Recently, anionic activity, such as oxygen redox reaction, has been discovered in the electrochemical processes of rechargeable lithium ion batteries, providing extra reversible capacity for certain transition-metal oxides. Consequently, a more complete understanding and precise controlling on anionic electrochemical activity in these high-capacity oxides have become a flourishing, yet challenging subject. This talk highlights (see the figure below): (1) key features of the anionic electrochemical activities; (2) computational and experimental tools to characterize and quantify the anionic activity; (3) design principles that correlate the chemical and structural compositions with high reversible capacity to accelerate the discovery of novel cathode oxides for next generation Li-ion batteries.