7 The influence of electrode material crystal structure on battery performance

Energy storage demands are increasing as a result of the growing use of electric vehicles and intermittent energy sources. Lithium-ion batteries, commercialized over two decades ago, have enabled the widespread use of portable electronics, and these are being implemented both in electric vehicles and to store intermittently available energy. This type of battery operates with the so-called “rocking-chair” mechanism, where lithium ions are reversibly exchanged between two electrodes. The mechanism relies on the reversible insertion of lithium into sites within the electrode material crystal structure, with the repeated processes of lithium insertion and extraction generating atomic-level change that the bulk electrode material must accommodate. These are both the short- and long-range structural changes within electrodes that dictate, to a large degree, the performance of the whole battery. Hence, the characterization of electrode crystal structure, particularly during battery cycling, is key to understanding and improving energy storage in batteries. In this chapter, we explore the relationship between the crystal structure of electrode materials and their performance in lithium-ion batteries, with a focus on structure types that have found commercial applications. The discussion identifies what crystallographic features are useful for electrode materials and how crystal structure influences electrochemical behavior.