Solid-state Sodium-ion Batteries Research Articles

Investigation of Solid Polymer Electrolytes for NASICON-Type Solid-State Symmetric Sodium-Ion Battery.

The inevitable shift toward renewable energy and electrification necessitates earth-abundant sodium reserves for next-generation Na-based energy storage technologies. By coupling the benefits of solid electrolytes over traditional nonaqueous electrolytes due to their safety hazards, solid-state sodium-ion batteries hold huge prospects in the future. This work presents a comprehensively developed solid-state sodium-ion symmetric full cell operating at room temperature enabled through a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based polymer electrolyte and modified NASICON-structured positive and negative electrodes. Among the investigated polymer electrolytes, PVDF-HFP-NaTFSI was found to outperform other counterparts by achieving a higher ionic conductivity and delivered an appreciable electrochemical stability window. By further delving into the properties of PVDF-HFP-NaTFSI, it was found to possess the least crystallinity, minimal porous structure, lowest melting point, and fusion enthalpy, indicating better ion transport than other investigated polymer electrolytes. The as-assembled solid-state battery revealed a storage capacity of 74 mAh g-1 at 0.1 C with a specific energy density of 130 Wh kgcathode_active_material-1 and demonstrated an impressive capacity retention of 84% of the initial capacity after 200 cycles. The structure and morphology retention of the cycled electrode and electrolyte through postmortem analysis bolster the electrochemo-mechanical stability of the developed solid cell. The findings reported here on polymer electrolytes persuade expedient solutions for developing ambient temperature solid-state sodium-ion batteries with promising electrochemical performance for commercialization in the near future.

Electrospun Nano-Porous Cellulose Acetate Membrane Casted with Chitosan for Solid-State Sodium-Ion Batteries

Emerging as a safe and economically viable alternative to lithium-ion batteries, the solid-state sodium ion battery (ss-SIB) has captured increasing attention as a transformative technology for realizing a decarbonized economy and ensuring a sustainable energy supply. Here we report a nanoarchitecture strategy of biodegradable, biocompatible, and naturally abundant cellulose derivative (cellulose acetate, CA) and chitosan (CH) biopolymer-based nano-porous electrospun composite electrolyte (ECE) for flexible and wearable ss-SIBs. A simple combination of electrospinning and solution casting was utilized to fabricate mechanically robust (13.76 MPa), thin-film (0.067 mm), highly flexible, and high room temperature Na-ion conductive (1.04 x 10-4 S.cm-2) ECE. Lower activation energy (Ea = 0.13 eV) indicates easy charge carrier diffusion ability of as prepared ECE. The electrochemical stability window (ESW = 3.45 V) of ECE is studied by the linear sweep voltammetry (LSV) with respect to stainless steel and sodium metal electrodes. Uniform galvanostatic Na plating and stripping at room temperature is observed over 900 hrs at 0.5 mA•cm-2 current density in symmetric (Na|ECE|Na) cell performance, this underscores impressive electrochemical stability and compatibility with sodium metal. Using Na3V2(PO4)3 (NVP) as cathode, ECE, and Na metal as anode in the full cell, specific discharge capacity of 83 mA×h×g-1 at room temperature was attained at 0.1 C rate, highlighting the practical applicability of the nanostructured electrospun composite electrolyte for flexible and wearable ss-SIBs. Keywords Cellulose acetate, chitosan, electrospun, solid-state sodium-ion battery, specific discharge capacity.

Composite scaffold of electrospun nano-porous cellulose acetate membrane casted with chitosan for flexible solid-state sodium-ion batteries

