The Center for Electrochemical Energy Science (CEES): An Overview

The Center for Electrochemical Energy Science (CEES) seeks to develop a fundamental understanding of the lithium ion electrochemistry of oxides in lithium ion battery systems.  Controlling electrochemical reactions is a significant challenge, due to the extreme structural and chemical changes that take place as lithium ions are incorporated in the active electrode material.  We are approaching this through coordinated studies of three types of lithium ion chemistries with a focus on oxide electrodes: 1) Insertion reactions (e.g., Li + M-O ↔ LiM-O) into a host oxide matrix; 2) Conversion reactions (e.g., 2Li + M-O ↔ M + Li₂O) that disrupt the oxide lattice upon lithiation, leading to phase separation of the metal and Li₂O phases; and 3) “Hybrid” Li-O₂/Li-ion reactions (e.g., 4nLi⁺ + nO₂ + MO_y ↔ (Li₂O)_2nMO_y) that involve disruption of the host lattice, along with insertion of Li and O.  Specifically our primary focus is on studies of well-defined model systems that enable a fundamental understanding of these reactions.  One broad theme in these studies is the role of interfaces in these reactions.  I will also review recent work in which we seek to isolate and understand the role of interfacial reactivity in these systems through in-situ, real-time, observations of lithiation reactions of well-defined model electrode-electrolyte interfaces using X-ray reflectivity.  These results reveal novel insights into the role of interfacial reactivity in conversion reactions (e.g., Si, CrO_x, NiO) that can be used to control the complex reaction lithiation pathway through the use of thin-film and multilayer electrode structures.

Acknowledgment: This work was supported as part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.  The work was done in collaboration with T. Fister, S. S. Lee (ANL), J. Esbenshade, B. Long, A. Gewirth (University of Illinois at Urbana-Champaign), X. Chen, G. Evmenenko, M. Bedzyk (Northwestern University).