The latest news in energy storage has Drexel University with a new piece out that notes in a paper published in Science by John Chmiola doubling supercapacitors storage and then MIT Technology Review marking it up to triple. It’s a little amusing, yet Chmiola is on to something.
Chmiola idea is to use an electrode material called carbide-derived carbon (CDC), in which metal atoms are etched from a metal carbide, such as titanium carbide (TiC), to form a porous carbon with very high surface area. Chmiola and his colleagues had experience with CDC in powdered form so the team took some cues from the microelectronics industry, starting with conductive TiC substrates, then etching a very thin electroactive layer (Ti-CDC) to store the electron charge. Thus a new microfabrication-type technique.
The genius innovation here is in connecting up technologies in the use of “bulk” thin films. Chmiola explains, “In the traditional sandwiched construction, the electroactive materials that store the charge are loosely held together particles pressed onto some metal that transports electrons to and away from these materials and separated by some other material that keeps the individual electrodes from shorting to one another. The whole sandwich is then rolled up and put in a little soda can or plastic bag.” That’s just what most everyone else has been working on.
Chmiola and his colleagues avoided many of the pitfalls of the “sandwich” method, such as poor contact between electroactive particles in the electrode; large void space between the particles, which contributes significantly to mass and volume because it is filled with electrolyte, but does not store charge; and poor contact with the materials that carry electrons out of the electroactive materials and to the external circuitry.
The team uses a high-vacuum method called chemical vapor deposition to create thin films of metal carbides such as titanium carbide on the surface of a silicon wafer. The films are then chlorinated to remove the titanium, leaving behind a porous film of carbon. In each place where a titanium atom was, a small pore is left behind.
Chmiola’s advisor group leader is Yury Gogotsi, professor of materials science and engineering at Drexel University explains the film is like a molecular sponge, where the size of each pore is equal to the size of a single ion. This matching means that when used as the charge-storage material in an ultracapacitor, the carbon films can accumulate a large amount of total surface charge.
The Drexel researchers complete the device by adding metal electrodes to either surface to carry current into and out of the device and adding a liquid electrolyte to carry and dispense the charges. They found that the performance of the device is best when the carbon material is about 50 micrometers thick, about the same as the width of a human hair.
Thin film deposition solves some major issues. Conventional ultracapacitors are made from powdered activated carbon. But powders can’t be used to make large, thin films because they won’t stick to a surface. Other groups have developed printable thin-film ultracapacitors based on carbon nanotubes, a technology with lots of potential too.
Gogotsi says the Chmiola team’s devices can store more charge. Gogotsi notes that in theory there is no limit to the size of the films that could be made using these methods that are used by the solar industry and display industries to make panels as large as nine square meters. Because the carbon films are thin and can be made at temperatures as low as 200º C, it might be possible to integrate them with flexible plastic based electronics.
Even if the Drexel team’s work isn’t double or triple the current stage of ultracapacitor capacity they have solved the difficulty getting high enough total energy storage using practical fabrication methods using films.
This is important – Eestor seems to be fading, and the ultracapacitor field has trouble with for applications that require steady power over a long period, such as running a laptop or a motor.
A well-built ultracapacitor has a virtually unlimited lifetime, capacitors can live longer than any electronic device and some designs never need to be replaced. A steady long time period drain with near instant charge is electron charge storage nirvana. If they are cheap to make, and can match or better batteries in volume and weight the electron issue as energy storage, transport and use is over. It will be interesting to see how this develops.
The full Drexel team includes John Chmiola, Celine Largeot, Pierre-Louis Taberna, Patrice Simon, Yury Gogotsi for the Science paper entitled Monolithic Carbide-Derived Carbon Films for Micro-Supercapacitors.
Chmiola is on his way; he received a National Science Foundation IGERT and Graduate Research Fellowships for his Ph.D. studies, and is now a postdoctoral researcher in the Environmental Energy Technologies Division at Lawrence Berkeley National Laboratory. The effort is his second paper in Science magazine.
Now that this innovative design is out what others can do will be fascinating. The materials have already been licensed by Pennsylvania startup Y-Carbon.
The original is here: New Energy and Fuel
When you couple ultracapacitors with lithium batteries performance of an electric vehicle is dramatically boosted. Ultracapacitors give electric vehicles the instant response needed to get going, recover braking energy, work across a wide temperature range, and charge very quickly for thousands or millions of cycles. There is more out there than Eestor, and some are going to market right now.
