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In the search for high energy density cathodes for next-generation lithium-ion batteries, the disordered rocksalt oxyfluorides are receiving significant attention due to their high capacity and lower voltage hysteresis compared with ordered Li-rich layered compounds. However, a deep understanding of these phenomena and their redox chemistry remains incomplete. Using the archetypal oxyfluoride, Li₂MnO₂F, we show that the oxygen redox process in such materials involves the formation of molecular O₂ trapped in the bulk structure of the charged cathode, which is reduced on discharge. The molecular O₂ is trapped rigidly within vacancy clusters and exhibits minimal mobility unlike free gaseous O₂, making it more characteristic of a solid-like environment. The Mn redox process occurs between octahedral Mn³⁺ and Mn⁴⁺ with no evidence of tetrahedral Mn⁵⁺ or Mn⁷⁺. We furthermore derive the relationship …