Enhancing the lithium storage performance of α-Ni(OH)2 with Zn2+ doping

Abstract

Flower-like Zn 2+ doped α -Ni(OH) 2 samples were synthesized via a facile hydrothermal method. The Zn 2+ doped α -Ni(OH) 2 sample with Zn 2+ /Ni 2+ molar ratio of 45% (45-ZN) exhibits much-improved cycling stability, high-rate capability, and electrochemical reaction kinetics due to the unique flower-like nanostructures and the synergetic effect between Ni 2+ and Zn 2+ . • Zn 2+ doped α -Ni(OH) 2 was prepared by homogeneous precipitation method. • The Zn 2+ doped α -Ni(OH) 2 was evaluated as an anode material for LIBs. • Zn 2+ doping effectively enhanced the cycling stability and high-rate capability. • The Zn 2+ doped α -Ni(OH) 2 exhibited an obvious pseudocapacitive behavior. To enhance the lithium storage performance of α -Ni(OH) 2 , different amount of Zn 2+ (with Zn 2+ /Ni 2+ molar ratio of 0 %, 15 %, 30 %, 45 %, and 60 %, respectively) was introduced into the lattice of α -Ni(OH) 2 samples by a facile hydrothermal method. The influence of Zn 2+ doping on the microstructure and lithium storage performance of α -Ni(OH) 2 was investigated in detail. The results demonstrate that with the increase of Zn 2+ /Ni 2+ molar ratio, the microstructure of the as-prepared samples transforms from an urchin-like morphology to flower-like morphology, accompanied by the phase structure transforming from pure-phase α -Ni(OH) 2 to mixed-phase α -Ni(OH) 2 /Zn(OH) 2 . Electrochemical characterizations reveal that Zn 2+ doping can effectively enhance the lithium storage performance of α -Ni(OH) 2 . In particular, the Zn 2+ doped α -Ni(OH) 2 with Zn 2+ /Ni 2+ molar ratio of 45 % (45-ZN) exhibits superior cycling stability (maintaining a reversible capacity of 713 mA h g −1 at a current density of 0.5 A/g after 50 cycles), outstanding high-rate capability (delivering a high specific capacity of 485 mA h g −1 at 2.0 A/g), and fast electrochemical reaction kinetics. GITT analysis demonstrates that the lithium ions diffusion coefficient of the 45-ZN varies in the range of 10 −10 –10 −12 cm 2 s −1 , higher than that (10 −10 –10 −13 cm 2 s −1 ) of pure α -Ni(OH) 2 . In addition, the 45-ZN sample presents an obvious pseudocapacitance behavior during the discharging/charging process. The synergetic effect between Ni 2+ and Zn 2+ can account for the improved electrochemical performance of the Zn 2+ doped α -Ni(OH) 2 . The work provides clues for the preparation and performance optimization of α -Ni(OH) 2 as an anode material for lithium-ion batteries from the aspect of metal ions doping.