San Diego-based Maxwell thinks it has a cost-effective solution for carmakers. The company makes the K2 2000 ultracapacitor a unit about the size of a soda can that could be of excellent strategic use with electric vehicles. Maxwell Technologies is supplying a major European automaker that expects to release a hybrid vehicle this year that couples advanced batteries with the company’s ultracapacitors.
Maxwell is suggesting they have a partner in the European deal, the $30 billion Continental AG parts supplier, who is a competitor to Bosch in Europe. Continental expanded recently with acquisition of another high-profile European auto supplier, Siemens VDO, in 2007. These are not firms that go to market with immature technology.
Maxwell CEO Dave Schramm said of the project, “They’re ramping up the car now,” adding that he expects the model’s volume to double by 2012. “We’re already shipping product.” Schramm said that starting the car’s gasoline engine, especially in cold weather, is the largest load batteries go through. Ultracapacitors allow a much smaller pack. “We’re definitely taking cost out of the system,” Schramm said. “Batteries don’t like the kind of power spikes you get with the start-stop cycle, but that’s the way ultracaps work best.”
The primary driver for Maxwell is the European fuel economy standards, which strongly incentivizes “start stop technology” where the engine is always shut down for a stop. The technology is expected to be employed across Europe in the majority of new cars by 2015 in addition to the “Micro-hybrids” that are already selling well. For the U.S. start stop isn’t likely, as the fuel economy advantage isn’t credited by the EPA’s system –no incentive payoff – technology denied.
Maxwell’s ultracapacitors are installed in about 2,000 hybrid buses with regenerative braking. The firm is involved in the Ford Transit Connect electric van with Azure Dynamics. These and other automotive ultracapacitor projects have pushed Maxwell sales from $57 million in 2007 to $100 million in 2009.
Meanwhile, Eestor has gotten its saga into trouble. Words like ridiculous, mystical and sham are coming out from various writers. The hard facts are Eestor has missed its own promise to introduce and show the world a working ultracapacitor by the end of last year. Now that a full calendar quarter has passed and most of another month, the credibility matter is the lead Eestor item for news and blogs. To add injury to the situation, a major source of information, the tiny ZENN Motors, has stopped building their cars entirely, leaving the firm with nothing other than its license with Eestor for any form of revenue. ZENN seems to dream of being the sole supplier of Eestor ultracapacitors to automotive capacitors. The question is quickly becoming will there be a ZENN at all if the Eestor products do come to market.
Technology never waits, even when you’re Eestor. Last week saw Popular Science cover the “Electric Luxury Racer” an exercise in engineering with the latest technology. Of note the vehicle sports a graphene-based ultracapacitor—a device currently being developed in university labs, which uses sheets of carbon only one atom thick to store twice as much electricity as today’s capacitors offering immediate bursts of power. The question is will the unnamed university labs come up with production prototypes. Doubling capacitor storage might not get the idea to ultracapacitor status, but graphene-based caps seem quite possible.
The face of the capacitor market is changing fast. Ioxus of Oneonta New York has announced 1,000-, 3,000- and 5,000-Farad (F) ultracapacitors. These are quite different numbers from micro or pico farads. Ioxus prides itself with smaller dimensions packed in rectangles that offer more power density than the competition.
Right now ultracapacitors can be used as rechargeable energy storage devices to prolong the lifespan of other energy sources, such as batteries. They are lightweight, weighing one-fifth the weight of a comparable battery, and their manufacture and disposal has no detrimental effects to the environment.
Ultracapacitors can take on all of the power functions, except for extended time operation, and this is actually only dependent on the ultracapacitor system size. The state of charge of the battery array does not affect the characteristics of ultracapacitor energy delivery capability. Due to buffering by the ultracapacitor array, the battery array is not subjected to large current loading, which makes its operating conditions, under all conditions of line and load more moderate, extending the battery life. It’s very hard to imagine a smart electric power storage system without ultracapacitor support.
One of the more interesting capacitor applications can be seen on the Ioxus site where they offer a white paper about capacitor use for starting diesel locomotives in Russia.
Will Eestor get from stealth mode to supplying working samples to amaze and impress all of us? Time will tell, but a near four-month delay on a one’s own announcement doesn’t encourage folks. In the meantime there are ultracapacitors out there. Maybe the available products are not so amazing as the Eestor leaked power, but the real products are intensely valuable for supporting electrification of transportation.
Go here to see the original: New Energy and Fuel
Lithium based batteries are a hot research field with lithium air and lithium sulfur compounds at the top of research listings. Stanford’s Yi Cui, builds the battery anode in the form of silicon nanowires, giving the silicon room to grow and shrink without damage. That neatly solves silicon’s swelling when charged with positively charged lithium and shrinks during discharge such that the silicon has a tendency to self “pulverize.”
