Ni-rich layered cathodes in sodium-ion batteries: perspectives or déjà vu?

Abstract

Sodium-ion batteries (SIBs) are emerging as promising energy storage devices due to the widespread availability of low-cost sodium and their electrochemical mechanism, which bears similarities to lithium-ion batteries (LIBs). The promising potential of Ni-rich layered oxides, coupled with the sense of déjà vu from the advancements seen in LIBs, strongly suggests the practical application of these compounds in SIBs. For the first time, the recent advancements in cathode materials for SIBs are highlighted, focusing on Ni-rich layered transition metal oxides such as NaNi_xCo_yMn_zO₂ (Na-NCM), NaNi_xCo_yAl_zO₂ (Na-NCA), Na–Ni_xFe_yMn_zO₂ (Na-NFM) and NaNi_xCo_yMn_z[TM]_{1−x−y−z}O₂ (Na-NCM[TM], TM = other transition metal) with x ≥ 0.60 (x + y + z = 1). These materials offer practical synthesis methods, impressive specific capacity, and environmental friendliness. However, challenges remain, including energy density and cycle life. Strategies to engineer high-energy-density SIBs are being pursued, notably developing Ni-rich layered oxide cathode materials. In conclusion, an outlook that assesses the strengths and limitations of this field is pointed out, providing valuable insights to steer future research efforts toward enhancing Ni-rich cathodes, thereby paving the way for further advancements.