Emerging as a safe and economically viable alternative to lithium-ion batteries, the solid-state sodium ion battery (ss-SIB) has captured increasing attention as a transformative technology for realizing a decarbonized economy and ensuring a sustainable energy supply. Here we report a nanoarchitecture strategy of biodegradable, biocompatible, and naturally abundant cellulose derivative (cellulose acetate, CA) and chitosan (CH) biopolymer-based nano-porous electrospun composite electrolyte (ECE) for flexible and wearable ss-SIBs. A simple combination of electrospinning and solution casting was utilized to fabricate mechanically robust (13.76 MPa), thin-film (0.067 mm), and highly flexible ECE. The ionic conductivity of ECE was enhanced through optimization, taking into account the amount of sodium salt (NaPF6). The resulting ECE exhibited a sodium-ion conductivity of 1.04 ×10−4 S·cm−1 and a sodium ion transference number of 0.48 at room temperature (RT=23 °C). The obtained Na+ transference number of 0.48 and a low activation energy (Ea = 0.13 eV) indicate the easy charge carrier diffusion ability of as-prepared ECE. The electrochemical stability window (ESW = 4.04 V) of ECE is studied by the linear sweep voltammetry (LSV) with the assembly of stainless steel and sodium metal electrodes. Without any interfacial modification, a uniform, stable, and long-time room temperature (RT) galvanostatic Na plating-stripping was observed for 1000 hrs at 0.5 mA·cm−2 current density in a symmetric (Na|ECE|Na) cell, this underscores impressive electrochemical stability and compatibility of ECE with sodium metal. Utilizing Na3V2(PO4)3 (NVP) as cathode, fabricated ECE, and Na metal as anode in a hybrid full cell, a notable RT specific discharge capacity of 98.1 mA·h·g−1 was attained at a rate of 0.1 C with a capacity retention of 93.4 % over 120 charge-discharge cycles. This highlights the practical applicability of the nanostructured electrospun composite electrolyte for flexible and wearable ss-SIBs.

A Potential Cathode for Quasi Solid-State Sodium-Ion Batteries with Trivalent Doping of La3+ in Sodium Iron Phosphate

A Potential Cathode for Quasi Solid-State Sodium-Ion Batteries with Trivalent Doping of La3+ in Sodium Iron Phosphate

Ionic Conductivity Analysis of NASICON Solid Electrolyte Coated with Polyvinyl-Based Polymers

The global environmental crisis necessitates reliable, sustainable, and safe energy storage solutions. The current systems are nearing their capacity limits due to the reliance on conventional liquid electrolytes, which are fraught with stability and safety concerns, prompting the exploration of solid-state electrolytes, which enable the integration of metal electrodes. Solid-state sodium-ion batteries emerge as an appealing option by leveraging the abundance, low cost, and sustainability of sodium. However, low ionic conductivity and high interfacial resistance currently prevent their widespread adoption. This study explores polyvinyl-based polymers as wetting agents for the NASICON-type NZSP (Na3Zr2Si2PO12) solid electrolyte, resulting in a combined system with enhanced ionic conductivity suitable for Na-ion solid-state full cells. Electrochemical impedance spectroscopy (EIS) performed on symmetric cells employing NZSP paired with different wetting agent compositions demonstrates a significant reduction in interfacial resistance with the use of poly(vinyl acetate)—(PVAc-) based polymers, achieving an impressive ionic conductivity of 1.31 mS cm−1 at room temperature, 63.8% higher than the pristine material, notably reaching 7.36 mS cm−1 at 90 °C. These results offer valuable insights into the potential of PVAc-based polymers for advancing high-performance solid-state sodium-ion batteries by reducing their total internal resistance.

Research Progress on the Solid Electrolyte of Solid-State Sodium-Ion Batteries

Research Progress on the Solid Electrolyte of Solid-State Sodium-Ion Batteries

The Crystallization Behavior of a Na2O-GeO2-P2O5 Glass System: A (Micro)Structural, Electrical, and Dielectric Study.

