P2-type layered transition metal oxides (Na x TMO 2 TM are transition metal elements) are air-stability and low-cost but intrinsically limited in capacity, necessitating elevated charging voltages to unlock deeper Na + extraction and higher energy density. However, practical high-voltage operation over wide temperature ranges is impeded by sluggish Na + desolvation, aggravated parasitic reactions, and rapid cycling degradation. Here, we identify 1,1,1-trifluoro- N, N -dimethylmethanesulfonamide (Me 2 TFMSA) as a polar inducer that restructures Na + solvation by confining carbonate molecules predominantly within the first solvation sheath, suppressing free-carbonate preferential accumulation at the cathode interface and enabling rapid ligand exchange during desolvation, while FSI – coordination forms an aggregate-rich solvation structure with weakened Na + –solvent interaction. This confining solvation electrolyte (CSE) allows a 4.3 V cutoff (vs 4.1 V conventionally) and delivers a 25.8% capacity gain for P2-type Na 0.6 Mg 0.04 Ca 0.02 Ti 0.1 Mn 0.55 Ni 0.29 O 2 (NaNMO) cathodes, effectively suppressing parasitic reactions, transition-metal dissolution, surface phase reconstruction, and impedance growth. In 4.3-V-class Ah-level hard carbon||NaNMO pouch cells with the CSE deliver 74.8% capacity retention after 800 cycles at 0.5 C, whereas conventional carbonate electrolytes fail within 200 cycles. Stable performance is achieved from −30 to 45 °C, with good cycling performance at −20 °C. These results correlate solvation confinement with interfacial stability and 4.3-V-class pouch-cell performance in P2-type sodium-ion batteries.
LIU et al. (Sun,) studied this question.