Aluminum-cobalt-nickel trimetallic oxyhydroxide cathodes for high-energy-density aqueous magnesium-ion batteries

Abstract

The growing demand for efficient and sustainable energy storage systems has accelerated research into aqueous magnesium-ion batteries (AMIBs). However, the development of AMIBs faces cathode-related challenges including sluggish Mg²⁺diffusion kinetics, limited energy density and poor cycling stability. In this study, we synthesize a novel aluminum-cobalt-nickel trimetallic oxyhydroxide (ACNOOH) cathode material designed to overcome these limitations through strategic modification of nickel oxyhydroxide (NiOOH) with aluminum and cobalt. By regulating the electronic structure of the cathode material, aluminum lowers its Fermi level, thereby increasing the discharge voltage and energy density, and cobalt element mitigates the loss of Ni³⁺ during the cycle, thereby enhancing the cycling performance. Compared to NiOOH, ACNOOH exhibits superior energy density, improved rate performance, and enhanced cycling stability. The energy densities of the fabricated AMIBs are 127.07 Wh kg^-1 at 1 A g^-1 and 74.25 Wh kg^-1 at 5 A g^-1 with excellent capacity retention. These results indicate that ACNOOH can significantly improve the energy density and stability of AMIBs, which is a promising cathode material,and the present work offers a feasible elemental modification strategy for next-generation energy storage systems.