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1.
Herein, a new P2‐type layered oxide is proposed as an outstanding intercalation cathode material for high energy density sodium‐ion batteries (SIBs). On the basis of the stoichiometry of sodium and transition metals, the P2‐type Na0.55[Ni0.1Fe0.1Mn0.8]O2 cathode is synthesized without impurities phase by partially substituting Ni and Fe into the Mn sites. The partial substitution results in a smoothing of the electrochemical charge/discharge profiles and thus greatly improves the battery performance. The P2‐type Na0.55[Ni0.1Fe0.1Mn0.8]O2 cathode delivers an extremely high discharge capacity of 221.5 mAh g?1 with a high average potential of ≈2.9 V (vs Na/Na+) for SIBs. In addition, the fast Na‐ion transport in the P2‐type Na0.55[Ni0.1Fe0.1Mn0.8]O2 cathode structure enables good power capability with an extremely high current density of 2400 mA g?1 (full charge/discharge in 12 min) and long‐term cycling stability with ≈80% capacity retention after 500 cycles at 600 mA g?1. A combination of electrochemical profiles, in operando synchrotron X‐ray diffraction analysis, and first‐principles calculations are used to understand the overall Na storage mechanism of P2‐type Na0.55[Ni0.1Fe0.1Mn0.8]O2.  相似文献   

2.
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.  相似文献   

3.
Thanks to low costs and the abundance of the resources, sodium‐ion (SIBs) and potassium‐ion batteries (PIBs) have emerged as leading candidates for next‐generation energy storage devices. So far, only few materials can serve as the host for both Na+ and K+ ions. Herein, a cubic phase CuSe with crystal‐pillar‐like morphology (CPL‐CuSe) assembled by the nanosheets are synthesized and its dual functionality in SIBs and PIBs is comprehensively studied. The electrochemical measurements demonstrate that CPL‐CuSe enables fast Na+ and K+ storage as well as the sufficiently long duration. Specifically, the anode delivers a specific capacity of 295 mA h g?1 at current density of 10 A g?1 in SIBs, while 280 mA h g?1 at 5 A g?1 in PIBs, as well as the high capacity retention of nearly 100% over 1200 cycles and 340 cycles, respectively. Remarkably, CPL‐CuSe exhibits a high initial coulombic efficiency of 91.0% (SIBs) and 92.4% (PIBs), superior to most existing selenide anodes. A combination of in situ X‐ray diffraction and ex situ transmission electron microscopy tests fundamentally reveal the structural transition and phase evolution of CuSe, which shows a reversible conversion reaction for both cells, while the intermediate products are different due to the sluggish K+ insertion reaction.  相似文献   

4.
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 Ti3+/4+ (≈2.1 V), Mn2+/3+ (≈3.5 V), and Mn3+/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.  相似文献   

5.
3D batteries continue to be of widespread interest for flexible energy storage where the 3D nanostructured cathode is the key component to achieve both high energy and power densities. While current work on flexible cathodes tends to emphasize the use of flexible scaffolds such as graphene and/or carbon nanotubes, this approach is often limited by poor electrical contact and structural stability. This communication presents a novel synthetic approach to form 3D array cathode for the first time, the single‐crystalline Na3(VO)2(PO4)2F (NVOPF) by using VO2 array as a seed layer. The NVOPF cathode exhibits both high‐rate capability (charge/discharge in 60 s) and long‐term durability (10,000 cycles at 50 C) for Na ion storage. Utilizing in situ X‐ray diffraction and first principles calculations, the high‐rate properties are correlated with the small volume change, 2D fast ion transport, and the array morphology. A novel all‐array flexible Na+ hybrid energy storage device based on pairing the intercalation‐type NVOPF array cathode with a cogenetic pseudocapacitive VO2 nanosheet array anode is demonstrated.  相似文献   

