Cellulose-based all-in-one supercapacitor with robust interfaces and mechanical stability

The unstable electrode-electrolyte interfaces of flexible supercapacitors hinder their further development as the energy supply for wearable electronic devices. Herein, reduced graphene oxide/cobalt nickel double hydroxide nanocomposites (marked as rGO/CoNi-LDH) with a stable multi-level nanosheet structure are synthesized through template etching. Benefiting from the synergistic effect of rGO with highly conductive network and CoNi-LDH with high theoretical specific capacitance, the rGO/CoNi-LDH nanocomposites demonstrate excellent specific capacitance and outstanding cycling stability. Subsequently, the composite flexible electrodes (marked as BC/CNTs/RL) composed of bacterial cellulose (BC, enhances mechanical flexibility), carbon nanotubes (CNTs, improves conductivity), and rGO/CoNi-LDH (marked as RL) are constructed. Notably, the assembled symmetrical supercapacitors (SSCs) with BC/CNTs/RL as electrodes present areal capacitance of 630.7 mF cm⁻² and significant area energy density (0.17 mWh cm⁻² at 5 mA cm⁻²). On this basis, the solid-state all-in-one SSCs are assembled by continuous vacuum filtration process, which demonstrate excellent interface stability (84.8 % capacitance retention after 1000 bending deformations) and electrochemical output stability (92.5 % capacitance retention under 3D winding). This research provides ideas for enhancing the performance of nanomaterials, rapidly and conveniently constructing all-in-one supercapacitors with robust interfaces.