Pre-intercalation Strategy And Zinc Ions Storage Properties Of Vanadium-based Materials

Rechargeable aqueous zinc-ion batteries(ZIB s)have received incremental interest due to the advantages of metallic Zn anode,including low cost,environmental friendliness,good compatibility with water,high theoretical capacity(819 mAh g-1)and low redox potential(-0.762 V versus standard hydrogen electrode).However,the development of ZIBs is mainly hindered by the lack of suitable cathode materials with favorable specific capacity and high cycling stability.Vanadium pentoxide(V2O5),with an open-framework crystal structure and multivalence,demonstrates high capacity.However,the sluggish Zn2+ diffusion and poor structural stability limit their further application in ZIBs.Herein,in view of the problems,the method based on co-doping different guest species into V2O5 cathode has been carried out.The main contents are as follows:Firstly,a new strategy is proposed to introduce metal ions and conjugated conductive polymers into layered hydrated V2O5 as the cathode material of ZIBs.For demonstration,Li+and polyaniline(PANI)are co-intercalated into hydrated V2O5(LPVO)resulting in an enlarged spacing of 14.4 (?).A ZIB with this LPVO cathode exhibits a capacity of 377 mAh g-1 at a current density of 0.1 A g-1,which is higher than that of a single Li+pre-intercalated hydrated V2O5(LVO)or PANI pre-intercalated host(PVO).Besides,a long cycling stability(94%capacity retention after 800 cycles at 5 A g-1)is achieved.The synergistic effect of pre-intercalated Li+and PANI in LPVO is originated from the weak electrostatic interactions between Zn2+ and the host O2-.Density functional theory(DFT)calculation results clearly show that LPVO possesses the lowest binding energy of 1.67 eV for Zn2+ insertion into the host(2.41 eV for LVO,1.84 eV for PVO),indicating favorable reaction kinetics in LPVO,which is also confirmed by the fastest Zn2+ diffusion coefficient of LPVO among the three samples.The enlarged lattice space and stabilized host structure also improve the cycle performance.Our study elucidates the advantages of co-intercalated alien species in host and provides a facile strategy to obtain high performance ZIB s.In addition,a new strategy was proposed to introduce metal cations and non-metal anions into layered hydrated V2O5 as ZIBs cathode materials.N,Mn co-doped V2O5 cathode(N-MnVO)is prepared and electrochemical test results show that pre-intercalation of Mn can effectively enlarge the interlayer spacing and increase the specific capacity of pure VO electrode from 215 to 393 mAh g-1(0.1 A g-1).Besides,after further N doping,the rate capability and cycle stability of N-MnVO are effectively imcreased.At a current density of 5 A g-1,the capacity of N-MnVO can be stabilized at 197 mAh g-1 after 2000 cycles with a capacity retention of 88%.The superior electrochemical performance can be ascribed to the increased oxygen vacancies arising from the N doping,which provides enhanced active sites and a shorter Zn2+ diffusion path.Besides,GITT test also confirmed the fast reaction kinetics of N-MnVO.