - replacing it when it's no longer working. Then there's the ecological aspect to consider (I don't really care if the car is cheaper than my gasoline powered one. If it makes it more likley that alternative power stations will be built I'm willing to shell out afew more bucks)

That would mean you have to do 39 miles each and every day

That's about the size of my commute, anyways. I have an electric car on my list as 'next big thing to buy'. Just waiting for a sensible model to come out.
RealScience
not rated yet Jul 18, 2011
antialias - Eu 1 = US$1.40, and US gallon is 3.785 litres, so Eu 1,62/litre is $8.59/gallon.
tahrey - nice to see real world 26x so closely match the 28x from theory.

Eikka - Ford 1.6l Ecoboost is 251 lbs. Ford F150 HEV electric is 2.92 HP/lb, so 100-150 HP would be ~50 lbs. The 200 lbs of difference is very significant compared to 10-gallon tank = ~60lbs of gasoline. Transmission is also simpler and lighter, 1 speed for EV versus 5-6 speed for IC.
Taking engine and transmission weight into account, EV range per fuel motor transission mass for a commuter-range car is ~8x less than IC, which matches SemiNerd's 1/8 the range.
And battery replacement in 10 year will have dropped 2x-4x, so EV resale value > $0.
My car is at 320k km, so I agree on durability of IC. I also travel more than 100 km regularly, so EV range rules it out for me.
An EV is not for you or for me, but we aren't everyone. For someone with a perfect-length commute and high gas prices it is close to even already.
antialias_physorg
not rated yet Jul 18, 2011
antialias - Eu 1 = US$1.40, and US gallon is 3.785 litres, so Eu 1,62/litre is $8.59/gallon.

Oops. Damn you Windows Calculator *shakes fist*
hb_
5 / 5 (1) Jul 19, 2011
It is a great pity that the researchers did not continue to discharge the battery for more than 150 cycles. If the curve would have remained at a similar decline for 1000 cycles, then I would have been excited. Also, a cost estimate of the electrode would have been relevant.
hb_
not rated yet Jul 19, 2011
To all of you discussing number of cycles: shallow discharge cycles typically wear a lot less on the battery than deep discharge cycles, even when one has discharged the same number of "net" discharge cycles. A car that is used for short trips may get a lot miles (up to 4 times!) to the battery than a long haul vehicle..

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