Unsaturated Ni/V centers and short Ni·V/Ni distances in nickel vanadate for high-performance zinc-ion battery

3D rotation electron diffraction, Rietveld refinement and spherical aberration-corrected TEM reveal that Ni 0.22 V 2 O 5 (o-NiVO) possesses a novel 3D framework with unsaturated Ni/V centers and short Ni ··· V/Ni distances, which shows high capacity, good rate capability and long-term durability with a low Zn 2+ migration barrier. • O-NiVO possesses unsaturated Ni/V centers with short Ni V/Ni distances. • The structure of o-NiVO is confirmed by rotation electron diffraction and HAADF-STEM. • O-NiVO possesses outstanding rate capability and long-term cyclability. • DFT calculations prove a low Zn 2+ migration barrier in o-NiVO. • O-NiVO shows an intercalation mechanism of Zn 2+ /H + and partial phase transformation. Ni 0.22 V 2 O 5 (H 2 O) 0.94 (NiVO) nanobelts were synthesized via a facile one-step hydrothermal method, which exhibited a 3D framework built by [Ni(H 2 O) 6 ] 2+ pillars connecting 2D V-O-V layers. Upon subsequent annealing, Ni 0.22 V 2 O 5 (o-NiVO) nanobelts with a large d spacing of 9.2 Å were obtained. 3D rotation electron diffraction (cRED), Rietveld refinement and spherical aberration-corrected TEM reveal that o-NiVO displays a novel 3D framework. Annealing led to atom arrangement and partial Ni 2+ ions entered into 2D V-O-V layer of o-NiVO with unsaturated Ni/V centers and short Ni ··· V (2.463 Å)/Ni ···Ni distances (2.401 Å), which can facilitate the electron transfer from O → Ni and improve the electron conductivity with a low Zn 2+ migration barrier (0.64 eV) in o-NiVO, as evidenced by DFT calculations. Therefore, o-NiVO can deliver a high initial capacity of 445 mAh g −1 at 0.1 A g −1 with good rate capability and fast Zn 2+ diffusion kinetics. Meanwhile, o-NiVO also possesses excellent long-term durability with capacity retention of 99.8 % over 1500 discharge/charge cycles. The fully discharged o-NiVO nanobelts was characterized by cRED, which disclosed the structural integrity of o-NiVO during the discharge process. A series of ex situ characterizations of the o-NiVO electrode reveal a co(de)intercalation mechanism of Zn 2+ /H + along with partial phase transformation of o-NiVO → Zn 3 (OH) 2 V 2 O 7 (H 2 O) 2 .