Preparation And Properties Of Layered Oxide Cathode Materials For Sodium Ion Batteries

With the development of new energy vehicles and the extensive research of secondary batteries,people pay more and more attention to energy storage materials.Nowadays,because of its advantages of high output voltage and high energy density,lithium-ion batteries are widely used.However,the distribution of lithium resources in the earth’s crust is short and uneven,so it is necessary to find an energy storage battery to replace lithium-ion batteries.Sodium and lithium have similar chemical properties.Sodium is abundant in the earth’s crust and its price is low.Therefore,sodium ion battery becomes one of the most ideal substitutes for lithium-ion battery.The performance of the cathode material affects the electrochemical performance of the battery.Manganese nickel oxide has high discharge voltage and high energy density.Based on this,the research on Na_0.67Ni_0.33Mn_0.67O₂ mno-ni oxide was proposed to improve the electrochemical performance by doping Sn ions to regulate the proportion of P2 and O3 phases and coating Al₂O₃,which opened up a new way to improve the performance of cathode materials for sodium ion batteries.P2/O3-Na_0.67Ni_0.33Mn_0.67-xSn_xO₂（x=0.0,0.05,0.10,0.20）were prepared by solid-state synthesis and doped with different contents of Sn ions into P2-Na_0.67Ni_0.33Mn_0.67-xSn_xO₂.The properties of different battery materials were analyzed by X-ray diffraction,X-ray photoelectron spectroscopy and electrochemical workstation.The results show that the electrochemical performance of Na_0.67Ni_0.33Mn_0.67-xSn_xO₂ with 1:1 ratio of P2 and O3 and Sn ion doping is the best when x=0.10.The discharge capacity is 138 m Ah·g^-1 at 20 m A·g^-1and voltage of 2.0-4.3 V,and the first cycle efficiency can reach 98.55%.The recycling performance of the material can be further improved by Al₂O₃ coating,with 0,0.5 wt%,1wt%and 2wt%Al₂O₃ coating on the surface of P2-Na_0.67Ni_0.33Mn_0.67O₂,respectively.The results show that when the Al₂O₃ coating amount is 1wt%,the cycling performance of the modified material is the best.The results show that the electrochemical performance of P2 phase Na_0.67Ni_0.33Mn_0.67O₂ is greatly improved by doping Sn ion into P2/O3composite and coating with Al₂O₃.