Batteries improved by 10x

[Ender]

linka

Stanford researchers have found a way to use silicon nanowires to reinvent the rechargeable lithium-ion batteries that power laptops, iPods, video cameras, cell phones, and countless other devices.

The new technology, developed through research led by Yi Cui, assistant professor of materials science and engineering, produces 10 times the amount of electricity of existing lithium-ion, known as Li-ion, batteries. A laptop that now runs on battery for two hours could operate for 20 hours, a boon to ocean-hopping business travelers.

"It's not a small improvement," Cui said. "It's a revolutionary development."

The breakthrough is described in a paper, "High-performance lithium battery anodes using silicon nanowires," published online Dec. 16 in Nature Nanotechnology, written by Cui, his graduate chemistry student Candace Chan and five others.

The greatly expanded storage capacity could make Li-ion batteries attractive to electric car manufacturers. Cui suggested that they could also be used in homes or offices to store electricity generated by rooftop solar panels.

"Given the mature infrastructure behind silicon, this new technology can be pushed to real life quickly," Cui said.

The electrical storage capacity of a Li-ion battery is limited by how much lithium can be held in the battery's anode, which is typically made of carbon. Silicon has a much higher capacity than carbon, but also has a drawback.

Silicon placed in a battery swells as it absorbs positively charged lithium atoms during charging, then shrinks during use (i.e., when playing your iPod) as the lithium is drawn out of the silicon. This expand/shrink cycle typically causes the silicon (often in the form of particles or a thin film) to pulverize, degrading the performance of the battery.

Cui's battery gets around this problem with nanotechnology. The lithium is stored in a forest of tiny silicon nanowires, each with a diameter one-thousandth the thickness of a sheet of paper. The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture.

Research on silicon in batteries began three decades ago. Chan explained: "The people kind of gave up on it because the capacity wasn't high enough and the cycle life wasn't good enough. And it was just because of the shape they were using. It was just too big, and they couldn't undergo the volume changes."

Then, along came silicon nanowires. "We just kind of put them together," Chan said.

For their experiments, Chan grew the nanowires on a stainless steel substrate, providing an excellent electrical connection. "It was a fantastic moment when Candace told me it was working," Cui said.

Cui said that a patent application has been filed. He is considering formation of a company or an agreement with a battery manufacturer. Manufacturing the nanowire batteries would require "one or two different steps, but the process can certainly be scaled up," he added. "It's a well understood process."

Outstanding work.

[Singular Intellect]

I greatly look forward to seeing practical implementation soon then.

[Gil Hamilton]

Chemistry, bitches!

That's awesome. I can't wait until they polish the process and start making batteries.

[Zixinus]

Of course this shitter is going to be much more expensive to make. It will be worth it though, most likely will help with the dream of the electric car.

[Singular Intellect]

Of course this shitter is going to be much more expensive to make. It will be worth it though, most likely will help with the dream of the electric car.

If the price is ten fold, then technically it breaks even with it's gain for what we have now.

[Gil Hamilton]

If the price is ten fold, then technically it breaks even with it's gain for what we have now.

Costing ten fold now doesn't mean it will cost ten fold later. This should be vigorously pursued.

[Singular Intellect]

If the price is ten fold, then technically it breaks even with it's gain for what we have now.

Costing ten fold now doesn't mean it will cost ten fold later. This should be vigorously pursued.

I quite agree; I was merely pointing out how even ten times the price would justify the system, never minding the obvious reduction in price with mass production and establishment of the technology.

[Eulogy]

If the price is ten fold, then technically it breaks even with it's gain for what we have now.

Costing ten fold now doesn't mean it will cost ten fold later. This should be vigorously pursued.

I quite agree; I was merely pointing out how even ten times the price would justify the system, never minding the obvious reduction in price with mass production and establishment of the technology.

Besides, an electric vehicle with ten times the available power would have MUCH more endurance and solve one of the biggest problems it curently has. Thirding this.

[Jaepheth]

Besides, an electric vehicle with ten times the available power would have MUCH more endurance and solve one of the biggest problems it currently has. Thirding this.

I'm almost certain that 10x capacity =/= 10x power, but someone with better understanding of energy storage will have to verify this.

Though I also agree this needs to be pursued post haste.

[Steel]

Besides, an electric vehicle with ten times the available power would have MUCH more endurance and solve one of the biggest problems it currently has. Thirding this.

I'm almost certain that 10x capacity =/= 10x power, but someone with better understanding of energy storage will have to verify this.

Though I also agree this needs to be pursued post haste.

