Preparation And Electrochemical Performance Of Cathode Materials For Manganese-Based Sodium Ion Batteries

Due to the gradual shortage of lithium resources,it is imperative to develop new sustainable alternative new energy sources.In fact,sodium element is rich in the earth's crust and cheap,so researchers have invested a lot of work in sodium ion battery research in recent years.In this paper,the high-temperature solid-phase method was used to synthesize the cathode material Na_0.44MnO₂ for Sodium ion battery.The surface and electrochemical properties of the materials were studied by X-ray diffraction?XRD?,scanning electron microscopy?SEM?and other electrochemical tests.The Sodium-ion battery cathode material was synthesized by high-temperature solid-phase method with NaOH as sodium source and MnO₂ as manganese source.The ratio of sodium to manganese in the cathode material was investigated.Finally,the cathode material with sodium to manganese ratio of Na:Mn=0.44 was selected due to having the best electrochemical performance.The electrochemical detection results showed that the initial discharge specific capacity of Na_0.44MnO₂ was 51.96 mAh·g^-1with a capacity efficiency of 95%after 30 cycles.It has excellent cycle performance.Then,based on the optimal ratio of sodium to manganese,the effects of sintering atmosphere,sintering temperature and sintering time on the structure,morphology and electrochemical performance of cathode material Na_0.44MnO₂ during sintering were studied.Finally,the optimal process was determined:The precursor was pre-fired at350°C for 5 h under an oxygen atmosphere,and calcined at 800°C for 8 h to obtain the final cathode material.XRD and SEM results showed that the final synthesized product had complete crystal form,high crystallinity,uniform particle size,obvious regular rod structure and better electrochemical performance.A series of cathode materials with different aluminum doping amount,Na_0.44Mn_1-xAl_xO₂?x=0.1,0.2,0.3 and 0.4?were successfully synthesized by high-temperature solid-phase method.The crystal structure of the material was characterized by XRD,and the aluminum content was investigated in the cathode material.When the doping amount x was equal to 0.3,the positive electrode material Na_0.44Mn_0.7Al_0.3O₂ had a discharge specific capacity of 184.76 mAh·g^-1 during the first charge and discharge,and the polarization of the battery was small,and the material had good electrochemical performance.The Na_0.44MnO₂ cathode material was doped with lithium and the lithium element was used to replace the sodium element in the material to prepare the cathode material Na_0.44-xLi_xMnO₂?x=0.06,0.08,0.10 and 0.12?.A suitable lithium element ratio for excellent electrochemical performance.The results showed that the crystallization of the sample was best when the doping amount was 0.10,and the powder formed at this time was fine,and the first discharge specific capacity reached 106.35 mAh·g^-1.Compared with the samples formed by other doping amounts,Na_0.34Li_0.10MnO₂ had more excellent electrochemical properties.After the aluminum and lithium ions were co-doped with Na_0.44MnO₂,the optimum ratio of the two ion doping was selected,and the positive electrode material was compound doped,and the positive electrode material Na_0.34Li_0.10Mn_0.7Al_0.3O₂ was synthesized by high temperature solid phase method.The sample particles formed by the positive electrode material were uniform,and the initial discharge amount reached110.20 mAh·g^-1,and the cycle performance was also excellence,which was higher than the first discharge under doping only with lithium ions,which might be due to the fineness of lithium ions.After the particles were formed,suitable aluminum ion doping made the material more stable.