Rational Design of Na(Li1/3Mn2/3)O2 Operated by Anionic Redox Reactions for Advanced Sodium-Ion Batteries

In an effort to develop high-energy-density cathodes for sodium-ion batteries (SIBs), low-cost, high capacity Na(Li1/3Mn2/3)O-2 is discovered, which utilizes the labile O 2p-electron for charge compensation during the intercalation process, inspired by Li2MnO3 redox reactions. Na(Li1/3Mn2/3)O-2 is systematically designed by first-principles calculations considering the Li/Na mixing enthalpy based on the site preference of Na in the Li sites of Li2MnO3. Using the anionic redox reaction (O2-/O-), this Mn-oxide is predicted to show high redox potentials (approximate to 4.2 V vs Na/Na+) with high charge capacity (190 mAh g(-1)). Predicted cathode performance is validated by experimental synthesis, characterization, and cyclic performance studies. Through a fundamental understanding of the redox reaction mechanism in Li2MnO3, Na(Li1/3Mn2/3)O-2 is designed as an example of a new class of promising cathode materials, Na(Li1/3M2/3)O-2 (M: transition metals featuring stabilized M4+), for further advances in SIBs.