摘要
Prussian blue analogue Na2Ni[Fe(CN)6](Ni-PB)has been widely studied as a cathode material for sodium-ion battery due to its excellent cycling performance.However,Ni-PB has a low theoretical capacity of 85 mAh g^(−1) because of the electrochemical inertness of Ni.Herein,ternary Ni-PB is successfully synthesized by double doping with Co and Fe at Ni-site,and the effect of doping with Co and Fe on the electrochemical performance of Ni-PB is systematically investigated through theoretical calculations and electrochemical tests.The first principles calculations confirm that double doping with Co and Fe can significantly reduce the energy barrier and bandgap of Ni-PB.X-ray diffraction and composition analysis results indicate that ternary NiCoFe-PB composite not only has good crystallinity and high Na content but also has low defects and crystal water.Electrochemical tests reveal that,besides the capacity contribution of high-spin Co/Fe and low-spin Fe,Co-doping enhances the electrochemical activity of low-spin Fe and Fe-doping improves the activity of high-spin Co;moreover,double doping can decrease the diffusion resistance of Na+ions through solid electrolyte interface film,accelerate the kinetics for both ion diffusion process and Faradic reaction,and increase active sites.Under the synergistic effect of Co and Fe,this ternary NiCoFe-PB exhibits outstanding electrochemical performance with a high initial discharge capacity of 120.4 mAh g^(−1) at 20mA g^(−1) and an extremely low capacity fading rate of 0.0044%per cycle at a high current density of 2 A g^(−1) even after 10,000 cycles,showing great application potential of ternary NiCoFe-PB in the field of large-scale energy storage.
基金
National Natural Science Foundation of China,Grant/Award Number:52072217,51802261,51772169
National Key R&D Program of China,Grant/Award Number:2018YFB0905400
Major Technological Innovation Project of Hubei Science and Technology Department,Grant/Award Number:2019AAA164。
