Sulfur Polymers Could Enable Long-Lasting, High-Capacity Batteries

MTorrice writes "Lithium-sulfur batteries promise to store four to five times as much energy as today's best lithium-ion batteries. But their short lifetimes have stood in the way of their commercialization. Now researchers demonstrate that a sulfur-based polymer could be the solution for lightweight, inexpensive batteries that store large amounts of energy. Battery electrodes made from the material have one of the highest energy-storage capacities ever reported" Litihium Ion batteries should maintain capacity for about 1000 cycles, whereas Lithium-sulfur batteries traditionally went kaput after about 100. But it looks like they are getting pretty close to something feasible, from the article: "The best performing copolymer consisted of 90% sulfur by mass. Batteries using this copolymer had an initial storage capacity of 1,225 mAh per gram of material. After 100 charge-discharge cycles, the capacity dropped to 1,005 mAh/g, and after 500 cycles it fell to about 635 mAh/g. In comparison, a lithium-ion battery typically starts out with a storage capacity of 200 mAh/g but maintains it for the life of the battery, Pyun says."

Comments

Still a ways to go

[mykepredko]

I saw an interesting graph in Aviation Week some time ago about the energy density of batteries versus the same mass of hydrocarbon fuel. The article was in relation to the idea of creating (plug-in) hybrid airliners.

The batteries used in the 787 store four orders of magnitude less energy than the equivalent mass of jet fuel.

I'm mentioning this because it looks like these batteries would bring the difference up to three orders of magnitude.

Still a ways to go before batteries can compete against hydrocarbon/fossil fuels.

myke

Re:Still a ways to go

[Anonymous Coward]

I saw an interesting graph in Aviation Week some time ago about the energy density of batteries versus the same mass of hydrocarbon fuel. The article was in relation to the idea of creating (plug-in) hybrid airliners.

The batteries used in the 787 store four orders of magnitude less energy than the equivalent mass of jet fuel.

I'm mentioning this because it looks like these batteries would bring the difference up to three orders of magnitude.

Still a ways to go before batteries can compete against hydrocarbon/fossil fuels.

myke

Based on a back-of-the-envelope calculation, that number seems wrong. Could you have misread Aviation Week?

Jet fuel has an energy density close to 45 MJ/kg. A lithium-ion battery has an energy density of (approximately) 150 Wh/kg, which is 540 KJ/kg. That's about 1.2% of the energy density of the jet fuel, which is more like 2 orders of magnitude, not 4.

4 orders of magnitude below jet fuel is more in the range of supercapacitors than batteries.

Re:Still a ways to go

[Gravis Zero]

I saw an interesting graph in Aviation Week some time ago about the energy density of batteries versus the same mass of hydrocarbon fuel.

the problem with that comparison is that it considers that the engines and motors will have the same efficiency which is not true at all. hypothetically, if your motor is four times as efficient as an engine but your battery has only half the energy storage of the engine's fuel, the motor is still going to run twice as long as the engine.

it's systems, not components that matter.

Re:Still a ways to go

[haruchai]

Have a look at molten-air batteries - http://phys.org/news/2013-09-m...

With an iron anode, the energy content is roughly the same as petrol - ~ 10000 watt-hours per liter. But the most you can hope for an a straight gasoline ICE is about 30%, whereas a battery is likely to be 2.5x as efficient. A carbon anode, which is more likely to be developed is nearly double that of iron so if this tech pans out and it looks to be quite affordable, it'll kill the demand for fossil fuels in almost all light-duty vehicles and make it possible to have hybrid long-haul trucks.

Many exciting developments in batteries

[cold fjord]

There have been a lot of materials developments in battery designs over the last year or two. Some of them are providing 10x or better power storage with varying lifetimes. I'm really looking forward to seeing some of this make it into production. It would be better if they could couple improved batteries with some minimalist portable computer designs. People comfortable with Unix would get by with something with much lower specks than is typical today (assuming a minimalist interface), and the battery could probably last for hundreds of hours. I wouldn't mind that a bit.

