Particle Contamination in Commercial Lithium-Ion Cells—Risk Assessment with Focus on Internal Short Circuits and Replication by Currently Discussed Trigger Methods

Abstract

A possible contamination with impurities or material weak points generated in cell production of lithium-ion batteries increases the risk of spontaneous internal short circuits (ISC). An ISC can lead to a sudden thermal runaway (TR) of the cell, thereby making these faults especially dangerous. Evaluation regarding the criticality of an ISC, the development of detection methods for timely fault warning and possible protection concepts require a realistic failure replication for general validation. Various trigger methods are currently discussed to reproduce these ISC failure cases, but without considering a valid basis for the practice-relevant particle properties. In order to provide such a basis for the evaluation and further development of trigger methods, in this paper, the possibilities of detecting impurity particles in production were reviewed and real particles from pouch cells of an established cell manufacturer were analysed. The results indicate that several metallic particles with a significant size up to 1 mm × 1.7 mm could be found between the cell layers. This evidence shows that contamination with impurity particles cannot be completely prevented in cell production, as a result of which particle-induced ISC must be expected and the need for an application-oriented triggering method currently exists. The cause of TR events in the field often cannot be identified. However, it is noticeable that such faults often occur during the charging process. A new interesting hypothesis for this so-far unexplained phenomenon is presented here. Based on all findings, the current trigger methods for replicating an external particle-induced ISC were evaluated in significant detail and specific improvements are identified. Here, it is shown that all current trigger methods for ISC replication exhibit weaknesses regarding reproducibility, which results mainly from the scattering random ISC contact resistance.

Early-Stage ISC Fault Detection for Ship Lithium Batteries Based on Voltage Variance Analysis

“…Based on the diaphragm failure mechanism and various abuse conditions, ISC faults in lithium battery packs can be classified into three primary types: (1) mechanical abuse-induced ISC; (2) electrical abuse-induced ISC; and (3) thermal abuse-induced ISC. ISC resulting from mechanical or thermal abuse tends to rapidly generate significant heat, often leading directly to thermal runaway [35]. Conversely, ISC triggered by electrical abuse typically generates less heat that is insufficient to provoke thermal runaway.…”

Current Chemistry Investigators (CCI): Development and Evaluation of a Scientist in a Classroom Electrochemistry Workshop

“…It has been reported that lithium-ion batteries can fail due to variances in the concentration of electrolytes as well as due to the introduction of contaminants. 48 The workshop presents the students with the problem of identifying why and how the battery malfunctioned, through a guided "electro-analytical" workshop consisting of two major parts: (1) a quantitative section and…”

“…Aluminum, copper, and iron are some of the most common contaminants in lithium-ion battery electrolytes, since all three are already present within batteries. 48 A qualitative test for aluminum, copper, and iron cations involves the use of NaOH to produce the equivalent metal hydroxides, which results in the formation of a precipitate. Iron(III) forms a yellowishbrownish precipitate; copper(II) forms a blue precipitate, and aluminum(III) forms a white precipitate (Figure 3).…”

“…The use of a story or narrative can increase engagement in a topic through humanization and by providing context for abstract concepts. − The story for the CCI workshop is based on a battery malfunction, providing the students with a topical, real-world problem to solve. It has been reported that lithium-ion batteries can fail due to variances in the concentration of electrolytes as well as due to the introduction of contaminants . The workshop presents the students with the problem of identifying why and how the battery malfunctioned, through a guided “electro-analytical” workshop consisting of two major parts: (1) a quantitative section and (2) a qualitative section.…”

A novel method for simultaneous triggering and in situ sensing of internal short circuit in lithium-ion cells

“…17 Although many ISC triggering methods have been developed, some of which have been adopted by industrial standards, 7,18 each method has advantages and disadvantages. 19 For example, nail penetration testing, pinch-testing, indentation testing and laser heating can be implemented without modification of Li-ion cells, but these methods cannot control the types of ISC. Embedding a nickel particle can control the types of ISC, but it requires disassembly of fully charged Li-ion cells which is difficult and dangerous.…”