Compared to present lithium-ion batteries, Stanford’s design is “significantly safer” and currently achieves 80 percent more capacity, but it’s nowhere near being commercially viable with just 40 to 50 charge cycles (conventional Li-ion does “300 to 500″) due to the compound’s still rapid degradation. There is still a theoretical quadruple boost in capacity as the technology matures.
Yi Cui has announced a new cathode consisting of a similarly high capacity lithium sulfide nanostructure. The cathode is mesoporous carbon/Li2S nanocomposite. A company has formed based on the technology, but the cycle life remains a major problem.
The Stanford team thinks they have found their answer: a proof-of-concept lithium-sulfide cathode with 10 times the power density of conventional lithium-ion cathodes. Together, the anode and cathode could yield a battery that lasts four times as long and is significantly safer than existing lithium-ion batteries. The new battery cannot achieve the 10 times the energy storage capacity because the new cathode has significantly lower conductivity than the lithium metals used in conventional batteries.
All this represents an approximately 80 percent increase in the energy density over commercially available lithium-ion batteries. But by the fifth cycle the capacity is down by a third and the batteries are, well, dead by the 50th cycle. There’s lots of hope here though. Just getting the silicon to work at all is a major achievement. Cui is said to be thinking the capacity loss is likely due to polysulfides, chemicals that form during normal discharging and recharging. If allowed to dissolve into the battery’s liquid electrolyte, polysulfides can poison the battery by blocking future charging and discharging.
The past weekend saw researchers at the Università degli Studi di Roma La Sapienza announce development of a novel polymer tin sulfur lithium-ion battery that takes advantage of the high theoretical specific energy and energy density of the lithium-sulfur battery chemistry. It’s a whole new take – rather than taking the more conventional approach of using a sulfur cathode and a lithium metal anode, Jusef Hassoun and Bruno Scrosati have developed a lithium-metal-free battery, using a carbon lithium sulfide composite as the cathode and a tin carbon composite anode.
The difference here is Li-ion batteries use a process called intercalation to store lithium ions by inserting the ions between molecules in the electrode, while lithium-sulfur batteries rely on a multi-step redox reaction with sulfur that results in a number of stable intermediate sulfide ions. This storage process, in theory, reduces limitations of electrode structure – thus enabling higher capacity in similar volumes.
“(One) major hurdle is the high solubility in the organic electrolyte of the polysulfides Li2Sx (1≤x≤8) that form as intermediates during both charge and discharge processes. This high solubility results in a loss of active mass, which is reflected in a low utilization of the sulfur cathode and in a severe capacity decay upon cycling. The dissolved polysulfide anions, by migration through the electrolyte, may reach the lithium metal anode, where they react to form insoluble products on its surface; this process also negatively impacts the battery operation,” Hassoun and Scrosati say in their paper.
The pair goes on to explain, “The key challenge is then to totally renew the chemistry of this battery such as to achieve an advanced configuration that can consistently provide high capacity, a long cycle life, and safe operation. Herein, we report an example of a lithium metal- free new battery version and demonstrate that, to a large extent, it can effectively meet these targets. In contrast to most of the Li–S batteries proposed to date, which are fabricated in the “charged” state, that is, using a carbon–sulfur composite cathode that necessarily requires a lithium metal counter electrode (anode) to assure the 16Li+S8→8Li2S discharge process, we propose to fabricate the battery in the “discharged” state by using a carbon lithium sulfide composite as the cathode.”
The pair has also replaced the common liquid organic solutions with a gel-type polymer membrane. Since the lithium ions necessary to drive the electrochemical process are provided by the Li2S/C cathode, any material capable of accepting and releasing lithium ions can be chosen as anode to replace lithium metal, they said. They chose a tin/carbon nanocomposite, with Sn/C at 1:1 by weight. The specific capacity of the improved Sn/C electrode matches that of the Li2S/C electrode, and the Sn/C has high chemical stability.
It’s a slick take on the problem – the chemical process goes from the conversion of lithium sulfide into sulfur with the release of lithium ions, which travel through the electrolyte to reach the anode where they form an alloy with the tin. Completing the process cycle is the reversible reaction of the lithium – tin alloy with elemental sulfur to form tin metal and lithium sulfide.
The pair is saying the results are effective in controlling most of the sulfur based lithium technology problems. Their calculation shows the innovation could drive specific energy to the order of 1100 Wh kg-1, a value not previously achieved for a lithium metal-free battery.
