Ahsan Muhammad Tayyab, Ali Zeeshan, Qiu Daping, Biao Zhang, Wang Jing Jing, Hou Yanglong
School of Materials Science and Engineering, Peking University, Beijing, 100871, China.
Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, College of Electrical Engineering & New Energy, China Three Gorges University, Yichang, Hubei, 443002, China.
Small. 2024 Oct;20(43):e2402275. doi: 10.1002/smll.202402275. Epub 2024 Aug 18.
Mn-based sodium superionic conductors have driven attention to the low-cost advanced cathode materials for sodium-ion batteries (SIBs). However, low-rate capability and unsatisfactory cyclic performance due to the Jahn teller effect of Mn redox couple which occurs from the change in Mn-O bond length at the octahedral site of crystal structure during charge-discharge, eventually limiting their application. Herein, a disordered and sodium deficient NASICON NaMn(FeVCrTi)(PO) (termed as NaMn(HE)) is synthesized to mitigate this Jahn teller effect to achieve high rate and ultrastable cathode material. Interestingly, the as-prepared NaMn(HE) shows five reversible electron reactions (i.e., Ti/Ti, Fe/Fe, V/V, Mn/Mn, and Mn/Mn) and demonstrates 141 mA h g at 0.2 C with 80% capacity retention at 1 C after 500 cycles which is far superior to its counterparts binary Mn-based materials. The excellent cyclic performance is due to the remediation of the Jahn teller effect in sodium-deficient entropy-stabilized material. The structural reversibility, enhanced kinetics, and electronic properties are further studied in detail by in situ X-ray diffraction (XRD), ex situ X-ray photoelectron spectroscopy (XPS), and first principal calculations. NaMn(HE)//HC full cell delivered 89.7 mAh g capacity at 0.2 C. This work sheds light on designing Mn-based cathodes with superior electrochemical performance for wide energy storage applications.
锰基钠超离子导体已引发了人们对钠离子电池（SIBs）低成本先进阴极材料的关注。然而，由于在充放电过程中晶体结构八面体位置的Mn-O键长变化导致Mn氧化还原对的 Jahn 效应，使得其倍率性能较低且循环性能不理想，最终限制了它们的应用。在此，合成了一种无序且缺钠的NASICON NaMn(FeVCrTi)(PO)（称为NaMn(HE)）以减轻这种 Jahn 效应，从而获得高倍率和超稳定的阴极材料。有趣的是，所制备的NaMn(HE)表现出五个可逆电子反应（即Ti/Ti、Fe/Fe、V/V、Mn/Mn和Mn/Mn），在0.2 C下的比容量为141 mA h g，在1 C下循环500次后容量保持率为80%，这远远优于其对应的二元锰基材料。优异的循环性能归因于缺钠熵稳定材料中Jahn效应的修复。通过原位X射线衍射（XRD）、非原位X射线光电子能谱（XPS）和第一性原理计算进一步详细研究了其结构可逆性、增强的动力学和电子性质。NaMn(HE)//HC全电池在0.2 C下的容量为89.7 mAh g。这项工作为设计具有优异电化学性能的锰基阴极以用于广泛的储能应用提供了思路。
