Zinc-Doping Strategy on P2-Type Mn-Based Layered Oxide Cathode for High-Performance Potassium-ion Batteries.

Mn-based layered oxide is extensively investigated as a promising cathode material for potassium-ion batteries due to its high theoretical capacity and natural abundance of manganese. However, the Jahn-Teller distortion caused by high-spin Mn 3+ (t 2g 3 e g 1 ) destabilizes the host structure and reduces the cycling stability. Here, K 0.02 Na 0.55 Mn 0.70 Ni 0.25 Zn 0.05 O 2 (denoted as KNMNO-Z) is reported to inhibit the Jahn-Teller effect and reduce the irreversible phase transition. Through the implementation of a Zn-doping strategy, higher Mn valence is achieved in the KNMNO-Z electrode, resulting in a reduction of Mn 3+ amount and subsequently leading to an improvement in cyclic stability. Specifically, after 1000 cycles, a high retention rate of 97% is observed. Density functional theory calculations reveals that low-valence Zn 2+ ions substituting the transition metal position of Mn regulated the electronic structure around the MnO bonding, thereby alleviating the anisotropic coupling between oxidized O 2- and Mn 4+ and improving the structural stability. K 0.02 Na 0.55 Mn 0.70 Ni 0.25 Zn 0.05 O 2 provided an initial discharge capacity of 57 mAh g -1 at 100 mA g -1 and a decay rate of only 0.003% per cycle, indicating that the Zn-doped strategy is effective for developing high-performance Mn-based layered oxide cathode materials in PIBs.