The commercial success of Lithium-ion batteries and their subsequent proliferation in a plethora of products and uses has resulted in a need for a continued development in the understanding both the performance and safety of these cells. In the consumer sector, there is an ongoing rapid acceleration in the number of cells in circulation. A larger quantity of cells on the market increases the likelihood of a device failure event, even with increasing quality of cells, and this risk can be exacerbated due to cell deterioration over time. In addition to this, the push for longer battery lives and smaller battery sizes in consumer devices has driven energy densities to ever higher values. In the industrial and automotive sectors, the demand for lithium-ion battery cells is also growing due to the rapid growth of renewable energy storage, frequency regulation, energy shifting and load levelling and EV markets. Individual dangers due to these larger battery assemblies be can more acute than for smaller consumer devices due to sheer scale.

The failure of Lithium-ion batteries can lead to a range of consequences, from failure to meet performance expectations, to exposure of toxic electrolyte liquids or vapours, to dangerous release of heat, toxic gases, or fire in the case of a so-called “thermal runaway event.”
Root-cause failure analysis of Lithium-ion batteries provides important feedback for cell design, manufacturing, and the prevention of such failures in the future. When field failures occur, it is critical to thoroughly investigate them to help ensure the safety of systems already in the field as well as future systems in development. Battery failures can occur due to a range of factors and thus should be evaluated from various perspectives such as mechanical design, thermal design, cell chemistry and control electronics. Exploring and understanding these aspects is necessary to ensure root-case has been properly established.

In this presentation, a failure analysis methodology is discussed which takes a holistic view of the battery system – from the exterior electronics to the interior cell chemistry. It is possible to identify critical features observed in certain failures and some essential analytical techniques used to pinpoint a root cause are discussed. In addition to this, the challenges related to failure analysis of batteries with larger form factors and higher energy densities will be discussed, and how failure analysis methodology can be adapted to the characteristics of such batteries.