Preparation Of Zinc-ion Battery Cathode Material And Its Electrochemical Performance

Due to the environmental pollution and energy crisis brought by traditional energy storage technology,people have been researching and developing high-energy density and environmentally friendly grid-scale energy storage devices.Lithium-ion batteries have been widely used as commercial energy storage devices owing to their advantages of high efficiency in delivering energy,high voltage,long cycling life,but it also has the disadvantage of high cost and many problems.As one of the new and most promising alternative energy storage technologies,zinc-ion rechargeable battery has recently received much attention owing to the unique properties of its rich natural resources,intrinsic safety and low cost.At present,the reported cathode materials of zinc-ion battery mainly include manganese-based oxides,vanadium-based oxides and Prussian blue analogs.However,the low capacity,undesirable ionic conductivity,and poor cycling performance weaken the potential application of these cathode materials in ZIBs.In light of these poor qualities,the development of new materials for ZIB cathodes is still in high demand.Transition metal chalcogenides also have great potential to become high-quality zinc-ion electrode materials due to their high conductivity and large layer spacing.In this paper,two cathode materials of bismuth selenide(Bi₂Se₃)and bismuth telluride(Bi₂Te₃)were synthesized by hydrothermal method,and the electrochemical property of these two cathode materials in aqueous zinc-ion batteries were studied.At the same time,the energy storage mechanism of the batteries was proposed by in-situ XRD technique.The main achievements are as follows:(1)The bismuth selenide nanosheets(TBSNs)were synthesized by two-step hydrothermal method,and the Zn/Bi₂Se₃ battery was designed and constructed for the first time.The results show that Bi₂Se₃ nanoplate cathode delivers a high specific capacity of 263.2 mAh g^-1 at 100 mA g^-1 and maintains 80 mAh g^-1 after 500 cycles even at an ultra-high current density of 10 A g^-1,this indicates that Bi₂Se₃ nanoplate is a cathode material with good reversibility and high rate performance The results show that the excellent performance of the TBSNs is attributed to the prominent capacitive-controlled kinetics process.Combined with the in-situ synchrotron radiation XRD technique,the energy storage mechanism of Zn/Bi₂Se₃ battery with dual charge carriers was revealed:the sequential insertion/extraction of H⁺and Zn²⁺in the TBSNs during the charge/discharge process.Density functional theory analysis approves the low adsorption energy and preferential embedding process of protons,and that can further optimize Zn²⁺adsorption and migration abilities in bismuth selenide nanoplate,which is mainly responsible for the excellent performance.(2)Bi₂Te₃ nanosheets were prepared by one-step hydrothermal method and explored as cathode material of aqueous zinc-ion battery.Electrochemical tests show that the maximum discharge specific capacity of the material can reach 133.9 mA h·g^-1 at the current density of 100 mA g^-1 and the capacity retention rate can reached 73.2%after 50 cycles.In order to further study the reaction mechanism of Bi₂Te₃ cathode material,in-situ synchrotron radiation X-ray diffraction(XRD)technique was used to track the changes of structure of Bi₂Te₃ nanosheets during the charge-discharge process of the battery.The highly reversible proton intercalation was disclosed during the reaction process,which responsible for the practical battery operation.