Self-discharge in electrochemical energy storage systems, particularly in electric double-layer capacitors, poses significant challenges due to the spontaneous dissipation of stored charges at electrode/electrolyte interfaces, which compromises device performance and energy efficiency. Despite decades of research, the underlying mechanisms of self-discharge remain a subject of debate. In this study, we use multilayered graphene-based membranes with adjustable nanoslit sizes as an additive-free electrode material platform to revisit the self-discharge in nanoporous electrodes. By integrating a hybrid self-discharge model with a comprehensive electrochemical characterization, we identified activation-controlled Faradaic reactions as the primary driver of self-discharge, but ruled out traditionally suggested reactions like carbon oxidation and water splitting in carbon-based electric double-layer capacitors with aqueous electrolytes. Furthermore, the observed ion identity-dependent self-discharge underscores the pivotal role of electrolyte ions in self-discharge, highlighting this overlooked aspect in the conventional hybrid model. Our findings highlight the inherent challenges in studying self-discharge and the need to further develop advanced research methods and models to address this enduring problem.

中文翻译：

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重新审视以多层石墨烯膜为模型纳米多孔电极的超级电容器的自放电


电化学储能系统中的自放电，尤其是双电层电容器中的自放电，由于在电极/电解质界面处存储的电荷会自发耗散，从而影响器件性能和能效，因此带来了重大挑战。尽管进行了数十年的研究，但自我放电的潜在机制仍然是一个争论的话题。在这项研究中，我们使用具有可调节纳米狭缝尺寸的多层石墨烯基膜作为无添加剂的电极材料平台，以重新审视纳米多孔电极中的自放电。通过将混合自放电模型与全面的电化学表征相结合，我们确定了活化控制的法拉第反应是自放电的主要驱动因素，但排除了传统上建议的反应，如碳基双电层电容器与水性电解质中的碳氧化和水分解。此外，观察到的离子身份依赖性自放电强调了电解质离子在自放电中的关键作用，突出了传统混合模型中被忽视的这一方面。我们的研究结果强调了研究自放电的固有挑战以及进一步开发先进研究方法和模型来解决这一长期问题的必要性。