Effect of separators on thermal runaway performance for Li-ion battery
This study investigates the surface morphology, tensile strength, puncture resistance, and additional properties of polyethylene (PE) -based separators with varying thicknesses and double-sided ceramic coatings. Among these, three were chosen for constructing high-capacity prismatic batteries to conduct thermal runaway tests. The findings indicate that ceramic coatings of different thicknesses exhibit a dense surface, a broad particle size distribution, and similar morphological characteristics. The tensile and puncture strengths of the ceramic-coated separators, all based on a 12 μm PE film, showed no significant variance across different coating thicknesses or between single-and double-coated films of the same thickness. Under identical testing conditions, the thermal shrinkage rates of the separators were observed in the order: (12+2+2) μm, (12+1.5+1.5) μm<(12+4) μm<(12+3) μm<(12+2) μm. The state of charge at which thermal runaway occurred for batteries using (12+2) μm and (12+4) μm separators were 116.94％ and 117.64％, with peak temperatures reaching 530.9 ℃ and 430.7 ℃, respectively. The experiments demonstrate that an increase in ceramic coating thickness delays thermal runaway and reduces peak temperatures. Furthermore, the battery constructed with the (12+2+2) μm double-coated separator experienced thermal runaway during the heating phase postovercharge, reaching a maximum temperature of only 369.5 ℃. An analysis of the experimental outcomes offers insights into battery design optimization, highlighting the critical nature of designing the overhang-where the separator's width exceeds that of the negative electrode, and the dimensions of the negative electrode surpass those of the positive electrode-for battery safety. Comprehensive evaluation of usage scenarios and extreme conditions is essential in battery design, taking into account the thermal shrinkage rates of chosen separators to calculate the contraction ratio, thereby ensuring the overhang design meets safety standards throughout the battery's lifecycle.
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维普