Sodium-phosphate-based glass-ceramics (GCs) are promising materials for a wide range of applications, including solid-state sodium-ion batteries, microelectronic packaging substrates, and humidity sensors. This study investigated the impact of 24 h heat-treatments (HT) at varying temperatures on Na-Ge-P glass, with a focus on (micro)structural, electrical, and dielectric properties of prepared GCs. Various techniques such as powder X-ray diffraction (PXRD), infrared spectroscopy-attenuated total reflection (IR-ATR), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) were employed. With the elevation of HT temperature, crystallinity progressively rose; at 450 °C, the microstructure retained amorphous traits featuring nanometric grains, whereas at 550 °C, HT resulted in fully crystallized structures characterized by square-shaped micron-scale grains of NaPO3. The insight into the evaluation of electrical and dielectric properties was provided by Solid-State Impedance Spectroscopy (SS-IS), revealing a strong correlation with the conditions of controlled crystallization and observed (micro)structure. Compared to the initial glass, which showed DC conductivity (σDC) on the order of magnitude 10-7 Ω-1 cm-1 at 393 K, the obtained GCs exhibited a lower σDC ranging from 10-8 to 10-10 Ω-1 cm-1. With the rise in HT temperature, σDC further decreased due to the crystallization of the NaPO3 phase, depleting the glass matrix of mobile Na+ ions. The prepared GCs showed improved dielectric parameters in comparison to the initial glass, with a noticeable increase in dielectric constant values (~20) followed by a decline in dielectric loss (~10-3) values as the HT temperatures rise. Particularly, the GC obtained at @450 stood out as the optimal sample, showcasing an elevated dielectric constant and low dielectric loss value, along with moderate ionic conductivity. This research uncovers the intricate relationship between heat-treatment conditions and material properties, emphasizing that controlled crystallization allows for precise modifications to microstructure and phase composition within the remaining glassy phase, ultimately facilitating the fine-tuning of material properties.

The problems with solid-state sodium ion battery electrolytes and their solutions

In the context of the continuous growth of global demand for energy storage, electrochemical energy storage systems stand out among many energy storage technologies due to their excellent performance. At present, batteries as one of the most mainstream forms of electrochemical energy storage, such as fuel cells, lithium-ion batteries, and solid-state batteries, have been widely used. In particular, as the safety hazards existing in lithium-ion batteries due to the inclusion of organic electrolytes have gradually been recognized, solid-state batteries have received extensive attention and in-depth research for their higher safety performance. As an emerging electrochemical energy storage device, the most prominent feature of solid sodium-ion batteries is that they use solid electrolytes instead of traditional liquid electrolytes, which greatly improves the safety of batteries theoretically. Unfortunately, while solid electrolytes exhibit excellent chemical stability and good electrochemical performance, they still face a number of challenges in practical applications, including low ionic conductivity, poor interface contact, and short life span. In this paper, the characteristics, challenges, and solutions of electrolytes in solid-state sodium-ion batteries are discussed.

Na6MCl8 rock-salt compounds with M = Mg, Ca, Ba, Zn, Sr as components for solid-state sodium ion batteries.

We investigate a new series of rock-salt type structures, Na6MCl8 with M = Mg, Ca, Ba, Zn and Sr using advanced atomistic simulations. Calculated results show a direct relationship between the size of the M2+ cation and lattice parameters as well as the defect formation energy variation. The NaCl Schottky defect type is highly favourable, and the Na6BaCl8 structure possesses the lowest values of defect formation energies. These structures are predicted to be mechanically stable and ductile, implying their compatibility with possible use as electrodes/electrolytes. The Na6MCl8 structures exhibit semiconductor characteristics with an energy gap ranging between 4.1-4.6 eV, which differs from the previous value of Na6MgCl8. A 3D migration pathway is identified in each rock-salt structure. Despite the small variation of the Na diffusivity and conductivity at 250 K within the structures considered, the Na6BaCl8 is characterized by the highest conductivity at 250 K, while the Na6MgCl8 structure has the highest conductivity and diffusivity values. The outstanding properties predicted for a Na ion battery suggest future development of synthetic strategies for their actual preparation.

A dual aliovalent ion doped NASICON ceramic filler embedded in the PEO–NaTFSI polymer matrix for high-performance solid-state sodium-ion batteries

Demonstrating a high-performance all-solid-state sodium-ion battery system, with a maximum discharge capacity of ∼105 mA h g−1 at 0.1C, achieved for NVP symmetric cells enabled via polymer–ceramic composite electrodes and electrolytes.

