Lin Li

Ether-based electrolytes have attracted considerable attention due to their excellent ion-transport kinetics and favorable interfacial compatibility with hard carbon anodes. However, their poor thermal stability severely limits the long-term stable operation of sodium-ion batteries (SIBs) under high-temperature operating conditions. Herein, a multi-anion ether-based electrolyte is proposed to concurrently boost the high-temperature tolerance and fast-charging performance of SIBs by regulating solvation structures and enriching electrolyte molecular diversity. The introduction of FSI– and TFSI– anions not only favors the formation of an anion-reinforced solvation microenvironment but also substantially diminishes the size of ionic clusters. The anion-reinforced solvation structure lowers the desolvation energy barrier and promotes the formation of robust, inorganic-rich electrode–electrolyte interphases, which significantly improves high-temperature stability. Meanwhile, the smaller ionic clusters facilitate higher ionic conductivity and homogeneous Na+ flux distribution, thereby effectively suppressing sodium plating under fast-charging conditions. As a result, the Prussian blue||hard carbon full cell delivers superior rate performance and cycling stability at a wide temperature range of 10–100 °C. In addition, Ah-level pouch cells exhibit stable cycling at 55 °C with a reversible capacity of 1023.58 mAh after 800 cycles (80.8% retention) and deliver a high discharge capacity of 1008.99 mAh at 2.0 C.

The application of sodium-ion batteries (SIBs) in wide-temperature and fast-charging scenarios is severely constrained by the performance limitations of electrolytes. Conventional ester-based electrolytes struggle to simultaneously achieve high ionic conductivity, low desolvation energy, and excellent interfacial stability. Herein, we propose a hybrid solvent system comprising ethyl propionate and ethoxy(pentafluoro)cyclotriphosphazene (PFPN), aiming to synergistically enhance the rate capability and temperature adaptability of SIBs. The relatively weak coordination ability of both solvents effectively promotes anion participation in solvation structure, significantly lowering the Na+ desolvation energy barrier and inducing the formation of stable, inorganic-rich electrode/electrolyte interphases. Meanwhile, the dual-solvent combination increases the diversity of solvation configurations and reduces ion clustering, thereby enhancing ionic conductivity. The intrinsic nonflammability and excellent film-forming ability of PFPN further enhance safety and synergistically strengthen interfacial stability. Therefore, Prussian blue||hard carbon full cells operate stably over a wide temperature range from −50 to 100 °C. Notably, ampere-hour-level pouch cells deliver a capacity retention of 86.3% after 300 cycles at 25 °C and maintain stable operation for over 100 cycles even at −20 and 80 °C. This solvent synergy strategy offers a practical new pathway for the development of electrolytes for SIBs in extreme environments.

Li–O2 batteries suffer from sluggish Li2O2 oxidation kinetics at electrode/electrolyte interfaces, leading to large charge polarization and low energy efficiency. Soluble redox mediators (RMs) provide a solution-mediated pathway for Li2O2 decomposition and reduce the charge overpotential. However, the chemical oxidation of Li2O2 by oxidized RMs remains kinetically sluggish, resulting in persistent charge polarization. Herein, iodine monochloride (ICl), an interhalogen compound, is electrochemically generated in situ during the charge process to promote the oxidation of Li2O2. The large electronegativity difference between I and Cl promotes intramolecular charge transfer from I to Cl, creating an electrophilic iodine center (Iδ+) that increases the I–Cl bond polarity and strengthens the interaction with Li2O2. This lowers the decomposition barrier of Li2O2 from 2.39 to 0.77 eV, thereby facilitating its chemical oxidation. The Li–O2 battery delivers a low discharge/charge polarization of 0.52 V, effectively mitigating parasitic reactions at high voltages and enabling an extended cycling lifespan exceeding 800 h. This work provides a valuable design principle for developing redox mediators for efficient Li2O2 oxidation.

In situ alloying of Zn with Cr forms a robust ZnCr interphase stabilizing Zn anodes, while atomic force microscopy enables real-time visualization of nucleation and lateral growth, offering mechanistic insights for aqueous zinc metal batteries.

Sodium-ion batteries (SIBs) for grid-scale energy storage require electrolytes with high-temperature durability and intrinsic safety. Here, we report a nonflammable triethyl phosphate/tetrahydrofuran (TEP/THF) hybrid electrolyte for high-temperature SIBs. Weakly coordinating THF increases anion participation in the Na+ solvation structure, promoting robust inorganic-rich interphases on both electrodes, while its low viscosity accelerates Na+ transport, enabling fast ion kinetics and stable interfacial chemistry. As a result, Prussian blue||hard carbon full cells exhibit good rate capability and retain 76.0% capacity after 500 cycles at 80 °C, and 18650 cylindrical cells maintain 80.6% capacity after 300 cycles at 80 °C. Nail-penetration tests show no combustion or smoke, with a peak temperature of only 88.9 °C. Moreover, the electrolyte also supports stable cycling of layered oxide cathodes at 80 °C. This work provides a viable electrolyte design strategy for high-temperature and high-safety SIBs.

