## Panasonic to Begin Volume Production of New 4.0Ah Li-ion Cells with Si-Alloy Anode in 2012

##### 02 March 2010

Nikkei Electronics Asia. Panasonic will begin volume production of its new 4.0Ah Li-ion secondary batteries featuring an enhanced nickel (Ni) cathode and silicon (Si) alloy anode (earlier post) in fiscal 2012. At its announcement of the cells in December 2009, Panasonic had said volume production would begin in fiscal 2013 (ending March 2013).

Initially intended for use in notebook PCs, the 18650 format cells offer a high volumetric energy density of 800 Wh/L, compared to the 620 Wh/L in the current 2.9 Ah cells; however, the gravimetric density is about 252 Wh/kg—comparable with existing graphite designs. The new high energy density cells weigh about 54 g per cell, about 10 g more than the NCR18650A model.

Although silicon offers a very high capacity as an anode material, lithium ion insertion into and extraction from silicon are accompanied by a volume change of up to 300%, which induces a strong stress on the silicon particles and causes pulverization and rapid capacity fading.

Panasonic claims to have addressed that issue through its fabrication techniques and made other unspecified modifications in the material, and that after 500 charge/discharge cycles, the cells retain at least 80% capacity.

Panasonic’s success in solving the technical issues when using silicon anodes instead of graphite anodes is a huge breakthrough that cannot be understated. Cells that are using graphite anodes are almost as good as they get with Panasonic’s also forthcoming 265 Wh/kg 18650 cells. The shift to silicon anodes means the development of higher energy density cells can continue at full speed. Moreover, I am almost certain that the silicon based cells are safer because silicon can’t burn unlike graphite that burns well.

Note also how small the silicon based cells are in a vehicle application. The LEAF by Nissan only needs 24 kWh to go 100 miles or 30 liters of these silicon cells (=24/0.8kW/l). Such a battery pack can be made to measure 100 cm * 30 cm * 20 cm = 60 liter or plenty to accommodate both cells and packaging material. A small pack like that can easily fit under the back seats of a car to be swapped in less than 2 minutes at a battery swapping station. Moreover, with a pack weight of only about 120 kilo it will also not make the BEV more heavy than a regular car as the electric drive train could be about 120 kilo less heavy than the transmission and the IC engine in a regular car.

If the price of these batteries is low it does not matter much that they only last 500 times to 20% degradation as they can be swapped with a new battery at a battery swapping station.

An idear - Battery swapping standardization.

As I wrote above you can fit a 24 kWh battery pack in a convenient form factor measuring only 100 cm *30 cm * 20 cm using these new Panasonic cells. Such a pack could go under the back seat of the car but it could also fit under the rear of the car or 2 packs of this size could fit under the front of the car. This allows for a lot of design flexibility with regard to battery electric vehicles (BEVs). Future battery swapping stations could be made to use the same form factor for these battery packs and be able to swap batteries in any of these four locations under the car. For instance, such a system would allow a heavy SUVs to use up to four of these 24 kWh packs in combination giving a total of 4*24 kWh = 96 kWh. This is enough for almost 200 miles EV range in such a vehicle.

If battery swapping companies like Better Place can agree on a standard for batteries like the suggested form factor any kind of passenger vehicle can be accommodated.

Heavy duty vehicles, such as long-haul trucks, could use a larger battery form factor and a bigger battery swapping station that can handle for example 500 kg batteries.

This is another step in the right direction. More are coming soon from many labs and start ups.

Advanced batteries will eventually reach an energy density of over 1000 Wh/Kg and will be adequate for 500+ Km BEVs. It is just a matter of time. Many expect those batteries to be around by 2020 or shortly thereafter.

Will mass production and worldwide competition reduce the price to between $100 to$200 per Kwh by 2020? Could be so.

Standardized plug-in modules could introduce more flexibility and choice for buyers. A 150 Km city e-vehicle could be turned into a 500+ Km long range e-vehicle by installing 3 to 4 more plug-in modules.

That is impressive from a 18650 format cell that is just a bit bigger than a AA battery. Good news for laptops, but I still would not want to make an EV battery pack out of thousands of them.

When you look up laptop batteries, there are hundreds of different makes, models, form factors, voltages when just standardizing would have made it simpler and cheaper.

Standardization and innovation are not opposites but can be standardization can be an impediment to advancing the state of the art.

Mandated commonality and high volume as the way to reduce costs can often be simplistic and ineffective.

The Soviet block can make one microwave oven design and they are unaffordable and unreliable. The free market makes no two alike (almost), they are cheap and very reliable.

Of course the magnetrons inside (more comparable to batteries then the whole oven) may be from only a few sources - but that is not mandated, just more free market rewarding the best design.

A battery pack shape is not innovation. Laptops mostly have the same configuration with a slide in battery and they all have DC to DC converters. I would not compare industry standards to Soviet microwave ovens.

Battery improvements are driven by innovation and mandates are not the answer.

TT, right about the market building and selecting best design - usually. But not always. e.g. the VHS vs Beta wars. Sometimes marketing muscle overrides best design and we get... VHS. With regard to small cell batteries - there already are standardized forms.

As for large size batts - I'd say it's far too soon with too many variables to try to build to a fixed standard. Issues like cooling systems and shape will be custom to EVs for a while yet.

One design for every buddie? Nyet.

But not always. e.g. the VHS vs Beta wars.
Yes. Not always.

But neither standardization, mass productin mor massive government grants should be the automatic response to a needed technology advance.

I am not advocating mandates, but industry standards. The diskette, the USB flash drive and other products are not part of any mandate, they just make sense. People like standardization, you can have flash cards or the Sony memory stick. People would like the readily available industry standard flash cards. No need to make this into a political ideological diatribe.

The comments to this entry are closed.