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Structures,phase stabilities, and electrical potentials of Li-Si battery anode materials

机译:锂硅电池负极材料的结构,相稳定性和电势

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The Li-Si materials system holds promise for use as an anode in Li-ion battery applications.For this system,we determine the charge capacity, voltage profiles, and energy storage density solely by ab initio methods without any experimental input.We determine the energetics of the stable and metastable Li-Si phases likely to form during the charging and discharging of a battery.Ab initio molecular dynamics simulations are used to model the structure of amorphous Li-Si as a function of composition, and a genetic algorithm coupled to density-functional theory searches the Li-Si binary phase diagram for small-cell, metastable crystal structures.Calculations of the phonon densities of states using density-functional perturbation theory for selected structures determine the importance of vibrational, including zero-point, contributions to the free energies.The energetics and local structural motifs of these metastable Li-Si phases closely resemble those of the amorphous phases, making these small unit cell crystal phases good approximants of the amorphous phase for use in further studies.The charge capacity is estimated, and the electrical potential profiles and the energy density of Li-Si anodes are predicted.We find, in good agreement with experimental measurements, that the formation of amorphous Li-Si only slightly increases the anode potential.Additionally, the genetic algorithm identifies a previously unreported member of the Li-Si binary phase diagram with composition Li_5Si_2 which is stable at 0 K with respect to previously known phases.We discuss its relationship to the partially occupied Li_7Si_3 phase.
机译:锂硅材料系统有望在锂离子电池应用中用作阳极。对于该系统,我们仅通过从头算的方法即可确定充电容量,电压曲线和能量存储密度,而无需任何实验输入。电池充电和放电过程中可能形成的稳定和亚稳态Li-Si相的能量学。从头算分子动力学模拟用于根据成分对非晶Li-Si的结构进行建模,并采用遗传算法密度泛函理论在Li-Si二元相图中搜索小晶胞,亚稳态晶体结构。使用密度泛函摄动理论对选定结构进行声子密度计算,确定了振动(包括零点)对振动的贡献的重要性。这些亚稳定的Li-Si相的能量和局部结构基序与非晶相的相似,从而使它们较小的晶胞晶相与非晶相的良好近似,可用于进一步的研究。估算电荷容量,并预测Li-Si阳极的电势曲线和能量密度。我们发现,与实验测量结果非常吻合,此外,遗传算法还确定了成分为Li_5Si_2且相对于已知相稳定在0 K的Li-Si二元相图中以前未报道的成员。讨论其与部分占据的Li_7Si_3相的关系。

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