Xie Lingling, Wang Xinwei, Xia Changle, Huang Huilin, Zhu Limin, Han Qing, Qiu Xuejing, Cao Xiaoyu
School of Environmental Engineering, Henan University of Technology, Zhengzhou 450001, China.
Henan Engineering Technology Research Center of Electrochemical Energy Storage, Key Laboratory of High Specific Energy Materials for Electrochemical Power Sources of Zhengzhou City, Henan University of Technology, Zhengzhou 450001, China.
Dalton Trans. 2024 Oct 29;53(42):17370-17380. doi: 10.1039/d4dt02228a.
The search for suitable electrode materials for sodium storage in sodium-ion batteries (SIBs) poses significant challenges. NaMnO (NMO) has emerged as a promising candidate among various cathode materials due to its distinct three-dimensional tunnel structure, which facilitates Na diffusion and governs structural stress fluctuations during Na intercalation/deintercalation. However, NMO faces obstacles such as limited electronic conductivity, lattice distortion induced by the Jahn-Teller effect of Mn during cycling, and Mn disproportionation leading to material dissolution, which affects cycling durability. To overcome these problems, NaMnO/polypyrrole (NMO/PPy) composites were fabricated through surface modification of the conductive PPy using an ultrasonically assisted dispersion method. Experimental results show that NMO/PPy with a 7 wt% PPy content exhibits superior sodium storage capabilities. Specifically, at a current density of 0.5C, the initial specific discharge capacity reaches 135.2 mA h g, a 12.1% increase over pristine NMO, with a capacity retention of 94.5% after 100 cycles. Of particular note is a capacity retention of 82% after 500 cycles at 1C, attributed to the PPy coating, which suppresses Mn side reactions, enhances the structural stability and electronic conductivity of NMO, and accelerates Na diffusion. These results suggest that the use of conductive polymer coatings represents a simple and effective strategy to improve the sodium storage capacity of NMO, paving the way for the further development of high-performance SIB cathodes.
寻找适用于钠离子电池（SIBs）储钠的电极材料面临着重大挑战。由于其独特的三维隧道结构，NaMnO（NMO）在各种阴极材料中已成为一种有前景的候选材料，这种结构有利于Na扩散，并在Na嵌入/脱嵌过程中控制结构应力波动。然而，NMO面临着诸如电子导电性有限、循环过程中Mn的 Jahn-Teller 效应引起的晶格畸变以及Mn歧化导致材料溶解等障碍，这会影响循环耐久性。为克服这些问题，采用超声辅助分散法通过对导电聚吡咯（PPy）进行表面改性制备了NaMnO/聚吡咯（NMO/PPy）复合材料。实验结果表明，PPy含量为7 wt%的NMO/PPy表现出优异的储钠性能。具体而言，在0.5C的电流密度下，初始比放电容量达到135.2 mA h g，比原始NMO提高了12.1%，在100次循环后容量保持率为94.5%。特别值得注意的是，在1C下500次循环后容量保持率为82%，这归因于PPy涂层，它抑制了Mn的副反应，增强了NMO的结构稳定性和电子导电性，并加速了Na扩散。这些结果表明，使用导电聚合物涂层是提高NMO储钠容量的一种简单有效的策略，为高性能SIB阴极的进一步发展铺平了道路。