Some of the other battery tech could be very useful for emergency situations.

This might be one to keep an eye on: A Battery That Runs On Sugar Could Soon Be Powering Your Electronics

Re:Many exciting developments in batteries

[bluefoxlucid]

The varying lifetime is less important than people think. If you have a 300 mile range electric vehicle battery that can handle 1,000 charges and you replace it with a 3,000 mile range battery that can handle 100 charges, you can still go 300,000 miles. It just turns out you can go 3000 miles in one trip.

Still a ways to go...until we get where?

[Immerman]

First off that's a bald-faced lie: Energy density of:
Gasoline: ~46 MJ/kg
Lithium-ion battery: 0.36-0.875 MJ/kg (1/127 - 1/52 times gasoline)
Lead-acid battery: 0.17 MJ/kg (1/270 times gasoline)

So even lead acid batteries are only two orders of magnitude less energy dense than gasoline.

As for the suitability in vehicles - that depends entirely on the application. For aircraft the energy density per both unit mass and unit volume is very important, so I doubt we'll see electric jetliners any time soon. For automobiles and other short-range land vehicles on the other hand batteries are already adequate for a lot of applications, and cost is the primary limiting factor. A measly 5x increase in capacity could extend the range of the 85kWh Tesla Model S from 265 miles to 1325 miles - still not enough for a long road trip on a single charge, but a lot further than most people care to drive in a single day, and overnight charging in hotel parking lots could be extremely convenient.

And for stationary applications the energy density per dollar is the only particularly important metric, and other battery technologies are probably more applicable to such applications.

Re:Still a ways to go...until we get where?

[strack]

Don't forget that gasoline engines typically turn only about 20-30% of the chemical energy into mechanical energy, whereas electric motors are about 90%. And you get rid of a heavy gasoline engine.

Re:Still a ways to go...until we get where?

[Anonymous Coward]

Energy density is more important here... not specific energy.

the Tesla model S will be using new Panasonic batteries, quoted at 735wh/L, or 2.65 MJ/Liter
Gasoline is ~36 MJ/Liter

so that's an order of magnitude difference.

BUT

Electric cars are 3 to 4 times more efficient at taking electricity and converting it to forward motion that an internal combustion engine. This is basically due to the fact that 1) electric motors are about 90% efficient, with IC about 30%, and electric cars can get energy back when braking.

So... instead of 36/2.65 = `3.6 times better for gas it's more like

36/(3*2.65) = 4.52 times better for gas

So yes... we are almost there.

Re:Still a ways to go...until we get where?

[Anonymous Coward]

that was supposed to be

  of 36/2.65 = 13.6

little typo there...

Re:Still a ways to go...until we get where?

[skids]

Ah, so we're throwing the aircraft through the air with the power of pixie dust and unicorn farts.

Aircraft engines are a red herring here, since the target of these batteries is automotive. But for what it's worth, jet turbines also only convert a portion of the fuel's chemical energy into kinetic energy. Combustion efficiency is 90%+, but cycle efficiency in turbojet and similar is nearer to 30%.

For automotive, in contrast to ICE+drivetrain at about 25%, shows average values of about 36% and this is in part due to the efficiency of electric drive trains and in part due to the efficiency of the fuel cell process, but of course externals in the fuel production.

Batteries win hands down against both of those options for efficiency, with externals excluded, so the same amount of energy in a battery is worth more miles than the equivalent amount of chemically stored energy in gasoline once it is onboard.

Re:Still a ways to go...until we get where?

[TubeSteak]

I misspoke by using the words "self discharge."

Lithium Ion batteries lose a fixed amount of capacity every year, regardless of usage.
The only way to slow this process is refrigeration, which slows the chemical reaction that reduces capacity.

Even howstuffworks mentions it.

Re:Still a ways to go...until we get where?

[strack]

well, you attached your name to some sarcastic pablum, and it still didnt make it worthwhile to say. But hey, at least now you know 1 more thing than you did before. have a gold star.

Re:Still a ways to go...until we get where?

