Modification And Electrochemical Properties Of Nb₂O₅ Nanomaterials

Transition metal oxides have attracted more and more attention worldwide due to their excellent electrochemical performance,relatively low cost and environmentally friendly properties,and play an important role in energy storage and conversion technologies in lithium-ion batteries.Among them,niobium pentoxide（Nb₂O₅）material has excellent cycle performance and rate performance,which is a promising alternative anode material for lithium-ion batteries.However,the relatively low capacity,poor intrinsic conductivity and low Li⁺diffusion efficiency severely limit the comprehensive performance and practical application of Nb₂O₅.In order to solve the above problems,this paper used the three-phase coexisting Nb₂O₅nanosheets annealed at 750℃as the substrate to compound the carbon materials to explore the changes in the electrochemical properties of the composites.Firstly,Nb₂O₅nanosheets with three crystal phases were successfully synthesized by hydrothermal and subsequent annealing at 750°C,which contained a large number of nanodomains belonging to T-,M-,and H-phases and interlaced phase boundaries.Use different concentrations of Na BH₄to modify its surface,and then undergo a spontaneous redox reaction with graphene oxide to composite.The strong bonding between the two not only provides a convenient channel for the rapid transmission of electrons,also the crushing and destruction of the electrode under high current density is avoided,and the interlaced phase boundary also accommodates more active Li⁺.The sample treated with 5 m M Na BH₄and then composited with graphene has better rate performance.At a current density of 35 C,a reversible specific capacity of 104.5 m A h g^-1can still be maintained.Secondly,in order to enhance the strength of the nanosheets,the calcination temperature was adjusted to 800℃to obtain the optimized Nb₂O₅nanosheets.Using 5 m M Na BH₄for liquid phase treatment,and then compounding with different proportions of graphene oxide,the optimized nanosheets still have nanodomains with different crystal phases.These crystal phase interfaces provide enough space for lithium storage.And the close combination of graphene oxide and nanosheets also improves the overall conductivity of the material.When the volume ratio of Nb₂O₅:graphene oxide is 100:5,the sample has the best performance,which can cycle for 800 cycles at a rate of 5 C,and still retains a reversible capacity of 220m A h g^-1,the capacity loss is almost zero.Finally,since the three-phase coexisting Nb₂O₅nanosheets themselves have a rich defect concentration,the stability of the overall structure can be enhanced by coating different proportions of 3-Hydroxytyramine hydrochloride on the surface.The coated amorphous carbon layer not only stabilizes the structure of the composite material,but also eliminates the anisotropy of electron and ion transmission on the surface of the structure,improves the transmission efficiency of electrons,and achieves consistent capacitive energy storage,thus effectively improving the rate performance and cycling stability of the electrode material.When the mass ratio of Nb₂O₅and 3-Hydroxytyramine hydrochloride is 5:1,the sample performance is the best.The reversible specific capacity of 116.8 m A h g^-1can still be maintained after repeated charging and discharging at a large rate of 35 C.