Zinc‐Doping Strategy on P2‐Type Mn‐Based Layered Oxide Cathode for High‐Performance Potassium‐ion Batteries
Yunshan Zheng, Junfeng Li, Shunping Ji, Kwan San Hui, Shuo Wang, Xu Huifang, Kaixi Wang, Duc Anh Dinh, Chenyang Zha, Zongping Shao, Kwun Nam Hui
Abstract
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 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 MnO 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.