Recent progress and strategic perspectives of inorganic solid electrolytes: fundamentals, modifications, and applications in sodium metal batteries

Copper-doped metal-organic framework-74 solid-state electrolytes for high performance all-solid-state sodium metal batteries

Rechargeable solid sodium metal batteries are attractive by virtue of their high energy density and cost-effectiveness. However, the inefficient Na+ transport dynamics and short lifepan hinder the practical application of solid sodium battery. Mg-MOF-74 nanomaterials have emerged as promising candidates for solid-state electrolytes because of their homogeneous porous structure and highly exposed metal sites. Nonetheless, the Na+ conductivity of pristine Mg-MOF-74 solid-state electrolytes is limited by sluggish ion movement. In this study, we successfully developed a series of bimetallic MOFs, specifically Cu2Mg8-MOF-74, by introducing copper doped metal to Mg-MOF-74. This metal-doped MOF electrolytes possess excellent Na+ transport and enhanced electrochemical stability in solid sodium metal batteries. The bimetallic sites of Cu2Mg8-MOF-74 deliver a superior capability to anchor anion ClO4- than single Mg sites in Mg-MOF-74, as validated by density functional theory calculation. Benefiting from that, Cu2Mg8-MOF-74 electrolytes substantially increase the ionic conductivity to 3.18 × 10-3 S cm-1 and the Na+ transference number to 0.86 at room temperature. Additionally, Na3V2(PO4)3|Cu2Mg8-MOF-74|Na cells demonstrated a high specific capacity of 104.5 mAh g-1 at 1C, with an impressive capacity retention rate of 91 %. Overall, this study delivers a viable method to optimize MOF materials for improved Na+ conductivity in future applications.

Amorphous-Nanocrystalline Fluorinated Halide Electrolytes with High Ionic Conductivity and High-Voltage Stability

All-solid-state sodium-ion batteries (ASSSIBs) offer a cost-effective, scalable alternative to rechargeable lithium-ion batteries, but their advancement requires solid electrolytes with high ionic conductivity, wide electrochemical stability, and robust interfacial compatibility. Here, a fluorine-doped halide solid electrolyte (2NaF-ZrCl4, 2-NFZC) featuring an amorphous-nanocrystalline structure with high ionic conductivity (2.35 × 10-4 S cm-1 at 25 °C) and good high-voltage stability is presented. Fluorine doping in 2-NFZC promotes Zr-F bonding with limited Na-F interaction, which facilitates fast Na-ion transport through disordered regions and the NaF/amorphous phase interface. Paired with a NaNi1/3Fe1/3Mn1/3O2 cathode, a Na15Sn4 anode, and a Na3PS4 anode interlayer, the all-solid-state cell with the 2-NFZC electrolyte demonstrates a discharged capacity of 137.1 mAh g-1, 81.1% capacity retention over 600 cycles, and suppressed interfacial side reactions. These findings highlight the potential of fluorine doping in designing advanced solid electrolytes for high-performance all-solid-state Na-ion batteries.

Computational approaches to electrolyte design for advanced lithium-ion batteries

Theoretical calculations have shown great potential as an instructional, reliable, and robust tool for designing and optimizing electrolyte formulations for lithium-ion batteries. However, there is still a lack of clear understanding of the design principles and synergistic effects between each component of electrolytes, including lithium salts, solvents, additives, etc., especially on how to optimize each part of electrolytes from the atomic scale and molecular scale. In this review, we cover the quantum chemistry in lithium salt selection, functional additive design, solid electrolyte interphase film study, and reaction mechanism speculation; molecular dynamics simulations in solvation structures, interphase simulations, and dendrite growth studies; and high throughput simulations in functional electrolyte screening. Meanwhile, the limitations of each type of simulation are discussed. Finally, conclusions and an outlook regarding theoretical calculations for the electrolyte design of lithium-ion batteries are presented.

Bilayer Mn-based Prussian blue cathode with high redox activity for boosting stable cycling in aqueous sodium-ion half/full batteries

The Mn-based Prussian blue analogs (PBAs) have garnered significant attention due to their high specific capacity, stemming from the unique multi-electron reactions with Na+. However, the structural instability caused by multi-ion insertion impacts the cycle life, thus limiting their further application in aqueous sodium-ion batteries (ASIBs). To address this issue, this work employed an in situ epitaxial solvent deposition method to homogeneously grow Ni hexacyanoferrate (NiHCF) on the surface of MnPBA, which can effectively overcome the de-intercalation instability. The resulting heterostructured MnPBA@NiHCF integrates the multiple redox-active centers of MnPBA with the confinement ability of the outer NiHCF layer, thereby maintaining overall structural stability. As a cathode material for ASIBs, MnPBA@NiHCF achieves a reversible specific capacity of 66.2 mAh/g after 200 cycles at 1 A/g, significantly outperforming the single-component MnPBA and NiHCF, respectively. Moreover, it demonstrates ultralong cycling stability with only 0.0002 % capacity fade per cycle over 20,000 cycles at 10 A/g. Extensive kinetic analyses further confirm its superior Na+ diffusion behaviors with disclosed redox mechanism through the comprehensive in situ Raman and ex situ analysis. A full cell built with a polyimide (PI) anode achieved an energy density of up to 59.9 Wh kg-1, displaying a power output of 1200.4 W kg-1 and exceptional cycle stability. This work provides innovative insights for developing stable PBA cathodes for ASIB applications.

In Situ Assembly Engineering-Induced 3D MOF-Driven MXene Framework for Highly Stable Na Metal Anodes

Sodium metal, with its high theoretical capacity, low redox potential, and cost-effectiveness, presents a promising anode candidate for next-generation high-energy-density batteries. However, the development of Na metal anodes is significantly challenged by issues such as uncontrolled dendrite growth, uncontrolled volume expansion, and associated safety concerns. Designing and developing advanced materials to enhance the conductivity of sodium metal anodes and promote uniform sodium ion deposition are of urgent importance. Herein, a MXene-based hybrid material was developed by integrating MOF-derived Zn, Co, N, and C dopants with Ti3C2Tx MXene to serve as a hosting substrate for the Na metal anode. The MXene provided a conductive framework, while the MOF-derived dopants introduced sodiophilic sites, promoting uniform Na deposition and mitigating volume expansion. The optimized material demonstrated an average Coulombic efficiency of 99.99% over 3000 cycles and stable cycling for over 5000 h in symmetrical cells and maintained over 80% capacity retention at 3 C after 500 cycles in full-cell tests, highlighting its potential as a robust Na metal anode material.

