A direct-write method for preparing a bimetal sulfide/graphene composite as a free-standing electrode for high-performance microsupercapacitors.

It is a great challenge to ideally integrate graphene with its unique two-dimensional (2D) and porous structure into the pseudocapacitive materials. In this paper, a simple technique, direct-laser-writing (DLW), was developed to fabricate microsupercapacitors (MSCs) with excellent electrochemical performance, marked as Ni-Co-S/laser induced graphene (LIG) that exhibit a high areal specific capacitance of 680 mF cm at the current density of 1 mA cm. A symmetric MSC device was assembled using Ni-Co-S/LIG as a positive electrode and active carbon (AC) as the negative electrode, and exhibited a high areal energy density of 56.9 μW h cm at the power density of 800 μW cm, and excellent cycling stability maintaining 89.6% of the areal specific capacitance after 8000 cycles. The synergistic effect of bimetallic Ni-Co-S and the LIG with the 2D structure results in the excellent electrochemical performance. This work demonstrates a method to integrate Ni-Co-S pseudocapacitive materials into porous graphene with a direct-laser-writing technique. The produced integrated materials possess high energy density that can be used in MSCs.