Confined Solvation Electrolyte for 4.3-V-Class High-Voltage Sodium-Ion Pouch Cells.
basic_science · Level V
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- Record sourced from PubMed, PMID 42437358.
- Also identified by DOI 10.1021/acsnano.6c03000.
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Abstract
P2-type layered transition metal oxides (Na<sub><i>x</i></sub>TMO<sub>2</sub> TM are transition metal elements) are air-stability and low-cost but intrinsically limited in capacity, necessitating elevated charging voltages to unlock deeper Na<sup>+</sup> extraction and higher energy density. However, practical high-voltage operation over wide temperature ranges is impeded by sluggish Na<sup>+</sup> desolvation, aggravated parasitic reactions, and rapid cycling degradation. Here, we identify 1,1,1-trifluoro-<i>N</i>,<i>N</i>-dimethylmethanesulfonamide (Me<sub>2</sub>TFMSA) as a polar inducer that restructures Na<sup>+</sup> 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<sup>-</sup> coordination forms an aggregate-rich solvation structure with weakened Na<sup>+</sup>-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<sub>0.6</sub>[Mg<sub>0.04</sub>Ca<sub>0.02</sub>Ti<sub>0.1</sub>Mn<sub>0.55</sub>Ni<sub>0.29</sub>]O<sub>2</sub> (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.