In Situ Construction of a 3D Superionic Skeleton in Sodium Anode for Solid-State Sodium Batteries with a 15 000-Cycle Lifespan at 3C

Solid-state sodium-metal batteries (SSSMBs) have emerged as a promising candidate for next-generation energy storage systems due to their natural abundance, cost-effectiveness, and high safety. However, the intrinsically low ionic conductivity of sodium anode (SA) and poor wettability to solid-state electrolyte (SSE) severely hinder the development of SSSMBs. In this study, a 3D superionic transport skeleton Na3P is in situ constructed within the sodium anode by simply melting inexpensive and low-density red phosphorus with sodium, which successfully enhances the ion diffusion rate from 2.54 × 10‒8 to 1.33 × 10‒7 cm2 s‒1. Moreover, Na3P in the composite sodium anode (CSA) effectively induces the uniform deposition of Na on the surface of SSE, significantly reducing the interface impedance of symmetric cells from the initial value of 749.15 to 14.97 Ω cm2. Enabled by the integrated 3D superionic transport skeleton, the symmetric cell achieves exceptional cycle stability of over 7000 h at 0.1 mA cm‒2 and 4000 h at 0.3 mA cm‒2. Furthermore, SSSMBs incorporating CSA demonstrate an ultralong lifespan of over 15 000 cycles at 3C while maintaining a high-loading operation capability, significantly outperforming previously reported studies. This study highlights the crucial role of cost-effective CSA design with enhanced ion transport in advancing high-performance SSSMBs.

Robust and Antioxidative Quasi-Solid-State Polymer Electrolytes for Long-Cycling 4.6 V Lithium Metal Batteries

Quasi-solid-state polymer electrolytes (QSPEs) have been considered as one of the most promising electrolytes for high-safety high-energy-density lithium metal batteries (LMBs). However, their inadequate mechanical properties and instability under high voltages pose significant challenges for practical applications. Herein, robust and antioxidative QSPEs are developed based on a polymer-brush-based rigid supporting film (BC-g-PLiMTFSI-b-PPFEMA, BC: bacterial cellulose, PLiMTFSI: poly(lithium (3-methacryloyloxypropylsulfonyl) (trifluoromethylsulfonyl)imide), PPFEMA: poly(2-(perfluorohexyl)ethyl methacrylate)). The robust BC nanofibril backbone can produce a highly porous supporting structure with outstanding mechanical strength. More importantly, the PLiMTFSI-b-PPFEMA side-chains can not only obviously increase the conversion ratio of easily oxidized monomers in QSPEs, but also possess strong interaction with unstable electrolyte components. With such QSPEs as solid-state electrolytes, the Li/LiNi0.8Mn0.1Co0.1O2 full cell with a high cathode loading (20.3 mg cm-2) exhibits a specific discharge capacity of 200.7 mAh g-1 at 0.5 C and demonstrates a long lifespan of 137 cycles with a highly retained capacity of 170.7 mAh g-1 under a cut-off voltage of 4.5 V. More importantly, under a high cut-off voltage of 4.6 V, a high specific capacity of 147.0 mAh g-1 after 187 cycles can be retained for solid-state Li/LiCoO2 cells. This work provides a feasible development strategy of QSPEs for practical long-cycling high-voltage LMBs.

Advanced Interphases Layers for Dendrite-Free Sodium Metal Anodes

Sodium (Na) metal anode is considered the cornerstone of next-generation energy storage technology, owing to its high theoretical capacity and cost-effectiveness. However, the development of Na metal batteries is hindered by the instability and nonuniformity of the solid electrolyte interphase (SEI) and notorious formation of Na dendrites. Recently, various advanced artificial interphase designs have been developed to control notorious dendrite growth and stabilize the SEI layer. In this Review, we provide a comprehensive overview of artificial interphase designs, focusing on inorganic interphase layer, organic interphase layer, and hybrid inorganic/organic interphase layer, all aimed at inhibiting the notorious Na dendrites growth. Finally, future interphase engineering strategies are also envisioned to offer new insights into the optimization of Na anodes.

Fluorinated amorphous halides with improved ionic conduction and stability for all-solid-state sodium-ion batteries

Designing halide solid electrolytes with high ionic conductivity and good (electro)chemical stability is essential for the advancement of all-solid-state sodium-ion batteries. Unfortunately, most sodium-based halide solid electrolytes experience limited ionic conductivities and ambiguous correlations between their structure features and ion transport properties. Here we report a design strategy to boost the conductivities of sodium halides by regulating vacancy and charge carrier concentrations through a facile Na- and Cl-deficient compositions method. This approach achieves a balanced structure with optimal vacancy and carrier content, rendering several-fold conductivities enhancement of series sodium halides. Furthermore, a fluorination-induced amorphization protocol is employed to enhance (electro)chemical stability and interfacial compatibility without detrimentally influencing conductivities. The promoted conductivities of the fluorinated sample are primarily due to increased local structural disorder and enhanced prismatic Na coordination. When paired with an uncoated Na3V2(PO4)3 positive electrode and a Na3PS4-coated Na15Sn4 negative electrode, the Na0.5ZrCl4F0.5 catholyte enables the battery to run for 300 cycles, retaining 94.4% of its initial discharge capacity at room temperature. This study provides a versatile pathway for creating inorganic ion conductors with high conductivity and long-term cyclability, advancing the development of all-solid-state sodium-ion batteries.

