Synthesis and characterization of lithium manganese oxides with core-shell Li4Mn5O12@Li2MnO3 structure as lithium battery electrode materials

By a facile LiNO3 flux method, lithium manganese oxide composites (xLi4Mn5O12∙ yLi2MnO3) were synthesized using a hierarchical organization precursor of manganese dioxide. Li4Mn5O12 and Li2MnO3 have spinel and rocksalt structures, respectively. The lithiation and structural transformation from the precursor to the composites occurred topotactically from exterior toward interior in the precursor particle with the increase of reaction time, and the composites had core-shell spinel@rocksalt structures in addition to the original hierarchical core-shell organization. The electrochemical measurements at 50 °C after 50 cycles confirmed that a typical spinel@rocksalt cathode had higher capacity retention (87.1%) than that with the composition close to the stoichiometric spinel (64.6%), indicating the Li2MnO3 shell can improve cycling stability for the composite electrode at elevated temperature.

► Lithium manganates are prepared by a LiNO3 flux method.
► Manganate composites have core-shell structures.
► Spinel@rocksalt composite shows improved capacity retention at 50 °C.
► Li2MnO3 on the surface of Li4Mn5O12 may reduce dissolution of Mn during cycling.