All-solid-state sodium metal batteries paired with solid polymer electrolytes (SPEs) are considered a promising candidate for high energy-density, low-cost, and high-safety energy storage systems. However, the low ionic conductivity and inferior interfacial stability with Na metal anode of SPEs severely hinder their practical applications. Herein, an anion-trapping 3D fiber network enhanced polymer electrolyte (ATFPE) is developed by infusing poly(ethylene oxide) matrix into an electrostatic spun fiber framework loading with an orderly arranged metal-organic framework (MOF). The 3D continuous channel provides a fast Na+ transport path leading to high ionic conductivity, and simultaneously the rich coordinated unsaturated cation sites exposed on MOF can effectively trap anions, thus regulating Na+ concentration distribution for constructing stable electrolyte/Na anode interface. Based on such advantages, the ATFPE exhibits high ionic conductivity and considerable Na+ transference number, as well as enhanced interfacial stability. Consequently, Na/Na symmetric cells using this ATFPE possess cyclability over 600 h at 0.1 mA cm-2 without discernable Na dendrites. Cooperated with Na3 V2 (PO4 )3 cathode, the all-solid-state sodium metal batteries (ASSMBs) demonstrate significantly improved rate and cycle performances, delivering a high discharge capacity of 117.5 mAh g-1 under 0.1 C and rendering high capacity retention of 78.2% after 1000 cycles even at 1 C.
Abstract Sodium metal batteries (SMBs) using gel polymer electrolytes (GPEs) with high theoretical capacity and low production cost are regarded as a promising candidate for high energy‐density batteries. However, the inherent flammability of GPEs and uncontrolled Na dendrite caused by inferior mechanical properties and interfacial stability hinder their practical applications. Herein, an anion‐trapping fireproof composite gel electrolyte (AT‐FCGE) is designed through a chemical grafting–coupling strategy, where functionalized boron nitride nanosheets (M‐BNNs) used as both nanosized crosslinker and anion capturer are coupled with poly(ethylene glycol)diacrylate in poly(vinylidene fluoride‐co‐hexafluoropropylene) matrix, to expedite Na + transport and suppress dendrite growth. Experimental and calculation studies suggest that the anion‐trapping effect of M‐BNNs with abundant Lewis‐acid sites can promote the dissociation of salts, thus remarkably improving the ionic conductivity and Na + transference number. Meanwhile, the formation of highly crosslinked semi‐interpenetrating network can effectively in situ encapsulate non‐flammable phosphate without sacrificing the mechanical properties. Consequently, the resulting AT‐FCGE shows significantly enhanced Na + conductivity, mechanical properties, and excellent interfacial stability. The AT‐FCGE enables a long‐cycle stability dendrite‐free Na/Na symmetric cell, and prominent electrochemical performance is demonstrated in solid‐state SMBs. The approach provides a broader promise for the great potential of fire‐retardant gel electrolytes in high‐performance SMBs and the beyond.
Uncontrolled dendrite growth and water-related side reactions in mild electrolytes are the main causes of poor cycling stability of zinc anodes, resulting in the deterioration of aqueous zinc-based batteries. Herein, a multifunctional fluorapatite (Ca5(PO4)3F) aerogel (FAG) interface layer is proposed to realize highly stable zinc anodes via the integrated regulation of Zn2+ migration kinetics and Zn (002) orientation deposition. Owing to the well-defined aerogel nanochannels and the rich Zn2+ adsorption sites resulting from the ion exchange between Ca2+ and Zn2+, the FAG interface layer could significantly accelerate the Zn2+ migration and effectively homogenize the Zn2+ flux and nucleation sites, thus promoting rapid and uniform Zn2+ migration at the electrode/electrolyte interface. Additionally, during the cycling process, the F atoms from FAG promote the in situ generation of ZnF2, which facilitates the manipulation of the preferred Zn (002) orientation deposition, thus efficiently suppressing dendrite growth and side reactions by combining with the above synergistic effects. Consequently, the FAG-modified Zn anode displays a stable cycle life of over 4000 h at 1 mA cm-2 and exhibits highly reversible Zn plating/stripping behavior. Meanwhile, the Zn||MnO2 full cells exhibit improved cycle stability over 2000 cycles compared with that of the bare Zn, highlighting the virtues of the FAG protective layer for highly reversible Zn anodes. Our work brings the insight in to stabilize Zn anodes and power the commercial applications of aqueous zinc-based batteries.
