As much as 50% of the heat transferred from a Li-ion cell to the environment during oven exposure testing could be by radiation. The effectiveness of radiation heat transfer depends on the emissivity of the outermost surface of the cell, normally the label. We show that the tolerance of Li-ion cells to thermal abuse is dramatically improved when suitable labels are used on the cell. Selecting labels with the highest possible emissivity (ε = 1) will lead to cells with the greatest thermal tolerance. A comparison between labels on commercial cells suggests that major manufacturers are not aware of these advantages and that the inherent safety of the technology in the marketplace can be easily improved.
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