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Built-In Electric Field in Si/Ge Heterojunction Suppressing Li+ Trapping Boosts High Initial Coulombic Efficiency of Silicon Anodes
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DOI：10.1002/asia.70700.png)
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Abstract
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Silicon (Si) anodes are promising candidates for surpassing the energy density limits of current lithium-ion batteries, owing to the ultra-high theoretical capacity (4200 mAh g(-1)). However, their practical implementation is hindered by irreversible lithium (Li) loss, which originates from the continuous formation of the solid electrolyte interphase (SEI) and the irreversible trapping of Li+ within the silicon matrix due to sluggish Li+ diffusion kinetics. To address these issues, a Si/Ge@C heterojunction anode has been designed. In this configuration, a conformal carbon coating effectively mitigates volume expansion and suppresses parasitic reactions on the Si surface, thereby reducing excessive SEI formation. Moreover, the Si/Ge heterojunction establishes a built-in electric field oriented from Si to Ge, which reduces Li+ trapping. This built-in electric field not only facilitates Li+ migration toward Ge during lithiation but also provides an additional driving force to extract trapped Li+ from Si during delithiation. Consequently, the optimized Si/Ge@C anode delivers a high initial Coulombic efficiency (ICE) of 92.47% and maintains a high capacity of 539.77 mAh g(-1) over 500 cycles at 200 mA g(-1).
Keywords:
built-in electric field
heterojunction
initial coulombic efficiency
lithium trapping
silicon anode
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