Abstract Sodium iron hexacyanoferrate (FeHCF) is one of the most promising cathode materials for sodium‐ion batteries (SIBs) due to its low cost theoretical capacity. However, the low electrochemical activity of Fe LS (C) in FeHCF drags down its practical capacity and potential plateau. Herein, FeHCF with high Fe LS (C) electrochemical activity (C‐FeHCF) is synthesized via a facile citric acid‐assisted solvothermal method. As the cathode of SIBs, C‐FeHCF shows superior cycling stability (ca. 87.3% capacity retention for 1000 cycles at 10 C) and outstanding rate performance (ca. 68.5% capacity retention at 50 C). Importantly, the contribution of Fe LS (C) to the whole capacity was quantitatively analyzed via combining dQ/dV and discharge curve for the first time, and the index reaches 44.53% for C‐FeHCF, close to the theoretical value. In‐situ X‐ray diffraction proves the structure stability of C‐FeHCF during charge–discharge process, ensuring its superior cycling performance. Furthermore, the application feasibility of the C‐FeHCF cathode in quasi‐solid SIBs is also evaluated. The quasi‐solid SIBs with the C‐FeHCF cathode exhibit excellent electrochemical performance, delivering an initial discharge capacity of 106.5 mAh g −1 at 5 C and high capacity retention of 89.8% over 1200 cycles. This work opens new insights into the design and development of advanced cathode materials for SIBs and the beyond.
Abstract Composite polymer electrolytes demonstrate the predictable potential for achieving high‐performance all‐solid‐state sodium metal batteries (ASSMBs). However, the insufficient ionic conductivity resulting from the sluggish Na + transport kinetics and the inferior interfacial stability caused by simultaneous Na + and anion transport have hindered practical applications. Herein, a rational structural design strategy is proposed to construct an anion‐trapping boron‐contained covalent organic framework (B‐COF) network in the polymer matrix to facilitate selective Na + migration and interfacial compatibility for ASSMBs. The abundant Lewis‐acid sites on the B‐COF network can promote the dissociation of sodium salt and simultaneously constrain the migration of TFSI − anions through the strong anion‐capturing effect. Moreover, the well‐defined ion‐conducting channel formed by the in situ generation of intimately packed B‐COF combined with the above synergistic effects can afford continuous and accessible pathways for selectively rapid Na + transport, which significantly elevates the ionic conductivity and Na + transference number, respectively. Surprisingly, the Na plating/stripping with small polarization is retained under 0.1 mA cm −2 for more than 365 d (>8800 h), representing a record‐high cycling stability for ASSMBs. As proof of applied studies, the ASSMBs exhibit a high capacity retention (≈81.2%) after 1200 cycles at 1 C, signifying promising application in all‐solid‐state electrochemical energy storage systems.
Abstract Dendritic deposition and side reactions have been long‐standing interfacial challenges of Zn anode, which have prevented the development of practical aqueous zinc‐based batteries. Herein, an oxygen vacancy‐rich CeO 2 aerogel (VAG‐Ce) interface layer that simultaneously integrates Zn 2+ selectivity, porosity, and is lightweight is reported as a new strategy to achieve dendrite‐free and corrosion‐free Zn anodes. The well‐defined and uniform nanochannels of VAG‐Ce can act as ion sieves that redistribute Zn 2+ at the Zn anode surface by regulating Zn 2+ flux, leading to uniform Zn deposition and significantly suppressing dendrite growth. Importantly, the abundant oxygen vacancies exposed on VAG‐Ce surface can strongly capture SO 4 2− , forming a negatively charged layer that can attract Zn 2+ and accelerate the Zn 2+ migration kinetics, while the subsequent repulsion of additional anions can effectively suppress the generation of (Zn 4 SO 4 (OH) 6 · x H 2 O) byproducts, thereby realizing very stable Zn anodes. Consequently, VAG‐Ce modified Zn anode (VAG‐Ce@Zn) enables a long‐term lifespan over 4000 h at 4 mA cm −2 and a record‐high cycle life of 1200 h is achieved under an ultrahigh 85% Zn utilization at 8 mA cm −2 , which enables excellent capacity retention and cycling performance of VAG@Zn/MnO 2 cells. This work contributes an innovative design concept by introducing oxygen vacancy‐rich aerogels and provides a new horizon for stabilizing Zn anode for large‐scale energy storage.
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