New Na‐Ion Solid Electrolytes Na4−xSn1−xSbxS4 (0.02 ≤ x ≤ 0.33) for All‐Solid‐State Na‐Ion Batteries

Sulfide Na‐ion solid electrolytes (SEs) are key to enable room‐temperature operable all‐solid‐state Na‐ion batteries that are attractive for large‐scale energy storage applications. To date, few sulfide Na‐ion SEs have been developed and most of the SEs developed contain P and suffer from poor chemical stability. Herein, discovery of a new structural class of tetragonal Na_4?xSn_1?xSb_xS₄ (0.02 ≤ x ≤ 0.33) with space group I4₁/acd is described. The evolution of a new phase, distinctly different from Na₄SnS₄ or Na₃SbS₄, allows fast ionic conduction in 3D pathways (0.2–0.5 mS cm^?1 at 30 °C). Moreover, their excellent air stability and reversible dissolution in water and precipitation are highlighted. Specifically, TiS₂/Na–Sn all‐solid‐state Na‐ion batteries using Na_3.75Sn_0.75Sb_0.25S₄ demonstrates high capacity (201 mA h (g of TiS₂)^?1) with excellent reversibility.     

Nature of Novel 2D van der Waals Heterostructures for Superior Potassium Ion Batteries

Novel 2D van der Waals heterostructures with innovative bimetallic oxychloride (Bi‐ and Sb‐based oxychloride) nanosheets that are well dispersed on reduced graphene oxide nanosheets, are established through element engineering for superior potassium ion battery (PIBs) anodes. This material displays an exceptional electrochemical performance, obtaining a discharge capacity as high as 360 mAh g^?1 at 100 mA g^?1 after running 1000 cycles for over 9 months with a capacity preservation percentage of 88.5% and achieving a discharge capacity as high as 319 mAh g^?1 at 1000 mA g^?1, in addition to the low charge/discharge plateaus for anodes and promising full cell performance. More significantly, the nature of such 2D van der Waals heterostructures, including the element engineering for morphology control, the function of each component of heterostructures, the mechanism of potassium ion storage, and the process of K⁺ intercalation accompanied with the lattice distortion and chemical bond breakages, is explored in depth. This study is critical for not only paving the way for the practical application of PIBs but also shedding light on fundamentals of potassium ion storage in 2D van der Waals heterostructures.     

Dual stator dynamics in the Shewanella oneidensis MR‐1 flagellar motor

The bacterial flagellar motor is an intricate nanomachine which converts ion gradients into rotational movement. Torque is created by ion‐dependent stator complexes which surround the rotor in a ring. Shewanella oneidensis MR‐1 expresses two distinct types of stator units: the Na⁺‐dependent PomA₄B₂ and the H⁺‐dependent MotA₄B₂. Here, we have explored the stator unit dynamics in the MR‐1 flagellar system by using mCherry‐labeled PomAB and MotAB units. We observed a total of between 7 and 11 stator units in each flagellar motor. Both types of stator units exchanged between motors and a pool of stator complexes in the membrane, and the exchange rate of MotAB, but not of PomAB, units was dependent on the environmental Na⁺‐levels. In 200 mM Na⁺, the numbers of PomAB and MotAB units in wild‐type motors was determined to be about 7:2 (PomAB:MotAB), shifting to about 6:5 without Na⁺. Significantly, the average swimming speed of MR‐1 cells at low Na⁺ conditions was increased in the presence of MotAB. These data strongly indicate that the S. oneidensis flagellar motors simultaneously use H⁺ and Na⁺ driven stators in a configuration governed by MotAB incorporation efficiency in response to environmental Na⁺ levels.     