Mn Dopant Na3Zr2Si2PO12 with Enhanced Ionic Conductivity for Quasi-Solid-State Sodium-Metal Battery

As a promising solid electrolyte, the NASICON-type Na3Zr2Si2PO12 holds excellent application in solid-state sodium-ion batteries, which are an alternative to lithium batteries. However, its insufficient conductivity is one of the key factors impeding its applications. Herein, we report Mn2+-doped Na3Zr2Si2PO12, demonstrating enhanced ionic conductivity and electrochemical properties. We systematically investigate the effect of doping content on the ionic conductivity. The results show that Na3.4Zr1.8Mn0.2Si2PO12 has an extremely high room-temperature ionic conductivity of 3.3 mS cm-1, which is 4 times that of undoped Na3Zr2Si2PO12. According to the Meyer-Nedle rule, it can be known that as the activation energy decreases, the ionic conductivity shows a gradually increasing trend. Additionally, the Na symmetric batteries using Mn2+-doped Na3Zr2Si2PO12 exhibit improved cycling performance. The quasi-solid-state sodium-metal battery using Na3V2(PO4)3 achieves a high discharge specific capacity of 91.3 mAh g-1 at 0.1C, with a high capacity retention of 92.2% after 260 cycles, far surpassing the counterpart based on undoped Na3Zr2Si2PO12. This work provides an effective strategy for enhancing the performance of Na3Zr2Si2PO12 for its application in sodium-metal batteries.

Sulfide electrolytes for all-solid-state sodium batteries: fundamentals and modification strategies

Sulfide solid-state electrolytes (SSSEs) have garnered overwhelming attention as promising candidates for high-energy-density all-solid-state sodium batteries (ASSSBs) due to their high room-temperature ionic conductivity and excellent mechanical properties. However, the poor chemical/electrochemical stability, narrow electrochemical windows, and limited adaptability to cathodes/anodes of SSSEs hinder the performance and application of SSSEs in ASSSBs. Consequently, a comprehensive understanding of the preparation methods, fundamental properties, modification techniques, and compatibility strategies between SSSEs and electrodes is crucial for the advancement of SSSE-based ASSSBs. This review summarizes the SSSEs based on their compositional makeup and crystal structure, aiming to elucidate the Na+ conduction mechanisms. It also provides an overview of modification strategies designed to enhance ionic conductivity, chemical/electrochemical stability, and interfacial compatibility with electrodes. Furthermore, we outline the challenges and strategies related to the interfaces of SSSEs with cathodes/anodes. Finally, we discuss the existing challenges facing SSSEs and propose the future research directions for SSSE-based ASSSBs.

Multifunctional Nanocomposite Polymer-integrated Ca-doped CeO2 Electrolyte for Robust and High-rate All-solid-state Sodium-ion Batteries

Due to the seamless interfaces between solid polymer electrolytes (SPEs) and electrode materials, SPEs-based all-solid-state sodium-ion batteries (ASSSIBs) are considered promising energy storage systems. However, the sluggish Na+ transport and uncontrollable Na dendrite propagation still hinder the practical application of SPEs-based ASSSIBs. Herein, Ca-doped CeO2 (Ca-CeO2) nanotube framework is synthesized and integrated with poly (ethylene oxide) methyl ether acrylate-perfluoropolyether copolymer (PEOA-PFPE), resulting in multifunctional solid nanocomposite electrolytes (namely SNEs, i.e., PEOA-PFPE/Ca-CeO2). Our investigations demonstrate that the fluorous effect incurred by the fluorine-containing PEOA-PFPE and the oxygen vacancy effect induced by the Ca-CeO2 framework could synergistically promote the dissociation of sodium salt, ultimately enhancing the Na+ mobility in SNEs. Besides, the resultant SNEs construct rapid Na+ transport channels and homogenize the Na deposition in SNEs/Na interface, which effectively prevents the Na dendrite growth. Furthermore, the assembled carbon-coated sodium vanadium phosphate (NVP@C)||PEOA-PFPE/Ca-CeO2||Na coin cell delivers impressive rate capability of 97.9 mAh g-1 at 2 C and outstanding cycling stability with capacity retention of 84.3 % after 300 cycles at 1 C. This work illustrates that constructing multifunctional SNEs via incorporating functional inorganic frameworks into fluorine-containing SPEs could be a promising strategy for the commercialization of robust and high-performance ASSSIBs.

A modified separator based on ternary mixed-oxide for stable lithium metal batteries

Li metal batteries (LMBs) are among the most promising options for next-generation secondary batteries under the rapidly growing demand for high-energy-density electrochemical energy storage. However, the implementation of LMBs are hindered by major obstacles such as dentritic Li deposition and low cycling Coulombic efficiency. A practical functional separator is developed in this study, which consists of a Lewis acidic mixed oxide of ZrO2-SiO2-Al2O3 as a functional coating with anion anchoring ability to modulate ion transport in the vicinity of the Li metal anode, delivering a high Li+ transference number of 0.88 in carbonate electrolytes that suppresses dendrite formation. The strong Lewis acid sites in ZrO2-SiO2-Al2O3 originate from coordinatively unsaturated Zr4+ ions, which immobilize anions and reduce their decomposition rate. This significantly improves the chemical stability of the electrolyte and induces a more stable solid electrolyte interphase layer. The modified separator enables an anode-free cell containing a high-loading LiNi0.8Co0.1Mn0.1O2 cathode to present stable charge and discharge cycling for 150 cycles at 0.5C. By effectively suppressing Li dendrite growth and supporting the long-term operation of anode-free LMBs, this study offers a novel approach to rationally design mixed oxides with high Lewis acidity for functional separators.

