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[Display omitted] Metal selenides are promising anode candidates for sodium ion batteries (SIBs) because of their high theoretical capacity, low cost, and environmental friendship. However, the low rate capability at high current density due to its inherent low electrical conductivity and poor cycle stability caused by inevitable volume variations during cycling frustrate its practical applications. Herein, we have developed a simple metallic-organic frameworks (MOFs)-derived selenide strategy to synthesize a series of heterogeneous bimetallic selenides encapsulated within graphene aerogels (GA) as anodes for SIBs. The bimetallic selenides/GA composites have unique structural characteristics that can shorten the migration path for Na+/electrons and accommodate the volume variations via additional void space during cycling. The built-in electric fields induced at the heterointerfaces can greatly reduce the activation energy for rapid charge transfer kinetics and promote the diffusion of Na+/electrons. GA is also beneficial for accommodating the volume variations during cycling and improving conductivity. As an advanced anode for SIBs, the MoSe2-Cu1.82Se@GA with a special porous octahedron can deliver the highest capacity of 444.8 mAh/g at a high rate of 1 A/g even after 1000 cycles among the bimetallic selenides/GA composites. [ABSTRACT FROM AUTHOR]

The extraction of vanadium from spent industrial catalysts is a widely practiced process globally due to the large quantities of material available with appreciable vanadium content. However, some of these spent catalysts are unresponsive to established extraction methods because they have different properties. Therefore, separate studies are necessary to deal with specific cases. This work demonstrates how the leaching step can limit the recovery of vanadium to the solution before the coprecipitation step. The NH4Cl‐H2SO4 synergetic system achieved a high vanadium leaching rate of up to 95 %, resulting in the preparation of high‐purity NH4VO3 with 75.45 % V2O5 content. This demonstrates the potential of the prepared V2O5 as a precursor for vanadium materials used in sodium‐ion batteries, allowing for the adjustment of the valence of vanadium. The Na3V2(PO4)3@C particles exhibit a discharge capacity of 110 mAh g−1 at a current density of 0.1 C and 90 mAh g−1 at 1 C. The synergistic leaching system provides a sustainable method for the recovery and reuse of vanadium from spent vanadium catalysts. This contributes to recycling efforts and the development of sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Constructing heterostructures containing multiple active components is proven to be an efficient strategy for enhancing the sodium storage capability of anode materials in sodium‐ion batteries (SIBs). However, performance enhancement is often attributed to the unclear synergistic effects among the active components. A comprehensive understanding of the reaction mechanisms on the interfaces at the atomic level remains elusive. Herein, the carbon‐coated Fe3Se4/CoSe (Fe3Se4/CoSe‐C) anode material as a model featuring atomic‐scale contact interfaces is synthesized. This unique heterogeneous architecture offers an adjustable electronic structure, which facilitates rapid reaction kinetics and enhances structural integrity. In situ microscopic and ex situ spectral characterization techniques, along with theoretical simulations, confirm that the heterointerface with strong electric fields promotes Na+ ion migration. Based on solid‐state nuclear magnetic resonance (NMR) analysis, an interface charge storage mechanism is revealed, resulting in the enhanced specific capacity of the anode materials. When employed as an anode in SIBs, the Fe3Se4/CoSe‐C electrode demonstrates excellent rate capabilities (218 mAh g−1 at 7 A g−1) and prolonged cycling stability (258 mAh g−1 at 5 A g−1 after 1000 cycles). This work highlights the significance of heterointerface engineering in electrode material design for rechargeable batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] In this work, the nanocables of few-layered ReS 2 nanosheets sandwiched between carbon nanotubes (CNTs) and nitrogen-doped amorphous carbon (NC) coating (i.e., CNT@ReS 2 @NC) are synthesized as high-performance anodes of both potassium-ion batteries (PIBs) and sodium-ion batteries (SIBs). The CNT@ReS 2 @NC nanocables with dual carbon modifications have the several advantages for efficient K+/Na+ storage. The few-layered ReS 2 nanosheets with a wide interlayer spacing of 0.64 nm contribute to accelerated reaction kinetics for fast K+/Na+ intercalation/extraction. The carbon nanotube skeleton with a hollow interior can effectively relieve the volume change and serve as a robust conductive network to boost structural stability. The NC layer provides rich defects as active sites and suppresses the shuttle effect of polysulfides produced in discharge/charge processes. Consequently, the CNT@ReS 2 @NC nanocables possess outstanding electrochemical performance in both PIBs and SIBs owing to the synergistic effect from the different components. A long cycling lifespan of 3500 cycles with a maintained discharge capacity of 125 mAh/g is achieved for CNT@ReS 2 @NC at 1 A/g in PIBs. In SIBs, it can keep a high capacity of 202 mAh/g over 3000 cycles at 5 A/g. Moreover, the CNT@ReS 2 @NC||Na 3 V 2 (PO 4) 3 full cell can exhibit remarkable cycling performance, yielding a low capacity decay rate of 0.019 % per cycle over 1000 cycles at 2C. [ABSTRACT FROM AUTHOR]

Iron oxychloride (FeOCl) with a layered structure may be a potential cathode material for rechargeable sodium ion batteries, due to its large interlayer spacing and high theoretical capacity. Here, the FeOCl material is employed as the cathode material for sodium ion batteries for the first time. Its morphology, electrochemical sodium storage performance, and reaction mechanisms are systematically investigated. The as-prepared FeOCl cathode exhibits a high discharge capacity of 321 mAh g−1 in the voltage range of 1.4–4.0 V (vs. Na/Na+) at 10 mA g−1 during the first cycle; however, the discharge capacity fades to 69 mAh g−1 after 30 cycles due to the large volume change of FeOCl and phase separation during cycling. The intercalation and conversion reaction mechanism of FeOCl during reversible sodium ion storage is demonstrated by the results of energy-dispersive spectroscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Bismuth (Bi) possesses an ultrahigh theoretical volume capacity (3800 mAh cm−3) and low embedding potential stimulated considerable attention as anodes for sodium‐ion batteries (SIBs). However, its practical application is still hampered by the huge volume variation during the charge/discharge process. To settle this issue, Bi@C nanosheet arrays (Bi@C‐NSA) are fabricated on copper foam via a facile galvanic replacement followed by in situ polymerization of dopamine and an annealing procedure. The carbon‐coated nanosheet array structure not only accommodates the volume expansion during cycling and maintains electrode stability, but also facilitates rapid electron/ion transport. Due to the unique structural design, this Bi@C‐NSA exhibits an impressive capacity of 315.72 mAh g−1 after 1500 cycles under 1 A g−1. Furthermore, a series of in situ/ex situ techniques reveal that this Bi@C‐NSA possesses superior reaction kinetics and undergoes a typical alloying/dealloying storage mechanism. Furthermore, Bi@C‐NSA also achieves commendable reversible capacity and cycling stability in a wide temperature range (0 °C–60 °C). Notably, the assembled Na3V2(PO4)3//Bi@C‐NSA full cell demonstrates a capacity of 325 mAh g−1 after 50 cycles at 0.05 A g−1, which promises for practical applications. This galvanic replacement strategy spearheads a way to prepare nanoarray electrodes and will accelerate the development of sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Ferrous sulfides with the high theoretic capacity are the promising anode for sodium ion batteries. However, capacity fading and inferior rate capability still hinder their practical application. In this work, Na‐doped Fe7S8 microrods with cationic vacancies and weakened Fe─S bond are constructed through a facile and scalable sulfurized route. The experimental results combined with theoretical analysis thoroughly reveal the generation of Fe vacancies and weakened Fe─S bond strength induced by sodium doping, which modulates the energy band structure of Na‐doped Fe7S8, provides more active sites, and accelerates the sodiation/desodiation reaction kinetics, simultaneously. Moreover, the pre‐doping sodium delivers a strong guiding effect on the formation of thin and stable solid electrolyte interface films. As the result, the optimal sample exhibits the excellent sodium storage performance, including the high and stable reversible capacity (674 mAh g−1 after 200 cycles at 0.5 A g−1 and 503 mAh g−1 after 1500 cycles at 10 A g−1), superior rate capability, and increased initial coulombic efficiency. Furthermore, the full cell paired with commercial Na3V2(PO4)3 also displays the outstanding cyclic stability with 95.9% capacity retention at 0.5 A g−1 after 100 cycles. [ABSTRACT FROM AUTHOR]

