Our increasing dependence on lithium-ion batteries for energy storage applications calls for continual performance improvements of their positive electrodes, which have so far relied solely on cationic redox of transition-metal ions for driving the electrochemical reactions. Great hope has recently been placed on the emergence of anionic redox -a transformational approach for designing positive electrodes as it leads to a near-doubling of capacity -hence generating much research interest in recent years. However, questions have been raised on the fundamental origins of anionic redox and whether its full potential can be realised in applications. In this Review, we discuss the underlying science that triggers a reversible and stable anionic redox activity. Furthermore, we highlight its practical limitations and outline possible approaches for improving such materials and designing novel ones. We also summarize their chances for market implementation in face of the competing nickel-based layered cathodes that are prevalent today.