Preparation And Electrochemical Performance Investigation For Ternary Niobium-based Oxide

In the past decade,ternary lithium rich anode materials?Li-Ti-O?have been widely studied in the field of lithium ion battery anode materials due to their excellent cycling performance and high power.Compared with lithium titanate,ternary niobium oxide?M-Nb-O?not only has higher specific capacity and similar de-intercalated potential,but also shows excellent cycle performance and rate performance,which is expected to be the next generation of new-type anode materials.The results show that the two electron pairs(Nb⁵⁺/Nb⁴⁺,Nb⁴⁺/Nb³⁺)of Nb element have redox reaction during charge/discharge process,which can effectively improve the energy density of the battery system.This paper focuses on ternary niobium-based oxides(K₆Nb_10.8O₃₀,BNb₃O₉ and BiNbO₄),which were synthesized by electrostatic spinning method.And their morphologies,electrochemical properties and mechanism of lithium intercalation and delithium were also analyzed in this paper.Its specific contents are as follows:Firstly,the synthesis methods and electrochemical properties of the groove K₆Nb_10.8O₃₀nanobelts and nanowires are discussed in the section one.In this chapter,the roller and porcelain boat are used for electrostatic spinning,so that the evaporation time of the spinning solvent in the air is different.After calcination,one-dimensional K₆Nb_10.8O₃₀0 nanobelts and nanowires are obtained respectively.Electrochemical tests showed that the charging specific capacity of K₆Nb_10.8O₃₀0 nanowire at 100 mA g^-11 was 85.19 mAh g^-11 after 1000 cycles.The groove K₆Nb_10.8O₃₀nanobelts have more outstanding electrochemical performance.Under the same test conditions,the groove K₆Nb_10.8O₃₀0 nanobelts show its charging specific capacity is up to 161.5 mAh g^-11 after 1000cycles.Finally,the lithium storage mechanism of K₆Nb_10.8O₃₀0 was speculated by in situ XRD.Secondly,the synthesis methods,electrochemical properties and lithium storage mechanism of hollow BNb₃O₉ nanobelts are reported.The hollowed-out BNb₃O₉ nanobelts were prepared by electrostatic spinning with controllable voltage.In addition,at the current density of 700 mA g^-1,reversible capacity of the hollowed-out BNb₃O₉ nanobelts was maintained at 116.1 mAh g^-1after1000 cycles.Moreover,the key discovery was that the formation mechanism of the hollow BNb₃O₉ nanobelts was investigated by scanning electron microscope.Last,the structure evolution and lithium storage mechanism of BNb₃O₉ were studied by in situ XRD techique.Finally,the fabrication,electrochemical properties and lithium storage mechanism of one-dimensional BiNbO₄ nanowire are analyzed.The spinning precursor was obtained from the stainless steel mesh cage collector by the simple electrostatic spinning method,and the one-dimensional BiNbO₄ nanowire was obtained after the high-temperature calcination.Through the electrochemical performance test,it was found that the capacity retention rate was still 60%at high-current density after for 700 cycles.In situ XRD was used to confirm that the conversion of Li₃Bi alloy provided reversible capacity,and then a possible lithium storage mechanism was proposed.