posted April 20, 2012
Capturing, storing, and using electrical energy has always been a key issue in the design of spacecraft. Lately, it’s also become a hot topic in the automotive world, and The Aerospace Corporation is ready to contribute its expertise in batteries.
Several years ago, Aerospace was hired by CODA Automotive to evaluate batteries that the Los Angeles-based company was considering for its new all-electric sedan. CODA has not yet begun selling its cars, but it is taking orders.
The CODA sedan uses lithium iron phosphate batteries, a type of lithium-ion battery, which Aerospace evaluated for them.
“They wanted an independent evaluation of the battery quality,” said Dr. Simon Liu, director of the Energy Technology Department (ETD) in the Physical Sciences Laboratories. “What they needed was a detailed baseline of the battery’s physical structure and performance characteristics.”
With that knowledge, CODA will know in the future whether any changes in battery performance are related to physical changes, however slight, made by the battery manufacturer.
“The CODA people really did their homework in checking out who in the country has the battery evaluation capability they needed and they selected Aerospace,” said Alonzo Prater, manager of the Battery Evaluation Section of ETD. Dr. Warren Hwang, the director of ETD when CODA approached Aerospace, quickly recognized that this work could act as a springboard to working with larger-format lithium-ion battery cells of similar size to those being tested for national security space missions.
CODA representatives attended the 2009 Space Power Workshop and afterward approached Aerospace about doing the battery evaluation. Although Aerospace had never worked on terrestrial automobile batteries before, its engineers and scientists felt confident that they could do the work requested by CODA.
“CODA came to us with a long list, about 30 items, of things they wanted to know about the battery they were considering for their cars,” said Dr. Joanna Cardema, senior MTS in the Energy Storage Section of ETD. “These were things like characterization of the cathode and anode materials, composition of the binder, what was in the electrolyte solvent mix, the burst pressure of the rupture disk, and tortuosity of the separator, to name a few.”
Because the battery maker is a Chinese company, Aerospace is required to comply with the International Traffic in Arms Regulation (ITAR) in doing its work for CODA, which is a privately held U.S. company.
This meant, for example, that without a validated export license, Aerospace could evaluate a battery and give CODA measurements of various battery characteristics, but could not suggest ways to improve the battery, said Dr. Jeanne McGraw, manager of the Energy Storage Section.
Aerospace’s work for CODA was divided into two parts — testing of the battery’s power characteristics, which was done by Prater’s section of James Matsumoto, David Wang, and Jasen Ross; and physical examination of the battery cell components, done under the direction of McGraw by her section of Cardema, Dr. E. Joseph Nemanick, and Michael Quinzio.
Both sections developed new testing procedures and equipment for the CODA tests.
The Battery Evaluation Section built a new charge control system to perform dynamic stress tests on the CODA batteries. These are tests that replicate the stresses when a battery is subjected to varying load requirements, such as when a car suddenly accelerates or has to go up a hill, then down a hill.
The Energy Storage Section devised new testing equipment and procedures for carrying out what are called “destructive physical analysis” or DPA tests with lithium-ion batteries.
McGraw explained that the materials inside a lithium-ion battery react with moisture in the atmosphere, which causes changes in parts of the battery, thus making it impossible to measure characteristics of a working battery. Aerospace scientists developed tools to open cells and perform most analyses in a “glove box” filled with inert gas. She pointed out that Aerospace is one of the few facilities with this type of testing capability for lithium-ion batteries.
McGraw also noted that the CODA project drew on the expertise of people elsewhere in the Physical Sciences Laboratories, in addition to those in the Energy Technology Department. Further, Mark Rochlin and Homa Taraji from Civil and Commercial Operations assisted in bringing this work on contract.
The success of the DPAs in the glove box, and their importance to future space programs, led to the construction of a “dry room,” which has less than 1 percent moisture in the air. Under those conditions, lithium-ion batteries can be safely opened on an open workbench while maintaining their electrochemical integrity, allowing for easier access to the battery than using the glove box.
No major national security space program today uses lithium-ion batteries to power satellites, but there is great interest in doing so if the batteries can be shown to meet the requirements necessary for use in space. Aerospace’s work for CODA has given the Energy Technology Department valuable experience that can be applied to space battery testing — the CODA project, for example, provided one of the first opportunities to apply Aerospace’s DPA techniques to larger format lithium-ion batteries.
“We have been able to refine our techniques in DPA by working on terrestrial batteries, which are about one-hundredth the cost of a space-rated battery,” said Liu. “This work for a commercial customer ends up being a win-win-win situation – CODA gets work done that it would be hard-pressed to have done anywhere else, we gain valuable experience, and our space customers have received the benefit of our new knowledge and capability.”