Probing the Dynamic Na Metal/Nasicon Interface in Sodium-Ion Batteries

Interest in solid-state sodium-ion batteries (SSIBs) have resurged remarkably as a means of diversification in energy storage devices to address climate issues and further propelled by the movement of ‘Beyond-Li’. State of the art SSIBs not only offer energy security and sustainability but also comparable power and energy densities to their counter-parts. Yet to fully capitalise on the technology, the fundamental processes taking place between the anode and interface or ‘point of contact’ needs to be understood. Previous iterations of SSIBs have employed various solid-electrolyte candidates – most notable being beta-alumina – however with the recent advancements in synthesis and dopants more prominent solid-electrolytes have become interesting, one in particular being NaSICON (Sodium Super Ionic Conductor). NaSICON has several advantages, one of which is the reduction in operating temperatures of SSIBs due to its inherent fast sodium-ion transport1. This would broaden the potential applications of SSIBs, making the technology more accessible to a wider range of markets.Current perspectives on NaSICON solid-electrolytes have focused on optimising conductivity through means of additive dopants2 and synthesis procedures3. Yet at present, the understanding of the fundamentals of interfacial inhomogeneities that affect the performance of these materials in SSIBs is limited. With consideration of the direct implications on performance that surface chemistry has, understanding of this is paramount.Evaluation of the chemical evolution of the Na metal/NaSICON interface has been achieved through assessing the changes of the chemical landscape that take place at the surface and near-surface, through surface characterisation techniques that probe the area of interest at varying depths – X-Ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). This has been conducted on samples that have been electrochemically cycled and comparison made to samples in pristine condition. The compositions used to conduct this investigation are Na3Zr2Si2PO12 and Na3.4Zr2Si2.4P0.6O12 – the latter of which has been shown to have one of the highest room temperature sodium-ion conductivity4. Through this, the electronic structure, and hence chemical state, can be deduced alongside a 3D chemical map that will correlate surface chemical changes with electrochemical performance. Thus, a preliminary means of understanding the fundamentals of chemical evolution can be established. References Lu, G. Xia, J. P. Lemmon, Z. Yang, ‘Advanced materials for sodium-beta alumina batteries: Status, challenges and perspectives’, Journal of Power Sources, Vol. 195, p. 2431-2442, 2010. Samiee, B. Radhakrishnan, Z. Rice, Z. Deng, Y. Meng, S. Ong, J. Luo, ‘Divalent-doped Na3Zr2Si2PO12 natrium superionic conductor: Improving the ionic conductivity via simultaneously optimizing the phase and chemistry of the primary and secondary phases’, Journal of Power Sources, Vol. 347, p. 229-237, 2017. Jalalian-Khakshour, C. Phillips, L. Jackson, T. Dunlop, S. Margadonna, D. Deganello, ‘Solid-state synthesis of NASICON (Na3Zr2Si2PO12) using nanoparticle precursors for optimisation of ionic conductivity’, Journal of Materials Science, Vol. 55, 2020. Ma, C-L. Tsai, X-K. Wei, M. Heggen, F. Tietz, J. T. S. Irvine, ‘Room temperature demonstration of a sodium superionic conductor with grain conductivity in excess of 0.01 S cm−1 and its primary applications in symmetric battery cells’ J. Mater. Chem. A, Vol. 7, p. 7766-7776, 2019.

Investigation of Aliovalent Substitution in the Solid Sodium Ion Electrolyte Na2ZrCl6

