This book presents studies and discussions on anionic redox, which can be used to boost the capacities of cathode electrodes by providing extra electron transfer. This theoretically and practically significant book facilitates the implementation of anionic redox in electrodes for real-world use and accelerates the development of high-energy-density lithium-ion batteries. Lithium-ion batteries, as energy storage systems, are playing a more and more important role in powering modern society. However, their energy density is still limited by the low specific capacity of the cathode electrodes. Based on a profound understanding of band theory, the author has achieved considerable advances in tuning the redox process of lithium-rich electrodes to obtain enhanced electrochemical performance, identifying both the stability mechanism of anionic redox in lithium-rich cathode materials, and its activation mechanism in these electrode systems.