Weigu Li1 Donglei (Emma) Fan1

1, The University of Texas at Austin, Austin, Texas, United States

It is highly desirable to develop supercapacitors with large areal capacitance for direct integration with flexible electronics and powering their performances with small footprints. Here, we report an innovative approach to synthesize dendritically porous graphite foams (DPGFs) by strategically creating 3D catalytic foams with hierarchical microscale dendrites and pores. A large array of graphitic microdendrites (2-5 µm in width, ~30 µm in length) can be readily grown on the interconnected struts of DPGF and even fill the 100-200 µm voids between these struts, which results in substantial increase of the volumetric surface area by at least three times. The obtained dendritically porous graphite enables a high loading of pseudocapacitive Mn3O4 materials at 3.91 mg cm-2 and 78 wt%. Without utilization of binders or conductive additives, the half DPGF/Mn3O4 (DPGM) electrodes provide an areal capacitance as high as 820 mF cm-2 (1 mV s-1), and retain 88% capacitance and 98% coulombic efficiency after 3,000 continuous galvanotactic charge/discharge cycles at 20 mA cm-2. The DPGMs are further assembled into all-solid-state symmetric supercapacitors, which outperform most manganese oxide/GF based supercapacitors with a full cell capacitance of 191 mF cm-2 (2 mV s-1) and 81% capacitance retention after 1 000 cyclic mechanical bending. Finally, the potential of the flexible supercapacitors is demonstrated in successfully powering an all-portable nanomotor manipulation system, which can propel nanomotors to trace letters “U” and “T”. This work could inspire a new paradigm in designing and creating 2D and 3D porous microsuperstructures for an array of flexible energy and electronic applications.