In situ generation of CeCoSx bimetallic sulfide derived from ?egg-box? seaweed biomass on S/N co-doped graphene aerogels for flexible all solid-state supercapacitors

Practical applications of flexible electrochemical energy storage devices are still limited by the lack of robust mechanical structures and high capacitive storage capabilities. Herein, the 3D CeCoSx-SA/GF porous aerogels are designed and prepared based on sodium alginate, which possess a special structure that can be explained by the so-called "egg-box" model. Each metal ion can be paired with the carboxyl and hydroxyl groups of the G monomer on two adjacent sodium alginate molecular chains. Melamine foam is used as carrier for graphene/ sodium alginate impregnation and plays an important role on significantly limiting the agglomeration of graphene nanosheets due to their strong 7C-7C stacking. The fabricated electrode based on CeCoSx-SA/GF shows an excellent electrochemical capacitance of 873.3F/g at the current density of 1A/g. In addition, the capacitance retention rate can still remain 87.1 % after 5000 cycles at a high current density of 8 A/g. Moreover, the fabricated all-solid state asymmetric supercapacitor device assembled with CoCeSx-SA/GF and active carbon shows an energy density of 29.58 Wh kg-1 at a power density of 801 W kg-1. For practical applications, the fabricated supercapacitor device can power a multifunctional display for 28 mins and illuminate a small light bulb for 3 mins. Moreover, the KOH/polyvinyl alcohol gel-electrolyte was used to fabricate high-strength and flexible CeCoSx-SA/GF/PVA/KOH composite film electrode, which can be bent at various angles (0 degrees -180 degrees) and can be twisted into various shapes. Notably, the CeCoSx-SA/GF/PVA/KOH composite film can lift plastic bottles containing 500 mL (500 g) and 1000 mL (1 kg) water, respectively, indicating that it has great application potential for wearable and portable electronic devices.