Influence of mass loading and current collector choice on self-discharge in environmentally-friendly supercapacitors

A comparative study of self-discharge in eco-friendly, carbon-based supercapacitors was conducted using ethyl cellulose (EC) as a sustainable cellulose-derived binder and a neutral aqueous electrolyte (1 M Na₂SO₄). The influence of current collector, mass loading and electrochemical active surface area (ECSA) on self-discharge was examined using three types of current collectors over a range of operating voltages. Self-discharge behaviour was analysed from open-circuit voltage (OCV) decay, leakage current and hybrid model fitting, revealing charge redistribution as the dominant contribution under tested conditions. The magnitude of self-discharge is strongly influenced by the type of current collector while the effects of ECSA and electrode loading are mediated with respect to their influence on charge redistribution and interfacial properties. These findings highlight the importance of electrode architecture and interfacial properties in regulating voltage retention and leakage current. This is particularly relevant for supercapacitors operating under intermittent charging conditions or long resting periods as in case of integration with low-power energy-harvesting devices such as triboelectric nanogenerators. This work provides insights into design of sustainable aqueous supercapacitors for effective charge retention and reliable delivery for low-power, self-powered applications.