Adjusting the Anisotropy of 1D Sb2Se3 Nanostructures for Highly Efficient Photoelectrochemical Water Splitting

Sb₂Se₃ has recently spurred great interest as a promising light‐absorbing material for solar energy conversion. Sb₂Se₃ consists of 1D covalently linked nanoribbons stacked via van der Waals forces and its properties strongly depend on the crystallographic orientation. However, strategies for adjusting the anisotropy of 1D Sb₂Se₃ nanostructures are rarely investigated. Here, a novel approach is presented to fabricate 1D Sb₂Se₃ nanostructure arrays with different aspect ratios on conductive substrates by simply spin‐coating Sb‐Se solutions with different molar ratios of thioglycolic acid and ethanolamine. A relatively small proportion of thioglycolic acid induces the growth of short Sb₂Se₃ nanorod arrays with preferred orientation, leading to fast carrier transport and enhanced photocurrent. After the deposition of TiO₂ and Pt, an appropriately oriented Sb₂Se₃ nanostructure array exhibits a significantly enhanced photoelectrochemical performance; the photocurrent reaches 12.5 mA cm^?2 at 0 V versus reversible hydrogen electrode under air mass 1.5 global illumination.     

Realizing Three‐Electron Redox Reactions in NASICON‐Structured Na3MnTi(PO4)3 for Sodium‐Ion Batteries

Developing multielectron reaction electrode materials is essential for achieving high specific capacity and high energy density in secondary batteries; however, it remains a great challenge. Herein, Na₃MnTi(PO₄)₃/C hollow microspheres with an open and stable NASICON framework are synthesized by a spray‐drying‐assisted process. When applied as a cathode material for sodium‐ion batteries, the resultant Na₃MnTi(PO₄)₃/C microspheres demonstrate fully reversible three‐electron redox reactions, corresponding to the Ti^3+/4+ (≈2.1 V), Mn^2+/3+ (≈3.5 V), and Mn^3+/4+ (≈4.0 V vs Na⁺/Na) redox couples. In situ X‐ray diffraction results reveals that both solid‐solution and two‐phase electrochemical reactions are involved in the sodiation/desodiation processes. The high specific capacity (160 mAh g^?1 at 0.2 C), outstanding cyclability (≈92% capacity retention after 500 cycles at 2 C), and the facile synthesis make the Na₃MnTi(PO₄)₃/C a prospective cathode material for sodium‐ion batteries.     

Realizing Reversible Conversion‐Alloying of Sb(V) in Polyantimonic Acid for Fast and Durable Lithium‐ and Potassium‐Ion Storage

Finding suitable electrode materials for alkali‐metal‐ion storage is vital to the next‐generation energy‐storage technologies. Polyantimonic acid (PAA, H₂Sb₂O₆ · nH₂O), having pentavalent antimony species and an interconnected tunnel‐like pyrochlore crystal framework, is a promising high‐capacity energy‐storage material. Fabricating electrochemically reversible PAA electrode materials for alkali‐metal‐ion storage is a challenge and has never been reported due to the extremely poor intrinsic electronic conductivity of PAA associated with the highest oxidation state Sb(V). Combining nanostructure engineering with a conductive‐network construction strategy, here is reported a facile one‐pot synthesis protocol for crafting uniform internal‐void‐containing PAA nano‐octahedra in a composite with nitrogen‐doped reduced graphene oxide nanosheets (PAA?N‐RGO), and for the first time, realizing the reversible storage of both Li⁺ and K⁺ ions in PAA?N‐RGO. Such an architecture, as validated by theoretical calculations and ex/in situ experiments, not only fully takes advantage of the large‐sized tunnel transport pathways (0.37 nm²) of PAA for fast solid‐phase ionic diffusion but also leads to exponentially increased electrical conductivity (3.3 S cm^?1 in PAA?N‐RGO vs 4.8 × 10^?10 S cm^?1 in bare‐PAA) and yields an inside‐out buffer function for accommodating volume expansion. Compared to electrochemically irreversible bare‐PAA, PAA?N‐RGO manifests reversible conversion‐alloying of Sb(V) toward fast and durable Li⁺‐ and K⁺‐ion storage.     

