Design, development and optimization of highly reliable 2 V solid-state supercapacitor device based on graphene-doped carbon gel and MnO2 electrodes

Supercapacitors are revolutionising smart electronics devices by offering an excellent lifetime, outstanding energy and high power densities. In this context, we report on the synthesis of manganese dioxide using a convenient co-precipitation method, exploring its application as a positive pseudocapacitive electrode material, as well as the synthesis of carbon xerogel for use as a negative electrode, alongside the use of a solid-state electrolyte based on Na+-form Aquivion membrane. When the device is merged in an asymmetric external configuration, the resulting solid-state supercapacitor exhibits good electrochemical performance, as demonstrated by: i) a high specific capacitance of 110 F·g−1, ii) a high energy density of 16.7 Wh·kg−1 at a power density of 207 W·kg−1; and iii) an outstanding capacitance retention of 78 % after 50,000 cycles with an expanded voltage window of 2 V. To demonstrate their practical applicability, the developed devices were connected in series to power a fan and red LEDs with an external and internal configurations (up to 4 V), successfully powering them for several minutes. The proposed fabrication approach is simple to scale up and provides a sustainable, cost-effective manufacturing process for freestanding electrodes based on carbon xerogel/MnO2 nanocomposites towards next generation smart electronic devices.