GM Battery manufactured in Michigan
The French paper Le Monde has published a number of articles about the safety of Lithium Ion batteries with respect to electric and hybrid vehicles: Le Monde Aritcle 1, Le Monde Article 2. They cite the concerns publicly raised by director of research at Centre National de la Recherche Scientifique (CRNS) Michael Armand regarding the safety of the batteries being put on the market by automobile manufacturers such as GM and Renault (Nissan). Mr. Armand, who contributed to the development of Lithium Iron Phosphate technology along with inventor John Goodenough, is quoted as saying it is his “duty to science to express” his concern. Armand estimates that “a probability of failure of the batteries of the order of 1 in 10,000″ with potentially lethal effects due to the emission of harmful gases created by the electrolyte in the event of fire or explosion. He proposes that LiFePO4, despite its lower energy density, is the only lithium battery safe enough for automobile applications.
Another article in Le Monde discusses that intellectual property rights play a significant role in the choice for auto manufacturers.
This is a subject of great interest at LiFePO4-info.com. Automakers such as GM and Renault (Nissan) have elected to use Lithium Manganese Oxide batteries in their vehicles. MIT’s technology review (with admitted ties to A123) notes that GM’s decision to go with LG Chem (LiMnO2) and not A123 (LiFePO4) may have come down to the readiness of manufacturing capabilities and costs more than safety and performance of the cells. While LG Chem and other LiMnO2-based battery manufacturers take care to improve the safety of the cells through novel separator design and careful battery thermal and electrical management systems, the fact remains that Lithium-Metal-Phosphate compounds are inherently much more stable than the Lithium-Metal-Oxides. In addition, LiFePO4 are renowned for having a much longer useful lifetime (number of charge/discharge cycles) than the other Lithium chemistries.
Co-inventor of LiFePO4 Christian Masquelier points out that the primary hurdle facing LiFePO4 is its energy density because LiFePO4 generates around 3.2-3.3 V per cell versus 3.6-3.7 V per cell for metal-oxide cathodes.
Clearly, the debate has many facets: energy density, power density, charging times, safety, cell costs, lifetime, intellectual property, manufacturing maturity, costs of battery management systems, etc. LiFePO4 does not win in all categories, but certainly has key advantages in safety and lifetime. The stakes are extremely high. One catastrophic battery failure threatens to dramatically alter the landscape of lithium-battery-powered vehicles. It will be interesting to see how the industry continues to address these challenges.
