Synthesis And Modification Of NaTi₂?PO₄?₃ Anode Materials For Sodium Ion Batteries Prepared By Using MOF As Template

Metal-Organic frameworks?MOFs?have attracted considerable attention in the energy storage field.We preparation of NTP/C composites as anode materials for sodium-ion batteries by using MIL-125 as template for the first time.NTP/C composites were further coated with poly-dopamine to obtained modified NTP/C material which show better performance than the unmodified NTP/C material.We investigated the preparation method,crystal structure and morphology,and the electrochemical performance of these materials.The detailed works were as follows:?1?MIL-125 and NH₂-MIL-125 were prepared by the solvothermal method.The particle size of MIL-125 was tuned by adding CTAB in the synthesis stage of MIL-125.?2?MIL-125 and NH₂-MIL-125 were used as both titanium sources and carbon sources to synthesize NTP/C composites materials.Respectively,the influence of different calcination conditions on material crystalline properties and electrochemical properties was investigated by XRD?SEM and electrochemical test.The experimental results showed that NTP/C electrode materials with good crystalline properties and excellent electrochemical properties,which can be prepared by using MIL-125 or NH₂-MIL-125 at a reasonable calcination conditions?900? for 1 h?.When MIL-125was used as a template after calcinating at 900?for 1 h,NTP/C material demonstrated a high reversible capacity of 270 mAh/g at a current rate of 0.5C,and an excellent capacity retention of 86%after 200 cycles at 100mA/g.The cycle performance and rate performance of the material prepared by NH₂-MIL-125 precursor is superior to material prepared by MIL-125.After 200 cycles at current density of 100mAh/g,the NTP/C material prepared by NH₂-MIL-125 delivered a high charge capacity of 285 mAh/g,corresponding to a capacity retention of 67%,exhibiting a superior rate capability of127 mAh/g at the current density of 4000mA/g.The thesis provide a new idea for modification of materials with adjusting the organic ligands to change morphology and electrochemical of NTP materials.?3?The NTP/C prepared by MOFs coated with poly-dopamine was investigated and the influence on material properties by adding different amount of the poly-dopamine was studied.The results show that the cycle and rate performance of the coated material have been significantly improved and modified NTP material exhist of excellent performance with 0.04g poly-dopamine,the capacity of modified NTP can reach to330mAh/g and hasn't decaied after 200 cycles at the current density of 100mA/g,The capacity can be maintained at about 180 mAh/g at a current density of 4000 mA/g,which is much higher than the specific capacity of the unmodified material of 90 mA/g.