Lithium-ion (Li-ion) cells are increasingly used in high-voltage and high-capacity modules. The Li-ion chemistry has the highest energy density of all rechargeable battery chemistries, but associated with that energy is the issue of catastrophic thermal runaway with a fire. With recent incidents in the commercial aerospace and electronics sectors, it was necessary to find methods to prevent cell-to-cell thermal runaway propagation.

The work carried out here is not specific to any existing battery design, and was started with the goal of achieving a common method to trigger a cell into thermal runaway and determine if one can consistently obtain this thermal runaway event. The second goal was to determine if cell-to-cell thermal runaway can be prevented.

Li-ion cell-to-cell thermal runaway propagation was studied using a heat-to-vent/thermal runaway method. The trigger method was a commercial heater tape. Different cell designs of various Li-ion chemistries, as well as physical formats, were studied. Testing consisted of designing the cell modules with just spacing between the cells, introduction of a radiant barrier, and placing the cells in a module manufactured using intumescent materials. It was determined that at least 2-mm spacing was required for cylindrical cell designs. For cell formats that had vents on the side, a physical separation between neighboring cells was required. This was achieved by using intumescent materials as well as the radiant barrier.

The methods and designs used to prevent cell-to-cell thermal runaway in Li-ion modules consisted of increased cell-to-cell spacing, introduction of a radiant barrier between the cells, the use of intumescent cell modules that provide physical separation between the cells, and a method to absorb the heat from the cells, preventing the heat from directly affecting the neighboring cells by lowering the heat spread to the neighboring cells.

This work was done by Judith Jeevarajan and Joseph Orieukwu of Johnson Space Center, and Carlos Lopez of Texas A&M University. NASA is seeking partners to further develop this technology through joint cooperative research and development. For more information about this technology and to explore opportunities, please contact This email address is being protected from spambots. You need JavaScript enabled to view it.. MSC-25942-1

NASA Tech Briefs Magazine

This article first appeared in the October, 2016 issue of NASA Tech Briefs Magazine.

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