[beanpoppa]

At the risk of sounding 'Applely', Think different. Right now, I have to stop to 'recharge' my ICE car for 5-10 minutes, once a week. That's, on average, about 6 hours a year I wait for my car to 'recharge'. If I had an electric car, I would be plugging it in every night. For most weeks of my commuting year, it would eliminate any time waiting at the gas pump.

Re:Quick Discharge batteries?

[skids]

This. And the goal of this line of battery research isn't to provide "blasts of current" as we've already got that covered with ultracaps and Li-ion for burst needs. The goal is to provide slightly more current than is required to propel a vehical at highway speeds, and do so for a long time between charges, and to do so for many charges.

Try beating an airliner turbine

[dutchwhizzman]

Airliner turbines are extremely efficient at transforming energy into air movement. Because of expanding gasses in the burn process inside the turbine, roughly 9 times the amount of air being used in the burn process is being "propelled" on the outside of the engine. The mix of these at the back of the engine is also very carefully engineered. This results in an extremely efficient transformation, compared to a combustion engine as used in cars.
Getting the same amount of efficiency from an electrically driven turbine will be a challenge. Getting the same or better amount of efficiency from the system, including the primary generation of electricity, transporting it, battery losses and converting it in the electrical turbine doesn't sound very feasible at all. It's systems that matter, not components, right?

mAh is only half the equation

[imsabbel]

What matters, in the end, is the amount of energy a battery can store.

With Lithium Sulfur cells, the voltage is a little more than half as high as for Lithium Ion batteries, so the initial advantage is not as large as it might seem from the mAh numbers.

Re:Forget cars

[Neil Boekend]

You recycle batteries. The elements are not wasted, usually they lost their specific shape or a not intended molecule is being formed once in a while, and that molecule does not release electric energy. All these things are reversible.
In fact, never ever throw a battery in a landfill. Most are quite bad for the environment when not recycled properly.

Re:Forget cars

[Joce640k]

I'm not looking forward to garbage lots filled to the sky with used batteries.

Is it as bad is the air being filled to the sky with CO2?

Re:could and should and all that

[Required Snark]

First, you have to prove that you deserve a flying car.

Then you have to prove that you can be trusted to dive/pilot a flying car.

Given how the vast majority of people drive, almost no one passes the second test.

I'm not claiming that I do either. I also know that I should not ride a motorcycle because I don't have the right kind of attention for it.

Dat envelope

[strack]

Lets see what the range on a typical light aircraft would be if you ripped out the full fuel tanks and gasoline engine and stuffed it with a equivalent power electric engine and these new batteries to the same weight. So it says it will store 4-5 times as much energy as todays best lithium-ion batteries. the best li-ion today is lithium cobalt, at about 165 wh/kg. So x4 of that is 660 wh/kg.

now, lets take a light plane for which I can find enough info to do this with, the jabiru j160D ok. so the fuel in it weighs (135L * 0.72kg/L) = 97.2kg. Now, the engine in it, the Jabiru 2200cc Aircraft Engine, weighs 62.8kg, and has a max power output of 60kw, and cruises at 75% power, so lets assume 50kw cruise power to account for takeoff and landing. So in total, engine and fuel weight 97.2 + 62.8 = 160kg

so lets rip that 160kg out and replace it with a EMRAX228 Brushless AC electric Motor with a 100kw power output and weighing in at 11.9kg, leaving us 148.1 kg worth of batteries, with a energy storage capacity of 148.1 * 0.66 = 97.746 kwh. so, at the cruise speed of 100knots = 185.2km/h, your looking at a range of (97.746kwh / 50kw) * 185.2km/h = 362km in about 2 hours.

The gasoline version can fly at the same speed for 8.5 hours. So, sure, the range is a quarter of the gasoline one, but you could ditch a passenger, chuck another 100kg of batteries in there and get that up to about 3.5 hours and 630km of range. Pretty damn good for a few dollars of electricity, negligible maintainence costs on a electric engine vs gasoline engine. sure as hell beats the $100+ youll pay for fuel alone for that same 3.5 hour trip.