The Roll-to-Roll Battery Revolution
By Bill Moore
There's a quiet revolution taking place in the rechargeable battery industry. It is occurring at the confluence of modern nano-technology and 140 year-old printing technology. The result is a small, high-powered, light-weight rechargeable lithium-based battery with unprecedented flexibility.
One of the firms pioneering the lithium revolution is Voltaflex, located in Menlo Park, California. A relatively new start-up, the company licensed two years ago nano-scale polymer technology from MIT that replaces liquid, gel and paste electrolytes commonly found in most rechargeable batteries with a dry solid polymer electrolyte or DSPE. The advantage of this approach is that it now enables batteries to be fabricated at high speed on roll-to-roll machinery similar to modern web-fed printing presses that join the various layers that make up the battery in a continuous run process.
To learn more about this technology, EV World talked with Voltaflex Chief Operating Officer, Glenn Sanders. He explained that the company is small and is presently focused on developing the materials, the synthesis process and the design of the battery.
He noted that the Voltaflex's battery is not intended for high current applications like those found in either portable power tools or electric-drive vehicles. Instead, the company plans to first sell the polymer electrolyte material to other battery makers, then concentrate on offering both component materials for the fabrication of lithium polymer batteries for use in low-current applications including RFID tags and smart cards.
"Our claim to fame is what goes into the center of the battery", he stated, meaning the proprietary dry solid polymer electrolyte.
Unlike competing "dry" electrolytes, which Sanders said are essentially gels in a flexible lattice framework, Voltaflex's electrolyte is synthesized from a liquid compound that contains binders and a solvent. The solvent evaporates in the coating process, leaving behind the actual dry electrolyte material. This eliminates the "mess" or potential leakage problems associated with non-solid materials like gels and pastes.
He said that when it dries is feels somewhat like silicone caulk. This material also has the ability to work at higher temperatures than competing approaches.
"Our polymer actually works better the warmer it gets".
Because Voltaflex licensed their electrolyte chemistry from MIT, as has another lithium battery company called A123, I asked Sanders if they were both using the same technology. He responded that while there are similarities, A123 is using their chemistry to develop batteries for the portable power tool market.
Because of its DSPE chemistry, Sanders isn't overly concerned about the safety of lithium ion batteries that use VoltaFlex's electrolyte. He's confident that they won't demonstrate "thermal runaway" in which the lithium essentially catches fire and melts at the temperature of molten lava, no a good thing to happen to your PDA, cell phone or medical device. He pointed out that because of this, he's been getting inquires from medical device makers for more information on the technology.
Not Ready for EV Prime Time
The disadvantage of DSPE, for the moment at least, is its ion-conducting capacity.
"Our current technology is not well-suited for high-current applications", he said. "We're doing development now to improve that, but we have useful technology for low current situations or situations that require short bursts of high current, which we can handle with capacitors. The main challenge with electric drive vehicles or the hybrid vehicles is the high discharge rate that is required. Our technology is not ready for that yet."
He does see a marked advantage of a battery that is light weight for mobile applications like an electric car, but Voltaflex isn't there yet, although they are conducting some research into improving ion conduction in the electrolyte.
With respect to the question of costs, he explained that the company eventually hopes to see a mass-produced line of batteries using their materials that will be less expensive than what is presently on the market. They also hope to do custom battery applications for companies, but that will obviously be more expensive. He wasn't willing to offer specific numbers, which seems understandable given the company's current development stage. It will begin shipping the polymer to customers shortly.
He sees two primary markets for Voltaflex products: extremely thin batteries and batteries that must operate at high temperatures. He also don't envision any "scale-up" problems where what works in the laboratory may not work on the factory floor. He said their materials are specifically designed for mass production.
He thinks the market for a high-power, low current, light-weight, ultra-thin rechargeable battery could be large, in the neighborhood of several hundred million dollars annually.
So, while we can't expect to see "Voltaflex Inside" tomorrow's electric-drive cars, the company and its competitors are paving the way to batteries that will someday make electric cars not only feasible but practical and affordable.
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