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NEC develops prototype 4.5V, long-life manganese Li-ion battery; 30% more energy density, high capacity and light weight

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High voltage lithium-ion battery prototype. Click to enlarge.

NEC Corporation has developed a prototype next-generation manganese lithium-ion battery featuring cathodes that support higher voltage operations (4.5V rather than 3.8V) and an electrolyte solution that improves the stability of the higher voltage operations. These developments could help increase the range of electric vehicles in the future while reducing the weight of the batteries.

The new cathode and electrolyte solution improve battery energy density by approximately 30%, increase battery capacity and decrease battery weight, all while maintaining a high level of safety, based on the results of safety tests using a multilayer laminate-type cell. NEC presented the new cell at PRIME 2012, the Pacific Rim Meeting on Electrochemical and Solid-State Science, in Honolulu.

NEC currently develops and produces lithium-ion batteries with cathodes made with manganese. These technologies are used in large capacity storage batteries for electric vehicles as well as residential use. However, improving a battery’s energy density has been a challenging issue for further development. In order to solve this issue, NEC introduced higher voltage to batteries and made progress in the development of an electrolyte solution that suppresses the oxidative decomposition of the electrolyte solution that is generated on the surface of cathodes from the higher voltage.

These developments can contribute to increasing the driving range of electric vehicles, enabling the production of light weight storage systems and simplifying the management of battery systems by decreasing the number of cells. Furthermore, these new batteries provide high voltage drive and the same long operating life as conventional 4V lithium-ion batteries.

— Hidenori Shimawaki, General Manager, Smart Energy Research Laboratories, NEC Corporation

The new batteries are able to perform higher voltage operations as a result of using nickel in replacement of a material in existing spinel-structured manganese-based cathodes, which have a high level of safety while recharging.

The use of these cathodes and graphite anodes enables the average operating voltage to increase to a high voltage of 4.5V from the 3.8V of existing technologies. As a result, energy density increased by approximately 30% to 200 Wh/kg from 150 Wh/kg. This increases stored energy by approximately 30% when compared to existing batteries of the same weight. Alternatively, these new batteries are about 30% lighter when compared to existing batteries with the same energy storage.

To enable this, NEC changed the solvent of the electrolyte solution from a conventional carbonate-based solvent to a fluorinated solvent that is highly resistant to oxidation. This enables the suppression of oxidative decomposition where the electrolyte solution and the cathodes interface, which has posed a challenge for existing techniques.

These batteries maintain approximately 80% of their original capacity after undergoing tests with 500 full charge and discharge cycles in conditions below room temperature (20 °C), while maintaining roughly 60% when above room temperature (45 °C). Furthermore, the batteries demonstrate life span performance equivalent to that of conventional 4V batteries.

The practicality of these batteries are further demonstrated by the suppression of gas formation within cells and a significant reduction in the battery swelling ratio to 10% (more than 100% swelling in conventional batteries) after cycle tests conducted at above room temperature.

NEC says it will continue to drive research and development that supports greater capacity, life span and reliability for these batteries in preparation for their adoption by electric vehicles and large, stationary storage batteries alike.

Comments

Bob Wallace

Doug -

http://enviasystems.com/technology/

Energy density 400Wh/kg. 1,000 100% DoD cycles.

The 1,000 cycles may apply only to the cathode. In the anode portion of the page they state " This anode will be ready for commercialization in 2012 and will complement Envia’s high capacity cathode very well.".

wintermane2000

Ok sense some still dont seem to get the issue... if the POWER density is low enough you get a 60 kwh pack that only has enough power to move a moped. There are in fact batteries like that right now...

So will this battery at say 60 kwh pack size produce 30kw 60 kw 100 kw of power?

Bob Wallace

Their web site doesn't seem to say. I emailed Envia to see if we can get an answer to that question along with overall battery life (number of cycles).

Bob Wallace

Just something - some of the testing on the Envia was done at C/3 to 80%. If I understand that correctly the battery was 80% discharged over 3 hours which would suggest a decent power rating.

(I'm wading on my tip-toes at this point. Someone with better knowledge should step in.)

Davemart

Hi Bob.
We have considerable insight into these questions from previous discussions with Atul on this site.
I use extensive bookmarks to try to keep up.
Here is his comment on cycle life:
'@Davemart: All USABC specs for BEV are @ C/3 rate. Faster charge and discharge is possible - but for a 200 mile BEV a 5C rate is unnecessary. If it was a 12-15 mile pack (i.e. 10 KwH pack) I can imagine that the 5C rate is key. But for a 150-300 mile pack, C/3 is good enough.