Vacancy and Low-Energy 3p-Orbital Endow Na4Fe3(PO4)2(P2O7) Cathode with Superior Sodium Storage Kinetics

Iron-based phosphate Na4Fe3(PO4)2(P2O7) (NFPP) has been regarded as the most promising cathode for sodium-ion batteries (SIBs) thanks to its cost-effectiveness and eco-friendliness. However, it is in a predicament from the intrinsic low ionic/electronic conductivity, becoming a great challenge for its practical application. Herein, the significant roles of the low-energy 3p-orbital and transition metal vacancies are emphasized in facilitating charge rearrangement and reconstructing ion-diffusion channels, from the perspectives of crystallography and electron interaction for the first time, and the modification mechanism is fully explored by various characterizations and theoretical calculations. As proof of this concept, the designed Na4Fe2.85Al0.1(PO4)2(P2O7) (NF2.85A0.1PP) delivers prominent electrochemical performance, achieving high energy density (≈350 Wh kg⁻¹), superior kinetics (62 mAh g⁻¹ at 10 A g⁻¹), excellent power density (23 kW kg⁻¹, 143 Wh kg⁻¹), and extraordinary cycling stability (with negligible attenuation after 10 000 cycles). This work provides a brand-new perspective for designing ultra-endurable high-rate polyanion cathodes.

Na3Zr2Si2PO12-Polymer Composite Electrolyte for Solid State Sodium Batteries

The integration of the flexibility of organic polymer electrolyte and high ionic conductivity of the ceramic electrolyte is attempted in search of efficient and safer battery. Composite solid polymer electrolyte (CSPE) provides high ionic conductivity with a sustainable thin film of electrolyte having the synergistic effect of ionic liquid and active inorganic filler. The CSPE is synthesized by the solution cast technique using Na3Zr2Si2PO12 (NZSP) as ceramic and poly(vinylidene fluoride-hexafluoropropylene) with Salt-Ionic liquid as polymer electrolyte. X-ray diffraction (XRD) of CSPE includes amorphous nature due to the polymer part as well as crystalline peaks of ceramic NZSP, simultaneously. The prepared CSPE sample shows homogeneous and interconnected surface morphology is observed by Scanning electron microscopy (SEM) image. Thermogravimetric analysis (TGA) shows electrolyte is thermally stable up to 200 °C and differential scanning calorimetry (DSC) reveals decrease in degree of crystallinity due to NZSP addition in the CSPE. By complex impedance spectroscopy (CIS), room temperature ionic conductivity of the prepared CSPE is found ~1.03 mS/cm. The dielectric behaviour of the prepared electrolyte is also studied to investigate the ion dynamics within the sample. The cationic transference number is 0.53 and the electrochemical stability window (ESW) of the CSPE is 4.9 V which is suitable for sodium solid-state batteries applications.

Application of Sodium-Rich Multifunctional Hard Carbon Synthesized via Multi-Alloy Grafting Strategy for Presodiation in High-Performance Sodium-Ion Batteries

In sodium-ion pouch batteries based on hard carbon, an additional source of active sodium significantly enhances the battery's initial coulombic efficiency and compensates for the loss of active sodium ions during cycling. This study investigates the interaction between metallic sodium with carbon materials and develops a composite powder material of sodium-rich lithium-aluminum using a multi-alloy grafting strategy, to replenish the initial loss of active sodium in the hard carbon materials. To enhance the stability and utilization of this highly active sodium source, a novel slurry system based on polyethylene oxide (PEO) as a binder and dimethyl carbonate (DMC) as a solvent is introduced. Furthermore, this study designs a hard carbon composite electrode structure with a stable layer and sacrificial layer (NPH), which not only accommodates current battery processing environments but also demonstrates excellent potential in practical applications. Ultimately, the soft-packed sodium-ion battery consists of NPH electrodes with composite sodium ferric pyrophosphate (NFPP) and demonstrates excellent initial coulombic efficiency (91%) and ultra-high energy density (205 Wh kg-1). These results indicate significant technological and application implications for future energy storage.

Enhancing the Filler Utilization of Composite Gel Electrolytes via In Situ Solution-Processable Method for Sustainable Sodium-Ion Batteries

The composite gel electrolyte (CGE), which combines the advantages of inorganic solid-state electrolytes and solid polymer electrolytes, is regarded as the ultimate candidate for constructing batteries with high safety and superior electrode-electrolyte interface contact. However, the ubiquitous agglomeration of nanofillers results in low filler utilization, which seriously reduces structural uniformity and ion transport efficiency, thus restricting the development of consistent and durable batteries. Herein, a solution-processable method to in situ construct CGE with high filler utilization is introduced. The homogeneous metal-organic framework fillers contribute to uniform ionic and electronic filed distribution, realizing a stable electrode-electrolyte interface. Consequently, the CGE with high filler utilization achieves an ultra-long lifespan of 10 000 cycles with a capacity retention of 80.2%. This work provides guidance for constructing high-performance CGEs in electrochemical energy-storage devices.

Edge Electron Effect Induced High-Entropy SEI for Durable Anode-Free Sodium Batteries

Anode-free sodium metal batteries represent great promising as high-energy-density and resource-rich electrochemical energy storage systems. However, the savage growth of sodium metal and continuous consumption hinder its stable capacity output. Herein, ordered flower-edges of zinc on Al substrate can induce high-entropy solid electrolyte interphase (SEI) to adjust sodium uniform deposition and extremely reduce electrolyte consumption with ultrahigh initial Coulombic efficiency (97.05%) for prolong batteries cycling life. Theoretical and experimental studies have demonstrated that the electron-donating property and exposed edge sites between (100) and (101) facets in zinc flower enhance anion adsorption onto the inner Helmholtz plane accelerating its interface decomposition. Additionally, the ordered zinc edges serve as homogeneous-nucleating template, leading to thin and inorganic-rich SEI layer (18 nm, ZnF2, NaZn13, NaF, and Na2CO3) with high-entropy discrete multicomponent distribution, so that fast and high-flux Na ions transport field, thereby reducing the critical nucleation barrier and promoting sodium high density nucleation (7.36 × 1013 N cm-2) and pyknotic growth (3 mAh cm-2, 22 µm). The assembled anode-free sodium batteries exhibit high stability (86%, 90 cycles) under ultrahigh cathode loading (32 mg cm-2). Moreover, the anode-less single-layer pouch batteries exhibit a durable capacity retention of 99% after 600 cycles.

