控制高能量密度电池用纳米结构非晶硅倍率性能的原子尺度因素
Atomic-scale factors that control the rate capability of nanostructured amorphous Si for high-energy-density batteries
摘要：
纳米结构的硅是最有前途的高容量负极材料，可显著提高锂离子电池的能量密度。与传统材料相比，其低速率能力是剩下的挑战之一。为了更好地了解是什么控制了Li在非晶Li-Si合金中的扩散，我们使用了一种新的机器学习势，该势经过了超过40，000次从头计算和纳秒级分子动力学模拟的训练，首次可视化了整个LiSi纳米颗粒的脱锂。我们的研究结果表明，Si主机是不是静态的，但经历了从孤立的原子，链，簇的动态重排，与Li扩散强烈受此Si重排。我们发现，Li扩散率是最高的Si偏析成团簇时，使Li扩散通过跳跃的Si团簇之间进行。因此，Si团簇的平均尺寸和Si团簇发生的浓度范围可以用作开发基于改性Si的速率改进的阳极的设计标准。
英文摘要：
Nanostructured Si is the most promising high-capacity anode material to substantially increase the energy density of Li-ion batteries. Among the remaining challenges is its low rate capability as compared to conventional materials. To understand better what controls the diffusion of Li in the amorphous Li-Si alloy, we use a novel machine-learning potential trained on more than 40,000 ab-initio calculations and nanosecond-scale molecular dynamics simulations, to visualize for the first time the delithiation of entire LiSi nanoparticles. Our results show that the Si host is not static but undergoes a dynamic rearrangement from isolated atoms, to chains, and clusters, with the Li diffusion strongly governed by this Si rearrangement. We find that the Li diffusivity is highest when Si segregates into clusters, so that Li diffusion proceeds via hopping between the Si clusters. The average size of Si clusters and the concentration range over which Si clustering occurs can thus function as design criteria for the development of rate-improved anodes based on modified Si.
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