November 24, 2011
Could the days of the humble lithium-ion battery be numbered thanks to the everlasting battery?
Researchers at Stanford University have revealed a new nanoparticle material which could be used to create everlasting batteries suitable for electrical grids.
According to the researchers, the material could be used for batteries that would be good for 30 years of useful life. The short lifetime of large batteries has been a major drawback limiting their use, but the new material could produce batteries that could undergo 100 times as many charging cycles as today’s batteries.
The researchers said they used nanoparticles of a copper compound to develop a high-power battery electrode that is inexpensive to make, rechargeable, very efficient and extremely durable.
The potential for this technology is exciting because it could solve one of the major problems associated with wind turbines and solar panels – that power is only delivered with the sun shines or the wind blows. The super-battery would store power until it is needed.
The researchers have not yet built the revolutionary battery itself, but the crystalline copper-based nanoparticles would be a key component for its electrodes.
Apparently, in laboratory tests, the electrode survived a staggering 40,000 cycles of charging and discharging, after which it could still be charged to more than 80 percent of its original charge capacity. The average lithium ion battery in comparison can only handle about 400 charge/discharge cycles before it deteriorates too much to be of practical use.
“At a rate of several cycles per day, this electrode would have a good 30 years of useful life on the electrical grid,” said Colin Wessells, a graduate student in materials science and engineering who is the lead author of a paper describing the research, published in Nature Communications.
“That is a breakthrough performance – a battery that will keep running for tens of thousands of cycles and never fail,” said Yi Cui, an associate professor of materials science and engineering, who is Wessell’s adviser and a co-author of the paper.
How It Works
It seems that the electrode’s durability is down to the atomic structure of the crystalline copper hexacyanoferrate used to make it. These crystals apparently have an open framework that allows ions – those electrically charged particles whose movements en masse either charge or discharge a battery – to easily go in and out without damaging the electrode. Most batteries apparently fail or deteriorate because of accumulated damage to the crystal structure.
“Because the ions can move so freely, the electrode’s cycle of charging and discharging is extremely fast, which is important because the power you get out of a battery is proportional to how fast you can discharge the electrode,” the researchers said.
The researchers said that they had to use the right size ions to make use of the open framework, because too small they would stick to one side of an atom, and too big they could damage the crystal structure when they moved in and out of the electrode.
Apparently the right-sized ion turned out to be hydrated potassium, a much better fit compared with other hydrated ions such as sodium and lithium.
“It fits perfectly – really, really nicely,” said Cui. “Potassium will just zoom in and zoom out, so you can have an extremely high-power battery.”
Meanwhile the race by researchers to improve the performance of batteries continues.
Back in March, a team of electrical engineers at Illinois University revealed they were developing a new type of battery that could extend the running time of mobile phones a hundredfold.
That battery uses carbon nanotubes, which are 10,000 times thinner than a human hair, rather than traditional metal wires. According to the engineers, the energy consumption of a battery is proportional to the size of the components used to store and retrieve information, so smaller wires result in lower energy usage.
Other researchers from the University of Maryland have also been working to improve the capacity of lithium-ion batteries. Last year it was reported that a biological virus known as the Tobacco mosaic virus (TMV) could increase the surface area of electrodes in a battery, resulting in a ten-fold increase in energy capacity.
Meanwhile in September scientists at the University of Leeds invented a jelly lithium battery. The flexible polymer gel batteries can be shaped and bent to fit virtually any device and can be made just nanometres thick at a rate of ten metres per minute.