Energy

Hybrid supercapacitor offers NiMH energy density, charges much faster

Hybrid supercapacitor offers N...
QUT researchers have demonstrated a hybrid supercapacitor design that stores vastly more energy than a regular supercap while offering charge/discharge rates much higher than lithium batteries
QUT researchers have demonstrated a hybrid supercapacitor design that stores vastly more energy than a regular supercap while offering charge/discharge rates much higher than lithium batteries
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QUT researchers have demonstrated a hybrid supercapacitor design that stores vastly more energy than a regular supercap while offering charge/discharge rates much higher than lithium batteries
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QUT researchers have demonstrated a hybrid supercapacitor design that stores vastly more energy than a regular supercap while offering charge/discharge rates much higher than lithium batteries

Researchers at the Queensland University of Technology have added another hybrid supercapacitor design to the mix, promising the near-instant charge and discharge of a supercap with vastly improved energy storage on par with NiMH batteries.

The key concepts to understand here are energy density (Wh/kg), referring to the total amount of energy a device can store per weight, and power density (W/kg), referring to how quickly the device can move power in and out while charging and discharging.

Lithium batteries store energy in a chemical form, and are widely used because they offer a relatively high energy density, but as anyone who owns a smartphone or electric car knows, they charge fairly slowly. Supercapacitors, on the other hand, store energy statically rather than in a chemical form, meaning they can charge and discharge much, much faster without degrading their internal structures. Thus, they have a very high power density, but this is offset by the fact that their energy density is much, much lower than chemical batteries.

In recent times we've covered a number of devices that sit somewhere in between the two: hybrid supercapacitors that lean into the middle on both metrics, storing a lot more energy than a regular supercapacitor, while charging almost as quickly. Your car or phone battery won't last as long with one of these on board, but it'll charge so fast that range might cease to be an issue.

In new research published in Advanced Materials in December, the QUT team describes a design that uses a capacitor-style titanium carbide-based negative electrode and a battery-style graphene-hybrid positive electrode. The result, says the team, is a hybrid capacitor with a power density (and thus charging capability) "about 10 times that of lithium batteries", and an energy density "close to that of nickel metal hydride batteries."

The actual figures are a tested energy density up to 73 Wh/kg – thus about 28 percent of what today's state of the art EV batteries offer – and a sky-high power density up to 1,600 W/kg, where lithium batteries offer around 250-340 W/kg. So let's say you pop a pack like this in the Tesla Model S Plaid+. Instead of a 520-mile (837-km) range, you'd be getting more like 145 miles (233 km), but you'd be able to charge at least five times faster if the infrastructure allows. And yes, infrastructure is a bottleneck right now. Super-high-rate charge stations will get into the megawatt range, placing extreme strain on the energy grid unless they have huge energy storage capacity on site.

The more demented acceleration freaks among us would be pleased to note that power density works both ways, meaning the battery pack would provide no impediment to truly monstrous power outputs. Where today's Plaid+ Tesla makes a ridiculous 1,100-plus horsepower, a hybrid supercap-based equivalent would have a battery pack capable of feeding five times that power to the motors. Completely impractical, but that's never stopped performance car lovers in the past.

The QUT team is pleased to note that these hybrid supercaps also last about twice as long as lithium batteries on the test bench, retaining 90 percent of their initial storage capacity after 10,000 full charge/discharge cycles.

These numbers are in the ballpark of what Kurt.Energy is finding with the low-density hybrid powercapacitors it's receiving from Shenzen Toomen New Energy, what the Skeleton SuperBattery is promising, and what Chinese/British researchers found with their design last year. Thus, while not appearing to blow anything out of the water, and without any immediate commercialization plans, this news adds even more academic credibility to the hybrid supercapacitor sector as a whole.

While electric car battery packs are an easy point of comparison to current technology, hybrid supercaps are unlikely to replace lithium batteries in the EV world, where range anxiety is still such an issue for buyers. But as Skeleton points out, there are plenty of other applications where these in-between solutions will find their place. They may replace the lead-acid board net batteries that are still required in today's lithium-powered EVs. They will be excellent for quick-response power-smoothing and peak load management in industrial settings.

The research is available for free access in the peer-reviewed Advanced Materials journal.

Source: QUT

10 comments
10 comments
ClauS
This is a nice development albeit a little to late. It could have been used in hybrid vehicles where high instant power was required for acceleration and regenerative braking, but now the shift to plug-in hybrids made the lithium batteries a must. Also the article is misleading that the hybrid-Scap is offering about 28 percent of state of the art EV batteries offer. Today's state of the art EV's are using lithium batteries, and Tesla's cell is reaching around 250 Wh/kg specific energy, almost three and a half more than this capacitor.
paul314
Sounds as if what's needed is a hybrid-hybrid battery pack: enough supercap batteries to supply motors at full acceleration (for some relatively short time) and then as many lithium batteries in the main store as needed to keep the supercaps topped up and supply energy for long range.

@ClauS it seems that the article is being conservative if your number for Tesla is right. 73 Wh/kg is a touch over 29% of 250 Wh/kg.
EJ222
These would be a perfect match for the limited range EV + backup generator setup.


I don't understand why that fell out of vogue. One gets all the advantages of EVs, with the range and infrastructure of hydrocarbons when needed, plus more efficiency than a traditional hybrid setup. And a tiny generator doesn't add very much weight to a pure EV, especially if the battery size can be reduced.
jerryd
Whenever you hear the words supercapacitor and battery combine, hold onto you wallet as another scam.
For instance the new Tesla battery pack will not only put out 4Mw but do it for a while.
Tesla bought the biggest SC producer, Maxwell, got the dry process but couldn't sell the SC line because SC cost, weight, space 30x lithium batteries of the same specific power, SC so called only point..
Daishi
Rather than a hybrid automobile consisting of ICE + battery it could be made from a battery + capacitor. The idea behind the capacitor is that it could be charged quickly while you are stopped for a brief amount of time potentially even at a place like a red light. To give an example: If the capacitor only has a 4 mile total range and you recharge it every 8 miles then you would get 1,000 miles of range out of an EV with a 500 mile main battery because you are only relying on it half the time. Other cool tricks with such a system would be things like preparing the car for "launch mode" by not discharging it in regular driving or by charging it from the main battery to prepare for a single ludicrous 0-60 or 1/4 launch. Even in a lithium ion powered auto industry super capacitors offer the opportunity to throw some interesting curve balls into the mix of options.
DaveWesely
This nails it: "They will be excellent for quick-response power-smoothing and peak load management in industrial settings." Stationary battery for backup and Cat III EV charging do not need a high energy density. In those cases, cost and longevity are the main concerns. Not only does this fit the bill, it also allows for quick power dumps to EV's at fast charge stations.
toni24
by placing one of these in the standard EV battery pack one could do some serious regenerative braking and very impressive acceleration while only using the standard EV portion for maintaining standard highway speeds. And for the sci-fi nuts among us it omes close to the power requirements for "ray guns"
Philip Argy
Is it feasible to fast-charge the on-board capacitor and then use that to charge the battery whilst in transit (or when next stationary if that has to be the case)? So essentially you just have an on-board charging station?
Mark Griffiths
The hybrid capacitor is 16,000 w/kg power density. Automotive grade Lithium ion is more around 800-1200 w/kg, with some high performance lithium ion batteries around 3000 w/kg (formula e) and even up to 7500 w/kg for ultra high performance batteries.
ljaques
I'll wait for either 1) a 4-10x lithium efficiency jump or 2) the Mr. Fusion, please.