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Sodium-ion batteries (SIBs) are recognized as promising energy storage devices. However, they suffer from rapid capacity decay at ultra-low temperatures due to high Na + desolvation energy barrier and unstable solid electrolyte interphase (SEI). Herein, a weakly solvating electrolyte (WSE) with decreased ion-dipole interactions is designed for stable sodium storage in hard carbon (HC) anode at ultra-low temperatures. 2-methyltetrahydrofuran with low solvating power is incorporated into tetrahydrofuran to regulate the interactions between Na + and solvents. The reduced Na + -dipole interactions facilitate more anionic coordination in the first solvation sheath, which consistently maintains anion-enhanced solvation structures from room to low temperatures to promote inorganic-rich SEI formation. These enable WSE with a low freezing point of -83.3 °C and faster Na + desolvation kinetics. The HC anode thus affords reversible capacities of 243.2 and 205.4 mAh g -1 at 50 mA g -1 at -40 and -60 °C, respectively, and the full cell of HC||Na 3 V 2 (PO 4 ) 3 yields an extended lifespan over 250 cycles with high capacity retention of ~100 % at -40 °C. This work sheds new lights on the ion-dipole regulation for ultra-low temperature SIBs., (© 2024 Wiley‐VCH GmbH.)

Li-O 2 batteries have garnered much attention due to their high theoretical energy density. However, the irreversible lithium plating/stripping on the anode limits their performance, which has been paid little attention. Herein, a solvation-regulated strategy for stable lithium anodes in tetraethylene glycol dimethyl ether (G4) based electrolyte is attempted in Li-O 2 batteries. Trifluoroacetate anions (TFA - ) with strong Li + affinity are incorporated into the lithium bis(fluorosulfonyl)imide (LiTFSI)/G4 electrolyte to attenuate the Li + -G4 interaction and form anion-dominant solvates. The bisalt electrolyte with 0.5 M LiTFA and 0.5 M LiTFSI mitigates G4 decomposition and induces an inorganic-rich solid electrolyte interphase (SEI). This contributes to decreased desolvation energy barrier from 58.20 to 46.31 kJ mol -1 , compared with 1.0 M LiTFSI/G4, for facile interfacial Li + diffusion and high efficiency. It yields extended lifespan of 120 cycles in Li-O 2 battery with a limited Li anode (7 mAh cm -2 ). This work gains comprehensive insights into rational electrolyte design for Li-O 2 batteries., (© 2023 Wiley-VCH GmbH.)

Aprotic Li-O 2 batteries have attracted extensive attention in the past decade owing to their high theoretical energy density; however, they are obstructed by the sluggish reaction kinetics at the cathode and large voltage hysteresis. We regulate the spin state of partial Ni 2+ metal centers (t 2g 6 e g 2 ) of conductive nickel catecholate framework (Ni II -NCF) nanowire arrays to high-valence Ni 3+ (t 2g 6 e g 1 ) for Ni III -NCF. The spin-state modulation enables enhanced nickel-oxygen covalency in Ni III -NCF, which facilitates electron exchange between the Ni sites and oxygen adsorbates and accelerates the oxygen redox kinetics. Upon discharging, the high affinity of Ni 3+ sites with the intermediate LiO 2 promotes formation of nanosheet-like Li 2 O 2 in the void space among Ni III -NCF nanowires. The Li-O 2 battery based on Ni III -NCF offers remarkably reduced discharge/charge voltage gaps, superior rate capability, and a long cycling stability of over 200 cycles. This work highlights the importance of electron spin state on the redox kinetics and will provide insight into electronic structure regulation of electrocatalysts for Li-O 2 batteries and beyond., (© 2021 Wiley-VCH GmbH.)