Hassoun and Scrosati note the “the road to a practical lithium-sulfide battery is still long,” with optimization of the electrode morphology and cell structure needed to further improve the cycle life and the rate capability.
This is progress, offered in multiples of capacity that should excite the electron storage folks quite nicely. Lets hope the puzzle of cycle life and costs come up solved and low cost.
Go here to see the original: New Energy and Fuel
Tags: energy, is lithium sulfide soluble, lithium sulfide, lithium sulfide battery, lithium sulfide higher theoretical capacity, lithium sulfide solubility, lithium sulphide battery, new, picture of sulfur battery, structure of lithium polymer battery, sulfide as a cathode material li battery, sulfide battery, technology, ultracapacitor
Aug 2, 2013 Energy Talks
EEStor, the now famed ultracapacitor maker of the future is one step closer to having a product coming to market. Last week saw information escape that EEStor has contracted with Polarity of Rancho Cordova, California to design and specify the construction details of the ultracapacitor’s power converter. A power converter would ideally provide a combined capacitor and controller set to deliver steady electrical energy at optimal voltage and amperage.
The power converter would be effectively a transformer, a device that steps down the ultracapacitor’s high voltage to a lower voltage that can be used in motors and other devices. Reports have it that the EEStor capacitor’s voltage peak is about 35 to 37 hundred volts, much more than electric motors are currently designed to cope with. Although high voltage allows smaller wires, lighter weights, and other attributes, insulating for high volts has it own issues such as more dimensional needs meaning a larger physical size, voltage insulation that can contain the “pressure” as high voltage much more easily jumps away to grounds, penetrates insulation, and can heat conductors very quickly.
The power converter speculation is supposed to reduce the voltage to the more familiar 600-volt range. Many insulation types can deal with voltages in that range at low cost and the dimensional issue nears optimal with today’s technology. At to 400 to 600 volt range, particularly using alternating current very high power output can come from very small packages.
This writer is also assuming that Polarity will offer the power converter with an internal method of providing steady output voltage from capacitors that one expects have voltage drop as they are drained. Thus the transformer inside would be a variable type that adjusts to the available voltage while the load voltage is a constant.
Some sites are crediting Polarity’s photos, links and products to the EEStor contract. Those assumptions are certain to be in error, even if interesting. A little closer reading of the Polarity site makes clear that the products on hand have existing markets. Most products have generator or battery input voltages; no mention is easily seen of ultracapacitor input products. As noted the voltage decline will entail certain design modifications to extract the maximum available charge.
Meanwhile snoopy reports have it that EEStor will prove publicly the capabilities of their technology before the end of September 2009. The context of these, blogs, hypetype news media, etc. tend to overstate the ‘proving” but EEStor may well have announcements in that area.
Factually though the whole thing is based on Polarity’s tight acknowledgment saying on their site, “Awarded contract from EESTOR to integrate Polarity’s high power HV to LV converter into EESTOR’s EESU that will be used in Zenn Motor Company’s small to medium size electric car.” EESU would be “electrical energy storage unit.”
It seems to be time for those seriously interested in electron storage to come up to speed with EEStor. This is a link to a transcript of Mr Weir, of EEStor and Tyler Hamilton, senior energy reporter and columnist for the Toronto Star. Significantly, at 14:04 where Weir says,
“We’ve taken those specifications to our circuits company that builds our circuits for us. A company called Polarity. They’re out of California. ZENN has gone there and came back very impressed. I was lead to them by the Air Force Research Labs because they’re so effective in building high performance converter circuits for them. However there are multitudes of companies around the world that could build these circuits in high volume. But, I got started with them so … they’re building our circuits right now. They’re actually putting the ZENN circuits together literally as we speak. I’ll be going out there, if not next week the following week after that to have a long session with them to talk about getting the parts in here quickly so I can not only do … I don’t want to stop and build circuits for component testing I want to use their circuits for full EESU testing. Which is also component testing. So I kill 2 birds with 1 stone there. And get that in here and get that tested and get UL in here start looking at it. So, that’s going quite well.”
Of major note, Weir is suggesting that UL aka Underwriters Laboratories has been invited in to start their process. Things are much further along than thought.
While much is made of the impact the EEStor device might make across the whole of the electric spectrum Weir reminds us at 24.28 that:
“You can take the grids of the world and put our batteries on it and charge ‘em at night and dump ‘em during the day. Well known fact you can put 45% more electricity on the grid and do nothing more than put our batteries on there.”
This could be a very advantageous development for consumers when peak demand generation has serious competition.
Go here to see the original: New Energy and Fuel