Well in a capactior the rate of discharge is proportional to the stored charge, so 10x the charce stored gives at that time, 10x the power.

This is however totally irrelevant to batteries in general. I think he just meant 10x the total stored energy.

[starslayer]

Okay, first up is the differences between capacitors and batteries, and then on to what this means for the new tech:

A basic capacitor consists of two plates separated by a dielectric. The charge on a capacitor is given by Q = CV, where C is the capacitance and V is the voltage between the plates. As Steel mentioned, the rate of discharge is proportional to how much charge is on the capacitor. This means that the current decays over time as the capacitor discharges, as does the voltage.

Now for batteries. Batteries provide emfs like capacitors, but they provide a relatively constant emf as they discharge. This is because a battery generates electricity through chemical reactions, not simply moving stored charge. As a result, batteries close to death can provide nearly as much current as when they were fully charged, just not for very long before they die.

All batteries have an internal resistance, so they do not deliver as much voltage as they could. The given voltage for a battery is the terminal voltage, i.e., the voltage after the internal resistance is taken into account. Anyways, this resistance increases as the battery is placed under a higher load, and as the battery discharges. So, 10x the capacity does not equal 10x the instantaneous current for the same amount of time as an old battery, due to this fact of increasing internal resistance. What's happening is that you reach a limit on how fast reactions can occur; I'm not sure what the current draw limit is on current Li-ion batteries.

As for why batteries die, there is only a finite supply of unreacted chemicals in the battery (duh). As this runs out, the battery's internal resistance increases (fewer conductive ions left), and thus the terminal voltage decreases. After a while, the battery can no longer provide its rated voltage, and it is "dead." It may still be able to provide enough power for other applications, however.

Upon some examination of the article, it appears current draw may not be improved at all. The lithium still must find its way onto the anode, and while the anode is more accommodating, it does not appear to let the lithium on faster, but rather just let more of it on in the first place. I could be wrong though. I'll have to read their paper on the stuff.

[Gil Hamilton]

In my opinion, it's not the amount discharged that is the issue. Even if the battery didn't discharge a single watt more than a normal battery, having 10 times the capacity and being fulling rechargeable would be a rather stunning improvement. It would make the power sources for BEVs a heck of alot lighter, for instance.

[Darth Holbytlan]

As for why batteries die, there is only a finite supply of unreacted chemicals in the battery (duh). As this runs out, the battery's internal resistance increases (fewer conductive ions left), and thus the terminal voltage decreases. After a while, the battery can no longer provide its rated voltage, and it is "dead."

That's why non-rechargeable batteries die. Rechargeable batteries like the ones described in the article reverse the reaction when charging and return to their original state. They die mostly due to ordinary wear-and-tear from repeated cycling.

Upon some examination of the article, it appears current draw may not be improved at all. The lithium still must find its way onto the anode, and while the anode is more accommodating, it does not appear to let the lithium on faster, but rather just let more of it on in the first place. I could be wrong though. I'll have to read their paper on the stuff.

Naturally it will depend on the details, but I think you are wrong here. One of the major effects of using nanowires is vastly increasing the surface area of the silicon that absorbs the lithium, and it's generally the surface area that determines how quickly the reaction happens.

Consider the major difference between a deep cycle lead-acid battery and a car battery: The former has thick lead plates with little surface area while the latter has multiple thin ones with more, allowing the latter to deliver the much greater current needed for starting a car. The trade-off is that it is also more fragile, damaged by deep discharges. Fully discharging a car battery will ruin it.

Something similar may happen here, where the battery has more capacity due to using silicon, but with a lower usable proportion thanks to the fragility of the nanowires. Reduced lifespan of the batteries is also a real possibility.

Accepting the article's claim that these batteries will be easy to manufacture, I would predict batteries of similar price to Li-ion but much greater power and capacity, although less than 10x in effective capacity. But the reduced lifespan would make them more expensive on a Joule-for-Joule basis. A car based on them may have more range and power, but would require battery replacements more frequently and thus a greater operating cost.

[Pu-239]

I'd be more excited about developments that increase the lifespan of the batteries rather than capacity. Biggest peeve w/ Li-Ions is they start losing capacity with age from the date of manufacture.

[Sea Skimmer]

I'd be more excited about developments that increase the lifespan of the batteries rather than capacity. Biggest peeve w/ Li-Ions is they start losing capacity with age from the date of manufacture.

Read the article. They specifically say this same technology will reduce battery degradation.

[Darth Holbytlan]

Read the article. They specifically say this same technology will reduce battery degradation.

