Synergistic integration of amorphous trimetallic phosphates with porous plate-like architecture for high-performance hybrid supercapacitors

The development of energy storage materials with superior electrochemical performance has attracted growing attention to address the increasing demand for multifunctional energy devices. In this work, we investigate the effects of incorporating different ternary metals (Mn, Fe, or Cu) into bimetallic nickel‑cobalt phosphate (NiCoPO) and evaluate the resulting physicochemical properties and electrochemical performance for hybrid supercapacitors. The resulting NiCoXPO (X = Mn, Fe, or Cu) samples preserve the amorphous nature, good size uniformity, and two-dimensional (2D) plate-like morphology of NiCoPO. These trimetallic phosphate samples exhibit battery-type behavior, dominated by Faradaic redox processes. Among the tested metal phosphates, the specific capacitance (capacity) follows the order: NiCoMnPO > NiCoCuPO > NiCoFePO > NiCoPO at a current density of 1.5 A g −1 in 6 M KOH, highlighting the advantages of the trimetallic composition. The superior charge-storage performance of NiCoMnPO is attributed to its enhanced charge-transfer ability and increased number of electrochemically active sites, arising from its hierarchical porous structure and the abundance of redox couples (Ni 2+ /Ni 3+ , Co 2+ /Co 3+ , Mn 2+ /Mn 3+ , and Mn 3+ /Mn 4+ ) in NiCoMnPO. Furthermore, the hybrid supercapacitor (HSC) assembled using NiCoMnPO as the positive electrode and activated carbon (AC) as the negative electrode (NiCoMnPO//AC) exhibits high energy density of 114.29 Wh kg −1 at a power density of 375 W kg −1 , exceeding many previously reported phosphate-based HSCs. The HSC also demonstrates excellent cycling stability, retaining 97% of its initial capacitance after 10,000 cycles at 10 A g −1 . These findings highlight NiCoMnPO as a promising electrode material for next-generation hybrid supercapacitors. • Trimetallic phosphates with amorphous two-dimensional structures are reported • Trimetallic NiCoXPO (X = Mn, Fe, Cu; PO = phosphate) shows battery-like behavior • Trimetallic NiCoXPO electrodes show enhanced charge transfer and active sites. • Trend in charge storage performance: NiCoMnPO > NiCoCuPO > NiCoFePO > NiCoPO • NiCoMnPO displays a high specific capacity of 670C g −1 at 1.5 A g −1 • NiCoMnPO//AC hybrid supercapacitor exhibits an energy density of 114.29 Wh kg −1