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Scientists develop fire-extinguishing system for lithium-ion batteries
Published:  17 January, 2017

The in-built smart technology activates when batteries enter a state of thermal runaway.

The solution comprises a free-standing separator that is positioned between the anode and cathode. The separator is made of microfibres with a core-shell structure containing the flame retardant triphenyl phosphate (TPP).

Thermal activity melts the microfibre’s outer polymer shell and releases the flame retardant into the highly flammable electrolyte, suppressing the ignition and burning electrolytes in as little as 0.4 seconds, according to tests.

The research by Stanford University was published in the peer-reviewed journal Science Advances in January and is titled Electrospun core-shell microfiber separator with thermal-triggered flame-retardant properties for lithium-ion batteries.

The research also found that although the microfibre could absorb the electrolyte and swell a little bit during long-term cycling, causing a small amount of TPP to gradually diffuse out of the fibres and dissolve into the electrolyte, this did not significantly affect the electrochemical performance of batteries because of the low concentration of TPP in the electrolyte.

The paper’s authors anticipate that this type of smart separator could be used in other high-energy storage devices to counter thermal runaway safety issues, but further mechanical and electrical abuse tests involving large-format cells would be needed for further practical applications.

In February 2016 the US National Transportation Safety Board issued safety recommendations regarding lithium-ion batteries. It advised that they should be separated from other flammable hazardous materials stowed on cargo aircraft and that maximum loading density requirements should be established to restrict the quantities of lithium batteries and flammable hazardous materials.