Please quote the bit where they say this. I see nothing in the article suggesting that they will be more durable than current Li-ion batteries.

[Xon]

Your redaing comprehension sucks

The electrical storage capacity of a Li-ion battery is limited by how much lithium can be held in the battery's anode, which is typically made of carbon. Silicon has a much higher capacity than carbon, but also has a drawback.

Silicon placed in a battery swells as it absorbs positively charged lithium atoms during charging, then shrinks during use (i.e., when playing your iPod) as the lithium is drawn out of the silicon. This expand/shrink cycle typically causes the silicon (often in the form of particles or a thin film) to pulverize, degrading the performance of the battery.

Cui's battery gets around this problem with nanotechnology. The lithium is stored in a forest of tiny silicon nanowires, each with a diameter one-thousandth the thickness of a sheet of paper. The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture.

[Darth Holbytlan]

Your redaing comprehension sucks

The electrical storage capacity of a Li-ion battery is limited by how much lithium can be held in the battery's anode, which is typically made of carbon. Silicon has a much higher capacity than carbon, but also has a drawback.

Silicon placed in a battery swells as it absorbs positively charged lithium atoms during charging, then shrinks during use (i.e., when playing your iPod) as the lithium is drawn out of the silicon. This expand/shrink cycle typically causes the silicon (often in the form of particles or a thin film) to pulverize, degrading the performance of the battery.

Cui's battery gets around this problem with nanotechnology. The lithium is stored in a forest of tiny silicon nanowires, each with a diameter one-thousandth the thickness of a sheet of paper. The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture.

No, I'm afraid that's your reading comprehension that sucks (not to mention your typing). That says that they fixed problems with the silicon batteries that made them degenerate far too fast to be usable. It says nothing about them being better, or even as good as, standard Li-ion batteries, which is the real issue.

[Xon]

Transposing letters are common mistakes and easily doable with keyboards(typing speeds). Comprehension is more fundamental.

The article outright state that anodes using silicon (nano-wires or otherwise) can hold greater charge than using carbon. The anodes with nano-wires have the potential of the greater capacity of silicon anodes but without the massive decrease in cycle life.

[starslayer]

That's why non-rechargeable batteries die. Rechargeable batteries like the ones described in the article reverse the reaction when charging and return to their original state. They die mostly due to ordinary wear-and-tear from repeated cycling.

True. However, can't a rechargeable battery be declared "dead" before it is recharged? Just because you can resurrect something doesn't mean it isn't dead.

Naturally it will depend on the details, but I think you are wrong here. One of the major effects of using nanowires is vastly increasing the surface area of the silicon that absorbs the lithium, and it's generally the surface area that determines how quickly the reaction happens. <and snip the rest>

True, although the point of the nanowires was that they weren't fragile like the original silicon block anodes. Therefore, I would think that although the surface area and thus reaction rate is increased, they have also managed to increase the anode's durability, thus probably precluding heavy damage from a deep discharge.

[Wyrm]

True. However, can't a rechargeable battery be declared "dead" before it is recharged? Just because you can resurrect something doesn't mean it isn't dead.

We (that is me and DH) usually say "drained". 'Dead' connotes more finality.

[starslayer]

We (that is me and DH) usually say "drained". 'Dead' connotes more finality.

Ah, okay. That makes sense.

[Darth Holbytlan]

Transposing letters are common mistakes and easily doable with keyboards(typing speeds). Comprehension is more fundamental.

If you had demonstrated the latter, I wouldn't have commented on the former.

The article outright state that anodes using silicon (nano-wires or otherwise) can hold greater charge than using carbon.

Yes it did. That has nothing to do with durability, however.

The anodes with nano-wires have the potential of the greater capacity of silicon anodes but without the massive decrease in cycle life.

Yes, but avoiding the massive decrease in cycle life doesn't mean that there is no reduction at all. The article never makes a clear comparison, even if we believe it reports the subject accurately. I doubt even the experimenters will know for sure how it until they try to commercialize it. It would be a mistake to assume that they are just as good for the reasons I gave earlier.

True, although the point of the nanowires was that they weren't fragile like the original silicon block anodes. Therefore, I would think that although the surface area and thus reaction rate is increased, they have also managed to increase the anode's durability, thus probably precluding heavy damage from a deep discharge.

I see no reason to assume that. It's possible, but all we really know is they don't destroy themselves the way that solid silicon anodes do. And there are obvious reasons to think that silicon nanowires might not be as durable as a solid carbon plate. I'd love to be wrong, though.