Study On Lithium/sodium Storage Performance And Mechanism Of Lepidocrocite A_xM_yTi_2-yO₄-Based Anode Materials

The lepidocrocite type A_xTi_2-yM_yO₄(A=K,Rb or Cs,M=vacancy or Li,Mg,Co,Ni,Cu,Zn or Mn)of titanium-based material is an important lithium/sodium ion battery anode with an intercalation reaction.This anode electrode material has the advantages of low cost,high stability,long cycle life,and small volume change during the insertion/extraction of lithium/sodium ions,which has attracted wide attention from researchers.However,due to the low theoretical capacity and inherent low conductivity,its specific capacity is low and the rate performance is poor,which limits the further development of lepidocrocite-type A_xTi_2-yM_yO₄ in energy storage devices.In this paper,the Fe-doped KLTO@r GO composite material is prepared by surface coating and bulk doping of the lepidocrocite-type titanium-based material K_0.8Li_0.27Ti_1.73O₄(KLTO).H_1.07Ti_1.73O₄(HTO)micron materials with larger spacing are obtained by the method of ion-exchange.And it can be used as anode materials for lithium-ion batteries to improve the electrochemical performance of lepidocrocite-type titanium-based materials.In addition,HTO@r GO composite material is prepared by the positive and negative charge attraction method and studied sodium storage performance,the specific content is as follows:(1)Research on the lithium storage performance of KLTO-based anode materials:Fe₂-KLTO@r GO composite material with optimized Fe doping ratio was prepared by Fe doping and r GO coating.The capacity of Fe₂-KLTO@r GO can still reach 126.6m A h g^-1 after 3000 cycles stably at a maximum current density of 50C(1C=175 m A g^-1).In addition,LFPO||Fe₂-KLTO@r GO full battery can also stabilize at a current density of 200 m A g^-1 after 200 cycles with the specific capacity of 64.5 m A h g^-1.(2)Research on the lithium storage performance of the HTO anode electrode:HTO was prepared from the the source material KLTO to through a simple ion exchange method,and it exhibits good rate performance and cycle stability as a lithium battery anode electrode.At a current density of 5 A g^-1,a reversible capacity of 101 m A h g^-1 remains after 3000 cycles.The LFPO||HTO full battery has a capacity of 73 m A h g^-1 after 200 cycles at a current density of 500 m A g^-1.(3)Research on the sodium storage performance of HTO@r GO composite anode material:HTO@r GO composite material is obtained by coating r GO on the surface of HTO through the positive and negative charge attraction method,then it is used as a sodium ion battery anode material to study its electrochemical performance.In addition,the mechanism of sodium storage in HTO is studied by calculating the contribution rate of pseudocapacitance,calculating the diffusion coefficient of sodium ions,and in-situ transmission electron microscopy study.