Electrode mass loading is an important device parameter for supercapacitors and its effect on electrochemical properties such as energy density, rate performance, and cycle stability has been widely reported. However, how the self-discharge of supercapacitors varies under different mass loadings has not been examined systematically. In this study, we prepared porous activated carbon (AC) electrodes with a series of mass loadings and investigated their self-discharge behavior. It is found that with the increase in mass loadings, the decay rates of open circuit voltages (OCVs) are reduced substantially. Specifically, when the electrode mass loading increased from 0.6 to 10.6 mg cm⁻², the cell OCV decay rate at a charging voltage of 1.6 V dropped from 1.07 to 0.05 mV mF⁻¹ hr⁻¹, indicating much slower self-discharge rates at higher mass loadings. Analysis of the self-discharge mechanism suggests that faradaic reactions are the major self-discharge processes for the supercapacitors after float charging. While the OCV decays due to both activation-controlled and diffusion-controlled faradaic reactions are reduced at high mass loadings, the self-discharge attributing to diffusion-controlled faradaic reactions is more affected due to the deeper pores and longer diffusion paths for electrolyte and reactive species in thicker electrodes.

电极质量负载是超级电容器的重要器件参数，其对能量密度、倍率性能和循环稳定性等电化学性能的影响已被广泛报道。然而，尚未系统地研究超级电容器的自放电在不同质量负载下的变化情况。在这项研究中，我们制备了具有一系列质量负载的多孔活性炭 (AC) 电极，并研究了它们的自放电行为。研究发现，随着质量载荷的增加，开路电压 (OCV) 的衰减率显着降低。具体而言，当电极质量负载从 0.6 增加到 10.6 mg cm ^-2时，1.6 V 充电电压下的电池 OCV 衰减率从 1.07 下降到 0.05 mV mF ^-1 hr^-1，表明在更高的质量负载下自放电率要慢得多。自放电机理分析表明，法拉第反应是超级电容器浮充后的主要自放电过程。虽然 OCV 由于激活控制和扩散控制的法拉第反应在高质量负载下减少而衰减，但由于更深的孔隙和更长的电解质和反应性扩散路径，扩散控制的法拉第反应导致的自放电受到更大影响较厚电极中的物种。