Experimental chlorine battery holds 6 times more charge than lithium-ion

Experimental chlorine battery holds 6 times more charge than lithium-ion
Scientists have developed a chlorine-based prototype battery with six times the capacity of today's lithium-ion devices
Scientists have developed a chlorine-based prototype battery with six times the capacity of today's lithium-ion devices
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Scientists have developed a chlorine-based prototype battery with six times the capacity of today's lithium-ion devices
Scientists have developed a chlorine-based prototype battery with six times the capacity of today's lithium-ion devices

Stanford University scientists experimenting with a decades-old, single-use battery architecture have developed a new version that is not only rechargeable, but offers around six times the capacity of today's lithium-ion solutions. The breakthrough hinges on the stabilization of volatile chlorine reactions within the device, and could one day provide the basis for high-performance batteries that power smartphones for a week at a time.

The new battery is described as an alkali metal-chlorine battery, and is based on chemistry that first emerged in the 1970s called lithium-thionyl chloride. These batteries are highly regarded for their high energy density, but rely on highly reactive chlorine that makes them unsuitable for anything other than a single use.

In a regular rechargeable battery, the electrons travel from one side to the other during discharging and then are reverted to their original form as the battery is recharged. In this case, however, the sodium chloride or lithium chloride is converted to chlorine, which is too reactive to be converted back to chloride with any great efficiency.

The authors of this new study may well have come up with a solution to this problem. The team was experimenting with sodium chloride and chlorine to try and improve this battery's performance, but found that the chemical had actually stabilized, which enabled the battery some degree of rechargeability. Subsequent investigations led the team to develop a new electrode material made of porous carbon that acts like a sponge, soaking up the erratic chlorine molecules and safely storing them to be converted back into sodium chloride.

“The chlorine molecule is being trapped and protected in the tiny pores of the carbon nanospheres when the battery is charged,” says Guanzhou Zhu. “Then, when the battery needs to be drained or discharged, we can discharge the battery and convert chlorine to make NaCl – table salt – and repeat this process over many cycles. We can cycle up to 200 times currently and there’s still room for improvement.”

A well maintained lithium-ion battery, for context, can be good for 500-1000 cycles.

Through their experiments, the team also demonstrated a very high energy density for the prototype battery, clocking 1,200 mAh per gram of the electrode material, around six times more than is offered by today's lithium-ion battery technology.

“A rechargeable battery is a bit like a rocking chair. It tips in one direction, but then rocks back when you add electricity,” says study author Hongjie Dai. “What we have here is a high-rocking rocking chair.”

The team imagines the battery finding use in hearing aids or remote controls, or being used to power devices that only require infrequent recharging like satellites or remote sensors that could be topped up with solar. For use in smartphones and electric vehicles, the scientists will need to scale up the battery and engineer a suitable structure, while also increasing the number of times it can be safely cycled.

The research was published in the journal Nature

Source: Stanford

One thing to note is this: OK, so they have the battery to 200 charge cycles at 6x the capacity of Lion batteries. Lion batteries can do 500 to 1000. BUT the salt battery only needs to be charged 1/6 as often, so it ALREADY has surpassed the utility of Lion -- it is effectively the same as a Lion battery that can do 1200 cycles. To put this in context, if one builds an electric car using it, its range would be as far as 1800 miles per charge. Most people would only need to charge it 6x per YEAR to cover their driving.
That is fine,but it will still need ~10 years of development to reach the consumer,and I ain't getting any younger.
After >200 years of development, the internal combustion engine is still ridiculous. Dirty, inefficient and a crazy number of moving parts.

If 5% of the money that was wasted on ICE development were invested in battery research instead, we could all be driving EVs with 700 mile ranges instead of staring down the barrel of a climate-induced collapse.
Not bad for proof of concept - and the material cost (except for exotic carbon electrodes if needed) is so much better than lithium for manufacture or recycling. So what is the downside? What do we not know? Hopefully when this proof of concept gets to mass production status the cycling limitations will be pushed back - and maybe even more energy density will be achieved! Keep writing on these Nick - this is fascinating!
Adrian Akau
Theoretically, the strongest battery would be a lithium fluoride structure but right now this is not possible as both elements are too reactive to control.
I'd rather be,er, positive than negative - but the researchers and author strangely fail to explain why the number of cycles is so low(200). What kind of degradation is causing this ?
It's usually dendrites of course - but the article is largely focused on the researchers' success in overcoming that problem. So why just 200 cycles ? Do they know or at least suspect what the cause may be ?
Paul G
Expanded Viewpoint
200 charge/discharge cycles for something that is brand new isn't too bad! How many c/d cycles were LIon batteries at this early in the game? What's to say that they can't double or triple that number in the next few months?
Something that the battery powered cars fanatics ALWAYS miss on, is where do we get the power to charge them up with?? Oh, yeah, we'll just drive coal powered cars, like those Teslas out there!!
6x the energy density means a given battery size has 6x the energy that can be released in a catastrophic failure. Though perhaps it won't have liion's thermal runaway.

When it comes to reactivity, lithium is practically boring compared to chlorine. And chlorine, being a gas, is much more likely to find it's way into lungs before reacting.

It'd be great if they make it reliable, but these seem like very substantial hurdles.
I suspect the major showstopper with these batteries will be thermal runaway with six times the energy density. Ouch.