有序介孔硅/碳复合结构负极材料的制备与电化学性能研究

以SBA-15( SiO₂)有序介孔模板为前驱体, 通过镁热还原和碳包覆修饰路线, 制备出二维定向组装的束捆状有序介孔覆碳纳米组织(OMP-Si/C), 并细致研究了SBA-15的镁热还原过程, 对OMP-Si/C复合结构进行电化学性能测试。经XRD测试分析发现: 镁热还原过程中存在Mg₂Si中间相反应路径, 基于此提出反应温度-时间(T-t)相转变图; DSC/TG表明, Mg相通过反应-熔化协调联动作用, 在低于熔点(648℃)时熔化, 且发生液/固反应。从FE-SEM观察到SBA-15柱状单元被装配成类藕根链束捆状Si有序介孔组织, 并基于镁液微涡流场卷吸作用机理解释了该二维定向组装过程。所得致密纳米组织能有效抵消充放电过程中Si相的固有体积变化, 从而表现出优异的循环稳定性能和倍率性能。

Preparation and Electrochemical Performance of Ordered Mesoporous Si/C Composite for Anode Material

Using SBA-15 of SiO₂ template as precursor, a bundle-shaped ordered mesoporous nanoarchitecture Si/C composite (OMP-Si/C) was successfully assembled 2D-directionally by a magnesiothermic reduction reaction (MRR) route and the ensuing carbon-coating modification processing, and the MRR process of the SBA-15 was investigated in depth, the electrochemical performance of as-prepared OMP-Si/C composites was tested. Analysis based on XRD data reveals the presence of a reaction path of Mg₂Si intermediate phase in MRR process, on which a T-t (reaction temperature-reaction time) phase transition diagram is proposed. DSC/TG analysis shows that Mg particles may melt below its melting point (648℃) upon reaction, and in liquid-solid reaction pattern react with SiO₂ via melting-reaction teamwork. Observed from FE-SEM, SBA-15 column units are validated to assemble into a lotus-root-chain-bundle shaped nanoarchitecture of ordered mesoporous silicon, which can effectively offset the drastic volume change of Si material inherent in the charge/discharge process, and exhibit excellent cycling stability and rate capability. Based on the micro-fluid field assembling mechanism, the two-dimensional directional assembly process can be reasonably interpreted.