School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States.
Nano Lett. 2012 Sep 12;12(9):5039-47. doi: 10.1021/nl302841y. Epub 2012 Aug 20.
Electrochemical experiments were conducted on {100}, {110}, and {111} silicon wafers to characterize the kinetics of the initial lithiation of crystalline Si electrodes. Under constant current conditions, we observed constant cell potentials for all orientations, indicating the existence of a phase boundary that separates crystalline silicon from the amorphous lithiated phase. For a given potential, the velocity of this boundary was found to be faster for {110} silicon than for the other two orientations. We show that our measurements of varying phase boundary velocities can accurately account for anisotropic morphologies and fracture developed in crystalline silicon nanopillars. We also present a kinetic model by considering the redox reaction at the electrolyte/lithiated silicon interface, diffusion of lithium through the lithiated phase, and the chemical reaction at the lithiated silicon/crystalline silicon interface. From this model, we quantify the rates of the reactions at the interfaces and estimate a lower bound on the diffusivity through the lithiated silicon phase.
电化学实验在{100}、{110}和{111}硅片上进行，以表征晶体硅电极初始锂化的动力学。在恒流条件下，我们观察到所有取向的电池电位都保持恒定，表明存在一个相界，将晶体硅与非晶锂化相分开。对于给定的电位，我们发现{110}硅的相界速度比其他两个取向更快。我们表明，我们对不同相界速度的测量可以准确地解释晶体硅纳米柱中各向异性形态和断裂的发展。我们还通过考虑电解质/锂化硅界面的氧化还原反应、锂通过锂化相的扩散以及锂化硅/晶体硅界面的化学反应，提出了一个动力学模型。从这个模型中，我们量化了界面上反应的速率，并估计了通过锂化硅相的扩散率的下限。
