Structure-Enhanced Mechanically Robust Graphite Foam with Ultrahigh MnO₂ Loading for Supercapacitors

With the fast bloom of flexible electronics and green vehicles, it is vitally important to rationally design and facilely construct customized functional materials with excellent mechanical properties as well as high electrochemical performance. Herein, by utilizing two modern industrial techniques, digital light processing (DLP) and chemical vapor deposition (CVD), a unique 3D hollow graphite foam (HGF) is demonstrated, which shows a periodic porous structure and robust mechanical properties. Finite element analysis (FEA) results confirm that the properly designed gyroidal porous structure provides a uniform stress area and mitigates potential structural failure caused by stress concentrations. A typical HGF can show a high Young's modulus of 3.18 MPa at a low density of 48.2 mg cm^-3. The porous HGF is further covered by active MnO₂ material with a high mass loading of 28.2 mg cm^-2 (141 mg cm^-3), and the MnO₂/HGF electrode still achieves a satisfactory specific capacitance of 260 F g^-1, corresponding to a high areal capacitance of 7.35 F cm^-2 and a high volumetric capacitance of 36.75 F cm^-3. Furthermore, the assembled quasi-solid-state asymmetric supercapacitor also shows remarkable mechanical properties as well as electrochemical performance.