Two-Dimensional Siloxene Nanosheets: Impact of Morphology and Purity on Electrochemistry

Two-dimensional (2D) siloxene (Si6O3H6) has shown promise as a negative electrode material for Li-ion batteries due to its high gravimetric capacity and superior mechanical properties under (de)lithiation compared to bulk Si. In this work, we prepare purified siloxene nanosheets through the removal of bulk Si contaminants, use ultrasonication to control the lateral size and thickness of the nanosheets, and probe the effects of the resulting morphology and purity on the electrochemistry. The thin siloxene nanosheets formed after 4 h of ultrasonication deliver an average capacity of 810 mA h/g under a 1000 mA/g rate over 200 cycles with a capacity retention of 76%. Interestingly, the purified siloxene shows lower initial capacity but superior capacity retention over extended cycling. The 2D morphology benefit is illustrated where the parent siloxene nanosheet morphology and structure were largely maintained based on operando optoelectrochemistry, in situ Raman, ex situ scanning electron microscopy, and ex situ transmission electron microscopy. Furthermore, the purified siloxene-based electrode free from crystalline Si impurity experiences the least expansion upon (de)lithiation as visualized by cross-section electron microscopy of samples recovered post-cycling.

Automated summary

By removing bulk Si contaminants, we prepared purified thin siloxene nanosheets with controlled lateral size and thickness using ultrasonication, and studied the effects of morphology and purity on electrochemical performance. The resulting thin siloxene nanosheets after 4 hours of ultrasonication exhibited an average capacity of 810 mA h/g at a rate of 1000 mA/g over 200 cycles, with a capacity retention of 76%. Interestingly, the purified siloxene showed lower initial capacity but superior capacity retention during cycling. The 2D morphology of siloxene nanosheets was largely maintained, and the purified siloxene-based electrode experienced minimal expansion upon (de)lithiation.