Rational element doping is demonstrated as an effective strategy to optimize crystal stability and enhance the electronic conductivity of Prussian blue analogs (PBAs) to achieve a satisfactory sodium storage performance. However, unraveling the dopant selection principles is still a big challenge. Herein, the integrated crystal orbital Hamilton population (ICOHP) function is adopted to evaluate the strength of chemical bonds of N‐transition metals (N‐TM) and guide the dopant selection. Among the series of ICOHP values for N‐TM (TM = Mn, Fe, Co, Ni, Cu, Zn), the Cu─N bond exhibits the lowest ICOHP value, which indicates that Cu doping can improve the stability of PBAs compared to other dopants. Experimentally, among TM‐substituted Fe‐based PBAs (TMFeHCFs), the as‐prepared sample with 20 at.% Cu doping (CuFeHCF‐2) exhibits the best cycling performance, with a capacity retention of 83.5% after 400 cycles at 1 C, which is consistent with the theoretical calculation results. In addition, in situ XRD and in situ, Raman reveal a highly reversible monoclinic‐cubic two‐phase conversion and redox‐active pairs, respectively. This study provides valuable guidelines for dopant selection to enhance the performance of PBAs cathodes. [ABSTRACT FROM AUTHOR]

The search for advanced electrode materials to solve slow ion diffusion and poor conductivity issues has spurred the development of fast‐charging sodium‐ion batteries (SIBs). Herein, a 2D metallic anode, KCu4S3, is reported expertly crafted using a KSCN molten salt approach, laying the foundation for fast‐charging SIBs. It is found that the mixed metal‐valence states within this compound provide substantial advantages, particularly in enhancing the high‐rate capability and ensuring long‐term durability. The mechanism that appears to facilitate these benefits can be traced to the formation of NaCu2S2 intermediate, which assist in electron transfer during Na+ (de)intercalation. In situ observations confirm the sodiation products of NaCu2S2 and sodium polysulfide can recover to the original phase upon desodiation. Such distinctive characteristics endow KCu4S3 with remarkable electrochemical performances, including an impressive capacity of 355 mAh g−1 at 20 A g−1 and 100% capacity retention within 3000 cycles. Moreover, the full cell exhibits a high energy density of 332 Wh kg−1 and retains 92% of its capacity across 150 cycles at 1 A g−1. This work opens new horizons in the field of fast‐charging materials, making a significant step forward in shaping the future of SIBs. [ABSTRACT FROM AUTHOR]

[Display omitted] Na 3 V 2 (PO 4) 3 is considered as one of the most promising cathodes for sodium ion batteries owing to its fast Na+ diffusion, good structural stability and high working potential. However, its practical application is limited by its low intrinsic electronic conductivity. Herein, a carbon coated Cu2+-doped Na 3 V 2 (PO 4) 3 cathode was prepared. The carbon coating not only improve its apparent conductivity, but also inhibit crystal growth and prevent agglomeration of particles. Moreover, Cu2+ doping contributes to an enhanced intrinsic conductivity and decreased Na+ diffusion energy barrier, remarkably boosting its charge transfer kinetics. Based on the structure characterizations, electrochemical performances tests, charge transfer kinetics analyses and theoretical calculations, it's proved that such an elaborate design ensures the excellent rate performances (116.9 mA h g−1 at 0.1C; 92.6 mA h g−1 at 10C) and distinguished cycling lifespan (95.8 % retention after 300 cycles at 1C; 84.8 % retention after 3300 cycles at 10C). Besides, a two-phase reaction mechanism is also confirmed via in-situ XRD. This research is expected to promote the development of Na 3 V 2 (PO 4) 3 -based sodium ion batteries with high energy/power density and excellent cycling lifespan. [ABSTRACT FROM AUTHOR]

Metal sulfide (MS) is regarded as a promising candidate of the anode materials for sodium‐ion battery (SIB) with ideal capacity and low cost, yet still suffers from the inferior cycling stability and voltage degradation. Herein, the coordination relationship between the discharge product Na2S with the Na+ (NaPF6) in the electrolyte, is revealed as the root cause for the cycling failure of MS. Na+‐coordination effect assistants the dissolution of Na2S, further delocalizing Na2S from the reaction interface under the function of electric field, which leads to the solo oxidation of the discharge product element metal without the participation of Na2S. Besides, the higher highest occupied molecular orbital of Na2S suggest the facilitated Na2S solo oxidation to produce sodium polysulfides (NaPSs). Based on these, lowering the Na+ concentration of the electrolyte is proposed as a potential improvement strategy to change the coordination environment of Na2S, suppressing the side reactions of the solo‐oxidation of element metal and Na2S. Consequently, the enhanced conversion reaction reversibility and prolonged cycle life are achieved. This work renders in‐depth perception of failure mechanism and inspiration for realizing advanced conversion‐type anode. [ABSTRACT FROM AUTHOR]

[Display omitted] Na 3 V 2 (PO 4) 2 F 3 (NVPF), recognized for its Na superionic conductor architecture, emerges as a promising candidate among polyanion-type cathodes for sodium ion batteries (SIBs). However, its adoption in practical applications faces obstacles due to its inherently low electronic conductivity. To address this challenge, we employ a binary co-doped strategy to design Na 3.3 K 0.2 V 1.5 Mg 0.5 (PO 4) 2 F 3 cathode with nitrogen-doped carbon (NC) coating layer. This configuration enhances electronic conductivity and reduces diffusion barriers for sodium ion (Na+). The strategy of incorporating nitrogen-doped carbon coating not only facilitates the formation of a porous structure but also introduces additional defects and active sites. Such modifications accelerate the reaction kinetics and augment electrolyte interaction through an expanded specific surface area, thus streamlining the electrochemical process. Concurrently, strategic heteroatom substitution leads to a more efficient engagement of Na+ in the electrochemical activities, thereby bolstering the cathode's structural integrity. The vanadium fluorophosphate Na 3.3 K 0.2 V 1.5 Mg 0.5 (PO 4) 2 F 3 @NC exhibits an electrochemical performance, including a high discharge specific capacity of 124.3 mA h g−1 at 0.1C, a long lifespan of 1000 cycles with a capacity retention of 93.1 % at 10C, and a rate property of 73.2 mA h g−1 at 20C. This research provides a method for preparing binary doped NVPF for energy storage electrochemistry. [ABSTRACT FROM AUTHOR]

