Conti Debora Maria, Urru Claudia, Bruni Giovanna, Galinetto Pietro, Albini Benedetta, Milanese Chiara, Pisani Silvia, Berbenni Vittorio, Capsoni Doretta
Department of Chemistry, Physical Chemistry Section & C.S.G.I. (Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase), University of Pavia, Via Taramelli 16, 27100 Pavia, Italy.
Department of Physics, University of Pavia, 27100 Pavia, Italy.
Molecules. 2024 Apr 20;29(8):1885. doi: 10.3390/molecules29081885.
The NASICON-structured NaMnZr(PO) compound is a promising high-voltage cathode material for sodium-ion batteries (SIBs). In this study, an easy and scalable electrospinning approach was used to synthesize self-standing cathodes based on NaMnZr(PO) loaded into carbon nanofibers (CNFs). Different strategies were applied to load the active material. All the employed characterization techniques (X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), and Raman spectroscopy) confirmed the successful loading. Compared to an appositely prepared tape-cast electrode, NaMnZr(PO)/CNF self-standing cathodes demonstrated an enhanced specific capacity, especially at high C-rates, thanks to the porous conducive carbon nanofiber matrix. Among the strategies applied to load NaMnZr(PO) into the CNFs, the electrospinning (vertical setting) of the polymeric solution containing pre-synthesized NaMnZr(PO) powders resulted effective in obtaining the quantitative loading of the active material and a homogeneous distribution through the sheet thickness. Notably, NaMnZr(PO) aggregates connected to the CNFs, covered their surface, and were also embedded, as demonstrated by TEM and EDS. Compared to the self-standing cathodes prepared with the horizontal setting or dip-drop coating methods, the vertical binder-free electrode exhibited the highest capacity values of 78.2, 55.7, 38.8, 22.2, 16.2, 12.8, 10.3, 9.0, and 8.5 mAh/g at C-rates of 0.05C, 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, and 20C, respectively, with complete capacity retention at the end of the measurements. It also exhibited a good cycling life, compared to its tape-cast counterpart: it displayed higher capacity retention at 0.2C and 1C, and, after cycling 1000 cycles at 1C, it could be further cycled at 5C, 10C, and 20C.
NASICON结构的NaMnZr(PO)化合物是一种很有前景的钠离子电池（SIBs）高压正极材料。在本研究中，采用了一种简便且可扩展的静电纺丝方法来合成基于负载在碳纳米纤维（CNF）中的NaMnZr(PO)的自支撑正极。应用了不同的策略来负载活性材料。所有采用的表征技术（X射线粉末衍射（XRPD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、能量色散X射线光谱（EDS）、热重分析（TGA）和拉曼光谱）都证实了负载成功。与适当制备的流延电极相比，NaMnZr(PO)/CNF自支撑正极表现出更高的比容量，特别是在高C倍率下，这得益于多孔导电的碳纳米纤维基质。在将NaMnZr(PO)负载到CNF中的策略中，含有预合成NaMnZr(PO)粉末的聚合物溶液的静电纺丝（垂直设置）有效地实现了活性材料的定量负载以及在整个片层厚度上的均匀分布。值得注意的是，TEM和EDS表明，与CNF相连的NaMnZr(PO)聚集体覆盖了它们的表面并且也被嵌入其中。与采用水平设置或滴涂法制备的自支撑正极相比，垂直无粘结剂电极在0.05C、0.1C、0.2C、0.5C、1C、2C、5C、10C和20C的C倍率下分别表现出78.2、55.7、38.8、22.2、16.2、12.8、10.3、9.0和8.5 mAh/g的最高容量值，并且在测量结束时容量完全保持。与流延对应物相比，它还表现出良好的循环寿命：在0.2C和1C时它显示出更高的容量保持率，并且在1C下循环1000次后，它可以在5C、10C和20C下进一步循环。
