Enhancing energy storage of nickel-zinc battery through comprehensive d-p orbital hybridization regulation

Developing high-performance Ni cathodes and understanding the relationship between electron states of Ni 3d orbital and energy storage mechanism from an atomic-orbital perspective are crucial yet challenging for alkaline nickel-zinc batteries. Herein, we innovatively design P-NiMoO4/NiSe2 heterostructures with rich oxygen vacancy via a selective component segregation. The P substitution in NiMoO4 activate Ni atoms, leading to the spin-state transition of Ni-3d orbitals from high-spin to low-spin, which promote the uniform and rapid nucleation of NiSe2 on the surface of NiMoO4 during subsequent selenization process. After selenization, the in situ formed P-NiMoO4/NiSe2 heterostructures exhibits continuous increased unoccupied states of Ni 3d-orbitals and higher Ni valence state. The synergistic effect of P doping and selenization modulate the d-band center (ɛd) level of Ni 3d, thereby promoting d-p orbital hybridization between Ni 3d and O 2p of OH− as well as OH− adsorption ability. Consequently, the P-NiMoO4/NiSe2 exhibits a top-level specific capacity of 390.7 mA h g−1 at 1 A g−1, 2.8-fold higher than that of pristine NiMoO4, accompanied by remarkable rate capability and structural stability. Moreover, the assembled pouch-type battery and flexible devices demonstrate the practical application potential. This work provides fundamental insights into orbital-level engineering of battery materials for enhanced redox kinetics and cycling stability.