In Situ Formed Core–Shell LiZn_xMn_2–xO₄@ZnMn₂O₄ as Cathode for Li-Ion Batteries

Elemental doping and surface modification are commonly used strategies for improving the electrochemical performance of LiMn₂O₄, such as the rated capacity and cycling stability. In this study, in situ formed core–shell LiZn_xMn_2–xO₄@ZnMn₂O₄ cathodes are prepared by tuning the Zn-doping content. Through comprehensive microstructural analyses by the spherical aberration-corrected scanning transmission microscopy (Cs-STEM) technique, we shed light on the correlation between the microstructural configuration and the electrochemical performance of Zn-doped LiMn₂O₄. We demonstrate that part of Zn²⁺ ions dope into the spinel to form LiZn_xMn_2–xO₄ in bulk and other Zn²⁺ ions occupy the 8a sites of the spinel to form the ZnMn₂O₄ shell on the outermost surface. This in situ formed core–shell LiZn_xMn_2–xO₄@ZnMn₂O₄ contributes to better structural stabilization, presenting a superior capacity retention ratio of 95.8% after 700 cycles at 5 C at 25 °C for the optimized sample (LiZn_0.02Mn_1.98O₄), with an initial value of 80 mAh g^–1. Our investigations not only provide an effective way toward high-performance LIBs but also shed light on the fundamental interplay between the microstructural configuration and the electrochemical performance of Zn-doped spinel LiMn₂O₄.