Preparation of Chemical Manganese Dioxide by Dilute Sulphuric Acid Pickling of Mn₃O₄ and Its Application to the Synthesis of LiMn₂O₄

Abstract

Chemical manganese dioxide (CMD) was obtained by pickling Mn3O4 with dilute sulfuric acid. Atomic absorption spectroscopy (AAS) showed that S, Na, Ca and Mg impurities in CMD were less than in electrolytic manganese dioxide (EMD). Spinel lithium manganese oxide (LiMn2O4) samples were synthesized using CMD or EMD precursor mixed with Li2CO3 via high temperature solid‐phase reactions. The oxides were applied as the cathode material for lithium ion batteries. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) showed that the crystallinity was high and the size‐distribution was uniform for CMD. The crystallinity of the spinel‐type LiMn2O4 synthesized by the CMD was high as well. Electrochemical tests showed that LiMn2O4 synthesized by the CMD precursor exhibited greater discharge capacity and better rate capability than the sample synthesized by the EMD precursor. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicated that LiMn2O4 synthesized by CMD or EMD precursor both showed good kinetics for Li+ ion transport, but LiMn2O4 synthesized by the CMD precursor showed a lower electrochemical impedance. Meanwhile, the synthesis process was simple, cheap, and easy for large‐scale production.