All About Lithium Ion Batteries
If it sometimes seems like EVERYONE is on a cell phone these days, it might just be because they are. According the Pew Research, 91% of Americans now have a cellphone, compared to just 63% ten years ago. In the last ten years, cell phones have become not only more numerous, but also smaller and smarter. At least some of this progress can be attributed to advances in lithium ion battery technology.
Lithium ion batteries are used to power a wide variety of electronics, ranging from smartphones and laptops to Teslas and Boeing 787s. Lithium has long been recognized as having great potential for batteries. It the lightest metal, has the greatest electrochemical potential, and provides the largest energy density for weight. Research into lithium batteries started in 1912. However, it wasn’t until the 1970’s that a viable lithium battery was developed. Early lithium batteries were plagued by safety issues because lithium is inherently unstable, especially during recharging cycles. Researchers eventually solved the problem by switching to a non-metallic alternative using lithium ions.
Sony was the first company that successfully brought the lithium ion batteries into commercial use in 1991 to power its newly developed handheld video cameras. While Sony was able to reduce the size of the video cameras from a traditional shoulder mount device to one small enough to fit into a palm, nickel cadmium batteries just did not provide enough energy density to power the devices in similar size reduction. For higher energy density while supporting the new camera’s form, Sony turned to the only battery chemistry that is capable of doing both—lithium ions. Sony became the first mass manufacturer of the modern rechargeable lithium ion batteries.
By mid-1990’s lithium ion batteries had virtually taken over the entire camera industry that used rechargeable batteries. The revolution soon spread to the laptop industry and the then nascent cell phone industry. Today rechargeable lithium ion batteries are the dominant form of mobile power supply for almost all consumer electronics. The same success is also repeating itself in the energy industry and the automobile industry as lithium ion batteries become an integrated part of the smart power grids and electric vehicles.
Anti-Dentrite Formation Technology
A startup in California has developed a new way of rapidly recharging conventional lithium-ion batteries. With Qnovo’s technology, you can get six hours of phone life from just 15 minutes of charging — compared to just 1-2 hours from conventional charging. The secret, according to Qnovo, is that no two batteries are identical — and knowing exactly how much power you can pump into the battery without damaging it can significantly improve recharge times. There are many reasons for LIBs to lose charge and efficiency, but one of the most pesky is the creation of dendrites – mossy deposits of lithium that ooze out of cracks in the anode that form during charging (the sudden influx of ions caused by recharging causes the anode to expand and crack). These dendrites can reach out towards the electrolyte and cause short circuits, seriously reducing the battery’s capacity. Now, device makers already know that charging a lithium-ion battery is pretty dangerous because of dendrite formation. So, to ensure the dendrites don’t form, the amount of current flowing into the battery is reduced to a trickle. This results in longer battery life, which is good — but also significantly longer recharge times. Qnovo has designed an intelligent feedback loop that constantly checks the battery’s status to ensure that it gets the optimal amount of current. Apparently, simply by simply sending a pulse into the battery, and then registering the voltage response, Qnovo can work out the battery’s temperature, age, and other factors that affect charging. By continually polling the battery as it charges, the current can be constantly tweaked.
Carbon Nanosphere Coating
Similar to other recent battery breakthroughs, nanotech is the key to Stanford’s new lithium electrode. One of the main problems with lithium is that it expands dramatically when it absorbs ions during charging, creating cracks in the metal. Lithium ions then ooze out of these cracks, forming “mossy” metal deposits known as dendrites. These dendrites very quickly lower the battery’s efficiency, so that it’s fairly useless after just a handful of cycles. To prevent these cracks and dendrites from forming, Stanford deposits a layer of carbon nanospheres on the surface of the lithium anode. As you can see in the photos, these nanospheres create an interconnected series of domes that are strong enough to maintain the lithium’s structural integrity, while still allowing the electricity-carrying ions to pass back and forth. This protective layer, which is about 20nm thick, also prevents the lithium from reacting explosively with the electrolyte. All told, in technical terms, this new lithium anode has a coulombic (Faraday) efficiency of 99% after 150 cycles. Cui says this is short of the 99.9% required for a commercially viable design, but “while we’re not quite to that 99.9 percent threshold, where we need to be, we’re close and this is a significant improvement over any previous design. With some additional engineering and new electrolytes, we believe we can realize a practical and stable lithium metal anode that could power the next generation of rechargeable batteries.”
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