Improved Electrochemical Performances of Silicon Nanowires Anode with Optimized Cycling Conditions
SEM images of the electrode were made in the delithiated state, at different stages of the cycling, to investigate the evolution of the electrode morphology and thickness. It appears that the reduced delithiation cut-off voltage leads to the formation of a more compact Solid Electrolyte Interphase (SEI) at the beginning of the cycling and less cracks are formed in the material at the end of the delithiation. A partial dissolution or reoxydation of the SEI layer probably occurs at higher potential, which is detrimental for the reversibility of the cycling and for the mechanical strength of the electrode. In the case of a reduced cut-off voltage, however, once the thick layer of SEI is formed, the morphology of the electrode remains rather stable. This SEI probably works as a mechanical support for the electrode and prevent further electrolyte degradation, which leads to the exceptional electrochemical stability.
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