Recent advances in nickel-manganese phosphates-based electrodes for hybrid supercapacitors

Nickel‑manganese phosphates (NMPs) are emerging as highly promising electrode materials for hybrid supercapacitors, combining rich pseudocapacitive redox activity, structural robustness, and compositional tunability. Integration with conductive carbon frameworks, MOF-derived architectures, and bimetallic designs has enhanced conductivity, energy and power density, and cycling stability, with laboratory studies reporting specific capacitances exceeding 1100 F/g and excellent long-term retention. Translating these advances to practical devices requires addressing key challenges, including scalable and sustainable synthesis, intrinsic conductivity limitations, and device-level validation beyond half-cell tests. Deeper mechanistic insights into charge storage, ion diffusion, and degradation pathways are needed, which can be achieved through in-situ and operando characterization. Tailored electrolytes, hybrid composites, and heterostructured electrode designs offer pathways to optimize ionic transport, redox performance, and structural stability. By integrating rational material design, advanced characterization, and electrolyte engineering, NMP-based electrodes can achieve high energy and power density with long-term durability. These developments position nickel‑manganese phosphates as versatile candidates for next-generation hybrid supercapacitors.