As lithium-ion batteries evolve toward higher cell voltage and capacity, developing detailed knowledge of the electrolyte/electrode interface is critically important. The solid electrolyte interphase (SEI) region plays a significant role in the reversibility and kinetics of the cell chemistry, e.g. by serving as the location for Li-ion solvation/desolvation and preventing persistent decomposition of the electrolyte while maintaining acceptable Li-ion transport. Additives to ethylene carbonate (EC) based electrolytes improve Li-ion battery performance, possibly by altering the physical or chemical properties of the SEI. While there is general agreement on the formation of the SEI on graphitic anodes from decomposed electrolyte, the morphology and composition dependence on additives is not well described. The inherent nature of the SEI, including its location on the electrodes, has impeded developing a well-supported understanding of its physical properties, composition, and true thickness. Primarily using in-situ electrochemical atomic force microscopy (EC-AFM), we have systematically studied the relationship between the electrolyte and the resulting SEI formed on graphitic anodes. A key observation was that electrolytes with performance-enhancing additives formed thinner SEIs than additive-free electrolytes. Our results, coupled with the known benefits of these additives on battery performance, indicate that a more compact SEI is advantageous. SEI engineering through manipulation of additive chemistry could be the key to making high performance electrode-electrolyte pairs for high voltage Li-ion cells and perhaps alternative systems.

Effect of electrolyte additives on solid electrolyte interphase properties in Li-ion batteries as analyzed by in-situ atomic force microscopy

246th National Meeting (2013)

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