Independent Testing Shows Safety of Valence Lithium-Ion Phosphate Batteries
08 August 2007
Testing by Exponent, Inc., an engineering and scientific consulting firm, found that it is “improbable” that Valence’s lithium-ion phosphate batteries will incur the thermal runaway that can cause other li-ion batteries to burst into flames or explode.
Commercially available lithium metal oxide batteries were also tested and shown to heat to temperatures up to four times that of Valence’s lithium phosphates.
The phosphate cathode material used in Valence’s batteries is proving to be a key component for the next generation of lithium-ion batteries for applications where safety is of paramount importance.
In our comparative testing, the lithium-ion batteries using the phosphate cathode materials have proved to be the safest. In a real-world environment comparable to a battery being left in a parked car on a summer’s day, Valence’s phosphate cathode material was proven to have a greater thermal stability to withstand battery cell decomposition than batteries using lithium cobalt oxide or lithium mixed metal oxide.
—Dr. Quinn Horn, Managing Engineer, Exponent
The move towards hybrid cars has also forced closer examination of the risks of using lithium metal oxide batteries in vehicles or as a backup power solution for mission critical services such as telecommunications.
The enabling abilities of large format lithium phosphate batteries are extensive—they can create new markets and, transform existing markets such as automotive. The broad adoption of large format lithium phosphate batteries has been challenged by concerns about safety. This report shows that Valence’s lithium phosphate batteries are able to avoid the dangers of traditional lithium cobalt oxide batteries.
—Robert L. Kanode, President and CEO of Valence
The comparative testing included three primary tests performed on the batteries.
The Crush Test showed that Valence phosphate cells did not reach temperatures sufficiently high enough to cause melting or ejecting, flaming and/or burning debris. In addition, the peak external temperature of the Valence phosphate cells was more than 100 degrees C below the temperature required to initiate thermal runaway.
The External Heat Test showed that the peak temperature reached by the Valence phosphate cells was several hundred degrees lower than the cells of the other chemistries tested, and no ignition of nearby combustible material was observed during venting.
The Accelerating Rate Calorimetry test (ARC) was conducted to determine the rate of temperature increase and evaluates a material's reactivity/ instability under elevated temperature conditions to assess any potential hazards for such material. Valence phosphate chemistry showed a much lower self-heating rate, more than 100 times slower, compared to either commercially available lithium cobalt oxide/mixed metal oxide cell chemistry tested.
The thermal instability of lithium metal oxide batteries—LiCoO2, in particular—is directly related to the ease of oxygen liberation from the LiCoO2 structure.
By comparison, strong covalent bonding between oxygen and P5+ in an iron phosphate cathode (LiFePO4) form (PO4)3- units for greater stabilization of the structure compared to the layered oxide materials, where the oxide layers are more weakly bound.
Valence developed a novel olivine lithium iron phosphate complex (P1a)—the core of the proprietary Saphion Technology—for use as a cathode material. Even under severe abusive conditions this material will not liberate oxygen and therefore does not pose a significant safety hazard.
Resources:
"Improbable" hardly inspires confidence, though the rest of the article suggests that this term is just the consultants covering their legal behinds. Li-ion battery fires are very rare even with the less stable cobalt-based cathode chemistry.
With safety addressed, the remaining targets are longevity in carefully managed conditions, power density, energy density and low cost. Chances are, you can have any three.
My preference would be for electric storage to focus initially on power density over energy density. Full-fledged BEVs are really expensive if they are to have any meaningful range at all. A better step would be to make micro- and mild hybrids much more commonplace. The objective should be to apply only just enough electric propulsion to support aggressive downsizing of the ICE and, to eliminate or mask its least attractive operating conditions (e.g. idling, turbo lag, engine braking). In most cases, ~50Nm torque @ ~1500 RPM (~8kW) for just a few seconds at a time should be quite sufficient.
If advanced batteries can do this better or at least less expensively than ultracaps, great. Just put them in a LOT of models to get prices down so affordable and reliable PHEVs and BEVs can follow in the course of the next decade.
Posted by: Rafael Seidl | 08 August 2007 at 10:32 AM
I looked into getting these for my bike. They were a great fit in every way (including the standard motorcycle battery format) except price. ($5000 for 3KWH) Of all the attributes that Rafael just listed the price is number one on my list.
Rafael are you primarily concerned with power density as it relates to PHEV batteries for cars? For BEV motorcycles I find energy density to be more of an issue.
Posted by: Neil | 08 August 2007 at 10:37 AM
Raphael:
Couldn't you satisfy both power and energy densities with the proper combination of ultracaps and batteries? Of course, cost may shoot up but that's what normally happens with more requirements.
Posted by: | 08 August 2007 at 11:07 AM
Don't most of the mild hybrids add a lot of drag to the drive train? How do you get around that?
