Nickel Diaminonaphthoquinone Complexes with Nickel–Nitrogenand Hydrogen Bonding toward Enhanced Lithium-Ion Storage

Stable metal–organic clusters (MOCs) with multiple redox-active sites may offer high specific capacity, fast electrochemical reaction kinetics, and long cycling lifespan, making them appealing candidates for efficient lithium storage in lithium-ion batteries. Herein, a novel MOC material, nickel-coordinated diamino-naphthoquinone (Ni-DANQ), is designed to achieve high-capacity and stable lithium-ion storage. The material features dual redox centers from quinone and imine moieties of DANQ ligands, connected by robust square-planar Ni–N₄ linkages and naphthoquinone-diamine structural units that form π–π interactions between adjacent molecules. The Ni-DANQ chains self-assemble into an extended π-d-conjugated two-dimensional (2D) structure via hydrogen bonds, enabling high electronic conductivity. Benefiting from robust Ni–N bonds and superior electronic conductivity, the Ni-DANQ electrode delivers exceptional performance with reversible capacities of ∼416 mAh g^–1 at 0.05 A g^–1 and ∼309 mAh g^–1 at 2 A g^–1, as well as excellent rate capability and high capacity retention. Ex situ Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies combined with density functional theory (DFT) calculations reveal that the conductive Ni-DANQ enables reversible Li⁺ storage through a two-step 6-electron transfer reaction. This work demonstrates the potential of Ni-DANQ as a promising electrode material for lithium-ion batteries.