The Fe‐based anode of sodium‐ion batteries attracts much attention due to the abundant source, low‐cost, and high specific capacity. However, the low electron and ion transfer rate, poor structural stability, and shuttle effect of NaS2 intermediate restrain its further development. Herein, the Fe3O4/Fe/FeS tri‐heterojunction node spawned N‐carbon nanotube scaffold structure (FHNCS) was designed using the modified MIL‐88B(Fe) as a template followed by catalytic growth and sulfidation process. During catalytic growth process, the reduced Fe monomers catalyze the growth of N‐doped carbon nanotubes to connect the Fe3O4/Fe/FeS tri‐heterojunction node, forming a 3D scaffold structure. Wherein the N‐doped carbon promotes the transfer of electrons between Fe3O4/Fe/FeS particles, and the tri‐heterojunction facilitates the diffusion of electrons at the interface, to organize a 3D conductive network. The unique scaffold structure provides more active sites and shortens the Na+ diffusion path. Meanwhile, the structure exhibits excellent mechanical stability to alleviate the volume expansion during circulation. Furthermore, the Fe in Fe3O4/Fe heterojunction can adjust the d‐band center of Fe in Fe3O4 to enhance the adsorption between Fe3O4 and Na2S intermediate, which restrains the shuttle effect. Therefore, the FHNCS demonstrates a high specific capacity of 436 mAh g−1 at 0.5 A g−1, 84.7% and 73.4% of the initial capacities are maintained after 100 cycles at 0.5 A g−1 and 1000 cycles at 1.0 A g−1. We believe that this strategy gives an inspiration for constructing Fe‐based anode with excellent rate capability and cycling stability. [ABSTRACT FROM AUTHOR]

Differential electrochemical mass spectrometry (DEMS) is a powerful operando method for analyzing side reactions in batteries. We describe our DEMS setup highlighting the relevance for implementing a reference electrode. Although the method provides valuable information, the correct assignment of the DEMS signals to types of gases and quantifying the amounts released can be challenging. A frequent limitation is that gas concentrations are calculated from single m/z ratios. This has the drawback of overlooking unexpected gases which can cause misinterpretation of the signal intensities, or even attributing to gases which are not actually formed. We present a multiple concentration determination (MCD) algorithm that uses the full MS‐spectra, which allows a more reliable determination of the gas release. We demonstrate this approach for Na‐ion half‐cells with P2‐Na0.67Mn3/4Ni1/4O2 (NaMNO) as cathode active material (CAM). Studying the gassing behavior for two electrolyte formulations (1 M NaPF6 in propylene carbonate (PC) and in diglyme (2G)). Against the general belief that glymes lead to more gassing at high potentials, we find that gas evolution for PC electrolytes is larger compared to 2G electrolytes. Dimethyl ether is found to be a decomposition product of 2G. Pressure change measurements are used to independently validate the gas quantification. [ABSTRACT FROM AUTHOR]

[Display omitted] Heterojunctions and controllable anionic vacancies are perceived to be powerful means of ameliorating the performance of sodium-ion batteries assignable to their unique physical and chemical properties. However, the mechanism by which heterojunction and vacancy structures affect sodium-ion battery storage remains to be systemically explored. In this study, the Se doped CoS 2 @CoS 1.035 @Carbon (Se-CoS 2 @CoS 1.035 @C) heterostructure with anion vacancy was synthesized by a one-step calcination. These heterostructures with lower metal oxidation states and anionic vacancies exhibit exceptional Na+ storage performance (554.3 mA h g−1 after 1500 cycles at 5.0 A g−1). Both electrochemical tests and theoretical calculations demonstrate excellent pseudocapacitive behavior and enhanced Na+ adsorption during discharge because of anionic vacancies and Se doping. Additionally, introducing weaker Co-Se bonds and extending Co-S and Co-Se bonds reduce binding energies, which effectively accelerates the conversion reaction. Our findings provide a feasible way to rationally design and facilely prepare heterostructured anode materials with rich anionic vacancies for sodium-ion batteries. [ABSTRACT FROM AUTHOR]

The PPy-coated Na 0.67 Ni 0.33 Mn 0.67 O 2 cathode undergoes reversible structural evolution during charging/discharging process. The Na-ion full cell exhibits a high capacity retention of 88.2% after 150 cycles. [Display omitted] • PPy-coated P 2-Na 0.67 Ni 0.33 Mn 0.67 O 2 is prepared by in situ polymerization process. • The PPy-coated cathode showed enhanced cycling stability and rate capability. • The PPy coating layer can inhibit side reactions stemming from the electrolyte. P 2-Na 0.67 Mn 0.67 Ni 0.33 O 2 is a promising cathode material for sodium ion batteries (SIBs) due to its low cost, high theoretical capacity, and non-toxicity. However, it still suffers from unsatisfactory cycling stability mainly incurred by the Jahn-Teller effect of Mn3+ and electrolyte decomposition on the electrode/electrolyte interface. Herein, the P 2-Na 0.67 Ni 0.33 Mn 0.67 O 2 @PPy (NNMO@PPy) composite applied as cathode materials for SIBs is obtained by introducing conductive polypyrrole (PPy) as coating layer on the P 2-Na 0.67 Ni 0.33 Mn 0.67 O 2 (NNMO) microspheres. Numerous physical characterization methods indicate that the PPy layer was uniformly coated on the surface of NNMO microspheres without change in phase structure and morphology. The PPy coating layer can alleviate Mn dissolution and effectively suppress the side reactions between the electrolyte and electrode during cycling. The optimal NNMO@PPy-9 with 9 wt% PPy delivers a high capacity of 127.4 mAh/g at the current density at 150 mA g−1, an excellent cyclic stability with high capacity retention of 80.5 % after 300 cycles, and enhanced rate performance (169.3 mAh/g at 15 mA g−1 while 89.8 mAh/g at 600 mA g−1). Furthermore, hard carbon (−)//NNMO@PPy-9 (+) full cell delivers a high energy density of 305.1 Wh kg−1 and superior cycling stability with 88.2 % capacity retention after 150 cycles. In-situ X-ray diffraction experiment and electrochemical characterization verify the highly reversible structure evolution and robust P 2-type phase structure of NNMO@PPy-9 for fast and stable Na+ diffusion. This effective strategy of using conductive PPy as a coating layer may provide a new insight to modify NNMO surface, improving the cycling stability and rate capability. [ABSTRACT FROM AUTHOR]

