Hitachi Automotive Systems supplying 5 kW/kg high power density prismatic Li-ion cells for MY 2016 Malibu Hybrid
20 May 2015
Hitachi Automotive Systems, Ltd. will supply 5,000 W/kg high power density prismatic lithium-ion battery cells for the new MY 2016 Chevrolet Malibu Hybrid (earlier post). Featuring a new full-hybrid powertrain which leverages technology from the Chevrolet Volt, the 2016 Malibu Hybrid will offer an estimated combined fuel economy rating exceeding 45 mpg (5.22 l/100 km).
The Hitachi Li-ion cells employ heat resistant separators to ensure the ionic conductivity between the electrodes, achieving not only a high output power density of 5,000W/kg, but also a high level of safety. In addition to this, the battery’s ability to maintain its high output power density in GM evaluations, even under extremely low temperatures such as the -30 ˚C cold region test, led to its adoption.
Hitachi uses an NMC cathode paired with a hard carbon anode.
| Cell Specs | ||
|---|---|---|
| Size (mm) | 120×80×12 | |
| Weight (kg) | 0.24 | |
| Average Voltage (V) | 3.7 | |
| Capacity (Ah) | 5.2 | |
| Output Density (W/kg) | 5,000 | |
| Energy Density (Wh/kg) | 80 | |
The new cell is a modification of Hitachi’s 5.3 Ah prismatic cell, which featured a specific power of 3,400 W/kg and specific energy of 76 Wh/kg.
GM had earlier used Hitachi’s cylindrical 4.4 Ah Li-ion cell—a downsized and lightweighted version of the 5.5 Ah cylindrical cell in use in hybrid-electric trucks, buses and trains—in hybrid products. Those 4.4 Ah cylindrical cells had a specific power of 3,000 W/kg and specific energy of 61 Wh/kg.
Hitachi’s lithium-ion battery operations for vehicles began in 1999. To date, a total of more than 5 million lithium-ion batteries have been introduced into the market for commercial hybrid buses and trucks, as well as hybrid passenger cars.
Last year, Hitachi Automotive Systems integrated the lithium-ion battery manufacturer Hitachi Vehicle Energy’s design and R&D departments, advancing lithium-ion batteries by using the electronic, control, and software technology the company possessed toward battery control system development. (Earlier post.)
That is pretty good energy density for such high power.
I was shocked when I discovered that the battery in a Prius at ~1kwh weighs in at 50kgs!
There would be plenty of overheads at the pack level for this too, but we can hope that the weight might come down to a more reasonable ~25kgs or so for a hybrid.
Posted by: Davemart | 20 May 2015 at 08:48 AM
Pretty; but, With a density of 80 Wh/Kg this is not what I'm waiting for. The 2011 Nissan battery was 141 Wh/Kg. I would like to see a 300 Wh/Kg battery...then, I'm excited.
Posted by: Lad | 20 May 2015 at 09:23 AM
@Lad:
The far smaller, high cycling batteries in a hybrid are a totally different matter to those in a PHEV, let alone a BEV.
The energy density is way less as you need much more power and lots more cycles.
Posted by: Davemart | 20 May 2015 at 09:32 AM
This small much lighter unit could replace the heavy 50+ Kg unit used in regular Toyota Prius?
Alternatively, 50 Kg of this battery could run a regular Prius on electricity only for 5+ Km instead of 1 Km.
Posted by: HarveyD | 20 May 2015 at 09:44 AM
Harvey:
If you are building a PHEV you can get much higher energy density than these do as you don't need the same power or cycle life.
Different problem, different solution.
Posted by: Davemart | 20 May 2015 at 09:50 AM
IIRC, the Malibu pack is 1.5kWh, so that's 78 of these cells, or 18kg of cells (plus harnesses, wiring, module, pack, thermal). At 5kW/kg, that's 90kW of power from this small battery pack. Impressive!
Posted by: Anthony F | 20 May 2015 at 12:56 PM
DM...this battery is no great breakthrough (with regards to energy density) but it would be much superior to the one Toyota uses in their regular Prius and Camry Hybrids.
Could also be superior as a main battery for future 48-V vehicles equipped with stop-start feature. .
Posted by: HarveyD | 20 May 2015 at 01:05 PM
@Harvey:
As far as I could find out, Toyota have simply put the Prius battery into the Mirai FCEV.
The lithium battery in the Hyundai Tucson i35 FCEV also weighs about the same.
Saving 25kgs or so would be handy for both.
I can't quite work out where all the weight in in them, the balance of system must weigh one heck of a lot, as the CF tank, fuel cell stack and so on don't come out to the total weight, even with the 50kg battery in it.
Posted by: Davemart | 20 May 2015 at 01:22 PM
Is the Prius battery not NiMh.
It certainly used to be.
Surely that would explain the weight (Mass).
Posted by: mahonj | 20 May 2015 at 01:36 PM
@mahonj:
That's what I had assumed, but the heavy duty cycle that these hybrids need meant to my surprise that the lithium batteries have no weight advantage over the NiMH, or didn't up to this new generation of batteries from Hitachi, and likely others.
That is why Toyota stuck to this robust and economical chemistry.
Perhaps they can also rise to the challenge and improve their energy density, but it seems rather unlikely.
Posted by: Davemart | 20 May 2015 at 01:42 PM
This is no new thing, similar cells from A123 are already used in some European hybrids, not to mention F1 and Porsche 919 KERS systems.
Toyota also used li-ion (Panasonic?) in their 7 sitter Prius+, it's placed between front two seats, probably half the size and weight of regular Ni-Mh.
