The Samsung Galaxy Note 7 debacle was probably the most prominent event of 2016, at least in the electronics world. All that damage due to those explosive lithium-ion batteries. There have been countless happenings of LiPo explosions, but more concerns rose after it began to happen with the devices of the most reputable smartphone brand. It will not even be a slight overstatement if we say that LiPo batteries run our lives. Our phones, laptops, now our cars, and maybe our entire houses in the future.
We do not want either of these on fire, do we? One can make these batteries safer, but the urgent need in today’s world is a battery that cannot be set to fire no matter what. Seeo Inc., a startup from the University of California, Berkeley, is working on lithium-ion batteries that are based on solid polymers. The company says their LiPo cells are safer, cheaper, lighter, and will last longer than the conventional batteries. The batteries use thin films of the polymer as an electrolyte and much lighter electrodes. Test units of the said batteries are now being produced at Lawrence Berkely National Laboratory.
A study based on their works was published in the journal Joule that was co-authored by Kang Xu from the US Army Research Laboratory (ARL), who says
“In the past, if you wanted high energy, you would choose a non-aqueous lithium-ion battery, but you would have to compromise on safety. If you preferred safety, you could use an aqueous battery such as nickel/metal hydride, but you would have to settle for lower energy, now we are showing that you can simultaneously have access to both high energy and high safety.”
Conventional LiPo batteries use cobalt oxide electrodes and a liquid electrolyte that is a solution of lithium salts in an organic solvent. When such batteries are punctured or overcharged, the electrode material may release oxygen, thus causing the solvent to catch fire that may result in an explosion. Seeo solves the problem with a solid electrolyte that is not flammable, making the entire pack much safer. Mohit Singh, the Seeo co-founder, says,
“Lifetime data suggests that conventional lithium-ion systems lose about 40 percent capacity in 500 cycles. We get a much better cycle life. We can go through 1,000 cycles with less than 5 percent capacity loss.”
The solid electrolyte allows the use of lithium metal films for the electrodes that are much lighter. Moreover, it allows the battery to have an energy density of 300 watt-hours per kilogram; about 50 percent greater than the conventional lithium ion batteries. The manufacturing process becomes much cheaper once a liquid electrolyte is out of the picture.
Making solid electrolytes is not half as easy as it might sound. After years and years of research, Seeo has solved the problem with block copolymers that are made with two linked polymer chains that self-assemble into nano structures. One forms an array of conductive cylinders while the other one works as the support matrix. This solid electrolyte is as conductive as liquid electrolytes while being significantly strong.
A polymer electrolyte battery is the need of the time, but it comes with its disadvantages and as Singh puts it,
“Polymers will always be limited by lower ionic conductivity compared to liquids. But these polymers wouldn’t be able to address quick-charge applications like hybrid-electric vehicles or power tools.”
The development is still quite an achievement. A few more years of research and improvement on the technology could mean safer electronics, not just in our gadgets and houses but our vehicles as well.
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