Forming multilayered solid electrolyte interphase structures on high capacity electrodes

摘要

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.

主权项

1. An electrode of an electrochemical cell, the electrode comprising:
an electrochemically active structure comprising a high capacity active material; and a multilayered SEI structure formed on a surface of the electrochemically active structure, the multilayered SEI structure comprising:
an inner SEI layer over the electrochemically active structure; andan outer SEI layer over the inner SEI layer,wherein the inner SEI layer has a different composition and/or morphology than the outer SEI layer, wherein the inner SEI layer has a higher ionic conductivity than the outer SEI layer, and wherein the inner SEI layer is at least about twice as thick as the outer SEI layer.