by Rideeta Raquib ’19
Smartphones are an integral part of today’s society, but they are also a huge fire hazard. Lithium-ion batteries, commonly used in rechargeable devices, have a reputation of being susceptible to combustion. Dr. Jie Sun from the Institute of NBC Defense and the Tsinghua University in China collaborated to study the deleterious emissions of Li-ion batteries or LIBs.
Two types of LIBs were placed into stainless steel chambers with an opening as a gas outlet. A 2-3 cm high flame ignited the LIBs and a SiO2 grid was employed in order to ensure equal distribution of heat on all sides. The volatile organic compounds or VOCs, which refer to the toxic emissions of the battery, were examined using a method called GC-Mass. This method utilizes gas chromatography and mass spectrometry to differentiate the gases from one another. A chemical identification tool called INFICON® HAPSite ER was used to detect each specific VOC and a multi-gas monitor called M40 was used to detect carbon monoxide. CO2 and HF were emitted and absorbed by saturated sodium hydrate solution at negative pressure, and a solution of CO32−, PO43−, and F−1 remained. To compare the ratio of carbon monoxide to the rest of the gas mixture, the solution was diluted twenty times and examined by an ion chromatography. Furthermore, the toxicity of each gas detected was analyzed, using the China National Standard as a guideline.
Various LIBs, such as LiMn2O4 (LMO), NMC, LiCoO2 (LCO), and LiFePO4(LFP), were combusted in a similar fashion to the previous test and the observations were compared. The LMO and NMC had about a 10 to 15 cm height flame, and the LMO combusted in a violent manner after 2 minutes. On the other hand, white smoke appeared after 1 minute and 2 seconds for NMC and no explosion was observed. LCO also exhibited high combustion, but LFP had a milder response as opposed to the other three types. Overall, the trends depicted in the study helped scientists identify LFP as the safer type of Li-ion battery because it was less prone to combustion. In the future, smartphone manufacturers can innovate safer products for consumers.
- Jie Sun, et al. Toxicity, a serious concern of thermal runaway from commercial Li-ion battery. Nano Energy 27 (2016). doi: 10.1016/j.nanoen.2016.06.031.
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