Enhanced supercapacitor stability through irreversible oxygen removal from activated carbon

Commercial activated carbon, commonly used in supercapacitors, typically retains about 5 % oxygen content, which is introduced during the activation process. This residual oxygen, when present in electrode materials, tends to generate gases, oxidize the electrolyte, and consequently degrade the reliability of supercapacitors. This study addresses these challenges by employing a solvent heat treatment method using a low-concentration urea solution, effectively reducing the oxygen content in activated carbon to 0.15 at.%. Remarkably, this reduction in oxygen levels is shown to be irreversible, with no increase in oxygen content even after prolonged storage. To evaluate the practical implications of this enhancement, a supercapacitor of the 1300F class was fabricated and subjected to a high-temperature reliability test at 85 °C for 1000 h. The results demonstrate significant improvements in both the storage capacity and resistance stability of the supercapacitor, underlining the potential of this method for advancing supercapacitor technology.