Study Of Controlled Preparation And Electrochemical Properties Of Nanometer Mn_XO_Y Liquid Phase

With the rapid development of lithium battery industry,the demand for manganese oxides was increasing,and more stringent requirements were put forward for the performance of its products.Manganese oxide has large specific surface area,good pore structure,and the microstructure was spherical or spinel,which was similar to the structure of lithium manganese oxide cathode material.Lithium manganese oxide was used as manganese source to prepare lithium manganese oxide cathode material.Other impurities were not introduced into the product,and the internal structure did not change dramatically,which was conducive to improving the electrochemical performance of the material.However,there were many kinds of manganese oxides with complex crystal forms.The structure and properties of many manganese oxides still need further study.In this paper,manganese oxide was prepared by using manganese sulfate solution as raw material,air as oxidant and compound additive as p H regulator,and spinel lithium manganese oxide cathode material was prepared by using new manganese oxide as manganese source.A high purity and economic manganese oxide controllable preparation method and excellent electrochemical performance of spinel lithium manganese oxide cathode material were explored.Manganese oxides were prepared with ammonia,sodium hydroxide and complex additives as p H regulators.The effects of three p H regulators on the phase composition,microstructure,element content and physical adsorption properties of the products were studied.The results show that the main component of manganese oxide prepared by ammonia as p H regulator was Mn₃O₄,which contains a small amount of manganese ammonia complex[（NH₄）Mn₈O₁₆],with poor crystallinity and serious burr phenomenon.The microstructure was spherical particles agglomerated,with uniform particle size of about 80 nm,Mn/O ratio of 1.65,and specific surface area of 20.88 m²/g.The main component of manganese oxide prepared with sodium hydroxide as p H regulator was also Mn₃O₄,which contains a small amount of sodium ion complex（Na₂Mn₃O₇）.The microstructure was formed by the agglomeration of spherical particles with uneven particle size of 50-200 nm and Mn/O ratio of 1.39.specific area was 26.43 m²/g,the main component of manganese oxide prepared with compound additives as p H regulator was also Mn₃O₄.The product has good crystallinity,obvious diffraction peaks,no other impurity diffraction peaks,and good purity.The micro-morphology was composed of spherical particles,the particle size was uniform,the particle size was about 120 nm,the ratio of manganese to oxygen was 1.18.The specific surface area is 10.47 m²/g.Compound additives were selected as p H regulators to study the effects of different reaction time,temperature,p H value of solution,air flow rate,and Mn²⁺concentration on the morphology and physicochemical properties of manganese oxides.The results showed that when the reaction time was 6 h,the temperature was80℃,the solution p H was 9,the air flow rate was 20 L/min,and the Mn²⁺concentration was 30 g/L,the prepared manganese oxide had excellent performance.The composition of the product was Mn₃O₄,and the crystallinity was high.The baseline was stable,and the diffraction peak was obvious.There was no diffraction peak of other impurities,and the purity was high.The micro-morphology was composed of nanometer spherical particles with good dispersion and uniform particle size.The particle size was about 150 nm,the minimum specific surface area was 9.6m²/g,and the maximum tap density was 1.91 g/cm³,All the properties of the product meet the standard of soft ferrite manganese oxide GBT21836-2008.Spinel Li Mn₂O₄cathode materials were prepared by high-temperature solid-state reaction of new manganese oxides and lithium hydroxide with compound additives as p H regulators at a molar ratio of 2:1.The effects of calcination temperature and time on the phase composition,morphology and electrochemical properties of the products were investigated.The results showed that when the calcination temperature was 800℃and the calcination time was 12 h,the product had high crystallinity,no other impurity diffraction peaks and good purity.The microstructure was a spinel octahedron structure with good dispersion and uniform particle size.The particle size was about 200 nm,and the grain boundary and outline were clear.The initial discharge capacity was 130.7 m Ah/g at 1 C,and the discharge capacity was 116.2 m Ah/g after 200 cycles.The capacity retention was 88.9%.At high rate of 5 C and 10 C,the sample still has high discharge capacity of 89.5 m Ah/g and 70.6 m Ah/g,respectively.