ABSTRACT 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 .
Zhang et al. (Sun,) studied this question.