Preparation Of P2 Type Na_0.8Li_0.08Mn_0.6Co_0.16Ni_0.16O₂ Hexagonal Cathode Material And Its Doping And Coating

Considering the increasingly serious problem of climate warming and fossil fuel shortage,it is necessary to effectively integrate renewable energy through large-scale electrochemical energy storage and conversion technology.In the chemical energy storage system,lithium-ion batteries have achieved great success in the application of electronic product market applications.However,with the rapid growth of lithium-ion battery production,the low concentration of lithium resources has caused thinking of people’s sustainable development.Taking into account the advantages of cost and sustainable supply,the sodium ion battery has the possibility of replacing the lithium-ion battery in some areas,especially the potential to show the potential of energy storage and conversion in energy storage and conversion.The layered transition metal oxide material is one of the most attractive sodium ion battery cathode materials due to its simple synthetic process,large specific capacity,high ion conductivity,but is generally dynamic,and the multi-phase evolution,and the air stability is poor.Lack of comprehensive performance,limit its commercial application.Therefore,how to develop new sodium-based transition metal oxide cathode materials with dynamic stability and good electrochemical properties provide a greater possibility to apply them to actual production.In this paper,P2 type Na_0.8Li_0.08Mn_0.6Co_0.16Ni_0.16O₂ cathode electrode material is prepared by simple high temperature sintering method,and the sintering process having a hexagonal shape cathode electrode material is prepared,and then the hexagonal shape cathode material is doped and Wrap to study its impact on battery performance,the main research contents are as follows:1.First,the transition metal hydroxide precursor Mn_0.6Co_0.16Ni_0.16（HO）₂ is synthesized by template auxiliary co-precipitation method,and P2 type Na_0.8Li_0.08Mn_0.6Co_0.16Ni_0.16O₂ cathode material（Na NCM）is prepared by different temperature rate and annealing temperatures and compare and study their morphology and electrochemical properties.The results show that the synthesized Na NCM at different annealing temperatures,and the spatial group is P63/mmc.When the annealing temperature is 1000℃（Na NCM1000）,the material has a hexagonal sheet shape,the thickness is 0.97μm,the grain section size is 7.36μm,and the discharge ratio capacity at 0.1C current densities is 117.1 m Ah/g,0.5 C（1C=175 m Ah/g）magnification discharge ratio capacity is 91.3 m Ah/g,the capacity retention rate at the time of circulation 70 cycles can reach 97%;when the annealing temperature is 850℃（Na NCM 850）,the material has a hexagon block.The shape is 0.46μm-0.88μm,the grain size is 1.35μm,and the discharge ratio is 110.9 m Ah/g at 0.1C current density,at 0.5 C magnification discharge ratio capacity of 90.2 m Ah/g,circulating 70 cycles,the capacity retention ratio is 80.7%;when the annealing temperature is 750℃（Na NCM750）,the material has a hexapherographic morphology,the column is 0.75μm,the hexagonal size is 0.48μm,and the discharge ratio is discharged at 0.1C current density.It was 115.8 m Ah/g,at 0.5 C magnification discharge ratio capacity of89.8 m Ah/g,and the capacity retention rate at the time of circulating 70 cycles was 93.2%.Since the material NCM750 and the material NCM1000 have a close capacity retention ratio,and the capacity difference is not large,the material NCM750 has a larger lattice parameter c,which is more advantageous for Na⁺ions.For economic practical considerations,low temperature sintering is lowered.Therefore,the subsequent material NCM750 is modified by doping and coating to increase the magnification performance.2.By exploiting different concentrations of anion doping on material micro-morphology,crystal structure and electrochemical storage properties.The results show that as the Br content increases,the grain size is gradually uniform,and when the 3 mol%concentration of Br is doped,the capacity retention ratio of the material is the highest,and the discharge ratio capacity is 126.0 m Ah/g at 0.1C,the capacity retention after 100 circles is 93.3%at 0.5 C,the capacity can reach 79.2 m Ah/g at 5C.The reason is that the anion-doping manner is used,and the position of the Br substituted portion O is reduced by the loss of O₂,and the capacity retention of the material is further improved.3.By coating Al₂O₃,TiO₂ on the material Na NCM750,the effects of micro-morphology and electrochemical properties of different concentrations of coating on cathode electrode materials were explored.The results show that when the Na NCM750 is covered with an Al₂O₃ concentration of 0.5%,the capacity retention ratio of the material at a 0.1C current density is about 75.8%,and when the Na NCM 750is covered with an Al₂O₃ concentration of 1%,the material is discharged at high magnification.The capacity is high;when the Na NCM750 is covered with TiO₂ at a concentration of 0.5%,the capacity retention at 0.1C is up to about 76.7%,and higher than the retention 46.1%of the Na NCM750.The reason is that the metal oxide cladding layer alleviates the cathode electrode material in the electrochemical cycle process,while the Ti⁴⁺in TiO₂ coating layer will further stabilize the layered structure.