Cation-disordered rocksalt-type high-entropy cathodes for Li-ion batteries.

2 Mn-based Li-excess cation-disordered rocksalt (DRX) oxyfluorides are promising candidates for 3 next-generation rechargeable battery cathodes owing to their large energy densities, earth-4 abundance of Mn and potential for low cost. In this work, we synthesized and electrochemically 5 tested four representative compositions in the Li-Mn-OF DRX chemical space with various Li 6 and F content. 7 material with high Li-excess (1.3333 per formula unit, Li x Mn2x O2y F y) and moderate fluorination 8 9 Higher fluorination (0.6667 per formula unit) at moderate Li-excess (1.25 per formula unit) can Wh/kg) initial capacity (specific energy) with more than 85% retained after 30 cycles. We show that the Li-site distribution (i.e., Li percolation properties) plays a more important role than the metal-redox capacity in determining the initial capacity, whereas the metal-redox capacity is more closely related to the cyclability of the materials. We apply these insights and generate a capacity map of the Li-Mn-OF chemical space, Li x Mn2x O2y F y (1.167 ≤ x ≤ 1.333, 0 ≤ y ≤ 0.667), which predicts both the accessible Li capacity and Mn-redox capacity. This map allows to design compounds which balance high capacity with good cyclability. activate Mn 2+ /Mn 4+ redox and there by balance capacity with cycle life, achieving 256 mAh/g (822 (0.3333 per formula unit) achieves 349 mAh g-1 initial capacity and 1068 Wh kg-1 specific energy. While all compositions tested achieve higher than 200 mAh g-1 initial capacity, the

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Here, we synthesized a series of α-MnO2 samples with differing K+ content but similar physical properties allowing direct study of the role of tunnel K+ on the electrochemistry of α-MnO2 cathodes.