GM Formally Unveils the Production Version of the Volt
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GM Working on New Li-Ion Anode and Cathode Materials with 3X Present Capacity

While lithium-ion has become the battery platform of choice for electric-based transportation, none of the different existing lithium-ion cathode/anode chemistry pairs can meet all four of the most important criteria for longer-term, broader application: performance, life, abuse tolerance and cost, said Tien Duong, Team Leader in the US Department of Energy’s (DOE) Vehicle Technology Program, in the opening talk at the 1st International Conference on Advanced Lithium Batteries for Automobile Applications (ALBAA), organized by Argonne National Laboratory.

Dr. G. Abbas Nazri from GM Research was a bit more blunt in his talk at ALBAA, saying “most of the current chemistry is not going to make it for plug-in and particularly for EV applications.” GM, said Dr. Abbas, is looking for about a three-fold increase in anode and cathode capacity over that provided by the conventional combination of carbonaceous anodes and layered oxide cathodes.

Two promising approaches GM Research is exploring on the anode side to reach this target are the use of silicon-coated carbon nanofiber; and the use of metal hydrides. On the cathode side, Abbas said that GM had developed a material with capacity close to the 3X target, but that he could not discuss that yet.

Nazri
Voltage profile of C-Si composite anode optimized for 1,000-1,500 mAh/g, and morphology of the composite anode plate. Click to enlarge.

The Li-C-Si anode is produced by layering silicon atop a carbon nanofiber. The anode material is produced first by reacting natural gas over a catalyst to produce the carbon nanofibers, and then using silane (SiH4) to put the silicon on top. GM is also looking at using the excess heat from the first reaction to support the second, further improving the cost and energy profile of the process.

The charge capacity of the resulting material can range approximately between 1,000 - 1,500 mAh/g; GM is seeking to optimize the system at around 1,000 mAh/g.

GM is also exploring using the Si-C nanocomposite anode material to form a carbon fiber anode plate, then using only copper tabs attached to the plate as a means to get expensive copper current collectors out of the system.

The other approach outlined by Dr. Nazri is the use of metal hydrides to produce a new generation of anode. In its work, GM has used a magnesium hydride, although the conversion reaction can be extended to all metallic and intermetallic hydrides, he said. GM improved the reversible electrochemical reaction of metal hydrides in a lithium cell through the formation of nano-sized particles of a hydride-carbon composite.

Theoretical capacity of the MgH2 anode is 2,038 mAh/g. GM has reached 1,510 mAh/g in its work with MgH2 materials, and further optimization of the cycle life is in progress.

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Comments

Ben

What ever happened to lithium sulfur cell research?

HarveyD

This may translate into a 300+ Wh/Kg battery pack.

That would be equivalent to the existing Electrovaya MN series (330 Wh/Kg) and may be OK for first generation PHEVs.

Much better performance batteries will certainly be available within five years.

Second generation PHEVs and practrical extended range BEVs will need 450 to 500 Wh/Kg batteries.

Aussie

I'm hearing echoes of the hydrogen car letdown. Perhaps in five years time those who can still afford cars will run them entirely on very expensive carbon based synfuel.

sjc

A bridge to getting there could be cellulose bio fuels and natural gas with HEV. We have seen advances in batteries lately, but a more practical approach might be more conventional. HEV/PHEV will advance the state of the art in batteries for BEV. One step at a time is a more solid method.

Ben

Lithium Sulfur can do up to ~500 Wh/kg

Allen

Which kind of cathode material?
Not NMC LFP LMO?

Mohsen

I am not convinced. Least of all that GM now wants to advance the state of the art in electrochemistry.

rob

I'm convinced. About a year ago GM's top brass finally realized that petroleum dependence represented a limit on their own growth potential. Events of the past year have only reinforced that. Nice to hear they're making progress on their next-gen of batteries.

Aussie

I don't envisage high temperature batteries in private cars. This 'solar electric bus' with Zebra batteries is either running or on recharge 24/7, not parked all day outside an office.

Andrew

These industry experts are waiting for all the ducks to line up in row before declaring a Li-ion automotive battery solution. They have vested interest in battery development projects, so I will take a grain of salt with their opinion.

As the article points out: Battery robustness, life and cost are all important factors. Energy density is just one of the performance factors for BEV's.

To my mind energy density is not as critical for BEV's as re-charge time, life and cost. When cost comes down enough, battery depreciation will be offset by gas savings. Energy density of 80-130 Wh/kg should be good enough for most automotive applications.

I'm pretty sure a vehicle can be designed to accomodate a lot of additional battery pack weight. I don't really see performance and range being heavily penalised by the 200Kg of additional weight.

Battery pack size is dependent on the end user usage pattern and re-charge facilities. A major obstacle for BEV acceptance is unwillingness to compromise on range.

I hope this will change. When one country or city goes electric in a major way, the advantages and trade offs should be more obvious. Buyers can make a more informed choice.

Bob H

What GM has decided is that a flex fuel approach is the way to go. That is why they are investigating fuel cells, batteries as well as pursueing advanced ICE engines. My suggestion is to get the power stering, air conditioning and heating off of the power trane and into the electric system. This will work on which ever car of the future technology wins.

GreenPlease

@Bob

They have done this for the Volt. The development costs for these simple technologies should be spread over GM's entire product line as eventually every product will feature these technologies as part of a mild hybrid package.

IMO: GM's fuel cell project should be ditched unless they have a skunkworks project working on a DCFC or SOFC, but to date this has not been the case: they have only showed their work on PEM FCs.

@everyone

I thought a silicon anode could potentially hold 1,000kw/hr?

sjc

"My suggestion is to get the power [stering], air conditioning and heating off of the power [trane]...

Heating for the passenger compartment from the engine cooling system makes sense. Electric assisted power steering makes sense. Even electric AC has merit, but I do not know what you mean by "heating off of the power [trane]..."

creativforce

Anyone who thinks lithium batteries are going to save us from dependance on oil should read: ^ "The Trouble With Lithium 2". Meridian International Research (May 28, 2008). Retrieved on 2008-07-07. Available online in the footnotes of the Wikipedia article on Lithium. There is a global shortage of lithium that is growing and clearly not enough of the metal available in the world to supply even 10% of the auto industry.

clett

creativforce, please try to keep up. There is no shortage of lithium as explained in the numerous subsequent reports replying to the uninformed ravings contained within the article you cite.

Colin R

What am I missing here in the calculations? GM has a cell operating at 1,510 mAh/g, or 1,510 Ah/kg, and is aiming for a capacity of 1,000 mAh/g, or 1,000 Ah/kg. At a cell voltage of 3.7v, that is 3.7 kWh/kg. Is that an order of magnitude higher than typically obtained? Thanks for the clarification.

Andrew

I also get confused. We often see high energy capacity claims for anodes or cathodes.

I don't understand the relationship but the final battery capacity always seems to be an order of magnitude lower than the theoretical anode or cathode capacity. I guess voltage is dependant on anode and cathode pairing.

If they say 3X current capacity, it depends what they are comparing with. Could be low energy 80 Wh/kg or polymer 330 Wh/kg.

I guess they are looking anywhere in the 300 Wh/Kg - 1000 Wh/Kg range. Probably don't know what they have yet.

Mannstein

Actually GM may not be around to carry out the lithium ion play. They have screwed up so many times the deserve to go belly up.

If I were a customer for an electric car I'd vote for a Zebra battery pack. If nothing else it would be cheaper and still work in winter.

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