Bai Yansong, Zhang Xiaoyan, Shu Hongbo, Luo Zhigao, Hu Hai, Zhao Qinglan, Wang Ying, Wang Xianyou
National Base for International Science & Technology Cooperation, National Local Joint Engineering Laboratory for Key Materials of New Energy Storage Battery, Hunan Province Key Laboratory of Electrochemical Energy Storage & Conversion, School of Chemistry, Xiangtan University, Hunan 411105, China.
School of Mechanical Engineering, Xiangtan University, Hunan 411105, China.
ACS Appl Mater Interfaces. 2020 Aug 5;12(31):34858-34872. doi: 10.1021/acsami.0c07894. Epub 2020 Jul 28.
The poor electronic conductivity of NaFeSiO always limits its electrochemical reactivities and no effective solution has been found to date. Herein, the novel Ni-substituted NaFeNiSiO@C nanospheres (50-100 nm) encapsulated with a 3D hierarchical porous skeleton (named as alveolation-like configuration) constructed using carbon are first synthesized a facile sol-gel method, and the effects of Ni substitution combined with the design of a unique carbon network on Na-storage properties are assessed systematically, focusing on alleviating the inherent defects of the NaFeSiO cathode material. A series of characterization technologies such as X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and so forth, coupled with the electrochemical measurements and first-principles calculations, are used to explore the structure, morphology and electrochemical behaviors of the as-prepared materials. The results show that the synergism between Ni substitution and the special alveolation-like configuration enables fast Na ions mobility (from 10 to 10 cm s), reduces band gap energy (from 2.82 to 1.79 eV) and lowers Na-ion diffusion barriers, finally reciprocating the vigorous electrochemical kinetics of the electrode. Especially, the elaborately designed material-NaFeNiSiO@C-displays superior Na-storage properties of around 197.51 mA h g (corresponding to 1.43 Na intercalation) at 0.1 C within 1.5-4.5 V along with desirable capacity retention (84.44% after 100 cycles), and the rate capability is also markedly enhanced (a capacity of 133.62 mA h g at 2 C). Such the effective methodology employed in this work opens a potential pathway to synthesize the silicate cathode material with excellent electrochemical properties.
NaFeSiO较差的电子导电性一直限制着其电化学反应活性，迄今为止尚未找到有效的解决方法。在此，首次采用简便的溶胶 - 凝胶法合成了新型的Ni取代的NaFeNiSiO@C纳米球（50 - 100 nm），其被用碳构建的三维分级多孔骨架（称为蜂窝状结构）包裹，并且系统地评估了Ni取代与独特碳网络设计相结合对储钠性能的影响，重点在于缓解NaFeSiO正极材料的固有缺陷。使用一系列表征技术，如X射线衍射、透射电子显微镜、X射线光电子能谱等，结合电化学测量和第一性原理计算，来探究所制备材料的结构、形态和电化学行为。结果表明，Ni取代与特殊的蜂窝状结构之间的协同作用使得Na离子能够快速迁移（从10到10 cm s），降低了带隙能量（从2.82到1.79 eV）并降低了Na离子扩散势垒，最终使电极具有活跃的电化学动力学。特别是，精心设计的材料NaFeNiSiO@C在1.5 - 4.5 V范围内，0.1 C时显示出约197.51 mA h g的优异储钠性能（对应于1.43个Na嵌入）以及良好的容量保持率（100次循环后为84.44%），并且倍率性能也显著提高（2 C时容量为133.62 mA h g）。这项工作中采用的这种有效方法为合成具有优异电化学性能的硅酸盐正极材料开辟了一条潜在途径。
