Lithium-ion cells for electronics and automotive applications have an excellent safety record. However, safety-related events can sometimes occur during routine testing of prototype designs, especially in the case of designs using new electrode materials, new separators and/or new electrolytes. High precision measurements of coulombic efficiency have recently been shown to have great value in predictions of the impact of electrolyte additives on cell lifetime. In order to apply those methods to prototype automotive cells, special compact temperature-controlled boxes were required that could maintain the temperature to ± 0.05 • C precision and ensure the safety of the laboratory. These versatile temperature-controlled boxes were designed to accommodate cells as small as coin cells and as large as 40 Ah automotive pouch cells. The ability of the design to prevent cell-to-cell fire propagation and to channel smoke and flame away from the rest of the laboratory was experimentally verified. It is hoped that the information presented here will be of value to those designing precision testing facilities for large Li-ion cells. The summer 2012 issue of Electrochemical Society Interface is devoted to Li-ion battery safety. Doughty and Roth 1 state that the failure rate, leading to a safety incident, of Li-ion rechargeable battery cells in the field is very small, less than 1 in 10 million. Li-ion cells that are in use in the field have all been subjected to a large number of mandatory tests to demonstrate that they are safe under normal conditions of use and also under some conditions of electrical and mechanical abuse.2 Prototype Li-ion batteries in the R + D stage, that may be hand assembled, with higher energy density, new designs, new electrode materials and/or new electrolytes may be less safe than commercial cells and hence must be handled appropriately in the testing phase in the laboratory.Our research group has recently been applying precision measurements of the coulombic efficiency of Li-ion batteries to the study of cell lifetime and the efficacy of electrolyte additives.3-5 High precision coulometry measurements made over a period of a few weeks can be used to rank electrolyte additives and their combinations for effectiveness in prolonging cell lifetime. Applying such methods to automotive-scale Li-ion batteries is expected to yield similar advantages in cell lifetime predictions.Smith et al. 3 published requirements for testing equipment to perform high precision coulometry on Li-ion cells. These experiments are generally made at low rates, C/10 and slower, but need to be made at a very stable temperature (preferably stable to better than ±0.1• C) for measurements of extremely high precision. Therefore, there is a need for temperature-controlled boxes designed for high precision cycling of automotive cells that can maintain strict temperature stability while ensuring laboratory safety.One of the authors recently visited or contacted many makers of large Li-ion cells (>20 Ah) to learn about the chambers use...
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