THERMODYNAMIC VS. KINETIC CONTROL OVER SEI FORMATION ON SILICON ANODE AND ITS OPTIMIZATION IN LI-ION BATTERY

It has been well established that the SEI layer plays a key role in determining the cycling performance of the graphite anode in lithium ion batteries (LIBs) [1-3]. Silicon is being identified as one of the most attractive anode materials to replace graphite for the next generation of LIBs owing to its appropriate working voltage and the highest known specific capacity. However, a clear understanding on the composition, formation mechanism and characteristics of SEI layer on Si/electrolyte interface has not yet been well developed so far. In this work, the influence of C-rate, potential, and electrolyte additives on the phase composition, uniformity, thickness, and reaction pathway of Si SEI layer was investigated from both kinetics and thermodynamic perspectives. This was achieved by in-situ FTIR, in-situ EQCM, chronopotentiometry and chronoamperometry techniques. These measurements allowed to determine the nature of the SEI layer built on the silicon surface and correlate with the cycling performance of the silicon based anode materials.

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