No abstract

High‐performance electrochemical applications have expedited the research in high‐power devices. As such, supercapacitors, including electrical double‐layer capacitors (EDLCs) and pseudocapacitors, have gained significant attention due to their high power density, long cycle life, and fast charging capabilities. Yet, no device lasts forever. It is essential to understand the mechanisms behind performance degradation and aging so that these bottlenecks can be addressed and tailored solutions can be developed. Herein, the factors contributing to the aging and degradation of supercapacitors, including electrode materials, electrolytes, and other aspects of the system, such as pore blocking, electrode compositions, functional groups, and corrosion of current collectors are examined. The monitoring and characterizing of the performance degradation of supercapacitors, including electrochemical methods, in situ, and ex situ techniques are explored. In addition, the degradation mechanisms of different types of electrolytes and electrode materials and the effects of aging from an industrial application standpoint are analyzed. Next, how electrode degradations and electrolyte decompositions can lead to failure, and pore blocking, electrode composition, and other factors that affect the device's lifespan are examined. Finally, the future directions and challenges for reducing supercapacitors' performance degradation, including developing new materials and methods for characterizing and monitoring the devices are summarized.

We report on electrical double‐layer capacitors (EDLCs) performing effectively at low temperature (down to −40 °C), owing to the tuned characteristics of both the ionic liquid (IL) electrolyte and carbonaceous electrodes. The transport properties of the electrolyte have been enhanced by adding a low‐viscosity IL with the tetracyanoborate anion, [EMIm][TCB], to a mixture of [EMIm][FSI] with [EMIm][BF4], which was already successfully applied for this application. The formulated ternary electrolyte, [EMIm][FSI]0.6[BF4]0.1[TCB]0.3, remained in the liquid state until it reached the glass transition at −99 °C and displayed a relatively low viscosity and high conductivity (η=23.6 mP s and σ=14.2 mS cm−1 at 20 °C, respectively). The electrodes were made of a hierarchical SiO2‐templated carbon with well‐defined and uniform mesopores of ∼9 nm facilitating ion transport to the interconnected micropores accounted for the charge storage, whereas the high density of the electrodes promoted high volumetric energy outputs of the cells.

No abstract

No abstract