"Quantitative Nanoscale Mapping of Stacking Faults in Spinel Oxides for Reversible Mult-Valent Ion Insertion"
Multivalent ion batteries are promising next-generation energy storage systems with high volumetric capacity, low cost, good safety, and environmental friendliness. However, the insertion of multivalent ions in the cathode materials usually induces large lattice distortion, which impedes ion migration and impacts battery performance. In this work, a novel method is developed to introduce stacking faults into spinel oxide cathode materials to enhance their electrochemical performance through thermal treatment. These stacking faults expand local spinel lattices and enhance inserted ion diffusion. We map the distribution of stacking faults across the entire particles at nanometer resolution through four-dimensional scanning transmission electron microscopy (4D-STEM). By correlating 4D-STEM with electron energy loss spectroscopy to reveal the distribution of inserted ions in the cathodes upon electrochemical cycling, we demonstrate that stacking faults enable reversible Zn-ion insertion and extraction, which is otherwise prohibited in perfectly crystalline λ-MnO2. This reversibility significantly increases the cyclability of Zn-ion batteries, which can be extended to other multivalent ion systems, such as Mg2+ and Ca2+.
