Jiang Chenxi, Yu Qinqin, Wu Chunyang, Huang Bowen, Wei Xinlai, Ding Yuan-Li
School of Biology, Food and Environment, Anhui Key Laboratory of Sewage Purification and Ecological Rehabilitation Materials, Hefei University, Hefei, 230601, China.
College of Materials and Chemical Engineering, Pingxiang University, Pingxiang, 337055, China.
Small Methods. 2025 Aug;9(8):e2500393. doi: 10.1002/smtd.202500393. Epub 2025 May 2.
Iron-manganese-based polyanionic compounds (NaFeMn(PO)PO) have attracted extensive interest as cathode for sodium ion batteries (SIBs) owing to higher working voltage, and higher energy density compared to NaFe(PO)PO. However, such cathode suffers from sluggish Na diffusion, severe voltage hysteresis, and large structural strain caused by Jahn-Teller distortion of Mn. Taking NaFeMn(PO)PO (NFMPP) as an example, herein, a synergistic engineering strategy of vacancy and doping for constructing NaFeMnNb□(PO)PO cathodes (□: vacancy) is developed where vacancies endow rigid MnO octahedra more flexible for boosting Na mobility while Nb doping stabilize crystal structure. Based on theoretical calculations and electrochemical characterizations, the optimized NaFeMnNb□(PO)PO exhibits the lowest Na diffusion energy barrier, the best rate capability and cyclability at both room temperature and elevated temperature than those of NFMPP with only vacancy/doping. Such cathode shows a specific capacity of 63.6 mAh g at 50 C, a capacity retention of 91.0% after 10 000 cycles at 10 C, and a capacity retention of 70.1% after 3 000 cycles at 10 C (50 °C) in half cell, and also delivers a reversible capacity of 96.5 mAh g at 0.1 C and a capacity retention of 88.2% after 300 cycles in full cell.
铁锰基聚阴离子化合物（NaFeMn(PO)PO）作为钠离子电池（SIBs）的阴极受到了广泛关注，因为与NaFe(PO)PO相比，其工作电压更高，能量密度更高。然而，这种阴极存在Na扩散缓慢、严重的电压滞后以及由Mn的 Jahn-Teller 畸变引起的大结构应变等问题。本文以NaFeMn(PO)PO（NFMPP）为例，开发了一种空位和掺杂协同工程策略来构建NaFeMnNb□(PO)PO阴极（□：空位），其中空位使刚性MnO八面体更具柔韧性以促进Na迁移，而Nb掺杂稳定晶体结构。基于理论计算和电化学表征，优化后的NaFeMnNb□(PO)PO在室温及高温下均表现出比仅有空位/掺杂的NFMPP更低的Na扩散能垒、最佳的倍率性能和循环稳定性。这种阴极在半电池中，在50 C时的比容量为63.6 mAh g，在10 C下10000次循环后的容量保持率为91.0%，在10 C（50 °C）下3000次循环后的容量保持率为70.1%，在全电池中，在0.1 C时的可逆容量为96.5 mAh g，300次循环后的容量保持率为88.2%。
