Study On Controllable Preparation Of Antimony Tellurium Heterojunctions And Their Sodium Storage Properties

Sodium-ion batteries have come into the limelight because of their similar working principle,good safety and low production cost.However,the graphite anode material,which is suitable for lithium ion battery and is low cost and easy to prepare,cannot be used in sodium ion battery due to the problem of laminar structure collapse caused by the insertion of large sodium ions.Therefore,it is very important to find high performance anode materials suitable for sodium ion battery.Among them,antimony based materials have attracted attention due to their abundant environmentally friendly reserves and high theoretical capacity,but their stability is poor and their dynamics lag.Because of its special structure,heterojunction can spontaneously form internal electric field,promote charge transfer and relieve stress,which is an ideal method to solve this problem.However,the controllable preparation of two-dimensional heterojunctions remains a great challenge.In this paper,a variety of antimony based heterojunctions with different morphologies were prepared to be used as anode materials for sodium ion batteries,and their electrochemical properties and mechanism of sodium storage were studied systematically.The specific content is described as follows:1.The heat dissipating sheet Sb₂Te₃-Te nanoheterojunction composed of one nanorod and several nanosheets was prepared by a two-step solvothermal method.The heterojunction can be easily adjusted by the engineering feed ratio.There are many tiny internal electric fields formed between the nanosheets,which accelerate the ion diffusion rate,which is proved by the high contribution rate of the pseudocapacitance.In addition,electrochemical impedance spectroscopy（EIS）,constant current batch titration（GITT）tests and density functional theory（DFT）calculations also confirm that the heterogeneous structure effectively improves the electron conductivity..When used as the negative electrode of a sodium ion battery,the reversible capacity of the nanoheterojunction reached 463.2m Ah g^-1after 200 cycles at a current density of 100 m A g^-1,and remained at 305.5m Ah g^-1 after 1000cycles at a high current of 1.5 A g^-1.2.T-type Sb₂Te₃-Te nanoheterojunction consisting of a nanorod and nanosheet at its end was prepared by solvothermal method.The structure of the heterojunction is simple and easy to prepare.The unique structure improves the first coulomb efficiency and cycle life of the electrode material.When used as the anode material of sodium ion battery,the nanoheterojunction showed A reversible capacity of 426.1 m Ah g^-1 at 100 m A g^-1 after 200cycles,and the capacity retention rate remained 70.5%after 500 cycles at 1 A g^-1 current,and the first coulomb efficiency was 83.7%.3.A new shell-like composite Sb₂Te₃-Te@C was synthesized by solvothermal method.Due to the protective effect of the outer carbon nanoshell,the cycle stability and rate performance of the electrode materials are greatly improved.When used as the anode material of sodium ion battery,the reversible capacity of the composite material reached458.9 m Ah g^-1 after 200 cycles of 100 m A g^-1,and after 1000 cycles of 1 A g^-1 current,the capacity retention rate is still 76.1%,and the first coulomb efficiency is as high as 93.8%.