Extreme volume expansion upon lithiation remains a key challenge for Silicon (Si)-based anode materials, which commonly results in electrochemi-mechanical degradation and subsequent fast capacity fading. Pitch-derived carbon coating is an efficient strategy to alleviate the expansion of Si. However, clarifying the relationship between the microstructures of pitch-derived carbon and its expansion confinements properties is still difficult due to the complexity of pitch composition. Herein, we develop core-shell Si@C anode materials with robust protective pitch-derived carbon coating by pitch fraction separation and confirm the expansion confinements properties is connected to molecular structure and weight of pitch fractions. Small and disordered microcrystalline units of light fractions confer high resilience to the derived carbon coating which is less prone to rupture. The compressive stress from resilience coating leads to the transformation of lithium-silicon alloys to amorphous silicon during the early stages of lithiation, which allows for reduction in the expansion of Si. The composites of light fractions derived carbon with Si exhibits the best cycling stability. This work provides new insights into the understanding of expansion confinements in silicon-carbon anode materials.

中文翻译：

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轻质沥青可在硅阳极上实现坚固的涂层：通过自脱锂抑制体积膨胀

锂化时的极端体积膨胀仍然是硅基负极材料的一个关键挑战，这通常会导致电化学机械降解和随后的快速容量衰减。沥青衍生碳涂层是缓解硅膨胀的有效策略。然而，由于沥青成分的复杂性，阐明沥青衍生碳的微观结构与其膨胀限制性能之间的关系仍然很困难。在此，我们通过沥青馏分分离开发了具有坚固的保护性沥青衍生碳涂层的核壳Si@C阳极材料，并确认膨胀限制性能与沥青馏分的分子结构和重量有关。小而无序的轻质馏分微晶单元赋予衍生的碳涂层高弹性，不易破裂。弹性涂层产生的压应力导致锂硅合金在锂化的早期阶段转变为非晶硅，从而减少硅的膨胀。轻质碳与硅的复合材料表现出最好的循环稳定性。这项工作为理解硅碳阳极材料的膨胀限制提供了新的见解。