Status of Li(Na)-based anionic redox materials for better batteries

For decades, Li-ion batteries are serving as a transformative technology in propelling off-network energy use as exemplified by the prosperity of portable electronics and electric vehicles. However, they are suffering from the shortage of energy density for modern-society energy storage, as the conventional way of Li-ion batteries work solely relies on redox reaction of transition metal (cationic redox) upon Li removal/uptake. This situation has been changed since the emergence of anionic redox, i.e., anions is redox center, that offers extra capacity in Li-rich electrode materials. In this chapter, we aim to briefly introduce how anionic redox chemistry concept rises and revolutionizes the cathode materials design in Li(Na)-ion batteries. We revisit the fundamental science behind anionic redox, and indicate how these knowledge opened new dimensionalities of electrode material design. We also summarize the progresses in understanding and solving the practical roadblocks for anionic redox, and highlight the remaining issues deserving to be explored in the future.