Tag Archives: Lithium Ion Batteries

Salt Water Makes Li-Ion Batteries Safer

So far, high-energy lithium-ion batteries were always a matter of concern on account of safety. If you wanted to remain safe from exploding batteries, an aqueous battery such as made from nickel/metal hydride would be preferable, but then it would give you lower energy.

Usually, 3-V batteries using aqueous electrolyte technologies are unable to achieve higher voltages because of the cathodic challenge. This happens as the aqueous solution degrades one end of the battery made from either lithium or graphite. One research team solved this problem by covering the graphite or lithium anode with a gel polymer electrolyte coating.

As the coating is hydrophobic, it does not allow water molecules to reach the electrode. However, when the battery charges for the first time, the coating decomposes, forming a stable layer separating the solid anode from the liquid electrolyte. The layer protects the anode from side reactions that could deactivate the anode. This allows the battery to use anode materials that are more effective, such as lithium metal or graphite, and allowing the battery reach higher energy densities and cycling abilities. The gel coating improves the safety of the battery, and is now comparable to the safety standards of non-aqueous lithium-ion batteries.

Organic solvents used in non-aqueous batteries are highly flammable. In comparison, aqueous lithium-ion batteries use water-based electrolytes that are non-flammable. Another advantage of this gel polymer coating is if this layer is damaged, the reaction with the lithiated graphite or lithium anode is very slow, preventing smoking, fire, or explosion that would normally happen if in the damaged battery the metal came into direct contact with the electrolyte.

This aqueous lithium-ion battery with the gel covering the anode has power and energy density matching its counterpart with non-aqueous electrolyte, and is suitable for commercial applications. However, the researchers intend to improve on the number of full-performance cycles the battery can complete. According to the researchers, this will reduce material expenses as far as possible. Although at present the battery is able to complete only 50-100 cycles, the team intends to increase that to 500 or more.

The researchers are also trying to manipulate the electrochemical process to allow the battery achieve 4 V on its terminals. According to the researchers, this is the first time they have been able to stabilize the reactive anodes such as lithium and graphite in aqueous media. They feel this opens a huge field of possibilities into several different topics in electrochemistry. For instance, this could cover not only lithium-ion batteries, but also lithium-sulfur, sodium-ion batteries, and other batteries using multiple ion chemistry technologies such as magnesium and zinc, and electrochemical and electroplating synthesis.

The researchers understand that interphase chemistry requires to be perfected before they can commercialize their product. They also feel that they need to work more towards scaling up the technology so that big cells can be used for testing. However, the researchers are confident they will be able to commercialize their product within the next five years, provided they are able to gather more funding.

Non-Toxic Batteries for Humans and Fish

Lithium-ion batteries are very popular nowadays, as everyone has one in their cell phones. Although people use batteries of a large variety of technologies and form factors, everyone wants one with high energy density, low weight and volume, superior charge/discharge characteristics, and low cost. The Lithium-ion chemistry is popular, as it tends to meet most of the above desirable characteristics, even though it has several variations.

However, some applications need batteries with unusual construction, form factor, and chemistry, those that the Lithium-ion battery will simply be unable to meet. Consider, for instance, the research under the guidance of Professor Christopher Bettinger, at the Carnegie Mellon University.

The CMU researchers are interested in developing edible, biocompatible batteries. They want to use non-toxic material already present within the body for parts of the battery, such as the acid in the stomach, which they want to use as the electrolyte. For this, the team has developed anodes made of manganese dioxide, already present in the body, and cathodes based on melanin, which the body contains as a pigment. They also claim to have developed other versions of batteries consisting of body-friendly materials.

The researchers are interested in developing body-friendly batteries where the electrodes can dissolve harmlessly within the body after use. Among the batteries the group has developed using different types of soluble cations, most have terminal voltages ranging from 0.5 to 0.7 volts. Although information is still sketchy, one battery was able to deliver about 5 mill watts of power for nearly 20 hours.

