Toward the development of flexible printed electrodes on carbon cloth for solid-state supercapacitors

The important growing demand for flexible and wearable smart electronic devices has driven the urgent need for cost-effective, safe and flexible energy storage devices. In response to this challenge, we propose the development of a flexible supercapacitor based on carbon xerogel (CX) as the negative electrode and manganese dioxide (MnO2) as the positive electrode, both printed onto a carbon cloth substrate. Comprehensive structural and electrochemical characterisations were performed using a combination of Raman, ATR-FTIR and X-ray photoelectron spectroscopy (XPS) to elucidate the relationship between the chemical structure and performance. Combined spectroscopic analysis reveals that the MnO2 is predominantly amorphous with short-range α-MnO2- like ordering and a mixed of Mn4+/Mn3+ sites associated with Mn structural defects and oxygen vacancies. These mixed-valence centres promote fast, reversible surface redox reactions, thereby enhancing pseudocapacitive charge storage while preserving structural stability during cycling. The resulting device demonstrates superior performance, with a high specific capacitance of 580 mF⋅cm􀀀 2 and an energy density of 261 μWh⋅cm􀀀 2 at a power density of 2 mW⋅cm􀀀 2. However, lower performances were observed when the flexible electrodes were assembled into free-standing devices. Furthermore, the fabricated devices were subjected to various mechanical and flexibility tests while powering a ring-shaped LED module containing 30 LEDs integrated into a lab-coat textile. The two devices in series maintained stable illumination for 50 s with no performance degradation, demonstrating their excellent mechanical strength and potential for integration into wearable textiles.