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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||Na3V2(PO4)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. [ABSTRACT FROM AUTHOR]

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||Na3V2(PO4)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. [ABSTRACT FROM AUTHOR]

Hard carbon (HC) is a promising anode material for sodium‐ion batteries, yet still suffers from low initial Coulombic efficiency (ICE) and unstable solid electrolyte interphase (SEI). Herein, sodium diphenyl ketone (Na‐DK) is applied to realize dual‐function presodiation for HC anodes. It compensates the irreversible Na uptake at the oxygen‐containing functional groups and reacts with carbon defects of five/seven‐membered rings for quasi‐metallic sodium in HC. The as‐formed sodium induces robust NaF‐rich SEI on HC in 1.0 M NaPF6 in diglyme, favoring the interfacial reaction kinetics and stable Na+ insertion and extraction. This renders the presodiated HC (pHC) with high ICE of ≈100 % and capacity retention of 82.4 % after 6800 cycles. It is demonstrated to couple with Na3V2(PO4)3 cathodes in full cells to show high capacity retention of ≈100 % after 700 cycles. This work provides in‐depth understanding of chemical presodiation and a new strategy for highly stable sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Hard carbon (HC) is a promising anode material for sodium‐ion batteries, yet still suffers from low initial Coulombic efficiency (ICE) and unstable solid electrolyte interphase (SEI). Herein, sodium diphenyl ketone (Na‐DK) is applied to realize dual‐function presodiation for HC anodes. It compensates the irreversible Na uptake at the oxygen‐containing functional groups and reacts with carbon defects of five/seven‐membered rings for quasi‐metallic sodium in HC. The as‐formed sodium induces robust NaF‐rich SEI on HC in 1.0 M NaPF6 in diglyme, favoring the interfacial reaction kinetics and stable Na+ insertion and extraction. This renders the presodiated HC (pHC) with high ICE of ≈100 % and capacity retention of 82.4 % after 6800 cycles. It is demonstrated to couple with Na3V2(PO4)3 cathodes in full cells to show high capacity retention of ≈100 % after 700 cycles. This work provides in‐depth understanding of chemical presodiation and a new strategy for highly stable sodium‐ion batteries. [ABSTRACT FROM AUTHOR]