Na‐Ion Intercalation and Charge Storage Mechanism in 2D Vanadium Carbide

2D vanadium carbide MXene containing surface functional groups (denoted as V₂CT_x , where T_x are surface functional groups) is synthesized and studied as anode material for Na‐ion batteries. V₂CT_x anode exhibits reversible charge storage with good cycling stability and high rate capability through electrochemical test. The charge storage mechanism of V₂CT_x material during Na⁺ intercalation/deintercalation and the redox reaction of vanadium are studied using a combination of synchrotron based X‐ray diffraction, hard X‐ray absorption near edge spectroscopy (XANES), and soft X‐ray absorption spectroscopy (sXAS). Experimental evidence of a major contribution of redox reaction of vanadium to the charge storage and the reversible capacity of V₂CT_x during sodiation/desodiation process are provided through V K ‐edge XANES and V L _2,3‐edge sXAS results. A correlation between the CO₃^2? content and the Na⁺ intercalation/deintercalation states in the V₂CT_x electrode observed from C and O K ‐edge in sXAS results implies that some additional charge storage reactions may take place between the Na⁺‐intercalated V₂CT_x and the carbonate‐based nonaqueous electrolyte. The results of this study provide valuable information for the further studies on V₂CT_x as anode material for Na‐ion batteries and capacitors.     

Na4‐αM2+α/2(P2O7)2 (2/3 ≤ α ≤ 7/8, M = Fe,Fe0.5Mn0.5, Mn): A Promising Sodium Ion Cathode for Na‐ion Batteries

A new polyanion‐based compound, Na_3.12M_2.44(P₂O₇)₂ (M = Fe, Fe_0.5Mn_0.5, Mn) is synthesized and examined as a cathode for Na ion batteries. Off‐stoichiometric synthesis induces the formation of a Na‐rich phase, Na_3.32Fe_2.34(P₂O₇)₂ ‐ a member of the solid solution series Na_4‐αFe_2+α/2(P₂O₇)₂ (2/3 ≤ α ≤ 7/8) ‐ which delivers a reversible capacity of about 85 mA h g^?1 at ca. 3 V vs. Na/Na⁺ and exhibits very stable cycle performance. Above all, it shows fast kinetics for Na ions, delivering an almost constant 72% reversible capacity at rates between C/10 and 10C without the necessity for nanosizing or carbon coating. We attribute this to the spacious channel size along the a‐axis, along with a single phase transformation upon de/sodiation.     

Synthesis and Operando Sodiation Mechanistic Study of Nitrogen‐Doped Porous Carbon Coated Bimetallic Sulfide Hollow Nanocubes as Advanced Sodium Ion Battery Anode

Due to the obvious advantages of utilizing naturally abundant and low cost sodium resources, sodium ion batteries (SIBs) show great potential for large‐scale energy storage applications. And the high theoretical capacities of transition metal sulfides (TMSs) make them appealing anode materials for SIBs; however, structural collapse caused by the severe volume change during de/sodiation processes results in poor capacity retention and rate capabilities. Compared to the development of new materials and the improvement of their electrochemical performance, the studies on their reaction mechanisms are still rare, especially the operando characterizations. Herein, the synthesis, anode application, and the operando observation of the de/sodiation mechanism of a nitrogen‐doped porous carbon coated nickel cobalt bimetallic sulfide hollow nanocube ((Ni_0.5Co_0.5)₉S₈@NC) composite are reported. Such a material is synthesized via facile sulfidation of phenol formaldehyde coated Ni₃[Co(CN)₆]₂ metal–organic framework precursors with Na₂S followed by calcination. The nanocomposite displays a remarkable specific capacity of 752 mAh g^?1 at 100 mA g^?1 after 100 cycles and outstanding rate capability due to the synergistic effect of several appealing features. Particularly, the pseudocapacitive effect appears to substantially contribute to the sodium storage capability. Operando X‐ray diffraction reveals the conversion reaction mechanism of (Ni_0.5Co_0.5)₉S₈@NC, forming Ni, Co, Na₂S, and Na₂S₅.     

