Opportunities and Challenges in the Development of Layered Positive Electrode Materials for High-Energy Sodium Ion...

In recent years, high-energy-density sodium ion batteries (SIBs) have attracted enormous attention as a potential replacement for LIBs due to the chemical similarity between Li and Na, high natural abundance, and low cost of Na. Despite the promise of high energy, SIBs with layered cathode materials face several challenges including irreversible capacity loss, voltage hysteresis, voltage decay, irreversible TM migrations that lead to fast capacity fading, and structural degradation. However, their electrochemical performance can be improved by introducing reversible anionic redox along with conventional cationic redox. This Perspective systematically summarizes different factors that trigger the irreversible anionic redox in Na-based cathode materials. Additionally, this Perspective highlights the mechanistic understanding and key challenges for reversible anionic redox and proposes plausible solutions to overcome these limitations. The overview of various existing experimental and theoretical approaches presented here could provide a futuristic pathway to design Na-based cathode materials for high-energy-density SIBs.