리튬이차전지용 무질서 암염 양극 소재에서의 델타 상에 대한 최신 연구 동향

Recent Progress on Delta Phase in Disordered Rocksalt Cathodes for Lithium-Ion Batteries

Disordered rocksalt (DRX) cathodes are emerging as promising high-capacity materials for next-generation lithium-ion batteries due to their structural flexibility and compositional tunability. A recently discovered structural motif, known as the δ-phase, has drawn significant attention. This partially ordered, spinel-like structure forms progressively during electrochemical cycling, particularly in Mn-based DRX systems. The δ-phase contributes to improved electrochemical performance by enhancing capacity, rate capability, and cycling stability. In this review, we provide a comprehensive summary of recent advances in the understanding of δ-phase formation and its impact on DRX cathodes. We examine its structural characteristics, electrochemical behavior, and its role in enabling favorable Li-ion diffusion pathways through site energy homogenization and 0-TM percolation networks. Moreover, the thermodynamic and kinetic origins of δ-phase formation, which are governed by transition metal migration, oxidation states, and composition, are discussed based on both experimental and computational findings. Lastly, we highlight recent strategies to intentionally induce δ-phase formation, such as electrochemical pulse treatments and low-temperature annealing following chemical delithiation. These approaches enable faster and more controlled δ-phase development, suggesting a viable route toward practical DRX cathode implementation. Understanding and controlling the δ-phase will be pivotal in unlocking the electrochemical potential of DRX cathodes and accelerating the development of next-generation lithium-ion batteries.