[Display omitted] Flexible electrodes based on conversion-type materials have potential applications in low-cost and high-performance flexible sodium-ion batteries (FSIBs), owing to their high theoretical capacity and appropriate sodiation potential. However, they suffer from flexible electrodes with poor mechanical properties and sluggish reaction kinetics. In this study, freestanding CoS 2 nanoparticles coupled with graphene oxides and carbon nanotubes (CoS 2 /GO/CNTs) flexible films with robust and interconnected architectures were successfully synthesized. CoS 2 /GO/CNTs flexible film displays high electronic conductivity and superior mechanical properties (average tensile strength of 21.27 MPa and average toughness of 393.18 KJ m−3) owing to the defect bridge for electron transfer and the formation of the π–π interactions between CNTs and GO. In addition, the close contact between the CoS 2 nanoparticles and carbon networks enabled by the Co-N chemical bond prevents the self-aggregation of the CoS 2 nanoparticles. As a result, the CoS 2 /GO/CNTs flexible film delivered superior rate capability (213.5 mAh g−1 at 6 A g−1, better than most reported flexible anode) and long-term cycling stability. Moreover, the conversion reaction that occurred in the CoS 2 /GO/CNTs flexible film exhibited pseudocapacitive behavior. This study provides meaningful insights into the development of flexible electrodes with superior mechanical properties and electrochemical performance for energy storage. [ABSTRACT FROM AUTHOR]

Purposes Exploration of anode materials with excellent electrochemical properties is essential to improve the performance of sodium ion batteries (SIBs). High-entropy oxides (HEO), with their unique structural characteristics, tailorable chemical composition, and tunable functional properties, have drawn increasing interest in the fields of environmental science and renewable energy technology. However, when HEO are directly used as anode materials for SIBs, a problem of agglomeration limits the electrochemical performance. In general, carbon nanotubes (CNT) are used to optimize battery performance because of their high electrical conductivity and good mechanical stability. Methods Spinel-type high-entropy oxide (FeCoNiCuMn)3O4/CNT composites (HEO/CNT) with space group Fd-3m have been synthesized through hydrothermal treatment followed by annealing method. Findings As the anode material in SIBs, at a current density of 0.5 A/g, HEO/CNT has a reversible capacity of 231 mAh/g after 200 cycles. Additionally, the HEO/CNT exhibits high reversible capacities of 363.3, 350, 341.1, 310.2, and 290.2 mAh/g at the current densities 0.1, 0.2, 0.5, 1, and 2 A/g, respectively. In situ X-ray diffraction analysis has been employed to reveal that the sodium ion storage process is a result of a combined Na＋ intercalation and conversion reaction between Na＋ and HEO/CNT. Conclusions Thanks to the “high entropy effect” of the high entropy oxide/carbon material, the volume change of the active material is mitigated during the charge/discharge process. Therefore, HEO/CNT is expected to be an electrode material with good sodium storage performance. This work provides a new template strategy for the application of high entropy materials.

Co‐free O3‐type NaNi0.5Mn0.5O2 cathode material for sodium‐ion batteries has shown great promise due to its high theoretical capacity and plentiful Na reservoir. However, the rapid capacity recession caused by harmful phase transition and large volume strain severely restricts their practical application. Herein, the obstacle is well addressed by constructing a P2&O3 biphasic structure via a customized boron‐doping strategy. The light‐weight boron doping in the interstitial position reduces the energy gap of the formation energy of P2 and O3 structure, which induces the formation of P2&O3 biphase in high Na state. In addition, the biphasic structure exhibits near zero volume strain due to the lattice interlocking effect of P2&O3, as identified by in situ X‐ray diffraction measurement. As a result, it presents a remarkable cyclability with a capacity retention of 85.2% over 1000 cycles at a high rate of 5 C. More importantly, a pouch‐type full‐cell device can exhibit a long cycling life with 70.8% capacity retention over 150 cycles at 0.1 C. This work can offer a new inspiration for designing advanced high sodium electrode materials via light element doping for future energy storage devices. [ABSTRACT FROM AUTHOR]

Transition metal selenides (TMSes) are considered promising candidates for the anodes of sodium‐ion batteries (SIBs) due to their substantial theoretical capacity. However, TMSes still face with inferior cycling lifespan caused by sluggish Na+ diffusion kinetics and vigorous volume variations during dis/charge processes. Engineering heterostructure is an attractive solution for rapid Na+ transfer, and introducing carbonaceous materials also facilitates enhanced conductivity and structural stability. Herein, CoSe/MoSe2 heterostructure combined with homogeneous carbon composites are rational designed. The kinetic analysis and theoretical calculations verified that heterointerface engineering induced build‐in electric field effect can amplifies the Na+ diffusion kinetics, while carbon contributes to enhanced electrical conductivity and structural stability. Expectedly, the CoSe/MoSe2‐C exhibits high capacity and extremely ultra‐long lifespan (320.9 mAh g−1 at 2.0 A g−1 over 10,000 cycles with an average decay of only 0.01781 mAh g−1 per cycle). Furthermore, in situ X‐ray diffraction (XRD), ex situ X‐ray photoelectorn (XPS), and high‐resolution electron microscopy (HRTEM) are exploited to explore the Na+ storage mechanism. In addition, the Na3V2(PO4)3@rGO//CoSe/MoSe2‐C (NVP@rGO//CoSe/MoSe2‐C) pouch‐type full‐cells are successfully assembled and delivered satisfactory performance. This research presents a viable strategy for the targeted engineering of TMSes aimed at enhancing the efficiency of SIBs. [ABSTRACT FROM AUTHOR]

The exploration of waste graphite from used lithium ion batteries (LIBs) and its derivatives for versatile applications is an efficient route to promote the environmental and eco‐friendly recycling of used LIBs. Sodium ion batteries (SIBs) are alternative candidates to LIBs mainly due to similar electrochemical mechanism of SIBs to LIBs and rich natural resource of Na. Herein, a holey waste graphite (hGw) with well‐defined porous structure is produced by the annealing of lithiated waste graphite (Li/Gw) from used LIBs under a flow gas of H2O and subsequent lithium leaching in DI water. Benefiting from the holey structure of hGw, holey graphene nanoplatelets (hGnw) with ultrahigh‐level edge‐grafted oxygen groups (≈37.8 at%) are synthesized by mechanical balling of hGw. As anode for SIBs, the hGnw present outstanding sodium ion storage properties with high initial Coulombic efficiency of 82.4%, high reversible capacity (e.g., 416.1 mAh g−1 at 0.03 A g−1), excellent rate capability (e.g., 153.3 mAh g−1 at 2 A g−1), and long‐term cycling stability (e.g., 152.7 mAh g−1 after 400 cycles at 1.5 A g−1). [ABSTRACT FROM AUTHOR]

