Researchers make rechargeable batteries store six times more charge
An international team of researchers led by Stanford University have developed rechargeable batteries that can store up to six times more charge than ones that are currently commercially available.
The advance, detailed in a new paper published Aug. 25 in the journal Nature, could accelerate the use of rechargeable batteries and puts battery researchers one step closer toward achieving two top stated goals of their field: creating a high-performance rechargeable battery that could enable cellphones to be charged only once a week instead of daily and electric vehicles that can travel six times farther without a recharge.
The new so-called alkali metal-chlorine batteries, developed by a team of researchers led by Stanford chemistry Professor Hongjie Dai and doctoral candidate Guanzhou Zhu, relies on the back-and-forth chemical conversion of sodium chloride (Na/Cl2) or lithium chloride (Li/Cl2) to chlorine.
When electrons travel from one side of a rechargeable battery to the other, recharging reverts the chemistry back to its original state to await another use. Non-rechargeable batteries have no such luck. Once drained, their chemistry cannot be restored.
“A rechargeable battery is a bit like a rocking chair. It tips in one direction, but then rocks back when you add electricity,” Dai explained. “What we have here is a high-rocking rocking chair.”
Serendipitous discovery
The reason no one had yet created a high-performance rechargeable sodium-chlorine or lithium-chlorine battery is that chlorine is too reactive and challenging to convert back to a chloride with high efficiency. In the few cases where others were able to achieve a certain degree of rechargeability, the battery performance proved poor.
In fact, Dai and Zhu did not set out to create a rechargeable sodium and lithium-chlorine battery at all, but merely to improve their existing battery technologies using thionyl chloride. This chemical is one of the main ingredients of lithium-thionyl chloride batteries, which are a popular type of single-use battery first invented in the 1970s.
But in one of their early experiments involving chlorine and sodium chloride, the Stanford researchers noticed that the conversion of one chemical to another had somehow stabilized, resulting in some rechargeability. “I didn’t think it was possible,” Dai said. “It took us about at least a year to really realize what was going on.”
Over the next several years, the team elucidated the reversible chemistries and sought ways to make it more efficient by experimenting with many different materials for the battery’s positive electrode. The big breakthrough came when they formed the electrode using an advanced porous carbon material from collaborators Professor Yuan-Yao Li and his student Hung-Chun Tai from the National Chung Cheng University of Taiwan.
The carbon material has a nanosphere structure filled with many ultra-tiny pores. In practice, these hollow spheres act like a sponge, sopping up copious amounts of otherwise touchy chlorine molecules and storing them for later conversion to salt inside the micropores.
“The chlorine molecule is being trapped and protected in the tiny pores of the carbon nanospheres when the battery is charged,” Zhu explained. “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.”
The result is a step toward the brass ring of battery design—high energy density. The researchers have so far achieved 1,200 milliamp hours per gram of positive electrode material, while the capacity of commercial lithium-ion battery today is up to 200 milliamp hours per gram. “Ours has at least six times higher capacity,” Zhu said.
The researchers envision their batteries one day being used in situations where frequent recharging is not practical or desirable, such as in satellites or remote sensors. Many otherwise usable satellites are now floating in orbit, obsolete due to their dead batteries. Future satellites equipped with long-lived rechargeable batteries could be fitted with solar chargers, extending their usefulness many times over.
For now though, the working prototype they’ve developed might still be suitable for use in small everyday electronics like hearing aids or remote controls. For consumer electronics or electrical vehicles, much more work remains to engineer the battery structure, increase the energy density, scale up the batteries and increase the number of cycles.
See more here: techxplore.com
Header image: Guanzhou Zhu
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slandermen
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Timely, considering…especially the part relating to using common stuff like sodium chloride. Some of this stuff was mentioned in the recent EV or whatever article.
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slandermen
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And yet, improvement relating to multiple materials and enhancement properties are also possible. Vaguely I’d speculate silica and calcium (of the more “inert” potential enhancement factors).
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Howdy
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“1,200 milliamp hours per gram of positive electrode material,”
Why no mention of the negative electrode?
The image shows a tad over 12 milliamps from a “coin cell” as far as can be seen, running an LED, and since no current limiter is included, presumably at a voltage below the LED maximum, or because the cell voltage collapsed under this particular load. A lithium cell would over-drive an LED unless the internal impedance was so high that the current caused the output voltage to collapse. So, 12 milliamps at what voltage? What Is the open circuit voltage?
What i the discharge profile like. Lot of questions need answering.
“Ours has at least six times higher capacity,”
Again, at what voltage? How much degradation of the original rating after 200 cycles?
A standard cell shape like the above, of the type used in fx, a computer bios backup can do the same, and you can actually buy such a device, ready made as a torch in many places. Unless I’m missing something, I fail to see what all the fuss is about.
Early days I guess.
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T.C. Clark
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I wish I had a dollar for every new and improved battery…just read about one from Harvard…now one from Stanford…and Panasonic has one for cell phones at only twice the cost…and Goodenough was sup[posed to have some fantastic glass solid state battery years ago. I suspect battery chemistry is just not going to improve the existing performance much further….maybe super capacitors need more research.
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Squidly
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T.C., I agree with you. I used to race radio controlled cars way back in the day, owned a hobby store and race track. Even back then it seems every other day was some “new breakthrough” in battery technology. The reality has always equated to, “a little improvement” and I have witnessed few actual “breakthrough” technologies emerge. Yes, improvements have been made since then, but I have been hearing and reading about “super duper breakthrough” stuff for almost 4 decades now. This looks like just another one. I think it is nothing more than a way to continue to gas light people about EV’s and other such “green” nonsense.
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