However, it is not only humans who need such special batteries. Fish too need batteries to power tracking devices, so scientists can follow their trail and understand how they migrate. For instance, researchers at the Pacific Northwest National Laboratory have developed a battery small enough for injection, but powerful enough to enable tracking movements of salmon. This battery weighs only 70 mg, and has dimensions of 6×3 mm. It is handcrafted with several layers of rolled up material, thereby increasing the internal surface area, and reducing its internal resistance. The scientists have so far handmade over 1000 such rice-grain sized batteries, and implanted nearly 700 of them into fishes for powering tracking devices.

The tiny batteries supply enough power to send a 744-microsecond signal every three seconds for nearly three weeks, or every five seconds lasting over a month. That makes the average energy density of the batteries to be 240 WHr/kg. Compare this with standard silver oxide button microbatteries, which have an energy density of nearly 100 WHr/kg. So far, the scientists have not revealed how they made these measurements and whether the comparison is fair.

Making such small batteries comes with some peculiarly unique issues. One such issue is attaching leads for connection. The microbatteries from the Pacific Northwest have leads internally built in. However, it is not very clear how the researchers from the Carnegie Mellon University connect leads to their edible batteries, especially as the users of such special batteries do not have access to vendors for obtaining standard holders or connectors.

Explosion and Damage Proof High Energy Density Batteries

We seem to spend a major part of our waking life charging batteries of our smartphones, laptops, watches, wearables, and more. Although most of our gadgets work at lightning speeds, one common frustrating weakness lingers on—the batteries. Of course, they have improved tremendously in the last fifty years, yet they have retained characteristics such as being toxic, expensive, bulky, finicky, and most maddeningly, short-lived. The quest for a super battery does not end with smartphones alone, rather it continues with electric cars and renewable energy sources such as wind and solar power, holding the keys to a greener future.

Mike Zimmerman, a Professor at the Tufts University just outside Boston, and his team have created what they claim is the next generation of the Lithium-ion battery. The main characteristic of this new type of battery is it is safe to power up cars, phones, and other gadgets.

The current breed of Lithium-ion batteries relies on a liquid electrolyte between their positive and negative electrodes. When hit or pierced, the leaking liquid electrolyte makes the battery vulnerable to fire or even explosion. The Galaxy Note 7 phones from Samsung aptly demonstrated this—it had spontaneously exploding batteries that would catch fire as the battery casing caused one of the electrodes to bend, increasing the risk of short circuits.

However, Zimmerman’s battery won’t explode or catch fire even if most of it has been chopped away. Rather, it will continue to power the device. It will endure repeated damage without risk of fire or explosion, thanks to its solid electrolyte.

Besides being the Holy Grail for safe batteries, solid electrolytes can hold more charge for a given volume compared to what the liquid electrolytes can. The solid plastic electrolyte developed by Professor Zimmerman does not allow the formation of dendrites—tendrils of Lithium that originate from the electrodes and spread throughout the electrolyte—that cause the dangerous short-circuits.

Other researchers have been looking at charging times for batteries and trying to speed up the process. Rather than improve the charging times for Lithium-ions, scientists have been experimenting with different types of batteries, and claim to have hit success with batteries made from Aluminum foil.

Although research on Aluminum batteries has continued for years, most prototypes were incapable of withstanding more than a few dozen charges, before they lost their potency. Most cellphones, on the other hand, sustain more than a thousand charge cycles before their capacity deteriorates.

The Aluminum foil batteries can sustain a staggering 7,000 charge cycles. They are also safe—researchers could drill a hole into the battery while it was operating, and unlike a Lithium-ion battery, the Aluminum battery did not explode. However, Aluminum batteries are not yet ready for the market, as they are heavier than Lithium-ion batteries of the same capacity.

The researchers used a solution of Aluminum Trichloride dissolved in an organic solvent containing Chlorine. Although the Aluminum atom has three electrons in its outer shell, the present chemistry utilizes only one of them. Lithium atoms also do the same, as they have only one electron in their outer shell. However, Lithium atoms are only one-third as heavy as the Aluminum atoms.