A thin-film coating process for manufacturing thermal batteries - first used in nuclear weapons and other munitions, and which was invented at Sandia National Laboratories in Albuquerque, N.M. - will be industrialized under a new corporate partnership with a Maryland company. The process could lead to the creation of lighter batteries.
A thermal battery is a non-rechargeable single-use energy source that can remain inert for years at room temperature before becoming activated at temperatures as high as 1,100°F (~600°C). The thin-film coating process changes the way some thermal batteries have been made since the 1950s.
Sandia researchers also are looking into whether a patented binder used in its thin-film coating process has commercial applications. Examples include lithium-ion batteries in electric and hybrid vehicles and in batteries used in the petroleum industry when drilling deep underground in hot geothermal environments. Sandia and ATB Inc., a Cockeysville, Md.-based manufacturer of thermal batteries, have signed a cooperative research and development agreement to test the coating process for large-scale industrial production.
“We can take the developments that we’ve had in the lab, scale up the quantities of materials that we use and, instead of producing tens of batteries, we can produce hundreds of batteries in ATB’s facility,” says Tom Wunsch, manager of Sandia’s Advanced Power Sources Research and Development Group. “It’s beneficial to us to have an industrial partner to work with on these issues and for them to have this technology.”
Guy Chagnon, CEO of ATB, says his company and Sandia have been working independently on changing the process for producing thermal batteries. The goal “is to industrialize a new process, to manufacture, to build and to test the battery,” he says. “We’re putting our resources together to reduce the size and the cost of thermal batteries.”
Sandia’s expertise in thermal batteries stems from their use in nuclear weapons and other munitions, where they must be extremely reliable, remain inert for 30 years at room temperature and then spring into action on a moment’s notice. Sandia has developed about 30 thermal battery designs since 1975. Sandia researcher Frank Delnick led the effort to make the thermal battery components as thin-film coatings instead of pellets. The process will work best for thermal batteries that are active for a fraction of a second to a few minutes, he says.
Traditional thermal batteries are made by pressing powdered materials into electrochemically active pellets used as the anode, cathode and separator of the battery. The pellets must be a certain thickness to maintain mechanical integrity and prevent them from falling apart when handled. The amount of material required to achieve mechanical stability can be up to 10 times greater than what is needed to make the battery work. Therefore, considerable reduction in size can be achieved by making the components thinner, Delnick says. The goal of the agreement is to jointly develop thin-film coatings that will cut the time and materials need to make thermal batteries. Current thermal batteries are cylindrical and range in size from a man’s thumb to a one-pound coffee can. The first thermal battery made using the process was slightly thicker than a postage stamp and about the size of a quarter.
Chagnon says if the research and development are successful, large-scale manufacturing could begin by late 2012.
The process uses relatively inexpensive equipment common in the paint industry that coats the battery components as thin films onto stainless steel foil. The coatings are held together and bonded to the foil using a patented binder. The binder must withstand temperatures of about 660 to 1,100°F (350 to 600°C), which are required to melt the salt electrolyte and activate the battery. Once activated, the binder must remain chemically and mechanically stable throughout the discharge of the battery without emitting gas or producing other side reactions that could adversely affect the performance of the battery.
The coated materials in the batteries are much tougher than those in current models, says Delnick, who expects that thin-film thermal batteries will perform much better in high-shock environments and will be much more amenable to automated manufacturing. “Since the parts are more robust, you don’t have to handle them as gingerly,” he says.