Three-dimensional covalent organic framework-based artificial interphase layer endows lithium metal anodes with high stability

To gain a deeper understanding and address the scientific challenges of lithium dendrite growth, a robust solid-state electrolyte interface (SEI) with good mechanical properties and rapid ion conduction is crucial for the advancement of lithium metal batteries. Artificial SEI layers based on organic polymers, such as covalent organic frameworks (COF), have garnered widespread attention due to their flexible structural design and tunable functionality. In this work, a COF with 3D spatial geometric symmetry and a fully covalent dia topology was synthesized and used as artificial SEI layers. A combination of comprehensive DFT calculations and ex situ/in situ characterizations have unraveled the impact of interpenetrated chain segments and anchoring lithiophilic groups on the microscopic dynamics related to Li ion desolvation, charge transfer, migration pathways, and deposition morphology. The ultralow polarization voltage of 46 mV for 9400 hours with a symmetric Li|Li cell at a harsh current density of 10 mA cm-2, as well as the high Li+ utilization, low polarization voltage, and prolonged lifespan for 3D-COF-modified Li|S and Li|LFP full cells, unambiguously corroborate the interphase reliability. This work also aims to shed new light on the use of multi-dimensional porous polymer SEI layers to revive highly stable Li metal batteries.

Vacancies-regulated Prussian Blue Analogues through Precipitation Conversion for Cathodes in Sodium-ion Batteries with Energy Densities over 500 Wh/kg

Prussian blue analogues (PBAs) have been widely applied in many fields, especially as cathode materials of sodium-ion batteries on account of their low cost and open framework for fast ions transport. However, the capacity of reported PBAs has a great distance from its theoretical value. Herein, we proposed that [Fe(CN)6] vacancies are crucial point for the high specific capacity for the first time. The [Fe(CN)6] vacancies may create net electrons and reduce obstacles to ionic transport, which is conducive to rate performance of PBAs by increasing electronic and ionic conductivity to some extent. As a proof of concept, a series of PBAs have been prepared by co-precipitation method. And then, a novel precipitation conversion method has been designed, by which unique PBAs with a specific quantity of [Fe(CN)6] vacancies was successfully synthesized. Remarkably, the as-prepared PBAs possessing hierarchical hollow morphology have reached a unprecedent level of high capacity (168 mAh g-1 at 25 mA g-1, close to PBAs' theoretical capacity 170 mAh g-1), high rate performance (90 mAh g-1 at 5 A g-1), and high energy density (over 500 Wh kg-1).

Poly(ethylene oxide)-based composite solid electrolyte for long cycle life solid-state lithium metal batteries: Improvement of interface stability through a dual mechanism

Solid-state lithium metal batteries (SSLMBs) are promising candidates for safe and high-energy-density next-generation applications. However, harmful interfacial decomposition and uneven Li deposition lead to poor ion transport, a short cycle life, and battery failure. Herein, we propose a novel poly(ethylene oxide) (PEO)-based composite solid electrolyte (CSE) containing succinonitrile (SN) and zinc oxide (ZnO) nanoparticles (NPs), which improves interface stability through a dual mechanism. (1) By anchoring bis(trifluoromethanesulfonyl)imide (TFSI) anions to ZnO, a reliable solid electrolyte interface (SEI) later with abundant LiF can be obtained to inhibit interface decomposition. (2) The immobilization of escaping SN molecules in the SEI layer by ZnO NPs promotes the self-polymerization of SN and facilitates charge transfer through the interface. As a result, the ion conductivity of the stainless steel-symmetrical battery reaches 1.1 × 10-4 S cm-1 at room temperature, and a LiFePO4 (LFP) full battery exhibits ultrahigh stability (800 cycles) at 0.5 C. Thus, the present study provides valuable insights for the development of advanced PEO-based SSLMBs.

Inorganic Sodium Solid Electrolytes: Structure Design, Interface Engineering and Application

All-solid-state sodium batteries (ASSSBs) are particularly attractive for large-scale energy storage and electric vehicles due to their exceptional safety, abundant resource availability, and cost-effectiveness. The growing demand for ASSSBs underscores the significance of sodium solid electrolytes; However, the existed challenges of sodium solid electrolytes hinder their practical application despite continuous research efforts. Herein, recent advancements and the challenges for sodium solid electrolytes from material to battery level are reviewed. The in-depth understanding of their fundamental properties, synthesis techniques, crystal structures and recent breakthroughs is presented. Moreover, critical challenges on inorganic sodium solid electrolytes are emphasized, including the imperative need to enhance ionic conductivity, fortifying interfacial compatibility with anode/cathode materials, and addressing dendrite formation issues. Finally, potential applications of these inorganic sodium solid electrolytes are explored in ASSSBs and emerging battery systems, offering insights into future research directions.

Air-Stable High-Entropy Layered Oxide Cathode with Enhanced Cycling Stability for Sodium-Ion Batteries

O3-type layered oxides have been extensively studied as cathode materials for sodium-ion batteries due to their high reversible capacity and high initial sodium content, but they suffer from complex phase transitions and an unstable structure during sodium intercalation/deintercalation. Herein, we synthesize a high-entropy O3-type layered transition metal oxide, NaNi0.3Cu0.05Fe0.1Mn0.3Mg0.05Ti0.2O2 (NCFMMT), by simultaneously doping Cu, Mg, and Ti into its transition metal layers, which greatly increase structural entropy, thereby reducing formation energy and enhancing structural stability. The high-entropy NCFMMT cathode exhibits significantly improved cycling stability (capacity retention of 81.4% at 1C after 250 cycles and 86.8% at 5C after 500 cycles) compared to pristine NaNi0.3Fe0.4Mn0.3O2 (71% after 100 cycles at 1C), as well as remarkable air stability. Finally, the NCFMMT//hard carbon full-cell batteries deliver a high initial capacity of 103 mAh g-1 at 1C, with 83.8 mAh g-1 maintained after 300 cycles (capacity retention of 81.4%).

