Bimetallic phosphosulfide Zn-Ni-P-S nanosheets as binder-free electrodes for aqueous asymmetric supercapacitors with impressive performance

Although Ni-P based metal phosphides have high theoretical specific capacity, the poor rate capability and cycling stability hinder their practical application. Herein, we report bimetallic phosphosulfide Zn-Ni-P-S 2D nanosheets (ZNPS) by introduction of Zn cations and S anions into Ni-P metal phosphides, and they exhibit high rate capability and cycling stability in an aqueous asymmetric supercapacitor. The as-prepared ZNPS electrode shows a high specific capacity of 1180 C g(-1) at 2 A g(-1) in a three-electrode system. The ZNPS utilized in a two-electrode system shows a high energy density of 29.01 W h kg(-1) at a power density of 275.54 W kg(-1) and outstanding cycling stability (100% capacity retention after 15 000 cycles) and superior rate capability (94.99% capacity retention when the current density increases from 0.2 A g(-1) up to 1 A g(-1)). The simple and new strategy for ZNPS synthesis opens a path to design new electrode materials for aqueous asymmetric supercapacitors with an impressive performance.