Positive Electrode Materials for Li-Ion and Li-Batteries

Positive electrodes for Li-ion and lithium batteries (also termed cathodes) have been under intense scrutiny since the advent of the Li-ion cell in 1991. This is especially true in the past decade. Early on, carbonaceous materials dominated the negative electrode and hence most of the possible improvements in the cell were anticipated at the positive terminal; on the other hand, major developments in negative electrode materials made in the last portion of the decade with the introduction of nanocomposite Sn/C/Co alloys and Si-C composites have demanded higher capacity positive electrodes to match. Much of this was driven by the consumer market for small portable electronic devices. More recently, there has been a growing interest in developing Li-sulfur and Li-air batteries that have the potential for vastly increased capacity and energy density, which is needed to power large-scale systems. These require even more complex assemblies at the positive electrode in order to achieve good properties. This review provides an overview of the major developments in the area of positive electrode materials in both Li-ion and Li batteries in the past decade, and particularly in the past few years. Highlighted are concepts in solid-state chemistry and nanostructured materials that conceptually have provided new opportunities for materials scientists for tailored design that can be extended to many different electrode materials.