Binder-free trimetallic phosphate nanosheets as an electrode: Theoretical and experimental investigation

Abstract Transition metal phosphides and phosphates are newly emerging electrode material candidates in energy storage devices. For the first time, we report a uniformly distributed, interconnected, and well-aligned two-dimensional nanosheets made from trimetallic Zn-Co-Ga phosphate (ZCGP) electrode materials with preserved crystal phase. It is found that the ZCGP electrode material exhibits about 2.85 and 1.66 times higher specific capacity than mono- (Co-phosphate) and bimetallic phosphate (Zn-Co phosphate) electrode materials at the same current density. The trimetallic ZCGP electrode exhibits superior conductivity, lower internal resistance (IR) drop, and high coulombic efficiency compared to mono- and bimetallic phosphate. By means of density functional theory (DFT) calculations, ZCGP shows superior metallic conductivity due to the modified exchange splitting originating from 3d-orbitals of Co atoms in the presence of Zn and Ga. Moreover, hybrid supercapacitor (ZCGP//rGO) device is engineered which delivered a high energy density of 40 W h kg−1 and a high-power density of 7745 W kg−1, lighting 5 different colors of light emitting diodes (LEDs). These outstanding results confirm the promising battery-type electrode materials for energy storage applications.