Spontaneous repairing liquid metal/Si nanocomposite as a smart conductive-additive-free anode for lithium-ion battery

摘要

Silicon is a promising candidate for negative electrodes due to its high theoretical specific capacity (similar to 3579 mA h g(-1)) and low lithiation potential (similar to 0.40 V vs. Li). However, its practical applications in battery have been inhibited by the large volume change (similar to 400%) induced by Li+-insertion into Si lattices. Here, we attempt to resolve this issue at a fundamental level, and report for the first time a novel liquid metal (LM)-mediated spontaneous repairing conductive-additive-free Si anode for Li-ion battery. The fluidity of LM ensures the eternal contact between Si and the conducting-network during its repeated electrochemical reactions. The as-prepared nano-composite of LM/Si leads to superior performances as characterized by high capacity utilization (2300 mA h g(-1) at 500 mA g(-1)), long-term stability (968 mA h g(-1) after 1500 charge-discharge cycles at 8 A g(-1) with 81.3% retention), high rate capability (360 mA h g(-1) at 20 A g(-1), equivalence of 55C, or full charge/discharge in 65 s), and, in particular, an extra-ordinarily high initial coulombic efficiency (95.92%), which is not only the highest reported for Si to the best of our knowledge, but also higher than the mature graphitic carbon anodes. The unique approach described in this work not only resolves the basic stress challenges faced by the promising but often problematic alloy-type materials; in broader context it also provides a universal inspiration to all electrode materials whose electric properties suffer from extreme mechanic upheavals induced by the electrochemical strains during the cell reactions.