Preparation Of LiNi_0.8Mn_0.2O₂ Precursor And Material Properties For Cobalt-Free Nickel Based Cathode

Due to adjusting energy structure is promoted by Global warming,Global electrification has became an inevitable trend.The different application areas for lithium ion batteries need different kinds of cathode materials.Commercialized NCM and NCA are ternary cathode materials,which have the advantage of high energy density.However,the harmful cobalt is expensive in the worldwide,which goes against the development concept of clean and cheap new energy.In order to solve this problem,this paper proposes a cobalt free nickel based cathode material.Through Mn solid solution strengthening its structure,it hopes to improve its structural stability,obtaining a cobalt free nickel manganese solid solution cathode material with excellent comprehensive performance.Considering the energy density and cycle attenuation,it proposes to take Li Ni_0.8Mn_0.2O₂as the research object to study the synthesis process of material precursors respectively,The influence of solid state reaction mechanism and high specific surface area on the electrochemical properties of materials（small particle size precursors are synthesized by adding acetylene black）were characterized by XRD,laser particle size analyzer,tap density meter,SEM,free lithium meter,ICP,EDS,BET,respectively,As well as the electrochemical test of the cathode material,the results are as follows:（1）With the increase of ammonia concentration,the sphericity and particle size of precursor increase,and the tamping density increases accordingly,with a maximum of 1.93g/cm3 at C_NH3=0.9 mol/L;With the increase of p H,the precursor has good sphericity,the particle size increases,and the tamping density increases continuously.The charge discharge test showed that the highest initial discharge specific capacity of 178 m Ah/g was obtained at p H=11.3,C_NH3=0.3 mol/L,corresponding to the positive electrode material 0.1C.（2）With the increase of lithium content,the content of free lithium on the surface and lithium inside the cathode material increases continuously,and the primary particle size of the cathode is relatively small at 0%and 16%lithium content.XRD showed that 16%lithium lead to the existence of impurities in the materials,and 4%-12%lithium lead materials have lower lithium nickel mixed row and higher layer structure order degree;With the increase of sintering temperature,the content of free lithium on the surface decreases continuously,and the content of the material abnormally increases at 900℃due to the precipitation of lithium inside.The primary particle size increases with the increase of sintering temperature,the degree of lithium nickel mixing increases after 800℃,and the degree of order of layered structure increases with the increase of temperature.The cathode material synthesized at800℃with 8%lithium peroxide still has a discharge specific capacity of 175.2 m Ah/g after100 cycles at 1C,and the capacity retention rate is 105.2%.（3）With the increase of the content of acetylene black,the particle size of precursor decreases,and the particle size growth rate also slows down.BET showed that the specific surface area of the cathode material increased from 0.5246 m²/g（without acetylene black）to1.2847 m²/g（with 0.2%acetylene black）;XRD showed that the cell volume of the cathode material prepared with acetylene black precursor was smaller than that of the cathode material prepared without acetylene black precursor.Thanks to this,the electrochemical performance of the former was improved.The capacity retention rate of 100 cycles of 1C cycle increased from 74.9%（without addition）to 102%（0.6%Li435）,and the specific discharge capacity was137 m Ah/g.SEM after 100 cycles showed that the main reason for capacity attenuation was that cracks appeared on the surface of positive particles without added samples,leading to the aggravation of side effects.