We are looking for 150-200K mile life. So for a 50 mile pack, we will look for 3000-4000 cycles and for a 300 mile pack only 600-800 cycles. The number of cycles will determine the DOD and the energy window.'

http://www.greencarcongress.com/2012/02/envia-20120227/comments/page/2/#comments

And on their site the cycle life performance graphs:
http://enviasystems.com/announcement/

I don't directly have info on their power output, but they are basically trading off performance characteristics, and I would expect their highest specific energy battery to have relatively low power output, perhaps only enough to do the job in 75kwh and up packs.
The highest specific energy Panasonics have low specific power.

wintermane2000

Dang it c/3 rate is bad very bad... that means a 60 kwh pack can only output 20 kw of power... Thats 26 hp....

HarveyD

W-2000....is it possible that you may be 180 degrees out of phase on this one?

wintermane2000

Nope im right... unfortunely.

Bob Wallace

Wouldn't you expect C/3 was used as the average output rather than peak? I don't see anything on the site about max power output.

Davemart

The meme that batteries are ever improving on all criteria just is not happening, or at least at the pace that was forecast.
What is happening is trade offs in strengths.

I am starting to think that we will be lucky if we have much of a BEV industry by the spring.

Thank goodness that the Volt is doing pretty well.

wintermane2000

The problem bob is that if you up the drain all that much you lower lifespan quite a bit UNLESS you only need to do it very inoften... but at that low a power level it will need to do that too much. Remember mkost cars likely would only have sub 30 kwh packs thats only 10 kw of power most times and maybe 15-20 kw burst.... not good.

Bob Wallace

PHEVs would have a <30kWh pack. 200 mile range EVs will need twice 30.

It could be that periodic high power output could be Envia's weak point. Hopefully they will respond.

kelly

If power(rate of energy) output is the battery problem, parallel 5-10 sec. of super capacitor assist.

In reality, the max rated, WOT power of ICE or EV is less than a percent of use - unless one commutes by racetrack.

MG

@kelly,

You cannot just parallel supercaps to battery. There would be nothing to prevent current surge from battery to suppercaps when motor gets heavily loaded (during acceleration). Also current would rush to battery during strong regen braking (because battery and supercaps are directly connected, meaning the voltage will be the same)
The right way to use (larger) supercaps with battery in BEVs (and PHEVs) is to put a two-way DC-DC converter between supercaps and battery, which would limit max current that goes from/into battery.
Some simulations have shown that for some standard US driving cycles, for passenger cars, you could use supercap bank of no more than 200 Wh (3/4 of that being available, i.e. 1/2 VMAX discarge). That configuration could provide up to 3x max current of the battery pack, for short periods required in those driving cycles.
So by employing an extra two-way DC-DC converter you'd limit the max battery current, for the same max motor current. Also battery life could be significantly extended, as most current spikes would go through supercaps, not through battery
The price to pay for that benefit is extra DC-DC converter (sized for about 1/3 max motor current), and the supercaps bank. Supercaps are reportedly still very expensive - someone recently mentioned here $15,000 per kWh. I think that for the price of PHEVs to become affordable (the ones with smaller battery pack, paired with supercaps, used this way), the price of supercaps needs to drop by at least 60%, to $6,000/kWh. I expect the price of power components (for DC-DC) to keep going down, as it was always the case with mass produced electronics.
It looks very likely that batteries will always have to be designed either for high power (ie current) density, or for high energy density.
Once supercaps become much more affordable, small battery PHEVs will be possible, supercaps will provide high currents for short acceleration and braking periods.
Another advantage of this configuration is that the car can run in HEV mode with completely removed battery pack, just with supercaps bank. It would also increase resale price of older cars, with weak battery pack.

Davemart

@MG:
Supercapacitor/battery systems are already in extensive use in the Peugeot/Valeo/Maxwell system.
Clearly costs are way below that which you have indicated:
http://www.greencarcongress.com/2010/10/conti-20101014.html

A second or so of load to restart an engine or even the few seconds worth to recapture braking energy or provide acceleration uses tiny amounts of energy in terms of Wh, and so very small amounts of capacitors are needed, as they have massive specific power, which is what it is all about.

usbseawolf2000

They could use some high power density cells like A123 as a secondary battery and keep the high energy cells as a primary -- a hybrid battery pack.

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