Exploration of relationships between physiological parameters and growth performance of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) seedlings under salinity stress using multivariate analysis

Knowledge of relationships between physiological parameters and growth performance of seedlings and respective genotypic differences would permit selection of salt tolerance at early growth stages. The goals of this study were to investigate the relationships between physiological parameters and growth performance and quantify the respective genotypic differences using multivariate analysis.. Plants of thirty-one genotypes were grown in sand tanks in a greenhouse and irrigated with Yoshida nutrient solution. Two salinity treatments were imposed at 0.9 dSm^–1 (control) and 6.4 dSm^–1 with sodium chloride and calcium chloride (~ 6: 1 molar ratio). Seedlings were sampled 34 days after planting (7^th to 8^th leaf stage). The characters of Na⁺, K⁺, Ca²⁺, K-Na selectivity (SK,Na) and Na-Ca selectivity (S_Na,Ca) were measured as physiological parameters. The characters of tiller number, leaf area, plant height and shoot dry weight were measured as growth performance. Under salinity stress, S_K,Na increased whereas S_Na,Ca decreased compared to the controls. Canonical correlation analysis indicates a strong relationship between physiological parameters and growth performance. Tiller number is a desirable parameter among the growth parameters analyzed to predict seedling growth under salinity stress. Genotypes grouped into four clusters based on ion contents and ion selectivity using Wards minimum-variance cluster analysis. S_K,Na and shoot Na⁺ content contributed the most to the cluster formation. Similarly, genotypes grouped into four clusters based on growth performance. Ge notypes were classified into three categories based on ion cluster rankings: Category 1 with high S_K,Na and low shoot Na⁺ content; Category 2 with intermediate S_K,Na and shoot Na⁺ content; Category 3 with low S_K,Na and high shoot Na⁺ content. The classification of the genotypes into Categories 1 and 3 based on their high or low S_K,Na was generally consistent with their growth performance under salt stress. In contrast, ion selectivity was a less dominant mechanism controlling salt tolerance in Category 2 with intermediate S_K,Na. It was concluded that ion selectivity was a relatively dominant mechanism controlling salt tolerance among rice genotypes although multiple mechanisms may be involved under moderate salt stress. The results also provide the first example of the effectiveness of cluster analysis for physiological responses to salinity stress.     

Nitrogen and Sulfur Vacancies in Carbon Shell to Tune Charge Distribution of Co6Ni3S8 Core and Boost Sodium Storage

Recently, the metal sulfide‐carbon nanocomposites have been suggested as a low‐cost alternative to lithium ion batteries, but commercial application is seriously hindered by their relatively inferior cyclic performance. Herein, N and S vacancies in an N,S co‐doped carbon (NSC) shell for anchoring a new bimetallic sulfide core of Co₆Ni₃S₈ using Co‐Ni‐alginate biomass are introduced. The obtained Co₆Ni₃S₈/carbon aerogels (Co₆Ni₃S₈/NSCA) exhibit excellent sodium‐ion storage properties, high reversible capacity (568.1 mAh g^?1 at 1 A g^?1), and an excellent cycle stability (94.4% after 300 cycles). Density functional theory calculation results disclose that nitrogen and sulfur vacancies in the carbon shell can enhance the binding between the Co₆Ni₃S₈ core and NSC shell, ensuring an improved structural and electrochemical stability. In addition, an increased adsorption energy of Na⁺ (?1.88 eV) and a decreased barrier energy for Na⁺ diffusion (0.46 eV) are observed indicating a fast Na⁺ diffusion process. The powder X‐ray diffraction refinement confirms that the lattice parameters of Co₆Ni₃S₈ extend to 0.9972 nm compared with Co₉S₈ (0.9928 nm), suppressing the volume expansion in Na⁺ diffusion processes.     

