Preparation And Performance Study Of Mn₂O₃ For Lithium Ion Cathode Material

The research on lithium-ion batteries was in full swing,and manganese played an important role in it.The preparation process of manganese oxide was relatively simple,eco-friendly,and had the advantages of high specific capacity and stable voltage equality.It could better meet the application requirements than other oxide systems and had become one of the research hotspots.Starting from expanding the application channels of electrochemical performance of manganese oxides,this article studied the preparation of Mn₂O₃ precursors from manganese sulfate solution,and investigated the influence of p H regulators on the morphology and electrochemical performance of Mn₂O₃ precursors.The reaction mechanism and generation law of Mn₂O₃ precursor calcination to prepare Mn₂O₃ had been studied,and the influence of preparation conditions on the morphology,phase,and electrochemical performance of Mn₂O₃were investigated.Finally,the properties of Mn₂O₃ were thoroughly evaluated through the electrochemical properties of lithium manganese oxide prepared,and the effects of manganese lithium molar ratio,calcination temperature,and calcination time on the CV curve and cycling performance of lithium manganese oxide were investigated.The aim was to obtain suitable preparation conditions for Mn₂O₃ and its application regulation mechanism in lithium-ion batteries.（1）The research results of Mn₂O₃ precursor preparation showed that the phase of Mn₂O₃ precursor material prepared with manganese sulfate as raw material and ADD as regulator was almost Mn₃O₄,with no other impurities,it has high product purity,good crystallinity and large grains.Its shape was rod shaped,with a length of approximately 200nm,its surface area was of 60.47m²/g,the compacted density was1.11g/cm³.At a current density of 1C,the first discharge specific capacity was579m Ahg^-1,and after 200 cycles,the specific capacity was 382.2m Ahg^-1,and its specific capacity retention rate was 66%.The fitting impedance was 240Ω,so it had relatively good electrochemical performance and promising application prospects.（2）The research results on the preparation of Mn₂O₃ showed that as the roasting time prolonged,the content of the generated Mn₂O₃ crystal phase gradually increased,and the grain size gradually increased,but the degree of change in electrochemical performance was not significant.As the calcination temperature increased,the content of the generated Mn₂O₃ crystal phase gradually increased,the grain size gradually increased,and the electrochemical performance first gradually improved and then deteriorated.When the roasting time was 8 hours and the roasting temperature was700℃,Mn₂O₃ prepared had better physicochemical and electrochemical properties,with high crystal phase content,large grains,and high crystallinity.It was a rod-shaped structure with a particle length of approximately 700nm,it had large particle gaps and uniform size.The first discharge specific capacity was 1630.7m Ahg^-1,and after 200cycles,its discharge specific capacity was 712.1m Ahg^-1,with a fitting impedance of129Ω,which had an advantage over the specific capacity of most transition metal oxides.（3）The research results on the preparation of positive electrode materials using Mn₂O₃ indicated that as the manganese lithium molar ratio increased,the electrochemical performance of Li Mn₂O₄ first increased and then decreased.As the roasting time prolonged,the content of Li Mn₂O₄ crystal phase generated gradually increased,the grain size gradually increased,and the electrochemical performance first increased and then decreased.As the calcination temperature increased,the content of Li Mn₂O₄ crystal phase generated gradually increased,the grain size gradually increased,and the electrochemical performance gradually improved.When the manganese lithium molar ratio was 2:1.1,the calcination time was 6 hours,and the calcination temperature was 900℃,the electrochemical performance of lithium manganese oxide material was the best.The first charge discharge specific capacity was 130.8 m Ah/g and 128.6m Ah/g,respectively.After 200 cycles,the charge discharge specific capacity was 109.8m Ah/g and 108.9 m Ah/g respectively,and the charge discharge specific capacity retention rates were 83.6%and 84.1%.It could be seen that Mn₂O₃ could also be used as one of the manganese sources for lithium manganate,thereby expanding the application channels of Mn₂O₃.（4）The preparation of Mn₂O₃ precursor materials by adding ethanol and surfactants to the ammonia water regulator reduced the adsorption energy,facilitated the removal of impurities adsorbed on the material surface,increased the surface area,and improved electrochemical performance.The structural stability of Mn₂O₃ material prepared by calcination suppressed the problem of structural collapse caused by volume expansion in the reaction,further improving its electrochemical performance.After 200cycles,its discharge specific capacity was 712.1m Ahg^-1,which was much higher than traditional metal transition oxides and commercially commonly used lithium-ion negative electrode materials.Lithium manganese oxide prepared through Mn₂O₃ had superior electrochemical performance,expanding the application channels of Mn₂O₃ in lithium-ion batteries.