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Abstract：
Germanium (Ge)-based materials have been considered as potential anode materials for sodium-ion batteries owing to their high theoretical specific capacity. However, the poor conductivity and Na+ diffusivity of Ge-based materials result in retardant ion/electron transportation and insufficient sodium storage efficiency, leading to sluggish reaction kinetics. To intrinsically maximize the sodium storage capability of Ge, the nitrogen doped carbon-coated Cu3Ge/Ge heterostructure material (Cu3Ge/Ge@N-C) is developed for enhanced sodium storage. The pod-like structure of Cu3Ge/Ge@N-C exposes numerous active surface to shorten ion transportation pathway while the uniform encapsulation of carbon shell improves the electron transportation, leading to enhanced reaction kinetics. Theoretical calculation reveals that Cu3Ge/Ge heterostructure can offer decent electron conduction and lower the Na+ diffusion barrier, which further promotes Ge alloying reaction and improves its sodium storage capability close to its theoretical value. In addition, the uniform encapsulation of nitrogen-doped carbon on Cu3Ge/Ge heterostructure material efficiently alleviates its volume expansion and prevents its decomposition, further ensuring its structural integrity upon cycling. Attributed to these unique superiorities, the as-prepared Cu3Ge/Ge@N-C electrode demonstrates admirable discharge capacity, outstanding rate capability and prolonged cycle lifespan (178 mAh g-1 at 4.0 A g-1 after 4000 cycles).
摘要：
锗（Ge）基材料由于其高理论比容量而被认为是钠离子电池的潜在阳极材料。然而,Ge基材料的导电性和Na+扩散性较差，导致离子/电子传输受阻，钠储存效率不足，导致反应动力学迟缓。为了本质上最大化Ge的钠储存能力，开发了氮掺杂碳包覆的Cu3Ge/Ge异质结构材料（Cu3Ge/Ge@N-C），用于增强钠存储。Cu3Ge/Ge@N-C的豆荚状结构暴露了大量的活性表面以缩短离子传输途径，同时碳壳的均匀封装改善了电子传输。导致反应动力学增强。理论计算表明，Cu3Ge/Ge异质结构可以提供适当的电子传导并降低Na扩散势垒，这进一步促进了Ge的合金化反应，并将其钠储存能力提高到接近其理论值。此外,氮掺杂碳在Cu3Ge/Ge异质结构材料上的均匀封装有效地减轻了其体积膨胀并防止了其分解，进一步确保其结构的完整性，在循环。得益于这些独特的优势，制备的Cu3Ge/Ge@N-C电极显示出令人钦佩的放电容量，出色的倍率能力和延长的循环寿命（178mAhg-1在4000次循环后的4.0Ag-1）。
