China Nonferrous Metallurgy

As a key precursor for preparing lithium manganate, a cathode material for lithium-ion batteries, battery-grade manganese dioxide holds an important position in the new energy battery industry due to its unique crystal structure and electrochemical performance. However, traditional preparation methods have the drawback of high production costs. In this study, using the acid leaching solution of rhodochrosite from Kebang Manganese Industry as the raw material, battery-grade manganese dioxide was prepared through a process of preliminary impurity removal-deep impurity removal-oxidation precipitation. The purification process of the rhodochrosite acid leaching solution was deeply studied, and the effects of various factors in the oxidation precipitation process of the manganese purification solution on the preparation of battery-grade manganese dioxide were investigated in detail. The results showed that during the preliminary impurity removal, the addition of ammonium bicarbonate-sulfuric acid solution for the precipitation and redissolution of Mn and Mg enriched the Mn concentration to 122.5g/L and reduced the Mg concentration to 91.5mg/L. The concentrations of Cl, Na, K, and Si were significantly reduced to 6.2mg/L, 16.8mg/L, 2.3mg/L, and 9.8mg/L, respectively. In the deep impurity removal process, the addition of 1.0g/L BaS and 4.2g/L MnF₂ to remove heavy metals and Ca, Mg reduced the concentrations of Mg and Ca to 21.3mg/L and 11.6mg/L, respectively. The concentration of Pb was reduced to 1.3mg/L, and the concentrations of Zn, Ni, Cd, and Cu were all reduced to less than 1mg/L. The process conditions for preparing battery-grade manganese dioxide by direct oxidation were as follows: at a Mn concentration of 1mol/L, with oxygen as the oxidant, 2% ammonia water as the neutralizer, and a reaction temperature of 70℃, the reaction time was 12hours. After washing the product with 2% ammonia water and drying, spherical battery-grade manganese dioxide with a Mn content of 71%, a specific surface area of 0.813m²/g, a tap density of 2.53g/cm³, and a median particle size of 12.5μm, and with impurity content lower than the national standard was obtained.