Research On Preparation And Modification Of High Voltage Cathode Materials For Lithium Ion Batteries

The new type of renewable energy lithium-ion battery has received great attention.A key point in which lithium batteries are still limited is battery energy density.There are generally two viable measures to improve battery energy density,one is to increase the battery voltage platform,and the other is to increase specific capacity of the battery.The key to continuing to break through now is especially in the area of cathode materials.If it reaches a new height,it will greatly extend the cruising range of new energy vehicles.The focus of this article is on improving battery energy density.Therefore,we select two high-voltage cathode materials,including "5V material" LiNi0.5Mni.5O4 and lithium-rich material 0.5Li2MnO3·0.5LiNi0.6Co0.2Mn0.2O2.The main purpose is to overcome the shortcomings of the material by studying the synthesis methods and coating compound modification methods.The traditional synthesis process is always time-consuming and labor-intensive,with relatively high requirements on the environment and large restrictions on cost and scale.In this paper,we use a simple and rapid synthesis process to prepare highperformance materials.By understanding the relevant knowledge of solution reaction kinetics,it is found that by reducing the dielectric constant of the solution,the reaction rate can be greatly accelerated and the reaction time can be shortened.We use ethanol and water as co-solvent to promote nucleation of crystals.In this case,it takes only 1 hour to prepare the precursor.At the same time,we adjust the ratio of ethanol to water to find the best results.When the ratio is 1:3,the multi-level structure material synthesized after gradient annealing has the best morphology.At this time,the material exhibits excellent cycle rate performance.The batteries keep 94.2%retention after 200 cycles at 1 C.While at 10 C,114 mAh g-1 can be attached.In addition,it is matched with Li4Ti5012 to prepare a full cell,and also shows excellent performance.It performs well even at high temperatures of 55℃.This simpler and faster method can help commercialization.Also using the above method,we continue to study lithium-rich ternary materials.In this paper,we first compare and test the electrochemical performance of several materials with different ratios of Ni,Co and Mn elements,and select 0.5Li2MnO3·0.5LiNi0.6Co0.2Mn0.2O2 for further research,which has the best comprehensive performance in terms of capacity and voltage attenuation.Next,Li1.4Al0.4Ti1.4（PO4）3 material is used for simple surface coating and composite modification.The material owns the best performance when the 5%mass ratio is simply coated.The efficiency of the first lap is increased from 69%to 88%before coating.At this time,it delivers 295 mAh g-1 at 0.1 C,while the material maintains 235 mAh g-1 after 100 cycles at 1 C.Rate performance has also been significantly improved.In addition,both impedance and polarization are reduced,and voltage attenuation is significantly suppressed.