Posted by: HealthyBreeze | 08 August 2007 at 11:35 AM
Good Job Valence! But honestly this tell us anything that we didn't know already.
Posted by: paul | 08 August 2007 at 12:00 PM
"Mild" hybrid designs such as IMA add very little drag to the electric engine, compared to traditional belt/alternator systems. Alternators place a much greater load on the engine due to friction in the belt, heat loss in the belt due to slippage, increased friction due to the extra bearings in the alternator, friction of the brushes, losses in the rectification and regulation circuitry, and drag from the crudely shaped cooling fan on the alternator. "Mild" hybrid systems using a belt drive suffer many of these same losses, and incur weight penalties due to heavier wiring, windings, and magnetic structure, if the voltage is lower (48 volt). "Full" hybrids such as Synergy drive do incur losses as electric current must be continuosly generated to prevent the main hybrid motor/generator from free-wheelimg. These losses are compensated for by the ability of the Synergy system to run in a lossless electric mode at lower speeds and by the simplicity and low friction of the planetary drive system. The next generation of Synergy drive might get around this issue in part by using a brake on the main electric motor, or as is the case on certain Synergy drives , linking the hybrid system "through the road" by using a separate electric motor/generator on the rear axle.
Posted by: Kip Munro | 08 August 2007 at 12:27 PM
independent?
http://www.greencarcongress.com/2007/06/mit_students_el.html
Posted by: abc | 09 August 2007 at 02:23 AM
Nothing we do not already know - exactly. This is not news. We should all have it well engraved on the brain by now that LiCoOx is NOT acceptable for automobiles, let alone the Cobalt supply and cost problem (insurmountable). The nickelate or LiNiMnCo materials are also unsuitable - still too much Co and Ni plus cost and instability. The only viable LiIon technologies for cars are either LiFePO4 or MnO2 - either layered oxide or spinel. Manganate spinel has the best low cost potential since electrolytic MnO2 is dirt cheap and inexpensive to process, unlike the FePO4 (cheap material, expensive processing).
What IS the IP position on FePO4 with Valence, Texas A&M, A123 and Uncle Tom Connleigh?
Posted by: Emphyrio | 18 August 2007 at 12:45 PM
Valence, A123, and NITTO in Japan are all still embroiled in an IP lawsuit brought on them by Hydro Quebec who licensed the UT patents to Phostech Lithium, Canada from the original Goodenough Patented technology encompassing LiFePO4. It remains to be seen who wins this (besides lawyers) but is unresolved as of today.
LiFeBATT, Inc. makes large format LiFePO4 cells and complete battery packs with their own BMS & molded cases in Taiwan. We use the Phostech licensed process and a Hi-Power powder formula specially developed in Phostech's plant in Munich, Germany.
Our standard packs will be available in November, 2007 and complete pricing and order information can be seen on our new website: http://www.lifebatt.com/
Posted by: Don Harmon | 09 September 2007 at 10:08 AM
LiFePO4 cells supplied by Falconev in 8, 10, or 12Ah units are available individually or in packs.
P or E type. See website for more info.
Posted by: FalconEV | 29 January 2008 at 04:35 AM
Is the Lithium Battery Ready for Electric Vehicles?
In our lithium work at TRU we have proactively studied and read many reports on the readiness of the lithium-ion battery for HEV and EV. Most expert opinion says that in about five years 2013 the technology will be ready and as a result the electric vehicle market will take-off like the proverbial hockey-stick. Yet none of these experts can explain succinctly why they expect this breakthrough to occur. If you have the explanation we would like to have it and I am sure the readers of this forum will too!
Also if you are a company developing lithium batteries for electric vehicles please contact us at TRU urgently. We are engaged now - January 2008 - in developing a long range 2020 forecast of the lithium market and could include your company in our technical review of electric vehicle battery technology.
The lithium supply-demand issue is much more complicated. The lithium industry is controlled by very few players and is quite secretive. In addition it needs real experts to estimate lithium reserves and whether it is economic to extract them. On the lithium demand side many of the numbers published in the industry come from very doubtful sources and have been proven to be inaccurate. Some of the forecasts that have been put out and then widely circulated have no foundation. And regretfully many forecasts for the electric vehicles and the lithium battery for those vehicles fall into this category.
We at TRU have and are continuing to analyse the outlook for lithium on both the supply and demand side of the equation. However, our team includes lithium brine & mineral resource geologists, lithium processing specialists, battery & electric vehicle experts, lithium lubricants veterans, and the like. Our conclusions needless to say are very different from those usually presented.
Please contact me through this forum or visit our website trugroup.com. The link to the TRU Group Inc lithium page is http://trugroup.com/Lithium-Battery.html
Posted by: TRUGROUP | 05 February 2008 at 08:10 AM