Formation of Solid–Electrolyte Interfaces in Aqueous Electrolytes by Altering Cation‐Solvation Shell Structure

Aqueous lithium/sodium‐ion batteries (AIBs) have received increasing attention because of their intrinsic safety. However, the narrow electrochemical stability window (1.23 V) of the aqueous electrolyte significantly hinders the development of AIBs, especially the choice of electrode materials. Here, an aqueous electrolyte composed of LiClO₄, urea, and H₂O, which allows the electrochemical stability window to be expanded to 3.0 V, is developed. Novel [Li (H₂O)_x(organic)_y]⁺ primary solvation sheath structures are developed in this aqueous electrolyte, which contribute to the formation of solid–electrolyte interface layers on the surfaces of both the cathode and anode. The expanded electrochemical stability window enables the construction of full aqueous Li‐ion batteries with LiMn₂O₄ cathodes and Mo₆S₈ anodes, demonstrating an operating voltage of 2.1 V and stability over 2000 cycles. Furthermore, a symmetric aqueous Na‐ion battery using Na₃V₂(PO₄)₃ as both the cathode and anode exhibits operating voltage of 1.7 V and stability over 1000 cycles at a rate of 5 C.     

Surface Pseudocapacitive Mechanism of Molybdenum Phosphide for High‐Energy and High‐Power Sodium‐Ion Capacitors

Sodium‐based energy storage technologies are potential candidates for large‐scale grid applications owing to the earth abundance and low cost of sodium resources. Transition metal phosphides, e.g. MoP, are promising anode materials for sodium‐ion storage, while their detailed reaction mechanisms remain largely unexplored. Herein, the sodium‐ion storage mechanism of hexagonal MoP is systematically investigated through experimental characterizations, density functional theory calculations, and kinetics analysis. Briefly, it is found that the naturally covered surface amorphous molybdenum oxides layers on the MoP grains undergo a faradaic redox reaction during sodiation and desodiation, while the inner crystalline MoP remains unchanged. Remarkably, the MoP anode exhibits a pseudocapacitive‐dominated behavior, enabling the high‐rate sodium storage performance. By coupling the pseudocapacitive anode with a high‐rate‐battery‐type Na₃V₂O₂(PO₄)₂F@rGO cathode, a novel sodium‐ion full cell delivers a high energy density of 157 Wh kg^?1 at 97 W kg^?1 and even 52 Wh kg^?1 at 9316 W kg^?1. These findings present the deep understanding of the sodium‐ion storage mechanism in hexagonal MoP and offer a potential route for the design of high‐rate sodium‐ion storage materials and devices.     

Glucose-6-phosphate dehydrogenase-dependent hydrogen peroxide production is involved in the regulation of plasma membrane H+-ATPase and Na+/H+ antiporter protein in salt-stressed callus from Carex moorcroftii

Glucose‐6‐phosphate dehydrogenase (G6PDH) is important for the activation of plant resistance to environmental stresses, and ion homeostasis is the physiological foundation for living cells. In this study, we investigated G6PDH roles in modulating ion homeostasis under salt stress in Carex moorcroftii callus. G6PDH activity increased to its maximum in 100 mM NaCl treatment and decreased with further increased NaCl concentrations. K⁺/Na⁺ ratio in 100 mM NaCl treatment did not exhibit significant difference compared with the control; however, in 300 mM NaCl treatment, it decreased. Low‐concentration NaCl (100 mM) stimulated plasma membrane (PM) H⁺‐ATPase and NADPH oxidase activities as well as Na⁺/H⁺ antiporter protein expression, whereas high‐concentration NaCl (300 mM) decreased their activity and expression. When G6PDH activity and expression were reduced by glycerol treatments, PM H⁺‐ATPase and NADPH oxidase activities, Na⁺/H⁺ antiporter protein level and K⁺/Na⁺ ratio dramatically decreased. Simultaneously, NaCl‐induced hydrogen peroxide (H₂O₂) accumulation was abolished. Exogenous application of H₂O₂ increased G6PDH, PM H⁺‐ATPase and NADPH oxidase activities, Na⁺/H⁺ antiporter protein expression and K⁺/Na⁺ ratio in the control and glycerol treatments. Diphenylene iodonium (DPI), the NADPH oxidase inhibitor, which counteracted NaCl‐induced H₂O₂ accumulation, decreased G6PDH, PM H⁺‐ATPase and NADPH oxidase activities, Na⁺/H⁺ antiporter protein level and K⁺/Na⁺ ratio. Western blot result showed that G6PDH expression was stimulated by NaCl and H₂O₂, and blocked by DPI. Taken together, G6PDH is involved in H₂O₂ accumulation under salt stress. H₂O₂, as a signal, upregulated PM H⁺‐ATPase activity and Na⁺/H⁺ antiporter protein level, which subsequently resulted in the enhanced K⁺/Na⁺ ratio. G6PDH played a central role in the process.     