Why Toyota doesn't introduce li-ion to all of it's hybrids? Could be cost, durability or just Toyota being conservative, who knows?
Posted by: GasperG | 21 May 2015 at 12:21 AM
GasperG is correct. I know that some of the F1 teams were using a special one off A123 battery that was cranking out 20kW/kg!
Of course, they probably cost more than my Mercedes by themselves LOL
Posted by: DaveD | 21 May 2015 at 10:22 AM
As I recall, the Prius battery was once limited to about 15 kW.
Double that, as a reasonable first step. 30 kW of power at 5 kW/kg requires just 6 kg of cells, or 24-25 of these cells at 240g/ea. Alternatively, go for a reasonable battery mass of 20 kg, achieving 100 kW of peak power. That puts the stock Prius to shame.
If these cells don't cost an arm and a leg, they are going to make stop/start and hybrids a lot more smooth, powerful and successful in the marketplace.
At 80 Wh/kg, a 20 kg battery holds 1.6 kWh. If the SOC range isn't constrained too much, this allows significant PHEV capability (several miles) at the cost of a charger. With the charging connection comes the capability for e.g. cabin pre-conditioning, so this is a very worthwhile undertaking.
Posted by: Engineer-Poet | 22 May 2015 at 05:56 AM
Prius and Li -ion batteries having been mentioned I might add that :
Readied for release in the fall of 2008 the power battery for the 2009 Prius was intended to be of the more advanced Li-ion. However a year earlier there had been a series of fires associated with Sony laptops widely advertised as having Li-ion cells.
Since the Prius had no serious competitors at the time ( and IMO still doesn't ) their marketing dept decided why take the risk with these new cells if their adoption was likely to impact sales of their hybrid marque, consequently the MY 2008 car was allowed to carry through September 2008 and become the MY2009. Meanwhile the intended car was partially reverse engineered to enable its use to continue with the existing NiMh battery. Because of the delay the new design car for 2009 MY was eventually released as a 2010 MY in March /April 2009 instead. That car was manufactured continuously from December 2008 all the way through to July 2010. And then for MY 2011 for those ordering leather seats, tan colored seating became an available option. AFAIK that was the only change noted in the MY 2011 brochure as Toyota sought to recover its losses regarding the battery anomaly. Or at least that is my speculation.
Going back to the MY 2004 this was the first model year to use the 201Vdc battery with the newly introduced upconverter which allowed the MG1 and MG2 servomotors to run from 500Vdc and gave the Prius an acceptable driving characteristic. Both the earlier versions of previous years using the 273Vdc battery were known to be somewhat anaemic. Incidently both the 273Vdc and 201Vdc batteries were rated at 1.3 Kwh of storage. The conventional lead-acid installed within an ICE vehicle is around 0.9Kwh.
The 21Kw upconverter supplied effectively 28Hp from the 201Vdc battery which along with 76Hp from the 1.5L 1NZ-FXE engine supplied a total of 104Hp from 51mph to 99 mph (electronically speed limited). During (regenerative) braking the power fed back into the battery was limited to just 10Kw for battery longevity reasons no doubt. Recently I remarked to a Toyota mechanic that I had seen photographs of Prius brake rotors which seemed lightly used even after 50K miles. He responded that from his end brake corrosion was an issue since there was not enough subsequent friction braking to dry out the rotors from driving in wet weather.
For buyers wanting more than the 4 minutes of all-electric driving at speeds below 42mph, the Plug in Prius has been available but there have not been a large number of takers because of price sensitivity to this upgrade. For the same reason GM's Volt sales have not been all they could. Hopefully buyers will move away from this transitional technology and eventually go the full EV route now that public charging infrastructure is more prevalent. First however, manufacturers have to wise up and provide their snow belt customers with well insulated battery enclosures with good thermal management since costwise the battery is the car.
My opinion on the future for the Toyota Prius is for the company to realize that the emissions crown is moving over to EVs. Prius is no longer exempt to congestion charges nor allowed HOV privileges in increasing locales. Toyota has to realise that fuel consumption is becoming more the name of the game for hybrids as cash strapped governments move to establish new gas taxes. Smaller engine displacements along with compensatory higher engine speeds will be needed in future for the Prius to attract buyers and this will appear as a more economical route than simply beefing up existing electrical systems.
As regards battery chemistry the existing NiMh battery systems are proving good longevity and are unlikely to be swapped out any time soon. Neither do I see an AWD Prius be any more likely to attract buyers than AWD did for the Corolla back in the early nineties.
This Hitachi battery may improve the Malibu hybrid but didn't they already take this model off the market once before ?
Posted by: T2 | 22 May 2015 at 06:55 PM
HEVs with larger capacity battery pack become limited e-range PHEVs?
PHEVs with larger battery pack become limited e-range BEVs?
Real extended range BEVs need enough batteries to compete with today's ICEVs, specially in cold weather areas. Something like 4X (400+ kWh/Kg) lower cost ($100/kWh) batteries may be required. We may have to wait for 2020/2025 for for those competitive extended range BEVs to reach the market place.
Meanwhile, an acceptable short term compromise may be PHEVs with a small higher performance ICE or FC range extender?
Posted by: HarveyD | 23 May 2015 at 02:14 PM
HEVs using batteries batteries with a substantial SOC window, plus a charger, become limited-range PHEVs as well as a resource for grid regulation. If you have 500 Wh of charge to take on, and an hour to do it, you can switch the charger on and off to soak up temporary surpluses in power on the grid.
Posted by: Engineer-Poet | 24 May 2015 at 07:48 AM