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

Abstract

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 Mn3+ (t2g 3 eg 1 ) destabilizes the host structure and reduces the cycling stability. Here, K0.02 Na0.55 Mn0.70 Ni0.25 Zn0.05 O2 (denoted as KNMNO-Z) isreported to inhibit the Jahn-Teller effect and reduce the irreversible phase transition. Through the implementation of a Zn-doping strategy, higher Mn valence isachieved in the KNMNO-Z electrode, resulting in a reduction of Mn3+ amount and subsequently leading to an improvement in cyclic stability. Specifically, after 1000 cycles, a high retention rate of 97% isobserved. Density functional theory calculations reveals that low-valence Zn2+ ions substituting the transition metal position of Mn regulated the electronic structure around the MnO bonding, thereby alleviating the anisotropic coupling between oxidized O2- and Mn4+ and improving the structural stability. K0.02 Na0.55 Mn0.70 Ni0.25 Zn0.05 O2 provided an initial discharge capacity of 57 mAh g-1 at 100mA 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.