Ultrathin, Mechanically Durable, and Scalable Polymer-in-Salt Solid Electrolyte for High-Rate Lithium Metal Batteries

Polymer-in-salt solid-state electrolytes (PIS SSEs) are emerging for high room-temperature ionic conductivity and facile handling, but suffer from poor mechanical durability and large thickness. Here, Al2O3-coated PE (PE/AO) separators are proposed as robust and large-scale substrates to trim the thickness of PIS SSEs without compromising mechanical durability. Various characterizations unravel that introducing Al2O3 coating on PE separators efficiently improves the wettability, thermal stability, and Li-dendrite resistance of PIS SSEs. The resulting PE/AO@PIS demonstrates ultra-small thickness (25 µm), exceptional mechanical durability (55.1 MPa), high decomposition temperature (330 °C), and favorable ionic conductivity (0.12 mS cm-1 at 25 °C). Consequently, the symmetrical Li cells remain stable at 0.1 mA cm-2 for 3000 h, without Li dendrite formation. Besides, the LiFePO4|Li full cells showcase excellent rate capability (131.0 mAh g-1 at 10C) and cyclability (93.6% capacity retention at 2C after 400 cycles), and high-mass-loading performance (7.5 mg cm-2). Moreover, the PE/AO@PIS can also pair with nickel-rich layered oxides (NCM811 and NCM9055), showing a remarkable specific capacity of 165.3 and 175.4 mAh g-1 at 0.2C after 100 cycles, respectively. This work presents an effective large-scale preparation approach for mechanically durable and ultrathin PIS SSEs, driving their practical applications for next-generation solid-state Li-metal batteries.

Sodium layered oxide cathodes: properties, practicality and prospects

Rechargeable sodium-ion batteries (SIBs) have emerged as an advanced electrochemical energy storage technology with potential to alleviate the dependence on lithium resources. Similar to Li-ion batteries, the cathode materials play a decisive role in the cost and energy output of SIBs. Among various cathode materials, Na layered transition-metal (TM) oxides have become an appealing choice owing to their facile synthesis, high Na storage capacity/voltage that are suitable for use in high-energy SIBs, and high adaptivity to the large-scale manufacture of Li layered oxide analogues. However, going from the lab to the market, the practical use of Na layered oxide cathodes is limited by the ambiguous understanding of the fundamental structure-performance correlation of cathode materials and lack of customized material design strategies to meet the diverse demands in practical storage applications. In this review, we attempt to clarify the fundamental misunderstandings by elaborating the correlations between the electron configuration of the critical capacity-contributing elements (e.g., TM cations and oxygen anion) in oxides and their influence on the Na (de)intercalation (electro)chemistry and storage properties of the cathode. Subsequently, we discuss the issues that hinder the practical use of layered oxide cathodes, their origins and the corresponding strategies to address their issues and accelerate the target-oriented research and development of cathode materials. Finally, we discuss several new Na layered cathode materials that show prospects for next-generation SIBs, including layered oxides with anion redox and high entropy and highlight the use of layered oxides as cathodes for solid-state SIBs with higher energy and safety. In summary, we aim to offer insights into the rational design of high-performance Na layered oxide cathode materials towards the practical realization of sustainable electrochemical energy storage at a low cost.

Nonflammable Succinonitrile-Based Deep Eutectic Electrolyte for Intrinsically Safe High-Voltage Sodium-Ion Batteries

Intrinsically safe sodium-ion batteries are considered as a promising candidate for large-scale energy storage systems. However, the high flammability of conventional electrolytes may pose serious safety threats and even explosions. Herein, a strategy of constructing a deep eutectic electrolyte is proposed to boost the safety and electrochemical performance of succinonitrile (SN)-based electrolyte. The strong hydrogen bond between S═O of 1,3,2-dioxathiolane-2,2-dioxide (DTD) and the α-H of SN endows the enhanced safety and compatibility of SN with Lewis bases. Meanwhile, the DTD participates in the inner Na+ sheath and weakens the coordination number of SN. The unique solvation configuration promotes the formation of robust gradient inorganic-rich electrode-electrolyte interphase, and merits stable cycling of half-cells in a wide temperature range, with a capacity retention of 82.8% after 800 cycles (25 °C) and 86.3% after 100 cycles (60 °C). Correspondingly, the full cells deliver tremendous improvement in cycling stability and rate performance.

A Functional Air-Stable Li9.8GeP1.7Sb0.3S11.8I0.2 Superionic Conductor for High-Performance All-Solid-State Lithium Batteries

Solid-state electrolytes (SSEs) based on sulfides have become a subject of great interest due to their superior Li-ion conductivity, low grain boundary resistance, and adequate mechanical strength. However, they grapple with chemical instability toward moisture hypersensitivity, which decreases their ionic conductivity, leading to more processing requirements. Herein, a Li9.8GeP1.7Sb0.3S11.8I0.2 (LGPSSI) superionic conductor is designed with a Li+ conductivity of 6.6 mS cm-1 and superior air stability based on hard and soft acids and bases (HSAB) theory. The introduction of optimal antimony (Sb) and iodine (I) into the Li10GeP2S12 (LGPS) structure facilitates fast Li-ion migration with low activation energy (Ea) of 20.33 kJ mol-1. The higher air stability of LGPSSI is credited to the strategic substitution of soft acid Sb into (Ge/P)S4 tetrahedral sites, examined by Raman and X-ray photoelectron spectroscopy techniques. Relatively lower acidity of Sb compared to phosphorus (P) realizes a stronger Sb-S bond, minimizing the evolution of toxic H2S (0.1728 cm3 g-1), which is ∼3 times lower than pristine LGPS when LGPSSI is exposed to moist air for 120 min. The NCA//Li-In full cell with a LGPSSI superionic conductor delivered the first discharge capacity of 209.1 mAh g-1 with 86.94% Coulombic efficiency at 0.1 mA cm-2. Furthermore, operating at a current density of 0.3 mA cm-2, LiNbO3@NCA/LGPSSI/Li-In cell demonstrated an exceptional reversible capacity of 117.70 mAh g-1, retaining 92.64% of its original capacity over 100 cycles.

