Spinel‐Layered Heterostructure Enables Reversible Oxygen Redox in Lithium Manganese Oxide

Lithium‐rich manganese‐based layered oxides (LRMOs) have emerged as promising cathode materials for next‐generation lithium‐ion batteries (LIBs), primarily due to their exceptional capacity originating from oxygen redox chemistry. While Li2MnO3 (LMO) has been conventionally identified as the oxygen redox‐active component in LRMOs, this layered material shows neither bulk redox activity nor reversible anion redox behavior in the absence of other transition metals (e.g., Ni and Co). Herein, we report a structural‐engineered lithium manganese oxide with spinel‐layered heterostructures (designated as LMO‐SH), which exhibits reversible oxygen redox activities between lattice oxygen (O2‐) and molecular oxygen (O2) ‐ the first documented instance of such redox behavior in a manganese‐based material. Through combining experimental characterization and theoretical modeling, we establish that the interfacial architecture between the spinel and layered phases facilitates the Li+ diffusion kinetics while simultaneously activating bulk oxygen redox processes. This mechanistic understanding not only advances fundamental knowledge of redox chemistry in LMO‐based materials but also establishes new design principles for developing high‐capacity cathodes through strategic phase engineering.