The research community is working hard on the development of solid-state batteries (SSB) as an alternative to commercialized lithium-ion batteries, due to their higher energy density and enhanced safety. One of the core research areas of SSBs is the solid-state electrolyte (SE), which should fit the demand for high ionic conductivity and electrochemical stability at the same time. Recently, halide SEs have emerged because they are mechanochemical processable, similar to sulfidic SEs, but halide SEs exhibit excellent electrochemical oxidation stability compared to sulfidic SEs [1,2].However, the relatively low ionic conductivity at room temperature still hinders the application of halide SE in SSBs. Aliovalent substitution is a very widely used method to improve the ionic conductivity of SEs [3,4]. We are also motivated by the application of earth-abundance elements to reduce raw material costs.Recently, significant focus has been gained by Zr-based compounds such as Na2ZrCl6. We investigate here such compounds, focusing on elemental substitutions to gain increased ionic conductivity and on gaining insight into the influence of synthesis on SE crystal structure and electrochemical properties.In our work, different amounts of elemental substitutions are investigated, and the related materials are synthesized at different temperatures. In particular, the influence of a series of subsequent heating temperatures on the structure of the binary system is studied through XRD diffraction analysis and further refinement. The Ionic diffusion paths are also estimated through the band valence sum approach, in order to validate the electrochemical impedance spectroscopy (EIS) results.In summary, we report our early results on the development of novel solid electrolytes for Na-based solid-state batteries.REFERENCES[1] Kwak, H.; Lyoo, J.; Park, J.; Han, Y.; Asakura, R.; Remhof, A.; Battaglia, C.; Kim, H.; Hong, S.-T.; Jung, Y. S. Na2ZrCl6 enabling highly stable 3 V all-solid-state Na-ion batteries. Energy Storage Mater. 2021, 37, 47−54.[2] Tong Zhao, Alexander N. Sobolev, Roman Schlem, Bianca Helm, Marvin A. Kraft and Wolfgang G. Zeier. Synthesis-Controlled Cation Solubility in Solid Sodium Ion Conductors Na2+xZr1 - xInxCl6. ACS Appl. Energy Mater. 2023, XXXX, XXX, XXX-XXX.[3] Schlem, R.; Banik, A.; Eckardt, M.; Zobel, M.; Zeier, W. G. Na3-xEr1-xZrxCl6-A Halide-Based Fast Sodium-Ion Conductor with Vacancy-Driven Ionic Transport. ACS Appl. Energy Mater. 2020, 3, 10164−10173.[4] Wu, E. A.; Banerjee, S.; Tang, H.; Richardson, P. M.; Doux, J.M.; Qi, J.; Zhu, Z.; Grenier, A.;Li, Y.; Zhao, E.; Deysher, G.; Sebti, E.;Nguyen, H.; Stephens, R.; Verbist, G.; Chapman, K. W.; Clement, R.J.; Banerjee, A.; Meng, Y. S.; Ong, S. P. A stable cathode-solid electrolyte composite for high-voltage, long-cycle-life solid-state sodium-ion batteries. Nat. Commun. 2021, 12, 1256.

Computational Investigation of Halide Solid Electrolytes for Na-Based Batteries

Significant scientific and economic challenges are presented by developing battery systems with increased energy storage capacity. Geopolitical issues might pose supply chain risks for lithium (Li)-ion batteries, which are frequently used in portable electronics. As an alternative, sodium-ion batteries (NIBs), have drawn attention from researchers all over the world due to the perspective of being lower cost systems[1]. In comparison to lithium-ion batteries, solid-state sodium-ion batteries (SSSBs) promise as a safe, scalable, and environmentally friendly alternative. For the production of robust and adaptable SSSBs, the development of highly conductive, electrochemically stable, and chemically stable solid electrolytes (SEs) is essential [2]. With greater durability, adaptability, and safety, solid-state batteries with inorganic solid electrolytes are being heavily investigated as safer and perhaps more energy-dense alternatives to liquid electrolyte cells.Sulfides solid electrolytes have been extensively investigated due to their mechanical softness and high ionic conductivity. However, the electrochemical oxidation stability of those materials are as low as 2 V (vs. Na+/Na)[3]. Alternatively, the excellent ion conductivities and stability at high potentials have made halide compounds, intriguing candidates for solid electrolytes in batteries. These compounds offer fast ion transport, good stability at highly oxidative potentials, and are easily processed. A wide range of chemistries, such as A3MX6 (A = Li, Na; M = Sc, In, Y, Yb, Er, Hf, Ho, Dy, Al, Zr; X = F, Cl, Br, I), have been synthesized with tunable properties and the characterizations of those materials shows relevant electrochemical proprieties [2].In our work, we investigate different Na-based chloride compounds by Density Functional Theory (DFT). We expand beyond the reported compositions to consider possible cation-substituted compounds. Here, we report on the structures, ionic conduction pathways and ionic conductivity (computed by molecular dynamics methods) expected for such compounds. In the next months, we will also evaluate the compounds´ chemical and electrochemical stability. Our work moves us one step closer towards the development of stable and highly conductive solid electrolytes for Na-based solid-state batteries.References :[1] J. Mater. Chem. A, 2021,9, 281-292[2]J. Mater. Chem. A, 2022,10, 21565-21578[3] ACS Energy Lett. 2022, 7, 10, 3293–3301

Halide Heterogeneous Structure Boosting Ionic Diffusion and High-Voltage Stability of Sodium Superionic Conductors.

