Dynamic Lock-And-Release Mechanism Enables Reduced ΔG at Low Temperatures for High-Performance Polyanionic Cathode in Sodium-Ion Batteries

Orthogonal decoupling of an ionic-electronic transport microarchitectured vertical array cathode for flexible sodium-ion batteries

Vertically-aligned Na3V2O2(PO4)2F cathodes with orthogonal ion/electron pathways exhibit enhanced Na+ diffusion (5.8 × 10-12 m2 s-1), delivering 131 mA h g-1 at 0.2C, 85 mA h g-1 at 5C, and 96% capacity retention after 1000 cycles for flexible energy storage.

In Situ Converting Conformal Sacrificial Layer Into Robust Interphase Stabilizes Fluorinated Polyanionic Cathodes for Aqueous Sodium-Ion Storage

Sodium vanadium oxy-fluorophosphates (NVOPF), as typical fluorinated polyanionic compounds, are considered high-voltage and high-capacity cathode materials for aqueous sodium-ion storage. However, the poor cycle life caused by interfacial degradation (especially the attack of specific HF by-products) greatly hampers their application in aqueous electrolytes. Here, it is shown that in situ converting harmful HF derivate to F-containing cathode electrolyte interphase (CEI) can overcome the above challenge. As a proof-of-concept, a conformal Al2O3 sacrificial layer is precoated on NVOPF for on-site generating robust AlF3-rich CEI while eliminating continuous HF release. The evolved CEI chemistry mitigates interfacial side reactions, inhibits vanadium dissolution, and promotes Na+ transport kinetics, thus significantly boosting cycling stability (capacity retention rate increased to 3.15 times), rate capability, and even low-temperature performance (≈1.5 times capacity improvement at -20 °C). When integrated with pseudocapacitive zeolite-templated carbon anode and adhesive hydrogel electrolyte, a unique 2.3 V quasi-solid-state sodium-ion hybrid capacitor is developed, exhibiting remarkable cycle life (77.0% after 1000 cycles), high energy and power densities, and exceptional safety against extreme conditions. Furthermore, a photovoltaic energy storage module is demonstrated, highlighting the potential use in future smart/microgrids. The work paves new avenues for enabling the use of unstable electrode materials via interfacial engineering.

Designing Cellulose Triacetate-Based Universal Binder for High-Voltage Sodium-Ion Battery Cathodes with Enhanced Ionic Conductivity and Binding Strength

Binders play a pivotal role in the performance of sodium-ion battery (SIB) cathodes, but traditional binders often struggle to balance broad compatibility, high ionic conductivity, superior binding strength, and environmental sustainability. In this study, a universal cellulose triacetate (TAC)-based binder (TAC-MMT) composed of TAC and natural montmorillonite (MMT) is designed to facilitate rapid Na+ transport pathways and establish a robust hydrogen-bonding network. This innovative TAC-MMT binder features a unique chemical structure that achieves high ionic conductivity through a self-enrichment and fast-transport mechanism, while its superior binding strength is attributed to hydrogen-bonding crosslinks between proton acceptors (C═O) in TAC and proton donors (-OH) in MMT. More importantly, the outstanding solubility and film-forming properties of TAC-MMT contribute to stable electrode protection and broad compatibility with high-voltage SIB cathodes. Benefiting from these advantages, the Na3V2(PO4)2O2F (NVPOF) electrodes with the TAC-MMT binder demonstrate exceptional performance, including a high capacity retention of 95.2% over 500 cycles at 5C and a rapid rate response of up to 15C. The versatility of the TAC-MMT binder is further confirmed with high-voltage NaNi1/3Fe1/3Mn1/3O2 and Na0.61[Mn0.27Fe0.34Ti0.39]O2 cathodes. This study highlights the potential of biomass-based binders as a sustainable and effective solution for advancing high-performance sodium-ion batteries.