Binder-free laser induced graphene-MnO₂ composite electrodes for high areal energy density flexible supercapacitors

The synthesis of Laser-Induced Graphene (LIG) through the laser ablation process of carbon-containing materials is a rapid and scalable process which enables the production of graphene in a cost-effective manner. In recent years, metal oxide – graphene composite electrodes have gained a lot of importance due to their use in various Energy Storage Devices (ESDs). In our investigation, we manufacture composite electrodes of manganese dioxide (MnO₂) and LIG through a hydrothermal process and use it as electrodes in Flexible Supercapacitors. This method deviates from traditional procedures as it eliminates the requirement for binders in creating composite electrodes, given that MnO₂ can be directly deposited onto the LIG electrodes. The assembled all-Flexible Supercapacitor (FSC), featuring unique LIG-MnO₂ composite electrodes, showcased a remarkable areal capacitance of 66.5 mF cm⁻² at 5 mV s⁻¹ scan rate. The device also exhibited a very high areal energy density (2.3 mWh cm⁻²) and power density (19.7 mW cm⁻²) at 0.2 mA cm⁻² current density. Also, 82 % capacitance retention was observed at the end of 2000 cycles and the device also exhibited a good flexibility during bending tests, as evidenced by an 80 % capacitance retention after 100 bending cycles.