Preparation Of Li_1-xNa_xMn₂O₄ Cathode Material

In recent decades,the rapid development of science and technology provides people with convenient living conditions,but the over exploitation of nature makes people have to face worsening environmental problems and energy crisis.At the same time,the emerging electronic industry has a great demand for the product's power storage performance,which forces people to develop a cleaner,safer and more effective energy storage method.As a clean and efficient way of storing energy,batteries are getting more and more attention from researchers.Among all the battery types,LiMn₂O₄ batteries have been attracting attention because of their safety,environmental protection,low price,high electrical conductivity,good rate performance,and easy recycling.In recent years,sodium batteries have also been the focus of research.Na is cheaper than Li and has a similar ionic radius.However,compared with lithium-ion batteries,sodium batteries have generally lower specific discharge capacity and generally lower cycle performance.In this paper,Na and Li are doped to synthesize the cathode material,and the effect of Na doping on the electrochemical performance of the battery is analyzed.The solid-phase method is used in the experiment.Firstly,the synthesis of LiMn₂O₄ battery cathode materials is analyzed from three aspects of calcination temperature,different lithium content and different manganese sources.Then,the samples are analyzed from the aspects of XRD detection,SEM image characterization,electrochemical performance test and AC impedance.Finally,the comparison showed that when MnO₂ was used as the manganese source,and Li:Mn=1.05:2,when 750?continued calcining for 12 hours,the morphology of the sample is the most uniform and complete,and the electrochemical performance is the best.The specific capacity of the first discharge can reach 104.860 mAh·g^-1.After 30 cycles,the capacity retention rate is 91.02%.In order to discuss whether the doping of Na can improve the electrochemical performance of LiMn₂O₄ battery,the sample material Li_1.05-xNa_xMn₂O₄?x=0.10,0.15,0.20,0.25?is prepared by doping a certain proportion of sodium to replace part of lithium on the basis of LiMn₂O₄.When x=0.15,the particle morphology of the sample is the most uniform and complete,with the size of micrometer,which is the standard spinel structure without agglomeration.The first discharge specific capacity of the sample is the highest when x=0.15,and the capacity retention rate is 97.32%after 30cycles.Compared with the undoped LiMn₂O₄ sample,the capacity retention rate of Na doped sample is significantly improved,which shows that the addition of Na effectively reduces the capacity decay of the sample and improves the cycle performance of the battery.In the last part of the experiment,on the basis of the original LiMn₂O₄ doped Na,Al is used to replace part of Mn.The results of XRD and SEM show that the doping of Al does not change the original spinel structure.When x=0.15,the shape of the spinel particles is very complete,and the particle size is uniform to micron level,without agglomeration.The charge discharge test results show that the charge discharge performance is the best when x=0.15.The first discharge specific capacity is 125.461 mAh·g^-1.After 30 charge discharge cycles,the discharge specific capacity is 122.324 mAh·g^-11 and the capacity retention rate is 97.50%.Compared with the undoped LiMn₂O₄ samples,the charge discharge specific capacity and capacity retention rate are greatly improved,which shows that the doping modification is very helpful to the electrochemical performance of the samples.