Wu Honglun, Wen Tianzhuo, Chen Long, Ding Yan, Pu Xiangjun, Cao Yuliang, Chen Zhongxue
Key Laboratory of Hydraulic Machinery Transients, Ministry of Education, School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, China.
Hubei Key Laboratory of Electrochemical Power Sources, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China.
Small Methods. 2025 Jan;9(1):e2400642. doi: 10.1002/smtd.202400642. Epub 2024 Aug 19.
NaFe(PO)PO is regarded as the most promising polyanionic cathode for sodium-ion batteries (SIBs) due to its superior structural stability, cost-effectiveness, and environmental benignity. However, the low operating voltage inevitably weakens its competitiveness in energy density. Previous works have tried to enhance its operating voltage by Mn doping, which draws on the design idea of LiFeMnPO cathode for lithium-ion batteries, but with little success. In this context, uncovering the role of Mn substitution in NaFeMn(PO)PO (NFMPP) cathode is urgently needed. This work discloses the effect of Mn contents on the structure, sodium storage property, and reaction mechanism of NFMPP cathode for the first time. Introducing a moderate amount of Mn (0.6 ≤ x ≤ 1.2) into NFMPP can weaken the Fe-O bonding interaction, thus leading to the full utilization of Mn/Mn redox couple. As the representative, NFMPP cathode exhibited a high operating voltage of ≈3.3 V with a reversible capacity of 109.2 mAh g. Note that a Hard carbon||NFMPP full battery manifests considerably high-capacity retention of 92.3% over 1600 cycles. It is believed that an understanding of the role of Mn substitution in this work will promote the practical application of high voltage NFMPP cathodes for SIBs.
NaFe(PO)PO被认为是钠离子电池（SIBs）中最具前景的聚阴离子型正极材料，因其具有优异的结构稳定性、成本效益和环境友好性。然而，较低的工作电压不可避免地削弱了其在能量密度方面的竞争力。此前的研究试图通过锰掺杂来提高其工作电压，这借鉴了锂离子电池LiFeMnPO正极的设计理念，但收效甚微。在此背景下，迫切需要揭示锰取代在NaFeMn(PO)PO（NFMPP）正极中的作用。这项工作首次揭示了锰含量对NFMPP正极的结构、储钠性能和反应机理的影响。向NFMPP中引入适量的锰（0.6≤x≤1.2）可以削弱Fe-O键的相互作用，从而使Mn/Mn氧化还原对得到充分利用。作为代表，NFMPP正极表现出约3.3 V的高工作电压，可逆容量为109.2 mAh g。值得注意的是，硬碳||NFMPP全电池在1600次循环中表现出高达92.3%的高容量保持率。相信对这项工作中锰取代作用的理解将推动高电压NFMPP正极在SIBs中的实际应用。