6.
Layered lithium–nickel–cobalt–manganese oxide (NCM) materials have emerged as promising alternative cathode materials owing to their high energy density and electrochemical stability. Although high reversible capacity has been achieved for Ni‐rich NCM materials when charged beyond 4.2 V versus Li+/Li, full lithium utilization is hindered by the pronounced structural degradation and electrolyte decomposition. Herein, the unexpected realization of sustained working voltage as well as improved electrochemical performance upon electrochemical cycling at a high operating voltage of 4.9 V in the Ni‐rich NCM LiNi0.895Co0.085Mn0.02O2 is presented. The improved electrochemical performance at a high working voltage at 4.9 V is attributed to the removal of the resistive Ni2+O rock‐salt surface layer, which stabilizes the voltage profile and improves retention of the energy density during electrochemical cycling. The manifestation of the layered Ni2+O rock‐salt phase along with the structural evolution related to the metal dissolution are probed using in situ X‐ray diffraction, neutron diffraction, transmission electron microscopy, and X‐ray absorption spectroscopy. The findings help unravel the structural complexities associated with high working voltages and offer insight for the design of advanced battery materials, enabling the realization of fully reversible lithium extraction in Ni‐rich NCM materials.  相似文献   

7.
Carbon materials have attracted significant attention as anode materials for sodium ion batteries (SIBs). Developing a carbon anode with long‐term cycling stability under ultrahigh rate is essential for practical application of SIBs in energy storage systems. Herein, sulfur and nitrogen codoped mesoporous hollow carbon spheres are developed, exhibiting high rate performance of 144 mA h g?1 at 20 A g?1, and excellent cycling durability under ultrahigh current density. Interestingly, during 7000 cycles at a current density of 20 A g?1, the capacity of the electrode gradually increases to 180 mA h g?1. The mechanisms for the superior electrochemical performance and capacity improvement of the cells are studied by electrochemical tests, ex situ transmission electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, and Raman analysis of fresh and cycled electrodes. The unique and robust structure of the material can enhance transport kinetics of electrons and sodium ions, and maintain fast sodium storage from the capacitive process under high rate. The self‐rearrangement of the carbon structure, induced by continuous discharge and charge, lead to the capacity improvement with cycles. These results demonstrate a new avenue to design advanced anode materials for SIBs.  相似文献   

8.
Recently, sodium ion batteries (SIBs) have been widely investigated as one of the most promising candidates for replacing lithium ion batteries (LIBs). For SIBs or LIBs, designing a stable and uniform solid electrolyte interphase (SEI) at the electrode–electrolyte interface is the key factor to provide high capacity, long‐term cycling, and high‐rate performance. In this paper, it is described how a remarkably enhanced SEI layer can be obtained on TiO2 nanotube (TiO2 NTs) arrays that allows for a strongly improved performance of sodium battery systems. Key is that a Li+ pre‐insertion in TiO2 NTs can condition the SEI for Na+ replacement. SIBs constructed with Li‐pre‐inserted NTs deliver an exceptional Na+ cycling stability (e.g., 99.9 ± 0.1% capacity retention during 250 cycles at a current rate of 50 mA g?1) and an excellent rate capability (e.g., 132 mA h g?1 at a current rate of 1 A g?1). The key factor in this outstanding performance is that Li‐pre‐insertion into TiO2 NTs leads not only to an enhanced electronic conductivity in the tubes, but also expands the anatase lattice for facilitated subsequent Na+ cycling.  相似文献   

9.
Poor cycling stability is one of the key scientific issues needing to be solved for Li‐ and Mn‐rich layered oxide cathode. In this paper, sodium carboxymethyl cellulose (CMC) is first used as a novel binder in Li1.2Ni0.13Co0.13Mn0.54O2 cathode to enhance its cycling stability. Electrochemical performance is conducted by galvanostatic charge and discharge. Structure and morphology are characterized by X‐ray diffraction, scanning electronic microscopy, high‐resolution transmission electron microscopy, and X‐ray photoelectron spectroscopy. Results reveal that the CMC as binder can not only stabilize the electrode structure by preventing the electrode materials to detach from the current collector but also suppress the voltage fading of the Li1.2Ni0.13Co0.13Mn0.54O2 cathode due to Na+ ions doping. Most importantly, the dissolution of metal elements from the cathode materials into the electrolyte is also inhibited.  相似文献   