Incorporating oxygen radicals on asphalt precursor boosts the formation of closed-pore with enhanced plateau capacity of hard carbon. [Display omitted] • Carbon radicals on asphalt precursor exhibit a propensity to form long-range, well-ordered graphitic structures with lower sodium storage capacities. • Incorporating oxygen radicals on asphalt precursor require higher energy for ordering the graphitic structures. • Incorporated oxygen radicals boosts the formation of closed-pore with a four-fold increase in plateau capacity for sodium ion storage. Hard carbon (HC) has emerged as a highly promising anode material for sodium ion batteries, drawing tremendous interest in producing this material with low-cost and easily accessible precursors. The determination of the crucial parameters of precursors influencing the formation of key structures, such as closed pores, in the HC is of paramount importance. Considering the potential role of free radicals in the structural evolution of the precursors, we, for the first time, delve into the impact of radical species on the development of closed pores by electron paramagnetic resonance spectroscopy, with petroleum asphalt as the model system. Our findings reveal that carbon centred radicals, with the g value close to that of the free electron (2.0023), exhibit a propensity to form long-range, well-ordered graphitic structures with lower sodium storage capacity. Conversely, the deliberately incorporated oxygen radicals with the g value over 2.005 require a higher energy for ordering the graphitic structures, leading to the creation of closed pores. As a result, the optimal sample showcases a four-fold increase in plateau capacity for sodium ion storage due to the pore filling process. Our research underscores the pivotal role of employing electron paramagnetic resonance spectroscopy studying the critical structural evolution of functional carbon materials. [ABSTRACT FROM AUTHOR]

Vanadium based NASICON‐type cathodes are faced with the exorbitant cost and underdeveloped multi‐electrons reaction of V species. In this work, a strategy of increased covalency of the NASICON framework combined with the reversible activation of V4+/V5+ couple is proposed to improve the electrochemical performance together with energy density of V‐based cathodes. Making full use of V2+/V3+/V4+/V5+ and Ti3+/Ti4+ redox couples, Na2.5VTi0.5Al0.5(PO4)3 exhibits admirable electrochemical performance, including a high specific capacity of 160.9 mAh g−1 at 0.1 C and favorable cycling stability (a capacity retention of 88.3% at 20 C after 1000 cycles). Moreover, this cathode displays outstanding low temperature performance at 0 °C with a capacity retention of 89% after 1200 cycles at 5 C. In situ XRD and EIS analysis are conducted to reveal the Na+ storage mechanism. The cathode reveals a lattice volume variation of 2.16% upon cycling, which is responsible for the high structural stability during the extraction and intercalation process of Na+. Applying Na2.5VTi0.5Al0.5(PO4)3 as both cathode and anode electrode, the symmetric cell is assembled and displays exceptional capacity of 59.8 mAh g−1 at 20 C. The research provides an effective routine to stimulate the electrochemical potential of V‐based electrode materials. [ABSTRACT FROM AUTHOR]

Along with great attention to eco-friendly power solutions, sodium ion batteries (SIBs) have stepped into the limelight for electrical vehicles (EVs) and grid-scale energy storage systems (ESSs). SIBs have been perceived as a bright substitute for lithium ion batteries (LIBs) due to abundance on Earth along with the cost-effectiveness of Na resources compared to Li counterparts. Nevertheless, there are still inherent challenges to commercialize SIBs due to the relatively larger ionic radius and sluggish kinetics of Na+ ions than those of Li+ ions. Particularly, exploring novel anode materials is necessary because the conventional graphite anode in LIBs is less active in Na cells and hard carbon anodes exhibit a poor rate capability. Various metal compounds have been examined for high-performance anode materials in SIBs and they exhibit different electrochemical performances depending on their compositions. In this review, we summarize and discuss the correlation between cation and anion compositions of metal compound anodes and their structural features, energy storage mechanisms, working potentials, and electrochemical performances. On top of that, we also present current research progress and numerous strategies for achieving high energy density, power, and excellent cycle stability in anode materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Metal sulfides (MSs) have attracted much attention as anode materials for sodium-ion batteries (SIBs) due to their high sodium storage capacity. However, the unsatisfactory electrochemical performance induced by the huge volume change and sluggish kinetics hampered the practical application of SIBs. Herein, guided by the heterostructure interface engineering, novel multicomponent metal sulfide-based anodes, including SnS, FeS, and Fe 3 N embedded in N -doped carbon nanosheets (SnS/FeS/Fe 3 N/NC NSs), have been synthesized for high-performance SIBs. The as-prepared SnS/FeS/Fe 3 N/NC NSs with abundant heterointerfaces and high conductivity of N -doped carbon nanosheet matrix can shorten the Na+ diffusion path and promote reaction kinetics during the sodiation/desodiation process. Moreover, the presence of Fe 3 N can promote the reversible conversion of SnS and FeS during the cycling process. As a consequence, when evaluated as anode materials for SIBs, the SnS/FeS/Fe 3 N/NC NSs can maintain a high sodium storage capacity of 473.6 mAh g-1 after 600 cycles at 2.0 A g-1 and can still provide a high reversible capacity of 537.4 mAh g-1 even at 5.0 A g-1 This discovery offers a novel strategy for constructing metal sulfide-based anode materials for high-performance SIBs. [ABSTRACT FROM AUTHOR]

Considering environmental changes and the demand for more sustainable energy sources, stricter requirements have been placed on electrode materials for sodium and potassium‐ion batteries, which are expected to provide higher energy and power density while being affordable and sustainable. Vanadium sulfide‐based materials have emerged as intriguing contenders for the next generation of anode materials due to their high theoretical capacity, abundant reserves, and cost‐effectiveness. Despite these advantages, challenges such as limited cycle life and restricted ion diffusion coefficients continue to impede their effective application in sodium and potassium‐ion batteries. To overcome the limitations associated with electrochemical performance and circumvent bottlenecks imposed by the inherent properties of materials at the bulk scale, this review comprehensively summarizes and analyzes the crystal structures, modification strategies, and energy storage processes of vanadium sulfide‐based electrode materials for sodium and potassium‐ion batteries. The objective is to guide the development of high‐performance vanadium‐based sulfide electrode materials with refined morphologies and/or structures, employing environmentally friendly and cost‐efficient methods. Finally, future perspectives and research suggestions for vanadium sulfide‐based materials are presented to propel practical applications forward. [ABSTRACT FROM AUTHOR]

Flexible electrode is an important part of wearable electronics. Herein, flexible Prussian blue@Carbon nanofibers electrode is fabricated using electrospun carbon nanofiber as electron-donating agents and carbon skeletons. Cubic-shaped Prussian blue with an edge length of 140 nm is in situ deposited on the surface of carbon nanofibers by slow co-precipitation process. The unique design not only obtains the core–shell structure, which is efficient to shorten the diffusion path of sodium ions and improve the electronic conductivity, but also effectively improves the crystallinity of Prussian blue, which is conducive to the improvement of specific capacity and cyclic life. The flexible electrode exhibits superior sodium storage properties including excellent cycling stability (89 mAh g−1 after 2000 cycles at 10C with a considerable capacity retention of 92%) and exceptional rate capability (a capacity up to 90.2 mAh g −1 even at an ultrahigh current density of 50 C). In addition, the self-supporting structure effectively improves the overall energy density of the battery. The strategy using the electron-donating properties of carbon nanofibers open new perspectives to construct other flexible electrodes. [ABSTRACT FROM AUTHOR]