The development of solid-state sodium-ion batteries (SSSBs) heavily hinges on the development of an superionic Na+ conductor (SSC) that features high conductivity, (electro)chemical stability, and deformability. The construction of heterogeneous structures offers a promising approach to comprehensively enhancing these properties in a way that differs from traditional structural optimization. Here, this work exploits the structural variance between high- and low-coordination halide frameworks to develop a new class of halide heterogeneous structure electrolytes (HSEs). The halide HSEs incorporating a UCl3 -type high-coordination framework and amorphous low-coordination phase achieves the highest Na+ conductivity (2.7 mS cm-1 at room temperature, RT) among halide SSCs so far. By discerning the individual contribution of the crystalline bulk, amorphous region, and interface, this work unravels the synergistic ion conduction within halide HSEs and provides a comprehensive explanation of the amorphization effect. More importantly, the excellent deformability, high-voltage stability, and expandability of HSEs enable effective SSSB integration. Using a cold-pressed cathode electrode composite of uncoated Na0.85 Mn0.5 Ni0.4 Fe0.1 O2 and HSEs, the SSSBs present stable cycle performance with a capacity retention of 91.0% after 100 cycles at 0.2 C.

A flexible and free-standing composite solid electrolyte with a pomegranate-like structure for solid-state sodium-ion batteries

Solid sodium-ion batteries have the advantages of high energy density and good safety and are considered promising candidates for the next generation of energy storage systems. However, the sizeable interfacial resistance and dendrite growth between sodium and solid electrolytes, especially at high current densities, severely limit their development. Polymer-ceramic composite electrolytes are considered one of the potential candidates for solid electrolytes with high ionic conductivity and soft interface contact. In this study, a flexible self-supporting composite solid electrolyte with a pomegranate structure was prepared by a simple solution casting method. The addition of Na3Zr2Si2PO12 filler significantly improved the mechanical strength and electrochemical stability of the composite polymer electrolyte (CPE). The electrochemical stability window increases to 4.8 V relative to Na/Na+, and the conductivity reaches 1.069 × 10−4 S cm−1 at room temperature. Solid-state Na3V2(PO4)3/Na batteries using this CPE exhibit high cycle stability, with a high capacity retention rate at 1C (95.13%, coulomb efficiency of >98% after 290 cycles). These results indicate that PVDF-based CPE doped with inorganic Na3Zr2Si2PO12 packing is a promising composite electrolyte for solid sodium-ion batteries.

High-Entropy Layered Oxide Cathode Enabling High-Rate for Solid-State Sodium-Ion Batteries

HighlightsHigh-entropy oxides O3-Na0.95Li0.06Ni0.25Cu0.05Fe0.15Mn0.49O2 cathode constructed by compatible radius and different Fermi level ions was designed for solid-state Na-ion batteries.Na0.95Li0.06Ni0.25Cu0.05Fe0.15Mn0.49O2 cathode exhibits high-rate performance, air stability and electrochemically thermal stability.A series of characterizations were performed to explore energy storage mechanism of Na0.95Li0.06Ni0.25Cu0.05Fe0.15Mn0.49O2.

Scalable Synthesis of Selenide Solid-State Electrolytes for Sodium-Ion Batteries.

Solid-state sodium-ion batteries employing superionic solid-state electrolytes (SSEs) offer low manufacturing costs and improved safety and are considered to be a promising alternative to current Li-ion batteries. Solid-state electrolytes must have high chemical/electrochemical stability and superior ionic conductivity. In this work, we employed precursor and solvent engineering to design scalable and cost-efficient solution routes to produce air-stable sodium selenoantimonate (Na3SbSe4). First, a simple metathesis route is demonstrated for the production of the Sb2Se3 precursor that is subsequently used to form ternary Na3SbSe4 through two different routes: alcohol-mediated redox and alkahest amine-thiol approaches. In the former, the electrolyte was successfully synthesized in EtOH by using a similar redox solution coupled with Sb2Se3, Se, and NaOH as a basic reagent. In the alkahest approach, an amine-thiol solvent mixture is utilized for the dissolution of elemental Se and Na and further reaction with the binary precursor to obtain Na3SbSe4. Both routes produced electrolytes with room temperature ionic conductivity (∼0.2 mS cm-1) on par with reported performance from other conventional thermo-mechanical routes. These novel solution-phase approaches showcase the diversity and application of wet chemistry in producing selenide-based electrolytes for all-solid-state sodium batteries.