10.
Herein, P′2‐type Na0.67[Ni0.1Fe0.1Mn0.8]O2 is introduced as a promising new cathode material for sodium‐ion batteries (SIBs) that exhibits remarkable structural stability during repetitive Na+ de/intercalation. The O? Ni? O? Mn? O? Fe? O bond in the octahedra of transition‐metal layers is used to suppress the elongation of the Mn? O bond and to improve the electrochemical activity, leading to the highly reversible Na storage mechanism. A high discharge capacity of ≈220 mAh g?1 (≈605 Wh kg?1) is delivered at 0.05 C (13 mAg?1) with a high reversible capacity of ≈140 mAh g?1 at 3 C and excellent capacity retention of 80% over 200 cycles. This performance is associated with the reversible P′2–OP4 phase transition and small volume change upon charge and discharge (≈3%). The nature of the sodium storage mechanism in a full cell paired with a hard carbon anode reveals an unexpectedly high energy density of ≈542 Wh kg?1 at 0.2 C and good capacity retention of ≈81% for 500 cycles at 1 C (260 mAg?1).  相似文献   

11.
A series of F‐substituted Na2/3Ni1/3Mn2/3O2?xFx (x = 0, 0.03, 0.05, 0.07) cathode materials have been synthesized and characterized by solid‐state 19F and 23Na NMR, X‐ray photoelectron spectroscopy, and neutron diffraction. The underlying charge compensation mechanism is systematically unraveled by X‐ray absorption spectroscopy and electron energy loss spectroscopy (EELS) techniques, revealing partial reduction from Mn4+ to Mn3+ upon F‐substitution. It is revealed that not only Ni but also Mn participates in the redox reaction process, which is confirmed for the first time by EELS techniques, contributing to an increase in discharge specific capacity. The detailed structural transformations are also revealed by operando X‐ray diffraction experiments during the intercalation and deintercalation process of Na+, demonstrating that the biphasic reaction is obviously suppressed in the low voltage region via F‐substitution. Hence, the optimized sample with 0.05 mol f.u.?1 fluorine substitution delivers an ultrahigh specific capacity of 61 mAh g?1 at 10 C after 2000 cycles at 30 °C, an extraordinary cycling stability with a capacity retention of 75.6% after 2000 cycles at 10 C and 55 °C, an outstanding full battery performance with 89.5% capacity retention after 300 cycles at 1 C. This research provides a crucial understanding of the influence of F‐substitution on the crystal structure of the P2‐type materials and opens a new avenue for sodium‐ion batteries.  相似文献   

12.
Over the last decade, Na‐ion batteries have been extensively studied as low‐cost alternatives to Li‐ion batteries for large‐scale grid storage applications; however, the development of high‐energy positive electrodes remains a major challenge. Materials with a polyanionic framework, such as Na superionic conductor (NASICON)‐structured cathodes with formula NaxM2(PO4)3, have attracted considerable attention because of their stable 3D crystal structure and high operating potential. Herein, a novel NASICON‐type compound, Na4MnCr(PO4)3, is reported as a promising cathode material for Na‐ion batteries that deliver a high specific capacity of 130 mAh g?1 during discharge utilizing high‐voltage Mn2+/3+ (3.5 V), Mn3+/4+ (4.0 V), and Cr3+/4+ (4.35 V) transition metal redox. In addition, Na4MnCr(PO4)3 exhibits a high rate capability (97 mAh g?1 at 5 C) and excellent all‐temperature performance. In situ X‐ray diffraction and synchrotron X‐ray diffraction analyses reveal reversible structural evolution for both charge and discharge.  相似文献   

