Study On The Modification Of High Nickel NCM Lithium Cathode Material And NAVP Sodium Cathode Material

Out of concerns about the environmental pollution of fossil energy and the need for sustainable energy development,the research and development of new energy batteries is developing faster and faster.Among them,lithium-ion batteries in the field of power batteries and sodium-ion batteries in the field of large-scale energy storage batteries have received widespread attention.For lithium-ion batteries,the nickel content of the ternary materials widely used at this stage has restricted their development.Therefore,the research on the 9-series ternary materials that can achieve higher discharge capacity is imminent.In addition,most NCM cathode materials are micron-level secondary particles formed by agglomeration of primary nano-particles.The material with this morphology has a low compaction density and a large contact area with the liquid electrolyte.When the nickel content exceeds 90%,the negative impact on structural stability caused by this side reaction will be greater.For sodium ion batteries,sodium vanadium phosphate has a sodium fast ion conductor(NASICON)structure,which is conducive to the rapid transfer of sodium,but its ability to reach electrons is poor,its energy density is low,and the extensive use of vanadium will pollute the environment and improve cost.Based on the above two issues,this article mainly focuses on the following two tasks:1.Using commercial precursors and lithium salt,by comparing the amount of flux,lithiation temperature and time,and the amount of lithium salt to determine the best firing conditions that can obtain a single crystal NCM955 with uniform size and good morphology.When using 0.5%molar ratio of Na3(PO4)3 as flux,10%excess of lithium salt,calcination in the range of 800℃-830℃ for 9 h,the target sample can be obtained.Among them,when the calcination temperature is 815℃,the sample is better The first lap discharge capacity is 210.4 mAh/g.2.The sol-gel method was used to synthesize and electrochemically characterize NAVP samples doped with different aluminum content.Studies have shown that the doped sample has a new voltage plateau at 4.0 V,and the plateau becomes longer with the increase of aluminum,but the actual discharge capacity is reduced.Na3Al1/3V5/3(PO4)3 shows the best electrochemical characteristics.The discharge capacity of the first lap is 113.82 mAh/g.After 100 cycles of 0.5 C rate and 200 cycles of 1 C rate,the capacity retention rate is still 94.97%.