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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]

The sodium extraction/insertion in layered transition‐metal oxide (TMO) cathode materials are typically accompanied by slab sliding and lattice changes, leading to microstructure destruction and capacity decay. Herein, negative lattice expansion is observed in an O3 type Ni‐based layered cathode of Na0.9Ni0.32Zn0.08Fe0.1Mn0.3Ti0.2O2 upon Na+ extraction. It is attributed to the weak Zn2+−O2− orbital hybridization and increased electron density of the surrounding oxygen for reinforced interlayer O−O repulsive force. This enables gliding of TMO slabs for the intergrowth phase transition of P3→OP2 to alleviate lattice strain with moderate lattice shrinkage, which exhibits general interslab spacings and volume changes as low as 2.4 % and 1.9 %, respectively. The strong Ti−O bonds accommodate the internal distortion of TMO6 octahedra due to the flexibility of TiO6 octahedra during cycling. These endow a high specific capacity of 144.9 mAh g−1 and excellent cycling performance of pouch‐type sodium‐ion batteries with 93 % capacity retention after 3600 cycles. [ABSTRACT FROM AUTHOR]

The sodium extraction/insertion in layered transition‐metal oxide (TMO) cathode materials are typically accompanied by slab sliding and lattice changes, leading to microstructure destruction and capacity decay. Herein, negative lattice expansion is observed in an O3 type Ni‐based layered cathode of Na0.9Ni0.32Zn0.08Fe0.1Mn0.3Ti0.2O2 upon Na+ extraction. It is attributed to the weak Zn2+−O2− orbital hybridization and increased electron density of the surrounding oxygen for reinforced interlayer O−O repulsive force. This enables gliding of TMO slabs for the intergrowth phase transition of P3→OP2 to alleviate lattice strain with moderate lattice shrinkage, which exhibits general interslab spacings and volume changes as low as 2.4 % and 1.9 %, respectively. The strong Ti−O bonds accommodate the internal distortion of TMO6 octahedra due to the flexibility of TiO6 octahedra during cycling. These endow a high specific capacity of 144.9 mAh g−1 and excellent cycling performance of pouch‐type sodium‐ion batteries with 93 % capacity retention after 3600 cycles. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Layered transition‐metal oxides are promising cathode candidates for sodium‐ion batteries. However, the inferior interphase formation and particulate fracture during sodiation/desodiation result in structure degradation and poor stability. Herein, the interface chemistry of P2‐Na0.640Ni0.343Mn0.657O2 in an electrolyte of 1.0 mol/L NaPF6 in diglyme is unveiled to enable highly reversible Na extraction and intercalation. The uniform and robust cathode‐electrolyte interphase layer is in situ formed with decomposition of diglyme molecules and anions in initial cycles. The NaF‐ and CO‐rich CEI film exhibits high mechanical strength and ionic conductivity, which suppresses the reconstruction of its electrode interphase from P2 phase to spinel‐like structure and reinforces its structure integrity without cracks. This favours facile Na+ transport and stable bulk redox reactions. It is demonstrated to show long cycling stability with capacity retention of 94.4% for 180 cycles and superior rate capability. This investigation highlights the cathode interphase chemistry in 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]

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]