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Friday 9 August 2013

what is Lithium-ion Batteries ? New lithium-ion battery design that’s 2,000 times more powerful, recharges 1,000 times faster and How Lithium-ion Batteries Work

Researchers at the University of Illinois at Urbana-Champaign have developed a new lithium-ion battery technology that is 2,000 times more powerful than comparable batteries. According to the researchers, this is not simply an evolutionary step in battery tech, “It’s a new enabling technology… it breaks the normal paradigms of energy sources. It’s allowing us to do different, new things.”



Currently, energy storage is all about trade-offs. You can have lots of power (watts), or lots of energy (watt-hours), but you can’t generally have both. Supercapacitors can release a massive amount of power, but only for a few seconds; fuel cells can store a vast amount of energy, but are limited in their peak power output. This a problem because most modern applications of bleeding-edge tech — smartphones, wearable computers, electric vehicles — require large amounts of power and energy. Lithium-ion batteries are currently the best solution for high-power-and-energy applications, but even the best li-ion battery designs demand that industrial designers and electronic engineers make serious trade-offs when creating a new device.

Which brings us neatly onto the University of Illinois’ battery, which has a higher power density than a supercapacitor, and yet comparable energy density to current nickel-zinc and lithium-ion batteries. According to the university’s press release, this new battery could allow for wireless devices to transmit their signals 30 times farther — or, perhaps more usefully, be equipped with a battery that’s 30 times smaller. If that wasn’t enough, this new battery is rechargeable – and can be charged 1,000 times faster than conventional li-ion batteries. In short, this is a dream battery.




These huge advances stem from a brand new cathode and anode structure, pioneered by the University of Illinois researchers. In essence, a standard li-ion battery normally has a solid, two-dimensional anode made of graphite and a cathode made of a lithium salt. The new Illinois battery, on the other hand, has a porous, three-dimensional anode and cathode. To create this new electrode structure, the researchers build up a structure of polystyrene (Styrofoam) on a glass substrate, electrodeposit nickel onto the polystyrene, and then electrodeposit nickel-tin onto the anode and manganese dioxide onto the cathode. The diagram above does a good job of explaining the process.

The end result is that these porous electrodes have a massive surface area, allowing for more chemical reactions to take place in a given space, ultimately providing a massive boost to discharge speed (power output) and charging. So far, the researchers have used this tech to create a button-sized microbattery, and you can see in the graph below how well their battery compares to a conventional Sony CR1620 button cell. The energy density is slightly lower, but the power density is 2,000 times greater. On the opposite end of the bleeding-edge spectrum — increased energy density, but lower power density — then IBM’s lithium-air battery currently leads the pack




In real-world use, this tech will probably be used to equip consumer devices with batteries that are much smaller and lighter — imagine a smartphone with a battery the thickness of a credit card, which can be recharged in a few seconds. There will also be plenty of applications outside the consumer space, in high-powered settings such as lasers and medical devices, and other areas that normally use supercapacitors, such as Formula 1 cars and fast-recharge power tools. For this to occur, though, the University of Illinois will first have to prove that their technology scales to larger battery sizes, and that the production process isn’t prohibitively expensive for commercial production. Here’s hoping.

Lithium-ion batteries are incredibly popular these days. You can find them in laptops, PDAs, cell phones and iPods. They're so common because, pound for pound, they're some of the most energetic rechargeable batteries available.
Lithium-ion batteries have also been in the news lately. That’s because these batteries have the ability to burst into flames occasionally. It's not very common -- just two or three battery packs per million have a problem -- but when it happens, it's extreme. In some situations, the failure rate can rise, and when that happens you end up with a worldwide battery recall that can cost manufacturers millions of dollars.
So the question is, what makes these batteries so energetic and so popular? How do they burst into flame? And is there anything you can do to prevent the problem or help your batteries last longer? In this article, we'll answer these questions and more.
Lithium-ion batteries are popular because they have a number of important advantages over competing technologies:



  • They're generally much lighter than other types of rechargeable batteries of the same size. The electrodes of a lithium-ion battery are made of lightweight lithium and carbon. Lithium is also a highly reactive element, meaning that a lot of energy can be stored in its atomic bonds. This translates into a very highenergy density for lithium-ion batteries. Here is a way to get a perspective on the energy density. A typical lithium-ion battery can store 150 watt-hours of electricity in 1 kilogram of battery. A NiMH (nickel-metal hydride) battery pack can store perhaps 100 watt-hours per kilogram, although 60 to 70 watt-hours might be more typical. A lead-acid battery can store only 25 watt-hours per kilogram. Using lead-acid technology, it takes 6 kilograms to store the same amount of energy that a 1 kilogram lithium-ion battery can handle. That's a huge difference [Source: Everything2.com].
  • They hold their charge. A lithium-ion battery pack loses only about 5 percent of its charge per month, compared to a 20 percent loss per month for NiMH batteries.
  • They have no memory effect, which means that you do not have to completely discharge them before recharging, as with some other battery chemistries.
  • Lithium-ion batteries can handle hundreds of charge/discharge cycles.
That is not to say that lithium-ion batteries are flawless. They have a few disadvantages as well:
  • They start degrading as soon as they leave the factory. They will only last two or three years from the date of manufacture whether you use them or not.
  • They are extremely sensitive to high temperatures. Heat causes lithium-ion battery packs to degrade much faster than they normally would.
  • If you completely discharge a lithium-ion battery, it is ruined.
  • A lithium-ion battery pack must have an on-board computer to manage the battery. This makes them even more expensive than they already are.
  • There is a small chance that, if a lithium-ion battery pack fails, it will burst into flame.





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