There are batteries and there are supercapacitors. Both do the same thing — store electrical energy. Batteries charge relatively slowly and discharge slowly. Supercapacitors charge quickly and discharge quickly. Batteries are capable of storing large amounts of energy, supercapacitors are best for storing smaller amounts of energy. The bottom line is that batteries do some things better than supercapacitors and supercapacitors do some things better than batteries.
In coming years, supercaps, as they are known, may replace the lead acid batteries currently used by all electric cars to store power for such routine functions as operating door locks, providing interior lighting, and so forth. They also may permit electric car manufacturers to use them to do the things they do best — charge and discharge rapidly — while allowing the main storage battery to do what it does best — move the car down the road for many zero emissions miles.
Scientists at University College London and the Chinese Academy of Sciences claim they have developed a new flexible graphene-based supercapacitor that can safely charge at high speed, accumulate a record amount of energy, and store it for a long time, according to a report by TechExplorist. Their research was published on February 17 by the journal Nature Energy.
The new supercapacitor uses an innovative multi-layer graphene electrode. It can bend up to 180 degrees without losing its performance and does not require a liquid electrolyte, which minimizes the risk of explosion. The prototype developed by the research team has an energy density of 88.1 Wh per liter — equivalent to the best lead acid batteries. A typical conventional supercapicitor today has an energy density of about 8 Wh per liter. [Note: see Skeleton Technologies story below for more on this topic.] In addition, the scientists claim their invention has a power density of 10,000 watts per liter and retains 98.7% of its capacity after 5,000 charge/discharge cycles.
The new device could replace the batteries in smartphones and power wearable internet devices. And because it is much lighter and smaller than a lead acid battery, it could also replace the 12 volt standard battery used in all EVs today.
As with all energy storage news, this story requires a caveat. The new supercapacitor is merely a prototype, which means it may or may not be commercially viable. If it is, it may be several years before it gains acceptance by vehicle manufacturers. At this point, it is a development worth watching as the EV revolution continues.
Skeleton Technologies in the UK says it is also hard at work on advanced supercapacitors that could replace traditional lead acid batteries in automobiles, according to Bloomberg. CEO Taavi Madiberk admits supercaps do not yet have the energy density of lithium-ion batteries, but believes the technology is improving all the time. His company’s products have an energy density of 60 Wh per liter at the present time. He says his company is already in discussions with several automakers who would like to do away with the bulky lead acid batteries in their cars.
“Sometimes people think that lead is a problem of the past because it relates to internal combustion engines but in practice all electric vehicles have 12 volt lead acid batteries,” Madiberk says. “We are working on a viable alternative to replace all lead acid batteries.“ In 1999, lithium-ion batteries cost about $5,000 per kWh. Today they cost under $200 per kWh. [Tesla could be at or below $100 per kWh at the cell level today.] Madiberk believes supercapacitors are about to experience a similar rapid decline in cost.
Supercapacitors may be used for recovering energy in regenerative braking systems, says James Frith, an analyst with Bloomberg New Energy Finance who focuses on energy storage. “There’s been a lot of interest in supercapacitors over the years. The trouble is that lithium-ion batteries have been coming down in price quite rapidly,” he says. “There definitely is a lot of areas within the automotive market where they could find applications.”
If Tesla is working to include supercapacitors in its products, they will definitely be part of the future of electric transportation, a field in which improvements seem to happen on an almost daily basis.