Phase- and morphology-controlled MnO2: Its synthesis and influence on the electrochemical performance of spinel LiMn2O4 cathode materials

In this study, MnO 2 was synthesized via a hydrothermal method using four different oxidizing agents: KMnO 4 , K 2 S 2 O 8 , KClO 3 , and (NH 4 ) 2 S 2 O 8 . The KMnO 4 precursor led to the formation of aggregated α-MnO₂, while K 2 S 2 O 8 produced a mixed phase of α- and γ-MnO 2 . (NH 4 ) 2 S 2 O 8 promoted the formation of γ-MnO 2 at lower temperatures and induced a structural transition to β-MnO 2 at elevated temperatures. Among the lithium precursors investigated, LiOH was found to be the most effective in preserving the spherical morphology of LiMn 2 O 4 during synthesis. Electrochemical measurements revealed that the LiMn 2 O 4 sample synthesized from γ-MnO 2 exhibited the highest charge capacity of 132.59 mAh∙g −1 , while the α-MnO 2 -based LiMn 2 O 4 demonstrated the best stability. These results indicate that the initial MnO 2 phase significantly influences the electrochemical performance of the resulting spinel cathode. • MnO 2 was synthesized by a hydrothermal method employing various oxidizing agents. • The phase and morphology of MnO 2 were controlled by synthesis conditions. • Phase control of MnO 2 precursor affects the performance of LiMn 2 O 4 cathode.