Aug 9 2007
Comparative testing released today by Exponent, Inc., a respected engineering and scientific consulting firm, shows that it is "improbable" that Valence's lithium phosphate batteries will incur the thermal runaway that causes other 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 the 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," said Dr. Quinn Horn, Managing Engineer, Exponent. "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."
Consumers today take for granted the benefits of lithium-ion energy storage systems in cell phones, notebooks, PDAs, consumer appliances and other devices. However, recent recalls by the US Consumer Protection Commission have brought to light the potential hazards of lithium metal oxide batteries. These hazards were also highlighted by the Portable Rechargeable Battery Association (PRBA) which recently issued its tips for summer safety including avoiding leaving such electronic devices in areas that could get extremely hot.
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," said Robert L. Kanode, President and CEO of Valence. "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."
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 testing data is available on the Valence web site.