Transition metal sulfides (TMSs) still confront the challenges of capacity fading and inferior fast‐charging capability for sodium storage. The rational design of heterostructures enables a new approach to conquer these drawbacks. In this work, a hierarchical structure consisting of SnS2 nanosheets and FeS2 microrods with triphasic heterostructures is proposed by the facile secondary growth and sulfidation process. The introduction of tin sources regulates the proportion of pyrite and marcasite phases, thereby achieving the triphasic heterostructures comprising pyrite, marcasite FeS2, and SnS2. When served as anode material for sodium‐ion batteries, the optimized sample exhibits a high reversible capacity (901 mAh g−1) and durable cycling performances (827 mAh g−1 after 200 cycles at 1 A g−1 and 742 mAh g−1 after 700 cycles at 5 A g−1). Paring with the commercial Na3V2(PO3)3 cathodes, the full‐cell also delivers extraordinary cyclic stability with a high capacity of 618 mAh g−1 (based on the weight of anode material) after 200 cycles at 1 A g−1 (98.7% capacity retention). The hierarchical structure with adjustably triphasic heterogeneous interfaces alleviates the volumetric expansion and interfacial passivation of active material, while modulating the energy band structure and inducing the build‐in electric fields to boost Na+/electrons transport rate. [ABSTRACT FROM AUTHOR]

Polyanionic sodium ion cathodes have attracted lots of concern because of their excellent structural stability. However, the low specific capacity is still a pressing issue hampering their practical application. In this work, a medium‐entropy NASICON‐structure cathode Na3.5V0.5Mn0.5Fe0.5Ti0.5(PO4)3 (Me‐NVMP) is proposed. The Me‐NVMP achieves a highly reversible specific capacity of 165.8 mAh g−1 (1.8–4.4 V vs Na+/Na) at 0.1 C via the stepwise redox reactions of Ti3+/Ti4+‐Fe2+/Fe3+, V3+/V4+‐Mn2+/Mn3+, and V4+/V5+‐Mn3+/Mn4+. More impressively, the Me‐NVMP yields super rate capability and cycling stability via the regulation of configuration entropy in NASICON. Specifically, the Me‐NVMP cathode can preserve a capacity retention of 83.5% after 10,000 cycles at 100 C (17 A g−1). Furthermore, excellent cycling performance even at the temperature of 0 °C (capacity retention of 93.45% at 20 C after 1000 cycles) is also demonstrated. In situ X‐ray diffraction analysis reveals that the enhanced performance can be mainly attributed to the solid–solution‐type Na+ storage behavior in Me‐NVMP. Moreover, issues such as Jahn‐Teller distortion of Mn3+ and irreversible structural change at high voltage (>4.0 V vs Na+/Na) are effectively mitigated. This work inspires a new strategy to design high‐performance polyanionic electrode materials. [ABSTRACT FROM AUTHOR]

A NASICON-type high-entropy carbon-coated Na 3 V 1.9 (Mg, Cr, Al, Mo, Nb) 0.1 (PO 4) 2 F 3 (NVPF-HE@C) material was synthesized through the sol-gel route. The incorporation of high entropy elements (Mg, Cr, Al, Mg, Nb) improved the stability of Na2 sites in NVPF without altering its crystal structure, which suppressed the intermediate reactions of Na 3 V 2 (PO 4) 2 F 3 phase at low potential of 3.4V. This improvement further lifted the specific capacity, capacity retention and Na+ diffusion coefficient of NVPF-HE@C cathode. The fluctuation of Na+ diffusion coefficient at low voltage region decreased 10−14-10−10cm2s−1 to 10−12-10−10cm2s−1. NVPF-HE@C cathode displays the initial specific capacities of 128 mAhg−1 at 1C and 82 mAhg−1 at 5C, while maintaining a low capacity decay of 17% over 800 cycles. The introduction of high-entropy doping provides an effective approach as promoting the electrochemistry properties of NVPF cathode, with potential applicability to other electrode materials in energy storage applications. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides are attractive anode materials for sodium ion batteries (SIBs) due to their high theoretical capacity and large interlayer spacing. However, its practical application is hampered by the sluggish kinetics of Na+ insertion and structure collapse caused by Na+ insertion/deinsertion. Herein, the heterostructures of MoSe2 nanosheets vertically growing on bowl-like carbon (MoSe2@C) are designed and prepared by a template method coupled with selenization treatment to boost storage sodium performance. The hollow and collapse could provide enough storage space for Na+ and alleviate the volume expansion during the charge/discharge processes. MoSe2 nanosheets vertically grown on carbon could expose more active sites for adsorbing Na+ to enhance the utilization rate of electrode materials. Moreover, building heterostructures by combining different phase components could facilitate Na+ diffusion and advance reaction kinetics. Benefiting from these merits, the bowllike MoSe2@C shows outstanding reversible capacity (356.8 mAh·g−1 after 1500 cycles at 1 A·g−1) and remarkable rate performance (249.9 mAh·g−1 10 A·g−1). [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs) are considered the next‐generation candidates for future energy storage systems to partially substitute commercial lithium‐ion batteries because of their abundant sodium/potassium reserves, cost‐effectiveness, and high safety. Polyanionic cathode materials are widely used in alkali ion batteries due to their stable structural framework, high thermal stability, excellent alkali ion diffusion kinetics, and adjustable working voltage. Generally, the polyanionic cathodes used for SIBs surpass PIBs in the aspect of energy density and cycle life in most cases, however, the PIBs also have their unique advantages that are seldom reported. To this end, the polyanionic materials are classified by the valence states of active metal sites, the storage mechanism of Na+ and K+ in different crystal structures is summarized, and the electrochemical performance between SIBs and PIBs is compared. Particularly, some unique advantages of polyanionic cathodes in PIBs, such as high working voltage, superior rate capability, and excellent capacity retention are revealed, and the possible reasons are discussed in detail. Finally, various viable solutions are proposed to improve the battery performance of polyanionic compounds for future development. [ABSTRACT FROM AUTHOR]

"Carbon Peak and Carbon Neutrality" is an important strategic goal for the sustainable development of human society. Typically, a key means to achieve these goals is through electrochemical energy storage technologies and materials. In this context, the rational synthesis and modification of battery materials through new technologies play critical roles. Plasma technology, based on the principles of free radical chemistry, is considered a promising alternative for the construction of advanced battery materials due to its inherent advantages such as superior versatility, high reactivity, excellent conformal properties, low consumption and environmental friendliness. In this perspective paper, we discuss the working principle of plasma and its applied research on battery materials based on plasma conversion, deposition, etching, doping, etc. Furthermore, the new application directions of multiphase plasma associated with solid, liquid and gas sources are proposed and their application examples for batteries (e. g. lithium‐ion batteries, lithium‐sulfur batteries, zinc‐air batteries) are given. Finally, the current challenges and future development trends of plasma technology are briefly summarized to provide guidance for the next generation of energy technologies. [ABSTRACT FROM AUTHOR]