Sandwiched composite electrolyte with excellent interfacial contact for high-performance solid-state sodium-ion batteries

Solid-state sodium-ion batteries have attracted significant attention due to their rich resources, high safety, and high energy density. However, the lower ionic conductivity and inferior interfacial contact between solid-state electrolytes (SSEs) and electrodes limit their practical applications. Herein, polyvinylideneuoride-co-hexauoropropylene (PVDF-HFP) membrane is selected and a novel sandwiched composite PVDF-HFP/Na2.5Zr1.95Ce0.05Si2.2P0.8O11.3F0.7/PVDF-HFP (G-NZC0.05SPF0.7-G) SSEs is well designed. The ionic conductivity of Na3Zr2Si2PO12 is enhanced by Ce4+/F− co-doping. The effects of Ce4+ and F− doping on the crystal structure, density, and ionic conductivity for Na3Zr2Si2PO12 are well investigated. The optimal NZC0.05SPF0.7 delivers a high ionic conductivity of 1.39 × 10−3 S cm−1 at 25 ℃. Moreover, the PVDF-HFP membrane can significantly enhance the interface compatibility between NZC0.05SPF0.7 and electrodes. The as-prepared G-NZC0.05SPF0.7-G exhibits a large ionic conductivity of 1.07 × 10−3 S cm−1 at 25 ℃, wide electrochemical stability window up to 4.5 V, high critical current density of 1.2 A cm−2, and stable Na plating/stripping over 600 h at 0.3 A cm−2. The solid-state Na0.67Mn0.47Ni0.33Ti0.2O2/G-NZC0.05SPF0.7-G/Na battery delivers a remarkable cycling stability and rate capability at 25 ℃, indicating that the as-prepared G-NZC0.05SPF0.7-G has a promising application for solid-state SIBs. This study demonstrates an effective strategy to develop advanced solid-state electrolytes for solid-state SIBs.

Designing a Quasi-Liquid Alloy Interface for Solid Na-Ion Battery.

Solid-state sodium-ion batteries are attracting great attention due to their high energy density and high safety. However, the Na dendrite growth and poor wettability between sodium and electrolytes seriously limit its application. Herein, we designed a stable and dendrite-suppressed quasi-liquid alloy interface (C@Na-K) for solid sodium-ion batteries (SSIBs). The batteries exhibit excellent electrochemical performance thanks to better wettability and accelerated charge transfer and nucleation mode shifts. The thickness of the liquid phase alloy interface fluctuates along with the exotherm of the cell cycling process, which leads to better rate performance. The symmetrical cell can cycle steadily over 3500 h at 0.1 mA/cm2 at room temperature, and the critical current density can reach 2.6 mA/cm2 at 40 °C. The full cells with the quasi-liquid alloy interface also show outstanding performance; the capacity retention can reach 97.1%, and the average Coulombic efficiency can reach 99.6% of the battery at 0.5 C even after 300 cycles. These results proved the feasibility of using a liquid alloy interface of the anode for high-energy SSIBs, and this innovative approach to stabilizing the interface performance could serve as a basis for the development of next-generation high-energy SSIBs.

Impedance analysis of PEG plasticized PEO-based composite polymer electrolytes for sodium-ion batteries

Solid-state sodium-ion batteries (SSIBs) will be the next generation batteries due to the high safety, low price, and availability of sodium resources. Composite polymer electrolytes (CPEs) are promising electrolytes because of easy fabrication, good stability, and high flexibility facilitating a good electrolyte-electrode interface, although their ionic conductivities are still unsatisfied. In this work, a CPE made of polyethylene oxide (PEO), Na3Zr2Si2PO12, and NaClO4 has been fabricated. To further enhance the ionic conductivity and a good electrolyte–electrode interface, polyethylene glycol (PEG) is added as a plasticizer. The electrochemical impedance spectroscopy (EIS) demonstrates effect on conductivity by introducing PEG.