Safety abuse tolerance tests

The term Safety thus refers to a mutual agreement between the cell/pack manufacturers and the users on use of such cell/pack under specified operating conditions, and abuse tolerance tests without energetic thermal runaway. 

Advanced quality control measures play a critical role keeping a check on PPB level safety issue. Moreover, new safety evaluation methods like abuse tolerance tests for cycled Li-ion cells would provide a clear insight in understanding the influence of high-surface Li deposits toward cell safety, and further increase the confidence level toward implementing Li-ion systems for several advanced applications like EDV and ESS. 

Battery safety has been obviously given a special attention in this volume. Commercial lithium-ion cells and batteries are commonly used to power portable equipment, but they are also used to buildup larger batteries for ground (e.g. EVs), space and underwater applications. Chapter 17 provides test data on the safety of commercial lithium-ion cells and recommendations for safe design when these cells are used in much larger battery configurations. Chapter 18 focuses on safety aspects of LIBs at the cell and system level. In particular, abuse tolerance tests are explained with actual cell test data. Furthermore, internal short and lithium deposition occurring in lithium-ion cells and failure mechanism associated with them are discussed. In Chapter 19, the state of the art for safety optimization of all the battery elements is presented. This chapter also reports tests on not yet commercialized batteries, which pass all the security tests without the help of a BMS. 

Standardized Safety and Abuse Tolerance Test Procedures... 

The distinction between abuse tolerance and field-failure (internal shorts) is important for a number of reasons. It helps bring into focus the extent to which historic testing for safety is focused on abuse testing, even though the actual safety events that occur in the field are quite different. From a mechanistic perspective, the triggers are fundamentally different and the resulting responses... 

The lack of availability of suitable tests for the internal short should not be a surprise - any event that takes place rarely, is stochastic and exhibits some form of incubation process, arguably does not exhibit a detectable precondition at the point of manufacture and certainly does not exhibit a predisposal to the problem in every cell. Thus, the practice of removing a few cells from the manufacturing line to test for safety is fine for abuse triggers (for abuse tolerance) but is clearly inappropriate as a measure of susceptibility to development of an internal short in the field. 

This abuse tolerance versus field-failure framework is also a useful way to characterize testing work carried out by various researchers, or tests that purport to address safety. For example, various tests can be assessed with respect to whether they refiect or measure a property of all cells of the same design and materials (an abuse), or whether they reflect a rare condition that develops after time in the field. 

Abuse tolerance in lithium-ion cells is critical to public safety, and a number of screening tests for lithium-ion cells and batteries have been devised. Battery developers and users then test cells and batteries to screen for tolerance with respect to the given abuse, and then design cells and batteries with improved abuse tolerance. 

Standardization of tests is crucial to comparing safety and abuse response of batteries. For example, changes as simple as the magnitude of the current can affect the outcome of overcharge tests [17]. There are a number of standardized test procedures that evaluate the safety and abuse tolerance of cells and batteries. The test procedures are adapted to the intended applications. 

Batteries must have sufficient safety for any given application. Improved abuse tolerance and engineering for graceful failure is a challenge that encompasses many areas of study and specialization. The safety and abuse tolerance of electrochemical cells depends on materials, engineering, and chemical interactions. Standardized tests are available that allow developers and users to compare the abuse tolerance of materials and cell design modifications. 

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