Defect structure has attracted significant attention because of its importance as design factor for exploring high‐performance functional materials. This study reports a defect‐engineering strategy to optimize the electrode performance of transition metal dichalcogenides and a clear elucidation of the underlying mechanism on the benefit of defect engineering with cycling‐induced transformation into small nanoclusters. The intercalative hybridization of monolayered MoS2 nanosheets with bulky tetraalkylammonium cations is effective for generating abundant crystal vacancies in the MoS2 lattice and improving the sodium‐ion electrode performance, achieving one of the excellent performances among MoS2‐based sodium‐ion anode materials. The improved electrode activity of the tetrapropylammonium−MoS2 nanohybrid is ascribed to the vacancy‐assisted transformation from monolayered MoS2 nanosheets into trimeric/dimeric MoSx nanoclusters during electrochemical cycling. 23Na/1H magic angle spinning‐nuclear magnetic resonance analyses demonstrated that cycling‐induced defective MoSx nanoclusters yields a complex Na environment with high ion mobility and enhanced electrolyte absorptivity, promoting the excellent electrode functionality of tetrapropylammonium‐assembled MoS2 nanosheets. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are considered potential successors to lithium-ion batteries in the fields of energy storage and low-speed vehicles, thanks to their advantages such as abundant raw material sources, high energy density, and a wide operational temperature range. However, several scientific and engineering challenges still require attention in the development of sodium-ion batteries. Electrolyte salts, as a key component of sodium-ion battery electrolytes, play a critical role in battery performance. This paper provides a brief overview of the research progress on different electrolyte salt systems in sodium-ion batteries. It discusses characteristics such as ionic conductivity, electrochemical windows, electrochemical performance, and thermal safety in various solvent systems. Furthermore, the paper summarizes a series of strategies for controlling electrolyte and electrode interfaces, offering references for addressing the challenges in the mass production and application of sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Transition metal phosphides attract extensive concerns thanks to their high theoretical capacity in sodium ion batteries (SIBs). Nevertheless, the substantial volume fluctuation of metal phosphides during cycling leads to severe capacity decay, which largely hinders their large-scale deployment. In this regard, heterostructured Fe-Co-P (FeP/Co2P) arrays are firstly constructed in this work for SIBs. The novel self-supported construction without insulated binders favors fast charge migration and Na+ ion diffusion. In addition, the special heterostructure with abundant heterointerfaces could considerably mitigate the volume change during (de)sodiation and provide increased active sites for Na+ ions. Density functional theoretical (DFT) calculations confirm the built-in electric field in the heterointerfaces, which greatly hastens charge transfer and Na+ ion transportation, thereafter bringing about enhanced electrochemical performance. Most importantly, the FeP/Co2P heterostructure discloses higher electrical conductivity than that of bare FeP and Co2P based on the theoretical calculations. As anticipated, the heterostructured Fe-Co-P arrays demonstrate superior performance to that of Fe-P or Co-P anode, delivering high reversible capacities of 634 mAh g−1 at 0.2 A g−1 and 239 mAh g−1 at 1 A g−1 after 300 cycles. [ABSTRACT FROM AUTHOR]

Developing cost-effective cathode materials is conducive to accelerating the commercialization of sodium-ion batteries. Na4Fe3(PO4)2P2O7 (NFPP) has attracted extensive attention owning to its high theoretical capacity, stable structure, and low cost of raw materials. However, its inherent low conductivity hinders its further application. Herein, carbon-coated NFPP nanospheres are anchored to crumpled MXene nanosheets by an electrostatic self-assembly; this cross-linked structure induced by CTAB not only significantly expands the contact area between particles and improves the electronic conductivity, but also effectively reduces the aggregation of NFPP nanoparticles. The as-designed Na4Fe3(PO4)2(P2O7)@C/Ti3C2Tx (NFPP@MX) cathode exhibits a high discharge capacity (106.1 mAh g−1 g at 0.2 C), good rate capability (60.4 mAh g−1 at 10 C), and a long-life cyclic stability (85.2% capacity retention after 1000 cycles at 1 C). This study provides an effective strategy for the massive production of high-performance NFPP cathodes and broadens the application of MXene in the modification of other cathode materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new CoSe 2 -ZnSe@rGO composite with heterointerfaces is designed and synthesized. • The CoSe 2 -ZnSe@rGO composite behaves special structure characteristics. • The built-in electric field in the heterointerfaces is favorable for Na+ transfer. • The rGO could improve conductivity and alleviate volume variations of the active materials. • The CoSe 2 -ZnSe@rGO exhibits an enhanced coulombic efficiency and cycling stability. Transition metal selenides are promising anode candidates for sodium ion batteries (SIBs) because of their higher theoretical capacity and conductivity than metal oxides. However, the disadvantages of severe capacity degradation and poor magnification performance greatly limit their commercial applications. Herein, we have developed a new hollow bimetallic selenides (CoSe 2 -ZnSe)@reduced graphene oxide (rGO) composite with abundant heterointerfaces. The rGO could not only alleviate the volume variations of hollow CoSe 2 -ZnSe microspheres during cycling, but also improve the conductivity of composite. The presence of the heterointerfaces could help to accelerate ionic diffusion kinetics and improve electron transfer, resulting in the improved sodium storage performance. As an advanced anode for SIBs, the CoSe 2 -ZnSe@rGO exhibits an enhanced initial coulombic efficiency of 75.1% (65.2% of CoSe 2 @rGO), extraordinary rate capability, and outstanding cycling stability (540.3 mAh/g at 0.2 A/g after 150 cycles, and 395.2 mAh/g at 1 A/g after 600 cycles). The electrochemical mechanism was also studied by kinetic analysis, showing that the charging/discharging process of CoSe 2 -ZnSe@rGO is mostly related to a capacitive-controlled behavior. [ABSTRACT FROM AUTHOR]

[Display omitted] As an emerging class of layered transition metal carbides/nitrides/carbon-nitrides, MXenes have been one of the most investigated anode subcategories for sodium ion batteries (SIBs), due to their unique layered structure, metal-like conductivity, large specific surface area and tunable surface groups. In particular, different MAX precursors and synthetic routes will lead to MXenes with different structural and electrochemical properties, which actually gives MXenes unlimited scope for development. In this feature article, we systematically present the recent advances in the methods and synthetic routes of MXenes, together with their impact on the properties of MXenes and also the advantages and disadvantages. Subsequently, the sodium storage mechanisms of MXenes are summarized, as well as the recent research progress and strategies to improve the sodium storage performance. Finally, the main challenges currently facing MXenes and the opportunities in improving the performance of SIBs are pointed out. [ABSTRACT FROM AUTHOR]