A Critical Review on Room-Temperature Sodium-Sulfur Batteries: From Research Advances to Practical Perspectives

Room-temperature sodium-sulfur (RT-Na/S) batteries are promising alternatives for next-generation energy storage systems with high energy density and high power density. However, some notorious issues are hampering the practical application of RT-Na/S batteries. Besides, the working mechanism of RT-Na/S batteries under practical conditions such as high sulfur loading, lean electrolyte, and low capacity ratio between the negative and positive electrode (N/P ratio), is of essential importance for practical applications, yet the significance of these parameters has long been disregarded. Herein, it is comprehensively reviewed recent advances on Na metal anode, S cathode, electrolyte, and separator engineering for RT-Na/S batteries. The discrepancies between laboratory research and practical conditions are elaborately discussed, endeavors toward practical applications are highlighted, and suggestions for the practical values of the crucial parameters are rationally proposed. Furthermore, an empirical equation to estimate the actual energy density of RT-Na/S pouch cells under practical conditions is rationally proposed for the first time, making it possible to evaluate the gravimetric energy density of the cells under practical conditions. This review aims to reemphasize the vital importance of the crucial parameters for RT-Na/S batteries to bridge the gaps between laboratory research and practical applications.

Gel polymer electrolytes for rechargeable batteries toward wide-temperature applications

Rechargeable batteries, typically represented by lithium-ion batteries, have taken a huge leap in energy density over the last two decades. However, they still face material/chemical challenges in ensuring safety and long service life at temperatures beyond the optimum range, primarily due to the chemical/electrochemical instabilities of conventional liquid electrolytes against aggressive electrode reactions and temperature variation. In this regard, a gel polymer electrolyte (GPE) with its liquid components immobilized and stabilized by a solid matrix, capable of retaining almost all the advantageous natures of the liquid electrolytes and circumventing the interfacial issues that exist in the all-solid-state electrolytes, is of great significance to realize rechargeable batteries with extended working temperature range. We begin this review with the main challenges faced in the development of GPEs, based on extensive literature research and our practical experience. Then, a significant section is dedicated to the requirements and design principles of GPEs for wide-temperature applications, with special attention paid to the feasibility, cost, and environmental impact. Next, the research progress of GPEs is thoroughly reviewed according to the strategies applied. In the end, we outline some prospects of GPEs related to innovations in material sciences, advanced characterizations, artificial intelligence, and environmental impact analysis, hoping to spark new research activities that ultimately bring us a step closer to realizing wide-temperature rechargeable batteries.

Interface-Compatible Gel-Polymer Electrolyte Enabled by NaF-Solubility-Regulation toward All-Climate Solid-State Sodium Batteries

Gel-polymer electrolyte (GPE) is a pragmatic choice for high-safety sodium batteries but still plagued by interfacial compatibility with both cathode and anode simultaneously. Here, salt-in-polymer fibers with NaF salt inlaid in polylactide (PLA) fiber network was fabricated via electrospinning and subsequent in situ forming gel-polymer electrolyte in liquid electrolytes. The obtained PLA-NaF GPE achieves a high ion conductivity (2.50×10-3 S cm-1) and large Na+ transference number (0.75) at ambient temperature. Notably, the dissolution of NaF salt occupies solvents leading to concentrated-electrolyte environment, which facilitates aggregates with increased anionic coordination (anion/Na+ >1). Aggregates with higher HOMO realize the preferential oxidation on the cathode so that inorganic-rich and stable CEI covers cathode' surface, preventing particles' breakage and showing good compatibility with different cathodes (Na3V2(PO4)3, Na2+2xFe2-x(SO4)3, Na0.72Ni0.32Mn0.68O2, NaTi2(PO4)3). While, passivated Na anode induced by the lower LUMO of aggregates, and the lower surface tension between Na anode and PLA-NaF GPE interface, leading to the dendrites-free Na anode. As a result, the assembled Na || Na3V2(PO4)3 cells display excellent electrochemical performance at all-climate conditions.

Building Stable Anodes for High-Rate Na-Metal Batteries

Due to low cost and high energy density, sodium metal batteries (SMBs) have attracted growing interest, with great potential to power future electric vehicles (EVs) and mobile electronics, which require rapid charge/discharge capability. However, the development of high-rate SMBs has been impeded by the sluggish Na+ ion kinetics, particularly at the sodium metal anode (SMA). The high-rate operation severely threatens the SMA stability, due to the unstable solid-electrolyte interface (SEI), the Na dendrite growth, and large volume changes during Na plating-stripping cycles, leading to rapid electrochemical performance degradations. This review surveys key challenges faced by high-rate SMAs, and highlights representative stabilization strategies, including the general modification of SMB components (including the host, Na metal surface, electrolyte, separator, and cathode), and emerging solutions with the development of solid-state SMBs and liquid metal anodes; the working principle, performance, and application of these strategies are elaborated, to reduce the Na nucleation energy barriers and promote Na+ ion transfer kinetics for stable high-rate Na metal anodes. This review will inspire further efforts to stabilize SMAs and other metal (e.g., Li, K, Mg, Zn) anodes, promoting high-rate applications of high-energy metal batteries towards a more sustainable society.

