3D-Printed Ultralight, Superelastic Reduced Graphene Oxide/Manganese Dioxide Foam for High-Performance Compressible Supercapacitors

The rapid development of wearable electronic devices has put forward higher requirements for compressible energy storage devices. Three-dimensional (3D) hierarchical porous structures have been verified to be an excellent force-bearing structure, which is beneficial to disperse strain and stress, effectively improving stiffness and resilience. However, the development of a 3D hierarchical electrode with both excellent compressibility–resilience and a stable power output under deformation conditions is still facing significant challenges. Here, a 3D-printed ultralight and superelastic reduced graphene oxide-manganese dioxide foam (3DP-rGO-MnO2) is proposed to construct high-performance compressible supercapacitors via a simple in situ chemical reaction with a uniform loading of MnO2 on the printed rGO foam substrate. The rGO foam with a 3D hierarchical porous structure formed by 3D-printed regular macroscopic pores and freeze-drying-incorporated cellular microscopic pores can not only provide sufficient stress relief space for large mechanical deformation and ensure fast ion/electron transfer kinetics but also provide abundant active sites for MnO2 loading, effectively solving the issues of poor conductivity and volume expansion of MnO2 during charging and discharging. As a result, the constructed symmetrical supercapacitor exhibits excellent and long cycling stability (90.4% after 20,000 cycles) and a competitive energy/power density (18.4 W h/kg, 9000 W/kg). Meanwhile, the compressible devices can deliver a stable capacitance output under different compressive deformation from 0 to 90% and notably retain 93.9% capacity even under an ultimate compressive strain of 90%. This work provides a promising avenue for designing high-performance compressible energy storage devices.