Research On Controllable Preparation And Energy Storage Properties Of Niobium Phosphate

In recent years,niobium based materials have been excavated and studied by scientists because of their special structure and high theoretical capacity,and it is expected to be new generation anode materials in lithium ion batteries.At present,the research of titanium niobium oxides is mostly studied,and there are few reports on niobium phosphate materials.At the same time,one dimensional nanomaterials because of its unique microstructure and widely used in lithium ion battery cathode materials,electrospinning technology as one of the main methods of preparation,and its synthesis of one-dimensional nanomaterials can greatly improve the electrochemical performance of materials.Therefore,this paper will adopt the electrostatic spinning method to synthesize PNb₉O₂₅ with the structure of a nanowire,and use it as an anode material for lithium ion battery to study its energy storage performance.The main contents of the study are as follows:1.Synthesis by electrospinning,using the optimal calcination temperature and time to obtain the target product.The results of XRD,SEM,TEM test results show that the synthesized PNb₉O₂₅exhibits a high purity phase and has good crystallinity.By analyzing the electrochemical performance test results of PNb₉O₂₅,it can be seen that one-dimensional PNb₉O₂₅ nanowires exhibits the excellent electrochemical performance,which delivering a charge capacity of 265.2mAh g^-1 at the current density of 0.2C for the first cycle,and to exhibits reversible capacities of193.1 mAh g^-1 after 200 cycles corresponding to 72.81%capacity retention.The D⁺_Li value calculated by from EIS results were 2.573×10^-13 cm² s^-1.2.In order to further improve the electrochemical performance of PNb9O25 anode material,surface carbon coating treatment of PNb₉O₂₅ was carried out by the suspension method.The electron conductivity of PNb₉O₂₅ with carbon coating was significantly improved,and electrode polarization was reduced during charging and discharging.It can be concluded that carbon has been successfully coated on the surface of PNb9O25 through the analysis of XRD,SEM,TEM,RAMAN,XPS and other test results.PNb₉O₂₅5 with carbon coating delivering a charge capacity of263.6 mAh g^-1 at the current density of 0.2C for the first cycle,and to exhibits reversible capacities of 244.6 mAh g^-1 after 200 cycles corresponding to 88.01%capacity retention.Under the high current density of 10C,PNb9O25 with carbon coating delivering a reversible capacity of 211.6 mAh g^-1 for the first cycle,and to exhibits reversible capacity of 175.9 mAh g^-1 after 1000 cycles corresponding capacity retention ratio is 83.13%.The D⁺_Li value calculated by from EIS results were 3.799×10^-13 cm² s^-1.Moreover,this sample shows excellent rate performance with high charge capacities of 262.3?258.1?245.7?235.9?227.9?219.9?213.4?208?203.4?199.2?194 mAh g^-1 at the rates of 0.2?0.5?1?1.5?2?3?4?5?6?8?10C,respectively.According to the analysis of in-situ XRD test results,the structure of PNb₉O₂₅ with the carbon coating was almost unchanged in the process of lithium insertion/extraction.