Proton-exchange-membrane fuel cells (PEMFCs) have the characteristics of zero emissions, a low operating temperature and high power density, and have great potential in improving energy-utilization efficiency. However, fuel cells are still quite expensive as a result of the cost of key components, including the membranes, catalysts and bipolar plates of PEMFCs. As a result of the cost and importance of these items, most researchers have focused on improving the lifetime and performance of fuel-cell stacks in recent years. In contrast, seals, sealants and adhesives play a more mundane role in the overall performance of a fuel cell, but failure of these materials can lead to reduced system efficiency, system failure and even safety issues. Little attention has been paid to the performance and durability of these products but as other fuel-cell components improve, these seals are becoming an even more critical link in the long-term performance of fuel cells. This article highlights the importance and background of fuel-cell seals. The latest research progress on the mechanical properties and structural optimization of different sealing materials is reviewed.

To analyze the impact of two commonly neglected electrical abuse operations (overcharge and overdischarge) on battery degradation and safety, this study thoroughly investigates the high current overcharge/overdischarge effect and degradation on 18650-type Li-ion batteries (LIBs) thermal safety. Based on the temperature-voltage behavior and induced thermal runaway (TR) mechanisms, the overcharge and overdischarge-triggered TR processes are divided into four and three stages. Furthermore, the degradation effect is analyzed by analyzing the incremental capacity-differential voltage curves. During the high current cycling process, lithium inventory decreases significantly. Besides, the active material decreases when the battery degrades to a certain level. Lithium plating is the primary reason for lithium inventory loss; the plated lithium grows with the increment of degraded/overcharged level. Besides, the dissolution and deposition affect the internal short circuit degree, which can be observed from the electrode potential and cell voltage value. Moreover, battery cells undergo different degradation degrees, and different current rates of charging/discharging exhibit similar temperature-rising trends during the adiabatic TR tests. However, with the degradation degree increase, battery capacity fades, TR becomes easier to be triggered by the high current rate, and TR reactions are severe. This study guides early quantitative detection, safer battery cell design, and enhanced thermal safety management.