Sodium Sulfide Cathodes Superseding Hard Carbon Pre‐sodiation for the Production and Operation of Sodium–Sulfur Batteries at Room Temperature

This study demonstrates for the first time a room temperature sodium–sulfur (RT Na–S) full cell assembled based on a pristine hard carbon (HC) anode combined with a nanostructured Na₂S/C cathode. The development of cells without the demanding, time‐consuming and costly pre‐sodiation of the HC anode is essential for the realization of practically relevant RT Na–S prototype batteries. New approaches for Na₂S/C cathode fabrication employing carbothermal reduction of Na₂SO₄ at varying temperatures (660 to 1060 °C) are presented. Initial evaluation of the resulting cathodes in a dedicated cell setup reveals 36 stable cycles and a capacity of 740 mAh g_S^?1, which correlates to ≈85% of the maximum value known from literature on Na₂S‐based cells. The Na₂S/C cathode with the highest capacity utilization is implemented into a full cell concept applying a pristine HC anode. Various full cell electrolyte compositions with fluoroethylene carbonate (FEC) additive have been combined with a special charging procedure during the first cycle supporting in situ solid electrolyte interphase (SEI) formation on the HC anode to obtain increased cycling stability and cathode utilization. The best performing cell setup has delivered a total of 350 mAh g_S^?1, representing the first functional full cell based on a Na₂S/C cathode and a pristine HC anode today.     

Confining Ultrathin 2D Superlattices in Mesoporous Hollow Spheres Renders Ultrafast and High‐Capacity Na‐Ion Storage

Sodium‐ion batteries have attracted ever‐increasing attention in view of the natural abundance of sodium resources. Sluggish sodiation kinetics, nevertheless, remain a tough challenge, in terms of achieving high rate capability and high energy density. Herein, a sheet‐in‐sphere nanoconfiguration of 2D titania–carbon superlattices vertically aligned inside of mesoporous TiO₂@C hollow nanospheres is constructed. In such a design, the ultrathin 2D superlattices consist of ordered alternating monolayers of titania and carbon, enabling interpenetrating pathways for rapid transport of electrons and Na⁺ ions as well as a 2D heterointerface for Na⁺ storage. Kinetics analysis discloses that the combination of 2D heterointerface and mesoporosity results an intercalation pseudocapacitive charge storage mechanism, which triggers ultrafast sodiation kinetics. In situ transmission electron microscope imaging and in situ synchrotron X‐ray diffraction techniques elucidate that the sheet‐in‐sphere architecture can maintain robust mechanical and crystallographic structural stability, resulting an extraordinary high rate capability, remarkable stable cycling with a low capacity fading ratio of 0.04% per cycle over 500 cycles at 0.2 C, and exceptionally long‐term cyclability up to 20 000 cycles at 50 C. This study offers a method for the realization of a high power density and long‐term cyclability battery by designing of a hierarchical nanoarchitecture.     

