Bi-functional modular graphene network with high rate and cycling performance.

Three-dimensional bi-functional modular graphene network (3D bmG) is developed by using metal powder assisted soluble salt templates method. The 3D bmG contains two kinds of modules with different functions: the 3D graphene catalyzed by Ni powder (3D bmG-n) and the 3D graphene grown on NaCl crystals (3D bmG-s). The 3D bmG-n with high crystallization degree ensures the high electrical conductivity and structural stability and protects the 3D bmG-s from etching in electrolyte. The 3D bmG-s with more defects and pores provides high capacity and rate properties. Thus, the synergistic effects of the two modules endow the 3D bmG excellent electrochemical performance as both cathode and anode of lithium-ion capacitors (LICs). The as-prepared "all-carbon" bmG//bmG full LIC with a high voltage window of 4.5 V presents high energy densities of 278 Wh kg−1 and 52.2 Wh kg−1 at power densities of 405 W kg−1 and 16200 W kg−1, respectively, and excellent cycling stability with a capacity retention ratio of 88.57% after 3000 cycles, which is superior compared with LICs reported previously. These properties indicate promising application of 3D bmG in high performance energy storage devices, and the modular design in this work will inspire more designs and types of 3D materials. [Display omitted] • 3D bi-functional modular graphene network was successfully developed. • Two modules with specific structures ensure synergistic improvement of properties. • 4.5 V symmetrical LIC achieved high energy and power density and long cycle life. [ABSTRACT FROM AUTHOR]