13.
2D vanadium carbide MXene containing surface functional groups (denoted as V2CTx , where Tx are surface functional groups) is synthesized and studied as anode material for Na‐ion batteries. V2CTx anode exhibits reversible charge storage with good cycling stability and high rate capability through electrochemical test. The charge storage mechanism of V2CTx 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 V2CTx during sodiation/desodiation process are provided through V K ‐edge XANES and V L 2,3‐edge sXAS results. A correlation between the CO32? content and the Na+ intercalation/deintercalation states in the V2CTx 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 V2CTx and the carbonate‐based nonaqueous electrolyte. The results of this study provide valuable information for the further studies on V2CTx as anode material for Na‐ion batteries and capacitors.  相似文献   

14.
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.  相似文献   

15.
Recently, anionic‐redox‐based materials have shown promising electrochemical performance as cathode materials for sodium‐ion batteries. However, one of the limiting factors in the development of oxygen‐redox‐based electrodes is their low operating voltage. In this study, the operating voltage of oxygen‐redox‐based electrodes is raised by incorporating nickel into P2‐type Na2/3[Zn0.3Mn0.7]O2 in such a way that the zinc is partially substituted by nickel. As designed, the resulting P2‐type Na2/3[(Ni0.5Zn0.5)0.3Mn0.7]O2 electrode exhibits an average operating voltage of 3.5 V and retains 95% of its initial capacity after 200 cycles in the voltage range of 2.3–4.6 V at 0.1C (26 mA g?1). Operando X‐ray diffraction analysis reveals the reversible phase transition: P2 to OP4 phase on charge and recovery to the P2 phase on discharge. Moreover, ex situ X‐ray absorption near edge structure and X‐ray photoelectron spectroscopy studies reveal that the capacity is generated by the combination of Ni2+/Ni4+ and O2?/O1? redox pairs, which is supported by first‐principles calculations. It is thought that this kind of high voltage redox species combined with oxygen redox could be an interesting approach to further increase energy density of cathode materials for not only sodium‐based rechargeable batteries, but other alkali‐ion battery systems.  相似文献   

16.
Sodium (Na) super ion conductor structured Na3V2(PO4)3 (NVP) is extensively explored as cathode material for sodium‐ion batteries (SIBs) due to its large interstitial channels for Na+ migration. The synthesis of 3D graphene‐like structure coated on NVP nanoflakes arrays via a one‐pot, solid‐state reaction in molten hydrocarbon is reported. The NVP nanoflakes are uniformly coated by the in situ generated 3D graphene‐like layers with the thickness of 3 nm. As a cathode material, graphene covered NVP nanoflakes exhibit excellent electrochemical performances, including close to theoretical reversible capacity (115.2 mA h g?1 at 1 C), superior rate capability (75.9 mA h g?1 at 200 C), and excellent cyclic stability (62.5% of capacity retention over 30000 cycles at 50 C). Furthermore, the 3D graphene‐like cages after removing NVP also serve as a good anode material and deliver a specific capacity of 242.5 mA h g?1 at 0.1 A g?1. The full SIB using these two cathode and anode materials delivers a high specific capacity (109.2 mA h g?1 at 0.1 A g?1) and good cycling stability (77.1% capacity retention over 200 cycles at 0.1 A g?1).  相似文献   

17.
Nanosized hollandite‐type VO1.75(OH)0.5 is introduced as a novel cathode material for Na‐ion batteries. Structural investigation based on X‐ray diffraction and Rietveld refinement suggests the presence of numerous vacant sites for Na+ intercalation in the VO1.75(OH)0.5 structure. All of the possible Na+ sites and tunnel‐type Na+ diffusion pathways along the c‐axis are confirmed by bond‐valence‐sum analyses. The nanosized hollandite‐type VO1.75(OH)0.5 delivers an unexpectedly high specific capacity of ≈351 mAh g?1 at 15.5 mA g?1 in the voltage range of 1.0–3.7 V (vs Na+/Na), which agrees well with the results predicted by first‐principles calculations. In addition, combined studies using first‐principles calculations and several experimental techniques including in situ operando X‐ray diffraction and ex situ X‐ray absorption spectroscopy confirm that the nanosized hollandite‐type VO1.75(OH)0.5 undergoes a single‐phase reaction with a capacity retention of 71% over 200 cycles. Furthermore, the open structure and nanosized particles of hollandite‐type VO1.75(OH)0.5 contribute to its excellent power capability with 56% of the capacity measured at 0.05 C being delivered at 7 C.  相似文献   

