Gradient architecture to boost the electrochemical capacitance of hard carbon

Carbon-based supercapacitors with outstanding electrochemical performances are strongly desired for the development of portable and wearable electronics . From the free radical engineering point of view, this study innovatively developed carbon/carbon gradient-structured microspheres (CCGMs) by the strategy of “third-order graduation polymerization” and “dynamic radical oxidation”. Compared to conventional hybrid materials , for the first time, the gradient structure is proved to be extremely beneficial for improving the capacitive performance. Benefiting its gradient-structured advantages, the CCGMs exhibited “three-ultrahigh” performance with gravimetric , volumetric , and areal capacitances of 408.23 F g −1 , 741.11 F cm −3 , and 4390 μF cm −2 , respectively. In addition, the assembled all-solids-state micro-supercapacitors delivered superior volumetric and areal specific capacitances (7.704 F cm −3 and 9.245 mF cm −2 at 5 μA cm −2 ), excellent life-span (100% after 12000 cycles), excellent volumetric and areal energy densities (1070 mWh cm −3 and 1284 μWh cm −2 ). This work paves a new way to develop unique carbon composites for high‐performance energy storage devices.