A lithium ion cobalt oxide battery erupts in sparks under continued attack by a drill. View Slideshow 
A recent marketing video from battery maker Valence Technologies makes its point with all the subtlety of a Jerry Bruckheimer film: Unlike the competition's, its batteries don't blow up.
The Texas-based company is so confident of the safety of its product that it shot one with a bullet to see what would happen. Nothing much, it turns out. That's in stark contrast to the other lithium ion battery shown in the video, which explodes in a fiery ball.
It's simple chemistry. Lithium ion batteries are so potent that they've become ubiquitous in laptops and cell phones, but the cobalt oxide used to generate such prodigious amounts of electricity per gram is highly volatile. That's prevented larger-scale uses -- in cars, for example -- because the risk of a deadly explosion has simply been too great.
Not so with Valence's new Saphion battery, which is among a new generation of lithium ion cells that are beginning to crack the transportation market.
"It's an enabling technology," said Dean Bogues, Valence's president for North America and Europe. "We think, as batteries get better, that reliance on batteries to provide energy in your car will get larger."
Lithium ion batteries are more energy-dense than nickel metal hydride cells currently used in most hybrid and electric cars. That means a lithium ion battery can run at a higher power for a longer time than a nickel metal battery of the same weight. But most lithium cells use a cobalt oxide chemistry that can catch fire or explode if the battery is charged or discharged too quickly, or if it is physically damaged.
Products that use a large number of cells present a greater fire and explosion hazard than personal electronic devices that use a single small cell, so engineers have been hesitant to choose lithium ion batteries for automobiles and other "large-format" applications.
Valence is aiming to open up new markets for lithium ion technology by proving that lithium can be safe, a move that would challenge both nickel metal hydride and lithium ion cobalt oxide cells. Saphion cells hold significantly more energy per kilogram than nickel metal hydride cells, and although Saphion carries less energy per kilo than lithium ion cobalt, Valence is betting that many users will trade some energy for enhanced safety.
Saphion cells are drawing notice among hybrid car designers, but there are still some hurdles to overcome, notably price.
Tom Gage, president of AC Propulsion, a Southern California electric-vehicle company, said he is impressed by Valence's technology, but he is not ready to switch to Saphion.
AC Propulsion plans to begin converting Toyota Scions into electric vehicles early next year, and expects to use packs made of laptop-size lithium ion cobalt cells. Although the cells require complex battery-management systems to stay within safe operating range, Gage argues that Saphion batteries are still significantly more expensive. But he said he is eager for a lower-priced Saphion cell.
"Valence chemistry may yet prove to be one that is adopted on a wider basis," he said.
Valence officials hope that as they produce Saphion cells in larger volumes, costs will decline.
One of its first major customers is Segway, which released three Saphion-powered Human Transporters in April of this year. Phil LeMay, the electrical engineering director at Segway, is in charge of keeping tabs on battery technology and oversaw the process that selected Valence as a Segway supplier. LeMay said that he and his team "had been on the lookout for lithium ion because of its inherent benefits, but were looking for chemistries that were safe for large format."
Segway's Human Transporters can be involved in road accidents, and are often charged indoors, so combustible batteries are out of the question. LeMay's group chose Saphion because of "the inherent safety of the chemistry.... A failure in a large-format Saphion battery doesn't propagate to other cells, plus failure is dramatically less dramatic."
The longer range of the Saphion batteries enabled Segway to build its all-terrain XT model. After several months with Saphion Segways on the road, LeMay remains confident about his choice.
"We pretty much doubled the range with very little penalty in terms of weight," he said.
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