Due to the low price and high specific capacity, sodium ion batteries (SIBs) have become a crucial candidate for the future large‐scale energy storage power station, providing strong support for energy transition. Layered transition metal oxides (LTMOs), as one of the most promising cathode materials for SIBs, are usually accompanied by the sodiation/de‐sodiation during charging/discharging, which leads to the slippage and deformation of the layered structure, and consequently causes to the degradation of electrochemical performance. The degradation mechanisms of LTMOs attributed to the structural change are important references for improving the electrochemical performance of cathode materials. Here, this paper presents the main degradation mechanisms such as irreversible anion redox reaction, Na+/vacancy ordering transition and poor air stability as well as the corresponding modification means. It also summarizes the challenges faced by sodium‐ion LTMOs cathode materials, and gives an outlook on the key issues that need to be solved for future development. [ABSTRACT FROM AUTHOR]

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Lithium-based electrolytes are, at least from a thermodynamic standpoint, the most suitable ion-transport materials for energy storage systems. However, lithium-based ionic conductors suffer from safety concerns, and the limited availability of lithium in the Earth's crust is at the root of the need to consider alternative metal ions. Notably, sodium stands out as the sixth most-prevalent element; therefore, when considering mineral reserves, it as a very attractive candidate as an alternative to the status quo. Even if the specific energy and energy density of sodium are indeed inferior with respect to those of lithium, there is substantial economic appeal in promoting the use of the former metal in stationary energy storage applications. For these reasons, the promise of sodium is likely to extend to other commercial applications, including portable electronics, as well as hybrid and electric vehicles. Widely used organic liquid electrolytes, regardless of their chosen metal cation, are disadvantageous due to leakage, evaporation, and high flammability. Polymer electrolytes are acknowledged as the most effective candidates to overcome these obstacles and facilitate the advancement of next-generation energy storage applications. In this contribution, an in-depth and comprehensive review of sodium polymer electrolytes for primary and secondary batteries is proposed. The overarching goal was to gain insight into successful synthetic strategies and their implications for conduction parameters and conductivity mechanisms. The focus lies on solid, gel, and composite polymer electrolytes. Our hope is that the proposed discussion will be helpful to all operators in the field, whether in tackling fundamental research problems or resolving issues of practical significance. [ABSTRACT FROM AUTHOR]

Sodium ion batteries (SIBs) are promising technique for energy storage applications. Cathode materials are keys to improve the energy density of SIBs. P2-type layered cathodes with low Na ion diffusion barrier attract great attention. However, it suffers structural instability at a high working voltage. Though many attempts were made, the cycle stability of P2-type layered cathodes with a high working voltage is still not satisfactory. In this work, zinc was used as a doping element for modification. When the doping amount is x = 0.1 (Na0.7Ni0.25Mn0.65Zn0.1O2), it presents enhanced cycle stability in the voltage range of 2.5–4.2 V. The impacts of calcination temperature and cooling methods were investigated. It was found that the material shows excellent stability when the material was calcined at 950 °C followed by natural cooling, the discharge capacity is 64.9 mAh g−1 over 1000 cycles with a capacity retention of 84.0% after 1000 cycles at 170 mA g−1, superior to those reported in literature. In situ XRD reveals a reversible phase transition from P2 to OP4 at the high voltage contributes to the excellent cycle stability. [ABSTRACT FROM AUTHOR]

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The two‐phase reaction of Na3V2(PO4)3 – Na1V2(PO4)3 in Na3V2(PO4)3 (NVP) is hindered by low electronic and ionic conductivity. To address this problem, a surface‐N‐doped NVP encapsulating by N‐doped carbon nanocage (N‐NVP/N‐CN) is rationally constructed, wherein the nitrogen is doped in both the surface crystal structure of NVP and carbon layer. The surface crystal modification decreases the energy barrier of Na+ diffusion from bulk to electrolyte, enhances intrinsic electronic conductivity, and releases lattice stress. Meanwhile, the porous architecture provides more active sites for redox reactions and shortens the diffusion path of ion. Furthermore, the new interphase of Na2V2(PO4)3 is detected by in situ XRD and clarified by density functional theory (DFT) calculation with a lower energy barrier during the fast reversible electrochemical three‐phase reaction of Na3V2(PO4)3 – Na2V2(PO4)3 – Na1V2(PO4)3. Therefore, as cathode of sodium‐ion battery, the N‐NVP/N‐CN exhibited specific capacities of 119.7 and 75.3 mAh g−1 at 1 C and even 200 C. Amazingly, high capacities of 89.0, 86.2, and 84.6 mAh g−1 are achieved after overlong 10000 cycles at 20, 40, and 50 C, respectively. This approach provides a new idea for surface crystal modification to cast intermediate Na2V2(PO4)3 phase for achieving excellent cycling stability and rate capability. [ABSTRACT FROM AUTHOR]

Na 2 Ti 3 O 7 , a titanium-based compound for sodium ion batteries (SIBs), stands out among anode materials because of its ultralow voltage plateau which leads to advanced energy density. However, the poor electronic conductivity and mediocre sodium ion storage capability are the main bottlenecks for its large-scale development. In this regard, self-supported Se doped Na 2 Ti 3 O 7 arrays are innovatively proposed and different Se doping amounts are designed. It is concluded that the appropriate Se doping (Na 2 Ti 3 O 6 Se) could significantly enlarge the interlayer spacing, narrow the bandgap and decrease Na+ diffusion barrier, leading to enhanced reaction kinetics, which is also validated by the theoretical calculations in this work. As expected, the 0 anode exhibits a reversible capacity of 207 mAh g−1 after 100 cycles at 0.2 A g−1 in the voltage range of 0.01–3 V. A capacity of 155 mAh g−1 can be achieved after 1000 cycles at 1 A g−1. The experimental findings combined with theoretical calculations state that the Se doping protocol is an effective mean to modify the electrode materials. • A self supported Na 2 Ti 3 O 7 arrays with Se doping is designed. • The appropriate content Se doping into Na 2 Ti 3 O 7 improves the performance. • Se doping induces charge accumulation and stronger Na + adsorption capability. • Se doping improves the electronic conductivity. [ABSTRACT FROM AUTHOR]

Exploring special anode materials with high capacity, stable structure, and extreme temperature feasibility remains a great challenge in secondary sodium based energy systems. Here, a bimetallic Cu‐Fe selenide nanosheet with refined nanostructure providing confined internal ion transport channels are reported, in which the structure improves the pseudocapacitance and reduces the charge transfer resistance for making a significant contribution to accelerating the reaction dynamics. The CuFeSe2 nanosheets have a high initial specific capacity of 480.4 mAh g−1 at 0.25 A g−1, showing impressively excellent rate performance and ultralong cycling life over 1000 cycles with 261.1 mAh g−1 at 2.5 A g−1. Meanwhile, it exhibits a good sodium storage performance at extreme temperatures from −20 °C to 50 °C, supporting at least 500 cycles. Besides, the CuFeSe2||Na3V2(PO4)3/C full cell delivers a high specific capacity of 168.5 mAh g−1 at 0.5 A g−1 and excellent feasibility for over 600 cycles long cycling. Additionally, the Na+ storage mechanisms are further revealed by ex situ X‐ray diffraction (XRD) and in situ transmission electron microscopy (TEM) techniques. A feasible channelized structural design strategy is provided that inspires new instruction into the development of novel materials with high structural stability and low volume expansion rate toward the application of other secondary batteries. [ABSTRACT FROM AUTHOR]