Liquid Metal Mediated Heterostructure Fluoride Solid Electrolytes of High Conductivity and Air Stability for Sustainable Na Metal Batteries

Fluoride-based solid electrolytes (SEs) have emerged as a promising component for high-energy-density rechargeable solid-state batteries (SSBs) in view of their wide electrochemical window, high air stability, and interface compatibility, but they still face the challenge of low ion conductivity and the lack of a desired structure for sodium metal SSBs. Here, we report a sodium-rich heterostructure fluoride SE, Na3GaF6-Ga2O3-NaCl (NGFOC-G), synthesized via in situ oxidation of liquid metal gallium and in situ chlorination using low-melting GaCl3. The distinctive features of NGFOC-G include single-crystal Na3GaF6 domains within an open-framework structure, composite interface decoration of Ga2O3 and NaCl with a concentration gradient, exceptional air stability, and high electrochemical oxidation stability. By leveraging the penetration of gallium at NaF grain boundaries and the in situ self-oxidation to form Ga2O3 nanodomains, the solid-phase reaction kinetics of NaF and GaF3 is activated for facilitating the synthesis of main component Na3GaF6. The introduction of a small amount of a chlorine source during synthesis further softens and modifies the boundaries of Na3GaF6 along with Ga2O3. Benefiting from the enhanced interface ion transport, the optimized NGFOC-G exhibits an ionic conductivity up to 10-4 S/cm at 40 °C, which is the highest level reported among fluoride-based sodium-ion SEs. This SE demonstrates a "self-protection" mechanism, where the formation of a high Young's modulus transition layer rich in NaF and Na2O under electrochemical driving prevents the dendrite growth of sodium metal. The corresponding Na/Na symmetric cells show minimal voltage hysteresis and stable cycling performance for at least 1000 h. The Na/NGFOC-G/Na3V2(PO4)3 cell demonstrates stable capacity release around 100 mAh/g at room temperature. The Na/NGFOC-G/FeF3 cell delivers a high capacity of 461 mAh/g with an excellent stability of conversion reaction cycling.

MatGPT: A Vane of Materials Informatics from Past, Present, to Future

Combining materials science, artificial intelligence (AI), physical chemistry, and other disciplines, materials informatics is continuously accelerating the vigorous development of new materials. The emergence of "GPT (Generative Pre-trained Transformer) AI" shows that the scientific research field has entered the era of intelligent civilization with "data" as the basic factor and "algorithm + computing power" as the core productivity. The continuous innovation of AI will impact the cognitive laws and scientific methods, and reconstruct the knowledge and wisdom system. This leads to think more about materials informatics. Here, a comprehensive discussion of AI models and materials infrastructures is provided, and the advances in the discovery and design of new materials are reviewed. With the rise of new research paradigms triggered by "AI for Science", the vane of materials informatics: "MatGPT", is proposed and the technical path planning from the aspects of data, descriptors, generative models, pretraining models, directed design models, collaborative training, experimental robots, as well as the efforts and preparations needed to develop a new generation of materials informatics, is carried out. Finally, the challenges and constraints faced by materials informatics are discussed, in order to achieve a more digital, intelligent, and automated construction of materials informatics with the joint efforts of more interdisciplinary scientists.

Inorganic All-Solid-State Sodium Batteries: Electrolyte Designing and Interface Engineering

Inorganic all-solid-state sodium batteries (IASSSBs) are emerged as promising candidates to replace commercial lithium-ion batteries in large-scale energy storage systems due to their potential advantages, such as abundant raw materials, robust safety, low price, high-energy density, favorable reliability and stability. Inorganic sodium solid electrolytes (ISSEs) are an indispensable component of IASSSBs, gaining significant attention. Herein, this review begins by discussing the fundamentals of ISSEs, including their ionic conductivity, mechanical property, chemical and electrochemical stabilities. It then presents the crystal structures of advanced ISSEs (e.g., β/β''-alumina, NASICON, sulfides, complex hydride and halide electrolytes) and the related issues, along with corresponding modification strategies. The review also outlines effective approaches for forming intimate interfaces between ISSEs and working electrodes. Finally, current challenges and critical perspectives for the potential developments and possible directions to improve interfacial contacts for future practical applications of ISSEs are highlighted. This comprehensive review aims to advance the understanding and development of next-generation rechargeable IASSSBs.

Ultrahigh-Rate Na/Cl2 Batteries Through Improved Electron and Ion Transport by Heteroatom-Doped Bicontinuous-Structured Carbon

Rechargeable sodium/chlorine (Na/Cl2 ) batteries are emerging candidates for sustainable energy storage owing to their superior energy densities and the high abundance of Na and Cl elements. However, their practical applications have been plagued by the poor rate performance (e.g., a maximum discharge current density of 150 mA g-1 ), as the widely used carbon nanosphere cathodes show both sluggish electron-ion transport and reaction kinetics. Here, by mimicking the sufficient mass and energy transport in a sponge, we report a bicontinuous-structured carbon cubosome with heteroatomic doping, which allows efficient Na+ and electron transport and promotes Cl2 adsorption and conversion, thus unlocking ultrahigh-rate Na/Cl2 batteries, e.g., a maximum discharge current density of 16,000 mA g-1 that is more than two orders of magnitude higher than previous reports. The optimized solid-liquid-gas (carbon-electrolyte-Cl2 ) triple interfaces further contribute to a maximum reversible capacity and cycle life of 2,000 mAh g-1 and 250 cycles, respectively. This study establishes a universal approach for improving the sluggish kinetics of conversion-type battery reactions, and provides a new paradigm to resolve the long-standing dilemma between high energy and power densities in energy storage devices.

Ultrafast and ultrastable FeSe2embedded in nitrogen-doped carbon nanofibers anode for sodium-ion half/full batteries

Transition metal selenides are considered as promising anode materials for fast-charging sodium-ion batteries due to their high theoretical specific capacity. However, the low intrinsic conductivity, particle aggregation, and large volume expansion problems can severely inhibit the high-rate and long-cycle performance of the electrode. Herein, FeSe2nanoparticles embedded in nitrogen-doped carbon nanofibers (FeSe2@NCF) have been synthesized using the electrospinning and selenization process, which can alleviate the volume expansion and particle aggregation during the sodiation/desodiation and improve the electrical conductivity of the electrode. The FeSe2@NCF electrode delivers the outstanding specific capacity of 222.3 mAh g-1at a fast current density of 50 A g-1and 262.1 mAh g-1at 10 A g-1with the 87.8% capacity retention after 5000 cycles. Furthermore, the Na-ion full cells assembled with pre-sodiated FeSe2@NCF as anode and Na3V2(PO4)3/C as cathode exhibit the reversible specific capacity of 117.6 mAh g-1at 5 A g-1with the 84.3% capacity retention after 1000 cycles. This work provides a promising way for the conversion-based metal selenides for the applications as fast-charging sodium-ion battery anode.