The sodium storage structure–performance relationship of hard carbon anodes has long been regarded as an intrinsic material property and forms the basis for electrode design. This common view, however, does not hold with varying operating temperatures. At room temperature, optimally structured hard carbon with enhanced plateau capacity still exhibits poor rate performance due to kinetic limitations. In contrast, the same hard carbon delivers drastically improved high-rate capability at elevated temperatures from 36.89 mAh g–1 to 253.97 mAh g–1 at 1.0 A g–1, with the plateau capacity further increasing from 12.75 mAh g–1 to 203.42 mAh g–1, which cannot be explained by the conventional structure–performance relationship. Our mechanistic work shows that the accelerated ion/electron transport and a thin, inorganic-rich solid electrolyte interphase synergistically unlock pore-filling sodium storage, dominating the performance enhancement. These results go against the conventional steady view and establish a non-steady-state structure–performance relationship, where hard carbon’s sodium storage behavior is dynamically regulated by testing conditions. This concept is validated in Ah-level pouch cells (28.2% vs 85.0% high capacity retention at 0.75 A g–1) and commercial cylindrical cells (60.1% vs 84.5% at 6.0 A g–1), providing a new design guideline for sodium ion batteries under practical temperature-varying conditions.

Anionic redox reactions (ARR) are an effective strategy to enhance the reversible capacity of layered oxide cathode materials, thereby enabling high‐energy‐density sodium‐ion batteries (SIBs). However, ARR generates highly reactive and unstable oxygen species that may trigger nucleophilic attacks and compromise cathode–electrolyte interface (CEI) stability, causing structural degradation and rapid capacity fading. In this study, we introduce dimethyl 2‐fluoromalonate (2MDF) as a multifunctional cosolvent into a conventional carbonate electrolyte to stabilize ARR in Na _0.67 Li _0.24 Mn _0.64 Mg _0.06 Ti _0.06 O ₂ (NLMMT) cathode. 2MDF, characterized by its low coordination ability, preferential oxidation characteristics, and fluorinated ester groups, simultaneously modulates Na ⁺ solvation, promotes formation of a robust inorganic‐rich CEI, and suppresses nucleophilic attack by reactive oxygen species. Density functional theory calculations and electrochemical analyses reveal that 2MDF forms weaker interactions with reactive oxygen species than conventional carbonates, enabling superior interfacial stability and preferential sacrificial oxidation. Consequently, the NLMMT cathode exhibits a high reversible capacity of 255.3 mAh g ⁻¹ at 20 mA g ⁻¹ and outstanding cycling stability, retaining 72% capacity after 400 cycles at 400 mA g ⁻¹ in the voltage range of 1.5–4.5 V. This study establishes a rational electrolyte design strategy that balances oxidative stability and nucleophilic resistance, providing general guidance for achieving reversible ARR in high‐energy SIBs.

Hard carbon is the most practical anode for sodium‐ion batteries, yet its deployment is hindered by an unstable, non‐uniform solid electrolyte interphase (SEI) that causes irreversible Na loss, high interfacial resistance, and capacity fading. This review discusses SEI formation as a dynamic coupling between electrolyte chemistry and the local carbon interface, and discuss the interactions of solvation structure, anion chemistry, concentration, and additives with hard carbon surface groups, dopants, pores, and defects to govern SEI properties. Based on this understanding, we propose a perspective framework for electrolyte‐hard carbon interphase synergy, which includes four coupled design directions: (i) solvation‐pore coupling to balance desolvation, pore accessibility, and confined sodium storage; (ii) surface‐ and additive‐guided electrolyte decomposition to regulate SEI composition; (iii) pore‐defect‐electrolyte regulation to enable selective Na ⁺ transport while suppressing intrapore SEI growth; (iv) constructing chemically and mechanically robust interphases through inorganic‐organic hybrid architectures. A key gap remains the missing in operando link between interfacial electric fields and SEI evolution, hindering rational design of self‐limiting passivation. We outline future directions toward chemically robust, ultrathin, and ionically conductive interphases for high‐performance sodium‐ion batteries.

Sodium metal batteries (SMBs) hold great promise for next‐generation energy storage systems due to their abundant sodium resources, high theoretical specific capacity, and low redox potential. However, they suffer from rapid capacity degradation at low operating temperatures, which inevitably hinders their practical application. In this work, we employ a strongly coordinating anion and a weakly solvating cosolvent to fabricate anion‐rich and varied solvation structures, aiming to enhance the low‐temperature electrochemical performance of SMBs. This unique solvation configuration efficiently reduces the Na ⁺ desolvation energy barrier, alleviates concentration polarization, accelerates liquid‐phase ion transport, and facilitates the in‐situ formation of a stable, highly ion‐conductive electrode‐electrolyte interphase. Benefiting from the synergistic regulation of interfacial stability and ion transport kinetics, dendrite‐free sodium deposition is achieved at −20°C, enabling stable cycling for over 500 h at 0.5 mA cm ⁻² and 0.5 mAh cm ⁻² . Additionally, the assembled SMBs exhibit excellent rate performance and cycling stability, delivering a high capacity retention of 70.54% and 68.28% after 1000 cycles at −20°C and −40°C, respectively. This work provides a novel perspective for the rational design of advanced electrolytes for high‐performance low‐temperature SMBs and lays a solid foundation for their practical application in cold environments.