A 4 V Na+ Intercalation Material in a New Na‐Ion Cathode Family

Large‐scale electrochemical energy storage is a critical factor in the development of renewable energy sources to enable their intermittent power to become dispatchable. In this context, Na‐ion batteries are seen as promising alternatives to Li‐ion batteries, but their advancement requires the discovery of new materials, their electrochemical properties, and a better understanding of structure–property relationships that underpin the electrochemistry. This study presents a new class of Na⁺ insertion materials for Na‐ion batteries. By virtue of its moderately inductive polyanionic framework, the air and moisture stable selenite Na₂Co₂(SeO₃)₃ displays a highly suitable redox potential of ≈ 4 V versus Na/Na⁺ based on the Co²⁺/Co³⁺ couple, rendering it compatible with conventional liquid organic electrolytes. A microwave hydrothermal synthesis route is developed for the rapid synthesis of nanostructured Na₂Co₂(SeO₃)₃ and its conductive graphene oxide composite. The electrochemistry and structural evolution of Na₂Co₂(SeO₃)₃ determined on cycling the cathode in a Na battery was investigated by operando X‐ray diffraction, X‐ray photoelectron spectroscopy, and temperature dependent magnetic susceptibility measurements. These studies reveal good structural and electrochemical reversibility.     

New Binder‐Free Metal Phosphide–Carbon Felt Composite Anodes for Sodium‐Ion Battery

Metal phosphides are promising anode candidates for sodium‐ion batteries (SIBs) due to their high specific capacity and low operating potential but suffer from poor cycling stability caused by huge volume expansion and poor solid‐state ion transfer rate. Herein, a new strategy to grow a new class of mesoporous metal phosphide nanoarrays on carbon felt (CF) as binder‐free anodes for SIBs is reported. The resultant integrated electrodes demonstrate excellent cycling life up to 1000 times (>90% retention rate) and high rate capability of 535 mAh g^?1 at a current density of 4 A g^?1. Detailed characterization reveals that the synergistic effect of unique mesoporous structure for accommodating huge volume expansion during sodiation/desodiation process, ultrasmall primary particle size (≈10 nm) for providing larger electrode/electrolyte contact area and shorter ion diffusion distance, and 3D conductive networks for facilitating the electrochemical reaction, leads to the extraordinary battery performance. Remarkably, a full SIB using the new CoP₄/CF anode and a Na₃V₂(PO₄)₂F₃ cathode delivers an average operating voltage of ≈3.0 V, a reversible capacity of 553 mAh g^?1, and very high energy density of ≈280 Wh kg^?1 for SIBs. A flexible SIB with outstanding mechanical strength based on this binder‐free new anode is also demonstrated.     

Layered Na‐Ion Cathodes with Outstanding Performance Resulting from the Synergetic Effect of Mixed P‐ and O‐Type Phases

Herein, the synthesis of new quaternary layered Na‐based oxides of the type Na_xMn_yNi_zFe_0.1Mg_0.1O₂ (0.67≤ x ≤ 1.0; 0.5≤ y ≤ 0.7; 0.1≤ z ≤ 0.3) is described. The synthesis can be tuned to obtain P2‐ and O3‐type as well as mixed P‐/O‐type phases as demonstrated by structural, morphological, and electrochemical properties characterization. Although all materials show good electrochemical performance, the simultaneous presence of the P‐ and O‐type phases is found to have a synergetic effect resulting in outstanding performance of the mixed phase material as a sodium‐ion cathode. The mixed P3/P2/O3‐type material, having an average elemental composition of Na_0.76Mn_0.5Ni_0.3Fe_0.1Mg_0.1O₂, overcomes the specific drawbacks associated with the P2‐ and O3‐type materials, allowing the outstanding electrochemical performance. In detail, the mixed phase material is able to deliver specific discharge capacities of up to 155 mAh g^?1 (18 mA g^?1) in the potential range of 2.0–4.3 V. In the narrower potential range of 2.5–4.3 V the material exhibits high average discharge potential (3.4 V versus Na/Na⁺), exceptional average coulombic efficiencies (>99.9%), and extraordinary capacity retention (90.2% after 601 cycles). The unexplored class of P‐/O‐type mixed phases introduces new perspectives for the development of layered positive electrode materials and powerful Na‐ion batteries.