Forming multilayered solid electrolyte interphase structures on high capacity electrodes

Abstract

Provided are novel methods of fabricating electrochemical cells containing high capacity active materials that form multilayered solid electrolyte interphase (SEI) structures on the active material surface during cell fabrication. Combining multiple different SEI layers on one surface can substantially improve cell performance by providing each layer with different properties. For example, an outer layer having a high electronic resistance may be combined with an inner layer having a high ionic permeability. To form such multilayered SEI structures, formation may involve changing electrolyte composition, functionalizing surfaces, and/or varying formation conditions. For example, formation may start with a boron containing electrolyte. This initial electrolyte is then replaced with an electrolyte that does not contain boron and instead may contain fluorine additives. In certain embodiments, cell's temperature is changed during formation to initiate different chemical reactions during SEI formation. Variations in multilayered SEI structures may be also achieved by varying current rates.