Synthesis And Performance Of Ternary Li-Fe-Ni-Mn-O Li-ion Battery Material

Along with the energy, environmental issues are getting worse and the needs forthe development of clean energy technologies, the portable storage devices are facinghigher requirements, because of its broad applicability, lithium ion battery receivessignificant attention. The bottleneck of the development of lithium ion battery iscathode material. Although Li-Co-Ni-Mn-O layered ternary materials has got goodcycle performance, high capacity, structural stability and many other advantages byelemental synergies, it uses the toxic element of Co, harm the environment, and Co is astrategic metal, with prices rising in recent years, the field of its application isrestricted by the cost. The use of inexpensive, environmentally friendly Iron to replacecobalt is a good solution for these problems, the Li-Fe-Ni-Mn-O layered ternarymaterials was prepared by sol-gel in this article, and studied the effect of ion doping,manganese-rich on the structure, morphology and electrochemical performance of thismaterials.The Li1+x(Fe_0.2Ni_0.4Mn_0.4)1-xO₂layered ternary materials was synthesized by sol-gel method used LiNO₃, Ni（NO₃）₂·6H₂O, Mn（CH₃COO）₂·4H₂O, Fe（NO₃）₃·9H₂O andcitric acid, and studied the effect of sintering temperature, sintering time and thelithium content on the material properties. The results showed that theLi_1.15(Fe_0.2Ni_0.4Mn_0.4), which was sintering at700℃for16h had the bestelectrochemical performance. In the2.0⁴.5V voltage range,20mA/g constantcurrent charge and discharge test, the initial discharge capacity of147.6mAh/g, anddischarge capacity of112.9mAh/g after20charge-discharge cycles, the capacityretention was76.4%. As the charge cut-off voltage rised to4.7V, the initial dischargecapacity of166mAh/g, and discharge capacity of117.2mAh/g after20charge-discharge cycles, the capacity retention was70.6%.In order to improve the electrochemical properties of Li_1.15(Fe_0.2Ni_0.4Mn_0.4),the material was modified by ion doping and manganese-rich. Test results show that,Mg²⁺doped material reduces cycling performance, and its rate performance wasalmost no change. Al³⁺doped material improved cycling performance and rateperformance, when the amount of Al³⁺doped was0.01, the material showed thehighest cycling performance. The first discharge capacity of143.6mAh/g, anddischarge capacity of122.6mAh/g after20charge-discharge cycles, the capacityretention was85.4%.The study on manganese-rich modification showed that manganese-rich ternarymaterial could exhibit improved electrochemical performance only at a higher cut-offvoltage. In the2.0⁴.7V voltage range,20mA/g constant current charge and discharge test, Li_1.15Fe_0.17Ni_0.17Mn_0.51O₂had the initial discharge capacity of189mAh/g, anddischarge capacity of140.4mAh/g after20charge-discharge cycles, the capacityretention was74.3%. And the material also exhibited excellent rate performance,40mA/g,100mA/g,200mA/g and400mA/g constant current charge and discharge test,the discharge capacity were132mAh/g,102.6mAh/g,88mAh/g and68.5mAh/g.