The article discusses the fundamental understanding and practical challenges of anionic redox activity in Li-ion batteries. Anionic redox, which involves the redox of anions, has been proposed as a promising approach to significantly increase the capacity of Li-ion batteries. However, there are still many questions about the fundamental origins of anionic redox and whether it can be fully realized in practical applications. The article reviews the underlying science that enables reversible and stable anionic redox activity, highlights its practical limitations, and outlines possible approaches for improving such materials and designing novel ones. It also summarizes the chances of market implementation of anionic redox-based materials in the face of competing nickel-based layered cathodes. The article begins by discussing the history of anionic redox chemistry in electrode materials. It explains that classical positive electrodes for Li-ion batteries operate mainly via cationic redox of transition-metal ions. However, recent discoveries have shown that anionic redox can also play a significant role in certain materials, such as Li-rich Mn-based layered oxides. The article then discusses the science underlying the anionic redox process, including the band structure of insertion compounds and the role of oxygen in redox reactions. It also explores the practical challenges of anionic redox in Li-rich cathodes, such as voltage fade, hysteresis, and sluggish kinetics. The article concludes by discussing the perspectives and conclusions of anionic redox in Li-ion batteries. It highlights the importance of anionic redox in enabling high-capacity Li-ion batteries and the need for further research to overcome the practical challenges associated with this approach. The article also discusses the potential of anionic redox in other battery technologies, such as Na-ion batteries. Overall, the article provides a comprehensive overview of the current state of anionic redox in Li-ion batteries and the challenges that need to be addressed for its successful implementation.The article discusses the fundamental understanding and practical challenges of anionic redox activity in Li-ion batteries. Anionic redox, which involves the redox of anions, has been proposed as a promising approach to significantly increase the capacity of Li-ion batteries. However, there are still many questions about the fundamental origins of anionic redox and whether it can be fully realized in practical applications. The article reviews the underlying science that enables reversible and stable anionic redox activity, highlights its practical limitations, and outlines possible approaches for improving such materials and designing novel ones. It also summarizes the chances of market implementation of anionic redox-based materials in the face of competing nickel-based layered cathodes. The article begins by discussing the history of anionic redox chemistry in electrode materials. It explains that classical positive electrodes for Li-ion batteries operate mainly via cationic redox of transition-metal ions. However, recent discoveries have shown that anionic redox can also play a significant role in certain materials, such as Li-rich Mn-based layered oxides. The article then discusses the science underlying the anionic redox process, including the band structure of insertion compounds and the role of oxygen in redox reactions. It also explores the practical challenges of anionic redox in Li-rich cathodes, such as voltage fade, hysteresis, and sluggish kinetics. The article concludes by discussing the perspectives and conclusions of anionic redox in Li-ion batteries. It highlights the importance of anionic redox in enabling high-capacity Li-ion batteries and the need for further research to overcome the practical challenges associated with this approach. The article also discusses the potential of anionic redox in other battery technologies, such as Na-ion batteries. Overall, the article provides a comprehensive overview of the current state of anionic redox in Li-ion batteries and the challenges that need to be addressed for its successful implementation.