Suppressing Jahn‐Teller Effect of MnO 2 via Synergistically Crystalline and Electronic Structural Regulation for Efficient Ammonium Ion Capture

Layered manganese dioxide (δ‐MnO 2 ) is considered a promising ammonium ion capture electrode material for capacitive deionization (CDI) attributed to its high theoretical capacity and cost‐effectiveness. Nevertheless, it continues to encounter challenges including rapid capacity degradation, structural instability, and Jahn–Teller effect. Herein, a crystal and electron synergistically regulation engineering strategy is proposed for the suppression of the Jahn–Teller effect and the improvement of ammonium ion storage dynamics in F doped MnO 2 (MnOF). The induced action of F ions transforms the MnO 2 structure from the original cubic [MnO 6 ] octahedron into an asymmetric [Mn(OF) 6 ] octahedron with electron redistribution, and generates a localized charge imbalance along the O–Mn–F pathway, which promotes electron transfer from Mn to F direction, accelerates electron transfer, and reduces the energy barrier of ammonium ion diffusion. As a result, the prepared MnOF exhibited a maximum salt adsorption capacity of 144.3 mg g −1 and an exceptionally high salt adsorption rate of 18.25 mg g −1 min −1 , along with outstanding cycling stability. Besides, ex/in situ characterizations reveal that in MnOF, the formation/breaking of hydrogen bond is accompanied by the insertion/deinsertion of . Therefore, the rational introduction of highly electronegative anions provides a new direction for the development of advanced CDI electrode materials.