Zinc Storage Behavior Of Phosphate Cathode Materials

Among secondary battery systems,aqueous zinc-ion batteries are considered to be the most promising new technology for large-scale electrochemical energy storage,due to their abundant resource reserves,low cost,and high safety.Usually,the cathode materials for zinc storage include manganese oxides,vanadium oxides,phosphate materials,and Prussian blue analogs.Phosphate is a potential high specific energy cathode material,because of the stable crystal structure and high working voltage.VOPO₄ and Na₃V₂（PO₄）₃ with open crystal structures and abundant lattice gaps could provide sufficient space for Zn²⁺migration and storage,but problems such as material dissolution and capacity fading,limit their application in aqueous zinc-ion batteries.This thesis took typical phosphate materials VOPO₄ and Na₃V₂（PO₄）₃ as the main research objects,and explored the effects of interlayer structure regulation and electrolyte regulation on their electrochemical zinc storage behaviors,respectively.The main research contents and results are as follows:（1）The effects of interlayer structure regulation on VOPO₄ zinc storage behavior.A new type of VOPO₄/NC amorphous material was prepared by interlayer pre-insertion and in-situ carbonization of organic molecules,in which the introduction of nitrogen-doped carbon（NC）could provide abundant ionic reaction sites and strengthen the composites conductivity.Benefiting from the synergistic effect of stable structure and intercalated pseudocapacitive energy storage,as well as the simultaneous cationic(Vⁿ⁺/V^（n-1）+)and anionic(N^3-/N^2-)redox reactions,VOPO₄/NC cathode exhibited a high specific capacity of 187.9 m A h g^-1 and life up to1000 cycles.（2）The effects of electrolyte regulation on Na₃V₂（PO₄）₃ zinc storage behavior.The porous Na₃V₂（PO₄）₃ material was synthesized by sol-gel method,and the effect of solvent composition in Zn（CF₃SO₃）₂-based electrolyte on its zinc storage behavior was studied.Benefiting from the high activity of water molecules and low desolvation energy barrier induced by acetonitrile molecules in the electrolyte,when the water content in the mixed solvent of acetonitrile and water was 15%and 30%,the cycle stability and rate performance of Na₃V₂（PO₄）₃ could be obviously improved,and there was almost no capacity fading after 1000 cycles.