Robust interface for O3-type layered cathode towards stable ether-based sodium-ion full batteries

Developing a robust cathode-electrolyte interface (CEI) is crucial for stable layered cathode in sodium-ion batteries (SIBs). A CEI based on ester electrolytes often exhibit poor stability and robustness, which cannot address the issues of structural collapse and material dissolution in layered cathodes. However, there are few reports on constructing a stable CEI for layered cathode based on ether electrolytes. Here we develop a robust CEI for O3-type cathode via DME solvent, which enables a long-term stability of full SIBs. The results indicate that unique decomposition process of DME yields favorable organic component (e.g. RCH₂ONa) and high content of inorganic components (e.g. NaF and Na₂CO₃) in the CEI, which is quite different from ester electrolyte, improving Na⁺ diffusion kinetic and interfacial stability. Notably, the O3-NaNi_0.5Mn_0.5O₂||Na cell with the designed electrolyte demonstrates outstanding stability up to 500 cycles. Furthermore, the full cell exhibits remarkable cycling performance with a capacity retention of 85 % over 200 cycles. This work provides an opportunity for stable operation of layered cathode materials via inexpensive ether electrolytes.