Study on the morphology and application properties of small particle size nickel-manganese binary precursor Ni0.6Mn0.4(OH)2
The development of low cobalt or cobalt-free ternary precursor materials is of great significance for the development of low cost and high energy density ternary lithium electric materials.In recent years,due to the long-term high price of cobalt salt,it has become a constraint on the development of new energy vehicles.Among them,medium/high nickel or lithium rich manganese based cathode materials have attracted widespread attention.The electrochemical performance of cathode materials based on lithium batteries largely depends on the performance of precursors.It is particularly important to study the effects of ammonia concentration,pH value,nucleation method,and reaction temperature on surface morphology by preparing low cobalt or cobalt free precursors.The precursor material Ni06Mn04(OH)2 was prepared by coprecipitation controlled crystallization method with nickel sulfate and manganese sulfate as raw materials.During the preparation process,the effects of ammonia concentration,pH val-ue,nucleation method,and reaction temperature on the morphology of the product were mainly investigated.The effects of ammonia concentration,pH value,nucleation mode and reaction temperature on the surface morphology of the precursor were characterized by SEM and EDS.The effects of different ammonia concentrations on the phys-ical and chemical indicators of the material were characterized by carbon sulfur analyzer,tap density tester,and BET.The effect of different ammonia concentrations on the electrochemical performance of positive electrode ma-terials was characterized through electrochemical testing.The results show that when the ammonia concentration increases from 0 mol/L to 0.14 mol/L,the primary particles of the precursor grow gradually from filamentation to transverse broadening,and the increase of ammonia concentration is conducive to the preparation of low-sulfur and dispersive precursor.The influence of pH value on the surface morphology of precursors is mainly manifested in the nucleation rate and growth rate of precursors,as well as the degree of primary particle thickness.High pH val-ues prioritize nucleation with growth as a secondary factor,while low pH values have the opposite effect.Com-pared to the above two influencing factors,the nucleation method mainly affects the sphericity of the precursor and the core structure of the precursor.The nucleation method using nickel cobalt manganese solution,ammonia solu-tion,and sodium hydroxide solution simultaneously has poor sphericity,but high capacity and poor circulation.However,the nucleation method using nickel sodium solution simultaneously has high sphericity of the precursor,and good capacity and circulation of the positive electrode material.The reaction temperature mainly affects the thickness and sphericity of the precursor primary particles.The higher the temperature,the thicker the primary par-ticles,and the worse the sphericity.Finally,the ammonia concentration is determined to be 0.14 mol/L,with pH ranging from 11.5 to 11.6.The nucleation method uses nickel solution and sodium hydroxide solution simultane-ously to prepare precursor Ni0.6Mn04(OH)2 with good morphology and excellent electrochemical performance as the cathode material.The results show that the precursor products with excellent performance can be prepared only when the appropriate ammonia concentration matches the appropriate reaction pH value,nucleation method and re-action temperature.
small particle sizereaction conditionternary precursorsurface topographycathode material
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