18.
Na3V2(PO4)3 (NVP) has excellent electrochemical stability and fast ion diffusion coefficient due to the 3D Na+ ion superionic conductor framework, which make it an attractive cathode material for lithium ion batteries (LIBs). However, the electrochemical performance of NVP needs to be further improved for applications in electric vehicles and hybrid electric vehicles. Here, nanoflake‐assembled hierarchical NVP/C microflowers are synthesized using a facile method. The structure of as‐synthesized materials enhances the electrochemical performance by improving the electron conductivity, increasing electrode–electrolyte contact area, and shortening the diffusion distance. The as‐synthesized material exhibits a high capacity (230 mAh g?1), excellent cycling stability (83.6% of the initial capacity is retained after 5000 cycles), and remarkable rate performance (91 C) in hybrid LIBs. Meanwhile, the hybrid LIBs with the structure of NVP || 1 m LiPF6/EC (ethylene carbonate) + DMC (dimethyl carbonate) || NVP and Li4Ti5O12 || 1 m LiPF6/EC + DMC || NVP are assembled and display capacities of 79 and 73 mAh g?1, respectively. The insertion/extraction mechanism of NVP is systematically investigated, based on in situ X‐ray diffraction. The superior electrochemical performance, the design of hybrid LIBs, and the insertion/extraction mechanism investigation will have profound implications for developing safe and stable, high‐energy, and high‐power LIBs.  相似文献   

19.
Aqueous Zn‐ion batteries (ZIBs) have received incremental attention because of their cost‐effectiveness and the materials abundance. They are a promising choice for large‐scale energy storage applications. However, developing suitable cathode materials for ZIBs remains a great challenge. In this work, pioneering work on the designing and construction of aqueous Zn//Na0.33V2O5 batteries is reported. The Na0.33V2O5 (NVO) electrode delivers a high capacity of 367.1 mA h g?1 at 0.1 A g?1, and exhibits long‐term cyclic stability with a capacity retention over 93% for 1000 cycles. The improvement of electrical conductivity, resulting from the intercalation of sodium ions between the [V4O12]n layers, is demonstrated by single nanowire device. Furthermore, the reversible intercalation reaction mechanism is confirmed by X‐ray diffraction, Raman, X‐ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy analysis. The outstanding performance can be attributed to the stable layered structure and high conductivity of NVO. This work also indicates that layered structural materials show great potential as the cathode of ZIBs, and the indigenous ions can act as pillars to stabilize the layered structure, thereby ensuring an enhanced cycling stability.  相似文献   

20.
The achievement of the superior rate capability and cycling stability is always the pursuit of sodium‐ion batteries (SIBs). However, it is mainly restricted by the sluggish reaction kinetics and large volume change of SIBs during the discharge/charge process. This study reports a facile and scalable strategy to fabricate hierarchical architectures where TiO2 nanotube clusters are coated with the composites of ultrafine MoO2 nanoparticles embedded in carbon matrix (TiO2@MoO2‐C), and demonstrates the superior electrochemical performance as the anode material for SIBs. The ultrafine MoO2 nanoparticles and the unique nanorod structure of TiO2@MoO2‐C help to decrease the Na+ diffusion length and to accommodate the accompanying volume expansion. The good integration of MoO2 nanoparticles into carbon matrix and the cable core role of TiO2 nanotube clusters enable the rapid electron transfer during discharge/charge process. Benefiting from these structure merits, the as‐made TiO2@MoO2‐C can deliver an excellent cycling stability up to 10 000 cycles even at a high current density of 10 A g?1. Additionally, it exhibits superior rate capacities of 110 and 76 mA h g?1 at high current densities of 10 and 20 A g?1, respectively, which is mainly attributed to the high capacitance contribution.  相似文献   

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